Exploring developmental MeHg impact on extraembryonic and cardiac vessels and its effect on cardiomyocyte contractility.

The toxicity of methylmercury (MeHg) during embryonic development is a relevant issue that remains unclear and deserves investigation. In this sense, there is evidence that links the intake of contaminated food with cardiovascular pathologies in human adults and children. Thus, this study aimed to verify the impact of MeHg on the structure and integrity of extraembryonic and cardiac blood vessels and the contractile function of cardiomyocytes, also evaluating embryonic weight and the cardiosomatic index (CSI). Thus, chicken embryos, used as an experimental model, were exposed to a single dose of 0.1 µg MeHg/50 µl saline at E1.5 and analyzed at E10. After exposure, an increase in the number of extraembryonic blood vessels and the veins of the cardiac tissue was observed. These increases were accompanied by a reduction in the content of VEGF and VCAM proteins related to vessel growth and adhesiveness. Together, these results were related to reduced nitrite (NOx) levels. Furthermore, MeHg reduces the number of sarcomeres and increases the content of cardiac troponin I (cTnI), a protein that regulates contraction. In general, exposure to MeHg affected the integrity of extraembryonic and cardiac vessels and the contractile function of cardiomyocytes, which had a systemic impact evidenced by the reduction in embryonic weight gain and CSI.

Reproductive toxicity of Roundup WG® herbicide: impairments in ovarian follicles of model organism Danio rerio.

Glyphosate-based herbicides are widely used in global agriculture, and their effects on different non-target animal organisms have been the focus of many toxicological studies. Regarding the potential role of glyphosate-based herbicides as an endocrine disruptor, the present study aims to investigate the effects of the herbicide Roundup WG® (RWG) on female reproduction, specifically on the ovarian maturation of Danio rerio. Adult females were exposed to low concentrations of RWG (0.065, 0.65, and 6.5 mg L-1) for 15 days, and then the ovaries were submitted to structural and morphometric procedures, accompanied by analysis of the vitellin protein content. Our results showed an increase of initial ovarian follicle numbers, decrease of late ovarian follicles, and smaller diameter of ovarian follicles in fish exposed to 0.065 and 6.5 mg L-1. The thickness of vitelline envelope was reduced, and the vitellin protein content was increased in the ovarian follicle in the two highest concentrations. Ultrastructural changes in the ovarian follicular component were evident and expressed by the cell index; vacuolization in follicular cells, increase of perivitelline space, and impaired mitochondria in oocytes were observed. Therefore, RWG adversely affects the ovarian maturation in D. rerio, and these changes can lead to reproductive toxicity, compromising population dynamics.

Roundup® disrupts chitinolytic enzyme activity and ecdysteroid concentration in Macrobrachium potiuna.

The endocrine system of crustaceans regulates the molt cycle with ecdysteroid hormones, mainly the 20-hydroxyecdysone (20-HE). Moreover, the molt process requires the action of chitinolytic enzymes (e.g., chitinase, chitobiase) to break down the old cuticle. However, endocrine disrupting compounds (EDC) are capable of altering their normal functioning. Glyphosate-based herbicides (GBH), such as Roundup®, the most widely used herbicides, are found in freshwater environments and have been considered EDC for many aquatic organisms. Therefore, this study examined the effects of environmentally relevant GBH concentrations (0.0065, 0.065, and 0.28 mg L-1) on the 20-HE concentration and chitobiase activity in the decapod prawn Macrobrachium potiuna exposed for 14 days. Additionally, lipid peroxidation, a biomarker of membrane lipid degradation, was evaluated in hepatopancreas to assess cellular damage. Results showed that GBH decreased the 20-HE concentration in females at the two highest concentrations tested, while an increase was observed in males exposed to the highest GBH concentration. In addition, GBH also decreased chitobiase activity in males (all concentrations) and females (the two highest concentrations). Finally, GBH caused increased lipid peroxidation in males, indicating cellular damage in the hepatopancreas. In conclusion, this work suggests that GBH is an EDC for crustaceans by disrupting molting, which could lead to altered reproduction and thus population dynamics. Graphical abstract Decrease in the 20-HE concentration and chitobiase activity in muscle of males and females of the freshwater prawn Macrobrachium potiuna exposed to the herbicide Roundup® for 14 days.

Ultraviolet B radiation affects epithelial cell morphology and ultrastructure in the hepatopancreas of the freshwater decapod Macrobrachium olfersii.

The hepatopancreas is the digestive organ of crustaceans, and plays important roles also in the synthesis and secretion of sexual hormones, immunological defenses and xenobiotic detoxification. Although the importance of this organ in crustaceans cannot be underestimated, the effects of ultraviolet B (UVB) radiation on hepatopancreas are poorly understood. Moreover, Macrobrachium prawns, have a transparent carapace, which make them more susceptible to UVB radiation, since their internal organs, such as hepatopancreas, are easily reached by solar radiation. Therefore, we aimed to evaluate UVB radiation toxicity on the morphology and morphometry of hepatopancreatic epithelial cells, and to investigate these UVB effects in subcellular compartments of the ecologically-important freshwater decapod, Macrobrachium olfersii. Hepatopancreas from the UVB-irradiated group showed a granular cytoplasm, with non-defined cell limits. Morphometric analyses revealed that the UVB-irradiated group exhibited a higher frequency of fibrillar (F-cell), resorptive (R-cell) and midget (M-cell), and decreased the blister-like (B-cell). It was also observed increased vacuole frequencies and increased F-, B- and R-cell volumes in the UVB-irradiated group. In addition, it was observed increased B-cell vacuolar volumes and decreased R-cell vacuolar volumes. Ultrastructural alterations occurred in subcellular compartments in F- and R-cells, e.g. loss of mitochondrial crests, morphologically compatible with mitochondrial fission, rough endoplasmic reticulum cisternae dilation, dilation of Golgi lamellar sacs, and increased vacuole and concentric membrane formation in the UVB-irradiated group. Our data showed that the hepatopancreas is an important target of UVB radiation, as demonstrated by a series of organ-specific morphological and morphometric impairments. Therefore, cell damage caused by UVB radiation can compromise metabolic functions in epithelial cells from the hepatopancreas, potentially affecting absorption, secretion and digestion processes, vitellogenin synthesis, immune responses and xenobiotic detoxification.

Ultraviolet-B radiation induces transcriptional modulation of components associated with the extracellular matrix in embryos of decapod Macrobrachium olfersii.

The extracellular matrix (ECM) is a non-cellular and three-dimensional structure, constituted by a macromolecular dynamic network that involves the cells in all animal tissues, including embryonic ones. Several studies with vertebrates and cell cultures have reported deleterious effects of ultraviolet-B (UVB) radiation on the components associated with the ECM. However, studies focusing on the UVB radiation effects on ECM components of crustaceans during embryonic development are very scarce. Thus, the aim of this study was to identify the coding sequences of components associated with the ECM and to evaluate the effect of UVB radiation on embryos of the ecologically-important decapod Macrobrachium olfersii. To evaluate the modulation of these ECM components during embryonic development, the transcript levels of Col4α1, Itgß, Lamα, Mmp1 and Timp in M. olfersii embryos were analyzed at early developmental stages (E1, E3 and E4), intermediate developmental stage (E7) and late developmental stages (E10 and E14). In addition, embryos at E7, which correspond to a landmark of crustacean development, were analyzed after 12 h of UVB exposure to verify UVB effects on the ECM components. The ECM component sequences were similar to other decapods, suggesting conservation of these genes among crustaceans. The results showed modulations of the ECM components of M. olfersii embryos that reflect the need for each component in the cellular mechanisms, necessary for normal embryonic development. After UVB exposure, embryos showed opacity of embryonic tissues and it was found the overexpression of Col4α1, Itgß, Mmp1 and Timp transcript levels (1.82-, 1.52-, 2.34- and 6.27-fold, respectively). These impairments can compromise important events for normal embryonic development, such as growth of optic lobes, caudal papilla, ramification of appendages and differentiation of organic systems. The results presented here, together with the effects on morphology, cell proliferation, differentiation, and apoptosis demonstrated previously, strengthen the knowledge of the complex impacts of UVB radiation on freshwater embryos. Nevertheless, our results encourage further investigations focusing on the assessment of UVB effects on different organisms in order to better understand the myriad of UVB effects on ECM components.

Modulation of antioxidant gene expressions by Roundup® exposure in the decapod Macrobrachium potiuna.

Glyphosate-based herbicides (GBH), including Roundup®, are the most used herbicides in agricultural and non-agricultural areas, which can reach aquatic environments through drift during application or surface runoff. Some studies, mostly in fish, demonstrated that GBH caused oxidative stress in non-target animals. However, only few information is available on the GBH effects in the antioxidant and stress proteins of many other organisms, such as freshwater crustaceans. Thus, we aimed to investigate the effects of environmentally relevant GBH concentrations on the relative transcript expression (RTE) of the superoxide dismutase (sod1), catalase (cat), selenium-dependent glutathione peroxidase (gpx), glutathione-S-transferase (gst), thioredoxin (txn), heat shock protein (hsp70 and hsp90) in the hepatopancreas of the ecologically important freshwater prawn Macrobrachium potiuna. Moreover, this study aimed to assess the gender-differences responses to GBH exposure. Male and female prawns were exposed to three Roundup WG® concentrations (0.0065, 0.065 and 0.28 mg of glyphosate/L) and a control group (0.0 mg/L) for 7 and 14 days. In general, males had an under-expression of the studied genes, indicating an oxidative stress and possible accumulation of ROS in the hepatopancreas. In the opposite, females had an overexpression of the same genes, indicating a more robust antioxidant system, in order to cope with the possible ROS increase after Roundup WG® exposure. Therefore, results confirmed that gender could be a confounding factor in ecotoxicological assessment of GBH effects. Additionally, this work highlights that sod1, cat, gpx, gst, txn, hsp70 and hsp90 gene expressions seem to be useful biomarkers to investigate the oxidative stress caused by Roundup WG® in Macrobrachium sp.

Exposure to homocysteine leads to cell cycle damage and reactive gliosis in the developing brain.

Studies that investigate the cellular effects of homocysteine (Hcy) on the differentiation of neural cells, and their involvement in establishment of cell layers in the developing brain are scarce. This study evaluated how Hcy affects the neural cell cycle and proteins involved in neuronal differentiation in the telencephalon and mesencephalon using the chicken embryo as a model. Embryos at embryonic day 2 (E2) received 20 µmol D-L Hcy/50 µl saline and analyzed at E6. The Hcy treatment induced an increase in the ventricular length of the telencephalon and also a reduction of the mantle layer thickness. We observed that Hcy induced impairments to the neural cell cycle and differentiation, which compromised the cell layers establishment in the developing brain. Hcy treatment also induced changes in gene and protein expression of astrocytes, characteristic of reactive gliosis. Our results point to new perspectives of evaluation of cellular targets of Hcy toxicity.

Effects of low glyphosate-based herbicide concentrations on endocrine-related gene expression in the decapoda Macrobrachium potiuna.

Glyphosate-based herbicides (GBH) are the most used herbicides worldwide and are considered as endocrine-disrupting compounds (EDC) for non-target organisms. However, effects of GBH on their endocrine systems remain poorly understood. Thus, the aim of this study was to assess the effects of low concentrations of Roundup WG® on growth and reproduction process molecules in both males and females of the decapod crustacean Macrobrachium potiuna, by the relative transcript expression levels of the ecdysteroid receptor (EcR), the molt-inhibiting hormone (MIH), and the vitellogenin (Vg) genes. Prawns were exposed to three concentrations of GBH (0.0065, 0.065, and 0.28 mg L-1) for 7 and 14 days. The results revealed that only in males the three genes transcript levels were influenced by the GBH concentration, time of exposure, and the interaction between the concentrations and time of exposure, suggesting that males were more sensitive to GBH than females. For males, after 7 days of exposure at 0.065 mg L-1, EcR and MIH were over-expressed, while the Vg expression was only over-expressed after 14 days. The present study highlighted that GBH impacted endocrine systems of M. potiuna. Moreover, EcR and MIH gene expressions could be promising EDC biomarkers of exposure in crustaceans. These results also indicate that GBH concentrations, considered secure by regulatory agencies, should be reviewed to minimize the effects on non-target organisms. Potential effects of glyphosate-based herbicides on the endocrine system of decapods Macrobrachium sp.

Impact of homocysteine on vasculogenic factors and bone formation in chicken embryos.

Developmental endochondral ossification requires constant blood supply, which is provided by the embryonic vascular network. High levels of homocysteine (Hcy) have vasculotoxic properties, but it remains unclear how Hcy disrupts blood vessel formation in endochondral ossification. Thus, we investigated the toxicity of Hcy on contents of vasculogenic factors (VEGF, VCAM-1, NOS3) and osteocalcin, using developing limbs as model. Chicken embryos were submitted to treatment with 20 µmol D-L Hcy at 12H&H and the analyses occur at 29H&H and 36H&H. We did not identify differences in the area of limb ossification in Hcy-treated (7.5 × 105 µm2 ± 3.9 × 104) and untreated embryos (7.6 × 105 µm2 ± 3.3 × 104) at 36H&H. In Hcy-treated embryos, we observed a significantly decrease of 46.8% at 29H&H and 26.0% at 36H&H in the number of VEGF-reactive cells. Also, treated embryos showed decrease of 98.7% in VCAM-1-reactive cells at 29H&H and 34.6% at 36H&H. The number of NOS3-reactive cells was reduced 54.0% at 29H&H and 91.5% at 36H&H, in the limbs of Hcy-treated embryos. Finally, in Hcy-treated embryos at 36H&H, we observed a reduction of 58.86% in the number of osteocalcin-reactive cells. Here, we demonstrated for the first time that the toxicity of Hcy is associated with a reduction in the contents of proteins involved in blood vessel formation and bone mineralization, which interferes with endochondral ossification of the limb during embryonic development. Graphical abstract.

Periódicos científicos de ciências biológicas: estudo dos títulos classificados no estrato A1 do Qualis / Scientific journals of biological sciences: study of the titles classified in the stratum A1 of the Qualis / Revistas científicas de ciencias biológicas: studio de los títulos clasificados en el estracto A1 del Qualis

Este artigo apresenta um estudo dos periódicos em que é publicada a produção nacional da área de ciências biológicas com a finalidade de: a) descrever as características editoriais dos periódicos; b) identificara participação de editoras comerciais; e c) verificar a adoção do acesso aberto. O universo da pesquisa realizada no estudo é composto pelos periódicos classificados no estrato A1 do Qualis 2014 da área de Ciências Biológicas I, totalizando 131 títulos, e os dados foram coletados na Web of Science. Os resultados mostraram que, em sua totalidade, os títulos foram editados no exterior, com domínio de publicações nos Estados Unidos e no Reino Unido (83,21%). Os periódicos foram criados desde 1860, mas a sua expansão ocorreu a partir de 1960 (75,57%) e são mantidos por associações e editoras comerciais (83,96%), com evidente destaque dos grupos Elsevier (23,66%), Wiley (18,32%) e Springer (12,21%). A maioria dos artigos está publicada em língua inglesa (99,98%) e a adoção do acesso aberto por esses periódicos é baixa (8,4%).(AU)

This article presents a study of the journals in which the national production in the area of biological sciences is published, with the purpose of: a) to describe the editorial characteristics of the journals; b) to identify the participation of commercial publishers; and c) to verify the adoption of open access. The universeof the study is composed of journals classified in the stratum A1 of Qualis 2014 of the area of Biological Sciences I, totalling 131 journals, and the data were extracted from the Web of Science. The results of the research show that all the journals were edited in foreign countries, especially in United States and United Kingdon (83,21%). The journals were created since 1860, but their expansion started in 1960 (75,57%) and they are maintained by associations and commercial publishers (83,96%), being in an evident position of prominence the groups Elsevier (23,66%), Wiley (18,32%) and Springer (12,21%). The greatest number of articles is published in English (99,98%) and the offer of open access by these journals is low (8,4%).

Este artículo presenta un estudio de las revistas científicas en que se publica la producción nacionalen el campo de las ciencias biológicas, con el fin de: a) describir las características editoriales de lasrevistas; b) determinar la participación de las editoras comerciales; y c) verificar la adopción del accesoabierto. El universo de la investigación consiste en las revistas clasificadas en el estrato A1 del Qualis2014 del área de Ciencias Biológicas I, un total de 131 revistas, y los datos fueron recogidos en la Webof Science. Los resultados muestran que la totalidad de las revistas es publicada en el extranjero sobretodo en los Estados Unidos y en el Reino Unido (83,21%). Las revistas científicas fueron creadas desde1860, pero su expansión ocurrió a partir de 1960 (75,57%) y ellas son mantenidas por las asociaciones yeditoras comerciales (83,96%), con evidente relevancia de los grupos Elsevier (23,66%), Wiley (18,32%)y Springer (12,21%). La mayoría de los artículos es publicada en inglés (99,98%) y la adopción del acceso abierto por esas revistas es baja (8,4%)

Homocysteine-induced changes in cell proliferation and differentiation in the chick embryo spinal cord: implications for mechanisms of neural tube defects (NTD).

Maternal hyperhomocysteinemia during pregnancy is associated with increased risk of NTD in the offspring. Our study investigated the effects of homocysteine (Hcy) on proliferation and neuronal differentiation of the spinal cord cells in a chick embryo model. Embryos were treated with 20µmol D-L Hcy/50µL saline solution at embryonic day 2 (E2) and analyzed at embryonic days 4 (E4) and 6 (E6). Control embryos received exclusively 50µL saline solution. We performed immunolocalization and flow cytometry analyses using antibodies anti-phosphohistone H3 (pH3), anti-proliferating cell nuclear antigen (PCNA), anti-ß-tubulin III and anti-p53. Our results revealed that Hcy interferes in the proliferation of the neural cells, and that this effect is age-dependent and differed between Hcy-treated embryos with and without NTD. Also, Hcy induced a decrease of neuronal differentiation in the spinal cord at both embryonic ages. These findings contribute to clarifying the cellular bases of NTD genesis, under experimental hiperhomocysteinemia.

Exploring developmental gene toolkit and associated pathways in a potential new model crustacean using transcriptomic analysis.

The crustaceans are one of the largest, most diverse, and most successful groups of invertebrates. The diversity among the crustaceans is also reflected in embryonic development models. However, the molecular genetics that regulates embryonic development is not known in those crustaceans that have a short germ-band development with superficial cleavage, such as Macrobrachium olfersi. This species is a freshwater decapod and has great potential to become a model for developmental biology, as well as for evolutionary and environmental studies. To obtain sequence data of M. olfersi from an embryonic developmental perspective, we performed de novo assembly and annotation of the embryonic transcriptome. Using a pooling strategy of total RNA, paired-end Illumina sequencing, and assembly with multiple k-mers, a total of 25,636,097 pair reads were generated. In total, 99,751 unigenes were identified, and 20,893 of these returned a Blastx hit. KEGG pathway analysis mapped a total of 6866 unigenes related to 129 metabolic pathways. In general, 21,845 unigenes were assigned to gene ontology (GO) categories: molecular function (19,604), cellular components (10,254), and biological processes (13,841). Of these, 2142 unigenes were assigned to the developmental process category. More specifically, a total of 35 homologs of embryonic development toolkit genes were identified, which included maternal effect (one gene), gap (six), pair-rule (six), segment polarity (seven), Hox (four), Wnt (eight), and dorsoventral patterning genes (three). In addition, genes of developmental pathways were found, including TGF-ß, Wnt, Notch, MAPK, Hedgehog, Jak-STAT, VEGF, and ecdysteroid-inducible nuclear receptors. RT-PCR analysis of eight genes related to embryonic development from gastrulation to late morphogenesis/organogenesis confirmed the applicability of the transcriptome analysis.

Light-mediated DNA Repair Prevents UVB-induced Cell Cycle Arrest in Embryos of the Crustacean Macrobrachium olfersi.

High levels of ultraviolet-B (UVB) radiation can negatively affect aquatic animals. Macrobrachium olfersi is a prawn that lives in clear freshwaters and during the breeding season, females carry eggs in an external brood pouch. Therefore, we hypothesize that eggs are also exposed to environmental UVB radiation. The aim of this study was to investigate whether UVB radiation induces DNA damage and compromises cell cycle in embryos of M. olfersi. In laboratory, UVB irradiance (310 mW. cm(-2) ) that embryos receive in the natural environment was simulated. After irradiation, embryos were kept under different light conditions in order to recognize the presence of cell repair. UVB radiation induces DNA damage, specifically thymine dimers. After 48 h of UVB exposure, a significant decrease in the level of these dimers was observed in embryos kept under visible light while it remained constant in the dark. Moreover, under visible light and darkness, a decrease in proliferation was observed after 48 h of irradiation. An increase in PCNA expression and decrease in p53 expression were observed after, respectively, 1 and 48 h of exposure. Our results showed that UVB radiation disturbs the cell cycle and induces DNA damage in M. olfersi embryos. However, under visible light these embryos showed successful DNA repair.

Effects of homocysteine on mesenchymal cell proliferation and differentiation during chondrogenesis on limb development.

High levels of homocysteine (Hcy) are related to an increased risk of the occurrence of congenital anomalies, including limb defects. However, few evaluations about how toxic levels of Hcy affect limb development have been reported. We investigated whether Hcy can affect the cell cycle proteins and proteins involved in mesenchymal cell differentiation during limb development, in a chicken embryo model. Embryos were treated with 20 µmol d-l Hcy/50 µl saline at embryonic day 2 and analyzed at embryonic day 6. Untreated control embryos received exclusively 50 µl saline solution. To identify cells in proliferation and cell cycle proteins, as well as Pax1/9 and Sox9 proteins, we performed immunolocalization and flow cytometry analyses using the antibodies anti-phosphohistone H3, anti-p53, anti-p21, anti-proliferating cell nuclear antigen, anti-Pax1, anti-Pax9 and anti-Sox9. No significant differences in cell proliferation were observed between Hcy-treated and untreated embryos. We observed a decrease of the proliferating cell nuclear antigen and p21 proteins, both involved in the G1 phase of cell cycle progression. On the other hand, in mesenchymal cells of the limbs, Hcy induces an increase of p53 protein, which can be activated by DNA damage. In cell differentiation, Hcy induced an increase mainly of Pax9 and Sox9 proteins. Our data indicate that the treatment with Hcy changes the mesenchymal cell dynamics during limb development, but does not change the morphology of the cartilage molds. These findings provide information to understand better the cellular basis of the toxicity of Hcy on chondrogenesis during limb development.

Homocysteine causes disruptions in spinal cord morphology and changes the expression of Pax 1/9 and Sox 9 gene products in the axial mesenchyme.

BACKGROUND: Neural tube defects (NTD) involve disruptions in the axial mesenchyme, and are related to an imbalance between folic acid (FA) and homocysteine (Hcy). This study evaluated the effects of FA/Hcy imbalance on cell proliferation and expression of the Pax 1/9 and Sox 9 gene products in the axial mesenchyme of chickens. METHODS: Embryos were incubated (38°C) and pretreated at 24 h and treated at 46 h of incubation. The experimental groups were: FA-pretreated with saline and treated with 0.5 µg FA/saline; Hcy-pretreated with 50 µl saline and treated with 20 µmol D,L-Hcy/50 µl saline; FA+Hcy-pretreated with 0.5 µg FA/50 µl saline and treated with 20 µmol D,L-Hcy/50 µl saline; and the control embryos were pretreated and treated with saline. Embryos were analyzed at E4 and E6. Immunohistochemistry was performed to identify proliferating cells and the expression of the gene products of Pax 1/9 and Sox 9. Total RNA of the E4 embryos was extracted and a RT-qPCR assay was performed to quantify Pax 1/9 mRNA expression. RESULTS: Hcy treatment caused spinal NTD and abnormalities in axial mesenchyme development, affecting the distribution of sclerotomal cells and chondrification. Hcy also reduced cell proliferation and changed the expression of Pax 1/9 and Sox 9 in the mesenchyme. CONCLUSIONS: Our data clarified the relationship between spinal NTD genesis and disruptions of Pax 1/9 and Sox 9 gene products in the axial mesenchyme caused by the FA/Hcy imbalance.

Prenatal lead acetate exposure induces apoptosis and changes GFAP expression during spinal cord development.

Lead is an important heavy metal pollutant in the environment, and it induces neurodevelopmental toxicity, which is characterized by histological, ultrastructural, and neurochemical changes in the central nervous system. The aim of this study was to evaluate the effects of prenatal acute lead exposure on apoptosis, GFAP expression, and lead deposition in the developing spinal cord. Chick embryos were exposed to 150µg or 450µg doses of lead acetate via yolk sac at E3 or E5 embryonic ages and incubated for six days. Lead deposition was observed in the ependymal cells, developing dorsal, and ventral horns, and in the white matter of all the exposed embryos. TUNEL-positive cells were found in all layers of the spinal cord of the control and treated embryos, and lead exposure resulted in a significant increase in the numerical density of the apoptotic cells. Control embryos showed intense GFAP expression in the ependymal cells of the roof and floor plates, and in the gray and white matters; whereas exposure to lead reduced GFAP reactivity. In ovo lead exposure induces apoptosis, and reduces GFAP expression in the nervous system of the chick embryos, which may cause impairments during neuronal development and consequences in childhood and adulthood.

Acute exposure of rabbits to diphenyl diselenide: a toxicological evaluation.

The simple organoselenium compound diphenyl diselenide (PhSe)(2) is a promising new pharmacological agent. However, few toxicological evaluations of this molecule have been reported. We evaluated the effects of acute administration of (PhSe)(2) on toxicological parameters in rabbits. Adult New Zealand rabbits were exposed to (PhSe)(2) (5-500 micromol kg(-1) , intraperitoneally) once a day for 5 days. Exposure to 500 micromol kg(-1) caused 85% mortality. Exposure to 50 micromol kg(-1) of (PhSe)(2) increased the glutathione levels in the hippocampus, kidney, heart, muscle and blood, whereas lipoperoxidation (TBARS) decreased in the cerebellum and kidney after exposure to 5 micromol kg(-1) . The activity of glutathione peroxidase increased in the heart and muscle of rabbits treated with 50 micromol kg(-1) of (PhSe)(2) and glutathione reductase activity was reduced in the cerebellum, cerebral cortex and kidney. Treatment with (PhSe)(2) reduced the activity of δ-aminolevulinate dehydratase in the hippocampus and increased this activity in the heart, but did not alter the activity of complexes I and II of the respiratory chain in the liver and brain. Hepatic and renal biochemical and histological parameters were not modified by (PhSe)(2) and apoptosis was not detected in these tissues; however, the hepatic cells tended to accumulate fat vacuoles. These results indicated that acute toxicology to (PhSe)(2) in rabbit is dependent on the dose, which should motivate further experiments on the therapeutic properties of this compound.

Effects of inorganic selenium administration in methylmercury-induced neurotoxicity in mouse cerebral cortex.

Selenium can counteract methylmercury (MeHg) neurotoxicity. However, data about the neuroprotective effects of sodium selenite (Na(2)SeO(3)) on the activity of mitochondrial complexes and creatine kinase (mtCK) are scarce. Therefore, this study investigated the effects of the chronic exposure to Na(2)SeO(3) on brain energy metabolism and oxidative stress parameters in MeHg-poisoned mice. Adult male mice were orally treated with MeHg (40 mg L(-1) in drinking water, ad libitum) during 21 days and simultaneously administrated with daily subcutaneous injections of Na(2)SeO(3) (5 µmol kg(-1)), a potential neuroprotectant. Mitochondrial complexes I to IV and mtCK activities were measured in cerebral cortex mitochondria. The cerebro-cortical tissue was also used to evaluate the antioxidant enzymes glutathione peroxidase (GPx) and glutathione reductase (GR) activities, as well as lipid peroxidation. Metal deposition was followed autometalographically (AMG). Na(2)SeO(3) partially prevented MeHg-induced inhibition of complexes II-III, IV and mtCK activities; however, it was unable to prevent MeHg-induced complex I and II inhibition. MeHg increased lipid peroxidation, GR activity and decreased GPx activity in the cerebral cortex; however, Na(2)SeO(3) did not modify such events. Furthermore, Na(2)SeO(3)per se inhibited complexes I, II-III and IV and mtCK activities and increased GPx and GR activities and lipid peroxidation. These data show that inorganic selenium was ineffective in preventing most of the MeHg-induced brain biochemical alterations. However, the most prominent finding was the selenium-induced reduction of cells labelled for metal deposition. Although, the literature supports the beneficial effects of selenium against mercury toxicity, the toxic effects elicited by Na(2)SeO(3), alone or in combination with mercury, should be considered when this compound is proposed as a potential protective therapy for MeHg poisoning.

Effects of environmental and artificial UV-B radiation on freshwater prawn Macrobrachium olfersi embryos.

The recent decrease of the stratospheric ozone has resulted in an increase of ultraviolet-B (UV-B) radiation reaching the Earth's surface. In freshwater ecosystems with transparent water, UV-B rays easily penetrate and potentially cause harmful effects to organisms. In this study, embryos of the prawn Macrobrachium olfersi were used to evaluate the impact of UV-B rays in freshwater environments. We observed three groups of embryos: the first was to assess whether UV-B radiation produced morphological defects and/or biochemical impairments in the laboratory. The second was to check whether embryos with the same impairments as those observed in the laboratory were found in their environment, under natural solar radiation. The third group was the non-irradiated control. The embryos irradiated with 310 mW cm(-2) UV-B for 30 min showed morphological alterations similar to those observed in embryos from the environmental control group. The most important effects of the UV-B radiation observed in M. olfersi embryos were morphological (1.2% of the total number of embryos from the environment and 2.8% of the total number of irradiated embryos), pigmentation changes in the eyes (78.0% of the total number of embryos from the environment and 98.9% of the total number of irradiated embryos), and disruption of the chromatophores (46.9% of the total number of embryos from the environment and 95.5% of the total number of irradiated embryos). We also observed an increase in egg volume, which was accompanied by a significant increase in water content in UV-B irradiated groups when compared with aquaria control embryos. In addition, a significant decrease in the mitotic index in eggs exposed to UV-B radiation was detected (0.17 for the embryos from the aquaria control, 0.10 for the embryos of the environmental control, and 0.04 for the irradiated groups). The low levels of NPSH and high levels of TBARS indicated that UV-B rays directly compromised the antioxidant function of the embryonic cells, leading to oxidative stress. Our combined morphological and biochemical analyses revealed important effects induced by UV-B on M. olfersi embryos, and the results suggest that the recent changes in global conditions may have injurious effects, at least on the embryos of freshwater prawns.

Effects of folic acid and homocysteine on spinal cord morphology of the chicken embryo.

Maternal ingestion of folic acid (FA) reduces neural tube defects, which are associated with high homocysteine levels. Present study evaluated the effects of FA and homocysteine on cell proliferation and cell adhesion, as well as on apoptosis, throughout the development of the spinal cord and mesenchyme of chicken embryos. Normal closure of the neural tube and a regular distribution of the mesenchymal cells were observed in control and FA-treated embryos. All homocysteine-treated embryos and also 6 of 10 embryos treated with FA+homocysteine showed failure of closure of the neural tube. Homocysteine decreased the thickness of the mantle and marginal layers of the spinal cord, and FA did not prevent this effect. FA treatment reversed the decrease of proliferating cells in the spinal cord induced by homocysteine. FA-treated embryos showed the highest numerical density of apoptotic cells. Homocysteine treatment reduced NCAM expression in both spinal cord and mesenchymal tissue, and FA prevents this effect. These results are important because they demonstrate in situ that the imbalance between FA and homocysteine levels can lead to disruptions in spinal cord development, changing proliferation, apoptosis, and cell adhesion and consequently changing the arrangement of the spinal cord layers.