Roles of ephrinB ligands and EphB receptors in cardiovascular development: demarcation of arterial/venous domains, vascular morphogenesis, and sprouting angiogenesis

Eph receptor tyrosine kinases and their cell-surface-bound ligands, the ephrins, regulate axon guidance and bundling in the developing brain, control cell migration and adhesion, and help patterning the embryo. Here we report that two ephrinB ligands and three EphB receptors are expressed in and regulate the formation of the vascular network. Mice lacking ephrinB2 and a proportion of double mutants deficient in EphB2 and EphB3 receptor signaling die in utero before embryonic day 11.5 (E11.5) because of defects in the remodeling of the embryonic vascular system. Our phenotypic analysis suggests complex interactions and multiple functions of Eph receptors and ephrins in the embryonic vasculature. Interaction between ephrinB2 on arteries and its EphB receptors on veins suggests a role in defining boundaries between arterial and venous domains. Expression of ephrinB1 by arterial and venous endothelial cells and EphB3 by veins and some arteries indicates that endothelial cell-to-cell interactions between ephrins and Eph receptors are not restricted to the border between arteries and veins. Furthermore, expression of ephrinB2 and EphB2 in mesenchyme adjacent to vessels and vascular defects in ephB2/ephB3 double mutants indicate a requirement for ephrin-Eph signaling between endothelial cells and surrounding mesenchymal cells. Finally, ephrinB ligands induce capillary sprouting in vitro with a similar efficiency as angiopoietin-1 (Ang1) and vascular endothelial growth factor (VEGF), demonstrating a stimulatory role of ephrins in the remodeling of the developing vascular system.

Signal peptide and helical bundle domains of virulent canine distemper virus fusion protein restrict fusogenicity

Persistence in canine distemper virus (CDV) infection is correlated with very limited cell-cell fusion and lack of cytolysis induced by the neurovirulent A75/17-CDV compared to that of the cytolytic Onderstepoort vaccine strain. We have previously shown that this difference was at least in part due to the amino acid sequence of the fusion (F) protein (P. Plattet, J. P. Rivals, B. Zuber, J. M. Brunner, A. Zurbriggen, and R. Wittek, Virology 337:312-326, 2005). Here, we investigated the molecular mechanisms of the neurovirulent CDV F protein underlying limited membrane fusion activity. By exchanging the signal peptide between both F CDV strains or replacing it with an exogenous signal peptide, we demonstrated that this domain controlled intracellular and consequently cell surface protein expression, thus indirectly modulating fusogenicity. In addition, by serially passaging a poorly fusogenic virus and selecting a syncytium-forming variant, we identified the mutation L372W as being responsible for this change of phenotype. Intriguingly, residue L372 potentially is located in the helical bundle domain of the F(1) subunit. We showed that this mutation drastically increased fusion activity of F proteins of both CDV strains in a signal peptide-independent manner. Due to its unique structure even among morbilliviruses, our findings with respect to the signal peptide are likely to be specifically relevant to CDV, whereas the results related to the helical bundle add new insights to our growing understanding of this class of F proteins. We conclude that different mechanisms involving multiple domains of the neurovirulent A75/17-CDV F protein act in concert to limit fusion activity, preventing lysis of infected cells, which ultimately may favor viral persistence.

Increased NoGo-anteriorisation in first-episode schizophrenia patients during Continuous Performance Test

OBJECTIVE: NoGo-stimuli during a Continuous Performance Test (CPT) activate prefrontal brain structures such as the anterior cingulate gyrus and lead to an anteriorisation of the positive electrical field of the NoGo-P300 relative to the Go-P300, so-called NoGo-anteriorisation (NGA). NGA during CPT is regarded as a neurophysiological standard index for cognitive response control. While it is known that patients with chronic schizophrenia exhibit a significant reduction in NGA, it is unclear whether this also occurs in patients undergoing their first-episode. Thus, the aim of the present study was to determine NGA in a group of patients with first-episode schizophrenia by utilizing a CPT paradigm. METHODS: Eighteen patients with first-episode schizophrenia and 18 matched healthy subjects were investigated electrophysiologically during a cued CPT, and the parameters of the Go- and NoGo-P300 were determined using microstate analysis. Low resolution tomography analysis (LORETA) was used for source determination. RESULTS: Due to a more posterior Go- and a more anterior NoGo-centroid, NGA was greater in patients than in healthy controls. LORETA indicated the same sources for both groups after Go-stimuli, but a more anterior source in patients after NoGo-stimuli. In patients P300-amplitude responses to both Go- and NoGo-stimuli were decreased, and P300-latency to NoGo-stimuli was increased. After the Go-stimuli false reactions and reaction times were increased in patients. CONCLUSIONS: Attention was reduced in patients with first-episode schizophrenia, as indicated by more false reactions, prolongation of reaction time, P300-latencies and by a decrease in P300-amplitude. Significantly however, the NGA and prefrontal LORETA-sources indicate intact prefrontal brain structures in first-episode schizophrenia patients. Previously described changes in this indicator of prefrontal function may be related to a progressive decay in chronic schizophrenia. SIGNIFICANCE: The results support the idea of a possible new biological marker of first episode psychosis, which may be a useful parameter for the longitudinal measurement of changing prefrontal brain function in a single schizophrenia patient.

Continuous subcutaneous insulin infusion therapy: effects on quality of life

To compare the diabetes-specific quality of life in subjects with type 1 diabetes treating their diabetes with multiple daily injections (MDI) to that of subjects on continuous subcutaneous insulin infusion (CSII).

Continuous thoracic epidural anesthesia improves gut mucosal microcirculation in rats with sepsis

Microcirculatory dysfunction contributes significantly to tissue hypoxia and multiple organ failure in sepsis. Ischemia of the gut and intestinal hypoxia are especially relevant for the evolution of sepsis because the mucosal barrier function may be impaired, leading to translocation of bacteria and toxins. Because sympathetic blockade enhances intestinal perfusion under physiologic conditions, we hypothesized that thoracic epidural anesthesia (TEA) may attenuate microcirculatory perturbations during sepsis. The present study was designed as a prospective and controlled laboratory experiment to assess the effects of continuous TEA on the mucosal microcirculation in a cecal ligation and perforation model of sepsis in rats. Anesthetized Sprague-Dawley rats underwent laparotomy and cecal ligation and perforation to induce sepsis. Subsequently, either bupivacaine 0.125% (n = 10) or isotonic sodium chloride solution (n = 9) was continuously infused via the thoracic epidural catheter for 24 h. In addition, a sham laparotomy was carried out in eight animals. Intravital videomicroscopy was then performed on six to ten villi of ileum mucosa. The capillary density was measured as areas encircled by perfused capillaries, that is, intercapillary areas. The TEA accomplished recruitment of microcirculatory units in the intestinal mucosa by decreasing total intercapillary areas (1,317 +/- 403 vs. 1,001 +/- 236 microm2) and continuously perfused intercapillary areas (1,937 +/- 512 vs. 1,311 +/- 678 microm2, each P < 0.05). Notably, TEA did not impair systemic hemodynamic variables beyond the changes caused by sepsis itself. Therefore, sympathetic blockade may represent a therapeutic option to treat impaired microcirculation in the gut mucosa resulting from sepsis. Additional studies are warranted to assess the microcirculatory effects of sympathetic blockade on other splanchnic organs in systemic inflammation.

Clinical performance of a continuous viscometric affinity sensor for glucose

A viscometric affinity sensor has been developed to measure the interstitial glucose concentration continuously. In a pilot clinical study its performance was assessed under conditions close to everyday life. Additionally, different insertion sites were tested for their suitability to apply subcutaneous glucose sensors.

A genetically explicit model of speciation by sensory drive within a continuous population in aquatic environments

BACKGROUND: The sensory drive hypothesis predicts that divergent sensory adaptation in different habitats may lead to premating isolation upon secondary contact of populations. Speciation by sensory drive has traditionally been treated as a special case of speciation as a byproduct of adaptation to divergent environments in geographically isolated populations. However, if habitats are heterogeneous, local adaptation in the sensory systems may cause the emergence of reproductively isolated species from a single unstructured population. In polychromatic fishes, visual sensitivity might become adapted to local ambient light regimes and the sensitivity might influence female preferences for male nuptial color. In this paper, we investigate the possibility of speciation by sensory drive as a byproduct of divergent visual adaptation within a single initially unstructured population. We use models based on explicit genetic mechanisms for color vision and nuptial coloration. RESULTS: We show that in simulations in which the adaptive evolution of visual pigments and color perception are explicitly modeled, sensory drive can promote speciation along a short selection gradient within a continuous habitat and population. We assumed that color perception evolves to adapt to the modal light environment that individuals experience and that females prefer to mate with males whose nuptial color they are most sensitive to. In our simulations color perception depends on the absorption spectra of an individual's visual pigments. Speciation occurred most frequently when the steepness of the environmental light gradient was intermediate and dispersal distance of offspring was relatively small. In addition, our results predict that mutations that cause large shifts in the wavelength of peak absorption promote speciation, whereas we did not observe speciation when peak absorption evolved by stepwise mutations with small effect. CONCLUSION: The results suggest that speciation can occur where environmental gradients create divergent selection on sensory modalities that are used in mate choice. Evidence for such gradients exists from several animal groups, and from freshwater and marine fishes in particular. The probability of speciation in a continuous population under such conditions may then critically depend on the genetic architecture of perceptual adaptation and female mate choice.

Effects of continuous remifentanil administration on intra-operative subcutaneous tissue oxygen tension

Surgical stress response markedly increases sympathetic nerve activity and catecholamine concentrations. This may contribute to peripheral vasoconstriction, reduced wound perfusion and subsequent tissue hypoxia. Opioids are known to depress the hypothalamic-adrenal response to surgery in a dose-dependent manner. We tested the hypothesis that continuous remifentanil administration produces improved subcutaneous tissue oxygen tension compared to fentanyl bolus administration. Forty-six patients undergoing major abdominal surgery were randomly assigned to receive either fentanyl bolus administration or continuous remifentanil infusion. Mean subcutaneous tissue oxygen values over the entire intra-operative period were significantly higher in the remifentanil group, when compared to the fentanyl group: 8 (2) kPa vs 6.7 (1.5) kPa, % CI difference: - 2.3 kPa to - 0.3 kPa, p = 0.013. Continuous intra-operative opioid administration may blunt vasoconstriction caused by surgical stress and adrenergic responses more than an equi-effective anaesthetic regimen based on smaller-dose bolus opioid administration.

Effects of point mutations in the cytidine deaminase domains of APOBEC3B on replication and hypermutation of hepatitis B virus in vitro

APOBEC3 cytidine deaminases hypermutate hepatitis B virus (HBV) and inhibit its replication in vitro. Whether this inhibition is due to the generation of hypermutations or to an alternative mechanism is controversial. A series of APOBEC3B (A3B) point mutants was analysed in vitro for hypermutational activity on HBV DNA and for inhibitory effects on HBV replication. Point mutations inactivating the carboxy-terminal deaminase domain abolished the hypermutational activity and reduced the inhibitory activity on HBV replication to approximately 40 %. In contrast, the point mutation H66R, inactivating the amino-terminal deaminase domain, did not affect hypermutations, but reduced the inhibition activity to 63 %, whilst the mutant C97S had no effect in either assay. Thus, only the carboxy-terminal deaminase domain of A3B catalyses cytidine deaminations leading to HBV hypermutations, but induction of hypermutations is not sufficient for full inhibition of HBV replication, for which both domains of A3B must be intact.

Establishing glycaemic control with continuous subcutaneous insulin infusion in children and adolescents with type 1 diabetes: experience of the PedPump Study in 17 countries

AIMS/HYPOTHESIS: To assess the use of paediatric continuous subcutaneous infusion (CSII) under real-life conditions by analysing data recorded for up to 90 days and relating them to outcome. METHODS: Pump programming data from patients aged 0-18 years treated with CSII in 30 centres from 16 European countries and Israel were recorded during routine clinical visits. HbA(1c) was measured centrally. RESULTS: A total of 1,041 patients (age: 11.8 +/- 4.2 years; diabetes duration: 6.0 +/- 3.6 years; average CSII duration: 2.0 +/- 1.3 years; HbA(1c): 8.0 +/- 1.3% [means +/- SD]) participated. Glycaemic control was better in preschool (n = 142; 7.5 +/- 0.9%) and pre-adolescent (6-11 years, n = 321; 7.7 +/- 1.0%) children than in adolescent patients (12-18 years, n = 578; 8.3 +/- 1.4%). There was a significant negative correlation between HbA(1c) and daily bolus number, but not between HbA(1c) and total daily insulin dose. The use of <6.7 daily boluses was a significant predictor of an HbA(1c) level >7.5%. The incidence of severe hypoglycaemia and ketoacidosis was 6.63 and 6.26 events per 100 patient-years, respectively. CONCLUSIONS/INTERPRETATION: This large paediatric survey of CSII shows that glycaemic targets can be frequently achieved, particularly in young children, and the incidence of acute complications is low. Adequate substitution of basal and prandial insulin is associated with a better HbA(1c).

Prevention of delayed cerebral vasospasm by continuous intrathecal infusion of glyceroltrinitrate and nimodipine in the rabbit model in vivo

OBJECTIVE: Intrathecal bolus administration of nitric oxide donors and calcium channel antagonists has been proposed to reduce cerebral vasospasm (CVS) in animal subarachnoid hemorrhage (SAH) models. Intrathecal continuous administration of these substances for CVS prevention has not been extensively evaluated. This study compared the efficacy of continuous intrathecal infusions of the NO donor glyceroltrinitrate and nimodipine in preventing delayed CVS associated with SAH in an animal model in vivo. METHODS: New Zealand White rabbits were randomly assigned to six groups: no SAH/NaCl, no SAH/NO, no SAH/nimodipine, SAH/NaCl, SAH/NO, or SAH/nimodipine. Glyceroltrinitrate (GTN) at 0.5 microg/microl (0.5 microl/h) or nimodipine at 0.2 microg/microl (10 microl/h) or NaCl was continuously infused into the cisterna magna via an Alzet osmotic pump from day 0 to day 5 after injection of 1.0 ml autologous blood. The magnitude of spasm in the basilar artery was determined by comparison of pre- and posttreatment angiography and was calculated as proportional change in intraluminal diameter based on automatic measurements. RESULTS: A total of 55 experiments and 110 angiograms were performed. SAH was associated with vasoconstriction of the basilar artery (SAH/NaCl group 19.85+/-2.94%). Continuous intrathecal injection of GTN and nimodipine prevented SAH-induced CVS. There was significant prevention of CVS in animals treated with GTN (SAH/NO group 5.93+/-5.2%, n=11) and nimodipine (SAH/nimodipine group: 0.55+/-2.66%, n=9). There was no significant difference between the treatment groups and controls in prevention of CVS. CONCLUSIONS: This study demonstrates that prophylactic continuous intrathecal administration of either GTN or nimodipine equally prevents SAH-associated CVS in an animal model.