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>Studies on the development of growth hormone and prolactin cells in the rat pituitary gland by in situ hybridization
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Studies on the development of growth hormone and prolactin cells in the rat pituitary gland by in situ hybridization
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机译：Studies on the development of growth hormone and prolactin cells in the rat pituitary gland by in situ hybridization
Cytogenesis of growth hormone and prolactin cells in the rat pituitary gland was studied using in situ cDNA-mRNA hybridization and immunocytochemistry. Frozen or Paraplast sections of fetal and neonatal pituitaries were hybridized with3H-cDNAs for rat prolactin or growth hormone, and were then processed for autoradiography. A number of growth hormone mRNA-positive cells were encountered throughout the anterior lobe on day 19 of gestation. Individual variaction in growth hormone gene expression was observed between fetuses at day 19 of gestation (6 out of 8 fetuses examined were positive for growth hormone mRNA). In contrast, growth hormone mRNA was detected in the all fetuses examined on day 20 or later. The autoradiographic signal (number of reduced silver grains) appeared to increase with later stages of development. Fetal growth hormone mRNA-positive cells were evenly scattered throughout the anterior lobe. Most of them were isolated, however, small clusters of several growth hormone cells were infrequently observed. Prolactin mRNApositive cells were found first on the 22nd day (the last day of gestation) in 3 of 6 fetuses examined, but were rarely observed on earlier gestational days. By postnatal day 8, prolactin mRNA-positive cells were numerous and the grain density over prolactin cells increased. Both growth hormone and prolactin cells were found as early as 18 days of gestation using immunocytochemistry, although the number of positive cells was very small at this stage. Immunoreactive growth hormone cells increased sharply in number during the next 24 h, while the number of prolactin cells remained scarce until birth. The results suggest that many growth hormone cells are still in an immature state at 20∶00 of day 18 and that many begin to synthesize growth hormone mRNA during next 14 h. On the other hand, no substantial prolactin gene expression appears to take place until after birt
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