Muscle carnosine metabolism and β-alanine supplementation in relation to exercise and training

Carnosine is a dipeptide with a high concentration in mammalian skeletal muscle. It is synthesized by carnosine synthase from the amino acids L-histidine and beta-alanine, of which the latter is the rate-limiting precursor, and degraded by carnosinase. Recent studies have shown that the chronic oral ingestion of beta-alanine can substantially elevate (up to 80%) the carnosine content of human skeletal muscle. Interestingly, muscle carnosine loading leads to improved performance in high-intensity exercise in both untrained and trained individuals. Although carnosine is not involved in the classic adenosine triphosphate-generating metabolic pathways, this suggests an important role of the dipeptide in the homeostasis of contracting muscle cells, especially during high rates of anaerobic energy delivery. Carnosine may attenuate acidosis by acting as a pH buffer, but improved contractile performance may also be obtained by improved excitation-contraction coupling and defence against reactive oxygen species. High carnosine concentrations are found in individuals with a high proportion of fast-twitch fibres, because these fibres are enriched with the dipeptide. Muscle carnosine content is lower in women, declines with age and is probably lower in vegetarians, whose diets are deprived of beta-alanine. Sprint-trained athletes display markedly high muscular carnosine, but the acute effect of several weeks of training on muscle carnosine is limited. High carnosine levels in elite sprinters are therefore either an important genetically determined talent selection criterion or a result of slow adaptation to years of training. beta-Alanine is rapidly developing as a popular ergogenic nutritional supplement for athletes worldwide, and the currently available scientific literature suggests that its use is evidence based. However, many aspects of the supplement, such as the potential side effects and the mechanism of action, require additional and thorough investigation by the sports science community

The revival of unsedated colonoscopy through water infusion

Introduction : Unsedated colonoscopy using water infusion has been performed in a US veterans population, showing feasibility and even enhanced adenoma detection rate (Leung et al, J Interv Gastroenterol, 2011, 1, 8-13). Avoiding sedation or general anesthesia theoretically will avoid sedation related complications, could be time- and cost-saving, could improve patient satisfaction and reduce waiting lists for colonoscopy. Aim : To study the feasibility of unsedated colonoscopy by means of water infusion in a tertiary hospital setting. The primary endpoint of this trial is reaching the cecum without need for sedation. Methods : The water infusion technique for colonoscopy consists of using water at body temperature at insertion of the endoscope, instead of air insufflation. It is combined with removal of all residual colonic air by suction and residual feces by water exchange. Once the cecum is reached, air insufflation is used during withdrawal for mucosal inspection. All patients start the endoscopy unsedated but sedation and analgesia are administered if needed or asked for (midazolam 2,5 mg / pethidine 50 mg). When progression with water fails, switch to air insufflation is made. Pain scores are registred on a VAS (0=no pain, 10=maximal pain). Patient satisfaction and willing to repeat the procedure are also scored on a VAS (respectively: 0=very low, 10=high/ 0=not willing to repeat, 10=willing). Results : 38 patients (18F, 20M) with a mean age of 57 ± 11 yrs are included. Indications for colonoscopy are: cancer screening 24%, polyp surveillance 18%, diagnostic 58%. The primary endpoint, unsedated succesful cecal intubation, is reached in 27 patients (71,2%). The global cecal intubation rate is 94,7% (n=36). Mean insertion time was 14 ± 6 min. Mean length of the colonoscope at the cecum was 82 ± 10 cm. Mean volume of water infused upon arrival to the cecum is 332 ± 172 ml. In 11 patients (28,9%) temporary switch to air insufflation during insertion is needed (6 at the hepatic flexure, 5 in the sigmoid). Men reach the endpoint more readily than women (85% vs. 55,6%, p = 0,046). Age doesn’t make a difference (p = 0,62). Maximum mean pain score during insertion is 3,1 ± 2,7; pain at time of discharge is 1,5 ± 2,2. Patient satisfaction is 9,2 ± 1,2, willingness to repeat 9,7 ± 0,7. Mean withdrawal time is 8,8 + 4,6 min and the adenoma detection rate is 21%. Conclusions : Water-infused colonoscopy is a promising and simple technique to perform complete unsedated colonoscopy. This method may open perspectives for a new era in colonoscopy with high patient satisfaction and lower costs

The Ongoing Myth of TIPIC-Syndrome

Carotidynia is characterized by intense localized pain and tenderness at the level of the carotid bifurcation. The differential diagnosis is broad and includes vascular pathologies, infectious diseases or malignancies. Recent evidence now suggests a distinct entity called Transient Perivascular Inflammation of the Carotid Artery or TIPIC syndrome. The diagnosis is made per exclusionem and is based on typical radiological findings. This paper describes the clinical examination, laboratory results, radiological findings and treatment based on two case reports. TIPIC syndrome is an idiopathic syndrome which is usually a self-limiting disease of which a vascular surgeon should be aware

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

Pantropical variability in tree crown allometry

Aim Tree crowns determine light interception, carbon and water exchange. Thus, understanding the factors causing tree crown allometry to vary at the tree and stand level matters greatly for the development of future vegetation modelling and for the calibration of remote sensing products. Nevertheless, we know little about large‐scale variation and determinants in tropical tree crown allometry. In this study, we explored the continental variation in scaling exponents of site‐specific crown allometry and assessed their relationships with environmental and stand‐level variables in the tropics. Location Global tropics. Time period Early 21st century. Major taxa studied Woody plants. Methods Using a dataset of 87,737 trees distributed among 245 forest and savanna sites across the tropics, we fitted site‐specific allometric relationships between crown dimensions (crown depth, diameter and volume) and stem diameter using power‐law models. Stand‐level and environmental drivers of crown allometric relationships were assessed at pantropical and continental scales. Results The scaling exponents of allometric relationships between stem diameter and crown dimensions were higher in savannas than in forests. We identified that continental crown models were better than pantropical crown models and that continental differences in crown allometric relationships were driven by both stand‐level (wood density) and environmental (precipitation, cation exchange capacity and soil texture) variables for both tropical biomes. For a given diameter, forest trees from Asia and savanna trees from Australia had smaller crown dimensions than trees in Africa and America, with crown volumes for some Asian forest trees being smaller than those of trees in African forests. Main conclusions Our results provide new insight into geographical variability, with large continental differences in tropical tree crown allometry that were driven by stand‐level and environmental variables. They have implications for the assessment of ecosystem function and for the monitoring of woody biomass by remote sensing techniques in the global tropics

Integrating the pathogenesis of spondyloarthritis: gut and joint united?

Purpose of review : The association between spondyloarthritis (SpA) and inflammatory bowel disease (IBD) is well known. Additionally, about half of SpA patients show microscopic gut inflammation. Substantial progress has been made in understanding the pathogenesis of SpA and IBD, with new therapeutic targets for either of them in clinical development. Recent findings : Microscopic gut inflammation was found in early forms of SpA in about 50% of cases and is associated with age, sex, disease activity and degree of MRI inflammation on sacroiliac joints. Although prospective follow-up data in men and murine animal studies show a parallelism between gut and joint evolution in SpA, therapeutic outcomes are not always the same in SpA and IBD. These differences can be ascribed to differences in not only the cytokine pathways and cells involved in disease, tissue localization and environmental factors but also in pharmacokinetics and biodistribution. Summary : A significant amount of data all point in the direction of arthritis and gut inflammation being pathogenetically closely linked in the SpA concept. However, when it comes to therapeutic effectiveness, the gut and the joints do not always react in the same way. These differences in therapeutic effect could be attributed to the different ways in which cytokine pathways are involved in SpA and IBD

Jaarlijkse groei van Pterocarpus angolensis (Kiaat) en andere boomsoorten in Kavango, Namibië

De meest geprefereerde houtsoort voor zagerij in Namibië en het grootste deel van zuidelijk Afrika, is Pterocarpus angolensis (Kiaat). Er is echter niet genoeg informatie over de jaarlijkse groei van de soort om te bepalen of de oogst duurzaam is. De soort bereikt in Namibië de zuidelijke grens van zijn verspreidingsgebied en men zou kunnen verwachten dat de jaarlijkse groei lager is dan in andere landen waarvoor meer gegevens beschikbaar zijn binnen de literatuur. Deze studie wil bijdragen aan de bepaling van de jaarlijkse diametergroei van Kiaat in Namibië door het meten van de jaarlijkse groei in de regio Kavango. De diametergroei van Kiaat zal worden vergeleken met een paar andere soorten waarvoor boorkernen werden verzameld. Hierbij maakt men gebruik een presslerboor voor het winnen van boorspanen die worden geëgaliseerd met de Core-microtome om ze daaropvolgend met LintabTM software te analyseren. Er werd ook informatie gewonnen uit stamschijven die gedurende het onderzoek te beschikking werden gesteld voor manuele tellingen. Naast Kiaat werd een soortgelijke analyse uitgevoerd op Burkea africana, Baikiaea plurijuga, Terminalia sericea en Schinziophyton rautanenii om na te gaan of ook deze soorten geschikt zijn voor jaarringanalyse op basis van boorspanen. Het onderzoek centraliseert zich binnen de regio Kavango maar beoogt tevens vergelijkingen met naburige regionen binnen en buiten Namibië. Gekeken naar de kwaliteit van boorspanen en de vraag of andere houtsoorten bruikbaar zijn voor jaarringanalyse, merkt men vooral technische problemen door intern rot of holle stammen bij Baikiaea plurijuga en Burkea africana. Voor Terminalia sericea zijn goede boorspanen verzameld maar is het vooral moeilijk om daadwerkelijk tot de kern van de stam te geraken vanwege excentriciteit. Voor Schinziophyton rautanenii vermoedt men geen jaarringen te zien, aangezien het gaat om een stamsucculent. Uit de jaarringanalyse haalt men groeicurven die de relatie tussen diameter en leeftijd weergeven voor stamschijven. Voor boorspanen wordt met LintabTM software de effectieve ringbreedte bepaald en de daaruit volgende groeicurve. Uit een eerste reeks resultaten blijkt de groei in Kavango sneller te verlopen dan drogere gebieden maar trager dan in gebieden met meer neerslag. Terminalia sericea heeft als pioniersoort een snellere groei dan Pterocarpus angolensis, Baikiaea plurijuga en Burkea africana. Analyse toont aan dat de groei van bomen in Kavango onder andere wordt beïnvloed door neerslag en dat de groeipatronen per soort sterkt verschillen