Non-random distribution of aberrations and identification with C- and G-bindings of the position of breakage points on muntjac chromosomes induced by mitomycin C,bromodeoxyridine and hydroxylamine

The analysis of chromosomes from muntjac after treatment of its lymphocyte cultures with 3 chemical mutagens having different base-pair affinities and modes of action, namely mitomycin C (MC), 5-bromodeoxyuridine (BUdR) and hydroxylamine hydrochloride (HA), with G- and C-band staining displayed non-random distribution of chemically specific damage points on them. The randomness of the involvement of each site on the chromosomes was examined by assuming an expected value calculated on the basis of its relative mitotic length. The observation revealed that a large fraction of MC-induced aberrations was preferentially located in the C-band positive constitutive heterochromatin, especially in the long “neck-like” centromeric region of the X-chromosome. On the chromosomal arms, the light G-bands were involved in aberrations either in proportion to or higher than that expected. When the cells were treated with BUdR, the dark G-bands on all the chromosomes of the complement were the preferred sites, displaying statistically significant higher numbers of aberrations. A singe “hot-spot” for induced damage on 1 mid-q was also recorded. HA induced a very high frequency of damage in the secondary constriction regions of the chromosome pairs 1, X and Y₂, and the frequency was slightly lower than this in the centromeres of 1, 2 and X chromosomes.The observation of specific distribution of damage points induced by the 3 chemicals leads to the suggestion that, though the effect of a chemical on chromosome segments depends on several factors, each being partially responsible for the end result, it is perhaps primarily decided by the chemical's base-pair affinity and mode of action.A large variety of chemicals induce, in chromosomes, aberrations that are often distributed non-randomly. The non-random distribution of the chemically induced aberrations was noted even before the discovery of banding techniques, but with the use of conventional staining the identification of the exact location of induced break points, except for a few specific landmarks such as centromeres or secondary constrictions, was difficult and often unreliable too. Therefore, by using various banding techniques as a tool, a much more accurate assessment of the induced break points could be made. Several studies suggest that the involvement of specific chromosomes and/or chromosome segments are probably dependent upon the chemical used (Ayrand et al, 1976; Kaina, 1977; Kucerova and Polivkova, 1976; Morad et al., 1973; Morad and Zavahri, 1977; Reeves and Margoles, 1974). Meyne et. (1979) have suggested that, in addition to the nature of the chemicals used, the organization of chromosomes may also be responsible for the localized aberrations. To examine these points further, it was considered of interest to compare the extent of sensitivity of different chromosomal segments identified with banding techniques, after exposure to certain chemicals having different modes of action and base-pair affinities.In the present study, we compared the location of damage points on the chromosomes of the Indian barking deer Muntiacus muntjak, induced by 3 chemicals, namely (1) mitomycin C (MC), an antibiotic that acts by forming cross links with guanines between the complementary strands (Iyer and Szybalski, 1963), (ii) 5-bromodeoxyuridine (BUdR), a base analogue which is incorporated with concomitant thymine replacement into the DNA of mammalian cells (Djordjevic and Szybalski, 1960) and causes mutagenesis through a maispairing mechanism (Drake, 1970; Witkin and Parisi, 1974; Hutchinson and Stein, 1977; Rydberg, 1977), and (ii) hydroxylamine hydrochloride (HA), a reducing agent which reacts mainly with the cytosine moiety of the DNA by aminating only the C-4 atoms (Freese et al., 1961).     

Differential sensitivity of peripheral blood lymphocytes of untreated leprosy patients to mitomycin C

The effects of a bifunctional alkylating agent mitomycin C (MMC), an effective inducer of chromosome aberrations and sister-chromatid exchanges (SCEs), have been studied in untreated leprosy patients. This was done to study the mutagen sensitivity of the leprosy patients. The frequency of chromosomal aberrations induced by MMC (conc. 0.01 microgram/ml) was 2.5% in controls, 3.6% in paucibacillary (PB), and 6.8% in multibacillary (MB) patients. The difference in the frequency of MMC-induced chromosome aberrations between the 3 groups studied was highly significant (p less than 0.01). Cultures grown with MMC showed the frequency of SCEs/cell to be 12.70 +/- 1.19 in controls, 19.97 +/- 3.51 in PB, and 29.66 +/- 5.92 in MB patients. The differences in the frequency of MMC-induced SCEs between the 3 groups were found to be highly significant (p less than 0.01). The enhanced frequencies of spontaneous and MMC-induced chromosome aberrations and SCEs observed in PB and MB patients indicate a clear differential mutagen sensitivity between PB and MB patients who are known to have different immunological status and thereby differ in the severity of the disease.     

Characterization of G-banded chromosomes of the Indian muntjac and progression of banding patterns through different stages of condensation

Muntjac prophase and metaphase chromosomes were G-banded following methotrexate-mediated synchronization of peripheral lymphocytes. Bands and subbands were characterized from prophase through metaphase, and the progression of band patterns from late prophase to mid-metaphase was analyzed. Extended prophase chromosomes exhibited more bands and subbands, a number of which became fused with each other, giving rise to fewer and thicker bands in the condensed metaphase chromosomes. It appeared that the dark bands condensed relatively more than the light bands. Precise delineation of the bands and subbands on extended prophase chromosomes and the usage of a proposed banding pattern nomenclature should aid in better detection and localization of induced chromosomal rearrangements with this extremely useful experimental material.     

Effect of mitomycin C and bromodeoxyuridine on Fanconi anemia lymphocytes.

The authors studied the effect of mitomycin C (MMC) and bromodeoxyuridine (BrdU) on the induction of chromosome aberrations on lymphocytes of four patients with Fanconi anemia (FA) and of one normal subject. A control culture and six experiments were designed to test the possible synergic effect of MMC and BrdU. Their results revealed no evidence of MMC-BrdU synergism on the induction of chromosome aberrations in FA lymphocytes. However, chromosomes showed more damage when FA cells were harvested 24 h after MMC stress than when cells were harvested shortly after treatment. This can be explained by a DNA repair defect or by a toxic effect of oxygenation of cells during the procedure.     

Damage susceptibility of human lymphocyte chromosomes at different stages of the mitotic cycle in combined exposure to fast neutrons and postradiation hyperthermia

The combined action of gamma rays (1-4 Gy) and postradiation hyperthermia on the human lymphocyte culture induces intensification of the damaging effect at the stage of DNA synthesis, i.e. at the most radioresistant stage of the mitotic cycle, the thermal intensification factor (TIF) being 1.7-2.0. After the neutron action (0.5-1.5 Gy) the hyperthermia has no effect on the chromosome aberration spectrum, the TIF being 1.8-2.5 at G1 phase and 1.8-2.4 at S phase, which testifies to the possible modification of neutron irradiation.     

不同发育阶段的斑腿树蛙蝌蚪对敌敌畏遗传毒性的敏感性

敌敌畏是我国农田中使用最普遍的有机磷杀虫剂,它通过干扰对神经传导起重要作用的胆碱酯酶的活性,起到接触和摄入毒杀昆虫的作用,也对当地水生动物及种群造成很大威胁。本文以广泛分布于我国南方农田区域的斑腿树蛙蝌蚪为研究对象,用碱性单细胞电泳方法比较了暴露于不同浓度(2.08,4.16,6.24,8.32,10.40mg/L)的敌敌畏溶液中三个发育阶段的遗传毒性的差异。结果表明:敌敌畏溶液暴露24h,对早期和中期阶段的蝌蚪造成极显著的DNA损伤(P<0.01),甚至在敌敌畏浓度低达2.08mg/L的溶液中也产生显著的损伤(P<0.05);统计分析表明,DNA长宽比率与敌敌畏剂量之间呈显著的线性关系,早期阶段和中期阶段的相关系数分别为0.950(P<0.01)和0.954(P<0.01)。对于后期阶段的蝌蚪,所有浓度的敌敌畏溶液都未导致明显的DNA损伤,作者认为进入变态阶段的蝌蚪对敌敌畏的敏感性明显下降。结果同时也表明,早期和中期阶段的斑腿树蛙蝌蝌是一种监测环境遗传毒性的合适指示生物。     

Behavior of polytene chromosomes of rhynchosciara angelae at different stages of larval development

Summary Polytene chromosomes in cells of salivary gland, Malpighian tubules and intestine of Rhynchosciara angelae are very favorable for study. The polytene chromosomes of the salivary gland are among the largest available for cytogenetics work. The ones in Malpighian tubules and in some parts of the intestine are as large and as favorable for cytological studies as the salivary chromosomes of many species of Drosophila.Two additional characteristics of Rhynchosciara make these flies excellent material for studies on the development of polytene chromosomes. 1.It is possible to observe the banding pattern of the polytene chromosomes at many stages of the larval life for at least 30 days before pupation, and 2. since the gregarious larvae develop simultaneously, one can sample the group at any stage desired. Sampling the group every day, it is possible to follow the development of the chromosomes as though one studied a single individual by observing it every day.We have followed in detail the behavior of the bands in two sections of chromosome B and in one section of chromosome C, at different stages of larval development. Some regions of the chromosomes which are represented by typical euchromatic bands at one stage of the larval development may develop in enormous bulbs, and later on may return to the banded stage again.The formation of the bulbs is not uniform in different sections of the same or of different chromosomes. In section 2 of chromosome B a certain locus swells enormously and then develops an enormous bulb, and later returns to the banded stage. At the point where the bulb was formed there is an accumulation of DNA, in amounts probably several times greater than before the bulb formation. In section 3 of chromosome B and section 3 of chromosome C the extra accumulation of DNA preceeds the formation of the bulb and is maintained during and after it. In the bulb formed in section 3 of chromosome C a single band seems to be responsible for the process.As shown by several authors, experimental evidence suggests that a gene is located within a band. The bulb formation in polytene chromosomes may then be morphological evidence of gene activities. This type of bulb formations and of return to the banded stage is a property of many chromosomes bands, during larval development. This type of behavior of many bands in polytene chromosomes is related to the process of nucleolus formation. However, this behavior may be found in almost all (if not in all) bands of the polytene chromosomes. If so, the behavior of the nucleolus organizer region is only a special case of this general process.The accumulation of DNA in different parts of the chromosome in cells of the same or of different tissues may be an argument against the theory of the constancy of the amount of DNA in all cells of a species. The bulb formations is not peculiar to R. angelae but occurs in several other Diptera.     

不同发育期诸氏鲻虾虎鱼对钻井液的敏感性比较

目的筛选试验鱼适宜急性毒性试验的发育期。方法将诸氏鲻虾虎鱼早期仔鱼、中期仔鱼、晚期仔鱼、稚鱼、幼鱼及成鱼暴露于一定浓度的钻井液中,比较钻井液对不同发育期诸氏鲻虾虎鱼的急性毒性。结果早期仔鱼48 h LC50为157 mg/L,中期仔鱼48 h LC50大于500 mg/L;中期仔鱼96 h LC50为79 mg/L,晚期仔鱼96h LC50为625 mg/L,稚鱼、幼鱼、成鱼96 h LC50显著大于500 mg/L;卤虫无节幼体96 h LC50为105 mg/L;不同发育期诸氏鲻虾虎鱼对钻井液的敏感性顺序为：早期仔鱼〉中期仔鱼〉晚期仔鱼〉稚、幼、成鱼。结论诸氏鲻虾虎鱼的早期仔鱼适用于海洋污染物急性毒性评价。     

Differential sensitivity to X-ray of chromosomes of blood T-lymphocytes and B- and T-cell lines

Summary Normal T-lymphocytes, B-cell line (CCRF-SB) and T-cell line (CCRF-HSB-2) cells, all diploid in their chromosome constitution, were exposed in vitro to various doses of X-ray and analyzed at their first mitotic division for structural chromosome abnormalities. The irradiation effects were determined also by a viability test of the cells, using trypan blue dye. The irradiated T-cell line (CCRF-HSB-2) showed a remarkably high frequency of chromosome aberrations, including chromosome and chromatid deletions, chromatid exchanges, dicentrics, rings and acentric fragments. On the other hand, the chromosome aberrations observed in the irradiated B-cell line and normal T-lymphocytes consisted mainly of dicentrics, rings, deletions and acentric fragments; the frequency of chromosome and chromatid deletions was low as compared to that of the T-cell line. The cell viability test showed a significantly higher percent reduction of viable cells at every dose of X-ray in the irradiated T-cell line than in the B-cell line or the normal T-lymphocytes. It is possible that the increased radiosensitivity of the T-cell line is related to the original malignant nature of the cells, which originated from the lymphocytes of a patient with acute lymphoblastic leukemia. Supported in part by USPHS grants CA-14413 and CA-16935.     

Lamins A and C are not expressed at early stages of human lymphocyte differentiation

Lamins are major proteins of the nuclear envelope that are members of the intermediate filament protein family. In vertebrates, nuclei from differentiated tissues usually contain both lamins of the A and B subtypes, while embryonic tissues contain the B-type lamin only. We have examined the composition of the nuclear lamina in human B and T lymphocytes representative of distinct stages of lymphoid differentiation. We show here that, in both cell lineages, while lamin B is constitutively expressed at all stages of differentiation, A-type lamin expression is restricted to later developmental stages.     

Differential sensitivity to x-ray of chromosomes of blood T-lymphocytes and B-and T-cell lines.

Normal T-lymphocytes, B-cell line (CCRF-SB) and T-cell line (CCRF-HSB-2) cells, all diploid in their chromosome constitution, were exposed in vitro to various doses of X-ray and analyzed at their first mitotic division for structural chromosome abnormalities. The irradiation effects were determined also by a viability test of the cells, using trypan blue dye. The irradiated T-cell line (CCRF-HSB-2) showed a remarkably high frequency of chromosome aberrations, including chromosome and chromatid deletions, chromatid exchanges, dicentrics, rings and acentric fragments. On the other hand, the chromosome aberrations observed in the irradiated B-cell line and normal T-lymphocytes consisted mainly of dicentrics, rings, deletions and acentric fragments; the frequency of chromosome and chromatid deletions was low as compared to that of the T-cell line. The cell viability test showed a singificantly higher percent reduction of viable cells at every dose of X-ray in the irradiated T-cell line than in the B-cell line or the normal T-lymphocytes. It is possible that the increased radiosensitivity of the T-cell line is related to the original malignant nature of the cells, which originated from the lymphocytes of a patient with acute lymphoblastic leukemia.