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1.
In neonatal rat gonadotrophs, melatonin inhibits several GnRH-induced effects: stimulation of LH release as well as the increase of several second messengers as cAMP, diacylglycerol and [ Ca2+ ]i . Recently, GnRH has been shown to induce expression of immediate early genes of fos and jun family in adult rat gonadotrophs. The purpose of this study was to determine, whether melatonin inhibits the GnRH-induced induction of cFos in neonatal rat pituitary cells. 相似文献
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Ring-opening metathesis copolymerization of 5-norbornen-2-yl 1 System. name: bicyclo[2.2.1]hept-5-en-2-yl. acetate (NBEAc; 80% endo) with cyclooctene (COE) and norbornene 2 System. name: bicyclo[2.2.1]hept-2-ene. (NBE) was studied using WCl6/(CH3)4Sn as catalytic system. The copolymerization parameters (r1 = r2 = 1 for the NBEAc/NBE system and r1 = 1/r2 = 132 for the NBEAc/COE system) show that the reactivity of the monomers is not affected by the presence of an ester substituent but that it depends on the structure of the hydrocarbon cycle. Thus the well known inhibition effect of the ester group may be concluded not to lie in the propagation step of the catalytic cycle. 相似文献
5.
Holán V Vítová A Krulová M Zajícová A Neuwirth A Filipec M Forrester JV 《Immunology letters》2005,100(2):211-213
The effects of passive transfer of antisera containing cytotoxic antibodies to allo- and xenoantigens on survival of corneal allografts and xenografts were evaluated in experimental models. Corneas from allogeneic B10 or xenogeneic rat Lewis donors were grafted orthotopically into BALB/c mice. Recipient mice were treated with donor-specific antisera administered at the period of grafting or at 2 weeks after transplantation. Rejection was determined by the severity of corneal opacity using a standard scoring system. Treatment of graft recipients with donor-specific antisera accelerated the onset of graft rejection and significantly shortened survival times of both corneal allografts and xenografts. Corneal xenografts, which had been accepted after treatment with anti-CD4 monoclonal antibody, were acutely rejected by the passive transfer of antiserum against xenoantigens. The results suggest that corneal grafts are vulnerable to antibody-dependent immunity and that cytotoxic antibodies against graft donor antigens can mediate rejection of both corneal allografts and xenografts. 相似文献
6.
Telomeres, besides their main role in the protection and maintenance of chromosome ends, have several other vital functions
in the cell cycle. We studied their role in the achiasmatic meiosis of female Lepidoptera, insects with holokinetic chromosomes.
By fluorescence in-situ hybridization (FISH) with the insect telomeric probe, (TTAGG)
n
, we mapped the distribution of telomeric and interstitial telomeric sequences (ITS) in female meiotic chromosomes of two
species, Orgyia antiqua with a reduced chromosome number (2n=28) and Ephestia kuehniella mutants, possessing a radiation-induced chromosome fusion in the genome (2n=59). In addition to the strong typical telomeric signals, O. antiqua displayed weaker hybridization signals in interstitial sites of pachytene bivalents. The observed ITS most probably reflect
remnants of chromosomal rearrangements and support the hypothesis that the Orgyia karyotype had arisen by multiple fusions of ancestral chromosomes. On the other hand, the absence of ITS in the chromosome
fusion of Ephestia indicated the loss of telomeres before the two original chromosomes fused. When the telomeric probe was amplified by enzymatic
reaction with tyramid, the number of ITS observed increased in Orgyia, and a few ITS were also observed in several chromosomes of Ephestia but not in the fused chromosome. This suggests that the genomes of both species also contain ITS other than those originating
from chromosome fusions. The analysis of female meiotic prophase I revealed non-homologous associations of postpachytene bivalents
mediated by telomeric DNA, which were not observed in the pachytene stage. Surprisingly, in early postpachytene nuclei the
telomeric associations also involved ITS, whereas later postpachytene nuclei displayed chains of bivalents interconnected
only by true telomeres. This finding favours a hypothesis that telomeric associations between bivalents play a role in chromosome
segregation in the achiasmatic meiosis of female Lepidoptera.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Bastien N Robinson JL Tse A Lee BE Hart L Li Y 《Journal of clinical microbiology》2005,43(9):4567-4573
8.
CD19 is an important pan B cell marker and co-stimulatory protein in humans and mice. Efforts to further characterize B cell ontogeny in swine have been hampered by the lack of monoclonal antibodies (mAb) to valuable surface markers like Vpre-B, CD19, CD34 and CD43. We report here on the complete nucleotide and deduced amino acid sequence of porcine CD19, the cross-reactivity of anti-human CD19 monoclonals and efforts to prepare anti-porcine CD19 mAb to bacterially-expressed products. Porcine CD19 is highly homologous to those in the few other species studied, i.e. human, mouse and guinea pig, but only in certain domains. Among the 14 CD19 exons, homology approaches 90% to human CD19 in exons 6, 9, 11 and 12 and is approximately 80% with other species in this region. The highly homologous C-terminal cytoplasmic region contains nine tyrosines including the YEND/E motif that binds the SH2 domain of Fyn. Two different porcine CD19 isoforms that differ in their 3' UTRs were identified just as in human CD19. Thus, the signaling properties of CD19 may be similar to those in humans. On the other hand, only 60% sequence similarity was seen in exons 1-5 that encode the N-terminal extracellullar region that is involved in ligand binding and is the target of CD19-specific mAb. This probably explains why only 1 of the 17 anti-human CD19 mAb tested recognized swine B cells. Furthermore, when the extracellular domains of CD19 were expressed in E. coli, mAbs to the bacterially-expressed product did not recognize CD19 on porcine B cells suggesting that carbohydrate-dependent conformation may determine antigenicity. 相似文献
9.
Alena Jiroutova Rastislav Slavkovsky Martina Cermakova Lenka Majdiakova Irena Hanovcova Radka Bolehovska Milena Hajzlerova Hana Radilova Ema Ruszova Jiri Kanta 《Experimental and toxicologic pathology》2007,58(4):263-273
Hepatic stellate cells (HSC) and liver myofibroblasts (MFB) are two cell populations most likely responsible for the synthesis of most connective tissue components in fibrotic liver. They differ in their origin and location, and possibly in patterns of gene expression. Normal and carbon tetrachloride-cirrhotic livers from rats were used to isolate HSC. Liver was perfused with pronase and collagenase solutions, followed by centrifugation of the cell suspension on a density gradient. HSC were quiescent 2 days after plating on plastic but they became activated after another 5 days in culture. When the culture was passaged 5 times, its character changed profoundly as HSC were replaced by MFB. Microarray analysis was used to determine gene expression in quiescent HSC, activated HSC and MFB. The expression of 49 genes coding for connective tissue proteins, proteoglycans, metalloproteinases and their inhibitors, growth factors and cellular markers was determined. The pattern of gene expression changed during HSC activation and there were distinct differences between HSC and MFB. Little difference between normal cells and cells isolated from cirrhotic liver was found. 相似文献
10.
Central tolerance: good but imperfect 总被引:12,自引:0,他引:12
Summary: T-cell development is a highly coordinated process that depends on interactions between thymocytes, thymic epithelium, and bone marrow (BM)-derived dendritic cells (DCs). Before entering the peripheral T-cell pool, thymocytes are subject to negative selection, a process that eliminates (or deletes) T cells with high affinity toward self-antigens and therefore promotes self-tolerance. These self-antigens include those that are broadly expressed ubiquitous antigens and those whose expression is restricted to a few tissues, tissue-specific antigens (TSAs). Expression of TSAs in the thymus is mostly a property of medullary thymic epithelial cells (mTECs), and because these cells may be less capable than BM-derived DCs at mediating negative selection to ubiquitous antigens, we investigated the roles of both of these cell types in tolerance to TSAs. Here, we review our studies in which we found that mTECs were competent mediators of negative selection to a subset of TSA-reactive T cells, while thymic DCs extend the range of TSA-reactive T cells that undergo negative selection by capturing TSAs from mTECs. In addition, we recently investigated the efficiency of central tolerance to TSA during ontogeny, and we report that this process was less efficient in neonates than adult animals. 相似文献