C. Olivieri-Sangiacomo

On the fine structure of the perivascular cells in the neural lobe of rats

SummaryThe purpose of this study is to investigate the ultrastructural features of perivascular cells as found in the neural lobe of the hypophysis. In particular, an inquiry was made into the nature of the relationship of such cells to neurosecretory fibers and endings. The latter, in fact, are often invaginated within the perivascular cells and enveloped by their processes; furthermore, they often reveal a certain number of empty granules as well as characteristics of degenerative nature. In the course of this study the localization of the perivascular cells has been investigated as well as that of their processes within the extensive interlobular network typical of the hypophysial neural lobe of rodents. Based on the data gathered, the hypothesis is put forward that the perivascular cells play an important role in the turnover of neurosecretory endings, both under physiological and experimental conditions, contributing thereby to the release of post-hypophysial hormones.

Ultrastructural modifications of denervated taste buds

SummaryThe subject of this study is the ultrastructural alterations of the taste-bud cells of the foliate papilla of the rabbit after sectioning of the homolateral glossopharyngeal nerve. In the course of the experiment two different, and successive, degenerative patterns were observed: the first involves type I sensory cells and the development therein of numerous dense inclusion bodies with a marked polymorphism similar to the classic lysosomes in various stages of development. Some assume the character of autophagic vacuoles or cytosegregosomes with cytoplasmic organelles more or less altered. They prefer slightly differentiated cells and, in particular, a type of cell characterized by a clear cytoplasmic matrix and a scarsity of the organelles.The other degenerative pattern, which appertains to the type II cells, overwhelms the entire cytoplasmic organization and rapidly causes the destruction of the cell.These observations are discussed in relationship to:1.the evaluation of the autophagic function of the lysosomes and in particular the cytosegregosomes;2.the theory of the trophic function of nerves, in general, and sensory nerves, in particular.

Ultrastructural features of rat pituicytes in organotypic culture

SummaryNeural lobes of adult rats have been explanted and organ-cultured for 5–10 days. While perivascular cells and neurosecretory fibers undergo a progressive degeneration, scattered pituicyte-like cells are observed mostly associated with each other in number of two or three cells for group. Cultured pituicytes are quite similar to in vivo pituicytes except for some particular features as the shape of the nucleus and the number of dense bodies. Furthermore they share with the in vivo pituicytes the phagocytic capacity which appears even increased as far as neurosecretory fibers are concerned. Finally, degenerating pituicytes and free lipid droplets are observed in the intercellular spaces: the significance of these facts is discussed and tentatively interpreted. The organotypic culture of the neural lobe seems to represent an experimental model useful to obtain a relatively pure population of pituicytes.

Preliminary observations on pituicytes in tissue culture

Nella presente nota preliminare sono analizzati gli aspetti ultrastrutturali di lobi neurali postipofisari in coltura organotipica ove si è evidenziata la massiccia degenerazione delle fibre neurosecretorie e la presenza di cellule simil-pituicitarie attivamente fagocitanti le fibre stesse.

Degenerating pituicytes in the neural lobe of osmotically stressed rats

Nella presente nota sono descritti gli aspetti degenerativi di pituiciti appartenenti al lobo neurale ipofisario di ratti sottoposti a disidratazione sperimetale.

Developmental distributive pattern of acetylcholinesterase in chick embryo ciliary ganglion

AChE cytochemistry was performed in the chick ciliary ganglion (CG) during various embryonic stages. AChE first appeared in the RER of the neurons at 5 days of incubation (d.i.). Synaptic AChE appeared only later, parallely to the appearance of the calyciform synapses, i.e. at 9 d.i. At first AChE was mainly localized at the calyx side facing the satellite cell, thereafter extending to the neuronal side and especially labeling synaptic contacts occurring at points along the presynaptic membrane. Finally, at 15 d.i., i.e. when the calyx is morphologically mature, AChE reaction labels the whole contour of the calyciform nerve terminal. At 10 d.i., limited AChE-positive extrasynaptic areas of the ciliary neurons surface first appeared, thereafter extending up to affect at 15 d.i. large neuronal surfaces. Some hypotheses can be drawn from our results: (i) the earliest appearance of cytoplasmic AChE seems somehow independent of the establishing of functional synaptic contacts; (ii) the pattern of development of neuronal AChE suggests the existence of a sort of transynaptic control by presynaptic nerve terminals. However, it is possible that concomitant retrograde iris-dependent influences on ganglionic AChE concur in modulating neuronal AChE; (iii) the functional role possibly played by AChE localized at extra-synaptic level still remains to be clarified.

Acetylcholinesterase localization at synapses in chick embryo ciliary ganglion

The cytochemical localization of acetylcholinesterase (AChE) at calyciform synapses of the chick ciliary ganglion during embryonic development has been investigated. AChE activity is present at the surface membrane of newly formed calyciform synapses and closely follows the progressive enlargement of the synaptic area. The occurrence of a retrograde iris-dependent influence on ganglionic AChE is considered. AChE seems to be a suitable marker for synaptic maturation.

Alpha-bungarotoxin receptors in the chick ciliary ganglion: behaviour in vivo and in vitro

Abstract Cholinergic nicotinic receptors have been investigated in the ciliary ganglion of adult chick by means of [ 125 I]α-bungarotoxin binding to whole and homogenized ganglia. The behaviour of receptors has been compared in vivo (after simultaneous pre- and postganglionic axotomy) and in vitro (ganglia in organ culture). A decrease in receptor number was found both in vivo and in vitro , although the results differed quantitatively in the two cases. The loss of receptors was more evident in whole than in homogenized ganglia, suggesting that mechanisms of receptor degradation and masking may occur simultaneously. Additional experiments in vitro indicate that the behaviour of the receptors is influenced by inhibitors of energy metabolism (dinitrophenol plus iodoacetic acid, sodium cyanide) but not by an inhibitor of protein synthesis (cycloheximide). The receptor modifications in vitro are accompanied by a decrease of other cholinergic markers, such as acetylcholinesterase and cholinacetyltransferase activities. Morphological investigations of organ-cultured ganglia indicate that the biochemical modifications described above are not due to significant degenerative changes of ganglionic neurons. The results indicate that the α-bungarotoxin receptors behave rather similarly in vivo and, under our conditions, in vitro and suggest a dependence of these receptors on peripheral signals. These signals would appear to be mediated by energy-dependent processes without the synthesis of proteins being required.

Ultrastructural features of pituicytes in the neural lobe of adult rats. The peripheral processes.

Sono state analizzate le caratteristiche ultrastrutturali dei prolungamenti citoplasmatici dei pituiciti i quali formano un reticolo cellulare atto ad aumentare la superficie di contatto tra i pituiciti e le fibre neurosecretorie.

Fine features of pituicytes in the neural lobe of the green frog,Rana esculenta

Sono state esaminate le caratteristiche ultrastrutturali del lobo neurale diRana esculenta, in particolare dei pituiciti nei quali si osserva la presenza di numerosi fasci filamentosi.