Biocompatibility and Bioresorption of 3D-Printed Polylactide and Polyglycolide Tissue Membranes.

We studied biocompatibility and bioresorption of 3D-printed polylactide and polyglycolide tissue membranes. Ultrasound microscopy and histological examination showed that membranes fabricated of a copolymer of lactic and glycolic acids in a mass ratio of 1:9 are bioresorbed and have good biocompatibility with soft tissues (connective tissue, adipose tissue, and epithelium). An important feature of the copolymer membranes, which differs them from pure polylactide membranes, is the formation of a thin fibrous capsule that did not interfere its destruction by the mechanism of hydrolytic resorption.

[Orthotopic bone implants for bone regeneration].

Biotechnology industry is rapidly developing. The elaboration of new biomaterials for bone reconstruction is one of the most perspective directions in tissue engineering. There are millions of surgical operations associated with use of bone graft materials every year.

[Chemiluminescence of daphnia cultivating medium and optimization of conditions for its determination].

The article deals with the optimization of conditions for the chemiluminescence determination. The Daphnia habitat was shown to have no spontaneous chemiluminescence. This was revealed using hydrogen peroxide and luminol, the optimal concentrations of which were 23 and 1.

[Electrochemical sensor based on photopolymeric membranes for determining urea].

A new electrochemical enzymatic sensor based on the ion selective field effect transistors (ISFETs) and photocurable membrane was developed for the determination of urea. For the immobilization of urease on the gate surface of the ISFET a simple method, involving the use of liquid photocurable compositions on the basis of vinylpirollidone, oligouretanemetacrylate and oligocarbonatemetacrylate, was applied. The linearange of the response of the developed electrochemical sensor lies in the range 0.

[Exchange of vitamin D3 in placenta and fetal liver].

Metabolism of [3H]-vitamin D3 in placenta and fetus liver of rats on the 20-21st day of pregnancy was investigated. Biosynthesis in vivo of 25-hydroxyvitamin D3 occurs in placenta and fetus liver and the maximum observed 25-hydroxylation composes 15% in placenta and 13% in the fetus liver. It has been shown, that C-25-hydroxylation of vitamin D3 in the microsomal and mitochondrial fractions of hepatocytes take place.

[Vitamin D3 metabolism in the liver of pregnant rats].

The exchange of vitamin D3 in the liver of pregnant rats has been studied. Incorporation of (3H)-vitamin D3 into the liver of pregnant rats on the 13th and 21st day of pregnancy made up 85% and 90% respectively of the intensity of absorption of the summary label by controlled animals. It is found that the period of exchange of (3H)-cholecalciferol in these animals increases with prolongation of pregnancy.

[The effect of unilateral nephrectomy on vitamin D metabolism in pregnant rats].

Unilateral nephrectomy causes a decrease in provision of vitamin D dihydro derivatives in pregnant rats, which correlated with the development of hypocalcemia and hypophosphatemia as well as with an increased content of parathyroid hormone. Fetuses of these females contained less amount of mineral components and active metabolites of vitamin D. Neonates, being born by these females with the nephrectomy, had vitamin D deficiency, which was manifested as a decrease in content of active vitamin D metabolites and minerals as well as an increase in activity of alkaline phosphatase and in the content of parathyroid hormone.

[Erythrocyte membrane proteins in experimental D-hypovitaminosis].

Content of rat erythrocyte membrane proteins was studied in experimental rickets as well as during treatment of the disease with various doses of vitamin D3. Distinct alterations in content of spectrin and protein 3 simultaneously with approximately constant level of membrane total proteins were observed in D-hypovitaminosis. Composition of main membrane proteins tended to be normalized after administration of vitamin D3 (400 IU) into the animals with experimental rickets within 10 days, while the vitamin at a dose exceeding 100-fold the physiological requirements, caused a decrease in the content of membrane proteins.

[Effects of sterols having different chemical structure and squalene on osmotic resistance of erythrocytes].

The effects of sterols having different chemical structure and squalene on osmotic resistance of erythrocytes were studied. Changes in sterol and squalene content in the membranes were induced by incubation of erythrocytes with liposomes containing the additive. A decrease of the osmotic resistance of erythrocytes was shown to correlate with a cholesterol decrease in the membranes.

[Disturbanes in electrostatic balance of erythrocyte membranes in experimental D-hypovitaminosis].

Violation of electrostatic balance in the erythrocyte membranes with experimental D-hypovitaminosis is determined by the method of potentiometric titration. It is pronounced in modification of quantity and pK of accessible polar groups and in a decrease in total membrane electronegative charge. This violation is supposed to be provoked by a considerable increase in cholesterol content in the membranes and to reflect a modification in the character and bond strength of protein lipid complexes caused by interaction of cholesterol with membrane components.

[Lipids bound with blood plasma proteins in normal state and in experimental rachitis].

The lipid composition of transport and specific proteins was studied in normal state and with experimental rachitis. The amount of phospholipids in blood plasma proteins control animals is established to decrease as follows: albumins, immunoglobulins, alpha, beta-globulins, fibrinogen. The bulk of cholesterol and its ethers, lanosterol and squalenepare bound with albumins and alpha-, beta-globulins.

[Effect of sterols on erythrocyte membrane properties in experimental rickets].

Experimental rickets in rats was accompanied by a distinct increase in content of cholesterol and its esters, scvalene, lanosterol and 7-dehydrocholesterol in erythrocyte membranes with simultaneous decrease in content of total phospholipids. The alterations in lipid composition of erythrocyte membranes led to an increase in osmotic stability, to a decrease in glucose utilization and 45Ca incorporation into the erythrocytes. Acidic erythrogramms indicated an appearance in circulation of erythrocytes resistent to the effect of acidic hemolytics.

[Sterol content of rabbit erythrocyte membranes normally and in atherosclerosis].

The sterol composition of erythrocyte membranes was studied in norm and under experimental atherosclerosis. It is shown that in the normal animals the content of cholesterol in the membranes increases with age and practically reaches a relatively constant value by 5-6 months. In the experimental animals being on the atherogenic diet the amount of cholesterol in the membranes a month later is practically identical to the control.