Inducible processes in DNA replication and repair after gamma, UV-irradiation and action of some chemicals in mammalian cells

Restored DNA synthesis in mammalian gamma-, UV-irradiation and action of FdUrd was shown to be resistant to gamma- and UV-irradiation or heating. This correlates well with changes in chromatin structure and perhaps depends on the modification of the latter. For studying possible inducible characteristics of restored process of DNA synthesis the irradiated cells were incubated with cycloheximide (1 or 10 micrograms ml-1) or actinomycin D (0.05 ug ml-1). It was shown that in the presence of cycloheximide or actinomycin D restoration of DNA synthesis did not occur. A high rate of postreplicative DNA repair in UV-irradiated HeLa cells occurs after the previous action of FdUrd or UV-irradiation. Under these conditions daughter DNA strands have few gaps. Two-dimensional gel electrophoresis of proteins from the cells with resistant DNA synthesis demonstrates higher level some of these and lower one of the other proteins.     

Study of ceruloplasmin oxidase activity. The effect of pH

To find out the mechanism of ceruloplasmin (CP) oxidase activity CP interaction with organic substrates adrenaline (AD), catechol, p-phenylenediamine) and Fe2+ was investigated. CP was shown to interact with the above substrates according to the Theorell-Chance mechanism to form a kinetically insignificant ternary complex. The oxygen molecule binds first to CP followed by the molecule of electron donor: the inhibition of enzymatic oxidation by the reaction product is competitive. The effects of pH on kinetic parameters (Ksm, Vs) of oxidation reactions of AD and Fe2+ in the presence of CP were examined. AD was shown to be able to bind both to the protonated and to the non-protonated form of CP whereas Fe2+ interacts only with the protonated form: the rate of catalytic event (Vs) is influenced by pH in the presence of AD whereas in the presence of Fe2+ only binding to CP (Ksm) is affected by pH. Kinetic schemes describing the order of binding of hydrogen ions in the course of above reactions are proposed.     

Changes in functional connectivity of motor zones in the course of treatment with a regent multimodal complex exoskeleton in neurorehabilitation of post-stroke patients

The effect of a treatment course with a Regent multimodal complex exoskeleton (MCE) on the reorganization of cortical locomotor zones was studied in 14 patients with post-stroke hemiparesis, mainly in the chronic stage of the disease. Specific activation zones were identified prior to treatment in the primary sensorimotor and supplementary motor areas and the inferior parietal lobules of both affected and healthy hemispheres by functional magnetic resonance imaging (fMRI) used in a special passive sensorimotor paradigm. After a treatment course with the MCE, temporal characteristics of walking were found to improve, which was accompanied by a decrease in the activation zones of the inferior parietal lobules, especially in the healthy hemisphere, and a significant increase in the activation zones of the primary sensorimotor and supplementary motor areas. Significant changes in intrahemispheric and interhemispheric interactions were revealed by analyzing the functional connectivity of the zones under study before and after a course of treatment with the MCE.     

Chemical biology: Paper alert

A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in chemical biology.     

Protective effect rendered by human ceruloplasmin on erythrocytes in hepatocerebral dystrophy

In order to elucidate the protective effect of human ceruloplasmin (CP) on erythrocytes in patients with hepatocerebral dystrophy (HCD), the parameters reflecting the interaction of CP from the blood of healthy donors (n-CP) and of HCD patients (h-CP) with erythrocytes from healthy donors (n-ER) and from HCD patients (h-ER) were estimated. The protective effects of n-CP and h-CP on n-ER and h-ER during the Cu2+-induced lysis were compared. It was shown that the ability of h-CP to prevent the human ER breakdown upon Cu2+-induced lysis is much lower (approximately 3-fold) than that of n-CP. The differences in the protective effect of n-CP and h-CP are manifested in a greater degree during the n-ER lysis than during the h-ER lysis.     

Comparison of the protective effects on the erythrocytes of ceruloplasmin from the blood of healthy donors and patients with hepatocerebral dystrophy

The binding of the ceruloplasmin (CP) from the healthy donor's blood and of ceruloplasmin--like protein (p-CP) isolated from the Wilson disease patient's blood with erythrocytes (RBC) of healthy donors and with RBC of Wilson's patients (p-RBC) was investigated. It was shown, that the CP number of binding sites both on the RBC and p-RBC was significantly lower than that for p-CP, but Kd value for p-CP binding of the both types of erythrocytes was approximately 10 times higher than Kd value for CP. The protective action of CP on copper stimulated hemolysis is almost 3 times higher than that of p-CP. The protective action of CP on ferrous ion stimulated hemolysis doesn't correlate with its ferroxidase activity. On the contrary the protective effect of p-CP which has no ferroxidase activity is more powerful than that of CP.     

Evaluation of changes in the cortical gait control in post-stroke patients induced by the use of the “Regent” soft exoskeleton complex (SEC) by navigated transcranial magnetic stimulation

The mechanisms underlying the locomotion recovery in poststroke patients remain unknown. Navigated transcranial magnetic stimulation (nTMS) is a new method to evaluate the functional state of the motor system. Using of the “Regent” soft exoskeleton complex (SEC) allow to correct walking pattern significantly. The aim of this study was to evaluate the capability of nTMS to assess changes in gait cortical control using SEC in poststroke patients. 14 patients of the subcortical stroke (the mean age was 53.0 years, the mean time from stroke onset was 14.2 months) received 10 training sessions with SEC. The patients received nTMS before and after the sessions, as well as they were clinically evaluated by the Fugl–Meyer scale section for lower extremity and a 10-m walk test. Whereas a reliable reduction in the time of walking for 10 m was recorded after the sessions with the application of SEC, the Fugl-Meyer scale assessment remained unchanged. During nTMS, a reduction was recorded in the average latency of evoked motor response from the affected hemisphere, as well as various patterns of changes in the size and localization of cortical representations of the leg muscles. We have concluded that the nTMS method allowed us to identify the individual patterns of changes in the cortical representations of leg muscles as a result of the use of SEC in post-stroke patients with injuries in a group of locomotor system elements, thus identifying not only the fact of the undergoing neuroplastic processes, but also their direction.     

Characteristics of DNA synthesis in Chinese hamster cells in exponential and stationary culture growth stages after cell exposure to elevated temperature

Hyperthermia (43 degrees C for 1 hour) is shown to induce a reduction of DNA synthesis and a change in molecular weight distributions in the pool of newly synthesized DNA in cultured Chinese hamster cells. The DNA synthesis inhibition extent as well as the character of disturbances in DNA replication are different in cells of the exponential and the stationary cultures.     

Polyanions inhibit the binding of autoantibodies with some cellular proteins

Effect of polyanions on reaction of the Ig from sera of patients with systemic lupus erythematosus and scleroderma with cellular proteins was studied by immunoblotting. It has been shown that dextran sulfate, heparin, denatured DNA and poly I inhibited the binding of autoantibodies with some polypeptides. The molecular weight of these antigens was determined. The molecular mechanism of immunological reactions studied and it's role in pathogenesis of autoimmune diseases is discussed.