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At least 1,063 records · Page 59Linked to original sources
PubMed1986

Radiation-induced cytogenetic damage in relation to changes in interphase chromosome conformation.

The premature chromosome condensation (PCC) technique was used to study several factors that determine the yield of chromosome fragments as observed in interphase cells after irradiation. In addition to absorbed dose and the extent of chromosome condensation at the time of irradiation, changes in chromosome conformation as cells progressed through the cell cycle after irradiation affected dramatically the yield of chromosome fragments observed. As a test of the effect of chromosome decondensation, irradiated metaphase Chinese hamster ovary (CHO) cells were allowed to divide, and the prematurely condensed chromosomes in the daughter cells were analyzed in their G1 phase. The yield of chromosome fragments increased as the daughter cells progressed toward S phase and chromosome decondensation occurred. When early G1 CHO cells were irradiated and analyzed at later times in G1 phase, an increase in chromosome fragmentation again followed the gradual increase in chromosome decondensation. As a test of the effect of chromosome condensation, G0 human lymphocytes were irradiated and analyzed at various times after fusion with mitotic CHO cells, i.e., as condensation proceeded. The yield of fragments observed was directly related to the amount of chromosome condensation allowed to take place after irradiation and inversely related to the extent of chromosome condensation at the time of irradiation. It can be concluded that changes in chromosome conformation interfered with rejoining processes. In contrast, resting chromosomes (as in G0 lymphocytes irradiated before fusion) showed efficient rejoining. These results support the hypothesis that cytogenetic lesions become observable chromosome breaks when chromosome condensation or decondensation occurs during the cell cycle.

Animals↗
PubMed1987

[Morphometric analysis of the toxic effect of ethanol on the structure of chromatin in interphase nuclei of rat hepatocytes].

A method of automated morphometric analysis of hepatic cell interphase nuclear chromatin (CHIN) structure was elaborated using scanning microspectrophotometer SMP-05 ("Opton", FRG). Liver sections of rats were used to investigate hepatic cell CHIN structure. The animals were administered ethanol intraperitoneally once per day within a month period in doses 4, 6, 8, 10 g/kg (1/3-4/5 LD50). Morphometric indexes indicating dose-dependent changes in hepatic cell CHIN structure are demonstrated. Statistical analysis of morphometric data has led to the conclusion that hepatic cell CHIN structural modification depends on two factors: ethanol damaging effect and hepatic cell regeneration.

Alcoholic Intoxication↗
PubMed1987

[Interphase death of lymphoid cells: role in the genesis of radiation sickness and molecular mechanisms].

An analysis of the data on the effect of lymphoid cells on the proliferation and differentiation of hemopoietic stem cells has led to a conclusion that radiation injury of lymphocytes plays an important role in the pathogenesis of the cerebrospinal syndrome. The molecular mechanisms of lymphocyte interphase death were considered. It was shown that due to some peculiarities in the energy supply of these cells the appearance of breaks in DNA causes the development of biochemical processes resulting in a decrease in NAD, an increase in the activity of nucleases, a decrease in ATP, and the accumulation of active metabolites of glycolysis. These reactions result in an increase in the disintegration of DNA, chromatin and pyknosis of lymphocyte nuclei.

Animals↗
PubMedDate not supplied

[Lipid metabolism in rat tissues after irradiation at doses causing interphase cell death].

Irradiation of animals with doses eliciting interphase death of 50-80% of cells activates lipogenesis and decreases the cholesterol content of cells. Cholesterol synthesis is activated after irradiation with doses causing death of 50% of cells: a further increase in radiation dose decreases the cholesterol synthesis. It is assumed that as membranes are destructed by radiation the adaptive lipogenesis activated to restore them.

Animals↗
PubMed1986

Acute and late radiation injury in rhesus monkey parotid glands. Evidence of interphase cell death.

Acute and chronic salivary gland dysfunction are common sequelae of radiotherapy for head and neck cancer; but the associated morphologic changes, especially of the acute damage, have received relatively little study. For investigation of the morphologic characteristics of acute radiation injury to parotid glands, rhesus monkeys were studied 1-72 hours after parotid irradiation with single doses of 2.5-15.0 Gy. The acute damage from all doses was clearly expressed by 24 hours. Histologically, parotid glands irradiated with 2.5 or 5.0 Gy had random degeneration and necrosis of the serous acinar cells. Doses of 7.5-15.0 Gy produced widespread degeneration along with necrosis of whole acini. Serous cell damage was accompanied by neutrophilic inflammation that subsided after 24 hours to become replaced by plasma cell and lymphocytic infiltrates. Parotid glands receiving 7.5-15.0 Gy were atrophic at 16-22 weeks after irradiation and showed no recovery by 40 weeks. Although parotid acinar cells are well-differentiated nondividing cells, these observations show that they express lethal radiation injury in interphase within hours of receiving a radiation dose as low as 2.5 Gy. This is unlike most mammalian cells that express radiation injury during mitosis. Chronic atrophy is a consequence of this direct, irreversible, and early injury, rather than the result of radiation-induced changes in the vasculature.

Acute Disease↗
PubMedDate not supplied

[Determination of the radiosensitivity of interphase-dying cells in the thymus, spleen and bone marrow of rats by flow cytometry].

The flow cytofluorometry of cells stained with a DNA-specific probe was used to determine the share of dying cells (containing less than 2C DNA) in thymus, spleen and bone marrow cells of irradiated rats. The cell death curves for spleen and bone marrow had a plateau by the 6th h, and for thymus, by the 10th h following irradiation with different doses. On the basis of the dose-response relationship the share of cells dying in the interphase was determined in each organ under study, and dose-response curves shaped. All the curves had no shoulder. Do was 3.0, 3.0 and 3.7 Gy for thymus, spleen, and bone marrow cells, respectively.

Animals↗
PubMedDate not supplied

[Modification of the interphase death of thymocytes by using colcemid].

The pretreatment of thymocytes by colcemid (0.02 to 0.5 mu g/ml) induces a change in the plasma membrane state, registered by a pyrene fluorescent probe, and a decrease in the interphase cell death after 4 Gy X-irradiation. The authors discuss the role of the cell surface as a trigger initiating death program in irradiated lymphoid cells.

Animals↗
PubMed1986

Morphometric and topologic analysis of freeze-fractured interphase nuclei.

Interphase rat liver nuclei were studied by freeze fracturing followed by electron microscopic observations. This method permits information on the native organization of the nuclear components in the hydrated state to be obtained. Morphometric analyses, performed with a Leitz Texture Analysis System, gave precise information on the different nuclear components, based on the histograms of their size distribution in heterochromatin, interchromatin and nucleolar areas. The textural characteristics were analyzed by computer to determine the topologic distribution of the solenoid chromatin fibers, the nucleosome filaments and the ribonucleoproteins in the different nuclear domains.

Animals↗
PubMedDate not supplied

[Interphase death of thymus cells in combined radiation-thermal injury against a background of prophylactic administration of alpha-tocopherol and indomethacin].

The administration of alpha-tocopherol prior to radiation and thermal affection enhances chromatin degradation in thymocytes, increases the number of pyknomorphic cells in the critical zone of thymus, and enhances injury to erythrocyte membranes. The preventive administration of indomethacin does not influence the interphase cell death.

Animals↗
PubMed1985

The use of propidium iodide in cytochemical studies of interphase chromatin structure.

Different cytochemical conditions of using Propidium Iodide, a phenanthridinic fluorochrome specific for double-stranded nucleic acids, have been considered to study some structural aspects of the interphasic chromatin. Some molecular properties of the dye allow to define the structure of chromatin fibre (degree of condensation) by means of thermal denaturation of DNA, fluorochromization after extraction of different chromatin components and fluorochromization in condition of low dye-substrate molar ratio (relative unsaturation of DNA). Different biological situations such as cell specialization, neoplastic transformation and life cycles have been examined choosing some typical models (hepatocytes, nucleated erythrocytes, lymphocytes, endometrial cells).

Animals↗
PubMed1985

Changes in DNA capacity for actinomycin-D binding in nuclei of interphase cells.

3H-AMD binding to DNA in interphase nuclei was tested on asynchronous and synchronous LS/BL cell populations under physiological conditions and after exposure to gamma rays (60Co). 3H-AMD binding to DNA in an asynchronous cell population appeared to be nearly constant and independent of 3H-AMD concentration. However, in comparing individual cells, a great variability could be observed. In synchronized cells the DNA accessibility for 3H-AMD binding changed in the course of the cell cycle, with a maximum occurring at the late G1-phase (13.95 X 10(-12) mumol/nucleus) and a minimum at the late G2-phase (2.63 X 10(-12) mumol/nucleus). In irradiated cells the DNA capacity for 3H-AMD binding was growing with the increasing dose (5-80 Gy) from 4.9 to 11.2 X 10(-12) mumol 3H-AMD/nucleus.

Animals↗
PubMed1985

[Variation in the number of C-heterochromatin blocks in the interphase nuclei of the cells of a transplantable murine rhabdomyosarcoma].

By means of staining procedure which reveals the constitutive heterochromatin (CH), the number of CH-blocks was detected in the nuclei of interphase cells obtained from the subcutaneously growing rhabdomyosarcoma and from its 10 lung colonies. The range of variability of the number of CH-blocks in tumor cell populations was greater than in the populations of normal lung cells and lymphocytes. The mean numbers of CH-blocks varied from 17.8 +/- 0.9 to 28.0 +/- 1.2 in cells of different clones, the mean number of CH-blocks in clones being the same as in the subcutaneously growing uncloned tumor. The coefficient of heritability h2 of character "the number of CH-blocks", calculated on the basis of population and interclonal variances, was equal to 0.15, and that calculated by one-factor dispersional analysis was actually the same (0.16). It is concluded that the high heterogeneity of tumor cells may be conditioned not only by their high phenotypic instability, but also by a high frequency of mutations.

Animals↗
PubMed1979

On the association of centrioles with the interphase nucleus.

Preparations of nuclei from rat liver and bovine spleen purified by centrifugation through dense sucrose solutions are shown to contain centrioles. These centrioles retain their in situ ultrastructure and are surrounded by a network of filaments adjacent to the nucleus and probably attached to it. The number of centrioles in isolated nuclei depends on the conditions of cell homogenization. Under certain conditions of homogenization, the fraction of purified nuclei contains almost all centrioles of the original tissue. The number of centrioles in isolated nuclei sharply decreases if the nuclei are rehomogenized under conditions that do not cause damage to nuclei. The number of nucleus-associated centrioles does not decrease after solubilization of nuclear membranes by Triton X-100. Nuclei retain the associated centrioles after treatmentwith RNase-free DNase I. It is concluded that in interphase the centrioles are associated with the nucleus and that this association which is probably mediated by filaments involves nuclear structures other than nuclear membranes or whole chromatin.

Animals↗
PubMedDate not supplied

[Structure of the interphase chromatin in Bursaria truncatella macronucleus. I. Electron microscopic and autoradiographic study of the structural chromatin changes during differentiation and growth after division].

The structure of interphase chromatin from isolated individual macronuclei of Bursaria truncatella was studied at different moments after cell division. During the period 0,5-3 hours after division most of the macronuclear chromatin is represented by loose agglomerations of decondensed chromatin, where transcription complexes can be seen. The maximum quantity of decondensed chromatin is observed 0,5-1,5 hours after cell division. During the period 1,5-3 hours after the division the part of decondensed chromatin decreases along with the increase of the quantity of dense chromatin organized in chromatin clumps 0,12-0,18 mu in diameter. In completely developed vegetative cells nearly all the chromatin has the structure of closely packed chromatin clumps. Electronmicroscopic autoradiography data show that chromatin clumps are transcriptionally inert, whereas all the transcription processes take place in decondensed chromatin agglomerations. The structure of transcription complexes of B. truncatella macronucleus is discussed in detail.

Animals↗
PubMedDate not supplied

[Structure of the interphase chromatin in the ciliata Bursaria truncatella macronucleus. II. Loop organization of inactive chromatin clumps].

Electron microscopic study of chromatin organization in isolated macronuclei of a ciliate Bursaria truncatella showed macronuclear chromatin to be organized in compact clumps 120--180 nm in diameter linked with each other by one or several chromatin fibres. Macronucleus being dispersed in a solution of low ionic strength, radial loops basically of nucleosomal structure start appearing around chromatin clumps. Long-time dispersing of macronuclear chromatin brings complete decompactization of chromatin clumps into a set of nucleosome fibres. The way the fibres of interphase chromatin are packed in a chromatin clump is discussed.

Cell Nucleus↗