Seasonal variations in sex steroids of female rainbow trout (Salmo gairdneri Richardson)

17β-oestradiol, testosterone, 11 -ketotestosterone and calcium were measured in plasma of female rainbow trout over the course of a single spawning season. The patterns of rise and fall of the levels of 17β-oestradiol and calcium during sexual maturation were similar to those demonstrated by other workers. Very high levels of testosterone were found in plasma of sexually mature fish—mean level 211 ng ml-1 in November and 115 ng ml-1 in January. Ovulation occurred from December to February.     

The effect of exercise on plasma cortisol and blood sugar levels in the rainbow trout, Salmo gairdnerii Richardson

Preliminary experiments were performed to determine the diurnal variation in cortisol, using trout which had been cannulated three days previously. These results indicated that cortisol levels were reasonably stable between 10.00 and 18.00 hours, thus permitting experimentation during this period without diurnal fluctuations masking the cortisol response. Uncannulated fish were exercised in a flume for 2 h at 1, 2.6 and 5 bl s^-1 and plasma samples taken from groups of five animals at 15, 30, 60 and 120 min after the start of exercise and at 1½, 12 and 24 h after the exercise ceased. The cortisol levels in all cases were elevated after 15 min, but the magnitude of the elevation increased with swimming speed. At 1 bl s^-1 the cortisol levels increased from 76.4 (± 20.4) to 129.2 (± 20.4) ng ml^-1 [mean (± s.d. )]. At 2.6 bl s^-1 the increase was from 72.4 (± 17.1) to 254.4 (± 34.4) ng ml^-1 and at 5 bl s^-1 the increase was from 69.5 (± 27.5) to 326.4 (± 39.0) ng ml^-1. The cortisol levels were stable over the exercise period and all groups recovered to baseline levels after 24 h, though the sample taken 12 h after the termination of exercise was elevated due to regular nocturnal increases in cortisol levels. There were no dramatic changes in blood sugar levels during and after exercise at 1 and 3.2 bl s^-1.     

Genetic engineering in rainbow trout, Salmo gairdnerii Richardson, by the suppression of meiotic and mitotic metaphase

Diploid gynogenesis in rainbow trout eggs was induced by a heat shock applied after fertilization with UV irradiated sperm. Survivals were high when the heat treatment was given soon after fertilization at times corresponding to the completion of egg meiosis but were low at all other times. Increases in survival occurred, however, when the heat treatment was given at 4 h 30 min and 5 h after fertilization, with an incubation temperature of 10°C, and at 9 h after fertilization, with an incubation temperature of 5°C. Electrophoretic analysis at three enzyme loci demonstrated a significant increase in homozygous offspring from eggs given these later heat treatments when compared to offspring from eggs treated between 40 and 70 min after fertilization, again with an incubation temperature of 10°C. There was still a significant frequency of heterozygotes in these groups, however, probably of spontaneous origin via diploidization during meiosis. No tetraploid alevins were observed after normal fertilization and attempted suppression of first mitosis.     

Seasonal and diurnal rhythms of thyroidal status in the rainbow trout, Salmo gairdneri Richardson

The concentrations of thyroxine (T₄) and triiodothyronine (T₃) in the blood plasma of rainbow trout ( Salmo gairdneri Richardson) at intervals throughout the year have been measured by a chemically specific gas-liquid chromatographic (GLC) method. Mean hormone levels showed a seasonal variation, maximal levels of both hormones occurring in winter and minimal concentrations in mid summer. An apparent secondary maximum in mean T₄ and T₃ concentrations was observed in spring. (T₄)/(T₃) ratios have been found to be highest in winter and lowest in summer. A radioimmunoassay procedure, validated by GLC analyses, revealed the presence of a diurnal rhythm in serum T₄ levels of trout sampled in September and in April.     

Enzyme activities of plasma and selected tissues in rainbow trout Salmo gairdneri Richardson

This paper describes the determination in rainbow trout of the normal levels in the plasma of eight enzymes known to be significant in animal pathology. Some relationships between plasma enzyme levels and the enzyme activities in selected tissues are discussed. For LDH which is ubiquitously distributed, we chose, by way of saturation tests, the optimum concentrations of pyruvate and NADH in the assay medium. The LDH 'isoenzyme ratio' was determined for heart tissue, liver, and white muscle. When blood was withdrawn from caudal vessels, we observed a net increase of plasma enzyme activities, mainly of CPK and LDH, which was demonstrated to originate from surrounding muscle. Thus cardiac sampling was the only suitable way of obtaining blood for this kind of study. Slightly haemolyzed blood appeared suitable for enzyme determinations except for Alk Pase which is about 50 times more concentrated in erythrocytes than in plasma. CPK was highly concentrated in the heart and the muscle, GOT was concentrated in the heart while the liver appeared to be a valuable source of GDH (as well as the kidney) and GPT.     

Sexual maturation in triploid rainbow trout, Salmo gairdneri Richardson

This paper compares some morphological and endocrinological characteristics of diploid and triploid rainbow trout.
Significant differences were found between diploid and triploid females in GSI, condition factor, gut weight, liver weight and percentage dress-out, and between diploid and triploid males in GSI, condition factor and gut weight.
Diploid females had large, well-developed ovaries containing yolk-filled secondary oocytes whereas the triploids had only string-like ovaries containing nests of oogonia. No primary oocytes were present.
All the diploid males produced copious quantities of milt but it was possible to express a thin, watery milt containing motile spermatozoa from only two of the 12 triploid males. Testes weights in triploids were similar to those of diploids but, while the diploid testes were packed with spermatozoa, those of the triploids consisted mainly of spermatocytes and spermatids with few spermatozoa present. Measurements of the heads of spermatozoa revealed that those from triploids were larger and had a wider size range than those from diploids.
Levels of testosterone and 11-ketotestosterone in triploid and diploid males were not significantly different. However, levels of testosterone and 17β-oestradiol in diploid females were considerably higher than those of triploid females.     

Compensatory growth in the rainbow trout, Salmo gairdneri Richardson

The effect of a period of starvation and subsequent refeeding on the weight and length of rainbow trout at different times of the year has been investigated. Fish that have been starved for 3 weeks and then fed for 3 weeks show a weight gain equivalent to or greater than that of fish fed normally for the 6 week period, in four out of the five periods studied. The study provided evidence of the adaptation of the fish to starvation followed by what may be termed compensatory growth once feeding was resumed. The length changes of the fish indicate that the weight gains were due to growth rather than increases in gut fat deposits or increased water uptake.     

Estimation of growth potential by measurement of tissue protein synthetic rates in feeding and fasting rainbow trout, Salmo gairdnerii Richardson

Protein synthesis in liver, gill and muscle tissue was measured in vivo by constant infusion of ¹⁴C-tyrosine in fed and fasted freshwater rainbow trout, Salmo gairdnerii , at 12° C. Synthesis rates (percentage of tissue protein synthesized per day) were 15-17% in liver, 4–5% in gill and 0.38% in muscle of fed fish. Liver and gill synthesis rate showed no significant change in fish that had been without food for 15 days, whereas muscle protein synthesis fell to 0.09%. The greater susceptability of muscle protein synthesis to fasting, possibly results from the greater proportion of synthesis retained as growth in this tissue. Growth rates indicate little change in protein turnover in the muscle but increased protein degradation with fasting. The difference between fed and fasted synthesis rates in muscle may be used as a measurement of potential growth rate for a particular species.     

The influence of cellulose filler on feeding, growth and utilization of protein and energy in rainbow trout, Salmo gairdnerii Richardson

A nutrient source was diluted with indigestible filler in the form of α-cellulose. The trout compensated for up to 30% cellulose by increasing the total weight of food eaten, thereby stabilizing both nutrient intake and growth rate. The fish failed to compensate for levels of 40–50% cellulose and, despite evidence for an increase in the size of the stomach, nutrient intake was approximately halved. There was a slight reduction in food conversion efficiency and the growth rate declined accordingly. By contrast, faecal output rose considerably.     

Biosynthesis of rainbow trout (Salmo gairdnerii) hemoglobins in vitro

Cell free systems were established to analyze the biosynthesis of trout hemoglobins I, II and III. HbI, II and III were synthesized in trout erythroid cell lysates as well as in a mRNA dependent rabbit reticulocyte lysate supplemented with trout erythroid cell polyA-RNA. The newly synthesized hemoglobins apparently contained the N alpha-acetyl modification at their alpha-chain amino terminals since they co-migrated with carrier trout hemoglobins that are known to contain the modification. This observation suggests that the acetylation is determined by the information encoded in the mRNA.     

Plasma oestrogen levels in rainbow trout Salmo gairdneri Richardson

Levels of oestrogens in plasma of mature fall-spawning rainbow trout Salmo gairdneri were determined using a radio-immunoassay. No significant difference was found in oestrogen concentration between the sexes (male =2.5 ng/ml; female =4.4 ng/ml); between individual variability was great. Four blood samplings over a 24-h period via cardiac puncture of males revealed no diel variation or change in estrogen levels due to the stress of bleedings. Although no gonado-somatic index-estrogen relationship could be demonstrated for either sex, there was correlation between oestrogen and androgen levels in the female.     

Effects of gossypol on rainbow trout Salmo guirdneri Richardson

Rainbow trout were fed gossypol acetate or cottonseed meals containing gossypol for 14 months. Toxic effects were indicated by growth depression, reduced hematocrit, hemo-globin, and total plasma protein. Histological changes were noted, particularly in the liver and kidney.     

The saccus dorsalis of the rainbow trout,Salmo gairdneri Richardson

The saccus dorsalis of the brain of the rainbow trout, Salmo gairdneri Richardson, has been investigated by means of histological, cytochemical, enzyme-cytochemical, electron microscopical autoradiographical techniques. The saccus dorsalis is a rostro-dorsal evagination of the diencephalic roof, and consists of a partly folded epithelial wall separating the cerebrospinal fluid from the meningeal matrix fluid. The well-developed vascular system around the epithelial wall, consisting of capillaries with different diameters, seems to be part of the pineal vascular system. No structures were found that may be involved in a possible mechanical or nervous blood flow control. The single-layered epithelium consists of highly specialized cells of one specific type. These cells are mainly characterized by infolded basal membranes, long microvilli of a peculiar shape, non-folded lateral membranes bordering intercellular spaces, apical concentrations of elongate and cup-shaped macromitochondria, a basally located rough endoplasmic reticulum, an apically situated smooth endoplasmic reticulum and apical concentrations of micropinocytotic vesicles. Morphological evidence is presented of a multiple function of these cells: (1) fluid secretion, (2) extrusion of low molecular weight organic substances into the ventricular system, (3) uptake of high molecular weight substances, and (4) uptake of low molecular weight organic substances (aminergic neurotransmitters [GABA]) from the cerebrospinal fluid. The significance of light and dark cells is discussed. Indications of a possible innervation of the saccus dorsalis epithelial cells were not observed. The functional significance of the saccus dorsalis (possible analogue of the choroid plexus?) is discussed.