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961.
Potassium conductances in hippocampal neurons blocked by excitatory amino-acid transmitters 总被引:23,自引:0,他引:23
Excitatory amino acids mediate fast synaptic transmission in the central nervous system through the activation of at least three distinct ionotropic receptors: N-methyl-D-aspartate (NMDA), the alpha-amino-3-hydroxy-5-methyl-isoxasole-4-propionate (AMPA)/quisqualate (QUIS) and the kainate subtypes (for reviews, see refs 1, 2). They also activate the additional QUIS 'metabotropic' receptor (sensitive to trans-1-amino-cyclopentyl-1,3-dicarboxylate, ACPD) linked to inositol phospholipid metabolism. We have used hippocampal slice cultures to study the electrophysiological consequences of the metabotropic response. We find that activation of an ACPD-sensitive QUIS receptor produces a 'slow' excitation of CA3 pyramidal cells, resulting from depression of a Ca2(+)-dependent K+ current and a voltage-gated K+ current. Combined voltage-clamp and microfluorometric recordings show that, although these receptors can trigger an increase in intracellular Ca2+ concentration, suppression of K+ currents is independent of changes in intracellular Ca2+. These effects closely resemble those induced by activating muscarinic acetylcholine receptors in the same neurons and suggest that excitatory amino acids not only act as fast ionotropic transmitters but also as slow neuromodulatory transmitters. 相似文献
962.
Antibodies reacting with 3,5,3',5' tetraiodo-l-tyrosyl-l-tyrosine (I2Tyr-I2Tyr) were elicited in rabbits by immunization with an oxidized yeast conjugate coupled with I2Tyr-I2Tyr. Ion-exchange chromatography was used to purify immunoglobulins, in order to improve the specificity in measurement of I2Tyr-I2Tyr level in patient serum. IgG binding capacity versus I2Tyr-I2Tyr was considerably increased after immunoglobulin purification. 相似文献
963.
Injection of a soluble sperm fraction into sea-urchin eggs triggers the cortical reaction 总被引:8,自引:0,他引:8
Fertilization membranes form around unfertilized sea-urchin eggs after microinjection of a soluble spermatozoa fraction isosmotic with seawater. This demonstrates that the spermatozoon contains a chemical that triggers an increase in cytosolic calcium, leading to exocytosis of cortical granules. It also demonstrates that the triggering mechanism does not require an externally-activated egg-membrane process. Further experiments show that the chemical trigger is not calcium. 相似文献
964.
Summary In the respiratory lamellae of the gills of the atlantic hagfish,Myxine glutinosa, pillar cells are coupled by communicating junctions. It is suggested that these cells behave like a functional syncytium.Supported by the DFG, SFB 146. The authors are indebted to Drs F. Walvig and H. Stolte for kindly providing the hagfish. The expert technical assistance of G. Voss-Wermbter, Dipl.-Ing., and H. Heidrich is gratefully acknowledged. 相似文献
965.
Alloxan diabetes caused a decrease in cyclic AMP phosphodiesterase in all affected rat tissues. Cyclic GMP phosphodiesterase activity was, however, decreased in adipose and liver, but increased increased in heart and uterus. 相似文献
966.
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970.
A manifest presence of adenylate kinase activity in cerebrospinal fluid was found in patients with cerebral arteriosclerosis. This activity was significantly higher during treatment with co-dergocrine (Hydergin) compared with the two periods before and after treatment. 相似文献