Antimicrobial and antiviral activities of an actinomycete (Streptomyces sp.) isolated from a Brazilian tropical forest soil

A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions, obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type 1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action. This revised version was published online in August 2006 with corrections to the Cover Date.     

Stability of the Transthyretin Molecule as a Key Factor in the Interaction with A-Beta Peptide - Relevance in Alzheimer's Disease

Transthyretin (TTR) protects against A-Beta toxicity by binding the peptide thus inhibiting its aggregation. Previous work showed different TTR mutations interact differently with A-Beta, with increasing affinities correlating with decreasing amyloidogenecity of the TTR mutant; this did not impact on the levels of inhibition of A-Beta aggregation, as assessed by transmission electron microscopy. Our work aimed at probing differences in binding to A-Beta by WT, T119M and L55P TTR using quantitative assays, and at identifying factors affecting this interaction. We addressed the impact of such factors in TTR ability to degrade A-Beta. Using a dot blot approach with the anti-oligomeric antibody A11, we showed that A-Beta formed oligomers transiently, indicating aggregation and fibril formation, whereas in the presence of WT and T119M TTR the oligomers persisted longer, indicative that these variants avoided further aggregation into fibrils. In contrast, L55PTTR was not able to inhibit oligomerization or to prevent evolution to aggregates and fibrils. Furthermore, apoptosis assessment showed WT and T119M TTR were able to protect against A-Beta toxicity. Because the amyloidogenic potential of TTR is inversely correlated with its stability, the use of drugs able to stabilize TTR tetrameric fold could result in increased TTR/A-Beta binding. Here we showed that iododiflunisal, 3-dinitrophenol, resveratrol, [2-(3,5-dichlorophenyl)amino] (DCPA) and [4-(3,5-difluorophenyl)] (DFPB) were able to increase TTR binding to A-Beta; however only DCPA and DFPB improved TTR proteolytic activity. Thyroxine, a TTR ligand, did not influence TTR/A-Beta interaction and A-Beta degradation by TTR, whereas RBP, another TTR ligand, not only obstructed the interaction but also inhibited TTR proteolytic activity. Our results showed differences between WT and T119M TTR, and L55PTTR mutant regarding their interaction with A-Beta and prompt the stability of TTR as a key factor in this interaction, which may be relevant in AD pathogenesis and for the design of therapeutic TTR-based therapies.     

Virtual brain endocast of Antifer (Mammalia: Cervidae), an extinct large cervid from South America

A diverse fossil record of Cervidae (Mammalia) has been documented in the South American Pleistocene, when these animals arrived during the Great American Biotic Interchange. Using computed tomography-scanning techniques, it is possible to access the endocranial morphology of extinct species. Here, we studied the brain endocast of the extinct late Pleistocene cervid Antifer ensenadensis from southern Brazil, one of the largest forms that lived on this continent, using comparative morphology, geometric morphometrics, and encephalization quotients. The analyzed endocasts demonstrate that A. ensenadensis had a gyrencephalic brain, showing a prominent longitudinal sinus (=sagittal superior sinus), which is also observed in the large South American cervid Blastocerus dichotomus. The encephalization quotient is within the variation of extant cervids, suggesting maintenance of the pattern of encephalization from at least the late Pleistocene. Geometric morphometric analysis suggested a clear and linear allometric trend between brain endocast size and shape, and highlights A. ensenadensis as an extreme form within the analyzed cervids regarding brain morphology.     

Reassessment of the vocal repertoire of a nest-building gladiator frog,Boana pardalis (Anura,Hylidae, Cophomantinae): implications for its diagnosis within the B. faber species group

In this study, we re-describe the advertisement and territorial calls of Boana pardalis, carry out an acoustic comparison between the studied species and the other congeners of the B. faber group, and report for the first time the tympanic amplexus for the studied species. The advertisement call of B. pardalis can be used to supplement its diagnosis in the B. faber group based on temporal call traits, e.g. emission rate and emission pattern, as well as the call envelope.     

Detection of Infectious Astroviruses in Water

A method based on the infection of CaCo-2 cells and molecular hybridization with a specific cDNA probe has been developed for the detection of infectious astroviruses in environmental samples. By this procedure wild-type astroviruses have been detected in water from an area where a concurrent gastroenteritis outbreak was reported.     

A retrovirus carrying the polyomavirus middle T gene induces acute thrombocythemic myeloproliferative disease in mice.

Mice inoculated with an artificially constructed retrovirus carrying the middle T gene of polyomavirus develop acute myeloproliferative disease with severe thrombotic and hemorrhagic disorder and impaired platelet function. The megakaryocytic lineage appears to be a target for polyoma-murine leukemia virus infection and middle T gene expression. This newly described disease represents a unique model system for studying disorders of the megakaryocytic lineage.     

A constitutive description of contracting papillary muscle and its implications to the dynamics of the intact heart

A simple mathematical model capable of simulating the major biomechanical attributes of contracting cardiac muscle is presented. This model is based on the phenomenological observations on heart muscle. The form of the equation can be readily extended to describe the pressure-volume-time-velocity of the intact heart as well, thus allowing a direct bridge between the dynamics of papillary muscle and the dynamics of intact heart. Parameters that are sensitive to inotropic state of the muscle can be obtained directly from the isometric tension-time record of the muscle or the isovolumic pressure-time record of the ventricle. These parameters have the potential to serve as quantitative measures of cardiac health.     

Long-wavelength fluorescence of tyrosine and tryptophan solutions

We report in this paper the presence of fluorescence bands of tryptophan and tyrosine solutions centered above 550 nm. This long-wavelength fluorescence is of much lower intensity, (0.4-2.7)%, than the UV fluorescence of these aromatic aminoacids. The basic characteristic of these fluorescence bands are: (a) tyrosine: lambda em = 600 nm with two excitation peaks centered at 453 nm and 550 nm (b) tryptophan: lambda em = 675 nm with two excitation peaks centered at 455 and 560 nm. It has been found that irradiation of tyrosine solutions with a potent UV lamp promotes an important increase of absorption at 310 nm and above 400 nm.