PubMed Health⌕ Search

Biomedical subjects

S O Ebbesson

Publications and source records attributed to S O Ebbesson.

At least 19 recordsLinked to original sources
PubMed1992

Postsmolt change in numbers of acetylcholinesterase-positive cells in the pineal organ of the Pacific coho salmon.

We have examined the occurrence of acetylcholinesterase (AChE)-positive cells in the pineal organ of different developmental stages of the Pacific coho salmon. Large numbers of AChE cells were present in freshwater living alevins, in all stages of presmolts (n = 307-544), and in adult spawners (n = 696-1774), whereas seawater-living postmolts displayed a total lack of labeled cells. The AChE-reactive cells were evenly distributed within the pineal end-vesicle and stalk of the presmolts and adults. However, the AChE-positive cells that occurred in the pineal stalk were of a smaller type and more uniform in shape than the cells of the pineal end-vesicle. The dense populations of AChE-stained cells in the alevins were all situated in the caudal part of the pineal end-vesicle. We conclude that changes in pineal metabolism occur in postsmolt salmon that live in salt-water. It is not clear whether the observed change in pineal AChE expression is an "unspecific" change caused by the life in the sea, reflecting alterations that are related to aspects of osmoregulation, and/or is involved in the visual function of the pineal organ resulting from changes in the environmental lighting conditions, e.g., photoperiod, light-intensity, or spectral composition. This study adds to our previous findings of changes that occur in the central nervous system of the salmon during the time of the parr-smolt transformation and migration between limnic and marine environments, and indicates a possible central role of the pineal organ in the control of these events.

Acetylcholinesterase↗
PubMed1992

A morphometric study of age-related changes in serotonin-immunoreactive cell groups in the brain of the coho salmon, Oncorhynchus kisutch Walbaum.

In the coho salmon there is a transient increase in total brain concentrations of serotonin during smolt transformation which occurs midlife, just before down-stream migration to the ocean. There is also a gradual age-related increase in total brain serotonin concentrations. These increases may be due to reorganization of the central serotonergic system, changes in serotonin turnover, or both. They may be related to the specific physiological conditions during different life stages of salmon, or to ongoing growth and plastic changes of the brain. In the present study we have compared serotonin-immunoreactive (5-HTir) cell groups in 1-year-old freshwater presmolt and 2-year-old seawater postsmolt salmon. Our data indicate a continuous growth of the 5-HTir cell groups in terms of an increase in numbers of 5-HTir neurons in the cell groups of the pretectum and the brain stem, and an increase in the volumes of such neurons and cell groups. However, when related to the increase in total brain volume, i.e., the volume that may be innervated by the 5-HTir neurons, the ratio of 5-HTir neurons per mm3 decreased. The largest decreases were observed in the median raphe nucleus (P less than 0.005) and the B9 group (P less than 0.05). The ratio of volumes of the brain nuclei containing 5-HTir neurons relative to total brain volume was remarkably constant when comparing pre- and postsmolt brains: only the pretectal nucleus showed a significant decrease (P less than 0.01) in relative volume. The total volume of 5-HTir neurons increased in postsmolts (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1992

Changes in ligand binding to GABAA receptor sites in pacific salmon (Oncorhynchus) brain during spawning migration and "aging".

When several years old, pacific salmon return to the site of birth, to spawn. At this time, a rapid aging process begins and the fish die within a few weeks after reproducing. Age-related changes of high and low affinity GABA binding sites were studied in salmon brains at three different phases of the spawning migration, i.e. shortly after returning to the natal stream, at the time of spawning, and thereafter. High affinity GABA binding slightly increased while the fish deteriorated. The low affinity component showed a remarkable decrease in density and a concomitant increase in affinity during this final episode of salmon life.

Aging↗
PubMed1991

Ontogeny of the olfacto-retinalis projection in coho salmon (Oncorhynchus kisutch).

Filling of nucleus olfacto-retinalis neurons by cobaltous lysine injections into one eye of coho salmon of different ages revealed that the terminal nerve projection to the retina is established when the fish leave their freshwater environment. At this time salmons go through a metamorphosis termed "smoltification." FMRF-amide-like immunoreactive neurons in the nucleus olfacto-retinalis already exist in pre-smolts before the retino-petal projection is established. Thus, for the first time in any vertebrate, a projection of the terminal nerve is shown to develop during an advanced ontogenetic state.

Animals↗
PubMed1990

Distribution of FMRFamide-like immunoreactivity in the brain, retina and nervus terminalis of the sockeye salmon parr, Oncorhynchus nerka.

Neurons displaying FMRFamide(Phe - Met - Arg - Phe - NH2)-like immunoreactivity have recently been implicated in neural plasticity in salmon. We now extend these findings by describing the extent of the FMRF-like immunoreactive (FMRF-IR) system in the brain, retina and olfactory system of sockeye salmon parr using the indirect peroxidase anti-peroxidase technique. FMRF-IR perikarya were found in the periventricular hypothalamus, mesencephalic laminar nucleus, nucleus nervi terminalis and retina (presumed amacrine cells), and along the olfactory nerves. FMRF-IR fibers were distributed throughout the brain with highest densities in the ventral area of the telencephalon, in the medial forebrain bundle, and at the borders between layers III/IV and IV/V in the optic tectum. High densities of immunoreactive fibers were also observed in the area around the torus semicircularis, in the medial hypothalamus, median raphe, ventromedial tegmentum, and central gray. In the retina, immunopositive fibers were localized to the inner plexiform layer, but several fiber elements were also found in the outer plexiform layer. The olfactory system displayed FMRF-IR fibers in the epithelium and along the olfactory nerves. These findings differ from those reported in other species as follows: (i) FMRF-IR cells in the retina have not previously been reported in teleosts; (ii) the presence of FMRF-IR fibers in the outer plexiform layer of the retina is a new finding for any species; (iii) the occurrence of immunopositive cells in the mesencephalic laminar nucleus has to our knowledge not been demonstrated previously.

Amino Acid Sequence↗
PubMed1990

Tectal afferents in Rana pipiens. A reassessment questioning the comparability of HRP-results.

Studying afferents to the optic tectum in Rana pipiens by means of retrograde HRP transport, results were obtained, that cast doubt on the reliability of this neuronal tract tracing technique. The tectum was found to receive afferents from e.g. lateral mesencephalic tegmentum, torus semicircularis, contralateral large-celled pretectal nucleus, and ipsilateral thalamic nuclei, which have not previously been demonstrated. In addition, the data obtained lack evidence of projections reported earlier. We suggest, that neuronal projections may be subject to hormone and/or activity dependent changes, that alter the probability of accumulating sufficient amounts of the tracer to become labeled.

Animals↗
PubMed1989

Retino-petal neurons in the diencephalon of juvenile Lobotes surinamensis (teleostei).

Diencephalic retino-petal neurons in juvenile specimens of the teleost Lobotes surinamensis are not segregated into subpopulations that form discrete nuclei. A continuous band of such cells extends from the rostral to the caudal diencephalon. It includes some locations previously described as retino-petal nuclei in other teleosts. The vast majority of diencephalic retino-petal cells only projects to the contralateral eye in Lobotes.

Animals↗
PubMed1989

Retinopetal cells exist in the optic tectum of steelhead trout.

The existence of retinopetal cells in the tectum of various teleost fishes as been claimed by several authors. Others, however, have been unable to verify such observations and attribute the findings of retrogradely labelled tectal cells to methodological problems. In this study cobalt-lysine and HRP have been used as neuronal tracers. Evidence is provided for the presence of retinopetal cells in the tectum of steelhead trout. Dendritic arborizations of some of the cells are extremely elaborate. In salmon no such findings were made.

Animals↗
PubMed1988

FMRFamide-like immunoreactive neurons of the nervus terminalis of teleosts innervate both retina and pineal organ.

The tetrapeptide FMRFamide (Phe-Met-Arg-Phe-NH2) was first isolated from molluscan ganglia. Subsequently, it has become clear that vertebrate brains also contain endogenous FMRFamide-like substances. In teleosts, the neurons of the nervus terminalis contain an FMRFamide-like substance, and provide a direct innervation to the retina (Proc. Natl. Acad. Sci. U.S.A., 81 [1984] 940-944). Here we report the presence of FMRFamide-immunoreactive axonal bundles in the pineal organ of Coho salmon and three-spined sticklebacks. The largest numbers of axons were observed proximal to the brain, in the pineal stalk, while the distal part of the pineal organ contained only few axons. No FMRFamide-like-immunoreactive (IR) cell bodies were observed in the pineal organ. In adult fish it was not possible to determine the origin of these axons, due to the large numbers of FMRFamide-like IR axons in the teleost brain. However, by following the development of FMRFamide-like IR neurons in the embryonic and larval stickleback brain, it was possible to conclude that, at least in newly hatched fish, FMRFamide-like IR axons that originate in the nucleus nervus terminalis reach the pineal organ. Thus, it seems there is a direct connection between a specialized part of the chemosensory system and both the retina and the pineal organ in teleost fish.

Aging↗
PubMed1988

The left habenular nucleus contains a discrete serotonin-immunoreactive subnucleus in the coho salmon (Oncorhynchus kisutch).

By use of antibodies against serotonin, a discrete subnucleus of putatively serotoninergic neurons was observed in the dorsal subdivision of the left habenular nucleus in the brain of the coho salmon. The subnucleus was observed in salmon of different life-stages: in fingerlings, during smolt transformation, after smolt transformation (in seawater), and after spawning. This finding further emphasizes the close relationship between the pineal organ and the habenular nuclei-not only in terms of topographical proximity but also in terms of cytological similarities: cells of the habenular nucleus and the pineal complex have previously been shown to be immunoreactive also with antibodies directed against retinal phototransduction proteins. It also underlines the asymmetric organization of the epithalamic region.

Animals↗
PubMed1988

The use of cryostat microtomy in a simplified Golgi method for staining vertebrate neurons.

The use of cryostat and cryoprotective measures for processing Golgi impregnated brain tissue has shortened and simplified the method without loss of quality. The procedure contains the following steps: (1) the animal is perfused with phosphate-buffered paraformaldehyde and the brain removed for storage in the fixative; (2) the brain is rinsed in buffer, cut into 3- to 6-mm-thick blocks and placed in Ramon-Moliner's impregnation solution for 2-4 weeks; (3) the brain tissue is cryoprotected by soaking in 30% sugar for 24 h and then frozen and cut on a cryostat, the sections, being collected directly on slides; and (4) the mounted sections are then alkalized, fixed, rinsed, counterstained and rinsed again before dehydration, clearing and coverslipping.

Animals↗
PubMed1988

Retinal projections in sockeye salmon smolts (Oncorhynchus nerka).

The retinal projections in 2-year-old salmon smolt (Oncorhynchus nerka) are significantly different from those observed in other teleosts examined to date in that the projections are more extensive. Very noticeable are extensive projections to most of the dorsal thalamus, to all layers of the optic tectum, and into the periaqueductal gray of the torus semicircularis. The salmon smolt has bilateral retinal projections to the diencephalon and pretectum. A small retinal projection to the lateral habenular nucleus has not been described previously. Although these findings suggest striking differences in retinal projections among teleosts, this variation may relate to age differences since the previously studied teleosts were adults.

Animals↗
PubMed1987

Double labeling of neural circuits using horseradish peroxidase and cobalt.

This describes for the first time a non-fluorescent method for studying the connectional interrelationship of two neuronal systems in the same histological sections in which the systems are stained in two different colors (blue and brown). Since HRP and cobaltous-lysine are transported in both anterograde and retrograde directions, it is possible to manipulate the experiments to determine, for example, how the terminal fields of two systems overlap in a given neuropil, or cell aggregate, or how the projections of one system relate to retrogradely stained neurons of another system. The simple staining of HRP and cobalt is accomplished on cryostat sections and involves the combined technology of two previously published methods. The results described here are limited to a comparison of the overlap or lack of overlap of inputs to the thalamus from the two eyes in Xenopus, but the method has also proven useful in similar studies on Ambystoma tigrinum and Esox niger.

Ambystoma↗
PubMed1986

Some primary olfactory axons project to the contralateral olfactory bulb in Xenopus laevis.

Cobaltous lysine and horseradish peroxidase (HRP) were used to trace primary olfactory axons to their terminations. The tracers were taken up in the olfactory mucosa and transported to the olfactory bulb. The results suggest that either HRP or cobaltous-lysine methods are useful and simple tools for studying such connections. In addition to the ipsilateral projection, we report here for the first time a projection to the medial part of the contralateral olfactory bulb. The overlaps of ipsi- and contralateral inputs to the medial bulb provide further evidence that its functions in frogs may be different from the lateral part, because other connections differ as well.

Animals↗
PubMed1985

Axosomatic retinal projection to deep tectal neurons and retinopetal neurons in largemouth bass (Micropterus salmoides lacepede).

Retinal connections were studied in largemouth bass with a cobalt-lysine method. Retinopetal neurons were identified in the area ventralis pars ventralis of the telencephalon. The retinofugal pathways are the same as reported earlier, except for a massive projection to one layer of cells in the striatum griseum periventriculare of the optic tectum. Such a projection has not previously been reported in any vertebrate.

Animals↗
PubMed1985

Eye movements evoked from telencephalic stimulations in the piranha (Serrasalmus nattereri).

The telencephalon of spinally transsected, unanesthetized piranhas was systematically stimulated with microelectrodes to scan for eye movement inducing (EMI) sites which were then identified by histological means. EMI sites were found clustered in several distinct central and medial telencephalic areas. Various types of eye movements were evoked from these sites often in combination with movements of the jaw, gills and pectoral fins. It is concluded that eye movements evoked from the telencephalon may be mediated by the optic tectum.

Animals↗
PubMed1984

A simplified cobalt-lysine method for tracing axon trajectories in the central nervous system of vertebrates.

The cobalt-lysine method for tract tracing in the vertebrate CNS has been shortened and simplified to the following steps: (1) the cobalt-lysine is applied to the nerve or tract being studied; (2) the animal is perfused 1-2 days later by the following sequence of solutions: (a) phosphate-buffered ammonium sulfide, (b) phosphate buffer alone and (c) phosphate-buffered glutaraldehyde; (3) the brain is exposed to the fixative overnight and left in 30% sugar another night; (4) the brain is then frozen and cut on a cryostat; the sections being collected directly on slides; (5) the mounted sections are then put in an intensification solution before dehydration, clearing and coverslipping.

Ambystoma↗