Sterigmatocystin — incidence, fate and production byA versicolor in ras cheese

Sterigmatocystin (STG) is a toxic metabolite produced by severalAspergillus species. Because of its toxic and carcinogenic properties the occurrence of STG in food is considered to represent a potential hazard to man. The present study was designed to investigate following points:

Genetic variances, heritabilities and maternal effects on body weight, breast meat yield, meat quality traits and the shape of the growth curve in turkey birds

Background

Turkey is an important agricultural species and is largely used as a meat bird. In 2004, turkey represented 6.5% of the world poultry meat production. The world-wide turkey population has rapidly grown due to increased commercial farming. Due to the high demand for turkey meat from both consumers and industry global turkey stocks increased from 100 million in 1970 to over 276 million in 2004. This rapidly increasing importance of turkeys was a reason to design this study for the estimation of genetic parameters that control body weight, body composition, meat quality traits and parameters that shape the growth curve in turkey birds.

Results

The average heritability estimate for body weight traits was 0.38, except for early weights that were strongly affected by maternal effects. This study showed that body weight traits, upper asymptote (a growth curve trait), percent breast meat and redness of meat had high heritability whereas heritabilities of breast length, breast width, percent drip loss, ultimate pH, lightness and yellowness of meat were medium to low. We found high positive genetic and phenotypic correlations between body weight, upper asymptote, most breast meat yield traits and percent drip loss but percent drip loss was found strongly negatively correlated with ultimate pH. Percent breast meat, however, showed genetic correlations close to zero with body weight traits and upper asymptote.

Conclusion

The results of this analysis and the growth curve from the studied population of turkey birds suggest that the turkey birds could be selected for breeding between 60 and 80 days of age in order to improve overall production and the production of desirable cuts of meat. The continuous selection of birds within this age range could promote high growth rates but specific attention to meat quality would be needed to avoid a negative impact on the quality of meat.     

Low temperature delays timing and enhances the cost of nitrogen fixation in the unicellular cyanobacterium Cyanothece

Marine nitrogen-fixing cyanobacteria are largely confined to the tropical and subtropical ocean. It has been argued that their global biogeographical distribution reflects the physiologically feasible temperature range at which they can perform nitrogen fixation. In this study we refine this line of argumentation for the globally important group of unicellular diazotrophic cyanobacteria, and pose the following two hypotheses: (i) nitrogen fixation is limited by nitrogenase activity at low temperature and by oxygen diffusion at high temperature, which is manifested by a shift from strong to weak temperature dependence of nitrogenase activity, and (ii) high respiration rates are required to maintain very low levels of oxygen for nitrogenase, which results in enhanced respiratory cost per molecule of fixed nitrogen at low temperature. We tested these hypotheses in laboratory experiments with the unicellular cyanobacterium Cyanothece sp. {"type":"entrez-nucleotide","attrs":{"text":"BG043511","term_id":"12489990","term_text":"BG043511"}}BG043511. In line with the first hypothesis, the specific growth rate increased strongly with temperature from 18 to 30 °C, but leveled off at higher temperature under nitrogen-fixing conditions. As predicted by the second hypothesis, the respiratory cost of nitrogen fixation and also the cellular C:N ratio rose sharply at temperatures below 21 °C. In addition, we found that low temperature caused a strong delay in the onset of the nocturnal nitrogenase activity, which shortened the remaining nighttime available for nitrogen fixation. Together, these results point at a lower temperature limit for unicellular nitrogen-fixing cyanobacteria, which offers an explanation for their (sub)tropical distribution and suggests expansion of their biogeographical range by global warming.     

Ultrastructural immunogold labeling of lipid-laden enterocytes from patients with genetic malabsorption syndromes

Summary— Intestinal biopsies from patients having genetic disorders of lipoprotein assembly and secretion, such as abetalipoproteinemia (ABL) or Anderson's disease (AD), contain large amounts of lipids which are accumulated in the enterocytes. Determination of the intracellular sites in which the lipids accumulate and to which apolipoproteins the lipids are bound would help to identify the defects in these diseases and further elucidate the mechanisms by which lipoprotein assembly and secretion occur normally. Ultrastructural immunogold labeling, however, is hampered by the poor preservation of the lipids accumulated in the enterocytes of these patients. We have used routine electron microscopy (fixation and ultra-thin sectioning) along with three methods for immunogold labeling of lipid-laden enterocytes; ultrathin cryosectioning, low temperature freeze substitution with embedding in Lowicryl K4M, and ultra-low temperature freeze substitution with embedding in Lowicryl HM20, to establish a protocol for investigating the intestinal tissue from these patients. Ultracryosectioning, while preserving the overall morphology of the lipid laden enterocytes, did not preserve the lipid content and the immunogold labeling of apolipoprotein B (ApoB) appeared dislocated. Freeze substitution and low temperature embedding in Lowicryl K4M, in contrast, appeared to better preserve the lipid and lipoprotein structures; however, the antigenicity of both apoAI and apoB appeared to be lost and no specific labeling could be obtained. Freeze substitution and embedding in Lowicryl HM20 best preserved the lipid and lipoprotein structures while maintaining apoprotein antigenicity. In conclusion, immunogold labeling of apolipoproteins on lipid structures in the lipid-laden enterocytes of patients with ABL and AD is best obtained by freeze substitution and embedding in Lowicryl HM20.     

Rd7 genotyping of M. tuberculosis strains isolated from patients with lung tuberculosis in different areas of Kazakhstan

A three-primer PCR assay was designed for detection of possible deletions in the RD7 region of the Mycobacterium tuberculosis complex chromosome. The assay produced amplicons of different size depending on the presence or absence of the deletions. The PCR assay was applied to 176 isolates from patients with lung tuberculosis collected in different areas of Kazakhstan in summer 2004. The isolates were initially characterized by culture and biochemical tests. The RD7 genotyping results demonstrated no polymorphism and the absence of deletions in the RD7 genome region. Some strains were additionally characterized using PCR-RFLP analysis of gyrB and hsp64 genes. The RFLP-patterns obtained corresponded to the M. tuberculosis genotypes. The results of this work are consistent with certain previous studies, indicating population stability of the RD7 region in M. tuberculosis strains. Species characterization of the isolates shows that M. tuberculosis sensu stricto is the principal causative agent of human lung tuberculosis in Kazakhstan.     

Involvement of the amino-terminal beta-hairpin of the Aspergillus ribotoxins on the interaction with membranes and nonspecific ribonuclease activity

Ribotoxins are a family of potent cytotoxic proteins from Aspergillus whose members display a high sequence identity (85% for about 150 amino acid residues). The three-dimensional structures of two of these proteins, alpha-sarcin and restrictocin, are known. They interact with phospholipid bilayers, according to their ability to enter cells, and cleave a specific phosphodiester bond in the large subunit of ribosome thus inhibiting protein biosynthesis. Two nonconservative sequence changes between these proteins are located at the amino-terminal beta-hairpin of alpha-sarcin, a characteristic structure that is absent in other nontoxic structurally related microbial RNases. These two residues of alpha-sarcin, Lys 11 and Thr 20, have been substituted with the equivalent amino acids in restrictocin. The single mutants (K11L and T20D) and the corresponding K11L/T20D double mutant have been produced in Escherichia coli and purified to homogeneity. The spectroscopic characterization of the purified proteins reveals that the overall native structure is preserved. The ribonuclease and lipid-perturbing activities of the three mutants and restrictocin have been evaluated and compared with those of alpha-sarcin. These proteins exhibit the same ability to specifically inactivate ribosomes, although they show different activity against nonspecific substrate analogs such as poly(A). The mutant variant K11L and restrictocin display a lower phospholipid-interacting ability correlated with a decreased cytotoxicity. The results obtained are interpreted in terms of the involvement of the amino-terminal beta-hairpin in the interaction with both membranes and polyadenylic acid.     

<Emphasis Type="Italic">Strongyloides stercoralis</Emphasis> infection in a Finnish kennel

Background  

Intestinal threadworm Strongyloides stercoralis is a parasite of dog, cat and primates that occurs worldwide being most prevalent in tropical and subtropical countries. The adult parasitic worm is about 2 mm long and slender. It possesses both parasitic and free-living lifecycles. The parasitic worms are females. Strongyloides stercoralis infects the host via percutaneous, peroral or transmammary transmission in addition to autoinfection. Clinical disease varies from inapparent to severe enteritis and pneumonia. The diagnosis is based on demonstration of larvae in fresh faeces, which is best made by Baermann technique.     

Studies on the binding site of the galactose-specific agglutinin PA-IL from Pseudomonas aeruginosa

The binding properties of Pseudomonas aeruginosa agglutinin-I (PA-IL) with glycoproteins (gps) and polysaccharides were studied by both the biotin/avidin-mediated microtiter plate lectin-binding assay and the inhibition of agglutinin-glycan interaction with sugar ligands. Among 36 glycans tested for binding, PA-IL reacted best with two glycoproteins containing Galalpha1-->4Gal determinants and a human blood group ABO precursor equivalent gp, but this lectin reacted weakly or not at all with A and H active gps or sialylated gps. Among the mammalian disaccharides tested by the inhibition assay, the human blood group Pkactive Galalpha1-->4Gal, was the best. It was 7.4-fold less active than melibiose (Galalpha1-->6Glc). PA-IL has a preference for the alpha-anomer in decreasing order as follows: Galalpha1-->6 >Galalpha1-->4 >Galalpha1-->3. Of the monosaccharides studied, the phenylbeta derivatives of Gal were much better inhibitors than the methylbeta derivative, while only an insignificant difference was found between the Galalpha anomer of methyl- and p -NO2-phenyl derivatives. From these results, it can be concluded that the combining size of the agglutinin is as large as a disaccharide of the alpha-anomer of Gal at nonreducing end and most complementary to Galalpha1-->6Glc. As for the combining site of PA-IL toward the beta-anomer, the size is assumed to be less than that of Gal; carbon-6 in the pyranose form is essential, and hydrophobic interaction is important for binding.      

Structural genes of the mouse major urinary protein are on chromosome 4

The major urinary proteins (MUPs) of mouse are a family of at least three major proteins which are synthesized in the liver of all strains of mice. The relative levels of synthesis of these proteins with respect to each other in the presence of testosterone is regulated by the Mup-a locus located on chromosome 4. In an effort to determine the mechanism of this regulation in molecular terms, a cDNA clone containing most of the coding region of a MUP protein has been isolated and identified by partial DNA sequence analysis. Using a combination of hybridization analysis and somatic cell genetics, the structural gene family has been unambiguously mapped to mouse chromosome 4. These data suggest that Mup-a regulation operates in a cis fashion and that models proposing trans regulation of MUP protein synthesis are unlikely.