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The age-related loss of immune function, which is primarily due to loss of T-lymphocyte function, is also associated with accumulation in spleen lymphocytes of autofluorescent products indicative of peroxidation damage. In this study, we examined T-cell membranes for age-related changes which could be related to lipid peroxidation. Using fluorescence spectroscopy of CHCl3:CH3OH membrane extracts, we observed that old T-cells have a 2-fold greater accumulation of fluorescent products than old B-cells and that young T-cells, when exposed to free radicals in an in vitro system, accumulate significantly more fluorescent products over time than young B-cells. We used fluorescence polarization to show that young T-cell membranes are more fluid than young B-cell membranes. However, T-cell membrane fluidity decreases with age, whereas B-cell membrane fluidity does not change; in old mice, T-cell membranes are significantly less fluid than old B-cell membranes. Using two-dimensional electrophoresis, we showed that membrane extracts of old T-cells contain many more proteins than extracts of young T-cells. Our results indicate that age-related changes occur in T-cell membranes which could be due to their increased susceptibility to lipid peroxidation and these changes may contribute to the age-related decline in immune function. 相似文献
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A continuous nutrient flow system has been developed to measure microbial activity in soil with various concentrations of
added substrate. The system consists of a thin soil layer through which substrate was added continuously over periods up to
4.5 days. Substrate utilization was determined by effluent analysis. Respiration was measured manually by injecting a sample
into a gas chromatograph or automatically by coupling the growth chamber to a computer-controlled gas sampling valve. This
permitted respiratory CO2 to be measured by the gas chromatograph at intervals selected by the investigator. Software controlling the valve and gas
chromatograph not only automated gas phase sampling, but also provided a scan of CO2 evolution and a preliminary data summary. This included the date and time of sample, peak height, and percent CO2 in the gas phase. Data for growth on glucose using a microbial population native to a California annual grassland soil demonstrated
that the direct cell count and respiratory techniques for biomass estimation give comparable results. This procedure provides
the potential for detailed analyses of substrate utilization in studies of the growth and maintenance of soil microorganisms. 相似文献
5.
In examining the mechanical properties of the respiratory system during sleep in healthy humans, we observed that the inspiratory pressure-flow relationship of the upper airway was often flow limited and too curvilinear to be predicted by the Rohrer equation. The purposes of this study were 1) to describe a mathematical model that would better define the inspiratory pressure-flow relationship of the upper airway during sleep and 2) to identify the segment of airway responsible for the sleep-related flow limitation. We measured nasal and total supralaryngeal pressure and flow during wakefulness and stage 2 sleep in five healthy male subjects lying supine. A right rectangular hyperbolic equation, V = (alpha P)/(beta + P), where V is flow, P is pressure, alpha is an asymptote for peak flow, and beta is pressure at a flow of alpha/2, was used in its linear form, P/V = (beta/alpha) + (P/alpha). The goodness of fit of the new equation was compared with that for the linearized Rohrer equation P/V = K1 + K2V. During wakefulness the fit of the hyperbolic equation to the actual pressure-flow data was equivalent to or significantly better than that for the Rohrer equation. During sleep the fit of the hyperbolic equation was superior to that for the Rohrer equation. For the whole supralaryngeal airway during sleep, the correlation coefficient for the hyperbolic equation was 0.90 +/- 0.50, and for the Rohrer equation it was 0.49 +/- 0.25. The flow-limiting segment was located within the pharyngeal airway, not in the nose.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
6.
Immunoregulation in disseminated murine histoplasmosis: disturbances in the production of interleukins 1 and 2 总被引:4,自引:0,他引:4
S R Watson S K Schmitt D E Hendricks W E Bullock 《Journal of immunology (Baltimore, Md. : 1950)》1985,135(5):3487-3493
Production of IL 1 and IL 2 by splenocytes from C57BL/6 mice was measured at wk 1, 3, 8, and 14 after i.v. inoculation with 6 X 10(5) Histoplasma capsulatum (Hc) yeasts. As compared with age-matched controls, IL 1 production by splenocytes from Hc-infected mice was reduced severely at wk 1 and 3 of infection, greater than normal at wk 8, and within normal range at wk 14. IL 2 production was also reduced at wk 1 and 3 of infection; it was normal at wk 8 and was elevated at wk 14. Indomethacin and catalase failed to restore IL 1 production by splenocytes from infected mice, and exogenous IL 1 did not augment IL 2 production by these cells. A factor capable of suppressing the activity of IL 2 was detected in supernatants of concanavalin A-stimulated splenocytes from infected animals at wk 1 and 3 of infection, respectively. No factor capable of suppressing IL 1 activity was detected. Thus, the deficits of cell-mediated immunity in mice with systemic Hc infection may derive, in part, from impaired amplification of the immune response consequent to abnormal generation of IL 1 and IL 2. 相似文献
7.
Anaerobic Degradation of Cyanuric Acid, Cysteine, and Atrazine by a Facultative Anaerobic Bacterium 总被引:7,自引:5,他引:2 下载免费PDF全文
J. A. Jessee R. E. Benoit A. C. Hendricks G. C. Allen J. L. Neal 《Applied microbiology》1983,45(1):97-102
A facultative anaerobic bacterium that rapidly degrades cyanuric acid (CA) was isolated from the sediment of a stream that received industrial wastewater effluent. CA decomposition was measured throughout the growth cycle by using a high-performance liquid chromatography assay, and the concomitant production of ammonia was also measured. The bacterium used CA or cysteine as a major, if not the sole, carbon and energy source under anaerobic, but not aerobic, conditions in a defined medium. The cell yield was greatly enhanced by the simultaneous presence of cysteine and CA in the medium. Cysteine was preferentially used rather than CA early in the growth cycle, but all of the CA was used without an apparent lag after the cysteine was metabolized. Atrazine was also degraded by this bacterium under anaerobic conditions in a defined medium. 相似文献
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Simple, Reliable Cold Tray for the Recovery and Examination of Thermosensitive Organisms 总被引:1,自引:0,他引:1 下载免费PDF全文
A simple chamber is described for the isolation and handling of thermosensitive bacteria on board ship and in conventional research or classroom laboratories. 相似文献
10.
Action of Phytochrome During Prechilling of Amaranthus retroflexus L. Seeds 总被引:10,自引:8,他引:2 下载免费PDF全文
Dark germination of Amaranthus retroflexus L. seeds at 35° increased after several days of prechilling at 20° or lower. Irradiation with far-red light for short periods during the early hours of a prechilling period at 10° inhibited subsequent dark germination at 35°. The inhibition was completely reversible with red light. Far-red irradiation in the latter part of the prechilling period was less effective. Increased dark germination of A. retroflexus seeds following a prechilling period at 20° or less is attributed to action of preexistent PFR, the far-red absorbing form of phytochrome, within the seeds. Inactivation of PFR was found to proceed ca. 4 times more rapidly at 25° than at 20°. Failure of imbibition temperatures above 20° to increase dark germination of A. retroflexus seeds is attributed to the rapid thermal reversion of pre-existent PFR. We suggest that the action of prechilling (layering) on many other seed kinds arises in a similar way. 相似文献