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[Visualization of chromosome territories in interphase nuclei of ovarian nurse cells in Calliphora erythrocephala Mg. (Diptera: Calliphoridae)].

Analysis of localization of chromosomes 2, 3, and 6 of Calliphora erythrocephala Mg. in ovarian nurse cell nuclei with different chromatin structure has shown that the regions of DNA probe hybridization reduced with increasing chromatin compaction. Hybridization of DNA probes of chromosomes 3 and 6 to secondary reticular nuclei demonstrated that chromosomes retain their territories in the nuclei when the chromatin acquires a reticular structure. These results suggest regular organization of the chromosomal apparatus at all stages of the endomitotic cycle, including the stage of highly polyploid reticular nuclei. FISH of DNA probe of the chromosome 2 telomeric region to secondary reticular nuclei revealed a peripheral distribution of the signal. Zones of more intensive DNA probe hybridization have been distinguished. These zones probably are the regions of accumulation of telomeric and (or) centromeric chromosome regions.

Animals↗

[The effect of centrosome UV microbeam irradiation on cell behavior. II. The radiation sequelae in the anaphase: the completion of division and the fate of the interphase cell].

Ultraviolet (280 nm) microbeam irradiation of the centrosome (spindle pole) in the early anaphase slows down and then stops chromosome movement towards the irradiated pole. This happens as a result of rapid (in 1-2 min) disorganization of the half-spindle. Chromosome movement towards the opposite pole continues normally. Irradiation of the centrosome also affects cystotomy--the residual body is formed later than in the normal cell. In some cases additional constrictions are formed or the cytoplasm starts blebbing. Immediately after division the microtubule network in two daughter cells (one of them with irradiated centrosome) is similar. Two hours later in the irradiated cell the amount of microtubules is often less than in the sister cell. Incubation with nocodazole (0.5-1.5 h, 0.15 microgram/ml) shows that in the irradiated cells microtubules radiating from the centrosome are practically absent. Irradiation of other regions of the cytoplasm does not cause any of the effects described above.

Anaphase↗

[A quantitative study of the nucleoli in the interphase nuclei of rabbit lymphocytes].

The number of nucleoli was counted in the rabbit lymphocyte nuclei. This number was higher in meat rabbits than in skin-meat rabbits. We suppose that the polymorphism in the number of nucleoli reflecting the functional activity of ribosomal genes may be associated with biological-farming direction of productivity and energy of the animal growth.

Animals↗

[D2O inhibition of interphase thymocyte death].

Using the method of flow cytometry and biochemical analysis it was shown that D2O, an agent that stabilizes microtubules, prevented the internucleosome fragmentation of DNA in thymocytes exposed to gamma radiation and dexamethasone in vitro. It was also found that D2O is ineffective with respect to Ca2+/Mg2(+)-dependent nuclease. The transfer of irradiated cells from a medium containing 90% of D2O to a normal one caused rapid DNA degradation; the fragmentation process ceased with the irradiated cells being transferred from H2O to heavy water. The results obtained permit us to assume that the disturbance of microtubules is not a trigger mechanism of DNA degradation by apoptosis, but is some intermediate stage of cell death preceding the chromatin fragmentation proper.

Animals↗

Analysis of microtubule arms and bridges in mitotic and interphase amebae of Dictyostelium discoideum.

We have analyzed transparencies of electron micrographs from ultrathin longitudinal sections through mitotic spindles of undifferentiated amebae of Dictyostelium discoideum for the presence of arms on microtubules (MTs) and bridges between them. We used the technique of microdensitometer scanning and computer-based model matching by cross-correlation and autocorrelation. We also determined that spindle MTs are composed of 13 protofilaments. Although regularly arranged lateral appendages are not a universal feature of MTs in these cells, both cross-correlation and autocorrelation analysis revealed that bridges between a kinetochore MT and its neighbor, and between MTs in the zone of overlap of the central spindle were significantly arranged on a 12-dimer superlattice. In addition, the autocorrelation analysis indicated a slight match with the 12-dimer model for neighboring non-kinetochore MTs. Although electron micrographs revealed putative arms on cytoplasmic and astral MTs, as well as bridges between central spindle MTs outside the zone of overlap, their arrangement did not match any of the models tested. Bridges between non-kinetochore MTs in the half-spindles possibly serve to reinforce the spindle scaffold. Bridges between kinetochore MTs and their neighbors may contribute to the mechanical stability of kinetochore fibers or they may be involved in poleward movements of the chromosomes. In the zone of overlap of the central spindle, the occurrence of frequent and regularly spaced bridges is consistent with models predicting that a sliding mechanism operates between MTs of opposite polarity in this region of the spindle to produce its elongation.

Analog-Digital Conversion↗

[Chromosomal interrelations in the interphase nucleus].

The distribution of prekinetochores in human lymphocytes has been studied by indirect immunofluorescence with autoantibodies against kinetochore. Lymphocyte flattening that allowed a 5-6 increase in their size, was suggested in addition to a method of lymphocyte stretching allowing a 10-fold extension. Prekinetochores in flat and stretched lymphocytes are seen settled down as separate pairs. The equal pattern of staining of these prekinetochores in each pair suggests that homologous chromosomes located in pairs.

Autoantibodies↗

[Cytophotometric analysis of the chromatin structural conformity in interphase nuclei detected in UV light and by gallocyanine staining].

Geometric and optical parameters of chromatin of hepatocyte nuclei have been examined before (UV, lambda = 265 nm) and after gallocyanine staining. Quantitative parameters of the chromatin structure in the same nuclei measured in situ by a scanning microscope-photometer (step size 0.125 micron) before and after staining were equal. Tinctorial properties of chromatin granules (condensed part of the nuclear material) and its diffuse part were different. It is suggested that the difference between granules and the nongranular part of chromatin is not only of optical but also of chemical nature.

Animals↗

The use of scanning electron microscopy for investigations into the three dimensional organisation of the interphase nucleus.

In an attempt to elucidate three dimensional information on the organisation of the nucleus, nuclei have been extracted from ascites tumour cells or tissue culture cells by a variety of biochemical techniques, and prepared for high resolution scanning electron microscopy using an osmium-thiocarbo-hydrazide infiltration procedure which has previously proved successful for analysis of chromosome structure. Nuclei were prefixed with either Methanol-Acetic acid, glutaraldehyde or formaldehyde and then extracted by a variety of detergents with the aim of a 'biochemical dissection' of their outer elements to allow surface visualisation of the nuclear lamina. Continued extraction removed all aspects of the nuclear periphery and allowed direct visualisation of the in situ organisation of the chromatin, apparent as at least two levels of supercoiling.

Animals↗

Supernumerary chromosome 1 in interphase nuclei of atypical germ cells in paraffin-embedded human seminiferous tubules.

The so-called atypical germ cells or cells of carcinoma in situ morphologically resemble neoplastic cells in seminoma. Since seminomas show numerical aberrations of chromosome 1 we have used a DNA probe specific for chromosome region 1q12 to determine whether such aberrations can be detected in atypical germ cell nuclei in paraffin-embedded seminiferous tubules as well. One-third of intratubular nuclei, containing atypical germ cells, consistently showed three hybridization signals in contrast to two signals regularly observed in normal intestine and in spermatogonia. We thus show that cytogenetic studies of precancerous cells can be performed directly on the tissue where these cells originate.

Chromosome Aberrations↗

[Nature of breaks inducible in DNA at the early stages of interphase cell death].

Dynamics of changes in 3'-OH- and 5'-OH-ends of DNA was determined by "nick"-translation and direct polynucleotide kinase reaction, respectively, in animal thymocytes after irradiation and administration of hydrocortisone. Breaks bearing both 3'-OH- and 5'-OH-ends were found in DNA after irradiation. In 40 min repair of single-strand breaks was almost completed, and enzymatic breaks were accumulated with 3'-OH-ends only. 60 min after the administration of hydrocortisone, the number of nuclear DNA breaks containing 3'-OH-ends, but not 5'-OH-ends, sharply increased. Upon DNA autolysis in isolated nuclei acid nuclease produced 5'-OH-ends, and Ca2+/Mg2+-dependent nuclease, 3'-OH-ends. No activity of Mg2+-dependent nuclease was registered either in the nuclei of control thymocytes or in the nuclei isolated from thymocytes of exposed rats.

Animals↗