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101.
Direct effect of glucose on the preproinsulin mRNA level in isolated pancreatic islets 总被引:17,自引:0,他引:17
The effects of glucose on the preproinsulin mRNA level and the rate of (pro)insulin biosynthesis were examined in isolated mouse pancreatic islets. Relative concentrations of preproinsulin mRNA were quantitated by a RNA-dot hybridization procedure. The level of preproinsulin mRNA in islets incubated for up to 7 days at 20 mM glucose remained constant. In islets incubated at 3.3 mM glucose the preproinsulin mRNA level decreased and was after 24 h reduced to one tenth of the level at 20 mM glucose. Subsequent incubation at 20 mM glucose completely restored the preproinsulin mRNA level but only after 3 days of culture, while the insulin release was restored within 24 h. The insulin-biosynthetic activity of the islets was correlated to the variation in the level of the preproinsulin mRNA. These results suggest that glucose does have a direct influence on the level of preproinsulin mRNA and that the rate of (pro)insulin biosynthesis is limited by the level of the preproinsulin mRNA. 相似文献
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105.
T L Green D D Hunter W Chan J P Merlie J R Sanes 《The Journal of biological chemistry》1992,267(3):2014-2022
S-laminin, a homologue of the B1 chain of laminin, is concentrated in a subset of basal laminae (BLs), including the BL at the skeletal neuromuscular junction and bears an adhesive site for motoneuron-like cells. Here, we have begun to characterize the native form of the protein. We show that several muscle- and glia-like cell lines synthesize and secrete S-laminin as well as the A, B1, and B2 subunits of the conventional laminin trimer. Experiments using subunit-specific antibodies showed that S-laminin is complexed with the A and B2 subunits of laminin but not with B1, suggesting that S-laminin replaces B1 to form a novel laminin-like trimer. Comparison of material precipitated by different antibodies provided evidence for two immunochemically distinct forms of S-laminin, both of which associate with B2 and A-like subunits. Analysis of tunicamycin-treated cells indicated that N-linked glycosylation is required neither for the selective association of S-laminin with B2 and A subunits nor for the distinction between two forms of S-laminin. Finally, a full-length S-laminin cDNA was constructed and transfected into muscle and non-muscle cells. S-laminin was detected intracellularly in both cell types, in extracellular matrix of muscle cells, and in two immunochemically distinct forms. Thus, the cDNA contains sufficient information to permit assembly, secretion, and post-translational modification of S-laminin. 相似文献
106.
Micromanipulation of adhesion of a Jurkat cell to a planar bilayer membrane containing lymphocyte function-associated antigen 3 molecules 下载免费PDF全文
A T?zeren K L Sung L A Sung M L Dustin P Y Chan T A Springer S Chien 《The Journal of cell biology》1992,116(4):997-1006
Cell adhesion plays a fundamental role in the organization of cells in differentiated organs, cell motility, and immune response. A novel micromanipulation method is employed to quantify the direct contribution of surface adhesion receptors to the physical strength of cell adhesion. In this technique, a cell is brought into contact with a glass-supported planar membrane reconstituted with a known concentration of a given type of adhesion molecules. After a period of incubation (5-10 min), the cell is detached from the planar bilayer by pulling away the pipette holding the cell in the direction perpendicular to the glass-supported planar bilayer. In particular, we investigated the adhesion between a Jurkat cell expressing CD2 and a glass-supported planar bilayer containing either the glycosyl-phosphatidylinositol (GPI) or the transmembrane (TM) isoform of the counter-receptor lymphocyte function-associated antigen 3 (LFA-3) at a concentration of 1,000 molecules/microns 2. In response to the pipette force the Jurkat cells that adhered to the planar bilayer containing the GPI isoform of LFA-3 underwent extensive elongation. When the contact radius was reduced by approximately 50%, the cell then detached quickly from its substrate. The aspiration pressure required to detach a Jurkat cell from its substrate was comparable to that required to detach a cytotoxic T cell from its target cell. Jurkat cells that had been separated from the substrate again adhered strongly to the planar bilayer when brought to proximity by micromanipulation. In experiments using the planar bilayer containing the TM isoform of LFA-3, Jurkat cells detached with little resistance to micromanipulation and without changing their round shape. 相似文献
107.
Molecular variants of human papillomavirus type 16 from four continents suggest ancient pandemic spread of the virus and its coevolution with humankind. 总被引:7,自引:0,他引:7 下载免费PDF全文
S Y Chan L Ho C K Ong V Chow B Drescher M Dürst J ter Meulen L Villa J Luande H N Mgaya et al. 《Journal of virology》1992,66(4):2057-2066
We have amplified by the polymerase chain reaction, cloned, and sequenced genomic segments of 118 human papillomavirus type 16 (HPV-16) isolates from 76 cervical biopsy, 14 cervical smear, 3 vulval biopsy, 2 penile biopsy, 2 anal biopsy, and 1 vaginal biopsy sample and two cell lines. The specimens were taken from patients in four countries--Singapore, Brazil, Tanzania, and Germany. The sequence of a 364-bp fragment of the long control region of the virus revealed 38 variants, most of which differed by one or several point mutations. Phylogenetic trees were constructed by distance matrix methods and a transformation series approach. The trees based on the long control region were supported by another set based on the complete E5 protein-coding region. Both sets had two main branches. Nearly all of the variants from Tanzania were assigned to one (African) branch, and all of the German and most of the Singaporean variants were assigned to the other (Eurasian) branch. While some German and Singaporean variants were identical, each group also contained variants that formed unique branches. In contrast to the group-internal homogeneity of the Singaporean, German, and Tanzanian variants, the Brazilian variants were clearly divided between the two branches. Exceptions to this were the seven Singaporean isolates with mutational patterns typical of the Tanzanian isolates. The data suggest that HPV-16 evolved separately for a long period in Africa and Eurasia. Representatives of both branches may have been transferred to Brazil via past colonial immigration. The comparable efficiencies of transfer of the African and the Eurasian variants to the New World suggest pandemic spread of HPV-16 in past centuries. Representatives of the African branch were possibly transferred to the Far East along old Arab and Indonesian sailing routes. Our data also support the view that HPV-16 is a well-defined virus type, since the variants show only a maximal genomic divergence of about 5%. The small amount of divergence in any one geographic location and the lack of marked divergence between the Tanzanian and Brazilian African genome variants two centuries after their likely introduction into the New World suggest a very slow rate of viral evolution. The phylogenetic tree therefore probably represents a minimum of several centuries of evolution, if not an age equal to that of the respective human races. 相似文献
108.
E Beraud S Kotake R R Caspi S M Oddo C C Chan I Gery R B Nussenblatt 《Cellular immunology》1992,140(1):112-122
Autoimmune T lymphocytes can be used under appropriate conditions to induce resistance to the specific autoimmune disease that they usually produce. This practice, termed T cell vaccination, was found to be effective with the injection of a low (subpathogenic) number of autoaggressive T line lymphocytes. We report here that T cell vaccination produced marked resistance to the expression of experimental autoimmune uveoretinitis (EAU) in Lewis rats. In addition, vaccination led to the appearance of lymphoid cells in the vaccinated rats that demonstrated proliferative responses against idiotypic and ergotypic specificities of the injected T cells. This is the first report demonstrating the effector T lymphocytes specific for ocular antigens may be used as agents to modulate immunopathogenic responses responsible for EAU. 相似文献
109.
A biochemical genetic study of the enzyme malate dehydrogenase (MDH) was conducted in the grasshopperOxya j. japonica. Analysis of MDH electrophoretic variation in this species of grasshopper shows that one of the two autosomal loci for MDH in grasshoppers, the Mdh-2 locus, controlling the anodal set of MDH isozymes, is duplicated. Results of breeding studies confirm this and the observed polymorphism at theMdh-2 locus in the two populations ofOxya j. japonica studied can be attributed to three forms of linked alleles at the duplicated locus in equilibrium in both populations. In this respect, all individuals of this species possess heterozygous allelic combinations at the duplicatedMdh-2 locus, which may account for the spread of the duplicated locus in the populations of this species of grasshopper.This research was supported by a grant (Vote F) from the University of Malaya, Kuala Lumpur. 相似文献
110.
S T Butera V L Perez N J Besansky W C Chan B Y Wu G J Nabel T M Folks 《Journal of cellular biochemistry》1991,45(4):366-373
In this report, we describe a human immunodeficiency virus type-1 (HIV-1)-infected promyelocytic cell line, OM, derived from HL-60 cells. Although the OM cell line was biologically cloned twice, the pattern of HIV-1 expression during culture appeared analogous to a classical acute spreading infection and was inhibited by both azidothymidine and recombinant soluble CD4 treatment. The number of OM cells actually expressing HIV-1 at the beginning of culture was 0%, reached a peak of nearly 100% at 6 weeks, and then fell to less than 10% HIV-1+ cells by 10 weeks. Clonal analysis of the surviving cells verified that stable HIV-1+ OM cells resulted from the spreading infection. Southern analysis confirmed the transmission of HIV-1 through these OM cultures and the occurrence of stable clones which resulted. The initial percentage of OM cells actually harboring the HIV-1 genome was less than 0.1%, indicating nonfaithful transmission of an unintegrated HIV-1 genome during clonal expansion. These results demonstrate that extrachromosomal HIV-1 DNA can contribute to the spread of HIV-1 infection and give rise to cells which have stably integrated HIV-1 provirus. 相似文献