The adaptation of amphibian waste nitrogen excretion to dehydration

Balinsky, J.B.; Cragg, Mavis M.; Baldwin, Ernest

doi:10.1016/0010-406x(61)90009-3

Cited by 93 publications

(28 citation statements)

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“…One method to help retard water loss is to raise the osmolality of body fluids and, among anuran species that estivate or endure hypersalinity, the commonly occurring osmolyte is urea. Indeed, previous studies have shown that under osmotic or water stress, X. laevis reduce ammonia excretion, elevate the activities of urea cycle enzymes and accumulate urea (Balinsky et al, 1961;Janssens, 1964;Seiter et al, 1978). In the present study, plasma urea concentration increased sharply when frogs were dehydrated, rising by 27-and 33-fold, respectively, in the medium and high dehydration groups as compared with control values of 1.66 mmol l -1 (Table 1).…”

Section: Results and Discussion Metabolic Responses To Dehydrationsupporting

confidence: 55%

“…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%

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Activation of extracellular signal-regulated kinases during dehydration in the African clawed frog, Xenopus laevis

Malik

Storey

2009

Journal of Experimental Biology

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Section: Results and Discussion Metabolic Responses To Dehydrationsupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Activation of extracellular signal-regulated kinases during dehydration in the African clawed frog, Xenopus laevis

Malik

Storey

2009

Journal of Experimental Biology

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“…In some circumstances, such as when the adult Xenopus is exposed to dehydration and burrows in the mud, urea but not ammonia accumulates in their tissues (Balinsky et al, 1967). Urea accumulation can also be induced artificially by keeping the animals out of water or when the animals are placed in hypertonic saline (0.15 M sodium chloride) (Balinsky et al, 1961). The molecular mechanisms underlying developmental and hormonal regulation of urea cycle enzymes, or adaptational transition from ammonotelism to ureotelism as mentioned above, are not yet fully understood.…”

mentioning

confidence: 99%

Developmental and hormonal regulation of the Xenopus liver‐type arginase gene

Baker

Tata

1993

European Journal of Biochemistry

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Liver-type L-arginase is a major urea-cycle enzyme which is strongly induced during amphibian metamorphosis, but little is known about the molecular mechanisms underlying this induction. As a first step towards elucidating the possible mechanisms, we have isolated a cDNA clone for Larginase from an adult Xenopus luevis liver cDNA library. Sequence comparison of Xenopus livertype L-arginase cDNA shows a strong conservation at the amino acid level with those of human, rat and yeast. Using a Xenopus arginase cDNA fragment as a hybridization probe, we have shown by Northern blotting that the gene is highly expressed in the liver, and very slightly in kidney and spleen, of adult Xenopus. The expression is developmentally regulated. Only traces of arginase mRNA can be detected in pre-metamorphic tadpoles, but its accumulation increases very markedly at the onset of natural metamorphosis, being maintained at a high concentration constitutively upon completion of this developmental process. Amphibian metamorphosis is under the strict control of thyroid hormones. It is therefore significant that exposure of pre-metamorphic tadpoles (at stages before endogenous thyroid hormone secretion) to exogenous hormone (1 nM triiodothyronine) precociously activated the L-arginase gene. The time course of this precocious hormonal induction paralleled that of serum albumin gene in the liver. Polyclonal antibodies were raised against recombinant Xenopus L-arginase expressed in Escherichiu coli as a fusion protein with glutathione S-transferase in the plasmid expression vector pGEX. Western blotting using this antibody showed that, although arginase mRNA is present in high concentration in Xenopus tadpole liver at the onset of natural metamorphosis, the protein is detected only upon its completion. Our results show a complex transcriptional and post-transcriptional regulation of the Xenopus liver-type L-arginase gene during post-embryonic development. They also demonstrate that this gene can be exploited as a target for thyroid hormones in further studies to analyze the mechanisms underlying the establishment of the adult phenotype during amphibian metamorphosis.

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“…It has also been suggested that, in long or severe dehydration periods, the water in diluted urine is used, and the urine's urea concentration rises, compared to the lymph and blood, but with continued dehydration those concentrations become equal, and the osmoregulatory organs become isosmotic (Balinsky et al, 1961;Ruibal, 1962;Cartledge et al, 2006;Reynolds and Christian, 2009). Scaphiopus couchi, a desert anuran, was studied regarding its ability to withstand dehydration and its body's urea and electrolyte balance (McClanahan, 1967).…”

Section: Discussionmentioning

confidence: 99%

Effects of variations of osmolarity on behavior in Leptodactylus macrosternum Miranda-Ribeiro, 1926 (Leptodactylidae, Anura, Amphibia)

Bonfim

Napoli

Cruz

et al. 2014

reveto

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Amphibians experiencing evapotranspirative water loss may suffer dehydration. Another difficulty is their limited tolerance to brackish water. This study aimed to investigate the effect of water salinity on behavior (activity and water conservation posture) in Leptodactylus macrosternum, in normally hydrated animals with urine in their bladder, in normally hydrated animals without urine in their bladder and in dehydrated ones with urine removed from their bladder. Experiments were filmed, behaviors were registered, and a Behavioral Dehydration Protection Index (BDPI) was calculated, using a weighted average of the postures. A GLM and Kruskall Wallis test was performed with Dunn's multiple comparisons test to evaluate the effects of osmotic gradient stress on BDPI. It was found that emptied bladder and aerial dehydration did not influence BDPI (p = 0.832 and p = 0.142, respectively), contrary to what is seen in the literature. The different osmotic media had a significant effect on BDPI (p = 0.0003). Keywords: Osmotic stress; Leptodacytulus macrosternum; conservation posture.Anfíbios que experimentam perda de água podem sofrer desidratação. Outra dificuldade é a tolerância limitada à água salobra. Este trabalho teve como objetivo estudar o efeito da salinidade da água no comportamento (atividade e postura de conservação de água) de L. macrosternum, normalmente hidratados com urina armazenada na bexiga, normalmente hidratados com urina removida da bexiga e nos desidratados com urina removida da bexiga. Os experimentos foram filmados e foi calculado o índice de proteção comportamental da desidratação (BDPI) usando média ponderada. Realizamos modelo linear generalizado e teste Kruskall-Wallis com comparação múltipla de Dunn, para analisar o efeito dos gradientes de estresse osmótico sobre o BDPI. Observamos que a bexiga esvaziada e a desidratação exercida pelo ar não influenciam o aumento do BDPI (p = 0.832 e p = 0.142, respectivamente) sendo contrário ao visto em literatura. Os diferentes meios osmóticos tiveram efeito sobre o BDPI (p = 0.0003). Palavras-chave: Estresse osmótico; Leptodacytulus macrosternum; postura de conservação.

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The adaptation of amphibian waste nitrogen excretion to dehydration

Cited by 93 publications

References 9 publications

Activation of extracellular signal-regulated kinases during dehydration in the African clawed frog, Xenopus laevis

Activation of extracellular signal-regulated kinases during dehydration in the African clawed frog, Xenopus laevis

Developmental and hormonal regulation of the Xenopus liver‐type arginase gene

Effects of variations of osmolarity on behavior in Leptodactylus macrosternum Miranda-Ribeiro, 1926 (Leptodactylidae, Anura, Amphibia)

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