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Biomedical subjects

G Alessandri

Publications and source records attributed to G Alessandri.

At least 37 records · Page 2Linked to original sources
PubMed1990

Synergism between gangliosides and basic fibroblastic growth factor in favouring survival, growth, and motility of capillary endothelium.

The experiments reported were motivated by the observation that in vivo gangliosides promoted angiogenesis when the dose of the angiogenic factor was too low to be effective (Ziche et al.: Laboratory Investigation 61:629-634, 1989). As an approach to understanding the mechanism of this modulatory effect, we analysed the influence that gangliosides have on survival, growth, and migration of capillary endothelium when an angiogenesis factor like basic fibroblast growth factor (bFGF) was present in the culture medium. Clones of bovine capillary endothelium were cultivated in media unable to sustain survival over a 72 h period. With this experimental approach, cell survival was evaluated after addition of either bFGF or gangliosides or both to the medium. The Boyden chamber procedure was utilized to measure the influence of bFGF or gangliosides on cell mobilization across a micropore filter. Low doses of both molecules, ineffective when added singly to the culture media, improved all three parameters when added in combination. A synergic effect between bFGF and the gangliosides (GM1, GD1b, GT1b) was observed for the improvement of survival or growth and for the acceleration of endothelial cell migration. The removal of sialic acid from the ganglioside molecule prevented any effect on all three parameters. The addition of sialic acid alone to cultures was also totally ineffective. In the adult organism most angiogenic events occur under conditions of tissue damage. The synergism between gangliosides and bFGF can be interpreted as the initial phase of a process for which endothelial cell survival is the indispensable first step in the formation of a new vascular network.

Animals↗
PubMed1990

Gangliosides, copper ions and angiogenic capacity of adult tissues.

The report summarizes the work of our laboratory aimed at improving the understanding of the angiogenic response of adult tissues, an event that transforms a micro-embolus of neoplastic cells into a growing metastasis. Attention has been focused on tumor-induced angiogenesis. The following aspects of the subject are discussed: (a) relationship between size of vascular network and tumor growth rate or tumor cell population; (b) angiogenic capacity of tumors and role that prostaglandin E1 may have as an angiogenesis factor; (c) relationship between acquisition of angiogenic capacity and neoplastic transformation of a cell population; (d) modification of tissue composition at the onset of angiogenesis; (e) behaviour of copper ions and copper carriers in the course of the angiogenic response; (f) the influence of gangliosides on endothelial cell motility, survival and growth in vitro; (g) modulation of the angiogenic response by gangliosides (GM1, GT1b) in vivo.

Alprostadil↗
PubMed1990

Substance P stimulates neovascularization in vivo and proliferation of cultured endothelial cells.

We have investigated the possible effect of substance P (SP), a main mediator of neurogenic inflammation, on the growth of capillary vessels in vivo, and on the proliferation of cultured endothelial cells in vitro. Slow release preparations of SP were implanted into the avascular cornea of New Zealand White rabbits and vessel growth was monitored daily through a slit lamp stereomicroscope. SP (1-5 micrograms/pellet) induced a marked neovascularization. A selective NK-1 receptor agonist [beta-Ala4, Sar9, Met(O2)11]-SP(4-11) also induced neovascularization. The addition of SP to serum-free cultured endothelial cells, isolated from bovine adrenals (BACE) and from human umbilical cord veins (HUVE), increased proliferation of both cell lines in a concentration-dependent manner with maximal activity at 10(-8) M (BACE) and 10(-10) M (HUVE). The selective NK-1 receptor agonist induced a similar proliferative action on both cell lines, while the selective NK-2 receptor agonist [beta-Ala8]-NKA(4-10) and the selective NK-3 receptor agonist [MePhe7]-NKB had no significant effect. Two different SP antagonists [D-Pro2, D-Trp7,9]-SP and [D-Pro4, D-Trp7,9,Phe11]-SP (4-11) blocked the response to SP. These findings indicate that SP can directly stimulate the process of neovascularization, probably through induction of endothelial cell proliferation. This hitherto unraveled activity of SP could play a key role in the trophic action produced by activation of the efferent function of peripheral endings of primary sensory neurons.

Animals↗
PubMed1989

Gangliosides promote the angiogenic response.

Formation of new capillaries was induced in rabbit corneas by optimal doses of prostaglandin E1 (PGE1) or basic fibroblastic growth factor. Suboptimal doses of either of these angiogenesis inducers were unable to elicit corneal angiogenesis. However, the addition of gangliosides (GM1 or GT1b) to the insufficient dose of the angiogenic inducer, not only promoted neovascularization but strongly enhanced the number and growth rate of the newly formed capillaries as compared with the effect of an optimal dose of the angiogenesis inducer alone. Removal of the ganglioside stimulation led to the disappearance of the newly formed capillaries. Re-establishment of the ganglioside stimulation renewed the appearance of a conspicuous vascular network. Removal of sialic acid from the ganglioside molecule nullified its stimulatory effect on angiogenesis. GMI or GT1b or sialic acid were not angiogenic by themselves. Corneas ready to be invaded by newly formed capillaries induced by an optimal dose of an angiogenesis factor such as PGE1 had a ganglioside content about twice that of unstimulated corneas. The results are interpreted to indicate that ganglioside molecules influence capillary formation not as angiogenesis inducers but as promoters of vessel morphogenesis. The data support the hypothesis that in vivo the level of gangliosides in the tissue milieu could influence the evolution of pathologic processes in which new formation of capillaries is a critical event.

Alprostadil↗
PubMed1987

Influence of gangliosides on primary and metastatic neoplastic growth in human and murine cells.

The influence of gangliosides on tumor growth and frequency of metastasis in vivo as well as on growth and motility of neoplastic cells in vitro was tested utilizing human and rodent cell populations. In mice receiving injections of a ganglioside mixture twice daily the tumor volume, the number of spontaneous metastases per animal, and the number of mice with metastasis was approximately double that of controls. Preincubation of neoplastic cells with the ganglioside mixture doubled the number of metastatic foci in the lungs of mice receiving the cells by i.v. injection. Addition of a ganglioside mixture to the culture medium enhanced motility of neoplastic cells about 3-fold. This finding was similar to that observed for capillary endothelium. The presence of gangliosides in the culture media for a 48-h incubation period about doubled the number of neoplastic cells as compared to controls; the same was observed for capillary endothelium. The data are interpreted to indicate that gangliosides improve growth and mobilization of capillary endothelium and neoplastic cells. Both events may concur in enhancing tumor growth in vivo, the first by improving angiogenesis, the second by direct action on the neoplastic cell population.

Animals↗
PubMed1986

Inhibition of tumor angiogenesis by hexuronyl hexosaminoglycan sulfate.

The efficacy of heparin (HEP), the heparin analogue hexuronyl hexosaminoglycan sulfate (HHS), and hydrocortisone (HC) was studied in inhibiting the growth of four morphologically distinct pancreatic adenocarcinoma lines (CBP, LHP2, LSP3, and Pour-LVG) in hamsters. Animals were inoculated with LD100 doses of one of the four tumor lines and were randomly allocated to groups of five animals, which received in their drinking water either: HEP (1000 U/ml) alone, HHS (10 mg/ml) alone, HC (0.5 mg/ml) alone, HEP plus HC, HHS plus HC, or no additives (control). Tumors were measured, growth rates calculated, and nonparametric statistical comparisons made among the median growth rates of all of the treatment groups. All four tumors were tested in the rabbit cornea assay for their ability to induce angiogenesis. Extracts of tumors from control animals as well as from animals treated with HHS plus HC were prepared for quantitative testing in vitro by endothelial cell migration assay. All four tumor lines caused angiogenesis as measured in the rabbit cornea assay. A reduction in median tumor growth rates was observed in animals treated with HHS plus HC bearing the CBP, Pour-LVG, and LSP3 tumors. Similarly, in vitro capillary endothelial cell migration was decreased by HHS plus HC treatment in animals bearing CBP, Pour-LVG, and LSP3 tumors. Animals bearing the LHP2 tumor showed no effect of HHS plus HC treatment on tumor growth rate and no effect on endothelial cell migration. HEP alone, HHS alone, HC alone, and HEP plus HC showed no effect on tumor growth rate in any of the four tumors tested.

Animals↗
PubMed1986

Interaction of gangliosides with fibronectin in the mobilization of capillary endothelium. Possible influence on the growth of metastasis.

Mobilization of the capillary endothelium is one of the first events observed during angiogenesis, and the study of conditions that control or influence the mobilization of the endothelium in vitro has been assumed to offer information relevant to the understanding of angiogenesis in vivo. In vitro mobilization of the bovine capillary endothelium was substantially enhanced by addition of gangliosides to the culture medium. Optimal mobilization was obtained when the endothelium incorporated the gangliosides first and was then seeded on fibronectin anchored to collagen type I. Preincubation of the capillary endothelium with gangliosides, trisialoganglioside in particular, doubled the amount of fibronectin bound to the cells and enhanced the migration about 5-fold. 'Blockage' of ganglioside binding with cholera toxin or gamma-interferon substantially reduced migration. Rabbit corneas, treated in vivo with a variety of angiogenesis effectors to induce neovascularization, consistently showed an increase in sialic acid content just prior to the time the tissue would be penetrated by the capillaries. This finding was interpreted to indicate that an increment of the ganglioside content of the capillary endothelial cell membranes may play a determinant role in the mobilization of the capillary endothelium in vivo as shown here to take place in vitro. Since the formation of a tumor from a micrometastasis requires formation of new capillaries and highly metastasizing tumors very frequently have high levels of sialic acid on the cell surface, it is hypothesized that production and shedding of gangliosides from the surface of neoplastic cells may be a factor in promoting angiogenesis and metastatic growth.

Animals↗
PubMed1985

Cooperation between fibronectin and heparin in the mobilization of capillary endothelium.

Angiogenesis is indispensable to sustain promotion and growth of metastases. As a contribution to the understanding of the angiogenesis process, the experiments reported showed that: (a) fibronectin is involved in the mobilization of capillary endothelium which is the first event in angiogenesis; (b) antifibronectin serum can block the mobilization, and neutralization of the antiserum can restore it; (c) the combination of fibronectin + heparin is a powerful mobilizer of capillary endothelium, and (d) fragments of the fibronectin and heparin molecules in combination can mobilize capillary endothelium as effectively as the intact molecules. The results are interpreted to indicate that molecules normally present in the extracellular matrix like heparin and fibronectin, may act as angiogenesis effectors when the physiological structure of the tissue is altered, for instance by lytic enzymes released by metastatic neoplastic cells.

Animals↗
PubMed1984

Characterization of a chemoattractant for endothelium induced by angiogenesis effectors.

The mechanism of neovascularization was further explored by the use of chemically defined angiogenesis effectors. The vascularization of the rabbit cornea was selected as an experimental approach that permits comparison of one cornea treated by the angiogenesis effector with the contralateral cornea of the same subject treated by the same molecule deprived of angiogenic capacity. Under these conditions, we observed that neovascularization was initiated by the appearance of a chemoattractant for the bovine capillary endothelium only in the cornea treated by the angiogenesis effector. The chemoattractant was purified about 150-fold by a single-step procedure, using gelatin:Sepharose affinity chromatography. Chemoattraction resulted from the combined effect of a chemotactic factor(s) and an activating factor(s). The association of the two enhanced 5- to 8-fold the motility of the capillary endothelium in a concentration-dependent manner with optimum at 0.2 mg/ml. The activating factor(s) does not have chemotactic capacity, but without it, chemotaxis is reduced to about one half. The chemotactic complex was present in the cornea regardless of the nature of the angiogenesis effector used as the triggering device. Heat and proteases eliminated chemotaxis and destroyed the chemotactic complex. Thus, neovascularization may be triggered by effectors able to induce in the cornea proteins, normally not present, that influence angiogenesis via mobilization of capillary endothelium.

Angiogenesis Inducing Agents↗
PubMed1984

Angiogenesis in vivo and selective mobilization of capillary endothelium in vitro by heparin-copper complex.

The objective of this work was to contribute to the interpretation of the mechanisms of capillary formation in the adult tissues. We have observed that the heparin-copper complex is angiogenic in vivo and stimulates migration of capillary endothelium in vitro. This effect is specific for capillary endothelium since aortic endothelium or fibroblasts from the rabbit cornea or human skin were unresponsive.

Angiogenesis Inducing Agents↗
PubMed1983

Mobilization of capillary endothelium in vitro induced by effectors of angiogenesis in vivo.

An assay to measure endothelial cell mobilization on a gelatin substratum has been developed. Utilization of the gelatin-agarose and Boyden chamber assays established that: (a) fragments or extracts of corneas treated with several effectors of angiogenesis in vivo acquired the capacity to mobilize the capillary endothelium in vitro; (b) this mobilization was selective for the capillary endothelium; endothelium from aorta and fibroblasts from human skin or rabbit cornea were unresponsive; and (c) among the effectors of angiogenesis utilized alone; i.e., without the intermediary action of the cornea, none were able to mobilize the capillary endothelium in vitro, except for the heparin-copper complex. The data are interpreted to indicate that new formation of capillaries in vivo is the end result of a cascade of events of which heparin and copper are important components.

Adrenal Glands↗
PubMed1982

Ceruloplasmin, copper ions, and angiogenesis.

The ability to induce new formation of capillaries in the cornea was tested for ceruloplasmin, the copper carrier of serum, for fragments of the ceruloplasmin molecule with and without copper, for heparin, and for glycyl-L-histidyl-L-lysine, bound or not bound to copper ions. Male or female 2- to 3-kg New Zealand White rabbits were used. These experiments were prompted by the previous observation of copper accumulation in the cornea during angiogenesis and by the inability of copper-deficient rabbits to mount an angiogenic response. The results showed that the three different molecules were all able to induce angiogenesis provided that they were bound to copper. Fragments of the ceruloplasmin molecule also induced angiogenesis but only when copper was bound to the peptides. The data are interpreted to indicate that copper ions are involved in the sequence of events leading to angiogenesis and that the carrier molecules may be of quite a different nature.

Animals↗
PubMed1981

Tumour sublines with different metastatic capacity induce similar blood coagulation changes in the host.

This paper is aimed at investigating how metastatic tumour growth influenced the haemostatic system of the host. Blood platelet count, blood fibrinogen level, the activated partial thromboplastin time (APTT) and the prothrombin time (PT) were determined at various intervals during growth and metastasis of a murine fibrosarcoma (mFS6) or one of its sublines with different metastatic capacity. Progressive thrombocytopenia and increase in fibrinogen level were observed during development of the tumour in all the animal groups studied, irrespective of the metastatic potential of the various sublines. No significant changes were observed in the PT or APTT values. These data support the concept that primary rather than metastatic growth influences the haemostatic system of tumour-bearing animals.

Animals↗
PubMed1981

Procoagulant activity of sarcoma sublines with different metastatic potential.

It has been suggested that cancer cell procoagulant activity influences metastasis formation by promoting fibrin deposition around tumors. We have investigated the procoagulant activity of various tumor cell sublines with different metastatic capacity derived from metastatic nodules of a murine fibrosarcoma. All the cells tested possessed a marked thromboplastin-like activity; they were, however, heterogeneous as regards the degree of procoagulant activity; the two cell lines with virtually no metastatic capacity showed 6--8 times higher procoagulant activity than the cells from the parent line; in contrast, the procoagulant activity of the two sublines with higher metastatic capacity did not differ significantly from that of the parent line. These findings support the hypothesis that fibrin is part of a defence reaction against cancer cell invasiveness.

Animals↗
PubMed1980

Metastasizing capacity of tumour cells from spontaneous metastases of transplanted murine tumours.

We investigated the metastasizing capacity of spontaneous lung metastases from the MN/MCA1 and mFS6 sarcoma, the B16 melanoma and colon 26 carcinoma. Spontaneous metastases at other visceral organs (liver, spleen, kidney, ovary, uterus) from the M5076/73A (M5) ovarian carcinoma and colon 26 carcinoma were also studied. Tumour cells from individual spontaneous metastases were used immediately after isolation from the normal parenchyma (mFS6, M5 and colon 26) and/or after 1 s.c. passage in syngeneic mice (MN/MCA1, mFS6, B16 and M5). Spontaneous metastases were examined for all tumours and their secondaries after i.m. or s.c. inoculation of tumour cells; artificial lung colonies were measured after i.v. injection only of cells from the primary mFS6 and MN/MCA1 and B16 or their spontaneous metastases. Individual spontaneous metastases were to some extent heterogeneous in their metastatic potential, a minority of the secondaries having greater or lesser metastatic capacity than the appropriate primary. Overall, tumour cells from spontaneous metastases did not show greater metastasizing capacity than primary neoplasms, nor was there evidence that metastases from specific organs (e.g. spleen and kidney) tended to home to the specific anatomical sites from which they were originally isolated. These observations in a series of murine tumours of different histology, transplantation history and pattern of metastasis, do not support the hypothesis that metastases are the ultimate expression of strong selection of variant cells with greater intrinsic metastatic potential, pre-existing within the primary tumour.

Animals↗
PubMed1977

Activation of K cells in mice with transplanted tumours differing in immunogenicity and metastasizing capacity.

The effector arm of antibody-dependent cellular cytotoxicity (ADCC) was evaluated using 51Cr-labelled chicken erythrocytes as targets in BALB/c mice transplanted with the Moloney sarcoma virus-induced tumours T-MSV and MS2, and in C57BL/6 mice transplanted with the chemically induced FS6 sarcoma, Lewis lung carcinoma and B16 melanoma. Tumour-bearing animals showed higher levels of ADCC than normal mice, a stimulation confirmed in MS2-bearing mice, using SL2 lymphoma cells as targets in a cytostasis assay. ADCC effector-cell capacity was higher in animals transplanted with the immunogenic, spontaneously regressing T-MSV than in mice bearing the poorly immunogenic metastasizing MS2 sarcoma. The increased ADCC activity detectable in the spleen of tumour-bearing hosts was not abolished by removal of phagocytic-adherent cells.

Animals↗