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1.
The Effects of Light and Gravity on the Horizontal Curvature of Roots of Gravitropic and Agravitropic Arabidopsis thaliana L 总被引:4,自引:2,他引:2 下载免费PDF全文
Mirza JI 《Plant physiology》1987,83(1):118-120
In an attempt to study and distinguish the effects of light and gravity on the direction of horizontal root growth, wild-type and an agravitropic mutant of Arabidopsis thaliana L., aux-1 were examined. The mutant aux-1 seedling roots are agravitropic but do respond to light, thus allowing the effects of light and gravity on roots to be studied separately. It is shown that in addition to the recognized negative phototropic and positive gravitropic responses of the root, there are also horizontal curvatures (clockwise or counterclockwise) induced by both unilateral light and gravity. The effects of light and gravity in inducing the horizontal curvature of roots are synergistic when both act in the same direction, and are antagonistic when acting in opposite directions. The results indicate that light and gravity interact to determine the direction and magnitude of the horizontal curvature of roots. 相似文献
2.
Free radical damage to cultured porcine aortic endothelial cells and lung fibroblasts: Modulation by culture conditions 总被引:5,自引:0,他引:5
Clark T. Bishop Zermeena Mirza James D. Crapo Bruce A. Freeman 《In vitro cellular & developmental biology. Plant》1985,21(4):229-236
Summary Culture conditions modulating cell damage from xanthine plus xanthine oxidase-derived partially reduced oxygen species were
studied. Porcine thoracic aorta endothelial cells and porcine lung fibroblasts were maintained in monolayer culture. Cells
were prelabeled with51Cr before xanthine plus xanthine oxidase exposure. Endothelial cells showed 30 to 100% more lysis than fibroblasts and thus
seemed more sensitive to this oxidant stress. The effect of cell culture age, as indicated by population doubling level (PDL),
was examined. Response of low PDL endothelial cells and fibroblasts subjected to oxidant stress was compared with the response
of PDL 15 cells. Both low PDL endothelial cells and fibroblasts responded differently to the lytic effect of xanthine oxidase-derived
free radicals than did higher PDL cells. Specific activities of the antioxidant enzymes catalase, managanese superoxide dismutase,
copper-zinc superoxide dismutase, glutathione peroxidase, and glucose-6-phosphate dehydrogenase were measured in both low
and high PDL fibroblasts and endothelial cells. Antioxidant enzyme specific activities could only partially explain the differences
in response to oxidant stress between fibroblasts and endothelial cells and between low and high PDL cells. Cell culture medium
composition modulated the rate of production, and relative proportions of xanthine plus xanthine oxidase-derived partially
reduced species of oxygen, i.e. superoxide, hydrogen peroxide, and hydroxyl radical. Serum content of medium was important
in modulating free radical generation; superoxide production rates decreased 32%, H2O2 became undetectable, and hydroxyl radical generation decreased 54% in the presence of 10% serum. The medium protein and iron
content also modulated free radical generation. The data suggest that cell culture media constituents, cell type, and cell
culture age greatly affect in vitro response of cells subjected to oxidant stress.
Research supported by American Lung Association Fellowship Training Grant and Research Training Grant, the R. J. Reynolds
Corporation, and National Institutes of Health Grants HL29784 and 1 HL 23805. 相似文献
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5.
Alycia C. R. Lackey Alyssa C. Murray Nadia A. Mirza Thomas H. Q. Powell 《Journal of evolutionary biology》2023,36(6):882-892
The pace of divergence and likelihood of speciation often depends on how and when different types of reproductive barriers evolve. Questions remain about how reproductive isolation evolves after initial divergence. We tested for the presence of sexual isolation (reduced mating between populations due to divergent mating preferences and traits) in Rhagoletis pomonella flies, a model system for incipient ecological speciation. We measured the strength of sexual isolation between two very recently diverged (~170 generations) sympatric populations, adapted to different host fruits (hawthorn and apple). We found that flies from both populations were more likely to mate within than between populations. Thus, sexual isolation may play an important role in reducing gene flow allowed by early-acting ecological barriers. We also tested how warmer temperatures predicted under climate change could alter sexual isolation and found that sexual isolation was markedly asymmetric under warmer temperatures – apple males and hawthorn females mated randomly while apple females and hawthorn males mated more within populations than between. Our findings provide a window into the early speciation process and the role of sexual isolation after initial ecological divergence, in addition to examining how environmental conditions could shape the likelihood of further divergence. 相似文献
6.
The influence on lipase induction in Mucor hiemalis of different types of triglycerides containing mainly oleic acid (olive oil), erucic acid (mustard oil), or saturated fatty acids of 8 to 16 carbons (coconut oil) was studied. The fungus was grown in shake flasks in a fermentation medium containing peptone, minerals, and glucose or one of the oils as the carbon source. Maximum lipase was produced when the initial pH of the fermentation medium was kept at 4.0. Addition of Ca2+ to the medium did not increase lipase production. The optimum pH for activity of both the mycelial and extracellular lipases was found to be 7.0. The fungus produced a significant amount of lipase in the presence of glucose, but the lipase activity increased markedly when olive oil was added to the medium at the beginning of the fermentation. Addition of olive oil at a later stage did not induce as much enzyme. Studies with washed mycelia showed that a greater amount of lipase was released when olive oil was present than when glucose was present. Among the various types of triglycerides used as the carbon source, olive oil was found to be most effective in inducing the lipase. Olive oil and mustard oil fatty acids inhibited the lipase more than those of coconut oil. The lipase induced by a particular type of triglyceride did not seem to be specific for the same triglyceride, nor was it inhibited specifically by it. Irrespective of the triglyceride used in the fermentation medium, the lipase produced was most active against coconut oil triglyceride, and this specificity, as shown by lipase activities in an n-heptane system, was not found to be due to a better emulsification of this oil. The lipase of M. hiemalis can be considered to be both constitutive and inducible. 相似文献
7.
印度地鼠的性成熟和窝仔数 总被引:1,自引:0,他引:1
Rubina ARSHAD 《动物学报》2004,50(5):723-729
为有效地进行有害脊椎动物的控制 ,研究了栖息于巴基斯坦Punjab中部的 348只印度地鼠的繁殖模式。在所捕捉到的 10 7雄鼠和 2 4 1只雌鼠中 ,分别有 75只和 179只是性成熟的个体。性比偏雌。使用被捕个体标本的体重和体长作为指标 ,发现最小的性成熟的雄性个体体重为 70 - 89g ,体长 13 1- 14 0cm ;一窝仔里面的平均胚胎数为 2 74± 0 15 (范围 ,1- 5 ) ,而平均胎斑数为 4 2 9± 0 19(1- 11) .体重似乎对窝仔数有显著影响 ,而体长和估计的年龄对窝仔数没影响。当老鼠繁殖不活跃和不繁殖时 ,控制害兽最有效 相似文献
8.
Elicitor-induced hydroxycinnamoyl-CoA:tyramine hydroxycinnamoyltransferase in plant cell suspension cultures 总被引:4,自引:0,他引:4
Treatment of Nicotiana glutinosa L. cell suspension cultures with chitosan results in the co-induction of phenylalanine ammonia lyase, 4-eoumarate:CoA ligase, tyrosine decarboxylase and tyramine hydroxycinnamoyltransferase, all involved in the biosynthesis of hydroxycinnamoyltyramines. The highest enzyme activities were observed around 12 h after addition of 0.8 to 1 mg chitosan per g fresh weight of cells. No hydroxycinnamoyltyramines could be detected by TLC or HPLC of extracts made from non-treated or elicited cells. [14 C]-Tyramine was incorporated into insoluble polymeric material at a higher rate in elicitor-treated than in non-treated cells of N. glutinosa. Tyramine hydroxycinnamoyltransferase could be induced in suspension cultured cells of Eschscholtzia califortnca Cham, but not in cells of Phaseolus vulgaris L. or Catharanthus roseus (L.) G. Don by addition of a yeast elicitor to the growth medium. 相似文献
9.
Marian L. Kruzel Jeffrey K. Actor Michał Zimecki Jasen Wise Paulina Płoszaj Shaper Mirza Mark Kruzel Shen-An Hwang Xueqing Ba Istvan Boldogh 《Journal of biotechnology》2013
Lactoferrin, an iron-binding protein found in high concentrations in mammalian exocrine secretions, is an important component of the host defense system. It is also a major protein of the secondary granules of neutrophils from which is released upon activation. Due to its potential clinical utility, recombinant human lactoferrin (rhLF) has been produced in various eukaryotic expression systems; however, none of these are fully compatible with humans. Most of the biopharmaceuticals approved by the FDA for use in humans are produced in mammalian expression systems. The Chinese hamster ovary cells (CHO) have become the system of choice for proteins that require post-translational modifications, such as glycoproteins. 相似文献
10.
Farrukh Baig Mirza John S. Gray 《Journal of experimental marine biology and ecology》1981,54(2):181-207
The macrobenthic fauna of the organically enriched Oslofjord was sampled in Sept.–Nov. 1977. Seventy-six stations were sampled using a stratified random plan. A total of 146 species were identified, dominated by polychaetes, molluscs and echinoderms. The faunal data were analysed by a variety of methods including diversity indices, log-normal distribution of individuals among species, factor analysis and numerical classification. The primary aim was the detection of pollution-induced disturbance and to delimit the extent of pollution on the benthic fauna of Oslofjord. All of the methods used showed a gradient from heavy pollution at the innermost part of the fjord where few species occurred, together with high dominance and low diversity, to normal unpolluted conditions at the Drøbak sill with high species diversity. From the classification analysis a combination of both site and species data revealed a trend in species groupings which were broadly similar to data from other Scandinavian fjords and from Scotland. Hydrographical and biological data taken at the turn of the century and in the 1960's compared with the present data show declining conditions in Oslofjord, due primarily to organic enrichment combined with a naturally poor water exchange which leads to stagnation of the water mass. 相似文献