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141.
Homo- and heterosensory interaction were investigated in sensorimotor cortex neurons before and after picrotoxin application to anesthetized and immobilized kittens belonging to three age groups (12–30 days, 31–47 days, and 2–4 months old). Only slight inhibition of response to presentation of a second stimulus was observed in a small proportion of cells in the youngest age group at test intervals of 100, 200, and 300 msec. Picrotoxin application only produced the effect of raised background activity. Numbers of neurons with partially or fully inhibited response to test stimuli (especially spaced at 100 msec intervals) rose in the middle and older age groups. The dynamics of heterosensory interaction and how this is affected by picrotoxin application gradually approximated to that observed with adult animals. The subject of the development of inhibitory mechanisms and how they contribute to the organization of homo- and heterosensory interaction during early postnatal ontogenesis is considered in the light of the results obtained.A. A. Ukhtomsii Institute of Physiology, Leningrad. A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 20, No. 2, pp. 234–243, March–April, 1988. 相似文献
142.
143.
Subcellular Distribution of UDP-Galactose:Ceramide Galactosyltransferase in Rat Brain Oligodendroglia 总被引:4,自引:3,他引:1
Oligodendrocytes isolated from 18-19-day-old rat brain were homogenized in 0.32 M sucrose. The homogenate was centrifuged at 100,000 g for 50 min in a gradient containing 0.8, 1.05, and 1.3 M sucrose. Three discrete bands were obtained at the interfaces 0.32-0.8 (F1), 0.8-1.05 (F2), and 1.05-1.3 M (F3). The distribution of UDP-galactose:ceramide galactosyltransferase (CgalT) activity in each fraction was measured using liposomes containing normal fatty acid-containing ceramides (NFA-CgalT activity) or 2-hydroxy fatty acid-containing ceramides (HFA-CgalT activity). Although detection of both CgalT activities was possible in all fractions, HFA-CgalT activity was enriched in F1 and F2 fractions, which also showed an enrichment of Golgi and endoplasmic reticulum markers, respectively. It is interesting that NFA-CgalT activity was significantly enriched in the F2 fraction. These results suggest that hydroxylated and nonhydroxylated galactocerebrosides may be synthesized at different intracellular locations. 相似文献
144.
The effect of deoxyadenosine plus deoxycoformycin on replicative and repair synthesis of DNA in human lymphoblasts and isolated nuclei 总被引:2,自引:0,他引:2
Deoxyadenosine plus deoxycoformycin (dCf) causes increased DNA breaks in lymphoid cells. This study explored the possible inhibition of repair synthesis of DNA by dAdo plus dCf as a cause of DNA breakage. It was shown that DNA breaks accumulated in a human T-lymphoblast cell line, CCRF-CEM, following incubation with dAdo plus dCf and were not fully repaired 20 h after their removal. Analysis of the density distribution of radiolabeled DNA on alkaline CsCl gradient showed that incubation of CCRF-CEM cells with dAdo plus dCf caused inhibition of semiconservative, but not repair synthesis of DNA. Semiconservative synthesis of DNA was also inhibited in CCRF-CEM nuclei isolated from cells pretreated with dAdo and dCf, suggesting damage to DNA replicative machinery. However, no such inhibition was observed in the nuclei of a similarly treated CCRF-CEM mutant that was deficient in adenosine kinase and deoxycytidine kinase. This suggests that dAdo must be phosphorylated in intact cells to exert its effect. Using [3H]dTTP incorporation in isolated CCRF-CEM nuclei to measure DNA synthesis, it was found that a high concentration (greater than 100 microM) of dATP inhibits semiconservative but not repair synthesis of DNA. The present studies thus indicate that accumulation of DNA strand breaks induced by dAdo plus dCf is not the consequence of inhibition of repair DNA synthesis. This implies the mechanism may involve perturbation of DNA ligation or activation of a certain process which causes DNA strand breaks. In addition, dATP may interfere with some steps of semiconservative DNA synthesis, but not the repair synthesis of DNA. 相似文献
145.
The thermostable tailspike endorhamnosidase of bacteriophage P22 has been investigated by laser Raman spectroscopy to determine the protein's secondary structure and the basis of its thermostability. The conformation of the native tailspike, determined by Raman amide I and amide III band analyses, is 52 to 61% beta-sheet, 24 to 27% alpha-helix, 15 to 21% beta-turn and 0 to 10% other structure types. The secondary structure of the wild-type tailspike, as monitored by the conformation-sensitive Raman amide bands, was stable to 80 degrees C, denatured reversibly between 80 and 90 degrees C, and irreversibly above 90 degrees C. The purified native form of a temperature-sensitive folding mutant (tsU38) contains secondary structures virtually identical to those in the wild-type in aqueous solution at physiological conditions (0.05 M-Na+ (pH 7.5], at both permissive (20 degrees C) and restrictive (40 degrees C) temperatures. This supports previous results showing that the mutational defect at 40 degrees C affects intermediates in the folding pathway rather than the native structure. At temperatures above 60 degrees C the wild-type and mutant forms were distinguishable: the reversible and irreversible denaturation thresholds were approximately 15 to 20 degrees C lower in the mutant than in the wild-type protein. The irreversible denaturation of the mutant tailspikes led to different aggregation/polymerization products from the wild-type, indicating that the mutation altered the unfolding pathway. In both cases only a small percentage of the native secondary structure was altered by irreversible thermal denaturation, indicating that the aggregated states retain considerable native structure. 相似文献
146.
We have investigated the effects of clinically available calcium channel blockers (nifedipine, verapamil and diltiazem) on isoproterenol stimulated cyclic adenosine 3',5'-monophosphate (cyclic AMP) generation in intact human lymphocytes. After preincubation of various calcium antagonists with intact lymphocytes at 37 degrees C for 15 minutes, 10 microM nifedipine or verapamil partially inhibited isoproterenol induced cyclic AMP generation in the presence of cyclic AMP phosphodiesterase inhibitor (3-isobutyl-1-methylxanthine) while they alone had no effect on cyclic AMP level at a concentration of up to 100 microM. In contrast, 10 nM-1.0 microM nifedipine, verapamil or diltiazem potentiated cyclic AMP generation induced by isoproterenol in a dose dependent manner. Similar results were observed in the time course studies of cyclic AMP generation. These effects are somewhat similar to the effect of phenothiazine, a calmodulin inhibitor, which, at 10 microM (close to IC50), also potentiated the effects of isoproterenol. In contrast, lanthanum chloride (LaCl3), an extracellular inorganic calcium antagonist, at 1.0 mM, inhibited isoproterenol induced cyclic AMP generation. The biochemical mechanisms underlying these potentiating effects are unknown. It may be partly related to the effect of calcium channel blockers (at least for nifedipine) on preventing beta 2 adrenergic receptor desensitization. This may provide a potential mechanism for the synergistic effect between calcium channel blockers and beta 2 adrenoceptor agonists on bronchial dilatation. 相似文献
147.
从“湖北光敏感核不育水稻”的未受精子房和花药培养出单倍体植株 总被引:10,自引:0,他引:10
采用10种诱导培养基,培养湖北光敏感核不育水稻农垦58品种的未受精子房和花药。共培养未受精子房2790个,获得胚囊愈伤组织17块,最高诱导频率达3.33%,其中2块分化出绿苗。培养花药16740个,获得花药愈伤组织15块,最高诱导频率为0.92%,其中3块分化出苗,2丛白苗,1株绿苗。胚囊植株和花粉植株经根尖染色体检查为单倍体,2n=x=12。实验证明,液体培养、2,4-D0.2-0.5 mg/1、低温预处理对诱导胚囊愈伤组织及花粉愈伤组织的形成具良好效果。 相似文献
148.
149.
测定了3T3细胞、人和大鼠一些组织中DNA拓扑异构酶Ⅰ的活性;估计了核酸内切酶对拓扑酶Ⅰ松弛活性测定的干扰程度;发现增殖组织全细胞抽提液中酶比活高于正常分化组织,而且在异常增殖组织中酶比活的增高更为显著。 相似文献
150.
黑河林区驼鹿冬季食性研究 总被引:4,自引:0,他引:4
1987—1988年在黑龙江省黑河林区,应用粪便显微组织学分析技术,结合野外啃食调查,对驼鹿冬季食物组成、食物选择性和利用率进行了研究。结果表明,冬季驼鹿共采食31种(属)植物,其中柳、榛、桦、红松、杨和紫椴是主要的冬季食物(19.9%、18.0%、16.7%、14.9%、7.3%和6.7%)。驼鹿对杨、柳、红松和紫椴有正选择性,对榛、桦和毛赤杨有负选择性。选择性的强弱顺序为:杨>柳>红松>紫椴>榛>桦>毛赤杨。驼鹿对柳的选用率最高(32.1%),对桦的利用率最低(12.1%)。 相似文献