Biomedical subjects

E M Noniashvili

Publications and source records attributed to E M Noniashvili.

11 recordsLinked to original sources

PubMed1995

DNA-strand breaks in chromosomes of early mouse embryos as detected by in situ nick translation and gap filling.

The nick translation and gap filling procedures, without external addition of nicking enzymes, were performed in situ on fixed chromosomes of mouse preimplantation and postimplantation embryos and of bone marrow in order to detect possible DNA single-strand breaks (nicks and (or) gaps). All chromosome preparations were made using the same technique. Nick translation of chromosomal DNA with DNA polymerase I (Pol I) or gap filling with the Klenow fragment of Pol I in the presence of biotinylated-dUTP, demonstrated a regular absence of label on chromosomes of postimplantation embryos and bone marrow. No difference in sensitivity was found between the holoenzyme and the Klenow fragment. In preimplantation embryos, the chromosome reactivity in nick translation was highest at the blastocyst stage and varied according to cleavage divisions of the zygote.

Animals↗

PubMed1995

[Single-stranded DNA breaks in the chromosomes of early mouse embryos].

The occurrence and distribution pattern of spontaneous single-strand breaks (nicks) and/or gaps of mouse chromosomal DNA were studied with the help of nick-translation procedure omitting exogenous nucleases. The holoenzyme and a Klenow's fragment were used at a concentration of 0.I. U/20 microl of reaction mixture, resp. Bio-dUTP and streptavidin-alkaline phosphatase were used for labeling and detection. Chromosomes of postimplantation embryos and bone marrow were not stained. Chromosomes of all preimplantation stages of development were homogeneously stained with prominent dots of various size and intensities of grayish. DNA Pol I and the Klenow enzyme demonstrated a similar pattern of labelling. The centromeric heterochromatin was not labeled. The label was localized asymmetrically exclusive of NOR and telomeric regions.

Animals↗

PubMed1994

Single-strand DNA breaks in nuclei of early mouse embryos detected by in situ nick translation.

The nick translation procedure without external addition of nicking enzymes was performed in situ on fixed nuclei of mouse preimplantation, and postimplantation embryos, as well as bone marrow in order to detect possible DNA single-strand breaks. All preparations of nuclei were made using the same technique. Nick translation of nuclear DNA with DNA polymerase I in the presence of biotinylated-dUTP demonstrated a characteristic absence of label on nuclei of postimplantation embryos and bone marrow. The nuclear reactivity varied according to the cleavage divisions of the zygote, being highest at the four-cell stage.

Animals↗

PubMed1987

[Characteristics of the ultrastructural organization of metaphase chromosomes in mouse embryos in the early cleavage stages].

The structural organization of the mouse metaphase chromosomes in the early embryonic development (I-IV cleavages) was studied using serial ultrathin section. It was shown that in the first cleavage the metaphase chromosomes consist of DNP fibrils 20-25 nm in diameter, which are distributed nonuniformly along the chromosomes. It was suggested that parts of chromosomal arms formed by tightly packing DNP fibrils may correspond to the G-bands revealed by the routine Giemsa staining. In metaphase chromosomes of 8-16-cell embryos DNP fibrils form chromonema--thick threads about 90 nm in diameter. The chromonemata are evenly organized along chromosomal arms. The centromeric heterochromatin always consists of DNP fibrils tightly arranged in a block having no chromonemal level of organization. In all the cells studied chromosomes form structural contacts (associations) by their centromeric heterochromatin regions.

Animals↗

PubMedDate not supplied

[Localization of chromosomal nucleus organizing regions in one-cell mouse embryos and oocytes by fluorescence in situ hybridization].

In mouse zygotes, ribosomal genes (rDNA) are transcriptionally silent and so-called "nucleolar precursor bodies" are present instead of typical nucleoli. However, the functional significance of these structures remains obscure. Specifically, it remains unknown whether structural association between the nucleolar precursor bodies and rDNA are maintained when rDNA synthesis is switched off. Here, we studied for the first time the rDNA topology in one-cell mouse embryos and MII oocytes using fluorescence in situ hybridization and mouse rDNA probes. Our data suggest that in the pronuclei of one-cell embryos, rDNAs form rather compact clusters, whose number does not exceed that of nucleolus organizing chromosomes characteristic for the haploid set of mouse chromosomes. In zygotic pronuclei, not all nucleolar precursor bodies are associated with rDNA and not all rDNA repeats are attached to the nucleolar precursor bodies. Altogether, these data favor the idea that spatial interactions of nucleolus organizing chromosomes and nucleolar precursor bodies are not obligatory. We assume that associations between nucleolar precursor bodies and nucleolus organizing chromosomal regions are mediated by centromeric heterochromatin. The total numbers of silver stained nucleolus organizing chromosomes in CBA and C57BL mice are different. rDNA genes are unequally distributed among nucleolus organizing chromosomes and nucleolus organizing regions of sister chromatids.

Animals↗

PubMedDate not supplied

[Cytological research on the argentophilic nucleolus-organizer regions of the metaphase chromosomes in parthenogenetic mouse embryos].

Silver staining technique visualizing argentophilic nucleolus organizer regions (Ag-NORs) was used for studying parthenogenetic mouse embryos produced by artificial activation of oocytes in Ca(2+)-Mg(2+)-free medium. Ag-NOR-containing chromosomes were detected in metaphases of parthenogenetic embryos during six successive cleavage divisions starting with the two-cell stage. The frequency of metaphases with varying AG-NOR number in diploid parthenogenones was similar to that in the control (fertilized) embryos. Average number of metaphase Ag-NOR chromosomes (calculated per diploid chromosome set) in haploid parthenogenones exceeded that in the control; in some cases all NORs were stained by silver. This is evidence that latent ribosomal cistrons in some chromosomes can be activated.

Animals↗

PubMedDate not supplied

[Parthenogenetic development in response to the treatment of mouse oocytes with a weak alkali. Experiments with methylamine].

Ovulated mouse oocytes were incubated in methylamine-containing medium M16 for different periods of time. Methylamine appeared to activate oocytes, and most of them developed by haploid parthenogenesis. Methylamine action depended on its concentration and time of incubation. The data obtained suggest that the increase of intracellular pH unblocks meiosis and activates mammalian oocytes [correction of cocytes].

Animals↗

PubMedDate not supplied

[Parthenogenesis in mammals].

A review of studies dealing with spontaneous and induced parthenogenesis in mammals. The main methods of artificial egg activation, ways of their development and causes of mortality of the parthenogenetic mouse embryos are considered. The possibilities of using parthenogenesis for solving urgent problems of mammalian developmental biology are estimated and prospects of further studies in this field are outlined.

Animals↗

PubMedDate not supplied

[Factors determining the frequency and pathways of the parthenogenetic development of ethanol-activated mouse oocytes].

Ethanol activates the eggs inside the mother upon intraperitoneal, rather than intragastric, injection. The eggs are also activated and engaged into parthenogenetic development when the eggs or the whole oviducts with the ovulated eggs are placed in a culture medium with ethanol. The intensity of the activating effect of ethanol in vitro and ways of parthenogenetic development depend both on the ethanol concentration and temperature. At a temperature below 17 degrees ethanol did not activate the mouse eggs. There is a temperature optimum for each ethanol concentration studied (from 2 to 6.6%), at and ways of parthenogenetic development depend both on the ethanol concentration and the ability of parthenogenetic embryos to develop until the blastocyst stage are determined by the efficiency of activation and depend on the selection of optimal conditions for the action of ethanol. Cytochalasin B or D did not enhance the activating action of ethanol on the mouse eggs. The mechanisms of ethanol action on the eggs are discussed.

Animals↗

PubMedDate not supplied

[Parthenogenetic development of murine ova activated by heat shock].

The effects of heating oviducts up to 37-42 degrees on the ovulated mouse eggs have been studied. The heating of oviducts at 39.5 degrees for 7 min resulted in 85% activation. The subsequent increase in temperature did not raise the incidence of activation but led to the formation of micronuclei and other pathological changes in the pronuclei. The heating of oviducts at 39.5 degrees for 14 min demonstrated marked changes in heat resistance, which were dependent on the postovulatory age of eggs. The freshly ovulated eggs were characterized by a low resistance and were not activated by the heat shock. If the oviducts were first heated and then cooled, and again heated, most eggs were activated and their in vitro development was the best of all experimental series. The mechanisms of egg activation by heating are discussed.

Animals↗

PubMedDate not supplied

[Cytogenetic analysis of sister chromosome sets in the second polar body and in pronuclei of unicellular mouse embryos. I. Frequency and origin of aneuploidy in embryos heterozygous for the reciprocal chromosome translocation T[14;15]6Ca].

We carried out a cytogenetic study of ovulating oocytes and unicellular embryos, heterozygous by reciprocal chromosomal translocation T[14;15]6Ca. Okadaic acid was used to induce premature condensation of the interphase chromosomes in the embryos, and the number of G1 chromosomes was counted in the second polar body and pronuclei. It was shown that cytogenetic analysis of the sister chromosomal sets adequately determines the frequency of chromosomal segregation errors during oocyte meioses I and II. Trisomy and monosomy were observed in 36.2% embryos, while 2.2% featured tetrasomy or double monosomy. Errors of the first meiotic division caused aneuploidy in 28.5% embryos; trisomy and monosomy resulted from the homologs non-disjunction and chromatid presegregation in 17.6 and 10.9%, respectively. Numeral chromosomal aberrations in 4.1% of the embryos resulted from abnormal chromosomal segregation during oocyte meiosis II, while paternal chromosomal aberrations were found in 5.8% embryos. The main advantage of the proposed method is not only the higher accuracy in estimating the meiotic error frequency, but also the possibility to trace the origin of aneuploidy in mammalian embryos.

Aneuploidy↗