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The cohesin complex tethers sister chromatids together from the moment they are generated in S-phase until their separation in anaphase1,2. This fundamental phenomenon, called sister chromatid cohesion, underpins orderly chromosome segregation. The replisome complex coordinates cohesion establishment with replication of parental DNA3. Cohesion can be established by cohesin complexes bound to DNA before replication4,5, but how replisome interaction with pre-loaded cohesin complexes results in cohesion is not known. Prevailing models suggest cohesion is established by replisome passage through the cohesin ring or by transfer of cohesin behind the replication fork by replisome components5. Unexpectedly, by visualising single replication forks colliding with pre-loaded cohesin complexes, we find that cohesin is pushed by the replisome to where a converging replisome is met. Whilst the converging replisomes are removed during DNA replication termination, cohesin remains on nascent DNA. We demonstrate that these cohesin molecules tether the newly replicated sister DNAs together. Our results support a new model where sister chromatid cohesion is established during DNA replication termination, providing important insight into the molecular mechanism of cohesion establishment.

Cell-free extracts from Xenopus laevis eggs are a model system for studying chromosome biology. Xenopus egg extracts can be synchronised in different cell cycle stages, making them useful for studying DNA replication, DNA repair and chromosome organisation. Combining single-molecule approaches with egg extracts is an exciting development being used to reveal molecular mechanisms that are difficult to study using conventional approaches. Fluorescence-based single-molecule imaging of surface-tethered DNAs has been used to visualise labelled protein movements on stretched DNA, the dynamics of DNA–protein complexes and extract-dependent structural rearrangement of stained DNA. Force-based single-molecule techniques are an alternative approach to measure mechanics of DNA and proteins. In this essay, the details of these single-molecule techniques, and the insights into chromosome biology they provide, will be discussed.

Cases of neonatal jaundice due to Hyperbilirubinemia abound with some resulting in mortality especially arising from complications in Ceaserean Section. We studied biochemical patterns of some enzymes, hormones and other parameters in 1 - 4 days old neonates. Using spectrophotometnc and radioimmunoassay techniques we measured biochemical liver function parameters bilirubin, transaminases and gammaglutamyltransferase. Hormonal evaluation included cortisol, glucagon and adrenocortical hormone. Using SPSS version 23, paired sample test at 95% confidence intervals of difference shows 2 tail significance for bilirubin, transaminase; giucagon, cortisol and ACTH. Paired sample correlation also showed strong negative pattern with days. We conclude that the interplay of nervous system and self-regulating influence of stress hormones coupled with an immature liver triggers the formation of excess bilirubin.

External testing (public tests) is examined from a British point of view by George Cameron Allen and then responded to by an American. Allen discusses the history of external examinations in Britain, paying particular attention to the General Certificate of Education (GCE) examinations and the dichotomy that exists between language and literature portions of the test. Most students who are college bound are "done with English" at the age of sixteen; only those who specialize in English go on to higher level English tests focusing on literature, at the university level. In response to this traditional form of testing, the British reexamined their test forms, which resulted in an alternate-choice test, the Certificate of Secondary Education (CSE), which pays particular attention to the individual student, more closely relates language and literature, and provides an oral examination which the GCE ignored. The American paper responds by commenting on the College Entrance Examination Boards, noting the attention paid to vocabulary and multiple-choice items. Advantages and disadvantages of the Advance Placement English and the Graduate Record Examination in English are considered. The author concludes by suggesting that a profile of the student's writing may tell a great deal more than a straight examination. (HOD)

A ring-shaped helicase unwinds DNA during chromosome replication in all organisms. Replicative helicases generally unwind duplex DNA an order of magnitude slower compared to their in vivo replication fork rates. However, the origin of slow DNA unwinding rates by replicative helicases and the mechanism by which other replication components increase helicase speed are unclear. Here, we demonstrate that engagement of the eukaryotic CMG helicase with template DNA at the replication fork impairs its helicase activity, which is alleviated by binding of the single-stranded DNA binding protein, RPA, to the excluded DNA strand. Intriguingly, we found that, when stalled due to interaction with the parental duplex, DNA rezipping-induced helicase backtracking reestablishes productive helicase-fork engagement, underscoring the significance of plasticity in helicase action. Our work provides a mechanistic basis for relatively slow duplex unwinding by replicative helicases and explains how replisome components that interact with the excluded DNA strand stimulate fork rates., During eukaryotic chromosome replication cells utilize ring-shaped CMG helicase that separates the two strands of the DNA double helix. Here the authors reveal that CMG helicase activity is inhibited by duplex DNA engagement at the fork, which is relieved by binding of RPA to the lagging-strand template.

Columbia Journal of Environmental Law, Vol 9 No 2 (1984): Volume 9.2

The DNA double helix is unwound by the Cdc45/Mcm2-7/GINS (CMG) complex at the eukaryotic replication fork. While isolated CMG unwinds duplex DNA very slowly, its fork unwinding rate is stimulated by an order of magnitude by single-stranded DNA binding protein, RPA. However, the molecular mechanism by which RPA enhances CMG helicase activity remained elusive. Here, we demonstrate that engagement of CMG with parental double-stranded DNA (dsDNA) at the replication fork impairs its helicase activity, explaining the slow DNA unwinding by isolated CMG. Using single-molecule and ensemble biochemistry, we show that binding of RPA to the excluded DNA strand prevents duplex engagement by the helicase and speeds up CMG-mediated DNA unwinding. When stalled due to dsDNA interaction, DNA rezipping-induced helicase backtracking re-establishes productive helicase-fork engagement underscoring the significance of plasticity in helicase action. Together, our results elucidate the dynamics of CMG at the replication fork and reveal how other replisome components can mediate proper DNA engagement by the replicative helicase to achieve efficient fork progression.

Background Wildebeest associated malignant catarrhal fever (WA-MCF) is a fatal disease of cattle. Outbreaks are seasonal and associated with close interaction between cattle and calving wildebeest. In Kenya, WA-MCF has a dramatic effect on cattle-keepers who lose up to 10% of their cattle herds per year. The objective of this study was to report the impact of WA-MCF on a commercial ranch and assess the performance of clinical diagnosis compared to laboratory diagnosis as a disease management tool. A retrospective study of WA-MCF in cattle was conducted from 2014 to 2016 at Kapiti Plains Ranch Ltd., Kenya. During this period, 325 animals showed clinical signs of WA-MCF and of these, 123 were opportunistically sampled. In addition, 51 clinically healthy animals were sampled. Nested polymerase chain reaction (PCR) and indirect enzyme linked immunosorbent assay (ELISA) were used to confirm clinically diagnosed cases of WA-MCF. A latent class model (LCM) was used to evaluate the diagnostic parameters of clinical diagnosis and the tests in the absence of a gold standard. Results By PCR, 94% (95% C.I. 89–97%) of clinically affected animals were positive to WA-MCF while 63% (95% C.I. 54–71%) were positive by indirect ELISA. The LCM demonstrated the indirect ELISA had poor sensitivity 63.3% (95% PCI 54.4–71.7%) and specificity 62.6% (95% PCI 39.2–84.9%) while the nested PCR performed better with sensitivity 96.1% (95% PCI 90.7–99.7%) and specificity 92.9% (95% PCI 76.1–99.8%). The sensitivity and specificity of clinical diagnosis were 99.1% (95% PCI 96.8–100.0%) and 71.5% (95% PCI 48.0–97.2%) respectively. Conclusions Clinical diagnosis was demonstrated to be an effective method to identify affected animals although animals may be incorrectly classified resulting in financial loss. The study revealed indirect ELISA as a poor test and nested PCR to be a more appropriate confirmatory test for diagnosing acute WA-MCF. However, the logistics of PCR make it unsuitable for field diagnosis of WA-MCF. The future of WA-MCF diagnosis should be aimed at development of penside techniques, which will allow for fast detection in the field. Electronic supplementary material The online version of this article (10.1186/s12917-019-1818-8) contains supplementary material, which is available to authorized users.

Aim: This study was performed to better characterize accessibility to electronic health records (EHRs) among informatics professionals in various roles, settings, and organizations across the United States and internationally.Background: The EHR landscape has evolved significantly in recent years, though challenges remain in key areas such as usability. While patient access to electronic health information has gained more attention, levels of access among informatics professionals, including those conducting usability research, have not been well described in the literature. Ironically, many informatics professionals whose aim is to improve EHR design have restrictions on EHR access or publication, which interfere with broad dissemination of findings in areas of usability research.Methods: To quantify the limitations on EHR access and publication rights, we conducted a survey of informatics professionals from a broad spectrum of roles including practicing clinicians, researchers, administrators, and members of industry. Results were analyzed and levels of EHR access were stratified by role, organizational affiliation, geographic region, EHR type, and restrictions with regard to publishing results of usability testing, including screenshots.Results: 126 respondents completed the survey, representing all major geographic regions in the United States. 71.5 percent of participants reported some level of EHR access, while 13 percent reported no access whatsoever. Rates of no-access were higher among faculty members and researchers (19 percent). Among faculty members and researchers, 72 percent could access the EHR for usability and/or research purposes, but, of those, fewer than 1 in 3 could freely publish screenshots with results of usability testing and half could not publish such data at all. Across users from all roles, only 21 percent reported the ability to publish screenshots freely without restrictions.Conclusions: This study offers insight into current patterns of EHR accessibility among informatics professionals, highlighting restrictions that limit dissemination of usability research and testing. Further conversations and shared responsibility among the various stakeholders in industry, government, health care organizations, and informatics professionals are vital to continued EHR optimization.