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M Kemali

Publications and source records attributed to M Kemali.

At least 37 records · Page 2Linked to original sources
PubMed1983

The extracranial portion of the pineal complex of the frog (frontal organ) is connected to the pineal, the hypothalamus, the brain stem and the retina.

The central connections of the frontal organ of the frog Rana esculenta were studied by means of the cobalt-filling technique using the cobaltic lysine complex. The results showed that the frontal organ has surprisingly more extended connections than those demonstrated after the application of other techniques. In fact, we found that it is connected to the pineal, the hypothalamus, the brain stem and the retina. These connections, which neuroanatomically have not been reported before, suggest that the frontal organ of the frog participates, in some way, in several different functions, such as neuroendocrine activities, motor responses and lateral eyes photoreception interaction.

Animals↗
PubMed1983

Modification of the pigment screening of the frog retina following administration of neuroactive drugs.

Pigment screening (PS) occurs in the retina of lower vertebrates and consists of the bidirectional migration (vitreally or sclerally) of melanin granules into processes of the pigment epithelium that extend between photoreceptors, in response to changes in the illumination conditions. We have studied the effect of some neuroactive drugs on the PS of frogs maintained under cyclic lighting conditions or dark-adapted. The drugs, administered intravenously were: lysergic acid diethylamide (LSD), mescaline, d-amphetamine, the LSD analogue lisuride and the LSD derivative 2-bromolysergic acid (BOL). All the drugs used--with the exception of mescaline--modify the bidirectional migration of the pigment induced by the two illumination conditions in a different way. This suggests that in general these substances interact in some way with those processes which normally produce the well-defined PS pattern. It has been possible to discriminate two opposite effects on the retinal PS induced by two chemically related substances (LSD and lisuride) only one of which (LSD) has potent hallucinogenic properties.

Animals↗
PubMed1983

Central myelin in the shark Scyllium stellare (Elasmobranchii, Selachii).

The central myelin of the phylogenetically ancient shark Scyllium stellare (Elasmobranchii, Selachii) was examined at the electron microscope. The known different chemical compositions of the myelin in higher and lower vertebrates is not associated in the Scyllium with a lack of any basic structural myelin elements, but is probably linked to variations in the myelin compactness and periodicity. Several unusual myelin structures and irregular patterns of unknown origin have been observed. The relationship between myelin-forming cells and the most external layers of myelinated structures suggest the possibility that the cytoplasmic glial wrapping is not the only mechanism responsible for central myelination in this vertebrate.

Animals↗
PubMed1982

Third ventricle suprachoroidal cells.

Using transmission electron microscopy two types of cells on the choroid plexus of the third ventricle of the frog Rana esculenta have been located. They lie on the microvilli and cilia of the choroid epithelium. Their free surface is in contact with the cerebrospinal fluid. One type, Kolmer-like, has large, dense bodies in its cytoplasm. The cytoplasm of the other type is completely filled by large, ovoidal structures which have a limiting membrane and a polymorphic filamentous content. Their functional significance is unknown.

Animals↗
PubMed1982

The action of LSD on the isolated frog spinal cord: electrophysiological and ultrastructural data.

In the isolated hemisected frog spinal cord, LSD induced a substantial enhancement of spontaneous dorsal and ventral root activity and a general decrease of both orthodromic and antidromic root potentials. 2. These electrophysiological modifications were reversible. The LSD homologue compound--Lisuride--was without effect. 3. Electron microscopy of the LSD-treated spinal cord revealed synaptic "omega" figures and terminals almost depleted of vesicles. 4. The results suggest that LSD acts at the synaptic level favouring the spontaneous release of transmitters from those involved in the pathways tested.

Animals↗
PubMed1982

Quantitative evaluation of the number of fibers in the right and left fasciculus retroflexus using horseradish peroxidase.

A quantitative evaluation of the number of fibers in the right and left fasciculus retroflexus (FR) was conducted in the frog Rana esculenta after injections of horseradish peroxidase (HRP) in the habenular nuclei of the two sides of the brain and in the interpeduncular area in separate animals. It seems that the known morphological asymmetry of the habenular nuclei is not accompanied by a corresponding asymmetry of the FR and that there is an equivalent number of fibers in the FR after HRP injections in either the habenulae or the interpeduncular area.

Animals↗
PubMed1982

The morphology of the interpeduncular nucleus of man: a Golgi observation.

The interpeduncular nucleus (ITP) of man has been studied from a human brain impregnated "in toto" by the Golgi method. A wax model reconstructed from serial sections gives information on its size, its shape and its position within the brain. Its volume was also calculated. It overlies the interpeduncular cistern where is one of the major confluences of cerebrospinal fluid and blood vessels. The types of cells impregnated and their relationship to blood vessels and the underpial ventral surface are illustrated. In the ITP of man there are morphologic elements which do not exclude the possibility, at least for a portion of it, of a neurohormonal means of communication which could be exerted through the cerebrospinal fluid and blood vessels.

Adult↗
PubMed1981

Substance P-, met-enkephalin- and somatostatin-like immunoreactivity distribution in the frog spinal cord.

The distribution of substance P-, Met-enkephalin- and somatostatin-like immunoreactivity was studied in the thoracic spinal cord of the frog using immunohistochemical techniques. In fibres, probably nerve terminals, immunoreactivity was greatest in the grey matter (mainly dorsal horn), but it was also present in white matter regions. While substance P- and, perhaps, somatostatin-like immunoreactivity appeared to be contained in primary afferents, the presence of all 3 peptides in neuronal cells of the grey matter indicates the existence of a propriospinal peptidergic system.

Animals↗
PubMed1981

The effect of laser irradiation on the frog pineal.

The frog pineal is a functional photoreceptor with probable endocrine capabilities. Continuous wave Laser radiation at 514.5 nanometers for 300 sec at 200 mW, as focused on the pineal of the intact frog Rana esculenta to study the functional role of this structure. The investigation was carried out on 80 male specimens - 40 of which were controls - in light and in dark experimental conditions - during the months of March, July and November. The ratio gonad weight/body weight was used to measure the effect of the Laser. The response was consistently similar from control frogs kept in the dark and from Laser-irradiated frogs kept in the light. The same was observed in the opposite situation. Histological examination showed structural modifications of the gonads and skin of Laser-irradiated frogs. These results suggest a functional correlation between the pineal photoreceptor cells and the pineal secretory cells. We hypothesize that the pineal itself might influence gonadal activity through the secretion of an hormone within the third ventricle. The frog's skin did not change colour during the Laser irradiation, we therefore suppose that the structures responsible for the release of the hormone regulating colour changes are not effected by the Laser beam.

Animals↗
PubMed1980

Neuroanatomical identification of the frog habenular connections using peroxidase (HRP).

A study of the habenular nuclei connections by means of horseradish peroxidase (HRP) has never been carried out in amphibia. In the present paper we have investigated the afferent projections of the left and right habenular nuclei of the frog Rana esculenta using this technique. Cells, labelled by HRP, were either in a Golgi-like pattern or in a granular pattern. It appears that the habenular nuclei on the two sides of the epithalamus do not show different connections even though they are morphologically asymmetric. In fact, each habenula is connected bilaterally with the septal area and the bed nucleus of the hippocampal commissure, and ipsilaterally with the hypothalamic areas, the entopeduncular nucleus, the periventricular gray of the third ventricle and the interpeduncular nucleus. However, the habenular commissure has typical commissural fibres which apparently do not involve the medial portion of the left habenula. The habenular connections in the frog are generally similar to those reported in the literature for mammals. In addition, our results show the possibility that HRP is transported both retrograde and anterograde.

Animals↗
PubMed1980

Large granular vesicles in the frog spinal cord.

Two types of large granular vesicles have been demonstrated in the spinal cord of the frog Rana esculenta. Each type is contained in different fibres located in the neuropil of the ventral horn. The two types of vesicles differ in their diameter and quantity, in the smoothness of their limiting membrane and the electron density of their core. The possibility that they contain peptides is discussed.

Animals↗
PubMed1980

Lysergic acid diethylamide: morphological study of its effect on synapses.

A morphometric analysis of the effect of LSD on synapses was performed in the habenulae and the interpeduncular nucleus of the frog. The OsO4-fixed nervous tissue was treated with ethanol phosphotungstic acid (EPTA). Intersection of lattice lines with synapses were counted as a proportion of the total length of lines. LSD-treated frogs had a higher total area of synaptic contact than control frogs. Exocytosis profiles were observed only in LSD-treated frogs Other qualitative changes in the ultrastructural characteristic of synapses were appreciable after LSD administration.

Animals↗
PubMed1980

Asymmetry of the habenulae in the elasmobranch "Scyllium stellare". I. Light microscopy.

The habenular nuclei of the elasmobranch "Scyllium stellare" have been studied with conventional histological techniques for light microscopy. Their left-right asymmetry has been defined by the observation of serially cut sections. In addition, their cytoarchitectonic organization has been defined quantitatively. In all specimens observed, the left habenula was larger, longer and richer in myelin than the right. However, it appears that the right habenula is subdivided into more subnuclei than the left. We hypothesize that the morphologic asymmetry of the habenulae might reflect a functional specialization of the two sides of the epithalamus.

Animals↗
PubMed1980

Asymmetry of the habenulae in the elasmobranch "Scyllium stellare". II. Electron microscopy.

The structure of the habenular nuclei of the elasmobranch Scyllium stellare has been examined with the electron microscope. There is asymmetry of the left and right habenulae; difference is manifest in their cell types and myelin distribution. The presence in only the left habenula of cells bearing large granules - probably secretory - and of cells with myelinated perikarya suggest a functional diversification of the habenulae. A large variety of synaptic vesicles occur in the habenulae of both sides but we could not demonstrate a preferential localization of one particular type in specific habenular subnuclei. A feature common to all portions of the habenular complex is the presence of multilamellar astroglial formations wrapping cell bodies and synapses.

Animals↗
PubMed1979

Light- and electron-microscopic structure of cells protruding into the mesencephalic ventricle of Scyllium stellare (Elasmobranchii, Selachii).

In the elasmobranch fish, Scyllium stellare, a complex group of cells protrudes into the cavity of the mesencephalic ventricle of the optic tectum. It consists of six to seven large spherical perikarya which resemble neurons of the mesencephalic nucleus of the Vth cranial nerve. The bundled processes of these cells form a stalk connecting the protrusion with the brain tissue. The protrusion is located in the region where the mesencephalic ventricle joins the cerebral aqueduct. This complex was not found in all specimens examined in the present study. The functional role of this peculiar group of cells, which contain dense core granules and are bathed in the cerebrospinal fluid, is open to discussion.

Animals↗
PubMed1979

The habenular nuclei of the elasmobranch "Scyllium stellare": myelinated perikarya.

Some habenular cells of the elasmobranch, Scyllium stellare, have a perikaryon completely enveloped by myelin of the compact type. They are found only in the left habenula and not in the right. The myelin sheath accompanies the proximal segment of the process arising from the perikaryon, in a node of Ranvier-like pattern. The identity of these myelinated cells and the functional significance of their myelination are unknown.

Animals↗