Skeletal muscle precursors do not arise from bone marrow cells

Cell and Tissue Research - This paper tests the hypothesis that bone marrow stem cells can give rise to circulating muscle precursor cells. Irradiated host mice were reconstituted with bone marrow...     

Arginine-rich histones do not exchange between human and mouse chromosomes in hybrid cells

Following division of HeLa-3T3 heterokaryons, human and mouse chromosomes occupy distinct regions within the resulting hybrid nuclei. This favorable orientation of genomes has allowed us to determine whether histones exchange between chromosomes in vivo. Acrylamide gel electrophoresis of the proteins from HeLa cells labeled with ³H-arginine during S phase showed that the core histones were labeled preferentially, constituting 30% of the total cellular tritium and 50% of the label in a crude nuclear fraction. Autoradiographic analysis of cells formed by fusion of ³H-arginine-labeled HeLa cells and 3T3-4E cells showed that ³H-arginine-labeled proteins did not migrate between nuclei in heterokaryons; hybrid cells formed from such heterokaryons contained nuclei in which ³H proteins occupied a sector within the nucleus; “sectored nuclei” could persist for at least 4 days; and the unequal distribution of ³H proteins did not change during DNA synthesis. Electron microscopic examination of hybrid nuclei failed to reveal a physical partition between human and mouse chromosome sets. Sectored nuclei were also observed in synkaryons derived from ³H-arginine-labeled HeLa and unlabeled HeLa cells, indicating that the unequal distribution of ³H-arginine-labeled proteins in HeLa-3T3 hybrid cells did not result from species-specific binding of proteins and DNA. The persistent unequal distribution of ³H-arginine-labeled proteins within hybrid nuclei in the apparent absence of a barrier between mouse and human chromosomes indicates that histones, the principal ³H-arginine-labeled proteins, do not dissociate from DNA in vivo.     

Effect of low doses of ionizing radiation on bone marrow cell chromosomes in Microtus oeconomus Pall

It is shown that Microtus oeconomus Pall. living in conditions of enhanced natural radioactive background do not suffer from the increased radioactivity with regard to the induction of cytogenetic disturbances in bone marrow cells. It is supposed that these animals are more radioresistant than Microtus oeconomus Pall. living in vivaria.     

Why plant chromosomes do not show G-bands

Summary Giemsa techniques have refused to reveal G-banding patterns in plant chromosomes. Whatever has been differentially stained so far in plant chromosomes by various techniques represents constitutive heterochromatin (redefined in this paper). Patterns of this type must not be confused with the G-banding patterns of higher vertebrates which reveal an additional chromosome segmentation beyond that due to constitutive heterochromatin. The absence of G-bands in plants is explained as follows: 1) Plant chromosomes in metaphase contain much more DNA than G-banding vertebrate chromosomes of comparable length. At such a high degree of contraction vertebrate chromosomes too would not show G-bands, simply for optical reasons. 2) The striking correspondence of pachytene chromomeres and mitotic G-bands in higher vertebrates suggests that pachytene chromomeres are G-band equivalents, and that this may also be the case in plants. G-banded vertebrate chromosomes are on the average only 2.3 times shorter in mitosis than in pachytene; the chromomeric pattern therefore still can be shown. In contrast, plant chromosomes are approximately 10 times shorter at mitotic metaphase; their pachytene-like arrangement of chromomeres is therefore no longer demonstrable.     

Radioprotective effect of combinations of WR-2721 and mercaptopropionylglycine on mouse bone marrow chromosomes

The radioprotective and toxic effects of low to moderate doses of S-2-(3-aminopropylamino)ethyl phosphorothioic acid (WR-2721) and its combination with mercaptopropionylglycine (MPG, 20 mg/kg body wt) on the chromosomes of the bone marrow cells of Swiss albino mice were studied at 24 h and 14 days postirradiation. Significant protection against radiation-induced chromosome aberrations was observed with 50 mg/kg WR-2721. The protection increased with the dose of the drug administered, and the degree of protection per unit dose increment was more pronounced at lower than at higher doses. A combination of WR-2721 and MPG given before exposure resulted in a significantly greater number of normal metaphases at 24 h postirradiation compared to the respective single-drug treatment groups. On Day 14 postirradiation, when the presence of WR-2721 resulted in an increase in the frequency of aberrant cells, combination with MPG helped to reduce this value markedly, especially at WR-2721 doses below 200 mg/kg. On the basis of these results it is suggested that 150 mg/kg WR-2721 may be considered an optimum dose for combination with MPG for protection of chromosomes of bone marrow cells when repeated drug administrations are not needed. Changes in the level of glutathione (GSH) in the blood were studied at different times following the administration of 150 mg/kg WR-2721 and its combination with MPG (20 mg/kg) before sham irradiation or exposure to 4.5 Gy 60Co gamma rays. The results showed that WR-2721 elevated blood GSH levels significantly above normal values by the time radiation was delivered, while MPG did not. Glutathione appears to have an important role in the action of WR-2721, while protection by MPG may not be mediated through GSH. Injection of MPG after WR-2721 helps to maintain the higher GSH level for a longer duration compared to treatment with WR-2721 alone. It is possible that MPG delays the metabolism of GSH.     

Exogenous bone marrow cells do not rescue non-irradiated mice from acute renal tubular damage caused by HgCl2, despite establishment of chimaerism and cell proliferation in bone marrow and spleen

Abstract.   Objective : Various studies have shown that bone marrow stem cells can rescue mice from acute renal tubular damage under a conditioning advantage (irradiation or cisplatin treatment) favouring donor cell engraftment and regeneration; however, it is not known whether bone marrow cells (BMCs) can contribute to repair of acute tubular damage in the absence of a selection pressure for the donor cells. The aim of this study was to examine this possibility. Materials and methods : Ten-week-old female mice were assigned into control non-irradiated animals having only vehicle treatment, HgCl₂-treated non-irradiated mice, HgCl₂-treated non-irradiated mice infused with male BMCs 1 day after HgCl₂, and vehicle-treated mice with male BMCs. Tritiated thymidine was given 1 h before animal killing. Results : Donor BMCs could not alleviate non-irradiated mice from acute tubular damage caused by HgCl₂, deduced by no reduction in serum urea nitrogen combined with negligible cell engraftment. However, donor BMCs could home to the bone marrow and spleen and display proliferative activity. This is the first report to show that despite no preparative myeloablation of recipients, engrafted donor BMCs can synthesize DNA in the bone marrow and spleen. Conclusions : Exogenous BMCs do not rescue non-irradiated mice from acute renal tubular damage caused by HgCl₂, despite establishment of chimerism and cell proliferation in bone marrow and spleen.     

Frequency of micronucleated cells in the mouse bone marrow after exposure to various doses of gamma-radiation

The frequency of micronucleated cells was determined in the bone marrow of female BALB/c mice exposed to different doses of gamma-radiation at 1, 3, 10 and 14 days post irradiation. The frequency of micronucleated cells increased with the increase in exposure dose at all time period studied. However, the frequency of micronucleated cells declined with time irrespective of exposure dose. The dose-response curve thus obtained was linear.     

Dexamethasone ameliorates oxidative DNA damage induced by benzene and LPS in mouse bone marrow

Mice were grouped to receive vehicle, dexamethasone (DEX), lipopolysaccharide (LPS), benzene (BZ, 200 mg/kg) and combinations: LPS + DEX, BZ + DEX, LPS + BZ, LPS + DEX + BZ. The DNA damage in bone marrow cells from BZ group was enhanced 2.8-fold measured by nuclear 8-hydroxy-2 '-deoxyguanosine (8-oxodG) and 1.4-fold measured by Comet score (index of DNA breaks) (p < 0.05). In the BZ + DEX group, 8-oxodG level and the Comet score were lowered to 65% and 76% respectively of that in the BZ group (p < 0.05). The BZ + LPS caused a 3.9-fold increase in 8-oxodG and a 1.6-fold increase in the Comet score (p < 0.05). The LPS + DEX + BZ lowered 8-oxodG level and the Comet score to 50% and 78% of the values in the LPS + BZ group, respectively (p < 0.05). Nitrate/nitrite levels in serum were higher after BZ + LPS treatment than after all other treatments. Both 8-oxodG level and the Comet scores were correlated to the serum nitrate/nitrite level across all the treatments (r = 0.55, p < 0.01 and r = 0.69, p < 0.01, respectively). In bone marrow cells the 8-oxodG correlated with the Comet scores (r = 0.80, p < 0.01). We conclude that DEX administration can reduce the DNA damage from BZ treatment and from the combination of BZ and LPS. The correlation of DNA damage with nitrate/nitrite indicates the possible involvement of reactive nitrogen species (RNS) in the interaction between BZ and the inflammatory reaction stimulated by LPS. The 8-oxodG determination is more sensitive than strand break analysis by the Comet assay in bone marrow in vivo in mice for measuring the BZ-induced DNA damage.     

Ultradian biorhythms in mouse bone marrow

Ultradian oscillations in the number of karyocytes isolated from the femoral bone of intact ACR mice have been demonstrated. The periodicity of oscillations did not depend on the season or the site of mice breeding. The bone marrow also showed ultradian oscillations in relative and absolute amount of lymphoid, myeloid and mitotic cells. It is postulated that differentiation and migration of bone marrow cells might have ultradian biorhythms.     

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.     

In vitro alloreactivity of mouse bone marrow lymphocytes

Before characterizing alloreactive cells of the bone marrow, it was necessary to reevaluate the alloantigen response in this tissue. The results of previous studies using the parental-F₁ system in the mixed-lymphocyte reaction (MLR) are open to question because of the recently documented proliferation of F₁ stimulator cells (W. H. Adler, T.Takiguchi, B. Marsh, and R. T. Smith,J. Immunol. 105, 984, 1970; P. F. Piguet, H. K. Dewey, and P. Vassalli, J. Exp. Med. 146, 735, 1977). The culture system was optimized for measuring the MLR of bone marrow lymphocytes enriched on sucrose density gradients. The proliferative response of the enriched fraction (BML) to 2000-R irradiated allogeneic spleen cells was three times as high as the response of unfractionated bone marrow. For maximal responses, antigen concentration had to be twice as high for the BML as for the lymph node, and in a time course study the highest [³H]TdR uptake occurred on Day 3 in BML cultures and on Day 5 in the LN. In lymph node semiallogeneic cultures stimulator cell proliferation can be disregarded, while semiallogeneic BML MLR err significantly on the high side. When BML were matched with allogeneic stimulator cells at the H-2 locus, they gave good MLR responses, provided there was a minor Mls histocompatibility locus difference, while in the lymph node the response was greatly diminished in similar mixtures. The differences in the BML and lymph node alloantigen responses with respect to antigen concentration, kinetics and susceptibility to F₁ and Mls stimulation, suggest that the bone marrow alloantigen response is mediated by a cell population that is different than alloresponsive cells in the lymph node.