Biomedical subjects

Peter Müller

Publications and source records attributed to Peter Müller.

At least 55 records · Page 3Linked to original sources

PubMed2003

Analysis of the lipid composition of bull spermatozoa by MALDI-TOF mass spectrometry--a cautionary note.

In this study we demonstrated the combination of MALDI-TOF MS and TLC as a fast and powerful tool to investigate the phospholipid (PL) composition of organic extracts of bull spermatozoa. Since phosphatidylcholine (PC) is the dominant PL species, an adequate resolution of MALDI-TOF spectra for sphingomyelin (SM) or phosphatidylethanolamine (PE) was achieved only after previous PL separation by TLC. We found a poor diversity especially for PE and PC, mainly containing ether-linked fatty acids which were 1-palmityl-2-docosahexaenoyl-PL and the corresponding alkenyl-acyl compound (plasmalogen) 1-palmitenyl-2-docosahexaenoyl-PL. For PC, both lipids were quantified after phospholipase A2 digestion to represent 44.2 and 37.2%, respectively, of the total PC. In contrast, the diacyl-PC content of bull spermatozoa was comparatively low (18.6% of total PC). In the presence of trifluoroacetic acid (TFA), which is routinely added to the MALDI-TOF matrix to improve the signal to noise ratio, a high lysophospholipid (LPL) content was detected in the PL extracts of bull spermatozoa, whereas TLC did not reveal significant amounts of LPL. The TFA mediated hydrolysis of the acid-labile alkenyl-acyl PL to the corresponding LPL was shown to cause this discrepancy. This assumption was verified by analysing the PL composition by MALDI-TOF MS before and after (i) digestion of sperm cell lipids with phospholipase A2 and (ii) exposition of spermatozoa to HCl fumes. We conclude that the analysis of samples containing alkenyl-acyl-PL by MALDI-TOF has to be performed with great caution.

Animals↗

PubMed2003

[Involuntary hospitalisations in accordance with guardianship law during eight years tripled].

UNLABELLED: REQUEST: In 1992 the guardianship law came into force. A study about involuntary hospitalisations in accordance with guardianship law between 1992 and 2000 in a small social-psychiatrically well supplied region of Southern Lower Saxony should be made. METHODS: This study about hospitalisation and guardianship proceedings was made in the district courts of jurisdiction in the catchment area at the regional and the university hospital in Göttingen, including diagnosis, reason of hospitalisation and personal characteristics of patients. RESULTS: During study period a new guardianship law came into force, involuntary hospitalisations have doubled. Diagnostic and personal characteristics are described. A comparison: Hospitalisation in accordance with Mental Health law are more numerous and doubled during the last twelve years. CONCLUSIONS: Despite improved ambulant and in-hospital treatment involuntary hospitalisations considerably increased. Possible reasons are discussed: Better perception of necessity of in-hospital treatment, shorter but long-term unsuccessful in-hospital treatment, temptation because of the wording of the law sounds liberal, social demand of harder sanctions for unnormal behaviour. Psychiatrists, social workers and judges obviously support this social concurring behaviour or they are unable to prevent it.

Adolescent↗

PubMed2003

Identification of extracytoplasmic proteins in Bradyrhizobium japonicum using phage display.

A novel gene bank of Bradyrhizobium japonicum USDA110spc4 was constructed using pG3DSS, a phagemid vector designed for detecting genes encoding secreted proteins. In this phagemid, the phage protein III lacks its indigenous signal peptide required for protein secretion, thus recombinant fusion proteins are displayed on the phage surface only if a functional signal peptide is provided by an inserted DNA fragment. In addition, the N-terminal half of protein III has been replaced by a short linker region (the E-tag) that is recognized by a monoclonal antibody, which enables isolation of phages displaying a fusion protein. The expression library described here, therefore, provides a powerful means to affinity select for B. japonicum genes encoding extracytoplasmic proteins. In total, 182 DNA sequences were analyzed, among which 132 different putative extracytoplasmic proteins could be identified. The function of most proteins could be predicted and support an extracytoplasmic localization. In addition, genes encoding novel extracytoplasmic proteins were found. In particular, a novel family of small proteins has been identified that is characterized by a conserved pattern of four cysteine residues.

Amino Acid Sequence↗

PubMed2003

Intra-oesophageal pH profiles and pharmacokinetics of pantoprazole and esomeprazole: a crossover study in patients with gastro-oesophageal reflux disease.

AIM: To compare the effect of pantoprazole and esomeprazole on intra-oesophageal pH and investigate their pharmacokinetics in patients with symptomatic gastro-oesophageal reflux disease (GORD). METHODS: Double-blind, randomized, two-period crossover study. Caucasian men with symptomatic GORD (n=48) were selected on the basis of clinical records of typical GORD symptoms, confirmed by a pathological reflux time (oesophageal pH<4 for > or =6% of the time). They received oral pantoprazole 40 mg once daily (od) or esomeprazole 40 mg od for seven days. Continuous 24 h oesophageal pH-metry was performed at baseline and day 7. Evaluations included: pre- and post-treatment differences in the percentage of time with pH<4.0 and <3.0 between baseline and day 7; area under the curve (AUC), Cmax, and T(1/2); point estimates and 90% confidence intervals (CI) on days 1 and 7, calculated for ratios of the AUC and Cmax. RESULTS: Both drugs decreased the mean total number of reflux episodes and reduced the percentage of reflux time within 24 h to <3%. No pathological reflux was detectable after repeated administration of either drug. The 90% CI were within the predefined range at all time points; thus, equivalence of pantoprazole and esomeprazole was concluded. For pantoprazole, Cmax and AUC were unchanged on day 7 vs day 1, confirming its high and constant bioavailability. For esomeprazole, Cmax and AUC were increased on day 7 vs day 1 by 80% and 50%, respectively, indicating low initial bioavailability. No clinically relevant side effects were seen for either drug. CONCLUSION: Pantoprazole and esomeprazole have equivalent effect on oesophageal pH, since no pathological reflux was detected after treatment with either drug. For esomeprazole, the Cmax and AUC increased after multiple dosing; for pantoprazole the pharmacokinetics were predictable and independent of the number of administered doses.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2003

The Bradyrhizobium japonicum napEDABC genes encoding the periplasmic nitrate reductase are essential for nitrate respiration.

The napEDABC gene cluster that encodes the periplasmic nitrate reductase from Bradyrhizobium japonicum USDA110 has been isolated and characterized. napA encodes the catalytic subunit, and the napB and napC gene products are predicted to be a soluble dihaem c and a membrane-anchored tetrahaem c-type cytochrome, respectively. napE encodes a transmembrane protein of unknown function, and the napD gene product is a soluble protein which is assumed to play a role in the maturation of NapA. Western blots of the periplasmic fraction from wild-type cells grown anaerobically with nitrate revealed the presence of a protein band with a molecular size of about 90 kDa corresponding to NapA. A B. japonicum mutant carrying an insertion in the napA gene was unable to grow under nitrate-respiring conditions, lacked nitrate reductase activity, and did not show the 90 kDa protein band. Complementation of the mutant with a plasmid bearing the napEDABC genes restored both nitrate-dependent anaerobic growth of the cells and nitrate reductase activity. A membrane-bound and a periplasmic c-type cytochrome, with molecular masses of 25 kDa and 15 kDa, respectively, were not detected in the napA mutant strain incubated anaerobically with nitrate, which identifies those proteins as the NapC and the NapB components of the B. japonicum periplasmic nitrate reductase enzyme. These results suggest that the periplasmic nitrate reductase is the enzyme responsible for anaerobic growth of B. japonicum under nitrate-respiring conditions. The promoter region of the napEDABC genes has been characterized by primer extension. A major transcript initiates 66.5 bp downstream of the centre of a putative FNR-like binding site.

Amino Acid Sequence↗

PubMed2003

Bayesian meta-analysis for longitudinal data models using multivariate mixture priors.

We propose a class of longitudinal data models with random effects that generalizes currently used models in two important ways. First, the random-effects model is a flexible mixture of multivariate normals, accommodating population heterogeneity, outliers, and nonlinearity in the regression on subject-specific covariates. Second, the model includes a hierarchical extension to allow for meta-analysis over related studies. The random-effects distributions are decomposed into one part that is common across all related studies (common measure), and one part that is specific to each study and that captures the variability intrinsic between patients within the same study. Both the common measure and the study-specific measures are parameterized as mixture-of-normals models. We carry out inference using reversible jump posterior simulation to allow a random number of terms in the mixtures. The sampler takes advantage of the small number of entertained models. The motivating application is the analysis of two studies carried out by the Cancer and Leukemia Group B (CALGB). In both studies, we record for each patient white blood cell counts (WBC) over time to characterize the toxic effects of treatment. The WBCs are modeled through a nonlinear hierarchical model that gathers the information from both studies.

Bayes Theorem↗

PubMed2002

Is the bond-valence method able to identify metal atoms in protein structures?

The proper assignment of metal ions in X-ray structures of proteins is not always easy, but in many cases this knowledge can be important, e.g. for an understanding of enzyme mechanism. In this publication, the bond-valence approach is assessed critically. A simplified version, the calcium bond-valence sum (CBVS), is proposed for the convenient analysis of the geometric environment of potential sites with a view to metal-ion assignment. The bond-valence approach is found to be more reliable for structures determined from high-resolution data (1.5 A or better).

Algorithms↗

PubMed2002

Randomized study to evaluate the use of high-dose therapy as part of primary treatment for "aggressive" lymphoma.

PURPOSE: This trial of the German High-Grade Non-Hodgkin's Lymphoma Study Group compares the use of high-dose therapy (HDT) as part of primary treatment with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) plus etoposide followed by involved-field (IF) radiotherapy in a randomized, multicenter, phase III study. PATIENTS AND METHODS: Three hundred twelve patients with "aggressive" non-Hodgkin's lymphoma aged <or= 60 years with elevated serum lactate dehydrogenase levels were included from 1990 to 1997. Patients with at least a minor response after two cycles of CHOEP (CHOP + etoposide 3 x 100 mg/m(2)) were to receive three further cycles of CHOEP followed by IF radiotherapy (arm A) or one further cycle of CHOEP followed by autologous stem-cell transplantation and IF radiotherapy (arm B). RESULTS: Among 158 patients randomized to arm B, 103 (65%) received HDT. The complete remission rate at the end of treatment was 62.9% in arm A and 69.9% in arm B. With a median observation time of 45.5 months, overall survival for all 312 patients was 63% after 3 years (63% for arm A, 62% for arm B; P =.68). Event-free survival was 49% for arm A versus 59% for arm B (P =.22). Relapse in arm B was associated with a significantly worse survival rate than relapse in arm A (P <.05). Relapse after HDT occurred early (median interval, 3 months). Six patients developed secondary neoplasia, three in arm A and three in arm B. CONCLUSION: Results of the randomized trial comparing CHOP-like chemotherapy with early HDT do not support the use of HDT with carmustine, etoposide, cytarabine, and melphalan following shortened standard chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2002

Dynamics of lipid chain attached fluorophore 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) in negatively charged membranes determined by NMR spectroscopy.

We have determined the average location and dynamic reorientation of the fluorophore 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) attached to a C12 sn-2 chain of a phosphatidylserine (PS) analogue (C12-NBD-PS) in zwitterionic phosphatidylcholine (PC) and negatively charged phosphatidylserine (PS) host membranes. (1)H magic angle spinning nuclear Overhauser enhancement spectroscopy indicates a highly dynamic reorientation of the aromatic molecule in the membrane. The average location of NBD is characterized by a broad distribution function along the membrane director with a maximum indicating the location of the probe in the lipid/water interface of the lipid membrane. This behavior can be explained by a backfolding of the sn-2 chain towards the aqueous phase. Small differences in the distribution profiles of the NBD group along the membrane normal between PC and PS host membranes were found: in a PC host membrane, the NBD distribution has its maximum in the glycerol region; in a PS host membrane, NBD resides mostly in the upper chain region. These differences may be accounted for by packing differences in the PC versus PS host membranes. As seen by (2)H NMR order parameters, PS bilayers show a much higher packing density compared to PC membranes. Consequently, backfolding of the sn-2 chain with the NBD group attached causes a larger decrease of molecular order of the sn-1 chain in PS than in PC membranes. The broad distributions obtained for lipid chain attached NBD molecules reflect the motional freedom and molecular disorder in the liquid-crystalline lipid membrane.

4-Chloro-7-nitrobenzofurazan↗

PubMed2002

Transbilayer movement of monohexosylsphingolipids in endoplasmic reticulum and Golgi membranes.

The transbilayer movement of glycosphingolipids has been characterized in Golgi, ER, plasma, and model membranes using spin-labeled and fluorescent analogues of the monohexosylsphingolipids glucosylceramide and galactosylceramide and of the dihexosylsphingolipid lactosylceramide. In large unilamellar lipid vesicles, monohexosylsphingolipids underwent a slow transbilayer diffusion (half-time between 2 and 5 h at 20 degrees C). Similarly, the inward redistribution of these sphingolipids in the plasma membrane of the hepatocyte-like cell line HepG2 and of erythrocytes was slow. However, in rat liver ER and Golgi membranes, we found a rapid transbilayer movement of spin-labeled monohexosylsphingolipids (half-time of approximately 3 min at 20 degrees C), which suggests the existence of a monohexosylsphingolipid flippase. The transbilayer movement of glucosylceramide in the Golgi and the ER displayed a saturable behavior, was inhibited by proteolysis, did not require Mg-ATP, and occurs in both directions. Treatment with DIDS inhibited the flip-flop of glucosylceramide but not that of phosphatidylcholine. These data suggest that the transbilayer movement of monoglucosylceramide in the ER and in the Golgi involves a protein that could be distinct from that previously evidenced for glycerophospholipids in the ER. In vivo, transbilayer diffusion should promote a symmetric distribution of monohexosylsphingolipids which are synthesized in the cytosolic leaflet. This should allow glucosylceramide rapid access to the lumenal leaflet where it is converted to lactosylceramide. No significant transbilayer movement of lactosylceramide occurred in both artificial and natural membranes over 1 h. Thus, lactosylceramide, in turn, is unable to diffuse to the cytosolic leaflet and remains at the lumenal leaflet where it undergoes the subsequent glycosylations.

Animals↗

PubMed2002

Lymphotoxin-beta receptor immune interaction promotes tumor growth by inducing angiogenesis.

Growth of solid fibrosarcoma tumors in mice was inhibited by the release of a solublelymphotoxin-beta receptor inhibitor (LTbetaR-immunoglobulin fusion protein) from the tumor cells. Tumor growth arrest in mice deficient in the ligand LTalpha1beta2 demonstrated the requirement for activation of the LTbetaR on the tumor cells by host cell-derived LTalpha1beta2. Activation of the LTbetaR resulted in enhanced release of macrophage inflammatory protein-2. Blocked angiogenesis was revealed in LTbetaR inhibitor-producing tumor nodules by immunohistochemistry and in vivo microscopy. The growth arrest of LTbetaR inhibitor-producing fibrosarcomas was overcome by forced MIP-2 expression in the tumor cells. Thus, LTbetaR activation on tumor cells by activated host lymphocytes can initiate a novel proangiogenic pathway leading to organized tumor tissue development.

Animals↗

PubMed2002

Transport of phosphatidylserine via MDR1 (multidrug resistance 1)P-glycoprotein in a human gastric carcinoma cell line.

The ATP-binding cassette transporter multidrug resistance 1 P-glycoprotein (MDR1 Pgp) has been implicated with the transport of lipids from the inner to the outer leaflet of the plasma membrane. While this has been unambigously shown for the fluorescent lipid analogues [N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]hexanoyl (C6-NBD)-phosphatidylcholine, -phosphatidylethanolamine, -sphingomyelin and -glucosylceramide, by using a novel approach we have now found significantly increased outward transport also for C6-NBD-phosphatidylserine (C6-NBD-PS) in EPG85-257 human gastric carcinoma cells overexpressing MDR1 (coding for MDR1 Pgp). The increased transport of C6-NBD-PS is mediated by MDR1 Pgp, shown by transport reduction nearly to the level of controls in the presence of MDR1 Pgp inhibitors [PSC 833, cyclosporin A and dexniguldipine hydrochloride (Dex)]. Addition of MK 571, a specific inhibitor of the MDR protein MRP1, does not decrease transport in either of the two cell lines. The plasma-membrane association of FITC-annexin V, a fluorescent protein conjugate binding PS, is significantly increased in MDR1-overexpressing cells as compared with controls, and can be reduced by an MDR1 Pgp inhibitor. This suggests that MDR1 Pgp transports endogenous PS, the lipid exhibiting the most pronounced transverse asymmetry in the plasma membrane.

4-Chloro-7-nitrobenzofurazan↗

PubMed2002

Aggressive conventional chemotherapy compared with high-dose chemotherapy with autologous haemopoietic stem-cell transplantation for relapsed chemosensitive Hodgkin's disease: a randomised trial.

BACKGROUND: High-dose chemotherapy followed by transplantation of autologous haemopoietic stem cells (BEAM-HSCT) is frequently used to treat patients with relapsed Hodgkin's disease. We aimed to compare this treatment with conventional aggressive chemotherapy without stem-cell transplantation (Dexa-BEAM). METHODS: 161 patients between 16 and 60 years of age with relapsed Hodgkin's disease were randomly assigned two cycles of Dexa-BEAM (dexamethasone and carmustine, etoposide, cytarabine, and melphalan) and either two further courses of Dexa-BEAM or high-dose BEAM and transplantation of haemopoietic stem cells. Only patients with chemosensitive disease (complete or partial remission after two courses of Dexa-BEAM) proceeded to further treatment. The primary endpoint was freedom from treatment failure for patients with chemosensitive disease. Analysis was per protocol. FINDINGS: 17 patients were excluded from the study after randomisation (ten given Dexa-BEAM and seven given BEAM-HSCT). Median follow-up was 39 months (IQR 3-78). Freedom from treatment failure at 3 years was significantly better for patients given BEAM-HSCT (55%) than for those on Dexa-BEAM (34%; difference -21%, 95% CI -39.87 to -2.13; p=0.019). Overall survival of patients given either treatment did not differ significantly. INTERPRETATION: High-dose BEAM and transplantation of haemopoietic stem cells improves freedom from treatment failure in patients with chemosensitive first relapse of Hodgkin's disease irrespective of length of initial remission.

Adolescent↗

PubMed2002

Influence of the bovine seminal plasma protein PDC-109 on cholesterol in the presence of phospholipids.

The interaction of the major bovine seminal plasma protein PDC-109 with cholesterol was studied by employing spin-labelled analogues. It could be shown that PDC-109 does not interact directly with cholesterol molecules. However, in the presence of phospholipids we found a strong reduction of cholesterol motion by PDC-109. The fraction of immobilized cholesterol was largest for phosphorylcholine-containing lipids. This is consistent with the preferential interaction between PDC-109 and phosphatidylcholine. It is concluded that a stronger association and interaction of PDC-109 with phosphatidylcholine leads to an enhanced fraction of immobilized cholesterol analogues, but not to a phospholipid-dependent specific interaction between the protein and cholesterol. Moreover, the interaction of PDC-109 with various spin-labelled analogues of phosphatidylcholine (lysoPC, diacylPC) was investigated. In membranes of lipid vesicles the protein caused an immobilization of the phosphatidylcholine analogues mainly in the outer membrane leaflet, with no differences between diacylPC and lysoPC. The results are of relevance for understanding the physiological role of PDC-109 in the genesis of sperm cells.

Animals↗

PubMed2002

Transbilayer movement of fluorescent phospholipid analogues in the cytoplasmic membrane of Escherichia coli.

We investigated the transmembrane movement of fluorescent labeled phospholipids in inverted inner membrane vesicles (IIMV) of Escherichia coli (E. coli) wild-type strain (MG1655), as well as in proteoliposomes reconstituted from detergent extracts of the IIMV. The transbilayer movement of 1-myristoyl-2-[6-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]caproyl]-sn-glycero-3-phosphoethanolamine (M-C6-NBD-PE) and -phosphocholine (M-C6-NBD-PC) was measured by a fluorescence stopped-flow back-exchange assay. Both analogues were rapidly translocated across the IIMV membrane, with half-times of <1 min (outward movement) and approximately 3 min (inward movement). No flip-flop was detected in protein-free liposomes, but in IIMV-derived proteoliposomes flip-flop of M-C6-NBD-PE occurred similarly to IIMV and could be largely eliminated by proteinase K treatment.

4-Chloro-7-nitrobenzofurazan↗

PubMed2002

Normal stresses at the gelation transition.

A simple Rouse-type model, generalized to incorporate the effects of chemical cross-links, is used to obtain a theoretical prediction for the critical behavior of the normal-stress coefficients Psi(1) and Psi(2) in polymeric liquids when approaching the gelation transition from the sol side. While the exact calculation shows Psi(2) identical with 0, a typical result for these types of models, an additional scaling ansatz is used to demonstrate that Psi(1) diverges with a critical exponent l=k+z. Here, k denotes the critical exponent of the shear viscosity and z the exponent governing the divergence of the time scale in the Kohlrausch decay of the shear-stress relaxation function. For cross-links distributed according to mean-field percolation, this scaling relation yields l=3, in accordance with an exact expression for the first normal-stress coefficient based on a replica calculation. Alternatively, using three-dimensional percolation for the cross-link ensemble we find the value l approximately 4.9. Results on time-dependent normal-stress response are also presented.

Journal Article↗

PubMed2002

First vs multiple episode schizophrenia: two-year outcome of intermittent and maintenance medication strategies.

Results of studies on intermittent neuroleptic treatment strategies in first episode (FE) schizophrenia have not been published. Aims of the present study were to elucidate the comparative efficacy of prodrome-based neuroleptic intervention in first vs multiple episode (ME) schizophrenia. As to the methods, three randomly assigned open neuroleptic treatment strategies were compared over 2 years in 363 schizophrenic outpatients (115 FE, 248 ME; ICD-9, RDC): maintenance medication vs two intermittent medication strategies (prodrome-based intervention and crisis intervention). Concerning relapse prevention, the results demonstrate that ME patients seemed to profit most from maintenance medication compared to both intermittent treatments, whereas FE patients did equally well under maintenance medication and prodrome-based intervention treatment. Psychopathology, social adjustment, subjective well-being, and side-effects after two years did not differ significantly between the FE and ME patients irrespective of treatment strategy. Concerning treatment adherence, FE patients complied better with prodrome-based intervention than with maintenance medication. Cumulative neuroleptic dosage was lowest in FE patients under intermittent treatment. In conclusion, maintenance medication is the best strategy for relapse prevention in ME patients. In FE patients, prodrome-based intermittent intervention seems to be equivalent or even better with respect to compliance and dosage applied.

Adult↗

PubMed2002

[Intraoperative high frequency current ablation as therapy of atrial fibrillation. The Berlin modification].

BACKGROUND: The Cox-maze procedure combined with an operation for organic heart disease is highly successful in the elimination of chronic atrial fibrillation. However, it prolongs significantly the aortic cross-clamp and operating time. In this study, a simplified left atrial maze procedure, a short procedure performed using a surgical radiofrequency ablation probe, is added to elective open-heart procedures in patients with atrial fibrillation. PATIENTS AND METHODS: 95 adults with atrial fibrillation (duration, 6 months to 33 years) underwent elective open heart operations (isolated valve procedures or coronary artery bypass grafting, n = 51 patients; combined procedures, n = 44 patients) combined with intraoperative radiofrequency ablation of the left atrium. The postoperative follow-up period ranged from 1 to 24 months (mean, 8 months). Possible predictors for persistent postoperative atrial fibrillation were determined among 40 variables by univariate and multivariate analyses. RESULTS: Intraoperative radiofrequency ablation prolonged the aortic cross-clamp time for 6-14 minutes (mean, 11 minutes). Freedom from atrial fibrillation was 100% intraoperatively, 30% at 1 week after operation, and 84% and 84% at 6 and 12 months postoperatively. The only predictor of postoperative atrial fibrillation was the presence of coronary artery disease (odds ratio, 7.5; 80% confidence interval, 2.24-25.13). CONCLUSIONS: Intraoperative radiofrequency ablation of the left atrium combined with an operation for organic heart disease effectively eliminates atrial fibrillation without significant prolongation of the aortic cross-clamp and operative time. The presence of coronary artery disease decreases the success rate during the first 6 postoperative months.

Adult↗