[Various routes of L-tryptophan transport in the small intestine of the chick]. / Razlichnye puti transporta L-triptofana v tonkoi kishke tsypliat.

Presence of two mechanisms in the accumulation of L-tryptophan by the mucosal cells of chicken small intestine was determined in vitro: sodium-independent and sodium-dependent those, the latter being of a major importance. Analysis of the accumulation kinetics in the linear stage showed that at the replacement of sodium with potassium ions in the incubation medium, a decrease of Kt (from 4.44 mM to 1.05 mM) as well as V (from 0.78 mM/min/cm to 0.12 mM/min/cm) occurs. High level of L-threonine, L-alpha-alanine, L-valine (100 mM) considerably inhibit the accumulation of L-tryptophan from 0.24 or 2.40 mM solution, the highest inhibition (78-96%) being related to the sodium-dependent transport mechanism. No considerable changes in Kt (4.0 mM) were observed in the saturated stage of transport whereas V showed a rapid decrease (0.22 mM/min/cm). Adding of modifier 0.64 mM L-alpha-alanine was followed by the increase both in Kt (5.71 mM) and V (0.37 mM/min/cm).

[The effect of sodium ions on amino acid and peptide assimilation in the small intestine of developing chicks]. / Vliianie ionov natriia na usvoenie aminokislot i peptidov v tonkoi kishke razvivaiushchikhsia tsypliat.

The absorption of free glycine and L-tryptophan as well as amino acids released in the hydrolysis of glycil-L-leucine and glycil-L-tryptophan was studied in vitro with accumulating preparations of intestinal mucosa of 1-65-day old chicken. Two ways of absorption of free and peptide amino acids were found: sodium-dependent and sodium-independent. Intensity of each of them depended on the age of chicken and was dissimilar for the compounds. The sodium-independent way is more important for glycine than for free amino acid. Absorption of glycil-L-tryptophan as well as its amino acids is mainly performed by the sodium-dependent way.

[Assimilation of free and peptide glycine in the chick small intestine]. / Usvoenie svobodnogo i peptidnogo glitsina tonkoi kishke tsypliat.

Absorption of free and peptide glycine released at the hydrolysis of glycyl-L-leucine, L-leucyl-glycine, glycyl-L-valine was investigated in experiments in vitro with accumulating mucosal preparations of the chick small intestine. An active accumulation of free amino acid occurred in the mucosa depending on sodium and oxygen presence in the incubation medium. The participation of sodium-dependent and sodium-independent components in the transport was revealed. Absorption of peptide glycine released at the hydrolysis of glycyl-L-leucine and glycyl-L-valine appeared to be a sodium-independent process and demanded the energy of aerobic metabolism. The data indicate the effect of various amino acids on the transport of free and peptide glycine. Activating effect of some of them on the absorption of glycine is supposed to be determined for this amino acid by a mechanism of exchange transport in the chick small intestine.

[Peptide interactions in the intestines of birds]. / Vzaimodeistvie peptidov v kishechnike ptits.

Interaction among various dipeptides was studied during their uptake in the mucosa of the small intestine of chicks. The effects observed were either inhibiting (L-valyl-L-valine inhibited the uptake of glycyl-L-alpha-alanine, glycyl-L-proline, L-leucyl-glycine, glycylglycine, and L-alpha-alanyl-L-alpha-alanine inhibited the uptake of glycyl-L-proline and L-leucylglycine) or stimulating (L-valyl-L-valine activated the uptake of glycyl-L-leucine), or neutral (L-alpha-alanyl-L-alpha-alanine exerted no significant effect on the absorption of glycyl-L-leucine and glycyl-L-valine). The amount and direction of the modifying effect depended on the agent concentration. Effects observed during the interaction of dipeptides and mixtures of free amino acids equimolar to them were identical. It is only possible if hydrolytic processes precede the transport and are closely related to them.

[Peptide transport and peptidase localization in the small intestine of chickens]. / Peptidnyi transport i lokalizatsiia peptidaz v tonkoi kishke tsypliat.

The mechanism of peptide transport was studied in vitro in the small intestine of chicks and accumulating preparations of mucosa using glycyl-1-tryptophan. A special criterion was proposed to differentiate the processes of intracellular and membrane hydrolysis of dipeptide basing on the analysis of transport intensity of amino acids released into the serosal solution after hydrolysis of dipeptide. 1-tryptophan released at hydrolysis was transported considerably more slowly than free amino acid. 1-tryptophan from the mixture with glycyne demonstrated the highest transport intensity in serosal solution as well as the highest accumulation in the mucosa cells from all forms of 1-tryptophan. At the same time the peptide form of glycyne was transported with the same intensity as that from the mixture with 1-tryptophan. According to the criterion applied it is supposed that unequal levels of 1-tryptophan and glycyne in the serosal solution prove the membrane hydrolysis of glycyne-1-tryptophan during ist transport in enterocytes.

[The effect of hydrocortisone on pancreatic hydrolase activity in hungry and fed chicks]. / Vliianie gidrokortizona na aktivnost' gidrolaz podzheludochnoi zhelezy u golodnykh i sytykh tsypliat.

Hydrocortisone was shown to prompt the accumulation of pancreatic enzymes taking part in the processing of food protein components in food-deprived chicks. The quality of the enzymes synthetized under hormonal induction does not differ from that in control groups.

[Hydrolysis and absorption of lysozyme in the small intestine]. / Gidroliz i vsasyvanie lizotsima v tonkoi kishke.

Preparations of chicken small intestine were used in the experiment in vitro simulating processes of membranous digestion (inverted intestinal segments) and absorption (inverted intestinal myasis). It was established that lysozyme was hydrolyzed on the internal mucosa surface regardless of its concentration in the gastro-intestinal tract, and only insignificant quantity of lysozyme (0.027%) penetrates the intestinal wall. The method of lysozyme determination through its action on the cellular wall of Micrococcus lisodeicticus, and highly efficient liquid chromatography were used to study the transport process. The data presented have evidenced that lysozyme is well hydrolyzed under the action of intestinal peptide hydrolyses, and only insignificant amounts of non-splitted lysozyme can penetrate the blood.

[Effect of ascorbic acid on the intestinal transport of glycine in chick].

The effect of different doses of ascorbic acid on the absorptive functions of the gut has been investigated in chicks. The study describes evidence for the existence of a H+/glycine symport system in chick intestinal brush border, because in sodium-free conditions acidification of the apical medium with ascorbic acid causes a dose-dependent stimulation of glycine absorption. Under the above circumstances, potassium acts as a non-essential activator of H+-dependence glycine cotransport. Our results also suggest that glycine uptake is stimulated in a lesser degree by inward sodium gradient. Ascorbic acid stimulation of glycine uptake from K+- free sodium abundant media was diminished, when the dietary level of ascorbic acid was increased to 2000 mg in 1 kg of food. This may result from conformational change in the Na(-)-dependent glycine transporter protein that lowers glycine binding site affinity induced by the over-acidification of the gut lumen. In addition, there was a possible competition between sodium-dependent glycine and ascorbic acid transporters for sodium.

[Response of glycine and glycyl-L-valine uptake parametrs across in vitro everted sacs of chicken gut to variations in oxygenation rate and fasting].

Energy-dependent accumulation of glycine and glycyl-L-valine within the small intestinal mucosa in a chicken model of in vitro local oxygenation of the small intestinal preparation was studied. It has been shown that the most effective bilateral oxygenation significantly increase accumulation of glycyl-L-valine in the proximal segment as compared to that under oxygenation only from serosal surface both in the fed and 24-hour fasted chickens, whereas in other segments these differences was less apparent. This may be due to increased H+/ peptide cotransporter expression in the proximal segment. Thus the bilateral oxygenation probably may turn on an additional amount of already existing (but non-functional during serosal oxygenation) H+/ peptide co-transporters. Moreover, low glycine transporter expression may be the reason why supplemental oxygen (bilateral oxygenation) has no effect on glycine accumulation in the distal segment of fed chickens. A 48-hour fasting decreases glycyl-L-valine accumulation in the proximal (and medial) segments, possibly due to progressive decrease in villus height. It is concluded that: a) the accumulation rate of glycine was greater when presented as the glycyl-L-valine than when presented as the equivalent amount of free amino acid; b) the rates of accumulation of glycyl-L-valine are highest in the proximal segment, decrease in the medial segment and are the lowest in the distal segment; c) the serosal oxygenation is less effective than the mucosal and bilateral oxygenation, which markedly stimulates accumulation of nutrients in the intestinal mucosa; d) a 24-hour fasting increases glycyl-L-valine accumulation in the proximal segment only, while glycine uptake was increased in the distal segment.

[Coupling of protease activity and sodium loading with intestinal absorption of amino acids].

Membrane-bound serine proteases to play a certain role in activation of sodium transport in epithelial cells. To were found explain the protease activity and sodium-dependent L-tryptophan transport across chicken small intestine interaction, four experiments were conducted. One hundred chicks were fed diets that contained 0; 0.3; 3 or 6% of supplemental NaCl and were given distillated water ad libitum. Signs of salt toxicity observed were as follows: a decreased body weight, increased heart and kidney weights, formation of secondary lysosomes in enterocytes and lymphocytes. Such chickens were in the state of negative nitrogen balance. Intestinal absorption of L-tryptophan correlated with mucosal protease activity during increased dietary sodium chloride intake. Recent in vitro and in vivo experiments indicate that enterocyte proteases may be of critical importance in activation of sodium-dependent intestinal transporters for L-tryptophan.

[Effects of natural (zinc, vitamin E) and synthetic (diludin) antioxidants on the intestinal permeability in chicks with vitamin A deficiency]. / Deistvie prirodnykh (tsink, vitamin E) i sinteticheskikh (diludin) antioksidantov na pronitsaemost' kishechnogo bar'era u tsypliat pri nedostatochnosti vitamina A.

The main concern of this work was to examine the relation between altered antioxidant status on the one hand and increase in L-tryptophan absorption in the small intestine in order to bring further information regarding to possible role of vitamin A and zinc to maintaining of intestinal epithelial barrier integrity, on the other hand. In control, only some ideal tight junctions at the tip of the villi were permeable to ZnC1(2), whereas in A-hypovitaminosis permeability increased significantly. Studies demonstrate that an increased L-tryptophan accumulation in the intestinal mucous may result from a free radical damage to the mucous surface with formation of "leaky" junctions in the ilea. The results suggest that the zinc plays a crucial role in stabilizing biomembranes.

[The characteristics of amino acid transport in the small intestine of chicks with avitaminosis A]. / Osobennosti transporta aminokislot v tonkoi kishke tsypliat v usloviiakh A-avitaminoza.

An increased amino acid absorption occurred early in chicks in the vitamin A deficiency. This data suggests an effect of the vitamin A upon differentiation of amino acid channels within apical membrane of the absorbing cells.

[Alternative paths of zinc transepithelial transport in the small intestine]. / Al'ternativnye puti transépitelial'nogo transporta tsinka v tonkoi kishke.

Interrelations among changes in 11-oxycorticosteroids (11-OSC) in blood plasma, catecholamines (CA), and acetylcholinesterase (AChE) activity in nerve fibres of the thymus, as well as qualitative content and proliferative capacity of thymic and blood cells under the effect of the rat recombinant interleukin-1 beta (IL-1 beta) normally and under conditions of hypothalamic-pituitary-adrenocortical depression, were studied. The changes were the most obvious within 15 and 120 min following the IL-1 beta administration: elevation of the 11-OSC, increase in the CA content, and decrease in the AChE activity in thymic nerve fibres. Preliminary administration of dexamethasone prevented the effects.

[Effect of various methods of oxygenation in the isolated small intestine on the tryptophan and glycine accumulation]. / Vliianie razlichnykh sposobov oksigenatsii izolirovannoi tonkoi kishki na intensivnost' akkumuliatsii triptofana i glitsina.

The impact of various oxygenation types of intestinal preparations (mucosal, serosal and bilateral) on the transepithelial transport of amino acids and peptide according to the character of amino acids, their stereoisometry, incubation time, intestinal gradient and other factors, was investigated in fowl. Against-the-gradient-transport of L-tryptophan and glycine was observed at various oxygenation types, and its intensity decreased in the following sequence: bilateral, mucosal, serosal oxygenation. At various oxygenation types, the accumulation of L-tryptophan occurs more efficiently than that of DL-tryptophan and D-tryptophan. Using an in vitro bilateral intestinal oxygenation model system, we have demonstrated the plasma membrane of enterocyte microvilli to be rapidly impaired after oxidative stress. Glycine, but not L-tryptophan, attenuates oxidative injury in brush border membrane and alterations in amino acid transport activity. Overall, our data indicates that in vitro serosal oxygenation of the duodenum markedly improves glycine absorption, possibly involving the basolateral transporters.

[The role of zinc in the iliac absorption of various L-tryptophane forms in chickens]. / Rol' tsinka v protsesse vsasyvaniia razlichnykh form L-triptofana v podvzdoshnoi kishke tsypliat.

Zinc was found to enhance absorption of free and "peptide" L-tryptophan across the chick mucosal brush border. Intestinal absorption of free L-tryptophan can be partially inhibited by excessive amount of zinc. The findings suggest that zinc interacts with free and "peptide" L-tryptophan transports protecting them against degradation.