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Biomedical subjects

W S Lin

Publications and source records attributed to W S Lin.

At least 55 records · Page 3Linked to original sources
PubMed1984

Selenium suppresses the metabolism of benzo[a]pyrene by rat-liver extracts, and exerts a dual effect on its mutagenicity.

Liver homogenates from rats injected with 3-methylcholanthrene were employed for metabolism of benzo[a]pyrene (BP) and in assays of aryl hydrocarbon hydroxylase (AHH) activity in vitro. Sodium selenite inhibited AHH activity to a maximum of approximately 70%. It suppressed the overall metabolism of benzo[a]pyrene; a distinct reduction in the products was evident on h.p.l.c. analysis. Sodium thiosulphate also inhibited AHH activity by approximately 47%. Inclusion of S2O3(2-) and SeO3(2-), in combination, led to a cumulative inhibition of 87%. The mutagenicity of BP in the Salmonella auxotroph reversion system (Ames test) was enhanced by SeO3(2-) at concentrations below 0.2 mM. Above this level a significant antimutagenic effect was observed.

Animals↗
PubMed1984

Studies on the induction of aryl hydrocarbon(benzo[a]pyrene) hydroxylase in Neurospora crassa, and its suppression by sodium selenite.

Six fungal species were grown in the presence of benzo[a]pyrene (BP); four showed benzo[a]pyrene hydroxylase (aryl hydrocarbon hydroxylase, AHH) activity. Penicillium sp. and Neurospora crassa metabolized BP to a limited extent. N. crassa AHH activity was induced by BP, the major product of metabolism being 3-hydroxy-BP. Both induction of AHH activity and metabolism of BP were suppressed by sodium selenite in the growth medium. Two polypeptides, unique to BP-grown cells, were revealed by two-dimensional electrophoretic separation of [35S]methionine-labelled proteins in N. crassa cell extracts. In selenium-grown cells the synthesis of BP-specific polypeptides was severely inhibited.

Aryl Hydrocarbon Hydroxylases↗
PubMed1983

Hepatitis-B surface antigen and hepatocellular carcinoma in Taiwan. With special reference to types and localization of HBsAg in the tumor cells.

The relationship between hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC), with or without cirrhosis, was assessed immunopathologically through the detection of tissue hepatitis B surface antigen (HBsAg) on paraffin sections of 284 biopsy and surgical specimens of HCC, which were performed from 1970 to 1979, by the indirect immunoperoxidase technique. In 190 cases with nontumorous liver tissue available for histologic and etiologic analyses, cirrhosis was identified in 69.8% (37 of 53) in needle biopsy, 67.4% (31/46) in wedge, and 30.8% (28/91) in the resection or lobectomy group. HBsAg was detected in the nontumorous liver parenchyma in 85.7% in the whole series, and 90.6% in the cirrhotic cases (96.8% in wedge and 100% in resection cases). The HBsAg positivity in the noncirrhotic cases of the resection group was 84.1% (53/63), whereas the 10 negative cases in this group were all noncirrhotic. This clearly demonstrates a strong association of HBsAg and HCC in both cirrhotic and noncirrhotic patients in Taiwan, particularly in the cirrhotic group, as evidenced by the high prevalence of HBsAg in wedge and resection series. On the other hand, the etiology in the HBsAg-negative and noncirrhotic group, which also had a less evident male predominance (male:female = 3.3:1 versus 6-19.5:1) and significantly less liver cell dysplasia than HBsAg-positive or cirrhotic groups, remains to be explained. In 223 cases where tumor tissue met the minimal requirement for analysis, HBsAg was demonstrated in 27 cases (12.1%) in the tumor cells (15% in the resection group). This investigation indicates an important etiologic role of HBV in hepatocellular carcinogenesis, and the development of HCC does not depend on the coexistence of cirrhosis in Taiwan.

Adolescent↗
PubMed1979

Regeneration of human liver after hepatic lobectomy studied by repeated liver scanning and repeated needle biopsy.

Regeneration of the residual lobe of the liver after hepatic lobectomy in humans was studied by repeated liver scanning in seven noncirrhotic and three cirrhotic patients. Each patient was studied for several months during the study which lasted from 1-12 years. Regeneration was apparent in noncirrhotic liver remnants following hepatic lobectomy. In the case of a long standing, space occupying lesions such as benign giant cysts, the liver remnant would complete its regeneration process rather early, usually within a few months of hepatic lobectomy. In hepatoma cases, however, regeneration of the residual lobe after hepatic resection usually took five or six months for completion. On the contrary, no definite increase in the size of the liver remnant was seen on repeated liver scanning in cirrhotic patients. Histologic study of the residual lobe was repeated on needle biopsy specimens in two noncirrhotic and four cirrhotic patients. Regenerative hyperplasia of liver cells with large hyperchromatic, or double nuclei never seen in the preresection liver appeared in the liver remnant five, 11, and 27 days after hepatic lobectomy in noncirrhotic patients. In cirrhotics, however, there were no histologic changes between the preresection liver and the postresection remnant studied three, five, 15, 40 days or even two years and 8 months after hepatic lobectomy.

Biopsy, Needle↗
PubMed1978

Effects of superoxide dismutase, dithiothreitol and formate ion on the inactivation of papain by hydroxyl and superoxide radicals in aerated solutions.

Losses in enzyme activity and sulphydryl content have been studied in aerated papain solutions containing formate, superoxide dismutase and dithiothreitol. Both formate and dithiothreitol converted .OH to .O2-, whereas superoxide dismutase completely suppressed the inactivation by .O2-. Using results from all three systems, the fraction of .O2- reactions with papain that caused inactivation of the enzyme was 0.33 +/- 0.07. The results also showed that the fraction of .OH reactions, which cause inactivation of papain, is significantly higher in aerated than in oxygen-free solutions.

Cobalt Radioisotopes↗
PubMed1978

Purification and studies of some physicochemical properties of glutamine synthetase of Neurospora crassa.

Glutamine synthetase (EC 6.3.1.2) of Neurospora crassa was purified to near homogeneity by chromatography on a glutamate-Sepharose affinity column. Its properties, including molecular weight, subunit structure, amino acid composition, and approximate alpha-helix content, have been examined. In the native state, this enzyme has been demonstrated by gel filtration to be an octamer of molecular weight 360,000 and as having a sedimetation coefficient of 13.2 S by sedimentation velocity measurements. Circular dichroism spectra in the far ultraviolet range suggest an approximate alpha-helix content of 23-24%. The subunit generated by treatment with urea was found to be 45,000 daltons by gel filtration methods and a molecular weight of 46,000 was calculated for the monomer obtained by sodium dodecyl sulphate (SDS) treatment and electrophoresis in SDS-polyacrylamide gels. Interprotomeric cross-linking experiments, using diimidoesters, suggest the presence of two noncovalently linked tetramers comprising the native octameric structure. Amino acid analyses revealed the presence of six tryptophans, four half cystines, and nine methionine residues per monomer of 45,000 daltons.

Amino Acids↗