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1.
The effects of lithium (Li+) on the adenylyl cyclase and inositol phospholipid receptor signalling pathways were compared directly in noradrenergic and carbachol stimulated rat brain cortical tissue slices. Li+ was a comparatively weak inhibitor of noradrenaline-stimulated cyclic AMP accumulation with an IC50 of approx. 20 mM. By contrast, half-maximal effects of Li+ on inositol monophosphate (InsP) accumulation in [3H]inositol labelled tissue slices occurred at about 1 mM. A similar IC50 for Li+ of about 1 mM was also obtained for noradrenaline-stimulated accumulation of CMP-phosphatidate (CMPPA), a sensitive indicator of intracellular inositol depletion, in tissue slices that had been prelabelled with [3H]cytidine. The effect of myo-inositol (inositol) depletion on the prolonged activity of phosphoinositidase C (PIC) was examined in carbachol-stimulated corticol slices using a novel mass assay fro InsP. Exposure to a maximal dose of carbachol for 30 min in the presence of 5 mM Li+ caused a 10-fold increase in the level of radioactivity associated with the InsP fraction, but only a 2-fold increase in InsP mass. During prolonged incubations in the presence of both carbachol and Li+ the accumulation of InsP mass was enhanced if 30 mM inositol was included in the medium. The results are comptable with the inositol depletion hypothesis of Li+ action but do not support the concept that adenylyl cyclase or guanine nucleotide dependent proteins represent therapeutically relevant targets of this drug. 相似文献
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长白山劲松林场植物群落的分类和排序 总被引:7,自引:2,他引:5
将长白山白河林业局劲松林场的54块样地用聚类分析法划分成6个植被类群,再用PC-VTAB程序中经过改进的Braun-Blanquet学派的植被排表分析法进行综合,产生了鉴别概要表,为各个等级的植被类群筛选出诊断种。此外,还用鉴别种地样地记录进行主成分分析,以验证诊断种的有效性,结果表明,PC-VTAB中的植被排表分析法是筛选鉴别种的有效方法,而鉴别种以显著地提高植被分析和排序的质量。 相似文献
4.
Shin-Ichi Yamamoto 《Ecological Research》1994,9(3):295-302
Gap regeneration was studied in a typical primary evergreen broad-leaved forest withoutDistylium racemosum, at the Kasugayama Forest Reserve, southwestern Japan and the results were compared with those from other primary evergreen
broad-leaved forests in southwestern Japan, whereD. racemosum was the dominant species. Several common types of gap regeneration behavior were recognized among the major tree species
and forests with or withoutD. racemosum consisted of three typical regeneration guilds which could be detected in the principal component analysis.Castanopsis cuspidata frequently regenerated in gaps from saplings recruited before gap formation in the forest withoutD. racemosum, although elsewhere, in forests withD. racemosum, it lacked advanced regeneration and regenerated in gaps from saplings recruited after gap formation. Some evergreenQuercus had their regenerations in gaps of the forest withoutD. racemosum, although elsewhere, in forests withD. racemosum, evergreenQuercus might not regenerate. The results indicate that tree species may change their regeneration behavior depending on the presence
or absence of another key dominant species. This suggests that the presence and the dominance of a potential competitor induces
shifts in the regeneration niche of other coexisting tree species. 相似文献
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We have used [2-13C]d-glucose and carbon-13 nuclear magnetic resonance (NMR) spectroscopy to investigate metabolic fluxes through the major pathways of glucose metabolism in intact human erythrocytes and to determine the interactions among these pathways under conditions that perturb metabolism. Using the method described, we have been able to measure fluxes through the pentose phosphate pathway, phosphofructokinase, the 2,3-diphosphoglycerate bypass, and phosphoglycerate kinase, as well as glucose uptake, concurrently and in a single experiment. We have measured these fluxes in normal human erythrocytes under the following conditions: (1) fully oxygenated; (2) treated with methylene blue; and (3) deoxygenated. This method makes it possible to monitor various metabolic effects of stresses in normal and pathological states. Not only has 13C-NMR spectroscopy proved to be a useful method for measuring in vivo flux through the pentose phosphate pathway, but it has also provided additional information about the cycling of metabolites through the non-oxidative portion of the pentose phosphate pathway. Our evidence from experiments with [1-13C]-, [2-13C]-, and [3-13C]d-glucoses indicates that there is an observable reverse flux of fructose 6-phosphate through the reactions catalyzed by transketolase and transaldolase, even in the presence of a net flux through the pentose phosphate pathway. 相似文献
7.
JULIE M. BRENNAN DAPHNE J. FAIRBAIRN 《Biological journal of the Linnean Society. Linnean Society of London》1995,54(2):151-171
We examined morphological variation among populations of the stream-dwelling waterstrider, Aquarius remigis. A previous analysis of allozyme variation along a transect from southern Quebec to southern North Carolina revealed two distinct 'types' of A. remigis, north and south of a transition zone in southern New York and northern Pennsylvania. To assess the concordance of morphological and allozyme differentiation, adults were sampled from 15 populations along the original transect, as well as 11 additional populations in New York, Connecticut and New Jersey. Eight measurements of leg and body size were taken of preserved individuals. Univariate and multivariate analyses (multiple regression, PCA, discriminant analysis) reveal significant differentiation between northern and southern populations with a transition zone between latitudes 39o and 42o north. Strong clines within each region and a clear transition between regions support previous suggestions that there are two distinct 'types' of this species in eastern North America. The transition zone, in morphology coincides with that revealed by the allozyme variation, but extends further south. The covariance of allozyme frequency and morphometric traits suggests that differentiation has occurred through vicariance and secondary contact, and that in this system, cladistic and adaptive differentiation are coupled. 相似文献
8.
A method is described for the preparation of concentrated tissue extracts for nucleotideanalysis by high-performance liquid chromatography (hplc). Ten to one hundred milligrams of tissue was extracted in a combined weighing-homogenizing-centrifuge tube using a trichloracetic acid (TCA)-methanol extractant containing a radioactive internal standard. This extractant eliminated nucleotide interconversion which was found to occur when TCA alone was employed. High ATP/ADP and ATP/AMP ratios were observed and recoveries of greater than 97% were obtained with exogenous radioactive nucleotides. The method has been applied successfully in studies on muscle, heart, liver, kidney, lung, brain, and subcellular fractions. 相似文献
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10.
Immediate hypersensitivity reactions in schistosoma japonicum infections were examined in both man and experimental animals. In man higher reaction to soluble egg antigen than to adult worm antigen was detected by the use of the radioallergosorbent test (RAST). Blood-collecting filter paper can be used in RAST for seroepidemiological study in place of a skin test. Reaginic antibody formation against egg antigen was detected at the approximate time of egg deposition in strains of mice, Mongolian gerbils, cotton rats, and laboratory rats by the use of passive cutaneous anaphylaxis or Prausnitz-Küstner-type skin tests. At the same time circumoval precipitin tests were positive. Results with athymic nude mice suggest that these reactions are T-cell dependent. No detectable reagin synthesis against adult worm antigen was found in the animals so far examined, confirming stronger allergenic reaction to egg antigen than to that of adult worms in S. japonicum infections in man and animals. 相似文献