Size distribution and buoyant density of <Emphasis Type="Italic">Burkholderia pseudomallei</Emphasis>

The size and density of microbial cells determine the time that pathogens can remain airborne and thus, their potential to infect by the respiratory route. We determined the density and size distribution of Burkholderia pseudomallei cells in comparison with other Burkholderia species, including B. mallei and B. thailandensis, all prepared and analyzed under similar conditions. The observed size distribution and densities of several bacterial strains indicates that aerosolized particles consisting of one or of a few B. pseudomallei cells should be efficiently retained in the lungs, highlighting the risk of transmission of melioidosis by the respiratory route when the pathogen is present in fluids from infected patients or aerosolized from the environment.     

Distinct cardiac and renal effects of ETA receptor antagonist and ACE inhibitor in experimental type 2 diabetes

Diabetic nephropathy is associated with cardiovascular morbidity. Angiotensin-converting enzyme (ACE) inhibitors provide imperfect renoprotection in advanced type 2 diabetes, and cardiovascular risk remains elevated. Endothelin (ET)-1 has a role in renal and cardiac dysfunction in diabetes. Here, we assessed whether combination therapy with an ACE inhibitor and ET(A) receptor antagonist provided reno- and cardioprotection in rats with overt type 2 diabetes. Four groups of Zucker diabetic fatty (ZDF) rats were treated orally from 4 (when proteinuric) to 8 mo with vehicle, ramipril (1 mg/kg), sitaxsentan (60 mg/kg), and ramipril plus sitaxsentan. Lean rats served as controls. Combined therapy ameliorated proteinuria and glomerulosclerosis mostly as a result of the action of ramipril. Simultaneous blockade of ANG II and ET-1 pathways normalized renal monocyte chemoattractant protein-1 and interstitial inflammation. Cardiomyocyte loss, volume enlargement, and capillary rarefaction were prominent abnormalities of ZDF myocardium. Myocyte volume was reduced by ramipril and sitaxsentan, which also ameliorated heart capillary density. Drug combination restored myocardial structure and reestablished an adequate capillary network in the presence of increased cardiac expression of VEGF/VEGFR-1, and significant reduction of oxidative stress. In conclusion, in type 2 diabetes concomitant blockade of ANG II synthesis and ET-1 biological activity through an ET(A) receptor antagonist led to substantial albeit not complete renoprotection, almost due to the ACE inhibitor. The drug combination also showed cardioprotective properties, which however, were mainly dependent on the contribution of the ET(A) receptor antagonist through the action of VEGF.     

Influence of Therapy with Metformin on the Concentration of Certain Divalent Cations in Patients with Non-insulin-Dependent Diabetes Mellitus

Research was performed on a group of 30 patients with non-insulin-dependent diabetes mellitus (NIDDM), who never received antidiabetic medication before, and on a group of 17 healthy adults. The patients were administered treatment with metformin, 1,000 mg/day. Plasmatic and urinary concentration of magnesium have been measured, copper and zinc along with the concentrations of glucose, HDL, LDL, cholesterol, tryglicerides, HbA1c, and total erythrocyte magnesium, in advance and after 3 months of treatment. Data showed significant differences in the NIDDM group vs the control group: for plasma magnesium—1.95 ± 0.19 vs 2.20 ± 0.18 mg/dl, p < 0.001; urine magnesium—237.28 ± 34.51 vs 126.25 ± 38.22 mg/24 h, p < 0.001; erythrocyte magnesium—5.09 ± 0.63 vs 6.38 ± 0.75 mg/dl, p < 0.001; plasma zinc—67.56 ± 6.21 vs 98.41 ± 20.47 μg/dl, p < 0.001; urine zinc—1,347.54 ± 158.24 vs 851.65 ± 209.75 μg/24 h, p < 0.001; plasma copper—111.91 ± 20.98 vs 96.33 ± 8.56 μg/dl, p < 0.001; and urine copper—51.70 ± 23.79 vs 36.00 ± 11.70 μg/24 h, p < 0.05. Treatment with metformin for 3 months modified significant erythrocyte magnesium—5.75 ± 0.61 vs 5.09 ± 0.63 mg/dl, p < 0.001 and urine magnesium—198.27 ± 27.07 vs 237.28 ± 34.51 mg/24 h, p < 0.001, whereas it did not modify significant the plasmatic and urinary concentration of the other cations. The erythrocyte magnesium concentration was inversely correlated with HbA1c (r = −0.438, p = 0.015). The plasma level of copper was positively correlated with HbA1c (r = 0.517, p < 0.003), tryglicerides (r = 0.534, p < 0.003), and cholesterol (r = 0.440, p < 0.05), and the plasma level of zinc was inversely correlated with glycemia (r = −0.399, p = 0.029). Our data show a significant action of metformin therapy, by increasing the total intraerythrocyte magnesium concentration and decreasing the urinary magnesium elimination, positively correlated with the decrease of glycemia and HbA1c in NIDDM patients.     

Rheumatoid nodule and combined pulmonary carcinoma: topographic correlations; a case report and review of the literature

An association between rheumatoid arthritis (RA) and malignancies has been ascertained and patients with RA appear to be at higher risk of lymphoma and lung cancer. The higher risk of the latter malignancy may be related to rheumatoid interstitial lung disease and immunosuppressive therapies. Herein we illustrate the case of a 59-year-old male smoker affected by RA and treated with cortisone, methotrexate and TNF-α antagonists, who underwent right lower lobectomy for a nodular lesion. On microscopic examination, the lesion consisted of two distinct areas: a central area of fibrinoid necrosis, bordered by histiocytes in a palisaded arrangement, lymphocytes and a 0.4 cm thick peripheral area constituted by a combined small cell anaplastic carcinoma, adenocarcinoma and squamous cell carcinoma. The combination of three histotypes is very rare in such a small tumour. In our case, it may be hypothesized that synchronous, heterogeneous mutations occurred in different type of committed cells or in stem cells, due to the production of cytokines by RA nodule histiocytes and lymphocytes, which are contiguous to the carcinomatous area. Since few studies have evaluated the topographic correlation between tumors and rheumatoid lung lesions, further morphological and molecular studies are needed to clarify this association and the pathogenetic relationship between RA and cancer of the lung.     

Signal transduction pathways through cytoprotective, apoptotic and hypertrophic stimuli: a comparative study in adult cardiac myocytes

In response to pathophysiological stresses, cardiac myocytes undergo hypertrophic growth or apoptosis. Multiple signalling pathways have been implicated in these responses and among them, kinases such as mitogen‐activated protein kinases (MAPKs) and Akt. However, the distinction between signalling pathways originally believed to be specific for either hypertrophy, apoptosis or cell survival is fading. The existing data, coming from different experimental systems, often are conflicting. In this study, we sought to compare aspects of intracellular signalling activated by diverse stimuli in a single experimental system, adult rat cardiac myocytes. Furthermore, we assessed the role of these stimuli in eliciting a particular cell phenotype, i.e. whether they promote hypertrophy, cell survival or apoptosis. The results demonstrate that the hypertrophic agonist phenylephrine is the most potent activator of MAPKs/mitogen and stress‐ activated kinase MSK1, although its effect on Akt phosphorylation is relatively minor. The pro‐apoptotic concentration of H₂O₂ activates strongly both MAPKs and PI3K/Akt pathways. Insulin‐like growth factor‐1 has a minimal effect on phosphorylation of MAPKs/MSK1, but it is a potent activator of Akt. In conclusion, hypertrophic, pro‐survival or apoptotic stimuli operate through the same signalling pathways with different time course and amplitude of kinase activation. Thus, to determine the effect of different stimuli on cell fate, it is important to assess signalling pathways as a network and not as a single pathway. Copyright © 2011 John Wiley & Sons, Ltd.     

Nuclear but not cytosolic phosphoinositide 3-kinase beta has an essential function in cell survival

Class I(A) phosphoinositide 3-kinases (PI3Ks) are heterodimeric enzymes composed of a p85 regulatory and a p110 catalytic subunit that induce the formation of 3-polyphosphoinositides, which mediate cell survival, division, and migration. There are two ubiquitous PI3K isoforms p110α and p110β that have nonredundant functions in embryonic development and cell division. However, whereas p110α concentrates in the cytoplasm, p110β localizes to the nucleus and modulates nuclear processes such as DNA replication and repair. At present, the structural features that determine p110β nuclear localization remain unknown. We describe here that association with the p85β regulatory subunit controls p110β nuclear localization. We identified a nuclear localization signal (NLS) in p110β C2 domain that mediates its nuclear entry, as well as a nuclear export sequence (NES) in p85β. Deletion of p110β induced apoptosis, and complementation with the cytoplasmic C2-NLS p110β mutant was unable to restore cell survival. These studies show that p110β NLS and p85β NES regulate p85β/p110β nuclear localization, supporting the idea that nuclear, but not cytoplasmic, p110β controls cell survival.     

Biomechanics of actin filaments: a computational multi-level study

The actin microfilament (F-actin) is a structural and functional component of the cell cytoskeleton. Notwithstanding the primary role it plays for the mechanics of the cell, the mechanical behaviour of F-actin is still not totally explored. In particular, the relationship between the mechanics of F-actin and its molecular architecture is not completely understood. In this study, the mechanical properties of F-actin were related to the molecular topology of its building monomers (G-actin) by employing a computational multi-level approach. F-actins with lengths up to 500 nm were modelled and characterized, using a combination of equilibrium molecular dynamics (MD) simulations and normal mode analysis (NMA). MD simulations were performed to analyze the molecular rearrangements of G-actin in physiological conditions; NMA was applied to compute the macroscopic properties of F-actin from its vibrational modes of motion. Results from this multi-level approach showed that bending stiffness, bending modulus and persistence length are independent from the length of F-actin. On the contrary, the orientations and motions of selected groups of residues of G-actin play a primary role in determining the filament flexibility. In conclusion, this study (i) demonstrated that a combined computational approach of MD and NMA allows to investigate the biomechanics of F-actin taking into account the molecular topology of the filament (i.e., the molecular conformations of G-actin) and (ii) that this can be done using only crystallographic G-actin, without the need of introducing experimental parameters nor of reducing the number of residues.