In vivo effect of aluminium upon the physical properties of the erythrocyte membrane

Aluminium (Al (III)) is a metal with no biological function. Its organic accumulation can lead to toxic effects. To elucidate the in vivo effect of Al (III) upon the rheological properties of the erythrocyte membrane, male adult Wistar rats have been submitted to periodical injections of Al(OH)3 during three months. Significant decreases in haematocrit (34+/-0.37% versus 36+/-0.20%, p<0.0001) and blood haemoglobin concentration (10.7+/-0.15 g/dl versus 12.3+/-0.49 g/dl, p<0.005) have been found. Haemolysis curves shifted towards the left, indicating that erythrocytes became more resistant to hypotonic haemolysis. Significant increments in rigidity index (29.6+/-1.59 versus 9.2+/-0.40, p<0.0001), relative viscosity at native haematocrit (3.6+/-0.03 versus 3.5+/-0.03, p<0.04), and relative viscosity at standard haematocrit (4.5+/-0.06 versus 3.9+/-0.05, p<0.0001) have been observed. The decrease in the erythrocyte aggregate size (1.6+/-0.01 versus 1.7+/-0.01, p<0.002) and the aggregation rate (0.5+/-0.02 versus 0.6+/-0.03, p<0.002) indicated a significantly dropped aggregability process. In conclusion, Al (III) disorganised the erythrocyte membrane by altering its mechanical properties, suggesting a reduction of the middle life of circulating erythrocytes, which could play a major role in the anaemia of these animals.     

Direct detection of Mycobacterium tuberculosis complex in pulmonary and extrapulmonary samples by BDProbeTec ET system

BDProbeTec ET (Becton Dickinson, Sparks, Md, USA) is a fully automated walkaway system based on strand displacement amplification (SDA) technology that provides a method for the direct detection of Mycobacterium tuberculosis complex (MTBC) target sequence. The purpose of this study was to evaluate the ability of BDProbeTec ET system to detect MTBC directly from clinical specimens and compare the results with staining and culture. From February 2002 through December 2003 a total of 1521 [pulmonary (n=1329) and extrapulmonary (n=192)] specimens from 1518 patients were examined by BDProbeTec ET system for the detection of MTBC and the results were compared to those obtained by microscopy and liquid culture (BACTEC 9000 MB, Becton Dickinson). MTBC was cultivated from 65 specimens (60 pulmonary and 5 extrapulmonary) of which 43 (66.2%) (42 pulmonary and 1 extrapulmonary) were smear positive and 22 (33.8%) (18 pulmonary and 4 extrapulmonary) were smear negative. BDProbeTec ET detected MTBC in 58 (55 pulmonary and 3 extrapulmonary) of the 65 culture-positive specimens. Although the BDProbeTec ET system gave five false-negative results among the 18 smear-negative culture-positive pulmonary specimens, our results demonstrate that the BDProbeTec ET system is a reliable tool in smear-positive samples and given its technical characteristics it can be used for the rapid detection of MTBC in either pulmonary or extrapulmonary samples.     

Aminolevulinic acid: from its unique biological function to its star role in photodynamic therapy

Porphyrins are molecules essential for life. They are involved in the key processes of photosynthesis and respiration. The biosynthesis of tetrapyrroles in all living cells occurs through several steps where the formation of aminolevulinic acid (ALA) is the first committed intermediate. Two alternative routes for the formation of ALA have been proposed: one involves the condensation of Succinyl CoA and glycine catalyzed by ALA synthetase taking place in the mitochondria, and the second one is the so called 5-carbon route, occurring in the stroma of plastids. Eight molecules of ALA are used in the formation of protoporphyrin IX. Specific deficiencies in one of the enzymes of the heme pathway produce the porphyrias. In the acute porphyrias, the pathogenesis of the neurological dysfunction is attributed to the accumulation of ALA. Fluorescent and photosensitizing properties of protoporphyrin accumulated after the exogenous administration of ALA, can be used to visualize and destroy malignant cells in the so-called photodynamic diagnosis (PDD) and photodynamic therapy (PDT) of cancer. Many clinical ALA-PDT applications to malignant and non-malignant pathologies are currently in use. Different approaches to enhance ALA penetration in cells are under investigation, including the use of more lipophilic ALA derivatives and studies of the transport mechanisms of ALA. ALA has also been proposed to be used as a biodegradable herbicide, as an insecticide and as a plant growth regulator.     

Stromal cell-derived factor-1alpha (SDF-1alpha/CXCL12) stimulates ovarian cancer cell growth through the EGF receptor transactivation

Ovarian cancer (OC) is the leading cause of death in gynecologic diseases in which there is evidence for a complex chemokine network. Chemokines are a family of proteins that play an important role in tumor progression influencing cell proliferation, angiogenic/angiostatic processes, cell migration and metastasis, and, finally, regulating the immune cells recruitment into the tumor mass. We previously demonstrated that astrocytes and glioblastoma cells express both the chemokine receptor CXCR4 and its ligand stromal cell-derived factor-1 (SDF-1), and that SDF-1alpha treatment induced cell proliferation, supporting the hypothesis that chemokines may play an important role in tumor cells' growth in vitro. In the present study, we report that CXCR4 and SDF-1 are expressed in OC cell lines. We demonstrate that SDF-1alpha induces a dose-dependent proliferation in OC cells, by the specific interaction with CXCR4 and a biphasic activation of ERK1/2 and Akt kinases. Our results further indicate that CXCR4 activation induces EGF receptor (EGFR) phosphorylation that in turn was linked to the downstream intracellular kinases activation, ERK1/2 and Akt. In addition, we provide evidence for cytoplasmic tyrosine kinase (c-Src) involvement in the SDF-1/CXCR4-EGFR transactivation. These results suggest a possible important "cross-talk" between SDF-1/CXCR4 and EGFR intracellular pathways that may link signals of cell proliferation in ovarian cancer.     

RNA silencing platforms in plants

Since the discovery of RNAi, its mechanism in plants and animals has been intensively studied, widely exploited as a research tool, and used for a number of potential commercial applications. In this article, we discuss the platforms for delivering RNAi in plants. We provide a brief background to these platforms and concentrate on discussing the more recent advances, comparing the RNAi technologies used in plants with those used in animals, and trying to predict the ways in which RNAi technologies may further develop.