Male Rainbow Trout (male + rainbow_trout)

Distribution by Scientific Domains

Selected Abstracts

Dynamics of 17,-Ethynylestradiol exposure in rainbow trout (Oncorhynchus mykiss): Absorption, tissue distribution, and hepatic gene expression pattern

Ann D. Skillman
Abstract 17,-Ethynylestradiol (EE2) is a synthetic estrogen identified in sewage effluents. To understand better the absorption kinetics of EE2 and the induction of vitellogenin (VTG) and estrogen receptor , (ER,) mRNA, we subjected male rainbow trout (Onchorynchus mykiss) to continuous water exposures of 125 ng/L of EE2 for up to 61 d. Trout were either repetitively sampled for blood plasma or serially killed at selected time intervals. Vitellogenin, ER, mRNA, and EE2 were measured using enzymelinked immunosorbent assay and using quantitative polymerase chain reaction and gas chromatography,mass spectrometry, respectively. In separate experiments, trout were exposed to EE2 for 7 d, and hepatic gene expression was assessed using a low- and high-density cDNA microarray. The EE2 was rapidly absorbed by the trout, with an apparent equilibrium at 16 h in plasma and liver. The ER, mRNA levels also increased rapidly, reaching near-peak levels by 48 h. In contrast, plasma levels of VTG continuously increased for 19 d. After 61 d, tissues with the highest levels of VTG were the liver, kidney, and testes. Microarray-based gene expression studies provided unexpected results. In some cases, known estrogen-responsive genes (e.g., ER,) were unresponsive, whereas many of the genes that have no apparent link to estrogen function or EE2 toxicity were significantly altered in expression. Of the two microarray approaches tested in the present study, the high-density array appeared to be superior because of the improved quality of the hybridization signal and the robustness of the response in terms of the number of genes identified as being EE2 responsive. [source]

Prostaglandins in rainbow trout (Oncorhynchus mykiss Walbaum, 1792) sperm biology , searching for answers

R. K. Kowalski
Summary The purpose of this study was to determine the concentrations of prostaglandins E2 and F2, (PGE2 and PGF2,) in the blood, testis and seminal plasma of mature male rainbow trout and in the ovarian fluid to assess the effects of these prostaglandins on sperm motility parameters when present in activation media. Also prolonged incubation with prostaglandins on sperm motility and calcium influx were studied. The profile of PGE2 and PGF2, differed in concentration between blood, testicular supernatant and seminal plasma. PGE2 was predominant in the blood sample (0.29 ng ml,1) and testicular supernatant (3.1 ng ml,1) whereas their level in seminal plasma was lower than PGF2, (0.23 ng ml,1). The concentrations of PGF2, in blood, testis and seminal plasma were 0.04, 0.99, 1.3 ng ml,1, respectively. In the ovarian fluid the concentrations of both prostaglandins were higher than in the male reproductive tract. Adding both prostaglandins to activation buffer (at concentrations 15 and 70 ng ml,1) had no effect on any CASA parameters. Calcium influx related to rainbow trout sperm incubations with PGE2, and PGF2, was not detected. After 24 h incubation of sperm in artificial seminal plasma solution without and with prostaglandins all sperm samples increased their motility potential and intracellular calcium concentration. Therefore, this effect was not related to the presence of prostaglandins. In summary PGE2, and PGF2, were present in the rainbow trout male reproductive tract, and their profile varies from that of blood, testis and seminal plasma. The specific role of both prostaglandins in salmonid sperm biology remains unclear. [source]

A molecular analysis of hybridization between native westslope cutthroat trout and introduced rainbow trout in southeastern British Columbia, Canada

E. Rubidge
Restriction site variation in the Ikaros gene intron was used to assess the incidence of westslope cutthroat trout (Oncorhynchus clarki lewisi), rainbow trout (O. mykiss) and interspecific hybrids at 11 localities among eight streams tributary to the upper Kootenay River system in south-eastern British Columbia, Canada. Out of 356 fish assayed by this technique, hybrids (n=16) were found at seven of the 11 sites across five different streams. Rainbow trout (n=6) were found at two of the 11 sites. Analysis of hybrids with a second genetic marker (heat shock 71 intron) indicated that most represented either backcrosses to both westslope cutthroat and rainbow trout, or post F1 hybrids. Mitochondrial DNA analysis indicated that hybrid matings occur between male rainbow trout and female westslope cutthroat trout and vice versa. Comparison of present hybridization in five tributaries relative to an allozyme-based analysis in the mid-1980s, that documented hybrids in only a single tributary of seven that were common to the two studies, suggests that hybridization and introgression has increased in upper Kootenay River tributaries. The present analysis is a conservative estimate of genetic interaction between the species because introgression was not tested in the majority of samples. Identification of genetically pure westslope cutthroat trout populations, and why they might be resistant to introgression from rainbow trout, are crucial conservation priorities for this unique subspecies of cutthroat trout. [source]

Effect of GnRHa injection on milt volume in recently stripped rainbow trout Oncorhynchus mykiss

Fatemeh Paykan Heyrati
Abstract In this study, the effect of gonadotropin-releasing hormone agonist (GnRHa) injection on milt production in spent rainbow trout was investigated. On day 0, 25 newly matured male rainbow trout (Oncorhynchus mykiss) were stripped manually, and sperm quantity (vol: mL fish,1) and quality, spermatocrit (%), sperm count (cell mL,1), motile sperm percentage and motility duration (s) were evaluated. After stripping, fish were randomly divided into five groups: intact; sham (injected with propylene glycol as a hormone vehicle); and groups receiving 4, 8 or 16 ,g kg,1 BW of [d -Ala6 Des-Gly10] mGnRHa. On day 7, the fish were stripped again and the same sperm characteristics as on day 0 were measured. At the beginning of the experiment, there were no significant differences in any of the sperm quantity characteristics between groups. On day 7, expressible milt volume was significantly reduced compared with day 0 (P<0.05, t -test) in the intact and sham groups but milt quality remained the same (P>0.05, t -test). The present study shows that GnRHa injection with a concentration as low as 4 ,g kg,1 BW after first stripping could prevent a significant reduction in milt quantity collected 7 days later without any adverse effects on sperm quality. [source]