A new Miocene local fauna from the Sierra Madre Oriental at San Luis Potosí, Central-East Mexico,and its paleontologic significance

Mexico's Late Neogene mammal faunas are largely known from localities in the Trans-Mexican Volcanic Belt; those from other morphotectonic provinces are few and far apart. Thus, the discovery of Late Miocene vertebrates in western Sierra Madre Oriental at San Luis Potosí, the Paso del Águila local fauna, significantly adds to this meager record. The assemblage was collected from the floodplain facies of the San Nicolás Formation, a ∼1100-m thick, dominantly fluviolacustrine and calcilithitic, 15°–20° NE dipping sequence preserved in the Peotillos-Tolentino Graben, between 22°11’–22°19’ N and 100°30’–100°39° W. It includes remains of cf. Trachemys, a small to medium-sized emydid chelonian, a large camelid, a small cervid and a new species of the equini Pliohippus s.s., comparable in size, cranial morphology and odontographic characters to the Clarendonian-Early Hemphillian horses of the Pliohippus clade. Ar-Ar dates from ash-fall tuffs seemingly above and below the fossiliferous strata, bracket the age between 12.33 and 7.41 Ma (i.e., late Middle to Late Miocene), that is, within the Late Clarendonian-Early Hemphillian NALMA interval, making this fauna the first in Mexico from this age. The Paso del Águila local fauna is at least partly correlative with the Hemphillian local faunas from the TMVB and adjacent areas (e.g., Rancho El Ocote, Guanajuato and Tecolotlán, Jalisco), the Central Plateau (e.g., Arroyo Los Fragmentos, Zacatecas), and the Sierra Madre Occidental (e.g., Yepómera). Elsewhere, it is broadly correlative with the Late Clarendonian-Early Hemphillian faunas from the California Coast Ranges (e.g., North Tejon Hills, Ricardo and Dove Springs in the Mohave Desert), and the Gulf Coast Plain, Florida (McGehee Farm and Mixon). The Paso del Águila local fauna was part of a subtropical savannah and pine-oak forest (with a well-developed understory) biome that thrived on a climate regime much more humid than today.     

Organogenesis and histological development of the wedge sole <Emphasis Type="Italic">Dicologoglossa cuneata</Emphasis> M. larva with special reference to the digestive system

In this work, several features during the wedge sole larval development have been described. The newly hatched larva presented an acidophilic yolk with some oil drops. The digestive tract began to differentiate at 1 DAH, with a loop being discernible. The pancreas and liver were completely formed at 2 DAH, the former showing its typical basophilic acinar structure and acidophilic zymogen granules. The first supranuclear vesicles in enterocytes were seen at 3 DAH. At 4 DAH, yolk reserves were completely exhausted, the number of oesophagus and intestine mucous cells increased, and the heart was differentiated into four chambers: the venous sinus, atrium, ventricle, and arterious bulb. The development was fast and almost all organs were differentiated at 2 DAH. It is important to emphasize that gastric glands were not detected, a factor that should be considered when deciding diet formulation and feeding strategies for the rearing of this species.     

Kinetic studies of Gly28:Ser mutant form of Bacillus pumilus lipase: Changes in kcat and thermal dependence

Lipases are useful catalysts for a wide variety of industrial purposes. Herein we report the stability and thermal dependence of the activity of wild-type Bacillus pumilus lipase (BplA) and four site-directed mutants designed to improve its thermal stability. The Gly28:Ser mutation produces a dramatic four-fold increase in its k_cat and a remarkable increase in its stability. While the increase in k_cat is temperature-independent, the increase in stability shows that the resultant interactions of this mutation have a strong enthalpic component. Thermal dependence of stability, k_cat, K_M and k_cat/K_M were analysed to gain insight on the structural effects of mutations on BplA. Our results are consistent with a gain in enzyme mobility for those mutants displaying enhanced catalytic properties; the analysis of thermal dependence of kinetic parameters indicates that the mutations did not change either the catalytic mechanism or the rate-limiting step of catalysis.     

A Biochemical Guide to Yeast Adhesins: Glycoproteins for Social and Antisocial Occasions

Fungi are nonmotile eukaryotes that rely on their adhesins for selective interaction with the environment and with other fungal cells. Glycosylphosphatidylinositol (GPI)-cross-linked adhesins have essential roles in mating, colony morphology, host-pathogen interactions, and biofilm formation. We review the structure and binding properties of cell wall-bound adhesins of ascomycetous yeasts and relate them to their effects on cellular interactions, with particular emphasis on the agglutinins and flocculins of Saccharomyces and the Als proteins of Candida. These glycoproteins share common structural motifs tailored to surface activity and biological function. After being secreted to the outer face of the plasma membrane, they are covalently anchored in the wall through modified GPI anchors, with their binding domains elevated beyond the wall surface on highly glycosylated extended stalks. N-terminal globular domains bind peptide or sugar ligands, with between millimolar and nanomolar affinities. These affinities and the high density of adhesins and ligands at the cell surface determine microscopic and macroscopic characteristics of cell-cell associations. Central domains often include Thr-rich tandemly repeated sequences that are highly glycosylated. These domains potentiate cell-to-cell binding, but the molecular mechanism of such an association is not yet clear. These repeats also mediate recombination between repeats and between genes. The high levels of recombination and epigenetic regulation are sources of variation which enable the population to continually exploit new niches and resources.     

Effects of relative humidity on development, fecundity and survival of three storage mites

The developmental rate of immature stages and the reproduction of adults of Tyrophagus putrescentiae (Schrank), T. neiswanderi Johnston and Bruce and Acarus farris (Oudemans) were examined at 70, 80 and 90% r.h. and a constant temperature of 25°C. At 70% r.h., T. putrescentiae and A. farris immature stages failed to reach the protonymph stage as 100% of the larvae died, whereas T. neiswanderi was able to complete development. The developmental time of all immature stages for the three species was significantly increased as relative humidity was reduced. The mobile stages were particularly susceptible, as the time needed to complete their development at lower relative humidities suffered greater increases than the egg stage. At 70% r.h., T. putrescentiae and A. farris were not able to lay eggs and only 24% of T. neiswanderi pairs were fertile. The reproductive parameters of the three species at the relative humidities at which they were able to lay eggs showed significant differences, except for the percentage of fertile mating at 80 and 90% r.h. As relative humidity increased, preoviposition period was reduced and fecundity and daily fecundity was increased, whereas the oviposition period showed different patterns for the three species. The intrinsic rate of increase (r _m ) of T. neiswanderi at 70% r.h. was negative indicating that, at these conditions, mite populations of this species will diminish until they disappear. As relative humidity increased from 80 to 90% r.h. this parameter was almost twofold for both Tyrophagus species. The r _m obtained for A. farris at 90% r.h. was similar to that of T. neiswanderi at the same humidity while at 80% r.h. it was very small so that the population doubling time was more than 84 days. The influence of relative humidity on biology of these mites and its practical application as control measure are discussed.     

Novel avenues for passion fruit in vitro regeneration from endosperm culture,and morpho-agronomic and physiological traits of triploid Passiflora cincinnata Mast. emblings

The present study describes a new regeneration system based on somatic embryogenesis from mature endosperm Passiflora cincinnata Mast. cultures. Moreover, the morpho-agronomic and phenological traits, as well as enzymatic activity of regenerated triploid emblings are compared to those of diploids. Mature endosperms were cultured on Murashige and Skoog medium supplemented with various concentrations (4.5–45.2 µM) of 2,4-dichlorophenoxyacetic acid (2,4-D) and 4.5 μM 6-benzylaminopurine (BA). No plant growth regulators were included in the control group. Embryogenic calli were observed only in treatments supplemented with 13.6 and 18.1 µM 2,4-D?+?4.5 µM BA, with the highest number of somatic embryos per explant and regenerated plants (emblings) obtained with 18.1 µM 2,4-D. Most emblings (70%) were triploid (2n?=?3x?=?27), with a DNA amount (4.38 pg) similar to that of endosperm and 1.5 times greater than in diploid P. cincinnata seedlings (2n?=?2x?=?18), that contained 2.98 pg of DNA. While the number of organs and/or structures was akin to that in diploids, triploid emblings generally exhibited larger and longer vegetative and floral structures. The flower lifespan was also slightly altered by triploidy, nectar concentration was 27% higher, and the activity of plant defense enzymes β-1,3-glucanase and polyphenol oxidase was 29.8% and 22.1% higher. This study describes a new regeneration system for the production of phenotypic variants of this ornamental passion fruit species, opening new perspectives for future studies on genetic passion fruit breeding.

     

Gastrin-stimulated Gα13 Activation of Rgnef Protein (ArhGEF28) in DLD-1 Colon Carcinoma Cells

The guanine nucleotide exchange factor Rgnef (also known as ArhGEF28 or p190RhoGEF) promotes colon carcinoma cell motility and tumor progression via interaction with focal adhesion kinase (FAK). Mechanisms of Rgnef activation downstream of integrin or G protein-coupled receptors remain undefined. In the absence of a recognized G protein signaling homology domain in Rgnef, no proximal linkage to G proteins was known. Utilizing multiple methods, we have identified Rgnef as a new effector for Gα₁₃ downstream of gastrin and the type 2 cholecystokinin receptor. In DLD-1 colon carcinoma cells depleted of Gα₁₃, gastrin-induced FAK Tyr(P)-397 and paxillin Tyr(P)-31 phosphorylation were reduced. RhoA GTP binding and promoter activity were increased by Rgnef in combination with active Gα₁₃. Rgnef co-immunoprecipitated with activated Gα₁₃Q226L but not Gα₁₂Q229L. The Rgnef C-terminal (CT, 1279–1582) region was sufficient for co-immunoprecipitation, and Rgnef-CT exogenous expression prevented Gα₁₃-stimulated SRE activity. A domain at the C terminus of the protein close to the FAK binding domain is necessary to bind to Gα₁₃. Point mutations of Rgnef-CT residues disrupt association with active Gα₁₃ but not Gα_q. These results show that Rgnef functions as an effector of Gα₁₃ signaling and that this linkage may mediate FAK activation in DLD-1 colon carcinoma cells.     

Feather microstructure predicts size and colour intensity of a melanin‐based plumage signal

Feather microstructure affects the light absorbed by plumage pigments. However, the effect of particular elements of feather microstructure on the expression of pigmentary colours or on the size of colour patches has never been investigated. Here I use a model of avian visual perception and scanning electron microscope imaging of feathers to show that part of variation in the size and colour properties of a melanin‐based plumage signal of quality, the black breast stripe of great tits Parus major, is explained by three elements of feather microstructure (barbule density, barb cortex size and barb pith size). The strongest associations were between large stripes and low barbule density, between dark stripes and high barbule density, and between stripes with high relative long reflectance and high barbule density and thin barb cortex. By contrast, carotenoid‐based colour was not related to microstructural elements. Thus, it is possible that not all variation in melanin‐based colour is determined by melanin content, but also by feather microstructure. These findings should be considered by studies on the evolution of signals of quality.