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M Hartung

Publications and source records attributed to M Hartung.

At least 73 records · Page 4Linked to original sources
PubMed1981

Sex vesicle-associated nucleolar organizers in mouse spermatocytes: localization, structure, and function.

Selective silver staining demonstrated that autosomal bivalents containing transcriptively active nucleolar organizers associated with the sex vesicle during pachytene of mouse spermatocytes. Later in pachytene, the nucleolar organizers covered the portion of the sex vesicle furthest from the attachment to the nuclear envelope. Hybridization in situ revealed the presence of rDNA in the silver-positive material. The nucleolus, formed from an autosomal bivalent, exhibited a large fibrillar center surrounded by an electron-opaque fibrillar zone. The nucleolar association with the sex vesicle was studied at early, middle, and late pachytene by hybridization in situ, NOR silver staining, and electron microscopy. These observations enabled us to further define the relationships of the nucleolar components with the X-Y pair.

Animals↗
PubMed1980

[The influence on mood and performance in healthy subjects by lithium carbonate (author's transl)].

Lithium carbonate was administered during a double-blind crossover experiment lasting 8 weeks, involving 11 healthy volunteers. In psychological tests, no deterioration in mood, performance or memory could be shown. Informal diary entries made by the subjects, however, refer to complaints, particularly relating to vegetative functions, more frequently under lithium medication than during the placebo period. In the interpretation of the findings, it is important to take into account the very high motivation of the subjects.

Adolescent↗
PubMed1980

Association of ribosomal genes in the fibrillar center of the nucleolus: a factor influencing translocation and nondisjunction in the human meiotic oocyte.

Prophase I meiosis was studied in the human oocyte obtained from 16- to 24-week-old fetuses. Electron microscopy and silver stainihg showed that, at pachytene, the ribosomal genes belonging to several chromosomes are gathered in the same nucleolar fibrillar center, where they are embedded in an argyrophilic protein. The nucleolus showed spontaneous segregation of its components due to temporary inactivation of the ribosomal genes. The fibrillar center, separated from the other nucleolar components, was penetrated as midpachytene by chromatin fibers containing rDNA emanating from one to three nucleolar bivalents. Thus, the ribosomal genes from 4-12 chromatids are temporarily juxtaposed inside the same structure. Such a structural arrangement is completely different from that observed in the pachytene-stage mouse oocyte, where two independent and active nucleoli, each displaying its own fibrillar center, were formed on the bivalents containing paired ribosomal genes. These different structural patterns are correlated with the high frequency of nondisjunction in the human oocyte and the relative infrequency of such in the mouse oocyte. The pattern observed in the human oocyte may be a cause of translocations.

Animals↗
PubMed1979

Nucleolar organizers in human oocytes at meiotic prophase I, studied by the silver-NOR method and electron microscopy.

Use of the silver-NOR method to study the nucleolar organizers in human oocytes demonstrates that topographic and quantitative variations occur during meiotic prophase. In the oogonia nucleolus the nucleolar organizers are dispersed, whereas beginning at leptotene and throughout the remaining stages of meiotic prophase they occupy a marginal position in the nucleolus. At leptotene, a modal number of seven nucleolar organizers can be observed, whereas this number falls to 2.5 at pachytene and rises to ten at diplotene, thus showing that there is intense rRNA synthesis during the latter stage of meiosis. During pachytene, one end of the bivalents containing the ribosomal cistrons is always associated with the Ag-positive zone of the nucleolus. Observation of pachytene in the electron microscope shows that the secondary constriction region of D and G bivalents is constantly associated with the fibrillar center of the nucleolus. Comparison of these two methods of investigation reveals that the silver-stained regions of the nucleolus correspond to the fibrillar centers. The latter are surrounded by a layer of electron-dense fibrils corresponding to the zone of rDNA transcription. This electron-dense layer is absent during pachytene when the nucleolus displays spontaneous segregation of its components; this absence is related to temporary arrest of rDNA transcription. The affinity of the fibrillar centers for silver-NOR staining confirms that these structures contain ribosomal cistrons. During the diplotene stage, numerous micronucleoli are formed outside the nucleolar organizers of D and G chromosomes. Most of these micronucleoli present an Ag-positive granule on one of their margins, thus indicating that they contain an actively transcribed sequence of rDNA. This observation confirms the existence of amplification of ribosomal genes in the human oocyte.

Cell Nucleolus↗
PubMed1978

Autoradiographic study of RNA synthesis during meiotic prophase in the human oocyte.

The incorporation of 3H-uridine in oogonia and oocytes during meiotic prophase I was studied in three human fetuses 13, 18, and 19 weeks old. Following a 40- or 60-min pulse, intense nuclear and nucleolar labeling was observed in oogonia. During the preleptotene chromosome condensation stage, the heteropycnotic masses were unlabeled, while numerous silver grains were seen on the filaments persisting around these masses. During leptotene, chromosomal and nucleolar RNA synthesis was significant, but less than that in the oogonia. The rate of incorporation declined rapidly during zygotene and fell to a very low level at early pachytene. Throughout pachytene no nucleolar RNA synthesis was observed. Chromosomal RNA synthesis progressively recovered during middle pachytene, was of moderate intensity at late pachytene, and increased again at early diplotene. Nucleolar RNA synthesis was very intense at early diplotene, at the same time as nucleolar size and basophilia increased.

Autoradiography↗
PubMed1977

Preleptotene chromosome condensation in mouse oogenesis.

In the embryonic mouse ovary, studies of meiotic onset reveal the existence of a preleptotene stage of chromosome condensation. This stage begins with the appearance of very fine and irregular filaments, which gather around the chromocenters constituted by centromeric heterochromatin. At maximal condensation the nucleus contains 40 compact chromosomal masses. Decondensation engenders the reappearance of filaments more dense and regular than those seen at the onset of the condensation stage. The filaments elongate while progressively taking on the appearance of leptotene-stage chromosomes. The oocytes at different phases of condensation stage represent 41% of the germ cels in the 13-day-old mouse embryo. This proportion reaches 63% at 14 days and then declines to 3% at 17 days. Spectrophotometric studies of the condensation-stage nucleus, following staining by the Feulgen reaction, indicated that the nucleus contains 4C DNA. This observation, together with the morphologic characteristics of this stage, suggests that the oocyte is already engaged in prophase. Time studies indicate that the condensation stage occurs immediately prior to leptotene.

Animals↗
PubMed1976

Chromosomal constitution of nucleolus-associated chromatin in man.

Use of specific stains permits analysis of the frequency of nucleolus-associated heterochromatin in chromosomes 1 and 9 from human fibroblasts. In 81 per cent of interphase nuclei the heterochromatic segment of both No. 1 chromosomes is associated with the nucleolus, while in 19 per cent only one heterochromatic segment shows such an association with the other occupying a random position in the nucleoplasm. The nucleolar association of chromosome 9 heterochromatin is less constant: in 42.3 per cent of the nuclei both segments are associated with the nucleolus, in 39 per cent of the nuclei only one heterochromatic segment presents such an association, and in 18.7 per cent neither of the two heterochromatic segments is in nucleolar association. In 6 per cent of the cells, one or two chromosome 9 heterochromatic segments are in contact with the nuclear membrane. In situ hybridization using tritium-labeled 28S and 18S RNA shows that in the interphase nucleus the acrocentric short arms, carriers of ribosomal cistrons, are associated with the nucleolus. These observations demonstrate the complexity of the nucleolus-associated chromatin which, in addition to segments of chromosomes 1, 9, 13, 14, 15, 21, 22, may include the Y chromosome. They also confirm that the nucleolus constitutes one of the orientation points determining the relative localization of chromosomes in the interphase nucleus.

Cell Nucleolus↗
PubMed1976

Incorporation of tritiated uridine during pachytene and diplotene stages in the oocytes of the Japanese quail (Coturnix coturnix japonica).

Incorporation of 3H-uridine was studied during pachytene and diplotene stages of quail oocytes. No labelling could be detected during early pachytene. During advanced and late pachytene, labelling simultaneously appeared on the macrochromosomes and on certain michromosomes in the zone where they emerge from the chromocentric surface periphery. The latter localization corresponds to the region of ribosomal RNA synthesis. At diplotene the same localizations were labelled with a considerably increased intensity.

Animals↗
PubMed1976

[Anxiety and stress in dental practice. 3. Results of studies in adults].

By means of clinical appreciation and determination of the adrenocortical function, the stressor effects of various dental procedures were evaluated in 110 patients aged from 18 to 77 years. The stress of stomatological treatment (extraction, filling therapy, prosthodontic procedures) may vary with age, the patient's psychic condition being of particular importance. Apart from premedication, psychic conditioning seems to be beneficial in case of tooth extraction.

Adolescent↗
PubMed1975

Pulmonary alveolar proteinosis and histoplasmosis: report of three cases.

Pulmonary alveolar proteinosis (PAP), in addition to acute generalized histoplasmosis, was found at autopsy of three adult males, 23, 51, and 52 years of age. All three patients became ill in the same region of Venezuela, south of Lake Maracaibo, an area considered highly endemic for histoplasmosis. The PAP may be due to an environmental factor.

Adrenal Cortex↗