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B L Tufts – 1st expert on this subject based on the ideXlab platform

  • 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, 1999
    Co-Authors: Matthieu R Gervais, B L Tufts


    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.

  • evidence for membrane bound carbonic anhydrase in the air bladder of Bowfin amia calva a primitive air breathing fish
    The Journal of Experimental Biology, 1998
    Co-Authors: Matthieu R Gervais, B L Tufts


    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.

  • 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, 1994
    Co-Authors: B L Tufts, R C Drever, B Bagatto, B Cameron


    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 – 2nd expert on this subject based on the ideXlab platform

  • Characterization of two molecular forms of vasoactive intestinal polypeptide (VIP) from the pallid sturgeon, Scaphirhynchus albus (Acipenseriformes)
    Fish Physiology and Biochemistry, 2001
    Co-Authors: B.a. Barton, J M Conlon


    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.

  • Bradykinin and its receptors in non-mammalian vertebrates.
    Regulatory peptides, 1999
    Co-Authors: J M Conlon


    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.

  • isolation localization and cardiovascular activity of tachykinins from the stomach of the Bowfin amia calva
    American Journal of Physiology-regulatory Integrative and Comparative Physiology, 1995
    Co-Authors: David Waugh, John H Youson, K E Groff, B Platzack, K R Olson, J M Conlon


    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.

Michael J Conlon – 3rd expert on this subject based on the ideXlab platform

  • the endocrine cells in the gastroenteropancreatic system of the Bowfin amia calva l an immunohistochemical ultrastructural and immunocytochemical analysis
    Journal of Morphology, 2001
    Co-Authors: John H Youson, Azza Almahrouki, Diana Naumovski, Michael J Conlon


    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.

  • purification and structural characterization of vasoactive intestinal polypeptide from the trout and Bowfin
    General and Comparative Endocrinology, 1995
    Co-Authors: Yunxia Wang, Michael J Conlon


    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.

  • isolation and biological activity of trp5 bradykinin from the plasma of the phylogenetically ancient fish the Bowfin and the longnosed gar
    Peptides, 1995
    Co-Authors: Michael J Conlon, John H Youson, Luciano E Marra, B Platzack, K R Olson


    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.