共查询到20条相似文献,搜索用时 0 毫秒
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Thyroxine (T4)-prolactin interactions on hepatic arginase and ornithine transcarbamylase (OTC) as well as hind legs, tail, digestive tract and median eminence were investigated in tadpoles, Rana catesbeiana. Prolactin completely blocked T4-induced tail resorption, but failed to suppress hind-leg growth, shortening of digestive tract and promotion by T4 of the median eminence development. Prolactin blocked T4-induced increase in hepatic arginase activity but not in hepatic OTC activity. A possibility that T4 and prolactin are regulating the hepatic arginase indirectly is discussed. 相似文献
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Albumin synthesis during induced and spontaneous metamorphosis in the bullfrog Rana catesbeiana 总被引:1,自引:0,他引:1
Treatment of premetamorphic tadpoles with triiodothyronine (T3) alters the in vivo distribution of radioactive amino acids among serum protein fractions. The effects on the albumin fraction have been interpreted as reflections of the relative rate of synthesis. About 12 hr after intraperitoneal injection of 2.5 × 10?10 mole of T3 per gram, there is an increase in the relative rate of albumin synthesis. The effect peaks on day 3 at 5 × the untreated level and returns to near the untreated level by day 6. Continuous immersion in 1 × 10?7M T3 results in a similar stimulation of albumin synthesis, but with no decline after day 3. The timing of the response is independent of dose or route of T3 administration. The effect of T3 on the relative rate of albumin synthesis is also observed in froglets. There is a 6-fold increase in the relative rate of albumin synthesis during spontaneous metamorphosis peaking at stage XXI and returning to the premetamorphic level by stage XXV. The following was concluded: (1) The increase in the relative rate of albumin synthesis during metamorphosis results from increased endogenous thyroid levels. (2) Following a peak, the decline in albumin synthesis observed in induced and spontaneously metamorphosing animals is a result of decreasing thyroid hormone levels. (3) The effect of T3 on albumin synthesis may be the summation of two effects, a direct effect of T3 and a stimulation by amino acids from the resorbing tail. (4) A decreased relative rate of albumin degradation or a sparing of albumin is probably responsible for the elevated relative concentration of albumin in the serum of postmetamorphic animals. 相似文献
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K D Cole G H Little 《Comparative biochemistry and physiology. B, Comparative biochemistry》1983,76(3):503-506
1. Cold-acclimated (1 degree C) goldfish (Carassius auratus) branchial Na/K-ATPase activity was elevated 100% while renal Na/K-ATPase activity was not significantly affected compared with warm-acclimated (20 degrees C) goldfish. 2. Cold-acclimated goldfish branchial and renal Mg-ATPase activity was reduced 18 and 30% on a per mg protein basis, respectively. 3. Renal Na/K-ATPase activity was 4.6- and 1.6-fold greater than gill in cold- and warm-acclimated fish, respectively. 4. The elevated branchial Na/K-ATPase activity and the unchanged renal Na/K-ATPase activity are consistent with the maintenance of the reduced blood ion level in cold-acclimated goldfish. 相似文献
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C Alonso 《Journal of insect physiology》1973,19(11):2135-2142
Determinations of total protein and RNA at various times after the beginning of the pharate pupal stage of Drosophila hydei, revealed an increase in both substances during the first 25 hr and a sudden decrease thereafter until 52 hr. From this time on the total amount of both protein and RNA increases slightly until emergence of the flies at 160 hr after the beginning of the pharate pupal stage. A similar pattern of changes was recorded for the total radioactivity as well as the specific activity of RNA labelled with 3H-uridine after the injection of the isotope immediately before the beginning of the pharate pupal stage.The migration profile of RNA labelled with 3H-uridine during larval development, revealed that shortly after the onset of the pharate pupal stage an essentially normal larval pattern consisting of major fractions of 28, 18, 8 to 9, and 4 to 7 S RNA. At 52 hr only the low molecular weight RNA was present. The ‘normal’ pattern was restored at the time of emergence of the flies, indicating re-utilization of degradation products of previously labelled RNA. 相似文献
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G H Little C W Garner J W Pelley 《Comparative biochemistry and physiology. B, Comparative biochemistry》1979,62(2):163-165
1. Alanine aminopeptidase activity and autolysis increase concomitantly in tail tissue of Rana catesbeiana tadpoles during metamorphosis. 2. significant increases first appear at Taylor and Kollros state XX and coincide with the beginning of tail regression as determined by the tail wt body wt ration. 3. The results suggest a role of alanine aminopeptidase in the mechanism of tail resorption. 相似文献
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M. Takada 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(4):271-276
Regional differences in potential difference and short-circuit current between the body (dorsal) and the tail skin during metamorphosis of Rana catesbeiana tadpoles were investigated. In body skin, the potential difference and the short-circuit current across the skin develop in two successive steps. At stage XX, the potential difference and the short-circuit current across the body skins were amiloride-insensitive (1st step). At stage XXII, however, amiloride-sensitive potential difference and the short circuit current appeared (2nd step). By contrast, in tail skin the potential difference and the short-circuit current remained amiloride-insensitive (1st step) even at stage XXIII. Since the tail regresses after stage XXIII, the appearance of the second step could not be followed in vivo. To determine whether or not the second step can be induced in the tail, tail skin was cultured under conditions where the skin survives for a much longer period than it does in normally developing tadpoles. Such cultured tail skin generated the amiloride-sensitive potential difference and the short-circuit current and cultured body skin also generated them. Therefore, development of the 2nd step in the tail skin may be delayed in vivo. To characterize the differences between body and tail skin, skins were mutally grafted between body and tail at stage XIII–XV. The body skin grafted on the tail underwent both the 1st and 2nd steps by stage XXII, whereas the tail skin grafted on the body only showed the 1st step by the same stage. These results suggest that the regional specificity of the skin is already established before the prometamorphic stage.Abbreviations CMFS Ca2+- and Mg2+-free saline - CTS charcoal-treated serum - EDTA ethylene diamine tetra-acetate - I current - PD potential difference - R skin resistance - SCC short-circuit current 相似文献
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Dr. F. Sasaki D. Baxter Grillo T. Horiguchi K. Watanabe 《Cell and tissue research》1985,239(3):511-517
Summary In anuran tadpole tails, the myelinated motor nerve fibers branch in the myoseptum to innervate both red and white muscle fibers at, or near, their ends. There are no significant ultrastructural differences between the nerve endings of the two types of muscle fibers.Intense acetylcholinesterase reaction product was observed in synaptic clefts and junctional folds, as well as in transverse tubules. As metamorphosis proceeded, the junctional folds of the nerve endings disappeared, however, acetylcholinesterase reaction product was still observed in the synaptic clefts. As muscle fibers began to degenerate, nerve endings began to separate from them. However, after nerve endings were completely separated from the surfaces, degenerated muscle fibers, synaptic and cored vesicles were still well preserved although no acetylcholinesterase reaction product was found. It seems clear that the mechanism of the muscle degeneration in the tadpole tail during metamorphosis is not the result of the degeneration of its nerve endings. 相似文献
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J W Crim 《The Journal of experimental zoology》1984,229(2):327-337
The distribution of immunoreactive luteinizing hormone-releasing hormone (ir-LH-RH) in brains of bullfrogs (Rana catesbeiana) during spontaneous metamorphosis has been studied by combination of an unlabeled antibody enzyme immunocytochemical technique and an adjacent serial section approach. In prometamorphic tadpoles, immunocytochemical staining for ir-LH-RH was absent from the brain, including a structurally simple median eminence (ME) and perikarya in the anterior preoptic area (aPOA). In metamorphic tadpoles, speckled patches of immunostaining occurred over the outer layer of a modestly developed ME; coincident faint staining of a small number of medial, unpaired cell bodies was localized in the aPOA. In newly metamorphosed juvenile frogs, more diffuse and intense staining of the outer layer of the ME accompanied increased morphological differentiation of this neurohemal area; immunoreactive perikarya again were found in the aPOA, but an increased number of neurons exhibited comparatively greater (moderate) immunostaining. Changes in the quality of immunostaining and in the numbers of cells stained, therefore, were coincident with metamorphic development. Concomitant alterations of ir-LH-RH immunostaining and progressive structural development of the ME suggest a coordinated differentiation of brain neuroendocrine systems during metamorphosis of the bullfrog tadpole. 相似文献
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Takashi Hasebe Hiroyuki Oshima Kosuke Kawamura and Sakae Kikuyama 《Development, growth & differentiation》1999,41(5):639-643
Mechanisms of hemoglobin transition during bullfrog metamorphosis were investigated by labeling red blood cells from larvae (L-RBC) and from froglets (A-RBC) with a fluorescent dye, PKH26. The life span of the labeled L-RBC in systemic circulation was significantly shorter when they were injected into the animals at the metamorphic climax, compared to injection into pre- or postmetamorphic animals. The A-RBC had a long life span regardless of the metamorphic stage of the recipient animal. Therefore, L-RBC were selectively removed from the systemic circulation at the time of metamorphic climax. During climax, the labeled L-RBC were ingested by hepatic and splenic macrophages, indicating that macrophages are involved in the specific elimination of L-RBC. 相似文献
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Molecular cloning of hepatic mRNAs in Rana catesbeiana responsive to thyroid hormone during induced and spontaneous metamorphosis 总被引:1,自引:0,他引:1
Amphibian metamorphosis affords a useful experimental system in which to study thyroid hormone regulation of gene expression during postembryonic vertebrate development. In order to isolate gene-specific cDNA probes which correspond to thyroid hormone-responsive mRNAs, we employed differential colony hybridization of a cDNA library constructed from poly(A)+ RNA of thyroxine-treated premetamorphic tadpole liver. From an initial screening of about 6000 transformants, 32 "potentially positive" colonies were obtained. The recombinant cDNA-plasmids from 13 of these colonies plus two "potentially negative" colonies were purified for further study. Southern blot analysis of the plasmid DNA was employed to determine whether different cDNAs encoded for the same mRNA. The effect of thyroid hormone on the relative levels of specific mRNA species was examined by Northern analysis of liver RNA from premetamorphic tadpoles, thyroxine-treated tadpoles, and adult bullfrogs. Three independent cDNA clones were obtained which encoded thyroid hormone-enhanced mRNAs. We also obtained two independent cDNA clones encoding thyroid hormone-inhibited mRNAs and three independent clones encoding thyroid hormone-unresponsive mRNAs. The levels of two thyroid hormone-enhanced mRNAs and one thyroid hormone-inhibited mRNA were essentially the same in the thyroid hormone-treated tadpole liver and adult liver, suggesting that thyroid hormone induces stable changes in liver gene expression during spontaneous metamorphosis. Using selected cDNAs, RNA dot blot analysis of liver mRNA from tadpoles at different stages of metamorphosis showed that the level of one thyroid hormone-enhanced mRNA increased during late prometamorphosis and metamorphic climax. Similarly, a mRNA which was strongly inhibited by thyroid hormone treatment was observed to decline during prometamorphosis and reach undetectable levels during metamorphic climax. One mRNA was detected which was reproducibly inhibited by thyroid hormone treatment but which remained essentially unchanged during spontaneous metamorphosis. These results provide the first direct evidence for the coordinate and selective pretranslational regulation by thyroid hormone of several liver genes during the developmental process of metamorphosis. 相似文献