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Biomedical subjects

A A Benson

Publications and source records attributed to A A Benson.

At least 37 records · Page 2Linked to original sources
PubMed1978

Arsoniumphospholipid in algae.

A novel phospholipid containing arsenic was formed by all marine algae cultured in [(74)As]arsenate. Components of the labeled algal extracts readily separated by two-dimensional paper radiochromatography. Base-catalyzed deacylation of the major lipid yielded a phosphodiester identical to one of the two major water-soluble compounds. Acid or enzymic hydrolysis of the phosphodiester produced a product identified as trimethylarsoniumalactic acid. The structure of the phospholipid therefore is O-phosphatidyltrimethylarsoniumlactic acid. Detoxication of arsenate by marine algae leads to accumulation of the arsoniumphospholipid as a major reservoir for arsenic. Its degradation to trimethylarsoniumbetaine, dimethylarsinic acid, methanearsonic acid, and arsenate in marine food chains and its metabolism in human beings are of considerable interest.

Journal Article↗
PubMed1977

Partial characterization of the bile salt-dependent triacylglycerol lipase from the leopard shark pancreas.

Leopard shark triacylglycerol lipase has been characterized as a crude pancreatic preparation. The enzyme demonstrated an absolute requirement for trihydroxy bile salts for activity with natural bile salts of the shark giving a 4-fold greater stimulation of activity than pure sodium taurocholate. Bile salts also protected the enzyme from apparent inactivation by p-chloromercuribenzoate and trypsin treatment. The shark lipase demonstrated a temperature optimum of 36 degrees C and was rapidly inactivated at 50 degrees C even in the presence of bile salts. Divalent metal ions were required for activity with Ca2+ providing the greatest stimulation. At 22 degrees C, pH 8.5 and in the presence of natural bile salts, the apparent V was about 0.6 mumol fatty acid released/min per mg protein. The shark enzyme hydrolyzed over 90% of the fatty acids from trioleovylglycerol and methyl esters of pancreatic lipase-resistant fatty acids were hydrolyzed at the same rate as typical fatty acid methyl esters. Hydrolysis of triacylglycerol proceeded about ten-times faster than wax ester hydrolysis. The kinetic properties of the leopard shark enzyme were compared to other bile salt-dependent lipolytic enzymes. Pancreatic lipase activity was not detected.

Animals↗
PubMed1977

Calcitonin: Its hormonal action on the gill.

When isolated salmon gills were perfused under simulated in vivo conditions, norepinephrine increased and calcitonin decreased the rate of flow of perfusate and the influx of calcium and phosphate through the gill. Only the increased water flow was mediated by beta-adrenergic receptors. Differences in sensitivity to both hormones were observed with gills from prespawning and postspawning salmon; gills from freshwater-adapted fish were less sensitive to norepinephrine and more sensitive to calcitonin, suggesting a decreased production of this hormone in the late stage of the life cycle. The antagonistic effects of calcitonin and norepinephrine on the gill strongly implicate their regulatory role for calcium homeostasis in vivo; the major process being regulated is the influx of calcium into the gill. In fish, calcitonin performs an important role in regulating gill function.

Journal Article↗
PubMed1977

An improved method for the preparation of unsaturated phosphatidylcholines: acylation of sn-glycero-3-phosphorylcholine in the presence of sodium methylsulfinylmethide.

An improved method for the partial chemical synthesis of unsaturated and radioactively labeled phosphatidylcholines is described. This procedure offers advantages over conventional acylation methods in that it can be carried out on a millimole or micromole scale under mild conditions and it does not require a large excess of the fatty acid acylating reagent. In this procedure sn-glycero-3-phosphorylcholine is reacted with twice the theoretical amount of fatty acid imidazolide and sodium methylsulfinylmethide in dimethylsulfoxide for several minutes at 17 degrees C. Phosphatidylcholine, which was purified by gradient-elution chromatography on silicic acid, was isolated in 60% yield and was estimated to be about 99% pure. The preparations of 1,2-dioleoyl-, 1,2-dilinoleoyl-, and 1,2-dilinolenoyl-sn-glycero-3-phosphorylcholine are described. The reaction was also carried out on a small scale for the preparation of high specific activity 1,2-di[ 1'(-14)C]oleoyl-sn-glycero-3-phosphorylcholine in 38% yield with a specific activity of about 9.7 muCi/mumol.

Acylation↗
PubMed1975

Specificity of digestive lipases in hydrolysis of wax esters and triglycerides studied in anchovy and other selected fish.

The physiological specificity of fat digestion in several species of marine fish was studied by incubating a variety of synthetic and natural lipid substrates in fish intestinal fluid. Wax ester and triglyceride hydrolyses were studied in vivo and in vitro. In vivo feeding studies showed triglyceride hydrolysis and reesterification in the gut occurred 4 times faster than wax ester metabolism. In vitro comparisons of wax and triglyceride lipolysis always showed triglycerides to be hydrolyzed faster than wax esters; however, wide variation in the ratio occurred among different batches of intestinal juice. Ca. 50% of the 2 monoglycerides formed in the lipolytic sequence were hydrolyzed. Esters of lipase resistent fatty acids (20:4 and 20:5) were cleaved faster than normal fatty acid esters (18:2 and 18:3). Two of the species studied, the northern anchovy, Engraulis mordax and the jack mackerel, Trachurus symmetricus, empty lipase(s) into their gall bladders and produce-phospholipid free bile.

Animals↗
PubMed1974

Carotenoid transformations in the chloroplast envelope.

The envelope of the spinach chloroplast is a yellow membrane system with a unique carotenoid composition. Envelopes prepared from dark-treated leaves had a violaxanthin content up to 3.5 times the lutein plus zeaxanthin content, whereas in chloroplast envelopes from illuminated leaves this ratio was only 0.75. Light-catalyzed changes in violaxanthin content also occurred in the thylakoid fraction.The role of this reversible light-catalyzed de-epoxidation of violaxanthin in the function of the envelope of the chloroplast is discussed.

Journal Article↗
PubMed1972

Petroleum hydrocarbons: uptake and discharge by the marine mussel Mytilus edulis.

The common marine mussel Mytilus edulis has been observed to rapidly take up mineral oil, [(14)C]heptadecane, 1,2,3,4-tetrahydronaphthalene, [(14)C]toluene, [(14)C]naphthalene, and [(3)C]3,4-benzopyrene from seawater solution. This species of mussel did not metabolize any of these compounds, and transfer of the mussel to fresh seawater, after exposure to the hydrocarbon in solution, resulted in the discharge of most of the hydrocarbon, although significant amounts remained (between 1 and 400 micrograms per mussel). The nontoxic paraffinic hydrocarbons mineral oil and heptadecane were taken up (10 milligrams per mussel) to a much greater extent than the aromatic hydrocarbons (2 to 20 micro-grams per mussel).

Alkanes↗