Vyznam diapauzy pro chladovou odolnost plostic Pyrrhocoris apterus (L.) a graphosoma lineatum (L.) v predzimnim obdobi.

Text also in EnglishAvailable from STL, Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

How insects survive the cold: molecular mechanisms - a review

Insects vary considerably in their ability to survive low temperatures. The tractability of these organisms to experimentation has lead to considerable physiology-based work investigating both the variability between species and the actual mechanisms themselves. This has highlighted a range of strategies including freeze tolerance, freeze avoidance, protective dehydration and rapid cold hardening, which are often associated with the production of specific chemicals such as antifreezes and polyol cryoprotectants. But we are still far from identifying the critical elements behind over-wintering success and how some species can regularly survive temperatures below -20°C. Molecular biology is the most recent tool to be added to the insect physiologist’s armoury. With the public availability of the genome sequence of model insects such as Drosophila and the production of custom-made molecular resources, such as EST libraries and microarrays, we are now in a position to start dissecting the molecular mechanisms behind some of these well-characterised physiological responses. This review aims to provide a state of the art snapshot of the molecular work currently being conducted into insect cold tolerance and the very interesting preliminary results from such studies, which provide great promise for the future

The non-palindromic adaptor-PCR method for the identification of the T-cell receptor genes of an interferon-gamma-secreting T-cell hybridomaspecific for trans-sialidase, an immunodominant Trypanosoma cruzi antigen

Cloning of the T-cell receptor genes is a critical step when generating T-cell receptor transgenic mice. Because T-cell receptor molecules are clonotypical, isolation of their genes requires reverse transcriptase-assisted PCR using primers specific for each different Valpha or Vß genes or by the screening of cDNA libraries generated from RNA obtained from each individual T-cell clone. Although feasible, these approaches are laborious and costly. The aim of the present study was to test the application of the non-palindromic adaptor-PCR method as an alternative to isolate the genes encoding the T-cell receptor of an antigen-specific T-cell hybridoma. For this purpose, we established hybridomas specific for trans-sialidase, an immunodominant Trypanosoma cruzi antigen. These T-cell hybridomas were characterized with regard to their ability to secrete interferon-gamma, IL-4, and IL-10 after stimulation with the antigen. A CD3+, CD4+, CD8- interferon-gamma-producing hybridoma was selected for the identification of the variable regions of the T-cell receptor by the non-palindromic adaptor-PCR method. Using this methodology, we were able to rapidly and efficiently determine the variable regions of both T-cell receptor chains. The results obtained by the non-palindromic adaptor-PCR method were confirmed by the isolation and sequencing of the complete cDNA genes and by the recognition with a specific antibody against the T-cell receptor variable ß chain. We conclude that the non-palindromic adaptor-PCR method can be a valuable tool for the identification of the T-cell receptor transcripts of T-cell hybridomas and may facilitate the generation of T-cell receptor transgenic mice

The involvement of activated T cells and growth-factor production in the early and late phase of chronic kidney allograft nephropathy in rats.

T cells are thought to play a regulatory role in chronic allograft nephropathy (CAN). Thus, we investigated whether lymphocyte inhibition influences CAN. Fisher rat (F-344) kidneys were transplanted orthotopically into Lewis rats. Animals received cyclosporin A (1.5 mg/kg per day, s.c.) for 10 days and were treated daily with either cyclosporin A (1.5 mg/kg), tacrolimus (0.16 mg/kg), or a vehicle thereafter ( n=15 per group). Kidneys were harvested at 16 or 24 weeks. Interleukin-2 (IL-2) and interleukin-2 receptor beta (IL-2Rbeta) mRNA synthesis were intense at 16 weeks and decreased thereafter. Unsurprisingly, both cyclosporin A and tacrolimus significantly inhibited IL-2 and IL-2Rbeta at both time points. Proteinuria increased more rapidly in controls than in treated animals. Morphologically, over 40% of glomeruli were sclerosed by 16 weeks in controls, and ED-1+ macrophages and CD5+ T cells infiltrated the graft. IL-2 mRNA synthesis paralleled the number of infiltrating cells. Inhibition of T-cell proliferation significantly reduced glomerulosclerosis and leukocyte infiltration at both time points. Transforming growth factor (TGF)-beta(1) and platelet-derived growth factor (PDGF) synthesis were highly upregulated in controls at 16 weeks, the time of peak infiltration. At 24 weeks, as cellular infiltration was replaced by scar formation, TGF-beta(1) mRNA returned to normal, while PDGF did not. Inhibition of T cells prevented the upregulation of TGF-beta(1) at both time points; however, PDGF was suppressed only at week 16. These results indicate a beneficial effect of continuous suppression of T cells in CAN. T cells are probably more important in the early, inflammatory phase