Analysis of chorion hardening of eggs of rainbow trout, Oncorhynchus mykiss

We estimated changes of chorion hardness of rainbow trout (Oncorhynchus mykiss) egg by the use of three parameters, namely increase of resistance of an egg to rupture by extraneously applied pressure, decrease of solubility of chorion proteins in 8 mol/L urea and a change in the content of γ-glutamyl-ε-lysine crosslink. Unfertilized egg chorions became hardened after egg activation. During chorion hardening, 49, 56 and 65 kDa protein components of the chorion gradually disappeared, high molecular weight intermediates (113,160–170 and higher than 250 kDa) were newly formed and, finally, all components became undetectable by sodium dodecylsulfate-polyacrylamide gel electrophoresis. The content of γ-glutamyl-ε-lysine (γ-Glu-ε-Lys) crosslink in the chorion increased after hardening. Chorion hardening was inhibited by the incorporation of monodansyl-cadaverine, a competitive inhibitor for transglutaminase (TGase), into the chorions. TGase activity was detected in unfertilized eggs and localized in the chorion fraction rather than in the ooplasmic fraction. The findings suggest that chorion hardening depends upon polymerization of the chorion components by TGase-dependent γ-Glu-ε-Lys crosslink formation.     

The effect of acidification on oogenesis of rainbow trout during sex differentiation

Rainbow trout larvae were kept in acid water from 16 to 55 days after hatching. Initially, the acid environment stimulated a significant increase of gametes in the gonads of females at all developmental stages, but after longer exposure the stimulation was replaced by inhibition of gonadal development in the treated fish. In some fish, gamete reserves increased, while in others there was increased growth and maturation of late-generation oocytes.     

Influence of growth rate on white muscle dynamics in rainbow trout and brook trout

In trout, fast growth stimulated white muscle fibre hypertrophy ( P 0·001) and hyperplasia ( P <0·01) in outer fibres but not in deep fibres. Glycogen was most prevalent in outer fibres ( P <0·01) and in brook trout ( P <0·01) that on average had three to four times larger fibres than rainbow trout.     

The in vitro effect of hydrogen peroxide on vaginal microbial communities

This study presents a series of experiments carried out in order to elucidate the role of H2O2 in antimicrobial activity of lactobacilli. Vaginal swabs were collected from 60 premenopausal women and checked for pH and Nugent score, and Lactobacillus species were cultured, phenotyped and genotyped. The main outcome measures involved: (1) species of vaginal lactobacilli most effective in liberating H2O2, (2) minimal microbicidal concentrations of added H2O2, (3) kinetics of H2O2 liberation in relation to oxygen tension, (4) antimicrobial activity of pure H2O2 versus one produced by selected vaginal lactobacilli and the total activity of their culture supernatants. Results showed that H2O2 was liberated especially by: Lactobacillus delbrueckii, Lactobacillus acidophilus, Lactobacillus crispatus, Lactobacillus johnsonii and L. gasseri. Hydrogen peroxide reached concentrations from 0.05 to 1.0 mM, which under intensive aeration increased even up to 1.8 mM. Microorganisms related to vaginal pathologies show varied resistance to the action of pure H2O2. Most potent inhibitory activity against bacteria and yeasts was presented by Lactobacillus culture supernate producing H2O2, followed by the nonproducing strain and pure H2O2. To conclude - the antimicrobial activity of lactobacilli is a summation of various inhibitory mechanisms in which H2O2 plays some but not a crucial role, in addition to other substances.     

Circadian rhythms of demand-feeding and locomotor activity in rainbow trout

Under free-running conditions, most rainbow trout displayed circadian feeding rhythms, although the expression of circadian rhythmicity depended on the experimental condition: 16·7% of fish under constant dim light (LL dim), 66·1% under a 45 :45 min light-dark cycle (LD pulses), and 83·8% under constant light (LL). Under LD pulses, the period length of the free-running rhythms for feeding was significantly shorter (21·9 ± 0·7 h, n =8) than under LL (26·2 ± 0·3 h, n =10). Period length for locomotor activity under LL was 25·8 ± 0·6 h ( n =4). Under LD conditions, the daily demand-feeding profile was always confined to the light phase and chiefly composed of two main episodes, directly after lights on (light elicited) and in anticipation to lights off (endogenous). Contrasting to feeding, the diel locomotor activity profile varied remarkably: a diurnal activity pattern at the bottom, while a clearly nocturnal pattern at the surface. These results contribute to a better understanding of feeding and locomotor rhythms of rainbow trout, providing evidence for the existence of a biological clock involved in their circadian control. This finding contrasts with the previously recorded lack of an endogenous oscillator in the pineal organ driving the rhythmic secretion of melatonin, which suggests different locations from the pineal for the circadian pacemakers in this species.     

Natural reproduction of anadromous rainbow trout in Norway

Six naturally reproduced 0+ rainbow trout were caught in a Norwegian river in 1994. This is the second report and first recorded sample of descendants from anadromous parents found in a Norwegian river. If this is not a unique event, the finding bodes ill for future conservation of native anadromous Salmonids.     

Effect of AC electroshock on blood features in juvenile rainbow trout

Brief AC electroshock caused significant elevations in plasma cortisol, glucose, osmolality, and chloride levels in rainbow trout within 15min, but plasma protein was reduced at 3h. Circulating granulocytes had declined by 15min, but other haematological features remained unchanged. Thus, AC electrofishing would not be suitable for monitoring physiological conditions in trout if short delays are encountered before blood is sampled.     

Assessment of cardiac output as a predictor of metabolic rate in rainbow trout

When water temperature was increased from 12 to 27°C at a rate of 2°C h⁻¹, oxygen consumption of rainbow trout Oncorhynchus mykiss was correlated strongly with both heart rate and blood oxygen extraction but the relationship with cardiac output was variable and weak. On the other hand, when water temperature was decreased from 21 to 12°C at a rate of 0·5°C h⁻¹, oxygen consumption was correlated with both heart rate and cardiac output but not with blood oxygen extraction. When fish were forced to swim increasingly faster, heart rate, cardiac output and blood oxygen extraction all correlated positively with oxygen consumption. For both cardiac output and heart rate, the slope of the regression line with oxygen consumption was elevated significantly more when the fish were forced to swim at increasingly higher swimming speeds than when water temperature was increased or decreased. The variation of the regression lines between cardiac output and oxygen consumption indicated that cardiac output presents few advantages over heart rate as a predictor of metabolic rate.     

Primary cell culture from gill explants of rainbow trout

Primary cultures of gill cells were initiated from gill filament explants of rainbow trout, Oncorhynchus mykiss . The explants were cultured in Leibovitz l -15 medium with 5, 10 or 20% foetal calf serum (FCS) and l -glutamine. The attachment efficiency was serum-dependent though increased FCS concentration did not stimulate further outgrowth of cells. The explants produced cell outgrowth 24 h after attachment as a sheet of cells which exhibited characteristics of gill pavement epithelial cells as indicated by surface microridges revealed by scanning electron micrographs. There was high proliferation for the first 14 days then a stable plateau for 30 days followed by a decline phase from 45 days. Following removal of cells, the explants produced further cell outgrowth which was especially active at the proliferation phase (14 days). Removal of these cells caused the explants to produce a further proliferation of cells reaching confluence in 10–14 days. After the third cell removal cell outgrowth from explants showed migratory activity but did not develop to resemble gill epithelial cells. The use of gill explants to establish primary cultures of fish gill cells has advantages which include longevity of the culture and successive proliferations from explants which could provide a useful tool for the investigation of long-term processes in cellular biology and reduce the number of culture preparations.     

利用RAPD法对虹鳟鱼基因组DNA多态性研究初报

本文通过利用RAPD（随机扩增多态DNA）方法,选用20种10bp的随机引物（OPC－01－OPC—20）,用于虹鳟鱼基因组DNA多态性分析,其中发现一种引物（OPC－02）在虹鳟鱼群体中能扩增出多条带,说明该引物能反映其基因组DNA的多态性,可用于检测出不同品系间的差异。     

Competitive ability is related to metabolic asymmetry in juvenile rainbow trout

Of 55 size–matched pairs of juvenile rainbow trout Oncorhynchus mykiss , each consisting of one high and one low relative metabolic rate fish (relative size difference <5%), the high relative metabolic rate fish was dominant in 36 pairs (65·5%), significantly more often than expected by chance. The probability of a fish winning was related to its relative metabolic rate (measured prior to introduction into the test arena); the higher the relative metabolic rate of a fish compared to its opponent, the greater its probability of being dominant. In the 36 pairs of fish where the low relative metabolic rate fish was the subordinate, its competitive ability was significantly correlated with how closely the two fish were matched in terms of their relative metabolic rates. The smaller the difference between the relative metabolic rates of the dominant high relative metabolic rate fish and subordinate low metabolic rate fish, the greater the competitive ability and feeding success of the low relative metabolic rate subordinate. However, no such relation was found in the 19 pairs of fish where the high relative metabolic rate fish was the subordinate. In these pairs, the competitive ability of the subordinate high relative metabolic rate fish was correlated with its size relative to its dyad partner. The larger the dominant low relative metabolic rate fish, the lower the competitive ability of the subordinate high relative metabolic rate fish.     

Successful shoreline spawning of rainbow trout in two Canadian alpine lakes

Successful shoreline spawning of rainbow trout Oncorhynchus mykiss has occurred for several decadal periods without hatchery stocking in Joe and Harry Lakes, two small (5–6 ha) alpine waters at >2000 m elevation in south-central British Columbia. Redds are most concentrated near groundwater inflows, in Joe Lake mainly on sand and gravel, in Harry Lake mainly over rocks and boulders.     

Absence of developmental incompatibility in hybrids between rainbow trout and two subspecies of cutthroat trout

We examined the developmental rate of hybrids between rainbow trout (Salmo gairdneri) and two subspecies of cutthroat trout: westslope cutthroat trout (Salmo clarki lewisi) and Yellowstone cutthroat trout (Salmo clarki bouvieri). These taxa show considerable genetic divergence at 42 structural loci encoding enzymes; the mean Nei's d between the rainbow trout and the two species of cutthroat trout is 0.22. We used four measures of developmental rate: time of hatching and yolk resorption, rate of increase in activity of four enzymes, and time of initial detection of seven isozyme loci. The two cutthroat trout subspecies reached hatching and yolk resorption earlier than rainbow trout. Cutthroat trout had higher relative enzyme activities than rainbow trout from deposition of eye pigment to hatching. There was no difference in the rate of increase in enzyme activity or time of initial expression of these loci between these species. Hybrids showed developmental rates intermediate or similar to that of the parental species using all measures. Our results indicate an absence of regulatory and developmental incompatibility between these taxa.This research was supported by NSF Grants ISP-8011449 and BSR-8300039. M.M.F. was supported by a postgraduate scholarship from the Natural Sciences and Engineering Research Council of Canada.     

Effect of reward level on individual variability in demand feeding activity and growth rate in Arctic charr and rainbow trout

Groups of Arctic charr and rainbow trout were fed by using demand feeders and their individual trigger actuations registered with a PIT-tag (Passive Integrated Transponder) system. Food was supplied at two reward levels, low and high, to five replicate groups of each species for 21 to 27 days. The reward level was defined as the amount of food obtained in response to a single trigger actuation. The effects of reward level on individual demand feeding activity and growth rale were assessed.
As a result of high demand feeding activity, the daily food rations for trout were in excess of their needs at both reward levels. This can be ascribed to the fact that they compensated a low reward level by increasing their bite activity. In contrast, demand feeding activity in charr did not differ significantly between reward levels. Instead, resulting food rations were limiting and excessive, at low and high reward levels, respectively. The variation in bite activity between individuals (measured as their proportional contribution to the total number of trigger actuations within a group) for charr was significantly higher in the low-reward treatment than in the high-reward level. For trout, the variation in bite activity did not differ significantly between treatments. Differences in response to reward level are suggested to be due to the fact that the social hierarchy is weaker in trout than in charr; i.e. the differences in bite activity between dominant and non-dominant individuals are smaller in trout. At both reward levels, the benefit of being dominant, measured in terms of growth rate was significant for charr but non-significant for trout.     

Brain distribution of myosin Va in rainbow trout Oncorhynchus mykiss

This study presents data on myosin Va localization in the central nervous system of rainbow trout. We demonstrate, via immunoblots and immunocytochemistry, the expression of myosin Va in several neuronal populations of forebrain, midbrain, hindbrain and spinal cord. The neuronal populations that express myosin Va in trout constitute a very diverse group that do not seem to have many specific similarities such as neurotransmitters used, cellular size or length of their processes. The intensity of the immunoreactivity and the number of immunoreactive cells differ from region to region. Although there is a broad distribution of myosin Va, it is not present in all neuronal populations. This result is in agreement with a previous report, which indicated that myosin Va is approximately as abundant as conventional myosin II and kinesin, and it is broadly involved in neuronal motility events such as axoplasmatic transport. Furthermore, this distribution pattern is in accordance with what was shown in rats and mice; it indicates phylogenetic maintenance of the myosin Va main functions.     

Recombination is suppressed over a large region of the rainbow trout Y chromosome

The previous genetic mapping data have suggested that most of the rainbow trout sex chromosome pair is pseudoautosomal, with very small X-specific and Y-specific regions. We have prepared an updated genetic and cytogenetic map of the male rainbow trout sex linkage group. Selected sex-linked markers spanning the X chromosome of the female genetic map have been mapped cytogenetically in normal males and genetically in crosses between the OSU female clonal line and four different male clonal lines as well as in outcrosses involving outbred OSU and hybrids between the OSU line and the male clonal lines. The cytogenetic maps of the X and Y chromosomes were very similar to the female genetic map for the X chromosome. Five markers on the male maps are genetically very close to the sex determination locus ( SEX ), but more widely spaced on the female genetic map and on the cytogenetic map, indicating a large region of suppressed recombination on the Y chromosome surrounding the SEX locus. The male map is greatly extended at the telomere. A BAC clone containing the SCAR (sequence characterized amplified region) Omy - 163 marker, which maps close to SEX , was subjected to shotgun sequencing. Two carbonyl reductase genes and a gene homologous to the vertebrate skeletal ryanodine receptor were identified. Carbonyl reductase is a key enzyme involved in production of trout ovarian maturation hormone. This brings the number of type I genes mapped to the sex chromosome to six and has allowed us to identify a region on zebrafish chromosome 10 and medaka chromosome 13 which may be homologous to the distal portion of the long arm of the rainbow trout Y chromosome.     

Plasma levels of gonadotropin and 17α,20β-dihydroxy-4-pregnen-3-one in relation to spawning behaviour of rainbow trout, Oncorhynchus mykiss(Walbaum)

Manipulation of the opportunity to spawn was used to investigate the relationship between endocrine events, egg viability and spawning behaviour in female rainbow trout. Females were prevented from spawning by isolating them from males and gravel for up to 21 days after ovula- tion. Blood samples were taken before pairing with a male, at the onset of nesting activity, and at the completion of spawning. Plasma hormone levels of gonadotropin (GtH) and 17α,20β-dihydroxy-4-pregnen-3-one (17,2OP) were measured by specific radioimmunoassays. There were no qualitative or quantitative differences in the spawning behaviour of females paired on the day of ovulation or 7. 14, or 21 days after ovulation. There was a general decrease in the viability of eggs with increasing retention times. In females paired on the day of ovulation, or after 7 or 14 days, GtH levels increased with the onset of nesting behaviour and declined as fish reached the post-spawning condition. By day 21, GtH levels before pairing were significantly higher than prepairing levels in the other three treatment groups, and did not increase at the onset of nesting, or decrease in post-spawning fish. Plasma 17,20P remained high in prepairing and nesting samples of all four groups and declined to low levels in fish in post-spawning condition. In females paired on the day of ovulation there was a significant increase in 17,20P from the prepairing to the nesting stage. These results suggest that 17,20P plays a key role in the synchronization of behavioural and maturational events at the time of spawning.     

Influence of temperature on silver accumulation and depuration in rainbow trout

To assess the influence of water temperature on silver uptake, rainbow trout Oncorhynchus mykiss ( c . 50 g; held at 13° C) were exposed to 0·1 μM AgNO₃ in ion‐poor water for 1 week at 4 and 16° C without previous temperature acclimation. To assess the influence of temperature on elimination of previously accumulated Ag, rainbow trout were exposed to 0·1 μM AgNO₃ in ion‐poor water for 1 week at 12° C, then were randomly divided amongst two Ag‐free water containers, differing only in temperature (3 and 16° C), for 2 months. In the uptake study greater accumulation of Ag was seen in the gills, plasma and especially the livers and bile of 'warm' rainbow trout (16° C) compared to 'cold' rainbow trout (4° C), which can be explained by the higher metabolic rates of the warmer fish. In the depuration study there was no net elimination of Ag from the livers and bile but there was biphasic elimination of Ag from the gills and plasma of 'warm' and 'cold' fish, but with few differences between them. This indicated that temperature‐dependent processes were less important in Ag elimination than in Ag uptake. Toxicokinetic modelling of Ag uptake by livers indicated four‐fold greater uptake of Ag by 'warm' rainbow trout compared to 'cold' rainbow trout (one compartment uptake model). Elimination of previously accumulated Ag from the plasma was best fitted by a two compartment rate‐constant based model, with approximately half the plasma Ag load eliminated within 24 h, followed by slower elimination of Ag over 2 months.