Presomal morphology and development of Prosthorhynchus formosus,Prosthenorchis elegans,and Moniliformis dubius (Acanthocephala)

Larvae removed at one-day intervals from laboratory infected intermediate hosts provided material for a comparative study of presomal development in Prosthorhynchus formosus (Van Cleave, '18) Travassos, '26, Prosthenorchis elegans (Diesing, 1851) Travassos, '15, and Moniliformis dubius Meyer, '33. Acanthellae begin development soon after entering intermediate hosts' hemocoels, and by the 18th day all three species possess three nuclear masses representing primordia of the proboscis, proboscis receptacle and ganglion, and trunk musculature and genitalia. Presomal development of P. formosus and P. elegans results in structures concurring with morphology of other adult palaeacanthocephalans and archiacanthocephalans. Development of M. dubius, however, differs from that of other archiacanthocephalans in that the muscular receptacle wall lines the entire surface of the nonmuscular sheath, failing to form a ventral cleft characteristic of other archiacanthocephalans. Unlike receptacle protrusor muscles of other archiacanthocephalan species, those of M. dubius spiral around the receptacle as they extend posteriad to attach individually to a pouchlike, muscular thickening at the receptacle's base. These protrusor muscles are distinct from the receptacle wall, as attested by their development alongside neck retractor muscles, not from the receptacle primordium, and the manner in which they are left to trail behind the receptacle when it is drawn anteriorly into the proboscis during larval development. The proboscis receptacle of M. dubius should not be thought of as being double-walled, as envisioned by previous workers.     

Cost-Effectiveness and Efficacy of spa,SCCmec, and PVL Genotyping of Methicillin-Resistant Staphylococcus aureus as Compared to Pulsed-Field Gel Electrophoresis

Pulsed-field gel electrophoresis (PFGE) is a valuable molecular typing assay used for methicillin-resistant Staphylococcus aureus (MRSA) surveillance and genotyping. However, there are several limitations associated with PFGE. In Alberta, Canada, the significant increase in the number of MRSA isolates submitted to the Provincial Laboratory for Public Health (ProvLab) for PFGE typing led to the need for an alternative genotyping method. In this study, we describe the transition from PFGE to Staphylococcus protein A (spa), Staphylococcal cassette chromosome (SCCmec), and Panton-Valentine leukocidin (PVL) typing. A total of 1915 clinical MRSA isolates collected from 2005 to 2009 were used to develop and validate an algorithm for assigning PFGE epidemic types using spa, SCCmec, and PVL typing and the resulting data was used to populate a new Alberta MRSA typing database. An additional 12620 clinical MRSA isolates collected from 2010 to 2012 as part of ongoing routine molecular testing at ProvLab were characterized using the new typing algorithm and the Alberta MRSA typing database. Switching to spa, SCCmec, and PVL from PFGE typing substantially reduced hands-on and turn-around times while maintaining historical PFGE epidemic type designations. This led to an approximate $77,000 reduction in costs from 2010 to 2012. PFGE typing is still required for a small subset of MRSA isolates that have spa types that are rare, novel, or associated with more than one PFGE epidemic type.     

Do intraspecific life history patterns follow interspecific predictions? A test using latitudinal variation in ringed seals

Mammals adapted to unpredictable and low-energy environments often evolve a “bet-hedging” life history strategy characterized by less costly reproductive outputs over a longer and slower-growing life. In contrast, species adapted to more predictable (i.e., low variation) and higher energy environments may evolve greater fecundity over a shorter and faster-growing life. We tested whether this known interspecific pattern also occurs within a species. We compared life history traits of the ringed seal (Pusa hispida) in the Canadian High Arctic to those closer to the southern limit of the species' circumpolar distribution. We found that northern seals grew slower than southern seals (Brody growth coefficient), achieved a greater asymptotic body weight (82 and 69 kg vs. 74 and 54 kg female and male, respectively), reached sexual maturity later (6.1 years vs. 4.5 years), had lower fecundity (1.8 years vs. 1.3 years interbirth interval), longer average lifespan (5 years vs. 3 years median age), and greater movements (1,269 vs. 681 km). Mating systems also likely differed with northern seals showing morphological evidence of a promiscuous mating system with potential sperm competition as indicated by greater relative testes size. The northern region was also characterized by more unpredictable environmental timing of seasonal events, such as spring sea ice breakup. Life history variation between the intraspecific groups of seals appears to agree with interspecific patterns and provides a better understanding of how species' life history parameters shift in concert with environmental conditions.     

Microdiversity and temporal dynamics of marine bacterial dimethylsulfoniopropionate genes

Dimethylsulfoniopropionate (DMSP) is an abundant organic sulfur metabolite produced by many phytoplankton species and degraded by bacteria via two distinct pathways with climate-relevant implications. We assessed the diversity and abundance of bacteria possessing these pathways in the context of phytoplankton community composition over a 3-week time period spanning September–October, 2014 in Monterey Bay, CA. The dmdA gene from the DMSP demethylation pathway dominated the DMSP gene pool and was harboured mostly by members of the alphaproteobacterial SAR11 clade and secondarily by the Roseobacter group, particularly during the second half of the study. Novel members of the DMSP-degrading community emerged from dmdA sequences recovered from metagenome assemblies and single-cell sequencing, including largely uncharacterized gammaproteobacteria and alphaproteobacteria taxa. In the DMSP cleavage pathway, the SAR11 gene dddK was the most abundant early in the study, but was supplanted by dddP over time. SAR11 members, especially those harbouring genes for both DMSP degradation pathways, had a strong positive relationship with the abundance of dinoflagellates, and DMSP-degrading gammaproteobacteria co-occurred with haptophytes. This in situ study of the drivers of DMSP fate in a coastal ecosystem demonstrates for the first time correlations between specific groups of bacterial DMSP degraders and phytoplankton taxa.     

Lower extremity joint moments during carrying tasks in children

Farm youth often carry loads that are proportionally large and/or heavy, and field measurements have determined that these tasks are equivalent to industrial jobs with high injury risks. The purpose of this study was to determine the effects of age, load amount, and load symmetry on lower extremity joint moments during carrying tasks. Three age groups (8-10 years, 12-14 years, adults), three load amounts (0%, 10%, 20% BW), and three load symmetry levels (unilateral large bucket, unilateral small bucket, bilateral small buckets) were tested. Inverse dynamics was used to determine maximum ankle, knee, and hip joint moments. Ankle dorsiflexion, ankle inversion, ankle eversion, knee adduction, and hip extension moments were significantly higher in 8-10 and 12-14 year olds. Ankle plantar flexion, ankle inversion, knee extension, and hip extension moments were significantly increased at 10% and 20% BW loads. Knee and hip adduction moments were significantly increased at 10% and 20% BW loads when carrying a unilateral large bucket. Of particular concern are increased ankle inversion and eversion moments for children, along with increased knee and hip adduction moments for heavy, asymmetrical carrying tasks. Carrying loads bilaterally instead of unilaterally avoided increases in knee and hip adduction moments with increased load amount.     

Functional Determinants of Temperature Adaptation in Enzymes of Cold- versus Warm-Adapted Mussels (Genus Mytilus)

Temperature is a strong selective force on the evolution of proteins due to its effects on higher orders of protein structure and, thereby, on critical protein functions like ligand binding and catalysis. Comparisons among orthologous proteins from differently thermally adapted species show consistent patterns of adaptive variation in function, but few studies have examined functional adaptation among multiple structural families of proteins. Thus, with our present state of knowledge, it is difficult to predict what fraction of the proteome will exhibit adaptive variation in the face of temperature increases of a few to several degrees Celsius, that is, temperature increases of the magnitude predicted by models of global warming. Here, we compared orthologous enzymes of the warm-adapted Mediterranean mussel Mytilus galloprovincialis and the cold-adapted Mytilus trossulus, a native of the North Pacific Ocean, species whose physiologies exhibit significantly different responses to temperature. We measured the effects of temperature on the kinetics (Michaelis-Menten constant-K(m)) of five enzymes that are important for ATP generation and that represent distinct protein structural families. Among phosphoglucomutase (PGM), phosphoglucose isomerase (PGI), pyruvate kinase (PK), phosphoenolpyruvate carboxykinase (GTP) (PEPCK), and isocitrate dehydrogenase (NADP) (IDH), only IDH orthologs showed significantly different thermal responses of K(m) between the two species. The K(m) of isocitrate of M. galloprovincialis-IDH was intrinsically lower and more thermally stable than that of M. trossulus-IDH and thus had higher substrate affinity at high temperatures. Two amino acid substitutions account for the functional differences between IDH orthologs, one of which allows for more hydrogen bonds to form near the mobile region of the active site in M. galloprovincialis-IDH. Taken together, our findings cast light on the targets of adaptive evolution in the context of climate change; only a minority of proteins might adapt to small changes in temperature, and these adaptations may involve only small changes in sequence.     

Spontaneous entrapment of polynucleotides upon electrostatic interaction with ethanol-destabilized cationic liposomes

This study describes the effect of ethanol and the presence of poly(ethylene) glycol (PEG) lipids on the interaction of nucleotide-based polyelectrolytes with cationic liposomes. It is shown that preformed large unilamellar vesicles (LUVs) containing a cationic lipid and a PEG coating can be induced to entrap polynucleotides such as antisense oligonucleotides and plasmid DNA in the presence of ethanol. The interaction of the cationic liposomes with the polynucleotides leads to the formation of multilamellar liposomes ranging in size from 70 to 120 nm, only slightly bigger than the parent LUVs from which they originated. The degree of lamellarity as well as the size and polydispersity of the liposomes formed increases with increasing polynucleotide-to-lipid ratio. A direct correlation between the entrapment efficiency and the membrane-destabilizing effect of ethanol was observed. Although the morphology of the liposomes is still preserved at the ethanol concentrations used for entrapment (25-40%, v/v), entrapped low-molecular-weight solutes leak rapidly. In addition, lipids can flip-flop across the membrane and exchange rapidly between liposomes. Furthermore, there are indications that the interaction of the polynucleotides with the cationic liposomes in ethanol leads to formation of polynucleotide-cationic lipid domains, which act as adhesion points between liposomes. It is suggested that the spreading of this contact area leads to expulsion of PEG-ceramide and triggers processes that result in the formation of multilamellar systems with internalized polynucleotides. The high entrapment efficiencies achieved at high polyelectrolyte-to-lipid ratios and the small size and neutral character of these novel liposomal systems are of utility for liposomal delivery of macromolecular drugs.