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E Puvion

Publications and source records attributed to E Puvion.

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

Effect of quinacrine on nuclear structure and RNA synthesis in cultured rat hepatocytes.

The effects of quinacrine, an antimetabolite which intercalates into DNA, on the ultrastructure of interphase nuclei and on RNA turnover were studied in primary cultures of rat hepatocytes. Procedures included ultrastructural cytochemical staining for ribonucleoprotein and DNA, autoradiography, and measurement of labeled uridine uptake and incorporation. Addition to the culture medium of a nontoxic dose (10 microM for 30 min) reduces the net accumulation of labeled uridine in RNA. This involves first heterogeneous RNA and then ribosomal RNA since their structural precursors, interchromatin fibrils and nucleolar fibrils, respectively, diminish in that order. Intranucleolar chromatin retracts, and perinucleolar chromatin becomes unusually condensed. A toxic dose (50 microM for 30 min) produces greater inhibition of tritiated uridine incorporation in RNA. This precedes and is not due to a drop in uridine uptake into the cells. Toxic doses produce unusually large clusters of interchromatin granules which are embedded in an unusual dense material which stains positively for ribonucleoprotein. Three regions of the chromatin are altered. (a) Perinuclear condensed chromatin retracts from the nuclear envelope, remaining attached by short DNA-containing bridges. (b) The normally dispersed nucleoplasmic chromatin condenses into a stainable network which retracts centrifugally. (c) Perinucleolar chromatin becomes a network of small highly condensed masses or bands interconnected by fibrils which are either decondensed or stretched. These alterations in chromatin structure probably form the basis of quinacrine-impaired nuclear metabolism.

Animals↗
PubMed1981

Organization of the nucleolar RNP components in cultured rabbit fibroblasts following mild loosening of the nuclear content.

The organization of the ribonucleoprotein (RNP) components of the nucleolus was studied in ultrathin sections by a recent method of mild loosening of the nuclear content. This investigation was carried out in cultured rabbit fibroblasts in which the nucleoli contain clearly separated fibrillar and granular RNP components. In addition, the demarcation between these two particulate components was accentuated by infection with herpes simplex type 1 virus (HSV1), by recovery at 37 degrees C after a heat shock, and by actinomycin D treatment. Except in actinomycin D-treated cells, it was possible to identify two distinct components which are not visible in routinely prepared sections: (1) highly contrasted fibrillar clusters resulting from the loosening of the fibrillar component, (2) a granular network composed of nucleolar granules interconnected by a thin filament of about 5 nm in thickness. In actinomycin D-treated cells, only the granular zone was observed. High resolution autoradiography carried out both on standard fixed and on loosened cells following a 5 min labeling with tritiated uridine revealed that the fibrillar clusters correspond to sections of nucleolar transcription complexes. When the same labeling was followed by 3 h chase only the granular network was labeled indicating that it corresponds to the site of pre-ribosomal ribonucleic acid (pre-rRNA) maturation. Infection by HSV1 did not change this result. Preferential RNP staining and deoxyribonucleic acid (DNA) specific staining failed to reveal the thin filaments interconnecting the nucleolar granules. We suggest that the latter filaments serve as support for pre-rRNA processing and for storage of large pre-ribosomal subunits.

Animals↗
PubMed1980

New aspects of intranuclear structures following partial decondensation of chromatin: a cytochemical and high-resolution autoradiographical study.

Exposure of cultured CVI monkey kidney cells to a hypotonic medium containing a nonionic detergent induces a partial decondensation of nuclear components which can be studied advantageously in ultrathin sections. In addition to previously described 20--25 nm, DNA-containing chromatin fibres arrayed perpendicularly to the nuclear lamina, a new nuclear configuration was found which consists of abundant clusters of 6--7 nm fibrils. These 'filamentous masses' are the most heavily labelled component of the nucleus in autoradiographs after brief (2 min) exposure to [5-3H]uridine, and they are greatly diminished in number after treatment of the cells with a low dose of actinomycin D. Therefore, we interpret the filamentous masses to be nascent RNP and to represent the fibrillar regions of the nucleolus which have become decondensed into partially spread 'Christmas-tree'-like figures detectable in situ in ultrathin sections. Similar structures occur in all cell types examined to date. This paper outlines the preparative procedure.

Animals↗
PubMed1980

Additive effects of cortisol and calf serum on RNA synthesis in isolated rat hepatocytes. Autoradiographic studies with the light and electron microscope.

The known stimulating effect of calf serum (10%) and cortisol (20 microgram/ml) on the incorporation of 2H uridine into the nuclei of isolated rat hepatocytes has been confirmed with the method of light and electron autoradiography. Moreover, it has been shown that cortisol and serum exert additive effects when they are applied jointly. In the presence of either serum or cortisol or both transcriptional activity increases gradually, reaching its maximum level after 6 h incubation. This effect is reduced when the incubation is prolonged up to 24 h. Autoradiographic ultrastructural studies have shown that both serum and cortisol enhance the nucleolar as well as extranucleolar transcriptional activity. The nuclei of hepatocytes cultivated in medium containing serum or both serum and cortisol shown a higher growth rate in comparison with those cultivated in a poor, control medium. Cortisol added to the serum-free medium does not stimulate the nuclear growth.

Animals↗
PubMed1979

[Monolayer culture of adult mouse hepatic cells secreting albumin and alpha fetoprotein].

Adult mouse liver cells obtained by enzymatic dispersion were maintained in primary cultures for up to 4 weeks. They retained some of the typical morphological and ultrastructural characteristics of hepatocytes. After 2 days of culture, structures similar to bile canaliculi were found and after 6 days clusters of small proliferating cells were noticed in the gaps of the monolayer formed by large well-spread hepatocytes. Almost all 3-day cultures began to secrete alphafetoprotein for about 2 weeks, whereas albumin was secreted throughout the period of culture.

Albumins↗
PubMed1975

Ultrastructural organization and biochemical characterization of chromatin - RNA - protein complexes isolated from mammalian cell nuclei.

Extranucleolar elements were isolated from mammalian cell nuclei and characterized by correlative biochemical-ultrastructural studies. These complex structures were shown to retain a supra-particle arrangement closely resembling the organization in situ of definite nuclear areas. In particular the morphological RNA - protein species, namely perichromatin fibrils and granules, were detected in association with characteristic regions of chromatin. By autoradiographic experiments, we were able to show that perichromatin fibrils represent the morphological state of newly formed heterogeneous nuclear RNA (hnRNA). Chromatin - RNA - protein complexes were further fractionated by means of a treatment dissociating the chromatin component. A minor part of DNA, possibly involved in the biosynthesis and the processing of hnRNA, remains linked to the resulting RNA - protein network.

Animals↗