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排序方式: 共有480条查询结果,搜索用时 15 毫秒
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Recovery of a marker strain of Escherichia coli from ozonated water by membrane filtration. 总被引:3,自引:3,他引:0 下载免费PDF全文
Selective and nonselective growth media were evaluated at two incubation temperatures, 35 and 44.5 degrees C, for the recovery of a nalidixic acid-resistant marker strain of Escherichia coli ATCC 11775 by membrane filtration from ozonated 0.05 M phosphate buffer (pH 6.9). There were significantly fewer bacteria recovered with the standard m-FC agar when compared with the same growth medium prepared without bile salts and rosolic acid. This effect was particularly noticeable at the elevated incubation temperature of 44.5 degrees C. These findings are contrary to previous work which concluded that the standard American Public Health Association membrane filtration procedure is suitable for recovery of fecal coliform indicator bacteria from ozonated wastewater. 相似文献
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We examined the expression of platelet-derived growth factor (PDGF)-A and the PDGF alpha-receptor in pre-implantation and early post-implantation mouse embryos. At two-cell and blastocyst stages, all cells express mRNA and protein for both ligand and receptor. In contrast, early post-implantation embryos express PDGF-A chain mRNA in both embryonic ectoderm and in the ectoderm lining the ectoplacental cavity, while mRNA for PDGF alpha-receptor is localized to the mesoderm layers of both embryonic and extra-embryonic membranes. At days 3.5 and 7.5, receptors are demonstrably functional in response to exogenous PDGF-AA. We propose that chronic autostimulation of PDGF alpha-receptors occurs in pre-implantation embryos, whereas, following implantation, early mesoderm development is dependent on stimulation by ectodermally produced PDGF-A. 相似文献
6.
Evidence supporting the existence of a host cell surface receptor for Trypanosoma cruzi 总被引:3,自引:0,他引:3
Membrane fragments from trypomastigote forms of Trypanosoma cruzi inhibited the association of intact trypomastigotes with rat heart myoblasts whereas a similar preparation from non-invasive epimastigotes did not. Furthermore, killed trypomastigotes bound to the host cell surface and prevented the attachment of living organisms. Conversely, the extent of association of killed parasites with the host cells was reduced by the presence of living flagellates. These results suggest the presence of a distinct structure(s) on the surface of rat heart myoblasts to which infective forms of T. cruzi can bind. 相似文献
7.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
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Characterization of Gypsy Moth (Lymantria dispar) Nuclear Polyhedrosis Virus 总被引:1,自引:0,他引:1 下载免费PDF全文
Characterization of the proteins and nucleic acid of the gypsy moth nuclear polyhedrosis virus isolated in Ithaca, N.Y. (LdNPV-IT) is presented. A total of 29 viral structural proteins were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis when the virus was isolated in the absence of alkaline protease activity. Fourteen surface envelope viral proteins were identified by lactoperoxidase iodination. Eleven proteins were associated with nucleocapsids prepared by Nonidet P-40 detergent treatment. Distinct alterations of viral proteins were documented when virions were purified in the presence of occlusion body-associated alkaline protease(s). Restriction enzyme digests of viral DNA indicated that this isolate was composed of a large number of genetic variants. On the basis of the major molar fragments resulting from EcoRI, BamHI, BglII, and HindIII digests, the molecular weight of the LdNPV genome was approximately 88 × 106. 相似文献
9.
Baydur A.; Swank S. M.; Stiles C. M.; Sassoon C. S. 《Journal of applied physiology》1989,67(3):1024-1031
To evaluate the effects of abnormal respiratory mechanics and neuromuscular drive on the various components of elastic load compensation, we studied 16 anesthetized patients with kyphoscoliosis whose mean passive and active respiratory elastance (Ers and E'rs, respectively), active respiratory resistance, and peak inspiratory occlusion pressure were, respectively, 89, 84, 100, and 37% greater and inspiratory duration (TI) 13% less than corresponding values in 13 anesthetized controls. Ers comprised approximately 66% of effective elastance (E*rs) in both groups. E'rs, reflecting the role of the force-length properties of the active inspiratory muscles in increasing the internal impedance, comprised 83.8 and 86.1% of E*rs in the kyphoscoliosis patients and controls, respectively (P less than 0.001). This demonstrates the influence of increased intrinsic elastance and resistance and decreased TI on tidal volume defense in kyphoscoliosis patients in the absence of vagal modulation. In some patients the difference between Ers and E*rs was substantial, despite an unchanged or even shortened TI, suggesting that the Hering-Breuer reflex may affect stability through ways other than altering TI (e.g., via graded volume-dependent "terminal inhibition"). Characteristics of elastic load compensation in anesthetized kyphoscoliosis patients are similar to those of anesthetized normal subjects. 相似文献
10.
W W Barrington K A Jacobson G L Stiles 《The Journal of biological chemistry》1989,264(22):13157-13164
A1 adenosine receptor-binding subunits can be visualized using high affinity antagonist and agonist photoaffinity radioligands. In the present study, we examined whether agonists and antagonists bind to the same receptor-binding subunit and if agonists and antagonists induce different conformational states of the receptor in intact membranes. It was demonstrated that several agonist and antagonist photoaffinity receptor-binding subunit. When the agonist and antagonist photoaffinity labeled peptides were denatured and subjected to partial peptide map analysis using a two-dimensional gel electrophoresis system similar peptide fragments were generated from each specifically labeled protein. This suggests that both classes of ligand label and incorporate into the same binding subunit. Proteolytic digestions of agonist- and antagonist-occupied receptors in native intact membranes revealed distinct and different peptide fragments depending on whether the ligand was an agonist or an antagonist. Manipulation of incubation conditions to perturb ligand-receptor interactions alter the pattern of peptide fragments generated with each specific protease. These data suggest that agonist and antagonist photoaffinity probes interact with an incorporate into the same binding subunit but that agonist binding is associated with a unique and detectable receptor conformation. 相似文献