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.     

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.     

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.     

High-Resolution Functional Profiling of the Norovirus Genome

Human noroviruses (HuNoV) are a major cause of nonbacterial gastroenteritis worldwide, yet details of the life cycle and replication of HuNoV are relatively unknown due to the lack of an efficient cell culture system. Studies with murine norovirus (MNV), which can be propagated in permissive cells, have begun to probe different aspects of the norovirus life cycle; however, our understanding of the specific functions of the viral proteins lags far behind that of other RNA viruses. Genome-wide functional profiling by insertional mutagenesis can reveal protein domains essential for replication and can lead to generation of tagged viruses, which has not yet been achieved for noroviruses. Here, transposon-mediated insertional mutagenesis was used to create 5 libraries of mutagenized MNV infectious clones, each containing a 15-nucleotide sequence randomly inserted within a defined region of the genome. Infectious virus was recovered from each library and was subsequently passaged in cell culture to determine the effect of each insertion by insertion-specific fluorescent PCR profiling. Genome-wide profiling of over 2,000 insertions revealed essential protein domains and confirmed known functional motifs. As validation, several insertion sites were introduced into a wild-type clone, successfully allowing the recovery of infectious virus. Screening of a number of reporter proteins and epitope tags led to the generation of the first infectious epitope-tagged noroviruses carrying the FLAG epitope tag in either NS4 or VP2. Subsequent work confirmed that epitope-tagged fully infectious noroviruses may be of use in the dissection of the molecular interactions that occur within the viral replication complex.