Lympho-granulocytic tissue associated with the wall of the spiral valve in the African lungfish Protopterus annectens.

We describe the structure of the lympho-granulocytic tissue associated with the wall of the spiral valve of the African lungfish Protopterus annectens. The study was performed under freshwater conditions and after 6 months of aestivation. The lympho-granulocytic tissue consists of nodes surrounded by reticular tissue.

The Chinese soft-shelled turtle, Pelodiscus sinensis, excretes urea mainly through the mouth instead of the kidney.

The Chinese soft-shelled turtle, Pelodiscus sinensis, is well adapted to aquatic environments, including brackish swamps and marshes. It is ureotelic, and occasionally submerges its head into puddles of water during emersion, presumably for buccopharyngeal respiration. This study was undertaken to test the hypothesis that the buccophyaryngeal cavity constitutes an important excretory route for urea in P.

The spleen of the African lungfish Protopterus annectens: freshwater and aestivation.

We describe the structure of the spleen of the African lungfish Protopterus annectens in freshwater conditions, and after 6 months of aestivation. The spleen is formed by cortical tissue that surrounds the splenic parenchyma. The cortex is a reticulum that contains two types of granulocytes, developing and mature plasma cells, and melanomacrophage centres (MMCs).

Hepatic carbamoyl phosphate synthetase (CPS) I and urea contents in the hylid tree frog, Litoria caerulea: transition from CPS III to CPS I.

The complete cDNA sequence of CPS I obtained from the liver of the hylid tree frog, Litoria caerulea, consisted of 4,485 bp which coded for 1,495 amino acids with an estimated molecular mass of 163.7 kDa. The deduced CPS I consisted of a mitochondrial targeting sequence of 33 amino acid residues, a glutaminase amidotransferase component spanning from tyrosine 95 to leucine 425, and a methylglyoxal synthetase-like component spanning from valine 441 to lysine 1566.

Roles of three branchial Na(+)-K(+)-ATPase α-subunit isoforms in freshwater adaptation, seawater acclimation, and active ammonia excretion in Anabas testudineus.

Three Na(+)-K(+)-ATPase (nka) α-subunit isoforms, nka α1a, nka α1b, and nka α1c, were identified from gills of the freshwater climbing perch Anabas testudineus. The cDNA sequences of nka α1a and nka α1b consisted of 3,069 bp, coding for 1,023 amino acids, whereas nka α1c was shorter by 22 nucleotides at the 5' end. In freshwater, the quantity of nka α1c mRNA transcripts present in the gills was the highest followed by nka α1a and nka α1b that was almost undetectable.

Cystic fibrosis transmembrane conductance regulator in the gills of the climbing perch, Anabas testudineus, is involved in both hypoosmotic regulation during seawater acclimation and active ammonia excretion during ammonia exposure.

This study aimed to clone and sequence the cystic fibrosis transmembrane conductance regulator (cftr) from, and to determine the effects of seawater acclimation or exposure to 100 mmol l⁻¹ NH₄Cl in freshwater on its mRNA and protein expressions in, the gills of Anabas testudineus. There were 4,530 bp coding for 1,510 amino acids in the cftr cDNA sequence from A. testudineus.

Both seawater acclimation and environmental ammonia exposure lead to increases in mRNA expression and protein abundance of Na⁺:K⁺:2Cl⁻ cotransporter in the gills of the climbing perch, Anabas testudineus.

The freshwater climbing perch, Anabas testudineus, is an obligatory air-breathing teleost which can acclimate to seawater, survive long period of emersion, and actively excrete ammonia against high concentrations of environmental ammonia. This study aimed to clone and sequence the Na⁺:K⁺:2Cl⁻ cotransporter (nkcc) from the gills of A. testudineus, and to determine the effects of seawater acclimation or exposure to 100 mmol l⁻¹ NH₄Cl in freshwater on its branchial mRNA expression.

The alimentary canal of the African lungfish Protopterus annectens during aestivation and after arousal.

We describe the structural modifications that occur in the alimentary canal of the African lungfish Protopterus annectens during aestivation and after arousal. With fasting, all gut segments undergo structural modifications. The epithelium covering the intestinal vestibule undergoes bursts of activation at 4 months of aestivation, adopting a more quiescent appearance at 6 months.

The gut of the juvenile African lungfish Protopterus annectens: a light and scanning electron microscope study.

We describe the microstructure of the alimentary canal of the juvenile lungfish Protopterus annectens. Following the oesophagus, the gut is formed by a long segment that extends down to the pyloric valve. This segment, classically named stomach, is lined by a transitional epithelium but lacks all characteristics of the vertebrate stomach.

The anatomy of the gastrointestinal tract of the African lungfish, Protopterus annectens.

The gastrointestinal tract of the African lungfish Protopterus annectens is a composite, which includes the gut, the spleen, and the pancreas. The gut is formed by a short oesophagus, a longitudinal stomach, a pyloric valve, a spiraling intestine, and a cloaca. Coiling of the intestine begins dorsally below the pylorus, winding down to form six complete turns before ending into the cloaca.

Glutamine accumulation and up-regulation of glutamine synthetase activity in the swamp eel, Monopterus albus (Zuiew), exposed to brackish water.

The swamp eel, Monopterus albus, is an air-breathing teleost which typically lives in freshwater but can also be found in estuaries, where it has to deal with ambient salinity fluctuations. Unlike other teleosts, its gills are highly degenerate. Hence, it may have uncommon osmoregulatory adaptations, but no information is available on its osmoregulatory capacity and mechanisms at present.

Increased urea synthesis and/or suppressed ammonia production in the African lungfish, Protopterus annectens, during aestivation in air or mud.

The objective of this study was to elucidate how the African lungfish, Protopterus annectens, ameliorated ammonia toxicity during 12 or 46 days of aestivation in air or in mud. Twelve days of aestivation in air led to significant increases in contents of urea, but not ammonia, in tissues of P. annectens.

Differential NOS expression in freshwater and aestivating Protopterus dolloi (lungfish): heart vs kidney readjustments.

African lungfish Protopterus dolloi is an obligatory air-breather, which aestivates in a cocoon during the dry season. Aestivation associates with functional modifications in many tissues and organs, including heart and kidney. Due to its pleiotropic modulatory effects, nitric oxide (NO), generated by nitric oxide synthases (NOSs), may coordinate organ rearrangement, allowing adaptive adjustments under stressful environmental conditions.

Changes in tissue free amino acid contents, branchial Na+/K+ -ATPase activity and bimodal breathing pattern in the freshwater climbing perch, Anabas testudineus (Bloch), during seawater acclimation.

This study aimed to examine effects of short- or long-term acclimation to brackish water or seawater on the climbing perch, Anabas testudineus, which is an aquatic air-breathing teleost living typically in freshwater. A. testudineus exhibits hypoosmotic and hypoinoic osmoregulation; the plasma osmolality, [Na+] and [Cl-] of fish acclimated to seawater were consistently lower than those of the external medium.

Active ammonia transport and excretory nitrogen metabolism in the climbing perch, Anabas testudineus, during 4 days of emersion or 10 minutes of forced exercise on land.

The climbing perch, Anabas testudineus, inhabits large rivers, canals, stagnant water bodies, swamps and estuaries, where it can be confronted with aerial exposure during the dry season. This study aimed to examine nitrogen excretion and metabolism in this fish during 4 days of emersion. Contrary to previous reports, A.

Nitrogen metabolism and excretion in the aquatic chinese soft-shelled turtle, Pelodiscus sinensis, exposed to a progressive increase in ambient salinity.

This study aimed to determine effects of 6-day progressive increase in salinity from 1 per thousand to 15 per thousand on nitrogen metabolism and excretion in the soft-shelled turtle, Pelodiscus sinensis. For turtles exposed to 15 per thousand water on day 6, the plasma osmolality and concentrations of Na+, Cl- and urea increased significantly, which presumably decreased the osmotic loss of water. Simultaneously, there were significant increases in contents of urea, certain free amino acids (FAAs) and water-soluble proteins that were involved in cell volume regulation in various tissues.

Postprandial increases in nitrogenous excretion and urea synthesis in the Chinese soft-shelled turtle, Pelodiscus sinensis.

The objective of this study was to determine the effects of feeding on the excretory nitrogen (N) metabolism of the aquatic Chinese soft-shelled turtle, Pelodiscus sinensis, with a special emphasis on the role of urea synthesis in ammonia detoxification. P. sinensis is ureogenic and possesses a full complement of ornithine-urea cycle enzymes in its liver.

Light induces an increase in the pH of and a decrease in the ammonia concentration in the extrapallial fluid of the giant clam Tridacna squamosa.

The objective of this study was to examine whether 12 h of light exposure would lead to an increase in the pH of and a decrease in the concentration of total ammonia in the extrapallial fluid of the giant clam Tridacna squamosa. We also aimed to elucidate indirectly whether movements of ammonia and/or protons (H(+)) occurred between the extrapallial fluid and the outer mantle epithelium. The pH of the extrapallial fluid of T.

Increases in urea synthesis and the ornithine-urea cycle capacity in the giant African snail, Achatina fulica, during fasting or aestivation, or after the injection with ammonium chloride.

The objectives of this study are to determine whether a full complement of ornithine-urea cycle (OUC) enzymes is present in the hepatopancreas of the giant African snail Achatina fulica, and to investigate whether the rate of urea synthesis and the OUC capacity can be up-regulated during 23 days of fasting or aestivation, or 24 hr post-injection with NH(4)Cl (10 micromol g(-1) snail) into the foot muscle. A. fulica is ureotelic and a full complement of OUC enzymes, including carbamoyl phosphate synthetase III (CPS III), was detected from its hepatopancreas.

The interplay of increased urea synthesis and reduced ammonia production in the African lungfish Protopterus aethiopicus during 46 days of aestivation in a mucus cocoon.

This study was undertaken to test the hypothesis that the rate of urea synthesis in Protopterus aethiopicus was up-regulated to detoxify ammonia during the initial phase of aestivation in air (day 1-day 12), and that a profound suppression of ammonia production occurred at a later phase of aestivation (day 35-day 46) which eliminated the need to sustain the increased rate of urea synthesis. Fasting apparently led to a greater rate of nitrogenous waste excretion in P. aethiopicus in water, which is an indication of increases in production of endogenous ammonia and urea probably as a result of increased proteolysis and amino acid catabolism for energy production.

Ornithine-urea cycle and urea synthesis in African lungfishes, Protopterus aethiopicus and Protopterus annectens, exposed to terrestrial conditions for six days.

The objectives of this study were (1) to determine the type of carbamoyl phosphate synthetase (CPS) present, and the compartmentalization of arginase, in the livers of the African lungfishes, Protopterus aethiopicus and Protopterus annectens, and (2) to elucidate if these two lungfishes were capable of increasing the rates of urea synthesis and capacities of the ornithine-urea cycle (OUC) during 6 days of aerial exposure without undergoing aestivation. Like another African lungfish, Protopterus dolloi, reported elsewhere, the CPS activities from the livers of P. aethiopicus and P.

A molecular epidemiologic study of thalassemia using newborns' cord blood in a multiracial Asian population in Singapore: results and recommendations for a population screening program.

DNA technology provides a new avenue to perform neonatal screening tests for single-gene diseases in populations of high frequency. Thalassemia is one of the high-frequency single-gene disorders affecting Singapore and many countries in the malaria belt. The authors explored the feasibility of using PCR-based diagnostic screening on 1,116 unselected sequential cord blood samples for neonatal screening.

Exposure to air, but not seawater, increases the glutamine content and the glutamine synthetase activity in the marsh clam Polymesoda expansa.

Polymesoda expansa spends a considerable portion of its life exposed to air in mangrove swamps where salinity fluctuates greatly. Thus, the aim of this study was to evaluate the effects of aerial exposure (transfer from 10 per thousand brackish water directly to air) or salinity changes (transfer from 10 per thousand brackish water directly to 30 per thousand seawater) on nitrogen metabolism in P. expansa.

African sharptooth catfish Clarias gariepinus does not detoxify ammonia to urea or amino acids but actively excretes ammonia during exposure to environmental ammonia.

The African sharptooth catfish Clarias gariepinus lives in freshwater, is an obligatory air breather, and exhibits high tolerance of environmental ammonia. This study aimed at elucidating the strategies adopted by C. gariepinus to defend against ammonia toxicity during ammonia exposure.

Nitrogen metabolism in the African lungfish (Protopterus dolloi) aestivating in a mucus cocoon on land.

This study aimed to elucidate the strategies adopted by the African slender lungfish, Protopterus dolloi, to ameliorate the toxicity of ammonia during short (6 days) or long (40 days) periods of aestivation in a layer of dried mucus in open air in the laboratory. Despite decreases in rates of ammonia and urea excretion, the ammonia content in the muscle, liver, brain and gut of P. dolloi remained unchanged after 6 days of aestivation compared with the control fasted for 6 days.