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Biomedical subjects

A A Benson

Publications and source records attributed to A A Benson.

At least 19 recordsLinked to original sources
PubMed1996

Identification of a new calcitonin gene in the salmon Oncorhynchus gorbuscha.

Three isoforms of calcitonin (CT) exist in salmonids. Isohormones I and II are expressed in the pink salmon Oncorhynchus gorbuscha. We report here the existence in this species of a CT gene and of its transcripts, which encode for a fourth isohormone, the salmon CT (sCT) IV. This new CT gene was identified by PCR from genomic DNA and by sequencing the amplified DNA. The expression of this CT gene was established in ultimobranchial body and brain, by reverse transcription-PCR, hybridization and sequencing. The sCT IV gene, like the sCT I gene, is a complex transcription unit, containing exons encoding for a CT as a calcitonin gene-related peptide (CGRP) molecule. The predicted peptide, sCT IV, has a greater homology with the eel CT and the sCT II than with the sCT I. Alignment of the sCT IV with other fish and chicken CT showed amino acid modifications in similar positions as those found during evolution. The predicted salmon CGRP IV peptide is highly homologous to the known CGRP molecules in other species, confirming the high conservation of the molecule during evolution. This identification of a new salmon CT gene is interesting both for the therapeutic potential represented by the new molecules encoded by this gene and for phylogenetic studies.

Amino Acid Sequence↗
PubMed1994

The calcitonin gene is expressed in salmon gills.

Calcitonin is an important physiological regulator of salmon gills. Although the calcitonin receptor was found in salmon gills, the critical question concerning the source of the hormone remained unanswered. In this communication, evidence is presented for expression of calcitonin mRNA and its encoded peptide in gills of the pink salmon, Oncorhynchus gorbuscha. The expression of calcitonin gene transcripts was demonstrated by reverse transcription-polymerase chain reaction, Southern hybridization, and sequencing. The sequencing identified a sequence corresponding to that of exon 4 of the salmon calcitonin gene. Expression of the encoded calcitonin gene in gills was detected by radioimmunoassay in gill extracts. This synthesis of calcitonin in gills, which also possess specific receptors to the peptide, suggests function of an autocrine or paracrine process producing calcitonin in this tissue. These observations confirm and extend previous reports on the physiological role of calcitonin in fish gills.

Animals↗
PubMed1992

The path of carbon in photosynthesis: improved crop yields with methanol.

Foliar sprays of aqueous 10-50% methanol increased growth and development of C3 crop plants in arid environments. The effects of low levels (< 1 ml per plant) of methanol were observed for weeks after the brief time necessary for its rapid metabolism. Within several hours, foliar treatment with methanol resulted in increased turgidity. Plants treated with nutrient-supplemented methanol showed up to 100% increases in yields when maintained under direct sunlight in desert agriculture. In the shade and when winter crops were treated with methanol, plants showed no improvement of growth. When repeatedly treated with nutrient-supplemented methanol, shaded plants showed symptoms of toxicity. Repeated methanol treatments with glycine caused increased turgidity and stimulated plant growth without injury under indirect sunlight, but indoors with artificial illumination, foliar damage developed after 48 hr. Addition of glycerophosphate to glycine/methanol solutions allowed treatment of artificially illuminated plants indoors without injury. Plants with C4 metabolism showed no increase in productivity by methanol treatment. Plants given many applications of aqueous methanol showed symptoms of nutrient deficiency. Supplementation with a source of nitrogen sustained growth, eliminating symptoms of deficiency. Adjustment of carbon/nitrogen ratios was undertaken in the field by decreasing the source of nitrogen in the final application, resulting in early maturation; concomitantly, irrigation requirements were reduced.

Carbon↗
PubMed1990

The gill lipids of spawning Pacific salmon.

The gill phospholipids of 2 Pacific salmon species, Oncorhynchus keta and O gorbuscha, were composed of 38-43% phosphatidylcholine (PC) and 19-22% phosphatidylethanolamine (PE). Ether phosphoglycerides constituted 4-8% of the total PC fraction and 37-51% of the PE fraction. No significant changes in gill phospholipids were observed between those of pre-spawning fish in sea water and those of spawned salmon in the river. Cholesterol, however, was higher in the latter (0.59% vs 0.38%).

Animals↗
PubMed1985

Plasmalogens in the gill lipids of aquatic animals.

Lipids constituted 0.6-2.2% wet wt of the gills of 11 species of aquatic animals (4 bivalves, a crustacean and 6 fishes). Phospholipids, largely phosphatidylcholine (PC) and phosphatidylethanolamine (PE), are major components of all species. The plasmalogen contents of these lipids were 47-291 mumol/g, with the highest values found for bivalve gill total lipids and the catfish phospholipid fraction.

Animals↗
PubMed1985

Calcium-regulating hormones modulate carbonic anhydrase II in the human erythrocyte.

The effect of calcitonin (CT) and parathyroid hormone (PTH) on carbonic anhydrase (carbonate hydrolyase, EC 4.2.1.1.) activity was tested in human erythrocyte hemolysates and with purified carbonic anhydrases I and II. The most important effect was on carbonic anhydrase II: CT showed a 2-fold increase and PTH showed a 50% decrease of carbonic anhydrase activity. This effect was observed at low hormonal concentrations and suggests the importance of CT in regulating carbonic anhydrase activity in the two important sites of CO2 exchange, erythrocyte and lung.

Calcitonin↗
PubMed1981

Arsenic accumulation in Great Barrier Reef invertebrates.

Arsenic concentrates in the kidneys of the giant clams of Australia's Great Barrier Reef. The highest concentrations measured were 1004 parts per million, of which most, 2066 parts per million, were in the water-soluble fraction containing trimethylarsoniumlactate and its derivatives. This accumulation is ascribed to a mechanism in which oceanic arsenate is assimilated by symbiotic zooxanthellae and subsequently deposited in host tissues. The gills are the major site of arsenic excretion by these animals. Gill membrane arsenolipids mediate exposure of their trimethylarsonium groups to the sea and its biological oxidative activities.

Animals↗
PubMed1981

Characterization of specific receptors for calcitonin in porcine lung.

The binding of salmon calcitonin was investigated in subcellular fractions obtained from normal porcine lung. Only the membrane fraction (density, 1.14 g/cm3) showed specific binding for calcitonin. Specific binding of 125I-labeled salmon calcitonin was competitively inhibited by concentrations of unlabeled homologous hormone in the range 0.01-1 nM. Half-maximal inhibition of binding was observed with 0.12 nM salmon calcitonin. Scatchard analysis of the data suggested the presence of one class of binding sites with a mean affinity constant of 0.9 X 10(10) M-1 and a mean receptor number of 40 X 10(8)/mg of protein. The binding of salmon calcitonin was highly specific; half-maximal inhibition of binding was observed with 63.8 nM bovine calcitonin, the hormone corticotropin having no effect in this system.

Animals↗
PubMed1980

Calcitonin, a major gill hormone.

Isolated salmon gills, under simulated in vivo conditions, transported calcium ion into the ambient seawater when perfused with Ringer's solution containing salmon calcitonin. Similar enhancement of phosphate efflux was observed. Calcitonin caused simultaneous decreases in perfusate flow rates. The effects act synergistically to diminish net plasma calcium concentrations.

Animals↗
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

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↗