Basic fibroblast growth factor-induced angiogenesis in the chick embryo chorioallantoic membrane: an electron microscopy study.
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Allantois↗
Biomedical subjects
B Nico
Publications and source records attributed to B Nico.
Endocytosis of horseradish peroxidase by brain microvascular and umbilical vein endothelial cells in culture: an ultrastructural and morphometric study.
The ability to form tight junctions and the paucity of fluid phase endocytosis showed by brain microvacular endothelial cells (BMECs) make up the structural basis of the blood-brain barrier (BBB). Most studies on cultured BMECs focused on intercellular junctions, whereas endocytosis received lesser attention. We studied endocytosis of horseradish peroxidase in primary and passage 1 and 2 BMEC cultures from rat brain as well as in human umbilical vein endothelial cell (HUVEC) culture. Endocytic activity was also analyzed in passage 1 BMECs treated with lipopolysaccharide (LPS, 1 microg/ml for 4 h), which mimics BBB disruption in bacterial meningoencephalitis. The percent of cytoplasmic area occupied by endocytic profiles (vesicles <70 nm and vacuoles >70 nm) and their mean number per cell were significantly lower in primary and passaged BMEC than in HUVEC cultures. The area and number of endocytic profiles significantly increased in BMECs after exposure to LPS. BMECs cultured under standard conditions may be a suitable model for studying the mechanism of increased fluid phase endocytosis in certain diseases and injury states.
Animals↗
Antiphosphatidylserine antibodies in human immunodeficiency virus-1 patients with evidence of T-cell apoptosis and mediate antibody-dependent cellular cytotoxicity.
Serum reactivities to a panel of phospholipid antigens, including cardiolipin (CL), phosphatidylserine (PS), sphingomyelin, phosphatidylcholine, and phosphatidylethanolamine, were measured by enzyme-linked immunosorbent assay in 196 human immunodeficiency virus-l+ (HIV-1+) patients with CDC II to IVC clinical disease. Significant levels of IgG to CL, PS, or both were observed in 23 patients lacking evidence of thrombophilic events or any peculiar clinical feature of HIV-1 infection. Fluorescence-activated cell sorting analyses showed that in vitro apoptosis of T cells was increased in patients with high serum anti-PS IgG, whereas the overexpression of Fas/Apo-1 marker was detected in all patients regardless of their antiphospholipid reactivities. Macrophages from patients with significant titers of anti-PS IgG antibodies were not activated by the presence of apoptotic CEM lymphoblasts or by purified anti-PS IgG from the same patients. By contrast, these antibodies greatly improved the effector functions of autologous macrophages in antibody-dependent cellular cytotoxicity (ADCC) assays using 51Cr-labeled CEM cells, whereas polyspecific IgG were unable to induce an equivalent cytotoxicity in all instances. An increasing effect on ADCC was also observed in tests using macrophages from healthy controls to CEM coated with anti-PS IgG. These results support a potential correlation of anti-PS specificity with T-cell apoptosis in HIV-1 infection. Because PS is exteriorized by apoptotic lymphocytes, its persistence may stimulate antibodies which cooperate with macrophages in the clearance of dead cells by an enhanced ADCC mechanism. This interpretation could explain the absence of thrombophilia in HIV-1+ patients with serum elevations of antiphospholipid reactivities.
Antibodies, Antiphospholipid↗
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↗
Expression of tenascin is related to histologic malignancy and angiogenesis in b-cell non-Hodgkin's lymphomas.
The topography of and the area covered by tenascin, laminin and type IV collagen (all components of the subendothelial basement membrane), and the microvessel area (an index of angiogenesis), as evaluated with factor VIII, were investigated immunohistochemically in 61 B-cell non-Hodgkin's lymphomas (B-NHL) and 30 benign lymphadenopathies as controls. The three components were located in the microvessels and in a microvessel-bound stromal reticular network, the expression of tenascin being always more extended and finer than the other components. Of the lymphadenopathies, reactive and atypical lymphoid hyperplasias showed vessels and stromal network in the interfollicular zone only, whereas in Castleman's and angioimmunoblastic forms these structures were widely scattered in the tissue, and the area of the three components and that of the microvessels were significantly larger. Of the low-grade B-NHL, follicular subtypes had vessels and stromal network confined to the interfollicular inflammatory zone, but not in tumor follicles, whereas these structures were irregularly distributed throughout the small lymphocytic subtype. The levels of areas in low-grade B-NHL overlapped those of Castleman's and angioimmunoblastic lymphadenopathies. Among the intermediate-grade tumors, the follicular subtype resembled the follicular tumors, and the diffuse subtypes displayed vessels and stromal network throughout the tissue in close association with the neoplastic cells, and with significant increments of both the tenascin and the microvessel areas, but with a significant reduction of both the laminin and the type IV collagen areas. Distribution was similar in high-grade B-NHL, but tenascin and microvessel area variations, on the one hand, and those of laminin and type IV collagen areas were still more apparent than in the intermediate-grade. A high correlation was demonstrated in all groups of tissues between tenascin and microvessel area. In addition, in the diffuse intermediate-grade and high-grade B-NHL highly immature vessels were frequently detected by ultramicroscopy. The results show that tenascin expression and angiogenesis are closely related, and that both increase in function of tumor malignancy. Unlike laminin and type IV collagen, tenascin is associated with highly immature vessels in B-NHL. We suggest that tenascin expression and angiogenesis are governed by the B-NHL-associated inflammatory infiltrate, as well as by the B-NHL cells, particularly in more malignant tumors.
Endothelium, Vascular↗
Endogenous basic fibroblast growth factor is implicated in the vascularization of the chick embryo chorioallantoic membrane.
Chorioallantoic membrane (CAM) and chorioallantoic fluid (CAF) of the chick embryo were studied for the presence of immunoreactive and biologically active basic fibroblast growth factor (bFGF) from Day 6 to Day 18 of incubation. An immunoreactive M(r) 16,000 bFGF-like molecule was detected both in CAM and in CAF. This molecule was identified as bFGF on the basis of its molecular weight, its affinity for heparin, and its capacity to induce plasminogen activator production in cultured endothelial GM 7373 cells. The levels of biologically active and immunoreactive bFGF vary in CAM and CAF during embryonic development, maximal concentrations being observed between Days 10 and 14 of incubation. At all time points investigated, absolute concentrations of bFGF were significantly higher in CAM (ranging from 25 to 183 ng/g of wet tissue) than in CAF (ranging from 0.2 to 4 ng/ml). In a parallel series of experiments performed at Day 8 and evaluated at Day 12 of chick embryo development, human recombinant bFGF and neutralizing anti-bFGF antibody were investigated for their capacity to affect the vasoproliferative processes of the CAM. The two molecules either were applied onto the surface of the CAM or were injected into the allantoic sac. When bFGF or anti-bFGF antibodies were absorbed on methylcellulose discs and applied on the top of the CAM, they exerted a strong angiogenic or anti-angiogenic effect, respectively. On the contrary, when bFGF or the corresponding neutralizing antibody was injected into the allantoic sac, no modifications of the vasoproliferative processes of the CAM were observed at either the macroscopic or the microscopic level. These results provide evidence indicating that endogenous bFGF has a rate-limiting role in the vascularization of the CAM during chick embryogenesis. bFGF located within the CAM, rather than that present in the CAF, appears to be involved in this developmental process.
Allantois↗
Left ventricular hypertrophy in spontaneously hypertensive rat: effects of ACE-inhibition on myocardiocyte ultrastructure.
The aim of this study is to investigate the effects of two ACE-inhibitors with different chemical formulae, cilazapril (CLZ) and captopril (CPT), on left ventricular myocardiocytes from spontaneously hypertensive rats (SHR), characterized by ultrastructural alterations associated with left ventricular hypertrophy, and from Wistar-Kyoto (WKY) rats, considered as controls. After CLZ-treatment, not remarkable changes are observed in WKY myocardiocytes, whereas SHR ones show a considerable reduction in their original alterations in ultrastructure. After CPT-treatment, both SHR and WKY myocardiocytes are altered in ultrastructure. The morphometric investigation confirms that CPT and CLZ produce different effects. Even if the drugs induce a similar decrease in blood pressure and left ventricular mass index, CLZ unlike CPT seems to improve the ultrastructural abnormalities associated with left ventricular hypertrophy. These changes could be related to the different chemical structure of CLZ and CPT, or to a different affinity of the two drugs for the local renin-angiotensin system.
Angiotensin-Converting Enzyme Inhibitors↗
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↗
Early ultrastructural changes of articular cartilage and synovial membrane in experimental vitamin A-induced osteoarthritis.
OBJECTIVE: To evaluate the sequential ultrastructural changes of the articular cartilage and synovial membrane in the earliest phases of the vitamin A model of osteoarthritis (OA) in the rabbit. METHODS: The superficial layer of the weight bearing zone of the articular cartilage and the synovial membrane from femorotibial joints of 12 osteoarthritic rabbits were evaluated 3, 6, and 9 days after the triggering intraarticular injection of 100,000 i.u. of retinol palmitate. Four uninjected rabbits were used as controls. RESULTS: At 3 days, ultrastructural changes of chondrocytes could be seen (hypertrophic cells with increased lipid droplets, chondrocytes rich in microfilaments and glycogen, and some degenerating cells) with no evident lesions of the matrix. The synovium was similar to that of the control rabbits. At 6 days, chondrocyte changes seemed almost identical to those of 3 days, while the synovial membrane appeared markedly involved, substituted by a single layer of A-type cells lying on fibrous subsynovial tissue in which lymphocytes, mast cells, and blood vessels could be seen. Conspicuous alterations and necrobiosis of the cartilaginous cells characterized later stages (9 days). The intercellular matrix was mainly made up of amorphous material and bundles of collagen fibers. The synovial membrane was transformed into a thick fibrous tissue partially covered with scattered cells no longer distinguishable as A or B type. CONCLUSION: Our data suggest that in the vitamin A model of OA the initial metabolic changes of the chondrocytes have a pivotal role in determining the relentless cascade of events leading to the full expression of this disease. Moreover, although several studies have been carried out on the early changes in experimental OA, no complete morphological evaluations on the developmental aspect of this model have been available.
Animals↗
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↗
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↗
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↗
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↗
[Left ventricular hypertrophy in spontaneously hypertensive rats: effect of angiotensin converting enzyme inhibitors on morphologic ultrastructure].
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Animals↗
Vascular supply in embryonic neural transplants.
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Animals↗
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↗
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↗
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↗