Carcinogenic N-hydroxylaminopurine derivatives do not act as base analog mutagens in Salmonella typhimurium

N-Hydroxylaminopurines are highly mutagenic for growing as well as resting Salmonella typhimurium strain TA100 and to a lesser extent for strain TA98. Aminopurines, under similar conditions, are not mutagenic. N-Methylhydroxylaminopurine, under similar conditions, exhibits only minimal activity. The results are taken to indicate that unlike non-hydroxylated aminopurines, N-hydroxylaminopurines exert their mutagenicity not by acting as base analogs but by direct covalent binding with DNA-guanine.     

Molecular analysis of the composition of the bifidobacterial and lactobacillus microflora of humans.

The bifidobacterial and lactobacillus populations of fecal samples collected from two human subjects during a 12-month period were studied. The total numbers of bifidobacteria were stable throughout the study period in both subjects, but lactobacillus numbers were less constant. Analysis of the composition of the bifidobacterial populations by using ribotyping or pulsed-field gel electrophoresis to differentiate between bacterial strains demonstrated major differences between the subjects. Subject 1 harbored five strains of bifidobacteria throughout the 12-month period, and one strain was numerically predominant. In contrast, subject 2 harbored a more complex bifidobacterial population (five to six strains per sample) whose composition fluctuated throughout the 12 months. One lactobacillus strain was numerically predominant throughout the study in both subjects. Strains of bifidobacteria and lactobacilli common to both subjects were not detected.     

Isolation of Mutations in the Drosophila Homologues of the Human Neurofibromatosis 2 and Yeast Cdc42 Genes Using a Simple and Efficient Reverse-Genetic Method

Reverse genetic analysis in Drosophila has been greatly aided by a growing collection of lethal P transposable element insertions that provide molecular tags for the identification of essential genetic loci. However, because the screens performed to date primarily have generated autosomal P-element insertions, this collection has not been as useful for performing reverse genetic analysis of X-linked genes. We have designed a reverse genetic screen that takes advantage of the hemizygosity of the X chromosome in males together with a cosmid-based transgene that serves as an autosomally linked duplication of a small region of the X chromosome. The efficacy and efficiency of this method is demonstrated by the isolation of mutations in Drosophila homologues of two well-studied genes, the human Neurofibromatosis 2 tumor suppressor and the yeast CDC42 gene. The method we describe should be of general utility for the isolation of mutations in other X-linked genes, and should also provide an efficient method for the isolation of new alleles of existing X-linked or autosomal mutations in Drosophila.     

Factors affecting blood pressure during heavy weight lifting and static contractions.

Brachial arterial pressure was directly recorded in 31 healthy male volunteers through protocols examining the effects of the Valsalva maneuver, muscle size and strength, contraction force, contraction type (concentric, isometric, eccentric), changes in joint angle, and muscle fatigue on the blood pressure response to resistance exercise. Weight lifting at the same relative intensity produced similar increases in blood pressure, regardless of individual differences in muscle size or strength. Concentric, isometric, or eccentric exercise at the same relative intensity caused similar increases despite differences in force production. In weight lifting, the greatest increase in blood pressure occurred at the joint angle corresponding to the weakest point in the strength curve and the least at the angle corresponding to the strongest point. Isometric contractions of the same relative intensity at different joint angles produced identical blood pressures despite differences in absolute force production. When subjects attempted to maintain a maximum isometric contraction for 45 s, the blood pressure increase remained the same despite a marked diminution in force. Thus the magnitude of the blood pressure response depends on the degree of effort or central command and not actual force production. A brief Valsalva maneuver, which exaggerates the increase in blood pressure, is unavoidable when desired force production exceeds approximately 80% maximum voluntary contraction.     

Complex floral traits shape pollinator attraction to ornamental plants

Background and AimsOrnamental flowering plant species are often used in managed greenspaces to attract and support pollinator populations. In natural systems, selection by pollinators is hypothesized to result in convergent multimodal floral phenotypes that are more attractive to specific pollinator taxa. In contrast, ornamental cultivars are bred via artificial selection by humans, and exhibit diverse and distinct phenotypes. Despite their prevalence in managed habitats, the influence of cultivar phenotypic variation on plant attractiveness to pollinator taxa is not well resolved.MethodsWe used a combination of field and behavioural assays to evaluate how variation in floral visual, chemical and nutritional traits impacted overall attractiveness and visitation by pollinator taxonomic groups and bee species to 25 cultivars of five herbaceous perennial ornamental plant genera.Key resultsDespite significant phenotypic variation, cultivars tended to attract a broad range of pollinator species. Nonetheless, at the level of insect order (bee, fly, butterfly, beetle), attraction was generally modulated by traits consistent with the pollination syndrome hypothesis. At the level of bee species, the relative influence of traits on visitation varied across plant genera, with some floral phenotypes leading to a broadening of the visitor community, and others leading to exclusion of visitation by certain bee species.ConclusionsOur results demonstrate how pollinator choice is mediated by complex multimodal floral signals. Importantly, the traits that had the greatest and most consistent effect on regulating pollinator attraction were those that are commonly selected for in cultivar development. Though variation among cultivars in floral traits may limit the pollinator community by excluding certain species, it may also encourage interactions with generalist taxa to support pollinator diversity in managed landscapes.     

Increasing cell biomass in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> increases recombinant protein yield: the use of a respiratory strain as a microbial cell factory

Background  

Recombinant protein production is universally employed as a solution to obtain the milligram to gram quantities of a given protein required for applications as diverse as structural genomics and biopharmaceutical manufacture. Yeast is a well-established recombinant host cell for these purposes. In this study we wanted to investigate whether our respiratory Saccharomyces cerevisiae strain, TM6*, could be used to enhance the productivity of recombinant proteins over that obtained from corresponding wild type, respiro-fermentative strains when cultured under the same laboratory conditions.