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Biomedical subjects

M Levitt

Publications and source records attributed to M Levitt.

At least 235 records · Page 13Linked to original sources
PubMed1975

A genetic study of plasma dopamine beta hydroxylase activity in man.

Plasma dopamine beta hydroxylase (DBH) activity was determined in MZ twins and in siblings of both sexes. The enzyme activities were found to be virtually identical in MZ twins. DBH activity was less similar in same-sex sibs, but still significantly correlated. These results indicate that plasma DBH activity is genetically determined.

Adult↗
PubMed1975

Norepinephrine metabolism in mouse heart after lithium and rubidium treatment.

This report describes the effects of treatment with lithium (Li), rubidium (Rb) and sodium (Na; 1 mEq/kg/day) for 7 days on norepinephrine (NE) turnover in mouse heart. The effects of several drugs which modify the uptake and storage of NE were also studied in similarly pretreated mice. A method based on the combustion of tissue tritium to tritiated water was used to assay tritiated l-norepinephrine (l-NE-3H) concentrations in individual hearts. The rate of decline of tissue tritium concentrations in groups of pretreated mice maintained at ambient temperature (23--24 degrees C) or in the cold (4--5 degrees C) was determined. The results indicate that, compared to Na, Li and Rb did not modify the tritium turnover rate in mouse heart. Pretreatment with Li or Rb did not modify the uptake of tritiated NE in the heart. The effects of desipramine. cocaine, bretylium and chlorpromazine on NE uptake were not altered by the alkali ions. Further, pretreatment did not modify NE release by tyramine, metaraminol and guanethidine. These studies suggest that Li and Rb do not modify NE uptake, release and storage in mouse heart.

Animals↗
PubMed1975

A genetic study of plasma dopamine beta-hydroxylase in affective disorder.

Plasma DBH activity was studied in patients with affective illness (unipolar or bipolar) and in their families. We found diagnosis, mood state or lithium treatment did not modify plasma DBH activity. In family studies we found same-sex siblings to show significant correlations for plasma DBH activity regardless of diagnosis. Monozygotic twins had almost identical DBH activities; 4 pairs of monozygotic twins discordant for affective illness were concordant for DHB activity. The heritability estimate for plasma DBH activity is greater than 0.90, indicating a strong genetic influence. These studies reveal that affective illness does not modify plasma DBH activity and that familial factors play an important role in controlling plasma DBH activity.

Adult↗
PubMed1973

Studies on the mechanism of action of nalidixic acid.

With three independent techniques (absorption spectrophotometry, measurement of the deoxyribonucleic acid [DNA] melting temperature, and equilibrium dialysis), no evidence has been found for the binding of nalidixic acid to purified DNA. Also, no evidence has been found to support the hypothesis that nalidixic acid is permanently modified to a new, active compound by the bacterial cell. By using an in vitro DNA replication system developed by Bonhoeffer and colleagues, soluble extracts from nalidixic acid-sensitive cells have been shown to confer nalidixic acid sensitivity on the DNA synthesis of lysates from nalidixic acid-resistant cells. The activity in the extracts is only present in sensitive cells and is nondialyzable and heat sensitive. Finally, two known nalidixic acid-resistant mutants of Escherichia coli, mapping at nal A and nal B, respectively, have been tested to determine whether either of them is a transport mutant. It has been shown that nal B(r) is a transport mutant whereas nal A(r) is not.

DNA Replication↗