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Biomedical subjects

M K Pulatova

Publications and source records attributed to M K Pulatova.

At least 19 recordsLinked to original sources
PubMed1999

The activation of ribonucleotide reductase in animal organs as the cellular response against the treatment with DNA-damaging factors and the influence of radioprotectors on this effect.

Cellular requirements for deoxyribonucleotide (dNTP) pools during DNA synthesis are related to ensuring of the accuracy of DNA copying during replication and repair. This paper covers some problems on the reactions of dNTP synthesis system in organs of animals against the treatment with DNA-damaging agents. Ribonucleoside diphosphate reductase (NDPR) is the key enzyme for the synthesis of dNTP, since it catalyses the reductive conversion of ribonucleotides to deoxyribonucleotides. The results obtained show that the rapid and transient increase in NDPR activity in animal organs occurs as cellular response against the treatment with DNA-damaging agents (SOS-type activation). We have also found the intensive radioprotector-stimulated activation of deoxyribonucleotide synthesis as well as DNA and protein synthesis in mice organs within 3 days after the administration of two radioprotectors, indralin and indometaphen, that provide the high animal survival. Our studies suggest that these effects are the most important steps in the protective mechanism of the radioprotectors and are responsible for the high animal survival.

Animals↗
PubMed1976

[EPR and low temperature spectrophotometric study of the phototransformation products of bacteriorhodopsin].

It is shown that BR and intermediate products of its phototransformation P600, P550 and P415 (the maximum at -196 degrees C at 419 nm) are not paramagnetic. Illumination of samples containing P415 (P419) at -- 196 degrees C with light in the region of 360-480 nm results in the formation of paramagnetic centres with a sunglet spectrum deltaH=18 Oe and g=2.002 (R1). In parallel formation of a new photoproduct P421 in the absorption spectrum is observed. During subsequent heating at -140 degrees C formation of an asymmetric signal with deltaH=45 Oe and g=2.006 and g=2.03 was observed. In the absorption spectra a dark transition. P421-P565 was observed under the same conditions. P565 differs from initial BR P570 as to its photochemical properties. R1 is identified as retinal radical, R2 as a peroxide radical of the BR-complex lipids. Paramagnetic, spectral, and photochemical properties of some products of BR transformation are compared. A scheme of oxidative-phosphorylation processes with participation of Mn ions in BR phototransformation.

Bacteriorhodopsins↗
PubMedDate not supplied

[Reactions of deoxyribonucleotide synthesis system to irradiation and their modification by radioprotectors].

The paper covers the problem on reactions of deoxyribonucleotide (dNTP) synthesis system in blood-forming organs of animals induced by irradiation. The synthesis of dNTP is a rate-limiting stage for DNA synthesis. Cellular requirements for dNTP pools during DNA synthesis are related with ensuring of the accuracy of DNA copying during replication and repair. It has been shown that organism defence mechanisms against irradiation include the following stages: 1. The prompt SOS-activation of dNTP synthesis 30 min later after irradiation, playing the important role in protecting of cell's genetic apparatus from damage. 2. The inhibition of dNTP synthesis within 3-24 h after irradiation resulting to the imbalance of four dNTP and the decrease of their pools. As result of that, the abnormal repair is observed due to depurinations, errors of base incorporations and "misrepair". 3. The restore of dNTP synthesis occurred 2 days later after irradiation. The increase of dNTP pools promotes the increase of DNA synthesis rate as well as proliferative activity of cells. Confirming the fact that the alterations in dNTP pools play essential role in the production of DNA lesions became an important step in understanding of the multistage process leading to radioprotection. To get high and balanced pools of dNTP needed for the increase in the volume of repair of DNA lesions the radioprotectors with high efficiency relative to the survival test were used in experiments. They induced the elevated dNTP synthesis in bone marrow and spleen during the time when the irradiation alone caused the essential prolonged suppression of dNTP synthesis as well as DNA and protein synthesis in organs of nonprotected animals. It has been shown that substances with antioxidant and antiradical activity induced the dNTP synthesis, too. In vivo regulatory factors of dNTP synthesis have been studied to elucidate the mechanisms of getting of high and balanced dNTP pools by using of different substances.

Animals↗
PubMedDate not supplied

[The dose dependence of the development of compensatory-restorative body reactions to irradiation. The EPR method].

The study deals with the mechanism of organism's adaptive responses to the effect of radiation in widely ranging dose. Post-irradiation metabolic changes were evaluated in canine blood as well as in murine blood, spleen, bone marrow and liver using the EPR spectroscopy. It was shown that the dynamics of changes in transferrin and ceruloplasmin pools and ribonucleotide reductase activity were phase-dependent with the maxima at the 2nd, 6th and 10-12th days after irradiation. Such dynamics was observed at various irradiation doses applied. The data allow us to suggest that the nonspecific compensatory--adaptive reactions of organisms develop as the response to irradiation. The dose-response function of the reaction intensity was found to be linear. The shape of the dose-response curve indicates that the minimum response of organism depends on the dose linearly up to 3.2 Gy (for dogs) as well as the maximum one. However, in the case of low-dose irradiation (0.25 or 0.5 Gy) there were deviations of maximum responses from the linearity, i.e. the amplification of the amplitude of compensatory adaptive reactions. These effect were shown to be dependent upon initial individual characteristics of animal blood and to be related to the "depressed" or "activated" state of organism prior to irradiation. The ribonucleotide reductase activity was measured in bone marrow and spleen of animals by the EPR method. The nature of non-repairable DNA damage is discussed in view of the inactivation of ribonucleotide reductase.

Adaptation, Physiological↗
PubMedDate not supplied

[Reaction of rats organ cells to inhibition of protein biosynthesis by sublethal doses of cycloheximide].

Time-dependent responses of cellular systems in rat organs and Fe(3+)-transferrin and Cu(2+)-ceruloplasmin pools in blood to the blocking of translation by sublethal doses of cycloheximide (CHI) was studied by EPR spectroscopy and radioisotope techniques. It was shown that, within the early post-CHI-treatment time, the suppression of deoxyribonucleotide and DNA biosynthesis, the activation of catabolic enzymes, the inhibition of electron transfer in the mitochondrial electron transport chain, the activation and the following inactivation of cytochrome P-450, and an intensive production of nitrosyl complexes in rat blood and organs occur. In addition, the activation of the synthesis of steroid hormones in adrenal gland was revealed within 1-24 h after cycloheximide injection. In response to these metabolic disturbances, nonspecific compensatory recovery reactions developed, first of all, the "reprograming" of the translation process to produce new protein-synthesizing elements instead of cycloheximide-blocked ones. The activation of protein synthesis promotes the recovery of deoxyribonucleotide and DNA synthesis, the restoration of the redox state of mitochondrial and microsomal electron transport chains in organs as well as an increase of Fe(3+)-transferrin and Cu(2+)-ceruloplasmin pools in rat blood. These metabolic processes result in the full recovery of the functional ability of organs.

Animals↗
PubMedDate not supplied

[Time- and dose-dependent post-irradiation changes of Fe3+-transferrin and Cu2+-ceruloplasmin pools in blood, their influence on ribonucleotide reductase activity in animal tissues and the effects of radioprotectors].

The time- and dose-dependent changes of Fe(3+)-transferrin (Fe(3+)-TF) and Cu(2+)-ceruloplasmin (Cu(2+)-CP) pools, of superoxide dismutase activity and the inhibitory activity of alpha 2-macroglobulin in blood as well as changes in synthesis rates of deoxyribonucleotides (dNTP), DNA and proteins in organs (spleen, liver, bone marrow, thymus) of mice and dogs given total body irradiation have been studied using of ESR spectroscopy, radioisotope techniques and biochemical determination of enzymatic activity. The experimental data have allowed us to reveal the sequence of organism's response reactions against irradiation and their modifications by radioprotectors. Changes in blood Fe(3+)-TF pool is one of the most informative, highly radiosensitive and rapidly reactive marker against irradiation and drug administrations. This irontransport protein controls a rate-limiting iron-dependent stage for DNA synthesis--the synthesis of dNTP, catalyzed by iron-containing ribonucleotide reductase (Fe(3+)-RR). It has been shown that time-dependent post-irradiation changes of Fe(3+)-TP pool in blood are characterized by three distinct stages: 1) the prompt increase of pool (SOS-type response) playing the important role in protecting of cell's genetic apparatus from damage; 2) the decrease of its pool within 3-18 h after irradiation resulting in the loss of Fe(3+)-RR activity in tissues of blood-forming organs that make more stronger radiation-induced damage; 3) the following phase-dependent increase in Fe(3+)-TF pool at the 2-nd, 6th, 10-17th days after irradiation due to an increase in transferrin synthesis. This increase may be considered as compensatory reaction of blood-forming organs directed at restoring blood and organ's cells. The time-dependent courses of the reactions are independent from radiation doses indicating to the universal and nonspecific response of organism against irradiation. But, the intensity of this compensatory-adaptive response at 2-nd and 6th days grows with increasing radiation dose up to lethal that, and organism's response becomes abnormal and physiologically hypertrophic. The prolonged "stressful syndrome of biochemical tense state" should be attributed to negative effects for organism, since it may result in the failure of compensatory adaptive organism's reactions and animal killing. The radioprotectors ward off the appearance of this dangerous state. Dogs with initial individual characteristics of blood which were typical for "suppressed" or "activated" states had abnormal response against irradiation by low doses 0.25 or 0.5 Gy. In these cases the intensity of response reactions of organism was essentially increased and markedly deviated from linear dose dependence. The phase-dependent increase of Fe(3+)-TF pool in blood in post-irradiation time resulted to the increase of Fe(3+)-RR activity in blood-forming organs. The key event ensuring the development of compensatory adaptive reactions is the increase of capacity of protein-synthesizing apparatus, the activation of biosynthesis of dNTP and DNA against the treatment with damaging factors.

Adaptation, Physiological↗
PubMedDate not supplied

[Anabolic effect of natural and synthetic antioxidants].

The order of responses of cell systems of organs and changes in the content of some proteins of mouse and dog blood in response to addition of natural (alpha-tocopherol) and synthetic (ionol) antioxidants was studied at the whole-body level using ERP spectroscopy, radioisotope analysis, and chemiluminescence technique. Responses were evaluated by the temporary and concentration-dependence changes in the activity of ribonucleotide reductase and the rate of protein and DNA synthesis in organs of mice, as well as by the changes in the pools of Fe3+ -transferrin and Cu2+ -ceruloplasmin in blood and the antiradical activity of blood plasma of dogs and mice. During the first 24 h of exposure to alpha-tocopherol, the activity ribonucleotide reductase in bone marrow rapidly increased, whereas the activity of this enzyme and the rate of DNA synthesis in the thymus and spleen were suppressed by 30-50% compared to the control. The changes in these parameters had a phase mode with maxima on days 2-3 and 6-8. The stimulatory effect of the antioxidant on the processes of synthesis was concentration-dependent. We found that the optimal stimulation of the synthesis of deoxyribonucleotides, DNA, and protein was achieved by single administration of alpha-tocopherol at a dose of 20 mg per dog with an average weight of 15 kg and 17 mg/kg in the case of mice. Single or repetitive administration of higher doses of alpha-tocopherol was either ineffective or even suppressed the synthesis of DNA and deoxyribonucleotides. Ionol administered at a dose of 60 mg/kg increased DNA and protein synthesis in mouse organs in 2-4 and 1.2-1.5 times, respectively, compared to the control. It was also shown that single and repetitive administration of alpha-tocopherol to dogs increased the pool of Fe3+ -transferrin and Cu2+ -ceruloplasmin in blood in 2-3 times and by 20-30%, respectively, compared to the control. It is suggested that changes in Fe3+ -transferrin pool in peripheral blood may be used for evaluation of the stimulatory effect of antioxidants on the synthesis of macromolecules in organs and for the determination of dependence of this effect on the concentration of antioxidants.

Animals↗
PubMedDate not supplied

[Activation of deoxyribonucleotide synthesis by radioprotectants and antioxidants as a key stage in formation of body resistance to DNA-damaging factors].

The responses of the systems of synthesis of deoxyribonucleotides (dNTPs), DNA, and proteins in hematopoietic organs and liver of animals to gamma-radiation, administration of radioprotectants and antioxidants as well as the dependence of these responses on the doses of radiation and drugs were studied. Radioprotectants of acute (indralin) and durable effects (indomethaphen) as well as natural (alpha2-tocopherol) and synthetic anti-oxidants (ionol or 2,6-di-tert-butyl-4-methylphenol) efficient in survival test were used. Three stages could be recognized in the standard unspecific response of the studied systems to radiation: (1) immediate increase in ribonucleotide reductase activity in the tissues within the first 30 min as a part of the integrated SOS response to DNA damage, which activates dNTP synthesis; (2) inhibition of the synthesis of dNTPs, DNA, and and (3) restoring ribonucleotide reductase activity and integral increase in the production of dNTPs, DNA, and total protein, which is essential for the development of compensatory and restorative responses of the organism. The radioprotectants significantly increased ribonucleotide reductase activity, which increased intracellular concentrations of the four dNTP types in organs during radiation exposure and three following days. Within this period, ribonucleotide reductase activity was inhibited by 40-50% in animals not treated with radioprotectants as compared to control. Balanced high pools of dNTPs in the organs of radioprotectant-treated animals provided for high-performance repair of DNA damage. The radioprotectant-induced activation of dNTP synthesis during the development of compensatory and restorative responses provides for an earlier restoration of the cellular composition and functioning of the organs. Antioxidants stimulated the synthesis of dNTPs, DNA, and proteins in animal tissues in a strict dose interval. Their effect on the studied syntheses was dose-dependent: single or multiple long-term administration of high antioxidant doses inhibited synthesis of dNTPs, DNA, and proteins. Radioprotectants and antioxidants affected the pool of blood protein Fe3+-transferrin controlling the synthesis of iron-containing ribonucleotide reductase activity in hematopoietic organs, and hence, the iron-dependent stage in DNA synthesis--dNTP synthesis. Activation of protein synthesis in organs by the studied substances increased the pools of Fe3+-transferrin and Cu2+-ceruloplasmin in the blood, which activated dNTP and DNA synthesis. Activated synthesis of dNTP, DNA, and proteins in the organs and increased pools of studied plasma proteins underlay the formation of body resistance to DNA-damaging factors.

Animals↗
PubMedDate not supplied

[Ribonucleotide reductase--a "target" of the action of nitrosomethylurea].

The antitumor and toxic effects of methylnitrosourea (MNU) are determined through its metabolic pathways. In organism MNU is subject to hydrolytic decomposition and denitrosation. It has been shown in vivo studies that MNU abdominal injections of therapeutic doses caused the inhibition of ribonucleotide reductase in mouse spleen, and therefore the DNA synthesis depress. The effect may apparently contribute to antitumor property of MNU. It has been estimated that destruction of M2 subunit of the enzyme is occurred. The relation between the loss of ribonucleotide reductase activity and the inhibition of protein synthesis was discussed. Besides, the cancerogenic and mutagenic properties of MNU were discussed as a result of imbalance of DNA precursor pools. Changes in contents of Fe(3+)-transferrin, ceruloplasmin, methemoglobin in blood and spleen of animals after MNU injections have been found. The changes were reversible after single MNU injection and became irreversible after multiple injections.

Animals↗