Urea Tolerance Research Articles

Amidosulfobetaines, a family of detergents with improved solubilization properties: Application for isoelectric focusing under denaturing conditions

The synthesis of a family of new detergents and their use for isoelectric focusing are described. These detergents differ from the conventional sulfobetaines by the presence of an amido group bridging the hydrophobic linear tail and the polar head, which increases their water solubility and urea tolerance considerably. Four different linear alkyl hydrophobic tails were tested, together with three different polar heads. The solubilization of red blood cell ghosts by the 12 resulting detergent performances was evaluated both in solution and in isoelectric focusing runs. Six chemicals gave performances equal or better than those of conventional detergents and could replace them for general use in focusing experiments. In addition, the synthesis of a whole range of compounds allowed valuable insights in the empirical understanding of protein-detergent interactions, which are extensively discussed.

Water retention and plasma and urine composition in toads (Bufo viridis Laur.) under burrowing conditions

Osmoregulation in the terrestrial toad,Bufo viridis, was studied under burrowing conditions in the laboratory. The toads can live for over 3 months burrowed in soil containing 9–10% moisture, maintaining constant body volume due to a large increase in the plasma osmolality, contributed mainly by urea. Water content of the tissues remains constant. Relatively large volumes of urine are stored in the urinary bladder during water restriction. The osmolality of the urine does not exceed that of the plasma. Urea uptake across the skin was measured in vitro and was greatly elevated in skins from the burrowed toads. The increase in plasma osmolality enables greater water absorption from the soil under water restricted conditions while the water content of the tissues is maintained constant since cell membranes are highly permeable to urea. It is concluded that the urea accumulating ability and urea tolerance form the basis for both the terrestriality and salt adaptability of this and other amphibian species.

Urea tolerance and osmoregulation in Bufo viridis and Rana ridibunda.

1. The tolerance and adaptation to urea solutions by terrestrial green toads (Bufo viridis) and semi-aquatic frogs (Rana Ridibunda) were studied. 2. the green toad showed tolerance to urea solution of 800 mM and the frogs showed tolerance only to about 400 mM urea solution. 3. The plasma concentrations of both species was hyperosmotic to the external medium in all the different urea solutions. 4. Blood osmolality, urea, Na+ and Cl- concentrations of B. viridis were always higher than in R. ridibunda. 5. The urea concentration in muscle of R. ridibunda was higher than the urea concentration in muscle of B. viridis. 6. The muscle tissue weight loss of B. viridis was significantly lower than R. ridibunda.

Methylamine osmoregulatory solutes of elasmobranch fishes counteract urea inhibition of enzymes

AbstractThe intracellular fluids of marine elasmobranchs contain a set of methylamine compounds (trimethylamine oxide, betaine, and sarcosine) which are able to counteract the perturbing effects of urea on enzyme function (apparent Michaelis constant (Km) and maximal velocity). The counteracting effects of the methylamine compounds and urea are maximal at a 2:1 ratio [urea]:[methylamines]. This is the same concentration ratio for these osmolytes found in the cells of marine elasmobranchs, holocephalans, and the coelacanth.The counteracting effects of the methylamine solutes and urea are observed with enzymes from non‐elasmobranchs as well as elasmobranchs, indicating that the enzymes of elasmobranchs are not specially adapted to function in the presence of urea or the methylamine osmolytes. Rather, the effects of urea and the methylamines on enzymes probably reflect fundamental protein‐solute interactions.The urea tolerance conferred by the methylamine solutes may have played an important role in elasmobranch evolution. The relief from urea perturbation afforded by these methylamines may have precluded the requirement for widespread modifications in the sequences of elasmobranch proteins to allow these proteins to function in the presence of perturbing urea concentrations.

The efficacy of protein supplementation in overcoming urea toxicity in sheep.

1. In the first experiment sheep taken from pasture were given a low-protein diet for six weeks in individual pens. Then, for 1 week, groups were given a supplement of lucerne chaff, safflower meal or lucerne chaff plus safflower meal. In the second experiment eighteen sheep maintained on lucerne chaff rather than pasture were then depleted of protein to a greater extent by feeding on a restricted low-protein diet. Six of the sheep received a supplement of molasses throughout the period of protein depletion while six of the sheep on the basal ration received a supplement of safflower meal after 6 weeks on the low-protein diet. 2. The urea tolerance of the sheep, is indicated by blood ammonia levels after oral dosing with aqueous solutions of urea, was determined after the period of supplementation. "Arginine synthetase" activity (combined activities of argininosuccinate synthetase (EC 6.3.4.5) and argininosuccinate lyase (EC 4.3.2.1) was determined in liver samples obtained by biopsy at various intervals during the experiment. 3. Supplementation for 7 d with 73 g crude protein (nitrogen X 6-25)/d increased the tolerance to urea as indicated by reduced blood NH3 levels, and also increased "arginine synthetase" activity. 4. Giving supplements of molasses delayed the onset of urea toxicity but not the extent of toxicity. 5. It is suggested that short-term feeding of protein concentrates to sheep before giving urea supplements can increase their tolerance to urea.

Urea tolerance as a molecular adaptation of elasmobranch hemoglobins.

Urea is maintained at moderately high concentrations in the blood and tissues of marine elasmobranchs. Functional properties of the hemoglobins fromn several elasmobranch species are unaffected by urea concentrations as high as 5 molar. This in. sensitivity to urea, which is not observed with human hemoglobin, is accompanied by an increased sensitivity to sodium chloride.

Comparison of some parameters of serum and uterine fluid of pregnant, viviparous sharks ( Carcharhinus leucas) and serum of their near-term young

1. 1. In eight females, serum urea concentrations of 134–336 mM/l. were interpreted as indications of previous environmental salinities. 2. 2. Fetal serum solute concentrations usually resembled those of the mother, but in two cases where fetal urea was higher, it was interpreted as a lag in urea reduction following movement from salt to fresh water. 3. 3. Uterine fluid was similar to maternal serum in all parameters except for its very low protein content. 4. 4. No flushing of the uteri with environmental water occurs. 5. 5. Independent osmoregulation apparently does not occur before birth, although required mechanisms may be present. 6. 6. The full range of urea tolerance is present before birth.

Urea Tolerance in Growing and Adult Chickens

IT HAS BEEN demonstrated repeatedly that chickens are not able to utilize urea as a source of nitrogen (Ackerson et al., 1940; Heller and Penquite, 1941; Bice and Dam, 1942; Jones and Combs, 1953). Only with purified diets devoid of non-essential amino acids (Featherston et al., 1962), or with diets in which methionine and glycine are replaced by their hydroxy analogues (Sullivan and Bird, 1957) has there been any evidence that urea is beneficial to the chick.The utilization of the Pacific coast dogfish, Squalus suckleyi, for meal production has been suggested periodically. Because meal made from dogfish contains approximately 2.5 percent urea (more or less depending upon the method of manufacture, March et al. (1971), dogfish meal for poultry feeding would have to be used on the basis of its actual protein nitrogen rather than crude protein calculated from the total nitrogen content. If it is assumed that urea…