In Vitro Investigation of the Impact of Aortic Valve Stenosis Severity on Left Coronary Artery Flow

Patients with aortic valve stenosis (AS) may experience angina pectoris even if they have angiographically normal coronary arteries. Angina is associated with a marked increase in the risk of sudden death in AS patients. Only a few in vitro models describing the interaction between the left ventricular and aortic pressures, and the coronary circulation have been reported. These models were designed for specific research studies and they need to be improved or modified when other specific studies are required. Consequently, we have developed an in vitro model that is able to mimic the coronary circulation in presence of aortic stenosis. First, we have validated the model under physiological conditions. Then, we have examined and quantified the hemodynamic effects of different degrees of AS (from normal to severe AS) on the coronary flow using a model of the normal left coronary artery. In the coronary in vitro model without AS (normal valve), the amplitude and shape of coronary flow were similar to those observed in in vivo measurements obtained under physiological conditions, as described by Hozumi et al. (1998, “Noninvasive Assessment of Significant Left Anterior Descending Coronary Artery Stenosis by Coronary Flow Velocity Reserve With Transthoracic Color Doppler Echocardiography,” Circulation, 97, pp. 1557–1562). The presence of an AS induced an increase in the maximum and mean coronary flow rates (97% and 73%, respectively, for a very severe AS). Furthermore, when AS was very severe, a retrograde flow occurred during systole. This study allowed us to validate our coronary in vitro model under physiological conditions, both in the absence and presence of AS. These changes could explain the fact that even if patients have angiographically normal epicardial coronary arteries, we can observe the occurrence of angina pectoris in these patients in the presence of an AS.

Endogenous TasiRNAs mediate non-cell autonomous effects on gene regulation in Arabidopsis thaliana

Background

Different classes of small RNAs (sRNAs) refine the expression of numerous genes in higher eukaryotes by directing protein partners to complementary nucleic acids, where they mediate gene silencing. Plants encode a unique class of sRNAs, called trans-acting small interfering RNAs (tasiRNAs), which post-transcriptionally regulate protein-coding transcripts, as do microRNAs (miRNAs), and both sRNA classes control development through their targets. TasiRNA biogenesis requires multiple components of the siRNA pathway and also miRNAs. But while 21mer siRNAs originating from transgenes can mediate silencing across several cell layers, miRNA action seems spatially restricted to the producing or closely surrounding cells.

Principal Findings

We have previously described the isolation of a genetrap reporter line for TAS3a, the major locus producing AUXIN RESPONS FACTOR (ARF)-regulating tasiRNAs in the Arabidopsis shoot. Its activity is limited to the adaxial (upper) side of leaf primordia, thus spatially isolated from ARF-activities, which are located in the abaxial (lower) side. We show here by in situ hybridization and reporter fusions that the silencing activities of ARF-regulating tasiRNAs are indeed manifested non-cell autonomously to spatially control ARF activities.

Conclusions/Significance

Endogenous tasiRNAs are thus mediators of a mobile developmental signal and might provide effective gene silencing at a distance beyond the reach of most miRNAs.

Impairment of coronary flow reserve in aortic stenosis

Coronary flow reserve (CFR) is markedly reduced in patients with severe aortic valve stenosis (AS), but the exact mechanisms underlying this impairment of CFR in AS remain unclear. Reduced CFR is the key mechanism leading to myocardial ischemia symptoms and adverse outcomes in AS patients. The objective of this study was to develop an explicit mathematical model formulated with a limited number of parameters that describes the effect of AS on left coronary inflow patterns and CFR. We combined the mathematical V3 (ventricular-valvular-vascular) model with a new lumped-parameter model of coronary inflow. One thousand Monte-Carlo computational simulations with AS graded from mild up to very severe were performed within a wide range of physiological conditions. There was a good agreement between the CFR values computed with this new model and those measured in 24 patients with isolated AS ( r = 0.77, P < 10−4). A global sensitivity analysis showed that the valve effective orifice area (EOA) was the major physiological determinant of CFR (total sensitivity index = 0.87). CFR was markedly reduced when AS became severe, i.e., when EOA was <1.0 cm2, and was generally exhausted when the EOA was <0.5–0.6 cm2. The reduction of CFR that is associated with AS can be explained by the concomitance of 1) reduced myocardial supply as a result of decreased coronary perfusion pressure, and 2) increased myocardial metabolic demand as a result of increased left ventricular workload.

Diagnosis and treatment of tuberculosis in undocumented migrants in low- or intermediate-incidence countries

SETTING

Countries with low or intermediate tuberculosis (TB) incidence.

OBJECTIVES

1) To gather information on individuals and TB patients who are undocumented migrants and their access to TB diagnostic and treatment services; 2)to discuss interventions to strengthen diagnosis and treatment and 3) to formulate recommendations on how to ensure adequate TB prevention and control.

DESIGN

Questionnaires sent to members of the Working Group (WG) on Transborder Migration and TB, managers of national TB programmes and EuroTB correspondents; literature research and development of a paper by a writing committee through consultation.

RESULTS

Undocumented migrants represent 5-30% of immigrants and 5-10% of TB cases. Most countries reported full access to diagnosis and treatment, but in practice there were limitations. Most countries also reported that they could and did deport cases who were on TB treatment. A variety of activities to ensure access were reported from different countries.

CONCLUSION

The WG recommends that 1) health authorities and/or health staff should ensure easy access to low-threshold facilities where undocumented migrants who are TB suspects can be diagnosed and treated without giving their names and without fear of being reported to the police or migration officials. Health authorities should remind health staff that they have an obligation of confidentiality; 2) each country should ensure that undocumented migrants with TB are not deported until completion of treatment; and 3) authorities and non-governmental sectors should raise awareness among undocumented migrants about TB, emphasising that diagnosis and treatment should be free of charge and wholly independent of migratory status.

Factors influencing the breeding density of Bearded Vultures, Egyptian Vultures and Eurasian Griffon Vultures in Catalonia (NE Spain): management implications

Using multivariate analyses we examined differences in breeding density of the Bearded Vulture Gypaetus barbatus, the Eurasian Griffon Vulture Gyps fulvus and the Egyptian Vulture Neophron percnopterus in NE Spain (Catalonia) in relation to trophic, orographic-landscape and anthropic variables. Sampling units used were regional divisions (comarques). High density of Bearded Vulture was principally linked to areas with scant vegetation and low human population density. In contrast, high densities of both the Egyptian and Eurasian Griffon Vultures were associated with availability of trophic resources (sheep and goats). Positive effects were detected in relation to low density of inhabitants (Egyptian Vulture) and altitudes between 1,000-2,000 m and landscape with low tree cover (Eurasian Griffon Vulture). The Bearded Vulture seemed to be the most selective species in relation to environmental characteristics while the Eurasian Griffon and the Egyptian Vultures displayed a higher degree of ecological plasticity. Future conservation actions should bear these results in mind in order to optimise management. Food resources from extensive livestock farming, in particular, seem fundamental for the conservation of scavenger species. Preference monitoring and conservation efforts are needed in the regions with highest vulture densities (Alta Ribagorça, Pallars Jussà and Alt Urgell), while regions with low vulture populations should be managed in order to favour the geographical expansion and recolonisation of zones currently not occupied by these species. Conservation priorities should be based on favouring extensive livestock practices, and as an alternative to muladares (traditional animal carcass disposal sites) farmers should be encouraged to leave animal carcasses in the field, while ensuring compliance with health regulations.

The effects of multifocal refractive lenses on occipital extension and forward head posture during a visual task

The purpose of this study was to determine if a change in forward head posture and occipital extension occurred in participants who wore multifocal lenses vs. those persons with non-multifocal lenses while performing an 8-min visual reading task on a visual display unit (VDU). Forty-two healthy human participants were recruited for this study. Thirty-three participants completed the study. Fourteen participants wore multifocal lenses and 19 wore frames with non-multifocal lenses. To evaluate the degree of change of forward head posture and occipital extension digital photographs of cervical posture were taken at four different time intervals: prior to performing the reading task and at 3, 5 and 8 min during the reading task. The digital photographs were analysed utilizing a computer program. Two one-way ANOVA were utilized to determine the degree of change of forward head posture and occipital extension between groups. A significant difference was identified between groups for changes in degrees of forward head posture while performing a visual reading task on a VDU. However, no significant difference between groups was found for occipital extension while performing the same task. Multifocal wearers exhibit greater degrees of change in forward head posture and occipital extension than non-multifocal wearers. These postural changes may place them at a greater risk for musculoskeletal disorders and headaches.

Signal losses with real-time three-dimensional power Doppler imaging

Power Doppler imaging (PDI) has been shown to be influenced by the wall filter when assessing arterial stenoses. Real-time 3-D Doppler imaging may likely become a widespread practice in the near future, but how the wall filter could affect PDI during the cardiac cycle has not been investigated. The objective of the study was to demonstrate that the wall filter may produce unexpected major signal losses in real-time 3-D PDI. To test our hypothesis, we first validated binary images obtained from analytical simulations with in vitro PDI acquisitions performed in a tube under pulsatile flow conditions. We then simulated PDI images in the presence of a severe stenosis, considering physiological conditions by finite element modeling. Power Doppler imaging simulations revealed important signal losses within the lumen area at different instants of the flow cycle, and there was a very good concordance between measured and predicted PDI binary images in the tube. Our results show that the wall filter may induce severe PDI signal losses that could negatively influence the assessment of vascular stenosis. Clinicians should therefore be aware of this cause of signal loss to properly interpret power Doppler angiographic images.

X-ray powder diffraction structural characterization of Pb1-xBaxZr0.65Ti0.35O3 ceramic

The structure of Pb(1-x)Ba(x)Zr(0.65)Ti(0.35)O(3) (PBZT) ceramic materials with 0.00 < or = x < or = 0.40 was studied using synchrotron X-ray powder diffraction data. According to the Rietveld refinements, the structure of PBZT ceramics with x = 0.00, 0.10 and 0.20 at room temperature was rhombohedral R3c. A phase transition from rhombohedral to cubic was observed at 543 and 463 K for x = 0.10 and 0.20, respectively. The refinement for the compositions x = 0.30 and x = 0.40 showed a cubic structure from 10 to 450 K, in good agreement with the dielectric properties of these samples.

Noninvasive Assessment of the Right Ventricular Filling Pressure Gradient

Background— The physiological basis of right ventricular (RV) diastolic function remains incompletely studied in humans. The driving force responsible for RV filling, the pressure gradient along the RV inlet from the right atrium to the RV apex, has never been measured in the clinical setting.

Methods and Results— We validated a method for measuring the RV filling pressure difference (RVFPD) from color Doppler M-mode recordings in 12 pigs undergoing interventions on RV preload, afterload, and lusitropic states (error, −0.1±0.4 mm Hg compared with micromanometers; intraclass correlation coefficient, 0.88). Peak early RVFPD correlated directly with mean right atrial pressure and inversely with the time constant of RV relaxation. In 21 patients with dilated cardiomyopathy, the peak RVFPD was 1.0 mm Hg (95% CI, 0.8 to 1.2), significantly lower than in age-matched control subjects (1.4 mm Hg; 95% CI, 1.2 to 1.6). In another population of 19 young healthy volunteers, the peak RVFPD was 2.3 mm Hg (95% CI, 2.0 to 2.6), which was reduced by nitroglycerine and esmolol and was augmented by volume overload and atropine infusions. RVFPD was generated almost exclusively by inertial forces.

Conclusions— For the first time, the RV driving filling force can be accurately measured noninvasively in the clinical setting, and the method is sensitive to detect the effects of preload, chronotropic, and lusitropic states. In patients with dilated cardiomyopathy, the RV filling force is markedly reduced, indicating severely impaired RV relaxation. These findings suggest that this is a useful tool for improving the clinical assessment of RV diastolic function.

Biochip array-based analysis of plasma cytokines in HIV patients with immunological and virological discordance

Assessment of cytokines in body fluids or cells provides important information in understanding the disease process and designing treatment strategies. Recent introduction of antibody-based protein arrays have provided investigators simultaneous and specific detection of multiple analytes in a single sample using minimum volumes. In this study, we used a biochip array system capable of measuring 12 cytokines and growth factors (IL-2, IL-4, IL-6, IL-8, IL-10, IL-1alpha, IL-1beta, IFN-gamma, TNF-alpha, monocyte chemoattractant protein-1 (MCP-1), vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF)) in HIV patients with immunological and virological discordance (discordant) to find out differences if any, in their plasma cytokine profiles when compared with concordant HIV-infected individuals. A sandwich chemiluminescent assay was performed with plasma specimens of 110 HIV patients (55 discordant, 55 concordant) and 22 normal healthy individuals followed by enzyme-linked immunosorbent assay (ELISA) to the confirm levels of cytokines and growth factors that showed significant differences in the two groups. The discordant HIV patients showed significantly higher levels of plasma VEGF (P = 0.001) and EGF (P = 0.034) levels when compared with concordant patients. Overall, the patients showed significantly higher levels of TNF-alpha, MCP-1 and VEGF when compared with the normal healthy controls (P < 0.05). ELISA for VEGF (P < 0.001) and EGF (P = 0.004) confirmed the comparison obtained with biochip array, between the discordant and concordant patients. The results of cytokine quantitation by biochip array and ELISA confirmed that this technology is not only comparable but also has a good potential in the future applications involving measurement of multiple cytokines with limiting specimens.