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Biomedical subjects

W Yang

Publications and source records attributed to W Yang.

At least 577 records · Page 32Linked to original sources
PubMed1985

Defect in alpha-ketobutyrate metabolism: a new inborn error.

A pair of siblings with clinical symptoms of cyclic vomiting and ketoacidosis were found to have a biochemical triad of normoglycemia, ketoacidosis and elevated levels of alpha-hydroxy- and alpha-aminobutyrate in plasma and urine. Methionine loading studies in both sibs produced prompt rises in plasma methionine and alpha-aminobutyrate levels, with a subsequent increase in urinary alpha-hydroxybutyrate, as well. Leukocytes from both siblings showed normal oxidation of [3-14C]propionate. Increased inorganic sulfate excretion after methionine loading implied an intact transsulfuration pathway in both siblings. On the basis of the studies detailed in this report, we conclude that these siblings suffer from a defect in alpha-ketobutyrate oxidation, a newly described defect of organic acid metabolism.

Acidosis↗
PubMed1985

Hardness, softness, and the fukui function in the electronic theory of metals and catalysis.

The concepts of hardness eta = (2E/N2)nu and fukui function f(r) = [rho (r)/N]nu, which have recently been associated with the theory of chemical reactivity in molecules, are extended to the theory of metals. It is shown that at T = 0, 1/eta = g(epsilon F) and f(r) = g(epsilon F, r)/g(epsilon F), where g(epsilon F), and g(epsilon F, r) are the density of states and the local density of states, at the Fermi energy epsilon F. Softness S and local softness s(r) are defined as 1/eta and Sf(r), respectively, and it is shown that (formula; see text) where the averages are over a grand canonical ensemble. It is pointed out that the postulate that f(r) or g(epsilon F, r) determines site selectivity for metals in chemisorption and catalysis is synonymous with the recent argument by Falicov and Somorjai [Falicov, L. M. & Somorjai, G. A. (1985) Proc. Natl. Acad. Sci. USA 82, 2207-2211] that such selectivity is determined by low-energy density fluctuations.

Chemical Phenomena↗
PubMed1983

Medium-chain acyl-CoA dehydrogenase deficiency in children with non-ketotic hypoglycemia and low carnitine levels.

Three children in two families presented in early childhood with episodes of illness associated with fasting which resembled Reye's syndrome: coma, hypoglycemia, hyperammonemia, and fatty liver. One child died with cerebral edema during an episode. Clinical studies revealed an absence of ketosis on fasting (plasma beta-hydroxybutyrate less than 0.4 mmole/liter) despite elevated levels of free fatty acids (2.6-4.2 mmole/liter) which suggested that hepatic fatty acid oxidation was impaired. Urinary dicarboxylic acids were elevated during illness or fasting. Total carnitine levels were low in plasma (18-25 mumole/liter), liver (200-500 nmole/g), and muscle (500-800 nmole/g); however, treatment with L-carnitine failed to correct the defect in ketogenesis. Studies on ketone production from fatty acid substrates by liver tissue in vitro showed normal rates from short-chain fatty acids, but very low rates from all medium and long-chain fatty acid substrates. These results suggested that the defect was in the mid-portion of the intramitochondrial beta-oxidation pathway at the medium-chain acyl-CoA dehydrogenase step. A new assay for the electron transfer flavoprotein-linked acyl-CoA dehydrogenases was used to test this hypothesis. This assay follows the decrease in electron transfer flavoprotein fluorescence as it is reduced by acyl-CoA-acyl-CoA dehydrogenase complex. Results with octanoyl-CoA as substrate indicated that patients had less than 2.5% normal activity of medium-chain acyl-CoA dehydrogenase. The activities of short-chain and isovaleryl acyl-CoA dehydrogenases were normal; the activity of long-chain acyl-CoA dehydrogenase was one-third normal. These results define a previously unrecognized inherited metabolic disorder of fatty acid oxidation due to deficiency of medium-chain acyl-CoA dehydrogenase.

Acyl-CoA Dehydrogenase, Long-Chain↗
PubMed1982

Diet and vitamin nutrition of the high esophageal cancer risk population in Linxian, China.

In order to examine the nutritional status of the population of Linxian (in Henan, China) known to be at high risk for esophageal cancer (EC), we analyzed blood samples and conducted 3-day dietary surveys on 3 groups of normal adults, age 40-50, from Henan province. Two groups were from Linxian, where the EC mortality rate is about 138/100,000 (Group C, consisting of volunteers with a family history of EC, and Group NC, consisting of those who did not have a family history of EC). The third group, Group F, was from Fanxian, where the EC mortality rate is about 24/100,000. The average plasma retinol level was found to be about 0.27 micrograms/ml in all 3 groups; about 13%-20% of the individuals had a level less than 0.2 micrograms/ml. The average plasma carotene level of all 3 groups appeared to be adequate, ranging from 0.5-1.0 micrograms/ml. About 23% of the subjects in both Groups C and NC had low (less than 2 micrograms/ml) plasma ascorbate levels; in Group F, 16% had low ascorbate levels. Less than 12% of the individuals in each of the 3 groups had erythrocyte glutathione reductase activation coefficients less than 1.2, indicating a widely occurring riboflavin deficiency. Consumption of alcoholic beverages was not found to be a contributing factor to EC. The results of the present study reveal a deficiency of vitamins in the study populations, but do not indicate that the average nutritional status of the volunteers in Group C was worse than that of Groups NC and F with regard to vitamin A, ascorbate, and riboflavin.

Adult↗
PubMed1982

Prenatal administration of biotin in biotin responsive multiple carboxylase deficiency.

Biotin responsive multiple carboxylase deficiency was suspected in a third trimester conceptus on the basis of enzymatic confirmation in fibroblasts cultured from an earlier sibling who suffered a demise in the immediate neonatal period. Maternal urinary organic acid profile was normal throughout the final 4 wk of pregnancy. Oral administration of biotin, 10 mg/day to the mother resulted in a 100-fold increase in urinary biotin excretion within 7 days. Urinary biotin excretion over the subsequent 2 wk decreased steadily, suggesting either decreased maternal absorption or increased fetal sequestration. After the birth of nonidentical twins, cord blood and urinary organic acid profiles of the infants were normal. However, cord blood biotin concentration was 4 to 7-fold that of normal newborns. Subsequent enzymatic and genetic complementation studies utilizing cultured skin fibroblasts from the infants demonstrated one of them to be affected by the multiple carboxylase defect, although he was clinically and biochemically normal throughout the neonatal period. Thus, prenatal therapy of this inborn enzymatic defect can be safely and effectively accomplished by administration of pharmacologic biotin doses in the last month of pregnancy.

Biotin↗
PubMed1981

Rapid gas chromatographic-mass spectrometric analysis of [15N]urea: application to human metabolic studies.

A rapid gas chromatographic-mass spectrometric method for [15N]urea analysis is described which is based on the formation of a TFA-urea derivative. The method is extremely sensitive, being capable of detecting less than 0.2 atom % excess [15N]urea in as little as 50 microliter of plasma and 10 microliter of urine with a coefficient of variation of 11%. The method was used to measure in vivo the disappearance of [15N]urea from plasma and the incorporation of [15N]ammonium acetate into [15N]urea. The values obtained for urea pool size and flux are 4.5 +/- 0.30 g nitrogen/total body weight and 16.2 +/- 1.34 g nitrogen per 24 h per 1.73 m2. Following the ingestion of [15N]ammonium acetate nearly 90% of the 15N label was incorporated into [15N]urea by 30 min.

Adult↗
PubMed1981

Serum and urinary biotin levels during treatment of holocarboxylase synthetase deficiency.

Measurements of blood and urine biotin levels have been performed during treatment of a patient with holocarboxylase synthetase deficiency. During the first 24 hours of therapy, the infant progressed from a moribund, shock-like state to a clinically normal baby. Urinary biotin concentration increased more that 100-fold after 12 hours of treatment. Within 48 hours of treatment, blood biotin levels were greater than 10 times control levels. On the basis of the data presented, it is suggested that therapeutic blood levels of biotin can be achieved by enteral administration of 10 mg of biotin per day.

Apoproteins↗