Hepatectomy in rainbow trout (Salmo gairdneri). A preliminary study

1. Partial hepatectomy (25% of liver mass removed) has been performed on rainbow trout using a procedure allowing a high level of survival. 2. The liver regeneration was complete from the point of view of liver weight, at the 30th post-operative day. 3. During the first weeks after surgery, the NH-excretion rate in both hepatectomized and shamoperated trout was higher than in intact controls. Likewise, the food intake was lower in the operated animals. 4. Both facts can be attribute to the stress situation caused by the surgical manipulations rather than the removal of the liver.     

Spermiogenesis in the rainbow trout (Salmo gairdneri)

In an ultrastructural study on the spermiogenesis of the rainbow trout (Salmo gairdneri R.) four spermatogenetic stages were identified. In young round spermatids, the nuclear chromatin was first heterogeneous (euchromatin and heterochromatin). Subsequently, it became more homogeneous and started to condense in the form of coarse granules and fibers and then into fibrils associated in ribbon-like elements which eventually partly fused together. During early spermiogenesis, a juxtanuclear vacuole appeared in the area where the nuclear envelope was specialized due to condensation of material between the two envelopes and a slight accumulation of nuclear material. This area was finally located in the anterior part of spermatids and spermatozoa; it probably plays a role during fertilization. A flagellar rootlet appeared early in spermiogenesis; it may play a role in the attachment of the flagellum to the nucleus since it persisted until the centriolar complex was definitively fixed in the implantation fossa. The flagellum did not display a plasma membrane and was first located in the cytoplasm, but when it was later extruded from the cell, it acquired a membrane. The cytoplasm was rich in ribosomes (free or in small groups) but poor in membranous organelles. The few mitochondria polarized around the centriolar complex were finally organized into an annular mid-piece. The spermatids remained connected by intercellular bridges until the end of spermiogenesis. The complexity of trout spermiogenesis is intermediate between that in poecilids and that in carp and pike, which have very simple spermatozoa. The role of the material from the nucleus and the cytoplasm reaching the Sertoli cell in the control of spermatogenesis has been discussed.     

Apomorphine-induced vomiting in rainbow trout (Salmo gairdneri)

1. The LD50 for a 7-day period following intraperitoneal injection of apomorphine-HCl was calculated to be 158 mg/kg in rainbow trout. 2. Intraperitoneal injection of apomorphine at doses of 60 mg/kg or greater caused vomiting of plastic balls which had been placed in the stomachs of rainbow trout. 3. Apomorphine-induced effects included vomiting, vomiting behavior, toxicity, increased respiration, impaired motor control and equilibrium, and increased aggression. 4. The vomiting control mechanism of trout may be similar to that described in mammals.     

Tooth replacement in the upper jaw of the rainbow trout (Salmo gairdneri).

The present paper describes the pattern of tooth replacement in the upper jaw of two size ranges of rainbow trout (standard lengths 12-15 cm and 20-23 cm) as determined from wax impressions of the dentitions taken twice weekly on anaesthetised fish. There was considerable variation in the nature of replacement waves (lines constructed on dental charts linking eruption times of alternate teeth) between fish for both the premaxillary/maxillary and vomerine/palatine rows. The wave patterns obtained showed the same consistency of form for any one animal which is to be expected when consecutive generations show constant or proportionately changing life spans. Data relating to the life span of the teeth is given. The results are compared with those derived for the lower jaw and the significance of wave form discussed.     

The preparation and characterization of vitellogenin messenger RNA from rainbow trout (Salmo gairdneri).

Agarose-gel electrophoresis of polyadenylated RNA from livers of oestrogen-treated male rainbow trout revealed a major high-Mr species (7200 nucleotides), which is absent from the polyadenylated RNA isolated from hormonally unstimulated male trout liver. Translation in vitro of the RNA from oestrogen-treated males in a mRNA-dependent rabbit reticulocyte lysate produced a protein (Mr 200 000) that could be immunoprecipitated with antibodies against trout serum vitellogenin, but no immunoprecipitable protein was synthesized with RNA from control animals. DNA complementary to the RNA from oestrogen-stimulated and control male trout liver was synthesized and back-hybridized, with R0t1/2 of 3.8 X 10(-2) and 1 X 10(-1) mol X litre-1 X s for RNA from hormone-treated and control animals respectively. The 9% increase in the abundant mRNA after oestrogen stimulation is due to the induction of vitellogenin mRNA.     

Comparative studies on heart and skeletal muscle AMP-deaminase from rainbow trout (Salmo gairdneri).

1. AMP-deaminases from fish heart and skeletal muscle have been isolated, and their kinetic and regulatory properties compared. 2. The results obtained indicate that the enzyme variants present in fish heart and skeletal muscle, in contrast to their mammalian counterparts, show very similar chromatographic, kinetic and regulatory characteristics. 3. The above may reflect evolutionary programmed differences in AMP-deaminase gene(s) organization.     

Robertsonian polymorphism and constitutive heterochromatin distribution in chromosomes of the rainbow trout (Salmo gairdneri).

White-blood-cell culture was used to examine the chromosomes of 53 rainbow trout (Salmo gairdneri) from three locations in the Pacific Northwest of the United States. A Robertsonian chromosome polymorphism is present, resulting in diploid numbers of 60, 59, or 58 in different individuals with 104 chromosome arms. The low level of intraindividual Robertsonian variation, differences in the number of subtelocentric chromosomes between individuals with different chromosome numbers, and frequencies of fish with different chromosome numbers in one population suggest that the interindividual differences are inherited and not somatic. C-banding shows that constitutive heterochromatin is localized near the centromeres and near the secondary constriction one chromosome pair.     

Fatty acid and sterol synthesis by hepatocytes of thermally acclimated rainbow trout (Salmo gairdneri).

Incorporation of tritium from tritiated water into lipid fractions was measured in isolated hepatocytes from rainbow trout (Salmo gairdneri) acclimated to 5 degrees C and 20 degrees C. Hepatocytes from cold-acclimated trout exhibited significantly higher rates of tritium incorporation into both fatty acid and sterol fractions at assay temperatures of 15 degrees C and 20 degrees C than did hepatocytes from warm-acclimated trout. Tritium incorporation into the fatty acid fraction was nearly temperature independent in hepatocytes from warm-acclimated trout (Q10 = 1.39) but markedly temperature dependent (Q10 = 2.63) in hepatocytes from cold-acclimated trout; in contrast, rates of sterol synthesis were more temperature dependent in warm-acclimated trout. At 5 degrees C, fatty acid lipogenesis comprised a significantly greater percentage of the total tritium incorporation in hepatocytes from warm-acclimated trout and the percentage of total lipogenesis attributable to fatty acids decreased significantly in warm-acclimated trout as the assay temperature increased; the opposite trends were observed in cold-acclimated trout.     

Meristic variation among world hatchery stocks of rainbow trout,Salmo gairdneri Richardson

Synopsis Sixteen meristic characters were examined among 10 stocks of rainbow trout to establish their inter- and intrastock variability and relative discriminating power. The number of vertebrae, dorsal fin rays, scales above and below and lateral line, oblique scale rows and pectoral fin rays were found to be the most useful meristic characters in identifying stocks. Examination of the extent of meristic divergence among 10 hatchery or naturalized stocks from various regions of the world, using analysis of variance, the generalized distance function and per cent overlap, revealed that each stock exhibited highly significant differences in at least one meristic character, thereby demonstrating a high degree of intraspecific variability in meristic expression.In multivariate terms, stocks from Idaho and Alaska were almost totally divergent from all other stocks examined. Multivariate analysis of meristic features proves to be a useful method for identifying the extent of phenotypic variability among and within divergent stocks of rainbow trout. The observed meristic variability in test stocks of hatchery fish is seemingly genetically set within the limits previously described for native populations of rainbow trout.     

Chromosome polymorphism in the rainbow trout (Salmo gairdneri Richardson)

Chromosome preparations from lymphocyte cultures of 50 rainbow trout were studied. Diploid chromosome numbers of 59, 60, 61, 62 and 63 were found in different individuals in which the arm number (NF) was 104. Intraindividual polymorphism was found at a low level in 25 of the fish. The results suggest that numerous chromosome polymorphisms exist in rainbow trout.     

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.     

Crystallization of the rainbow trout (Salmo gairdneri) haemoglobin IV

Crystals of rainbow trout (Salmo gairdneri) haemoglobin IV were grown in mini batches from a solution of ammonium sulphate. Large single crystals grew over five days and were up to 2 mm in length. X-ray diffraction experiments indicated a space group of C222(1) with unit cell dimensions of a = 85.3 A, b = 94.6 A and c = 105.7 A. The crystals diffract to better than 2.5 A but exhibit some mosaicity along the c axis.     

Nutritional regulation of glycolysis in rainbow trout (Salmo gairdneri R.)

1. Some physico-chemical constants and the nutritional regulation of pyruvate kinase (PK), phosphofructokinase (PFK) and hexokinase (HK) from rainbow trout liver was investigated. 2. The maximum activity pH for the three enzymes appears to be in a physiological range. 3. The PK-enzyme shows sigmoid kinetic with respect to PEP with a Hill-coefficient of 3.1; the other two enzymes show michaelian kinetic for their substrates. 4. The nutritional treatments show that HK-enzyme increases its level with high carbohydrate diet and decreases with high protein diet and starvation. 5. PFK-enzyme decreases with high protein diet and starvation. 6. PK-enzyme only shows a decrease in level with starvation conditions.