摘要:

Summary—Cryomethods occupy a privileged position among the procedures used for the preparation of biological samples for the various studies that may be performed in electron microscopy (ultrastructural, immunocytochemical and microanalysisin situ). In general, cryomethods are specific to one, or a maximum of 2 types of application. The (3‐Cryo) methods (cryofixation, cryosubstitution without fixatives and cryoembedding in the new Lowicryl resins (K11M or HM23) are a set of methods for correlating new structural information with analytical and biochemical data. However, these 3‐Cryomethods are delicate, complicated and expensive. To demonstrate that they can be performed, at least in part, with home‐made systems at a reasonable cost, we have carried out a structural and immunocytochemical study on the oviduct of the laying quail. We studied the localization of 2 proteins, one cytoplasmic (ovalbumin) and the other nucleolar (B‐36). The results provided by the 3‐Cryomethods are compared with those obtained with other immunocytochemical methods, including tissue processed by conventional chemical fixation and high or low temperature embedding, or by 2‐Cryomethods (cryofixation and cryo

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90091-Z

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—The aim of the present study was to investigate the regulation of cAMP by tamoxifen in quail oviduct. A single injection of tamoxifen to immature female quails induced a transient activation of adenylate cyclase. Enzyme activity began to increase 3 h after the injection, peaked at 6 h and then dropped to control level at 12 h. The same time‐response curves were observed following the injection of estradiol benzoate or estradiol benzoate + tamoxifen. Moreover, adenylcyclase exhibited the same sensitivity to exogenous activators (guanylylimidodiphosphate and forskolin) in the different treated groups. Phosphodiesterase activity was left unchanged during the prereplicative period and cAMP concentration was significantly increased at 6 h (+ 44.3%). Then, cAMP concentration continued to increase (+ 73.8% at 24 h) while cAMP phosphodi esterase and adenylcyclase activities remained at control levels. Injected concurrently with estradiol benzoate, tamoxifen completely inhibited the growth promoting effect of estradiol. Tamoxifen also inhibited the activation of adenylcyclase and cAMP phosphodiesterase induced by the hormone alone during the proliferative phase of the tissue. Moreover, the combined treatment led to a sustained elevation of cAMP in the oviduct, whereas estradiol benzoate alone decreased the level of cAMP. These results and those of our previous studies showing a significant correlation between the growth inhibitory potency of triphenylethylene derivativesin vivoand their efficiency to inhibit calmodulin‐dependent cAMP phosphodiesterasein vitro, strongly suggest that the differential regulation of cAMP levels by estradiol and tamoxifen is essential for the growth promoting or growth inhibiting activities of these mole

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90092-2

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY