Biomedical subjects

David Berry

Publications and source records attributed to David Berry.

24 records · Page 2Linked to original sources

PubMed2004

Tissue collection, transport and isolation procedures required to optimize human hepatocyte isolation from waste liver surgical resections. A multilaboratory study.

BACKGROUND: The European Center for Validation of Alternative Methods (ECVAM) has funded a prevalidation study in three laboratories (France, USA and UK) on the use of human hepatocyte cultures to predict cytochrome P-450 induction. AIMS AND METHODS: As first stage of this prevalidation study, the purpose of the present work was to set criteria for optimization and harmonization of hepatocyte isolation from human tissue among laboratories to establish a routine procedure. This was achieved by combining and/or comparing the data generated by the two independent European laboratories (France and UK). RESULTS: The results confirmed that surgical waste material is a valuable source for obtaining high quality hepatocytes under certain pre-, intra- and post-operative conditions: cell yield of viable hepatocytes was not significantly affected by age and sex of patients, nor indications for resection, steatosis or cholestasis. Cold ischeamia up to 5 hours did not influence viable cell yield allowing transport of material. CONCLUSION: The use of biopsy sizes between 50-100 g, cannulation with 2-4 cannulae, digestion with collagenase-containing digestion medium at a flow rate of 25 ml/cannula for 20 minutes, with cut surface being glued in order to reform Glisson's capsule, should optimize the total yield of viable human hepatocytes obtained per preparation of waste liver surgical resections.

Adult↗

PubMed2003

Heparan sulphate glycosaminoglycans derived from endothelial cells and smooth muscle cells differentially modulate fibroblast growth factor-2 biological activity through fibroblast growth factor receptor-1.

Fibroblast growth factor (FGF) signalling is involved in a wide range of important biological activities with differential effects in various cell types. The activity of FGF is modulated by heparin/heparan sulphate-like glycosaminoglycans (HSGAGs), found both in the extracellular matrix and on the cell surface. HSGAGs affect FGF signalling by interacting with both the growth factor and the FGF receptor (FGFR). In this study we sought to investigate whether HSGAGs at the cell surface of bovine aortic endothelial cells (BAEC) and smooth muscle cells (SMC) can differentially modulate FGF signalling in these cell types and modulate their differential response to FGF. We find that SMC and BAEC express the same FGFR isoforms and bind FGF2 with equal affinity at the cell surface, yet FGF has a markedly higher proliferative effect on SMC than on BAEC. Isolated HSGAGs from these two cell types were found to elicit distinct patterns of proliferation in chlorate-treated cells. Furthermore, examination of focal sequences reveals that HSGAGs from SMC, but not those from BAEC, retain the sulphation pattern necessary to induce FGF2 activity. As such, the differences in FGF2-mediated proliferation can be explained by the distinct cell surface HSGAGs of the two cell types. We conclude that the focal sequences of cell surface HSGAGs from SMC and BAEC govern, at least in part, the differential activity of FGF2 on these two cell types.

Animals↗

PubMed2003

Lung endothelial heparan sulfates mediate cationic peptide-induced barrier dysfunction: a new role for the glycocalyx.

The endothelial glycocalyx is believed to play a major role in microvascular permeability. We tested the hypothesis that specific components of the glycocalyx, via cytoskeletal-mediated signaling, actively participate in barrier regulation. With the use of polymers of arginine and lysine as a model of neutrophil-derived inflammatory cationic proteins, we determined size- and dose-dependent responses of cultured bovine lung microvascular endothelial cell permeability as assessed by transendothelial electrical resistance (TER). Polymers of arginine and lysine >11 kDa produced maximal barrier dysfunction as demonstrated by a 70% decrease in TER. Monomers of l-arginine and l-lysine did not alter barrier function, suggesting a cross-linking requirement of cell surface "receptors". To test the hypothesis that glycosaminoglycans (GAGs) are candidate receptors for this response, we used highly selective enzymes to remove specific GAGs before polyarginine (PA) treatment and examined the effect on TER. Heparinase III attenuated PA-induced barrier dysfunction by 50%, whereas heparinase I had no effect. To link changes in barrier function with structural alterations, we examined actin organization and syndecan localization after PA. PA induced actin stress fiber formation and clustering of syndecan-1 and syndecan-4, which were significantly attenuated by heparinase III. PA-induced cytoskeletal rearrangement and barrier function did not involve myosin light chain kinase (MLCK) or p38 MAPK, as ML-7, a specific MLCK inhibitor, or SB-20358, a p38 MAPK inhibitor, did not alter PA-induced barrier dysfunction. In summary, lung endothelial cell heparan sulfate proteoglycans are key participants in inflammatory cationic peptide-induced signaling that links cytoskeletal reorganization with subsequent barrier dysfunction.

Animals↗

PubMed2002

A tissue-engineered stent for cell-based vascular gene transfer.

Cell-based gene transfer using a stent platform would provide a significant advantage in terms of site-specific gene expression in the vasculature. The current study presents a novel stent design that allows stable in vivo transgene expression over a 4-week period in the vasculature. A mesh-stent coated with fibronectin provided an excellent platform for adherent porcine smooth muscle cells (SMC). Autologous porcine SMC were stably transduced with a plasmid encoding green fluorescence protein (GFP), seeded at high density in the mesh-stent, and deployed in the porcine coronary artery. Stable in vivo GFP expression within the mesh-stent (5.2 x 10(5) GFP-positive cells/cm(2) mesh) was demonstrated 1 month after implantation in the porcine coronary artery by fluorescence microscopy and flow cytometry. No significant change in GFP positive cell number within the stent occurred over a 1-month period in vivo when compared to preinsertion. Angiographic and histologic analysis revealed mild neointimal proliferation and no inflammatory infiltrate in the stented segment. This study has implications for treatment of cardiovascular and other diseases where long-term cell-based delivery of transgene is a desirable therapeutic option.

Animals↗

PubMed1995

Nonlinear dynamics of the voice: Signal analysis and biomechanical modeling.

Irregularities in voiced speech are often observed as a consequence of vocal fold lesions, paralyses, and other pathological conditions. Many of these instabilities are related to the intrinsic nonlinearities in the vibrations of the vocal folds. In this paper, bifurcations in voice signals are analyzed using narrow-band spectrograms. We study sustained phonation of patients with laryngeal paralysis and data from an excised larynx experiment. These spectrograms are compared with computer simulations of an asymmetric 2-mass model of the vocal folds. (c) 1995 American Institute of Physics.

Journal Article↗

PubMedDate not supplied

A developmental model of infantile nystagmus.

The possibility that infantile nystagmus (IN) may reflect a failure in early sensorimotor integration has been proposed for more than a century, but is only recently being borne out in animal studies. The underlying neural and genetic substrate for this plasticity is complex. We propose that, in most cases, IN develops as a developmental response to reduced contrast sensitivity to high-spatial frequencies in an early "critical period," however caused, whether by structural malformations (e.g. foveal hypoplasia) or poor optics (e.g. cataract). As shown by psychophysics, contrast sensitivity to low spatial frequencies is enhanced by motion of the image across the retina. Based on our previous theoretical study (Harris & Berry, Nonlinear Dynamics, 2006), we argue that the best compromise between moving the image and maintaining the image near the fovea (or its remnant) is to oscillate the eyes with jerk nystagmus with increasing velocity waveforms, as seen empirically. The generation of jerk waveforms relies heavily on the saccadic system, which is immature in infancy. Pendular waveforms may therefore provide an alternative to jerk waveforms, and may explain why they are seen more often in young infants. We discuss the implications of this developmental model for the need to synchronize sensory and motor developments in normal development. Failure of this synchronization may also explain some idiopathic cases.

Eye Movements↗