Bergmann's rule states that, within species of mammals, individuals tend to be larger in cooler environments. However, the validity of the rule has been debated. We examined the relationship between size and latitude as well as size and temperature within various species of mammals. We also tested the idea that smaller mammals follow Bergmann's rule more strongly than larger mammals, as expected if heat conservation is the cause of the rule. When all studies were included, the percentage of species showing a positive correlation between size and latitude was significantly >50% (78 of 110 species). Similarly, the percentage of species showing a negative correlation between size and temperature was significantly >50% (48 of 64). Analyses using only significant studies or only studies that sampled extensively also support Bergmann's rule. The size-latitude and size-temperature trends were consistent within all orders and most families for which data are available. We did not find support for the hypothesis that smaller mammals conform more strongly to Bergmann's rule than larger mammals. Thus, we found broad support for Bergmann's rule as a general trend for mammals; however, our analyses do not support heat conservation as the explanation.
Background: Surgical mortality data are collected routinely in high-income countries, yet virtually no low-or middle-income countries have outcome surveillance in place. The aim was prospectively to collect worldwide mortality data following emergency abdominal surgery, comparing findings across countries with a low, middle or high Human Development Index (HDI).Methods: This was a prospective, multicentre, cohort study. Self-selected hospitals performing emergency surgery submitted prespecified data for consecutive patients from at least one 2-week interval during July to December 2014. Postoperative mortality was analysed by hierarchical multivariable logistic regression.
Axonal growth, guidance and synapse formation are controlled by receptors on neuronal growth cones that can recognize positive and inhibitory cues in the local microenvironment. Four well characterized receptor systems are known that recognize the growth-promoting activities associated with the extracellular matrix and the membranes of cells such as astrocytes, muscle cells and Schwann cells; these are the integrins and the homophilically binding cell adhesion molecules neural-cell adhesion molecule (NCAM), N-cadherin and L1 (refs 5-12). Alternative splicing generates 20-30 isoforms of NCAM and these can also be differentially glycosylated. There are two sites where alternative splicing changes the extracellular structure of membrane-bound NCAM and one of these (the MSD1 region) does not obviously affect function. Here we report that the variable alternatively spliced exon (VASE) in immunoglobulin domain 4 downregulates the neurite outgrowth-promoting activity of NCAM. The high level of VASE expression in the adult central as compared with peripheral nervous system could contribute to the poor regenerative capacity of the former.
Aims To investigate the pharmacokinetics of the antimalarial artemisinin in the field setting using sparsely collected data. Methods Artemisinin concentrations were determined by h.p.l.c. in a total of 107 capillary plasma samples collected on the first day and in 33 samples on the last day of a 5-day oral artemisinin regimen of 10 mg kg −1 day −1 in 23 paediatric (aged 2-12 years) and 31 adult (aged 16-45 years) Vietnamese patients with uncomplicated falciparum malaria. The population model was developed using NONMEM, incorporating interoccasion variability and accounting for a systematic change in artemisinin pharmacokinetics with time, modelled as a change in oral bioavailability. Results Clinical efficacy, in terms of parasite clearance and fever subsidence times, was comparable between children and adults. A one-compartment model with separate pharmacokinetic estimates for children and adults was found best to describe the disposition of artemisinin after oral administration. The population estimates for artemisinin clearance and distribution volume, respectively, were 432 l h −1 and 1600 l for adults and 14.4 l h −1 kg −1 and 37.9 l kg −1 for children, with an intersubject variability (collectively for both age groups) of 45% and 104%, respectively. The oral bioavailability was estimated to decrease from Day 1 to Day 5 by a factor of 6.9, a value found to be similar for children and adults. Conclusions Artemisinin pharmacokinetic data was successfully derived in both paediatric and adult patients using 2-3 capillary blood samples taken in conjunction with parasitaemia monitoring. This study's findings advocated the dosing of artemisinin to children according to bodyweight and to adults according to a standard dose.
Tree species in tropical rain forests exhibit a rich panoply of spatial patterns that beg ecological explanation. The analysis of tropical census data typically relies on spatial statistics, which quantify the average aggregation tendency of a species. In this article we develop a cluster-based approach that complements traditional spatial statistics in the exploration and analysis of ecological hypotheses for spatial pattern. We apply this technique to six study species within a fully mapped 50-ha forest census in peninsular Malaysia. For each species we identify the scale(s) of spatial aggregation and the corresponding tree clusters. We study the correlation between cluster locations and abiotic variables such as topography. We find that the distribution of cluster sizes exhibits equilibrium and nonequilibrium behavior depending on species life history. The distribution of tree diameters within clusters also varies according to species life history. At different spatial scales, we find evidence for both niche-based and dispersal-limited processes producing spatial pattern. Our methodology for identifying scales of aggregation and clusters is general; we discuss the method's applicability to spatial problems outside of tropical plant ecology.
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