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Biomedical subjects

Markus Müller

Publications and source records attributed to Markus Müller.

At least 19 recordsLinked to original sources
PubMed2003

Target site penetration of fosfomycin in critically ill patients.

OBJECTIVE: The present study was undertaken to investigate the target site penetration properties of fosfomycin, an antibiotic particularly suitable for treatment of soft tissue infections (STIs) in critically ill patients. METHODS AND RESULTS: The study population included nine patients with sepsis. Penetration of fosfomycin into the interstitial space fluid of skeletal muscle was measured using the microdialysis technique, following a single intravenous administration of 8.0 g of fosfomycin to patients. The median (range) fosfomycin area under the concentration versus time profile for plasma and skeletal muscle were 673 (459-1108) and 477 (226-860) mg x h/L (P < 0.011), respectively. Interstitial maximum concentrations were lower than plasma values (P < 0.029). Median fosfomycin concentrations in the interstitium and plasma exceeded 70 mg/L throughout the observation period of 4 h and covered MICs for Streptococcus pyogenes, Staphylococcus aureus and Pseudomonas aeruginosa. Simulation of bacterial growth inhibition of S. pyogenes, based on tissue concentration data, confirmed the bactericidal properties of fosfomycin described in previous studies. CONCLUSION: Fosfomycin concentrations in muscle interstitium and plasma exceeded the MICs for a range of clinically relevant pathogens in critically ill patients. Thus, fosfomycin exhibits a tissue pharmacokinetic profile, which appears to offer an alternative to other broad-spectrum antibiotics in intensive care patients suffering from STI.

Aged↗
PubMed2003

Strategies for the determination of cefazolin in plasma and microdialysis samples by short-end capillary zone electrophoresis.

Capillary zone electrophoresis was employed to determine cefazolin, a first-generation cephalosporin antibiotic, in plasma and microdialysis samples from patients. To shorten the analysis, the samples were injected from the short end of the capillary, resulting in a separation time of < 3 min. Due to a high ionic strength of the biological matrices it was necessary to optimize the stacking conditions. For microdialysis samples a 1:10 dilution with water before injection was sufficient to obtain good peak shape. For plasma samples a protein removal step was required to obtain clean electropherograms and a good peak shape. Acetonitrile was used as precipitant resulting in an enhanced sample stacking in comparison to water dilution. The disadvantage of using acetonitrile was severe evaporation loss making quantitation impossible. A self-sealing film was used to seal each individual sample vial to suppress evaporation during long-term sequences. The calibration curves for spiked plasma and cefazolin in Ringer's solutions were linear in the range from 2-500 and 2.5-100 microg/mL, respectively. Limits of detection were 1.0 and 2.0 microg/mL in plasma and microdialysis samples, respectively. The assay was successfully applied to plasma and microdialysis samples obtained in vivo from the interstial space fluid of subcutaneous adipose and muscle tissue of patients undergoing cardiac surgery.

Acetonitriles↗
PubMed2003

Real-time quantitative reverse transcriptase-polymerase chain reaction for luteinizing hormone-releasing hormone receptor gene mRNA expression in human prostate cancer.

OBJECTIVES: To determine quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) detection of luteinizing hormone-releasing hormone (LHRH) receptor mRNA expressing prostate cancer (CaP) and benign prostatic hyperplasia (BPH) tissue by sequence-specific detection with hybridization probes using the LightCycler. Various in vitro studies have indicated that LHRH agonists and antagonists may have a direct inhibitory effect on CaP mediated by specific LHRH receptors. The incidence of LHRH receptor mRNA expression was demonstrated in 50% to 100% of clinical CaP and BPH tissue by current RT-PCR methods. However, qualitative RT-PCR can only demonstrate the existence of a gene; an exact quantification of LHRH-receptor mRNA expression has not yet been done. METHODS: Quantitative real-time RT-PCR for LHRH receptor mRNA was performed using the LightCycler system and the RNA Amplification Kit hybridization probes in 35 patients with CaP and 38 patients with BPH. RESULTS: Thirty-one (88.6%) of the 35 patients with CaP and 36 (94.7%) of the 38 patients with BPH had positive RT-PCR for LHRH receptor mRNA. The number of positive amplifications per 1 microg total RNA was not significantly lower in CaP at 695,428 +/- 350,860 than in BPH at 1,617,654 +/- 787,874. Patients with CaP evidenced a significant negative correlation between the amplification rate for LHRH receptor mRNA and Gleason score (r = -0.476; P = 0.004). CONCLUSIONS: In the past, the potential mechanisms acting on LHRH receptors in CaP have been identified as possible antitumor strategies for this type of cancer. Our study is the first to show that CaP does not have a higher expression of LHRH receptor mRNA expression than BPH when using quantitative sequence-specific oligonucleotide hybridization probes that only detect certain PCR products.

Adenocarcinoma↗
PubMed2003

Synthesis of fluorine-18-labeled ciprofloxacin for PET studies in humans.

Ciprofloxacin (1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-quinoline-3-carboxylic acid), a widely-prescribed antibiotic, was labeled with fluorine-18 with the aim to perform positron emission tomography studies in humans for pharmacokinetic measurements. Due to a lack of chemical activation of ciprofloxacin for a direct nucleophilic exchange reaction a novel two-step synthetic approach, which employed an activated 6-fluoro-7-chloro substituted precursor molecule, was developed. The radiosynthesis yielded, starting from 52.5 +/- 11.3 GBq of [(18)F]fluoride, 1.3 +/- 0.6 GBq (n = 13) [(18)F]ciprofloxacin ready for intravenous administration in about 130 min synthesis time. A series of analytical tests was performed in order to prove the identity of the radiolabeled compound and its suitability for human applications.

Anti-Infective Agents↗
PubMed2003

[Clinico-pharmacologic explanation models of cerivastatin associated rhabdomyolysis].

Because of fatal cases of rhabdomyolysis the HMG-CoA-reductase inhibitor cerivastatin had to be withdrawn from the global market in 2001. The high frequency and severity of cerivastatin-associated rhabdomyolysis caused concerns about the safety of the entire class of HMG-CoA-reductase inhibitors (statins). Still, the frequency of deadly incidents of rhabdomyolysis with cerivastatin was 16 to 80 times higher than with other statins. This seems to be due to a combination of several pharmacokinetic and pharmacodynamic characteristics of cerivastatin. Cerivastatin shows the highest oral bioavailability within its class. Interactions with other drugs like gemfibrocil may cause further elevation of cerivastatin plasma levels, thereby leading to higher frequencies of side effects in peripheral organs. With approximately 1 pM cerivastatin shows the lowest IC50 for inhibition of HMG-CoA-reductase of all statins. The combination of high systemic drug levels and high intrinsic activity potentially leads to apoptosis and energy-depletion of skeletal-muscle cells. Therefore cerivastatin-associated fatal rhabdomyolysis seems to be based on specific pharmacokinetic and pharmacodynamic properties of cerivastatin, and is not a general characteristic of all members of this drug-class. The experiences with cerivastatin support the importance of clinical studies even about well established drugs, and underline the relevance of precise reporting of adverse events by each physician.

Animals↗
PubMed2003

Single- and multiple-dose pharmacokinetics of oral creatine.

Supplementation with exogenous creatine (Cr) has shown physiological benefits in humans, but little is known about the pharmacokinetics of Cr in humans. Six healthy males completed an open-label study consisting of a full pharmacokinetic analysis following a single oral dose of Cr monohydrate (71 mg kg-1) and at steady-state after 6 days of Cr administration (71 mg kg-1 qid). After the single oral dose, the clearance (CL/F) was 0.20 +/- 0.066 L h-1 kg-1, tmax was 1.9 +/- 0.88 hours, and Cmax = 102.1 +/- 11.2 mg h L-1. At steady-state, CL/F decreased to 0.12 +/- 0.016 L h-1 kg-1, tmax did not change, and Cmax increased to 162.2 +/- 30.0 mg L-1. Penetration (AUCMUSCLE/AUCPLASMA) of Cr into the interstitial muscle space, as determined by microdialysis, was 0.47 +/- 0.09 and 0.37 +/- 0.27 for the single dose and at steady-state, respectively. Plasma and muscle data were simultaneously fitted with a model incorporating a saturable absorption and first-order elimination process. In conclusion, repeated dosing of Cr caused a reduction in clearance that could result from saturation of the skeletal muscle pool of Cr.

Administration, Oral↗
PubMed2002

The differentiation status of primary gonadal germ cell tumors correlates inversely with telomerase activity and the expression level of the gene encoding the catalytic subunit of telomerase.

BACKGROUND: The activity of the ribonucleoprotein enzyme telomerase is detectable in germ, stem and tumor cells. One major component of telomerase is human telomerase reverse transcriptase (hTERT), which encodes the catalytic subunit of telomerase. Here we investigate the correlation of telomerase activity and hTERT gene expression and the differentiation status of primary testicular germ cell tumors (TGCT). METHODS: Telomerase activity (TA) was detected by a quantitative telomerase PCR ELISA, and hTERT mRNA expression was quantified by online RT-PCR in 42 primary testicular germ cell tumors. The control group consisted of benign testicular biopsies from infertile patients. RESULTS: High levels of telomerase activity and hTERT expression were detected in all examined undifferentiated TGCTs and in the benign testicular tissue specimens with germ cell content. In contrast, differentiated teratomas and testicular control tissue without germ cells (Sertoli-cell-only syndrome) showed no telomerase activity and only minimal hTERT expression. CONCLUSIONS: These findings demonstrate an inverse relationship between the level of telomerase activity and hTERT mRNA expression and the differentiation state of germ cell tumors. Quantification of telomerase activity and hTERT mRNA expression enables a new molecular-diagnostic subclassification of germ cell tumors that describes their proliferation potential and differentiation status.

Catalytic Domain↗
PubMed2002

Microdialysis: an in vivo approach for measuring drug delivery in oncology.

Microdialysis (MD) is a catheter-based sampling method that provides the opportunity to directly study tumor drug exposure and metabolism in a minimally invasive way. Tumor drug exposure, which is directly linked to clinical outcome, may be substantially reduced due to diffusion barriers in solid tumors. Therefore plasma drug profiles are frequently inappropriate for predicting outcome in oncology. This contribution focuses on the application of MD in preclinical and clinical oncological research and presents an overview of the current literature. It is concluded that MD, in combination with pharmacokinetic/pharmacodynamic modeling, has the potential to contribute to the design of optimal treatment schedules and to select appropriate drug candidates, doses, and dosing intervals for established and new anticancer drugs.

Animals↗
PubMed2002

Telomerase: its clinical relevance in the diagnosis of bladder cancer.

More than 50 years ago, Papanicolaou recognized the importance of a non-invasive technique for the diagnosis and follow-up of patients with carcinoma of the urinary bladder. Cystoscopy, however, has remained the 'gold standard' since no currently available non-invasive method can compete with cystoscopy's sensitivity and specificity. The detection of the ribonucleoprotein telomerase or the telomerase subunits human telomerase RNA (hTR) and human telomerase reverse transcriptase (hTERT) in urine samples offer new diagnostic perspectives. The present article presents a review of publications in the literature and evaluates their clinical relevance. The experimental studies reported to date are very promising and show that telomerase exactly fulfils the requirements for a good diagnostic marker for carcinoma of the urinary bladder. The diagnostic application remains in an experimental stage and telomerase is still several steps away for routine use as a clinical parameter. The remaining steps leading to its routine clinical application will be discussed.

Biomarkers, Tumor↗
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↗