Biomedical subjects

Tai-Horng Young

Publications and source records attributed to Tai-Horng Young.

28 records · Page 2Linked to original sources

PubMed2003

Change in electrophoretic mobility of PC12 cells after culturing on PVA membranes modified with different diamines.

The cell-biomaterial interaction is of extreme importance in regulating the numerous functions necessary for cell adhesion, growth, and differentiation. In the current study, electrophoresis was used to investigate the interactions between cells and biomaterials by measuring the change in electrophoretic mobility of pheochromocytoma (PC12) cells after they were cultured on the poly (vinyl alcohol) membranes modified with different diamines. Variations in cellular activity and electrophoretic mobility of cultured cells were compared. It was found that the intracellular metabolism and the cell surface charge properties were altered after cells contacting biomaterials and the variation of the latter occurred earlier than that of the former. Although the precise mechanism by which the variation of electrophoretic mobility of cultured PC12 cells was unknown, the biomaterials could influence the cell mobility within a short incubation time. It was hypothesized that changes in extracellular matrix components of cell surface may be in part responsible.

Animals↗

PubMed2003

Behavior of MG-63 cells on nylon/chitosan-blended membranes.

In this work, the properties of nylon, chitosan, and their blended membranes were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction analysis. The SEM photographs show that the undulating surface of the nylon membrane became less obvious by blending with chitosan. The DSC and X-ray diffraction analysis show that constitutionally different features in the combination of two polymer chains were revealed, suggesting that nylon and chitosan are immiscible at the microscopic level in the blended membranes. Furthermore, an attempt was made to understand whether the two components contribute independently to the adhesion, growth, and activation of MG-63 osteoblastlike cells. The cell adhesion increased with increasing chitosan content, indicating that the affinity between the cells and the membranes increased with increasing chitosan content. Although the blended membranes with higher nylon content exerted an inhibitory effect on cell adhesion, cells cultured on the nylon membrane proliferated at higher rates and the nylon membrane was the least stimulating of MG-63 cell cytokine production over a 4-day period when compared with all the other membranes. Combined with the result of cell growth and cell activation, the chitosan content in the blended membrane did not proportionally influence the behavior of MG-63 cells. It is proposed that cell's size was larger than the scale of nylon or chitosan domain in the blended membranes because of the incomplete miscibility between them. Therefore, even if the composition of the blended membranes is systematically changed, every cell covers a multiphase surface that is considered a totally new material for cells. Consequently, cell growth and cell activation on a blended membrane are not simply proportional to their composition. In contrast, cell adhesion is a simpler process, like a physical adsorption process, which is related to the bulk property of a blended membrane.

Biocompatible Materials↗

PubMed2003

Electrophoresis of biological cells: charge-regulation and multivalent counterions association model.

The electrophoresis of a biological cell is analyzed theoretically. An entity, which is of amphoteric nature, is used to simulate its electrophoretic behavior. To reflect conditions of practical interest, we assume that the liquid phase contains mixed (a:b)+(c:b) electrolytes, where a and c are the valences of cations, and b is the valence of anions. We consider the case where the surface of a cell contains both bivalent acidic and monovalent basic functional groups, the dissociation/association of them yields fixed surface charge, and the multivalent cations in the liquid phase are allowed to combine with dissociated acidic functional groups, which has the effect of lowering the charge density on cell surface. The electrophoretic behaviors of a cell under various conditions are illustrated. The results obtained can be used to identify the types of functional groups that may be present on cell surface. On the other hand, if the surface functional groups involved in cell electrophoresis are known, then their density and the associated dissociation/association constants can be estimated from experimental data.

Cations↗

PubMed2003

Covalent bonding of lysine to EVAL membrane surface to improve survival of cultured cerebellar granule neurons.

Polylysine is a commonly used coating material in the preparation of neuronal cultures. In the present study, poly (ethylene-co-vinyl alcohol) (EVAL) membranes were modified by the covalent bonding of lysine via isocyanation of surface hydroxyl groups to improve cell behavior in cultured cerebellar granule neurons from 7-day-old Wistar rats. Cell survival and death ratio were assayed by MTT reduction activity and lactate dehydrogenase release, respectively. Cell morphology and neurite growth were observed by a scanning electron microscope. It was found that immobilizing lysine onto the EVAL membranes could improve neuronal MTT reduction activity and delay the death rate of neurons. In addition, neurons seeded on the lysine-immobilized EVAL membrane were able to regenerate with the formation of an extensive neuritic network, indicating that the surface modification on the EVAL membrane should be useful for culturing of neurons. Furthermore, the influence exerted by the modification of different amino acids (glycine, arginine and ornithine) onto the EVAL membranes on the neuronal behavior were investigated. We found that the effect of the terminal primary amine of the side chain of the basic amino acids on the neuronal behavior should be taken into account because the immobilized glycine molecules did not improve neuronal cultures. In order to interpret the phenomenon further, in the surface modification process, both the two amino groups of lysine were designed to react with the EVAL membrane surface to form a cyclic structure. On such a surface, neuronal MTT reduction activity was decreased and neuronal death was not delayed. The result shows that the lysine molecules immobilized on the EVAL membrane surface can mediate cellular response to promote neuronal cell survival and guidance of neuritic processes, indicating a delicate interaction of neuron with lysine molecules on the EVAL membrane surface.

Animals↗

PubMed2003

Kinetic modelling of blood glucose variation in a bioartificial pancreas.

Methods are presented for assessing the performance of biomaterials for a bioartificial pancreas using a kinetic model of blood glucose variation. The model is composed of simultaneous differential equations that simulate variation of blood glucose concentration of rats outside the biomaterial and decrease of islet number inside the biomaterial. The resulting calculations agree well with the in vivo experimental data and indicate that the characteristics of bioartificial pancreas can be expressed as the actually working number of islets from the viewpoint of rats, regardless of the functioning of the bioartificial pancreas. The contributions of the capability of a biomaterial permeable to insulin and against immune rejection, and other factors that may induce cell death were involved in the actually working number of islets, i.e., the model used a lumped-parameter expression for assessment of the performance of biomaterials for a bioartificial pancreas. This model would be useful as a research tool for analysis of clinical investigation of bioartificial pancreas and physiological significance of blood glucose variation dynamics.

Animals↗

PubMed2002

Electrophoretic behavior of cerebellar granule neurons.

The electrophoresis of cerebellar granule neurons is observed, and a theoretical model proposed to simulate its electrophoretic behavior. We assume that the surface of a neuronal cell carries dissociable acidic functional groups, and the liquid phase contains a mixed (a:b) + (c:b) electrolyte, where a and c are the valences of cations and b is the valence of anions. The cations of valence c are allowed to bind to dissociated functional groups. The model proposed is readily applicable to the prediction of the surface properties of cerebellar granule neurons such as the density of dissociable functional groups and the equilibrium constant of the dissociation reaction. The applicability of the present model is justified by fitting it to the measured electrophoretic mobility data.

Animals↗

PubMed2002

Assessment and modeling of poly(vinyl alcohol) bioartificial pancreas in vivo.

Pancreatic islets surrounded by a semipermeable membrane to prevent an immune response by the host immunosystem is a potential way of treating type I diabetes mellitus. Our previous in vitro studies have demonstrated that poly(vinyl alcohol) (PVA) membranes satisfy the basic requirements for a bioartificial pancreas. This study was designed to evaluate the performance of PVA tubular membrane chambers containing islets in vivo. When the m-2 type of PVA chamber was implanted into streptozotocin-induced diabetic rats, nonfasting blood glucose levels dropped from 500 +/- 35 mg/dl to the lowest value 210 +/- 22 mg/dl. Furthermore, the performance of the bioartificial pancreas can be enhanced by the increased numbers of implanted chambers. If three m(-2) chambers were implanted, nonfasting blood glucose levels in the diabetic rats decreased to 130-160 mg/dl and such a low blood glucose value was maintained for 1 month. This indicates that implanting three m-2 chambers in the diabetic rats could provide improved permeability of insulin to normalize blood glucose levels and improved survival of islets from the immune system of the recipient. For improving the design of the bioartificial pancreas, a mathematical model was developed to account for the changes in blood glucose levels of the diabetic rats. We demonstrated such a mathematical analysis was helpful to understand the characteristics of islet inside an artificial environment.

Animals↗

PubMed2002

Particle size and morphology of UHMWPE wear debris in failed total knee arthroplasties--a comparison between mobile bearing and fixed bearing knees.

Osteolysis induced by ultrahigh molecular weight polyethylene wear debris has been recognized as the major cause of long-term failure in total joint arthroplasties. In a previous study, the prevalence of intraoperatively identified osteolysis during primary revision surgery was much higher in mobile bearing knee replacements (47%) than in fixed bearing knee replacements (13%). We postulated that mobile bearing knee implants tend to produce smaller sized particles. In our current study, we compared the particle size and morphology of polyethylene wear debris between failed mobile bearing and fixed bearing knees. Tissue specimens from interfacial and lytic regions were extracted during revision surgery of 10 mobile bearing knees (all of the low contact stress (LCS) design) and 17 fixed bearing knees (10 of the porous-coated anatomic (PCA) and 7 of the Miller/Galante design). Polyethylene particles were isolated from the tissue specimens and examined using both scanning electron microscopy and light-scattering analyses. The LCS mobile bearing knees produced smaller particulate debris (mean equivalent spherical diameter: 0.58 microm in LCS, 1.17 microm in PCA and 5.23 microm in M/G) and more granular debris (mean value: 93% in LCS, 77% in PCA and 15% in M/G).

Aged↗

PubMed2001

Electrophoretic Properties of Latex Particles with Immobilized Bovine Serum Albumin.

In this study, bovine serum albumin (BSA) was covalently immobilized onto the surfaces of methyl methacrylate/methyl acrylic acid core-shell latex particles by the carbodiimide method, and the variation of the zeta potential of the BSA-latex complex as a function of the amount of BSA immobilized was measured. The experimental data revealed that the absolute zeta potential of BSA-latex complex exhibited a local minimum at 0.05 mg/m(2) of immobilized BSA. A two-layer model for the description of the electrophoretic behavior of the BSA-latex complex is proposed which is capable of explaining the behavior of the variation of the zeta potential as a function of the amount of BSA immobilized. Copyright 2001 Academic Press.

Journal Article↗

PubMedDate not supplied

Proliferation and phenotypic preservation of rat parotid acinar cells.

The purpose of this study is to develop an initial step in salivary gland tissue engineering through proliferation and phenotypic preservation of rat parotid acinar cells in vitro. By using the explant outgrowth technique and M199 medium with the addition of sialic acid, acinar cells not only survived for more than 30 days in the absence of basement membrane substrates but also proliferated to yield cells with acinar phenotypic expression. Furthermore, we tested whether chitosan can be used as a synthetic extracellular matrix to culture salivary acinar cells. Chitosan is a deacetylated product of chitin, which is a plentiful polysaccharide found in nature and is safe for the human body, but little is known about the utility of chitosan in culturing salivary acinar cells. It was found that coating fibronectin on chitosan membrane improved the attachment of acinar cells in the initial stage. However, the poor attachment of acinar cells on pure chitosan membrane did not affect cell growth after longer culture times, indicating that chitosan is potentially useful as a tissue-engineering scaffold of the salivary gland. These in vitro results are encouraging because such a culture system may serve as an artificial salivary gland for future use in the treatment of patients with salivary hypofunction.

Animals↗