Pleistocene and Holocene Carbonate Environments on San Salvador Island, Bahamas: A Field Trip Guide

Although isolated and small in size, San Salvador Island is in many ways a unique place - an all carbonates setting on a small, tectonically stable platform, surrounded by deep oceanic waters, and an historical footnote as the widely accepted first landing site of Christopher Columbus in the New World in 1492. Columbus\u27 stay here was brief, and the major events of subsequent history largely have passed San Salvador by. This is not a tourist island; the natural beauty, floras, and faunas of the Bahamas are well preserved here. The overview theme of this series of field excursions on San Salvador will be interpretation of paleodepositional environments for the well-exposed Pleistocene and Holocene carbonate rocks that cap the island and recognition of modem analogues from the varied carbonate environments found on the island and its surrounding shelf. Questions of sea level history, diagenetic change, and the surficial processes operating on carbonate island terranes also will be considered. Our trip will begin with a low-attitude overflight to view features of the main Bahama platform enroute to San Salvador, which lies just beyond the eastern edge of the platform. The field trip leaders all have been working on San Salvador and elsewhere in the Bahamas for the past decade. We have experienced the good and the bad - a pleasant tropical climate, warm and alive marine waters, a generally unspoiled setting, and the friendly Bahamian people, along with sometimes fierce no-see-um attacks, sun-burnt skin, and unexpected soakings from tropical storms. Throughout, the experiences have been rewarding and the challenges of geologic interpretation great. We look forward to sharing some of our findings and experiences with you. Welcome to the Bahamas and San Salvador Island! See other Smith authored Field Trip Guides of Gerace Research Centre

Biochemical enrichment and biophysical characterization of a taste receptor for L-arginine from the catfish, Ictalurus puntatus

BACKGROUND: The channel catfish, Ictalurus punctatus, is invested with a high density of cutaneous taste receptors, particularly on the barbel appendages. Many of these receptors are sensitive to selected amino acids, one of these being a receptor for L-arginine (L-Arg). Previous neurophysiological and biophysical studies suggested that this taste receptor is coupled directly to a cation channel and behaves as a ligand-gated ion channel receptor (LGICR). Earlier studies demonstrated that two lectins, Ricinus communis agglutinin I (RCA-I) and Phaseolus vulgaris Erythroagglutinin (PHA-E), inhibited the binding of L-Arg to its presumed receptor sites, and that PHA-E inhibited the L-Arg-stimulated ion conductance of barbel membranes reconstituted into lipid bilayers. RESULTS: Both PHA-E and RCA-I almost exclusively labeled an 82–84 kDa protein band of an SDS-PAGE of solubilized barbel taste epithelial membranes. Further, both rhodamine-conjugated RCA-I and polyclonal antibodies raised to the 82–84 kDa electroeluted peptides labeled the apical region of catfish taste buds. Because of the specificity shown by RCA-I, lectin affinity was chosen as the first of a three-step procedure designed to enrich the presumed LGICR for L-Arg. Purified and CHAPS-solubilized taste epithelial membrane proteins were subjected successively to (1), lectin (RCA-I) affinity; (2), gel filtration (Sephacryl S-300HR); and (3), ion exchange chromatography. All fractions from each chromatography step were evaluated for L-Arg-induced ion channel activity by reconstituting each fraction into a lipid bilayer. Active fractions demonstrated L-Arg-induced channel activity that was inhibited by D-arginine (D-Arg) with kinetics nearly identical to those reported earlier for L-Arg-stimulated ion channels of native barbel membranes reconstituted into lipid bilayers. After the final enrichment step, SDS-PAGE of the active ion channel protein fraction revealed a single band at 82–84 kDa which may be interpreted as a component of a multimeric receptor/channel complex. CONCLUSIONS: The data are consistent with the supposition that the L-Arg receptor is a LGICR. This taste receptor remains active during biochemical enrichment procedures. This is the first report of enrichment of an active LGICR from the taste system of vertebrata

The sea lamprey Petromyzon marinus genome reveals the early origin of several chemosensory receptor families in the vertebrate lineage

<p>Abstract</p> <p>Background</p> <p>In gnathostomes, chemosensory receptors (CR) expressed in olfactory epithelia are encoded by evolutionarily dynamic gene families encoding odorant receptors (OR), trace amine-associated receptors (TAAR), V1Rs and V2Rs. A limited number of OR-like sequences have been found in invertebrate chordate genomes. Whether these gene families arose in basal or advanced vertebrates has not been resolved because these families have not been examined systematically in agnathan genomes.</p> <p>Results</p> <p><it>Petromyzon </it>is the only extant jawless vertebrate whose genome has been sequenced. Known to be exquisitely sensitive to several classes of odorants, lampreys detect fewer amino acids and steroids than teleosts. This reduced number of detectable odorants is indicative of reduced numbers of CR gene families or a reduced number of genes within CR families, or both, in the sea lamprey. In the lamprey genome we identified a repertoire of 59 intact single-exon CR genes, including 27 OR, 28 TAAR, and four V1R-like genes. These three CR families were expressed in the olfactory organ of both parasitic and adult life stages.</p> <p>Conclusion</p> <p>An extensive search in the lamprey genome failed to identify potential orthologs or pseudogenes of the multi-exon V2R family that is greatly expanded in teleost genomes, but did find intact calcium-sensing receptors (CASR) and intact metabotropic glutamate receptors (MGR). We conclude that OR and V1R arose in chordates after the cephalochordate-urochordate split, but before the diversification of jawed and jawless vertebrates. The advent and diversification of V2R genes from glutamate receptor-family G protein-coupled receptors, most likely the CASR, occurred after the agnathan-gnathostome divergence.</p

Personal Papers (MS 80-0002)

Letter from John H. Teeter to Mr. and Mrs. Kempner thanking them for their contribution to the Damon Runyon Memorial Fund for Cancer Research, Inc