Neural responses to natural and enhanced speech edges in children with and without dyslexia

Sensory-neural studies indicate that children with developmental dyslexia show impairments in processing acoustic speech envelope information. Prior studies suggest that this arises in part from reduced sensory sensitivity to amplitude rise times (ARTs or speech "edges") in the envelope, accompanied by less accurate neural encoding of low-frequency envelope information. Accordingly, enhancing these characteristics of the speech envelope may enhance neural speech processing in children with dyslexia. Here we applied an envelope modulation enhancement (EME) algorithm to a 10-min story read in child-directed speech (CDS), enhancing ARTs and also enhancing low-frequency envelope information. We compared neural speech processing (as measured using MEG) for the EME story with the same story read in natural CDS for 9-year-old children with and without dyslexia. The EME story affected neural processing in the power domain for children with dyslexia, particularly in the delta band (0.5-4 Hz) in the superior temporal gyrus. This may suggest that prolonged experience with EME speech could ameliorate some of the impairments shown in natural speech processing by children with dyslexia.

Respiratory virus infections in decedents in a large, urban medical examiner's office

OBJECTIVE

Most respiratory virus surveillance relies on medically attended respiratory illness, but an understanding of the true patterns of infection independent of care-seeking behaviour would enhance clinical and public health responses to respiratory virus outbreaks. We evaluated the potential of decedent surveillance by estimating the burden of respiratory virus infection in decedents in a large, urban medical examiner's office.

STUDY DESIGN

Observational.

METHODS

In 2020-2022, we tested nasopharyngeal swabs from 4121 decedents in Detroit, Michigan for 15 respiratory viruses, including SARS-CoV-2, respiratory syncytial virus, and influenza virus A and B. We analysed infection prevalence over time and by age, sex, race/ethnicity, and manner of death.

RESULTS

Of 4113 valid tests, 30.2% were positive for at least one virus, and 6.1% were positive for multiple viruses. All viruses were detected except for influenza A/H1N1 and influenza B. The most prevalent viruses were SARS-CoV-2 (15.7%), rhinovirus (11.2%), and adenovirus (4.9%), which were detected in all months. Most viruses exhibited decreasing prevalence with age, higher prevalence among Black and Hispanic than among White decedents and lower prevalence among deaths from natural causes; SARS-CoV-2 was a notable exception to the patterns by age and manner of death, instead reflecting community trends in catchment counties.

CONCLUSIONS

There was high prevalence and diversity of respiratory viruses in decedents entering a large, urban medical examiner's office. Decedent surveillance could offer a clearer picture of the true underlying burden of infection, motivating public health priorities for intervention and vaccine development, and augmenting data for real-time response to respiratory virus outbreaks.

Behavioral and physiological responses to an inspired-air supplemental cooling system for dairy cows in free-stall housing

During heat stress, dairy cows spend less time lying down to dissipate heat. Heat stress abatement strategies generally target cows outside of their resting areas. However, cooling cows while in their stalls could help alleviate heat stress without compromising lying behavior. The objective of this study was to assess the effects of an inspired-air supplemental cooling system (SCS) on respiration rate, rectal temperatures, lying behavior, rumination time, and milk production (energy-corrected milk, ECM) of lactating dairy cows. A free-stall pen was retrofitted with custom stall partitions to deliver cooled air and mist. The pen, including the stall platform, was divided into two separate sides. Twenty-eight lactating Holstein cows were randomly sorted into two groups, each housed on one side of the experimental pen. Cows experienced four treatments (control, CTRL; cooled air, AIR; mist, MIST; cooled air and mist, AIR + MIST) in a four-treatment, four-period, two-sequence crossover design, with each period lasting seven days. Cooled air was provided continuously, and mist was cycled 3 min on, 12 min off from 0900 to 2100 h. Respiration rates were observed hourly between 0900 and 1500 h, and only measurements recorded while cows were lying down were used in the analysis. Rectal temperatures of 16 focal cows were recorded at 1545 h once per day. Lying behavior and rumination were recorded continuously, and milk yields recorded twice daily were used to calculate ECM. Throughout the experimental period, the average temperature-humidity index was 66.4 ± 6.07. During the MIST treatment, the respiration rate was lower than the CTRL (45.7 vs 49.0 ± 1.92 breaths/min) and AIR (45.7 vs 48.7 ± 1.92 breaths/min). CTRL and AIR did not differ (48.7 vs 49.0 ± 1.92 breaths/min), and MIST and AIR + MIST (45.7 vs 47.1 ± 1.92 breaths/min) did not differ. All other variables were not significantly different between treatments. In conclusion, the SCS appeared to be tolerated by cows and shows the potential to assist in alleviating heat stress. The cooling capacity needs to be evaluated under more extreme environmental conditions causing heat stress than those experienced during this study. Further testing is required to determine the cooled air temperature specifications and mist delivery frequency.

Integrated multimodal cell atlas of Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia in older adults. Neuropathological and imaging studies have demonstrated a progressive and stereotyped accumulation of protein aggregates, but the underlying molecular and cellular mechanisms driving AD progression and vulnerable cell populations affected by disease remain coarsely understood. The current study harnesses single cell and spatial genomics tools and knowledge from the BRAIN Initiative Cell Census Network to understand the impact of disease progression on middle temporal gyrus cell types. We used image-based quantitative neuropathology to place 84 donors spanning the spectrum of AD pathology along a continuous disease pseudoprogression score and multiomic technologies to profile single nuclei from each donor, mapping their transcriptomes, epigenomes, and spatial coordinates to a common cell type reference with unprecedented resolution. Temporal analysis of cell-type proportions indicated an early reduction of Somatostatin-expressing neuronal subtypes and a late decrease of supragranular intratelencephalic-projecting excitatory and Parvalbumin-expressing neurons, with increases in disease-associated microglial and astrocytic states. We found complex gene expression differences, ranging from global to cell type-specific effects. These effects showed different temporal patterns indicating diverse cellular perturbations as a function of disease progression. A subset of donors showed a particularly severe cellular and molecular phenotype, which correlated with steeper cognitive decline. We have created a freely available public resource to explore these data and to accelerate progress in AD research at SEA-AD.org.

Protocol for the Systematic Fixation, Circuit-Based Sampling, and Qualitative and Quantitative Neuropathological Analysis of Human Brain Tissue

Human brain tissue has long been a critical resource for neuroanatomy and neuropathology, but with the advent of advanced imaging and molecular sequencing techniques, it has become possible to use human brain tissue to study, in great detail, the structural, molecular, and even functional underpinnings of human brain disease. In the century following the first description of Alzheimer's disease (AD), numerous technological advances applied to human tissue have enabled novel diagnostic approaches using diverse physical and molecular biomarkers, and many drug therapies have been tested in clinical trials (Schachter and Davis, Dialogues Clin Neurosci 2:91-100, 2000). The methods for brain procurement and tissue stabilization have remained somewhat consistently focused on formalin fixation and freezing. Although these methods have enabled research protocols of multiple modalities, new, more advanced technologies demand improved methodologies for the procurement, characterization, stabilization, and preparation of both normal and diseased human brain tissues. Here, we describe our current protocols for the procurement and characterization of fixed brain tissue, to enable systematic and precisely targeted diagnoses, and describe the novel, quantitative molecular, and neuroanatomical studies that broadly expand the use of formalin-fixed, paraffin-embedded (FFPE) tissue that will further our understanding of the mechanisms underlying human neuropathologies.

Development of binaural temporal fine structure sensitivity in children

The highest frequency for which the temporal fine structure (TFS) of a sinewave can be compared across ears varies between listeners with an upper limit of about 1400 Hz for young normal-hearing adults (YNHA). In this study, binaural TFS sensitivity was investigated for 63 typically developing children, aged 5 years, 6 months to 9 years, 4 months using the temporal fine structure-adaptive frequency (TFS-AF) test of Füllgrabe, Harland, Sęk, and Moore [Int. J. Audiol. 56, 926-935 (2017)]. The test assesses the highest frequency at which an interaural phase difference (IPD) of ϕ° can be distinguished from an IPD of 0°. The values of ϕ were 30° and 180°. The starting frequency was 200 Hz. The thresholds for the children were significantly lower (worse) than the thresholds reported by Füllgrabe, Harland, Sęk, and Moore [Int. J. Audiol. 56, 926-935 (2017)] for YNHA. For both values of ϕ, the median age at which children performed above chance level was significantly higher (p < 0.001) than for those who performed at chance. For the subgroup of 40 children who performed above chance for ϕ = 180°, the linear regression analyses showed that the thresholds for ϕ = 180° increased (improved) significantly with increasing age (p < 0.001) with adult-like thresholds predicted to be reached at 10 years, 2 months of age. The implications for spatial release from masking are discussed.

The Delayed Neuropathological Consequences of Traumatic Brain Injury in a Community-Based Sample

The late neuropathological effects of traumatic brain injury have yet to be fully elucidated, particularly with respect to community-based cohorts. To contribute to this critical gap in knowledge, we designed a multimodal neuropathological study, integrating traditional and quantitative approaches to detect pathologic changes in 532 consecutive brain autopsies from participants in the Adult Changes in Thought (ACT) study. Diagnostic evaluation including assessment for chronic traumatic encephalopathy (CTE) and quantitative immunoassay-based methods were deployed to examine levels of pathological (hyperphosphorylated) tau (pTau) and amyloid (A) β in brains from ACT participants with (n = 107) and without (n = 425) history of remote TBI with loss of consciousness (w/LOC). Further neuropathological assessments included immunohistochemistry for α-synuclein and phospho-TDP-43 pathology and astro- (GFAP) and micro- (Iba1) gliosis, mass spectrometry analysis of free radical injury, and gene expression evaluation (RNA sequencing) in a smaller sub-cohort of matched samples (49 cases with TBI and 49 non-exposed matched controls). Out of 532 cases, only 3 (0.6%-none with TBI w/LOC history) showed evidence of the neuropathologic signature of chronic traumatic encephalopathy (CTE). Across the entire cohort, the levels of pTau and Aβ showed expected differences for brain region (higher levels in temporal cortex), neuropathological diagnosis (higher in participants with Alzheimer's disease), and APOE genotype (higher in participants with one or more APOE ε4 allele). However, no differences in PHF-tau or Aβ1-42 were identified by Histelide with respect to the history of TBI w/LOC. In a subset of TBI cases with more carefully matched control samples and more extensive analysis, those with TBI w/LOC history had higher levels of hippocampal pTau but no significant differences in Aβ, α-synuclein, pTDP-43, GFAP, Iba1, or free radical injury. RNA-sequencing also did not reveal significant gene expression associated with any measure of TBI exposure. Combined, these findings suggest long term neuropathological changes associated with TBI w/LOC may be subtle, involve non-traditional pathways of neurotoxicity and neurodegeneration, and/or differ from those in autopsy cohorts specifically selected for neurotrauma exposure.

Why is mock care not a good proxy for predicting hand contamination during patient care?

BACKGROUND

Healthcare worker (HCW) behaviours, such as the sequence of their contacts with surfaces and hand hygiene moments, are important for understanding disease transmission.

AIM

To propose a method for recording sequences of HCW behaviours during mock vs actual procedures, and to evaluate differences for use in infection risk modelling and staff training.

METHODS

Procedures for three types of care were observed under mock and actual settings: intravenous (IV) drip care, observational care and doctors' rounds on a respiratory ward in a university teaching hospital. Contacts and hand hygiene behaviours were recorded in real-time using either a handheld tablet or video cameras.

FINDINGS

Actual patient care demonstrated 70% more surface contacts than mock care. It was also 2.4 min longer than mock care, but equal in terms of patient contacts. On average, doctors' rounds took 7.5 min (2.5 min for mock care), whilst auxiliary nurses took 4.9 min for observational care (2.4 min for mock care). Registered nurses took 3.2 min for mock IV care and 3.8 min for actual IV care; this translated into a 44% increase in contacts. In 51% of actual care episodes and 37% of mock care episodes, hand hygiene was performed before patient contact; in comparison, 15% of staff delivering actual care performed hand hygiene after patient contact on leaving the room vs 22% for mock care. The number of overall touches in the patient room was a modest predictor of hand hygiene. Using a model to predict hand contamination from surface contacts for Staphylococcus aureus, Escherichia coli and norovirus, mock care underestimated micro-organisms on hands by approximately 30%.

Luminex-based quantification of Alzheimer's disease neuropathologic change in formalin-fixed post-mortem human brain tissue

The vast majority of archived research and clinical pathological specimens are stored in the form of formalin fixed, paraffin-embedded (FFPE) tissues, but, unlike fresh frozen tissue samples, highly quantitative measures in FFPE tissues are limited to immunohistochemical and immunofluorescence thresholding image analysis studies, cell counting, and ordinal ranking systems. This poses a significant obstacle for clinical investigations that aim to correlate diagnostic markers of neurodegenerative diseases like Alzheimer's disease (AD) with parameters like age, gender, drug exposures, genotype, disease stage, co-morbidities, or environmental factors. To overcome this limitation, we have developed Luminex-based techniques and protocols for the quantification of amyloid β and hyperphosphorylated Tau in FFPE brain sections. We validated the Luminex assay in FFPE sections from prefrontal cortex, hippocampus, and neostriatum from 30 cases that underwent prior neuropathological diagnostic assessment of AD following the current NIA-AA recommendations for AD: 10 cases diagnosed as not or low, 10 cases as intermediate, and 10 cases as high AD neuropathologic change. Consistent with the neuropathologic assessment, Luminex assay detected high amounts of amyloid beta in the frontal cortex and striatum, and high amounts of hyperphosphorylated Tau in the frontal cortex and hippocampus, of cases with high AD neuropathologic change. This assay can be expanded to detect diverse antigenic targets of interest, as we show here with IBA1 and GFAP. This novel approach supports multiplexed highly quantitative, molecularly specific neuropathology measures to further explore mechanisms of neurodegeneration in AD.

Neuropathological and transcriptomic characteristics of the aged brain

As more people live longer, age-related neurodegenerative diseases are an increasingly important societal health issue. Treatments targeting specific pathologies such as amyloid beta in Alzheimer’s disease (AD) have not led to effective treatments, and there is increasing evidence of a disconnect between traditional pathology and cognitive abilities with advancing age, indicative of individual variation in resilience to pathology. Here, we generated a comprehensive neuropathological, molecular, and transcriptomic characterization of hippocampus and two regions cortex in 107 aged donors (median = 90) from the Adult Changes in Thought (ACT) study as a freely-available resource (http://aging.brain-map.org/). We confirm established associations between AD pathology and dementia, albeit with increased, presumably aging-related variability, and identify sets of co-expressed genes correlated with pathological tau and inflammation markers. Finally, we demonstrate a relationship between dementia and RNA quality, and find common gene signatures, highlighting the importance of properly controlling for RNA quality when studying dementia.

Movement patterns of cheetahs (Acinonyx jubatus) in farmlands in Botswana

Botswana has the second highest population of cheetah (Acinonyx jubatus) with most living outside protected areas. As a result, many cheetahs are found in farming areas which occasionally results in human-wildlife conflict. This study aimed to look at movement patterns of cheetahs in farming environments to determine whether cheetahs have adapted their movements in these human-dominated landscapes. We fitted high-time resolution GPS collars to cheetahs in the Ghanzi farmlands of Botswana. GPS locations were used to calculate home range sizes as well as number and duration of visits to landscape features using a time-based local convex hull method. Cheetahs had medium-sized home ranges compared to previously studied cheetah in similar farming environments. Results showed that cheetahs actively visited scent marking trees and avoided visiting homesteads. A slight preference for visiting game farms over cattle farms was found, but there was no difference in duration of visits between farm types. We conclude that cheetahs selected for areas that are important for their dietary and social needs and prefer to avoid human-occupied areas. Improved knowledge of how cheetahs use farmlands can allow farmers to make informed decisions when developing management practices and can be an important tool for reducing human-wildlife conflict.

How realistic is a racehorse simulator?

Race jockey training is demanding and technical. Increased horse care costs and demands on time have led to greater availability and use of racehorse simulators during training. Little is known about the accuracy of the simulated movement and therefore how effective they are for developing the desired technique. We quantified and compared sacral rotation and displacement vectors for a racehorse simulator and a real galloping horse. A single inertial measurement unit was placed on the sacrum of six horses (horse) during a training gallop along an all-weather seven furlong gallop and on the highest speed setting 'four' on the simulator. Displacements were calculated in all three axes before being cut into cycles and analysed along with roll and pitch. Displacement and rotation amplitudes were extracted and compared for the horse and simulator. Horse sacral movement parameters were more varied than those recorded on the simulator. The real horse exhibited greater dorso-ventral, medio-lateral and roll amplitude but smaller cranio-caudal displacement amplitude and no difference in pitch amplitude. Displacement trajectory of the simulator when viewed laterally from the left side, was anticlockwise, the opposite direction to that of the real horse leaving the regular use of a simulator during jockey training under question. Use of the racehorse simulator is beneficial to develop specific fitness and to enable physical manipulation into the optimal position. Care must be taken to avoid any detrimental effects of training with the opposite movement trajectory to that experienced during a race. The programming of the simulators may benefit from adaptations to maximise their benefits.

The kinematics and kinetics of riding a racehorse: A quantitative comparison of a training simulator and real horses

Movement of a racehorse simulator differs to that of a real horse, but the effects of these differences on jockey technique have not been evaluated. We quantified and compared the kinematics and kinetics of jockeys during gallop riding on a simulator and real horses. Inertial measurement units were attached mid-shaft to the long bones of six jockeys and the sacrum of the horse or simulator. Instrumented stirrups were used to measure force. Data were collected during galloping on a synthetic gallop or while riding a racehorse simulator. Jockey kinematics varied more on a real horse compared to the simulator. Greater than double the peak stirrup force was recorded during gallop on real horses compared to the simulator. On the simulator stirrup forces were symmetrical, whereas on a real horse peak forces were higher on the opposite side to the lead limb. Asymmetric forces and lateral movement of the horse and jockey occurs away from the side of the lead leg, likely a result of horse trunk roll. Jockeys maintained a more upright trunk position on a real horse compared to simulator, with no change in pitch. The feet move in phase with the horse and simulator exhibiting similar magnitude displacements in all directions. In contrast the pelvis was in phase with the horse and simulator in the dorso-ventral and medio-lateral axes while a phase shift of 180° was seen in the cranio-caudal direction indicating an inverted pendulum action of the jockey.

Perception of Filtered Speech by Children with Developmental Dyslexia and Children with Specific Language Impairments

Here we use two filtered speech tasks to investigate children’s processing of slow (<4 Hz) versus faster (∼33 Hz) temporal modulations in speech. We compare groups of children with either developmental dyslexia (Experiment 1) or speech and language impairments (SLIs, Experiment 2) to groups of typically-developing (TD) children age-matched to each disorder group. Ten nursery rhymes were filtered so that their modulation frequencies were either low-pass filtered (<4 Hz) or band-pass filtered (22 – 40 Hz). Recognition of the filtered nursery rhymes was tested in a picture recognition multiple choice paradigm. Children with dyslexia aged 10 years showed equivalent recognition overall to TD controls for both the low-pass and band-pass filtered stimuli, but showed significantly impaired acoustic learning during the experiment from low-pass filtered targets. Children with oral SLIs aged 9 years showed significantly poorer recognition of band pass filtered targets compared to their TD controls, and showed comparable acoustic learning effects to TD children during the experiment. The SLI samples were also divided into children with and without phonological difficulties. The children with both SLI and phonological difficulties were impaired in recognizing both kinds of filtered speech. These data are suggestive of impaired temporal sampling of the speech signal at different modulation rates by children with different kinds of developmental language disorder. Both SLI and dyslexic samples showed impaired discrimination of amplitude rise times. Implications of these findings for a temporal sampling framework for understanding developmental language disorders are discussed.

Clinical utility of neuronal cells directly converted from fibroblasts of patients for neuropsychiatric disorders: studies of lysosomal storage diseases and channelopathy

Methodologies for generating functional neuronal cells directly from human fibroblasts [induced neuronal (iN) cells] have been recently developed, but the research so far has only focused on technical refinements or recapitulation of known pathological phenotypes. A critical question is whether this novel technology will contribute to elucidation of novel disease mechanisms or evaluation of therapeutic strategies. Here we have addressed this question by studying Tay-Sachs disease, a representative lysosomal storage disease, and Dravet syndrome, a form of severe myoclonic epilepsy in infancy, using human iN cells with feature of immature postmitotic glutamatergic neuronal cells. In Tay-Sachs disease, we have successfully characterized canonical neuronal pathology, massive accumulation of GM2 ganglioside, and demonstrated the suitability of this novel cell culture for future drug screening. In Dravet syndrome, we have identified a novel functional phenotype that was not suggested by studies of classical mouse models and human autopsied brains. Taken together, the present study demonstrates that human iN cells are useful for translational neuroscience research to explore novel disease mechanisms and evaluate therapeutic compounds. In the future, research using human iN cells with well-characterized genomic landscape can be integrated into multidisciplinary patient-oriented research on neuropsychiatric disorders to address novel disease mechanisms and evaluate therapeutic strategies.

Unisexual reproduction in Huntiella moniliformis

Sexual reproduction in fungi is controlled by genes present at the mating type (MAT) locus, which typically harbors transcription factors that influence the expression of many sex-related genes. The MAT locus exists as two alternative idiomorphs in ascomycetous fungi and sexual reproduction is initiated when genes from both idiomorphs are expressed. Thus, the gene content of this locus determines whether a fungus is heterothallic (self-sterile) or homothallic (self-fertile). Recently, a unique sub-class of homothallism has been described in fungi, where individuals possessing a single MAT idiomorph can reproduce sexually in the absence of a partner. Using various mycological, molecular and bioinformatic techniques, we investigated the sexual strategies and characterized the MAT loci in two tree wound-infecting fungi, Huntiella moniliformis and Huntiella omanensis. H. omanensis was shown to exhibit a typically heterothallic sexual reproductive cycle, with isolates possessing either the MAT1-1 or MAT1-2 idiomorph. This was in contrast to the homothallism via unisexual reproduction that was shown in H. moniliformis, where only the MAT1-2-1 gene was present in sexually reproducing cultures. While the evolutionary benefit and mechanisms underpinning a unisexual mating strategy remain unknown, it could have evolved to minimize the costs, while retaining the benefits, of normal sexual reproduction.

Evaluation of respiratory syncytial virus (RSV) direct antigen detection assays for use in point-of-care testing

RSV infections cause lower respiratory tract infections and result in surges in physician's office, emergency department visits and hospitalizations, especially in infants and toddlers. Point-of-care (POC) testing reduces healthcare costs and permits informed decisions on treatment, however, optimal POC assays must be sensitive, easy to perform and provide rapid results. A prospective study tested 230 patient nasopharyngeal specimens using 4 RSV direct antigen detection assays (Directigen, Quickvue, Sofia and Veritor) and RT-PCR. A RSV dilution study was also performed to evaluate sensitivity. RSV fluorescent antibody testing in 46/230 patients was also evaluated. Sensitivity values obtained for the Sofia, Veritor, Directigen and Quickvue assays (%) were 85, 72.5, 70 and 57.5, respectively. Fluorescent result interpretation may account for Sofia's enhanced sensitivity. Specificity (%) was 97-100 among assays. Sensitivity data were confirmed in the dilution studies. Fluorescent antibody testing demonstrated 64% sensitivity compared with RT-PCR. Objective result reporting, walk away testing and high sensitivity make the Sofia a valuable choice for POC testing. Veritor's sensitivity may also render it acceptable in POC. Lack of objective results by Directigen and the poor sensitivity observed by Quickvue may preclude their value in diagnostic testing.

Inflammation and oxidative stress markers and esophageal adenocarcinoma incidence in a Barrett's esophagus cohort

BACKGROUND

Persons with Barrett's esophagus experience increased risk of esophageal adenocarcinoma. Prediagnostic inflammation markers predict several cancers, but their role in predicting esophageal adenocarcinoma is unknown.

METHODS

We investigated whether biomarkers of inflammation [C-reactive protein (CRP), interleukin-6 (IL6), soluble tumor necrosis factor (sTNF) receptors I and II], and of oxidative stress (F2-isoprostanes) predicted progression to esophageal adenocarcinoma in a prospective cohort of 397 patients with Barrett's esophagus, 45 of whom developed esophageal adenocarcinoma. Biomarkers were measured in stored plasma samples from two time points during follow-up, the mean of which served as the primary predictor. Adjusted hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox regression.

RESULTS

CRP level above the median was associated with an 80% increased risk of esophageal adenocarcinoma. The HR and 95% CI adjusted for age, gender, and further adjusted for waist-hip ratio and smoking were 1.98 (1.05-3.73) and 1.77 (0.93-3.37), respectively, with Ptrend for continuous CRP = 0.04. Persons with IL6 levels above the median also had almost 2-fold increased risk [HR and 95% CI adjusted for age and gender, and further adjusted for waist-hip ratio and smoking were 1.95 (1.03-3.72) and 1.79 (0.93-3.43), respectively, but no evidence of a trend was observed]. Concentrations of TNF receptors and F2-isoprostanes were not associated with esophageal adenocarcinoma risk.

CONCLUSIONS

Further research is needed to evaluate the role of inflammation and associated markers in esophageal adenocarcinoma development in persons with Barrett's esophagus.

IMPACT

This prospective study suggests that inflammation markers, particularly CRP and IL6, may help identify persons at higher risk of progression to esophageal adenocarcinoma.

Speed and incline during thoroughbred horse racing: racehorse speed supports a metabolic power constraint to incline running but not to decline running

We used a radio tracking system to examine the speed of 373 racehorses on different gradients on an undulating racecourse during 33 races, each lasting a few minutes. Horses show a speed detriment on inclines (0.68 m · s(-1) · 1% gradient(-1), r(2) = 0.97), the magnitude of which corresponds to trading off the metabolic cost (power) of height gain with the metabolic cost (power) of horizontal galloping. A similar relationship can be derived from published data for human runners. The horses, however, were also slower on the decline (-0.45 m · s(-1) · 1% gradient(-1), r(2) = 0.92). Human athletes run faster on a decline, which can be explained by the energy gained by the center of mass from height loss. This study has shown that horses go slower, which may be attributable to the anatomical simplicity of their front legs limiting weight support and stability when going downhill. These findings provide insight into limits to athletic performance in racehorses, which may be used to inform training regimens, as well as advancing knowledge from both veterinary and basic science perspectives.

Gene therapy for retinal ganglion cell neuroprotection in glaucoma

Glaucoma is the leading cause of irreversible blindness worldwide. The primary cause of glaucoma is not known, but several risk factors have been identified, including elevated intraocular pressure and age. Loss of vision in glaucoma is caused by the death of retinal ganglion cells (RGCs), the neurons that convey visual information from the retina to the brain. Therapeutic strategies aimed at delaying or halting RGC loss, known as neuroprotection, would be valuable to save vision in glaucoma. In this review, we discuss the significant progress that has been made in the use of gene therapy to understand mechanisms underlying RGC degeneration and to promote the survival of these neurons in experimental models of optic nerve injury.

An elevated apolipoprotein B/AI ratio is independently associated with microalbuminuria in male subjects with impaired fasting glucose

BACKGROUND AND AIMS

The ratio of apolipoprotein B/AI (apo B/AI) has been used as a marker to predict the risk of coronary artery disease. Recent studies have suggested an association between apolipoprotein B level and microalbuminuria in diabetic subjects. This study was performed to assess a possible association between the apo B/AI ratio and microalbuminuria in male subjects with impaired fasting glucose (IFG).

METHODS AND RESULTS

In 1266 patients with fasting serum glucose level in the pre-diabetic range, urine albumin-to-creatinine ratio (UACR, μg mg(-1)) was measured from single morning voided urine. The presence of microalbuminuria was defined as a UACR between 30 and 299 μg mg(-1). Participants were stratified into four groups by apo B/AI quartiles, from the lowest to the highest. Apo B/AI was higher with increasing body mass index, higher serum triglyceride and serum low-density lipoprotein cholesterol, systolic and diastolic blood pressure values, but lower with higher high-density lipoprotein cholesterol concentrations. After adjusting for these and other confounding factors, an increased apo B/AI ratio was independently associated with the presence of microalbuminuria. In receiver operating characteristic (ROC) curve analyses, apo B/AI ratio showed the highest correlation with the presence of microalbuminuria among the variables, although statistically not different.

CONCLUSION

These findings indicate that apo B/AI ratio shows significant association with microalbuminuria in Korean male subjects with IFG.

Virtual histology: a window to the heart of atherosclerosis

Intravascular ultrasound has done much to improve our understanding of atherosclerosis and the impact of percutaneous intervention on the coronary artery. However, subjectivity in interpreting the acoustic reflection of the ultrasound signal has spawned the development of other progressive technologies. Virtual histology intravascular ultrasound (VHIVUS) utilises the ultrasound backscatter signal in order to colour code plaque into four pre-specified subtypes based on their histological composition. We review the background behind traditional grey scale intravascular ultrasound (IVUS) and examine the current evidence for VHIVUS and its potential for use in clinical interventional practice.

The relationship between in vivo limb and in vitro tendon mechanics after injury: a potential novel clinical tool for monitoring tendon repair

REASONS FOR PERFORMING THE STUDY

Highly prevalent superficial digital flexor tendon (SDFT) injury results in compromised tendon function through fibrosis and high frequency of re-injury due to altered biomechanical function. This study investigated the consequences of SDF tendinopathy on limb mechanics in relation to the mechanical properties of injured tendon.

OBJECTIVES

To develop and validate a noninvasive in vivo assessment of tendon mechanics to investigate the effect of recent SDFT injury on limb stiffness index, providing an objective method to assess quality of healing.

HYPOTHESES

Limb stiffness index would reduce as a consequence of SDFT injury and progressively increase during tendon healing and correlate with in vitro mechanical properties of the respective SDFTs.

METHODS

Kinematic analysis was performed at walk in 10 horses that had sustained career-ending SDFT injury. Stiffness index was derived from limb force recorded via a series of force plates and measurement of change in metacarpophalangeal joint angle using 3D motion analysis software. Horses were subjected to euthanasia 7 months after injury, the SDFTs removed and subjected to nondestructive in vitro mechanical testing.

RESULTS

Limb stiffness index was reduced following SDFT injury in comparison with the contralateral limb and increased during the convalescent period, approximating that of the contralateral limb by 7 months post injury. There was a significant positive correlation between in vivo limb stiffness index and in vitro SDFT stiffness.

CLINICAL RELEVANCE

The ability to assess and monitor SDFT mechanical competence through limb stiffness measurement techniques in horses recovering from SDFT injury and the possibility of corroborating this with functional tendon healing may permit a more objective and accurate assessment of optimal tendon repair in the horse. This technique may be a useful method for assessing the efficacy of treatment regimens for tendinopathy and could be utilised to predict time to safe return to performance or re-injury.

Increased cerebrospinal fluid F2-isoprostanes are associated with aging and latent Alzheimer's disease as identified by biomarkers

Alzheimer's disease (AD) is a common age-related chronic illness with latent, prodrome, and fully symptomatic dementia stages. Increased free radical injury to regions of brain is one feature of prodrome and dementia stages of AD; however, it also is associated with advancing age. This raises the possibility that age-related free radical injury to brain might be caused in part or in full by latent AD. We quantified free radical injury in the central nervous system with cerebrospinal fluid (CSF) F(2)-isoprostanes (IsoPs) in 421 clinically normal individuals and observed a significant increase over the adult human lifespan (P < 0.001). Using CSF amyloid (A) β(42) and tau, we defined normality using results from 28 clinically normal individuals <50 years old, and then stratified 74 clinically normal subjects ≥60 years into those with CSF that had normal CSF Aβ(42) and tau (n = 37); abnormal CSF Aβ(42) and tau, the biomarker signature of AD (n = 24); decreased Aβ(42) only (n = 4); or increased tau only (n = 9). Increased CSF F(2)-IsoPs were present in clinically normal subjects with the biomarker signature of AD (P < 0.05) and those subjects with increased CSF tau (P < 0.001). Finally, we analyzed the relationship between age and CSF F(2)-IsoPs for those clinically normal adults with normal CSF (n = 37) and those with abnormal CSF Aβ(42) and/or tau (n = 37); only those with normal CSF demonstrated a significant increase with age (P < 0.01). These results show that CSF F(2)-IsoPs increased across the human lifespan and that this age-related increase in free radical injury to brain persisted after culling those with laboratory evidence of latent AD.

Plasma glutamine concentrations in the horse following feeding and oral glutamine supplementation

REASONS FOR PERFORMING STUDY

Pharmacological benefits of glutamine supplementation have been shown in athletically and clinically stressed human subjects. In the horse, infection and intense exercise have also been shown to significantly decrease plasma glutamine concentrations, but little is known on how best to supplement.

OBJECTIVE

To evaluate whether ingestion of different foodstuffs, with or without L-glutamine (G) or a peptide (Pep) containing 31.5% w/w G in a water-stable form, could affect plasma glutamine concentrations (P-GC).

MATERIALS AND METHODS

Nine feeds (molassed sugar beet-pulp (mSB); naked oats (nO); commercial mix (CM); mSB with 30 or 60 mg/kg bwt G or the G-molar equivalent of Pep; and CM with 60 mg/kg bwt G or equivalent Pep) were offered to 6 healthy mature horses on different days following overnight food restriction. The changes in P-GC were monitored for 8 h post feeding.

RESULTS

After 1.5 h mean +/- s.d. AP-GC were -0.9 +/- 10.2% (mSB), +12.5 +/- 7.1% (nO) and +44.7 +/- 15.9% (CM; P<0.05). deltaP-GC with mSB supplemented with G was +60.9 +/- 30.0% (30 mg; P<0.05) and +156.8 +/- 34.6% (60 mg; P<0.05) at 1 h; deltaP-GC with Pep was 51.0 +/- 31.0% (30 mg equivalent, P<0.05) and +91.1 +/- 9.5% (60 mg equivalent, P<0.05) at 1 h. After 10 days of supplementation with 60 mg/kg bwt G, AP-GC following a further 60 mg/kg bwt G challenge showed a similar increase at 1 h of +154.3 +/- 37.9%; prevalues were unchanged. G and Pep added to CM, increased P-GC by 246.3 +/- 55.3 (+99.2%) and 252.3 +/- 94.2 micromol/l (96.7%) at 1.5 h with concentrations still above prevalues at 8 h (P<0.05). Apart from the CM (with or without supplement), pre P-GC was always regained by 4 h. Plasma NH3 and plasma protein concentrations were unaffected by supplementation with G or Pep.

CONCLUSION

P-GC may be modified by appropriate supplementation with no apparent adverse effects.

POTENTIAL RELEVANCE

Increasing P-GC through appropriate supplementation may be of benefit in the athletically or clinically stressed horse with lowered plasma glutamine concentrations.

A comparison of the moment arms of pelvic limb muscles in horses bred for acceleration (Quarter Horse) and endurance (Arab)

Selective breeding for performance has resulted in distinct breeds of horse, such as the Quarter Horse (bred for acceleration) and the Arab (bred for endurance). Rapid acceleration, seen during Quarter Horse racing, requires fast powerful muscular contraction and the generation of large joint torques, particularly by the hind limb muscles. This study compared hind limb moment arm lengths in the Quarter Horse and Arab. We hypothesized that Quarter Horse hind limb extensor muscles would have longer moment arms when compared to the Arab, conferring a greater potential for torque generation at the hip, stifle and tarsus during limb extension. Six Quarter Horse and six Arab hind limbs were dissected to determine muscle moment arm lengths for the following muscles: gluteus medius, biceps femoris, semitendinosus, vastus lateralis, gastrocnemius (medialis and lateralis) and tibialis cranialis. The moment arms of biceps femoris (acting at the hip) and gastrocnemius lateralis (acting at the stifle) were significantly longer in the Quarter Horse, although the length of the remaining muscle moment arms were similar in both breeds of horse. All the Quarter Horse muscles were capable of generating greater muscle moments owing to their greater physiological cross-sectional area (PCSA) and therefore greater isometric force potential, which suggests that PCSA is a better determinant of muscle torque than moment arm length in these two breeds of horse. With the exception of gastrocnemius and tibialis cranialis, the observed muscle fascicle length to moment arm ratio (MFL : MA ratio) was greater for the Arab horse muscles. It appears that the Arab muscles have the potential to operate at slower velocities of contraction and hence generate greater force outputs when compared to the Quarter Horse muscles working over a similar range of joint motion; this would indicate that Arab hind limb muscles are optimized to function at maximum economy rather than maximum power output.

Reliability of conformational measurements in the horse using a three-dimensional motion analysis system

REASONS FOR PERFORMING STUDY

The importance of a reliable method for conformation studies is generally acknowledged, but there are only limited data on the accuracy and precision of current assessment methods.

OBJECTIVES

To assess (1) the accuracy and repeatability of marker placement, (2) influence of stance of the horse on conformational parameters, (3) practicality of a computerised motion analysis system and (4) to compare the computerised motion analysis system to photographic systems of assessment.

METHODS

Twenty-eight reflective markers placed over anatomical landmarks were located in 3D using a computerised motion analysis system and their coordinates used to calculate segment lengths and joint angles. Four experiments, involving a cadaver study, a series of repeated measures on a single Thoroughbred and repeat measurements on 108 racehorses were performed.

RESULTS

Identification of anatomical landmarks was found to introduce the biggest variation in the measurements for proximal conformation parameters with the interoperator being larger than intraoperator variation. Length measurements were least influenced by stance, with distal interphalangeal and metacarpo/metatarsophalangeal joint angles being the most variable. In some measurements, the variation between stances within a horse proved to be almost as large as between horses, rendering these parameters less useful as predictors of performance or orthopaedic health.

CONCLUSIONS

A computerised motion analysis system allows 3D assessment of conformation with high accuracy and precision. It eliminates 3 major sources of error associated with photography-based methods and increases accuracy of conformational assessment by allowing repeat measurements in a relatively short period.

POTENTIAL RELEVANCE

Studies on conformation should be viewed in the light of the limitations of the measurement technique used. The presented method maximises accuracy and precision and is a valuable basis for future studies investigating the effect of conformation on performance or orthopaedic health.

Relationship of foot conformation and force applied to the navicular bone of sound horses at the trot

REASONS FOR PERFORMING STUDY

Collapsed heels conformation has been implicated as causing radical biomechanical alterations, predisposing horses to navicular disease. However, the correlation between hoof conformation and the forces exerted on the navicular bone has not been documented.

HYPOTHESIS

The angle of the distal phalanx in relation to the ground is correlated to the degree of heel collapse and foot conformation is correlated to the compressive force exerted by the deep digital flexor tendon on the navicular bone.

METHODS

Thirty-one shod Irish Draught-cross type horses in routine work and farriery care were trotted over a forceplate, with 3-dimensional (3D) motion analysis system. A lateromedial radiograph of the right fore foot was obtained for each horse, and various measurements taken. Correlation coefficients were determined between hoof conformation measurements and between each of these and the force parameters at the beginning (15%) of stance phase, the middle of stance (50%) and at the beginning of breakover (86% of stance phase). Significance was defined as P<0.05.

RESULTS

The force exerted on the navicular bone was negatively correlated (P<0.05) to the angle of the distal phalanx to the ground and to the ratio between heel and toe height. This was attributed to a smaller extending moment at the distal interphalangeal joint. There was not a significant correlation between the angle of the distal phalanx and the degree of heel collapse, and heel collapse was not significantly correlated to any of the force parameters.

CONCLUSIONS

Hoof conformation has a marked correlation to the forces applied to the equine foot. Heel collapse, as defined by the change in heel angle in relation to toe angle, appears to be an inaccurate parameter. The forces applied on the foot are well correlated to the changes in the ratio of heel to toe heights and the angles of the distal phalanx.

POTENTIAL RELEVANCE

Assessment of hoof conformation should be judged based on these parameters, as they may have clinical significance, whereas parallelism of the heel and toe is of less importance.

Variation in conformation in a cohort of National Hunt racehorses

REASONS FOR PERFORMING THE STUDY

Assessment of conformation is commonly used in the selection of horses for performance purposes. Little information is available on the normal range of conformational traits within the Thoroughbred population.

OBJECTIVES

To describe variations in conformation in a cohort of racing Thoroughbreds in order to provide a set of baseline standards within which conformational traits can be considered normal.

MATERIALS AND METHODS

Ninety-eight conformational parameters were measured in a cohort of 108 National Hunt racehorses using a digital motion analysis system. The measurements consisted of segment lengths, joint angles in 2D and 3D, inclinations, deviations and circumference measurements. The differences between left and right sides were determined to obtain a measure of asymmetry. Conformational parameters were related to each horse's country of origin, preferred race distance and race type.

RESULTS

The majority of parameters followed a normal distribution with the biggest relative variation in hoof related measurements and in stifle and coxal angle. All circumference measurements and the majority of the length measurements were significantly correlated with the height of the horse at the withers. No underlying pattern of combinations of conformational parameters was identified. Twenty-five per cent of the parameters showed a significant difference between left and right-sided measurements. A significant difference in girth and intermandibular width was observed between Irish and French horses.

CONCLUSIONS

Thoroughbreds differ from other breeds, not only with regard to segment lengths but also with regard to joint angles and deviations. Variation in conformational parameters was relatively small and no distinct pattern of combinations of conformational traits identified.

CLINICAL RELEVANCE

The variation in conformational measurements in Thoroughbred racehorses establishes a set of baseline measurements of conformational range against which individual horses can be assessed.

The effect of conformation on orthopaedic health and performance in a cohort of National Hunt racehorses: preliminary results

REASONS FOR PERFORMING STUDY

There is a lack of scientific data and studies on the effect of conformation on performance or on orthopaedic health.

OBJECTIVES

To investigate the relationship between conformation, injury and performance in racehorses used for racing over fences.

METHODS

Over 2 years, 108 National Hunt racehorses were followed and their medical and performance data recorded. Conformation was measured in 3D with a computerised motion analysis system. Linear multiple regression models were used to evaluate the effect of conformation on measures of race performance and stepwise forward logistic regression models to assess the effect on risk of injury.

RESULTS

An increase in intermandibular width, flexor angle of the shoulder joint and coxal angle (the angle between the ilium and ischium) was demonstrated to have a positive effect on performance. Performance decreased with increasing girth, length of the hind digit and valgus conformation of the metacarpophalangeal joint. The risk of suffering from superficial digital flexor tendon injury increased with increasing metacarpophalangeal joint angle and with carpus valgus conformation. The risk of pelvic fracture increased with valgus conformation of the tarsus and decreased with an increasing coxal angle.

CONCLUSION

Valgus deformation was demonstrated to be detrimental to performance or increased risk of injury, perhaps resulting in higher loads on musculoskeletal structures. The coxal angle was the only parameter to have an effect on both risk of injury and performance. An alignment of the muscles with the axis of the pelvis may be beneficial for force transmission and decrease the bending moment of the muscles on the bones. The statistical power of this study is limited, however it provides preliminary data necessary for the planning of a larger scale study on the effect of conformation on performance and risk of injury.

CLINICAL RELEVANCE

Studies of the effects of conformation on performance and risk of injury may aid in identifying individuals likely to perform well on the racecourse and avoid risks of injury.

The use of MP3 recorders to log data from equine hoof mounted accelerometers

REASONS FOR PERFORMING STUDY

MP3 recorders are readily available, small, lightweight and low cost, providing the potential for logging analogue hoof mounted accelerometer signals for the characterisation of equine locomotion. These, however, require testing in practice.

OBJECTIVES

To test whether 1) multiple MP3 recorders can maintain synchronisation, giving the ability to synchronise independent recorders for the logging of multiple limbs simultaneously; and 2) features of a foot mounted accelerometer signal attributable to foot-on and foot-off can be accurately identified from horse foot mounted accelerometers logged directly into an MP3 recorder.

METHODS

Three experiments were performed: 1) Maintenance of synchronisation was assessed by counting the number of samples recorded by each of 4 MP3 recorders while mounted on a trotting horse and over 2 consecutive 30 min periods in 8 recorders on a bench. 2) Foot-on and foot-off times obtained from manual transcription of MP3 logged data and directly logged accelerometer signal were compared. 3) MP3/accelerometer acquisition units were used to log accelerometer signals from racehorses during extended training sessions.

RESULTS

Mean absolute error of synchronisation between MP3 recorders was 10 samples per million (compared to mean number of samples, range 1-32 samples per million). Error accumulation showed a linear correlation with time. Features attributable to foot on and foot off were equally identifiable from the MP3 recorded signal over a range of equine gaits.

CONCLUSIONS

Multiple MP3 recorders can be synchronised and used as a relatively cheap, robust, reliable and accurate logging system when combined with an accelerometer and external battery for the specific application of the measurement of stride timing variables across the range of equine gaits during field locomotion.

POTENTIAL RELEVANCE

Footfall timings can be used to identify intervals between the fore and hind contacts, the identification of diagonal advanced placement and to calculate stride timing variables (stance time, protraction time and stride time). These parameters are invaluable for the characterisation and assessment of equine locomotion.

Deep digital flexor tendon force and digital mechanics in normal ponies and ponies with rotation of the distal phalanx as a sequel to laminitis

REASONS FOR PERFORMING STUDY

Previous studies have implicated tension in the deep digital flexor tendon (DDFT) in the rotation of the distal phalanx (DP) after the breakdown of the dorsal laminae caused by laminitis. Howeveer, once the DP has rotated, the DDFT should become shorter, reducing the force it exerts on the DP.

OBJECTIVE

To compare DDFT force and ground reaction forces (GRFs) in normal ponies and ponies with rotation of the DP as a sequel to laminitis.

METHODS

Six normal ponies (Group 1) and 6 sound ponies with 6-13 degrees of rotation of the DP in relation to the dorsal hoof wall (Group 2) were assessed at trot using forceplate and motion analysis. The force in the DDFT was calculated by assuming that the extending moment at the distal interphalangeal (DIP) joint resulting from the GRF was equal to the flexing moment created by the force in the DDFT during the stance phase (inverse dynamics).

RESULTS

In early stance, the peak DDFT force (mean+/-s.d.) in the normal ponies was 1.92+/-1.63 N/kg. However, in Group 2, the point of zero moment was palmar to the centre of rotation of the DIP joint for the first 40% of stance and hence DDFT force was zero. Force in the DDFT reached a peak of 10.00+/-3.56 N/kg at 60.7+/-5.6% of stance in Group 1 and 6.41+/-1.37 N/kg at 79.2+/-9.6% of stance in Group 2.

CONCLUSIONS

DDFT force in Group 2 laminitic ponies was much reduced until late stance, when it neared normal values.

POTENTIAL RELEVANCE

Further studies of ponies with rotation of the DP as a sequel to laminitis should assist farriery aimed at reducing the force in the DDFT through the breakover phase of stance to protect damaged dorsal laminae.

Identification of glutathione S-transferase pi as a protein involved in Parkinson disease progression

Parkinson disease (PD) typically affects the cortical regions during the later stages of disease, with neuronal loss, gliosis, and formation of diffuse cortical Lewy bodies in a significant portion of patients with dementia. To identify novel proteins involved in PD progression, we prepared synaptosomal fractions from the frontal cortices of pathologically verified PD patients at different stages along with age-matched controls. Protein expression profiles were compared using a robust quantitative proteomic technique. Approximately 100 proteins displayed significant differences in their relative abundances between PD patients at various stages and controls; three of these proteins were validated using independent techniques. One of the confirmed proteins, glutathione S-transferase Pi, was further investigated in cellular models of PD, demonstrating that its level was intimately associated with several critical cellular processes that are directly related to neurodegeneration in PD. These results have, for the first time, suggested that the levels of glutathione S-transferase Pi may play an important role in modulating the progression of PD.

Exploring the mechanical basis for acceleration: pelvic limb locomotor function during accelerations in racing greyhounds (Canis familiaris)

Animals in their natural environments are confronted with a regular need to perform rapid accelerations (for example when escaping from predators or chasing prey). Such acceleration requires net positive mechanical work to be performed on the centre of mass by skeletal muscle. Here we determined how pelvic limb joints contribute to the mechanical work and power that are required for acceleration in galloping quadrupeds. In addition, we considered what, if any, biomechanical strategies exist to enable effective acceleration to be achieved. Simultaneous kinematic and kinetic data were collected for racing greyhounds undergoing a range of low to high accelerations. From these data, joint moments and joint powers were calculated for individual hindlimb joints. In addition, the mean effective mechanical advantage (EMA) of the limb and the ;gear ratio' of each joint throughout stance were calculated. Greatest increases in joint work and power with acceleration appeared at the hip and hock joints, particularly in the lead limb. Largest increases in absolute positive joint work occurred at the hip, consistent with the hypothesis that quadrupeds power locomotion by torque about the hip. In addition, hindlimb EMA decreased substantially with increased acceleration - a potential strategy to increase stance time and thus ground impulses for a given peak force. This mechanism may also increase the mechanical advantage for applying the horizontal forces necessary for acceleration.

Functional anatomy and muscle moment arms of the thoracic limb of an elite sprinting athlete: the racing greyhound (Canis familiaris)

We provide quantitative muscle-tendon architecture and geometry data for the racing greyhound thoracic limb. Muscle mass, belly length, fascicle lengths, pennation angles and moment arms were measured, as were tendon masses and lengths. Maximum isometric force and maximum power were estimated for muscles, and maximum stress and strain were estimated for tendons. Results are compared with other fast quadrupedal runners, and to previously published data in mixed-breed dogs. The implications of the functional adaptations of the greyhound thoracic limb for sprinting performance are discussed. The thoracic limb was found to benefit from a similar proportion of locomotor muscle mass to the pelvic limb, suggesting that it may be used to some extent in propulsion, or alternatively that stabilisation is very important in this animal. Extrinsic muscles, especially latissimus dorsi and pectoralis profundus, were predicted to be powerful and important for generating net positive work during accelerations. Proximal biarticular muscles show specialisation toward preventing collapse of the shoulder and elbow joints to enable strut-like limb function, or some form of dynamic control. Distal muscles did not appear specialised for elastic energy storage, a functional difference to pelvic limb muscles, and the equivalents in horse thoracic limbs. The greyhound thoracic limb appears to possess substantial differences from both that of more 'sub-maximal specialist' quadrupeds, and from the greyhound pelvic limb.

The mechanism for efficacy of eccentric loading in Achilles tendon injury; an in vivo study in humans

OBJECTIVE

Degenerative disorders of tendons present an enormous clinical challenge. They are extremely common, prone to recur and existing medical and surgical treatments are generally unsatisfactory. Recently eccentric, but not concentric, exercises have been shown to be highly effective in managing tendinopathy of the Achilles (and other) tendons. The mechanism for the efficacy of these exercises is unknown although it has been speculated that forces generated during eccentric loading are of a greater magnitude. Our objective was to determine the mechanism for the beneficial effect of eccentric exercise in Achilles tendinopathy.

METHODS

Seven healthy volunteers performed eccentric and concentric loading exercises for the Achilles tendon. Tendon force and length changes were determined using a combination of motion analysis, force plate data and real-time ultrasound.

RESULTS

There was no significant difference in peak tendon force or tendon length change when comparing eccentric with concentric exercises. However, high-frequency oscillations in tendon force occurred in all subjects during eccentric exercises but were rare in concentric exercises (P < 0.0001).

CONCLUSION

These oscillations provide a mechanism to explain the therapeutic benefit of eccentric loading in Achilles tendinopathy and parallels recent evidence from bone remodelling, where the frequency of the loading cycles is of more significance than the absolute magnitude of the force.