Hydrogen peroxide production was measured in non-elicited rat peritoneal macrophages using luminol-dependent chemiluminescence (LDCL). Isolated cells were activated by a chemotactic peptide (FMLP) or by a phorbol ester (PMA) or by the combination of both. A hundred-fold higher LDCL intensity was achieved with PMA relative to FMLP. However, when FMLP was added subsequently to PMA it produced approximately the same response as did PMA. These measurements were carried out with cells isolated from controls and from animals exposed to normobaric hypoxia (10 % O2) for 3 hours, 3 days, or 21 days. Hypoxia had a dual effect. Acutely (within 3 hours) it attenuated the production of hydrogen peroxide triggered by PMA, whilst during longer exposure (3 or 21 days) it increased the response induced by FMLP. Hypoxia can thus modulate the capacity of respiratory burst in peritoneal macrophages.
Haploid parthenogenesis in facultatively apomictic Pilosella generated polyhaploid progeny (with half the maternal chromosome set) both in natural populations and garden experiments. Production of polyhaploids varied considerably among different species, hybridogenous species and hybrids. In the field (14 localities), the highest frequency of polyhaploids exceeded 80% of the total seed progeny produced by some recent hybrids. A similar diversity in the production of polyhaploids was also recorded in garden experiments. A two-step process by which new genotypes of both P. aurantiaca (tetraploid) and P. rubra (hexaploid) were formed under garden conditions during a polyploid–polyhaploid–polyploid cycle is described. In the first step, the maternal plants generated dihaploid and trihaploid F1 progeny, respectively. Although a substantive part of this polyhaploid progeny was either non-viable or sterile, the apomictic polyhaploids occasionally doubled their genome. Consequently, the F2 progeny resulting from the second step had a double ploidy level, identical to that of the original maternal parent. The complete process was autonomous, without contribution of pollen from parent genotype. This cycle necessarily implicates increasing homozygosity in F2 progeny compared to the original maternal polyploid plant. The probabilities of particular steps of this process occurring in Pilosella and the variation in polyhaploids are estimated and described, and the ability of polyhaploid plants to survive under field conditions discussed. Probability of the complete cycle (haploid parthenogenesis followed by doubling of the genome), which occurred under garden conditions in P. rubra, is estimated to be in the order of hundredths of percent. Despite this low probability, it can result in the production of new homozygous genotypes in populations of apomicts, especially in those occurring in disturbed habitats with little competition.
Matrix metalloproteinases (MMPs) is a family of proteolytic enzymes involved in remodeling of extracellular matrix. Although proteolytic enzymes are produced by many cell types, mast cells seem to be more important than other types in remodeling of pulmonary arteries during hypoxia. Therefore, we tested in vitro production of MMPs and serine proteases in four cell types (mast cells, fibroblasts, vascular smooth muscle cells and endothelial cells) cultivated for 48 h under normoxic or hypoxic (3 % O2) conditions. MMP-13 was visualized by immunohistochemistry, MMP-2 and MMP-9 were detected by zymography in cell lysates. Enzymatic activities (MMPs, tryptase and chymase) were estimated in the cultivation media. Hypoxia had a minimal effect on total MMP activity in the cultivation media of all types of cells, but immunofluorescence revealed higher intensity of MMP-13 in the cells exposed to hypoxia except of fibroblasts. Tryptase activity was three times higher and chymase activity twice higher in mast cells cultivated in hypoxia than in those cultured in normoxia. Among all cell types studied here, mast cells are the most abundant source of proteolytic enzymes under normoxic and hypoxic conditions. Moreover, in these cells hypoxia increases the production of both specific serine proteases tryptase and chymase, which can act as MMPs activators., H. Maxová ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
We studied growth rates in four eublepharid species in which mass-metabolic allometry was available from the literature. The lizards were reared in a common garden environment and the growth data were analysed using the production/growth model (W e s t et al. 2001: Nature 413: 628–631). The model fits well our data in eublepharid geckos, and thus the applicability of this model to reptile growth was demonstrated. Estimated values of growth-rate parameter (a) fell within the range known in other ectotherm animals. As expected from theoretical parameter derivation, species sharing the same mass-metabolic allometry (Eublepharis macularius, Coleonyx mitratus, Coleonyx elegans) show comparable a in spite of considerable interspecific differences in asymptotic body mass. Moreover, in accordance with theoretical predictions, the only examined species with the elevated metabolic scaling, i.e. Coleonyx brevis, showed higher a than the other species.
We solve the long standing problem of characterizing the class of strongly Fréchet spaces whose product with every strongly Fréchet space is also Fréchet.
Katherine Terell., Popsáno podle obálky, Pod názvem: Center for Economic Research and Graduate Education. Faculty of Social Sciences. Charles University, and Obsahuje bibliografii