Accumulation of methylene blue by erythrocytes and determination of its maximum sensitivity to cell damage

The accumulation of methylene blue in native and damaged erythrocytes treated by cetyltrimethylammonium bromide at different initial concentrations (c0) of methylene blue and different volume ratios between external solution and cells (Vs/Vc) was studied. It was shown that at low methylene blue concentrations (c0 < 200 microM), the sorption of the dye by cells made the main contribution to its accumulation. As a result, the internal concentration of methylene blue exceeded manifold its external concentration and their ratio Q was 4-6 for native and 6-9 for damaged cells. As Vs/Vc decreased and especially as c0 increased, the diffusion of methylene blue inward the cells increased concentration gradient, and Q sharply fell to 0.9-1.0. The optimal values of c0 and Vs/Vc that provide the maximum sensitivity of Q to cell damage were determined. The advantages of using Q over other parameters of methylene blue accumulation were shown.     

Physiological tremor and control of limb position in 1 and 0 G

Muscle and skeletal mechanoreceptors play an important role for the regulation of muscular tone and the genesis of normal Physiological Tremor (PT). For example if a big limb as the arm or leg is kept against the gravity vector, the la afferent spindle discharges continuously control the load bearing flexor in a negative feedback manner in order to compensate the gravity vector and to the stabilize arm position. This servo-like action, denoted as 'stretch reflex', not only increases static postural stability (tonic stretch reflex) but also counteracts against external disturbances by dynamically increasing the muscle tone. Muscle spindles are very sophisticated sensory organs. They have an own innervation and the endings of the nuclear bag fibres are highly sensitive for small microstretches. EMG and microneurografic studies showed their importance in the mechanism of the 8-12 Hz component for PT. In a 0 G a limb becomes position controlled. In contrast to 1g, where control of limb position is a subordinated function of force compensation in the load bearing muscle, an antagonistic control scheme is necessary in 0 G to compensate the arm against positional drifts. As a consequence there is a shift from load dependent (muscular) to position dependent (skeletal) mechanoreceptors that become involved in the neural control process. As the control process is reflected in the tremor pattern, we investigated arm tremor in a constant limb position in 1 and 0 G.     

Radiation diagnosis of uncomplicated compression spinal fractures in children

Experiments on rabbits compared the X-ray, morphological, and magnetic resonance imaging of compression fractures of the vertebral body. Edema of the bone marrow of the vertebral body was ascertained to be a basic morphological substrate that evokes a modified MR signal. The data on 178 children with suspected compression fracture of the vertebral body were used to consider the potentialities of MRI and X-ray study in this pathology. The MRI semiotics of uncomplicated compression fractures of vertebral bodies is presented. The sensitivities of MRI and spondylography in the diagnosis of compression fractures of vertebral bodies were 100 and 62.5%, respectively.     

Intercellular interactions as a reason for the influence of the erythrocyte concentration on the parameters of detergent hemolysis

Possible reasons are discussed for the abnormal erythrocyte concentration influence on the course of detergent hemolysis curves. The data obtained lead to a conclusion that erythrocyte plasma membrane properties and, as a consequence, the parameters of erythrocyte-detergent interaction are dependent on cell concentration. The dependence is more sharply expressed for concentrations 5.10(7) cell/ml. In the concentration range (5-20) X 10(7) cell/ml the state of erythrocyte membrane remains apparently unchanged.     

The effect of cleavable cross-linking reagents on the mitochondrial respiratory chain]

It is shown that cleavable cross-linking reagents reversibly inhibit proton translocation with concomitant stimulation of respiration in the mitochondria respiratory chain. It is concluded that a definite level of dynamic mobility of proteins is needed for proton translocation.     

Structural transformation of human erythrocyte membranes initiated by group specific antibodies

Some changes have been found in the rates of the desintegration by sodium dodecylsulfate of human erythrocite membranes (EM) after incubation with specific group antibodies (GA) from incompatible blood. GA have no effect on the disintegration rates of EM by sodium desoxycholate and Triton X-100. The data are considered as the evidence of the structural transition in EM induced by GA and resulting in modification of integrative coupling forces primarily in the protein components of the membrane. The stopflow technique has been used to investigate the dependence of the desintegration rates in the quick phase (10 to 100 ms) upon the GA concentrations in the incubation medium and upon the incubation time. The obtained curves are distinctly S-shaped that is peculiar of cooperative processes.     

Change in the replicative synthesis of DNA and in respiration during gamma-irradiation of cultured human lymphocytes

The onset of 3H-thymidine incorporation in DNA precedes a short-term activation of cell respiration. gamma-Irradiation (5 Gy, 0.1 Gy/s) significantly inhibits oxygen consumption by human peripheral blood lymphocytes. It should be noted that time dependence maxima of oxygen consumption are shifted towards later times of cultivation.     

Structural rearrangements in synaptosomal membranes of the brain]

Studies were carried out on structural state of synaptosomes and synaptic plasma membranes from brain of rats and guinea pigs at 5--50C. In membranes from guinea pig brain there were two breaks at 8 and at 18--20C in the curves of temperature dependence of light scattering. At the same temperatures adhesive properties of membranes had changed in jump-like manner when evaluating the degree of aggregation at pH4. The degree of aggregation in membranes from rat brain as well as rate of solubilization by 0.2% SDS (stoped-flow measurements) are characterized by single break point at 27C in Arrhenius curves. The breaks were interpreted as phase transitions with membrane surface involvement. Chlorpromazine and tetraciane (10(4)--10(3) M) abolished or modified these transitions. Because the number of negative charges and tryptophanyl and ANS fluorescence parameters were unchanged it was suggested that redistribution of ionogenic and hydrophobic goups took place at membrane surface during phase transitions.     

Calcium transport in brain synaptosomes during depolarization. The role of potential-dependent channels and Na+/Ca2+ metabolism

The contribution of Ca2+ channels and Na+/Ca2+ exchange to Ca2+ uptake in rat brain synaptosomes upon long- (t greater than or equal to 30 s) and short-term (t less than 30 s) depolarization by high K+ was studied by measuring the 45Ca content and free Ca2+ concentration (from Quin-2 fluorescence). At 37 degrees C, the system responsible for the K+-stimulated uptake of 45Ca (t greater than or equal to 30 s) and the Na+/Ca+ exchanger are characterized by a similar concentration dependence of external Ca2+ (Ca0(2+] and K0+ as well as by an equal sensitivity to verapamil (Ki = approximately 20-40 microM) and La2+ (Ki = approximately 50 microM). These data and the results from predepolarization suggest that the 45Ca entry into synaptosomes at t greater than or equal to 30 s is due to the activation of Na+/Ca+ exchange caused by its electrogenic component, while the insignificant contribution of Ca2+ channels can be accounted for by their inactivation. At low temperatures (2-4 degrees C) which decelerate the inactivation, the initial phase of 45Ca uptake is fully provided for by Ca2+ channels, showing a lower (as compared to the exchanger) affinity for Ca0(2+) (K0.5 greater than 1 mM)m a greater sensitivity to La3+ (Ki = approximately 0.2-0.3 microM) and verapamil (Ki = approximately 2-3 microM); these channels are fully inactivated by predepolarization with K0+, ouabain and batrachotoxin. The Ca2+ channels can be related to T-type channels, since they are not blocked by nicardipine and niphedipine.