Chemical crosslinking of different forms of the simian virus 40 large T antigen using bifunctional reagents

Chemical crosslinking was used for a direct analysis of the different forms of large tumor (T) antigen, the simian virus 40 A gene product. The first subclass, sedimenting at 14-16S, is composed of monomeric to tetrameric units, whereas the second, sedimenting at 5-6S, only contains dimers and monomers of T. The occurrence of oligomeric structures of T in solution which are higher than dimers suggests the possibility of direct binding of such trimers or tetramers to the origin of replication of the viral DNA as an alternative to the formation of these structures by aggregation of bound dimers or monomers after their sliding along the DNA.     

Haemostatic alterations in malaria correlate to parasitaemia

Fibrin(ogen) degradation products, platelet counts, antithrombin III, and the components of the Factor VIII complex were studied in a total of 80 patients with Plasmodium falciparum, Plasmodium vivax or Plasmodium ovale infections. The haemostatic findings were correlated to the numbers of parasitized erythrocytes and to each other. The results indicate that haemostatic changes in malaria correlate with the degree of parasitaemia. Evidence for moderate hyperfibrinolysis was found in patients with high P. falciparum parasitaemias only. Thrombocytopenia closely corresponded to parasitaemia and to von Willebrand factor levels, but appeared not to be linked to a consumption of coagulation factors. It was concluded that thrombocytopenia in malaria is not indicative of disseminated intravascular coagulation (DIC) but may relate to endothelial damage.     

Saccharomyces cerevisiae: Population Divergence and Resistance to Oxidative Stress in Clinical,Domesticated and Wild Isolates

Background

Saccharomyces cerevisiae has been associated with human life for millennia in the brewery and bakery. Recently it has been recognized as an emerging opportunistic pathogen. To study the evolutionary history of S. cerevisiae, the origin of clinical isolates and the importance of a virulence-associated trait, population genetics and phenotypic assays have been applied to an ecologically diverse set of 103 strains isolated from clinics, breweries, vineyards, fruits, soil, commercial supplements and insect guts.

Methodology/Principal Findings

DNA sequence data from five nuclear DNA loci were analyzed for population structure and haplotype distribution. Additionally, all strains were tested for survival of oxidative stress, a trait associated with microbial pathogenicity. DNA sequence analyses identified three genetic subgroups within the recombining S. cerevisiae strains that are associated with ecology, geography and virulence. Shared alleles suggest that the clinical isolates contain genetic contribution from the fruit isolates. Clinical and fruit isolates exhibit high levels of recombination, unlike the genetically homogenous soil isolates in which no recombination was detected. However, clinical and soil isolates were more resistant to oxidative stress than any other population, suggesting a correlation between survival in oxidative stress and yeast pathogenicity.

Conclusions/Significance

Population genetic analyses of S. cerevisiae delineated three distinct groups, comprising primarily the (i) human-associated brewery and vineyard strains, (ii) clinical and fruit isolates (iii) and wild soil isolates from eastern U.S. The interactions between S. cerevisiae and humans potentiate yeast evolution and the development of genetically, ecologically and geographically divergent groups.     

Domains of human U4atac snRNA required for U12-dependent splicing in vivo

U4atac snRNA forms a base-paired complex with U6atac snRNA. Both snRNAs are required for the splicing of the minor U12-dependent class of eukaryotic nuclear introns. We have developed a new genetic suppression assay to investigate the in vivo roles of several regions of U4atac snRNA in U12-dependent splicing. We show that both the stem I and stem II regions, which have been proposed to pair with U6atac snRNA, are required for in vivo splicing. Splicing activity also requires U4atac sequences in the 5' stem-loop element that bind a 15.5 kDa protein that also binds to a similar region of U4 snRNA. In contrast, mutations in the region immediately following the stem I interaction region, as well as a deletion of the distal portion of the 3' stem-loop element, were active for splicing. Complete deletion of the 3' stem-loop element abolished in vivo splicing function as did a mutation of the Sm protein binding site. These results show that the in vivo sequence requirements of U4atac snRNA are similar to those described previously for U4 snRNA using in vitro assays and provide experimental support for models of the U4atac/U6atac snRNA interaction.     

Ochratoxin A in human blood serum – retrospective long-term data

In a long-term study (1990–1997) on ochratoxin A (OTA) in human blood serum, 102 serum samples from 36 persons of the Munich Institute for Hygiene and Technology of Food of Animal Origin were analysed by enzyme immunoassay (EIA), and by high performance liquid chromatography (HPLC) for control. Detection limits were at 50 pg/ml (EIA) and 50–70 pg/ml (HPLC), recoveries were 80–120% (EIA) and 30–60% (LC). OTA was detected in 98% (EIA, 368 ± 217 pg/ml) and 93% (HPLC, 271 ± 170 pg/ml) of samples (maximum 1,290 pg/ml). Using published conversion factors for serum/intake estimates (1.34 or 1.97), the mean daily OTA intake of these 36 persons was 493–725 pg/kg bw. Long-term individual mean OTA levels of nine persons ranged from 162 ± 80 pg/ml to 549 ± 172 pg/ml. Our data were compared with published OTA serum levels (1985–2008) for apparently healthy persons from a total of 30 countries. On a worldwide basis, the mean of means for OTA in human serum was estimated to be 700 pg/ml, corresponding to a mean daily OTA intake of 940–1380 pg/kg bw. This level, which was relatively stable over the last decades, is well below published tolerable daily intake values (14,000–18,000 pg/kg bw).     

Inter‐oceanic variation in patterns of host‐associated divergence in a seabird ectoparasite

Aim Parasites with global distributions and wide host spectra provide excellent models for exploring the factors that drive parasite diversification. Here, we tested the relative force of host and geography in shaping population structure of a widely distributed and common ectoparasite of colonial seabirds, the tick Ixodes uriae. Location Two natural geographic replicates of the system: numerous seabird colonies of the North Pacific and North Atlantic Ocean basins. Methods Using eight microsatellite markers and tick samples from a suite of multi‐specific seabird colonies, we examined tick population structure in the North Pacific and compare patterns of diversity and structure to those in the Atlantic basin. Analyses included population genetic estimations of diversity and population differentiation, exploratory multivariate analyses, and Bayesian clustering approaches. These different analyses explicitly took into account both the geographic distance among colonies and host use by the tick. Results Overall, little geographic structure was observed among Pacific tick populations. However, host‐related genetic differentiation was evident, but was variable among host types and lower than in the North Atlantic. Main conclusions Tick population structure is concordant with the genetic structure observed in seabird host species within each ocean basin, where seabird populations tend to be less structured in the North Pacific than in the North Atlantic. Reduced tick genetic structure in the North Pacific suggests that host movement among colonies, and thus tick dispersal, is higher in this region. In addition to information on parasite diversity and gene flow, our findings raise interesting questions about the subtle ways that host behaviour, distribution and phylogeographic history shape the genetics of associated parasites across geographic landscapes.     

Characterization of the coral reefs off veracruz/mexico characterización de los arrecifes de corales de Veracruz/Mexico

In May 1965 and June 1966 an ecological study of the Arrecife Blanquilla, Arrecife Pajaros, Bajo Verde and Anegada de Adentro coral reefs off Veracruz, Mexico was made using aqualungs. The present work summarizes and discusses the existing knowledge about these reefs which is still incomplete. Similarly structured reef portions and similar features found in a number of reefs in ecologically comparable locations led the author to conclude that the reefs as a whole are similar to each other. In their position on the shelf, their round-oval shape, their elevated ridges, their shallow lagoon-type centres and their tendency to form islands they are basically comparable to the platform reefs of the Australian Great Barrier Reef. The coral associations have been produced by the environmental factors prevailing in the three recognizable habitats, the surf zone, the shallow body of calm water, and the steep slopes with moderate water movement. The coral fauna was found to be poorer than that of other reef areas in the West Indies.     

A comparison of four different fine root production estimates with ecosystem carbon balance data in a Fagus–Quercus mixed forest

The controversy on how to measure fine root production of forests (P) most accurately continues. We applied four different approaches to determine annual rates of P in an old-growth temperate Fagus sylvatica–Quercus petraea stand: sequential soil coring with minimum–maximum calculation, sequential coring with compartmental flow calculation, the ingrowth core method, and a recently developed root chamber method for measuring the growth of individual fine roots in situ. The results of the four destructive approaches differed by an order of magnitude and, thus, are likely to introduce large errors in estimating P. The highest annual rates of P were obtained from the sequential coring approach with compartmental flow calculation, intermediate rates by sequential coring with minimum–maximum calculation, and low ones by both the root growth chamber and ingrowth core approaches. A carbon budget for the stand was set up based on a model of annual net carbon gain by the canopy and measurements on carbon sink strength (annual leaf, branch and stem growth). The budget implied that a maximum of 27% of the net carbon gain was available for allocation to fine root growth. When compared to the carbon budget data, the sequential coring/compartmental flow approach overestimated annual fine root production substantially; whereas the ingrowth core and root growth chamber approaches grossly underestimated P rates. With an overestimation of about 25% the sequential coring/minimum–maximum approach demonstrated the best agreement with the carbon budget data. It is concluded that the most reliable estimate of P in this temperate forest will be obtained by applying the sequential coring/minimum–maximum approach, conducted with a large number of replicate samples taken on a few dates per season, in conjunction with direct root growth observation by minirhizotrons.