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Biomedical subjects

C L Stone

Publications and source records attributed to C L Stone.

8 recordsLinked to original sources
PubMed1989

Stereospecific oxidation of secondary alcohols by human alcohol dehydrogenases.

The human liver alpha alpha alcohol dehydrogenase exhibits a different substrate specificity and stereospecificity for secondary alcohols than the human beta 1 beta 1, and gamma 1 gamma 1 or horse liver alcohol dehydrogenases. All of the enzymes efficiently oxidize primary alcohols, but alpha alpha oxidizes secondary alcohols far more efficiently than human beta 1 beta 1 and gamma 1 gamma 1 or horse liver alcohol dehydrogenase. Specifically, alpha alpha oxidizes four- and five-carbon secondary alcohols with efficiencies 0.06-2.2 times that of primary homologs and oxidizes these secondary alcohols with efficiencies up to 3 orders of magnitude greater than those of the three other isoenzymes. Whereas the human beta 1 beta 1, gamma 1 gamma 1 and horse isoenzymes show a distinct preference toward (S)-(+)-3-methyl-2-butanol, the alpha alpha isoenzyme prefers (R)-(-)-3-methyl-2-butanol. Computer-simulated graphics demonstrate that the horse subunit accommodates (S)-(+)-3-methyl-2-butanol within the active site much better than the opposite stereoisomer, primarily due to steric hindrance caused by Phe-93. Human alpha may accommodate (R)-(-)-3-methyl-2-butanol better than (S)-(+)-3-methyl-2-butanol because of close contacts between the latter and Thr-48. These observations suggest that substitutions at positions 93 and 48 in the active site of human liver alcohol dehydrogenase isoenzymes may determine their substrate specificity for secondary alcohols.

Alcohol Dehydrogenase↗
PubMed1977

Delta-aminolevulinic acid dehydratase--a sensitive indicator of lead exposure in Japanese quail.

Red blood cell delta-aminolevulinic acid dehydratase (RBC-ALAD) activity has proven to be a sensitive indicator of lead exposure in humans. The depressed enzyme activity and its negative correlation to blood lead concentrations are well-known effects of lead exposure in man. The sensitivity of RBC-ALAD activity in young Japanese quail exposed to low levels of lead as lead acetate was investigated. Two groups of nine birds each were fed purified diets containing either no added lead or 25 micrograms of lead per g. of diet. After 2 weeks, blood samples for hematocrit, hemoglobin, and enzyme determinations and renal, hepatic, duodenal, and tibial tissues were collected. There were no significant differences between controls and lead-fed birds in body, kidney, duodenal, and tibial weights, or in hematocrit and hemoglobin concentrations. However, the renal, hepatic, duodenal, and tibial lead concentrations were significantly (P less than 0.001) greater in the lead-treated birds. The activity of RBC-ALAD in the group fed lead was 45% of that in the control group; these values were significantly different (P less than 0.001). RBC-ALAD activity expressed as the log. base 10 showed significant (P less than 0.02) negative correlation with both hepatic and tibial lead. The study demonstrates that the activity of RBC-ALAD in the Japanese quail is a very sensitive indicator of lead exposure.

Animals↗
PubMed1976

The effect of dietary selenium level on lead toxicity in the Japanese quail.

Previous studies (Parizek et al., 1969) have shown significant interactions between selenium and certain heavy metals, particularly mercury and cadmium. Since these elements have an affinity for sulfhydryl groups, it was proposed that a similar interaction might exist with lead. In an initial experiment, adult quail hens were given diets supplemented with 0 and 1 p.p.m. selenium and 0, 500 and 1000 p.p.m. lead in a 2 X 3 factorial arrangement. After 32 days of feeding, body weight, liver weight and egg production decreased in birds fed lead while kidney weights increased. Highly significant decreases in red blood cell delta-aminolevulinic acid dehydratase (RBC-ALAD) activity occurred when lead was added to the diet. Control RBC-ALAD activity was 1337 versus 105, 91, 156 and 110 nmol. porphobilogen produced per ml. of erythrocyte per hour (nmol. PBG/ml. RBC/hr.) for the 500, 1000, 500 plus selenium and 1000 plus groups, respectively. After 85 days of feeding lead to male birds in a second study, selenium appeared to have variable effects on the concentration of lead in liver, kidney and tibia. Selenium supplementation to lead diets resulted in significantly increased levels of lead in kidney tissue while little or no effects were observed on liver or tibia lead levels. RBC-ALAD activity was significantly reduced with lead supplementation and no effect of selenium addition was observed. Electrophoretic gels of serum from birds fed lead containing diets showed increased protein bands in the transferrin and globulin regions regardless of the presence of 1 p.p.m. selenium. A third study was conducted to determine the effects of supplementing an isolated soy protein diet with 0 and 1 p.p.m. selenium and 0 and 3000 p.p.m. lead. Selenium supplementation improved body weights over controls while lead additions caused reduced egg production and ALAD activity. Lead feeding increased tibia/body weight ratios and lead concentrations in liver, kidney and tibia. No significant interaction between lead and selenium was observed.

Animals↗
PubMedDate not supplied

The use of utilization review nurses to decrease reimbursement denials.

Since the implementation of HCFA forms 484, 486, and 487, the home health industry has experienced a dramatic increase in the rate of reimbursement denials. One agency responded by developing a utilization review program that has successfully reduced technical and medical denials.

Home Care Services↗
PubMedDate not supplied

A rapid bioassay system for lead using young Japanese quail.

A rapid bioassay of lead was established in young japanese quail. Each group of 10 day-old birds received deionized water and a purified diet ad libitum for 2 wk. The diet contained 0.2 microgram lead/g. Lead acetate was added to give 14.8, 34.4, 51.2, 74.4, 234, 563, or 1223 microgram total lead/g by analysis. The duodenum, kidneys, liver and tibias were assayed for lead. Consumption of a diet containing either 563 or 1223 ppm lead caused a decrease (P less than or equal to 0.05) in body weight after 1 wk and an increase in free erythrocyte protoporphyrin after 2wk. Inhibition of red blood cell delta-aminolevulinic acid dehydratase (RBC-ALAD) activity occurred in birds consuming as little as 14.8 ppm lead. Packed cell volumes and hemoglobin concentrations were not affected by the dietary treatments. Lead concentrations in tissues from birds fed the lowest level of added lead were greater than those found in the corresponding tissues of control birds. The concentration of lead in the tibia showed the most distinguishable group means and the most nearly linear response; the highest slope was between 14.8 and 110 ppm dietary lead, using log-log transformations. The rapid bioassay is suitable for investigating high lead foods.

Animals↗