Short-term hardening effects on survival of acute and chronic cold exposure by Drosophila melanogaster larvae

We quantified the variation and plasticity in cold tolerance among four larval stages of four laboratory strains of Drosophila melanogaster in response to both acute (<2 h of cold exposure) and chronic (7 h of cold exposure) cold exposure. We observed significant differences in basal cold tolerance between the strains and among larval stages. Early larval instars were generally more tolerant of acute cold exposures than third-instar larvae. However, wandering larvae were more tolerant of chronic cold exposures than the other stages. Early stages also displayed a more pronounced rapid cold-hardening response than the later stages. Heat pre-treatment did not confer a significant increase in cold tolerance to any of the strains at any stage, pointing to different mechanisms being involved in resolving heat- and cold-elicited damage. However, when heat pre-treatment was combined with rapid cold-hardening as sequential pre-treatments, both positive (heat first) and negative (heat second) effects on cold tolerance were observed. We discuss possible mechanisms underlying cold-hardening and the effects of acute and chronic cold exposures.     

Chill-coma temperature in Drosophila: effects of developmental temperature, latitude, and phylogeny

We modify and apply a nonlethal technique for rapidly quantifying the cold tolerance of large numbers of Drosophila and other small insects. Flies are transferred to individual vials, cooled in groups in progressive 0.5 degrees C steps, and checked for loss of righting response (chill-coma temperature [T(cc)]). Flies recover quickly when transferred to ambient temperature, and thus this technique potentially can be used in selection experiments. We applied this technique in several experiments. First, we examined the sensitivity of T(cc) to developmental temperature. Drosophila melanogaster (Congo, France), Drosophila subobscura (Spain, Denmark), and Drosophila ananassae (India) were reared from egg to adult at 15 degrees, 18 degrees, 25 degrees, or 29 degrees C, transferred to 15 degrees C for several days, and then progressively chilled: T(cc) was positively related to developmental temperature, inversely related to latitude of the population, but independent of sex. The sensitivity of T(cc) to developmental temperature (acclimation flexibility) was marked: T(cc) shifted on average 1 degrees for each 4 degrees C shift in developmental temperature. Among 15 species of the obscura group of Drosophila, T(cc) varied from -0.1 degrees to 4.5 degrees C; T(cc) was inversely related to latitude in both nonphylogenetic and phylogenetically based ANCOVA (standardized independent contrasts) and was unrelated to body size.     

Oxidative stress adaptation with acute,chronic, and repeated stress

Oxidative stress adaptation, or hormesis, is an important mechanism by which cells and organisms respond to, and cope with, environmental and physiological shifts in the level of oxidative stress. Most studies of oxidative stress adaption have been limited to adaptation induced by acute stress. In contrast, many if not most environmental and physiological stresses are either repeated or chronic. In this study we find that both cultured mammalian cells and the fruit fly Drosophila melanogaster are capable of adapting to chronic or repeated stress by upregulating protective systems, such as their proteasomal proteolytic capacity to remove oxidized proteins. Repeated stress adaptation resulted in significant extension of adaptive responses. Repeated stresses must occur at sufficiently long intervals, however (12-h or more for MEF cells and 7 days or more for flies), for adaptation to be successful, and the levels of both repeated and chronic stress must be lower than is optimal for adaptation to acute stress. Regrettably, regimens of adaptation to both repeated and chronic stress that were successful for short-term survival in Drosophila nevertheless also caused significant reductions in life span for the flies. Thus, although both repeated and chronic stress can be tolerated, they may result in a shorter life.     

Epistasis and maternal effects in experimental adaptation to chronic nutritional stress in Drosophila

Based on ecological and metabolic arguments, some authors predict that adaptation to novel, harsh environments should involve alleles showing negative (diminishing return) epistasis and/or that it should be mediated in part by evolution of maternal effects. Although the first prediction has been supported in microbes, there has been little experimental support for either prediction in multicellular eukaryotes. Here we use a line‐cross design to study the genetic architecture of adaptation to chronic larval malnutrition in a population of Drosophila melanogaster that evolved on an extremely nutrient‐poor larval food for 84 generations. We assayed three fitness‐related traits (developmental rate, adult female weight and egg‐to‐adult viability) under the malnutrition conditions in 14 crosses between this selected population and a nonadapted control population originally derived from the same base population. All traits showed a pattern of negative epistasis between alleles improving performance under malnutrition. Furthermore, evolutionary changes in maternal traits accounted for half of the 68% increase in viability and for the whole of 8% reduction in adult female body weight in the selected population (relative to unselected controls). These results thus support both of the above predictions and point to the importance of nonadditive effects in adaptive microevolution.     

Modulatory effects of Tabebuia impetiginosa (Lamiales, Bignoniaceae) on doxorubicin-induced somatic mutation and recombination in Drosophila melanogaster

The wing Somatic Mutation and Recombination Test (SMART) in D. melanogaster was used to study genotoxicity of the medicinal plant Tabebuia impetiginosa. Lapachol (naphthoquinone) and β-lapachone (quinone) are the two main chemical constituents of T. impetiginosa. These compounds have several biological properties. They induce apoptosis by generating oxygen-reactive species, thereby inhibiting topoisomerases (I and II) or inducing other enzymes dependent on NAD(P)H:quinone oxidoreductase 1, thus affecting cell cycle checkpoints. The SMART was used in the standard (ST) version, which has normal levels of cytochrome P450 (CYP) enzymes, to check the direct action of this compound, and in the high bioactivation (HB) version, which has a high constitutive level of CYP enzymes, to check for indirect action in three different T. impetiginosa concentrations (10%, 20% or 40% w/w). It was observed that T. impetiginosa alone did not modify the spontaneous frequencies of mutant spots in either cross. The negative results observed prompted us to study this phytotherapeuticum in association with the reference mutagen doxorubicin (DXR). In co-treated series, T. impetiginosa was toxic in both crosses at higher concentration, whereas in the HB cross, it induced a considerable potentiating effect (from ~24.0 to ~95.0%) on DXR genotoxity. Therefore, further research is needed to determine the possible risks associated with the exposure of living organisms to this complex mixture.     

Anti-oxidative stress effects of Herba leonuri on ischemic rat hearts

Our current study was to test the hypothesis that the extract of Herba leonuri (HL) would have antioxidant and cardioprotective effects on ischemic myocardium. The extract of HL (400 mg/kg/day) was administered orally (daily) starting from 1 week before and continuing until 3 weeks after myocardial infarction (MI). Surviving rats were sacrificed at different time points to obtain left ventricles for biochemical assays. Our study demonstrates for the first time that HL does have antioxidant effects both in vitro and in vivo. The antioxidant effects of HL are exerted only under the condition of oxidative stress, by selectively preserving the activities of superoxide dismutase and glutathione peroxidase, as well as depressing the formation of malondialdehyde, especially in the acute phase of acute MI. Its effects of scavenging free radicals and inhibiting the formation of reactive oxygen species may play a key role in protecting the endogenous antioxidant system from oxidative stress in vivo.     

温度胁迫对小金蝠蛾幼虫抗氧化酶活性的影响

小金蝠蛾Hepialus xiaojinensis Tu.是我国名贵中药材冬虫夏草的寄主昆虫之一,适宜在高海拔低温地区(8℃-12℃)生存。本文研究了小金蝠蛾在不同温度(4℃、12℃、16℃、20℃、24℃、28℃)条件下处理4 h和12 h后4龄幼虫体内超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)、谷胱甘肽硫转移酶(GSTs)的活力变化,以及总抗氧化能力(T-AOC)和丙二醛(MDA)含量的变化。结果表明,小金蝠蛾在正常生长发育情况下SOD具有较高活性;经温度胁迫后,SOD活力持续维持在较高活性,CAT、POD活性以及T-AOC活性显著性升高(P0.05);GSTs在24℃以上活性有降低趋势,MDA含量有上升趋势。     

Plasticity of Drosophila melanogaster wing morphology: effects of sex, temperature and density

In this paper we use an adjusted ellipse to the contour of the wings of Drosophila as an experimental model to study phenotypic plasticity. The geometric properties of the ellipse describe the wing morphology. Size is the geometric mean of its two radii; shape is the ratio between them; and, the positions of the apexes of the longitudinal veins are determined by their angular distances to the major axis of the ellipse. Flies of an inbred laboratory strain of Drosophila melanogaster raised at two temperatures (16.5°C and 25°C) and two densities (10 and 100 larvae per vial) were used. One wing of at least 40 animals of each sex and environmental condition were analyzed (total = 380), a measurement of thorax length was also taken. Wing size variation could be approximately divided into two components: one related to shape variation and the other shape independent. The latter was influenced primarily by temperature, while the former was related to sex and density. A general pattern could be identified for the shape dependent variation: when wings become larger they become longer and the second, fourth and fifth longitudinal veins get closer to the tip of the wing. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of contingent versus yoked temperature feedback on voluntary temperature control and cold stress tolerance

Twenty-four male internals(locus of control) and 24 externals were instructed to increase finger temperature under one of three conditions:(1) contingent feedback(CF),(2) yoked sham feedback(YF), or(3) no feedback(NF). Five 13-min training sessions were given. Feedback was then removed and subjects tested for voluntary temperature control. Finally, the cold pressor test, a laboratory analogue of natural cold stress, was administered under no-feedback conditions. Results demonstrated voluntary control of peripheral temperature following contingent feedback training, but not after yoked feedback temperature training. Contrary to expectation, the acquisition of voluntary control did not attenuate the stress response to thermal pain. Differences between internals and externals throughout the study were generally insignificant.     

Metabonomic studies on the physiological effects of acute and chronic psychological stress in Sprague-Dawley rats

The biochemical effects of acute and chronic psychological stress have been investigated in male Sprague-Dawley rats using a combination of 1H NMR spectral analysis of plasma and conventional hematological analyses. Animals were subjected to 35 consecutive days of 6-h sessions of stress, and following a 9 day break, were stressed for a further 6-h period. Plasma samples were collected at 0, 1, 3, and 6 h on days 1, 9, 21, 35, and 44, measured using 600 MHz 1H NMR spectroscopy, and analyzed by Principal Components Analysis. Time-dependent biochemical effects of psychological stress on a range of endogenous metabolites were evident and were correlated with the intensity of the stress response as defined by corticosterone and hematological parameters. Following acute stress, increases in the levels of glucose and ketone bodies, and decreases in the levels of acetate, alanine, isoleucine, lactate, leucine, valine, and lipoproteins, were observed. Chronic stress-induced increases in plasma levels of alanine, lactate (day 9), and leucine, valine, and choline (day 44) and decreases in acetate (day 9) and lipoprotein concentrations were observed. Positive correlations between plasma corticosterone level and glucose and glycerol, and between plasma lipoprotein concentrations and hemoglobin levels, were established using Projection to Latent Structures (PLS) analysis. This study indicates the potential of using NMR-based metabonomic strategies for the characterization of endogenous metabolic perturbations induced by psychological stressors and lifestyle choices.     

Estimating temperature effects on Drosophila suzukii life cycle parameters

1. Drosophila suzukii is an invasive, polyphagous pest of soft-skinned fruits, having huge impact on fruit production in Asia, North and South America and Europe including Germany.
2. To investigate the effect of temperature on oviposition, egg-to-adult development success and duration, as well as immature heat survival and adult cold survival for a German D. suzukii population several experiments were conducted under different constant temperatures in the laboratory. The resulting life cycle data were described mathematically as functions of temperature and compared with experimental results of other researchers in a summary table.
3. Curve fittings used herein revealed that minimum, optimum and maximum temperatures are: 13.2, 26.7 and 33.6 °C for oviposition, 14.1, 22.6 and 30.0 °C for egg-to-adult development success, and 9.6, 27.3 and 35.7 °C for egg-to-adult development duration. Eggs and larvae of D. suzukii showed a reduced heat survival within the tested temperature range of 29 to 41 °C and exposure durations from 1 to 8 h. A cold survival rate of 50% was measured at e.g. −6 °C for 4 h in summer morph adults and at e.g. −6 °C for 45 h in winter morph adults confirming that the latter are more cold tolerant.
4. Results obtained in this study for a German population of D. suzukii are similar to those obtained for populations of other origins such as Canada, Japan, Spain and USA. Thus, presumably, present data based on a German D. suzukii population can be used for a new or fine-tune of already existing population dynamics models of D. suzukii in order to support an effective pest management strategy.

     

Relationship between cold tolerance and generation of suppressor macrophages during acute cold stress

Kizaki, Takako, Tomomi Ookawara, Tetsuya Izawa, JunichiNagasawa, Shukoh Haga, Zsolt Radák, and Hideki Ohno.Relationship between cold tolerance and generation of suppressormacrophages during acute cold stress. J. Appl.Physiol. 83(4): 1116-1122, 1997.Acute coldstress induces suppressor macrophages expressing large numbers ofreceptors to the crystallizable fragment (Fc) portion ofimmunoglobulin G(MAC-1⁺FcRII/III^brightcells), resulting in the immunosuppression of splenocyte mitogenesis. The generation ofMAC-1⁺FcRII/III^brightcells is mediated by the action of glucocorticoids (GCs) through theGC-receptor. In the present study, the generation ofMAC-1⁺FcRII/III^brightcells in peritoneal exudate cells was closely related to the decreaseof rectal temperature during 3-day exposure to 5°C. We nextinvestigated the effects of improved cold tolerance on the generationofMAC-1⁺FcRII/III^brightcells during acute cold stress. Mice were adapted to cold by exposureto 5°C for 3 wk (cold-acclimated mice) and then reexposed to5°C for 3 h (acute cold stress) after living at 25°C for 24 h.The rectal temperature of cold-acclimated mice was not decreased by theacute cold stress. In addition, the proportion ofMAC-1⁺FcRII/III^brightcells in peritoneal exudate cell population from cold-acclimated micewas unaffected by the acute cold stress. The cold acclimation significantly attenuated the increases in serum corticosterone levelsand the expression of the GC-receptor mRNA on peritoneal exudate cellsin response to acute cold stress. These results suggest that thealtered GC response to acute cold stress by the improvement of coldtolerance inhibits the generation of suppressor macrophages duringacute cold stress.

     

Effects of contingent versus yoked temperature feedback on voluntary temperature control and cold stress tolerance.

Twenty-four male internals (locus of control) and 24 externals were instructed to increase finger temperature under one of three conditions: (1) contingent feedback (CF), (2) yoked sham feedback (YF), or (3) no feedback (NF). Five 13-min training sessions were given. Feedback was then removed and subjects tested for voluntary temperature control. Finally, the cold pressor test, a laboratory analogue of natural cold stress, was administered under no-feedback conditions. Results demonstrated voluntary control of peripheral temperature following contingent feedback training, but not after yoked feedback temperature training. Contrary to expectation, the acquisition of voluntary control did not attenuate the stress response to thermal pain. Differences between internals and externals throughout the study were generally insignificant.     

The effects of acclimation to alternating environmental temperature on metabolic and endocrine responses in guinea pigs,during acute heat and cold exposure

Male Guinea pigs (n=80) were divided into four groups and maintained in a climatic chamber for three weeks in one of the following environmental conditions: (1) T_a20°C and 55% RH; (2) T_a35°C and 30–35% RH from 08:00 to 20:00 h and 5°C; 60–65% RH, from 20:00 h to 08:00 h; (3) T_a5°C and 60–65% RH; (4) T_a35°C and 30–35% RH. At the end of this period the animals were exposed to either –5°C, 60–65% RH or 45°C, 30–35% RH, for a period of 20 min, following which T_re, plasma 11-OHCS, thyroxin, glucose, and FFA, and body and organ weights were determined. The cold-warm adapted animals seemed to develop a more efficient adaptability to acute heat and cold exposure. It is suggested that on acute exposure to severe environmental conditions the endocrine and the nervous system play a dominant role in maintaining optimal body temperature, while on chronic exposure the metabolic rate of the various organs becomes relatively more important.     

A review on temperature and humidity effects on Drosophila suzukii population dynamics

1. Drosophila suzukii is an invasive polyphagous pest of wild and cultivated soft‐skinned fruits, which can cause widespread economic damage in orchards and vineyards.
2. The simulation and prediction of D. suzukii's population dynamics would be helpful for guiding pest management. Therefore, we reviewed and summarized the current knowledge on effects of air temperature and relative humidity on different life cycle parameters of D. suzukii.
3. The literature summary presented shows that high oviposition rates can occur between 18 and 30 °C. Temperatures between 16 and 25 °C resulted in fast and high egg‐to‐adult development success of more than 80%. Oviposition and adult life span were positively affected by high relative humidity; however, the factor humidity is so far rarely investigated.
4. We assume that this is one reason why relative humidity usually is not considered in modelling approaches, which are summarized herein. The high number of recently published research articles on D. suzukii's life cycle suggests that there is already a lot of knowledge available on its biology. However, there are still considerable research gaps mentioned in the literature, which are also summarized herein.
5. Nevertheless, we conclude that sufficient temperature data in the literature are suitable to understand and predict population dynamics of D. suzukii, in order to assist pest management in the field.