猫尾核头部前区对三叉神经尾端脊束核的抑制作用及其方式

在清醒麻痹状态下的55只猫上,观察了电刺激尾核头部前区(Cd)对三叉神经尾端脊束核(cST)中了齿槽神经(AI)伤害性刺激所诱发的放电的影响。刺激 Cd 可以抑制大多数 cST 神经元的伤害性反应,抑制持续约100—500ms。抑制时程可为静脉注射戊巴比妥钠和安定而延长,注射印防己毒素可使其缩短。马钱子素使抑制时程稍有延长。这些结果提示,Cd 对 cST神经元的抑制作用是通过突触前抑制的方式实现的。     

人工补充寄主卵对松林内卵蜂种群消长的影响

在不同生境的松林中,人工补充寄主卵都能提高寄生效果。但林地生境不同,寄生率有明显差异。在松阔混交林中补充寄主,其寄生率比对照提高5.5—16.2倍。植被稀疏的纯松林效果较差,补充的寄生率比对照提高3.0倍。 卵蜂种群消长随季节温度而变化,全年以5月中旬至6月下旬和9月中旬至10月中旬为两个寄生高峰。卵蜂种群与松毛虫种群的消长存在较明显的相依关系,卵蜂种群随着松毛虫种群的消长而消长。施药对卵蜂种群有较大影响,施药区比对照区的寄生率约降低一倍。在混交林中填充寄主卵,能促进卵蜂种群世代延续。在逐步改善林地生境的基础上,利用人工补充寄主,可以代替人工繁蜂放蜂。     

Anion transport across the red blood cell membrane mediated by dielectric pores

Summary The anion transport across the red blood cell membrane is assumed to occur by ionic diffusion through dielectric pores which are formed by protein molecules spanning the red blood cell membrane. The access of anions to the dielectric pores is regulated by anion adsorption sites positioned at the entrances of the pores. The adsorption of small inorganic anions to the adsorption sites is facilitated by ionizing cationic groups setting up a surface potential at the respective membrane surfaces. Applying the transition state theory of rate processes, flux equations for the unidirectional flux were derived expressing the unidirectional flux as a function of the fractional occupancies of anion adsorption sites at both membrane surfaces.The basic properties of the transport model were investigated. The concentration-dependence and the pH-dependence of the unidirectional fluxes were shown to depend upon the surface charge density and upon the affinity of the transported anion species to the anion binding sites. The concentration-response and the pH-response of the unidirectional fluxes of different anion species may differ substantially even if the anion species are transported by the same anion transport system. The model predicts a characteristic behavior of the Lineweaver-Burk plot and of the Dixon plot.A comparison between computer simulated and experimentally determined flux curves was made. By choosing a suitable set of parameters, the anion transport model is capable of simulating the concentration-dependencies and the pH-dependencies of the unidirectional sulfate and chloride flux. It is sufficient to change one single constant in order to convert the sulfate transport system into a chloride transport system. Furthermore, the model is capable of predicting the inhibitory action of chloride on the sulfate transport system. No attempts were made to fit the experimental data to the model. The behavior of the model was qualitatively in accordance with the experimental results.     

现代化经济建设与生态科学——试论当代生态学工作者的任务

宇宙空间是无限的,但适于人类生活和生物生存的生物圈则是有限的,它是个松散结构的大系统,其中包括许多类型的生物集团与无机环境结合而成的功能单元,即生态系统。在长期进化过程中,通过物质循环与能量交换,生物圈与生态系统之间建立了相互协调与补偿关系,并使生物圈及生态系统都具有一定限度的调节功能。人类对自然界的依存关系,以及自然界所形成的生态平衡是长期演化而形成的,人类亦参与和适应了此平衡过程。维持这种平衡的基础是有规律的物质循环和能量交換。此种质能流动则是通过     

中国吻额蛛属一新种（蜘蛛目：皿蛛科：微蛛亚科）

本文描述了作者1986年采自湖北省神农架林区的吻额蛛属Aprifrontalia一新种:膨大吻额蛛,新种Aprifrontalia afflata sp.nov.。目前,除本新种外,世界仅报道过1种:Aprifrontalia mascula,本新种雄蛛最显著的特征是:其额向前突呈吻状,触肢胫节前端甚膨大。外雌器形成一斜向下方的突起。模式标本保存于白求恩医科大学生物教研室。     

Genetic analysis of epidermin biosynthetic genes and epidermin-negative mutants of Staphylococcus epidermidis.

Epidermin is produced by Staphylococcus epidermidis Tü3298 which harbors the 54-kb plasmid, pTü32. The plasmid contains not only the epidermin structural gene epiA, but also a flanking DNA region which is necessary for epidermin biosynthesis. The DNA sequence of this region revealed, in addition to epiA, five additional open reading frames, epiB, C, D, Q and P [Schnell, N., Engelke, G., Augustin J., Rosenstein, R., Ungermann, V., G?tz, F. & Entian, K.-D. (1992) Eur. J. Biochem. 204, 57-68]. We isolated a number of stable mutants from strain Tü3298 which are unable to produce biologically active epidermin. Complementation studies using the newly constructed staphylococcal plasmid vectors pT181mcs and pCU1 led to their classification as epiA, epiB, epiC or epiD mutants. Furthermore, evidence is presented that epiB lacks its own promoter and is co-transcribed from the epiA promoter. There is evidence that epiC and D possess their own promoters. Although epiQ and epiP mutants were not isolated, it could be shown by heterologous gene expression in S. carnosus and S. xylosus that the corresponding DNA region is involved in epidermin biosynthesis. We can not exclude the possibility that, in addition to the four open reading frames, epiA, B, C, D, and the DNA region comprising epiQ and P, host-encoded functions are necessary for epidermin production. Thus, the genetic information for epidermin biosynthesis in S. carnosus and S. xylosus is located on an 8-kb DNA fragment of pTü32. A further characterization of the two epiA mutants revealed that in both mutants, the preepidermin nucleotide sequence was changed. In one mutant, the mutation led to a substitution of Ser3 by Asn; in the other of Gly10 by Glu.     

Anaerobic degradation of sorbic acid by sulfate-reducing and fermenting bacteria: pentanone-2 and isopentanone-2 as byproducts

Strictly anaerobic bacteria were enriched and isolated from freshwater sediment sources in the presence and absence of sulfate with sorbic acid as sole source of carbon and energy. Strain WoSo1, a Gram-negative vibrioid sulfate-reducing bacterium which was assigned to the species Desulfoarculus (formerly Desulfovibrio) baarsii oxidized sorbic acid completely to CO₂ with concomitant stoichiometric reduction of sulfate to sulfide. This strain also oxidized a wide variety of fatty acids and other organic compounds. A Gram-negative rod-shaped fermenting bacterium, strain AmSo1, fermented sorbic acid stoichiometrically to about equal amounts of acetate and butyrate. At concentrations higher than 10 mM, sorbic acid fermentation led to the production of pentanone-2 and isopentanone-2 (3-methyl-2-butanone) as byproducts. Strain AmSo1 fermented also crotonate and 3-hydroxybutyrate to acetate and butyrate, and hexoses to acetate, ethanol, hydrogen, and formate. The guanine-plus-cytosine content of the DNA was 41.8±1.0 mol%. Sorbic acid at concentrations higher than 5 mM inhibited growth of this strain while strain WoSo1 tolerated sorbic acid up to 10 mM concentration.     

幼年大鼠诱发排卵条件下卵巢前列腺素(PGs)的含量变化及其生理作用

本实验用幼年大鼠经PMSG/hCG诱发排卵,研究了印巢PGE_2、PGF_(2α) 、6-酮-PGF_(1α) 及TXB_2在排卵过程中的变化。实验表明卵巢PGE_2、PGF_(2α) 及6-酮-PGF_(1α) 在排卵前达到峰值,在排卵后,均趋下降。TXB_2未出现明显变化。受试动物经消炎痛处理后,不仅使排卵受到严重抑制,而对上述三种PGs在排卵前的上升也表现了显著的抑制。提示在卵泡破裂过程中PGs的重要调节作用,PGE_2、PGF_(2α)均可能参与排卵,其中尤以PGE_2的作用最为显著。