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排序方式: 共有188条查询结果,搜索用时 15 毫秒
1.
2.
The Philly mouse develops a hereditary cataract about 5 weeks after birth. Although the causative agent is not known, data suggest that there is a correlation between cataract formation and the selective absence of a 27 kilodalton (27K) beta-crystallin lens polypeptide. The ontogeny of the 27K beta-crystallin polypeptide was examined in normal mice in order to evaluate its role in normal development and determine what impact its absence may have on the Philly mouse lens. A monoclonal antibody was used with the PAP method to immunocytochemically localize the 27K polypeptide in lenses of normal mice during development. beta-Crystallins detected with polyclonal antisera were found in differentiated fiber cells throughout the lens. In contrast, the 27K beta-crystallin polypeptide detected with a specific monoclonal antibody was not found in the fiber cells of the inner part of the lens (nucleus), but was specifically localized in the fiber cells of the outer part of the lens called the cortex. The polypeptide was found only in elongating and differentiated fiber cells and not in mitotically active epithelial cells. Although a minor component of the 2-day-old lens, the 27K polypeptide comprised a large portion of the 16-day-old lens including the anterior and posterior poles. These data show that the 27K polypeptide is a minor component of the embryonic lens, but becomes a major contributor to the postnatal lens. The 27K beta-crystallin lens polypeptide is abundant in the fiber cells of the normal postnatal mouse lens. The absence of the 27K polypeptide in the Philly mouse may contribute to the observed failure of fiber cells to differentiate in the Philly mouse after birth or may be deleterious in some other manner to normal lens development. The selective absence of the 27K beta-crystallin polypeptide, a defect which precedes cataract formation in the Philly mouse, is intriguing since it suggests a relationship between this major lens polypeptide and lens clarity. 相似文献
3.
W R Carper D D Stoddard D F Martin 《Biochemical and biophysical research communications》1973,54(2):721-725
Monoamine oxidase from pig liver has been isolated and purified approximately three hundred-fold. This enzyme has a molecular weight of 1,200,000, is highly polymeric, and contains subunits of molecular weight 146,000, as determined by Sephadex chromatography. The apparent Km at 25°C is 1.28 × 10?6 M at pH 9.0 (0.05 M glycine) and 1.74 × 10?5 M at pH 7.2 (0.2 M phosphate) using benzylamine as a substrate. This enzyme contains approximately 8 copper(II) ions per 1,200,000 molecular weight. 相似文献
4.
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
5.
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
6.
Induction of aldose reductase expression in rat kidney mesangial cells and Chinese hamster ovary cells under hypertonic conditions 总被引:4,自引:0,他引:4
M Kaneko D Carper C Nishimura J Millen M Bock T C Hohman 《Experimental cell research》1990,188(1):135-140
Rat kidney cortex mesangial cells (MES) and Chinese hamster ovary cells (CHO) responded to hypertonicity (600 mosmol/kg) in culture by accumulating sorbitol. The accumulation of sorbitol was due to increased aldose reductase (AR) activity, apparently brought about by increased levels of AR mRNA and protein. The levels of AR mRNA increased approximately 60-fold in MES cells and 30-fold in CHO cells by 24 h in culture media (300 mosmol/kg supplemented with 150 mM NaCl, 600 mosmol/kg total). AR activity also markedly increased (14- to 16-fold above control), but MES took 4 days and CHO 6 days to reach this maximum. Other osmolytes, raffinose and sorbitol (at concentrations of 250 to 300 mM) elicited the same response as that of 150 mM NaCl. These data show that AR expression is induced in MES and CHO cells under hypertonic conditions. Of special interest is the induction of large amounts of AR in rat kidney cortex mesangial cells, a target tissue of diabetes and a site where excessive accumulation of sorbitol is suspected to be a critical factor in diabetic nephropathy. 相似文献
7.
W R Carper M L Toews R E Thompson C M Buess 《Archives of biochemistry and biophysics》1976,175(1):312-320
Utilizing a temperature-sensitive mutant of Escherichia coli K-12 defective in the coupling of metabolic energy to active transport, we have demonstrated that the uptake systems for arabinose, galactose, valine, histidine, and glutamine, which are sensitive to the osmotic shock treatment of L. A. Heppel (1965) (J. Biol. Chem.240, 3685), are all totally defective at the nonpermissive temperature (42 °C) whereas the intracellular ATP levels increase twofold. Phosphate bond energy alone is therefore not sufficient to energize the transport of these substrates. We have confirmed the findings of E. A., Berger and L. A. Heppel (1974) (J. Biol. Chem. 249, 7747) regarding a severe arsenate I inhibition of the uptake of substrates belonging to osmotic shock-sensitive transport systems and therefore conclude that both ATP and a functional ecf gene product are required for the coupling of energy to the transport of these solutes. 相似文献
8.
Gregory V. Stark James P. Long Diana I. Ortiz Melicia Gainey Benjamin A. Carper Jingyu Feng Stephen M. Miller John E. Bigger Eric M. Vela 《PloS one》2013,8(3)
Influenza A viruses continue to pose a threat to human health; thus, various vaccines and prophylaxis continue to be developed. Testing of these products requires various animal models including mice, guinea pigs, and ferrets. However, because ferrets are naturally susceptible to infection with human influenza viruses and because the disease state resembles that of human influenza, these animals have been widely used as a model to study influenza virus pathogenesis. In this report, a statistical analysis was performed to evaluate data involving 269 ferrets infected with seasonal influenza, swine influenza, and highly pathogenic avian influenza (HPAI) from 16 different studies over a five year period. The aim of the analyses was to better qualify the ferret model by identifying relationships among important animal model parameters (endpoints) and variables of interest, which include survival, time-to-death, changes in body temperature and weight, and nasal wash samples containing virus, in addition to significant changes from baseline in selected hematology and clinical chemistry parameters. The results demonstrate that a disease clinical profile, consisting of various changes in the biological parameters tested, is associated with various influenza A infections in ferrets. Additionally, the analysis yielded correlates of protection associated with HPAI disease in ferrets. In all, the results from this study further validate the use of the ferret as a model to study influenza A pathology and to evaluate product efficacy. 相似文献
9.
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
10.