Showing papers on "Chromosome breakage published in 1976"

The Micronucleus Test for Cytogenetic Analysis

Abstract: Micronuclei originate from chromatin which for different reasons has been lagging in anaphase (Fig. la-d). In the course of telophase this material is included into one or the other daughter cell where it either can fuse with the main nucleus or form one or several secondary nuclei. These are, as a rule, considerably smaller than the principal nucleus and are therefore called micronuclei. Lagging has two main causes: chromosome breakage and malfunction of the spindle apparatus. In the first case the lagging elements are acentric chromosome fragments and di- or multicentrics connected by bridges, and in the second case they consist of entire chromosomes.

Ten model mutagens evaluated by the micronucleus test.

Abstract: The following ten mutagenic compounds were subjected to the micronucleus bone marrow test (MNT) in the mouse: cyclophosphamide (CTX), thiotepa (TT), vincristin (VCR), colcemid (COLC), adriamycin (AM), bleomycin (BM), cytosin arabinoside (ARA C), 6-mercaptopurine (6-MP), methotrexate (MTX) and 5-fluorouracil (5-FU) Dose-effect curves were established for all compounds With the exception of CTX, COLC and AM, the drugs also were subjected to chromosome analyses on Chinese hamster fibroblasts in vitro The MNT revealed loss of chromatin due to chromosome breakage and rearrangements by CTX, TT and AM, to breakage by ARA C, 6-MP, MTX and 5-FU, as well as loss of entire chromosomes caused by impairment of the spindle by VCR and COLC With the exception of BM, the effects were demonstrable in the therapeutic dose range The MNT, provided it is carried out by the methodology of the authors, not only reveals chromatin loss but permits important conclusions in regard to the proliferative state of the bone marrow and the specific time of action of the mutagens in the cell cycle If arrest of the cell cycle occurs, as in the case of anti-metabolites MTX and 5-FU particularly, the routine scheme of investigation needs to be modified since micronucleated cells appear only after release of the metabolic block, ie after a delay of 24 h The negative bone marrow results obtained with BM emphasize the importance of combining in vivo and in vitro tests

The Radiotoxicity of Iodine-125 in Mammalian Cells: II. A Comparative Study on Cell Survival and Cytogenetic Responses to 125 IUdR, 131 IUdR, and 3 HTdR

Abstract: Hydrogen-3, iodine-125, or iodine-131 was incorporated into cellular DNA in the form of thymidine or its analog 5-iodo-2-deoxyuridine. The effects of these radionuclides on cell survival and chromosomes were examined in the V79 Chinese hamster cell line. It was found that in terms of cell killing, iodine-125 was considerably more effective than iodine-131 and hydrogen-3. The mean radioactivity contents at 37 percent survival were 0.10, 1.16, and 1.64 pCi per cell for iodine-125, iodine-131, and hydrogen-3, respectively. Similarly, iodine-125 was much more effective in inducing chromosome aberrations than iodine-131 or hydrogen-3. For example, 0.1 pCi per cell of iodine-125 gave rise to three chromosome breaks per cell; it took 1.0 pCi per cell of iodine-131 or 1.7 pCi per cell of hydrogen-3 to produce the same effect. The cytogenetic consequences of irradiation by these radionuclides, which decay by disparate processes, were directly related to their lethal effects and strengthens the theory that radiation-induced cell death results from damage in chromatin structures.

Identification with G and R banding of the position of breakage points induced in human chromosomes by in vitro x-irradiation.

Abstract: SummaryThe aberrations seen in chromosomes of human peripheral-blood lymphocytes, X-irradiated in vitro, have been analysed in three types of preparations, treated to give G-banding; R-banding; and G-banding followed by R-banding on the same cells. The data from cells subjected to both banding techniques reveals that 30 per cent of the sites of chromosome breakage are situated at the interfaces between dark- and light-stained bands. The results of all the analyses show that approximately 30 per cent of all breaks were located in either the telomere (19·5 per cent) or centromere (11·3 per cent) regions. Chromosomes rich in R-band material were not preferentially damaged, but chromosomes 12, 15, and particularly 17, were involved in aberrations more frequently than would be expected on the basis of their length. No breaks were found on the Y chromosome in the 114 male cells analysed, but the X did not appear to be spared from damage either in the male cells or the 136 female cells analysed.G and/or R-bandin...

Chemical mutagen hypersensitivity in ataxia telangiectasia

Abstract: THE growth of knowledge about DNA replication and repair in bacteria has been aided by the availability of a series of mutations specifically affecting these processes. Almost invariably, defects in repair processes result in an alteration in the sensitivity of cells to ionising radiation and other mutagenic agents. Knowledge is much less advanced for animal cells, although information has been obtained using cells from patients with, for example, xeroderma pigmentosum which have provided six possible mutants in DNA repair1,2. The diseases classified as chromosome breakage syndromes—ataxia telangiectasia (AT), Fanconi's anaemia and Bloom's syndrome—may also provide a rich source of DNA metabolic mutants. The frequent association of defective DNA metabolism with mutagen sensitivity has suggested an approach to the study of chromosome breakage syndromes. Finkelberg et al.3 have found that Fanconi's anaemia cells are abnormally sensitive to mitomycin C (MC). We have now used this approach to determine whether cells from AT patients are potentially defective in DNA metabolism. We examined their sensitivity to actinomycin D, MC and methyl methane sulphonate (MMS), and the results indicate that AT cells are clearly more sensitive to actinomycin D and that responses to MMS and MC are more variable.

Detection of sister chromatid exchanges by 4′-6-diamidino-2-phenylindole fluorescence

Abstract: This paper describes a 4′-6-diamidino-2-phenylindole (DAPI) fluorescent technique for differentiation of sister chromatids and for the study of sister chromatid exchanges (SCE) in mouse chromosomes. The advantages of the DAPI fluorescent technique are also described. Differences in the occurrence of SCE between the centromeric heterochromatin (C-banded) and the chromosomal arm chromatin were studied in mouse cells (RAG) with or without mitomycin C treatment. Single strand exchanges between the DNA double helices in the sister chromatids were not detected. SCE and chromosome breakage appeared to occur more frequently in the centromeric region than in the chromosomal arm. This might play an important role in chromosome evolution in mice.

A cytogenetic analysis of meiotic drive in the mosquito, Aedes aegypti (L.)

Abstract: Meiotic drive in Aedes aegypti (L.) is shown by a Giemsa C-banding technique to be associated with preferential isochromatid breakage of the X chromosome during male meiosis. These breaks remain open at least until anaphase-I and, since the range of cells affected is proportional to the sensitivity of the X chromosome to the Distorter gene, it is argued that they are directly related to the decreased number of spermatozoa found in distorting males. This reduction is considered to be attributable to the degeneration of more X- than Y-bearing spermatids but it is probable that some non-functional X-bearing spermatozoa are also produced. Chromosome breakage is almost completely confined to four sites, two adjacent to the centromere, one just proximal to the intercalary band and another about the centre of the unbanded arm. Although the first three of these lie within a region in which crossing-over does not take place, fragmentation occurs more frequently in a chiasmate arm than in one devoid of chromatid exchange.

The capacity of Drosophila for detecting relevant genetic damage.

Abstract: For the detection and study of mutagenic agents, Drosophila offers many advantages. It is a higher organism with a short generation time that is cheap and easy to breed in large numbers. The simple genetic testing methods provide unequivocal answers about the whole spectrum of relevant genetic damage. A comparison of the detection capacity of assays sampling different kinds of genetic damage revealed that various substances are highly effective in inducing mutations, but do not produce chromosome breakage effects at all, or only at much higher concentrations than those required for mutation induction. Of the different assay systems available, the classical sex-linked recessive lethal test thus deserves priority, in view of its superior capacity to detect mutagens. Of practical importance is also its high sensitivity, because a large number of loci in one-fifth of the genome is tested for newly induced forward mutations, including small deletions. Drosophila is capable of carrying out the same metabolic activation reactions as the mammalian liver. An additional advantage, in this respect, is the capacity of Drosphila for detecting short-lived activation products, because intracellular activation occurs within the spermatids and spermatocytes. These properties make the test for recessive sex-linked lethals a useful tool for verifying results obtained in the pre-screening of potential mutagens with fast microbial assay systems. In studies on non-disjunction, detailed genetic analysis of the induced changes is possible, and these may shed light on the mechanisms involved. A new adaptation of the bithorax transvection method by Mendelson permits the recovery of high yields of chromosome aberrations in a fast one-generation test.

Mutagenic potential of the condiments, ginger and turmeric.

Abstract: The effects of the two commonly used condiments, ginger and turmeric on cell divisions in root tip cells of onion have been studied. The predominant type of aberration in both cases was chromosome breakage. C-mitosis, somatic segregations, multipolar anaphases etc. were also observed. The present study has shown that extracts of fresh rhizomes of Zingiber officinale (ginger) and Curcuma longa (turmeric) are radiomimetic and may be mutagenic.

The effect of continuous intake of tritiated water (HTO) on the liver chromosomes of mice.

Abstract: Chromosomal damage in the livers of mice exposed to continuous intake of triated water (HTO) was evaluated. Hale--Stoner Brookhaven mice were maintained on HTO (3 ..mu..Ci/ml) for 90, 330, (500, 560), and 700 days. The experimental animals and age-matched controls were partially hepatectomized to stimulate liver cell division and the frequency of chromosome aberrations in metaphase cells of the liver was used as an index of radiation-induced change. When liver cell chromosomes from mice on HTO water were compared with those from age-matched controls, there was a higher level of damage in the animals on HTO. This was true for both hyperdiploid and diploid cells. At the 5% level, however, the increase was not statistically significant. When the data were analyzed without four animals, one with a clone of abnormal cells and three with an unusual distribution of chromosome damage, there was a significant increase in the level of chromosome damage in the livers of mice on HTO for either 330 or (500, 560) days. The level of chromosome damage following HTO ingestion was similar on a per rad basis to that seen in Chinese hamster livers after protracted /sup 60/Co gamma exposure or internally deposited /sup 144/Ce, an energeticmore » beta emitter. The data support the concept that on a per rad basis the risk for chromosome breakage following tritium exposure as HTO is similar to that from other beta--gamma emitters.« less

Dose, Dose Rate, Radiation Quality, and Host Factors for Radiation-Induced Life Shortening

Abstract: This paper reviews the effects of ionizing radiations on disease incidence and life shortening in experimental animals, with the aim of establishing a phenomenological model of the dose and time kinetics for the production of late radiation damage. Aspects of this problem have been discussed previously (Sacher, 1956a). At that time, mammalian cellular radiology had barely begun its dramatic development, and there were no experimental data against which to test the hypothesis adopted then, that the phenomena of radiation life shortening are due to chromosome breakage and rejoining. This hypothesis was stated most explicitly by Muller (1950), but it was also implicit in the discussion of lethal effects in cells by Lea (1947), and in a real sense it was a development that epitomized the classical period of radiation genetics.

Genotype-hormone interaction in the induction of chromosome aberrations: Effect of 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin on tissue cultures from nicotiana SPP. ☆

Abstract: The effect of a synthetic auxin-like substance (2,4-D) and a synthetic cell division factor (kinetin) on the induction of chromosome aberrations was studied on tissue cultures of Nicotiana glauca and the tumorous amphidiploid hybrid Nicotiana glauca × Nicotiana langsdorffii The aberration frequencies in normal Nicotiana glauca tissue were proportional to the length of time of culture in the presence of 2,4-D Moreover, both 2,4-D and kinetin increased chromosome breakage in the habiatouated Nicotiana glauca tissue but not in the amphidiploid hybrid tissue The data are discussed in terms of genotype-hormone equilibria in long-term development of plant tissue culture

Enlarged euchromatic chromosomes (“megachromosomes”) in hybrids between Nicotiana tabacum and N. plumbaginifolia

Abstract: The gigantic chromosomes (“megachromosomes”) described previously as occurring spontaneously in hybrid combinations between N. tabacum and species of the Tomentosae section of Nicotiana were due to an enlargement of heterochromatic segments introduced from the latter into a N. tabacum background. Only chromosomes with large heterochromatic segments became megachromosomes and the enlarged parts themselves showed at interphase and prophase the intense staining characteristic of heterochromatin. Euchromatic arms of the same chromosomes did not undergo enlargement. In contrast, megachromosomes described here for N. tabacum x N. plumbaginifolia hybrids originate from chromosomes which have no heterochromatic blocks. These megachromosomes are not recognizable at interphase and when distinguished at prophase are found to be stained lightly like the rest of the euchromatin. The mode of origin of megachromosomes is still unknown. Spontaneous chromosome breakage is frequent in all hybrids in which megachromosomes are found and is probably associated in some way with their formation, but an origin of megachromosomes by breakage and end-to-end fusion of broken strands is unlikely. This leaves as a possibility an origin by repeated replication from the same template. Other examples of very large chromosomes with characteristics of megachromosomes found in the literature are briefly discussed. They all arose in atypical situations of interspecific hydribization, exposure to mutagens or in tumors and cell cultures.

Analysis of combined effects of benzene with radiation on chromosomes in cultured human leukocytes.

Abstract: Three experiments were carried out on 53-hr cultured human leukocytes on chromosome mutagenicity of benzene with particular reference to combined effects with gamma-radiation and inhibitory effect on rejoining of radiation-induced chromosome breaks. The results and their analyses were summarized as follows: 1) Benzene can induce mainly chromatid-type deletions, especially gaps, suggesting that the cells in their late S-G2 stage have a higher susceptibility to chromosome breakage by benzene. 2) The aberration tield of dicentrics and rings induced by 100 rads irradiation can significantly be enhanced by the treatment of benzene equal to or in excess of 0.2 mM. 3) Quantitative analyses using newly defined "Synergetic effect factor" revealed that combined cytogenetic effect of benzene with radiation could be synergetic exclusively in dicentrics and rings, being almost additive in the other types of aberration. 4) The experiment with dosage fractionation method showed that the more strongly benzene could inhibit the rejoining of radiation-induced chromosome breaks, the higher concentration it was treated at. Related iwth these results, possible inducps, and the repair and its inhibition of radiation-induced DNA-strand(s) breaks. Further studies for related effects by benzene are needed on protein synthesis, activities of repair enzymes and fine structure of chromosomes.

Consequences of a nationwide ban on spray adhesives alleged to be human teratogens and mutagens.

Abstract: A report of an association of chromosome breakage and birth defects with spray adhesive exposure resulted in a ban on the sale of these products and nationwide publicity warning exposed women. Six months later the ban was removed; the association could not be confirmed. Replies to questionnaires sent to medical genetics centers throughout the United States revealed that more than 1100 inquiries had been received and more than 1200 working days were expended because of the issue. Eleven exposed women underwent diagnostic amniocentesis, and on elected to abort her fetus. Eight other women who were exposed also elected to do so, but without first undergoing diagnostic amniocentesis. The episode illustrates some of the unexpected and unnecessary consequenes that can arise from the false identification of an environmental agent as a mutagen or teratogen.

Cytogenetical studies on the effects of high natural radiation levels in Tityus bahiensis (Scorpiones, Buthidae) from Morro do Ferro, Brazil

Abstract: The external radiation level in Morro do Ferro in the State of Minas Gerais, Brazil, ranges from 0.1 to 3.2 mR/h, suggesting a mean level among the highest reported anywhere in the world. Cytogenetical effects which might be due to the high natural level of ionizing radiation were searched for in males of Tityus bahiensis, a species which inhabits an area where radiation levels range from 0.8 to 1.5 mR/h. These scorpions have a nonlocalized centric system which allows chromosomal breakage without loss of genetic material. The results indicate that there is a statistically significant difference (X/sup 2/ = 116.75, p less than 0.00005) in the number of cells with chromosome breaks observed in spermatocytes of scorpions from Morro do Ferro and control areas. A total of 13,968 and 16,373 spermatocyte cells of scorpions from Morro do Ferro and control areas, respectively, were analyzed.

Assaying potential carcinogens with Drosophila.

Abstract: Drosophila offers many advantages for the detection of mutagenic activity of carcinogenic agents. It provides the quickest assay system for detecting mutations in animals today. Its generation time is short, and Drosophila is cheap and easy to breed in large numbers. The simple genetic testing methods give unequivocal answers about the whole spectrum of relevant genetic damage. A comparison of the detection capacity of assays sampling different kinds of genetic damage revealed that various substances are highly effective in inducing mutations but do not produce chromosome breakage effects at all, or only at much higher concentrations than those required for mutation induction. Of the different assay systems available, the classical sex-linked recessive lethal test deserves priority, in view of its superior capacity to detect mutagens. Of practical importance is also its high sensitivity, because a large number of loci in one fifth of the genome is tested for newly induced forward mutations, including small deletions. The recent findings that Drosophila is capable of carrying out the same metabolic activation reactions as the mammalian liver makes the organism eminently suitable for verifying results obtained in prescreening with fast microbial assay systems. An additional advantage in this respect is the capacity of Drosophila for detecting short-lived activation products, because intracellular metabolic activation appears to occur within the spermatids and spermatocytes.

Patterns of mitosis and differentiation in cells derived from pea root protoplasts

Abstract: of mitoses in these cultures. The patterns of the time course of both DNA synthesis and cell division in the protoplast cultures were similar to such pattems observed in the culture of intact root explants, although longer lag periods were observed in the protoplast cultures. Mitotic abnormalities including both chromosome breakage and spindle disfunction were observed in protoplast cultures. A large portion of the cell pairs derived from mitoses (27 % in one experiment) contained Feulgen-positive micronuclei. An accumulation of an as yet unidentified differentiation product termed dense cytoplasmic protoplast derivative was observed. Some of the conditions influencing the development of these derivatives are reported. THE PEA ROOT CORTICAL explant was selected as a source of tissue for protoplast isolation because of the existing background data concerning DNA synthesis and the developmental capacity of the system. Cells of the cortex of pea roots are involved in the formation of nitrogen-fixing nodules during symbiotic interactions with the bacteria, Rhizobium (Torrey and Barrios, 1969). The cortical cells are also capable of differentiation into tracheids in culture (Torrey and Fosket,

Effects of Δ8-Tetrahydrocannabinol, Δ9-Tetrahydrocannabinol, and Crude Marihuana on Human Cells in Tissue Culture

Abstract: In recent years a moderate controversy has arisen with respect to the possible cytotoxic effects of marihuana and its related compounds. Neu et al. [6] studied Δ9-tetrahydrocannabinol (Δ9-THC) in in vitro experiments with human leukocytes and found no increase in chromosome abnormalities. Stenchever and Allen [9] demonstrated similar negative findings in an experiment in which the Δ9-THC was placed in tissue culture media after phytohemag-glutinin had been added to the leukocytes. In these experiments the Δ9-THC was present throughout the entire 72 hr of culture, and a number of concentrations ranging from 0.1–100 µg/cc of culture medium were studied. At the higher concentrations, there was a noticeable increase in cell death and decreased mitotic activity. Pace et al. similarly could find no chromosome damage in rat cells after exposure to marihuana resins [8]. Martin and coworkers [4] exposed both embryonic rat fibroblasts and human leukocytes to cannabis resins in vitro in separate studies and demonstrated a dose-related decrease in mitotic rate but no increase in chromosome abnormalities.

Genetically controlled chromosome breakage as an isolation barrier in the origin and maintenance of secale ancestrale

Abstract: Meiosis in hybrids derived from crosses of Secale ancestrale Zhuk. with related species is highly irregular: chiasmata fail to terminalize; numerous AI and AII bridges form but are usually unaccompanied by fragments; acentric fragments without true bridges are left behind at AI and AII; numerous micronuclei are produced at TII. These anomalies appear to be the result of genetically induced subchromatid exchanges. This appears to be a mechanism established by natural selection for reproductive isolation, thereby permitting this narrowly endemic species to successfully continue in sympatric association with closely related species.

Chemical mutagens: alkylating agents. I: Genetical effects

Abstract: Tests for mutagenic effects of chemicals are almost as old as modern genetics (see article by Auerbach in Vol. 1 of ‘Chemical Mutagens’; Bibliography). In 1914, T.H. Morgan had already tried to produce mutations in Drosophila by treatment with alcohol and ether, but without success. In the twenties and thirties, Muller’s techniques for the determination of mutation rates in Drosophila (Chapter 5) were applied to a variety of chemicals. Russian workers claimed success for ammonia, iodine, potassium permanganate and copper sulphate; for the last-named substance, confirmatory data were published in U.S.A. In most of these experiments, the differences between the frequencies of sex-linked lethals in controls and treated flies were statistically significant, but treatment effects were small. Lethal frequencies in the treated series rarely exceeded or even reached 1%, which is roughly the upper limit for untreated flies. A fact that was not known at the time but meanwhile has been clearly established, is the dependence of spontaneous mutation frequency on breeding procedure and on the brood tested (1). This raises the possibility that the chemicals used in these early experiments had yielded increased mutation frequencies not by inducing mutations but by affecting the rate of sperm utilization in such a way that the samples from treated males contained a higher proportion of mutationbearing spermatozoa than did those from the control flies.

Consequences of a nationwide ban on spray adhesives alleged to be human teratogens and mutagens

Abstract: A report of an association of chromosome breakage and birth defects with spray adhesive exposure resulted in a ban on the sale of these products and nationwide publicity warning exposed women. Six months later the ban was removed; the association could not be confirmed. Replies to questionnaires sent to medical genetics centers throughout the United States revealed that more than 1100 inquiries had been received and more than 1200 working days were expended because of the issue. Eleven exposed women underwent diagnostic amniocentesis, and on elected to abort her fetus. Eight other women who were exposed also elected to do so, but without first undergoing diagnostic amniocentesis. The episode illustrates some of the unexpected and unnecessary consequenes that can arise from the false identification of an environmental agent as a mutagen or teratogen.

Mutagenesis by ultraviolet and visible light. I: Early work on macro-organisms

Abstract: Research on the mutagenic action of UV started very soon after the discovery of X-ray mutagenesis. By the early thirties, it had been established that UV can produce mutations in Drosophila and flowering plants. Research was carried on with three principal aims in mind. One concerned the relationship between intragenic mutations and intergenic structural changes, which was then a very much debated topic. The X-ray data allowed no decision as to whether the two types of event have the same cause. Indeed, as mentioned in Chapter 6, some geneticists believed that all X-ray induced mutations were in reality chromosome rearrangements. Since UV, in contrast to X-rays and other high-energy radiation, produces only atomic excitations but no ionizations, the question could be asked whether perhaps structural changes required ionization for their production. The answer, as we shall see presently, was negative. All the same, the proportion of rearrangements among UV-induced mutations was generally low, and this led to the second aim, which was to analyse the nature of gene mutations by means of an agent that is less destructive than X-rays. This approach was to bear full fruit later, when the chemical nature of the genetic material had been elucidated.

[Distribution of chromosome breakage point induced by arabinosylcytosine on in-vitro human lymphocytes].

Abstract: The cytogenetic effects of arabinosyl cytosine on human leukocytes in vitro has been studied using continuous and discontinuous treatments. Optimum activity occurs at the end of the S period. Interchromosomal distribution of breaks is non-random. The hypothesis of a very late replication for some chromatid segments is discussed. The relations between banding and the position of breaks are discussed.

Chromosome breakage in low birth weight newborns.

Abstract: The frequency of chromosome aberrations in cells cultured from umbilical cord blood was determined for 50 low birth weight (LBW) and 50 normal birth weight (NBW) euploid newborns matched for sex, race, and maternal age. The metaphase spreads had been prepared in the course of an earlier study of frequency of aneuploidy and results are from 72-h cultures, i.e., presumably, at the second division in vitro. There were no significant differences between the two groups in the frequency of cells with chromosome breakage, chromosome gaps, or hyperdiploid cells. There was, however, a significantly higher frequency of hypodiploid cells in the LBW group. The present findings differ from those of others who have reported an increase in chromosome breakage in premature newborns.

Repair of X-ray damage I: Repair of chromosome breaks

Abstract: We have seen in Chapter 2 that chromosome breakage may have one of three consequences (1) The breaks rejoin in the old order — restitution (2) The breaks rejoin in a new, wrong order — formation of rearrangements (3) The breaks remain open This leads to either terminal deletion or chromosome loss via a breakage-fusion-bridge cycle Since there is no essential difference between the types of rejoining that result in restitution or in the formation of rearrangements, we shall consider both as forms of repair Sobels has introduced the useful term ‘misrepair’ for the production of rearrangements