Modelling how plant cell-cycle progression leads to cell size regulation.

Populations of cells typically maintain a consistent size, despite cell division rarely being precisely symmetrical. Therefore, cells must possess a mechanism of "size control", whereby the cell volume at birth affects cell-cycle progression. While size control mechanisms have been elucidated in a number of other organisms, it is not yet clear how this mechanism functions in plants. Here, we present a mathematical model of the key interactions in the plant cell cycle. Model simulations reveal that the network of interactions exhibits limit-cycle solutions, with biological switches underpinning both the G1/S and G2/M cell-cycle transitions. Embedding this network model within growing cells, we test hypotheses as to how cell-cycle progression can depend on cell size. We investigate two different mechanisms at both the G1/S and G2/M transitions: (i) differential expression of cell-cycle activator and inhibitor proteins (with synthesis of inhibitor proteins being independent of cell size), and (ii) equal inheritance of inhibitor proteins after cell division. The model demonstrates that both these mechanisms can lead to larger daughter cells progressing through the cell cycle more rapidly, and can thus contribute to cell-size control. To test how these features enable size homeostasis over multiple generations, we then simulated these mechanisms in a cell-population model with multiple rounds of cell division. These simulations suggested that integration of size-control mechanisms at both G1/S and G2/M provides long-term cell-size homeostasis. We concluded that while both size independence and equal inheritance of inhibitor proteins can reduce variations in cell size across individual cell-cycle phases, combining size-control mechanisms at both G1/S and G2/M is essential to maintain size homeostasis over multiple generations. Thus, our study reveals how features of the cell-cycle network enable cell-cycle progression to depend on cell size, and provides a mechanistic understanding of how plant cell populations maintain consistent size over generations.

Anal endosonographic assessment of the accuracy of clinical diagnosis of obstetric anal sphincter injury.

INTRODUCTION AND HYPOTHESIS: Obstetric anal sphincter injuries (OASIS) are a common cause of maternal morbidity with an overall incidence in the UK of 2.9% (range 0-8%). They can cause a range of physical symptoms and psychological distress. This study aims to assess the accuracy of clinical diagnosis of OASIS using endoanal ultrasound (EAUS) and the correlation between confirmed injury and change to anorectal physiology squeeze pressure and the incidence of bowel symptoms. METHODS AND MATERIALS: Retrospective study of prospectively collected data from 1135 women who attended the Third- and Fourth-Degree Tears Clinic at our institution, 12 weeks post-delivery, between June 2008 and October 2019. RESULTS: OASIS was confirmed in 876 (78.8%) women and 236 (21.3%) had no injury. Of the women who underwent anorectal physiology, 45.6% had a mean maximal resting pressure below the normal range and 68.8% had a mean incremental squeeze pressure below normal. Women with confirmed OASIS had significantly lower pressures (p < 0.001) than those without a confirmed sphincter injury. Three hundred ninety-three (34.8%) women reported bowel symptoms, with those with endosonographic evidence of injury more likely to develop flatus incontinence. CONCLUSION: Of the women in this study with a suspected OASIS, 21.2% could be reassured that they did not have an injury. This information is useful for women considering future mode of delivery. Those with confirmed injury are more likely to complain of flatus incontinence and have reduced anal sphincter pressures.

Environmental factors influencing spotted hyena and lion population biomass across Africa.

The spotted hyena (Crocuta crocuta Erxleben) and the lion (Panthera leo Linnaeus) are two of the most abundant and charismatic large mammalian carnivores in Africa and yet both are experiencing declining populations and significant pressures from environmental change. However, with few exceptions, most studies have focused on influences upon spotted hyena and lion populations within individual sites, rather than synthesizing data from multiple locations. This has impeded the identification of over-arching trends behind the changing biomass of these large predators. Using partial least squares regression models, influences upon population biomass were therefore investigated, focusing upon prey biomass, temperature, precipitation, and vegetation cover. Additionally, as both species are in competition with one other for food, the influence of competition and evidence of environmental partitioning were assessed. Our results indicate that spotted hyena biomass is more strongly influenced by environmental conditions than lion, with larger hyena populations in areas with warmer winters, cooler summers, less drought, and more semi-open vegetation cover. Competition was found to have a negligible influence upon spotted hyena and lion populations, and environmental partitioning is suggested, with spotted hyena population biomass greater in areas with more semi-open vegetation cover. Moreover, spotted hyena is most heavily influenced by the availability of medium-sized prey biomass, whereas lion is influenced more by large size prey biomass. Given the influences identified upon spotted hyena populations in particular, the results of this study could be used to highlight populations potentially at greatest risk of decline, such as in areas with warming summers and increasingly arid conditions.

Double or Nothing? Cell Division and Cell Size Control.

Size is a fundamental property that must be tightly regulated to ensure that cells and tissues function efficiently. Dynamic size control allows unicellular organisms to adapt to environmental changes, but cell size is also integral to multicellular development, affecting tissue size and structure. Despite clear evidence for homeostatic cell size maintenance, we are only now beginning to understand cell size regulation in the actively dividing meristematic tissues of higher plants. We discuss here how coupled advances in live cell imaging and modelling are uncovering dynamic mechanisms for size control mediated at the cellular level. We argue that integrated models of cell growth and division will be necessary to predict cell size and fully understand multicellular growth and development.

Evaluation of the provision of helicopter emergency medical services in Europe.

BACKGROUND: Helicopter emergency medical services (HEMS) are a useful means of reducing inequity of access to specialist emergency care. The aim of this study was to evaluate the variations in HEMS provision across Europe, in order to inform the further development of emergency care systems. METHODS: This is a survey of primary HEMS in the 32 countries of the European Economic Area and Switzerland. Information was gathered through internet searches (May to September 2016), and by emailing service providers, requesting verification and completion of data (September 2016 to July 2017). HEMS provision was calculated as helicopters per million population and per 1000 km2 land area, by day and by night, and per US$10 billion of gross domestic product (GDP), for each country. RESULTS: In 2016, the smallest and least prosperous countries had no dedicated HEMS provision. Luxembourg had the highest number of helicopters by area and population, day and night. Alpine countries had high daytime HEMS coverage and Scandinavia had good night-time coverage. Most helicopters carried a doctor. Funding of services varied from public to charitable and private. Most services performed both primary (from the scene) and secondary (interfacility) missions. CONCLUSIONS: Within Europe, there is a large variation in the number of helicopters available for emergency care, regardless of whether assessed with reference to population, land area or GDP. Funding of services varied, and did not seem to be clearly related to the availability of HEMS.

PID/WAG-mediated phosphorylation of the Arabidopsis PIN3 auxin transporter mediates polarity switches during gravitropism.

Intercellular distribution of the plant hormone auxin largely depends on the polar subcellular distribution of the plasma membrane PIN-FORMED (PIN) auxin transporters. PIN polarity switches in response to different developmental and environmental signals have been shown to redirect auxin fluxes mediating certain developmental responses. PIN phosphorylation at different sites and by different kinases is crucial for PIN function. Here we investigate the role of PIN phosphorylation during gravitropic response. Loss- and gain-of-function mutants in PINOID and related kinases but not in D6PK kinase as well as mutations mimicking constitutive dephosphorylated or phosphorylated status of two clusters of predicted phosphorylation sites partially disrupted PIN3 phosphorylation and caused defects in gravitropic bending in roots and hypocotyls. In particular, they impacted PIN3 polarity rearrangements in response to gravity and during feed-back regulation by auxin itself. Thus PIN phosphorylation, besides regulating transport activity and apical-basal targeting, is also important for the rapid polarity switches in response to environmental and endogenous signals.

Coordination of meristem and boundary functions by transcription factors in the SHOOT MERISTEMLESS regulatory network.

The Arabidopsis homeodomain transcription factor SHOOT MERISTEMLESS (STM) is crucial for shoot apical meristem (SAM) function, yet the components and structure of the STM gene regulatory network (GRN) are largely unknown. Here, we show that transcriptional regulators are overrepresented among STM-regulated genes and, using these as GRN components in Bayesian network analysis, we infer STM GRN associations and reveal regulatory relationships between STM and factors involved in multiple aspects of SAM function. These include hormone regulation, TCP-mediated control of cell differentiation, AIL/PLT-mediated regulation of pluripotency and phyllotaxis, and specification of meristem-organ boundary zones via CUC1. We demonstrate a direct positive transcriptional feedback loop between STM and CUC1, despite their distinct expression patterns in the meristem and organ boundary, respectively. Our further finding that STM activates expression of the CUC1-targeting microRNA miR164c combined with mathematical modelling provides a potential solution for this apparent contradiction, demonstrating that these proposed regulatory interactions coupled with STM mobility could be sufficient to provide a mechanism for CUC1 localisation at the meristem-organ boundary. Our findings highlight the central role for the STM GRN in coordinating SAM functions.

Living well with dementia groups: changes in participant and therapist verbal behaviour.

OBJECTIVES: This paper reports two related analyses of verbal material from seven Living Well with Dementia groups: the first examines changes in the verbal behaviours of participants across the course of the sessions in all seven groups; while the second contrasts therapist behaviour in two groups. METHODS: In the first analysis, recordings of three sessions from each group were transcribed and participant descriptions of dementia were analysed using the Markers of Assimilation of Problematic Experiences of Dementia (MAPED) rating procedure. In the second analysis, therapist behaviour in weeks 2 and 8 from two groups (F and G) was analysed using the Hill Counsellor Verbal response rating scale. Inter-rater reliabilities for the two sets of ratings were 'good' and 'very good', respectively. RESULTS: For the MAPED ratings, a five by four contingency table was analysed using chi-squared, which indicated a highly significant change in assimilation. There were significant higher levels of level 1 and 2 markers in the first two sessions and level 4 for sessions 5 and 6. Facilitators used significantly more direct guidance and information giving behaviour in the second session at Location F compared to Location G. CONCLUSIONS: The results suggest that important changes occurred in the way that dementia was described across the seven LivDem groups: this includes both reductions in the avoidance of direct references to dementia after the first two sessions, as well as an increase in 'insight' statements. Directive facilitator behaviour may be associated with poorer outcomes.

Cell-size dependent progression of the cell cycle creates homeostasis and flexibility of plant cell size.

Mean cell size at division is generally constant for specific conditions and cell types, but the mechanisms coupling cell growth and cell cycle control with cell size regulation are poorly understood in intact tissues. Here we show that the continuously dividing fields of cells within the shoot apical meristem of Arabidopsis show dynamic regulation of mean cell size dependent on developmental stage, genotype and environmental signals. We show cell size at division and cell cycle length is effectively predicted using a two-stage cell cycle model linking cell growth and two sequential cyclin dependent kinase (CDK) activities, and experimental results concur in showing that progression through both G1/S and G2/M is size dependent. This work shows that cell-autonomous co-ordination of cell growth and cell division previously observed in unicellular organisms also exists in intact plant tissues, and that cell size may be an emergent rather than directly determined property of cells.

Grossly delayed massive subcutaneous emphysema following laparoscopic left hemicolectomy: A case report.

INTRODUCTION: Surgical emphysema is a known early complication of laparoscopic surgery, common during upper gastrointestinal and gynaecological surgery; the authors present the first case of delayed subcutaneous emphysema following a laparoscopic left hemicolectomy. PRESENTATION OF CASE: A 52-year-old woman underwent a laparoscopic left hemicolectomy for a sigmoid malignancy; on the third post-operative day after an uneventful procedure, she developed a massive surgical emphysema involving her face, neck and chest with associated pneumoperitoneum but without any evidence of pneumothorax. A gastrograffin enema ruled out an anastomotic leak. Apart from a borderline tachycardia, mildly low saturations and an area of erythema in her right flank, she was totally asymptomatic. The emphysema resolved spontaneously around the 6th post-operative day. DISCUSSION: Massive subcutaneous surgical emphysema after laparoscopic colorectal surgery is a rare complication and can me managed conservatively with a good outcome. CONCLUSION: To our knowledge, this represents the first case of delayed massive surgical emphysema following colorectal surgery, the aetiology of which has still not been clearly explained, after exclusion of the most common causes.

A multi-site controlled trial of the R&R2MHP cognitive skills program for mentally disordered female offenders.

This study aimed to evaluate the acceptability and efficacy of delivering the Reasoning and Rehabilitation Mental Health Program (R&R2MHP) to female mentally disordered offenders detained in medium and low secure hospital settings. Group treatment participants (N = 18) and control participants receiving treatment as usual (N = 20) completed self-report measures pre- and post-group. An informant measure of ward behavior was also completed by staff. Violent attitudes and locus of control were assessed at 3-month follow-up. Program completion was excellent (89%). A conservative intention-to-treat analysis found significant treatment effects post-group for positive problem-solving orientation, rational problem-solving style, and locus of control (medium-large effect), but no treatment effect for violent attitudes, anger, and ward behavior. At follow-up, a large treatment effect was found for locus of control. Ad hoc per protocol analyses found a large treatment effect for ward behavior. The findings provide preliminary support for the feasibility and utility of delivering R&R2MHP to females in secure psychiatric settings.

Systems analysis of shoot apical meristem growth and development: integrating hormonal and mechanical signaling.

The shoot apical meristem (SAM) is a small population of stem cells that continuously generates organs and tissues. This review covers our current understanding of organ initiation by the SAM in Arabidopsis thaliana. Meristem function and maintenance involves two major hormones, cytokinins and auxins. Cytokinins appear to play a major role in meristem maintenance and in controlling meristematic properties, such as cell proliferation. Self-organizing transport processes, which are still only partially understood, lead to the patterned accumulation of auxin at particular positions, where organs will grow out. A major downstream target of auxin-mediated growth regulation is the cell wall, which is a determinant for both growth rates and growth distribution, but feedbacks with metabolism and the synthetic capacity of the cytoplasm are crucial as well. Recent work has also pointed at a potential role of mechanical signals in growth coordination, but the precise mechanisms at work remain to be elucidated.

A multi-site controlled trial of a cognitive skills program for mentally disordered offenders.

BACKGROUND: The effectiveness of offending behaviour programs in forensic mental health settings is not well established. Thus this study aimed to evaluate the Reasoning and Rehabilitation Mental Health program (R&R2 MHP) among a mentally disordered offender (MDO) population. METHODS: A sample of 121 adult males drawn from 10 forensic mental health sites completed questionnaires at baseline and post-treatment to assess violent attitudes, locus of control, social problem-solving and anger. An informant measure of social and psychological functioning, including disruptive behaviour, was completed by unit staff at the same time. At three month follow-up patients completed again the violent attitudes and locus of control questionnaires. The data of 67 patients who participated in the group condition were compared with 54 waiting-list controls who received treatment as usual. RESULTS: 78% of group participants completed the program. In contrast to controls, significant treatment effects were found at outcome on self-reported measures of violent attitudes, rational problem-solving and anger cognitions. Improvements were endorsed by informant ratings of social and psychological functioning within the establishments. At follow-up significant treatment effects were found for both violent attitudes and locus of control. CONCLUSIONS: R&R2 MHP was effective in a sample of MDOs and had a comparatively low drop-out rate. Future research should use a randomized controlled design.

Gravity-induced PIN transcytosis for polarization of auxin fluxes in gravity-sensing root cells.

Auxin is an essential plant-specific regulator of patterning processes that also controls directional growth of roots and shoots. In response to gravity stimulation, the PIN3 auxin transporter polarizes to the bottom side of gravity-sensing root cells, presumably redirecting the auxin flux toward the lower side of the root and triggering gravitropic bending. By combining live-cell imaging techniques with pharmacological and genetic approaches, we demonstrate that PIN3 polarization does not require secretion of de novo synthesized proteins or protein degradation, but instead involves rapid, transient stimulation of PIN endocytosis, presumably via a clathrin-dependent pathway. Moreover, gravity-induced PIN3 polarization requires the activity of the guanine nucleotide exchange factors for ARF GTPases (ARF-GEF) GNOM-dependent polar-targeting pathways and might involve endosome-based PIN3 translocation from one cell side to another. Our data suggest that gravity perception acts at several instances of PIN3 trafficking, ultimately leading to the polarization of PIN3, which presumably aligns auxin fluxes with gravity vector and mediates downstream root gravitropic response.

Auxin transport through non-hair cells sustains root-hair development.

The plant hormone auxin controls root epidermal cell development in a concentration-dependent manner. Root hairs are produced on a subset of epidermal cells as they increase in distance from the root tip. Auxin is required for their initiation and continued growth, but little is known about its distribution in this region of the root. Contrary to the expectation that hair cells might require active auxin influx to ensure auxin supply, we did not detect the auxin-influx transporter AUX1 in root-hair cells. A high level of AUX1 expression was detected in adjacent non-hair cell files. Non-hair cells were necessary to achieve wild-type root-hair length, although an auxin response was not required in these cells. Three-dimensional modelling of auxin flow in the root tip suggests that AUX1-dependent transport through non-hair cells maintains an auxin supply to developing hair cells as they increase in distance from the root tip, and sustains root-hair outgrowth. Experimental data support the hypothesis that instead of moving uniformly though the epidermal cell layer, auxin is mainly transported through canals that extend longitudinally into the tissue.

Postmortem MR imaging of the fetal and stillborn central nervous system.

BACKGROUND AND PURPOSE: Changes in the public perception of postmortem procedures in the United Kingdom have led to reduced numbers of autopsies being performed in the fetus and neonate. When autopsy is performed in this group, the brain is now usually studied without being formalin-fixed, which limits the available information. We evaluated the diagnostic accuracy of postmortem MR imaging of the fetal brain and spine when compared with the reference standard, autopsy. METHODS: We obtained high-spatial-resolution T2-weighted images (in-plane resolution approximately 0.4 mm) of the brain and spine in 40 fetuses and stillborn neonates (14-42 weeks gestational age) who were referred for autopsy. The MR findings were compared with those of autopsy, the reference standard, which had been performed independently. RESULTS: In eight cases, the autopsy did not provide structural information of the brain or spine, because assessment of the unfixed tissue was impossible. There was agreement between MR and autopsy findings in 31 (97%) of 32 cases in which comparison could be made. Eleven cases showed normal brain, and 20 cases showed a wide range of developmental and acquired abnormalities. The sensitivity of MR was 100%, specificity 92%, positive predictive value 95%, and negative predictive value 100%. CONCLUSION: MR imaging has a useful role in providing structural information of the central nervous system in fetuses and stillborn neonates.