Degradation of DNA by bisulfite treatment

A significant level of target degradation was caused by bisulfite treatment for methylcytosine-selective hydrolysis. The depyrimidination proceeded via addition of bisulfite to pyrimidines in DNA. The quantification with real-time PCR after conventional bisulfite treatment showed a large decrease in the amount of full-length DNA.     

Chromosome breakage induced by alkyl-alkane-sulfonates under different physical treatment conditions

A detailed study of chromosome breakage induced by three alkane sulfonates, which differ in chemical structure, functionality and reaction mechanism has been made in barley under different treatment conditions of temperature and hydrogen ion concentration. This study has indicated that, (i) the frequency and the types of chromosome breakage, at mitosis and meiosis, indicate certain qualitative and quantitative differences between the biological action of these three chemicals, (ii) the temperature of the treatment solution profoundly influences the frequency of chromosome breakage — a high frequency of breakage is observed at higher temperature, (iii) the effect of pH, though not very significant, is evident from the production of appreciably low frequency of breakage at alkaline pH for a given dose of chemical, (iv) by appropriate manipulation of treatment conditions, increase or decrease in the frequency of chromosome breakage can be accomplished to a considerable extent, (v) the qualitative and quantitative differences observed with respect to chromosoma breakage reflect the differences in the mode of biological action of these agents.     

Chromosome aberrations induced by aphidicolin

The expression of aphidicolin (apc)-produced common fragile sites and chromosome aberrations observed 24 h after apc treatment was studied in a normal individual. The chromosome lesions (gaps and breaks) induced by apc are expressed as full chromosomal aberrations in later cell divisions. We compared chromosome rearrangements or anomalies induced by apc (detected in 45.4% of metaphases analyzed) with those present in human neoplasia or involved in primate evolution. We found that 55.7% of deletions observed in our study coincided with deletions implicated in several types of neoplasia. However, none of 49 translocations observed in our study coincided with those described as recurrently associated with human neoplasia, probably due to their unbalanced nature. When chromosome aberrations detected in our study (only deletions and inversions were taken into account) were compared to those involved in primate evolution, we found a low rate of coincidence. The low coincidence between chromosome alterations in neoplasia and evolution and those observed in our study could be explained because we analyzed chromosome alterations that had not been selected, whereas those present in chromosome evolution and in neoplasia had been subjected to a selection process.     

Chromosome damage induced by chemicals

During the past half century there has been a substantial increase in the number and extent of usage of drugs, food additives, pesticides and other environmental chemicals. As a result, mutation-induced susceptibility to disease, once largely self-eradicating, is now being conserved and even propagated. In addition, we have over the same time period, added to our internal and external environments, numerous synthetic chemicals, the cytogenetic properties of some of which have been reviewed, and to which man's metabolism has not necessarily been conditioned and adapted, and which may have the potential to augment the number of mutations of each succeeding generation.We need to know far more about what we are doing to ourselves and our planet, and the foetuses of our unborn children, and to the genetic heritage of these children, by the permissive use of the chemical wonders of our age. It would surely be impracticable that one should wait for time to reveal harmful mutations before we try to research out and eliminate the chemical mutagens.Chromosomal studies and evaluation of mutagenic potential of all new and established drugs, food additives and environmental chemicals should therefore be integral aspects of the current practices of safety evaluation of these materials, and the same stringent principles should be applied to the numerous chemicals met with as solvents and intermediates in industrial processes. Persons exposed to high risk, such as those working in chemical industries, or patients on continuous chemotherapy, should be offered routine chromosomal monitoring, and the appearance of adverse effects and abnormalities notified and correlated.     

Cytogenetic damage induced in human lymphocytes by sodium bisulfite.

The frequencies of chromosomal aberrations (CA), sister-chromatid exchanges (SCE), and micronuclei (MN) in human blood lymphocytes exposed to sodium bisulfite (sulfur dioxide) at various concentrations ranging from 5 x 10(-5) M to 2 x 10(-3) M in vitro were studied. It was shown that sodium bisulfite (NaHSO3 and Na2SO3, 1:3 M/M) caused an increase in SCE and MN in human blood lymphocytes in a dose-dependent manner, and also induced mitotic delays and decreased mitotic index. For CA, our results indicated that sodium bisulfite induced an increase of chromatid-type aberrations in lymphocytes from three of four donors in a dose-dependent manner. The chemical at low concentrations induced chromatid-type aberrations, but not chromosome-type aberrations; high concentrations induced both chromatid- and chromosome-type aberrations. No cytogenetic damage in human lymphocytes was induced by sodium sulfate. The results have confirmed that sulfur dioxide is a clastogenic and genotoxic agent.     

Chromosome damage induced by semicarbazide in spermatocytes of a grasshopper

Semicarbazide hydrochloride (0.1 M in glass-distilled water), on injection, showed mutagenic action on the spermatocyte chromosomes of the grasshopper, Spathosternum prasiniferum. Aberrations such as chromatid and chromosome breaks, translocations, fragments and bridges were encountered. The sex chromosome and the long autosomes were affected. Semicarbazide, perhaps, reacts with DNA and the chromosome in a way similar to that of hydroxylamine and hydrazines.     

Chromosome aberrations induced by 9-aminoacridine derivatives

The induction of chromosomal aberrations by 5 derivatives of nitro-9-aminoacridine in V79 Chinese hamster cells was observed. The clastogenic activity of the compounds tested depended on the position of the NO2 group in the acridine ring. The strongest clastogens were derivatives with NO2 in position 1. The remaining derivatives placed in decreasing order of clastogenic activity were: 3-nitro, 4-nitro and 2-nitro. In addition, 2-nitro and 3-nitro derivatives produced hyperdiploid/polyploid metaphases.     

Non-apoptotic chromosome condensation induced by stress: delineation of interchromosomal spaces

Chromosomes are known to occupy distinct territories, suggesting the existence of definite borders. Visualization of these borders requires chromatin condensation like that seen in prophase cells. We developed a novel method to induce chromosome condensation in all cells regardless of cell cycle stage using a complex set of stresses. The cells were not apoptotic, as indicated by the absence of DNA damage, maintenance of the intact lamina and scaffold attachment factor A, and by the continuation of metabolic processes as well as proliferative capacity. That the appearance of chromosome condensation did not represent a premature mitotic event was shown by the absence of fibrillarin and Ki67 envelopment of chromosomes, continued protein synthesis and the reversibility of chromosome condensation. That chromosome condensation was achieved was demonstrated by the removal of chromatin from the nuclear envelope and chromosome painting. Specific genetic sites known to be at the surface of chromosomes retained their positions as shown by in situ hybridization. Stress-induced chromosome condensation was used to prove that specific nuclear domains such as ND10 are interchromosomally located and that green fluorescent protein-tagged ND10-associated proteins are useful markers for chromosomal boundaries after adenovirus 5 track formation in vivo. From these observations we conclude that chromosomal territories appear to have boundaries that exclude developing macromolecular aggregates. Received: 26 November 1999 / Accepted: 29 February 2000     

Chromosome malsegregation and embryonic lethality induced by treatment of normally ovulated mouse oocytes with nocodazole

The mouse egg is ovulated with its nucleus arrested at the metaphase-II stage of meiosis. Sperm entry triggers the completion of the second meiotic division. It has been speculated that damage to the meiotic spindle of normally ovulated eggs at around the time of sperm entry could result in chromosome malsegregation and the death of conceptuses with numerical chromosome anomalies. This hypothesis was tested using nocodazole, a microtubule inhibitor. Nocodazole was administered either to maturing preovulatory oocytes or to normally ovulated eggs at one of the following stages: (1) the time of sperm entry, (2) early pronuclear stage, (3) pronuclear DNA synthesis, (4) prior to first cleavage division, (5) early 2-cell stage, or (6) prior to the second cleavage division. Little or no effect was observed for treatment times other than the time of sperm entry, when the egg is being activated to complete the second meiotic division. Remarkably high frequencies of embryonic lethality, expressed at around the time of implantation, were induced at this stage. Cytogenetic analysis of first cleavage metaphases of zygotes treated at the time of sperm entry revealed a high incidence of varied numerical chromosome anomalies, with changes in ploidy being predominant.