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C Willems

Publications and source records attributed to C Willems.

At least 19 recordsLinked to original sources
PubMed1983

The effect of calcium on the secretion of factor VIII-related antigen by cultured human endothelial cells.

Cultured human endothelial cells derived from the umbilical cord vein are able to release factor VIII-related antigen into the culture medium. The experiments described in this paper show the presence of two pathways for the secretion of factor VIII-related antigen from endothelial cells. There is a basal release of this antigen, independent of the presence of extracellular calcium ions. This release can be inhibited by cycloheximide and is therefore directly related to de novo protein synthesis. Besides this basal release, there is an extra release of factor VIII-related antigen that can be stimulated by thrombin, the Ca2+-ionophore A23187 or phorbol myristate acetate. As demonstrated by immunofluorescence, the stimulus-inducible release originates from storage granules in the cells. This stimulus-inducible release is dependent on extracellular Ca2+ but independent of intracellular cAMP.

Antigens↗
PubMed1983

Endothelial cell dysfunction in homocystinuria.

This report describes the isolation and culture of venous endothelial cells from the umbilical cord of an obligate heterozygote for homocystinuria. The effect of different sulphur-containing amino acids on the viability and function of these cells was studied and compared with cultured normal endothelial cells. When endothelial cells were cultured in the presence of methionine (10 mmol/l) or homocystine (10 mmol/l), differences occurred between the viability and function of the heterozygote and normal cells in terms of 51Cr release and ability to prevent platelet adherence. The Cr release corrected for spontaneous release increases for the heterozygote cells after incubation/for 21 h in the presence of methionine to 81.3% (control cells, range: 0-23.3%, n = 5) and in the presence of homocystine to 141% (control cells, range: 13.5-55.2%, n = 5). The total number of platelets that adhere to confluent monolayers increases for heterozygote cells cultured in the presence of methionine to 0.98 X 10(7) platelets cm-2 (normal cells, range: 0.56-0.72 X 10(7) platelets cm-2) and in the presence of homocystine to 1.41 X 10(7) platelets cm-2 (normal cells, range: 0.94-1.06 X 10(7) platelets cm-2). Both normal and control cells were sensitive to homocysteine. This study/indicates for the first time what vascular endothelial cells, derived from an obligate heterozygote, are (partly) deficient in cysthathionine synthase and are more susceptible to methionine- and homocystine-mediated injury than normal endothelial cells. Consequently, in homocystinuria, due to dysfunction of the endothelial cells, toxic sulphur-containing amino acids may accumulate in these cells, causing injury of these cells.

Cells, Cultured↗
PubMed1982

Arachidonate metabolism in cultured human vascular endothelial cells. Evidence for two prostaglandin synthetic pathways sensitive to acetylsalicylic acid.

The effect of acetylsalicylic acid on endothelial prostaglandin synthesis was measured in the presence of exogenous and endogenous substrates. In both types of measurement, a rate of inhibition was found similar to that observed for acetylsalicylic acid inhibition of cyclooxygenase activity in platelets. After withdrawal of acetylsalicylic acid, a rapid restoration of cyclooxygenase activity was observed when exogenous [1-14C]arachidonate was used as a substrate (50% of initial activity at 5 h). However, when endogenous substrate, released after phospholipase activation induced by thrombin treatment of the cells, was used to test cyclooxygenase activity, only partial restoration of enzymic activity was observed (30% after 48 h). Phospholipase activity, measured by the release of free fatty acids, was not inhibited by acetylsalicylic acid. Measurement of turnover times by incubating the cells with cycloheximide revealed a short turnover time for the enzymic activity tested with exogenous [1-14C]arachidonate (2.3 h) and a relatively long turnover time for the cyclooxygenase activity tested with endogenous substrate released after thrombin treatment of the cells (54 h). These results suggest that at least two pools of cycloxygenase are involved in endothelial prostaglandin synthesis.

6-Ketoprostaglandin F1 alpha↗
PubMed1982

Increase of hybridoma formation by human lymphocytes after stimulation in vitro; effect of antigen, endothelial cells, and PWM.

Peripheral blood lymphocytes from antibody-producing Rh- donors were fused with mouse myeloma cells, and the hybrids were screened for anti-Rh antibody production. Although the resulting hybrids were not stable in long-term culture, they provided a useful test system for an investigation of ways to stimulate human lymphocytes in vitro before fusion in order to maximize the recovery of hybrids producing antibodies with a desired specificity. Although 6-day culture with PWM or with antigen (Rh+ erythrocytes) increased slightly the yield of desired hybrids, exposure of the PBL to antigen in the presence of human endothelial cells was dramatically more effective. This effect was not produced with endothelial cell culture supernatants (HECS) that had been shown previously to enhance hybridoma growth. Culture of PBL before fusion with both PWM and antigen also improved the proportion of active hybridomas, and incubation with antigen plus endothelial cells plus PWM resulted in a very high number of hybridomas, with a very high proportion producing antibody to the immunizing antigen. There are several alternatives to explain the mechanisms involved, but in any case, the technique should be particularly useful when the possibility of fusion of human PBL with a human myeloma line becomes more widely available.

Adult↗
PubMed1981

Effect of ascorbate on abnormal neutrophil, platelet and lymphocytic function in a patient with the Chediak-Higashi syndrome.

A diminished chemotactic response was observed with the neutrophils of a patient with the Chediak-Higashi syndrome, who was not in the accelerated phase of the disease. An abnormally low release of myeloperoxidase from these cells during phagocytosis was also noted; this resulted in a decreased iodination capacity and probably also caused the defect in the intracellular killing of bacteria by the neutrophils. The level of cyclic AMP in these cells was elevated, but decreased after treatment with ascorbate either in vitro or in vivo. During ascorbate therapy, the bactericidal activity of the neutrophils normalized, whereas the chemotactic response remained low. Nevertheless, the patient had significantly less infections during ascorbate therapy. The bleeding tendency, due to a storage-pool disorder of the Chediak-Higashi platelets, was unaffected by treatment with ascorbate. The patient's lymphocytes did not display any activity in antibody-dependent lymphocytotoxicity. This defect was not affected by treatment with ascorbate either.

Adenosine Diphosphate↗
PubMed1981

Human endothelial culture supernatant (HECS): evidence for a growth-promoting factor binding to hybridoma and myeloma cells.

Human endothelial culture supernatant (HECS) contains a factor(s) that enhances the proliferation of hybridoma cells as we reported previously. In the present paper, we found that, in comparison with endothelial cells, their supernatant exerts a much stronger growth-promoting effect on hybridoma cells, which can also be detected earlier. In a confluent culture of endothelial cells, detectable amounts of this factor(s) are produced after 2 hr of incubation, and the production is linear in time for 3 days. The enhancing effect of HECS on the proliferation of hybridoma cells appears to be independent of the concentration of cells in the culture. The activity of HECS is adsorbed to hybridoma or myeloma cells, but not to thymocytes. HECS acts on hybridoma cells by delivering a growth-promoting signal that induces the hybridoma cells to proliferate.

Adsorption↗
PubMed1980

Human endothelial culture supernatant (HECS): a growth factor for hybridomas.

Human endothelial culture supernatant (HECS) had strong growth-promotion activity for hybridoma cells: the yield of hybridomas after fusion was increased at least 2-fold over that in the presence of feeder cells, such as mouse macrophages and spleen cells. Moreover, HECS could substitute for feeder cells when hybridomas were cultured at the single-cell level, and strongly enhanced the proliferation of hybrid cells. furthermore, the presence of human endothelial cells prolonged the stability of human-mouse hybridomas, producing human immunoglobulin, hybrids known to survive poorly during culture in vitro.

Animals↗
PubMed1975

Effects of microtubule inhibitors and cytochalasin B on thyroid metabolism in vitro.

Mitotic spindle inhibitors (colchicine, vinblastine, vincristine, 020, ethanol) and cytochalasin B inhibit the phagocytosis of colloid by thyroid cells and the secretion of thyroid hormones. This inhibition has been linked to interferences with the microtubular microfilament system of the follicular cell. In order to test the possibility of using such inhibitors to selectively block secretion, the action of suppressing or highly inhibitory concentrations on other metabolic parameters has been studied on dog thyroid slices in vitro: glucose oxidation, lactate formation, iodide binding to protein, cyclic 3'5' AMP accumulation. It is shown that at a concentration of 10 mM colchicine is entirely non specific as it greatly inhibits all facets of metabolism and all the stimulatory effects of cyclic 3'5' AMP and thyrotropin. The other mictrotubule inhibitors, although affecting thyroid metabolism in various ways were more specified. The enhancement by vineblastine of glucose oxidation ald iodine binding to proteins suggests an activation of they thyroid H2O2 generating system. D2O on the other hand selectively inhibits secretion and the binding of iodide to proteins. Cytochalasin B, presumably by inhibiting hexose transport, decreased glycolysis and the uptake of iodide. However this effect cannot account for the complete inhibition of thyroid secretion.

Animals↗
PubMed1975

Inhibition by iodide of the activation of the thyroid cyclic 3',5'-AMP system.

The action of iodide on the cyclic AMP system of dog thyroid slices has been studied. Iodide inhibits the enhancement of cyclic AMP accumulation in the presence of TSH. Such an effect is also observed in horse, beef and sheep thyroid slices, but not in dog kidney slices stimulated by parathyroid hormone or in rat parotid slices stimulated by isoproterenol. The effect in dog thyroid slices is suppressed by 1mM NaClO4, 1mM methimazole and 1mM propylthiouracil. Similar data have been obtained for prostaglandin E1 stimulation. Effects of thyrotropin mediated by cyclic AMP, i.e., activation of iodothyronine secretion, 1-14C-glucose oxidation, and lactate formation, were also inhibited by iodide but not by iodide and methimazole. Similar activations when caused by dbcAMP were not inhibited by iodide. The data suggest a model in which an intracellular agent resulting from the oxidation of iodide acts on the thyroid cyclic AMP system.

Animals↗