Evolution of reduced pre-adult viability and larval growth rate in laboratory populations of Drosophila melanogaster selected for shorter development time

Four large (n > 1000) populations of Drosophila melanogaster, derived from control populations maintained on a 3 week discrete generation cycle, were subjected to selection for fast development and early reproduction. Egg to eclosion survivorship and development time and dry weight at eclosion were monitored every 10 generations. Over 70 generations of selection, development time in the selected populations decreased by approximately 36 h relative to controls, a 20% decline. The difference in male and female development time was also reduced in the selected populations. Flies from the selected populations were increasingly lighter at eclosion than controls, with the reduction in dry weight at eclosion over 70 generations of selection being approximately 45% in males and 39% in females. Larval growth rate (dry weight at eclosion/development time) was also reduced in the selected lines over 70 generations, relative to controls, by approximately 32% in males and 24% in females. However, part of this relative reduction was due to an increase in growth rate of the controls populations, presumably an expression of adaptation to conditions in our laboratory. After 50 generations of selection had elapsed, a considerable and increasing pre-adult viability cost to faster development became apparent, with viability in the selected populations being about 22% less than that of controls at generation 70 of selection.     

Membrane electrical excitability is necessary for the free-running larval Drosophila circadian clock

Drosophila larvae and adult pacemaker neurons both express free-running oscillations of period (PER) and timeless (TIM) proteins that constitute the core of the cell-autonomous circadian molecular clock. Despite similarities between the adult and larval molecular oscillators, adults and larvae differ substantially in the complexity and organization of their pacemaker neural circuits, as well as in behavioral manifestations of circadian rhythmicity. We have shown previously that electrical silencing of adult Drosophila circadian pacemaker neurons through targeted expression of either an open rectifier or inward rectifier K(+) channel stops the free-running oscillations of the circadian molecular clock. This indicates that neuronal electrical activity in the pacemaker neurons is essential to the normal function of the adult intracellular clock. In the current study, we show that in constant darkness the free-running larval pacemaker clock-like that of the adult pacemaker neurons they give rise to-requires membrane electrical activity to oscillate. In contrast to the free-running clock, the molecular clock of electrically silenced larval pacemaker neurons continues to oscillate in diurnal (light-dark) conditions. This specific disruption of the free-running clock caused by targeted K(+) channel expression likely reflects a specific cell-autonomous clock-membrane feedback loop that is common to both larval and adult neurons, and is not due to blocking pacemaker synaptic outputs or disruption of pacemaker neuronal morphology.     

Circadian pathway: the other shoe drops

Three new papers report the long-awaited functional characterization of the Drosophila receptor for the circadian-rhythm-regulating signalling molecule PIGMENT DISPERSING FACTOR (PDF). The discovery of the PDF receptor heralds progress in understanding the circadian pacemaker circuit and output pathways in insects.     

A case for multiple oscillators controlling different circadian rhythms in Drosophila melanogaster

A population of the fruit fly Drosophila melanogaster was raised in periodic light/dark (LD) cycles of 12:12 h for about 35 generations. Eclosion, locomotor activity, and oviposition were found to be rhythmic in these flies, when assayed in constant laboratory conditions where the light intensity, temperature, humidity and other factors which could possibly act as time cue for these flies, were kept constant. These rhythms also entrained to a LD cycle of 12:12 h in the laboratory with each of them adopting a different temporal niche. The free-running periods (tau) of the eclosion, locomotor activity and oviposition rhythms were significantly different from each other. The peak of eclosion and the onset of locomotor activity occurred during the light phase of the LD cycle, whereas the peak of oviposition was found to occur during the dark phase of the LD cycle. Based on these results, we conclude that different circadian oscillators control the eclosion, locomotor activity and oviposition rhythms in the fruit fly D. melanogaster.     

Is abdominal compression useful in lung stereotactic body radiation therapy? A 4DCT and dosimetric lobe-dependent study

PurposeTo determine the usefulness of abdominal compression in lung stereotactic body radiation therapy (SBRT) depending on lobe tumor location.Materials and methodsTwenty-seven non-small cell lung cancer patients were immobilized in the Stereotactic Body Frame? (Elekta). Eighteen tumors were located in an upper lobe, one in the middle lobe and nine in a lower lobe (one patient had two lesions). All patients underwent two four-dimensional computed tomography (4DCT) scans, with and without abdominal compression. Three-dimensional tumor motion amplitude was determined using manual landmark annotation. We also determined the internal target volume (ITV) and the influence of abdominal compression on lung dose-volume histograms.ResultsThe mean reduction of tumor motion amplitude was 3.5 mm (p = 0.009) for lower lobe tumors and 0.8 mm (p = 0.026) for upper/middle lobe locations. Compression increased tumor motion in 5 cases. Mean ITV reduction was 3.6 cm³ (p = 0.039) for lower lobe and 0.2 cm³ (p = 0.048) for upper/middle lobe lesions. Dosimetric gain of the compression for lung sparing was not clinically relevant.ConclusionsThe most significant impact of abdominal compression was obtained in patients with lower lobe tumors. However, minor or negative effects of compression were reported for other patients and lung sparing was not substantially improved. At our institute, patients with upper or middle lobe lesions are now systematically treated without compression and the usefulness of compression for lower lobe tumors is evaluated on an individual basis.     

Does the difference in the timing of eclosion of the fruit fly Drosophila melanogaster reflect differences in the circadian organization?

The eclosion rhythm of a laboratory population of Drosophila melanogaster was studied under 12h light, 12h dark (LD 12:12) cycles. Although most of the flies were found to eclose just after “lights on” in LD 12:12, termed within gate (WG) flies, a few flies were found to eclose nearly 10h after peak eclosion, termed outside gate (OG) flies. The circadian parameters of the clocks controlling oviposition rhythms in the WG and the OG flies were estimated to understand the cause of such differences in the timing of eclosion. The distribution of the fraction of individual flies exhibiting single, multiple, and no significant period in the WG flies was significantly different from distribution in the OG flies. Compared to the WG flies, more OG flies were found to exhibit oviposition rhythm with multiple periodicity, whereas more WG flies exhibited an oviposition rhythm with a single significant period. The fraction of flies with arrhythmic oviposition was similar in both the WG and the OG flies. Free-running period τ in constant darkness (DD) and the phase angle difference ψ in LD 12:12 for the oviposition rhythm of WG and OG flies were significantly different. These results suggest that the differences in the time of eclosion between the flies eclosing within the gate and outside the gate of eclosion are probably due to differences in the circadian system controlling eclosion, which is reflected by the differences in their oviposition rhythm. (Chronobiology International, 18(4), 601-612, 2001)     

Studies on the protective effect of dietary fish oil on gentamicin-induced nephrotoxicity and oxidative damage in rat kidney

Gentamicin (GM)-induced nephrotoxicity limits its long-term clinical use. Several agents/strategies were attempted to prevent GM nephrotoxicity but were not found suitable for clinical practice. Dietary fish oil (FO) retard the progression of certain types of cancers, cardiovascular and renal disorders. We aimed to evaluate protective effect of FO on GM-induced renal proximal tubular damage. The rats were pre-fed experimental diets for 10 days and then received GM (80 mg/kg body weight/day) treatment for 10 days while still on diet. Serum/urine parameters, enzymes of carbohydrate metabolism, brush border membrane (BBM), oxidative stress and phosphate transport in rat kidney were analyzed. GM nephrotoxicity was recorded by increased serum creatinine and blood urea nitrogen. GM increased the activities of lactate and glucose-6-phosphate dehydrogenases whereas decreased malate, isocitrate dehydrogenases; glucose-6 and fructose-1,6-bisphosphatases; superoxide dismutase, catalase, glutathione peroxidase and BBM enzymes. In contrast, FO alone increased enzyme activities of carbohydrate metabolism, BBM and oxidative stress. FO feeding to GM treated rats markedly enhanced resistance to GM elicited deleterious effects and prevented GM-induced decrease in 32Pi uptake across BBM. Dietary FO supplementation ameliorated GM-induced specific metabolic alterations and oxidative damage due to its intrinsic biochemical/antioxidant properties.     

Pyocyanin: production,applications, challenges and new insights

Pseudomonas aeruginosa is an opportunistic, Gram-negative bacterium and is one of the most commercially and biotechnologically valuable microorganisms. Strains of P. aeruginosa secrete a variety of redox-active phenazine compounds, the most well studied being pyocyanin. Pyocyanin is responsible for the blue-green colour characteristic of Pseudomonas spp. It is considered both as a virulence factor and a quorum sensing signalling molecule for P. aeruginosa. Pyocyanin is an electrochemically active metabolite, involved in a variety of significant biological activities including gene expression, maintaining fitness of bacterial cells and biofilm formation. It is also recognised as an electron shuttle for bacterial respiration and as an antibacterial and antifungal agent. This review summarises recent advances of pyocyanin production from P. aeruginosa with special attention to antagonistic property and bio-control activity. The review also covers the challenges and new insights into pyocyanin from P. aeruginosa.     

Vibriostatic effects of probiotic Bacillus licheniformis Dahb1 and its molecular phylogeny resolved through RAPD markers

The in vitro vibriostatic effects of probiotic Bacillus licheniformis strains (Dahb1 to Dahb7) from both wild and commercial sources were evaluated against pathogenic Vibrios isolated from shrimp hatcheries and farms. Agar antagonism assay results showed that, out of seven B. licheniformis strains, strain Dahb1 showed the biggest inhibitory zone (6–12 mm) tested against 162 isolates of Vibrio spp. viz., V. harveyi (53 isolates), V. anguillarum (42 isolates), V. vulnificus (31 isolates) and Photobacterium damselae ssp. damselae (36 isolates) obtained from Penaeus monodon culture hatcheries and ponds. The genetic status of these seven strains were analyzed through randomly amplified polymorphic DNA analysis using 18 random primers. Of the 18 primers studied, only 6 generated repeatable polymorphic DNA bands with sizes ranging from 250 to 1,000 bp in seven isolates of B. licheniformis. The dendrogram generated from resolved gel profiles showed two major branches with three clusters. The results of the present study allow us to conclude that B. licheniformis Dahb1 can be used as an effective probiotic to control Vibrios. Field studies are needed to evaluate probiotic efficiency to control diseases in aquatic organisms.