3,262 research outputs found
Characterisation of modified glass-ionomer cements for medical applications
Medical-grade glass ionomer cements (GICs) are commercially available for surgical implantation in otology. GICs have advantageous properties as a bone replacement material, including the ability to bond to mineralised tissue such as bone and a good biocompatibility in vivo. However, cement compositions are largely based on the GIC dental cement compositions they were derived from and are not optimised for use in medical applications. The specific objective of this project was to produce improved GICs for surgical application in otology, based upon a commercially available bone cement and tailor the properties to the specific needs of the surgeon while preserving the beneficial properties of the original composition.
Novel GICs based on the substitution of calcium with either strontium, barium or a mixture of species in the ionomer glass component were fabricated and characterisation of the glass and cements undertaken in addition to NMR (nuclear magnetic resonance) analysis of the effect of additives in GICs setting reactions.
The substitution of strontium and barium ions produced cements with improved properties that compared favourably with the commercial material (SerenoCem®) used as a control in this study. Radiopacity and biocompatibility were enhanced without a significant negative effect on the cement properties. XRD (X-Ray Diffraction) of the heat-treated glasses identified Sr/Ba analogous phases present to those reported previously in the literature.
It was concluded that modified ionomer glasses based on the SerenoCem® medical cement composition, tailored for improved properties, will allow the material to accommodate the specific needs of the surgeon and therefore increase clinical viability in bone replacement surgery
The amyloid precursor protein: A biochemical enigma in brain development, function and disease
AbstractFor 20years the amyloid cascade hypothesis of Alzheimer disease (AD) has placed the amyloid-β peptide (Aβ), formed from the amyloid precursor protein (APP), centre stage in the process of neurodegeneration. However, no new therapeutic agents have reached the clinic through exploitation of the hypothesis. The APP metabolites, including Aβ, generated by its proteolytic processing, have distinct physiological functions. In particular, the cleaved intracellular domain of APP (AICD) regulates expression of several genes, including APP itself, the β-secretase BACE-1 and the Aβ-degrading enzyme, neprilysin and this transcriptional regulation involves direct promoter binding of AICD. Of the three major splice isoforms of APP (APP695, APP751, APP770), APP695 is the predominant neuronal form, from which Aβ and transcriptionally-active AICD are preferentially generated by selective processing through the amyloidogenic pathway. Despite intensive research, the normal functions of the APP isoforms remain an enigma. APP plays an important role in brain development, memory and synaptic plasticity and secreted forms of APP are neuroprotective. A fuller understanding of the physiological and pathological actions of APP and its metabolic and gene regulatory network could provide new therapeutic opportunities in neurodegeneration, including AD
Angiotensin-Converting Enzyme 2: The First Decade
The
renin-angiotensin system (RAS) is a critical
regulator of hypertension, primarily through the
actions of the vasoactive peptide Ang II, which
is generated by the action of angiotensin-converting enzyme (ACE) mediating an increase in
blood pressure. The discovery of ACE2, which
primarily metabolises Ang II into the
vasodilatory Ang-(1-7), has added a new
dimension to the traditional RAS. As a result
there has been huge interest in ACE2 over the
past decade as a potential therapeutic for
lowering blood pressure, especially elevation
resulting from excess Ang II. Studies focusing
on ACE2 have helped to reveal other actions of
Ang-(1-7), outside vasodilation, such as
antifibrotic and antiproliferative effects.
Moreover, investigations focusing on ACE2 have
revealed a variety of roles not just catalytic
but also as a viral receptor and amino acid
transporter. This paper focuses on what is
known about ACE2 and its biological roles,
paying particular attention to the regulation of
ACE2 expression. In light of the entrance of
human recombinant ACE2 into clinical trials, we
discuss the potential use of ACE2 as a
therapeutic and highlight some pertinent
questions that still remain unanswered about
ACE2
Thermal kinetic inductance detectors for ground-based millimeter-wave cosmology
We show measurements of thermal kinetic inductance detectors (TKID) intended
for millimeter wave cosmology in the 200-300 GHz atmospheric window. The TKID
is a type of bolometer which uses the kinetic inductance of a superconducting
resonator to measure the temperature of the thermally isolated bolometer
island. We measure bolometer thermal conductance, time constant and noise
equivalent power. We also measure the quality factor of our resonators as the
bath temperature varies to show they are limited by effects consistent with
coupling to two level systems.Comment: 8 pages, 4 figures. Submitted to Journal of Low Temperature Physic
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Ambulatory Blood Pressure Monitoring in Clinical Practice: A Review
Abstract:
Ambulatory blood pressure monitoring offers the ability to collect blood pressure readings several times an hour across a 24-hour period. Ambulatory blood pressure monitoring facilitates the identification of white-coat hypertension, the phenomenon whereby certain individuals who are not taking antihypertensive medication show elevated blood pressure in a clinical setting but show nonelevated blood pressure averages when assessed by ambulatory blood pressure monitoring. In addition, readings can be segmented into time windows of particular interest, for example, mean daytime and nighttime values. During sleep, blood pressure typically decreases, or dips, such that mean sleep blood pressure is lower than mean awake blood pressure. A nondipping pattern and nocturnal hypertension are strongly associated with increased cardiovascular morbidity and mortality. Approximately 70% of individuals have blood pressure dips of ≥10% at night, whereas 30% have nondipping patterns, when blood pressure remains similar to daytime average or occasionally increases above daytime average. The various blood pressure categorizations afforded by ambulatory blood pressure monitoring are valuable for clinical management of high blood pressure because they increase the accuracy for diagnosis and the prediction of cardiovascular risk.
Keywords:
Ambulatory blood pressure monitoring; High blood pressure; Masked hypertension; Nocturnal blood pressure; White-coat hypertensio
Practices of strength and conditioning coaches in professional sports:A systematic review
The practices of strength and conditioning (S&C) coaches have been reported in various professional sports. This study aims to comprehensively assess this available evidence to help establish whether theoretical, practical, and evidence-based guidelines align with the practices employed by these experienced S&C coaches. Three databases were searched (PubMed, SPORTDiscus, and Cochrane) until November 2020. Studies surveying the practices of S&C coaches in professional sports using a survey design with common questions, written in English, and published in peer-reviewed journals were reviewed. Eight studies (n = 318 S&C coaches) were finally included. All studies adapted a similar survey, providing a strong basis for comparison between sports. Periodization strategies were widely used (89%), with training volume consistently reduced during the in-season period. Olympic weightlifting was commonly used across sports, except in baseball (29%). Plyometric exercises were predominantly prescribed for speed development (74%) and lower body power (68%), which were mostly programed as complex training (45%) and conducted all year round (52%). Flexibility exercises were mostly performed before practice (83%) for 6–10 min (40%). Physical tests were mainly conducted during the pre-season period (66%), with body composition (86%) being the most used test. S&C coaches generally adhered to current guidelines and research in S&C concerning training prescription and physical testing. Whereas, Intersport differences were also noted and further discussed. Results of this study can be used by S&C coaches to plan, implement, and review their professional practices. Furthermore, may inform the development of general and sport-specific guidelines, and future research in S&C
Haemoglobin mass responses and performance outcomes among high-performance swimmers following a three-week Live-High, Train-High camp at 2,320m
Greater quantification and characterisation of training load (TL) throughout Live-High, Train-High (LHTH) altitude (ALT) training is required to identify periodisation strategies that may lead to physiological and performance improvements in swimmers. Purpose: This study aimed to examine the physiological responses and performance outcomes of fourteen high-performance swimmers (FINA points: 836.0 ± 35.1) following three-weeks of LHTH at 2,320m, while characterising the training load periodisation strategy adopted during the intervention. Methods: Haemoglobin (Hb) mass was measured pre-, seven- and fourteen-days post-ALT via CO rebreathing. Performance in each athlete’s primary event at national standard meets were converted to FINA points and compared from pre-to-post ALT. TL was quantified at sea level (SL) and ALT through session rating of perceived exertion (RPE), where duration of each session was multiplied by its RPE for each athlete, with all sessions totalled to give a weekly TL. Pre-to-post ALT changes were evaluated using repeated-measures ANOVA.Results: Hb mass increased significantly from 798±182g pre-ALT, to 828±187g at seven-days post (p=0.013) and 833±205g 14-days post-ALT (p=0.026). Weekly TL increased from SL (3179±638 au) during week one (4797±1349 au, p<0.001) and week two (4373±967 au, p<0.001), but not week three (3511±730 au, p=0.149). No evidence of improved SL swimming performance was identified. Conclusion: A periodisation strategy characterised by a sharp spike in TL followed by a slight de-load towards the end of a LHTH intervention led to improved physiological characteristics but no change in the competitive performance of high-performance swimmers.<br/
Fatigue does not increase limb asymmetry or induce proximal joint power shift in habitual, multi-speed runners
During prolonged jogging, joint moment and work tend to decrease in the distal (ankle) joint but increase at proximal (hip/knee) joints as performance fatigue manifests, and such adaptations might be expected to occur in sprinting. Fatigue is also thought to increase inter-limb asymmetries, which is speculated to influence injury risk. However, the effects of fatigue on sprint running gait have been incompletely studied, so these hypotheses remain untested. Using statistical parametric mapping, we compared 3-D kinematics and ground reaction force production between the dominant (DL) and non-dominant (NDL) legs of 13 soccer players during both non-fatigued and fatigued sprint running. Contrary to the tested hypotheses, relative between-leg differences were greater in non-fatigued than fatigued sprinting. DL generated higher propulsive impulse due to increased ankle work, while NDL exhibited greater vertical impulse, potentially due to greater hip flexion prior to downward foot acceleration. Whilst few changes were detected in DL once fatigued, NDL shifted towards greater horizontal force production, largely resulting from an increase in plantar flexion (distal-joint) moments and power. After fatiguing running, inter-limb asymmetry was reduced and no distal-to-proximal shift in joint work was detected. These adaptations may attenuate decreases in running speed whilst minimising injury risk
Goal-directed attention alters the tuning of object-based representations in extrastriate cortex
Humans survive in environments that contain a vast quantity and variety of visual information. All items of perceived visual information must be represented within a limited number of brain networks. The human brain requires mechanisms for selecting only a relevant fraction of perceived information for more in-depth processing, where neural representations of that information may be actively maintained and utilized for goal-directed behavior. Object-based attention is crucial for goal-directed behavior and yet remains poorly understood. Thus, in the study we investigate how neural representations of visual object information are guided by selective attention. The magnitude of activation in human extrastriate cortex has been shown to be modulated by attention; however, object-based attention is not likely to be fully explained by a localized gain mechanism. Thus, we measured information coded in spatially distributed patterns of brain activity with fMRI while human participants performed a task requiring selective processing of a relevant visual object category that differed across conditions. Using pattern classification and spatial correlation techniques, we found that the direction of selective attention is implemented as a shift in the tuning of object-based information representations within extrastriate cortex. In contrast, we found that representations within lateral prefrontal cortex (PFC) coded for the attention condition rather than the concrete representations of object category. In sum, our findings are consistent with a model of object-based selective attention in which representations coded within extrastriate cortex are tuned to favor the representation of goal-relevant information, guided by more abstract representations within lateral PFC
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