Electromechanical stability of planar lipid membranes from bipolar lipids of the thermoacidophilic archebacterium Sulfolobus acidocaldarius

Stable planar membranes have been obtained from the bipolar lipid glycerol dialkyl nonitol tetraether (GDNT) extracted from the thermoacidophilic archebacterium Sulfolobus acidocaldarius. The electric capacity Cm, the resistance Rm and tension sigma of these membranes were measured. The dependence of the bipolar lipid membranes mean life time tau 1 on voltage was investigated. It was shown that the irreversible electric breakdown of membranes from GDNT and usual phospholipids is due to the same mechanism, viz., due to formation of a hydrophilic pore with an overcritical radius. Under electric field the GDNT molecules take U-shape, and the polar headgroups of such molecules cover the pore's interior.     

Aggressive behavior and radiosensitivity in rats'

This paper aims to present the study of rats' individual radiosensitivity dependence on their individual aggressiveness. On total irradiation in sublethal doses (1.0, 1.5 and 3.5 Gy) and in doses close to LD50/30 (6, 7 and 8 Gy) there was investigated comparative radiosensitivity of non-aggressive and aggressive rats of Wistar line, as well as that of non-aggressive individuals during provoked aggressiveness by means of blocking serotonin synthesis with intraperitoneal (i/p) injection of 400 mg/kg of parachlorphenylalanine (pCPA). Muricidity served as a criterion for aggressiveness and as a criterion of radiosensitivity--cumulative function of survival, the changes of behavior in "Open feald", serotonine and catecholamine content in various brain structures and the dose dependence on the radiation modification of muricidity. It has been found that after 1 Gy total X-irradiation the rats do not lose aggressiveness. Nevertheless the ethalogical parameters change in considerable degree. In the doses of 1.5 and 3.5 Gy muricidity is eluminated in 15-18 and 5-9 days, correspondingly. I/p injection of pCPA after the elimination of aggressiveness provokes transient muricidity in the same terms and duration as it is in case of non-aggressive rats. The elimination of muricidity is associated with changes in content and distribution of biogenic amines in various structures of brain, as well as with reduction of locomotor and reference-research activity, on the one hand and with an increase of emotionality and stereotype activity, on the other hand. After X-irradiation in 6, 7 and 8 Gy the regression coefficients of the dependence of functions type of survival on irradiation dose in aggressive rats is significantly reliable both in comparison with non-aggressive rats and animals with provoked aggressiveness. The change of mortality-rate per unit of changing irradiation dose not depend on blocking of serotonin synthesis, which deficit is one of the distinct determinant of aggressiveness, on the one hand, and higher radiosensitivity, on the other hand. The obtained data allow to suppose that elimination of muricidity after the irradiation of rats in the sublethal doses is conditioned not only by the consequenses of radiation damage of neurobiological structures responsible for the organization of aggressive behavior but the activation of serotonergic system in the process of restitution after radiation trauma. On the other hand, higher radiosensitivity of aggressive rats compared with non-aggressive ones is connected with low serotonin content, thiols and some other biologically active substances which are endogenous radioprotectors determining individual radioresistance.     

Initial heart rate variability and radiosensitivity in rabbits

The goal of the work was to investigate the rabbits' radiosensitivity dependence on the initial functional state of the autonomous nervous system (ANS), as assessed by time-frequency parameters of the heart rate variability (HRV). Survival rate and rhythm-cardiologic correlates of the pathological processes following total X-irradiation, at doses of 2 and 12 Gy, were studied with an aid of modern computer technologies of measurement and data analysis. It has been found that the animals with initial prevailing of adrenergic influences on the HRV ("sympathicotonics") are significantly more sensitive to irradiation than those in which the parasympathetic prevalence was evident ("vagotonics"). The most characteristic and determining difference between these two groups of animals is initial level of the sum regulatory influences on the heart rhythm, which is manifested in value of total power of spectral density (TP) of HRV. In the sympathicotonics the TP is significantly lower than in the vagotonics. The primary HRV response to irradiation practically does not differ according to the dose and manifests in sharp suppression of the TP in both groups of the animals. At 12 Gy this process is irreversible. In the sympathicotonics it develops earlier and terminates with death much sooner than in the vagotonics. An average life-span of the rabbits, at this dose, is 18.8 +/- 2.6 days in vagotonics, and 10.3 +/- 1.3 days in sympathicotonics (p < 0.02). At 2 Gy initial sharp decrease of the TP in the vagotonics lasts one week only. Then the sum regulatory influence of the ANS on the heart rate increases (rebound) and this condition, which probably points at general resistance of the organism, could be seen within two months; at the end of third month it stabilizes at the initial level. In the sympathycotonics initial sharp decrease of the TP also occurred, however no rebound was observed. The results obtained show that low initial level of the TP of HRV is sufficiently correct marker for higher radiosensitivity in the sympathotonic rabbits against the vagotonic ones.