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1.
Peptides ; 27(3): 483-92, 2006 Mar.
Article in English | MEDLINE | ID: mdl-16309789

ABSTRACT

The GGNG peptides are excitatory neuropeptides identified from earthworms, leeches and polychaeta. Two structurally related peptides were purified and characterized from a mollusk, Thais clavigera (prosobranch gastropod). The peptides designated as Thais excitatory peptide-1 (TEP-1) (KCSGKWAIHACWGGN-NH2) and TEP-2 (KCYGKWAMHACWGGN-NH2) are pentadecapeptides having one disulfide bond and C-terminal GGN-NH2 structures, which are shared by most GGNG peptides. TEP augmented the motilities of Thais esophagus and penial complex. TEP-like immunoreactivity is distributed in both the neurons of the central nervous system and nerve endings in the penial complex. Thus, the involvement of TEP in the contraction of the digestive and reproductive systems is suggested. Substitution of amino acids in TEP revealed that two tryptophan residues in TEP are important for maintaining bioactivity.


Subject(s)
Neuropeptides/physiology , Amino Acid Sequence , Animals , Aplysia , Chromatography, High Pressure Liquid , Esophagus/drug effects , Female , Gastropoda/chemistry , Genitalia/drug effects , Male , Molecular Sequence Data , Neuropeptides/chemistry , Neuropeptides/isolation & purification , Peptides, Cyclic/immunology , Tissue Distribution
2.
J Exp Biol ; 207(Pt 14): 2507-18, 2004 Jun.
Article in English | MEDLINE | ID: mdl-15184522

ABSTRACT

The catecholamine dopamine is present in both the central nervous system and in the peripheral tissues of molluscs, where it is involved in regulating reproduction. Application of exogenous dopamine to the isolated albumen gland of the freshwater pulmonate snail Helisoma duryi (Wetherby) induces the secretion (release) of perivitelline fluid. The major protein component of the perivitelline fluid of Helisoma duryi is a native 288 kDa glycoprotein that is secreted around individual eggs and serves as an important source of nutrients for the developing embryos. The secretion of glycoprotein by the albumen gland is a highly regulated event that must be coordinated with the arrival of the fertilized ovum at the carrefour (the region where the eggs receive albumen gland secretory products). In order to elucidate the intracellular signalling pathway(s) mediating dopamine-induced glycoprotein secretion, albumen gland cAMP production and glycoprotein secretion were measured in the presence/absence of selected dopamine receptor agonists and antagonists. Dopamine D1-selective agonists dihydrexidine, 6,7-ADTN and SKF81297 stimulated cAMP production and glycoprotein secretion from isolated albumen glands whereas D1-selective antagonists SCH23390 and SKF83566 suppressed dopamine-stimulated cAMP production. Dopamine D2-selective agonists and antagonists generally had no effect on cAMP production or protein secretion. Based on the effects of these compounds, a pharmacological profile was obtained that strongly suggests the presence of a dopamine D1-like receptor in the albumen gland of Helisoma duryi. In addition, secretion of albumen gland glycoprotein was not inhibited by protein kinase A inhibitors, suggesting that dopamine-stimulated protein secretion might occur through a protein kinase A-independent pathway.


Subject(s)
2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/analogs & derivatives , Dopamine/metabolism , Exocrine Glands/drug effects , Exocrine Glands/metabolism , Glycoproteins/metabolism , Signal Transduction/physiology , Snails/metabolism , 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology , Animals , Benzazepines/pharmacology , Cyclic AMP/metabolism , Cyclic AMP-Dependent Protein Kinases/antagonists & inhibitors , Dopamine Agonists/pharmacology , Dopamine Antagonists/pharmacology , Dose-Response Relationship, Drug , Electrophoresis, Polyacrylamide Gel , Fresh Water , Phenanthridines/pharmacology , Receptors, Dopamine D1/metabolism , Reproduction/physiology , Tetrahydronaphthalenes/pharmacology
3.
Peptides ; 24(10): 1533-44, 2003 Oct.
Article in English | MEDLINE | ID: mdl-14706532

ABSTRACT

The distribution and function of an Aplysia cardioexcitatory peptide, NdWFamide, were examined in the nervous system of pulmonate snails. We chemically identified the authentic NdWFamide from a land snail (Euhadra congenita) and a freshwater snail (Lymnaea stagnalis). NdWFamide potentiated the heartbeat of those snails. Immunohistochemistry using anti-NdWFamide antibody demonstrated the distribution of NdWFamide-containing neurons and fibers in the central nervous system, as well as peripheral tissues, such as the cardiovascular region and accessory sex organs. These results suggest that NdWFamide is a neuropeptide mediating the neural regulation of the activity of the cardiovascular and reproductive systems of snails.


Subject(s)
Aplysia/chemistry , Oligopeptides/metabolism , Oligopeptides/pharmacology , Snails/drug effects , Snails/physiology , Animals , Central Nervous System/chemistry , Heart/drug effects , Heart/physiology , Immunohistochemistry , Oligopeptides/isolation & purification , Organ Specificity , Snails/chemistry
4.
Acta Biol Hung ; 51(2-4): 243-53, 2000.
Article in English | MEDLINE | ID: mdl-11034149

ABSTRACT

The albumen gland in Helisoma secretes a perivitelline fluid which surrounds each egg and is made up of several 66 kDa protein subunits and polysaccharide complexes. Forskolin, an adenylate cyclase activator, stimulated the secretion and release of the perivitelline fluid. An acidic extract of the central nervous system increased the intracellular concentration of cAMP in the albumen gland and this results in the release of the 66 kDa molecule and other proteins. Digestion of the brain extract with proteases abolished this activity, suggesting that the factor is a peptide. Cyclic AMP analogues and [BMX also stimulated the protein secretion in dose-dependent manner. Forskolin when added with the brain factor had an additive response. SQ22536, a non-competitive inhibitor of adenylate cyclase, inhibited brain extract dependent adenylate cyclase activity whereas aluminum fluoride, a G protein activator, was found to stimulate adenylate cyclase. Dopamine also stimulates protein secretion by the albumen gland and through the application of various agonists and antagonists of dopamine, it was established that the neurotransmitter acts via D1-like receptors by stimulating adenylate cyclase.


Subject(s)
Mollusca/physiology , Animals , Colforsin/pharmacology , Dopamine/pharmacology , Dopamine Agonists/pharmacology , Dopamine Antagonists/pharmacology , Exocrine Glands/metabolism , Female , Male , Neurons/physiology , Proteins/metabolism
5.
Biochem Cell Biol ; 78(3): 261-79, 2000.
Article in English | MEDLINE | ID: mdl-10949078

ABSTRACT

Activins are growth and differentiation factors belonging to the transforming growth factor-beta superfamily. They are dimeric proteins consisting of two inhibin beta subunits. The structure of activins is highly conserved during vertebrate evolution. Activins signal through type I and type II receptor proteins, both of which are serine/threonine kinases. Subsequently, downstream signals such as Smad proteins are phosphorylated. Activins and their receptors are present in many tissues of mammals and lower vertebrates where they function as autocrine and (or) paracrine regulators of a variety of physiological processes, including reproduction. In the hypothalamus, activins are thought to stimulate the release of gonadotropin-releasing hormone. In the pituitary, activins increase follicle-stimulating hormone secretion and up-regulate gonadotropin-releasing hormone receptor expression. In the ovaries of vertebrates, activins are expressed predominantly in the follicular layer of the oocyte where they regulate processes such as folliculogenesis, steroid hormone production, and oocyte maturation. During pregnancy, activin-A is also involved in the regulation of placental functions. This review provides a brief overview of activins and their receptors, including their structures, expression, and functions in the female reproductive axis as well as in the placenta. Special effort is made to compare activins and their receptors in different vertebrates.


Subject(s)
Inhibins/physiology , Reproduction , Activin Receptors , Activins , Animals , Female , Hypothalamus/metabolism , Inhibins/chemistry , Models, Biological , Ovary/metabolism , Pituitary Gland/metabolism , Placenta/metabolism , Pregnancy , Receptors, Growth Factor/chemistry , Receptors, Growth Factor/metabolism , Signal Transduction
6.
J Comp Physiol A ; 182(6): 817-25, 1998 Jun.
Article in English | MEDLINE | ID: mdl-9631557

ABSTRACT

The albumen gland is a compound tubular exocrine gland found in the female reproductive tract of freshwater pulmonate snails such as Helisoma duryi. It secretes a perivitelline fluid, composed of protein and polysaccharide complexes, and coats each fertilized egg. A 288-kDa native glycoprotein, composed of several 66-kDa subunits, was identified in soluble extracts of albumen gland. Forskolin stimulates the release of secretory granules, containing both proteins and polysaccharides, from the cytoplasm of the glandular cells. An acid extract of the central nervous system or the adenosine-3', 5'-cyclic monophosphate (cAMP) analogue 8-bromo cAMP, stimulates protein secretion from the gland. Pretreatment of the albumen gland with cAMP antagonist (Rp isomer of cAMP) inhibits the stimulatory effect of a brain extract. Digestion of brain extract with proteolytic enzymes abolishes its activity, suggesting the factor from the brain is peptidergic. The neuroactive agents serotonin, Phe-Met-Arg-Phe-amide, Tyr-Gly-Gly-Phe-Met-Arg-Phe-amide, small cardioactive peptide B, and caudodorsal cell hormone were also tested for potential secretion-promoting ability. Brain extracts were partially purified with a Sep-Pak C18 reverse-phase cartridge and indicate the peptide is relatively hydrophobic. These results suggest that a brain peptide promotes the secretion of perivitelline fluid, and this is mediated by the adenylate cyclase/cAMP signal transduction pathway.


Subject(s)
Exocrine Glands/metabolism , Polysaccharides/metabolism , Proteins/metabolism , Snails/metabolism , Animals , Brain Chemistry , Central Nervous System/chemistry , Colforsin/pharmacology , Cyclic AMP/pharmacology , Cytoplasmic Granules/metabolism , Exocrine Glands/drug effects , Female , GTP-Binding Proteins/metabolism , Immunoblotting , Tissue Extracts/pharmacology
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