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排序方式: 共有319条查询结果,搜索用时 156 毫秒
1.
Willoughby de Broke Rudyard Kipling Hugh Elliot E. Ray Lankester Leonard Hill Laurence R. Philipps Wm. Arbuthnot Lane James Crichton-Browne H. Bryan Donkin Francis Lloyd R. A. Lyster John MacAlister F. W. Mott William Osler C. W. Saleeby J. H. Sequeira Humphry Rolleston Hugh Wansey Bayly 《BMJ (Clinical research ed.)》1919,2(3074):725
2.
3.
S K Cunningham S J Sequeira J Chambers A Heffernan T J McKenna 《Journal of steroid biochemistry》1988,31(1):125-130
We have demonstrated that conventional methods for measuring total urinary aldosterone (TUA) may markedly and inconsistently underestimate aldosterone output, since under the conditions usually employed (pH 1.0), the hydrolysis of aldosterone conjugates in urine is incomplete. The use of more acidic hydrolysis conditions (pH 0.2) overcomes this problem. However free aldosterone may be damaged at this pH. Therefore to accurately measure TUA output, it is necessary to isolate the undamaged aldosterone chromatographically and to correct for procedural losses based on the recovery of aldosterone tracer added to the urine prior to hydrolysis. We compared a number of laboratory estimates of aldosterone status (including urinary free aldosterone) with the 24-h urinary sodium output in normal subjects, since this provides a good bioassay of aldosterone. Sodium output correlated best with "optimised" 24 h TUA, i.e. hydrolysed at pH 0.2, (r = -0.589, P less than 0.001), and with plasma aldosterone (r = -0.504, P less than 0.005). Both aldosterone in random urine specimens and plasma renin activity correlated poorly with 24-h sodium output. Therefore, while the measurement of optimised TUA excretion provides the best index of aldosterone activity, assay of aldosterone in random specimens of plasma, which is more convenient for patient and laboratory, may be adequate for many clinical purposes. 相似文献
4.
Summary Adult size (in terms of dry weight; DW) and development time (T
p
) of the solitary parasitoidAphidius ervi varied when reared in different nymphal instars of its host, apterous virginoparae of the pea aphid (Acyrthosiphon pisum). Parasitoid DW increased with an increase in the DW of the host at parasitization, from the first to the third aphid instar. Female wasps gained 1.1 times more in DW than their male counterparts in all four host classes, butT
p
did not significantly differ between the sexes. Parasitoid DW was consistently more variable thanT
p
. The two traits covaried positively with an increase in host size from the first to the third instar, but they varied independently in parasitoids from fourth-instar hosts. The host size (and stage) at the time of parasitization imposes constraints on the growth and development of immatureA. ervi that are reflected in the pattern of covariation between DW andT
p
. When growing in aphids below a certain size threshold, parasitoids can maximize fitness by a trade-off between DW andT
p
. Consequently, the assumption implicit in host-size models of parasitoid oviposition decisions — that females incur a relatively greater reduction in size (used as an index of fecundity) than males when developing in poor quality hosts — can be falsified. 相似文献
5.
A suicide vector was constructed by cloning the transfer genes of the wide-host-range (IncW group) plasmid R388 into the BamHI site of pBR325. This plasmid can deliver Tn5 into Pseudomonas solanacearum at frequencies ranging from 10(-6) to 10(-9) per recipient. 相似文献
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8.
We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
9.
C Möller G Weber MM Dreyfuss 《Journal of industrial microbiology & biotechnology》1996,17(5-6):359-372
Intraspecific variation among 84 isolates of the anamorphic fungusChaunopycnis alba from 26 different geographical locations was analyzed by investigating optimal growth temperatures, differences in the production of secondary metabolites and presence or absence of the cyclosporin synthetase gene. The genetic diversity was assessed using random amplified polymorphic DNA (RAPD). Analysis of these data showed high genetic, metabolic and physiological diversity within this species. Isolates from the Antarctic represented the most homogeneous group withinC. alba and together with isolates from the Arctic these polar strains differed from alpine, temperate and tropical strains by low optimal growth temperatures and by low production of secondary metabolites. Isolates from tropical climes were characterized by high optimal growth temperatures and by the production of comparatively diverse metabolite spectra. Most of the isolates that were similar in the combination of their physiological and metabolic characters were also genetically related. Isolates from different geographical origins did not show many similarities, with the exception of the cyclosporin A-producing isolates, and large diversity could be observed even within a single habitat. This leads us to the suggestion that for pharmaceutical screening programs samples should be collected from a diversity of different geographical and climatic locations. For the selection of strains for screening the RAPD assay seems to be the most powerful tool. It reflected the highest intraspecific diversity and the results corresponded well with the other characteristics. 相似文献
10.
A gene cluster required for coordinated biosynthesis of lipopolysaccharide and extracellular polysaccharide also affects virulence of Pseudomonas solanacearum.
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Bacterial cell surface components can be important determinants of virulence. At least three gene clusters important for extracellular polysaccharide (EPS) biosynthesis have been previously identified in the plant pathogen Pseudomonas solanacearum. We have found that one of these gene clusters, named ops, is also required for lipopolysaccharide (LPS) biosynthesis. Mutations in any complementation unit of this cluster decreased EPS production, prevented the binding of an LPS-specific phage, and altered the mobility of purified LPS in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, restoration of LPS biosynthesis alone was not sufficient to restore virulence to the wild-type level, suggesting that EPS is important for pathogenesis. 相似文献