Activity Of Deoxyribonucleic Acid Research Articles

Activation of reparative liver regeneration following the combined transplantation of multipotent mesenchymal stromal cells and hepatic stellate cells

Aim. To study the effect of combined transplantation of multipotent mesenchymal stromal and hepatic stellate cells on the reparative liver regeneration.
 Methods. Laboratory mice were given intravenous administration of multipotent mesenchymal stromal and hepatic stellate cells after partial hepatectomy. The mice were divided into four groups: control, experimental 1 (injection of multipotent mesenchymal stromal cells), experimental 2 (co-transplantation of multipotent mesenchymal stromal cells and hepatic stellate cells), the comparison group. Comparison of the experimental groups with the control group and the comparison group was carried out. Each group consisted of 14 animals. The control and experimental groups underwent partial hepatectomy. The experimental mice were injected with the cells into the lateral tail vein 1 hour after the operation. Multipotent mesenchymal stromal cells were administered at a dose of 4 million cells/kg (120 thousand cells/mouse), hepatic stellate cells in the amount of 9 million cells/kg (270 thousand cells/mouse), suspended in 0.2 ml 0.9% NaCl solution. The control group animals were injected with 0.2 ml 0.9% NaCl solution into the lateral tail vein. The comparison group consisted of mice without partial hepatectomy, injected with 0.2 ml 0.9% NaCl solution. To assess reparative regeneration of the liver, morphometric parameters of the liver, blood biochemical parameters on the 3rd and 7th days after partial hepatectomy were studied. The severity of apoptosis was assessed by the immunohistochemical method, the activity of deoxyribonucleic acid (DNA) repair enzymes of the poly (ADP-ribose) polymerases was determined by flow cytometry. The number of micronucleated hepatocytes was also determined. The hepatocyte growth factor (HGF) content was measured by using an enzyme-linked immunosorbent assay in serum. The significance of differences in the compared samples was determined by using the Student's t-test. Statistical data processing was performed by using the SPSS Statistics software version 17.0.
 Results. It was found that the combined transplantation of multipotent mesenchymal stromal and stellate liver cells causes restoration of the activity of alanine aminotransferase (a decrease of 30.3%, p=0.016), aspartate aminotransferase (a decrease of 27.7%, p=0.021), alkaline phosphatase (a decrease of 21.1%, p=0.036), an increase in the protein synthetic function of the liver (increase in albumin level by 36.6%, p=0.009), an increase in hepatocyte growth factor level by 74.3%. These changes were accompanied by the restoration of liver morphometric parameters: there was an increase in the mitotic activity of hepatocytes by 28.7% (p=0.008), the nuclear area of hepatocytes by 26.7% (p=0.006), the number of binucleated hepatocytes by 26.1% (p=0.004), which led to the restoration of liver mass. There was a decrease in the level of apoptosis by 28.8% (p=0.006) and a decrease in the number of micronucleated hepatocytes by 22.7% (p=0.001) compared with the control group, which may be related to an increase in the activity of Poly (ADP-ribose) polymerase repair enzymes detected in the study. The deviations were presented as a difference relative to the indicators of the control group (operated animals that were injected with 0.9% NaCl solution).
 Conclusion. Combined transplantation of multipotent mesenchymal stromal and hepatic stellate cells activates reparative liver regeneration after partial hepatectomy.Keywords: multipotent mesenchymal stromal cells, MSC, hepatic stellate cells, HSC, liver regeneration, partial hepatectomy.

Lack of Diurnal Variation in Tritiated Thymidine Labelling Index of Human Leukaemic Blast Cells

VARIOUS renewal systems of mammalian cells exhibit diurnal variations in proliferative activity as evidenced by rhythmical fluctuations in mitotic index and labelling index (percentage of cells labelled) after ‘flash-labelling’ with tritiated thymidine. In other tissues, it is not possible to demonstrate such variations1–4. In general, it appears that diurnal variations in proliferative activity are found in cell systems with a low rate of cell renewal but not if the cell renewal rate is high. In tumours, diurnal variations in mitotic index have been reported5, but in other investigations such fluctuations have not been demonstrated1,6. In some animal tumours, the specific activity of deoxyribonucleic acid (DNA) after tritiated thymidine labelling is higher at night than during the day7, thus indicating diurnal changes in rate of DNA-synthesis per cell, changes in fraction of total cells in DNA-synthesis, or both.

Transforming activity of deoxyribonucleic acid labelled with 5-bromouracil.

Ephrati-Elizur and Zamenhof1 demonstrated that deoxyribonucleic acid from Bacillus subtilis grown in 5-bromouracil-supplemented media contained this analogue and retained its transforming activity. It thus became important to determine the specific transforming activity for purified fractions of each of the three molecular variants of deoxyribonucleic acid which can be extracted from organisms treated with 5-bromouracil : (1) unlabelled deoxyribonucleic acid molecules, and those in. which 5-bromouracil has been substituted for thymine in (2) one strand (‘unifilar’ labelling) or in (3) both strands (‘bifilar’ labelling) of the double helix. Two strains of Bacillus subtilis, wild type2 and uracil-requiring strain 265 (kindly supplied by Dr. R. Guthrie), served as the donors of deoxyribonucleic acid. These were first grown with aeration at 37° C. for 4 hr. in nutrient broth supplemented with thymidine (10 µgm. per ml.), and afterwards incubated for 2–3 generations in minimal broth2 containing 2–5 µgm. 5-fluorodeoxyuridine (serving as the thymidylic acid synthetase inhibitor3), 25 µgm. uridine (to suppress the conversion of 5-fLuorodeoxyuridine to 5-fluorouracil and 5-fluorouridine) and 50–250 µgm. 5-bromodeoxyuridine per ml. Under these conditions, similar to those first employed for Escherichia coli by Lorkiewicz and Szybalski4, the molar ratio of 5-bromouracil to 5-bromouracil + thymine (5-bromouracil substitution) in non-fractionated deoxyribonucleic acid varied from 35 to 61 per cent as assessed by Chromatographic determination5.

Destruction of the Activity of Deoxyribonucleic Acid in Irradiated Cells

The radiosensitivity of deoxyribonucleic acid within irradiated pneumococcus cells has been studied by extracting the deoxyribonucleic acid after irradiation and measuring its ability to transform a related strain of pneumococcus to streptomycin resistance. The inactivation curves found are exponential over several orders of magnitude, and the measured D/sub 37/'s are: irradiation in the dry state, 3.0 MR; irradiation in the wet anoxic state, 1.2 MR; wet, with oxygen, 0.4 MR; wet with oxygen and 1% cysteamine, 1.2 MR. The data in the dry state are consistent with a unit of transforming activity with a molecular weight of 240,000. The increase in radiosensitivity from the dry state to the wet state can be understood on the assumption of radiationproduced radicals from water diffusing a distance of the order of 10 A. The deoxyribonucleic acid radiosensitivity varies with oxygen and with cysteamine concentrations in the same way as the ability of irradiated cells to reproduce, and the significance of this similarity is discussed. (auth)