54101
|
Lietz M, Ullrich A, Schulte-Eversum C, Oberhoffner S, Fricke C, Müller HW, Schlosshauer B. Physical and biological performance of a novel block copolymer nerve guide. Biotechnol Bioeng 2005; 93:99-109. [PMID: 16187339 DOI: 10.1002/bit.20688] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Although the ability to regenerate is evident in the nervous system, lesioned neurites are unable to cross gaps in neuronal pathways. In order to bridge gaps, guiding cues are essential to direct neurite regrowth. To overcome many of the shortcomings of polymer-based nerve guides, we developed a bioresorbable nerve guide composed of a novel trimethylene carbonate-caprolacton block copolymer (TMC-CL). Pore formation was controlled by using special solvent/precipitation media compositions in combination with the pore forming agent poly ethylene glycol (PEG). NMR spectroscopy, shear force-, compression-, and permeation assays were used for conduit characterization. The polymer conduit has a semipermeable wall with submicron pores to allow free metabolite/drug exchange. In order to investigate the principle of temporally controlled expression of therapeutic proteins in nerve guides, Neuro-2a cells were genetically engineered to express the reporter gene product green fluorescent protein (GFP) under the control of the Tet-On system. When these transduced cells were encapsulated in nerve guides, GFP expression could be induced for days by adding the antibiotic tetracycline derivative doxycycline to the nerve guide environment. Furthermore, encapsulated dorsal root ganglia (DRG) produced long neurites in vitro. In subsequent in vivo experiments, nerve guides filled with Schwann cells (SC) were implanted into lesioned spinal cords of adult rats. Regeneration of spinal cord axons into nerve guides was promoted by co-implanted Schwann cells. The data suggest that the novel TMC-CL nerve guides provide a promising tool for neuroregeneration.
Collapse
Affiliation(s)
- M Lietz
- NMI Naturwissenschaftliches und Medizinisches Institut an der Universität Tübingen Markwiesenstr, 55, D-72770 Reutlingen, Germany
| | | | | | | | | | | | | |
Collapse
|
54102
|
Polymer cell culture substrates with combined nanotopographical patterns and micropatterned chemical domains. ACTA ACUST UNITED AC 2005. [DOI: 10.1116/1.2127951] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
54103
|
Galloni P, Lovisolo GA, Mancini S, Parazzini M, Pinto R, Piscitelli M, Ravazzani P, Marino C. Effects of 900 MHz electromagnetic fields exposure on cochlear cells' functionality in rats: Evaluation of distortion product otoacoustic emissions. Bioelectromagnetics 2005; 26:536-47. [PMID: 16037958 DOI: 10.1002/bem.20127] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In recent years, the widespread use of mobile phones has been accompanied by public debate about possible adverse consequences on human health. The auditory system is a major target of exposure to electromagnetic fields (EMF) emitted by cellular telephones; the aim of this study was the evaluation of possible effects of cellular phone-like emissions on the functionality of rat's cochlea. Distortion Products OtoAcoustic Emission (DPOAE) amplitude was selected as cochlea's outer hair cells (OHC) status indicator. A number of protocols, including different frequencies (the lower ones in rat's cochlea sensitivity spectrum), intensities and periods of exposure, were used; tests were carried out before, during and after the period of treatment. No significant variation due to exposure to microwaves has been evidenced.
Collapse
Affiliation(s)
- Paolo Galloni
- Toxicology and Biomedical Sciences Unit, Enea Casaccia, Rome, Italy.
| | | | | | | | | | | | | | | |
Collapse
|
54104
|
Keinan-Adamsky K, Shinar H, Navon G. The effect of detachment of the articular cartilage from its calcified zone on the cartilage microstructure, assessed by 2H-spectroscopic double quantum filtered MRI. J Orthop Res 2005; 23:109-17. [PMID: 15607882 DOI: 10.1016/j.orthres.2004.06.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2004] [Indexed: 02/04/2023]
Abstract
Most studies on articular cartilage properties have been conducted after detachment of the cartilage from the bone. In the present work we investigated the effect of detachment on collagen fiber architecture. We used one-dimensional (2)H double quantum filtered MRI on cartilage bone plugs equilibrated in deuterated saline. The quadrupolar splittings observed in the different zones were related to the degree of order and the density of the collagen fibers. The method is non-destructive, allowing for measurements on the same plug without the need for fixation, dehydration, sectioning and decalcification. Detachment of the radial from the calcified zone resulted in swelling of the cartilage plug in physiological saline and a concomitant decrease in the quadrupolar splitting. The effect of mechanical pressure on the (2)H quadrupolar splittings for the detached cartilage and for the calcified zone-bone plugs were compared with those of the same zones in the intact cartilage-bone plug. The splitting in the radial zone of the detached cartilage collapsed at much smaller loads compared to the intact cartilage-bone plug. The effect of the load on the size of the cartilage was also greater for the detached plug. These results indicate that anchoring of the cartilage to the bone through the calcified zone plays an important role in retaining the order of the collagen fibers. The water (2)H quadrupolar splitting in intact and proteoglycan-depleted cartilage was the same, indicating that the proteoglycans do not contribute to the ordering of the collagen fibers.
Collapse
|
54105
|
|
54106
|
Muraki S, Kita Y. A survey of medical applications of 3D image analysis and computer graphics. ACTA ACUST UNITED AC 2005. [DOI: 10.1002/scj.20393] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
54107
|
Sviridov A, Chernomordik V, Hassan M, Russo A, Eidsath A, Smith P, Gandjbakhche AH. Intensity profiles of linearly polarized light backscattered from skin and tissue-like phantoms. JOURNAL OF BIOMEDICAL OPTICS 2005; 10:14012. [PMID: 15847593 DOI: 10.1117/1.1854677] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Anisotropy of mouse and human skin is investigated in vivo using polarized videoreflectometry. An incident beam (linearly polarized, wavelength 650 nm) is focused at the sample surface. Two types of tissuelike media are used as controls to verify the technique: isotropic delrin and highly anisotropic demineralized bone with a priori knowledge of preferential orientation of collagen fibers. Equi-intensity profiles of light, backscattered from the sample, are fitted with ellipses that appear to follow the orientation of the collagen fibers. The ratio of the ellipse semiaxes is well correlated with the ratio of reduced scattering coefficients obtained from radial intensity distributions. Variation of equi-intensity profiles with distance from the incident beam is analyzed for different initial polarization states of the light and the relative orientation of polarization filters for incident and backscattered light. For the anisotropic media (demineralized bone and human and mouse skin), a qualitative difference between intensity distributions for cross- and co-polarized orientations of the polarization analyzer is observed up to a distance of 1.5 to 2.5 mm from the entry point. The polarized videoreflectometry of the skin may be a useful tool to assess skin fibrosis resulting from radiation treatment.
Collapse
Affiliation(s)
- Alexander Sviridov
- National Institutes of Health, National Institute of Child Health and Human Development, Bethesda, Maryland 20892-0924, USA
| | | | | | | | | | | | | |
Collapse
|
54108
|
Laib S, Krieg A, Häfliger P, Agorastos N. DNA-intercalation on pyrene modified surface coatings. Chem Commun (Camb) 2005:5566-8. [PMID: 16358065 DOI: 10.1039/b511716j] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Utilising the strong affinity between nucleic acids and an intercalating pyrene derivate, a novel efficient method for unspecific immobilisation of double-stranded DNA on to solid support for applications in bioanalytic, biophysics and microbiology is presented.
Collapse
Affiliation(s)
- Stephan Laib
- Institute for Physical Chemistry, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland.
| | | | | | | |
Collapse
|
54109
|
Wang K, Xu JJ, Chen HY. A novel glucose biosensor based on the nanoscaled cobalt phthalocyanine–glucose oxidase biocomposite. Biosens Bioelectron 2005; 20:1388-96. [PMID: 15590294 DOI: 10.1016/j.bios.2004.06.006] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2004] [Revised: 06/04/2004] [Accepted: 06/09/2004] [Indexed: 11/19/2022]
Abstract
We report on the utilization of a novel nanoscaled cobalt phthalocyanine (NanoCoPc)-glucose oxidase (GOD) biocomposite colloid to create a highly responsive glucose biosensor. The biocomposite colloid is constructed under enzyme-friendly conditions by adsorbing GOD molecules on CoPc nanoparticles via electrostatic interactions. The glucose biosensor can be easily achieved by casting the biocomposite colloid on a pyrolytic graphite electrode (PGE) without any auxiliary matter. It has been found that GOD can be firmly immobilized on PGE surface and maintain its bioactivity after conjugating with NanoCoPc. NanoCoPc displays intrinsic electrocatalytic ability to the oxidation of the product of enzymatic reaction H2O2 and shows a higher catalytic activity than that of bulk CoPc. Under optimal conditions, the biosensor shows a wide linear response to glucose in the range of 0.02-18 mM, with a fast response (5s), high sensitivity (7.71 microA cm(-2) mM(-1)), as well as good thermostability and long-term life. The detection limit was 5 microM at 3 sigma. The general interferences coexisted in blood except ascorbic acid and L-cysteine do not affect glucose determination, and further coating Nafion film on the surface of the biosensor can effectively eliminate the interference from ascorbic acid and L-cysteine. The biosensor with Nafion film has been used for the determination of glucose in serum with an acceptable accuracy.
Collapse
Affiliation(s)
- Kun Wang
- The Laboratory of Life Analytical Chemistry, Department of Chemistry, Nanjing University, 22 Hankou Road, Nanjing 210093, PR China
| | | | | |
Collapse
|
54110
|
Rudin M, Beckmann N, Rausch M. Evaluation of drug candidates: efficacy readouts during lead optimization. PROGRESS IN DRUG RESEARCH. FORTSCHRITTE DER ARZNEIMITTELFORSCHUNG. PROGRES DES RECHERCHES PHARMACEUTIQUES 2005; 62:185-255. [PMID: 16329258 DOI: 10.1007/3-7643-7426-8_6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Affiliation(s)
- Markus Rudin
- Institute for Biomedical Engineering, University of Zurich/ETH Zurich, Switzerland.
| | | | | |
Collapse
|
54111
|
Abstract
Accurate, fast, and affordable analysis of the cellular component of blood is of prime interest for medicine and research. Yet, most often sample preparation procedures for blood analysis involve handling steps prone to introducing artifacts, whereas analysis methods commonly require skilled technicians and well-equipped, expensive laboratories. Developing more gentle protocols and affordable instruments for specific blood analysis tasks is becoming possible through the recent progress in the area of microfluidics and lab-on-a-chip-type devices. Precise control over the cell microenvironment during separation procedures and the ability to scale down the analysis to very small volumes of blood are among the most attractive capabilities of the new approaches. Here we review some of the emerging principles for manipulating blood cells at microscale and promising high-throughput approaches to blood cell separation using microdevices. Examples of specific single-purpose devices are described together with integration strategies for blood cell separation and analysis modules.
Collapse
Affiliation(s)
- Mehmet Toner
- BioMEMS Resource Center, Center for Engineering in Medicine and Surgical Services, Massachusetts General Hospital, Shriners Hospital for Children, and Harvard Medical School, Boston, Massachusetts 02114
| | - Daniel Irimia
- BioMEMS Resource Center, Center for Engineering in Medicine and Surgical Services, Massachusetts General Hospital, Shriners Hospital for Children, and Harvard Medical School, Boston, Massachusetts 02114
| |
Collapse
|
54112
|
Lutolf MP, Hubbell JA. Synthetic biomaterials as instructive extracellular microenvironments for morphogenesis in tissue engineering. Nat Biotechnol 2005; 23:47-55. [PMID: 15637621 DOI: 10.1038/nbt1055] [Citation(s) in RCA: 3039] [Impact Index Per Article: 159.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
New generations of synthetic biomaterials are being developed at a rapid pace for use as three-dimensional extracellular microenvironments to mimic the regulatory characteristics of natural extracellular matrices (ECMs) and ECM-bound growth factors, both for therapeutic applications and basic biological studies. Recent advances include nanofibrillar networks formed by self-assembly of small building blocks, artificial ECM networks from protein polymers or peptide-conjugated synthetic polymers that present bioactive ligands and respond to cell-secreted signals to enable proteolytic remodeling. These materials have already found application in differentiating stem cells into neurons, repairing bone and inducing angiogenesis. Although modern synthetic biomaterials represent oversimplified mimics of natural ECMs lacking the essential natural temporal and spatial complexity, a growing symbiosis of materials engineering and cell biology may ultimately result in synthetic materials that contain the necessary signals to recapitulate developmental processes in tissue- and organ-specific differentiation and morphogenesis.
Collapse
Affiliation(s)
- M P Lutolf
- Integrative Biosciences Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Building AA-B 039, CH-1015 Lausanne, Switzerland.
| | | |
Collapse
|
54113
|
Engelmayr GC, Rabkin E, Sutherland FWH, Schoen FJ, Mayer JE, Sacks MS. The independent role of cyclic flexure in the early in vitro development of an engineered heart valve tissue. Biomaterials 2005; 26:175-87. [PMID: 15207464 DOI: 10.1016/j.biomaterials.2004.02.035] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2003] [Accepted: 02/09/2004] [Indexed: 11/25/2022]
Abstract
Tissue engineered heart valves (TEHV) are being investigated as an alternative to current non-viable prosthetic valves and valved conduits. Studies suggest that pulse duplicator bioreactors can stimulate TEHV development. In the current study, a model system was used to determine if cyclic flexure, a major mode of heart valve deformation, has independent effects on TEHV cell and extracellular matrix (ECM) development. Ovine vascular smooth muscle cells (SMC) were seeded for 30 h onto strips of non-woven 50:50 polyglycolic acid (PGA) and poly-L-lactic acid (PLLA) scaffold. After 4 days of incubation, SMC-seeded and unseeded scaffolds were either maintained under static conditions (static group), or subjected to unidirectional cyclic three-point flexure at a physiological frequency and amplitude in a bioreactor (flex group) for 3 weeks. After seeding or incubation, the effective stiffness (E) was measured, with SMC-seeded scaffolds further characterized by DNA, collagen, sulfated glycosaminoglycan (S-GAG), and elastin content, as well as by histology. The seeding period was over 90% efficient, with a significant accumulation of S-GAG, no significant change in E, and no collagen detected. Following 3 weeks of incubation, unseeded scaffolds exhibited no significant change in E in the flex or static groups. In contrast, E of SMC-seeded scaffolds increased 429% in the flex group (p<0.01) and 351% in the static group (p<0.01), with a trend of increased E, a 63% increase in collagen (p<0.05), increased vimentin expression, and a more homogenous transmural cell distribution in the flex versus static group. Moreover, a positive linear relationship (r2=0.996) was found between the mean E and mean collagen concentration. These results show that cyclic flexure can have independent effects on TEHV cell and ECM development, and may be useful in predicting the mechanical properties of TEHV constructed using novel scaffold materials.
Collapse
Affiliation(s)
- George C Engelmayr
- Engineered Tissue Mechanics Laboratory, McGowan Institute for Regenerative Medicine and the Department of Bioengineering, University of Pittsburgh, 100 Technology Drive, Suite 200, Pittsburgh, PA 15219, USA
| | | | | | | | | | | |
Collapse
|
54114
|
Dailey LA, Wittmar M, Kissel T. The role of branched polyesters and their modifications in the development of modern drug delivery vehicles. J Control Release 2005; 101:137-49. [PMID: 15588900 DOI: 10.1016/j.jconrel.2004.09.003] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2004] [Accepted: 09/16/2004] [Indexed: 11/16/2022]
Abstract
Branched polyesters consisting of poly (vinyl alcohol) (PVA) grafted with chains of poly (lactic-co-glycolic acid) (PLGA) represent a new class of biodegradable polymers showing significant potential for the development of a variety of drug delivery vehicles. The amphiphilic character and the resulting increase in hydrophilicity of this class of polymers provide advantages when packaging sensitive drug molecules, such as proteins, peptides or DNA. Furthermore, the PVA backbone can be modified, for example, with sulfobutyl moieties or amine structures, to create polymers with negative or positive charges. The ability to modify not only the backbone but also the length of the PLGA side chains results in an extremely flexible polymer system, which can be adapted to meet the needs of almost any drug substance. Further, the rate of biodegradation may also be manipulated through polymer modification to achieve half-lives ranging from several hours to several weeks. This review provides an overview of the three major groups of branched polyesters based upon poly (vinyl alcohol)-grafted poly (lactic-co-glycolic acid) (PVA-g-PLGA), namely, the neutrally charged PVA-g-PLGA, the negatively charged sulfobutyl-modified PVA-g-PLGA and the positively charged amine-modified PVA-g-PLGA, as well as their use in various drug delivery systems.
Collapse
Affiliation(s)
- Lea Ann Dailey
- Department of Pharmaceutics and Biopharmacy, Philipps University Marburg, Ketzerbach 63, 35037 Marburg, Germany
| | | | | |
Collapse
|
54115
|
Mastrobattista E, Bravo SA, van der Aa M, Crommelin DJA. Nonviral gene delivery systems: From simple transfection agents to artificial viruses. DRUG DISCOVERY TODAY. TECHNOLOGIES 2005; 2:103-109. [PMID: 24981762 DOI: 10.1016/j.ddtec.2005.04.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The introduction of nucleic acids into cells for therapeutic intervention is greatly impeded by the size and charge of these molecules and therefore requires sophisticated vectors that facilitate cellular uptake. Both viral and nonviral vectors have been developed for this purpose, each with their own advantages and shortcomings. The engineering of artificial viruses by dismantling virus particles or incorporating viral features into nonviral vectors represents a novel strategy to combine "the best of both worlds".:
Collapse
Affiliation(s)
- Enrico Mastrobattista
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, P.O. Box 80082, 3508 TB Utrecht, The Netherlands.
| | - Silvina A Bravo
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, P.O. Box 80082, 3508 TB Utrecht, The Netherlands
| | - Marieke van der Aa
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, P.O. Box 80082, 3508 TB Utrecht, The Netherlands
| | - Daan J A Crommelin
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, P.O. Box 80082, 3508 TB Utrecht, The Netherlands
| |
Collapse
|
54116
|
Oh KT, Shim HM, Kim KN. Properties of titanium-silver alloys for dental application. J Biomed Mater Res B Appl Biomater 2005; 74:649-58. [PMID: 15806569 DOI: 10.1002/jbm.b.30259] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The purpose of this study was to develop titanium-silver alloys with biocompatibility, high corrosion resistance, and low ion-release rate, and to evaluate the electrochemical properties of titanium-silver alloys in artificial saliva. Titanium-silver alloys with silver contents ranging from 0 to 4.5 at % in steps of 0.5 at % were designed. The alloys were arc melted, homogenized at 950 degrees C for 72 h, hot rolled to 2 mm in thickness, and finally solution heat treated at 950 degrees C for 1 h and quenched in water. Chemical compositions, phases, hardnesses, electrochemical properties, and the cytotoxicity of the alloys were investigated. The purity of titanium-silver alloys was maintained above 99.9%, because few impurities were introduced through their manufacture. In the case of alloys containing silver in the range 2.0-4.0 at %, the formation of an acicular alpha phase was observed inside the beta phase. The acicular phase got thinner with increasing amounts of silver. This means that silver is a beta-phase stabilizing element in titanium-silver alloys. The hardness value tended to rise with increasing silver content and increased largely over 3.5 at %, and the increase of the hardness value versus pure titanium was about 33%. It is believed that the substantial increases in hardness was due to the effects of solid solution strengthening and of alpha-beta phase transition. Moreover, titanium-silver alloys had higher corrosion resistances than pure titanium. These results mean that silver additions to titanium can improve alloy corrosion resistance. Passive current densities in the potentiodynamic polarization curves were dependent on the chemical compositions of the titanium-silver alloys. However, they did not show a linear relationship with respect to silver contents. Titanium-silver alloys did not show pitting corrosion in artificial saliva. It is believed that silver addition to titanium strengthened the passive film due to titanium dissolution induced by the different electromotive forces of titanium and silver. In the agar overlay test, the cytotoxicity of the titanium-silver alloys and of titanium were none or mild. In summary, titanium-silver alloys had higher mechanical properties and corrosion resistance than titanium, and toxicities that were similar to titanium. Therefore, it is recommended that titanium-silver alloys be adopted cautiously by the biomedical and dental fields.
Collapse
Affiliation(s)
- Keun-Taek Oh
- Research Institute of Dental Biomaterials and Bioengineering, College of Dentistry, Yonsei University
| | | | | |
Collapse
|
54117
|
Hunter P, Smith N, Fernandez J, Tawhai M. Integration from proteins to organs: the IUPS Physiome Project. Mech Ageing Dev 2005; 126:187-92. [PMID: 15610778 DOI: 10.1016/j.mad.2004.09.025] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The IUPS Physiome Project is an internationally collaborative open source project intended to provide a public domain framework for computational physiology, including the development of modeling standards, computational tools and web-accessible databases of models of structure and function at all spatial scales and across all organ systems. Here, we illustrate the application of this multi-scale modeling approach to three organ systems: the heart, the lungs and the musculo-skeletal system, and in each case we show how the organ level models incorporate tissue and cell-level physiology. Although the computational physiology framework presented here does not yet incorporate models of ageing processes, the model-based approach is certainly capable of describing ageing and disease-related processes both via parameter changes within the models of normal physiological processes and via models of additional processes added to the framework.
Collapse
Affiliation(s)
- Peter Hunter
- Bioengineering Institute, University of Auckland, 70 Symonds Street, Auckland, New Zealand.
| | | | | | | |
Collapse
|
54118
|
Lopez-Poveda EA. Spectral processing by the peripheral auditory system: facts and models. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2005; 70:7-48. [PMID: 16472630 DOI: 10.1016/s0074-7742(05)70001-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Affiliation(s)
- Enrique A Lopez-Poveda
- Instituto de Neurociencias de Castilla y León, Universidad de Salamanca, Salamanca 37007, Spain
| |
Collapse
|
54119
|
Aucamp JP, Cosme AM, Lye GJ, Dalby PA. High-throughput measurement of protein stability in microtiter plates. Biotechnol Bioeng 2005; 89:599-607. [PMID: 15672379 DOI: 10.1002/bit.20397] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The direct determination of protein stability at high throughput has applications in proteomics, directed evolution, and formulation. Each application places different requirements on the accuracy of stability or transition midpoint determination. The measurement of protein stability by chemical denaturation has been previously performed at medium throughput and high accuracy using autotitrating fluorometers, after removal of proteins from the 96-well plate format in which they were expressed and purified. Herein we present a higher-throughput method for measuring and indexing the stability of proteins maintained within the 96-well format using a fluorescence microplate reader. Protein unfolding transitions were monitored by tryptophan fluorescence at 340 nm and assessed using bovine and equine cytochrome c (cyt c), as well as bovine serum albumin (BSA) stabilized with various amounts of palmitic acid. Two different approaches for generating unfolding curves in microtiter plates have been evaluated for their accuracy and applicability. Unfolding curves generated by the serial addition of denaturant into single wells allowed high-throughput stability screens capable of identifying protein variants with unfolding midpoint differences of 0.15 M denaturant concentration or larger. Such a method would be suitable for screening large numbers of proteins, as typically generated for directed evolution. Unfolding curves generated using one well per denaturant concentration allowed for medium-throughput stability screening and generated more accurate and precise stability values (C(1/2) +/- 0.05 M, m(G), and DeltaG(H2O)) for cyt c that are similar to values reported in literature. This method is suitable for screening the smaller numbers of proteins generated in proteomic research programmes. By using BSA stabilized with various palmitate concentrations and simple numerical indexing, it was shown that both experimental methods can successfully rank the order of protein stability.
Collapse
Affiliation(s)
- Jean P Aucamp
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, Torrington Place, London, WC1E 7JE, United Kingdom
| | | | | | | |
Collapse
|
54120
|
Henkelman RM, Chen XJ, Sled JG. Disease phenotyping: structural and functional readouts. PROGRESS IN DRUG RESEARCH. FORTSCHRITTE DER ARZNEIMITTELFORSCHUNG. PROGRES DES RECHERCHES PHARMACEUTIQUES 2005; 62:151-84. [PMID: 16329257 DOI: 10.1007/3-7643-7426-8_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Affiliation(s)
- R Mark Henkelman
- Mouse Imaging Centre (MICe), Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, Ontario, Canada MSG 1X8.
| | | | | |
Collapse
|
54121
|
Adams AM, Pratt SL, Stice SL. Knockdown of the Dnmt1s transcript using small interfering RNA in primary murine and bovine fibroblast cells. Mol Reprod Dev 2005; 72:311-9. [PMID: 16078273 DOI: 10.1002/mrd.20357] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
RNA interference (RNAi) has rapidly developed into one of the most widely applied technologies in molecular and cellular research, and although young, is now an essential experimental tool. The versatility of RNAi, especially in mammalian species, lends to its potential applications in a wide array of fields. Without having to genetically manipulate the genome, the ability to selectively reduce the level of a specific transcript using small interfering RNA (siRNA) molecules has great appeal in studying reprogramming issues in somatic cell nuclear transfer (SCNT) embryos. In such embryos, the aberrant expression of the somatic isoform of Dnmt1 (Dnmt1s), the enzyme responsible for maintaining DNA methylation in all somatic cells, has been implicated as one factor in the improper reprogramming of the donor genome. In the present study, the ability to develop a method allowing for the knockdown, or reduction, of Dnmt1s in primary fibroblast cells, like those commonly used as karyoplast donors in SCNT studies, was investigated in primary murine and bovine fibroblast cells as well as in a compromised cell line (NIH/3T3). Two Dnmt1s-specific siRNA candidates were designed and tested. Using optimized conditions, these siRNAs were transiently transfected into the cells with total RNA and nuclear protein being collected. A 56.5% knockdown in Dnmt1s was achieved in the compromised and primary murine cells whereas Dnmt1s was reduced by 15.4% in the primary bovine cells. A reduction in Dnmt1s mRNA did not correspond to a reduction in protein as determined by immunodetection of Western blots. Overall, this study demonstrated the ability of siRNA to knockdown Dnmt1s mRNA in primary fibroblast donor cells. In order to substantially increase the efficiency while decreasing the anomalies seen in SCNT, novel techniques, like the one proposed, are needed to assist the oocyte's ability to reprogram a differentiated genome.
Collapse
Affiliation(s)
- A M Adams
- Animal and Dairy Science Department, University of Georgia, 425 River Road, Athens, Georgia 30602, USA
| | | | | |
Collapse
|
54122
|
Natarajan A, Xiong CY, Albrecht H, DeNardo GL, DeNardo SJ. Characterization of Site-Specific ScFv PEGylation for Tumor-Targeting Pharmaceuticals. Bioconjug Chem 2004; 16:113-21. [PMID: 15656582 DOI: 10.1021/bc0498121] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
New radiopharmaceuticals are possible using site-specific conjugation of small tumor binding proteins and poly(ethylene glycol) (PEG) scaffolds to provide modular multivalent, homo- or heterofunctional cancer-targeting molecules having preferred molecular size, valence, and functionality. Residence time in plasma can be optimized by modification of the size, number, and charge of the protein units. However, random PEG conjugation (PEGylation) of these small molecules via amine groups has led to variations of structural conformation and binding affinity. To optimize PEGylation, scFvs have been recombinantly produced in a vector that adds an unpaired cysteine (c) near the scFv carboxy terminus (scFv-c), thus providing a specific site for thiol conjugation. To evaluate the general applicability of this unpaired cysteine for PEGylation of scFv-c, conjugation efficiency was determined for four different scFvs and several PEG molecules having thiol reactive groups. The effect of the PEG molecular format on scFv-c PEG malignant cell binding was also addressed. ScFvs produced as scFv-c and purified by anti E-TAG affinity chromatography were conjugated using PEG molecules with maleimide (Mal) or o-pyridyl disulfide (OPSS). Conjugations were performed at pH 7.0, with 2 molar excess TCEP/scFv and PEG-(Mal) or PEG-OPSS, using 5:1 (PEG/scFv). PEG-Mal conjugation efficiency was also evaluated with 1:5 (PEG/scFv). PEGylation efficiency was determined for each reaction by quantitation of the products on SDS-PAGE. ScFv-c conjugation with unifunctional maleimide PEGs resulted in PEG conjugates incorporating 30-80% of the scFv-c, but usually above 50%. Efficiency of scFv-c conjugation to both functional groups of the bifunctional PEG-(Mal)2 varied between the PEG and scFv-c molecules studied. A maximum of 45% of scFv-c protein was conjugated as PEG- (scFv-c)2 using the smallest PEG-(Mal)2 (2 kDa). No significant increase in scFv-c conjugation was observed by the use of greater than a 5 molar excess of PEG/scFv-c. Under the same conjugation conditions, PEG as OPSS yielded less than 10% PEG-scFv-c. PEG-(scFv)2 conjugates had increased binding in ELISA using malignant cell membranes, when compared with unmodified scFv-c. PEGylated-scFv binding was comparable with unmodified scFv-c. In summary, scFv-c can be PEGylated in a site-specific manner using uni- or bivalent PEG-Mal, either linear or branched. ScFv-c was most efficiently conjugated to smaller PEG-Mal molecules, with the smallest, 2 kDa PEG-Mal, usually PEGylating 60-90% of the scFv-c. ScFv-c conjugation to form PEG-(scFv-c)2 reached greatest efficiency at 45%, and its purified form demonstrated greater binding than the corresponding scFv-c.
Collapse
Affiliation(s)
- Arutselvan Natarajan
- University of California Davis Medical Center, Sacramento, California 95816, USA
| | | | | | | | | |
Collapse
|
54123
|
Garny A, Noble D, Kohl P. Dimensionality in cardiac modelling. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2004; 87:47-66. [PMID: 15471590 DOI: 10.1016/j.pbiomolbio.2004.06.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The development of mathematical models of the heart has been an ongoing concern for many decades. The initial focus of this work was on single cell models that incorporate varyingly detailed descriptions of the mechanisms that give rise to experimentally observed action potential shapes. Clinically relevant heart rhythm disturbances, however, are multicellular phenomena, and there have been many initiatives to develop multidimensional representations of cardiac electromechanical activity. Here, we discuss the merits of dimensionality, from 0D single cell models, to 1D cell strands, 2D planes and 3D volumes, for the simulation of normal and disturbed rhythmicity. We specifically look at models of: (i) the origin and spread of cardiac excitation from the sino-atrial node into atrial tissue, and (ii) stretch-activated channel effects on ventricular cell and tissue activity. Simulation of the spread of normal and disturbed cardiac excitation requires multicellular models. 1D architectures suffer from limitations in neighbouring tissue effects on individual cells, but they can (with some modification) be applied to the simulation of normal spread of excitation or, in ring-like structures, re-entry simulation (colliding wave fronts, tachycardia). 2D models overcome many of the limitations imposed by models of lower dimensionality, and can be applied to the study of complex co-existing re-entry patterns or even fibrillation. 3D implementations are closest to reality, as they allow investigation of scroll waves. Our results suggest that 2D models offer a good compromise between computational resources, complexity of electrophysiological models, and applicability to basic research, and that they should be considered as an important stepping-stone towards anatomically detailed simulations. This highlights the need to identify and use the most appropriate model for any given task. The notion of a single and ultimate model is as useful as the idea of a universal mechanical tool for all possible repairs and servicing requirements in daily life. The ideal model will be as simple as possible and as complex as necessary for the particular question raised.
Collapse
Affiliation(s)
- Alan Garny
- Department of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
| | | | | |
Collapse
|
54124
|
Warfield SK, Haker SJ, Talos IF, Kemper CA, Weisenfeld N, Mewes AUJ, Goldberg-Zimring D, Zou KH, Westin CF, Wells WM, Tempany CMC, Golby A, Black PM, Jolesz FA, Kikinis R. Capturing intraoperative deformations: research experience at Brigham and Women's Hospital. Med Image Anal 2004; 9:145-62. [PMID: 15721230 DOI: 10.1016/j.media.2004.11.005] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
During neurosurgical procedures the objective of the neurosurgeon is to achieve the resection of as much diseased tissue as possible while achieving the preservation of healthy brain tissue. The restricted capacity of the conventional operating room to enable the surgeon to visualize critical healthy brain structures and tumor margin has lead, over the past decade, to the development of sophisticated intraoperative imaging techniques to enhance visualization. However, both rigid motion due to patient placement and nonrigid deformations occurring as a consequence of the surgical intervention disrupt the correspondence between preoperative data used to plan surgery and the intraoperative configuration of the patient's brain. Similar challenges are faced in other interventional therapies, such as in cryoablation of the liver, or biopsy of the prostate. We have developed algorithms to model the motion of key anatomical structures and system implementations that enable us to estimate the deformation of the critical anatomy from sequences of volumetric images and to prepare updated fused visualizations of preoperative and intraoperative images at a rate compatible with surgical decision making. This paper reviews the experience at Brigham and Women's Hospital through the process of developing and applying novel algorithms for capturing intraoperative deformations in support of image guided therapy.
Collapse
Affiliation(s)
- Simon K Warfield
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
54125
|
Olivier V, Faucheux N, Hardouin P. Biomaterial challenges and approaches to stem cell use in bone reconstructive surgery. Drug Discov Today 2004; 9:803-11. [PMID: 15364068 DOI: 10.1016/s1359-6446(04)03222-2] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
As life expectancy increases, so does the need to treat large bone defects. New biomaterials combined with osteogenic cells are now being developed as an alternative to autogenous bone grafts. The goal is to make the stem cells adhere to the scaffold, and then grow to differentiate into functional osteogenic cells and organize into healthy bone as the scaffold degrades. Decisive improvements have been made in the fields of stem cell biology, 3-D scaffold fabrication and tissue engineering, but the ideal bone substitute that fulfils all functional and safety requirements has yet to be developed.
Collapse
Affiliation(s)
- Valerie Olivier
- LR2B, Université du Littoral Côte d'Opale, INSERM ERI 002, 52 Rue du Docteur Calot, 62608 Berck, France
| | | | | |
Collapse
|
54126
|
Abraham LC, Vorrasi J, Kaplan DL. Impact of collagen structure on matrix trafficking by human fibroblasts. J Biomed Mater Res A 2004; 70:39-48. [PMID: 15174107 DOI: 10.1002/jbm.a.30057] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Biodegradation of collagen biomaterial matrices and the deposition of new collagen extracellular matrix (ECM) are critical to the integration of in vitro bioengineered materials and tissues in vivo. In previous studies, we observed significant impact of collagen matrix structure on primary lung fibroblast behavior in vitro. In the present work, to begin to understand the mechanistic basis for our previous observation, the response of human fibroblasts (IMR-90) to the structural state of collagen matrices was studied with respect to cell proliferation, cell morphology, beta-galactosidase level, and transcript content for collagen (Col-1), matrix metalloproteinases (MMP-1, MMP-2), tissue inhibitors of matrix metalloproteinase (TIMP-1 and TIMP-2). Collagen digestion was assessed quantitatively by uptake of collagen-coated fluorescent beads incorporated in the preformed collagen matrix. Transcript levels related to the deposition of new ECM proteins varied as a function of the structure of the collagen matrix presented to the cells. Col-1 expression was 2-fold higher and expression for MMP-1, MMP-2, TIMP-1, and TIMP-2 increased for cells when grown on 156 microg/cm2 denatured collagen compared with cells grown on tissue culture (TC) plastic. On 156 microg/cm2 nondenatured (native) collagen, Col-1 expression was decreased by half and MMP-2 was increased by 2.5-fold compared with cells grown on TC plastic. On 78 microg/cm2 denatured collagen, Col-1 expression was 80% whereas the MMPs and TIMPs were increased by 1.25- to 2-fold compared with cells grown on TC plastic. On 78 microg/cm2 nondenatured collagen expression of all 5 transcripts was reduced 60-90% of the levels determined for the cells grown on TC plastic. Cell viability, based on cell morphology and beta-galactosidase activity, was improved on the denatured collagen. A higher level of collagen matrix incorporation was observed for cells grown on denatured collagen than on nondenatured collagen or TC plastic. These data suggest that tissue engineering matrices incorporating denatured collagen may promote more active remodeling toward new ECM in comparison to cells grown on nondenatured collagen or cells grown on TC plastic.
Collapse
Affiliation(s)
- Leah C Abraham
- Departments of Chemical and Biological Engineering and Biomedical Engineering; and Bioengineering Center, Tufts University, Medford, Massachusetts 02155, USA
| | | | | |
Collapse
|
54127
|
Städler B, Falconnet D, Pfeiffer I, Höök F, Vörös J. Micropatterning of DNA-tagged vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:11348-11354. [PMID: 15595756 DOI: 10.1021/la0482305] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We present a novel concept for the creation of lipid vesicle microarrays based on a patterning approach termed Molecular Assembly Patterning by Lift-off (MAPL). A homogeneous MAPL-based single-stranded DNA microarray was converted into a vesicle array by the use of vesicles tagged with complementary DNAs, permitting sequence-specific coupling of vesicles to predefined surface regions through complementary DNA hybridization. In the multistep process utilized to fulfill this achievement, active spots consisting of PLL-g-PEGbiotin with a resistant PLL-g-PEG background, as provided by the MAPL process, was converted into a DNA array by addition of complexes of biotin-terminated DNA and NeutrAvidin. This was then followed by addition of POPC vesicles tagged with complementary cholesterol-terminated DNA, thus providing specific coupling of vesicles to the surface through complementary DNA hybridization. Quartz crystal microbalance with dissipation (QCM-D) and optical waveguide lightmode spectroscopy monitoring were used to optimize the multistep surface modification process. It was found that the amount of adsorbed biotinDNA-NeutrAvidin complexes decreases with increasing molar ratio of biotinDNA to NeutrAvidin and decreasing ionic strength of the buffer solution. Modeling of the QCM-D data showed that the shape of the immobilized vesicles depends on the amount of available anchoring groups between the vesicles and the surface. Fluorescent microscopy images confirmed the possibility to create well-defined patterns of DNA-tagged, fluorescently labeled vesicles in the micrometer range.
Collapse
Affiliation(s)
- Brigitte Städler
- BioInterfaceGroup, Laboratory for Surface Science and Technology, Department of Materials, Swiss Federal Institute of Technology (ETH) Zurich, CH-8093 Zurich, Switzerland
| | | | | | | | | |
Collapse
|
54128
|
Lee JN, Jiang X, Ryan D, Whitesides GM. Compatibility of mammalian cells on surfaces of poly(dimethylsiloxane). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:11684-91. [PMID: 15595798 DOI: 10.1021/la048562+] [Citation(s) in RCA: 220] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This paper describes the influence of the composition of poly(dimethylsiloxane) (PDMS) on the attachment and growth of several different types of mammalian cells: primary human umbilical artery endothelial cells (HUAECs), transformed 3T3 fibroblasts (3T3s), transformed osteoblast-like MC3T3-E1 cells, and HeLa (transformed epithelial) cells. Cells grew on PDMS having different ratios of base to curing agent: 10:1 (normal PDMS, PDMSN), 10:3 (PDMSCA), and 10:0.5 (PDMSB). They were also grown on "extracted PDMS" (normal PDMS that has reduced quantities of low molecular-weight oligomers, PDMSN,EX) and normal PDMS that had been extracted and then oxidized (PDMSN,EX,OX); all surfaces were exposed to a solution of fibronectin prior to cell attachment. Generally, fibronectin-coated PDMS is a suitable substrate for culturing mammalian cells. Compatibility of cells on some surfaces, however, was dependent on the cell type: PDMSN,EX,OX caused cell detachment of 3T3 fibroblasts and MC3T3-E1 cells, and PDMSCA caused detachment of HUAECs and HeLa cells. Growth of cells on PDMSN, PDMSN,EX, and PDMSB was comparable to growth on tissue culture-treated polystyrene for most of the cell types. All cells grew at similar rates on PDMS substrates regardless of the stiffness of the substrate, for substrates having Young's moduli ranging from E=0.60 +/- 0.04 to 2.6 +/- 0.2 MPa (for PDMSB and PDMSN,EX, respectively).
Collapse
Affiliation(s)
- Jessamine Ng Lee
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138
| | | | | | | |
Collapse
|
54129
|
Agarwal S, Deschner J, Long P, Verma A, Hofman C, Evans CH, Piesco N. Role of NF-kappaB transcription factors in antiinflammatory and proinflammatory actions of mechanical signals. ACTA ACUST UNITED AC 2004; 50:3541-8. [PMID: 15529376 PMCID: PMC4950930 DOI: 10.1002/art.20601] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
OBJECTIVE The mechanisms by which chondrocytes convert biomechanical signals into intracellular biochemical events are not well understood. In this study, we sought to determine the intracellular mechanisms of the magnitude-dependent actions of mechanical signals. METHODS Chondrocytes isolated from rabbit articular cartilage were grown on flexible membranes. Cells were subjected to cyclic tensile strain (CTS) of various magnitudes in the presence or absence of interleukin-1beta (IL-1beta), which was used as a proinflammatory signal for designated time intervals. The regulation of NF-kappaB was measured by reverse transcriptase-polymerase chain reaction, electrophoretic mobility shift assay, and immunofluorescence. RESULTS CTS of low magnitudes (4-8% equibiaxial strain) was a potent inhibitor of IL-1beta-dependent NF-kappaB nuclear translocation. Cytoplasmic retention of NF-kappaB and reduction of its synthesis led to sustained suppression of proinflammatory gene induction. In contrast, proinflammatory signals generated by CTS of high magnitudes (15-18% equibiaxial strain) mimicked the actions of IL-1beta and induced rapid nuclear translocation of NF-kappaB subunits p65 and p50. CONCLUSION Magnitude-dependent signals of mechanical strain utilize the NF-kappaB transcription factors as common elements to abrogate or aggravate proinflammatory responses. Furthermore, the intracellular events induced by mechanical overload are similar to those that are initiated by proinflammatory cytokines in arthritis.
Collapse
Affiliation(s)
- Sudha Agarwal
- Biomechanical and Tissue Engineering Laboratory, Section of Oral Biology, Ohio State University, 305 West 12th Avenue, Columbus, OH 43210, USA.
| | | | | | | | | | | | | |
Collapse
|
54130
|
de Bivort B, Huang S, Bar-Yam Y. Dynamics of cellular level function and regulation derived from murine expression array data. Proc Natl Acad Sci U S A 2004; 101:17687-92. [PMID: 15598744 PMCID: PMC539730 DOI: 10.1073/pnas.0406707102] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A major open question of systems biology is how genetic and molecular components interact to create phenotypes at the cellular level. Although much recent effort has been dedicated to inferring effective regulatory influences within small networks of genes, the power of microarray bioinformatics has yet to be used to determine functional influences at the cellular level. In all cases of data-driven parameter estimation, the number of model parameters estimable from a set of data is strictly limited by the size of that set. Rather than infer parameters describing the detailed interactions of just a few genes, we chose a larger-scale investigation so that the cumulative effects of all gene interactions could be analyzed to identify the dynamics of cellular-level function. By aggregating genes into large groups with related behaviors (megamodules), we were able to determine the effective aggregate regulatory influences among 12 major gene groups in murine B lymphocytes over a variety of time steps. Intriguing observations about the behavior of cells at this high level of abstraction include: (i) a medium-term critical global transcriptional dependence on ATP-generating genes in the mitochondria, (ii) a longer-term dependence on glycolytic genes, (iii) the dual role of chromatin-reorganizing genes in transcriptional activation and repression, (iv) homeostasis-favoring influences, (v) the indication that, as a group, G protein-mediated signals are not concentration-dependent in their influence on target gene expression, and (vi) short-term-activating/long-term-repressing behavior of the cell-cycle system that reflects its oscillatory behavior.
Collapse
Affiliation(s)
- Benjamin de Bivort
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
| | | | | |
Collapse
|
54131
|
Abstract
Selective antiangiogenesis and vascular targeting drugs hold out the promise of improved efficacy and tolerability for anticancer treatments. Early phase 1 drug trials have shown good tolerability for antiangiogenesis agents with biological activity below the maximum tolerated dose. Advanced clinical trials have demonstrated that morphological assessments of tumour response are of limited value in gauging the efficacy of treatment. MRI is a versatile technique which is sensitive to contrast mechanisms that can be affected by antivascular treatments; this use for MRI has been validated in xenografts and humans. Dynamic contrast-enhanced MRI (DCE-MRI), which demonstrates tissue perfusion and permeability, is being used clinically as a pharmacodynamic indicator of biological activity for antivascular cancer drugs. Early data show that DCE-MRI studies can define the biologically active dose and predict the efficacy of treatment on the basis of changes observed. MRI with macromolecular contrast media (MMCM) depicts microvessel permeability and fractional plasma volume. Xenograft studies with MMCM have shown great promise for evaluating antivascular treatments but this has not been used clinically. Intrinsic susceptibility-weighted MRI, which is sensitive to blood oxygenation and flow, is emerging as a technique that may be able to monitor vascular targeting therapies.
Collapse
Affiliation(s)
- A R Padhani
- Paul Strickland Scanner Centre, Mount Vernon Hospital, Rickmansworth Road, Northwood, Middlesex HA6 2RN, UK
| |
Collapse
|
54132
|
Abstract
We used a novel uniaxial stretching rheometer to measure the creep function J(t) of an isolated living cell. We show, for the first time at the scale of the whole cell, that J(t) behaves as a power-law J(t) = At(alpha). For N = 43 mice myoblasts (C2-7), we find alpha = 0.24 +/- 0.01 and A = (2.4 +/- 0.3) 10(-3) Pa(-1) s(-alpha). Using Laplace Transforms, we compare A and alpha to the parameters G(0) and beta of the complex modulus G*(omega) = G(0)omega(beta) measured by other authors using magnetic twisting cytometry and atomic force microscopy. Excellent agreement between A and G(0) on the one hand, and between alpha and beta on the other hand, indicated that the power-law is an intrinsic feature of cell mechanics and not the signature of a particular technique. Moreover, the agreement between measurements at very different size scales, going from a few tens of nanometers to the scale of the whole cell, suggests that self-similarity could be a central feature of cell mechanical structure. Finally, we show that the power-law behavior could explain previous results first interpreted as instantaneous elasticity. Thus, we think that the living cell must definitely be thought of as a material with a large and continuous distribution of relaxation time constants which cannot be described by models with a finite number of springs and dash-pots.
Collapse
Affiliation(s)
- Nicolas Desprat
- Laboratoire de Biorhéologie et d'Hydrodynamique Physico-chimique, Université Paris VII, France
| | | | | | | |
Collapse
|
54133
|
Remme EW, Young AA, Augenstein KF, Cowan B, Hunter PJ. Extraction and quantification of left ventricular deformation modes. IEEE Trans Biomed Eng 2004; 51:1923-31. [PMID: 15536894 DOI: 10.1109/tbme.2004.834283] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have developed a method that decomposes the deformation of the left ventricle (LV) between end diastole (ED) and end systole (ES) into separate deformation modes such as longitudinal shortening, wall thickening, and twisting. The deformation was initially found from the motion of an LV finite-element mesh that was fitted to clinically obtained magnetic resonance (MR) tagged images. A mode coefficient was calculated for each deformation mode to quantify the different modes and, thus allowing for discrimination of normal and abnormal deformation patterns. We applied the method to 13 normal subjects and 13 diabetes patients. By using the ED mesh as reference and adding the extracted deformation modes multiplied by their mode coefficients, an approximate ES mesh was calculated and compared with the "true" ES mesh found from the MR images. For the 26 subjects the average Euclidean distance was less than 1.7+/-0.9 mm between the nodes of the approximated and true ES meshes. The coefficient values for the patient group showed significantly less longitudinal shortening, less wall thickening, more longitudinal twisting and also more bulging of the septum into the LV when compared with the normal subjects. We conclude that the developed method successfully quantifies the deformation into several modes of deformation and is capable of distinguishing the deformation of a group of patients from a group of normal subjects.
Collapse
Affiliation(s)
- Espen W Remme
- Bioengineering Institute, University of Auckland, New Zealand.
| | | | | | | | | |
Collapse
|
54134
|
Vaidya AA, Norton ML. DNA attachment chemistry at the flexible silicone elastomer surface: toward disposable microarrays. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:11100-11107. [PMID: 15568863 DOI: 10.1021/la048509l] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This paper describes the preparation and surface characterization of maleimide-activated silicone elastomer (PDMS(MCC)) followed by covalent functionalization using thiol-terminated DNA sequences (primary oligo). The stability of this attachment chemistry was demonstrated by the retention of the primary oligo through the process of hybridization with a labeled complementary DNA sequence. In these studies, the hybridized labeled DNA oligomers were detected using confocal fluorescence microscopy. We have employed a vapor deposition technique in which a plasma-treated silicone elastomer (PDMS(OH)) was exposed to vapors of 3-(aminopropyl)triethoxysilane (APTS) under vacuum, to yield the amine-functionalized silicone elastomer (PDMS(NH)(2)). PDMS(NH)(2) was further coupled with a heterofunctional cross-linker, sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate to obtain PDMS(MCC). The surface functionalities of the elastomers were characterized using contact angle measurements and X-ray photoelectron spectroscopy. Surface-modified silicone elastomers appear to be promising substrates for use as substrates for disposable microarrays.
Collapse
Affiliation(s)
- Ashish A Vaidya
- Department of Chemistry, Marshall University, Huntington, West Virginia 25755, USA.
| | | |
Collapse
|
54135
|
Dodge A, Turcatti G, Lawrence I, de Rooij NF, Verpoorte E. A microfluidic platform using molecular beacon-based temperature calibration for thermal dehybridization of surface-bound DNA. Anal Chem 2004; 76:1778-87. [PMID: 15018583 DOI: 10.1021/ac034377+] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This work presents a simple microfluidic device with an integrated thin-film heater for studies of DNA hybridization kinetics and double-stranded DNA melting temperature measurements. The heating characteristics of the device were evaluated with a novel, noninvasive indirect technique using molecular beacons as temperature probes inside reaction chambers. This is the first microfluidic device in which thermal dehybridization of surface-bound oligonucleotides was performed for measurement of double-stranded DNA melting temperatures with +/- 1 degrees C precision. Surface modification and oligonucleotide immobilization were performed by continuously flowing reagents through the microchannels. The resulting reproducibility of oligonucleotide surface densities, at 9% RSD, was better than for the same modification chemistries on glass slides in unstirred reagent solutions (RSD=20%). Moreover, the surface density of immobilized DNA probe molecules could be varied controllably by changing the concentration of the reagent solution used for immobilization. Thus, excellent control of surface characteristics was made possible, something which is often difficult to achieve with larger devices. Solid-phase hybridization reactions, a fundamental aspect of microarray technologies often taking several hours in conventional systems, were reduced to minutes in this device. It was also possible to determine forward rate constants for hybridization, k. These varied from 820,000 to 72,000 M(-1) s(-1), decreasing as surface densities increased. Surface densities could therefore be optimized to obtain rapid hybridization using such an approach. Taken together, this combined microfluidic/small-volume heating approach represents a powerful tool for surface-based DNA analysis.
Collapse
Affiliation(s)
- Arash Dodge
- Sensors, Actuators and Microsystems Laboratory, Institute of Microtechnology, University of Neuchâtel, Rue Jaquet-Droz 1, CH-2007 Neuchâtel, Switzerland
| | | | | | | | | |
Collapse
|
54136
|
Hervás F. Chip-mediated techniques: how close are we to generalised use in the infectious disease clinic? Clin Microbiol Infect 2004; 10:865-7. [PMID: 15373878 DOI: 10.1111/j.1469-0691.2004.00787.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This could be the beginning of a new molecular era for the diagnosis of infectious diseases. Biological chips (biochips or microarrays and labchips) offer a potentially important shortcut to early diagnosis and treatment. It is also possible to develop multiplex assays for use in complex diagnostic situations; however, this technology depends crucially on the robotics developed to support these functions, and the soundness of the mathematics employed to analyse the output. Although the number of research applications is increasing, the question as to when, or if, chip-mediated techniques will be used routinely in the infectious disease clinic remains unanswered at present.
Collapse
Affiliation(s)
- F Hervás
- Servicio de Microbiología Clinica, Hospital Central de la Defensa, Madrid, Spain.
| |
Collapse
|
54137
|
Singh SM, McDonald P, Murphy B, O'Reilly R. Incidental neurodevelopmental episodes in the etiology of schizophrenia: an expanded model involving epigenetics and development. Clin Genet 2004; 65:435-40. [PMID: 15151498 DOI: 10.1111/j.1399-0004.2004.00269.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Epidemiological data favors genetic predisposition for schizophrenia, a common and complex mental disorder in most populations. Search for the genes involved using candidate genes, positional cloning, and chromosomal aberrations including triplet repeat expansions have established a number of susceptibility loci and genomic sites but no causal gene(s) with a proven mechanism of action. Recent genome-wide gene expression studies on brains from schizophrenia patients and their matched controls have identified a number of genes that show an alteration in expression in the diseased brains. Although it is not possible to offer a cause and effect association between altered gene expression and disease, such observations support a neurodevelopmental model in schizophrenia. Here, we offer a mechanism of this disease, which takes into account the role of developmental noise and diversions of the neural system. It suggests that the final outcome of a neural developmental process is not fixed and exact. Rather it develops with a variation around the mean. More important, the phenotypic consequence may cross the norm as a result of fortuitous and/or epigenetic events. As a result, a normal genotype may develop as abnormal with a disease phenotype. More important, susceptible genotypes may have reduced penetrance and develop as a normal phenocopy. The incidental episodes in neurodevelopment will explain the frequency of schizophrenia in most populations and high discordance of monozygotic twins.
Collapse
Affiliation(s)
- S M Singh
- Molecular Genetics Unit, Department of Biology and Division of Medical Genetics, University of Western Ontario, London, Ontario, Canada N6A 5B7, USA.
| | | | | | | |
Collapse
|
54138
|
Abstract
Morphometry offers new approaches for in vivo characterization of many neurologic and psychiatric pathologies. A survey of recent publications only hints at the attractiveness of magnetic resonance-based morphometry: published findings are heterogeneous, partly contradictory, and not always plausible in terms of known neuropathologic correlates. Hence, the sensitivity of the applied methods should be questioned. Three parameters affect the variance in morphometric findings: (1) knowledge about normal morphologic variability, (2) confounding physiologic parameters, and (3) methodologic misuse. Sound knowledge about the morphologic variability of the normal brain is vital for the assessment of volumetric findings. Large morphologic variability may also interfere with the precision of morphometric methods. The multitude of possible confounding physiologic parameters raises the necessity of precise subject control. Magnetic resonance scanning artefacts require rigid protocols, and application of the rather complex and sensitive methods demands profound insight into the techniques.
Collapse
Affiliation(s)
- M Tittgemeyer
- Max-Planck-Institut für Kognitions- und Neurowissenschaften, Leipzig.
| | | |
Collapse
|
54139
|
Stokols S, Tuszynski MH. The fabrication and characterization of linearly oriented nerve guidance scaffolds for spinal cord injury. Biomaterials 2004; 25:5839-46. [PMID: 15172496 DOI: 10.1016/j.biomaterials.2004.01.041] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2003] [Accepted: 01/20/2004] [Indexed: 11/28/2022]
Abstract
Strategies to promote axonal extension through a site of injury, including the provision of nervous system growth factors and supportive substrates, produce growth of axons, that is highly random and does not extend past the lesion site and into the host tissue (Brain Res. Bull 57(6) (2002) 833). Physically guiding the linear growth of axons across a site of injury, in addition to providing neurotrophic and/or cellular support, would help to retain the native organization of regenerating axons across the lesion site and into distal host tissue, and would potentially increase the probability of achieving functional recovery. In the present study, a novel procedure was developed for using freeze-dry processing to create nerve guidance scaffolds made from agarose, with uniaxial linear pores. The hydrated scaffolds were soft and flexible, contained linear guidance pores extending through their full length, were stable under physiological conditions without chemical crosslinking, and could be readily loaded with diffusible growth stimulating proteins.
Collapse
Affiliation(s)
- Shula Stokols
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | | |
Collapse
|
54140
|
Logothetis NK, Pfeuffer J. On the nature of the BOLD fMRI contrast mechanism. Magn Reson Imaging 2004; 22:1517-31. [PMID: 15707801 DOI: 10.1016/j.mri.2004.10.018] [Citation(s) in RCA: 231] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2004] [Accepted: 10/15/2004] [Indexed: 10/25/2022]
Abstract
Since its development about 15 years ago, functional magnetic resonance imaging (fMRI) has become the leading research tool for mapping brain activity. The technique works by detecting the levels of oxygen in the blood, point by point, throughout the brain. In other words, it relies on a surrogate signal, resulting from changes in oxygenation, blood volume and flow, and does not directly measure neural activity. Although a relationship between changes in brain activity and blood flow has long been speculated, indirectly examined and suggested and surely anticipated and expected, the neural basis of the fMRI signal was only recently demonstrated directly in experiments using combined imaging and intracortical recordings. In the present paper, we discuss the results obtained from such combined experiments. We also discuss our current knowledge of the extracellularly measured signals of the neural processes that they represent and of the structural and functional neurovascular coupling, which links such processes with the hemodynamic changes that offer the surrogate signal that we use to map brain activity. We conclude by considering applications of invasive MRI, including injections of paramagnetic tracers for the study of connectivity in the living animal and simultaneous imaging and electrical microstimulation.
Collapse
Affiliation(s)
- Nikos K Logothetis
- Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Spemannstrasse 38, 72076 Tübingen, Germany.
| | | |
Collapse
|
54141
|
Chen YL, Graham MD, de Pablo JJ, Randall GC, Gupta M, Doyle PS. Conformation and dynamics of single DNA molecules in parallel-plate slit microchannels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 70:060901. [PMID: 15697334 DOI: 10.1103/physreve.70.060901] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2004] [Indexed: 05/14/2023]
Abstract
The conformation and diffusion of a single DNA molecule confined between two parallel plates are examined using both single molecule experiments and Brownian dynamics simulations accounting for hydrodynamic interactions. The degree of chain stretching and the diffusivity are characterized as a function of the chain confinement and the channel geometry. Good agreement is found between the simulations, experiments, and scaling theory predictions.
Collapse
Affiliation(s)
- Y-L Chen
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53703, USA
| | | | | | | | | | | |
Collapse
|
54142
|
Kida I, Maciejewski PK, Hyder F. Dynamic imaging of perfusion and oxygenation by functional magnetic resonance imaging. J Cereb Blood Flow Metab 2004; 24:1369-81. [PMID: 15625411 DOI: 10.1097/01.wcb.0000141501.12558.9b] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cerebral blood flow can be measured with magnetic resonance imaging (MRI) by arterial spin labeling techniques, where magnetic labeling of flowing spins in arterial blood water functions as the endogenous tracer upon mixing with the unlabeled stationary spins of tissue water. The consequence is that the apparent longitudinal relaxation time (T1) of tissue water is attenuated. A modified functional MRI scheme for dynamic CBF measurement is proposed that depends on extraction of T1 weighting from the blood oxygenation level-dependent (BOLD) image contrast, because the functional MRI signal also has an intrinsic T1 weighting that can be altered by variations of the excitation flip angle. In the alpha-chloralose-anesthetized rat model at 7T, the authors show that the stimulation-induced BOLD signal change measured with two different flip angles can be combined to obtain a T1-weighted MRI signal, reflecting the magnitude of the CBF change, which can be deconvolved to obtain dynamic changes in CBF. The deconvolution of the T1-weighted MRI signal, which is a necessary step for accurate reflection of the dynamic changes in CBF, was made possible by a transfer function obtained from parallel laser-Doppler flowmetry experiments. For all stimulus durations (ranging from 4 to 32 seconds), the peak CBF response measured by MRI after the deconvolution was reached at 4.5 +/- 1.0 seconds, which is in good agreement with (present and prior) laser-Doppler measurements. Because the low flip angle data can also provide dynamic changes of the conventional BOLD image contrast, this method can be used for simultaneous imaging of CBF and BOLD dynamics.
Collapse
Affiliation(s)
- Ikuhiro Kida
- Magnetic Resonance Research Center, Department of Diagnostic Radiology, Yale University, New Haven, Connecticut 06510, USA
| | | | | |
Collapse
|
54143
|
Zhang W, Pibulsonggram T, Edwards A. Determinants of basal nitric oxide concentration in the renal medullary microcirculation. Am J Physiol Renal Physiol 2004; 287:F1189-203. [PMID: 15280161 DOI: 10.1152/ajprenal.00125.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In this study, we modeled the production, transport, and consumption of nitric oxide (NO) in the renal medullary microcirculation under basal conditions. To yield agreement with reported NO concentrations of ∼60–140 nM in medullary tissues (Zou AP and Cowley AW Jr. Hypertension 29: 194–198, 1997; Am J Physiol Regul Integr Comp Physiol 279: R769–R777, 2000) and 3 nM in plasma (Stamler JS, Jaraki O, Osborne J, Simon DI, Keaney J, Vita J, Singel D, Valeri CR, and Loscalzo J. Proc Natl Acad Sci USA 89: 7674–7677, 1992), the permeabilities of red blood cells (RBCs), vascular walls, and pericytes to NO are all predicted to lie between 0.01 and 0.1 cm/s, and the NO production rate by vasa recta endothelium is estimated to be on the order of 10−14μmol·μm−2·s−1. Our results suggest that the concentration of NO in RBCs, which is essentially controlled by the kinetics of NO scavenging by hemoglobin, is ∼0.01 nM, that is, 103times lower than that in plasma, pericytes, and interstitium. Because the basal concentration of NO in pericytes is on the order of 10 nM, it may be too low to active guanylate cyclase, i.e., to induce vasorelaxation. Our simulations also indicate that basal superoxide concentrations may be too low to affect medullary NO levels but that, under pathological conditions, superoxide may be a very significant scavenger of NO. We also found that although oxygen is a negligible NO scavenger, medullary hypoxia may significantly enhance NO concentration gradients along the corticomedullary axis.
Collapse
Affiliation(s)
- Wensheng Zhang
- Department of Chemical and Biological Engineering, Tufts University, 4 Colby St., Medford, MA 02155, USA.
| | | | | |
Collapse
|
54144
|
Geary CD, Zudans I, Goponenko AV, Asher SA, Weber SG. Electrochemical Investigation of Pb2+ Binding and Transport through a Polymerized Crystalline Colloidal Array Hydrogel Containing Benzo-18-crown-6. Anal Chem 2004; 77:185-92. [PMID: 15623295 DOI: 10.1021/ac048616k] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The transport of Pb2+ through a sensory gel, a polymerized crystalline colloidal array hydrogel with immobilized benzo-18-crown-6, is important for understanding and optimizing the sensor. Square wave voltammetry at a Hg/Au electrode reveals many parameters. The partition coefficient for Pb2+ into a control gel (no crown ether), K(p), is 1.00 +/- 0.018 (errors reported are SEM). The porosity, epsilon, of the gel is 0.90 +/- 0.01. Log K(c) for complexation in the gel is 2.75 +/- 0.014. Log K(c) in aqueous solution for Pb2+ with the ligand 4-acryloylamidobenzo-18-crown-6 is 3.01 +/- 0.010 with dissociation rate k(d) = (8.34 +/- 0.45) x 10(2) s(-1) and association rate k(f) = (8.79 +/- 0.025) x 10(7) M(-1) s(-1). The partition coefficient of the ligand 4-acryloylamidobenzo-18-crown-6 into the control gel, K(p,L) is 2.07 +/- 0.15. The diffusion coefficient of Pb2+ in the control gel is 6.72 x 10(-6) +/- 0.12 cm(2)/s. For the sensor gel, but not control gel, diffusion coefficients are location dependent. The range of diffusion coefficients for Pb2+ in the probed locations was found to be (6.11-12.60) x 10(-7) cm(2)/s for 0.91 mM Pb2+ and (2.84-9.39) x 10(-7) cm(2)/s for 0.35 mM Pb2+. Lead binding in the sensor gel is slightly less avid than in solution. This is attributed, in part, to the demonstrated affinity of the ligand 4-acryloylamidobenzo-18-crown-6 to the gel. Diffusion coefficients determined for the sensor gel were found to be location dependent. This is attributed to heterogeneities in the crown concentration in the gel. Analysis of diffusion coefficients and rate constants show that diffusion and not chemical relaxation will limit the time response of the material.
Collapse
Affiliation(s)
- Caroline D Geary
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | | | | | | | | |
Collapse
|
54145
|
Okamura AM. Methods for haptic feedback in teleoperated robot-assisted surgery. THE INDUSTRIAL ROBOT 2004; 31:499-508. [PMID: 16429611 PMCID: PMC1317565 DOI: 10.1108/01439910410566362] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Teleoperated minimally invasive surgical robots can significantly enhance a surgeon's accuracy, dexterity and visualization. However, current commercially available systems do not include significant haptic (force and tactile) feedback to the operator. This paper describes experiments to characterize this problem, as well as several methods to provide haptic feedback in order to improve surgeon's performance. There exist a variety of sensing and control methods that enable haptic feedback, although a number of practical considerations, e.g. cost, complexity and biocompatibility, present significant challenges. The ability of teleoperated robot-assisted surgical systems to measure and display haptic information leads to a number of additional exciting clinical and scientific opportunities, such as active operator assistance through "virtual fixtures" and the automatic acquisition of tissue properties.
Collapse
Affiliation(s)
- A M Okamura
- is based in the Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, USA
| |
Collapse
|
54146
|
Wang M, Lau C, Matsen FA, Kim Y. Personal health information management system and its application in referral management. ACTA ACUST UNITED AC 2004; 8:287-97. [PMID: 15484434 DOI: 10.1109/titb.2004.834397] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We developed a web-based personal health record (PHR) that can be used by patients to collect and manage their health information (e.g., medical history, past surgeries, medications, and allergies), to request self-referrals, and to store a record of their consultations. The PHR also includes a messaging system that can be structured into the workflow of referral management as well as allowing more general communications. A preliminary study was conducted with 61 patients. Thirty-two patients completed a survey in which 85% of respondents were satisfied with the usability and 94% were satisfied with the overall online referral process. The consulting physicians were satisfied with the content of subjects' personal health information and referral problem descriptions and found the information detailed enough to triage all requested referrals. Patients, physicians, and patient care coordinators reported that their communications were enhanced by the system and found the messaging component convenient to use.
Collapse
Affiliation(s)
- Maisie Wang
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
| | | | | | | |
Collapse
|
54147
|
Popper M, Morgado AM, Quadrado MJ, Van Best JA. Corneal Cell Density Measurement in vivo by Scanning Slit Confocal Microscopy: Method and Validation. Ophthalmic Res 2004; 36:270-6. [PMID: 15583433 DOI: 10.1159/000081207] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2003] [Accepted: 04/30/2004] [Indexed: 11/19/2022]
Abstract
PURPOSE Method and validation of a technique to quantify cell density in vivo in 6 corneal layers with a scanning slit confocal microscope (SSCM). METHOD A confocal image of a small volume in a corneal layer is registered on videotape. Cells or nuclei according to a layer classification are counted manually using an unbiased frame. Surface cell density is calculated from an image on the screen, and volumetric density is obtained using stereological methods. RESULTS Image distortion on the screen is less than 3%. The classification of a cell layer is verified by determining the position of the measurement volume in the cornea. Validation of density measurements is performed by comparing confocal results with those obtained by histology. The difference between the two methods varies from -24.1% (posterior stroma) to +16.4% (basal layer). Intersession and intrasession repeatability are 8.3 and 5.8%, respectively. The cell density (mean +/- SD) in 20 healthy controls in the superficial, basal and endothelial layers was 759 +/- 162, 5,817 +/- 632 and 2,743 +/- 285 cells.mm(-2) (surface), and in the anterior, mid and posterior stroma 28,616 +/- 3,081, 19,578 +/- 4,421 and 26,073 +/- 5,962 cells.mm(-3) (volumetric). These results are in accordance with those of other investigators. CONCLUSIONS The SSCM can produce repeatable quantitative measurements of corneal cell density in conscious humans.
Collapse
Affiliation(s)
- Mónika Popper
- Department of Ophthalmology, Institute of Biomedical Research on Light and Image, Coimbra, Portugal.
| | | | | | | |
Collapse
|
54148
|
Li Q, Lee JS, Ha C, Park CB, Yang G, Gan WB, Chang YT. Solid-Phase Synthesis of Styryl Dyes and their Application as Amyloid Sensors. Angew Chem Int Ed Engl 2004. [DOI: 10.1002/ange.200461600] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
|
54149
|
Li Q, Lee JS, Ha C, Park CB, Yang G, Gan WB, Chang YT. Solid-Phase Synthesis of Styryl Dyes and their Application as Amyloid Sensors. Angew Chem Int Ed Engl 2004; 43:6331-5. [PMID: 15558663 DOI: 10.1002/anie.200461600] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Qian Li
- Department of Chemistry, New York University, New York, NY 10003, USA
| | | | | | | | | | | | | |
Collapse
|
54150
|
Fernández JL, Mano N, Heller A, Bard AJ. Optimization Of “Wired” Enzyme O2-Electroreduction Catalyst Compositions by Scanning Electrochemical Microscopy. Angew Chem Int Ed Engl 2004; 43:6355-7. [PMID: 15558668 DOI: 10.1002/anie.200461528] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- José L Fernández
- Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712, USA
| | | | | | | |
Collapse
|