Search

In this study, we examined differences among the gonadotropin-inhibitory hormone (GnIH), kisspeptin 1 (Kiss1), Kiss 1 receptor (G-protein-coupled receptor 54; GPR54), melatonin receptor 1 (MT1), and melatonin levels in brain cells of goldfishCarassius auratusexposed to white fluorescent light and three light-emitting diode (LED) wavelength and melatonin treatments in the culture medium. In the green and blue LED treatment groups, GnIH and MT1 mRNA expression levels were significantly lower than in the other groups; conversely, levels significantly increased in the melatonin treatment groups. Additionally, expression levels of Kiss1 and its receptor, GPR54, in the white fluorescent and red LED light groups were significantly lower than the other groups, but levels also significantly decreased in the melatonin treatment groups. These results suggest that white fluorescent and red wavelengths downregulate the production of neurohormones in the brains ofC. auratusand thus may inhibit sexual maturation in goldfish. [ABSTRACT FROM PUBLISHER]

We investigated the effects of light spectra on circadian rhythms under high thermal stress using red, green and purple light-emitting diodes (LEDs). To assess differences in circadian rhythms during high thermal stress under different LED light spectra, we measured changes in the expression of the melatonin receptor 1 (MT1),period 2(Per2), andcryptochrome 1(Cry1) genes and MT1 protein, and in the plasma melatonin and glucose levels. Under high water temperatures and red light conditions, MT1 expression and plasma melatonin and glucose were significantly higher than under low water temperatures and other light spectra, butPer2andCry1expressions were significantly lower. Thus, high water temperatures induce oxidative stress and melatonin acts as an antioxidant molecule. Further, melatonin regulates circadian rhythms via clock genes, and green and purple lights may be suitable for maintaining circadian rhythms in goldfishCarassius auratus, as these wavelengths generally penetrate freshwater more efficiently than does red light. [ABSTRACT FROM AUTHOR]

The objective of this study was to test the effects of ophthalmectomy on the circadian rhythms in response to various wavelengths in yellowtail clownfish. The responses were evaluated by measuring rhodopsin (RH) and melatonin receptor 1 (MT1) mRNA and protein expression, and plasma melatonin levels. The RH, MT1 mRNA, and protein expression in ophthalmectomized fish were significantly lower than in intact fish. However, RH and MT1 mRNA and protein expression levels in green and blue light-emitting diode groups were similar between intact and ophthalmectomized fish. Furthermore, we found that the number of the RH-immunoreactive cells observed in the retina was almost in agreement with mRNA and protein expression patterns. These findings suggest that circadian rhythm involves the perception of light by the eye and the transduction of this signal through the circadian rhythm axis. Furthermore, short wavelengths lights may be most suitable for control of the circadian rhythm in fish. [ABSTRACT FROM AUTHOR]

The study aimed to test differences in immune ability and clock gene expression between intact fish and ophthalmectomized yellowtail clownfish exposed to light-emitting diodes (LEDs). Clock genes (Period 2, Per2; Cryptochrome 1, Cry1) and melatonin receptor 1 mRNA and protein expression in all wavelengths groups were significantly lower in ophthalmectomized fish than in intact fish, but ophthalmectomized fish exposed to green and blue LEDs showed expression levels similar to intact fish. Furthermore, indicators of immune activity (immunoglobulin M; IgM mRNA and protein expression and lysozyme activity) were significantly higher in ophthalmectomized fish exposed to green and blue LEDs than other groups of ophthalmectomized fish. Also, plasma H2O2levels in ophthalmectomized fish exposed to green and blue LEDs showed their levels similar to intact fish. These results suggest that short wavelengths affect the daily rhythms of fish and enhance the immune ability, even in the absence of an eye. [ABSTRACT FROM AUTHOR]

We investigated the regulatory effects of recombinant growth hormone (rGH) on growth and immunity in an ornamental seawater fish species, the cinnamon clownfish (Amphiprion melanopus). Cinnamon clownfish received intraperitoneal injections of rGH or saline at doses of 0.1 or 1 µg/g, weekly, for 12 weeks. At the end of the experiment, the rGH injection group exhibited the greatest total length (5.3±0.3 and 5.6±0.2 cm, respectively, for the two doses). Moreover, after injection of rGH, the expression levels of pituitary GH mRNA and liver insulin-like growth factor I (IGF-I) mRNA increased significantly (by 18.9-fold and 5.7-fold, respectively), as assessed by quantitative real-time polymerase chain reaction, while the splenic levels of immunoglobulin M protein increased significantly (by 10.5-fold) as assessed by Western blot analysis. Plasma lysozyme and melatonin levels also increased by 2.1- and 1.37-fold, respectively, over those of the control group. Plasma alanine and aspartate aminotransferase levels at 12 weeks (764±46.4 and 3002±101.2 IU/l, respectively) were significantly higher than those at baseline; however, treatment with rGH decreased these values at 12 weeks (276±30.4 and 600.5±59.2 IU/l, respectively). These findings support the hypothesis that rGH plays important roles in the regulation of the GH–IGF-I axis for growth and immunity in the cinnamon clownfish. [ABSTRACT FROM AUTHOR]

The study aimed to test differences in the hormones of the hypothalamus–pituitary–gonad axis, Kisspeptin (Kiss) and sex steroids, and the sexual maturation of goldfish (Carassius auratus) according to various photoperiods: 10 h light (L):14 h dark (D) (short day), 12L:12D (control), and 14L:10D (long day). To investigate the sexual maturation under various photoperiods, quantitative real-time PCR (QPCR) assays for salmon gonadotropin-releasing hormone, chicken gonadotropin-releasing hormone, gonadotropin hormones (GTHs), Kisspeptin 1 (Kiss1), and its receptor, G protein-coupled receptor 54 (GPR54), were developed. mRNA expression was monitored in cultured pituitary cells (in vitro) of various photoperiod groups. Furthermore, we injected or treated the animals with Kiss and found that Kiss treatment increases the mRNA expression levels of GTHs. We measured the plasma follicle-stimulating hormone (FSH), luteinizing hormone (LH), and 17α-hydroxypregnenolone levels. The gonadotropin-releasing hormones (GnRHs), GTHs, Kiss1/GPR54 mRNA expression, plasma FSH, LH, and 17α-hydroxypregnenolone levels in the 14L:10D group were significantly higher than in the other groups. These results suggest that light length regulates sex maturation by GnRH and Kiss1 in the brain of the goldfish. [ABSTRACT FROM PUBLISHER]

Benzo[a]pyrene (BaP) is generated by the incomplete combustion of organic substances such as oil and coal, and is a widespread organic environmental contaminant in terrestrial and aquatic ecosystems. To determine the effects of BaP on organisms, we investigated its time- and dose-related effects on the levels of cytochrome P4501A (P4501A) mRNA in the liver and gills of the olive flounder (Paralichthys olivaceus) using quantitative polymerase chain reaction (QPCR) and measured the plasma glucose, cortisol, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels. The full-length olive flounder P4501A cDNA consists of 1566 nucleotides and encodes a 521-amino-acid protein. In the liver and gills, the expression of P4501A mRNA was highest 6 h after exposure to both 10 and 30 µg l-1 BaP, and then decreased. In addition, the plasma parameters increased with exposure. These results suggest that P4501A plays an important role in the detoxification of BaP, which stressed the olive flounder. Therefore, these physiological parameters may be indicators of BaP-induced stress responses. [ABSTRACT FROM AUTHOR]

We cloned complementary DNA (cDNA) encoding the arginine vasotocin receptor (AVT-R) from the kidney of olive flounder (Paralichthys olivaceus). Olive flounder AVT-R cDNA consists of 1155 bp, and encodes a protein of 384 amino acids. To investigate the stress responses and osmoregulatory abilities of olive flounder in changing salinities (35, 17.5, 8.75, 4, and 0 psu), we examined the expression of AVT-R, prolactin (PRL), and PRL receptor (PRL-R) messenger RNA (mRNA) in osmoregulatory organs using quantitative real time PCR (QPCR). AVT-R and PRL-R were expressed in the gill, kidney, and intestine, whereas PRL mRNA was expressed only in the pituitary gland. In addition, we measured the levels of plasma glucose, cortisol, aspartate aminotransferase (AST), and alanine aminotransferase (ALT). The mRNA expression and plasma parameters increased in hypoosmotic environments. Furthermore, osmolality decreased significantly according to salinity concentration decreased. These results suggest that AVT-R, PRL, and PRL-R mRNA play important roles in the hormonal regulation of osmoregulatory organs, thereby improving the osmoregulatory ability of olive flounder in hypoosmotic environments. [ABSTRACT FROM AUTHOR]