Inhibition of DNA replication in Escherichia coli by dibromophenol and other uncouplers.

DNA replication in Escherichia coli is inhibited by uncouplers such as 2,4-dibromophenol and 3,3'4',5-tetrachlorosalicylanilide. Inhibition occurs in either aerobically or anaerobically growing cells or in cells made permeable by toluene. With anaerobically growing cells, inhibition by dibromophenol is reversible and occurs under conditions in which there is no change in pools of ATP or deoxynucleoside triphosphates. With toluenized cells, inhibition is not due to breakdown of deoxynucleoside triphosphates. The rates of protein and RNA synthesis are not inhibited either in vivo or in toluenized cells by concentrations of dibromophenol or tetrachlorosalicylanilide which inhibit replication. It is generally believed that uncouplers inhibit many other cellular processes by collapsing a proton gradient across a membrane. However, the relative effectiveness of eight uncouplers and related compounds to inhibit replication did not parallel their ability to transport protons into E. coli cells. Therefore, the inhibition by uncouplers does not suggest that replication depends on a chemiosmotic process. A possible explanation for the uncoupler sensitivity is provided by the finding that many of the purified enzymes tested, including DNA polymerases II and III, are inhibited by dibromophenol and tetrachlorosalicylanilide.     

adrift, a novel bnl-induced Drosophila gene, required for tracheal pathfinding into the CNS

Neurons and glial cells provide guidance cues for migrating neurons. We show here that migrating epithelial cells also contact specific neurons and glia during their pathfinding, and we describe the first gene required in the process. In wild-type Drosophila embryos, the ganglionic tracheal branch navigates a remarkably complex path along specific neural and glial substrata, switching substrata five times before reaching its ultimate target in the CNS. In adrift mutants, ganglionic branches migrate normally along the intersegmental nerve, but sporadically fail to switch to the segmental nerve and enter the CNS; they wind up meandering along the ventral epidermis instead. adrift encodes a novel nuclear protein with an evolutionarily conserved motif. The gene is required in the trachea and is expressed in the leading cells of migrating ganglionic branches where it is induced by the branchless FGF pathway. We propose that Adrift regulates expression of tracheal genes required for pathfinding on the segmental nerve, and FGF induction of adrift expression in migrating tracheal cells promotes the switch from the intersegmental to the segmental nerve.     

Temperature dependence of predation depends on the relative performance of predators and prey

The temperature dependence of predation rates is a key issue for understanding and predicting the responses of ecosystems to climate change. Using a simple mechanistic model, we demonstrate that differences in the relative performances of predator and prey can cause strong threshold effects in the temperature dependence of attack rates. Empirical data on the attack rate of northern pike (Esox lucius) feeding on brown trout (Salmo trutta) confirm this result. Attack rates fell sharply below a threshold temperature of +11°C, which corresponded to a shift in relative performance of pike and brown trout with respect to maximum attack and escape swimming speeds. The average attack speed of pike was an order of magnitude lower than the escape speed of brown trout at 5°C, but approximately equal at temperatures above 11°C. Thresholds in the temperature dependence of ecological rates can create tipping points in the responses of ecosystems to increasing temperatures. Thus, identifying thresholds is crucial when predicting future effects of climate warming.     

Phylogenetic relationships in Blumea (Asteraceae: Inuleae) as evidenced by molecular and morphological data

The present study, based on sequences of cpDNA (trnL-F & psbA-trnH) and nrDNA (ITS) and morphology, examined the evolutionary relationships in Blumea and its position among related genera. The results confirmed that the closest relatives of Blumea are Caesulia, Duhaldea and Pentanema p.p., and showed that the monotypic genera Blumeopsis and Merrittia are nested within Blumea. In Blumea s.l., two major, well-supported clades were recognised and a single species, the widespread Blumea balsamifera, that could not be placed with certainty relative to the two main clades. The two main clades differ in habit, ecology and distribution. The Blumea densiflora clade contains shrubs and subshrubs of evergreen forests, distributed from continental Asia to New Guinea and Polynesia, whereas the Blumea lacera clade is a widespread paleotropical group that comprises mostly annual, weedy herbs of open forests and fields.     

Replication of kinetoplast DNA maxicircles

The kinetoplast DNA of Crithidia fasciculata is a massive network composed of thousands of topologically interlocked circles. Most of these circles are minicircles (2.5 kb), and about 50 are maxicircles (37 kb). Previous studies showed that minicircles replicate, after release from the network, via Cairns (theta) intermediates. Here we show that maxicircles replicate, while attached to the network, by an entirely different mechanism involving rolling circle intermediates. After the network-bound maxicircle has finished replication, the branch of the rolling circle is apparently cleaved off to form a linear free maxicircle. A restriction map of the linearized free maxicircles shows that these molecules have unique termini, one of which presumably corresponds to the replication origin.     

Investigation of Chlamydiaceae in semen and cauda epididymidis and seroprevalence of Chlamydophila abortus in breeding bulls

Background

Reproductive disorders associated with chlamydial infection have been reported worldwide in cattle and there are indications of potential venereal transmission.

Methods

Semen samples from 21 dairy bulls and cauda epididymidis tissue samples from 43 beef bulls were analysed for chlamydial agent by real-time polymerase chain reaction (PCR) including an internal amplification control (mimic). Additionally, presence of antibodies against Chlamydophila (Cp.) abortus among the bulls was investigated with the commercial Pourquier^® ELISA Cp. abortus serum verification kit.

Results

No chlamydial agent was detected by PCR in either the semen samples or in the tissue samples. Additionally, no antibodies against Cp. abortus were detected.

Conclusions

The results suggest that Cp. abortus is very rare, or absent in Swedish bulls and thus the risk for venereal transmission of chlamydial infection through their semen is low. However, because Chlamydophila spp. infection rates seem to differ throughout the world, it is essential to clarify the relative importance of transmission of the infection through semen on cattle fertility.     

Effectiveness of motivational interviewing and physical activity on prescription on leisure exercise time in subjects suffering from mild to moderate hypertension

Background

Depression and anxiety disorders have a high disease burden and as many as 15% of young people report mental health problems. Binge drinking, which is a particularly harmful way of consuming alcohol, is common among secondary school students. The aim of this study was to examine the association between binge drinking and self-reported mental health in boys and girls aged 12 to 18 years.

Findings

This cross-sectional analysis was performed on data collected by the Community Health Service (GGD) Brabant Zuidoost, the Netherlands, in 2007. In this Youth Survey, 10 090 randomly selected adolescents aged 12 tot 18 years were each sent a letter, a questionnaire, and a user name and log-in code for if they preferred to complete the Internet version of the questionnaire. Mental health was assessed using the Mental Health Inventory (MHI-5), a short 5-item questionnaire to detect feelings of depression and anxiety. Participants were asked about current alcohol consumption, their relationship with their parents, drug use, and sociodemographic data. Corrected for confounders, binge drinking and mental health problems were associated in the 12 to 15 year old girls (OR 2.43; 95% CI 1.86-3.17, p = 0.000) and boys (OR 1.64, 95% CI 1.19-2.27, p = 0.003). The majority of the 16 to 18 year old adolescents had been binge drinking in the previous 4 weeks (69.6% boys and 56.8% girls). In this age group, boys with mental health problems were less likely to be classified as binge drinkers than were boys without mental health problems (OR 0.63, 95% CI 0.45-0.87, p = 0.005). No such association between binge drinking and mental health was found in girls of this age.

Conclusion

Girls and boys aged 12-15 years were classified as binge drinkers significantly more often when they reported poor mental health. Because binge drinking damages the brain, especially at a young age, it is important that health professionals are alert to possible binge drinking when young adolescents report mental health problems and should ask their patients about their drinking behaviour. Likewise, if youngsters under 16 present with binge drinking, they should be asked whether they are anxious or depressed.