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31.
Testosterone inhibits cAMP-induced de Novo synthesis of Leydig cell cytochrome P-450(17 alpha) by an androgen receptor-mediated mechanism 总被引:4,自引:0,他引:4
The regulation of the novo synthesis of the microsomal cytochrome P-450 enzyme, P-450(17 alpha), was studied in mouse Leydig cell cultures. Chronic treatment with 0.05 mM 8-Br-cAMP (cAMP) caused a time-dependent increase in 17 alpha-hydroxylase activity and in the amount of P-450(17 alpha), quantitated by immunoblotting. This increase in both activity and amount was enhanced by inhibiting testosterone production with aminoglutethimide, an inhibitor of cholesterol side-chain cleavage or SU 10603, an inhibitor of 17 alpha-hydroxylase. To examine the mechanism by which cAMP or cAMP plus inhibitors of testosterone production increased the activity and amount of P-450(17 alpha), changes in the rate of de novo synthesis were studied by measuring [35S]methionine incorporation into newly synthesized protein. Treatment with cAMP plus aminoglutethimide or SU 10603 caused a 2-fold or greater increase in the rate of de novo synthesis of P-450(17 alpha) compared to treatment with cAMP only. The addition of exogenous testosterone reversed this increase in the rate of synthesis, indicating that testosterone modulates the extent of cAMP-stimulated induction of P-450(17 alpha). This negative effect of testosterone could be mimicked by the addition of the androgen agonist, mibolerone, and prevented by the addition of the antiandrogen, hydroxyflutamide. Neither estradiol nor dexamethasone had any effect on the synthesis of P-450(17 alpha). Studies on the degradation of newly synthesized P-450(17 alpha) demonstrated that testosterone had no effect on the decay of P-450(17 alpha) during the first 24 h but caused a significant increase in the rate of decay between 24 and 48 h. These data indicate that testosterone produced during cAMP induction of P-450(17 alpha) negatively regulates the amount of this cytochrome P-450 enzyme by two distinct mechanisms: by repressing cAMP-induced synthesis of P-450(17 alpha) by an androgen receptor-mediated mechanism and by increasing the rate of degradation of P-450(17 alpha). A model is proposed for the regulation of P-450(17 alpha) in Leydig cells. 相似文献
32.
本文选择两种溶剂体系,用两次单向薄层层析,从小麦抗寒与不抗寒品系天然橡胶胶乳分离提纯出6种单半乳糖和双半乳糖双甘油酯。并比较了它们的疏水侧链的脂肪酸组成。小麦糖脂疏水侧链脂肪酸的不饱和指数远大于天然胶乳糖脂。抗寒品系胶乳糖脂疏水侧链脂肪酸不饱和指数大于不抗寒品系。双半乳糖双甘油酯疏水侧链脂肪酸不饱和指数均大于其单半乳糖糖脂。 相似文献
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The kinematics of an area-conserving tank-treading disk-shaped red blood cell membrane is studied using the stream function
method suggested by Secomb and Skalak (Q. Jl Mech. appl. Math.
35, Pt 2, 233–247, 1982). Two simple area-conserving velocity fields are superimposed to satisfy the continuity condition at
the curved edges of the disk. A differential equation for the trajectory of any material point of the membrane is derived.
The requirement of synchrony of the cycle for all membrane points leads to an integral equation which determines a magnitude
function. An approximate solution is made possible by assuming small trajectory deflections. 相似文献
35.
Yuzuru Mikami Sen Feng Yu Katsukiyo Yazawa Kazutaka Fukushima Akio Maeda Jun Uno Kiyoshi Terao Naoki Saito Akinori Kubo Ken -ichiro Suzuki 《Mycopathologia》1990,112(2):113-118
During our studies on toxic substances from clinically isolated Nocarida, a new isolate identified as Nocardia otitidiscaviarum from cutaneous nocardiosis was found to produce a toxic substance called HS-6 that had strong in vitro as well as in vivo toxicity. The mouse intraperitoneal LD50 value was 1.25 mg/kg and the ED50 value for L1210 cultured cells was 0.3 ng/ml. The structure of HS-6 was determined and found to belong to the 16-membered macrocyclic group with a molecular formula of C43H68O12. HS-6 also showed activity against pathogenic fungi such as Cryptococcus neoformans. 相似文献
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An in-vivo measurement and analysis of viscoelastic properties of the spinal cord of cats 总被引:6,自引:0,他引:6
An in-vivo experimental technique was employed to determine the linear and nonlinear characteristics of viscoelastic properties of the spinal cord of anesthetized cats. The stress relaxation and recovery curves were reproducible in a group of cat experiments. The data of linear viscoelastic properties were used to develop a power law model with Boltzmann's convolution integral. The model was capable of predicting a prolonged stress relaxation and recovery curve. For larger deformation, the results were quantified using a nonlinear analysis of viscoelastic response of the spinal cord under the uniaxial experiment. 相似文献
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转铁蛋白结构与功能的研究——骆驼血清转铁蛋自的分离纯化及其含单一铁结合部位的结构域的制备和鉴定 总被引:1,自引:0,他引:1
分离纯化获得的骆驼血清转铁蛋白由分子量为73,000和63,000两个组分组成。两者至少N-端五肽顺序相同(Met-Pro-Asp-Lys-Thr)。骆驼血清转铁蛋白在生理pH下不能与人胎盘转铁蛋白受体结合。用胰蛋白酶酶解骆驼转铁蛋白可以同时得到两个合单一铁结合部位的结构域,分别来自转铁蛋白分子的N-端称N-端结构域(分子量34,700和40,700)和C-端称C-端结构域(分子量35,100)。在上述结果的基础上指出并讨论了反刍动物转铁蛋白在结构和功能上存在更多的共同性,而与其它哺乳动物的转铁蛋白有着明显的区别。 相似文献