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Biomedical subjects

R Braun

Publications and source records attributed to R Braun.

At least 181 records · Page 10Linked to original sources
PubMed1981

[Echocardiographic septal motion in 50 patients with coronary artery disease. A correlative study with coronary angiographic findings (author's transl)].

The literature about pathological septal motion in coronary artery disease is contradictory. Purpose of this study was to reveal the sensitivity and specificity of the echocardiography for diagnosis of stenoses and occlusions (S/O) of the left anterior descending artery (LAD). 50 patients with CAD were studied using coronary angiography and echocardiography. In 32 of the cases a critical stenosis (over 70% narrowing) of the LAD was present. History of old infarction was found in 80% of the patients. Angina pectoris was absent at the time of the investigation. It was proven that the sensitivity of the echocardiography for the diagnosis of coronary stenoses and for proximal and peripheral LAD-S/O is not high (44%-61%). 50 percent of all LAD-S/O and 61% of the proximal LAD-S/O have a pathological septal movement. In presence of a pathological septal motion, however, it may be concluded that there is a critical stenosis in one or more of the three main coronary arteries (predictive value 91%). The diagnosis of the localization of the occlusion by echocardiography is not possible. 1/3 of peripheral LAD-S/O also lead to a dyscinetic septum which mostly is found in proximal LAD-S/O. The number of false positive (pathological) echocardiographic septal dyscinetic motion is low (12%). The sensitivity of echocardiographic method for diagnose of coronary alteration is increased when using the differentiation between stenosis and occlusion of LAD. By that it can be revealed that full occlusions of the LAD lead in 80% to septal dyscinetic motion, whereas stenoses are only rarely combined with pathological septum (36%). It is concluded that not only the localization but predominantly the degree of the vessel-narrowing influences the septal movement. Perhaps these findings may help to declare the contradictory results in literature.

Adult↗
PubMed1980

Processing of ribosomal precursor RNAs in Physarum polycephalum.

The processing of intermediates of Physarum rRNA has been investigated using two cloned rDNA restriction fragments as sequence specific probes. The size of the largest stable pre-rRNA detected is 11.8 Kb, as determined by denaturing gel electrophoresis. R-loop analysis revealed that this pre-rRNA fraction mainly consists of transcripts which do not contain the two insertion sequences present in the 26 S gene. However, a small number of molecules are found which still contain one or the other, or both, of these introns. These observations suggest that the two introns are transcribed but spliced out in a random order before RNA synthesis has reached the 3-end of the primary transcript. Transcription starts at about 17.7 Kb and stops at 4.4 Kb as measured from the ends of the linear palindromic rDNA molecule. Besides the 11.8 Kb transcript several further ribosomal RNA precursors have been identified, ranging in size from 2.5 to 8.8 Kb. In addition, the genes for 5.8 S RNA have been located by R-loop mapping.

Cloning, Molecular↗
PubMed1980

Testing of drugs for combined mutagenesis with sodium nitrite in the host-mediated assay.

Mutagenic activity of the drugs analgine and aminophenazone was tested in the intraperitoneal and intrasanguine host-mediated assay after oral application together with equimolar doses of sodium nitrite. Salmonella typhimurium strain G46 was used as genetic indicator system; mice served as host animals for the bacteria. Analgine was found to be weakly mutagenic in the dose 2 mM/kg together with nitrite, aminophenazone was a strong mutagen in combination with nitrite in the doses 2 mM/kg and 0.2 mM/kg using the intrasanguine test with 1 h incubation of bacteria in the liver. In the intraperitoneal variant with 3 h incubation time of bacteria only aminophenazone was slightly mutagenic at the highest dose tested, 2 mM/kg. The relative nitrosation rate for aminophenazone was calculated by means of regression lines for mutagenic activity of dimethylnitrosamine and was found to be in the range of 2% in both systems for a dose of 2 mM/kg precursors.

Aminopyrine↗
PubMed1979

Mutagenic activity of cytostatic methyl hydrazones with different strains of Salmonella typhimurium.

Experiments are performed to ascertain the mutagenic properties of four new cytostatic methyl-hydrazones in the Ames test using different strains of Salmonella typhimurium. As could be demonstrated all four hydrazones are mutagenic per se without a metabolic activation through rat liver microsomes (S-9 fraction). Whereas the beta-chloroethyl hydrazones B1 and B2 cause a base-pair substitution with the strains TA100 and TA1535 the methyl-hydrazones EB4 and CyB4 both cause base-pair substitution with TA100 and frameshift mutation with TA98. At both strains the mutagenic activity of Cy84 ist powerful. Furthermore, no relation could be detected between the mutagenic properties of the methyl-hydrazones and their alkylating behaviour on 4-(4-nitrobenzyl)-pyridine.

Methylhydrazines↗
PubMed1979

Accessibility of the ribosomal genes to micrococcal nuclease in Physarum polycephalum.

In Physarum polycephalum most genes coding for ribosomal RNA are not integrated in chromosomes, but are located in many copies in the nucleolus as plasmid-like palindromic DNA molecules. To find out whether coding sequences of rDNA are organized in a chromatin-like structure similar to that of bulk chromatin, nuclei were treated with micrococcal nuclease and DNA fragments were isolated. From bulk chromatin multimers of a basic unit of 170-180 base pairs were obtained. Nuclease fragmented DNA hybridized with labelled 19-S + 26-S rRNA was found to give the same saturation value as did unfragmented control DNA. No preferential degradation of ribosomal genes to acid soluble products was observed. A more detailed analysis of the nuclease degradation products was carried out with fragments separated by preparative gel electrophoresis. DNA eluted from the gels was hybridized in solution with labelled 19-S + 26-S rRNA. The coding sequences of rRNA were found to be degraded to approximately nucleosome size slightly more quickly than was the DNA of bulk chromatin. However, the distribution of the rDNA fragments on the gels did not coincide with the distribution of the fragments derived from bulk chromatin nucleosomes and their oligomers. The amount of rDNA in the interband regions was about intermediate between that found in the two adjacent bands. These results lead to the conclusion that the ribosomal genes, most of which are presumably active during rapid growth, are protected by proteins, probably histones. However, the ribosomal genes are present in a structure differing in some way from that of bulk chromatin.

DNA↗
PubMed1979

Isolation of a minichromosome containing the ribosomal genes from Physarum polycephalum.

The ribosomal genes of Physarum polycephalum are located on linear DNA molecules (rDNA) of 38 x 10(6) daltons present in each nucleolus in 100--200 copies. The rDNA is not part of the large chromosomal DNA. These molecules have now been solubilized in the form of transcriptionally active deoxyribonucleoprotein complexes from nucleoli purified through Percoll gradients. The ribosomal chromatin (rDNP) sediments in sucrose gradients as a homogeneous fraction with an approximate sedimentation coefficient of 100 S. It contains alpha-amanitin-resistant RNA polymerase I activity and rDNA as its major (or sole) DNA component. Buoyant density analysis indicates that ribosomal chromatin contains, besides RNA polymerase I, significant amounts of additional protein. RNA synthesized in vitro by the endogenous RNA polymerase is complementary to rDNA and is transcribed mainly from the sequences coding for 19S and 26S ribosomal RNA.

Amanitins↗
PubMed1979

[The influence of cytostatic and immunosuppressive methyl hydrazones on myelo- and lymphopoiesis in vitro (author's transl)].

The cytostatic and immunosuppressive N'-methyl-N'-beta-chloroethylbenzaldehyde hydrazones B1 and B2 inhibit the colony growth of mouse bone marrow cells and PHA-stimulated human lymphocytes in vitro in a dose-dependent manner. In the presence of B1, however, in contrast to B2, the inhibition of 3H-thymidine (3H-Tdr) uptake by the bone marrow cells and lymphocytes is insignificant. Two further benzaldehydrazones CyB4 and EB4 show little or no influence both on clony growth and nucleoside uptake. On the other hand, CyB4 inhibits the 3H-Tdr uptake by ConA- or LPS-stimulated mouse spleen cells to a gretaer degree than does B1 or B2, although CyB4 unlike B1 or B2 does not display any immunosuppressive effects in the mouse. These findings demonstrate that the 3H-Tdr method is less sensitive than the colony assays and is hence only of limited value as a measure of the vitro proliferation of mammalian cells treated with cytostatics.

Animals↗
PubMed1979

Liver injury by the false morel poison gyromitrin.

After oral application of the mushroom poison gyromitrin a time and dose dependent decrease of cytochrome P-450 was found in rat liver microsomes. The maximal decrease to about 50-60% of the control (after 200 mg/kg, 80% of LD50) was observed 8-12h after application, a normalization after 48 h. The inhibition of cytochrome P-450 mediated metabolism of aminopyrine and p-nitroanisole corresponds to the decrease of cytochrome P-450. The specific activity of cytochrome P-450 remains unchanged while that of cytochrome P-448 is decreased as shown by means of the metabolism of ethoxycoumarin or ethoxyresorufin. Comparable results were obtained after application of N-methyl-N-formylhydrazine (MFH) which is formed from gyromitrin rapidly by hydrolysis. An attack on the endoplasmatic membrane with a stimulation of lipid peroxidation is discussed.

Acetaldehyde↗
PubMed1979

Polyamine-mediated phosphorylation of a nucleolar protein from Physarum polycephalum that stimulates rRNA synthesis.

An acidic nucleolar phosphoprotein with a subunit M(r) of 70,000 was purified as an apparent dimer of 139,000 from isolated nuclei of the slime mold Physarum polycephalum. The protein was purified without the aid of strong dissociating agents after its selective phosphorylation in isolated nuclei by a polyamine-mediated reaction. Its amino acid composition resembled that of a nucleolar phosphoprotein from Novikoff hepatoma ascites cells. The phosphoprotein stimulated rRNA synthesis 5-fold by RNA polymerase I within a nucleolar, ribosomal deoxyribonucleoprotein complex isolated from nucleoli of P. polycephalum. It was also identified as a component of the complex. It bound with high affinity and specificity to the palindromic ribosomal DNA of 38 x 10(6)M(r) from P. polycephalum, which contained two coding sequences for 5.8S, 19S, and 26S rRNA. It also bound to three fragments of ribosomal DNA of M(r) 21.2 x 10(6), 17.1 x 10(6), and 8.1 x 10(6), prepared by cleavage with restriction endonucleases HindIII, PstI, and BamHI, respectively. All of these fragments included the symmetry axis of the palindromic ribosomal DNA. The phosphoprotein that had been treated with alkaline phosphataseagarose to hydrolyze the phosphate groups did not stimulate transcription and did not bind to ribosomal DNA or to the restriction fragments indicated. We have thus isolated a specific phosphoprotein with the capacity to stimulate transcription of a specific set of genes in a eukaryote. These findings suggest that this phosphoprotein may specifically regulate functions of ribosomal DNA in a manner dependent on its degree of phosphorylation.

Amino Acids↗