Linear Dose Response of Acrocentric Chromosome Associations (Aca) To Gamma Irradiation In Human Lymphocytes

Purpose: The frequency of acrocentric chromosome associations (ACA) was studied to determine the possible dose-response relation with low doses of gamma irradiation in lymphocytes. Methods: Peripheral blood collected from three healthy donors were irradiated with 0, 0.1, 0.25, 0.5, 0.75, and 1 Gy gamma radiation. Chromosomal preparations were made after 48 hrs culture as per the standard guidelines. Results: The average number of ACA and ACA % were increased significantly with an increase in a dose. The D-G and D-D type of association was most prominent and showed a dose-dependent increase. The ACA frequency in irradiated lymphocytes showed an increase concerning the dose. The fitted regression equation was y=0.4759x+0.1663 (R2=0.9635; p=0.0005). An assessment of dicentric chromosomes (DC) was carried for the same slides. The correlation curve was prepared for ACA frequencies versus DC frequencies, resulting in a regression equation as y=8.659x+0.2.37 (R2=0.8275; p=0.0119). Conclusion: Our results showed an increase in frequencies of ACA in irradiated lymphocytes with an increase in radiation dose and followed a similar linear trend with DC frequency, thus, ACA may serve as a candidate cytogenetic biomarker for radiation biodosimetry especially for low radiation doses.

Human Chromosome 18 and Acrocentrics: A Dangerous Liaison

The presence of thousands of repetitive sequences makes the centromere a fragile region subject to breakage. In this study we collected 31 cases of rearrangements of chromosome 18, of which 16 involved an acrocentric chromosome, during genetic screening done in three centers. We noticed a significant enrichment of reciprocal translocations between the centromere of chromosome 18 and the centromeric or pericentromeric regions of the acrocentrics. We describe five cases with translocation between chromosome 18 and an acrocentric chromosome, and one case involving the common telomere regions of chromosomes 18p and 22p. In addition, we bring evidence to support the hypothesis that chromosome 18 preferentially recombines with acrocentrics: (i) the presence on 18p11.21 of segmental duplications highly homologous to acrocentrics, that can justify a NAHR mechanism; (ii) the observation by 2D-FISH of the behavior of the centromeric regions of 18 respect to the centromeric regions of acrocentrics in the nuclei of normal subjects; (iii) the contact analysis among these regions on published Hi-C data from the human lymphoblastoid cell line (GM12878).

Chromosomes of Eupristina verticillata Waterston, 1921 and an overview of known karyotypes of chalcid wasps of the family Agaonidae (Hymenoptera)

The karyotype of Eupristina verticillata Waterston, 1921 (Agaonidae) from Italy was studied for the first time using chromosome morphometrics. The present study showed that this species has n = 6 and 2n = 12, with five larger metacentrics and a smaller acrocentric chromosome in the haploid set. A brief overview of known karyotypes of chalcid wasps of the Agaonidae is given; certain features of karyotype evolution of this family are discussed.

Karyotypes of three species of Hyperophora Brunner von Wattenwyl, 1878 (Tettigoniidae, Phaneropterinae) enable morphologically similar species to be distinguished

Phaneropterinae is the largest subfamily of Tettigoniidae, distributed across the globe. There are few cytogenetic studies regarding this group, as in the case of the genus group Aniarae, which represents only two karyotyped species. The current study aims to analyze cytogenetically three species of Hyperophora Brunner von Wattenwyl, 1878 from Brazil. The male diploid number of Hyperophoraminor Brunner von Wattenwyl, 1891 and Hyperophoramajor Brunner von Wattenwyl, 1878 is 2n♂= 31, whereas Hyperophorabrasiliensis Brunner von Wattenwyl, 1878 has shown 2n♂= 29. These three species possess an X0 sex chromosome system and telo/acrocentric chromosome morphology. The only species found in the Pantanal biome, H.brasiliensis, can be chromosomally distinguished from the Cerrado biome species H.major and H.minor, due to the difference in chromosome number (2n♂= 29 and 2n♂= 31, respectively).

Karyotypic variation in the long-whiskered catfish Pimelodus blochii Valenciennes, 1840 (Siluriformes, Pimelodidae) from the lower Tapajós, Amazonas and Trombetas Rivers

The genus Pimelodus LaCépède, 1803 comprises 35 formally recognized species distributed along the major neotropical river basins. Despite conservatism in diploid number with 2n=56, an intense variation of chromosomal morphology (karyotypic formula) has been documented in Pimelodus species. In the present study, we analyzed karyotypes of 20 specimens, identified as Pimelodusblochii Valenciennes, 1840 and collected from the lower courses of the Tapajós, Amazonas and Trombetas Rivers. The karyotypes were characterized by Giemsa conventional staining, C-banding, silver staining (Ag-NOR) and fluorescent in situ hybridization (FISH) with 5S and 18S rDNA probes. The karyotypes showed 2n=56 chromosomes in fish from the Tapajós River. In contrast, fish from the Amazonas and Trombetas Rivers had 2n=58. The nucleolus organizing regions were labeled on the short arm of an acrocentric chromosome as demonstrated by silver staining and FISH. Signals for 18S and 5S rDNA were co-localized on one chromosome pair. Our results demonstrate karyotypic divergence between Tapajós and Amazonas-Trombetas populations of P.blochii, interpreted as supporting the existence of a species complex in this taxon.

Frequency and Spectrum of Chromosomal Aberrations, Acrocentric Chromosome Associations Among Long Livers with Arterial Hypertension and Osteoarthritis Residing in the Carpathian Region

The frequency and spectrum of chromosomal aberrations, acrocentric chromosome associations among 264 long livers with arterial hypertension and osteoarthritis residing in the Carpathian region were analyzed. The obtained results were compared between patients with arterial hypertension and osteoarthritis, patients with arterial hypertension only, patients with osteoarthritis only and healthy individuals. The indices of the average frequency of chromosomal aberrations in all long livers was as follows: (2.82±0.27) in long livers with arterial hypertension and osteoarthritis and (2.17±0.47) in healthy individuals. In long livers with arterial hypertension and those with osteoarthritis, the frequency of chromosomal aberrations was 1.38 times higher compared to the control group (healthy long livers). The frequency of chromosomal abnormalities in long livers with arterial hypertension and those with osteoarthritis was (2.93±0.09) and (2.64±0.37), respectively.At the same time, there was observed the individual variability in chromosomal aberration frequency from 0.2 to 5%. In the spectrum of chromosomal aberrations, unstable chromosomal aberrations (dicentrics, rings, fragments) predominated in all long livers. When studying the index of acrocentric chromosome associations there was revealed that the difference in the indices between studied groups was identical to that when studying the frequency of chromosomal aberrations. In long livers with arterial hypertension and osteoarthritis, the index of the average number of acrocentric chromosome associations per cell was 1.07 times higher than that in long livers with arterial hypertension only, 1.32 times higher compared to that in long livers with osteoarthritis only and 1.75 times higher compared to healthy individuals (p<0.05).