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排序方式: 共有71条查询结果,搜索用时 31 毫秒
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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
3.
D H Malin B J Novy A E Lett-Brown R E Plotner B T May S J Radulescu M K Crothers L D Osgood J R Lake 《Life sciences》1992,50(13):939-944
Galanin is a neuropeptide that coexists with acetylcholine in the septohippocampal pathway. Galanin appears to have a negative modulating influence on cholinergic transmission, suggesting that it might interfere with memory formation on a one-trial discriminative reward learning task. The apparatus was a starburst maze with five radiating alleys, one an ascending baited alley. The subjects were 38 two to three month old Sprague-Dawley rats cannulated in the body of the lateral ventricles and deprived to 80% of initial weight. Ten rats were infused i.c.v. over six mins. with 8 micrograms galanin in 24 microliters saline and 10 with saline alone. Twenty mins. after completion of infusion, each rat was placed in the maze and observed under "blind" conditions for number of errors (blind alleys entered) and latency to reach reward. Each rat's speed score was 100 sec./latency. One day later, each rat was retested in the maze. Each rat's retention scores were its decrease in errors and increase in speed between the single training trial and the retention trial. Galanin infused rats showed significantly less retention by both measures. In a second experiment, either the same dose of galanin or saline alone was infused 20 mins. before the retention trial. There was no significant effect, suggesting that galanin may interfere with memory formation rather than memory retrieval or task performance. 相似文献
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Selective inhibition of human lung cancer cell growth by peptides derived from retinoblastoma protein 总被引:1,自引:0,他引:1
Peptides containing retinoblastoma protein (RB) fragment 649-654 (LFYKKV) were tested for their ability to block the proliferation of RB-negative and RB-positive human non-small cell lung cancer (NSCLC) cells. These peptides potently restrained the growth of both types of tumor cells, as measured by metabolic (MTT) and cellular viability (trypan blue exclusion) assays. As such, and remarkably, the peptides were able to overcome the resistance of RB-positive cells usually observed with RB gene or protein replacement therapy. Compared to the overall performance of conventional chemotherapy tested in parallel, the peptides were more cytotoxic against RB-negative neoplastic cells and equipotent toward RB-positive tumor cells, yet less toxic toward normal human cells. Thus, these new molecules hold great promise to evolve into an efficient therapy for human lung cancer, a common malignancy still defying treatment and holding a poor prognosis, as well as for other human neoplasias. 相似文献
6.
Razvan T. Radulescu William C. Duckworth Janet Fawcett 《Biochemical and biophysical research communications》2010,395(2):196-199
Previous investigations on proteasomal preparations containing insulin-degrading enzyme (IDE; EC 3.4.24.56) have invariably yielded a co-purifying protein with a molecular weight of about 110 kDa. We have now found both in MCF-7 breast cancer and HepG2 hepatoma cells that this associated molecule is the retinoblastoma tumor suppressor protein (RB). Interestingly, the amount of RB in this protein complex seemed to be lower in HepG2 vs. MCF-7 cells, indicating a higher (cytoplasmic) protein turnover in the former vs. the latter cells. Moreover, immunofluorescence showed increased nuclear localization of RB in HepG2 vs. MCF-7 cells. Beyond these subtle differences between these distinct tumor cell types, our present study more generally suggests an interplay between RB and IDE within the proteasome that may have important growth-regulatory consequences. 相似文献
7.
The Golgi apparatus is a highly dynamic organelle whose organization is maintained by a proteinaceous matrix, cytoskeletal components, and inositol phospholipids. In mammalian cells, disassembly of the organelle occurs reversibly at the onset of mitosis and irreversibly during apoptosis. Several pharmacological agents including nocodazole, brefeldin A (BFA), and primary alcohols (1-butanol) induce reversible fragmentation of the Golgi apparatus. To dissect the mechanism of Golgi reassembly, rat NRK and GH3 cells were treated with 1-butanol, BFA, or nocodazole. During washout of 1-butanol, clathrin, a ubiquitous coat protein implicated in vesicle traffic at the trans-Golgi network and plasma membrane, and abundant clathrin coated vesicles were recruited to the region of nascent Golgi cisternae. Knockdown of endogenous clathrin heavy chain showed that the Golgi apparatus failed to reform efficiently after BFA or 1-butanol removal. Instead, upon 1-butanol washout, it maintained a compact, tight morphology. Our results suggest that clathrin is required to reassemble fragmented Golgi elements. In addition, we show that after butanol treatment the Golgi apparatus reforms via an initial compact intermediate structure that is subsequently remodeled into the characteristic interphase lace-like morphology and that reassembly requires clathrin. 相似文献
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9.
Boulter L Govaere O Bird TG Radulescu S Ramachandran P Pellicoro A Ridgway RA Seo SS Spee B Van Rooijen N Sansom OJ Iredale JP Lowell S Roskams T Forbes SJ 《Nature medicine》2012,18(4):572-579
During chronic injury a population of bipotent hepatic progenitor cells (HPCs) become activated to regenerate both cholangiocytes and hepatocytes. Here we show in human diseased liver and mouse models of the ductular reaction that Notch and Wnt signaling direct specification of HPCs via their interactions with activated myofibroblasts or macrophages. In particular, we found that during biliary regeneration, expression of Jagged 1 (a Notch ligand) by myofibroblasts promoted Notch signaling in HPCs and thus their biliary specification to cholangiocytes. Alternatively, during hepatocyte regeneration, macrophage engulfment of hepatocyte debris induced Wnt3a expression. This resulted in canonical Wnt signaling in nearby HPCs, thus maintaining expression of Numb (a cell fate determinant) within these cells and the promotion of their specification to hepatocytes. By these two pathways adult parenchymal regeneration during chronic liver injury is promoted. 相似文献
10.
Eugen Radulescu 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1935,7(12):324-326
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