Extra-chromosomal telomeric DNA in cells from Atm(-/-) mice and patients with ataxia-telangiectasia

Ataxia-telangiectasia (AT) is an autosomally recessive human genetic disease with pleiotropic defects such as neurological degeneration, immunodeficiency, chromosomal instability, cancer susceptibility and premature aging. Cells derived from AT patients and ataxia-telangiectasia mutated (ATM)-deficient mice show slow growth in culture and premature senescence. ATM, which belongs to the PI3 kinase family along with DNA-PK, plays a major role in signaling the p53 response to DNA strand breaks. Telomere maintenance is perturbed in yeast strains lacking genes homologous to ATM and cells from patients with AT have short telomeres. We examined the length of individual telomeres in cells from ATM(-/-) mice by fluorescence in situ hybridization. Telomeres were extensively shortened in multiple tissues of ATM(-/-) mice. More than the expected number of telomere signals was observed in interphase nuclei of ATM(-/-) mouse fibroblasts. Signals corresponding to 5-25 kb of telomeric DNA that were not associated with chromosomes were also noticed in ATM(-/-) metaphase spreads. Extrachromosomal telomeric DNA was also detected in fibroblasts from AT patients and may represent fragmented telomeres or by-products of defective replication of telomeric DNA. These results suggest a role of ATM in telomere maintenance and replication, which may contribute to the poor growth of ATM(-/-) cells and increased tumor incidence in both AT patients and ATM(-/-) mice.     

Improved high-performance liquid chromatography assay of doxorubicin: Detection of circulating aglycones in human plasma and comparison with thin-layer chromatography

Summary We compared doxorubicin and metabolite pharmacokinetic data obtained from thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) assay of plasma samples from six patients who had been treated with doxorubicin. Duplicate 1-ml samples were extracted with chloroform: isopropanol (1:1) and assayed using a sensitive HPLC system incorporating a dual pump gradient with tetrahydrofuran as the mobile phase and fluorescence detection. Duplicate 1-ml samples from the same specimens were assayed using a modification of a previously described TLC assay. Areas under the curve for doxorubicin by HPLC (3.36±2.30 M · h) and TLC (4.16±2.50 M · h) were not significantly different (P=0.5). Terminal half-life of doxorubicin by HPLC (28.0±6.98 h) and TLC (23.2±7.8) (P=0.29) and the calculated total-body clearances by HPLC (0.55±0.29 l/min) and TLC (0.45±0.23) (P=0.55) were not significantly different. Areas under the curve for doxorubicinol by HPLC (2.75±1.4 M · h) and TLC (2.53±7.1 M · h) (P=0.73) showed no significant differences. HPLC detected a mixed 7-deoxydoxorubicinol aglycone-doxorubicin aglycone peak, 7-deoxydoxorubicin aglycone, and two nonpolar, unidentified metabolites. TLC detected the following aglycone metabolites: doxorubicin aglycone, doxorubicinol aglycone, 7-deoxydoxorubicinol aglycone, an unidentified polar metabolite, and several unidentified nonpolar metabolites. From these data we conclude that HPLC and TLC detect concentrations of doxorubicin and doxorubicinol from human plasma equally well to concentrations of 7.0 nM (4 pmol injected doxorubicin). Aglycones do circulate in human plasma at concentrations above the detection limits of both assays. Doxorubicinol aglycone, which is detected by TLC but not by HPLC, may be formed from artifactual breakdown of doxorubicinol during TLC development. Unidentified nonpolar compounds seen on HPLC and TLC may represent further doxorubicin metabolism than previously described.     

In vitro pharmacodynamic evaluation of VP-16-213 and implications for chemotherapy

Summary VP-16-213 (Etoposide) is an active antineoplastic agent which has undergone extensive evaluation of clinical dose escalation. To corroborate a putative dose-response relationship, we studied, in a modified clonogenic assay, various doses and durations of exposure. VP-16-213 at doses of 0.01, 0.05, 0.10, 0.50, 1.0, 5.0 and 10.0 g/ml, each with exposure durations of 1, 3, 18, and 30 h, was studied in vitro against two human tumor cell lines, MOLT and 9812. The doses and durations of exposure were chosen to approximate some of the pharmacokinetic values achievable in either standard-dose or high-dose clinical studies. The results, summarized as linear regression lines, demonstrate with statistical significance (p<0.03) that there is correlation between dose and cytotoxicity and between dose x duration of exposure (representing the area under the concentration-time curve) and cytotoxicity. Our in vitro data thus support the concept of intensive use of VP-16-213 to maximize antitumor activity. However, how best to accomplish the manipulation of dose and duration of exposure is not yet clear and will be the subject of future clinical investigations.Supported in part by Grant ROI CA39686 from the NIH (KR Hande)     

The association between trans fatty acids,infertility and fetal life: a review

Trans fatty acids (TFAs) are thought to affect reproductive health by causing adverse effects on sperm morphology and ovum quality as a result of changing membrane lipid composition which, in turn, leads to impairment in metabolic pathways. This literature review examines the evidence for the effects of dietary TFAs on male and female infertility. Studies conducted between 2007 and 2017 on the effect of dietary TFAs on human reproductive health and fetal life have been included. They indicate that TFA intakes are inversely proportional to sperm concentration and total sperm count and exhibit a positive correlation with asthenospermia, as well as an adverse association on sperm concentration and semen quality. In the female TFAs intakes are associated with an increase in the risk of ovulatory infertility, adversely affect the length of gestation leading to fetal developmental defects and fetal loss. The findings suggest that high TFA intake (more than 1% of energy consumption) constitute a risk factor for infertility in both sexes.     

Folate deficiency is associated with the formation of complex nuclear anomalies in the cytokinesis‐block micronucleus cytome assay

Chromosomal instability (CIN) is an important hallmark to oncogenesis and can be diagnosed morphologically by the presence of nuclear anomalies such as micronuclei (MN), nucleoplasmic bridges (NPBs), and nuclear buds (NBuds). We have identified additional nuclear anomalies formed under folate‐deficient conditions, defined as “fused” nuclei (FUS), “circular” nuclei (CIR), and “horse‐shoe” nuclei (HS) and investigated their suitability for inclusion as additional CIN biomarkers in the lymphocyte cytokinesis‐block micronucleus cytome (CBMN‐Cyt) assay. Although the morphological appearance of FUS, CIR, and HS suggested an origin from multiple NPB in the fusion region between the two nuclei, the very low frequency of dicentric chromosomes in metaphase spreads from these cultures did not support this model. Fluorescence in situ hybridization (FISH) analysis of cytokinesis‐blocked binucleated (BN) cells with peptide nucleic acid probes for telomeres and centromeres (PNA–FISH) revealed a high proportion of fusion regions contained both centromeric and telomeric DNA. This suggests that folate deficiency may disrupt the process of sister chromatid separation and chromosome segregation during mitosis. It was concluded that the FUS, CIR, and HS morphologies represent promising biomarkers of CIN that are sensitive to folate deficiency, and further validation and investigation of the mechanisms responsible for their formation is warranted. Mol. Mutagen. 2012. © 2012 Wiley Periodicals, Inc.