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Electrospray/tandem mass spectrometry was used to quantify lipid remodeling in mouse liver and plasma during inhibition of polyunsaturated fatty acid synthesis by the delta6 fatty acid desaturase inhibitor, SC-26196. SC-26196 caused increases in linoleic acid and corresponding decreases in arachidonic acid and docosahexaenoic acid in select molecular species of phosphatidylcholine, phosphatidylethanolamine, and cholesterol esters but not in phosphatidylserine, phosphatidylinositol, or triglycerides. For linoleic acid-, arachidonic acid-, and docosahexaenoic acid-containing phospholipid species, this difference was, in part, determined by the fatty acid at the sn-1 position, namely, palmitic or stearic acid. An understanding of phospholipid remodeling mediated by delta6 desaturase inhibition should aid in clarifying the contribution of arachidonic acid derived via de novo synthesis or obtained directly in the diet during inflammatory responses.

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Decreased synthesis of arachidonic acid by inhibition of the Delta6 or Delta5 desaturase was evaluated as a means to mitigate inflammation. Using quantitative in vitro and in vivo radioassays, novel compounds representing five classes of Delta5 desaturase inhibitors and one class of Delta6 desaturase inhibitor were identified. The Delta6 desaturase inhibitor, SC-26196, had pharmacokinetic and pharmacodynamic profiles in mice that allowed for the evaluation of the pharmacological effects of chronic inhibition of desaturase activity. SC-26196 decreased edema to the same extent as indomethacin or essential fatty acid deficiency in the carrageenan paw edema model in the mouse. The antiinflammatory properties of SC-26196 were consistent with its mechanism of action as a Delta6 desaturase inhibitor: 1) A correlation existed between inhibition of liver Delta6 desaturase activity and decreases in edema. 2) The onset of the decrease in edema was time dependent. 3) Selective reduction of arachidonic acid occurred dose dependently in liver, plasma and peritoneal cells. 4) In the presence of SC-26196, controlled refeeding of arachidonic acid, but not oleic acid, reversed the changes resulting from desaturase inhibition. The Delta6 desaturase may be a target for development of antiinflammatory drugs whose mechanism of action is unique.

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Controlled feeding of linoleic acid (LA) or arachidonic acid (AA) to essential fatty acid-deficient (EFAD) rats was used to define the relationship between dietary AA and the inflammatory response evoked during adjuvant-induced arthritis. Based on energy percentage, EFAD rats were fed AA at the human daily equivalent (1x; 5.5 mg/day) or 10 times that amount (10x; 55 mg/day) or, alternatively 0.5x of LA (273 mg/day). Feeding of 0.5x LA restored the plasma level of AA to that in chow-fed controls. In contrast, feeding of 1x AA only partially restored the plasma level of AA; 10x AA was required to fully replete AA. In parallel to the degree of repletion of AA in plasma, there were accompanying decreases in the levels of palmitoleic acid, oleic acid, and Mead acid. Compared to rats fed the standard laboratory chow diet (Control), edema in the primary hind footpads was decreased by 87% in EFAD, 71% in EFAD + 1x AA, 45% in EFAD + 10x AA, and 30% in EFAD + 0.5x LA. The decrease in edema in the footpads of EFAD rats was nearly identical to the decrease in edema in the footpads of Control rats dosed with indomethacin. Hind footpad edema correlated with the final AA plasma level and eicosanoid levels extracted from hind footpad tissue, but not with neutrophil infiltration. The data showed that 0.5x LA and 10x AA, but not 1x AA, could quickly replete AA, accompanied by the synthesis of AA-derived eicosanoids and restoration of edema. These results suggest that in humans consumption of the average daily amount of AA without concurrent ingestion of LA would not alleviate an EFAD state.

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Two studies were designed to examine the pharmacokinetic and galactopoietic potency of three molecular variants of recombinant-derived bovine GH (rbGH): [Met1, Leu127]-bGH, [Ala1, Val127]-bGH and [Ala1, Val127, His133]-bGH. Histidine substitution for arginine at residue 133 of rbGH was shown to impart thrombin resistance. In a Latin square design, nine lactating Holstein cows received a 25 mg rbGH bolus infusion via the jugular vein followed by frequent blood sampling over the next 12 h. The serum GH concentration data were found to fit a two-compartment open model. Neither primary nor secondary kinetic parameter estimates differed significantly (P > 0.05) among the three rbGH variants. Thus, the disposition of GH concentration at time t was described by the equation C(t) = (1295.5 micrograms/l) (e-(0.11/min)(t)) + (317.3 micrograms/l)(e-(0.03/min)(t)). Overall averages were: area under the curve = 27.1 mg.min per l, clearance = 0.15 litres/min per 100 kg and volume of distribution of the central compartment = 2.59 litres/100 kg. The t 1/2 for the two compartments averaged 8.2 and 29.1 min. In the second study, 36 lactating Holstein cows received i.m. injections of one of four oil-based formulation treatments: control vehicle or 500 mg of one of the three rbGH variants every 14 days for 42 days. Average and maximum serum GH concentrations and area under the curve estimates were increased by approximately 3-6 micrograms/l, 5-15 micrograms/l and 40-90 micrograms.day per 1 respectively. Ala1, Val127 rbGH treatments elicited greater blood GH concentrations than [Met1, Leu127]-bGH when administered in an oil-based formulation. Blood GH responses did not directly translate into milk response differences, possibly due to differences in biopotency or receptor availability. Thrombin resistance resulting from substitution of histidine at position 127 of rbGH did not affect blood GH pharmacokinetic parameters or milk response over other rbGH variants.

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Recombinant bovine prolactin (rbPRL) or bovine growth hormone (rbGH) was administered to mature female rats (10/treatment group) by daily subcutaneous injection for 10 days. Doses ranged from 7 to 5,000 micrograms/day (0.03-24 mg/kg body wt). Both rbPRL and rbGH increased body weight gain and food intake, but these parameters were increased at lower doses of rbPRL (7-63 micrograms/day) than rbGH (> 190 micrograms/day). Weight gain and food intake were maximally stimulated by 190 micrograms/day rbPRL, whereas maximal increased weight gain was obtained with the highest dose of rbGH (5,000 micrograms/day). Total carcass protein was increased by both hormones; however, protein as a percentage of body weight was unchanged. Similarly, neither rbPRL nor rbGH changed the percentage of carcass moisture. Percentage of body fat was increased by rbPRL but was decreased by rbGH. Weight of the gastrointestinal tract and kidneys was increased by both hormones, but increases were in proportion to body weight gain. These data confirm that ungulate prolactin is a hyperphagic agent in the female rat. In addition, they suggest that, while prolactin stimulates growth in mature female rats, this growth is probably not via a somatogenic mechanism.

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High levels of active HIV-1 protease (PR) were produced in Escherichia coli, amounting to 8-10% of total cell protein. High production levels were achieved by altering the following parameters: (1) codon preference of the coding region, (2) A+T-richness at the 5' end of the coding region, and (3) promoter. To circumvent the toxicity of HIV-1 PR in E. coli, the gene was expressed as a fusion protein with two different proteolytic autocleavage sequences. In both the cases, the fusion protein could be cleaved in vivo to give an active molecule with the native sequence at the N terminus.

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Bovine somatotropin (bST) has been isolated from pituitary glands and compared in a variety of chemical analyses and bioassays with somatotropin derived from recombinant Escherichia coli. Comparison of pituitary extracts and purified bST by Western blot analysis of two-dimensional gels suggested that the immunoreactive somatotropin species present in the extract were also present in the purified material, with no significant losses or degradation as a result of the purification method. NH2-terminal sequence analysis indicated the presence of equal quantities of Ala-Phe-Pro-Ala-Met-Ser-Leu-Ser- and Phe-Pro-Ala-Met-Ser-Leu-Ser- sequences. The Met-Ser-Leu-Ser-NH2-terminal sequence, a degradation product observed in NIH standard lots, was not detected. Assay of bioactivity in a bovine liver receptor-binding assay and in a female rat growth assay showed pituitary bST and recombinant methionyl-bovine somatotropin to be equipotent. Tryptic maps and sequence analysis of pituitary-derived somatotropin suggest the presence of isoaspartate derivatization at Asp128.

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The expression of phosphorylase kinase was investigated in rat skeletal muscle cells developing in vitro. The enzyme was immunoprecipitated from cells cultured in the presence of [35S]methionine, and the 35S-labeled alpha-, alpha'-, and beta-subunits of the kinase were resolved by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Fusion of myoblasts into myotubes was associated with marked increases in the amounts of kinase activity and the three 35S-labeled subunits. In 2-wk-old myotubes, the net amount of alpha'-subunit represented less than 20% of the total alpha-subunits (alpha + alpha'); however, alpha'-subunits appeared to be synthesized at least as rapidly as alpha-subunits. That alpha'-subunits were degraded more rapidly was confirmed by pulse-chase experiments, which also indicated that alpha'-subunits were not formed by proteolytic processing of the larger alpha-subunit. Inhibition of the spontaneous contractile activity of the myotubes with lidocaine markedly increased both phosphorylase kinase activity and the amounts of the 35S-labeled subunits. The divalent cation ionophore, A23187, decreased the alpha-subunits by 60%, but did not change levels of the alpha'-subunits. Taken together, the present results indicate that rat myotubes synthesize the two isozymes of phosphorylase kinase, and that levels of both are controlled by differentiation and muscle activity.

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Phosphorylase kinase was quantitatively immunoprecipitated from extracts of different rabbit skeletal muscles, subjected to electrophoresis on polyacrylamide gels in the presence of sodium dodecyl sulfate, and stained with silver. Amounts of the two isozymes, enzymes r and w. were determined by the staining intensities of the alpha'- and alpha -subunits, respectively. The kinase in muscles composed primarily of slow oxidative fibers was almost entirely enzyme r, but several times more of this isozyme was found in muscles with a high proportion of fast oxidative-glycolytic fibers. Enzyme w predominated in muscles composed mostly of fast glycolytic fibers. To investigate the possible role of muscle activity in controlling isozyme levels, tibialis anterior muscles were activated by chronic electrical stimulation of the peroneal nerves. After 10 wk of continuous stimulation, the amount of phosphorylase kinase was decreased by approximately 80%, and the ratio of enzyme r to enzyme w was doubled. These results demonstrate that increased muscle activity can decrease levels of phosphorylase kinase and suggest that activity may regulate the expression of the isozymes in different muscle fiber types.

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We have investigated the potential role of adenosine 3',5'-cyclic monophosphate (cAMP) in controlling levels of enzymes of energy metabolism in primary cultures of rat skeletal muscle cells. Incubating myotubes with cholera toxin or forskolin (2 persistent activators of adenylate cyclase) significantly increased the levels of two enzymes of oxidative metabolism, fumarase and malate dehydrogenase. These enzymes were also increased (1.5- to 2.0-fold) by phosphodiesterase inhibitors (caffeine, theophylline, theobromine, 3-isobutyl-1-methylxanthine, papaverine, MJ 1988, Ro 20-1724, or SQ 20009) and the cAMP derivatives: 8-bromo-cAMP or dibutyryl cAMP. In contrast two enzymes of glycolytic metabolism, lactate dehydrogenase and pyruvate kinase, were not consistently affected by these agents. The results presented provide strong evidence that an increase in cAMP can lead to an increase in certain enzymes of oxidative energy metabolism.

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The control of phosphorylase levels was investigated in rat skeletal muscle cells developing in vitro. The amount of enzyme was directly measured after immunoprecipitation using specific antibodies. The rate of phosphorylase synthesis was estimated by measuring the initial rate of formation of [3H]phosphorylase after incubating cells with [3H]tyrosine. Rates of degradation were determined either from pulse-chase experiments using [3H]tyrosine or by the loss of enzymatic activity following inhibition of protein synthesis. A large increase in phosphorylase occurred at the time myoblasts were fusing into myotubes. The accumulation of enzyme was preceded by a marked increase in the synthetic rate and was associated with a severalfold increase in the half-life of the enzyme. Following fusion, the myotubes began to spontaneously contract, and shortly thereafter, decreases in both the half-life and amount of phosphorylase were observed. The paralytic agents tetrodotoxin and lidocaine were without effect on phosphorylase levels before the onset of spontaneous activity; however, both agents increased the amount of enzyme when added to contracting myotubes. Tetrodotoxin had little effect on synthesis of [3H]phosphorylase but doubled the half-life of the enzyme. These and other results indicate that the increase in phosphorylase in differentiating muscle cells results from the coordinate control of both its synthesis and degradation, and that muscle activity decreases phosphorylase by increasing its degradation.

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We have investigated the effects of inhibiting the spontaneous activity of cultured rat myotubes on several representative enzymes of glycolytic and oxidative metabolism. The results presented demonstrate that contractile activity in the absence of nerves can regulate the amounts of these enzymes and indicate that muscle activity may partially control development of the metabolic types of muscle fibers. Control muscle cells have relatively high levels of glycolytic enzymes and low oxidative enzymes and metabolically most closely resemble fast glycolytic fibers. The divalent cation ionophore A23187 caused enzyme levels of the cultured cells to change towards those found in tonically contracting skeletal muscle fibers in vivo. The evidence presented suggests that calcium may mediate certain of the effects associated with muscle contraction on enzymes of energy metabolism.

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Reactions between near equimolar amounts of antithrombin and Factors IXa or Xa resulted in the formation of a free proteolytically modified, two-chain form of the inhibitor, in addition to the inactive antithrombin-protease complexes. The modified inhibitor produced by either enzyme was electrophoretically identical with that formed in the reaction with thrombin. As in the latter reaction, the formation of the modified antithrombin by Factor Xa was increased in the presence of heparin, while only small amounts were produced by Factor IXa both in the absence and presence of the polysaccharide. NH2-terminal sequence analyses of the isolated modified inhibitor formed by Factor Xa showed that a single Arg-Ser bond in the COOH-terminal end of the inhibitor had been cleaved. This cleavage site is identical with that identified in free thrombin-modified antithrombin. The purified antithrombin-Factor IXa and antithrombin-Factor Xa complexes were dissociated by ammonia or hydroxylamine into free enzyme and a modified two-chain form of the inhibitor. Electrophoresis studies and NH2-terminal sequence analyses showed that the modified antithrombin obtained from either complex was identical with that produced in free form by the two enzymes and also with the modified inhibitor that is released from the antithrombin-thrombin complex. The fact that identical results were obtained for the reactions between antithrombin and three enzymes with different specificities strongly suggests that the observed Arg-Ser cleavage site is the active site of antithrombin.

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