Biosynthesis of monensins a and b: the role of isoleucine

Isoleucine added to the cultivation medium of Streptomyces cinnamonensis C-100-5 induced a relative increase of the production of monensin B at the expense of monensin A. U-14C-Isoleucine was found not to be a specific monensin B precursor. The incorporation of 1-13C-2-methylbutyrate into monensins A and B showed the label to be evenly incorporated in both products at carbon atoms originating from C(1) of propionate. In regulatory mutants insensitive to 2-amino-3-chlorobutyrate isoleucine influenced the production of monensins only slightly but strains resistant to 2-aminobutyrate and norleucine decreased their total production by 2-12% in the presence of isoleucine which was associated with a decrease of monensin A content by 14-52%. The inhibitory effect of isoleucine on the biosynthesis of valine, a specific precursor of the butyrate unit of monensin A, is discussed.     

Benzothiazolium salts—relationships between their structure,toxicity and effect on the plastid system ofEuglena gracilis

The effects of 41 benzothiazolium salts on Euglena gracilis were characterized with regard to the influence on growth and on chlorophyll synthesis, and to their ability to induce permanent loss of chloroplasts. Some salts induced white mutants of E. gracilis (the first benzothiazole derivatives with this activity). The relationship between the biological effect and chemical structure was confirmed and expressed quantitatively by means of Free - Wilson and Fujita - Ban analysis.     

Glutamicin CBII,a bacteriocin-like substance produced by

Corynebacterium glutamicum CBII, in the stationary phase of growth, was found to produce spontaneously a substance resembling bacteriocins by its bactericidal properties. This substance designated glutamicin CBII was observed to exhibit bactericidal activity against coryneform bacteria (12 species tested) but not against unrelated gram-positive (3) and gram-negative (3) bacteria, while its action on bacteria with no quite known relatedness to the coryneform group (14) was found to be variable. Glutamicin CBII was partially purified by precipitation with ammonium sulphate (70% saturation), selective heat precipitation and gel chromatography on Sepadex G-50. The antibacterial substance diffused through cellophane membrane with an approximate cut-off of 10000 dalton and its sedimentation coefficient was determined to be 1.1. S by ultracentrifugation. Heating at 100°C for 30 min had no effect on its activity. Glutamicin CBII was proved to be resistant to chloroform, trypsin, chymotrypsin, pronase, and subtilisin. According to its staining behaviour and ¹H NMR spectra it probably represents a glycoprotein containing only a minor protein component.

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一种新病毒——兔出血症病毒的鉴定初报

从我国新发生的一种家兔急性败血性传染病死兔内脏抽提物中,观察到典型的病毒粒子,回归兔可引起典型发病,再从病死兔内脏回收到同样病毒,证明该病系病毒性传染病,暂定名为“兔病毒性出血症”,病原暂定为“兔出血症病毒”。经初步鉴定,认为本病毒可能是一种首次发现的新病毒,属双股RNA病毒。但从病毒大小和核酸节段看,又不同于呼肠病毒科。最终归属正在进一步研究。     

百日咳杆菌去内毒素及保护性抗原的纯化

内毒素(Endotoxin,简称ET)是百日咳全菌苗(Bordetellapertussis vaccine)产生副作用的主要毒素之一,且不易除去。现有的分离方法,如蔗糖密度梯度离心法,较繁琐,成本高。本文采用Sepha-cryl S-300凝胶层折法可以简便有效的去除大部分内毒素。初步毒素试验结果表明:已达到日本生物制品规格的要求。两种保护性抗原FHA和LPF-HA也得到进一步分离纯化,为今后研制高效的百日咳组分菌苗提供了实验条件。     

Seasonal changes in the photosynthetic response ofMercurialis perennis plants from different light regime conditions

Curves relating net photosynthetic rate to irradiance [P(I) curve relation] were estimated and analysed inMercurialis perennis L. plants stemming from three forest (spruce, beech and ash) stands with different tree leaf canopy development and different light regime. The saturating irradiance (I_s) reached the highest values in plants of all three stands in spring (spruce forest: 438 W m⁻², beech forest: 440 W m⁻² and ash forest: 367 W m⁻²), it declined sharply in the middle of the growing season (283, 285 and 297 W m^-2, respectively) and this I_s level persisted until autumn. A pronounced dynamics in plants from spruce and beech forests made itself manifest also in the adaptation (I_a) and compensating (I_c) irradiances, respectively. After a sudden decline in summer, values in autumn were close to those of the vernal season. The most pronounced parameter, which optimally expressed the adaptation ofMercurialis perennis to various light conditions, was the photosynthetic efficiency (α) calculated as the slope of the linear part of the curve relating net photosynthetic rate to irradiance. At the time of the highest P_{N sat.} value in course of the growing season (August) (spruce forest: 100, beech forest: 98.7 and ash forest: 85.8 μg CO₂ m⁻² s⁻¹), R_D was in its minimum; in autumn P_{N sat.} reached the lowest values which corresponded to the most intensive R_D. It was found thatMercurialis perennis plants stemming from forest stands with different light conditions did not make use equally of the altering light conditions in the course of the growing season. By the underlying analysis of P(I) curves this rhizomatous perennial herb (geophyte) may be characterized as a shade tolerant species.     

Effect of lysosomotropic amines on the secretory pathway and on the recycling of the asialoglycoprotein receptor in human hepatoma cells

We studied the intracellular transport of secretory and membrane proteins in the human hepatoma cell line HepG-2 infected with vesicular stomatitis virus. Cells were pulse-labeled in the presence of [35S]methionine and chased in the presence of the lysosomotropic agent primaquine. At a concentration of 0.3 mM primaquine effectively inhibited the secretion of albumin and, to a lesser extent, that of orosomucoid and transferrin. The drug also prevented the budding of virus particles at the cell surface. The intracellular transport to the Golgi complex of the membrane protein VSV-G was not affected by primaquine as it acquires resistance to endo-beta-N-acetylglucosaminidase H at the same rate as in control cells. Addition of primaquine at various times after the initiation of the chase period indicates that the effect of primaquine occurs just before secretion. In confirmation of the biochemical data, immunocytochemical localization of albumin in cells treated with NH4Cl demonstrated that albumin accumulated in vesicles at the trans side of the Golgi complex. The effect of primaquine on secretion was also compared with its effect on receptor recycling. The dose-response characteristics of the effect of primaquine on receptor recycling are identical to those of the effects on protein secretion and virus budding. These results indicate that both processes involve the same transport mechanism, and/or that they occur via at least one identical intracellular compartment.