Regulation of enzymes and isoenzymes of carbohydrate metabolism in the yeast Saccharomyces cerevisiae

An electrophoretic method has been devised to investigate the changes in the enzymes and isoenzymes of carbohydrate metabolism, upon adding glucose to derepressed yeast cell. (i) Of the glycolytic enzymes tested, enolase II, pyruvate kinase and pyruvate decarboxylase were markedly increased. This increase was accompanied by an overall increase in glycolytic activity and was prevented by cycloheximide, an inhibitor of protein synthesis. (ii) In contrast, respiratory activity decreased after adding glucose. This decrease was clearly shown to be the result of repression of respiratory enzymes. A rapid decrease within a few minutes of adding glucose, by analogy with the so-called ‘Crabtree effect’, was not observed in yeast. (iii) The gluconeogenic enzymes, fructose-1,6-bisphosphatase and malate dehydrogenase, which are inactivated after adding glucose, showed no significant changes in electrophoretic mobilities. Hence, there was no evidence of enzyme modifications, which were postulated as initiating degradation. However, it was possible to investigate cytoplasmic and mitochondrial malate dehydrogenase isoenzymes separately. Synthesis of the mitochondrial isoenzyme was repressed, whereas only cytoplasmic malate hydrogenase was subject to glucose inactivation.     

Disentangling invasion processes in a dynamic shipping-boating network

The relative importance of multiple vectors to the initial establishment, spread and population dynamics of invasive species remains poorly understood. This study used molecular methods to clarify the roles of commercial shipping and recreational boating in the invasion by the cosmopolitan tunicate, Botryllus schlosseri. We evaluated (i) single vs. multiple introduction scenarios, (ii) the relative importance of shipping and boating to primary introductions, (iii) the interaction between these vectors for spread (i.e. the presence of a shipping-boating network) and (iv) the role of boating in determining population similarity. Tunicates were sampled from 26 populations along the Nova Scotia, Canada, coast that were exposed to either shipping (i.e. ports) or boating (i.e. marinas) activities. A total of 874 individuals (c. 30 per population) from five ports and 21 marinas was collected and analysed using both mitochondrial cytochrome c oxidase subunit I gene (COI) and 10 nuclear microsatellite markers. The geographical location of multiple hotspot populations indicates that multiple invasions have occurred in Nova Scotia. A loss of genetic diversity from port to marina populations suggests a stronger influence of ships than recreational boats on primary coastal introductions. Population genetic similarity analysis reveals a dependence of marina populations on those that had been previously established in ports. Empirical data on marina connectivity because of boating better explains patterns in population similarities than does natural spread. We conclude that frequent primary introductions arise by ships and that secondary spread occurs gradually thereafter around individual ports, facilitated by recreational boating.     

Differences between horse selection based on two forms of osteochondrosis in fetlock

Horses lose potential opportunities because of health problems. Available breeding strategies are not effective enough, probably also because of the different definition used and its genetic usefulness. The aim of the study was to compare the genetic background estimated by the genome-wide association study (GWAS) for osteochondrosis using two different scaling osteochondrosis (OC)/healthy and osteochondrosis dissecans (OCD)/healthy systems for evaluating the disease status of investigated fetlock joints. Two hundred one Warmblood horses trained for performance tests (87 stallions and 114 mares) were phenotyped and genotyped. Four fetlock x-ray images per horse were collected using the RTG Girth HF 80 and Vet Scan ray 3600. The DNA of each horse was genotyped using the BeadChip 70K. To identify SNPs that significantly affect the probability of osteochondrosis, two different methods were applied: the Cochran-Armitage test based on an additive mode of inheritance and logistic regression. The genetic background for osteochondrosis, expressed in the number of SNPs found with significant associations with osteochondrosis, was higher by evaluation in the scale of OCD/healthy horses (16 SNPs on several chromosomes mainly on the ECA1 and ECA10) than OC/healthy (2 SNPs on the ECA15 and one SNP on the ECA10). Detailed definition of osteochondrosis is needed in breeding and in veterinary practice. The genetic background for osteochondrosis and osteochondrosis dissecans seems not the same. Suggestive SNPs could be the candidate markers for osteochondrosis but should be checked on a larger population before usage.     

Ueber Eucalypti-Anpflanzungen

Ohne Zusammenfassung     

The Drosophila ribosomal protein L14-encoding gene, identified by a novel Minute mutation in a dense cluster of previously undescribed genes in cytogenetic region 66D

The Minute phenotype results from mutations at?>50 loci scattered throughout the genome of Drosophila. Common traits of the Minute phenotype are short and thin bristles, slow development, and recessive lethality. Here, we report a novel P-element induced Minute mutation, P{lacW}M(3)66D ¹ , that maps to region 66D on chromosome 3L. Flies heterozygous for P{lacW}M(3)66D ¹ have a strong Minute phenotype. Molecular characterisation of the chromosomal region revealed three previously undescribed Drosophila genes clustered within a 5-kb genomic fragment. Two of the genes have significant sequence homology to genes for the mammalian ribosomal proteins L14 and RD, respectively, and share a joint 240-bp promoter region harbouring the P-element insert. Quantitative Northern blot analyses showed the mutation to affect RPL14 mRNA levels only. Interestingly, the reduction in abundance of RPL14 mRNA is not constitutive, indicating that the promoter function abolished by the inserted P-element is utilised with different efficiencies in different developmental situations. Remobilisation of the P element produced wild-type flies with normal levels of RPL14 mRNA, demonstrating that the mutant phenotype is caused by the insertion. P{lacW}M(3)66D ¹ joins a growing list of Minute mutations associated with ribosomal protein-haploinsufficiency.     

Besprechungen

Ohne Zusammenfassung     

Metabolism of thyrotropin releasing factor in two clonal cell lines of nervous system origin

Immunoreactive thyrotropin releasing factor (TRF) was detected in homogenates of two clonal cell lines, BN1010-1 and BN1010-3, derived from a rat central nervous system tumor. TRF was present in logarithmically-growing cells; daily medium changes with slightly acid culture medium (pH 6.8) greatly increased the TRF content of these cells. In contrast, TRF could not be detected in stationary phase cells. TRF peptidases were <1% as active in homogenates of BN1010 cells as those in homogenates of guinea pig brain or hypothalamus. It is expected that these cells will provide an excellent model system for the study of various aspects of TRF metabolism.