Hexylresorcinol induces chromosome aberrations in mouse peripheral blood cells

Hexylresorcinol has been demonstrated to induce chromosome aberrations in eukaryotic cells at doses of 0.5, 0.05, and 0.005 mg/g body weight. The metabolic transformation of hexylresorcinol in mice decreases its genotoxic effect. The mutagenic effect is retained for three days only after the administration of the highest dose of hexylresorcinol (0.5 mg/g); during the first two days, lower doses are also genotoxic. Therefore, hexylresorcinol doses lower than 0.5 mg/g body weight are metabolized within two days to the extent precluding the expression of the cytotoxic effect. After a single administration to mice, exogenous hexylresorcinol is transformed at a rate of 0.0025-0.025 mg/day.     

Study of external low irradiation dose effects on induction of chromosome aberrations in Pisum sativum root tip meristem

The effects of low doses of ionizing radiation have been a matter of important debate over the last few years. The point of discussion concerns the validity of the linear dose-response extrapolation for low doses, used by international organizations, to establish radio-protection norms. Here, we contributed to this discussion by investigating the induction of chromosome aberrations by low to moderate doses ranging from 0 to 10 Gy in root meristem cells of 6-day-old Pisum plantlets. After acute irradiation of plantlets by a (60)Co source, the percentage of root tip meristem cells displaying chromosome aberrations was estimated immediately after irradiation and after 20 h recovery time. The dose-effect curves show non-linear responses, especially in the low dose range (0- 1 Gy), which is of particular interest. After 20 h of recovery, a steep increase of aberrations was observed for cells exposed to 0.4 Gy, followed by a plateau for doses until 1 Gy. There was an irradiation effect on plant growth during the first and second generations, showing the persistence of cell division anomalies as a long term effect of acute irradiation. This result suggests the induction of a genomic instability.Our results, in agreement with some obtained in animals, show rather non-linear dose-effect responses, with notably higher biological effects of low doses than expected.     

Human cytomegalovirus UL76 induces chromosome aberrations

Background  

Human cytomegalovirus (HCMV) is known to induce chromosome aberrations in infected cells, which can lead to congenital abnormalities in infected fetuses. HCMV UL76 belongs to a conserved protein family from herpesviruses. Some reported roles among UL76 family members include involvement in virulence determination, lytic replication, reactivation of latent virus, modulation of gene expression, induction of apoptosis, and perturbation of cell cycle progression, as well as potential nuclease activity. Previously, we have shown that stable expression of UL76 inhibits HCMV replication in glioblastoma cells.     

Aluminum induces changes in the orientation of microtubules and the division plane in root meristem of Zea mays

Aluminum (Al) induces agricultural problems limiting crop productivity in acid soils. Since Al causes morphological changes in roots, and because microtubules (MTs) play important roles in determination of tissue morphology, we investigated whether Al affects the arrangement of MTs in maize root meristem using immunolocalization techniques. When seedling roots were treated with 50 μM Al, the orientations of MTs were dramatically altered in a population of cells located in the protoderm and the two outer layers of cortex: interphase cortical MT arrays lost their normal transverse organization and became random or longitudinal; the preprophase band of MTs, mitotic spindle, and phragmoplast developed at planes 90° rotated compared to their counterparts in controls. These changes in MT orientation resulted in the change of the division plane from transverse to longitudinal, producing daughter cells positioned side by side instead of above and below. The rotation of the otherwise normal MT arrays and the division plane in Al-treated roots indicates that Al interferes with the normal polarity sensing mechanism, which may contribute to the reduced axial growth of the Al-treated roots.     

Ultrastructural changes associated with the induction of premature chromosome condensation in Vicia faba root meristem cells

Key message

PCC induction is regulated by several signaling pathways, and all observed effects associated with PCC induction are strongly dependent on the mechanism of action of each PCC inducer used.

Abstract

Electron microscopic observations of cells with symptoms of premature chromosome condensation (PCC) showed that the interphase chromatin and mitotic chromosomes differed with respect to a chemical compound inducing PCC. Induction of this process under the influence of hydroxyurea and caffeine as well as hydroxyurea and sodium metavanadate led to a slight decrease in interphase chromatin condensation and the formation of chromosomes with a considerably loosened structure in comparison with the control. Incubation in the mixture of hydroxyurea and 2-aminopurine brought about clear chromatin dispersion in interphase and very strong mitotic chromosome condensation. Electron microscopic examinations also revealed the characteristic features of the structural organization of cytoplasm of Vicia faba root meristems, which seemed to be dependent on the type of the PCC inducer used. The presence of the following was observed: (i) large plastids filled with starch grains (caffeine), (ii) mitochondria and plastids of electron dense matrix with dilated invaginations of their internal membranes (2-aminopurine), and (iii) large mitochondria of electron clear matrix and plastids containing protein crystals in their interior (sodium metavanadate). Moreover, since caffeine causes either the most effective loosening of chromatin fibrils (within the prematurely condensed chromosomes) or induction of starch formation (in the plastids surrounding the nuclei), this may be a proof that demonstrates the existence of a link between physical accessibility to chromatin and the effectiveness of cellular signaling (e.g., phosphothreonine-connected).     

Spontaneous chromosome aberrations in human somatic cells

Conclusion In conclusion it is necessary to say that at present, we cannot consider whether there may be a geographical difference in frequency of spontaneous chromosome aberrations in somatic cells. For that purpose, a very abundant experimental material is required, as well as an improvement in methodology: what causes the difference in the results of various investigators; what methodical principles should be used for collection of data.Important factors in the differences of frequencies of spontaneous chromosome aberrations are likely to be the conditions of cultivation and making the preparations, as well as the methods of scoring the chromosome aberrations. The international standardisation of the cultivation conditions and of the estimates of chromosome aberrations is needed for the further study of the rate and reasons of the spontaneous mutation process in somatic cells.     

Modification of chromosome aberrations caused by kilham virus in rat embryo cells]

Mutagenic effect of Kilham virus on the frequency of chromosome aberrations in the cells of primary and continous rat embryo cultures and the modification effect of cadmium salt on the mutagenic potential of this virus was studied. The frequency of chromosome aberrations increased in the primary rat embryo culture after Kilham virus enfection. Rat embryo culture chronically infected with Kilham virus did not differ from control continuous cells in the frequency level of chromosome aberrations. Isertion of cadmium in the process of cultivation increased the mutagenic effect of kilham virus in the primary rat embryo culture.     

Metaphase chromosome accumulation and flow karyotypes in rice (Oryza sativa L.) root tip meristem cells.

Highly efficient cell synchronization and metaphase chromosome accumulation in rice root tip cells were achieved. Flow cytometric analysis was performed for obtaining optimal parameters to synchronize the cell cycles. High mitotic indices (about 57.6% in root tip meristemic area) were obtained by treating seedlings with 0.5 cm length using 0.5 mM hydroxyurea at 30 degrees C for 4 h, incubating in a hydroxyurea-free solution for 30 min, and then treating with 0.3 microM trifluralin for 3 h. After trifluralin treatment, incubation in distilled water for 15 min reduced chromosome clumping on metaphase spread. Uniformity of seed germination at the time of treatment is a critical parameter for obtaining high metaphase index. Isolated rice chromosomes were suitable for flow cytometric analysis and chromosome sorting. The morphology of flow sorted metaphase chromosomes was intact.     

Liposomes induce chromosome aberrations in human cultured cells

The genotoxic effect of multilamellar lipid vesicles (MLV) was analysed on cultured heteroploid and diploid human cells. Dose-dependent reduction of cell survival and mitotic rate as well as induction of chromosome aberrations were observed. Chromatid and chromosome breaks and chromatid exchanges were found in 24-h culture after liposome treatment, whereas chromosome rearrangements were prevalent at 48 h. Neutral (PC/Chol) and positive (PC/SA) MLV showed a greater damage than negative (PS/PC; PS) MLV. Fibroblasts were the most sensitive cell type. In the case of PC/Chol MLV vesicles, control experiments with PC and Chol of controlled purity ruled out the possibility that the observed chromosome aberrations were caused by toxic oxidation products present in commercial preparations.     

The HIV-Tat protein induces chromosome number aberrations by affecting mitosis

To analyze the effects of the HIV-Tat-tubulin interaction, we microinjected HIV-Tat purified protein into Drosophila syncytial embryos. Following the Tat injection, altered timing of the cortical nuclear cycles was observed; specifically, the period between the nuclear envelope breakdown and anaphase initiation was lengthened as was the period between anaphase initiation and the formation of the next nuclear envelope. These two periods correspond to kinetochore alignment at metaphase and to mitosis exit, respectively. We also demonstrated that these two delays are the consequence of damage specifically induced by Tat on kinetochore alignment and on the timing of sister chromatid segregation at anaphase. Furthermore, we show that the expression of Tat in Drosophila larvae brain cells produces a significant percentage of polyploid and aneuploid cells. The results reported here indicate that Tat impairs the mitotic process and that Tat-tubulin interaction appears to be responsible for the observed defects. The presence of polyploid and aneuploid cells is consistent with a delay or arrest in the M phase of a substantial fraction of the cells expressing Tat, suggesting that mitotic spindle checkpoints are overridden following Tat expression.     

Effect of fractionated exposure to carbon ions on the frequency of chromosome aberrations in tobacco root cells

The induction of chromosome aberrations in tobacco root tip cells was measured after exposure to either 18 MeV/n carbon ions or 2 MeV electrons. The RBE value for acute exposure was found to be about 10. Splitting the dose into two fractions did not produce any significant effect on the yield of aberrations following carbon-ion exposure, whereas a clear decrease was observed after exposure to electrons thereby indicating an induction/activation of error-free repair after the first fraction. Moreover, this decrease appeared to be independent of the types of chromosome aberrations. On the other hand, it was suggested that the lack of any significant effect on the yield of aberrations is either due to a lack of error-free repair or to a less efficient damage repair after exposure to carbon ions. Received: 26 February 2001 / Accepted: 28 June 2001     

Effect of cisplatin on Allium cepa root meristem cells

Allium cepa root growth was retarded by cisplatin treatment in a dose-dependent manner. A decrease in the mitotic index (MI) and an increase in the number of interphase cells was seen in cisplatin treated root tips. An increase in the frequency of abnormal mitoses and chromosomal aberrations was also observed in cisplatin treated groups which indicates its genotoxic effect on plant cells. The endogenous glutathione (GSH) level in the root tips decreased significantly after cisplatin treatment which may favour its increased interaction with cellular DNA thereby developing enhanced chromosomal aberrations and affecting cell divisions and root growth. It is suggested that the decrease in endogenous GSH may be related to the development of cisplatin-mediated genotoxic effects in plants.     

Identification of chromosome aberrations observed in human cancerous cells by labeling of R bands]

A precise identification of chromosome abnormalities observed in cancerous human cells may be demonstrated by chromosome banding. The types of newly formed chromosomes seem to indicate the possibility of a correlation between chromosome rearrangements and regions of heterochromatin. The evolution of neoplastic cells would be due to a balance between an increase in the level of chromosome mutation and stable changes.     

Ability of root canal antiseptics used in dental practice to induce chromosome aberrations in human dental pulp cells

Root canal antiseptics are topically applied to root canals within the pulpless teeth to treat the root canal and periapical infections. Because the antiseptics that are applied to root canals can penetrate through dentin or leak out through an apical foramen into the periodontium and distribute by the systemic circulation, it is important to study the safety of these antiseptics. In the present study, we examined the ability to induce chromosome aberrations in human dental pulp cells of five root canal antiseptics, namely, carbol camphor (CC), camphorated p-monochlorophenol (CMCP), formocresol (FC), calcium hydroxide, and iodoform which are most commonly used in dental practice. Statistically significant increases in the levels of chromosome aberrations were induced by CC, FC, or iodoform in a concentration-dependent manner. Conversely, CMCP and calcium hydroxide failed to induce chromosome aberrations in the absence or presence of exogenous metabolic activation. The percentages of cells with polyploid or endoreduplication were enhanced by FC or iodoform. Our results indicate that the root canal antiseptics that exhibited a positive response are potentially genotoxic to human cells.     

Variations in the size of mitotic cells in the root meristem

Variations in the length of mitotic and interphase cells were analyzed in various tissues of wheat roots and in the cortex of maize roots. Reliable differences were shown in the length of mitotic cells in individual files-clones of cells of the same tissue. The mean lengths of dividing cells in different roots differed to a lesser extent than those of different files in the same tissue of one root. Within the file, the length of sister simultaneously dividing cells differed the least, while the difference of lengths of neighbor simultaneously dividing nonsister cells was bigger. The mean length of interphase cells in any file was always less than that of mitotic cells by a factor of 1.45. This ratio was almost invariable for files and tissues in both plants we studied and corresponded to that of an exponentially growing cell population. In addition, a very small number of cells were found (less than 1%) in meristems, which are longer than the mitotic cells. The length of these cells exceeded those of mitotic cells by less than twice. The origin of such cells is discussed. The length of mitotic cells near the quiescent center is more variable than in the middle of the meristem in the cortex of both plants. In the meristem basal part, the mitotic cells were no longer than those in the middle of the meristem but there were no small dividing cells. In the wheat epidermis, the cells are differentiated into trichoblasts and atrichoblasts and, therefore, the length of dividing cells is highly variable. The cell length is essential for their transition to mitosis for all studied proliferating meristem cells.     

Spontaneous chromosome aberrations in the oogenesis of laboratory rats]

Cytological preparations were made by Tarkovsky's method from 2335 rat oocytes obtained after an induced superodulation. The chromosomes could be counted exactly in 861 oocytes. In 797 oocytes (92.7%) euploidy (metaphase II with 21 chromosomes) and in 64 oocytes (7.5%) aneuploidy was found. 60 oocytes were hypoploid, but only 4 oocytes (0.4%) were hyperploid (with 22 chromosomes). Hypoploidy can often be due to the presence of artefacts. Probably the rate of spontaneous aneuploidy in rat oogenesis is about 0.8%, this being significantly lower than the rate of spontaneous aneuploidy in mice oogenesis.