Spreading of persistent infections in heterogeneous populations

Up to now, the effects of having heterogeneous networks of contacts have been studied mostly for diseases which are not persistent in time, i.e., for diseases where the infectious period can be considered very small compared to the lifetime of an individual. Moreover, all these previous results have been obtained for closed populations, where the number of individuals does not change during the whole duration of the epidemics. Here, we go one step further and analyze, both analytically and numerically, a radically different kind of diseases: those that are persistent and can last for an individual's lifetime. To be more specific, we particularize to the case of tuberculosis' (TB) infection dynamics, where the infection remains latent for a period of time before showing up and spreading to other individuals. We introduce an epidemiological model for TB-like persistent infections taking into account the heterogeneity inherent to the population structure. This sort of dynamics introduces new analytical and numerical challenges that we are able to sort out. Our results show that also for persistent diseases the epidemic threshold depends on the ratio of the first two moments of the degree distribution so that it goes to zero in a class of scale-free networks when the system approaches the thermodynamic limit.

Implosion experiments using glass ablators for direct-drive inertial confinement fusion

Direct-drive implosions with 20-microm-thick glass shells were conducted on the Omega Laser Facility to test the performance of high-Z glass ablators for direct-drive, inertial confinement fusion. The x-ray signal caused by hot electrons generated by two-plasmon-decay instability was reduced by more than approximately 40x and hot-electron temperature by approximately 2x in the glass compared to plastic ablators at ignition-relevant drive intensities of approximately 1x10(15) W/cm2, suggesting reduced target preheat. The measured absorption and compression were close to 1D predictions. The measured soft x-ray production in the spectral range of approximately 2 to 4 keV was approximately 2x to 3x lower than 1D predictions, indicating that the shell preheat caused by soft x-rays is less than predicted. A direct-drive-ignition design based on glass ablators is introduced.

Voxel-based morphometry comparison between first episodes of psychosis with and without evolution to schizophrenia

First episodes (FE) of psychosis may evolve or not to schizophrenia in ensuing years, but there is a lack of reliable predictors of which patients will have to face such an unfavorable outcome. Given the replicated structural alterations of the brain in schizophrenia, it seems advisable to assess whether the alterations of this kind that can be detected at the time of an initial psychotic episode are different depending on the outcome of the patients. To this end, here we applied voxel-based morphometry to assess whether the degree of cerebral abnormalities differ between 30 FE patients who evolved to schizophrenia in the ensuing 2years and another 14 FE patients who could not be diagnosed as such during that period. Forty-one controls were also included in the study. We found that the FE patients who evolved to schizophrenia had a significantly lower GM value than the controls bilaterally in the left dorsolateral prefrontal (BA 9) and in left anterior cingulate (BA 33) regions while the FE patients who did not develop schizophrenia showed a distinct, right-sided pattern of deviation (visual cortex, superior temporal gyrus and inferior frontal). The direct comparison between FE patients who evolved or not evolved to schizophrenia did not reveal significant differences. Taken together, our results support the notion that brain abnormalities may be different in psychotic FE patients depending on their evolution in the medium term.

Imaging techniques and the evaluation of the right heart and the pulmonary circulation

Since the right side of the heart and the pulmonary circulation are regarded as secondary components of the circulatory system, their role in disease has traditionally not received the same attention as their counterparts in the systemic circulation. This was partly because precise noninvasive study of these structures was difficult. For many years, chest radiography and invasive angiography were the only techniques available for imaging the minor circulation. The development of transthoracic echocardiography and nuclear techniques has produced a significant leap forward for noninvasive imaging, particularly of the right ventricle. More recently, novel echocardiographic techniques, and advances in computed tomography and magnetic resonance imaging, in particular, have expanded our diagnostic armamentarium and provided new insights into the anatomy and function of the pulmonary circulation in both health and disease. This article contains a review of the current status of techniques for imaging the right side of the heart and the pulmonary circulation.

The cardioprotection granted by metoprolol is restricted to its administration prior to coronary reperfusion

BACKGROUND

Myocardial infarct size is a strong predictor of cardiovascular events. Intravenous metoprolol before coronary reperfusion has been shown to reduce infarct size; however, it is unknown whether oral metoprolol initiated early after reperfusion, as clinical guidelines recommend, is similarly cardioprotective. We compared the extent of myocardial salvage associated with intravenous pre-reperfusion-metoprolol administration in comparison with oral post-reperfusion-metoprolol or placebo. We also studied the effect on suspected markers of reperfusion injury.

METHODS

Thirty Yorkshire-pigs underwent a reperfused myocardial infarction, being randomized to pre-reperfusion-metoprolol, post-reperfusion-metoprolol or placebo. Cardiac magnetic resonance imaging was performed in eighteen pigs at day 3 for the quantification of salvaged myocardium. The amounts of at-risk and infarcted myocardium were quantified using T2-weighted and post-contrast delayed enhancement imaging, respectively. Twelve animals were sacrificed after 24h for reperfusion injury analysis.

RESULTS

The pre-reperfusion-metoprolol group had significantly larger salvaged myocardium than the post-reperfusion-metoprolol or the placebo groups (31 ± 4%, 13 ± 6%, and 7 ± 3% of myocardium at-risk respectively). Post-mortem analyses suggest lesser myocardial reperfusion injury in the pre-reperfusion-metoprolol in comparison with the other 2 groups (lower neutrophil infiltration, decreased myocardial apoptosis, and higher activation of the salvage-kinase phospho-Akt). Salvaged myocardium and reperfusion injury pair wise comparisons proved there were significant differences between the pre-reperfusion-metoprolol and the other 2 groups, but not among the latter two.

CONCLUSIONS

The intravenous administration of metoprolol before coronary reperfusion results in larger myocardial salvage than its oral administration initiated early after reperfusion. If confirmed in the clinical setting, the timing and route of β-blocker initiation could be revisited.

Noninvasive evaluation of a coronary-pulmonary artery fistula

Coronary angiography can be used to identify the size and anatomical features of coronaryartery fistulas (CAF), but it may fail to depict the drainage site of the CAF or its relation to other structures. In our case, the combined use of CT and CMR provided all the necessary information forclinical management.

Evaluation of cardiac valves using multidetector CT

Cardiac CT is an accurate and reasonable alternative modality for valvular imaging. It is used primarily for the evaluation of coronary artery disease; however, important information regarding valvular anatomy and function can be derived from CT. Calcification is a common CT finding in various valvular abnormalities and carries important diagnostic and prognostic value. In addition, valvular morphology, stenosis, and regurgitation also are detected on contrast enhanced scans, with good correlation with trans-thoracic echocardiography and other techniques.

[Visualizing arterial macrophage warfare with nuclear magnetic resonance, positron-emission tomography and computerized tomography]

The macrophage is the principal immune cell found in atherosclerotic plaque. Although its function is to phagocytose foreign bodies present in the vascular endothelium, it can undergo a process of sustained activation that gives rise to a pattern of chronic inflammation, which may even trigger an acute coronary syndrome. The cellular response underlying this disease process is mediated by a complex molecular signaling cascade. Cytokines released by activated macrophages ultimately produce significant tissue damage by perpetuating the ongoing inflammatory response. Recent studies have shown that a defective interaction between the macrophage and its substrate could provide a mechanism for destabilizing atherosclerotic plaque by stimulating digestion of the artery and promoting plaque rupture. A key element in the life cycle of macrophages is that, when they cannot effectively remove the foreign bodies that have resulted in their activation, they initiate cell death (i.e., apoptosis), thereby releasing substances into the extracellular milieu that are even more toxic than inflammatory mediators. The significant advances in noninvasive molecular imaging techniques that have taken place in recent years have helped to unravel fundamental features of macrophage biology and have made it possible to explore the potential benefits of specific therapeutic interventions. Nanomarkers designed to home in on specific molecular targets have enabled imaging techniques to be used not only to study the pathophysiological mechanisms of atherosclerotic disease but also to diagnose such disease, and have made it possible to imagine the development of a form of nanomedicine based on administering treatment that can target a single cell type.

The CFTR frameshift mutation 3905insT and its effect at transcript and protein level

Cystic fibrosis (CF) is one of the most common genetic diseases in the Caucasian population and is characterized by chronic obstructive pulmonary disease, exocrine pancreatic insufficiency, and elevation of sodium and chloride concentrations in the sweat and infertility in men. The disease is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, which encodes a protein that functions as chloride channel at the apical membrane of different epithelia. Owing to the high genotypic and phenotypic disease heterogeneity, effects and consequences of the majority of the CFTR mutations have not yet been studied. Recently, the frameshift mutation 3905insT was identified as the second most frequent mutation in the Swiss population and found to be associated with a severe phenotype. The frameshift mutation produces a premature termination codon (PTC) in exon 20, and transcripts bearing this PTC are potential targets for degradation through nonsense-mediated mRNA decay (NMD) and/or for exon skipping through nonsense-associated alternative splicing (NAS). Using RT-PCR analysis in lymphocytes and different tissue types from patients carrying the mutation, we showed that the PTC introduced by the mutation does neither elicit a degradation of the mRNA through NMD nor an alternative splicing through NAS. Moreover, immunocytochemical analysis in nasal epithelial cells revealed a significantly reduced amount of CFTR at the apical membrane providing a possible molecular explanation for the more severe phenotype observed in F508del/3905insT compound heterozygotes compared with F508del homozygotes. However, further experiments are needed to elucidate the fate of the 3905insT CFTR in the cell after its biosynthesis.

Association between cerebral metabolic and structural abnormalities and cognitive performance in schizophrenia

The possible association in schizophrenia between frontal abnormalities, such as hypofrontality and frontal grey matter (GM) deficits, and neuropsychological deficits is not yet well defined. Our objective was to study such an association and to clarify the cognitive relevance of metabolic and anatomical variability across schizophrenia patients. To do so, we studied dorsolateral prefrontal (DLPF) metabolism during an attention test using fluoro-deoxy-glucose positron emission tomography and DLPF structure with magnetic resonance imaging (MRI) in 22 schizophrenia patients [9 neuroleptic-naïve (NN) first episodes]. These patients also underwent a comprehensive battery of neuropsychological tests aimed at evaluating global intelligence and the proposed domains of cognitive alteration in schizophrenia, i.e., attention, visual and verbal learning and memory, working memory, problem solving and processing speed. The metabolic activity in the right DLPF region was significantly and directly related to processing speed, and a measure of structural deficit in the same area was directly related to working memory scores. In the NN group studied alone, these associations were replicated. We may conclude that hypofrontality during cognitive activation, and the degree of DLPF structural deficit may be associated to a particular profile of cognitive deficit, including lower processing speed and working memory capacity.

Promoting mechanisms of vascular health: circulating progenitor cells, angiogenesis, and reverse cholesterol transport

To understand and promote vascular health, we must reduce the aggression to the vessel wall and enhance the physiologic mechanisms leading to restoration of vessel wall function. Three main defense mechanisms are responsible for maintaining cardiovascular homeostasis: the regenerative production of endothelial progenitor cells, vessel wall angiogenesis, and macrophage-mediated reverse cholesterol transport. Endothelial progenitor cells can restore vessel wall function and reduce atherosclerosis. In patients with risk factors, high levels of circulating progenitor cells increase event-free survival from cardiovascular events. Mobilization of progenitor cells includes physical and pharmacological approaches, of which exercise and statin therapy have great potential. Angiogenesis is a pivotal defense mechanism to counteract hypoxia and is needed for plaque regression. However, neovessels are susceptible for intraplaque hemorrhage, particularly in diabetes mellitus. In these patients, the haptoglobin 2-2 genotype is the more affected, and may benefit from an antioxidant approach. Finally, the reverse cholesterol transport system is the main mechanism for plaque regression. In addition to high-density lipoprotein cholesterol, apolipoprotein A-I therapies and the promotion of cholesterol efflux from macrophages by the ABCA1 and ABCG1 transporter systems hold great promise and may be available for therapeutic application in the near future.

Prevalence of HLA-B*5701 in HIV-infected patients in Spain (results of the EPI Study)

BACKGROUND

A hypersensitivity reaction (HSR) is associated with abacavir (ABC), a nucleoside reverse transcriptase inhibitor. Genetic association of ABC HSR with the presence of HLA-B*5701 has been demonstrated in PREDICT-1 study, showing a prevalence of 5.6% in HIV-infected population. However the prevalence of this allele in HIV-infected patients in Spain has not been established yet.

METHOD

This is a cross-sectional epidemiological study that included 1,198 patients in 74 centers that serve the HIV-infected population of Spain. HLA-B*5701 was checked both in the hospital lab and one central lab, showing an overall prevalence of this allele of 6%.

RESULTS

HLA-B*5701 was most prevalent in Caucasian population (6.5%). Concordance between the local and central lab was very high for positive and negative results (95.7% and 99.3%, respectively).

CONCLUSION

These aspects define this test as a useful tool for the management of HIV-infected patients.

Evaluation of pulmonary artery stiffness in pulmonary hypertension with cardiac magnetic resonance

OBJECTIVES

This study sought to evaluate indexes of pulmonary artery (PA) stiffness in patients with pulmonary hypertension (PH) using same-day cardiac magnetic resonance (CMR) and right heart catheterization (RHC).

BACKGROUND

Pulmonary artery stiffness is increased in the presence of PH, although the relationship to PH severity has not been fully characterized.

METHODS

Both CMR and RHC were performed on the same day in 94 patients with known or suspected PH. According to the RHC, patients were classified as having no PH (n = 13), exercise-induced PH (EIPH) only (n = 6), or PH at rest (n = 75). On CMR, phase-contrast images were obtained perpendicular to the pulmonary trunk. From CMR and RHC data, PA areas and indexes of stiffness (pulsatility, compliance, capacitance, distensibility, elastic modulus, and the pressure-independent stiffness index beta) were measured at rest.

RESULTS

All quantified indexes showed increased PA stiffness in patients with PH at rest in comparison with those with EIPH or no PH. Despite the absence of significant differences in baseline pressures, patients with EIPH had lower median compliance and capacitance than patients with no PH: 15 (interquartile range: 9 to 19.8) mm2/mm Hg versus 8.4 (interquartile range: 6 to 10.3) mm2/mm Hg, and 5.2 (interquartile range: 4.4 to 6.3) mm3/mm Hg versus 3.7 (interquartile range: 3.1 to 4.1) mm3/mm Hg, respectively (p < 0.05). The different measurements of PA stiffness, including stiffness index beta, showed significant correlations with PA pressures (r2 = 0.27 to 0.73). Reduced PA pulsatility (<40%) detected the presence of PH at rest with a sensitivity of 93% and a specificity of 63%.

CONCLUSIONS

Pulmonary artery stiffness increases early in the course of PH (even when PH is detectable only with exercise and before overt pressure elevations occur at rest). These observations suggest a potential contributory role of PA stiffness in the development and progression of PH.