Chromosome fragment

The pathway of delivery seems to be an important determinant in the geno-toxicity of nickel compounds in vitro. Regarding X-chromosome fragmentation in CHO cells [306, 444], nickel chloride was reported to be ineffective by contrast to crystalline NiS. Delivery and uptake by phagocytosis of NiCl2, artificially encapsulated in liposomes, induced fragmentation. 

Detection of chromosome fragments. Individuals with Turner s syndrome are, in some cases, mosaic for a portion of or for the entire Y chromosome (46,XY/45,X). Since such individuals may be at increased risk for gonadal tumors, Southern blot or PCR analysis has been used to detect the presence of Y chromosome segments in studies of DNA from peripheral blood samples. Similarly, the fetal sex as well as the presence of some aneuploid states (e.g., trisomy 18) can be determined by analysis of DNA from chorionic villi or amniotic fluid cells. 

The test is used for the detection of cytogenetic damage to the chromosomes or the mitotic apparatus of erythroblasts by analysis of erythrocytes for formation of micronuclei (small nuclei, separate from and additional to the main nuclei of cells, produced during the telophase of mitosis (meiosis) by lagging chromosome fragments or whole chromosomes). When a bone marrow erythroblast develops into a polychromatic erythrocyte (immature erythrocyte), the main nucleus is extruded any micronucleus that has been formed may remain behind in the otherwise anucleated cytoplasm. 

The test is used to detect DNA repair synthesis and for the detection of micronuclei in the cytoplasm of interphase cells. These micronuclei may originate from acentric fragments (chromosome fragments lacking a centromere) or whole chromosomes that are unable to migrate with the rest of the chromosomes during the... 

CS has been tested for its ability to cause chromosomal damage in a micronucleus test in mice. Micronucleus tests detect small nuclei that arise from chromosomal fragments or chromosomes that fail to be incorporated into normal daughter nuclei when cells divide. An increased frequency of micronuclei is evidence of chromosomal break-... 

Micronucleus Test The micronucleus test is an in vivo test usually carried out in mice. The animals are treated in vivo, and the erythrocyte stem cells from the bone marrow are stained and examined for micronuclei. Micronuclei represent chromosome fragments or chromosomes left behind at anaphase. It is basically a test for compounds that cause chromosome breaks (clastogenic agents) and compounds that interfere with normal mitotic cell division, including compounds that affect spindle fiber function. 

Related Tests. Many cells exposed to test chemicals can be scored for chromosome aberrations by staining procedures followed by visual examination with the aid of the microscope. These include Chinese hamster ovary cells in culture treated in a protocol very similar to that used in the test for SCEs, bone marrow cells from animals treated in vivo, or lymphocytes from animals treated in vivo. The types of aberrations evaluated include chromatid gaps, breaks, and deletions chromosome gaps, breaks, and deletions chromosome fragments translocations and ploidy. 

Cytogenetic damage Mouse Micronucleus test Chromosomal fragments in erythrocyte stem cells <1 mo M M M M... 

Several assays in mammals permit a determination of the incidence of micronuclei 393 of these, the only one sufficiently developed to be a standard assay is the in vivo mammalian bone marrow polychromatic-erythrocyte assay.155 Micronuclei are formed from chromosomes or chromosomal fragments that are not incorporated into daughter nuclei at the time of cell division. Ihus, this very rapid test serves as an in vivo somatic cell screening test for finding genotoxic chemicals that might break chromosomes or cause nondisjunction in germ cells. It has been applied to more than 150 chemicals.158... 

MICRONUCLEUS A nucleus, separate from and additional to the main nucleus of a cell, produced during telophase of mitosis or meiosis by lagging chromosomes or chromosomal fragments derived from spontaneous or experimentally induced chromosomal structural changes the smaller of the two nuclei that occur in the cells of ciliate protozoans. 

Chromosome changes Increase in dicentric chromosomes and chromosome fragments noted. 

Immunocyto- chemistry Antigenic proteins or protein complexes, constitutive or foreign Polyclonal or monoclonal antibodies Multiple-epitope- or single-epitope-specific Localization of kineticore protein on chromosome fragments in micronuclei using labeled antibody to kineticore protein... 

After Giemsa staining, the numbers of chromosomes and their normal or abnormal appearance in metaphase spreads are determined. In the micronucleus test, femoral bone marrow smears are stained with Giemsa or a fluorescent dye such as acridine orange, and the numbers of polychromatic erythrocytes containing micronuclei are determined. Normal polychromatic erythrocytes contain no nuclei. In the process of red blood cell maturation, the nucleus is expelled just prior to the polychromatic erythrocyte stage. Micronuclei represent chromosomes or chromosome fragments that are left behind in the cell after expulsion of the nucleus. 

Dowd MA, Gaulden ME, Proctor BL, et al. 1986. Formaldehyde-induced acetric chromosome fragments and chromosome stickiness in Chortophaga neuroblasts. Environ Mutagen 8 401-411. 

Figure 5.25 Genome comparison. A schematic comparison of the human genome and the mouse genome shows reassortment of large chromosomal fragments.

Chromosomally located genes that are unique to Y. pestis and make up the dispensable part of its genome are laterally acquired mobile genomic elements. Until now, there has been no direct evidence of their effect on pathogenicity. Perhaps further analysis of a larger collection of Yersinia strains might further reduce the number of Y. /ie.sf/.s-specific chromosomal fragments. 

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