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PubMed1999

Characterization of microtubule-associated proteins in teleosts.

Although microtubules are known to play an important role in many cellular processes, they have been virtually neglected in fish. In this report, microtubule-associated proteins (MAPs) in fish (teleost) were characterized using antibodies (Abs) directed against the mammalian MAPs tau, MAP1A and B, and MAP 2. Two different populations of tau-like proteins (TLPs) were found in fish brain using the anti-tau Abs Tau-1, Tau-2, tau5', and tau3'. The TLPs that were recognized by Tau-1, Tau-2, and tau5' were (1) heat-stable; (2) the same molecular weight as mammalian TLPs: 59-62 kDa; (3) not enriched in microtubules prepared from catfish brain; and (4) localized to the cell body of neurons in fish brains. While the TLPs recognized by tau3' Abs were (1) heat-stable; (2) lower molecular weight than mammalian TLPs: 32-55 vs. 50-65 kDa; (3) enriched in microtubule fractions prepared from catfish brain, and (4) localized to the axons of neurons. These results are consistent with two different populations of TLPs being present in fish brains. While MAP2 was found to be approximately the same molecular weight, 250 kDa, in zebrafish and goldfish as in mammals and to be distributed to dendrites in the fish brain, both MAP1A and MAP1B were found to be about 25% the mass of their mammalian homologs. These results suggest that MAPS in fish have some characteristics similar to their mammalian counterparts, but also possess some unique properties that require further study to elucidate their function.

Animals↗
PubMed1996

Nonspecific cell-mediated cytotoxicity in the seawater teleosts (Sparus aurata and Dicentrarchus labrax): ultrastructural study of target cell death mechanisms.

BACKGROUND: In higher vertebrates, cytolytic lymphocytes lyse their targets by the mechanisms of cell death called necrosis and apoptosis. However, the mechanisms of target cell death mediated by fish cytotoxic cells have not been established. We report the ultrastructure of target cell death mediated by the seawater teleosts gilthead seabream (Sparus aurata) and sea bass (Dicentrarchus labrax). METHODS: Head-kidney, blood, and peritoneal exudate leukocytes were incubated with HeLa or B16 melanoma tumor cells, as targets, and processed for transmission electron microscopic studies. RESULTS: After incubation of tumor cells with leukocytes, substantial ultrastructural changes typically associated with both necrosis and apoptosis were observed in the plasmalemma, nucleus, and cytoplasm of the tumor cells. These morphological changes included loss of microvilli, the formation of long cytoplasmic processes and blebs, condensation and margination of the chromatin, swelling of the organelles, and vacuolation and condensation of the cytoplasm. CONCLUSIONS: Our results indicate that leukocytes from gilthead seabream and sea bass are able to kill their targets by the mechanisms of necrosis and apoptosis, in a similar way to mammalian cytotoxic cells.

Animals↗
PubMed1999

Bulbus arteriosus of the Antarctic teleosts. II. The red-blooded Trematomus bernacchii.

The structure of the bulbus arteriosus of the Antarctic teleost, Trematomus bernacchii, has been studied by light, scanning, and transmission electron microscopy. The wall of the bulbus arteriosus is divided into endocardial, subendocardial, middle and external layers. The endocardial endothelium covers the inner surface of the bulbus wall and invaginates into the subendocardium to form solid epithelial cords that show secretory activity. The subendocardial tissue is divided into finger-like ridges. Ridge cells located under the endocardium appear in niches limited by collagen fibers and thin cell extensions. Away from the endocardium ridge cells cluster into small groups, show some of the characteristics of smooth muscle cells, and appear enmeshed in a filamentous meshwork that lacks collagen and elastin fibers. The middle bulbus layer is formed by typical smooth muscle cells that are enmeshed in a filamentous meshwork similar to that observed in the ridges. The ridges and the middle layer appear to be formed by the same cell type, smooth muscle, with a gradient of differentiation from the endocardium toward the middle layer. In the absence of elastin fibers the filamentous meshwork should confer elastic properties to the bulbus wall. The stretching of the meshwork along the main axis of the middle layer cells, and between different cellular layers, suggests the existence of tensile stress and, hence, the involvement of smooth muscle cells in bulbus wall dynamics. The external layer is formed by numerous cellular types embedded in a collagenous matrix. Among these cellular types, myofibroblasts, macrophages, granulocytes, lymphocytes, dendrite-like cells, degenerating cells, and plasma cells can be recognized. The subepicardial tissue appears to be a specialized site involved in the production of the humoral immune response and displays many of the morphological characteristics of a germinal center. The outer limiting layer of the bulbus, the visceral pericardium, is formed by epithelial cells that show desmosomes and tight junctions. This suggests a close control of permeability with respect to the pericardial fluid.

Animals↗
PubMed1997

Pharmacology of the serotonergic inhibition of steroid-induced reinitiation of oocyte meiosis in the teleost Fundulus heteroclitus.

Serotonin (5-HT) was found to inhibit steroid (17 alpha,20 beta-dihydroxy-4-pregnen-3-one; 17,20 beta P)-induced resumption of oocyte meiosis (oocyte maturation) in vitro in the teleost Fundulus heteroclitus. Serotonin inhibited both follicle-enclosed and denuded oocytes, which indicates the presence of oocyte-associated 5-HT sensitive sites. The response of oocytes to 5-HT was characterized pharmacologically, i.e., the capacity of serotonergic agonists and antagonists to mimic or block the 5-HT inhibition of the steroid-induced oocyte maturation was assessed by the changes in the percentage of oocyte germinal vesicle breakdown (GVBD). Dose-response curves for each compound were drawn and compared. The rank order of potency among the agonists was: 5-HT > 5-methoxytryptamine > tryptamine = 5,6-diHT = 5-carboxidotryptamine > 5,7-diHT = 5-methoxy-dimethyltryptamine > alpha-methyl-5HT > 2-methyl-5HT. Incubation of ovarian follicles with high doses of some antagonists (mianserin and metergoline) induced oocyte GVBD, although this effect was associated with high levels of oocyte atresia during GVBD or shortly after maturation. Consequently, doses of the antagonist too low to induce GVBD were tested for their ability to block the 5-HT inhibitory action; the rank order of potency was: MDL-72222 = metoclopramide > metergoline > propanolol > ketanserin. Dopamine, acetylcholine, epinephrine, and norepinephrine could also inhibit 17,20 beta P-induced GVBD, although at doses much higher than those of 5-HT; melatonin and histamine had no effect on oocyte maturation. These results suggest that specific receptors mediate the inhibitory action of 5-HT on the steroid-triggered meiosis resumption. The pharmacological profile of these 5-HT receptors is different from those of any known mammalian 5-HT receptor, although they showed some similarities to the 5-HT1A, 5-HT2, and 5-HT3 receptors, as well as to 5-HT receptors on oocytes of some bivalve molluscs.

17-alpha-Hydroxyprogesterone↗
PubMed2000

Calretinin expression in specific neuronal systems in the brain of an advanced teleost, the grey mullet (Chelon labrosus).

The distribution of calretinin (CR) in the brain of an "advanced" teleost, the grey mullet, was studied by using immunoblotting and immunocytochemical techniques. In immunoblots of protein extracts of rat and mullet brains, the CR antibody stained a single band of about 29 kDa. CR immunoreactivity was observed in specific neuronal populations of all brain regions. The primary olfactory system, the optic nerve fibers, and some sensory fibers of other cranial nerves exhibited strong CR immunoreactivity. In the forebrain, the CR-immunoreactive (CR-ir) populations were scarce in the telencephalon and hypophysiotrofic hypothalamus, but numerous in many specialized nuclei of the diencephalon (preglomerulosus complex, nucleus glomerulosus, anterior glomerular nucleus, nucleus diffusus) and pretectum (parvocellular and magnocellular superficial pretectal nuclei, central pretectal nucleus), which are related to sensory systems. The two main forebrain bundles, medial and lateral, contained numerous CR-ir fibers. The midbrain sensory centers (optic tectum and torus semicircularis) exhibited numerous CR-ir cells and fibers. Likewise, the secondary gustatory nucleus of the isthmus is one of the nuclei exhibiting more intense CR immunoreactivity. Characteristically, the efferent cerebellar system (eurydendroid cells and brachium conjunctivum) and some afferent cerebellar fibers were CR-ir. In the medulla oblongata, a number of reticular cells, the inferior olive, and the magnocellular octaval nucleus exhibited CR immunoreactivity. CR-ir motoneurons were also observed in the spinal cord and in the oculomotor nucleus. Together with results obtained in other vertebrates, present results suggest that neural systems using calretinin to maintain intracellular calcium concentration have been rather well conserved during vertebrate evolution.

Animals↗
PubMed2000

Afferent sources to the ganglion of the terminal nerve in teleosts.

Afferent sources to the ganglion (ggl) of the terminal nerve (TN) were studied in percomorph teleosts the tilapia and dwarf gourami. After tracer applications to the TN-ggl and the surrounding bulbus olfactorius, retrogradely labeled neurons were present in the area dorsalis telencephali pars posterior (Dp), area ventralis telencephali pars ventralis et supracommissuralis (Vv and Vs), nucleus tegmento-olfactorius of Prasada Rao and Finger (1984), and locus coeruleus. In the contralateral bulbus olfactorius labeled cells were observed, and terminals were seen in the TN-ggl. Tracer injection experiments to the possible sources of origin to the TN-ggl were then performed. Tracer applications to the nucleus tegmento-olfactorius labeled abundant terminals in the TN-ggl but labeled very few in the bulbus olfactorius proper. Retrogradely labeled neurons were present in the nucleus ventromedialis thalami, nucleus commissurae posterioris, area pretectalis pars dorsalis et ventralis, nucleus sensorius nervi trigemini, and formatio reticularis pars superius et medius. Tracer applications to the Dp or Vs/Vv labeled terminals mainly in the bulbus olfactorius proper. However, terminals to the TN-ggl were supplied from labeled axons on their way to the bulbus olfactorius. Tracer injections to the locus coeruleus labeled only a few fibers around the TN-ggl. These results suggest that the TN-ggl receives somatosensory and visual inputs from the nucleus tegmento-olfactorius and olfactory inputs from the bulbus olfactorius and telencephalic subdivisions, which receive secondary olfactory projections. The locus coeruleus may also send fibers to the TN-ggl.

Afferent Pathways↗
PubMed1991

Retinal regeneration in teleost fish.

The neural retina in teleost fish can regenerate after surgical or neurotoxic destruction. Whereas in amphibians the retina regenerates by transdifferentiation of pigmented retinal epithelial cells, in goldfish (Carassius auratus) the source of regenerated retinal cells is a population of scattered proliferating cells located in the outer nuclear layer within the differentiated retina. These proliferating cells are modified neuroepithelial cells termed 'rod precursors' because in the intact retina they produce only rod photoreceptor cells and do so continuously, inserting new rods into the growing adult retina. Although rod precursors normally exhibit a restricted developmental fate they appear not to be committed to the rod lineage. When retinal neurons are destroyed, rod precursors cease producing rods and give rise to clusters of primitive neuroepithelial cells which divide vigorously and reconstitute the retina in an orderly temporal pattern that mimics the process of normal development. Only after production of cones and other retinal neurons has ceased do rod precursors again appear and resume the generation of rods. We conclude that rod precursors respond to local cues in their environment that regulate the differentiation and choice of cell fate by their progeny.

Animals↗
PubMed1983

Histochemical and biochemical studies of carbonic anhydrase activity in the opercular epithelium of the euryhaline teleost, Fundulus heteroclitus.

Carbonic anhydrase (CAH) activity was biochemically measured and histochemically localized (at both the light and electron microscope levels) in isolated opercular membranes from teleost fish, Fundulus heteroclitus, adapted to freshwater (FW), seawater (SW), and double-strength seawater (2 x SW). The normal morphology of this membrane showed that its epithelial portion consisted of five cell types: (1) chloride cells, which have been previously implicated as responsible for the active chloride transport across the epithelium; (2) mucous cells; (3) pavement cells, which formed the major portion of the free epithelial surface; (4) supportive cells, which had an abundance of intermediate (10 nm)-type filaments suggesting a structural role for these cells; and (5) vesicular cells, which were characterized by various types of membrane-bound vesicles, including lysosomes, and numerous free ribosomes. Vesicular cells may be stem cells and/or endocrine cells. Hansson's histochemical method for CAH revealed cobalt sulfide reaction product confined to the following structures in fish from each environment: (1) chloride cells: throughout the cytoplasm and some nuclear staining; (2) mucous cells: throughout the cytoplasm, some nuclear staining, and some in mucous granules; (3) vesicular cells: confined to lysosomes, some of the vesicles, and nucleoli; (4) a small portion of the intracellular space between adjacent vesicular cells and supportive cells; and (5) supportive cells: in nucleoli and occasionally in larger membrane-bound lysosomelike structures. Acetazolamide (10(-5) M) and potassium cyanate (KCNO) (10(-1) M) in Hansson's incubation medium completely inhibited the formation of reaction product. Biochemical determination of CAH activity on vascularly perfused, isolated opercular membranes showed no statistically significant difference in enzyme activity between environmental groups. The following units of activity/mg opercular membrane protein were measured: FW: 0.63 +/- 0.02; SW: 0.43 +/- 0.08; 2 x SW: 0.64 +/- 0.09.

Animals↗
PubMed1990

Ultrastructural study of the cellular types in the pineal organ of Gambusia affinis (teleost).

The pineal organ of Gambusia affinis was studied via light and electron microscopy. The cell types studied included photoreceptor cells, supporting cells, and a third cell type. The photoreceptor cells, which appear to form clusters, are divided into four regions: outer segment, inner segment, cell soma, and synaptic pedicle. Synaptic ribbons are commonly observed in the synaptic pedicle. The supporting cells separate the photoreceptor cells from the thick basal lamina that surrounds the entire pineal organ. The supporting cells show highly organized membrane formations, some lipid-like inclusions, and a diplosome. One of the centrioles gives rise to an invaginated cilium. The third cell type is observed infrequently and appears to be located mainly in the vicinity of the outer segments. The morphological characteristics of this cell type are similar to those of phagocytic cells. The ultrastructural features of the pineal organ of G. affinis are compared with those of other teleosts.

Animals↗
PubMed1990

Pericyte of a teleost fish: ultrastructure, position, and role in neoplasia as revealed by a fish model.

The morphology and position of the pericyte, a periendothelial cell, is described for a teleost fish, Cyprinodon variegatus. This cell was found attached to the abluminal surfaces of capillaries, venules, and arterioles of the submucosa of the midgut of the fish. The cell was encompassed by a thin basal lamina, possessed numerous plasmalemmal vesicles, a "sole region" which contained thinner actin-like filaments and possibly thicker myosin-like filaments, and ranged in form from ovoid to stellate, with long cytoplasmic extensions that partially covered the endothelium of the associated microvessel. The pericyte of C. variegatus has been shown to give rise to hemangiopericytomas (experimentally induced with diethylnitrosamine) and possibly to pericytomas. The range of phenotypic expression of these pericyte-derived neoplasms is broad, and dependent upon the degree of differentiation of their constituent cells which range from clear cell pericytes to myofilamentous laden cells that resemble smooth muscle cells. In this regard and in regard to its normal ultrastructural morphology, and anatomical position, in relationship to microvasculature in this fish, the cell is very similar to other vertebrate pericytes. Limited evidence suggests that small fish species may be excellent study models for further elucidation of pericyte form, function, and role in disease.

Animals↗
PubMed1992

Protein-gold transport in the endocytic complex of trophotaenial absorptive cells in the embryos of a goodeid teleost.

This paper reports adsorptive endocytosis of exogenous proteins by the trophotaenial absorptive cells (TACs) in the viviparous goodeid teleost, Ameca splendens. In vitro incubations were performed with gold conjugated to bovine serum albumin (Au-BSA), human transferrin (Au-HTf), fetuin (Au-Fet), and asialofetuin (Au-ASFet). Localization of gold label on the TAC surface was nearly exclusive to patches of an amorphous coat associated with part of the intermicrovillous plasma membrane. On addition of excess BSA, HTf, Fet, or ASFet to incubation media containing, respectively, Au-BSA, Au-HTf, Au-Fet, or Au-ASFet, the density of gold particles adsorbed on the TAC surface decreased drastically. Moreover, attachment of the four protein-gold complexes to the same plasma membrane sites was suggested by reciprocal inhibitory effects. Further proteins such as hemoglobin, myoglobin, and cytochrome c were as well potent inhibitors of Au-BSA and Au-HTf binding and uptake. Binding of TACs of native BSA or HTf was visualized by immunogold labeling. The interactions between proteins and binding sites required both the presence of Ca2+ and appropriate pH greater than 6.6. Analyses of the concentration-dependent BSA and HTf binding curves, plotted from morphometric data, resulted in apparent dissociation constants, Kds, of approximately 5 x 10(-7) M and 4 x 10(-7) M, respectively. Following binding at the TAC surface and internalization via clathrin-coated pits and vesicles the several ligands were routed along the lysosomal pathway with transit through the endosomal compartment. Prolonged incubation periods led to massive intracellular accumulation of tracer proteins. The effects of NH4Cl (10 mM) treatment on TACs included enormous cytoplasmic vacuolation, a reversible loss of protein binding sites on the plasma membrane, and a block in the transport of protein-gold complexes to lysosomes.

Absorption↗
PubMed1994

Ultrastructure of nonspecific cytotoxic cells in teleosts. I. Effector-target cell binding in a marine and a freshwater species (seabream: Sparus aurata L., and carp: Cyprinus carpio L.).

BACKGROUND: Fish cytotoxic effectors form a cell population whose ultrastructure and properties of conjugation with target cells have not been completely established. We report the ultrastructure of the nonspecific cytotoxic cells in a seawater teleost (Sparus aurata L.) and compare it to a freshwater species (Cyprinus carpio L.). METHODS: Blood leucocytes were incubated with HeLa or B16 melanoma cells. Samples were processed for transmission electron microscopic study. RESULTS: Conjugates consisting of leucocytes binding targets were regularly observed after 30 min, 1 hr, or 2 hr of incubation. In both species leucocytes binding to targets showed ultrastructural features of either monocyte-like or lymphocyte-like cells. Monocyte-like cells usually appeared flattened against the targets and seemed to enclose fragments of the target to form cytoplasmic vesicles and the content of their scarce cytoplasmic granules seemed to be delivered into these vesicles. In the seabream lymphocyte-like cells, dense cytoplasmic granules occurred only occasionally, and neither microvilli nor cell processes were present at the contact areas with the targets. In the carp, the contacts were more numerous and formed regularly interdigitating contact areas and the lymphocytes showed granules with characteristic dense and fibrillar contents. CONCLUSIONS: We conclude that seabream and carp have a leucocyte cell population with ultrastructural features of either monocytes or lymphocytes showing nonspecific cytotoxic ability.

Animals↗
PubMed1995

Reticulo-endothelial stroma of the head-kidney from the seawater teleost gilthead seabream (Sparus aurata L.): an ultrastructural and cytochemical study.

BACKGROUND: Head-kidney, considered the major fish lympho-haemopoietic tissue, consists of cells of the different haemopoietic series supported by a network of stromal cells whose morphofunctional properties have not been established. We report the ultrastructure and cytochemical features of the reticulo-endothelial stroma of the head-kidney from the seawater teleost gilthead seabream (Sparus aurata L.). METHODS: Samples of head-kidney were processed for electron microscopic study. Some of the samples were incubated for acid and alkaline phosphatase, peroxidase, glucose-6-phosphatase, or ATPase. RESULTS: The reticulo-endothelial stroma of gilthead seabream head-kidney consists of sinusoidal cells (endothelial and adventitial cells) and reticular cells (macrophage-type reticulum and fibroblast-like reticular cells). Transcytosis vesicles and rounded medium electron-dense granules were observed in the cytoplasm of the endothelial cells. The adventitial cells partially covered the outside surface of the endothelial cells and were joined by desmosomes. The macrophage-type reticulum cells were characterized by their cytoplasmic processes and acid phosphatase positive lysosomes. The fibroblast-like reticular cells were joined by desmosomes and formed an extensive network between the haemopoietic parenchyma. They were peroxidase negative and acid and alkaline phosphatase, glucose-6-phosphatase, beta-glucuronidase, and ATPase positive. CONCLUSIONS: The ultrastructural and cytochemical features of the reticulo-endothelial stroma of the gilthead seabream head-kidney are similar to those of mammalian bone marrow, suggesting phylogenetic analogies between both tissues.

Animals↗
PubMed2005

Development of the endoplasmic reticulum in the rodlet cell of two teleost species.

The rodlet cell found in different tissues and the blood of teleosts is distinguished by a thick capsule and bipartite rodlets, each consisting of club-like sac and a dense protein core. The development of its rough endoplasmic reticulum (RER) was ultrastructurally investigated in gill and intestinal epithelium of trout (Salmo trutta L., Oncorhynchus kisutch). The RER showed signs of hypertrophy beginning already in immature cells. The typical vesicular appearance noted in the mature cell as well as the apical labyrinth, an accumulation of dislodged mitochondria and vesicles, derives from RER dilatations shedding their ribosomes and pervading the cytoplasm. These dilatations extend also into extracapsular protrusions formerly supposed to be nutritive. A possible role of RER in the formation of the rodlets is indicated by the close association of RER-derived vesicles with rodlet sacs. Conspicuous undulations of the membranes of the sacs as well as the occurrence of tubules (ø = 30 nm) in the dilated RER, rodlet sacs, and along the core support the proposed hypothesis of hypertrophy. Both features signal the storage of (membrane) protein during altered conditions ranging from slowed metabolism to viral infections. The differentiation of apical microvillar projections replaced later by cytoplasmic blebbing and disruption is compatible with surplus production resulting in discharge by pressure. Together with the occasional presence of junctional complexes, these observations argue for an aberrant cell differentiation due to an unknown cause, representing an alternative to the current interpretation of the rodlet cell as a migrating secretory or leucocytic cell with a defensive function.

Animals↗
PubMed2006

Chromaffin cells in the adrenal homolog of Aphanius fasciatus (teleost fish) express piecemeal degranulation in response to osmotic stress: a hint for a conservative evolutionary process.

The effect of severe osmotic stress on the ultrastructural morphology of chromaffin cells in the adrenal homolog of Aphanius fasciatus, a small eurhyaline teleost living in saltpans, was evaluated by electron microscopy quantitative analysis. Fishes were transferred from salt water, whose salinity was 3.7%, to dechlorinated tap water and chromaffin cells were studied at resting condition and after 2 and 48 hr from the beginning of the experiment. Ultrastructural examination revealed a series of granule and cytoplasmic changes highly specific for piecemeal degranulation (PMD), a secretory process based on vesicular transport of cargoes from within granules for extracellular release, which was previously described in chromaffin cells of the mouse, rat, and human adrenal medulla. There was indeed a significant trend toward loss of content material from chromaffin granules accompanied by enlargement of granule size. Remarkably, chromaffin granules maintained their individual close structure during the whole releasing process and eventually transformed into large empty containers. A dramatic increase in the density of small, membrane-bound, variably electron-dense vesicles free in the cytoplasm or attached to granules was recognized during the first 2 hr of stress response. These features fell to control levels after 48 hr. A similar time-course pattern was observed concerning the formation of budding projections from the surface of chromaffin granules. This study provides new insight into PMD physiology and suggests that PMD is part of an adaptive secretory response to severe osmotic stress in fishes. From an evolutionary point of view, this study lends support to the concept that PMD is a secretory mechanism highly conserved throughout vertebrate classes.

Adrenal Medulla↗
PubMed2002

Embryonic origin of the eyes in teleost fish.

The developmental history of the vertebrate eye begins at an early embryonic stage, with the formation of the body axes and induction of neural tissue. Several recent experimental embryological and genetic studies in teleost fish have produced new insights into the morphogenetic and molecular regulation of eye formation. Molecular signaling pathways and patterned expression of transcription factors implicated in eye determination are discussed, and the importance of morphogenetic cell movements is emphasized.

Animals↗
PubMed1992

Actin-dependent myoid elongation in teleost rod inner/outer segments occurs in the absence of net actin polymerization.

In the retinas of teleost fish, rod photoreceptors elongate in response to light. Light-activated elongation is mediated by the myoid of the rod inner segment and is actin-dependent. Inner segment F-actin filaments form bundles running parallel to the cell's long axis. We examined the mechanism of rod elongation using mechanically-detached rod fragments, consisting of the motile inner segment and sensory outer segment (RIS-ROS). When RIS-ROS are isolated from dark-adapted green sunfish and cultured in the light, they elongate 15 microns at 0.3-0.6 microns/min. Elongation was inhibited 65% by 0.1 microM Cytochalasin D, suggesting a requirement for actin assembly. To determine the extent of assembly during elongation, we used three approaches to measure the F-actin content in RIS-ROS: detection of pelletable actin by SDS-PAGE after detergent-extraction of RIS-ROS; quantification of fluorescein-phalloidin binding by fluorimetry, fluorescence-activated cell sorting and image analysis; estimation of total F-actin filament length by electron microscopy. All three assays indicated that no net assembly of RIS-ROS F-actin accompanied myoid elongation. An increase in F-actin content within the elongated myoid was counterbalanced by a decrease in F-actin content within the 13 microvillus-like calycal processes located at the end of the inner segment opposite to the growing myoid. O'Connor and Burnside (Journal of Cell Biology 89:517-524, 1981) showed that minus-ends of rod F-actin filaments are oriented towards the elongating myoid while plus-ends are oriented towards the shortening calycal processes. Our observations suggest that RIS-ROS elongation entails actin polymerization at the minus-ends of filaments coupled with depolymerization at the filament plus-ends.

Actin Cytoskeleton↗
PubMed2002

Monoaminergic and peptidergic axonal projections to the vagal motor cell column of a teleost, the filefish Stephanolepis cirrhifer.

In an immunohistochemical study, the vagal motor nucleus of a teleost, the filefish Stephanolepis cirrhifer, could be divided into a rostral part and a caudal part, and the former into a dorsolateral group and a ventromedial group. The dorsolateral group consisted of neurons immunoreactive for calcitonin gene-related peptide, whereas the ventrolateral-caudal group was negative for calcitonin gene-related peptide. The latter group was retrogradely labeled after dextran amine injection to the visceral ramus of the vagus nerve, suggesting that it is a general visceral efferent column, made up of parasympathetic preganglionic neurons, whereas the dorsolateral rostral group is a special visceral efferent column. In the general visceral efferent column, a dense concentration of nerve fibers immunoreactive for serotonin, tyrosine hydroxylase, cholecystokinin-8, and substance P, and a small number of fibers immunoreactive for neuropeptide Y was observed. Perikarya in contact with varicose terminals immunoreactive for these substances were frequently seen. In contrast, in the special visceral efferent column, only a moderate concentration of neuropeptide Y-immunoreactive nerve fibers and a sparse distribution of fibers immunoreactive for tyrosine hydroxylase were observed. Perikarya in contact with varicose terminals immunoreactive for these substances were rare. These results suggest that the vagal parasympathetic preganglionic neurons might receive multiple inputs of monoaminergic and peptidergic fibers involved in the regulation of the visceral organs. On the other hand, monoaminergic and peptidergic afferent fibers might be of much less significance in the activity of the special visceral efferent component of the vagus nerve.

Animals↗