Exposure to power frequency electromagnetic fields (EMF) may cause adverse health effects in humans. Some epidemiological studies support an association between exposure to EMF and the incidence of different types of cancer, which may be associated with the presence of chromosomal aneuploidy. In this study, fluorescence in situ hybridization (FISH) was used to detect numerical chromosomal aberrations induced by occupational exposure to EMF. The labeled probes used in this study were repetitive α-satellite probes for chromosomes 7, 12, 17 and heterochromatic region of the Y chromosome. This study was conducted using 23 male individuals, 18 of which are occupationally exposed to EMF whereas the other 5 individuals are used as controls. Our study shows monosomy of chromosomes 7 and 17 in 4 and 3 exposed individuals, respectively. The mean percentages of nuclei with monosomy of chromosomes 7 and 17 in these affected individuals are 18.3% and 16.1%, respectively. The loss of Y chromosome was detected in 6 exposed individuals and the mean percentage of nuclei showing this aberration is 15.8%. In control individuals, the mean percentages of nuclei with monosomy of chromosomes 7, 17 and loss of the Y chromosome were 3.2%, 3.7% and 4.5%, respectively. The increase in monosomy of chromosomes 7 and 17 and the loss of Y chromosome compared to the control is statistically significant (P<0.001). No significant increase in numerical aberrations of chromosome 12 was observed in exposed individuals.
Four asparagus cultivars were cytologically studied by conventional staining and in situ hybridization, in order to evaluate both the variability among cultivars and the distribution pattern of 18S-25S rRNA genes. The mitotic and meiotic analysis with conventional chromosome staining did not show heteromorphisms or differences between cultivars. In situ hybridization with 18S and 25S rDNA probes showed 6 chromosomes with 18S-25S rDNA sites in the 4 studied genotypes. The New Jersey, Waltam Washington and G4 × 14 cultivars presented 4 chromosomes with larger subterminal sites and 2 with interstitial sites of smaller size. In the Deco cultivar, heteromorphism was verified in the size of the rDNA sites, which were larger and subterminal in 3 chromosomes, and small and interstitial in 3 other chromosomes. The results suggest that asparagus cultivars may present only small differences in the number and distribution of rDNA loci.
Mitotic chromosomes were studied from the bone marrow of male and female, H. fasciatus fasciatus. A diploid chromosome number of 2n =40 was recorded for the species with a chromosome fundamental number (NF) of 50. The karyotype is divisible into 2 main size groups namely, chromosome pair, number 1 which is the longest and chromosomes 2-40 which fairly intergraded in size. Neither microchromosomes nor heteromorphic pairs were observed. Possible mode of inheritance of chromosome variation in the genus, Hemidactylus also received some comments.
The potential genotoxicity of the natural pyrethrins and the synthetic lambda (λ) cyhalothrin was evaluated in mice in vivo. Single oral treatment with the doses 45, 90, 180 mg kg-1 b.wt. of pyrethrins and 1.25, 2.5, 5 mg kg-1 b.wt. of λ cyhalothrin (1/8, 1/4, 1/2 LD50) induced modest but statistically significant increase in the frequency of sister chromatid exchanges (SCE's) in bone-marrow cells. Such frequency reached 8.20±0.41 and 8.67 ±0.24 per cell after treatment with the highest tested dose of both insecticides respectively compared with 5.32 ± 0.28 for the control. Marked induction of SCE frequency (12.40±0.90) per cell was observed after treatment with mitomycin C which is used as a positive control. Single oral treatment with the doses 90, 180 mg kg-1 b.wt. of pyrethrins and 1.25, 2.5, 5 mg kg-1 b.wt. of λ cyhalothrin, induced significant increase in the percentage of chromosomal aberrations in mouse bone-marrow. With respect to germ cells only the highest tested dose of both insecticides (1/2 LD50) induced a significant percentage of chromosomal aberrations in mouse spermatocytes after single oral treatment. Chromosomal aberrations were also recorded after repeated treatment. For studying sperm abnormalities mice were orally treated for 5 consecutive days with 22.5, 45, 90 mg kg-1 b.wt. of pyrethrins and 0.63, 1.25 and 2.5 mg kg-1 b.wt. of λ cyhalothrin. Significant percentage of sperm abnormalities was observed after treatment with the 2 higher doses of both insecticides. In conclusion, both insecticides pyrethrins and λ cyhalothrin induced some clastogenic effects with the high tested doses.
Present paper deals with the detailed morphological, cytological and cytotaxonomical studies on 3 cytotypes of N hyalina f. hyalina, collected from Mudasarilova tank (Visakhapatnam), Sakhya Sagar dam (Shivpuri) and Tighra dam (Gwalior). The cytological preparations reveal the occurrence of chromosomes counts of n=15, 18 and 21, respectively. Count of 3 chromosomes numbers in 3 different cytotypes clearly established polyploidy in this taxon, if x=3 considered as the ancestral number. It was found that polyploidy is certainly associated with the morphological diversifications. As the chromosome numbers increased certain additional characters appeared, while, with reduction in chromosome numbers these additional characters have not been observed.
Four facultatively apomictic varieties of bahia grass (Paspalum notatum Flugge) were studied for making it clear the mechanism of multiple embryo seed set development in polyembryonic ovules. Over 300 ovaries at and after anthesis were collected from each variety, treated with Herr's clearing fluid and observed with Nomarski differential interference-contrast optics. At anthesis, the formed typical embryo sac located in micropylar end (first sac) were 92.5 to 100%, and those in the other ends (other sacs) were 40.4 to 86.0% among the 4 varieties. After anthesis, the first sac divided dominantly when compared with the other sacs. At 4 d after anthesis, the rates of the ovules contained the developed first sacs were 56 to 87% comparable to 0 to 1% of the other sacs among the 4 varieties. However, 4 to 17% of the other sacs also showed embryo formations but endosperm. In final, the first sac developed well and occupied the whole space of the ovule, and the embryos formed in the other sacs coexisted with the first sac. From the above results, it can be concluded that the first sac has temporal dominant in embryo sac formation, and has the positional dominant in fertilization and subsequent development of embryo sac when compared with the other sacs in polyembryonic ovules. The egg cell of the other sac (2n) located close to the endosperm of micropylar sac, divided with stimulation of the first sac development, and finally also formed seed-forming embryo. That is why twin, thrice or four seedlings were observed when in germination. The estimation of degree of sexual or apomixis was also discussed based on the observations.
Cold shocks at 10°C, 12°C, 15°C and heat shocks at 32°C, 35°C or 38°C were administered to 4 h-or 6 h-fertilized eggs of the giant freshwater prawns, Macrobrachium rosenbergii, for a period of 4 h or 6 h. The treated eggs were further cultured in vitro at room temperature (29°C). The control was in vitro cultured at room temperature to hatching. Both cold and heat shocks caused an abnormal chromosome separation resulting in a formation of fused nuclei. Mosaics, individuals containing both diploid and polyploid cells, rather than complete polyploids were induced. Cold shocks at 10°C were detrimental while at 15°C were inefficient. Whereas application of 12°C to 4 h-fertilized eggs for 6 h or to 6 h-fertilized eggs for 4 h produced polyploid mosaics and enlarged embryos but caused great reduction in the survival rates. Heat shocks at 32°C did not induce mosaicism or enlarged embryo, while at 38°C were detrimental. Application of 35°C to 4 h-fertilized eggs for a long duration of 6 h or to 6 h-fertilized eggs for 4 h produced some mosaics and enlarged embryos. Though, enlarged embryos appeared to develop normally and survived to the hatching days (18-19 days), none engaged in hatching. Defect in the hatching enzymes upon the treatments was suggested.
Chromosome analysis in pachytene has been considered a powerful tool in cytogenetic and evolutionary studies carried out in several plant species. Many morphological details of chromosomes can be observed during this stage, although overlapping of chromosomes may hinder the analysis. Considering this limitation, a new cytogenetic methodology was developed for maize meiotic chromosomes. This method consists of submitting the pollen mother cells (PMCs) to an enzymatic solution, which promotes PMC release from the anthers and subsequent digestion of the cell wall. The bivalents are mechanically released into the cytoplasm and spread out over the slide. In this slide preparation the chromosomes were isolated and spread over in the same plane of focus. The preservation of morphological traits of the bivalents, and the near complete absence of background or artifacts, resulted in high quality preparations, adequate for cytogenetic analysis. The obtainance of individual chromosomes allowed for the detailed analysis of the 10 maize bivalents. This analysis revealed additional data on the morphology and longitudinal differentiations of the chromosomes, facilitating their identification and morphological characterization.
This work presents a procedure to perform nuclear halos, nuclear matrix with the associated DNA loops, from Drosophila salivary gland polytene nucleus. The purification with hypo-osmotic buffers in the absence of polyamines, as spermine and spermidine, whose function seems to be related to the chromatin compaction, was considered essential. The non-compacted polytene chromosome in the giant nucleus could be used for protein extraction that allows the liberation of the loops. The profile of the DNA matrix and loop fractions, left after nuclear halo digestion with restriction enzyme, confirms the relationship between these fractions suitable for functional analysis. This procedure could be important to obtain a direct relationship between nuclear matrix association and transcription process in the interphase polytene chromosomes of Drosophila salivary gland nucleus.
Two amphidiploids of Scilla scilloides collected in Matsuyama, Japan, had new secondary constrictions at the interstitial region of the long arm of one subtelocentric chromosome in addition to the secondary constriction at the proximal region of the short arms of a pair of subtelocentric b1 chromosomes commonly found in amphidiploids. In situ hybridization using a 45S rDNA probe revealed 3 strong signals at the secondary constrictions and 2 weak signals. Genomic in situ hybridization using 45S rDNA and genomic DNA from either genome A or B indicated that the subtelocentric chromosome with the new 45S rDNA locus was chromosome a3 of genome A. Genomic Southern analysis showed that the rDNA at the new locus of chromosome a3 originated from the 45S rDNA of genome B.
The aim of this study was to analyse phenotype and cytogenetic behaviour of Zea mays ssp. mays and Zea mays ssp. parviglumis (Zpa) hybrids with different ploidy levels. Maize 2n =20 (Zm20) and Zpa hybrid plants (MPa20) were obtained naturally, they showed regular meiosis and fertile progeny (+80%). Otherwise, maize 2n=40 (Zm40) and Zpa hybrids (MPa30) were obtained by embryo rescue, they showed irregular meiosis and sterile progeny (0-8%). Meiotic configurations more frequently observed in the species and the hybrids were : Zm20 (10II); Zm40 (3.24II+8.341V); Zpa (0.461+9.76II); MPa20 (0.40I+9.54II+0.05III+0.65IV); MPa30 (5.97I+5.93II+4.05III). After colchicine treatment the number of IV increased in Zm20, Zpa and MPa20 and 10III were observed MPa30, because of homoeologous chromosomes pairing. In conclusion, Zm20 (AmAm BmBm) and Zpa (ApaApa BpaBpa) are allotetraploids with 2 homoeologous genomes. Whilst in the hybrids, the homoeologous genomes A pair in all cases, genomes B only do if their homologous competing during pairing, does not exist except in colchicine-treated plants which also show homoeologous genomes B pairing.
The cytoplasmically inherited bacterial symbiont, Wolbachia is well known for inducing a variety of reproductive abnormalities in the diverse arthropod hosts it infects. Wolbachia has been implicated in causing cytoplasmic incompatibility, parthenogenesis, and the feminization of genetic males in different hosts. In the present investigation, electron microscopy and PCR technology was applied on uzi flies of Exorista species (Diptera : Tachinidae), serious pests of silkworm Bombyx mori L. TEM examination of uzi flies of Exorista species showed Wolbachia in the reproductive tissues. Details of the ultrastructure of Wolbachia are described. The application of PCR technique revealed that the Wolbachia is present in uzi fly populations of Exorista species collected from different localities. Thereby it creates a lot of scope for future research on the management of uzi flies by means of Wolbachia.
Spiramycine is a macrolide antibiotic used for the treatment and prophylaxis of local and systemic bacterial and mycoplasmal infections. It is also an effective drug for the treatment of toxoplasmosis. In order to assay its mutagenic potential in mammalian cells, chromosomal aberrations in both somatic and germ cells and sperm abnormalities were examined in mice after oral treatment (gavage) with spiramycine. Mice were treated subacutely (for 3, 5, 10 consecutive days) with 3 dose levels of spiramycine 104, 208, 416 mg kg-1 b.wt. Spiramycine was found to induce a significant increase in the percentage of chromosomal aberrations in bone-marrow and spermatocyte cells after successive treatments with the doses 208 and 416 mg kg-1 b.wt. This percentage increased with increasing the dose. The effect was more prominent 8 h post treatment with spiramycine compared with that after 24 h. Spiramycine had no significant effect on the mitotic activity in mouse bone-marrow cells compared to the control. For studying sperm abnormalities mice were treated for 5 consecutive days with 104, 208 and 416 mg/kg. Morphological sperm abnormalities increased significantly after treatment with the 2 higher doses of spiramycine. The percentage of abnormal sperms increased with increasing the dose. It reached 3.74±0.60, 6.34±0.66 (p<0.01), 9.28±0.29 (p<0.01) after treatment with the 3 tested doses respectively compared with 3.02±0.50 for the control vehicle. These results show that spiramycine has some clastogenic potential on somatic and germ cells as well as on sperm morphology.
We studied chromosome aberrations and survival in normal and dechorionated embryos of Misgurnus anguillicaudatus (Cobitidae, Pisces) exposed to mitomycin C (MMC) at concentrations of 25, 50 and 100μg/ml. The survival rates of dechorionated embryos exposed to MMC decreased dose-dependently but those of normal embryos exposed to 25 and 50μg/ml of MMC were not significantly different from the controls. On the other hand, the frequencies of chromosome aberrant cells in both normal and dechorionated embryos, which were observed in the blastula stage, increased dose-dependently. The frequencies in dechorionated embryos were not significantly higher in all doses than those in normal embryos. These results suggest that in normal embryos a large amount of MMC passed through the chorion and induced chromosome aberrations. For detecting chromosome aberrations, dechorionated embryos are more sensitive but normal embryos may also be sufficiently sensitive. The use of both normal and dechorionated embryos may give more detailed and useful information related to the properties of genotoxic chemicals. A chromosome aberration test using fish embryos showing a clear dose-response would be useful for monitoring genotoxic contaminants in the water environment.
The nucleolus of rapidly growing tobacco BY-2 cells displayed several distinctive features at the electron microscopic level such as remarkable development of the dense fibrillar component and vigorous dispersion of the granular component from the nucleolar surface toward the cytoplasm. The fibrillar centers (FCs) where resting ribosomal RNA genes (rDNA) reside were found as low electron-dense patches. These FCs were detected as dots at the light microscopic level by fluorescence in situ hybridization (FISH). We examined the relationship between appearances of the FCs and the development of the nucleolus. There was a positive correlation between the multiplication of the FCs and the nucleolar size : The nucleolus became large as the number of the FCs increased while the nucleolus degenerated concurrently with a numerical reduction and an enlargement of the FCs, probably due to fusion among them. These results are discussed in favor of the concept that the multiplication of the FCs produces many sites for actively transcribing rDNA.
The behaviors of the chloroplast FtsZ ring and outer cytosolic and inner stromal plastid dividing rings (PD rings) of chloroplast division were investigated in the higher plant Pelargonium zonale using immuno-fluorescence and electron microscopy. For these studies, we used embryonic cap cells from early embryos, in which small chloroplasts duplicate by multiple fission of a pleomorphic chloroplast. FtsZ proteins were localized to several rings at future division sites preceding contraction. FtsZ rings were found at the leading edges of the chloroplast constriction sites throughout division. In contrast, the PD rings were observed at the constriction sites after the formation of the FtsZ rings. These observations demonstrate that FtsZ rings differ from PD rings, and indicate that the FtsZ ring determines the dividing plane before the initiation of chloroplast contraction and then, in concert with the PD rings, promotes chloroplast division.