Activation of Coagulation Factor V by a Platelet Protease

Factor V must be converted to Factor V_a in order to bind to a high affinity platelet surface site and participate in prothrombin activation. Osterud et al. (10) presented data that suggested that human platelets contain an activated form of Factor V and a Factor V activator. We find that the Factor V released when platelets are disrupted by freezing and thawing or sonication is activated 3- to 10-fold by thrombin as determined by coagulation assay and is therefore stored as the relatively inactive procofactor rather than in the active form Factor V_a.     

Left atrial volume determination by echocardiography

To validate echocardiographic left atrial volume measurements, 25 patients with mitral stenosis were studied before and after mitral balloon valvuloplasty. Seven normals served as controls. The modified Simpson's rule was used for echocardiographic and angiographic left atrial volume determination from two orthogonal planes. Left atrial antero-posterior diameter was measured from parasternal long axis view and supero-inferior and medio-lateral diameters from apical four-chamber view. Transthoracic echocardiographic left atrial volume correlated well, but systematically underestimated angiographic left atrial volume (y=0.4x+27, r=0.92). Monoplane transesophageal echocardiography did not improve correlation, nor the underestimation. Out of the several left atrial diameters, antero-posterior dimension showed the closest correlation with angiographic volume (r=0.91), which persisted after exclusion of patients with atria >400 ml (r=0.84). Futhermore, relative changes of antero-posterior diameter after mitral valvuloplasty were closely related to the relative changes observed in left atrial volume (r=0.82). Our results suggest that, in spite of a consistent underestimation, bidimensional, transthoracic echocardiographic and angiographic left atrial assessment correlate closely. Moreover, it is suggested that the mere antero-posterior diameter from transthoracic two-dimensional image is sufficient in clinical practice for routine follow-op of left atrial volume.     

Effect of deriving periosteal and endosteal contours from microCT scans on computation of cross‐sectional properties in non‐adults: the femur

Derivation of periosteal and endosteal contours taken from transversal long bone cross‐sections limits the accuracy of calculated biomechanical properties. Although several techniques are available for deriving both contours, the effect of these techniques on accuracy of calculated cross‐sectional properties in non‐adults is unknown. We examine a sample of 86 non‐adult femora from birth to 12 years of age to estimate the effect of error in deriving periosteal and endosteal contours on cross‐sectional properties. Midshaft cross‐sections were taken from microCT scans and contours were derived using manual, fully automatic, spline, and ellipse techniques. Agreement between techniques was assessed against manually traced periosteal and endosteal contours using percent prediction error (%PE), reduced major axis analysis, and limits of agreement. The %PEs were highest in the medullary area and lowest in the total area. Mean %PEs were sufficiently below the 5% level of acceptable error, except for medullary areas, but individual values can greatly exceed this 5% boundary given the high standard deviation of %PE means and wide minimum–maximum range of %PEs. Automatic processing produces greater errors than does combination with manual, spline, and ellipse processing. Although periosteal contour is estimated with stronger agreement compared with endosteal contour, error in deriving periosteal contour has a substantially greater effect on calculated section moduli than does error in deriving endosteal contours. We observed no size effect on the resulting bias. Nevertheless, cross‐sectional properties in a younger age category may be estimated with greater error compared with in an older age category. We conclude that non‐adult midshaft cross‐sectional properties can be derived from microCT scans of femoral diaphyses with mean error of < 5% and that derivation of endosteal contour can be simplified by the ellipse technique because fully automatic derivation of endosteal contour may increase the resulting error, especially in small samples.     

实验性短期电刺激引起的机体紊乱

SourcepapersdealingwiththeuseofLateralElectricSurfaceStimulation（LESS）totreatidiopathicscoliosis（IS）inchildrenandadolescentshavesofarpresentedcontroversialopinions犤５，６，８，１０，１２，１６，１７犦．Authorsrecommendingthistreatmentusuallyapplyitfor９hoursatnight．Theymention，however，thatthetherapywhichmaylastuntilthebonesarefullydeveloped，oftenresultsinskincomplications，e．g．burns，emotionalandpsychicaldiscomfortofpatientsduringnoc－turnalrest，aswellasstressorevendisturbances…     

Cytomegalovirus reactivation and mortality in patients with acute respiratory distress syndrome

Purpose

Cytomegalovirus (CMV) reactivation occurs frequently in patients with the acute respiratory distress syndrome (ARDS) and has been associated with increased mortality. However, it remains unknown whether this association represents an independent risk for poor outcome. We aimed to estimate the attributable effect of CMV reactivation on mortality in immunocompetent ARDS patients.

Methods

We prospectively studied immunocompetent ARDS patients who tested seropositive for CMV and remained mechanically ventilated beyond day 4 in two tertiary intensive care units in the Netherlands from 2011 to 2013. CMV loads were determined in plasma weekly. Competing risks Cox regression was used with CMV reactivation status as a time-dependent exposure variable. Subsequently, in sensitivity analyses we adjusted for the evolution of disease severity until onset of reactivation using marginal structural modeling.

Results

Of 399 ARDS patients, 271 (68 %) were CMV seropositive and reactivation occurred in 74 (27 %) of them. After adjustment for confounding and competing risks, CMV reactivation was associated with overall increased ICU mortality (adjusted subdistribution hazard ratio (SHR) 2.74, 95 % CI 1.51–4.97), which resulted from the joint action of trends toward an increased mortality rate (direct effect; cause specific hazard ratio (HR) 1.58, 95 % CI 0.86–2.90) and a reduced successful weaning rate (indirect effect; cause specific HR 0.83, 95 % CI 0.58–1.18). These associations remained in sensitivity analyses. The population-attributable fraction of ICU mortality was 23 % (95 % CI 6–41) by day 30 (risk difference 4.4, 95 % CI 1.1–7.9).

Conclusion

CMV reactivation is independently associated with increased case fatality in immunocompetent ARDS patients who are CMV seropositive.

     

Assessment of renal artery stenosis: side-by-side comparison of angiography and duplex ultrasound with pressure gradient measurements.

AIMS: A ratio of distal renal pressure to aortic pressure (P(d)/P(a)) <0.90 can be considered a threshold for defining a significant renal artery stenosis (RAS). The aim of this study was to compare renal angiography (QRA) and colour duplex ultrasound (CDUS) to pressure measurements in assessing RAS. METHODS AND RESULTS: In 56 RAS, percent diameter stenosis (DS(angio)), minimal luminal diameter (MLD), Doppler-derived peak systolic velocity (PSV), end-diastolic velocity (EDV), and renal-to-aortic ratio (RAR) were obtained and compared with the P(d)/P(a) measured with a 0.014" pressure wire. P(d)/P(a) correlated with angiography- and CDUS-derived parameters. The best correlation was observed with EDV (R = -0.61). To identify stenosis associated with a P(d)/P(a) < 0.90, the diagnostic accuracy of DS(angio) > 50%, MLD < 2 mm, PSV > 180 cm/s, EDV > 90 cm/s and RAR > 3.5 were, respectively, 60%, 77%, 45%, 77% and 79%, yet, with a high proportion of false positives (38%, 15%, 55%, 11% and 15%, respectively) indicating an overestimation of the severity of the RAS by both QRA and CDUS. New cut-off values for QRA- and CDUS-derived indices were proposed. CONCLUSION: Generally accepted QRA and CDUS-derived indices of RAS severity overestimate the actual severity of RAS. This 'overdiagnosis' is likely the main cause of the disappointing results of renal angioplasty for renovascular hypertension.     

Modulation of the Substitution Pattern of 5-Aryl-2-Aminoimidazoles Allows Fine-Tuning of Their Antibiofilm Activity Spectrum and Toxicity

We previously synthesized several series of compounds, based on the 5-aryl-2-aminoimidazole scaffold, that showed activity preventing the formation of Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa biofilms. Here, we further studied the activity spectrum of a number of the most active N1- and 2N-substituted 5-aryl-2-aminoimidazoles against a broad panel of biofilms formed by monospecies and mixed species of bacteria and fungi. An N1-substituted compound showed very strong activity against the biofilms formed by Gram-negative and Gram-positive bacteria and the fungus Candida albicans but was previously shown to be toxic against various eukaryotic cell lines. In contrast, 2N-substituted compounds were nontoxic and active against biofilms formed by Gram-negative bacteria and C. albicans but had reduced activity against biofilms formed by Gram-positive bacteria. In an attempt to develop nontoxic compounds with potent activity against biofilms formed by Gram-positive bacteria for application in antibiofilm coatings for medical implants, we synthesized novel compounds with substituents at both the N1 and 2N positions and tested these compounds for antibiofilm activity and toxicity. Interestingly, most of these N1-,2N-disubstituted 5-aryl-2-aminoimidazoles showed very strong activity against biofilms formed by Gram-positive bacteria and C. albicans in various setups with biofilms formed by monospecies and mixed species but lost activity against biofilms formed by Gram-negative bacteria. In light of application of these compounds as anti-infective coatings on orthopedic implants, toxicity against two bone cell lines and the functionality of these cells were tested. The N1-,2N-disubstituted 5-aryl-2-aminoimidazoles in general did not affect the viability of bone cells and even induced calcium deposition. This indicates that modulating the substitution pattern on positions N1 and 2N of the 5-aryl-2-aminoimidazole scaffold allows fine-tuning of both the antibiofilm activity spectrum and toxicity.     

Stromal cell-derived factor 1 promotes angiogenesis via a heme oxygenase 1-dependent mechanism

Stromal cell-derived factor 1 (SDF-1) plays a major role in the migration, recruitment, and retention of endothelial progenitor cells to sites of ischemic injury and contributes to neovascularization. We provide direct evidence demonstrating an important role for heme oxygenase 1 (HO-1) in mediating the proangiogenic effects of SDF-1. Nanomolar concentrations of SDF-1 induced HO-1 in endothelial cells through a protein kinase C zeta-dependent and vascular endothelial growth factor-independent mechanism. SDF-1-induced endothelial tube formation and migration was impaired in HO-1-deficient cells. Aortic rings from HO-1(-/-) mice were unable to form capillary sprouts in response to SDF-1, a defect reversed by CO, a byproduct of the HO-1 reaction. Phosphorylation of vasodilator-stimulated phosphoprotein was impaired in HO-1(-/-) cells, an event that was restored by CO. The functional significance of HO-1 in the proangiogenic effects of SDF-1 was confirmed in Matrigel plug, wound healing, and retinal ischemia models in vivo. The absence of HO-1 was associated with impaired wound healing. Intravitreal adoptive transfer of HO-1-deficient endothelial precursors showed defective homing and reendothelialization of the retinal vasculature compared with HO-1 wild-type cells following ischemia. These findings demonstrate a mechanistic role for HO-1 in SDF-1-mediated angiogenesis and provide new avenues for therapeutic approaches in vascular repair.     

Role of tension receptors in dyspeptic patients with hypersensitivity to gastric distention

BACKGROUND & AIMS: Studies in health have shown that tension-sensitive mechanoreceptors mediate sensitivity to gastric distention. A role for these mechanoreceptors in perception or symptoms in hypersensitive functional dyspepsia (FD) has not been established. Tension-sensitive mechanoreceptors are activated during phasic contractions and inactivated during gastric relaxation. The aim of the present study was to investigate whether hypersensitive FD patients perceive spontaneous changes in fundic wall tension and whether fundus-relaxing drugs decrease sensitivity to gastric distention and meal-related symptoms. METHODS: Fifty patients were selected after a barostat study established gastric hypersensitivity. In 12 patients, an intragastric balloon was inflated with a fixed volume just below perception thresholds and patients were asked to indicate changes in perception on a keypad, and the relationship between perception and contractions was analyzed. In 20 patients, we studied the influence of the fundus-relaxing drug sumatriptan on sensitivity to gastric distention. In, respectively, 10 and 8 patients, we studied the influence of the fundus-relaxing drugs sumatriptan and clonidine on meal-related symptoms. RESULTS: The majority of patients had a statistically significant association between perception and phasic isovolumetric contractions. Pretreatment with sumatriptan increased both pressures and volumes needed to induce first perception and discomfort. Pretreatment with sumatriptan and clonidine both significantly decreased meal-induced symptoms. CONCLUSIONS: Patients with hypersensitivity to gastric distention perceive isovolumetric phasic contractions of the proximal stomach. Fundus-relaxing drugs decrease sensitivity to gastric distention and decrease meal-induced symptoms in these patients. The findings are compatible with involvement of tension mechanoreceptors in symptom generation in hypersensitive FD.