激光光漂恢复技术测定林蛙卵第一次卵裂前卵表面的运动

激光光漂恢复技术测定了异硫氰基荧光素标记的林蛀卵表面分子在第一次卵裂前的运动。发现固着在玻片上的剥离“细胞膜”的分子运动形式为扩散。扩散系数为(4.6±1.3)×10~(-12)cm~2/s,可动部份为15%。完整卵子上的分子运动形式为流动。细胞膜在不停地流动着。它可能起着协助细胞质运动的作用。细胞膜流动的速度随时间而异,卵裂前不久,在大多数的卵子上,出现两个流动较慢的谷,少数细胞只测到一个谷。这可能与光漂起始时间,光斑与未来分裂沟的距离,和卵子间的差异有关。也讨论了这种速度变化与表面收缩波的关系。     

电刺激大鼠延髓头端腹外侧区对交感节前神经元单位放电的影响

本实验用氨基甲酸乙酯麻醉和箭毒化的雄性大鼠,细胞外记录脊髓胸2节段的交感节前神经元(SPN)单位放电,电刺激同侧颈交感干,逆向激活 SPN,以确定所记录的神经元为交感节前神经元。共分析了80个 SPN 单位放电,其中有自发活动和无自发活动的单位各40个。SPN 轴突传导速度为0.59—3.75m/s。实验观察到电刺激同侧延髓头端腹外侧区(Rostralventrolateral medulla:RVL)可兴奋多数有自发活动的 SPN(19/25),并可使少数静止SPN 产生诱发反应(4/23),潜伏期为6—115ms。电刺激对侧 RVL 结果类似:多数自发活动的 SPN(6/9)呈兴奋反应,及少数静止 SPN(3/17)产生诱发反应,潜伏期为11—105ms。表明 RVL 对双侧 SPN 有兴奋性影响。     

Expression of C4-like photosynthesis in several species of Flaveria

Abstract Photosynthetic metabolism was investigated in leaves of five species of Flaveria (Asteraceac), all previously considered to be C₄ plants. Leaves were exposed to ¹⁴CO₂ for different intervals up to 16s. Extrapolation of ¹⁴C-product curves to zero time indicated that only F. trinervia and F.bidentis assimilated atmospheric CO₂ exclusively through phosphoenolpyruvate carboxylase. The proportion of direct fixation of ¹⁴CO₂ by ribulose-I, 5-bisphosphate carboxylase/oxygenase (Rubisco) ranged from 5 to 10% in leaves of F. australasica. F. palmeri and F. vaginata. Protoplasts of leaf mesophyll and bundle sheath cells were utilized to examine the intercellular compartmentation of principal photosynthetic enzymes. Leaves of F. australasica, F. palmeri and F. vaginata contained 5 to 7% of the leaf's Rubisco activity in the mesophyll cells, while leaves of F. trinervia and F. bidentis contained at most 0.2 to 0.8% of such activity in their mesophyll cells. Thus, F. trinervia and F. bidentis have the complete C₄ syndrome, while F. australasica, F. palmeri and F. vaginata are less advanced, C₄-like species.     

Fibrinogen--proteolysis in acute myelogenous leukemia (AML)

Fibrinopeptides were measured as direct indices of thrombin, plasmin and elastase in plasma samples obtained from patients with AML. Peptide patterns observed were consistent with spontaneous or drug induced plasmin-specific fibrinogenolysis (AML FAB M 1/3), elastase mediated proteolysis (AML FAB M 3/4) or DIC (AML FAB 4/5). DIC was also observed in septic, agranulocytotic patients.     

Isolation and characterization of a family of alpha-D-galactosyl-containing glycopeptides from Ehrlich ascites tumor cells

A family of glycopeptides that contain nonreducing terminal alpha-D-galactosyl residues has been isolated from Pronase digests of delipidated Ehrlich ascites tumor cells. The glycopeptides, which comprise 17.2% of the total plasma membrane hexose, have an average molecular weight of 7500 and are precipitated by Griffonia simplicifolia B4 isolectin, wheat germ agglutinin, and Ricinus communis lectin. Exo- and endoglycosidase digestion, periodate oxidation, permethylation analysis, and lectin reactivity provided evidence for a tentative carbohydrate structure for the glycopeptide mixture. The glycopeptides possess tetraantennary branched structures containing a trimannosyl core N-glycosidically linked via an N,N'-diacetylchitobiosyl unit to an asparagine residue. Each branch contained repeating leads to 3)-beta-D-Galp-(1 leads to 4)-beta-D-GlcNAcp-(1 leads to units resulting in a keratan-like structure, terminated with alpha-D-Galp-(1 leads to 3)-[alpha-D-Galp-(1 leads to 6)]-beta-D-Galp-units. The variation in the molecular weight observed for the glycopeptide mixture can be attributed to the variable amounts of leads to 3)-beta-D-Galp-(1 leads to 4)-beta-D-GlcNAcp-(1 leads to units found in the branch chains.     

Molecular basis for modulated regulation of gene expression in the arginine regulon of Escherichia coli K-12.

We compare the nucleotide sequences of the regulatory regions of five genes or groups of genes of the arginine regulon of Escherichia coli K-12: argF, argI, argR, the bipolar argECBH operon and the carAB operon. All these regions harbour one or two copies of a conserved 18 bp sequence which appears to constitute the basic arginine operator sequence (ARG box). We discuss the influence of ARG box copy number, degree of dyad symmetry, base composition, and position relative to the cognate promoter site on the derepression-repression ratios of the genes of the regulon. A novel hypothesis, based on structural considerations, is also put forward to account for the absence ot attenuation control.     

Distribution of Metabolites and Enzymes of Nitrogen Metabolism between the Mesophyll and Paraveinal Mesophyll of Non-Nodulated Glycine max

The distribution of amino acids and key enzymes involved innitrogen metabolism was determined in mesophyll cells (MC),mesophyll protoplasts (MP), and paraveinal mesophyll protoplasts(PVMP) isolated from fully expanded trifoliolate leaves of non-nodulatedsoybean. Qualitative and quantitative differences were foundin the distribution of amino acids, with MP containing the highestconcentrations. Activity of nitrate reductase, glycolate oxidase,glutamine synthetase and glutamate dehydrogenase was measuredin both tissue types and differences in activities between thetissue types were seen. PVMP had high glutamate dehydrogenaseactivity when compared to MP. Activities of glycolate oxidaseand glutamine synthetase were much higher in MP on a protoplastbasis while nitrate reductase activity was similar between thetwo protoplast types. These results, on the distribution ofmetabolites and associated enzymes, are discussed as to theirpossible significance to nitrogen metabolism in the soybeanleaf. Key words: Amino acids, glutamate dehydrogenase, Glycine max, nitrate reductase, nitrogen metabolism, paraveinal mesophyll, protoplasts     

谷氨酸钠兴奋尾侧导水管周围灰质腹外侧部的升压反应及其在脑干内的传出通路

实验用乌拉坦麻醉、箭毒化、人工呼吸的大鼠,观察到:(1) 胞体兴奋剂L-谷氨酸钠(Glu)注入尾侧导水管周围灰质腹外侧部(PAG)引起明显的加压反应,(2) 该效应可被双侧延髓头端腹外侧(RVL)加压区内注射酚妥拉明或心得安衰减,但不受阿托品注入RVL影响;表明此升压反应是通过RVL及其内的α-及β-受体实现的。(3) RVL内注入心得安也可衰减电刺激腹侧臂旁核(NPV)的加压作用,却不影响Glu注入NPV的升压效应;结合以往的实验结果,提示尾侧PAG腹外侧部的神经元发出的轴突,可能一方面路过臂旁核直接作用于RVL内的β-受体,另一方面可能在臂旁核内换元,然后作用于RVL内的α-受体,而起升压作用。