Reduction In Reproductive Capacity Research Articles

Paeoniflorin attenuates polystyrene nanoparticle-induced reduction in reproductive capacity and increase in germline apoptosis through suppressing DNA damage checkpoints in Caenorhabditis elegans

Due to high sensitivity to environmental exposures, Caenorhabditis elegans is helpful for toxicity evaluation and toxicological study of pollutants. Using this animal model, we investigated the reproductive toxicity of 20 nm polystyrene nanoparticle (PS-NP) in the range of μg/L and the following pharmacological intervention of paeoniflorin. After exposure from L1-larvae to young adults, 10–100 μg/L PS-NP could cause the reduction in reproductive capacity reflected by the endpoints of brood size and number of fertilized eggs in uterus. Meanwhile, the enhancements in germline apoptosis analyzed by AO staining and germline DNA damage as shown by alteration in HUS-1::GFP signals were detected in 10–100 μg/L PS-NP exposed nematodes, suggesting the role of DNA damage-induced germline apoptosis in mediating PS-NP toxicity on reproductive capacity. Following the exposure to 100 μg/L PS-NP, posttreatment with 25–100 mg/L paeoniflorin increased the reproductive capacity and inhibited both germline apoptosis and DNA damage. In addition, in 100 μg/L PS-NP exposed nematodes, treatment with 100 mg/L paeoniflorin modulated the expressions of genes governing germline apoptosis as indicated by the decrease in ced-3, ced-4, an egl-1 expressions and the increase in ced-9 expression. After exposure to 100 μg/L PS-NP, treatment with 100 mg/L paeoniflorin also decreased expressions of genes (cep-1, clk-2, hus-1, and mrt-2) governing germline DNA damage. Molecular docking analysis further demonstrated the binding potential of paeoniflorin with three DNA damage checkpoints (CLK-2, HUS-1, and MRT-2). Therefore, our data suggested the toxicity of PS-NP in the range of μg/L on reproductive capacity after exposure from L1-larvae to young adults, which was associated with the enhancement in DNA damage-induced germline apoptosis. More importantly, the PS-NP-induced reproductive toxicity on nematodes could be inhibited by the following paeoniflorin treatment.

Pacific walrus (Odobenus rosmarus divergens) reproductive capacity changes in three time frames during 1975–2010

Reductions in sea ice and increases in air and seawater temperatures have been documented in the Arctic, making female Pacific walruses (Odobenus rosmarus divergens) vulnerable to changes in foraging, energy budgets, and reproductive fitness. The aim of the present study was to assess how walrus reproductive capacity has changed over a span of 35 years analyzing ovaries from three distinct time frames: 1975, 1994 to 1999 and 2008 to 2010. Ovarian weights and volumes, corpora lutea diameter, total number of corpora lutea and albicantia, and the percent of females ovulating in their current cycle were used to evaluate reproductive capacity. Ovaries were collected from walruses hunted by Alaska Native communities for subsistence purposes. There were no differences in ovarian weights or percent of quiescent females between 1975 and 2008 to 2010. Ovaries from 1994 to 1999 were significantly heavier, exhibited more corpora, and all females from this time frame were ovulating at the time of harvest. Reproductive capacity was limited during 1975, due to known density-dependent stressors; reproductive capacity increased during 1994–1999, as harvests increased and more resources became available, and in 2008–2010, females were as reproductively limited as those of 1975. The cause for this reduction in reproductive capacity is unknown, but maybe a result of multiple factors, including an increase in population size coincident with a decrease in carrying capacity, and cumulative stressors relating to sea ice loss, contaminants, and anthropogenic impacts.

Airborne toluene exposure causes germline apoptosis and neuronal damage that promotes neurobehavioural changes in Caenorhabditis elegans

Toluene is a highly volatile organic solvent present in gasoline. Exposure mainly occurs by absorption via the pulmonary tract and easily reaches the central nervous system, which causes toxic effects. Toluene toxicity has been described but not well established. The present work aimed to evaluate the effects of airborne exposure to toluene, the in vivo model Caenorhabditis elegans was assessed to determine whether nematode could be used to evaluate the effects of exposure to toluene and the possible mechanisms of toxicity of the solvent. Worms at the first or fourth larval stages were exposed to toluene for 48 or 24 h, respectively, in a laboratory-developed vapor chamber at concentrations of 450, 850, 1250 and 1800 ppm. We observed increases in worm mortality and significant developmental delays that occurred in a concentration-dependent manner. An increased incidence of apoptotic events in treated germline cells was shown, which was consistent with observed reductions in reproductive capacity. In addition, toluene promoted significant behavioural changes affecting swimming movements and radial locomotion, which were associated with changes in the fluorescence intensity and morphology of GABAergic and cholinergic neurons. We conclude that toluene exposure was toxic to C. elegans, with effects produced by the induction of apoptosis and neuronal damage.

Reduction of Reproductive Capacity in Aedes albopictus (Diptera: Culicidae) in Hot, Dry Summer.

The summer of 2018 was very hot and dry with little rain nationwide in Japan. Particularly in July, temperature was 3°C higher in comparison with the normal year. We collected adults, pupae, third or fourth instar larvae of Aedes albopictus (Skuse) in Sendai city, Niigata city, and Kanazawa city in late July and early August 2018. Wild-collected adults were examined for reproductive capacity. On the other hand, wild-collected larvae and pupae were raised to adults in the laboratory and then examined for reproductive capacity. They did not lay eggs after single blood feeding. When they were supplied with bloodmeals twice or three times, they laid a small number of eggs, but these eggs did not hatch. When these adult individuals were maintained at 25°C for 3 wk and then fed with blood, they laid healthy eggs which developed to embryos. It is thought that extreme heat and/or extreme low humidity due to low precipitation reduced female reproductive capacity even if they could take bloodmeals.

Histone methylation-associated transgenerational inheritance of reproductive defects in Caenorhabditis elegans exposed to crude oil under various exposure scenarios

As part of a study to explore the long-term effects of the Hebei Spirit oil spill accident, transgenerational toxicity and associated epigenetic changes were investigated in the nematode Caenorhabditis elegans. Under experimental conditions, worms were exposed to Iranian heavy crude oil (IHC) under three different scenarios: partial early-life exposure (PE), partial late-life exposure (PL), and whole-life exposure (WE). Growth, reproduction, and histone methylation were monitored in the exposed parental worms (P0) and in three consecutive unexposed offspring generations (F1-3). Reproductive potential in the exposed P0 generation in the WE treatment group was reduced; additionally, it was inhibited in the unexposed offspring generations of the P0 worms. This suggests that there was transgenerational inheritance of defective reproduction. Comparison of developmental periods of exposure showed that IHC-treated worms in the PL group had a greater reduction in reproductive capacity than those in the PE group. Decreased methylation of histone H3 (H3K9) was found in the IHC-exposed parental generation. A heritable reduction in reproductive capacity occurred in wildtype N2 but was not found in a H3K9 histone methyltransferase (HMT) mutant, met-2(n4256), suggesting a potential role for HMT in transgenerational toxicity. Our results suggest that the reproductive toxicity after IHC exposure could be heritable and that histone methylation is associated with the transmission of the inherited phenotype.

A dynamic energy-based model to analyze sublethal effects of chronic gamma irradiation in the nematode Caenorhabditis elegans

ABSTRACTUnderstanding how toxic contaminants affect wildlife species at various levels of biological organization (subcellular, histological, physiological, organism, and population levels) is a major research goal in both ecotoxicology and radioecology. A mechanistic understanding of the links between different observed perturbations is necessary to predict the consequences for survival, growth, and reproduction, which are critical for population dynamics. In this context, experimental and modeling studies were conducted using the nematode Caenorhabditis elegans. A chronic exposure to external gamma radiation was conducted under controlled conditions. Results showed that somatic growth and reproduction were reduced with increasing dose rate. Modeling was used to investigate whether radiation effects might be assessed using a mechanistic model based upon the dynamic energy budget (DEB) theory. A DEB theory in toxicology (DEB-tox), specially adapted to the case of gamma radiation, was developed. Modelling results demonstrated the suitability of DEB-tox for the analysis of radiotoxicity and suggested that external gamma radiation predominantly induced a direct reduction in reproductive capacity in C. elegans and produced an increase in costs for growth and maturation, resulting in a delay in growth and spawning observed at the highest tested dose rate.

Sperm Affects Head Sensory Neuron in Temperature Tolerance of Caenorhabditis elegans.

Tolerance to environmental temperature change is essential for the survival and proliferation of animals. The process is controlled by various body tissues, but the orchestration of activity within the tissue network has not been elucidated in detail. Here, we show that sperm affects the activity of temperature-sensing neurons (ASJ) that control cold tolerance in Caenorhabditis elegans. Genetic impairment of sperm caused abnormal cold tolerance, which was unexpectedly restored by impairment of temperature signaling in ASJ neurons. Calcium imaging revealed that ASJ neuronal activity in response to temperature was decreased in sperm mutant gsp-4 with impaired protein phosphatase 1 and rescued by expressing gsp-4 in sperm. Genetic analysis revealed a feedback network in which ASJ neuronal activity regulates the intestine through insulin and a steroid hormone, which then affects sperm and, in turn, controls ASJ neuronal activity. Thus, we propose that feedback between sperm and a sensory neuron mediating temperature tolerance.

Impacts of Synthetic and Botanical Pesticides on Beneficial Insects

Sustainable methods to control insect pests that affect crop yield have become a great challenge to mainly smallholder farmers. Beneficial insects in agricultural fields play an important role in natural pest control and pollination. The use of synthetic and botanical pesticides has detrimental effects to both natural enemies and pollinators in agricultural fields. The pesticides affect the survival of a range of life cycle stages, reductions in reproductive capacity, changes in the suitability of hosts for parasitising or predation, reduced emergence of parasitoids from sprayed host eggs and cause direct mortality. This has caused a serious menace to biological control agents and pollinators. When natural enemies are reduced, even more serious consequences may result for pest population dynamics which include the phenomena of resurgence and eruption of secondary pests. The decrease in pollinators reduces agricultural productivity. This review aims at exploring the side effects of synthetic and botanical pesticides on beneficial insects to give the basis for research on the negative impacts of synthetic and botanical pesticides on these insects. This information will assist in optimizing the use of pesticides in integrated pest management programmes by employing more sustainable and ecosystem benign practices such as the use of right dosage and selective pesticides in agricultural fields.

Potential Toxicity of Differential Functionalized Multiwalled Carbon Nanotubes (MWCNT) in Human Cell Line (BEAS2B) and Caenorhabditis elegans

The aim of this study was to evaluate in vitro (human bronchial epithelial cells, BEAS2B cells) and in vivo (the nematode Caenorhabditis elegans, C. elegans) toxicity outcomes following exposure to pristine as well as surface-functionalized multiwalled carbon nanotubes (MWCNT) following hydroxylation-oxygenation (O+), amination (NH2), or carboxylation (COOH) of the carbon nanotubes (CNT). Cell viability and proliferation were measured by Ez-Cytox, trypan blue exclusion, and colony formation assays. The genotoxic potential of the MWCNT was determined by using the alkaline comet assay. In addition, survival and reproduction were used as endpoints for detection of toxicity of MWCNT in C. elegans. The carboxylated (COOH)-MWCNT was found most toxic as evidenced by cytotoxic and genotoxic among all tested compounds. The order of sensitivity was COOH > O+ > NH2 > pristine. There were almost no marked changes in survival following exposure of C. elegans to MWCNT. It is of interest that only pristine MWCNT exerted significant reduction in reproductive capacity of C. elegans. Surface functionalization significantly influenced the bioactivity of MWCNT, which displayed species as well as target-organ specificity. The mechanisms underlying these specific modes of nano-biological interactions need to be elucidated.

Time to pregnancy and exposure to pesticides in farmers in the West Bank, occupied Palestinian territory: a 1-year follow-up of newly married couples

Background Pesticides have been associated with a reduction in reproductive capacity. In the occupied Palestinian territory, agricultural work is a family enterprise rendering all members at risk of occupational or paraoccupational exposure. We investigated the effects of pesticide exposure on couples' fecundability (probability of conception in a menstrual cycle). Methods 331 newly married couples (women aged 16–66 years and men 15–42 years) from two Palestinian villages in the Hebron Governorate, West Bank, who were attempting to conceive for the first time during 2005–07, were identified from the Thalassaemia Centre, Hebron, where all individuals who are planning to marry are obliged to register. Couples were followed up prospectively from marriage until pregnancy or a maximum of 12 months. We assessed male exposure on the basis of current use of pesticides by creating a time-dependent exposure variable covering the month of follow-up and the 2 months before the follow-up. In women, work in farming was used as an indicator of exposure. We estimated the adjusted fecundability density ratio (aFDR) with discrete proportional hazards regression. Covariates for the multivariable model, selected on the basis of a-priori assumptions, were coital frequency reported by the women, and for men and women body-mass index, age and education, and village of residence. SPSS (version 16.0) and Stata (version 10.0) were used for statistical analyses. The study was done in accordance with the current revision of the Helsinki Declaration and was approved by Hebron University. All participants provided written informed consent and were informed that participation was voluntary and that they could withdraw from the study at any time. Findings Follow-up was completed in all but four couples. 288 (87%) of 331 couples became pregnant during follow-up with a mean fecundability of 0·20 (95% CI 0·19–0·22). Fecundability was moderately reduced in association with pesticide exposure in men (aFDR 0·72; 0·52–1·00) and farming in women (0·68; 0·42–1·09). Interpretation Exposure to pesticides was associated with reduced fecundability in couples. Furthermore, in the Palestinian population, the first menstrual cycle at risk could be defined accurately because premarital sex or having children outside of marriage are cultural and religious taboos and because all couples stated that they intended to start attempting to conceive immediately after the wedding. The main limitation was that pesticide exposure was reported as crude data, which could lead to an underestimation of the effect of pesticide exposure. Further research with improved exposure data is warranted. Funding Norwegian Programme for Development, Research and Education.

The sublethal effects of the entomopathic fungus Leptolegnia chapmanii on some biological parameters of the dengue vector Aedes aegypti.

The mosquito Aedes aegypti (L.) (Diptera: Culicidae) is the primary vector of dengue in the Americas. The use of chemical insecticides is recommended during outbreaks of dengue in order to reduce the number of adult mosquitoes; however, because Ae. aegypti is highly synanthropic, the use of insecticides in densely populated areas is a dangerous practice. Leptolegnia chapmanii Seymour (Straminipila: Peronosporomycetes) is an entomopathogenic microorganism that has demonstrated marked pathogenicity toward the larvae of a number of mosquito species, with little or no effect on non-target insects. Therefore, the purpose of this study was to determine the sublethal effects of L. chapmanii on fecundity, number of gonotrophic cycles, fertility, and relationship between wing length and fecundity in Ae. aegypti females. Ae. aegypti females that survived infection with L. chapmanii laid fewer eggs, had a smaller number of gonotrophic cycles, had shorter wings, and were less fertile than controls. This is the first study on the sublethal effects experienced by specimens of Ae. aegypti that survived infection with zoospores of L. chapmanii. Although field studies should be carried out, the results obtained in this study are encouraging because the high and rapid larval mortality caused by L. chapmanii coupled with the reduction of reproductive capacity in Ae. aegypti females seem to cause a significant reduction in the number of adults in the mid and long term, thereby reducing the health risks associated with Ae. aegypti.

Linking ascorbic acid production in Ribes nigrum with fruit development and changes in sources and sinks.

Understanding the synthesis of ascorbic acid (l-AsA) in green tissues in model species has advanced considerably; here we focus on its production and accumulation in fruit. In particular, our aim is to understand the links between organs which may be sources of l-AsA (leaves) and those which accumulate it (fruits). The work presented here tests the idea that changes in leaf and fruit number influence the accumulation of l-AsA. The aim was to understand the importance of leaf tissue in the production of l-AsA and to determine how this might provide routes for the manipulation of fruit tissue l-AsA. The experiments used Ribes nigrum (blackcurrant), predominantly in field experiments, where the source-sink relationship was manipulated to alter potential leaf l-AsA production and fruit growth and accumulation of l-AsA. These manipulations included reductions in reproductive capacity, by raceme removal, and the availability of assimilates by leaf removal and branch phloem girdling. Natural variation in fruit growth and fruit abscission is also described as this influences subsequent experimental design and the interpretation of l-AsA data. Results show that fruit l-AsA concentration is conserved but total yield of l-AsA per plant is dependent on a number of innate factors many of which relate to raceme attributes. Leaf removal and phloem girdling reduced fruit weight, and a combination of both reduced fruit yields further. It appears that around 50 % of assimilates utilized for fruit growth came from apical leaves, while between 20 and 30 % came from raceme leaves, with the remainder from 'storage'. Despite being able to manipulate leaf area and therefore assimilate availability and stored carbohydrates, along with fruit yields, rarely were effects on fruit l-AsA concentration seen, indicating fruit l-AsA production in Ribes was not directly coupled to assimilate supply. There was no supporting evidence that l-AsA production occurred predominantly in green leaf tissue followed by its transfer to developing fruits. It is concluded that l-AsA production occurs predominantly in the fruit of Ribes nigrum.

Blastocysts from patients with polycystic ovaries exhibit altered transcriptome and secretome

Polycystic ovaries (PCO) is a common phenotype of women presenting for infertility treatment. This study investigated whether blastocysts derived from women with PCO have an altered molecular signature which could be a causative factor contributing to reproductive failure. Morphologically similar blastocysts derived from women with PCO and donor oocyte cycles were analysed for transcription and protein secretion. Unsupervised hierarchical clustering demonstrated that the transcriptome profiles of blastocysts derived from PCO patients and control blastocysts were markedly different with complete branch separation. Statistical analysis revealed 829 genes with significantly different expression: 784 decreased (94.6%) and 45 increased (5.4%) in blastocysts derived from women with PCO compared with controls (P<0.05). Functional annotation of these genes revealed predominant gene ontology biological processes including protein metabolism (30%), transcription (22%), signal transduction (15%), biosynthesis (15%) and cell cycle (14%). Proteomic profiling identified 12 biomarkers that displayed significant decrease in expression in blastocysts derived from women with PCO compared with controls (P<0.05). These data indicate molecular alterations in human blastocysts derived from PCO patients, potentially demonstrating for the first time a link between patient aetiology/phenotype and subsequent embryo development, which in part may explain the observed reduction in reproductive capacity.

Longevity and lack of senescence in the red sea urchin Strongylocentrotus franciscanus

The red sea urchin Strongylocentrotus franciscanus is a long-lived species and may live in excess of 100 years based on tagging studies in the field and corroboration from radiocarbon analyses as reported in the literature. Size-specific survival estimates reported here show no change in annual survival probability across the 6 largest 0.5 cm size classes from 14.6 to 18.1 cm. In addition to no change in survival probability there is no reduction in reproductive capacity with size. Red sea urchins show no evidence of senescence and so do not fit well within the context of the disposable soma theory of the evolution of longevity.

Administration of the anabolic androgenic steroid nandrolone decanoate to female rats causes alterations in the morphology of their uterus and a reduction in reproductive capacity

Objective The aim of the present investigation was to characterize the effects of supraphysiological doses of the anabolic androgenic steroid nandrolone decanoate (ND) on the fertility of female rats, as well as on the morphology of their uterus. Study design Female Wistar rats ( n = 15) received a subcutaneous injection of ND (15 mg/kg) once daily during a 2-week period, while the control animals ( n = 10) were administered vehicle alone (arachidis oleum) in the same manner. Estrus behavior was evaluated 4 weeks after termination of this treatment and in cases where signs of receptivity were present, the female rat was given the opportunity to copulate with a male. After breeding, the female animals were sacrificed and their uteri examined histomorphologically. Results All ND-treated animals exhibited abnormal vaginal smears, whereas all of the control smears were normal. Most (73%) of the treated females demonstrated normal estrus behavior (i.e., willingness) on the day of mating, but none got pregnant; whereas all of the control rats became pregnant. The female rats receiving the ND showed an enhanced rate of weight gain and the myometrium thickness of their uteri was significantly increased, while the endometrium was significantly thinner. Furthermore, ND caused a significant proportion of the treated animals to display tortuous and irregularly branching endometrial glands, as well as a lack of the physiologically normal infiltration of eosinophilic leukocytes into the endometrium (endometrial eosinophilic homing), a finding that has not been reported previously. Conclusion The present findings indicate that high doses of ND cause morphological and physiological alterations in the uterus of female rats that are associated with a suppression of their reproductive capacity.

Effects of 4-nonylphenol on reproduction of Japanese medaka, Oryzias latipes.

We exposed mature Japanese medaka (Oryzias latipes) to 4-nonylphenol (4-NP) to elucidate its reproductive effects and estrogenic responses. For each treatment, eight breeding pairs were exposed for 3 weeks at measured 4-NP concentrations of 24.8, 50.9, 101, and 184 micrograms/L. Egg production of the pairs during the third week of exposure (15-21 d) was significantly decreased in the > or = 101-microgram/L treatment group, and fertility was significantly decreased in the 184-microgram/L group. Induction of testis-ova was observed in male fish at all 4-NP concentrations, whereas abnormality of spermatogenesis was found only in those receiving the 184-microgram/L treatment. The gonadosomatic index of the males in the 184-microgram/L group was also remarkably reduced. Hepatic vitellogenin (VTG) levels were significantly increased in both sexes receiving 4-NP treatments of > or = 50.9 micrograms/L. Overall, the lowest-observed effective concentrations (LOECs) of 4-NP for decreasing reproductive capacity (fecundity and fertility) and eliciting estrogenic responses (induction of testis-ova and VTG) were 101 and < or = 24.8 micrograms/L, respectively. The LOEC for reduced reproduction in medaka was at least four-fold greater than that required to elicit estogenic responses in male fish. Thus, we suggest that the estrogenic responses expressed in male fish are not responsible for the reduction in reproductive capacity.

Maternal undernutrition alters triiodothyronine concentrations and pituitary response to GnRH in fetal sheep.

The aims of this study were to determine which hormones may have a role in the expression of maternal undernutrition effects on reproductive function, in both the developing fetus and the adult offspring. This was undertaken by measuring the effects of long-term maternal undernutrition on metabolic hormone profiles and pituitary responses to single doses of GnRH and GH-releasing factor (GRF) in fetal sheep. From mating, groups of ewes were fed rations providing either 100% (HIGH) or 50% (LOW) of estimated metabolisable energy requirements for pregnancy throughout the experiment until slaughter at approximately 119 days of gestation. Fetal and maternal blood samples were collected from 113 until 119 days of gestation, via carotid and jugular catheters respectively, and assayed for insulin, IGF-I, GH, thyroxine and triiodothyronine (T(3)). Undernutrition had no effects on fetal weight, fetal gonad weight of either sex, fetal insulin or IGF-I concentrations. Male LOW fetuses exhibited a significantly attenuated response (P<0.05) to a bolus challenge of GnRH compared with HIGH fetuses. Basal fetal GH concentrations and the response to exogenous GRF were similar in both treatment groups, although LOW fetuses exhibited more secretory episodes (P<0.01). Mean T(3) concentrations were significantly lower in both the maternal (P<0.01) and fetal (P<0.05) plasma of LOW animals compared with HIGH animals. It is concluded that pituitary function was altered in fetal males and could influence male reproductive development. On the other hand, in female sheep, fetal gonadal abnormalities and reductions in reproductive capacity in adult life which are associated with fetal undernutrition are unlikely to be attributable to altered pituitary function. Additionally, these studies raise the possibility that thyroid hormones may have a role in the expression of maternal undernutrition effects on fetal development.

Evidence for the utility of the Bm86 antigen from Boophilus microplus in vaccination against other tick species.

The Bm86 antigen, as originally identified in Boophilus microplus, is the basis of commercial tick vaccines against this tick species. The potential for using this antigen or homologues of the antigen in vaccination against other tick species has been assessed. We have conducted vaccine trials in cattle using the B. microplus-derived recombinant Bm86 vaccine (TickGARD) using pairs of vaccinated calves and control calves. These were infested with B. microplus and Boophilus decoloratus larvae simultaneously. For both species, the numbers of engorged female adult ticks, their weight and egg-laying capacity were all reduced, leading to a reduction in reproductive capacity of 74% for B. microplus and 70% for B. decoloratus. Hyalomma anatolicum anatolicum ticks were fed both as immatures as well as adults on vaccinated calves and non-vaccinated controls. There was an overall 50% reduction in the total weight of nymphs engorging on vaccinated calves, and a suggestion of a subsequent effect on feeding adults. For Hyalomma dromedarii there was a 95% reduction in the number of nymphs engorging and a further 55% reduction in weight of those ticks surviving. Rhipicephalus appendiculatus and Amblyomma variegatum ticks were fed simultaneously both as immatures and subsequently as adults. There was no evidence for a significant vaccination effect. Finally, the amino acid sequence of a Bm86 homologue found in H. a. anatolicum unequivocally demonstrated the conservation of this molecule in this species. Our strategy for the development of multivalent anti-tick vaccines is discussed in relation to these findings.

Reproductive potential of the parasitic wasp Microplitis rufiventris Kok. reared in hosts treated with the growth regulator precocene II

Abstract: The reproductive potential of Microplitis rufiventris Kok. females resulted from Spodoptera littoralis (Boisd.) larvae topically treated by a constant dose (70 pg/5 pl) of the growth regulator precocene II at different intervals of post-parasitism was studied in the laboratory. The obtained results showed that the effects of PH vary according to the timing of treatment relative to larval development of the parasitoid. Reduction in reproductive capacity of the parasitoid occurred when PII was applied on host larvae containing young parasitoid larvae. Workers should be aware from the delayed effects of precocenes which may occur in later stages of the non-target insects.

Environmental oestrogen-mimics display liposomal membrane-antioxidant ability: importance of molecular modelling predictions

Oestrogen-like biological activity towards male fish has been demonstrated previously for degradation products of some detergents and industrial feed-stock chemicals, released into water environments. The endogenous oestrogen, 17β-oestradiol, is a particularly effective membrane-antioxidant, which may confer beneficial properties in addition to its genomic-mediated effects. Some of the most widely quoted environmental oestrogen-mimics were tested for liposomal membrane-antioxidant ability, measured as inhibition of lipid peroxidation. 4-Nonylphenol and bisphenol A (4,4-isopropylidenediphenol) were best able to mimic the antioxidant action of 17β-oestradiol by displaying effective inhibition of liposomal-membrane lipid peroxidation, whereas dibutylphthalate ester and phthalic acid diethylether (PADE) were considerably less effective antioxidants. The computer-based molecular modelling used in this study indicated a close structural similarity between these compounds and 17β-oestradiol (or the partial oestrogen/antioestrogen tamoxifen, a xenoestrogen drug used in breast cancer therapy), thus predicting their environmental action as oestrogen-mimics: genomic effects mediated by oestrogen receptor binding and non-genomic effects as membrane-antioxidants. Furthermore, 17β-oestradiol itself liberated initially into sewage-treatment lagoons from protein-bound 17β-oestradiol in human faeces, is now thought to be one of the main causes of the observed hermaphroditism of the male fish in the water-borne environment. Dietary phytoestrogens and their metabolites (also membrane-antioxidants) may have a similar activity in partial feminization, which could result from their excretion throughout the environment (aquatic and soil). Computer-assisted predictions have proved valuable in these comparative studies on these environmental xenoestrogens in the liposomal model-membrane system and could be generally utilized to monitor the likely extent of oestrogenic exposure after discharge of particular chemicals in industrial, domestic and sewage-treatment effluents. Paradoxically, a reduction in reproductive capacity in these fish may be, in part, compensated for by protection of their membranes against the oxidative stress generated by exposure to other pollutants in water environments. © 1998 Society of Chemical Industry