Protopterus

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Yuen K Ip - One of the best experts on this subject based on the ideXlab platform.

  • l gulono γ lactone oxidase expression and vitamin c synthesis in the brain and kidney of the african lungfish Protopterus annectens
    The FASEB Journal, 2014
    Co-Authors: Biyun Ching, Wai P Wong, Shit F Chew, You Rong Chng, Xiu Ling Chen, Yuen K Ip
    Abstract:

    This study aimed to test the hypothesis that the brain of Protopterus annectens expressed l-gulono-γ-lactone oxidase (gulo/Gulo), the enzyme catalyzing the last step of ascorbate biosynthesis, and could maintain high concentrations of ascorbate during estivation. We cloned and sequenced gulo from the kidney of P. annectens and performed quantitative PCR to determine its mRNA expression in kidney and brain. Gulo activity was assayed and its protein abundance was determined by Western blot using custom-made anti-Gulo antibody. Effects of estivation on concentrations of ascorbate and dehydroascorbate in the kidney and brain were also determined. Both brain and kidney, but not liver, of P. annectens expressed gulo/Gulo. Desiccation induced P. annectens to estivate, and 6 mo of estivation led to drastic decreases in gulo/Gulo expression and ascorbate concentration in the kidney. However, high concentrations of ascorbate and ascorbate + dehydroascorbate were maintained in the brain during estivation, probably r...

  • nitric oxide synthase dependent on off switch and apoptosis in freshwater and aestivating lungfish Protopterus annectens skeletal muscle versus cardiac muscle
    Nitric Oxide, 2013
    Co-Authors: Daniela Amelio, Yuen K Ip, Wai P Wong, Filippo Garofalo, S F Chew, M C Cerra, Bruno Tota
    Abstract:

    Abstract African lungfishes (Protopterus spp.) are obligate air breathers which enter in a prolonged torpor (aestivation) in association with metabolic depression, and biochemical and morpho-functional readjustments during the dry season. During aestivation, the lungfish heart continues to pump, while the skeletal muscle stops to function but can immediately contract during arousal. Currently, nothing is known regarding the orchestration of the multilevel rearrangements occurring in myotomal and myocardial muscles during aestivation and arousal. Because of its universal role in cardio-circulatory and muscle homeostasis, nitric oxide (NO) could be involved in coordinating these stress-induced adaptations. Western blotting and immunofluorescence microscopy on cardiac and skeletal muscles of Protopterus annectens (freshwater, 6 months of aestivation and 6 days after arousal) showed that expression, localization and activity of the endothelial-like nitric oxide synthase (eNOS) isoform and its partners Akt and Hsp-90 are tissue-specifically modulated. During aestivation, phospho-eNOS/eNOS and phospho-Akt/Akt ratios increased in the heart but decreased in the skeletal muscle. By contrast, Hsp-90 increased in both muscle types during aestivation. TUNEL assay revealed that increased apoptosis occurred in the skeletal muscle of aestivating lungfish, but the myocardial apoptotic rate of the aestivating lungfish remained unchanged as compared with the freshwater control. Consistent with the preserved cardiac activity during aestivation, the expression of apoptosis repressor (ARC) also remained unchanged in the heart of aestivating and aroused fish as compared with the freshwater control. Contrarily, ARC expression was strongly reduced in the skeletal muscle of aestivating lungfish. On the whole, our data indicate that changes in the eNOS/NO system and cell turnover are implicated in the morpho-functional readjustments occurring in lungfish cardiac and skeletal muscle during the switch from freshwater to aestivation, and between the maintenance and arousal phases of aestivation.

  • ionoregulatory physiology of two species of african lungfishes Protopterus dolloi and Protopterus annectens
    Journal of Fish Biology, 2009
    Co-Authors: Monika Patel, Fathima I Iftikar, Erin M Leonard, Yuen K Ip, Chris M Wood
    Abstract:

    : Basic ionoregulatory physiology was characterized in two species of African lungfish, slender African lungfish Protopterus dolloi and West African lungfish Protopterus annectens, largely under aquatic conditions. There were no substantive differences between the two species. Plasma [Na], [Cl] and [Ca] were only 60-80% of those typical of freshwater teleosts, and plasma Ca activity was particularly low. Unidirectional Na and Cl influx rates from water were also very low, only c. 10% of teleost values, whereas unidirectional Ca influx rates were comparable with teleost rates. Protopterus spp. were fed a 3% ration of bloodworms every 48 h. The bloodworm diet provided similar amounts of Na and Ca as uptake from water, but almost no Cl. Efflux rates of Na and Cl through the urine were greater than via the faeces, whereas the opposite was true for Ca. Net ion flux measurements and ionic balance sheet calculations indicated that (1) both water and dietary uptake routes are important for Na and Ca acquisition; (2) the waterborne route predominates for Cl uptake; (3) unidirectional ion effluxes across the body surface (gills and skin) rather than urine and faeces are the major routes of loss for Na, Cl and Ca. Tissues (muscle, liver, lung, kidney, intestine and heart) and plasma ions were also examined in P. dolloi'terrestrialized' in air for up to 5 months, during which plasma ion concentrations (Na, Cl, Ca and Mg) did not change and there were only a few alterations in tissue ions, that is, increased [Na] in intestine, decreased [Cl] in kidney and increased [Ca] in liver and kidney.

  • water balance and renal function in two species of african lungfish Protopterus dolloi and Protopterus annectens
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2009
    Co-Authors: Monika Patel, Fathima I Iftikar, Yuen K Ip, Richard W Smith, Chris M Wood
    Abstract:

    Abstract The basic physiology of water balance and kidney function was characterized in two species of African lungfish, Protopterus dolloi and Protopterus annectens. Diffusive water efflux rate constants were low (0.13 h− 1–0.38 h− 1 in various series) relative to values in freshwater teleost fish. Efflux rate constants increased approximately 3-fold after feeding in both species, and were greatly decreased after 8 months terrestrialization (P. dolloi only tested). Urine flow rates (UFR, 3.9–5.2 mL kg− 1 h− 1) and glomerular filtration rates (GFR, 6.6–9.3 mL kg− 1 h− 1) were quite high relative to values in most freshwater teleosts. However urinary ion excretion rates were low, with net re-absorption of > 99% Na+, > 98% Cl−, and > 78% Ca2+ from the primary filtrate, comparable to teleosts. Net water re-absorption was significantly greater in P. dolloi (56%) than in P. annectens (23%). We conclude that renal function in lungfish is similar to that in other primitive freshwater fish, but there is an interesting dichotomy between diffusive and osmotic permeabilities. Aquatic lungfish have low diffusive water permeability, an important pre-adaptation to life on land, and in accord with greatly reduced gill areas and low metabolic rates. However osmotic permeability is high, 4–12 times greater than diffusive permeability. A role for aquaporins in this dichotomy is speculated.

  • control of breathing in african lungfish Protopterus dolloi a comparison of aquatic and cocooned terrestrialized animals
    Respiratory Physiology & Neurobiology, 2008
    Co-Authors: S F Perry, Yuen K Ip, Ai M Loong, S F Chew, R M Euverman, T Wang
    Abstract:

    Abstract African lungfish, Protopterus dolloi exhibited constant rates of O 2 consumption before (0.95 ± 0.07 mmol kg −1  h −1 ), during (1.21 ± 0.32 mmol kg −1  h −1 ) and after (1.14 ± 0.14 mmol kg −1  h −1 ) extended periods (1–2 months) of terrestrialization while cocooned. Although a breathing event in terrestrialized fish consisted of multiple bouts of inspiration and expiration in rapid succession, the mean frequency of pulmonary breathing events was unaltered in the terrestrialized fish (16.7 ± 1.4 h −1 versus 20.1 ± 4.9 h −1 in the aquatic and terrestrialized fish, respectively). Hypoxia (∼20 mmHg) increased the frequency of breathing events by 16 and 23 h −1 in the aquatic and terrestrialized fish, respectively. Hyperoxia (∼550 mmHg) decreased breathing event frequency by 10 and 15 h −1 in the aquatic and terrestrialized animals. Aquatic hypercapnia (∼37.5 mmHg) increased pulmonary breathing frequency (from 15.3 ± 2.3 to 28.7 ± 5.4 h −1 ) in free swimming lungfish, whereas aerial hypercapnia was without effect in aquatic or terrestrialized fish.

Lauren J Chapman - One of the best experts on this subject based on the ideXlab platform.

  • The relationship between temperature and standard rate of metabolism in African lungfish, Protopterus aethiopicus , from Uganda
    African Journal of Aquatic Science, 2020
    Co-Authors: Ashley W Seifert, Lauren J Chapman
    Abstract:

    The relationship between temperature and metabolism among ancient (non-teleost) fishes, while largely unknown, is essential to an understanding of the effects of temperature on fish energetics. This study quantifies the effect of temperature on the standard rate of metabolism in the African lungfish, Protopterus aethiopicus . We present a Q 10 value of 3.3 for individuals ranging in body mass from 42–222g across an ecologically-relevant 10°C temperature range. Protopterus aethiopicus showed a positive bilogarithmic (log-log) relationship between the rate of oxygen consumption and body mass (range = 44–222g) at three water temperatures (20, 25, 30°C). However, adjusted mean rates of oxygen consumption differed among all three temperatures. A Q 10 value derived as the means of Q 10 values calculated for each individual lungfish averaged 3.3 ± 0.4 (SE) for 20–30°C. A comparison of literature-derived Q 10 values for both tropical and temperate fishes suggests a higher Q 10 in tropical species (n = 3) than in temperate species (n = 10) across an ecologically-relevant thermal range. Keywords: air-breathing fish, ecophysiology, metabolic rate, Q 10 , respirometry African Journal of Aquatic Science 2007, 32(3): 299–303

  • respiratory allocation and standard rate of metabolism in the african lungfish Protopterus aethiopicus
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2006
    Co-Authors: Ashley W Seifert, Lauren J Chapman
    Abstract:

    This paper quantifies the relationship between respiratory allocation (air vs. water) and the standard rate of metabolism (SMR) in the primitive air-breathing lungfish, Protopterus aethiopicus. Simultaneous measurements of oxygen consumed from both air and water were made to determine the SMR at ecologically relevant aquatic oxygen levels for juveniles 2 to 221 g. Total metabolic rate was positively correlated with body mass with a scaling exponent of 0.78. Aerial oxygen consumption averaged 98% (range=94% to 100%) of total respiratory allocation under low aquatic oxygen levels. Measurements of oxygen consumption made across a gradient of dissolved oxygen from normoxia to anoxia showed that P. aethiopicus maintains its SMR despite a change in respiratory allocation between water and air.

  • decline of the african lungfish Protopterus aethiopicus in lake victoria east africa
    African Journal of Ecology, 2002
    Co-Authors: K P Goudswaard, Frans Witte, Lauren J Chapman
    Abstract:

    Catch and effort data for the period 1973–1990 demonstrate a dramatic decline of lungfish in the Tanzanian waters of Lake Victoria. Bottom trawl catches in the Mwanza Gulf showed a decline in catch rates from 67.5 kg h−1 in 1973 to 5.5 kg h−1 in 1986. Trawling of commercial vessels in the Speke Gulf revealed a decline in lungfish catches from 1.3 kg h−1 in 1986 to 0.07 kg h−1 in 1990. The development of anoxia in the deeper waters of Lake Victoria, the algal blooms, and the decline of water transparency, all associated with eutrophication, are not likely to have contributed to the decreased catch rate. However, the lungfish decline may reflect the interaction of overexploitation by the fishery and a low level of Nile perch predation that restricts lungfish to wetland refugia. We suggest that this may have been reinforced over the past few decades by large-scale conversion of wetlands to agricultural land and harvesting of nest-guarding male lungfish leading to decreased recruitment of young. Resume Les donnees sur les prises et les efforts de capture pour la periode qui va de 1973 a 1990 montrent un declin spectaculaire des protopteres dans les eaux tanzaniennes du lac Victoria. Les prises faites au chalut dans le golfe de Mwanza montraient une reduction des taux de prises de 67,5 kg/h en 1973 a 5,5 kg/h en 1986. Les bateaux commerciaux qui pechent au chalut dans le golfe de Speke ont rapporte un declin de leurs prises de protopteres de 1,3 kg/h en 1986 a 0,07 kg/h en 1990. L'extension de l'anoxie dans les eaux profondes du lac Victoria, la profusion d'algues et la diminution de la transparence de l'eau, qui sont toutes associees a l'eutrophisation, sont peu susceptibles d'avoir contribue au declin du taux de prises. Le declin des protopteres peut cependant refleter l'interaction entre la surexploitation par la peche et un faible taux de predation de la perche du Nil qui repousse les protopteres vers les refuges marecageux. On suggere que ce phenomene a peut-etre ete renforce ces dernieres decennies par la transformation a grande echelle de terrains marecageux en terres agricoles et par le fait que les prelevements de protopteres mâles qui gardent les nids ont entraine une reduction du nombre de jeunes qui grandissent.

M L Purkerson - One of the best experts on this subject based on the ideXlab platform.

Shit F Chew - One of the best experts on this subject based on the ideXlab platform.

  • l gulono γ lactone oxidase expression and vitamin c synthesis in the brain and kidney of the african lungfish Protopterus annectens
    The FASEB Journal, 2014
    Co-Authors: Biyun Ching, Wai P Wong, Shit F Chew, You Rong Chng, Xiu Ling Chen, Yuen K Ip
    Abstract:

    This study aimed to test the hypothesis that the brain of Protopterus annectens expressed l-gulono-γ-lactone oxidase (gulo/Gulo), the enzyme catalyzing the last step of ascorbate biosynthesis, and could maintain high concentrations of ascorbate during estivation. We cloned and sequenced gulo from the kidney of P. annectens and performed quantitative PCR to determine its mRNA expression in kidney and brain. Gulo activity was assayed and its protein abundance was determined by Western blot using custom-made anti-Gulo antibody. Effects of estivation on concentrations of ascorbate and dehydroascorbate in the kidney and brain were also determined. Both brain and kidney, but not liver, of P. annectens expressed gulo/Gulo. Desiccation induced P. annectens to estivate, and 6 mo of estivation led to drastic decreases in gulo/Gulo expression and ascorbate concentration in the kidney. However, high concentrations of ascorbate and ascorbate + dehydroascorbate were maintained in the brain during estivation, probably r...

  • an investigation of the role of carbonic anhydrase in aquatic and aerial gas transfer in the african lungfish Protopterus dolloi
    The Journal of Experimental Biology, 2005
    Co-Authors: S F Perry, Kathleen M Gilmour, E R Swenson, Branka Vulesevic, Shit F Chew, Yuen K Ip
    Abstract:

    Experiments were performed on bimodally breathing African lungfish Protopterus dolloi to examine the effects of inhibition of extracellular vs total (extracellular and intracellular) carbonic anhydrase (CA) activity on pulmonary and branchial/cutaneous gas transfer. In contrast to previous studies on Protopterus , which showed that the vast majority of CO2 is excreted into the water through the gill and/or skin whereas O2 uptake largely occurs via the lung, P. dolloi appeared to use the lung for the bulk of both O2 uptake (91.0±2.9%) and CO2 excretion (76.0±6.6%). In support of the lung as the more important site of CO2 transfer, aerial hypercapnia ( P CO2=40 mmHg) caused a significant rise in partial pressure of arterial blood CO2 ( P aCO2) whereas a similar degree of aquatic hypercapnia was without effect on P aCO2. Intravascular injection of low levels (1.2 mg kg-1) of the slowly permanent CA inhibitor, benzolamide, was without effect on red blood cell CA activity after 30 min, thus confirming its suitability as a short-term selective inhibitor of extracellular CA. Benzolamide treatment did not affect CO2 excretion, blood acid–base status or any other measured variable within the 30 min measurement period. Injection of the permeant CA inhibitor acetazolamide (30 mg kg-1) resulted in the complete inhibition of red cell CA activity within 10 min. However, CO2 excretion (measured for 2 h after injection) and arterial blood acid–base status (assessed for 24 h after injection) were unaffected by acetazolamide treatment. Intra-arterial injection of bovine CA (2 mg kg-1) caused a significant increase in overall CO2 excretion (from 0.41±0.03 to 0.58±0.03 mmol kg-1 h-1) and an increase in air breathing frequency (from 19.0±1.3 to 24.7±1.8 breaths min-1) that was accompanied by a slight, but significant, reduction in P aCO2 (from 21.6±1.6 to 19.6±1.8 mmHg). The findings of this study are significant because they (i) demonstrate that, unlike in other species of African lungfish that have been examined, the gill/skin is not the major route of CO2 excretion in P. dolloi , and (ii) suggest that CO2 excretion in Protopterus may be less reliant on carbonic anhydrase than in most other fish species.

  • ornithine urea cycle and urea synthesis in african lungfishes Protopterus aethiopicus and Protopterus annectens exposed to terrestrial conditions for six days
    Journal of Experimental Zoology Part A: Comparative Experimental Biology, 2005
    Co-Authors: Ai M Loong, Shit F Chew, Kum C Hiong, Wai Peng Wong, Yuen K Ip
    Abstract:

    The objectives of this study were (1) to determine the type of carbamoyl phosphate synthetase (CPS) present, and the compartmentalization of arginase, in the livers of the African lungfishes, Protopterus aethiopicus and Protopterus annectens, and (2) to elucidate if these two lungfishes were capable of increasing the rates of urea synthesis and capacities of the ornithine-urea cycle (OUC) during 6 days of aerial exposure without undergoing aestivation. Like another African lungfish, Protopterus dolloi, reported elsewhere, the CPS activities from the livers of P. aethiopicus and P. annectens had properties similar to that of the marine ray (Taeniura lymma), but dissimilar to that of the mouse (Mus musculus). Hence, they possessed CPS III, and not CPS I as reported previously. CPS III was present exclusively in the liver mitochondria of both lungfishes, but the majority of the arginase activities were present in the cytosolic fractions of their livers. Glutamine synthetase (GS) activity was also detected in the hepatic mitochondria of both specimens. Therefore, our results suggest that the evolution of CPS III to CPS I might not have occurred before the evolution of extant lungfishes as suggested previously, prompting an examination of the current view on the evolution of CPS and OUC in vertebrates. Aerial exposure led to significant decreases in rates of ammonia excretion in P. aethiopicus and P. annectens, but there were no accumulations of ammonia in their tissues. However, urea contents in their tissues increased significantly after 6 days of aerial exposure. The estimated rates of urea synthesis in P. aethiopicus and P. annectens increased 1.2- and 1.47-fold, respectively, which were smaller than that in P. dolloi (8.6-fold) reported elsewhere. In addition, unlike P. dolloi, 6 days of aerial exposure had no significant effects on the hepatic CPS III activities of P. aethiopicus and P. annectens. In contrast, aerial exposure induced relatively greater degrees of reductions in ammonia production in P. aethiopicus (34%) and P. annectens (37%) than P. dolloi (28%) as previously reported. Thus, our results suggest that various species of African lungfishes respond to aerial exposure differently with respect to nitrogen metabolism and excretion, and it can be concluded that P. aethiopicus and P. annectens depended more on reductions in ammonia production than on increases in urea synthesis to ameliorate ammonia toxicity when exposed to terrestrial conditions. J. Exp. Zool. 303A:354–365, 2005. © 2005 Wiley-Liss, Inc.

  • Ornithine-urea cycle and urea synthesis in African lungfishes, Protopterus aethiopicus and Protopterus annectens, exposed to terrestrial conditions for six days.
    Journal of Experimental Zoology Part A: Comparative Experimental Biology, 2005
    Co-Authors: Ai M Loong, Shit F Chew, Kum C Hiong, Wai Peng Wong, Yuen K Ip
    Abstract:

    The objectives of this study were (1) to determine the type of carbamoyl phosphate synthetase (CPS) present, and the compartmentalization of arginase, in the livers of the African lungfishes, Protopterus aethiopicus and Protopterus annectens, and (2) to elucidate if these two lungfishes were capable of increasing the rates of urea synthesis and capacities of the ornithine-urea cycle (OUC) during 6 days of aerial exposure without undergoing aestivation. Like another African lungfish, Protopterus dolloi, reported elsewhere, the CPS activities from the livers of P. aethiopicus and P. annectens had properties similar to that of the marine ray (Taeniura lymma), but dissimilar to that of the mouse (Mus musculus). Hence, they possessed CPS III, and not CPS I as reported previously. CPS III was present exclusively in the liver mitochondria of both lungfishes, but the majority of the arginase activities were present in the cytosolic fractions of their livers. Glutamine synthetase (GS) activity was also detected in the hepatic mitochondria of both specimens. Therefore, our results suggest that the evolution of CPS III to CPS I might not have occurred before the evolution of extant lungfishes as suggested previously, prompting an examination of the current view on the evolution of CPS and OUC in vertebrates. Aerial exposure led to significant decreases in rates of ammonia excretion in P. aethiopicus and P. annectens, but there were no accumulations of ammonia in their tissues. However, urea contents in their tissues increased significantly after 6 days of aerial exposure. The estimated rates of urea synthesis in P. aethiopicus and P. annectens increased 1.2- and 1.47-fold, respectively, which were smaller than that in P. dolloi (8.6-fold) reported elsewhere. In addition, unlike P. dolloi, 6 days of aerial exposure had no significant effects on the hepatic CPS III activities of P. aethiopicus and P. annectens. In contrast, aerial exposure induced relatively greater degrees of reductions in ammonia production in P. aethiopicus (34%) and P. annectens (37%) than P. dolloi (28%) as previously reported. Thus, our results suggest that various species of African lungfishes respond to aerial exposure differently with respect to nitrogen metabolism and excretion, and it can be concluded that P. aethiopicus and P. annectens depended more on reductions in ammonia production than on increases in urea synthesis to ameliorate ammonia toxicity when exposed to terrestrial conditions.

  • circulating catecholamines and cardiorespiratory responses in hypoxic lungfish Protopterus dolloi a comparison of aquatic and aerial hypoxia
    Physiological and Biochemical Zoology, 2005
    Co-Authors: S F Perry, Kathleen M Gilmour, Branka Vulesevic, Shit F Chew, Brian Mcneill, Yuen K Ip
    Abstract:

    Abstract Circulating catecholamine levels and a variety of cardiorespiratory variables were monitored in cannulated bimodally breathing African lungfish (Protopterus dolloi) exposed to aquatic or aerial hypoxia. Owing to the purported absence of external branchial chemoreceptors in lungfish and the minor role played by the gill in O2 uptake, it was hypothesized that plasma catecholamine levels would increase only during exposure of fish to aerial hypoxia. The rapid induction of aquatic hypoxia (final \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{do...

Edward W Dempsey - One of the best experts on this subject based on the ideXlab platform.

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