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Biomedical subjects

R Braun

Publications and source records attributed to R Braun.

At least 163 records · Page 9Linked to original sources
PubMed1983

Genetic and cytogenetic effects of 1,3-dimethyl-3-phenyl-1-nitrosourea in Salmonella typhimurium and Chinese hamster V79 cells.

1,3-Dimethyl-3-phenyl-1-nitrosourea (DMPNU) shows no spontaneous decomposition in aqueous buffered solution (pH 7.0) at 37 degrees C over a measuring period of 10 days, but it is directly genotoxic in all assays applied. This compound induces base substitutions in Salmonella typhimurium (especially in the plasmid harbouring strain TA 100), gene mutations at the HGPRT+ locus of Chinese hamster V79 cells, and is a very potent inducer of clastogenic damage and sister chromatid exchanges in V79 cells. Data on gene mutation induction by 1-methyl-1-nitrosourea are included for comparison. The findings on DMPNU are discussed in comparison with trialkylnitrosoureas. In contrast to these latter compounds, DMPNU is active without addition of S9 mix in vitro. It is assumed that its genotoxic activity is due to an intracellular catalytic degradation favoured by the electron-withdrawing effect of the phenyl group.

Animals↗
PubMed1983

Replication of herpes simplex virus in human T lymphocytes.

The replication of herpes simplex virus (HSV) in cultures of human T lymphocytes was investigated. Virus replication occurred only in lymphocyte cultures prestimulated with mitogen. At least one of the factors responsible for this phenomenon is adsorption of the virus to the cells, which was 5 times less efficient in nonstimulated cells than in stimulated cultures. Growth of virus in infected cultures was restricted to lymphocytes of T origin. This was shown by successful infection of highly purified T-cell cultures and by virus replication in four continuous T-cell lines. No virus production was obtained in cultures of lymphocytes of other than T-cell origin. Virus titers in T-lymphocyte cultures reached 10(7) PFU/ml, which was a four log10 step increase over the input dose. Lymphocytes infected with a syn strain of HSV, HSV-ANG, induced polykaryocyte formation in the cultures and therefore generated a CPE visible by microscopic examination. Infection with syn+ strains of HSV (i.e., strains which do not cause cell fusion) did not lead to such phenomena. Not more than 1% of infected T cells was replicating HSV, as revealed by infectious center assays. In contrast, about 5% of these cells showed positive immunofluorescence with anti-HSV antibodies, indicating the presence of cells which express viral protein but do not actively produce infectious virus.

Antigens, Viral↗
PubMed1982

Rapid separation of T cell subpopulations with monoclonal antibodies and affinity chromatography.

A rapid method for isolation of highly enriched helper and suppressor T cell subsets and their corresponding helper and suppressor cell depleted cell populations is described. The method is based on the binding of monoclonal antibodies to helper and suppressor cells and subsequent affinity chromatography with covalently bound rabbit anti-mouse antibodies. As assessed by indirect immunofluorescence, purity of the enriched subpopulations exceeds 90%, whereas no contamination with helper or suppressor cells is detectable in populations depleted of the respective subsets. The cells isolated by this method show no functional defects in helper and suppressor assays and respond with increased DNA synthesis to stimulation with phytohemagglutinin (PHA) plus 2-mercaptoethanol (2-ME).

Animals↗
PubMed1982

Sequence-specific cleavage of chromatin by staphylococcal nuclease can generate an atypical nucleosome pattern.

We have investigated the nucleosomal organization of ribosomal genes in the acellular slime mold Physarum polycephalum. When probed with staphylococcal nuclease, the ribosomal genes appear to be uniformly packed in nucleosomes, in an arrangement which is indistinguishable from the pattern obtained with bulk chromatin. During this study, an unusual pattern of digestion was obtained from a DNA region immediately upstream of the initiation site of rRNA transcription, in addition to the nucleosomal profile, a second regular ladder of fragments with a repeat length of 30-40 basepairs was generated from this region. We established that this pattern of degradation reflects the strong preference of staphylococcal nuclease for certain nucleotide arrangements on the DNA, rather than a particular chromatin configuration. These observations clearly show that great caution needs to be exerted whenever data from staphylococcal nuclease digestions are interpreted in terms of chromatin structure.

Base Sequence↗
PubMed1982

Activity of organophosphorus insecticides in bacterial tests for mutagenicity and DNA repair--direct alkylation vs. metabolic activation and breakdown. I. Butonate, vinylbutonate, trichlorfon, dichlorvos, demethyl dichlorvos and demethyl vinylbutonate.

The following organophosphates were tested for their ability to induce DNA damage in a rec-type repair test with Proteus mirabilis strains PG713 (rec- hcr-) and PG273 (wild type) and point mutations in his- strain TA100 of Salmonella typhimurium--butonate: O,O-dimethyl-(1-n-butyryloxy-2,2,2-trichloroethyl)-phosphonate; vinylbutonate: O,O-dimethyl-(n-butyryloxy-2,2-dichlorovinyl)-phosphonate; trichlorfon: O,O-dimethyl-(1-hydroxy-2,2,2-trichloroethyl)-phosphonate; dichlorvos: O,O-dimethyl-O-(2,2-dichlorovinyl)-phosphate; the demethylated derivatives--demethyldichlorvos: O-methyl-O-(2,2-dichlorovinyl)-phosphoric acid; demethyl vinylbutonate: O-methyl-(1-n-butyryloxy-2,2-dichlorovinyl)phosphonic acid. Of the six compounds tested, dichlorvos and trichlorfon induced base pair substitutions and DNA damage. No mutagenicity and DNA damage were found in experiments with butonate, vinylbutonate, demethyl vinylbutonate and demethyl dichlorvos. Genotoxic activity for dichlorvos and the absence of both mutagenic and RNA damaging properties for its non-alkylating demethyl derivative favors the hypothesis that alkylation of DNA is the essential step for mutation induction by this organophosphate. Furthermore, the absence of genetic effects after treatment with vinylbutonate and demethyl dichlorvos does not support a crucial role of vinyl or allyl groups in side chains of organophosphates for genetic activity. Microsomal enzymes decreased genetic activity of dichlorvos and trichlorfon in vitro. No evidence for a role of metabolic activation in the mutagenic activity of any of these compounds was found.

Alkylating Agents↗
PubMed1982

Comparison of different methods for assessment of rubella infection and immunity.

The different enzyme-linked immunosorbent assays (ELISA), a fluorescence immunoassay (FIAX), and a hemolysis-in-gel test (HIG) were examined for sensitive detection of specific antibodies in sera of persons with acute and previous rubella infection. In comparison to hemagglutination inhibition (HI), all tests were able to detect previously formed rubella antibodies. In sera of patients with acute rubella infection, only the FIAX system showed always positive results. Nevertheless, it remains unclear, if these findings are due to a higher sensitivity of the FIAX system or are possible non-specific results. In some cases, however, this test system failed to detect significant titre rises seen in HI, because it showed high antibody titres already in the first serum sample.

Antibodies, Viral↗
PubMed1982

[Influence of the mushroom poison gyromitrin on the lipids of rat liver (author's transl)].

Gyromitrin, the main poison of the false morel Gyromitra esculenta, causes enlargement of the liver in rats. The content of triglycerides and total cholesterol were increased in the liver homogenate and microsomal fraction but not in the mitochondrial fraction. On the other hand the content of phospholipids was found to be decreased. The enhanced incorporation of [14c]-acetate into the lipids of rat livers after gyromitrin indicates an increased rate of lipids synthesis. The diminution of the phospholipids is caused mainly by a loss of phosphatidyl ethanolamine (PE) although after a short pulse with [14C]-ethanolamine the specific radioactivity of the isolated phosphatidyl ethanolamine corresponded to that of the controls. Since the content of phosphatidylcholine (PC) remained unchanged, the PC/PE-ratio was shifted from 2.3 to 4.5. These effects were reversible within 48 h. Inhibition of the synthesis of highly unsaturated fatty acids by the microsomal monoxygenase system is discussed as the primary reason for the above observations this inhibition possibly being due to active metabolites of gyromitrin which destroy the monoxygenases.

Acetaldehyde↗
PubMed1981

Functional recovery and orthopedic management of brachial plexus palsies.

Functional recovery in 133 patients with brachial palsy is documented over a five-year period. Clinical examination is more reliable than electromyogram or myelogram for obtaining prognostic information. Erb's C V, VI palsies have improved function with cuff transfers and elbow flexor plasties. Posterior cord palsies often require extension plasties of the hand and glenohumeral fusions. C V, VI, VII palsies may require all of these procedures. Klumpke C VIII-T I palsies develop arm-trunk holding power. Adults with total palsies often complain of continued pain, which may be relieved by orthoses.

Adolescent↗
PubMed1981

[Frequency of Escherichia coli resistance in Switzerland].

Monitoring the drug resistance of bacteria is necessary at regional, national and international levels. Over a two-week period in October 1978, 2561 strains of Escherichia coli and coliforms were isolated from stool specimens obtained from 19 civilian institutions (1338 strains) and from 9 army training camps (1223 strains) located all over Switzerland. Only a few of the donors had undergone recent antimicrobial therapy. The bacterial strains were rapidly distributed among 7 Swiss army microbiological field laboratories and tested for resistance against ampicillin, gentamycin, tetracycline and cotrimoxazole by standard disc diffusion techniques. Criteria for the interpretation of inhibition zones were adapted from WHO and NCCLS guidelines. E. coli ATCC 25922 served as a control strain. The overall resistance rates of E. coli and coliforms were 18% for ampicillin, 0.3% for gentamycin, 33% for tetracycline and 4% for cotrimoxazole. Multiple drug resistance patterns involving these four drugs plus sulfisoxazole, streptomycin, kanamycin, chloramphenicol, cefalothin and colistin were analyzed. Many combinations of drug resistances occurred in far higher numbers than was expected from individual drug resistance frequencies, a fact which suggested linkage of resistance genes. The resistance frequencies observed were shown by several tests of reproducibility to be subject to a modest overall error of approximately 20%.

Adult↗
PubMed1981

Considerations on the carcinogenicity of the mushroom poison gyromitrin and its metabolites.

Monomethylhydrazine (MMH) and unsymmetrical dimethylhydrazine (UDMH), but not N-methyl-N-formylhydrazine (MFH), a mushroom poison, can be oxidized by the weak oxidant 2,6-dichlorophenolindophenol. Hydrogen peroxide is formed by this oxidation, and has been found to cause decay of DNA in aqueous solution as measured by the decreased viscosity of a DNA solution in the presence of the hydrazines. Furthermore, MMH and UDMH but not MFH inhibit the incorporation of [3H]thymidine and [3H]uridine into DNA and RNA of Ehrlich ascites carcinoma (EAC) cells. These experiments show that MFH is an inactive compound in contrast to MMH and UDMH. Since the hydrolysis rate of MFH, to produce MMH, is low, it is concluded that MFH must be activated in vivo into toxic metabolites which are ultimately responsible for the known high carcinogenicity of MFH.

Acetaldehyde↗
PubMed1981

Comparison of different methods for the detection of rubella-specific IgM antibodies.

The rubella specific IgM titer in the serum specimens originating from healthy persons and from patients with clinical signs of rubella infection was determined by hemagglutination inhibition or hemagglutination reduction after IgM separation with the following methods: (a) density gradient centrifugation; (b) polyacrylamide agarose gel chromatography; (c) ion exchange chromatography with diethylaminoethyl cellulose columns; (d) solid-phase immunosorbent technique using microplates; (e) solid-phase immunosorbent technique using polyacrylamide microimmunobeads. Alternatively, we removed IgG and IgA by the use of protein A, anti-IgG, and anti-IgA, covalently coupled to controlled-pore glass (f). The titers obtained by the different methods showed qualitatively good correlations when combined with mercaptoethanol reduction. The quantitative measurement of specific IgM titers, however, revealed a lower sensitivity of column chromatography and methods of removal of IgG/IgA.

Antibodies, Viral↗
PubMed1981

On interactions of cytostatic benzylidine hydrazines with SH-groups.

The cytostatic and mutagenic compound N'-methyl-N'-cyano-(p-chloro)-benzaldehyde hydrazone (CyB4) has been found to be a strong SH-blocking agent since it reacts with the thiol groups of glutathione and of the cell membrane of Ehrlich ascites carcinoma cells (EAC). Furthermore, it decreases the intracellular, non-proteinogenic SH(NPSH)-level of tumor cells. CyB4 is not able to alkylate 4-(p-nitrobenzyl)-pyridine (NBP) by a nucleophilic substitution reaction, but it could be shown that the reactivity of CyB4 with thiol groups is due to a Michael-addition-type reaction of SH-groups with the cyano-group of CyB4. On the other hand, cytostatic beta-chloroethyl hydrazones showed a negligible reactivity against glutathione and led even to an increase of thiol groups, detectable by the 5,5'-dithiobis-2-nitrobenzoic acid (DTNB)-method, at the cell membrane of EAC when incubated in the presence of beta-chloroethyl hydrazones N-benzylidene-N'-methyl-N'-(2-chloroethyl) hydrazine (B1) and N-(4-dimethylaminobenzylidene)-N'-methyl-N'-(2-chloroethyl) hydrazine (B2). Therefore, it is concluded that the cytostatic efficiency of CyB4 is due to its SH-blocking while that of the beta-chloroethyl hydrazones is due to a rearrangement of the tumor cell membrane, as indicated by the increased level of reactive SH-groups.

Alkylating Agents↗
PubMed1981

Rapid detection of rubella-specific IgM antibodies by the use of microimmunobeads (MIB-IgM).

A simple haemagglutination (HA) titre reduction assay for the detection of rubella-specific IgM antibodies has been developed. Serum IgM is rapidly isolated by immune adsorption to heavy chain-specific anti-human IgM antibodies covalently coupled to polyacrylamide microimmunobeads. The immobilized immunocomplexes are incubated with rubella virus HA antigen. Subsequently, the particles are centrifuged from the solution, and the reduction of the HA titre is determined. This procedure has proven to be as reliable as haemagglutination inhibition (HAI) tests carried out with IgM fractions separated on a sucrose density gradient.

Antibodies, Viral↗
PubMed1981

The toxicology of 1-acetyl-2-methyl-2-formyl hydrazine (Ac-MFH).

The hepatotoxic and cancerogenic N-methyl-N-formyl hydrazine (MFH), which is formed from the mushroom poison, gyromitrin, by hydrolytic cleavage in vivo and in vitro during food processing, loses its hepatotoxicity and its influence on the renal function of rats after acetylation at the free NH2-moiety. The importance of MFH-acetylation with regard to an inhibition of microsomal conversion of MFH into a toxic nitrosamide is considered. The known genetically determined heterogeneity of the acetylation rate for hydrazine derivates in man may explain the observed differences in sensitivity towards the mushroom toxins.

Animals↗
PubMed1981

Influence of the immunomodulating compound BM 12.531 (azimexone) on radioresistance and granulopoietic colony forming units in mice.

BM 12.531 (azimexone) increases the survival of mice exposed to 650 rad. Levamisole, isoprenosine or aristolochia acid have no effects in this system. After administration of 25 mg/kg azimexone to C57 Bl/6-mice a statistically significant increase in CFUc was found. Maybe this increase in CFUc can explain the radioprotective effect of azimexone.

Adjuvants, Immunologic↗