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排序方式: 共有1310条查询结果,搜索用时 9 毫秒
1.
Male farm-reared alligators were injected with mammalian FSH, LH, hCG, prolactin, or saline. A blood sample was taken immediately prior to injection of hormone and at 24 h postinjection. Testosterone concentrations in the plasma were then determined by radioimmunoassay. Only the alligators injected with FSH showed a significant increase in plasma testosterone. In a second series of experiments male alligators were injected with ovine LH, ovine FSH, or saline and bled at 0, 2, 4, 16, and 24 h postinjection. Again, only the alligators injected with FSH showed significant increases in plasma testosterone at 16 and 24 h postinjection. Mammalian LH does not appear to stimulate testosterone secretion in male alligators. 相似文献
2.
Biochemical pathways in prokaryotes can be traced backward through evolutionary time 总被引:10,自引:0,他引:10
For the first time, a credible prokaryotic phylogenetic tree is being
assembled by Woese and others using quantitative sequence analysis of
oligonucleotides in the highly conservative rRNA. This provides an
evolutionary scale against which the evolutionary steps that led to the
arrangement and regulation of contemporary biochemical pathways can be
measured. This paper presents an emerging evolutionary picture of aromatic
amino acid biosynthesis within a large superfamily assemblage of
prokaryotes that is sufficiently developed to illustrate a new perspective
that will be applicable to many other biochemical pathways.
相似文献
3.
M L Heiman W A Murphy M V Nekola V A Lance D H Coy 《Biochemical and biophysical research communications》1984,124(1):217-222
The aim of this study was to investigate whether anterior pituitary responsiveness to human pancreatic growth hormone-releasing factor containing 29 amino acids (GRF-29) can be modulated by GRF-29 itself. Male rats were injected (sc) daily for 3 days with 50 ug of GRF-29, or were treated twice daily for 14 days with 5 ug of [D-Ala-2]-GRF-29 (a potent GRF agonist). Control animals were injected with saline. After the last injection, pituitaries were removed, dispersed, cultured for 96 h and then challenged with either GRF-29 or [D-Trp-6]-LHRH (a LHRH agonist). Cultured cells from analog-treated rats were more responsive to GRF-29 stimulation than were cells obtained from controls. In contrast, neither treatment altered the response to [D-Trp-6]-LHRH. These studies indicate that periodic administration of GRF analogs can increase hypophyseal GRF responsiveness. Such control may be an important component in the physiological regulation of GH secretion and has important implications for potential therapeutic uses of GRF analogs. 相似文献
4.
W A Murphy V A Lance J Sueiras-Diaz D H Coy 《Biochemical and biophysical research communications》1983,112(2):469-474
Synthetic human pancreatic growth hormone-releasing factor containing 40 amino acids ([hpGRF (1-40)]-OH) significantly stimulated plasma growth hormone (GH) levels in both sodium pentobarbital and urethane anesthetized rats. Synthetic secretin, gastric inhibitory polypeptide (GIP), and glucagon significantly decreased plasma GH levels while synthetic vasoactive intestinal peptide (VIP) had no effect. Secretin and GIP also altered the in vivo plasma GH response to [hpGRF(1-40)]-OH. Whether this effect is the result of an interaction at the pituitary level or is due to an extra-pituitary effect of secretin and GIP awaits further study. 相似文献
5.
Metabolic Processes in Cytoplasmic Particles of the Avocado Fruit. IX. The Oxidation of Pyruvate and Malate during the Climacteric Cycle 总被引:8,自引:7,他引:1 下载免费PDF全文
Mitochondria isolated from preclimacteric avocado fruit oxidize pyruvate at a much lower rate than those separated from climacteric fruit. The external addition of thiamine pyrophosphate (TPP) increased the rate of pyruvate oxidation in both cases.The study of the influence of TPP on the rate of oxidation of malate by mitochondria obtained from both preclimacteric and climacteric fruit indicated that the effect of this cofactor could be understood by assuming that malate was converted to pyruvate. TPP stimulation of malate oxidation was prevented by arsenite, an inhibitor of keto acid oxidation. The addition of glutamate increased the rate of malate oxidation through the transamination of oxaloacetate. This suggests that the rate of oxidation of malate is highly dependent upon mechanisms which remove oxaloacetate efficiently.Incubation of mitochondria from preclimacteric fruit with malate-U-(14)C resulted in the labeling of oxaloacetate and the accumulation of labeled pyruvate. Addition of TPP to this system induced the rapid formation of citrate. This conversion was completely inhibited by arsenite.The results indicate that the ability to carry out the oxidative decarboxylation of alpha-ketoacids improves as the ripening process progresses. The idea was advanced that TPP available to the mitochondria plays an important controlling role. 相似文献
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7.
Endogenous nitric oxide decreases xanthine oxidase-mediated neutrophil adherence: role of P-selectin
Terada Lance S.; Repine John E.; Piermattei Dale; Hybertson Brooks M. 《Journal of applied physiology》1997,82(3):913-917
Terada, Lance S., John E. Repine, Dale Piermattei, andBrooks M. Hybertson. Endogenous nitric oxide decreases xanthine oxidase-mediated neutrophil adherence: role of P-selectin.J. Appl. Physiol. 82(3): 913-917, 1997.The oxygen radical-producing enzyme xanthine oxidase (XO) canpromote neutrophil adherence to endothelium. Recognizing that a balanceoften exists in inflammatory processes, we sought to determine whetherXO initiates antiadherent pathways. We found that bovine pulmonaryarterial endothelial cells (EC) exposed to XO released increasedamounts of nitrite into the media, reflecting an increased productionof nitric oxide (NO). When EC were subjected to shear stress, treatmentwith XO and/or the NO synthase inhibitorN-nitro-L-arginine(L-NNA) increased neutrophilrolling behavior and firm neutrophil adherence to EC in an additivefashion. Both rolling and adherent interactions were abolished bymonoclonal antibodies directed against P-selectin. In addition,treatment of EC with XO and/orL-NNA increased both surfaceexpression of P-selectin and release of von Willebrand factor intomedia. Finally, treatment of EC with the NO donor sodium nitroprussidedecreased XO-mediated neutrophil rolling and adherence. We concludethat XO stimulates EC to produce NO and that NO decreases theP-selectin-dependent neutrophil adhesion initiated by XO. Suchincreases in endogenous NO may constitute an importantnegative-feedback response to the acute proadhesive effects of XO. 相似文献
8.
Leah Wetherill Dongbing Lai Emma C. Johnson Andrey Anokhin Lance Bauer Kathleen K. Bucholz Danielle M. Dick Ahmad R. Hariri Victor Hesselbrock Chella Kamarajan John Kramer Samuel Kuperman Jacquelyn L. Meyers John I. Nurnberger Jr Marc Schuckit Denise M. Scott Robert E. Taylor Jay Tischfield Bernice Porjesz Alison M. Goate Howard J. Edenberg Tatiana Foroud Ryan Bogdan Arpana Agrawal 《Genes, Brain & Behavior》2019,18(6)
Genetic influences on alcohol and drug dependence partially overlap, however, specific loci underlying this overlap remain unclear. We conducted a genome‐wide association study (GWAS) of a phenotype representing alcohol or illicit drug dependence (ANYDEP) among 7291 European‐Americans (EA; 2927 cases) and 3132 African‐Americans (AA: 1315 cases) participating in the family‐based Collaborative Study on the Genetics of Alcoholism. ANYDEP was heritable (h 2 in EA = 0.60, AA = 0.37). The AA GWAS identified three regions with genome‐wide significant (GWS; P < 5E‐08) single nucleotide polymorphisms (SNPs) on chromosomes 3 (rs34066662, rs58801820) and 13 (rs75168521, rs78886294), and an insertion‐deletion on chromosome 5 (chr5:141988181). No polymorphisms reached GWS in the EA. One GWS region (chromosome 1: rs1890881) emerged from a trans‐ancestral meta‐analysis (EA + AA) of ANYDEP, and was attributable to alcohol dependence in both samples. Four genes (AA: CRKL, DZIP3, SBK3; EA: P2RX6) and four sets of genes were significantly enriched within biological pathways for hemostasis and signal transduction. GWS signals did not replicate in two independent samples but there was weak evidence for association between rs1890881 and alcohol intake in the UK Biobank. Among 118 AA and 481 EA individuals from the Duke Neurogenetics Study, rs75168521 and rs1890881 genotypes were associated with variability in reward‐related ventral striatum activation. This study identified novel loci for substance dependence and provides preliminary evidence that these variants are also associated with individual differences in neural reward reactivity. Gene discovery efforts in non‐European samples with distinct patterns of substance use may lead to the identification of novel ancestry‐specific genetic markers of risk. 相似文献
9.
10.
The low incidence of intraspecific combat in territorial systems has traditionally been accounted for by theories that emphasize the bio-energetic advantages or the diminished risk of injury of threat display posture when compared with combat. Recently, however, it has been suggested that territory-holding passerines engaging in highly aggressive defensive behaviour are likely to pay a cost in terms of reduced vigilance for avian predators. To examine this further, two defensive options (combat and threat display) were evoked and observed in territorial European Robins Erithacus rubecula , in both winter and summer. It was found that Robins that engaged in combat during simulated territorial intrusion were significantly slower to react to a stuffed Sparrowhawk Accipiter nisus , than those eliciting threat display. Therefore, the decreased vigilance in escalated fighting may result in higher vulnerability to predation, and this might help, in part, to explain why threat display is favoured over direct combat. Moreover, the mean time to evade the predator was significantly longer in summer than in winter in threat-displaying Robins. In addition to this finding, a clear difference in the type of behaviour adopted between the seasons was observed, with lower incidence of combatative response during the winter months. This difference in response to the appearance of a predator is discussed in relation to reduced levels of safe cover, a reduction in the availability of alternative prey during the winter months and to seasonal fluctuations in plasma androgen levels. 相似文献