medaka

Despite the theoretical risk of forming halogenated methylparabens (halo-MePs) during water chlorination in the absence or presence of bromide ions, there remains a lack of in vivo toxicological assessments on vertebrate organisms for halo-MePs. This research addresses these gaps by investigating the lethal (assessed by embryo coagulation) or sub-lethal (assessed by hatching success/heartbeat rate) toxicity and teratogenicity (assessed by deformity rate) of MeP and its mono- and di-halogen derivatives (Cl- or Br- ) using Japanese medaka embryos...

Pacific saury (Cololabis saira) is a commercially important small pelagic fish species in Asia. In this study, we conducted the first-ever whole genome sequencing of this species, with single molecule, real-time (SMRT) sequencing technology. The obtained high-fidelity (HiFi) long-read sequence data, which amount to ~30-folds of its haploid genome size that was measured with quantitative PCR (1.17 Gb), were assembled into contigs. Scaffolding with Hi-C reads yielded a whole genome assembly containing 24 chromosome-scale sequences, with a scaffold N50 length of 47...

The inheritable impact of exposure to graphene oxide nanoparticles (GO NPs) on vertebrate germline during critical windows of gamete development remain undetermined to date. Here, we analyzed the transgenerational effects of exposure to nano-graphene oxide particles (nGO) synthesized in house with lateral dimensions 300-600 nm and surface charge of -36.8 mV on different developmental stages of germ cells (GCs): (1) during GCs undergoing early development and differentiation, and (2) during GCs undergoing gametogenesis and maturation in adulthood...

There is global concern that microplastics may harm aquatic life. Here, we examined the effects of fine polystyrene microplastics (PS-MPs, 2-μm diameter, 0.1 mg/L, 2.5 × 107 particles/L) on the behavior and the microbiome (linked to brain-gut interaction) of a fish model using medaka, Oryzias latipes. We found that shoaling behavior was reduced in PS-MP-exposed medaka compared with control fish during the exposure period, but it recovered during a depuration period. There was no difference in swimming speed between the PS-MP-exposed and control groups during the exposure period...

Triclocarban (TCC), a novel antimicrobial agent found in personal care products, has been extensively detected in marine environments. However, research on the toxic effects of TCC on marine organisms remains inadequate. This study delved into the subchronic toxic effects of TCC on the early life stages of marine medaka (Oryzias melastigma, O. melastigma), revealing that TCC could reduce embryo heart rate and hatching rate while diminishing the survival rate of larvae. Biomarker assays indicated that TCC could inflict damage on the embryos' antioxidant and nervous systems...

Methylosome protein 50 (Mep50) functions as a partner to protein arginine methyltransferase 5. MEP50 serves as a coactivator for both the androgen receptor and estrogen receptor in humans. Mep50 plays a crucial role in the development of germ cells in Drosophila. The precise role of Mep50 in oogenesis remains unclear in vertebrates. The objective of this study was to investigate the role of Mep50 in oogenesis in medaka fish. Disruption of Mep50 resulted in impaired oogenesis and the formation of multiple oocyte follicles in medaka...

The telencephalon of ray-finned fishes undergoes eversion, which is very different to the evagination that occurs in most other vertebrates. Ventricle morphogenesis is key to build an everted telencephalon. Thus, here we use the apical marker zona occludens 1 to understand ventricle morphology, extension of the tela choroidea and the eversion process during early telencephalon development of four teleost species: giant danio (Devario aequipinnatus), blind cavefish (Astyanax mexicanus), medaka (Oryzias latipes), and paradise fish (Macroposus opercularis)...

OBJECTIVES: Bone tissue in bony fish demonstrates a remarkable ability to regenerate, particularly evident following induction of extensive bone defects, such as fin amputation. This regenerative capacity has been reported to be promoted by the immunosuppressant FK506, yet its precise effects on bone cells during fin regeneration remains insufficiently elucidated. This study aims to investigate the effects of FK506 treatment on bone morphology, osteoblasts, and osteoclasts in the bony fin rays of osterix promoter-DsRed/TRAP promoter-EGFP double transgenic (Tg) medaka...

Progress in evolutionary developmental biology (evo-devo) has deepened our understanding of how intrinsic properties of embryogenesis, along with natural selection and population genetics, shape phenotypic diversity. A focal point of recent empirical and theoretical research is the idea that highly developmentally stable phenotypes are more conserved in evolution. Previously, we demonstrated that in Japanese medaka (Oryzias latipes), embryonic stages and genes with high stability, estimated through whole-embryo RNA-seq, are highly conserved in subsequent generations...

Somatic growth in vertebrates is regulated endocrinologically by the somatotropic axis, headed by the growth hormone (GH) and the insulin growth factor-I (IGF-I). Somatostatin (Sst), a peptide hormone synthesized in the hypothalamus, modulates GH actions through its receptors (Sstr). Four Sstr subtypes (Sstr 1-3 and 5) have been identified in teleosts. However, little is known about whether they have a specific function or tissue expression. The aim of this study was to determine the role of sstr2 and sstr5 in the growth of the medaka (Oryzias latipes)...

BACKGROUND: Eukaryotes' whole-genome sequencing is crucial for species identification, gene detection, and protein annotation. Oxford Nanopore Technology (ONT) is an affordable and rapid platform for sequencing eukaryotes; however, the relatively higher error rates require computational and bioinformatic efforts to produce more accurate genome assemblies. Here, we evaluated the effect of read correction tools on eukaryote genome completeness, gene detection and protein annotation. METHODS: Reads generated by ONT of four eukaryotes, C...

The intrinsic biomechanical properties of cancer cells remain poorly understood. To decipher whether cell stiffness modulation could increase melanoma cells' invasive capacity, we performed both in vitro and in vivo experiments exploring cell stiffness by atomic force microscopy (AFM). We correlated stiffness properties with cell morphology adaptation and the molecular mechanisms underlying epithelial-to-mesenchymal (EMT)-like phenotype switching. We found that melanoma cell stiffness reduction was systematically associated with the acquisition of invasive properties in cutaneous melanoma cell lines, human skin reconstructs, and Medaka fish developing spontaneous MAP-kinase-induced melanomas...

Androgen receptor (AR) agonists have strong endocrine disrupting effects in fish. Most studies mainly investigate AR binding capacity using human AR in vitro. However, there is still few methods to rapidly predict AR agonists in aquatic organisms. This study aimed to screen AR agonists of fish species using machine learning and molecular models in water-relevant list from NORMAN, a network of reference laboratories for monitoring contaminants of emerging concern in the environment. In this study, machine learning approaches (e...

Air pollution is a growing threat to human health. Airborne pollution effects on respiratory, cardiovascular and skin health are well-established. The main mechanisms of air-pollution-induced health effects involve oxidative stress and inflammation. The present study evaluates the potential of a polyphenol-enriched food supplement ingredient comprising Lippia citriodora , Olea europaea , Rosmarinus officinalis , and Sophora japonica extracts in mitigating the adverse effects of environmental pollution on skin and cardiopulmonary systems...

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The marine medaka is emerging as a potential behavioral model organism for ocean studies, namely on marine ecotoxicology. However, not much is known on the behavior of the species and behavioral assays lack standardization. This study assesses the marine medaka as a potential model for chemical communication. We investigated how short exposure to visual and chemical cues mediated the stress response to social isolation with the light/dark preference test (LDPT) and the open field test (OFT). After a 5-day isolation period, and 1 h before testing, isolated fish were randomly assigned to one of four groups: (1) placed in visual contact with conspecifics; (2) exposed to a flow of holding water from a group of conspecifics; (3) exposed to both visual and chemical cues from conspecifics; or (4) not exposed to any stimuli (controls)...

Microplastics (MPs) and nanoplastics (NPs) are emerging pollutants in the ocean, but their transfer and toxicity along the food chains are unclear. In this study, a marine rotifer (Brachionus plicatilis)-marine medaka (Oryzias melastigma) food chain was constructed to evaluate the transfer of polystyrene MPs and NPs (70 nm, 500 nm, and 2 μm, 2000 μg/L) and toxicity of 70 nm PS-NPs (0, 20, 200, and 2000 μg/L) on marine medaka after long-term food chain exposure...

Ageing is the greatest risk factor for a multitude of age-related diseases including sarcopenia -the loss of skeletal muscle mass and strength - which occurs at remarkable rates each year. There is an unmet need not only to understand the mechanisms that drive sarcopenia, but also to identify novel therapeutic strategies. Given the ease and affordability of husbandry, along with advances in genomics, genome editing technologies and imaging capabilities, teleost models are increasingly used for ageing and sarcopenia research...

In comparisons between mutant and wild-type genotypes, transcriptome analysis can reveal the direct impacts of a mutation, together with the homeostatic responses of the biological system. Recent studies have highlighted that, when the effects of homozygosity for recessive mutations are studied in non-isogenic backgrounds, genes located proximal to the mutation on the same chromosome often appear over-represented among those genes identified as differentially expressed (DE). One hypothesis suggests that DE genes chromosomally linked to a mutation may not reflect functional responses to the mutation but, instead, result from an unequal distribution of expression quantitative trait loci (eQTLs) between sample groups of mutant or wild-type genotypes...

Several immune-related genes, including Toll-like receptors (TLR), are associated with circadian rhythms in mammals. However, information on the circadian rhythmic expression of TLRs in fish is limited. In this study, we aimed to analyze the regulation of diel oscillations in the expression of TLR genes in Japanese medaka (Oryzias latipes). The expression analysis revealed diel expression patterns of tlr1, tlr5m, tlr21, and clock genes (bmal1 and clock1) under a 12 h light:12 h dark cycle. The clock gene response element (E-box) was identified in the transcriptional regulatory regions of tlr1, tlr5m, and tlr21...