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21.
In a sensitive ACTH bioassay system using isolated rat adrenal cells, we tested the effect of gamma-MSH related peptides on ACTH-induced steroidogenesis. Peptides, including synthetic gamma1-, gamma2-, gamma3- and Lys-gamma3-MSH, exerted no effect in augmenting ACTH-induced steroidogenesis. None of the 16 kilodalton fragment of ACTH/beta-lipotropin precursor and its cleaved fragment had such an activity. The results are in contrast with previous reports concerning ACTH-potentiating activity of gamma-MSH related peptides and, therefore, indicate the necessity of further investigation of the principle involved in this unique biological activity. 相似文献
22.
Kaoru Miyazaki Keisuke Mashima Nobuhiko Yamashita Jinpei Yamashita Takekazu Horio 《In vitro cellular & developmental biology. Plant》1985,21(1):62-66
Summary We have previously reported the transformation by Rous sarcoma virus of a cloned epithelial cell line (BRL) established from
Buffalo rat liver by H. Coon. The nontransformed (BRL) and transformed (RSV-BRL) cells grew at comparable rates in culture,
whereas only the transformed cells were tumorigenic in vivo. We report here on the existence in rat and mouse sera of a growth
inhibitor for the nontransformed BRL cells. The transformed BRL cells (RSV-BRL) were insensitive to this inhibitor. The inhibitory
activity was not prominent in sera from other species of animals tested except for rabbit; this serum inhibited the growth
of RSV-BRL cells more strongly than that of BRL cells. The growth inhibitor was partially purified from rat serum. It is a
protein free of lipid and has a molecular weight of about 220 000. The inhibitor could be separated into three components
of pI 4.6, 5.2 (major) and 5.6 by isoelectric electrophoresis.
EDITOR'S STATEMENT Although compelling theoretical arguments sometimes can be made for the likely existence of growth-inhibitory
substances of physical relevance in the control of cell proliferation, experiments aimed at identifying and studying such
factors often are difficult to design and interpret, and little strong data exists to suggest that growth-inhibitory substances
are important regulatorsin vivo. The information presented in this paper represents a start toward developing a useful system for studying growth-inhibitory
factor. David W. Barnes 相似文献
23.
Summary The vacuolar system in the absorptive cells of the goldfish hindgut was studied by rapid freeze-substituted and cytochemical techniques. The apical cytoplasm of the absorptive cells contained two types of vacuoles: endosomes and lysosomes. The former were characterized by an absence of acid phosphatase activity, a dot-like distribution of material at the peripheral rim, the labelling of the inner surface with horseradish peroxidase (HRP), and by frequent connections to cytoplasmic tubules (CT), which were also free of acid phosphatase activity. The latter vacuole was preferentially located in the deeper cytoplasm and was characterized by the presence of acid phosphatase activity, an electron-dense interior matrix, a peripheral electron-lucent region (a halo), and by the detachment of HRP from the inner surface. Connections between CTs and these latter vacuoles were rarely seen. In the deeper cytoplasm, fusion between endosomes and lysosomes was sometimes observed. These results suggest that the vacuoles which are associated with CTs are endosomes, but not lysosomes, and that internalized materials are transported through the endosome-lysosome system to a giant food vacuole in the cell. 相似文献
24.
Keisuke Kohmoto Kazuya Akimitsu Tetsuyuki Kohguchi Hiroshi Otani John M. Gardner 《Plant cell reports》1986,5(1):54-56
Amberlite XAD-7, a nonionic polyacrylate adsorbent, was found to be a very effective protectant for isolating mitochondria from tissues rich in oils and phenolics. Physiologically active, well-coupled mitochondria were successfully prepared from young green leaf tissues of citrus, apple, pear and tobacco.Abbreviations DNP
2,4-dinitrophenol
- CCCP
carbonyl cyanide m-chlorophenylhydrazone
- BSA
bovine serum albumin
- PVP
polyvinylpyrrolidone 相似文献
25.
Sadayuki Ban Shozo Iida Hachiro Shimba Akio A. Awa Suzanne M. Nowak Tsutomu Sugahara 《Biochemical and biophysical research communications》1983,113(1):142-147
Endoreduplication (ER) could be induced very effectively in Chinese hamster V79 cells exposed to cytosine arabinoside (1-β-D-arabinofuranosylcytosine; Ara-C). Cells were cultured for 48 hours in Ara-C containing medium. ER frequency increases rapidly after Ara-C release. About 60% of metaphase cells were endoreduplicated at 8–10 hours after release from Ara-C (5 μg/ml). Induction of ER also depends on Ara-C concentrations. 相似文献
26.
The genomes of three plaque-forming recombinant phages between phage P1 and plasmid p15B were characterized by restriction cleavage analysis and electron microscopic heteroduplex studies. The structure of all three P1-15 hybrid genomes differs from that of P1 DNA in the res mod region coding for restriction and modification systems EcoP15 and EcoP1, respectively. P1-15 hybrid 2 shows an additional major difference to P1 around the site of the residential IS1 element of P1 and it does not carry an IS1 in its genome. 相似文献
27.
Sequence of the site-specific recombinase gene cin and of its substrates serving in the inversion of the C segment of bacteriophage P1. 总被引:24,自引:6,他引:18
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Inversion of the 4.2-kb C segment flanked by 0.6-kb inverted repeats on the bacteriophage P1 genome is mediated by the P1-encoded site-specific cin recombinase. The cin gene lies adjacent to the C segment and the C inversion cross-over sites cixL and cixR are at the external ends of the inverted repeats. We have sequenced the DNA containing the cin gene and these cix sites. The cin structural gene consists of 561 nucleotides and terminates at the inverted repeat end where the cixL site is located. Only two nucleotides in the cixL region differ from those in the cixR and they are within the cin TAA stop codon. The cin promoter was localized by transposon mutagenesis within a 0.1-kb segment, which contains probable promoter sequences overlapping with a 'pseudo-cix' sequence cixPp. In a particular mutant, integration of an IS1-flanked transposon into the cin control region promoted weak expression of the cin gene. The cin and cix sequences show homology with corresponding, functionally related sequences for H inversion in Salmonella and with cross-over sites for G inversion in phage Mu. Based on a comparison of the DNA sequences and of the gene organizations, a possible evolutionary relationship between these three inversion systems and the possible significance of the cixPp sequence in the cin promoter are discussed. 相似文献
28.
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30.
Larvae of genus Pieris in the northern part of Kyoto City are parasitized by two tachinid flies:Epicampocera succincta, a specialist on genus Pieris, and Compsilura concinnata, a generalist with very wide host-range. We surveyed the parasitism rates of Pieris by both flies for two years at six study areas. In these study areas, there lived three host species in the genus Pieris: P. rapae, P. melete, and P. napi, but neither tachinid parasitized P. napi to any significant extent. In the mountainous district, P. rapae and P. melete coexisted and their populations were relatively continuous, while in the lowland, only P. rapae larvae were abundant in spring and autumn, but even they disappeared in summer. Parasitisms by E. succincta occurred mainly in mountainous district and never in the lowland. C. concinnata parasitized Pieris in all the areas, but its parasitisms occurred mainly in autumn. We analyzed the factors affecting the spatial and temporal patterns of parasitism rates and presumed that the temporal discontinuity of host population restricted the distribution of the specialist parasitoid. 相似文献