Mutagenic effects of streptomycin in chlamydomonas

Summary Growth of a green streptomycin-resistant strain of Chlamydomonas reinhardi on a sub-lethal concentration of streptomycin on agar led to the appearance of yellow mutant cells in almost every colony. The time of appearance of the mutants varied greatly among the 9 isolates studied, each of which was selected as a single colony after repeated cloning of the parental strain. 2 isolates gave rise to colonies which responded rapidly to streptomycin (class I), 2 isolates produced yellow sub-clones as papillae only after formation of normal green colonies (class II), and 2 isolates produced stable yellow sub-clones only after a second subculture on streptomycin-agar (class III). 3 isolates were mixtures of classes II and III.The evidence that these yellow mutants arose under the mutagenic action of streptomycin is discussed in relation to the alternative possibility of their selection by the drug from a pool of pre-existing mutants. The physiological and genetic effects of streptomycin upon chlorophyll formation in Chlamydomonas are compared with reported effects of the drug upon the green flagellate, Euglena gracilis.Dedicated with appreciation and affection to Professor Dr. E. G. Pringsheim on the occasion of his 80th birthday.     

Mutagenic activity in wastewater concentrates from dye plants.

Wastewater concentrates from the wastewater treatment systems of three dye plants were tested for mutagenic activity in Salmonella typhimurium TA98 and Escherichia coli WP2uvrA using a fluctuation assay. Concentrates were prepared by passing samples of wastewater (5-6 or 30 litres) through two porous resins (XAD-2 and XAD-7) in series. S. typhimurium in the presence of microsomal activation proved to be the more sensitive marker of mutagenicity. Mutagenic responses were observed in concentrates from all three plants tested. The results show that mutagenic activity was particularly high in the incoming waters and increased after active, biological treatment. Physico-chemical treatment may be effective in decreasing mutagenic activity, but only if appropriately used.     

Mutagenic action of heavy ions on Escherichia coli cells

Induction of direct mutations in the lactose operon of E. coli cells by gamma-radiation and accelerated heavy ions with different LET was studied. The experiments were performed with the wild-type PolA and LexA strains. A quadratic dependence of the mutation rate on the dose of different radiations for the wild-type strain and the PolA mutant was observed. However, different types of radiation showed different relative genetic effectivenesses (RGE). The dependence of RGE on LET for the wild-type and PolA strain has a maximum. A LexA strain showed much reduced mutation rates and a linear dose response. The RGE decreased with increasing LET of ionizing radiation.     

Mutagenic action of monochromatic UV radiation in the solar range on human cells

Mutations to ouabain resistance (selecting for base modifications at the co-dominant Na+K+-dependent ATP-ase locus) and thioguanine resistance (selecting for a wide range of genetic changes at the recessive hypoxanthine-guanine phosphoribosyl transferase locus) were measured in a repair-proficient human lymphoblastoid line with defined monochromatic radiations in the UVC (254 nm), UVB (302 nm, 313 nm), UVA (334 nm, 365 nm) and visible (405 nm) ranges. No mutations were detected at wavelengths in the range 334-405 nm. At 254 nm and 313 nm, both mutations to thioguanine resistance and survival were consistent with those expected from the relative levels of cyclobutane-type pyrimidine dimers induced. However, at 313 nm, the ratio of ouabain-resistant to thioguanine-resistant mutants is 10 times higher than at 254 nm, indicating that a unique type of pre-mutagenic base damage is induced at the longer wavelength. Radiation in the UVA (334 nm) range reduced the induction of mutations by a UVC (254 nm) wavelength at both mutation markers. These results suggest, first, that distinct types of biologically expressed genetic damage may be induced in the UVB region of sunlight and, second, that strong interactions may occur between the different wavelength regions of sunlight that can modify the expression of this genetic damage in human cells.     

Mutagenic effects of thioacetamide in Drosophila melanogaster

Thioacetamide, which is carcinogenic in mice and rats, has been reported as negative in Ames's test on Salmonella his⁻ with and without liver microsomal fraction (S 9 mix). Tests on Drosophila reported here showed a significant increase in sex-linked recessive lethals after treatment with thioacetamide, both after injection and after feeding of males.     

Cytogenetic effects induced by accelerated carbon ions with shielding

Our work aims to understand the effects of shielding on the induction of biological damage by heavy charged particles and to compare the shielding effects of different materials at the same LET from two aspects: the biological effectiveness including or not including secondary particles emitted at large angles and the biological effectiveness at different angles with respect to the beam direction. We designed and conducted biological experiments to determine the biological effectiveness of 200 MeV/u carbon ions after traversing different shielding materials (Lucite and aluminium). Whole blood samples, which were either attached to the shielding material (48 mm Lucite or 29 mm aluminium)or positioned at 300 cm away from it at different angles with respect to the beam axis, were exposed to carbon ion beams. For comparison, whole blood samples were exposed directly to 200 MeV/u carbon ions. Chromosomal aberrations in lymphocytes were scored. The results indicated that the biological effectiveness per unit dose was not significantly changed by 48 mm Lucite or 29 mm aluminium, and no significant differences were observed in lymphocytes attached to the target and in lymphocytes positioned at a distance of 300 cm away from the target, at 0o angle of the beam axis. However, when plotted as a function of the number of ions hitting the shielding target, the curves are separated and the shield increases the effectiveness per unit ion. The frequency of chromosomal aberrations at tilted angles behind 29 mm Al and 48 mm Lucite was almost the same. These lesions were considered to be caused by secondary particles due to the passage of particles through the shielding materials.     

入侵植物的生理生态特性对碳积累的影响

随着国际贸易的发展和人们交往的增加以及全球环境的变化,生物种类在全球扩散的机会也大大增加,从而为生物入侵创造了机会。生物入侵不仅给农林牧生产造成损失,而且具有长期的生态学效应。外来种的成功入侵不是其自身某一个特性决定的,而是其特性与新的生境综合作用的结果。外来入侵种生理生态特性的研究对其预测和防治具有重要的意义。目前对入侵种生理生态特性的研究较少。已有的研究表明,与本地种相比入侵种可能通过提高光合能力、资源利用率、表型可塑性、化感作用,以及降低繁殖成本等增加植株碳积累,促进其入侵。但并不是所有的入侵种都同时具有这些特性。生境不同限制性资源不同,入侵机制就不同。成功的入侵种应该能够高效地利用生境中的限制性资源,并且能够较快地调节自身的生理特性以适应波动的资源环境。     

Mutagenic effects of direct electric current

Mutagenic effect of direct electric current on sprouts of Vicia faba L. was detected. The effect manifested itself in increase in percentage of cells with chromosome aberrations in root meristem. The most considerable injuries are observed when root meristem contacts with the positive electrode during current passing. Typical peculiarity of mutagenic effect of current is appearance of dicentrics which exceed the control value 4 times. By the end of the first mitotic cycle, gradual reduction of percentage of injured cells, reaching the control value, is observed.     

Mutagenic and cytotoxic effects of acrylates

Increasing amount of fructose-1-phosphate aldolase activity in rat blood serum and induction of chromosomal aberrations in rat bone marrow cells were observed after injection of acrylamide. The cytotoxic activity of acrylamide in rat depended on the dose. Methylmethacrylate and butyl methacrylate demonstrated no such activity.     

大气二氧化碳浓度升高对植物的影响

现代人类的活动,特别是矿场燃料的大量使用和植被的破坏,导致大气CO2浓度持续上升。该文阐述了CO2浓度升高对植物的形态、生理、产量和品质,种群消长,群落组成,生态系统结构与功能的影响。     

大气中CO2浓度升高对植物的影响

大气中CO_2浓度升高以及由此所引起的温室效应已成为人们普遍关注的议题。在未来的世界里,CO_2浓度将持续上升。预计到21世纪中叶,CO_2浓度可能达到700ppm。一些试验结果表明;CO_2浓度升高对多数植物的个体生长发育有促进作用,其中包括种子的发芽率提高,幼苗生长加快,叶面积增大,根系数量增多,气孔数量减少,茎干生长轮加宽,开花期提早,种子产量提高等。但是,CO_2浓度升高对植物也有不利影响。在高CO_2浓度环境中,由于过量产生的碳水化合物在叶片中的积累和矿物质的不平衡,许多植物在生长后期生长缓慢或出现负增长;个体生长发育规律的变化将导致一些增长种群逐渐向衰退种群过渡;C_3类杂草的加速生长将引起农业欠收;群落结构与组成的变化将促使一些植物走向绝灭;植物残渣中碳氮比的改变将引起生态系统生产力的下降等。因此,对于今后大气中CO_2浓度升高的影响还要做大量的研究。     

Mutagenic effects of thioacetamide in Drosophila melanogaster.

Thioacetamide, which is carcinogenic in mice and rats, has been reported as negative in Ames's test on Salmonella his- with and without liver microsomal fraction (S 9 mix). Tests on Drosophila reported here showed a significant increase in sex-linked recessive lethals after treatment with thioacetamide, both after injection and after feeding of males.     

Microdosimetry near the trajectory of high-energy heavy ions

Single-event energy distributions were measured in a 1.3-micron-diameter site as a function of radial distance from the trajectory of high-energy iron ions having an energy of about 600 MeV/amu. It was found that beyond distances of a few micrometers the average lineal energy of the (mostly single) secondary electrons (delta rays) is of the order of 3 keV/micron. This is similar to the value found in a medium irradiated by 170-keV photons. The frequency-mean specific energy for delta rays occurring at large distances from the path of the primary ion exceeds the calculated (radial) absorbed dose by two orders of magnitude.     

Mutagenic activity of promutagens in plants: indirect evidence of their activation

This review summarizes data concerning mutagenic activity of promutagens in various plant in vivo assays. These data are compared with the present knowledge about the metabolism of xenobiotics and activation of promutagens in plants obtained by biochemical studies and by the separation of the activation process from the genetic endpoints assayed for the mutagenicity. The article documents a differential response of plant species in the endogenous transforming of various classes of promutagens into mutagens. Attention is devoted to the following types of promutagens: nitrosamines, polycyclic aromatic hydrocarbons and aromatic amines, aflatoxins, pyrrolizidine alkaloids, diallate, styrene, vinylchloride, ethanol, cycasin, nitrofurans, sodium azide, s-triazine herbicides, 1,2-dibromoethane and maleic hydrazide.