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B L Tufts - One of the best experts on this subject based on the ideXlab platform.
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characterization of carbonic anhydrase and anion exchange in the erythrocytes of Bowfin amia calva a primitive air breathing fish
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 1999Co-Authors: Matthieu R Gervais, B L TuftsAbstract:The purpose of this study was to investigate the characteristics of carbonic anhydrase (CA) and the Cl−/HCO3− exchanger (Band 3; AE1) in the erythrocytes of Bowfin (Amia calva), a primitive air-breathing fish, in order to further understand the strategies of blood CO2 transport in lower vertebrates and gain insights into the evolution of the vertebrate erythrocyte proteins, CA and Band 3. A significant amount of CA activity was measured in the erythrocytes of Bowfin (70 mmol CO2 min−1 ml−1), although it appeared to be lower than that in the erythrocytes of teleost fish. The turnover number (Kcat) of Bowfin erythrocyte CA was intermediate between that of the slow type I CA isozyme in agnathans and elasmobranchs and the fast type II CA in the erythrocytes of the more recent teleost fishes, but the inhibition properties of Bowfin erythrocyte CA were similar to the fast mammalian CA isozyme, CA II. In contrast to previous findings, a plasma CA inhibitor was found to be present in the blood of Bowfin. Bowfin erythrocytes were also found to possess a high rate of Cl−/HCO3− exchange (6 nmol HCO3− s−1 cm−2) that was sensitive to DIDS. Visualization of erythrocyte membrane proteins by SDS-PAGE revealed a major band in the 100 kDa range for the trout, which would be consistent with the anion exchanger. In contrast, the closest major band for the membranes of Bowfin erythrocytes was around the 140 kDa range. Taken together, these results suggest that the strategy for blood CO2 transport in Bowfin is probably similar to that in most other vertebrates despite several unique characteristics of erythrocyte CA and Band 3 in these primitive fish.
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evidence for membrane bound carbonic anhydrase in the air bladder of Bowfin amia calva a primitive air breathing fish
The Journal of Experimental Biology, 1998Co-Authors: Matthieu R Gervais, B L TuftsAbstract:The purpose of this study was to examine the subcellular distribution and isoenzyme characteristics of carbonic anhydrase from the gills and respiratory air bladder of Bowfin Amia calva, a primitive air-breathing fish. Separation of subcellular fractions by differential centrifugation revealed that the vast majority of carbonic anhydrase from the gills of Bowfin originated from the cytoplasmic fraction. Washing of the gill microsomal pellet also indicated that the carbonic anhydrase originally associated with this pellet was largely due to contamination from the cytoplasmic fraction. Experiments with a carbonic anhydrase inhibitor, sulphanilamide, and the plasma carbonic anhydrase inhibitor from this species confirmed that the Bowfin gill probably contains only one carbonic anhydrase isoenzyme which had properties resembling those of CA II. In contrast to the situation in the gills, a relatively large percentage (27%) of the total air bladder carbonic anhydrase was associated with the microsomal fraction. Washing of the air bladder microsomal pellet removed little of the carbonic anhydrase activity, indicating that most of the carbonic anhydrase in the microsomal fraction was associated with the membranes. Like the mammalian pulmonary CA IV isoenzyme, microsomal carbonic anhydrase from the Bowfin air bladder was less sensitive to the Bowfin plasma carbonic anhydrase inhibitor, sodium dodecylsulphate (SDS) and sulphanilamide than was cytoplasmic carbonic anhydrase from the air bladder. Microsomal carbonic anhydrase from the Bowfin air bladder also resembled CA IV in that it appears to be anchored to the membrane via a phosphatidylinositol-glycan linkage which could be cleaved by phosphatidylinositol-specific phospholipase C. Taken together, these results suggest that a membrane-bound carbonic anhydrase isoenzyme resembling mammalian CA IV in terms of inhibition characteristics and membrane attachment is present in the air-breathing organ of one of the most primitive air-breathing vertebrates.
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in vitro analysis of volume and ph regulation in the red blood cells of a primitive air breathing fish the Bowfin amia calva
Canadian Journal of Zoology, 1994Co-Authors: B L Tufts, R C Drever, B Bagatto, B CameronAbstract:In the Bowfin (Amia calva), a decrease in extracellular pH in vitro was associated with an increase in the water content and chloride concentration in the red blood cells that could be inhibited by the anion-exchange blocker, 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS). After a step increase in CO2 tension, the extracellular total CO2 concentration was also significantly reduced by DIDS. Finally, over most of the experimental pH range, the red blood cell pH observed in the presence of DIDS was significantly elevated compared with that of controls. Taken together, these results indicate that as in most other fishes, chloride–bicarbonate exchange is clearly present and functional in Bowfin red blood cells. Moreover, within the physiological pH range, ion movements across the anion exchanger have a marked influence on both the volume and the pH of Bowfin red blood cells. In sharp contrast to the rainbow trout (Oncorhynchus mykiss), catecholamines had no effect on the volume, pH, or intracellula...
J M Conlon - One of the best experts on this subject based on the ideXlab platform.
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Characterization of two molecular forms of vasoactive intestinal polypeptide (VIP) from the pallid sturgeon, Scaphirhynchus albus (Acipenseriformes)
Fish Physiology and Biochemistry, 2001Co-Authors: B.a. Barton, J M ConlonAbstract:Vasoactive intestinal polypeptide (VIP) was isolated in two molecular forms from an extract of the gastroenteropancreatic system of the pallid sturgeon Scaphirhynchus albus (Acipenseriformes). VIP-1 was identical to the peptide previously isolated from the rainbow trout Oncorhynchus mykiss and the Bowfin, Amia calva , consistent with the proposed sister group relationship of the Acipenseriformes and the Neopterygii. Sturgeon VIP-2 contained the amino acid substitution (Ala^4 to Ser) at a site previously regarded as invariant. The isolation of two distinct VIP gene products provides some support for the hypothesis that S. albus , with approximately 120 chromosomes, is functionally tetraploid but the alternative view that the species is functionally diploid and the two peptides arose from a local duplication of the VIP gene within the Scaphirhynchus lineage cannot be rejected.
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Bradykinin and its receptors in non-mammalian vertebrates.
Regulatory peptides, 1999Co-Authors: J M ConlonAbstract:The generation of bradykinin (BK) in blood by the action of the kallikrein-kinin system has been studied intensively in mammals but the system has received relatively little attention in non-mammalian vertebrates. The plasma of crocodilians and Testudines (turtles and tortoises) contains all the components of the kallikrein-kinin system found in mammals (prekallikrein activator, prekallikrein, kininogen, and kininases) and activation results in generation of [Thr6]-BK. Plasma of birds and snakes probably lacks a prekallikrein activator analogous to mammalian Factor XII but treatment with exogenous proteases (pig pancreatic kallikrein and/or trypsin) generates [Thr6, Leu8]-BK (chicken), [Ala1, Thr6]-BK (python) and [Val1, Thr6]-BK (colubrid snakes). The skins of certain frogs, particularly of the genus Rana, contain very high concentrations of BK-related peptides but their pathway of biosynthesis involves the action of cellular endoproteinase(s) cleaving at the site of single arginyl residues rather than by the action of the kallikrein-kinin system. Evidence for a prekallikrein activator in fish plasma is lacking but treatment with exogenous proteases generates [Arg0, Trp5, Leu8]-BK (trout and cod), [Trp5]-BK (Bowfin and gar), [Met1, Met5]-BK (sturgeon). The cardiovascular actions and effects upon gastrointestinal smooth muscle of these peptides in their species of origin differ markedly. For example, intra-arterial injections of the native BK peptides into unanesthetized fish produce transient hypertension in the cod, complex depressor and pressor responses in the trout and Bowfin and hypotension in the sturgeon. Pharmacological studies in snakes and fish and with the recombinantally expressed chicken BK receptor have demonstrated that the BK receptors in the tissues of non-mammalian vertebrates have appreciably different ligand binding properties from the well-characterized mammalian B1 and B2 receptors.
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isolation localization and cardiovascular activity of tachykinins from the stomach of the Bowfin amia calva
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 1995Co-Authors: David Waugh, John H Youson, K E Groff, B Platzack, K R Olson, J M ConlonAbstract:The Bowfin is an extant representative of an ancient group of ray-finned fish with evolutionary connections to modern teleosts. A peptide with substance P-like immunoreactivity was isolated from an extract of Bowfin stomach and its primary structure was established as Ser-Lys-Ser-His-Gln-Phe-Tyr-Gly-Leu-Met-NH2. This amino acid sequence resembles mammalian substance P only in the COOH-terminal region of the peptide. A second tachykinin with neurokinin A-like immunoreactivity isolated from the extract comprises 23 amino acid residues and shows limited structural similarity to mammalian neuropeptide-gamma. A randomly distributed population of cells in the gastric glands of the Bowfin were immunostained with an antiserum raised against substance P, but no immunopositive structures were identified in the surface epithelium, lamina propria, or the nerve plexuses of the submucosa. Bolus injections of synthetic Bowfin substance P (0.1-10 nmol/kg) into the bulbus arteriosus of unanesthetized Bowfin resulted in a significant and dose-dependent rise in vascular resistance and arterial blood pressure (P < 0.01) and a fall in cardiac output (P < 0.05) without change in heart rate. After 5-10 min, arterial pressure and vascular resistance returned to preinjection levels, but cardiac output significantly (P < 0.05) increased over baseline values. The response to the peptide was unaffected by pretreatment of the animals with phentolamine. The study has shown that the stomach of the Bowfin synthesizes tachykinins with novel structural features that display cardiovascular activity in this species.
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structure and biological activity of glucagon and glucagon like peptide from a primitive bony fish the Bowfin amia calva
Biochemical Journal, 1993Co-Authors: J M Conlon, John H Youson, T P MommsenAbstract:The Bowfin, Amia calva (order Amiiformes) occupies an important position in phylogeny as a surviving representative of a group of primitive ray-finned fishes from which the present-day teleosts may have evolved. Glucagon and glucagon-like peptide (GLP) were isolated from an extract of Bowfin pancreas and their primary structures determined. Bowfin glucagon shows only four amino acid substitutions compared with human glucagon, and Bowfin glucagon was equipotent and equally effective as human glucagon in stimulation of glycogenolysis in dispersed hepatocytes from a teleost fish, the copper rockfish, Sebastes caurinus. In contrast, Bowfin GLP shows 15 amino acid substitutions and three amino acid deletions compared with the corresponding region of human GLP-1-(7-37)-peptide. In particular, the Bowfin peptide contains an N-terminal tyrosine residue rather than the N-terminal histidine residue found in all other glucagon-related peptides so far characterized. Bowfin GLP stimulated glycogenolysis in rockfish hepatocytes, but was 3-fold less effective and 23-fold less potent than human GLP-1-(7-37)-peptide. We speculate that selective mutations in the GLP domain of Bowfin preproglucagon may be an adaptive response to the previously demonstrated low biological potency of Bowfin insulin.
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structure and receptor binding activity of insulin from a holostean fish the Bowfin amia calva
Biochemical Journal, 1991Co-Authors: J M Conlon, John H Youson, Jonathan WhittakerAbstract:The holostean fishes are the extant representatives of the primitive ray-finned fishes from which the present-day teleosts may have evolved. The primary structure of insulin from a holostean fish, the Bowfin (Amia calva), was established as: A-chain: Gly-Ile-Val-Glu-Gln-Cys-Cys-Leu-Lys-Pro-Cys-Thr-Ile-Tyr-Glu-Met-Glu- Lys-Tyr-Cys-Asn B-chain: Ala-Ala-Ser-Gln-His-Leu-Cys-Gly-Ser-His-Leu-Val-Glu-Ala-Leu-Phe-Leu- Val-Cys-Gly-Glu-Ser-Gly-Phe-Phe-Tyr-Asn-Pro-Asn-Lys-Ser This amino acid sequence contains several substitutions (methionine at A16, phenylalanine at B16 and serine at B22) at sites that have been strongly conserved in other vertebrate species and that may be expected to influence biological activity. Consistent with this prediction, Bowfin insulin was approx. 14-fold less potent than pig insulin in inhibiting the binding of [125I-Tyr-A14](human insulin) to transfected mouse NIH 3T3 cells expressing the human insulin receptor.
Michael J Conlon - One of the best experts on this subject based on the ideXlab platform.
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the endocrine cells in the gastroenteropancreatic system of the Bowfin amia calva l an immunohistochemical ultrastructural and immunocytochemical analysis
Journal of Morphology, 2001Co-Authors: John H Youson, Azza Almahrouki, Diana Naumovski, Michael J ConlonAbstract:The gastroenteropancreatic (GEP) endo- crine system of Bowfin (Amia calva) was described using light and electron microscopy and immunological meth- ods. The islet organ (endocrine pancreas) consists of dif- fusely scattered, mostly small islets and isolated patches of cells among and within the exocrine acini. The islets are composed of abundant, centrally located B cells immuno- reactive to bovine and lamprey insulin antisera and D cells showing a widespread distribution and specificity to somatostatin antibodies. A and F cells are present at the very periphery of the islets and are immunoreactive with antisera against glucagon (and glucagon-like peptide) and several peptides of the pancreatic polypeptide (PP)-family, respectively. The peptides of the two families usually col- locates within the same peripheral islet cells and are the most common immunoreactive peptides present in the extra-islet tissue. Immunocytochemistry and fine struc- tural observations characterised the granule morphology for B and D cells and identified two cell types with gran- ules immunoreactive to glucagon antisera. These two pu- tative A cells had similar granules, which were distinct from either B or D cells, but one of the cells had rod- shaped cytoplasmic inclusions within cisternae of what appeared to be rough endoplasmic reticulum. The inclu- sions were not immunoreactive to either insulin or gluca- gon antisera. Only small numbers of cells in the stomach and intestine immunoreacted to antisera against soma- tostatin, glucagon, and PP-family peptides. The paucity of these cells was reflected in the low concentrations of these peptides in intestinal extracts. The GEP system of Bowfin is not unlike that of other actinopterygian fishes, but there are some marked differences that may reflect the antiq- uity of this system and/or may be a consequence of the ontogeny of this system in this species. J. Morphol. 250: 208 -224, 2001. © 2001 Wiley-Liss, Inc.
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purification and structural characterization of vasoactive intestinal polypeptide from the trout and Bowfin
General and Comparative Endocrinology, 1995Co-Authors: Yunxia Wang, Michael J ConlonAbstract:Vasoactive intestinal polypeptide (VIP) was purified from extracts of the stomachs of the rainbow trout, Oncorhynchus mykiss, and Bowfin, Amia calva. The primary structure of VIP from both species was the same: His-Ser-Asp-Ala-IIe-Phe-Thr-Asp-Tyr10-Ser-Arg-Phe-Arg-Lys-Gln-Met-Ala-Val-Lys20-Lys-Tyr-Leu-Asn-Ser-Val-Leu-Thr. This amino acid sequence shows only one amino acid substitution (Val5 → Ile) compared with the common sequence of VIP from the chicken, alligator, and European green frog. The structure identity of VIP from the trout and Bowfin is consistent with the close phylogenetic relationship between the Salmoniformes and the Amiiformes and the data indicate that pressure to conserve the complete primary structure of VIP during vertebrate evolution has been very strong.
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isolation and biological activity of trp5 bradykinin from the plasma of the phylogenetically ancient fish the Bowfin and the longnosed gar
Peptides, 1995Co-Authors: Michael J Conlon, John H Youson, Luciano E Marra, B Platzack, K R OlsonAbstract:Abstract The holostean fish occupy an important position in vertebrate phylogeny as extant representatives of a ancient group of ray-finned fish with evolutionary connections to present-day teleosts. Incubation of heat-denatured plasma from the Bowfin Amia calva with trypsin generated bradykinin-like immunoreactivity. The primary structure of Bowfin bradykinin was established as Ala-Pro-Pro-Gly-Trp-Ser-Pro-Phe-Arg. This amino acid sequence contains one amino acid substitution (Phe 5 → Trp) compared with mammalian bradykinin. The same peptide was generated in heat-denatured plasma from the longnosed gar Lepisosteus osseus . Treatment of plasma from either the Bowfin or gar with glass beads under conditions previously shown to activate Factor XII in the plasma of mammals and reptiles did not generate bradykinin. Bolus injections of synthetic Bowfin bradykinin (0.1, 0.3, and 1.0 nmol/kg) into the bulbus arteriosus of unanesthetized Bowfin resulted in an immediate fall in arterial blood pressure of 5–10 min duration that was followed by a dose-dependent rise in pressure that was sustained for 30–60 min. There was no change in heart rate following bradykinin administration. The data suggest that the kallikrein-kinin system may predate the appearance of teleosts and may play a role in cardiovascular regulation in holosteans.
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purification and characterization of galanin from the phylogenetically ancient fish the Bowfin amia calva and dogfish scyliorhinus canicula
Peptides, 1994Co-Authors: Yunxia Wang, Michael J ConlonAbstract:Abstract Galanin was purified to near homogeneity from an extract of the stomachs of the holostean fish, the Bowfin and the elasmobranch fish, the European common dogfish. Bowfin galanin contains an α-amidated C- terminal residue and the primary structure of the peptide (GWTNL SAGYL LGPHA VDNHR SLNDK HGLA) shows only four amino acid substitutions (Val 16 → Ile, Leu 22 → Phe, Asn 23 → His, and His 26 → Tyr) compared with pig galanin. Dogfish galanin was isolated in a truncated form for which amino acid sequence was identical to residues (1–20) of Bowfin galanin. The isolation of this fragment is indicative of processing at the site of a single arginyl residue, and an analogous peptide has been previously isolated from human intestine. The data demonstrate that peptides with close structural similarity to mammalian galanins are present in the gastrointestinal tracts of phylogenetically ancient fish.
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prosomatostatin i is processed to somatostatin 26 and somatostatin 14 in the pancreas of the Bowfin amia calva
Regulatory Peptides, 1993Co-Authors: Yunxia Wang, John H Youson, Michael J ConlonAbstract:Abstract With the exception of the Agnatha (lampreys and hagfishes), somatostatin-14 is the predominant molecular form of somatostatin in the pancreas of species from all classes of vertebrates yet studied. The pancreas of the holostean fish, Amia calva (Bowfin; order Amiiformes) contained somatostatin-like immunoreactivity that was resolved by reversed phase HPLC in two components. The primary structure of the more abundant peptide (somatostatin-26) was established as: Ser-Ala-Asn-Pro-Ala 5 -Leu-Ala-Pro-Arg-Glu 10 -Arg-Lys-Ala-Gly-Cys 15 -Lys-Asn-Phe-Phe-Trp 20 -Lys-Thr-Phe-Thr-Ser 25 -Cys. This amino acid sequence shows one substitution (Leu for Met at position 6) and two deletions compared with mammalian somatostatin-28. The minor component was identical to somatostatin-14. The data show that the pathway of post-translational processing of prosomatostatin-I in the Bowfin pancreas is appreciably different from the corresponding pathway in teleost fish and higher vertebrates.
John H Youson - One of the best experts on this subject based on the ideXlab platform.
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Primary structure of stanniocalcin in two basal Actinopterygii
General and Comparative Endocrinology, 2004Co-Authors: Yutaka Amemiya, John H YousonAbstract:Abstract The primary structure of stanniocalcin (STC), the principal product of the corpuscles of Stannius (CS) in ray-finned fishes, was deduced from STC cDNA clones for two species of holostean, the gar, Lepisosteus osseus and the Bowfin, Amia calva. Overlapping partial cDNA clones were amplified by polymerase chain reaction (PCR) from single-strand cDNA of the CS. Excluding the poly(A) tail, the cDNAs of 1863 base pairs [bp] (gar) and 914 bp (Bowfin) contained the 5′ untranslated region followed by the coding region and the 3′ untranslated region. Both the gar and Bowfin STC cDNA encode a prehormone of 252 amino acids (aa) with a signal peptide of 32 aa and a mature protein of 220 aa. The deduced aa sequence of gar STC shows 87% identity with Bowfin STC, 60–72% identity with most vertebrate STCs and 26% identity with mouse STC2. Phylogenetic analysis of the sequences support a view that the gar and Bowfin form a monophyletic holostean clade. RT-PCR revealed in the gar and Bowfin that, just as in mammals and rainbow trout, the expression of STC mRNA is widely spread in many tissues and organs. Since the gar and Bowfin are representatives of the most ancient fishes known to possess CS, the corpuscular-derived STC molecule in fish has had a conserved evolution.
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the endocrine cells in the gastroenteropancreatic system of the Bowfin amia calva l an immunohistochemical ultrastructural and immunocytochemical analysis
Journal of Morphology, 2001Co-Authors: John H Youson, Azza Almahrouki, Diana Naumovski, Michael J ConlonAbstract:The gastroenteropancreatic (GEP) endo- crine system of Bowfin (Amia calva) was described using light and electron microscopy and immunological meth- ods. The islet organ (endocrine pancreas) consists of dif- fusely scattered, mostly small islets and isolated patches of cells among and within the exocrine acini. The islets are composed of abundant, centrally located B cells immuno- reactive to bovine and lamprey insulin antisera and D cells showing a widespread distribution and specificity to somatostatin antibodies. A and F cells are present at the very periphery of the islets and are immunoreactive with antisera against glucagon (and glucagon-like peptide) and several peptides of the pancreatic polypeptide (PP)-family, respectively. The peptides of the two families usually col- locates within the same peripheral islet cells and are the most common immunoreactive peptides present in the extra-islet tissue. Immunocytochemistry and fine struc- tural observations characterised the granule morphology for B and D cells and identified two cell types with gran- ules immunoreactive to glucagon antisera. These two pu- tative A cells had similar granules, which were distinct from either B or D cells, but one of the cells had rod- shaped cytoplasmic inclusions within cisternae of what appeared to be rough endoplasmic reticulum. The inclu- sions were not immunoreactive to either insulin or gluca- gon antisera. Only small numbers of cells in the stomach and intestine immunoreacted to antisera against soma- tostatin, glucagon, and PP-family peptides. The paucity of these cells was reflected in the low concentrations of these peptides in intestinal extracts. The GEP system of Bowfin is not unlike that of other actinopterygian fishes, but there are some marked differences that may reflect the antiq- uity of this system and/or may be a consequence of the ontogeny of this system in this species. J. Morphol. 250: 208 -224, 2001. © 2001 Wiley-Liss, Inc.
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isolation localization and cardiovascular activity of tachykinins from the stomach of the Bowfin amia calva
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 1995Co-Authors: David Waugh, John H Youson, K E Groff, B Platzack, K R Olson, J M ConlonAbstract:The Bowfin is an extant representative of an ancient group of ray-finned fish with evolutionary connections to modern teleosts. A peptide with substance P-like immunoreactivity was isolated from an extract of Bowfin stomach and its primary structure was established as Ser-Lys-Ser-His-Gln-Phe-Tyr-Gly-Leu-Met-NH2. This amino acid sequence resembles mammalian substance P only in the COOH-terminal region of the peptide. A second tachykinin with neurokinin A-like immunoreactivity isolated from the extract comprises 23 amino acid residues and shows limited structural similarity to mammalian neuropeptide-gamma. A randomly distributed population of cells in the gastric glands of the Bowfin were immunostained with an antiserum raised against substance P, but no immunopositive structures were identified in the surface epithelium, lamina propria, or the nerve plexuses of the submucosa. Bolus injections of synthetic Bowfin substance P (0.1-10 nmol/kg) into the bulbus arteriosus of unanesthetized Bowfin resulted in a significant and dose-dependent rise in vascular resistance and arterial blood pressure (P < 0.01) and a fall in cardiac output (P < 0.05) without change in heart rate. After 5-10 min, arterial pressure and vascular resistance returned to preinjection levels, but cardiac output significantly (P < 0.05) increased over baseline values. The response to the peptide was unaffected by pretreatment of the animals with phentolamine. The study has shown that the stomach of the Bowfin synthesizes tachykinins with novel structural features that display cardiovascular activity in this species.
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isolation and biological activity of trp5 bradykinin from the plasma of the phylogenetically ancient fish the Bowfin and the longnosed gar
Peptides, 1995Co-Authors: Michael J Conlon, John H Youson, Luciano E Marra, B Platzack, K R OlsonAbstract:Abstract The holostean fish occupy an important position in vertebrate phylogeny as extant representatives of a ancient group of ray-finned fish with evolutionary connections to present-day teleosts. Incubation of heat-denatured plasma from the Bowfin Amia calva with trypsin generated bradykinin-like immunoreactivity. The primary structure of Bowfin bradykinin was established as Ala-Pro-Pro-Gly-Trp-Ser-Pro-Phe-Arg. This amino acid sequence contains one amino acid substitution (Phe 5 → Trp) compared with mammalian bradykinin. The same peptide was generated in heat-denatured plasma from the longnosed gar Lepisosteus osseus . Treatment of plasma from either the Bowfin or gar with glass beads under conditions previously shown to activate Factor XII in the plasma of mammals and reptiles did not generate bradykinin. Bolus injections of synthetic Bowfin bradykinin (0.1, 0.3, and 1.0 nmol/kg) into the bulbus arteriosus of unanesthetized Bowfin resulted in an immediate fall in arterial blood pressure of 5–10 min duration that was followed by a dose-dependent rise in pressure that was sustained for 30–60 min. There was no change in heart rate following bradykinin administration. The data suggest that the kallikrein-kinin system may predate the appearance of teleosts and may play a role in cardiovascular regulation in holosteans.
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structure and biological activity of glucagon and glucagon like peptide from a primitive bony fish the Bowfin amia calva
Biochemical Journal, 1993Co-Authors: J M Conlon, John H Youson, T P MommsenAbstract:The Bowfin, Amia calva (order Amiiformes) occupies an important position in phylogeny as a surviving representative of a group of primitive ray-finned fishes from which the present-day teleosts may have evolved. Glucagon and glucagon-like peptide (GLP) were isolated from an extract of Bowfin pancreas and their primary structures determined. Bowfin glucagon shows only four amino acid substitutions compared with human glucagon, and Bowfin glucagon was equipotent and equally effective as human glucagon in stimulation of glycogenolysis in dispersed hepatocytes from a teleost fish, the copper rockfish, Sebastes caurinus. In contrast, Bowfin GLP shows 15 amino acid substitutions and three amino acid deletions compared with the corresponding region of human GLP-1-(7-37)-peptide. In particular, the Bowfin peptide contains an N-terminal tyrosine residue rather than the N-terminal histidine residue found in all other glucagon-related peptides so far characterized. Bowfin GLP stimulated glycogenolysis in rockfish hepatocytes, but was 3-fold less effective and 23-fold less potent than human GLP-1-(7-37)-peptide. We speculate that selective mutations in the GLP domain of Bowfin preproglucagon may be an adaptive response to the previously demonstrated low biological potency of Bowfin insulin.
William K Milsom - One of the best experts on this subject based on the ideXlab platform.
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characterisation of putative oxygen chemoreceptors in Bowfin amia calva
The Journal of Experimental Biology, 2014Co-Authors: Cosima S Porteus, Patricia A Wright, William K MilsomAbstract:Serotonin containing neuroepithelial cells (NECs) are putative oxygen sensing cells found in different locations within the gills of fish. In this study we wished to determine the effect of sustained internal (blood) hypoxaemia versus external (aquatic) hypoxia on the size and density of NECs in the first gill arch of Bowfin ( Amia calva ), a facultative air breather. We identified five different populations of serotonergic NECs in this species (Types I–V) based on location, presence of synaptic vesicles (SV) that stain for the antibody SV2, innervation and labelling with the neural crest marker HNK-1. Cell Types I–III were innervated, and these cells, which participate in central O 2 chemoreflexes, were studied further. Although there was no change in the density of any cell type in Bowfin after exposure to sustained hypoxia (6.0 kPa for 7 days) without access to air, all three of these cell types increased in size. In contrast, only Type II and III cells increased in size in Bowfin exposed to sustained hypoxia with access to air. These data support the suggestion that NECs are putative oxygen-sensing cells, that they occur in several locations, and that Type I cells monitor only hypoxaemia, whereas both other cell types monitor hypoxia and hypoxaemia.
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the effect of sustained hypoxia on the cardio respiratory response of Bowfin amia calva implications for changes in the oxygen transport system
Journal of Fish Biology, 2014Co-Authors: Cosima S Porteus, Patricia A Wright, William K MilsomAbstract:This study examined mechanisms underlying cardio-respiratory acclimation to moderate sustained hypoxia (6.0 kPa for 7 days at 22° C) in the Bowfin Amia calva, a facultative air-breathing fish. This level of hypoxia is slightly below the critical oxygen tension (pcrit ) of A. calva denied access to air (mean ± s.e. = 9.3 ± 1.0 kPa). Before exposure to sustained hypoxia, A. calva with access to air increased air-breathing frequency on exposure to acute progressive hypoxia while A. calva without access to air increased gill-breathing frequency. Exposure to sustained hypoxia increased the gill ventilation response to acute progressive hypoxia in A. calva without access to air, regardless of whether they had access to air or not during the sustained hypoxia. Additionally, there was a decrease in Hb-O2 binding affinity in these fish. This suggests that, in A. calva, acclimation to hypoxia elicits changes that increase oxygen delivery to the gas exchange surface for oxygen uptake and reduce haemoglobin affinity to enhance oxygen delivery to the tissues.
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time domains of the hypoxic cardio respiratory response in Bowfin amia calva
Respiratory Physiology & Neurobiology, 2014Co-Authors: Cosima S Porteus, Patricia A Wright, William K MilsomAbstract:Abstract The aim of this study was to determine whether time domains exist in the hypoxic ventilatory (HVR) and cardiac responses (HCR) of Bowfin ( Amia calva ), a facultative air breather, exposed to sustained hypoxia (SH) (26 mm Hg at 8 °C or 45 mm Hg at 22 °C). It was hypothesized that time domains would be evident in the HVR and HCR of Bowfin when denied access to air during SH, as have been reported in mammals. It was also hypothesized that they would not be present in Bowfin with access to air during SH because their oxygen supply should not be limited due to air breathing. Bowfin without access to air during SH exhibited time domains of the HVR and some time domains of the HCR. As hypothesized, Bowfin with access to air did not exhibit time dependent changes in the gill breathing, air breathing, or cardiac responses to SH. The extent to which these reflect homologous processes to those underlying time domains in mammals remains to be determined.
