Stem Cells Propagate Their DNA by Random Segregation in the Flatworm Macrostomum lignano

Adult stem cells are proposed to have acquired special features to prevent an accumulation of DNA-replication errors. Two such mechanisms, frequently suggested to serve this goal are cellular quiescence, and non-random segregation of DNA strands during stem cell division, a theory designated as the immortal strand hypothesis. To date, it has been difficult to test the in vivo relevance of both mechanisms in stem cell systems. It has been shown that in the flatworm Macrostomum lignano pluripotent stem cells (neoblasts) are present in adult animals. We sought to address by which means M. lignano neoblasts protect themselves against the accumulation of genomic errors, by studying the exact mode of DNA-segregation during their division

Measurement of S-phase duration of adult stem cells in the flatworm Macrostomum lignano by double replication labelling and quantitative colocalization analysis

Platyhelminthes are highly attractive models for addressing fundamental aspects of stem cell biology in vivo. These organisms possess a unique stem cell system comprised of neoblasts that are the only proliferating cells during adulthood. We have investigated T-s (S-phase duration) of neoblasts during homoeostasis and regeneration in the flatworm, Macrostomum lignano. A double immunohistochemical technique was used, performing sequential pulses with the thymidine analogues CldU (chlorodeoxyuridine) and IdU (iododeoxyuridine), separated by variable chase times in the presence of colchicine. Owing to the localized nature of the fluorescent signals (cell nuclei) and variable levels of autofluorescence, standard intensity-based colocalization analyses could not be applied to accurately determine the colocalization. Therefore, an object-based colocalization approach was devised to score the relative number of double-positive cells. Using this approach, T-s (S-phase duration) in the main population of neoblasts was similar to 13 h. During early regeneration, no significant change in T-s was observed

Triage of ASC-H : a meta-analysis of the accuracy of high-risk HPV testing and other markers to detect cervical precancer

BACKGROUND : Women with a cytological diagnosis of atypical squamous cells, cannot exclude high-grade squamous intraepithelial lesion (ASC-H) are usually immediately referred for colposcopy. However, triage may reduce the burden of the diagnostic workup and prevent overtreatment. METHODS : A meta-analysis was conducted to assess the accuracy of high-risk human papillomavirus (hrHPV) testing and testing for other molecular markers for the detection of grade 2 cervical intraepithelial neoplasia or worse (CIN2+) or grade 3 cervical intraepithelial neoplasia or worse (CIN3+) in women with ASC-H. An additional question that was assessed was whether triage would be useful in light of the relatively high pretriage probability of underlying precancer. RESULTS : The pooled absolute sensitivity and specificity of the Hybrid Capture 2 (HC2) assay for CIN2+(derived from 19 studies) were 93% (95% confidence interval [CI], 89%-95%) and 45% (95% CI, 41%-50%), respectively. p16(INK4a) staining (only 3 studies) had similar sensitivity (93%; 95% CI, 75%-100%) but superior specificity (specificity ratio, 1.69) to HC2 for CIN2+. Testing for paired box 1 gene methylation (only 1 study) showed a superior specificity of 95% (specificity ratio, 2.08). The average pretest risk was 34% for CIN2+and 20% for CIN3+. A negative HC2 result decreased this to 8% and 5%, respectively, whereas a positive result upgraded the risk to 47% and 28%, respectively. CONCLUSIONS : Because of the high probability of precancer with a diagnosis of ASC-H, the utility of triage is limited. The usual recommendation for referring women with ASC-H for colposcopy is not altered by a positive triage test, whatever test is used. A negative hrHPV DNA or p16(INK4a) test may allow repeat testing, but this recommendation will depend on local decision thresholds for referral. Cancer Cytopathol 2016;124:261-72. (c) 2015 American Cancer Society. Because of the high probability of precancer in patients with a diagnosis of atypical squamous cells, cannot exclude high-grade squamous intraepithelial lesion (ASC-H), the utility of triage is limited. The usual recommendation of referring women with ASC-H to colposcopy is not altered by a positive triage test, whatever test is used. A negative high-risk human papillomavirus DNA or p16(INK4a) test may allow repeat testing, but this recommendation will depend on local decision thresholds for referral