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11.
Estrogen can regulate the cell cycle in the early G1 phase of yeast by increasing the amount of adenylate cyclase mRNA 总被引:4,自引:0,他引:4
The effects of beta-estradiol (estrogen; a minor component of yeast cells) on S. cerevisiae cells in the G0 and G1 phases were examined. Results showed that estrogen stimulated the recovery of growth from G0 arrest induced by nutrient limitation or ts mutation of cdc35 (adenylate cyclase) in the early G1 phase, and inhibited entry into the resting G0 phase by increasing the intracellular cAMP level. However, estrogen had no effect on late G1 arrest induced by the alpha factor or ts mutation of cdc36. Estrogen was found to lead to higher steady-state levels of adenylate cyclase mRNA but not to affect the expression of the RAS1 and RAS2 genes, although these can also alter the intracellular cAMP level. These results suggest that estrogen influences the cell cycle of yeast in the early G1 phase by controlling the level of cAMP through the increase of adenylate cyclase mRNA. 相似文献
12.
Kenzo Yamanaka Akira Hasegawa Ryoji Sawamura Shoji Okada 《Biological trace element research》1989,21(1):413-417
DNA damage induced by administration of dimethylarsinic acid (DMAA) to rats and mice was investigated. At 12 h after administration of DMAA, DNA single-strand breaks were induced markedly in lung. The majority of dimethylarsine, one of the main metabolites, in the expired air was excreted within 6–18 h after administration of DMAA to rats. In vitro experiments using nuclei isolated from lung of mice indicated that DNA strand breaks were caused by dimethylarsine. Furthermore, the strand breaks after exposure to dimethylarsine were reduced in the presence of catalase and/or superoxide dismutase. These results strongly suggest that the strand breaks are induced not by dimethylarsine itself but by active oxygen, e.g., O 2 ? and ·OH, produced both by dimethylarsine and molecular oxygen. When DNA was exposed to dimethylarsine, thiobarbituric acid (TBA)-reactive intermediates andcis-thymine glycol were produced. Dimethylarsine appears to induce DNA damage by the mechanism similar to the damage produced by ionizing radiation. 相似文献
13.
Japanese encephalitis (JE) virus was shown to grow in in vitro cultures of human monocytes. Interferon (IFN)-alpha and IFN-gamma inhibited JE virus production by the infected monocytes in the absence of anti-JE virus antibody, but interleukin (IL)-1 alpha, IL-2, IL-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte-CSF (G-CSF), and tumor necrosis factor (TNF)-alpha did not show a significant inhibition. Antibody against JE virus increased the JE virus production by the infected monocytes probably by enhanced uptake of virus-antibody complexes via Fc receptors. IFN-gamma and GM-CSF increased JE virus production by monocytes in the presence of anti-JE virus antibody, whereas IFN-alpha inhibited JE virus production even in the presence of the antibody. The other 5 cytokines (IL-1 alpha, IL-2, IL-3, G-CSF, and TNF-alpha) did not show a significant effect on JE virus production by monocytes in the presence or absence of the antibody. 相似文献
14.
Kiyoshi Akeo Yasuhiko Tanaka Tatsuji Fujiwara 《In vitro cellular & developmental biology. Plant》1988,24(7):705-710
Summary The endocytotic process in cultured human RPE cells was observed after 1 min, 20 min, and 2 h incubation with cationized ferritin.
Within 1 min the ferritin particles were seen to attach to the cell membrane, especially between microvilli. Uncoated and
coated pits could be recognized on the cell membranes, and uncoated and coated endocytotic vesicles were found in the cytoplasm
after 20 min of incubation. These vesicles were surrounded by abundant microfilaments and had no visible membranes. Loss of
membrane may be an initial step in the process of developing into the irregular clumps of ferritin particles found inside
the plasma membrane. With time, more irregular clumps of ferritin, smaller than the particles introduced during incubation,
appeared just beneath the cell membrane. Lysosomes were adjacent to the clumps of ferritin particles associated with microtobules
and finally degraded these particles. The phagolysosomes containing many particles were surrounded by many microtubules. Small
ferritin particles surrounded but had not entered the rough endoplasmic reticulums, and no particles were seen either around
or in the Golgi apparatus.
Presented at the 7th International Congress of Eye Research, Nagoya, Japan, 27 September 1986. 相似文献
15.
16.
Phototropic stimulation does not induce unequal distribution of indole-3-acetic acid in maize coleoptiles 总被引:3,自引:0,他引:3
Distribution of endogenous diffusible auxin into agar blocks from phototropically stimulated maize coleoptile tips was studied using a bioassay and a physicochemical assay, to clarify whether phototropism in maize coleoptiles involves a lateral gradient in the amount of auxin. At 50 min after the onset of phototropic stimulation, when the phototropic response was still developing, direct assay of the blocks with the Avena curvature test showed that the auxin activity in the blocks from the shaded half-tips was twice that of the lighted side, at both the first and second positive phototropic curvatures. However, physicochemical determination following purification showed that the amount of indole-3-acetic acid (IAA) was evenly distributed in the blocks from lighted and shaded coleoptile half-tips at both the first and second positive phototropic curvatures. The even distribution of the IAA was also confirmed with the Avena curvature test following purification by HPLC. These results indicate that phototropism in maize coleoptiles is not caused by a lateral gradient of IAA itself and thus cannot be described by the Cholodny-Went theory. Furthermore, the lower auxin activity in the blocks from the lighted half-tips suggests the presence of inhibitor(s) interfering with the action of auxin and their significant diffusion from unilaterally illuminated coleoptile tips. 相似文献
17.
S Hirano M Hasegawa J Kinugawa 《International journal of biological macromolecules》1991,13(5):316-317
Positions of substitution with sulphate in three water-soluble sulphated derivatives of chitosan were analysed by 13C n.m.r. The structures of N-acetylchitosan 3,6-O-disulphate, sodium chitosan N-, 6-O-disulphate, and sodium chitosan 6-O-monosulphate were confirmed. 相似文献
18.
Cell type-specific expression of the human renin gene. 总被引:2,自引:0,他引:2
A Fukamizu S Uehara K Sugimura Y Kon M Sugimura T Hasegawa M Yokoyama T Nomura M Katsuki K Murakami 《Journal of biological regulators and homeostatic agents》1991,5(3):112-116
We have previously produced transgenic mice carrying the human renin gene, whose expression is regulated in a tissue-specific manner. In the present study, we further characterized expression of the transgene. Northern blot analysis showed that the human renin gene is expressed in the kidney but not in the liver of two lines of transgenic mice with 10 and 50 copies of the transgene, suggesting that the integrated copy number of the human renin gene does not influence the dominant-renal expression pattern. Immunohistochemical study using a monoclonal antibody specific for human renin demonstrated that expression of human renin in the transgenic mouse kidney is confined to the epithelioid juxtaglomerular cells. Transfection experiments indicated that the chloramphenicol acetyltransferase fusion gene containing the 3-kb upstream sequences of the renin gene is activated only in human epithelioid embryonic 293 cells derived from kidney but not in human HepG2 cells from liver. These findings suggest that transfer of the cloned renin gene into mice and in vitro cultured cell lines can give rise to cell type-specific expression. 相似文献
19.
Compressibility-structure relationship of globular proteins 总被引:16,自引:0,他引:16
The adiabatic compressibility, -beta s, of 11 globular proteins in water was determined by means of sound velocity measurements at 25 degrees C. All the proteins studied except for subtilisin showed positive -beta s values, indicating the large internal compressibility of the protein molecules. The intrinsic compressibility of proteins free from the hydration effect appeared to be comparable to that of normal ice. The compressibility data for 25 proteins, including 14 reported previously [Gekko, K., & Noguchi, H. (1979) J. Phys. Chem. 83, 2706-2714], were statistically analyzed to examine the correlation of the compressibility with some structural parameters and the amino acid compositions of proteins. It was found that -beta s increases with increasing partial specific volume and hydrophobicity of proteins. The helix element also seemed to be a dynamic domain to increase -beta s. Four amino acid residues (Leu, Glu, Phe, and His) greatly increased -beta s, and another four (Asn, Gly, Ser, and Thr) decreased it. Some empirical equations were derived for the estimation of the -beta s values of unknown proteins on the basis of their amino acid compositions. The volume fluctuations of proteins revealed by the compressibility data were in the range of 30-200 mL/mol, which corresponded to about 0.3% of the total protein volume. The conformational fluctuation seemed to enhance the thermal stability of proteins. 相似文献
20.
The agglutinability-masking factors (AMFs) of a and mating types of Issatchenkia scutulata var. scutulata were prepared from culture fluids. AMFs masked the agglutinability of opposite mating-type cells sex-specifically, just like agglutination substances responsible for sexual cell agglutination. a AMF adsorbed to cells was eluted by incubating the cells at 60°C for 10 min. AMF was prepared directly from culture fluids of cells by DEAE-cellulose ion exchange chromatography. The active part of the AMFs is thought to be a peptidyl moiety because of the sensitivity to subtilisin. The pretreatment of cells with AMF of the opposite mating-type was shown to promote zygote formation. AMF slightly inhibited growth in a cells but not in cells, while a AMF did not show any growth-inhibitory effect on either a or x cells. 相似文献