Physiological characterization of osmotolerant yeast<Emphasis Type="Italic">Pichia sorbitophila</Emphasis> and comparison with a putative synonym<Emphasis Type="Italic">Pichia farinosa</Emphasis>

The osmotolerant yeast Pichia sorbitophila was found to differ from other yeast species, not only from the conventional ones (Saccharomyces cerevisiae, Schizosaccharomyces pombe), but also from those widely known as osmotolerant (Debaryomyces hansenii, Zygosaccharomyces rouxii). P. sorbitophila was able to survive extremely high extracellular concentrations of salts (e.g., saturated solution of KCl) and other osmolytes (70% glucitol), although it is not classified as halophilic (or osmophilic). P. sorbitophila assimilated a broad range of carbon and nitrogen sources with extreme effectiveness. On solid media, P. sorbitophila created colonies of variable shapes and sizes in relation to media composition, number of colonies on the plate and cultivation conditions. Colonies were able to produce long-distance signals between each other that resulted in growth inhibition of the facing parts of both colonies, but were not inhibited by colonies of other yeast species growing on the same plate. Though sometimes P. sorbitophila has been indicated as a synonym of P. farinosa, comparative physiological studies together with PCR amplification of P. farinosa DNA fragments homologous to known P. sorbitophila genes provided a strong indication that this strain should be classified as a separate species.     

Bone tumorigenesis induced by alpha-particle radiation: mapping of genetic loci influencing predisposition in mice

The present study was carried out to determine the extent to which genetic factors modify the incidence of radiation-induced bone tumorigenesis in mice, and to map putative susceptibility genes. We conducted a genome-wide linkage analysis in a cohort of 47 interstrain backcrossed mice. After the mice were injected with the bone-seeking alpha-particle-emitting radionuclide (227)Th, 21 of the mice developed osteosarcomas. Two loci, one on chromosome 7 close to D7Mit145 and a second on chromosome 14 (D14Mit125), exhibited suggestive linkage to osteosarcoma predisposition, with LOD scores of 1.37 and 1.05, respectively. The LOD score increased considerably when interaction between these two loci was taken into account (LOD = 3.48). Nine of 12 mice inheriting a susceptibility allele at both loci developed osteosarcomas after (227)Th injection, compared to only four osteosarcomas in 18 animals that did not inherit either of the susceptibility alleles. Variance component analysis revealed that these genetic factors determine approximately one-fifth of the total incidence of osteosarcomas. This study demonstrates the presence of a genetic component that modulates predisposition to radiation-induced osteosarcoma.     

Hereditary minisatellite mutations among the offspring of Estonian Chernobyl cleanup workers

A single accidental event such as the fallout released from the Chernobyl reactor in 1986 can expose millions of people to non-natural environmental radiation. Ionizing radiation increases the frequency of germline mutations in experimental studies, but the genetic effects of radiation in humans remain largely undefined. To evaluate the hereditary effects of low radiation doses, we compared the minisatellite mutation rates of 155 children born to Estonian Chernobyl cleanup workers after the accident with those of their siblings born prior to it. All together, 94 de novo paternal minisatellite mutations were found at eight tested loci (52 and 42 mutants among children born after and before the accident, respectively). The minisatellite mutation rate was nonsignificantly increased among children born after the accident (0.042 compared to 0.036, OR 1.33, 95% CI 0.80-2.20). Furthermore, there was some indication of an increased mutation rate among offspring born after the accident to workers who had received doses of 20 cSv or above compared with their siblings born before the accident (OR 3.0, 95% CI 0.97-9.30). The mutation rate was not associated with the father's age (OR 1.04, 95% CI 0.94-1.15) or the sex of the child (OR 0.95, 95% CI 0.50-1.79). Our results are consistent with both no effect of radiation on minisatellite mutations and a slight increase at dose levels exceeding 20 cSv.     

Heterologous expression of leader-less <Emphasis Type="Italic">pga</Emphasis> gene in <Emphasis Type="Italic">Pichia pastoris</Emphasis>: intracellular production of prokaryotic enzyme

Background  

Penicillin G acylase of Escherichia coli (PGA_Ec) is a commercially valuable enzyme for which efficient bacterial expression systems have been developed. The enzyme is used as a catalyst for the hydrolytic production of β-lactam nuclei or for the synthesis of semi-synthetic penicillins such as ampicillin, amoxicillin and cephalexin. To become a mature, periplasmic enzyme, the inactive prepropeptide of PGA has to undergo complex processing that begins in the cytoplasm (autocatalytic cleavage), continues at crossing the cytoplasmic membrane (signal sequence removing), and it is completed in the periplasm. Since there are reports on impressive cytosolic expression of bacterial proteins in Pichia, we have cloned the leader-less gene encoding PGA_Ec in this host and studied yeast production capacity and enzyme authenticity.     

Non-invasive corticosterone treatment changes foraging intensity in red-eyed vireos Vireo olivaceus

Corticosterone is thought to play an important role in food caching and foraging behaviour. However, the direct influence of increased plasma corticosterone on feeding behaviour is still unclear. In this study the effect of increased corticosterone on feeding behaviour in migratory active red-eyed vireos Vireo olivaceus was investigated. We hypothesized that if increased corticosterone levels facilitate foraging behaviour, an increased number of visits to the food bowl by corticosterone treated birds would be seen. In addition to ad lib food during the experiment, the vireos were fed every full hour between 09.00–13.00 h with one meal worm injected either with 4 μg corticosterone dissolved in 20 μl DMSO, or with DMSO only as a control treatment. The presence or absence of a bird in the food bowl was recorded by a motion detector between 09.00–15.00 h. The non-invasive corticosterone treatment increased plasma corticosterone levels and caused vireos to visit the food bowl more frequently compared to control treated individuals between 11.00–12.00 h and 13.00–15.00 h. Our data indicate that corticosterone has an effect on feeding behaviour in birds.     

Primary structure and in vitro antibacterial properties of the Drosophila melanogaster attacin C Pro-domain

In Drosophila melanogaster, seven distinct families of antimicrobial peptides with different structures and specificities are synthesized by the fat body and released into the hemolymph during the immune response. Using microscale high performance liquid chromatography, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and Edman degradation, we have isolated and characterized from immune-challenged Drosophila two novel induced molecules, under the control of the Imd pathway, that correspond to post-translationally modified antimicrobial peptides or peptide fragments. The first molecule is a doubly glycosylated form of drosocin, an O-glycosylated peptide that kills Gram-negative organisms. The second molecule represents a truncated form of the pro-domain of the Drosophila attacin C carrying two post-translational modifications and has significant structural similarities to proline-rich antibacterial peptides including drosocin. We have synthesized this peptide and found that it is active against Gram-negative bacteria. Furthermore, this activity is potentiated when the peptide is used in combination with the Drosophila antimicrobial peptide cecropin A. The synergistic action observed between these two molecules suggests that the truncated post-translationally modified pro-domain of attacin C by itself may play an important role in the antimicrobial defense of Drosophila.     

Chronic administration of leptin in Asian Blue Quail

It is well known that leptin has the capacity to reduce food intake, cause body weight loss, and increase energy expenditure in several vertebrate species. In this study, we investigated the effects of chronically elevated leptin levels on behavior and physiology of Asian Blue Quail (Coturnix chinensis). Fifteen male quail were treated with chicken leptin dissolved in phosphate-buffered saline (PBS) via subcutaneously inserted osmotic pumps that released approximately 1 microg/g body weight/day during a 14-day period. Another 15 males acted as controls and their pumps released PBS only. All males were housed together with two females. We observed a decrease in body weight and feeding behavior in leptin-treated birds, but not in control birds, after 2 days of treatment. Thereafter, all birds increased in weight. Males treated with leptin were more active and more likely to preen the day after the beginning of the treatment. Plasma cholesterol levels in leptin birds decreased during the first week of treatment and plasma triglycerides tended to remain lower compared to the controls during the whole 2-week period of treatment. Glucose levels appeared stable during the observation period. Leptin-treated males remained closer to accompanying females than did control males, and females together with leptin males took longer to lay their first egg compared to females together with control males. This is the first article showing the effect of leptin on cholesterol and triglyceride levels in birds. We also observed a change in the activity and male-female interaction pattern in tested quail.     

Models of epileptic seizures in immature rats

Models of basic types of epileptic seizures are elaborated not only in adult but also in immature rodents. It is important because at least half of human epilepsies starts during infancy and childhood. This paper presents a review of chemically and electrically induced models of generalized convulsive and nonconvulsive (absence) seizures as well as models of partial simple (neocortical) and complex (limbic) seizures in immature rats. These models can also serve as a tool for study the development of central nervous system and motor abilities because the level of maturation is reflected in seizure semiology. Age-dependent models of epileptic seizures (absences and flexion seizures) are discussed. Models of seizures in immature animals should be used for testing of potential antiepileptic drugs.     

Hybridization between Cottus gobio and Cottus poecilopus in the Odra River drainage basin (Czech Republic)

Comparisons of morphology, nuclear gene sequencing and microsatellites were used to identify 19 hybrids between the related species Cottus poecilopus and Cottus gobio in three rivers of the Odra River drainage basin. All hybrids were the results of backcrossing and no F1 generation hybrid was found. The resulting progeny are fertile and continue in backcrossing with parental conspecifics. A high representation of backcrosses appears to indicate a lack of reproduction barriers within the hybridization process. It was impossible to differentiate individual back-cross categories on the sole basis of six loci. Mitochondrial haplotypes indicate that this is not a one-way process. In our study, hybridization was asymmetrical in favour of Cottus poecilopus.