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1.
DNA content of the tadpole tail fin was increased appreciably by the treatment of animals with bovine prolactin. Incorporation of 3 H-thymidine into DNA in the hormone-treated tail fins was remarkably stimulated as compared to the control ones. From the experiment on the effect of prolactin on the DNase activity, it is concluded that prolactin not only stimulates the synthetic parthway, but also suppresses significantly the catabolic one of the DNA metabolism. 相似文献
2.
EFFECT OF PROLACTIN ON THE TADPOLE TAIL FIN. III. EFFECT OF PROLACTIN ON THE HYDROXYLATION OF PROTOCOLLAGEN-PROLINE OF THE TAIL FIN 总被引:1,自引:1,他引:0
The fact that bovine prolactin stimulates the collagen synthesis of the tadpole tail fin was confirmed by the present experiments, in which specific radioactivity of 14 C-hydroxyproline hydroxylated from the incorporated 14 C-proline was measured by the method different from that of the previous report (Y oshizato and Y asumasu , 1970). Stimulatory effect of prolactin on the incorporation of 14 C-proline into the collagen fraction did not disappear even under the conditions, where the activity of protocollagen-proline hydroxylase was inhibited by α,α'-dipyridyl. In fact prolactin had not a significant effect on the activity of the emzyme. It, therefore, is concluded that the hormone promotes the incorporation of 14 C-proline into collagen without affecting the hydroxylation step of the protein synthesis. 相似文献
3.
In the case of hyaluronic acid and collagen, treatment of tadpoles with bovine prolactin produced remarkable increase in the content of the two metabolites in the tail fin in accord with the stimulatory effect of the hormone on the incorporation of labeled precursors into hyaluronic acid and collagen. RNA content of the tissue was increased appreciably by the prolactin treatment, whereas the hormone had no effect on the incorporation of 14 C-uridine into RNA. Prolactin had inhibitory effect on the activities of hyaluronidase and RNase of the tail fin. The experiments on the protein catabolism also revealed that prolactin inhibited the process of protein turn-over in the tissue. 相似文献
4.
Injection of 14 C-proline into the tadpole causes labeling of protein in the collagen fraction of the thigh bone and tail fin. The radioactivity of the 14 C-hydroxyproline residue is about 26% of the total radioactivity in the 14 C-labeled protein of the collagen fraction in the thigh bone as well as in the tail fin. In 14 C-proline-loaded tadpoles into which prolactin has been injected, the radioactivity in the collagen fraction in these tissues is markedly higher than that in control animals. In thyroxine-treated tadpoles, the 14 C-radioactivity of the collagen fraction in the thigh bone is always higher than that of the controls, but it is markedly low in the tail fin. During the incubation of thigh bone and tail fin isolated from 14 C-proline-loaded tadpoles, low molecular weight materials containing 14 C-hydroxyproline are released from the 14 C-labeled protein of these tissues. The rate of 14 C-hydroxyproline release, which represents the rate of collagen breakdown, is higher in thigh bone and tail fin isolated from thyroxine-treated tadpoles and is markedly lower in these tissues isolated from prolactin-treated tadpoles than in those isolated from controls. In these tissues, the high rate of collagen breakdown in thyroxine-treated tadpoles is reduced by prolactin injection. 相似文献
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The rate of 14 C-proline incorporation into collagen in the thigh bone of the Rana catesbeiana tadpole was determined in vitro. Intraperitoneal injection of bovine prolactin caused an increase in the rate of collagen synthesis during the premetamorphic stages (stages 12–16) and the early metamorphic stage (stage 18), but it exerted no effect on collagen synthesis in the metamorphic stages (stages 20–25). On the other hand, injection of growth hormone stimulated the rate of collagen synthesis in the metamorphic stages and caused a slight increase in the premetamorphic stages. When a tadpole in the early premetamorphic stages (stages 12–14) was kept in 5 × 10−8 M thyroxine solution for several days, the rate of collagen synthesis became higher than that in the bone of the control animal. The rate of collagen synthesis was not enhanced by prolactin in the thyroxine-treated tadpole, but was stimulated by growth hormone, even when the thyroxine-treated animal remained in the premetamorphic stages. With the treatment of the tadpole by thyroxine, prolactin-sensitivity seems to be reduced, and growth hormone-sensitivity becomes apparent. 相似文献
7.
In thigh bones isolated from a Rana catesbeiana tadpole which has been kept in a 5 × 10−8 M thyroxine solution for several days, the rate of 14 C-leucine incorporation into protein becomes higher than that in the thigh bones of control animals. Intraperitoneal injection of prolactin also results in an increase in the rate of 14 C-leucine incorporation into protein in the thigh bones at a rate very similar to that in thyroxine-treated animals. In the thigh bones of the thyroxine-treated tadpoles, the rate of 14 C-proline incorporation into protein is markedly higher than that of control animals. Prolactin treatment of the tadpoles also causes an increase in the rate of 14 C-proline incorporation, but the rate is lower than that found in thyroxine-treated animals. The injection of prolactin into thyroxine-treated tadpoles fails to cause further increase in the rates of incorporation of these amino acids into protein. In the thigh bones of tadpoles at the climax of metamorphosis, prolactin injection does not cause any increase in the rates of 14 C-labeled proline and leucine incorporation, whereas both rates become slightly higher in the thigh bones of thyroxine-treated tadpoles at this stage. The thigh bones probably become insensitive to prolactin when they are exposed to thyroxine. 相似文献
8.
KAZUTOSHI YAMAMOTO SAKAÉ KIKUYAMA IKUO YASUMASU 《Development, growth & differentiation》1979,21(3):255-261
Small segments of tail of Bufo bufo japonicus tadpoles were cultured in medium containing thyroxine (T4 ) and dibutyryl cyclic AMP (dbcAMP). Like prolactin, the cyclic nucleotide blocked T4 -induced shrinkage or tail pieces. Histological study of the segments after 4-days culture revealed that dbcAMP suppressed degenerative changes induced by T4 . The inhibitory effect of prolactin on T4 -induced tail regression was promoted by caffeine, an inhibitor of adenosine 3', 5'-cyclic monophosphate (cyclic AMP)-phosphodiesterase.
The effect of prolactin on the level of cyclic AMP in the tail was also studied in vivo . Sixty min after prolactin injection, the cyclic AMP level was 2–3 times the control value. Possible involvement of cyclic AMP in the action of prolactin, which blocks tail resorption induced by T4 , was discussed. 相似文献
The effect of prolactin on the level of cyclic AMP in the tail was also studied in vivo . Sixty min after prolactin injection, the cyclic AMP level was 2–3 times the control value. Possible involvement of cyclic AMP in the action of prolactin, which blocks tail resorption induced by T
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TISSUE DEGRADATION PATTERNS OF AMPHIBIAN TADPOLE TAIL: HISTOLOGICAL AND BIOCHEMICAL STUDIES 总被引:1,自引:1,他引:0
The pattern of tissue degradation in the tadpole tail of the bullfrog, Rana catesbeiana , was studied histologically and biochemically. Tadpoles at four metamorphic stages (premetamorphic stage, stage XIII; prometamorphic stage, stage XVIII; early to middle climax stage, stage XXII; late climax stage, stage XXIII) were examined. In the histological study, tissues were stained by two different methods, i.e., Masson's trichrome stain and Van Gieson's stain. The results are summarized as follows: 1) Muscle tissues degenerated earlier thatn connective tissues; 2) Collagen density increased as tissue degraded; 3) At stage XXIII, degenerating and fragmented muscle tissues, surrounded by connective tissues, were seen, and 4) At the late climax stage, cell density was greatly increased as compared to preceding stages.
The biochemical studies are summarized as follows; 1) The general catabolic pattern of tail proteins seems to differ between the premetamorphic and late climax stages; 2) The total hydroxyproline content per unit wet weight of the tail increased significantly at the late climax stage as compared to the premetamorphic stage, supporting the histological observations, and 3) Collagen degradation products were obtained at the late climax stage on Sephadex G-75 columns. 相似文献
The biochemical studies are summarized as follows; 1) The general catabolic pattern of tail proteins seems to differ between the premetamorphic and late climax stages; 2) The total hydroxyproline content per unit wet weight of the tail increased significantly at the late climax stage as compared to the premetamorphic stage, supporting the histological observations, and 3) Collagen degradation products were obtained at the late climax stage on Sephadex G-75 columns. 相似文献
11.
在绵羊睾丸间质细胞体外无血清长期培养的条件下,研究了催乳素对睾丸间质细胞睾酮分泌的调节作用。实验结果表明,催乳素可增强细胞对人绒毛膜促性腺激素(hCG)刺激的反应。催乳素的这种作用呈双相调节。睾酮分泌量显著高于hCG和催乳素单独作用时的总和。在hCG存在下,不同的底物转化为睾酮的量不同。其中雄烯二酮和孕酮转化为睾酮的方式存在着双相性。脱氢表雄酮转为睾酮的量少,不存在双相性,而与其剂量成正比。催乳素在hCG存在下可调节底物转化为睾酮。低剂量的催乳素(1ng/ml)可使一定剂量的孕酮(10~30ng/ml)转化为睾酮的量明显增加,而高剂量的催乳素(>10ng/ml)却明显地抑制孕酮转化为睾酮。催乳素可明显地抑制雄烯二酮转化为睾酮,与剂量无关。可见催乳素对于孕酮和雄烯二酮这两个关键底物转化为睾酮的调节是不同的。催乳素增强hCG刺激睾酮分泌的作用可能部分是通过其促进孕酮转化为睾酮来实现的。 相似文献
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Pancreatic enzyme secretion in rats anesthesized by pentobarbital was stimulated by intravenous perfusion of the hormone pancreozymin, as indicated by a decreased amylase level in the pancreas and by specific, fine structural changes observed in an electron microscope. Rates of protein synthesis were determined by pulse labeling. Amylase, total protein, and valine were purified from pancreas and counted. Pancreozymin promotes an 8 to 10 times increase in the rate of biosynthesis of pancreatic enzymes, as compared to rats similarly anesthesized but without hormone. This stimulation effect is obtained very rapidly (2 hr) and is not inhibited by actinomycin D. Secretin alone has no effect, whereas pentobarbital is inhibitory. 相似文献
14.
The possibility that tadpole tail regression might be initiated by thyroid hormone-induced synthesis of new proteins was investigated. Changes in the newly-synthesized proteins of cultured Xenopus laevis tadpole tails treated with 1.5 × 10?7 M tri-iodothyronine (T3) were studied, using polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate for protein separation. After initial studies of unfractionated tail proteins, fractionated mixtures of [3H]methionine and [35S]methionine labelled proteins derived from control and hormone-treated tails respectively were examined for hormone-induced changes. Using a new procedure developed to allow effective analysis of small differences in distribution of two isotopes within gel slices, it was shown that no significant changes in synthesis of fractionated tail proteins are induced by the hormone during the first 3–4 days in culture. The average detection limit was approx. 0.02% of total tail protein synthesis. Although no changes in the synthesis of the tissue structural or enzymic proteins are induced by the hormone this study still leaves open the possibility of changes in the synthesis of regulatory proteins. Based on the known method of activation of the tadpole tail collagenase (which is shown here directly for the first time to be involved in T3-induced tail regression), it is suggested that many of the initial hormone-induced changes might result from T3-induced activation of proteolytic “cascades”. 相似文献
15.
Manoj Panchal 《Preparative biochemistry & biotechnology》2013,43(4):276-285
Recombinant prolactin (PRL) from water buffalo (Bubalus bubalis) has been cloned and expressed in a prokaryotic expression system. The hormone was also successfully refolded into a biologically active form. Total RNA was purified from buffalo pituitaries and the buPRL cDNA was synthesized using primers designed on bovine PRL sequence. This prolactin cDNA was cloned in a pET 28a vector and expressed in Escherichia coli strain BL21(DE3)pLysS. Most of the expressed protein was present as insoluble inclusion bodies. The inclusion bodies were solubilized and buPRL was purified by Ni-NTA column. The purified protein was refolded by gradually decreasing the concentration of denaturant during dialysis. Total yield of the refolded and soluble prolactin was 22 mg/L from 100 mL bacterial culture in LB medium. The recombinant prolactin was as active as native prolactin in stimulating growth of Nb2 lymphoma cells. 相似文献
16.
本文讨论梭德氏蛙蝌蚪的腹吸盘,经它与湍蛙属蝌蚪的腹吸盘是同功器官,因而前者不可能与后者是同民各关系。按照“丰家争鸣”方针,我们主张对科学的问题采取科学的方式加以讨论,欢迎不同意见在国内外任何刊物上撰文发表,只有通过学术讨论才有得达到共识,取得尽可能符合客观实际的结论。 相似文献
17.
Kanasaki H Yonehara T Yamamoto H Takeuchi Y Fukunaga K Takahashi K Miyazaki K Miyamoto E 《Biology of reproduction》2002,67(1):107-113
We examined the possible involvement of mitogen-activated protein (MAP) kinase activation in the secretory process and gene expression of prolactin and growth hormone. Thyrotropin-releasing hormone (TRH) rapidly stimulated the secretion of both prolactin and growth hormone from GH3 cells. Secretion induced by TRH was not inhibited by 50 microM PD098059, but was completely inhibited by 1 microM wortmannin and 10 microM KN93, suggesting that MAP kinase does not mediate the secretory process. Stimulation of GH3 cells with TRH significantly increased the mRNA level of prolactin, whereas expression of growth hormone mRNA was largely attenuated. The increase in prolactin mRNA stimulated by TRH was inhibited by addition of PD098059, and the decrease in growth hormone mRNA was also inhibited by PD098059. Transfection of the cells with a pFC-MEKK vector (a constitutively active MAP kinase kinase kinase), significantly increased the synthesis of prolactin and decreased the synthesis of growth hormone. These data taken together indicate that MAP kinase mediates TRH-induced regulation of prolactin and growth hormone gene expression. Reporter gene assays showed that prolactin promoter activity was increased by TRH and was completely inhibited by addition of PD098059, but that the promoter activity of growth hormone was unchanged by TRH. These results suggest that TRH stimulates both prolactin and growth hormone secretion, but that the gene expressions of prolactin and growth hormone are differentially regulated by TRH and are mediated by different mechanisms. 相似文献
18.
Max Hamburgh Young Kim George Tung Ronald Crenshaw Lorenzo A. Mendoza 《Developmental biology》1981,81(2):392-398
Tail fin disks removed from tadpoles of Rana pipiens that were immersed in thyroxine or triiodothyronine for 3 days (referred to as donors) were fused to premetamorphic tail fin blocks that had never been exposed to this hormone (referred to as recipients) so that triplets were formed, consisting of one recipient tail block sandwiched between two donor tail fin blocks. Such recipient tail blocks responded with characteristic resorptive activity within 24 or 48 hr, instead of the minimum 72-hr latent period normally intervening in donor blocks, until shrinkage was initiated in response to triiodothyronine (T3) or tetraiodothyronine (T4). The presence of T3 or T4 hormone was not required continuously throughout the latent period. Hormone could be withdrawn after 30 hr contact in vivo and after 24 hr contact in vitro without interfering with the rate of tissue regression of tadpole tail fins, suggesting that the “latent period” probably does not coincide with the “critical period” during which subtle biochemical changes presumably occur that precede regression of the tadpole tail during metamorphosis. It is suggested that during the latent period active intermediates may be synthesized that are subsequently transferred from donor tail fins to recipients, thus reducing the latent period of the latter. 相似文献
19.
Mitogen-activated protein kinase activation by stimulation with thyrotropin-releasing hormone in rat pituitary GH3 cells. 总被引:2,自引:0,他引:2
We examined whether mitogen-activated protein (MAP) kinase is activated by thyrotropin-releasing hormone (TRH) in GH3 cells, and whether MAP kinase activation is involved in secretion of prolactin from these cells. Protein kinase inhibitors--such as PD098059, calphostin C, and genistein--and removal of extracellular Ca2+ inhibited MAP kinase activation by TRH. A cAMP analogue activated MAP kinase in these cells. Effects of cAMP on MAP kinase activation were inhibited by PD098059. TRH-induced prolactin secretion was not inhibited by levels of PD098059 sufficient to i activation but was inhibited by wortmannin (1 microM) and KN93. Treatment of GH3 cells with either TRH or cAMP significantly inhibited DNA synthesis and induced morphological changes. The effects stimulated by TRH were reversed by PD098059 treatment, but the same effects stimulated by cAMP were not. Treatment of GH3 cells with TRH for 48 h significantly increased the prolactin content in GH3 cells and decreased growth hormone content. The increase in prolactin was completely abolished by PD098059, but the decrease in growth hormone was not. These results suggest that TRH-induced MAP kinase activation is involved in prolactin synthesis and differentiation of GH3 cells, but not in prolactin secretion. 相似文献