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PubMed1989

Cyclic adenosine monophosphate as a second messenger in horizontal cell uncoupling in the teleost retina.

The reduction in the receptive field of horizontal cells of the teleost Eugerres plumieri observed upon dopamine (DA) superfusion is thought to be due to cell uncoupling. The possible mechanisms by which activation of DA receptors modify the electric coupling between horizontal cells were studied in the present work. It was found that the effect of DA in different preparations is mediated by a modification of intracellular concentration of cAMP and H+. The effects of intracellular injection of cAMP and H+ were studied in retinal horizontal cells of the teleost E. plumieri. A triple microelectrode was used to inject the ion iontophoretically, to pass current pulses, and to record voltages from the same cell, while a fourth microelectrode was used to record voltages from a neighboring cell in the same retinal layer. Responses evoked by light spots and annuli were evaluated simultaneously. Coupling ratios between neighboring horizontal cells ranged from 0.22 to 0.45. The intercellular resistance (Rc), 0.5-3.5 x 10(6) ohms, and that of the remaining cell membrane resistance (Rm), 2.5-18 x 10(6) ohms, were calculated by means of a passive electrical model that has a hexagonal array. The microinjection of H+ with injection current from +5 to +30 nA for 40 to 100 sec led to temporary and reversible light response reduction. The coupling ratio between two impaled cells was reduced by about 30%, and intercellular resistance (Rc) increment was 320% while cell membrane resistance (Rm) did not change consistently. There was also a temporary and reversible Rm reduction (70-85%) and an Rc increment of 170-330% when cyclic adenosine monophosphate was iontophoretically injected with current from -30 to -40 nA for 50 to 170 sec. The coupling ratio between two impaled cells was reduced by about 40%, and light responses recorded from the injected cell showed a reduction in amplitude with the same time course as that of the resistive changes. The injection of Lucifer yellow into a horizontal cell under normal conditions always results in pronounced fluorescence for more distant cells; however, under constant injection of H+ or cAMP only the injected cell is fluorescent, which provides direct evidence of the reduction in the effectiveness of coupling between horizontal cells. The observed effects of intracellular H+ or cAMP injection correspond to the resistive changes in Rc and coupling ratio that occur in the horizontal cell network upon superfusion with a dopamine (DA) solution.

Animals↗
PubMed2004

Ovarian cysteine proteinases in the teleost Fundulus heteroclitus: molecular cloning and gene expression during vitellogenesis and oocyte maturation.

The cysteine proteinases cathepsins B and L are members of the multigene family of lysosomal proteases that have been implicated in the processing of yolk proteins (YPs) in teleost oocytes. However, the full identification of the type of cathepsins expressed in fish ovarian follicles and embryos, as well as their regulatory mechanisms and specific function(s), are not yet elucidated. In this study, cDNAs encoding cathepsins B, L, F, K, S, Z, C, and H have been isolated from the teleost Fundulus heteroclitus, and the analysis of their deduced amino acid sequences revealed highly similar structural features to vertebrate orthologs, and confirmed in this species the existence of cathepsin L-like, cathepsin B-like, and cathepsin F-like subfamilies of cysteine proteinases. While all identified cathepsins were expressed in ovarian follicles, the corresponding mRNAs showed different temporal expression patterns. Thus, similar mRNA levels of cathepsins L, F, S, B, C, and Z were found throughout the oocyte growth or vitellogenesis period, whereas those for cathepsin H and K appeared to decrease as vitellogenesis advanced. During oocyte maturation, a transient accumulation of cathepsins L, S, H, and F mRNAs, approximately a 3-, 1.5-, 1.6-, and 6-fold increase, respectively, was detected in ovarian follicles within the 20-25 hr after hormone stimulation, coincident with the maximum proteolysis of the oocyte major YPs. The specific temporal pattern of expression of these genes may indicate a potential role of cathepsin L-like and cathepsin F proteases in the YP processing events occurring during fish oocyte maturation and/or early embryogenesis.

Amino Acid Sequence↗
PubMed2006

Molecular characterization of three forms of vitellogenin and their yolk protein products during oocyte growth and maturation in red seabream (Pagrus major), a marine teleost spawning pelagic eggs.

Full-length cDNAs encoding three forms of vitellogenin (Vg) were obtained from a liver cDNA library of estrogen-treated red seabream, Pagrus major. Two of the three Vg sequences had high homology with type-A and -B Vgs (VgA and VgB) of other teleosts. The third red seabream Vg was classified as a type-C or phosvitinless (Pvl) Vg due to its lack of a phosvitin (Pv) domain. Two Vg preparations (610 and 340 kDa) from blood serum of estradiol-treated fish were biochemically characterized. Analyses of precursor-product relationships by examination of N-terminal amino acid sequences verified cleavage of the 610 kDa Vg into a 540 kDa lipovitellin (Lv) and a 32 kDa beta'-component. Each of these yolk preparations comprising both VgA- and VgB-derived polypeptides. The 340 kDa Vg, which was immunologically verified to be a PvlVg, was accumulated by vitellogenic oocytes with no alterations to its native molecular mass. During oocyte maturation, the VgA- and VgB-derived yolk proteins were differentially processed, presumably to generate a pool of free amino acids for oocyte hydration or for allocation of specific types of nutrients, amino acids, and proteins, to the developing embryo. Conversely, the 340 kDa Vg-derived yolk protein is unlikely to contribute to oocyte hydration or diffusible nutrients since the molecule underwent only minor proteolytic nicking during oogenesis. The present study elucidates for the first time specific functions of three different forms of Vg and their product yolk proteins in a higher taxonomic group of marine teleosts that spawn pelagic eggs.

Amino Acid Sequence↗
PubMed1999

Immunodetection of lymphocyte subpopulations involved in allograft rejection in a teleost, Dicentrarchus labrax (L.).

Monoclonal antibodies which recognize antigenic determinants expressed by T-cells and Ig-bearing cells, respectively, allowed lymphocyte subpopulations involved in allograft rejection of muscle transplants to be identified in the teleost fish Dicentrarchus labrax (L.). The monoclonal antibody DLT15 first allowed recognizing T-cells involved in an in vivo antigen-driven cellular response in teleosts. Immunohistochemical studies showed a high density of lymphocytes in allografts and provided evidence of predominance of T-cells. The heterogeneity of the cell populations recognized by the antibodies was evidenced by the different size, cytology, and staining patterns of T-cells and Ig-bearing cells.

Animals↗
PubMed1993

Light-activation of teleost rod photoreceptor elongation.

Rod photoreceptors in the retinas of teleost fish undergo changes in cell length in response to changing ambient light intensities. In the dark rods shorten and in the light rods elongate. These movements are mediated by actin-dependent processes which occur in the ellipsoid and myoid of the inner segment. As an approach to examining the underlying intracellular signaling pathways that link light absorption to actin-dependent motility in the inner segment, we have investigated the quantitative aspects of the light stimulus required to activate elongation in isolated rod inner/outer segments (RIS-ROS) of the green sunfish (Lepomis cyanellus). The intensity thresholds and strength-duration characteristics of the light stimulus required to activate teleost rod elongation were found to differ from those reported to activate vertebrate rod membrane hyperpolarization. In response to brief pulses of light, RIS-ROS elongated in a graded manner, both as a function of increasing light pulse intensity and light pulse duration. Half maximal activation of light-induced RIS-ROS elongation was produced by a stimulus of roughly 6 x 10(15) photons cm-2, which is calculated to bleach approximately 20% of the photopigment molecules in green sunfish rod outer segments. This degree of photopigment bleach is approximately 6-7 orders of magnitude greater than that required to elicit half maximal changes in membrane potential in other vertebrate rod preparations. Furthermore, the reciprocal relationship between light pulse intensity and duration in eliciting an equal elongation response held for relatively long light pulse durations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Retinomotor movements in isolated teleost retinal cone inner-outer segment preparations (CIS-COS): effects of light, dark and dopamine.

Teleost cone inner segments elongate and contract in response to light and circadian signals. Previous studies have shown that teleost cone contraction is triggered by light or dopamine, while cone elongation is triggered by darkness or experimental elevation of cAMP. We have developed procedures for isolating and purifying motile cone fragments consisting of inner and outer segments (CIS-COS) to permit more detailed analysis of light and dopamine regulation of cone retinomotor movements. When retinas are dissected from long-term dark-adapted fish, CIS-COS break off at the base of the ellipsoid and remain attached to the RPE. CIS-COS can be detached from the RPE by brief protease treatment, thereby generating a highly enriched CIS-COS suspension. CIS-COS retain normal morphology and extend new myoids when cultured in darkness or in light plus forskolin, an activator of adenylate cyclase. The microtubule and actin cytoskeletons of the new myoids resemble those of intact cone myoids in vivo. Light inhibits CIS-COS myoid elongation, suggesting that light reception by the outer segment can directly influence cone motility. In dark-cultured CIS-COS, myoid elongation is inhibited half-maximally by nanomolar concentrations of dopamine, suggesting that dopamine effects on motility are mediated by D2-family receptors present on the cone inner and/or outer segment. After dark-induced elongation in culture, CIS-COS myoids can be induced to contract by subsequent culture in the light or with dopamine. Thus isolated cone inner and outer segments possess sufficient cytoskeletal and regulatory machinery to exhibit light- and dopamine-regulation retinomotor movement similar to that observed in intact cones in situ.

Animals↗
PubMed1998

Apoptosis after injuries in the cerebellum of adult teleost fish.

In contrast to mammals, all teleost fish examined thus far exhibit an enormous potential to regenerate not only neuronal processes (axonal regeneration), but even whole neurons (neuronal regeneration) after injuries in the central nervous system. By application of lesions to one subdivision of the cerebellum, the corpus cerebelli, the role of apoptosis in neuronal regeneration was examined in the gymnotiform fish, Apteronotus leptorhynchus. Apoptotic cells were identified by examination of cryosections with the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling (TUNEL) reaction, an in situ technique employed for detection of nuclear DNA fragmentation. Additional evidence for the apoptotic nature of dying cells was obtained through analysis of morphologies displayed at both the light microscopic and the ultrastructural level. The first TUNEL-positive cells at the site of the lesion appeared as rapidly as 5 min following mechanical damage of the tissue. Thirty minutes after stab wound lesion, their number reached maximum levels. Starting with 2 days of postlesioning survival time, a gradual decline in the number of TUNEL-positive cells was evident, until this process reached background levels 20 days after the lesion. We hypothesize that apoptosis is used in A. leptorhynchus as an efficient mechanism for the removal of cells damaged through injury in the central nervous system. Since apoptosis is not accompanied by the side-effects known from necrosis (which is predominant after injuries in the mammalian central nervous system), this "clean" type of cell death may, at least partially, explain the tremendous regenerative capability of teleosts.

Animals↗
PubMed1999

Cell proliferation after lesions in the cerebellum of adult teleost fish: time course, origin, and type of new cells produced.

In contrast to mammals, fish exhibit an enormous capacity to replace damaged neurons following injuries to the adult central nervous system. As the mechanisms controlling this so-called neuronal regeneration are unknown, we have, in the present study, examined the role of cell proliferation in this process. Lesions were applied to one subdivision of the cerebellum, the corpus cerebelli, in the teleost fish Apteronotus leptorhynchus. Proliferative activity was monitored through incorporation of the thymidine analogue 5-bromo-2'-deoxyuridine into replicating DNA. Cerebellar lesions induce high proliferative activity especially in areas in close vicinity to the injury, although the number of cells produced is also increased in other regions of the corpus cerebelli. Many of the cells generated in these areas become, after migration, specifically incorporated at the site of the lesion. The vast majority of them is dividing between 1 and 10 days following the lesion, with the maximum proliferative activity occurring at 5 days. Remarkably, also cells dividing 2 days prior to applying a lesion participate, at a significant number, in the regenerative process. Combination of 5-bromo-2'-deoxyuridine labeling with retrograde tract-tracing techniques demonstrated that at least some of the new cells that replace damaged neurons are cerebellar granule cells. This ability to generate new neurons, together with the previously described occurrence of apoptosis to remove damaged cells, is likely to form the basis for the enormous capacity of teleost fish to perform neuronal regeneration.

Animals↗
PubMed2000

Cloning and sequencing hybrid striped bass (Morone saxatilis x M. chrysops) transforming growth factor-beta (TGF-beta), and development of a reverse transcription quantitative competitive polymerase chain reaction (RT-qcPCR) assay to measure TGF-beta mRNA of teleost fish.

A transforming growth factor (TGF)-beta was isolated and cloned from hybrid striped bass (Morone saxatilis x M. chrysops) anterior kidney mononuclear cells. This isolate (Genbank accession number AF140363) contains an open reading frame of 1146 bases coding for a 382 amino acid protein most similar to rainbow trout TGF-beta (57.3 and 78.6% identity with precursor and active protein, respectively) and rat TGF-beta 1 (41.1 and 68.8% identity with precursor and active protein, respectively). Consensus primers were demonstrated to amplify specifically by polymerase chain reaction (PCR), a TGF-beta segment from 14 species of teleost fish comprising 10 taxonomic families in 7 orders. A reverse transcription quantitative competitive polymerase chain reaction (RT-qcPCR) assay was devised to measure TGF-beta mRNA expression in teleost fish. Higher levels of TGF-beta mRNA expression were detected in mononuclear cells of peripheral blood than from spleen or anterior kidney.

Amino Acid Sequence↗
PubMed2000

Analysis of a cDNA sequence encoding the immunoglobulin heavy chain of the Antarctic teleost Trematomus bernacchii.

A spleen cDNA library was constructed from the Antarctic teleost Trematomus bernacchii and immunoscreened with rabbit IgG specific for T. bernacchii Ig heavy chain. Eleven cDNA clones, varying in size and encoding the entire heavy chain or parts of it, were isolated. Here the complete nucleotide and deduced amino acid sequences of clone 2C2 encoding the secretory IgH chain form are reported. Comparison of the amino acid sequence of the entire constant region of the T. bernacchii Ig heavy chain with those from other teleosts and two holostean fish showed percent identity ranging 53.6-60.6%, with the highest values found for Salmoniformes. The multiple sequence alignment revealed the presence of two remarkable insertions: one at the VH-CH1 boundary and a second one, not found in any other IgM heavy chain, localised at the CH2-CH3 boundary. The latter occurred in the region proposed to act as a 'hinge', and resulted in a CH2-CH3 hinge peptide longer than any other IgM hinge. Differences were also found in the number and position of putative N-glycosylation sites of the compared sequences. It is suggested that the unusual features found in the T. bernacchii Ig heavy chain might contribute to the flexibility of the Ig molecule and help understand more about the adaptation of Ig molecules to the polar sea environment.

Amino Acid Sequence↗
PubMed1993

Purification and characterization of urotensin II from the brain of a teleost (trout, Oncorhynchus mykiss) and an elasmobranch (skate, Raja rhina).

Peptides related to urotensin II have been isolated in pure form from an extract of whole brain of a teleost, the rainbow trout (Oncorhynchus mykiss) and of an elasmobranch, the longnose skate (Raja rhina). The primary structure of the trout peptide [Gly-Gly-Asn-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val] is similar to that of urotensin II peptides isolated from the urophyses of other teleost fish. For example, trout urotensin II contains only one amino acid substitution (Thr4-->Ser) compared with urotensin II beta 1 isolated from the urophysis of the carp. The primary structure of the skate peptide [Asn-Asn-Phe-Ser-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val] is the same as urotensin II isolated from the caudal spinal cord region of the dogfish Scyliorhinus canicula. The data provide chemical evidence to support the conclusion of earlier morphological studies [Yulis, C. R., and Lederis, K. (1988) Gen. Comp. Endocrinol. 70, 301-311) that certain species of fish possess an extensive extraurophyseal distribution of urotensin II-immunoreactive neurons.

Amino Acid Sequence↗
PubMed1997

Adrenocortical and adrenomedullary homologs in eight species of adult and developing teleosts: morphology, histology, and immunohistochemistry.

Morphology, histology, and immunohistochemistry of the adrenocortical and adrenomedullary homologs (adrenal glands) of the following developing and adult teleosts were examined: Salmoniformes-Oncorhynchus mykiss (rainbow trout), Salmo trutta fario (brown trout), Coregonus lavaretus (white fish); Cyprinodontiformes-Gambusia affinis (mosquito fish). Perciformes-Dicentrarchus labrax (sea bass), Sparus aurata (sea bream), Diplodus sargus (white bream), Oblada melanura (saddled bream). The anatomical relationships of the gland with the renal system and venous vessels were also noted. In adults of all species steroidogenic and catecholaminergic chromaffin cells were found in the head kidney, which is pronephric in origin and subsequently transformed into a hematopoietic lymphatic organ. In Perciformes, chromaffin cells are distributed around the anterior and posterior cardinal veins and ducts of Cuvier; in Salmoniformes, around the posterior cardinal veins and in the hematopoietic tissue; and in G. affinis, around the ducts of Cuvier and posterior cardinal veins, while a few are visible also around the sinus venosus. In Perciformes and Salmoniformes, numerous chromaffin cells are also present in the posterior kidney, derived from the opisthonephros, in contact with the caudal vein. Steroidogenic cells are always confined to the head kidney. During development chromaffin and steroidogenic cells appear early after hatching in the pronephric kidney, at the level of the ducts of Cuvier and of the cephalic part of the posterior cardinal veins. Later, chromaffin cells in Perciformes reach the anterior cardinal veins, and subsequently, in both Perciformes and Salmoniformes, they reach the developing posterior kidney. Their localization along the posterior kidney is still in progress about 4 months after hatching and is completed about a year after hatching. These findings support the concept that the structure of the adrenal gland in teleosts is intermediate between that of the other actinopterygians and that of tetrapods. The development differs from that of tetrapods in that it occurs mainly in the pronephros and only later do chromaffin cells reach the opisthonephric kidney.

3-Hydroxysteroid Dehydrogenases↗
PubMed1998

Evidence for growth hormone/insulin-like growth factor I axis regulation of seawater acclimation in the euryhaline teleost Fundulus heteroclitus.

The ability of ovine growth hormone (oGH), recombinant bovine insulin-like growth factor I (rbIGF-I), recombinant human insulin-like growth factor II (rhIGF-II), and bovine insulin to increase hypoosmoregulatory capacity in the euryhaline teleost Fundulus heteroclitus was examined. Fish acclimated to brackish water (BW, 10 ppt salinity, 320 mOsm/kg H2O) were injected with a single dose of hormone and transferred to seawater (SW, 35 ppt salinity, 1120 mOsm/kg H2O) 2 days later. Fish were sampled 24 h after transfer and plasma osmolality, plasma glucose, and gill Na+, K+-ATPase activity were examined. Transfer from BW to SW increased plasma osmolality and gill Na+,K+-ATPase activity. Transfer from BW to BW had no effect on these parameters. rbIGF-I (0.05, 0.1, and 0.2 microg/g) improved the ability to maintain plasma osmolality and to increase gill Na+, K+-ATPase activity in a dose-dependent manner. oGH (0.5, 1, and 2 microg/g) also increased hypoosmoregulatory ability but only the higher doses (2 microg/g) significantly increased gill Na+,K+-ATPase activity. oGH (1 microg/g) and rbIGF-I (0.1 microg/g) had a significantly greater effect on plasma osmolality and gill Na+,K+-ATPase activity than either hormone alone. rhIGF-II (0.05, 0.1, and 0.2 microg/g) and bovine insulin (0.01 and 0.05 microg/g) were without effect. The results suggest a role of GH and insulin-like growth factor I (IGF-I) in seawater acclimation of F. heteroclitus. Based on these findings and previous studies, it is concluded that the capacity of the GH/IGF-I axis to increase hypoosmoregulatory ability may be a common feature of euryhalinity in teleosts.

Adaptation, Physiological↗
PubMed1999

Streptozotocin dose-response curve in tilapia, a glucose-responsive teleost fish.

Streptozotocin (STZ) causes beta cell necrosis and insulin-dependent diabetes in many species. The specificity of this beta cell toxin relates to its structure as an alkylating agent with an attached glucose moiety. STZ uptake by rodent beta cells appears to be via the GLUT-2 glucose transporter. Teleost fish, in general, are severely glucose intolerant. The effects of STZ were examined in tilapia, a teleost fish with highly glucose-responsive islets. Fasted tilapia were given 0, 100, 150, 200, 250, 300, or 350 mg/kg STZ iv. Plasma glucose levels were followed for 72 h and the fish autopsied. Histological sections of islets were stained by immunoperoxidase for tilapia insulin. Severe hyperglycemia was seen in 20, 80, and 100% of fish receiving 250, 300, and 350 mg/kg doses; however, sections of islets showed only partial degranulation with no evidence of beta cell necrosis. Another group of fish receiving the highest dose were followed longer to determine whether beta cell necrosis and permanent hyperglycemia ensued. All fish died or were killed within 9 days because of severe hepatic failure characterized by hepatic necrosis, jaundice, and ascites; islet morphology was relatively normal suggesting, even in a glucose-sensitive species, that fish islets either do not take up STZ or are highly resistant to its "diabetogenic" effects. Tilapia may thus be a useful model to elucidate mechanisms of action of STZ. Furthermore, STZ may provide important insights into differences in glucose uptake and metabolism by mammalian and piscine beta cells.

Animals↗
PubMed2000

Gonadotropin-releasing hormones in the brain and pituitary of the teleost, the white sucker.

The present study investigated GnRH forms within the brain of a representative of the order Cypriniformes, the white sucker, Catostomus commersoni, using HPLC, RIA, and immunocytochemistry. Several immunoreactive (ir) GnRH forms were identified in the brain of the white sucker by chromatography and radioimmunoassay, including ir-salmon GnRH, ir-lamprey GnRH-I and -III, and ir-chicken GnRH-II. Results from immunocytochemical studies were consistent with multiple GnRH forms distributed in different patterns, particularly for fibers. Neuronal perikarya containing ir-salmon GnRH and ir-lamprey-like GnRH were found laterally within the preoptic area and rostral hypothalamus. Cells containing exclusively ir-salmon GnRH appeared slightly more rostrally, but in the same region. Fibers containing ir-salmon GnRH and ir-lamprey-like GnRH were seen throughout the caudal telencephalon and extended into the diencephalon, toward the pituitary. Fibers containing ir-chicken-II-like GnRH were also seen in the caudal telencephalon, but were concentrated more dorsally in the diencephalon. Within the pituitary, fibers containing ir-salmon GnRH and ir-lamprey-like GnRH entered the neurohypophysis, but differed in their destinations. Fibers containing ir-salmon GnRH remained within the neurohypophysis, while fibers containing ir-lamprey-like GnRH targeted adenohypophyseal tissue. These findings are consistent with the hypothesis that multiple GnRH forms with multiple functions exist within the brain and pituitary of teleosts and provide further evidence of a lamprey-like GnRH within an early evolved teleost species.

Amino Acid Sequence↗
PubMed2002

Conservation of the T-cell receptor alpha/delta linkage in the teleost fish Tetraodon nigroviridis.

T-cell specific receptors (TCR) are present in all groups] from the jawed vertebrates to the mammals. In teleosts, however, the genes encoding the gamma- and delta-chains have not yet been found, the alpha- and beta-chains have been characterized mainly at the expression level, and genomic organization of these loci remains largely unknown. Here we describe both the genomic organization of the TCR alpha/delta locus in Tetraodon nigroviridis and the transcription of TCRA and TCRD. The TCR alpha/delta locus consists of 13 V alpha/delta segments, a Calpha gene, and 12 Jalpha segments, followed by a Cdelta gene, two Jdelta segments, and several Ddelta segments. However, the genomic organization found in this teleost differs significantly from that which has been observed in mammals and birds: a common set of V segments is used to generate either an alpha- or a delta-chain by genomic inversion, and the size of the locus is small in this vertebrate.

Amino Acid Sequence↗
PubMed1996

An electron microscopic investigation into the possible source of new muscle fibres in teleost fish.

This study is based on transmission electron microscopic (TEM) investigations of deep (fast, 'white') teleost fish muscle proliferation in early developmental stages of three European cyprinid species and the rainbow trout. Our fine structural findings provide evidence that early myotomal growth in these animals may utilize different mechanisms that are activated in close succession during early life history. First, initial enlargement of the deep muscle bulk in the embryo seems to be due to hypertrophy of the somite-cell derived stock of muscle fibres. Second, we suggest that deep muscle growth becomes additionally powered by attachment of presumptive myogenic cells that originate from and proliferate within the adjacent mesenchymal tissue lining. Third, mesenchyme-derived muscle cell precursors are thought to enter the myotomes via the myosepta. After migration between the pre-established muscle fibres these cells may function as myosatellite cells, thus at least partly providing the stem cell population for subsequent rapid hyperplastic growth. Finally, there is evidence that presumptive deep muscle satellite cells also proliferate by mitotic division in situ. A similar process of myogenic cell migration and proliferation may foster intermediate fibre differentiation. The model of myogenic cell migration is discussed in view of in vitro and in vivo data on satellite cell migratory power and with respect to temperature-induced and species dependent differences. As for the latter, our results indicate that patterns of muscle differentiation may diverge between a fast growing salmonid species and a moderately growing cyprinid species of similar final size. The model is compatible with the well-established idea that teleost muscle growth may rely on different subclasses of myosatellite cells.

Animals↗
PubMed1981

Fine structure and metabolism of multiply innervated fast muscle fibres in teleost fish.

Both the fast and slow muscle fibres of advanced teleost fish are multiply innervated. The fraction of slow-fibre volume occupied by mitochondria is 31.3%, 25.5%, and 24.6%, respectively, for the myotomal muscles of brook trout (Salvelinus fontinalis), crucian carp (Carassius carassius), and plaice (Pleuronectes platessa), respectively. The corresponding figures for the fast muscles of these species are 9.3%, 4.6% and 2.0%, respectively. Cytochrome-oxidase and citrate-synthetase activities in the fast muscles of 9 species of teleost range from 0.20-0.93 mumoles substrate utilised, g wet weight muscle(-1) min(-1) (at 15 degrees C) or around 4-17% of that of the corresponding slow fibres. Ultrastructural analyses reveal a marked heterogeneity within the fast-fibre population. For example, the fraction of fibres with less than 1% or greater than 10% mitochondria is 0, 4, 42% and 36, 12 and 0%, respectively, for trout, carp and plaice. In general, small fibres (less than 500 micrometers(2)) have the highest and large fibres (greater than 1,500 micrometers(2)) the lowest mitochondrial densities. The complexity of mitochondrial cristae is reduced in fast compared to slow fibres. Hexokinase activities range from 0.4-2.5 in slow and from 0.08-0.7 mumoles, g wet weight(-1) min(-1) in fast muscles, indicating a wide variation in their capacity for aerobic glucose utilisation. Phosphofructokinase activities are 1.2 to 3.6 times higher in fast than slow muscles indicating a greater glycolytic potential. Lactate dehydrogenase activities are not correlated with either the predicted anaerobic scopes for activity or the anoxic tolerances of the species studied. The results indicate a considerable variation in the aerobic capacities and principal fuels supporting activity among the fast muscles of different species. Brook trout and crucian carp are known to recruit fast fibres at low swimming speeds. For these species the aerobic potential of the fast muscle is probably sufficient to meet the energy requirements of slow swimming.

Animals↗