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101.
C Hoff W C James R B Hester P Nolan R D Peterson 《Human biology; an international record of research》1991,63(2):129-135
Twelve healthy, anal-receptive, homosexual Caucasian males who were seronegative for HIV antibody were typed for HLA-DR antigens. Flow cytometry was used to immunophenotype peripheral blood lymphocytes bearing the CD4, CD8, LEU7, and combined CD8 and LEU7 antigens. These individuals had reported a large number of sexual partners within a five-year period preceding this study. Each individual was assigned a score based on the Hardy-Weinberg frequency of their HLA-DR phenotype in the Caucasian population. The larger the value of this score, the more common the HLA-DR phenotype, the smaller the score, the rarer the phenotype in the population at large. A significant inverse correlation was observed between this score and the proportion of lymphocytes with CD8 and LEU7 antigens. Lymphocytes bearing these two antigens have in vitro suppressor activity and are elevated in patients with human immunodeficiency virus (HIV) infection. The inverse association between CD8+/LEU7+ cells and frequency of HLA-DR phenotypes is consistent with the hypothesis that individuals with rarer phenotypes whose partners are drawn from the population at large are more likely to be challenged during anal insemination, which results in immunosuppression (alloantigenic challenge hypothesis). On the other hand, it is possible that an association exists between certain HLA-DR phenotypes and immune status. Although these observations were made in a very small sample, we believe that the strength of this association provides justification for further investigation into the possibility that alloantigenic challenge may increase the risk for infection, if exposed to HIV, and augment the immunosuppressive action of HIV once significant infection has occurred. 相似文献
102.
S E Guggino J A Wagner A M Snowman L D Hester B Sacktor S H Snyder 《The Journal of biological chemistry》1988,263(21):10155-10161
(-)-[3H]Desmethoxyverapamil ((-)-DMV) binds saturably to homogenates of the osteoblast-like cell lines UMR 106 and ROS 17/2.8 with KD values of 45 and 61 nM and Bmax values of 6.0 and 5 pmol/mg protein, respectively. Binding is stereoselective with (-)-DMV 8-10 times more potent than (+)-DMV. None of the dihydropyridine or benzothiazepine Ca2+ antagonists examined affect (-)-[3H]DMV binding. Monovalent cations such as Li+, Na+, and K+ inhibit (-)[3H]DMV binding in the 100-400 mM range. Divalent cations such as Ba2+, Sr2+, Ca2+, and Mg2+ are effective binding inhibitors in the 2-5 mM range. ROS 17/2.8 cells express a channel on the apical plasma membrane which conducts Ba2+ and Ca2+. With 110 mM BaCl2 or CaCl2 as charge carriers the single channel conductance is 3-5 picosiemens. In cell-excised patches the channel selects for Ba2+ over Na+ 3.3:1. In the absence of divalent ions the channel conducts Na+ ions with a single channel conductance of 13 picosiemens. This Na+ conductance decreases with physiological levels of Ca2+. The channel appears related to the (-)-[3H]DMV binding site, since its conductance is blocked by verapamil in a dose-dependent manner. Moreover, DMV blocks the channel stereoselectively with relative potencies of the isomers corresponding to their affinities for the binding site. The dihydropyridine drugs BAY K 8644 or (+)-202-791 do not affect channel opening. These binding and biophysical data indicate that osteoblast cells have a phenylalkylamine receptor associated with a Ca2+ channel. 相似文献
103.
Unaltered Nodulation Competitiveness of a Strain of Bradyrhizobium sp. (Lotus) after a Decade in Soil 总被引:2,自引:2,他引:0
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A Bradyrhizobium sp. (Lotus) strain that formed a soil population that was highly competitive for nodulation of Lotus pedunculatus 11 years after its introduction into a field soil and a culture of the same strain stored lyophilized were compared with an antibiotic-resistant mutant in respect of their nodulation competitiveness. The mutant was less competitive than the wild-type strain it was isolated from and had to be present at a cell ratio of 5.76:1 in mixed inoculum in sand culture to form 50% of the nodules on L. pedunculatus (50% nodulation value, 5.76). The 50% nodulation values for a soil population of the mutant mixed with soil populations of the lyophilized and field soil strain were, respectively, 6.83 and 5.77, indicating that the field soil strain was not significantly different from the lyophilized strain in nodulation competitiveness. A 50% nodulation value of 11.18 obtained when soil containing a recently established mutant population was mixed with the field soil containing the population established 11 years before, indicating that the plant infection technique underestimated cell numbers of the field soil population by 100%. Nodulation competitiveness was unaffected by the size of the strain populations in the range of 100 to 1,000 cells per g of soil; at 10 cells per g a significant correlation between strain ratios in nodules and in soil was still evident. The results indicated that apparently superior nodulation competitiveness of a well-established soil population relative to that of a subsequently introduced strain may not necessarily reflect the intrinsic competitive abilites of the strain(s) involved. The soil strain did not differ from laboratory-maintained cultures in antigenic properties, effectiveness, or whole cell protein electrophoresis profiles. 相似文献
104.
The use of stacked polyurethane-covered mammary implants has proven useful in improving results in the correction of deficiencies of mammary form and projection that can occur in certain cases of congenital and acquired breast deformity. The method has been used in 57 patients (102 breasts). The rate of significant complications, including seroma, rash, infection, hematoma, and capsular contracture, has been low (1 to 6 percent). Polyurethane-covered implants will maintain their position when used in a stacked system because of their unique biophysical characteristics, which include tissue bonding and a high friction coefficient between the implant surfaces. 相似文献
105.
106.
A new positional isotope exchange method has been developed that can be used for the analysis of enzyme-catalyzed reactions which have ping-pong kinetic mechanisms. The technique can be used to measure the relative rates of ligand dissociation from enzyme-product complexes. Enzyme is incubated with the labeled substrate and an excess of the corresponding unlabeled product. The partitioning of the enzyme-product complex back toward free enzyme is determined from the rate of positional isotope exchange within the original labeled substrate. The partitioning of the enzyme-product complex forward toward free enzyme is determined from the rate of formation of totally unlabeled substrate. It has been shown that the ratio of the two rates provides a lower limit for the release of product from the enzyme-product complex. The technique has been applied to the reaction catalyzed by galactose-1-phosphate uridyltransferase. The lower limit for the release of glucose 1-phosphate from the uridyl-enzyme relative to the maximal velocity of the reverse reaction was determined to be 3.4 +/- 0.5. 相似文献
107.
N W S Hester 《BMJ (Clinical research ed.)》1984,289(6451):1074-1075
108.
109.
Roxana T. Shafiee Joseph T. Snow Svenja Hester Qiong Zhang Rosalind E. M. Rickaby 《Environmental microbiology》2022,24(2):835-849
Dissolved iron (Fe) is vanishingly low in the oceans, with ecological success conferred to microorganisms that can restructure their biochemistry to maintain high growth rates during Fe scarcity. Chemolithoautotrophic ammonia-oxidising archaea (AOA) are highly abundant in the oceans, constituting ~30% of cells below the photic zone. Here we examine the proteomic response of the AOA isolate Nitrosopumilus maritimus to growth-limiting Fe concentrations. Under Fe limitation, we observed a significant reduction in the intensity of Fe-dense ferredoxins associated with respiratory complex I whilst complex III and IV proteins with more central roles in the electron transport chain remain unchanged. We concomitantly observed an increase in the intensity of Fe-free functional alternatives such as flavodoxin and plastocyanin, thioredoxin and alkyl hydroperoxide which are known to mediate electron transport and reactive oxygen species detoxification, respectively. Under Fe limitation, we found a marked increase in the intensity of the ABC phosphonate transport system (Phn), highlighting an intriguing link between Fe and P cycling in N. maritimus. We hypothesise that an elevated uptake of exogenous phosphonates under Fe limitation may either supplement N. maritimus' endogenous methylphosphonate biosynthesis pathway - which requires Fe - or enhance the production of phosphonate-containing exopolysaccharides known to efficiently bind environmental Fe. 相似文献
110.
Thérèse S Lapperre Jacob K Sont Annemarie van Schadewijk Margot ME Gosman Dirkje S Postma Ingeborg M Bajema Wim Timens Thais Mauad Pieter S Hiemstra 《Respiratory research》2007,8(1):85-9