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Y B Chiao

Publications and source records attributed to Y B Chiao.

14 recordsLinked to original sources
PubMed1986

Characterization of rat testicular alcohol dehydrogenase.

A protein from rat testes that catalyzes the oxidation of ethanol in the presence of NAD+, but not NADP+, has been characterized enzymatically and compared to that of hepatic alcohol dehydrogenase obtained from the same animals. The testicular enzyme, like the hepatic enzyme, has a Km value for ethanol in the 0.5-1.0-mM range and can utilize other alcohols such as n-propanol, n-butanol, and isobutanol, although the Km values for these other alcohols are considerably lower (0.03-0.08 mM) that that for ethanol. The testicular enzyme is more heat-labile than is the hepatic enzyme. Finally, the testicular enzyme catalyzes the oxidation of retinol and its retinol dehydrogenase activity is inhibited by ethanol.

Alcohol Dehydrogenase↗
PubMed1983

Biochemical mechanisms that contribute to alcohol-induced hypogonadism in the male.

The above review has presented most if not all of the available evidence supporting a role for alcohol and acetaldehyde as putative environmental Leydig cell toxins for man and animals. Despite a considerable data base and much progress, particularly in the last decade, much yet remains to be learned concerning this phenomenon. It is hoped that this review, and this symposium, will contribute to future progress in this area by providing a basis for new and provocative observations and hypotheses to be tested by a new generation of clinical investigators.

3-Hydroxysteroid Dehydrogenases↗
PubMed1981

Purification and characterization of a cytosolic broad specificity beta-glucosidase from human liver.

A cytoplasmic beta-glucosidase has been isolated and purified 9,000-fold to homogeneity from the liver of a case of type 1 Gaucher's disease to a specific activity of 400,000 nmol/h/mg of protein. Although markedly elevated above control levels in this case of adult Gaucher's disease, the activity of this cytosolic liver enzyme was found to be markedly deficient in two cases of neurologic Gaucher's disease. The purification scheme employs QAE-Sephadex, DE52 cellulose, CM-Sephadex, hydroxylapatite, and Cibacron blue-Sepharose chromatography, and preparative isoelectric focusing. The beta-glucosidase preparations isolated from the liver of the case of adult Gaucher's disease and control liver have similar physical properties. Both enzymes have a molecular weight of approximately 53,000, sw,20 of 4.3, pI of 4.5-4.6, a pH optimum between 5 and 6, and a high affinity for 4-methylumbelliferyl-beta-D-glucopyranoside (Km = 0.06-0.07 mM). The enzymes from both sources also have a broad specificity and will hydrolyze the 4-methylumbelliferyl derivatives of beta-D-galactose, beta-D-fucose, beta-D-xylose, and alpha-L-arabinose in addition to several aryl-galactosides and steroid-glucosides. The cytoplasmic beta-glucosidase will not hydrolyze glucocerebroside and shows no cross-reactivity with antibodies prepared against lysosomal glucocerebrosidase. Both cytoplasmic beta-glucosidase and glucocerebrosidase will hydrolyze 17 beta-estradiol-17'-beta-D-glucose, and the activity of both enzymes on this substrate is increased more than 15-fold in the presence of the Gaucher spleen heat-stable factor. The role of this cytoplasmic beta-glucosidase in the etiology of Gaucher's disease and its possible relationship to lysosomal glucocerebrosidase are discussed.

Cytosol↗
PubMed1981

Effect of chronic ethanol feeding on testicular content of enzymes required for testosteronogenesis.

Ethanol is a known inducer of microsomal enzymes as well as a testicular toxin. In order to evaluate the effect of chronic ethanol ingestion upon the microsomal enzymes required for testosterone synthesis, we examined the activity of four testicular enzymes (3 beta-hydroxysteroid dehydrogenase/isomerase, 17 alpha-hydroxylase, 17,20-lyase, and 17 beta-hydroxysteroid dehydrogenase) in 14 pairs of adult chronic alcohol-fed rats and their age-matched isocaloric controls. Ethanol feeding enhanced the activity of 17,20-lyase when expressed as either activity/mg of protein (p less than 0.05) or activity/g of testis (P less than 0.025). Similarly, the activity of 17 alpha-hydroxylase was increased in testes of the alcohol-fed animals (p less than 0.025) compared to controls. In contrast, chronic ethanol feeding reduced total activity of 3 beta-hydroxysteroid dehydrogenase/isomerase in alcohol-fed animals (p less than 0.05) compared to controls. No effect of ethanol feeding was seen on activity of 17 beta-hydroxysteroid dehydrogenase. Based upon these studies we conclude that chronic ethanol ingestion (1) increases testicular 17 alpha-hydroxylase and 17,20-lyase and (2) reduces 3 beta-hydroxysteroid dehydrogenase/isomerase in rat testicular microsomes. Therefore, we would propose that the major effect of chronic ethanol ingestion upon the enzymes required for testosterogenesis is the reduction of 3 beta-hydroxysteroid dehydrogenase/isomerase activity, the rate limiting step in sex steroid production from pregnenolone.

17-Hydroxysteroid Dehydrogenases↗
PubMed1980

Alcohol and sexual function.

The pathophysiologic factors which either document or which have been shown to be responsible for not only the hypogonadism and feminization of chronic alcoholic men but also the loss of gonadal function with resultant defeminization of chronic alcoholic women are reviewed. Evidence is presented which suggests that alcohol abuse is associated with the production of a primary form of hypogonadism characterized by loss of endocrine and reproductive function of the gonads. Moreover, evidence is presented which suggests that alcohol abuse is associated with the production of an associated hypothalamic-pituitary defect in gonadotropin secretion which prevents appropriate enhancement of gonadotropin secretion in response to the primary gonadal injury. Finally, the factors which have been found to partially explain the feminization often seen in chronic alcoholic men with advanced liver disease are discussed individually and a composite mechanism incorporating each is presented.

Alcoholism↗
PubMed1978

Multiple glycosidase deficiencies in a case of juvenile (type 3) Gaucher disease.

Biochemical investigations were performed on autopsy tissues obtained from an 11-year-old girl who died with the juvenile, subacute neuropathic form of Gaucher disease. In addition to the expected deficiency of glucocerebrosidase activity, extracts of both liver and kidney from this individual displayed a profound (greater than or equal to 90%) deficiency of "soluble" beta-glucosidase, beta-xylosidase, and beta-galactosidase activities. Fibroblasts obtained from this individual also contained markedly reduced levels of beta-xylosidase activity but normal levels of beta-D-fucosidase and beta-galactosidase activity. Because the soluble beta-glucosidase, beta-xylosidase, and a portion of the beta-galactosidase activities from control human liver all cochromatographed on a gel filtration column of Sephadex G-200, it is suggested that these activities all reside in a single enzyme, analogous to the situation described in a number of nonhuman, mammalian tissues. This demonstration of multiple glycosidase deficiencies in addition to the deficiency of glucocerebrosidase in a case of subacute neuropathic Gaucher disease suggests that other biochemical aberrations, in addition to a deficiency of glucocerebrosidase, might contribute to pathology in some cases of Gaucher disease.

Child↗