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Biomedical subjects

P Müller

Publications and source records attributed to P Müller.

At least 109 records · Page 6Linked to original sources
PubMed1999

Development of cellulose sulfate-based polyelectrolyte complex microcapsules for medical applications.

Microencapsulation, as a tool for immunoisolation for allogenic or xenogenic implants, is a rapidly growing field. However most of the approaches are based on alginate/polylysine capsules, despite this system's obvious disadvantages such as its pyrogenicity. Here we report a different encapsulation system based on sodium cellulose sulfate and polydiallyldimethyl ammonium chloride for the encapsulation of mammalian cells. We have characterized this system regarding capsule formation, strength and size of the capsules as well as viability of the cells after encapsulation. In addition, we demonstrate the efficacy of these capsules as a "microfactory" in vitro and in vivo. Using encapsulated hybridoma cells we were able to demonstrate long-term release of antibodies up to four months in vivo. In another application we could show the therapeutic relevance of encapsulated genetically modified cells as an in vivo activation center for cytostatic drugs during tumor therapy.

Alginates↗
PubMed1999

Protein-mediated inward translocation of phospholipids occurs in both the apical and basolateral plasma membrane domains of epithelial cells.

The translocation of spin-labeled analogues of phosphatidylcholine (4-doxylpentanoyl-PC, SL-PC), phosphatidylethanolamine (SL-PE), phosphatidylserine (SL-PS), and sphingomyelin (SL-SM) from the outer to the inner leaflet of the plasma membrane bilayer was investigated in dog kidney MDCK II and human colon Caco-2 cells. Disappearance from the outer leaflet was assayed using back-exchange to serum albumin. Experiments with cells in suspension as well as with polarized cells on filters were performed at reduced temperatures (10 and 20 degreesC) to suppress endocytosis and hydrolysis of spin-labeled lipids. For both epithelial cell lines, a fast ATP-dependent inward movement of the aminophospholipids SL-PS and SL-PE was found, while SL-SM was only slowly internalized without any effect of ATP depletion. The kinetics of redistribution of SL-PC were clearly different between the two cell lines. In MDCK II cells, SL-PC was rapidly internalized in an ATP-dependent and N-ethylmaleimide-sensitive manner and at a rate similar to that of the aminophospholipids. In contrast, in Caco-2 cells the inward movement of SL-PC was much slower than that of the aminophospholipids, did not depend on ATP, and was not N-ethylmaleimide-sensitive. Inhibitor studies indicated that the outward-translocating multidrug resistance P-glycoprotein present in these cells did not affect the kinetics of inward translocation. Internalization was always similar on the apical and basolateral cell surface, suggesting the presence of the same phospholipid translocator(s) on both surface domains of epithelial cells. We propose that Caco-2 cells contain the well-known aminophospholipid translocase, while MDCK II cells contain either two translocases, namely, the aminophospholipid translocase and a phosphatidylcholine-specific translocase, or one translocase of a new type, translocating aminophospholipids as well as phosphatidylcholine.

Adenosine Triphosphate↗
PubMed1999

Lipid domains in the exoplasmic and cytoplasmic leaflet of the human erythrocyte membrane: a spin label approach.

The existence of different lipid domains in the monolayers of the human erythrocyte membrane was investigated at 4 degrees C by employing spin-labelled phospholipid analogues. Spectra of analogues located exclusively either in the exoplasmic or in the cytoplasmic leaflet of erythrocyte membranes were recorded. Spectra were simulated by variation of order parameter describing the average amplitude of motion of the long molecular axis of the nitrogen 2 p pi orbital of the spin label and of the respective correlation times. For both leaflets at least three components were required to fit the experimental spectra, differing mainly in the order parameter. While the parameters of each component are not very different between both membrane halves, the relative contribution of each component to the spectrum is different between the exoplasmic and cytoplasmic leaflet. The order parameter of the most fluid component, presumably resembling the lipid bulk phase, is smaller in the cytoplasmic leaflet in comparison to the exoplasmic one. The lateral coexistence of different lipid domains in the human red blood cell membrane is concluded. The molecular nature of those domains is discussed.

Biophysical Phenomena↗
PubMed1999

The MAP kinase kpp2 regulates mating and pathogenic development in Ustilago maydis.

In the phytopathogenic fungus Ustilago maydis, fusion of compatible haploid cells is a prerequisite for infection. This process is genetically controlled by the biallelic a locus, encoding pheromone precursors and receptors. These are presumed to be coupled to a heterotrimeric G protein and a MAP kinase cascade, leading to activation of the HMG domain transcription factor Prf1. Here, we have demonstrated that putative MAP kinase sites in Prf1 are required for its activity during mating. In addition, we have identified a gene, kpp2, which encodes a putative MAP kinase related to Pmk1 of Magnaporthe grisea and Fus3p of Saccharomyces cerevisiae. kpp2 deletion mutants are attenuated in several steps of development: cell fusion, induction of pheromone-responsive genes and pathogenicity. Epistasis analysis shows that kpp2 does not affect pheromone gene expression through the cAMP signalling cascade. Pathogenicity of kpp2 mutants can be partially restored by overexpressing the b genes, indicating a regulation of Prf1 by Kpp2. These data support the hypothesis that the MAP kinase Kpp2 transmits the pheromone signal.

Amino Acid Sequence↗
PubMed1999

[Direct and indirect costs of schizophrenia].

In the present study the costs of schizophrenia in Germany were studied using the "bottom up" prevalence-based method. In a random sample of 180 schizophrenic patients stratified according to the most important care institutions, direct and indirect costs were retrospectively documented for a 12-month period. Depending on the place of recruitment and the extent of care provided, total yearly costs result between about DM 33,000 for a patient treated predominantly on an outpatient basis and about DM 126,000 for a patient requiring hospital care and about DM 135,000 for a patient in job rehabilitation. The direct yearly treatment costs were, as expected, lowest for patients recruited in the private practice of a psychiatrist and predominantly treated on an outpatient basis (DM 5,788), and were the highest in the psychiatric hospital (DM 64,661) and in job rehabilitation (DM 79,996). In the patients recruited in the outpatient domain, doctors' fees and medication together were responsible for only 4.5% of the total costs, whereas the indirect costs (e.g., through work incapacity) were responsible for 87% of the total yearly costs. For methodological reasons the total costs caused by schizophrenic psychoses in Germany per year can at present be estimated only roughly. A conservative estimate is between 8.5 and 18 billion DM per year. The study shows that schizophrenia is a very expensive illness, the direct and indirect costs of which are on the whole comparable to those of the common somatic illnesses. Therefore, also for economical reasons, sufficient financial means should be invested in the research and treatment of this severe illness.

Adult↗
PubMed1999

A novel 53-kDa nodulin of the symbiosome membrane of soybean nodules, controlled by Bradyrhizobium japonicum.

A nodule-specific 53-kDa protein (GmNOD53b) of the symbiosome membrane from soybean was isolated and its LysC digestion products were microsequenced. cDNA clones of this novel nodulin, obtained from cDNA library screening with an RT-PCR (reverse-transcriptase polymerase chain reaction)-generated hybridization probe exhibited no homology to proteins identified so far. The expression of GmNOD53b coincides with the onset of nitrogen fixation. Therefore, it is a late nodulin. Among other changes, the GmNOD53b is significantly reduced in nodules infected with the Bradyrhizobium japonicum mutant 184 on the protein level as well as on the level of mRNA expression, compared with the wild-type infected nodules. The reduction of GmNOD53b mRNA is related to an inactivation of the sipF gene in B. japonicum 184, coding for a functionally active signal peptidase.

Amino Acid Sequence↗
PubMed1999

A Bayesian hierarchical approach for combining case-control and prospective studies.

Motivated by the absolute risk predictions required in medical decision making and patient counseling, we propose an approach for the combined analysis of case-control and prospective studies of disease risk factors. The approach is hierarchical to account for parameter heterogeneity among studies and among sampling units of the same study. It is based on modeling the retrospective distribution of the covariates given the disease outcome, a strategy that greatly simplifies both the combination of prospective and retrospective studies and the computation of Bayesian predictions in the hierarchical case-control context. Retrospective modeling differentiates our approach from most current strategies for inference on risk factors, which are based on the assumption of a specific prospective model. To ensure modeling flexibility, we propose using a mixture model for the retrospective distributions of the covariates. This leads to a general nonlinear regression family for the implied prospective likelihood. After introducing and motivating our proposal, we present simple results that highlight its relationship with existing approaches, develop Markov chain Monte Carlo methods for inference and prediction, and present an illustration using ovarian cancer data.

Bayes Theorem↗
PubMed1999

Growth and cell cycle abnormalities of fibroblasts from Tangier disease patients.

We have investigated the abnormal proliferation and morphology of fibroblasts from patients with Tangier disease (TD), a high density lipoprotein (HDL) deficiency syndrome that is characterized by impairment of HDL3-mediated lipid efflux and Gi-protein-mediated signaling via phosphatidylinositol-specific phospholipase C (PI-PLC) and phospholipase D (PLD). TD fibroblasts displayed a 30% to 50% reduced in vitro growth rate and a 1.6-fold increased cell surface area. The response to different mitogens was diminished, and asynchronously growing TD fibroblasts showed 4.4+/-0.3% S-phase and 19.1+/-0.5% G2/M-phase cells compared with 9.7+/-0.6% and 7.8+/-0.5%, respectively, in controls. Monensin, but not brefeldin A, induced an S- and G2/M-phase distribution in control cells similar to that found in TD fibroblasts. This effect of monensin was accompanied by an increase of ceramide levels in controls, whereas TD fibroblasts already had a 2.5-fold increased basal ceramide concentration. Incubation of control cells with C2 ceramide and threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) mimicked the effect of monensin on the cell cycle. The inhibition of neither Gi protein function by pertussis toxin nor PLD by butanol resulted in a G2/M-phase arrest. Propranolol, known to increase phosphatidic acid levels, was ineffective in reversing the G2/M-phase arrest in TD fibroblasts. In addition, cDNA sequences and mRNA expression of the participants of PI-PLC or PLD signaling, ie, G-protein subunits alphai1, alphai2, and alphai3; phosphatidylinositol transfer proteins-alpha and -beta; and ADP ribosylation factors 1 and 3 were found to be normal. Thus, growth and cell cycle abnormalities in TD fibroblasts are likely to be related to impaired Golgi function and sphingolipid signaling rather than inoperative G-protein signal transduction. Because PDMP was also found to decrease HDL3-mediated lipid efflux in control but not TD fibroblasts, similar pathways seem to be involved in the disturbances of lipid transport and growth retardation.

ADP-Ribosylation Factors↗
PubMed1999

Micrometastases of bone marrow in localized prostate cancer: correlation with established risk factors.

PURPOSE: The presence of cytokeratin 18-positive cells in bone marrow correlates with conventional risk factors in many tumors. We examined whether this was also valid for localized or lymphatically spread prostate cancer. PATIENTS AND METHODS: Immediately before radical prostatectomy, bone marrow aspirates from both sides of the iliac crest were taken from 287 patients. The presence of cells containing cytokeratin 18 was interpreted as micrometastasis. RESULTS: In patients with negative lymph nodes (n = 219), conventional risk factors (Gleason score, pathologic stage, ploidy, and preoperative prostate-specific antigen) did not correlate with the preoperative detection of cells containing cytokeratin 18. There was also no correlation with lymph node metastases. Furthermore, there was no interdependency between the preoperatively detected number of cells and the established risk factors. CONCLUSION: We assume the presence of epithelial cells in bone marrow to be an independent parameter, the clinical importance of which must be substantiated by further studies.

Adenocarcinoma↗
PubMed1999

Stability of transbilayer phospholipid asymmetry in viable ram sperm cells after cryotreatment.

The transbilayer dynamics of lipids in the plasma membrane of mammalian sperm cells is crucial for the fertilization process. Here, the transbilayer movement and distribution of phospholipids in the plasma membrane of fresh, ejaculated and cryopreserved ram spermatozoa was studied by labeling cells with fluorescent analogues of phosphatidylserine and phosphatidylcholine. By co-labeling cells with the DNA-binding dye propidiumiodide as well as by employing fluorescence microscopy and flow cytometry we were able to determine the transbilayer redistribution of fluorescent phospholipid analogues in intact (propidiumiodide-negative) and in impaired (propidiumiodide-positive) spermatozoa. The transbilayer distribution of the fluorescent phosphatidylserine and phosphatidylcholine analogues was not perturbed in intact sperm cells after cryopreservation. In those cells, the phosphatidylserine analogue became rapidly enriched on the cytoplasmic leaflet by the activity of a putative aminophospholipid translocase similar to intact cells of fresh, ejaculated samples. However, upon cryopreservation the activity of the putative aminophospholipid translocase was significantly reduced in intact cells. Employing annexin V-FITC, we found that even after cryopreservation the sequestering of endogenous phosphatidylserine to the cytoplasmic leaflet is maintained in intact cells, but not in impaired cells. The phosphatidylcholine analogue redistributed very slowly remaining essentially confined to the exoplasmic leaflet of the plasma membrane of intact cells from both fresh, ejaculated and cryopreserved samples. The physiological consequences of a perturbed transbilayer asymmetry in sperm plasma membranes is discussed.

4-Chloro-7-nitrobenzofurazan↗
PubMed1999

Simple method for DNA extraction from pancreatic juice for PCR amplification assays.

CONCLUSION: Preparation of DNA from pancreatic juice for subsequent polymerase chain reaction (PCR) is difficult, but manageable. The protocol presented offers a simple and fast solution. This method might be applicable to other complicated samples, such as saliva, would secretions, or stool washings. BACKGROUND: Of all the biological samples used for PCR amplification, pancreatic juice is the most problematic because of the presence of potential inhibitory substances and the amount of nucleases. This demands a DNA preparation procedure that is suitable for routine diagnostic PCR, and is therefore efficient and safe. This is particularly true for pancreatic juice obtained during routine endoscopy. METHODS: We describe here a simple method utilizing modified phenol/chloroform extraction and precipitation directly from native pancreatic juice suitable for diagnostic PCR applications, such as oncogenes. RESULTS: DNA could be prepared in quantitative amounts from routine endoscopic specimens. DNA could also be prepared from samples kept several days at room temperature.

DNA↗
PubMed1999

[The efficacy of repeated disinfection of disposable gloves during usage].

The efficacy of disinfecting medical gloves with isopropanol 60% (v/v) while they are worn was assessed for 4 different brands of latex gloves (Biogel Diagnistic (A), Safeskin Satin Plus (B), Safeskin LPE (C) and Baxter Non-Sterile Latex Exam Gloves (D)) and one latex-free nitrile glove (100% Nitrile N-Dex (E)). Even in the presence of coagulated blood disinfection of the gloves was more efficient than disinfection of the bare hand. The efficacy of the disinfection of glove C, D and E decreased if 10 disinfections were carried out successively. An increase of perforations detected with the water inflation test according to EN 455-1 was found for brand E. As gloves of brand C and D became tacky after 10 disinfections, they were inappropriate for manual work. As a result, disinfection with isopropanol 60% (v/v) can be recommended for gloves of brand A and B only. Disinfection of these gloves is admissible e.g. after indirect patient contact, taking blood samples or laboratory work if no visible contamination or perforation has occurred. However, after contact with patients suffering from an infectious disease or carrying multiresistant organisms the gloves have to be changed. The same holds true if the gloves might be contaminated with naked viruses (e.g. Poliomyelitis virus), since virucidal alcoholic hand disinfectants require high concentration thus leading to materials incompatibility.

2-Propanol↗
PubMed1999

[Attitude of family to clozapine].

AIM: Evaluations of clozapine treatment by relatives of schizophrenic patients were assessed as part of an exploratory study and compared with the patients' own assessment. METHOD: 46 relatives of individuals suffering from schizophrenia were questioned by means of a problem-centred interview. RESULTS: In addition to the positive effects on the schizophrenic illness, relatives strikingly often pointed out the calming, sleep-improving effect of clozapine. As opposed to the patients, the majority of relatives were well aware of the risks associated with discontinuing the drug treatment. Both patients and relatives complained about the sedative effect and the increased need for sleep associated with clozapine treatment. However, diverging evaluations were given with regard to hypersalivation, anticholinergic effects, and weight gain. Relatives were more concerned about possible organ damage occurring as a long-term effect than the patients. Further, indications were found that relatives were more worried by the risk of haematotoxic effects resulting from clozapine treatment than the patients. It could be said that, among the relatives, there was a slightly greater awareness of the advantages of clozapine treatment in comparison with conventional neuroleptics than there was with the patients. CONCLUSION: The importance of relatives' views in the effort to secure adequate neuroleptic treatment despite the current economic restrictions should not be under-estimated.

Adult↗
PubMed1999

["Rather overweight and mentally present...". Patients evaluate clozapine].

OBJECTIVE: Subjective evaluations by schizophrenic patients of clozapine treatment were assessed as part of an exploratory study. METHODS: A problem-centred interview was carried out with 80 patients at discharge from in-patient or day hospital treatment. RESULTS: In addition to expected effects (improvement or stabilisation of one's state of mental health, antipsychotic effects), patients surprisingly often highlighted clozapine's calming and relaxing effect as well as improved sleep as particularly positive. While more than half of the respondents expected a worsening of their condition in case they stopped taking their medication, only every fifth patient feared a relapse. Among the negative effects, fatigue and sedation were cited by far the most often. The absence of extrapyramidal side effects was clearly noted as an advantage of clozapine. Only every tenth of those questioned was aware of the risks for the haemotopoietic system associated with the drug. With regard to the obligatory blood tests, a surprisingly large number of patients was indifferent or stated that they had no opinion on the matter. DISCUSSION: Possible implications for patient information and compliance will be discussed.

Adolescent↗
PubMed1999

Deletion of chromosome 1p and loss of expression of alkaline phosphatase indicate progression of meningiomas.

Meningiomas are cytogenetically characterized by loss of one chromosome 22 as a typical primary aberration and progression-associated secondary chromosome changes, of which monosomy 1p is the most common. The aim of this study was to evaluate the significance of monosomy 1p and enzyme activity loss of tissue nonspecific alkaline phosphatase (ALPL), whose gene maps to chromosome 1p36.1-p34, as parameters for the diagnosis of progression-prone meningiomas. We analyzed smear preparations of 56 meningiomas and additional paraffin sections of 17 of the cases by two-color fluorescence in situ hybridization (FISH) using the D1Z1 and D1Z2 probes and by a metaphase cytogenetic analysis of 30 of these tumors. The results were compared to clinical and morphological parameters and the expression of ALPL. Smear preparations showed deletion of 1p36 in 27% of common-type, 70% of atypical (intermediate-type), and 100% of anaplastic meningiomas. Monosomy 1p, as detected by FISH or the karyotype, was strongly associated with complete loss of ALPL activity. Intermediate-type and anaplastic meningiomas of younger patients displayed an increasing rate of cells with trisomy 1q and relative loss of 1p. The highly significant correlation of FISH results and ALPL histochemistry with clinical parameters gives evidence of their strong prognostic relevance. The complete activity loss of ALPL and the immunologically detected loss of ALPL protein in areas of meningiomas with monosomy 1p indicate a cytogenetically undetectable inactivation of the homologous Alpl allele. The apparently homozygous loss of expression of ALPL supports the notion that Alpl is a candidate tumor suppressor gene in meningiomas.

Alkaline Phosphatase↗