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Biomedical subjects

M Mohaupt

Publications and source records attributed to M Mohaupt.

15 recordsLinked to original sources
PubMed2006

Statin therapy induces ultrastructural damage in skeletal muscle in patients without myalgia.

Muscle pain and weakness are frequent complaints in patients receiving 3-hydroxymethylglutaryl coenzymeA (HMG CoA) reductase inhibitors (statins). Many patients with myalgia have creatine kinase levels that are either normal or only marginally elevated, and no obvious structural defects have been reported in patients with myalgia only. To investigate further the mechanism that mediates statin-induced skeletal muscle damage, skeletal muscle biopsies from statin-treated and non-statin-treated patients were examined using both electron microscopy and biochemical approaches. The present paper reports clear evidence of skeletal muscle damage in statin-treated patients, despite their being asymptomatic. Though the degree of overall damage is slight, it has a characteristic pattern that includes breakdown of the T-tubular system and subsarcolemmal rupture. These characteristic structural abnormalities observed in the statin-treated patients were reproduced by extraction of cholesterol from skeletal muscle fibres in vitro. These findings support the hypothesis that statin-induced cholesterol lowering per se contributes to myocyte damage and suggest further that it is the specific lipid/protein organization of the skeletal muscle cell itself that renders it particularly vulnerable.

Adult↗
PubMed2006

Endovascular stenting of a renal transplant vein.

We describe successful endovascular stenting of a high-grade stenosis of a renal transplant vein in a 53-year old patient. Kidney transplantation had been performed due to IgA nephropathy and the patient had become symptomatic two months after uneventful recovery from operation.

Angioplasty, Balloon↗
PubMed2001

Prophylactic hemodialysis after radiocontrast media in patients with renal insufficiency is potentially harmful.

PURPOSE: Acute renal failure induced by contrast media is an important cause of hospital-acquired renal insufficiency. Preexisting renal failure and the dose of contrast media are known risk factors for the development of radiocontrast nephropathy. We performed a randomized trial to test whether radiocontrast nephropathy can be avoided by prophylactic hemodialysis immediately after the administration of contrast media in patients with impaired renal function. SUBJECTS AND METHODS: Renal function and other parameters, hemodialysis requirement, and relevant clinical events were recorded before and during the 6 days after administration of contrast media in 113 patients with a baseline serum creatinine level >200 microm/L (>2.3 mg/dL). Patients were randomly assigned to either hemodialysis (n = 55) or nonhemodialysis (n = 58) treatment after parenteral low-osmolality contrast media. RESULTS: The characteristics of the patients in the two groups were similar. Compared with baseline levels, the mean [+/- SD] serum creatinine level decreased at day 1 (277 +/- 95 microm/L), peaked at day 4 (353 +/- 126 microm/L), and returned to baseline at day 6 (327 +/- 119 microm/L, P <0.05 by analysis of variance) after administration of contrast media in the hemodialysis group, whereas in the nonhemodialysis group, no significant changes in mean serum creatinine level were observed. Eleven patients required 1 or more hemodialyses (8 in the hemodialysis group and 3 in the nonhemodialysis group, P = 0.12), 6 of whom (4 vs. 2, P = 0.44) required 3 or more hemodialyses. Clinically relevant events included pulmonary edema (1 vs. 4 patients, P = 0.36), myocardial infarction (2 vs. 2), stroke (2 vs. 0, P = 0.24), and death (1 vs. 1). CONCLUSIONS: The strategy of performing hemodialysis immediately after the administration of low-osmolality contrast media in all patients with a reduced renal function did not diminish the rate of complications, including radiocontrast nephropathy.

Acute Kidney Injury↗
PubMed2001

The role of toll-like receptors (TLRs) in bacteria-induced maturation of murine dendritic cells (DCS). Peptidoglycan and lipoteichoic acid are inducers of DC maturation and require TLR2.

Toll-like receptors (TLRs) have been found to be key elements in pathogen recognition by the host immune system. Dendritic cells (DCs) are crucial for both innate immune responses and initiation of acquired immunity. Here we focus on the potential involvement of TLR ligand interaction in DC maturation. TLR2 knockout mice and mice carrying a TLR4 mutation (C3H/HeJ) were investigated for DC maturation induced by peptidoglycan (PGN), lipopolysaccharide (LPS), or lipoteichoic acids (LTAs). All stimuli induced maturation of murine bone marrow-derived DCs in control mice. TLR2(-)/- mice lacked maturation upon stimulation with PGN, as assessed by expression of major histocompatibility complex class II, CD86, cytokine, and chemokine production, fluorescein isothiocyanate-dextran uptake, and mixed lymphocyte reactions, while being completely responsive to LPS. A similar lack of maturation was observed in C3H/HeJ mice upon stimulation with LPS. DC maturation induced by LTAs from two different types of bacteria was severely impaired in TLR2(-)/-, whereas C3H/HeJ mice responded to LTAs in a manner similar to wild-type mice. We demonstrate that DC maturation is induced by stimuli from Gram-positive microorganisms, such as PGN and LTA, with similar efficiency as by LPS. Finally, we provide evidence that TLR2 and TLR4 interaction with the appropriate ligand is essential for bacteria-induced maturation of DCs.

Animals↗
PubMed2001

Osteoprotegerin, a crucial regulator of bone metabolism, also regulates B cell development and function.

Osteoprotegerin (OPG) is a CD40-regulated gene in B cells and dendritic cells (DCs). We investigated the role of OPG in the immune system by generating opg(-/-) mice. Like its role as a regulator of bone metabolism, OPG also influences processes in the immune system, notably in B cell development. Ex vivo, opg(-/-) pro-B cells have enhanced proliferation to IL-7, and in opg(-/-) spleen, there is an accumulation of type 1 transitional B cells. Furthermore, opg(-/-) bone marrow-derived DCs are more effective in stimulating allogeneic T cells than control DCs. When challenged with a T-dependent Ag, opg(-/-) mice had a compromised ability to sustain an IgG3 Ag-specific response. Thus, in the immune system, OPG regulates B cell maturation and development of efficient Ab responses.

Animals↗
PubMed2000

Angiotensin II receptor subtypes determine induced NO production in rat glomerular mesangial cells.

Angiotensin II (ANG II) and nitric oxide (NO) have contrasting vascular effects, yet both sustain inflammatory responses. We investigated the impact of ANG II on lipopolysaccharide (LPS)/interferon-gamma (IFN)-induced NO production in cultured rat mesangial cells (MCs). LPS/IFN-induced nitrite production, the inducible form of nitric oxide synthase (NOS-2) mRNA, and protein expression were dose dependently inhibited by ANG II on coincubation, which was abolished on ANG II type 2 (AT(2)) receptor blockade by PD-123319. Homology-based RT-PCR verified the presence of AT(1A), AT(1B), and AT(2) receptors. To shift the AT receptor expression toward the type 1 receptor, two sets of experiments were performed: LPS/IFN preincubation for 24 h was followed by 8-h coincubation with ANG II; or during 24-h coincubation of LPS/IFN and ANG II, dexamethasone was added for the last 6-h period. Both led to an amplified overall expression of NOS-2 protein and NO production that was inhibitable by actinomycin D in the first setup. Induced NO production was enhanced via the AT(1) receptor; however, it was diminished via the AT(2) receptor. In conclusion, induced NO production is negatively controlled by the AT(2), whereas AT(1) receptor stimulation enhanced NO synthesis in MCs. The overall NO availability depended on the onset of the inflammatory stimuli with respect to ANG II exposure and the available AT receptors.

Angiotensin II↗
PubMed1998

Constitutive IL-10 production accounts for the high NK sensitivity, low MHC class I expression, and poor transporter associated with antigen processing (TAP)-1/2 function in the prototype NK target YAC-1.

Tumor cells that are treated with rIL-10 or transfected with the IL-10 gene show phenotypic changes. These include low but peptide-inducible expression of MHC class I, low sensitivity to specific CTL-mediated lysis, and increased NK sensitivity. In vitro-established mouse tumor lines were screened for IL-10 expression and production, and a large proportion of plasmocytomas or T cell lymphomas were found to produce IL-10. Since one of these lines was the prototype NK target cell YAC-1, we investigated whether the high IL-10 production of this cell line was related to its high NK sensitivity and its defects in MHC class I expression. The decrease in H-2 expression following the in vitro culture of in vivo-passaged YAC-1 cells was accompanied by a gradual increase in IL-10 production, whereas the reverse was found when passing in vitro-grown YAC-1 in vivo as an ascites tumor in syngenic mice. In addition, differences in YAC-1 MHC class I expression correlated with alterations in the functional activity of TAP-1/2 proteins. YAC-1 cells that were transduced with a retroviral IL-10 antisense construct (Y-IL-10 AS) only produced about half of the IL-10 that was produced by YAC-1 transduced with the control construct (Y-IL-10 Mock). Relative to Y-IL-10 Mock cells, the expression of H-2 on Y-IL-10 AS cells was markedly increased, and NK sensitivity was decreased. These data argue for a mechanism wherein IL-10 production is causally related to the low H-2 expression, decreased TAP function, and high NK sensitivity of YAC-1 cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Interleukin-10 prevents dendritic cell accumulation and vaccination with granulocyte-macrophage colony-stimulating factor gene-modified tumor cells.

A wide variety of human tumors express IL-10 for reasons poorly understood. We have analyzed the effect of spontaneous IL-10 expression by a mouse tumor (J558L) on its immunoparalyzing effect. Because "cross-priming" of T cells by host Ag-presenting cells for MHC class I-restricted tumor Ags is a major pathway for induction of tumor immunity and that is enhanced by granulocyte-macrophage (GM) CSF, we expressed this cytokine in J558L cells. GM-CSF-secreting cells were not effective when used for immunization against challenge with the parental tumor. Inhibition of IL-10 expression through an IL-10 antisense retrovirus restored the vaccine efficacy of GM-CSF-producing J558L cells, demonstrating a direct role of IL-10 in paralyzing the GM-CSF-induced antitumor immune response. Since the tumor used for challenge produced IL-10, we conclude that IL-10 interfered primarily with the initiation but not the effector phase of the immune response. Immunohistochemical analysis of the vaccine site showed a GM-CSF-induced accumulation of dendritic cells (DC) (MHC class II+ and DEC-205+) in the absence of IL-10. In the presence of IL-10, DC accumulation was completely inhibited. Together, our results demonstrate an antagonistic effect of IL-10 with respect to GM-CSF-induced DC accumulation and tumor immunity and suggest a new mechanism by which tumors escape immune recognition: namely by preventing APC from obtaining access to tumor Ags.

Animals↗
PubMed1994

Altered nitric oxide production and exogenous nitric oxide do not affect the proliferation of rat mesangial cells.

OBJECTIVE: To examine the hypothesis that nitric oxide (NO) acts as an autocrine, antiproliferative regulator and that exogenous NO donor inhibitors the proliferation of cultured rat mesangial cells. DESIGN AND METHODS: The cellular effects of endogenous and exogenous NO were studied in rat mesangial cells in a two-dimensional culture of early mesangial cell passages. The proliferation of mesangial cells was determined by cell-counting and uptake of [3H]-thymidine. NO generation was induced by incubation with interleukin-1 beta (5 u/ml) or bacterial lipopolysaccharide (10 micrograms/ml) for 24 h. NO release by mesangial cells was assessed by measuring the accumulation of nitrite, the major stable end-product of NO, in mesangial cell supernates. In addition, cyclic GMP (cGMP) formation was measured by radioimmunoassay as an indicator for NO generation. RESULTS: The formation of nitrite and cGMP was significantly increased after incubation of mesangial cells with interleukin-1 beta or lipopolysaccharide. This effect was greatly reduced by an inhibitor of NO synthesis. NG-monomethyl-L-arginine (L-NMMA; 0.1 mmol/l). The NO donor 3-morpholino-sydnonimine-HCl also increased the cGMP concentrations in the mesangial cells. The proliferation of mesangial cells was analysed in growth-arrested and mitogen-stimulated (platelet-derived growth factor, platelet-derived growth factor plus ATP and fetal calf serum) mesangial cells in the presence and absence of L-NMMA and the NO synthase substrate L-arginine (1 mmol/l). At 48 h platelet-derived growth factor (50 ng/ml), and platelet-derived growth factor (50 ng/ml) plus ATP (0.1 mmol/l) and fetal calf serum 5% each significantly increased the uptake of [3H]-thymidine in mesangial cells. These effects were not altered in the presence of L-NMMA or L-arginine. Pretreatment with interleukin-1 beta or with lipopolysaccharide also failed to affect the uptake of [3H]-thymidine in resting or proliferating mesangial cells. 3-Morpholino-sydnonimine-HCl (10(-3) to 10(-6) mol/l) did not suppress the mitogen-induced proliferation of mesangial cells, even when it was administered three times a day. CONCLUSIONS: The present findings support recent observations that interleukin-1 beta and lipopolysaccharide strongly induce NO production in mesangial cells, as is shown indirectly by the greatly increased formation of nitrite and cGMP. However, these effects were not associated with antiproliferative action on mitogen-stimulated mesangial cells. Similarly, the exogenous NO donor 3-morpholino-sydnonimine-HCl induced cGMP formation but failed to inhibit proliferation of mesangial cells when used at a non-toxic dose. Our observations do not support the contention that the formation of NO and cGMP constitutes an autocrine downregulating mechanism in the control of the growth of mesangial cells. It remains to be seen what pathophysiological role the induction of NO release plays in the regulation of the behaviour of mesangial cells, e.g. during an inflammatory response to glomerular injury.

Animals↗
PubMed1992

Role of calcium in the progression of renal disease: experimental evidence.

Intracellular calcium mediates a wide array of cell functions in mesenchymal as well as in epithelial and endothelial cells. These comprise regulation of vascular tone, cell proliferation and synthesis of prostanoids and cytokines. Therefore, it is not surprising that a substantial body of evidence has emerged to suggest a crucial role of calcium in the initiation and perpetuation of renal disease. Increased deposition of calcium was found in the renal cortex of rats with remnant kidney and in kidney tissue of patients with end-stage renal failure. Calcium plays an important role in altered intrarenal and glomerular hemodynamics with increased glomerular wall tension as well as in cellular proliferation and in recurrent ischemic events leading to glomerulosclerosis and interstitial fibrosis. Besides hemodynamic mechanisms, additional calcium-dependent mechanisms must be considered for glomerular hypertrophy and/or mesangial proliferation to develop, namely the role of growth factors, prostanoids and cytokines. Their signals include receptor-regulated production of inositol-trisphosphate and diacylglycerol and the consecutive stimulation of protein kinase C and the Na/H-antiport. Full activation of this antiport, which raises intracellular pH and thereby stimulates protooncogenes, again requires the presence of calcium. Recurrent focal glomerular ischemia may result in cellular and mitochondrial calcium overload that may interfere with cellular energy metabolism. Calcium also activates proteinases and the production of oxidants to enhance neutrophil-mediated cell injury. These deleterious effects of calcium may initiate and perpetuate the progression of renal disease and eventually lead to end-stage renal failure.

Animals↗
PubMed1990

Kinin- and non-kinin-mediated interactions of converting enzyme inhibitors with vasoactive hormones.

The antihypertensive effect of inhibitors of the angiotensin I-converting enzyme (ACE = kininase II) results from their vasodilatory and natriuretic effects as well as their effect on baroreceptor function. In addition to the inhibition of systemic and local angiotensin II formation, other local hormonal systems may also be involved in this effect at multiple target sites. Thus, potentiation of the vasodilator and natriuretic kinin system following inhibition of kininase II is thought to contribute to the persistent hypotensive effect of ACE inhibitors despite normalization of circulating ACE activity. Although increased plasma bradykinin levels cannot be detected, we found that the enhanced kinin-dependent local vascular prostacyclin production can be blunted in vitro by aprotinin, a kallikrein inhibitor. ACE inhibition may affect the atrial natriuretic peptide (ANP) system as the renin-angiotensin system and ANP appear to play antagonistic roles at the peripheral and central nervous system levels. Inhibition of kallikrein or of kininase II were both shown to modulate the natriuretic and vasorelaxant effects of ANP. In hypertensive subjects, we found that ACE inhibition with blood pressure normalization reduces basal and stimulated plasma ANP and blunts the renal sodium excretion in response to saline loading. In contrast, we did not observe effects of acute ACE inhibition in healthy sodium-depleted volunteers on plasma vasopressin under basal conditions or in response to passive tilt. Finally, we investigated the interaction of ACE inhibition with substance P, a powerful endogenous diuretic and natriuretic peptide that may have a transmitter function in the baroreceptor reflex arch.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1989

[Dyspnea at rest].

A 54 year old woman complained about progressive dyspnea. She was markedly obese and presented with right-sided pleural effusion of undetermined origin. Treatment for congestive heart failure did not reduce the pleural effusion. Pleural or pulmonic tumor was not found, a large intraabdominal mass contained ovarian tumor-cells. The exudative pleural fluid was interpreted as Meigs'-syndrome in view of the coexisting ascites.

Diagnosis, Differential↗
PubMedDate not supplied

Acute ischemic renal failure: review of experimental studies on pathophysiology and potential protective interventions.

More than 70% of acute renal failure in man is of circulatory nature and results from hypoxic injury to the kidney. Since intrarenal hemodynamic and metabolic events cannot be accurately assessed in human acute renal failure, various experimental models of renal hypoperfusion or complete interruption of renal blood supply, such as norepinephrine-induced acute renal failure or clamping of the renal artery, have been employed to obtain more direct insight into the pathophysiological events and consequences of hypoxia, although none of these models may truly mimic human acute renal failure. In addition, the severity of experimental acute renal failure, that is, oliguric or nonoliguric acute renal failure resulting from renal hypoperfusion, depends not only on the model employed but also largely on the experimental conditions. In the hemodynamic models a vascular component is incriminated in the initial phase, and persistent tubular tissue dysfunction in the maintenance phase of ischemic acute renal failure. Hypoxic vascular injury will lead to vasoconstriction; a decrease in glomerular filtration pressure, glomerular capillary surface area, and permeability; and thus to a decrease in glomerular filtration rate. In contrast to previous concepts which incriminated the renal cortex as the main target tissue of hypoxic injury, in recent years attention has been focused on impaired medullary perfusion as the most prominent pathophysiological event leading to the decrease in total renal blood flow and glomerular filtration rate. Medullary congestion may result from hypoxic cell swelling with vascular compression.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗