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At least 775 records · Page 43Linked to original sources
PubMed1981

Retinofugal pathways in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata.

Retinofugal pathways in the spotted dogfish Scyliorhinus canicula and the thornback ray Raja clavata were studied with reduced silver techniques following unilateral eye enucleations. Optic nerve axons decussate in the chiasma opticum, except for a small ipsilateral projection to the area preoptica. After crossing, retinal projections distribute to the area preoptica, the thalamus dorsalis pars lateralis, the thalamus ventralis pars lateralis, the corpus geniculatum laterale, the nucleus pretectalis, and the superficial layers of the tectum mesencephali. In Scyliorhinus most primary optic fibers terminate in the stratum medullare externum of the mesencephalic tectum, while in Raja the zona externa of the stratum cellulare externum receives the bulk of the retinal input. A basal optic tract could be identified in Raja, but not in Scyliorhinus. The retinofugal pathways of the two species studied are compared with those of other cartilaginous fishes and other anamniotes. It is concluded that the primary visual system in chondrichthyans resembles that of actinopterygians and amphibians. However, there is a striking difference in the way in which the primary optic fibers reach the tectal target areas. In elasmobranch fish the optic nerve fibers enter the tectum through the zona interna of the stratum cellulare externum and send their axons into the more superficial tectal layers, while in actinopterygians and amphibians the majority of the optic fibers enter the tectum through the superficial layer and distribute their axons to deeper tectal layers.

Animals↗
PubMed1982

The afferent connections of the tectum mesencephali in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata.

The afferent connections of the tectum mesencephali were studied in the spotted dogfish Scyliorhinus canicula and the thornback ray Raja clavata by means of the horseradish peroxidase (HRP) technique. Following unilateral injections in the tectum, labeled neurons could be identified in all main divisions of the brain and in the cervical spinal cord. Telencephalic neurons which project to the tectum mesencephali were observed in the caudal part of the pallium. Diencephalic projections to the tectum originate from the thalamus dorsalis pars medialis, the thalamus ventralis pars lateralis, the nucleus medius infundibuli, and the pretectal area. In Scyliorhinus labeled neurons could also be found in the corpus geniculatum laterale. Mesencephalic cells of origin of tectal afferent pathways were identified in the stratum cellulare externum of the contralateral tectum, in the nucleus tegmentalis lateralis, in the ventrolateral tegmentum, and in the nucleus ruber. Rhombencephalic cells projecting to the tectum could be identified in the nucleus cerebelli (only in Scyliorhinus), the nucleus vestibularis superior, the reticular formation, the nucleus funiculi lateralis, the nucleus tractus descendens nervi trigemini, and the nucleus dorsalis and intermedius areae octavolateralis. In addition a number of small-and medium-sized cells of the reticular formation were found labeled. Diffusely scattered labeled cells could be observed in the dorsal part of the cervical spinal cord. It is concluded that the tectal afferent connections in the chondrichthyans studied in general resemble those of other vertebrates, but that some striking differences exist. In particular, tectal afferents originating from the nucleus medius infundibuli, the nucleus cerebelli, and the nucleus dorsalis and intermedius areae octavolateralis have not been reported in other vertebrates.

Afferent Pathways↗
PubMed1988

Dense-cored vesicle-containing components of the terminal nerve of sharks and rays.

This paper describes electron microscopic observations of dense-cored vesicle-containing axons, cell bodies, and endings of the terminal nerve in several elasmobranchs. The vesicles are found in two apparent cell types, one with a polymorphic nucleus and another with an oval nucleus. The types may correspond to cells producing one each of two neuropeptides (LHRH and FMRF-amide) that have previously been localized in the nerve. Dense-cored vesicles are found in many unmyelinated fibers in both the terminal nerve proper and its major ganglia. Some of these form complicated structures with interdigitation and wrapping of membranes. Vesicle-containing fibers branch from the nerve, run along nearby blood vessels, and appear to end adjacent to endothelial cells which demonstrate vesicular activity. The observations suggest terminal nerve neurosecretion into the cerebral circulation. Synapses are found in and near the ganglia where they appear to be axodendritic, with multiple contacts in some cases.

Animals↗
PubMed1982

Production, characterization and application of protein isolates from shark. Part 3. Characterization of protein isolates.

The functional and nutritional characterization of two isolates elaborated through cleaning-extraction processes, as well as that of a third isolate obtained by means of a chemical modification (alkaline heat treatment) from one of the former, was carried out. The first two isolates exhibit in general similar properties, are nutritionally comparable with casein and show a fairly high water absorption, having a potentially great value for instance in bakery and meat products and pastes. The modified isolate is essentially different from the isolate used as raw material in many of the characterized parameters, having a high nitrogen solubility index (NSI) by pH 3.5 and 7.0 and thus offering its possible use in such food systems as soft drinks where a high solubility is desired.

Amino Acids↗