The clinical and immunological characteristics of lymphoid tumors were compared in 591 children with acute lymphoblastic leukemia (ALL) and non-Hodgkin's lymphoma (NHL). Comprehensive investigation of a tumor cell by using cytological, morphological, and immunological studies revealed the most significant criteria for differential diagnosis of ALL and NHL in children and showed the specific features of the site of a tumor and the extent of its growth in ALL and NHL in relation to the immunological affiliation of a tumor cell. The predominance of immature forms, such as stem-cell CD34+, pre-pre-B, pre-B and less commonly T-cell forms with almost none peripheral B- and T-cell markers could be immunophenotypically detected in ALL. NHL was, on the contrary, characterized by the prevalence of mature immunological subtypes with peripheral B- and T-cell markers and much less frequently pre-B and pre-T cells and at the same time there was no CD34 antigen in the tumor cells. Anaplastic giant lymphoma was a peculiar type of NHL characterized by the presence of large cells having marked anaplasia and expression on the surface of CD30 antigen. A comprehensive study of lymphoid tumors in children showed that immunophenotyping was of great value, whose results were associated with the specific feature of tumor growth and prognosis, which should be borne in mind while planning antitumor therapy programmes.

Stem cells in the central nervous system were usually considered as relevant for evaluation only in embryonic time. Recent advances in molecular cloning and immunological identification of the different cell types prove the presence of neurogenesis of the new neurons in adult mammals brains. New neurons are born in two areas of the mammal and human brain--sybventricular zone and subgranular zone of dentate gyrus. New born granular neurons of dentate gyrus have a great importance for memory and learning. New neurons originate from precursors which in culture and in situ could also transform into astrocytes and oligodendrocytes, thus fulfill criteria of neural stem cells. In culture, mitotic activity of these stem sells depends on fibroblast growth factor 2 and epidermal growth factor. Depletion of cultural medium of these factors and addition of serum, other growth factors (Platelet-derived growth factor and ciliary neurotrophic factor) leads to generation of neurons and astrocytes. Isolation and clonal analysis of stem cells is based on immunological markers such as nestin, beta-tubulin III, some types of membrane glicoproteids. Identification and visualization of stem cells in brain revealed two populations of cells which have properties of stem cells. In embryonic time, radial glia cells could give origin to neurons, in mature brain cells expressing glial fibrillar acidic protein typical marker of astrocytes fulfill criteria for stem cells. Neural stem cells could transform not only into mature neurons and glial cells but also into blood cells, thus revealing broad spectrum of progenitors from different embryonic tissues. Further progress in this field of neurobiology could give prosperity in the cell therapy of many brain diseases.

The dominant nana (na) mutation localized to the upper arm of Arabidopsis thaliana chromosome 1 blocks cell proliferation in apical meristem (AM) of the flower-bearing stem at its early development and suppresses the subsequent elongation of its internode cells. The na mutation reduces the sensitivity of cells of the flower-bearing stem to gibberellin (GA) and paclobutrazole (PBZ) and prevents resting and immature seeds from restoring the germinating ability in response to exogenous GA. On the other hand, exogenous GA and PBZ affects the onset of flowering, hypocotyl length, and leaf color; i.e., the na mutant displays a distortion of only several, rather than all, GA-dependent processes. Based on the results obtained, the product of the NA gene was assumed to play a role in the negative regulation of GA signaling and to act later than the products of the known GAI and SPY genes.

This paper formulates a conception of cluster organization of the genetic material, responsible for cell determination and differentiation in multicellular organisms. According to this conception, gene controlling each particular stage of these processes are functionally integrated via genes-activators into gene groups (clusters) of different levels of hierarchy. Besides, some hypotheses of molecular mechanisms providing the action of these gene groups have been put forward. Attempts were made to elucidate some phenomena of cell differentiation, specifically a drop or a complete loss of dividing ability in highly specialized cells, in addition to a property of the cell to remember the history of its own development inside the organism, and to inherit the ancestor's direction of differentiation. Attention was paid to a mechanism (originating from this conception) of the emergency of malignant tumors, which means that cells giving rise to tumors are known to evade primarily their involvement in the process of further specialization. Besides, mechanisms of a molecular supply of positional information are examined. Phylogenetic aspects concerning the standing of the fragment of genetic apparatus controlling cell specialization, and the development of its inner hierarchy that involves subordination of some clusters to other ones.

The myelotoxicity and the hemopoiesis recovery effect of etoposide, an antitumor preparation of the podophyllotoxin group, were experimentally studied on mice. It was found that the main role in the hemopoiesis recovery after etoposide administration is related to accelerated proliferation and increased differentiation of the hemopoietic precursor cells.

It is concluded that a dose range from background dose to several cGy may be separated into two parts: a) first--the interval of small doses limited from above by D* which is determined from (1 g (D*/Doc)) < -0.51 g (n/2)), where Dse is an average dose of a single event, n--quantity of irradiated cells; in this interval only one track intersects a sensitive volume; b) second--the interval of low doses, in which in average one track intersects the volume and which is ranged from top D* to bottom Dse. Because events in this region qualitatively are similar to background events, cells in the dose range b) may be adapted to the influence of radiation. The first stage of the adaptive response of cells is associated with chromosome loci (centromere) movement in a cell nucleus and as we suggest the latter is the fundamental mechanism for repairing DSB DNA and switching of gene transcription. Because the movement of chromosome loci both in the resting cells under the adapting doses and in the normal dividing cells is much the same (but the latter lose their function characteristic for differentiated resting cells), it could be assumed that the resting cells under the adapting doses also lose their functional parameters. Under chronic exposure to low doses this functional changes can be principal for discussion on the influence of low doses on health.

Large-dose chemotherapy (LDCT) with auto- and allogenic transplantation of blood stem cells (BSC) in pediatric oncology remains so far the last hope for many patients. The number of such procedures made in Europe increases by 10% every year. At the same time many issues of the place and role of transplantation in pediatric oncology remains unclear. Based on 240 sessions of cytopheresis, the author show that BSC can be sampled from severe pretreated patients despite the drug therapy regimen. The efficacy of G-KSF and GM-KSF used to stimulate BSC secretion is similar. After LDCT with BSC autotransplantation, the relapse-free survival rates in patients with Ewing's sarcoma and acute myeloblast-cell leukemia were 55.4 and 44.4%, respectively (in the first and second remissions). Consolidation as LDCT with BSC autotransplantation without cleansing the material from malignant cells is not a sufficient therapeutical measurement in disseminated neuroblastoma. Whether partial compatible related BSC transplantation can be possible made after non-myeloablative preparation regimens is shown.

Embryonic stem cells (ESC) are widely employed as an experimental model owing to the similarity of molecular events occurring in their in vitro differentiation and in early embryo development. Subtraction hybridization was used to clone genes that display enhanced transcription in simple embryoid bodies (EB), which are formed on ESC culturing in suspension and are characterized by the presence of endodermal cells. The cloned sequences proved to include three new genes lacking homologs in databases. Northern analysis of the transcript tissue distribution in adult mice confirmed higher expression of these genes in differentiated cells compared with ESC.

A short history of embryonic stem cell (ESC) discovery, cell line isolation, phenotyping and cell behavior both in situ and in vitro is outlined. The path of ESC differentiation into restricted specialized cell types mediated by signal network in culture and by grafting cell into recipient tissues is considered. Potentialities of ESC as the generator of spare parts of organs for regenerative medicine and related bioethical issues are briefly outlined.

To clarify the effect of cyclosporin A (CSA) on the apoptosis and proliferative activity of bone marrow cells in patients with aplastic syndromes by trepanobiopsy evidence.

The paper presents the results of experimental studies on the kinetics and proliferative potential of hemopoietic stem cells in CBA-line mice under the conditions of chronic gamma-exposure at a dose rate of 0.16 Gy/day until the cumulative dose of 43.2 Gy was reached. It was possible based on the exo-colonization test to trace the status of the stem pool in the bone marrow and spleen. The study included an assessment of the proliferative and differentiating potentials of CFUs in the hemopoiesis components of interest. The observations conducted at late times of chronic radiation exposure (at days 180-270) allowed to identify a new status of the hemopoietic system which is characterized by activation of CFUs proliferation and redistribution of cell subpopulations at differentiation stage.

The plants of potato (Solanum tuberosum L., var. Desire) have been transformed with a pH22Kneo vector carrying the gene ac2, encoding the fungicidal peptide (defensin) from the seed of amaranth (Amaranthus caudatus L.). The transformation involved co-cultivation of potato stem explants (excised from aseptically grown plants) and Agrobacterium tumefaciens on solid MS medium. Factors affecting in vitro regeneration of the explants and the transformation efficiency were optimized. Regenerated potato plants harboring the amaranth defensin gene were selected by two traits, growth and ability to form roots on kanamycin-supplemented MS medium. The transgenic state was confirmed PCR analysis of ac2 in tissues of the kanamycin-resistant plants. The transgenic organisms thus obtained differed from the original ambiol-treated plants in growth patterns and proton translocation across the plasma membrane of the tuber cells.

It was studied on mice how prior whole body hyperthemia affects a colony-forming ability of bone marrow after gamma-irradiation. It was found that heating of the animals (42 degrees C, 10 min) 18-22 h before their total irradiation (4 Gy) increases 2-fold the level of CFUs8 and CFUs12 determined in the spleen exotest. The induced radioresistance correlated with accumulation of heat shock proteins, HSP70 and HSP25, in tissues of preheated mice. Injection of quercetin (a selective inhibitor of the heat shock protein synthesis) 0.5 h before the heating fully abolished both the subsequent heat shock protein accumulation and the rise in CFUs populations as compared with control. It is suggested that heat shock proteins, whose expression increases in response to hyperthermia, can play a role of endogenous radioprotectors. Possible mechanisms of their protective action under irradiation are discussed.

The recent achievements in isolation, primary and long term culturing, cell Immunophenotyping, SAGE--mRNA--profiling, the clonogenic growth parameters of embryonic stem cells and mesenchymal stem cells have been outlined in connection with cell pluripotency and restricted differentiation, mediated by signals both in culture and in situ. Multidisciplinary data obtained by cell biologists, embryologists with recent functional genomic data give the new way for practical implementation of bioimplants derived from embryonic stem cell for cell-replacement therapy.