Evolution of DNA replication origin specification and gene silencing mechanisms

DNA replication in eukaryotic cells initiates from replication origins that bind the Origin Recognition Complex (ORC). Origin establishment requires well-defined DNA sequence motifs in Saccharomyces cerevisiae and some other budding yeasts, but most eukaryotes lack sequence-specific origins. A 3.9 Å structure of S. cerevisiae ORC-Cdc6-Cdt1-Mcm2-7 (OCCM) bound to origin DNA revealed that a loop within Orc2 inserts into a DNA minor groove and an α-helix within Orc4 inserts into a DNA major groove. Using a massively parallel origin selection assay coupled with a custom mutual-information-based modeling approach, and a separate analysis of whole-genome replication profiling, here we show that the Orc4 α-helix contributes to the DNA sequence-specificity of origins in S. cerevisiae and Orc4 α-helix mutations change genome-wide origin firing patterns. The DNA sequence specificity of replication origins, mediated by the Orc4 α-helix, has co-evolved with the gain of ORC-Sir4-mediated gene silencing and the loss of RNA interference.

Contrary to most eukaryotes that lack sequence-specific origins of replication, S. cerevisiae origins are defined by specific DNA sequence motifs. Here the authors reveal that multiple subunits of ORC, including Orc2 and Orc4, contribute to the sequence-specificity of origins in S. cerevisiae.

Community management of intellectual disabilities in Pakistan: a mixed methods study

BACKGROUND

Pakistan has one of the highest reported rates of childhood intellectual disabilities (ID) in the world. Prevalence estimates vary from 19.1/1000 for serious ID to 65/1000 for mild ID.

METHODS

We surveyed carers of persons with ID (n = 100) using quantitative and qualitative instruments. We conducted in-depth interviews of carers (n = 16) and key primary health providers (n = 10). We also carried out focus groups (n = 7). Data were triangulated and interpreted in light of peer reviewed literature.

RESULTS

There was a delay of 2.92 (95% CI 1.9 to 3.94) to 4.17 (95% CI 2.34 to 6.01) years between detection and seeking of care. Parental stress associated with caring for these children was high (mean Self-Reporting Questionnaire score 8.4; 95% CI 6.80 to 9.91). Home management consisted mainly of physical containment. Stigma associated with ID contributed to decreased opportunity for these children and families to participate in community activities. There was a lack of knowledge about causation and effective interventions for ID.

CONCLUSIONS

Our findings suggest that there is significant delay in detection of ID especially in rural setting where more than 70% of population of Pakistan resides. This missed opportunity for rehabilitation in early formative years is a cause of significant distress for the caregivers who rarely receive valid information about course, prognosis and what remedial action to take. There is a need to develop feasible, cost-effective, community level interventions, which can be integrated into existing healthcare systems.

Primary care treatment for child and adolescent neuropsychiatric conditions in remote rural Punjab, Pakistan - a cross-sectional survey

BACKGROUND

Pakistan is one of the most populous regions of the world. Previous work has demonstrated that there is reliance on traditional healthcare systems when seeking psychiatric care; however, there is a lack of information on help seeking for child and adolescent population. The aim of this study was to describe types of treatments and families' perceptions of the effectiveness of those treatments for childhood neuropsychiatric disorders in remote rural Punjab.

METHOD

Cross-sectional survey of consecutive attendees at an advertised mental health consultation day in a remote rural area.

RESULTS

The effectiveness of these treatments, as rated by patients and their families, was variable, with highest reported effectiveness for general practitioner treatments. In families with a past history of care from a general practitioner, those who had epilepsy reported treatments to be more effective than those with mental retardation. Carers and users described consulting five different types of primary healthcare practitioners that used both physical and psychotherapeutic treatments.

CONCLUSIONS

There is considerable variation in treatments available for child and adolescent neuropsychiatric disorders in remote rural areas of Punjab, a large proportion of which are considered ineffective by the users and carers. This highlights the need to develop effective interventions for child and adolescent neuropsychiatric conditions that can be administered by primary health workers. Our data suggest that the need for this is greatest for mental retardation.

Resin-to-enamel bonds: effect of cleaning the enamel surface with prophylaxis pastes containing fluoride or oil

A thorough dental prophylaxis before acid-etching of enamel is often recommended. In the method most commonly used, a slurry of pumice is applied with a rubber cup. Oil-based and fluoride-containing prophylaxis pastes are not generally recommended because of fears that they might hinder the etching process. This study assessed the 24-hour shear strength of resin (Scotchbond 2/Silux Plus) bonded to etched enamel which had been cleaned before acid-etching with a slowly rotating rubber cup loaded with: (1) wet pumice; (2) fluoride-containing non-oil-based pastes (En-De-Kay fluoride paste, Nupro fluoride paste); (3) non-fluoride oil-based paste (Kemdent); and (4) nonfluoride non-oil-based pastes (Nupro, Orapol). The bond strength values obtained after using the various cleaning agents were similar. Furthermore, bond failure in all the test groups was of the cohesive type. It therefore appears that prophylaxis pastes containing fluoride or oil may be used to clean the enamel before acid-etching.