Structure of the complex I-like molecule NDH of oxygenic photosynthesis.

Cyclic electron flow around photosystem I (PSI) is a mechanism by which photosynthetic organisms balance the levels of ATP and NADPH necessary for efficient photosynthesis1,2. NAD(P)H dehydrogenase-like complex (NDH) is a key component of this pathway in most oxygenic photosynthetic organisms3,4 and is the last large photosynthetic membrane-protein complex for which the structure remains unknown. Related to the respiratory NADH dehydrogenase complex (complex I), NDH transfers electrons originating from PSI to the plastoquinone pool while pumping protons across the thylakoid membrane, thereby increasing the amount of ATP produced per NADP+ molecule reduced4,5. NDH possesses 11 of the 14 core complex I subunits, as well as several oxygenic-photosynthesis-specific (OPS) subunits that are conserved from cyanobacteria to plants3,6. However, the three core complex I subunits that are involved in accepting electrons from NAD(P)H are notably absent in NDH3,5,6, and it is therefore not clear how NDH acquires and transfers electrons to plastoquinone. It is proposed that the OPS subunits-specifically NdhS-enable NDH to accept electrons from its electron donor, ferredoxin3-5,7. Here we report a 3.1 Å structure of the 0.42-MDa NDH complex from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1, obtained by single-particle cryo-electron microscopy. Our maps reveal the structure and arrangement of the principal OPS subunits in the NDH complex, as well as an unexpected cofactor close to the plastoquinone-binding site in the peripheral arm. The location of the OPS subunits supports a role in electron transfer and defines two potential ferredoxin-binding sites at the apex of the peripheral arm. These results suggest that NDH could possess several electron transfer routes, which would serve to maximize plastoquinone reduction and avoid deleterious off-target chemistry of the semi-plastoquinone radical.

A participatory ergonomics intervention to re-design work and improve the musculoskeletal health of paramedics: protocol for a cluster randomised controlled trial.

BACKGROUND: In this paper, we present the protocol for a cluster randomised controlled trial to evaluate the effectiveness and implementation of a participative risk management intervention to address work-related musculoskeletal disorders (WMSDs). The aims of the study include to evaluate the implementation process and the impact of the intervention on work related musculoskeletal pain and discomfort and exposure to physical and psychosocial hazards in paramedics over a 12-month period. METHODS: The intervention in this study is to implement A Participative Hazard Identification and Risk Management (APHIRM) toolkit in an ambulance service. Eighteen work groups containing eligible participants (registered paramedics) will be randomised into the intervention or wait-list control arm in one of three rolling recruitment periods. The APHIRM toolkit survey will be offered at baseline and 12 months later, to all current eligible participants in each work group allocated to the trial. The intervention work groups will receive the remainder of the APHIRM toolkit procedures. Identifying data about individual participants will not be collected in the survey, to protect participant privacy and encourage participation. Changes in primary (musculoskeletal pain and discomfort) and secondary (exposure to physical and psychosocial hazards at work) outcomes measured in the survey will be analysed comparing the baseline and follow up response of the cluster. A process evaluation is included to analyse the implementation and associated barriers or facilitators. DISCUSSION: This study is important in providing a comprehensive approach which focusses on both physical and psychosocial hazards using worker participation, to address WMSDs, a well-known and significant problem for ambulance services. The effectiveness of the intervention in work groups will be rigorously evaluated. If significant positive results are observed, the intervention may be adopted in ambulance services, both nationally and internationally. TRIAL REGISTRATION: ISRCTN77150219. Registered 21 November 2021.

Controlling peripheral intravenous catheter failure by needleless connector design: A pilot randomised controlled trial.

AIM: To test the feasibility of a study protocol that compared the efficacy of neutral- and negative-pressure needleless connectors (NCs). DESIGN: A single-centre, parallel-group, pilot randomised control trial. METHODS: Our study compared neutral-(intervention) and negative-pressure (control) NCs among adult patients in an Australian hospital. The primary feasibility outcome was measured against predetermined criteria (e.g. eligibility, attrition). The primary efficacy outcome was all-cause peripheral intravenous catheter failure, analysed as time-to-event data. RESULTS: In total, 201 (100 control; 101 intervention) participants were enrolled between March 2020 and September 2020. All feasibility criteria were met except eligibility, which was lower (78%) than the 90% criterion. All-cause peripheral intravenous catheter failure was significantly higher in the intervention group (39%) compared to control (19%). CONCLUSION: With minor modifications to participant screening for eligibility, this randomised control trial is feasible for a large multicentre randomised control trial. The neutral NC was associated with an increased risk of peripheral intravenous catheter failure. IMPLICATIONS FOR THE PROFESSION AND/OR PATIENT CARE: There are several NC designs available, often identified by their mechanism of pressure (positive, negative and neutral). However, NCs can contribute to peripheral intravenous catheter failure. This is the first randomised controlled trial to compare neutral and negative NC designs. Negative pressure NCs had lower PIVC failure compared to neutral NCs, however the results might not be generalisable to other brands or treatment settings. Further high-quality research is needed to explore NC design. REPORTING METHOD: Study methods and results reported in adherence to the CONSORT Statement. PATIENT OR PUBLIC CONTRIBUTION: No patient or public contribution.

Dimers of mitochondrial ATP synthase induce membrane curvature and self-assemble into rows.

Mitochondrial ATP synthases form dimers, which assemble into long ribbons at the rims of the inner membrane cristae. We reconstituted detergent-purified mitochondrial ATP synthase dimers from the green algae Polytomella sp. and the yeast Yarrowia lipolytica into liposomes and examined them by electron cryotomography. Tomographic volumes revealed that ATP synthase dimers from both species self-assemble into rows and bend the lipid bilayer locally. The dimer rows and the induced degree of membrane curvature closely resemble those in the inner membrane cristae. Monomers of mitochondrial ATP synthase reconstituted into liposomes do not bend membrane visibly and do not form rows. No specific lipids or proteins other than ATP synthase dimers are required for row formation and membrane remodelling. Long rows of ATP synthase dimers are a conserved feature of mitochondrial inner membranes. They are required for cristae formation and a main factor in mitochondrial morphogenesis.

Does Sleep Position Influence Sleep-Disordered Breathing in Infants With Cleft Palate: A Feasibility Study?

OBJECTIVE: Cleft palate (CP) can affect breathing, leading to sleep-disordered breathing (SDB). Sleep position can affect SDB, but the optimum sleep position for infants with CP is unknown. We aimed to determine the design of a pragmatic study to investigate the effect of the 2 routinely advised sleep positions in infants with CP on oxygen saturations. DESIGN: A multicentered observational cohort. SETTING: Four UK-based cleft centers, 2 advising supine- and 2 side-lying sleep positions for infants with CP. PARTICIPANTS: Infants with isolated CP born July 1, 2015, and December 31, 2016. Of 48 eligible infants, 30 consented (17 side-lying; 13 supine). INTERVENTIONS: Oxygen saturation (SpO2) and end-tidal carbon dioxide (ETCO2) home monitoring at age 1 and 3 months. Qualitative interviews of parents. OUTCOME MEASURES: Willingness to participate, recruitment, retention, and acceptability/success (>90 minutes recording) of SpO2 and ETCO2 monitoring. RESULTS: SpO2 recordings were obtained during 50 sleep sessions on 24 babies (13 side-lying) at 1 month (34 sessions >90 minutes) and 50 sessions on 19 babies (10 side-lying) at 3 months (27 sessions >90 minutes). The ETCO2 monitoring was only achieved in 12 sessions at 1 month and 6 at 3 months; only 1 was >90 minutes long. The ETCO2 monitoring was reported by the majority as unacceptable. Parents consistently reported the topic of sleep position in CP to be of importance. CONCLUSIONS: This study has demonstrated that it is feasible to perform domiciliary oxygen saturation studies in a research setting and has suggested that there may be a difference in the effects of sleep position that requires further investigation. We propose a study with randomization is indicated, comparing side-lying with supine-lying sleep position, representing an important step toward better understanding of SDB in infants with CP.

Horizontal membrane-intrinsic α-helices in the stator a-subunit of an F-type ATP synthase.

ATP, the universal energy currency of cells, is produced by F-type ATP synthases, which are ancient, membrane-bound nanomachines. F-type ATP synthases use the energy of a transmembrane electrochemical gradient to generate ATP by rotary catalysis. Protons moving across the membrane drive a rotor ring composed of 8-15 c-subunits. A central stalk transmits the rotation of the c-ring to the catalytic F1 head, where a series of conformational changes results in ATP synthesis. A key unresolved question in this fundamental process is how protons pass through the membrane to drive ATP production. Mitochondrial ATP synthases form V-shaped homodimers in cristae membranes. Here we report the structure of a native and active mitochondrial ATP synthase dimer, determined by single-particle electron cryomicroscopy at 6.2 Å resolution. Our structure shows four long, horizontal membrane-intrinsic α-helices in the a-subunit, arranged in two hairpins at an angle of approximately 70° relative to the c-ring helices. It has been proposed that a strictly conserved membrane-embedded arginine in the a-subunit couples proton translocation to c-ring rotation. A fit of the conserved carboxy-terminal a-subunit sequence places the conserved arginine next to a proton-binding c-subunit glutamate. The map shows a slanting solvent-accessible channel that extends from the mitochondrial matrix to the conserved arginine. Another hydrophilic cavity on the lumenal membrane surface defines a direct route for the protons to an essential histidine-glutamate pair. Our results provide unique new insights into the structure and function of rotary ATP synthases and explain how ATP production is coupled to proton translocation.

Conserved in situ arrangement of complex I and III2 in mitochondrial respiratory chain supercomplexes of mammals, yeast, and plants.

We used electron cryo-tomography and subtomogram averaging to investigate the structure of complex I and its supramolecular assemblies in the inner mitochondrial membrane of mammals, fungi, and plants. Tomographic volumes containing complex I were averaged at ∼4 nm resolution. Principal component analysis indicated that ∼60% of complex I formed a supercomplex with dimeric complex III, while ∼40% were not associated with other respiratory chain complexes. The mutual arrangement of complex I and III2 was essentially conserved in all supercomplexes investigated. In addition, up to two copies of monomeric complex IV were associated with the complex I1III2 assembly in bovine heart and the yeast Yarrowia lipolytica, but their positions varied. No complex IV was detected in the respiratory supercomplex of the plant Asparagus officinalis Instead, an ∼4.5-nm globular protein density was observed on the matrix side of the complex I membrane arm, which we assign to γ-carbonic anhydrase. Our results demonstrate that respiratory chain supercomplexes in situ have a conserved core of complex I and III2, but otherwise their stoichiometry and structure varies. The conserved features of supercomplex assemblies indicate an important role in respiratory electron transfer.

Rotary ATPases: A New Twist to an Ancient Machine.

Rotary ATPases are energy-converting nanomachines found in the membranes of all living organisms. The mechanism by which proton translocation through the membrane drives ATP synthesis, or how ATP hydrolysis generates a transmembrane proton gradient, has been unresolved for decades because the structure of a critical subunit in the membrane was unknown. Electron cryomicroscopy (cryoEM) studies of two rotary ATPases have now revealed a hairpin of long, horizontal, membrane-intrinsic α-helices in the a-subunit next to the c-ring rotor. The horizontal helices create a pair of aqueous half-channels in the membrane that provide access to the proton-binding sites in the rotor ring. These recent findings help to explain the highly conserved mechanism of ion translocation by rotary ATPases.

Implementation and evaluation of short peripheral intravenous catheter flushing guidelines: a stepped wedge cluster randomised trial.

BACKGROUND: Peripheral intravenous catheters (PIVCs) are ubiquitous medical devices, crucial to providing essential fluids and drugs. However, post-insertion PIVC failure occurs frequently, likely due to inconsistent maintenance practice such as flushing. The aim of this implementation study was to evaluate the impact a multifaceted intervention centred on short PIVC maintenance had on patient outcomes. METHODS: This single-centre, incomplete, stepped wedge, cluster randomised trial with an implementation period was undertaken at a quaternary hospital in Queensland, Australia. Eligible patients were from general medical and surgical wards, aged ≥ 18 years, and requiring a PIVC for > 24 h. Wards were the unit of randomisation and allocation was concealed until the time of crossover to the implementation phase. Patients, clinicians, and researchers were not masked but infections were adjudicated by a physician masked to allocation. Practice during the control period was standard care (variable practice with manually prepared flushes of 0.9% sodium chloride). The intervention group received education reinforcing practice guidelines (including administration with manufacturer-prepared pre-filled flush syringes). The primary outcome was all-cause PIVC failure (as a composite of occlusion, infiltration, dislodgement, phlebitis, and primary bloodstream or local infection). Analysis was by intention-to-treat. RESULTS: Between July 2016 and February 2017, 619 patients from 9 clusters (wards) were enrolled (control n = 306, intervention n = 313), with 617 patients comprising the intention-to-treat population. PIVC failure was 91 (30%) in the control and 69 (22%) in the intervention group (risk difference - 8%, 95% CI - 14 to - 1, p = 0.032). Total costs were lower in the intervention group. No serious adverse events related to study intervention occurred. CONCLUSIONS: This study demonstrated the effectiveness of post-insertion PIVC flushing according to recommended guidelines. Evidence-based education, surveillance and products for post-insertion PIVC management are vital to improve patient outcomes. TRIAL REGISTRATION: Trial submitted for registration on 25 January 2016. Approved and retrospectively registered on 4 August 2016. Ref: ACTRN12616001035415 .

Structure of a Synthetic ß-Carboxysome Shell.

Carboxysomes are capsid-like, CO2-fixing organelles that are present in all cyanobacteria and some chemoautotrophs and that substantially contribute to global primary production. They are composed of a selectively permeable protein shell that encapsulates Rubisco, the principal CO2-fixing enzyme, and carbonic anhydrase. As the centerpiece of the carbon-concentrating mechanism, by packaging enzymes that collectively enhance catalysis, the carboxysome shell enables the generation of a locally elevated concentration of substrate CO2 and the prevention of CO2 escape. A functional carboxysome consisting of an intact shell and cargo is essential for cyanobacterial growth under ambient CO2 concentrations. Using cryo-electron microscopy, we have determined the structure of a recombinantly produced simplified ß-carboxysome shell. The structure reveals the sidedness and the specific interactions between the carboxysome shell proteins. The model provides insight into the structural basis of selective permeability of the carboxysome shell and can be used to design modifications to investigate the mechanisms of cargo encapsulation and other physiochemical properties such as permeability. Notably, the permeability properties are of great interest for modeling and evaluating this carbon-concentrating mechanism in metabolic engineering. Moreover, we find striking similarity between the carboxysome shell and the structurally characterized, evolutionarily distant metabolosome shell, implying universal architectural principles for bacterial microcompartment shells.

In situ structure of trypanosomal ATP synthase dimer reveals a unique arrangement of catalytic subunits.

We used electron cryotomography and subtomogram averaging to determine the in situ structures of mitochondrial ATP synthase dimers from two organisms belonging to the phylum euglenozoa: Trypanosoma brucei, a lethal human parasite, and Euglena gracilis, a photosynthetic protist. At a resolution of 32.5 Å and 27.5 Å, respectively, the two structures clearly exhibit a noncanonical F1 head, in which the catalytic (αß)3 assembly forms a triangular pyramid rather than the pseudo-sixfold ring arrangement typical of all other ATP synthases investigated so far. Fitting of known X-ray structures reveals that this unusual geometry results from a phylum-specific cleavage of the α subunit, in which the C-terminal αC fragments are displaced by ∼20 Å and rotated by ∼30° from their expected positions. In this location, the αC fragment is unable to form the conserved catalytic interface that was thought to be essential for ATP synthesis, and cannot convert γ-subunit rotation into the conformational changes implicit in rotary catalysis. The new arrangement of catalytic subunits suggests that the mechanism of ATP generation by rotary ATPases is less strictly conserved than has been generally assumed. The ATP synthases of these organisms present a unique model system for discerning the individual contributions of the α and ß subunits to the fundamental process of ATP synthesis.

Collaboration between parents and SLTs produces optimal outcomes for children attending speech and language therapy: Gathering the evidence.

BACKGROUND: Collaboration between parents and speech and language therapists (SLTs) is seen as a key element in family-centred models. Collaboration can have positive impacts on parental and children's outcomes. However, collaborative practice has not been well described and researched in speech and language therapy for children and may not be easy to achieve. It is important that we gain a deeper understanding of collaborative practice with parents, how it can be achieved and how it can impact on outcomes. This understanding could support practitioners in daily practice with regard to achieving collaborative practice with parents in different contexts. AIMS: To set a research agenda on collaborative practice between parents and SLTs in order to generate evidence regarding what works, how, for whom, in what circumstances and to what extent. METHODS & PROCEDURES: A realist evaluation approach was used to make explicit what collaborative practice with parents entails. The steps suggested by the RAMESES II project were used to draft a preliminary programme theory about collaborative practice between parents and SLTs. This process generates explicit hypotheses which form a potential research agenda. DISCUSSION & CONCLUSIONS: A preliminary programme theory of collaborative practice with parents was drafted using a realist approach. Potential contextual factors (C), mechanisms (M) and outcomes (O) were presented which could be configured into causal mechanisms to help explain what works for whom in what circumstances. CMO configurations were drafted, based on the relevant literature, which serve as exemplars to illustrate how this methodology could be used. In order to debate, test and expand our hypothesized programme theory for collaborative practice with parents, further testing against a broader literature is required alongside research to explore the functionality of the configurations across contexts. This paper highlights the importance of further research on collaborative practice with parents and the potential value of realist evaluation methodology. What this paper adds Current policy in education, health and social care advocates for family-centred care and collaborative practice with parents. Thereby, collaborative practice is the preferred practice for SLTs and parents. In this paper, we explore collaborative practice and use a realist evaluation approach to achieve the aim of setting a research agenda in this area. Researchers use realist evaluation, a methodology originally developed by Pawson and Tilley in the 1990s, to explore the causal link between interventions and outcomes, summarized as what works, how, for whom, in what circumstances and to what extent. Realist evaluation provides a framework to explore configurations between contexts (C), mechanisms (M) and outcomes (O). We used this methodology to take a first step at making explicit what collaborative practice is and how it might be achieved in different contexts. We did this by drafting a preliminary programme theory about collaborative practice, where we made explicit what context factors and mechanisms might influence outcomes in collaborative practice between parents and SLTs. Based on this programme theory, we argue for the need to develop a research agenda on collaborative practice with parents of children with speech, language and communication needs. The steps between a programme theory and a research agenda could entail exploring each CMO, or step in the programme theory, and evaluating it against the existing literature-both within and beyond speech and language therapy-to see how far it stands up. In this way, gaps could be identified that could be converted into research questions that would stimulate debate about a research agenda on collaborative practice. Understanding how collaborative practice can be achieved in different contexts could support SLTs to use mechanisms to optimise collaborative practice intentionally and tailor interventions to the specific needs of families, thereby enhancing collaborative practice between parents and SLTs.

Applying a new concept of embedding qualitative research: an example from a quantitative study of carers of people in later stage dementia.

BACKGROUND: Qualitative methods are increasingly included in larger studies to provide a richer understanding of people's experience. This paper explores the potential of using a novel approach to embedded qualitative design as part of an observational study examining the effectiveness of home support for people in later stage dementia in England. The method involved collecting and analysing unsolicited conversational comments made by participants as they completed standardised measures. An evaluation of the method is presented using the voices of participants to illustrate its potential. METHODS: The conversations of 17 carers recruited to an observational study were audio recorded to gather commentary made while completing a structured interview. Data were interrogated using thematic analysis to investigate the feasibility of conducting an embedded qualitative study, the potential richness of the material and participants' reactions to formal questioning and participating in research. RESULTS: The findings revealed that qualitative data were available from this approach. Analysis generated three themes from carers: conflicting carer emotions; the importance of maintaining normality and agency within day-to-day life; and tensions between these desires and making use of formal services. Important issues for carers were revealed establishing the benefit of using the method. The advantages of exploiting unsolicited conversation included enhancing understanding of people's lived experience, reducing participant burden in research and easing the process of data collection. In addition, it provided an opportunity to evaluate individuals' experience of the research process. CONCLUSIONS: The findings demonstrate how unsolicited comments during structured interviews may appear incidental but can reveal important aspects of living with dementia. The method also emphasised methodological challenges for research in dementia, including the influence and impact of the research context. Further research is required to evaluate the method with other groups including people with dementia themselves.

Helical arrays of U-shaped ATP synthase dimers form tubular cristae in ciliate mitochondria.

F1Fo-ATP synthases are universal energy-converting membrane protein complexes that synthesize ATP from ADP and inorganic phosphate. In mitochondria of yeast and mammals, the ATP synthase forms V-shaped dimers, which assemble into rows along the highly curved ridges of lamellar cristae. Using electron cryotomography and subtomogram averaging, we have determined the in situ structure and organization of the mitochondrial ATP synthase dimer of the ciliate Paramecium tetraurelia. The ATP synthase forms U-shaped dimers with parallel monomers. Each complex has a prominent intracrista domain, which links the c-ring of one monomer to the peripheral stalk of the other. Close interaction of intracrista domains in adjacent dimers results in the formation of helical ATP synthase dimer arrays, which differ from the loose dimer rows in all other organisms observed so far. The parameters of the helical arrays match those of the cristae tubes, suggesting the unique features of the P. tetraurelia ATP synthase are directly responsible for generating the helical tubular cristae. We conclude that despite major structural differences between ATP synthase dimers of ciliates and other eukaryotes, the formation of ATP synthase dimer rows is a universal feature of mitochondria and a fundamental determinant of cristae morphology.

SLTs' conceptions about their own and parents' roles during intervention with preschool children.

BACKGROUND: Current research investigating collaboration between parents and speech and language therapists (SLTs) indicates that the SLT role is characterized by therapist-led practice. Co-working with parents of children with speech and language difficulties is less frequently described. In order to embrace co-working during intervention, the SLT role may need to be reframed, focusing on acquiring skills in the role of coach as well as the role of planning intervention and treating children. AIMS: To report (1) SLTs' conceptions about their own roles during intervention for pre-school children with speech and language difficulties; and (2) SLTs' conceptions of parents' roles during intervention. METHODS & PROCEDURES: A qualitative study used individual, semi-structured interviews with 12 SLTs working with pre-school children. Open-ended questions investigated SLTs' expectation of parents, experience of working with families, and the SLTs' conception of their roles during assessment, intervention and decision-making. Thematic network analysis was used to identify basic, organizational and global themes. RESULTS & OUTCOMES: SLTs had three conceptions about their own role during intervention: treating, planning and coaching. The roles of treating and planning were clearly formulated, but the conception of their role as coach was more implicit in their discourse. SLTs' conception of parents' roles focused on parents as implementers of activities and only occasionally as change agents. CONCLUSIONS & IMPLICATIONS: Collaboration that reflects co-working may necessitate changes in the conception about the role for both SLTs and parents. SLTs and parents may need to negotiate roles, with parents assuming learner and adaptor roles and SLTs adopting a coaching role to activate greater involvement of parents. Applying conceptual change theory offers new possibilities for understanding and enabling changes in SLTs' conception of roles, potentially initiating a deeper understanding of how to achieve co-working during speech and language intervention.

Parental Experience of Sleep-Disordered Breathing in Infants With Cleft Palate: Comparing Parental and Clinical Priorities.

OBJECTIVE: To identify outcomes relating to sleep-disordered breathing (SDB) that are relevant to parents, during the early weeks of caring for infants with cleft palate (CP), and compare these with clinical outcomes identified in a systematic search of research literature. DESIGN: A qualitative study using telephone/face-to-face interviews with parents explored their understanding of breathing and respiratory effort in infants with CP. SETTING: Care provided by 3 specialist cleft centers in the United Kingdom, with study conducted in parents' homes. PARTICIPANTS: Criteria for participation were parents of infants with isolated CP aged 12 to 16 weeks. Thirty-one parents of infants with CP (over 12 weeks) were invited to participate in the interview. Interviews were completed with 27 parents; 4 parents could not be contacted after completing the sleep monitoring. RESULTS: Parents' description of infants' sleep suggests that breathing is not considered as a separate priority from their principal concerns of feeding and sleeping. They observe indicators of infants' breathing, but these are not perceived as signs of SDB. Parents' decision to use lateral or supine sleep positioning reflects their response to advice from specialists, observation of their infants' comfort, ease of breathing, and personal experience. Outcomes, identified in published research of SDB, coincide with parents' concerns but are expressed in medical language and fit into distinct domains of "snoring," "sleep," "gas exchange," and "apnea." CONCLUSIONS: Parents' description of sleeping and respiration in infants with CP reflect their everyday experience, offering insight into their understanding, priorities, and language used to describe respiration. Understanding parents' individual priorities and how these are expressed could be fundamental to selecting meaningful outcomes for future studies of airway interventions.

Longitudinal investigation of neuroinflammation and metabolite profiles in the APPswe ×PS1Δe9 transgenic mouse model of Alzheimer's disease.

There is increasing evidence linking neuroinflammation to many neurological disorders including Alzheimer's disease (AD); however, its exact contribution to disease manifestation and/or progression is poorly understood. Therefore, there is a need to investigate neuroinflammation in both health and disease. Here, we investigate cognitive decline, neuroinflammatory and other pathophysiological changes in the APPswe ×PS1Δe9 transgenic mouse model of AD. Transgenic (TG) mice were compared to C57BL/6 wild type (WT) mice at 6, 12 and 18 months of age. Neuroinflammation was investigated by [18 F]DPA-714 positron emission tomography and myo-inositol levels using 1 H magnetic resonance spectroscopy (MRS) in vivo. Neuronal and cellular dysfunction was investigated by looking at N-acetylaspartate (NAA), choline-containing compounds, taurine and glutamate also using MRS. Cognitive decline was first observed at 12 m of age in the TG mice as assessed by working memory tests . A significant increase in [18 F]DPA-714 uptake was seen in the hippocampus and cortex of 18 m-old TG mice when compared to age-matched WT mice and 6 m-old TG mice. No overall effect of gene was seen on metabolite levels; however, a significant reduction in NAA was observed in 18 m-old TG mice when compared to WT. In addition, age resulted in a decrease in glutamate and an increase in choline levels. Therefore, we can conclude that increased neuroinflammation and cognitive decline are observed in TG animals, whereas NAA alterations occurring with age are exacerbated in the TG mice. These results support the role of neuroinflammation and metabolite alteration in AD and in ageing.

Longitudinal changes in global and domain specific cognitive function in the very-old: findings from the Newcastle 85+ Study.

OBJECTIVE: Ageing is associated with changes in cognition in some, but not all domains. In young-old adults, defined as persons aged 65-84 years, baseline cognitive function has been shown to impact on cognitive trajectories. Whether similar patterns occur in the very-old, defined as persons aged 85 years and over, is not known. METHODS: Longitudinal changes (5 years' follow-up) in global and domain specific cognitive function including memory, attention and speed were investigated in participants from the Newcastle 85+ Study (n = 845). At baseline, participants were grouped using Mini-Mental State Examination cut-off scores and dementia status into the following: not impaired, mildly impaired or severely impaired/dementia groups. RESULTS: Only a limited number of cognitive measures showed significant decline in performance over time. Where observed, change generally occurred only in the severely impaired group. In the severely impaired group, small differences in baseline age were associated with poorer performance over time on most measures. Education was not protective against cognitive decline in any group. CONCLUSIONS: There are individuals who maintain a high level of cognitive function or only show mild impairments even into their ninth decade of life. This group of successful cognitive agers may provide insight for identifying predictors of cognitive integrity in later life. In individuals with severe impairment, cognitive performance shows significant decline over time, especially in measures of attention and speed. Further work to identify those individuals at highest risk of cognitive decline is necessary to implement early support and intervention strategies in this rapidly expanding age group. © 2017 The Authors. International Journal of Geriatric Psychiatry published by John Wiley & Sons Ltd.

Cross-strand binding of TFAM to a single mtDNA molecule forms the mitochondrial nucleoid.

Mammalian mitochondrial DNA (mtDNA) is packaged by mitochondrial transcription factor A (TFAM) into mitochondrial nucleoids that are of key importance in controlling the transmission and expression of mtDNA. Nucleoid ultrastructure is poorly defined, and therefore we used a combination of biochemistry, superresolution microscopy, and electron microscopy to show that mitochondrial nucleoids have an irregular ellipsoidal shape and typically contain a single copy of mtDNA. Rotary shadowing electron microscopy revealed that nucleoid formation in vitro is a multistep process initiated by TFAM aggregation and cross-strand binding. Superresolution microscopy of cultivated cells showed that increased mtDNA copy number increases nucleoid numbers without altering their sizes. Electron cryo-tomography visualized nucleoids at high resolution in isolated mammalian mitochondria and confirmed the sizes observed by superresolution microscopy of cell lines. We conclude that the fundamental organizational unit of the mitochondrial nucleoid is a single copy of mtDNA compacted by TFAM, and we suggest a packaging mechanism.

Grip strength and inflammatory biomarker profiles in very old adults.

Background: weak grip strength (GS) and chronic inflammation have been implicated in the aetiology of sarcopenia in older adults. Given the interrelationships between inflammatory biomarkers, a summary variable may provide better insight into the relationship between inflammation and muscle strength. This approach has not been investigated in very old adults (aged ≥85) who are at highest risk of muscle weakness. Methods: we used mixed models to explore the prospective association between GS over 5 years in 845 participants in the Newcastle 85+ Study, and inflammatory components identified by principal component analysis (PCA). Cut-offs of ≤27 kg (men) and ≤16 (women) were used to define sub-cohorts with weak and normal GS at each assessment. Results: PCA identified three components, which explained 70% of the total variance in seven baseline biomarkers. Basal interleukin-6 (IL-6) and tumour necrosis factor (TNF-α) had the highest loadings on Component 1; stimulated IL-6 and TNF-α and homocysteine the highest on Component 2; high-sensitivity C-reactive protein (hsCRP) loaded positively and albumin negatively to Component 3. In adjusted mixed models, only Component 3 was associated with GS. One SD increase of Component 3 was associated with a 0.41 kg lower GS initially (P = 0.03) in all participants, but not with GS decline over time. Similar conclusions held for those in the weak and normal GS sub-cohorts. Conclusion: an inflammatory profile including hsCRP and albumin was independently associated with baseline GS. Future studies linking inflammatory profiles and muscle strength are needed to corroborate these findings in older adults.