The opportunity of faster closing deep burn wounds by using fibroblast-like mesenchymal bone marrow stem cells (FMSC) and embryonic fibroblasts (EF) was investigated in rats. It was shown that FMSC as well as EF transplanted onto burn surfaces reduced the expression of cell infiltration but accelerated the formation of vessels de novo and granulation tissue in the wounds. These changes form the conditions for faster closing the burn wounds as compared to the control wounds (without cell transplantation). High rate of wound closing induced by FMSC and EF is thought to be caused by a long period (up to 30 days) of vital activity of the cells grafted on the burn surface. It was also found out that the rate of wound regeneration induced by FMSC was higher that that induced by EF.

The review presents the analysis of advances in fundamental studies of the optic nerve regeneration and degeneration mechanisms. It is concluded that current experimental morphological investigations of mechanisms of pathogenesis and sanogenesis of the optic nerve atrophies are developing in several major directions. These include: 1) development of techniques for restoration of the integrity of the optic nerve stem, including those that use peripheral nerve grafts; 2) development of measures to decrease the retinal ganglionic cell (RGC) response to injury and to stimulate RGC repair processes; 3) search for the ways for axon growth stimulation in lesioned and undamaged RGC; 4) usage of RGC apoptosis inhibitors; 5) grafting of embryonic retina. Results of the experimental studies are evaluated in the context of their possible application in clinical practice.

The purpose of the present investigation was to study the morphological peculiarities of chromaffinoblasts and to determine their interrelations with the surrounding cellular elements of the fetal cortex at the early stages (embryonic weeks 4-7) of their migration into the developing adrenal gland of a pig. At week 5 neuro-cellular cords, consisting of so-called "naked" axons, neuroblasts, lemmoblasts, undifferentiated cells, chromaffinoblast clusters and chromaffinocytes, grow into the fetal cortex from side of abdominal aorta. In fetal cortex parenchyma chromaffin elements form cords, lobes, "medullary globes", which are enveloped by a basal membrane, which is a derivative of satellitocytes. Chromaffinocytes are stained with Wood's stain, potassium bichromate and, judging by the presence of secretory granules in their cytoplasm, are capable to synthesize summary catecholamines and to release them into the blood at the early stages of development. "Medullary globes" are the centers of proliferation and differentiation of the chromaffin cells in the adrenal medulla. The problem of chromaffin tissue stem cells is discussed.

The purpose of the present study was the investigation of human neural stem/progenitor cells (SPC) cultured in vitro, with special reference to their capacity for grafting, migration and differentiation after transplantation into adult rat brain. SPC were isolated from the brain of 9-week-old human embryos and were cultured in a selective medium for 3 weeks. For transplantation, cell suspension or whole neurospheres were used; they were studied 4 weeks following the transplantation in hippocampus, striatum and lateral ventricle of adult rat brain. For the analysis of transplanted SPC, various histological and immunohistochemical staining methods were applied (bisbenzidine, BrdU, antibodies against human nuclei, vimentin, beta-tubulin, neurofilaments, GFAP), that allowed an independent evaluation of their state and differentiation. Transplanted human brain SPC were shown to survive well for one month in all the areas of adult rat brain without immunosuppression. Cells from suspension transplants actively migrated and differentiated into neurons and glial cells. Meanwhile, cell migration from the transplanted whole neurospheres was limited or absent due to the formation of glial barrier.

We studied the effect of the growth factor LIF on the development of parthenogenetic mouse embryos (CBA x C57BL/6)F1. LIF was added to the culture medium at 10, 50, 100, and 250 ng/ml at the morula stage and parthenogenetic embryos were cultivated in vitro until the late blastocysts stage and then transplanted in the uterus of pseudopregnant females, which were then sacrificed on day 12 of pregnancy. All the LIF doses used improved the development of parthenogenetic mouse embryos at the preimplantation stages and increased the amount of blastocysts by 16%, on average, as compared to the control. LIF at 50 and 100 ng/ml increased approximately twice the number of embryos that reached the somatic stages. Some of them reached the stage of 32-45 somites and had fore and hind limb buds. No such embryos were found in the control. Well formed placenta was observed in 6% of the embryos treated with LIF and the most pronounced effect was recorded at 100 ng/ml. The data we obtained suggest that exogenous LIF can improve pre- and postimplantation development of parthenogenetic mouse embryos due, possibly, to increased survival rate of embryonic stem cells derived from the inner cell mass of blastocysts. LIF improves not only the development of the parthenogenetic embryo per se, but also the formation of its extraembryonic envelopes, which leads to the development of a larger placenta in LIF-treated parthenogenetic embryos, as compared to the control.

The uppermost cells of the root and shoot apical meristems are considered as stem cells. They are similar, in many features, to the stem cells of animals. But, unlike animals, the stem cells can repeatedly arise in plants during morphogenesis and regeneration or in tissue culture from actively dividing or differentiated cells. When the stem cells are removed, they can be repeatedly restored from the actively dividing cells. The maintenance of the population of stem cells is determined by interaction between the stem cells and actively dividing cells located below according to the feedback principle. The protein synthesized in the stem cells determines how the lower located cells affect the stem cells. Specificity of stem cell identification in plants is discussed.

The main approaches have been considered to studying the genetic control of plant cell totipotency in an in vitro culture. The capacity of cultured plants for callusogenesis, organ formation, and somatic embryogenesis depends on the activity of genes that determine and maintain the meristematic state of cells, level of hormones in the cells, and sensitivity to hormones, as well as on the activity other genes that control different stages of plant morphogenesis.

Feeding of the retina, whose thickness does not exceed 130 mu km, is possible at the account of chriocapillary diffusion. Should this threshold be topped (approximately by the 3.5th prenatal month), it will result in a relative hypoxia of the uttermost internal strata of the retina, which induces the appearance of new feeding source, i.e. retinal vessels. First, dense cellular steaks of the sequential fusiform cells originating from the visual-stem depth located near the wall of a. hyaloidea emerge in the surface retinal strata. These cells (angioblasts) formed the peripapillary plexus, shaped as a vascular pattern, and represented a non-lumenized prototype, or matrix, of a future capillary network. Later, main arterioles emerged, in the outward direction from them, and after that venules took shape from the above network through a partial reduction of vessels and a redistribution of blood circulation. The second deep capillary stratum was formed rather through a prolongation and "sagging" of the surface capillary loops than through gemmation; it is common for the entire retina and, unlike the surface stratum, is not divided by main arterioles into adjoining segments. By the 8th fetal-life month the evolution of the retinal bloodstream is not entirely completed, though it resembles, to a great extent, a definitive one.

To estimate the incidence of cytomegaloviral (CMV) infection and CMV disease in patients with acute leukemia at different stages of chemotherapy and in patients after transplantation of hemopoietic cells.

The viability and genetic variability of mouse hepatoma MH-22a were studied by RAPD-PCR method using 3 primers, and the genetic structure of the tumor hepatocyte population based on the number of clonal fingerprint rearrangements was identified: 56% of hepatocytes made up clones with 0-3 rearrangements (the stem line of the population); 32%--the variable part with 4-7 rearrangements per clone and 12%--the aberrant part with 8-12 rearrangements per clone. The stem line appeared the most viable featuring zero or least genetic variability while the clones characterized by the greatest genetic variability were least viable.

Cyclic changes of the midgut epithelium were observed in females of 5 ticks species of the genus Ixodes during 7-10 days of feeding. The midgut epithelium of unfed females is represented by the digestive cells of nymphal phase and stem cells. The digestive cells of nymphal phase are functional during 1.5-2 days after attachment of the tick, and then, after the tearing away they go into the gut lumen. The secretory cells substitute the digestive cells of nymphal phase and finish their growth during the 4-4.5 days. Secretion of digestive enzymes is performed by the holocrine type with tearing away a whole cell. Intracellular digestion takes place in the digestive cells of four consequent generations. The secretory and digestive cells form a peritrophic matrix on their surface. The presence of peritrophic matrix gives an evidence the maturity and functional activity of the secretory and digestive cells. We suggest, that the peritrophic matrix takes part in intracellular digestion, namely in the process of micropinocytosis. The phagocytosis was not found in the ticks investigated. Digestion in the midgut lumen is performed by enzymes of the ruptured secretory and digestive cells, that is proved by the haemolysis of erythrocytes in the zone of their contact with these cells. The digestive cells of each generation functioned almost synchronously, with largest difference in starting about 12 hours.

The paper presents a critical review of various current concepts of the structure and kinetics of unmyelinated nerve fiber. A classification of nerve fibers, different from the earlier ones, is proposed, that demonstrates not only the morphological fiber types, but also the kinetics of their reversible transition stages from non-glial to myelinated fiber. Evidence is presented to show the erroneousness of conceptions, still appearing in many publications, that consider the unmyelinated nerve fiber as "the Remak's cable type fiber". According to the current data, "Remak's fiber" is a glial-neurite complex, i.e. a bundle of unmyelinated nerve fibers covered with a single glial cell. Using the electron microscope, it was demonstrated that comparable glial-neurite complexes of myelinated nerve fibers, formed in CNS in a similar way by a single oligodendrocyte, cannot be named a single fiber. Cutting the nerves makes visible that the single fibers forming "the Remak's fiber" stem from different cells, therefore they cannot be a single "fiber". It has been shown for the first time experimentally, that in extreme situations, as a result of contraction of gliocyte processes, unmyelinated fibers may "leave" the glial-neurite complexes and become the nonglial fibers. Some data are presented that may serve as criteria for differentiation of unmyelinated fiber with a stratified sheath from developing myelinated fiber.

Mobilization of bone marrow stem cells by granulocyte-colony-stimulating factor (G-CSF) is considered to be an alternative to invasive transplantation of autologous myoblasts or stem cells directly into injured cardiac tissue. We have started a 24 week randomized open study in order to elucidate effects of G-CSF (filgrastim) on clinical, hemodynamic and neurohumoral status of patients with NYHA class II-IV chronic heart failure due to ischemic heart disease with zones of nonviable myocardium and left ventricular ejection fraction <40% as well as to assess safety of addition of G-CSF to standard therapy with ACE inhibitors and beta-blockers. It is planned to include 20 patients into each filgrastim (5 mg/kg/day) and control (0.9% NaCl) groups. Methods to be used: dobutamine stress echocardiography for detection of myocardial viability, magnetic resonance tomography, 6-minute walk test, quality of life questionnaire. By the present time 5 patients were included (4 in filgrastim and 1 in control group) and passed 3-6 months points. A control patient died suddenly on 11th week. All patients in filgrastim group are alive (1 experienced obvious improvement, 2 remained stable, and 1 deteriorated and required urgent hospitalization). None of the patients had signs of appearance of 'regenerated' myocardial zones. The patient with positive clinical dynamics was characterized by young age (48 years), moderately severe heart failure (NYHA class II) and pronounced leukocyte reaction to filgrastim (12 fold increase in white blood cell count with appearance of myelocytes and myeloblasts ). In contrast patients without improvement were older than 60 years, had NYHA class III heart failure and experienced just 6-8 fold increases in leukocyte count. These factors are suggested to be predictors of clinical efficacy of G-CSF in patients with heart failure.

We studied the behavior and differentiation of pluripotent embryonic stem cells of R1 mice in vivo. Undifferentiated embryonic stem cells and differentiating embryoid bodies grafted in abdominal cavity of the irradiated mice were shown to form tumors with derivatives of all germinal layers. Cells of the embryoid bodies form tumors two weeks after the grafting, while the undifferentiated embryonic stem cells form tumors only by week three.

The possibility of differentiation of insulin-producing cells and neural and glial elements was demonstrated in the culture of bone marrow stromal cells. The perspectives of use of the bone marrow stromal cells in clinical medicine are considered.

In the hybrid cells obtained by fusion of embryonic stem cells with adult differentiated cells, homologous chromosomes are in two ontogenetic configurations: pluripotent and differentiated. In order to assess the role of cis- and trans-regulation in the maintenance of these states, we studied a set of clones of hybrid cells of the type embryonic stem cells-splenocytes and used two approaches: segregation of parental chromosomes and comparison of pluripotency of the past hybrid cells and embryonic stem cells. The segregation test showed that the hybrid cells lost only the homologs of the somatic partner and this process was sharply accelerated when the cells were cultivated in nonselective conditions, thus suggesting the full or partial preservation of the initial differences in the organization of parental homologs. The descendants of the former hybrid cells, which had the karyotype similar to that of embryonic stem cells, demonstrated the level of pluripotency, comparable with that of embryonic stem cells despite the long-term effect of trans-acting factors from the somatic partner in the genome of hybrid cells. The data obtained are interpreted in the framework of the concept of "chromosome memory", in the maintenance of which the key role is played by cis-regulatory factors.

Isolation and cultivation of stem and progenitor cells of human embryos and fetuses at the age of 7-12 weeks of gestation have been described. The embryonic cells of human brain formed neurospheres with heterogenous composition. Cell differentiation took place not only in the presence of serum or as a result of attachment of neurosphere to a sublayer, but also in floating neurospheres in the presence of mitogens. In most neurospheres, the nestin-immunopositive cells were located near the surface while the cells stained for beta-tubulin III and glial fibrillar acid protein, as compact groups inside the neurospheres.

Spontaneous formation of embryoid bodies and subsequent differentiation of some cells into cardiomyocytes were demonstrated on murine embryonic stem cells of R1 line. The lines of embryonic stem cells were obtained that had been transfected with genetic constructs carrying expressing regulatory genes of the human immunodeficiency virus tat and nef and "green protein" gene (GFP). The transfection of embryonic stem cells with the gene tat stimulated their proliferative activity, while this activity decreased in the cells transfected with the gene nef. The time necessary for the formation of embryoid bodies by all lines of transfected cells was similar to that in the control cells. In the cultures of cells transfected with nef and tat, the number of embryoid bodies and the percentage of embryoid bodies with contracting cardiomyocytes were higher and lower than in the control, respectively. Thus, an inverse correlation was observed between the effects of regulatory genes of the human immunodeficiency virus on proliferation and differentiation embryonic stem cells.