Membrane fluidity and myotonia: Effects of cholesterol and desmosterol on erythrocyte membrane fluidity in rats with 20,25-diazacholesterol-induced myotonia and on phospholipid liposomes

Previous spin-label and electromyographic experiments with rats fed 20,25-diazacholesterol, an inhibitor of the biosynthetic conversion of desmostero[ to cholesterol, demonstrated an increased erythrocyte membrane fluidity and myotonia, a prolonged muscle contraction upon stimulation. The current studies with rats showed normal erythrocyte fluidity in animals fed 20,25-diazacholesterol but maintained on a high-cholesterol diet and no myotonia. Studies of model membrane systems composed of phospholipid vesicles containing desmosterol, cholesterol, or both demonstrated that desmosterol increased membrane lipid fluidity relative to cholesterol, suggesting that in 20,25-diazacholesterol-induced myotonia, in which desmosterot accounts for 85% of the plasma sterol, the increased membrane fluidity previously observed in erythrocytes and sarcolemma m this animal model of human congenital myotonia may be due to desmosterol.     

Interaction of influenza virus proteins with planar bilayer lipid membranes II. Effects of rimantadine and amantadine

The dependence of the surface potential difference (ΔU), transversal elasticity module (E₁) and membrane conductivity (G₀) on the concentrations of the antiviral drugs, rimantadine and amantadine was studied in the planar bilayer lipid membrane system. The method used was based on independent measurements of the second and third harmonics of the membrane capacitance current. The binding constants of bilayer lipid membranes obtained from the drug adsorption isotherms were 2.1 · 10⁵ M^?1 and 1.3 · 10⁴ M^?1 for rimantadine and amantadine, respectively. The changes in G₀ took place only after drug adsorption saturation had been achieved. The influence of rimantadine and amantadine on the interaction of bilayer lipid membranes with matrix protein from influenza virus was also investigated. The presence of 70 μg/ml rimantadine in the bathing solution resulted in an increase in the concentration of M-protein at which the adsorption and conductance changes were observed. The effects of amantadine were similar to those of rimantadine but required a higher critical concentration of amantadine. The results obtained suggest that the antiviral properties of rimantadine and amantadine may be related to the interaction of these drugs with the cell membrane, which can affect virus penetration into the cell as well as maturation of the viral particle at the cell membrane.     

Evidence for a highly asymmetric arrangement of ether- and diacyl-phospholipid subclasses in the plasma membrane of Krebs II ascites cells

(1) Krebs II ascites cells were taken as a model of the neoplastic cells to investigate the transverse distribution of phospholipids in the plasma membrane. The experimental procedure was based on non-lytic degradation of phospholipids in the intact cell by Naja naja phospholipase A₂ and Staphylococcus aureus sphingomyelinase C and on phopholipid analysis of purified plasma membranes. It was shown that the three major phospholipids, i.e., phosphatidylcholine, phosphatidylethanolamine and sphingomyelin, are randomly distributed between the two halves of the membranes, whereas phosphatidylserine remains located in the inner leaflet. (2) The membrane localization of phosphatidylcholine and phosphatidylethanolamine subclasses (diacyl, alkylacyl and alkenylacyl) was also examined, using a new procedure of ether-phospholipid determination. The method involves a selective removal of diacyl species by guinea pig pancreas phospholipase A₁ and of alkenylacyl species by acidolysis. This analysis revealed a 50% increase of ether phospholipids in the plasma membrane as compared to the whole cell (36.5 and 23.1% of total phospholipid, respectively). Furthermore, a strong membrane asymmetry was demonstrated for the three phosphatidylcholine subclasses, since 1-alkyl-2-acyl-sn-glycerol-3-phosphocholine (alkylacyl-GPC) was entirely found in the inner leaflet, whereas both diacyl- and alkenylacyl-GPC displayed an external localization. The same pattern was observed for phosphatidylethanolamine subclasses, except for 1-alkenyl-2-acyl-sn-glycero-3-phosphoethanolamine, which was found randomly distributed. These results are discussed in relation to the process of cell malignant transformation and to the biosynthesis of platelet-activating factor (PAF-acether or 1-alkyl-2-acetyl-GPC).     

Morphology,physiology and infectivity of twoFrankia isolates An 1 and An 2 from root nodules ofAlnus nitida

Summary Two different strains, An 1 and An 2, were obtained from root nodules ofAlnus nitida Endl., collected from one locality in the area of its natural habitat near Bahrin, District Swat, Pakistan. The light and electron microscopy of the isolates revealed the occurrence of septate and branched hyphae bearing sporangia and vesicles. The strains differed in their growth requirements, nitrogen-fixing ability and production of extracellular pigments, thus indicating the existence of more than oneFrankia strain in the same locality. In the absence of combined nitrogen in the medium strain An 1 formed vesicles and fixed N₂ (up to 200 nmol C₂H₄. mg protein^–1.h^–1), while strain An 2 under the experimental conditions formed only few vesicles and fixed N₂ at a very low rate (ca 10 nmol C₂H₄. mg protein^–1 .h^–1). The nitrogenase activity of strain An 1 was strongly affected by the O₂ concentration.Frankia An 1 and An 2 were infective and effective onA. nitida andA. glutinosa but not onDatisca cannabina andElaeagnus umbellata. Both An 1 and An 2 strains were more infective and effective onA. glutinosa thanFrankia strains AvcIl and CpI1.     

The influence of postnatal nutrition on lipoprotein lipase activity and hormone sensitive lipolysis in vitro of rat adipose tissue

In rats grown up in small and large nests the lipolytic activity of adipose tissue was studied in vitro in dependence on age. Independent of age and sex a significantly higher lipoprotein lipase activity as well as a lower basal or norepinephrine stimulated lipolysis and reesterification (absolute) occurred in rats from small nests compared with rats from large nests. The calculated degree of reesterification was independent of the nest size, but decreased from 80% to 30% from one month to one year of age. The marked differences in the lipolytic activities of adipose tissue emphasize the distinct influence of the post-natal nutrition on metabolic functions in the later life and lead to the conclusion that the metabolism of adipose tissue of animals from small nests is directed towards a long-term increased storage of lipids.     

Effect of temperature on the protein and nucleic acid content of thermotolerant yeasts

Summary The effect of growth at 30°, 35° and 40° on the biomass yield and on the nucleic acid and protein content of twelve isolates of yeast has been studied. Although yields of 41.6% and a true protein content of 34% were obtained, each of the strains exhibited a lower yield and protein content at 40° than at the lower temperatures. Nucleic acid levels were also reduced at 40°.     

Some blood genetic markers of selected tribes in Western Saudi Arabia

A total of 292 randomly selected subjects belonging to two indigenous Arab tribes (Harbi and Ghamid) and two immigrant tribes (Mograbi and Mowallad), residents in Western Saudi Arabia, have been tested for genetic variants of six blood groups, four serum proteins, and five red cell enzyme systems. The distribution of the polymorphic systems was different between indigenous and immigrant tribes, and the present Arab population shows a considerable degree of admixture from the surrounding countries, in particular Africa.     

Survival of Curvularia lunata var. aeria in soil

Spore suspensions from 7 day old cultures of Curvularia lunata (Wakker) Boedijn var. aeria (Batista, Lima and Vasconcelos) M.B. Ellis were added to soil samples originally devoid of Curvularia propagules. The test fungus disappeared after six weeks of inoculation irrespective of soil amendments, like the application of green manure, urea, superphosphate, or soil cropped to Sorghum (dura) or cotton seedlings.     

Biometric variations in Solea vulgaris acclimatized in Lake Quarun, Upper Egypt

A population of Solea vulgaris was transplanted in 1938 from the Mediterranean to a land locked brackish lake. In 1977, the morphology of these fishes was investigated and a number of measurements made and compared with those of fish caught in the Mediterranean. Among these variations was less vertebrae and fewer dorsal fin rays in the lake soles.