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A Contestabile

Publications and source records attributed to A Contestabile.

At least 109 records · Page 6Linked to original sources
PubMed1981

Biogenic amine terminals in the goldfish cerebellum and optic tectum: a fluorescence and autoradiographic study.

The intraventricular administration of 3H-noradrenaline was used to demonstrate the presence and the distribution of the monoaminergic terminals in the goldfish cerebellum and optic tectum. Monoaminergic terminal can be selectively labelled by tritiated neurotransmitter and are visualized by light and electron microscopic autoradiography. Further evidence of the presence of catecholamines in these encephalic areas was furnished by the induced-fluorescence technique.

Animals↗
PubMed1980

Evidence of intrinsic cholinergic circuits in the optic tectum of teleosts.

Choline acetyltransferase (CAT) was assayed in the optic tectum of 4 teleost species with different visual powers. The results showed a close relationship between the enzyme levels in the optic tectum and the development of the visual system. In the more visual species, the trout, CAT activity in the optic tectum was about 30-fold higher than in the catfish, whose visual system is much less developed. Two species with intermediate development of the visual system, the goldfish and the tench, showed intermediate levels of CAT activity. Kainic acid treatment caused a significant decrease in both CAT and acetylcholinesterase (AChE) in the goldfish optic tectum. Concomitant histological examination showed, among other effects, the disappearance of most neurons belonging to the pyramidal and fusiform type in the striatum fibrosum and griseum superficiale of the tectum. The comparative and experimental data therefore suggest that the relationship between cholinergic mechanisms and the visual function is, to a significant extent, connected with the presence of intrinsic cholinergic circuits in the optic tectum. The relevance of these findings, also in relation to the problem of the identification of the retino-tectal transmitter, is discussed.

Acetylcholinesterase↗
PubMed1980

Vascular permeability associated with axonal regeneration in the optic system of the goldfish.

An association between axonal regeneration and failure of the blood-brain barrier to plasma proteins has been studied in the goldfish. Vascular permeability was examined by fluorescence microscopy following injection of rhodamine B-labelled bovine serum albumin. Axonal regeneration was studied in adjacent silver-stained sections. Following transection of axons by crushing one optic nerve, it was found that a zone of increased vascular permeability accompanied the advancing front of regenerating axons through the optic nerve, chiasma and tract and into the stratum opticum of the tectum. These observations lend support to a hypothesis in which it is postulated that axons are able to regenerate only when plasma proteins are available to their growth-cones. However, it is also possible that the increased permeability is a consequence rather than a cause of the presence of regenerated axons.

Animals↗
PubMed1979

Disappearance and recovery of catecholamine innervation in brain regions of adult goldfish following 6-hydroxydopamine treatment.

The effect of 6-OHDA treatment on catecholamine innervation was studied in the cerebellum, optic tectum and lobus vagi of the goldfish. Catecholamine terminals completely disappeared in less than two weeks after intraventricular injection of 10 microgram 6-OHDA. In periods comprised between 40 days and 4 months after drug injection, catecholamine terminals reappeared to a different degree. The cerebellum showed the highest recovery and, as far as the valvula cerebelli was concerned, also over-innervation. The remarkable power to restore catecholamine innervation led to a distribution of reappearing terminals similar to that of normal animals in the different layers of the three structures examined.

Animals↗
PubMed1979

Ultrastructural localization of acetylcholinesterase in retino-deprived optic tectum of the goldfish.

The ultrastructural localization of AChE has been studied in the optic tectum of the goldfish after unilateral eye ablation. 1 or 4 months after the operation the patterns of enzyme localization were essentially the same in the normal and affected optic tectum, despite structural modifications caused by the degeneration of retinal terminals and dendritic atrophy of some tectal neurons. The results are discussed in relation to the different hypotheses put forward concerning possible cholinergic mechanisms in the optic tectum of teleosts.

Acetylcholinesterase↗
PubMed1979

Electron microscope histochemistry of acetylcholinesterase distribution in the optic tectum of teleosts.

An ultrastructural analysis was made on acetylcholinesterase (AChE) localization in the optic tectum of two teleosts, the goldfish and the catfish. Electron microscope histochemistry reveals several details on synthesis, distribution and possible sites of utilization of the enzyme in the different tectal layers. The results show that AChE is synthesized by all the neuronal types present in the optic tectum. The final localization of the enzyme is the result of its synthesis in cell bodies, its storage and transport along dendrites and its release in extracellular spaces. The differences in AChE localization between the two teleosts examined mainly derive from differential enzyme release in the corresponding layers of the optic tectum. Cholinergic synapses cannot be precisely identified by means of AChE histochemistry, but the layers in which maximum release of enzyme in the extracellular spaces occurs most likely correspond to areas where cholinergic mechanisms are operating. In this connection some interesting differences of AChE localization in the superficial tectal layers (stratum marginale, stratum opticum and stratum fibrosum et griseum superficiale) are discussed. Electron microscopic histochemistry of AChE confirms its usefulness in better understanding some links between the anatomical and functional organization of complex neural structures.

Acetylcholinesterase↗
PubMed1978

Acetylcholinesterase activity in the normal and retino-deprived optic tectum of the quail. Light and electron microscopic histochemistry and biochemical determination.

Acetylcholinesterase localization has been studied by electron microscopic histochemistry in the quail optic tectum. Ultrastructural analysis reveals that the different neuronal types in the tectum possess the metabolic pathways for AChE synthesis to different degrees. From the site of synthesis in cell bodies the enzyme spreads towards areas of neuropil. In the neuropil of AChE-rich areas a balance seems to exist between enzyme stored in dendrites (and sometimes axon terminals) and enzyme released into the extracellular spaces. Precise identification of cholinergic synapses by means of AChE localization is in most cases impossible, due to extensive spread of the enzyme through the extracellular compartments of the neuropil. Unilateral ocular ablation causes disappearance of the stratum opticum and decrease in thickness of the superficial tectal layers in the contralateral optic tectum, but only minor modifications in AChE localization. This finding is in agreement with biochemical results which show equivalence of the relative concentration of AChE in the right and left optic tectum 1 or 2 months after ablation of the right eye. The experimental evidence suggests that cholinergic mechanisms are not related to the discharge of retinal afferents on receptive tectal neurons, but more likely to intrinsic neural circuits which might be involved in the modulation of tectal activity.

Acetylcholinesterase↗
PubMed1978

Acetylcholinesterase decrease in the optic lobe after unilateral eye deprivation.

Unilateral eye enucleation in a teleost and a turtle results in progressive AChE decrease in the optic lobe controlateral to the extirpated eye. The final difference reaches 15% in teleost and more than 20% in turtle. No drastic differences in localization, but a rearrangement of histochemical pattern, due to the degeneration of retinal fibres, is noticed.

Acetylcholinesterase↗
PubMed1978

Methodological aspects of the histochemical localization and activity of some cerebellar dehydrogenases.

In a detailed study focused on the methodological problems in dehydrogenase histochemistry [e.g., fixation, diffusion of enzymes and of reduced inermediates, conversion of NADPH and NADP to NADH and NAD, respectively, penetration of tetrazolium salt and formazan substantivity, 'nothing dehydrogenase' reaction, use of exogenous CoQ10 and of flavoprotein substitute (PMS)], the distribution and activity of succinate dehydrogenase, NAD(P)H-tetrazolium reductase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase (H and M types), and of L-glutamate dehydrogenase (E.C.1.4.1.2 and E.C.1.4.1.3) have been investigated in the rat cerebellum. It was evident from the study that reliable results could only be obtained if all the aforementioned factors had been considered. The image of actual concentration of SDH in the neuropil of the molecular layer could only be recorded by adding CoQ10, while other structures exhibited greater balance between SDH and endogenous mitochondrial CoQ. Contrary to previous studies, a reversed localization of the activity of G-6-PDH and LDH was noticed. The elements of molecular and Purkinje layers were rich in G-6-PDH, while the granular layer was nearly depleted. The actual level of LDH could only be recorded if NADH-tetrazolium reductase was bypassed with PMS. The H and M types of LDH coexisted in the three cortical layers, the H type being prevalent and the M type attaining its highest level in synaptic glomeruli followed by the structures of the molecular layer and the Purkinje cells. High activity of GDH was noticed in Bergmann glia followed by synaptic glomeruli, while most other structures showed weak to moderate activity. The two GDH types coexisted in all structures showing activity, except for Bergmann cells, which only showed presence of the E.C. 1.4.1.3 type. Furthermore, Bergmann glia was exceptional by showing no activity of SDH and LDH, but strong activity of G-6-PDH and NADPH-tetrazolium reductase. The granular cells were exceptional by showing weak or no activity of all enzymes in question.

Animals↗
PubMed1977

Ultastructural analysis on acetylcholinesterase localization in the cerebellar cortex of teleosts.

The histochemical localization of acetylcholinesterase (AChE) was studied by electron microscopy in the cerebellar cortex of the goldfish and the catfish. The patterns of enzyme distribution show noticeable differences in the two teleost species at the level of the corresponding cerebellar structures. Among the most distinctive features is the prevailing intracellular localization of enzyme activity in the goldfish and the prevailing extracellular localization in the catfish in the molecular layer and, to a lesser extent, the granular layer. Only quantitative differences in the ability to synthesize AChE can be recorded among the different cerebellar neurons in the two species, since all these neurons exhibit different amounts of enzyme activity linked to their cytoplasmic structures. Comparing the results obtained with those of previous histochemical, experimental and developmental researches, the hypothesis seems well founded that the embryonic pool of cerebellar neurons is made up of AChE-synthesizing nruroblasts which, during development, loss or maintain to a different the mechanisms for AChE synthesis. In addition the light and electron microscope histochemistry reveals at different levels of resolution that the final pattern of AChE distribution in the cerebellar cortex is the sum of different degress of AChE synthesis by cerebellar neurons and different degrees of enzyme release in extracellular spaces.

Acetylcholinesterase↗
PubMed1977

Ultrastructural pattern of acetylcholinesterase distribution in the cerebellar cortex of the quail.

The ultrastructural localization of acetylcholinesterase (AChE) was studied in the cerebellar cortex of the quail by means of histochemical method. The greater amount of AChE was detected at leve of the molecular layer in the intracellular spaces between parallel fibers and between parallel fibers and dendritic terminals. Many neurons showed intracellular localization of enzyme activity: the AChE positive neurons were all Golgi cells, most stellate the basket cells and different aliquots of Purkinje and granule cells. The enzymatic activity was usually localized in the cisternae of endoplasmic reticulum, in the nuclear envelope (but this last localization was not present in Purkinje cells- and sometimes in the Golgi apparatus; reaction granules were usually scarce in the different dendritic branches ramifying in the molecular layer. On the basis of the ultrastructural pattern of AChE distribution, some considerations are developed on the methodological aspects concerning the reliability of histochemical methods, the differences recorded at light and electron microscope level, the problems related to extracellular localization of enzyme, the difficulty of establishing a precise correlation between AChE localization in a cerebellar neuron and its possible cholinergic and/or cholinoceptive nature.

Acetylcholinesterase↗
PubMed1977

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

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.

Acetylcholinesterase↗
PubMed1977

Cholinesterase patterns in the cerebellum of reptiles.

In the cerebellum of four species belonging to the three main reptilian orders the histochemical localization of cholinesterases has been studied. The use of different substrate-inhibitor combinations permits to record the distribution patterns of acetylcholinesterase and pseudocholinesterase, mainly revealed as butyrylcholinesterase activity. From the neurological point of view it is interesting to note that acetylcholinesterase activity shows three different distribution patterns in reptilian cerebellum, thus confirming the characteristic variability previously noticed in the cerebellar cortex of other vertebrates.

Acetylcholinesterase↗
PubMed1976

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

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.

Acetylcholinesterase↗
PubMed1976

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.

Acetylcholinesterase↗