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排序方式: 共有359条查询结果,搜索用时 15 毫秒
1.
Inhibition of glucagon-induced glycogenolysis in isolated rat hepatocytes by the Rp diastereomer of adenosine cyclic 3',5'-phosphorothioate 总被引:6,自引:0,他引:6
The ability of the Rp diastereomer of adenosine cyclic 3',5'-phosphorothioate (Rp cAMPS) to inhibit glucagon-induced glycogenolysis was studied in hepatocytes isolated from fed rats. Preincubation of the cells for 20 min with progressively higher concentrations of Rp cAMPS followed by a 1 X 10(-9) M glucagon challenge resulted in a 50% inhibition of glucose production over a 30-min period at 2-3 X 10(-6) M Rp cAMPS. A maximal inhibition of 50-74% was achieved, the actual value depending upon the length of preincubation with Rp cAMPS. The inhibitory effect did not increase when the concentration of Rp cAMPS was increased from 3 X 10(-6) to 3 X 10(-4) M. Addition of 1 X 10(-5) M Rp cAMPS to the cells followed by 10(-11) to 10(-6) M glucagon shifted the glucagon concentration required for half-maximal glucose production measured at 10 min to 6-fold higher glucagon concentrations and the concentration of glucagon required for apparent maximal glucose production measured at 10 min to greater than 10-fold higher glucagon concentrations. The cAMP-dependent protein kinase activation curve was similarly shifted to higher concentrations of glucagon. These data show that Rp cAMPS acts as a cAMP antagonist capable of opposing the glucagon-induced activation of cAMP-dependent protein kinase and the concomitant activation of the glycogenolytic cascade. 相似文献
2.
Inhibition of hepatic gluconeogenesis by the Rp-diastereomer of adenosine cyclic 3'',5''-phosphorothioate. 下载免费PDF全文
The specific intracellular cyclic AMP-dependent protein kinase antagonist, the Rp-diastereomer of adenosine cyclic 3',5'-phosphorothioate (Rp-cAMPS), inhibited both basal and cyclic AMP-agonist-induced rates of gluconeogenesis in hepatocytes isolated from fasted rats. Incubation of the cells in the presence of pyruvate and lactate and either the Sp-diastereomer of adenosine cyclic 3',5'-phosphorothioate (Sp-cAMPS) or glucagon produced a concentration-dependent increase in the rate of gluconeogenic glucose production which was shifted to higher concentrations of Sp-cAMPS or glucagon in the presence of Rp-cAMPS. Incubation of the cells with Rp-cAMPS in the absence of agonist produced no increase in the rate of glucose production and, in most cases, 100 microM-Rp-cAMPS resulted in 14-20% decrease in the substrate-stimulated rate of glucose production. Sp-cAMPS-induced gluconeogenesis was inhibited half-maximally at 1 microM-Rp-cAMPS and glucagon-induced gluconeogenesis was inhibited half-maximally at 12 microM-Rp-cAMPS. Approx. 10-15% of the inhibition of gluconeogenesis observed in the presence of Rp-cAMPS was due to conversion of glucose 6-phosphate to liver glycogen, consistent with Rp-cAMPS-induced reactivation of glycogen synthase. The remaining 85-90% inhibition of gluconeogenic glucose production resulted from the action of Rp-cAMPS on the cyclic AMP-sensitive enzymes controlling the rate of gluconeogenesis. 相似文献
3.
Inhibition of glycogenolysis in isolated rat hepatocytes by the Rp diastereomer of adenosine cyclic 3',5'-phosphorothioate 总被引:5,自引:0,他引:5
J D Rothermel W J Stec J Baraniak B Jastorff L H Botelho 《The Journal of biological chemistry》1983,258(20):12125-12128
The diastereomeric forms of adenosine cyclic 3',5'-phosphorothioate, Rp cAMPS and Sp cAMPS, were studied in isolated hepatocytes from fed rats for their ability to interact with the intracellular cAMP-dependent protein kinase and to affect the phosphorylase kinase-phosphorylase glycogenolytic cascade. Incubation of the cells with increasing concentrations of Sp cAMPS produced a concentration-dependent activation of cAMP-dependent protein kinase with a concomitant increase in the glycogenolytic rate. Half-maximal and maximal velocities of glycogenolysis were reached at 8 X 10(-7) and 1 X 10(-5) M Sp cAMPS, respectively. Incubation of the cells with 10(-9) to 10(-4) M Rp cAMPS had no effect on basal glucose production or on cAMP-dependent protein kinase activity. Incubation of the cells simultaneously with 3 X 10(-6) M Sp cAMPS and increasing concentrations of Rp cAMPS produced half-maximal inhibition of glycogenolysis at 1 X 10(-5) M Rp cAMPS and maximal inhibition at 1 X 10(-4) M. The concentrations of Sp cAMPS required for half-maximal and maximal activation of glycogenolysis were increased 10-fold when 1 X 10(-5) M Rp cAMPS was present. These data imply that Sp cAMPS is a cAMP-agonist while Rp cAMPS is a cAMP-antagonist. 相似文献
4.
5.
The ATP-binding-cassette transmembrane transporters (ABC transporters)
known from vertebrates belong to four major subfamilies: (1) the P-
glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance
regulators (CFTR); (3) the Tap proteins encoded with the major
histocompatibility complex of mammals; and (4) the peroxisomal membrane
proteins. Both Pgp and CFTR have a structure suggesting a past internal
gene duplication; a phylogenetic analysis indicated that these duplications
occurred independently, while an independent tandem gene duplication
occurred in the case of the Tap family. Both the Pgp and Tap proteins show
evidence of relationship to bacterial ABC transporters lacking internal
duplication, and both are significantly more closely related to the HlyB
and MsbA families of transporters from purple bacteria than they are to ABC
transporters from nonpurple bacteria. The simplest hypothesis to explain
this observation is that eukaryotic Pgp and Tap genes are descended from a
mitochondrial gene or genes that were subsequently translocated to the
nuclear genome. The Pgp genes of eukaryotes are characterized by a
remarkable degree of convergent evolution between the ATP-binding cassettes
of their N- terminal and C-terminal halves, whereas no such convergence is
seen between the two halves of CFTR genes or between the duplicated Tap
genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain
not found in other ABC transporters apart from CFTR, showed high levels of
both synonymous and nonsynonymous difference in comparisons among different
mammalian species, suggesting that this region is a mutational hot spot.
相似文献
6.
7.
Amanda dos Santos Marina Tenório Botelho Willian Reina Joviano Vicente Gomes José Roberto Machado Cunha da Silva Gisela de Aragão Umbuzeiro 《Invertebrate Biology》2023,142(1):e12394
Hemocytes are circulating blood cells that play a crucial function in amphipods and other crustacean immune systems. The hemocytes of the marine tropical amphipod Parhyale hawaiensis have been used for the evaluation of DNA damage and micronuclei, but they have not been characterized in the scientific literature. The aim of this study was to describe the hemolymph cells of P. hawaiensis and study their phagocytotic activity. Basic dyes were used to differentiate the cell types and the presence of lipids. The total hemocyte counts (THCs) and the proportion and sizes of the hemocyte types were determined. Hemolymph was exposed to Escherichia coli for verification of the presence of phagocytosis. Three cell types, all containing lipids, were identified in P. hawaiensis: granulocytes (oval shape, 13.4 × 7.6 μm), semi-granulocytes (oval shape, 14.1 × 7.2 μm), and hyalinocytes (round shape, 9.6 × 7.2 μm). Those three cell types were found in different percentages in males (64.8%, 31.1%, and 4.2%) and females (70.1%, 28.2%, and 1.7%). THCs for males were 9007 ± 3800 cells per individual and 4695 ± 1892 cells per individual for females. The cells of E. coli were phagocytized by the hemocytes. Our findings increased the knowledge of hemocytes in P. hawaiensis and is a step forward in using hemocyte-based immune responses as an endpoint in ecotoxicology. 相似文献
8.
X Xiao G Hintermann AL Demanin J Piret 《Journal of industrial microbiology & biotechnology》1996,16(4):261-262
Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis. 相似文献
9.
H A El-Dorry D K Chu A Dzugaj L H Botelho S Pontremoli B L Horecker 《Archives of biochemistry and biophysics》1977,182(2):763-773
Digestion of rabbit liver fructose 1,6-bisphosphatase with subtilisin followed by denaturation of the protein yields a peptide containing 60 amino acid residues, including the blocked NH2-terminus. This peptide has the following sequence: Ac-Ala-Asp-Lys-Ala-Pr o-Phe-Asp-Thr-Asp-Ile-Ser-Thr-Met-Thr-Arg-Phe-Val-Met-Glu-Glu-Gly-Arg-Ly s-Ala-Gly-Gly-Thr-Gly-Glu-Met-Thr-Gln-Leu-Leu-Asn-Ser-Leu-Cys-Thr-Ala-Va l-Lys-Ala-Ile-Ser-Thr-Ala-Val-Arg-Lys-Ala-Gly-Ile-Ala-His-Leu-Tyr-Gly-Ile-Ala. 相似文献
10.
J B Matthew S H Friend L H Botelho L D Lehman G I Hanania F R Gurd 《Biochemical and biophysical research communications》1978,81(2):416-421
The modified Tanford-Kirkwood theory of Shire et al. for intramolecular electrostatic interactions has been applied to hydrogen ion equilibria of sperm whale ferrimyoglobin, human hemoglobin α-chain and horse cytochrome c. The model employs two sets of parameters derived from the crystalline protein structures, first, the atomic coordinates of charged amino acid residues and, second, static accessibility factors to reflect their solvent exposure. In addition, a consistent set of intrinsic pK values (pKint) for the individual groups is employed. The theoretical pK values at half-titration for individual groups in each protein correspond to the available observed pK values, and the theoretical titration curves compare closely with experimental potentiometric curves. 相似文献