Nonparallelism in MHCIIβ diversity accompanies nonparallelism in pathogen infection of lake whitefish (Coregonus clupeaformis) species pairs as revealed by next‐generation sequencing

Major histocompatibility (MHC) immune system genes may evolve in response to pathogens in the environment. Because they also may affect mate choice, they are candidates for having great importance in ecological speciation. Here, we use next‐generation sequencing to test the general hypothesis of parallelism in patterns of MHCIIβ diversity and bacterial infections among five dwarf and normal whitefish sympatric pairs. A second objective was to assess the functional relationships between specific MHCIIβ alleles and pathogens in natural conditions. Each individual had between one and four alleles, indicating two paralogous loci. In Cliff Lake, the dwarf ecotype was monomorphic for the most common allele. In Webster Lake, the skew in the allelic distribution was towards the same allele but in the normal ecotype, underscoring the nonparallel divergence among lakes. Our signal of balancing selection matched putative peptide binding region residues in some cases, but not in others, supporting other recent findings of substantial functional differences in fish MHCIIβ compared with mammals. Individuals with fewer alleles were less likely to be infected; thus, we found no evidence for the heterozygote advantage hypothesis. MHCIIβ alleles and pathogenic bacteria formed distinct clusters in multivariate analyses, and clusters of certain alleles were associated with clusters of pathogens, or sometimes the absence of pathogens, indicating functional relationships at the individual level. Given that patterns of MHCIIβ and bacteria were nonparallel among dwarf and normal whitefish pairs, we conclude that pathogens driving MHCIIβ evolution did not play a direct role in their parallel phenotypic evolution.     

Effect of floral orifice width and shape on hummingbird-flower interactions

Nectar guides are common among insect-pollinated plants, yet are thought to be rare or absent among hummingbird-pollinated plants. We hypothesize that the lower lips and trumpet-shaped orifices of many hummingbird flowers act as nectar guides to direct hummingbirds to the flowers' nectar and orient the birds for pollination. To test this hypothesis we conducted laboratory experiments using flowers of Monarda didyma (bee balm) and M. fistulosa (wild bergamot), which have orifice widths of about 4 mm and 2 mm, respectively, and latex flowers with orifice widths of 4 mm and 2 mm and three orifice shapes (trumpet, lipped, and lipless). Rubythroated hummingbirds (Archilochus colubris) made fewer errors during bill insertion and spent a smaller proportion of their feeding visit in error at M. didyma flowers than at M. fistulosa flowers, and at unaltered flowers of both species than at flowers with lower lips removed. Handling times were longer at both lipped and lipless flowers of M. didyma than at those of M. fistulosa, and at lipped than at lipless flowers of M. didyma. The average duration of contact between a hummingbird and a flower's anthers and stigma was longer at M. didyma than at M. fistulosa for both lipped and lipless flowers, and at lipped than at lipless M. didyma flowers. Hummingbirds missed the openings of latex flowers with their bills more frequently and spent a greater percentage of their total feeding visit in error at (i) 2-mm than at 4-mm flowers of all three shapes, (ii) lipless flowers than at trumpet or lipped flowers, and (iii) lipped flowers than at trumpet flowers of both widths. The duration of hummingbird/anther contact was longer at (i) 2-mm than at 4-mm flowers of all shapes, (ii) lipped than at trumpet or lipless flowers, and (iii) lipless than at trumpet flowers for both widths. No significant differences in handling times of hummingbirds were observed among any of the latex flower shapes or widths. Our results demonstrate that orifice shapes can act as guides by reducing the frequency of feeding errors by visiting hummingbirds, and that effects of orifice shape on pollination must be considered in conjunction with flower widths and locations of anthers and stigmas.     

The Number and Location of Glycans on Influenza Hemagglutinin Determine Folding and Association with Calnexin and Calreticulin

Calnexin and calreticulin are homologous molecular chaperones that promote proper folding, oligomeric assembly, and quality control of newly synthesized glycoproteins in the endoplasmic reticulum (ER). Both are lectins that bind to substrate glycoproteins that have monoglucosylated N-linked oligosaccharides. Their binding to newly translated influenza virus hemagglutinin (HA), and various mutants thereof, was analyzed in microsomes after in vitro translation and expression in live CHO cells. A large fraction of the HA molecules was found to occur in ternary HA– calnexin–calreticulin complexes. In contrast to calnexin, calreticulin was found to bind primarily to early folding intermediates. Analysis of HA mutants with different numbers and locations of N-linked glycans showed that although the two chaperones share the same carbohydrate specificity, they display distinct binding properties; calreticulin binding depends on the oligosaccharides in the more rapidly folding top/hinge domain of HA whereas calnexin is less discriminating. Calnexin's binding was reduced if the HA was expressed as a soluble anchor-free protein rather than membrane bound. When the co- and posttranslational folding and trimerization of glycosylation mutants was analyzed, it was observed that removal of stem domain glycans caused accelerated folding whereas removal of the top domain glycans (especially the oligosaccharide attached to Asn81) inhibited folding. In summary, the data established that individual N-linked glycans in HA have distinct roles in calnexin/calreticulin binding and in co- and posttranslational folding.     

Stable baselines of temporal turnover underlie high beta diversity in tropical arthropod communities

While the high species diversity of tropical arthropod communities has often been linked to marked spatial heterogeneity, their temporal dynamics have received little attention. This study addresses this gap by examining spatio‐temporal variation in the arthropod communities of a tropical montane forest in Honduras. By employing DNA barcode analysis and Malaise trap sampling across 4 years and five sites, 51,596 specimens were assigned to 8,193 presumptive species. High beta diversity was linked more strongly to elevation than geographic distance, decreasing by 12% when only the dominant species were considered. When sampling effort was increased by deploying more traps at a site, beta diversity only decreased by 2%, but extending sampling across years decreased beta diversity by 27%. Species inconsistently detected among years, likely transients from other settings, drove the low similarity in species composition among traps only a few metres apart. The dominant, temporally persistent species substantially influenced the cyclic pattern of change in community composition among years. This pattern likely results from divergence–convergence dynamics, suggesting a stable baseline of temporal turnover in each community. The overall results establish that large sample sizes are necessary to reveal species richness, but are not essential for quantifying beta diversity. This study further highlights the need for standardized methods of sampling and species identification to generate the comparative data required to evaluate biodiversity change in space and time.     

Short Daily versus Conventional Hemodialysis for Hypertensive Patients: A Randomized Cross-Over Study

Background

Treatment of end stage renal disease patients with short daily hemodialysis has been associated with an improvement in blood pressure. It is unclear from these studies if anti-hypertensive management had been optimized prior to starting short daily hemodialysis. Also, the potential mechanism(s) of blood pressure improvement remain to be fully elucidated.

Study Design, Setting and Participants

We undertook a randomized cross-over trial in adult hypertensive patients with ESRD treated with conventional hemodialysis to determine: 1) if short-daily hemodialysis is associated with a reduction in systolic blood pressure after a 3-month blood pressure optimization period and; 2) the potential mechanism(s) of blood pressure reduction. Blood pressure was measured using Canadian Hypertension Education Program guidelines. Extracellular fluid volume (ECFV) was assessed with bioimpedance. Serum catecholamines were used to assess the sympathetic nervous system. Interleukin-6 (IL-6) and thiobarbituric acid reactive substances (T-BARS) were used as markers of inflammation and oxidative stress respectively.

Results

After a 3-month run-in phase in which systolic blood pressure improved, there was no significant difference in pre-dialysis systolic pressure between short-daily and conventional hemodialysis (p = 0.39). However, similar blood pressures were achieved on fewer anti-hypertensive medications with short daily hemodialysis compared to conventional hemodialysis (p = 0.01). Short daily hemodialysis, compared to conventional hemodialysis, was not associated with a difference in dry weight or ECFV (p = 0.77). Sympathetic nervous system activity as assessed by plasma epinephrine (p = 1.0) and norepinephrine (p = 0.52) was also not different. Markers of inflammation (p = 0.42) and oxidative stress (p = 0.83) were also similar between the two treatment arms.

Conclusions

Patients treated with short daily, compared to conventional hemodialysis, have similar blood pressure control on fewer anti-hypertensive medications. The mechanism(s) by which short daily hemodialysis allows for decreased anti-hypertensive medication use remains unclear but effects on sodium balance and changes in peripheral vascular resistance require further study.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00759967","term_id":"NCT00759967"}}NCT00759967     

CHANGES OCCURRING IN THE CHEMICAL COMPOSITION OF THE CENTRAL NERVOUS SYSTEM DURING FOETAL AND POST-NATAL DEVELOPMENT OF THE SHEEP

(1) The chemical composition of the CNS (separated into cerebrum, cerebellum, brain stem and spinal cord) was determined in sheep during foetal and post-natal development and in adults. (2) The spinal cord differed from the remainder of the CNS in growing more after the period studied (50-day-old foetuses to 5-week-old lambs) than before it. This was largely attributable to lipid accumulation. (3) Chemical growth (accumulation of DNA, protein and lipid) proceeded linearly in spinal cord, logarithmically in cerebrum and cerebellum while in brain stem growth was described by a sigmoid function. (4) Fat-free dry matter, protein, total lipid, cholesterol and phospholipid concentrations increased progressively in all parts of the CNS but DNA concentrations changed little. In the cerebrum alone there was an increase in DNA concentration during maturation suggesting an increased cell population. Cholesterol was present predominantly in the free form but esters were detected in foetal tissues from 70 up to 120 days gestation. (5) Cerebroside, the characteristic lipid of myelin, increased in concentration soon after 85 days of gestation, up to which point very low values were recorded, the rate varying according to the region of the CNS examined. Rates of increase in total regional cerebroside content were used to identify periods of myelination and the results suggest that there are two periods of peak activity, one about 20 days before birth and the other at 10-20 days after birth. (6) The composition of lipids added during the two phases of myelination and during maturation were characteristically different. In the spinal cord, lipid analyses best reflect changes in myelin composition.     

Comprehensive DNA barcode coverage of North American birds

DNA barcoding seeks to assemble a standardized reference library for DNA-based identification of eukaryotic species. The utility and limitations of this approach need to be tested on well-characterized taxonomic assemblages. Here we provide a comprehensive DNA barcode analysis for North American birds including 643 species representing 93% of the breeding and pelagic avifauna of the USA and Canada. Most (94%) species possess distinct barcode clusters, with average neighbour-joining bootstrap support of 98%. In the remaining 6%, barcode clusters correspond to small sets of closely related species, most of which hybridize regularly. Fifteen (2%) currently recognized species are comprised of two distinct barcode clusters, many of which may represent cryptic species. Intraspecific variation is weakly related to census population size and species age. This study confirms that DNA barcoding can be effectively applied across the geographical and taxonomic expanse of North American birds. The consistent finding of constrained intraspecific mitochondrial variation in this large assemblage of species supports the emerging view that selective sweeps limit mitochondrial diversity.     

Biological identifications through DNA barcodes

Although much biological research depends upon species diagnoses, taxonomic expertise is collapsing. We are convinced that the sole prospect for a sustainable identification capability lies in the construction of systems that employ DNA sequences as taxon 'barcodes'. We establish that the mitochondrial gene cytochrome c oxidase I (COI) can serve as the core of a global bioidentification system for animals. First, we demonstrate that COI profiles, derived from the low-density sampling of higher taxonomic categories, ordinarily assign newly analysed taxa to the appropriate phylum or order. Second, we demonstrate that species-level assignments can be obtained by creating comprehensive COI profiles. A model COI profile, based upon the analysis of a single individual from each of 200 closely allied species of lepidopterans, was 100% successful in correctly identifying subsequent specimens. When fully developed, a COI identification system will provide a reliable, cost-effective and accessible solution to the current problem of species identification. Its assembly will also generate important new insights into the diversification of life and the rules of molecular evolution.     

A randomized,placebo controlled,trial of preoperative sustained release Betamethasone plus non-controlled intraoperative Ketorolac or Fentanyl on pain after diagnostic laparoscopy or laparoscopic tubal ligation [ISRCTN52633712

BACKGROUND: Gynecological laparoscopic surgery procedures are often complicated by postoperative pain resulting in an unpleasant experience for the patient, delayed discharge, and increased cost. Glucocorticosteroids have been suggested to reduce the severity and incidence of postoperative pain. METHODS: This study examines the efficacy of a sustained release betamethasone preparation to reduce postoperative pain and the requirement for pain relief drugs after either diagnostic laparoscopy or tubal ligation. Patients were recruited, as presenting, after obtaining informed consent. Prior to surgery, patients were randomly selected by a computer generated table to receive either pharmacy-coded betamethasone (12 mg IM Celestone trade mark ) or an optically identical placebo injection of Intralipid trade mark and isotonic saline mixture. The effect of non-controlled prophylactic intraoperative treatment with either fentanyl or ketorolac per surgeon's orders was also noted in this study. Blood samples taken at recovery and at discharge times were extracted and analyzed for circulating betamethasone. Visual analog scale data on pain was gathered at six post-recovery time points in a triple blind fashion and statistically compared. The postoperative requirement for pain relief drugs was also examined. RESULTS: Although the injection achieved a sustained therapeutic concentration, no beneficial effect of IM betamethasone on postoperative pain or reduction in pain relief drugs was observed during the postoperative period. Indeed, the mean combined pain scores during the 2 hour postoperative period, adjusted for postoperative opioids as the major confounding factor, were higher approaching statistical significance (P = 0.056) in the treatment group. Higher pain scores were also observed for the tubal ligation patients relative to diagnostic laparoscopy. Intraoperative fentanyl treatment did not significantly lower the average pain score during the 2 hour postoperative period. Intraoperative ketorolac treatment significantly lowered (P = 0.027) pain scores and reduced the postoperative requirement for additional pain relief drugs. CONCLUSIONS: There was a lack of efficacy of preoperative sustained release betamethasone in reducing postoperative pain despite maintaining a therapeutic concentration during the postoperative period. Intraoperative Ketorolac did afford some short-term pain relief in the postoperative period and reduced the need for additional pain relief drugs.