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Biomedical subjects

G Jansen

Publications and source records attributed to G Jansen.

151 records · Page 9Linked to original sources
PubMedDate not supplied

The influence of Enterococcus faecalis on the morphology and the antibody-binding capacity of the intestinal bacteria of ten healthy human volunteers.

The influence of Enterococcus faecalis on the morphology of the bacterial cells which make up the gut microflora and on the levels of circulating IgG bound to the gut microflora was assessed. After 29 days of pretreatment monitoring, ten healthy human volunteers ingested 10(7) viable cells of E. faecalis three times daily, for 21 days. After this treatment another 21 days of follow-up completed the study. Each volunteer delivered eleven faecal samples during the entire study period of 71 days with a 7 day interval. Before and after the faeces sampling period, blood samples were collected from all volunteers. The influence of the ingestion of E. faecalis on the morphology of the gut microflora was measured by image analysis. In addition, the binding of circulating IgG to intestinal bacteria in all intermediate faecal samples was measured by means of quantitative immunofluorescence. The oral administration of E. faecalis resulted in a significant change of the morphological composition of the gut microflora and in a significant decrease in IgG-binding capacity of the gut microflora.

Adult↗
PubMedDate not supplied

The non-enzymatic inactivation of thirteen beta-lactam antibiotics in human faeces.

In order to obtain a method that could predict the in vitro inactivation of an antibiotic in the digestive tract, the non-enzymatic inactivation of 13 beta-lactam antibiotics by human faeces was investigated. Benzylpenicillin, amoxicillin, amoxicillin/clavulanate, cloxacillin, piperacillin, temocillin, cefuroxime, cefamandole, cephradine, cefotaxime, ceftazidime, aztreonam and imipenem were mixed in six graded concentrations with faecal suspensions of 30 healthy volunteers. After incubation the remaining antimicrobial activity was measured by means of a serial dilution method. A relationship between the initial antibiotic concentration (Aia) and the remaining antimicrobial activity after incubation (Asd) was derived, namely: Asd = 1/2[(Aia-K-F)+square root ((Aia-K-F)2 + 4 K Aia)]. The parameters K and F represent the intrinsic dissociation constant and the amount of available bindingsites in the faeces, respectively. Asd values were predicted with a reasonable degree of accuracy for all thirteen antibiotics. Dissociation constants differed significantly between the penicillins and the cephalosporins but F- values did not differ between cephalosporins and penicillins.

Adsorption↗
PubMedDate not supplied

The in vitro inactivation of thirteen beta-lactam antibiotics by other mechanisms than adsorption to faecal substance.

We have investigated the antibiotic inactivating capacity of intestinal contents in vitro in faeces. In the presently reported study the influence of beta-lactamase catalyzed hydrolysis on the antimicrobial activity of 13 commonly used beta-lactam antibiotics was investigated, while the influence of non-specific adsorption of antibiotics to faecal compounds was also taken into account. The following antibiotics were tested: benzylpenicillin, amoxicillin, amoxicillin/clavulanate, cloxacillin, piperacillin, temocillin, cefuroxime, cefamandole, cephradine, cefotaxime, ceftazidime, aztreonam and imipenem. Faecal samples were obtained from 30 healthy volunteers. Six different concentrations of each antibiotic were added to 1 g of faeces. After 24 h of incubation at 37 degrees C the remaining amount of active antibiotic was determined by means of a "growth inhibition assay". The contribution to the test results of non-specific adsorption to macromolecules was calculated by means of a model and the inactivation data were subsequently corrected. The amount of antibiotic non-specifically bound to faecal macromolecules varied from 0% to 80% of the amount of antibiotic initially added to the faeces. A considerable difference was found in the degree of inactivation of several antibiotics. However, in contrast to earlier investigations, the results of this study show that in a normal population the influence of beta-lactamase catalyzed hydrolysis on the activity of beta-lactam antibiotics is apparently very small when compared to the influence of non-specific adsorption of beta-lactam antibiotics to faecal compounds.

Adsorption↗
PubMedDate not supplied

Efficacy and pharmacokinetics of teicoplanin in hemodialysis patients.

In order to establish guidelines for the dosage of teicoplanin, a new glycopeptide antibiotic, in patients with end stage renal failure, 40 cases of suspected or proven gram-positive infections were treated with teicoplanin. Three different dosage regimens were used and peak/trough serum levels measured. Thirty-one patients were cured and six patients died. Teicoplanin was well tolerated. For severe cases of septicemia with staphylococci in patients undergoing hemodialysis a teicoplanin therapy consisting of 800 mg on day 1 followed by administrations of 400 mg on days 2, 3, 5, 12, and 19 is recommended. Minor infections are treated initially with 800 mg followed by administration of 400 mg at weekly intervals.

Adult↗
PubMedDate not supplied

Protection goals for residents in the vicinity of civil airports.

Based on extensive and detailed reviews the present paper suggests evaluation criteria for aircraft noise for the prediction of noise effects and for the protection of residents living in the vicinity of (newly constructed or extended) civil airports. The protection concept provides graded evaluation criteria: Critical loads indicate noise loads that shall be tolerated only exceptionally during a limited time. Protection Guides are central evaluation criteria for taking actions to reduce noise immission. Threshold values inform about measurable physiological and psychological reactions due to noise exposures where long term adverse health effects are not expected. Evaluation criteria are provided for various protection goals, for hearing, communication and sleep, for the avoidance of annoyance and of suspected cardiovascular diseases. As protection of the residents is understood as a dynamic process, these criteria must be repeatedly tested and adapted to new scientific findings.

Aircraft↗
PubMedDate not supplied

Membrane transport of methotrexate in a squamous carcinoma cell line adapted to low folate concentrations.

Membrane transport characteristics of the folate analogue methotrexate (MTX) were studied in a human squamous carcinoma cell line of the head and neck (HNSCC) adapted to grow in tissue culture media with nanomolar reduced folate concentrations (SCC-11B-LF), as compared to SCC-11B cells grown in standard medium containing high folate concentrations. We observed that SCC-11B-LF cells exhibited a 10.5-fold increased uptake of [3H]-MTX via the reduced folate/MTX carrier system compared to SCC-11B cells. Affinity labelling of the reduced folate/MTX carrier system suggests that the up-regulation of [3H]-MTX transport mainly results from an increased rate of carrier translocation, and only to a minor extent (15-20%) from an increased amount of carrier protein. The upregulation of MTX transport resulted in a 2.4-fold increased growth inhibitory effect by MTX. These results suggest that membrane transport may play a more important role in MTX-cytotoxicity when SCC-11B cells in vitro are grown in more physiological folate concentrations.

Adaptation, Physiological↗