A stable isotope trace method to measure silicic acid uptake by marine phytoplankton.

A tracer method is described that uses the stable isotope ³⁰Si to measure rates of silicic acid uptake by diatom cultures and natural populations of marine phytoplankton. The method involves (i) incubation of organisms requiring silicic acid for growth in the presence of ³⁰Si-labeled silicic acid, (ii) collection of the resulting particulate silicon, (iii) conversion of the particulate silicon to BaSiF₆, (iv) determination of the ³⁰Si content of BaSiF₆ by solid sample mass spectrometry, and (v) calculation of the uptake rate from the ³⁰Si enrichment of the particulate matter during the incubation. The maximum overall error in the uptake rate measurement is ±10%.     

Electrophoretic protein analysis in the conditioned captive wild coyote, Canis latrans

Total protein, albumin and serum protein values were determined on 19 male and 14 female captive, vaccinated, wild coyotes. Male coyotes had significantly higher total protein, alpha 1 and alpha 2 globulin levels than female coyotes. Captive, wild coyotes had lower values for total protein, albumin and beta globulins, and higher values for alpha 2 and gamma globulins than similar values for laboratory dogs. Albumin values determined by bromcresol green were slightly higher than values derived by electrophoresis. This difference was non-significant.     

Contrasting Patterns of Genetic Differentiation among Blackcaps (Sylvia atricapilla) with Divergent Migratory Orientations in Europe

Migratory divides are thought to facilitate behavioral, ecological, and genetic divergence among populations with different migratory routes. However, it is currently contentious how much genetic divergence is needed to maintain distinct migratory behavior across migratory divides. Here we investigate patterns of neutral genetic differentiation among Blackcap (Sylvia atricapilla) populations with different migratory strategies across Europe. We compare the level of genetic divergence of populations migrating to southwestern (SW) or southeastern (SE) wintering areas with birds wintering in the British Isles following a recently established northwesterly (NW) migration route. The migratory divide between SW and SE wintering areas can be interpreted as a result of a re-colonization process after the last glaciation. Thus we predicted greater levels of genetic differentiation among the SW/SE populations. However, a lack of genetic differentiation was found between SW and SE populations, suggesting that interbreeding likely occurs among Blackcaps with different migratory orientations across a large area; therefore the SW/SE migratory divide can be seen as diffuse, broad band and is, at best, a weak isolating barrier. Conversely, weak, albeit significant genetic differentiation was evident between NW and SW migrants breeding sympatrically in southern Germany, suggesting a stronger isolating mechanism may be acting in this population. Populations located within/near the SW/SE contact zone were the least genetically divergent from NW migrants, confirming NW migrants likely originated from within the contact zone. Significant isolation-by-distance was found among eastern Blackcap populations (i.e. SE migrants), but not among western populations (i.e. NW and SW migrants), revealing different patterns of genetic divergence among Blackcap populations in Europe. We discuss possible explanations for the genetic structure of European Blackcaps and how gene flow influences the persistence of divergent migratory behaviors.     

Haemosporidian parasitism in the blackcap Sylvia atricapilla in relation to spring arrival and body condition

Parasites can exert strong selection on hosts. Throughout the year migrants are exposed to different sets of parasites, which may affect life history traits such as migratory schedules. Here, we studied the relationship between parasite infection and arrival date of blackcaps Sylvia atricapilla to their breeding grounds in Germany throughout a period of six years (2007–2012). We used two data sets, one that included all blackcaps and one that included only recaptured birds. We assesed whether parasites influence spring arrival to breeding grounds, and for the recaptured data set, we analysed temporal variation in parasitism (i.e. infection status and parasitaemia) throughout the breeding season. We used both microscopy and PCR (a fragment of ? 479 bp of the mtDNA cyt b) to determine haemosporidian infection. Blackcaps were mostly infected with Haemoproteus parabelopolskyi (lineages SYAT01 and SYAT02). Infection status, but not parasitaemia, was constant through time for individual birds; meaning that once a bird is infected, it most likely will retain the infection for life. We found that infection by haemosporidian parasites has no relationship to arrival date in this blackcap population; however, infection by H. parabelopolskyi has a marginally significant effect on arrival date of recaptured blackcaps, somewhat delaying their arrival to breeding grounds. Birds captured later in the season were more likely to be infected than those from early spring, and parasitaemia was frequently lower in birds captured earlier in the season compared to those captured later (summer).     

Associations between dru Types and SCCmec Cassettes

Molecular typing is an important tool in the investigation of methicillin resistant Staphylococcus aureus (MRSA) outbreaks and in following the evolution of MRSA. The staphylococcal cassette chromosome mec (SCCmec) contains a hypervariable region with a variable number of 40 bp repeats named direct repeat units (dru). The dru region has been suggested as a supplementary typing method for MRSA and an international nomenclature exists. The purpose of this study was to investigate the diversity and variability of the dru region in a diverse collection of MRSA. We studied 302 MRSA isolates harbouring SCCmec types I to VI. The isolates represented a broad genetic background based on Staphylococcal protein A (spa) typing and multilocus sequence typing (MLST) and included 68 isolates (68 patients) from an outbreak with t024-ST8-IVa and 26 isolates from the same patient. Sequencing identified 53 dru types (dt) in 283 isolates, while eighteen isolates contained no dru repeats and one isolate resisted sequencing. The most common dru type, dt10a, was present in 53% of the sequenced isolates and was found in all SCCmec types, except type II. Seven (10%) of the 68 epidemiologically related patients had isolates with dru type variants indicating that dru typing is not useful as a first line epidemiological typing tool. However, MRSA isolates cultured from a single patient over a three year period exhibited a single dru type. The finding of dt10a in most SCCmec types suggests that dru and mecA originate from the same Staphylococcus species.     

Subpopulations of Staphylococcus aureus Clonal Complex 121 Are Associated with Distinct Clinical Entities

We investigated the population structure of Staphylococcus aureus clonal complex CC121 by mutation discovery at 115 genetic housekeeping loci from each of 154 isolates, sampled on five continents between 1953 and 2009. In addition, we pyro-sequenced the genomes from ten representative isolates. The genome-wide SNPs that were ascertained revealed the evolutionary history of CC121, indicating at least six major clades (A to F) within the clonal complex and dating its most recent common ancestor to the pre-antibiotic era. The toxin gene complement of CC121 isolates was correlated with their SNP-based phylogeny. Moreover, we found a highly significant association of clinical phenotypes with phylogenetic affiliations, which is unusual for S. aureus. All isolates evidently sampled from superficial infections (including staphylococcal scalded skin syndrome, bullous impetigo, exfoliative dermatitis, conjunctivitis) clustered in clade F, which included the European epidemic fusidic-acid resistant impetigo clone (EEFIC). In comparison, isolates from deep-seated infections (abscess, furuncle, pyomyositis, necrotizing pneumonia) were disseminated in several clades, but not in clade F. Our results demonstrate that phylogenetic lineages with distinct clinical properties exist within an S. aureus clonal complex, and that SNPs serve as powerful discriminatory markers, able to identify these lineages. All CC121 genomes harboured a 41-kilobase prophage that was dissimilar to S. aureus phages sequenced previously. Community-associated MRSA and MSSA from Cambodia were extremely closely related, suggesting this MRSA arose in the region.     

Eco1 is important for DNA damage repair in S. cerevisiae

The cohesin network has an essential role in chromosome segregation, but also plays a role in DNA damage repair. Eco1 is an acetyltransferase that targets subunits of the cohesin complex and is involved in both the chromosome segregation and DNA damage repair roles of the network. Using budding yeast as a model system, we find that mutations in Eco1, including a genocopy of a human Roberts syndrome allele, do not cause gross defects in chromosome cohesion. We examined how mitotic and meiotic DNA damage repair is affected by mutations in Eco1. Strains containing mutations in Eco1 are sensitive to DNA damaging agents that cause double-strand breaks, such as X-rays and bleomycin. While meiotic crossing over is relatively unaffected in strains containing the Roberts mutation, reciprocal mitotic crossovers occur with extremely low frequency in this mutant background. Our results suggest that Eco1 promotes the reciprocal exchange of chromosome arms and maintenance of heterozygosity during mitosis.Key words: cohesin, recombination, double-strand break, acetyltransferase, Roberts syndrome     

‘You Say You’re Happy, but…’: Contested Quality of Life Judgments in Bioethics and Disability Studies

In this paper, I look at several examples that demonstrate what I see as a troubling tendency in much of mainstream bioethics to discount the views of disabled people. Following feminist political theorists who argue in favour of a stance of humility and sensitive inclusion for people who have been marginalized, I recommend that bioethicists adopt a presumption in favour of believing rather than discounting the claims of disabled people. By taking their claims at face value and engaging with disabled people in open dialogue over impairment and disadvantage, bioethicists may take to heart an important lesson about human fragility and resilience.     

Effects of 17 alpha-methyltestosterone on uterine morphology and heat shock protein expression are mediated through estrogen and androgen receptors

Testosterone and the synthetic androgen, 17 alpha-methyltestosterone (MT), have been shown to increase uterine weights and alter uterine morphology. However, whereas the mechanism of action of testosterone in the uterus has been studied, it is not known if the actions of MT are mediated through androgen (AR) or estrogen (ER) receptors. In the present study, we have shown that MT, at 0.5 or 10 mg/kg per day, increases uterine weight and alters uterine morphology in a dose-dependent manner. Co-administration of the anti-androgen, flutamide, or the anti-estrogen, ICI 182,780, with MT revealed that the effects of the low dose of MT are mediated through the ER, whereas those of the high dose are mediated through both the ER and AR. In addition, we have studied the effects of MT on uterine heat shock proteins (hsps), a group of estrogen-regulated proteins whose levels increase in response to growth signals and protein damage. MT increased levels of hsp90 alpha, hsp72, and grp94. All effects on uterine hsp levels were antagonized by the anti-estrogen and not the anti-androgen. Collectively, the results of the present study indicate that the effects of MT in the uterus are mediated through the AR and ER.