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.     

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.     

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.     

Metabolic utilization of diets by polyploid rainbow trout (Salmo gairdneri)

1. Nitrogen (NH4) excretion and oxygen consumption were measured in four groups of juvenile rainbow trout (36-40 g): triploids obtained by a heat shock treatment (3n); triploids obtained by mating diploid females with tetraploid males (3n/4n); tetraploids (4n) and a diploid control (2n). 2. No differences in daily N excretion patterns and in N excretion rate measured as a percentage of N intake were detected between groups. 3. Oxygen consumption of the 2n group was significantly inferior to that of the 3n and 4n groups but not to the 3n/4n group. 4. SDA, specific dynamic action (measured as a percentage of the energy intake), ranged from 5.6 to 8.6% and was not different between groups. 5. Protein energy catabolism measured as per cent of total energy expenditure was significantly higher in the 2n group than in polyploid groups.     

Synthesis of platelet activating factor by tissues from the rainbow trout, Salmo gairdneri

In mammals, platelet activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a lipid mediator with biological activity at concentrations in the subnanomolar range. Although PAF is known to have many activities in mammals, little is known about its synthesis and importance in other vertebrate groups. We demonstrate here the synthesis of PAF from [3H]acetate by slices of trout gill, kidney, liver and spleen. PAF synthesis was stimulated by the calcium ionophore A23187 and was time-dependent. The radiolabeled PAF produced was characterized by TLC, HPLC, derivatization and by saponification and phospholipase A2 hydrolysis. These findings suggest that PAF may be an important mediator in fish.     

Ultrastructure of the physostomatous swimbladder of rainbow trout (Salmo gairdneri)

Summary Rainbow trout swimbladder epithelium consists of non-ciliated and ciliated cells in the ratio of greater than 21. Non-ciliated cells contain vesicles filled with a mucus-like material and similar material is found lining the surface of the swimbladder lumen. Morphological evidence for discharge of the vesicle contents was obtained. In addition, nonciliated cells contain osmiophilic lamellar bodies which resemble the cytosomes of lung alveolar cells of air-breathing vertebrates. The non-ciliated cells do not appear to be involved in a process of active gas secretion.Supported by a research grant from the American Cancer Society, Oregon Division, Inc.     

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.     

Some blood parameters of the rainbow trout (Salmo gairdneri Richardson)

Some of the blood constituents of male, female and immature rainbow trout of the Shasta variety, maintained in known environmental and dietetic conditions, were examined and the results statistically treated. The parameters for male and female trout were similar, only the erythrocyte count exhibiting a significant difference. Large but expected differences were evident between the parameters for mature and immature fish.     

Some blood parameters of the rainbow trout (Salmo gairdneri Richardson)

Fifty rainbow trout of the Kamloops strain were examined for 12 haematological parameters: erythrocyte sedimentation rate, haemoglobin, packed cell volume, erythrocyte count, erythrocyte diameters, mean cell volume, mean cell haemoglobin, mean cell haemoglobin concentration, leukocyte count, differential leukocyte count, plasma total protein and plasma glucose concentration. The fish had been held under known environmental and dietetic conditions, and at the time of sampling were 14 months old. The majority of results for erythrocyte sedimentation rate, haemoglobin, packed cell volume, erythrocyte count, erythrocyte diameters, total protein and differential leukocyte count fell within narrow ranges. The total leukocyte counts and glucose levels were more widely spread. The results are discussed and compared with those already published for Idaho and Shasta strains. It is impossible to say whether the differences that were observed between Kamloops and these other varieties were due to strain alone, since other variables were present. Some problems associated with establishing normal ranges for these parameters in fish are discussed.     

Seasonal changes in reproductive function of the rainbow trout (Salmo gairdneri)

The sequential changes in serum oestradiol 17β (measured by specific radioimmunoassay), vitellogenin (measured by phosphoprotein phosphorus content) and total calcium (measured by fluorimetry) in male and female rainbow trout under a simulated natural photoperiod cycle were investigated. Resting levels of 130 pg/ml serum oestradiol in both male and female fish were found in April and May. In the female, levels reached a peak of 4800 pg/ml in October, and almost returned to resting levels just prior to spawning in mid-January. No significant change from resting levels was seen in the male fish.
In both male and female fish levels of 25 μg/ml serum phosphoprotein phosphorus and 10–14 mg % total serum calcium were found from April to July. Coincident with the rise in oestradiol 17β, in the females serum levels of phospho-protein phosphorus and total calcium increased to 400 uβg/ml and 58 mg% respectively just prior to spawning. In the males no significant change in either of these values was observed throughout the cycle. These results strongly support the hypothesis that photoperiod is the major factor in the environmental control of reproductive activity in the rainbow trout.     

Microvasculature of the pineal organ of the rainbow trout (Salmo gairdneri)

Summary The angioarchitecture of the pineal organ of the rainbow trout (Salmo gairdneri) was investigated by means of the corrosion-cast preparation method and scanning electron microscopy. Two main arteries (aa. epiphyseales) supply the pineal parenchyma. They emerge from the aa. cerebri anteriores and run in the fissure between the prosencephalon and the mesencephalon. After entering the pineal stalk, the aa. epiphyseales branch off into several arterioles, most of which extend to the pineal end-vesicle where they give rise to a lobular, bilaterally symmetric capillary network. Capillaries establishing the main portion of the pineal vessels appear widened in comparison to those supplying other portions of the brain and resemble capillaries in other endocrine organs. In Salmo gairdneri, no specialized system of portal vessels appears to exist between the pineal organ and other portions of the brain.     

Ultrastructural development of the saccus vasculosus in rainbow trout (Salmo gairdneri)

Summary The morphology of crown cells and supporting cells of the saccus vasculosus has been described by numerous investigators. A third type of cell has been mentioned by several authors and referred to variously as undifferentiated crown cells, pseudo-coronet cells, pear-shaped cells and, most recently, as liquor-contact neurons. A developmental study of the organ was undertaken as a possible means of characterizing this third cell type and determining its origin.The epithelium of the saccus vasculosus and the ependyma of the third ventricle are different and distinguishable at the time of hatching in rainbow trout. Initially, apical protrusions from crown cells extend slightly into the lumen and a few end knobs or motile cilia project from them. Basal bodies with cross-striated rootlets occur frequently. In swim-up fry, end knobs are more numerous and heavily vacuolated, although cross-striated rootlets are less apparent.Evidence is presented that is consistent with a hypothesis of secretory activity in the crown cells. Further, portions of end knobs containing this material appear to be pinched off from the remainder of the crown cell. The possible presence of bipolar neurons is also discussed.Supported by Research Grant 5 R01 NS0627 from the National Institute of Neurological Diseases and Stroke.     

Induction of antibody-producing cells in rainbow trout, Salmo gairdneri Richardson; by flush exposure

Splenic antibody-producing cells were produced by rainbow trout that had been exposed to O-antigens extracted from Yersinia ruckeri and Aeromonas salmonicida by adding the concentrated antigen preparation directly into the water of the tank holding the fish for a flush exposure. This method was compared with the proven techniques of exposure: intraperitoneal injection or a 2 minute immersion of the fish in the antigen preparation. Dosage experiments showed that the production of antibody-producing cells was induced by the immersion of trout for 2 minutes in water with 5.0 μg/ml-1 (or more) with the Y. ruckeri O-antigen, or 500 μg ml-1 (or more) of the A. salmonicida O-antigen. Similar differences were evident when the respective antigens were added directly to the water.     

Degradation of extracellular thymidine by cultured hepatocytes from rainbow trout (Salmo gairdneri)

1. Trout hepatocytes cultured as attached monolayers had low rates of [3H]-thymidine ([3H]-TdR) incorporation during replicative or repair synthesis of DNA. 2. Within 2 hr, most [3H]-TdR was metabolized by trout hepatocytes to a major product that eluted in advance of intact [3H]-TdR on Sephacryl S-200 columns. 3. Metabolism of [3H]-TdR by trout hepatocytes rapidly destroyed its ability to label replicating indicator cultures of proliferating rat hepatocytes. 4. These studies demonstrate that [3H]-TdR tracer assays for DNA synthesis cannot be reliably used in cultured trout hepatocytes which catabolize thymidine much more rapidly than do rat hepatocytes.