Residual γH2AX foci as an indication of lethal DNA lesions

<p>Abstract</p> <p>Background</p> <p>Evidence suggests that tumor cells exposed to some DNA damaging agents are more likely to die if they retain microscopically visible γH2AX foci that are known to mark sites of double-strand breaks. This appears to be true even after exposure to the alkylating agent MNNG that does not cause direct double-strand breaks but does produce γH2AX foci when damaged DNA undergoes replication.</p> <p>Methods</p> <p>To examine this predictive ability further, SiHa human cervical carcinoma cells were exposed to 8 DNA damaging drugs (camptothecin, cisplatin, doxorubicin, etoposide, hydrogen peroxide, MNNG, temozolomide, and tirapazamine) and the fraction of cells that retained γH2AX foci 24 hours after a 30 or 60 min treatment was compared with the fraction of cells that lost clonogenicity. To determine if cells with residual repair foci are the cells that die, SiHa cervical cancer cells were stably transfected with a RAD51-GFP construct and live cell analysis was used to follow the fate of irradiated cells with RAD51-GFP foci.</p> <p>Results</p> <p>For all drugs regardless of their mechanism of interaction with DNA, close to a 1:1 correlation was observed between clonogenic surviving fraction and the fraction of cells that retained γH2AX foci 24 hours after treatment. Initial studies established that the fraction of cells that retained RAD51 foci after irradiation was similar to the fraction of cells that retained γH2AX foci and subsequently lost clonogenicity. Tracking individual irradiated live cells confirmed that SiHa cells with RAD51-GFP foci 24 hours after irradiation were more likely to die.</p> <p>Conclusion</p> <p>Retention of DNA damage-induced γH2AX foci appears to be indicative of lethal DNA damage so that it may be possible to predict tumor cell killing by a wide variety of DNA damaging agents simply by scoring the fraction of cells that retain γH2AX foci.</p

Mouse but not human embryonic stem cells are deficient in rejoining of ionizing radiation-induced DNA double-strand breaks

Mouse embryonic stem (mES) cells will give rise to all of the cells of the adult mouse, but they failed to rejoin half of the DNA double-strand breaks (dsb) produced by high doses of ionizing radiation. A deficiency in DNA-PKcs appears to be responsible since mES cells expressed <10% of the level of mouse embryo fibroblasts (MEFs) although Ku70/80 protein levels were higher than MEFs. However, the low level of DNA-PKcs found in wild-type cells appeared sufficient to allow rejoining of dsb after doses <20 Gy even in G1 phase cells. Inhibition of DNA-PKcs with wortmannin and NU7026 still sensitized mES cells to radiation confirming the importance of the residual DNA-PKcs at low doses. In contrast to wild-type cells, mES cells lacking H2AX, a histone protein involved in the DNA damage response, were radiosensitive but they rejoined double-strand breaks more rapidly. Consistent with more rapid dsb rejoining, H2AX¯/¯ mES cells also expressed 6 times more DNA-PKcs than wild-type mES cells. Similar results were obtained for ATM−/− mES cells. Differentiation of mES cells led to an increase inDNA-PKcs, an increase in dsb rejoining rate, and a decrease in Ku70/80. Unlike mouse ES, human ES cells were proficient in rejoining of dsb and expressed high levels of DNA-PKcs. These results confirm the importance of homologous recombination in the accurate repair of double-strand breaks in mES cells, they help explain the chromosome abnormalities associated with deficiencies in H2AX and ATM, and they add to the growing list of differences in the way rodent and human cells deal with DNA damage

Значение химических и физических свойств пластмасс при аллопластике

BACKGROUND:South Africa has one of the highest rates of HIV-1 (HIV) infection world-wide, with the highest rates among young women. We analyzed the molecular epidemiology and evolutionary history of HIV in young women attending high school in rural South Africa. METHODS:Samples were obtained from the HPTN 068 randomized controlled trial, which evaluated the effect of cash transfers for school attendance on HIV incidence in women aged 13-20 years (Mpumalanga province, 2011-2015). Plasma samples from HIV-infected participants were analyzed using the ViroSeq HIV-1 Genotyping assay. Phylogenetic analysis was performed using 200 pol gene study sequences and 2,294 subtype C reference sequences from South Africa. Transmission clusters were identified using Cluster Picker and HIV-TRACE, and were characterized using demographic and other epidemiological data. Phylodynamic analyses were performed using the BEAST software. RESULTS:The study enrolled 2,533 young women who were followed through their expected high school graduation date (main study); some participants had a post-study assessment (follow-up study). Two-hundred-twelve of 2,533 enrolled young women had HIV infection. HIV pol sequences were obtained for 94% (n = 201/212) of the HIV-infected participants. All but one of the sequences were HIV-1 subtype C; the non-C subtype sequence was excluded from further analysis. Median pairwise genetic distance between the subtype C sequences was 6.4% (IQR: 5.6-7.2). Overall, 26% of study sequences fell into 21 phylogenetic clusters with 2-6 women per cluster. Thirteen (62%) clusters included women who were HIV-infected at enrollment. Clustering was not associated with study arm, demographic or other epidemiological factors. The estimated date of origin of HIV subtype C in the study population was 1958 (95% highest posterior density [HPD]: 1931-1980), and the median estimated substitution rate among study pol sequences was 1.98x10-3 (95% HPD: 1.15x10-3-2.81x10-3) per site per year. CONCLUSIONS:Phylogenetic analysis suggests that multiple HIV subtype C sublineages circulate among school age girls in South Africa. There were no substantive differences in the molecular epidemiology of HIV between control and intervention arms in the HPTN 068 trial

The effect of a conditional cash transfer on HIV incidence in young women in rural South Africa (HPTN 068) : a phase 3, randomised controlled trial

Background: Cash transfers have been proposed as an intervention to reduce HIV-infection risk for young women in sub-Saharan Africa. However, scarce evidence is available about their effect on reducing HIV acquisition. We aimed to assess the effect of a conditional cash transfer on HIV incidence among young women in rural South Africa. Methods: We did a phase 3, randomised controlled trial (HPTN 068) in the rural Bushbuckridge subdistrict in Mpumalanga province, South Africa. We included girls aged 13–20 years if they were enrolled in school grades 8–11, not married or pregnant, able to read, they and their parent or guardian both had the necessary documentation necessary to open a bank account, and were residing in the study area and intending to remain until trial completion. Young women (and their parents or guardians) were randomly assigned (1:1), by use of numbered sealed envelopes containing a randomisation assignment card which were numerically ordered with block randomisation, to receive a monthly cash transfer conditional on school attendance (≥80% of school days per month) versus no cash transfer. Participants completed an Audio Computer-Assisted Self-Interview (ACASI), before test HIV counselling, HIV and herpes simplex virus (HSV)-2 testing, and post-test counselling at baseline, then at annual follow-up visits at 12, 24, and 36 months. Parents or guardians completed a Computer-Assisted Personal Interview at baseline and each follow-up visit. A stratified proportional hazards model was used in an intention-to-treat analysis of the primary outcome, HIV incidence, to compare the intervention and control groups. This study is registered at ClinicalTrials.gov (NCT01233531). Findings: Between March 5, 2011, and Dec 17, 2012, we recruited 10 134 young women and enrolled 2537 and their parents or guardians to receive a cash transfer programme (n=1225) or not (control group; n=1223). At baseline, the median age of girls was 15 years (IQR 14–17) and 672 (27%) had reported to have ever had sex. 107 incident HIV infections were recorded during the study: 59 cases in 3048 person-years in the intervention group and 48 cases in 2830 person-years in the control group. HIV incidence was not significantly different between those who received a cash transfer (1·94% per person-years) and those who did not (1·70% per person-years; hazard ratio 1·17, 95% CI 0·80–1·72, p=0·42). Interpretation: Cash transfers conditional on school attendance did not reduce HIV incidence in young women. School attendance significantly reduced risk of HIV acquisition, irrespective of study group. Keeping girls in school is important to reduce their HIV-infection risk. Funding: National Institute of Allergy and Infectious Diseases, National Institute of Mental Health of the National Institutes of Health

HPTN 068 study cohort flowchart.

<p>The figure provides an overview of the study cohort, including the number of samples tested and the number of HIV genotyping results obtained in each participant group: infected at enrollment, infected during the main study (between enrollment and their expected graduation date), or infected during the follow-up study (after their expected graduation date). Abbreviations: mL: milliliter. Footnote for Fig 1: ^aFour participants were excluded due to unknown HIV status.</p

GMRF Bayesian Skyride plot of HIV subtype C.

<p>The GMRF Bayesian Skyride plot was reconstructed from the 200 <i>pol</i> gene sequences. Bold black line indicates the median effective population size through time; blue shaded area represents the 95% highest posterior density (HPD) interval. The vertical dotted lines represent the estimated date of origin (1958) of HIV subtype C, and lower and upper 95% HPD intervals (1931–1980).</p

Transmission clusters from approximately maximum-likelihood phylogenetic tree.

<p>Phylogenetic clusters were detected in the approximately maximum-likelihood phylogenetic tree (FastTree) at a 4.5% genetic distance threshold. Each row represents one of the twenty-one phylogenetic clusters. Symbols representing participants in clusters are colored in red (intervention) or blue (control). Symbols represent the timing of participants’ first positive HIV test (enrollment, main study, follow-up study). Data from participants are shown on the x-axis (calendar time) according to the date of their first HIV-positive visit in the study. Drug resistant viruses are denoted with an asterisk.</p

Short Communication: Dried Blood Spots Stored at Room Temperature Should Not Be Used for HIV Incidence Testing

The limiting antigen (LAg)-avidity assay is a serologic assay used for cross-sectional HIV incidence testing. We compared the results obtained with the LAg-avidity assay using dried blood spot (DBS) samples stored at room temperature (18°C-25°C) or stored frozen at -80°C with results obtained from matched plasma samples. Matched DBS and plasma samples (306 paired samples) were collected in the HIV Prevention Trials Network (HPTN) 068 trial in South Africa (2012-2014). The DBS were stored at room temperature before testing. Matched DBS and plasma samples (100 paired samples) from the Consortium for the Evaluation and Performance of HIV Incidence Assays (CEPHIA) were collected in 2016 and were stored at -80°C. All DBS testing was performed in 2017. Differences in normalized optical density (ODn) were compared between matched DBS and plasma samples. For DBS samples stored at room temperature (HPTN 068), the average difference in ODn values for plasma versus DBS was 1.49 (95% confidence intervals [CI]: 1.36-1.62). In contrast, when DBS samples were stored at -80°C (CEPHIA), the average difference in ODn values for plasma versus DBS was -0.22 (95% CI: -0.32 to -0.13). DBS samples stored at room temperature should not be used for cross-sectional HIV incidence testing with the LAg-avidity assay

Family-Centred Functional Therapy for Children with Cerebral Palsy

In this paper we describe the development and initial evaluation of a family-centred functional approach to therapy for young children with cerebral palsy. The family-centred functional therapy approach is based on theoretical concepts from family-centred service and a systems approach to motor development. Principles of this approach include an emphasis on functional performance, and providing therapy when movement behaviors are amenable to change. Therapy focuses on identifying and changing performance constraints in the task, the child or the environment. Four initial studies were completed to develop and evaluate the feasibility of the family-centred functional therapy approach. Results indicate that children receiving this approach improve in functional performance over the course of intervention. Development of the therapy approach needs to continue to enable therapists to develop methods to identify a broader range of factors that enable or constrain task performance. Further development of specific therapeutic strategies is also required, particularly strategies that focus on changing the task or the environment around the child as a means to improve performance