Assessment of the genotoxicity of atenolol in human peripheral blood lymphocytes: correlation between chromosomal fragility and content of micronuclei

Toward 20 T magnetic resonance for human brain studies: opportunities for discovery and neuroscience rationale

An initiative to design and build magnetic resonance imaging (MRI) and spectroscopy (MRS) instruments at 14 T and beyond to 20 T has been underway since 2012. This initiative has been supported by 22 interested participants from the USA and Europe, of which 15 are authors of this review. Advances in high temperature superconductor materials, advances in cryocooling engineering, prospects for non-persistent mode stable magnets, and experiences gained from large-bore, high-field magnet engineering for the nuclear fusion endeavors support the feasibility of a human brain MRI and MRS system with 1 ppm homogeneity over at least a 16-cm diameter volume and a bore size of 68 cm. Twelve neuroscience opportunities are presented as well as an analysis of the biophysical and physiological effects to be investigated before exposing human subjects to the high fields of 14 T and beyond.

Ameliorative effect of grapefruit juice on amiodarone-induced cytogenetic and testicular damage in albino rats

OBJECTIVE

To evaluate the ameliorative role of grapefruit juice on the cytogenetic and testicular damage induced by the antiarrythmic drug amiodarone in albino rats.

METHODS

Animals were divided into four groups. Group I was considered as control. Group II was given grapefruit juice at a dose level of 27 mL/kg body weight. Group III was orally administered amiodarone (18 mg/kg body weight) daily for 5 weeks. Animals were sacrificed after 5 weeks of treatment. Bone marrow was collected from the femurs for analysis of chromosomal aberrations and mitotic indices. Testes were removed and stained with H&E for histological examination. Sperms were collected from epidedymis for detection of sperm head abnormalities. Comet assay was used to detect DNA damage.

RESULTS

Amiodarone treatment caused a significant increase in the percentage of chromosomal aberrations, decreased the mitotic index and increased DNA damage. The testis showed many histopathological alterations, inhibition of spermatogenesis and morphometric changes. The number of sperm head abnormalities was increased. Treating animals with amiodarone and grapefruit juice caused a reduction in chromosomal aberrations, mitotic index, DNA damage and testicular alterations caused by amiodarone.

CONCLUSIONS

The results of this study indicated that grapefruit juice ameliorates the cytotoxicty and testicular alterations induced by amiodarone in albino rats and this is may be due to the potent antioxidant effects of its components.

Study of FMR1 gene association with ovarian dysfunction in a sample from the Basque Country

Premature ovarian failure (POF) is defined as cessation of menses before the age of 40. The most significant single gene associated with POF is the Fragile X Mental Retardation 1 gene (FMR1). In the present work we screened women with fertility problems from the Basque Country in order to determine, whether in these women, FMR1 CGG repeat size in the intermediate and premutation range was associated with their pathology, and whether intermediate and premutation carriers had endocrine signs of diminished ovarian function, using the most established measure of ovarian reserve, the gonadotropin FSH. A patient sample of 41 women with ovarian insufficiency and a control sample of 32 women with no fertility problems from the Basque Country were examined. The patient sample was classified into three categories according to the results of the retrospective assessment of their ovarian function. In group 2 of patients, women with irregular cycles, reduced fecundity and FSH levels ≥ 10IU/l, there is a significant increase in the number of intermediate and premutation FMR1 alleles (35-54 CGG repeats). In group 3 of patients, women with amenorrhea for at least four consecutive months and FSH levels ≥ 10IU/l, a significant increase in the number of intermediate FMR1 alleles (35-54 CGG repeats) was found in patients compared with controls. In this group all the patients had a serum concentration > 40 IU/l. The results suggest that in the analysed Basque sample the FMR1 gene has a role in the aetiology of POF. However, elevated FSH levels are more related to the menstrual cycle pattern than to the CGG repeat size.

The role of fragile sites in sporadic papillary thyroid carcinoma

The incidence of thyroid cancer is increasing, especially papillary thyroid carcinoma (PTC), making it currently the fastest-growing cancer among women. Reasons for this increase remain unclear, but several risk factors including radiation exposure and improved detection techniques have been suggested. Recently, the induction of chromosomal fragile site breakage was found to result in the formation of RET/PTC1 rearrangements, a common cause of PTC. Chromosomal fragile sites are regions of the genome with a high susceptibility to forming DNA breaks and are often associated with cancer. Exposure to a variety of external agents can induce fragile site breakage, which may account for some of the observed increase in PTC. This paper discusses the role of fragile site breakage in PTC development, external fragile site-inducing agents that may be potential risk factors for PTC, and how these factors are especially targeting women.

DNA instability at chromosomal fragile sites in cancer

Human chromosomal fragile sites are specific genomic regions which exhibit gaps or breaks on metaphase chromosomes following conditions of partial replication stress. Fragile sites often coincide with genes that are frequently rearranged or deleted in human cancers, with over half of cancer-specific translocations containing breakpoints within fragile sites. But until recently, little direct evidence existed linking fragile site breakage to the formation of cancer-causing chromosomal aberrations. Studies have revealed that DNA breakage at fragile sites can induce formation of RET/PTC rearrangements, and deletions within the FHIT gene, resembling those observed in human tumors. These findings demonstrate the important role of fragile sites in cancer development, suggesting that a better understanding of the molecular basis of fragile site instability is crucial to insights in carcinogenesis. It is hypothesized that under conditions of replication stress, stable secondary structures form at fragile sites and stall replication fork progress, ultimately resulting in DNA breaks. A recent study examining an FRA16B fragment confirmed the formation of secondary structure and DNA polymerase stalling within this sequence in vitro, as well as reduced replication efficiency and increased instability in human cells. Polymerase stalling during synthesis of FRA16D has also been demonstrated. The ATR DNA damage checkpoint pathway plays a critical role in maintaining stability at fragile sites. Recent findings have confirmed binding of the ATR protein to three regions of FRA3B under conditions of mild replication stress. This review will discuss recent advances made in understanding the role and mechanism of fragile sites in cancer development.

Assessment of genotoxicity associated with hydroxyurea therapy in children with sickle cell anemia

Hydroxyurea induces fetal hemoglobin, improves laboratory parameters, and ameliorates clinical complications of sickle cell anemia (SCA), but its long-term efficacy and safety in this patient population remain incompletely defined. Although generally considered non-DNA reactive, an important safety concern is that hydroxyurea may indirectly cause genotoxic damage. To better address this safety issue of hydroxyurea in patients with SCA, we measured the production of micronuclei (MN) in red blood cells (RBCs) as a marker of genotoxicity. Blood samples were collected from children with SCA enrolled in the Hydroxyurea Study of Long-term Effects (ClinicalTrials.gov NCT00305175). Flow cytometry quantified circulating MN-containing erythrocyte sub-populations before and during hydroxyurea exposure. The frequency of micronucleated reticulocytes (MN-CD71(+)) and micronucleated mature erythrocytes (MN-RBC) was then tested for associations with laboratory and clinical data. In cross-sectional analysis of 293 blood samples from 105 children with SCA and a median of 2 years of hydroxyurea therapy, exposure to hydroxyurea was associated with significantly increased frequencies of MN-CD71(+) and MN-RBC compared to baseline. The increases were evident by 3 months of therapy, and did not escalate further with up to 12 years of continuous drug exposure. In prospective longitudinal analysis, substantial inter-individual variation in the effect of hydroxyurea on %MN-CD71(+) was observed that was associated with the expected laboratory effects of hydroxyurea. In conclusion, clinically relevant exposure to hydroxyurea is associated with increased MN production consistent with erythroblast genotoxicity but with substantial inter-patient variability. Associations between increased %MN-CD71(+) and laboratory benefits suggest that hydroxyurea effects on MN production may be related to individual patient sensitivity to hydroxyurea within the bone marrow.