Altered Membrane Properties Research Articles

Graphic Analysis of Osmotic Fragility of Erythrocytes

A precise and highly reproducible method for analyzing the osmotic fragility of erythrocytes with a minute amount of blood (less than 10 mul) is described. The osmotic fragility curves are recorded with a coil planet centrifuge with accessories and a scanning photodensitometer. The recorded curves are transcribed by a DuPont Curve Resolver and their components are analyzed. Normal fragility curves obtained from healthy adults revealed slightly skewed Gaussian curves and they were resolved into several typical Gaussian components which differed according to the physical and clinical conditions of subjects. Each resolved component is supposed to correspond to the population of erythrocytes having a nearly identical osmotic fragility. The method is proved to be useful for the detection of altered membrane properties of erythrocytes in various diseases.

Membrane-mediated drug resistance and phenotypic reversion to normal growth behavior of Chinese hamster cells.

Development of resistance to actinomycin D, daunomycin, or vincristine in Chinese hamster cells growing in vitro resulted in reversion to or retention of normal phenotypes in comparison to spontaneously transformed drug-sensitive parent populations. Sublines resistant or cross-resistant to actinomycin D showed reduced uptake of antibiotic in proportion to degree of resistance. The cells with acquired resistance were either weakly tumorigenic or nontumorigenic when tested in the cheek pouches of weanling Syrian hamsters treated with cortisone. In contrast, parent cells and several amethopterin (methotrexate)-resistant sublines produced many tumors. Antibiotic- and Vinca-alkaloid-resistant cell lines showed oriented growth patterns often associated with the behavior of normal cells in culture; antibiotic-sensitive, tumorigenic lines had morphologic characteristics of malignant cells. The altered cell membrane properties that accompanied development of resistance or cross-resistance to actinomycin D appeared to account also for the lower oncogenic potential and greater cell adhesiveness of resistant cells relative to their malignant counterparts.

Effects of synthetic buffers on reflexes in the isolated frog spinal cord

Substitution of synthetic buffers (Tris, TES, HEPES, or 3,3-dimethylglutarate) for CO2-bicarbonate buffer in Ringer solution perfusing the isolated in vitro frog spinal cord preparation altered membrane properties and reflex activity. Perfusion with Ringer solution gassed with O2 and containing synthetic bu,fers consistently produced a depolarization of motoneurons and dorsal root fibers, decreased the amplitude (and usually the duration) of ventral and dorsal root potentials, and had variable effects on motoneuron and dorsal root reflex discharges. With Tris-Ringer these discharges decreased in amplitude; with Ringer containing one of the other synthetic buffers, these discharges were augmented. All changes were reversible when the cord was returned to bicarbonate-buffered Ringer aerated with 95% O2/5% CO2. The use of a combined buffer system-one containing a synthetic buffer and bicarbonate-induced smaller or minimal changes in bioelectric activity. At present the data are insufficient to allow firm conclusions concerning the mechanisms underlying these results; but it is evident 1) that changes in PCO2 and bicarbonate concentration and 2) that the pharmacological properties of synthetic buffers are important variables.

A thermally induced alteration in lysosome membranes: Salt permeability at 0 and 37 °C

Preparations of radioactive lysosomes were obtained from mouse kidney after injection of radioactive iodine-labeled bovine ribonuclease. Stability of these lysosomes in various media was estimated from measurements of proteolytic activity towards the ribonuclease, and of ribonuclease retention in particles. The lysosomes were stable at 37 °C in isotonic, sucrose-free solutions of KCl, NaCl and potassium acetate, and in mixtures of these with MgCl 2, showing that these salts are relatively impermeant through the lysosomal membranes. The membranes were less permeable to Na + than to K +. Both KCl and NaCl exerted their optimal protective effects over a broad concentration range above 0.125 M in 0.025 M acetate buffer. Mg 2+ enhanced the protective effect of both K + and Na +; the osmotic effect of 0.075 M NaCl-0.05 M MgCl 2 was indistinguishable during the entire course of ribonuclease digestion from that of isotonic sucrose. Osmotic protection by KCl-MgCl 2 was demonstrated over the pH range 5.5–7.0. A marked alteration in membrane properties occurs at lower temperatures in 0.11 M KCl-0.01 M MgCl 2 such that, at 0 °C, K + permeability is much higher than at 37 °C, as shown by a several-fold decrease in stability at the lower temperature.

Early elevations of glycosidase, acid phosphatase, and acid proteolytic enzyme activity in denervated skeletal muscle

Evidence is presented that denervation of rat extensor digitorum longus is rapidly followed by selective increases in the activity of glycosidase, acid phosphatase, and acid proteolytic enzymes. A novel double-denervation paradigm was used to demonstrate that the elevation in at least two enzyme activities, β- d-mannosidase and α- l-fucosidase is influenced by something in, or some process mediated by, the nerve. The nature of this elevation in enzyme activity points to a sensitive, neurally influenced control mechanism established in the normal relationship between nerve and muscle, but which is upset by denervation. The possible relationships of increased acid hydrolytic enzyme activity to general muscle atrophy is discussed, and a hypothesis is presented that the early metabolic changes triggered by denervation result in the altered membrane properties of denervated muscle.

Influence of Phenolic Acids on Ion Uptake

The influence of naturally occurring phenolic acids on phosphate uptake by barley (Hordeum vulgare L. cv. Karlsberg) roots was examined using (32)P-labeled phosphate. Without exception, all compounds tested, namely, benzoic, 2-hydroxybenzoic, 4-hydroxybenzoic, 3,4-dihydroxybenzoic, 3,4,5-trihydroxybenzoic, 4-hydroxy-3-methoxybenzoic, 4-hydroxy-3,5-dimethoxybenzoic, cinnamic, 2-hydroxycinnamic, 4-hydroxycinnamic, 3,4-dihydroxycinnamic, 4-hydroxy-3-methoxycinnamic, and 4-hydroxy-3,5-dimethoxycinnamic acids, inhibited uptake.The degree of inhibition correlated well with the lipid solubility of these phenolic compounds. This as well as kinetic data support the hypothesis of inhibition through altered membrane properties.

Properties of lipid bilayer membranes separating two aqueous phases: The effects of Fe+3 on electrical properties

Ferric ion has been found to alter the electrical properties of lecithincholesterol-decane bilayer membranes. Within minutes after the addition of microgram quantities of FeCl3 to the ambient aqueous phase, the resistance of the membrane falls by a factor of 10(5) to 10(6). No change in capacitance is observed. The resistance change is obtained with membranes made from synthetic lecithin (fully saturated fatty acids) as well as by those formed from egg lecithin. The conductance of the modified membrane exhibits both time and voltage dependent behavior; the time dependence of the current is similar to that of an inductance, and the voltage dependence of the current is exponential. Concomitant with the resistance change, the modified membrane becomes permselective, passing chloride almost to the complete exclusion of sodium. Anion selectivity can be converted to cation selectivity by the subsequent addition of certain chelating agents. Area-conductance measurements show the resistance change occurs in the thin film. The addition of a reducing agent causes the effect of the ferric ion to be reversed, and the conductance returns to that characteristic of unmodified membranes. When ferric ion is added to only one side of the membrane, the system rectifies with current ratios of up to 20∶1. It is concluded that the alteration of membrane properties owes its origin to the hydrolysis of membrane-bound ferric ion. The interaction of ferric ion with aqueous dispersions of lecithin has been investigated by several techniques, and evidence is presented that the dispersions bind charged species of iron and that this charge diminishes under conditions where iron hydrolysis occurs.

Membrane matrix disruption by melittin

Electron spin resonance spectroscopy was used to examine the interaction of the lytic polypeptide, melittin, with model membrane systems in order to determine the physical basis for its alterations of membrane properties. Sonically dispersed egg lecithin (phosphatidylcholine), phosphatidylserine, extracted Escherichia coli phospholipids, and isolated E. coli membranes were spin-labeled with fatty acid probes and treated with melittin solutions. Spectral analysis indicates that melittin induces a disruption of the phospholipid matrix without a significant change in the mobility of extensive regions of the acyl chains. This perturbation causes a melittin concentration dependent alteration in the capacity of the lipid matrix for spin label such that more of the probe is taken up. The effects are independent of phospholipid composition and the presence of membrane proteins. It is suggested that melittin participates in a hydrophobic interaction with the hydrocarbon region of the bilayer and acts as a disrupter of matrix ordering.

Ion transport by heart mitochondria. The effects of Cu 2+ on membrane permeability

Cu 2+ binds to protein-binding sites in the membrane of the isolated heart mitochondrion with high affinity. The binding of from 5 to 10 nmoles of Cu 2+ per milligram of protein results in a number of alterations in membrane properties. These include increased passive permeability to both cations and anions, increased energy-dependent cation uptake under the appropriate conditions, increased ATPase activity, uncoupling of phosphorylation, and inhibition of the phosphate transport system. The effect of Cu 2+ on respiration in vitro depends upon which of the above listed effects of Cu 2+ on the membrane predominate under the conditions of measurement. A given amount of Cu 2+ is more effective in altering membrane properties in energized as opposed to nonrespiring or uncoupled mitochondria. It appears that Cu 2+ is able to react with and alter certain crucial sites in the membrane which control permeability to ions and that this alteration occurs more rapidly in the presence than in the absence of metabolic energy.

Penicillin-induced segmental myoclonus. I. Motor responses and intracellular recording from motoneurons.

The lumbar spinal cord of rats and cats has been used as a model system to study the epileptogenic effects of penicillin. Within a few minutes after the application of penicillin, segmental myoclonus develops. Intracellular recording from cat motoneurons demonstrates that penicillin induces periodic large spontaneously occurring depolarizing synaptic potentials. Either these responses or directly applied intracellular current pulses evoked prolonged depolarization of the motoneuron soma, which represent an alteration in membrane properties of motoneurons. The prolonged depolarization has a threshold for termination by a hyperpolarizing current.

Effect of ethylene on the permeability of excised cantaloupe fruit tissue.

C(hanges in tisstue permeability are associated with the matutration and ripening of fruits. Blackman and Parija (3) suggested that permeability changes may cause the climacteric rise in respiration which is a characteristic of ripening in most fruits. Sacher (13) showed that leakage of solutes increased progressively with the climacteric rise in ripening banana and avocado fruits, and he noted that these results were consistent with the hvpothesis that alteration in membrane properties may catuse the climacteric. Ben-Yehoshua (2) reported that leakage of cellular materials from excised disks of avocado fruits began before the onset of the climacteric and continued to increase during the rise in respiration. He agreed with Sacher that changes in membrane permeability may bear a causal relationship to the climacteric. Baur and Workman (1) noted that changes in permeability and the onset of the climacteric apparently occulrred simultaneously in banana fruits. Bturg et al. (5) concluded that solute efflux from banana tissue was simply a reflection of sugar content, and that permeability did not change with ripening. However, using solute uptake to estimate free space, Sacher (14) has shown conclusively that permeability does increase with ripening of banana frtuits and, indeed, that changes in permeability precede the onset of the climacteric rise. There is evidence that an increase in ethylene prodtuction also precedes the climacteric rise in respiration. This has been shown in bananas (4) and in Honey Dew melons (12). Recalculation of the data of Lyons et al. (7) indicates that an increase in internal ethylene concentration probably precedes the onset of the climacteric in cantaloupe fruits, also.