Influence of UV radiation on immunological system and occurrence of autoimmune diseases

During the last three decades scientists worldwide have investigated how ultraviolet radiation (UVR) influences the immune system. The vast majority of the researchers was primarily focused on the local immunomodulatory role of UVR. But today evidence is increasing in favor of plural immune activation and systemic reaction of the organism. Most of the attention is directed toward the regulatory T lymphocytes which are responsible for the local and systemic immunosuppressive response under the impact of sunlight. The role of regulatory T cells in autoimmune diseases is well studied on patients with systemic lupus erythematosus (SLE). Epidemiological research shows a proportional interdependence of latitude and prevalence of autoimmune diseases such as multiple sclerosis (MS), insulin-dependent diabetes mellitus (IDDM) and rheumatoid arthritis (RA). There is evidence that UVR has direct influence on the level of antibodies against the SNF2-superfamily helicase (Mi-2), distinctive for dermatomyositis (DM). On this basis a hypothesis is established that UVR is a risk factor for DM. A Croatian epidemiologic study o f systemic sclerosis (SSc) gave results consistent with the hypothesis that there is a higher prevalence of SSc in the Mediterranean regions of Croatia. Such discoveries encouraged further studies that found that not only regulatory T cells are responsible for a systemic immunosuppressive response, but that there is a complex interactive network of immune cells and mediators such as cytokines, neuropeptides, and chromophores like urocanic acid involved. Present findings require continued research on the importance of UVR on autoimmune disease prevalence and immunopathophysiology. Finally, it is necessary to distinguish whether UVR is a protective factor for some autoimmune diseases or a risk factor for their induction.     

Floristic diversity of an eastern Mediterranean dwarf shrubland: the importance of soil pH

Questions: Does plant species richness and composition of eastern Mediterranean dwarf shrubland (phrygana) correlate with soil pH? How important is the effect of pH on species diversity in relation to other environmental factors in this ecosystem? What is the evolutionary background of the diversity–pH relationship? Location: Western Crete, Greece. Methods: Species composition of vascular plants, soil and other environmental variables were sampled in 100‐m² plots on acidic and basic bedrock in phrygana vegetation. The relationships between species composition and environmental variables (including climate) were tested using canonical correspondence analysis, and relationships between species richness and environment using correlation and regression analyses. Data were analysed separately for different plant functional types based on life form and life span. Results: Although soil pH varied across a narrow range (5.9‐8.1), species composition changed significantly along the pH gradient within all plant functional types. For most functional types, the effect of soil pH on species composition was stronger than that of other environmental variables. Species richness of annuals, geophytes and suffruticose chamaephytes increased with soil pH, while richness of hemicryptophytes and shrubs was not correlated with pH. Conclusions: The results are consistent with the evolutionary species pool hypothesis. High numbers of calcicole annuals, geophytes and suffruticose chamaephytes may be a result of the evolution of these groups on base‐rich dry soils in the Mediterranean climate. In contrast, hemicryptophytes, a life form typical of the temperate zone, evolved on both acidic and basic soils and therefore their species numbers do not respond to soil pH across the narrow range studied. The lack of a relationship between shrub species richness and pH is difficult to explain: it may reflect the more diverse or older origin of Mediterranean woody species and their conservative niches.     

Redundancy in antigen-presenting function of the HLA-DR and -DQ molecules in the multiple sclerosis-associated HLA-DR2 haplotype

The three HLA class II alleles of the DR2 haplotype, DRB1*1501, DRB5*0101, and DQB1*0602, are in strong linkage disequilibrium and confer most of the genetic risk to multiple sclerosis. Functional redundancy in Ag presentation by these class II molecules would allow recognition by a single TCR of identical peptides with the different restriction elements, facilitating T cell activation and providing one explanation how a disease-associated HLA haplotype could be linked to a CD4+ T cell-mediated autoimmune disease. Using combinatorial peptide libraries and B cell lines expressing single HLA-DR/DQ molecules, we show that two of five in vivo-expanded and likely disease-relevant, cross-reactive cerebrospinal fluid-infiltrating T cell clones use multiple disease-associated HLA class II molecules as restriction elements. One of these T cell clones recognizes >30 identical foreign and human peptides using all DR and DQ molecules of the multiple sclerosis-associated DR2 haplotype. A T cell signaling machinery tuned for efficient responses to weak ligands together with structural features of the TCR-HLA/peptide complex result in this promiscuous HLA class II restriction.     

Trichothecene mycotoxins in kernels and head fusariosis susceptibility in winter triticale

A single isolates ofFusarium graminearum Schwabe KF 366 andFusarium culmorum (W.G.Sm.) Sacc. KF 365 were used to infect 10 genotypes (9 lines and one cultivar) of winter triticale, 1 rye cultivar and 1 wheat cultivar, and amounts of mycotoxins in kernels were analysed at the same stage of development. One genotype of triticale CHD 353/79 and rye “Chodan” were found to be most resistant towards both species infection with lowest amount of mycotoxins (deoxynivalenol) content in kernels and also the lowest yield reduction. The most susceptible line CZR 142 cumulated in kernels about ten times higher amount of mycotoxins (up 53 mg DON/kg and 16 mg 3AcDON/kg, and 5 mg zearalenone/kg). GenerallyF, culmorum formed higher level of mycotoxins in kernels of infected heads thanF. graminearum. In kernels of more susceptible genotypes except deoxynivalenol, 3 acetyldeoxynivalenol and zearalenone also were present.     

1,2-Dioxetanes: Novel chemiluminescent enzyme substrates. Applications to immunoassays

We have synthesized and studied two 1,2-dioxetane-based chemiluminescent enzyme substrates: 3-(2′-spiroadamantane)-4-methoxy-4-(3″-phosphoryloxy)phenyl-1,2-dioxetane (AMPPD), and, 3-(2′-spiroadamantane)-4-methoxy-4- (3″-β-D ′-galactopyrano-yloxy)phenyl-1,2-dioxetane (AMPGD), which can be activated to chemiluminescence at 470 nm by alkaline phosphatase and βD -galactosidase, respectively. In addition, we observed that certain macromolecules enhance the luminescence of AMPPD. For example, the addition of 0.1% bovine serum albumin amplifies the luminescent signal and improves the detection limit for alkaline phosphatase by approximately one order of magnitude under certain conditions. This effect is due to the presence of a hydrophobic microenvironment provided by the enhancer which ‘stabilizes’ the dephosphorylated AMPPD emitter. Alkaline phosphatase catalysed chemiluminescence from AMPPD is constant for a prolonged period of time. Using AMPPD we were able to detect 0.01 attomole quantities of alkaline phosphatase immobilized on membrane supports and imaged on photographic film and, in solution, measured in a luminometer. AMPPD and AMPGD offer alternatives to colorimetric and fluorescent subsrates for alkaline phosphatase and β-D -galactosidase labels used in enzyme immunoassays. The simplicity and sensitivity of this chemiluminescent readout allowed the development of rapid clinical assays (e.g. β-hCG, LH, TSH and others).     

Investigations on some hybrids from theArabis hirsuta complex

Natural and artificial hybrids between the tetraploidArabis hirsuta (L.)Scop. s. str. and two diploid speciesA. sagittata (Bertol.) DC. orA. planisiliqua (Pers.)Reichenb. are the main subject of this paper. The investigations concern pollination behaviour, sterility, occurrence and frequency of hybrids, their morphology and cytology. Some questions concerning relations of the taxa within the complex and the significance of hybrids in the variability of natural mixed populations are discussed.