Search PubMed⌕ Search

Biomedical subjects

H Shichi

Publications and source records attributed to H Shichi.

At least 91 records · Page 5Linked to original sources
PubMed1985

Preparation of a uveitogenic peptide by chymotryptic digestion of bovine S-antigen.

Limited proteolysis of bovine S-antigen with alpha-chymotrypsin resulted in the accumulation of three peptides of MW 24,000, 16,000, and 12,000 daltons, respectively. By ELISA (enzyme-linked immunosorbent assay), MW 24,000 peptide was found to react with anti-S antibodies, but the other two peptides did not react with the antibodies under the assay conditions. The reactive peptide was separated from the smaller peptides by gel filtration on Sephadex G-75 and Sephadex G-50. When the MW 24,000 peptide was injected into Lewis rats, severe to mild uveitis was produced in all injected animals. The results indicate that the pathogenic determinant is on the MW 24,000 peptide.

Animals↗
PubMed1984

GTP binding protein: properties and lack of activation by phosphorylated rhodopsin.

Taking advantage of the capability of GTP binding protein to bind GTP, we purified the catalytic subunit (G alpha) of bovine rod GTP binding protein by nucleotide-affinity chromatography on Blue Sepharose CL6B. Purified G alpha was essentially free of bound guanine nucleotide and activated by photoactivated rod membranes. Circular dichroism spectra suggested that a significant portion of the protein would be in alpha-helical conformation. No appreciable differences were detected in the circular dichroism spectra when G alpha . GDP and G alpha . GppNp were compared. The extent of G protein activation by rod membranes was reduced moderately by phosphorylation of rhodopsin during photolysis. However, if the pigment had been phosphorylated and regenerated, the ability of rhodopsin to activate G protein was markedly suppressed.

Animals↗
PubMed1984

Radioimmunocytochemical localization of retinal S-antigen with monoclonal antibodies.

Two monoclonal antibodies (RSA1/83 and RSA2/83) were developed against a homogeneous preparation of bovine retinal S-antigen. The two hybridomas produced by mouse X mouse hybrid myeloma cells secrete immunoglobulin G. Indirect autoradiography on glutaraldehyde-fixed preparations of bovine explants was used to locate the antigenic site. Antibody RSA1/83 recognizes the antigen primarily in the apical region of the rod outer segment, while antibody RSA2/83 located the antigen both in the outer and inner segments of the rod photoreceptor cells. A distinct band of silver grains also appeared along the inner limiting membrane with both antibodies. Control explants showed no specific labeling pattern over the various retinal compartments.

Animals↗
PubMed1983

Rhodopsin phosphorylation occurs at metarhodopsin II level.

Photolyzed rhodopsin was phosphorylated in bovine rod outer segments incubated at -10 degrees C. In the experiment in which urea-treated outer segments and rhodopsin kinase were incubated with ATP in the presence of 30% glycerol, the extent of phosphate incorporation at -10 degrees C was about 30% of that at 37 degrees C. Separation of phosphorylated rhodopsin by isoelectric focusing indicated that a limited number of sites were phosphorylated at -10 degrees C. The partially phosphorylated pigment incorporated more phosphates when the temperatures was raised to 37 degrees C. This was partly due to decreased inhibition of phosphorylation by glycerol at higher temperature. Since the maximum phosphorylation at -10 degrees C (at which metarhodopsin II is stable) occurred at a pH value (6.0) lower than the pKa for metarhodopsin I-metarhodopsin II transition, metarhodopsin II was suggested to be the preferred substrate for rhodopsin kinase at -10 degrees C. Limited proteolysis with thermolysin of rhodopsin phosphorylated at 37 degrees C released peptides containing about 50% of the total phosphate incorporated. In contrast, proteolytic digestion of rhodopsin phosphorylated at -10 degrees C released negligible amounts of phosphate-containing peptides. The results were taken to suggest that the incorporation of phosphates at metarhodopsin II level under the present condition occurred in the residues other than those removed by thermolysin digestion.

Animals↗
PubMed1983

Carbohydrate structures of bovine kidney gamma-glutamyltranspeptidase.

The carbohydrate moieties of gamma-glutamyltranspeptidase (gamma-GTP) purified from bovine kidney were chemically released as oligosaccharides. The oligosaccharide mixture was fractionated into a neutral fraction and three groups of acidic fractions containing one, two, and three sialic acid residues. Both the neutral fractions and the neutral oligosaccharide mixture obtained from the pooled sample of all acidic fractions by sialidase treatment were separated into seven components by Bio-Gel P-4 column chromatography. Structural studies of these components by sequential exoglycosidase digestion in combination with methylation analysis indicated that the gamma-GTP contains at least twelve neutral sugar chains which are either the high mannose type, or the bi- and triantennary complex type, and thirteen acidic sugar chains of the bi-, tri-, and tetraantennary complex type. The characteristics feature of the sugar chains of the gamma-GTP is that most of the complex type sugar chains contain an N-acetylglucosamine residue at the C-4 position of the beta-mannosyl residue of their trimannosyl core, and their outer chain moieties are enriched in non-reducing terminal beta-N-acetylglucosamine residues.

Animals↗
PubMed1982

Genetic differences in drug metabolism associated with ocular toxicity.

The tissue localization and subcellular distribution of drug-metabolizing enzymes in the eye are described. With the use of inbred strains of mice, the [Ah] complex is shown to be an important experimental system for probing genetic differences in drug metabolism and related drug toxicities. Although the genetic system described in detail here involves mice, there is ample evidence that the same system operates in man. Genetic differences in acetaminophen- and naphthalene-induced cataract formation and and other ocular degeneration are shown to be related to the [Ah] complex. Because this toxicity appears similar to senile cataracts, we propose that certain types of drug-induced cataracts might exist among clinical populations of senile cataracts but that any cause-and-effect relationship would be very difficult to determine because of underlying interindividual differences in genetic predisposition. It is therefore suggested that genetic differences in drug metabolism be an important consideration in the clinical assessment of ocular toxicity caused by drugs and other environmental pollutants.

Acetaminophen↗
PubMed1981

Resemblance between rhodopsin kinase and S-antigen induced uveitis.

The retinal S-antigen (S-Ag) has been shown to induce uveitis effectively in subhuman primates, and lymphocytes from patients with certain uveitic conditions show cell-mediated responses to this antigen. Rhodopsin kinase (RK), an enzyme probably unique to the mammalian eye, is reported here to resemble the retinal S-Ag in its capacity to induce uveitis in experimental animals. A histological comparison of rat eyes taken 2 and 3 weeks after immunisation with either RK or S-Ag reveals essentially identical pathological alterations. Ocular inflammation is seen in both the anterior and posterior portion of the globe. Areas of focal degeneration of the photo-receptor layer, from which both the S-Ag and RK are extracted, could be seen in both RK and S-Ag immunised animals. Cells from draining lymph nodes of both groups responded by increased thymidine incorporation when cultured in the presence of either RK or S-Ag. In addition antibodies directed against the S-Ag were detected in both groups. These findings, in addition to the biochemical similarities of these preparations, reported elsewhere, would strongly suggest that RK and S-Ag are one and the same. The identification of potentially uveitogenic ocular antigens could help to reclassify uveitic entities that at present have clinically similar courses.

Animals↗
PubMed1980

The N-terminal residue of bovine rhodopsin is acetylmethionine.

By affinity chromatography on a concanavalin A-Sepharose column and gel filtration on a Sephadex G-25 column, a glycopeptide of 16 amino acid residues has been separated from a tryptic digest of reduced and carboxymethylated bovine rhodopsin. The glycopeptide was treated with cyanogen bromide and products were subjected to high-voltage paper electrophoresis. N-Blocked homoserine separated was reacted first with anhydrous hydrazine and then with dansyl chloride. The product was identified by thin-layer chromatography to be 1-acetyl-2-dansyl hydrazine, thus showing that the N-terminal blocking group was an acetyl group. The remaining peptide after cyanogen bromide treatment was partially sequenced by the Edman dansylation method. The present results and previously reported findings on the binding site of the sugar moiety, taken together, indicate that the N-terminal heptapeptide has the following structure: acetylMet-Asn(carbohydrate)-Gly-Thr-Glx-Gly-Pro.

Amino Acid Sequence↗