Drosophila melanogaster as a model system of aluminum toxicity and aging

The aim of this study was to investigate the toxic effects of aluminum （A1） on the model organism-Drosophila melanogaster. The study is especially concerned with the effects of aluminum on the fruit fly＇s development, life span, and circadian rhythm in rest and activity. Flies were exposed to aluminum in concentrations from 40 to 280 mg/kg in rearing media or the flies were raised on control medium. Moreover, the life span of insects exposed to aluminum containing 40, 120, or 240 mg/kg of A1 in the medium, only during their larval development, during the whole life cycle and only in their adult life was tested. To check if aluminum and aging cause changes in D. melanogaster behavior, the locomotor activity of flies at different ages was recorded. Results showed that aluminum is toxic in concentrations above 160 mg/kg in the rearing medium. Depending on A1 concentration and time of exposure, the life span of the flies was shortened. At intermediate concentrations （120 mg/kg）, however, A1 had a stimulating effect on males increasing their life span and level of locomotor activity. At higher concentration the aluminum exposure increased or decreased the level of locomotor activity ofD. melanogaster depending on age of flies. In addition, in the oldest insects reared on aluminum supplemented media and in mid-aged flies reared on the highest concentration of A1 the daily rhythm of activity was disrupted.     

Host permissiveness to baculovirus in flue nces time-dependent immune responses and fitness costs

Insects possess specific immune responses to protect themselves from different types of pathogens.Activation of immune cascades can inflict significant developmental costs on the surviving host.To characterize infection kinetics in a surviving host that experiences baculovirus inoculation,it is crucial to determine the timing of immune responses.Here,we investigated time-dependent immune responses and developmental costs elicited by inoculations from each of two wild-type baculoviruses,Autographa californica multiple nucleopolyhedrovirus(AcMNPV)and Helicoverpa zea single nucleopolyhedrovirus(HzSNPV),in their common host H.zea.As H.zea is a semi-permissive host of AcMNPV and fully permissive to HzSNPV,we hypothesized there are differential immune responses and fitness costs associated with resisting infection by each virus species.Newly molted 4th-instar larvae that were inoculated with a low dose(LD15)of either virus showed signify icantly higher hemolymph FAD-glucose dehydrogenase(GLD)activities compared to the corresponding control larvae.Hemolymph phenoloxidase(PO)activity,protein concentration and total hemocyte numbers were not increased,but instead were lower than in control larvae at some time points post-inoculation.Larvae that survived either virus inoculation exhibited reduced pupal weight;survivors inoculated with AcMNPV grew slower than the control larvae,while survivors of HzSNPV pupated earlier than control larvae.Our results highlight the complexity of immune responses and fitness costs associated with combating different baculoviruses.     

Post-fire ecological succession: A theoretical modeling framework

The effects of starvation on larval growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum at the temperature of 19.6–21.6 °C, the salinity of 34‰ and pH of 8.0 were investigated from May 18 to July 18, 2006. In this study, the early, middle and late umbo-veliger larvae with the shell lengths of 100, 140, and 190 μm were subject to temporary food deprivation for up to 4.5, 20, and 25d at 0.5, 4, 5d intervals, followed by refeeding for the remaining of a 24, 20, 25d period, respectively. The results suggested that the larvae should have shown considerable tolerance to starvation due to their endogenous and exterior nutrition material, for larvae and time to the point-of-no-return (PNR: the threshold point during starvation after which larvae could no longer metamorphose even if food is provided) were calculated to be 4.25, 17.54, and 22.17d. As the starvation period prolonged, the mean shell length of larvae starved got close to constants at 1.5, 4, and 15d after starvation, which were different for larvae at different stages when starvation began, survival of larvae decreased, and was lower in treatments starved earlier in development than those starved later, for the early, middle and late umbo-veliger larvae, after 4.5, 20 and 25d of starvation period, few larvaes were alive. After starvation period, the alive larvaes were able to metamorphose and had a capability of compensatory growth when refeeding was given. Starvation not only affected metamorphosis rate, but also caused the delay in the time to metamorphosis and the decrease in the metamorphosed sizes. For example, for the continuously-fed larvae, duration to metamorphosis was 20.7d, for larvae with a size of 100-μm starved for up to 4d, larvae with a size of 140-μm starved for up to 16d, larvae with a size of 190-μm starved for up to 20d, duration to metamorphosis were 29.7, 31.7, and 37.7d, the delay in duration to metamorphosis were 9, 11, and 17d, respectively. Furthermore, importance of nutrition material for maintaining larval survival during starvation and the compensatory growth on larvae at the same feeding time were discussed.     

Effects of starvation on larval growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum

The effects of starvation on larval growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum at the temperature of 19.6–21.6 °C, the salinity of 34‰ and pH of 8.0 were investigated from May 18 to July 18, 2006. In this study, the early, middle and late umbo-veliger larvae with the shell lengths of 100, 140, and 190 μm were subject to temporary food deprivation for up to 4.5, 20, and 25d at 0.5, 4, 5d intervals, followed by refeeding for the remaining of a 24, 20, 25d period, respectively. The results suggested that the larvae should have shown considerable tolerance to starvation due to their endogenous and exterior nutrition material, for larvae and time to the point-of-no-return (PNR: the threshold point during starvation after which larvae could no longer metamorphose even if food is provided) were calculated to be 4.25, 17.54, and 22.17d. As the starvation period prolonged, the mean shell length of larvae starved got close to constants at 1.5, 4, and 15d after starvation, which were different for larvae at different stages when starvation began, survival of larvae decreased, and was lower in treatments starved earlier in development than those starved later, for the early, middle and late umbo-veliger larvae, after 4.5, 20 and 25d of starvation period, few larvaes were alive. After starvation period, the alive larvaes were able to metamorphose and had a capability of compensatory growth when refeeding was given. Starvation not only affected metamorphosis rate, but also caused the delay in the time to metamorphosis and the decrease in the metamorphosed sizes. For example, for the continuously-fed larvae, duration to metamorphosis was 20.7d, for larvae with a size of 100-μm starved for up to 4d, larvae with a size of 140-μm starved for up to 16d, larvae with a size of 190-μm starved for up to 20d, duration to metamorphosis were 29.7, 31.7, and 37.7d, the delay in duration to metamorphosis were 9, 11, and 17d, respectively. Furthermore, importance of nutrition material for maintaining larval survival during starvation and the compensatory growth on larvae at the same feeding time were discussed.     

Effects of starvation on larval growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum

The effects of starvation on larval growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum at the temperature of 19.6–21.6 °C, the salinity of 34‰ and pH of 8.0 were investigated from May 18 to July 18, 2006. In this study, the early, middle and late umbo-veliger larvae with the shell lengths of 100, 140, and 190 μm were subject to temporary food deprivation for up to 4.5, 20, and 25d at 0.5, 4, 5d intervals, followed by refeeding for the remaining of a 24, 20, 25d period, respectively. The results suggested that the larvae should have shown considerable tolerance to starvation due to their endogenous and exterior nutrition material, for larvae and time to the point-of-no-return (PNR: the threshold point during starvation after which larvae could no longer metamorphose even if food is provided) were calculated to be 4.25, 17.54, and 22.17d. As the starvation period prolonged, the mean shell length of larvae starved got close to constants at 1.5, 4, and 15d after starvation, which were different for larvae at different stages when starvation began, survival of larvae decreased, and was lower in treatments starved earlier in development than those starved later, for the early, middle and late umbo-veliger larvae, after 4.5, 20 and 25d of starvation period, few larvaes were alive. After starvation period, the alive larvaes were able to metamorphose and had a capability of compensatory growth when refeeding was given. Starvation not only affected metamorphosis rate, but also caused the delay in the time to metamorphosis and the decrease in the metamorphosed sizes. For example, for the continuously-fed larvae, duration to metamorphosis was 20.7d, for larvae with a size of 100-μm starved for up to 4d, larvae with a size of 140-μm starved for up to 16d, larvae with a size of 190-μm starved for up to 20d, duration to metamorphosis were 29.7, 31.7, and 37.7d, the delay in duration to metamorphosis were 9, 11, and 17d, respectively. Furthermore, importance of nutrition material for maintaining larval survival during starvation and the compensatory growth on larvae at the same feeding time were discussed.     

Exposure of silver carp (Hypophthalmichthys molitrix) to environmentally relevant levels of cadmium:hematology,muscle physiology,and implications for stock enhancement in the Xiangjiang River (Hunan,China)

Cadmium is a non-essential metal with a wide distribution that has severe toxic effects on aquatic animals. Changes in hematology and muscle physiology were examined in silver carp (Hypophthalmichthys molitrix) exposed to environmentally relevant levels of cadmium (0.01 mg L-1 ) for 96 h. Cadmium exposure induced significant increases in the red blood cell count, and in the plasma concentrations of cortisol, glucose, and lactate. This suggests that the dose of cadmium was sufficient to cause stress, possibly associated with impaired gas exchange at the gills. There were no changes in hemoglobin concentration or plasma protein concentration. Significant decreases in muscle energy fuels (ATP and glycogen), and increases in muscle lactate persisted until the end of the exposure period, respectively. The changes in muscle lactate and protein in silver carp differed from those observed in response to exposure of fish to cadmium and heavy metals in other studies. The study highlights the importance of selecting unpolluted release sites with suitable water conditions for the survival of newly released individuals for stock enhancement of the Xiangjiang River.     

Effects of Elevated Carbon Dioxide on the Growth and Foliar Chemistry of Transgenic Bt Cotton

A field study was carried out to quantify plant growth and the foliar chemistry of transgenic Bacillus thuringiensis （Bt） cotton （cv. GK-12） exposed to ambient CO2 and elevated （double-ambient） CO2 for different lengths of time （1, 2 and 3 months） in 2004 and 2005. The results indicated that CO2 levels significantly affected plant height, leaf area per plant and leaf chemistry of transgenic Bt cotton. Significantly, higher plant height and leaf area per plant were observed after cotton plants that were grown in elevated CO2 were compared with plants grown in ambient CO2 for 1, 2 and 3 months in the investigation. Simultaneously, significant interaction between CO2 level x investigating year was observed in leaf area per plant. Moreover, foliar total amino acids were increased by 14%, 13%, 11% and 12%, 14%, 10% in transgenic Bt cotton after exposed to elevated CO2 for 1, 2 or 3 months compared with ambient CO2 in 2004 and 2005, respectively. Condensed tannin occurrence increased by 17%, 11%, 9% in 2004 and 12%, 11%, 9% in 2005 in transgenic Bt cotton after being exposed to elevated CO2 for 1, 2 or 3 months compared with ambient CO2 for the same time. However, Bt toxin decreased by 3.0%, 2.9%, 3.1% and 2.4%, 2.5%, 2.9% in transgenic Bt cotton after exposed to elevated CO2 for 1, 2 or 3months compared with ambient CO2 for same time in 2004 and 2005, respectively. Furthermore, there was prominent interaction on the foliar total amino acids between the CO2 level and the time of cotton plant being exposed to elevated CO2. It is presumed that elevated CO2 can alter the plant growth and hence ultimately the phenotype allocation to foliar chemistical components of transgenic Bt cotton, which may in turn, affect the plant-herbivore interactions.     

Effects of heavy metals on structure,function, and metabolism of ciliated respiratory epithelium in vitro

Summary Tracheal explants were used to evaluate the relative ciliostatic and cytotoxic potential of heavy metal salts (cadmium chloride, chromium chloride, nickel chloride, and copper sulfate). Explants from hamster, rat, and guinea pig were all sensitive to the metals, though guinea pig explants showed the greatest difference between the untreated and metal treated tissues. Dosage levels were 50, 100, and 500μM, for 24 to 148 h. Cadmium caused the greatest degree of ciliostasis and cell necrosis. Copper was less toxic, and nickel and chromium caused marginal damage when tested at 100μM or lower. In each instance, damage became detectable at approximately 24 to 48 h and was nearly stabilized by 72 h. A significant loss of ciliary motion was always accompanied by a decrease in metabolic activity (dehydrogenase activity and ATP content). Transmission and scanning electron microscopy revealed a severely necrotic epithelium after exposure to cadmium, with only subtle morphological alterations after exposure to other metals. With all of the treatments there was no overt structural damage to cilia and little alteration in membranes of cells remaining in the epithelium. Some coagulation or vacuolization was noted in cadmium and copper treated explants but most cellular organelles did not display obvious damage. The most significant changes in the tracheal epithelium exposed to heavy metal salts in vitro were a loss of ciliary motion and a decrease in total ATP content. This study was supported in part by Grant HL 26880 from the National Heart, Lung and Blood Institute, Bethesda, MD.     

Effect of five diatomaceous earth formulations against Tribofium castaneum （Coleoptera： Tenebrionidae）, Oryzaephflus surinamensis （Coleoptera： Silvanidae） and Rhyzopertha dominica （Coleoptera： Bostrychidae）

Laboratory bioassays were conducted to determine the effect of food source on the survival of Tribolium castaneum Herbst, Oryzaephilus surinamensis L. and Rhyzopertha dominica F., after exposure to five diatomaceous earth （DE） formulations： Protect-It, Insecto, Perma-GuardTM, Dryacide and SilicoSec. Adults of these species were exposed to DEs at the rate of 0.5 mg/cm^2 for 1 day on filter paper inside plastic Petri dishes. After exposure, the initial mortality was counted and live individuals of the three species were held for a week in glass vials containing 50 mg wheat flour, rice and whole wheat, respectively. In the second experiment, after 1 day exposure to DEs, beetles were transferred to Petri dishes without food and held for a week to determine if the presence of food source would decrease the mortality of beetles. Experiments were carried out at 27℃ and 55% RH in the dark. The initial mortality in both of the experiments reached 100% for the three species exposed to Protect-It and in the case ofR. dominica and O. surinamensis exposed to Dryacide. In contrast, low level of mortality （〈 10%） was observed for T. castaneum exposed to Perma-GuardTM and Insecto. The mortality after the post-treatment period on food was decreased for the three species exposed to Perma-GuardTM and in the case of T. castaneum and R. dominica exposed to Insecto and SilicoSec. Adults of O. surinamensis were the most susceptible followed by R. dominica and 100% adult mortality was obtained, whereas T. castaneum were the least susceptible beetles to DEs. Protect-It and Dryacide were the most efficient DE formulations and can be used effectively in a stored grain integrated pest management program.     

Ni2+胁迫对斜纹夜蛾幼虫血淋巴中能量物质水平的适应性调节

为明确食物中重金属胁迫对昆虫血淋巴能量物质和生长的影响,本研究测定了饲料中不同浓度的Ni²⁺ （1~40 mg/kg）对连续3个世代斜纹夜蛾Spodoptera litura Fabricius 5龄始龄（0 h）至6龄末幼虫（分别记为0,24,48,72,96和120 h幼虫）血淋巴中能量物质总糖、蛋白质和脂肪含量,血淋巴中热量值及5龄和6龄幼虫体重的影响。结果表明：第1和2代48 h和96 h幼虫血淋巴的总糖含量均低于对照;而连续3代其他处理幼虫血淋巴中的总糖含量均在低浓度Ni²⁺（1~5 mg/kg）胁迫下增高,在高浓度Ni²⁺ （20~40 mg/kg）胁迫下降低。连续3个世代的Ni²⁺胁迫均显著降低了0~48 h幼虫血淋巴中的蛋白含量;低浓度Ni²⁺（1~5 mg/kg）胁迫增加了连续3代72~120 h幼虫血淋巴中的蛋白含量,而高浓度Ni²⁺（20~40 mg/kg）胁迫只降低了第1代72~120 h幼虫以及第2代72 h幼虫血淋巴中的蛋白含量。第1代0 h,48~72 h和120 h幼虫血淋巴中的脂肪含量在1~20 mg/kg Ni²⁺胁迫下均高于对照,但24 h和96 h幼虫血淋巴中的脂肪含量均低于对照中的含量。连续3代0~48 h幼虫血淋巴中的热量值均随饲料中Ni²⁺浓度的增加而降低;低浓度Ni²⁺胁迫（1~5 mg/kg）增加,而高浓度Ni²⁺（20~40 mg/kg）的胁迫降低第2和3代72 ~120 h幼虫血淋巴中热量值。同时,低浓度Ni2+胁迫增加而高浓度Ni²⁺胁迫降低了第3代5龄和6龄幼虫的体重。因此推测,Ni²⁺胁迫对S. litura幼虫血淋巴的能源物质含量以及热量值的影响与能量物质的种类、虫体的发育阶段和Ni²⁺的胁迫世代等都有一定的联系。     

Cd胁迫对舞毒蛾幼虫食物利用的影响及其Cd的外泌机制

为探明植食性昆虫对受重金属胁迫的寄主植物的生理生态响应机制,本研究用Cd胁迫下银中杨的叶片饲养舞毒蛾幼虫,分析舞毒蛾幼虫对食物的利用情况以及其对Cd的排毒代谢机制.结果表明: 取食Cd胁迫下银中杨的叶片后,舞毒蛾3～6龄幼虫体内的Cd浓度和Cd含量均显著高于对照,但随着幼虫龄期增长,其体内Cd浓度显著降低,而Cd含量有不同程度的提高;舞毒蛾幼虫粪便和虫蜕中的Cd浓度均显著高于对照;舞毒蛾3～5龄幼虫的食物消耗率显著高于对照,而转化率显著低于对照;3～4龄幼虫的食物利用率均与对照差异不显著,但在5龄时显著低于对照.说明在Cd胁迫下,舞毒蛾幼虫能通过有效的排毒代谢途径将体内富集的部分Cd排出体外,且高龄幼虫的排毒代谢能力强于低龄幼虫;舞毒蛾幼虫体质量的增加会对体内的Cd浓度形成一种稀释效应;舞毒蛾幼虫能通过调整食物消耗率和转化率之间的比例,来维持其正常生长发育所需的食物利用率,但超过一定限度后仍会造成食物利用率降低.     

几种植物源化合物对棉铃虫海藻糖酶活性及相关碳水化合物含量的影响

碳水化合物对昆虫的能量代谢和物质合成具有重要的作用。本研究选用2种一般性生物碱（氢溴酸东莨菪碱和烟碱）以及2种β-葡萄糖苷类化合物（七叶灵和皂角苷）, 研究其在不同浓度下对棉铃虫Helicoverpa armigera (Hübner)幼虫体内海藻糖酶活性及相关碳水化合物代谢的影响。结果表明: 用饲喂法处理3龄幼虫96 h后, 皂角苷对棉铃虫幼虫的活体抑制效果明显, 且随添加物浓度增高, 棉铃虫死亡率上升, 10, 20, 40 g/L浓度下棉铃虫的均重分别是0.194, 0.089和0.034 g, 分别为对照的86.99%, 39.91%和15.24%。对海藻糖酶活性及其相关代谢酶的测定结果表明, 2种苷类化合物显著抑制中肠海藻糖酶活性, 饲喂40 g/L皂角苷的试虫中肠海藻糖酶比活力仅是对照组的54.21%; 饲喂30 g/L七叶灵的试虫中肠海藻糖酶比活力为对照组的83.73%。而2种生物碱类化合物显著抑制血淋巴和脂肪体中海藻糖酶活性, 20 g/L氢溴酸东莨菪碱对棉铃虫血淋巴和脂肪体组织的海藻糖酶活性抑制率分别为7.24%和71.43%; 而20 g/L烟碱对试虫血淋巴和脂肪体组织的海藻糖酶活性抑制率为26.29%和33.44%。用氢溴酸东莨菪碱、 烟碱和七叶灵处理试虫后, 血淋巴海藻糖含量都有所增高。4种化合物能够导致试虫糖原磷酸化酶活性变化, 其中, 皂角苷在中肠和脂肪体表现为显著抑制作用, 而随外源化合物浓度变化, 糖原含量和糖原磷酸化酶活性表现为此消彼长关系。饲喂4种植物源化合物的试虫血淋巴中葡萄糖浓度变化和其海藻糖变化一致。本研究证明β-葡萄糖苷类化合物是海藻糖酶抑制剂, 在作为先导化合物进行农药创制开发方面具有重要意义。     

Cd2+急性胁迫下方格星虫体腔液消化酶活力和游离氨基酸的变化

为了解Cd2+急性胁迫下方格星虫体腔液消化酶活力和游离氨基酸的变化规律, 采用毒理学试验方法, 在确定Cd2+对方格星虫毒性强度的基础上, 选取48h最低致死浓度为试验浓度, 研究该浓度Cd2+胁迫下方格星虫体腔液消化酶活力和游离氨基酸的动态变化。结果表明: 方格星虫死亡率随着Cd2+浓度的升高而增加,Cd2+对方格星虫的24h和48h的LC50分别为37.80和22.68 mg/L。在48h最小致死浓度下, Cd2+对方格星虫体腔液蛋白酶和淀粉酶活力在试验周期内均表现为抑制, 且淀粉酶活力受到的抑制作用较强; Cd2+胁迫前期脂肪酶活力显著升高(P0.05), 24h后又显著降低(P0.05), 48h时仅为初始水平的40%, 说明低浓度Cd2+对脂肪酶活力有诱导作用, 高浓度Cd2+则产生抑制。方格星虫体腔液游离氨基酸的组成和含量在Cd2+胁迫48h内均有显著变化(P0.05)。各游离氨基酸含量及氨基酸总量在24h前均无显著变化(P0.05), 24h后先上升后下降(P0.05),36h的游离氨基酸总量达到初始水平的2倍以上, 为145.50 mg/100 mL, 大部分游离氨基酸组成百分比也在24h前较稳定, 24h后呈现峰值变化。总之, Cd2+急性胁迫对方格星虫体腔液消化酶活力和游离氨基酸均有显著影响(P0.05), 且消化酶活力与游离氨基酸含量和组成的变化与胁迫时间有关。     

Effect of cold acclimation on the antioxidant defense system of two larval lepidoptera (noctuidae)

Activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), glutathione-S-transferase (GST), as well as total glutathione (tGSH) concentration were analyzed in the hemolymph and fat body of the European corn borer Ostrinia nubilalis Hubn. and the Mediterranean borer Sesamia cretica Led. (Lepidoptera, Noctuidae). Controls were maintained at 8°C while experimental groups of larvae were exposed to –3°C for ten days and then to –12°C for 23 days (only for Ostrinia). Cold exposure significantly increased fat body SOD, GR, and GST activities of Ostrinia larvae. Only GST activity and tGSH levels increased significantly in Ostrinia larval hemolymph on cold exposure. In Sesamia larvae after cold exposure, hemolymph CAT activity was significantly lower, while fat body tGSH increased. The antioxidant defense systems of these two species show differences, probably influenced by their respective cold-hardiness metabolism. According to its antioxidant profile, the response of Ostrinia suggests a significant physiological alteration in its metabolism during cold exposure, indicating a compensatory mechanism. By contrast this is not evident in Sesamia.Arch. Insect Biochem. Physiol. 36:1–10, 1997. © 1997 Wiley-Liss, Inc.     

Expression of mt2 and smt-B upon cadmium exposure and cold shock in zebrafish (Danio rerio)

Metallothionein-2 (mt2) and similar to metallothionein-B (smt-B) are included in the MT gene family. The objective of this study was to compare mt2 and smt-B messenger (m)RNA expressions after cadmium exposure and cold shock with whole-mount in situ hybridization in immature zebrafish (Danio rerio) and with a semi-quantitative RT-PCR in mature zebrafish. Three-day post-fertilization (dpf) larvae were treated with 0, 0.08, 0.26, and 0.89 microM cadmium for 24 and 48 h, and some larvae were challenged with a normal (28.5 degrees C) or low temperature (12 degrees C) for 12, 24, and 48 h. Results were obtained. (1) During embryonic and larval development, mt2 mRNA existed at 6 h post-fertilization (hpf), and the level rapidly increased to 24 hpf, then it gradually increased with further larval growth. smt-B was found at 12 hpf, and it also rapidly increased to 24 hpf, but remained constant during further larval development. (2) The mt2 mRNA signals and whole-body Cd contents displayed dose- and time-dependent responses after Cd exposure. After cold shock, mt2 mRNA signals also showed time-dependent expression. But smt-B mRNA signals were not appeared by either challenge. Besides, mature zebrafish were treated with 1.78 microM Cd and found that the highest levels of smt-B mRNA (smt-B/beta-actin) appeared in brain, and seems a reverse expression between smt-B mRNA and mt2 in brain after Cd exposure. Apparently, mt2 is possibly more relevant to Cd detoxification and cold shock adaptation in zebrafish larvae compared to smt-B, but smt-B might be related to certain physiological functions in neural (or brain) of mature zebrafish.     

Maternal cadmium exposure induces mt2 and smtB mRNA expression in zebrafish (Danio rerio) females and their offspring

The present study aimed to identify the effects of maternal cadmium (Cd(2+)) exposure on the mRNA expression of mt2 (metallothionein-2) and smtB (similar to metallothionein-B) in female zebrafish (Danio rerio) and their offspring (F1 larvae). Zebrafish females were exposed to 0, 8.9, 17.8, and 35.6 μM Cd(2+) for 72 h, and their ovaries and F1 larvae were collected to measure their Cd(2+) contents and their smtB and mt2 mRNA expression. Cd(2+) contents and the mRNA expression of smtB and mt2 in F1 larvae all showed positive correlations with the maternal Cd(2+) treatment dose. The mt2 was 1.9- to 3.4-fold higher than smtB in F1 larvae. Furthermore, F1 larvae had noticeably enhanced Cd(2+) tolerance after maternal Cd(2+) treatment. These results demonstrate that maternal Cd(2+) was transferred to larval fish and induced mt2 and smtB mRNA expression to protect larva against the impacts of Cd(2+). In female ovaries, mt2 expression showed a noticeable increase after exposure to a metal environment, while smtB did not show exactly the same effect. The study can only conclude that smtB might have a much different role other than just protecting against the impacts of metals.     

Evaluation of thiamethoxam and imidacloprid as seed treatments to control European corn borer and Indianmeal moth (Lepidoptera: Pyralidae) larvae

Efficacy of thiamethoxam (Cruiser) and imidacloprid (Gaucho) were evaluated as seed treatments for controlling European corn borer, Ostrinia nubilalis (Hübner) and Indianmeal moth, Plodia interpunctella (Hübner) larvae in stored grain. At approximately 22-26 degrees C, all fifth instar European corn borers died after two or 4 d of exposure to corn treated with 250 and 500 ppm thiamethoxam, respectively, while mortality of larvae exposed for two and 4 d on corn treated with 6.3-937.5 ppm imidacloprid did not exceed 48% at any concentration. At 29 degrees C, all nondiapausing fifth instars were killed after 3, 4, and 6-d exposure to 400, 300 and 200-ppm thiamethoxam, respectively, while survival increased at successively lower concentrations of 100, 50, 25, and 12.5 ppm. At 29 degrees C, the LC50 decreased from 85.9 to 7.2 ppm as the duration of exposure on treated corn increased from 2 to 6 d. All second and third instar Indianmeal moth larvae died after a 5 d exposure period to corn grain treated with thiamethoxam at 50 ppm or higher, but as the larvae aged, higher concentrations and longer exposure periods were required to give 100% mortality of each larval instar. Similar results were obtained when larval Indianmeal moths were exposed on corn treated with imidacloprid, or on sorghum treated with thiamethoxam. Mature wandering phase fifth instars were the most tolerant larval stage of the Indianmeal moth.     

Divergence of larval resource acquisition for water conservation and starvation resistance in Drosophila melanogaster

Laboratory selection experiments have evidenced storage of energy metabolites in adult flies of desiccation and starvation resistant strains of D. melanogaster but resource acquisition during larval stages has received lesser attention. For wild populations of D. melanogaster, it is not clear whether larvae acquire similar or different energy metabolites for desiccation and starvation resistance. We tested the hypothesis whether larval acquisition of energy metabolites is consistent with divergence of desiccation and starvation resistance in darker and lighter isofemale lines of D. melanogaster. Our results are interesting in several respects. First, we found contrasting patterns of larval resource acquisition, i.e., accumulation of higher carbohydrates during 3rd instar larval stage of darker flies versus higher levels of triglycerides in 1st and 2nd larval instars of lighter flies. Second, 3rd instar larvae of darker flies showed ~40?h longer duration of development at 21°C; and greater accumulation of carbohydrates (trehalose and glycogen) in fed larvae as compared with larvae non-fed after 150?h of egg laying. Third, darker isofemale lines have shown significant increase in total water content (18%); hemolymph (86%) and dehydration tolerance (11%) as compared to lighter isofemale lines. Loss of hemolymph water under desiccation stress until death was significantly higher in darker as compared to lighter isofemale lines but tissue water loss was similar. Fourth, for larvae of darker flies, about 65% energy content is contributed by carbohydrates for conferring greater desiccation resistance while the larvae of lighter flies acquire 2/3 energy from lipids for sustaining starvation resistance; and such energy differences persist in the newly eclosed flies. Thus, larval stages of wild-caught darker and lighter flies have evolved independent physiological processes for the accumulation of energy metabolites to cope with desiccation or starvation stress.     

Stimulated synthesis of the female-specific storage protein in male larvae of the silkworm Bombyx mori treated with juvenile hormone analog

Application of methoprene to fourth (penultimate) instar larvae of the silkworm Bombyx mori induced the appearance of the feeding dauer larvae at the fifth (last) instar and prevented pupal metamorphosis. Methoprene also increased the protein concentrations of hemolymph last instar larvae by preventing sequestration of storage proteins by the fat body. Usually, the female-specific storage protein 1 (SP1)* disappears from the male hemolymph at the time of the last larval instar. However, exposure of male larvae to methoprene at the penultimate instar enhanced the accumulation of SP1 in the hemolymph. The SP1 accumulated in males did not differ in molecular weight and immunoreactivity from the SP1 produced in female larvae. Both sexes of fourth instar larvae allatectomized on day 1 instantly accumulated SP1 in the hemolymph, and methoprene application after allatectomy suppressed the hemolymph accumulation of the SP1. In contrast, if allatectomy was carried out at a later stage of the fourth larval instar, SP1 concentration in hemolymph of fifth instar larvae did not increase, suggesting the different juvenile hormone action for regulation of SP1 synthesis in the penultimate instar larvae of silkworms.