Biomedical subjects

W Dairman

Publications and source records attributed to W Dairman.

29 records · Page 2Linked to original sources

PubMed1971

Decrease in adrenal tyrosine hydroxylase and increase in norepinephrine synthesis in rats given L-dopa.

When large doses of L-dopa (1000 milligrams per kilogram, given subcutaneously) were administered to rats, the rate of catecholamine synthesis was increased in both the heart and adrenal gland. It is likely that increases also occur in other sympathetically innervated tissues. When the same dose of L-dopa was given daily for 4 or 7 days, the levels of tyrosine hydroxylase in the adrenal were lowered in comparison to controls. These findings may be a further indication of the existence of a regulatory mechanism which modifies endogenous levels of tyrosine hydroxylase in response to changes in the biosynthetic demand for norepinephrine.

Adrenal Glands↗

PubMed1971

Condensation of ninhydrin with aldehydes and primary amines to yield highly fluorescent ternary products. I. Studies on the mechanism of the reaction and some characteristics of the condensation product.

Explore the source record for details and available documents.

Aldehydes↗

PubMed1971

Condensation of ninhydrin with aldehydes and primary amines to yield highly fluorescent ternary products. II. Application to the detection and assay of peptides, amino acids, amines, and amino sugars.

Explore the source record for details and available documents.

Aldehydes↗

PubMed1971

Decrease in liver aromatic L-amino-acid decarboxylase produced by chronic administration of L-dopa.

L-Dopa, an intermediate in the biosynthesis of catecholamines, is now widely used in the treatment of parkinsonism. A number of clinical observations suggested that L-dopa may induce changes in its own metabolism during the course of therapy. In the present study, it was found that when L-dopa was administered to rats, the activity of liver aromatic L-amino-acid decarboxylase, the enzyme which catalyzes the conversion of dopa to dopamine, was reduced by as much as 50%. There were no corresponding changes in enzyme activity in heart, adrenals, kidneys, and brain. Decarboxylase activity in the liver continued to decrease for at least 5 days after the last dose of L-dopa. The reduction of enzyme activity in the liver occurred when L-dopa was administered either subcutaneously or orally at doses comparable to those used clinically. In vitro and in vivo experiments indicated that this action of L-dopa is not due to some effect on the cofactor, pyridoxal phosphate. Immunological evidence was obtained that enzyme protein is reduced in the same proportion as enzyme activity. By a reduction of decarboxylase activity in liver without any affect on the enzyme in brain, more L-dopa should be made available to the brain for decarboxylation to dopamine. These findings may explain the clinical observations that the therapeutic efficacy of the drug increases with continued administration.

Administration, Oral↗

PubMed1970