Comparative analysis of population structure of endemic Western Atlantic hermit crab Loxopagurus loxochelis (Decapoda, Anomura) in two regions of state of Sao Paulo, Brazil

This work characterized the population structure of the hermit crab Loxopagurus loxochelis (Moreira, 1901) in terms of size frequency distribution and sex ratio. Specimens were collected monthly, over a period of one year (from July 2002 to June 2003), in seven transects (from 5 to 35 m of depth) using fishing boat equipped with two double-rig trawl nets, in Caraguatatuba and Ubatuba regions (state of Sao Paulo, Brazil). A total of 366 hermit crabs were collected in Caraguatatuba [222 males (60.65%), 114 non-ovigerous females (31.15%) and 30 ovigerous females (8.20%)] and 126 hermit crabs in Ubatuba [81 males (64.28%), 38 non-ovigerous females (30.16%) and seven ovigerous females (5.56%)]. In Caraguatatuba the highest incidence of ovigerous females occurred during winter (July 2002), whereas in Ubatuba, the number was incipient. The cephalothoracic shield length ranged from 2.0 to 7.9mm (5.29 +/- 0.96mm) in Caraguatatuba, and from 2.7 to 7.5mm (5.32 +/- 0.95mm) in Ubatuba. The mean size of males was significantly larger than the mean size of females in both regions. Overall sex ratio was in favor of males (1.54:1 in Caraguatatuba and 1.9:1 in Ubatuba). Sexual dimorphism was recorded to L. loxochelis by the presence of males in the largest size classes, following the standard pattern observed in Decapoda. There was an unimodal size distribution for both sexes, with normal distributions in both regions. The higher number of males in relation to females may indicate the existence of different growth and mortality rates between the sexes. Despite of the different geomorphologic characteristics between Caraguatatuba and Ubatuba regions, the dynamics of development was similar for both populations.

Tissue-specific expression of head-to-tail cyclized miniproteins in Violaceae and structure determination of the root cyclotide Viola hederacea root cyclotide1

The plant cyclotides are a family of 28 to 37 amino acid miniproteins characterized by their head-to-tail cyclized peptide backbone and six absolutely conserved Cys residues arranged in a cystine knot motif: two disulfide bonds and the connecting backbone segments form a loop that is penetrated by the third disulfide bond. This knotted disulfide arrangement, together with the cyclic peptide backbone, renders the cyclotides extremely stable against enzymatic digest as well as thermal degradation, making them interesting targets for both pharmaceutical and agrochemical applications. We have examined the expression patterns of these fascinating peptides in various Viola species (Violaceae). All tissue types examined contained complex mixtures of cyclotides, with individual profiles differing significantly. We provide evidence for at least 57 novel cyclotides present in a single Viola species (Viola hederacea). Furthermore, we have isolated one cyclotide expressed only in underground parts of V, hederacea and characterized its primary and three-dimensional structure. We propose that cyclotides constitute a new family of plant defense peptides, which might constitute an even larger and, in their biological function, more diverse family than the well-known plant defensins.

XAS characterization of the RuO(2)-Ta(2)O(5) system local (crystal) structure

The influence of the preparation method on the structural properties of the RuO(2)-Ta(2)O(5) system was investigated. Both thin films on Ti substrates and powder samples of nominal composition Ti/RuO(2)-Ta(2)O(5) (Ru:Ta = 100:0, 90:10, 80:20, 30:70, and 0:100 at.%) were prepared through thermal decomposition of polymeric precursors (DPP). The thin films and powder samples were investigated using X-ray absorption spectroscopy (XAS). XANES analyses showed that Ru and Ta are present in the Ru(IV) and Ta(V) oxidation states. EXAFS signals of all the samples were analyzed, to obtain the average bond length (r), coordination number, and the Debye-Waller factor (sigma(2)) for each Ru-O, Ru-Ru, Ta-O nearest-neighbor. The first shell Ru-O distance was found at 1.91-1.92 angstrom with coordination number of 1.8-2.1, and at 2.01-2.02 angstrom with coordination number of 3.9-4.1. The Ta-O distance obtained for all the samples and in both modes (transmission and fluorescence) had significantly different values from the theoretical ones. The results revealed that the local structure around both the Ru and Ta sites are similar, and that they consist of distorted M-O(6) octahedra (where M = Ru or Ta). (C) 2010 Elsevier B.V. All rights reserved.

Chitosan as a Bioadhesive Agent Between Porphyrins and Phospholipids in a Biomembrane Model

Porphyrins are currently used in photodynamic therapy as photosensitizers. In this paper we studied the interaction of two charged porphyrins, 5, 10, 15, 20-mesotetrakis(N-metyl-4-pyridyl) porphyrin, (TMPyP/chloride salt) cationic, and 5, 10, 15, 20-meso-tetrakis(sulfonatophenyl) porphyrin, (TPPS(4)/sodium salt) anionic, nanoassembled in phospholipid Langmuir monolayers and Langmuir-Blodgett films. Furthermore, we used chitosan to mediate the interaction between the porphyrins and the model membrane, aiming to understand the role of the polysaccharide in a molecular level. The effect of the interaction of the photosensitizers on the fluidity of the lipid monolayer was investigated by using dilatational surface elasticity. We also used photoluminescence (PL) spectroscopy to identify the porphyrins adsorbed in the phospholipid films. We observed an expansion of the monolayer promoted by the adsorption of the porphyrins into the lipid-air interface which was more pronounced in the case of TMPyP, as a consequence of a strong electrostatic interaction with the anionic monolayer. The chitosan promoted a higher adsorption of the porphyrins on the phospholipid monolayers and enabled the porphyrin to stay in its monomeric form (as confirmed by PL spectroscopy), thus demonstrating that chitosan can be pointed out as a potential photosensitizer delivery system in photodynamic therapy.

Reverse Microemulsion Synthesis, Structure, and Luminescence of Nanosized REPO(4):Ln(3+) (RE = La, Y, Gd, or Yb, and Ln = Eu, Tm, or Er)

A surfactant-mediated solution route for the obtainment of nanosized rare-earth orthophosphates of different compositions (LaPO(4):Eu(3+), (Y,Gd)PO(4):Eu(3+),LaPO(4):Tm(3+), YPO(4):Tm(3+), and YbPO(4):Er(3+)) is presented, and the implications of the morphology control on the solids properties are discussed. The solids are prepared in water-in-heptane microemulsions, using cetyltrimethylammonium bromide and 1-butanol as the surfactant and cosurfactant; the alteration of the starting microemulsion composition allows the obtainment of similar to 30 nm thick nanorods with variable length. The morphology and the structure of the solids were evaluated through scanning electron microscopy and through powder X-ray diffractometry; dynamic light scattering and thermal analyses were also performed. The obtained materials were also characterized through vibrational (FTIR) and luminescence spectroscopy (emission/excitation, luminescence lifetimes, chromaticity, and quantum efficiency), where the red, blue, and upconversion emissions of the prepared phosphors were evaluated.

THE ANTERIOR CINGULATE CORTEX IS A TARGET STRUCTURE FOR THE ANXIOLYTIC-LIKE EFFECTS OF BENZODIAZEPINES ASSESSED BY REPEATED EXPOSURE TO THE ELEVATED PLUS MAZE AND FOS IMMUNOREACTIVITY

Prior experience with the elevated plus maze (EPM) increases the avoidance of rodents to the open arms and impairs the anxiolytic-like effects of benzodiazepines on the traditional behaviors evaluated upon re-exposure to the maze, a phenomenon known as one-trial tolerance. Risk assessment behaviors are also sensitive to benzodiazepines. During re-exposure to the maze, these behaviors reinstate the information-processing initiated during the first experience, and the detection of danger generates stronger open-arm avoidance. The present study investigated whether the benzodiazepine midazolam alters risk assessment behaviors and Fos protein distribution associated with test and retest sessions in the EPM. Naive or maze-experienced Wistar rats received either saline or midazolam (0.5 mg/kg i.p.) and were subjected to the EPM. Midazolam caused the usual effects on exploratory behavior, increasing exploratory activity of naive rats in the open arms and producing no effects on these conventional measures in rats re-exposed to the maze. Risk assessment behaviors, however, were sensitive to the benzodiazepine during both sessions, indicating anxiolytic-like effects of the drug in both conditions. Fos immunohistochemistry showed that midazolam injections were associated with a distinct pattern of action when administered before the test or retest session, and the anterior cingulate cortex, area 1 (Cg1), was the only structure targeted by the benzodiazepine in both situations. Bilateral infusions of midazolam into the Cg1 replicated the behavioral effects of the drug injected systemically, suggesting that this area is critically involved in the anxiolytic-like effects of benzodiazepines, although the behavioral strategy adopted by the animals appears to depend on the previous knowledge of the threatening environment. (C) 2009 IBRO. Published by Elsevier Ltd. All rights reserved.

Interfacial interactions and structure of organic-inorganic nanohybrids

Understanding the interfacial interactions and structure is important to better design and application of organic-inorganic nanohybrids. This paper presents our recent molecular dynamic studies on organoclays and polymer nanocomposites, including the layering behavior of organoclays, structural and dynamic properties of dioctadecyldimethyl ammoniums in organoclays, and interfacial interactions and structure of polyurethane nanocomposites. The results demonstrate that the layering behaviors of organoclays are closely related to the chain length of quaternary alkyl ammoniums and cation exchangeable capacity of clays. In addition to typical layered structures such as monolayer, bilayer and pseudo-trilayer, a pseudo-quadrilayer structure was also observed in organoclays modified with dioctadecyldimethyl ammoniums (DODDMA). In such a structure, alkyl chains do not lie flat within a single layer but interlace, and also jump to the next layer or even the next nearest layer. Moreover, the diffusion constants of nitrogen and methylene atoms increase with the temperature and methelene towards the tail groups. For polyurethane nanocomposite, the van der Waals interaction between apolar alkyl chains and soft segments of polyurethane predominates the interactions between organoclay and polyurethane. Different from most bulk polyurethane systems, there is no distinct phase-separated structure for the polyurethane.

The crystal structure of free human hypoxanthineguanine phosphoribosyltransferase reveals extensive conformational plasticity throughout the catalytic cycle

Human hypoxanthine-guanine phosphoribosyltransferase (HGPRT) catalyses the synthesis of the purine nucleoside monophosphates, IMP and GMP, by the addition of a 6-oxopurine base, either hypoxanthine or guanine, to the 1-beta-position of 5-phospho-U-D-ribosyl-1-pyrophosphate (PRib-PP). The mechanism is sequential, with PRib-PP binding to the free enzyme prior to the base. After the covalent reaction, pyrophosphate is released followed by the nucleoside monophosphate. A number of snapshots of the structure of this enzyme along the reaction pathway have been captured. These include the structure in the presence of the inactive purine base analogue, 7-hydroxy [4,3-d] pyrazolo pyrimidine (HPP) and PRib-PP. Mg2+, and in complex with IMP or GMP. The third structure is that of the immucillinHP.Mg2+.PPi complex, a transition-state analogue. Here, the first crystal structure of free human HGPRT is reported to 1.9 angstrom resolution, showing that significant conformational changes have to occur for the substrate(s) to bind and for catalysis to proceed. Included in these changes are relative movement of subunits within the tetramer, rotation and extension of an active-site alpha-helix (D137-D153), reorientation of key active-site residues K68, D137 and K165, and the rearrangement of three active-site loops (100-128, 165-173 and 186-196). Toxoplasina gondii HGXPRT is the only other 6-oxopurine phosphoribosyltransferase structure solved in the absence of ligands. Comparison of this structure with human HGPRT reveals significant differences in the two active sites, including the structure of the flexible loop containing K68 (human) or K79 (T gondii). (c) 2005 Elsevier Ltd. All rights reserved.

Molecular epidemiology: A multidisciplinary approach to understanding parasitic zoonoses

Sound application of molecular epidemiological principles requires working knowledge of both molecular biological and epidemiological methods. Molecular tools have become an increasingly important part of studying the epidemiology of infectious agents. Molecular tools have allowed the aetiological agent within a population to be diagnosed with a greater degree of efficiency and accuracy than conventional diagnostic tools. They have increased the understanding of the pathogenicity, virulence, and host-parasite relationships of the aetiological agent, provided information on the genetic structure and taxonomy of the parasite and allowed the zoonotic potential of previously unidentified agents to be determined. This review describes the concept of epidemiology and proper study design, describes the array of currently available molecular biological tools and provides examples of studies that have integrated both disciplines to successfully unravel zoonotic relationships that would otherwise be impossible utilising conventional diagnostic tools. The current limitations of applying these tools, including cautions that need to be addressed during their application are also discussed.(c) 2005 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.