Microtubule length distributions in the presence of protein-induced severing

Microtubules are highly regulated dynamic elements of the cytoskeleton of eukaryotic cells. One of the regulation mechanisms observed in living cells is the severing by the proteins katanin and spastin. We introduce a model for the dynamics of microtubules in the presence of randomly occurring severing events. Under the biologically motivated assumption that the newly created plus end undergoes a catastrophe, we investigate the steady state length distribution. We show that the presence of severing does not affect the number of microtubules, regardless of the distribution of severing events. In the special case in which the microtubules cannot recover from the depolymerizing state (no rescue events) we derive an analytical expression for the length distribution. In the general case we transform the problem into a single ODE that is solved numerically.Comment: 9 pages, 4 figure

The Plasmodium falciparum, Nima-related kinase Pfnek-4: a marker for asexual parasites committed to sexual differentiation

<b>Background</b> Malaria parasites undergo, in the vertebrate host, a developmental switch from asexual replication to sexual differentiation leading to the formation of gametocytes, the only form able to survive in the mosquito vector. Regulation of the onset of the sexual phase remains largely unknown and represents an important gap in the understanding of the parasite's complex biology. <b>Methods:</b> The expression and function of the Nima-related kinase Pfnek-4 during the early sexual development of the human malaria parasite Plasmodium falciparum were investigated, using three types of transgenic Plasmodium falciparum 3D7 lines: (i) episomally expressing a Pfnek-4-GFP fusion protein under the control of its cognate pfnek-4 promoter; (ii) episomally expressing negative or positive selectable markers, yeast cytosine deaminase-uridyl phosphoribosyl transferase, or human dihydrofolate reductase, under the control of the pfnek-4 promoter; and (iii) lacking a functional pfnek-4 gene. Parasite transfectants were analysed by fluorescence microscopy and flow cytometry. In vitro growth rate and gametocyte formation were determined by Giemsa-stained blood smears. <b>Results:</b> The Pfnek-4-GFP protein was found to be expressed in stage II to V gametocytes and, unexpectedly, in a subset of asexual-stage parasites undergoing schizogony. Culture conditions stimulating gametocyte formation resulted in significant increase of this schizont subpopulation. Moreover, sorted asexual parasites expressing the Pfnek-4-GFP protein displayed elevated gametocyte formation when returned to in vitro culture in presence of fresh red blood cells, when compared to GFP- parasites from the same initial population. Negative selection of asexual parasites expressing pfnek-4 showed a marginal reduction in growth rate, whereas positive selection caused a marked reduction in parasitaemia, but was not sufficient to completely abolish proliferation. Pfnek-4- clones are not affected in their asexual growth and produced normal numbers of stage V gametocytes. <b>Conclusions:</b> The results indicate that Pfnek-4 is not strictly gametocyte-specific, and is expressed in a small subset of asexual parasites displaying high rate conversion to sexual development. Pfnek-4 is not required for erythrocytic schizogony and gametocytogenesis. This is the first study to report the use of a molecular marker for the sorting of sexually-committed schizont stage P. falciparum parasites, which opens the way to molecular characterization of this pre-differentiated subpopulation

Sport and exercise-based interventions for young people in alternative provisions ‘what, where, how, and for who’: a realist review

Pupils in alternative provisions face unique educational, health, economic, and behavioural challenges. Sport and exercise-based interventions represent an innovative means of addressing these challenges. However, given the sparsity of peer-reviewed research, little is known regarding the what, how, and for whom, that facilitates successful intervention implementation. The purpose of this realist review is to address this gap and provide recommendations as to how interventions can be implemented successfully. Due to the absence of peer-reviewed literature; evidence was drawn from wider fields including interventions conducted in mainstream schools including children with similar characteristics to the target population. Nine initial-rough-programme-theories were developed including two rival theories. These data are formed to highlight the interweaving interactions within context-mechanism-outcome configurations. Sport and exercise-based interventions can influence pupils’ academic attainment, attendance, and relationships by promoting citizenship, facilitating exposure to green environments, and fostering belongingness. However, circumstances exist where changes in context or mechanism can result in contrasting outcomes. The context-mechanism-outcome configurations formed the foundations of the recommendations made to intervention developers and implementers aiming at making sport and exercise-based interventions in alternative provisions accessible and successful. Finally, findings of this paper are underpinned by the fundamental need for adequate space and resources within alternative provisions

Chemical pavement modifications to reduce ice adhesion

The formation of ice and snow on road pavement surfaces is a recurring problem, creating hazardous driving conditions, restricting public mobility as well as having adverse economic effects. It would be desirable to develop new and improved ways of modifying the pavement surface, to prevent or at least delay the build-up of ice and to weaken the pavement–ice bond, and making the ice which forms easier to remove. This development could lead to economic, environmental and safety benefits for winter service providers and road users. This paper describes how environmental scanning electron microscopy was used to examine the mechanism by which de-icing chemicals, added as a filler replacement to bituminous materials, can be transferred to the pavement surface. The paper assesses the potential for chemical modifications to reduce the adhesion between ice and the pavement surface by means of work of adhesion calculations, based on surface energy parameters and a new physical ice bond test. The paper also examines the influence that the chemical modifications have on the durability of the pavement surface course

Health and social care professionals’ experiences of providing end of life care during the COVID-19 pandemic: A qualitative study

Background: Health and social care professionals’ ability to address the needs of patients and their relatives at end of life is likely to have been impacted by the COVID-19 pandemic. Aim: To explore health and social care professionals’ experiences of providing end of life care during the COVID-19 pandemic to help inform current/future clinical practice and policy. Design: A qualitative interview study. Data were analysed using thematic analysis. Setting/participants: Sixteen health and social care professionals working across a range of clinical settings in supporting dying patients during the first wave (March–June 2020) of the COVID-19 pandemic in the United Kingdom. Results: Participants reported emotional and practical challenges to providing end of life care during the pandemic, including increases in patient numbers, reduced staffing levels and relying on virtual platforms for sensitive, emotive conversations with relatives. Participants were central to promoting connections between patients and their families at end of life and creating opportunities for a final contact before the death. However, the provision of support varied as a consequence of the pressures of the pandemic. Results are discussed under two themes: (1) challenges and facilitators to providing end of life care, and (2) support needs of relatives when a family member was dying during the COVID-19 pandemic. Conclusion: There is a need for flexible visiting arrangements at end of life during a pandemic. A systems-level approach is necessary to promote the wellbeing of health and social care professionals providing end of life care during and after a pandemic

Sport and physical activity in the lives of looked-after children: a ‘hidden group’ in research, policy and practice

Looked-after children are arguably one of the most disadvantaged groups in society and constitute a ‘hidden group’ in relation to sport and physical activity research, policy and practice. Research on looked-after children has explored the views of caregivers, practitioners and policy-makers who have often been asked to speak for children on their behalf. Through the use of the mosaic approach and innovative participatory methods, including peer interviewing, the purpose of this paper was to provide an insight into a new area of research in the field of sport and physical activity. As such, it reports on initial findings from a wider project with looked-after children that explores their sport and physical activity experiences. Specifically, it asks the following: (1) What are the sport and physical activity experiences of looked-after children? (2) What meanings and values do looked-after children ascribe to their engagement in sport and physical activity? Findings from the voices of four male looked-after children highlight that these young people used sport as a means to an end; to spend time with friends and develop stocks of social capital. However, due to changes in placement, they also experienced disrupted patterns of engagement coupled with additional institutional constraints that shaped access to sporting activities

A single base mutation in the androgen receptor gene causes androgen insensitivity in the testicular feminized rat.

The complete form of androgen insensitivity is an inherited X-linked syndrome in which genetic males fail to undergo masculinization in utero due to defective functioning of the androgen receptor (AR). The molecular basis of androgen insensitivity was investigated in the testicular feminized (Tfm) rat with this syndrome. AR mRNA size and amount, as well as nuclear AR protein revealed by immunocytochemistry, suggested normal expression of the AR gene in the Tfm rat. Sequence analysis of the AR coding region from Tfm and wild-type littermate male rats revealed a single transition mutation, guanine to adenine, within exon E, changing arginine 734 to glutamine within the steroid-binding domain of the AR. This arginine is highly conserved among the family of nuclear receptors and may be part of a phosphorylation recognition site. A recreated mutant AR (Arg734----Gln) expressed in COS cells had only 10-15% of the androgen-binding capacity of wild-type AR; the reduced androgen-binding capacity was similar to that of AR in tissue extracts of the Tfm rat. Stimulation of transcriptional activity by the recreated mutant AR was reduced relative to wild-type AR in cotransfection assays in CV1 cells using as reporter plasmid the mouse mammary tumor virus promoter linked to the chloramphenicol acetyltransferase gene. Thus, arginine 734 appears essential for normal AR function both in androgen binding and transcriptional activation. Absence of these functions results in androgen insensitivity and lack of male sexual development