Biochemical disturbances of the reactive oxygen species metabolism revealed in subjects with Down's syndrome (DS), and the findings indicating that heat-induced cell alterations have been, at least, ...partly mediated by reactive oxygen species, made the elucidation of the response of trisomic cells to elevated temperatures of special interest. Kinetic analysis of cell-survival curves, accompanied by the flow cytometry and the scanning electron microscopy (SEM) examinations, and their relationship with the cell membrane fluidity, were undertaken. At each temperature (48–54°C),
D
q parameters, representing the ability to accumulate sublethal damages, were similar for both cell groups.
D
0 parameters (inverse leakage rates;
D
0=1/
k) were greater for DS cells at each temperature below 54°C. The haemolysis sensitivity ratio (HSR) showed that DS erythrocytes were, in average, 1.60 times more resistant to heat injury than those from normal subjects. Activation energies of haemolysis, calculated according to the Arrhenius equation, were similar both for normal (290.8±6.5 kJ/mol) and DS erythrocytes (288.0±5.5 kJ/mol). Flow cytometry studies showed that the scattering properties of intact DS erythrocytes (reflecting size, volume, shape and cell membrane surface morphology) were different than those of normal cells. Scanning electron micrographs and scattering diagrams obtained for cells submitted to heat stress (51°C) confirmed that DS erythrocytes were more resistant, to a certain extent, to heat-induced disruption than normal cells. The steady-state fluorescence anisotropy of TMA-DPH (1-(4-trimethyl-ammoniumphenyl)-6-phenyl-1,3,5-hexatriene) showed that untreated DS erythrocytes had substantially lower fluidity (
r=0.356±0.008) of the outer monolayer of cell membranes as compared to normal cells (
r=0.324±0.011). The increase of the cell membrane fluidity during exposure to heat was observed. The greatest elevation of cell membrane fluidity occurred during the preleakage period, immediately upon the heat treatment and was considered as a rate-limiting step of heat-induced haemolysis.
Counteraction of drug resistance is a major challenge in cancer therapy, particularly in advanced stages. The main mechanism of multidrug resistance is related to an increased drug efflux. In the ...present study we examined the effect of modifying cell membrane lipid fluidity on uptake of adriamycin (ADR) in cells of AKR lymphoma malignancy variants. Modification of cell membrane fluidity, either by lecithin or by lecithin-cholesterol mixtures, induced in a high proportion of cells of all variants a higher capacity to accumulate ADR. The chemosensitizing effect, for lecithin in particular, was proportional to the degree of malignancy of the lymphoma variants. The increased ADR uptake was up to 1.4-fold in the variant of lowest malignancy and up to 5-fold in the one of highest aggressiveness. This tendency correlates with our previous studies and is of particular value since highly-malignant tumors are often drug resistant. The cholesterol-lecithin mixture, induced, however, in part of the variants the appearance of a small subpopulation with very low ADR permeability. Cell membrane rigidification is of value for exposing tumor cell cryptic antigens but may be deleterious when used in conjunction with chemotherapy.
Changes in multidrug resistance by resistance modifiers such as R-verapamil cause changes in fluidity of the cell membrane. The extent to which these changes involve structural alterations in ...membrane lipids has been investigated in CHO cells.
Sensitive (AUXB1) and resistant (CH(R)C5) chinese hamster ovary cells (CHO) were grown in culture. Incubations were carried out with R-verapamil (0-10 microM) or the membrane perturbing agents tauro-cheno-deoxycholate (0-1.6 mM, TCDC) and tauro-urso-deoxycholate (0-3.5mM, TUDC). Cell membrane fluidity was determined by electron-paramagnetic resonance spectroscopy and membrane lipids by HPLC and TLC.
The resistant CH(R)C5 subline had a higher cell membrane order (lower fluidity, S = 0.7234) in the interface region of the cell membrane than sensitive AUXB1 cells (S = 0.6984) determined using EPR. The MDR-modulator R-verapamil and TCDC, but not TUDC, lowered cell membrane order in a concentration-dependent manner and increased membrane fluidity of the resistant CH(R)C5 subline. TCDC and R-verapamil were without effect on the cell membrane fluidity of AUXB1 cells. These changes were accompanied by alterations in the fatty acid composition of the plasma membrane. Untreated sensitive AUXB1 cells had higher levels of unsaturated fatty acids than resistant CH(R)C5 cells. In CH(R)C5 cells, R-verapamil increased the content of poly-unsaturated fatty acids and TCDC, but not TUDC, increased the content of mono-unsaturated fatty acids.
The results demonstrate that resistance modifiers such as verapamil may influence cytostatic drug action by producing structural changes to lipid domains in the plasma membrane.
To study the effect of silverionized drinking water on erythrocyte membrane fluidity, serum lipids and vascular endothelial cells in tail-suspended rats.
Thirty male SD rats were randomly divided ...into ground control group (GC), simulated weightlessness control group (SC), simulated weightlessness and silverionized water drinking group (SS). Number of circulating endothelial cells (CEC), serum lipids and erythrocyte membranes fluidity was measured on the 21st day of tail suspension.
Levels of serum TC, TG, HDL-C, HDL-C/TC and erythrocyte membrane fluidity in SC rats were significantly lower than those in GC rats; LDL-C/HDL-C ratio and number of CEC in SC rats were markedly higher than those in GC rats. Levels of serum TC, LDL-C and LDL-C/HDL-C in SS rats were higher than those in SC rats; HDL-C/TC ratio and erythrocyte membrane fluidity in SS rats were lower than those in SC rats.
Drinking silverionized water has a negative effect on lipid metabolism in tail-suspended rats.
In a spectrum of raptorial birds hemorrheologic factors were determined compared to normal human values. Significant findings were that Hageman factor (factor XII) levels were very low, the red-cell ...filteration rate was low, but the platelet-aggregate ratio was in the normal range. Relatively large, nucleated red cells appeared to be less flexible-deformable--than normal human red cells. Microvessel density (MVD) appeared to be in the normal range, but increased average capillary diameter may explain the lack of microvascular abnormalities. Hageman factor deficiency in raptors is comparable to human hemophilia D. However, the mechanisms of the lack of obvious thromboembolic and/or hemorrhagic phenomena may require further investigation.
In this chapter, basics and mechanisms of electroporation are presented. Most important electric pulse parameters for electroporation efficiency for different applications that involve introduction ...of small molecules and macromolecules into the cell or cell membrane electrofusion are described. In all these applications, cell viability has to be preserved. However, in some biotechnological applications, such as liquid food sterilization or water treatment, electroporation is used as a method for efficient cell killing. For all the applications mentioned above, besides electric pulse parameters, other factors, such as electroporation medium composition and osmotic pressure, play significant roles in electroporation effectiveness. For controlled use of the method in all applications, the basic mechanisms of electroporation need to be known. The phenomenon was studied from the single-cell level and dense cell suspension that represents a simplified homogenous tissue model, to complex biological tissues. In the latter, different cell types and electric conductivity that change during the course of electric pulse application can significantly affect the effectiveness of the treatment. For such a complex situation, the design and use of suitable electrodes and theoretical modeling of electric field distribution within the tissue are essential. Electroporation as a universal method applicable to different cell types is used for different purposes. In medicine it is used for electrochemotherapy and genetherapy. In biotechnology it is used for water and liquid food sterilization and for transfection of bacteria, yeast, plant protoplast, and intact plant tissue. Understanding the phenomenon of electroporation, its mechanisms and optimization of all the parameters that affect electroporation is a prerequisite for successful treatment. In addition to the parameters mentioned above, different biological characteristics of treated cell affect the outcome of the treatment. Electroporation, gene electrotransfer and electrofusion are affected by cell membrane fluidity, cytoskeleton, and the presence of the cell wall in bacteria yeast and plant cells. Thus, electroporation parameters need to be specifically optimized for different cell types.
Thromboembolic disorders are frequent complications in polycythemia vera. In addition to thrombocytosis with hyperaggregability, leukocytosis, and high hematocrit, hyperviscosity syndrome, a new ...component, is described in the pathophysiology of this phenomenon. There is decreased red cell membrane fluidity with decreased deformability which increases the susceptibility to microvascular occlusion and also increases the chance of disseminated intravascular coagulation (DIC). Periodic phlebotomies improved the hematologic picture in these patients and results in the removal of the "stiff" red cells with an increased production of young red cells, greater membrane fluidity, deformability and less chance of microvascular occlusion.
Exercise-induced hypoxaemia (EIH) has been associated with an oxygen diffusion limitation. Because polyunsaturated fatty acids (PUFA) administration can modify cell membrane fluidity, we hypothesized ...that the importance of EIH could be reduced after a 6-week PUFA diet. Resting pulmonary functions and a maximal cycling test were performed before and after the diet, in eight master athletes -48 (SD 6 years)-. The partial pressure of O2 in arterial blood (PaO2), alveolar ventilation (VA) and ideal alveolar-arterial oxygen partial pressure difference (P(Ai-a) O2) were obtained at each exercise intensity. The extent of EIH at maximal exercise was significantly lower after PUFA PaO2-17.2 (SEM 1.9) vs -12.9 (SEM 2.2). Before PUFA, VA accounted for 50% of the variance in the fall in P (Ai-a) for intensities below 80% maximal oxygen uptake (VO2max) and P(Ai-a)O2 for 60% between 70% and 100% VO2max. After PUFA, the reduction in EIH was highly correlated (r2 = 0.85; P < 0.001) to resulting changes in P(Ai-a)O2 and resting pulmonary diffusing capacity (DLCO)/VA but not with changes in ideal alveolar partial pressure of oxygen. The improvement in EIH following PUFA could be related to an increase in alveolar-arterial oxygen conductance following improved pulmonary diffusion.
The lipids of all higher organisms contain appreciable quantities of polyunsaturated fatty acids (PUFAs) with methylene-interrupted, i.e., with two or more double bonds of the cis-configuration ...separated by a single methylene group. The term “homo-allylic” is occasionally used to describe this molecular feature.
NAKAZAWA, I. and IWAIZUMI, M. A Role of the Cancer Cell Membrane Fluidity in the Cancer Metastases: An ESR Study. Tohoku J. Exp. Med., 1989, 157 (3), 193-198 - AH66F or Yoshida sarcoma (YS) cells ...were transplanted intraperitoneally into male Donryu rats. Cancer cells obtained from ascites were suspended in saline solution (107cells/ml) after washing. Then, 0.1ml of each suspension obtained from both strains was injected into the tail vein of 5 rats, respectively. Each metastatic nodule, 1mm or less in a diameter, thus obtained was then injected into the peritoneal cavity in which these metastatic cells come to free. After 10 days, cancer cells obtained from each ascites were suspended in phosphate buffered saline (Ca2+ and Mg2+ free, pH 7.2) after washing. Each suspension (107cells/ml) was violently vibrated with a definite amo unt of 5-doxylstearic acid and spin labeling of cancer cell membrane was done. Furthermore, each specimen thus obtained was subjected to the electron spin resonance (ESR) measurement and the order parameter was determined from the spectra. In both YS and AH66F strains, the cell membrane fluidity of the metastatic cancer cell was increased at each temperature measured from 5°C through 35°C. The results obtained here suggest that the change of the cell membrane fluidity of cancer cell is closely related with the cancer metastases.
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