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排序方式: 共有111条查询结果,搜索用时 31 毫秒
1.
Amidation of C3 at the thiolester site: stimulation of chemiluminescence and phagocytosis by a new inflammatory mediator 总被引:4,自引:0,他引:4
D L Gordon R A Krueger P G Quie M K Hostetter 《Journal of immunology (Baltimore, Md. : 1950)》1985,134(5):3339-3345
We studied the ability of particle-bound and fluid-phase C3b monomers and monomeric amidated C3 (prepared by treatment of purified human C3 with ammonium chloride or methylamine) to stimulate chemiluminescence of human polymorphonuclear leukocytes (PMN) and monocytes and to promote phagocytosis in the absence of antibody. Particle-bound C3b evoked chemiluminescence from both PMN and monocytes, and fluid-phase C3b (0.5 mg/ml) elicited significant chemiluminescence from PMN but not from monocytes. Amidated forms of C3, both particle bound and fluid phase, were potent stimulators of chemiluminescence from phagocytic cells and caused a significantly greater response than did C3b. The phagocytosis of 1-micron microspheres by PMN and monocytes was enhanced by coating them with purified C3b in an antibody-free system. Microspheres coated with amidated C3 were avidly phagocytized, and to a greater degree than were C3b-coated microspheres. In a direct binding assay with tritiated monomeric C3b and amidated C3, the affinity of the PMN complement receptor type 1 for C3b (Ka = 4.9 X 10(7) L/M) was similar to that for amidated C3 (Ka = 5.7 X 10(7) L/M). However, there was a fourfold increase in the number of apparent binding sites for amidated C3. This increase did not reflect binding of amidated C3 to the complement receptor type 3, because blocking of CR3 with the monoclonal antibody OKM 10 failed to decrease binding of amidated C3. In sites of increased ammoniagenesis, such as the kidney in chronic renal failure, amidated C3 may play a role as an inflammatory mediator by stimulating oxidative metabolism in phagocytic cells. 相似文献
2.
Emile CL. Marnette Harm Houweling Herman Van Dam Jan Willem Erisman 《Biogeochemistry》1993,23(2):119-144
The chemical composition of surface waters of two Dutch moorland pools and of incident precipitation, was monitored from 1982
to 1990. For this period, sulfur and water budgets were calculated using a hydrochemical model developed for well-mixed non-stratifying
lakes. Total atmospheric deposition of S decreased significantly after 1986 at both locations. A model describing the sulfur
budget in terms of input, output and reduction/oxidation processes predicted a fast decrease of pool water SO4
2− concentrations after a decrease of atmospheric input. However, SO4
2− concentrations in the surface water was lowered only slightly or remained constant. Apparently a source within the lake caused
the unexpectedly high SO4
2− concentrations. The possible supply of SO4
2− from the sediment through regulation by (K-)Al-SO4 containing minerals or desorption of SO4
2− from positively charged surfaces in the sediment was evaluated. Solubility calculations of pore water with respect to alunite,
basaluminite and jurbanite indicated that SO4
2− concentration was not regulated by these minerals. It is suggested here (1) that desorption of SO4
2− from peaty sediments may account for the estimated SO4
2− supply provided that the adsorption complex is periodically recharged by partial oxidation of the upper bottom sediments
and (2) that because of exposure of a part of the pool bottom to the atmosphere during dry summers and subsequent oxidation
of reduced S, the amount of SO4
2− may be provided which complements the decreasing depositional SO4
2− input. In future research these two mechanisms need to be investigated. 相似文献
3.
Initial Cu++ sorption by Cyclotella meneghiniana Kütz. (Cu++-sensitive) and Chlamydomonas reinhardtii Dangeard (Cu++-resistant) was rapid in the first 5 min of Cu++ incubation with little sorption after 2 h. On a cell to cell basis, Cyclotella sorbed ca. five times more Cu++ from the medium than Chlamydomonas. In MBL medium with EDTA Cyclotella and Chlamydomonas cells sorbed 21.0 and 4.41 nM Cu++/106 cells respectively in 6 h with 0.3 mg Cu++/l in the medium. Proportionally similar quantities of Cu++ were sorbed when the cells were Cu++ incubated in MBL + citrate or filtered lake water. Cleaned cell walls of Cyclotella sorbed little Cu++ (1.7 nM/106 cells) as compared to living cells (17.5 nM Cu++/106 cells) in 3 h. Therefore, in living Cyclotella most of the Cu++ taken up must be absorbed by the protoplasm or perhaps by the organic layer surrounding the silica wall. Cleaned cell walls of Chlamydomonas sorbed 3.5 nM Cu++/106 cells and living Chlamydomonas cells sorbed 2.6 nM Cu++/106 cells. This indicates that most of the Cu++ sorbed by Chlamydomonas cells remained bound to the cell wall and probably did not readily enter into the protoplasm: When placed in Cu++ free medium after Cu++ incubation, Cyclotella and Chlamydomonas cells released 46 and 59% respectively of the Cu++ sorbed. 相似文献
4.
Sulfate reduction and S-oxidation in a moorland pool sediment 总被引:3,自引:2,他引:1
In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO4
2– reduction rates in the sediment, (2) depletion of SO4
2– in the overlying water column and (3) release of35S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO4
2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core35SO4
2– injection. Rates of SO4
2– consumption in the overlying water were estimated by changes in SO4
2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m–2 d–1. Rates of SO4
2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m–2 d–1 (November) to 0.43–1.81 mmol m–2 d–1 (July, August and April). Maximum rates of oxidation to SO4
2– in July 1990 estimated by combination of SO4
2– reduction rates and rates of in situ SO4
2– uptake in the enclosed water column were 10.3 and 10.5 mmol m–2 d–1 at an organic rich and at a sandy site respectively.Experiments with35S2– and35SO4
2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO4
2– and (2) the presence of mainly non SO4
2–-S derived from reduced S transported from the sediment into the overlying water. A35S2– tracer experiment showed that about 7% of35S2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author 相似文献
5.
Linkage of bipolar affective disorders to markers on chromosome 11p is excluded in a second lateral extension of Amish pedigree 110. 总被引:2,自引:0,他引:2
D L Pauls D S Gerhard L G Lacy A M Hostetter C R Allen S D Bland M C LaBuda J A Egeland 《Genomics》1991,11(3):730-736
Linkage between markers on chromosome 11p and bipolar affective disorders can be excluded in a second large lateral extension of the original Amish Pedigree 110. These results, together with previous negative linkage findings, suggest that there is not one single gene on 11p conferring susceptibility for bipolar affective disorders among the Old Order Amish. 相似文献
6.
MARTIN CLÉMENT CAROLINE CHAMBERLAND JACQUELINE PÉRODIN RICHARD LEDUC GAÉTAN GUILLEMETTE EMANUEL ESCHER 《Journal of receptor and signal transduction research》2013,33(5-6):417-433
Several models of activation mechanisms were proposed for G protein-coupled receptors (GPCRs), yet no direct methods exist for their elucidation. The availability of constitutively active mutants has given an opportunity to study active receptor conformations within acceptable limits using models such as the angiotensin II type 1 (AT1)1 receptor mutant N111G-hAT1 which displays an important constitutive activity. Recently, by using methionine proximity assay, we showed for the hAT1 receptor that TMD III, VI, and VII form the ligand-binding pocket of the C-terminal amino acid of an antagonistic AngII analogue. In the present contribution, we investigated whether the same residues would also constitute the ligand-binding contacts in constitutively activated mutant (CAM) receptors. For this purpose, the same Met mutagenesis strategy was carried out on the N111G double mutants. Analysis of 43 receptors mutants in the N111G-hAT1 series, photolabeled and CNBr digested, showed that there were only subtle structural changes between the wt-receptor and its constitutively active form. 相似文献
7.
Rachel J. Derscheid Jack M. Gallup Cory J. Knudson Steven M. Varga Drew D. Grosz Albert van Geelen Shannon J. Hostetter Mark R. Ackermann 《PloS one》2013,8(12)
Respiratory syncytial virus (RSV) is the most frequent cause of bronchiolitis in infants and children worldwide. There are currently no licensed vaccines or effective antivirals. The lack of a vaccine is partly due to increased caution following the aftermath of a failed clinical trial of a formalin-inactivated RSV vaccine (FI-RSV) conducted in the 1960’s that led to enhanced disease, necessitating hospitalization of 80% of vaccine recipients and resulting in two fatalities. Perinatal lamb lungs are similar in size, structure and physiology to those of human infants and are susceptible to human strains of RSV that induce similar lesions as those observed in infected human infants. We sought to determine if perinatal lambs immunized with FI-RSV would develop key features of vaccine-enhanced disease. This was tested in colostrum-deprived lambs immunized at 3–5 days of age with FI-RSV followed two weeks later by RSV infection. The FI-RSV-vaccinated lambs exhibited several key features of RSV vaccine-enhanced disease, including reduced RSV titers in bronchoalveolar lavage fluid and lung, and increased infiltration of peribronchiolar and perivascular lymphocytes compared to lambs either undergoing an acute RSV infection or naïve controls; all features of RSV vaccine-enhanced disease. These results represent a first step proof-of-principle demonstration that the lamb can develop altered responses to RSV following FI-RSV vaccination. The lamb model may be useful for future mechanistic studies as well as the assessment of RSV vaccines designed for infants. 相似文献
8.
Oylum Erkus Victor CL de Jager Maciej Spus Ingrid J van Alen-Boerrigter Irma MH van Rijswijck Lucie Hazelwood Patrick WM Janssen Sacha AFT van Hijum Michiel Kleerebezem Eddy J Smid 《The ISME journal》2013,7(11):2126-2136
Maintenance of a high degree of biodiversity in homogeneous environments is poorly understood. A complex cheese starter culture with a long history of use was characterized as a model system to study simple microbial communities. Eight distinct genetic lineages were identified, encompassing two species: Lactococcus lactis and Leuconostoc mesenteroides. The genetic lineages were found to be collections of strains with variable plasmid content and phage sensitivities. Kill-the-winner hypothesis explaining the suppression of the fittest strains by density-dependent phage predation was operational at the strain level. This prevents the eradication of entire genetic lineages from the community during propagation regimes (back-slopping), stabilizing the genetic heterogeneity in the starter culture against environmental uncertainty. 相似文献
9.
At ceremonies held in Baltimore Maryland on May, 4, 2002, Dr. Howard A Pearson, Professor of Pediatrics, was awarded the John A. Howland award of the American Pediatric Society, probably the most prestigious award of American Pediatrics. Dr. Pearson had been nominated for the award by Dr. Norman Siegel. The Department of Pediatrics Grand Rounds on Wednesday noon, October 26, 2002 was originally scheduled as a repetition of the presentation by Dr. Siegel and the acceptance by Dr. Pearson for those who could not be in Baltimore. However; in a number of meetings, unknown to Dr. Siegel, it was unanimously decided that it would be very appropriate to instead honor him as he stepped down from his position as Vice- and Interim Chairman of Pediatrics, and to formally thank him for his long and faithful service to the Department of Pediatrics, the Yale University School of Medicine, and the Yale New Haven Hospital. 相似文献
10.