A Spatially Explicit Model of Synchronization in Fiddler Crab Waving Displays

Fiddler crabs (Uca spp., Decapoda: Ocypodidae) are commonly found forming large aggregations in intertidal zones, where they perform rhythmic waving displays with their greatly enlarged claws. While performing these displays, fiddler crabs often synchronize their behavior with neighboring males, forming the only known synchronized visual courtship displays involving reflected light and moving body parts. Despite being one of the most conspicuous aspects of fiddler crab behavior, little is known about the mechanisms underlying synchronization of male displays. In this study we develop a spatially explicit model of fiddler crab waving displays using coupled logistic map equations. We explored two alternative models in which males either direct their attention at random angles or preferentially toward neighbors. Our results indicate that synchronization is possible over a fairly large region of parameter space. Moreover, our model was capable of generating local synchronization neighborhoods, as commonly observed in fiddler crabs under natural conditions.     

Euclein: A new binaphthaquinone from Euclea pseudebenus

7-MethyljugIone, 8,8′-dihydroxy-4,4′-dimethoxy-6,6′-dimethyl-2,2′-binaphthyl-1,1′-quinone, 2-methylnaphthazarin, mamegakinone and euclein have been isolated from Euclea pseudebenus. Euclein is the 3,6′-dimer of 7-methyljuglone.     

Antitumour activities of levans produced by Zymomonas mobilis strains

Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect.     

Volume regulation in the early proximal tubule of theNecturus kidney

Summary The ability of early proximal tubule cells of theNecturus kidney to regulate volume was evaluated using light microscopy, video analysis and conventional microelectrodes.Necturus proximal tubule cells regulate volume in both hyperand hyposmotic solutions. Volume regulation in hyperosmotic fluids is HCO ₃ ^– dependent and is associated with a decrease in the relative K⁺ conductance of the basolateral cell membrane and a decrease in the resistance ratio,R _a /R _bl . Volume regulation in hyposmotic solutions is also dependent upon the presence of HCO ₃ ^– but is also inhibited by 2mm Ba²⁺ in the basolateral solution. Hyposmotic regulation is accompanied by an increase in the relative K⁺ conductance of the basolateral cell membrane and an increase inR _a /R _bl . Neither hypo- nor hyposmotic regulation have any affect on the depolarization of the basolateral cell membrane potential induced by HCO ₃ ^– removal. We conclude that volume regulation in the early proximal tubule of the kidney involves both HCO ₃ ^– -dependent transport systems and the basolateral K⁺ conductance.     

Molecular analysis of yellow fever virus 17DD vaccine strain.

The Oswaldo Cruz Foundation produces most of the yellow fever (YF) vaccine prepared worldwide. As part of a broader approach to determine the genetic variability in YF 17D seeds and vaccines and its relevance to viral attenuation the 17DD virus was purified directly from chick embryo homogenates which is the source of virus used for vaccination of millions of people in Brazil and other countries for half a century. Neutralization and hemagglutination tests showed that the purified virus is similar to the original stock. Furthermore, radioimmune precipitation of 35S-methionine-labeled viral proteins using mouse hyperimmune ascitic fluid revealed identical patterns for the purified 17DD virus and the YF 17D-204 strain except for the 17DD E protein which migrated slower on SDS-PAGE. This difference is likely to be due to N-linked glycosylation. Finally, comparison by northern blot hybridization of virion RNAs of purified 17DD with two other strains of YF 17D virus revealed only genome-sized molecules for all three viruses. These observations suggest that the vaccine phenotype is primarily associated with the accumulation of mutations.     

Predator avoidance behaviour in the buffy-headed marmoset,Callithrix flaviceps

The predator avoidance behaviour of a free-ranging group of buffy-headed marmosets,Callithrix flaviceps, was recorded in detail during the course of a long-term study of behavioural ecology at the Fazenda Montes Claros, southeastern Brazil. Four distinct patterns of predator avoidance behaviour, each with specific vocalisations, were recognised and are described here. The selection and use of sleeping sites by the study group are also described. An analysis of the records indicates that these small monkeys are generally most vulnerable to predation by aerial raptors. Variations in the frequency of alarm calls also indicate that the marmosets tend to be more vigilant at higher levels in the forest and when the leaf cover is less extensive. The implications of group size and social structure for both the evolution and the efficacy of the anti-predator behaviour of marmosets are also discussed.     

Histoplasma capsulatum peritonitis associated with continuous ambulatory peritoneal dialysis

This paper reports a case of infection byHistoplasma capsulatum apparently restricted to the peritoneum in a woman submitted to continuous ambulatory peritoneal dialysis. Diagnosis was established by culture of dialysis fluid and peritoneal nodule and by histopathologic examination.     

Chemical composition and larvicidal activity of essential oils of three Artemisia species

Aedes aegypti L. (Diptera: Culicidae) is a vector for serious diseases in tropical regions. This pest is mainly controlled by commercial larvicides but the application of such products has led to environmental problems. Essential oils (EO) have been consistently reported as molecules with insecticidal activity and can be used to produce more environmentally friendly larvicides in the control of A. aegypti. In this study, the larvicidal effect of essential oils (EO) from the leaves of three Artemisia species was evaluated against A. aegypti. The oils were obtained from steam distillation and their chemical composition was determined by gas chromatography–mass spectrometry. The EO of Artemisia camphorata was the most active in the screening bioassay and presented LC₅₀ and LC₉₅ of 64.95 and 74.18 μg ml⁻¹, respectively. In addition, we found that germacrene D-4-ol was the constituent responsible for the toxicity of this EO. Artemisia camphorata EO and its major constituent, germacrene D-4-ol, are promising for the development of natural larvicides against A. aegypti.