Free energy of a two-liquid system of charge carriers in strongly coupled electron and phonon fields and common nature of three phases in hole-doped cuprates.

Hole-doped cuprates exhibit partially coexisting pseudogap (PG), charge ordering (CO) and superconductivity; we show that there exists a class of systems in which they have a single nature as it has recently been supposed. Since the charge-ordered phase exhibits large frozen deformation of the lattice, we develop a method for calculating the phase diagram of a system with strong long-range (Fröhlich) electron-phonon interaction. Using a variational approach, we calculate the free energy of a two-liquid system of carriers with cuprate-like dispersion comprising a liquid of autolocalized carriers (large polarons and bipolarons) and Fermi liquid of delocalized carriers. Comparing it with the free energy of pure Fermi liquid and calculating (with standard methods of Bose liquid theory) a temperature of the superfluid transition in the large-bipolaron liquid we identify regions in the phase diagram with the presence of PG (caused by the impact of the (bi)polarons potential on delocalized quasiparticles), CO and superconductivity. They are located in the same places in the diagram as in hole-doped cuprates, and, as in the latter, the shape of the calculated phase diagram is resistant to wide-range changes in the characteristics of the system. As in cuprates, the calculated temperature of the superconducting transition increases with the number of conducting planes in the unit cell, the superfluid density decreases with doping at overdoping, the bipolaron density (and bipolaronic plasmon energy) saturates at optimal doping. Thus, the similarity of the considered system with hole-doped cuprates is not limited to the phase diagram. The results obtained allow us to discuss ways of increasing the temperature of the superfluid transition in the large-bipolaron liquid and open up the possibility of studying the current-carrying state and properties of the bipolaron condensate.

Increased Yield of Residual γH2AX Foci in p53-Deficient Human Lung Carcinoma Cells Exposed to Subpicosecond Beams of Accelerated Electrons.

We studied quantitative yield of residual (24 h post-irradiation) phosphorylated histone (γH2AX) foci as a marker of DNA double strand breaks in wild-type A549 and p53-deficient H1299 human lung carcinoma cells after exposure to subpicosecond (energy 4 MeV, pulse duration 400 fsec, peak dose rate during the pulse 16 GGy/s) and quasi-continuous (energy 3.6 MeV) beams of accelerated electrons in a dose range of 0.5-10.0 Gy. The efficiency of pulse irradiation in A549 and H1299 cells assessed by the yield of residual foci was higher than the efficiency of quasi-continuous exposure by 1.8 and 5.3 times, respectively. Significant differences in quantitative yield of residual γH2AX foci between wild-type and p53-deficient cell lines were observed only after exposure to subpicosecond, but not quasi-continuous beams of accelerated electrons.

[TRANSFORMATION OF INDIVIDUAL CONTRACTILE RESPONSES DURING TETANUS IN FAST AND SLOW RAT SKELETAL MUSCLES].

The last contractile responses (LCRN), where N is the number of individual contractile responses within tetanus, were separated from the integral tetanic responses of fast, m. Extensor digitorum longus (m. EDL), and slow, m. Soleus, rat muscles using a computer-graphic technique. The average amplitude of LCR5 in m. Soleus at a 20 Hz stimulation rate decreased to 64 ± 9 % re the amplitude of a single contraction. As N was increasing, a restoration of LCRN was observed with their subsequent rise to values almost twofold exceeding the initial single contractile responses of that muscle (up to 211 ± 10 % for LCR50). Simultaneously, against the background of rise of individual contractile responses of these muscles, a considerable shortening of their half-life time (to ≈ 50%) and formation of a stationary plateau within LCRN were observed. In m. EDL at a 50 Hz stimulation rate only single-phase rise of LCRN was observed (up to 165 ± 18% for LCR50) without change of their half-life time and plateau formation. After the end of tetanic responses in muscles of both types a prolonged (up to 30 s) "hyper-relaxation effect was shown to develop manifested as a decrease of muscle tension with its subsequent restoration to the initial values. Possible mechanisms of these effects are discussed. It is supposed that transformation of individual contractile responses in skeletal muscles may be executed at the expense of specialized microdomains in muscle fibers regulating accumulation and extrusion levels of Ca2+ ions during tetanic activity. The possible involvement of an additional, Ca(2+)-induced Ca2+ release (CICR), in the basic, depolarization-induced Ca2+ release (DICR), is analyzed.

[PROPERTIES OF INDIVIDUAL CONTRACTILE RESPONSES WITHIN TETANUS OF RAT SLOW MUSCLE UNDER CONDITIONS OF MODULATION OF SARCOPLASMIC RETICULUM Ca²âº RELEASE].

During direct stimulation of m. Soleus by trains of 5, 10 and 50 stimuli with a frequency of 20 Hz in control experiments (n = 16) a biphasic change was observed in the amplitude of the last contractile responses (LCRN) depending on N, where N is the number of individual contractile responses within the te- tanus. Thus, an initial decrease of LCRN amplitude (up to 54 ± 8 % for LCR5) was replaced by their subsequent growth (up 218 ± 14 % for LCR5o) associated with a significant shortening of their half-relaxation time relative to the initial response (to 44 ± 8 % for LCR50). Caffeine at concentrations of 5 mM (n = 6) and 10 mM (n = 4), at the background of developing characteristic stationary contracture respon- ses, increased LCR5 depression during the initial inhibitory phase (31 ± 8 % and 15 ± 4 %, respectively). The subsequent growth of LCRN amplitude was significantly lower than in the control (114 ± 18 % and 46 ± 9 % for LCR50 at 5 and 10 mM caffeine, respectively). LCR50 half-relaxation time during the action of both caffeine concentrations remained still considerably shorter than the individual responses recorded both in the presence of caffeine and in control. In contrast to the control and caffeine effects, LCR5 and 10 (to 143 ± 14 %) than was observed in the control muscle. Additionally, dantrolene enhanced muscle relaxation at rest. Caffeine (10 mM), at the background of dantrolene, restored the dynamics of changes of amplitude time characteristics of the last contractile responses to values close to the control. The time-amplitude characteristics of the extracellular AP recorded in individual muscle fibers in m. Soleus did not change significantly during tetanic stimulation under protocol similar to that used for mechanografical experiments. These data can be interpreted to support the previously suggested theory about the participation of <> as an additional mechanism of excitation-contraction coupling in skeletal muscle under conditions of tetanic stimulation [1, 2].

[Effect of insulin on characteristics of contractile responses of fast and slow skeletal muscles of rats with streptozotocin-induced overt diabetes].

Comparison of amplitude-time characteristics of fast (m. EDL) muscles in rats with acute model of streptozotocin diabetes (SD) (12 and 30 days after treatment with streptozotocin) did not reveal significant changes in strength of single normalized contractile responses as compared with control. In slow (m. Soleus) muscles of rats with the 30-day SD there were observed essential changes in amplitude-time characteristics of such contractile responses: a decrease of their amplitude and an increase of duration. In diabetic rats treated with a course of insulin, resistance of skeletal muscles to both types of exogenous insulin is developing. Both in control and in diabetic animals the fatiguing stimulation of m. EDL by firing from 5 impulses did not reveal significant differences at early (up to 3 min) terms of development of fatigue. Under similar conditions, fatigue of m. Soleus in rats of both diabetic groups developed significantly faster as compared with control (as early as 30 s after the beginning of stimulation). Insulin at a concentration of 5-1 nM produced a dose-dependent decrease of amplitude of single contractile responses in fast and slow muscles of rats with the acute SD model (the negative inotropic action). The same effect of insulin, but at the higher concentrations, we demonstrated earlier in health rats. Insulin at a concentration of 10 nM did not produce essential effect on the time course of depression of responses in the course of development of fatigue at tetanic stimulation of m. EDL and m. Soleus both in control and in diabetic rats, but affected essentially the time course of change in duration of the half-decline (T(hd)) of their tetanic responses. The presence of insulin in the bath solution led to stabilization of the muscle relaxation period in the course of development fatigue in all studied animal groups.

[Action of insulin on contraction and electrical responses of rat skeletal muscle].

The effect of insulin on contractility of directly stimulated skeletal muscles was studied in experiments in isolated preparations of rat fast, extensor digitorum longus (m. EDL), slow, soleus (m. SOL) and mixed, diaphragm muscles. In addition (diaphragm only) characteristics of extracellularly recorded muscle fiber action potentials (APs) were evaluated before and after addition of insulin to a bath solution. Insulin (0.5-10 nM) decreased muscle twitch force. This negative inotropic effect of insulin was dose-dependent, with m. SOL appearing to be more sensitive to insulin than either m. EDL or diaphragm. Insulin did not affect strength of isotonic KCL- or caffeine-induced muscle contractures, but decreased second and increased first and third phases of extracellularly recorded muscle fiber APs. The analysis of the data obtained in this study and the data from the literature suggests changes in electrogenesis of the muscle fiber's t-tubular plasma membrane as a key element of the negative inotropic effect of the hormone on contractility of mammalian skeletal musculature. Possible mechanisms of such putative changes are discussed.

Comet-assay in combination with PNA-FISH detects mutagen-induced DNA damage and specific repeat sequences in the damaged DNA of transformed cells.

The Comet-assay was applied to three transformed cell lines (HT1080, CCRF-CEM line and CHO) which were treated with the cytostatics bleomycin (BLM) or mitomycin C (MMC). In addition, PNA probes for the telomere repeat (TTAGGG)(n) were used for detection of telomeric DNA sequences in the damaged DNA. Data were compared with previously obtained results from peripheral leukocytes. The amount of migrating DNA increased in all cell types in a dose-dependent manner after BLM exposure. CHO cells reacted sensitively at low doses of the mutagen, and leukocytes had the highest dose-related effect up to 25 IU/ml which, however, did not further increase. A rather linear dose response characterized the HT1080 cells, the effect was lowest for the CCRF-CEM cells. While MMC at lower doses increased the percentage of migrating DNA in a dose-dependent manner, the higher doses induced shorter comets, on average, than the lower ones in all cell lines. With PNA-Comet-FISH obvious differences were found between the studied cell lines with respect to quantitative head/tail distribution of telomeric signals after BLM exposure. A large number of signal spots of various sizes were found in CHO cells, very small signals could be detected in the comets of both neoplasia cell lines. Dose-dependence of telomeres in the tail was most pro-nounced in CCRF-CEM and normal leukocytes, less in HT1080. The steepest dose-related increase of telomeric signals in the tail was found in CHO cells. The ratio between the migrated DNA and the telomeric signals in the tail varied distinctly between the examined cell types from 3:1 to 1:1. Taken together, Comet-FISH can detect mutagenic effects on specific DNA sequences. This may be of high practical value if amplified DNA sequences will be addressed by those examinations in future.

Responses of respiratory neurons in the medulla oblongata to stimulation of the septal nuclei during hypoxia.

Dynamic studies were performed in conditions of hypoxia on the effects of stimulation of the ventral, lateral, and medial nuclei of the septum on the spike activity of bulbar respiratory neurons and respiration. The various phases of hypoxia provided a model experiment over which the overall effects of the septal neurons were summed. Electrical stimulation of these septal nuclei in conditions of normal atmospheric pressure had both facilitatory and inhibitory effects on the spike activity of respiratory neurons in the respiratory center of the medulla oblongata, inhibitory effects being predominant. The ventral nucleus had the most effective inhibitory effect on the activity of respiratory neurons. Electrical stimulation of the septal nuclei in the initial phase (4000-5000 m) of hypoxia, on the background of activation, had a predominantly inhibitory influence on the activity of respiratory neurons. During the phase of severe hypoxia (7500-8000 m), on the background of marked hypoxic suppression of respiratory neuron activity, stimulation of the septal nuclei produced no characteristic changes in the activity of these neurons.

The incidence of various types of childhood leukemia in Armenia (1991-2002).

PURPOSE: To analyse the incidence of various types of childhood leukemia in Armenia for the period 1991-2002. MATERIALS AND METHODS: The results presented in this communication were based on the official data obtained from the Center of Haematology, Yerevan, Armenia, where all patients with leukemia are diagnosed and treated. The types of leukemia were classified according to ICD-10; C91.0 - acute lymphoid leukemia (ALL), C91.1 - acute myeloid leukemia (AML) and C92.0 - chronic myeloid leukemia (CML). RESULTS: There was a substantial prevalence of ALL among all cases (85.6%, mean value for 12 years). ALL varied from 74.4% in 1998 to 95.4% in 1992. The mean percentage of AML and CML were 12.3 and 2.1, respectively. The proportion of ALL/AML + CML in Armenian children varied from 20.5 in 1992 to 3.2 in 1998 with a mean value of 7.2. There was not any regularity in various leukemia types in children during the observed period of time. CONCLUSION: No regularity in the incidence of various childhood leukemia types was revealed during 1991-2002. Like in most countries, a substantial prevalence of ALL incidence was observed.

Chromosome aberrations in lymphocytes of persons exposed to an earthquake in Armenia.

OBJECTIVE: This study attempted to determine the level of chromosome aberrations in lymphocytes of victims of the 1988 earthquake in Armenia. METHODS: Chromosome aberrations were measured in blood samples taken from 41 victims of the earthquake that hit Armenia in 1988 and in samples of 47 reference blood donors. The victims suffered from severe psychoemotional stress but were otherwise healthy. All the samples were taken 2 to 3 weeks after the earthquake. All the subjects were lifetime nonsmokers. The cells were scored blind as to the exposure status. RESULTS: The subjects exposed to the earthquake had a higher proportion of cells with chromosome aberrations [3.1 (SD 2.1)%] than the referents [1.7 (SD 1.3)%, P-value for the difference 0.0009]. The difference persisted when the values were adjusted for age and gender [relative risk (RR) 1.9, 95% confidence interval (95% CI) 1.4-2.5]. The difference was present for double breaks (RR 4.1, 95% CI 2.6-6.4), but not for single breaks (RR 1.1, 95% CI 0.8-1.7). The exposed subjects also had a lower percentage of cells with 46 chromosomes (P=0.03) than the referents. CONCLUSIONS: This study suggests an increase in chromosome aberrations in the lymphocytes of victims of a severe earthquake as compared with the levels of referents. If not due to bias or confounding, the difference may reflect the effect of either environmental exposures related to the earthquake or severe psychogenic stress. The levels of chromosome aberrations found among the earthquake victims in this study are comparable with those found in prospective studies of long-term cancer risk.

Chromosome painting for cytogenetic monitoring of occupationally exposed and non-exposed groups of human individuals.

The suitability of a three-color fluorescence in situ suppression hybridization technique was examined for monitoring five different groups of individuals: 30 occupied in radiology, 26 occupied in nuclear medicine or radiation physics, 32 patients with breast cancer, 26 occupied with military waste disposal, all presumably exposed to low doses of radiation or chemical mutagens and a non-exposed control group (N=29). The average frequency of breaks constituting the various aberrations did not significantly differ between the groups of medical radiation appliers and the control group. However, breast tumor patients and military waste disposers, as groups, showed a higher aberration rate than did healthy controls. Stable rearrangements mainly characterized the groups of controls, tumor patients, and radiation appliers, while a higher proportion of unstable aberrations was found in the chemically exposed individuals. Individuals with an increased frequency of aberrations could be detected within each examined group, which clearly determined the average values of the whole group. With respect to interchromosomal distribution of the breakpoints constituting the found aberrations and the involvement of the labeled chromosomes in rearrangements, the observed values were very close to the expected ones in the controls. A rather similar trend of deviations from expectation was observed in all other groups. Chromosome 4 was slightly over-affected, while chromosome 2 was slightly underrepresented in all analyzed groups (except tumor patients). Rearrangements of the labeled chromosomes with the unlabeled ones exceeded expectation. In conclusion, chromosome painting if included in further attempts of human population monitoring will broaden the basis of argumentation with respect to health risks introduced by mutagen exposure.

In situ monitoring of the ambient air around the chloroprene rubber industrial plant using the Tradescantia-stamen-hair mutation assay.

The city of Yerevan, the capital of Armenia, has been one of the heavily polluted cities since the earlier USSR era. A Chloroprene Rubber Industrial Plant has been the major contributor of air pollution in this city. The first attempt has been undertaken to detect the mutagenic effect of the ambient air around this industrial complex using the Tradescantia-stamen-hair-mutation (Trad-SHM) assay. Tradescantia clone 02 was used for this study. Pots of Tradescantia plants were exposed to ambient air in 10 different locations around the industrial establishment during the months of May and June, 1991 and 1992. Three series of in situ monitoring experiments were carried out. In the first series, sites numbers 1 through 4 were located in the industrial complex, and the second series, sites numbers 5 through 7 were located 1.0-1.3 km away from the Rubber Plant and the third series, sites numbers 8 though 10 were situated 1.5 km from the chemical plant and the monitoring plants were elevated at 5, 13, and 32 m above ground. A control group of plants were grown in a greenhouse about 13 km away from the polluted air from the chemical plant. Results of these two consecutive year's study show significantly elevated high levels of pink mutation events (PME) over the control at sites 1, 2, and 4 in the first series of the study. Positive responses were observed at all sites in the second series of the study. Only site 8 (June 1991) in the third series of the study was significantly higher in PME over the control.

Familial Mediterranean fever: clastogenic plasma factors correlated with increased O2(-)--production by neutrophils.

Familial Mediterranean fever (FMF) is an autosomal recessive disease predominantly affecting Armenians and non-Ashkenazi Jews. The disease begins in childhood with paroxysmal attacks of pain and fever accompanied by peritonitis, pleuritis, and synovitis. During the acute phase, there is a massive influx of polymorphonuclear leukocytes into the serosal membranes, connected with degranulation of the neutrophils and with secretion of lysosomal enzymes and pyrogenic substances. An increase in the lipoxygenase product, leukotriene B4, a chemotactic agent, and a decrease in the activity of the inhibitor of chemotaxis, C5a, in serosal fluids have been considered responsible. Previous work from our laboratories had shown that the chromosomal instability observed in blood cultures of patients with FMF is secondary to circulating clastogenic factors (CFs), and that the antioxidant enzyme superoxide dismutase, as well as lipoxygenase inhibitors, reduce the chromosome damaging effects. CFs are observed in chronic inflammatory diseases and in various other pathological conditions accompanied by oxidative stress. Similar clastogenic materials were found in supernatants of neutrophils and monocytes after a respiratory burst and were shown to contain lipid peroxidation products and cytokines. In the present study we compared the clastogenic effects exerted by plasma ultrafiltrates from 20 adult patients with FMF to the unstimulated O2- production of their neutrophils. In comparison to 20 age- and sex-matched controls, which were studied simultaneously, the O2- production by patient's neutrophils was routinely higher than that of controls. The clastogenic effects of patient's plasma, expressed as the number of chromosomal aberrations induced in test cultures of healthy donors, were correlated with the importance of O2- production by their neutrophils (r = 0.5235). Even if the relative contribution of disturbance in arachidonic acid metabolism, neutrophil activation, and CF formation in the disease process remains unclear, the demonstration of oxidative stress in this genetic disorder suggests the use of antioxidants and free radical scavengers, in particular during acute attacks, when the classical colchicine treatment is without effect.

Physical performance and skeletal muscle characteristics after 2-week hind-limb unweighting.

It is well-known that 2 weeks of hind-limb suspension or space flight induce the sufficient decrease of the physical performance and simultaneously changes of muscle contractile properties and fiber size. However, the data on enzyme activities changes at present are contradictory. Numerous authors have pointed to the increase, reduction of its activity as well as its stability after experiments of the similar design. In previous studies it was shown that beta-GPA (beta-guanidino-propionic acid) administration increased the oxidative enzyme activities in the skeletal muscles and improved their contractile properties in hind-limb suspended rats. The aim of our study is to clear out what determines changes of the physical performance after 2 weeks of hind-limb suspension and beta-GPA administration.

Contractile properties of rat skeletal muscles after hindlimb unloading and beta-GPA administration.

NASA: Soleus and EDL muscles of rats were examined following hindlimb unloading. Some of the rats were given beta-GPA, a creatine analog which depletes high-energy phosphates in muscle tissue, in their food. The contractile properties and fatigue resistance of these muscles were studied, with and without incubation in calcium solution. The increased fatigue resistance after beta-GPA feeding was less in calcium-free solution.^ieng

Clastogenic factors in the plasma of Chernobyl accident recovery workers: anticlastogenic effect of Ginkgo biloba extract.

Clastogenic factors are found in the plasma of persons irradiated accidentally or therapeutically. They persisted in the plasma of A-bomb survivors over 30 years. Clastogenic factors were found in 33 of 47 Chernobyl accident recovery workers (often referred to as liquidators) in a previous study (I. Emerit et al., J. Cancer Res. Clin. Oncol. 120, 558-561, 1994). In the present study, we show that there is a positive correlation between clastogenic activity and dose and that these biomarkers of oxidative stress can be influenced successfully by appropriate antioxidant treatment. With the authorization of the Armenian Ministry of Health, 30 workers were treated with antioxidants from Ginkgo biloba leaves. The extract EGb 761 containing flavonoids and terpenoids was given at a daily dose of 3 x 40 mg (Tanakan, IPSEN, France) during 2 months. The clastogenic activity of the plasma was reduced to control levels on the first day after the end of the treatment. A 1-year follow-up showed that the benefit of the treatment persisted for at least 7 months. One-third of the workers again had clastogenic factors after 1 year, demonstrating that the process which produced clastogenic factors continued. However, the observation that antioxidants do not have to be given continuously is encouraging for intervention trials on a large-scale basis. These appear justified, since clastogenic factors are thought to be risk factors for the development of late effects of irradiation.

Radiation-induced clastogenic factors: anticlastogenic effect of Ginkgo biloba extract.

Clastogenic factors (CFs) were first described in the blood of persons irradiated accidentally or for therapeutic reasons. Work of our laboratory has shown that they occur also under other circumstances, which are characterized by oxidative stress, and that CF-induced chromosome damage is regularly prevented by superoxide dismutase (SOD). Recently we found CFs in a high percentage of salvage personnel of the Chernobyl reactor accident. These liquidators represent a high-risk population and might benefit from cancer chemoprevention by antioxidants. SOD would have to be injected and is not appropriate for long-term prophylactic treatment. In the present study, we therefore evaluated the anticlastogenic effect of the Ginkgo biloba extract EGb 761, which is known for its superoxide scavenging properties. EGb 761 was tested on CF-treated blood cultures of healthy donors. After establishing the optimal protective EGb concentration, using CFs produced by irradiation of whole blood from healthy volunteers, the extract was tested on cultures exposed to CFs from plasma of persons irradiated as liquidators. The anticlastogenic effect could be confirmed for a final concentration of 100 micrograms/ml. In 12 consecutive experiments, CFs induced an average of 18.00 +/- 4.41 aberrations/100 cells. This was reduced to 7.33 +/- 3.08 in the parallel cultures receiving 100 micrograms/ml EGb 761 (p < .001). SOD was anticlastogenic in the same system at concentrations of 30 cytochrome C units/ml (approximately 10 micrograms/ml). Preliminary results obtained in a small series of liquidators showed regression or complete disappearance of CFs in the plasma after 2 months of treatment with EGb 761 (3 x 40 mg/d).

Chromosome damage in PUVA-treated human lymphocytes is related to active oxygen species and clastogenic factors.

Besides the direct interaction of psoralens with DNA and other macromolecules, the role of reactive oxygen species in the PUVA-induced cellular injury has been stressed. The present study shows that treatment of human blood cultures with 5-methoxypsoralen or 8-methoxypsoralen, followed by UVA exposure, results in chromosome damage. The supernatant of these cultures contains secondarily formed chromosome damaging material, called clastogenic factor (CFs). Not only CF formation, but also CF action is inhibited by superoxide dismutase (SOD), suggesting that superoxide is formed on the pathway to chromosome aberration. CF is detectable in the cell culture supernatants after a minimal delay of 18 h, and reaches a plateau at 24 h of cultivation. SOD is no longer protective if added after 24 h, i.e., the enzyme can prevent, but not repair the oxyradical-induced damage.

The comparative clastogenic activity of mainstream tobacco smoke from cigarettes widely consumed in Armenia.

Whole-body exposure of male albino Swiss mice to the mainstream smoke produced by 10 types of cigarettes widely consumed in Armenia resulted in a significant increase (2.4-5.6-fold) of the number of micronucleated bone marrow polychromatic erythrocytes. The smoke produced by cigarettes manufactured in Armenia, Russia and Bulgaria was more clastogenic than the smoke produced by cigarettes manufactured in the USA. A high direct correlation was observed between the number of micronucleated polychromatic erythrocytes and the content of tar and nicotine.