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D. P. Kelly 《Archives of microbiology》1967,58(2):99-116
Summary Cultures of Thiobacillus neapolitanus strain C assimilate 14C-labelled acetate and aspartate. Both carbon atoms of acetate are incorporated, and 25% of the cell carbon can arise from acetate. Aspartate-14C contributes 4–5% of the cell carbon, and is found in pyrimidines and in protein as aspartate and its related amino acids. Acetate-14C contributes to lipid, glutamate, arginine, proline and leucine, but not to aspartate. Acetate assimilation by washed organisms requires carbon dioxide and energy from thiosulphate oxidation. Degradation of 14C-glutamic acid from acetate-14C-labelled bacteria; the accumulation of 14C-citrate in the presence of fluoroacetate and [14C] acetate; short-term kinetic experiments on acetate-14C turnover; and the demonstration of citrate synthesis by cell-free extracts all indicate glutamate synthesis from -ketoglutarate formed by reactions of the tricarboxylic acid cycle. The cycle is believed to be incomplete, probably not proceeding further than -ketoglutarate, and functions as a glutamate-synthesising system, using oxaloacetate derived solely from carbon dioxide fixation. Malate synthase (and the glyoxylate cycle) appear to be insignificant in the metabolism, but extracts did form citramalate from acetate and pyruvate. 相似文献
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Beta-adrenergic relaxation of dog trachealis: contractile agonist-specific interaction 总被引:1,自引:0,他引:1
Koenig S. M.; Mitchell R. W.; Kelly E.; White S. R.; Leff A. R.; Popovich K. J. 《Journal of applied physiology》1989,67(1):181-185
The phenomenon of contractile agonist-dependent relaxation by isoproterenol (ISO) of active tension elicited by acetylcholine (ACh), histamine (HIS), serotonin (5-HT), and potassium chloride-substituted Krebs-Henseleit solution (KCl) was studied in 210 tracheal smooth muscle (TSM) strips from 28 mongrel dogs in vitro. All TSM strips were contracted to similar active tensions [target tension (TT) = 50% of the maximal active tension elicited by 127 mM KCl] with ACh, HIS, 5-HT, or KCl and relaxed with either ISO, forskolin (FSK), N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate (db-cAMP), or 3-isobutyl-1-methylxanthine (IMX). The concentrations of ISO causing 50% relaxation from TT (RC50) were ACh (2.9 +/- 1.1 x 10(-6) M) greater than 5-HT (8.4 +/- 1.5 x 10(-8) M) approximately KCl (8.1 +/- 2.1 x 10(-8) M) greater than HIS (1.6 +/- 0.2 x 10(-8) M). FSK and IMX relaxed TSM in the same rank order of potency as ISO. In contrast to the contractile agonist-dependent relaxation elicited by ISO, FSK, and IMX, db-cAMP was nearly equipotent in relaxing similarly contracted strips. These results are consistent with contractile agonist-specific interaction with cAMP production by ISO and FSK. These data demonstrate that the phenomenon of contractile agonist-dependent relaxation by ISO is not related specifically to the beta-adrenoceptor. 相似文献