Search PubMed⌕ Search

Biomedical subjects

M Hartung

Publications and source records attributed to M Hartung.

At least 55 records · Page 3Linked to original sources
PubMed1984

The association of the nucleolus and the short arm of acrocentric chromosomes with the XY pair in human spermatocytes: its possible role in facilitating sex-chromosome acrocentric translocations.

Sex vesicle-nucleolus association was observed in 12% of zygotene and pachytene human spermatocytes using Giemsa and NOR-silver stained preparations. The silver-positive area of the nucleolus, corresponding to the nucleolus organizer (NOR), was usually close to the XY pair. C-banding frequently showed the terminal chromomere, formed by the condensed short arm of an acrocentric bivalent, attached to the sex vesicle. When a nucleolus produced by transcription of rDNA was connected to the short arm, it seemed to be secondarily associated with the sex vesicle. Non-transcribed ribosomal genes, which did not form a nucleolus, were revealed by in situ hybridization. Autoradiographs showed the rDNA-containing short arm of acrocentric bivalents associated with the sex vesicle in 18% of spermatocytes. The difference with the frequency of nucleolus-XY pair association was partially explained by the presence of inactive ribosomal genes. Moreover, electron microscopy showed that the dimensions of the newly formed nucleoli at early zygotene did not exceed 0.5 micron; they can be missed in light microscope investigations. From early zygotene to late pachytene, close relationships were observed between the sex vesicle chromatin and that of the associated acrocentric bivalent, especially in the short arm region. These relationships might explain the frequent involvement of acrocentrics in Y-autosome and X-autosome translocations occurring during male meiosis.

Cell Nucleolus↗
PubMed1984

Distribution of fibrillar centers and silver-stained components in the nucleolus of human Sertoli cells.

The nucleolus of the human Sertoli cell consistently showed three distinct, spontaneously segregated parts: 1. one or two large, silver-positive fibrillar centers; 2. strands of dense fibrillar component continuous with the dense cords surrounding the fibrillar center. These components were also silver-positive; 3. a granular, silver-negative mass. These observations show that in the human Sertoli cell the number of fibrillar centers is far lower than the diploid number of NORs. They also suggest that the fibrillar center might contain several NORs in this cell type.

Cell Nucleolus↗
PubMed1984

Biological monitoring in the metal working industry.

N-Nitrosodiethanolamine (NDELA) is a strong carcinogen in animal experiments. Its occurrence in cutting and grinding fluids represents a major risk for workers who come into contact with those compounds. But until now it was not possible to describe the extent of N-nitrosodiethanolamine exposure at the workplace. Since 60-90% of N-nitrosodiethanolamine given by oral, intravenous, epicutaneous or intratracheal application in rat experiments is excreted unchanged in the urine, N-nitrosodiethanolamine should be found in the urine of workers in the metal working industry. Analyses of grinding fluids containing di- and triethanolamine in combination with up to 30% nitrite showed concentrations of up to 593 mg/kg N-nitrosodiethanolamine in the original, concentrated fluid and up to 90 mg/kg in ready-to-use emulsions. In preliminary investigations, it was also found in the urines of metal grinders: of 264 urines analysed, 166 showed positive results (greater than 0.5 micrograms/kg) with levels up to 103 micrograms/kg N-nitrosodiethanolamine. These results indicate that workers' exposure to NDELA can be monitored by urine analysis.

Air Pollutants, Occupational↗
PubMed1983

Association of centromeric heterochromatin with the nucleolus in mouse Sertoli cells.

In adult Sertoli cells of most strains of mice, all the centromeric heterochromatin is condensed in two chromocenters, one on each side of a single, large nucleolus. In a random-bred Swiss OF-1 strain, however, the nucleus has a different structural organization. Part of the heterochromatin Is seen as chromocenters in contact with the nucleolus; the rest of it is dispersed in granules of unequal size in the nucleoplasm. Such an unusual spatial arrangement of heterochromatin in interphase nucleus cannot be explained either by a difference in the nucleolar organizing regions or by a polymorphism of the C-banding of metaphase chromosomes.

Animals↗
PubMed1983

Structural basis for Robertsonian translocations in man: association of ribosomal genes in the nucleolar fibrillar center in meiotic spermatocytes and oocytes.

The spatial relationships of acrocentric chromosomes were studied during prophase I of meiosis in human oocytes and spermatocytes by using cytogenetic techniques, electron microscopy, and in situ hybridization. Ultrastructural investigations revealed an ordered arrangement of nucleolar bivalents at the zygotene and pachytene stages. The end of the bivalent corresponding to the cytological satellite was consistently attached to the nuclear envelope. The fibrillar center of the nucleolus always contained rDNA chromatin fibers emanating from the secondary constriction region. Association of ribosomal genes from two bivalents in the same fibrillar center was frequently observed. Ultrastructural studies demonstrated the close proximity of chromatids in the short arm region of the involved nonhomologous acrocentrics. A breakage/reunion model based on our data can explain the formation of all observed types of Robertsonian translocations: monocentrics and dicentrics with or without rDNA.

Cell Nucleolus↗
PubMed1983

Nucleoli, micronucleoli, and nucleolus-like structures in human oocytes at meiotic prophase I studied by the silver-NOR technique.

Meiotic nuclei preparations obtained from human fetal ovaries were studied with the silver-NOR technique. At leptotene, the NOR's were located at the periphery of the nucleoli. The mean number of NOR's per nucleus was 6.4. Moreover, 2-12 micronucleoli, each containing an Ag-positive zone, were observed. At pachytene, each nucleolus was divided into two zones, one of which was Ag-positive. The mean number of Ag-positive zones was 2.1 per nucleus. The subterminal region of the short arm of nucleolar bivalents was in contact with the argyrophilic nucleolar zone. In most cells, micronucleoli were dispersed between the bivalents. A single rounded body which stained heavily with silver was consistently observed. At early diplotene, the NOR's separated, appearing again as distinct rounded Ag-positive structures embedded in the peripheral part of the nucleoli. The silver-stained round body was still visible. Eight to twelve micronucleoli were observed. At a more advanced stage of diplotene, the number of micronucleoli increased, varying from 20 to 50 per nucleus. These observations suggest that the micronucleoli, already visible at the leptotene stage, are the morphological expression of an early transcription of amplified rDNA. The biological significance of the Ag-positive round body remains obscure, but the consistency of its appearance suggests that it has a specific function somehow related to nucleolar proteins.

Cell Nucleolus↗
PubMed1983

[Experimental study on the activity of the triazolo-benzodiazepine GP 55 129 compared with diazepam and placebo in healthy volunteers].

Animal studies have led to the hypothesis that GP 55 129 sedates less than diazepam while possessing the same anxiolytic qualities. This hypothesis was tested on 60 healthy, emotionally labile volunteers. The drugs were administered once in a double-blind test at a dosage of 10 mg diazepam and 4 mg GP 55 129. A video camera and very difficult tests were used to induce anxiety in the subjects. Multivariate analysis of the 15 factors in the adjective check list showed a global drug effect (P less than 0.025). Comparison of the profiles of mean values indicated that the subjects under diazepam felt more tired and groggy than those with GP 55 129 and placebo medication at the dosage level used. However, the individual comparisons were not statistically significant. There was a significant reduction for both drugs in relation to the placebo in the "excitation" factor of the polarity profile. Free description showed a typical tranquilizer profile for both drugs. Significant achievement decrements (concentration-performance test by Düker, Viennese determination instrument, pursuit rotor, critical flicker fusion frequency) were not evident for either drug after a single dose of the strength we were examining. Subjective verbal tests yielded some significant sex differences without showing any interaction between sex and drug. To summarize the results, it can be said that the new substance possesses tranquilizing effects marked by a general suppression of excitation. The profile differences on the adjective check list showed a trend toward confirmation of the hypothesis, but must be replicated in further tests.

Anti-Anxiety Agents↗
PubMed1983

[Pulmonary fibrosis caused by hard-metal dusts].

Hardmetals are broadly used in many different branches. In the FRG lung fibrosis caused by hardmetal-dust are recognized as occupational diseases (no. 4107). New findings concerning pathogenesis of this disease should be considered. Not only the dust of the presintered material is hazardous but also the inhalation of the sintered material. There is a special risk for tool-grinders. Cobalt is suspected to be the causal agent. In tool-grinders an elevated external and internal Cobalt-burden has been objectified. We report about 14 persons who suffered from lung fibrosis and worked in the hard metal industry. X-ray and pathohistological examinations may give some hints but there is no specific histological correlate. So the notifying procedure may be difficult. For this reason any case of aetiologically unknown lung fibrosis the lung biopsy and quantitative chemical analysis using AAS should be performed. In one patient the Cobalt-level in lung-tissue was significantly elevated. Toleration of invasive diagnostic measurements can not be demanded. Tool-grinders need more medical surveillance in future. As a preventive strategy the cobalt-exposure is to be reduced to a minimum. The external cobalt-burden at work-place can be estimated by the determination of the renal Cobalt-excretion.

Adult↗
PubMed1982

On the question of the pathogenetic importance of cobalt for hard metal fibrosis of the lung.

Pulmonary fibrosis in hard metal grinders has been observed to an increasing degree in recent years. Most authors attribute the cause of this disease to the influence of the cobalt contained in hard metals. The present case dealt with a 36-year-old man who had been exposed to the grinding dust from sintered hard metal parts for more than 10 years. Biopsy of the lung revealed an advanced, active pulmonary fibrosis. In the biopsy specimens cobalt was determined by flameless atomic absorption. The cobalt content in the biological specimens of the patient (urine: 7.5 micrograms/l; lung: 1010 micrograms/kg wet weight) was significantly increased compared with the values measured in normal controls.

Adult↗