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Biomedical subjects

L Roncali

Publications and source records attributed to L Roncali.

At least 109 records · Page 6Linked to original sources
PubMed1989

Computerized three-dimensional reconstruction of the developing blood-brain barrier.

Computer-aided techniques for three-dimensional reconstruction of images were employed in a morphological and morphometrical study of blood-brain barrier (BBB) development in the microvasculature of the chick embryo optic tectum. The method proved very useful for understanding the spatial relationships between BBB vascular and perivascular components, and of their modifications during embryonic life. The results indicate that the perivascular astrocytic endfeet, the main periendothelial components of the BBB, appear on the 14th incubation day and form an almost continuous perivascular envelope at hatching time.

Animals↗
PubMed1989

Right ventricular dysplasia: an ultrastructural study.

Ultrastructural observations on myocardial biopsies from patients developing clinical and/or echocardiographic and haemodynamic signs of dysplasia of the right ventricle did not reveal morphological defects of the myocardiocyte contraction apparatus, but showed evidence of fibrosis of the myocardial interstitium and modifications of the structures involved in the transmission of the action potential into the cardiac cells as well as of the junctional system between them. Interstitial adipocytes and intracellular lipid droplets were not increased in number.

Adipose Tissue↗
PubMed1989

Morphometric analysis on the effects of hypoxia during the central nervous system vasculogenesis.

A morphometric analysis was carried out on the optic tectum microvascolature in chicken embryos developing under normal and hypoxic conditions in order to evaluate the effects of an environmental O2 reduction on growing neural blood vessels. The vessel number, the vessel diameter and the distance intervening between contiguous vessels were measured. In the developing tectum under hypoxia the results evidenced a remarkable, progressive increase in vessel number, higher than in the controls; a transitory increment of the vessel diameter, which in later embryonic development returned similar to that recorded during normal tectum vasculogenesis; a value of the distance between contiguous vessels always much lower than under normal conditions. The possible significances of these morphological evidences were discussed and a capacity on the part of the growing neural vascular bed for adapting itself to a reduced oxygen concentration was noted.

Animals↗
PubMed1989

Methylcarbamate effects on Meckel's cartilages in the chick embryo.

On the basis of previous observations on the teratogenic effects of a variety of organophosphorus and methylcarbamate compounds on the avian skeletal apparatus, the Meckel's cartilage shape and structure were analyzed in carbaryl (1-naphthyl N-methylcarbamate) treated and control chick embryos of 9, 10, 12 days of incubation. The results indicate that both during normal development and under experimental conditions these cartilages undergo similar deformities, apparently subsequent to chondroblast death and regressive processes in the extracellular matrix. Since the macro- and microscopical cartilage alterations are significantly more frequent in the treated embryos than in the controls, a hypothesis is advanced that the methylcarbamate may increase the spontaneous tendency of the above mentioned cartilaginous anlagen to be affected by degenerative processes during embryogenesis.

Animals↗
PubMed1989

Ethyl-oxide effects on a newly formed blood-brain barrier.

The morphofunctional effects of ethyl-oxide, utilized as anaesthetic, on the optic tectum blood-brain barrier were investigated in hatching chick embryos (21st incubation day) and young chickens in which the barrier to the marker of vascular permeability horseradish peroxidase is complete after the 18th incubation day. Results indicate that ethyl-oxide administration produces horseradish peroxidase extravasation by opening the tight interendothelial junctions. The escape rate of the marker is higher in the tecta of hatching embryos than in those of chickens and in both horseradish peroxidase extravascular diffusion is more frequent at the level of vessel bifurcation than along the branchless vessel tracts.

Animals↗
PubMed1988

The barrier systems in the choroidal plexuses of the chick embryo studied by means of horseradish peroxidase.

The development of the blood-cerebrospinal fluid (CSF) and cerebrospinal fluid-blood barriers, and the differentiation of the choroidal vessel wall, have been ultrastructurally investigated in the choroidal plexuses of the lateral ventricles of 10, 15, 18 and 21 day chicken embryos, fixed in normal conditions and also after intracardial and intraventricular injection of horseradish peroxidase. In all the analyzed developmental stages the choroidal epithelial cells seem able to endocytose and degradate, in their lysosomal apparatus, the tracer molecules reaching their ventricular and basolateral sides. The intravascularly injected horseradish peroxidase can enter the ventricular cavity by interepithelial route only at 10th incubation day, when the tight intercellular junctions are not formed everywhere, while a transepithelial transport is always hindered. The marker injected into the ventricular cavity reaches the subepithelial compartment and the blood stream, at 10th incubation day by interepithelial as well as transepithelial route and, successively, by transepithelial vesicular transport alone. The differentiation processes undergone by the choroidal blood vessels consist in a progressive thinning of the endothelial cells, appearance of pores, already numerous at 15th incubation day, and formation of the endothelial basement lamina, the final event in vessel wall maturation.

Animals↗
PubMed1987

Effects of exogenous heparin on the vasculogenesis of the chorioallantoic membrane.

On the basis of the well-known stimulating role played by heparin on blood vessel neoformation in the chorioallantoic membrane (CAM), demonstrated by means of slow-release polymers soaked in this substance and placed on CAMs, a new technique of introducing heparin directly into the allantoic sac is proposed. According to observations carried out in ovo and after fixation, morphological modifications are demonstrated in the developing vasculature of the heparin-treated CAMs which, compared with the control CAMs, show dilated and sinuous arterial and venous branches, denser and irregular capillary networks, and a high number of vascular primordia. The results, confirming that heparin is involved in angiogenesis, indicate the suitability of the technique and suggest that the effects of this substance could be enhanced by growth factors released by CAM tissues rapidly growing up from the 5th to the 7th incubation day.

Allantois↗
PubMed1987

Ultrastructural features of the vasculogenetic processes in the thyroid and suprarenal glands of the chick embryo.

This paper reports the results of an ultrastructural investigation on the differentiation of the blood capillary network in the thyroid and suprarenal glands of the chick embryo, from the 6th to the 21st incubation day. Apart from some morphological features of the capillary wall, which change in the same way during gland organogenesis (thickness of the endothelium, quantity and distribution of cytoplasmic organelles, pores), differences have been pointed out concerning the beginning and temporal evolution of the maturative events of the endothelium lining and the pericapillary spaces. Close relationships between morphofunctional maturation of the secretory cells and blood vessel differentiation have been emphasized, and the roles played by intraendothelial vacuoles and endothelial basement lamina during the capillarogenesis are discussed.

Adrenal Glands↗
PubMed1987

Mast cells in the chick embryo choroid plexuses.

The existence of mast cells in the choroid plexuses of the chick embryo lateral ventricles has been investigated by a microscopical and ultrastructural study carried out from the 9th incubation day to hatching. These cells have been seen within the perivascular connective of the choroid plexuses in the later stages of their embryonic development and are morphologically similar to those present in the connective stroma of other organs. A role of these cells in the regulation of the choroid vessel permeability as well as of the exchanges between plasma and cerebrospinal fluid (and viceversa) is suggested.

Animals↗
PubMed1986

Process of differentiation of cerebellar Purkinje neurons in the chick embryo.

The microscopic and ultrastructural differentiation of Purkinje neurons has been studied in 40 chicken embryo cerebella, from the 10th incubation day to hatching, and the transverse diameter of the cell body measured, for each developmental stage, on 30 electron micrographs of sagittally cut Purkinje cells. The developing Purkinje cell bodies, bipolar, at first, given the presence of two processes emerging from the opposite poles of the oval perikaryon, grow progressively in size. After the 12th incubation day, they develop a branched dendritic tree, and, shortly before hatching time, the cells acquire the characteristic flask or pear-shaped configuration. On the 10th incubation day, microtubules are already detectable together with Golgi complexes and a few vesicles of rough endoplasmic reticulum; on the 14th incubation day, RER cisterns are recognizable in the supranuclear cytoplasm, later extending into the whole perikaryon, and attaining their definitive distribution by the 18th incubation day. Pinocytotic and coated vesicles, as well as subsurface cisterns are seen during the whole embryonic life. In the earliest stages of development, three distinct types of junctional contacts between Purkinje cells and surrounding axons are described, and their functional role in relation to synaptogenetic processes is discussed. Beginning with the 16th incubation day, some Purkinje neurons undergo degenerative changes similar to those described in other types of neurons of the central and peripheral nervous system.

Animals↗
PubMed1986

Microscopical and ultrastructural investigations on the development of the blood-brain barrier in the chick embryo optic tectum.

The formation of a blood-brain barrier to horseradish peroxidase was microscopically and ultrastructurally investigated in the tectum opticum of the chick during development of the intraneural blood vessel network from the 6th incubation day to hatching, and in adult specimens. Extravasation of the circulating marker, apparently unimpeded during early stages of vasculogenesis, starts to diminish from the 14th incubation day (i.d.) and is prevented after the 18th i.d. The tracer seems to get out of the vessel lumina through the sites of reciprocal contact between adjacent endothelial cells, and the differentiation of tight junctions there hinders the passage of peroxidase particles. The formation of numerous endothelial vacuoles during early vasculogenesis and the setting of the blood-brain barrier are discussed in connection with the mechanisms of transendothelial transport, and respectively, the processes of moulding of the growing endothelia.

Animals↗
PubMed1986

Effects of the chronic hypoxia on the developing blood-brain barrier in the chick embryo optic tectum.

The blood-brain barrier to horseradish peroxidase has been investigated microscopically and ultrastructurally in the optic tectum of hatching chicken embryos which were kept under hypoxic conditions from the 3rd incubation day. The results indicated that the weakness sites of the blood-brain barrier correspond to the tight interendothelial junctions, whose breakdown allows extravasation of the marker into limited areas of the tectum wall.

Animals↗
PubMed1985

[Use of horseradish peroxidase as a marker in studies of the formation of the blood-brain barrier (optic tectum of the normal and experimentally-treated chick embryo)].

The development of the blood brain barrier (BBB) and the vessel permeability to horseradish peroxidase (HRP) have been analyzed in the optic tectum of chick embryos developed under normal and hypoxic conditions, normal chickens, and chickens born from fertilized eggs incubated under hypoxia but kept in the open air after hatching. The development of chick embryos under a situation of chronic hypoxia was obtained by covering, a half of the shell of fertilized eggs with a thick layer of melted paraffin to obtain a reduction of the exchanges normally occurring between embryonic blood vessels and open air. In the tecta developed in normal conditions the BBB to HRP begins to form on the 14th i.d. and it is complete on the 17th i.d. The O2 deprivation, producing remarkable alterations of the neural substratum, does not affect the development of the BBB to HRP, since in chicks of 17 i.d., grown up under hypoxic conditions, the tectal microvessels are not permeable to the tracer, being it mainly confined within the vessel lumina. Nevertheless in specimens kept under hypoxia until hatching, areas of perivascular spread of the marker have been observed corresponding to the vessel wall tracts presumably damaged by the experimental conditions along which the BBB to HRP is not complete.

Animals↗