[Study of nutritive value of modified casein].

It has been shown that modified casein purified from carbohydrate components contains several times less phosphorus and calcium as compared to initial casein. Figures close to experimental and potential biological value were obtained in experiments on growing rats with modified and initial casein as a protein component-milk substitute.

[The experimental effect of growth stimulants on protein assimilation].

In experiments on rats it was established that the compound CAM-300 in a dose of 2 mg/kg did not induce body mass growth, protein biological value increase or pepsinogen concentration change in the gastric mucosa. Fenobolin stimulation of growth in the experimental animals was attended by a three-fold rise in pepsinogen concentration in the gastric mucosa, the pure utilization of protein being unchanged. The action of the compound 6-(6,10-dioxyundecyl)-beta-resorcin acid gamma-lacton (International Minerals Corporation) did not change biological value and the pure utilization of protein, pepsinogen concentration in the gastric mucosa was slightly lowered.

[Characteristics of proteolysis in the gastrointestinal tract in the early postnatal period].

The activity of proteinases was increased, when we used experimental casein for artificial feeding of newborn rats. Control casein contained in milk substitutes delayed protein evacuation from the stomach. The activity of intestine pancreatic proteinases was increased when we used experimental casein and decreased, for control casein.

[Initial stages of protein assimilation in artificial feeding in an experiment].

The content of pepsinogen in the gastric mucosa and acid phosphatase activity in the gastric chyme are adaptively altered in animals with change from natural to artificial feeding. This change is attended by redistribution of gly-gly-dipeptidase activity along the small intestine. It has been established that fibrinogen and casein are characterized by similar values of the compensation coefficient.

[Protein assimilation and acid proteinases in the postnatal gastrointestinal tract in experimental studies].

Proximal-distant gradient of the lysosomal proteinase activity distribution is observed in the mammals at the postnatal period of development. In various species of mammals the proximal-distal gradient of the lysosomal proteinase distribution is attended by the shift of the final stages of the intestinal digestion to the distal part of the small intestine. These features are typical of the protein digestion in the mammals at the postnatal period of development.

[Proteolysis of blood plasma proteins in the stomach in early ontogeny].

Proteolysis of milk substitutes containing fibrinogen, casecid and bovine serum albumin as protein components was studied. Artificial feeding of newborn rats has shown high casecid and fibrinogen utilization. Casecid and fibrinogen contained in milk substitutes delayed protein evacuation from the stomach, while bovine serum albumin intensified protein evacuation.

[Comparative study of splitting of fibrinogen and bovine serum albumin by digestive proteinases].

Fibrinogen attackability by digestive proteinases rises insignificantly after thermodenaturation and does not change after exposure to the denaturation action of urea. The degree of fibrinogen splitting by digestive proteinases is considerably lower as compared to that of the globular protein such as bovine serum albumin.

[Characteristics of protein digestion in artificial feeding in an experiment].

It has been established that during artificial feeding with milk substitute containing different protein components (casecite, bovine serum albumin, fibrinogen), the proximal-distal gradient of cavitary digestion of proteins is observed, with this gradient being more demonstrable as compared with natural feeding of postnatal animals. It has been shown that during experimental natural feeding, the proximal-distant gradient is observed in the distribution of acid proteinases in the small bowel, whereas during artificial feeding one can see a uniform distribution of acid proteinases in the proximal and distal parts of the small bowel. The activity of acid proteinases in the gastric mucosa of 18-day-old animals kept on natural feeding does not differ from the activity of these proteinases under artificial feeding with a substitute containing casecite as protein component.

[Lysosomal proteinase activity and the the lysosomes of the small intestine in postnatal ontogeny].

It has been shown that in postnatal animals, the activity of lysosomal proteinases in the distal part of the small intestine was considerably higher than in the proximal one. With transition from milk to definitive nutrition, the activity of lysosomal proteinases gets equalized in the proximal and distal parts of the small intestine. The data concerning the proximo-distal gradient of distribution of the activity of lysosomal proteinases have been supported.

[Proteolysis of milk proteins in young children].

Distinct pancreatic activity was observed in duodenal chyme of newly born children. Rapid evacuation of protein from stomach was noted in artificial feeding. The tryptic activity was increased in duodenal contents after the introduction of artificial feeding.

[Experimental study of the gastric digestion of milk proteins and the lysosomal proteinases in young animals].

The content of proteinases (proenzymes of pepsin and rennin) in the stomach of newborn rats was found to be significant. However, the proteolytic activity in the gastric contents during milk feeding proper (the first 12 days of life) was fairly low. The activity of marker lysosomal enzymes (acid phosphatase and cathepsins) in lysosomal fraction isolated from the gastric mucosa of the newborn animals was 2 times higher than that seen towards the end of milk feeding.

[Lysosomal proteinase activity in the small intestine in postnatal ontogeny].

A lysosomal fraction was isolated from various parts of small intestinal mucose of rats at postnatal periods of growth as well as from adult animals. Activity of marked lysosomal enzymes (acid phosphatase and cathepsins) was 3-fold higher in ileum than the jejunum of young rats at the lactation periods of growth. In adult animals the enzymatic activity was similar both in proximal and distal parts of small intestines.

[Experimental study of lysosomal proteinase activity of the gastric mucosa at an early age].

It was established that during milk feeding of rats, the lysosomal fraction of the gastric mucosa shows an appreciable amount of acid phosphatase and cathepsins. By the end of milk feeding their activity reduces more than 2-fold. In adult animals, activity of lysosomal proteinases was slightly higher than in 20-day-old rats but significantly lower than in 3-day-old ones.

[Characteristics of hydrolytic protein breakdown at an early age].

Proteolysis of milk proteins occurring within the gastrointestinal tract was distinctly manifested in young rats during the period of milk feeding as shown by gel filtration of nitrogenous components from contents of various parts of small intestine of 3, 20 and 30 days old rats as well as by means of ion exchange chromatography of free amino acids and estimation of their concentration and the rate of the amino acids liberation after incubation of the content of these parts of the intestine in vitro. In 3-20 days old rats the cavitary proteolysis was competed in the distal part of small intestine, in adult animals--in the proximal part. The amino acids might be divided into two groups: the rapidly liberated substances (leucine, isoleucine, lysine, arginine, tyrosine, serine) and the slowly liberated compounds (proline, glutamic and aspartic acids).

[Milk protein digestion and lysosomal proteinases of the ileal mucosa in young rats].

The proteolytic activity of lysosomal and pancreatic proteinases was studied in the chyme and tissue homogenates of the jejunum and ileum of 12- and 30-day rats in order to elucidate whether lysosomal proteinases of the mucous membrane of the ileum participate in cavitary digestion. During milk feeding the proteolytic activity of acid (lysosomal) proteinases in the ileum was 3 times greater than in the jejunum, which has been demonstrated both for the mucous membrane and the contents of these parts of the small intestine. In rats on definitive nutrition the activity of acid proteinases from the jejunum and ileum remained almost unchanged both in the mucous membrane and in the contents.

[Trypsin and chymotrypsin activity during early postnatal development in the rat].

Activities of trypsin and chymotrypsin were studied in pancreas as well as in chyme from three departments of small intestine of rats of various age. Distinct decrease in content of chymotrypsinogen and increase in content of trypsinogen were observed in pancreas at first four days of rat life. In pancreas content of trypsinogen and chymotrypsinogen was as high in 4--20 days old rats as that one in 30-days old animals, maintained at definitive diet.

[Characteristics of milk protein digestion in the early postnatal period of development].

It is found that in the period of the 1st to the 20th day of life there takes place shifting of the cavitary digestion of milk proteins toward the distal part of the small intestine. The change-over from the milk to the definite alimentation is accompanied by a shift of the process of the milk proteins digestion to the proximal part of the small intestine. The jejunum chyme of the 3, 12 and 20-day old rats contains roughly equal amounts of free amino acids, whereas in the jejunum chyme of the 30-day old animals their concentration is twice as high.

[Milk protein digestion in the stomach at an early age].

In the mucosa and gastric contents of young rats proteolytic activity was investigated. The pepsinogen content in the mucosa and proteolytic activity of the gastric contents does not change over a period from the 1st till the 11th day and then abruptly increase. A change-over from milk to mixed nourishment in the period from 12 to 20 days of life is attended by a growing pepsinogen content and a drastically reduced prorennin content in the gastric mucosa.