PubMed Health⌕ Search

Biomedical subjects

M Bertossi

Publications and source records attributed to M Bertossi.

At least 37 records · Page 2Linked to original sources
PubMed1997

Glucose transporter GLUT1 in human brain microvessels revealed by ultrastructural immunocytochemistry.

The brain glucose transporter GLUT1 is a transmembrane glycoprotein belonging to the glucose carrier family comprising five isoforms characterized by different functional properties and tissue specificity. Biochemical and immunohistochemical analyses have demonstrated that GLUT isoform 1 is localised within the brain microvascular endothelium, where it controls glucose uptake through the blood-brain barrier (BBB). In this study the expression of GLUT1 was analysed by means of light and electron immunocytochemistry in the adult human cerebellar cortex. The glucose transporter is strongly expressed in cerebellum microvessels, and is localised not only within endothelial cells but also in microvascular pericytes. Moreover, some glial expression of GLUT1 was observed in the neutrophil and in perivascular glial sheaths. The observations demonstrate that different cellular types are involved in the control of brain glucose homeostasis by GLUT1 expression at the BBB site, and support the postulated highly specialised role of brain microvascular pericytes.

Adult↗
PubMed1996

Vasoactive intestinal polypeptide-like immunoreactivity in astrocytes of the human brain.

Vasoactive intestinal polypeptide-like immunoreactive (VIP-LIR) astrocytes were found in the subcortical white matter of the human forebrain parietal lobe. Astrocytes expressing VIP-LIR represented a minority (0.97%) of the GFAP-stained astrocyte population in the white matter. The close anatomical relationship between the VIP-LIR astrocyte bodies and processes and the brain vasculature strongly suggests that they may play a role in the local control of blood flow and of the barrier properties of the vessel walls.

Astrocytes↗
PubMed1996

Morphological aspects of the vascularization in intraventricular neural transplants from embryo to embryo.

Intraventricular transplants of neural tissues were performed in ovo from embryo to embryo. Fragments of the nervous wall of the optic lobe (tectum) from 14-day chick or 12-day quail embryos (donor) were inserted into the ventricle of the right optic lobe of 6-day chick or 5-day quail embryos (host). Chick-to-chick, chick-to-quail and quail-to-chick grafts were carried out. The vascularization changes occurring in the host tectum and in the grafted neural tissues were analysed under light, transmission, and scanning electron microscopes and by morphometric methods. In the host embryo tectum, the neural graft stimulates a statistically significant increment in vessel density and a vessel sprouting into the ventricle of the optic lobe. The vascular sprouts reach the transplanted tissue and establish connections with its native microvasculature. The chick-to-quail and quail-to-chick grafts, submitted to immunoreaction with a quail-specific antibody which recognizes an antigen (MB1) present on endothelial cells, indicate that re-establishment of the circulation in the graft depends upon anastomoses between host and donor vasculatures and the rapid new growth of host-derived and donor-native vessels. The presence of macrophage-like cells escorting the new-growing vessels suggests that these cells are involved in the host and donor tissue angiogenesis.

Animals↗
PubMed1996

Urothelium damage as the primary cause of ureteropelvic junction obstruction: a new hypothesis.

Ten infants under 6 months old underwent surgery for obstruction of the ureteropelvic junction. Craniocaudal light microscopy showed subdivision of the resected ureteropelvic junction into three portions: prestenotic, stenotic, and poststenotic. The prestenotic portion was characterized by dilatation of the ureteral lumen, flattening of its mucosal folds and thinning of the urothelium; the stenotic tract showed partial or total loss of the epithelium and fibrosis of the mucosal and fibromuscular coats. No modifications were detected in the poststenotic portion. We advance the hypothesis that a primary epithelial break might cause urine to spread inside the ureteral wall and consequently the mastocytes to migrate and degranulate within the mucosal and fibromuscular coats. The histamine and prostaglandins produced by the mastocytes could induce prolonged muscular spasm, in turn responsible for increasing the intrapelvic pressure and so causing enlargement of the epithelial break. A connective tissue reaction of the ureteral wall would thus occur, which should be considered a secondary event leading to fibrotic stenosis of the ureteropelvic junction.

Child, Preschool↗
PubMed1995

Glial cells and blood-brain barrier in the human cerebral cortex.

The spatial relationship established between glial cells and microvasculature in the human cerebral cortex was analysed on peritumoral tissue of the parietal lobe removed during surgery. Observations performed by light microscope immunocytochemistry demonstrated that processes of astrocytes, strongly immunoreactive to both glial fibrillary acidic protein and S-100 protein, form sheaths to the capillaries, and that isolated cells positive to the oligodendrocyte marker 2',3'-cyclic nucleotide 3'-phosphodiesterase are detectable in perivascular areas. Morphometrical analysis by transmission electron microscopy showed that 80% of the vascular endothelium-pericyte layer is invested by small endfeet of astrocyte processes. This study demonstrates that either astrocyte bodies or oligodendrocytes as well as microgliocytes may substitute the astrocytic endfeet adhering to the capillary basement lamina.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1995

A compared TEM/SEM investigation on the pericytic investment in developing microvasculature of the chick optic tectum.

The pericytes have been ultrastructurally and morphometrically analyzed in the neural vessels of the chick embryo optic tectum, under the transmission and scanning electron microscopes. The observations demonstrated that shape and surface features of pericytes, as well as their spatial relation with the endothelium, remarkably change during development, whereas their ultrastructure does not substantially modify from the early to the late embryonic stages. The pericytes have an ovoid body, broad processes, smooth surfaces, and are closely applied to the endothelial tube on days 5-7; they show convolute shape, highly irregular surfaces, and are complicately interdigitated with the endothelial cells, when a vivacious vessel growth takes place, on days 12-14; finally, they are flattened, smooth, highly branched, and completely enclosed in the basement lamina on days 20-21, when a definitive vascular pattern is established. The contribution of pericytes to the formation of the basement lamina has been confirmed by the detection of exocytotic vesicles discharging their content toward the subendothelial cleft. The morphometric evaluations revealed that pericytes provide the growing neural microvessels with an almost continuous coverage which, however, undergoes a significant reduction within hatching time. On the whole, the results suggest that the pericytes are as active as the endothelial cells during the vessel growth and play an inhibitory role on the endothelial proliferation only later on, when they are closely adherent to the endothelium and are encompassed by the basement lamina.

Animals↗
PubMed1994

Left-ventricular hypertrophy in the spontaneously hypertensive rat: effect of ACE inhibitors on ultrastructural morphology.

The ACE inhibitors cilazapril and captopril were administered at 10 and 100 mg/day, respectively, to spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto rats (WKY) from the 12th to the 22nd week of life. Both drugs produced statistically significant reductions in systolic and diastolic blood pressure, left-ventricular mass and index of left-ventricular hypertrophy in SHR. After cilazapril treatment, the morphology of SHR cardiocytes became similar to that in untreated normotensive rats, while in captopril-treated rats, myofibrils were disarranged, obliquely oriented and smaller than normal, with areas of electron-transparent sarcoplasm separating the myofibril bundles; mitochondria were also altered. In WKY rats, we observed no statistically significant changes in blood pressure, ventricular weight and hypertrophy index between the two drugs; however, there were different effects of the two drugs on the ultrastructural morphology of the myocardium. These observations suggest that these two molecularly dissimilar ACE inhibitors act differently at the tissue level despite similar effects on blood pressure and left-ventricular mass.

Animals↗
PubMed1994

Orthogonal arrays of particles (OAPs) in perivascular astrocytes and tight junctions in endothelial cells. A comparative study in developing and adult brain microvessels.

The plasmamembranes of the astrocyte processes, which envelop the capillaries of the adult brain, contributing to the blood-brain barrier constitution, are characterized by peculiar aggregates of intramembrane particles (IMPs) packed in orthogonal arrays (orthogonal arrays of particles, OAPs). With the aim of investigating the maturation sequence of the cerebral microvasculature, the IMPs distribution has been analysed in the plasmamembranes of both perivascular astrocytes and endothelial cells of fractured microvessels, in 16-, 20-, 21-day chick embryo and 10-day chicken optic tecta. The IMPs distribution undergoes remarkable changes from late embryonic to early postnatal life in the astrocytes and endothelial cells as well. In the astrocyte plasmamembranes, short chains of individual particles and linear units of packed ones precede the appearance of complete OAPs; in the endothelium junctional plasmamembranes, fibrils of fused particles precede the formation of fibrillary networks which express the tight junction setting up. The parallel formation of the astrocytic OAPs and the endothelial tight junctions further supports the suggestion that mutual relationships establish between perivascular glia and endothelium in the cerebral microvasculature differentiation during the blood-brain barrier development.

Animals↗
PubMed1993

Perivascular astrocytes and endothelium in the development of the blood-brain barrier in the optic tectum of the chick embryo.

The role played by perivascular astrocytes in neural vessel maturation was investigated in microvessels of the chick embryo optic tectum. Three-dimensional reconstructions and quantitative analyses were made, and permeability was studied. On embryonic days 14-16, 12.5% of the microvessel wall is surrounded by astrocyte endfeet which, in most cases (82%), are located under endothelium junctions; the latter, at this stage, partly prevent the extravascular escape of the marker horseradish peroxidase. On days 18-21, the astrocyte processes form a nearly complete perivascular sheath enveloping 96% of the microvessel perimeter; the junctions of the endothelial cells are much wider and impermeable owing to extensive fusion of the endothelial plasma membranes. This investigation suggests a close relationship between the perivascular arrangement of glia and differentiation of the endothelium tight junctions and indicates that the morphofunctional maturation of the latter takes place progressively during the prenatal organogenesis of the chick central nervous system.

Animals↗
PubMed1993

The development of the blood-brain barrier in the chick. Studies with evans blue and horseradish peroxidase.

The development of the blood-brain barrier was microscopically examined in the optic tectum of the chick. The permeability of neural vessels to Evans blue and horseradish peroxidase decreases progressively during the period of incubation. Diffusion is massive on the 6th and 10th days of incubation and is reduced on the 14th day; on the 18th-21st day of incubation the vascular walls still allow Evans blue to diffuse but prevent extravasation of horseradish peroxidase completely. In one month old chickens the nervous substrate is free of both tracers.

Animals↗
PubMed1993

Vimentin- and GFAP-immunoreactivity in developing and mature neural microvessels. Study in the chicken tectum and cerebellum.

The expression of the cytoskeletal filaments vimentin and GFAP has been analyzed by immunocytochemical techniques in endothelial cells, pericytes, and astrocyte perivascular endfeet of microvessels of chicken optic tectum and cerebellum during embryonic development and in adulthood. Endothelial cells and pericytes were characterized by strong vimentin-immunoreactivity in both tectum and cerebellum only in early developmental stages (11-15 incubation days, i.d.). Astrocyte processes closely associated with the vessel wall were vimentin stained in the 11 i.d. cerebellum and vimentin-and GFAP-reactive in 15 i.d. tectum. These perivascular endfeet became GFAP-immuno-stained in the tectum and cerebellum by the 21st i.d. The results indicate that intermediate filament expression in the cells of the brain microvasculature is developmentally regulated, and suggest that the vimentin to GFAP transition in perivascular astrocytes parallels the vessel wall maturation.

Animals↗
PubMed1992

GFAP-immunoreactive perivascular glia in the chick optic tectum.

Immunocytochemical staining of the glial fibrillary acidic protein (GFAP) was utilized to characterize the processes of the astrocytes enveloping the vessel wall in the central nervous system. The study was carried out in the mesencephalic lobes of 18 and 20 incubation-day chick embryos and of 20 day chickens. A perivascular GFAP positivity was mainly detectable in the vessel portions running within the tectum white layers, while it was scarce, or absent, in the grey ones. The perivascular GFAP negativity in the tectum cellular layers was not considered result of the absence of astrocytic endfeet since our previous electronmicroscopical studies evidenced an almost complete perivascular astrocytic ring throughout the tectum layers at hatching time. Present data rather suggest that the expression of the GFAP-made intermediate filaments in developing astrocytes might be controlled by the surrounding microenvironment.

Animals↗
PubMed1992

Permeability-related structures in developing and mature microvessels of the chicken optic tectum.

The mode and the temporal sequence of the modifications undergone by permeability-related structures in the neural microvessels have been ultrastructurally and morphometrically investigated in optic tecta of 6, 14, and 18 incubation day (i.d.) chicken embryos and of 30 day chickens. Horseradish peroxidase was utilized as a permeability marker. The endo- and exocytosis-related structures (vesicles and vacuoles) and the interendothelial junctions remarkably change during development: the density of the vacuoles is decreased at the 14th i.d., while that of the vesicles becomes significantly low at the 18th i.d., both reaching lowest values in the chicken; the passage of the marker through the endothelial junctions begins to be hindered from the 14th i.d., parallel to the perivascular arrangement of astrocytic glia endfeet, and it is completely blocked at hatching time. The findings suggest that the optic tectum microvessels are permeable, and thus immature, in the early development and progressively acquire morphofunctional features of vessels provided with barrier devices during the pre- and post-natal development of the brain.

Animals↗
PubMed1992

A correlative SEM/TEM examination of the endothelium surface in neural capillaries.

The modifications of the endothelial surfaces were analyzed in growing neural microvessels by scanning and transmission electron microscopes in the optic tecta of chick embryos and chickens. The endothelial inner aspect appears regular and smooth in the early stages of the vessel growth (7th incubation day). Later (14th incubation day) both the abluminal and luminal surfaces of the endothelium follow a very sinuous course and the luminal ones appear extremely rich in pleomorphic microprojections. When the endothelium differentiation is concluded (5-day-old chicken), the cells are very thin and again exhibit regular and smooth surfaces. These findings reveal a great mobility of the cell membrane of the endothelial cells when they are growing longer and thinner by a moulding process. Moreover, the presence of a number of pinocytotic pits in the embryo vessels would indicate that the neutral vessels, provided with a typically low pinocytotic activity in the adult life, are engaged in this function during development.

Aging↗
PubMed1992

Tight endothelial junctions in the developing microvasculature: a thin section and freeze-fracture study in the chick embryo optic tectum.

The development of the interendothelial tight junctions was studied in the microvessels of the otpic tectum of chick embryos, at the 14th-16th and 18th-20th incubation day (i.d.), and in post-hatching chickens, using thin sections and freeze-fracture techniques. At the 14th-16th i.d., the junctional plasmamembranes of the endothelial cells are simply apposed or fused for brief tracts showing a pentalaminar or trilaminar configuration. In the replicas the P-faces of the fractured junctional membranes are either lacking in intramembrane particles (IMPs) and characterized by finger-like depressions, or provided with discrete IMPs aligned in rows. At the 18th-20th i.d., the thin peripheral expansions of the endothelial cells are superimposed and welded by continuous pentalaminar junctions. Their fracture P-faces display junctional strands formed by parallel fibrils of fused IMPs, with or without interconnections. In the 10-day-old chickens the junctions consist of highly complex networks of fibrils. The results have made it possible to recognize precise relationships between the features of the developing endothelial junctions in the ultrathin sections and, respectively, in the replicas. Moreover, the observations suggest that tight junction formation occurs progressively in the cerebral microvessels by processes of alignment and fusion of the IMPs, which conclude with the arrangement of fibrils in networks.

Animals↗