Yordanka Martinova

The effect of in vitro fibroblast growth factors on cell proliferation in pancreas from normal and streptozotocin-treated rats

Fibroblast growth factors (FGFs) are potent mitogens for a wide variety of cells. In the present study we examined the potential morphogenic activities of the growth factors FGF1, FGF2 and FGF7, and cellular processes underlying morphogenesis, in pancreatic cells from streptozotocin diabetic newborn rats. The pancreases from control and diabetic newborn rats were microdissected and cultured in the presence of different doses of FGF1, 2 and 7 for 48 h. An additional incubation for 24 h was undertaken in the presence of bromo-deoxyuridine. The effect of the FGFs on bromo-deoxyuridine incorporation was analysed by means of immunocytochemistry. The most prominent stimulatory effect was found after application of FGF2 and 7 at a dose of 100 ng/l in endocrine and exocrine cells of diabetic rats. It is concluded that FGF2 and 7 might act as putative key-signalling molecules in the differentiation of pancreatic cells.

Role of FGF1, FGF2 and FGF7 in the development of the pancreas from control and streptozotocin-treated hamsters.

Abstract.  Although progress has been made with respect to the growth and transcription factors implicated in pancreatic development, many questions remain unsolved. It has been established that during embryonic life, both endocrine and acinar cells are derived from pancreatic epithelial precursor cells. Growth factors control the proliferation of precursor cells and their ability to differentiate into mature cells, both in pre‐natal and in early post‐natal life. Pancreatic development during the early post‐natal period is an area of great interest for many scientists. In this study we have examined the structure characteristics, functional and proliferative activity of control and diabetic hamster pancreatic ductal, exocrine and β cells, following treatment with FGFs 1, 2 and 7 in vitro. Light and electron microscopic studies indicated active synthetic processes in these cells under the influence of the investigated FGFs. In our experimental model of diabetes, the labelling index of the cells was significantly higher than in corresponding control groups of hamsters. We established that FGF2 at a concentration of 10 ng/l was responsible for the most prominent effect on ductal cells and β cells in the diabetic groups. FGF1 at a concentration of 10 ng/l displayed the highest stimulatory effect on exocrine cells in the diabetic groups at post‐natal day 10. Taken together these data strongly suggest that FGF1 and FGF2 induce proliferation of pancreatic epithelial cells during the early post‐natal period whereas FGF7 is not strictly specific for pancreatic cell proliferation.

Species-specific effect of proteins secreted by cultured pre-pubertal rat Sertoli cells on natural killer cell activity

The effect of proteins secreted by cultured pre-pubertal rat Sertoli cells (pSCP) on natural killer (NK) cell activity of rat, mice and guinea pig splenocytes and human peripheral blood lymphocytes was estimated. The results indicate that pSCP inhibited, in a dose-dependent manner, NK cell activity of mice, guinea pig and human lymphocytes but did not suppress lysis of YAC-1 target cells by rat NK cells. Species-specific differences in the effect of pSCP on NK cell activity probably result from differences in the binding of proteins within the effector cells. These data indicate that in the pre-pubertal period of gonadal development immature Sertoli cells synthesize a factor/s which might contribute to the maintenance of specific testis immunological environment.

Miltefosine decreases the cytotoxic effect of epirubicine and cyclophosphamide on mouse spermatogenic, thymic and bone marrow cells

A new class of potent anticancer drugs, alkylphosphocholines has been recognized lately. Miltefosine (Hexadecylphosphochlorine, HPC) has been found to express select antineoplastic effect on human breast cancer skin metastases with simultaneous preservation of bone marrow proliferative activity and low clastogenicity. In the current study, we present data about the specific effect of two widely used cytostatics Cyclophosphamide (CP) and Epirubicine (ERb) applied separately or in combination with Miltefosine. C57BL6 mice were treated per os or intraperitonieally in doses corresponding to that in clinical use. Morphological, autoradiographic, ultrastructural and cytogenetic studies on spermatogenic, thymic and bone marrow cells were performed. It is found that compared with separate application, combinations of ERb or CP with Miltefosine slightly decreases spermatogonial proliferation and exerts milder effect on the structure of germinal and thymic cells. In addition, a lot of plasmocytes showed signs of active protein (antibody) synthesis. A significant reduction of aberrant chromosomes (clastogenicity) without changes in proliferative activity of bone marrow cells were recorded. In conclusion, the combine application of Miltefosine with ERb and CP decreased the destructive cytotoxic effects of ERb and CP on mouse spermatogenic and hematopoietic cells.

Differential effects of prepubertal rat Sertoli cell secreted proteins on somatic testicular and nontesticular cells.

There is little information on the mitogenic and immunoregulatory activities of proteins, secreted by prepubertal Sertoli cells during the stage of meiosis initiation and before creation of the blood-testis barrier. We have previously demonstrated dose-dependent and age-related stimulation of BALB/c 3T3 fibroblasts and quiescent rat prespermatogonia (Kancheva et al., 1990) as well as inhibition of natural killer cell activity of mice, guinea pigs and human lymphocytes (Nikolova et al., 1992) by Sertoli cell-conditioned medium derived from 12-day-old rats. In the current study, using splenic lymphocytes stimulated by PHA, LPS and Con A, we have shown a dose-dependent inhibition of T and B lymphocyte proliferation by prepubertal Sertoli cell-secreted proteins (pSCSP). These results suggest that by the time the blood-testis barrier had been formed, Sertoli cell in rat testis had already synthesized immunoregulatory proteins. In addition we have found that pSCSP stimulate the proliferation of TM3 Leydig but not TM4 Sertoli cells. The differential effect of pSCSP is an expression of the different balance between growth factors secreted by Sertoli cells, which in turn is dependent on the requirements of the cell types at each stage of testicular development.