State of nucleolus organizers in hybrids of pluripotent and somatic mouse cells cultivated under different conditions

In the present work, we studied the state of chromosomal nucleolar organizing regions (NOR) in hybrid cells obtained by fusion of cells of embryonal carcinoma of a murine line PCC4aza1 and of cells of adult mouse spleen at cultivation of hybrids under different conditions. The obtained results have shown that long-term cultivation of hybrid cells in a selective medium containing HAT (hypoxanthine, aminopterin, thymidine) promotes preservation of nucleolar organizing chromosomes (NO chromosomes), whereas in nonselective medium predominant elimination of NO chromosomes was revealed. Under nonselective conditions, an increased number of active, i.e., Ag-positive, NORs was observed as compared to under selective conditions. These observations directly show that reprogramming of parent cell genomes in hybrids includes changes in the state of NO chromosomes. The number of active NORs depends on the conditions of cultivation of hybrid cells and can change in two main ways, i.e., by the elimination of NO chromosomes (under nonselective conditions) or by the inactivation of some NORs with maintenance of NO chromosomes (under selective conditions).     

Rapid detection of yeast rRNA genes with primed in situ (PRINS) labeling

In yeast, rRNA genes can be detected with the FISH technique using rRNA gene probes. This technique yields reliable, reproducible and precise results, but is time-consuming. Here, the primed in situ DNA synthesis (PRINS) procedure has been optimized for rapid detection of yeast rRNA genes. PRINS, which is as sensitive as PCR and allows cytological localization of analyzed sequences, can be adapted for various screening tests requiring fast labeling of rRNA genes.     

Nucleolar protein Spindlin1 recognizes H3K4 methylation and stimulates the expression of rRNA genes

The tandem Tudor-like domain-containing protein Spindlin1 has been reported to be a meiotic spindle-associated protein. Here we report that Spindlin1 is not associated with the spindle in mouse embryonic fibroblast cells during mitotic divisions. In interphase cells, Spindlin1 specifically localizes to the nucleoli. Moreover, Spindlin1 is a histone methylation effector protein that specifically recognizes H3K4 methylation. Finally, Spindlin1 localizes to the active ribosomal DNA (rDNA) repeats, and Spindlin1 facilitates the expression of rRNA genes.     

Nucleologenesis: use of non-isotopic in situ hybridization and immunocytochemistry to compare the localization of rDNA and nucleolar proteins during mitosis

Using in situ hybridization and immunocytochemistry during interphase and mitosis, we have compared the distribution of ribosomal DNA (rDNA) to that of the nucleolar proteins fibrillarin and RNA polymerase I. During interphase, nucleolar proteins were localized at sites throughout the nucleolus while the bulk of rDNA was localized in a single restricted nucleolar area. During metaphase and anaphase, all six NORs were detected by in situ hybridization, Ag-staining, or by the immunolocalization of RNA polymerase I. During telophase, rDNA and RNA polymerase I were found in a distinct subset of the prenucleolar bodies (PNBs) which obviously must contain the nucleolar organizers. Other numerous PNBs are smaller in size and do not contain detectable amounts of rDNA or RNA polymerase I. Therefore, reconstruction of the nucleolus originates in telophase-specific domains which contain both rDNA and RNA polymerase I.     

The time-related subcellular distribution of chromium in the rat liver cell after intravenous administration of Na2 51CrO4

After intravenous administration of Na₂ ⁵¹CrO₄ to rats the subcellular distribution of⁵¹Cr was determined at different time intervals after dosage. A time-related compartment shift from the cytosol into the mitochondrial and nuclear fractions was demonstrated. Dialysis studies indicated a firmer binding of⁵¹Cr to the mitochondrial and nuclear fractions than to the cytosol. Indirect evidence is presented that reduction from CrVI to CrIII takes place primarily inside the mitochondria. The hypothesis is put forward that reduction from Cr^VI to Cr^III may take place at any intracellular site where electron donors are available. Electron donors in the different intracellular organelles are discussed.     

Modification of the cytotoxicity of aflatoxin B1 in rat liver cells by steroids

The addition of steroids with aflatoxin B1 (AFB1) to rat liver cells in culture has been shown to increase the toxin's inhibitory action on growth and protein synthesis. In contrast the inhibition of RNA synthesis by AFB1 was unaffected. The steroid potentiates the direct action of AFB1 at initiation of translation.     

Specific binding sites for corticosterone in isolated cells and plasma membrane from rat liver

Summary The specific binding of [³H]corticosterone to hepatocytes is a nonsaturable, reversible and temperature-dependent process. The binding to liver purified plasma membrane fraction is also specific, reversible and temperature dependent but it is saturable. Two types of independent and equivalent binding sites have been determined from hepatocytes. One of them has high affinity and low binding capacity (K _D=8.8nm andB _max=1477 fmol/mg protein) and the other one has low affinity and high binding capacity (K _D=91nm andB _max=9015 fmol/mg). In plasma membrane only one type of binding site has been characterized (K _D=11.2nm andB _max=1982 fmol/mg). As it can be deduced from displacement data obtained in hepatocytes and plasma membrane the high affinity binding sites are different from the glucocorticoid, progesterone nuclear receptors and the Na⁺,K⁺-ATPase digitalis receptor. Probably it is of the same nature that the one determinate for [³H]cortisol and [³H]corticosterone in mouse liver plasma membrane. Beta-and alpha-adrenergic antagonists as propranolol and phentolamine did not affect [³H]corticosterone binding to hepatocytes and plasma membranes; therefore, these binding sites are independent of adrenergic receptors. The binding sites in hepatocytes and plasma membranes are not exclusive for corticosterone but other steroids are also bound with very different affinities.     

Distribution of 5S and 35S rRNA gene sites in 34 Chenopodium species (Amaranthaceae)

Studies on Chenopodium chromosomes are scarce and restricted mainly to chromosome number estimation. To extend our knowledge on karyotype structure of the genus, the organization of 5S and 35S rRNA genes in Chenopodium chromosomes was studied. The rDNA sites were predominantly located at chromosomal termini, except in a few species where 5S rDNA sites were interstitial. The majority of the diploid species possessed one pair each of 35S and 5S rDNA sites located on separate chromosomes. Slightly higher diversity in rDNA site number was observed in polyploid accessions. One or two pairs of 35S rDNA sites were observed in tetraploids and hexaploids. Tetraploid species had two, four or six sites and hexaploid species had six or eight sites of 5S rDNA, respectively. These data indicate that, in the evolution of some polyploid species, there has been a tendency to reduce the number of rDNA sites. Additionally, polymorphism in rDNA site number was observed. Possible mechanisms of rDNA locus evolution are discussed. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, ??, ??–??.     

Effect of dietary nickel and iron on the trace element content of rat liver

The level and/or form of dietary iron, dietary nickel, and the interaction between them affected the trace element content of rat liver. Livers were from the offspring of dams fed diets containing 10–16 ng, or 20 μg, of nickel/g. Dietary iron was supplied as ferric chloride (30 μg/g) or ferric sulfate (30 μg, or 60 μg). In nickel-deprived rats fed 60 μg of iron/g of diet as ferric sulfate, at age 35 days, levels of iron and zinc were depressed in liver and the level of copper was elevated. At age 55 days, iron was still depressed, copper was still elevated, but zinc also was elevated. In rats fed 30 μg of iron/g of diet as ferric chloride, liver iron content was higher in nickel-deprived than in nickel-supplemented rats at 30, but not at 50, days of age. Also manganese and zinc were lower in nickel-deprived than in nickel-supplemented rats at age 35 days if their dams had been on experiment for an extended period of time (i.e., since age 21 days). Thus, the levels of copper, iron, manganese, and zinc in liver were affected by nickel deprivation, but the direction and extent of the affects depended upon the iron status of the rat.