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排序方式: 共有692条查询结果,搜索用时 93 毫秒
1.
Fabián Michelangeli Dalia M. Sulcas Marie-Christine Ruiz 《Cell and tissue research》1987,250(2):413-419
Summary This study is concerned with electron-microscopic observations on endocrine or paracrine cells in the fundic gastric mucosa of the bullfrog. Also, an attempt was made to identify the histamine-releasing cells involved in the secretagogue response. At least three distinct endocrine-like cell types were found. The classification is based on the appearance of secretory granules and other organelles, and the relationship of endocrine-like cells with other cells in the tissue. The amphibian endocrine-like cells resemble the ECL, D and EC cells of mammals. Type-I (ECL) cells showed degranulation after repeated stimulation with tetragastrin (TG), acetylcholine (ACh) and K+ depolarizing solution, all of which release histamine. 相似文献
2.
TRK1 encodes a plasma membrane protein required for high-affinity potassium transport in Saccharomyces cerevisiae. 总被引:30,自引:10,他引:20
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We identified a 180-kilodalton plasma membrane protein in Saccharomyces cerevisiae required for high-affinity transport (uptake) of potassium. The gene that encodes this putative potassium transporter (TRK1) was cloned by its ability to relieve the potassium transport defect in trk1 cells. TRK1 encodes a protein 1,235 amino acids long that contains 12 potential membrane-spanning domains. Our results demonstrate the physical and functional independence of the yeast potassium and proton transport systems. TRK1 is nonessential in S. cerevisiae and maps to a locus unlinked to PMA1, the gene that encodes the plasma membrane ATPase. Haploid cells that contain a null allele of TRK1 (trk1 delta) rely on a low-affinity transporter for potassium uptake and, under certain conditions, exhibit energy-dependent loss of potassium, directly exposing the activity of a transporter responsible for the efflux of this ion. 相似文献
3.
We propose a conformational nomenclature for amphiphilic lipid molecules that is general and compatible with the stereospecific numbering scheme, in contrast to earlier methods in which discrepancies with the sn-scheme lead to contradictory assignments of the absolute configuration of the system. The present method can be rationally extended to different classes of lipids, both natural and synthetic. It is simple and provides a convenient framework for conformational studies on widely varying classes of lipids. 相似文献
4.
TRK1 and TRK2 encode structurally related K+ transporters in Saccharomyces cerevisiae. 总被引:24,自引:5,他引:19
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We describe the cloning and molecular analysis of TRK2, the gene likely to encode the low-affinity K+ transporter in Saccharomyces cerevisiae. TRK2 encodes a protein of 889 amino acids containing 12 putative membrane-spanning domains (M1 through M12), with a large hydrophilic region between M3 and M4. These structural features closely resemble those contained in TRK1, the high-affinity K+ transporter. TRK2 shares 55% amino acid sequence identity with TRK1. The putative membrane-spanning domains of TRK1 and TRK2 share the highest sequence conservation, while the large hydrophilic regions between M3 and M4 exhibit the greatest divergence. The different affinities of TRK1 trk2 delta cells and trk1 delta TRK2 cells for K+ underscore the functional independence of the high- and low-affinity transporters. TRK2 is nonessential in TRK1 or trk1 delta haploid cells. The viability of cells containing null mutations in both TRK1 and TRK2 reveals the existence of an additional, functionally independent potassium transporter(s). Cells deleted for both TRK1 and TRK2 are hypersensitive to low pH; they are severely limited in their ability to take up K+, particularly when faced with a large inward-facing H+ gradient, indicating that the K+ transporter(s) that remains in trk1 delta trk2 delta cells functions differently than those of the TRK class. 相似文献
5.
Averell Gnatt Dalia Ginzberg Judy Lieman-Hurwitz Ronit Zamir Haim Zakut Hermona Soreq 《Cellular and molecular neurobiology》1991,11(1):91-104
1. Various hybridization approaches were employed to investigate structural and chromosomal interrelationships between the human cholinesterase genes CHE and ACHE encoding the polymorphic, closely related, and coordinately regulated enzymes having butyrylcholinesterase (BuChE) and acetylcholinesterase (AChE) activities. 2. Homologous cosmid recombination with a 190-base pair 5' fragment from BuChEcDNA resulted in the isolation of four overlapping cosmid clones, apparently derived from a single gene with several introns. The Cosmid CHEDNA included a 700-base pair fragment known to be expressed at the 3' end of BuChEcDNA from nervous system tumors and which has been mapped by in situ hybridization to the unique 3q26-ter position. In contrast, cosmid CHEDNA did not hybridize with full-length AChEcDNA, proving that the complete CHE gene does not include AChE-encoding sequences either in exons or in its introns. 3. The chromosomal origin of BuChE-encoding sequences was further examined by two unrelated gene mapping approaches. Filter hybridization with DNA from human/hamster hybrid cell lines revealed BuChEcDNA-hybridizing sequences only in cell lines including human chromosome 3. However, three BuChEcDNA-homologous sequences were observed at chromosomal positions 3q21, 3q26-ter, and 16q21 by a highly stringent in situ hybridization protocol, including washes at high temperature and low salt. 4. These findings stress the selectivity of cosmid recombination and chromosome blots, raise the possibility of individual differences in BuChEcDNA-hybridizing sequences, and present an example for a family highly similar proteins encoded by distinct, nonhomologous genes. 相似文献
6.
R Bredehorst F S Ligler A W Kusterbeck E L Chang B P Gaber C W Vogel 《Biochemistry》1986,25(19):5693-5698
Liposome stability during and after covalent coupling of Fab' antibody fragments was investigated. Large unilamellar vesicles containing entrapped 5(6)-carboxyfluorescein (CF) as a marker for liposomal integrity were prepared by extrusion through polycarbonate membranes. N-[4-(p-Maleimidophenyl)-butyryl]phosphatidylethanolamine (MPB-PE) was employed as a liposomal anchor for the covalent coupling of Fab' fragments. We observed that coupling of Fab' fragments to liposomes containing 5 mol % MPB-PE caused a concentration-dependent increase in size and polydispersity of the liposomes. Dependent on the concentration of the MPB-PE anchor in the membrane and the concentration of Fab' added, coupling was associated with the release of up to 95% of the entrapped CF. Rupture of the liposomes was identified as the primary mechanism of CF release during Fab' coupling. Reduction of the MPB-PE concentration to 1 mol % resulted in liposomes that were stable during and after Fab' coupling. The increased stability of these liposomes was due to the lower MPB-PE concentration and not to the lower number of attached Fab' fragments. By proper adjustment of the experimental conditions for coupling, the number of Fab' fragments attached to the 1 mol % MPB-PE liposomes could be increased without affecting the stability of the resulting liposomes. These stable liposomes, made by an extrusion method that avoids the use of organic solvents, detergents, or sonication, are therefore suitable for entrapment of labile compounds and can be used for immunotargeting or immunoassays. 相似文献
7.
Degeneration of the knee joint and increase of anterior-posterior tibial displacement are resulting from total meniscectomy, especially in knees with anterior cruciate deficiency. Vascularisation of the meniscus was studied in 12 cadaver knees after latex injection of vessels. Vascularisation of the anterior and posterior horns was found to be much better than that of the body of meniscus. All vessels originated from the popliteal artery, but variably in importance, and formed the perimeniscal and subsynovial network. 11 peripheral meniscus tears (8 freshly injured, 3 ruptures older than 2 months) were repaired by refixation, followed by immobilisation for 6 weeks. Arthroscopy 3 months postoperatively showed complete healing of all tears. Clinical examinations--follow-up for 14 months--showed no signs of rerupture in any of the patients. 相似文献
8.
Summary Cytoplasmic male sterility (cms) and nuclear male sterility (nms) in Petunia were described respectively as possible autonomous and integrated states of the same genetic element by Frankel (1971). In the present study we describe genetic analysis of the interaction between the cms, the nuclear gene for male sterility (e) and the fertility restorer allele (Rf). The main findings in this study are: (1) The nuclear sterility allele can coexist in one or two dosages with the cytoplasmic male sterility elements (ste) in somatic cells or female gametes; (2) the presence of the fertility restorer allele Rf is not required for the coexistence of ste and e and (3) Rf does not interact epistatically with e, e.g., the expression of e is independent of Rf—the genotypes (S) RfRfee and (S) Rfrfee are male sterile.Contribution from the Agricultural Research Organization. The Volcani Center, Bet Dagan, Israel. 1983 series No. 846 E 相似文献
9.
Frameshift Suppression in SACCHAROMYCES CEREVISIAE VI. Complete Genetic Map of Twenty-Five Suppressor Genes 总被引:14,自引:4,他引:10
Five previously unmapped frameshift suppressor genes have been located on the yeast genetic map. In addition, we have further characterized the map positions of two suppressors whose approximate locations were determined in an earlier study. These results represent the completion of genetic mapping studies on all 25 of the known frameshift suppressor genes in yeast.—The approximate location of each suppressor gene was initially determined through the use of a set of mapping strains containing 61 signal markers distributed throughout the yeast genome. Standard meiotic linkage was assayed in crosses between strains carrying the suppressors and the mapping strains. Subsequent to these approximate linkage determinations, each suppressor gene was more precisely located in multi-point crosses. The implications of these mapping results for the genomic distribution of frameshift suppressor genes, which include both glycine and proline tRNA genes, are discussed. 相似文献
10.
Abstract: The present study compares the effects of chronic administration of basic fibroblast growth factor (bFGF) and nerve growth factor (NGF) on various hippocampal cholinergic parameters in rats with partial unilateral fimbrial transections. Lesions resulted in marked reductions of several presynaptic cholinergic parameters: choline acetyltransferase (ChAT) activity (by 50%), [3H]-acetylcholine ([3H]ACh) synthesis (by 59%), basal and ve-ratridine (1 μM)-evoked [3H]ACh release (by 44 and 57%, respectively), and [3H]vesamicol binding site densities (by 35%). In addition, [3H]AF-DX 116/muscarinic M2 binding site densities were also modestly decreased (by 23%). In contrast, [3H]pirenzepine/muscarinic M1 and [3H]AF-DX 384/muscarinic M2/M4 binding site densities were not altered by the lesions, nor were they affected by any of the treatments. Intracerebroventricular administration of bFGF (10 ng, every other day, for 21 days) partially prevented the lesion-induced deficit in hippocampal ChAT activity, an effect that was not markedly different from that measured in the NGF-treated (1 μg intracerebroventricularly, every other day, for 21 days) rats. In rats treated with a combination of bFGF and NGF, ChAT activity was not different from that in rats treated with the individual factors alone. In contrast, the lesion-induced deficits in the other cholinergic parameters were not attenuated by bFGF treatment, although they were at least partially prevented by NGF administration. To determine whether higher concentrations of bFGF are necessary to affect cholinergic parameters other than hippocampal ChAT activity, rats were treated with 1 μg (every other day, 21 days) of the growth factor. In this group of rats, detrimental effects of bFGF, manifested by an increased death rate (46%), and marked reductions in body weight of the survivors, were observed. In addition, this concentration of bFGF appeared to exacerbate the lesion-induced reduction in [3H]ACh synthesis by hippocampal slices; [3H]ACh synthesis in lesioned hippocampi represented 36 and 52% of that in contralateral unlesioned hippocampi for the bFGF-treated and control groups, respectively. In conclusion, although bFGF administration attenuates the deficit in hippocampal ChAT activity induced by partial fimbrial transections, this does not appear to translate into enhanced functional capacity of the cholinergic terminals. This is clearly in contrast to NGF, which enhances not only hippocampal ChAT activity, but also other parameters indicative of increased function in the cholinergic terminals. 相似文献