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Markus Müller

Publications and source records attributed to Markus Müller.

At least 109 records · Page 6Linked to original sources
PubMed2002

Closed-chest microdialysis to measure antibiotic penetration into human lung tissue.

The majority of bacterial lung infections are localized to the interstitial space fluid, which is therefore an important target site for antimicrobial chemotherapy. Direct measurement of interstitial concentrations of antimicrobial agents in human lung tissue would allow for a more informed approach to appropriate dosing of antimicrobial agents, but until now this was beyond technical reach. In this exploratory pharmacokinetic study, we measured the time versus concentration profile of cefpirome after a single intravenous dose administration of 2 g in the lung interstitial fluid by flexible microdialysis catheters, which were implanted during lung surgery for pulmonary tumors in five patients. Cefpirome concentrations in lung interstitial fluid were 66% of corresponding plasma values within the first 240 min, and exceeded minimal inhibitory concentrations of most relevant bacteria. The experimental procedure was well tolerated by the patients and no adverse events were observed. The present study provides evidence for the first time that closed chest microdialysis of the human lung is a feasible and safe method to measure lung concentrations in patients in vivo. The present data also corroborate the use of cefpirome as a valuable agent in the treatment of lung infections with most extracellular bacteria.

Aged↗
PubMed2002

Molecular scanner experiment with human plasma: improving protein identification by using intensity distributions of matching peptide masses.

The development of high throughput utilities to identify proteins is a major challenge in present research in the field of proteomics. One such utility, the molecular scanner, uses proteins separated by two-dimensional polyacrylamide gel electrophoresis that are digested in the gel and during transfer onto a collecting membrane. After adding a matrix, the membrane is inserted into a matrix-assisted laser desorption/ionization-time of flight mass spectrometer and a peptide mass fingerprint (PMF) is measured for every scanned site. Since the spacing between scanned sites is much smaller than the size of the most abundant protein spots, there is a certain redundancy in the data that was used in an earlier experiment with Escherichia coli [1] to improve mass calibration and PMF identification results. It was observed that the signal intensity of a peptide mass as a function of the position on the membrane showed similar patterns if peptides stemmed from the same protein. Taking account of these similarities a clustering algorithm was used to find lists of experimental masses with similar intensity distributions, which provided clearer identification of the corresponding proteins. Here, these methods are applied to a human plasma scan, where proteins were highly modified and less separated. The presence of very abundant proteins like albumin and immunoglobulins added another difficulty. The calibration of the initial PMFs was not satisfactory and masses had to be recalibrated. After discarding chemical noise, the membrane was partitioned into regions and for each region protein identification was carried out separately. A new scoring method was used, where the PMF score was multiplied by a factor that measures the similarity of matching peptides. This method proved to be more robust than the method developed in [1] if the region where a protein was found had an extended, nonspherical shape and strong overlap with regions of other proteins. Many proteins annotated on the SWISS-2D PAGE human plasma master gel could be clearly identified and many interesting properties were observed.

Algorithms↗
PubMed2002

Methylation-specific PCR for detection of neoplastic DNA in biopsy washings.

Epigenetic DNA alterations such as promoter hypermethylation of glutathione S-transferase P1 (GSTP1) in prostatic adenocarcinoma frequently constitute tumour biomarkers. Neoplastic transformation was identified in washings of prostate biopsies by GSTP1 promoter hypermethylation, using methylation-specific PCR (MSP). Twenty-six patients undergoing sextant transrectal prostate biopsies for clinically suspected prostate cancer were enrolled. All ten patients diagnosed with adenocarcinoma (100%) and four of six patients with prostatic intraepithelial neoplasia (67%), but none of ten patients with benign hyperplasia (0%), exhibited GSTP1 promoter hypermethylation in at least one out of six biopsy washings. Since this approach is transferable to various cancer entities, a sensitive and specific DNA-based analysis of biopsy material seems generally feasible without impeding routine histopathological examination.

Adenocarcinoma↗
PubMed2002

Some tumors of the bladder are polyclonal in origin.

PURPOSE: Clonality assays can be used to address different questions of neoplasm development. The study of the X chromosome inactivation pattern in female patients provides a useful and most commonly used indirect approach to demonstrate the monoclonal status of a cell population. We used this approach to examine whether recurrent tumors of the bladder supposed to be of monoclonal origin derive from different, independently transformed cells or whether they arise from 1 primary tumor. MATERIALS AND METHODS: We analyzed 45 archival or fresh frozen bladder tumors from 27 female patients. We assessed the X inactivation status of each tumor by a polymerase chain reaction based method after HpaII digestion. RESULTS: Surprisingly 16 of the 45 tumors revealed a polyclonal pattern. The amount of undigested DNA far exceeded what was explained by contamination with normal cells, as determined on histological sections indicating that these tumors were in fact polyclonal. This polyclonal status was further confirmed by a comprehensive series of controls. CONCLUSIONS: Some bladder tumors are polyclonal in origin. Our findings are at variance with earlier observations and possibilities for explanation are proposed.

DNA Methylation↗
PubMed2002

DNA alterations in body fluids as molecular tumor markers for urological malignancies.

OBJECTIVES: DNA-based tumor markers are characterized by unique specificity rendering them an attractive target for molecular diagnosis of cancer in body fluids like blood serum/plasma and urine. Both cell-free tumor DNA circulating in plasma/serum and cellular tumor DNA are detectable by minimally invasive measures. METHODS: Three main detection methods, microsatellite analysis, mutation analysis in genomic or mitochondrial DNA and gene promoter hypermethylation analysis are applied. Detection of gene promoter hypermethylation by methylation-specific PCR enables the best methodical sensitivity requiring a ratio of tumor DNA within normal DNA of less than 1:1000. RESULTS/CONCLUSIONS: Tumor DNA derived from renal cell carcinoma, bladder cancer or prostate cancer is detectable in considerably more than 50% of plasma/serum samples and more than 70% of urine samples from these patients. Because the targeted DNA alterations are absent or very rare in controls, the specificity of DNA-based tumor detection methods reaches almost 100%. Although the methodology currently is experimental, automatization will make it easier and less expensive. This review is focused on the potential clinical value of DNA-based analysis of body fluids for the initial diagnosis and the follow-up of urologic cancer patients.

Biomarkers, Tumor↗
PubMed2002

Rational dosing of antibiotics: the use of plasma concentrations versus tissue concentrations.

At the moment, the most common pharmacokinetic/pharmacodynamic (PK/PD) approaches for anti-infective agents, such as time above MIC, C(max)/MIC and AUC(24)/MIC, rely on plasma concentration as the PK input value and minimum inhibitory concentration (MIC) as the PD input value. However, only the free tissue concentrations of antibiotics at the target site are responsible for the therapeutic effect. Using plasma concentrations frequently overestimates the target site concentrations and therefore clinical efficacy. Microdialysis is a new technique that allows direct measurement of unbound tissue concentrations. Furthermore, a better PD approach, bacterial time-kill curves, can offer more detailed information about the antibacterial activity as a function of time and antibiotic concentration than MICs.

Anti-Bacterial Agents↗
PubMed2002

Visualization and analysis of molecular scanner peptide mass spectra.

The molecular scanner combines protein separation using gel electrophoresis with peptide mass fingerprinting (PMF) techniques to identify proteins in a highly automated manner. Proteins separated in a 2-dimensional polyacrylamide gel (2-D PAGE) are digested in parallel and transferred onto a membrane keeping their relative positions. The membrane is then sprayed with a matrix and inserted into a matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometer, which measures a peptide mass fingerprint at each site on the scanned grid. First, visualization of PMF data allows surveying all fingerprints at once and provides very useful information on the presence of chemical noise. Chemical noise is shown to be a potential source for erroneous identifications and is therefore purged from the mass fingerprints. Then, the correlation between neighboring spectra is used to recalibrate the peptide masses. Finally, a method that clusters peptide masses according to the similarity of the spatial distributions of their signal intensities is presented. This method allows discarding many of the false positives that usually go along with PMF identifications and allows identifying many weakly expressed proteins present in the gel.

Algorithms↗
PubMed2002

Quantification of cyclin A1 and glyceraldehyde-3-phosphate dehydrogenase expression in testicular biopsies of infertile patients by fluorescence real-time RT-PCR.

The objective of this study was to establish a classification of meiotic disorders by detection of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and cyclin A1 mRNA in patients presenting with non-obstructive azoospermia. GAPDH and cyclin A1 expression levels were detected in 37 histologically classified testicular tissue specimens by one-line RT-PCR. Levels of cyclin A1 expression (NCyclinA1) were high in tissue specimens with full spermatogenesis [3.519 +/- 3.141 (mean +/- SD)] but only minimal in those without haploid germ cells. A lack of cyclin A1 expression was seen in most sertoli-cell-only syndrome (SCOS) specimens. The criteria for an ideal internal standard were only partially met by GAPDH, as we detected decreased expression in tissue samples with maturation arrest [(268.2 +/- 106.2 relative gene expression (mean +/- SD)] and SCOS (201.7 +/- 95.2) compared to those with normal histological findings (325.1 +/- 129.3). It was concluded that the level of cyclin A1 mRNA expression predicts meiotic disorders during spermatogenesis. GAPDH is not an ideal internal standard for specific gene expression in testicular tissue specimens.

Adult↗
PubMed2002

Cyclin A1 and gametogenesis in fertile and infertile patients: a potential new molecular diagnostic marker.

BACKGROUND: The study aim was to evaluate cyclin A1 mRNA expression levels as a potential molecular diagnostic parameter in the work-up of testicular tissue from fertile versus infertile patients. METHODS: Cyclin A1 expression was quantified in 55 cryopreserved testicular tissue specimens by fluorescence real-time RT-PCR. A conventional histological work-up was performed concomitantly in all tissue specimens with additional semi-thin sectioning in all cases of non-obstructive azoospermia (n = 12), maturation arrest (n = 17) and Sertoli cell-only syndrome (SCOS; n = 9). RESULTS: The mean (+/- SD) normalized cyclin A1 expression (N(CyclinA1)) was 3.82 +/- 2.23 relative gene expression (RGE) in tissue specimens with normal spermatogenesis, and 0.625 +/- 0.221 RGE in those with maturation arrest at the level of early spermatids. Only minimal N(CyclinA1) was detected in tissue specimens with spermatogonia only or maturation arrest at the level of primary spermatocytes (0.005 +/- 0.008). Cyclin A1 expression was absent in the majority of SCOS specimens (0.002 +/- 0.002). CONCLUSIONS: These investigations suggested that cyclin A1 expression is altered in cases of spermatogenic disorders. Moreover, the level of cyclin A1 mRNA expression correlates with gametogenic disorders and seems well suited for a molecular-diagnostic classification supplementing the histopathological evaluation of spermatogenic disorders.

Biomarkers↗
PubMed2002

Interstitial tissue concentrations of cefpodoxime.

Microdialysis is a technique that allows the measurement of concentrations of free antibiotic in tissue. The free antibiotic concentration is responsible for the antibacterial effect at the target site. We used microdialysis in animal and human studies to investigate the tissue penetration of cefpodoxime. In the animal study, total plasma and free muscle and lung concentrations of cefpodoxime were measured after male Wistar rats had received either 10 mg/kg or 20 mg/kg i.v. cefpodoxime over 5 h or a continuous i.v. infusion of 260 microg/h cefpodoxime after a loading dose of 6 mg/kg. Free muscle concentrations of cefpodoxime were similar to free lung concentrations and therefore provided a surrogate measure of cefpodoxime concentrations at the pulmonary target site. In an open, randomized, two-way crossover, single-dose study in six healthy male volunteers, total plasma and free muscle concentrations were measured after a single oral dose of cefpodoxime 400 mg or cefixime 400 mg. The total plasma concentrations of each antibiotic were similar and higher than free muscle concentrations. The tissue penetration of cefpodoxime was, however, greater than that of cefixime, as shown by two-fold higher peak free muscle concentrations after dosing with cefpodoxime than with cefixime (2.1 mg/L versus 0.9 mg/L). In addition, the area under the curve for tissue (AUC(t)) of cefpodoxime (400 mg) was more than double that of cefixime (400 mg), based on free antibiotic concentrations (15.4 mg x h/L versus 7.3 mg x h/L). These findings indicate that, taking into account pharmacokinetic/pharmacodynamic considerations, cefpodoxime is likely to be more efficacious than cefixime, due to its greater tissue penetration.

Animals↗
PubMed2002

Plasma and tissue pharmacokinetics of cefpirome in patients with sepsis.

OBJECTIVE: Broad initial antibiotic treatment is crucial for patients experiencing septic shock or severe sepsis. Fourth-generation beta-lactam antibiotics, such as cefpirome, are frequently favored in these conditions because of their low toxicity and wide antimicrobial coverage. From recent data, however, there is circumstantial evidence that one reason for the high mortality rate of patients with sepsis might be an impaired penetration of antimicrobial agents from the central compartment to the infectious focus. Thus, the present study aimed at describing penetration properties of cefpirome to the target site of many bacterial infections, which is the extracellular space fluid of soft tissues. DESIGN: Prospective comparative study of two groups. SETTING: An intensive care unit and research ward in a university hospital. SUBJECTS: The study population included 12 patients with septic shock or severe sepsis and a control group of six overall age-matched healthy volunteers. INTERVENTIONS: To measure cefpirome penetration into the interstitial space fluid of skeletal muscle, we employed microdialysis after single intravenous administration of 2.0 g of cefpirome to patients and healthy volunteers. MEASUREMENTS AND MAIN RESULTS: Maximum concentration and area under the concentration vs. time values in interstitium were significantly lower in patients compared with the control group (p <.004). Cefpirome area under the concentration time values for plasma were 16.0 +/- 1.1 mg.min/mL (mean +/- sem) and 18.8 +/- 1.1 mg.min/mL in patients and healthy volunteers, respectively (p =.075, not significant). In both study groups, mean cefpirome concentrations in interstitium and plasma exceeded 28 microg/mL throughout the observation period of 240 mins and covered completely minimal inhibitory concentration values for a range of clinically relevant pathogens. CONCLUSION: Cefpirome concentrations reached in tissue interstitium and plasma exceeded minimal inhibitory concentrations of most clinically relevant pathogens in patients with sepsis. Thus, cefpirome exhibits a tissue pharmacokinetic profile, which seems to be particularly valuable for the empirical therapy of patients with sepsis.

Aged↗
PubMed2002

Target site concentrations of ciprofloxacin after single intravenous and oral doses.

To characterize the potential of ciprofloxacin penetration into human soft tissues following intravenous (i.v.) and oral (p.o.) administration, we measured the free ciprofloxacin concentrations in interstitial space fluid of skeletal muscle and subcutaneous adipose tissue by microdialysis. In addition, ciprofloxacin concentrations were measured in cantharis-induced skin blisters, saliva, and capillary plasma and were compared to the total concentrations in venous plasma. Furthermore, a pharmacodynamic in vitro model was used to simulate in vivo pharmacokinetics in bacterial culture. Eight healthy volunteers received ciprofloxacin in an open randomized crossover fashion either as a single i.v. infusion of 400 mg over 60 min or as a single p.o. dose of 500 mg. For both tissues the mean areas under the concentration-time curves (AUCs) for interstitial space fluid (AUC(interstitial fluid)s) were significantly lower than the corresponding AUC(plasma)s, with AUC(interstitial fluid)/AUC(plasma) ratios ranging from 0.38 to 0.68. For skeletal muscle, the AUC(interstitial fluid) was significantly higher after administration of 400 mg i.v. than after administration of 500 mg p.o., with a ratio of the AUC after p.o. administration/AUC after i.v. administration of 0.64. The ratio of the concentration in skeletal muscle/concentration in plasma increased over the entire observation period, implying that ciprofloxacin concentrations were not at steady state. The ratio of the concentration in skin blister fluid/concentration in plasma reached values above 4, indicating a preferential penetration of ciprofloxacin into inflamed lesions. The concentrations in saliva and capillary blood were similar to the corresponding total levels in plasma. In vitro both in vivo ciprofloxacin concentration-time profiles were equally effective against select bacterial strains. In conclusion, single-dose administration of two bioequivalent dosage forms of ciprofloxacin might lead to differences in target site pharmacokinetics. These differences, however, are not related to a difference in target site pharmacodynamics.

Administration, Oral↗
PubMed2002

Activation of NF-kappaB is essential for hepatocyte growth factor-mediated proliferation and tubulogenesis.

Hepatocyte growth factor (HGF) and its receptor, Met, regulate a number of biological functions in epithelial and nonepithelial cells, such as survival, motility, proliferation, and tubular morphogenesis. The transcription factor NF-kappaB is activated in response to a wide variety of stimuli, including growth factors, and is involved in biological responses in part overlapping with those triggered by HGF. In this work we used the liver-derived MLP29 cell line to study the possible involvement of NF-kappaB in HGF/Met signaling. HGF stimulates NF-kappaB DNA binding and transcriptional activation via the canonical IkappaB phosphorylation-degradation cycle and via the extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase cascades. Phosphatidylinositol 3-kinase is not involved in Met-mediated NF-kappaB activation. Blockage of NF-kappaB activation in MLP29 cells by forced expression of the NF-kappaB super-repressor IkappaB(alpha)2A does not interfere with HGF-induced scatter but inhibits proliferation and tubulogenesis. Surprisingly, in the same cells NF-kappaB appears to be dispensable for the antiapoptotic function of HGF.

Animals↗
PubMed2002

Tumor necrosis factor-alpha inhibits renin gene expression.

Renin, produced in renal juxtaglomerular (JG) cells, is a fundamental regulator of blood pressure. Accumulating evidence suggests that cytokines may directly influence renin production in the JG cells. TNF-alpha, which is one of the key mediators in immunity and inflammation, is known to participate in the control of vascular proliferation and contraction and hence in the pathogenesis of cardiovascular diseases. Thus TNF-alpha may exert its effects on the cardiovascular system through modulation of renal renin synthesis. Therefore we have tested the effect of TNF-alpha on renin transcription in As4.1 cells, which represent transformed mouse JG cells, and in native mouse JG cells in culture. Renin gene expression was also determined in mice lacking the gene for TNF-alpha (TNF-alpha knockout mice). TNF-alpha inhibited renin gene expression via an inhibition of the transcriptional activity, targeting the proximal 4.1 kb of the renin promoter in As4.1 cells. TNF-alpha also attenuated forskolin-stimulated renin gene expression in primary cultures of mouse JG cells. Mice lacking the TNF-alpha gene had almost threefold higher basal renal renin mRNA abundance relative to the control strain. The general physiological regulation of renin expression by salt was not disturbed in TNF-alpha knockout mice. Our data suggest that TNF-alpha inhibits renin gene transcription at the cellular level and thus may act as a modulator of renin synthesis in (physio)pathological situations.

Animals↗
PubMed2002

Comparative target site pharmacokinetics of immediate- and modified-release formulations of cefaclor in humans.

Optimal dosing of beta-lactam antibiotics aims at maximizing the time at which drug levels in the interstitial space fluid (ISF)--the fluid that surrounds the causative microorganisms at the target site--exceed the minimal inhibitory concentration (MIC). One potentially attractive strategy to achieve this goal is to administer antibiotics as oral sustained-release formulations. The present study was designed to test the hypothesis that sustained-release formulations could lead to a more suitable pharmacokinetic profile in the ISF at the relevant target site. For this purpose, time versus cefaclor concentration profiles attained in the ISF were measured following administration of two formulations, an immediate- (500 mg IR) and a modified-release formulation in two different doses (500 mg MR and 750 mgMR) in a three-way crossover study of healthy male volunteers (n = 12). For the measurement of unbound cefaclor concentrations in the ISF of human skeletal muscle, the in vivo microdialysis technique was employed. For all three formulations, unbound cefaclor concentration in the ISF closely followed individual plasma concentration profiles in a dose-dependent pattern, with ISF to unbound plasma ratios ranging from 0.67 to 0.73. The mean residence time was found to be significantly longer for the MR formulations versus the IR formulation. The data of the present study indicate that time above MIC values at the target site can be substantially prolonged if an antibiotic is administered as a sustained-release product.

Adult↗