scholarly journals Dogmas and controversies in the handling of nitrogenous wastes: 5-HT2-like receptors are involved in triggering pulsatile urea excretion in the gulf toadfish, Opsanus beta

2004 ◽  
Vol 207 (12) ◽  
pp. 2003-2010 ◽  
Author(s):  
M. D. McDonald
Keyword(s):  
Opsanus Beta ◽  
Urea Excretion ◽  
Gulf Toadfish

scholarly journals A waterborne chemical cue from Gulf toadfish, Opsanus beta, prompts pulsatile urea excretion in conspecifics

2017 ◽  
Vol 171 ◽  
pp. 92-99 ◽  
Author(s):  
Jeremy Fulton ◽  
Christophe M.R. LeMoine ◽  
Carol Bucking ◽  
Kevin V. Brix ◽  
Patrick J. Walsh ◽  
...  
Keyword(s):  
Chemical Cue ◽  
Opsanus Beta ◽  
Urea Excretion ◽  
Gulf Toadfish

Molecular characterization of a urea transporter in the gill of the gulf toadfish (Opsanus beta)

2000 ◽  
Vol 203 (15) ◽  
pp. 2357-2364 ◽  
Author(s):  
P.J. Walsh ◽  
M.J. Heitz ◽  
C.E. Campbell ◽  
G.J. Cooper ◽  
M. Medina ◽  
...  
Keyword(s):  
Morphological Data ◽  
Northern Analysis ◽  
Xenopus Laevis Oocytes ◽  
Urea Transporter ◽  
Reading Frame ◽  
Opsanus Beta ◽  
Urea Excretion ◽  
Pulse Cycle ◽  
A Minor ◽  
Gulf Toadfish

Urea excretion by the gulf toadfish (Opsanus beta) has been shown in previous studies to be a highly pulsatile facilitated transport, with excretion probably occurring at the gill. The present study reports the isolation of an 1800 base pair (kb) cDNA from toadfish gill with one open reading frame putatively encoding a 475-residue protein, the toadfish urea transporter (tUT). tUT, the first teleostean urea transporter cloned, has high homology with UTs (facilitated urea transporters) cloned from mammals, an amphibian and a shark, and most closely resembles the UT-A subfamily. When expressed in Xenopus laevis oocytes, tUT increased urea permeability (as measured by [(14)C]urea uptake) five- to sevenfold, and this permeability increase was abolished by phloretin, a common inhibitor of other UTs. Northern analysis using the 1.8 kb clone was performed to determine the tissue distribution and dynamics of tUT mRNA expression. Of six tissues examined (gill, liver, red blood cells, kidney, skin and intestine), only gill showed expression of tUT mRNA, with a predominant band at 1.8 kb and a minor band at 3.5 kb. During several points in the urea pulse cycle of toadfish (0, 4, 6, 12 and 18 h post-pulse), measured by excretion of [(14)C]urea into the water, gill mRNA samples were obtained. Expression of tUT mRNA was found to be largely invariant relative to expression of beta-actin mRNA over the pulse cycle. These results further confirm the gill localization of urea transport in the toadfish and suggest that tUT regulation (and the regulation of pulsatile urea excretion) is probably not at the level of mRNA control. The results are discussed in the context of the mechanisms of vasopressin-regulated UT-A in mammalian kidney and morphological data for the toadfish gill.

Does Pulsatile Urea Excretion Serve as a Social Signal in the Gulf Toadfish Opsanus beta?

2005 ◽  
Vol 78 (5) ◽  
pp. 724-735 ◽  
Author(s):  
Katherine A. Sloman ◽  
M. Danielle McDonald ◽  
John F. Barimo ◽  
Olivier Lepage ◽  
Svante Winberg ◽  
...  
Keyword(s):  
Opsanus Beta ◽  
Urea Excretion ◽  
Social Signal ◽  
Gulf Toadfish

Extrinsic nerves are not involved in branchial 5-HT dynamics or pulsatile urea excretion in Gulf toadfish, Opsanus beta

2017 ◽  
Vol 214 ◽  
pp. 58-65 ◽  
Author(s):  
Maria C. Cartolano ◽  
Molly H.B. Amador ◽  
Velislava Tzaneva ◽  
William K. Milsom ◽  
M. Danielle McDonald
Keyword(s):  
Opsanus Beta ◽  
Urea Excretion ◽  
Extrinsic Nerves ◽  
Gulf Toadfish

Do circulating plasma AVT and/or cortisol levels control pulsatile urea excretion in the gulf toadfish (Opsanus beta)?

2001 ◽  
Vol 129 (4) ◽  
pp. 859-872 ◽  
Author(s):  
Chris M. Wood ◽  
Justin M. Warne ◽  
Yuxiang Wang ◽  
M.Danielle McDonald ◽  
Richard J. Balment ◽  
...  
Keyword(s):  
Opsanus Beta ◽  
Urea Excretion ◽  
Cortisol Levels ◽  
Gulf Toadfish

Effects of feeding and confinement on nitrogen metabolism and excretion in the gulf toadfish Opsanus beta

1995 ◽  
Vol 198 (7) ◽  
pp. 1559-1566 ◽  
Author(s):  
P Walsh ◽  
C Milligan
Keyword(s):  
Total Nitrogen ◽  
Ammonia Excretion ◽  
Nitrogen Loading ◽  
Nitrogen Excretion ◽  
Turnover Rates ◽  
Opsanus Beta ◽  
Urea Excretion ◽  
Dietary Nitrogen ◽  
Excretion Rates ◽  
Gulf Toadfish

In order to elucidate further the cues for, and the biochemical mechanisms of, the transition to ureogenesis in the gulf toadfish Opsanus beta, experiments on the effects of feeding (i.e. nitrogen loading) were carried out. Baseline nitrogen excretion rates were first measured on solitary toadfish in large water volumes (i.e. unconfined conditions). These nitrogen excretion rates were higher, and had a higher proportion as ammonia (61 %), than previously published 'control' measurements. Feeding of unconfined toadfish elevated total nitrogen excretion approximately threefold, with little change in the proportion of urea versus ammonia. During the first 24 h of confinement of unfed toadfish, absolute levels of urea excretion remained constant while ammonia excretion rates fell to near zero, so that toadfish became 90 % ureotelic. When fed prior to confinement, urea excretion rates remained constant for the first 24 h, and the bulk of the nitrogen was excreted as ammonia (80 %); excretion of the excess dietary nitrogen took up to 48 h to complete. If pre-adapted to confinement and then fed, toadfish excreted only about 55 % of their nitrogenous waste as ammonia, and excretion of excess dietary nitrogen was completed by 24 h. Elevations of hepatic glutamine synthetase (GNS) activities accompanied confinement and were shown to be almost exclusively in the cytosolic compartment and to be correlated with a decrease in the ratio of hepatic levels of glutamate:glutamine. These GNS activity increases also appear to account in part for the decrease in the percentage of ammoniotely in toadfish under conditions of nitrogen loading after confinement. However, additional means of regulating total nitrogen excretion (e.g. changes in protein turnover rates) and the degree of ureogenesis versus ammoniogenesis (e.g. N-acetylglutamate stimulation of carbamoylphosphate synthetase) must be postulated to account fully for changes in nitrogen excretion rates and activation of ureogenesis under some circumstances.

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