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Biomedical subjects

G Müller

Publications and source records attributed to G Müller.

At least 91 records · Page 5Linked to original sources
PubMed2001

A possible noninvasive method for the detection of bladder cancer in patients: microsatellite analysis of free DNA in urine and blood.

Six microsatellite markers were selected to detect shifts or loss of heterozygosity (LOH) in urine, serum, and plasma samples of 44 bladder cancer patients. After centrifugation at 15,000 g, we used supernatants for DNA analysis only. Tumor specimens were obtained by transurethral resection (TUR). Genetic alterations were detected in 33 of the 44 bladder tumors (75%). After polymerase chain reaction (PCR), DNA was detectable in 96% of all body fluid samples. Twenty-six percent of the detected microsatellite alterations of free DNA were tumor-specific, but 82% of all microsatellite changes of the tumors could be detected in body fluids. The study indicates that the simultaneous and multiple investigations of highly specific microsatellite markers could have a clinical relevance as a noninvasive tool for diagnosis and screening of bladder cancer. However, new ways for the sensitive DNA isolation of body fluids are needed.

Aged↗
PubMed2001

Redistribution of glycolipid raft domain components induces insulin-mimetic signaling in rat adipocytes.

Caveolae and caveolin-containing detergent-insoluble glycolipid-enriched rafts (DIG) have been implicated to function as plasma membrane microcompartments or domains for the preassembly of signaling complexes, keeping them in the basal inactive state. So far, only limited in vivo evidence is available for the regulation of the interaction between caveolae-DIG and signaling components in response to extracellular stimuli. Here, we demonstrate that in isolated rat adipocytes, synthetic intracellular caveolin binding domain (CBD) peptide derived from caveolin-associated pp59(Lyn) (10 to 100 microM) or exogenous phosphoinositolglycan derived from glycosyl-phosphatidylinositol (GPI) membrane protein anchor (PIG; 1 to 10 microM) triggers the concentration-dependent release of caveolar components and the GPI-anchored protein Gce1, as well as the nonreceptor tyrosine kinases pp59(Lyn) and pp125(Fak), from interaction with caveolin (up to 45 to 85%). This dissociation, which parallels redistribution of the components from DIG to non-DIG areas of the adipocyte plasma membrane (up to 30 to 75%), is accompanied by tyrosine phosphorylation and activation of pp59(Lyn) and pp125(Fak) (up to 8- and 11-fold) but not of the insulin receptor. This correlates well to increased tyrosine phosphorylation of caveolin and the insulin receptor substrate protein 1 (up to 6- and 15-fold), as well as elevated phosphatidylinositol-3' kinase activity and glucose transport (to up to 7- and 13-fold). Insulin-mimetic signaling by both CBD peptide and PIG as well as redistribution induced by CBD peptide, but not by PIG, was blocked by synthetic intracellular caveolin scaffolding domain (CSD) peptide. These data suggest that in adipocytes a subset of signaling components is concentrated at caveolae-DIG via the interaction between their CBD and the CSD of caveolin. These inhibitory interactions are relieved by PIG. Thus, caveolae-DIG may operate as signalosomes for insulin-independent positive cross talk to metabolic insulin signaling downstream of the insulin receptor based on redistribution and accompanying activation of nonreceptor tyrosine kinases.

Adipocytes↗
PubMed2001

GM1-gangliosidosis in Alaskan huskies: clinical and pathologic findings.

Three Alaskan Huskies, two females and one male, were diagnosed with GM1-gangliosidosis. Clinically, diseased animals exhibited proportional dwarfism and developed progressive neurologic impairment with signs of cerebellar dysfunction at the age of 5-7 months. Skeletal lesions characterized by retarded enchondral ossification of vertebral epiphyses were revealed by radiographs of the male dog at 5.5 months of age. Histologic examination of the central nervous system (CNS) revealed that most neurons were enlarged with a foamy to granular cytoplasm due to tightly packed vacuoles that displaced the Nissl substance. Vacuoles in paraffin-embedded sections stained positively with Luxol fast blue and Grocott's method, and in frozen sections vacuoles were periodic acid-Schiff positive. Foamy vacuolation also occurred within neurons of the autonomic ganglia. Extracerebral cells such as macrophages and peripheral lymphocytes also displayed foamy cytoplasm and vacuolation. In the CNS of diseased animals, a mild demyelination and axonal degeneration was accompanied by a significant astrogliosis (P < 0.05) in the gray matter as compared with age- and sex-matched control dogs. There was also a significant loss (P < 0.05) of oligodendrocytes in the gray and white matter of affected animals as compared with controls. Ultrastructurally, the neuronal storage material consisted of numerous circular to concentric whorls of lamellated membranes or stacks of membranes in parallel arrays. GM1-gangliosidosis in Alaskan Huskies resembles beta-galactosidase deficiency in other canine breeds, and these CNS disorders may be a consequence of neuronal storage and disturbed myelin processing.

Animals↗
PubMed2001

Signal transduction by the chemokine receptor CXCR5: structural requirements for G protein activation analyzed by chimeric CXCR1/CXCR5 molecules.

The human chemokine receptors CXCR5 and CXCR1 activate signaling pathways via pertussis toxin-sensitive as well as insensitive G proteins. CXCR5 induces Ca2+ signaling and chemotaxis independently of inhibitory G proteins, whereas the same signaling pathways are entirely dependent on inhibitory G proteins for CXCR1. In contrast, activation of the MAP kinase cascade via ERK1/2 is a pertussis toxin-sensitive signaling event for both receptors. Using chimeric CXCR1/CXCR5 receptors we investigated structural requirements for the activation of signal transduction pathways by CXCR5. Individual or multiple intracellular domains of CXCR1 were exchanged for the corresponding sequences of CXCR5, leading to receptors resembling CXCR5 at the cytoplasmic surface to a varying extent. Replacing the second intracellular domain of CXCR1 had a major influence on signaling mediated by inhibitory G proteins, whereas the exchange of the third or carboxy-terminal intracellular domain had only minor effects on signal transduction. Activation of the MAP kinase cascade via ERK1/2 and chemotaxis are largely reduced in chimeras comprising the second intracellular domain of CXCR5, although coupling to inhibitory G proteins is retained in all chimeric receptors. In summary, these data characterize the contribution of the intracellular domains of CXCR5 to receptor signaling, thereby disclosing unique structural requirements that modulate G protein coupling by the receptor.

Amino Acid Sequence↗
PubMed2001

The DSL analog free testosterone assay: serum levels are not related to sex hormone-binding globulin in normative data throughout childhood and adolescence.

In this study we tested the performance of easy-to-use and rapid, commercially available immunoassays to measure free testosterone (fT) and sex hormone-binding globulin (SHBG). We asked whether fT and SHBG serum levels are age-dependent and whether or not there is a gender dependence of fT and SHBG in this age group. Finally, by measuring fT and SHBG in sera of a cohort of healthy children and adolescents using commercially available immunoassays, we established normative data for fT and SHBG in this age group: in boys fT levels increased significantly (r=0.83, p<0.0001) from 0.63 pmol/l (median) in the age group below 5 years to 56.9 pmol/l in the age group 16-20 years. In girls fT levels also increased with age (r=0.66, p<0.0001): from 0.72 pmol/l (median) in the age group below 5 years to 3.34 pmol/l in the age group 16-20 years. In contrast, SHBG serum concentrations significantly decreased with age in boys (r=-0.62, p<0.0001) but remained constant in girls (r=0.04, n.s.). Importantly, fT values were independent of SHBG levels as determined by our methods. In conclusion, fT can be measured in an acceptable quality using the DSL analog tracer-based immunoassay and normative data are now available. In addition, SHBG levels in healthy children and adolescents are also given and may permit for studies of pathophysiologic states in this age group.

Adolescent↗
PubMed2001

Obesity in childhood and adolescence: clinical diagnosis and management.

The industrialized countries around the world are experiencing an epidemic of childhood obesity. The level of fatness of a child at which morbidity increases acutely and/or later in life is determined on an individual basis. Overall, however, childhood obesity substantially increases the risk of subsequent morbidity whether or not obesity persists into adulthood. The genetic basis of childhood obesity has been elucidated to some extent through the discovery of leptin, the ob gene product, and the increasing knowledge of the role of neuropeptides such as pro-opiomelanocortin, neuropeptide Y and the melanocyte-concentrating hormone receptors. Environmental and exogenous factors are the main contributors to the development of a high degree of body fatness early in life. Studies involving twins suggest that approximately 50% of the tendency toward obesity is inherited. There are numerous disorders, including a number of endocrine disorders, such as Cushing's syndrome and hypothyroidism, and genetic syndromes, such as Prader-Labhard-Willi syndrome and Bardet-Biedl syndrome, that can present with obesity. A simple diagnostic algorithm allows for differentiation between primary and secondary obesity. Among the most common sequelae of primary childhood obesity are hypertension, dyslipidemia, back pain and psychosocial problems. It is somewhat ironic that the definition of obesity in childhood is not an easy one. Direct measurements of body fat content, such as hydrodensitometry, bioimpedance, or dual-energy X-ray absorptiometry, are useful tools in scientific studies. Body mass index (BMI) is, however, now generally accepted to be a good clinical measure for the definition of obesity in children and adolescents. In preadolescent boys, BMI also relates to muscle mass and should be used for the definition of fat mass with great caution. An increased risk of death from cardiovascular disease in adults has been found in patients whose BMI had been greater than the 75th percentile as adolescents. Therapeutic strategies include psychological and family therapy, modification of lifestyle and behavior, and nutritional education. The role of regular exercise and exercise programs is emphasized, while surgical procedures and drugs used in adult obesity are still not generally recommended for obese children. Obesity is the most common chronic disorder in industrialized countries, and its impact on individual lives as well as on health economics must be recognized by physicians and the public alike. This review aims to increase awareness of the health burden and economic dimension of the epidemic of childhood obesity that is occurring around the globe.

Adolescent↗
PubMed2000

Antibody reactions after aerogenous or subcutaneous immunization of pigs with Pasteurella multocida antigens.

Depending upon the antigens used and the initial titres, subcutaneous immunization of weaner pigs by means of a temperature-sensitive mutant of live Pasteurella multocida (serovar A), resulted in a significant rise of the level of specific IgG antibody already present in blood serum, but not in lung lavage fluid, and a specific stimulation of lung clearance as compared to non-immunized controls. Aerogenous immunization of a total of 108 animals in 18 experiments did not influence serum antibody titres but produced a significant rise in lung antibodies and P. multocida clearance as compared to an identical number of controls. In all 12 immunization experiments using the live mutant, increased specific IgA antibodies and in seven out of 10 experiments, elevated IgG antibodies were measured. Only aerogenous immunization was found to be capable of reducing the severity of pneumonia induced by intrabronchial infection.

Aerosols↗
PubMed2000

Brain oscillations control hand orthosis in a tetraplegic.

The aim of the present study was to investigate whether self-induced brain potential changes could be useful as control signals for patients with severe motor impairment, i.e. due to high-level spinal cord injury. The pilot project was performed in a tetraplegic patient (T.S.), whose residual muscle activity of the upper limbs is restricted to the left biceps. To restore the hand grasp function, an electrical driven hand orthosis fitting his left hand was developed. The operation of this device is directly based on the bioelectrical signals of the brain. After some months of training, T. S. has learned to operate the hand orthosis by mental imagination of specific motor commands.

Adult↗
PubMed2000

Stable plasma membrane expression of the soluble domain of the human insulin receptor in yeast.

The soluble cytoplasmic kinase domain of the human insulin receptor was N-terminally equipped with either an N-acetylation or a dual-acylation motif (MGC box, to allow myristoylation/palmitoylation) and expressed in yeast cells under the control of the inducible CUP1 promoter. Although the cellular concentration was about the same in both instances (reflecting similar stability against proteolysis), only the myristoylated protein was capable of autophosphorylation to a significant extent and was active to phosphorylate endogenous yeast proteins at tyrosine residues in vivo. Cellular subfractionation showed that the insulin receptor was associated with plasma membranes, from where it was not extractable with high salt or alkali, but a significant fraction was also localized in the nuclear fraction. The myristoylated protein is absent from the cytoplasm. No effect of expression of either the acetylated or the myristoylated version on growth and respiration on various carbon sources was detected, suggesting a failure of the active insulin receptor kinase domain to couple to yeast (glucose) signalling cascades.

Blotting, Western↗
PubMed2000

The suramin analogue NF279 is a novel and potent antagonist selective for the P2X(1) receptor.

The suramin analogue 8,8'-(carbonylbis(imino-4, 1-phenylenecarbonylimino-4,1-phenylenecarbonylimino)) bis(1,3,5-naphthalenetrisul fonic acid) (NF279) was analysed with respect to its potency and P2X receptor subtype selectivity. Two-electrode voltage-clamp measurements were performed with Xenopus laevis oocytes expressing homomultimeric rat P2X(1), P2X(2), P2X(3) and human P2X(4) receptors. For the fast desensitising P2X(1) and P2X(3) receptors, IC(50) values strongly depended on whether oocytes were pre-incubated with NF279 prior to ATP superfusion or exposed to NF279 simultaneously with ATP. With a 10 s pre-incubation period of NF279, IC(50) values of 19 nM and 1.62 microM were obtained for rat P2X(1) and P2X(3), respectively. Without pre-incubation, IC(50) values amounted to 2 microM and 85.5 microM for P2X(1) and P2X(3), respectively. For the non-desensitising rat P2X(2) receptor NF279 appeared to act as a competitive antagonist with an IC(50) value of 0.76 microM and a K(B) value of 0.36 microM, as derived from Schild analysis. P2X(4) receptors were the least sensitive subtypes for NF279 (IC(50)>300 microM). The antagonism was fully reversible at all P2X subtypes analysed. Our results indicate that NF279 is a potent P2X(1) receptor-selective and reversible antagonist.

Adenosine Triphosphate↗
PubMed2000

Immunohistological and serological investigation of morbillivirus infection in harbour porpoises (Phocoena phocoena) from the German Baltic and North Sea.

The role of morbillivirus infection as a cause of disease or death in harbour porpoises (Phocoena phocoena) from the German North and Baltic Sea was investigated by serology, histology and immunohistochemistry. Blood and tissue samples of lung, brain and lymph nodes from 74 stranded or by-caught harbour porpoises from German waters were collected between 1991 and 1997. According to dentinal growth layers and body length, animals were grouped into four age classes (neonates, 0-1, 1-4, 4-16 years of age). Formalin-fixed, paraffin-embedded sections were stained by hematoxylin and eosin (HE). Immunohistology was done in all lung tissues using the avidin-biotin-peroxidase technique and a polyclonal canine distemper virus (CDV) nucleoprotein-specific antibody, which cross-reacts with porpoise morbillivirus (PMV) antigen. A virus neutralization assay for detection of (Onderstepoort-strain) CDV- and PMV-specific antibodies was performed. Due to the cytotoxicity of some sera, only titres of 1:20 or greater were considered positive. PMV or CDV-specific neutralizing antibody titres were found in 88 and 50% of the animals, respectively. Titres were always highest against PMV indicating infection with a homologous porpoise virus strain. There were no significant differences in neutralizing antibody titres between animals of the different age groups. No histological lesions specific for morbillivirus infection were detected and by immunohistology all cases were negative for morbillivirus antigen. The absence of morbillivirus antigen and the lack of characteristic morbillivirus-specific lesions showed that morbillivirus infection was not a cause of death or illness in the investigated population. However, the high incidence of PMV-specific antibodies in all age groups indicated a continuous spread of infection with a morbillivirus among harbour porpoises from the German Baltic and North Sea.

Age Factors↗
PubMed2000

Monoclonal antibodies against porcine macrophages.

Two mouse monoclonal antibodies (MAB) (clones 2G6 and 2B10) directed against porcine macrophages are described that are suitable for use in immunohistochemistry, FACS analysis and western blot. As immunogen, porcine cells from bronchoalveolar lavage (BAL) were used. The MABs obtained belonged to the mouse IgG1 subclass. The molecular weights of the corresponding antigens were detected by western blot under non-reducing conditions (2G6: 140-150kDa; 2B10: 140-145kDa). For specificity screening, porcine snap-frozen tissues of lung, lung lymph node, tonsil, spleen, thymus, brain, liver, gut and kidney were used. The MABs were able to identify cell populations of the mononuclear phagocytic system in these organs. While MAB 2G6 detected tissue macrophages (sinusoidal lymph node macrophages, red pulp spleen macrophages, Kupffer cells, Langerhans cells, thymus macrophages, macrophages of lung and macrophages of kidney), MAB 2B10 stained cells scattered in the lymph node (subsinusoidal, interfollicular and follicular macrophages) and in the lung interstitium. Additionally, it showed reactivity with Kupffer cells, spleen and kidney macrophages. An immunoreactivity of the MABs could be established also for human but not for bovine and avian macrophages. By flow cytometric analysis, MAB 2B10 reacted with a subpopulation of BAL and peritoneal cells. Antibody 2G6 detected macrophages of the BAL and the peritoneal fluid as well as peripheral blood monocytes.

Animals↗
PubMed2000

Photochemistry of 4'-benzophenone-substituted nucleoside derivatives as models for ribonucleotide reductases: competing generation of 3'-radicals and photoenols.

Ribonucleotide reductases (RNRs) catalyze the 2'-reduction of ribonucleotides, thus providing 2'-deoxyribonucleotides, the monomers for DNA-biosynthesis. The current mechanistic hypothesis for the catalysis effected by this class of enzymes involves a sequence of radical reactions. A 3'-hydrogen abstraction, effected by a radical at the enzyme's active site, is believed to initiate the catalytic cycle. As models for this substrate-enzyme interaction, the photochemically induced intramolecular hydrogen abstraction in a series of 4'-benzophenone-substituted nucleoside analogues was studied. Model compounds with hydroxy-, methoxy-, mesyloxy-groups or a cyclic carbonate in 2'- and 3'-positions were investigated. Depending on the substitution pattern, two different types of photoproducts were observed: Those which result from photoenol formation (gamma-H-abstraction) and those which result from abstraction of the 3'-H-atom (delta-H-abstraction). Photoenol formation was further supported by H/D-exchange experiments. Thus, the 3'-H-abstraction postulated as the initial step in RNR action was successfully modeled by photolysis of 4'-benzophenone-substituted nucleoside analogues. The regioselectivity of the photochemical H-abstraction and thus of the product distribution as a function of the 2'- and 3'-substituents was rationalized on the basis of a conformational analysis of the four model systems, utilizing molecular mechanics simulations.

Benzophenones↗
PubMed2000

Insulin-like signaling in yeast: modulation of protein phosphatase 2A, protein kinase A, cAMP-specific phosphodiesterase, and glycosyl-phosphatidylinositol-specific phospholipase C activities.

Previously, we have described significant effects of human insulin on glucose metabolism in the yeast Saccharomyces cerevisiae under conditions of growth limitation. These regulations apparently rely on a transmembrane receptor capable of binding human insulin and responding by tyrosine/serine phosphorylation of a specific set of polypeptides [Müller, G., Rouveyre, N., Crecelius, A., and Bandlow, W. (1998) Biochemistry 37, 8683-8695; Müller, G., Rouveyre, N., Upshon, C., Gross, E., and Bandlow, W. (1998) Biochemistry 37, 8696-8704; Müller, G., Rouveyre, N., Upshon, C., and Bandlow, W. (1998) Biochemistry 37, 8705-8713]. To characterize the molecular link between the initial steps in insulin-like signaling in yeast and the changes in the activities of glycogen synthase and glycogen phosphorylase, we examined here the effects of human insulin on a set of key regulatory enzymes of glycogen metabolism, protein phosphatase 2A (PP2A), cAMP-specific phosphodiesterase (cAMP-PDE), and protein kinase A (PKA). PP2A was activated about 2-fold by insulin in spheroplasts and in intact cells, whereas the fraction of active PKA was significantly reduced in a cAMP-independent manner as well as through a subsequent up to 3-fold increase in particulate cAMP-PDE activity accompanied by a 50% decrease in cytosolic cAMP levels. In addition, glycosyl-phosphatidylinositol-specific phospholipase C (GPI-PLC), which in isolated rat adipocytes is activated by insulin, was stimulated to up to 5-fold by glucose and 10-fold by glucose plus insulin in both yeast spheroplasts and intact cells leading to a concentration-dependent leftward shift of the glucose-response curve for activation of the GPI-PLC. GPI-PLC was most pronouncedly stimulated by authentic human insulin compared to various insulin analogues and insulin-like growth factor I. In addition to lipolytic cleavage by GPI-PLC, the GPI anchor of the cAMP-binding ectoprotein, Gce1p, was secondarily processed by a rapid proteolytic event. As the GPI-PLC reaction is rate limiting, the efficiency of the two-step anchor cleavage was significantly increased when insulin was present together with glucose as compared to glucose alone. The insulin concentrations effective in modulating PP2A, PKA, cAMP-PDE, and GPI-PLC activities correlate well with those required for half-saturation of the specific binding sites as well as for stimulation of protein phosphorylation and glycogen accumulation. The data suggest that mammalian insulin-sensitive cells and yeast share (part of) the key regulatory mechanism (consisting of PP2A, PKA, cAMP-PDE, and GPI-PLC) involved in the transduction of the insulin signal from the respective receptor systems to glycogen synthase and phosphorylase.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

In vitro action of a combination of selected antimicrobial agents and chondroitin sulfate.

Chondroitin sulfate (CS), a highly anionic polymer and the most predominant sulfated glycosaminoglycan in connective tissues, was investigated regarding to its interaction with cationic disinfectants, which are used as antiinfectives in humans. Combinations of cetylpyridiniumchloride (CPC), chlorhexidine (CHex), and polyhexamethylene biguanide (PHMB) with CS, respectively, were prepared and the resulting microbicidal activity of the mixtures was tested in the quantitative suspension test without organic matter. Polyvidone-iodine and Ringer's solution were used as controls. Even precipitated, the resulting test combinations behave differently against Staphylococcus aureus, Enterococcus faecium, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. CPC/CS demonstrated only microbicidal activity against Gram-positive bacteria, and CHex/CS was more active against Gram-negative bacteria and C. albicans. PHMB/CS, especially in combination with CS-A, only revealed an antimicrobial effect against P. aeruginosa after 60 min action. The interaction of cationic disinfectants with CS showed depending on the investigated microorganism a more or less controlled sustained release manner of the microbicidal agent from the precipitated complex, with the only exception of PHMB in combination with CS-C, which is completely neutralized. Polyvidone-iodine and Ringer's solution were not affected by CS.

Anti-Infective Agents, Local↗
PubMed2000

The use of water-jetting technology in prostheses revision surgery-first results of parameter studies on bone and bone cement.

Water-jet cutting techniques have been used in industrial applications for many different materials. Recently these techniques have been developed into a revolutionary cutting tool for soft tissues in visceral surgery. The present study investigates the usage of this cutting technology for the revision surgery of endoprostheses. In the first part of the study, samples of bovine bone and acrylic bone cement (PMMA) were cut using an industrial jet cutting device with pure water. Below 400 bar, only PMMA was cut; above 400 bar, bone was also cut, but only pressures above 800 bar resulted in clinically useful rates of material removal (cut depth 2. 4 mm at 10 mm/min traverse speed). In the second part of the study, the effect of adding biocompatible abrasives to the water in order to reduce the required pressure was investigated, resulting in a significantly higher removal of material. At 600 bar, PMMA was cut 5. 2 mm deep with plain water and 15.2 mm deep with added abrasives. The quality of the cuts was increased by the abrasive. Though there was no clear selectivity between bone and PMMA any more, the rate of material removal at similar pressures was significantly higher for PMMA than for bone (600 bar: 1.6 mm cut depth for bone samples, 15.2 mm for PMMA). The measured cut depths with either method were not influenced by a change of the cutting direction with respect to the main direction of the osteons in the bone. However, a reduction of the jet surface angle (90 degrees to 23 degrees ) resulted for bone in a significantly lower cut depth at 600 bar (plain water: 0.62 mm vs. 0.06 mm; abrasive: 1.61 mm vs. 0.60 mm). The laboratory experiments indicate that abrasive water jets may be suitable for cutting biomaterials like bone and bone cement.

Analysis of Variance↗