The endogenous colony formation and immunogenesis in mice of CBA and C57BL strains immunized with various doses of sheep red blood cells (SRBC) were studied. An absolute or relative increase of antibody forming cells under the action of growing SRBC dose from 2.10(7) to 2.10(8) as well as a decrease following 2.10(9) dose administration were noted. The number of endogenous hemopoietic spleen colonies augmented depending on increased antigen dose. Strain differences in the number of endogenous spleen colonies remained. It is suggested that the stimulation mode of hemopoietic lines is based on a specific RES blockade by SRBC resulting in enhanced proliferative effect of stem cells.

Products of mouse peritoneal macrophage destruction (PMD) obtained by aseptic freezing-thawing of the cells, repeated thrice, were found to elicit in syngeneic mice injected with PMD intraperitoneally an increase of CFUs count in the hemopoietic bone marrow tissue and the spleen, as demonstrated by the Till and McCullooch technique. This proved to be a true increase since the transplatned stem cell fraction sorbed by the recipient's spleen was relatively lower in donor mice given PMD than in the control. Although PMD caused an increase of both erythropoietic (E) and granulocytopoietic-monocytic (G) colonies number, the E/G ratio was decreased; one of the mechanisms of the described effect could be the influence of PMD on the hemopoiesis-inducing microenvironment, as the same effects were obtained in mice injected repeatedly with PMD prior to the transplantation of bone marrow tissue of normal donors. Other possible mechanisms of these effects were analyzed, with consideration to the fact that in experiments with preincubation of bone marrow tissue with PMD prior to injection to the lethally irradiated mice no direct stimulating influence of PMD on the stem cell could be revealed.

Radiosensitivity of the bone-marrow colony-forming cells was determined by a modified method of hemopoietic cells cloning in vivo in semihard agar gel in diffusion chambers. Do for the commited precursor cells of granulopoiesis (CFUc) was 144 +/- 14.8 rad (n = 0.8), and Do for the precursor cells forming "stellate" colonies of fibroblast-like cells (PFUf) was 468 +/- 35.8 rad (n == 0.9). A conclusion was drawn that PFUf were referred to the class of stromal precursors of the hemopoietic organs. This system can be applied for a simultaneous study of the hemopoietic and stromal precursor cells in dogs.

The experiments on irradiated mice (600 and 800 r) demonstrated that under the influence of flogogenic factors the quantity of colonies in the spleen increases and their morphological structures change. It is suggested that under the action of the damaging agent the "hypothetic factor" which causes the pointed changes, is formed in the skin.

In the site of hemopoiesis produced by implantation of an irradiated bone marrow plug beneath the kidney capsule all dividing hemopoietic cells were of recipient origin, as shown by karyologic analysis. In such implants hybrid resistance was of the donor's type. It is suggested that the migrating cells of hemopoietic origin, including lymphocytes and macrophages, do not participate in producing the hybrid resistance.

Hemopoietic cells including CFUs could be washed off from the organ culture of fetal liver periodically for 4 weeks. Under the cultivation conditions employed this treatment did not reduce the CFUs content of the culture essentially; thus, the washings off could be used to elevate the CFUs yield per culture.

Lymphocytes of mice F1 (CBA X M523) and F1 (A X M523) transplanted to 1000 R irradiated CBA or A mice responded to the test antigens--SRBC or S. typhi Vi-antigen--by formation of 100--1000 times less antibody forming cells than in syngeneic recipients. An intermediate result is achieved when the lymphoid cells are transplanted to the irradiated M523 mice. Lymphocytes of mice F1 (A X CBA), F1 (CBA X C57Bl/6), or F1 (A X A.CA) developed a similar immune response in the irradiated syngeneic mice and in both parental lines. The ability of parental line M523 to respond to SRBC was the same as in the other lines studied when examined in situ or in adoptive transfer experiments. The stem hemopoietic cells of mice F1 (CBA X M523) develop in the spleen of CBA mice 2--2.5 times less hemopoietic colonies than in the spleen of syngeneic animals. A conclusion was drawn that mutation M523 in CBA mice inhibited the proliferation and differentiation of hemopoietic and lymphoid cells in the irradiated nonsyngeneic recipients.

Kinetics of the number and direction of CFU differentiating in mice after a single infusion of hydrocortisone in a dose of 5 mg per mouse was studied using the method of an exogenous cloning of the stem cells in the spleen and the bone marrow of the irradiated recipients. Against the background of the long-term involution of the thymicolymphoid apparatus a change of the number and direction of the CFU differentiating occurred. Along with this, CFU concentration in the spleen and bone marrow of mice remained constant. Under the hormone action CFU differentiating capacity in the spleen and bone marrow in the direction of erythro- and myelopoiesis sharply changes; CFU of the bone marrow behaves as CFU of the spleen, and CFU of the spleen behaves as CFU of the bone marrow of normal mice. It is suggested that the described effects of the CFU of the spleen and bone marrow of mice given hydrocortisone were due to the redistribution of T-lymphocytes and not to direct cytotoxic effect of hydrocortisone on the CFU population.

Electron microscopic examinations of lung cancer showed the tumor cells to be capable of specific ultrastructural differentiation owing to which a tumor represents a combination of cells with different degrees of differentiation. This capacity of tumor cells to specific ultrastructural differentiation and formation of tumors consisting of nondifferentiated cells alone or of nondifferentiated and differentiated cells of one or several types, as well as the discovery of differentiated cells simultaneously with signs of cells of two types (chimera cells) suggest that either polypotent (stem cells) or monopotent (precursor cells) cells undergo malignancy. Accordingly, the histogenetic (cytogenetic) appurtenance of a tumor depends not upon its development from one to another type of differentiated cells but upon further direction of differentiation of transformed cells.

Cells of origin of the spinobular, spinomesencephalic and spinothalamic tracts in the cat brain were identified by the retrograde horseradish peroxidase transport technique. A conclusion is made that neurons in laminae IV and V give rise to ascending fibres to the ipsilateral dorsal column nuclei and neurons in the lateral parts of laminae V and VI and in lamina VIII establish direct connections with the contralateral thalamus (CM, MD, CL) and reticular formation of the brain stem. Throughout the spinal cord the labelled neurons were present in the intermediate zone of both sides.

The number of stem hematopoietic cells in the hematopoietic organs of mice of BALB/c and CC57BR strains and (CC57BRXBALB/c)F1 hybrids was studied by the method of exogenous colony-forming units. The assay of migration of stem cells from the bone marrow to the spleen was carried out. It was found that the spleen and the bone marrow of mice of the studied genotypes contain approximately the same relative number of hematopoietic stem cells. The number of stem cells which migrate from the bone marrow to the spleen is greater in the mice of BALB/c strain than in the CC57BR mice.

An analysis was accomplished of pathomorphological changes in the brains of 10 newborns, who died of intranatal asphyxia and of 1 adult brain with mental retardation, due to asphyxia during delivery. The dynamics of hypoxic changes of an irreversible character in the brain of the newborn and the existence of chronic hypoxic encephalopathy with pronounced cellular devastation in the late period of asphyxia indicate common genesis of the pathological process in the brain, conditioning its progression. The role of intranatal asphyxia in the pathogenesis of changes in postnatal development of neuropsychic activity is discussed.