Laminar Acetylcholinesterase localization in the optic tectum of five seawater teleosts.

The histochemical localization of acetylcholinesterase in the optic tectum of seawater teleosts shows a characteristic laminar distribution which parallels the histological structure of the nervous centre. Significant differences have been observed between Gobius and the other 4 species of teleosts examined. It seems likely that cholinergic mechanisms play an important role in the function of teleost optic tectum.     

Comparative survey on enzyme localization,ultrastructural arrangement and functional organization in the optic tectum of non-mammalian vertebrates

Summary The histochemical localization of some enzymatic activities is surveyed in the optic tectum of vertebrates from cyclostomes to birds. These data are compared with results arising from ultrastructural and experimental works in order to outline some possible connections between enzyme localization and functional organization of the optic tectum. The most interesting result derives from acetylcholinesterase which, in the majority of vertebrate species, is localized in tectal layers in which visual and other sensitive afferents discharge. Such a situation, together with some experimental and developmental results, suggests that cholinergic mechanisms play an important role in the function of the optic tectum and that these mechanisms are worthy of further and more detailed investigations.Acknowledgments. The author is grateful to Prof.S. Leghissa, Dr. F. Ciani andDr. L. Villani for the permission to use the photographs 8–11 of the present paper.     

Enzymatic patterns in reptilian brain. Histochemical characterization of the optic tectum

Summary The enzymatic patterns present in the optic tectum of 4 species belonging to different reptilian orders seem related to the degree of structural and functional organization reached by the nervous centre, as in other vertebrates. In particular the AChE localization in reptiles is representative of a evolutionary sequence in the distribution of this enzyme in the optic tectum along the tetrapode series.     

Existence of a non-retinotopic contralateral retino-tectal visual projection in the normal frog Rana esculenta L]

In the Frog, after unilateral optic nerve and tract section, contralateral visual responses were recorded in the tectum ipsilateral to the section. These responses were elicited by stimulation of a unique spatial region located near the projection of the contralateral eye optic axis and could be randomly recorded on the tectal surface. The possible pathways and the role of such retino-tectal afferences are discussed.     

Selectivity to spatial frequencies in the pigeon's optic tectum cells]

Extracellular cell recordings in the pigeon optic tectum show a selectivity of response to different sine-wave gratings presented in motion. The optimal frequencies are found to be between 0.4 and 0.9 cycle/degree and are independent of direction, orientation and velocity.     

Nerve endings isolated from chick embryonic optic tectum. 2. Developmental aspects of synaptosomal membrane

Summary Fractions enriched in nerve endings (synaptosomes) have been isolated from chick embryonic optic tectum during development. After osmotic shock, these fractions appeared to be enriched in membranes which during development acquire typical features of mature synaptosomal membranes.     

Histochemical remarks on monoamine oxidase and acetylcholinesterase in some regions of amphibian brain

Summary The histochemical localization of monoamine oxidase and acetylcholinesterase has been studied in the cerebellum, optic tectum and telencephalon of three amphibian species. For acetylcholinesterase in particular, different histochemical methods and selective inhibitors have been used in order to investigate the actual nature of enzymatic activity revealed.     

Migratory patterns of clonally related cells in the developing central nervous system

Summary Neurons and glioblasts that arise in the ventricular zone migrate to form discrete nuclei and laminae as the central nervous system develops. By stably labeling precursor cells in the ventricular zone, pathways taken by different cells within an individual clone can be described. We have used recombinant retroviruses to label precursor cells with a heritable marker, theE. coli lacZ gene; clones of lacZ-positive cells are later mapped histochemically. Here we review results from three regions of the chicken central nervous system — the optic tectum, spinal cord, and forebrain - and compare them with previous results from mammalian cortex and other regions of the vertebrate CNS. In particular, we consider the relationship between migratory patterns and functional organization, the existence of multiple cellular sources of migratory guidance, and the issue of whether a cell's choice of migratory pathway influences its ultimate phenotype.     

Nerve endings isolated from chick embryonic optic tectum. 1. Developmental aspects of intact synaptosomes

Summary Fractions enriched in nerve endings (synaptosomes) have been isolated from optic tectum of chick embryos at 16 and 18 days of incubation and of chicks immediately after hatching. Morphological aspects of nerve endings have been examined with special regard to the appearance of synaptic thickenings and synaptic vesicles.     

Zum Vorkommen von RNS im Nervenfaserbereich

Summary The incorporation of 3H-uridine into the RNA of the perikaryal and fibrous region of the optic tectum of the fish brain was investigated by means of radioautography after incubation times of 11 min to 96 h. There is no transport of RNA from the cell body to the nerve fibres. After RNase-treatment 90% of perikaryal RNA-labelling is washed out, but only a very small amount of the previous very few labelling of the nerve fibres.     

Immunocytochemical localization of GnRH (gonadotropin releasing hormone) systems in the brain of a marine teleost fish,the sole

Summary The GnRH system was studied in the brain of the sole by immunocytochemistry (peroxidase-antiperoxidase method) (PAP) using antibodies to synthetic salmon GnRH (s-GnRH). Two centers containing immunoreactive cell bodies were observed in the forebrain, one located at the junction between the olfactory bulbs and the telencephalon and the other in the preoptic area. Numerous immunoreactive fibers were found, especially in the telencephalon, hypothalamus, pituitary, optic tectum and retina.     

Radioautographic analysis of retinofugal projections in the primitive bony fish Polypterus senegalus C.]

Retinofugal pathways of Polypterus senegalus C. have been examined by means of the radioautographic method. Contralaterally the retina projects to the hypothalamus, thalamus, pretectum and tectum. An important ipsilateral component has been observed. No retinal projection to the mesencephalic tegmentum has been identified. Comparing the primary optic system of Polypterus with that of other body Fish, indicates that this species possesses a combination of characteristics which are both actinopterygian and sarcopterygian. The significance of this mozaic arrangement is discussed.     

Topography of the tecto-tectal component of the main ipsilateral visual pathway of the frog (Rana esculenta L.)]

The detailed topography of the tecto-tectal component of the Frog's ipsilateral visual pathway is electrophysiologically obtained by mapping the optic lobes. This linkage transfers the visual information explored along a transversal tectal row on to an homologous line oriented at 130 degrees on the opposite tectum. The ipsilateral projection of the temporo-nasal axis of the retina, but not of the antero-posterior axis of the visual field, is reversed compared to its contralateral projection. Finally, the majority of the homologous tectal points are asymmetrical with respect to the animal's sagittal axis.     

Der Einfluss von Colchizin und Ethidium-Bromid auf den Gehalt radioaktiv markierter Uridin-Verbindungen in optischen Axonen von Teleosteern

Summary After application of colchicine to one eye, and subsequent injections of³H-histidine or³H-uridine into both eyes, a blockage of the transport in the optic system of teleosts could be demonstrated only for the fast protein-components. However, colchicine is able to depress the effectivity of ethidium-bromide, a blocker of mitochondrial RNA-synthesis. This finding is discussed in connection with the possibility that axonal mitochondria are associated with the neurotubules.

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Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft, die Herrn Prof. Dr.H. Rahmann (Münster) die Mittel zu dieser Untersuchung zur Verfügung stellte.     

Migratory patterns of clonally related cells in the developing central nervous system

Neurons and glioblasts that arise in the ventricular zone migrate to form discrete nuclei and laminae as the central nervous system develops. By stably labeling precursor cells in the ventricular zone, pathways taken by different cells within an individual clone can be described. We have used recombinant retroviruses to label precursor cells with a heritable marker, the E. coli lacZ gene; clones of lacZ-positive cells are later mapped histochemically. Here we review results from three regions of the chicken central nervous system--the optic tectum, spinal cord, and forebrain--and compare them with previous results from mammalian cortex and other regions of the vertebrate CNS. In particular, we consider the relationship between migratory patterns and functional organization, the existence of multiple cellular sources of migratory guidance, and the issue of whether a cell's choice of migratory pathway influences its ultimate phenotype.     

Dynamics of increase in muscle fibers in fishes in relation to size and growth

Summary Dynamics of increase of white myotomal muscle fibers of four species of freshwater teleosts (Salmo gairdneri, Pimephales notatus, Esox masquinongy andE. americanus vermiculatus) from three families (Salmonidae, Cyprinidae, Esocidae) representing a variety of maximum attainable sizes and growth rates, have been investigated. There are at least three major differences in these dynamics, and there appears to be an association between the ability of a fish species to attain large size (and grow fast) and its ability to recruit new fibers into this predominant tissue of the myotomal mass.     

Metabolism of the snailCryptozona ligulata during regeneration of optic tentacles

Summary The biochemical changes in the hemolymph and tissues were followed during regeneration of the optic tentacles of the snailCryptozona ligulata (Pulmonata-Stylommatophora). There is a remarkable increase in total carbohydrates in hemolymph and tissues and glycogen in tissues at the expense of free amino acids and fatty acids. It is clear that ablation of the optic tentacles stimulates carbohydrate synthesis through glyconeogenic routes. The optic tentacles regenerate completely in 18–21 days.     

Regulation of carbohydrate metabolism by the optic tentacles of the garden snailCryptozona ligulata (Gastropoda-Stylommatophora)

Summary The presence of a hyperglycemic factor in the optic tentacles of the snailC. ligulata is reported here. A preliminary characterization based on crude extracts indicates the factor to be water-soluble, heat labile and to be an albumin. The ablation of optic tentacles and injection of optic tentacle extract into operated and normal snails caused a rise in blood sugar, total carbohydrate and glycogen in the foot muscle and mantle and a decrease in hepatopancreatic glycogen. The ablation also caused a fall in blood free amino acids and a rise in the tissues, which was reversed in the blood and foot muscle by injection of the extract. Possible conversion of amino acids to total carbohydrates and glycogen by gluconeogenesis is suggested.