Distribution and accumulation of 10 nm silver nanoparticles in maternal tissues and visceral yolk sac of pregnant mice, and a potential effect on embryo growth.

We examined the distribution of silver in pregnant mice and embryos/fetuses following intravenous injections of 10 nm silver nanoparticles (AgNPs) or soluble silver nitrate (AgNO3) at dose levels of 0 (citrate buffer control) or 66 µg Ag/mouse to pregnant mice on gestation days (GDs) 7, 8 and 9. Selected maternal tissues and all embryos/fetuses from control, AgNP- and AgNO3-treated groups on GD10 and control and AgNP-treated groups on GD16 were processed for the measurement of silver concentrations, intracellular AgNP localization, histopathology and gross examination of tissue morphology. Inductively-coupled plasma mass spectrometry revealed silver in all examined tissues following either AgNP or AgNO3 treatment, with highest concentrations of silver in maternal liver, spleen and visceral yolk sac (VYS), and lowest concentrations in embryos/fetuses. For VYS, mean silver concentration following AgNO3 treatment (4.87 ng Ag/mg tissue) was approximately two-fold that following AgNP treatment (2.31 ng Ag/mg tissue); for all other tissues examined, mean silver concentrations following either AgNP or AgNO3 treatment were not significantly different from each other (e.g. 2.57 or 2.84 ng Ag/mg tissue in maternal liver and 1.61 or 2.50 ng Ag/mg tissue in maternal spleen following AgNP or AgNO3 treatment, respectively). Hyperspectral imaging revealed AgNP aggregates in maternal liver, kidney, spleen and VYS from AgNP-treated mice, but not AgNO3-treated mice. Additionally, one or more embryos collected on GD10 from eight of ten AgNP-treated mice appeared small for their age (i.e. Theiler stage 13 [GD8.5] or younger). In the control group (N = 11), this effect was seen in embryos from only one mouse. In conclusion, intravenous injection of 10 nm AgNPs to pregnant mice resulted in notable silver accumulation in maternal liver, spleen and VYS, and may have affected embryonic growth. Silver accumulation in embryos/fetuses was negligible.

Distribution of silver nanoparticles in pregnant mice and developing embryos.

The objective of this study was to evaluate the distribution of silver nanoparticles (NPs) in pregnant mice and their developing embryos. Silver NPs (average diameter 50 nm) were intravenously injected into pregnant CD-1 mice on gestation days (GDs) 7, 8, and 9 at dose levels of 0, 35, or 66 µg Ag/mouse. Mice were euthanised on GD10, and tissue samples were collected and analysed for silver content. Compared with control animals injected with citrate buffer vehicle, silver content was significantly increased (p < 0.05) in nearly all tissues from silver NP-treated mice. Silver accumulation was significantly higher in liver, spleen, lung, tail (injection site), visceral yolk sac, and endometrium compared with other organs from silver NP-treated mice. Furthermore, silver NPs were identified in vesicles in endodermal cells of the visceral yolk sac. In summary, the results demonstrated that silver NPs distributed to most maternal organs, extra-embryonic tissues, and embryos, but did not accumulate significantly in embryos.

Developmental regulation of catecholamine levels during sea urchin embryo morphogenesis.

Results of a number of pharmacological studies suggest that catecholamines play a regulatory role in cleavage, morphogenesis and cell differentiation during early animal embryonic development. Few studies, however, have actually assayed for levels of catecholamines in these early embryos by methods that are both sensitive and specific. In this investigation the catecholamines dopamine, norepinephrine and epinephrine and their precursor, dopa and metabolites were determined in eight different embryonic stages of the sea urchin, Lytechinus pictus from hatched blastula to late pluteus larva, using high performance liquid chromatography with electrochemical detection. Levels of each of the catecholamines exhibited unique developmental profiles and are consistent with a role for epinephrine in blastula and early gastrula embryos and for norepinephrine in gastrulation. Changes in levels of catecholamine precursor and metabolites suggest a changing pattern of synthetic and metabolic enzyme activity, which can, for the most part, explain the fluctuations in catecholamine levels during development from blastula to the pluteus larva stage.

Regulation of uterine hsp90alpha, hsp72 and HSF-1 transcription in B6C3F1 mice by beta-estradiol and bisphenol A: involvement of the estrogen receptor and protein kinase C.

We have previously demonstrated that bisphenol A (BPA)- and beta-estradiol (E2)-induced increases in uterine weight and heat shock protein (hsp) 90alpha and hsp72 levels are mediated through the estrogen receptor (ER). It is not, however, clear if BPA and E2 regulation of hsps is at the transcriptional or post-transcriptional level. Therefore, in this study we examined the ability of BPA and E2 to increase uterine weight and regulate transcription of these hsps and of heat shock factor (HSF)-1 in ovariectomized B6C3F1 mice at 6 or 24 h after a single subcutaneous injection of E2 (1 microg/kg) or BPA (100 mg/kg). The role of the ER and protein kinase C (PKC) in these E2 and BPA effects was evaluated by co-administration of the antiestrogen ICI 182,780 (5 mg/kg) or the PKC inhibitor GF 109203X (0.5 mg/kg), respectively. The results demonstrated ER involvement in uterine weight increases. Uterine hsp mRNA levels are increased by E2 and BPA through a direct effect on their transcription and/or, in the case of E2, through an increase in HSF-1 mRNA. PKC is involved in the BPA-induced increases in hsp90alpha mRNA levels. We conclude that E2 and BPA regulate hsp90alpha and hsp72alpha transcription via similar and distinct pathways.

The gene encoding the sea urchin complement protein, SpC3, is expressed in embryos and can be upregulated by bacteria.

Sea urchins have an innate immune response that functions in the absence of adaptive capabilities. It is mediated, in part, by components of the complement system, an important subsystem of the innate response in mammals. A homologue of complement C3, SpC3, has been identified in adult Strongylocentrotus purpuratus and is expressed in coelomocytes. In this study, transcript levels from the gene, Sp064, which encodes SpC3, were examined in developing embryos and found to be present in unfertilized eggs and throughout embryogenesis with a peak in transcript levels just prior to and during gastrulation. In addition, continuous exposure of embryos, beginning with the hatched blastula stage, to heat killed Vibrio diazatrophicus, a marine pathogen of sea urchins, significantly increased Sp064 message content in plutei compared to unexposed controls. These results suggest that sea urchin embryos may use a complement-based immune system for defense against pathogens in their aquatic environment.

Mercury, cadmium, and arsenite enhance heat shock protein synthesis in chick embryos prior to embryotoxicity.

BACKGROUND: Cells respond to adverse environmental stimuli by enhancing the expression of specific genes, the products of which include a suite of proteins known as heat shock proteins (hsps), a response often attributed to cellular protection. METHODS: In this study, we characterized alterations in hsp expression in chick embryos (Hamburger-Hamilton stage 17, 72 h) exposed in ovo to arsenite (As), mercury (Hg), and cadmium (Cd), known developmental toxicants. Embryos were incubated for 2 h following exposure to 3, 10, 30, or 100 nmol metal, or for 2, 4, 12, or 24 h following treatment with 10 nmol metal. RESULTS: An enhanced de novo synthesis of 24-, 70-, and 90-kD, 70- and 90-kD, and 70-kD proteins was observed with As, Hg, and Cd treatments, respectively. These responses were transient; apparent rates of protein synthesis were maximal 2-4 h after exposure and returned to control rates by 24 h. Actinomycin D experiments demonstrated that arsenite-induced expression of these proteins is transcriptionally regulated. Immunoblotting experiments identified the 24-, 70-, and 90-kD proteins as the heat shock proteins hsp24, hsp70, and hsp90, respectively. Exposure duration-related abnormalities were noted in the neural tube with all metals and in the ganglia and somites with Cd and As. Retina, allantois, and limb defects were specific to Cd-treated embryos, and branchial arch defects were specific to As-treated embryos. CONCLUSIONS: The data support metal-induced developmental abnormalities, which are preceded by synthesis of stress proteins.

Increases in mouse uterine heat shock protein levels are a sensitive and specific response to uterotrophic agents.

There is increasing consensus that the uterotrophic estrogenicity assay should be coupled with other morphometric or molecular end points that might enhance its sensitivity. We have previously shown that bisphenol A (BPA), similarly to 17ss-estradiol (E2), increases levels of uterine heat shock proteins (hsps), mainly hsp90alpha and glucose-regulated protein (grp) 94. In this study we investigated whether increases in uterine hsp levels are a specific response of estrogens or estrogen mimics. We therefore examined the ability of a) E2, diethylstilbestrol (DES), and tamoxifen (TAM); b) the xenoestrogens coumestrol (CM), methoxychlor (MXC), BPA, and dibutyl phthalate (DBP); c) the progestin medroxyprogesterone (MED); d) the glucocorticoid dexamethasone (DEX); and e) phytol (PHY), a precursor to a retinoid X and peroxisome proliferator-activating receptor agonist, to increase uterine weights and alter uterine morphology and hsp levels. We showed that DES, TAM, CM, MXC, and BPA significantly increased uterine weights and uterine hsp90alpha and grp94 levels. Even though the doses of CM, MXC, and BPA used were much higher than the E2 dose, those treatments resulted in lower increases in uterine weight. On the other hand, increases in grp94 levels were equal to those induced by E2 treatment. Treatments with MED, DEX, DBP, or PHY did not significantly alter uterine weight or morphology and had no significant effects on uterine hsp levels. The results of this study suggest that only the estrogens increase uterine hsp90alpha and grp94 levels, and that this hsp effect is a more sensitive uterotrophic response than uterine weight increase.

Organizational and activational effects of estrogenic endocrine disrupting chemicals

A desregulação endócrina é uma hipótese de um modo de ação comum capaz de definir um conjunto de substâncias químicas estruturalmente variadas, tanto naturais quanto sintéticas. O modo de ação comum pode sugerir que produzam ou contribuam para efeitos tóxicos semelhantes, embora tal hipótese tenha sido difícil de demonstrar. Evidências provenientes da biologia do desenvolvimento sugerem que o desenvolvimento de sistemas sensíveis aos hormônios, tais como o cérebro e o trato genito-urinário, podem ser particularmente sensíveis aos desreguladores endócrinos. Uma vez que tais sistemas são organizados, e depois ativados, por hormônios, o cérebro e a vagina podem representar modelos importantes para estudar a toxicidade dos desreguladores endócrinos e para elucidar os mecanismos pelos quais parecem afetar a função a longo prazo.

Organizational and activational effects of estrogenic endocrine disrupting chemicals.

Endocrine disruption is a hypothesis of common mode of action that may define a set of structurally varied chemicals, both natural and synthetic. Their common mode of action may suggest that they produce or contribute to similar toxic effects, although this has been difficult to demonstrate. Insights from developmental biology suggest that development of hormone sensitive systems, such as the brain and the genitourinary tract, may be particularly sensitive to EDCs. Because these systems are both organized and later activated by hormones, the brain and vagina may be valuable model systems to study the toxicity of EDCs in females and to elucidate mechanisms whereby early exposures appear to affect long term function.

Effects of 17 alpha-methyltestosterone on uterine morphology and heat shock protein expression are mediated through estrogen and androgen receptors.

Testosterone and the synthetic androgen, 17 alpha-methyltestosterone (MT), have been shown to increase uterine weights and alter uterine morphology. However, whereas the mechanism of action of testosterone in the uterus has been studied, it is not known if the actions of MT are mediated through androgen (AR) or estrogen (ER) receptors. In the present study, we have shown that MT, at 0.5 or 10 mg/kg per day, increases uterine weight and alters uterine morphology in a dose-dependent manner. Co-administration of the anti-androgen, flutamide, or the anti-estrogen, ICI 182,780, with MT revealed that the effects of the low dose of MT are mediated through the ER, whereas those of the high dose are mediated through both the ER and AR. In addition, we have studied the effects of MT on uterine heat shock proteins (hsps), a group of estrogen-regulated proteins whose levels increase in response to growth signals and protein damage. MT increased levels of hsp90 alpha, hsp72, and grp94. All effects on uterine hsp levels were antagonized by the anti-estrogen and not the anti-androgen. Collectively, the results of the present study indicate that the effects of MT in the uterus are mediated through the AR and ER.