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。     

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。     

Dilatometric study of binary mixtures of phosphatidylcholines.

Volumes of lipid dispersions as a function of temperature have been measured for two different kinds of binary mixtures of lecithins, (1) DMPC and DSPC and (2) DMPC and DC20PC. Emphasis was placed on DMPC-rich compositions so as to resolve ambiguities regarding solid-phase immiscibility in DMPC-DSPC mixtures. Special attention has been paid to problems of equilibration in the low-temperature phase and to methods of mixing the lipids. We find that there is no solid-solid immiscibility in DMPC-DSPC mixtures, although this system is close to exhibiting such immiscibility, and that DMPC-DC20PC mixtures exhibit pronounced solid immiscibility.     

The methylenetetrahydrofolate-mediated biosynthesis of ribothymidine in the transfer-RNA of Streptococcus faecalis: incorporation of hydrogen from solvent into the methyl moiety.

The methyl carbon of ribothymidine in the tRNA of Streptococcus faecalis is derived from 5,10-methylenetetrahydrofolate, not S-adenosylmethionine. Isotope labeling experiments have shown that the reduction of the methylene carbon of the folate cofactor to the methyl carbon of the modified residue involves a mechanism in which hydrogen from solvent is incorporated into the methyl moiety. Although the identity of the reducing agent involved directly in this novel methylation remains to be established, data suggest that reduced flavin serves this function in vitro.     

Lecithin bilayers. Density measurement and molecular interactions.

Density measurement are reported for bilayer dispersions of a series of saturated lecithins. For chain lengths with, respectively, 14, 15, 16, 17, and 18 carbons per chain, the values for the volume changes at the main transition are 0.027, 0.031, 0.037, 0.040 and 0.045 ml/g. The main transition temperature extrapolates with increasing chain length to the melting temperature of polyethylene. Volume changes at the lower transition are an order of magnitude smaller than the main transition. Single phase thermal expansion coefficients are also reported. The combination of X-ray data and density data indicated that the volume changes are predominantly due to the hydrocarbon chains, thus enabling the volume vCH2 of the methylene groups to be computed as a function of temperature. From this and knowledge of intermolecular interactions in hydrocarbon chains, the change in the interchain van der Waals energy, delta UvdW, at the main transition is computed for the lecithins and also for the alkanes and polyethylene at the melting transition. Using the experimental enthalpies of transition and delta UvdW, the energy equation is consistently balanced for all three systems. This yields estimates of the change in the number of gauche rotamers in the lecithins at the main transition. The consistency of these calculations supports the conclusion that the most important molecular energies for the main transition in lecithin bilayers are the hydrocarbon chain interactions and the rotational isomeric energies, and the conclusion that the main phase transition is analogous to the melting transition in the alkanes from the hexagonal phase to the liquid phase, but with some modifications.