Rudist decline in the Maastrichtian Cardenas Formation (East-central Mexico)

Five sections of the Cardenas and Tabaco formations in east-central Mexico have been analyzed by means of bio-, Sr-isotope, and sequence stratigraphy, in order to evaluate their age as well as the timing of rudist decline.Ammonites [Pachydiscus (Pachydiscus) neubergicus (Hauer), Sphenodiscus pleurisepta (Conrad), Coahuilites sheltoni Böse] indicate an early Maastrichtian age for the topmost lower member of the Cardenas Formation and planktic foraminifera [e.g., Globotruncanita stuarti (de Lapparent), Archaeoglobigerina cretacea (d’Orbigny), Globotruncanella petaloidea (Gandolfi), Gansserina gansseri (Bolli), Globotruncana linneiana (d’Orbigny)] a late early Maastrichtian age for the middle member corresponding to the foraminiferal zones CF5 and CF6. Sr-isotope stratigraphic data yield an early late Maastrichtian age (66.93 Ma < 67.98 Ma < 68.96 Ma) for the last rudist assemblage in the topmost upper member of the Cardenas Formation, coinciding with the foraminiferal zone CF4.17 small-scale and 3 large-scale depositional cycles have been identified, which correspond to para- and depositional sequences. The progradational pattern of the large-scale cycles indicates an overall regression trend, which terminated in subaerial exposure of the area, indicated by paleosoils in the red beds of the Tabaco Formation. The correlation of the large-scale cycles with the global sea level charts indicate that eustatic sea level fall caused the regression and led to the exposure during the middle late Maastrichtian. This subaerial exposure resulted in the loss of habitat and thus the disappearance of rudists in east-central Mexico.     

Immune cross-reactivity in celiac disease: anti-gliadin antibodies bind to neuronal synapsin I

Celiac disease is an immune-mediated disorder triggered by ingestion of wheat gliadin and related proteins in genetically susceptible individuals. In addition to the characteristic enteropathy, celiac disease is associated with various extraintestinal manifestations, including neurologic complications such as neuropathy, ataxia, seizures, and neurobehavioral changes. The cause of the neurologic manifestations is unknown, but autoimmunity resulting from molecular mimicry between gliadin and nervous system proteins has been proposed to play a role. In this study, we sought to investigate the immune reactivity of the anti-gliadin Ab response toward neural proteins. We characterized the binding of affinity-purified anti-gliadin Abs from immunized animals to brain proteins by one- and two-dimensional gel electrophoresis, immunoblotting, and peptide mass mapping. The major immunoreactive protein was identified as synapsin I. Anti-gliadin Abs from patients with celiac disease also bound to the protein. Such cross-reactivity may provide clues into the pathogenic mechanism of the neurologic deficits that are associated with gluten sensitivity.     

The UT-A1 urea transporter interacts with snapin, a SNARE-associated protein

The UT-A1 urea transporter mediates rapid transepithelial urea transport across the inner medullary collecting duct and plays a major role in the urinary concentrating mechanism. To transport urea, UT-A1 must be present in the plasma membrane. The purpose of this study was to screen for UT-A1-interacting proteins and to study the interactions of one of the identified potential binding partners with UT-A1. Using a yeast two-hybrid screen of a human kidney cDNA library with the UT-A1 intracellular loop (residues 409-594) as bait, we identified snapin, a ubiquitously expressed SNARE-associated protein, as a novel UT-A1 binding partner. Deletion analysis indicated that the C-terminal coiled-coil domain (H2) of snapin is required for UT-A1 interaction. Snapin binds to the intracellular loop of UT-A1 but not to the N- or C-terminal fragments. Glutathione S-transferase pulldown experiments and co-immunoprecipitation studies verified that snapin interacts with native UT-A1, SNAP23, and syntaxin-4 (t-SNARE partners), indicating that UT-A1 participates with the SNARE machinery in rat kidney inner medulla. Confocal microscopic analysis of immunofluorescent UT-A1 and snapin showed co-localization in both the cytoplasm and in the plasma membrane. When we co-injected UT-A1 with snapin cRNA in Xenopus oocytes, urea influx was significantly increased. In the absence of snapin, the influx was decreased when UT-A1 was combined with t-SNARE components syntaxin-4 and SNAP23. We conclude that UT-A1 may be linked to the SNARE machinery via snapin and that this interaction may be functionally and physiologically important for urea transport.     

Activation of the heterodimeric central complex SoxYZ of chemotrophic sulfur oxidation is linked to a conformational change and SoxY-Y interprotein disulfide formation

The central protein of the four component sulfur oxidizing (Sox) enzyme system of Paracoccus pantotrophus, SoxYZ, carries at the SoxY subunit the covalently bound sulfur substrate which the other three proteins bind, oxidize, and release as sulfate. SoxYZ of different preparations resulted in different specific thiosulfate-oxidizing activities of the reconstituted Sox enzyme system. From these preparations SoxYZ was activated up to 24-fold by different reductants with disodium sulfide being the most effective and yielded a uniform specific activity of the Sox system. The activation comprised the activities with hydrogen sulfide, thiosulfate, and sulfite. Sulfide-activation decreased the predominant beta-sheet character of SoxYZ by 4%, which caused a change in its conformation as determined by infrared spectroscopy. Activation of SoxYZ by sulfide exposed the thiol of the C-terminal Cys-138 of SoxY as evident from alkylation by 4-acetamido-4'-maleimidylstilbene-2,2'-disulfonic acid. Also, SoxYZ activation enhanced the formation of the Sox(YZ)2 heterotetramer as evident from density gradient gel electrophoresis. The tetramer was formed due to an interprotein disulfide between SoxY to yield a SoxY-Y dimer as determined by combined high pressure liquid chromatography and mass spectrometry. The significance of the conformational change of SoxYZ and the interprotein disulfide between SoxY-Y is discussed.     

Evolution and function of B chromosome 45S rDNA sequences in Brachycome dichromosomatica.

The origin and activity of 45S rDNA located on micro B chromosomes of the daisy Brachycome dichromosomatica were analysed. The internal transcribed spacer 2 (ITS2) of the 45S rRNA gene was sequenced for micro B, large B, and A chromosomes of B. dichromosomatica cytodeme A2, and conserved differences were identified between sequences originating from A and both types of B chromosomes. Phylogenetic analysis did not identify a species containing an ITS2 sequence more similar to either of the B chromosome sequences than the B. dichromosomatica A chromosome sequences. Thus, an origin of the B chromosomes from A chromosomes at a time prior to the divergence of the 4 cytodemes of B. dichromosomatica is suggested. The frequent (70%) nucleolar non-association of micro B chromosomes suggests inactivity of micro B 45S rDNA.     

Pupal remodeling and the evolution and development of alternative male morphologies in horned beetles

Background  

How novel morphological traits originate and diversify represents a major frontier in evolutionary biology. Horned beetles are emerging as an increasingly popular model system to explore the genetic, developmental, and ecological mechanisms, as well as the interplay between them, in the genesis of novelty and diversity. The horns of beetles originate during a rapid growth phase during the prepupal stage of larval development. Differential growth during this period is either implicitly or explicitly assumed to be the sole mechanism underlying differences in horn expression within and between species. Here I focus on male horn dimorphisms, a phenomenon at the center of many studies in behavioral ecology and evolutionary development, and quantify the relative contributions of a previously ignored developmental process, pupal remodeling, to the expression of male dimorphism in three horned beetle species.     

Cellular defibrillation: interaction of micro-scale electric fields with voltage-gated ion channels

We study the effect of micro-scale electric fields on voltage-gated ion channels in mammalian cell membranes. Such micro- and nano-scale electric fields mimic the effects of multiferroic nanoparticles that were recently proposed [1] as a novel way of controlling the function of voltage-sensing biomolecules such as ion channels. This article describes experimental procedures and initial results that reveal the effect of the electric field, in close proximity of cells, on the ion transport through voltage-gated ion channels. We present two configurations of the whole-cell patch-clamping apparatus that were used to detect the effect of external stimulation on ionic currents and discuss preliminary results that indicate modulation of the ionic currents consistent with the applied stimulus.