猫体感皮层神经元对同时刺激隐神经的A类和C类纤维的反应型式

记录了麻痹猫的体感皮层(SI)神经元的自发和隐神经的A类和C类纤维传入诱发放电(A-ED和C-ED)。用NCCVF分析神经元放电。结果表明,SI区神经元对同时刺激隐神经的A类和C类纤维的反应呈多种型式:(1)A-ED和C-ED共存,包括Ⅰ.A-ED和C-ED始终相互伴随出现;Ⅱ.在刺激之初,只出现A-ED,但是,当阻断A类纤维传入并由C类纤维传入诱发神经元放电后,再同时刺激A类和C类纤维时,A-ED和C-ED便同时出现。(2)A-ED制约C-ED,特点是,只要A-ED存在,C/ED就不出现。只有阻断A类纤维传入后,C-ED才产生。(3)单一A-ED,不管在什么刺激条件下,这类神经元都只有A-ED,而不产生C-ED 结论:根据反应型式的不同,可将SI区的神经元分为Ⅰ.A类和C类纤维传入同时驱动的神经元;Ⅱ.A-ED制约C-ED的神经元;Ⅲ.只由A类纤维传入驱动的神经元。     

带有隐含神经元的单层神经网络模型

提出了一种带有隐含神经元的单层神经网络模型。把网络的记忆容量区分为信息记忆容量和物理记忆容量。新模型能记忆相关图样,其信息容量α_i(最大记忆图样数/表达神经元数)首次超过了1。所作出的计算机模拟结果,表明了理论分析的正确性,证实了由5×5个显神经元组成的点阵能记住包含26个英文字母和4个任选图样的30个图样,因此该模型为神经网络的广泛应用提供了一条重要途径。     

主养青鱼池塘生态系统能量转换率的研究

1985—1987年对苏州市郊区主养青鱼池塘生态系统的能量转换率进行了分析。结果表明,主养青鱼净产7.5、11.25、15t/ha 3个产量级型池塘青鲤团头鲂产出能占养鱼总产出能的比例分别为82.49、78.03、79.34％;总投入能(太阳辐射能+辅助能)转移到鱼的总产出能转换率分别为0.19、0.24、0.31％;太阳辐射能转移到毛和净初级生产力的能量转换率分别为0.76、0.90、0.96％和0.61、0.72、0.77％;净初级生产力转移到滤食性鱼净产量的能量转换率分别为4.02、4.63、5.27％;辅助能转移到鱼净产量的能量转换率分别为12.20、11.33。11.74％。在3个产量级型池塘中,以15t/ha产量级的能量转换率为最佳型。     

Oxytocin and an oxytocin agonist administered centrally decrease food intake in rats.

Intracerebroventricular administration of oxytocin (OT) and an OT agonist significantly decreased food intake in a dose-related manner in fasted rats. Central administration of an OT antagonist by itself (up to doses of 8 nmol) did not potentiate deprivation-induced food intake, but pretreatment with the OT receptor antagonist prevented the expected inhibition of food intake produced by OT and the OT agonist. Once-daily ICV injections of OT led to the development of tolerance to the inhibitory effects on food intake by the third day of treatment, but daily pretreatment with the OT antagonist prevented the development of this tolerance. In addition to causing decreased food intake, ICV administration of OT significantly increased grooming behavior but produced no dyskinesias. The inhibitory effect of OT on food intake was characterized by decreased amounts of food intake but a normal pattern of ingestion. The anorexia produced was central in nature and was not associated with altered plasma levels of hormones involved in caloric homeostasis or with changes in blood glucose. The OT agonist had relatively little effect on water intake when given in doses that significantly inhibited food intake. These results support the hypothesis that specific OT receptors within the central nervous system participate in the inhibition of feeding under certain conditions in rats.     

REPRODUCTIVE ISOLATION AND DISTINCT POPULATION STRUCTURES IN TWO TYPES OF THE FRESHWATER SHRIMP PALAEMON PAUCIDENS

Twenty local populations of the Japanese freshwater shrimp Palaemon paucidens were electrophoretically and morphologically surveyed. Based on the diagnostic distributions of some alleles at Gpi, Mpi, Mdh-1, and Mdh-2, these populations were largely classified into two types (A and B). The A type occurred in lakes, ponds, and rivers, while the B type was observed only in rivers. Average Nei's genetic distance (D) between the two types fell into the subspecies range . The coefficient of gene differentiation, G_ST, varied considerably between the two types. In 12 populations of the A type, with a G_ST value of 0.281, nine pond and lake populations showed a higher G_ST (0.246) than the three river populations (0.151). On the other hand, G_ST was 0.036 for the eight local populations of the B type. The lower rostrum tooth number had a mode of two in type A and three in type B. Type-A populations largely varied in the upper rostrum tooth number and egg size but type B did not. Under laboratory conditions, mating frequently occurred within each type, but not between types. Furthermore, no embryonic development was observed in the few cases of intertype mating. These results indicate that the A and B types had experienced cladogenic separation with pre- or postmating isolation, whereafter the A type, under geographic isolation, underwent genetic and phenotypic differentiation, while the B type, under extensive gene flow, did not undergo differentiation.     

Structure of turnip crinkle virus. III. Identification of a unique coat protein dimer

The minor structural protein (p80), found in about one copy per virion in turnip crinkle virus (TCV), is shown by amino acid analysis and peptide mapping to be a covalent dimer of the major coat protein (p40). The covalent linkage occurs near the N termini of the crosslinked chains. These data suggest that TGV and related viruses contain 178 copies of p40 (89 non-covalent dimers) and one copy of p80 (covalent dimer of two additional p40 chains). The presence of p80 in the salt-stable RNA-protein complex formed when TCV dissociates, as described in an accompanying paper, indicates that the covalent modification affects binding to RNA. We suggest that p80 might be the final dimer to be incorporated into the shell and that it might also be the site for initiation of uncoating.     

Identification and physical characterization of yeast glucoamylase structural genes

Summary Each one of at least three unlinked STA loci (STA1, STA2 and STA3), in the genome of Saccharomyces diastaticus controls starch hydrolysis by coding for an extracellular glucoamylase. Cloned STA2 sequences were used as hybridization probes to investigate the physical structure of the family of STA genes in the genomes of different Saccharomyces strains. Sta⁺ strains, each carrying a single genetically defined STA locus, were crossed with a Sta^– strain and the segregation behavior of the functional locus (i.e. Sta⁺) and sequences homologous to a cloned STA2 glucoamylase structural gene at that locus were analyzed. The results indicate that in all strains examined there is a multiplicity of sequences that are homologous to STA2 DNA but that only the functional STA loci contain extensive 5 and 3 homology to each other and can be identified as residing on unique fragments of DNA; that all laboratory yeast strains examined contain extensive regions of the glucoamylase gene sequences at or closely linked to the STA1 chromosomal position; that the STA1 locus contains two distinct glucoamylase gene sequences that are closely linked to each other; and that all laboratory strains examined also contain another ubiquitous sequence that is not allelic to STA1 and is nonfunctional (Sta^–), but has retained extensive sequence homology to the 5 end of the cloned STA2 gene. It was also determined that the DEX genes (which control dextrin hydrolysis in S. diastaticus), MAL5 (a gene once thought to control maltose metabolism in yeast) and the STA genes are allelic to each other in the following manner: STA1 and DEX2, STA1 and MAL5, and STA2 and DEX1 and STA3 and DEX3.