Ichtyotoxic activity of extracts from Mexican marine macroalgae

Seventy-three species of macroalgae from the Mexican Pacific, Atlantic and Caribbean coast were screened for ichtyotoxic activity. Ethanolic, acetonic and aqueous extracts were prepared and tested against the fish Carassius auratus. The extracts were classified on the basis of their effects as: toxic if the fish died in two hours or less; moderately toxic, if the organism behaved abnormally but death did notoccur, and non-toxic if the fish did not display any change. 79% species were ichtyotoxic to some degree. Extracts of 39 species were toxic, with at least one extract with lethal effects, 19 were moderately toxic and 15 species were non-toxic. Only the extracts ofDictyota bartayresiana, Dictyota cervicornis,Lobophora variegata, Bryothamnion triquetrum and Laurencia obtusa were toxic in all three solvents. The acetone and ethanol extracts were more active, and therefore are more suitable for extraction of toxic substances. This revised version was published online in August 2006 with corrections to the Cover Date.     

Interstitial deletion (2)(p13p15)

Summary A dysmorphic 5-year-old girl with severe growth and mental deficiency was studied. She presented a de novo interstitial 2p deletion. Karyotype: 46,XX,del(2)(p13p15).     

Genome Sequences of Burkholderia sp. Strains CCGE1002 and H160, Isolated from Legume Nodules in Mexico and Brazil

The genome sequences of Burkholderia sp. strains CCGE1002 from Mexico and H160 from Brazil, isolated from legume nodules, are reported. Their gene contents in relation to plant-microbe interactions and xenobiotic degradation are discussed.     

The growth ring concept: seeking a broader and unambiguous approach covering tropical species

The concept of growth rings is little discussed in the literature and their treatment remains somewhat confusing in terms of the diversity of structures described. This situation has a major impact on the study of growth rings in tropical species, in which variations and complexity are greater and accuracy of identification less good. The rigid conceptual delimitations used by dendrochronologists and wood anatomists of temperate regions cannot be applied to the study of growth rings in most tropical species, which has led to neglect of this subject. With the objective of discussing the concept of growth rings, the present study consists of a survey of anatomical, periodicity, causal and evolutionary aspects of the treatment of these structures as evidenced in previous studies, and the evaluation of their application and limitations to the development of this concept. Anatomical aspects arise through radial integrity, or the presence of early and late wood; the degree of distinction of the rings, which may vary from well to poorly defined; and tangential continuity, meaning that rings may form a complete circle in the transverse section of the trunk, or instead be tangentially discontinuous, lens‐shaped or in wedges. In addition there are a diversity of anatomical markers which enable us to recognize growth rings. Regarding periodicity, the rings may be annual, infra‐annual or supra‐annual. Causal aspects include genetic, endogenous and environmental components. Evolutionary aspects continue to be insufficiently investigated, and although most comparative studies treat growth rings recognized by different markers as though they were a single character, it remains questionable whether they can be regarded as homologous or the result of homoplasy. We conclude that the elaboration of a robust but broad definition which can include all the variation observed in growth rings of tropical species is a complex task, which is only possible by overcoming the restrictions adopted by dendrochronologists and wood anatomists of temperate regions for whom growth rings are essentially annual, strongly demarcated, tangentially continuous and restricted to the most pronounced markers.     

Stress distribution of three-unit fixed partial prostheses (conventional and pontic) supported by three or two implants: 3D finite element analysis of ductile materials

In implantology, when financial or biological feasibility limitations appear, it is necessary to use prostheses with geometries that deviate from the conventional, with a pontic in the absence of an intermediate implant. The aim of this study was analyze and understand the general differences in the stresses generated in implants, components and infrastructures according to the configuration of the prosthesis over three or two implants. Thus, this paper analyzes the von Mises equivalent stresses (VMES) of ductile materials on their external surfaces. The experimental groups: Regular Splinted Conventional Group (RCG), which had conventional infrastructures on 3 regular-length Morse taper implants (4x11?mm); Regular Splinted Pontic Group (RPG), which had infrastructures with intermediate pontics on 2 regular-length Morse taper implants (4x11?mm). The simulations of the groups were created with Ansys Workbench 10.0 software. The results revealed that the RPG presented greater areas of possible fragility due to higher stress concentrations, for example, in the cervical area of the union between the implant and component the top platform of the abutment, as well as greater coverage of the stress by the cervical implant threads. The RPG infrastructure was also more affected by stresses in the connection areas between the prostheses and on the occlusal surface. There is an advantage to using prostheses supported by a greater number of implants (RCG) because this decreases the stress in the analyzed structures and consequently improves stress dissipation to the supporting bone, which would preserve the system.     

Talisia esculenta lectin and larval development of Callosobruchus maculatus and Zabrotes subfasciatus (Coleoptera: Bruchidae)

Bruchid larvae cause major losses in grain legume crops throughout the world. Some bruchid species, such as the cowpea weevil and the Mexican bean weevil, are pests that damage stored seeds. Plant lectins have been implicated as antibiosis factors against insects, particularly the cowpea weevil, Callosobruchus maculatus. Talisia esculenta lectin (TEL) was tested for anti-insect activity against C. maculatus and Zabrotes subfasciatus larvae. TEL produced ca. 90% mortality to these bruchids when incorporated in an artificial diet at a level of 2% (w/w). The LD(50) and ED(50) for TEL was ca. 1% (w/w) for both insects. TEL was not digested by midgut preparations of C. maculatus and Z. subfasciatus. The transformation of the genes coding for this lectin could be useful in the development of insect resistance in important agricultural crops.     

Molecular and biochemical characterization of a highly stable bacterial laccase that occurs as a structural component of the Bacillus subtilis endospore coat

The Bacillus subtilis endospore coat protein CotA shows laccase activity. By using comparative modeling techniques, we were able to derive a model for CotA based on the known x-ray structures of zucchini ascorbate oxidase and Cuprinus cereneus laccase. This model of CotA contains all the structural features of a laccase, including the reactive surface-exposed copper center (T1) and two buried copper centers (T2 and T3). Single amino acid substitutions in the CotA T1 copper center (H497A, or M502L) did not prevent assembly of the mutant proteins into the coat and did not alter the pattern of extractable coat polypeptides. However, in contrast to a wild type strain, both mutants produced unpigmented colonies and spores unable to oxidize syringaldazine (SGZ) and 2'2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). The CotA protein was purified to homogeneity from an overproducing Escherichia coli strain. The purified CotA shows an absorbance and a EPR spectra typical of blue multicopper oxidases. Optimal enzymatic activity was found at < or =pH 3.0 and at pH 7.0 for ABTS or SGZ oxidation, respectively. The apparent K(m) values for ABTS and SGZ at 37 degrees C were of 106 +/- 11 and 26 +/- 2 microm, respectively, with corresponding k(cat) values of 16.8 +/- 0.8 and 3.7 +/- 0.1 s(-1). Maximal enzyme activity was observed at 75 degrees C with ABTS as substrate. Remarkably, the coat-associated or the purified enzyme showed a half-life of inactivation at 80 degrees C of about 4 and 2 h, respectively, indicating that CotA is intrinsically highly thermostable.     

Immunocytolocalization of tryptophan decarboxylase in Catharanthus roseus hairy roots

We investigated the intracellular distribution of tryptophan decarboxylase (TDC) (EC 4.1.1.28) in Catharanthus roseus hairy roots using immunofluorescence and immunogold techniques. TDC was detected by immunofluorescence localization in the cytosol and in the apoplastic region of the meristematic cells of the roots, with a slight enrichment in the epidermal cells of the root cap and in the meristematic region. In the enlargement zone, TDC was localized only in the first three layers of the cortex. In the maturation zone, the enzyme was not present. Immunogold studies confirmed that the enzyme was localized in the cytosol of the meristematic region, and intense gold labeling was found in the apoplastic zone. A protein fraction isolated from the apoplastic zone and assayed for TDC activity showed high activity.