Improvement of a Vero cell assay to determine diphtheria antitoxin content in sera

Diphtheria antitoxin content in sera were determined automatically in Vero cell assay by spectrophotometric determination of the equivalence point between toxin and antitoxin followed by computer analysis of absorption values. The method was more accurate than visual reading and made handling of many samples easy.     

Effect before Cause: Supramodal Recalibration of Sensorimotor Timing

Background

Our motor actions normally generate sensory events, but how do we know which events were self generated and which have external causes? Here we use temporal adaptation to investigate the processing stage and generality of our sensorimotor timing estimates.

Methodology/Principal Findings

Adaptation to artificially-induced delays between action and event can produce a startling percept—upon removal of the delay it feels as if the sensory event precedes its causative action. This temporal recalibration of action and event occurs in a quantitatively similar manner across the sensory modalities. Critically, it is robust to the replacement of one sense during the adaptation phase with another sense during the test judgment.

Conclusions/Significance

Our findings suggest a high-level, supramodal recalibration mechanism. The effects are well described by a simple model which attempts to preserve the expected synchrony between action and event, but only when causality indicates it is reasonable to do so. We further demonstrate that this model successfully characterises related adaptation data from outside the sensorimotor domain.     

Caribbean corals in crisis: record thermal stress, bleaching, and mortality in 2005

Background

The rising temperature of the world''s oceans has become a major threat to coral reefs globally as the severity and frequency of mass coral bleaching and mortality events increase. In 2005, high ocean temperatures in the tropical Atlantic and Caribbean resulted in the most severe bleaching event ever recorded in the basin.

Methodology/Principal Findings

Satellite-based tools provided warnings for coral reef managers and scientists, guiding both the timing and location of researchers'' field observations as anomalously warm conditions developed and spread across the greater Caribbean region from June to October 2005. Field surveys of bleaching and mortality exceeded prior efforts in detail and extent, and provided a new standard for documenting the effects of bleaching and for testing nowcast and forecast products. Collaborators from 22 countries undertook the most comprehensive documentation of basin-scale bleaching to date and found that over 80% of corals bleached and over 40% died at many sites. The most severe bleaching coincided with waters nearest a western Atlantic warm pool that was centered off the northern end of the Lesser Antilles.

Conclusions/Significance

Thermal stress during the 2005 event exceeded any observed from the Caribbean in the prior 20 years, and regionally-averaged temperatures were the warmest in over 150 years. Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch''s Degree Heating Weeks) and bleaching intensity. This severe, widespread bleaching and mortality will undoubtedly have long-term consequences for reef ecosystems and suggests a troubled future for tropical marine ecosystems under a warming climate.     

Evidence for a novel Entamoeba histolytica lectin activity that recognises carbohydrates present on ovalbumin

Entamoeba histolytica, an intestinal amoeba that causes dysentery and liver abscesses, acquires nutrients by engulfing bacteria in the colonic lumen and phagocytoses apoptotic cells during tissue invasion. In preliminary studies to identify ligands that stimulate amoebic phagocytosis, we used ovalbumin immobilized on latex particles as a potential negative control protein. Surprisingly, ovalbumin strongly stimulated E. histolytica particle uptake. Experiments using highly purified ovalbumin confirmed the specificity of this finding. The mechanism of particle uptake was actin-dependent, and the Entamoeba phagosome marker amoebapore A localised to ovalbumin-bead containing vacuoles. The most well described amoebic receptor is a Gal/GalNAc-specific lectin, but d-galactose had no effect on ovalbumin-stimulated phagocytosis. Ovalbumin has a single N-glycosylation site (Asn₂₉₂) and is modified with oligomannose and hybrid-type oligosaccharides. We used both trifluoromethanesulfonic acid and N-glycanase to deglycosylate ovalbumin and tested the effect. Both methods substantially reduced the stimulatory effect of ovalbumin. Biotinylated ovalbumin bound the surface of fixed E. histolytica trophozoites saturably; furthermore, denatured ovalbumin and native ovalbumin both specifically inhibited ovalbumin-biotin binding, but deglycosylated ovalbumin had no effect. Collectively, these data suggest that E. histolytica has a previously unrecognised surface lectin activity that binds to carbohydrates on ovalbumin and stimulates phagocytosis.     

Leishmanicidal effect of Spiranthera odoratíssima (Rutaceae) and its isolated alkaloid skimmianine occurs by a nitric oxide dependent mechanism

Leishmaniasis is one of the neglected diseases. High cost, systemic toxicity, and diminished efficacy due to development of resistance by the parasites has a negative impact on the current treatment options. Thus, the search for a new, effective and safer anti-leishmanial drug becomes of paramount importance. Compounds derived from natural products may be a better and cheaper source in this regard. This study evaluated the in vitro anti-leishmanial activity of Spiranthera odoratíssima (Rutaceae) fractions and isolated compounds, using promastigote and amastigote forms of different Leishmania species. J774 A.1 macrophage was used as the parasite host cell for the in vitro assays. Evaluations of cytoxicity, nitric oxide (NO), interleukin-10 and in silico analysis were carried out. In vitro experiments showed that the fruit hexanic fraction (Fhf) and its alkaloid skimmianine (Skm) have a significant (P<0·001) effect against L. braziliensis. This anti-L. braziliensis activity of Fhf and Skm was due to increased production of NO and attenuation of IL-10 production in the macrophages at concentrations ranging from 1·6 to 40·0 μg/ml. The in silico assay demonstrated significant interaction between Skm and amino acid residues of NOS2. Skm is thus a promising drug candidate for L. braziliensis due to its potent immunomodulatory activity.