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41.
Uichiro Kishimoto Yuko Takeuchi Taka-aki Ohkawa Nobunori Kami-ike 《The Journal of membrane biology》1985,86(1):27-36
Summary The current-voltage curve (I–V curve) of theChara membrane was obtained by applying a slow ramp hyper- and depolarization by use of voltage clamp. By inhibiting the electrogenic pump with 50m DCCD (dicyclohexylcarbodiimide), theI–V curve approached a steadyI–V curve within two hours, which gave thei
d
-V curve of the passive diffusion channel. Thei
p
-V curve of the electrogenic pump channel was obtained by subtracting the latter from the former. The sigmoidali
p
-V curve could be simulated satisfactorily with a simple reaction kinetic model which assumes a stoichiometric ratio of 2. The emf of the pump (E
p
) is given as the voltage at which the pump current changes its sign. The conductance of the pump (g
p
) can be calculated as the chord conductance from thei
p
-V curve, which is highly voltage dependent having a peak at a definite voltage. The changes of emf and conductance during excitation were determined by use of the current clamp (I=0). Since theE
p
andg
p
(V) are known, the changes, during excitation, of emf (E
d
) and conductance (g
d
) of the passive diffusion channel can be calculated. The marked increase of the membrane conductance and the large depolarization during the action potential are caused by the marked increase of the conductance of the passive diffusion channel and the large depolarization of its emf. The conductance of the electrogenic pump decreases to about half at the peak of action potential, while the pump current increases almost to a saturated level. 相似文献
42.
Phylogenetic relationships among eukaryotic kingdoms inferred from ribosomal RNA sequences 总被引:9,自引:0,他引:9
Masami Hasegawa Yoichi Iida Taka-aki Yano Fumio Takaiwa Masaki Iwabuchi 《Journal of molecular evolution》1985,22(1):32-38
Summary Phylogenetic trees among eukaryotic kingdoms were inferred for large- and small-subunit rRNAs by using a maximum-likelihood method developed by Felsenstein. Although Felsenstein's method assumes equal evolutionary rates for transitions and transversions, this is apparently not the case for these data. Therefore, only transversiontype substitutions were taken into account. The molecules used were large-subunit rRNAs fromXenopus laevis (Animalia), rice (Plantae),Saccharomyces cerevisiae (Fungi),Dictyostelium discoideum (Protista), andPhysarum polycephalum (Protista); and small-subunit rRNAs from maize (Plantae),S. cerevisiae, X. laevis, rat (Animalia), andD. discoideum. Only conservative regions of the nucleotide sequences were considered for this study. In the maximum-likelihood trees for both large- and small-subunit rRNAs, Animalia and Fungi were the most closely related eukaryotic kingdoms, and Plantae is the next most closely related kingdom, although other branching orders among Plantae, Animalia, and Fungi were not excluded by this work. These three eukaryotic kingdoms apparently shared a common ancestor after the divergence of the two species of Protista,D. discoideum andP. polycephalum. These two species of Protista do not form a clade, andP. polycephalum diverged first andD. discoideum second from the line leading to the common ancestor of Plantae, Animalia, and Fungi. The sequence data indicate that a drastic change occurred in the nucleotide sequences of rRNAs during the evolutionary separation between prokaryote and eukaryote. 相似文献
43.
Summary The relationship between the external Ca2+ concentrations [Ca2+]0 and the electrical tolerance (breakdown) in theChara plasmalemma was investigated. When the membrane potential was negative beyond –350–400 mV (breakdown potential, BP), a marked inward current was observed, which corresponds to the so-called punch-through (H.G.L. Coster,Biophys. J.
5:669–686, 1965). The electrical tolerance of theChara plasmalemma depended highly on [Ca2+]0. Increasing [Ca2+]0 caused a more negative and decreasing it caused a more positive shift of BP. BP was at about –700 mV in 200 M La3+ solution. [Mg2+]0 depressed the membrane electrical tolerance which was supposed to be due to competition with Ca2+ at the Ca2+ binding site of the membrane. Such a depressive effect of Mg2+ was almost masked when the [Ca2+]0/[Mg2+]0 ratio was roughly beyond 2. 相似文献
44.
The effect of chronic suppression of growth hormone (GH) secretion by SMS 201-995 on lactation was studied in primiparous C3H/He mice. Mammary gland DNA content on day 12 of lactation was significantly lower in SMS 201-995 treated mice than in the control. There were little differences between groups in mammary gland RNA content and litter growth on day 12 of lactation. That was associated with a slightly higher RNA/DNA ratio and a significant increase in food intake during lactation. These results indicate that inhibited mammary gland growth by GH suppression has little effect on lactation. The smaller mammary gland can compensate by increasing its secretory activity. 相似文献
45.
M Mizunuma K Dohmae Y Tajima U Koshimizu D Watanabe Y Nishimune 《Journal of cellular physiology》1992,150(1):188-193
C57BL/6(B6)-jsd/jsd mice are sterile due to the defective spermatogenesis in the testes. To know the cause of the deficient spermatogenesis in B6-jsd/jsd mice, we examined whether the problem is within or outside the seminiferous tubules by transplanting tubules from cryptorchid testes of B6- +/+ mice into B6-jsd/jsd testes or tubules from B6-jsd/jsd mice into testes of (WB x C57BL/6)F1-W/Wv (hereafter, WBB6F1-W/Wv) mice. Type A spermatogonia differentiated into spermatids in seminiferous tubules from cryptorchid testes transplanted into B6-jsd/jsd testes. In contrast, in B6-jsd/jsd tubules transplanted into WBB6F1-W/Wv testes, type A spermatogonia were stimulated to mitotic proliferation, but didn't proceed to any differentiated germ cells. The present results suggest that the cause of the deficient spermatogenesis in B6-jsd/jsd mice is a defect of intratubular environment to support germ cell differentiation. 相似文献
46.
47.
Atsushi Takata Noriko Miyake Yoshinori Tsurusaki Ryoko Fukai Satoko Miyatake Eriko Koshimizu Itaru Kushima Takashi Okada Mako Morikawa Yota Uno Kanako Ishizuka Kazuhiko Nakamura Masatsugu Tsujii Takeo Yoshikawa Tomoko Toyota Nobuhiko Okamoto Yoko Hiraki Ryota Hashimoto Naomichi Matsumoto 《Cell reports》2018,22(3):734-747
48.
The loss of PSII activity (water 相似文献
49.
Hirai Nobuhiro; Kojima Yasuhiro; Shinozaki Masateru; Koshimizu Koichi; Murofushi Noboru; Takimoto Atsushi 《Plant & cell physiology》1995,36(7):1265-1271
Seedlings of Pharbitis nil strain Violet werecultured at a low temperature, which induces their floweringeven in continuous light, with or without prior exposure tohigh-intensity light, which enhances the flower-inducing effectof the exposure to low temperature. Analysis by HPLC of extractsof cotyledons showed that the level of an unstable compoundincreased during these treatments, in addition to the increasein levels of phenylpropanoids reported previously. The compoundwas identified as ascorbic acid from the spectroscopic data.The change in the concentration of ascorbic acid at low temperaturewas correlated with the increase in the induction of floweringand the increase in levels of the phenylpropanoids. The rapidincrease in level of ascorbic acid after exposure to high-intensitylight reflected the promotive effect of high-intensity lighton the induction of flowering at low temperature. However, levelsof ascorbic acid also increased in seedlings of P. nil strainKidachi that were cultured in high-intensity light,a treatment that does not induce flowering in this strain. Thus,ascorbic acid cannot be associated with the induction of floweringby high-intensity light alone. Ascorbic acid increased the rateof formation of caffeic acid from p-coumaric acid in vitro,a result that suggests that ascorbic acid might be involvedin the increases in levels of phenylpropanoids in the seedlings. (Received April 17, 1995; Accepted August 1, 1995) 相似文献
50.
Tsutsui Izuo; Ohkawa Taka-aki; Nagai Reiko; Kishimoto Uichiro 《Plant & cell physiology》1986,27(6):1197-1200
We examined a role of Ca2+ in the activation of the two majorion channels, i.e., Cl and K+ channels at the excitationof the characean plasmalemma. The current-voltage relation (I-Vcurve) of the Chara membrane was compared under the ramp voltageclamp condition before and after external application of 20µMof La3+ (a Ca2+ channel blocker). The transient inward currentcomponent, which is carried mainly by the efflux of Cl,disappeared almost completely in about 30 min with La3+ treatment.On the other hand, no effect was observed on the late largeoutward current, which is mainly carried by the efflux of K+in a large depolarization region (less negative than 50mV). These results suggest that the Cl channel in theChara plasmalemma is activated by Ca2+ influx, while the K+channel is simply activated by depolarization. (Received April 7, 1986; Accepted June 6, 1986) 相似文献