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Biomedical subjects

W Schumacher

Publications and source records attributed to W Schumacher.

At least 19 recordsLinked to original sources
PubMed1998

Dehalobacter restrictus gen. nov. and sp. nov., a strictly anaerobic bacterium that reductively dechlorinates tetra- and trichloroethene in an anaerobic respiration.

The highly enriched anaerobic bacterium that couples the reductive dechlorination of tetrachloroethene to growth, previously referred to as PER-K23, was obtained in pure culture and characterized. The bacterium, which does not form spores, is a small, gram-negative rod with one lateral flagellum. It utilized only H2 as an electron donor and tetrachloroethene and trichloroethene as electron acceptors in an anaerobic respiration process; it could not grow fermentatively. Acetate served as a carbon source in a defined medium containing iron as the sole trace element, the two vitamins thiamine and cyanocobalamin, and the three amino acids arginine, histidine, and threonine. The cells contained menaquinones and b-type cytochromes. The G+C content of the DNA was 45.3 +/- 0.3 mol%. The cell wall consisted of type-A3gamma peptidoglycan with ll-diaminopimelic acid and one glycine as an interpeptide bridge. The cells are surrounded by an S-layer; an outer membrane was absent. Comparative sequence analysis of the 16S rRNA sequence showed that PER-K23 is related to gram-positive bacteria with a low G+C content of the DNA. Based on the cytological, physiological, and phylogenetic characterization, it is proposed to affiliate the isolate to a new genus, Dehalobacter, with PER-K23 as the type strain of the new species Dehalobacter restrictus.

Anaerobiosis↗
PubMed1997

Redox chemistry of cobalamin and iron-sulfur cofactors in the tetrachloroethene reductase of Dehalobacter restrictus.

Respiration of Dehalobacter restrictus is based on reductive dechlorination of tetrachloroethene. The terminal component of the respiratory chain is the membrane-bound tetrachloroethene reductase. The metal prosthetic groups of the purified enzyme have been studied by optical and EPR spectroscopy. The 60-kDa monomer contains one cobalamin with Em(Co[1+/2+]) = -350 mV and Em(Co[2+/3+]) > 150 mV and two electron-transferring [4Fe-4S](2+;1+) clusters with rather low redox potentials of Em approximately -480 mV. The cob(II)alamin is present in the base-off configuration. A completely reduced enzyme sample reacted very rapidly with tetrachloroethene yielding base-off cob(II)alamin rather than trichlorovinyl-cob(III)alamin.

Bacteria, Anaerobic↗
PubMed1997

Contaminated environments in the subsurface and bioremediation: organic contaminants.

Due to leakages, spills, improper disposal and accidents during transport, organic compounds have become subsurface contaminants that threaten important drinking water resources. One strategy to remediate such polluted subsurface environments is to make use of the degradative capacity of bacteria. It is often sufficient to supply the subsurface with nutrients such as nitrogen and phosphorus, and aerobic treatments are still dominating. However, anaerobic processes have advantages such as low biomass production and good electron acceptor availability, and they are sometimes the only possible solution. This review will focus on three important groups of environmental organic contaminants: hydrocarbons, chlorinated and nitroaromatic compounds. Whereas hydrocarbons are oxidized and completely mineralized under anaerobic conditions in the presence of electron acceptors such as nitrate, iron, sulfate and carbon dioxide, chlorinated and nitroaromatic compounds are reductively transformed. For the aerobic often persistent polychlorinated compounds, reductive dechlorination leads to harmless products or to compounds that are aerobically degradable. The nitroaromatic compounds are first reductively transformed to the corresponding amines and can subsequently be bound to the humic fraction in an aerobic process. Such new findings and developments give hope that in the near future contaminated aquifers can efficiently be remediated, a prerequisite for a sustainable use of the precious-subsurface drinking water resources.

Benzene Derivatives↗
PubMed1996

Nutritional intake of 2868 IDDM patients from 30 centres in Europe. EURODIAB IDDM Complications Study Group.

The EURODIAB IDDM Complications Study, a cross-sectional, clinic-based study, was designed to measure the prevalence of diabetic complications in stratified samples of European insulin-dependent diabetic (IDDM) patients. As diet may be related to diabetic complications, nutritional intake was analysed in the study population. The aims of this first nutritional paper are to describe the nutrient intake in 2868 IDDM patients from 30 centres in 16 countries throughout Europe, to investigate the degree of regional differences in nutrient intake and to compare current intakes with recommended levels. Nutritional intake from 1458 male and 1410 female IDDM patients was assessed by a validated 3-day record (two weekdays, Sunday) and centrally analysed. Mean energy intake for all patients was 2390 +/- 707 kcal/day. Mean protein intake was 1.5 +/- 0.5 g/kg body weight. Carbohydrate intake was 43% and fibre intake 18 g/day. Alcohol intake for the total cohort was 2% of energy. Total fat contributed 38% of energy, with 14% from saturated fat. The Italian centres reported lower total and saturated fat intakes compared with other centres. Recommendations from the Diabetes and Nutrition Study Group of the EASD for total fat, saturated fatty acids and carbohydrate were only achieved by 14%, 14% and 15% of patients, respectively. The data of the present study clearly indicate current problems in the nutritional intake of European IDDM patients. These findings contribute to the definition of future targets in the nutritional management of IDDM patients, to be achieved as part of the initiatives taken by the St. Vincent Declaration action programme.

Adolescent↗
PubMed1996

The proton/electron ration of the menaquinone-dependent electron transport from dihydrogen to tetrachloroethene in "Dehalobacter restrictus".

In the anaerobic respiration chain of "Dehalobacter restrictus," dihydrogen functioned as the electron donor and tetrachloroethene (PCE) functioned as the electron acceptor. The hydrogenase faced the periplasm, and the PCE reductase faced the cytoplasmic side of the membrane. Both activities were associated with the cytoplasmic membrane. UV spectroscopy showed that membrane-bound menaquinone (MQ) was reduced by oxidation of H2 and reoxidized by reduction of PCE, indicating that MQ functions as an electron mediator. Fast proton liberation (t1/2 = 6 +/- 2 s) during electron transport from H2 to PCE and to trichloroethene (TCE) after addition of either PCE or TCE to H2-saturated cells resulted in an extrapolated H+/e- ratio of 1.25 +/- 0.2. This ratio indicated that besides the formation of protons upon oxidation of H2, vectorial translocation of protons from the inside to the outside could also occur. Proton liberation was inhibited by carbonylcyanide m-chlorophenylhydrazone (CCCP), 2-n-heptyl-4-hydroxyquinoline N-oxide (HOQNO), and CuCl2. Fast proton liberation with an H+/e- ratio of 0.65 +/- 0.1 was obtained after addition of the MQ analog 2,3-dimethyl-1,4-naphthoquinone (DMN) as an oxidant pulse. This acidification was also inhibited by CCCP, HOQNO, and CuCl2. Oxidation of reduced DMN by PCE was not associated with fast acidification. The results with DMN indicate that the consumption and release of protons associated with redox reactions of MQ during electron transfer from H2 to PCE both occurred at the cytoplasmic side of the membrane. The PCE reductase was photoreversibly inactivated by 1-iodopropane, indicating that a corrinoid was involved in the PCE reduction.

Bacteria↗
PubMed1994

Ammonia-forming cytochrome c nitrite reductase from Sulfurospirillum deleyianum is a tetraheme protein: new aspects of the molecular composition and spectroscopic properties.

Ammonia-forming cytochrome c nitrite reductase from Sulfurospirillum deleyianum contains four covalently bound heme c groups/55 kDa subunit as determined by atomic absorption spectroscopy and the pyridine Fe(II)-hemochrome technique. Nitrite reductase was isolated from the membrane fraction as a monomer (M(r) 55 +/- 2 kDa) and as a heterooligomeric complex. Both the monomeric and the complex form of the enzyme exhibited a high specific activity, with up to 1050 mumol NO2-min-1 mg-1. The complex was built from four 55 kDa units and contained a 22 kDa c-type cytochrome which was absent in the monomeric form. EPR spectra of the complex displayed a prominent feature at g 4.83 (baseline crossing). This resonance, which was not observed in the spectra of the monomeric nitrite reductase, was assigned to the 22 kDa c-type cytochrome subunit. Identical results were obtained for the enzyme from Wolinella succinogenes which had been reinvestigated for comparison.

Bacteria↗
PubMed1994

Reductive dehalogenation as a respiratory process.

Anaerobic bacteria can reductively dehalogenate aliphatic and aromatic halogenated compounds in a respiratory process. Only a few of these bacteria have been isolated in pure cultures. However, long acclimation periods, substrate specificity, high dehalogenation rates, and the possibility to enrich for the dehalogenation activity by subcultivation in media containing an electron donor indicate that many of the reductive dehalogenations in the environment are catalyzed by specific bacteria. Molecular hydrogen or formate appear to be good electron donors for the enrichment of such organisms. Furthermore, systems have to be employed which supply the cultures with the halogenated compounds beyond their toxicity level. All bacteria that are presently available in pure culture and grow with a halogenated compound as electron acceptor are members of new genera. Based on experimental results with the membrane-impermeable electron mediator methyl viologen, a model of the respiration system of Dehalobacter restrictus, a tetrachloroethene-dechlorinating bacterium, is presented. Further studies of the biochemistry and energetics of respiratory-dehalogenating strains will help to understand the mechanisms involved and perhaps reveal the evolutionary origin of the dehalogenating enzyme systems.

Anaerobiosis↗
PubMed1994

[Pneumothorax in laparoscopic cholecystectomy (II)].

This case report deals with pneumothorax during elective laparoscopic cholecystectomy in a young woman with no history of severe pulmonary disease. After inflating the capnoperitoneum, pulse oximetry and capnography raised suspicion of pneumothorax whereas the physical examination showed no irregularities. Surgical drapes provided a lack of information from percussion and auscultation. Changing respiratory parameters including the use of pressure-controlled ventilation in absence of tension pneumothorax enabled sufficient ventilation until the insertion of a chest tube. There were no further postoperative complications. Pulse oximetry, capnography and relaxometry proved helpful in monitoring. There may be a benefit from the use of pressure-controlled-ventilation in certain situations, if all changes in volume-controlled-ventilation fail.

Carbon Dioxide↗
PubMed1993

Antineoplastic activity and tolerability of a novel heterocyclic alkylphospholipid, D-20133.

Octadecyl-[2-(N-methylpiperidinio)ethyl]-phosphate (OMPEP, D-20133), a heterocyclic analogue of hexadecylphosphocholine (MIL), has been synthesized in an attempt to increase the therapeutic range of the parent compound. The antineoplastic activity of the novel alkylphospholipid was compared with that of MIL in dimethylbenz(a)anthracene-induced mammary carcinoma of the rat. Using tumors of different sizes and repeated daily doses as well as high single doses, we achieved marked remissions with either compound. However, the therapeutic range of OMPEP was broader than that of the parent drug. Furthermore, the emetic potential of OMPEP tested on ferrets was distinctly less pronounced than that of MIL. In vitro the new alkylphospholipid proved to be more active than MIL in all cell lines tested, and its differentiation-inducing capacity turned out to be superior to that of MIL. No hematological toxicity was observed at various OMPEP doses during a 3-week treatment period.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1993

Effects of D-penicillamine on human cell lines.

The effect of penicillamine on the proliferation and viability of human T, B and premacrophage/promyelocytic cell lines was evaluated. Whereas Raji cells and U937 cells were not negatively influenced by the addition of 0.03-0.97 mmol/l D-penicillamine (D-Pen, Trolovol, CAS 52-67-5), other cell lines such as H9, NC37 and HL60 were clearly impaired by concentrations between 0.12 and 0.49 mmol/l. Similar effects on the uptake of 3H-thymidine, 3H-uridine and 3H-leucine were observed with the addition of other stereoisomeric forms of penicillamine, D,L- and L-penicillamine to H9 cell cultures. The evaluation of cell number and viability by light microscopy revealed similar actions of penicillamine on cell cultures. By these means its repressing effect on Jurkat, NC37 and even on U937 became more transparent.

B-Lymphocytes↗
PubMed1990

D-19466, a new cyclobutane-platinum complex with antitumor activity.

D-19466, a new platinum complex, was characterized. It showed no nephrotoxic side-effects as determined by the measurement of blood urea. It was cytotoxic in vitro for tumor cells in concentrations comparable to or lower than cytotoxic concentrations of cisplatin. It had excellent anticancer activity in vivo against a number of murine experimental tumors, including a cisplatin-resistant P388 line. Clinical evaluation of this compound has therefore been initiated.

Animals↗
PubMed1988

Characterization of the antitumor activity of hexadecylphosphocholine (D 18506).

Hexadecylphosphocholine (HPC) differs from ether lipids with known antitumor activity by its lack of the glycerol part. In the experiments described here HPC revealed outstanding antitumor activity in dimethylbenzanthracene (DMBA)-induced rat mammary tumors. A dose-response relationship was seen after daily oral treatment with complete suppression of tumor growth at doses of 46.4 mg/kg/day. There was no schedule dependence and the therapeutic efficacy was independent of the tumor weight at the initiation of therapy. Another autochthonous tumor, the benzo[a]pyrene-induced sarcoma of the rat did not respond to HPC treatment, indicating a highly selective spectrum of activity of the test compound. In comparison to an optimal single dose of cyclophosphamide, a single high dose of HPC was considerably more active against the DMBA tumor. At therapeutic dose levels no major toxicity of HPC was observed. Bone marrow suppression was not encountered, on the contrary, at high doses leukocytosis became apparent. The available pharmacological and toxicological data suggest that HPC may be useful in the treatment of human cancer.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1987

New technique for treating occlusive and stenosing tumours of the trachea and main bronchi: endobronchial irradiation by high dose iridium-192 combined with laser canalisation.

A new technique is described for treating patients with inoperable malignant tumours causing occlusion or stenosis of the trachea or main bronchi. High dose iridium-192 (20 Ci) was introduced by an afterloading device under computer control via a 4 mm delivery tube into the tumour mass. In 29 of the 56 patients the tumour mass was canalised by a neodymium-YAG laser immediately before the afterloading delivery tube was introduced. In 44 (79%) of the patients, there was impressive relief of dyspnoea, accompanied by tumour regression observed at endoscopy and also by highly significant improvement in ventilatory function values, lung perfusion scans, and levels of arterial oxygen tension. In the other 12 patients (21%) there was no detectable improvement. The findings suggest that this recently developed combination treatment is of value in patients with advanced tumours of the trachea and main bronchi in whom there is no possibility of further treatment by external irradiation or repeated laser coagulation.

Aged↗