Nitrogen excretion: three end products, many physiological roles.

1995 ◽  
Vol 198 (2) ◽  
pp. 273-281 ◽  
Author(s):  
P A Wright
Keyword(s):  
Uric Acid ◽  
Organic Compounds ◽  
Marine Invertebrates ◽  
Chemical Properties ◽  
Nitrogen Excretion ◽  
Acid Base ◽  
Ammonia Metabolism ◽  
Waste Products ◽  
End Products

There are diverse physiological functions of nitrogen end products in different animal groups, including excretion, acid-base regulation, osmoregulation and buoyancy. Animals excrete a variety of nitrogen waste products, but ammonia, urea and uric acid predominate. A major factor in determining the mode of nitrogen excretion is the availability of water in the environment. Generally, aquatic animals excrete mostly ammonia, whereas terrestrial animals excrete either urea or uric acid. Ammonia, urea and uric acid are transported across cell membranes by different mechanisms corresponding to their different chemical properties in solution. Ammonia metabolism and excretion are linked to acid-base regulation in the kidney, but the role of urea and uric acid is less clear. Both invertebrates and vertebrates use nitrogen-containing organic compounds as intracellular osmolytes. In some marine invertebrates, NH4+ is sequestered in specific compartments to increase buoyancy.

Some applications of polarography for investigation of equlibria in aqueous solutions of organic compounds

2009 ◽  
Vol 74 (11-12) ◽  
pp. 1777-1789 ◽  
Author(s):  
Petr Zuman
Keyword(s):  
Aqueous Solutions ◽  
Organic Compounds ◽  
Carbonyl Compounds ◽  
Limiting Current ◽  
Nitroso Compounds ◽  
Primary Amines ◽  
Acid Base ◽  
Fast Reactions ◽  
Half Wave

There are two possibilities how to follow equilibria of organic compounds established in aqueous solutions using polarography: for very fast reactions, information can be obtained from shifts of half-wave potentials. For slowly established equilibria, the changes in the limiting current are followed. In both cases variation of the half-wave potentials or limiting currents with concentration of a reactant, present in excess, is followed. The types of reactions, which had been followed in this way, are as follows: hydration–dehydration equilibria, additions of hydroxide ion to carbonyl and nitroso compounds, the role of slowly established acid–base equilibria involving C-acids; further also reactions involving the addition of ammonia, primary amines, hydroxylamine, and hydrazine to carbonyl compounds.

Nitrogen excretion in germ-free and conventional chickens: effects of an alkali load

1978 ◽  
Vol 39 (1) ◽  
pp. 99-104 ◽  
Author(s):  
J. Okumura ◽  
D. Hewitt ◽  
Marie E. Coates
Keyword(s):  
Amino Acids ◽  
Uric Acid ◽  
Ammonia Excretion ◽  
Nitrogen Excretion ◽  
Acid Base Balance ◽  
Acid Base ◽  
Total N ◽  
Germ Free ◽  
Base Balance ◽  
Micro Organisms

1. Groups of three colostomized germ-free (GF) and conventional (CV) chickens aged 4 months were maintained for successive periods of 8 d on a diet containing 200 g casein/kg without and with sodium bicarbonate at the rate of 20 mmol/d and a nitrogen-free diet without and with NaHCO3at 9 mmol/d. Urine and faeces were collected during the last 3 d of each period.2. Total N, uric acid- and ammonia-N were determined in urine and total N in faeces. Amino acids were measured in hydrolysates of faeces collected during the periods when no NaHCO3was included in the diets.3. The CV birds excreted more N on the casein diets but less on the N-free diets than did their GF counterparts, the differences being mainly shown in the urine.4. On both diets hydrolysates of the faeces of CV birds contained smaller amounts of amino acids. On the N-free diet the proportions (g/160 g N) of serine, proline and threonine were reduced, suggesting some conservation of endogenous N by micro-organisms, and the proportions of histidine, alanine, lysine and methionine increased, possibly through microbial synthesis; on the casein diet, proportions of most amino acids were less, probably because bacterial deamination had occurred.5. Urinary excretion of total N, uric acid and ammonia was much greater on the casein than on the N-free diets. Inclusion of NaHCO3caused a sharp fall in urinary ammonia on both diets and in both environments.6. It was concluded that the level of dietary protein and the regulation of acid-base balance have more effect than microbial activity on the urinary ammonia excretion.

Nitrogen excretion and the uricolytic enzymatic system in the nephridia and hepatopancreas of the snail Xeropicta arenosa

1989 ◽  
Vol 67 (10) ◽  
pp. 2473-2477 ◽  
Author(s):  
Martha Kaloyianni ◽  
Maria Lazaridou-Dimitriadou
Keyword(s):  
Uric Acid ◽  
Chemical Analysis ◽  
Waste Product ◽  
Complete Sequence ◽  
The Other ◽  
Nitrogen Excretion ◽  
Radiochemical Analysis ◽  
Uric Acid Concentration ◽  
Enzymatic System ◽  
Waste Products

The quantitative and qualitative examination of the uricolytic system in the nephridia and hepatopancreas of the terrestrial snail Xeropicta arenosa showed the presence of all the metabolites of uric acid catabolism, and examination of the metabolites of the uricolytic system in the snails waste products revealed that uric acid was the main nitrogenous waste product excreted. Correlation of excretion capability with the age of the snails revealed that (i) uric acid concentration was nine times higher in the waste products of the juveniles than in those of the old snails, (ii) urea was detectable only in waste products of old snails, (iii) traces of ammonia were detected in the waste products of snails of both ages, and (iv) the amount of allantoin present in the old snails' nephridia and heart was significantly higher than in those of the juveniles. On the other hand, all snails, regardless of age, stored most uric in the nephridia. Uric acid nitrogen represented 1% of the total nitrogen in the nephridia. Data from chemical analysis were confirmed by radiochemical analysis and showed the existence of the complete sequence of uricolytic catabolites in the snails' waste products and nephridia.

scholarly journals Cyclodextrins: Structural, Chemical, and Physical Properties, and Applications

2021 ◽  
Vol 3 (1) ◽  
pp. 1-31
Author(s):  
Benjamin Gabriel Poulson ◽  
Qana A. Alsulami ◽  
Abeer Sharfalddin ◽  
Emam. F. El Agammy ◽  
Fouzi Mouffouk ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Chemical Properties ◽  
Aqueous Solubility ◽  
Industrial Applications ◽  
Physical And Chemical Properties ◽  
To Come ◽  
Novel Applications ◽  
Physical And Chemical ◽  
And Chemical Properties

Due to their unique structural, physical and chemical properties, cyclodextrins and their derivatives have been of great interest to scientists and researchers in both academia and industry for over a century. Many of the industrial applications of cyclodextrins have arisen from their ability to encapsulate, either partially or fully, other molecules, especially organic compounds. Cyclodextrins are non-toxic oligopolymers of glucose that help to increase the solubility of organic compounds with poor aqueous solubility, can mask odors from foul-smelling compounds, and have been widely studied in the area of drug delivery. In this review, we explore the structural and chemical properties of cyclodextrins that give rise to this encapsulation (i.e., the formation of inclusion complexes) ability. This review is unique from others written on this subject because it provides powerful insights into factors that affect cyclodextrin encapsulation. It also examines these insights in great detail. Later, we provide an overview of some industrial applications of cyclodextrins, while emphasizing the role of encapsulation in these applications. We strongly believe that cyclodextrins will continue to garner interest from scientists for many years to come, and that novel applications of cyclodextrins have yet to be discovered.

scholarly journals Acid-base regulation of hepatic glutamine metabolism and ureagenesis: study with 15N.

1993 ◽  
Vol 3 (7) ◽  
pp. 1416-1427
Author(s):  
I Nissim ◽  
C Cattano ◽  
Z Lin ◽  
I Nissim
Keyword(s):  
Isolated Hepatocytes ◽  
Glutamine Metabolism ◽  
Carbamoyl Phosphate ◽  
Acid Base ◽  
Ammonia Metabolism ◽  
Urea Production ◽  
Glutamine Synthesis ◽  
Series Of Experiments ◽  
15N Urea

The metabolism of (5-15N)glutamine and (2-15N) glutamine has been studied by isolated hepatocytes obtained from either control, chronically acidotic, or alkalotic rats. The main goal was to elucidate the mechanism(s) by which altered acid-base state affects hepatic ureagenesis from glutamine. Isolated hepatocytes were incubated in Krebs buffer (pH 7.4) supplemented with 0.1 mM ornithine plus either 1 mM (5-15N)glutamine or (2-15N)glutamine. To elucidate the role of glutamine cycling in net ammonia metabolism, a separate series of experiments were performed with 1 mM unlabeled glutamine plus 1 mM (15N)H4Cl. Net glutamine utilization was significantly lower in hepatocytes obtained from chronically acidotic rats compared with control or alkalotic rats. The sum of the rates of 15NH3 and (15N)urea production from (5-15N)glutamine was decreased in acidosis compared with alkalosis. After incubations of 50 min, approximately 75, 65, or 90% of the N in carbamoyl-phosphate was derived from the 5-N of glutamine in control, acidosis, or alkalosis respectively. In experiments with (2-15N)glutamine, the production of singly and doubly labeled (15N)urea as well as (15N)aspartate and (15N)H3 was significantly smaller in acidosis compared with alkalosis. Furthermore, a correlation was observed between production rates of (15N)aspartate and (15N)urea, suggesting that alterations in urea production may depend on aspartate formed from glutamine. However, the production of (15N)alanine was higher in acidosis compared with alkalosis with apparent correlation between the production of (15N)alanine and 2-oxoglutaramate, a product of the glutamine aminotransferase pathway. In addition, the rate of glutamine recycling was significantly higher in acidosis compared with control or alkalosis, indicating that both flux through glutamine aminotransferase and flux through glutamine synthetase were elevated in acidosis compared with alkalosis. These data suggest that decreased formation of aspartate from glutamine may limit ureagenesis in chronic metabolic acidosis. The formation of aspartate may depend on the availability of oxaloacetate rather than diminished flux through transaminase reaction. The enhancement of alanine production and glutamine synthesis may provide an alternate route of N disposal in cases of diminished urea formation.

Nutrition of algal-invertebrate symbiosis. I. Utilization of soluble organic nutrients by symbiont-free hosts

1974 ◽  
Vol 186 (1085) ◽  
pp. 357-368 ◽  
Keyword(s):  
Organic Compounds ◽  
Marine Invertebrates ◽  
General Phenomenon ◽  
Dissolved Nutrients ◽  
Aiptasia Pallida ◽  
Algal Symbionts ◽  
Photosynthetic Products ◽  
Organic Nutrients ◽  
Convoluta Roscoffensis

The uptake and utilization of organic compounds, known to be present in the photosynthetic products excreted by algal symbionts, has been examined in an aposymbiotic anemone, Aiptasia pallida , and newly hatched, symbiont-free larvae of the turbellarian, Convoluta roscoffensis . Results indicate that these compounds are rapidly assimilated by the hosts, and subsequently metabolized to provide both energy, and a source of stable cell constituents. The role of these metabolic patterns in intact associations is discussed, and the data is further related to the general phenomenon of dissolved nutrients in seawater, and their significance to the nutrition of marine invertebrates.

The role of acid–base equilibria in formal hydrogen transfer reactions: tryptophan radical repair by uric acid as a paradigmatic case

2017 ◽  
Vol 19 (23) ◽  
pp. 15296-15309 ◽  
Author(s):  
Leonardo Muñoz-Rugeles ◽  
Annia Galano ◽  
Juan Raúl Alvarez-Idaboy
Keyword(s):  
Electron Transfer ◽  
Uric Acid ◽  
Hydrogen Transfer ◽  
Transfer Reactions ◽  
Acid Base ◽  
Transfer Mechanisms ◽  
Hydrogen Transfer Reactions

The sequential proton gain electron transfer and proton electron sequential transfer mechanisms play the most important roles in tryptophan repair by uric acid.

The Excretory Role of Pteridines in Insects

1966 ◽  
Vol 45 (1) ◽  
pp. 1-13
Author(s):  
R. HARMSEN
Keyword(s):  
Uric Acid ◽  
Related Species ◽  
Pieris Brassicae ◽  
Soluble Nitrogen ◽  
Relative Role ◽  
Dry Storage ◽  
End Products ◽  
Quantitative Basis ◽  
Metabolic Mechanism

1. Previous work on the storage excretion theory of pteridines is summarized briefly, and the controversial aspects of this theory are discussed. 2. A general model for all nitrogen-containing substances in an animal body is presented. The possible pathways for pteridines in this model are discussed, and the storage excretion hypothesis is related to the model. 3. Storage and excretion of nitrogen-containing substances in Pieris brassicae were compared chromatographically on a quantitative basis. Only traces of the pteridines are excreted, the majority being stored, mostly in the adult cuticular scales. Only 20% of the uric acid is excreted; the xanthine is quantitatively stored in the fatbody. 4. Removal of part of the wing storage potential increases excretion and fatbody storage only very slightly. There is a reduction in overall pteridine synthesis. 5. A partly scaleless mutant, cerula, of P. brassicae also shows a slight increase in pteridine excretion coupled with an overall decrease in pteridine synthesis. 6. Vanessa io, a related species not containing large quantities of pteridines, was closely compared with P. brassicae. In Vanessa nearly half the pupal pteridines are excreted with the meconium, and no storage is found in the cuticular scales. 7. Several insects of other orders were investigated quantitatively. Only in some Hemiptera were pteridines found, stored in quantities comparable to those in Pieridae. 8. Using an ultra-micro Kjeldahl technique for total soluble nitrogen, the relative role of purines, pteridines, and some other minor substances, both in storage and excretion, was established. 9. It is obvious that in Pieridae the pteridines account for a much higher percentage of the total highly oxidized nitrogen produced (14%) than they account for in most other insects. The Pieridae differ further in storing most of these pteridines irreversibly in the cuticular scales of the adult. 10. The evidence strongly suggests that the Pieridae have evolved a metabolic mechanism of which pteridines are the general end-product as well as a mechanism of dry storage excretion for these end-products. 11. The pigmentation effect of cuticular pteridine deposition is considered a side-effect.

Characteristics Of The Structure Formation Of Gypsum Binder Modified With Zinc Hydrosilicates

2020 ◽  
pp. 40-46
Keyword(s):  
Synergistic Effect ◽  
Physicochemical Properties ◽  
Structure Formation ◽  
Silicic Acid ◽  
Chemical Properties ◽  
Crystal Formation ◽  
Ability To Act ◽  
Chemical Factors ◽  
Sorption Characteristics

The authors' methodic for assessing the role of chemical and physic-chemical factors during the structure formation of gypsum stone is presented in the article. The methodic is also makes it possible to reveal the synergistic effect and to determine the ranges of variation of controls factors that ensure maximum values of such effect. The effect of a micro-sized modifier based on zinc hydro-silicates on the structure formation of building gypsum is analyzed and corresponding dependencies are found. It is shown that effects of influence of modifier on the properties of gypsum compositions are determined by chemical properties of modifier. Among the mentioned properties are sorption characteristics (which depend on the amount of silicic acid and its state) and physicochemical properties - the ability to act as a substrate during crystal formation. The proposed method can also be extended to other binding substances and materials. This article contributes to the understanding of the processes that occur during the structure formation of composites, which will make it possible to control the structure formation in the future, obtaining materials with a given set of properties.

Sign in / Sign up

Export Citation Format

Share Document