Imidazolium-based ionic liquids binding to DNA: Mechanical effects and thermodynamics of the interactions

We performed a robust characterization of the molecular interactions between the DNA molecule and two imidazolium-based ionic liquids (ILs): 1-Butyl-3-methylimidazolium chloride ([bmim]Cl) and 1-Octyl-3-methylimidazolium chloride ([omim]Cl), using single molecule approaches (optical and magnetic tweezers) and bulk techniques (isothermal titration calorimetry and conductivity measurements). Optical and magnetic tweezers allowed us to obtain the changes on the mechanical properties of the DNA complexes formed with both ILs, as well as the relevant physicochemical (binding) parameters of the interaction. Despite the weak binding measured between DNA and the two ILs, we identify a transition on the regime of polymer elasticity of the complexes formed, which results in a relevant DNA compaction for high IL concentrations. In addition, isothermal titration calorimetry and conductivity complemented the single molecule investigation, giving a complete thermodynamic characterization of the interactions and allowing the identification of the most relevant driving forces at various different concentration ranges of the ILs. Based on the results obtained with all the employed techniques, we propose a model for the binding schemes involving DNA and both [bmim]Cl and [omim]Cl.

Caffeine modulates the intercalation of drugs on DNA: A study at the single molecule level

We use optical tweezers to characterize the ability of Caffeine (Caf) to modulate the intercalation of drugs into the DNA double-helix at the single molecule level. When previously bound to the double-helix, Caf hinders ethidium bromide (EtBr) intercalation, decreasing its effective equilibrium binding constant with DNA. The dominant mechanism of such singular ability is a direct binding of Caf to the intercalating drugs in solution, which decreases the effective concentration of such compounds available to interact with DNA. When EtBr intercalation into the DNA double-helix occurs firstly, on the other hand, the measured cooperativity between Caf molecules interacting with DNA can be modulated, a feature also correlated to the Caf-EtBr interaction in solution. The results achieved here unveil many peculiarities about the details of such interactions at the molecular level and provide new insights on the use of Caf in therapeutic applications.

Olfactory response of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) to volatiles induced by transgenic maize

Plants not only respond to herbivorous damage but adjust their defense system after egg deposition by pest insects. Thereby, parasitoids use oviposition-induced plant volatiles to locate their hosts. We investigated the olfactory behavioral responses of Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) to volatile blends emitted by maize (Zea mays L.) with singular and stacked events after oviposition by Spodoptera frugiperda Smith, 1797 (Hymenoptera: Trichogrammatidae) moths. Additionally, we examined possible variations in gene expression and on oviposition-induced volatiles. We used a Y-tube olfactometer to test for the wasp responses to volatiles released by maize plants oviposited by S. frugiperda and not-oviposited plants. Using the real-time PCR technique (qRT-PCR), we analyzed the expression of lipoxygenase and three terpene synthases genes, which are enzymes involved in the synthesis of volatile compounds that attract parasitoids of S. frugiperda. Olfactometer tests showed that T. pretiosum is strongly attracted by volatiles from transgenic maize emitted by S. frugiperda oviposition (VTPRO 3, more than 75% individuals were attracted). The relative expression of genes TPS10, LOX e STC was higher in transgenic hybrids than in the conventional (isogenic line) hybrids. The GC-MS analysis revealed that some volatile compounds are released exclusively by transgenic maize. This study provides evidence that transgenic hybrids enhanced chemical cues under oviposition-induction and helped to increase T. pretiosum efficiency in S. frugiperda control. This finding shows that among the evaluated hybrids, genetically modified hybrids can improve the biological control programs, since they potentialize the egg parasitoid foraging, integrating pest management.

The predatory mite Neoseiulus californicus (Acari: Phytoseiidae) does not respond for volatiles of maize infested by Tetranychus urticae (Acari: Tetranychidae)

Among the plants defense mechanisms, the induction and emission of volatile organic compounds, which can be used to attract natural enemies, such predators insects. Although well studied, the induction of plant volatiles that attract natural enemies can vary according to intensity of infestation of herbivores and the species of host plant. We investigated the olfactory behavioral responses of the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) to the volatiles of infested maize (Zea mays) plants by the two-spotted spider mite Tetranychus urticae (Koch, 1836) (Acari: Tetranychidae) in early and advanced infestations. The Bt (Viptera) maize cultivar Impact® was used for tests the behavior of N. californicus. After initial and advanced infestations, the phytophagous mites T. urticae were removed, and the plants were tested using a "Y" olfactometer. The following treatments were evaluated: air vs. air, uninfested plants vs. air, uninfested plants vs. plants infested with 10 females of T. urticae, uninfested plants vs. plants infested with 100 females of T. urticae, uninfested plants vs. plants infested with 200 females of T. urticae and plants infested with 10 vs. plants infested with 200 females of T. urticae. The predatory mite N. californicus did not show preference to the treatments tested, suggesting that maize plants infested by T. urticae do not induce volatiles capable of attracting the predatory mite N. californicus. We concluded that N. californicus is not attracted by maize plants infested by T. urticae.

Bessel beam optical tweezers for manipulating superparamagnetic beads

We propose a Bessel beam optical tweezers setup that can stably trap superparamagnetic beads. The trap stiffness measured is practically independent of the radius of the Bessel beam and of the bead height (distance from the coverlip of the sample chamber), indicating that the beads can be trapped with high accuracy within a wide range of such parameters. On the other hand, the trap stiffness exhibits the expected linear increase with the laser power, despite the non-negligible absorption coefficient of the superparamagnetic beads. A geometrical optics model that considers spherical aberration and light absorption by the beads was used to predict the optical forces and trap stiffness, showing excellent agreement with the experimental data. We believe the results presented here advance the field of optical trapping manipulation of absorbing magnetic particles, and future applications will involve, for example, the design of new hybrid optomagnetic tweezers.

77 Occurrence of early regression of corpora lutea in Dorper ewes subjected to a conventional superovulatory regimen

The early regression of corpora lutea (ERCL) is a functional alteration that occurs more often in animals subjected to multiple ovulation followed by embryo transfer (MOET) technique. Although it is mainly reported in goats, sheep are also susceptible to this disorder. The ERCL may compromise the quality and viability of embryos, and even embryonic recovery rate. Thus, the non-diffusion of the animal genetic material on a commercial scale increases costs, decreasing efficiency. This study aimed to assess the occurrence of ERCL in embryo donor ewes subjected to the MOET programs in different seasons. The research was carried out in a commercial herd in São Luís do Paraitinga city (23°22′S and 45°26′W), Brazil, over 4 years (2017–2020). Forty-four Dorper multiparous ewes aged between 3 and 9 years old and with body condition score (BCS) between 2 and 4.5 (1 to 5 scale) were used. Each ewe was used at least once for MOET and a maximum of 5 times, totalling 104 procedures. Regardless of the day of the oestrous cycle or anovulatory period (Day 0), ewes received a conventional superovulatory protocol consisting of an intravaginal device treatment with 0.33mg of progesterone (CIDR®, Zoetis). On Day 7, the device was replaced with a new one and ewes administered i.m. 0.24mg of sodium cloprostenol (Sincrocio®, Ourofino). The superovulatory treatment [256mg of FSH (Folltropin®, Vetoquinol)] started on Day 12 and consisted of decreasing doses (20, 20, 15, 15, 10, 10, 5, and 5%) administered intramuscularly (IM) every 12h for 4 days plus 200IU of equine chorionic gonadotrophin (eCG, Novormon®, Zoetis) at device removal on Day 14 and 0.1mg of gonadotrophin-releasing hormone (Fertagyl®, MSD) IM 1 day later (Day 15). Laparoscopic AI was performed twice on Day 16 using cooled semen. Five days after AI, ovaries were assessed by laparoscopy to check the presence and viability of corpora lutea (CL). Ewes that had avascular CL (pinkish to whitish colour) were classified as ERCL and embryo collection was not performed. The occurrence of ERCL in each season and category of BCS was checked by either chi-squared or Fisher test. Logistic regression was performed according to the incidence of ERCL in each category of age. Values of P<0.05 were considered as significant. From 104 procedures, ERCL was identified in 26 cases, totalling 25% of occurrence. The proportion of occurrence did not differ (P>0.05) among seasons: breeding (10/43: 23%), transition (10/36, 28%), or anoestrous (6/25, 24%). There was no difference in ERCL incidence in ewes presenting different BCS categories: lower/thin (2 to 2.5: 3/12, 25%); average/good (3 to 3.5: 15/66, 22%) and higher/fat (4 to 4.5: 8/26, 31%). Indeed, there was no association (P>0.05) between ERCL and age. In conclusion, a relevant occurrence of ERCL was detected in superovulated embryo donor ewes but this incidence was not associated with season, age, or BCS of Dorper ewes. These data highlight the importance of pharmacological measures to control ERCL in MOET protocols for commercial sheep herds.

Hydroxychloroquine Exhibits a Strong Complex Interaction with DNA: Unraveling the Mechanism of Action

In the past months, the use of the drug hydroxychloroquine has considerably increased in many countries, associated with a proposed treatment for the COVID-19 disease. Although there is no conclusive evidence about the efficacy of the drug for this purpose, surprisingly there are no conclusive studies in the literature concerning its mechanism of action inside cells, which is related to its interaction with nucleic acids. Here, we performed a robust characterization of the interaction between hydroxychloroquine and double-stranded DNA using single-molecule force spectroscopy and gel electrophoresis. Two different binding modes were identified, namely, minor groove binding for low drug concentrations and intercalation for high drug concentrations, and the sets of binding parameters were determined for each of these modes. Such results have unraveled in detail the molecular mechanism of action of the drug as a DNA ligand.

Dodecyltrimethylammonium bromide surfactant effects on DNA: Unraveling the competition between electrostatic and hydrophobic interactions

We present a new study on the interaction of the DNA molecule with the surfactant dodecyltrimethylammonium bromide (DTAB), performed mainly with optical tweezers. Single-molecule force spectroscopy experiments performed in the low-force entropic regime allowed a robust characterization of the DNA-DTAB interaction, unveiling how the surfactant changes the mechanical properties of the biopolymer, the binding parameters, and the competition of the two mechanisms involved in the interaction: electrostatic attraction between the cationic surfactant heads and the negative phosphate backbone of the DNA and hydrophobic interactions between the tails of the bound DTAB molecules, which can result in DNA compaction in solution depending on the quantity of bound surfactant. Finally, force clamp experiments with magnetic tweezers and gel electrophoresis assays confirm that DTAB compacts DNA depending not only on the surfactant concentration but also on the conformation of the biopolymer in solution. The present study provides new insights on general aspects of the DNA-surfactant complexes formation, contributing to the fundamental knowledge of the physics of such interactions.

Transplatin ineffectiveness against cancer from a molecular perspective: A single-molecule force-spectroscopy study

By performing single-molecule force spectroscopy with optical tweezers, we have characterized the interaction between the platinum-based compound transplatin and the DNA molecule, establishing a critical comparison with its isomer cisplatin. While transplatin is ineffective against tumor cells, its isomer is one of the most used drugs in current chemotherapies, and a molecular study on this difference performed at the single-molecule level was lacking until the present work. Our experiments show that transplatin binds DNA under low chloride concentrations (a situation usually found inside many cells) with an equilibrium association binding constant about four orders of magnitude lower than cisplatin. In addition, we have found that, at saturation, transplatin binds preferentially forming interstrand cross links and monoadducts, a situation very different from cisplatin, which forms preferentially intrastrand cross links. Such differences explain the ineffectiveness of transplatin in killing tumor cells. From a physical point of view, the present study advances in using the mechanical properties of the DNA molecule as sensors to evaluate the therapeutic efficiency of drugs.

Silicon microparticles as handles for optical tweezers experiments

We study the behavior of silicon microparticles in a 1064 nm Gaussian-beam optical tweezers, showing that this semiconductor can be used to perform different types of optical manipulation experiments. Depending on the focal position and the laser power used, the particles can present an oscillatory dynamics in the tweezers or can be stably 3D-trapped with a trap stiffness that allows the application of femtoNewton forces with accuracy. A new, to the best of our knowledge, interpretation based on the photoexcitation of electrons in the valence band is proposed to explain the oscillations, and the quantities associated with such dynamics (e.g., amplitude, period, etc.) were characterized as a function of relevant parameters to optical tweezers setups.

Pixantrone anticancer drug as a DNA ligand: Depicting the mechanism of action at single molecule level

In this work we use single molecule force spectroscopy performed with optical tweezers in order to characterize the complexes formed between the anticancer drug Pixantrone (PIX) and the DNA molecule, at two very different ionic strengths. Firstly, the changes of the mechanical properties of the DNA-PIX complexes were studied as a function of the drug concentration in the sample. Then, a quenched-disorder statistical model of ligand binding was used in order to determine the physicochemical (binding) parameters of the DNA-PIX interaction. In particular, we have found that the PIX molecular mechanism of action involves intercalation into the double helix, followed by a significant compaction of the DNA molecule due to partial neutralization of the phosphate backbone. Finally, this scenario of interaction was quantitatively compared to that found for the related drug Mitoxantrone (MTX), which binds to DNA with a considerably higher equilibrium binding constant and promotes a much stronger DNA compaction. The comparison performed between the two drugs can bring clues to the development of new (and more efficient) related compounds.

Insulinoma: A retrospective study analyzing the differences between benign and malignant tumors

BACKGROUND/OBJECTIVES

Insulinoma is a rare pancreatic tumor and, usually, a benign disease but can be a malignant one and, sometimes, a highly aggressive disease. The aim of this study was to determine differences between benign and malignant tumors.

METHODS

Retrospective study of 103 patients with insulinoma treated in a tertiary center. It was analyzed demographic, clinical, laboratory, localization and histologic analysis of tumor and follow up data of subjects in order to identify differences between individuals benign and malignant disease.

RESULTS

Almost all patients (87%) had a benign tumor and survival rates of 100% following pancreatic tumor surgery. Those with malignant tumors (13%) have a poor prognosis, 77% insulinoma-related deaths over a period of 1-300 months after the diagnosis with a survival rate of 24% in five years. The following factors are associated with an increased risk of malignant disease: duration of symptoms < 24 months, fasting time for the occurrence of hypoglycemia < 8 h, blood plasma insulin concentration ≥ 28 μU/mL and C-peptide ≥ 4.0 ng/mL at the glycemic nadir and tumor size ≥ 2.5 cm.

CONCLUSIONS

Our data help to base the literature about these tumors, reinforcing that although insulinoma is usually a single benign and surgically treated neoplasia, the malignant one is difficult to treat. We highlight the data that help predict a malignancy behavior of tumor and suggest a long follow up after diagnosis in these cases.

Enteric viruses' dissemination in a private reserve of natural heritage

This study aimed to assess anthropogenic impact of surrounding population in the Private Reserve of Natural Heritage at Pantanal, the world's largest freshwater wetland ecosystem located in the centre of South America. Viral aetiological agents of acute gastroenteritis as rotavirus A (RVA), noroviruses, human adenoviruses, klassevirus and of hepatitis, as hepatitis A virus, were investigated in different aquatic matrices. Annual collection campaigns were carried out from 2009 to 2012, alternating dry and rainy seasons. Viral particles present in the samples were concentrated by the adsorption-elution method, with negatively charged membranes, and detected by qualitative and quantitative PCR. From a total of 43 samples at least one virus was detected in 65% (28) of them. Viruses were detected in all matrices with concentrations ranging from 2 × 10² to 8·3 × 10⁴ genome copies per litre. A significant higher RVA frequency was observed in the dry season. Our data revealing dissemination of human enteric viruses in water matrices both inside and outside the reserve could be useful to trace faecal contamination in the environment and to minimize the risk of infection by exposure of susceptible individuals.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is part of a collaborative project designed to investigate the environmental and health conditions of the Private Reserve of Natural Heritage at Pantanal, the largest seasonally flooded wetland in the world. The project aimed to promote health and quality of human and wildlife extending technical-scientific knowledge about pathogens present in the region. By assessing the occurrence of human enteric viruses in different water matrices we demonstrated the anthropogenic impact of surrounding population and pointed out the potential risk of infection by exposure of susceptible individuals.

Force spectroscopy unravels the role of ionic strength on DNA-cisplatin interaction: Modulating the binding parameters

In the present work we have gone a step forward in the understanding of the DNA-cisplatin interaction, investigating the role of the ionic strength on the complexes formation. To achieve this task, we use optical tweezers to perform force spectroscopy on the DNA-cisplatin complexes, determining their mechanical parameters as a function of the drug concentration in the sample for three different buffers. From such measurements, we determine the binding parameters and study their behavior as a function of the ionic strength. The equilibrium binding constant decreases with the counterion concentration ([Na]) and can be used to estimate the effective net charge of cisplatin in solution. The cooperativity degree of the binding reaction, on the other hand, increases with the ionic strength, as a result of the different conformational changes induced by the drug on the double-helix when binding under different buffer conditions. Such results can be used to modulate the drug binding to DNA, by appropriately setting the ionic strength of the surrounding buffer. The conclusions drawn provide significant new insights on the complex cooperative interactions between the DNA molecule and the class of platinum-based compounds, much used in chemotherapies.

β-Cyclodextrin polymer binding to DNA: Modulating the physicochemical parameters

Cyclodextrins and cyclodextrins-modified molecules have interesting and appealing properties due to their capacity to host components that are normally insoluble or poorly soluble in water. In this work, we investigate the interaction of a β-cyclodextrin polymer (poly-β-CD) with λ-DNA. The polymers are obtained by the reaction of β-CD with epichlorohydrin in alkaline conditions. We have used optical tweezers to characterize the changes of the mechanical properties of DNA molecules by increasing the concentration of poly-β-CD in the sample. The physical chemistry of the interaction is then deduced from these measurements by using a recently developed quenched-disorder statistical model. It is shown that the contour length of the DNA does not change in the whole range of poly-β-CD concentration (<300μM). On the other hand, significant alterations were observed in the persistence length that identifies two binding modes corresponding to the clustering of ∼2.6 and ∼14 polymer molecules along the DNA double helix, depending on the polymer concentration. Comparing these results with the ones obtained for monomeric β-CD, it was observed that the concentration of CD that alters the DNA persistence length is considerably smaller when in the polymeric form. Also, the binding constant of the polymer-DNA interaction is three orders of magnitude higher than the one found for native (monomeric) β-CD. These results show that the polymerization of the β-CD strongly increases its binding affinity to the DNA molecule. This property can be wisely used to modulate the binding of cyclodextrins to the DNA double helix.

DNA-doxorubicin interaction: New insights and peculiarities

We have investigated the interaction of the DNA molecule with the anticancer drug doxorubicin (doxo) by using three different experimental techniques: single molecule stretching, single molecule imaging, and dynamic light scattering. Such techniques allowed us to get new insights on the mechanical behavior of the DNA-doxo complexes as well as on the physical chemistry of the interaction. First, the contour length data obtained from single molecule stretching were used to extract the physicochemical parameters of the DNA-doxo interaction under different buffer conditions. This analysis has proven that the physical chemistry of such interaction can be modulated by changing the ionic strength of the surrounding buffer. In particular we have found that at low ionc strengths doxo interacts with DNA by simple intercalation (no aggregation) and/or by forming bound dimers. For high ionic strengths, otherwise, doxo-doxo self-association is enhanced, giving rise to the formation of bound doxo aggregates composed by 3 to 4 molecules along the double-helix. On the other hand, the results obtained for the persistence length of the DNA-doxo complexes is strongly force-dependent, presenting different behaviors when measured with stretching or non-stretching techniques.

Unraveling the physical chemistry and the mixed binding modes of complex DNA ligands by single molecule stretching experiments

In this work we present a complete methodology to unravel the physical chemistry and the mixed binding modes of complex DNA ligands.

Controlling Cooperativity in β-Cyclodextrin-DNA Binding Reactions

We have investigated the interaction between the native neutral β-cyclodextrin (CD) and the DNA molecule by performing single-molecule stretching experiments with optical tweezers. In particular, we have monitored the changes of the mechanical properties of the CD-DNA complexes as a function of the CD concentration in the sample. By using a quenched disorder statistical model, we were also capable to extract important physicochemical information (equilibrium binding constants, cooperativity degree) of such interaction from the mechanical data. In addition, we have found that the interaction occurs by two different mechanisms, first with the formation of relatively large CD clusters along the double helix, which thereafter can locally denature the DNA molecule by forming hydrogen bonds with the base pairs that eventually flip out. A prediction of our quenched disorder model was that cooperativity could be controlled by adjusting the surface charge of β-CD molecules. This prediction is confirmed in the present work.

Force-dependent persistence length of DNA-intercalator complexes measured in single molecule stretching experiments

By using optical tweezers with an adjustable trap stiffness, we have performed systematic single molecule stretching experiments with two types of DNA-intercalator complexes, in order to investigate the effects of the maximum applied forces on the mechanical response of such complexes. We have explicitly shown that even in the low-force entropic regime the persistence length of the DNA-intercalator complexes is strongly force-dependent, although such behavior is not exhibited by bare DNA molecules. We discuss the possible physicochemical effects that can lead to such results. In particular, we propose that the stretching force can promote partial denaturation on the highly distorted double-helix of the DNA-intercalator complexes, which interfere strongly in the measured values of the persistence length.

Extracting physical chemistry from mechanics: a new approach to investigate DNA interactions with drugs and proteins in single molecule experiments

In this review we focus on the idea of establishing connections between the mechanical properties of DNA–ligand complexes and the physical chemistry of DNA–ligand interactions.

Gastroenteric virus dissemination and influence of rainfall events in urban beaches in Brazil

AIMS

This study was conducted to assess rotavirus A (RV-A), genogroup II (GII) norovirus (NoV), and human adenovirus (HAdV) dissemination in recreational water in an urban beach located in the city of Rio de Janeiro and their persistence during rainfall events.

METHODS AND RESULTS

Viruses, including bacteriophage (PP7), used as internal control, were concentrated, reverse transcribed and quantified by a low-cost method based on organic flocculation with skimmed milk coupled with quantitative polymerase chain reaction protocols. The analysis of 74 superficial water samples obtained during 6 months of monitoring detected HAdV (66%), RV-A (37%) and GII NoV (14%), with a mean viral load of 4·1 log10 genome copies l(-1) (g.c. l(-1) ), 4·3 log10 g.c l(-1) and 3·8 log10 g.c. l(-1) , respectively. Investigation of those viruses during two rainfall events showed a longer permanence after rainfall events compared with bacterial indicators.

CONCLUSIONS

The results highlight the need for further monitoring using viral parameters to determine the microbiological quality of recreational waters to allow bath in these waters, especially during rainy events.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides data on virus contamination in recreational waters on tourist beaches frequented throughout the year, emphasizing the importance of viral parameters for assessing microbiological quality of water, as well as the potential risk of waterborne infections.

On the effects of intercalators in DNA condensation: a force spectroscopy and gel electrophoresis study

In this work we have characterized the effects of the intercalator ethidium bromide (EtBr) on the DNA condensation process by using force spectroscopy and gel electrophoresis. We have tested two condensing agents: spermine (spm(4+)), a tetravalent cationic amine which promotes cation-induced DNA condensation, and poly(ethylene glycol) (PEG), a neutral polymer which promotes DNA ψ-condensation. Two different types of experiments were performed. In the first type, bare DNA molecules disperse in solution are first treated with EtBr for intercalation, and then the condensing agent is added to the sample with the purpose of verifying the effects of the intercalator in hindering DNA condensation. In the second experiment type, the bare DNA molecules are first condensed, and then the intercalator is added to the sample in order to verify its influence on the previously condensed DNA. The results obtained with the two different experimental techniques used agree very well, indicating that previously intercalated EtBr can hinder both cation-induced and ψ-condensation, being more efficient in the first case. On the other hand, EtBr has little effect on the previously formed cation-induced condensates, but is efficient in unfolding the ψ-condensates.

Combined hepato-cholangiocarcinoma arising in a gallbladder intracystic papillary neoplasm. A new view on so-called "hepatoid adenocarcinoma of the gallbladder"

A 62-year-old female presented with abdominal pain, weight loss of 20 kg in the prior 6 months, and a palpable mass in the right upper quadrant during physical exam. Standard liver tests, including screening for hepatitis B and C and alpha-fetoprotein were negative or within normal limits. Computerized tomography depicted a transmural gallbladder tumor infiltrating into the adjacent liver with an irregular ill-defined mass occupying segments IV-V-VI, measuring 13.0 x 9.2 x 8.5 cm, with a solid-cystic component and heterogeneous captation of endovenous contrast media. Complete surgical resection of the neoplasm was achieved through an extended cholecystectomy and excision of hepatic segments IV, V and VI, with an uneventful follow-up 29 months until now. Morphological and immunohistochemical assessment favored a diagnosis of combined hepatocellular-cholangiocarcinoma arising in a gallbladder intracystic papillary neoplasm with invasive carcinoma. This case raises the hypothesis that the so-called "hepatoid adenocarcinoma of the gallbladder" may presently be better understood as a neoplasm derived from hepatobiliary stem/progenitor cells. Such cells have been recognized in the canals of Hering, in peribiliary glands within the liver and in the extrahepatic biliary tree, and in gallbladder mucosa.

Quantitative assessment of the interplay between DNA elasticity and cooperative binding of ligands

Binding of ligands to DNA can be studied by measuring the change of the persistence length of the complex formed, in single-molecule assays. We propose a methodology for persistence length data analysis based on a quenched disorder statistical model and describing the binding isotherm by a Hill-type equation. We obtain an expression for the effective persistence length as a function of the total ligand concentration, which we apply to our data of the DNA-cationic β-cyclodextrin and to the DNA-HU protein data available in the literature, determining the values of the local persistence lengths, the dissociation constant, and the degree of cooperativity for each set of data. In both cases the persistence length behaves nonmonotonically as a function of ligand concentration and based on the results obtained we discuss some physical aspects of the interplay between DNA elasticity and cooperative binding of ligands.

Furosemide is associated with acute kidney injury in critically ill patients

Acute kidney injury (AKI) is common in critically ill patients. Diuretics are used without any evidence demonstrating a beneficial effect on renal function. The objective of the present study is to determine the incidence of AKI in an intensive care unit (ICU) and if there is an association between the use of furosemide and the development of AKI. The study involved a hospital cohort in which 344 patients were consecutively enrolled from January 2010 to January 2011. A total of 132 patients (75 females and 57 males, average age 64 years) remained for analysis. Most exclusions were related to ICU discharge in the first 24 h. Laboratory, sociodemographic and clinical data were collected until the development of AKI, medical discharge or patient death. The incidence of AKI was 55% (95%CI = 46-64). The predictors of AKI found by univariate analysis were septic shock: OR = 3.12, 95%CI = 1.36-7.14; use of furosemide: OR = 3.27, 95%CI = 1.57-6.80, and age: OR = 1.02, 95%CI = 1.00-1.04. Analysis of the subgroup of patients with septic shock showed that the odds ratio of furosemide was 5.5 (95%CI = 1.16-26.02) for development of AKI. Age, use of furosemide, and septic shock were predictors of AKI in critically ill patients. Use of furosemide in the subgroup of patients with sepsis/septic shock increased (68.4%) the chance of development of AKI when compared to the sample as a whole (43.9%)

Angiotensin II-induced JNK activation is mediated by NAD(P)H oxidase in isolated rat pancreatic islets

Angiotensin II (AII), the active component of the renin angiotensin system (RAS), plays a vital role in the regulation of physiological processes of the cardiovascular system, but also has autocrine and paracrine actions in various tissues and organs. Many studies have shown the existence of RAS in the pancreas of humans and rodents. The aim of this study was to evaluate potential signaling pathways mediated by AII in isolated pancreatic islets of rats. Phosphorylation of MAPKs (ERK1/2, JNK and p38MAPK), and the interaction between proteins JAK/STAT were evaluated. AII increased JAK2/STAT1 (42%) and JAK2/STAT3 (100%) interaction without altering the total content of JAK2. Analyzing the activation of MAPKs (ERK1/2, JNK and p38MAPK) in isolated pancreatic islets from rats we observed that AII rapidly (3 min) promoted a significant increase in the phosphorylation degree of these proteins after incubation with the hormone. Curiously JNK protein phosphorylation was inhibited by DPI, suggesting the involvement of NAD(P)H oxidase in the activation of protein.

Cellular hypomethylation is associated with impaired nitric oxide production by cultured human endothelial cells

Hyperhomocysteinemia (HHcy) is a risk factor for vascular disease, but the underlying mechanisms remain incompletely defined. Reduced bioavailability of nitric oxide (NO) is a principal manifestation of underlying endothelial dysfunction, which is an initial event in vascular disease. Inhibition of cellular methylation reactions by S-adenosylhomocysteine (AdoHcy), which accumulates during HHcy, has been suggested to contribute to vascular dysfunction. However, thus far, the effect of intracellular AdoHcy accumulation on NO bioavailability has not yet been fully substantiated by experimental evidence. The present study was carried out to evaluate whether disturbances in cellular methylation status affect NO production by cultured human endothelial cells. Here, we show that a hypomethylating environment, induced by the accumulation of AdoHcy, impairs NO production. Consistent with this finding, we observed decreased eNOS expression and activity, but, by contrast, enhanced NOS3 transcription. Taken together, our data support the existence of regulatory post-transcriptional mechanisms modulated by cellular methylation potential leading to impaired NO production by cultured human endothelial cells. As such, our conclusions may have implications for the HHcy-mediated reductions in NO bioavailability and endothelial dysfunction.

Effects of ursodeoxycholic acid in esophageal motility and the role of the mucosa. An experimental study

Esophageal motor abnormalities are frequently found in patients with gastroesophageal reflux disease. The role of bile in reflux-induced dysmotility is still elusive. Furthermore, it is questionable weather mucosal or muscular stimulation leads to motor dysfunction. The aims of this study were to analyze (i) the effect of bile in the amplitude of esophageal contractions; and (ii) the effect of mucosal versus muscular stimulation. Eighteen guinea pig esophagi were isolated, and its contractility assessed with force transducers. Three groups were studied. In group A (n= 6), the entire esophagus was incubated in 100 µmL ursodeoxycholic acid for 1 hour; in group B (n= 6) the mucosal layer was removed and the muscular layer incubated in 100 µmL ursodeoxycholic acid for 1 hour; and in group C (n= 6) (control group) the entire esophagus was incubated in saline solution. In all groups, five sequential contractions induced by 40 mm KCl spaced by 5 minutes were measured before and after incubation. Contractions amplitudes before incubation were 1.319 g, 0.306 g, and 1.795 g, for groups A, B, and C, respectively. There were no differences between groups A and C (P= 0.633), but there were differences between groups A and B (P= 0.039), and B and C (P= 0.048). After incubation amplitude of contraction were 0.709 g, 0.278 g, and 1.353 g for groups A, B, and C, respectively. Only group A showed difference when pre and post-stimulation amplitudes were compared (P= 0.030). Our results show that (i) bile exposure decreases esophageal contraction amplitude; and (ii) the esophageal mucosa seems to play an important role in esophageal motility.

Association of NAD(P)H oxidase with glucose-induced insulin secretion by pancreatic beta-cells

We previously described the presence of nicotinamide adenine dinucleotide phosphate reduced form [NAD(P)H]oxidase components in pancreatic beta-cells and its activation by glucose, palmitic acid, and proinflammatory cytokines. In the present study, the importance of the NAD(P)H oxidase complex for pancreatic beta-cell function was examined. Rat pancreatic islets were incubated in the presence of glucose plus diphenyleneiodonium, a NAD(P)H oxidase inhibitor, for 1 h or with the antisense oligonucleotide for p47(PHOX) during 24 h. Reactive oxygen species (ROS) production was determined by a fluorescence assay using 2,7-dichlorodihydrofluorescein diacetate. Insulin secretion, intracellular calcium responses, [U-(14)C]glucose oxidation, and expression of glucose transporter-2, glucokinase and insulin genes were examined. Antisense oligonucleotide reduced p47(PHOX) expression [an important NAD(P)H oxidase cytosolic subunit] and similarly to diphenyleneiodonium also blunted the enzyme activity as indicated by reduction of ROS production. Suppression of NAD(P)H oxidase activity had an inhibitory effect on intracellular calcium responses to glucose and glucose-stimulated insulin secretion by isolated islets. NAD(P)H oxidase inhibition also reduced glucose oxidation and gene expression of glucose transporter-2 and glucokinase. These findings indicate that NAD(P)H oxidase activation plays an important role for ROS production by pancreatic beta-cells during glucose-stimulated insulin secretion. The importance of this enzyme complex for the beta-cell metabolism and the machinery involved in insulin secretion were also shown.

Topographic trace-elemental analysis in the brain of Wistar rats by X-ray microfluorescence with synchrotron radiation

Knowledge about the spatial distribution and the local concentration of trace elements in tissues is of great importance, since trace elements are involved in many biological functions of living organisms. However, there are few methods available to measure the spatial (two (three)-dimensional) elemental distribution in animal brain. X-ray microfluorescence with synchrotron radiation is a multielemental mapping technique, which was used in this work to determine the topographic of iron, zinc and copper in coronal sections of female Wistar rats of different ages. Young (14 days old) and middle-aged (20 months old) rats (n = 8) were analyzed. The measurements were carried out at the XRF beam line at the Synchrotron Light National Laboratory (Campinas, Brazil). Two-dimensional scanning was performed in order to study the tendency of elemental concentration variation. The acquisition time for each pixel was 10 s/step and the step size was 300 microm/step in both directions. It was observed that the iron distribution was more conspicuous in the cortical area, thalamus and bellow the thalamus. On the other hand, the zinc distribution was more pronounced in the hippocampus. The iron, copper and zinc levels increased with advancing age. Therefore, this study reinforces the idea that these elements are involved in the chemical mechanisms of the brain that induce some neurological diseases, since they are also present in high levels in specific areas of the brain, such as the hippocampus and the substantia nigra of patients with these disorders.

Ethanol bone evaluation using 3D microtomography

The study of trabecular structures is important for understanding the mechanism of alcohol related to bone changes. Alcohol consumption can compromise the body mineral composition, affecting the bone metabolism and compromising the skeleton. The effects of the ethanol treatment on the internal microarchitecture of bone samples through 3D microcomputed tomography are shown in this study. The data was acquired from a radiographic system with a micro focus X-ray conic beam and it was used the Feldkamp's technique was used to carry out the 3D reconstructions. The measured microstructure parameters, which were based on stereological concepts, were bone volume fraction, relationship between bone surface and volume, trabecular number, separation and thickness. The results show that this technique is able to analyze these kinds of structures, especially rat bone, as these structures in rats (trabecular diameter) are thinner than in human bones.

Transition on the entropic elasticity of DNA induced by intercalating molecules

We use optical tweezers to perform stretching experiments on DNA molecules when interacting with the drugs daunomycin and ethidium bromide, which intercalate the DNA molecule. Our results show that the persistence length of the DNA-drug complexes increases strongly as the drug concentration increases up to some critical value. Above this critical value, the persistence length decreases abruptly and remains approximately constant for larger drug concentrations, at least in the concentration range used in our experiments. Measured intercalators critical concentrations for the persistence length transition coincide with the reported values for the helix-coil transition of DNA-drug complexes obtained from sedimentation experiments. The contour length of the molecules increases monotonically and saturates as the drug concentration increases. The neighbor exclusion model fits to our results for the total drug concentration as a function of the relative increase of the contour length.

Towards absolute calibration of optical tweezers

Aiming at absolute force calibration of optical tweezers, following a critical review of proposed theoretical models, we present and test the results of Mie-Debye-spherical aberration (MDSA) theory, an extension of a previous (MD) model, taking account of spherical aberration at the glass-water interface. This first-principles theory is formulated entirely in terms of experimentally accessible parameters (none adjustable). Careful experimental tests of the MDSA theory, undertaken at two laboratories, with very different setups, are described. A detailed description is given of the procedures employed to measure laser beam waist, local beam power at the transparent microspheres trapped by the tweezers, microsphere radius, and the trap transverse stiffness, as a function of radius and height in the (inverted microscope) sample chamber. We find generally very good agreement with MDSA theory predictions, for a wide size range, from the Rayleigh domain to large radii, including the values most often employed in practice, and at different chamber heights, both with objective overfilling and underfilling. The results asymptotically approach geometrical optics in the mean over size intervals, as they should, and this already happens for size parameters not much larger than unity. MDSA predictions for the trapping threshold, position of stiffness peak, stiffness variation with height, multiple equilibrium points, and "hopping" effects among them are verified. Remaining discrepancies are ascribed to focus degradation, possibly arising from objective aberrations in the infrared, not yet included in MDSA theory.

DNA-psoralen interaction: a single molecule experiment

By attaching one end of a single lambda-DNA molecule to a microscope coverslip and the other end to a polystyrene microsphere trapped by an optical tweezers, we can study the entropic elasticity of the lambda-DNA by measuring force versus extension as we stretch the molecule. This powerful method permits single molecule studies. We are particularly interested in the effects of the photosensitive drug psoralen on the elasticity of the DNA molecule. We have illuminated the sample with different light sources, studying how the different wavelengths affect the psoralen-DNA linkage. To do this, we measure the persistence length of individual DNA-psoralen complexes.

Characterization of objective transmittance for optical tweezers

We have measured the overall transmittance of a laser beam through an oil immersion objective as a function of the transverse size of the laser beam, using the dual-objective method. Our results show that the objective transmittance is not uniform and that its dependence on the radial beam's position can be modeled by a Gaussian function. This property affects the intensity distribution pattern in the sample region and should be taken into account in theoretical descriptions of optical tweezers. Moreover, one must consider this position dependence to determine the local laser power delivered at the sample region by the dual-objective method, especially when the beam overfills the objective's back entrance. If the transmittance is assumed to be uniform, the local power is overestimated.

Low bone density and low serum levels of soluble RANK ligand are associated with severe arterial calcification in patients with Takayasu arteritis

OBJECTIVE

Takayasu arteritis (TA) is a chronic inflammatory disorder affecting the aorta and its branches. Vascular calcification has been described in 29-54% of cases of TA, although its aetiology remains unknown. Recently the osteoprotegerin/RANKL/RANK system has emerged as an important contributing factor to atherogenesis and osteogenesis. Our aim is to investigate the association between vascular calcification, bone mineral density (BMD) and the osteoprotegerin/RANK/RANKL system in TA.

METHODS

Thirty pre-menopausal female TA patients and 30 age- and sex-matched controls were studied. BMD was measured by dual X-ray absorptiometry. Arterial calcification in TA patients was analysed by computed tomography in thoracic and abdominal sites. Serum levels of osteoprotegerin and soluble receptor activator of nuclear factor kappaB ligand (sRANKL) were quantified by enzyme-linked immunosorbent assay.

RESULTS

Patients with severe arterial calcification showed lower BMD values than controls in lumbar spine (0.965 +/- 0.055 vs 1.126 +/- 0.153 g/cm2, P = 0.009) and total body (0.993 +/- 0.065 vs 1.085 +/- 0.082 g/cm2, P = 0.019). In contrast, TA patients without calcification presented BMD values similar to controls (P > 0.05). Interestingly, lower serum levels of sRANKL (1.89 +/- 2.35 vs 2.80 +/- 2.23 pg/ml, P = 0.031) and a longer disease duration (12.20 +/- 6.61 vs 3.56 +/- 5.33 yr, P = 0.004) were observed in TA patients with severe calcification compared with patients without calcification.

CONCLUSIONS

Severe arterial calcification in TA is associated with low values of BMD and sRANKL, reinforcing the possible link between bone and vascular disease.

[Cerebral vasculitis and Basedow-Graves disease: report of two cases]

OBJECTIVE

To report two cases of patients with cerebral vasculitis and Basedow-Graves disease.

CASE REPORT

Two young female patients presented at emergency with acute neurological picture of hemiparesis and speech distress. The first patient, 22 year-old, has been on clinical treatment for hyperthyroidism for one month. On clinical examination she had an elevated cardiac rate, bilateral exophthalmia and a diffuse goiter. On neurological examination we could observe a mild dysarthria and left hemiparesis. The second patient was a 15 year-old girl, who presented sudden conscious loss, aphasia and right hemiparesis.

RESULTS

CT scan and MRI showed areas of cerebral infarcts. Angiographic study showed multiple vascular stenosis similar to an arteritic angiographic pattern. Extensive medical and laboratorial workout disclosed no other risk factor for stroke or for nervous system vasculitis. The antimicrosomal and antithyreoglobulin antibodies were positive and thyroidian hormones confirmed hyperthyroidism.

CONCLUSION

The concurrence of cerebral arteritis and Basedow-Graves' disease suggest a possible pathogenic link between Graves' disease and specific cerebral vascular disorders, possibly through a common autoimmune mechanism.

[Relapsing polychondritis associated with meningoencephalitis: case report]

Polychondritis is a disease manifesting as an episodic inflammation of cartilagenous structures throughout the body with progressive course. We describe a patient with a presentation picture of two episodes of meningoencephalitis and after the outcome with polychondritis. Neurological involvement is rare in this disease as neurologic presenting symptoms do. The diagnostic precision was determinant for a satisfactory outcome with corticosteroids and methotrexate.