The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Michael J. Tyler - One of the best experts on this subject based on the ideXlab platform.
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Skin peptide and cDNA profiling of Australian anurans: Genus and species identification and evolutionary trends
Peptides, 2010Co-Authors: Rebecca J. Jackway, Michael J. Tyler, Tara L. Pukala, Stephen C. Donnellan, Patrick J. Sherman, John H. BowieAbstract:Host defense peptides of 35 species of Australian frogs from the hylids Cyclorana and Litoria, and the myobatrachids Crinia, Limnodynastes and Uperoleia have been identified. The biological activities of the majority of these peptides have been determined and include hormones, neuropeptides, opioids, immunomodulators, membrane active peptides [including antimicrobial, anticancer, antiviral (enveloped viruses like HIV and Herpes) and antifungal peptides], neuronal nitric oxide synthase inhibitors, pheromones and individual peptides with other specific activities. The host defense peptide Skin profile can be diagnostic at both the species and higher taxonomic levels; for example, species of Crinia, Litoria and Uperoleia each produce quite different types of peptides. Species of Cyclorana and Limnodynastes are more difficult to characterize by Skin peptides alone: species of both genera produce similar peptides with no apparent activity. The Skin peptide profiles of frogs from the genera Crinia, Litoria and Uperoleia may be used together with morphological and cognate methods, to differentiate between sub-species and even different population clusters of the same species. Nucleotide sequencing of cDNAs of precursors (pre-pro peptides) of bioactive peptides from the Skin Glands of various species of the genus Litoria show that the majority of these peptides originated from a single ancestor gene before the break away of Australia from Gondwana. The exceptions are the caerulein neuropeptides {e.g. caerulein [pEQDY(SO3H)TGWMDF(NH2)]} which have a different origin to that of other Litoria peptides. Disulfide containing peptides from Skin Glands of species of Crinia show a different evolutionary route to peptides from species of Litoria.
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Antipredator Mechanisms of Australian Frogs
Journal of Herpetology, 2000Co-Authors: Craig R. Williams, Michael J. Tyler, Edmund D. Brodie, Steven J. WalkerAbstract:We examined the antipredator mechanisms of 19 Australian hylid species (two genera) and 23 myobatrachid species (nine genera). Frogs of 39 of the 42 species exhibited one or more defensive mech- anisms (other than escape), including postures, bright coloration, adhesive Skin secretions, and/or calls. De- fensive posturing occurred in individuals of 38 species, and varied in relationship to morphology and lo- calization of Skin Glands. Bright colors, when present, typically were displayed during defensive postures. We documented dramatic geographic variation in the antipredator display of one species, Limnodynastes tasmaniensis. Defensive postures were accompanied by secretions from dorsal Skin Glands. These secretions were sometimes associated with a distinctive odor. Adhesive Skin secretions were present in burrowing frogs of three genera. Defensive calls were emitted by most hylids but none of the myobatrachids. We offer a hypothesis of mimicry to explain the behavior pattern of exposing the bold black and white ventral surface in Pseudophryne and Crinia species.
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Peptides from the Skin Glands of the Australian Buzzing Tree Frog Litoria electrica. Comparison with the Skin Peptides of the Red Tree Frog Litoria rubella
Australian Journal of Chemistry, 1999Co-Authors: Paul A. Wabnitz, John H. Bowie, John C Wallace, Michael J. TylerAbstract:Eleven peptides have been isolated from the Skin Glands of the ‘buzzing tree frog’ Litoria electrica. The two most abundant peptides are tryptophyllin L 3.1 [Phe Pro Trp Pro (NH2)] and electrin 1 [Phe Val Pro Ile Tyr Met (NH2)]. These peptides show neither significant antimicrobial nor smooth muscle activity. Tryptophyllin L 3.1 is thought to be a neuromodulator or neurotransmitter, and it is similar in structure to the human endomorphins [e.g. Tyr Pro Trp Phe (NH2)] which act on the γ-receptor. Both Litoria electrica and the ‘red tree frog’ Litoria rubella produce tryptophyllin peptides: it is considered that both species evolved from the same ancestor.
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New caerin antibacterial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera. Part 2. Sequence determination using mass spectrometry and associated techniques.
Rapid Communications in Mass Spectrometry, 1997Co-Authors: Simon T. Steinborner, Russell J. Waugh, John H. Bowie, Michael J. TylerAbstract:: Mass spectrometric sequencing, enzymic digestion and Edman degradation provide the structures of the two antimicrobial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera as:- Gly Leu Phe Ser Val Leu Gly Ala Val Ala Lys His Val Leu Pro His Val Val Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.6), and Gly Leu Phe Lys Val Leu Gly Ser Val Ala Lys His Leu Leu Pro His Val Ala Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.7).
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New caerin antibacterial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera.
Journal of Peptide Science, 1997Co-Authors: Simon T. Steinborner, Russell J. Waugh, John H. Bowie, Michael J. Tyler, John C Wallace, Steven Lewis RamsayAbstract:: The secretion of the Skin Glands of the 'orange-thighed frog' Litoria xanthomera contains seven peptides. One of these is the know hypotensive peptide caerulein. Two new peptides, caerin 1.6 [GLFSVLGAVAKHVLPHVVPVIAEKL(NH2)], and caerin 1.7 [GLFKVLGSVAKHLLPHVAPVIAEKL(NH2)] show antibacterial properties. Two other peptides lack the first two amino acid residues of caerins 1.6 and 1.7 and show no antibacterial activity. The identification of the peptides in Litoria xanthomera confirms that this species is related to Litoria caerula, Litoria gilleni and Litoria splendida but not as closely as those three species are related to each other.
John H. Bowie - One of the best experts on this subject based on the ideXlab platform.
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Skin peptide and cDNA profiling of Australian anurans: Genus and species identification and evolutionary trends
Peptides, 2010Co-Authors: Rebecca J. Jackway, Michael J. Tyler, Tara L. Pukala, Stephen C. Donnellan, Patrick J. Sherman, John H. BowieAbstract:Host defense peptides of 35 species of Australian frogs from the hylids Cyclorana and Litoria, and the myobatrachids Crinia, Limnodynastes and Uperoleia have been identified. The biological activities of the majority of these peptides have been determined and include hormones, neuropeptides, opioids, immunomodulators, membrane active peptides [including antimicrobial, anticancer, antiviral (enveloped viruses like HIV and Herpes) and antifungal peptides], neuronal nitric oxide synthase inhibitors, pheromones and individual peptides with other specific activities. The host defense peptide Skin profile can be diagnostic at both the species and higher taxonomic levels; for example, species of Crinia, Litoria and Uperoleia each produce quite different types of peptides. Species of Cyclorana and Limnodynastes are more difficult to characterize by Skin peptides alone: species of both genera produce similar peptides with no apparent activity. The Skin peptide profiles of frogs from the genera Crinia, Litoria and Uperoleia may be used together with morphological and cognate methods, to differentiate between sub-species and even different population clusters of the same species. Nucleotide sequencing of cDNAs of precursors (pre-pro peptides) of bioactive peptides from the Skin Glands of various species of the genus Litoria show that the majority of these peptides originated from a single ancestor gene before the break away of Australia from Gondwana. The exceptions are the caerulein neuropeptides {e.g. caerulein [pEQDY(SO3H)TGWMDF(NH2)]} which have a different origin to that of other Litoria peptides. Disulfide containing peptides from Skin Glands of species of Crinia show a different evolutionary route to peptides from species of Litoria.
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Peptides from the Skin Glands of the Australian Buzzing Tree Frog Litoria electrica. Comparison with the Skin Peptides of the Red Tree Frog Litoria rubella
Australian Journal of Chemistry, 1999Co-Authors: Paul A. Wabnitz, John H. Bowie, John C Wallace, Michael J. TylerAbstract:Eleven peptides have been isolated from the Skin Glands of the ‘buzzing tree frog’ Litoria electrica. The two most abundant peptides are tryptophyllin L 3.1 [Phe Pro Trp Pro (NH2)] and electrin 1 [Phe Val Pro Ile Tyr Met (NH2)]. These peptides show neither significant antimicrobial nor smooth muscle activity. Tryptophyllin L 3.1 is thought to be a neuromodulator or neurotransmitter, and it is similar in structure to the human endomorphins [e.g. Tyr Pro Trp Phe (NH2)] which act on the γ-receptor. Both Litoria electrica and the ‘red tree frog’ Litoria rubella produce tryptophyllin peptides: it is considered that both species evolved from the same ancestor.
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New caerin antibacterial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera. Part 2. Sequence determination using mass spectrometry and associated techniques.
Rapid Communications in Mass Spectrometry, 1997Co-Authors: Simon T. Steinborner, Russell J. Waugh, John H. Bowie, Michael J. TylerAbstract:: Mass spectrometric sequencing, enzymic digestion and Edman degradation provide the structures of the two antimicrobial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera as:- Gly Leu Phe Ser Val Leu Gly Ala Val Ala Lys His Val Leu Pro His Val Val Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.6), and Gly Leu Phe Lys Val Leu Gly Ser Val Ala Lys His Leu Leu Pro His Val Ala Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.7).
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New caerin antibacterial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera.
Journal of Peptide Science, 1997Co-Authors: Simon T. Steinborner, Russell J. Waugh, John H. Bowie, Michael J. Tyler, John C Wallace, Steven Lewis RamsayAbstract:: The secretion of the Skin Glands of the 'orange-thighed frog' Litoria xanthomera contains seven peptides. One of these is the know hypotensive peptide caerulein. Two new peptides, caerin 1.6 [GLFSVLGAVAKHVLPHVVPVIAEKL(NH2)], and caerin 1.7 [GLFKVLGSVAKHLLPHVAPVIAEKL(NH2)] show antibacterial properties. Two other peptides lack the first two amino acid residues of caerins 1.6 and 1.7 and show no antibacterial activity. The identification of the peptides in Litoria xanthomera confirms that this species is related to Litoria caerula, Litoria gilleni and Litoria splendida but not as closely as those three species are related to each other.
Simon T. Steinborner - One of the best experts on this subject based on the ideXlab platform.
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New caerin antibacterial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera. Part 2. Sequence determination using mass spectrometry and associated techniques.
Rapid Communications in Mass Spectrometry, 1997Co-Authors: Simon T. Steinborner, Russell J. Waugh, John H. Bowie, Michael J. TylerAbstract:: Mass spectrometric sequencing, enzymic digestion and Edman degradation provide the structures of the two antimicrobial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera as:- Gly Leu Phe Ser Val Leu Gly Ala Val Ala Lys His Val Leu Pro His Val Val Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.6), and Gly Leu Phe Lys Val Leu Gly Ser Val Ala Lys His Leu Leu Pro His Val Ala Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.7).
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New caerin antibacterial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera.
Journal of Peptide Science, 1997Co-Authors: Simon T. Steinborner, Russell J. Waugh, John H. Bowie, Michael J. Tyler, John C Wallace, Steven Lewis RamsayAbstract:: The secretion of the Skin Glands of the 'orange-thighed frog' Litoria xanthomera contains seven peptides. One of these is the know hypotensive peptide caerulein. Two new peptides, caerin 1.6 [GLFSVLGAVAKHVLPHVVPVIAEKL(NH2)], and caerin 1.7 [GLFKVLGSVAKHLLPHVAPVIAEKL(NH2)] show antibacterial properties. Two other peptides lack the first two amino acid residues of caerins 1.6 and 1.7 and show no antibacterial activity. The identification of the peptides in Litoria xanthomera confirms that this species is related to Litoria caerula, Litoria gilleni and Litoria splendida but not as closely as those three species are related to each other.
Russell J. Waugh - One of the best experts on this subject based on the ideXlab platform.
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New caerin antibacterial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera. Part 2. Sequence determination using mass spectrometry and associated techniques.
Rapid Communications in Mass Spectrometry, 1997Co-Authors: Simon T. Steinborner, Russell J. Waugh, John H. Bowie, Michael J. TylerAbstract:: Mass spectrometric sequencing, enzymic digestion and Edman degradation provide the structures of the two antimicrobial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera as:- Gly Leu Phe Ser Val Leu Gly Ala Val Ala Lys His Val Leu Pro His Val Val Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.6), and Gly Leu Phe Lys Val Leu Gly Ser Val Ala Lys His Leu Leu Pro His Val Ala Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.7).
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New caerin antibacterial peptides from the Skin Glands of the Australian tree frog Litoria xanthomera.
Journal of Peptide Science, 1997Co-Authors: Simon T. Steinborner, Russell J. Waugh, John H. Bowie, Michael J. Tyler, John C Wallace, Steven Lewis RamsayAbstract:: The secretion of the Skin Glands of the 'orange-thighed frog' Litoria xanthomera contains seven peptides. One of these is the know hypotensive peptide caerulein. Two new peptides, caerin 1.6 [GLFSVLGAVAKHVLPHVVPVIAEKL(NH2)], and caerin 1.7 [GLFKVLGSVAKHLLPHVAPVIAEKL(NH2)] show antibacterial properties. Two other peptides lack the first two amino acid residues of caerins 1.6 and 1.7 and show no antibacterial activity. The identification of the peptides in Litoria xanthomera confirms that this species is related to Litoria caerula, Litoria gilleni and Litoria splendida but not as closely as those three species are related to each other.
Erik Hviid Larsen - One of the best experts on this subject based on the ideXlab platform.
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Membrane potential and conductance of frog Skin gland acinar cells in resting conditions and during stimulation with agonists of macroscopic secretion.
Pflügers Archiv: European Journal of Physiology, 1999Co-Authors: Jakob B Sorensen, Erik Hviid LarsenAbstract:Frog Skin Glands were stripped of connective tissue and investigated using the nystatin-permeabilized whole-cell patch-clamp configuration. The membrane potential in unstimulated acinar cells was –69.5±0.7 mV, and the conductance was dominated by K+, based on ion substitution experiments. The cells were electrically coupled through heptanol- and halothane-sensitive gap junctions. During application of gap junction blockers, the whole-cell current/voltage relationship displayed strong outward rectification. Outward currents were blocked by barium. Stimulation by agonists known to cause increases in either cytosolic cAMP ([cAMP]c) (isoproterenol, prostaglandin E2, both at 2 µM) or free cellular Ca2+ concentration ([Ca2+]c) (noradrenaline, 10 µM, added with propranolol, 5 µM; carbachol, 100 µM) in the frog Skin Glands caused reversible depolarization: by 34±3 mV, 36±3 mV, 25±3 mV (plateau-phase), and 20±3 mV, respectively. Ion substitution experiments showed that stimulation through either pathway (cAMP or Ca2+) resulted in the activation of a Cl– conductance. Application of noradrenaline or adrenaline resulted in a faster depolarization (rates 22 mV/s, 26 mV/s) than stimulation by isoproterenol or prostaglandin E2 (5.6–5.7 mV/s). Cells that were depolarized by exposure to isoproterenol or prostaglandin E2 partially repolarized when stimulated by noradrenaline. The repolarization was blocked by Ba2+ (5 mM) or prazosine (1 µM), consistent with the activation of Ca2+-dependent K+ channels via α1-adrenergic receptors. We conclude that in the frog Skin gland both Ca2+-dependent and cAMP-dependent Cl– channels are present in the apical membrane. Increases in free [Ca2+]c in the cAMP-stimulated gland results in the activation of K+ channels, thereby increasing the driving force for Cl– exit.
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Ion secretion and isotonic transport in frog Skin Glands.
The Journal of Membrane Biology, 1996Co-Authors: Hans H. Ussing, F. Lind, Erik Hviid LarsenAbstract:The aim of this study was to clarify the mecha- nism of isotonic fluid transport in frog Skin Glands. Sta- tionary ion secretion by the Glands was studied by mea- suring unidirectional fluxes of 24 Na + , 42 K + , and carrier- free 134 Cs + in paired frog Skins bathed on both sides with Ringer's solution, and with 10 ˛5 M noradrenaline on the inside and 10 ˛4 M amiloride on the outside. At transepi- thelial thermodynamic equilibrium conditions, the 134 Cs + flux ratio, JCs /J in , varied in seven pairs of preparations from 6 to 36. Since carrier-free 134 Cs + entering the cells is irreversibly trapped in the cellular compartment (Ussing & Lind, 1996), the transepithelial net flux of 134 Cs + indicates that a paracellular flow of water is drag- ging 134 Cs + in the direction from the serosal- to outside solution. From the measured flux ratios it was calculated that the force driving the secretory flux of Cs + varied from 30 to 61 mV among preparations. In the same ex- periments unidirectional Na + fluxes were measured as well, and it was found that also Na + was subjected to secretion. The ratio of unidirectional Na + fluxes, how- ever, was significantly smaller than would be predicted if the two ions were both flowing along the paracellular route dragged by the flow of water. This result indicates that Na + and Cs + do not take the same pathway through the Glands. The flux ratio of unidirectional K + fluxes indicated active secretion of K + . The time it takes for steady-state K + fluxes to be established was significantly longer than that of the simultaneously measured Cs + fluxes. These results allow the conclusion that — in ad- dition to being transported between cells — K + is sub- mitted to active transport along a cellular pathway. Based on the recirculation theory, we propose a new model which accounts for stationary Na + ,K + ,C l ˛ and water secretion under thermodynamic equilibrium con- ditions. The new features of the model, as compared to the classical Silva-model for the shark-rectal gland, are: (i) the sodium pumps in the activated gland transport Na + into the lateral intercellular space only. (ii) A bar- rier at the level of the basement membrane prevents the major fraction of Na + entering the lateral space from returning to the serosal bath. Thus, Na + is secreted into the outside bath. It has to be assumed then that the Na + permeability of the basement membrane barrier (PNa )i s smaller than the Na + permeability of the junctional mem- brane (PNa ), i.e., PNa /PNa > 1. The secretory paracellu- lar flow of water further requires that the Na + reflection coefficients (sNa) of the two barriers are governed by the conditions, sNa >0 , and s Na > sNa . (iii) Na + channels are located in the apical membrane of the activated gland cells, so that a fraction of the Na + outflux appearing downstream the lateral intercellular space is recirculated by the gland cells. Based on measured unidirectional fluxes, a set of equations is developed from which we estimate the ion fluxes flowing through major pathways during stationary secretion. It is shown that 80% of the sodium ions flowing downstream the lateral intercellular space is recycled by the gland cells. Our calculations also indicate that under the conditions prevailing in the present experiments 1.8 ATP molecule would be hydro- lyzed for every Na + secreted to the outside bath.