Giuseppe Minelli

Ultrastructural localization of alkaline phosphatase in cultures of nervous tissuein vitro

SummaryThe fine localization of alkaline phosphatase in culturesin vitro of chick embryo spinal cord, explanted at early stages of development, was studied. Enzyme localization was found to vary in the different areas of the culture. In the central region, the reaction product was present only on the membranes of non-nervous cells and fibres directly in contact with the culture medium, while in the migration area the reaction product was also localized on membranes of deeper cells and fibres and on all membranes at the periphery of the culture. However, the membranes of nerve cells and their processes showed no evidence of reaction product when they were in direct contact with the medium. These observations are compared with data on the distribution of alkaline phosphatase in nervous tissue during embryonic development and in adults, and in relation to the possible role of alkaline phosphatase at the level of the haematoencephalic barrier. The hypothesis is considered that selective trophic mechanisms characteristic of nervous tissuein vivo may also occur in cultures.

Enzymic activities in dissociated neurons differentiated in cultures in vitro.

Abstract— The appearance of the enzymes succinate dehydrogenase, lactate dehydrogenase, acid phosphatase, monoamine oxidase and acetylcholinesterase in cultures of dissociated spinal cord, dorsal root ganglia and cerebellum removed at different stages of development have been studied. The neurons differentiated in vitro have morphological and cytochemical characteristics similar to those of the normally developing neurons. On the basis of the results obtained, it is argued that in this experimental model the histogenetic determination of the neuroblasts at the time of the explant may start and bring to an end the morphological and biochemical differentiation of the various types of neurons even under conditions extremely different from those of normal development.

Regenerative capacity of the optic tectum in Lacerta viridis

Abstract Regenerative capacity of the optic tectum in reptiles was studied in adults of Lacerta viridis kept for 24 hours at 4°C before extraction of a dorsomedial portion of the right optic tectum. Five months after surgery brain sections were prepared with standard autoradiographic techniques. From this investigation it emerged that five months after surgery, cell divisions in the brain were still very numerous, while in the lesioned area continuity of the ependyma had been regained. Above the ependyma in some areas, a zone of reformed nervous tissue was present with clear signs of cell and fibre stratification. These observations strengthen the hypothesis of a connection between loss of regenerative capacity by the C.N.S. with installation of blood-brain barrier and, conversely, of the reinstating of such capacity after alteration of this barrier.

Choroidal and iris angioarchitecture of the newt : a scanning electron-microscopic study of vascular corrosion casts

The corrosion cast technique provided for the first time an excellent three-dimensional visualization of the vascular pattern of the choroid and iris in the newt eye. The results show the presence of a single arterial afference to the choroidal and iris capillaries: the ophthalmic artery is the origin fo both ciliary arteries and the long posterior ciliary artery. Slightly behind the equatorial circumference of the eyeball the venous drainage consists of a single vessel on the dorsal side and two distinct vessels on the ventral one. It receives blood from both iris and choroid. The surface of the plastic endocasts shows some details of fine luminal structures of the endothelial cells. Shallow depressions may be regarded as imprints of endothelial cell nuclei, and they are distinctly different for arteries and capillaries. The angioarchitecture of the newt eye differs from that of brain in that hairpin-shaped capillary loops are not observed at all.

The fine localization of ATPases in culturesin vitro of chick embryo spinal cord

SummaryA histochemical study of the ultrastructural localization of ATPases in cultures of chick embryo spinal cord has been carried out. The localization of Ca2+ and Mg2+ activated membrane ATPases appears similar: both enzyme activities are localized on the outer surfaces of plasma membranes of all kinds of cell present in the cultures, with the exception of the membranes in direct contact with the culture medium. The results are discussed in relation to data concerning the localization and function of ATPasesin vivo and in relation to the possible establishment of mechanisms of nutrient uptake and transfer in cultures of nervous tissue.

Perivascular acetylcholinesterase activity in the brain of Rana esculent a tadpole

Abstract The appearance and distribution of acetylcholinesterase (AChE) activity in the nervous parenchyma and intracerebral capillaries in Rana esculenta tadpoles were studied. Histochemical data showed that at the onset of metamorphosis (stage 34), AChE activity was low and limited to a few scattered neurons. At the capillary level, AChE was found only in a few short tracts of the basal membrane. In the following stages AChE activity increased because neurons synthetized greater amounts of the enzyme and because the number of AChE‐synthetizing neurons had increased. The amount of the enzyme in the intracerebral capillaries progressively increased up to stage 50, at which point the whole basal membrane was AChE‐positive. Biochemical assays confirmed that the AChE level progressively increased from stage 34 to stage 50 to reach a level similar to that found in the adult animal.