The Feet of Overweight and Obese Young Children: Are They Flat or Fat?

Objective: The purpose of this study was to determine whether the flat feet displayed by young obese and overweight children are attributable to the presence of a thicker midfoot plantar fat pad or a lowering of the longitudinal arch relative to that in non‐overweight children. Research Methods and Procedures: Foot anthropometry, an arch index derived from plantar footprints, and midfoot plantar fat pad thickness measured by ultrasound were obtained for 19 overweight/obese preschool children (mean age, 4.3 ± 0.9 years; mean height, 1.07 ± 0.1 m; mean BMI, 18.6 ± 1.2 kg/m²) and 19 non‐overweight children matched for age, height, and sex (mean age, 4.3 ± 0.7 years; mean height, 1.05 ± 0.1 m; mean BMI, 15.7 ± 0.7 kg/m²). Results: Independent t tests revealed no significant between‐subject group differences (p = 0.39) in the thickness of the midfoot plantar fat pad. However, the overweight/obese children had a significantly lower plantar arch height (0.9 ± 0.3 cm) than their non‐overweight counterparts (1.1 ± 0.2 cm; p = 0.04). Discussion: The lower plantar arch height found in the overweight/obese children suggests that the flatter feet characteristic of overweight/obese preschool children may be caused by structural changes in their foot anatomy. It is postulated that these structural changes, which may adversely affect the functional capacity of the medial longitudinal arch, might be exacerbated if excess weight bearing continues throughout childhood and into adulthood.     

Structural correlation between collagen VI microfibrils and collagen VI banded aggregates

Collagen VI is a component of the extracellular matrix that is able to form structural links with cells. Collagen VI monomers cross-link into tetramers that come together to form long molecular chains known as microfibrils. Collagen VI tetramers are also the most likely candidates for the formation of banded aggregates with an axial periodicity of about 105 nm that are seen in the retinas of people suffering from age-related macular degeneration and Sorsby's fundus dystrophy, in the vitreous of patients with full thickness macular holes and in the intervertebral discs of normal individuals. Here, a protocol is developed to carry out a structural comparison between the microfibrils, which are known to be made of collagen VI tetramers, and the banded aggregates. The comparison shows that the banded aggregates are easily explained as being a lateral assembly of microfibrils, thus supporting the hypothesis that they too are made of collagen VI. Understanding the role played by the collagen VI aggregates in normal and pathological conditions will help to throw light on the pathologies with which they are associated.     

Molecular phylogeny of the assassin bugs (Hemiptera: Reduviidae), based on mitochondrial and nuclear ribosomal genes

The first comprehensive cladistic analysis of Reduviidae, the assassin bugs, based on molecular data is presented and discussed in the context of a recently-published morphological analysis. Assassin bugs are essential components of ecosystems, but also important in agriculture and medicine. Sampling included 94 taxa (89 Reduviidae, 5 outgroups) in 15 subfamilies and 24 tribes of Reduviidae and is based on 3300 base pairs of mitochondrial (16S) and nuclear (18S, 28SD2, 28SD3-5) ribosomal DNA. Partitions of the dataset were aligned using different algorithms implemented in MAFFT and the combined dataset was analyzed using parsimony, partitioned maximum likelihood and partitioned Bayesian criteria. Clades recovered in all analyses, independent of alignment and analytical method, comprise: Cimicomorpha and Reduviidae; Hammacerinae; Harpactorinae; Apiomerini; Peiratinae; Phymatinae; Salyavatinae; Triatominae; Phymatinae + Holoptilinae; the higher Reduviidae (Reduviidae excluding Hammacerinae and the Phymatine Complex); Ectrichodiinae + Tribelocephalinae; (Triatominae + Zelurus) + Stenopodainae. Hammacerinae are rejected as sister group to all remaining Reduviidae in all analyses, as is the monophyly of Reduviinae, Emesinae and Harpactorini. High support values for Triatominae imply that blood-feeding has evolved only once within Reduviidae. Stenopodainae and part of Reduviinae are discussed as close relatives to Triatominae.     

Epidemiological investigation into the re-emergence and control of an outbreak of infectious salmon anaemia in the Shetland Islands, Scotland

Infectious salmon anaemia (ISA) is an orthomyxoviral disease, primarily affecting marine-phase farmed Atlantic salmon, which can result in high levels of mortality. ISA first emerged in Norway in the 1980s and subsequently has occurred in Canada, the USA, the Faeroe Islands and Chile. An outbreak occurred in Scotland in 1998-1999, but was eradicated at a cost of over pounds sterling 20M. The epidemiology of a new outbreak of ISA in the Scottish Shetland Islands during 2008-2009 is described. Six sites have been confirmed ISA-positive. Spread of the virus via transport of fish between marine sites, harvest vessels, smolts and wild fish appears to have been of little or no importance, with spread primarily associated with marine water currents. The use of management areas by Marine Scotland to control the event appears to have been effective in restricting spread to a small area. This localised outbreak contrasts with the 1998-1999 outbreak that spread over a wide geographic area with transported fish and harvest vessels. The development and application of industry codes of good practice, good husbandry and biosecurity practices, limited marine site-to-site movement of live fish and improved disinfection of vessels and processing plant waste that occurred subsequent to the 1998-1999 outbreak may explain the localised spread of infection in 2008-2009. Depopulation of confirmed sites has been achieved within 7 wk (mean = 3.7 wk); however, it is likely that subclinical infection persisted undetected for months on at least 1 site. The origin of the 2008-2009 outbreak remains unknown. Potential sources include evolution from a local reservoir of infection or importation. Synchronous fallowing of management areas, with good husbandry and biosecurity, reduces the risk of ISA recurring. Movement of fish between sites in different management areas represents the greatest risk of regional-scale spread, should this occur.     

Atomistic basis for the on–off signaling mechanism in SAM-II riboswitch

Many bacterial genes are controlled by metabolite sensing motifs known as riboswitches, normally located in the 5′ un-translated region of their mRNAs. Small molecular metabolites bind to the aptamer domain of riboswitches with amazing specificity, modulating gene regulation in a feedback loop as a result of induced conformational changes in the expression platform. Here, we report the results of molecular dynamics simulation studies of the S-adenosylmethionine (SAM)-II riboswitch that is involved in regulating translation in sulfur metabolic pathways in bacteria. We show that the ensemble of conformations of the unbound form of the SAM-II riboswitch is a loose pseudoknot structure that periodically visits conformations similar to the bound form, and the pseudoknot structure is only fully formed upon binding the metabolite, SAM. The rate of forming contacts in the unbound form that are similar to that in the bound form is fast. Ligand binding to SAM-II alters the curvature and base-pairing of the expression platform that could affect the interaction of the latter with the ribosome.     

A vitalistic model to describe the thermal inactivation ofListeria monocytogenes

Summary Thermal inactivation of microorganisms has traditionally been described as log-linear in nature, that is the reduction in log numbers of survivors decreases in a linear manner with time. This is despite a plethora of data that shows consistent deviations from such kinetics for a wide range of organisms and conditions and that cannot be accounted for by experimental artifacts. Existing thermal death models fail to take such deviations into account and also fail to quantify the effects of heating menstruum on heat sensitivity. The thermal inactivation ofListeria monocytogenes ATCC 19115 has been investigated using a factorially-designed experiment comparing 45 conditions of salt concentration, pH value and temperature. Heating was carried out using a Submerged Coil heating apparatus that minimized experimental artifacts. Low pH values increased, whilst high salt concentrations decreased heat sensitivity. Results showed a significant and consistent deviation from log-linear kinetics, particularly at low temperatures. A number of distributions were tested for suitability to describe the variability of heat sensitivity within the population of heated cells (vitalistic approach). The use of the logistic function and log dose (log time) allowed the development of an accurate unifying predictive model across the whole range of heating conditions. It is proposed that this approach should be tested as a generalized modeling technique for death kinetics of vegetative bacteria.     

Novel haem co-ordination variants of flavocytochrome P450BM3

Bacillus megaterium flavocytochrome P450 BM3 is a catalytically self-sufficient fatty acid hydroxylase formed by fusion of soluble NADPH-cytochrome P450 reductase and P450 domains. Selected mutations at residue 264 in the haem (P450) domain of the enzyme lead to novel amino acid sixth (distal) co-ordination ligands to the haem iron. The catalytic, spectroscopic and thermodynamic properties of the A264M, A264Q and A264C variants were determined in both the intact flavocytochromes and haem domains of P450 BM3. Crystal structures of the mutant haem domains demonstrate axial ligation of P450 haem iron by methionine and glutamine ligands trans to the cysteine thiolate, creating novel haem iron ligand sets in the A264M/Q variants. In contrast, the crystal structure of the A264C variant reveals no direct interaction between the introduced cysteine side chain and the haem, although EPR data indicate Cys(264) interactions with haem iron in solution. The A264M haem potential is elevated by comparison with wild-type haem domain, and substrate binding to the A264Q haem domain results in a approximately 360 mV increase in potential. All mutant haem domains occupy the conformation adopted by the substrate-bound form of wild-type BM3, despite the absence of added substrate. The A264M mutant (which has higher dodecanoate affinity than wild-type BM3) co-purifies with a structurally resolved lipid. These data demonstrate that a single mutation at Ala(264) is enough to perturb the conformational equilibrium between substrate-free and substrate-bound P450 BM3, and provide firm structural and spectroscopic data for novel haem iron ligand sets unprecedented in nature.     

Determinants of Fluidlike Behavior and Effective Viscosity in Cross-Linked Actin Networks

The actin cortex has a well-documented ability to rapidly remodel and flow while maintaining long-range connectivity, but how this is achieved remains poorly understood. Here, we use computer simulations to explore how stress relaxation in cross-linked actin networks subjected to extensional stress depends on the interplay between network architecture and turnover. We characterize a regime in which a network response is nonaffine and stress relaxation is governed by the continuous dissipation of elastic energy via cyclic formation, elongation, and turnover of tension-bearing elements. Within this regime, for a wide range of network parameters, we observe a constant deformation (creep) rate that is linearly proportional to the rate of filament turnover, leading to a constant effective viscosity that is inversely proportional to turnover rate. Significantly, we observe a biphasic dependence of the creep rate on applied stress: below a critical stress threshold, the creep rate increases linearly with applied stress; above that threshold, the creep rate becomes independent of applied stress. We show that this biphasic stress dependence can be understood in terms of the nonlinear force-extension behavior of individual force-transmitting network elements. These results have important implications for understanding the origins and control of viscous flows both in the cortex of living cells and in other polymer networks.