An experimental study of biomaterials resistant to calcinosis and thrombosis]

Creation of hemocompatible materials resistant to calcinosis for plastic cardiosurgery call for employment of combined methods of their evaluation in experiment. The present study deals with some biochemical and physico-chemical aspects of biomaterial calcification inhibition on reduction of their porosity by means of N-vinylpyrrolidone, and also on immobilization of diphosphonates, phosphonates, and anti-aggregants. The method of radiation copolymerization was employed for immobilization of active agents. The effects of different biotissue specimens of varying modifications (pig aortal valves and cattle pericardium) and of Lavsan (polyethyleneterephthalate) on coagulation factor activation were studied in vivo (in goat) and in vitro. The specimen surface was inspected prior to and after the contact with blood and plasma using the techniques of scanning electron microscopy and photoelectron spectroscopy. The influence of the modifications on the calcium and phosphorus accumulation were studied after subcutaneous implantation of the specimens to rats, and the aggregating capacity of blood platelets was determined in incubation of Lavsan treated with an anti-aggregant. Combined studies revealed the optimal modification routine and the most active agents enabling one to obtain biomaterials that not only are resistant to calcification but also possess good hemocompatibility.     

An experimental and mathematical analysis of lymphopoiesis dynamics under continuous irradiation

A mathematical model describing the dynamics of lymphopoiesis in mammals continuously exposed to ionizing radiation has been developed. It is based on the theory of chalone regulation of hematopoiesis. The model comprises a system of nine differential equations. Results from the model were compared with our experimental data for bone marrow and blood lymphocytes of rats continuously exposed to gamma radiation in a wide range of dose rates. The model reproduces the lymphopoiesis dynamics that we observed in our experiment, in particular, the radiation hormesis at low dose rates, the reduction of lymphopoiesis at intermediate dose rates, and extinction of lymphopoiesis at high dose rates of continuous radiation. The possible explanation of the hormesis is suggested by the framework of the model. The model can be used for predicting the lymphopoiesis dynamics in mammals under continuous irradiation.     

Prognostic importance of the tumor receptor status in patients with ovarian cancer

Estrogen (ER), progesterone (PR), androgen (AR) and glucocorticoid (GR) receptor levels were assayed in 70 malignant epithelial ovarian tumors from untreated patients and in 23 malignancies from those receiving preoperative chemotherapy. Both PR+ and AR+ frequency and their mean levels in tumor were found to be relatively lower after preoperative chemotherapy. The prognostic significance of receptor status in tumor was identified: the efficacy of combined chemotherapy in PR- and RA- tumor patients was much lower as compared with PR+ and RA+ tumors; a 2-year recurrence-free survival of 12.5% and median duration of remission of 6 months were observed in the former group, while in the latter the disease-free survival rate was as high as 66.7%, and a median duration of remission had not been reached at 24 months of follow-up.     

The role of the hypophysis and STH in the regulation of the androgenic receptor level of the rat liver and in the realization of the sex-differentiating action of gonadal hormones

The role of the pituitary gland was investigated in the regulation of the level of rat liver androgenic receptors (AR) and in the realization of polydifferentiating action of gonadal hormones. The level of AR in the female and male rat liver was shown not to depend directly on the presence of the pituitary gland or STH administration. The pituitary gland is not a mediator in the realization of polydifferentiating action of androgens and estrogens. STH enhances the development of a positive effect of androgens on the level of AR.     

Properties of (Ala5, Orn9)-somatostatin. The inhibition of pancreatic and hypophyseal hormone secretion in cell culture

Ability of Ala5, Orn9-somatostatin to inhibit the secretion of insulin, glucagon, somatotropic hormone (STH) and prolactin was tested on the model of primary monolayer culture of isolated insular pancreatic and adenohypophyseal cells. Chemical substitution performed between positions 5 and 9 in somatostatin molecule failed to change essentially hormone's biologic activity in suppression of insulin and glucagon in the culture of pancreatic insular cells isolated from newborn rats. Somatostatin analog revealed its natural hormonal ability to inhibit STH secretion but failed to affect that of prolactin. The results are suggestive of the principal possibility to produce somatostatin biologically active analog through lyzine residue substitution in position 9 with obligatory simultaneous substitution amino acid residue in position 5.