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Biomedical subjects

W Lovenberg

Publications and source records attributed to W Lovenberg.

At least 127 records · Page 7Linked to original sources
PubMed1979

Dopamine-beta-hydroxylase in the cerebrospinal fluid: relationship to disulfiram-induced psychosis.

Cerebrospinal fluid (CSF) dopamine-beta-hydroxylase (DBH) activity in 32 male alcoholics was measured using a modification of the radioenzymatic method of Molinoff et al. In most, the CSF was obtained before treatment with disulfiram, while in others it was obtained while they were on the drug (250 or 500 mg). As expected, treatment with this reversible DBH inhibitor had no effect on the activity of the enzyme measured in our in vitro assay. However, low pretreatment DBH activity was found to correlate with adverse reactions to disulfiram. Mean DBH activity of four individuals who went on to become psychotic on disulfiram was 0.13 +/- 0.02 nmole/ml per hr (mean +/- SEM). An additional four individuals who developed dysphoric but nonpsychotic reactions had a mean DBH of 0.23 +/- 0.03. Both these values were significantly lower than the mean DBH activity of the remaining 24 individuals treated with disulfiram who had no adverse side effects, 0.53 +/- 0.06 p less than 0.02 and p less than 0.05, respectively, 2-tailed t-test.

Adolescent↗
PubMed1978

Tyrosine hydroxylase. Activation by protein phosphorylation and end product inhibition.

Protein phosphorylation activates tyrosine hydroxylase in crude extracts of rat striatum, hypothalamus, and adrenal glands by a reduction in the apparent Km value for 6-methyltetrahydropterin. Removal of endogenous catecholamines by gel filtration or cation exchange results in a similar activation. Phosphorylation causes only a small additional reduction in the apparent Km for reduced pterin in striatal extracts from which catecholamines have been removed. Kinetic analysis indicates that protein phosphorylation causes a significant increase in the Ki for end product dopamine, whereas gel filtration or cation exchange treatment has little effect on the dopamine Ki value. None of the above treatments appears to change the molecular weight of the enzyme. At physiological concentrations of dopamine, the increase in Ki by phosphorylation would effectively release tyrosine hydroxylase from end product feedback inhibition.

Adrenal Glands↗
PubMed1978

Modification of the tyrosine hydroxylase assay. Increased enzyme activity in the presence of ascorbic acid.

A modification of the tyrosine hydroxylase assay is described in which ascorbate, rather than 2-mercaptoethanol or dihydropteridine reductase with NADPH, is used as the reductant. Enzyme activity is 3-4 times higher with ascorbate than with the other reducing agents. Low blanks are obtained with the ascorbate system provided that catalase is also included. The tissue distribution and kinetic activation of the enzyme have been studied with the ascorbate assay. The results obtained are consistent with the biological and regulatory properties of the enzyme which have been determined with the other reducing systems.

Adrenal Glands↗