酸敏感离子通道与脑梗死

急性脑梗死约占全部脑卒中的70%,病死率和致残率高,且极易复发。但目前针对急性脑梗死在时间窗内溶栓、抗凝等治疗手段不能从根本上切实有效地修复受损脑组织,且伴有出血等风险。寻找脑梗死形成发展的原因并予以治疗迫在眉睫。酸中毒是引起缺血性脑损伤的重要机制。大量实验研究表明,酸中毒能加重神经元的缺血性损伤,且其梗死面积与酸中毒的程度直接相关。但缺血产生的酸中毒如何引起神经元损伤的确切机制尚不明确。最近研究发现酸中毒能激活一种在中枢及周围神经中广泛存在的膜通道,即酸敏感离子通道,它对Ca2+通透,能引起细胞内Ca2+超载,同时能激活胞内酶引起细胞内蛋白质、脂类及核酸的降解,加重缺血后脑损伤。本文就酸敏感离子通道1a与脑梗死做一综述。     

Productivity-diversity relationships for plants, bryophytes, lichens, and polypore fungi in six northern forest landscapes

We investigated the relationship between site productivity and diversity of vascular plants, bryophytes, lichens, and polypore fungi in forests based on species richness data in 0.25 ha forest plots (grain size), selected from six 150–200 ha study areas (focus), and spanning over a latitudinal distance of 1350 km (extent) in Norway. We 1) searched for prevailing productivity-diversity relationships (PDRs), 2) compared PDRs among taxonomic groups and species found in different micro-habitats, and 3) investigated the effect of increasing plot (grain) size on PDRs. Using vegetation types as a surrogate for site productivity, we found a general pattern of increasing species richness with site productivity. On average total species richness doubled with a ten-fold increase in productivity. Lichens PDRs stood out as less pronounced and more variable than for other species groups investigated. PDRs of species associated with downed logs tended to level off at high-productive sites, a pattern interpreted as an effect of disturbance. Increasing the grain size >10-fold did not change the proportional difference in species richness between sites with high and low productivity.     

Formation of the apical pole of epithelial (Madin-Darby canine kidney) cells: polarity of an apical protein is independent of tight junctions while segregation of a basolateral marker requires cell-cell interactions

The time course of development of polarity of an apical (184-kD) and a basolateral (63-kD) plasma membrane protein of Madin-Darby canine kidney cells was followed using semiquantitative immunofluorescence on semithin (approximately 0.5-micron) frozen sections and monoclonal antibody probes. The 184-kD protein became highly polarized to the apical pole within the initial 24 h both in normal medium and in 1-5 microM Ca2+, which results in well-spread, dome-shaped cells, lacking tight junctions and other lateral membrane interactions. In contrast, the basolateral 63-kD membrane protein developed full polarity only after incubation in normal Ca2+ concentrations for greater than 72 h, a time much longer than that required for the formation of tight junctions (approximately 18 h) and failed to polarize in 1-5 microM Ca2+. These results demonstrate that intradomain restriction mechanisms independent of tight junctions, such as self-aggregation or specific interactions with the submembrane cytoskeleton, participate in the regionalization of at least some epithelial plasma membrane proteins. The full operation of these mechanisms depends on the presence of normal cell-cell interactions in the case of the basolateral 63-kD antigen but not in the case of the apical 184-kD protein.     

黑龙江省三江平原丹顶鹤的数量分布

在地面调查的基础上,我们使用Y-11轻型飞机对黑龙江省三江平原地区的丹顶鹤的数量分布近行了调查,调查时飞行高度80米,航速140公里/小时,续航里程共3748公里。调查结果表明,丹顶鹤在三江平原主要分布在8个地区,其中嘟噜河下游、洪河自然保护区、七星河流域和兴凯湖低地是主要繁殖地,总数量共309只。     

Substrate interactions during aerobic biodegradation of benzene.

This study dealt with the interactions with benzene degradation of the following aromatic compounds in a mixed substrate: toluene, o-xylene, naphthalene, 1,4-dimethylnaphthalene, phenanthrene, and pyrrole. The experiment was performed as a factorial experiment with simple batch cultures. The effect of two different types of inocula was tested. One type of inoculum was grown on a mixture of aromatic hydrocarbons; the other was grown on a mixture of aromatic hydrocarbons and nitrogen-, sulfur-, and oxygen-containing aromatic compounds (NSO compounds), similar to some of the compounds identified in creosote waste. The culture grown on the aromatic hydrocarbons and NSO compounds was much less efficient in degrading benzene than the culture grown on only aromatic hydrocarbons. The experiments indicated that toluene- and o-xylene-degrading bacteria are also able to degrade benzene, whereas naphthalene-, 1,,4-dimethylnaphthalene-, and phenanthrene-degrading bacteria have no or very little benzene-degrading ability. Surprisingly, the stimulating effect of toluene and o-xylene was true only if the two compounds were present alone. In combination an antagonistic effect was observed, i.e., the combined effect was smaller than the sum from each of the compounds. The reason for this behavior has not been identified. Pyrrole strongly inhibited benzene degradation even at concentrations of about 100 to 200 micrograms/liter. Future studies will investigate the generality of these findings.     

Expression of ACh-activated channels and sodium channels by messenger RNAs from innervated and denervated muscle

Xenopus oocytes were used to express polyadenylated messenger RNAs (mRNAs) encoding acetylcholine receptors and voltage-activated sodium channels from innervated and denervated skeletal muscles of cat and rat. Oocytes injected with mRNA from denervated muscle acquired high sensitivity to acetylcholine, whereas those injected with mRNA from innervated muscle showed virtually no response. Hence the amount of translationally active mRNA encoding acetylcholine receptors appears to be very low in normally innervated muscle, but increases greatly after denervation. Conversely, voltage-activated sodium currents induced by mRNA from innervated muscle were about three times larger than those from denervated muscle; this result suggests that innervated muscle contains more mRNA coding for sodium channels. The sodium current induced by mRNA from denervated muscle was relatively more resistant to block by tetrodotoxin. Thus a proportion of the sodium channels in denervated muscle may be encoded by mRNAs different from those encoding the normal channels.     

四川省西部鱼类寄生粘孢子虫——1.粘体虫属六新种(粘孢子纲:双壳目)

本文报导四川省西部鱼类寄生粘孢子虫粘体虫属六新种,即异型粘体虫,新种Myxosoma disparis sp.nov.,四川粘体虫,新种Myxosoma sichuanensis sp.nov.,光唇粘体虫,新种Myxosoma acrossochilusi sp.nov.鳅粘体虫,新种Myxosoma nemachilusi sp.nov.斜囊粘体虫,新种Myxosoma obliqua sp.nov.,雅安粘体虫,新种Myxosoma yaanensis sp.nov.。     

Distribution of tyrosinated and nontyrosinated alpha-tubulin during mitosis

The C-terminus of alpha-tubulin undergoes a reversible posttranslational tyrosination/detyrosination. The distributions of the tyrosinated (Tyr) and nontyrosinated (Glu) species during mitosis of cultured cells have been investigated by immunofluorescence using antibodies directed against the C-terminus of either Tyr or Glu tubulin. The distribution of Tyr tubulin differed from that of Glu tubulin at each stage of mitosis; in general, the distribution of Tyr tubulin was similar to that of total tubulin, whereas Glu tubulin had a more restricted distribution. The Glu species was found in half-spindle fibers but was not detected in astral fibers at any stage and was seen in the interzone only during telophase. These results were confirmed by a direct comparison of the distributions of Tyr and Glu tubulin in cells double-labeled with the two antibodies. Evidence for the occurrence of Tyr and Glu tubulin in each class of half-spindle fibers (kinetochore and polar) was obtained from the staining patterns of the two antibodies in cold-treated cells. Immunoblots of extracts prepared from synchronous mitotic cells showed that Glu tubulin was a minor species of the total tubulin in the spindle; no changes in the amount of either Tyr or Glu tubulin were detected at any stage of mitosis. These results show that Tyr tubulin is the major species in the mitotic spindle and is found in all classes of spindle fibers, whereas Glu tubulin is present in small amounts and shows a more restricted distribution. The presence of two biochemically distinct forms of alpha-tubulin in the spindle may be important for spindle function.     

A transient inward current elicited by hyperpolarization during serotonin activation in Xenopus oocytes

Activation of serotonin, glutamate or muscarinic receptors, incorporated into the membrane of Xenopus oocytes following injection of messenger RNA from rat brain, caused the development of a transient inward (Tin) current when the membrane was hyperpolarized. A detailed study was made of the Tin current induced during serotonin activation. The current is due principally to efflux of chloride ions, and is presumably activated by an influx of calcium ions, because it was blocked by removal of calcium from the bathing medium, by addition of manganese, cobalt or lanthanum, or by intracellular injection of EGTA. During application of serotonin, the amplitude of the Tin current increased slowly, and after washing it persisted for longer than the direct serotonin-induced current. The amplitude of the Tin current was sensitive to temperature and pH, and was abolished at pH 6.5 or by cooling to 12 degrees C. The Tin current may be of importance in regulating the excitability of neurons in the central nervous system.