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91.
Mouse fibroblasts, 3T3 cells, require a solid surface for continuous growth, but when 3T3 cells, during their exponential phase in Petri dishes, were transferred to a suspension culture, the number of cells roughly doubled by 30 h. During the suspension culture the number of pairing cells (c2) increased, but that of the single cells decreased. When cells synchronized at mitosis or at the G1-S boundary were transferred to the suspension culture, the number of pairing cells peaked at 30 min and at 10 h, respectively. DNA synthesis began immediately after the cells, which were cultured for 16 h in the suspension, had settled onto the surface of the Petri dishes. When cells in a confluent culture were arrested at an early G1 period and were suspended, the number of pairing cells did not increase. These results indicate that the most important locus for anchorage growth seems to be at a late G1 period of the cell cycle. 相似文献
92.
Sodium ion discharge from pig kidney Na+, K+-ATPase Na+-dependency of the E1P-E2P equilibrium in the absence of KCl 总被引:3,自引:0,他引:3
The two phosphoenzymes (E1P and E2P) of Na+,K+-ATPase were measured as ADP-sensitive and K+-sensitive fractions. The sum of these fractions was nearly 1 in the range of 50 to 1,200 mM NaCl. The effects of Na+ on the levels of E1P and E2P, on the rate constant of E2P leads to E1P transition (k2), on the rate constant of E2P dephosphorylation (k3), on the rate constant of E1P leads to E2P transition (k1) and on the apparent equilibrium constant between E1P and E2P (Kapp) were examined. k1 was found to decrease with increasing Na+ concentration, whereas k2 increased. Kapp was found to be directly proportional to the third power of Na+ concentration. k3 increased with increasing Na+ concentration and saturated at about 1 M NaCl. These results are consistent with a simple model in which ATP hydrolysis occurs through effectively only two phosphoenzyme intermediates in the absence of K+ and three sodium ions are discharged cooperatively from the enzyme during the E1P leads to E2P conversion. 相似文献
93.
We compared several Na,K-ATPase preparations from various organs of the rat. The brain Na,K-ATPase differed from the enzymes of other organs in its pH dependence and responses to ouabain and N-ethylmaleimide in spite of similarities in the kinetic parameters of activation by Na+, K+, Mg2+, and ATP. The optimum pH of the brain MaI-enzyme was at 7.4 to 7.5 at 37 degrees D. The Lubrol extract of this brain enzyme preparation showed a lower optimum oH of 6.6. When the Lubrol extract of the brain was fractionated wtih (NH4)2SO4, the activity of the precipitate in the neutral pH region was restored. On the other hand, the optimum pH of the kidney NaI-enzyme was slightly affected by Lubrol and ammonium sulfate treatments (pH 7.5 leads to 7.3). The brain enzyme (K 1/2 = 0.9 microM) showed about 100-fold higher sensitivity to ouabain than the enzymes from other organs (I 1/2 = 100 microM) in the presence of 120 mM Na+ and 10 mM K+. In a Hill plot of the ouabain inhibition, the former failed to give a linear relationship, while the latter gave a straight line with a Hill coefficient of 1.0. The effect of K4 on the brain enzyme-ouabain interaction led us to consider that the brain enzyme might have two components as regards ouabain affinity, high and low affinity components. The time course of N-ethylmaleimide inhibition of the brain enzyme was rapid and biphasic, while the kidney enzyme showed only a slow phase following pseudo-first order kinetics. ATP protected the kidney enzyme activity completely agai,st N-ethylmaleimide inhibition, but the protection of the brain enzyme activity by ATP was only partial. We divided rat Na,K-ATPases into two groups, the brain type, which is restricted to the central nervous system, and the kidney type, which is found in most organs. 相似文献
94.
Summary When a bacterial immunopotentiator, OK-432, was injected to intact DDI mice, a viral inhibitor with the properties of immune interferon (IF) was induced in the circulation. The maximum titer of antiviral activity (10,240 units/ml) was observed 24 h after intraperitoneal (IP) injection of 50 KE OK-432/kg body weight. The possibility that the induction of immune IF may depend upon the action of thymus-derived (T) lymphocytes and macrophages was inferred from experiments with thymus-defective nude mice and DDI mice treated with either X-rays or immunosuppressive agents. 相似文献
95.
Keishi Abe Yoichi Otsuka Minoru Yasujima Satoru Ciba Masahide Seino Nobuo Irokawa Kaoru Yoshinaga Fumio Hirata Shiro Ohki Nobuhiko Nakazawa Toshio Hanyu 《Prostaglandins & other lipid mediators》1976,12(5):843-848
The excretion rates of main urinary metabolite of PG F2α were measured radioimmunologically in 4 healthy persons and in 13 essential hypertensives. The resting values were 9.3±0.73 in the former and 10.4±2.17 ng/min in the latter. There was no significant differences between them. The excretion of the metabolite decresed prominently after the administration of furosemide. The percent decrease was 57% in healthy persons and 70% in essential hypertension. The percent result supports that furosemide inhibit the catabolism of PG F2α. 相似文献
96.
W Mori O Yamauchi Y Nakao A Nakahara 《Biochemical and biophysical research communications》1975,66(2):725-730
The absorption, circular dichroism (CD), and magnetic circular dichroism (MCD) spectra in the visible region have been measured for hemocyanin at 77, 198, and 293K. From the temperature dependence of the CD spectra of oxyhemocyanin, the bands observed at 450, 565, and 700 nm were resolved into those centered at 430, 490, 565, 600, and 700 nm. Since these five peaks are most probably due to the d-d transitions, the two copper ions at the oxygenated active center are inferred to be Cu(II) ions each in a non-equivalent coordination geometry of very low symmetry. The MCD spectral data confirm the view and reasonably explain the diamagnetism of oxyhemocyanin. 相似文献
97.
98.
99.
A new diterpene glucoside has been isolated from Leucothoe grayana. Its structure was elucidated by X-ray diffraction analysis of a dehydrated product of the aglycone and conversion of the same to leucothol A. 相似文献
100.