Cuticular lipids correlate with age and insemination status in queen honeybees

Eusocial insects exhibit reproductive division of labour, in which one or a few queens perform almost all of the reproduction, while the workers are largely sterile and assist in rearing their siblings. Consequently, many of the colony’s tasks (e.g. nest construction and brood rearing) should be modulated depending on whether the queen is fertile. Here, we tested whether queens’ cuticular lipids could provide reliable signals of fertility in the honeybee Apis mellifera, as they do in other social Hymenoptera. Specifically, we tested whether cuticular lipids differ between virgin queens of different ages, and between queens exposed to different artificial insemination treatments being semen (sperm and seminal fluid), seminal fluid only or saline control. Using gas chromatography–mass spectrometry, we found 27 lipids: 21 different hydrocarbons, namely alkanes, alkenes and dienes, as well as six wax esters. The lipid profile changed dramatically in the first 10 days after eclosion, and there were differences in lipid composition between virgin and artificially inseminated queens. Insemination with semen, seminal fluid or saline did not result in distinct chemical profiles. Our findings indicate that the physical stimulus of insemination was responsible for the observed changes in the cuticular profile in honeybee queens. Our results demonstrate that cuticular lipid profiles encode information on queen age, fertility and mating status, which could in principle be utilised by workers and rival queens.     

Effects of implant design parameters on fluid convection, potentiating third-body debris ingress into the bearing surface during THA impingement/subluxation

Aseptic loosening from polyethylene wear debris is the leading cause of failure for metal-on-polyethylene total hip implants. Third-body debris ingress to the bearing space results in femoral head roughening and acceleration of polyethylene wear. How third-body particles manage to enter the bearing space between the closely conforming articulating surfaces of the joint is not well understood. We hypothesize that one such mechanism is from convective fluid transport during subluxation of the total hip joint. To test this hypothesis, a three-dimensional (3D) computational fluid dynamics (CFD) model was developed and validated, to quantify fluid ingress into the bearing space during a leg-cross subluxation event. The results indicated that extra-articular joint fluid could be drawn nearly to the pole of the cup with even very small separations of the femoral head (<0.60mm). Debris suspended near the equator of the cup at the site of maximum fluid velocity just before the subluxation began could be transported to within 11 degrees from the cup pole. Larger head diameters resulted in increased fluid velocity at all sites around the entrance to the gap compared to smaller head sizes, with fluid velocity being greatest along the anterosuperolateral cup edge, for all head sizes. Fluid pathlines indicated that suspended debris would reach similar angular positions in the bearing space regardless of head size. Increased inset of the femoral head into the acetabular cup resulted both in higher fluid velocity and in transport of third-body debris further into the bearing space.     

The red death meets the abdominal bristle: Polygenic mutation for susceptibility to a bacterial pathogen in Caenorhabditis elegans

Understanding the genetic basis of susceptibility to pathogens is an important goal of medicine and of evolutionary biology. A key first step toward understanding the genetics and evolution of any phenotypic trait is characterizing the role of mutation. However, the rate at which mutation introduces genetic variance for pathogen susceptibility in any organism is essentially unknown. Here, we quantify the per‐generation input of genetic variance by mutation (VM) for susceptibility of Caenorhabditis elegans to the pathogenic bacterium Pseudomonas aeruginosa (defined as the median time of death, LT50). VM for LT50 is slightly less than VM for a variety of life‐history and morphological traits in this strain of C. elegans, but is well within the range of reported values in a variety of organisms. Mean LT50 did not change significantly over 250 generations of mutation accumulation. Comparison of VM to the standing genetic variance (VG) implies a strength of selection against new mutations of a few tenths of a percent. These results suggest that the substantial standing genetic variation for susceptibility of C. elegans to P. aeruginosa can be explained by polygenic mutation coupled with purifying selection.     

Root Dynamics of Cultivar and Non‐Cultivar Population Sources of Two Dominant Grasses during Initial Establishment of Tallgrass Prairie

Dominance of warm‐season grasses modulates tallgrass prairie ecosystem structure and function. Reintroduction of these grasses is a widespread practice to conserve soil and restore prairie ecosystems degraded from human land use changes. Seed sources for reintroduction of dominant prairie grass species include local (non‐cultivar) and selected (cultivar) populations. The primary objective of this study was to quantify whether intraspecific variation in developing root systems exists between population sources (non‐cultivar and cultivar) of two dominant grasses (Sorghastrum nutans and Schizachyrium scoparium) widely used in restoration. Non‐cultivar and cultivar grass seedlings of both species were isolated in an experimental prairie restoration at the Konza Prairie Biological Station. We measured above‐ and belowground net primary production (ANPP and BNPP, respectively), root architecture, and root tissue quality, as well as soil moisture and plant available inorganic nitrogen (N) in soil associated with each species and source at the end of the first growing season. Cultivars had greater root length, surface area, and volume than non‐cultivars. Available inorganic N and soil moisture were present in lower amounts in soil proximal to roots of cultivars than non‐cultivars. Additionally, soil NO₃–N was negatively correlated with root volume in S. nutans cultivars. While cultivars had greater BNPP than non‐cultivars, this was not reflected aboveground root structure, as ANPP was similar between cultivars and non‐cultivars. Intraspecific variation in belowground root structure and function exists between cultivar and non‐cultivar sources of the dominant prairie grasses during initial reestablishment of tallgrass prairie. Population source selection should be considered in setting restoration goals and objectives.     

Occult renal cell carcinoma manifesting with epistaxis in a woman: a case report

Introduction

Metastatic disease in the sinonasal region occurs rarely and the primary site may be elusive. This case highlights the possibility of an occult renal tumor manifesting with nasal symptoms and the risk of severe bleeding following nasal biopsy.

Case presentation

We report the case of a 79-year-old Caucasian woman who presented with a six-week history of intermittent left-sided nosebleeds. She was fit, without previous surgery or anticoagulation. Nasal endoscopy and computed tomography showed a hemorrhagic mass occupying her left ethmoid cells and middle meatus. After a highly hemorrhagic biopsy, the lesion was histologically confirmed as clear cell carcinoma. Screening revealed a right kidney mass with widespread metastases. Palliative radiotherapy to the sinonasal metastasis and systemic treatment rendered her free of symptoms nine months after initial presentation.

Conclusions

General practitioners and ear, nose and throat (ENT) doctors are very often confronted with epistaxis. A small minority of patients with epistaxis show a primary or metastatic nasal mass. Detection of the origin of secondary sinonasal masses requires a high index of suspicion and examination of infraclavicular sites by a multidisciplinary team. Renal cell carcinoma metastases are prone to severe bleeding during any surgical intervention, therefore, preoperative embolization is recommended. Resection or radiotherapy to the sinonasal metastasis of renal origin is justified in order to prevent recurrent nosebleeds.

     

How and When Selection Experiments Might Actually be Useful

Laboratory natural selection and artificial selection are vitaltools for addressing specific questions about evolutionary patternsof variation. Laboratory natural selection can illuminate whethera putative selective agent is capable of generating long-term,sustained changes in individual traits and suites of traits.Artificial selection is the essential tool for understandingthe general evolvability of traits and the extent to which geneticcorrelations constrain evolution. We review the contexts inwhich each type of experiment seems capable of offering keyinsights into important evolutionary issues. We also discusstheoretical and methodological considerations that play criticalroles in designing selection experiments that are relevant toevolutionary patterns of trait variation. In particular, wefocus on the critical role of selection intensity and the consequencesof experiments with different intensities. While selection experimentsare not practical in many cases, sophisticated selection experiments—designedwith careful consideration of the theory of selection—shouldbe taken beyond model organisms and used in well-chosen naturalsystems to understand natural patterns of variation.     

Heritability of sperm length in the bumblebee Bombus terrestris

Sperm length is highly variable, both between and within species, but the evolutionary significance of this variation is poorly understood. Sexual selection on sperm length requires a significant additive genetic variance, but few studies have actually measured this. Here we present the first estimates of narrow sense heritability of sperm length in a social insect, the bumblebee Bombus terrestris. In spite of a balanced and straightforward rearing design of colonies, and the possibility to replicate measurements of sperm within single males nested within colonies, the analysis proved to be complex. Several appropriate statistical models were derived, each depending on different assumptions. The heritability estimates obtained ranged from h ² = 0.197 ± 0.091 to h ² = 0.429 ± 0.154. All our estimates were substantially lower than previous estimates of sperm length heritability in non-social insects and vertebrates.     

High-resolution characterization of antibody fragment/antigen interactions using Biacore T100

A Biacore T100 optical biosensor was used to characterize the binding kinetics of a panel of antigen binding fragments (Fabs) directed against the PcrV protein from Pseudomonas aeruginosa. PcrV protein forms part of the type III secretion system complex of this opportunistic pathogen. We demonstrate that the biosensor response data for each Fab collected from three different surface densities of the antigen could be fit globally to a simple 1:1 interaction model. Importantly, we found that the Fabs with the slowest dissociation rate provided the best protection in cell cytotoxicity studies. To further characterize the Fab interactions, binding data were automatically acquired at different temperatures and under different buffer conditions. The comprehensive characterization of these Fabs shows how Biacore T100 can be used to complement protein therapeutic discovery programs from basic research to the selection of therapeutic candidates.