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Biomedical subjects

H R Bhagat

Publications and source records attributed to H R Bhagat.

11 recordsLinked to original sources
PubMed1995

Uptake and transport of copolymer biodegradable microspheres by rabbit Peyer's patch M cells.

In this study, we demonstrate the role of M cells in uptake of poly(D-L-lactic-co-glycolic acid) (PLGA) microspheres and transport into rabbit Peyer's patches. Microspheres 1 to 10 microns in diameter composed of 50:50 lactic acid:glycolic acid were instilled into intestinal segments containing jejunal or ileal Peyer's patches, and uptake by M cells was examined by electron microscopy. PLGA microspheres visualized as electron-lucent, spherical particles were taken up by M cells by pseudopod-like extensions of the M cell apical membrane and translocated to the pocket region containing mononuclear leukocytes within 60 min. These results indicate that PLGA microspheres can be directed to M cell apical surfaces for delivery to immunocompetent cells in gut-associated lymphoid tissues.

Animals↗
PubMed1994

Comparative efficacy of biodegradable liposomes and microspheres as carriers for delivery of Vibrio cholerae antigens in the intestine.

The effect of the encapsulated antigens of Vibrio cholerae and their route of administration in induction of immune response was studied in experimental cholera. The antigenic proteins of V. cholerae El Tor strain KB207 were obtained by fractionation of cell-free lysate by high-performance liquid chromatography. The antigenic proteins were pooled and encapsulated in biodegradable liposomes and poly(D,L) lactic co-glycolic acid microspheres. Rabbits were immunized with free as well as encapsulated antigens by different routes. Liposome-encapsulated antigens delivered intraintestinally offered maximum protection. Orally or intraintestinally delivered antigens in microspheres failed to elicit a significant immune response, although as a carrier microspheres were comparable to liposomes when judged by the subcutaneous route. The results suggested that liposomes and microspheres could be used as carriers of protective antigens of V. cholerae for effective immunization.

Animals↗
PubMed1994

Development and validation of capillary electrophoresis assay for ribonuclease A.

A quick and reproducible capillary electrophoresis assay was developed and validated for bovine pancreatic Ribonuclease A (Rnase A). Effects of separation buffer pH and concentration as well as separation power were evaluated on Rnase A samples in phosphate buffered saline in the 5-100 micrograms ml-1 concentration range. The separation variables yielded significant influence on peak elution, with phosphate buffer (pH 2.5; 0.2 M) at separation power of 2 W providing an optimum peak at about 4 min. The peak sharpness and detection limit was further improved by a base/sample/acid injection technique. The optimized method showed good linearity with inter- and intraday RSD of peak area in the 2-5% range. Heat, as well as guainidine hydrochloride denatured samples, showed loss of enzymatic activity, changes in tyrosine fluorescence and abnormal electropherograms. The assay was also compared to a bicinchoninic acid assay that is routinely used for protein quantitation, and found to have greater sensitivity and reproducibility.

Buffers↗
PubMed1994

Lymphocyte compartments in antigen-sampling regions of rabbit mucosal lymphoid organs.

Uptake and delivery of antigens to immunocompetent cells in the gut are critical factors for the development of oral vaccines. Particulate antigens are transported within minutes by M cells to intraepithelial lymphocytes and into the follicle dome. The dome contains B cells, CD4+ T cells, and macrophages, indicating that the cells involved in antigen presentation are located below the dome's epithelium. The high number of M cells in rabbits and the development of monoclonal antibodies against rabbit lymphocytes have enabled the detailed study of lymphocytes associated with M cells. The follicle epithelium of rabbit Peyer's patches contains B cells and a population of CD4-/CD8-, major histocompatibility complex class II+ mononuclear cells of unknown function. These cells are phenotypically distinct from T cells in follicle domes, in T cell-dependent areas, in villus epithelium, or in villus lamina propria. In addition, lymphocytes in M-cell pockets express an activation antigen (3B6) not found on CD4+ or CD8+ cells in T cell-dependent areas. These results indicate that M-cell pocket lymphocytes in follicle epithelium form a phenotypically distinct compartment situated at the interface between M-cell-driven antigen uptake and the mucosal immune system.

Animals↗
PubMed1993

Development and standardization of levothyroxine analysis by high-performance capillary electrophoresis.

This study demonstrates the development of a stability indicating capillary electrophoretic assay of levothyroxine. The optimum separation environment of the assay was determined by examining the effect of pH, buffer concentration, and sample additives on the levothyroxine peak resolution. Phosphate buffer (100 mM), pH 2.5, in a 27-cm capillary produced a satisfactory levothyroxine peak at approximately 10 min. An increase in the concentration of separation buffer increased the migration time and peak area of the levothyroxine peak. The peak symmetry was improved with the addition of methanol and acetonitrile in the sample matrix. However, acetonitrile and methanol concentrations above 25% produced current leakage, probably caused by the formation of microbubbles within the capillary. Standard plot of levothyroxine was established in the range of 3.75 to 60.00 micrograms/ml; with a sample size of 20 nl, this corresponds to 75-2000 micrograms of levothyroxine detected per run. Intra- and interday variability remained < 5% for the standard samples. Separation of levothyroxine from its possible deiodinated degradation products, triiodo- and diiodothyronine T3 and T2, was also obtained under these operating conditions.

Buffers↗
PubMed1992

Optimization and validation of analytical conditions for bovine serum albumin using capillary electrophoresis.

A quick and reproducible capillary electrophoresis method was optimized and validated for the assay of bovine serum albumin (BSA). The effects of various parameters such as pH of buffer, concentration of buffer, capillary dimensions, use of coated capillaries, and additives such as surfactants and protein solubilizers were evaluated. The capillary coatings or additives did not give any advantage in reducing the surface adsorption of BSA on the capillary walls. The optimized conditions include use of borate buffer, pH 8.5 having a concentration of 150 mM in a 27 cm capillary with an aperture window of 100 x 200 microns for detection. The optimized method for the detection of BSA was validated. The interday and intraday coefficient of variation was not greater than 7.59% at BSA concentrations of 25-1000 micrograms/ml. The method developed was reproducible and accurate.

Animals↗
PubMed1992

Cytotoxicity evaluation of a new radiopaque resin additive--triphenyl bismuth.

Triphenyl bismuth (Ph3Bi) is a promising new additive for making biomedical resins visible on x-ray images. We evaluated the cytotoxicity of Ph3Bi, both alone and as a component of a denture resin, as an initial step in determining its biocompatibility. These experimental materials were compared with several types of dental materials that are in current clinical use (PMMA denture acrylic resin, two photo-cured sealants, and two glass-ionomer cements). Human embryonic lung fibroblast tissue cultures (WI-38 cells) were exposed to 24-hour aqueous extracts of the materials. Changes in cell growth, cell viability, and the visual appearance of cells were used for the assessment of toxic response. Only a slight degree of cytotoxicity was observed for Ph3Bi, both alone and in combination with self-cured PMMA. All clinical materials showed a higher level of cytotoxicity than did Ph3Bi. The sealants and cements exhibited the most cytotoxicity and PMMA acrylic the least. The cytotoxicity of PMMA was elevated slightly by inclusion of Ph3Bi, probably due to decreased monomer conversion. When stored in water, the already low levels of cytotoxicity of both PMMA and PMMA with added Ph3Bi were reduced even further. From these results, we can predict a high level of safety for Ph3Bi as a radiopaque additive for biomedical resins. Any toxicity associated with Ph3Bi-containing resins can be reduced or avoided by prior extraction. Alternatively, curing conditions can be selected that would drive the polymerization reaction to a higher level of conversion.

Acrylic Resins↗
PubMed1991

A novel, self-correcting membrane coating technique.

A novel coating process, leading to formation of uniform, defect-free coating on solid dosage forms, is proposed. The coating process, termed "diffusion-controlled interfacial complexation," involves a chemical reaction between a reactant incorporated in the solid unit to be coated and a polymer solution, forming the coating medium. The reaction results in the formation of an insoluble reactant-polymer film around the solid. The rate of film/membrane formation is controlled by the rate of diffusion of reactant through the reactant-polymer film. In the model system, calcium acetate was selected as the reactant and algin as the polymer. The coating process was mathematically characterized in terms of rate of increase in film thickness, film weight, and depletion of reactant. Compressed tablets coated using the above process provided zero-order release in distilled water.

Dosage Forms↗
PubMedDate not supplied

Evaluation of biodegradable microspheres as vaccine adjuvant for hepatitis B surface antigen.

Biodegradable microspheres were evaluated as vaccine adjuvants based on their ability to provide prolonged release of incorporated agents. Hepatitis B surface antigen (HBSA) prepared by recombinant DNA technology was chosen as a model antigen and encapsulated into polyglycolic acid (PGA) by solvent extraction and solvent evaporation techniques. Five microsphere formulations were prepared to evaluate effect of microsphere size and the presence of immunostimulants such as muramyl dipeptide (MDP) or aluminum hydroxide. The microspheres were characterized for size distribution, surface morphology and antigenicity. Guinea pigs were chosen as the animal model for evaluation of antigenicity of the formulations. The animals were divided into seven groups of four animals each and the microsphere formulations were injected intraperitoneally, using alum adsorbed HBSA as positive control and placebo microspheres as negative control. Blood samples were withdrawn from the animals by toe clipping at two, four, six and sixteen weeks and plasma was analyzed for antibodies against hepatitis B by an enzyme linked immunoassay. At sixteen weeks, the animals were reinjected and evaluated for antibody response at two, four and six weeks post second injection. Antibody response to the microspheres was higher than control. Smaller size microspheres elicited earlier antibody response while the larger size microspheres provided delayed and longer duration of antibody production. Microspheres with MDP potentiated the antibody response. The results demonstrate the applicability of biodegradable microspheres for immunization against hepatitis B.

Adjuvants, Immunologic↗