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Biomedical subjects

J E Seely

Publications and source records attributed to J E Seely.

27 records · Page 2Linked to original sources
PubMed1982

Purification of ornithine decarboxylase from kidneys of androgen-treated mice.

Ornithine decarboxylase has been purified to homogeneity from kidneys of androgen-treated mice. Such kidneys have an enzyme content 2 orders of magnitude greater than that of other mammalian tissues such as induced rat liver, and only a 10350-fold purification was needed for purification. The enzyme preparation gave a single band on isoelectric focusing and on polyacrylamide gel electrophoresis under native and denaturing conditions. These bands corresponded to the enzyme activity and to the migration of ornithine decarboxylase labeled by reaction with alpha-(difluoromethyl) [5-14C]ornithine, a specific inhibitor. The enzyme has a Mr of about 100 000 and is a dimer of subunit Mr 53 000. The Km for L-ornithine was 75 micron and for pyridoxal phosphate, 0.3 micron. The preparation had a specific activity of 50 mumol of CO2 produced min-1 mg-1 and bound a stoichiometric amount of the irreversible inhibitor, alpha-(difluoromethyl)ornithine (one molecule per subunit). The purified enzyme was unstable even in the presence of 2.5 mM dithiothreitol and 40 micron pyridoxal phosphate unless 0.02% Brij 35 was added. In the presence of this detergent, the enzyme could be stored with little loss of activity.

Androgens↗
PubMed1982

Carnosine-synthetase inhibition of beta-alanine analogues.

A number of beta-alanine analogues were tested for their ability to inhibit carnosine-synthetase from rat and chick skeletal muscle. Of the analogues tested, 3-aminopropane-sulfonic acid (APS) was the most effective inhibitor of enzyme from either source. 5-Aminovaleric acid (5-AV) also inhibited the enzyme from rat, but did not inhibit the enzyme from chick. 2-Aminoethylphosphonic acid and o-phosphoethanolamine had a small amount of inhibitory activity on both rat and chick enzymes, while 3-aminopropanephosphonic acid, aminooxyacetic acid and nipecotic acid had a small amount of inhibitory activity on the rat enzyme only. None of the analogues tested acted as substrates for either enzyme under our conditions. Kinetic data indicated that the inhibition by APS was competitive with respect to beta-alanine for both rat and chick enzymes. Inhibition of the rat enzyme by 5-AV was non-competitive with respect to beta-alanine for both rat and chick enzymes. Inhibition of the rat enzyme by 5-AV was noncompetitive with respect to beta-alanine. APS and 5-AV were also shown to inhibit carnosine-synthetase from rat brain and heart. Chronic injections of either APS or 5-AV failed to produce significant changes in carnosine levels in rat skeletal muscle or brain; however preliminary results indicate that APS injections may produce a lowering of carnosine levels in rat heart.

Alanine↗
PubMed1982

Polyamine biosynthesis and interconversion in rodent tissues.

Polyamine levels in rodent tissues are regulated by the activities of three enzymes: ornithine decarboxylase, S-adenosylmethionine decarboxylase, and spermidine/spermine N1-acetyltransferase. These enzymes are present in the cell in very small amounts, have very short half-lives, and are highly inducible. Ornithine decarboxylase was purified to homogeneity (about 10,000-fold) from androgen-treated mouse kidneys, which have enzyme levels several hundred times higher than those in other fully induced mammalian tissues. This decarboxylase could be specifically labeled either in vitro or in vivo by reaction with radioactive alpha-difluoromethylornithine, an enzyme-activated irreversible inhibitor. Such covalent binding of alpha-difluoromethylornithine was used to titrate the number of molecules of the enzyme and to estimate its purity. It was also used for autoradiographic localization of the enzyme within tissues and to follow the degradation of the protein in vivo. S-Adenosylmethionine decarboxylase has been purified from rat liver and psoas muscle, and significant differences between the enzyme forms present in these tissues were observed. The rate-limiting enzyme in the interconversion of the polyamines, spermidine/spermine N1-acetyltransferase was purified more than 100,000-fold from carbon tetrachloride-induced rat liver. This acetylase acts on both spermine and spermidine to form N1-acetyl derivatives, which are then oxidized by polyamine oxidase forming spermidine and putrescine, respectively.

Acetyltransferases↗
PubMed1981

Carnosine levels in blood.

Carnosine levels were determined in chick erythrocytes (2510 nmoles/g cells) and plasma from chick (27 nmoles/ml),rat and rabbit. Carnosine was also measured in rabbit reticulocyte-rich blood (105 nmoles/g cells), normal blood (18 nmoles/g cells) and in bone marrow.

Animals↗
PubMed1981

Formation of putrescine in rat liver.

Two pathways exist for the formation of putrescine in rat liver. Putrescine can be produced by the action of L-ornithine decarboxylase, an inducible enzyme which can be irreversibly inhibited by the drug, alpha-difluoromethylornithine. A method for quantitating the amount of active ornithine decarboxylase protein present in the liver under various conditions by measuring the binding of [5-14C]alpha-difluoromethylornithine is described. The results indicated that, even when maximally induced, less than 0.0002% of the liver cytosol protein is ornithine decarboxylase. A second pathway for the production of putrescine occurs in the liver by means of the acetylation of spermidine to N1-acetylspermidine and its oxidation to putrescine and N-acetyl-3-aminopropionaldehyde by polyamine oxidase. This pathway is controlled by the activity of spermidine N1-acetyltransferase which is induced by hepatotoxins. Both ornithine decarboxylase and spermidine N1-acetyltransferase turn over rapidly as indicated by the loss of activity in response to cycloheximide. Following treatment with either carbon tetrachloride or thioacetamide, changes in spermidine N1-acetyltransferase activity precede those in ornithine decarboxylase and experiments with appropriate inhibitors indicate that the early enhancement of hepatic putrescine levels if brought about by the acetylase/oxidase pathway. Subsequently, enhanced ornithine decarboxylase activity maintains the putrescine levels and restores the depleted spermidine content of the liver.

Acetyltransferases↗
PubMed1971

Cigarette smoking: objective evidence for lung damage in teen-agers.

High school students with 1 to 5 years' smoking experience have excessive cough, sputum production, and shortness of breath. When maximum expiratory flow is plotted against maximum expired volume, the curves of nonsmokers and smokers differ in shape. The smokers have lower flow rates at mid-vital capacity and at lower lung volumes. This probably reflects small airway obstruction in the smokers.

Adolescent↗