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排序方式: 共有317条查询结果,搜索用时 15 毫秒
1.
Tn5 insertion mutants of Pseudomonas aeruginosa deficient in surface expression of ferripyochelin-binding protein. 总被引:7,自引:3,他引:4 下载免费PDF全文
P A Sokol 《Journal of bacteriology》1987,169(7):3365-3368
Transposon (Tn5) insertion mutants were isolated in Pseudomonas aeruginosa PAO. These mutants were screened for expression of the ferripyochelin-binding protein with monoclonal antibody in a whole-cell immunoblot assay. Fourteen mutants were identified which did not express ferripyochelin-binding protein on the cell surface. These mutants did not take up 59Fe-labeled pyochelin and grew slowly in the presence of iron chelators. 相似文献
2.
The effect of several sulfhydryl-modifying reagents (HgCl2, p-chloromercuribenzenesulfonic acid (PCMBS), N-ethylmaleimide) on the renal organic anion exchanger was studied. The transport of p-amino[3H]hippurate, a prototypic organic anion, was examined employing brush-border membrane vesicles isolated from the outer cortex of canine kidneys. HgCl2, PCMBS and N-ethylmaleimide inactivated p-aminohippurate transport with IC50 values of 38, 78 and 190 microM. The rate of p-aminohippurate inactivation by N-ethylmaleimide followed apparent pseudo-first-order reaction kinetics. A replot of the data gave a linear relationship between the apparent rate constants and the N-ethylmaleimide concentration with a slope of 0.8. The data are consistent with a simple bimolecular reaction mechanism and imply that one molecule of N-ethylmaleimide inactivates one essential sulfhydryl group per active transport unit. Substrate (1 mM p-aminohippurate) affected the rate of the N-ethylmaleimide (1.3 mM) inactivation: the t1/2 values for inactivation in the presence and absence of p-aminohippurate were 7.4 and 3.7 min, respectively. The results demonstrate that there are essential sulfhydryl groups for organic anion transport in the brush-border membrane. Moreover, the ability of substrate to alter sulfhydryl reactivity suggests that the latter may play a dynamic role in the transport process. 相似文献
3.
Essential disulfide and sulfhydryl groups for organic cation transport in renal brush-border membranes 总被引:1,自引:0,他引:1
The disulfide reducing agent, dithiothreitol (DTT) and the sulfhydryl-modifying reagents p-chloromercuribenzenesulfonic acid and N-ethylmaleimide (NEM) were employed to assess the role of disulfide and sulfhydryl groups in organic cation transport. The transport of N1-[3H]methylnicotinamide (NMN), a prototypic organic cation, was examined employing brush-border membrane vesicles isolated from the outer cortex of canine kidneys. DTT inhibited NMN transport reversibly with an IC50 of 250 microM/mg of protein. 5 mM NMN protected against DTT inactivation. The specificity of substrate protection was demonstrated by showing that D-glucose had no effect on the DTT inactivation of NMN transport and conversely that NMN had no effect on the DTT inactivation of D-glucose transport. Disulfide bonds reduced by DTT could be reoxidized by washing with excess buffer or by addition of 0.02% H2O2 thereby restoring NMN transport. p-Chloromercuribenzenesulfonic acid reversibly inactivated NMN transport with an IC50 of 25 microM/mg of protein. 5mM NMN protected against inactivation. NEM irreversibly inactivated transport with an IC50 of 250 microM/mg of protein. The rate of NMN inactivation by NEM followed pseudo-first order reaction kinetics. A replot of the data gave a linear relationship between the apparent rate constants and the NEM concentration with a slope of 1.3. The data are consistent with a simple bimolecular reaction mechanism and imply that one molecule of NEM inactivates 1 sulfhydryl group/active transport unit. The presence of 5 mM NMN affected the rate of NEM (2.5 mM) inactivation: the t1/2 values for inactivation in the presence and absence of substrate were 7.3 and 2.0 min, respectively. The results demonstrate an essential requirement for disulfide and sulfhydryl groups. 相似文献
4.
Lead toxicity and the hypothalamic-pituitary-testicular axis 总被引:2,自引:0,他引:2
Environmental exposure to toxic levels of lead occurs in a number of industries with potential adverse effects on the reproductive capacity of exposed men. Clinical and animal studies indicate that abnormalities of spermatogenesis result from toxic lead exposure, but the pathogenetic mechanisms involved have not been identified. In order to ascertain what reproductive abnormalities occur in experimental animals when exposed to low levels of lead, 52-day-old animals were treated with water containing 0.0% (control), 0.1%, or 0.3% lead acetate for 30 days prior to killing. Whole blood serum lead levels were below detection (less than 7 micrograms/dl) in the control animals, 34 +/- 3 micrograms/dl in the 0.1% group, and 60 +/- 4 micrograms/dl in the 0.3% group (P less than 0.001). Significant negative correlations between whole blood lead levels and serum and intratesticular testosterone values were found (r = 0.64, P less than 0.001 and r = 0.6, P less than 0.001, respectively). As the level of lead exposure increased, intratesticular sperm counts significantly decreased (r = 0.81, P less than 0.001). No significant changes in serum luteinizing hormone (LH) values were found, but sperm follicle-stimulating hormone (FSH) values were significantly suppressed (P less than 0.05) after lead treatment. There was a significant decrease in ventral prostate weight (P less than 0.05), but no differences in testicular or seminal vesicle weights. Our data indicate that dietary exposure to lead resulting in whole blood serum lead values considered acceptable in the workplace (less than or equal to 40 micrograms/dl) causes inhibition of testicular function.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
5.
Morphometric methods have been used to analyse the ultrastructural characteristics of human blood monocytes in 20 normal adults. Data were obtained relating to whole cell, nucleus and mitochondria and, using a method not previously applied to blood cells, for the distribution of heterochromatin and euchromatin. The results provide a normal baseline against which monocyte changes in disease can be assessed. 相似文献
6.
Treatment of rabies virus with the nonionic detergent Nonidet P-40 resulted in solubilization of viral lipids and in a preferential release of the envelope glycoprotein. The other viral proteins and the viral ribonucleic acid remained associated in "core" particles sedimenting at a rate similar to that of intact virions. After fractionation of treated virus by velocity centrifugation in a sucrose density gradient, the amount of residual glycoprotein recovered in the "core" particle fraction and the extent of contamination of the glycoprotein fraction by other viral components were dependent on the ratio of detergent to viral protein used. 相似文献
7.
ИЗyчaл0C044A; Bлияниe НeкOTOpыX ФaкTopoB (pH, OTHoшeниe КpacиTeля к бeлкy, КOнпeнTpaция КOMпoнeнTOB, пpиcyTcTBиe opraничecкиX pacTBopиTeлeй B peaгиpyюшeй cмecи, TeMпepaTypa, Bpeмя peaкции) Ha эффeкTиBн0CTъ кOнъюгaции γ-глoбyлинa c флyopecцeинизOTиoциaнaTOM. КoличecTBO КpacиTeля, CBязaннoгo c γ-глoбyлинOM, знaч иTeлънO пoBышaлocъ, кoгдa пoBышaлcя B пpeдeлax 7,0–10,0pH peaгиpyющeй cмeCи, Toгдa кaк ocTaлъныe фaкTopы нe oкaзыBaли нa мeчeныe бeлки B иccлeдyeмыx пpeдeлax cyщecTBeннoгo Bлияния. БылO ycTaнOBлeнo, чTO cпeцифичecкaя флyopecцeнпия cBязaннoгo кpacиTeля зaмeTнo пoнижaлacъ c пOBышeниeм мeчeннOcTи бeлкOB, a пoэTOмy нaибoлee цeлecooбpaзным пpeдcTaBляeTCя иcпoлъзOBaниe для мeTOдa флyopecцeнTныx aнTиTeл-кOнъюгaTOB c BecoBым COOTнOшeниeм бeлкOB и кpacиTeля, paBным пpиблизиTeльнO 60. 相似文献
8.
Chronic intermittent hemodialysis may relieve some medical problems of terminal uremia (for example, azotemia, acidosis, hypertension, neuro-muscular disorders, bleeding, pericarditis) to such a degree that many patients are able to resume their normal activity. There remain, however, problems which are not readily changed by hemodialysis (anemia, peripheral neuropathy, pruritus, sexual impotence, renal osteodystrophy). These, together with medical problems possibly caused by hemodialysis (for example, osmotic disequilibrium, errors in dialysate composition, hepatitis, hemosiderosis, isoimmunization from blood transfusions, shunt problems and psychological problems of dependency upon the artificial kidney) represent a limitation of the present type of hemodialysis therapy. 相似文献
9.
10.
Nathalie Doerflinger Catherine Linder Karim Ouahchi Gabor Gyapay Jean Weissenbach Denis Le Paslier Philippe Rigault Samir Belal Christiane Ben Hamida Faycal Hentati Mongi Ben Hamida Massimo Pandolfo Stephano DiDonato Ronald Sokol Herbert Kayden Pierre Landrieu Alexandra Durr Alexis Brice Fran?oise Goutières Alfried Kohlschütter Pascal Sabouraud Ali Benomar Mohamed Yahyaoui Jean-Louis Mandel Michel Koenig 《American journal of human genetics》1995,56(5):1116-1124
Ataxia with vitamin E deficiency (AVED) is an autosomal recessive disease characterized clinically by neurological symptoms with often striking resemblance to those of Friedreich ataxia. This disorder has been reported previously as familial isolated vitamin E deficiency. We have mapped recently the AVED locus to a 5-cM confidence interval on chromosome 8q by homozygosity mapping in six Mediterranean families. We have now analyzed six new and two previously described families and demonstrate genetic homogeneity despite important clinical variability and wide geographic origins. Analysis of nine new tightly linked microsatellite markers, including four characterized in this study, revealed a predominant but not unique mutation in northern African populations, where this condition is more frequent. Haplotype analysis but also classical recombinations allowed us to refine the AVED position to a 1-cM interval. A YAC contig over this interval was constructed from marker STSs and YAC fingerprint data, in order to facilitate the search of the AVED gene. 相似文献