... nitrogen in the gills, kidney, rectal gland and gut, but as yet, the latter are not well characterized. Intestinal sac preparations of the Pacific spiny dogfish shark ( Squalus acanthias suckleyi ) incubated in vitro strongly reabsorbed urea from the lumen after feeding, but mucosal fluid ammonia...

... oxygen consumption and ammonia excretion rates in the two compartments and found that, at rest, squid only obtain enough oxygen cutaneously to meet the demand of the skin tissue locally (12% of total) and excrete little ammonia across the skin. The majority of oxygen is obtained via the traditional...

... filaments and tertiary water channels ( Norton and Jones, 1992 ), and is known to take part in the absorption of ammonia and phosphate ( Fitt et al., 1993a ; Rees et al., 1994 ). Hence, it is probable that the ctenidial DUR3-like participates in the uptake of exogenous urea. Indeed, the apical localization...

...Alexander M. Clifford; Alex M. Zimmer; Chris M. Wood; Greg G. Goss ABSTRACT Hagfish skin has been reported as an important site for ammonia excretion and as the major site of systemic oxygen acquisition. However, whether cutaneous O 2 uptake is the dominant route of uptake remains under debate; all...

...Sandra Fehsenfeld; Dirk Weihrauch ABSTRACT Numerous electrophysiological studies on branchial K + transport in brachyuran crabs have established an important role for potassium channels in osmoregulatory ion uptake and ammonia excretion in the gill epithelium of decapod crustaceans. However, hardly...

...Li Zhang; C. Michele Nawata; Chris M. Wood SUMMARY Ammonia has been documented as a respiratory gas that stimulates ventilation, and is sensed by peripheral neuroepithelial cells (NECs) in the gills in ammoniotelic rainbow trout. However, the hyperventilatory response is abolished in trout...

...Carol Bucking; Christophe M. R. LeMoine; Paul M. Craig; Patrick J. Walsh SUMMARY Digestion affects nitrogen metabolism in fish, as both exogenous and endogenous proteins and amino acids are catabolized, liberating ammonia in the process. Here we present a model of local detoxification of ammonia...

... in water. Buccopharyngeal urea excretion in P. sinensis was highly efficient during emersion because the sum total of nitrogenous (ammonia-N + urea-N) excretion through the mouth and the urine ( Table 2 ) during forced emersion accounted for >90% of the nitrogenous wastes excreted by control turtles...

...Tamara M. Rodela; M. Danielle McDonald; Patrick J. Walsh; Kathleen M. Gilmour SUMMARY In their native environment, gulf toadfish excrete equal quantities of ammonia and urea. However, upon exposure to stressful conditions in the laboratory (i.e. crowding, confinement or air exposure), toadfish...

... the movement of NH 3 across cell membranes. This study examines the effects of crowding and feeding on ammonia excretion in gulf toadfish ( Opsanus beta ) within the context of Rh glycoproteins and the ammonia-fixing enzyme, glutamine synthetase (GS). Four Rh isoforms (Rhag, Rhbg, Rhcg1 and Rhcg2) were...

...Quanxi Zhang; Ziqiang Meng SUMMARY Ammonia (NH 3 ) is a common exogenous gas in the atmosphere, as well as an endogenous chemical produced by amino acid catabolism and other pathways in vivo . Physiological and pathophysiological roles of NH 3 in the nervous system have been studied. Recently...

...L. Gerardo Herrera M.; Jazmín Osorio M.; Carlos A. Mancina G. SUMMARY We tested the role of increased ammonia in urine as an energy- and/or nitrogen (N)-saving mechanism in the great fruit-eating bat Artibeus lituratus (Phyllostomidae). We compared N excretion in two groups of bats fed energy-rich...

...Li Zhang; Colin A. Nurse; Michael G. Jonz; Chris M. Wood SUMMARY Ammonia, the third respiratory gas in teleost fish, acts as an acute stimulant to ventilation in ammoniotelic rainbow trout. We investigated whether this sensitivity is maintained in trout chronically exposed (1+ months) to high...

...Tammy Laberge; Patrick J. Walsh; M. Danielle McDonald SUMMARY The gulf toadfish ( Opsanus beta ) is a facultatively ureotelic fish that excretes primarily urea under conditions of crowding or confinement. To examine the relationship between ammonia production, urea production and the ornithine–urea...

..., because the former would not disrupt macromolecular function( Brown and Simpson, 1972 ; Yancey, 2001 ). For M. albus exposed to salinity stress, there were significant decreases in the rate of ammonia and urea excretion, specifically during the phase of acclimation to 20‰ and 25‰ water. Theoretically...

..., and metabolic fuel usage in the African lungfish Protopterus annectens. Can. J. Zool. 80 , 790 -800. Ip, Y. K., Yeo, P. J., Loong, A. M., Hiong, K. C., Wong, W. P. and Chew, S. F. ( 2005 ). The interplay of increased urea synthesis and reduced ammonia production in the African lungfish Protopterus...

... synthetase I or III activity was detected in its liver. It was ammonotelic in water, and did not detoxify ammonia through increased urea synthesis during the 4 days of emersion. Unlike many air-breathing fishes reported elsewhere, A. testudineus could uniquely excrete ammonia during emersion at a rate...

...John F. Barimo; Patrick J. Walsh SUMMARY Because urea is bioenergetically expensive to synthesize, few aquatic teleostean (bony) fish make or excrete much urea beyond early development and excrete the majority of nitrogenous waste as the readily diffusible ammonia. The gulf toadfish is one of a few...

...D. J. Randall; T. K. N. Tsui SUMMARY The gills are the major site of acid–base regulation in most fish. Acid–base transfer across fish gills is dominated by carbon dioxide and ammonia excretion, especially the former. Bicarbonate buffering in the blood is less than that found in mammals; regulation...

... intake. However, there were significant reductions in daily rates of ammonia and urea excretion in H. signifer during salinity changes, especially between day 5 (in 10‰water) and day 10 (in 15‰ water) when compared to those of the control kept in 1‰ water. Consequently, there was a significant decrease...