Microcystis aeruginosa inactivation and microcystin-LR degradation by the photo-Fenton process at the initial near-neutral pH.

Of all cyanobacteria, Microcystis aeruginosa is the most commonly found species in bloom episodes all over the world. This species is known to produce cyanopeptides with hepatotoxic effects, namely microcystins (MCs). In this regard, Advanced Oxidation Processes (AOPs) have been widely studied for cyanotoxin degradation, but very few studies focused on cyanobacteria inactivation combined with toxin removal. To our knowledge, this is the first report of the photo-Fenton process application focusing on M. aeruginosa inactivation and microcystin-LR (MC-LR) degradation. This research work aimed to evaluate the photo-Fenton process under three different conditions with regard to Fe2+/H2O2 ratios (0.6/10, 5/50, and 20/100 mg L-1) at the initial near-neutral pH. Process efficiency was measured by immediate cell density reduction, growth inhibition, effect on MC-LR concentrations, and scanning electron microscopy (SEM) to analyze any alterations in cell morphology. Growth inhibition test (GIT) results pointed to cell inactivation under all conditions tested, and MC-LR concentrations were reduced below WHO's maximum limit at medium and higher concentrations of reagents. The possible mechanisms of cell inactivation by oxidative species are discussed.

Improved biovolume estimation of Microcystis aeruginosa colonies: A statistical approach.

The Microcystis aeruginosa complex (MAC) clusters many of the most common freshwater and brackish bloom-forming cyanobacteria. In monitoring protocols, biovolume estimation is a common approach to determine MAC colonies biomass and useful for prediction purposes. Biovolume (µm3 mL-1) is calculated multiplying organism abundance (orgL-1) by colonial volume (µm3org-1). Colonial volume is estimated based on geometric shapes and requires accurate measurements of dimensions using optical microscopy. A trade-off between easy-to-measure but low-accuracy simple shapes (e.g. sphere) and time costly but high-accuracy complex shapes (e.g. ellipsoid) volume estimation is posed. Overestimations effects in ecological studies and management decisions associated to harmful blooms are significant due to the large sizes of MAC colonies. In this work, we aimed to increase the precision of MAC biovolume estimations by developing a statistical model based on two easy-to-measure dimensions. We analyzed field data from a wide environmental gradient (800 km) spanning freshwater to estuarine and seawater. We measured length, width and depth from ca. 5700 colonies under an inverted microscope and estimated colonial volume using three different recommended geometrical shapes (sphere, prolate spheroid and ellipsoid). Because of the non-spherical shape of MAC the ellipsoid resulted in the most accurate approximation, whereas the sphere overestimated colonial volume (3-80) especially for large colonies (MLD higher than 300 µm). Ellipsoid requires measuring three dimensions and is time-consuming. Therefore, we constructed different statistical models to predict organisms depth based on length and width. Splitting the data into training (2/3) and test (1/3) sets, all models resulted in low training (1.41-1.44%) and testing average error (1.3-2.0%). The models were also evaluated using three other independent datasets. The multiple linear model was finally selected to calculate MAC volume as an ellipsoid based on length and width. This work contributes to achieve a better estimation of MAC volume applicable to monitoring programs as well as to ecological research.

Canine cerebellar protoplasmic astrocytoma: clinical, histopathological and immunohistochemical features

Protoplasmic astrocytomas are uncommon in humans and animals. A 14-year-old, intact female German Shepherd dog presented with a history of ataxia of the pelvic limbs, left-side head torsion and hypermetric response of the right side for approximately 15 days. Neurological examination revealed the presence of cerebellar syndrome and paradoxical vestibular syndrome. Medical therapy was initiated, but neurological signs were progressive, and the owner opted for euthanasia. Gross examination showed no cerebellar lesion. Microscopic features were characterized by prominent background microcystic degeneration and the presence of spindle cells with scant cytoplasm and delicate glial fibers. The immunohistochemical assay showed positive staining for GFAP (glial fibrillar acidic protein), vimentin and S100, and negative staining for factor VIII. A definitive diagnosis of protoplasmic astrocytoma was made on the basis of the histological and immunohistochemical findings.

Canine cerebellar protoplasmic astrocytoma: clinical, histopathological and immunohistochemical features

Protoplasmic astrocytomas are uncommon in humans and animals. A 14-year-old, intact female German Shepherd dog presented with a history of ataxia of the pelvic limbs, left-side head torsion and hypermetric response of the right side for approximately 15 days. Neurological examination revealed the presence of cerebellar syndrome and paradoxical vestibular syndrome. Medical therapy was initiated, but neurological signs were progressive, and the owner opted for euthanasia. Gross examination showed no cerebellar lesion. Microscopic features were characterized by prominent background microcystic degeneration and the presence of spindle cells with scant cytoplasm and delicate glial fibers. The immunohistochemical assay showed positive staining for GFAP (glial fibrillar acidic protein), vimentin and S100, and negative staining for factor VIII. A definitive diagnosis of protoplasmic astrocytoma was made on the basis of the histological and immunohistochemical findings.(AU)

Static electric fields interfere in the viability of cells exposed to ionising radiation.

PURPOSE: The interference of electric fields (EF) with biological processes is an issue of considerable interest. No studies have as yet been reported on the combined effect of EF plus ionising radiation. Here we report studies on this combined effect using the prokaryote Microcystis panniformis, the eukaryote Candida albicans and human cells. MATERIALS AND METHODS: Cultures of Microcystis panniformis (Cyanobacteria) in glass tubes were irradiated with doses in the interval 0.5-5 kGy, using a (60)Co gamma source facility. Samples irradiated with 3 kGy were exposed for 2 h to a 20 V . cm(-1) static electric field and viable cells were enumerated. Cultures of Candida albicans were incubated at 36 degrees C for 20 h, gamma-irradiated with doses from 1-4 kGy, and submitted to an electric field of 180 V . cm(-1). Samples were examined under a fluorescence microscope and the number of unviable (red) and viable (apple green fluorescence) cells was determined. For crossing-check purposes, MRC5 strain of lung cells were irradiated with 2 Gy, exposed to an electric field of 1250 V/cm, incubated overnight with the anti-body anti-phospho-histone H2AX and examined under a fluorescence microscope to quantify nuclei with gamma-H2AX foci. RESULTS: In cells exposed to EF, death increased substantially compared to irradiation alone. In C. albicans we observed suppression of the DNA repair shoulder. The effect of EF in growth of M. panniformis was substantial; the number of surviving cells on day-2 after irradiation was 12 times greater than when an EF was applied. By the action of a static electric field on the irradiated MRC5 cells the number of nuclei with gamma-H2AX foci increased 40%, approximately. CONCLUSIONS: Application of an EF following irradiation greatly increases cell death. The observation that the DNA repair shoulder in the survival curve of C. albicans is suppressed when cells are exposed to irradiation + EF suggests that EF likely inactivate cellular recovering processes. The result for the number of nuclei with gamma-H2AX foci in MRC5 cells indicates that an EF interferes mostly in the DNA repair mechanisms. A molecular ad-hoc model is proposed.