The expression of Rho proteins decreases with human brain tumor progression: Potential tumor markers

Astrocytic tumors are the most common human brain tumors. Establishment of tumor grade is a key determinant both in the choice of a therapeutic approach and in the prognosis. The diagnosis of astrocytic tumors is currently determined following histopathological analysis. The identification of molecular markers would offer a complementary tool for characterizing tumors with respect to their clinical behavior. In this study we determined the expression levels of 3 small GTP binding proteins (RhoA, RhoB and Rac1), of their inhibitor RhoGDI and of caveolin-1 in 24 human astrocytic tumors of grades I to IV. Our results demonstrated that the expression of RhoA and RhoB decreased significantly in all brain tumors studied and was inversely related with tumor of grade II to IV malignancy. The amount of caveolin-1 immunodetected was not significantly different from normal brain samples while the Rac1 expression level was diminished in astrocytic tumors of grades III and IV. Our finding that RhoA and RhoB expression levels are correlated to tumor malignancy suggests that they may serve as novel and efficient diagnostic markers for astrocytic brain tumors of histological grade II to IV and complement currently applied histopathological analysis.     

Role of the wbt locus of Francisella tularensis in lipopolysaccharide O-antigen biogenesis and pathogenicity

Francisella tularensis is a highly infectious bacterial pathogen, responsible for the zoonotic disease tularemia. We screened a bank of transposon insertion mutants of F. tularensis subsp. holarctica LVS for colony morphology alterations and selected a mutant with a transposon insertion in wbtA, the first gene of the predicted lipopolysaccharide O-antigen gene cluster. Inactivation of wbtA led to the complete loss of O antigen, conferred serum sensitivity, impaired intracellular replication, and severely attenuated virulence in the mouse model. Notably, this mutant afforded protection against a challenge against virulent LVS.     

Impact of Aortic Valve Calcification,as Measured by MDCT,on Survival in Patients With Aortic Stenosis : Results of an International Registry Study

Background

Aortic valve calcification (AVC) load measures lesion severity in aortic stenosis (AS) and is useful for diagnostic purposes. Whether AVC predicts survival after diagnosis, independent of clinical and Doppler echocardiographic AS characteristics, has not been studied.

Objectives

This study evaluated the impact of AVC load, absolute and relative to aortic annulus size (AVC_density), on overall mortality in patients with AS under conservative treatment and without regard to treatment.

Methods

In 3 academic centers, we enrolled 794 patients (mean age, 73 ± 12 years; 274 women) diagnosed with AS by Doppler echocardiography who underwent multidetector computed tomography (MDCT) within the same episode of care. Absolute AVC load and AVC_density (ratio of absolute AVC to cross-sectional area of aortic annulus) were measured, and severe AVC was separately defined in men and women.

Results

During follow-up, there were 440 aortic valve implantations (AVIs) and 194 deaths (115 under medical treatment). Univariate analysis showed strong association of absolute AVC and AVC_density with survival (both, p < 0.0001) with a spline curve analysis pattern of threshold and plateau of risk. After adjustment for age, sex, coronary artery disease, diabetes, symptoms, AS severity on hemodynamic assessment, and LV ejection fraction, severe absolute AVC (adjusted hazard ratio [HR]: 1.75; 95% confidence interval [CI]: 1.04 to 2.92; p = 0.03) or severe AVC_density (adjusted HR: 2.44; 95% CI: 1.37 to 4.37; p = 0.002) independently predicted mortality under medical treatment, with additive model predictive value (all, p ≤ 0.04) and a net reclassification index of 12.5% (p = 0.04). Severe absolute AVC (adjusted HR: 1.71; 95% CI: 1.12 to 2.62; p = 0.01) and severe AVC_density (adjusted HR: 2.22; 95% CI: 1.40 to 3.52; p = 0.001) also independently predicted overall mortality, even with adjustment for time-dependent AVI.

Conclusions

This large-scale, multicenter outcomes study of quantitative Doppler echocardiographic and MDCT assessment of AS shows that measuring AVC load provides incremental prognostic value for survival beyond clinical and Doppler echocardiographic assessment. Severe AVC independently predicts excess mortality after AS diagnosis, which is greatly alleviated by AVI. Thus, measurement of AVC by MDCT should be considered for not only diagnostic but also risk-stratification purposes in patients with AS.     

Localization of orexins and their receptors in the rat olfactory system: possible modulation of olfactory perception by a neuropeptide synthetized centrally or locally

Orexin-A and -B, also known as hypocretins, are two neuropeptides acting on feeding and sleep. They are specific ligands for two different receptors belonging to the G-protein coupled receptors family. Orexin fibers and orexin receptor neurons have been previously described in the forebrain olfactory system. Using immunocytochemistry, we showed that both orexin-A and -B as well as their receptors were present at different levels of the olfactory system, from the nasal mucosa to nuclei of the amygdala. A punctuated staining for orexins and their receptors was detected at the apical part of the olfactory epithelium; in the lamina propria of the mucosa, the staining was localized around olfactory nerves. At the ultrastructural level, olfactory neurons and supporting cells were found immunoreactive for orexins and their receptors. The labeling was localized in dendritic knobs and cilia of neurons, in the apical part and microvilli of supporting cells. The finding of immunolabeled cisternae of reticulum strongly suggests a local synthesis of both peptides and receptors, confirmed by RT-PCR experiments. In forebrain and amygdala regions, we detected numerous orexin fibers. Orexin receptors were present in mitral-tufted cells of the bulb and in many neuronal perikarya in the anterior olfactory nuclei, piriform cortex and amygdala nuclei. Altogether, these results show that orexins and their receptors are present at all levels of the olfactory system, from cilia where odors bind to their receptors to central regions where integration of olfactory signals occurs. They suggest a possible modulation of olfactory perception by these neuropeptides.     

Opportunities and challenges in antiparasitic drug discovery

New antiparasitic drugs are urgently needed to treat and control diseases such as malaria, leishmaniasis, sleeping sickness and filariasis, which affect millions of people each year. However, because the majority of those infected live in countries in which the prospects of any financial return on investment are too low to support market-driven drug discovery and development, alternative approaches are needed. In this article, challenges and opportunities for antiparasitic drug discovery are considered, highlighting some of the progress that has been made in recent years, partly through scientific advances, but also by more effective partnership between the public and private sectors.     

Acamprosate (Aotal): could adverse effects upset the treatment of alcohol dependence?

Acamprosate, a stimulant of central inhibitory GABA neurotransmision and an antagonist of excitatory amino acids, is used in alcohol withdrawal and for the maintenance of abstinence. After identification of several cases of treatment discontinuation during alcohol abstinence because of acamprosate-induced adverse drug reactions (ADRs), a retrospective study was conducted in order to investigate and quantify acamprosate-induced ADRs. Up to July 2002, 472 patients were included for treatment of alcohol withdrawal: of these, 68% (n = 322) received acamprosate. At least one ADR occurred in 98 patients (30%). The mean age of the patients was 41.5 +/- 8.8 years (range: 24-65) and 70% were male. All ADRs were classified as 'non serious'. However, ADRs required a dose decrease in 61 cases or acamprosate discontinuation in 76 cases (62.2% and 77.5%, respectively, of patients with an ADR). We identified mainly gastrointestinal ADRs in 67 patients (mean delay before occurrence: 7.6 days), i.e. 20.8% of patients treated with acamprosate (corresponding to 68.3% of ADRs), with a positive rechallenge in five cases. Moreover, cutaneous ADRs (pruritus) occurred in 29 patients (mean delay before occurrence: 9.0 days), and required acamprosate withdrawal in 22 patients (75.9%) with a prior dose decrease in 18 of these patients (62.1%). Our results show that a dose decrease or withdrawal of acamprosate was necessary in 18.9% and 23.6%, respectively, of patients because of the occurrence of ADRs. The present study shows the important role of acamprosate-induced ADRs among the various causes for failure of alcohol abstinence.     

A comparative transmission electron microscopy study of titanium dioxide and carbon black nanoparticles uptake in human lung epithelial and fibroblast cell lines

Several studies suggest that the biological responses induced by manufactured nanoparticles (MNPs) may be linked to their accumulation within cells. However, MNP internalisation has not yet been sufficiently characterised. Therefore, the aim of this study was to compare the intracellular uptake of three different MNPs: two made of carbon black (CB) and one made of titanium dioxide (TiO(2)), in 16HBE bronchial epithelial cells and MRC5 fibroblasts. Transmission electron microscopy was used to evaluate the intracellular accumulation. Different parameters were analysed following a time and dose-relationship: localisation of MNPs in cells, percentage of cells having accumulated MNPs, number of aggregated MNPs in cells, and the size of MNP aggregates in cells. The results showed that MNPs were widely and rapidly accumulated in 16HBE cells and MRC5 fibroblasts. Moreover, MNPs accumulated chiefly as aggregates in cytosolic vesicles and were absent from the mitochondria or nuclei. CB and TiO(2) MNPs had similar accumulation patterns. However, TiO(2) aggregates had a higher size than CB aggregates. Intracellular MNP accumulation was dissociated from cytotoxicity. These results suggest that cellular uptake of MNPs is a common phenomenon occurring in various cell types.