Amino acid metabolism and urea synthesis in naturally aestivating Xenopus laevis

Balinsky, J.B.; Choritz, E.L.; Coe, C.G.L.; Schans, Gerda S. van der

doi:10.1016/0010-406x(67)90166-1

Cited by 103 publications

(36 citation statements)

References 12 publications

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“…13) (356, 585). Naturally estivating X. laevis experience increases of 2-to 3-fold in ammonia concentration and of 15-to 22-fold in urea concentrations of the liver, thigh muscle, and plasma (24). Following 6 to 9 months of estivation, plasma and urine urea levels have increased by 6-and 7-fold, respectively, for S. couchi (356,357).…”

Section: Estivationmentioning

confidence: 96%

Integrative Physiology of Fasting

Secor

Carey

2016

Comprehensive Physiology

138

144

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Extended bouts of fasting are ingrained in the ecology of many organisms, characterizing aspects of reproduction, development, hibernation, estivation, migration, and infrequent feeding habits. The challenge of long fasting episodes is the need to maintain physiological homeostasis while relying solely on endogenous resources. To meet that challenge, animals utilize an integrated repertoire of behavioral, physiological, and biochemical responses that reduce metabolic rates, maintain tissue structure and function, and thus enhance survival. We have synthesized in this review the integrative physiological, morphological, and biochemical responses, and their stages, that characterize natural fasting bouts. Underlying the capacity to survive extended fasts are behaviors and mechanisms that reduce metabolic expenditure and shift the dependency to lipid utilization. Hormonal regulation and immune capacity are altered by fasting; hormones that trigger digestion, elevate metabolism, and support immune performance become depressed, whereas hormones that enhance the utilization of endogenous substrates are elevated. The negative energy budget that accompanies fasting leads to the loss of body mass as fat stores are depleted and tissues undergo atrophy (i.e., loss of mass). Absolute rates of body mass loss scale allometrically among vertebrates. Tissues and organs vary in the degree of atrophy and downregulation of function, depending on the degree to which they are used during the fast. Fasting affects the population dynamics and activities of the gut microbiota, an interplay that impacts the host's fasting biology. Fasting-induced gene expression programs underlie the broad spectrum of integrated physiological mechanisms responsible for an animal's ability to survive long episodes of natural fasting.

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Section: Estivationmentioning

confidence: 96%

Integrative Physiology of Fasting

Secor

Carey

2016

Comprehensive Physiology

138

144

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“…Although almost exclusively aquatic, in their native environment in southern Africa this species is faced with seasonal drying of its ponds and responds in one of two ways: (1) by nocturnal overland migration to a new water source or (2) by digging into the cooler, damper subsoil of their evaporating pond and entering aestivation (Alexander & Bellerby, 1938). These frogs can endure substantial desiccation (losing as much as 32-35% of total body water) (Romspert, 1975;Malik and Storey, 2009a) and under dehydration stress they elevate the production of nitrogenous osmolytes including amino acids, ammonia (twofold to threefold increase) and urea (15-to 20-fold increase) to enhance water retention and/or uptake from damp soil (Balinsky et al, 1967).…”

Section: Otala Lacteamentioning

confidence: 99%

Aestivation: signaling and hypometabolism

Storey

2012

Journal of Experimental Biology

137

116

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SummaryAestivation is a survival strategy used by many vertebrates and invertebrates to endure arid environmental conditions. Key features of aestivation include strong metabolic rate suppression, strategies to retain body water, conservation of energy and body fuel reserves, altered nitrogen metabolism, and mechanisms to preserve and stabilize organs, cells and macromolecules over many weeks or months of dormancy. Cell signaling is crucial to achieving both a hypometabolic state and reorganizing multiple metabolic pathways to optimize long-term viability during aestivation. This commentary examines the current knowledge about cell signaling pathways that participate in regulating aestivation, including signaling cascades mediated by the AMPactivated kinase, Akt, ERK, and FoxO1.

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“…have been widely studied since the 1950s as laboratory model animals, most extensively as a model of embryonic development (Beck and Slack, 2001). However, less is known about the responses of this species to environmental stresses, although some studies have looked at nitrogen metabolism and changes in the activities of urea cycle enzymes during dehydration and estivation (Balinsky et al, 1961;Balinsky et al, 1967). The molecular signaling mechanisms that allow adult Xenopus to deal with environmental dehydration stress have not been explored.…”

Section: Introductionmentioning

confidence: 99%