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911.
Marion T. Hierowski 《FEBS letters》1983,154(1):92-96
Quantitative analyses of LH-RH-like membrane receptors were performed in five tumors from the transplantable Dunning R3372H rat prostatic adenocarcinoma. The binding of D-Trp6-LH-RH, an agonist of LH-RH, was observed in all 5 tumors. The antagonist [Ac-Dp-Cl-Phe1,2,D-Trp3,D-Lys6,D-Ala10]-LH-RH was bound to 4 tumors. The apparent equilibrium dissociation constant (Kd) for D-Trp6-LH-RH receptor was from 2.6–3.9 × 10?10 M. The apparent equilibrium Bmax values (maximum number of binding sites) were from 17.2–86.0 fmol/mg membrane protein for D-Trp6-LH-RH receptor. The Kd for the antagonist was from 2.4–2.7 × 10?10 M and the Bmax values were from 35.5–66.0 fmol/mg membrane protein. Similar binding studies performed in 6 normal rat prostates showed no binding capacities. 相似文献
912.
Epidermal growth factor stimulated cell proliferation in a primary mammary epithelial cell culture derived from mice at different stages of pregnancy. Moreover, the peptide hormone inhibited casein production induced by the synergistic actions of insulin, cortisol and prolactin. The inhibitory effect of epidermal growth factor was influenced by the gestational stages of the mammary gland. These effects of epidermal growth factor were exerted at physiological concentrations. The dual actions of epidermal growth factor on mammary cells implicate its participation in regulation of the growth and differentiation of the mammary gland during pregnancy. 相似文献
913.
914.
E D Gundelfinger 《FEBS letters》1983,157(1):133-138
The interaction between the three Drosophila DNA-dependent RNA polymerases (EC 2.7.7.6) and the DNA template or the RNA product was investigated by photochemical cross-linking and binding studies, using RNA polymerase subunits immobilized on nitro-cellulose filters. It can be shown that the two largest subunits are responsible for the binding of the enzymes to both template and newly-synthesized RNA. 相似文献
915.
Streptozotocin diabetes results in increased responsiveness of adipocyte lipolysis to glucagon 总被引:3,自引:0,他引:3
Adipocytes from streptozotocin-diabetic rats are approximately 50-times more sensitive to the lipolytic action of glucagon. This change is only perceived in the presence of a small quantity of adenosine deaminase which itself has little effect on basal lipolysis. Insulin treatment restores glucagon sensitivity to normal. 相似文献
916.
917.
A Pfohl-Leszkowicz S Galiegue-Zouitina B Bailleul M H Loucheux-Lefebvre G Dirheimer 《FEBS letters》1983,163(1):85-88
Both the initial velocity and the overall methylation of Ac-4HAQO modified DNA by a calf brain DNA (cytosine-5-)-methyltransferase are increased as compared to native DNA. The affinity of the modified DNA for the enzyme decreases as a function of the extent of the modification. Heat-denatured, single-stranded DNA shows exactly the opposite results: the more it is modified, the less it is methylated. The poly(dG-dC) X poly(dG-dC) modified by 4NQO is as well methylated as the non-modified one. The carcinogen may induce a tertiary structure favouring the 'walking' of the enzyme along the DNA. The hypermethylation caused by this carcinogen could have a significance in gene activity and cellular differentiation. 相似文献
918.
919.
Calcium-dependent activation and deactivation of rod outer segment phosphodiesterase is calmodulin-independent 总被引:2,自引:0,他引:2
ATP-dependent activation and deactivation of retinal rod outer segment phosphodiesterase is affected by calcium [Kawamura, S. and Bownds, M. D., J. Gen. Physiol. 77:571-591(1981)]. Our data demonstrate that although calmodulin has been found in rod outer segments [Liu, Y. P. and Schwartz, H., Biochim. Biophys. Acta 526:186-193(1978); Kohnken, R. E. et al, J. Biol. Chem. 256:12517-12522(1981)], this protein is not involved in calcium-dependent phosphodiesterase activation at light levels at which calcium clearly affects this enzyme's activity. Furthermore, calmodulin does not mediate the calcium-dependent deactivation of phosphodiesterase. 相似文献
920.
(1) Exposure of phospholipids at the outer surface of activated and control platelets was studied by incubation with a mixture of phospholipase A2 from Naja naja and bee venom, solely or in combination with sphingomyelinase from Staphylococcus aureus, using conditions under which cell lysis remained below 10%. (2) Incubation with phospholipase A2 alone revealed a markedly increased susceptibility of the phospholipids in platelets activated by a mixture of collagen plus thrombin, by the SH-oxydizing compound diamide, or by calcium ionophore A23187, as compared to control platelets or platelets activated separately by collagen or thrombin. (3) Collagen plus thrombin, diamide, and ionophore treated platelets revealed an increased exposure of phosphatidylserine at the outer surface accompanied by a decreased exposure of sphingomyelin, as could be concluded from incubations with a combination of phospholipase A2 and sphingomyelinase. These alterations were much less apparent in platelets activated either by thrombin or by collagen alone. (4) The increased exposure of phosphatidylserine in activated platelets is accompanied by an increased ability of the platelets to enhance the conversion of prothrombin to thrombin by coagulation factor Xa, in the presence of factor Va and calcium. (5) It is concluded that the altered orientation of the phospholipids in the plasma membrane of platelets activated by collagen plus thrombin, by diamide, or by calcium ionophore, is the result of a transbilayer movement. Moreover, the increased exposure of phosphatidylserine in platelets stimulated by the combined action of collagen and thrombin might be of considerable importance for the hemostatic process. 相似文献