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51.
We labeled the DNA of Chinese hamster lung V79 cells with 125I in the form of iododeoxyuridine and subsequently measured the elution of the DNA through polycarbonate filters at pH 9.6 and pH 7.2. Since decay of incorporated 125I produces predominantly double-strand breaks (DSB) in DNA at a rate close to one DSB per 125I decay, this measurement provides an absolute calibration for the assay of DSBs by neutral filter elution. Neutral elution profiles are not first order with respect to elution time; thus we have examined the relationships between accumulated 125I decays and several functions of retention of DNA on the filter at various times during the elution process. At both pH 9.6 and pH 7.2 there were linear relationships between accumulated decays and certain retention functions. The retention function most closely correlated to 125I decays for both pH values was the logarithm of the ratio of the retention of control DNA to that of 125I-labeled DNA, both evaluated at the 9th fraction (13.5 h of elution). The linear relationship between this ratio and 125I decays allows DSB induction to be determined directly from retention values. The calibration was used to measure DSBs induced by X rays. 相似文献
52.
53.
Guillermo Ortega Diego A. Golombek Dino Otero Lilia Romanelli Daniel P. Cardinali 《Chronobiology international》1992,9(2):137-147
The two-oscillator model of human circadian rhythmicity was analyzed when a zeitgeber relative intensity of 1, 0.5, or 0.1 was introduced into the equations. Fourier analysis was compared with dynamic analysis such as attractor reconstruction or Liapunov exponent calculation. After a 50 or 90% reduction in zeitgeber intensity, the dynamics of the system became equivalent and differed significantly from those of a system with maximal zeitgeber intensity. When 10% aleatory noise was added to the data, the analysis was still applicable, and the results obtained were essentially the same as in the absence of noise. Dynamic analysis could thus provide a distinct classification for periodic data, based on the type of analysis. 相似文献
54.
55.
R. R. Hill Jr. F. L. Kolb H. G. Marshall 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1991,81(1):79-82
Summary Parameters estimated from a Gardner-Eberhart analysis of the F2 generation of a six-parent diallel in oats (Avena sativa L.) were used to compare methods for predicting the performance of F3 row plots. The prediction methods were: (1) individual F2 plant performance (F2I), (2) parent average plus F2 plot deviations (PF2), (3) parent average plus weighted F2 plot deviations (PF2P), (4) best linear unbiased prediction (BLUP) of parent average plus F2 plot deviations (BPF2), and (5) BLUP plus weighted F2 deviations (BF2). The F2 single-plant traits used for prediction were biological yield to predict F3 biological yield, whole plant and primary tiller grain yield for prediction of F3 grain yield, and whole plant and primary tiller harvest index (HI) to predict F3 HI. Prediction methods were evaluated by correlations between predicted and observed F3 performance. Prediction methods and traits for which correlations were greater than for F2I included: BF2 for biological yield, PF2, PF2P and BF2 for whole plant grain yield, PF2, BPF2, and BF2 for primary tiller grain yield. None had a correlation significantly greater than F2I for either measure of HI, where heritability was large. PF2 is the recommended method for traits with low heritability because of its simplicity and because it had the largest or nearly the largest correlation for each of the yield traits. F2I is the recommended method for traits with larger heritability.Contribution No. 8821 of the U.S. Regional Pasture Research LaboratoryDeceased 相似文献
56.
Cecilia Zazueta José A. Holguín Jorge Ramírez 《Journal of bioenergetics and biomembranes》1991,23(6):889-902
We describe a calcium transport that is sensitive to ruthenium red in liposomes reconstituted with mitochondrial extracts. This system is able to build an internally negative membrane potential, which allows the electrogenic influx of Ca2+ and Sr2+. Proteins with molecular weights higher than 35 kDa were incorporated to the vesicles, and enhanced the accumulation of the cation in an energy-dependent fashion. 相似文献
57.
Comparisons were made with human subjects of repellency of free flying Anopheles gambiae using soaps containing deet and permethrin or permethrin alone. The reduction in biting did not differ statistically significantly between these two forms of repellent soap. Some mosquitoes which touched the permethrin soap layer without biting died within the next day. The soap with deet was compared with the same amount of deet in a commercially available stick or as a liquid. Only in the latter form did the repellent show resistance to being washed off by cold water.Electrically heated vaporizing mats containing bio-allethrin were shown to be more effective than smouldering coils containing natural pyrethrins, in that there was more complete prevention of biting, and more rapid knock-down and kill. Operation of the vaporizing mat caused deposition of insecticide on the room surfaces. 相似文献
58.
The direct electrochemistry of redox proteins has been achieved at a variety of electrodes, including modified gold, pyrolytic graphite and metal oxides. Careful design of electrode surfaces and electrolyte conditions are required for the attainment of rapid and reversible protein-electrode interaction. The electron transfer reactions of more complex systems, such as redox enzymes, are now being examined. The 'well-behaved' electrochemistry of redox proteins can be usefully exploited by coupling the electrode reaction to enzymes for which the redox proteins act as cofactors. In systems where direct electron transfer is very slow, small electron carriers, or mediators, may be employed to enhance the rate of electron exchange with the electrode. The organometallic compound ferrocene and its derivatives have proved particularly effective in this role. A new generation of electrochemical biosensors employs ferrocene derivatives as mediators. 相似文献
59.
Effects of Chromosomal Inversion on Cell Fitness in Escherichia Coli K-12 总被引:14,自引:0,他引:14 下载免费PDF全文
In an effort to learn what factors might mitigate the establishment of Escherichia coli variants bearing major chromosomal rearrangements, we have examined the effects on cell growth of two inversions between rRNA operons. One of these inversions, IN(rrnD-rrnE), had been propagated in a commonly used subline of E. coli K-12 for approximately 30 yr before its discovery, a fact that illustrates the absence of obvious detrimental effects associated with the inversion. We found that culturing under conditions requiring repeated transition from stationary phase to rapid growth led to the replacement of IN(rrnD-rrnE) cells by cells that had undergone either of two types of additional chromosomal inversion: one type fully restored the wild-type order, while the other partially restored it. The partial reinversion was also between rrn operons, but it left a small transposition. The tendency for overgrowth by these revertants persisted through several rounds of periodic selection. In contrast, the other inversion, IN(rrnG-rrnE), was associated with severe, detrimental effects. The effects of IN(rrnG-rrnE) were also alleviated by full or partial reinversion. The probable relationship between the severity of the effects caused by the inversions and the degree of displacement of the replication origin is discussed. Spontaneous inversion events between rrn operons separated by 18% of the chromosome were estimated to occur at a frequency of roughly 10(-5). If extended to natural situations, the growth disadvantage together with the relatively high frequency of reinversion suggest that clones of cells with an inversion between these rrn operons would be readily overgrown by revertants. 相似文献
60.
Narrow- and Broad-Host-Range Symbiotic Plasmids of Rhizobium spp. Strains That Nodulate Phaseolus vulgaris 总被引:11,自引:4,他引:7 下载免费PDF全文
Susana Brom Esperanza Martinez Guillermo Dvila Rafael Palacios 《Applied microbiology》1988,54(5):1280-1283
Agrobacterium transconjugants containing symbiotic plasmids from different Rhizobium spp. strains that nodulate Phaseolus vulgaris were obtained. All transconjugants conserved the parental nodulation host range. Symbiotic (Sym) plasmids of Rhizobium strains isolated originally from P. vulgaris nodules, which had a broad nodulation host range, and single-copy nitrogenase genes conferred a Fix+ phenotype to the Agrobacterium transconjugants. A Fix− phenotype was obtained with Sym plasmids of strains isolated from P. vulgaris nodules that had a narrow host range and reiterated nif genes, as well as with Sym plasmids of strains isolated from other legumes that presented single nif genes and a broad nodulation host range. This indicates that different types of Sym plasmids can confer the ability to establish an effective symbiosis with P. vulgaris. 相似文献