The Experts below are selected from a list of 831 Experts worldwide ranked by ideXlab platform
J. Michael Conlon - One of the best experts on this subject based on the ideXlab platform.
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Peptides from frog skin with potential for development into agents for Type 2 diabetes therapy.
Peptides, 2017Co-Authors: J. Michael Conlon, Milena Mechkarska, Yasser Abdel-wahab, Peter R FlattAbstract:Several frog skin peptides, first identified as result of their antimicrobial or immunomodulatory activities, have subsequently been shown to stimulate insulin release both in vitro and in vivo and so show potential for development into incretin-based drugs for treatment of patients with Type 2 diabetes mellitus. However, their therapeutic potential as anti-diabetic agents is not confined to this activity as certain frog skin-derived peptides, such as magainin-AM2 and CPF-SE1 and analogs of hymenochirin-1B, tigerinin-1R, and esculentin-2CHa, have been shown to increase insulin sensitivity, promote β-cell proliferation, suppress pancreatic and circulating glucagon concentrations, improve the lipid profile, and selectively alter expression of genes involved in insulin secretion and action in mice with diet-induced obesity, insulin resistance and impaired glucose tolerance. This review assesses the therapeutic possibilities of peptides from frogs belonging to the Pipidae, Dicroglossidae, and Ranidae families, focusing upon work that has been carried out since 2014.
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Actions of PGLa-AM1 and its [A14K] and [A20K] analogues and their therapeutic potential as anti-diabetic agents
Biochimie, 2017Co-Authors: Bosede O. Owolabi, Peter R Flatt, J. Michael Conlon, Vishal Musale, Opeolu O. Ojo, R. Charlotte Moffett, Mary K. Mcgahon, Tim M. Curtis, Yasser Abdel-wahabAbstract:PGLa-AM1 (GMASKAGSVL10GKVAKVALKA20AL.NH2) was first identified in skin secretions of the frog Xenopus amieti (Pipidae) on the basis of its antimicrobial properties. PGLa-AM1 and its [A14K] and [A20K] analogues produced a concentration-dependent stimulation of insulin release from BRIN-BD11 rat clonal β-cells without cytotoxicity at concentrations up to 3 μM. In contrast, the [A3K] analogue was cytotoxic at concentrations ≥ 30 nM. The potency and maximum rate of insulin release produced by the [A14K] and [A20K] peptides were significantly greater than produced by PGLa-AM1. [A14K]PGLa-AM1 also stimulated insulin release from mouse islets at concentrations ≥ 1 nM and from the 1.1B4 human-derived pancreatic β-cell line at concentrations > 30 pM. PGLa-AM1 (1 μM) produced membrane depolarization in BRIN-BD11 cells with a small, but significant (P
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Effects of tigerinin peptides on cytokine production by mouse peritoneal macrophages and spleen cells and by human peripheral blood mononuclear cells.
Biochimie, 2014Co-Authors: Jelena Pantic, Milena Mechkarska, Miodrag L. Lukic, J. Michael ConlonAbstract:Abstract The tigerinins are a family of cationic, cyclic peptides of unknown biological function produced in the skins of diverse frog species. Tigerinin-1R (RVCSAIPLPICH.NH2) from Hoplobatrachus rugulosus (Dicroglossidae), tigerinin-1V (RICYAMWIPYPC) from Lithobates vaillanti (Ranidae), and tigerinin-1M (WCPPMIPLCSRF.NH2) from Xenopus muelleri (Pipidae) did not inhibit growth of Escherichia coli and Staphylococcus aureus at concentrations up to 500 μg/ml and were not hemolytic. Incubation of peritoneal macrophages from both BALB/c and C57BL/6 mice with tigerinin-1M, -1R and -1V (20 μg/ml) significantly (P
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Caerulein precursor fragment (CPF) peptides from the skin secretions of Xenopus laevis and Silurana epitropicalis are potent insulin-releasing agents.
Biochimie, 2012Co-Authors: Dinesh K. Srinivasan, Milena Mechkarska, Yasser Abdel-wahab, Peter R Flatt, J. Michael ConlonAbstract:Abstract Peptidomic analysis of norepinephrine-stimulated skin secretions of the tetraploid clawed frog Xenopus laevis (Pipidae) led to the identification of 10 peptides with the ability to stimulate the release of insulin from the rat BRIN-BD11 clonal β cell line. These peptides were purified to near homogeneity and structural characterization showed that they belong to the magainin (2 peptides), peptide glycine-leucine-amide (PGLa) (1 peptide), xenopsin precursor fragment (1 peptide), and caerulein precursor fragment (CPF) (6 peptides) families. CPF-1, CPF-3, CPF-5 and CPF-6 were the most potent producing a significant (P
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The hymenochirins: A family of host-defense peptides from the Congo dwarf clawed frog Hymenochirus boettgeri (Pipidae)
Peptides, 2012Co-Authors: Milena Mechkarska, Hubert Vaudry, Jérôme Leprince, Manju Prajeep, Laurent Coquet, Thierry Jouenne, Jay King, J. Michael ConlonAbstract:Skin secretions of frogs from the subfamily Xenopodinae (Xenopus+Silurana) within the family Pipidae are a rich source of antimicrobial peptides with therapeutic potential but species from the sister taxon Hymenochirus in the subfamily Pipinae (Hymenochirus+Pseudhymenochirus+Pipa) have not been investigated. Peptidomic analysis of norepinephrine-stimulated skin secretions from two distinct populations of the Congo dwarf clawed frog Hymenochirus boettgeri (Tornier, 1896) has led to identification of five structurally related peptides with broad-spectrum antimicrobial activity. Hymenochirin-1B (IKLSPETKDNLKKVLKGAIKGAIAVAKMV.NH(2)) is C-terminally α-amidated whereas hymenochirins-2B-5B have the general structure XKIPX(2)VKDTLKKVAKGX(2)SX(2)AGAX(3).COOH. Hymenochirin-3B (IKIPAVVKDTLKKVAKGVLSAVAGALTQ) was the most abundant peptide in the secretions. The hymenochirins show very low structural similarity with the antimicrobial peptides isolated from skin secretions of Silurana tropicalis and Xenopus laevis consistent with the proposed ancient divergence of the Pipinae and Xenopodinae. Synthetic replicates of hymenochirin-1B-4B inhibit the growth of Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus (MIC in the range 10-40 μM) and Candida albicans (MIC=80 μM). The peptides display relatively weak hemolytic activity against human erythrocytes (LC(50) in the range 160 to >300 μM).
John Measey - One of the best experts on this subject based on the ideXlab platform.
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Competition and feeding ecology in two sympatric Xenopus species (Anura: Pipidae).
PeerJ, 2017Co-Authors: Solveig Vogt, F. Andre De Villiers, Flora Ihlow, Dennis Rödder, John MeaseyAbstract:CITATION: Vogt, S., et al. 2017. Competition and feeding ecology in two sympatric Xenopus species (Anura: Pipidae). PeerJ, 5:e3130, doi:10.7717/peerj.3130/table-1.
Jay D. King - One of the best experts on this subject based on the ideXlab platform.
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peptidomic analysis of skin secretions of the mexican burrowing toad rhinophrynus dorsalis rhinophrynidae insight into the origin of host defense peptides within the Pipidae and characterization of a proline arginine rich peptide
Peptides, 2017Co-Authors: Michael J Conlon, Jérôme Leprince, Laurent Coquet, Thierry Jouenne, Laure Guilhaudis, Maria Luisa Mangoni, Samir Attoub, Jay D. KingAbstract:Abstract The Mexican burrowing toad Rhinophrynus dorsalis is the sole extant representative of the Rhinophrynidae. United in the superfamily Pipoidea, the Rhinophrynidae is considered to be the sister-group to the extant Pipidae which comprises Hymenochirus, Pipa, Pseudhymenochirus and Xenopus. Cationic, α-helical host-defense peptides of the type found in Hymenochirus, Pseudhymenochirus, and Xenopus species (hymenochirins, pseudhymenochirins, magainins, and peptides related to PGLa, XPF, and CPF) were not detected in norepinephrine-stimulated skin secretions of R. dorsalis. Skin secretions of representatives of the genus Pipa also do not contain cationic α-helical host-defense peptides which suggest, as the most parsimonious hypothesis, that the ability to produce such peptides by frogs within the Pipidae family arose in the common ancestor of (Hymenochirus + Pseudhymenochirus) + Xenopus after divergence from the line of evolution leading to extant Pipa species. Peptidomic analysis of the R. dorsalis secretions led to the isolation of rhinophrynin-27, a proline-arginine-rich peptide with the primary structure ELRLPEIARPVPEVLPARLPLPALPRN, together with rhinophrynin-33 containing the C-terminal extension KMAKNQ. Rhinophrynin-27 shows limited structural similarity to the porcine multifunctional peptide PR-39 but it lacks antimicrobial and cytotoxic activities. Like PR-39, the peptide adopts a poly- l -proline helix but some changes in the circular dichroism spectrum were observed in the presence of anionic sodium dodecylsulfate micelles consistent with the stabilization of turn structures.
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Purification and properties of antimicrobial peptides from skin secretions of the Eritrea clawed frog Xenopus clivii (Pipidae).
Comparative Biochemistry and Physiology C-toxicology & Pharmacology, 2011Co-Authors: J. Michael Conlon, Jay D. King, Eman Ahmed, Milena Mechkarska, Hubert Vaudry, Jérôme Leprince, Koji TakadaAbstract:Abstract Five peptides with antimicrobial activity were isolated from norepinephrine-stimulated skin secretions of the tetraploid frog Xenopus clivii Peracca, 1898 (Pipidae). Characterization of the peptides demonstrated that they are structurally similar to magainins (2 peptides), caerulein-precursor fragments, CPF (2 peptides), and xenopsin-precursor fragments, XPF (1 peptide) that have been previously isolated from other species of the genus Xenopus. The magainins and the XPF peptide were active only against the Gram-negative microorganism Escherichia coli whereas the CPF peptides were also active against the Gram-positive Staphylococcus aureus. The most abundant antimicrobial peptide in the secretions, CPF-C1 (GFGSLLGKALRLG ANVL.NH2) inhibited the growth of the Gram-negative bacteria Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa (MIC ≤ 25 μM) suggesting potential for development into an anti-infective agent for use against these emerging antibiotic-resistant pathogens.
Measey John - One of the best experts on this subject based on the ideXlab platform.
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Competition and feeding ecology in two sympatric Xenopus species (Anura: Pipidae)
'PeerJ', 2017Co-Authors: Vogt Solveig, De Villiers F. Andre, Ihlow Flora, Rodder Dennis, Measey JohnAbstract:CITATION: Vogt, S., et al. 2017. Competition and feeding ecology in two sympatric Xenopus species (Anura: Pipidae). PeerJ, 5:e3130, doi:10.7717/peerj.3130/table-1.The original publication is available at https://peerj.comPublication of this article was funded by the Stellenbosch University Open Access Fund.The widespread African clawed frog (Xenopus laevis) occurs in sympatry with the IUCN Endangered Cape platanna (Xenopus gilli) throughout its entire range in the south-western Cape, South Africa. In order to investigate aspects of the interspecific competition between populations of X. laevis and X. gilli, an assessment of their niche differentiation was conducted through a comprehensive study on food composition and trophic niche structure at two study sites: the Cape of Good Hope (CoGH) and Kleinmond. A total of 399 stomach contents of X. laevis (n = 183) and X. gilli (n = 216) were obtained together with samples of available prey to determine food preferences using the Electivity index (E*), the Simpson’s index of diversity (1 − D), the Shannon index (H′), and the Pianka index (Ojk). Xenopus gilli diet was more diverse than X. laevis, particularly in Kleimond where the Shannon index was nearly double. Both species were found to consume large amounts of tadpoles belonging to different amphibian species, including congeners, with an overall higher incidence of anurophagy than previously recorded. However, X. laevis also feeds on adult X. gilli, thus representing a direct threat for the latter. While trophic niche overlap was 0.5 for the CoGH, it was almost 1 in Kleinmond, suggesting both species utilise highly congruent trophic niches. Further, subdividing the dataset into three size classes revealed overlap to be higher in small frogs in both study sites. Our study underlines the importance of actively controlling X. laevis at sites with X. gilli in order to limit competition and predation, which is vital for conservation of the south-western Cape endemic.https://peerj.com/articles/3130/Publisher's versio
Milena Mechkarska - One of the best experts on this subject based on the ideXlab platform.
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Peptides from frog skin with potential for development into agents for Type 2 diabetes therapy.
Peptides, 2017Co-Authors: J. Michael Conlon, Milena Mechkarska, Yasser Abdel-wahab, Peter R FlattAbstract:Several frog skin peptides, first identified as result of their antimicrobial or immunomodulatory activities, have subsequently been shown to stimulate insulin release both in vitro and in vivo and so show potential for development into incretin-based drugs for treatment of patients with Type 2 diabetes mellitus. However, their therapeutic potential as anti-diabetic agents is not confined to this activity as certain frog skin-derived peptides, such as magainin-AM2 and CPF-SE1 and analogs of hymenochirin-1B, tigerinin-1R, and esculentin-2CHa, have been shown to increase insulin sensitivity, promote β-cell proliferation, suppress pancreatic and circulating glucagon concentrations, improve the lipid profile, and selectively alter expression of genes involved in insulin secretion and action in mice with diet-induced obesity, insulin resistance and impaired glucose tolerance. This review assesses the therapeutic possibilities of peptides from frogs belonging to the Pipidae, Dicroglossidae, and Ranidae families, focusing upon work that has been carried out since 2014.
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Effects of tigerinin peptides on cytokine production by mouse peritoneal macrophages and spleen cells and by human peripheral blood mononuclear cells.
Biochimie, 2014Co-Authors: Jelena Pantic, Milena Mechkarska, Miodrag L. Lukic, J. Michael ConlonAbstract:Abstract The tigerinins are a family of cationic, cyclic peptides of unknown biological function produced in the skins of diverse frog species. Tigerinin-1R (RVCSAIPLPICH.NH2) from Hoplobatrachus rugulosus (Dicroglossidae), tigerinin-1V (RICYAMWIPYPC) from Lithobates vaillanti (Ranidae), and tigerinin-1M (WCPPMIPLCSRF.NH2) from Xenopus muelleri (Pipidae) did not inhibit growth of Escherichia coli and Staphylococcus aureus at concentrations up to 500 μg/ml and were not hemolytic. Incubation of peritoneal macrophages from both BALB/c and C57BL/6 mice with tigerinin-1M, -1R and -1V (20 μg/ml) significantly (P
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Caerulein precursor fragment (CPF) peptides from the skin secretions of Xenopus laevis and Silurana epitropicalis are potent insulin-releasing agents.
Biochimie, 2012Co-Authors: Dinesh K. Srinivasan, Milena Mechkarska, Yasser Abdel-wahab, Peter R Flatt, J. Michael ConlonAbstract:Abstract Peptidomic analysis of norepinephrine-stimulated skin secretions of the tetraploid clawed frog Xenopus laevis (Pipidae) led to the identification of 10 peptides with the ability to stimulate the release of insulin from the rat BRIN-BD11 clonal β cell line. These peptides were purified to near homogeneity and structural characterization showed that they belong to the magainin (2 peptides), peptide glycine-leucine-amide (PGLa) (1 peptide), xenopsin precursor fragment (1 peptide), and caerulein precursor fragment (CPF) (6 peptides) families. CPF-1, CPF-3, CPF-5 and CPF-6 were the most potent producing a significant (P
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The hymenochirins: A family of host-defense peptides from the Congo dwarf clawed frog Hymenochirus boettgeri (Pipidae)
Peptides, 2012Co-Authors: Milena Mechkarska, Hubert Vaudry, Jérôme Leprince, Manju Prajeep, Laurent Coquet, Thierry Jouenne, Jay King, J. Michael ConlonAbstract:Skin secretions of frogs from the subfamily Xenopodinae (Xenopus+Silurana) within the family Pipidae are a rich source of antimicrobial peptides with therapeutic potential but species from the sister taxon Hymenochirus in the subfamily Pipinae (Hymenochirus+Pseudhymenochirus+Pipa) have not been investigated. Peptidomic analysis of norepinephrine-stimulated skin secretions from two distinct populations of the Congo dwarf clawed frog Hymenochirus boettgeri (Tornier, 1896) has led to identification of five structurally related peptides with broad-spectrum antimicrobial activity. Hymenochirin-1B (IKLSPETKDNLKKVLKGAIKGAIAVAKMV.NH(2)) is C-terminally α-amidated whereas hymenochirins-2B-5B have the general structure XKIPX(2)VKDTLKKVAKGX(2)SX(2)AGAX(3).COOH. Hymenochirin-3B (IKIPAVVKDTLKKVAKGVLSAVAGALTQ) was the most abundant peptide in the secretions. The hymenochirins show very low structural similarity with the antimicrobial peptides isolated from skin secretions of Silurana tropicalis and Xenopus laevis consistent with the proposed ancient divergence of the Pipinae and Xenopodinae. Synthetic replicates of hymenochirin-1B-4B inhibit the growth of Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus (MIC in the range 10-40 μM) and Candida albicans (MIC=80 μM). The peptides display relatively weak hemolytic activity against human erythrocytes (LC(50) in the range 160 to >300 μM).
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Purification and properties of antimicrobial peptides from skin secretions of the Eritrea clawed frog Xenopus clivii (Pipidae).
Comparative Biochemistry and Physiology C-toxicology & Pharmacology, 2011Co-Authors: J. Michael Conlon, Jay D. King, Eman Ahmed, Milena Mechkarska, Hubert Vaudry, Jérôme Leprince, Koji TakadaAbstract:Abstract Five peptides with antimicrobial activity were isolated from norepinephrine-stimulated skin secretions of the tetraploid frog Xenopus clivii Peracca, 1898 (Pipidae). Characterization of the peptides demonstrated that they are structurally similar to magainins (2 peptides), caerulein-precursor fragments, CPF (2 peptides), and xenopsin-precursor fragments, XPF (1 peptide) that have been previously isolated from other species of the genus Xenopus. The magainins and the XPF peptide were active only against the Gram-negative microorganism Escherichia coli whereas the CPF peptides were also active against the Gram-positive Staphylococcus aureus. The most abundant antimicrobial peptide in the secretions, CPF-C1 (GFGSLLGKALRLG ANVL.NH2) inhibited the growth of the Gram-negative bacteria Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa (MIC ≤ 25 μM) suggesting potential for development into an anti-infective agent for use against these emerging antibiotic-resistant pathogens.