Argiopine,argiopinines, and pseudoargiopinines as glutamate receptor blockers in hippocampal neurons

A homologous set of low-molecular weight compounds selectively blocking ionic currents were purified from venom from the spiderArgiope lobata with a selective blocking action on ionic currents activated by applying glutamate and its agonist kainic acid (KA) to the membrane of neurons isolated from the rat hippocampus. Three groups of these compounds — argiopine, argiopinines, and pseudoargiopinines, produced voltage-dependent glutamate- and KA-activated ionic currents at concentrations of 10^–6-10^–4 M, interacting primarily with agonist-activated ionic channels without affecting K_d values of the agonist. The blocking action could be partially reversed by argiopine application but only slightly when argiopinines and pseudoargiopinines were used. Kinetics of toxin effects on Ka-activated ionic currents showed at least two exponential components with different time constants. Simple and reversed rate constants of interaction between toxins and ionic channels were estimated from the plot of the kinetics of ionic current blockade and recovery against toxin concentration. Argiopine, argiopinines, and pseudoargiopinines lend themselves to further research into glutamate receptors of the mammalian CNS employing electrophysiological and biochemical techniques.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev, M. M. Shemyakin Institute of Bioorganic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 6, pp. 748–756, November–December, 1989.     

Heterochromatic regions in different Drosophila melanogaster stocks contain similar arrangements of moderate repeats with inserted copia-like elements (MDG1)

Seven out of twenty 30–50 kb genome fragments with an MDG1 copia-like element cloned in cosmids were found to carry homologous sequences which belong to a new family of non-mobile heterochromatic moderate repeats (the HMR family). These repeats along with the MDG1 copies inserted in them are under-replicated in polytene chromosomes. Such repeats may also be located in the intercalary heterochromatin site 12E of the X chromosome. Chromosomal heterochromatic regions are enriched with one of the two main genomic variants of MDG1, MDG1^het, identifiable by EcoRI restriction. From Southern DNA blot analysis the number of MDG1^het copies and their sites within the heterochromatin are invariant in all the stocks examined, while there is not a single MDG1 site along the polytene chromosomes shared by all the stocks in question.     

躯体和内脏传入冲动在大鼠束旁核内的会聚

在麻痹的大鼠上,分别刺激迷走神经、内脏大神经、坐骨神经、腓肠神经、睾丸和副睾,在对侧丘脑束旁核记录到了45个细胞的单位放电。根据诱发反应的潜伏期、时程和放电频谱分布的不同,可将他们分为五种类型,并且认为这些类型和刺激引起的感觉性质有关。在观察到的45单位中,29个的反应具有痛放电的特性,而且对躯体及内脏的传入冲动呈聚合性反应。其中2个单位只对内脏传入冲动产生反应。这项研究的结果表明,束旁核不仅是接受内脏传入的丘脑结构,而且也是一个整合内脏与躯体传入信息的中枢。     

Excitation of feline cutaneous mechanosensitive C-fiber sensory units by intraarterial administration of potassium ions

Response of low- and high-threshold mechanosensitive C fiber sensory units (MSU) in n. saphenus to close-arterial injection of potassium ions in subnoxious and noxious concentrations (SC and NC) were investigated in anesthetized cats. Two groups of high-threshold units were found: 1) MSU reacting to K⁺ at both SC and NC, but responding very differently to each of these concentrations and 2) MSU responding to NC only. Findings would indicate that high-rather than lowthreshold MSU participate in the perception of noxious stimuli. The possibility of differentiation between subnoxious and noxious stimuli by a proportion of high-threshold MSU is considered. High-threshold MSU discharges accompanying excitation of these units by subnoxious and noxious chemical stimuli are quantified.National Cardiology Research Center, Academy of Medical Sciences of the USSR, Moscow. translated from Neirofiziologiya, Vol. 20, No. 2, pp. 147–154, March–April, 1988.     

Receptor-like cytokinin-binding protein(s) from barley leaves

Purified fractions of soluble proteins from barley leaves have been shown to contain specific binding sites fortrans-zeatin, a natural cytokinin. Such binding is very strong in vitro in concentrated solutions of some salts (ammonium sulfate or potassium phosphate) with optimum at pH 7–8 and temperature within the range 0–20°C. The cytokinin-binding sites have high affinity for zeatin (K_d1.5·10^–8 M) and low capacity corresponding to 1–1.5 pmol zeatin per milligram of initial soluble protein. Cytokinin binding is reversible; it is due to protein (or proteins) with molecular weight 40–45 kDa. This protein(s) does not bind³H-adenine and³H-abscisic acid. The ability of various compounds to displace³H-zeatin from its high-affinity binding sites is in strict accordance with their biological cytokinin activities. Other phytohormones as well as fusicoccin do not displace³H-zeatin from its binding sites. Specific zeatin binding is sensitive to heat, alkali, and pronase, but not to RNase treatment. The 150- to 200-fold purification of cytokinin-binding proteins was achieved by a combination of ammonium sulfate precipitation and Ultrogel AcA-54- and DEAE-cellulose chromatography. The zeatin-binding protein(s) from barley leaves is suggested to take part in cytokinin action in vivo.     

A hypothalamic activator of calmodulin-dependent enzymes is thymosin β4 (1–39)

A new class of stimulators of basal activity of a number of calmodulin-dependent enzymes have been previously isolated from bovine hypothalamus. One of these stimulators, denoted as C₃, has been purified to homogeneity by reverse phase HPLC and tentatively identified as thymosin ₄ (1–39) by mass spectrometry and Edman microsequence analysis. The stimulating effect of C₃ on rabbit skeletal muscle MLCK basal activity was compared with that of thymosin ₁ and thymosin ₄ (16–38). Evidence is presented that all the indicated compounds are Ca²⁺-independent high-affinity MLCK stimulators. The potency of the stimulators in activating the enzyme was: C₃>₄>(CaM+Ca²⁺>₁.This revised version was published online in June 2005 with corrections to the author name Gurvits.     

内皮素对大鼠肠系膜微血管的作用

应用显微电视录象技术可观察到内皮素(ET)对戊巴比妥钠麻醉的 Wistar 大鼠的肠系膜微血管有收缩作用,血液流速减慢,甚至产生微循环障碍,这个作用相当持久,并呈剂量依赖关系。ET 的这个作用远高于去甲肾上腺素。这些结果提示,ET 作为强烈的微血管收缩剂,在微循环紊乱疾病的发病学中可能具有重要意义。     

Regulation of multiple forms of cyclic nucleotide phosphodiesterase from bovine hypothalamus: New factors modulating enzyme activity

Studies of bovine hypothalamic cyclic nucleotide phosphodiesterase (PDE) indicate the presence of several peaks of PDE activity, distinguishable by DEAE-cellulose column chromatography, displaying different substrate specificities, kinetic behavior, and regulatory properties. Evidence is presented that chromatographically separated forms of PDE activity are subject to control by Ca²⁺-calmodulin, cyclic nucleotides, limited proteolysis, reagents affecting sulfhydryl groups, and neurohormone “C”—one of several new cardioactive compounds isolated from hypothalamic magnocellular nuclei of animals—in a complex substrate-specific and concentration-dependent manner. Of particular interest is the finding that each of the forms of cGMP PDE, being Ca²⁺/calmodulin-dependent, possesses sensitivity to activation by cAMP, especially under conditions favoring the oxidation of thiol groups of PDE, resulting in a loss in responsiveness of the enzyme to the activation by calmodulin. This effect appears to be relatively stable but readily reversible by sulfhydryl reducing reagents, which restore both the cGMP PDE sensitivity to competitive inhibition by cAMP and the responsiveness of the enzyme to activation by calmodulin. A reinterpretation of the regulatory properties of multiple forms of PDE is proposed. Special Issue dedicated to Dr. Eugene Kreps.     

农田步甲的生物学研究

本文报道12种农田常见步甲的种群动态和捕食习性,施用杀虫剂对步甲的影响。     

Telomeres and P-element of Drosophila melanogaster contain sequences that replicate autonomously in Saccharomyces cerevisiae

Summary We have isolated restriction fragments from a shotgun collection of Drosophila DNA which function as autonomously replicating sequences (ARS) in Saccharomyces cerevisiae and hybridize with telomeric regions of the 2L, 2R, 4, and X chromosomes. In an independently obtained set of D. melanogaster clones five fragments hybridize in situ with telomeres and a number of internal sites. Two of them also contain ARSs. A Drosophila mobile P-element also possesses ARS activity in yeast.