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Biomedical subjects

R Montesano

Publications and source records attributed to R Montesano.

At least 163 records · Page 9Linked to original sources
PubMed1988

Phorbol ester stimulates macrophage invasion of fibrin matrices.

Macrophages migrate through a fibrin-rich extracellular matrix in chronic inflammation, wound healing, and other pathophysiological processes. To investigate the factors that might influence the ability of mononuclear phagocytes to invade fibrin matrices, we cultured macrophage-like P388D1 cells as well as resident and thioglycollate-elicited mouse peritoneal macrophages on three-dimensional fibrin gels, and we examined the effect of agents known to stimulate a variety of macrophage functions, including the production of fibrinolytic enzymes. Cells grown on fibrin gels under control conditions, as well as cells treated with either bacterial lipopolysaccharide or concanavalin A, remained confined to the gel surface. In contrast, the tumor promoter 4 beta-phorbol 12-myristate 13-acetate (PMA) induced both P388D1 cells and peritoneal macrophages to invade the underlying fibrin matrix. The invasive behavior of PMA-treated P388D1 cells was not affected by protease inhibitors of various specificities. These results demonstrate that certain exogenous signals can profoundly modify the ability of macrophages to migrate through fibrin matrices.

Animals↗
PubMed1988

Induction of angiogenesis in vitro by vanadate, an inhibitor of phosphotyrosine phosphatases.

We have previously shown that capillary endothelial cells grown on the surface of three-dimensional collagen gels can be induced to invade the underlying fibrillar matrix and to form capillary-like tubular structures in response to tumor-promoting phorbol esters or the angiogenic agent fibroblast growth factor (FGF). Since both phorbol esters and FGF stimulate phosphorylation of tyrosine residues, we treated endothelial cells with vanadate, an inhibitor of phosphotyrosine-specific phosphatases, to determine whether this agent could induce the expression of an angiogenic phenotype in these cells. We show here that vanadate stimulates endothelial cells to invade collagen matrices and to organize into characteristic tubules resembling those induced by FGF or phorbol esters. We have further observed that vanadate concomitantly stimulates endothelial cells to produce plasminogen activators (PAs), proteolytic enzymes which are induced by phorbol esters and FGF, and which have been implicated in the neovascular response; this stimulation can be accounted for by an increase in the levels of urokinase-type PA and tissue type PA mRNA. These results suggest a role for tyrosine phosphorylation in the regulation of the angiogenic phenotype in capillary endothelial cells.

Animals↗
PubMed1988

Transforming growth factor beta stimulates collagen-matrix contraction by fibroblasts: implications for wound healing.

An important event during wound healing is the contraction of newly formed connective tissue (granulation tissue) by fibroblasts. The role of polypeptide growth factors in the process of wound contraction was investigated by analyzing the influence of transforming growth factor beta (TGF-beta), platelet-derived growth factor on the ability of fibroblasts to contract a collagen matrix in an in vitro system. TGF-beta, but not the other growth factors tested, markedly enhanced the ability of BHK-21,3T3-L1, and human foreskin fibroblasts to contract collagen gels. These results suggest that TGF-beta released from platelets and inflammatory cells at sites of tissue injury stimulates fibroblasts to contract the provisional wound matrix and that this effect contributes to the ability of TGF-beta to accelerate wound healing.

Animals↗
PubMed1988

Repair of O-alkylpyrimidines in mammalian cells: a present consensus.

Enzymatic repair of the O-alkylpyrimidines (O2- and O4-alkylthymine, O2-alkylcytosine) and alkyl phosphotriesters has been studied in Escherichia coli, and the two proteins involved, a glycosylase (DNA-3-methyladenine glycosylase) and a methyltransferase (DNA-O6-methylguanine:protein-L-cysteine S-methyltransferase, EC 2.1.1.63), have been well characterized. In mammals or mammalian cells treated with carcinogenic alkylating agents, loss of these derivatives has been demonstrated repeatedly. Nevertheless, mammalian repair proteins that are analogous to those from E. coli do not detectably act on these alkyl derivatives. A variety of techniques has been used by many investigators in the United States and Europe, who conclude here that the mode of O-alkylpyrimidine and alkyl phosphotriester repair in mammalian cells differs from that in E. coli. New approaches and methods are needed to characterize these processes at the biochemical and molecular level.

Alkylating Agents↗
PubMed1988

Intracellular diaphragmed fenestrae in cultured capillary endothelial cells.

The endothelium of visceral capillaries is characterized by the occurrence of numerous fenestrae, which are usually bridged by a thin, single-layered diaphragm. Both in vivo and in vitro, diaphragmed fenestrae perforate the endothelial cell cytoplasm in the most attenuated regions of the cell. We report here that in capillary endothelial cells grown under experimental conditions promoting the development of intracellular lumina (for example, suspension within a three-dimensional collagen matrix), diaphragmed fenestrae can form in a unique, previously undescribed intracellular location - that is, within thin cytoplasmic septa separating contiguous luminal compartments.

Adrenal Cortex↗
PubMed1988

In vitro modulation of endothelial fenestrae: opposing effects of retinoic acid and transforming growth factor beta.

Cultured endothelial cells isolated from fenestrated capillaries express many properties characteristic of their in vivo differentiated phenotype, including the formation of a limited number of fenestrae. In this study, we have investigated whether physiological factors that control cell differentiation might regulate the surface density of fenestrae in capillary endothelial cells. We have found that treatment of the cultures with retinoic acid (10 microM) induces a more than threefold increase in the surface density of endothelial fenestrae, whereas transforming growth factor beta (TGF beta) (2 ng ml-1) causes a sevenfold decrease in the surface density of these structures. These results show that the expression of endothelial fenestrae is susceptible to bidirectional modulation by physiological signals, and suggest that retinoids and TGF beta may participate in the regulation of fenestral density of capillary endothelium in vivo.

Animals↗
PubMed1988

Application of antibody methods to the detection of aflatoxin in human body fluids.

Four different approaches to the quantification of human exposure to aflatoxins (AF) are presented: (i) analysis of urinary AF metabolites and DNA adducts, (ii) assay of AF bound to blood proteins and to lymphocyte DNA, (iii) immunocytochemical localization of AF in individual cells, and (iv) detection of AF in human breast milk. The potential applications of these approaches for assessing the role of both AF and hepatitis B virus (HBV) in primary hepatocellular carcinoma (HCC) are presented. The advantages and limitations of the methods for use in large-scale epidemiological studies are discussed, with particular attention to sensitivity.

Aflatoxins↗
PubMed1988

Detection in human cells of alkylated macromolecules attributable to exposure to nitrosamines.

Various methods for detecting DNA alkylation adducts are described briefly, with emphasis on immunoassays using antibodies against O6-methyldeoxyguanosine (O6-medGua), O4-methylthymidine (O4-meThy) and 7-methyldeoxyguanosine (7-medGua). The application of these methods to epidemiological studies is discussed, and results obtained so far on the presence of DNA alkylation adducts in human tissues are presented.

Alkylation↗
PubMed1987

Aflatoxin detected in human breast milk by immunoassay.

Several epidemiological studies have shown a positive association between dietary exposure to aflatoxin (AF) and an increased incidence of primary hepatocellular carcinoma (PHC). One area in which little information is available is the exposure of newborn children to AF in human breast milk. We report the development, validation and application of an enzyme-linked immunosorbent assay (ELISA) to the detection of AF in human breast milk. The assay allows the quantitation of 2 pg AFM1 per ml of milk using less than 10 ml of sample. A good correlation was observed between ELISA and an hplc-fluorescence technique using naturally contaminated milk at levels up to 40 pg AF per ml. Of 54 samples collected from women in rural villages in Zimbabwe, 6 were found to be positive (11%) in ELISA with levels up to 50 pg AF per ml. No positive samples were detected out of 42 milk samples obtained from women in France. This sensitive and rapid methodology will be useful in examining the importance of and interaction between exposure to AF and infection with hepatitis B virus (HBV) early in life.

Aflatoxins↗
PubMed1987

Comparison of regulations on occupational carcinogens in several industrialized countries.

Regulations controlling the manufacture and use of carcinogens in the industrial setting of various countries are examined. In addition, the occupational exposure limits (OEL) of chemicals known or suspected to be carcinogenic in humans are listed, and criteria for the establishment of OELs are discussed. It is also stressed that control measures should not be confined to a few developed countries, and it is hoped that attracting attention to their unevenness will contribute to the implementation of a more efficient primary prevention of cancer.

Carcinogens↗
PubMed1987

Additive effects of interleukin 1 and tumour necrosis factor-alpha on the accumulation of the three granulocyte and macrophage colony-stimulating factor mRNAs in human endothelial cells.

The control of haematopoietic colony-stimulating factors (CSF) gene expression by interleukin 1 (IL-1) and tumour necrosis factor alpha (TNF-alpha) in cultured endothelial cells was studied by RNA hybridization and nuclear gene transcription. Both IL-1 and TNF-alpha induced, with somewhat different kinetics, a slow but marked accumulation of granulocyte-macrophage (GM)- and granulocyte (G)-CSF mRNAs in endothelial cells; macrophage (M)-CSF mRNA increased more rapidly but more moderately. Simultaneous treatment with maximally stimulating concentrations of both IL-1 and TNF-alpha had an additive effect on the accumulation of the three mRNAs, suggesting that both mediators act via independent pathways. The mechanism of CSF mRNA accumulation in endothelial cells was explored by nuclear run-on experiments, which showed that both IL-1 and TNF-alpha increase GM-CSF, G-CSF and M-CSF gene transcription to varying degrees.

Cells, Cultured↗
PubMed1987

Phorbol esters induce angiogenesis in vitro from large-vessel endothelial cells.

We have shown previously that the tumor promoter phorbol myristate acetate (PMA) induces capillary endothelial cells grown on the surface of three-dimensional collagen gels to invade the underlying matrix as capillary-like tubular structures, a phenomenon mimicking angiogenic processes that occur in vivo (Montesano and Orci: Cell 42:469, 1985). To establish whether the potential to invade the extracellular matrix as capillary-like sprouts is restricted to microvascular endothelial cells or is also shared by large vessel endothelium, we have examined the response to PMA of endothelial cells isolated from the human umbilical vein and the calf pulmonary artery. The results of these experiments show that both types of macrovascular endothelial cells are able to penetrate into collagen gels as vessel-like tubes following treatment with PMA. This demonstrates that endothelial cells derived from large vessels can, in response to appropriate signals, express invasive properties thought to be associated specifically with capillary endothelial cells in vivo.

Animals↗
PubMed1987

Phorbol ester induces cultured endothelial cells to invade a fibrin matrix in the presence of fibrinolytic inhibitors.

We have previously shown that the tumor promoter 4 beta-phorbol 12-myristate 13-acetate (PMA) induces capillary endothelial cells grown to confluency on the surface of three-dimensional collagen gels to invade the underlying matrix and to form capillary-like tubular structures, a phenomenon mimicking angiogenic processes that occur in vivo (Montesano and Orci: Cell, 42:469-477, 1985). Since angiogenesis frequently occurs within a fibrin-rich extracellular matrix, we have examined the ability of PMA-treated endothelial cells to invade fibrin gels. Control endothelial cells grown on fibrin gels formed a confluent monolayer on the gel surface and did not invade the underlying matrix. Treatment of the cultures with PMA resulted in a progressive lysis of the substrate without invasion of the fibrin matrix. However, if the cells were treated with PMA either in the presence of fibrinolytic inhibitors (Trasylol, epsilon-aminocaproic acid) or in the absence of detectable plasminogen, dissolution of the substrate was prevented, and the endothelial cells invaded the fibrin gel, forming vessel-like tubular structures similar to those previously observed with collagen gels. These results demonstrate that the invasive and morphogenetic events induced by PMA do not necessarily require an interaction between endothelial cells and collagen fibrils but can also occur with other biologically relevant substrata. They also suggest (1) that invasion may occur via a plasmin-independent mechanism and (2) that in vivo, neutralization of excess proteolytic activity may play an important permissive role in angiogenesis and other invasive processes by preventing uncontrolled matrix degradation.

Aminocaproic Acid↗
PubMed1987

Urokinase-type plasminogen activator is induced in migrating capillary endothelial cells.

Cellular migration is an essential component of invasive biological processes, many of which have been correlated with an increase in plasminogen activator production. Endothelial cell migration occurs in vivo during repair of vascular lesions and angiogenesis, and can be induced in vitro by wounding a confluent monolayer of cells. By combining the wounded monolayer model with a substrate overlay technique, we show that cells migrating from the edges of an experimental wound display an increase in urokinase-type plasminogen activator (uPA) activity, and that this activity reverts to background levels upon cessation of movement, when the wound has closed. Our results demonstrate a direct temporal relationship between endothelial cell migration and uPA activity, and suggest that induction of uPA activity is a component of the migratory process.

Adrenal Cortex↗
PubMed1987

[Effect of molybdenum Mo on the alkylation of DNA in the liver of rats treated with 14C-diethylnitrosamine].

Effect of molybdenum on the alkylation of DNA in the liver of rats treated with 14C-diethylnitrosamine was studied. When administered orally at a dose of 1 mg/rat/day as (HN4)6 Mo7O24 for 30 days, Mo inhibited the alkylation of DNA in the liver of rats. The level of 3-ethylguanine, N7-ethylguanine and O6-ethylguanine decreased. Simultaneously, the exhalation of 14CO2 and the urinary excretion of 14C- were increased as compared to the controls. At a dose of 5 mg/rat/day, Mo increased the alkylation of DNA in the liver. The amount of 3-ethylguanine, N7-ethylguanine and O6-ethylguanine was higher than that of the controls. The exhalation of 14CO2 and the urinary excretion of 14C- were decreased. The authors believe that the dose of molybdenum is relevant to the role it plays in the carcinogenesis of cell. The role of molybdenum in the carcinogenesis is discussed.

Alkylation↗
PubMed1987

Phorbol ester induces diaphragmed fenestrae in large vessel endothelium in vitro.

The endothelium of visceral capillaries is fenestrated, whereas that of large vessels is not. We show here that the tumor promoter, 4 beta-phorbol 12-myristate 13-acetate (PMA), triggers formation of diaphragmed fenestrae in endothelial cells cultured from the calf pulmonary artery and the human umbilical vein. This demonstrates that large vessel endothelial cells have the potential to express, in response to exogenous signals, a structural specialization uniquely associated with the endothelium of visceral capillaries in vivo.

Animals↗
PubMed1987

Radioimmunoassay used to detect DNA alkylation adducts in tissues from populations at high risk for oesophageal and stomach cancer.

N-Nitrosamines are alkylating agents capable of forming various covalent adducts with DNA in vivo. Since formation of promutagenic DNA adducts, particularly O6-methyldeoxyguanosine (O6-medGuo), has been implicated as an initiating event in nitrosamine-induced carcinogenesis, we have used radioimmunoassay (RIA) to probe for such damage in surgical tissue samples from cancer patients in populations likely to be exposed environmentally to nitrosamines.

Alkylation↗