Biomedical subjects

L Roncali

Publications and source records attributed to L Roncali.

157 records · Page 9Linked to original sources

PubMedDate not supplied

Cell-mediated delivery of fibroblast growth factor-2 and vascular endothelial growth factor onto the chick chorioallantoic membrane: endothelial fenestration and angiogenesis.

Fibroblast growth factor-2 (FGF2) and vascular endothelial growth factor (VEGF) exert their angiogenic activity by interacting with endothelial cells in a distinct manner. In this study, we investigated the morphological features of endothelial cells of the chick embryo chorioallantoic membrane (CAM) microvasculature after stimulation with FGF2 or VEGF. In order to provide a continuous delivery of the growth factor, we utilized a recently developed gelatin sponge/CAM assay in which a limited number of FGF2- or VEGF-transfected cells were adsorbed onto gelatin sponges and applied on the top of the CAM on day 8 of development. Their angiogenic activity was compared to that exerted by a single bolus of the corresponding growth factor. All the angiogenic stimuli induced a comparable vasoproliferative response, as demonstrated by the appearance of similar numbers of immature blood vessels within the sponge on day 12. No angiogenic response was observed in CAMs implanted with the corresponding parental cell lines or vehicle. Electron microscopy demonstrated that VEGF-overexpressing cells modified the phenotype of the endothelium of the blood vessels at the boundary between the implant and the surrounding CAM mesenchyme. The endothelial lining of 30% of these vessels showed segmental attenuations, was frequently interrupted and became fenestrated, mimicking what is observed in tumor vasculature. In contrast, the vessels consisted of continuous endothelium sealed by tight junctions in all the other experimental conditions. These results indicate that FGF2 and VEGF interact with endothelial cells of the CAM in a distinct manner. Both growth factors induce a potent angiogenic response, but only VEGF delivered in a continuous manner by its transfectants can modify the phenotype of the otherwise quiescent endothelium of CAM blood microvessels. The gelatin sponge/CAM assay may constitute a new model to study the mechanisms leading to endothelial fenestration in tumor growth.

Adsorption↗

PubMedDate not supplied

New model for the study of angiogenesis and antiangiogenesis in the chick embryo chorioallantoic membrane: the gelatin sponge/chorioallantoic membrane assay.

Several methods for the in vivo study of angiogenesis are available, and each angiogenic assay presents distinct advantages and disadvantages. In this study, we present a new method for the quantitation of angiogenesis and antiangiogenesis in the chick embryo chorioallantoic membrane (CAM), based on the implantation of gelatin sponges on the top of growing CAM, on day 8 of incubation. After implantation, the sponges were treated with a stimulator (recombinant human basic fibroblast growth factor, FGF2) or an inhibitor (a rabbit polyclonal anti-FGF2 antibody) of blood vessel formation. Blood vessels growing vertically into the sponge and at the boundary between sponge and surrounding CAM mesenchyme were counted by a morphometric method on day 12. In addition, to assess whether the gelatin sponge is an appropriate vehicle to deliver cultured cells and evaluate their angiogenic potential, mouse aortic endothelial cells were cotransfected with human FGF2 and the Escherichia coli beta-galactosidase (beta-GAL) reporter gene. Stable transfectants were absorbed by the sponge, and evaluation of the angiogenic response was paralleled by beta-GAL staining to visualize implanted cells. This technique may facilitate the discovery and development of agonists or antagonists of angiogenesis.

Allantois↗

PubMedDate not supplied

Exogenous heparin induces an increase in glycosaminoglycans of the chick embryo chorioallantoic membrane: its possible role in the regulation of angiogenic processes.

In this study heparin (HE) was injected into the allantoic sac of chick embryo eggs at 5, 9, 14 days of incubation. 48 h after injection glycosaminoglycan (GAG) concentration was measured in the chorioallantoic membrane (CAM) in order to verify if HE-related CAM angiogenic activity previously demonstrated [Ribatti et al: Acta Anat 1987; 130:257-263] might be correlated with changes in GAG concentration. The results showed that HE inoculation induced an increase of 3H-glucosamine incorporation into total GAGs in comparison to control CAMs. Furthermore, HE altered the balance between the GAG classes, and in particular it produced a significant increase in the accumulation of hyaluronic acid and heparan sulfate between 7 and 11 days of incubation in comparison to control CAMs.

Allantois↗

PubMedDate not supplied

Pyogenic granuloma stimulates angiogenesis in the chick embryo chorioallantoic membrane.

Ten samples of pyogenic granuloma and 10 of normal skin from age- and sex-matched controls were grafted onto the chick embryo chorioallantoic membrane (CAM) to investigate their possible angiogenic activity. The angiogenic response in pathological and control implants was assessed on histologic sections by a planimetric point-count method 4 days after grafting. The CAM mast cells were also quantified. The vascular counts in the area underlying the pyogenic granuloma were four times higher than those of normal skin. A higher number of mucosa-like mast cells was detected in the intermediate mesenchyme of the CAM in pathological samples in comparison to controls. Pyogenic granuloma may promote angiogenesis leading to release of several angiogenic factors. The role played in angiogenic response by the inflammatory cells, mainly mast cells, forming the perilesional infiltrate was supported by this study.

Adolescent↗

PubMedDate not supplied

Human recombinant interferon alpha-2a inhibits angiogenesis of chick area vasculosa in shell-less culture.

In vivo suppression of neovascularization by in situ administration of human recombinant interferon alpha 2a (hrIFN-alpha 2a) was tested on the chick embryo area vasculosa (AV). Methylcellulose discs, each containing 5 IU of hrIFN-alpha 2a were implanted onto the AV at Hamburger-Hamilton (HH) stage 13, and inhibition of blood vessel growth was morphometrically evaluated between HH stages 20 and 27. Our results show: (i) a decreased extent of the AV; (ii) a decreased AV total vessel length; (iii) modified percent ratios of different classes of AV vessels having a definite length. The observed effects of treating with hrIFN-alpha 2a are likely attributable to inhibition of endothelial cell proliferation.

Animals↗

PubMedDate not supplied

Ultrastructural and morphometric investigation of human brain capillaries in normal and peritumoral tissues.

Capillaries of peritumoral and normal brain tissues were ultrastructurally and morphometrically investigated to evaluate the changes in peritumoral capillaries connected with the tumor-associated vasogenic edema. The endothelial cells of peritumoral capillaries showed varying thickness, electron-lucent cytoplasm, and structurally normal tight junctions. The basal lamina was thickened, rarefied, and vacuolated. The pericytes were provided with pinocytotic vesicles and phagocytic bodies. The astrocytic glia appeared empty or swollen, with few glycogen granules and a disarranged cytoskeleton; well-preserved glia was occasionally observed. The brain tissue was slightly edematous. No statistically significant differences were observed between normal and peritumoral capillaries as regards diameter, wall thickness, endothelial thickness, and endothelial vesicle density. Instead, the peritumoral capillaries displayed three times as many endothelial surface-connected vesicles, a markedly thicker basal lamina, and significantly reduced extension of pericytic and glial investments. The kind and severity of the vascular modifications, compared with the slight edematous appearance of the nervous tissue, strengthen the hypothesis that peritumoral capillaries could be involved in the edema resolution process.

Astrocytoma↗

PubMedDate not supplied

Effects of Aroclor 1254 on intercellular communication in human keratinocytes.

It has been previously described that Aroclor 1254 can inhibit GJIC in rodent liver cells where it is known to be a tumor promoter, while the possibility that Aroclor 1254 exerts its inhibitory effects on GJIC in human keratinocytes and acts as a human skin tumor promoter, deserves further attention. In the present study the effects of Aroclor 1254 were examined on gap junction channel permeability, on connexin 43 (Cx 43) expression at mRNA and protein level and on ultrastructural modification to add further experimental evidence to its inhibitory effect on GJIC. The results were compared to those induced by 12-O-tetradecanoylphorbol-13 acetate (TPA), a tumor promoter known to be a potent inhibitor of GJIC in human skin cells and to those induced by benzo[a]pyrene (B[a]P) known for its genotoxic activity. Our data show increased Cx 43 protein expression in Aroclor 1254 and TPA-treated cultures compared to controls, decreased Cx 43 protein level in those exposed to B[a]P, while Cx 43 gene expression (Cx 43 mRNA) was unaffected by the treatments. In Aroclor and TPA-treated keratinocytes, the ultrastructural examination showed residues of junctional systems expressed by specular, short tracts of the faced plasma membranes. In contrast, the contacts between plasma membranes of adjacent B[a]P treated keratinocytes were more extended. A clear inhibition of gap junction channel permeability due to Aroclor 1254 and TPA was also manifest by Lucifer yellow dye test compared to B[a]P-treated cultures where dye spreading to the neighbouring cells and to the extracellular space occurred. The present data, in addition to confirming inhibition of GJIC mediated by Aroclor 1254 in human keratinocytes, which were found to be comparable to those induced by TPA, suggest that GJIC inhibition is associated with increased Cx 43 protein expression without significant modification of its gene expression.

Analysis of Variance↗

PubMedDate not supplied

Angiogenesis, angiogenic factor expression and hematological malignancies.

Solid tumor growth consists of an avascular and a subsequent vascular phase. Several studies have now shown that, as in solid tumors, angiogenesis also plays a critical role in the progression of hematological malignancies. Monoclonal gammopathy of undetermined significance (MGUS) and non-active to active multiple myeloma (MM) progress when plasma cells induce angiogenesis and this in turn promotes progression. The increased bone marrow neovascularization, increased angiogenic and proteolytic potential of plasma cells may explain the frequent occurrence of extramedullary localization in MM. As observed in active MM, enhanced bone marrow neovascularization is apparent in acute untreated lymphoblastic leukemia. In B-cell non-Hodgkin's lymphomas, angiogenesis is significantly enhanced in relation to progression. Angiostatic molecules, such as thalidomide, could also be considered for the clinical management of hematological tumors.

Angiogenesis Inducing Agents↗

PubMedDate not supplied

Angiogenesis induced by B-cell non-Hodgkin's lymphomas. Lack of correlation with tumor malignancy and immunologic phenotype.

Correlations of malignancy grade, immunologic phenotype and angiogenic capacity were studied in B-cell non-Hodgkin's lymphomas grafted onto chorioallantoic membranes of chicken embryos. The angiogenic response elicited by the tumors was significantly greater than the response to normal lymph nodes, but it did not correlate with either the malignancy grade or the immunologic phenotype of the tumors. The elevated angiogenic capacity of neoplastic tissues is confirmed. The results also suggest that the extensive vasoproliferative response required by a rapidly growing tumor is not only controlled by the neoplastic cell population but, probably, by the host-response as well.

Adult↗

PubMedDate not supplied

Angiogenesis under normal and pathological conditions.

Angiogenesis, i.e. the generation of new blood capillaries, occurs in utero (during embryonal and fetal development) and in both physiological and pathological situations during extrauterine life. Several angiogenic factors have now been isolated, including angiogenin, acidic and basic fibroblast growth factors, and alpha and beta transforming growth factors. Their amino acid sequences have been determined and their genes cloned. Other factors await complete characterisation. An account is given of techniques used in the investigation of angiogenesis, both in vivo (transparent chambers; corneal micropockets; implantation on chick chorioallantoic membrane; employment of polymers for the sustained release of angiogenesis factors) and in vitro (cloning and long-term culture of capillary endothelial cells). The angiogenesis induced by solid tumours differs from other forms in that it is not self-limited and continues indefinitely until eradication of the tumour or death of the host. Anti-angiogenic factors have also been identified, particularly a new class of nonglucocorticoid steroids. Their employment in tumour therapy is a possibility, since neoplastic expansion is essentially dependent on angiogenesis.

Angiogenesis Inducing Agents↗

PubMedDate not supplied

Ultrastructure and permeability of immature neural and extraneural blood vessels.

The ultrastructure and permeability to the marker horseradish peroxidase in the leptomeningeal and neural vessels of the optic lobes, and in the wing bud vessels, were compared, during early stages of chick embryo vasculogenesis, in order to ascertain whether young neural vessels, like mature ones, possess structural specificity preventing the free transport of molecules through their wall (blood-brain barrier). The results demonstrated that immature endothelia are always permeable to the tracer, since the marker passes the vessel wall through the interendothelial clefts (paracellular route) as well as by endo-exocytotic mechanisms (transcellular route). Nevertheless, the transport by vesicles is somewhat reduced in the neural vessels compared to that in the extraneural ones, suggesting that the former may be influenced by the surrounding neuropile to differentiate in a specific manner right from early development.

Animals↗

PubMedDate not supplied

[Ultrastructure of the myocardial junctions of the chick embryo at an early stage in the organogenesis of the heart].

The ultrastructural features of the myocardiocyte junctional systems have been studied in the heart right myocardium of 6 day chick embryos in order to analyze the relationships between the spatial arrangement of the myocardial fibres and the formation of the myocardiocyte junctions. The myocardiocytes are remarkably branched, joined in small fibres to form a loose network with large intercellular spaces and appear well differentiated, rich in organelles, myofibrils and glycogen. Adherent-type junctions and well differentiated desmosomes are detectable at the level of the termino-terminal contacts between myocardiocytes, where the plasma membranes appear more or less complicately interconnected; nexus-type junctions are seen in the latero-lateral contact regions. The results indicate that already at an early stage of the heart organogenesis the myocardium intercellular junctions are similar, on the whole, to those described in the adult, so that they would not seem to be transitory or modifiable structures. The changes in the spatial orientation of the myocardial fibres, which take place after the 6th incubation day, could be allowed by the network-like arrangement of the primitive myocardium and presumably conditioned by the blood flow in the developing heart.

Animals↗

PubMedDate not supplied

[Effects of carbaryl on the morphogenesis of the extremities in chick embryos].

Experimental studies have been carried out to evaluate the effects of carbaryl (l.-naphthyl-methyl-carbamate)- an anticholinesterase pesticide - on the morphogenesis and development of the chick embryo. A solution containing 0.5 mg of carbaryl has been injected in the allantoic sac of the embryos treated (n = 130), at the 5th or 6th incubation day. In comparison with a control group (= 70), some morphological alterations have been found in the embryos treated, at the expense of the skeleton apparatus, particularly in the most distal portions of the lower limbs, as tibial and metatarsal angulations, with their curtailment. Such effects might be related to an interference in the synthesis of NAD (nicotinamide-adenine-dinucleotide), as reported for other organophosphoric pesticides.

Abnormalities, Drug-Induced↗