Experimental demonstration of optical stochastic cooling.

Particle accelerators and storage rings have been transformative instruments of discovery, and, for many applications, innovations in particle-beam cooling have been a principal driver of that success1. Stochastic cooling (SC), one of the most important conceptual and technological advances in this area2-6, cools a beam through granular sampling and correction of its phase-space structure, thus bearing resemblance to a 'Maxwell's demon'. The extension of SC from the microwave regime up to optical frequencies and bandwidths has long been pursued, as it could increase the achievable cooling rates by three to four orders of magnitude and provide a powerful tool for future accelerators. First proposed nearly 30 years ago, optical stochastic cooling (OSC) replaces the conventional microwave elements of SC with optical-frequency analogues and is, in principle, compatible with any species of charged-particle beam7,8. Here we describe a demonstration of OSC in a proof-of-principle experiment at the Fermi National Accelerator Laboratory's Integrable Optics Test Accelerator9,10. The experiment used 100-MeV electrons and a non-amplified configuration of OSC with a radiation wavelength of 950 nm, and achieved strong, simultaneous cooling of the beam in all degrees of freedom. This realization of SC at optical frequencies serves as a foundation for more advanced experiments with high-gain optical amplification, and advances opportunities for future operational OSC systems with potential benefit to a broad user community in the accelerator-based sciences.

Hepatobiliary circulation and dominant urinary excretion of homogentisic acid in a mouse model of alkaptonuria.

Altered activity of specific enzymes in phenylalanine-tyrosine (phe-tyr) metabolism results in incomplete breakdown of various metabolite substrates in this pathway. Increased biofluid concentration and tissue accumulation of the phe-tyr pathway metabolite homogentisic acid (HGA) is central to pathophysiology in the inherited disorder alkaptonuria (AKU). Accumulation of metabolites upstream of HGA, including tyrosine, occurs in patients on nitisinone, a licenced drug for AKU and hereditary tyrosinaemia type 1, which inhibits the enzyme responsible for HGA production. The aim of this study was to investigate the phe-tyr metabolite content of key biofluids and tissues in AKU mice on and off nitisinone to gain new insights into the biodistribution of metabolites in these altered metabolic states. The data show for the first time that HGA is present in bile in AKU (mean [±SD] = 1003[±410] µmol/L; nitisinone-treated AKU mean [±SD] = 45[±23] µmol/L). Biliary tyrosine, 3(4-hydroxyphenyl)pyruvic acid (HPPA) and 3(4-hydroxyphenyl)lactic acid (HPLA) are also increased on nitisinone. Urine was confirmed as the dominant elimination route of HGA in untreated AKU, but with indication of biliary excretion. These data provide new insights into pathways of phe-tyr metabolite biodistribution and metabolism, showing for the first time that hepatobiliary excretion contributes to the total pool of metabolites in this pathway. Our data suggest that biliary elimination of organic acids and other metabolites may play an underappreciated role in disorders of metabolism. We propose that our finding of approximately 3.8 times greater urinary HGA excretion in AKU mice compared with patients is one reason for the lack of extensive tissue ochronosis in the AKU mouse model.

Determining concentric and eccentric force-velocity profiles during squatting.

PURPOSE: The force-velocity relationship of muscular contraction has been extensively studied. However, previous research has focussed either on isolated muscle or single-joint movements, whereas human movement consists of multi-joint movements (e.g. squatting). Therefore, the purpose of this study was to investigate the force-velocity relationship of isovelocity squatting. METHODS: Fifteen male participants (24 ± 2 years, 79.8 ± 9.1 kg, 177.5 ± 6 cm) performed isovelocity squats on a novel motorised isovelocity device (Kineo Training System) at three concentric (0.25, 0.5, and 0.75 m s-1) and three eccentric velocities (- 0.25, - 0.5, and - 0.75 m s-1). Peak vertical ground reaction forces, that occurred during the isovelocity phase, were collected using dual force plates (2000 Hz) (Kistler, Switzerland). RESULTS: The group mean squat force-velocity profile conformed to the typical in vivo profile, with peak vertical ground reaction forces during eccentric squatting being 9.5 ± 19% greater than isometric (P = 0.037), and occurring between - 0.5 and - 0.75 m s-1. However, large inter-participant variability was identified (0.84-1.62 × isometric force), with some participants being unable to produce eccentric forces greater than isometric. Sub-group analyses could not identify differences between individuals who could/could not produce eccentric forces above isometric, although those who could not tended to be taller. CONCLUSIONS: These finding suggest that variability exists between participants in the ability to generate maximum eccentric forces during squatting, and the magnitude of eccentric increase above isometric cannot be predicted solely based on a concentric assessment. Therefore, an assessment of eccentric capabilities may be required prior to prescribing eccentric-specific resistance training.

Utility of CD4 count measurement in the era of universal antiretroviral therapy: an analysis of routine laboratory data in Botswana.

OBJECTIVES: National guidelines in Botswana recommend baseline CD4 count measurement and both CD4 and HIV viral load (VL) monitoring post-antiretroviral therapy (ART) initiation. We evaluated the utility of CD4 count measurement in Botswana in the era of universal ART. METHODS: CD4 and VL data were analysed for HIV-infected adults undergoing CD4 count measurement in 2015-2017 at the Botswana Harvard HIV-Reference Laboratory. We determined (1) the proportion of individuals with advanced HIV disease (CD4 count < 200 cells/µL) at initial CD4 assessment, (2) the proportion with an initial CD4 count ≥ 200 cells/µL experiencing a subsequent decline in CD4 count to < 200 cells/µL, and (3) the proportion of these immunologically failing individuals who had virological failure. Logistic regression modelling examined factors associated with advanced HIV disease. CD4 count trajectories were assessed using locally weighted scatterplot smoothing (LOWESS) regression. RESULTS: Twenty-five per cent (3571/14 423) of individuals with an initial CD4 assessment during the study period had advanced HIV disease at baseline. Older age [≥ 35 years; adjusted odds ratio (aOR) 1.9; 95% confidence interval (CI) 1.8-2.1] and male sex were associated with advanced HIV disease. Fifty per cent (7163/14 423) of individuals had at least two CD4 counts during the study period. Of those with an initial CD4 count ≥ 200 cells/µL, 4% (180/5061) experienced a decline in CD4 count to < 200 cells/µL; the majority of CD4 count declines were in virologically suppressed individuals and transient. CONCLUSIONS: One-quarter of HIV-positive individuals in Botswana still present with advanced HIV disease, highlighting the importance of baseline CD4 count measurement to identify this at-risk population. Few with a baseline CD4 count ≥ 200 cells/µL experienced a drop below 200 cells/µL, suggesting limited utility for ongoing CD4 monitoring.

The Microalbuminuria Education Medication and Optimisation (MEMO) study: 4 years follow-up of multifactorial intervention in high-risk individuals with type 2 diabetes.

AIMS: The Microalbuminuria Education Medication and Optimisation (MEMO) study, revealed improved cardiovascular risk and glycaemic control with 18 months of intensive multifactorial intervention in high-risk people with type 2 diabetes, without any increase in severe hypoglycaemia. Our aim was to assess longer-term outcomes at 4-year follow-up in these participants. METHODS: Some 189 individuals with type 2 diabetes and microalbuminuria were recruited from a multi-ethnic population in Leicestershire, UK. The intervention group (n = 95) received multifactorial intervention with self-management education, and the control group (n = 94) received usual care. The primary outcome was change in HbA1c , and secondary outcomes were blood pressure (BP), cholesterol, microalbuminuria, estimated GFR, cardiovascular risk scores and major adverse cardiovascular events. RESULTS: Some 130 participants (68.7%), mean (sd) age 60.8 (10.4) years, duration of diabetes 11.5 (9.7) years, completed 4 years of follow-up. Mean change [95% confidence intervals (CI)] in HbA1c over 4 years was greater with intensive intervention compared with control (-3 mmol/mol, 95% CI -4.95,-1.11; -0.4%, 95% CI -0.67,-0.15; P = 0.002). Significant improvements over the 4 years were also seen in systolic BP (-7.3 mmHg, 95% CI -11.1, -3.5; P < 0.001), diastolic BP (-2.9 mmHg, 95% CI -5.4, -0.3; P = 0.026), cholesterol (-0.3 mmol/l, 95% CI -0.52,-0.12; P = 0.002), and 10-year coronary heart disease (-5.3, 95% CI -8.2,-2.3; P < 0.001) and stroke risk (-4.4, 95% CI -7.5, -1.3; P < 0.001). CONCLUSION: Multifactorial intervention with structured diabetes self-management education compared with usual diabetes care has benefits for cardio-metabolic risk factor profile. There was no increase in severe hypoglycaemia and cardiovascular mortality despite intensive glycaemic control, although the study was not powered to assess these outcomes.

Nitisinone arrests ochronosis and decreases rate of progression of Alkaptonuria: Evaluation of the effect of nitisinone in the United Kingdom National Alkaptonuria Centre.

QUESTION: Does Nitisinone prevent the clinical progression of the Alkaptonuria? FINDINGS: In this observational study on 39 patients, 2 mg of daily nitisinone inhibited ochronosis and significantly slowed the progression of AKU over a three-year period. MEANING: Nitisinone is a beneficial therapy in Alkaptonuria. BACKGROUND: Nitisinone decreases homogentisic acid (HGA), but has not been shown to modify progression of Alkaptonuria (AKU). METHODS: Thirty-nine AKU patients attended the National AKU Centre (NAC) in Liverpool for assessments and treatment. Nitisinone was commenced at V1 or baseline. Thirty nine, 34 and 22 AKU patients completed 1, 2 and 3 years of monitoring respectively (V2, V3 and V4) in the VAR group. Seventeen patients also attended a pre-baseline visit (V0) in the VAR group. Within the 39 patients, a subgroup of the same ten patients attended V0, V1, V2, V3 and V4 visits constituting the SAME Group. Severity of AKU was assessed by calculation of the AKU Severity Score Index (AKUSSI) allowing comparison between the pre-nitisinone and the nitisinone treatment phases. RESULTS: The ALL (sum of clinical, joint and spine AKUSSI features) AKUSSI rate of change of scores/patient/month, in the SAME group, was significantly lower at two (0.32 ±â€¯0.19) and three (0.15 ±â€¯0.13) years post-nitisinone when compared to pre-nitisinone (0.65 ±â€¯0.15) (p < .01 for both comparisons). Similarly, the ALL AKUSSI rate of change of scores/patient/month, in the VAR group, was significantly lower at one (0.16 ±â€¯0.08) and three (0.19 ±â€¯0.06) years post-nitisinone when compared to pre-nitisinone (0.59 ±â€¯0.13) (p < .01 for both comparisons). Combined ear and ocular ochronosis rate of change of scores/patient/month was significantly lower at one, two and three year's post-nitisinone in both VAR and SAME groups compared with pre-nitisinone (p < .05). CONCLUSION: This is the first indication that a 2 mg dose of nitisinone slows down the clinical progression of AKU. Combined ocular and ear ochronosis progression was arrested by nitisinone.

Evidence for contrasting roles for prolactin in eusocial naked mole-rats, Heterocephalus glaber and Damaraland mole-rats, Fukomys damarensis.

Elevated prolactin (PRL) has been associated with the expression of social and cooperative behaviours in a number of vertebrate species, as well as suppression of reproduction. As social mole-rats exhibit both of these traits, PRL is a prime candidate in mediating their social phenotype. While naked and Damaraland mole-rats (NMRs and DMRs) have evolved eusociality independently within their family, both species exhibit an extreme skew in lifetime reproductive success, with breeding restricted to a single female and one or two males. Non-breeding NMRs of both sexes are physiologically inhibited from reproducing, while in DMRs only the non-breeding females are physiologically suppressed. Newly emerging work has implicated the dopamine system and PRL as a component in socially induced reproductive suppression and eusociality in NMR, but the DMR remains unstudied in this context. To investigate evolutionary convergence in the role of PRL in shaping African mole-rat eusociality, we determined plasma PRL concentrations in breeders and non-breeders of both sexes, comparing DMRs with NMRs. Among samples from non-breeding NMRs 80% had detectable plasma PRL concentrations. As a benchmark, these often (37%) exceeding those considered clinically hyperprolactinaemic (25 ng ml-1) in humans: mean ± s.e.m.: 34.81 ± 5.87 ngml-1; range 0.00-330.30 ng ml-1 Conversely, 85% of non-breeding DMR samples had undetectable values and none had concentrations above 25 ng ml-1: 0.71 ± 0.38 ng ml-1; 0.00-23.87 ngml-1 Breeders in both species had the expected variance in plasma PRL concentrations as part of normal reproductive function, with lactating queens having significantly higher values. These results suggest that while elevated PRL in non-breeders is implicated in NMR eusociality, this may not be the case in DMRs, and suggests a lack of evolutionary convergence in the proximate control of the social phenotype in these mole-rats.

Frequency of Desaturation and Association With Hemodynamic Adverse Events During Tracheal Intubations in PICUs.

OBJECTIVES: Oxygen desaturation during tracheal intubation is known to be associated with adverse ICU outcomes in critically ill children. We aimed to determine the occurrence and severity of desaturation during tracheal intubations and the association with adverse hemodynamic tracheal intubation-associated events. DESIGN: Retrospective cohort study as a part of the National Emergency Airway Registry for Children Network's quality improvement project from January 2012 to December 2014. SETTING: International PICUs. PATIENTS: Critically ill children younger than 18 years undergoing primary tracheal intubations in the ICUs. INTERVENTIONS: tracheal intubation processes of care and outcomes were prospectively collected using standardized operational definitions. We defined moderate desaturation as oxygen saturation less than 80% and severe desaturation as oxygen saturation less than 70% during tracheal intubation procedures in children with initial oxygen saturation greater than 90% after preoxygenation. Adverse hemodynamic tracheal intubation-associated event was defined as cardiac arrests, hypo or hypertension requiring intervention, and dysrhythmia. MEASUREMENTS AND MAIN RESULTS: A total of 5,498 primary tracheal intubations from 31 ICUs were reported. Moderate desaturation was observed in 19.3% associated with adverse hemodynamic tracheal intubation-associated events (9.8% among children with moderate desaturation vs 4.4% without desaturation; p < 0.001). Severe desaturation was observed in 12.9% of tracheal intubations, also significantly associated with hemodynamic tracheal intubation-associated events. After adjusting for patient, provider, and practice factors, the occurrence of moderate desaturation was independently associated with hemodynamic tracheal intubation-associated events: adjusted odds ratio 1.83 (95% CI, 1.34-2.51; p < 0.001). The occurrence of severe desaturation was also independently associated with hemodynamic tracheal intubation-associated events: adjusted odds ratio 2.16 (95% CI, 1.54-3.04; p < 0.001). Number of tracheal intubation attempts was also significantly associated with the frequency of moderate and severe desaturations (p < 0.001). CONCLUSIONS: In this large tracheal intubation quality improvement database, we found moderate and severe desaturation are reported among 19% and 13% of all tracheal intubation encounters. Moderate and severe desaturations were independently associated with the occurrence of adverse hemodynamic events. Future quality improvement interventions may focus to reduce desaturation events.

Bidirectional band-selective magnetization transfer along the protein backbone doubles the information content of solid-state NMR correlation experiments.

Resonance assignment is the first stage towards solving the structure of a protein. This is normally achieved by the employment of separate inter and intra residue experiments. By utilising the mixed rotation and rotary recoupling (MIRROR) condition it is possible to double the information content through the efficient bidirectional transfer of magnetization from the CO to its adjacent Cα and the Cα of the subsequent amino acid. We have incorporated this into a 3D experiment, a 3D-MIRROR-NCOCA, where correlations present in the 3D spectrum permit the sequential assignment of the protein backbone from a single experiment as we have demonstrated on a microcrystalline preparation of GB3. Furthermore, the low-power requirements of the MIRROR recoupling sequence facilitate the development of a low-power 3D-NCOCA experiment. This has enabled us to realise significant reductions in acquisition times, allowing the acquisition of a single 3D-NCOCA spectrum suitable for a full backbone resonance assignment of GB3 in less than 24 h.

Promoters and Barriers to Implementation of Tracheal Intubation Airway Safety Bundle: A Mixed-Method Analysis.

OBJECTIVES: To describe promoters and barriers to implementation of an airway safety quality improvement bundle from the perspective of interdisciplinary frontline clinicians and ICU quality improvement leaders. DESIGN: Mixed methods. SETTING: Thirteen PICUs of the National Emergency Airway Registry for Children network. INTERVENTION: Remote or on-site focus groups with interdisciplinary ICU staff. Two semistructured interviews with ICU quality improvement leaders with quantitative and qualitative data-based feedbacks. MEASUREMENTS AND MAIN RESULTS: Bundle implementation success (compliance) was defined as greater than or equal to 80% use for tracheal intubations for 3 consecutive months. ICUs were classified as early or late adopters. Focus group discussions concentrated on safety concerns and promoters and barriers to bundle implementation. Initial semistructured quality improvement leader interviews assessed implementation tactics and provided recommendations. Follow-up interviews assessed degree of acceptance and changes made after initial interview. Transcripts were thematically analyzed and contrasted by early versus late adopters. Median duration to achieve success was 502 days (interquartile range, 182-781). Five sites were early (median, 153 d; interquartile range, 146-267) and eight sites were late adopters (median, 783 d; interquartile range, 773-845). Focus groups identified common "promoter" themes-interdisciplinary approach, influential champions, and quality improvement bundle customization-and "barrier" themes-time constraints, competing paperwork and quality improvement activities, and poor engagement. Semistructured interviews with quality improvement leaders identified effective and ineffective tactics implemented by early and late adopters. Effective tactics included interdisciplinary quality improvement team involvement (early adopter: 5/5, 100% vs late adopter: 3/8, 38%; p = 0.08); ineffective tactics included physician-only rollouts, lack of interdisciplinary education, lack of data feedback to frontline clinicians, and misconception of bundle as research instead of quality improvement intervention. CONCLUSIONS: Implementation of an airway safety quality improvement bundle with high compliance takes a long time across diverse ICUs. Both early and late adopters identified similar promoter and barrier themes. Early adopter sites customized the quality improvement bundle and had an interdisciplinary quality improvement team approach.

New insulins and newer insulin regimens: a review of their role in improving glycaemic control in patients with diabetes.

The legacy effect of early good glycaemic control in people with diabetes shows it is associated with reduction of microvascular and macrovascular complications. Insulin therapy is essential and lifesaving in individuals with type 1 diabetes and beneficial for those with type 2 diabetes who fail to achieve optimal glycaemic targets with other classes of glucose-lowering therapies. Since the introduction of insulin analogues, insulin management has changed. This follow-up review attempts to update our earlier publication from 2009 and discusses the role of new insulin analogues and newer insulin regimens. Recognising the advent of new quality and economic initiatives both in the UK and worldwide, this paper reviews current insulin prescribing and the pros and cons of prescribing analogues in comparison to the human insulins that are now gaining more acceptance in everyday clinical practice.

A refined QSAR model for prediction of chemical asthma hazard.

BACKGROUND: A previously developed quantitative structure-activity relationship (QSAR) model has been extern ally validated as a good predictor of chemical asthma hazard (sensitivity: 79-86%, specificity: 93-99%). AIMS: To develop and validate a second version of this model. METHODS: Learning dataset asthmagenic chemicals with molecular weight (MW) <1 kDa were identified from reports published in the peer-reviewed literature before the end of 2012. Control chemicals for which no reported case(s) of occupational asthma had been identified were selected at random from UK and US occupational exposure limit tables. MW banding was used in an attempt to categorically match the control group for MW distribution of the asthmagens. About 10% of chemicals in each MW category were excluded for use as an external validation set. An independent researcher utilized a logistic regression approach to compare the molecular descriptors present in asthmagens and controls. The resulting equation generated a hazard index (HI), with a value between zero and one, as an estimate of the probability that the chemical had asthmagenic potential. The HI was determined for each compound in the external validation set. RESULTS: The model development sets comprised 99 chemical asthmagens and 204 controls. The external validation showed that using a cut-point HI of 0.39, 9/10 asthmagenic (sensitivity: 90%) and 23/24 non-asthmagenic (specificity: 96%) compounds were correctly predicted. The new QSAR model showed a better receiver operating characteristic plot than the original. CONCLUSIONS: QSAR refinement by iteration has resulted in an improved model for the prediction of chemical asthma hazard.

On fragmenting, densely mineralised acellular protrusions into articular cartilage and their possible role in osteoarthritis.

High density mineralised protrusions (HDMP) from the tidemark mineralising front into hyaline articular cartilage (HAC) were first described in Thoroughbred racehorse fetlock joints and later in Icelandic horse hock joints. We now report them in human material. Whole femoral heads removed at operation for joint replacement or from dissection room cadavers were imaged using magnetic resonance imaging (MRI) dual echo steady state at 0.23 mm resolution, then 26-µm resolution high contrast X-ray microtomography, sectioned and embedded in polymethylmethacrylate, blocks cut and polished and re-imaged with 6-µm resolution X-ray microtomography. Tissue mineralisation density was imaged using backscattered electron SEM (BSE SEM) at 20 kV with uncoated samples. HAC histology was studied by BSE SEM after staining block faces with ammonium triiodide solution. HDMP arise via the extrusion of an unknown mineralisable matrix into clefts in HAC, a process of acellular dystrophic calcification. Their formation may be an extension of a crack self-healing mechanism found in bone and articular calcified cartilage. Mineral concentration exceeds that of articular calcified cartilage and is not uniform. It is probable that they have not been reported previously because they are removed by decalcification with standard protocols. Mineral phase morphology frequently shows the agglomeration of many fine particles into larger concretions. HDMP are surrounded by HAC, are brittle, and show fault lines within them. Dense fragments found within damaged HAC could make a significant contribution to joint destruction. At least larger HDMP can be detected with the best MRI imaging ex vivo.

Site-level variance for adverse tracheal intubation-associated events across 15 North American PICUs: a report from the national emergency airway registry for children*.

OBJECTIVE: Tracheal intubation in PICUs is associated with adverse tracheal intubation-associated events. Patient, provider, and practice factors have been associated with tracheal intubation-associated events; however, site-level variance and the association of site-level characteristics on tracheal intubation-associated event outcomes are unknown. We hypothesize that site-level variance exists in the prevalence of tracheal intubation-associated events and that site characteristics may affect outcomes. DESIGN: Prospective observational cohort study. SETTING: Fifteen PICUs in North America. SUBJECTS: Critically ill pediatric patients requiring tracheal intubation. INTERVENTIONS: None. MEASUREMENT AND MAIN RESULTS: Tracheal intubation quality improvement data were collected in 15 PICUs from July 2010 to December 2011 using a National Emergency Airway Registry for Children with robust site-specific compliance. Tracheal intubation-associated events and severe tracheal intubation-associated events were explicitly defined a priori. We analyzed the association of site-level variance with tracheal intubation-associated events using univariate analysis and adjusted for previously identified patient- and provider-level risk factors. Analysis of 1,720 consecutive intubations revealed an overall prevalence of 20% tracheal intubation-associated events and 6.5% severe tracheal intubation-associated events, with considerable site variability ranging from 0% to 44% tracheal intubation-associated events and from 0% to 20% severe tracheal intubation-associated events. Larger PICU size (> 26 beds) was associated with fewer tracheal intubation-associated events (18% vs 23%, p = 0.006), but the presence of a fellowship program was not (20% vs 18%, p = 0.58). After adjusting for patient and provider characteristics, both PICU size and fellowship presence were not associated with tracheal intubation-associated events (p = 0.44 and p = 0.18, respectively). Presence of mixed ICU with cardiac surgery was independently associated with a higher prevalence of tracheal intubation-associated events (25% vs 15%; p < 0.001; adjusted odds ratio, 1.81; 95% CI, 1.29-2.53; p = 0.01). Substantial site-level variance was observed in medication use, which was not explained by patient characteristic differences. CONCLUSIONS: Substantial site-level variance exists in tracheal intubation practice, tracheal intubation-associated events, and severe tracheal intubation-associated events. Neither PICU size nor fellowship training program explained site-level variance. Interventions to reduce tracheal intubation-associated event prevalence and severity will likely need to be contextualized to variability in individual ICUs patients, providers, and practice.

Vegetative fragment production as a means of propagule dispersal for tropical seagrass meadows.

BACKGROUND AND AIMS: Long distance dispersal (LDD) contributes to the replenishment and recovery of tropical seagrass habitats exposed to disturbance, such as cyclones and infrastructure development. However, our current knowledge regarding the physical attributes of seagrass fragments that influence LDD predominantly stems from temperate species and regions. The goal of this paper is to measure seagrass fragment density and viability in two tropical species, assessing various factors influencing their distribution. METHODS: We measured the density and viability of floating seagrass fragments for two tropical seagrass species (Zostera muelleri and Halodule uninervis) in two coastal seagrass meadows in the central Great Barrier Reef World Heritage Area, Australia. We assessed the effect of wind speed, wind direction, seagrass growing/senescent season, seagrass meadow density, meadow location and dugong foraging intensity on fragment density. We also measured seagrass fragment structure and fragment viability; i.e., potential to establish into a new plant. KEY RESULTS: We found that seagrass meadow density, season, wind direction and wind speed influenced total fragment density, while season and wind speed influenced the density of viable fragments. Dugong foraging intensity did not influence fragment density. Our results indicate that wave action from winds combined with high seagrass meadow density increases seagrass fragment creation, and that more fragments are produced during the growing than the senescent season. Seagrass fragments classified as viable for Z. muelleri and H. uninervis had significantly more shoots and leaves than non-viable fragments. We collected 0.63 (±0.08 SE) floating viable fragments 100 m-2 in the growing season, and 0.13 (±0.03 SE) viable fragments 100 m-2 in the senescent season. Over a third (38%) of all fragments collected were viable. CONCLUSION: There is likely to be a large number of viable seagrass fragments available for long distance dispersal. This study's outputs can inform dispersal and connectivity models that are used to direct seagrass ecosystem management and conservation strategies.

Ochronosis in a murine model of alkaptonuria is synonymous to that in the human condition.

OBJECTIVE: Alkaptonuria (AKU) is a rare genetic disease which results in severe early onset osteoarthropathy. It has recently been shown that the subchondral interface is of key significance in disease pathogenesis. Human surgical tissues are often beyond this initial stage and there is no published murine model of pathogenesis, to study the natural history of the disease. The murine genotype exists but it has been reported not to demonstrate ochronotic osteoarthropathy consistent with the human disease. Recent anecdotal evidence of macroscopic renal ochronosis in a mouse model of tyrosinaemia led us to perform histological analysis of tissues of these mice that are known to be affected in human AKU. DESIGN: The homogentisate 1,2-dioxygenase Hgd(+/)(-)Fah(-)(/)(-) mouse can model either hereditary tyrosinaemia type I (HT1) or AKU depending on selection conditions. Mice having undergone Hgd reversion were sacrificed at various time points, and their tissues taken for histological analysis. Sections were stained with haematoxylin eosin (H&E) and Schmorl's reagent. RESULTS: Early time point observations at 8 months showed no sign of macroscopic ochronosis of tissues. Macroscopic examination at 13 months revealed ochronosis of the kidneys. Microscopic analysis of the kidneys revealed large pigmented nodules displaying distinct ochre colouration. Close microscopic examination of the distal femur and proximal fibula at the subchondral junctions revealed the presence of numerous pigmented chondrocytes. CONCLUSIONS: Here we present the first data showing ochronosis of tissues in a murine model of AKU. These preliminary histological observations provide a stimulus for further studies into the natural history of the disease to provide a greater understanding of this class of arthropathy.

Identification of trabecular excrescences, novel microanatomical structures, present in bone in osteoarthropathies.

It is widely held that bone architecture is finely regulated in accordance with homeostatic requirements. Aberrant remodelling (hyperdensification and/or cyst formation in the immediately subchondral region) has previously been described in bone underlying cartilage in arthropathies. The present study examined the trabecular architecture of samples of bone, initially in the severe osteoarthropathy of alkaptonuria, but subsequently in osteoarthritis using a combination of light microscopy, 3D scanning electron microscopy and quantitative backscattered electron scanning electron microscopy. We report an extraordinary and previously unrecognised bone phenotype in both disorders, including novel microanatomical structures. The underlying subchondral trabecular bone contained idiosyncratic architecture. Trabecular surfaces had numerous outgrowths that we have termed "trabecular excrescences", of which three distinct types were recognised. The first type arose from incomplete resorption of branching secondary trabeculae arising from the deposition of immature (woven) bone in prior marrow space. These were characterised by very deeply scalloped surfaces and rugged edges. The second type had arisen in a similar way but been smoothed over by new bone deposition. The third type, which resembled coarse stucco, probably arises from resting surfaces that had been focally reactivated. These were poorly integrated with the prior trabecular wall. We propose that these distinctive microanatomical structures are indicative of abnormal osteoclast/osteoblast modelling in osteoarthropathies, possibly secondary to altered mechanical loading or other aberrant signalling. Identification of the mechanisms underlying the formation of trabecular excrescences will contribute to a better understanding of the role of aberrant bone remodelling in arthropathies and development of new therapeutic strategies.

The role of calcified cartilage and subchondral bone in the initiation and progression of ochronotic arthropathy in alkaptonuria.

OBJECTIVE: Alkaptonuria is a genetic disorder of tyrosine metabolism, resulting in elevated circulating concentrations of homogentisic acid. Homogentisic acid is deposited as a polymer, termed ochronotic pigment, in collagenous tissues, especially cartilages of weight-bearing joints, leading to a severe osteoarthropathy. We undertook this study to investigate the initiation and progression of ochronosis from the earliest detection of pigment through complete joint failure. METHODS: Nine joint samples with varying severities of ochronosis were obtained from alkaptonuria patients undergoing surgery and compared to joint samples obtained from osteoarthritis (OA) patients. Samples were analyzed by light and fluorescence microscopy, 3-dimensional scanning electron microscopy (SEM), and the quantitative backscattered electron mode of SEM. Cartilage samples were mechanically tested by compression to determine Young's modulus of pigmented, nonpigmented, and OA cartilage samples. RESULTS: In alkaptonuria samples with the least advanced ochronosis, pigment was observed intracellularly and in the territorial matrix of individual chondrocytes at the boundary of the subchondral bone and calcified cartilage. In more advanced ochronosis, pigmentation was widespread throughout the hyaline cartilage in either granular composition or as blanket pigmentation in which there is complete and homogenous pigmentation of cartilage matrix. Once hyaline cartilage was extensively pigmented, there was aggressive osteoclastic resorption of the subchondral plate. Pigmented cartilage became impacted on less highly mineralized trabeculae and embedded in the marrow space. Pigmented cartilage samples were much stiffer than nonpigmented or OA cartilage as revealed by a significant difference in Young's modulus. CONCLUSION: Using alkaptonuria cartilage specimens with a wide spectrum of pigmentation, we have characterized the progression of ochronosis. Intact cartilage appears to be resistant to pigmentation but becomes susceptible following focal changes in calcified cartilage. Ochronosis spreads throughout the cartilage, altering the mechanical properties. In advanced ochronosis, there is aggressive resorption of the underlying calcified cartilage leading to an extraordinary phenotype in which there is complete loss of the subchondral plate. These findings should contribute to better understanding of cartilage-subchondral interactions in arthropathies.

Evaluation of a new analyser for rapid measurement of blood propofol concentration during cardiac surgery.

We report laboratory and clinical evaluations of a blood propofol concentration analyser. Laboratory experiments used volunteer blood spiked with known propofol concentrations over the clinically relevant concentrations from 0.5 to 16 µg.ml(-1) to assess linearity and the influence of haematocrit and concurrent drug administration. Analyser concentrations demonstrated excellent linearity (R(2) = 0.999). Blood spiked with commonly used drugs showed no significant variation compared to unspiked controls. Propofol measurements were largely independent of haemoglobin concentration. A 6% decay in propofol concentration was observed at the highest prepared concentration. Clinical performance of the analyser was assessed using 80 arterial blood samples from 72 patients receiving propofol infusions during cardiac surgery. Samples were processed using the propofol analyser, and high performance liquid chromatography (HPLC) used as a gold-standard comparator. These data demonstrated excellent agreement between the propofol analyser and HPLC with a bias of 0.13 µg.ml(-1) and precision of -0.16 to 0.42 µg.ml(-1).