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Biomedical subjects

D Suciu

Publications and source records attributed to D Suciu.

At least 37 records · Page 2Linked to original sources
PubMed1980

High order packing of DNA as revealed by autodigestion of chromatin in small intestine cell nuclei.

Small intestine cell nuclei incubated in sucrose media released large fractions of DNA into the culture medium. This effect was partially or completely suppressed when incubation was carried out in the presence of a protease inhibitor, 10 to 30 mM NaHSO3. The DNA released in sucrose media containing NaHSO3 was precipitated as a DNA-protein complex by increasing the bivalent ion concentration to 10 mM Ca2+ or 20 mM Mg2+. Most of the released DNA was not precipitated by Ca2+ or Mg2+ when incubation was performed without NaHSO3. As determined by viscosity measurements the mean molecular weight of the DNA released in the absence of NaHSO3 was from 3.5-8.0 x 10(5) and increased to about 11 x 10(5) (corresponding to 8 nucleosomes) when the incubation mixture contained NaHSO3. End group analysis indicated that the DNA segments were terminated by 3'-OH groups. It is suggested that fragmentation of DNA in chromatin was produced by a endogenous alkaline endonuclease activity which was present in the fraction of released DNA. The data support the view that the third-order repeat structure of chromatin consists of subunits containing 8 nucleosomes.

Animals↗
PubMed1979

Role of alkaline endonucleases in the release of soluble chromatin from thymus, spleen and liver nuclei of normal and irradiated mice.

Thymus, spleen and liver nuclei released a large fraction of soluble chromatin in vitro when incubation was carried out in sucrose media containing low concentrations of CaCl2 and/or MgCl2. A significant fraction of deoxyribopolynucleotides (DPN) was also extracted from nuclei. After 30 min of incubation at 37 degrees C, the maximum release of soluble chromatin was observed near a pH of 8, which corresponds to the optimum pH of the alkaline endonuclease activity from thymus, spleen and liver. The soluble chromatin and DPN were precipitated by increasing the bivalent ion concentration of the medium. The protein/DNA ratio and the molecular weight of DNA suggest that the soluble chromatin and DPN represent nucleosome-like particles. The release of soluble chromatin in the first 4 hours of incubation was significantly increased if the nuclear fraction was isolated from the thymus and spleen of whole-body irradiated mice (1000 rad). This effect was absent in the liver nuclei.

Animals↗
PubMed1979

Characterization of metronidazole-phosphate, a water-soluble metronidazole derivative, as a radiosensitizer of hypoxic cells.

A water-soluble derivative of metronidazole (Flagyl) was synthetized with the purpose to overcome some practical difficulties in the clinical administration of the drug. The derivative, a phosphate ester of metronidazole, was characterized for different physical-chemical properties. It had a low toxicity both in vitro and in vivo. In vitro, it retained a radiosensitizing effect specific for hypoxic cells which was, however, decreased in comparison with the parent compound. The decreased sensitization was related to a decreased one-electron reduction potential and octanol/water partition coefficient. In mice, metronidazole-phosphate had a prolonged blood life in comparison to metronidazole.

Animals↗
PubMed1979

Cell proliferation in the thymus of Ehrlich ascites tumor bearing mice.

Thymic involution of Ehrlich ascites tumor bearing Swiss and NMRI mice was associated with an increased incorporation of 3H-thymidine into thymus DNA and an enhanced activity of adenosine deaminase. The apparent depletion time constants, which were determined by the following time course of the retention of 3H-DNA, indicated that the rate cell depletion was increased in the thymus of tumor bearing mice. The results suggest that the thymic involution was correlated with an increased proliferative activity and an accelerated depletion of thymic cells.

Adenosine Deaminase↗
PubMed1978

Cell kinetics in the spleen of Ehrlich ascites tumor-bearing mice.

During the period of 18 days after transplantation the uptake of 3H-thymidine into DNA was significantly increased in the spleen of Ehrlich ascites tumor-bearing Swiss and NMRI mice. Adenosine deaminase activity was within the control limits in tumor-bearing Swiss mice and significantly increased for the tumor-bearers of the NMRI strain. However, the increase in the DNA content, which is associated to splenic hyperplasia, was evident only for the Swiss strain. The time course of the retention of 3H-DNA revealed that the half life of spleen cells ranged from 41 to 46 h in normal and tumor-bearing Swiss mice and normal NMRI mice. For tumor-bearing NMRI mice the rate of cell depletion was significantly increased (t1/2 = 32h) compared with that found in normal NMRI mice (t1/2 =44 h). The mean survival time was 23.0 days for the tumor-bearing Swiss mice and 24.6 days for the NMRI mice. These data suggest that the immune responses were similar in both strains of mice, although cell kinetics was different in the spleen of tumor-bearing Swiss and NMRI mice.

Adenosine Deaminase↗
PubMed1977

Alkaline endonuclease(s) activity in the thymus and spleen of normal and irradiated mice.

Evidence has been found on an alkaline endonuclease activity in the cytoplasmic and nuclear fraction isolated from the thymus and spleen mice. The chromatin-associated endonuclease activity was identified only in the spleen. The enzyme(s) was active on both single- and double-stranded DNA, but the reaction was faster if single-stranded DNA was used as a substrate. Maximum activity was found in the pH range of 7.9 to 8.1 in the presence of 10 mM Mg2+ and 1 mM Ca2+. The enzyme(s) splits DNA, yielding 3'-hydroxyl terminated polynucleotides. It is suggested that this alkaline endonuclease(s) is responsible for the formation of deoxyribopolynucleotides in the thymus and spleen of irradiated mice.

Animals↗
PubMed1976

Recovery response of dividing cells in the thymus of whole-body gamma-irradiated mice.

Mice were irradiated with different doses of gamma-rays 30 min after the administration of 32P-orthophosphate. The dose-response curves determined at 72 hours after exposure showed an inflection point in the total activity present in the DNA in thymus and spleen. In the low dose-range, the dose-response curves have D0 = 55 rad (n = 2-5) for thymus and DO = 95 rad (n = 2-5) for the spleen. Thirty minutes after the administration of 32P-orthophosphate, the dividing cells from thymus were partially synchronized by the administration of 80 mg per kg body-weight hydroxyurea. At different time-intervals, the mice were irradiated with 80 rad, and the total activity of DNA was determined at 72 hours after synchronization. A significant maximum of recovery was found at 5 hours (S phase) after the administration of hydroxyurea. In similar conditions, the dose-response curves corresponding to the G1, S and M phase of the division cycle were also determined. The synchronization of dividing cells induced by hydroxyurea failed in the spleen.

Animals↗
PubMed1976

Release and retention of labelled DNA in the thymus and spleen of irradiated mice.

The process of release and retention of labelled DNA in thymus and spleen of normal and irradiated (60Co) mice has been studied after administration of 3H-thymidine. The results indicate that the dividing fraction of lymphoid cells is more resistant to radiation than the fraction of nondividing lymphocytes. The time courses of the specific activities of DNA in thymus and spleen were different especially after irradiation with lethal doses. It is suggested that the process of depletion in the lymphoid series is probably similar for both thymus and spleen but, the different cellular composition of these organs led to apparently unrelated results.

Animals↗
PubMed1976

Effect of cortisol on the release and retention of labelled DNA in the thymus and spleen of mice.

The lymphocytolytic effect of different doses of cortisol was studied in the thymus and spleen of mice previously injected with 3H-thymidine. The results indicate that in thymus the fraction of labelled cells was more resistant to cortisol than the unlabelled cell population. The release of DNA into the fraction of DNA soluble in 0.14 M NaC1 was delayed suggesting that cortisol controls indirectly the lymphocytolytic process. Up to 24 hours after administration of cortisol the loss of labelled spleen cells significantly exceeded the loss of unlabelled cells. The time course of the release of labelled DNA into the fraction of DNA soluble in 0.14 M NaC1 indicates that a fraction of labelled DNA was rapidly removed from the spleen after injection of cortisol.

Animals↗
PubMed1975

Evidence for reproductive death of dividing cells in thymus and spleen following whole-body gamma-irradiation of mice.

Mice were given whole-body gamma-irradiation with 300 and 800 rad 1 hour or 1 day after the administration of 3H-thymidine. The time-course of the specific activity of DNA in thymus and spleen and the release of radioactivity into the fraction of DNA soluble in 0-14 N NaCl were determined for 28 hours after exposure. The results indicate that on average the loss of mitotically-active cells was delayed compared with the loss of a representative fraction of non-dividing cells. This suggested that different mechanisms might be implicated in the dying process of the dividing and non-dividing lymphoid cells. Using a dose-fractionation method, the total activity of DNA was determined in thymus and spleen at 24 hours after the first exposure and 25 hours after the in vivo labelling of DNA. A parallelism has been found between the results of this experiment and the recovery effect of the Elkind-Sutton type. It may be concluded that the dying process responsible for the loss of the dividing cells from thymus and spleen after irradiation probably involves reproductive death.

Animals↗
PubMed1975

Effects of irradiation on the release and retention of labelled DNA in the small intestine of mice.

Mice were whole-body irradiated with 300, 500 and 800 rd (60Co) one hour or three days after administration of 3H-thymidine. The time courses of the total and specific activity of DNA indicate that three days after exposure with 500 and 800 rd the mitotically active cells were selectively lost from the small intestine. The release of labelled DNA was determined in the fraction of DNA soluble in 0.14 N NaCl. The results suggest that the relatively small fraction of soluble DNA belongs to the mitotically active cells probably having died in the interphase.

Animals↗
PubMedDate not supplied

Computerized studies of influenza epidemiology in the Sibiu county between 1968 and 1986.

The report presents a statistical synthesis (a microcomputer Junior was used) concerning the incidence of various acute infections of the upper respiratory tract (AIURT), the stages of their evolution, the distribution of cases among the population groups, the seasonal incidence and the values of epidemiologic parameters. We used clinical and epidemiologic data on AIURT of viral etiology (especially influenza). The structure of a data base on the epidemiology of AIURT of viral etiology is also presented.

Absenteeism↗