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John H. Youson - One of the best experts on this subject based on the ideXlab platform.

  • response by the corpuscles of stannius to hypotensive stimuli in three divergent ray finned fishes Amia calva anguilla rostrata and catastomus commersoni cardiovascular and morphological changes
    General and Comparative Endocrinology, 2003
    Co-Authors: David G Butler, John H. Youson, Gavin Y. Oudit, D H Zhang, R Villadiego, Moglani Z A Cadinouche
    Abstract:

    Abstract In accordance with their vital role in cardiovascular physiology ( Butler and Zhang, 2001 ) corpuscles of Stannius (CS) from two teleosts and an holostean species showed marked and consistent degranulation and exocytotic responses to hypotensive stimuli. In eels ( Anguilla rostrata LeSueur) acute blood withdrawal (hypovolemic hypotension) was followed by a prompt decrease in cardiac output (CO) and dorsal aortic pressure ( P DA ), a compensatory tachycardic response and an increase in systemic vascular resistance ( R SYS ). Isovolemic hypotension induced by papaverine i.v, led to a similar, but more prolonged, decrease in P DA but the heart rate (HR) continued to accelerate, thereby counterbalancing the severe and persistent decrease in R SYS . Both hypovolemic and isovolemic hypotension were followed by a significant depletion of cytoplasmic granules from eel CS even though plasma concentrations of Ca, Mg, Na + , and K + were normal. In an ancient holostean fish, the bowfin, Amia calva and a generalized teleost fish, Catastomus commersoni , the number of cytoplasmic granules decreased by 39% and 54%, respectively, 120 min after the acute withdrawal of 8 ml kg bw −1 of blood. These findings suggest that a primary role of the CS is to release cytoplasmic granules containing renin or isorenin into the blood circulation, in response to hypotension and/or hypovolemia.

  • 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
    Abstract:

    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.

  • 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, Diana Naumovski, A. A. Al-mahrouki, J. M. Conlon
    Abstract:

    The gastroenteropancreatic (GEP) endocrine system of bowfin (Amia calva) was described using light and electron microscopy and immunological methods. The islet organ (endocrine pancreas) consists of diffusely 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 immunoreactive 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 collocates within the same peripheral islet cells and are the most common immunoreactive peptides present in the extra-islet tissue. Immunocytochemistry and fine structural observations characterised the granule morphology for B and D cells and identified two cell types with granules immunoreactive to glucagon antisera. These two putative 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 inclusions were not immunoreactive to either insulin or glucagon antisera. Only small numbers of cells in the stomach and intestine immunoreacted to antisera against somatostatin, 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 antiquity of this system and/or may be a consequence of the ontogeny of this system in this species.

  • structure and biological activity of glucagon and glucagon like peptide from a primitive bony fish the bowfin Amia calva
    Biochemical Journal, 1993
    Co-Authors: John H. Youson, Thomas P. Mommsen
    Abstract:

    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.

  • prosomatostatin i is processed to somatostatin 26 and somatostatin 14 in the pancreas of the bowfin Amia calva
    Regulatory Peptides, 1993
    Co-Authors: Yunxia Wang, John H. Youson, Michael J Conlon
    Abstract:

    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.

William K Milsom - One of the best experts on this subject based on the ideXlab platform.

  • characterisation of putative oxygen chemoreceptors in bowfin Amia calva
    The Journal of Experimental Biology, 2014
    Co-Authors: Cosima S Porteus, Patricia A. Wright, William K Milsom
    Abstract:

    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.

  • 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, 2014
    Co-Authors: Cosima S Porteus, Patricia A. Wright, William K Milsom
    Abstract:

    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.

  • time domains of the hypoxic cardio respiratory response in bowfin Amia calva
    Respiratory Physiology & Neurobiology, 2014
    Co-Authors: Cosima S Porteus, Patricia A. Wright, William K Milsom
    Abstract:

    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.

  • AN EXAMINATION OF CENTRAL CHEMOSENSITIVITY IN AN AIR-BREATHING FISH (Amia calva)
    The Journal of Experimental Biology, 1991
    Co-Authors: Michael S Hedrick, David R Jones, Mark L. Burleson, William K Milsom
    Abstract:

    Summary The role of central chemosensitivity in the control of ventilation in fishes was investigated directly by perfusing a mock extradural fluid (EDF) through the cranial space in the medullary region of conscious air-breathing fish, Amia calva. Perfusions with Sudan Black dye showed that the mock EDF communicated with the cerebrospinal fluid (CSF) and entered the cerebral ventricles. Altering the Po2, Pco2 and/or pH of the mock EDF had no effect on gill- or air-breathing rates, heart rate or blood pressure during exposure to normoxic water. Aquatic hypoxia, however, stimulated gill ventilation and elevated blood pressure, but did not affect heart rate; altering the gas tensions and/or pH of mock EDF still had no effect on recorded variables. Sodium cyanide (NaCN) added to the mock EDF caused struggling at concentrations above 500 ^gmP 1 , but did not uniformly stimulate ventilation. These results suggest that central chemoreceptors, which mediate cardiovascular or ventilatory reflexes, are absent in Amia.

Moglani Z A Cadinouche - One of the best experts on this subject based on the ideXlab platform.

  • response by the corpuscles of stannius to hypotensive stimuli in three divergent ray finned fishes Amia calva anguilla rostrata and catastomus commersoni cardiovascular and morphological changes
    General and Comparative Endocrinology, 2003
    Co-Authors: David G Butler, John H. Youson, Gavin Y. Oudit, D H Zhang, R Villadiego, Moglani Z A Cadinouche
    Abstract:

    Abstract In accordance with their vital role in cardiovascular physiology ( Butler and Zhang, 2001 ) corpuscles of Stannius (CS) from two teleosts and an holostean species showed marked and consistent degranulation and exocytotic responses to hypotensive stimuli. In eels ( Anguilla rostrata LeSueur) acute blood withdrawal (hypovolemic hypotension) was followed by a prompt decrease in cardiac output (CO) and dorsal aortic pressure ( P DA ), a compensatory tachycardic response and an increase in systemic vascular resistance ( R SYS ). Isovolemic hypotension induced by papaverine i.v, led to a similar, but more prolonged, decrease in P DA but the heart rate (HR) continued to accelerate, thereby counterbalancing the severe and persistent decrease in R SYS . Both hypovolemic and isovolemic hypotension were followed by a significant depletion of cytoplasmic granules from eel CS even though plasma concentrations of Ca, Mg, Na + , and K + were normal. In an ancient holostean fish, the bowfin, Amia calva and a generalized teleost fish, Catastomus commersoni , the number of cytoplasmic granules decreased by 39% and 54%, respectively, 120 min after the acute withdrawal of 8 ml kg bw −1 of blood. These findings suggest that a primary role of the CS is to release cytoplasmic granules containing renin or isorenin into the blood circulation, in response to hypotension and/or hypovolemia.

  • angiotensin i and ii and norepinephrine mediated pressor responses in an ancient holostean fish the bowfin Amia calva
    General and Comparative Endocrinology, 1995
    Co-Authors: David G Butler, Gavin Y. Oudit, Moglani Z A Cadinouche
    Abstract:

    Abstract Dorsal aortic pressure ( P SYS , systolic; P DIAS , diastolic; and P DA ,mean) and heart rate (HR) were measured in resting freshwater bowfins (n = 6), Amia calva L., before and after iv injections of 50, 100, 200, 500, and 1000 ng · kg -1 of synthetic [Asn 1 , Val 5 ]-angiotensin II (ANG II). Baseline P SYS , P DIAS , and P DA were 27.7 ± 2.8, 22.4 ± 1.8, and 24.5 ± 2 mm Hg, respectively. Bowfins were only moderately responsive to ANG II in a stepwise manner and the increase in blood pressure became significant only at the two highest doses; lower doses tended only to increase arterial pressure. Pressor responses due to 200 and 500 ng · kg -1 decayed over a greater time period compared with other doses. α-Adrenergic blockade abolished 70% of the ANG II-mediated pressor responses. Eel, salmon, and goosefish angiotensin I (ANG I; 500 ng · kg -1 ) elicited similar vasopressor responses (magnitude and time course) which eliminated by prior angiotensin converting enzyme inhibition (captopril; 2-10 mg · kg -1 ). Bullfrog ANG I evoked a pressor effect only at a higher dose (5000 ng · kg -1 ). Consecutive norepinephrine (NE) injections (100, 200, 500, and 1000 ng · kg -1 ) increased P SYS , P DIAS , and P DA in a dose-dependent manner which was dependent on α-adrenoceptors since phentolamine (1-3 mg · kg -1 ) abolished 80% of the pressor actions of NE. P SYS was elevated by 100 ng · kg -1 of NE but P DIAS and P DA were significantly increased only at 200 ng · kg -1 . ANG II and NE had no measurable chronotropic effect and resting HR (27.2 ± 0.8 beats. min -1 ) was unchanged. Captopril and phentolamine treatments produced rapid hypotension and bradycardia (25-30%) which lasted from 15 to 30 and 20 to 40 min, respectively. The rising and decreasing phrases of the NE-mediated pressor responses had shorter durations than ANG II effects. Tachyphylaxis occurred with the high doses of ANG II and NE. The data show that in the ancient bowfin, which evidently lacks renal juxtaglomerular cells, the cardiovascular system can be regulated by the renin-angiotensin system and NE.

  • angiotensin i and ii and norepinephrine mediated pressor responses in an ancient holostean fish the bowfin Amia calva
    General and Comparative Endocrinology, 1995
    Co-Authors: David G Butler, Gavin Y. Oudit, Moglani Z A Cadinouche
    Abstract:

    Dorsal aortic blood pressure (PSYS, systolic; PDIAS, diastolic; and PDA, mean) and heart rate (HR) were measured in resting freshwater bowfins (n = 6), Amia calva L., before and after i.v. injections of 50, 100, 200, 500, and 1000 ng.kg-1 of synthetic [Asn1, Val5]-angiotensin II (ANG II). Baseline PSYS, PDIAS, and PDA were 27.7 +/- 2.8, 22.4 +/- 1.8, and 24.5 +/- 2 mm Hg, respectively. Bowfins were only moderately responsive to ANG II in a stepwise manner and the increase in blood pressure became significant only at the two highest doses; lower doses tended only to increase arterial pressure. Pressor responses due to 200 and 500 ng.kg-1 decayed over a greater time period compared with other doses. alpha-Adrenergic blockade abolished 70% of the ANG II-mediated pressor responses. Eel, salmon, and goosefish angiotensin I (ANG I; 500 ng.kg-1) elicited similar vasopressor responses (magnitude and time course) which were eliminated by prior angiotensin converting enzyme inhibition (captopril; 2-10 mg.kg-1). Bullfrog ANG I evoked a pressor effect, only at a higher dose (5000 ng.kg-1). Consecutive norepinephrine (NE) injections (100, 200, 500, and 1000 ng.kg-1) increased PSYS, PDIAS, and PDA in a dose-dependent manner which was dependent on alpha-adrenoceptors since phentolamine (1-3 mg.kg-1) abolished 80% of the pressor action of NE. PSYS was elevated by 100 ng.kg-1 of NE but PDIAS and PDA were significantly increased only at 200 ng.kg-1 ANG II and NE had no measurable chronotropic effect and resting HR (27.2 +/- 0.8 beats.min-1) was unchanged. Captopril and phentolamine treatments produced rapid hypotension and bradycardia (25-30%) which lasted from 15 to 30 and 20 to 40 min, respectively. The rising and decreasing phases of the NE-mediated pressor responses had shorter durations than ANG II effects. Tachyphylaxis occurred with the high doses of ANG II and NE. The data show that in the ancient bowfin, which evidently lacks renal juxtaglomerular cells, the cardiovascular system can be regulated by the renin-angiotensin system and NE.

David G Butler - One of the best experts on this subject based on the ideXlab platform.

  • response by the corpuscles of stannius to hypotensive stimuli in three divergent ray finned fishes Amia calva anguilla rostrata and catastomus commersoni cardiovascular and morphological changes
    General and Comparative Endocrinology, 2003
    Co-Authors: David G Butler, John H. Youson, Gavin Y. Oudit, D H Zhang, R Villadiego, Moglani Z A Cadinouche
    Abstract:

    Abstract In accordance with their vital role in cardiovascular physiology ( Butler and Zhang, 2001 ) corpuscles of Stannius (CS) from two teleosts and an holostean species showed marked and consistent degranulation and exocytotic responses to hypotensive stimuli. In eels ( Anguilla rostrata LeSueur) acute blood withdrawal (hypovolemic hypotension) was followed by a prompt decrease in cardiac output (CO) and dorsal aortic pressure ( P DA ), a compensatory tachycardic response and an increase in systemic vascular resistance ( R SYS ). Isovolemic hypotension induced by papaverine i.v, led to a similar, but more prolonged, decrease in P DA but the heart rate (HR) continued to accelerate, thereby counterbalancing the severe and persistent decrease in R SYS . Both hypovolemic and isovolemic hypotension were followed by a significant depletion of cytoplasmic granules from eel CS even though plasma concentrations of Ca, Mg, Na + , and K + were normal. In an ancient holostean fish, the bowfin, Amia calva and a generalized teleost fish, Catastomus commersoni , the number of cytoplasmic granules decreased by 39% and 54%, respectively, 120 min after the acute withdrawal of 8 ml kg bw −1 of blood. These findings suggest that a primary role of the CS is to release cytoplasmic granules containing renin or isorenin into the blood circulation, in response to hypotension and/or hypovolemia.

  • angiotensin i and ii and norepinephrine mediated pressor responses in an ancient holostean fish the bowfin Amia calva
    General and Comparative Endocrinology, 1995
    Co-Authors: David G Butler, Gavin Y. Oudit, Moglani Z A Cadinouche
    Abstract:

    Abstract Dorsal aortic pressure ( P SYS , systolic; P DIAS , diastolic; and P DA ,mean) and heart rate (HR) were measured in resting freshwater bowfins (n = 6), Amia calva L., before and after iv injections of 50, 100, 200, 500, and 1000 ng · kg -1 of synthetic [Asn 1 , Val 5 ]-angiotensin II (ANG II). Baseline P SYS , P DIAS , and P DA were 27.7 ± 2.8, 22.4 ± 1.8, and 24.5 ± 2 mm Hg, respectively. Bowfins were only moderately responsive to ANG II in a stepwise manner and the increase in blood pressure became significant only at the two highest doses; lower doses tended only to increase arterial pressure. Pressor responses due to 200 and 500 ng · kg -1 decayed over a greater time period compared with other doses. α-Adrenergic blockade abolished 70% of the ANG II-mediated pressor responses. Eel, salmon, and goosefish angiotensin I (ANG I; 500 ng · kg -1 ) elicited similar vasopressor responses (magnitude and time course) which eliminated by prior angiotensin converting enzyme inhibition (captopril; 2-10 mg · kg -1 ). Bullfrog ANG I evoked a pressor effect only at a higher dose (5000 ng · kg -1 ). Consecutive norepinephrine (NE) injections (100, 200, 500, and 1000 ng · kg -1 ) increased P SYS , P DIAS , and P DA in a dose-dependent manner which was dependent on α-adrenoceptors since phentolamine (1-3 mg · kg -1 ) abolished 80% of the pressor actions of NE. P SYS was elevated by 100 ng · kg -1 of NE but P DIAS and P DA were significantly increased only at 200 ng · kg -1 . ANG II and NE had no measurable chronotropic effect and resting HR (27.2 ± 0.8 beats. min -1 ) was unchanged. Captopril and phentolamine treatments produced rapid hypotension and bradycardia (25-30%) which lasted from 15 to 30 and 20 to 40 min, respectively. The rising and decreasing phrases of the NE-mediated pressor responses had shorter durations than ANG II effects. Tachyphylaxis occurred with the high doses of ANG II and NE. The data show that in the ancient bowfin, which evidently lacks renal juxtaglomerular cells, the cardiovascular system can be regulated by the renin-angiotensin system and NE.

  • angiotensin i and ii and norepinephrine mediated pressor responses in an ancient holostean fish the bowfin Amia calva
    General and Comparative Endocrinology, 1995
    Co-Authors: David G Butler, Gavin Y. Oudit, Moglani Z A Cadinouche
    Abstract:

    Dorsal aortic blood pressure (PSYS, systolic; PDIAS, diastolic; and PDA, mean) and heart rate (HR) were measured in resting freshwater bowfins (n = 6), Amia calva L., before and after i.v. injections of 50, 100, 200, 500, and 1000 ng.kg-1 of synthetic [Asn1, Val5]-angiotensin II (ANG II). Baseline PSYS, PDIAS, and PDA were 27.7 +/- 2.8, 22.4 +/- 1.8, and 24.5 +/- 2 mm Hg, respectively. Bowfins were only moderately responsive to ANG II in a stepwise manner and the increase in blood pressure became significant only at the two highest doses; lower doses tended only to increase arterial pressure. Pressor responses due to 200 and 500 ng.kg-1 decayed over a greater time period compared with other doses. alpha-Adrenergic blockade abolished 70% of the ANG II-mediated pressor responses. Eel, salmon, and goosefish angiotensin I (ANG I; 500 ng.kg-1) elicited similar vasopressor responses (magnitude and time course) which were eliminated by prior angiotensin converting enzyme inhibition (captopril; 2-10 mg.kg-1). Bullfrog ANG I evoked a pressor effect, only at a higher dose (5000 ng.kg-1). Consecutive norepinephrine (NE) injections (100, 200, 500, and 1000 ng.kg-1) increased PSYS, PDIAS, and PDA in a dose-dependent manner which was dependent on alpha-adrenoceptors since phentolamine (1-3 mg.kg-1) abolished 80% of the pressor action of NE. PSYS was elevated by 100 ng.kg-1 of NE but PDIAS and PDA were significantly increased only at 200 ng.kg-1 ANG II and NE had no measurable chronotropic effect and resting HR (27.2 +/- 0.8 beats.min-1) was unchanged. Captopril and phentolamine treatments produced rapid hypotension and bradycardia (25-30%) which lasted from 15 to 30 and 20 to 40 min, respectively. The rising and decreasing phases of the NE-mediated pressor responses had shorter durations than ANG II effects. Tachyphylaxis occurred with the high doses of ANG II and NE. The data show that in the ancient bowfin, which evidently lacks renal juxtaglomerular cells, the cardiovascular system can be regulated by the renin-angiotensin system and NE.

  • stanniocalcin like immunoreactivity in the corpuscles of stannius of the bowfin Amia calva l
    Cell and Tissue Research, 1992
    Co-Authors: Luciano E Marra, David G Butler, Henry G Friesen, John H. Youson, Graham F Wagner
    Abstract:

    We used an antiserum against salmon stanniocalcin in an immunohistochemical, immunocytochemical, and Western blot analysis of bowfin (Amia calva) corpuscles of stannius. The bowfin is one of two extant holostean species with ancient ancestral links to modern-day bony fishes. The corpuscles of Stannius (white corpuscles) of the bowfin were scattered throughout much of the kidney among the adrenocortical homolog (yellow corpuscles) but could be distinguished from the adrenocortical homolog by their positive staining with both the periodic acid-Schiff reaction and a salmon stanniocalcin antiserum. Immunoreactivity was confined to cytoplamic granules and was absent when the antiserum was blocked with salmon stanniocalcin or with a crude extract of bowfin corpuscles of Stannius. When bowfin corpuscle-of-Stannius extracts were subjected to sodium dodecyl sulphate electrophoresis and Western blot analysis, two closely spaced bands were evident (43–45 kDa). Staining of both bands was abolished by pre-absorption of the antiserum with salmon stanniocalcin. In comparison to salmon stanniocalcin, the reputed bowfin hormone migrated faster in gels, suggesting a smaller apparent size. The purification of bowfin stanniocalcin should yield important new information regarding the evolution of this unique calcium-regulating hormone.

J S Ballantyne - One of the best experts on this subject based on the ideXlab platform.

  • short term effects of triiodothyronine on the bowfin Amia calva holostei and the lake char salvelinus namaycush teleostei
    Journal of Experimental Zoology, 1992
    Co-Authors: J S Ballantyne, Thomas D Singer, T. M. John, Oommen V. Oommen
    Abstract:

    To assess the role of triiodothyronine (T3) in mediating short-term changes in metabolism, such as those occurring in circadian patterns, we examined the effects of intraperitoneal injection of T3 on the oxidation of substrates by isolated mitochondria from liver of the bowfin, Amia calva, and red muscle and liver of the lake char, Salvelinus namaycush. Selected enzymes were measured in red muscle and liver of the lake char. Three hours after intraperitoneal injection of T3, oxidation of some substrates by mitochondria isolated from the liver of the bowfin was reduced. Similar treatment had no effect on substrate oxidation in liver mitochondria isolated from lake char. Oxidation of substrates by lake char red muscle mitochondria was stimulated by T3 injection. Citrate synthase levels were increased in red muscle suggesting that changes in enzyme activity may be in part responsible for the short-term mitochondrial responses to T3 injection.

  • metabolic organization of a primitive fish the bowfin Amia calva
    Canadian Journal of Fisheries and Aquatic Sciences, 1991
    Co-Authors: Thomas D Singer, J S Ballantyne
    Abstract:

    Key enzymes in several metabolic pathways in five tissues were measured in primitive osteichthyan, the bowfin (Amia calva), the only living representative of the group of extant fishes most closely allied to the teleosts. Aspects of the metabolism of Amia differ from those of most teleosts studied. These differences include detectable levels of β-hydroxybutyrate dehydrogenase in all tissues, possibly a primitive metabolic feature of vertebrates, subsequently lost in most more advanced teleosts. Based on 3-hydroxyacyl CoA dehydrogenase and carnitine palmitoyltransferase activities, lipid metabolism in extrahepatic tissues of bowfin more closely resembles that of an elasmobranch rather than that of a teleost. The overall level of metabolism is lower than most teleosts as indicated by enzyme activities in red muscle and heart. Bowfin plasma nonesterified fatty acid concentrations are lower than most teleosts, but higher than those detected in any elasmobranch. These data suggest that the metabolic organizati...

  • Glutamine metabolism in a holostean (Amia calva) and teleost fish (Salvelinus namaycush
    1991
    Co-Authors: M. E. Chamberlin, H. C. Glemet, J S Ballantyne
    Abstract:

    metabolism was examined in mitochondria from the lateral red muscle of a teleost (lake char, Salvelinus namaycush) and a nonteleost fish (bowfin, Amia calva). Isolated mitochondria oxidize a wide variety of substrates and have high respiratory control ratios. In both species, glutamine is oxidized more rapidly than any other amino acid. The rate of glutamine oxidation by bowfin mitochondria exceeds that of lake char mitochondria, and the bowfin displays correspondingly higher levels of mitochondrial phosphate-dependent glutaminase. It is suggested that amino acids in general, and glutamine in partic-ular, are important oxidative substrates for nonteleost red muscle. The teleost red muscle, however, may rely on both glutamine and fatty acids as oxidative substrates. It appears that glutamate derived from glutamine is oxidized primarily via glutamate dehydrogenase, whereas exogenous glutamate i