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41.
Ole G. Mouritsen 《生物化学与生物物理学报:生物膜》1983,731(2):217-221
The gel-to-fluid first-order melting transition of lipid bilayers is simulated by the use of a microscopic interaction model which includes a variable number of lipid-chain conformational states. The results suggest that the experimental observation of ‘continuous melting’ in pure wet lipid bilayers, rather than being ascribed to the presence of impurities, may be explained as a result of kinetically caused metastability of intermediate lipid-chain conformations. 相似文献
42.
Effects on the aquatic biota of lime (CaCO3) application in acidified lakes and streams were studied in a number of waters. After treatment, lime-sensitive species of mosses (Sphagnum spp.) decreased, but species such as Potamogeton natans and Myriophyllum alterniflorum seemed to be favoured. A few years after liming species composition and diversity of phytoplankton, zooplankton and benthic insect larvae were almost identical to that found in oligotrophic and non-acid lakes. Molluscs and benthic crustaceans may have difficulties recolonizing. Reproduction of remaining species of fish was successful as soon as pH increased. High survival of larvae and fry can result in some extremely rich year classes with slow individual growth. In most cases restocking of depleted fish stocks was successful. 相似文献
43.
Na+, Cl− cotransport in Ehrlich ascites tumor cells activated during volume regulation (regulatory volume increase) 总被引:2,自引:0,他引:2
Else K. Hoffmann Carsten Sjøholm Lars Ole Simonsen 《The Journal of membrane biology》1983,76(3):269-280
Ehrlich ascites cells were preincubated in hypotonic medium with subsequent restoration of tonicity. After the initial osmotic shrinkage the cells recovered their volume within 5 min with an associated KCl uptake. The volume recovery was inhibited when NO-3 was substituted for Cl-, and when Na+ was replaced by K+, or by choline (at 5 mM external K+). The volume recovery was strongly inhibited by furosemide and bumetanide, but essentially unaffected by DIDS. The net uptake of Cl- was much larger than the value predicted from the conductive Cl- permeability. The undirectional 36Cl flux, which was insensitive to bumetanide under steady-state conditions, was substantially increased during regulatory volume increase, and showed a large bumetanide-sensitive component. During volume recovery the Cl- flux ratio (influx/efflux) for the bumetanide-sensitive component was estimated at 1.85, compatible with a coupled uptake of Na+ and Cl-, or with an uptake via a K+,Na+,2Cl- cotransport system. The latter possibility is unlikely, however, because a net uptake of KCl was found even at low external K+, and because no K+ uptake was found in ouabain-poisoned cells. In the presence of ouabain a bumetanide-sensitive uptake during volume recovery of Na+ and Cl- in nearly equimolar amounts was demonstrated. It is proposed that the primary process during the regulatory volume increase is an activation of an otherwise quiescent, bumetanide-sensitive Na+,Cl- cotransport system with subsequent replacement of Na+ by K+ via the Na+/K+ pump, stimulated by the Na+ influx through the Na+,Cl- cotransport system. 相似文献
44.
Delayed type hypersensitivity against antigens of Fasciola hepatica has been repeatedly documented in infected hosts. Evidence has been presented to suggest that the delayed reactivity may develop earlier in the regional lymph nodes of the parasitized organ than in other lymph nodes of the body (Soulsby 1971). 相似文献
45.
Cysteamine (2-aminoethanethiol) inhibited cell division in synchronously dividing cultures of Euglena gracilis at relatively low concentrations (0.005 M), Cystamine (2,2′-dithiobis(ethylamine). however, was only partially inhibitory at high concentrations (0.1 M). This differential inhibition may reflect certain unique features of nuclear division in euglenoid flagellates. 相似文献
46.
Effects of Red and Far-Red Light on the Hypocotyl of Picea Abies 总被引:1,自引:0,他引:1
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Lu Changya David V. Gallacher Robin F. Irvine Barry V. L. Potter Ole H. Petersen 《The Journal of membrane biology》1989,109(1):85-93
Summary We have examined the effects of various inositol polyphosphates, alone and in combination, on the Ca2+-activated K+ current in internally perfused, single mouse lacrimal acinar cells. We used the patch-clamp technique for whole-cell current recording with a set-up allowing exchange of the pipette solution during individual experiments so that control and test periods could be directly compared in individual cells. Inositol 1,4,5-trisphosphate (Ins 1,4,5 P3) (10–100 m) evoked a transient increase in the Ca2+-sensitive K+ current that was independent of the presence of Ca2+ in the external solution. The transient nature of the Ins 1,4,5 P3 effect was not due to rapid metabolic breakdown, as similar responses were obtained in the presence of 5mm 2,3-diphosphoglyceric acid, that blocks the hydrolysis of Ins 1,4,5 P3, as well as with the stable analoguedl-inositol 1,4,5-trisphosphorothioate (Ins 1,4,5 P(S)3) (100 m). Ins 1,3,4 P3 (50 m) had no effect, whereas 50 m Ins 2,4,5 P3 evoked responses similar to those obtained by 10 m Ins 1,4,5 P3. A sustained increase in Ca2+-dependent K+ current was only observed when inositol 1,3,4,5-tetrakisphosphate (Ins 1,3,4,5 P4) (10 m) was added to the Ins 1,4,5 P3 (10 m)-containing solution and this effect could be terminated by removal of external Ca2+. The effect of Ins 1,3,4,5 P4 was specifically dependent on the presence of Ins 1,4,5 P3 as it was not found when 10 m concentrations of Ins 1,3,4 P3 or Ins 2,4,5 P3 were used. Ins 2,4,5 P3 (but not Ins 1,3,4 P3) at the higher concentration of 50 m did, however, support the Ins 1,3,4,5 P4-evoked sustained current activation. Ins 1,3,4 P3 could not evoke sustained responses in combination with Ins 1,4,5 P3 excluding the possibility that the action of Ins 1,3,4,5 P4 could be mediated by its breakdown product Ins 1,3,4 P3. Ins 1,3,4,5 P4 also evoked a sustained response when added to an Ins 1,4,5 P(S)3-containing solution. Ins 1,3,4,5,6 P5 (50 m) did not evoke any effect when administered on top of Ins 1,4,5 P3. In the absence of external Ca2+, addition of Ins 1,3,4,5 P4 to an Ins 1,4,5 P3-containing internal solution evoked a second transient K+ current activation. Readmitting external Ca2+ in the continued presence internally of Ins 1,4,5 P3 and Ins 1,3,4,5 P4 made the response reappear. We conclude that both Ins 1,4,5 P3 and Ins 1,3,4,5 P4 play crucial and specific roles in controlling intracellular Ca2+ homeostasis. 相似文献