Multiphoton excited fabrication of collagen matrixes cross-linked by a modified benzophenone dimer: bioactivity and enzymatic degradation

Multiphoton excited (MPE) photochemistry is used to fabricate model tissue engineering scaffolds directly from types I, II, and IV collagen. A modified benzophenone dimer (BPD) provides the photoactivation and becomes incorporated into the resulting collagen matrixes. Unlike xanthene photochemistries, the benzophenone dimer can be used in acidic environments, where most forms of collagen have the greatest solubility. The minimum feature sizes are investigated by using two- and three-photon excitation, where the latter provides for superior "resolution" and suggests that collagen structures can be fabricated on the size scales of focal contacts. The resulting structures display excellent retention of bioactivity as evidenced by highly specific cell adhesion as well as immunofluorescence labeling. Structural and chemical aspects of the collagen matrixes are probed through measuring the enzymatic degradation through specific and nonspecific proteases, as the resulting relative rates are consistent with the activity of these enzymes. The degradation rates can also be controlled through varying the cross-link density in the matrixes, which is achieved through tuning the exposure dose during the fabrication process. The degradation rates are also found to be consistent with swelling/shrinking measurements and thus the average mesh size of the matrixes. In all cases the enzymatic degradations are well-fit single exponentials, suggesting that the matrixes can be fabricated with a priori knowledge of their structural properties. These results coupled with the resulting bioactivity suggest that the multiphoton fabrication process may be a powerful tool for the creation of cell-sized tissue engineering scaffolds.     

Molluscacide activity of piquerol A isolated from Piqueria trinervia (Compositae) on 8 species of pulmonate snails

In laboratory trials an aqueous solution of Piquerol A from Piqueria trinervia, collected in several regions of Mexico, showed a molluscicide action on the adults of eight different pulmonates snails species: Fossaria (Fossaria) humilis, F. (Bakerilymnaea) sp., Pseudosuccinea columella and Stagnicola attenuata from Mexico; F. (B.) cubensis and Physa cubensis from Cuba; P. columella and Biomphalaria glabrata from Brazil; B. glabrata from Puerto Rico; and S. elodes from U.S.A. The solution was tested at 50, 25 and 5 ppm concentration, for two periods of 6 and 24 hours, at room temperature (20-22 degrees C). A 100% mortality was obtained for all species at 50 ppm concentration after 6 hours of exposure; the same percentage at 25 ppm after 24 hours; and 60 to 100% mortality at 5 ppm concentration during 24 hours of exposure. No recovery was observed among any of the treated snails. Piquerol A is a sesquiterpene with low stability in nature and has previously only been tested as an insecticide and as an inhibitor of metabolism in cell cultures: no field trails have been made on its toxicity to other aquatic fauna as yet, but it is believed Piquerol A could be an excellent molluscicide for use in areas where focal transmission of schistosomiasis and fascioliasis are taking place. This is the first time experiments on molluscicides have been carried out in Mexico.     

A Novel Endogenous Betaretrovirus in the Common Vampire Bat (Desmodus rotundus) Suggests Multiple Independent Infection and Cross-Species Transmission Events

The Desmodus rotundus endogenous betaretrovirus (DrERV) is fixed in the vampire bat D. rotundus population and in other phyllostomid bats but is not present in all species from this family. DrERV is not phylogenetically related to Old World bat betaretroviruses but to betaretroviruses from rodents and New World primates, suggesting recent cross-species transmission. A recent integration age estimation of the provirus in some taxa indicates that an exogenous counterpart might have been in recent circulation.     

Information Retrieval during Free Listing Is Biased by Memory: Evidence from Medicinal Plants

Free listing is a methodological tool that is widely used in various scientific disciplines. A typical assumption of this approach is that individual lists reflect a subset of total knowledge and that the first items listed are the most culturally important. However, little is known about how cognitive processes influence free lists. In this study, we assess how recent memory of use, autonoetic and anoetic memory, and long-term associative memory can affect the composition and order of items in free lists and evaluate whether free lists indicate the most important items. Based on a model of local knowledge about medicinal plants and their therapeutic targets, which was collected via individual semi-structured interviews, we classify each item recorded in free lists according to the last time that the item was used by the informant (recently or long ago), the type of relevant memory (autonoetic or anoetic memory) and the existing associations between therapeutic targets (similar or random). We find that individuals have a tendency to recall information about medicinal plants used during the preceding year and that the recalled plants were also the most important plants during this period. However, we find no trend in the recall of plants from long-term associative memory, although this phenomenon is well established in studies on cognitive psychology. We suggest that such evidence should be considered in studies that use lists of medicinal plants because this temporal cognitive limit on the retrieval of knowledge affects data interpretation.     

Structural diversity of nuptial pads in Phyllomedusinae (Amphibia: Anura: Hylidae)

We studied the morphological variation of the nuptial pads using light microscopy and scanning electron microscopy (SEM) in 26 species of phyllomedusines (Anura: Hylidae), representing the five currently recognized genera. All phyllomedusines have single nuptial pads with dark colored epidermal projections (EPs). Spine‐shaped EPs occur in Cruziohyla calcarifer, Phrynomedusa appendiculata and in one species of Phasmahyla. The other species have roundish EPs. The density of the EPs on the pad is variable. Species in the Phyllomedusa hypochondrialis Group have EPs with a density that varies between 764 ± 58/mm² and 923 ± 160/mm². In all other studied species (including the Phyllomedusa burmeisteri and Phyllomedusa perinesos groups, Phyllomedusa camba, Phyllomedusa boliviana, Phyllomedusa sauvagii, Phyllomedusa bicolor, and Phyllomedusa tomopterna) the density of EPs varies between 108 ± 20/mm² and 552 ± 97/mm². Pores were observed with SEM in C. calcarifer, Agalychnis lemur, Agalychnis moreletii, but its presence is confirmed through histological sections on several other species. Its visibility using SEM seems to be related with the level of separation between adjacent EPs. The pores in the four studied species of Agalychnis are shown with SEM and histological sections to have a characteristic epidermal rim, that is absent in the otherphyllomedusines. Unlike most previous reports on breeding glands, those of phyllomedusines are alcian blue positive, indicating the presence of acidic mucosubstances on its secretions. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

Genetic Characterization and Pathogenicity of Rhizoctonia solani Associated with Common Bean Web Blight in the Main Bean Growing area of Argentina

Common bean web blight (WB), caused by the fungus Rhizoctonia solani (teleomorph Thanatephorus cucumeris), is among the endemic fungal diseases of major impact in north‐western Argentina (NWA). This study aimed to analyse the genetic and pathogenic diversity of R. solani in Salta, NWA, where 97 isolates were recovered from commercial bean cultivars and wild beans showing WB symptoms in a major bean production area. The isolates were characterized on the basis of specific primers, rDNA‐ITS sequences and morphological characteristics. All the isolates were identified as R. solani AG 2‐2WB, and they exhibited considerable intragroup variation. The phylogenetic tree generated with the ITS sequences confirmed the isolates identification. Aggressiveness of the isolates towards bean seedlings was assessed in the greenhouse. A great variability in virulence was observed among the isolates analysed. On the basis of the disease reaction on foliar tissues, the isolates were grouped into three virulence categories as follows: weakly virulent (30%), moderately virulent (38%) and highly virulent (32%). However, no correlation between virulence and geographical origin was detected. The information generated in this study provides initial data on the population variability of the WB pathogen in north‐western Argentina and represents a valuable contribution to regional breeding programmes aimed to obtain cultivars with durable resistance.     

Energetics and conformational changes upon complexation of a phenothiazine drug with human serum albumin

The interactions and complexation process of the amphiphilic phenothiazine fluphenazine hydrochloride with human serum albumin in aqueous buffered solutions of pH 3.0 and 7.4 have been examined by zeta-potential, isothermal titration calorimetry (ITC), UV-vis spectroscopy, and dynamic light scattering (DLS) techniques with the aim of analyzing the effect of hydrophobic and electrostatic forces on the complexation process and the alteration of protein conformation upon binding. Thus, the energetics and stoichiometry of the binding process were derived from ITC data. The enthalpies of binding obtained are small and exothermic, so the Gibbs energies of binding are dominated by large increases in entropy, consistent with hydrophobic interactions at a acidic pH. However, at physiological pH, binding to the first class of binding sites is dominated by an enthalpic contribution due to the existence of electrostatic interactions and probably some hydrogen bonding. Binding isotherms were obtained from microcalorimetric data by using a theoretical model based on the Langmuir isotherm. zeta-Potential data showed a reversal in the sign of the protein charge at pH 7.4, as a consequence of the binding of the drug to the protein. Gibbs energies of drug binding per mole of drug were also derived from zeta-potential data. On the other hand, binding of the phenothiazine that causes a conformational transition on the protein structure was followed as a function of drug concentration using UV-vis spectroscopy, and the data were analyzed to obtain the Gibbs energy of the transition in water (deltaG(degree)w) and in a hydrophobic environment (deltaG(degree)hc). Finally, the population distribution of the different species in solution and the size of the complexes were analyzed through dynamic light scattering. The existence of an aggregation process of drug/protein complexes, as a consequence of the expanded structure of the protein induced by the drug and subsequent further binding, is in agreement with ITC data. In addition, detection of drug aggregates at concentrations below the drug critical micelle concentration was also detected by this technique.