Mitotic activity of rat bone marrow cells during injury

The mitotic regimen analysis in rat bone marrow cells was conducted 1, 3, 7, 14, 21 and 35 days after shock trauma. A sharp impairment of myelocyte reproductive function was registered against an increase in the mitotic index. It confirms a universal character of normal mitosis impairment in strong stresses, which was earlier established for epithelial tissues. Cell division disturbances in the bone marrow may be considered an pathogenic factor of a number of pathological processes occurring in the blood system in traumatic disease (anemia, immunodepression). A complex of drugs (sodium oxybutyrate, sodium oxiferriscarbon, Laevamizolum) is offered for the correction of proliferative processes in the bone marrow. This complex has no significant influence on mitotic index and causes relative reduction of pathological mitosis level, ensuring its earlier normalization.     

Immunoglobulin-positive cells in mouse bone marrow]

The content of Ig-bearing lymphocytes and their precursors in the mouse bone marrow was investigated 6 and 36 hours after the hydroxyurea treatment. Some increase of the B-cell content takes place in the trated bone marrow. Dividing and non-dividing B-cell precursors, except the stem cells, were practically absent.     

Mitotic Schwann cells in developing nerve: their changes in shape, fine structure, and axon relationships

The shape of mitotic Schwann cells and their relationships with axons and their interphase neighbors were studied in electron micrographs of longitudinally and transversely sectioned newborn rat sciatic nerves. During prophase, the radial extent of sheetlike processes surrounding axons was progressively reduced until the Schwann cell was spindle shaped. Numerous 100 nm vesicles were found in the cytoplasm as the surface area decreased; they disappeared during subsequent reextension of the radial processes. The axis of mitosis was parallel to the long axis of the cell and transverse cleavage of the cytoplasm occurred between the daughter nuclei. The earliest cytoplasmic outgrowth was identified in serial sections through an anaphase cell which was traced distally from its mid nuclear region. A slender process, originating near the spindle pole, arched over and grew longitudinally beside and beyond the dividing nucleus. Observed also in telophase, this process was thought to represent a daughter cell's new axial process and to be important in establishing the cell's longitudinal symmetry. Radial processes that surrounded axons reappeared in telophase; they began forming in the nuclear region and subsequently grew radially and extended peripherally toward both ends of the cell. Our results show that the changes in shape that occur in dividing Schwann cells and their interphase neighbors increase contacts between these Schwann cells and the axons they surround. These surface interactions probably are important in the selection of axons to be myelinated.     

Cloning stem cells in the bone marrow of irradiated mice]

Different amount of intact or irradiated bone marrow from syngenous donors was administered to mice irradiated with a lethal dose. There was revealed a linear dependence of the number of the 8-9-day colonies grown in the bone marrow of the femur on the amount of the administered cells, and an exponential dependence on the irradiation dose. Regularity of the stem cell cloning in the bone marrow was analogous to such in the spleen. Radiosensitivity of the colony-forming units (CFU) differed depending on the site (the spleen, the bone marrow) of their colony formation. The CFU settling in the marrow proved to be more radioresistant (D(0) equalled 160-200 P) in comparison with the CFU settling in the spleen (D(0) constituted 80-100 P). It is supposed that a different radiosensitivity of the CFU was caused by the presence of heterogenic population of the stem cells and also by specific peculiarities of the organ (the spleen, the bone marrow) in which the colonies formed.     

Hybrid resistance to precursor cells of bone marrow stroma]

A focusl of hemopoiesis appearing after the transplantation of a bone marrow fragment of C57BL mice to syngeneic mice (under the kidney capsule) contained more hemopoietic cells than in transplantation to the semisyngeneic (CBA X C57BL) FI recipient. Experiments were conducted with a secondary seeding by intravenous injection of hemopoietic cells of the C57BL transplant genotype into the transplant depopulated by irradiation; it was shown that these differences were caused by lesser dimensions of the hemopoietic microenvironment in the focus in the hybrid organism in comparison with such in the syngeneic system. Thus, the hybrid resistance was expressed not only to the hemopoietic cells, but also to the stromal precursors transferring the hemopoietic microenvironment.     

Characterization of natural killer cells and their precursors in the murine bone marrow

We have fractionated murine bone marrow cells according to their density on bovine serum albumin (BSA) gradient and studied (a) the NK activity against YAC-1 targets, (b) the proportion of asialo GM1+ lymphocytes, (c) and the presence of large granular lymphocytes (LGL) in the different fractions (A, B, C, D). The NK activity was found mainly in the C fraction, but the proportion of asialo GM1+ cells was the same in every fraction. No LGLs were found in the bone marrow. Cells from the various fractions were also transplanted into irradiated recipients. Seven days later the highest NK activity was found in the spleens of mice injected with cells from the A + B fractions indicating that the immediate precursors for NK cells reside in the low density fractions of the BSA gradient. Mice transplanted with C or D fractions needed longer time to develop normal NK levels. The treatment of bone marrow cells before transplantation with anti-asialo GM1+ complement did not inhibit the development of NK activity, so it can be concluded that the precursor for NK is asialo GM1-.     

Distribution of the bone marrow cells in the skeleton of mice]

The data on the content of nucleated bone marrow cells in 17 skeletal portions of the hybrid F1 (CBA X C57B1) laboratory mice weighing 18-21 g are presented. The bone marrow content in the bones of the spine, head, inferior limb, pelvis, upper limb, sternum and ribs constituted 33.7; 19.6; 17.6; 11.9; 8.2 and 9.0% of the total amount, respectively. The epxerimental results are compared with the literature data.     

Vitality studies in bone marrow cells by means of fluorescence microscopy]

In assessing the vitality of bone-marrow cells vital fluorochroming with acridine orange allows a differential, qualitative statement to be made about the degree of cell damage and in addition the single cell compartments to be relatively well differentiated in morphological respect. The stain exclusion test made for the purpose of comparison merely enables an approximate, quantitative evaluation to be obtained.     

Cytogenetic changes in the bone marrow cells of long-term irradiated rats]

The occurrence and characteristics of the chromosome structural changes in femur bone marrow cells under continuous irradiation with the exposure rate of 50 R/day within 90 days was followed. The 25% increase in the chromosome aberration frequency was observed within 7 days of the irradiation, and then the aberration rate was constant up to the end of the irradiation (90 days).     

Pluripotency of bone marrow stromal cells and perspectives of their use in cell therapy

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.     

Proliferative capability of nuclested rat bone marrow cells following freeze--thawing]

A study was made of the proliferative capacity of myelokariocytes of the rat bone marrow after freezing and thawing under protection of the oxyetyl derivative of the tetratomic alcohol; experiments were conducted on mouse-rat radiation chimerae. The rat bone marrow cells proved to retain their proliferative capacity.     

Characteristics of lymphocytoid cells detected during post-radiation bone marrow recovery]

As a result of complex study of lymphocyte-like cells which arise in the regenerating bone marrow of sublethally irradiated mice, it was established that: (1) X-cells precipitate in the 2nd and, partially, 3rd fractions of the albumin gradient, i. e. in the same fractions as the stem cells of intact animals; (2) X-cells do not belong to polypotent hemopoietic stem cells; (3) X-cells belong to B-lymphocytes, i. e. to thymus-independent lymphocytes.     

2 populations of bone marrow cells transfering the hematopoietic environment]

A bone marrow fragment transplanted under the kidney capsule created a focus of ectopic hemopoiesis, whose isze, measured by the number of hemopoietic cells, was proportional to the implant size. Dimensions of the focus proved to be 11/2--21/2 greater in the irradiated than in the intact recipients. Cells building up the focus of heterotopic hemopoiesis had a different radiosensitivity in the intact and irradiated recipients--their Do constituted about 160 and 350 rad, respectively. In this connection it is supposed that two cell populations of precursors took part in the creation of the focus. Their possible relations with the determined and inducible osteogenic precursor cells are discussed.     

Rb regulates interactions between hematopoietic stem cells and their bone marrow microenvironment

Hematopoiesis is maintained by stem cells (HSCs) that undergo fate decisions by integrating intrinsic and extrinsic signals, with the latter derived from the bone marrow (BM) microenvironment. Cell-cycle regulation can modulate stem cell fate, but it is unknown whether this represents an intrinsic or extrinsic effector of fate decisions. We have investigated the role of the retinoblastoma protein (RB), a central regulator of the cell cycle, in hematopoiesis. Widespread inactivation of RB in the murine hematopoietic system resulted in profound myeloproliferation. HSCs were lost from the BM due to mobilization to extramedullary sites and differentiation. This phenotype was not intrinsic to HSCs, but, rather, was the consequence of an RB-dependent interaction between myeloid-derived cells and the microenvironment. These findings demonstrate that myeloproliferation may result from perturbed interactions between hematopoietic cells and the niche. Therefore, RB extrinsically regulates HSCs by maintaining the capacity of the BM to support normal hematopoiesis and HSCs.