Influence of diet on life table parameters of <Emphasis Type="Italic">Iphiseius degenerans</Emphasis> (Acari: Phytoseiidae)

Studies on the reproduction, longevity and life table parameters of Iphiseius degenerans (Berlese) were carried out under laboratory conditions of 25 ± 1 °C, 75 ± 5% RH and 16L:8D h. As food sources for the predatory mite, Ricinus communis L. pollen, all stages of the spider mite Tetranychus urticae Koch, Frankliniella occidentalis (Pergande) larvae, and Ephestia kuehniella Zeller eggs were selected. All diets were accepted as food by the adult mites. Female longevity ranged from 29.5 to 42.4 days, the highest value was recorded on a diet of Ephestia eggs. The highest percentage of females escaping the experimental arena was observed on the diet consisting of thrips larvae. The highest oviposition rate (1.9 eggs/female.day) was recorded when the predator was fed on spider mites on an artificial substrate. For other diets, oviposition rates ranged from 1.0 to 1.3 eggs/female.day. The intrinsic rate of natural increase (r _m) of I. degenerans varied between 0.015 and 0.142 females/female.day. The diet consisting of castor bean pollen resulted in the highest population growth whereas the diet on spider mites brushed off onto a bean leaf arena resulted in the slowest population growth. This can be explained by the inability of the predator to cope with the webbing of T. urticae, and the high escape rate of the progeny when reared on spider mites. The percentage of females in the offspring ranged from 40 to 73%.This revised version was published online in May 2005 with a corrected cover date.     

Unraveling the mechanism of radiosensitization by gemcitabine: the role of TP53

Gemcitabine has excellent radiosensitizing properties, as shown in both preclinical and clinical studies. Radiosensitization correlated with the early S-phase block of gemcitabine. In the present study, we investigated the role of TP53 in the radiosensitizing effect of gemcitabine. Isogenic A549 cells differing in TP53 status were treated with gemcitabine during the 24 h prior to irradiation. Cell survival was determined 7 days after irradiation by the sulforhodamine B test. In addition, cell cycle perturbation was determined by flow cytometry and TP53 expression by Western blot analysis. Gemcitabine caused a concentration-dependent radiosensitizing effect in all cell lines. Transformed A549 cells were less sensitive to the cytotoxic effect of gemcitabine. The cell cycle arrest early in the S phase was dependent on the drug dose but was comparable in the different cell lines and was not related to functional TP53. Using isogenic cell lines, we have shown that neither TP53 status nor the transfection procedure influenced the radiosensitizing effect of gemcitabine. Since both the radiosensitizing effect at equitoxic concentrations and the cell cycle effect of gemcitabine were independent of TP53 expression, it is likely that TP53 protein does not play a crucial role in the radiosensitizing mechanism of gemcitabine.     

Microbial Biomass, Community Structure and Metal Tolerance of a Naturally Pb-Enriched Forest Soil

The effect of long-term elevated soil Pb levels on soil microbiota was studied at a forest site in Norway, where the soil has been severely contaminated with Pb since the last period of glaciation (several thousand years). Up to 10% Pb (total amount, w/w) has been found in the top layer. The microbial community was drastically affected, as judged from changes in the phospholipid fatty acid (PLFA) pattern. Specific PLFAs that were high in Pb-enriched soil were branched (especially br17:0 and br18:0), whereas PLFAs common in eukaryotic organisms such as fungi (18:2ω6,9 and 20:4) were low compared with levels at adjacent, uncontaminated sites. Congruent changes in the PLFA pattern were found upon analyzing the culturable part of the bacterial community. The high Pb concentrations in the soil resulted in increased tolerance to Pb of the bacterial community, measured using both thymidine incorporation and plate counts. Furthermore, changes in tolerance were correlated to changes in the community structure. The bacterial community of the most contaminated soils showed higher specific activity (thymidine and leucine incorporation rates) and higher culturability than that of control soils. Fungal colony forming units (CFUs) were 10 times lower in the most Pb-enriched soils, the species composition was widely different from that in control soils, and the isolated fungi had high Pb tolerance. The most commonly isolated fungus in Pb-enriched soils was Tolypocladium inflatum. Comparison of isolates from Pb-enriched soil and isolates from unpolluted soils showed that T. inflatum was intrinsically Pb-tolerant, and that the prolonged conditions with high Pb had not selected for any increased tolerance.     

Copper- and magnesium protoporphyrin complexes inhibit oxidative modification of LDL induced by hemin, transition metal ions and tyrosyl radicals

The oxidative modification of LDL may play an important role in the early events of atherogenesis. Thus the identification of antioxidative compounds may be of therapeutic and prophylactic importance regarding cardiovascular disease. Copper-chlorophyllin (Cu-CHL), a Cu²⁺-protoporphyrin IX complex, has been reported to inhibit lipid oxidation in biological membranes and liposomes. Hemin (Fe³⁺-protoporphyrin IX) has been shown to bind to LDL thereby inducing lipid peroxidation. As Cu-CHL has a similar structure as hemin, one may assume that Cu-CHL may compete with the hemin action on LDL. Therefore, in the present study Cu-CHL and the related compound magnesium-chlorophyllin (Mg-CHL) were examined in their ability to inhibit LDL oxidation initiated by hemin and other LDL oxidizing systems. LDL oxidation by hemin in presence of H₂O₂ was strongly inhibited by both CHLs. Both chlorophyllins were also capable of effectively inhibiting LDL oxidation initiated by transition metal ions (Cu²⁺), human umbilical vein endothelial cells (HUVEC) and tyrosyl radicals generated by myeloperoxidase (MPO) in presence of H₂O₂ and tyrosine. Cu- and Mg-CHL showed radical scavenging ability as demonstrated by the diphenylpicrylhydracylradical (DPPH)-radical assay and estimation of phenoxyl radical generated diphenyl (dityrosine) formation. As assessed by ultracentrifugation the chlorophyllins were found to bind to LDL (and HDL) in serum. The present study shows that copper chlorophyllin (Cu-CHL) and its magnesium analog could act as potent antagonists of atherogenic LDL modification induced by various oxidative stimuli. As inhibitory effects of the CHLs were found at concentrations as low as 1 μmol/l, which can be achieved in humans, the results may be physiologically/therapeutically relevant.     

Pro-inflammatory properties of stromal cell-derived factor-1 (CXCL12) in collagen-induced arthritis

CXCL12 (stromal cell-derived factor 1) is a unique biological ligand for the chemokine receptor CXCR4. We previously reported that treatment with a specific CXCR4 antagonist, AMD3100, exerts a beneficial effect on the development of collagen-induced arthritis (CIA) in the highly susceptible IFN-γ receptor-deficient (IFN-γR KO) mouse. We concluded that CXCL12 plays a central role in the pathogenesis of CIA in IFN-γR KO mice by promoting delayed type hypersensitivity against the auto-antigen and by interfering with chemotaxis of CXCR4⁺ cells to the inflamed joints. Here, we investigated whether AMD3100 can likewise inhibit CIA in wild-type mice and analysed the underlying mechanism. Parenteral treatment with the drug at the time of onset of arthritis reduced disease incidence and modestly inhibited severity in affected mice. This beneficial effect was associated with reduced serum concentrations of IL-6. AMD3100 did not affect anti-collagen type II antibodies and, in contrast with its action in IFN-γR KO mice, did not inhibit the delayed type hypersensitivity response against collagen type II, suggesting that the beneficial effect cannot be explained by inhibition of humoral or cellular autoimmune responses. AMD3100 inhibited the in vitro chemotactic effect of CXCL12 on splenocytes, as well as in vivo leukocyte infiltration in CXCL12-containing subcutaneous air pouches. We also demonstrate that, in addition to its effect on cell infiltration, CXCL12 potentiates receptor activator of NF-κB ligand-induced osteoclast differentiation from splenocytes and increases the calcium phosphate-resorbing capacity of these osteoclasts, both processes being potently counteracted by AMD3100. Our observations indicate that CXCL12 acts as a pro-inflammatory factor in the pathogenesis of autoimmune arthritis by attracting inflammatory cells to joints and by stimulating the differentiation and activation of osteoclasts.     

Defective CD4<Superscript>+</Superscript>CD25<Superscript>+</Superscript>regulatory T cell functioning in collagen-induced arthritis: an important factor in pathogenesis,counter-regulated by endogenous IFN-γ

Mice with a deficiency in IFN-γ or IFN-γ receptor (IFN-γR) are more susceptible to collagen-induced arthritis (CIA), an experimental autoimmune disease that relies on the use of complete Freund's adjuvant (CFA). Here we report that the heightened susceptibility of IFN-γR knock-out (KO) mice is associated with a functional impairment of CD4⁺CD25⁺ T_reg cells. Treatment of wild-type mice with depleting anti-CD25 antibody after CFA-assisted immunisation with collagen type II (CII) significantly accelerated the onset of arthritis and increased the severity of CIA. This is an indication of a role of T_reg cells in the effector phase of CIA. IFN-γR deficiency did not affect the number of CD4⁺CD25⁺ T cells in the central and peripheral lymphoid tissues. In addition, CD4⁺CD25⁺ T cells isolated from naive IFN-γR KO mice had a normal potential to suppress T cell proliferation in vitro. However, after immunisation with CII in CFA, the suppressive activity of CD4⁺CD25⁺ T cells became significantly more impaired in IFN-γR-deficient mice. Moreover, expression of the mRNA for Foxp3, a highly specific marker for T_reg cells, was lower. We further demonstrated that the effect of endogenous IFN-γ, which accounts for more suppressive activity in wild-type mice, concerns both T_reg cells and accessory cells. Our results demonstrate that the decrease in T_reg cell activity in CIA is counter-regulated by endogenous IFN-γ.     

Copper(I) and copper(II) complexes of biologically relevant tridentate ligands

The preparation of a series of tridentate ligands of formulae X(CH₂C₇H₅N₂)₂ (X = NH, S, O, S₂) is described. The ligands contain two benzimidazole moieties and one of NH, S, O, or S₂ as the donor groups. Cu(I) and Cu(II) complexes of these ligands are prepared and characterized. Spectroscopic and X-ray data imply that the geometric constraints of these ligands impose a distorted coordination geometry at copper. The implications and relevance of this chemistry to copper proteins is discussed.     

Duplication of the MECP2 region is a frequent cause of severe mental retardation and progressive neurological symptoms in males

Loss-of-function mutations of the MECP2 gene at Xq28 are associated with Rett syndrome in females and with syndromic and nonsyndromic forms of mental retardation (MR) in males. By array comparative genomic hybridization (array-CGH), we identified a small duplication at Xq28 in a large family with a severe form of MR associated with progressive spasticity. Screening by real-time quantitation of 17 additional patients with MR who have similar phenotypes revealed three more duplications. The duplications in the four patients vary in size from 0.4 to 0.8 Mb and harbor several genes, which, for each duplication, include the MR-related L1CAM and MECP2 genes. The proximal breakpoints are located within a 250-kb region centromeric of L1CAM, whereas the distal breakpoints are located in a 300-kb interval telomeric of MECP2. The precise size and location of each duplication is different in the four patients. The duplications segregate with the disease in the families, and asymptomatic carrier females show complete skewing of X inactivation. Comparison of the clinical features in these patients and in a previously reported patient enables refinement of the genotype-phenotype correlation and strongly suggests that increased dosage of MECP2 results in the MR phenotype. Our findings demonstrate that, in humans, not only impaired or abolished gene function but also increased MeCP2 dosage causes a distinct phenotype. Moreover, duplication of the MECP2 region occurs frequently in male patients with a severe form of MR, which justifies quantitative screening of MECP2 in this group of patients.