Morphological Alterations in the Early Developmental Stages of Zebrafish (Danio rerio; Hamilton 1822) Induced by Exposure to Polystyrene Microparticles.

Microplastics (MPs) are emerging pollutants of widespread concern in aquatic environments. The aim of this study was to evaluate the negative impact of pristine MPs of polystyrene of 100 µm on embryo and larvae of Danio rerio exposed to three environmentally relevant concentrations of polystyrene (3.84 × 10- 6, 3.84 × 10- 7, and 3.84 × 10- 8 g/mL). The exposure effect was evaluated through the general morphology score, biometrics, and integrated biomarker response version 2 index. No mortality was observed but the anatomical structure of fishes was affected showing pigmentation deficiency and alterations in the head region as the main affected endpoints. The general morphology score and the integrated biomarker response values were highly sensitive to address the effect of the three concentrations of MPs used here. Our results provide solid evidence of the negative impact of 100 µm pristine polystyrene MPs exposure on early stages of zebrafish.

The surfactant Dioctyl Sodium Sulfosuccinate (DOSS) exposure causes adverse effects in embryos and adults of zebrafish (Danio rerio).

Dioctyl Sodium Sulfosuccinate (DOSS, CAS 577-11-7) is a chemical emulsifying surfactant that is widely used in the food and the cosmetic industry, and it is also the major component of the crude oil chemical dispersant Corexit™. Despite of its wide use, the studies related to its negative effect have been evaluated mainly in marine environments showing that DOSS is highly bioactive, extremely low volatile, and potential to persist in the environment longer than other dispersant components. Up to date, there is no available information of DOSS concentration in freshwater environments, little is known about its downstream fate after excretion and its effect on freshwater organisms. The objective of this study was to evaluate the effect of DOSS at different concentrations in embryos and adults of zebrafish Danio rerio in an acute-static bioassays of 96 h. The median lethal concentration in embryos was 33.3 mg/L. Malformations started to be observed at 10 mg/L. In adults, the gene expression analysis in gill tissues showed a deregulation in genes associated with the antioxidant system and the nucleotide excision repair mechanism. Additionally, Micronuclei (DNA damage) in erythrocytes, and fat degeneration in liver, hypertrophy and hyperplasia in gills, and hyaline drops in kidney tissues were also observed. In conclusion, the concentrations of DOSS evaluated here would be of health relevance to fish based on morphological alterations in embryos and changes in the gene expression profile, DNA damage and tissue impairment in adults.

Gene expression analysis on growth, development and toxicity pathways of male Nile tilapia (Oreochromis niloticus), after acute and sub-chronic benzo (α) pyrene exposures.

Benzo[α]pyrene (BaP), a lipophilic polycyclic aromatic hydrocarbon (PAH), is a contaminant widely distributed in aquatic systems. Its presence in freshwater organisms is of great concern; particularly in Nile tilapia (Oreochromis niloticus), due to its economic relevance. The aim of this study is to evaluate the effects of acute and sub-chronic BaP exposures on molecular growth/development responses, toxicity to DNA pathways and xenobiotic metabolism. Negative morphometric changes (the growth condition factor, hepatosomatic and gonadosomatic indices), the fluorescent aromatic compounds (FACs) in bile were also studied in order to understand the mechanisms of action of BaP. Genes involved in the growth hormone GH/insulin-like growth factor 1 (IGF-1) were measured, such as IGF1-2 with the growth hormone receptor gene expression GHR1-2, and the endocrine disruption biomarker vitellogenin (VTG). Acute exposure elicited changes in the GH/IGF axis, mainly in the GHR1 and in IGF1 mRNA levels without affecting the GHR2 expression. While sub-chronic exposure had less effect on both GHR and IGF genes. The most notable tissue-specific effects and morphometric endpoints were observed upon sub-chronic exposure, such as changes in key genes involved in detoxification, DNA damage, and altered reproductive morphological endpoints; showing that sub-chronic BaP doses have longer-lasting toxic effects. This study shows that sub-chronic BaP exposure may compromise the health of Nile tilapia and sheds light on the changes of the GH/IGF axis and the biotransformation of the xenobiotics due to the presence of this contaminant.

Effect of Leptin, Pituitary Transcription Factor and Luteinizing Hormone Receptor Genes Polymorphisms on Reproductive Traits and Milk Yield in Holstein Cattle

Abstract The aim of this study was to estimate allelic and genotypic frequencies of markers in the leptin (LEP), pituitary transcription factor (PIT-1) and luteinizing hormone receptor (LHR) genes and evaluate their effects on reproductive traits and milk yield of Holstein cattle. Data from 147 cows from department of Francisco Morazán, Honduras, were collected and PCR-Restriction Fragment Length Polymorphism (RFLP) assays were performed to characterize the PIT-1-HinfI, LEP- A59V and LHR-rs41256848 polymorphisms. To estimate the effect of genotypes on reproductive traits and milk yield fixed and mixed linear models were fitted. The frequencies of the genotypes CC, CT and TT of A59V, AA, AB and BB of HinfI, and CC, CG and GG of rs41256848 were 0.46, 0.33 and, 0.21; 0.09, 0.32 and 0.58; and 0.37, 0.61 and 0.02, respectively. The genotypes of LEP and LHR showed deviations from Hardy-Weinberg equilibrium. The A59V polymorphism was significantly associated with the calving to conception interval (CCI) (p=0.01), being the C allele favorable. The HinfI and rs41256848 polymorphism were significantly associated (p=0.08 and p=0.04) with age to first calving (AFC), being the A and G the alleles favorable associated, respectively. The results suggest that LEP, PIT and LHR polymorphisms can probably act as candidate to be used in marker-assisted selection for AFC and CCI traits.