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排序方式: 共有426条查询结果,搜索用时 15 毫秒
351.
J J Bergeron R Rachubinski N Searle D Borts R Sikstrom B I Posner 《The journal of histochemistry and cytochemistry》1980,28(8):824-835
A tissue-screening survey employing quantitative radioautography was carried out at 2 min after the intravascular injection of 125I-insulin into laboratory rats. The results revealed a substantial binding of insulin to cells forming the proximal convoluted tubule in kidney, hepatocytes of liver, acinar cells of the pancreas, parenchymal cells of the adrenal cortex and medulla, and epithelial cells of the gastrointestinal tract. Control experiments indicated that this binding was due to a specific interaction with the insulin receptor, except in the case of kidney where the binding was shown to be nonspecific. Although the major target for insulin action (liver) clearly demonstrated specific insulin binding, several other classical targets (adipocytes, skeletal, cardiac, and smooth muscle cells) showed no specific 125I-insulin binding and therefore indicated the limits of sensitivity of the in vivo radioautographic method. Nevertheless, the working hypothesis of a direct correlation of insulin receptor density with insulin action points to the hitherto unemphasized targets of pancreas, adrenal gland, and gastrointestinal tract as major sites of insulin action in the body. 相似文献
352.
353.
Alan Shaver Jesse B. Ng David A. Hall Barry I. Posner 《Molecular and cellular biochemistry》1995,153(1-2):5-15
The inorganic coordination chemistry of peroxovanadium compounds relevant to insulin mimesis is reviewed. The structure and kinetic reactivity of solutions of vanadate anion, vanadyl complexes and peroxovanadate complexes are briefly compared. Peroxovanadium compounds contain an oxo group, one or two peroxo ligands (O2
2–) and an ancillary ligand which is usually bidentate. These compounds approximate a trigonal bipyramidal structure which can be divided conceptually into a polar oxo half and a relatively non-polar organic half. This presents a number of interesting design variations which are discussed with respect to the development of a rudimentary structure-activity correlation of insulin mimetic ability.Abbreviations phen
1,10-phenanthroline
- 4,7-Me2phen
4,7-dimethyl-1,10-phenanthroline
- 3,4,7,8-Me4phen
3,4,7,8-tetramethyl-1,10-phenanthroline
- 5-CH3phen
5-methyl-1,10-phenanthroline
- 5-NO2phen
5-nitro-1,10-phenanthroline
- 5-NH2phen
5-amino-1,10-phenanthroline
- bipy
2,2-bipyridine
- bipyH
2,2-bipyridinium
- 4,4-Me2bipy
4,4-dimethyl-2,2-bipyridine
- bipy-4,4-(COO)2
2,2-bipyridine-4,4-dicarboxylato
- pic
pyridine-2-carboxylato
- 3-OHpic
3-hydroxypyridine-2-carboxylato
- 3-acetpic
3-acetatoxypyridine-2-carboxylato
- m,n-pdc
pyridine-m,n-dicarboxylato
- ox
oxalato
- pzc
pyrazine-2-carboxylato
- 3-NH2pzc
3-aminopyrazine-2-carboxylato
- 4OH-2,6pdc
4-hydroxy-2,6-pyridinedicarboxylato
- IDA
iminodiacetato
- cit
citrato
- EDTA
ethylenediaminetetraacetato
- HEDTA
ethylene-diaminetetraacetic acid
- isoquin
isoquinoline-2-carboxylato
- quin
quinolato
- NTA
nitrilotriacetato
- glyH
glycine
- cystH
cysteine
- nicH
nicotinic acid
- Hheida
N-(2-hydroxyethyl)iminodiacetato 相似文献
354.
Functional and immunologic characterization of human immunodeficiency virus type 1 envelope glycoproteins containing deletions of the major variable regions. 总被引:30,自引:25,他引:5
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R Wyatt N Sullivan M Thali H Repke D Ho J Robinson M Posner J Sodroski 《Journal of virology》1993,67(8):4557-4565
Deletions of the major variable regions (V1/V2, V3, and V4) of the human immunodeficiency virus type 1 (HIV-1) gp120 exterior envelope glycoprotein were created to study the role of these regions in function and antigenicity. Deletion of the V4 region disrupted processing of the envelope glycoprotein precursor. In contrast, the deletion of the V1/V2 and/or V3 regions yielded processed exterior envelope glycoproteins that retained the ability to interact with the gp41 transmembrane glycoprotein and the CD4 receptor. Shedding of the gp120 exterior glycoprotein by soluble CD4 was observed for the mutant with the V3 deletion but did not occur for the V1/V2-deleted mutant. None of the deletion mutants formed syncytia or supported virus entry. Importantly, the affinity of neutralizing antibodies directed against the CD4-binding region for the multimeric envelope glycoprotein complex was increased dramatically by the removal of both the V1/V2 and V3 structures. These results indicate that, in addition to playing essential roles in the induction of membrane fusion, the major variable regions mask conserved neutralization epitopes of the HIV-1 gp120 glycoprotein from antibodies. These results explain the temporal pattern associated with generation of HIV-1-neutralizing antibodies following infection and suggest stratagems for eliciting improved immune responses to conserved gp120 epitopes. 相似文献
355.
356.
The purpose of this paper is to assess the extent of gene identity and
differentiation at 33 dinucleotide repeat loci (377 total alleles) within
and among three European and three Native American populations. In order to
do this, we show that a maximum-likelihood method proposed for phylogenetic
trees (Cavalli-Sforza and Piazza 1975) can be used to estimate gene
identity (Nei 1987) with respect to any hierarchical structure. This method
allows gene differentiation to be evaluated with respect to any internal
node of a hierarchy. It also allows a generalization of F- and G-statistics
to situations with unequal expected levels of differentiation. Our
principal finding is that levels of genetic differentiation are unique to
specific populations and levels of nesting. The populations of European
origin show very little internal differentiation; moreover, their
continental average is close to the total population defined by the
aggregate of Europeans and Native Americans. By contrast, the Native
American populations show moderate levels of internal differentiation, and
a great distance between their continental average and the total. The
results of analyses of subsets of loci that were selected to have high gene
diversities in either Europeans or Native Americans closely parallel those
from the total set of loci. This suggests that the principal results are
unlikely to be caused by a European ascertainment bias in locus selection.
In summary, our findings demonstrate that partitions of gene diversity into
within- and between-populations components are heavily biased by the
populations analyzed and the models fitted. Optimistically, however, more
information is available to analyze population history and evolution by
quantifying, as we have done, the uniqueness of patterns of
differentiation.
相似文献
357.
Lopez JV; Culver M; Stephens JC; Johnson WE; O'Brien SJ 《Molecular biology and evolution》1997,14(3):277-286
Differential rates of nucleotide substitution among different gene segments
and between distinct evolutionary lineages is well documented among
mitochondrial genes and is likely a consequence of locus-specific selective
constraints that delimit mutational divergence over evolutionary time. We
compared sequence variation of 18 homologous loci (15 coding genes and 3
parts of the control region) among 10 mammalian mitochondrial DNA genomes
which allowed us to describe different mitochondrial evolutionary patterns
and to produce an estimation of the relative order of gene divergence. The
relative rates of divergence of mitochondrial DNA genes in the family
Felidae were estimated by comparing their divergence from homologous
counterpart genes included in nuclear mitochondrial DNA (Numt, pronounced
"new might"), a genomic fossil that represents an ancient transfer of 7.9
kb of mitochondrial DNA to the nuclear genome of an ancestral species of
the domestic cat (Felis catus). Phylogenetic analyses of mitochondrial
(mtDNA) sequences with multiple outgroup species were conducted to date the
ancestral node common to the Numt and the cytoplasmic (Cymt) mtDNA genes
and to calibrate the rate of sequence divergence of mitochondrial genes
relative to nuclear homologous counterparts. By setting the fastest
substitution rate as strictly mutational, an empirical "selective
retardation index" is computed to quantify the sum of all constraints,
selective and otherwise, that limit sequence divergence of mitochondrial
gene sequences over time.
相似文献
358.
Camarodont sea urchins possess a rapidly evolving actin gene family whose
members are expressed in distinct cell lineages in a developmentally
regulated fashion. Evolutionary changes in the actin gene family of
echinoids include alterations in number of family members, site of
expression, and gene linkage, and a dichotomy between rapidly and slowly
evolving isoform-specific 3' untranslated regions. We present sequence
comparisons and an analysis of the actin gene family in two congeneric sea
urchins that develop in radically different modes, Heliocidaris
erythrogramma and H. tuberculata. The sequences of several actin genes from
the related species Lytechinus variegatus are also presented. We compare
the features of the Heliocidaris and Lytechinus actin genes to those of the
the actin gene families of other closely related sea urchins and discuss
the nature of the evolutionary changes among sea urchin actins and their
relationship to developmental mode.
相似文献
359.
J W Burgess I Wada N Ling M N Khan J J Bergeron B I Posner 《The Journal of biological chemistry》1992,267(14):10077-10086
In a previous study, we showed that the rat hepatic insulin receptor (IR) kinase of endosomes (ENs) was transiently activated to levels exceeding those of plasma membrane (PM) receptors following insulin injection. Phosphatase treatment of EN receptors abolished IR kinase activation implicating beta-subunit autophosphorylation as a mediator of the activation process (Khan, M. N., Baquiran, G., Brule, C., Burgess, J., Foster, B., Bergeron, J. J. M., and Posner, B. I. (1989) J. Biol. Chem. 264, 12931-12940). In the present study, the phosphotyrosine (PY) content of the IR beta-subunit in PM and ENs was estimated by two different methods. In one method, direct in vivo labeling with 32Pi followed by receptor immunoprecipitation was carried out. In the second method, immunoblotting with antibodies against the submembrane domain of the IR beta-subunit, encompassing residue 960 (alpha 960), and with antibodies against PY (alpha PY) was used to determine the content of PY/beta-subunit in PM and ENs following injection of insulin. By both methods, it was found that the PY content of PM IR was significantly greater than that of IR in ENs. With doses of 1.5 micrograms of insulin/100 g body weight (50% receptor occupancy) or 15 micrograms/100 g body weight (receptor saturation), the PY/beta-subunit of PM IR attained a level 2.0 to 2.5-fold of that observed for the IR of ENs. Surprisingly, the IR of ENs incorporated 3 to 5 times more PY/beta-subunit than those of PM consequent to autophosphorylation. Exogenous IR kinase activity (poly(Glu:Tyr)) in PM changed only slightly with insulin dose. In contrast, EN receptors exhibited a dose-dependent increase in kinase activity coincident with the decrease in PY/beta-subunit levels. A comparison of the proportion of receptor and kinase activity immunoprecipitated by alpha PY both before and after autophosphorylation indicated that ENs but not PM contained a small population of lightly phosphorylated but highly activated receptors. Since Thr12-Lys (IR kinase residues 1142-1153) efficiently inhibited IR autophosphorylation of both PM and EN receptors, Tris phosphorylation of beta-subunit regulatory tyrosines was unlikely. These results may be explicable by a dephosphorylation-dependent activation of IR kinase, as seen with the src family of tyrosine kinases. 相似文献
360.