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Biomedical subjects

M Christ

Publications and source records attributed to M Christ.

At least 73 records · Page 4Linked to original sources
PubMed1995

Oxysterol-induced apoptosis in human monocytic cell lines.

Oxysterols constitute a large family of natural compounds, endowed with various biological activities including cholesterol regulation, immunosuppression and antitumoral potency. In the present study, we examine and compare the cytotoxic effects of two representative members of this family: 7 beta-hydroxycholesterol (7 beta-OH) and 25-hydroxycholesterol (25-OH), in two human monocytic cell lines, U-937 and HL-60. In both cell lines 7 beta-OH at 30 mu M induces cell death by apoptosis within the first hours of treatment. Under the same conditions and in contrast with results previously obtained with lymphoma cells, 25-OH is cytostatic only. It is interesting to note that the simultaneous treatment of U-937 cells by equimolar concentrations of 7 beta-OH and 25-OH leads to a considerably decreased induction of apoptosis. Such an effect is not observed with HL-60 cells. Taken together, these results indicate for the first time that: 1) oxysterols hydroxylated on the sterol nucleus are also able to induce apoptosis, 2) apoptosis can be induced by these substances in cells belonging to the myeloid lineage and 3) as far as apoptosis is concerned, a combined treatment with 7 beta-OH and 25-OH can lead to opposite effects depending on the cell type.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1995

Rapid effects of aldosterone on sodium transport in vascular smooth muscle cells.

Increasing evidence has accumulated for rapid nongenomic steroid actions in various cell systems and, more recently, for rapid aldosterone effects on the Na(+)-H+ antiport in human mononuclear leukocytes. The aim of the present study was to demonstrate a rapid, nongenomic aldosterone action in rat vascular smooth muscle cells as a key effector cell in cardiovascular regulation. Basal 22Na+ influx in quiescent vascular smooth muscle cells was 22.1 +/- 1.9 nmol/mg protein per minute (mean +/- SEM, n = 9). Aldosterone (1 nmol/L) stimulated influx to 28.6 +/- 1.5 nmol/mg protein per minute after 4 minutes (n = 9, P < .05), with a half-maximal effect between 0.1 and 0.5 nmol/L; the effects were inhibited by ethylisopropylamiloride, the specific inhibitor of the Na(+)-H+ exchanger, demonstrating the involvement of this transport system in rapid effects of aldosterone. Hydrocortisone (1 mumol/L) was ineffective, and fludrocortisone and deoxycorticosterone increased influx with half-maximal effects at approximately 0.5 nmol/L. Canrenone, a classic antagonist of aldosterone action, did not inhibit stimulation by aldosterone at a 1000-fold excess concentration. Aldosterone significantly stimulated intracellular inositol 1,4,5-trisphosphate levels (P < .05) after 30 seconds; the inhibitors of phospholipase C, neomycin and U-73122, inhibited aldosterone-stimulated Na+ influx and increase of intracellular inositol 1,4,5-trisphosphate. The rapid stimulation of sodium transport in vascular smooth muscle cells and the pharmacological characteristics of this effect are clearly incompatible with the classic, genomic pathway of steroid action and represent further evidence for nongenomic effects of aldosterone.

Aldosterone↗
PubMed1995

Left ventricular hypercontractility in hypertensive patients with anginal pain and normal coronary angiograms.

This study was designed to assess left ventricular contractility in hypertensive patients with normal coronary angiography and anginal pain. An abnormally high percentage of hypertensive patients (approximately 30%) undergoing cardiac catheterization because of anginal pain and/or exercise-induced ST-segment depressions has angiographically normal coronary arteries. Possible reasons for these signs of ischemia include a microvasculopathy, metabolic abnormalities and an increased oxygen consumption as a result of left ventricular hypercontractility which was studied here. Left ventricular volumes and ejection fraction were determined in 50 patients with arterial hypertension (23 men, 27 women, age 60 +/- 8 years, RR 154 +/- 24/91 +/- 12 mm Hg) by cardiac catheterization and computerized analysis of laevocardiographies. The control group were 50 normotensives (30 men, 20 women, age 57 +/- 12 years, RR 128 +/- 12/76 +/- 8 mm Hg) without coronary artery disease. The angiographical data were correlated with age, sex. ECG, echocardiography, laboratory findings, medication and duration of hypertension. The left ventricular ejection fraction was significantly increased in the group of hypertensives (75.8 +/- 6.3 vs. 67.7 +/- 5.0%, p < 0.001). This difference was mainly due to a significantly reduced endsystolic left ventricular volume (37.1 +/- 15.3 vs. 47.7 +/- 10.8 ml, p < 0.001); enddiastolic left ventricular volume was not significantly different (140.5 +/- 26.8 vs. 149.0 +/- 27.5 ml, p > 0.1). A hyposystolic form of hypertensive heart disease was not observed in this group of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Rapid effects of aldosterone on free intracellular calcium in vascular smooth muscle and endothelial cells: subcellular localization of calcium elevations by single cell imaging.

Rapid in vitro effects of aldosterone on the intracellular concentrations of sodium, potassium and calcium, cell volume and the sodium-proton-antiport have been described in human mononuclear leukocytes and vascular smooth muscle cells (VSMC). These nongenomic effects are signalled through membrane receptors with a high affinity for aldosterone, but not for cortisol, and through the phosphoinositide pathway. In the present study, we demonstrate that free intracellular calcium is increased rapidly by aldosterone in VSMC and endothelial cells (EC) as determined by single cell imaging of Fura2-fluorescence. In VSMC, calcium elevation is localized to the perinuclear region whereas in EC, a predominant increase of subplasmalemmal calcium is seen. In VSMC, effects are half maximal at 0.1 nM aldosterone; cortisol is inactive up to 0.1 microM. These data show that intracellular signalling for aldosterone also involves calcium, but the subcellular localization of this signal varies between cell types.

Aldosterone↗
PubMed1994

Immune dysregulation in TGF-beta 1-deficient mice.

Approximately 2 wk after birth, mice having a TGF-beta 1 null mutation (TGF-beta 1(-/-)) exhibit a progressive wasting syndrome and death. Associated with this phenotype is a multifocal infiltration of lymphocytes and macrophages into target organs, especially the heart, lungs, and salivary glands. To explore the consequences of TGF-beta 1 deficiency on the immune system, lymphocyte phenotype and function were analyzed. Initially, lymphoid organ architecture seemed to be normal and, as symptoms developed, the thymus decreased in size, whereas lymph nodes were enlarged. Phenotypically, the TGF-beta 1(-/-) lymphoid cells seemed to be more differentiated in the thymus and activated in the lymph nodes, but remarkably unaffected in the spleen. Moreover, TGF-beta 1(-/-) spleen and lymph nodes displayed enhanced numbers of proliferating cells, as measured by proliferating cell nuclear Ag and/or cyclin-dependent kinase levels. Consistent with this hyperproliferative response, constitutive levels of IL-2 mRNA were elevated in the thymus and both IL-2 and IL-2R mRNA were increased in the lymph nodes. In contrast with the activation profile of TGF-beta 1(-/-) lymphoid cells in vivo, mitogen challenge of these cells in vitro revealed suppressed proliferation that was associated with a defect in inducible IL-2 mRNA expression and IL-2 secretion. Moreover, the addition of rIL-2 restored the deficient mitogen-induced proliferation. The mechanism leading to T cell anergy remains unclear; however, these data confirm the essential role for TGF-beta 1 in maintaining normal immune function.

Animals↗
PubMed1994

Synthetic fibronectin peptides interrupt inflammatory cell infiltration in transforming growth factor beta 1 knockout mice.

Pronounced mononuclear leukocyte (MNL) infiltration occurs in multiple organs of mice homozygous for a transforming growth factor beta 1 (TGF-beta 1) loss-of-function gene mutation [TGF-beta 1 (-/-)], followed by cachexia and eventually death. Consistent with the increased leukocyte adhesion and tissue infiltration, MNLs isolated from spleen, thymus, and peripheral blood of symptomatic TGF-beta 1 (-/-) mice, as compared to littermate controls, exhibited increased adhesion to extracellular matrix proteins and to endothelial cells in vitro. Incubation of TGF-beta 1 (-/-) MNLs with selected synthetic peptides corresponding to cell- and heparin-binding sequences of fibronectin (FN) significantly attenuated adhesion of these cells not only to FN but also to endothelial cells in vitro. Based on these observations, mice were treated with the FN peptides in an attempt to rescue them from tissue inflammation and cardiopulmonary failure. Daily injections of a combination of four synthetic FN peptides that interact with beta 1-integrins and/or cell surface proteoglycans blocked the massive infiltration of MNLs into the heart and lungs of TGF-beta 1 (-/-) mice. Peptide treatment initiated on day 8, coincident with the first evidence of increased leukocyte-endothelial cell interactions, not only blocked tissue infiltration but also moderated the lethal wasting syndrome.

Amino Acid Sequence↗
PubMed1994

Volumes and Na+/H+ antiporter activity of lymphocytes in patients with congestive heart failure.

Previous studies in patients with congestive heart failure (CHF) treated with diuretics and/or digoxin have shown abnormalities of cellular volume and electrolytes in biopsies of skeletal muscle. These abnormalities seem to play an important role with regard to the dysregulation of peripheral vascular resistance and characteristic clinical features of CHF, for example, muscular weakness. This study assessed the effect of angiotension-converting enzyme (ACE) inhibitor therapy on cell volume and cell volume regulation in patients with CHF. Cell diameters of human mononuclear leukocytes (HML) were determined electronically by a Coulter Counter. Cell diameters for 19 patients with decreased left ventricular ejection fraction (determined via levocardiography) on therapy with ACE inhibitors (group 1) were compared to those of HML from patients on diuretics alone (group 2, n = 16). The activity of the Na+/H+ antiporter was determined by cell swelling in isotonic propionate. The control group consisted of 20 normal, age- and sex-matched volunteers. HML diameters were significantly increased from 7.16 +/- 0.07 in normals to 7.24 +/- 0.08 microns (group 1; P < 0.01) and 7.23 +/- 0.11 microns (group 2; P < 0.05), indicating an abnormal regulation of cell volume. There were no statistically significant correlations between the individual ejection fraction or digoxin therapy and average cell diameters. In both patient groups ethylisopropylamiloride-sensitive swelling rates were normal compared to the control group indicating a normal activity of the Na+/H+ antiporter. In conclusion, increased cell sizes reflect a structural change in HML rather than a rapidly reversible functional abnormality which was not affected different by ACE inhibition and diuretic therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Non-classical receptors for aldosterone in plasma membranes from pig kidneys.

Rapid, nongenomic in vitro effects of aldosterone on intracellular electrolytes, cell volume and the sodium-proton antiporter have been found in human mononuclear leukocytes (HML), as have related membrane receptors. In the present study, binding of 125I-labeled aldosterone to plasma membrane preparations from pig kidneys was studied, since nongenomic in vitro effects of aldosterone have also been described in cultured kidney cells. In this preparation, binding of aldosterone shares important features with both functional and binding data in HML. These include a very low apparent Ki of approximately 0.1 nM for aldosterone, a high turnover rate and binding selectivity for aldosterone and fludrocortisone. Desoxycorticosterone acetate and corticosterone show intermediate affinity, with apparent Ki values of approximately 1 and 100 nM, with hydrocortisone even less active. Thus binding of aldosterone to kidney plasma membranes is compatible with the major features of its nongenomic renal effects.

Aldosterone↗
PubMed1994

Heterogeneous microvascular coronary vasodilation by adenosine and nitroglycerin in dogs.

We investigated the effects of adenosine and nitroglycerin (NTG) on coronary microvessel diameters (intravital fluorescence microscopy) and coronary perfusion (radioactive microspheres). Measurements were performed during baseline conditions (intravenous piritramid) and during controlled hypotension (mean arterial pressure approximately 60 mmHg) induced by halothane, adenosine, and NTG. Coronary vascular resistance (CVR) remained unchanged during halothane (-7%) but decreased during adenosine (-76%) and NTG (-29%). Coronary arteriolar diameters increased during all experimental steps. In the smallest vessels (20-40 microns), diameters increased by 14, 43, and 42% during halothane-, adenosine-, and NTG-induced hypotension, respectively. Diameter increases were less pronounced in larger vessels. The uniform action of adenosine and NTG in 20- to 500-microns arterial vessels is in contrast to the pronounced differences in reduction of CVR. Preferential dilation of arterioles < 20 microns or recruitment of coronary microvessels by adenosine might account for the more pronounced decrease of CVR during adenosine. Intracoronary application of adenosine (0.8 mg.kg-1.h-1) and NTG (1, 5, and 25 micrograms.kg-1.h-1) equally caused near-maximum dilation of coronary arterioles > 100 microns. However, NTG dilation of arterioles < 100 microns was dose dependent and exceeded large-vessel dilation only with the highest concentration of NTG.

Adenosine↗
PubMed1994

Palytoxin induces K+ efflux from yeast cells expressing the mammalian sodium pump.

Palytoxin causes potassium efflux and sodium influx in all investigated animals cells. Much evidence points to the sodium pump (Na+/K(+)-ATPase) as the target of the toxin. A heterologous expression system for mammalian Na+/K(+)-ATPase in the brewers yeast Saccharomyces cerevisiae has been used to test this hypothesis. Yeast cells do not contain endogenous sodium pumps but can be transformed with vectors coding for the alpha and beta subunits of the mammalian sodium pump. We now show that transformed yeast cells expressing both alpha and beta subunits of Na+/K(+)-ATPase are highly sensitive to the toxin, as measured by the loss of intracellular potassium. Palytoxin-induced potassium efflux is completely inhibited by 500 microM ouabain. In contrast, nontransformed yeast cells or cells expressing either the alpha or beta subunits are insensitive to palytoxin. Thus, the alpha/beta heterodimer of the sodium pump is required for the release of potassium induced by palytoxin. The results suggest that palytoxin converts the sodium pump into an open channel, allowing the passage of alkali ions.

Acrylamides↗
PubMed1994

Novel membrane receptors for aldosterone in human lymphocytes: a 50 kDa protein on SDS-PAGE.

Fast in vitro effects of aldosterone on the Na+/H(+)-exchanger, inositoltrisphosphate generation and corresponding specific binding to plasma membranes at Kd-values of approximately 0.1 nM have been found in human mononuclear leukocytes and vascular smooth muscle cells. The novel aldosterone membrane receptor was analyzed on SDS-PAGE after labeling of microsomal membranes from human mononuclear leukocytes with a [125I]-aldosterone-derivative by use of BASED as a photoactivatable crosslinker. Binding of 1 nM [125I]-aldosterone was found at a molecular weight of approximately 50 kDa which was absent with 1 microM cold aldosterone, but not cortisol in the binding media. This aldosterone-selectivity is typical and discriminatory for the new aldosterone membrane receptor. Solubilization of the receptor protein from membranes by high salt concentrations (1 M NaCl, 1 mM EDTA) was not achieved. It, thus, appears as an integral membrane protein. Dithiothreitol, a sulfhydryl agent, does not reduce specific aldosterone binding indicating the absence of SH-groups in the binding domain or sensitive structures of the receptors. The results are the first to characterize the novel membrane receptor for aldosterone with regard to molecular weight and basic properties. These findings and other related results are reviewed here.

Aldosterone↗
PubMed1993

Aneurysms of coronary arteries in a patient with adult polycystic kidney disease: arteriosclerosis or involvement by the primary disease?

Adult polycystic kidney disease is frequently associated with gastrointestinal and cardiovascular abnormalities. These include hypertension, mitral valve prolapse, mild dilation of the aortic root, abdominal aneurysms, and predisposition to aortic, mitral, and tricuspidal valve regurgitation reminiscent of Marfan's syndrome. Although the exact molecular mechanisms of adult polycystic kidney disease are not well established, a generalized defect of collagen structure is hypothesized. The most severe vascular problems, however, are typical intracranial aneurysms with a high incidence of subarachnoid hemorrhage and a high mortality rate. We report a case of dilated coronary arteries found incidentally in a patient with adult polycystic kidney disease and stress-induced angina pectoris. The typical angina pectoris of the patient is explained by left ventricular hypertrophy and coronary heart disease. Multiple liver cysts, mitral valve prolapse, and the coronary aneurysms in this patient with adult polycystic kidney disease appear to reflect the manifestation of a generalized connective tissue disorder in this syndrome.

Adult↗
PubMed1993

Effects of nitroso compounds and aromatic amines on fetal tracheal explants.

Tracheas were excised from fetal Syrian golden hamsters on the 15th day of gestation. Tracheal explants were cultured in vitro and exposed to different dose-levels of well known carcinogens. We chose two nitroso compounds, N-Methyl-N-nitro-N-nitrosoguanidine (MNNG) and Diethylnitrosamine (DEN) and two aromatic amines, Aminofluorene (AF) and Acetylaminofluorene (AAF). The tracheal explants were treated for 24 h in vitro, then the carcinogens were washed off and the tracheas were kept for 21, 28 or 35 days in culture. After fixation tracheal explants were transversely cut with serial section techniques and scored for morphological changes of the epithelium by light microscopy. Most of the control explants completed differentiation and had a normal morphology at the end of the in vitro culture period. Occasionally we found a decrease of the number of ciliated cells and some areas with squamous metaplasia in the respiratory epithelium. Carcinogen treatment with nitroso compounds led to a significant increase of the morphologic changes of the epithelium. These effects were especially obvious after DEN treatment. Morphologic changes of the epithelium such as metaplasia and hyperplasia were discussed as carcinogen-related events. In vitro exposure with aromatic amines did not induce marked metaplastic or hyperplastic changes in the respiratory epithelium of tracheal explants.

Animals↗
PubMed1993

The inositol-1,4,5-trisphosphate system is involved in rapid effects of aldosterone in human mononuclear leukocytes.

There is increasing evidence for rapid steroid action on electrolyte transport in human mononuclear leukocytes (HML). In HML, aldosterone stimulates the Na+/H+ antiporter within a few minutes. Because a variety of hormones and growth factors activate the Na+/H+ antiporter via protein kinase C and inositol phospholipids, a possible involvement of inositol-1,4,5-trisphosphate (IP3) in the rapid effects of aldosterone in HML was investigated. The stimulation of IP3 generation was started by the addition of aldosterone, concanavalin A, or other steroids. A significant increase in IP3 levels by aldosterone (1 nmol/L, P < 0.05) was found after 1 min, similar to that found after concanavalin A (25 micrograms/mL). Aldosterone caused a concentration-dependent elevation of IP3 levels, with an apparent EC50 of approximately 0.1 nmol/L. Fludrocortisone stimulated IP3 generation at similar concentrations, whereas a weaker IP3 stimulation by glucocorticoids (hydrocortisone, dexamethasone) occurred at micromolar concentrations only. Canrenone, a potent inhibitor of classical aldosterone action, was not effective up to a concentration of 100 nmol/L. These findings show kinetic and pharmacological similarities with both the functional data on Na+/H+ antiport stimulation by aldosterone and the studies of 125I-aldosterone binding to plasma membranes of HML. Thus, these data are the first to indicate an involvement of the phosphoinositide pathway in the rapid membrane effects of aldosterone.

Adult↗
PubMed1993

Apoptosis induced by oxysterols in murine lymphoma cells and in normal thymocytes.

Oxygenated derivatives of cholesterol (oxysterols), a family of naturally occurring compounds, possess marked anti-proliferative and immunosuppressive activities, in particular they have been shown to inhibit T-cell responses to different stimuli. 25-Hydroxycholesterol (25-OHC) and 7 beta,25-dihydroxycholesterol (7.25-OHC) are able to kill not only RDM4 murine lymphoma in vitro, but also, surprisingly, mouse thymocytes after several hours of incubation. In this study, we report that the death of RDM4 and thymocytes induced by oxysterols exhibits the features of apoptosis. This phenomenon was identified by agarose gel electrophoresis of DNA fragments extracted from the cells and quantified by flow cytometric analysis of the DNA fluorescence of propidium iodide-stained cells. Cycloheximide and actinomycin D were found to decrease the number of apoptotic cells and to increase cell viability, indicating a requirement for the synthesis of macromolecules in oxysterol-induced programmed cell death. The pathway by which 25-OHC and 7.25-OHC are able to induce apoptosis in this type of cell and the possible contribution of these compounds to thymus involution during development are discussed.

Animals↗
PubMed1992

Photoaffinity labeling of plasma membrane receptors for aldosterone from human mononuclear leukocytes.

Non-genomic effects of aldosterone on the sodium-proton-antiport have been shown in human mononuclear leukocytes which could be related to a new aldosterone membrane receptor. In the present paper plasma membranes from human mononuclear leukocytes were covalently photolabeled with a [125I]-aldosterone derivative. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed significant aldosterone binding at a molecular weight of approximately 50000 Dalton which was absent with 1 microM cold aldosterone, but not cortisol in the binding media. The presence of the sulfhydryl agent dithiothreitol did not affect results suggesting the absence of disulfide bridges in the steroid binding domain of the receptor. These data are the first to define the molecular weight of the membrane receptor for aldosterone.

Affinity Labels↗