Differential alterations in branched-chain amino acid decarboxylation in liver of hypophysectomized rats

Summary Valine decarboxylation was significantly increased and leucine decarboxylation was significantly decreased in rat liver slices following hypophysectomy. In both normal and hypophysectomized rats decarboxylation of leucine exceeded that of valine in slices whereas the reverse was observed with the respective keto acids and mitochondria.Acknowledgments. This study was supported by the National Institutes of Health and the Samuel A. Berger Foundation.     

Effect of sodium octanoate on leucine incorporation into protein of rat liver slices and of Yoshida ascites hepatoma cells.

7.38 X 10(-4) M octanoate does not significantly modify leucine incorporation into protein of rat liver slices, while in hepatoma cells a 19% inhibition has been noted. 3.69 x 10(-3) M octanoate reduces leucine incorporation to about the same extent (71-76%) in both liver slices and hepatoma cells.     

Effect of sodium octanoate on leucine incorporation into protein of rat liver slices and of Yoshida ascites hepatoma cells

Summary 7.38×10^–4 M octanoate does not significantly modify leucine incorporation into protein of rat liver slices, while in hepatoma cells a 19% inhibition has been noted.3.69×10^–3 M octanoate reduces leucine incorporation to about the same extent (71–76%) in both liver slices and hepatoma cells.     

Effects of cycloheximide on protein synthesis in human lung tumors, regenerating rat liver and hepatomas

10(-4) M cycloheximide (CHM) inhibits leucine incorporation to about the same degree in slices of human lung tumors, rat hepatomas, regenerating livers and normal tissues. At 10(-6) M, CHM has a more pronounced effect on tumor tissue and regenerating liver than on normal tissues. 10(-8) M CHM stimulates protein synthesis in normal rat liver slices.     

Effects of cycloheximide on protein synthesis in human lung tumors,regenerating rat liver and hepatomas

Summary 10^–4 M cycloheximide (CHM) inhibits leucine incorporation to about the same degree in slices of human lung tumors, rat hepatomas, regenerating livers and normal tissues. At 10^–6 M, CHM has a more pronounced effect on tumor tissue and regenerating liver than on normal tissues. 10^–8 M CHM stimulates protein synthesis in normal rat liver slices.     

Dopamine synthesis in rat striatum: mobilization of tyrosine from non-dopaminergic cells

Unilateral nigrostriatal lesions in rats that almost totally depleted striatal dopamine had no effect on striatal levels of dopamine's precursor, tyrosine, nor on those of leucine. Since prolonged electrical stimulation of the slices markedly depletes them of tyrosine (1,2) we conclude that tyrosine can be mobilized from non-dopaminergic striatal cells to augment dopamine release.     

Dopamine synthesis in rat striatum: Mobilization of tyrosine from non-dopaminergic cells

Summary Unilateral nigrostriatal lesions in rats that almost totally depleted striatal dopamine had no effect on striatal levels of dopamine's precursor, tyrosine, nor on those of leucine. Since prolonged electrical stimulation of the slices markedly depletes them of tyrosine (1, 2) we conclude that tyrosine can be mobilized from non-dopaminergic striatal cells to augment dopamine release.     

Einfluss der DOPA-Transaminierung auf die DOPA-Decarboxylierungin vitro

Summary In vitro the decarboxylation ofl-3,4-dihydroxyphenylalanine (DOPA) by total homogenate of rat liver and brain was markedly inhibited by 2.5 × 10^–3 M 3,4-dihydroxyphenylpyruvate, although the latter itself appeared to be aminated to a marked extent. In the homogenate or supernatant of various rat tissues, the decarboxylation of DOPA was not significantly affected by the simultaneous course of the DOPA--ketoglutarate-transamination.     

Plasma branched-chain amino acids in cold-and heat-acclimatised rats

Summary The concentrations of plasma branched-chain amino acids, valine, isoleucine and leucine, were significantly elevated in cold-acclimatised rats, while these values were significantly reduced in heat-acclimatised rats, in both 2-week and 4-week temperature acclimatisation.     

Plasma branched-chain amino acids in cold- and heat-acclimatised rats

The concentrations of plasma branched-chain amino acids, valine, isoleucine and leucine, were significantly elevated in cold-acclimatised rats, while these values were significantly reduced in heat-acclimatised rats, in both 2-week and 4-week temperature acclimatisation.     

Interaction of cortisol and epinephrine in the regulation of leucine kinetics in man

To assess the interaction of the two major stress hormones epinephrine and cortisol in the regulation of leucine kinetics in man, epinephrine (50 ng/kg/min) was infused either alone or in combination with cortisol (2 micrograms/kg/min) into two groups of 6 postabsorptive normal male subjects during 180 min. Plasma leucine concentrations decreased by 28% (p less than 0.05) from baseline during epinephrine treatment (plasma levels 515 pg/ml); this was due to a decrease of leucine appearance (determined by 1-13C-leucine infusions) by 23% (p less than 0.025); leucine oxidation decreased by 29% (p less than 0.05). However, when plasma cortisol concentrations were elevated to supraphysiological levels (16.3 mumol/l) during epinephrine administration, the decreases of leucine plasma concentrations, appearance and oxidation were abolished. Plasma glucose and FFA concentrations were similarly elevated during both kinds of treatment. Since leucine appearance represents a measurement of total body protein breakdown and leucine disappearance into non-oxidative pathways reflects protein synthesis, the data indicate that plasma epinephrine concentrations during severe stress exert a protein anabolic effect in man which may counteract catabolic properties of elevated plasma cortisol.     

Inhibition of arginase in sheep brain homogenates by some L-amino acids

Summary The effect of 16 L-amino acids on the activity levels of arginase in sheep brain homogenates was studied. The amino acids leucine, valine, lysine, and ornithine inhibited arginase activity significantly. The other amino acids tested did not show a significant influence on arginase activity. The inhibition was related to the carbon chain length of the amino acids.     

Effect of substrate pretreatment on renal organic ion transport in the adult rat.

The ability of renal cortical slices to accumulate PAH and NMN was not significantly affected by pretreatment of adult rats with large doses of PAH. Pretreatment of adult rats with THAM significantly increased PAH accumulation but had no effect on NMN. Inulin and PAH clearance and filtration fraction were significantly decreased by PAH pretreatment but unaffected by THAM pretreatment. The effects of pretreatment on transport are probably due to non-specific toxicity.     

Defect of uric acid uptake in Dalmatian dog liver

Summary The uptake rate of uric acid into liver slices of the Dalmatian dog was found to be significantly lower compared with that in the beagle. Since there was no difference in the hepatic uricase activity between the two breeds, the abnormality of uric acid metabolism in the Dalmatian dog is considered to result from a defective hepatic transport system for uric acid.     

Galactose and leucine transport in the developing rat small intestine

Summary Jejunal transport of galactose and leucine was studied in 9-45-day-old rats by means of the everted sac technique. Maximum transport was observed in 9-10-day-old rats, but then decreased until the 22nd day, and remained unchanged from then on. There were no remarkable differences in the pattern of galactose and leucine transport over this period.     

Biosynthesis of 1-alkenes in the defensive secretions ofTribolium confusum (Tenebrionidae); stereochemical implications

Summary The terminally unsaturated hydrocarbons of the defensive secretion ofTribolium confusum are biosynthesized from fatty acids by oxidative decarboxylation. The process involves an enantiospecific cleavage of the C–H bond of thepro-(S) C(3)–H atom and simultaneous decarboxylation of the acid into an 1-alkene and carbon dioxide via ananti-periplanar transition state geometry (anti-elimination). The stereochemistry of this biotranformation is identical in all respects with the same reaction in higher plants. The mechanism seems to be of general importance for the biosynthesis of many vinylic substructures of natural products from oxygen-containing precursors.     

Histamine formation by ruminal fluid from cattle in vitro

Summary Net histamine formation in ruminal fluid is shown to be the result of histidine decarboxylation and histamine deamination. Addition of 4.7 mM histidine increased the rate of net histamine synthesis by a factor of 20 compared to normal. Histamine production sharply decreases at pH values below the physiological range.     

Effect of substrate pretreatment on renal organic ion transport in the adult rat

Summary The ability of renal cortical slices to accumulate PAH and NMN was not significantly affected by pretreatment of adult rats with large doses of PAH. Pretreatment of adult rats with THAM significantly increased PAH accumulation but had no effect on NMN. Inulin and PAH clearance and filtration fraction were significantly decreased by PAH pretreatment but unaffected by THAM pretreatment. The effects of pretreatment on transport are probably due to non-specific toxicity.Supported in part by U. S. Public Health Service Grant No. AM10913.Supported in part by a predoctoral fellowship from the Upjohn Company.Acknowledgments. The technical assistance of Mr.Grant Moore and Ms.Peggy Wagner is gratefully acknowledged.     

Adenylate cyclase and phosphodiesterase from brain tissue: different stabilities during incubation of cerebral cortical slices.

Adenylate cyclase and phosphodiesterase were prepared from brain slices from guinea-pig. The specific activity of adenylate cyclase declined rapidly with increasing incubation time of tissue slices, while phosphodiesterase activity was almost uneffected by the incubation of brain slices.     

Adenylate cyclase and phosphodiesterase from brain tissue: Different stabilities during incubation of cerebral cortical slices

Summary Adenylate cyclase and phosphodiesterase were prepared from brain slices from guinea-pig. The specific acitivity of adenylate cyclase declined rapidly with increasing incubation time of tissue slices, while phosphodiesterase activity was almost uneffected by the incubation of brain slices.