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1.
A Schmidt B Crisp D Krause R H Silverman R B Herberman J R Ortaldo 《Natural immunity and cell growth regulation》1987,6(1):19-27
Pretreatment of human large granular lymphocytes (LGL) or unseparated peripheral blood mononuclear cells with interferon (IFN) resulted in a significant augmentation of natural killer (NK) activity. This increase was paralleled by an increase in the 2'-5'A synthetase activity. In order to investigate the possibility that IFN might be inducing augmentation of NK cells via the 2'-5'A pathway, we tested the effects of nonphosphorylated core material [(A2'p)2A] and of the triphosphorylated form of the 2'-5'A [ppp(A2'p)2A]. The core material had no detectable effect on NK activity. In contrast, when experiments were performed with the triphosphorylated form of 2'-5'A, NK activity was stimulated. In order to achieve activation, permeabilization of LGL with calcium chloride was necessary and, under these conditions, a dose-dependent augmentation of NK activity was seen. However, the calcium treatment had considerable toxic effects on basal levels of NK activity. Collectively, these results suggest that IFN may be inducing augmentation of NK activity via the 2'-5'A pathway. Further studies will be necessary to determine the effects of IFN and/or 2'-5'A on subsequent activation steps in the process leading to cytotoxicity by NK cells. 相似文献
2.
D. T. Crisp 《Journal of fish biology》1993,43(4):656-658
Artificial redds were used to examine the effect of layers of sand at the gravel surface upon the emergence of trout and salmon. Alevins of both species can negotiate sand layers up to 8 cm thick. 相似文献
3.
mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species 总被引:4,自引:0,他引:4
Reconstructions of the human-African great ape phylogeny by using
mitochondrial DNA (mtDNA) have been subject to considerable debate. One
confounding factor may be the lack of data on intraspecific variation. To
test this hypothesis, we examined the effect of intraspecific mtDNA
diversity on the phylogenetic reconstruction of another Plio- Pleistocene
radiation of higher primates, the fascicularis group of macaque (Macaca)
monkey species. Fifteen endonucleases were used to identify 10 haplotypes
of 40-47 restriction sites in M. mulatta, which were compared with similar
data for the other members of this species group. Interpopulational,
intraspecific mtDNA diversity was large (0.5%- 4.5%), and estimates of
divergence time and branching order incorporating this variation were
substantially different from those based on single representatives of each
species. We conclude that intraspecific mtDNA diversity is substantial in
at least some primate species. Consequently, without prior information on
the extent of genetic diversity within a particular species, intraspecific
variation must be assessed and accounted for when reconstructing primate
phylogenies. Further, we question the reliability of hominoid mtDNA
phylogenies, based as they are on one or a few representatives of each
species, in an already depauperate superfamily of primates.
相似文献
4.
Four experimental stream channels were used to study instantaneous downstream dispersal rates of young trout, Salmo trutta L., and salmon, S. salur L ., relative to four different water velocities.
Young salmon showed a high rate of dispersal at a low velocity of 7.5 cm s−1 and lower rates at higher velocities of 25 to 70cm s−1 . Trout showed their lowest rate at 25cm s−1 with a slightly higher rate at 7.5 cm s−1 and increasingly higher rates at velocities in excess of 25 cm s−1 . These results are consistent with field observations on the velocity preferences of young trout and salmon. 相似文献
Young salmon showed a high rate of dispersal at a low velocity of 7.5 cm s
5.
The general practice partners invited two medical ethicists (RC and TH) to meet them to develop the document. The partners met RC and TH for one and a half hours on eight occasions over one year and met without them on eight further occasions. The entire general practice also had an all day session to discuss in detail an advanced version of the draft. The developmental process was of great value to the partnership and has led to appreciable change in individuals'' views. The draft policy presented here is intended to start the ball rolling, so that proper guidelines will be developed at whatever level in the NHS is most appropriate. Comments and feedback are welcomed. 相似文献
6.
Methods are presented for the electrophoresis and detection of various acid phosphohydrolases on Cellogel. Isozymes of acid DNase, RNase, 3′-phosphodiesterase, and nonspecific phosphodiesterase are readily detectable with these techniques. The enzymes studied were extracted from vertebrate spleens and leukocytes. 相似文献
7.
We have developed a rapid, sensitive, and specific zymogram for detecting ribonuclease (RNase). The method makes use of an agarose gel containing the small substrate UpA [uridylyl (3′ → 5′)-adenosine]. UpA is hydrolyzed by RNase to adenosine, which is deaminated by adenosine deaminase. The inosine so formed is linked by a series of enzymatic reactions (nucleoside phosphorylase, xanthine oxidase) to formation of a blue tetrazolium salt. This method is superior in that it entails a staining reaction only at sites of RNase activity (positive zymogram) rather than clearing of a background of RNA (negative zymogram), a process which is often mimicked by protein devoid of RNase activity. 相似文献
8.
The development of Pomatoleios kraussii is extremely similar to that of Pomatoceros triqueter , and is completed under laboratory conditions in 1–3 weeks at 25–27°C. Mature larvae settle and metamorphose preferentially on the shells of adult conspecifics. 相似文献
9.
The population dynamics of trout (Salmo trutta L.) were studied in two high-altitude streams flowing westwards into the River Eden in northern England. The results from one (Knock Ore Gill), which is accessible to spawners from downstream, were compared with published data from an isolated population in a nearby stream which flows eastward into the River Tees. The Knock Ore Gill trout had a population density of 0.4–0.9 fish m–2, a biomass of 12.4 g m–2, annual production of 12–14 g m–2 year–1 and an instantaneous mortality rate of 0.97 year–1. Comparable values from the Tees tributary were 0.2, 3.3, 2.3 and 0.66 respectively. The Knock Ore Gill population also contrasted with that of the Tees tributary in having reliable recruitment from year to year. These differences were related to differences in the chemistry and spate characteristics of the two streams and to the fact that immigrants from downstream were responsible for over 30% of the annual oviposition in Knock Ore Gill. 相似文献
10.
T R Pilkington J C Gazet L Ang R S Kalucy A H Crisp S Day 《BMJ (Clinical research ed.)》1976,1(6024):1504-1505
Twenty grossly obese patients underwent ileojejunal bypass operations. Measurements of calories lost in faeces showed that the malabsorption could not account for the weight loss. Furthermore, the malabsorption was not decreased two years after bypass, when weight was no longer being lost. Dietary restriction is therefore largely responsible for the weight loss and increased food intake for weight maintenance. 相似文献