The Defecation Index as a Measure of Emotionality: Questions Raised by HPA Axis and Prolactin Response to Stress in the Maudsley Model.

The Maudsley Reactive and Maudsley Non-Reactive strains have been selectively bred for differences in open-field defecation (OFD), a putative index of stress. We investigated whether variations in the hypothalamic-pituitary-adrenal (HPA) axis are correlated with strain differences in OFD in the Maudsley model. Exposure to the open-field test did not result in increases in ACTH in male rats of either strain and there were no strain differences in the large increases in ACTH and corticosteroid that occurred in response to intermittent footshock. Parallel studies of prolactin showed that Maudsley Reactive rats had greater response to the open-field and to footshock than Maudsley Non-Reactive rats. The lack of correlation between strain differences in OFD and reactivity of the HPA axis is consistent with the idea that HPA response to stress and OFD reflect the output of different neural systems and that individual differences in emotionality, as indexed by OFD do not influence other measures of stress-reactivity in a simple manner, if at all. The reactivity of the prolactin system to the open-field test and lack of response of ACTH to the same situation is consistent with the idea that the prolactin system is sensitive to lower levels of stress than the HPA axis, a finding at variance with the presumed extreme sensitivity of the latter system. Earlier comparisons of the HPA axis in these strains implicate local factors such as neuropeptide-Y peptide in the adrenal in attenuating the response of the adrenal cortex to ACTH and hints at the complexity of regulation of the HPA axis.

Atrazine and breast cancer: a framework assessment of the toxicological and epidemiological evidence.

The causal relationship between atrazine exposure and the occurrence of breast cancer in women was evaluated using the framework developed by Adami et al. (2011) wherein biological plausibility and epidemiological evidence were combined to conclude that a causal relationship between atrazine exposure and breast cancer is "unlikely". Carcinogenicity studies in female Sprague-Dawley (SD) but not Fischer-344 rats indicate that high doses of atrazine caused a decreased latency and an increased incidence of combined adenocarcinoma and fibroadenoma mammary tumors. There were no effects of atrazine on any other tumor type in male or female SD or Fischer-344 rats or in three strains of mice. Seven key events that precede tumor expression in female SD rats were identified. Atrazine induces mammary tumors in aging female SD rats by suppressing the luteinizing hormone surge, thereby supporting a state of persistent estrus and prolonged exposure to endogenous estrogen and prolactin. This endocrine mode of action has low biological plausibility for women because women who undergo reproductive senescence have low rather than elevated levels of estrogen and prolactin. Four alternative modes of action (genotoxicity, estrogenicity, upregulation of aromatase gene expression or delayed mammary gland development) were considered and none could account for the tumor response in SD rats. Epidemiological studies provide no support for a causal relationship between atrazine exposure and breast cancer. This conclusion is consistent with International Agency for Research on Cancer's classification of atrazine as "unclassifiable as to carcinogenicity" and the United States Environmental Protection Agency's classification of atrazine as "not likely to be carcinogenic."

Developing a problem-based learning (PBL) curriculum for professionalism and scientific integrity training for biomedical graduate students.

A multidisciplinary faculty committee designed a curriculum to shape biomedical graduate students into researchers with a high commitment to professionalism and social responsibility and to provide students with tools to navigate complex, rapidly evolving academic and societal environments with a strong ethical commitment. The curriculum used problem-based learning (PBL), because it is active and learner-centred and focuses on skill and process development. Two courses were developed: Scientific Professionalism: Scientific Integrity addressed discipline-specific and broad professional norms and obligations for the ethical practice of science and responsible conduct of research (RCR). Scientific Professionalism: Bioethics and Social Responsibility focused on current ethical and bioethical issues within the scientific profession, and implications of research for society. Each small-group session examined case scenarios that included: (1) learning objectives for professional norms and obligations; (2) key ethical issues and philosophies within each topic area; (3) one or more of the RCR instructional areas; and (4) at least one type of moral reflection. Cases emphasised professional standards, obligations and underlying philosophies for the ethical practice of science, competing interests of stakeholders and oversight of science (internal and external). To our knowledge, this is the first use of a longitudinal, multi-semester PBL course to teach scientific integrity and professionalism. Both faculty and students endorsed the active learning approach for these topics, in contrast to a compliance-based approach that emphasises learning rules and regulations.

Problem-based learning for professionalism and scientific integrity training of biomedical graduate students: process evaluation.

OBJECTIVE: We conducted a process evaluation to (a) assess the effectiveness of a new problem-based learning curriculum designed to teach professionalism and scientific integrity to biomedical graduate students and (b) modify the course to enhance its relevance and effectiveness. The content presented realistic cases and issues in the practice of science, to promote skill development and to acculturate students to professional norms of science. METHOD: We used 5-step Likert-scaled questions, open-ended questions, and interviews of students and facilitators to assess curricular effectiveness. RESULTS: Both facilitators and students perceived course objectives were achieved. For example, respondents preferred active learning over lectures; both faculty and students perceived that the curriculum increased their understanding of norms, role obligations and responsibilities of professional scientists. They also reported an increased ability to identify ethical situations and felt that they had developed skills in moral reasoning and effective group work. CONCLUSIONS: These data helped to improve course implementation and instructional material. For example, to correct a negative perception that this was an 'ethics' course, we redesigned case debriefing activities to reinforce learning objectives and important skills. We refined cases to be more engaging and relevant for students, and gave facilitators more specific training and resources for each case. The problem-based learning small group strategy can stimulate an environment whereby participants are more aware of ethical implications of science, and increase their socialisation and open communication about professional behaviour.

Atrazine interaction with estrogen expression systems.

More than 40 publications have described results of atrazine responses in 17 estrogen-dependent systems and in more than a dozen different reporter and estrogen receptor-binding studies in vitro. Results from these studies have consistently failed to demonstrate that atrazine acts as an estrogen agonist. Moreover, a variety of indices of estrogen-dependent activity, in models that encompass cell incubations to whole animals, have failed to respond to atrazine. Researchers in more than a dozen laboratories have examined rats, rat tissues, human and prokaryotic cells, in addition to tissues from reptile, fish, amphibian, avian, molluscan, and insect sources, without eliciting estrogenic-like responses from atrazine. In contrast, studies of atrazine ability to antagonize estrogen-mediated responses have yielded equivocal results. Results of several studies show inhibition of estrogen-like activities by atrazine, yet many other tests have yielded negative results. Generally, in vivo models have more consistently shown that atrazine inhibits estrogen-mediated responses, whereas in more specific in vitro systems, inhibition is seldom observed. The implication is that in vivo effects of atrazine may result from inhibition of factors that are indirectly connected to the genomic interaction of estrogen (e.g., at the receptor). Potential targets of atrazine may be downstream of the ligand-receptor binding event. Atrazine may also interact with other, less specific, factors that are necessary for the completion of the estrogen-mediated response. Moreover, the apparent inhibition of cytosolic-ER binding by atrazine may, similarly, be relatively nonspecific. Observed inhibitory responses occur only at extreme doses or concentrations, i.e., several orders of magnitude greater than the level of estradiol presence in each test system. It is probable that the inhibitory effects result from very low affinity and/or low specificity interactions, which are unlikely to occur in nature. We conclude that atrazine is not an estrogen receptor agonist, but it may be a weak antagonist, when present at a high concentration under conditions of disequilibrium with estrogen. These conditions are not expected to occur as a result of normal environmental exposure.

Nature of the binding interaction for 50 structurally diverse chemicals with rat estrogen receptors.

This study was conducted to characterize the estrogen receptor (ER)-binding affinities of 50 chemicals selected from among the high production volume chemicals under the U.S. EPA's (U.S. Environmental Protection Agency's) Toxic Substances Control Act inventory. The chemicals were evaluated using the rat uterine cytosolic (RUC) ER-competitive binding assay, with secondary analysis using Lineweaver-Burk plots and slope replots to confirm true competitive inhibition and to determine an experimental K(i). Data from these ER-competitive binding assays represent the types of competitive binding curves that can be obtained when screening chemicals with broad structural diversity. True competitive inhibition was observed in 17 of 50 chemicals. Binding affinities were much lower than that of estradiol (E(2)) with K(i) concentrations ranging from 0.6 to 373 microM as compared with that of E(2) (0.77 nM). Other chemicals that appeared to displace radiolabeled E(2) binding to ER were, in fact, found not to be competitive inhibitors in the secondary K(i) experiments. These seven chemicals likely altered the stability of the assay by changing the buffer pH, denaturing ER, or disrupting the ER-binding kinetics. Thus, several conditions that may confound interpretation of RUC ER-binding assay data are illustrated. For another group of eight chemicals, neither an IC(50) nor K(i) could be determined due to solubility constraints. These chemicals exhibited slight (20-40%) inhibition at concentrations of 10-100 microM, suggesting that they could be competitors at very high concentrations, yet K(i) experiments were not possible as the limit of chemical solubility in the aqueous assay buffer was well above the IC(50). An additional 18 of the 50 chemicals were classified as nonbinders because in concentrations up to 100 microM they produced essentially no displacement of radiolabeled E(2). These results show that although the ER-competitive binding assay is a valuable tool for screening chemicals, secondary tests such as a double reciprocal Lineweaver-Burk experiment with slope replot should be used to confirm true competitive inhibition. This information will be useful for the ongoing validation of the RUC ER-competitive binding assay under the U.S. EPA's Endocrine Disruptor Screening Program, as well as to support research efforts to develop computational models designed to identify chemicals with the ability to bind to ER.

Ethanol consumption in the female Long-Evans rat: a modulatory role of estradiol.

The examination of various gonadal hormone manipulations on ethanol intake in human subjects and in rodent models has resulted in disparate findings. In the present study, we examined the effects of ovariectomy and subsequent estradiol (E(2)) replacement on ethanol intake in a within-subject design, as well as assessed the relevance of reproductive status on the efficacy of an E(2) stimulus in eliciting consumption. Female Long-Evans rats (n = 24) were given access to 10% ethanol and water in a continuous-access paradigm. After establishment of baseline intake values, rats were divided into four groups: sham/placebo (Shm+P), sham/estradiol (Shm+E(2)), ovariectomized/placebo (Ovx+P), and ovariectomized/estradiol (Ovx+E(2)). Rats in the Ovx+P group were found to have a large and permanent decline in ethanol intake that persisted more than 3 months postsurgery. Administration of E(2) to Ovx+E(2) rats was associated with restoration of ethanol consumption to baseline levels. When Shm+E(2) and Ovx+E(2) groups were compared, reproductive status was found to be a determining factor in the efficacy of E(2) to elicit ethanol intake. Together, these findings provide evidence that ovarian hormones, particularly estradiol, exert activational effects on estrogen-responsive substrates to modulate ethanol consumption in the adult female rat.