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J R Sargent

Publications and source records attributed to J R Sargent.

At least 73 records · Page 4Linked to original sources
PubMed1985

Fatty acid composition of phospholipids and neutral lipids during embryonic and early larval development in Atlantic herring (Clupea harengus, L.).

The fatty acid compositions of total polar and total neutral lipids of Atlantic herring eggs and larvae were determined immediately before fertilization, after fertilization and at various times during subsequent embryonic and early larval development. Within 3 hr after fertilization the percentage of total PUFA in neutral lipid decreased from 33% to 20%, with a reciprocal increase in monoenes. Thereafter the percentage of PUFA in the neutral lipids increased progressively, attaining the original level in ripe eggs by the time of yolk sac absorption. During the larval stages the percentage of PUFA continued to increase in the neutral lipid, reaching almost 44% of the total by day 32 after fertilization, although it was reduced to 32% by day 36. The percentage of monoenes in the neutral lipid displayed a progressive decrease during the whole period of development from 3 hr after fertilization. Throughout all the developmental periods the fatty acid composition of total polar lipids remained essentially constant. The polar lipids of the yolk sac displayed virtually the same fatty acid composition as the larval bodies, but the neutral lipids of the yolk sac were low in PUFA compared to the larval bodies. The results are discussed with reference to changes in lipid class composition during development. The conservation of high levels of PUFA in lipids during embryogenesis and early larval development reflects the importance of these fatty acids during development.

Animals↗
PubMed1985

Lipid class composition during embryonic and early larval development in Atlantic herring (Clupea harengus, L.).

The lipid class compositions of Atlantic herring eggs and larvae were determined immediately before fertilization, after fertilization and at various times during subsequent embryonic and early larval development. Total lipid constituted 15% of the dry wt of ripe eggs, 70% of the total lipid being polar lipid with phosphatidylcholine (PC) accounting for almost 90% of the polar lipid. In general, the total lipid content decreased gradually during embryogenesis and in particular during larval development. Within 3 hr after fertilization the relative percentage of neutral lipid decreased slightly. This was followed by a general decrease in polar lipid which, by the stage of yolk sac absorption, was reduced to 52% of the total lipid. The decreased percentage of polar lipid was due entirely to a decrease in PC, which was reduced to 66% of the polar lipids at the stage of yolk sac absorption. The accompanying increase in the percentage of neutral lipids was mainly due to increased percentages of triacylglycerols (TAG) up to yolk sac absorption and cholesterol esters in the larval stages. During the first 4 days after hatching, phospholipids and to a lesser extent cholesterol were preferentially depleted in the yolk sacs, which also had higher levels of free fatty acids. The results are discussed in relation to possible roles of different lipids during embryonic and early larval development.

Animals↗
PubMed1985

Chain-length specificities of mitochondrial and peroxisomal beta-oxidation of fatty acids in livers of rainbow trout (Salmo gairdneri).

Peroxisomes and mitochondria were prepared from livers of rainbow trout fed diets containing either 15% crude fish oil (CFO) or 11.5% partially hydrogenated fish oil (PHFO) plus 3.5% CFO. Peroxisomal preparations from the two dietary groups showed similar rates and substrate specificity patterns for acyl-CoA oxidation. The peroxisomal oxidation rate was highest with 12:0-CoA and decreased with increasing chain length, being negligible with 22-carbon acyl-CoA's. The trans isomer of 18:1(n-9) was oxidized at a higher rate than the cis isomer only by peroxisomes from the PHFO + CFO group. Mitochondria prepared from both groups of fish exhibited a broad chain-length specificity for the oxidation of acylcarnitines. Both polyunsaturated and trans monoenoic fatty acids were readily oxidized.

Acyl Coenzyme A↗
PubMed1985

Changes in the fatty acid composition of phospholipids from turbot (Scophthalmus maximus) in relation to dietary polyunsaturated fatty acid deficiencies.

Young turbot (1-20 g) were maintained for not less than 14 weeks on three diets: (1) a control diet containing normal amounts of polyunsaturated fatty acids (PUFA); (2) a diet totally deficient in PUFA; (3) a diet deficient in the (n-6) series of PUFA but containing (n-3) PUFA. At 14 weeks the fatty acid compositions of the phospholipids from liver, gut, gills and muscle were analysed. Large changes in the amounts of PUFA in the phospholipids were found. Fish maintained on the totally PUFA deficient diet 2 had retained arachidonic acid, 20:4(n-6), and docosahexaenoic acid, 22:6(n-3), at the expense of eicosapentaenoic acid, 20:5(n-3). Fish maintained on the (n-6) PUFA-deficient diet (3) contained decreased amounts of 20:4(n-6) and 22:6(n-3) while retaining 20:5(n-3). In all cases phosphatidylinositol had the lowest n-3/n-6 ratios. These results are discussed in terms of PUFA function.

Animals↗
PubMed1985

Inositol lipid turnover and adenosine 3,5 cyclic monophosphate in the salt-secreting rectal gland of the dogfish (Scyliorhinus canicula).

The rectal gland of the dogfish is rich in inositol lipids. Total phospholipids from the gland contained 9.1 mol% of phosphatidylinositol (PtdIns), 1.0 mol% of phosphatidylinositol 4-phosphate (PtdIns4P) and 0.9 mol% of phosphatidylinositol 4,5-biphosphate (PtdIns4,5P2). [32P]Orthophosphate was readily incorporated into PtdIns, phosphatidic acid (PtdA) and especially into PtdIns4P and PtdIns4,5P2 in salt gland slices incubated in elasmobranch Ringer with glucose and no other additions over a 2 hr period. The calcium ionophore A23187 stimulated incorporation into PtdIns and PtdA, but not into PtdIns4P or PtdIns4,5P2. Oxygen uptake by rectal gland slices was maximally stimulated by 0.08mM forskolin, 2.5mM 8-chlorophenylthio cyclic AMP, 2.0mM dibutyryl cyclic AMP and 0.25mM theophylline. Stimulated oxygen uptake was inhibited by 0.1mM ouabain in all cases. Incorporation of [32P]orthophosphate into PtdIns, PtdA, PtdIns4P and PtdIns4,5P2 was inhibited by 0.08mM forskolin and 2.0mM dibutyryl cyclic AMP over a 2 hr period. The results are discussed in relation to the control of salt secretion by the rectal gland.

Animals↗
PubMed1984

Distribution and some properties of bile salt-binding proteins in rainbow trout, Salmo gairdneri.

Trout liver cytosol has proteins that bind bile salts and 8-anilino-1-naphthalene sulphonate and that co-elute from Sephadex G-75. The binding of 8-anilino-1-naphthalene sulphonate is decreased by 90% in the presence of 33 microM lithocholate, implying the proteins are the same. Bile salt-binding protein is present in liver, but was not detected in gills, kidney, muscle or intestine. Bile salt-binding protein, partially-purified by Sephadex G-75 chromatography, was resolved into 2 fractions by cholate-affinity chromatography. Fatty acids do not appear to be bound by bile salt-binding protein. No fatty acid-binding protein was detected in trout liver cytosol.

Animals↗
PubMed1983

The transport of orthovanadate and similar oxyanions in relation to salt and water transport across the isolated intestine of the common eel, Anguilla anguilla.

An intestinal preparation from the common eel (Anguilla anguilla) was characterized for both mucosal to serosal and serosal to mucosal transport of water, alanine, sodium and chloride. The preparation showed a net outflux of water and a net influx of alanine, and no net fluxes of sodium or chloride. The influxes of all four substances and the outflux of water were inhibited by ouabain, while the outfluxes of alanine, sodium and chloride were increased by ouabain. Influxes and outfluxes of the oxyanions orthovanadate, phosphate, arsenate, sulphate, selenate and chromate were measured over a range of concentrations from 10(-8) M to 10(-4) M. The entry of each anion was dependent on the mucosal concentration, not saturable within the concentration range used or competitive with chloride. There were no net fluxes of these anions and pertechnecate from solutions containing equal mucosal and serosal concentrations of the anion.

Alanine↗
PubMed1981

Effects of orthovanadate on salt and water effluxes from the gills of seawater eels, Anguilla anguilla.

Orthovanadate (5 . 10(-7) M) perfused through isolated gills at a constant rate increased the perfusion pressure by 40% but inhibited the effluxes of Na+ and Cl- by 40%. Water efflux was unaltered. Ouabain (10(-4) M) and rotenone (10(-4) M) influenced salt and water effluxes in the same way but did not alter perfusion pressures. Orthovanadate (10(-5) M) perfused at constant rate increased the pressure nearly 2.5-fold; under these conditions effluxes of Na+, Cl- and H2O were all increased approximately 2.5-fold.

Anguilla↗
PubMed1981

The uptake from fresh water and subsequent clearance of a vanadium burden by the common eel (Anguilla anguilla).

The uptake of 48V vanadium from a solution of 10(-5) M 48V-orthovanadate by fresh-water elvers and the subsequent depletion of the vanadium burden was studied. At the end of the 8-week loading period, the levels of 48V were still increasing in the liver, kidney, bone and carcase. The uptake rate for the whole fish over the 8-week period was 760 pg atom/h/100 g body wt and the depletion rate over the following 5 weeks in clean water was about one tenth of this. Liver contained the highest amount of 48V at the end of the 8-week loading period, calculated as equivalent to 1.1 x 10(-4) g atom V/kg wet wt, and this level was unchanged at the end of the 5-week depletion period. Less than 1% of the carcase 48V was present in the fraction of MW under 2000.

Anguilla↗
PubMed1979

Biosynthesis of triacylglycerols in the intestines of rainbow trout (Salmo gairdnerii) fed marine zooplankton rich in wax esters.

Intestinal preparations from rainbow trout fed a diet rich in wax esters incorporated [1(-14)C]hexadecanoic acid and [1(-14)C]hexadecanol into triacylglycerols at the same rate. The ratio of the number of H atoms from C1 of hexadecanol to the number of molecules of hexadecanol incorporated into triacylglycerols was 1.6 : 3.0. [U-14C]Glucose was incorporated much faster into the glycerol moiety of triacylglycerols than was [U-14C]aspartic acid. We conclude that the oxidation of absorbed fatty alcohol to fatty acid and its subsequent incorporation into triacylglycerols is closely linked with the reductive formation of triacylglycerol-glycerol from glucose. The ability of trout intestines to metabolise fatty alcohol to triacylglycerols was the same in fish fed wax esters as in those fed triacylglycerols.

Animals↗
PubMed1979

An electron microscopic study of lipid absorption in the pyloric caeca of rainbow trout (Salmo gairdnerii) fed wax ester--rich zooplankton.

Rainbow trout were killed 4 and 18 h after being fed wax ester-rich marine zooplankton and the absorptive epithelium of the pyloric caeca examined by electron microscopy. Numerous osmiophilic drops were seen in the lamina propria underlying the epithelium of fish killed at both times, but these drops were only abundant within columnar epithelial cells of fish killed 4 h after feeding. Pinocytotic profiles were not common at the luminal plasma membranes, nor were osmiophilic droplets seen in the terminal web area between the luminal plasma membrane and the extensive smooth endoplasmic reticulum. Numerous osmiophilic droplets, 30--100 nm in diameter, were present in the cisternae of the smooth endoplasmic reticulum with up to five separate droplets per individual cisterna. Columnar epithelial cells also contained up to 100 large osmiophilic drops ("conglomerates") which tended to be concentrated in the supranuclear (Golgi) regions. The conglomerates were 250--1200 nm in diameter and were themselves made up of smaller droplets 30--400 nm in diameter. Conglomerates were present both within intracellular membranes and free in the cytoplasm. Osmiophilic droplets in the intercellular spaces and lamina propria were similar in size to individual droplets within conglomerates. We conclude that triacylglycerols are elaborated in the smooth endoplasmic reticulum, transferred to and processed in the Golgi region and finally discharged serosally as chylomicron-like particles of not greater than 400 nm diameter.

Animals↗
PubMed1979

The partial purification of sodium-plus-potassium ion-dependent adenosine triphosphatase from the gills of Anguilla anguilla and its inhibition by orthovanadate.

1. (Na+ +K+)-dependent ATPase was partially purified from eel gills by a procedure in which the microsomal fraction of crude preparations of chloride cells was selectively extracted with sodium dodecyl sulphate. 2. The microsomal specific activity was increased 2-fold during optimal treatment with detergent. 3. The final preparation (56% pure) had a specific activity of 341 mumol of ATP hydrolysed/h per mg of protein and a turnover number of 3560 min-1. The number of ouabain-binding sties equalled the number of sites phosphorylated by ATP. 4. Both sodium orthovanadate and ouabain inhibited the purified preparation more than the microsomal fraction, vanadate being more effective on an equimolar basis than ouabain. 5. Inhibition by orthovanadate was not enhanced at 28 mM-as compared with 1mM-MgCl2 and was not reversed by beta-adrenergic agonists (cf. Josephson & Cantley (1977) Biochemistry 16, 4572--4578). 6. Of various other metallic oxyanions tested only niobate proved an effective inhibitor of the enzyme although this anion was less effective than orthovanadate. 7. Orthovanadate partially inhibited phosphorylation of the enzyme by ATP in the presence of 28 mM-MgCl2.

Adenosine Triphosphate↗
PubMed1977

The activation of sodium-plus-potassium ion-dependent adenosine triphosphatase from marine teleost gills by univalent cations.

The apparent affinity constants for the binding of Cs+, Rb+, K+, Li+, Tl+ and NH4+ to (Na+ + K+)-dependent adenosine triphosphatase from teleost gills were measured and the values discussed in terms of the ion-selectivity isotherm described by Eisenman & Krasne (1975) [in MTP International Review of Science: Biochemistry Series One (Fox, C.F., ed.), vol. 2, pp. 27--59, Butterworths University Park Press, Baltimore]. The ion selectivity of the present enzyme is remarkably similar to that from nerve and brain.

Adenosine Triphosphatases↗
PubMed1977

Changes in the levels of chloride cells and (Na+ + K+)-dependent ATPase in the gills of yellow and silver eels adapting to seawater.

Changes were measured in the numbers of chloride cells and the levels of (Na+ + K+)-DEPENDENT ATPase in the gills of immature, yellow eels and mature, silver eels during adaptation from freshwater to seawater. The percentage of chloride cells in yellow eels more than doubled after six days in seawater; at this time the specific activity and concentration of (Na+ + K+)-dependent ATPase in gills start to increase in parallel to reach maxima after two weeks that are 2.5 times the starting values. It is concluded that adaptation of yellow eels to seawater involves an increase in the numbers of chloride cells in gills as well as an increased amount of (Na+ + K+)-dependent ATPase per chloride cell. Mature silver eels in freshwater had essentially the same numbers of chloride cells and the same specific activity of the enzyme in the gills as yellow eels fully adapted to seawater. Transferring silver eels to seawater did not alter the percentage of chloride cells in gills although the level of (Na+ + K+)-dependent ATPase and its specific activity increased slightly. Thus, although the silver eel is better prepared for life in seawater than the yellow eel, it still has to attain an increased level of (Na+ + K+)-dependent ATPase in its chloride cells to be fully adapted to seawater.

Adaptation, Physiological↗