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Biomedical subjects

D Ribatti

Publications and source records attributed to D Ribatti.

At least 163 records · Page 9Linked to original sources
PubMed1991

[Endothelial vesicles as a transport system in the blood-brain barrier. Morphometric study during development].

The vesicles and vacuoles of the endothelia, morphological expression of endocytosis and transendothelial transport, are quite absent in the mature neural endothelia. In order to study the temporal sequence of the vesicle and vacuole modifications during the blood brain barrier (bbb) setting up, the extent of these structures was morphometrically analyzed on electron micrographs of neural microvessels in the optic tectum of 8, 14, and 17 day chick embryos, fixed after an intracardial injection of the permeability marker horseradish peroxidase. During the development, endocytosis and transendothelial transport change, since a statistically significant reduction of both vesicles and vacuoles was recorded at the 17th incubation day. The temporal coincidence between decrease of endocytosis-transport processes and appearance of astrocytic endfeet close to the vessel wall, suggests that the glial cells might control, besides the tight junction formation, the expression of other properties of the bbb-provided endothelia.

Animals↗
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

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↗
PubMed1989

[Critics of perfection].

"In praise of imperfection" means to Rita Levi-Montalcini, Nobel prize for Medicine (1986), praise of man, as an unique being mixed of good and evil, whose greatness and dynamism is in its imperfection. Levi-Montalcini confesses her tendency to exclude herself, avoiding social contacts (a tendency she also improperly attributes to J. Watson). However, how can this be reconciled with a view such as that of Kundera: "Existence is not what has happened... Once again, existing means 'being in the world"'?

Autobiographies as Topic↗
PubMed1988

Early alteration of synovial membrane in osteoarthrosis.

Biopsy specimens of the synovial membrane were obtained during arthroscopy and surgical meniscectomy from the knees of 20 patients with meniscus lesions. The aim of this study was to identify the morphological and immunological changes which appear in the synovium during the earliest phase of osteoarthrosis. Interstitial deposits of IgG and, in some cases, C3 were found not only in patients with evident arthrotic degeneration (cartilaginous lesions and synovitis), but also in patients who showed no overt arthrotic changes. Furthermore, light and electron microscopy showed an increased number of mast-cells with peculiar semilunar or piecemeal aspects of their secretory granules. These ultrastructural modifications are characteristic of slow, chronic release of mediators in response to a constant, moderate degranulatory stimulus. Our findings suggest that synovial changes may occur before the advent of cartilage degeneration and that the latter may be directly influenced by early pathological changes in the synovial membrane.

Adolescent↗
PubMed1988

Do mast cells intervene in the vasoproliferative process of the rheumatoid synovitis?

On the basis of these evidences: a) the role played by heparin in the promotion of angiogenetic processes; b) the isolation of an angiogenetic factor in the synovial fluid from patients with rheumatoid arthritis; c) the significant increase of mast cells in the synovial membrane of the same patients, we suggest the possibility that the vasoproliferative processes in the course of rheumatoid arthritis may be mediated by heparin contained in the secretory granules of mast cells and released during the inflammatory process in response to numerous and heterogeneous stimuli.

Arthritis, Juvenile↗
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↗