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141.
A rapid coliphage analysis technique for enumerating coliphages in natural waters has been evaluated by water quality laboratories located throughout the United States. Correlations were established between coliphages and coliforms in natural water systems. These correlations were highly significant. This relationship can thus be used to determine the number of fecal or total coliforms present in natural water samples based on an enumeration of coliphages. With this method, coliphages in natural water systems (containing greater than or equal to six coliphages per 100 ml) can be enumerated within 6 h. 相似文献
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147.
Plasma lipoproteins promote the release of bacterial lipopolysaccharide from the monocyte cell surface 总被引:11,自引:0,他引:11
Kitchens RL Wolfbauer G Albers JJ Munford RS 《The Journal of biological chemistry》1999,274(48):34116-34122
When bacterial lipopolysaccharide (LPS) enters the bloodstream, it is thought to have two general fates. If LPS binds to circulating leukocytes, it triggers innate host defense mechanisms and often elicits toxic reactions. If instead LPS binds to plasma lipoproteins, its bioactivity is largely neutralized. This study shows that lipoproteins can also take up LPS that has first bound to leukocytes. When monocytes were loaded with [(3)H]LPS and then incubated in plasma, they released over 70% of the cell-associated [(3)H]LPS into lipoproteins (predominantly high density lipoprotein), whereas in serum-free medium the [(3)H]LPS remained tightly associated with the cells. The transfer reaction could be reproduced in the presence of pure native lipoproteins or reconstituted high density lipoprotein. Plasma immunodepletion experiments and experiments using recombinant LPS transfer proteins revealed that soluble CD14 significantly enhances LPS release from the cells, high concentrations of LPS-binding protein have a modest effect, and phospholipid transfer protein is unable to facilitate LPS release. Essentially all of the LPS on the monocyte cell surface can be released. Lipoprotein-mediated LPS release was accompanied by a reduction in several cellular responses to the LPS, suggesting that the movement of LPS from leukocytes into lipoproteins may attenuate host responses to LPS in vivo. 相似文献
148.
Interlimb Coordination During Locomotion 总被引:1,自引:0,他引:1
SYNOPSIS. Studies of interlimb control during cat locomotionare directed at four different levels of organization. Interlimbstepping patterns are described from studies of the timing ofelectromyographic activity of muscles of different limbs. Patternsof coordination are based on the frequency of occurrence ofthe phasing of step cycles of the different limbs. Selectivespinal cord lesions are used to perturb those patterns of coordinationand have implicated two ascending spinal systems in interlimbcontrol: long ascending propriospinal neurons (LAPNs) and neuronsof the ventral spinocerebellar tract (VSCT). The results ofneuroanatomical tract tracing experiments indicate that twodifferent populations of LAPNs exist which might provide directconnection between cervical and lumbosacral locomotor centersbut that neurons of the VSCT do not make such connections. Theseresults imply that the role of the VSCT in interlimb controlis by way of the cerebellum. Unit recordings made from axonsof the VSCT during treadmill locomotion are consistent withthe VSCT carrying information about the timing of both hindlimbstep cycles. 相似文献
149.
Evidence from nuclear sequences that invariable sites should be considered when sequence divergence is calculated 总被引:3,自引:1,他引:2
It has long been known, from the distribution of multiple amino acid
replacements, that not all amino acids of a sequence are replaceable. More
recently, the phenomenon was observed at the nucleotide level in
mitochondrial DNA even after allowing for different rates of transition and
transversion substitutions. We have extended the search to globin gene
sequences from various organisms, with the following results: (1) Nearly
every data set showed evidence of invariable nucleotide positions. (2) In
all data sets, substitution rates of transversions and transitions were
never in the ratio of 2/1, and rarely was the ratio even constant. (3) Only
rarely (e.g., the third codon position of beta hemoglobins) was it possible
to fit the data set solely by making allowance for the number of invariable
positions and for the relative rates of transversion and transition
substitutions. (4) For one data set (the second codon position of beta
hemoglobins) we were able to simulate the observed data by making the
allowance in (3) and having the set of covariotides (concomitantly variable
nucleotides) be small in number and be turned over in a stochastic manner
with a probability that was appreciable. (5) The fit in the latter case
suggests, if the assumptions are correct and at all common, that current
procedures for estimating the total number of nucleotide substitutions in
two genes since their divergence from their common ancestor could be low by
as much as an order of magnitude. (6) The fact that only a small fraction
of the nucleotide positions differ is no guarantee that one is not
seriously underestimating the total amount of divergence (substitutions).
(7) Most data sets are so heterogeneous in their number of transition and
transversion differences that none of the current models of nucleotide
substitution seem to fit them even after (a) segregation of coding from
noncoding sequences and (b) splitting of the codon into three subsets by
codon position. (8) These frequently occurring problems cannot be seen
unless several reasonably divergent orthologous genes are examined
together.
相似文献
150.
Upregulation of hepatic prolactin receptor gene expression by 17beta-estradiol following trauma-hemorrhage. 总被引:1,自引:0,他引:1
Yukihiro Yokoyama Williams C Kitchens Balazs Toth Martin G Schwacha Kirby I Bland Irshad H Chaudry 《Journal of applied physiology》2003,95(6):2530-2536
Although studies show protective effects of 17beta-estradiol (E2) or prolactin (PRL) treatment in male rats after trauma-hemorrhage (TH), the mechanism of the salutary effects of these agents remains unknown. Because E2 modulates PRL receptor (PRL-R) expression in the liver, we examined whether E2 treatment after T-H has any effects on hepatic PLR-R gene expression. Male Sprague-Dawley rats were subjected to trauma (i.e., 5-cm midline laparotomy) and hemorrhage (35-40 mmHg for 90 min) followed by fluid resuscitation (Ringer lactate) or sham operation and then treated with E2 (50 microg/kg body wt sc) or vehicle immediately before resuscitation. Liver samples were collected at 3 h thereafter, and PRL-R mRNA expression was determined by PCR. Liver expression of PRL-R short-form gene was unaffected by T-H, whereas that of the long-form gene was suppressed. Treatment of T-H rats with E2 significantly increased PRL-R short-form gene expression and normalized PRL-R long-form gene expression to sham levels. In the isolated hepatocytes, PRL-R short-form gene expression was predominant compared with the long-form gene. In contrast, only the short form was detected in Kupffer cells. In vitro treatment by E2 demonstrated an increase in the PRL-R long-form gene in hepatocytes, but E2 had no effect on PRL-R short-form gene expression in either the Kupffer cells or hepatocytes. Thus E2 treatment after T-H in males appears to directly upregulate PRL-R long-form gene expression in hepatocytes. However, the upregulation of the PRL-R short form might involve the interaction of multiple cell types in the liver. 相似文献