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排序方式: 共有193条查询结果,搜索用时 31 毫秒
1.
Certain strains of mice develop a symmetrical polyarthritis after immunization with type II collagen. The incidence of arthritis after such immunization is variable. To study the arthritogenic potential of T cells reactive with type II collagen, we isolated draining lymph node cells from mice that had developed arthritis after immunization with bovine type II collagen. From these immune lymph node cells we were able to clone T cells reactive with type II collagen. Two separate sets of T cell clones were isolated. The first set reacted with either native bovine or native chick type II collagen, but did not react with type I collagen. The second set of T cell clones reacted with bovine type II collagen, but did not respond to either native chick type II collagen or type I collagen. These clones will be tested for their influence on the development of arthritis in vivo. 相似文献
2.
THE EFFECTS OF IRON DEFICIENCY ON THE HEPATOCYTE: A BIOCHEMICAL AND ULTRASTRUCTURAL STUDY 总被引:4,自引:1,他引:3
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Effects of iron deficiency on the hepatocyte were studied quantitatively in the rat by combining ultrastructural and biochemical techniques. After 3–8 wk of an iron-deficient diet, the percentage of cytoplasm occupied by mitochondria increased progressively compared with complete diet values. The increment resulted primarily from an enlargement of individual mitochondria rather than from an increased mitochondrial number. Many mitochondria were completely divided by a double membrane, often at a point of constriction. After 2 days of iron administration, mitochondria were of heterogeneous size, shape, and electron opacity. After 5 days, essentially all mitochondria had become normal in configuration. The rate of reversal of the morphological abnormality was more rapid than would be anticipated if it coincided with known rates of renewal of mitochondrial DNA or protein. The concentrations of mitochondrial cytochromes were more rapidly depressed as a result of iron deprivation than those of microsomal cytochromes. Cytochromes c and a were decreased after 3 and 8 wk of exposure to the deficient regimen. Cytochrome P 450 was not decreased after a 3 wk exposure to the deficient diet and responded normally to phenobarbital treatment with a fourfold increase in total hepatic content; its concentration was depressed only after 8 wk of exposure to the deficient diet. There was no reduction in cytochrome b5 concentration. 相似文献
3.
4.
HETEROGENEOUS DISTRIBUTION OF ENZYMES IN SUBMICROSOMAL MEMBRANE FRAGMENTS 总被引:14,自引:9,他引:5
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Peter R. Dallman Gustav Dallner Anders Bergstrand Lars Ernster 《The Journal of cell biology》1969,41(2):357-377
Microsomal membranes are postulated to contain either a homogeneous arrangement of individual enzymes or groupings of functionally related enzymes. In the present study we attempt to distinguish between these hypotheses in subfractions of rough microsomes from rat liver. After sonication, the individual vesicles that make up the rough-membrane fraction average less than 1/100 of their previous mass. The vesicles in the sonicated suspension are fractionated roughly according to size on a continuous sucrose gradient. Enzyme activity or concentration in fractions of the gradient is expressed on a phospholipid basis. Fractions containing primarily small vesicles differ from those containing larger vesicles in a manner suggesting a certain degree of separation of NADH-linked from NADPH-linked enzymes. NADH-ferricyanide reductase, NADH-cytochrome c reductase and cytochrome b5 are most concentrated within the large vesicles in the lowest third of the gradient. In contrast, NADPH-cytochrome c reductase and cytochrome P-450 are found in highest concentration in the small vesicles that make up the upper third of the gradient. The results suggest a nonrandom distribution of these two enzyme groups in the membranes of the endoplasmic reticulum. 相似文献
5.
We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
6.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
7.
Schistosomiasis vector snails are subjected to extreme seasonal changes, particularly in ephemeral rivers and lentic waterbodies. In the tropics, aestivation is one of the adaptive strategies for survival and is used by snails in times of extremely high temperatures and desiccation. Aestivation therefore plays an important role in maintaining the transmission of schistosomiasis. This review assesses the possible impacts of climate change on the temporal and spatial distribution of schistosomiasis-transmitting snails with special emphasis on aestivation, and discusses the effect of schistosome infection on aestivation ability. The impacts of parasite development on snails, as well as physiological changes, are discussed with reference to schistosomiasis transmission. This review shows that schistosome-infected snails have lower survival rates during aestivation, and that those that survive manage to get rid of the infection. In general, snail aestivation ability is poor and survival chances diminish with time. Longer dry periods result in fewer, as well as uninfected, snails. However, the ability of the surviving snails to repopulate the habitats is high. 相似文献
8.
Attenuation of pattern recognition receptor signaling is mediated by a MAP kinase kinase kinase
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Sharon C Mithoe Christina Ludwig Michiel JC Pel Mara Cucinotta Alberto Casartelli Malick Mbengue Jan Sklenar Paul Derbyshire Silke Robatzek Corné MJ Pieterse Ruedi Aebersold Frank LH Menke 《EMBO reports》2016,17(3):441-454
Pattern recognition receptors (PRRs) play a key role in plant and animal innate immunity. PRR binding of their cognate ligand triggers a signaling network and activates an immune response. Activation of PRR signaling must be controlled prior to ligand binding to prevent spurious signaling and immune activation. Flagellin perception in Arabidopsis through FLAGELLIN‐SENSITIVE 2 (FLS2) induces the activation of mitogen‐activated protein kinases (MAPKs) and immunity. However, the precise molecular mechanism that connects activated FLS2 to downstream MAPK cascades remains unknown. Here, we report the identification of a differentially phosphorylated MAP kinase kinase kinase that also interacts with FLS2. Using targeted proteomics and functional analysis, we show that MKKK7 negatively regulates flagellin‐triggered signaling and basal immunity and this requires phosphorylation of MKKK7 on specific serine residues. MKKK7 attenuates MPK6 activity and defense gene expression. Moreover, MKKK7 suppresses the reactive oxygen species burst downstream of FLS2, suggesting that MKKK7‐mediated attenuation of FLS2 signaling occurs through direct modulation of the FLS2 complex. 相似文献
9.
Notch signalling in the regulation of peripheral T-cell function 总被引:3,自引:0,他引:3
Mckenzie GJ Young LL Briend E Lamb JR Dallman MJ Champion BR 《Seminars in cell & developmental biology》2003,14(2):127-134
The Notch signalling pathway plays a highly-conserved role in regulating the cellular differentiation and proliferation events that characterise pattern formation in the embryo. As cells in the embryo respond to environmental signals, similarly T-cells in the peripheral immune system must monitor their environment for antigens and respond accordingly by entering one of several potential differentiation pathways. Recent studies have identified a role for the Notch pathway in regulating the responses of T-cells in the periphery. In this review, we discuss these findings in the context of the Notch signalling pathway's role as an orchestrator of cellular differentiation, and propose a central role for Notch as a regulator of immune system function. 相似文献
10.
1-Thio-beta-D-galactofuranosides: synthesis and evaluation as beta-D- galactofuranosidase inhibitors
Marino C; Marino K; Miletti L; Manso Alves MJ; Colli W; de Lederkremer RM 《Glycobiology》1998,8(9):901-904
Beta-D-galactofuranosidase is a good chemotherapeutic target for the design
of inhibitors, since beta-D-galactofuranose is a constituent of important
parasite glycoconjugates but is not present in the host mammals. With this
aim, we have synthesized for the first time alkyl, benzyl and aryl
1-thio-beta-D-galactofuranosides by condensation of
penta-O-benzoyl-alpha,beta-D-galactofuranose with the corresponding thiols,
in the presence of SnCl4as catalyst. The complete chemical and
spectroscopical characterization of these compounds showed that the
reaction was stereoselective. Debenzoylation with sodium methoxide afforded
the beta-S-galactofuranosides in high yield. The thioglycosides were tested
as inhibitors of the beta-D- galactofuranosidase of Penicillium fellutanum,
using for the first time 4-nitrophenyl-beta-D-galactofuranoside as
chromogenic substrate. The 4- aminophenyl-1-thio-beta-D-galactofuranoside,
obtained by catalytic hydrogenation of the nitrophenyl derivative, was the
best inhibitor being then an adequate ligand for the preparation of an
affinity phase aimed at the isolation of beta-d-galactofuranosidases from
different sources. Also the inhibitory activity of d-galactono-1, 4-lactone
was shown.
相似文献