21 research outputs found
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Courtship-induced changes in female sexual receptivity : a neuroendocrine study in an amphibian
This thesis describes studies that investigated 1)
the effects of courtship on the neuroendocrine system of
female rough-skinned newts, Taricha granulosa, and 2)
whether the observed courtship-induced neuroendocrine
changes affected female sexual receptivity.
Sexual behaviors of female T. granulosa changed
dramatically during courtship. Initially, females
exhibited unreceptive behaviors to a courting male. After
several hours of courtship, females displayed receptive
behaviors, and males responded by attempting to transfer a
sperm cap. Once courtship, insemination and post-insemination
behaviors were complete, the female no longer
became receptive to future courtship.
Both telencephalic irLHRH and plasma estradiol
concentrations changed as females became receptive. Early
in courtship, when females were unreceptive, irLHRH
concentrations in the telencephalon were elevated, but by
the time females became receptive irLHRH concentrations
were low. The change in telencephalic irLHRH
concentration occurred in the nervus terminalis, a little
understood cranial nerve that may influence reproduction.
Plasma estradiol levels were low at courtship initiation,
but were elevated by the time females became receptive.
The observations, that irLHRH and estradiol concentrations
were associated with changes in female sexual behaviors
and that these hormones influence female sexual
receptivity in other vertebrates, suggested that courtship
by a male activates female sexual behavior by stimulating
endogenous changes in LHRH and estradiol.
Increasing or decreasing plasma estradiol
concentrations or blocking the action of this steroid in
the brain were found to have no effect on female
receptivity. Also, injecting LHRH or LHRH analogs into
brain was found to have no effect on female receptivity.
Progesterone implantation inhibited receptivity suggesting
that this steroid may be responsible for the post-insemination
decrease in female sexual behavior. These
results suggest that although courtship induces
physiological changes in female T. granulosa, the changes
in LHRH and estradiol may not be influencing receptivity
Role of Farmer Knowledge in Agroecosystem Science: Rice Farming and Amphibians in the Philippines
Rice (Oryza sativa) agriculture provides food and economic security for nearly half of the world’s population. Rice agriculture is intensive in both land and agrochemical use. However, rice fields also provide aquatic resources for wildlife, including amphibians. In turn, some species may provide ecosystem services back to the farmers working in the rice agroecosystem. The foundation for understanding the complexity of agroecosystem–human relationships requires garnering information regarding human perceptions and knowledge of the role of biodiversity in these rice agroecosystems. Understanding farmer knowledge and perceptions of the ecosystem services provided by wildlife in their fields, along with their understanding of the risks to wildlife associated with agrochemical exposure, can inform biodiversity preservation efforts. In June and July 2014, we used focus groups and structured and semi-structured interviews that engaged 22 individuals involved in rice agriculture operations in Laguna, Philippines, a village close to the International Rice Research Institute in Los Baños, Philippines, to learn more about farmer perceptions and knowledge of amphibians in their rice fields. We found that many, though not all farm workers (managers, tenants, and laborers) noted declines in amphibian populations over time, expressed how they incorporated frogs and toads (Anura) into their daily lives, and recognized the value of amphibians as ecosystem service providers. Specifically, farmers noted that amphibians provide pest-management through consumption of rice pests, act as biomonitors for pesticide-related health outcomes, and provide a local food and economic resource. Some farmers and farm workers noted the general cultural value of listening to the “frogs sing when it rains.” Overall, our findings demonstrate that farmers have an understanding of the value of amphibians in their fields. Future efforts can support how engagement with farmers and farm workers to evaluate the value of wildlife in their fields can lead to directed education efforts to support biodiversity conservation in agroecosystems
Chemical Toxicants in Water: A \u3ci\u3eGeoHealth\u3c/i\u3e Perspective in the Context of Climate Change
The editorial focuses on four major themes contextualized in a virtual GeoHealth workshop that occurred from June 14 to 16, 2021. Topics in that workshop included drinking water and chronic chemical exposure, environmental injustice, public health and drinking water policy, and the fate, transport, and human impact of aqueous contaminants in the context of climate change. The intent of the workshop was to further define the field of GeoHealth. This workshop emphasized on chemical toxicants that drive human health. The major calls for action emerged from the workshop include enhancing community engagement, advocating for equity and justice, and training the next generation
Exposure to 4-tert-octylphenol accelerates sexual differentiation and disrupts expression of steroidogenic factor 1 in developing bullfrogs.
Sex-specific gonadal steroidogenesis during development is critical to differentiation of the sexually dimorphic phenotype and reproductive function of adult organisms. Environmental contaminants may affect the process of sexual differentiation through disruption of steroid production and/or action. Control of the steroidogenic metabolic pathway is regulated partly by P450 cytochrome hydroxylases, and the expression of many of these enzymes is controlled by the orphan nuclear receptor, steroidogenic factor-1 (SF-1). In mammals, SF-1 expression is critical for development of the reproductive axis and adult reproductive function. In the bullfrog Rana catesbeiana, during sequential stages of development encompassing sexual differentiation, SF-1 protein expression becomes elevated in ovaries of sexually differentiating females, whereas expression in testes decreases. We exposed tadpoles to the industrial pollutant octylphenol (OP) for 24 hr before and during the critical stages of sexual differentiation to determine whether this known endocrine disruptor affects sex differentiation and SF-1 expression. We found that both females and males treated with an environmentally relevant low dose (10(-9)M) of OP underwent early gonadal differentiation. Furthermore, OP exposure disrupted the sexually dimorphic expression of SF-1 that occurs during sexual differentiation. Our results suggest that OP exposure may affect developmental processes that could ultimately influence adult reproductive function and that these disruptive effects may be mediated in partly through disturbances in gene regulation by SF-1
Drinking Water with Uranium below the U.S. EPA Water Standard Causes Estrogen Receptor–Dependent Responses in Female Mice
Background: The deleterious impact of uranium on human health has been linked to its radioactive and heavy metal-chemical properties. Decades of research has defined the causal relationship between uranium mining/milling and onset of kidney and respiratory diseases 25 years later. Objective: We investigated the hypothesis that uranium, similar to other heavy metals such as cadmium, acts like estrogen. Methods: In several experiments, we exposed intact, ovariectomized, or pregnant mice to depleted uranium in drinking water [ranging from 0.5 μg/L (0.001 μM) to 28 mg/L (120 μM). Results: Mice that drank uranium-containing water exhibited estrogenic responses including selective reduction of primary follicles, increased uterine weight, greater uterine luminal epithelial cell height, accelerated vaginal opening, and persistent presence of cornified vaginal cells. Coincident treatment with the antiestrogen ICI 182,780 blocked these responses to uranium or the synthetic estrogen diethylstilbestrol. In addition, mouse dams that drank uranium-containing water delivered grossly normal pups, but they had significantly fewer primordial follicles than pups whose dams drank control tap water. Conclusions: Because of the decades of uranium mining/milling in the Colorado plateau in the Four Corners region of the American Southwest, the uranium concentration and the route of exposure used in these studies are environmentally relevant. Our data support the conclusion that uranium is an endocrine-disrupting chemical and populations exposed to environmental uranium should be followed for increased risk of fertility problems and reproductive cancers
Non-Antioxidant Properties of α-Tocopherol Reduce the Anticancer Activity of Several Protein Kinase Inhibitors In Vitro
The antioxidant properties of α-tocopherol have been proposed to play a beneficial chemopreventive role against cancer. However, emerging data also indicate that it may exert contrasting effects on the efficacy of chemotherapeutic treatments when given as dietary supplement, being in that case harmful for patients. This dual role of α-tocopherol and, in particular, its effects on the efficacy of anticancer drugs remains poorly documented. For this purpose, we studied here, using high throughput flow cytometry, the direct impact of α-tocopherol on apoptosis and cell cycle arrest induced by different cytotoxic agents on various models of cancer cell lines in vitro. Our results indicate that physiologically relevant concentrations of α-tocopherol strongly compromise the cytotoxic and cytostatic action of various protein kinase inhibitors (KI), while other classes of chemotherapeutic agents or apoptosis inducers are unaffected by this vitamin. Interestingly, these anti-chemotherapeutic effects of α-tocopherol appear to be unrelated to its antioxidant properties since a variety of other antioxidants were completely neutral toward KI-induced cell cycle arrest and cell death. In conclusion, our data suggest that dietary α-tocopherol could limit KI effects on tumour cells, and, by extent, that this could result in a reduction of the clinical efficacy of anti-cancer treatments based on KI molecules
Volunteer Bias in Recruitment, Retention, and Blood Sample Donation in a Randomised Controlled Trial Involving Mothers and Their Children at Six Months and Two Years: A Longitudinal Analysis
BACKGROUND: The vulnerability of clinical trials to volunteer bias is under-reported. Volunteer bias is systematic error due to differences between those who choose to participate in studies and those who do not. METHODS AND RESULTS: This paper extends the applications of the concept of volunteer bias by using data from a trial of probiotic supplementation for childhood atopy in healthy dyads to explore 1) differences between a) trial participants and aggregated data from publicly available databases b) participants and non-participants as the trial progressed 2) impact on trial findings of weighting data according to deprivation (Townsend) fifths in the sample and target populations. 1) a) Recruits (n = 454) were less deprived than the target population, matched for area of residence and delivery dates (n = 6,893) (mean [SD] deprivation scores 0.09[4.21] and 0.79[4.08], t = 3.44, df = 511, p<0.001). b) i) As the trial progressed, representation of the most deprived decreased. These participants and smokers were less likely to be retained at 6 months (n = 430[95%]) (OR 0.29,0.13-0.67 and 0.20,0.09-0.46), and 2 years (n = 380[84%]) (aOR 0.68,0.50-0.93 and 0.55,0.28-1.09), and consent to infant blood sample donation (n = 220[48%]) (aOR 0.72,0.57-0.92 and 0.43,0.22-0.83). ii) Mothers interested in probiotics or research or reporting infants' adverse events or rashes were more likely to attend research clinics and consent to skin-prick testing. Mothers participating to help children were more likely to consent to infant blood sample donation. 2) In one trial outcome, atopic eczema, the intervention had a positive effect only in the over-represented, least deprived group. Here, data weighting attenuated risk reduction from 6.9%(0.9-13.1%) to 4.6%(-1.4-+10.5%), and OR from 0.40(0.18-0.91) to 0.56(0.26-1.21). Other findings were unchanged. CONCLUSIONS: Potential for volunteer bias intensified during the trial, due to non-participation of the most deprived and smokers. However, these were not the only predictors of non-participation. Data weighting quantified volunteer bias and modified one important trial outcome. TRIAL REGISTRATION: This randomised, double blind, parallel group, placebo controlled trial is registered with the International Standard Randomised Controlled Trials Register, Number (ISRCTN) 26287422. Registered title: Probiotics in the prevention of atopy in infants and children
Endosulfan Exposure Disrupts Pheromonal Systems in the Red-Spotted Newt: A Mechanism for Subtle Effects of Environmental Chemicals
Plasma and Brain Angiotensin Concentrations Associated with Water Response Behavior in the Desert Anuran, Scaphiopus Couchii under Natural Conditions in the Field
Terrestrial amphibians obtain water by absorption across a specialized region of the ventral skin and exhibit a behavior, the water absorption response (WR) to place that region in contact with moist surfaces. Spadefoot toads (Scaphiopus couchii) spend dry months of the year in burrows, then emerge during brief periods of summer rainfall and seek water sources for rehydration and reproduction. We tested the hypothesis that these toads have changes in plasma and/or central angiotensin concentrations that are associated with seasonal emergence and WR behavior. Immunoreactive concentrations of combined angiotensin II and III (ir-ANG) were measured in plasma samples and microdissected regions of brain tissue taken from toads moving across the road or toads showing WR behavior in shallow puddles on the road. Plasma ir-ANG concentrations were not significantly different between these groups, but were significantly higher in the periventricular region of the hypothalamus in toads showing WR behavior. Concentrations in other brain regions, while highly variable among individuals, were not different between groups. Within the context of the natural history of a specialized desert toad, these results support the hypothesis that ir-ANG is associated with WR behavior in spadefoot toads in a manner analogous to oral drinking exhibited by other vertebrate clades. (C) 2010 Elsevier Inc. All rights reserve