Thyroglobulin type-1 domain protease inhibitors exhibit specific expression in the cortical ooplasm of vitellogenic rainbow trout oocytes

The synthesis, uptake, and processing of yolk proteins remain poorly described aspects of oviparous reproductive development. In this study, we report the identification and characterization of two protease inhibitors in rainbow trout ovary whose expression and distribution are directly associated with yolk protein uptake in vitellogenic oocytes. The first transcript, termed “oocyte protease inhibitor-1” (OPI-1), is predicted to encode a 9.1 kDa, 87 amino acid protein containing a single thyroglobulin type-1 (TY) domain, identifying it as a putative TY domain inhibitor. The second transcript, termed OPI-2, is predicted to encode an 18.3 kDa, 173 amino acid protein with two similar, but not identical, TY domains. Messenger RNA expression of both genes was first detected in ovarian tissues at the onset of vitellogenesis, and persisted throughout the vitellogenic growth phase. We did not detect expression of either gene in previtellogenic ovaries, nor in any somatic tissues examined. Expression of OPI-1 mRNA was significantly reduced in atretic follicles as compared to healthy vitellogenic follicles, suggesting a downregulation of inhibitor expression during oocyte atresia. Western immunoblot analyses of whole yolk from vitellogenic oocytes revealed the presence of two immunoreactive proteins that corresponded to the predicted sizes of OPI-1 and OPI-2. We detected strong crossreactivity of this antiserum with specific vesicles in the cortical ooplasm of vitellogenic oocytes, in regions directly associated with vitellogenin processing. The identification of OPI-1 and OPI-2 provides new evidence for the expression of multiple TY domain protease inhibitors likely involved in the regulation of yolk processing during oocyte growth in salmonids. Mol. Reprod. Dev. 69: 205–214, 2004. © 2004 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/35088/1/20118_ftp.pd

The Reproductive Effects of Municipal Wastewater Effluents

There is a growing concern that pharmaceuticals and other chemicals present in the effluents (sewage discharged into a river) from municipal wastewater treatment plants enter the aquatic environment, where they may affect the fitness of fish. We conducted lab based experiments to determine the potential of effluents from different municipal wastewater plants in the Grand River Watershed to affect the reproduction of adult zebrafish.Southern Ontario Water Consortiu

Critical comments on the WHO-UNEP State of the Science of Endocrine Disrupting Chemicals – 2012

AbstractEarly in 2013, the World Health Organization (WHO) released a 2012 update to the 2002 State of the Science of Endocrine Disrupting Chemicals. Several significant concerns have been identified that raise questions about conclusions reached in this report regarding endocrine disruption. First, the report is not a state-of-the-science review and does not follow the 2002 WHO recommended weight-of-evidence approach. Second, endocrine disruption is often presumed to occur based on exposure or a potential mechanism despite a lack of evidence to show that chemicals are causally established as endocrine disruptors. Additionally, causation is often inferred by the presentation of a series of unrelated facts, which collectively do not demonstrate causation. Third, trends in disease incidence or prevalence are discussed without regard to known causes or risk factors; endocrine disruption is implicated as the reason for such trends in the absence of evidence. Fourth, dose and potency are ignored for most chemicals discussed. Finally, controversial topics (i.e., low dose effects, non-monotonic dose response) are presented in a one-sided manner and these topics are important to understanding endocrine disruption. Overall, the 2012 report does not provide a balanced perspective, nor does it accurately reflect the state of the science on endocrine disruption

Pharmaceuticals and personal care products in the environment: What are the big questions?

Background: Over the past 10-15 years, a substantial amount of work has been done by the scientific, regulatory, and business communities to elucidate the effects and risks of pharmaceuticals and personal care products (PPCPs) in the environment. Objective: This review was undertaken to identify key outstanding issues regarding the effects of PPCPs on human and ecological health in order to ensure that future resources will be focused on the most important areas. Data sources: To better understand and manage the risks of PPCPs in the environment, we used the "key question" approach to identify the principle issues that need to be addressed. Initially, questions were solicited from academic, government, and business communities around the world. A list of 101 questions was then discussed at an international expert workshop, and a top-20 list was developed. Following the workshop, workshop attendees ranked the 20 questions by importance. Data synthesis: The top 20 priority questions fell into seven categories: a) prioritization of substances for assessment, b) pathways of exposure, c) bioavailability and uptake, d) effects characterization, e) risk and relative risk, f) antibiotic resistance, and g) risk management. Conclusions: A large body of information is now available on PPCPs in the environment. This exercise prioritized the most critical questions to aid in development of future research programs on the topic.Centro de Investigaciones del Medioambient

Gonadotropin involvement in the control of oocyte maturation and ovulation in coho salmon (Oncorynchus kisutch) : neuroendocrine control of gonadotropin secretion, effects on steroid production and properties of ovarian gonadotropin binding sites

The involvement of gonadotropin in the regulation of reproductive development in coho salmon (Oncorhynchus kisutch) was studied by monitoring changes in plasma gonadotropin and steroid hormone levels and the induction of oocyte maturation and ovulation following the administration of gonadotropin releasing-hormones (Gn-RH). Further studies examined the properties of gonadotropin binding sites in ovaries from adult coho salmon and immature chum salmon (O. keta). Intraperitoneal injections of luteinizing hormone-releasing hormone (LH-RH), its active analog des-Gly¹⁰ [D-Ala⁶]LH-RH-ethylamide (LH-RHA DAIa⁶) and chum salmon Gn-RH caused an increase in plasma gonadotropin levels. LH-RHA DAla⁶, which had a more prolonged effect on the maintenance of elevated plasma gonadotropin levels than LH-RH and chum salmon Gn-RH, induced oocyte maturation and ovulation. Intraperitoneal injections of pimozide, a dopamine receptor antagonist, also increased plasma gonadotropin levels suggesting that endogenous dopamine may inhibit gonadotropin secretion. Pimozide potentiated the effects of LH-RHA DAla& on gonadotropin release. Studies comparing the effects of partially purified salmon gonadotropin (SG-G100) and LH-RHA DAla⁶ on the induction of ovulation demonstrated that the induction of ovulation was dependant on the duration rather than the magnitude of the initial increase in plasma gonadotropin levels. Plasma testosterone and 17α,20βdihydroxy-4-pregnene-3-one (17α2OβP) levels were increased and 17β-estradiol levels decreased following an elevation of plasma gonadotropin levels. High levels of 17α20βP were associated with both spontaneous and gonadotropin induced oocyte maturation. Declining 17β-estradiol production appears to determine the time of oocyte maturation and ovulation by having a permissive effect on 17α20βP production. The presence of a gonadotropin receptor was demonstrated for the first time in the salmonid ovary. Gonadotropin binding to immature chum salmon ovaries was a saturable process as the uptake of ¹²⁵I-labeled salmon gonadotropin was reduced .in a dose dependant manner by unlabeled gonadotropin. Gonadotropin binding was attributed to a single class of high affinity binding sites present in limited numbers. Similar sites were not present in liver, kidney or muscle. The ability of various teleost and mammalian gonadotropins to decrease the binding of ¹²⁵I-labeled salmon gonadotropin to ovarian tissue was in agreement with the ability of these hormone preparations to stimulate steroid production in vitro. Gonadotropin binding sites were demonstrated in thecal and granulosa cell layers from adult coho salmon, although the levels of binding were lower than those for immature chum salmon ovaries.Science, Faculty ofZoology, Department ofGraduat

Hormonal and cellular regulation and actions of IGF-III in the ovary of zebrafish (Danio rerio)

Insulin-like growth factors (IGF) are known paracrine/autocrine regulators of ovarian development in teleosts. Initial studies investigated the hormonal and intracellular signalling cascades involved in regulating the expression of ovarian-derived IGFs in zebrafish (Danio rerio). Quantitative real-time PCR was used to quantify the expression of igf3, igf2a, and igf2b in full grown immature (FG; 0.57-0.65 mm) and mid-vitellogenic (MV; 0.45-0.56 mm) follicles. Addition of the gonadotropin analogue human chorionic gonadotropin (hCG) and the adenylate cyclase activator forskolin increased igf3 expression in FG and MV follicles, but had no effect on igf2a or igf2b expression. The effects of hCG on igf3 expression were blocked by the addition of the protein kinase A inhibitor H-89. Pituitary adenylate cyclase activating peptide also stimulated a small increase in igf3 expression in FG follicles, while growth hormone and salmon gonadotropin releasing hormone had no effect on igf3, igf2a, or igf2b expression. Secondary studies investigated the involvement of ovarian-derived IGFs in mediating the ovarian actions of gonadotropins on cell survival and steroidogenesis. Treatment of FG follicles with recombinant human IGF-I, hCG, or forskolin inhibited the induction of caspase-3/7 activity, which was used as a measure of apoptosis. The effects of hCG and forskolin on caspase-3/7 were attenuated by co-treatment with NVP-AEW541, an IGF-I receptor antagonist. In other studies, hCG was shown to increase the production of the maturation-inducing steroid 17α, 20β-dihydroxy-4-pregnen-3-one, but this action was not affected by co-treatment with NVP-AEW541. These results suggest there is a high degree of hormonal specificity in regulating IGFs in the zebrafish ovary and the ovarian-derived IGFs, presumably IGF-III, are downstream mediators of gonadotropin-dependent cell survival, but are not involved in gonadotropin-induced steroidogenesis