全文获取类型
收费全文 | 492篇 |
免费 | 47篇 |
专业分类
539篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 21篇 |
2014年 | 29篇 |
2013年 | 32篇 |
2012年 | 30篇 |
2011年 | 24篇 |
2010年 | 21篇 |
2009年 | 23篇 |
2008年 | 25篇 |
2007年 | 21篇 |
2006年 | 22篇 |
2005年 | 17篇 |
2004年 | 14篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 14篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1974年 | 2篇 |
1971年 | 3篇 |
1968年 | 2篇 |
1967年 | 3篇 |
排序方式: 共有539条查询结果,搜索用时 15 毫秒
1.
Stimulation of aromatase activity in immature porcine Leydig cells by fibroblast growth factor (FGF)
J I Raeside M C Berthelon P Sanchez J M Saez 《Biochemical and biophysical research communications》1988,151(1):163-169
The effects of fibroblast growth factor (FGF) on testicular aromatase activity has been studied using primary cultures of porcine Leydig cells. After culture for 3 days in the absence or presence of FGF, the ability of the cells to produce estrogen was examined in a 4h-test period in which either (a) hCG (10(-9) M) or (b) androstenedione (3 x 10(-6) M) was added to the medium. FGF produced a 3- to 20-fold increase in estrogen formation from endogenous or exogenous substrate during the test period, in spite of a marked decrease (approximately equal to 60%) in [125I]-hCG binding and no significant change in testosterone concentration. Stimulation of estrogen secretion by FGF was dose-(ED50 approximately equal to 2 ng/ml) and time-dependent, the first and maximal effects were observed after 12h and 48h, respectively. Preliminary tests with several other factors (insulin, EGF, TGF-beta, FSH and hCG) showed that hCG alone directly stimulated aromatase activity. From these findings a role is suggested for FGF as a paracrine/autocrine agent in the control of estrogen secretion by Leydig cells. 相似文献
2.
The effects of FSH on the cytosolic protein synthesis by a primary culture of immature porcine Sertoli cells were studied. Cells were cultured in a chemically-defined medium for 3 days and, on day 3, they were incubated for 40 h in another medium containing labelled amino-acids either in the presence or absence of 50 ng/ml porcine FSH (pFSH). In control cells, about 107 spots (pI in the range of 5 to 8) were identified by a two-dimensional polyacrylamide gel electrophoresis of the radiolabelled cytosolic proteins. pFSH treatment produced a marked increase of seven proteins whose molecular weights and isoelectric points are respectively comprised between 25 to 58 K and 5.5 to 5.8. In addition, pFSH treatment induced a slight but constant increase of two other proteins (mol. wt: 24 and 12 K and isoelectric point: 5.3). 相似文献
3.
M Bernier W Gibb F Haour R Collu J M Saez J R Ducharme 《Biology of reproduction》1983,29(5):1172-1178
The steroidogenic capacity of purified immature porcine Leydig cells in culture was studied over several days. The cells were obtained by fractionating crude testicular interstitial cell suspensions on a discontinuous Percoll gradient (d = 1.037, 1.042, 1.052, 1.098 g/ml), and characterized by specific binding of 125I-human chorionic gonadotropin (hCG), testosterone (T) and cyclic adenosine 3':5'-monophosphate (cAMP) production in response to hCG, and the enzymatic determination of delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity. The Leydig cells were recovered in a density band between 1.052-1.068 g/ml and grown in a chemically defined medium (Mather et al., 1981). In the absence of hCG, T production was low throughout the 6 days of culture. However, in response to hCG (10 mIU/ml), the cultured Leydig cells showed a progressive increase in T synthesis, which reached a maximum at Days 3-4. 8-Br-cAMP (1 mM) induced a comparable rise in T production to that obtained with hCG throughout the culture period. In contrast, 8-Br-cAMP induced a near maximal increase in dehydroepiandrosterone (DHEA) production from Day 1. This paper demonstrates that purified immature porcine Leydig cells in primary culture are a valuable model to study the ontogeny of Leydig cell function. 相似文献
4.
Location,structure and behaviour of C-heterochromatin during meiosis in Dichroplus silveiraguidoi (Acrididae-Orthoptera) 总被引:1,自引:0,他引:1
The constitutive heterochromatin of Dichroplus silveiraguidoi, a species which shows an exceptionally low chromosome number (2n=8), was studied at meiosis with a staining technique on normal and hypotonically treated specimens. The results showed: 1) an unusual behaviour of the heterochromatic blocks located in the so-called synaptic region of the sex bivalent (Neo Y-Neo X), which remains paired from early prophase through metaphase I; 2) in normal or in hypotonically treated cells a heterogeneous configuration of the C-heterochromatic blocks was observed. This configuration is characterized by the existence of small positive granules interconnected by euchromatic filaments and is enhanced by treatment with a low ionic strength solution; 3) A weakly positive stained (intermediate) material was demonstrated in the Neo X chromosome; 4) A large amount of heterochromatin is distributed in the form of granular material along the length of the autosomes and as telomeric and centromeric blocks in all chromosomes. The possible evolutionary mechanisms involved and the significance of the C-band heterochromatin demonstrated in this species are discussed. 相似文献
5.
Hormonal regulation of insulin-like growth factor I secretion by bovine adrenal cells 总被引:5,自引:0,他引:5
A Penhoat D Naville C Jaillard P G Chatelain J M Saez 《The Journal of biological chemistry》1989,264(12):6858-6862
The role of insulin-like growth factor I (IGF-I) on the specific function of several steroidogenic cells has been recently reported. Since IGF-I is produced by several tissues, we have investigated whether bovine adrenal cells secrete this peptide. Purification of conditioned medium from adrenal cells incubated with [35S]methionine through affinity chromatography (monoclonal anti-IGF-I antibody), high pressure liquid chromatography, and polyacrylamide gel electrophoresis revealed a single band of similar Mr as pure recombinant IGF-I. Moreover, the purified adrenal-secreted IGF-I displaced bound 125I-IGF-I to its adrenal receptors, and pretreatment of adrenal cells with the purified peptide enhanced the acute corticotropin (ACTH)-induced cAMP production as recombinant IGF-I. The basal secretion of IGF-I (6 +/- 1 ng/48 h/10(6) cells) was stimulated 3-, 4.5-, and 9.5-fold by fibroblast growth factor, angiotensin II (A-II), and ACTH, respectively, but not by growth hormone. The stimulatory effects of A-II and ACTH were dose-dependent (ED50 congruent to 2.5 x 10(-8) and 1.5 x 10(-10) M, respectively), and the effects of both hormones were additive. Glucocorticoids were not the mediators of the effect of the two hormones on IGF-I secretion, since inhibition of their steroidogenic action by aminoglutethimide did not significantly modify IGF-I secretion. An immunoreactive IGF-I material was also secreted by mouse adrenal tumor cell line Y-1, but the stimulatory effect of ACTH was only 2-fold, and there was no effect of A-II. Since bovine adrenal cells contain specific IGF-I receptors and this peptide is required for the maintenance of some adrenal cell-specific function, the present data suggest that IGF-I may act in an autocrine fashion to stimulate adrenal cell differentiation stimulated by ACTH and A-II. 相似文献
6.
Summary Interactions between Leydig and Sertoli cells, as well as a stimulatory effect of FSH on Leydig cell activity, have been reported in many studies. In order to investigate these interactions, the ultrastructure of immature pig Leydig cells under different culture conditions has been studied. When cultured alone in a chemically defined medium, there is a marked regression of the Leydig cell smooth endoplasmic reticulum and a swelling of the mitochondria. Addition of FSH or hCG does not prevent these phenomena. Co-culturing of Leydig cells with Sertoli cells from the same animal maintains the smooth endoplasmic reticulum at the level seen in vivo and in freshly isolated Leydig cells. The addition of FSH to the co-culture stimulates its development and increases Leydig cell activity, as assessed by an increase in hCG binding sites and an increased steroidogenic response to hCG. These results suggest that Sertoli cells exert a trophic effect on Leydig cells, and that the stimulatory effect of FSH on Leydig cell function is mediated via the Sertoli cells. These results reinforce the concept of a local regulatory control of Leydig cell steroidogenesis.Post-Doctoral fellow supported by CIRIT, Generalitat de Catalunya, Spain 相似文献
7.
A Dazord D Gallet J M Saez 《Biochemical and biophysical research communications》1977,76(4):1238-1246
Corticotropin (1–24) tetracosapeptide (ACTH1–24) induces a small but significant increase in the incorporation of radioactive leucine into trichloracetic insoluble proteins of a mouse adrenal cell line Y1. Neither cyclic AMP, nor cholera toxin or a nitrophenyl sulfenyl derivative of ACTH1–24 (NPS-ACTH1–24) have any effects.After being labelled with radioactive leucine in the presence or absence of ACTH, the cells were solbilized in 1 % sodium dodecylsulfate and subjected to 20 % sodium dodecylsulfate polyacrylamide gels electrophoresis. ACTH1–24 was found to induce a dramatic increase in the incorporation of radioactive leucine into a small peptide (MW 3500). This effect was mimicked by other steroidogenic compounds such as cholera toxin, cyclic AMP, NPS-ACTH1–24 but not by ACTH11–24, a non steroidogenic analogue of ACTH. 相似文献
8.
Testicular levels of prostaglandin E2 and F2α were measured in decapsulated adult rat testis following hCG stimulation. Basal levels were, respectively, 342 ± 74 and 502 ± 89 pg/testis. Following hCG administration these basal values are not significantly modified up to 2 hours. From 2 to 24 hours the concentrations are clearly increased above the basal level: at 12 hrs they are 1925 ± 165 for E2 and 3200 ± 190 for F2α. Levels are back to normal at 48 hrs and remain so until 144 hrs. An identical pattern of prostaglandin release is observed in vitro in Leydig cell preparations isolated at different times following in vivo hCG injection. This suggests that prostaglandins are secreted by Leydig cells. In hypophysectomized animals the release of both prostaglandins E2 and F2α is similar to controls indicating that prostaglandin secretion is not directly linked to testosterone production. alternatively testosterone injections (10 mg) does not modify prostaglandin levels. Binding sites for prostaglandins E1, E2 and F2α are present on the Leydig cells and consequently Leydig cell function may be modulated by endogenous or exogenous prostaglandins. Their level is slightly increased at 24 hrs following hCG stimulation. Since the acute changes in prostaglandin E2 and F2α secretion occur during the period of “desensitization” and of acute “down regulation” of the LH-hCG receptor in the Leydig cells it is suggested that prostaglandins are involved in both phenomena. 相似文献
9.
ACTH in vivo stimulation of the synthesis of a specific mitochondrial protein in the rat 总被引:2,自引:0,他引:2
A Dazord D Gallet de Santerre J M Saez 《Biochemical and biophysical research communications》1981,98(4):885-891
Protein markers induced by hormones are the necessary probes to study hormone regulation of gene expression. We recently showed that ACTH was able to induce one of these markers in the cytosol of the rat adrenal (Dazord et al, Biochem. J. , 233–239, 1978). In this paper we described another protein marker whose localization is mitochondrial and whose MW is 134 K. Maximal stimulation is seen 2 hours after ACTH injection. Actinomycin D injected 30 min before or 1 hour after the hormone blocks the stimulation. In hypophysectomized rats both ACTH and cyclic AMP are able to stimulate the synthesis of this protein. 相似文献
10.
J M Saez F Haour A M Cathiard 《Biochemical and biophysical research communications》1978,81(2):552-558
The early mechanism of hCG induced down regulation of its own receptor as well as steroidogenesis refractoriness of rat Leydig cells to gonadotropin stimulation have been investigated. A single injection of 5, 12, 25, 50 and 100 IU of hCG in rats induced within 8 hours, Leydig cells desensitization. However, apparent receptor loss was significantly lower only in the rats who received 50 and 100 IU of hCG. Cycloheximide inhibits hCG-induced receptors loss but had no effect on hCG-induced desensitization. The most likely explanation for desensitization in the presence of binding sites and a normal adenylate cyclase, is a defective coupling between the receptor sites and the catalytic subunit. 相似文献