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21.
Summary Effects of divalent cations on oscillations of membrane potentials (i.e., spontaneous repetitive hyperpolarizing responses) and on hyperpolarizing responses induced by electrical stimuli as well as on resting potentials were studied in large nondividing L cells. Deprivation of Ca2+ from the external medium inhibited these hyperpolarizing responses accompanying slight depolarization of the resting potential. Sr2+ or Mn2+ applied to the external medium in place of Ca2+ was able to substitute for Ca2+ in the generation of hyperpolarizing responses, while Mg2+, Ba2+ or La3+ suppressed hyperpolarizing responses. The addition of A23187 to the bathing medium or intracellular injection of Ca2+, Sr2+, Mn2+ or La3+ induced membrane hyperpolarization. When the external Ca2+, Sr2+ or Mn2+ concentration was increased, the resting potential also hyperpolarized, in a saturating manner. The amplitude of maximum hyperpolarization produced by high external Ca2+ was of the same order of magnitude as those of hyperpolarizing responses and was dependent on the external K+ concentration. In the light of these experimental observations, it was deduced that the K+ conductance increase associated with the hyperpolarizing excitation is the result of an increase in the intracellular concentration of free Ca2+ mainly derived from the external solution. 相似文献
22.
M Eto H Mayumi Y Nishimura T Maeda Y Yoshikai K Nomoto 《Journal of immunology (Baltimore, Md. : 1950)》1991,147(8):2439-2446
The mechanisms of cyclophosphamide (CP)-induced tolerance were investigated by comparing with those of neonatally induced tolerance. When C3H/He Slc (C3H; H-2k, Mls-1b) mice were given i.v. either AKR/J Sea (AKR; H-2k, Mls-1a) or (AKR x C3H)F1 (AKC3F1; H-2k, Mls-1a/b) spleen cells and treated i.p. with CP 2 days later, a long-lasting skin allograft tolerance to AKR was induced in each case without any signs of graft-vs-host disease (GVHD). However, typical signs of GVHD were observed in the C3H mice neonatally tolerized with AKR spleen cells, but not in those tolerized with AKC3F1 spleen cells. The expression of TCR V beta 6, which is strongly correlated with the reactivity to Mls-1a Ag (of donor AKR origin), in the periphery was quite different between the two types of tolerant C3H mice. Namely, in the lymph nodes of the C3H mice tolerized with AKR spleen cells and CP, only CD4(+)-V beta 6+, but not CD8(+)-V beta 6+, T cells selectively disappeared, whereas both of them were abrogated in the lymph nodes of the C3H mice neonatally tolerized of AKR. By contrast, in the thymus of the two types of tolerant C3H mice, both CD4+CD8- and CD4-CD8+ single-positive thymocytes expressing TCR V beta 6 were clonally deleted, suggesting that the thymic involvement was the same in each type of tolerance. These results suggest that the preferential disappearance of the CD4(+)-V beta 6+ T cells (of host origin) and the effector T cells of GVHD (of donor origin) occurred only in the periphery of the C3H mice tolerized with AKR spleen cells plus CP and was attributable to the destruction of Ag-stimulated T cells by the CP treatment. In contrast, the intrathymic clonal deletion of immature V beta 6+ T cells was a common mechanism for both of the tolerance induction systems. 相似文献
23.
Tohru Kotera Akira Hashimoto Shunji Ueda Yasunobu Okada 《The Journal of membrane biology》1991,124(1):43-52
Summary Patch-clamp studies of whole-cell ionic currents were carried out in parietal cells obtained by collagenase digestion of the gastric fundus of the guinea pig stomach. Applications of positive command pulses induced outward currents. The conductance became progressively augmented with increasing command voltages, exhibiting an outwardly rectifying current-voltage relation. The current displayed a slow time course for activation. In contrast, inward currents were activated upon hyperpolarizing voltage applications at more negative potentials than the equilibrium potential to K+ (E
K). The inward currents showed time-dependent inactivation and an inwardly rectifying current-voltage relation. Tail currents elicited by voltage steps which had activated either outward or inward currents reversed at nearE
K, indicating that both time-dependent and voltagegated currents were due to K+ conductances. Both outward and inward K+ currents were suppressed by extracellular application of Ba2+, but little affected by quinine. Tetraethylammonium inhibited the outward current without impairing the inward current, whereas Cs+ blocked the inward current but not the outward current. The conductance of inward K+ currents, but not outward K+ currents, became larger with increasing extracellular K+ concentration. A Ca2+-mobilizing acid secretagogue, carbachol, and a Ca2+ ionophore, ionomycin, brought about activation of another type of outward K+ currents and voltage-independent cation currents. Both currents were abolished by cytosolic Ca2+ chelation. Quinine preferentially inhibited this K+ current. It is concluded that resting parietal cells of the guinea pig have two distinct types of voltage-dependent K+ channels, inward rectifier and outward rectifier, and that the cells have Ca2+-activated K+ channels which might be involved in acid secretion under stimulation by Ca2+-mobilizing secretagogues. 相似文献
24.
ATP-dependent Sr2+ transport was examined in vitro using basolateral membrane (BLM) vesicles isolated from rat renal cortex to clarify the discrimination
mechanisms between strontium (Sr) and calcium (Ca) in renal tubules during reabsorption. ATP-dependent Sr2+ uptake and Ca2+ uptake were observed in renal BLM vesicles and were inhibited by vanadate. Hill plots indicate similar kinetic behavior for
Ca2+ and Sr2+ uptake. The apparentK
m andV
max of ATP-dependent Sr2+ uptake were both higher than those for Ca2+ uptake. ATP-dependent Sr2+ uptake by BLM vesicles diminished in the presence of 0.1 μM Ca2+ and was more markedly inhibited by 1 μM Ca2+. Hill plots of Sr2+ uptake data with and without 0.1 μM Ca2+ showed that the cooperative behavior of Sr2+ uptake was not changed by Ca2+. In the presence of 0.1 μM Ca2+, the affinity of the transport system for Sr2+ and the velocity of Sr2+ uptake in the BLM were both decreased. However, the rate of Ca2+ uptake was not diminished by Sr2+ concentrations of <1.6 μM. These results suggest that Ca2+ is preferentially transported in the renal cortex BLM when Ca2+ and Sr2+ are present at the same time. 相似文献
25.
Tadao Ohno Kaoru Saijo-Kurita Naoko Miyamoto-Eimori Tomoko Kurose Yasunobu Aoki Sigehiro Yosimura 《Cytotechnology》1991,5(3):273-277
We developed a simple method for freezing anchorage-dependent cells, including primary cultured rat liver parenchymal cells, without detaching the cells from the culture dish. The method consists of preculture of the cells to confluence, changing the growth medium to a conventional freezing medium, packaging in a container, and storage at –80°C. After thawing and changing the freezing medium to regular growth medium, cell growth was nearly identical to that of cells freshly seeded into a new dish. 相似文献
26.
Clinical studies with TNF 总被引:4,自引:0,他引:4
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29.
- Tip potential (TP) of glass microelectrodes filled with 3 M KCl increased remarkably with the increase in the storage period in 3 M KCl solution at 37? C, while the electrode resistances decreased gradually.
- The electrical conductivity through the thin glass wall near the tip was found to increase in parallel with the TP increase.
- The e.m.f. across the thin glass wall in the tip region was directly measured. This seems to contribute to the TP generation of the microelectrode when the conductivity of the glass wall is significantly high in the tip region.
- Effects of the acid treatment of glass employed and the acidification of fillant electrolyte solution suggested that fixed negative charges on the glass wall play a fundamental role in the TP formation.
- Based on these experimental results, it was concluded that not only the diffusion potential through the tip pore but also the interfacial potential through the thin glass wall near the tip contributes to the TP generation, and the contribution of the latter increases with a long exposure period of the electrodes to electrolyte solution.
- In this connection, technical problems related to reduction of the tip potential were also discussed.
30.
Yoshio Osada Sohsuke Yamada Atsunori Nabeshima Yasunobu Yamagishi Kenji Ishiwata Susumu Nakae Katsuko Sudo Tamotsu Kanazawa 《Experimental parasitology》2013
Some parasitic helminths are known to protect their hosts from allergic and autoimmune disorders. Here, we tested the effects of a gastrointestinal nematode, Heligmosomoides polygyrus (Hp), on streptozotocin (STZ)-induced type 1 diabetes (T1D) in mice. Hp infection significantly suppressed hyperglycemia induced by multiple low-dose administration of STZ, but did not affect hyperglycemia induced by single high-dose administration of STZ. In the multiple low dose model, Hp infection prevented a decrease in pancreatic islet size. The augmentation of TNF-α and IL-1β expression in the pancreas was abrogated by Hp infection. The genetic absence of IL-10 or STAT6 did not abrogate the anti-hyperglycemic effect of Hp. Hp has a suppressive effect on immune mechanism-mediated experimental T1D via Th2 polarization-independent mechanisms. 相似文献