Feeding habits of the Magellan skate: effects of sex, maturity stage, and body size on diet

The aim of this study was to evaluate the effects of sex, maturity stage, and body size on the diet of the Magellan skate, Bathyraja magellanica, in the Southwest Atlantic off Argentina, by examining stomach contents using a multiple hypothesis modeling approach. Relationships between the number of prey and sex, maturity stage, and total length (TL) were assessed by built generalized linear models (GLM). Furthermore, we tested whether there was a threshold size at which B. magellanica started or quit consuming a given prey. The overall diet of B. magellanica was mainly consisted of teleosts, followed by amphipods, isopods, and decapods. Ontogenetic diet shifts were independent of sex and maturity stage. However, discrete shifts in diet with TL were found, with individuals larger than 554 and 623 mm TL ceasing to consume amphipods and isopods, respectively. The consumption of teleosts progressively increased with increasing predator size. Likewise, ontogenetic shifts in foraging behavior were also observed with smaller individuals showing specialization on amphipods with larger specimens consuming teleosts. These results confirm that ontogenetic shifts in diet of B. magellanica are more a function of predator size rather than any other life-history traits. We propose that these food shifts are probably related to morphological limitations and abilities associated with feeding habits of skate, so when specimens of B. magellanica reach an optimum body size, they may have access to higher quality trophic resources. Our results suggest that evaluating the importance of life-history stages on the feeding habits of a species is essential for understanding how that species exploits food resources, which, in turn, is an important factor in developing a suitable plan of marine ecosystem conservation.     

Changes in phosphomannosyl ligands correlate with cation-dependent mannose-6-phosphate receptors in rat liver during perinatal development

The co-existence of two mannose-6-phosphate receptors (CD-MPR and CI-MPR) in most cell types is still a dilemma to be resolved. In this study, some parameters were measured to explore lysosomal apparatus evolution in rat liver during perinatal development, and establish a possible involvement of CD- and/or CI-MPR in lysosome maturation. Activity of four acid hydrolases was measured in the whole organ at different ages and it was found that N-acetyl-beta-D-glucosaminidase (NAG), beta-galactosidase, and beta-glucuronidase change during development, reaching a peak at the 10th day after birth. These results correlated with the expression and binding properties of CD-MPR previously reported. We also used a method that recognizes phosphomannosylated ligands by using purified biotinylated CI-MPR as a probe, and found that the highest concentrations of ligands also appear around the 10th day. Binding assays were also carried out, incubating endogenous NAG from 10-day-old and adult rats with membranes from their respective ages, and the results indicated that cation-dependent mannose-6-phosphate receptor (CD-MPR) has more impact on trafficking of the enzyme at the 10th day after birth. We concluded that lysosome maturation in the rat liver occurs around the 10th day after birth, and that the CD-MPR may participate in that event.     

Glyoxyl agarose as a new chromatographic matrix

At alkaline pHs, glyoxyl agarose is able to immobilize most of the proteins contained in a crude extract. However, due to its special immobilization features, at pH 7.0 only proteins that contain at least two exposed low pK amino groups in the same plane were immobilized (β-galactosidase from Escherichia coli, catalase from bovine liver, and IgG from rabbit). However, with many other proteins, even multimeric ones, immobilization could not be achieved (e.g.: glucose oxidase from Aspergillus niger and Penicillium vitale; catalase from Micococcus sp., A. niger and bovine liver; alcohol oxidase from Pichia pastoris, Hansenula sp. and Candida boidinii, β-galactosidase from Thermus sp., etc.). Elution of the attached proteins under mild conditions was not simple, if the number of protein-support bonds was very high, only boiling in SDS allowed the elution of the proteins. However, using glyoxyl agarose 4BCL with only 20 μmol of aldheyde groups/g of support, proteins could be fully eluted by competition with amino compounds (e.g., Tris buffer). In this first approach, we have tried to take advantage of this specific immobilization at pH 7.0 to purify multimeric proteins, using a β-galactosidase from E. coli as a model. The enzyme could be eluted from the support using Tris–HCl buffer as eluting agent, with a high yield (80%) and a high purification factor (32).     

Improvement of the stability of alcohol dehydrogenase by covalent immobilization on glyoxyl-agarose

Immobilization of alcohol dehydrogenase (ADH) from Horse Liver inside porous supports promotes a dramatic stabilization of the enzyme against inactivation by air bubbles in stirred tank reactors. Moreover, immobilization of ADH on glyoxyl-agarose promotes additional stabilization against any distorting agent (pH, temperature, organic solvents, etc.). Stabilization is higher when using highly activated supports, they are able to immobilize both subunits of the enzyme. The best glyoxyl derivatives are much more stable than conventional ADH derivatives (e.g., immobilized on BrCN activated agarose). For example, glyoxyl immobilized ADH preserved full activity after incubation at pH 5.0 for 20h at room temperature and conventional derivatives (as well as the soluble enzyme) preserved less than 50% of activity after incubation under the same conditions. Moreover, glyoxyl derivatives are more than 10 times more stable than BrCN derivatives when incubated in 50% acetone at pH 7.0. Multipoint covalent immobilization, in addition to multisubunit immobilization, seems to play an important stabilizing role against distorting agents. In spite of these interesting stabilization factors, immobilization hardly promotes losses of catalytic activity (keeping values near to 90%). This immobilized preparation is able to keep good activity using dextran-NAD(+). In this way, ADH glyoxyl immobilized preparation seems to be suitable to be used as cofactor-recycling enzyme-system in interesting NAD(+)-mediated oxidation processes, catalyzed by other immobilized dehydrogenases in stirred tank reactors.     

Specificity of DC-SIGN for mannose- and fucose-containing glycans

The dendritic cell specific C-type lectin dendritic cell specific ICAM-3 grabbing non-integrin (DC-SIGN) binds to "self" glycan ligands found on human cells and to "foreign" glycans of bacterial or parasitic pathogens. Here, we investigated the binding properties of DC-SIGN to a large array of potential ligands in a glycan array format. Our data indicate that DC-SIGN binds with K(d)<2muM to a neoglycoconjugate in which Galbeta1-4(Fucalpha1-3)GlcNAc (Le(x)) trisaccharides are expressed multivalently. A lower selective binding was observed to oligomannose-type N-glycans, diantennary N-glycans expressing Le(x) and GalNAcbeta1-4(Fucalpha1-3)GlcNAc (LacdiNAc-fucose), whereas no binding was observed to N-glycans expressing core-fucose linked either alpha1-6 or alpha1-3 to the Asn-linked GlcNAc of N-glycans. These results demonstrate that DC-SIGN is selective in its recognition of specific types of fucosylated glycans and subsets of oligomannose- and complex-type N-glycans.     

Micropropagation and field performance of Yucca valida

Yucca valida is an important potential source of steroidal saponins closely related to Yucca schidigera, the species that is commercially exploited from the wild as a source of steroidal extracts. Neither of the species has been domesticated mainly because of their slow growth and long life span before harvesting. Here, we report a micropropagation method to generate isogenic or clonal lines for plantation purposes. Seventeen clonal lines were propagated and evaluated over a period of 26 months in an experimental plantation and compared with the performance of plants from seeds. The large variability found between the plants derived from seeds is manifested in the differences observed between the different clonal lines; however, these present a much smaller internal coefficient of variation than the one observed in the population of plants derived from seeds. Some clonal lines perform in a superior manner indicating that a process of selection and cloning can generate lines of fast growing individuals for plantations that can satisfy the demand for these materials without putting a natural resource at risk.     

Geonemy,ecology, reproductive biology and morphology of the tardigrade <Emphasis Type="Italic">Hypsibius zetlandicus</Emphasis> (Eutardigrada: Hypsibiidae) with erection of <Emphasis Type="Italic">Borealibius</Emphasis> gen. n.

The morphology, biology and geographic distribution of Hypsibius zetlandicus (Murray 1907) are considered. Scanning electron microscopy (SEM) and/or light microscopy (LM) analyses have been carried out on H. zetlandicus and the type species of Hypsibius: Hypsibius dujardini (Doyère 1840), with particular emphasis on the buccal–pharyngeal apparatuses. Some unusual characteristics of this apparatus in H. zetlandicus lead us to the erection of the new genus Borealibius, to which H. zetlandicus (Borealibius zetlandicus comb. n.) is transferred. In the light of new discoveries of this species from polar, sub-polar and alpine regions, and based on the available bibliographic references, we hypothesize a boreo–alpine distribution for this species. The presence of traits that are unusual and rare (in other tardigrade species) have been observed whilst analyzing the reproductive biology and ecology of B. zetlandicus (i.e., the presence of hermaphroditism, parental care and the colonization of very different substrates).