Endocrine-disrupting chemicals: Effects on neuroendocrine systems and the neurobiology of social behavior.

A contribution to SBN/ICN special issue. Endocrine-disrupting chemicals (EDCs) are pervasive in the environment. They are found in plastics and plasticizers (bisphenol A (BPA) and phthalates), in industrial chemicals such as polychlorinated biphenyls (PCBs), and include some pesticides and fungicides such as vinclozolin. These chemicals act on hormone receptors and their downstream signaling pathways, and can interfere with hormone synthesis, metabolism, and actions. Because the developing brain is particularly sensitive to endogenous hormones, disruptions by EDCs can change neural circuits that form during periods of brain organization. Here, we review the evidence that EDCs affect developing hypothalamic neuroendocrine systems, and change behavioral outcomes in juvenile, adolescent, and adult life in exposed individuals, and even in their descendants. Our focus is on social, communicative and sociosexual behaviors, as how an individual behaves with a same- or opposite-sex conspecific determines that individual's ability to exist in a community, be selected as a mate, and reproduce successfully.

Anxiety-like behaviors in adulthood are altered in male but not female rats exposed to low dosages of polychlorinated biphenyls in utero.

Exposure to polychlorinated biphenyls (PCBs), a class of endocrine-disrupting chemicals, can result in altered reproductive behavior in adulthood, especially when exposure occurs during critical periods of brain sexual differentiation in the fetus. Whether PCBs alter other sexually dimorphic behaviors such as those involved in anxiety is poorly understood. To address this, pregnant rat dams were injected twice, on gestational days 16 and 18, with the weakly estrogenic PCB mixture Aroclor 1221 (A1221) at one of two low dosages (0.5mg/kg or 1.0mg/kg, hereafter 1.0 and 0.5), estradiol benzoate (EB; 50µg/kg) as a positive estrogenic control, or the vehicle (3% DMSO in sesame oil). We also conducted a comprehensive assessment of developmental milestones of the F1 male and female offspring. There were no effects of treatment on sex ratio at birth and age at eye opening. Puberty, assessed by vaginal opening in females and preputial separation in males, was not affected in females but was advanced in males treated with A1221 (1.0). Males and females treated with A1221 (both dosages) were heavier in early adulthood relative to controls. The earliest manifestation of this effect developed in males prior to puberty and in females slightly later, during puberty. Anxiety-like behaviors were tested using the light:dark box and elevated plus maze tests in adulthood. In females, anxiety behaviors were unaffected by treatment. Males treated with A1221 (1.0) showed reduced indices of anxiety and increased activity in the light:dark box but not the elevated plus maze. EB failed to replicate the phenotype produced by A1221 for any of the developmental and behavioral endpoints. Collectively, these results indicate that PCBs increase body weight in both sexes, but their effects on anxiety-like behaviors are specific to males. Furthermore, differences between the results of A1221 and EB suggest that the PCBs are likely acting through mechanisms distinct from their estrogenic activity.

Age-related changes in sexual function and steroid-hormone receptors in the medial preoptic area of male rats.

Testosterone is the main circulating steroid hormone in males, and acts to facilitate sexual behavior via both reduction to dihydrotestosterone (DHT) and aromatization to estradiol. The mPOA is a key site involved in mediating actions of androgens and estrogens in the control of masculine sexual behavior, but the respective roles of these hormones is not fully understood. As males age they show impairments in sexual function, and a decreased facilitation of behavior by steroid hormones compared to younger animals. We hypothesized that an anatomical substrate for these behavioral changes is a decline in expression and/or activation of hormone receptor-sensitive cells in the mPOA. We tested this by quantifying and comparing numbers of AR- and ERα-containing cells, and Fos as a marker of activated neurons, in the mPOA of mature (4-5months) and aged (12-13months) male rats, assessed one hour after copulation to one ejaculation. Numbers of AR- and ERα cells did not change with age or after sex, but the percentage of AR- and ERα-cells that co-expressed Fos were significantly up-regulated by sex, independent of age. Age effects were found for the percentage of Fos cells that co-expressed ERα (up-regulated in the central mPOA) and the percentage of Fos cells co-expressing AR in the posterior mPOA. Interestingly, serum estradiol concentrations positively correlated with intromission latency in aged but not mature animals. These data show that the aging male brain continues to have high expression and activation of both AR and ERα in the mPOA with copulation, raising the possibility that differences in relationships between hormones, behavior, and neural activation may underlie some age-related impairments.

The effects of prenatal PCBs on adult social behavior in rats.

Endocrine disrupting chemical (EDC) exposures during critical periods of development may influence neuronal development and the manifestation of sexually dimorphic sociability and social novelty behaviors in adulthood. In this study, we assessed the effects of gestational exposure to PCBs on the social behavior of males and females later in adulthood. A weakly estrogenic PCB mixture, Aroclor 1221 (A1221, 0.5 or 1mg/kg) was administered to pregnant Sprague-Dawley rat dams. Both a positive control (estradiol benzoate; EB, 50µg/kg) and negative control (dimethylsulfoxide; DMSO in sesame oil vehicle) were similarly administered to separate sets of dams. The sexes responded differently in two tasks essential to sociality. Using a three-chamber apparatus that contained a caged, same-sex, gonadectomized stimulus animal and an empty stimulus cage, we found that both sexes showed a strong preference for affiliating with a stimulus animal (vs. an empty cage), an effect that was much more pronounced in the males. In the second task, a novel and a familiar stimulus animal were caged at opposite ends of the same apparatus. Females displayed a higher degree of novelty preference than the males. During both tests, females had significantly higher social approach behaviors while male engaged in significantly more interactive behaviors with the conspecific. Of particular interest, males born of dams that received prenatal A1221 (0.5mg/kg) exhibited an overall decrease in nose-to-nose investigations. These behavioral data suggest that the males are more sensitive to A1221 treatment than are females. In addition to behavioral analysis, serum corticosterone was measured. Females born of dams treated with A1221 (0.5mg/kg) had significantly higher concentrations of corticosterone than the DMSO female group; males were unaffected. Females also had significantly higher corticosterone concentrations than did males. Overall, our results suggest that the effects of gestational exposure to PCBs on adult social behavior are relatively limited within this particular paradigm.

Outcome of minimally invasive hip replacement in obese, overweight, and nonobese patients.

The goal of this study was to determine whether obesity affects implant positioning or early functional outcome after minimally invasive total hip replacement. The authors evaluated 119 patients who had undergone minimally invasive total hip replacement via a direct anterior approach. The patients were segregated according to World Health Organization body mass index categories: nonobese, overweight, or obese. Perioperative variables, resulting cup position, and early outcome (Harris Hip Score) were assessed. The only significant difference among the groups was mean operative time (obese > overweight > nonobese). Although the obese group's 2-year Harris Hip Score was the lowest, all patients had good to excellent results. In conclusion, minimally invasive hip replacement in obese patients provides early outcomes comparable to those in nonobese patients.

Amelioration of murine immune thrombocytopenia by CD44 antibodies: a potential therapy for ITP?

To explore the potential for monoclonal antibodies as a treatment for immune thrombocytopenia (ITP) and to further explore their mechanisms of action, we tested 8 monoclonal CD44 antibodies in murine ITP and found 4 antibodies that could successfully ameliorate ITP; 2 of these antibodies function at a full 3-log fold lower dosage compared with IVIg. Further characterization of the 2 most successful antibodies (5035-41.1D and KM114) demonstrated that, similar to IVIg: (1) the presence of the inhibitory IgG receptor FcγRIIB was required for their ameliorative function, (2) complement-deficient mice responded to anti-CD44 treatment, and (3) human transgenic FcγRIIA-expressing mice also responded to the CD44 therapeutic modality. Dissimilar to IVIg, the Fc portion of the CD44 antibody was not required. These data demonstrate that CD44 antibodies can function therapeutically in murine ITP and that they could potentially provide a very-low-dose recombinant therapy for the amelioration of human ITP.

CalDAG-GEFI deficiency protects mice in a novel model of Fcγ RIIA-mediated thrombosis and thrombocytopenia.

Platelet activation via Fcγ receptor IIA (FcγRIIA) is a critical event in immune-mediated thrombocytopenia and thrombosis syndromes (ITT). We recently identified signaling by the guanine nucleotide exchange factor CalDAG-GEFI and the adenosine diphosphate receptor P2Y12 as independent pathways leading to Rap1 small GTPase activation and platelet aggregation. Here, we evaluated the contribution of CalDAG-GEFI and P2Y12 signaling to platelet activation in ITT. Mice transgenic for the human FcγRIIA (hFcR) and deficient in CalDAG-GEFI(-/-) (hFcR/CDGI(-/-)) were generated. Compared with controls, aggregation of hFcR/CDGI(-/-) platelets or P2Y12 inhibitor-treated hFcR platelets required more than 5-fold and approximately 2-fold higher concentrations of a FcγRIIA stimulating antibody against CD9, respectively. Aggregation and Rap1 activation were abolished in P2Y12 inhibitor-treated hFcR/CDGI(-/-) platelets. For in vivo studies, a novel model for antibody-induced thrombocytopenia and thrombosis was established. FcγRIIA-dependent platelet thrombosis was induced by infusion of Alexa750-labeled antibodies to glycoprotein IX (CD42a), and pulmonary thrombi were detected by near-infrared imaging technology. Anti-GPIX antibodies dose-dependently caused thrombocytopenia and pulmonary thrombosis in hFcR-transgenic but not wild-type mice. CalDAG-GEFI-deficient but not clopidogrel-treated hFcR-transgenic mice were completely protected from ITT. In summary, we established a novel mouse model for ITT, which was used to identify CalDAG-GEFI as a potential new target in the treatment of ITT.

PRT-060318, a novel Syk inhibitor, prevents heparin-induced thrombocytopenia and thrombosis in a transgenic mouse model.

Heparin-induced thrombocytopenia (HIT) is a major cause of morbidity and mortality resulting from the associated thrombosis. Extensive studies using our transgenic mouse model of HIT have shown that antibodies reactive with heparin-platelet factor 4 complexes lead to FcγRIIA-mediated platelet activation in vitro as well as thrombocytopenia and thrombosis in vivo. We tested PRT-060318 (PRT318), a novel selective inhibitor of the tyrosine kinase Syk, as an approach to HIT treatment. PRT318 completely inhibited HIT immune complex-induced aggregation of both human and transgenic HIT mouse platelets. Transgenic HIT model mice were treated with KKO, a mouse monoclonal HIT-like antibody, and heparin. The experimental group received orally dosed PRT318, whereas the control group received vehicle. Nadir platelet counts of PRT318-treated mice were significantly higher than those of control mice. When examined with a novel thrombosis visualization technique, mice treated with PRT318 had significantly reduced thrombosis. The Syk inhibitor PRT318 thus prevented both HIT immune complex-induced thrombocytopenia and thrombosis in vivo, demonstrating its activity in HIT.

Two Hits of EDCs Three Generations Apart: Effects on Social Behaviors in Rats, and Analysis by Machine Learning.

All individuals are directly exposed to extant environmental endocrine-disrupting chemicals (EDCs), and indirectly exposed through transgenerational inheritance from our ancestors. Although direct and ancestral exposures can each lead to deficits in behaviors, their interactions are not known. Here we focused on social behaviors based on evidence of their vulnerability to direct or ancestral exposures, together with their importance in reproduction and survival of a species. Using a novel "two hits, three generations apart" experimental rat model, we investigated interactions of two classes of EDCs across six generations. PCBs (a weakly estrogenic mixture Aroclor 1221, 1 mg/kg), Vinclozolin (antiandrogenic, 1 mg/kg) or vehicle (6% DMSO in sesame oil) were administered to pregnant rat dams (F0) to directly expose the F1 generation, with subsequent breeding through paternal or maternal lines. A second EDC hit was given to F3 dams, thereby exposing the F4 generation, with breeding through the F6 generation. Approximately 1200 male and female rats from F1, F3, F4 and F6 generations were run through tests of sociability and social novelty as indices of social preference. We leveraged machine learning using DeepLabCut to analyze nuanced social behaviors such as nose touching with accuracy similar to a human scorer. Surprisingly, social behaviors were affected in ancestrally exposed but not directly exposed individuals, particularly females from a paternally exposed breeding lineage. Effects varied by EDC: Vinclozolin affected aspects of behavior in the F3 generation while PCBs affected both the F3 and F6 generations. Taken together, our data suggest that specific aspects of behavior are particularly vulnerable to heritable ancestral exposure of EDC contamination, that there are sex differences, and that lineage is a key factor in transgenerational outcomes.

Effects of endocrine-disrupting chemicals on hypothalamic oxytocin and vasopressin systems.

Exposures to endocrine disrupting chemicals (EDCs) perturb hormonal systems. EDCs are particularly problematic when exposure happens in the fetus and infant due to the high sensitivity of developing organisms to hormone actions. Previous work has shown that prenatal polychlorinated biphenyl (PCB) exposure disrupts hypothalamic development, reproductive physiology, mate preference behavior, and social behaviors in a sexually dimorphic manner. Based on evidence that EDCs perturb social behaviors in rodents, we examined effects of PCBs on the neuropeptides oxytocin (OXT) and vasopressin (AVP) that are involved in regulating these behaviors. Rats were exposed prenatally (gestational days 16 and 18) to the weakly estrogenic PCB mixture Aroclor 1221 (0.5 or 1 mg/kg), to estradiol benzoate (EB, a positive control), or to the vehicle (3% dimethyl sulfoxide). In adult (~P90) brains, we counted immunolabeled oxytocin and vasopressin cell numbers in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus. EDCs did not change absolute numbers of oxytocin or vasopressin cells in either region, although there were some modest shifts in the rostral-caudal distribution. Second, expression of genes for these nonapeptides (Oxt, Avp), their receptors (Oxtr, Avpr1a), and the estrogen receptor beta (Esr2), was determined by qPCR. In the PVN, there were dose-dependent effects of PCBs in males (Oxt, Oxtr), and effects of EB in females (Avp, Esr2). In the SON, Oxt, and Esr2 were affected by treatments in males. These changes to protein and gene expression caused by prenatal treatments suggest that transcriptional and posttranscriptional mechanisms play roles in mediating how EDCs reprogram hypothalamic development.

The clot thickens (or not).

In this issue of Blood, Gratacap and colleagues analyze the effects of the multikinase inhibitor dasatinib on platelets, helping to explain the occurrence of bleeding related to its use for CML patients resistant to or intolerant of imatinib.(1) In addition, by virtue of careful experimentation using multiple functional platelet assays, these authors are paving the way for the development of kinase inhibitors as antithrombotic agents.

Dominant expression of the inhibitory FcgammaRIIB prevents antigen presentation by murine plasmacytoid dendritic cells.

Plasmacytoid dendritic cells (pDCs) are key regulators of the innate immune response, yet their direct role as APCs in the adaptive immune response is unclear. We found that unlike conventional DCs, immune complex (IC) exposed murine pDCs neither up-regulated costimulatory molecules nor activated Ag-specific CD4(+) and CD8(+) T cells. The inability of murine pDCs to promote T cell activation was due to inefficient proteolytic processing of internalized ICs. This defect in the IC processing capacity of pDCs results from a lack of activating FcgammaR expression (FcgammaRI, III, IV) and the dominant expression of the inhibitory receptor FcgammaRIIB. Consistent with this idea, transgenic expression of the activating human FcgammaRIIA gene, not present in the mouse genome, recapitulated the human situation and rescued IC antigenic presentation capacity by murine pDCs. The selective expression of FcgammaRIIB by murine pDCs was not strain dependent and was maintained even following stimulation with TLR ligands and inflammatory cytokines. The unexpected difference between the mouse and human in the expression of activating/inhibitory FcgammaRs has implications for the role of pDCs in Ab-modulated autoimmunity and anti-viral immunity.

Knee arthrotomy repair with a continuous barbed suture: a biomechanical study.

We compared knee arthrotomy closures using interrupted biodegradable sutures and running bidirectionally barbed sutures in cadaveric specimens subjected to cyclic loading. During the initial 2000 flexion cycles, both groups maintained closure and no suture ruptured. Suture throws were then sequentially cut to weaken the repairs, and the knees were cyclically flexed after each cut. Both types of suture repairs survived the cutting of the first throw or stitch and subsequent cyclical testing. However, there was a significant difference in the repairs after multiple cuts (log-rank test, P < .003). None of the knees in the interrupted suture group survived more than 3 cuts, whereas in the barbed repair group, it took the severing of as many as 7 throws for failure to occur.

Social and neuromolecular phenotypes are programmed by prenatal exposures to endocrine-disrupting chemicals.

Exposures to endocrine-disrupting chemicals (EDCs) affect the development of hormone-sensitive neural circuits, the proper organization of which are necessary for the manifestation of appropriate adult social and sexual behaviors. We examined whether prenatal exposure to polychlorinated biphenyls (PCBs), a family of ubiquitous industrial contaminants detectable in virtually all humans and wildlife, caused changes in sexually-dimorphic social interactions and communications, and profiled the underlying neuromolecular phenotype. Rats were treated with a PCB commercial mixture, Aroclor 1221 (A1221), estradiol benzoate (EB) as a positive control for estrogenic effects of A1221, or the vehicle (4% DMSO), on embryonic day (E) 16 and 18. In adult F1 offspring, we first conducted tests of ultrasonic vocalization (USV) calls in a sociosexual context as a measure of motivated communications. Numbers of certain USV call types were significantly increased by prenatal treatment with A1221 in males, and decreased by EB in females. In a test of sociosexual preference for a hormone-vs. a non-hormone-primed opposite sex conspecific, male (but not female) nose-touching with opposite-sex rats was significantly diminished by EDCs. Gene expression profiling was conducted in two brain regions that are part of the social decision-making network in the brain: the medial preoptic nucleus (MPN) and the ventromedial nucleus (VMN). In both regions, many more genes were affected by A1221 or EB in females than males. In female MPN, A1221 changed expression of steroid hormone receptor and neuropeptide genes (e.g., Ar, Esr1, Esr2, and Kiss1). In male MPN, only Per2 was affected by A1221. The VMN had a number of genes affected by EB compared to vehicle (females: Kiss1, Kiss1r, Pgr; males: Crh) but not A1221. These differences between EB and A1221 indicate that the mechanism of action of A1221 goes beyond estrogenic pathways. These data show sex-specific effects of prenatal PCBs on adult behaviors and the neuromolecular phenotype.

Cholesterol enrichment of human monocyte/macrophages induces surface exposure of phosphatidylserine and the release of biologically-active tissue factor-positive microvesicles.

OBJECTIVE: Biologically significant amounts of two procoagulant molecules, phosphatidylserine (PS) and tissue factor (TF), are transported by monocyte/macrophage-derived microvesicles (MVs). Because cellular cholesterol accumulation is an important feature of atherosclerotic vascular disease, we now examined effects of cholesterol enrichment on MV release from human monocytes and macrophages. METHODS AND RESULTS: Cholesterol enrichment of human THP-1 monocytes, alone or in combination with lipopolysaccharide (LPS), tripled their total MV generation, as quantified by flow cytometry based on particle size and PS exposure. The subset of these MVs that were also TF-positive was likewise increased by cellular cholesterol enrichment, and these TF-positive MVs exhibited a striking 10-fold increase in procoagulant activity. Moreover, cholesterol enrichment of primary human monocyte-derived macrophages also increased their total as well as TF-positive MV release, and these TF-positive MVs exhibited a similar 10-fold increase in procoagulant activity. To explore the mechanisms of enhanced MV release, we found that cholesterol enrichment of monocytes caused PS exposure on the cell surface by as early as 2 hours and genomic DNA fragmentation in a minority of cells by 20 hours. Addition of a caspase inhibitor at the beginning of these incubations blunted both cholesterol-induced apoptosis and MV release. CONCLUSIONS: Cholesterol enrichment of human monocyte/macrophages induces the generation of highly biologically active, PS-positive MVs, at least in part through induction of apoptosis. Cholesterol-induced monocyte/macrophage MVs, both TF-positive and TF-negative, may be novel contributors to atherothrombosis.

Application of a novel social choice paradigm to assess effects of prenatal endocrine-disrupting chemical exposure in rats (Rattus norvegicus).

Endocrine-disrupting chemical (EDC) exposures during critical periods of gestation cause long-lasting behavioral effects, presumably by disturbing hormonal organization of the brain. Among such EDCs are polychlorinated biphenyls (PCBs), a class of industrial chemicals. PCB exposure in utero leads to alterations in mating behaviors and other sexually dimorphic social interactions in rats. Many of the previous studies on social behavior gave the experimental animal a single or binary choice. This study applied a more complex behavioral apparatus, an X-shaped Plexiglas apparatus (FourPlex), that enabled an experimental animal exposed to PCBs or a vehicle to distinguish and choose among 4 stimulus animals of the same or opposite sex, and of different hormonal status. We found that rats were able to differentiate among the stimuli in the FourPlex and showed the expected preference for an opposite sex, hormone-treated rat, particularly for behaviors conducted in proximity. Prenatal treatment caused subtle shifts in behavior toward stimulus rats in the FourPlex; more robust effects were seen for the sexual dimorphisms in behavior. Importantly, the results differ from our previous results of a simple binary choice model, showing that how an animal behaves in a more complex social paradigm does not predict the outcome in a simple choice model, and vice versa. (PsycINFO Database Record

Platelet FcgammaRIIA binds and internalizes IgG-containing complexes.

OBJECTIVE: The physiologic role of platelet FcgammaRIIA, the only Fc receptor for IgG on human platelets, is largely unknown. FcgammaRIIA is also expressed on phagocytes such as monocytes and neutrophils, where it mediates the binding and internalization of both soluble IgG-containing complexes and IgG-coated cells. We previously reported the creation and characterization of a transgenic mouse that expresses human FcgammaRIIA on platelets and macrophages at levels comparable to that seen in humans. Using the transgenic mouse model, we observed that FcgammaRIIA mediates the clearance of IgG-coated cells. With the hypothesis that FcgammaRIIA on platelets may serve to remove IgG complexes from the circulation, we studied the capacity of human platelet FcgammaRIIA to bind and internalize such complexes. METHODS: We demonstrated by flow cytometry and electron microscopy that human platelets at 37 degrees C can bind and endocytose IgG complexes. We also utilized platelets from FcgammaRIIA transgenic mice to study endocytosis of IgG complexes by platelet FcgammaRIIA. RESULTS: Wild-type mouse platelets do not express Fcgamma receptors. While platelets from wild-type mice did not bind or endocytose IgG complexes, the presence of transgenic FcgammaRIIA on mouse platelets allowed the platelets to bind and endocytose IgG complexes. CONCLUSION: Our data indicate that platelet FcgammaRIIA binds and internalizes IgG complexes and suggest that human platelets may function to clear soluble IgG complexes from the circulation.

Measured Neutron Spectra and Dose Equivalents From a Mevion Single-Room, Passively Scattered Proton System Used for Craniospinal Irradiation.

PURPOSE: To measure, in the setting of typical passively scattered proton craniospinal irradiation (CSI) treatment, the secondary neutron spectra, and use these spectra to calculate dose equivalents for both internal and external neutrons delivered via a Mevion single-room compact proton system. METHODS AND MATERIALS: Secondary neutron spectra were measured using extended-range Bonner spheres for whole brain, upper spine, and lower spine proton fields. The detector used can discriminate neutrons over the entire range of the energy spectrum encountered in proton therapy. To separately assess internally and externally generated neutrons, each of the fields was delivered with and without a phantom. Average neutron energy, total neutron fluence, and ambient dose equivalent [H* (10)] were calculated for each spectrum. Neutron dose equivalents as a function of depth were estimated by applying published neutron depth-dose data to in-air H* (10) values. RESULTS: For CSI fields, neutron spectra were similar, with a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate continuum between the evaporation and thermal peaks. Neutrons in the evaporation peak made the largest contribution to dose equivalent. Internal neutrons had a very low to negligible contribution to dose equivalent compared with external neutrons, largely attributed to the measurement location being far outside the primary proton beam. Average energies ranged from 8.6 to 14.5 MeV, whereas fluences ranged from 6.91 × 10(6) to 1.04 × 10(7) n/cm(2)/Gy, and H* (10) ranged from 2.27 to 3.92 mSv/Gy. CONCLUSIONS: For CSI treatments delivered with a Mevion single-gantry proton therapy system, we found measured neutron dose was consistent with dose equivalents reported for CSI with other proton beamlines.

Prepubertal exposure to arsenic(III) suppresses circulating insulin-like growth factor-1 (IGF-1) delaying sexual maturation in female rats.

Arsenic (As) is a prevalent environmental toxin readily accessible for human consumption and has been identified as an endocrine disruptor. However, it is not known what impact As has on female sexual maturation. Therefore, in the present study, we investigated the effects of prepubertal exposure on mammary gland development and pubertal onset in female rats. Results showed that prepubertal exposure to 10 mg/kg of arsenite (As(III)) delayed vaginal opening (VO) and prepubertal mammary gland maturation. We determined that As accumulates in the liver, disrupts hepatocyte function and suppresses serum levels of the puberty related hormone insulin-like growth factor 1 (IGF-1) in prepubertal animals. Overall, this is the first study to show that prepubertal exposure to As(III) acts peripherally to suppress circulating levels of IGF-1 resulting in delayed sexual maturation. Furthermore, this study identifies a critical window of increased susceptibility to As(III) that may have a lasting impact on female reproductive function.

Tuakana-Teina relationship and leadership in ancient Mangaia and Aotearoa.

The relationship between tuakana and teina (the older and younger sibling or cousin of same sex) is the tumu (foundation, origin, cause) of rank in eastern Polynesia. By examining historical documents from selected island societies, namely, Mangaia and Aotearoa, we can understand the dynamics of this relationship as part of their world-view. Normally tuakana and teina had close, cooperative, mutually respectful and loyal relationships; the teina supporting their elder. Sometimes, however, the moral balance between them was affected either by one of them acting inappropriately towards the other, or by hostile acts from others. To remedy these threats to social cohesion, various strategies were adopted, including peace-making, flight or spatial separation, or fighting. Stories about this relationship continue to serve as the tumu for today's younger generations.