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.     

Structure–antimicrobial activity of some natural isocoumarins and their analogues

Three naturally occurring isocoumarins (paepalantine, paepalantine 9-O-beta-D-glucopyranoside and paepalantine 9-O-beta-D-allopyranosyl(1 --> 6) glucopyranoside) and two semi-synthetic analogues, 9,10-acylated compound and 9-OH-10-methylated compound, structurally similar to paepalantine, were evaluated for antimicrobial activity using a spectrophotometric microdilution technique. The paepalantine was active against S. aureus, S. epidermidis, and E. faecalis while the other four compounds proved ineffective against all microorganisms tested at concentrations of 500 microg/ml. Variations in phenolic substitution at OH-9 and/or OH-10 in the paepalantine molecule resulted in compounds without antimicrobial activity. A combination of structural features, two phenolic groups as cathecolic system, forms an oxygenated system arrangement that may reflect the potentially antimicrobial properties of paepalantine.     

Growth-induced mass flows in fungal networks

Cord-forming fungi form extensive networks that continuously adapt to maintain an efficient transport system. As osmotically driven water uptake is often distal from the tips, and aqueous fluids are incompressible, we propose that growth induces mass flows across the mycelium, whether or not there are intrahyphal concentration gradients. We imaged the temporal evolution of networks formed by Phanerochaete velutina, and at each stage calculated the unique set of currents that account for the observed changes in cord volume, while minimizing the work required to overcome viscous drag. Predicted speeds were in reasonable agreement with experimental data, and the pressure gradients needed to produce these flows are small. Furthermore, cords that were predicted to carry fast-moving or large currents were significantly more likely to increase in size than cords with slow-moving or small currents. The incompressibility of the fluids within fungi means there is a rapid global response to local fluid movements. Hence velocity of fluid flow is a local signal that conveys quasi-global information about the role of a cord within the mycelium. We suggest that fluid incompressibility and the coupling of growth and mass flow are critical physical features that enable the development of efficient, adaptive biological transport networks.     

A mechanobiological model to study upstream cell migration guided by tensotaxis

Biomechanics and Modeling in Mechanobiology - Cell migration is a process of crucial importance for the human body. It is responsible for important processes such as wound healing and tumor...     

The Peculiar Facets of Nitric Oxide as a Cellular Messenger: From Disease-Associated Signaling to the Regulation of Brain Bioenergetics and Neurovascular Coupling

In this review, we address the regulatory and toxic role of ^·NO along several pathways, from the gut to the brain. Initially, we address the role on ^·NO in the regulation of mitochondrial respiration with emphasis on the possible contribution to Parkinson’s disease via mechanisms that involve its interaction with a major dopamine metabolite, DOPAC. In parallel with initial discoveries of the inhibition of mitochondrial respiration by ^·NO, it became clear the potential for toxic ^·NO-mediated mechanisms involving the production of more reactive species and the post-translational modification of mitochondrial proteins. Accordingly, we have proposed a novel mechanism potentially leading to dopaminergic cell death, providing evidence that NO synergistically interact with DOPAC in promoting cell death via mechanisms that involve GSH depletion. The modulatory role of NO will be then briefly discussed as a master regulator on brain energy metabolism. The energy metabolism in the brain is central to the understanding of brain function and disease. The core role of ^·NO in the regulation of brain metabolism and vascular responses is further substantiated by discussing its role as a mediator of neurovascular coupling, the increase in local microvessels blood flow in response to spatially restricted increase of neuronal activity. The many facets of NO as intracellular and intercellular messenger, conveying information associated with its spatial and temporal concentration dynamics, involve not only the discussion of its reactions and potential targets on a defined biological environment but also the regulation of its synthesis by the family of nitric oxide synthases. More recently, a novel pathway, out of control of NOS, has been the subject of a great deal of controversy, the nitrate:nitrite:NO pathway, adding new perspectives to ^·NO biology. Thus, finally, this novel pathway will be addressed in connection with nitrate consumption in the diet and the beneficial effects of protein nitration by reactive nitrogen species.

     

Measuring the heart rate of the spider, Aphonopelma hentzi: a non-invasive technique

In this work we describe a non‐invasive and precise technique to record the heartbeats of a spider. A linear output Hall effect transducer in conjunction with a small magnet was used to monitor the micromovements on the dorsal surface of the abdomen of the tarantula Aphonopelma hentzi (Girard) (Theraphosidae). The exoskeleton in this region is in direct contact with suspensory ligaments connected to the heart, and the dorsal cuticle of the opisthosoma moves with each heartbeat. The technique allowed the discrimination of the different stages of the spider's cardiac cycle. The method can be also adapted for a smaller spider or other arthropods. We believe that the method proposed in this paper allows investigators to gain insights into a spider's natural heart rate by gathering unbiased data with a non‐invasive and very precise technique. We have found the resting heart rate of A. hentzi to be 5.6 ± 1.47 beats/min, which is lower than previously reported values.     

Evidences for genetic differentiation within the highly endemic and endangered annual fish Austrolebias nigrofasciatus (Cyprinodontiformes: Rivulidae)

Samples of Austrolebias nigrofasciatus (n = 103), an endangered species of annual fish endemic to a small area of the Patos-Mirim lagoon system encompassing the São Gonçalo Channel lowlands, were collected from eight isolated temporary ponds, four located at the known distribution range of the species and four located along the Piratini River lowlands, where morphologically different individuals were found. In the laboratory, fragments of the mitochondrial cytochrome c oxidase I (coI), cytochrome b (cytb) and nuclear rhodopsin (rho) genes were amplified, purified and sequenced for 100, 99 and 58 of these individuals, respectively. Samples were further analysed using phylogenetic and phylogeographic methods to evaluate the patterns of genetic diversity and differentiation presented within and between populations, while assessing their evolutionary history, in order to guide the application of further conservation strategies. We found that the four new populations from the Piratini River lowlands encompass a different lineage of A. nigrofasciatus that diverged from that encountered in the São Gonçalo Channel at approximately 0.165 M years before present, during a population expansion and did not yet attain reciprocal monophyly. This divergence was associated with a glacial event that was preceded by an interglacial period putatively associated with the dispersal. Moreover, significant levels of genetic differentiation and a high number of exclusive haplotypes could be encountered even in micro-geographical scales, as in the comparisons between populations located within the same major lineage, indicating each of them may encompass independent management units. Conservation actions are certainly urgent, especially in the face of signs of a recent bottleneck.     

Theoretical calculation of partition coefficients of dimethoxypyrimidinylsalicylic acids

Despite their importance as herbicides, dimethoxypyrimidinylsalicylic acids has been poorly characterized from a physical-chemical point of view. This lack of information has prevented the assessment of their impact in the environment once they are released. In this study, environmentally important properties (free energy of solvation, Henry’s law constant, octanol/air, and octanol/water partition coefficients) of 39 dimethoxypyrimidinylsalicylic derived compounds are calculated by density functional theory (DFT) methods at B3LYP/6-31G(d,p) level of theory using the Poisson-Boltzmann solvation model. These properties have not been reported previously for this family of compounds, neither experimentally or theoretically.