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71.
Summary In the present study the effects of lipopolysaccharide (LPS) on the cellular composition and phagocytosis of India ink in the inner parts of the periarteriolar lymphocyte sheaths (PALS) are described.Staining for B-, T-lymphocytes, and reticulin fibers in the spleen of normal and LPS-injected mice shows that the B-dependent follicular area is increased in size after LPS administration. However, the number of T-lymphocytes in the inner PALS is reduced markedly and a relatively high number of B-lymphocytes can be found in this area. The significance of this phenomenon is discussed.In untreated mouse spleen, carbon particles become localized in strongly acid-phosphatase (AP)-positive macrophages of the red pulp, marginal zone and white pulp 24 h after an intravenous injection of India ink. All these macrophages contain numerous carbon particles. After LPS pretreatment, the phagocytosis of carbon particles in the inner PALS is dramatically diminished, although many strongly AP-positive macrophages can be found in this area. The phagocytosis of carbon particles in the other compartments of the spleen did not change. It appears that injection of 2 g LPS or more is sufficient to induce this phenomenon which is most significant when LPS is injected 24 or 48 h before exposure to India ink.Abbreviations
LPS
lipopolysaccharide
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PALS
periarteriolar lymphocyte sheath
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AP
acid phosphatase
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IDC
interdigitating cells 相似文献
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Recognizing the forest for the trees: testing temporal patterns of cladogenesis using a null model of stochastic diversification 总被引:2,自引:1,他引:1
Computer simulations are developed and employed to examine the expected
temporal distributions of nodes under a null model of stochastic lineage
bifurcation and extinction. These Markovian models of phylogenetic process
were constructed so as to permit direct comparisons against empirical
phylogenetic trees generated from molecular or other information available
solely from extant species. For replicate simulated phylads with n extant
species, cumulative distribution functions (cdf's) of branching times were
calculated, and compared (using the Kolmogorov-Smirnov test statistic D) to
those from three published empirical trees. Molecular phylogenies for
columbine plants and avian cranes showed statistically significant
departures from the null expectations, in directions indicating recent and
ancient species' radiations, respectively, whereas a molecular phylogeny
for the Drosophila virilis species group showed no apparent historical
clustering of branching events. Effects of outgroup choice and phylogenetic
frame of reference were investigated for the columbines and found to have a
predictable influence on the types of conclusions to be drawn from such
analyses. To enable other investigators to statistically test for
nonrandomness in temporal cladogenetic pattern in empirical trees generated
from data on extant species, we present tables of mean cdf's and associated
probabilities under the null model for expected branching times in phylads
of varying size. The approaches developed in this report complement and
extend those of other recent methods for employing null models to assess
the statistical significance of pattern in evolutionary trees.
相似文献
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JC Biro 《Theoretical biology & medical modelling》2006,3(1):15-12
Background
Prediction of protein folding and specific interactions from only the sequence (ab initio) is a major challenge in bioinformatics. It is believed that such prediction will prove possible if Anfinsen's thermodynamic principle is correct for all kinds of proteins, and all the information necessary to form a concrete 3D structure is indeed present in the sequence. 相似文献78.
The demonstration that interleukin 2 (IL-2) is a lectin specific for
oligomannosides allows to understand a new function for this cytokine: as a
bifunctional molecule when bound to its receptor ss, IL-2 associates the
latter which the CD3/TCR complex, interacting with oligosaccharides of CD3
through its carbohydrate-recognition domain (Zanetta et al. , 1996,
Biochem. J., 318, 49-53). This induces the tyrosine phosphorylation of the
IL-2R beta by ++p56(lck) , the first step of the IL-2-dependent signaling.
Since this specific association is disrupted in vitro by oligomannosides
with five and six mannose residues, we made the hypothesis that pathogenic
cells or microorganisms could bind IL-2, consequently disturbing the IL-2-
dependent response. This study shows that the pathogenic yeast Candida
albicans (in contrast with nonpathogenic yeasts) binds high amounts of IL-2
as did cancer cells. In contrast with cancer cells, yeasts do not bind the
Man6GlcNAc2-specific lectin CSL, an endogenous "amplifier of activation
signals" (Zanetta et al. , 1995, Biochem. J., 311, 629-636).
相似文献
79.
A. W. H. Neitz R. Gothe S. Pawlas H. T. Groeneveld 《Experimental & applied acarology》1993,17(7):551-559
The immune response of a natural host of Rhipicephalus evertsi evertsi to feeding by this tick species was investigated with respect to the effects of tick salivary gland extracts on the transformation of peripheral blood lymphocytes and the release of histamine by basophils obtained from repeatedly infested sheep.The results indicated that there was no stimulation of lymphocyte transformation but that histamine release was elevated 10 fold after four infestations.Although this suggests a hypersensitivity reaction, believed to be a major factor in resistance to tick feeding, it was observed that ticks fed normally even after four infestations with 28 day intervals in between. These results emphasize the adaptation of ticks to feeding on their natural hosts. 相似文献
80.