Implications for the future of obstetrics and gynaecology following the COVID-19 pandemic: a commentary.

In March 2020, the World Health Organization (WHO) declared COVID-19 a global pandemic. At the time of writing, more than 261,184 cases of COVID-19 have been confirmed in the UK resulting in over 36,914 directly attributable deaths.1 The National Health Service (NHS) has been confronted with the unprecedented task of dealing with the enormity of the resultant morbidity and mortality. In addition, the workforce has been depleted as a direct consequence of the disease, in most cases temporarily, but in some tragic cases permanently

Acute presentation of a heterotopic pregnancy following spontaneous conception: a case report

Spontaneous heterotopic pregnancy is a rare clinical condition in which intrauterine and extra uterine pregnancies occur at the same time. It can be a life threatening condition and can be easily missed with the diagnosis being overlooked. We present the case of a 40 year old patient who was treated for a heterotopic pregnancy. She had a transvaginal ultrasound because of a previous ectopic pregnancy and an intrauterine gestational sac was seen with false reassurances. The patient presented acutely with a ruptured tubal pregnancy and this was managed laparoscopically. The ectopic pregnancy was not suspected at her initial presentation. A high index of suspicion is needed in women with risk factors for an ectopic pregnancy and in low risk women who have free fluid with or without an adnexal mass with an intrauterine gestation

DNA replication stress restricts ribosomal DNA copy number

Ribosomal RNAs (rRNAs) in budding yeast are encoded by ~100–200 repeats of a 9.1kb sequence arranged in tandem on chromosome XII, the ribosomal DNA (rDNA) locus. Copy number of rDNA repeat units in eukaryotic cells is maintained far in excess of the requirement for ribosome biogenesis. Despite the importance of the repeats for both ribosomal and non-ribosomal functions, it is currently not known how “normal” copy number is determined or maintained. To identify essential genes involved in the maintenance of rDNA copy number, we developed a droplet digital PCR based assay to measure rDNA copy number in yeast and used it to screen a yeast conditional temperature-sensitive mutant collection of essential genes. Our screen revealed that low rDNA copy number is associated with compromised DNA replication. Further, subculturing yeast under two separate conditions of DNA replication stress selected for a contraction of the rDNA array independent of the replication fork blocking protein, Fob1. Interestingly, cells with a contracted array grew better than their counterparts with normal copy number under conditions of DNA replication stress. Our data indicate that DNA replication stresses select for a smaller rDNA array. We speculate that this liberates scarce replication factors for use by the rest of the genome, which in turn helps cells complete DNA replication and continue to propagate. Interestingly, tumors from mini chromosome maintenance 2 (MCM2)-deficient mice also show a loss of rDNA repeats. Our data suggest that a reduction in rDNA copy number may indicate a history of DNA replication stress, and that rDNA array size could serve as a diagnostic marker for replication stress. Taken together, these data begin to suggest the selective pressures that combine to yield a “normal” rDNA copy number

A Core Curriculum in the Biological and Biomedical Sciences for Dentistry

INTRODUCTION: The biomedical sciences (BMS) are a central part of the dental curriculum that underpins teaching and clinical practice in all areas of dentistry. Although some specialist groups have proposed curricula in their particular topic areas, there is currently no overarching view of what should be included in a BMS curriculum for undergraduate dental programmes. To address this, the Association for Dental Education in Europe (ADEE) convened a Special Interest Group (SIG) with representatives from across Europe to develop a consensus BMS curriculum for dental programmes. CURRICULUM: This paper summarises the outcome of the deliberations of this SIG and details a consensus view from the SIG of what a BMS curriculum should include. CONCLUSIONS: Given the broad nature of BMS applied to dentistry, this curriculum framework is advisory and seeks to provide programme planners with an indicative list of topics which can be mapped to specific learning objectives within their own curricula. As dentistry becomes increasingly specialised, these will change, or some elements of the undergraduate curriculum may move to the post-graduate setting. So, this document should be seen as a beginning and it will need regular review as BMS curricula in dentistry evolve

Particle-scale mechanics of sand crushing in compression and shearing using DEM

AbstractIn this paper, the discrete element method is used to explore why differing amounts of breakage, quantified using Hardin's relative breakage parameter (Br), are associated with the critical state line (CSL) and the normal compression line (NCL) at similar stress levels. Virtual samples, initially containing more than 20,000 spherical particles, were isotropically compressed to a range of confining pressures up to 56MPa and subjected to triaxial compression, both considering and disregarding particle crushing. A particle crushing model was developed for these simulations which is both computationally tractable and gives macro-scale results qualitatively in agreement with laboratory tests. The CSLs are both linear in q–p' space. A curved peak envelope, corresponding to a curved Mohr–Coulomb envelope, is obtained for the crushing simulations which is absent when crushing is disabled. Consideration of particle crushing reduces the peak stress, and the volumetric response is much more contractive with crushing at high p'. These simulations capture the behaviour in Br–p' space expected from published laboratory tests. The difference in behaviour along the NCL and CSL is explained by the larger fluctuations in contact force during triaxial shearing than during isotropic compression which was quantified using a newly-defined measure, the contact number ratio. Particle crushing continues after the critical state is attained, contributing to counteract the dilation induced by particle rearrangement