Biomedical subjects

V Senthil

Publications and source records attributed to V Senthil.

5 recordsLinked to original sources

PubMed1996

Type B dissection involving a right-sided aortic arch.

Type B dissection involving a right-sided aortic arch is a very rare condition. Here we describe such an occurrence in an elderly patient who was initially managed medically but later underwent successful surgical repair after developing symptoms of expanding dissection. The dissection was approached through a right thoracotomy. Because of the unusual origin of the arch vessels and the direction of the dissected segment, aortic clamps could not be positioned satisfactorily, necessitating the use of full cardiopulmonary bypass and deep hypothermic circulatory arrest for the repair. The indications for surgery in Type B dissection and the modifications in the surgical strategy necessitated by the abnormal anatomy are discussed.

Aged↗

PubMed1995

Diffuse optics determination of hemoglobin derivatives in red blood cells and liposome encapsulated hemoglobin.

High resolution optical absorption spectra of hemoglobin derivatives in red blood cells and phosphatidylcholine liposomes were calculated from diffuse reflection and transmission spectra by means of the one-dimensional diffusion approximation. The numerical technique of singular value decomposition was used to calculate the composition of red cell and liposome mixtures.

Animals↗

PubMed1994

Hypericin photosensitization in aqueous model systems.

Photosensitization of lysozyme, liposomes, ghosts and intact red blood cells (RBC) was investigated for aqueous hypericin. The effects of azide ion, 1,4-diazabicyclo(2.2.2)octane, and superoxide dismutase on photosensitized inactivation of lysozyme in 0.5% Triton X-100 indicate that singlet oxygen is the major inactivating intermediate with a contribution from superoxide. The singlet oxygen quantum yield (phi delta) scaled to methylene blue is 0.49 +/- 0.06 at monochromatic wavelengths from 514 to 600 nm. Relative values of phi delta based on lysozyme inactivation for different vehicles are: 0.5% Triton X-100 (1.13), human serum albumin (0.65), Cremophor-EL (0.76), Cremophor-RH40 (0.98), egg phosphatidylcholine (EPC) liposomes (0.04), hydrogenated soy phosphatidylcholine (HSPC) liposomes (< 0.01). Hypericin photosensitized lipid peroxidation of EPC liposomes and RBC ghosts. Extensive cross-linking of ghost membrane proteins occurred during the initial stages of lipid peroxidation. Prompt photohemolysis was used as the assay of RBC membrane damage. The photohemolysis curves are modeled with multihit target theory based on the "hit number" (n) and the target cross section (v). The values of v and the conventional "1/t50" parameter are equivalent determinants of the photohemolysis rate. The photohemolysis curves are in good agreement with n = 15 for incubation in phosphate-buffered saline at different hypericin concentrations and with additives. The measurements for other vehicles led to n = 19 for Cremophor-EL and n = 3 for EPC and HSPC liposomes, indicating that the kinetics of photohemolysis depend on the conditions of incubation.

Animals↗

PubMed1992

Photosensitization of aqueous model systems by hypericin.

Absorption and fluorescence measurements of purified hypericin (HY) were made in various media. Photosensitization of two aqueous systems was investigated: resealed red blood cell membranes (ghosts) and hen lysozyme (Lys). Solubilization of HY by ghost membranes was shown by means of diffuse reflectance spectroscopy. Visible light irradiation of the ghosts incorporating HY led to lipid peroxidation with evidence of singlet oxygen involvement. A binding model applicable for insoluble ligands is indicative of strong HY binding to HSA. The HY-HSA complex photosensitized inactivation of Lys. The pseudo-first-order reaction kinetics with protection by azide ion are consistent with a Type II mechanism mediated by singlet oxygen. The results are discussed in the context of the HY photodynamic and antiretroviral activities.

Animals↗

PubMedDate not supplied

Evaluating organic compound migration in poly(ethylene terephthalate): a simple test with implications for polymer recycling.

The safety of recycled plastics for food contact use is largely dictated by the ability of post-consumer organic contaminants to absorb into recycled materials and later diffuse from containers made from recycled plastics into the food supply. Diffusion and solubility data for organic contaminants in poly(ethylene terephthalate) (PET) are scarce. An approach for determining permeability constants, diffusion coefficients and solubility constants of slowly migrating contaminants in PET is described. Compounds (neat or in admixture) were heat-sealed in packets made from thin (0.00127 cm) PET films. Packets were placed in containers with GC sampling closures. Headspace (volatile compounds) or an external liquid medium (non-volatile compounds) was analysed for emergence of the compound. Diffusion coefficients were determined from non-steady state diffusion equations, permeability constants were determined from steady state permeation, and solubility constants were calculated from diffusion and permeability values. Diffusion coefficients (25 degrees C) ranged from 10(-9) to < 10(-16) cm2/s. The diffusion coefficient of benzene increased dramatically with concentration. Compounds with high permeation increased the transport rate of slower permeating volatiles.

Conservation of Natural Resources↗