Mechanism of micronuclei formation in polyploidizated cells of Allium cepa exposed to trifluralin herbicide

The trifluralin is an agent that promotes a cellular damage due to its direct action on the microtubules. This action leads to a decontrol in the cellular division, bringing about polyploid cells. In this work, we show the evidences that the exceeding genetical material of theses polyploidizated cells tends to be eliminated from the nucleus in the form of micronucleus. Our analyses prove this fact, both by the presence of a number of cells carrying micronucleus, and by the evidences of the elimination of the exceeding material itself, after exposition of the Allium cepa root tips tested with several concentration of trifluralin herbicide. It was noticed that the residual concentration induced a number of polyploid cells, micronuclei and mini cells. Inferences about the implications of the elimination of genetic material from micronuclei, such as cell viability and apoptosis, are also presented. (c) 2007 Elsevier B.V. All rights reserved.

X chromosome heterochromatic pattern and nucleolar synthesis in pupal ovaries of Aedes aegypti

C-banding and silver-staining techniques were used to examine pupal ovaries of Aedes aegypti from Sao Jose do Rio Preto (Brazil). Silver staining in ovary cystocytes showed two basic patterns relative to the nucleolar morphology: viz (1) a single, compact small body; and (2) multiple bodies encompassing large nuclear areas. These two types of cystocytes were present in the ratio of 7:1, which is the same as the number of nurse cells and oocytes, respectively, in each follicle. This suggests the possibility of eventually using such a nucleolar morphological difference to recognize both cell types in developmental stages before emergence. Silver nitrate staining in metaphase chromosomes revealed centromeric bands on all six chromosomes. The C-banding pattern in metaphase chromosomes showed an intercalary band in one of the X arms, as described previously in other populations. In ovary cystocytes (pachytene stage) this C-positive band seemed to consist of two chromomeres. Phase contrast microscopy showed that the nucleolus was associated with the distal chromomere of this intercalary C-band, indicating that the nucleolus organizer region was located in that part of the heterochromatic band.

CHROMOSOME-STUDIES IN MALES AFFECTED BY DUCHENNE OR BECKER MUSCULAR-DYSTROPHY

We studied cytogenetically 48 male patients with Duchenne or Becker muscular dystrophy. All of them showed normal X chromosomes. Fragility of Xp21 was investigated in 1400 G-banded chromosomes of 28 patients and only one break was observed at this band (0.07%). This low frequency of breakage excludes Xp21 as a fragile site in these patients.

SYNAPTONEMAL COMPLEX-ANALYSIS IN SPERMATOCYTES AND OOCYTES OF RAINBOW-TROUT, ONCORHYNCHUS-MYKISS (PISCES, SALMONIDAE) - THE PROCESS OF AUTOSOME AND SEX-CHROMOSOME SYNAPSIS

The surface-spreading synaptonemal complex (SC) technique was employed to analyze spermatocytes and oocytes of rainbow trout in order to visualize the process of autosome and sex chromosome synapsis in this species. The structure of lateral elements (LEs) of the SC and the chromosome synapsis process at the stages of leptotene, zygotene and pachytene are described. Comparative analysis of SCs of spermatocytes and oocytes showed a difference in the synaptic process, i.e. in spermatocytes all LEs were synapsed before the appearance of centromeric regions in the biarmed elements, while in the oocytes some fully synapsed LEs, including the centromeric region of the biarmed elements, were found together with fully or partially unsynapsed LEs. In males the sex chromosome synapsis starts only after all autosomes have synapsed. Irregular synapses involving three or four LEs were found in 3.4% of the cells analyzed in mid or late zygotene. Multivalents were found in males and females. Some aspects of initial meiotic development and their implications in rainbow trout cytogenetics, genetics and evolution are discussed.

CYTOGENETIC EVIDENCE OF INVOLVEMENT OF CHROMOSOME REGION-15Q12 AND REGION-12Q15 IN CONDITIONS WITH ASSOCIATED OVERGROWTH

Syndromes with associated overgrowth are poorly understood. Besides their mode of inheritance, nothing is known regarding the basic genetic alterations that lead to their abnormal phenotypic manifestations. The chromosome localization of the genes involved remains unknown for this group of syndromes, with the only exception being the Wiedemann-Beckwith syndrome.

LOSS OF THE SEX-CHROMOSOME IN HUMAN NEOPLASIAS OF THE NERVOUS-SYSTEM

Thirty-eight tumors (five grade I-II astrocytomas, three grade III astrocytomas, four glioblastomas, one oligodendroglioma, four ependymomas, one pineocytoma, three medulloblastomas, four acoustic nerve neurinomas, one intraspinal neurinoma, one neurofibroma, 10 meningiomas, and one craniopharyngioma) and three benign lesions of the nervous system were evaluated cytogenetically after in vitro culture. Sex chromosome loss was detected in 56% of the cases (-X in 13 of the 25 female patients and -Y in nine of the 16 male patients). The objective of the present report was to study the role of this abnormality in cells of the nervous system.

A nonisothermal study of the kinetics of the nanoporosity elimination in sonogels-derived silica xerogels

A nonisothermal study of the kinetics of the nanoporosity elimination in monolithic silica xerogels, prepared from acid and ultrasound catalyzed hydrolysis of tetraethylortosilicate (TEOS), has been carried out by means of in situ linear shrinkage measurements performed with different heating rates. The study could be applied up to almost alpha similar to 0.6 of the volume fraction alpha of eliminated pores. The activation energy was found increasing from about 3.2 x 10(2) kJ/mol for alpha similar to 0.06 up to about 4.4 x 10(2) kJ/mol for alpha. similar to 0.44. The sintering process accompanying the nanopore elimination in this set of xerogels is in agreement with a viscous flux sintering process with the hydroxyl content diminishing with the volume fraction of eliminated pores. All the volume fraction of eliminated pores versus temperature (T) curves can be matched onto a unique curve with an appropriate rescaling of the T axis, independent of the heating rate. This scaling property suggests that the path of sintering seems the same, regardless of the heating rate; the difference is that the rate is faster at higher temperature.

Use of primers derived from a new sequence of the bovine Y chromosome for sexing Bos taurus and Bos indicus embryos

A bovine male-specific marker was identified in our laboratory through random amplified polymorphic DNA (RAPD) analysis. This fragment of 3216 bp was cloned, sequenced and mapped by fluorescent in situ hybridization (FISH) on the taurine Yq. Primers derived from this sequence were initially screened by polymerase chain reaction (PCR) for their ability to detect Y-specific segments in zebu and taurine genomic DNA. Two of these primers amplified a 655 bp Y-specific sequence present in taurine and zebu male genomic DNA. These primers were then used for detecting the 655 bp male sequence in DNA from 173 zebu and 30 taurine embryos, which had been previously sexed using primers for the sequence BC 1.2. The results revealed an accuracy of 100%. (C) 2002 Elsevier B.V. All rights reserved.

DIFFERENTIATION OF DROSOPHILA-SERIDO (ISOFEMALE LINE A95F3) AND D-KOEPFERAE (ISOFEMALE LINE B20D2) - REPRODUCTIVE ISOLATION, DEVELOPMENT TIME AND POLYTENE CHROMOSOME-BANDING PATTERNS

Drosophila serido is considered to be a superspecies consisting of two species: D. serido, from Brazil and D. koepferae from Argentina and Bolivia. However this probably does not express the entire evolutionary complexity of its populations. Isofemale lines A95F3 (from Brazil) and B20D2 (from Argentina), at present representing, respectively, the first and second species, were analyzed for fertility and fecundity in pair-mating intracrosses and intercrosses, as well as for development time, banding patterns and asynapsis of polytene chromosomes in the isofemale lines and their hybrids.Although variations in experimental conditions resulted in some variability in the results, in general A95F3 fertility and fecundity were lower than in B20D2. Intercrosses of A95F3 females and B20D2 males showed lower fertility and fecundity than the reciprocal crosses, following more closely characteristics of the mother strains. This is in contrast to the results obtained by Fontdevilla et al. (An. Entomol. Soc. Amer. 81: 380-385, 1988) and may be due to the different geographic origin of D. serido strains they used in crosses to B20D2. This difference and others cited in the literature relative to aedeagus morphology, karyotype characteristics, inversion polymorphisms and reproductive isolation strongly indicate that A95F3 and D. serido from the State of Bahia, Brazil are not a single evolutionary entity, reinforcing the idea of greater complexity of the superspecies D. serido than is known today.The reproductive isolation mechanisms found operating between A95F3 and B20D2 were prezygotic and postzygotic, the latter included mortality at the larvae stage in both directions of crosses and sterility of male hybrids in intercrosses involving B20D2 females and A95F3 males. The two isofemale lines differed in egg-adult development time, which was also differently affected by culture medium composition.A95F3 and B20D2 also showed differences in the banding patterns of proximal regions of polytene chromosomes 2, 3 and X, a fixed inversion in chromosome 3 (here named 3t), apparently not described previously, and a high degree of asynapsis in hybrids.These observations, especially those related to reproductive isolation and chromosomal differentiation (including the karyotype, previously described, and the differentiation of banding patterns, described in this paper), as well as the extensive asynapsis observed in hybrids reinforces the distinct species status of A95F3 and B20D2 isofemale lines.

CYTOGENETICS OF 4 BRAZILIAN HYLA SPECIES (AMPHIBIA-ANURA) AND DESCRIPTION OF A CASE WITH A SUPERNUMERARY CHROMOSOME

The chromosomes of Hyla fuscovaria, H. hayii and II. prasina, with 2n=24, and of Hyla sp. (aff. circumdata), a new species, with 2n=24 and 2n=25, were studied.The karyotypes with 2n=24 in the four species were very similar, with almost no differences in the size and morphology of the chromosomes. The numerical variability found in Hyla sp. (aff. circumdata) is due to the occurrence of a supernumerary chromosome in some specimens. NOR data obtained for the first time in the four species and C banding analysis of H. prasina indicate that such types of banding may be useful to differentiate species with very similar karyotypes, contributing to the understanding of chromosome evolution and the establishment of phylogenetic relationships among Brazilian Hyla species.