Complex bioelectric impedance measurement system for the frequency range from 5 Hz to 1 MHz

Analytic techniques that have been successfully employed in materials science, and to a lesser extent in the study of biologic systems, have potential for improving the application of bioelectric impedance provided that both real and imaginary impedance components can be measured with sufficient accuracy over a given frequency range. Since biologic tissue, particularly animal tissue, is typically highly conductive, phase angles are small, making accurate measurements difficult. A practical four-terminal system employing commercial lock-in amplifiers is described and error sources and corrective tech-niques are discussed.     

An experimental study of freezing in erythrocytes

A unique experimental apparatus (termed cryomicroscope) has been developed for the study of freezing and thawing processes in living cells and has been used specifically to determine the conditions requisite for intracellular freezing in human erythrocytes. Careful measurements of the incidence of intracellular ice formation have been correlated directly with the magnitude of the cooling rate during the freezing process and degree of extracellular supercooling prior to nucleation of ice. The probability for intracellular freezing increases with the magnitudes of both the cooling rate and the extracellular supercooling. A 3-dimensional contour has been defined experimentally by which the frozen state of human erythrocytes can be predicted as a function of these two parameters. The influence of cooling rate and extracellular supercooling on the mode of ice formation may be explained in terms of physiochemical phenomena which are controlled by the balance between the rates of heat transfer and mass transfer across the cell membrane during freezing.     

Rheological properties of young and aged human erythrocytes

Summary Rheological properties were studied of young and old human erythrocytes from healthy adults. Viscosity measurements of packed erythrocyte suspensions as well as filtration of cells through polycarbonate sieves show that young cells are more flexible than aged ones. Since deformability of erythrocytes is the product of cell shape, flexibility of the membrane and fluidity of the intracellular hemoglobin, we studied the manner in which these factors are relevant to the diminished flexibility of aged erythrocytes. The biconcave cell shape is maintained during the process of aging. The viscosity of packed ghost suspensions from aged erythrocytes is increased versus that of young ones. The diminished flexibility of old ghosts correlates well with their smaller cell volume. The fluidity of the hemoglobin in the interior of the cells is decreased as indicated by an increased hemoglobin content of the isolated ghosts. We conclude that aged erythrocytes loose their deformability as a result of both a decreased fluidity of the intracellular hemoglobin and a diminished flexibility of the membrane.This work was supported by the Deutsche Forschungsgemeinschaft     

Acetylcholinesterase during aging of human erythrocytes

Acetylcholinesterase activity differs in the membranes of young, mature, and old human erythrocytes: It is highest in the mature and lowest in the old cells. The enzymes in young and mature erythrocytes is in the form of three, but in the old cells in the form of two molecular components. The results suggest that changes in the structural organization of acetylcholinesterase in the erythrocyte membrane have a direct bearing on the aging of red blood cells.Laboratory of Biochemistry, Institute of Hematology and Blood Transfusion, Leningrad. (Presented by Academician of the Academy of Medical Sciences of the USSR V. S. Il'in.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 10, pp. 1198–1200, October, 1976.     

Quantitative assessment of ultrasound-induced resistance change in saline solution

The purpose of the study was the experimental assessment of the interaction coefficient characterising the influence of pressure on the conductivity of electrolyte solutions. Pressure pulses were applied to samples of 9 gl⁻¹ sodium chloride contained in cuboid measurement cells of identical cross-sectional dimensions but different thickness along the acoustic beam axis. The magnitude of the changes induced in cell resistance was recorded for three values of applied pressure increment (ΔP=0.94, 1.39 and 1.78MPa) and three values of cell thickness (e=0.58, 1.13 and 1.62mm). A thick, focused transducer generated short (0.1μs), unipolar pressure pulses. A model accounting for the characteristics of the pressure pulse and the geometry of the measurement cell was developed to predict the ultrasound-dependent changes in the measured electrical resistance. Despite some discrepancy between theoretical and experimental results, discussed in the paper, the results validated the order of magnitude of the interaction coefficient (10⁻⁹ Pa⁻¹). The predictions varied from about 50% (e=1.62 mm, ΔP=0.94MPa) to 77% (e=0.58mm, ΔP=1.78MPa) of the experimental values.     

Specific impedance of canine blood

The specific impedance of canine erythrocytes suspended in plasma was measured in the frequency range from 5 kHz to 1 MHz in samples from three animals in the hematocrit range from zero to packed cells at a temperature of 39°C; measurements were made with a conductivity cell using four electrodes and a current density of 21 μA/cm². With the use of impedance spectroscopy, data were fitted to an equivalent circuit model; model parameters in turn were fitted as functions of hematocrit. The resultant model can be used to predict specific impedance (real and reactive components) as a function of hematocrit and frequency over a frequency range from 5 kHz to 1 MHz and a hematocrit range from 0 to 80. Over a normal range of hematocrits and at frequencies less than 100 kHz., the current is almost exclusively confined to the plasma, and the specific impedance is nearly equal to the real component; however, at higher frequencies, the complex nature of specific impedance becomes important.     

Difference between mechanisms of changes in platelet and erythrocyte aggregation in renal failure

Aggregation reactions of platelets and erythrocytes were studied in chronic renal failure. Differences in the mechanism of aggregation of platelets and erythrocytes are discussed on the basis of data showing opposite changes in the aggregation function of cells of the same subjects under similar conditions.Laboratory of Physiology of the Circulation, I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR. Department of Field Medicine, S. M. Kirov Military Medical Academy, Leningrad. (Presented by Academician of the Academy of Medical Sciences of the USSR V. N. Chernigovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 89, No. 3, pp. 263–265, March, 1980.     

梗阻性黄疸病患者红细胞流变特性研究

本文分别采用旋转式粘度计及微管吸吮系统，在宏观及微观层次上测量了梗阻性黄疾病患者红细胞流变学指标，实验对黑手术解除梗阻后一周的患者及健康人。结果表明，梗阻性黄症病人伴随着血液粘度升高，其宏观与微观红细胞变形性指标均有所升高，红细胞变形能力下降：但是解除梗阻后一周的病人的血液粘度却明显降低，同时红细胞变形性指标下降，红细胞变形能力提高，宏观与微观流变学指标具有很好的一致性。     

Einfluß von körperlichem Training auf die Blutfließeigenschaften bei Claudicatio intermittens-Patienten

Summary Abnormal blood flow in patients with intermittent claudication can be normalized by physical training. We found a decrease in blood viscosity with a decrease in the erythrocyte-aggregation tendency and significant simultaneous improvement in erythrocyte filtrability. Improvement in these haemorheological properties led to a significant increase in physical performance after training. This positive result can be obtained by regular physical training; the application of rheologically effective medicaments is not necessary.

Mit Unterstützung der Deutschen Forschungsgemeinschaft Ga 275/1-2     

Effect of heparin on lipid peroxidation reaction of erythrocytes and their resistance

In a physiological concentration (10 units/ml) heparin activates the ascorbate-dependent lipid peroxidation of lipids and reduces their resistance in citrate—phosphate buffer, pH 3.0. In a concentration of 100 units/ml heparin does not affect thermal (62°C) oxidation of methyloleate; this is evidence that heparin is not a direct-action prooxidant.Institute of Clinical and Experimental Medicine, Siberian Branch, Academy of Medical Sciences of the USSR, Novosibirsk. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 9, pp. 1086–1088, September, 1976.     

Electric current generated by ultrasonically induced Lorentz force in biological media

The ions of solutions exposed to the propagation of ultrasound in the presence of a magnetic field experience Lorentz force. Their movement gives rise to a local electric current density, which is proportional to the electric conductivity of the medium. In vitro assessment of this current is performed using simple models of biological media. A constant magnetic field of 0.35T and 500kHz pulsed ultrasound are used. The sensing electrodes are exposed to neither the pressure wave nor the magnetic field, thus ensuring that the signal is not due to any undesirable electrode effect. The experimental results confirm that the current is proportional to the electrical conductivity of the medium. The changes in the measured current against the width of the measurement chamber show that the electrodes only collect fraction of the current created within the medium. The magnitude of the measured current is 50nA in a saline solution of 0.5S/m conductivity. The technique enabled the determination of the conductivity of a porcine blood sample against haematocrit. It is concluded that this type of measurement has the potential to allow the electrical conductivity of a medium to be determined using ultrasound.     

He-Ne激光血管内照射对心肺疾病患者微循环的影响

本文总结60例心肺疾病患者应用低能量He-Ne激光血管内照射治疗,自身对比观察治疗前后患者甲襞微循环及红细胞变形力的变化,发现微循环的管襻数、异形管襻数、管襻长度、输入、输出枝,襻顶直径等参数及血流速度、流态、红细胞聚集、加权积分值等治疗后有显著的改变(P<0.01或P<0.05),红细胞变形能力亦有明显的增强(P<0.05)。提示He-Ne激光血管内照射有改善心肺疾病患者的微循环及提高红细胞变形能力的作用,探讨了其机理。     

基于头部组织不同电导率特性的阻抗成像正问题仿真研究

目的 通过建立5层有限元真实头模型,研究了各层组织非均质和颅骨、脑白质各向异性电特性对电阻抗成像问题中电磁场分布的影响.方法 对头部各组织建立4种电导率分布模型:均质分布、非均质分布以及颅骨和脑白质各向异性电导率模型;通过正问题数值求解得到不同模型下的磁场分布和电场分布,并通过定量的统计分析研究非均质和各向异性电导率特...     

Ultrastructural changes in UV-irradiated erythrocytes

M. F. Vladimirskii Moscow Regional Clinical Research Institute. Research Institute of Tuberculosis, Ministry of Health of the RSFSR, Moscow. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 109, No. 1, pp. 69–72, January, 1990.     

Morphological Characteristics of Peripheral Blood Erythrocytes in Rats Subjected to Chronic Inhalation of Ultradispersed Piezoelectric Ceramic Powder

In albino rats subjected to chronic inhalation of ultradispersed piezoceramic powder, scanning electron microscopy revealed changes in membrane surface of peripheral blood erythrocytes manifested as decreased number of diskocytes and increased number of transitional, prehemolytic, and degenerating forms. These parameters returned to normal 1 month after termination of inhalations.