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11.
THE EFFECT OF TRYPSIN, CHYMOTRYPSIN, RIBONUCLEASE, AND DESOXYRIBONUCLEASE ON ACTIVE, INACTIVE, AND REVERSIBLY INACTIVATED MEGATHERIUM PHAGE 下载免费PDF全文
John H. Northrop With the Technical Assistance of Marie King 《The Journal of general physiology》1955,39(2):251-258
The effect of trypsin, chymotrypsin, and desoxyribonuclease on active, reversibly inactivated, and heat-inactivated B. megatherium phage, and on living and dead B. megatherium and B. coli has been determined. The results are summarized in Table I. 相似文献
12.
Habitat area and fragmentation are confounded in many ecological studies investigating fragmentation effects. We thus devised an innovative experiment founded on fractal neutral landscape models to disentangle the relative effects of habitat area and fragmentation on arthropod community patterns in red clover (Trifolium pratense). The conventional approach in experimental fragmentation studies is to adjust patch size and isolation to create different landscape patterns. We instead use fractal distributions to adjust the overall amount and fragmentation of habitat independently at the scale of the entire landscape, producing different patch properties. Although habitat area ultimately had a greater effect on arthropod abundance and diversity in this system, we found that fragmentation had a significant effect in clover landscapes with ≤40 % habitat. Landscapes at these lower habitat levels were dominated by edge cells, which had fewer arthropods and lower richness than interior cells. Fragmentation per se did not have a direct effect on local-scale diversity, however, as demonstrated by the lack of a broader landscape effect (in terms of total habitat area and fragmentation) on arthropods within habitat cells. Fragmentation—through the creation of edge habitat—thus had a strong indirect effect on morphospecies richness and abundance at the local scale. Although it has been suggested that fragmentation should be important at low habitat levels (≤20–30 %), we show that fragmentation per se is significant only at intermediate (40 %) levels of habitat, where edge effects were neither too great (as at lower levels of habitat) nor too weak (as at higher levels of habitat). 相似文献
13.
On the interrelations of the Na+-and Cl?-influxes in the pulmonate freshwater snailLymnaea stagnalis 总被引:1,自引:1,他引:0
N. D. de With R. C. van der Schors 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1982,148(1):131-135
Summary In the freshwater snailLymnaea stagnalis the influxes of Na+ and Cl– were studied at different external concentrations of these ions. The characteristies of the Na+- and Cl–-influxes are similar with respect to saturation kinetics,K
m (0.1 mM) and activation by low-salt adaptation. In short-term experiments the Na+- and Cl–-influxes are independent. Because of the counter-ions (H+ and HCO
3
–
) involved, this indicates a potential acid-base regulatory capacity. Low-salt adaptation, due to either Na+-or Cl–-depletion, activates both the Na+- and the Cl–-influx. It is suggested that under both conditions the number of active integumental pumps, involved in Na+- as well as in Cl–-uptake, is increased. 相似文献
14.
Erwin Reiling Martijn E. T. Dollé Sameh A. Youssef Moonsook Lee Bhawani Nagarajah Marianne Roodbergen Piet de With Alain de Bruin Jan H. Hoeijmakers Jan Vijg Harry van Steeg Paul Hasty 《PloS one》2014,9(4)
Ku80 and DNA-PKCS are both involved in the repair of double strand DNA breaks via the nonhomologous end joining (NHEJ) pathway. While ku80−/− mice exhibit a severely reduced lifespan and size, this phenotype is less pronounced in dna-pkcs−/− mice. However, these observations are based on independent studies with varying genetic backgrounds. Here, we generated ku80−/−, dna-pkcs−/− and double knock out mice in a C57Bl6/J*FVB F1 hybrid background and compared their lifespan, end of life pathology and mutation frequency in liver and spleen using a lacZ reporter. Our data confirm that inactivation of Ku80 and DNA-PKCS causes reduced lifespan and bodyweights, which is most severe in ku80−/− mice. All mutant mice exhibited a strong increase in lymphoma incidence as well as other aging-related pathology (skin epidermal and adnexal atrophy, trabacular bone reduction, kidney tubular anisokaryosis, and cortical and medullar atrophy) and severe lymphoid depletion. LacZ mutation frequency analysis did not show strong differences in mutation frequencies between knock out and wild type mice. The ku80−/− mice had the most severe phenotype and the Ku80-mutation was dominant over the DNA-PKCS-mutation. Presumably, the more severe degenerative effect of Ku80 inactivation on lifespan compared to DNA-PKCS inactivation is caused by additional functions of Ku80 or activity of free Ku70 since both Ku80 and DNA-PKCS are essential for NHEJ. 相似文献
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Henry A. Murray Jr. With the Assistance of Yetta Porosowsky. 《The Journal of general physiology》1926,9(6):781-788
1. The Arrhenius equation giving the relationship between the velocity of chemical reaction and temperature, was found suitable for the special case of the contraction rate of embryonic heart muscle fragments. 2. There was no constancy in the values of µ for the rate of contraction in culture, nor was the scattering evenly distributed around certain (more than one) points. 3. There seemed to be no correlation between µ and other functions such as the contraction rate, the site from which the piece was removed, the age of the embryo, etc. 相似文献
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A. E. Cohn A. E. Mirsky With the Assistance of Yetta Porosowsky. 《The Journal of general physiology》1929,12(3):463-468
We have studied by means of glass electrodes the hydrogen ion concentration of the blood of chicken embryos from 8 to 20 days. When plotted as a curve, the average data show that a constant change takes place in the measurement, being acid at the beginning of this period and becoming alkaline toward its end. The acid reaction we think was characteristic not only of the embryos of fowl, but of the fetuses of cats and indeed as Warburg has shown of rapidly growing tissue in general. We have suggested the possibility, though we have no data to substantiate the suggestion, that the hydrogen ion concentration may under conditions like these, seeing that the curve of change resembles that of oxygen consumption, be expressive of changes in the rate of metabolism. 相似文献
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Pedersen Morten Foldager Filbee-Dexter Karen Norderhaug Kjell Magnus Fredriksen Stein Frisk Nicolai Lond Fagerli Camilla With Wernberg Thomas 《Oecologia》2020,192(1):227-239
Oecologia - The production and fate of seaweed detritus is a major unknown in the global C-budget. Knowing the quantity of detritus produced, the form it takes (size) and its timing of delivery are... 相似文献