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Biomedical subjects

F George

Publications and source records attributed to F George.

14 recordsLinked to original sources
PubMed1992

Rapid isolation of human endothelial cells from whole blood using S-Endo1 monoclonal antibody coupled to immuno-magnetic beads: demonstration of endothelial injury after angioplasty.

The presence in whole blood of circulating endothelial cells (EC) has been a subject of debate for many years. It could represent a good marker of vessel injury. We demonstrate here that human endothelial cells can be directly isolated and identified in circulating blood by means of an endothelial cell specific monoclonal antibody, S-Endo1, coupled to micromagnetic beads. The specificity and efficacy of the assay were established using normal blood samples with cultured EC added. Specific rosettes formed between EC and beads could subsequently be isolated with a magnet. The rosetted cells were recovered with a yield greater than 80%. Their endothelial origin was confirmed by the positive labelling of von Willebrand factor and thrombomodulin, as well as the presence of Weibel-Palade bodies. We applied this method to demonstrate significantly increased levels of EC in venous and arterial human blood samples in patients undergoing heart catheterization. This new whole blood immuno-separation method may be useful in determining endothelial cell injury in vascular disorders.

Antibodies, Monoclonal↗
PubMed1992

Diagnosis of Mediterranean spotted fever by indirect immunofluorescence of Rickettsia conorii in circulating endothelial cells isolated with monoclonal antibody-coated immunomagnetic beads.

Rickettsia conorii, an obligate intracellular bacterium that infects vascular endothelial cells, is the etiologic agent of Mediterranean spotted fever (MSF). A new procedure using indirect immunofluorescence was used to directly detect R. conorii in circulating endothelial cells (CEC). CEC were separated from other blood components by using anti-endothelial cell monoclonal antibody-coated magnetic beads. An anti-R. conorii polyclonal rabbit antiserum was used to stain rickettsiae. The entire procedure took 3 h. R. conorii was detected in CEC from 9 of 12 patients ultimately confirmed as having MSF. Among the patients, 5 with R. conorii isolated by centrifugation-shell vial assay were also positive by the new technique. None of 3 patients whose diagnosis was other than MSF had R. conorii detected in CEC. The procedure may be helpful for rapid diagnosis of MSF and may lead to new technical approaches for the diagnosis of infectious diseases caused by intracellular pathogenic microorganisms.

Adult↗
PubMed1992

von Willebrand factor release and thrombomodulin and tissue factor expression in Rickettsia conorii-infected endothelial cells.

Mediterranean spotted fever, a tick-borne rickettsiosis caused by Rickettsia conorii, may lead to small-vessel or deep-vein thrombosis. In order to evaluate the role of endothelial cell alteration in this lesion, we infected human endothelial cells derived from umbilical veins with R. conorii. We report the induction of two previously unreported prothrombotic mechanisms in rickettsial disease: (i) a progressive decline in thrombomodulin antigen and (ii) early expression of tissue factor, and, as described for R. rickettsii infection, later release of von Willebrand factor from Weibel-Palade bodies. Thrombomodulin expression in infected endothelial cells, measured by the thrombin-dependent activation of protein C or flow cytometric analysis, decreased steadily between 4 and 24 h after inoculation with rickettsiae. R. conorii infection induced tissue factor expression, measured by clotting assay and flow cytometric analysis, which was detectable 2 h postinoculation, reached its maximum 4 h postinoculation, and progressively decreased thereafter. Infection resulted in a relatively late release of von Willebrand factor antigen into the culture medium. A double-label immunofluorescence assay for the simultaneous evaluation of von Willebrand factor and R. conorii showed that the depletion of cytoplasmic von Willebrand factor stored in Weibel-Palade bodies was due to a direct effect of the intracellular R. conorii. These disturbances of endothelial function observed with R. conorii-infected cells may provide a paradigm for the elucidation of thrombotic pathobiology with Mediterranean spotted fever.

Cells, Cultured↗
PubMed1992

Acute monocytic leukemia: prevalent cutaneous lesions. Two cases.

The authors report two cases of acute myeloid leukemia with prevalent cutaneous lesions. The positivity of granulo-monocytic antibodies and the exclusive cutaneous site of the lesions drove them previously to the diagnosis of histiocytic sarcoma. These cases stress the problem of the immunological identification of cutaneous lymphomas of "histiocytic" type.

Aged↗
PubMed1991

Characterization of epitheloid cells from human omentum: comparison with endothelial cells from umbilical veins.

Capillary cells represent 95% of the vascular bed, and cells from large and micro-vessels do not express identical functions. In order to study the hormonal regulation of plasminogen activator inhibitor 1 (PAI-1) secretion by human capillary cells we used epithelial cells from omental tissue (HOTMEC). As their endothelial origin is subject to controversy, we attempted to determine their characteristics by comparing them to human umbilical vein endothelial cells (HUVEC). Morphological and biological criteria were studied. By phase contrast microscopy HOTMEC elicited a cobblestone pattern similar to HUVEC. Weibel-Palade bodies were not found in the cytoplasm with electron microscopy. Fluorescence microscopy studies indicated that HOTMEC took up acetylated-LDL more intensely than HUVEC, and showed no staining for von Willebrand factor. The phenotype of HOTMEC was studied by flow cytometry using monoclonal antibodies (mo Ab) directed against epitopes either specific for endothelial cells or for mesothelial cells. We showed that in our preparations only 10% of cells reacted with mo Ab specific for endothelial cells. About 60% of the HOTMEC were labelled with an antibody directed against mesothelial cells. HOTMEC expressed fibrinolytic factors. Tissue plasminogen activator (t-PA) levels in HOTMEC conditioned medium were 50 fold higher than those of HUVEC, and the PAI-1 secretions were identical in both cell types. Insulin which is known to increase PAI-1 synthesis by hepatocytes did not enhance the PAI-1 level either in HOTMEC or in HUVEC conditioned media. Our results suggested that morphological and functional methods did not allow discrimination between the cell types present in the omentum tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗
PubMed1991

Cytofluorometric detection of human endothelial cells in whole blood using S-Endo 1 monoclonal antibody.

It has long been debated whether endothelial cells are present at very low frequency in peripheral blood. Elevated concentrations of such circulating cells may represent a good marker of vascular injury. We have therefore designed an immunocytometric assay for the detection of rare endothelial cells in whole blood. This assay is based on a new monoclonal antibody (MAb) S-Endo 1, made against human umbilical vein endothelial cells (HUVEC) and specific for endothelial cells of various origins without detectable reactivity with blood cells. First, the sensitivity of the assay was established by using normal blood samples with admixed HUVEC as an in vitro model. A good correlation was obtained between added and counted endothelial cells; the recovery was greater than 90% and the minimum detectable concentration of HUVEC was about 0.2 cells/microliters whole blood. Using this rapid counting technique, no detectable levels of endothelial cells were found in the blood of normal individuals (CE less than or equal to 0.1 cells/microliters) while elevated concentrations (up to 8 cells/microliters) were detected in a human model of vascular injury corresponding to a traumatic venepuncture. Thus, this new whole blood immunocytometric assay using S-Endo 1 MAb may be useful in determining the levels of circulating endothelial cells in vascular disorders.

Animals↗
PubMed1991

Histological evolution of peripheral T-cell lymphomas. Study of six cases.

The authors report 6 cases of histological transformation in peripheral T-cell lymphomas of low grade of malignancy. The transformation occurs in 75% of the cases, in extra-nodal sites and corresponds to a monomorphic of pleiomorphic large cell type. There is no discordance in the immunologic results between the two phases. The transformation seems to occur earlier than in B lymphomas, with a relative frequency of hematological manifestations and no therapeutic response.

Aged↗
PubMed1990

Concomitant secretion by A431 cells of tissue plasminogen activator and a specific inhibitor masks EGF modulation of tPA activity.

It has previously been reported that EGF enhances uPA but not tPA in the A431 squamous carcinoma cell line. To determine whether the absence of tPA modulation by EGF reflected steady levels or the action of an anti-activator, we assayed tPA, PAI-1 and tPA/PAI-1 complexes by zymography and immunological assays. Under conditions in which EGF had no effect on tPA activity, tPA antigen paradoxically increased with a concomitant rise of tPA/PAI-1 complexes. This indicated that tPA was rapidly inactivated through the formation of a complex, immunologically and electrophoretically related to tPA/PAI-1. tPA antigen and tPA/PAI-1 complexes were modulated by EGF in a time and concentration dependent manner. PAI-1 antigen was secreted into A431 medium (CM) after a lag phase of 16 h in both control and EGF-treated cultures. Evidence is presented here that two forms of PAI-1 are present in A431 CM: an inactive form and an active form which neutralizes the tPA secreted, masking its enhancement by EGF in functional assays.

Electrophoresis, Polyacrylamide Gel↗
PubMed1990

Modulation of tPA, PAI-1 and PAI-2 antigen and mRNA levels by EGF in the A431 cell line.

It has been reported that EGF treatment enhances uPA but not tPA in the A431 epidermoid carcinoma cell line. To determine whether the absence of tPA modulation by EGF could be due to the action of inhibitors, we assayed tPA, PAI-1, PAI-2 and tPA/PAI-1 complexes by immunological assays and zymography in A431 serum-free medium. We found that, under conditions in which EGF had no effect on tPA activity, tPA antigen increased with a concomitant rise of tPA/PAI-1 complexes, indicating the action of an inhibitor. Both tPA antigen and tPA/PAI-1 complexes were modulated by EGF in a time and concentration dependent manner. tPA/PAI-1 complex levels were lower than tPA levels, suggesting the presence of other inhibitors. Immunological assays detected PAI-2 in addition to PAI-1 and showed a time and dose response to EGF. Modulation of tPA and the anti-activators by the growth factor was confirmed by identification of the corresponding transcripts with cDNA probes. We conclude that the net plasminogen activator activity in A431 cells is the result of a balance between activators and inhibitors.

DNA↗
PubMed1989

Modulation of plasminogen activator systems by matrix components in two breast cancer cell lines: MCF-7 and MDA-MB-231.

We have analyzed the plasminogen activator (PA) systems of two metastatic breast adenocarcinoma cell lines, MCF-7 and MDA-MB-231, as a function of 17 beta-estradiol stimulation when the cells were cultured on purified components of extracellular matrix. Laminin enhanced PA levels in both cell lines, but this enhancement seemed to occur via different mechanisms, including dissociation of inhibitor complexes. The major effect was the marked increase in cell-associated urokinase-type PA (u-PA); the increase was independent of estrogen in hormone-insensitive MDA-MB-231 cells grown on laminin-coated surfaces. In estrogen-sensitive MCF-7 cells, 17 beta-estradiol stimulated u-PA secretion in a similar fashion on plastic, laminin, fibronectin, or collagen but acted in synergy with laminin in the production and release of tissue-type PA.

Adenocarcinoma↗
PubMed1988

The maturational process of gonadotropin-releasing hormone neurons in the male rat: a role for the adrenal gland in the increase in secretory function.

The aim of this study was to define the maturational process of the LHRH neuron in the male rat and the role of the adrenal and testis. Maturing (7-week-old) and adult (12-week-old) male rats were adrenalectomized (ADX), castrated (TX), or ADX and TX; controls were sham operated. Two weeks later, LHRH release from explants of the median eminence area (MEA), MEA LHRH content, and serum testosterone (T) were determined. MEA were incubated for 5 min with 150 microM copper and then for 15 min with 10 microM prostaglandin E2 (Cu/PGE2). LHRH release in response to Cu/PGE2 increased 3-fold between 7 and 9 weeks of age [from 10.4 +/- 1.8 to 29.2 +/- 2.1 pg/15 min.MEA (mean +/- SE)], and there was no further increase thereafter. ADX, TX, or ADX plus TX of 7-week-old rats prevented the increase in Cu/PGE2-stimulated release. In contrast, ADX of 12-week-old rats did not alter LHRH release, whereas TX or ADX plus TX drastically reduced it (75%). The MEA content increased gradually between 7 and 14 weeks of age (from 2.0 +/- 0.2 to 3.0 +/- 0.3 ng). ADX of either 7- or 12-week-old rats did not alter LHRH content, whereas TX or ADX plus TX reduced it to 1.3 ng in both age groups. Serum T increased 6.7-fold between 7 and 9 weeks of age (from 1.06 +/- 0.42 to 6.70 +/- 0.57 ng/ml), and there was no further increase thereafter. ADX of 7-week-old rats did not alter serum T, whereas ADX of 12-week-old rats reduced serum T to 0.62 +/- 0.15 ng/ml. Serum T was undetectable in TX or ADX plus TX rats of both age groups. In summary, maturation of the male reproductive system is associated with a moderate increase in LHRH content of the median eminence and marked increases in the secretory function of the LHRH neuron and in serum T; the testis is essential for these maturational increases. In addition to the testis, the adrenal is necessary for the maturational increase in the secretory function of the LHRH neuron, but not for the increase in LHRH content or that in serum T. It is proposed that dissociable mechanisms regulate LHRH secretion and content in the maturing male, and that T and a substance of adrenal origin (steroid?) are required for the maturational increase in secretory function of the LHRH neuron.

Adrenal Glands↗
PubMedDate not supplied

[New developments of antiplatelet drugs].

A better knowledge of platelet activation mechanisms has made it possible to develop antiplatelet agents that are capable of inhibiting primary haemostasis at very precise levels. Many of these agents block the synthesis or receptor of an hemostasis I agonist. Thus, the thromboxane A2 receptor can be blocked, or its synthesis can be interrupted, by thromboxane synthetase inhibitors, by cyclooxygenase inhibitors, or by omega 3 fatty acids which are competitive inhibitors. Inhibitors of thrombin (hirudin), PAF acether and serotonin (ketanserin) also are available. Other antiplatelet agents secreted by endothelial cells act as haemostasis I antagonists by elevating platelet cAMP or cGMP levels (prostacyclins and analogues, nitrate derivatives). Monoclonal antibodies and RGD peptides directly inhibit the glycoproteins that are responsible for platelet adhesion or aggregation, but their users are faced with problems of cost and route of administration. Of all these new antiplatelet agents, only ticlopidine, which has an imperfectly known mode of action, has proved effective in multiple situations, but its use is limited by its side-effects.

Hemostasis↗