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51.
Previous studies in this laboratory utilizing monoclonal antibody-induced immunosuppression have demonstrated that the T-helper lymphocyte is primarily responsible for the T lymphocyte dependency of Trypanosoma musculi elimination from the bloodstream of mice, and that T-cytotoxic lymphocytes play a minimal role in this response. In the current study, these findings were extended by examining the effects of adoptive cell transfers on the course of infection with T. musculi using immune splenocytes enriched for T lymphocyte subpopulations. These studies demonstrated that adoptive transfer of immune splenic T lymphocytes resulted in a specific, dose-related enhancement of kinetics of trypanosome elimination. This effect was found to be due to the presence of L3T4+ T-helper cells in the immune splenocyte population. Adoptive transfer of Lyt-2+ T-cytotoxic cells or lymphokine-activated killer (LAK) cells was ineffective in altering the course of infection. In addition, it was found that immune B lymphocytes were equally capable of adoptively transferring immunity to T. musculi, suggesting that the primary role of the T-helper lymphocyte is to provide help in the induction of parasite-specific antibodies. 相似文献
52.
Summary Two alternative estimators of individual tree leaf area (A1) area are used to derive estimates of leaf-area index (L) for 40 plots in Pinus contorta Dougl. stands. One estimator of A1 is based on the common assumption of a constant ratio between A1 and sapwood cross-sectional area at breast height (As). The second estimator of A1 accounts for tree-to-tree variation in the relation between A1 and As. The apparent relationship between stand growth and leaf-area index is strongly dependent on the way leaf area is estimated. When L is derived from a constant A1As ratio, stand growth appears to be strongly correlated with L. However, when L is based on estmates of A1 that account for tree-to-tree variation in the A1 — As relation, stand growth is seen to be only weakly related to L. Stand structure, quantified as percent live-crown, accounts for a great deal of the observed variation in leaf-area efficiency. These contrasting relationships illustrate the importance of unbiased estimates of L in interpreting the link between stand-level processes and leaf area.Utah Aggriculural Experiment Station Journal Paper No. 3333 相似文献
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Roy E. Crabtree Edward C. Cyr Renée E. Bishop Laura M Falkenstein John M. Dean 《Environmental Biology of Fishes》1992,35(4):361-370
Synopsis Leptocephali were collected in June 1981 and July 1989 over the continental shelf and slope of the Florida west coast. Tarpon larvae ranged 5.5–24.4 mm standard length (SL) and were the second most abundant leptocephalus species. Sagittae examined with compound microscopes and scanning electron microscopy had increments that were presumed to be formed daily. Increment counts made using the two microscopic techniques were not significantly different. Estimated ages ranged 2–25 days with a growth rate (± standard error) of 0.92 ± 0.04 mm d–1 The least squares linear regression equation SL = 2.78 + 0.92 (age in days) best described the relationship between estimated age and length. Adult tarpon appear to undergo a substantial spawning migration from inshore areas frequented during spring and summer to offshore spawning grounds. Spawning occurs during May, June, and July, although the spawning season may be of greater duration. 相似文献
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David W. Cameron 《Primates; journal of primatology》1991,32(3):329-343
This paper examines the pattern(s) of sexual dimorphism within the upper dentition ofProconsul specimens from the early Miocene of east Africa. These fossils are compared against the corresponding dentition ofPan troglodytes andGorilla gorilla using principal components and cluster analyses. This paper demonstrates that both sexes ofPan andGorilla are characterized by their own distinctive shape patterns. It is also demonstrated that someProconsul specimens examined here display a pattern that is dissimilar from otherProconsul specimens also examined. This suggests that at least two species ofProconsul may have to be recognized as having lived in this region during the early Miocene. The identification of distinct patterns
withinProconsul also suggests that their overall shape and size range are more similar toPan than toGorilla. 相似文献
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B H Johnson R R Dean S M Moran E B Thompson 《The Journal of steroid biochemistry and molecular biology》1992,42(1):1-9
We have studied the growth effects of conditioned media, interleukin-2 and PGE prostaglandin analogs on the glucocorticoid-sensitive human leukemic T-cell clone, CEM-C7. After 4 days, the glucocorticoid dexamethasone at approximately 10 nM kills 50% of CEM-C7 cells. To test the hypothesis that glucocorticoid-mediated lymphocytolysis was due to suppression of lymphokine expression only, we attempted to protect CEM-C7 cells from lysis by provision of lymphokine(s). Conditioned media from interleukin-2 secreting Jurkat T-cells as well as the glucocorticoid-insensitive, but receptor positive clone, CEM-C1, failed to prevent lymphocytolysis; exogenous interleukin-2 also did not provide protection. There were complex, biphasic interactions between dexamethasone and the synthetic PGEs, enisoprost and enisoprost free acid. Low doses of enisoprost alone (0.01 to 1 microgram/ml) stimulated growth, and in combinations completely reversed the growth inhibitory effects of 10 nM dexamethasone. Higher concentrations of enisoprost were inherently lethal and were additive to the steroid effect. Thus the glucocorticoid-induced lymphocytolysis in this human leukemic T-cell line may be modified biphasically by PGE prostaglandins, depending on their concentration. However, interleukin-2 or components in the conditioned media assayed had no effect in ameliorating the lethal response to glucocorticoid. 相似文献
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