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Biomedical subjects

G Müller

Publications and source records attributed to G Müller.

At least 253 records · Page 14Linked to original sources
PubMed1995

Transcriptional activation by tetracyclines in mammalian cells.

A transcriptional transactivator was developed that fuses the VP16 activation domain with a mutant Tet repressor from Escherichia coli. This transactivator requires certain tetracycline (Tc) derivatives for specific DNA binding. Thus, addition of doxycycline to HeLa cells that constitutively synthesized the transactivator and that contained an appropriate, stably integrated reporter unit rapidly induced gene expression more than a thousandfold. The specificity of the Tet repressor-operator-effector interaction and the pharmacological characteristics of Tc's make this regulatory system well suited for the control of gene activities in vivo, such as in transgenic animals and possibly in gene therapy.

Amino Acid Sequence↗
PubMed1995

PKC zeta is a molecular switch in signal transduction of TNF-alpha, bifunctionally regulated by ceramide and arachidonic acid.

Tumor necrosis factor (TNF-alpha) stimulates a number of signal transduction pathways in which phospholipases produce lipid second messengers. However, the immediate molecular targets of these messengers, in particular those of ceramide and arachidonic acid (AA) and their role in TNF signaling are not well defined. In this study we investigated the relationship of ceramide and AA in regulating an atypical PKC isozyme, PKC zeta. U937 cells responding to TNF-alpha treatment with NF kappa B activation displayed enhanced phosphorylation of PKC zeta, which is already detectable 30 s after stimulation. [14C]ceramide specifically binds to and regulates kinase activity of PKC zeta in a biphasic manner. Binding studies indicate high and low affinity binding with bmax values of 60 and 600 nM and Kd values of 7.5 and 320 nM respectively. At ceramide concentrations as low as 0.5 nM an up to 4-fold increase in autophosphorylation is obtained, which, at concentrations > 60 nM, again declines to basal levels. Interestingly, AA competes for ceramide binding and inhibits basal and ceramide-stimulated PKC zeta kinase activity at < 100 nM. Metabolism of [14C]ceramide in cells is slow and is inhibited in the presence of equimolar concentrations of lyso-phosphatidylcholine. Based on the bifunctional modulation of PKC zeta by the lipid messengers ceramide and AA, a model of TNF signal pathways is suggested in which PKC zeta takes a central position, acting as a molecular switch between mitogenic and growth inhibitory signals of TNF-alpha.

Arachidonic Acid↗
PubMed1995

Biomonitoring of urinary aromatic amines and arylamine hemoglobin adducts in exposed workers and nonexposed control persons.

The renal excretion of arylamines in occupationally exposed and nonexposed subjects was measured by a gas chromatography-electron capture detector method. Additionally, in the occupationally exposed persons hemoglobin adduct levels of arylamines were determined by a liquid chromatography-electrochemical detector method, together with the individual acetylator status. The aromatic amines aniline, p-toluidine, 2-naphthylamine, and 4-chloro-o-toluidine were detected in the urine of nonsmoking subjects who were not occupationally exposed to arylamines. Significantly higher concentrations of aniline, o-toluidine, m-toluidine, 2-naphthylamine, and 4-methyl-1,3-phenylenediamine could be observed in the urine of smoking control persons in comparison to nonsmokers. Comparison of smokers and nonsmokers in a group of workers primarily exposed to aniline and 4-chloroaniline revealed significant differences (P < 0.05) in the formation of 4-aminodiphenyl hemoglobin adducts and in the renal excretion of 2-naphthylamine. The slow acetylators in this group produced significantly more hemoglobin adducts of aniline and 4-chloroaniline than did the fast acetylators. In slow acetylators among the smoking workers there was a significant increase in the formation of 4-aminodiphenyl hemoglobin adducts and in the renal excretion of 4-chloroaniline and m-toluidine. The results indicate that there are influences of smoking habits and acetylator status on the levels of arylamine hemoglobin adducts as well as urinary arylamine concentrations. Hemoglobin adducts seem to be good parameters for monitoring aniline and 4-chloroaniline exposure at the workplace, especially if the acetylator polymorphism can be taken into account. 4-Aminodiphenyl hemoglobin adducts might be good parameters for monitoring individual smoking habits. The determination of urinary arylamine concentrations provides additional information concerning acute exposures to aromatic amines.

Amines↗
PubMed1995

Anaesthetic considerations in progressive familial intrahepatic cholestasis (Byler's disease).

Progressive familial intrahepatic cholestasis (PFIC) or Byler's disease is one of the most common forms of intrahepatic cholestasis of metabolic and genetic origin. Affected children progress to terminal cirrhosis before adulthood and at present the only curative treatment of PFIC is orthotopic liver transplantation (OLT). We present a retrospective review of 40 general anaesthetics administered in our hospital to 22 patients with PFIC undergoing various procedures. The clinical features of PFIC and the anaesthetic implications of chronic cholestasis in children (malnutrition, cirrhosis, portal hypertension, chronic hypoxaemia) are reviewed.

Adolescent↗
PubMed1995

Occurrence of T lymphocytes in perivascular regions of the lung after intratracheal infection of swine with Pasteurella multocida.

The defence mechanisms of the lung acting against airborne antigens (bacteria) are not yet fully understood. Therefore, we investigated cell-derived immunological processes in porcine pulmonary tissue. The incidence and distribution of leukocyte subpopulations in lungs, lung lymph nodes and tonsils from eight animals intratracheally infected with Pasteurella multocida (P.m.) type A wild strain and from four non-infected control animals were established by immunohistochemistry, using a panel of monoclonal antibodies (mAbs) against specific porcine leukocyte antigens: MHC Class II (MHC II), SWC1, SWC3a, CD2a, CD4a, CD8b. In the test animals, a broad layer of SWC1+ cells and SWC3a+ cells emerged in the subsinusoidal region of lung lymph nodes and in the bronchoalveolar spaces of the lung as early as 4 and 24 h after infection, and in the subsinusoidal regions of the lung lymph nodes only very few cells could be stained with the mAb against the MHC II antigen. We could not detect any MHC Class II+ cells in the bronchoalveolar spaces at this time of the investigation. In the course of the disappearance of the SWC1+ cells and SWC3+ cells, CD2a+, CD4a+ and, in lower numbers, CD8b+ T lymphocytes seemed to concentrate in the perivascular and, partially, the peribronchial regions of the lung 72 h after infection. By means of the double immunostaining method, we could demonstrate an accumulation of CD4a+ cells and CD8b+ cells after infection which lacked the SWC1 antigen, indicating that these cells were activated T lymphocytes. The same cell types (SWC1-/CD4a+ and SWC1-/CD8b+ cells) as well as CD8b-/CD4a+ cells could be observed in the interstitium of the lung 72 h after infection.

Animals↗
PubMed1995

The molecular interaction of sulfonylureas with beta-cell ATP-sensitive K(+)-channels.

The molecular interaction of glimepiride and glibenclamide with the beta-cell sulfonylurea receptor was investigated by kinetic and steady state binding as well as photoaffinity labeling. The novel sulfonylurea, glimepiride, exhibits a significantly higher exchange rate with the sulfonylurea receptor but a 2.5-3 fold lower binding affinity compared to glibenclamide. [3H]Glimepiride was specifically incorporated into a 65-kDa polypeptide under conditions which led to predominant labeling of a 140-kDa protein by [3H]glibenclamide. Labeling of the 140-kDa protein by [3H]glibenclamide was inhibited by unlabeled glimepiride and, vice versa, glibenclamide inhibited labeling of the 65-kDa protein by [3H]glimepiride. The 65-kDa protein was also specifically photolabeled by the sulfonylurea [125I]35623, whereas an 4-azidobenzoyl derivative of glibenclamide, N3-[3H]33055, exclusively labeled a 33-kDa protein. Solubilization of beta-cell tumor membranes led to a shift of specific [3H]glibenclamide-binding from the 140-kDa to the 65-kDa protein, exclusively and to an increased labeling of the 65-kDa protein by [3H]glimepiride. The labeling of a unique protein is in agreement with similar Kd-values for binding to the sulfonylurea receptor measured for both sulfonylureas upon solubilization of beta-cell membranes. Photoaffinity labeling of intact cultured beta-cells led also to labeling of a 140-kDa protein by [3H]glibenclamide and of a 65-kDa protein by [3H]glimepiride. These studies suggest that the beta-cell sulfonylurea receptor consists of at least two protein subunits of M(r) 140,000 and 65,000 which bind sulfonylureas of different structure with different binding affinities and kinetic parameters. Furthermore, the exchange rate of a sulfonylurea determines the insulin releasing activity in vitro more closely than the binding affinity.

ATP-Binding Cassette Transporters↗
PubMed1995

Extrapancreatic effects of sulfonylureas--a comparison between glimepiride and conventional sulfonylureas.

The contribution of extrapancreatic effects of sulfonylureas to the blood glucose-decreasing activity was reevaluated in vivo and in vitro with several conventional sulfonylureas and with the new one glimepiride. In vivo, in dogs, after single approximately equipotent blood glucose-decreasing doses, the sulfonylureas were tested for a ranking in the ratios of mean plasma insulin-increasing and blood glucose-decreasing activity. Studies were also performed in hyperglycemic hyperinsulinemic KK-Ay mice under once daily treatment for 8 weeks. In vitro, glimepiride and glibenclamide were tested for the ranking of their extrapancreatic activity with respect to the stimulation of glucose transport and glucose metabolizing processes in normal and insulin-resistant fat cells as well as in the isolated diaphragm. Furthermore, in vitro studies were performed, especially with glimepiride, in order to characterize the molecular mechanism for the extrapancreatic activity. The dog studies revealed a marked ranking in the ratios of plasma insulin-increasing and blood glucose-decreasing activity between the different sulfonylureas (glimepiride < glipizide < gliclazide < glibenclamide). In the hyperglycemic hyperinsulinemic KK-Ay mice, glimepiride reduced blood glucose by 40%, plasma insulin by 50% and HBA1c by 33%, whereas glibenclamide and gliclazide had no effect on these parameters. In vitro, glimepiride and glibenclamide had extrapancreatic effects within the lower microM range, with glimepiride exhibiting 2-3-fold lower ED50 values than glibenclamide. In the absence of insulin, both stimulated glucose transport--up to 60% of the maximum insulin response in the rat diaphragm and up to 35% in 3T3 adipocytes. Glycogenesis was stimulated in the rat diaphragm--up to 55% of the maximum insulin effect; lipogenesis in 3T3 adipocytes--up to 40%. The studies on the molecular mechanism of extrapancreatic activity with rat adipocytes and diaphragm suggest that these direct insulin-mimetic effects rely on the induction of GLUT4 translocation from internal stores to the plasma membrane and on the activation of the key metabolic enzymes, glycogen synthase and glycerol-3-phosphate acyltransferase. These processes occur within the same drug concentration range and with the same ranking between glimepiride and glibenclamide as observed for glucose utilization and transport. The direct effects of sulfonylureas may ultimately be regulated by a glycosyl-phosphatidylinositol-specific phospholipase C, shown to be activated by glimepiride in rat adipocytes. Lipolytic cleavage products thereby generated from glycolipidic structures may in turn stimulate specific protein phosphatases which activate key regulatory proteins/enzymes of glucose and lipid metabolism.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipocytes↗
PubMed1995

Impaired resistance to oxidation of low density lipoprotein in cystic fibrosis: improvement during vitamin E supplementation.

Antioxidants such as vitamin E protect unsaturated fatty acids of LDL against oxidation. In the ex vivo model used, LDL was exposed to Cu2+ ions, a potent prooxidant capable of initiating the oxidation of LDL. The lag time, indicating the delay of conjugated diene formation in LDL due to antioxidant protection, was measured in 54 cystic fibrosis (CF) patients with plasma alpha-tocopherol levels below (Group A, n = 30) or above (Group B, n = 24) 15.9 mumol/L (mean - 2 SD of Swiss population). Patients were reevaluated after 2 months on 400 IU/d of oral RRR-alpha-tocopherol. In group A, alpha-tocopherol concentrations in LDL increased significantly from 3.2 +/- 1.6 mol/mol LDL to 8.2 +/- 2.8 mol/mol (P < 0.001) and lag times increased from 79 +/- 33 min to 126 +/- 48 min (P < 0.001), whereas in the vitamin E sufficient group B no further increase neither in LDL alpha-tocopherol concentrations or in lag times was observed. LDL oleic acid concentrations were higher, and linoleic acid concentrations were lower in patients than in controls. After efficient vitamin E supplementation, lag times were positively related to LDL alpha-tocopherol (P < 0.01) and negatively to LDL linoleic and arachidonic acid content (P < 0.001). The maximum rate of oxidation correlated positively with linoleic and arachidonic acid concentrations, as did the maximum conjugated diene absorbance. These results indicate that LDL resistance to oxidation is impaired in vitamin E deficient CF patients but can be normalized within 2 months when alpha-tocopherol is given in sufficient amounts. Linoleic and arachidonic acid content exhibit a major influence on the LDL resistance to oxidation.

Adult↗
PubMed1995

Cultured human myocardial fibroblasts of pediatric origin: natural human interferon-alpha is more effective than recombinant interferon-alpha 2a in carrier-state coxsackievirus B3 replication.

Cultured human myocardial fibroblasts of pediatric origin seem to be a useful species-specific model for studying various heart diseases which involve the myocardial interstitium, for example enterovirus heart disease. Cells were propagated from small samples of human ventricular tissues (0.2 g) obtained from standard surgical procedure for the correction of Fallot-tetralogy. Cultured cells exhibited typical fibroblastoid morphology over a period of 4 months and were uniformly immunoreactive with a monoclonal antibody directed against prolyl-4-hydroxylase, a marker enzyme of fibroblasts. Infection of cell cultures with coxsackievirus B3, a cardiotropic enterovirus, resulted in a typical carrier-state type of virus persistence. Average virus titers of 2.3 x 10(5) plaque-forming units/ml (SD = 9.9 x 10(4)) were maintained over a period of up to 10 weeks by productive infection of about 8-10% of the cell population. Coxsackievirus B3 carrier cultures of human myocardial fibroblasts were used to evaluate in vitro the long-term antiviral effects of recombinant interferon alpha-2a and natural human interferon-alpha. Recombinant interferon-alpha reduced virus yields by 90% with a concentration of 423 IU/ml, whereas with natural interferon-alpha a 90% reduction of virus yields was achieved with concentrations as low as 21 IU/ml. Antiviral effects of both recombinant and natural interferon-alpha were highly specific and not related to inhibition of cell-proliferation (< 50% with interferon-alpha concentrations as high as 6250 IU/ml). Since effective concentrations of interferon-alpha can be easily attained in vivo with subcutaneous application, interferon-alpha (in particular: natural interferon-alpha) may become useful in the treatment of patients with enterovirus myocarditis and enterovirus induced dilated cardiomyopathy.

Antiviral Agents↗