[Stimulating effect of vitamin A on the absorption and metabolism of zinc in chicks]. / Stimuliruiushchee deistvie vitamina A na obmen i vsasyvanie tsinka u tsypliat

Zinc metabolism and absorption were examined in chicks of two groups that differed in vitamin A supply. Five week chicks that were given a diet without an addition of vitamin A showed overt symptoms of A-avitaminosis. The condition was followed by marked changes in the zinc metabolism and absorption in the intestine and by insignificant changes in the calcium metabolism. Vitamin A was administered per os at a dose of 24,000 i. u. (in oil) and 72 hours later zinc absorption in the ileum increased noticeably and zinc balance in the body became positive.

[Rapid biological method for assessing D-vitamin supply of chicks]. / Biologicheskii ekspress-metod otsenki D-vitaminnoi obespechennosti tyspliat.

A segment of the small intestine of chicks turned inside out and pulled on a glass rod was placed into a buffer solution. The Ca2+ consumption from the solution was monitored, using the color murexide reaction. The Ca2+ binding during the first 5 min was much higher in the chicks well supplied with D-vitamin than in the D-vitamin deficient chicks. The level of binding was determined by the content of specific calcium-binding protein in the intestinal mucosa. A close correlation between the dosage of D3-vitamin and the amount of Ca2+ consumed by the intestine from the solution and bound with the mucosa was established. These findings together with the simplicity of the procedure suggest that measurement of the calcium binding capacity of an intestinal segment can be used as a rapid method of assaying the D-vitamin status of the animal.

[Plasma zinc content in patients with chronic renal insufficiency before and after kidney transplantation]. / Soderzhanie tsinka v plazme bol'nykh khronicheskoi pochechnoi nedostatochnost'iu do i posle transplantatsii pochki.

Zinc content in blood plasma was measured in patients with chronic renal failure (CRF) before and after kidney transplantation by atomic-absorption spectrophotometry. Plasma zinc was revealed to be lowered. However, routine intake of vitamin A by the patients led to an elevation in zinc content. Hemodialysis did not alter blood plasma zinc concentration. It was noted that during the postoperative period, the zinc level returned to normal. Patients with CRF show marked disturbances of taste sensitivity, which are manifested in the increased threshold of taste sensitivity and perversion of taste sensations.

[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.

Vitamin-A-dependent zinc-binding protein and intestinal absorption of Zn in chicks.

It was demonstrated that the development of experimental avitaminosis A in chicks led to secondary zinc deficiency. The balance of Zn in the chick became negative, while the Zn content of various tissues decreased. Thus in vitamin-A-deficient chicks the serum Zn content was 1258 (SD 26.3) micrograms/l which was considerably lower than 1652 (SD 97.8) micrograms/l in controls. Zn absorption was considerably reduced throughout the entire small intestine of vitamin-A-deficient chicks and most markedly in the ileal region. Within 72 h after retinyl acetate administration Zn absorption was fully restored in this region of the intestine. The 65Zn-binding capacity of soluble proteins, present in the supernatant fraction of ileal-mucosa homogenates of vitamin-A-deficient chicks, was found to increase 2.6 times by 72 h after the administration of a single dose of retinyl acetate. A vitamin-A-dependent Zn-binding protein (ZnBP), absent in vitamin-A-deficient chicks, was isolated from the ileal mucosa after their repletion with vitamin A. Competitive-binding studies (calcium, cadmium, copper) showed the protein to be highly specific for Zn ions. The molecular weight of ZnBP was 83 kDa. The association constant of the protein-Zn complex was 0.8 X 10(6)/mol. The protein was acidic with approximately 20% of its amino acid residues belonging to dicarboxylic acids. ZnBP was found to be a glycoprotein, and it contained hexose as a carbohydrate component. It is suggested that ZnBP is involved in the binding of Zn in the ileal mucosa of chicks.

[Disorders of zinc transport through the ileal epithelium in vitamin A deficiency and ischemia]. / Narushenie transporta tsinka cherez épitelii podvzdoshnoi kishki pri A-avitaminoze i ishemii.

By means of histochemical revealing of zinc and applying radioactive isotope 65Zn accumulation, absorption and distribution of cations of this metal in the mucous membrane of the iliac intestine have been studied in chicken, normal, at ischemia and at A-avitaminosis. An essential zinc-depositing ability is peculiar to coverings of mucus upon the intestine epithelium, and among intracellular components--to smooth endoplasmic reticulum. A-avitaminosis and especially ischemia result in increasing permeability of the apical part of the external membrane of epitheliocytes, in overloading of the latter with zinc cations, when they are introduced into the intestine, as well as in decreasing transepithelial transport of zinc. The changes mentioned are accompanied with certain disturbances in the barrier function of the intestinal epithelium.

[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.

[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.

[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.

[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.

[Morphofunctional analysis of zinc-accumulating capacity of digestive system organs]. / Morfofunktsional'nyi analiz tsinkdeponiruiushchei sposobnosti organovpishchevaritel'noi sistemy.

The distribution of zinc and related changes have been studied in zinc--loaded chick pancreas, ileum and liver at the ultrastructural level by sulphide--silver method. White Leghorn chicks fed a high zinc diets (50, 500, 1000, 2000 and 4000 mgZn/kg diet) for 6 weeks, were killed at intervals; portions of their organs were fixed for light and electron microscopy; other samples were analyzed for zinc by AA spectrophotometry. A drastic increase of zinc level in chick pancreas fed 2000 mg Zn/kg diet (as ZnCl2) was associated with acinar cell degeneration. Apoptosis was the predominant form of acinar cell deletion. This study provides support for a previously proposed theory that cell injury stimulates passive zinc accumulation.

[Absorption and localization of zinc in the ileum of chicks dependent on provision with vitamin A]. / Vsasyvanie i lokalizatsiia tsinka v podvszdoshnoi kishke tsypliat v zavisimosti ot obespechennosti ikh vitaminom A.

Vitamin A increase the accumulation and transport of zinc in the chick ileal mucosa. Regulating effect of this vitamin on the mentioned processes was already observed in the initial stage zinc uptake in the intestinal mucosa--its storage in the mucus layer. Stimulation of zinc absorption by vitamin A can be related to a specific carrier-vitamin A-dependent zinc-binding protein. Presence of zinc in the smooth endoplasmic reticulum of the enterocyte apical zone suggests the role of this organelle in the cation homeostasis in the cell.

[Direct stimulatory action of blood serum, vitamin D3, and its hydroxy-analogs on calcium transport in the small intestine of chicks in vitro]. / Priamoe stimuliruiushchee deistvie syvorotki krovi, vitamina D3 i ego oksi-analogov an transport kal'tsiia v tonkoi kishke tsypliat in vitro.

A study was made of the effect of blood serum, vitamin D3 and its hydroxy-analogs (25-hydroxyvitamin D4. 1 alpha-hydroxyvitamin D3) on Ca2+ transport across the wall of the noninverted small sac of D-avitaminosis chicken during incubation in vitro. It was shown that blood serum from chickens fed vitamin D3 in different doses (50--20 000 IU) and at varying time (1--72 h) before sacrifice produced a marked stimulating action on the cation transport 10 min after administration into the intestinal cavity as compared with the effect produced by the serum from D-avitaminosis chickens. Administration into the intestine of vitamin D3 or its hydroxy-analogs in physiological doses (6.25--25.0 ng) also significantly stimulated Ca+ transport over 10 min of incubation.