Mechanisms of beta-adrenergic stimulation of cardiac Ca2+ channels revealed by discrete-time Markov analysis of slow gating.

Individual cardiac Ca2+ channels cycle slowly between a mode of gating in which the channel is available to open, and one in which the channel remains silent. The regulation of this multisecond cycling process by isoproterenol was investigated by single-channel recording and the development of a discrete-time Markov model that describes the slow switching among modes in terms of (de) phosphorylation reactions. The results provide evidence that isoproterenol increases Ca2+ channel activity by a reciprocal regulatory mechanism: not only is the phosphorylation rate of the channel increased, but also the dephosphorylation rate decreased. The discrete-time Markov formalism should prove useful as a general tool for understanding the mode switching demonstrated by a number of ionic channels.     

Regulation of estrogen receptor protein and messenger ribonucleic acid by estradiol and progesterone in rat uterus

The objective of this study was to examine the mechanisms of estrogen receptor (ER) processing and replenishment in the uterus of ovariectomized rats after estradiol and progesterone treatment. Uterine ER binding activity, ER protein and ER mRNA were measured by receptor binding exchange assay, Western blot and slot blot, respectively. The regulation of ER levels in rat uterus by estradiol and progesterone was very dramatic. Changes in ER protein were faithfully reflected by changes in binding activity. Estradiol caused receptor “processing” within 4 h of administration followed by recovery or “replenishment” of ER levels to the initial level by 20 h. The term “processing” has previously been used to describe the loss of ER binding activity in the early phase of estradiol-action, but it was never clear whether the ligand binding site was inactivated by processing or if the receptor molecule actually disappeared. This study shows that receptor “processing” constitutes disappearance of receptor protein and the later “replenishment” phase represents new ER protein rather than recycling of “processed” receptor. Progesterone-action, on the other hand, influenced only the “replenishment” phase by blocking recovery of ER protein. ER mRNA was suppressed by estradiol at 8 h, after the receptor was “processed” and “replenishment” already initiated. Progesterone, on the other hand, did not alter the steady state level of the message. Other mechanisms, such as regulation of translation rate of existing mRNA and changes in the rate of degradation of ER proteins are more likely involved in acute regulation of ER by these ovarian steroid hormones.     

ε-聚赖氨酸抑菌性能的研究进展

ε-聚赖氨酸(ε-poly-L-lysine,ε-PL)是抑菌谱广泛的天然抑菌剂,由通过α-羧基与ε-氨基连接的25–35个赖氨酸聚合而成。ε-PL主要由白色链霉菌发酵生产所得,比化学生产更加高效和环保。ε-PL具有水溶性好、耐热和对环境无污染等特点,具有良好的应用前景。本文从发酵生产入手,着重综述了ε-PL对各种微生物抑菌性能、抑菌机制及抑菌机制模型的研究进展。推测ε-PL是通过对细胞膜的破坏而改变细胞的通透性,或者作用到细胞内引起活性氧(reactive oxygen species, ROS)胁迫而影响调节基因的表达,从而起到抑菌作用。根据这2种抑菌方式分别建立了相应的抑菌模型,即毡毯模型和ROS诱导细胞凋亡模型。本文可为ε-PL对微生物抑制性能的深入研究提供依据,同时也提出了ε-PL抑菌机制的新模型,为扩展ε-PL应用领域提供了一定的参考。     

氦氖激光对绵羊精清中酶活性效应的研究

本文研究结果表明低剂量的氦氖激光可以提高绵羊精清中GOT和LDH酶的活性,并对其机制作了初步的探讨。     

Quantitation of Rat Dopamine Transporter mRNA: Effects of Cocaine Treatment and Withdrawal

Dopamine transporter mRNA levels in the rat substantia nigra were quantified using a sensitive nuclease protection assay with a highly homologous human dopamine transporter cDNA clone. The same probe was also used to visualize dopamine transporter mRNA in the substantia nigra by in situ hybridization. Repeated cocaine administration (15 mg/kg, twice a day for 6.5 days) resulted in a greater than 40% decrease in nigral dopamine transporter mRNA levels. In contrast, dopamine transporter mRNA levels were unchanged after either acute treatment (4 h before death) or repeated cocaine treatment followed by a 72-h withdrawal period. Thus, blockade of the dopamine transporter by repeated cocaine administration may result in the down-regulation of dopamine transporter gene expression in dopamine neurons.     

The determination of the pKa of histidine residues in proteins by Raman difference spectroscopy

Sensitive Raman difference spectroscopy was used to monitor the protonation and deprotonation of histidine residues in apo-transferrin. We have shown previously that the behavior of small molecules and/or small molecular groups bound to proteins or other large macromolecules can be studied by Raman difference spectroscopy (Yue, K.T. et al. (1989) J. Raman Spectrosc. 20, 541-545). Using this method, we have measured the Raman difference spectra of human transferrin at different pH values with respect to pH 8.9, titrating its various histidine residues. About 12 +/- 2 of the 19 residues were titrated. The pH difference spectrum of transferrin obtained is very similar to that of histidine in solution, but with clear differences in the 1200-1400 cm-1 region. A titration curve with pKa of 6.08 +/- 0.01 fit the data of histidine in solution and a value of 6.56 +/- 0.02 was found for the average value of the 12 histidine residues inside transferrin. The technique has enough sensitivity at present to monitor a single histidine residue in a 130 kDa molecule and to determine the titration curve of one residue in a 40 kDa protein.     

时域—频域结合分析法—一种分析果蝇求爱歌的新方法

我们设计了一种时域-频域结合分析法,并用此方法分析了6个种群12种果蝇的求爱歌,发现如果将时域与频域的研究结合起来,对求爱歌进行频谱分析,可以定量地揭示出求爱歌的频域特性及其在时域上的细微变化。我们还对果蝇求爱歌的时域模式进行了初步的探讨,发现它们是在同一基本成分上进行调制而产生的,亲缘关系较近的种具有相近的调制方式。在对杂交后代的求爱歌的频谱分析中,我们还发现频谱上的某些特点是能够遗传的。这一新的研究方法为果蝇的进化遗传学和神经遗传的研究提供了一种新的手段。     

氨基酸酯水解酶产生菌的筛选及其合成头孢立新的研究

From ten genera and 146 bacterial strains, 22 strains producing alpha-amino acid ester hydrolase were selected. Among them, AS 1.586 and 41-2 were the best. The optimal conditions for synthesis of cephalexin by pseudomonas aeruginosa 1.204 were investigated. The optimal pH and temperature for enzymatic synthesis reaction was pH 6.8 and 25 degrees C, respectively. By using 1% 7-ADCA, 3% PGME and 4% biomass, about 70% of 7-ADCA was converted to cephalexin under the mentioned conditions.     

基于微生物模型的合作行为进化研究进展

生物间的合作行为如何在自然选择过程中显示出对欺骗者的优势,一直以来都是进化生物学上的经典问题。实验室构建的具有合作行为的微生物种群是研究这一问题的良好素材。本文综述了几种基于微生物模型的合作行为进化理论,如亲缘选择理论、辛普森悖论、竞争抑制理论、进化博弈理论等,对其中涉及到的微生物模型进行介绍和评价,并展望其研究前景。