Les Formes Du SystèMe Enzymatique De L'Uricolyse Et L'évolution Du Catabolisme Purique Chez Les Animaux

Florkin, Marcel; Duchateau, G

doi:10.3109/13813454309144823

Cited by 62 publications

(10 citation statements)

References 19 publications

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“…The one reported study of the Pacific lamprey (Entosphenus tridentatus) indicates that urea composes less than 1% of the total nitrogen excreted by this animal, and enzymatic analyses suggest that it arises from the breakdown of endogenous arginine stores, not from the OUC (Read 1968). The lack of uricolytic enzyme activity in the liver of river lampreys (Lampetra fluviatilis; Florkin and Duchâteau 1943) suggests that urea is unlikely to be produced via uricolysis in lampreys. Notably, these earlier studies focused on adult lampreys, yet most of the lamprey's life is spent as a larva (ammocoete).…”

Section: Introductionmentioning

confidence: 99%

“…The absence of significant uricolytic enzyme activity in the liver of the hagfish (Myxine glutinosa ;Read 1975) and the river lamprey (Florkin and Duchâteau 1943) led to the general conclusion that agnathans lack the enzymatic machinery to produce urea by this route. Adult lamprey were the focus of the latter study, however, in which rates of uricolysis could have been declining.…”

Section: The Mechanism Of Urea Productionmentioning

confidence: 99%

“…Most teleosts produce urea via uricolysis, in which uric acid arising from purine degradation is converted to urea (Florkin and Duchâteau 1943;Goldstein and Forster 1965;Cvancara 1969). Certain fishes, however, rely on urea production and excretion because they are subject to environmental constraints that impair ammonia excretion, such as periodic air exposure (Saha and Ratha 1989) or life in alkaline environments (Randall et al 1989).…”

Section: Introductionmentioning

confidence: 99%

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Nitrogenous waste excretion by the larvae of a phylogenetically ancient vertebrate: the sea lamprey (Petromyzon marinus)

Wilkie¹,

Wang²,

Walsh³

et al. 1999

Can. J. Zool.

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Larval sea lampreys (Petromyzon marinus) (ammocoetes) excreted significant quantities of urea, which composed 15-20% of the total nitrogenous waste excreted. Compared with teleosts of similar size, ammonia and urea excretion rates (J Amm and J Urea , respectively) in ammocoetes were relatively low, reflecting the low metabolic rate of these burrow-dwelling suspension feeders. Analyses of liver enzymes indicated that ammocoetes had all the enzymes necessary to produce urea via uricolysis, but not those of the ornithine-urea cycle (OUC). Further, exposure to 2 mmol·L -1 total ammonia for 5 d was accompanied by a 3-fold elevation of J Urea , but did not lead to greater OUC activity. Internal ammonia levels increased markedly, however, exceeding 2000 µmol·L -1 in plasma and 5000 µmol·L -1 in muscle after the 5-d exposure period. This high resistance to internal ammonia accumulation was related to the very high glutamine synthetase activities measured in ammocoete brains. The excretion and production of urea by ammocoetes demonstrates for the first time that agnathans are capable of producing physiologically relevant amounts of urea. Given the ancient origins and conserved evolution of lampreys, these observations also suggest that at least some of the early jawless vertebrates were able to produce and excrete urea.

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Section: Introductionmentioning

confidence: 99%

Section: The Mechanism Of Urea Productionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nitrogenous waste excretion by the larvae of a phylogenetically ancient vertebrate: the sea lamprey (Petromyzon marinus)

Wilkie¹,

Wang²,

Walsh³

et al. 1999

Can. J. Zool.

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“…The pig metabolizes uric acid: uricolysis occurs in this species mainly in the liver [Truszkowski and Goldntanowna, 1933], It has been suggested Swift, 1964: Baudhuin et a!., 1965;Afzelius, 1965;Shnitka, 1966] that there is a positive correlation be tween the presence of uncase, an enzyme that catalyzes the oxidation of uric acid to allantoin [Florkin and Duchateau, 1943], and the occur rence of crystalloid in microbodies. We have shown that hepatic microbodies of the pig display distinct crystalloids, the organization of which has been described in detail by Shnitka [ 1966] and Hruban and Rechcigl[ 1969], On the other hand, Flaks [1971] did not see crystalloids in liver microbodies of neonatal pigs.…”

Section: Discussionmentioning

confidence: 99%

Microbodies of the pig liver

Singh¹,

Williamson²,

Geissinger³

et al. 1978

Cells Tissues Organs

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The ultrastructure of hepatic microbodies of pigs was studied in liver samples fixed in phosphate-buffered 2% glutaraldehyde (pH 7.4) and postfixed in 2% osmium tetroxide. The microbodies were rounded or ovoid in shape and contained a granular matrix enclosed with a single limiting membrane. The matrix, in many of the organelles, contained an amorphous or an organized (crystalloid) area. The crystalloids were organized as fine, alternating electron-opaque and electron-lucent lines, or as groups of tubules arranged in more than one plane. Profiles of smooth endoplasmic reticulum were usually found near the microbodies. 34 micro-bodies were approximately 0.67 ± 0.02 μm (mean ± standard error) in length and were approximately 0.56 μm (± 0.02 μm) wide. The marginal plates consisted of strata which exhibited a periodicity. The average length and width of 17 plates was approximately 0.34 ± 0.03 μm and 0.002 μm, respectively. This study clearly establishes the occurrence of marginal plates in micro-bodies of porcine liver.

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“…Dans les tissus végétaux, le catabolisme des composés puriques suit la měme voie que dans les tissus animaux: composés puriques → hypoxanthine → xanthine → acide urique → allantoïne → acide allantoïque → 2 urée + acide glyoxylique (Hartman 1970); l'urée est décomposée en CO 2 + 2 NH 3 lorsque l'uréase est active. Alors que le fonctionnement de cette voie peut n'ětre que partiel dans le règne animal par suite de l'absence des enzymes des étapes terminales (Florkin et Duchateau 1943), chez les plantes supérieures, la dégradation des composés puriques est presque toujours complète et aboutit à la formation d'uréides glyoxyliques (Fosse 1939, Brunel et Capelle 1947, Barnes 1959, Butler et al 1961, Mothes 1961, Reinbothe 1961, Nguyen 1973c). Cependant, dans certains cas, la dégradation oxydative des purines ne dépasse pratiquement pas le stade de l'hypoxanthine (Barnes 1961, Silver et Gilmore 1969).…”

Section: Introductionunclassified

Mesure d'une activité métabolique in vivo. Cas du catabolisme purique chez le Pharbitis nil

Nguyen¹

1977

Physiologia Plantarum

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In vivo measurement of a metabolic activity. — Purine catabolism in Pharbitis nil cotyledons. To study the influence of light and darkness on the level of purine degradation, an in vivo method of measuring this catabolic pathway has been developed. Cotyledon discs of Pharbitis nil were incubated in an aqueous solution of hypoxanthine‐8‐14C. This purine base was first oxidized by a NAD+ dependent xanthine dehydrogenase. The metabolic flow was expressed either by the quantity of products (xanthine + uric acid + allantoin + allantoic acid) or by the rate of hypoxanthine degradation in the discs. This easy, reproducible and very sensitive technique of measurement has been investigated with respect to several variables including tissue quantity, length of incubation time, hypoxanthine and NAD+ concentrations, and pH. The quantity of products varied proportionally with the tissue quantity but the catabolic rate was not linked to this. The best conditions of measurement were to incubate discs for at least 60 min in distilled water containing only hypoxanthine‐8‐14C at low concentrations (below 0.25 mM). The values obtained represent the actual in vivo level of the studied metabolic pathway. The NAD+ concentration within the tissue does not seem to be a limiting factor for hypoxanthine degradation, the hypoxanthine concentration itself appears to be the only limiting factor in endogenous purine catabolism.

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Les Formes Du SystèMe Enzymatique De L'Uricolyse Et L'évolution Du Catabolisme Purique Chez Les Animaux

Cited by 62 publications

References 19 publications

Nitrogenous waste excretion by the larvae of a phylogenetically ancient vertebrate: the sea lamprey (Petromyzon marinus)

Nitrogenous waste excretion by the larvae of a phylogenetically ancient vertebrate: the sea lamprey (Petromyzon marinus)

Microbodies of the pig liver

Mesure d'une activité métabolique in vivo. Cas du catabolisme purique chez le Pharbitis nil

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