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Albumen Gland (albumen + gland)
Selected AbstractsAnatomy and systematics of the minute syrnolopsine gastropods from Lake Tanganyika (Caenogastropoda, Cerithioidea, Paludomidae)ACTA ZOOLOGICA, Issue 4 2008Ellen E. Strong Abstract The minute syrnolopsine gastropods endemic to Lake Tanganyika have been allied to a number of freshwater, marine and terrestrial groups as a consequence of superficial conchological similarity. Although early anatomical studies confirmed the cerithioid organization of this clade, their close relationship to other lake species was not consistently recognized. In several recent cladistic analyses based on molecular data, the higher taxonomic placement and sister group relationships of syrnolopsines have been unstable. The present analysis confirms that syrnolopsines possess a spermatophore-forming organ , a synapomorphy of the Paludomidae , corroborating their placement in this family. Consistent with the molecular data, syrnolopsine monophyly is supported by two characters that occur exclusively in this group (salivary gland ducts that bypass the nerve ring and a linear albumen gland). Several characters in Martelia tanganyicensis, the most diminutive syrnolopsine , are only evident in the smallest lake species thus far investigated (Bridouxia, Stormsia) namely reduction of ctenidial leaflets, sorting area, intestine length and number of statoconia. These features are interpreted as being correlated with reduction in size. Nevertheless, close examination reveals differences in detail that allow more refined hypotheses of homology and are consistent with their independent origin. [source] The role of calcium on protein secretion of the albumen gland in Helisoma duryi (Gastropoda)INVERTEBRATE BIOLOGY, Issue 4 2004Lana Kiehn Abstract. The albumen gland of the freshwater pulmonate snail Helisoma duryi produces and secretes the perivitelline fluid, which coats fertilized eggs and provides nutrients to the developing embryos. It is known that perivitelline fluid secretion is stimulated by dopamine through the activation of a dopamine D1 -like receptor, which in turn stimulates cAMP production leading to the secretion of perivitelline fluid. This paper examines the glandular release of perivitelline fluid and provides evidence for the role of Ca2+ in the regulated secretion of perivitelline fluid based on protein secretion experiments and inositol 1,4,5-trisphosphate assays. Dopamine-stimulated protein secretion by the albumen gland is reduced in Ca2+ -free medium or in the presence of plasma membrane Ca2+ channel blockers, although the Ca2+ channel subtype involved is unclear. In addition, dopamine-stimulated protein secretion does not directly involve phospholipase C-generated signaling pathways and Ca2+ release from intracellular stores. Sarcoplasmic/endoplasmic reticulum Ca2+ -ATPase inhibitors had little effect on protein secretion when applied alone; however, they potentiated dopamine-stimulated protein secretion. Dantrolene, an inhibitor of ryanodine receptors, 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride, a nonspecific inhibitor of intracellular Ca2+ channels, and 2-aminoethyldiphenylborate, an inhibitor of inositol 1,4,5-trisphosphate receptors, did not suppress protein secretion, suggesting Ca2+ release from internal stores does not directly regulate protein secretion. Thus, the influx of Ca2+ from the extracellular space appears to be the major pathway mediating protein secretion by the albumen gland. The results are discussed with respect to the role of Ca2+ in controlling exocytosis of proteins from the albumen gland secretory cells. [source] Tandem Exploitation of Helix pomatia Glycosyltransferases: Facile Syntheses of H-Antigen-Bearing OligosaccharidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2007Hagen Bretting Prof. Abstract Snails from the family Helicidae produce in their albumen glands a highly branched galactan, which consists almost exclusively of D - and L -galactose. The D -Gal residues are glycosydically ,(1,6)- or ,(1,3)-linked, whereas the L -Gal moieties are attached ,(1,2). Up until the present time, two ,(1,6)- D -galactosyl transferases and one ,(1,2)- L -galactosyl transferase have been identified in a membrane preparation of these glands. These were used to synthesise various oligosaccharides by successive addition of the NDP-activated (NDP=nucleoside-5,-diphosphate) D -Gal or L -Fuc moieties, up to a heptasaccharide by starting from the disaccharide D -Gal-,(1,3)- D -Gal-,(1,OMe. Even larger oligosaccharides up to a tridecasaccharide were obtained by starting with the hexasaccharide D -Gal-[,(1,3)- D -Gal]4 -,(1,4)- D -Glc as an acceptor substrate. This tandem exploitation process has high potential for the easy introduction of D -Gal and L -Fuc residues into a great variety of oligosaccharides, which can be used in ligand/acceptor studies. [source] | ||||||||||