P2X receptor stimulation amplifies complement-induced haemolysis

Activation of the complement system evokes cell damage by insertion of membrane attack complexes, which constitute the basis of the pathogenesis of various haemolytic disorders. Recently, we found that haemolysis caused by other types of membrane pore-forming proteins such as α-haemolysin (HlyA) from Escherichia coli, α-toxin from Staphylococcus aureus and leukotoxin from Aggregatibacter actinomycetemcomitans inflict their cytotoxic effects through P2 receptor activation. Here we show that similar to haemolysis induced by HlyA, leukotoxin and α-toxin, complement-induced haemolysis is amplified through ATP release and subsequent P2 receptor activation. Similar results were found both in murine, sensitised ovine and human erythrocytes, with either human plasma or guinea pig serum as complement donors. Non-selective P2 antagonists (PPADS and suramin) concentration-dependently inhibited complement-induced haemolysis. More specific P2 receptor antagonists imply that P2X₁ and P2X₇ are the main receptors involved in this response. Moreover, complement activation produces a sustained increase in [Ca²⁺]_i, which initially triggers significant erythrocyte shrinkage, most likely mediated by K_Ca3.1-dependent K⁺ efflux. These results indicate that complement, similar to HlyA and α-toxin, requires purinergic signalling for full haemolysis and that activation of erythrocyte volume regulation protracts the process. This finding points to several new pathways to interfere with haemolytic diseases and implies that P2 receptor antagonists potentially can be used to prevent intravascular haemolysis.     

Rinsing of allograft bone does not improve implant fixation

Background and purpose Impacted morselized allograft bone is a well-established method for reconstructing bone defects at revision surgery. However, the incorporation of bone graft is not always complete, and a substantial volume of fibrous tissue has been found around grafted implants. We hypothesized that rinsing the bone graft may improve graft incorporation by removing the majority of immunogenic factors present in blood, marrow, and fat.

Methods We implanted a cylindrical (10- × 6-mm) porous-coated Ti implant into each proximal tibia of 12 dogs. The implants were surrounded by a 2.5-mm gap into which morselized fresh frozen allograft bone was impacted. The bone graft was either (1) untreated or (2) rinsed in 37°C saline for 3 × 1 min. After 4 weeks, the animals were killed and implant fixation was evaluated by mechanical push-out and histomorphometry.

Results The groups (rinsed vs. control) were similar regarding mechanical implant fixation (mean (SD)): shear strength (MPa) 2.7 (1.0) vs. 2.9 (1.2), stiffness (MPa/mm) 15 (6.7) vs. 15 (5.6), and energy absorption (kJ/m²) 0.5 (0.2) vs. 0.6 (0.4), The same was evident for the new bone formation on the implant surface and around the implant: ongrowth (%) 6 vs. 7 and ingrowth (%) 9 vs. 9. Although not statistically significant, a 61% reduction in fibrous tissue ongrowth and 50% reduction in ingrowth were found in the rinsed group.

Interpretation Within the limits of this experimental model, we did not detect any benefits of rinsing morselized allograft bone prior to impaction grafting.     

Mortality and Causes of Death in Patients With Osteogenesis Imperfecta: A Register‐Based Nationwide Cohort Study

Osteogenesis imperfecta (OI) is a hereditary connective tissue disease that causes frequent fractures. Little is known about causes of death and length of survival in OI. The objective of this work was to calculate the risk and cause of death, and the median survival time in patients with OI. This study was a Danish nationwide, population‐based and register‐based cohort study. We used National Patient Register data from 1977 until 2013 with complete long‐term follow‐up. Participants comprised all patients registered with the diagnosis of OI from 1977 until 2013, and a reference population matched five to one to the OI cohort. We calculated hazard ratios for all‐cause mortality and subhazard ratios for cause‐specific mortality in a comparison of the OI cohort and the reference population. We also calculated all‐cause mortality hazard ratios for males, females, and age groups (0 to 17.99 years, 18.00 to 34.99 years, 35.00 to 54.99 years, 55.00 to 74.99 years, and >75 years). We identified 687 cases of OI (379 women) and included 3435 reference persons (1895 women). A total of 112 patients with OI and 257 persons in the reference population died during the observation period. The all‐cause mortality hazard ratio between the OI cohort and the reference population was 2.90. The median survival time for males with OI was 72.4 years, compared to 81.9 in the reference population. The median survival time for females with OI was 77.4 years, compared to 84.5 years in the reference population. Patients with OI had a higher risk of death from respiratory diseases, gastrointestinal diseases, and trauma. We were limited by the lack of clinical information about phenotype and genotype of the included patients. Patients with OI had a higher mortality rate throughout their life compared to the general population. © 2016 American Society for Bone and Mineral Research.     

Water and solute secretion by the choroid plexus

The cerebrospinal fluid (CSF) provides mechanical and chemical protection of the brain and spinal cord. This review focusses on the contribution of the choroid plexus epithelium to the water and salt homeostasis of the CSF, i.e. the secretory processes involved in CSF formation. The choroid plexus epithelium is situated in the ventricular system and is believed to be the major site of CSF production. Numerous studies have identified transport processes involved in this secretion, and recently, the underlying molecular background for some of the mechanisms have emerged. The nascent CSF consists mainly of NaCl and NaHCO₃, and the production rate is strictly coupled to the rate of Na⁺ secretion. In contrast to other secreting epithelia, Na⁺ is actively pumped across the luminal surface by the Na⁺,K⁺-ATPase with possible contributions by other Na⁺ transporters, e.g. the luminal Na⁺,K⁺,2Cl⁻ cotransporter. The Cl⁻ and HCO₃ ⁻ ions are likely transported by a luminal cAMP activated inward rectified anion conductance, although the responsible proteins have not been identified. Whereas Cl⁻ most likely enters the cells through anion exchange, the functional as well as the molecular basis for the basolateral Na⁺ entry are not yet well-defined. Water molecules follow across the epithelium mainly through the water channel, AQP1, driven by the created ionic gradient. In this article, the implications of the recent findings for the current model of CSF secretion are discussed. Finally, the clinical implications and the prospects of future advances in understanding CSF production are briefly outlined.     

The effect of activated protein C on plasma cytokine levels in a porcine model of acute endotoxemia

Objective To assess the anti-inflammatory effects of recombinant human activated protein C (rhAPC) in a porcine model of acute endotoxemia. Design and setting Animal randomized controlled study at the Laboratory of Clinical Institute, Aarhus University Hospital. Subjects Eighteen female landrace pigs (30 kg). Interventions By pairwise randomization, pigs were given either LPS or LPS and rhAPC. Both groups received a stepwise increasing LPS infusion for 30 min; whereafter the infusion continued at a lower rate (300 min LPS in both groups). The LPS+rhAPC group received rhAPC (100 μg/kg per hour) 15 min before the LPS infusion began and throughout the trial period. Results While rhAPC showed no modifying effects on peak plasma levels of pro- or anti-inflammatory cytokines (TNF-α, IL-6, IL-8, IL-10), TNF-α and IL-10 peaked significantly later in the rhAPC-treated animals. The profibrinolytic effects of rhAPC were confirmed by decreased plasminogen activator inhibitor 1 levels, while no differences were found in other coagulation markers, hemodynamic, metabolic, or leukocyte data between the two groups. Conclusions We found no significant effect of rhAPC on plasma levels of either pro- or anti-inflammatory cytokines in this porcine model of acute endotoxemia. However, TNF-α and IL-10 peaked significantly later in the rhAPC-treated animals.     

Skin pigmentation and genetic variants in an admixed Brazilian population of primarily European ancestry

International Journal of Legal Medicine - Although many genes have been shown to be associated with human pigmentary traits and forensic prediction assays exist (e.g. HIrisPlex-S), the genetic...     

Elucidating the Mechanism of Absorption of Fast-Acting Insulin Aspart: The Role of Niacinamide

Pharmaceutical Research - The aim of this work is to investigate the roles of solute carrier family 22 member 18 (SLC22A18) in lipid metabolism and in establishing the tumor phenotype of HepG2...