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.     

Predicted class-I aminoacyl tRNA synthetase-like proteins in non-ribosomal peptide synthesis

Background  

Recent studies point to a great diversity of non-ribosomal peptide synthesis systems with major roles in amino acid and co-factor biosynthesis, secondary metabolism, and post-translational modifications of proteins by peptide tags. The least studied of these systems are those utilizing tRNAs or aminoacyl-tRNA synthetases (AAtRS) in non-ribosomal peptide ligation.     

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...     

Variation in the diet of the viperine snake Natvix mama in relation to prey availability

The diet of the viperine snake was compared with food availability in the Ebro Delta, a wetland largely occupied by rice fields, in 1990 and 1991. Snake selection of prey type and size was studied seasonally and by snake group: males, females and immature snakes. Overall, feeding activity (percentage of individuals with prey and number of prey per stomach) increased with food availability. Diet analysis showed that viperine snakes mainly foraged on the green frog Rana perezi (adults and tadpoles) and the carp Cyprinus earpio. Conversely, viperine snakes rejected the mosquito fish Gambusia holbroki which is the most abundant species in autumn, when Natrix maura has a low feeding activity. Statistical comparisons between viperine snake diet and prey availability showed that males selected small carp, immature snakes selected tadpoles and, in spring, females selected frogs. The selection of small carp by males may reflect a sexual divergence of trophic niche related to sexual size dimorphism, as females are larger than males. As tadpoles are presumably easier to catch than fish, tadpole selection by immature individuals may reflect variance in capture abilities. In spring, the selection of frogs by females overlapped with vitellogenesis, suggesting that females compensate for the cost of reproduction by selecting green frogs, which have a greater biomass and higher energy content than fish. Carps eaten in spring were smaller than in summer. Moreover, in summer viperine snakes selected smaller carp than the available mean size. This divergent tendency between carp size selection and carp size availability reveals how seasonal diet shifts in prey size selection may be a response to an increase in prey size.     

Starvation promotes Dictyostelium development by relieving PufA inhibition of PKA translation through the YakA kinase pathway.

When nutrients are depleted, Dictyostelium cells undergo cell cycle arrest and initiate a developmental program that ensures survival. The YakA protein kinase governs this transition by regulating the cell cycle, repressing growth-phase genes and inducing developmental genes. YakA mutants have a shortened cell cycle and do not initiate development. A suppressor of yakA that reverses most of the developmental defects of yakA- cells, but none of their growth defects was identified. The inactivated gene, pufA, encodes a member of the Puf protein family of translational regulators. Upon starvation, pufA- cells develop precociously and overexpress developmentally important proteins, including the catalytic subunit of cAMP-dependent protein kinase, PKA-C. Gel mobility-shift assays using a 200-base segment of PKA-C's mRNA as a probe reveals a complex with wild-type cell extracts, but not with pufA- cell extracts, suggesting the presence of a potential PufA recognition element in the PKA-C mRNA. PKA-C protein levels are low at the times of development when this complex is detectable, whereas when the complex is undetectable PKA-C levels are high. There is also an inverse relationship between PufA and PKA-C protein levels at all times of development in every mutant tested. Furthermore, expression of the putative PufA recognition elements in wild-type cells causes precocious aggregation and PKA-C overexpression, phenocopying a pufA mutation. Finally, YakA function is required for the decline of PufA protein and mRNA levels in the first 4 hours of development. We propose that PufA is a translational regulator that directly controls PKA-C synthesis and that YakA regulates the initiation of development by inhibiting the expression of PufA. Our work also suggests that Puf protein translational regulation evolved prior to the radiation of metazoan species.     

Phenol oxidases from Rhodnius prolixus: Temporal and tissue expression pattern and regulation by ecdysone

Rhodnius prolixus 5th instar nymphs have significant PO enzymatic activity in the anterior midgut, fat body and hemolymph. The tissue with the major amount of PO activity is the anterior midgut while those with higher specific activities are the fat body and hemolymph. In this work the temporal pattern of PO enzymatic activity in different tissues was investigated. In fat body, PO peaks occur at 7, 12 and 16 days after a blood meal. In hemolymph, PO diminishes until day 7, and then recovers by day 14. In the anterior midgut tissue, PO peaks on day 9 and just before ecdysis; a similar pattern was observed in the anterior midgut contents. Some of these activities are dependent on the release of ecdysone, as feeding blood meal containing azadirachtin suppresses them and ecdysone treatment counteracts this effect. These results suggest that during the development of the 5th instar, the insect has natural regulating cycles of basal PO expression and activation, which could be related to the occurrence of natural infections. The differences in temporal patterns of activity and the effects of azadirachtin and ecdysone in each organ suggest that, at least in R. prolixus, different tissues are expressing different PO genes.     

Anticipatory Smooth Eye Movements in Autism Spectrum Disorder

Smooth pursuit eye movements are important for vision because they maintain the line of sight on targets that move smoothly within the visual field. Smooth pursuit is driven by neural representations of motion, including a surprisingly strong influence of high-level signals representing expected motion. We studied anticipatory smooth eye movements (defined as smooth eye movements in the direction of expected future motion) produced by salient visual cues in a group of high-functioning observers with Autism Spectrum Disorder (ASD), a condition that has been associated with difficulties in either generating predictions, or translating predictions into effective motor commands. Eye movements were recorded while participants pursued the motion of a disc that moved within an outline drawing of an inverted Y-shaped tube. The cue to the motion path was a visual barrier that blocked the untraveled branch (right or left) of the tube. ASD participants showed strong anticipatory smooth eye movements whose velocity was the same as that of a group of neurotypical participants. Anticipatory smooth eye movements appeared on the very first cued trial, indicating that trial-by-trial learning was not responsible for the responses. These results are significant because they show that anticipatory capacities are intact in high-functioning ASD in cases where the cue to the motion path is highly salient and unambiguous. Once the ability to generate anticipatory pursuit is demonstrated, the study of the anticipatory responses with a variety of types of cues provides a window into the perceptual or cognitive processes that underlie the interpretation of events in natural environments or social situations.