Nucleolar chromatin

About: Nucleolar chromatin is a research topic. Over the lifetime, 170 publications have been published within this topic receiving 6776 citations.

Diversity and distribution pattern of drosophilids (diptera, drosophilidae) along an altitudinal transect in uttarakhand and its implication in cytogenetics & molecular systematics study

Abstract: Extensive surveys were carried for past two years to assess drosophilid diversity under varied ecological habitats of the state. A final database comprised of 94 species representing 16 genera, species diversity and distribution pattern along altitudinal gradient and different forest zones were assessed. Most species were specialists occupying particular type of habitat; few were cosmopolitan inhabiting highly varied ecological habitats at different altitudes with highly varied temperature regimes and other climatic conditions. Some of these were successfully cultured for pure line and analysed for cytogenetic variations in nucleolus organizer region-nor and nucleolar chromatin threads-ncts. Mitochondrial cytochrome oxidase subunit II gene (mtcoII) was also amplified for some of the species.

Ribosomal Genes of Fractionated Chromatin from Nucleoli of Ehrlich Ascites Tumor Cells

Abstract: Chromatin from isolated Ehrlich ascites tumor cell nucleoli was fractionated on a sucrose gradient to examine the distribution of ribosomal genes. The isolated nucleoli were treated with polyvinylsulphate, and then the ribonucleoprotein particles were extracted with 20 mM dithiothreitol in buffer solution. The chromatin was then solubilized by sonication in 10 mM Tris-HCl buffer (pH 8.0). Centrifugation of solubilized chromatin fraction on a sucrose gradient gave two peaks of chromatin containing approximately equal amounts of DNA, regardless of whether the sonication period was 20 sec or 40 sec. Peak I (which sedimented slower) had less RNA than peak II. Ribonucleoprotein particles appeared to merely cosediment with peak II because the profiles of DNA component differed from RNA. Therefore, the presence of ribonucleoprotein particles was probably not the primary cause of the rapid sedimentation of peak II. Examination of the distribution of ribosomal genes in the fractionated nucleolar chromatin by hybridization of DNA with 32P-labeled ribosomal RNA showed that peak I contained three times more ribosomal genes than peak II. Fractionation of DNA in the chromatin fractionsby CsCl equilibrium density gradient centrifugation showed that the profiles of DNA complimentary to ribosomal RNA in the two fractions were essentially similar, but that peak I contained more ribosomal genes than peak II.

[The multidrug resistance phenotype: some morphological and biological characteristics except efflux pump].

Abstract: Recent data from the literature together with personal results strongly suggest that multidrug resistance phenotype is overwhelming the sole expression of P170 glycoprotein efflux pump. Morphological alterations have been put in evidence in MDR cells after transmission and scanning electron microscopy. They include presence of osmiophilic vesicles and modifications of nuclear and nucleolar chromatin. Biological characteristics include the hypersecretory pattern of lysosomal enzymes from MDR cells. Such a fact could be more or less related to the increased occurrence of mdr1 RNA in metastasis, especially in breast cancers, compared to primary tumors. If the P170-mediated efflux is one of the key mechanism of MDR, a decreased influx of anticancer drugs cannot be excluded. Liposomes, for instance made of cardiolipin, are thus able to increase the intracellular drug uptake of vinblastine without any action upon efflux mechanism.

Electron‐microscope investigations on the endonuclear DNA‐RNA bodies of the midgut epithelial cells of Bacillus rossius (insecta, cheleutoptera)

Abstract: Fourth instar larvae and adults of the stick insect B. rossius develop endonuclear bodies in about 10% of the columnar epithelial cells of the midgut. E.M. sections show that the bodies start as loose bundles of fibrils, independent from the intranucleolar chromatin. Large bodies retain a similar structure but also contain larger fibers and electron dense granules, sometimes clustered in small groups. In the nuclei containing these bodies, the other components are similar to those found in ordinary nuclei, apart from the frequent reduction in size and structural changes of the nucleoli. In the cytoplasm of both ordinary cells and those containing bodies, the rough endoplasmic reticulum is strikingly developed and towards the gut lumen many secretion vesicles are found. In EDTA treated sections the endonuclear bodies show intermingled bleached and unbleached areas, the electron density of unbleached structures being increased when compared with controls and reaching the same contrast as the fibrillar-granular components of the nucleolus. In DNase treated specimens both the chromatin and the endonuclear bodies lose their contrast; RNase solutions digest the electron dense granules of the endonuclear bodies and the combined action of RNase and DNase further disintegrates the bodies. Ultrastructural and enzyme digestion data therefore indicate a DNA-RNA composition for the endonuclear bodies and support, together with 3H-thymidine uptake, the hypothesis that they are the expression of a somatic gene amplification. Their origin distinct from the nucleolar chromatin further suggests that the DNA of the bodies is not rDNA and a possible link of the bodies with the production of digestive enzymes is indicated.

Relative Position of Nucleolar Chromatin and Nucleolar Components in Ciliate Didinium nasutum Somatic Nuclei

Abstract: According to our computer modeling data obtained earlier, nucleoli in interphase ciliates Didinium nasutum are complex netlike structures, in which the trabeculumor lamella-shaped fibrillar component is located on the periphery, and the granular component in the central part of the nucleolus. Chromatin bodies connected with nucleoli act as the nucleolar organizers in D. nasutum. In the present work, the arrangement of all chromatin bodies, which could correspond to nucleolar organizers by morphological criteria, is studied by means of a 3D-reconstruction. It is shown that all of these chromatin bodies are localized outside the nucleoli, on the fibrillar component’s periphery. Even those chromatin bodies which appeared to be completely surrounded by the fibrillar nucleolar component on single ultrathin sections are actually settled down in nucleolus cavities open to the nucleoplasm. This proves that the RNA processing in D. nasutum nucleoli is directed toward the center of nucleoli, where the granular component is located. The analysis of the nucleolar chromatin distribution made it possible to conclude that different parts of the complex interfase netlike nucleoli of D. nasutum have approximately the same activity.