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Biomedical subjects

G Valet

Publications and source records attributed to G Valet.

At least 91 records · Page 5Linked to original sources
PubMed1977

The trajectories of particles suspended in electrolytes under the influence of crossed electric and magnetic fields. Possible explanation of the sensitivity of organism to magnetic fields.

We observed that particles, suspended in an electrolyte and brought into crossed magnetic and electric fields of low intensities, will deviate in the central part of the electrophoresis chamber of a standard Zeiss Cytopherometer with a component vertical to both fields. The direction and magnitude, however, were sharply at variance with what would be expected by the action of the Lorentz force (EMF) on the surface of the particles. The magnitude of the deviation depends upon the magnetic and electric field strength, the ion concentration of the suspension medium and the geometry of the chamber. The movement of the particles is due to streaming of the electrolyte which is mainly caused by inhomogeneities of the electric field in the electrophoresis chamber. The magnitude of the effect is high enough to occur physiological conditions. Magneto-electrophoretic streaming might eventually act as a transducer mechanism which could explain the ability of some animals to orientate themselves in the geomagnetic field.

Electricity↗
PubMed1977

Influence of the time in culture on cellular and neuronal properties of neuroblastoma x glioma hybrid cells. With an appendix, mathematical description of the kinetics of the loss in cell volume.

The stability of a clonal mouse neuroblastoma x rat glioma hybrid cell line was examined. Cell volume and cellular content of DNA and protein were measured as functions of the passage number. They decreased with the number of serial subcultivations. Cellular volume was linearly related to cellular DNA and protein. Thus, measurements of cell volume can be used to monitor the loss of DNA from hybrid cells. After about 60 passages a stable population of hybrid cells arose, as judged by the constancy of cellular volume and by the decreased coefficient of variation of the cell volume distribution. A mathematical model for the kinetics of the simultaneous loss of cellular volume, DNA and protein is introduced. Several neuronal properties were investigated. The specific activity of the neurotransmitter enzyme choline acetyltransferase decreased by more than 50% during 56 passages. After 70 subcultivations, the hybrid cells were still capable of extending processes, action potentials could still be elicited electrically or by iontophoretic application of acetylcholine, and the cells still responded to prostaglandin E1 as they do at low passage number.

Action Potentials↗
PubMed1977

[Changes of protein metabolism after X-irradiation. III. Dose dependent changes of the protease activity, the protein and the free amino acids in the spleen, liver, blood plasma, erythrocytes, stomach- and intestinal wall and in the carcass of rats after whole body X-irradiation with 400-1000 R (author's transl)].

The protease activity against externally added haemoglobin as a substrate and the autolytic activity against the proteins of the organism were decreases in most of the organs and in the total organism on the 3rd day after irradiation. This contradicts the explanation of the protein loss by an increased protein degradation. The free amino acids in the organs and in the whole organisms are unchanged or diminished. An increase would be expected if an increased protein degradation had occured because the free amino acids are the end product of the protein degradation. The conclusion of this investigation is that other mechanisms than protein degradation are responsible for the protein loss of the organism 3-6 days after X-irradiation. The increase of the protease activity and of the free amino acids in the blood plasma from day 1-3 coincides with the end of the destruction phase in the organism between day 1-2 after irradiation. The changes of the protease activity in the erythrocytes between day 1-30 after irradiation are probably not caused by a direct effect of the radaition on the erythrocytes of the peripheral blood. They are rather the results of a transient suppression of the hematopoeitic differentiation.

Amino Acids↗
PubMed1976

The computer analysis of volume distribution curves. Demonstration of two erythrocyte populations of different size in the young guinea pig and analysis of the mechanism of immune lysis of cells by antibody and complement.

Guinea pig, rat and sheep erythrocytes were sized electrically using the hydrodynamic focusing technique. The experimental curves were approximated with a computer by linear and logarithmic normal distributions. Rat and guinea pig erythrocytes from adult animals were best approximated by one linear normal distribution. Two populations (I, II) of erythrocytes with different mean volume could be demonstrated in young guinea pigs by this analysis. Population I erythrocytes are small, have a lower electrophoretic mobility and are mainly present at birth. They are gradually replaced by the larger population II erythrocytes. Both types of erythrocytes are probably the result of separate differentiation pathways. The analysis of erythrocyte volume distribution curves during immune lysis by antibody and complement shows that intact and ghost erythrocytes are measured by electrical sizing. No volume changes were observed up to the EAC1-8 intermediate. After the addition of C9, a C9 dose-dependent part of the erythrocytes swell permanently to spheroids. The spheroid transformation is a temperature-dependent, all or nothing reaction which is independent of protein osmotic forces from the interior of the cell.

Animals↗
PubMed1976

[Changes of protein metabolism following irradiation. II. Protease activity, protease pattern, protein and free amino acids in the cytoplasm and cell organelles of the rat liver following 600 R whole-body irradiation].

The protease activity of cytoplasm and cell organelles of the rat liver against liver protein and hemoglobin as a substrate increases during an initial reaction phase on the first day after 600 R whole body X-irradiation. This is probably a consequence of the degradation of cellular debris. The protein, the protease activity and the free amino acids of the cytoplasm and the cell organelles decrease during the disease phase on day 3 and 4 after irradiation. The protein loss of the liver is therefore not explained by an increased protease activity. The protease activity and the free amino acids are increased in the cytoplasm and the cell organelles during the regeneration phase of the organism between day 15 and 18 after irradiation.

Amino Acids↗
PubMed1975

Electrical sizing of liver cell nuclei by the particle beam method. Mean volume, volume distribution and electrical resistance.

Electrical sizing of liver cell nuclei gives similar results as histological techniques for the mean volume, the volume distribution and the proportions of the different nuclear volume populations. The electrical method has, compared to histological technics, however, the advantage of higher rapidity and accuracy. Due to the good volume resolution of the improved electrical sizing method two populations of nuclei with different mean volumes can be distinguished in rat liver tissue besides di-, tetra- and octoploid cell nuclei. In addition to the volume distribution curves, the mean electrical resistance of isolated liver nuclei can be determined by the electrical sizing method. A newly developed micromehod provides enough cell nuclei for electrical sizing from only 10 mg liver tissue in a few minutes. This should enable the measurement of nuclear volume distribution curves of human biopsy material from the liver and gastrointestinal tract for diagnostic purposes on a larger scale.

Animals↗
PubMed1975

[Changes in protein metabolism following irradiation. 1. Activity of protease, protease pattern, protein and free amino acids in cytoplams and cell organelles of the rat spleem following 600 R whole-body X-ray irradiation].

The protease activity of cytoplasm and cell organelles of the rat spleen against spleen protein and hemoglobin as a substrate increases during an initial reaction phase of the organism on the first day after 600 R whole body X-irradiation. The alkaline proteases in the cytoplasm and the acid proteases in the cell organelles increase, whereas the protease activity against externally added hemoglobin as substrate decreases below the initial values. The protein, the protease activity and the free amino acids of the cytoplasm and the cell organelles decrease during the disease phase on day 3 and 4 after irradiation. The protein loss of the spleen is therefore not explained by an increased protease activity. Acid proteases appear in the cytoplasm which derive probably from the cell organelles. The protease activity and the free amino acids are increased in the cytoplasm and the cell organelles during the regeneration phase of the organism between day 15 and 18 after irradiation.

Amino Acids↗
PubMed1975

Mechanism of complement-induced cell lysis. Demonstration of a three-step mechanism of EAC1-8 cell lysis by C9 and of a non-osmotic swelling of erythrocytes.

Sheep erythrocytes were sized by an electrical method during lysis by antibody and complement. No volume changes were observed upon to the EAC1-8 cell intermediate. Three steps could be distinguished in the reaction of C9 with EAC1-8 cells: fixation of C9 to EAC1-8 cells, a process which proceeds also at 0 degrees C; temperature-dependent swelling of the EAC1-9 cells; and lysis of the cells. We could show that swelling of the erythrocytes induced by the complement reaction is independent of protein osmotic forces and is caused by an alteration of the erythrocyte membrane.

Animals↗