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Abadía Alvarado LK, Gómez Soler SC, Cifuentes González J. Gone with the pandemic: How did Covid-19 affect the academic performance of Colombian students? Int J Educ Dev 2023; 100:102783. [PMID: 37123870 PMCID: PMC10121134 DOI: 10.1016/j.ijedudev.2023.102783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 02/16/2023] [Accepted: 04/13/2023] [Indexed: 05/03/2023]
Abstract
The Covid-19 pandemic is an unprecedented shock that has tested the responsiveness of education systems around the world. The international literature that has studied the Covid-19 pandemic and school performance is still limited. Colombia presents an interesting scenario for the analysis due to the prolonged school closures and long lockdowns it experienced in 2020, and the availability of a rich dataset on the results of a high school exit examination (Saber11) that was administered even during the pandemic. Using this data, we estimate whether the COVID-19 pandemic is associated to lower levels of performance amongst graduating high school students using a school and time fixed effects model, finding a negative relation. Due to the significant reduction in the number of students taking the national standardized high school exit exam in 2020, we use inverse probability weighting (IPW) regressions to control for possible selection bias. The results of these regressions show that the Covid-19 pandemic has a negative and statistically significant relation with the scores obtained by students on the Saber11 exam. These results are relevant because they provide evidence to motivate the design of public policies that mitigate the side effects of the pandemic on educational outcomes.
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Affiliation(s)
| | - Silvia C Gómez Soler
- Department of Economics, Pontificia Universidad Javeriana, Cra. 7 # 40b - 36, Bogotá, Colombia
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Viana ER, Cifuentes N, González JC. Enhanced electronic transport properties of Te roll-like nanostructures. Beilstein J Nanotechnol 2022; 13:1284-1291. [PMID: 36447564 PMCID: PMC9663975 DOI: 10.3762/bjnano.13.106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 10/12/2022] [Indexed: 06/16/2023]
Abstract
In this work, the electronic transport properties of Te roll-like nanostructures were investigated in a broad temperature range by fabricating single-nanostructure back-gated field-effect-transistors via photolithography. These one-dimensional nanostructures, with a unique roll-like morphology, were produced by a facile synthesis and extensively studied by scanning and transmission electron microscopy. The nanostructures are made of pure and crystalline Tellurium with trigonal structure (t-Te), and exhibit p-type conductivity with enhanced field-effect hole mobility between 273 cm2/Vs at 320 K and 881 cm2/Vs at 5 K. The thermal ionization of shallow acceptors, with small ionization energy between 2 and 4 meV, leads to free-hole conduction at high temperatures. The free-hole mobility follows a negative power-law temperature behavior, with an exponent between -1.28 and -1.42, indicating strong phonon scattering in this temperature range. At lower temperatures, the electronic conduction is dominated by nearest-neighbor hopping (NNH) conduction in the acceptor band, with a small activation energy E NNH ≈ 0.6 meV and an acceptor concentration of N A ≈ 1 × 1016 cm-3. These results demonstrate the enhanced electrical properties of these nanostructures, with a small disorder, and superior quality for nanodevice applications.
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Affiliation(s)
- E R Viana
- Departamento Acadêmico de Física, Universidade Tecnológica Federal do Paraná, Campus Curitiba, 80230-901, Curitiba, Brazil
| | - N Cifuentes
- Departamento de Física, Universidade Federal de Minas Gerais, 30123-970, Belo Horizonte, Brazil
| | - J C González
- Departamento de Física, Universidade Federal de Minas Gerais, 30123-970, Belo Horizonte, Brazil
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Feres FH, Mayer RA, Wehmeier L, Maia FCB, Viana ER, Malachias A, Bechtel HA, Klopf JM, Eng LM, Kehr SC, González JC, Freitas RO, Barcelos ID. Sub-diffractional cavity modes of terahertz hyperbolic phonon polaritons in tin oxide. Nat Commun 2021; 12:1995. [PMID: 33790286 PMCID: PMC8012705 DOI: 10.1038/s41467-021-22209-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 02/18/2021] [Indexed: 02/01/2023] Open
Abstract
Hyperbolic phonon polaritons have recently attracted considerable attention in nanophotonics mostly due to their intrinsic strong electromagnetic field confinement, ultraslow polariton group velocities, and long lifetimes. Here we introduce tin oxide (SnO2) nanobelts as a photonic platform for the transport of surface and volume phonon polaritons in the mid- to far-infrared frequency range. This report brings a comprehensive description of the polaritonic properties of SnO2 as a nanometer-sized dielectric and also as an engineered material in the form of a waveguide. By combining accelerator-based IR-THz sources (synchrotron and free-electron laser) with s-SNOM, we employed nanoscale far-infrared hyper-spectral-imaging to uncover a Fabry-Perot cavity mechanism in SnO2 nanobelts via direct detection of phonon-polariton standing waves. Our experimental findings are accurately supported by notable convergence between theory and numerical simulations. Thus, the SnO2 is confirmed as a natural hyperbolic material with unique photonic properties essential for future applications involving subdiffractional light traffic and detection in the far-infrared range.
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Affiliation(s)
- Flávio H Feres
- Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, SP, Brazil
- Physics Department, Gleb Wataghin Physics Institute, University of Campinas (Unicamp), Campinas, SP, Brazil
| | - Rafael A Mayer
- Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, SP, Brazil
- Physics Department, Gleb Wataghin Physics Institute, University of Campinas (Unicamp), Campinas, SP, Brazil
| | - Lukas Wehmeier
- Institute of Applied Physics, Technische Universität Dresden, Dresden, Germany
- ct.qmat, Dresden-Würzburg Cluster of Excellence-EXC 2147, Technische Universität Dresden, Dresden, Germany
| | - Francisco C B Maia
- Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, SP, Brazil
| | - E R Viana
- Department of Physics, Universidade Tecnológica Federal do Paraná (UTFPR), Curitiba, PR, Brazil
| | - Angelo Malachias
- Department of Physics, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil
| | - Hans A Bechtel
- Advanced Light Source (ALS), Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - J Michael Klopf
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
| | - Lukas M Eng
- Institute of Applied Physics, Technische Universität Dresden, Dresden, Germany
- ct.qmat, Dresden-Würzburg Cluster of Excellence-EXC 2147, Technische Universität Dresden, Dresden, Germany
| | - Susanne C Kehr
- Institute of Applied Physics, Technische Universität Dresden, Dresden, Germany
| | - J C González
- Department of Physics, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil
| | - Raul O Freitas
- Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, SP, Brazil.
| | - Ingrid D Barcelos
- Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, SP, Brazil.
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Dueñas L, Arnal-Gómez A, Aparicio I, Balasch-Bernat M, López-Bueno L, González JC, Solves-Camallonga C, Alcántara E. Influence of age, gender and obesity on pressure discomfort threshold of the foot: A cross-sectional study. Clin Biomech (Bristol, Avon) 2021; 82:105252. [PMID: 33497989 DOI: 10.1016/j.clinbiomech.2020.105252] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 12/17/2020] [Accepted: 12/18/2020] [Indexed: 02/07/2023]
Abstract
BACKGROUND Foot pain is a highly prevalent health problem for which measures such as a pattern of Pressure Discomfort Threshold of the foot plantar surface can provide valuable information for orthosis design. This study aimed to describe such pattern as a tool for the assessment of painful conditions of the feet and to analyse how it modifies according to age, gender and obesity. METHODS A cross-sectional study was performed with participants allocated in: Group 1 people aged 20 to 35 years, Group 2 aged 50 to 65 years and Group 3 aged over 65. Pressure Discomfort Threshold on twelve points of the foot plantar surface was measured with an adapted manual dynamometer. Inferential analyses of the data were performed using one-way analysis of variance (ANOVA) considering foot areas, age group, gender and obesity. FINDINGS 36 participants were analysed. The pattern of Pressure Discomfort Threshold for all individuals showed a significantly higher threshold on the heel and external foot (P < 0.001, η2 = 0.124) and was statistical significantly influenced by age (P < 0.001, η2 = 0.17), especially in participants aged over 65; by gender, with women having higher values (P < 0.001, η2 = 0.13), and by obesity (P < 0.001, η2 = 0.19). INTERPRETATION A Pressure Discomfort Threshold pattern exists in the foot plantar surface. The characteristics of the discomfort pattern of the foot and its association with aging, gender and obesity may have considerable implications for orthosis and footwear design.
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Affiliation(s)
- L Dueñas
- Department of Physiotherapy, University of Valencia, Valencia, Spain; "Physiotherapy in Motion, Multi-specialty Research Group" (PTinMOTION), University of Valencia, Valencia, Spain.
| | - A Arnal-Gómez
- Department of Physiotherapy, University of Valencia, Valencia, Spain; Research Unit in Clinical Biomechanics (UBIC Research Group), University of Valencia, Valencia, Spain.
| | - I Aparicio
- Department of Physical Education, Research Group of Sports Biomechanic (GIBD) University of Valencia, Spain.
| | - M Balasch-Bernat
- Department of Physiotherapy, University of Valencia, Valencia, Spain; "Physiotherapy in Motion, Multi-specialty Research Group" (PTinMOTION), University of Valencia, Valencia, Spain.
| | - L López-Bueno
- Department of Physiotherapy, University of Valencia, Valencia, Spain.
| | - J C González
- Instituto de Biomécanica de Valencia, Valencia, Spain.
| | | | - E Alcántara
- Instituto de Biomécanica de Valencia, Valencia, Spain.
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Montenegro O, Illescas S, González JC, Padilla D, Villarejo P, Baladrón V, Galán R, Bejarano N, Medina-Prado L, Villaseca N, Pérez-Ortiz JM, Muñoz-Rodríguez JR, Santiago JL, Redondo FJ. Development of animal experimental model for bacterial peritonitis. Rev Esp Quimioter 2020. [PMID: 31795629 PMCID: PMC6987621 DOI: 10.37201/req/064.2019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Objetivo Desarrollar un modelo de sepsis abdominal en animal de experimentación. Material y métodos Se utilizan ratas Sprague-Dawley®, machos de 5 semanas con pesos entre 270-280 g en el momento de la inoculación (N=39). Inicialmente se realiza un estudio piloto (N=9), distribuyéndolas en 3 grupos (3/3/3) con inóculo de 1cc de Escherichia coli ATCC 25922 intraperitoneal en concentraciones de 108, 109 y 1010 UFC. En un segundo estudio (N=6) con distribución en dos grupos (3/3) se utilizan 1cc una concentración de E. coli 1010 UFC que se diluyen en 10 y 15 ml de agua destilada para su inoculación. Por último se inicia un ensayo experimental con aleatorización de 24 ratas en tres grupos de tratamiento tras la infección intraperitoneal: Grupo I con suero fisiológico (N=6), Grupo II con antibiótico (ceftriaxona) (N=9), Grupo III con antibiótico más adyuvante (ceftriaxona más alicina) (N=9). Se realizan muestras microbiológicas de sangre y líquido peritoneal, así como estudio histopatológico de órganos intraperitoneales (hígado, diafragma y peritoneo). Resultados Se observa muerte en el 100% de las ratas infectadas con la concentración de E. coli 1010 UFC con la dilución de 15 ml de agua destilada y sin antibiótico. El hemocultivo y cultivo de líquido peritoneal es positivo a la misma cepa en todas ellas. Se observa la formación de abscesos en la superficie del hígado e infiltración por polimorfonucleares en los tejidos. Conclusión Se establece que la dosis letal de E. coli es 1010 UFC diluida en 15 ml agua destilada en inyección intraperitoneal.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | - F J Redondo
- Fco Javier Redondo Calvo, Servicio de Anestesilogía y Reanimación. Unidad de Investigación Traslacional. Hospital General Universitario de Ciudad Real. C/Obispo General Torija s/n.13005. Ciudad Real. Spain.
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Ben Sedrine N, Ribeiro-Andrade R, Gustafsson A, Soares MR, Bourgard J, Teixeira JP, Salomé PMP, Correia MR, Moreira MVB, De Oliveira AG, González JC, Leitão JP. Fluctuating potentials in GaAs:Si nanowires: critical reduction of the influence of polytypism on the electronic structure. Nanoscale 2018; 10:3697-3708. [PMID: 29388656 DOI: 10.1039/c7nr08395e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this work, the effects of Si doping in GaAs nanowires (NWs) grown on GaAs (111)B by molecular beam epitaxy with different Si doping levels (nominal free carrier concentrations of 1 × 1016, 8 × 1016, 1 × 1018 and 5 × 1018 cm-3) are deeply investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), grazing incidence X-ray diffraction (GID), photoluminescence (PL) and cathadoluminescence (CL). TEM results reveal a mixture of wurtzite (WZ) and zinc-blende (ZB) segments along the NW axis independently of the Si doping levels. GID measurements suggest a slight increase of the ZB fraction with the Si doping. Low temperature PL and CL spectra exhibit sharp lines in the energy range 1.41-1.48 eV, for the samples with lower Si doping levels. However, the emission intensity increases and is accompanied by a clear broadening of the observed lines for the samples with higher Si doping levels. The staggered type-II band alignment only determines the optical properties of the lower doping levels in GaAs:Si NWs. For the higher Si doping levels, the electronic energy level structure of the NWs is determined by electrostatic fluctuating potentials intimately related to the amphoteric behavior of the Si dopant in GaAs. For the heavily doped NWs, the estimated depth of the potential wells is ∼96-117 meV. Our results reveal that the occurrence of the fluctuating potentials is not dependent on the crystalline phase and shows that the limitation imposed by the polytypism can be overcome.
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Affiliation(s)
- N Ben Sedrine
- Departamento de Física and I3N, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
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Viana ER, Ribeiro GM, de Oliveira AG, González JC. Metal-to-insulator transition induced by UV illumination in a single SnO 2 nanobelt. Nanotechnology 2017; 28:445703. [PMID: 28820739 DOI: 10.1088/1361-6528/aa871a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
An individual tin oxide (SnO2) nanobelt was connected in a back-gate field-effect transistor configuration and the conductivity of the nanobelt was measured at different temperatures from 400 K to 4 K, in darkness and under UV illumination. In darkness, the SnO2 nanobelts showed semiconductor behavior for the whole temperature range measured. However, when subjected to UV illumination the photoinduced carriers were high enough to lead to a metal-to-insulator transition (MIT), near room temperature, at T MIT = 240 K. By measuring the current versus gate voltage curves, and considering the electrostatic properties of a non-ideal conductor, for the SnO2 nanobelt on top of a gate-oxide substrate, we estimated the capacitance per unit length, the mobility and the density of carriers. In darkness, the density was estimated to be 5-10 × 1018 cm-3, in agreement with our previously reported result (Phys. Status Solid. RRL 6, 262-4 (2012)). However, under UV illumination the density of carriers was estimated to be 0.2-3.8 × 1019 cm-3 near T MIT, which exceeded the critical Mott density estimated to be 2.8 × 1019 cm-3 above 240 K. These results showed that the electrical properties of the SnO2 nanobelts can be drastically modified and easily tuned from semiconducting to metallic states as a function of temperature and light.
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Affiliation(s)
- E R Viana
- Departamento Acadêmico de Física (DAFIS), Universidade Tecnológica Federal do Paraná, Av. Sete de Setembro 3165, Rebouças, 80230-901, Curitiba/PR-Brazil. Departamento de Física, Universidade Federal de Minas Gerais, Av. Pres. Antônio Carlos, 6627, Pampulha, 31270-901, Belo Horizonte/MG-Brazil
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Rios FG, Viana ER, Ribeiro GM, González JC, Abelenda A, Peruzzo DC. Temperature evaluation of dental implant surface irradiated with high-power diode laser. Lasers Med Sci 2016; 31:1309-16. [PMID: 27365109 DOI: 10.1007/s10103-016-1974-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 05/24/2016] [Indexed: 11/27/2022]
Abstract
The prevalence of peri-implantitis and the absence of a standard approach for decontamination of the dental implant surface have led to searches for effective therapies. Since the source of diode lasers is portable, has reduced cost, and does not cause damage to the titanium surface of the implant, high-power diode lasers have been used for this purpose. The effect of laser irradiation on the implants is the elevation of the temperature surface. If this elevation exceeds 47 °C, the bone tissue is irreversibly damaged, so for a safety therapy, the laser parameters should be controlled. In this study, a diode laser of GaAsAl was used to irradiate titanium dental implants, for powers 1.32 to 2.64 W (real) or 2.00 to 4.00 W (nominal), in continuous/pulsed mode DC/AC, with exposure time of 5/10 s, with/without air flow for cooling. The elevation of the temperature was monitored in real time in two positions: cervical and apical. The best results for decontamination using a 968-nm diode laser were obtained for a power of 1.65 and 1.98 W (real) for 10 s, in DC or AC mode, with an air flow of 2.5 l/min. In our perspective in this article, we determine a suggested approach for decontamination of the dental implant surface using a 968-nm diode laser.
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Affiliation(s)
- F G Rios
- Centro de Pesquisas Odontológicas São Leopoldo Mandic (SLMANDIC), Dental Research Center, Rua Dr. José Rocha Junqueira 13, Ponte Preta, Campinas, SP, Brazil.
| | - E R Viana
- Physics Department (DAFIS), Universidade Tecnológica Federal do Paraná (UTFPR), Av. Sete de Setembro 3165, Rebouças, Curitiba, PR, Brazil.
| | - G M Ribeiro
- Physics Department, Universidade Federal de Minas Gerais (UFMG), Av. Presidente Antônio Carlos 6627, Pampulha, Belo Horizonte, MG, Brazil
| | - J C González
- Physics Department, Universidade Federal de Minas Gerais (UFMG), Av. Presidente Antônio Carlos 6627, Pampulha, Belo Horizonte, MG, Brazil
| | - A Abelenda
- Physics Department, Universidade Federal de Minas Gerais (UFMG), Av. Presidente Antônio Carlos 6627, Pampulha, Belo Horizonte, MG, Brazil
| | - D C Peruzzo
- Centro de Pesquisas Odontológicas São Leopoldo Mandic (SLMANDIC), Dental Research Center, Rua Dr. José Rocha Junqueira 13, Ponte Preta, Campinas, SP, Brazil
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Aguilera X, Martínez-Zapata MJ, Hinarejos P, Jordán M, Leal J, González JC, Monllau JC, Celaya F, Rodríguez-Arias A, Fernández JA, Pelfort X, Puig-Verdie LL. Topical and intravenous tranexamic acid reduce blood loss compared to routine hemostasis in total knee arthroplasty: a multicenter, randomized, controlled trial. Arch Orthop Trauma Surg 2015; 135:1017-25. [PMID: 25944156 DOI: 10.1007/s00402-015-2232-8] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Indexed: 11/26/2022]
Abstract
INTRODUCTION Tranexamic acid (TXA) is becoming widely used in orthopedic surgery to reduce blood loss and transfusion requirements, but consensus is lacking regarding the optimal route and dose of administration. The aim of this study was to compare the efficacy and safety of topical and intravenous routes of TXA with routine hemostasis in patients undergoing primary total knee arthroplasty (TKA). MATERIALS AND METHODS We performed a randomized, multicenter, parallel, open-label clinical trial in adult patients undergoing primary TKA. Patients were divided into three groups of 50 patients each: Group 1 received 1 g topical TXA, Group 2 received 2 g intravenous TXA, and Group 3 (control group) had routine hemostasis. The primary outcome was total blood loss. Secondary outcomes were hidden blood loss, blood collected in drains, transfusion rate, number of blood units transfused, adverse events, and mortality. RESULTS One hundred and fifty patients were included. Total blood loss was 1021.57 (481.09) mL in Group 1, 817.54 (324.82) mL in Group 2 and 1415.72 (595.11) mL in Group 3 (control group). Differences in total blood loss between the TXA groups and the control group were clinically and statistically significant (p < 0.001). In an exploratory analysis differences between the two TXA groups were not statistically significant (p = 0.073) Seventeen patients were transfused. Transfusion requirements were significantly higher in Group 3 (p = 0.005). No significant differences were found between groups regarding adverse events. CONCLUSION We found that 1 g of topical TXA and 2 g of intravenous TXA were both safe strategies and more effective than routine hemostasis to reduce blood loss and transfusion requirements after primary TKA. LEVEL OF EVIDENCE I.
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Affiliation(s)
- X Aguilera
- Orthopedic Surgery and Traumatology Department, Hospital de la Santa Creu i Sant Pau, Sant Antoni Mª Claret 167, 08025, Barcelona, Spain
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Portillo E, Ruiz de la Rosa M, Louzara G, Ruiz JM, Marín-Guirao L, Quesada J, González JC, Roque F, González N, Mendoza H. Assessment of the abiotic and biotic effects of sodium metabisulphite pulses discharged from desalination plant chemical treatments on seagrass (Cymodocea nodosa) habitats in the Canary Islands. Mar Pollut Bull 2014; 80:222-33. [PMID: 24495930 DOI: 10.1016/j.marpolbul.2013.12.048] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 12/11/2013] [Accepted: 12/20/2013] [Indexed: 05/20/2023]
Abstract
Reverse osmosis membranes at many desalination plants are disinfected by periodic shock treatments with sodium metabisulphite, which have potentially toxic effects to the environment for marine life, although no empirical and experimental evidence for this is yet available. The aim of this study was to characterise for the first time, the physico-chemical modification of the marine environment and its biological effects, caused by hypersaline plumes during these membrane cleaning treatments. The case study was the Maspalomas II desalination plant, located in the south of Gran Canaria (Canary Islands, Spain). Toxicity bioassays were performed on marine species characteristic for the infralittoral soft bottoms influenced by the brine plume (Synodus synodus and Cymodocea nodosa), and revealed a high sensitivity to short-term exposure to low sodium metabisulphite concentrations. The corrective measure of incorporating a diffusion system with Venturi Eductors reduced nearly all the areas of influence, virtually eliminating the impact of the disinfectant.
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Affiliation(s)
- E Portillo
- Instituto Tecnológico de Canarias, S.A. (Canary Islands Technological Institute) Playa de Pozo Izquierdo s/n, 35110 Santa Lucía, Las Palmas, Spain.
| | - M Ruiz de la Rosa
- ECOS, Estudios Ambientales y Oceanografía, S.L., C/Alfred Nobel 31B, 35013 Las Palmas de Gran Canaria, Spain.
| | - G Louzara
- ECOS, Estudios Ambientales y Oceanografía, S.L., C/Alfred Nobel 31B, 35013 Las Palmas de Gran Canaria, Spain
| | - J M Ruiz
- Instituto Español de Oceanografía, Centro Oceanográfico de Murcia, C/Varadero, 1, 30740 Murcia, Spain.
| | - L Marín-Guirao
- Instituto Español de Oceanografía, Centro Oceanográfico de Murcia, C/Varadero, 1, 30740 Murcia, Spain
| | - J Quesada
- Canaragua, S.A. Avda. Manuel Hermoso Rojas, 4, 38003 Santa Cruz de Tenerife, Spain.
| | - J C González
- Elmasa Tecnología del Agua, S.A., Av. de Tirajana no 39, Edificio Mercurio Torre 2, Sexta Planta, 35100 San Bartolomé de Tirajana, Las Palmas, Spain.
| | - F Roque
- Elmasa Tecnología del Agua, S.A., Av. de Tirajana no 39, Edificio Mercurio Torre 2, Sexta Planta, 35100 San Bartolomé de Tirajana, Las Palmas, Spain.
| | - N González
- Instituto Canario de Ciencias Marinas, Ctra. de Taliarte, s/n, 35200 Telde, Las Palmas, Spain.
| | - H Mendoza
- Instituto Tecnológico de Canarias, S.A. (Canary Islands Technological Institute) Playa de Pozo Izquierdo s/n, 35110 Santa Lucía, Las Palmas, Spain.
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Aguilera X, Martinez-Zapata MJ, Bosch A, Urrútia G, González JC, Jordan M, Gich I, Maymó RM, Martínez N, Monllau JC, Celaya F, Fernández JA. Efficacy and safety of fibrin glue and tranexamic acid to prevent postoperative blood loss in total knee arthroplasty: a randomized controlled clinical trial. J Bone Joint Surg Am 2013; 95:2001-7. [PMID: 24257657 DOI: 10.2106/jbjs.l.01182] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Postoperative blood loss in patients after total knee arthroplasty may cause local and systemic complications and influence clinical outcome. The aim of this study was to assess whether fibrin glue or tranexamic acid reduced blood loss compared with routine hemostasis in patients undergoing total knee arthroplasty. METHODS A randomized, single-center, parallel, open clinical trial was performed in adult patients undergoing primary total knee arthroplasty. Patients were divided into four groups. Group 1 received fibrin glue manufactured by the Blood and Tissue Bank of Catalonia, Group 2 received Tissucol (fibrinogen and thrombin), Group 3 received intravenous tranexamic acid, and Group 4 (control) had no treatment other than routine hemostasis. The primary outcome was total blood loss collected in drains after surgery. Secondary outcomes were the calculated hidden blood loss, transfusion rate, preoperative and postoperative hemoglobin, number of blood units transfused, adverse events, and mortality. RESULTS One hundred and seventy-two patients were included. The mean total blood loss (and standard deviation) collected in drains was 553.9 ± 321.5 mL for Group 1, 567.8 ± 299.3 mL for Group 2, 244.1 ± 223.4 mL for Group 3, and 563.5 ± 269.7 mL for Group 4. In comparison with the control group, Group 3 had significantly lower total blood loss (p < 0.001), but it was not significantly lower in Groups 1 and 2. The overall rate of patients who had a blood transfusion was 21.1% (thirty-five of 166 patients analyzed per protocol). Two patients required transfusion in Group 3 compared with twelve patients in Group 4 (p = 0.015). No significant difference was observed between the two fibrin glue groups and the control group with regard to the need for transfusion. There was no difference between groups with regard to the percentage of adverse events. CONCLUSIONS Neither type of fibrin glue was more effective than routine hemostasis in reducing postoperative bleeding and transfusion requirements, and we no longer use them. However, this trial supports findings from previous studies showing that intravenous tranexamic acid can decrease postoperative blood loss.
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Affiliation(s)
- X Aguilera
- Orthopedic Surgery and Traumatology Department (X.A., J.C.G., M.J., J.C.M., and F.C.) and Anesthesiology Department (J.A.F.), Hospital de la Santa Creu i Sant Pau, Sant Antoni Mª Claret 167, 08025 Barcelona, Spain
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12
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Abstract
The electrical observation of energy sub-band formation in the electronic structure, that gives rise to the phenomenon of quantized transport is reported in tin oxide (SnO2) nanobelt back-gate field-effect transistors, at low temperatures. Sub-band formation was observed as current oscillations in the drain current vs. gate voltage characteristics, and was analyzed considering the nanobelt as a "quantum wire" with a rectangular cross-section and hard walls. The lateral quantum confinement in the nanowires created conditions for the successive filling of the first twelve electron energy sub-bands, as the gate voltage increases. When the source-drain voltage is changed, the oscillations are not dislocated with respect to the gate voltage indicating flat-band energies, and that the observations are incompatible with the phenomena of Coulomb blockade and tunnelling oscillations. The separation of the energy sub-bands was found to be in good agreement with the measured cross-section dimensions of the nanobelt and with the threshold temperature, since for T > 60 K the oscillations tend to vanish.
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Affiliation(s)
- E R Viana
- Universidade Federal de Minas Gerais, Instituto de Ciências Exatas, Departamento de Física, Belo Horizonte/MG, 31720-901, Brazil.
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13
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Alvarez R, García-Martín JM, Macías-Montero M, Gonzalez-Garcia L, González JC, Rico V, Perlich J, Cotrino J, González-Elipe AR, Palmero A. Growth regimes of porous gold thin films deposited by magnetron sputtering at oblique incidence: from compact to columnar microstructures. Nanotechnology 2013; 24:045604. [PMID: 23299349 DOI: 10.1088/0957-4484/24/4/045604] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Growth regimes of gold thin films deposited by magnetron sputtering at oblique angles and low temperatures are studied from both theoretical and experimental points of view. Thin films were deposited in a broad range of experimental conditions by varying the substrate tilt angle and background pressure, and were analyzed by field emission scanning electron microscopy and grazing-incidence small-angle x-ray scattering techniques. Results indicate that the morphological features of the films strongly depend on the experimental conditions, but can be categorized within four generic microstructures, each of them defined by a different bulk geometrical pattern, pore percolation depth and connectivity. With the help of a growth model, a microstructure phase diagram has been constructed where the main features of the films are depicted as a function of experimentally controllable quantities, finding a good agreement with the experimental results in all the studied cases.
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Affiliation(s)
- R Alvarez
- Instituto de Ciencia de Materiales de Sevilla (CSIC-US), Americo Vespucio 49, E-41092 Seville, Spain.
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14
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González JC, López C, Carmona JU. Evaluación de un método manual para producir plasma rico en plaquetas-puro (P-PRP) en conejos: estudio hematológico. ACTA ACUST UNITED AC 2013. [DOI: 10.4067/s0301-732x2013000300006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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15
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González JC, Albiñana E, Baldelli P, García AG, Hernández-Guijo JM. Presynaptic muscarinic receptor subtypes involved in the enhancement of spontaneous GABAergic postsynaptic currents in hippocampal neurons. Eur J Neurosci 2010; 33:69-81. [PMID: 21091801 DOI: 10.1111/j.1460-9568.2010.07475.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We investigated the effects of muscarinic acetylcholine receptor (mAChR) activation on GABAergic synaptic transmission in rat hippocampal neurons. Current-clamp recordings revealed that methacholine produced membrane depolarization and action potential firing. Methacholine augmented the bicuculline-sensitive and GABA(A) -mediated frequency of spontaneous inhibitory postsynaptic currents (sIPSCs); the action of methacholine had a slow onset and longer duration. The increase in methacholine-evoked sIPSCs was completely inhibited by atropine and was insensitive to glutamatergic receptor blockers. Interestingly, methacholine action was not inhibited by intracellular perfusion with GDP-β-S, suggesting that muscarinic effects on membrane excitability and sIPSC frequency are mainly presynaptic. McN-A-343 and pirenzepine, selective agonist and antagonist of the m1 mAChR subtype, respectively, neither enhanced sIPSCs nor inhibited the methacholine effect. However, the m3-m5 mAChR antagonist 4-DAMP, and the m2-m4 mAChR antagonist himbacine inhibited the methacholine effect. U73122, an IP(3) production inhibitor, and 2APB, an IP(3) receptor blocker, drastically decreased the methacholine effect. Recording of miniature events revealed that besides the effect exerted by methacholine on membrane firing properties and sIPSC frequency, muscarinic receptors also enhanced the frequency of mIPSCs with no effect on their amplitude, possibly modulating the molecular machinery subserving vesicle docking and fusion and suggesting a tight colocalization at the active zone of the presynaptic terminals. These data strongly suggest that by activating presynaptic m2, m3, m4 and m5 mAChRs, methacholine can increase membrane excitability and enhance efficiency in the GABA release machinery, perhaps through a mechanism involving the release of calcium from the endoplasmic reticulum.
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Affiliation(s)
- J C González
- Instituto Teófilo Hernando, IIS Hospital Universitario de la Princesa, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
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16
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Leret ML, Rua C, Garcia-Montojo M, Lecumberri M, González JC. Influence of metyrapone treatment during pregnancy on the development and maturation of brain monoaminergic systems in the rat. Acta Physiol (Oxf) 2009; 197:333-40. [PMID: 19656124 DOI: 10.1111/j.1748-1716.2009.02027.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
AIM This study examines the effect of reducing the corticosterone levels of gestating rat dams on the postnatal development and maturation of monoaminergic systems in their offspring's brains. METHODS Metyrapone, an inhibitor of CORT synthesis, was administered to pregnant rats from E0 to E17 of gestation. Monoamine concentrations were determined in male and female offspring at postnatal days (PN) 23 and 90 in the hippocampus, hypothalamus and striatum. RESULTS Reducing maternal corticosterone (mCORT) during gestation led to alterations in dopamine and serotonin levels in all three brain areas studied at PN 23. Alterations persisted until at least PN 90 in the serotonergic systems; the dopamine content of the hippocampus also remained modified. Reduced mCORT during gestation also led to alterations in the development and maturation of the hypothalamic noradrenergic systems. Sexually dimorphic responses were observed in all these monoaminergic systems at different times. CONCLUSION These results suggest that while they are still developing, brain monoaminergic systems are particularly sensitive to epigenetic influences. An adequate foetal level of CORT is required for the normal ontogeny of brain monoaminergic systems. The present data also provide that during the critical period of brain development, maternal CORT plays an important role in the sexual differentiation of monoaminergic systems, with particular influence on brain serotonergic neurones.
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Affiliation(s)
- M L Leret
- Department of Animal Physiology, Complutense University of Madrid, Spain.
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17
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González JC, Hernández JC, López-Haro M, del Río E, Delgado JJ, Hungría AB, Trasobares S, Bernal S, Midgley PA, Calvino JJ. 3 D characterization of gold nanoparticles supported on heavy metal oxide catalysts by HAADF-STEM electron tomography. Angew Chem Int Ed Engl 2009; 48:5313-5. [PMID: 19544338 DOI: 10.1002/anie.200901308] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Living on the edge: Three-dimensional reconstructions from electron tomography data recorded from Au/Ce(0.50)Tb(0.12)Zr(0.38)O(2-x) catalysts show that gold nanoparticles (see picture; yellow) are preferentially located on stepped facets and nanocrystal boundaries. An epitaxial relationship between the metal and support plays a key role in the structural stabilization of the gold nanoparticles.
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Affiliation(s)
- J C González
- Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Facultad de Ciencias, Universidad de Cádiz, Puerto Real, 11510-Cádiz, Spain
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18
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Lopez-Richard V, González JC, Matinaga FM, Trallero-Giner C, Ribeiro E, Sousa Dias MR, Villegas-Lelovsky L, Marques GE. Markovian and non-Markovian light-emission channels in strained quantum wires. Nano Lett 2009; 9:3129-3136. [PMID: 19663458 DOI: 10.1021/nl9012024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We have achieved conditions to obtain optical memory effects in semiconductor nanostructures. The system is based on strained InP quantum wires where the tuning of the heavy-light valence band splitting has allowed the existence of two independent optical channels with correlated and uncorrelated excitation and light-emission processes. The presence of an optical channel that preserves the excitation memory is unambiguously corroborated by photoluminescence measurements of free-standing quantum wires under different configurations of the incoming and outgoing light polarizations in various samples. High-resolution transmission electron microscopy and electron diffraction indicate the presence of strain effects in the optical response. By using this effect and under certain growth conditions, we have shown that the optical recombination is mediated by relaxation processes with different natures: one a Markov and another with a non-Markovian signature. Resonance intersubband light-heavy hole transitions assisted by optical phonons provide the desired mechanism for the correlated non-Markovian carrier relaxation process. A multiband calculation for strained InP quantum wires was developed to account for the description of the character of the valence band states and gives quantitative support for light hole-heavy hole transitions assisted by optical phonons.
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Affiliation(s)
- V Lopez-Richard
- Departamento de Fisica, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil.
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19
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González JC, Malachias A, Andrade RR, de Sousa JC, Moreira MVB, de Oliveira AG. Direct evidences of enhanced Ga interdiffusion in InAs vertically aligned free-standing nanowires. J Nanosci Nanotechnol 2009; 9:4673-4678. [PMID: 19928133 DOI: 10.1166/jnn.2009.1285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Direct evidences of enhanced Ga interdiffusion in InAs free-standing nanowires grown at moderate temperatures by molecular beam epitaxy on GaAs (111)B are presented in this work. Scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction measurements in coplanar and grazing incidence geometries show that nominally grown InAs NWs are actually made of an In0.86Ga0.14As alloy. Unlike typical vapor-liquid-solid growth, these nanowires are formed by diffusion-induced growth combined with strong interdiffusion from substrate material. Based on the experimental results, a simple nanowire growth model accounting for the Ga interdiffusion is also presented. This growth model could be generally applicable to the molecular beam heteroepitaxy of III-V nanowires.
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Affiliation(s)
- J C González
- Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Postal Code 702, 30123-970 Belo Horizonte, Brazil
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20
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Aguilar EJ, García-Martí G, Martí-Bonmatí L, Lull JJ, Moratal D, Escartí MJ, Robles M, González JC, Guillamón MI, Sanjuán J. Left orbitofrontal and superior temporal gyrus structural changes associated to suicidal behavior in patients with schizophrenia. Prog Neuropsychopharmacol Biol Psychiatry 2008; 32:1673-6. [PMID: 18657587 DOI: 10.1016/j.pnpbp.2008.06.016] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Revised: 06/27/2008] [Accepted: 06/27/2008] [Indexed: 12/18/2022]
Abstract
Suicidal attempts are relatively frequent and clinically relevant in patients with schizophrenia. Recent studies have found gray matter differences in suicidal and non-suicidal depressive patients. However, no previous neuroimaging study has investigated possible structural abnormalities associated to suicidal behaviors in patients with schizophrenia. A whole-brain magnetic resonance voxel-based morphometric examination was performed on 37 male patients meeting the DSM-IV criteria for schizophrenia. Thirteen (35.14%) patients had attempted suicide. A non-parametric permutation test was computed to perform the comparability between groups. An analysis of covariance (AnCova) model was constructed with a statistical threshold of p<0.05 corrected for multiple comparisons. After controlling for age and severity of illness, results showed significant gray matter density reduction in left superior temporal lobe (p=0.03) and left orbitofrontal cortex (p=0.04) in patients who had attempted suicide when comparing with non-suicidal patients. Although sample size limitations and potential clinical heterogeneity preclude definitive conclusions, these data point to structural differences in key cerebral areas. Neuroimaging studies are necessary to expand our knowledge of biological mechanisms underlying suicide in schizophrenia.
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Affiliation(s)
- E J Aguilar
- Psychiatric Unit, Clinic University Hospital, Avda. Blasco Ibáñez, 17, 46010 Valencia, Spain.
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21
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Martínez-Granados B, Brotons O, Martínez-Bisbal MC, Celda B, Martí-Bonmati L, Aguilar EJ, González JC, Sanjuán J. Spectroscopic metabolomic abnormalities in the thalamus related to auditory hallucinations in patients with schizophrenia. Schizophr Res 2008; 104:13-22. [PMID: 18650068 DOI: 10.1016/j.schres.2008.05.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Revised: 02/25/2008] [Accepted: 05/25/2008] [Indexed: 10/21/2022]
Abstract
OBJECTIVE Previous studies have found neurochemical abnormalities in thalamic nuclei in patients with schizophrenia. These abnormalities have been associated with information processing deficiencies and symptom formation. There are no metabolic spectroscopy studies in patients with schizophrenia attending to auditory hallucinations. The aim of the present study is to explore metabolic Magnetic Resonance Spectroscopy (MRS) ratio differences in the thalamus between schizophrenic patients with and without auditory hallucinations and control subjects. METHODS MRS studies (MRI 1.5 T unit) were performed in 49 patients with schizophrenia (30 with auditory hallucinations and 19 without auditory hallucinations) and 37 controls. (1)H MRS imaging was used to acquire 2 transverse slices (TR/TE 2700/272 ms, region of interest 110 x 100 x 23 mm). In the quantitative analysis four elements of volume (9.2 x 9.2 x 23 x 4 mm), added into one spectrum representative of each thalamus, were chosen in the slice passing through the main body of the thalamus. The areas of metabolites were integrated with the jMRUI program. RESULTS The patients with schizophrenia had significantly lower bilateral NAA/Cho ratios when compared with healthy subjects. There was also a lower NAA/Cho ratio in the right thalamus in patients with auditory hallucinations compared to patients without auditory hallucinations and control subjects. Significant correlations were found between metabolic ratios and BPRS, PANSS and PSYRATS scores, age of onset of auditory hallucinations, and age of subjects. CONCLUSIONS Choline and NAA ratio abnormalities determined by thalamic spectroscopy may be related to the pathogenesis of auditory hallucinations in patients with schizophrenia.
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Affiliation(s)
- B Martínez-Granados
- Department of Physical Chemistry, University of Valencia, C/ Dr Moliner 50, 46100 Burjassot, Valencia, Spain.
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Arnaiz-Cot JJ, González JC, Sobrado M, Baldelli P, Carbone E, Gandía L, García AG, Hernández-Guijo JM. Allosteric modulation of alpha 7 nicotinic receptors selectively depolarizes hippocampal interneurons, enhancing spontaneous GABAergic transmission. Eur J Neurosci 2008; 27:1097-110. [PMID: 18312591 DOI: 10.1111/j.1460-9568.2008.06077.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The role of postsynaptic nicotinic receptors for acetylcholine (nAChRs) in mediating fast neurotransmission processes in the CNS is controversial. Here we have studied the modulation of synaptic transmission by an agonist (choline) and an allosteric modulator (5-OH-indole) of alpha7 nAChRs in rat hippocampal neuronal cultures. Choline evoked a fast inactivating inward current, causing neuron depolarization and action potential discharge, thereby enhancing the spontaneous postsynaptic current activity (sPSCs). This effect was markedly enhanced when both choline and 5-OH-indole were applied together and was blocked by the selective alpha7 nAChR antagonist methyllycaconitine. This choline action was suppressed by the GABA(A) receptor antagonist bicuculline, while the glutamatergic receptor antagonist kynurenic acid had no effect. Frequency, but not amplitude or area, of both excitatory and inhibitory miniature postsynaptic currents (mEPSCs and mIPSCs) were drastically reduced when Ca(2+) influx was blocked by Cd(2+). Additionally, nAChR activation did not modify the mIPSCs. These data suggest that Ca(2+) influx through the highly Ca(2+)-permeablealpha7 nAChRs was insufficient to directly activate neurotransmitter release, suggesting that a tight colocalization of this receptor with secretory hot spots is unlikely. In a few cases, the activation of alpha7 AChRs led to a suppression of spontaneous synaptic transmission. This effect may be related to the potentiation of GABAergic interneurons that inhibit the spontaneous activity of neurons making synapses with the cell under study. We suggest that GABA release is modulated by alpha7 nAChRs. Thus, selective allosteric modulators of alpha7 nAChRs could have potential therapeutic applications in brain disorders such as epilepsy and schizophrenia and in alterations of cognition and sensory processing.
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Affiliation(s)
- J J Arnaiz-Cot
- Instituto Teófilo Hernando, Facultad de Medicina, University Autónoma de Madrid, Avenida Arzobispo Morcillo 4, 28029 Madrid, Spain
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González JC, Muñoz M, García N, Barzola-Quiquia J, Spoddig D, Schindler K, Esquinazi P. Sample-size effects in the magnetoresistance of graphite. Phys Rev Lett 2007; 99:216601. [PMID: 18233237 DOI: 10.1103/physrevlett.99.216601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Indexed: 05/25/2023]
Abstract
Conduction electrons in graphite are expected to have micrometer large de Broglie wavelength as well as mean free path. A direct influence of these lengths in the electric transport properties of finite-size samples was neglected in the past. We provide a direct evidence of this effect through the size dependence of the magnetoresistance, which decreases with the sample size even for samples hundreds of micrometers large. Our findings may explain the absence of magnetoresistance in small few graphene layers samples and ask for a general revision of the experimental and theoretical work on the transport properties of this material.
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Affiliation(s)
- J C González
- Laboratorio de Física de Sistemas Pequeños y Nanotecnología, Consejo Superior de Investigaciones Científicas, E-28006 Madrid, Spain
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Burgos M, Pastor MD, González JC, Martinez-Galan JR, Vaquero CF, Fradejas N, Benavides A, Hernández-Guijo JM, Tranque P, Calvo S. PKCɛ upregulates voltage-dependent calcium channels in cultured astrocytes. Glia 2007; 55:1437-48. [PMID: 17676593 DOI: 10.1002/glia.20555] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Astrocytes express voltage-gated calcium channels (VGCCs) that are upregulated in the context of the reactive astrogliosis occurring in several CNS pathologies. Moreover, the ability of selective calcium channel blockers to inhibit reactive astrogliosis has been revealed in a variety of experimental models. However, the functions and regulation of VGCC in astrocytes are still poorly understood. Interestingly, protein kinase C epsilon (PKCepsilon), one of the known regulators of VGCC in several cell types, induces in astrocytes a stellated morphology similar to that associated to gliosis. Thereby, here we explored the possible regulation of VGCC by adenovirally expressed PKCepsilon in astrocytes. We found that PKCepsilon potently increases the mRNA levels of two different calcium channel alpha(1) subunits, Ca(V)1.2 (L-type channel) and Ca(V)2.1 (P/Q-type channel). The mRNA upregulation was followed by a robust increase in the corresponding peptides. Moreover, the new calcium channels formed as a consequence of PKCepsilon activation are functional, since overexpression of constitutively-active PKCepsilon increased significantly the calcium current density in astrocytes. PKCepsilon raised currents carried by both L- and P/Q-type channels. However, the effect on the P/Q-type channel was more prominent since an increase of the relative contribution of this channel to the whole cell calcium current was observed. Finally, we found that PKCepsilon-induced stellation was significantly reduced by the specific L-type channel blocker nifedipine, indicating that calcium influx through VGCC mediates the change in astrocyte morphology induced by PKCepsilon. Therefore, here we describe a novel regulatory pathway involving VGCC that participates in PKCepsilon-dependent astrocyte activation.
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Affiliation(s)
- M Burgos
- Unidad de Fisiología, Facultad de Medicina y Centro Regional de Investigaciones Biomedicas, Universidad de Castilla La Mancha, Albacete, Spain
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González JC, da Silva MIN, Lozano XS, Zanchet D, Ugarte D, Ribeiro E, Gutiérrez HR, Cotta MA. Structural and optical characterization of strained free-standing InP nanowires. J Nanosci Nanotechnol 2006; 6:2182-6. [PMID: 17025146 DOI: 10.1166/jnn.2006.353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The structural and optical properties of high-quality crystalline strained InP nanowires are reported in this article. The nanowires were produced by the vapor-liquid-solid growth method in a chemical-beam epitaxy reactor, using 20 nm gold nanoparticles as catalysts. Polarization-resolved photoluminescence experiments were carried out to study the optical properties of the InP nanowires. These experiments revealed a large blue shift of 74 meV of the first electron-to-heavy hole optical transition in the nanowires, which cannot be solely explained by quantum size effects. The blue shift is mainly attributed to the presence of biaxial compressive strain in the inward radial direction of the InP nanowires. High-resolution transmission electron microscopy Electron and selected area electron diffraction experiments show that the nanowires have high crystal quality and grow along a [001] axes. These experiments also confirmed the presence of 1.8% compressive radial strain and 2% tensile longitudinal strain in the nanowires. A simple theoretical model including both quantum confinement and strain effects consistently describes the actual energy position of the InP nanowires optical emission.
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Affiliation(s)
- J C González
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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Abstract
BACKGROUND There is still a significant proportion of psychotic patients who suffer from persistent auditory hallucinations (PAH) in spite of treatment. The objective of our study was to analyze those clinical dimensions that characterize persistent hallucinators in comparison with episodic hallucinators. SAMPLING AND METHODS Ninety-one outpatients with AH were assessed through semistructured interviews. The interviews included the Psychotic Symptom Rating Scales for AH and the Krawiecka scale. They elicited descriptions about the persistence of AH, existence of pleasurable hallucinations and other types of hallucinations. RESULTS Forty-five patients fulfilled criteria for reported PAH. Persistent hallucinators showed greater scores in frequency and duration of hallucinations, Krawiecka total score and incoherence of speech. Moreover, pleasurable experiences were more frequent in this group of patients. Logistic regression analysis rendered a model with the following variables: duration of voices, degree of control and pleasurable hallucinations. CONCLUSION Specific dimensions of AH can predict the possibility of treatment resistance.
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Sanjuán J, Lull JJ, Martí-Bonmati L, Aguilar EJ, Gadea M, Moratal-Pérez D, González JC, Robles M. Emotional auditory paradigm in neuroimaging: a base for the study of psychosis. Actas Esp Psiquiatr 2005; 33:383-9. [PMID: 16292722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
INTRODUCTION Since the arrival of neuroimaging numerous studies have tried to analyze the differences between emotional and non-emotional response. The majority of these studies use visual approach (faces) and begin with data in normal subjects. The present study introduces a new paradigm for the study of emotional response based on auditory approach and designed specifically for the study of psychoses. METHOD The most frequent words heard by psychotic patients with auditory hallucinations were analyzed. They were classified according to five categories which were compared with 13 other words with the same structure but with a neutral emotional valency. This paradigm was applied to see the cerebral activation with functional magnetic resonance imaging (fMRI) in 10 right handed healthy males. RESULTS In the preliminary analysis a clear differentiation is observed depending on the type of stimulus applied (emotional or non-emotional), both in the intensity of activation (right and left temporal cortex) as in the activation of specific areas (right precentral and supramarginal gyrus) only with the emotional stimulus. CONCLUSIONS The present paradigm allows the observation of a differentiation in the cerebral activation to emotional auditory stimulus and could be of utility in the study of psychotic patients.
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Affiliation(s)
- J Sanjuán
- Medicine Department, Psychiatry Unit, Universidad de Valencia, Spain.
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Sanjuan J, Toirac I, González JC, Leal C, Moltó MD, Nájera C, De Frutos R. A possible association between the CCK-AR gene and persistent auditory hallucinations in schizophrenia. Eur Psychiatry 2005; 19:349-53. [PMID: 15363473 DOI: 10.1016/j.eurpsy.2004.06.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2003] [Revised: 03/19/2004] [Accepted: 03/30/2004] [Indexed: 11/26/2022] Open
Abstract
Recent studies have suggested that DNA variations in the CCK-AR gene might predispose individuals to schizophrenia and particularly to auditory hallucinations (AH). The aim of this study is to assess the association between AH, using a specific scale for AH in schizophrenia (PSYRATS), and the CCK-AR polymorphism at 779 in a Spanish sample. A total of 105 DSM-IV schizophrenic patients with AH and 93 unrelated controls were studied. Twenty-two patients were considered as persistent auditory hallucinators, which showed similar clinical and demographic characteristic than patients with episodic AH, but with the exception of the PSYRATS values. The persistent AH group showed an excess of the A1 allele when was compared with episodic or control groups. Our data support the possible role of the CCK-AR gene in the development of persistent AH in schizophrenic patients.
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Affiliation(s)
- J Sanjuan
- Unidad de Psiquiatría, Facultad de Medicina, Hospital Clínico, Blasco Ibañez 15, Universitat de València, 46010 Valencia, Spain.
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29
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González JC, Rodrigues V, Bettini J, Rego LGC, Rocha AR, Coura PZ, Dantas SO, Sato F, Galvão DS, Ugarte D. Indication of unusual pentagonal structures in atomic-size Cu nanowires. Phys Rev Lett 2004; 93:126103. [PMID: 15447283 DOI: 10.1103/physrevlett.93.126103] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Indexed: 05/24/2023]
Abstract
We present a study of the structural and quantum conductance properties of atomic-size copper nanowires generated by mechanical stretching. The atomistic evolution was derived from time-resolved electron microscopy observations and molecular dynamics simulations. We have analyzed the quantum transport behavior by means of conductance measurements and theoretical calculations. The results suggest the formation of an unusual and highly stable pentagonal Cu nanowire with a diameter of approximately 0.45 nm and approximately 4.5 conductance quanta.
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Affiliation(s)
- J C González
- Laboratório Nacional de Luz Síncrotron, C.P. 6192, 13084-971 Campinas, São Paulo, Brazil
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Leret ML, Peinado V, Suárez LM, Tecedor L, Gamallo A, González JC. Role of maternal adrenal glands on the developing serotoninergic and aminoacidergic systems of the postnatal rat brain. Int J Dev Neurosci 2004; 22:87-93. [PMID: 15036383 DOI: 10.1016/j.ijdevneu.2003.12.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2003] [Revised: 12/09/2003] [Accepted: 12/11/2003] [Indexed: 11/17/2022] Open
Abstract
Serotonin, gamma-aminobutyric acid and glutamate, which are regulated by glucocorticoids in the central nervous system, are involved in neuroendocrine functions and the development of the brain. The present study investigates the effect of maternal adrenalectomy on the developing serotoninergic, GABAergic and glutamatergic systems. Neurotransmitter levels were measured in four brain areas of both male and female offspring on postnatal days 1, 8, 12 and 22. At postnatal day 1 and 8, the pups of adrenalectomized dams showed higher concentrations of serotonin than controls in all the brain areas studied. Serotonin levels decreased significantly in males at postnatal day 22 in the hippocampus and cortex. During the first 2 weeks of postnatal life, the lack of maternal corticosterone produced an increase in glutamate and a reduction in gamma-aminobutyric acid concentrations, mainly in males. Further, on postnatal day 1, increased serotonin and glutamate levels and lower levels of gamma-aminobutyric were observed in the hypothalamus of male pups born to adrenalectomized dams. The absence of maternal corticosterone affects the pattern of development of the serotoninergic system, especially in the hippocampus and cortex, and particularly in males. A delay in the maturation of the aminoacidergic systems, mainly of the GABAergic system and in males, was also seen. A sexually dimorphic response to the removal of maternal glucocorticoids was seen in terms of neurotransmitter levels, mainly in the hippocampus and hypothalamus.
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Affiliation(s)
- M L Leret
- Department of Animal Biology-II (Animal Physiology), Faculty of Biological Sciences, José Antonio Nováis, 2, Complutense University of Madrid, 28040 Madrid, Spain.
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Leret ML, Peinado V, González JC, Suárez LM, Rúa C. Maternal adrenalectomy affects development of adrenal medulla. Life Sci 2004; 74:1861-7. [PMID: 14761667 DOI: 10.1016/j.lfs.2003.07.050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2003] [Accepted: 07/31/2003] [Indexed: 10/26/2022]
Abstract
This work investigates the effects of maternal adrenalectomy (ADX) on the development of the adrenal medulla. Adrenal catecholamines (AC) were measured at postnatal day (PN) 1, 8, 12 and 22 in rat offspring of ADX dams and in pups of control dams. The pups of ADX rats showed a reduction in AC concentrations in the adrenal medulla at PN 1, 12 and 22, although these were higher than in the pups of sham dams at PN 8. Further, in the pups of control mothers, there was an increase in ACs during the first two weeks of life whereas pups of ADX mothers only showed increases in noradrenaline, dopamine and adrenaline levels at day 8. These results suggest that maternal absence of corticosterone affects the medulla catecholamine content during development. These data support the idea that a maternal glucocorticoids are involved in the differentiation or/and maturation of the adrenal medulla.
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Affiliation(s)
- M L Leret
- Department of Animal Biology-II (Animal Physiology), Faculty of Biological Sciences, Complutense University of Madrid, Madrid, Spain
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32
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Valenzuela J, Alvarado J, Cohen H, Damiao A, Francisconi C, Frugone L, González JC, Hernández A, Iade B, Itaqui Lopes MH, Latorre R, Prado J, Moraes-Filho P, Schmulson M, Soifer L, Valdovinos MA, Vesco E, Zalar A. Un consenso latinoamericano sobre el síndrome del intestino irritable. Gastroenterología y Hepatología 2004; 27:325-43. [PMID: 15117614 DOI: 10.1016/s0210-5705(03)70470-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- J Valenzuela
- Facultad de Medicina, Hospital Clínico, Universidad de Chile, Santiago, Chile.
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Velillas S, Rodríguez de la Rua E, Carrasco B, González JC, Pastor JC. [Progressive diffuse subretinal fibrosis syndrome: a case report]. Arch Soc Esp Oftalmol 2001; 76:259-62. [PMID: 11340517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
CASE REPORT The case of a 63 year old woman presenting fibrous subretinal lesions in the posterior pole on a routine ocular fundus check up is reported. The angiographic study showed a choroidal origin window defect next to hypofluorescence areas. The patient did not complain of vision loss or scotomas at any time. DISCUSSION This clinical picture could be classified as a progressive subretinal fibrosis syndrome with atypical features. However, a differential diagnosis with other choroidal inflammatory conditions should be carried out even though many authors may consider them as different developmental phases of the same entity.
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Affiliation(s)
- S Velillas
- Instituto de Oftalmobiología Aplicada (IOBA), Universidad de Valladolid, Valladolid, España
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González JC, Vieytes MR, Botana AM, Vieites JM, Botana LM. Modified mass action law-based model to correlate the solubility of solids and liquids in entrained supercritical carbon dioxide. J Chromatogr A 2001; 910:119-25. [PMID: 11263564 DOI: 10.1016/s0021-9673(00)01120-1] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The solubility of solids and liquids in supercritical CO2 with added entrainers was modeled with a modified version of the equation of Chrastil to include the effect of entrainers. By considering the formation of the solute-entrainer-solvent complexes an equation is obtained which predicts an exponential increase of solubility with fluid density and/or entrainer concentration. The correlating model was tested by non-linear regression through a computerized iterative process for several systems where an entrainer was present. Four experimental parameters are easily regressed from experimental data, hence the corresponding properties of components such as chemical potentials or critical parameters are not needed. Instead of its simplicity, this thermodynamical model provided a good correlation of the solubility enhancement in the presence of entrainer effect.
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Affiliation(s)
- J C González
- Departamento de Farmacologia, Facultad de Veterinaria, Universidade de Santiago de Compostela, Lugo, Spain
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35
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de la Torre X, González JC, Pichini S, Pascual JA, Segura J. 13C/12C isotope ratio MS analysis of testosterone, in chemicals and pharmaceutical preparations. J Pharm Biomed Anal 2001; 24:645-50. [PMID: 11272321 DOI: 10.1016/s0731-7085(00)00452-0] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The 13C/12C ratio can be used to detect testosterone misuse in sport because (semi)-synthetic testosterone is supposed to have a 13C abundance different from that of endogenous natural human testosterone. In this study, gas chromatography/combustion isotope ratio mass spectrometry (GC/C/IRMS) analysis for the measurement of the delta 13C/1000 value of testosterone from esterified forms of 13 pharmaceutical preparations, six reagent grade chemicals and three bulk materials (raw materials used in pharmaceutical proarations) obtained world-wide was investigated after applying a strong acidic solvolytic procedure. Mean delta 13C/1000 values of non esterified (free) testosterone from chemicals and bulk materials of several testosterone esters were in the range: -25.91/-32.82/1000 while the value obtained for a (semi)-synthetic, reagent grade, free testosterone was -27.36/1000. The delta 13C/1000 results obtained for testosterone from the pharmaceuticals investigated containing testosterone esters were quite homogeneous (mean and S.D. of delta 13C/1000 values of free testosterone: 27.43 +/- 0.76/1000), being the range between -26.18 and -30.04/1000. Values described above were clearly different from those reported by several authors for endogenous natural human testosterone and its main metabolites excreted into the urine in non-consumers of testosterone (delta 13C/1000 range: from -21.3 to -24.4/1000), while they were similar to those of urinary testosterone and metabolites from individuals treated with testosterone esters and testosterone precursors. This finding justifies the fact that administration of these pharmaceutical formulations led to a statistical decrease of carbon isotope ratio of urinary testosterone and its main metabolites in treated subjects.
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Affiliation(s)
- X de la Torre
- Pharmacology Research Unit, Institut Municipal d'Investigaciò Medica, Barcelona, Spain
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Köhler I, Jenett-Siems K, Mockenhaupt FP, Siems K, Jakupovic J, González JC, Hernández MA, Ibarra RA, Berendsohn WG, Bienzle U, Eich E. In vitro antiplasmodial activity of 4-phenylcoumarins from Exostema mexicanum. Planta Med 2001; 67:89-91. [PMID: 11270733 DOI: 10.1055/s-2001-10630] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The stem bark of Exostema mexicanum (Rubiaceae) is used in Latin American folk medicine as a quinine substitute for malaria treatment. Bioassay-guided fractionation of lipophilic and hydrophilic extracts from the stem bark and branches yielded two previously undescribed 4-phenylcoumarins: 4',8-dihydroxy-5,7-dimethoxy-4-phenylcoumarin (exomexin A) and 3',4'-dihydroxy-5,7,8-trimethoxy-4-phenylcoumarin (exomexin B). Together with five known derivatives the in vitro activities against a chloroquine-sensitive strain (poW) and a chloroquine-resistant strain (Dd2) of Plasmodium falciparum have been evaluated. The most lipophilic compound, 4',5,7,8-tetramethoxy-4-phenylcoumarin (O-methylexostemin) revealed the strongest antiplasmodial activity (IC50 values: 3.6 microg/ml [poW], 1.6 microg/ml [Dd2]).
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37
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González JC, Leira F, Vieytes MR, Vieites JM, Botana AM, Botana LM. Development and validation of a high-performance liquid chromatographic method using fluorimetric detection for the determination of the diarrhetic shellfish poisoning toxin okadaic acid without chlorinated solvents. J Chromatogr A 2000; 876:117-25. [PMID: 10823507 DOI: 10.1016/s0021-9673(00)00193-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A modification of the high-performance liquid chromatographic method with fluorimetric detection method for the determination of diarrhetic shellfish poisoning toxins was developed to completely avoid the use of dangerous chlorinated solvents. The method was validated for the toxin okadaic acid (OA) over a period of 6 months where 12 calibrations were performed and 72 samples were analyzed. Analysis of toxic and non-toxic mussels, clams and scallops demonstrated its selectivity. Linearity was observed in the tested range of interest for monitoring purposes of edible shellfish, from the limit of detection (0.3 microg OA/g hepatopancreas) to 13 microg OA/g hepatopancreas. Intra-assay precision of the method was 7% RSD at the quantification limit (0.97 microg OA/g hepatopancreas at S/N=10). Accuracy was tested in triplicate recovery experiments from OA-spiked shellfish where recovery ranged from 92 to 106% in the concentration range of 0.8 to 3.6 microg OA/g hepatopancreas. Useful information on critical factors affecting calibration and reproducibility is also reported. Good correlation (R=0.87) was observed between the results of the method and those of the method of Lee, after the analysis of 45 samples of mussels from the galician rias.
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Affiliation(s)
- J C González
- Departamento de Farmacología, Universidad de Santiago de Compostela, Lugo, Spain
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Guelrud M, González JC, Piñero R. The Venezuelan Section of Gastrointestinal Endoscopy. Gastrointest Endosc 1998; 48:229-30. [PMID: 9717802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Affiliation(s)
- M Guelrud
- Venezuelan Section of Gastrointestinal Endoscopy, Caracas
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González JC, Vieytes MR, Vieites JM, Botana LM. Improvement on sample clean-up for high-performance liquid chromatographic-fluorimetric determination of diarrhetic shellfish toxins using 1-bromoacetylpyrene. J Chromatogr A 1998; 793:63-70. [PMID: 9468651 DOI: 10.1016/s0021-9673(97)00845-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Okadaic acid (OA) and dinophysistoxin-2, two of the main diarrhetic shellfish toxins, can be determined by high-performance liquid chromatography coupled to fluorimetry as pyrenacyl esters. Toxin fluorescent derivatives were obtained after quantitative derivatization with 1-bromoacetylpyrene in acetonitrile. An efficient improvement in the silica gel clean-up procedure of the pyrenacyl derivatives is reported. The clean-up cartridge is washed with hexane-dichloromethane (1:1, v/v), dichloromethane-ethyl acetate (8:2, v/v), and finally the pyrenacyl esters were eluted with dichloromethane-methanol (9:1, v/v). We compare this procedure with other methods already described. Good results were obtained with mussels, scallops and clams. The clean-up procedure showed good robustness when checked against silica and solvents activity. Using samples of mussel hepatopancreas with an OA concentration ranging from 0 to 2 micrograms OA/g hepatopancreas, the inter-assay relative standard deviation ranged from 5.5 to 12.6%.
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Affiliation(s)
- J C González
- Departamento de Farmacología, Facultad de Veterinaria, Lugo, Spain
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Abstract
Cobalamin-independent methionine synthase (MetE) from Escherichia coli catalyzes the transfer of a methyl group from methyltetrahydrofolate to homocysteine. Previous work had shown the existence of a reactive thiol group, cysteine 726, whose alkylation led to loss of all detectable enzymatic activity [González, J.C., et al. (1992) Biochemistry 31, 6045-6056]. A site-directed mutation of MetE, Cys726Ser, was constructed to investigate the possible role of this cysteine. The Cys726Ser protein was purified to homogeneity, affording a protein with no detectable activity. To assess the possibility that cysteine726 functions as a metal ligand, inductively coupled plasma-atomic emission spectrometry was performed. The wild-type enzyme contains 1.02 equiv of zinc per subunit; the Cys726Ser mutant does not contain zinc, supporting the view that cysteine726 is required for metal binding. A loss of enzymatic activity is observed upon removal of zinc from the wild-type MetE by incubation in urea and EDTA; activity can subsequently be restored by zinc reconstitution, suggesting that zinc is required for catalysis. Circular dichroism measurements further suggest that there are no major differences in the secondary structures of the wild-type and the Cys726Ser mutant enzymes. Extended X-ray absorption fine structure analysis has established that the average zinc environment is different in the presence of homocysteine than in its absence and is consistent with the changes expected for displacement of an oxygen or nitrogen ligand by the sulfur of homocysteine. A possible model for zinc-dependent activation of homocysteine by MetE is presented.
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Affiliation(s)
- J C González
- Biophysics Research Division, University of Michigan, Ann Arbor 48109-1055, USA
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González JC, Roma-Millán J, Sancho JJ, Sanz F. [Informatics in medical schools and postgraduate education centers for health professionals. Survey on the situation in Spain]. Med Clin (Barc) 1995; 105:570-5. [PMID: 7500676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND Informatics is acquiring an increasing relevance in the medical profession. METHODS During the year 1993, a survey was carried out at the medical schools (MS) and postgraduate education centres (PEC) in Epidemiology, Public Health and Health Administration of Spain, on the available computer infrastructure and the teaching activities. The percentages of respondents were 81 at the MS and 100 at the PEC. RESULTS 81% of the MS and 100% of the PEC had a computer laboratory, mainly equipped with personal computers with MS-DOS operating system. The use of general purpose applications was predominant. The number of students using the computer laboratory was very variable (5-300 per day). 48% of the MS organized courses on microcomputer applications. 66% of the MS included subjects related with informatics in the new curricula. CONCLUSIONS Use of computers in the Spanish MS is heterogeneous. Compared with the Nord-American MS, they do not usually use applications of computer-assisted-instruction. The use of the computers at the PEC is much more generalized.
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Affiliation(s)
- J C González
- Department d'Informàtica Mèdica, Universitat Autònoma de Barcelona
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Drummond JT, Jarrett J, González JC, Huang S, Matthews RG. Characterization of nonradioactive assays for cobalamin-dependent and cobalamin-independent methionine synthase enzymes. Anal Biochem 1995; 228:323-9. [PMID: 8572314 DOI: 10.1006/abio.1995.1358] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Methionine synthase enzymes catalyze methyl group transfer from 5-methyltetrahydrofolate to homocysteine to give methionine and tetrahydrofolate. Assays for this enzyme activity usually monitor transfer of a 14C-methyl group from the N5-position of methyltetrahydrofolate to homocysteine to produce 14C-methionine that must be purified by anion-exchange chromatography. Alternatively, tetrahydrofolate may be derivatized with a formylating agent under acidic conditions to produce methenyltetrahydrofolate. We report optimization of this reaction for assay of cobalamin-dependent methionine synthase to give an economical method for determining enzyme activity that does not require the use of radioactive compounds. By heating for 10 min in 1 N hydrochloric acid containing 12% formic acid, the enzymatic product tetrahydrofolate is converted into methenyltetrahydrofolate, which absorbs light at 350 nm, while residual substrate 5-methyltetrahydrofolate does not contribute to the absorbance at 350 nm. The assay allows the derivatized product to be characterized in situ with a minimal increase in volume upon acidification. The results of the spectrophotometric assay given here have been compared with the radioactive assay to confirm the validity of the derivatization under the assay conditions. We also report the extension of this assay method for use in activity measurements of cobalamin-independent methionine synthase.
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Affiliation(s)
- J T Drummond
- Biophysics Research Division, University of Michigan, Ann Arbor 48109-1055, USA
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Eichel J, González JC, Hotze M, Matthews RG, Schröder J. Vitamin-B12-independent methionine synthase from a higher plant (Catharanthus roseus). Molecular characterization, regulation, heterologous expression, and enzyme properties. Eur J Biochem 1995; 230:1053-8. [PMID: 7601135 DOI: 10.1111/j.1432-1033.1995.tb20655.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Methionine synthases catalyze the formation of methionine by the transfer of a methyl group from 5-methyltetrahydrofolate to homocysteine. This reaction is the last step in L-methionine biosynthesis, and it also serves to regenerate the methyl group of S-adenosylmethionine, a cofactor required for biological methylation reactions. We describe the cloning, expression and characterization of a methionine synthase from the higher plant Catharanthus roseus. cDNAs were identified that encoded a protein of 85 kDa sharing 50% identify with the cobalamin-independent methionine synthase from Escherichia coli (MetE) and 41% identity with a partial sequence of a yeast homolog of MetE. The C. roseus protein was expressed at high levels in E. coli. The enzyme accepts the triglutamate form of methyltetrahydrofolate as a methyl donor but not the monoglutamate form, and it does not require S-adenosylmethionine or cobalamin for activity. The properties indicate that the enzyme is a cobalamin-independent methionine synthase (EC 2.1.1.14). In contrast to the E. coli MetE, the plant protein does not require phosphate or magnesium ions for activity. Immunoblots of plants extracts showed that the protein was localized in the cytosol, and was present in a variety of plant species. A nutritional downshift of the C. roseus cell culture revealed a strong, transient transcriptional activation, but no significant increment in the total level of the protein. The availability of the protein and the cDNA now provide tools to investigate the complexities of methionine biosynthesis in plants.
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Affiliation(s)
- J Eichel
- Institut für Biologie II, Universität Freiburg, Germany
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Abstract
A detailed description of the design procedure for a new concentrator, RX, and some examples of it's use are given. The method of design is basically the same as that used in the design of two other concentrators: the RR and the XR [Appl. Opt. 31, 3051 (1992)]. The RX is ideal in two-dimensional geometry. The performance of the rotational RX is good when the average angular spread of the input bundle is small: up to 95% of the power of the input bundle can be transferred to the output bundle (with the assumption of a constant radiance for the rays of the input bundle).
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González JC, Pulido M, Sanz F. [Evaluation of the use of statistical techniques in original articles published in the Medicina Clínica during 3 decades (1962-1992)]. Med Clin (Barc) 1995; 104:448-52. [PMID: 7739280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND The incorrect use of statistical techniques in medical articles may seriously compromise the validity of conclusions. This finding otherwise is relatively common. METHODS A total of 84 original articles published in Medicina Clínica between 1962 and 1992 were reviewed with the aim of assessing the use and appropriateness of statistical techniques. The use of statistics, the quality of the analyses performed, and the inaccuracy of the statistical techniques used were evaluated. We also classified the statistical techniques most commonly used throughout the study period. RESULTS There was a marked increase in the use of statistical analyses, from 8.3% in 1962 to 83.3% in 1992. It should be noted that a substantial part of this increase has been due to the use of inferential tests, which accounted up to 70% in the sample of articles published in 1992. This finding, however, was associated with an increase in the number of incorrect analyses. The most common statistical errors included assumption of normal distribution of data (with no mention of the test used to confirm this fact), mistake between standard deviation and standard error of the mean, inadequate inferences on the basis of the sample size, inappropriate use of the Student's t test, chi-square test, nonparametric tests or multivariate analyses as well as misunderstanding of linear regression and correlation. CONCLUSIONS High standards in scientific research have been accompanied by a significant increase in the number of clinical studies with statistical analysis of data. However, this apparently favorable situation has been associated with an increase in the number of inaccurate analyses. It has been found that sophisticated statistical tests are rarely used in articles published in Medicina Clínica.
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Affiliation(s)
- J C González
- Departament d'Informàtica Mèdica i Docència, Institut Municipal d'Investigació Mèdica (IMIM), Barcelona
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Pulido M, González JC, Sanz F. [Original articles published in Medicina Clínica during 30 years (1962-1992): number of authors, interval between acceptance and publication and bibliographic references]. Med Clin (Barc) 1994; 103:770-5. [PMID: 7861835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND To study different aspects of original articles published in Medicina Clínica (Barcelona) over a 30-year period (1962-1992), with special emphasis on references. METHODS We selected 12 articles per year at 5-year intervals (1962, 1967, 1972, 1977, 1982, 1987, 1992) using a systematic sampling procedure. The following variables were assessed: number of authors, interval between acceptance of the manuscript and publication in the journal, total number of references, language, document type, and name of the journal. RESULTS The mean (+/- standard deviation) number of authors showed a statistically significant increase (ANOVA; F = 13.666; p = 0.0001) from 1.83 +/- 0.71 in 1962 to 6.41 +/- 1.97 in 1992. The interval between acceptance and publication decreased from 315.72 +/- 20.48 days in 1982 to 206.16 +/- 89.23 in 1992 (ANOVA, F = 6.074; p = 0.0058). A total of 1816 references were found (24.2 references per article). English was the language of publication most commonly found (76.76%) followed by Spanish (12.6%). There was a statistically significant increase in the use of references corresponding to English articles over the study period (chi 2 = 314.431; p = 0.0001). A significant change was also observed in the type of document use (chi 2 = 143.996; p = 0.0001); references from journals increased from 73.51% in 1962 to 91.40% in 1992. In addition, 50.46% of the articles were published in only 7.84% of the journals. Eight journals devoted to internal medicine (1.79% of all journals) included 23.46% of the references. CONCLUSIONS The number of authors has shown a significant increase during the study period. The time elapsed between acceptance and publication has decreased significantly. Spanish authors acquired information mostly from the English literature. Articles published in journals are also mostly used as references. A large percentage of references consisted of articles published in core general journals. These journals accumulate a remarkable percentage of the information.
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Affiliation(s)
- M Pulido
- Unidad de Edición Médica, Universidad Autónoma de Barcelona
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Abstract
Medical informatics (MI) has been introduced to medical students in several countries. Before outlining a course plan it was necessary to conduct a survey on students' computer literacy. A questionnaire was designed for students, focusing on knowledge and previous computer experience. The questions reproduced a similar questionnaire submitted to medical students from North Carolina University in Chapel Hill (NCU). From the results it is clear that although almost 80% of students used computers, less than 30% used general purpose applications, and utilization of computer-aided search of databases or use in the laboratory was exceptional. Men reported more computer experience than women in each area investigated by our questionnaire but this did not appear to be related to academic performance, age or course. Our main objectives when planning an MI course were to give students a general overview of the medical applications of computers and instruct them in the use of computers in future medical practice. As our medical school uses both Apple Macintosh and IBM compatibles, we decided to provide students with basic knowledge of both. The programme was structured with a mix of theoretico-practical lectures and personalized practical sessions in the computer laboratory. As well as providing a basic overview of medical informatics, the course and computer laboratory were intended to encourage other areas of medicine to incorporate the computer into their teaching programmes.
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Affiliation(s)
- J J Sancho
- Departament d'Informàtica Mèdica i Docència, Facultat de Medicina, Universitat Autònoma de Barcelona, Spain
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Matos M, Capozzolo N, Golindano C, González JC, Guirola E, Ramirez R, Machado I. [Humoral immunologic changes in inflammatory colonic diseases]. G E N 1993; 47:129-35. [PMID: 8112548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We present the humoral immunological findings in 18 patients with ulcerative colitis and two with Crohn's disease. All of them had the disease for 3 months to five years. Fifteen were hispanics and five from European origin. There were ten males and ten females, and an average age of 38 years. All patients had active disease from clinical and endoscopy points of view. Thirteen patients had abnormal values in one of the immunoglobulins and normal in seven patients. IgA was increased in eleven, normal in seven and decreased in two. IgG increased in two, decreased in one and normal in seventeen cases. IgM was found to be increased in five and normal in the rest. IgA secretory determination in saliva, was performed twelve patients and was positive in all of them. Antinuclear antibodies were negative in eight. Anti-smooth muscle were positive in three of fifteen. Anti-mitochondrial were present in one and negative in thirteen. Values of C3 and C4 were lower than normal in 3 and 2 cases respectively from 4 cases studied. CH50 was decreased in 2 of 11 cases studied. In the patients, no correlation was found between low complement values, the positivity of auto antibodies and the clinical parameters previously mentioned. We conclude that there is quantitative alterations of the humoral response and it is necessary the immunological study in persons with inflammatory bowel disease others studies are needed to establish the real value of these findings.
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Affiliation(s)
- M Matos
- Unidad de Gastroenterología, Clínica El Avila, U.C.V. Caracas
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González JC, Banerjee RV, Huang S, Sumner JS, Matthews RG. Comparison of cobalamin-independent and cobalamin-dependent methionine synthases from Escherichia coli: two solutions to the same chemical problem. Biochemistry 1992; 31:6045-56. [PMID: 1339288 DOI: 10.1021/bi00141a013] [Citation(s) in RCA: 119] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In Escherichia coli, two enzymes catalyze the synthesis of methionine from homocysteine using methyltetrahydrofolate as the donor of the required methyl group: cobalamin-dependent and cobalamin-independent methionine synthases. Comparison of the mechanisms of these two enzymes offers the opportunity to examine two different solutions to the same chemical problem. We initiated the research described here to determine whether the two enzymes were evolutionarily related by comparing the deduced amino acid sequences of the two proteins. We have determined the nucleotide sequence for the metE gene, encoding the cobalamin-independent methionine synthase. Our results reveal an absence of similarity between the deduced amino acid sequences of the cobalamin-dependent and cobalamin-independent proteins and suggest that the two have arisen by convergent evolution. We have developed a rapid one-step purification of the recombinant cobalamin-independent methionine synthase (MetE) that yields homogeneous protein in high yield for mechanistic and structural studies. In the course of these studies, we identified a highly reactive thiol in MetE that is alkylated by chloromethyl ketones and by iodoacetamide. We demonstrated that alkylation of this residue, shown to be cysteine 726, results in complete loss of activity. While we are unable to deduce the role of cysteine 726 in catalysis at this time, the identification of this reactive residue suggests the possibility that this thiol functions as an intermediate methyl acceptor in catalysis, analogous to the role of cobalamin in the reaction catalyzed by the cobalamin-dependent enzyme.
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Affiliation(s)
- J C González
- Biophysics Research Division, University of Michigan, Ann Arbor 48109
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Abstract
A new method of designing nonimaging concentrators is presented and two new types of concentrators are developed. The first is an aspheric lens, and the second is a lens-mirror combination. A ray tracing of three-dimensional concentrators (with rotational symmetry) is also done, showing that the lens-mirror combination has a total transmission as high as that of the full compound parabolic concentrators, while their depth is much smaller than the classical parabolic mirror-nonimaging concentrator combinations. Another important feature of this concentrator is that the optically active surfaces are not in contact with the receiver, as occurs in other nonimaging concentrators in which the rim of the mirror coincides with the rim of the receiver.
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