Uric acid is involved in nitrogenous waste in animals, together with ammonia and urea. Uric acid has also antioxidant properties and is a surrogate marker of metabolic syndrome. We observed that the elevated plasma uric acid of high-fat fed mice was normalized by benzylamine treatment. Indeed, benzylamine is the reference substrate of semicarbazide-sensitive amine oxidase (SSAO), an enzyme highly expressed in fat depots and vessels, which generates ammonia when catalysing oxidative deamination. Ammonia interferes with uric acid metabolism/solubility. Our aim was therefore to investigate whether the lowering action of benzylamine on uric acid was related to an improvement of diabetic complications, or was connected with SSAO-dependent ammonia production. First, we observed that benzylamine administration lowered plasma uric acid in diabetic db/db mice while it did not modify uric acid levels in normoglycemic and lean mice. In parallel, benzylamine improved the glycemic control in diabetic but not in normoglycemic mice, while plasma urea remained unaltered. Then, uric acid plasma levels were measured in mice invalidated for AOC3 gene, encoding for SSAO. These mice were unable to oxidize benzylamine but were not diabetic and exhibited unaltered plasma uric levels. Therefore, activated or abolished ammonia production by SSAO was without influence on uric acid in the context of normoglycemia. Our observations confirm that plasma uric acid increases with diabetes and can be normalized when glucose tolerance is improved. They also show that uric acid, a multifunctional metabolite at the crossroads of nitrogen waste and of antioxidant defences, can be influenced by SSAO, in a manner apparently related to changes in glucose homeostasis., C. Carpéné ... [et al.]., and Obsahuje seznam literatury
14CO2 uptake in leaves of wheat plants (Triticum aestivum L.) fertilized by urea or Ca(NO3)2 (25 mol m-3) was investigated. The Warburg effect (inhibition of 14CO2 uptake by oxygen) under 0.03 vol. % CO2 concentration was observed only in non-fertilized plants. Under 0.03 vol. % CO2, the Warburg antieffect (stimulation of 14CO2 uptake by oxygen) was detected only in plants fertilized by Ca(NO3)2. Under saturating CO2 concentration (0.30 vol. %), the Warburg antieffect was observed in all variants. Under limitation of ribulose-1,5-bisphosphate carboxylase/oxygenase activity (0.30 vol. % CO2 + 1 vol. % O2), the rate of synthesis of glycollate metabolism products decreased in control and urea-fertilized plants but was enhanced in nitrate-fed plants. Hence, there was an activation of glycollate formation via transketolase reaction in fertilized plants, and the products of nitrate reduction function were oxidants in nitrate-fertilized plants whereas the superoxide radical played this role in urea-fertilized plants. and V. Chikov, G. Bakirova.
Our experiments on metabolic processes in the rumen were performed on sixteen 5-month-old lambs divided into 4 groups (defaunated - D, totally refaunated - T, partially refaunated - P and intact - 1). The absence or presence of protozoa in the rumen did not significantly affect the pH values. The greatest differences in NH3 concentration in the rumen before feeding were found between the T and D group (P<0.05). The animals of the T and I groups had higher NH3 concentrations than the D and P groups 1-5 hours after feeding (P<0.05 to PcO.OOl). Blood urea concentrations before and after feeding were significantly higher in the group I compared to the other groups (P<0.05 to PcO.OOl). Significant differences in the total nitrogen in rumen fluid were only found between groups D and I. The values of protozoan nitrogen in the rumen and their mutual relationship among the groups could be expressed by the following ratios: I>T>P>D. Proportions of the values of bacterial nitrogen followed in this order: D>P>T>I. The animals in group D had a significantly higher level of residual nitrogen than those in the other groups (P<0.05).
There is considerable evidence linking alcohol consumption and sedation and TRH in the brain septum. Moreover, innate septal TRH concentration is inversely related to the degree of ethanol preference. Recently we demonstrated in rats that four-week ethanol drinking increased the septal TRH content by 50 %. We had shown previously that ethanol induces neuronal swelling, which is known to evoke the secretion of hormones, peptides and amino acids from various types of cells. We have therefore explored the effect of hyposmotic medium and of 80 and 160 mM ethanol and 80 mM urea (both permeant molecules) in isosmotic and hyperosmotic (preventing cell swelling) media on the in vitro release of TRH by the rat septum. Lowering medium osmolarity resulted in a hyposmolarity-related increase in TRH secretion. Both ethanol and urea stimulated TRH release only in isosmolar solution. Our data indicate that ethanol in clinically relevant concentrations can induce TRH release from the septum by a mechanism involving neuronal swelling., J. Kučeorvá, V. Štrbák., and Obsahuje bibliografii