Search citation statements
Paper Sections
Citation Types
Year Published
Publication Types
Relationship
Authors
Journals
Three main aspects involved in the chemical induction of anaphase-telophase aberrations in the first mitosis after treatment were analyzed: 1) the relationship between the frequency of anaphase-telophase aberrations and the time of fixation after treatment; 2) the dose-response relationships; and 3) the proliferative rate of cells exposed to chemicals which interact with DNA by different mechanisms. Experiments were carried out using Chinese hamster ovary (CHO) cells. The compounds examined were adriamycin (ADR) and mitomycin C (MMC). The frequency of cells with chromatin bridges or with lagging chromosomes as well as the mitotic index was determined in each experiment. The results obtained showed that 1) chromatin bridges and lagging chromosomes are apparently induced during the S period of the previous interphase; 2) the increase in the cytotoxicity index (inferred from the mitotic index) and the frequency of cells with chromatin bridges and lagging chromosomes were proportional to the treatment lapse and to the dose employed; and 3) the effect of ADR on cell growth differs from the effect of MMC. While ADR decreased the mitotic activity of cells in logarithmic growth phase, MMC induced mitotic delay. In accordance with these results, the occurrence of chromatin bridges in anaphase-telophase could be explained by the induction of chromosome stickiness and, to a lesser extent, by the induction of exchange-type aberrations. On the other hand, lagging chromosomes seem to be the result of chromatid or chromosome breaks because the lagging chromosomes observed were primarily, if not all, fragments and not whole chromosomes. Our evaluation of the anaphase-telophase test indicates that it is very sensitive method for the detection of chemical clastogens, but other factors, such as mitotic depression, must be taken into account to avoid false-negative results.
Three main aspects involved in the chemical induction of anaphase-telophase aberrations in the first mitosis after treatment were analyzed: 1) the relationship between the frequency of anaphase-telophase aberrations and the time of fixation after treatment; 2) the dose-response relationships; and 3) the proliferative rate of cells exposed to chemicals which interact with DNA by different mechanisms. Experiments were carried out using Chinese hamster ovary (CHO) cells. The compounds examined were adriamycin (ADR) and mitomycin C (MMC). The frequency of cells with chromatin bridges or with lagging chromosomes as well as the mitotic index was determined in each experiment. The results obtained showed that 1) chromatin bridges and lagging chromosomes are apparently induced during the S period of the previous interphase; 2) the increase in the cytotoxicity index (inferred from the mitotic index) and the frequency of cells with chromatin bridges and lagging chromosomes were proportional to the treatment lapse and to the dose employed; and 3) the effect of ADR on cell growth differs from the effect of MMC. While ADR decreased the mitotic activity of cells in logarithmic growth phase, MMC induced mitotic delay. In accordance with these results, the occurrence of chromatin bridges in anaphase-telophase could be explained by the induction of chromosome stickiness and, to a lesser extent, by the induction of exchange-type aberrations. On the other hand, lagging chromosomes seem to be the result of chromatid or chromosome breaks because the lagging chromosomes observed were primarily, if not all, fragments and not whole chromosomes. Our evaluation of the anaphase-telophase test indicates that it is very sensitive method for the detection of chemical clastogens, but other factors, such as mitotic depression, must be taken into account to avoid false-negative results.
Wilson, G. B. (Michigan State U., East Lansing.), A. H. Sparrow, and Virginia Pond. Subchromatid rearrangements in Trillium erectum. I. Origin and nature of configurations induced by ionizing radiation. Amer. Jour. Bot. 46(4): 309–316. Illus. 1959.—Microsporocytes of Trillium erectum were x‐irradiated with 25 r at various stages of meiotic prophase and at first metaphase. Analysis of these cells at the following first and second anaphase revealed that post‐pachytene irradiation produces 2‐side‐arm bridges which are indicative of half‐chromatid exchanges. The occurrence of these bridges and knowledge of the structure and spatial relationship of chromatid strands in T. erectum have led to certain conclusions regarding the target and the number of strands broken by a single event: (1) the most likely target for primary effects is the 4 associated half‐chromatids of a half‐bivalent. The results of irradiation experiments suggest that the half‐bivalent is effectively as well as structurally quadripartite at stages following pachytene. (2) Consideration of the configurations which would result from breakage and rejoining of 2, 3 or all 4 strands of the half‐bivalent indicates that only 2 of the 4 half‐chromatids are broken by a single event. Exchanges between 2 half‐chromatids of sister chromatids will produce two recognizable types of 2‐side‐arm bridges: one with a true dicentric half‐chromatid and one in which the bridge results merely from an interlocking of coils. Whether a 2‐side‐arm bridge appears at first or second meiotic anaphase is determined by the position and number of chiasmata between the point of breakage and the kinetochore. No 2‐side‐arm bridges have been detected at microspore anaphase following meiotic prophase irradiation. The types of configurations which might be expected at microspore metaphase as a result of broken 2‐side‐arm bridges are noted.
The gametophyte of Trichomanes pinnatum is filamentous save for its club‐shaped archegoniophores. Gametangial structure is consistent with that of related species. The apogamous embryo originates from the archegonial jacket and contiguous tissue such that there is no external indication of apogamy. The life cycle follows the Döpp‐Manton scheme. Specimens were studied which were homozygous for a paracentric inversion and these showed chromosomal bridges and associated fragments at meiosis‐I, thus confirming cytologically the occurrence of homoeologous pairing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.