High-affinity uptake of γ-[3H]aminobutyric acid by isolated mouse oligodendrocytes in culture

Oligodendrocytes were isolated from mixed glial cultures of neonatal mouse forebrain and further grown in serum-free hormone supplemented culture medium. Cell populations were identified by indirect immunofluorescence using a range of specific antibodies, revealing a predominantly immature population of oligodendrocytes, the majority expressing the myelin glycolipids galactocerebroside and sulfatide on their plasma membrane. Astroglial contamination was found to be minimal. Simultaneous autoradiography and immunofluorescence demonstrated the presence of a transport system for the major inhibitory neurotransmitter GABA in the oligodendrocytes. The transport system was found to be energy, sodium and temperature dependent. Kinetic analysis revealed a high affinity system, with aK _m of 6.27 M and aV _max of 0.714 nmol/min/mg protein, which is comparable to that found previously for CNS neurons and astrocytes.Special Issue dedicated to Dr. E. M. Shooter and Dr. S. Varon.     

中国东方铃蟾(Bombina orientalis)皮肤中C_(-12-b)肽的分离与鉴定

东方铃蟾鲜皮的甲醇提取液,可引起大鼠离体平滑肌的收缩。此液经碱性氧化铝柱层析分离,其80%乙醇洗脱的 C 组分显示生物活性。C 组分再经葡聚糖凝胶 G-15柱分离,其活性较强的早期洗脱组分 C_(_12),可被糜蛋白酶水解灭活,但其活性并不被5-HT 拮抗剂赛庚啶[2×10~(-6)mol/L]完全拮抗。继用反相高效液相色谱(RP-HPLC)分析,见分离出的 C_(_12_h)峰与铃蟾肽~*(Bombesin,BBS)的出峰时间相同,且具相同的氨基酸组成。上述实验结果提示,C_(_12_h)肽可能就是铃蟾肽。     

Why are there so many species of bumble bees at Dungeness?

WILLIAMS, P. H., 1989. Why are there so many species of bumble bees at Dungeness? Dungeness is unique in the British Isles in that it has more species of bumble bees than any other locality. Three ideas about what governs the number of species at a locality are examined by locking at patterns of flower visits at Dungeness in comparison with those at Shoreham, a species-poor locality also in Kent. The species of bumble bees that are present at Dungeness but absent from Shoreham show no association in their distributions among 2 km grid-squares in Kent with the species of food-plants that they prefer at Dungeness, nor is there any correlation between the diversity of bees and diversity of food-plants at Dungeness and Shoreham. From the information available, Dungeness is most likely to have more species of bumble bees because it has a particularly high density of the more nectar-rich flowers that bumble bees can use. Bumble bees feed most profitably from deep flowers because these contain more nectar than shallow flowers, although direct access to deeper flowers is ultimately limited by the length of each bee's proboscis. The distribution of worker proboscis lengths among species in the species-pool in Kent is clumped about a median of 7.9 mm. The best foraging conditions for the maximum number of species should be provided when flowers of similar depths are present in sufficiently large numbers for all foragers to make near-optimal flower choices. Although there is no difference in median between the distributions of the bees' proboscis lengths and the depths of the flowers they use at Dungeness, at Shoreham the flower depths used are shorter than the proboscis lengths. Among the food-plants at Dungeness, high densities of Teucrium scorodonia and Echium vulgare are likely to be especially important.     

Enzymic synthesis,chemical characterisation and Sda activity of GalNAcß1-4[NeuAcα2-3]Galß1-4GlcNAc and GalNAcß1-4[NeuAcα2-3]Galß1-4Glc

The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and¹H-500 MHz NMR spectroscopy. In Sd^a serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity.     

Amino acid sequence and function of rebredoxin from Desulfovibrio vulgaris Miyazaki

Rubredoxin was purified from Desulfovibrio vulgaris Miyazaki. It was sequenced and some of its properties determined. Rubredoxin is composed of 52 amino acids. It is highly homologous to that from D. vulgaris Hildenborough. Its N-methionyl residue is partially formalated. The millimolar absorption coefficients of the rubredoxin at 489 nm and 280 are 8.1 and 18.5, respectively, and the standard redox potential is +5 mB, which is slightly higher than those of other rubredoxins. Rubredoxin, as well as cytochrome c-553, was reduced with lactate by the action of lactate dehydrogenase of this organism, and the rection was stimulated with 2-methyl-1, 4-naphthoquinone. It is suggested that rubredoxin, in collaboration with membraous quinone, functions as natural electron carrier for cytoplasmic lactate dehydrogenase of this organism, whereas cytochrome c-553 plays the same role for periplasmic lactate dehydrogenase.     

Use of pheromone chemistry to identify Grapholita lobarzewskii as an occasional pest of apple and plum

As shown by chemical analysis and field trapping, the sex pheromone of Grapholita lobarzewskii consists of a blend of (E)-8-dodecenyl acetate and (Z)-8-dodecenyl acetate. Maximum attractiveness was found at 80–95%. Dodecyl acetate and tetradecyl acetate, both present in the female gland, did not affect trap catch. G. lobarzewskii has recently gained importance as a pest of apple and plum, but has so far been referred to as Grapholita janthinana. The latter is attracted to the same two compounds, but in reversed portions (20% E).

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Zusammenfassung Chemische Analysen und Feldversuche zeigen, dass das Sexualpheromon des Kleinen Fruchtwicklers, G. lobarzewskii aus (E)-8-Dodecenylacetat (Z8-12:Ac) und (Z)-8-Dodecenylacetat (Z8-12:Ac) besteht. Die grösste Lockwirkung wurde mit einem Gemisch der beiden Substanzen bei einem E-Anteil von 80–95% erzielt. Dodecylacetat (12:Ac) und Tetradecylacetat (14:Ac) wurden ebenfalls in den weiblichen Pheromondrüsen nachgewiesen, hatten aber im Freiland keinen Einfluss auf die Lockwirkung. G. lobarzewskii tritt seit einiger Zeit in der Schweiz als Schädling von Apfel und Zwetschge auf und ist an ihrem charakteristischem Frassgang leicht erkennbar. Die Art wurde bisher irrtümlich als G. janthinana bezeichnet. G. janthinana lebt auf Rosaceen, und wird vom gleichen Substanzpaar angelockt, allerdings bei umgekehrtem Mischungsverhältnis (20% E).

     

20-羟蜕皮素对家蚕后部丝腺细胞超微结构的影响

应用超薄切片和电镜技术,详细观察了蜕皮激素(MH)对家蚕Bombyx mori后部丝腺细胞超微结构的影响.电镜观察表明,家蚕后部丝腺细胞对MH处理极为敏感.一经MH处理,其细胞核的形态结构和细胞质中各种细胞器的发生、发展都呈现出明显的变化,并且与MH处理时期及剂量有关:五龄前期适量MH(4μg/头)处理,能促进与丝蛋白合成有关细胞器的形成与发展,加速腺细胞的成熟生长;较高剂量(8—16μg/头)处理,则导致自噬体的过早发生.五龄中、后期MH处理,一方面促进了粗面内质网等细胞器的进一步发达,另一方面也提高了自噬体的发生数量;处理剂量越高,后一种倾向越突出.这些结果证明,后部丝腺细胞超微结构的变化受MH调节.     

Protein stability and electrostatic interactions between solvent exposed charged side chains

To investigate the contribution to protein stability of electrostatic interactions between charged surface residues, we have studied the effect of substituting three negatively charged solvent exposed residues with their side-chain amide analogs in bovine calbindin D9k--a small (Mr 8,500) globular protein of the calmodulin superfamily. The free energy of urea-induced unfolding for the wild-type and seven mutant proteins has been measured. The mutant proteins have increased stability towards unfolding relative to the wild-type. The experimental results correlate reasonably well with theoretically calculated relative free energies of unfolding and show that electrostatic interactions between charges on the surface of a protein can have significant effects on protein stability.     

Mechanisms of degradation of 2′-5′ oligoadenylates

We have studied the mechanisms of breakdown of 2'-5' oligoadenylates. We monitored the time-courses of degradation of ppp(A2'p5')nA (dimer to tetramer) and of 5'OH-(A2'p5')nA (dimer to pentamer) in unfractionated L1210 cell extract. The 5' triphosphorylated 2'-5' oligoadenylates are converted by a phosphatase activity. However, 2'-5' oligoadenylates are degraded mainly by phosphodiesterase activity which splits the 2'-5' phosphodiester bond sequentially at the 2' end to yield 5' AMP and one-unit-shorter oligomers. The nonlinear least-squares curve-fitting program CONSAM was used to fit these kinetics and to determine the degradation rate constant of each oligomer. Trimers and tetramers, whether 5' triphosphorylated or not, are degraded at the same rate, whereas 5' triphosphorylated dimer is rapidly hydrolyzed and 5'-OH dimer is the most stable oligomer. The interaction between degradation enzymes and the substrate strongly depends on the presence of a 5' phosphate group in the vicinity of the phosphodiester bond to be hydrolyzed; indeed, when this 5' phosphate group is present, as in pp/pA2'p5'A/or A2'/p5'A2'p5'A/, affinity is high and maximal velocity is low. Such a degradation pattern can control the concentration of 2'-5' oligoadenylates active on RNAse L either by limiting their synthesis (5' triphosphorylated dimer is the primer necessary for the formation of longer oligomers) and/or by converting them into inhibitory (e.g., monophosphorylated trimer) or inactive (e.g., nonphosphorylated oligomers) molecules.