Backpack load affects lower limb muscle activity patterns of female hikers during prolonged load carriage

This study investigated the effect of prolonged load carriage on lower limb muscle activity displayed by female recreational hikers. Electromyography (EMG) signals from vastus lateralis (VL), biceps femoris (BF), semitendinosus (ST), tibialis anterior (TA) and gastrocnemius (GM) were recorded for fifteen female hikers carrying four loads (0%, 20%, 30% and 40% body weight (BW)) over 8 km. Muscle burst duration, muscle burst onset relative to initial contact and integrated EMG signals (iEMG) were calculated to evaluate muscle activity, whereas the shift in mean power frequency (MPF) was used to evaluate muscle fatigue. Increased walking distance significantly decreased the MPF of TA; decreased the iEMG for VL, ST and GM; and shortened VL muscle burst duration. Furthermore, carrying 20–40% BW loads significantly increased VL and GM iEMG and increased BF muscle burst duration, whereas a 40% BW load caused a later VL muscle burst onset. The differences observed in muscle activity with increased load mass seem to be adjustments aimed at maintaining balance and attenuating the increased loads placed on the lower limbs during gait. Based on the changes in muscle activity, a backpack load limit of 30% BW may reduce the risk of lower limb injury for female hikers during prolonged walking.     

Tissue-specific analysis of glycogen synthase kinase-3α (GSK-3α) in glucose metabolism: effect of strain variation

Background

Over-activity and elevated expression of glycogen synthase kinase-3 (GSK-3) has been implicated in the etiology of insulin resistance and Type 2 diabetes. Administration of specific GSK-3 inhibitors to diabetic or obese rodent models improves glycaemic control and insulin sensitivity. However, due to the indiscriminatory nature of these inhibitors, the relative contribution of the two isoforms of GSK-3 (GSK-3α and GSK-3β) is not known. Recently, we demonstrated that an out-bred strain of mice (ICR) lacking expression of GSK-3α in all tissues displayed improved insulin sensitivity and enhanced hepatic glucose metabolism. We also found that muscle (but not liver) inactivation of GSK-3β conferred insulin and glucose sensitization in an in-bred strain of mice (C57BL/6).

Methodology/Principal Findings

Here, we have employed tissue-specific deletion of GSK-3α, to examine the relative contribution of two insulin-sensitive tissues, muscle and liver, towards the insulin sensitization phenotype originally observed in the global GSK-3α KO animals. We found that mice in which GSK-3α has been inactivated in either skeletal-muscle or liver displayed no differences in glucose tolerance or insulin sensitivity compared to wild type littermates. Given the strain differences in our original analyses, we examined the insulin and glucose sensitivity of global GSK-3α KO animals bred onto a C57BL/6 background. These animals also revealed no significant differences in glucose metabolism/insulin sensitivity compared to their wild type littermates. Furthermore, deletion of hepatic GSK-3α on the out-bred, ICR background failed to reproduce the insulin sensitivity manifested by the global deletion of this isoform.

Conclusions/Significance

From these data we conclude that the improved insulin sensitivity and hepatic glucose homeostasis phenotype observed upon global inactivation of GSK-3α is strain-specific. We surmise that the insulin-sensitization observed in the out-bred strain of mice lacking GSK-3α is mediated by indirect means that do not require intrinsic function of GSK-3α in skeletal muscle and liver tissues.     

Correlation of clinical trachoma and infection in Aboriginal communities

Background

Trachoma is the leading infectious cause of blindness due to conjunctival infection with Chlamydia trachomatis. The presence of active trachoma and evidence of infection are poorly correlated and a strong immunologically-mediated inflammatory response means that clinical signs last much longer than infection. This population-based study in five Aboriginal communities endemic for trachoma in northern Australia compared a fine grading of clinical trachoma with diagnostic positivity and organism load.

Methods

A consensus fine grading of trachoma, based on clinical assessment and photograding, was compared to PCR, a lipopolysacharide (LPS)-based point-of-care (POC) and a 16S RNA-based nucleic acid amplification test (NAAT). Organism load was measured in PCR positive samples.

Results

A total of 1282 residents, or 85.2% of the study population, was examined. Taking the findings of both eyes, the prevalence of trachomatous inflammation-follicular (TF) in children aged 1–9 years was 25.1% (96/383) of whom 13 (13.7%) were PCR positive on the left eye. When clinical data were limited to the left eye as this was tested for PCR, the prevalence of TF decreased to 21.4% (82/383). The 301 TF negative children, 13 (4.3%) were PCR positive. The fine grading of active trachoma strongly correlated with organism load and disease severity (rs = 0.498, P = 0.0004). Overall, 53% of clinical activity (TF₁ or TF₂) and 59% of PCR positivity was found in those with disease scores less than the WHO simplified grade of TF.

Conclusion

Detailed studies of the pathogenesis, distribution and natural history of trachoma should use finer grading schemes for the more precise identification of clinical status. In low prevalence areas, the LPS-based POC test lacks the sensitivity to detect active ocular infection and nucleic acid amplification tests such as PCR or the 16S-RNA based NAAT performed better. Trachoma in the Aboriginal communities requires specific control measures.     

Mariprofundus ferrooxydans PV-1 the first genome of a marine Fe(II) oxidizing Zetaproteobacterium

Mariprofundus ferrooxydans PV-1 has provided the first genome of the recently discovered Zetaproteobacteria subdivision. Genome analysis reveals a complete TCA cycle, the ability to fix CO(2), carbon-storage proteins and a sugar phosphotransferase system (PTS). The latter could facilitate the transport of carbohydrates across the cell membrane and possibly aid in stalk formation, a matrix composed of exopolymers and/or exopolysaccharides, which is used to store oxidized iron minerals outside the cell. Two-component signal transduction system genes, including histidine kinases, GGDEF domain genes, and response regulators containing CheY-like receivers, are abundant and widely distributed across the genome. Most of these are located in close proximity to genes required for cell division, phosphate uptake and transport, exopolymer and heavy metal secretion, flagellar biosynthesis and pilus assembly suggesting that these functions are highly regulated. Similar to many other motile, microaerophilic bacteria, genes encoding aerotaxis as well as antioxidant functionality (e.g., superoxide dismutases and peroxidases) are predicted to sense and respond to oxygen gradients, as would be required to maintain cellular redox balance in the specialized habitat where M. ferrooxydans resides. Comparative genomics with other Fe(II) oxidizing bacteria residing in freshwater and marine environments revealed similar content, synteny, and amino acid similarity of coding sequences potentially involved in Fe(II) oxidation, signal transduction and response regulation, oxygen sensation and detoxification, and heavy metal resistance. This study has provided novel insights into the molecular nature of Zetaproteobacteria.     

Attitudinal and demographic predictors of measles-mumps-rubella vaccine (MMR) uptake during the UK catch-up campaign 2008-09: cross-sectional survey

Background and Objective

Continued suboptimal measles-mumps-rubella (MMR) vaccine uptake has re-established measles epidemic risk, prompting a UK catch-up campaign in 2008–09 for children who missed MMR doses at scheduled age. Predictors of vaccine uptake during catch-ups are poorly understood, however evidence from routine schedule uptake suggests demographics and attitudes may be central. This work explored this hypothesis using a robust evidence-based measure.

Design

Cross-sectional self-administered questionnaire with objective behavioural outcome.

Setting and Participants

365 UK parents, whose children were aged 5–18 years and had received <2 MMR doses before the 2008–09 UK catch-up started.

Main Outcome Measures

Parents'' attitudes and demographics, parent-reported receipt of invitation to receive catch-up MMR dose(s), and catch-up MMR uptake according to child''s medical record (receipt of MMR doses during year 1 of the catch-up).

Results

Perceived social desirability/benefit of MMR uptake (OR = 1.76, 95% CI = 1.09–2.87) and younger child age (OR = 0.78, 95% CI = 0.68–0.89) were the only independent predictors of catch-up MMR uptake in the sample overall. Uptake predictors differed by whether the child had received 0 MMR doses or 1 MMR dose before the catch-up. Receipt of catch-up invitation predicted uptake only in the 0 dose group (OR = 3.45, 95% CI = 1.18–10.05), whilst perceived social desirability/benefit of MMR uptake predicted uptake only in the 1 dose group (OR = 9.61, 95% CI = 2.57–35.97). Attitudes and demographics explained only 28% of MMR uptake in the 0 dose group compared with 61% in the 1 dose group.

Conclusions

Catch-up MMR invitations may effectively move children from 0 to 1 MMR doses (unimmunised to partially immunised), whilst attitudinal interventions highlighting social benefits of MMR may effectively move children from 1 to 2 MMR doses (partially to fully immunised). Older children may be best targeted through school-based programmes. A formal evaluation element should be incorporated into future catch-up campaigns to inform their continuing improvement.     

Meiotic control of the APC/C: similarities & differences from mitosis

The anaphase promoting complex is a highly conserved E3 ligase complex that mediates the destruction of key regulatory proteins during both mitotic and meiotic divisions. In order to maintain ploidy, this destruction must occur after the regulatory proteins have executed their function. Thus, the regulation of APC/C activity itself is critical for maintaining ploidy during all types of cell divisions. During mitotic cell division, two conserved activator proteins called Cdc20 and Cdh1 are required for both APC/C activation and substrate selection. However, significantly less is known about how these proteins regulate APC/C activity during the specialized meiotic nuclear divisions. In addition, both budding yeast and flies utilize a third meiosis-specific activator. In Saccharomyces cerevisiae, this meiosis-specific activator is called Ama1. This review summarizes our knowledge of how Cdc20 and Ama1 coordinate APC/C activity to regulate the meiotic nuclear divisions in yeast.     

Microarray analysis of the Df1 mouse model of the 22q11 deletion syndrome

The 22q11 deletion syndrome (22q11DS; DiGeorge/velo-cardio-facial syndrome) primarily affects the structures comprising the pharyngeal arches and pouches resulting in arch artery, cardiac, parathyroid, thymus, palatal and craniofacial defects. Tbx1 haploinsufficiency is thought to account for the main structural anomalies observed in the 22q11DS. The Df1 deleted mouse provides a model for 22q11DS, the deletion reflecting Tbx1 haploinsufficiency in the context of the deletion of 21 adjacent genes. We examined the expression of genes in Df1 embryos at embryonic day (E) 10.5, a stage when the arch-artery phenotype is fully penetrant. Our aims were threefold, with our primary aim to identify differentially regulated genes. Second, we asked whether any of the genes hemizygous in Df1 were dosage compensated to wild type levels, and third we investigated whether genes immediately adjacent to the deletion were dysregulated secondary to a position effect. Utilisation of oligonulceotide arrays allowed us to achieve our aims with 9 out of 12 Df1 deleted genes passing the stringent statistical filtering applied. Several genes involved in vasculogenesis and cardiogenesis were validated by real time quantitative PCR (RTQPCR), including Connexin 45, a gene required for normal vascular development, and Dnajb9 a gene implicated in microvascular differentiation. There was no evidence of any dosage compensation of deleted genes, suggesting this phenomenon is rare, and no dysregulation of genes mapping immediately adjacent to the deletion was detected. However Crkl, another gene implicated in the 22q11DS phenotype, was found to be downregulated by microarray and RTQPCR.     

The calcineurin inhibitor gossypol impairs growth, cell signalling and development in Dictyostelium discoideum

The Dictyostelium genome harbors single copy genes for both the catalytic and regulatory subunits of the Ca2+/calmodulin-dependent protein phosphatase calcineurin. Since molecular genetic approaches to reduce the expression of these genes have failed so far, we attempted to pharmacologically target calcineurin activity in vivo by using the recently described calcineurin inhibitor, gossypol. Up-regulation of expression of the gene for the Ca2+-ATPase PAT1 in conditions of Ca2+ stress was reduced by gossypol. Dictyostelium wild-type cells treated with 12.5-100 microM gossypol showed reduced growth rates and impaired development. In addition, cell signalling was affected. A cell line that overproduces the catalytic subunit of calcineurin was more resistant to gossypol.     

Shape-specific nucleotide binding of single-stranded RNA by the GLD-1 STAR domain

Proteins containing the STAR RNA-binding domain fulfill vital roles in RNA biogenesis, yet a detailed understanding of STAR domain RNA binding specificity is lacking. In Caenorhabditis elegans, the STAR protein GLD-1 directly binds the 28 nucleotide recognition element TGE within the 3' untranslated region of tra-2 mRNA. The GLD-1:TGE interaction promotes translational silencing of tra-2 mRNA, marking a pivotal event in the spermatogenesis to oogenesis switch in C.elegans hermaphrodites. By measuring the binding affinities of both GLD-1 and TGE mutants, we have explored the molecular determinants of STAR domain specificity. Site-directed GLD-1 mutants were guided by sequence homology with human splicing factor 1 (SF1), for which an RNA:protein complex structure is available in the work done by Liu et al. The RNA binding affinity of 11 mutant GLD-1 proteins was measured, and their binding specificity was assessed with a series of TGE RNAs containing natural or modified nucleotides. This combinatorial analysis of both RNA and protein mutants revealed a diverse array of specificities of individual nucleotide-binding pockets along the interface. At nucleotide position 18, adenosine appears to be specified by the overall shape of a pocket lined with aliphatic side-chains. At position 19, the high preference for cytidine is dependent on both the length of an amino acid side-chain and the identity of terminal functional groups. The nucleotide 21 binding pocket exhibits low discrimination for cytidine, and accommodates most nucleobases. The highly hydrophobic binding interface and apparent small number of hydrogen bonding read-out interactions at these positions is consistent with our finding that few amino acids seem to function individually in establishing binding specificity. Rather, specificity is conferred by the shape of the nucleotide-binding pocket. Our data provide the first detailed, quantitative analysis of the STAR domain, and highlight features of STAR:RNA recognition that are distinct among single-stranded RNA-binding proteins.