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At least 19 recordsLinked to original sources
PubMed1978

The promise of the membrane artificial lung.

Membrane lungs are more physiologic than bubble or disc blood oxygenators. Membrane lungs are indispensable in long term perfusions. Recently, there has been a noticeable trend toward use of the membrane lung in open heart surgery. Improper use of the membrane lung lowers its optimum potential and may lead to disenchantment on the part of the user. It is important to recognize that for optimum performance of the membrane lung it is necessary to learn to correctly use the membrane lung.

Artificial Organs↗
PubMed1978

The influence of the lipid on the water permeability of artificial membranes.

The water permeabilities of artificial membranes formed formed from various monoglycerides or phospholipids in alkane solvents have been measured using an osmotic method, and it has been shown that the permeability depends upon the type of lipid used. For monoglycerides, the permeability was found to increase with the unsaturation and decrease with the length of the acyl chain. Membranes formed from either egg phosphatidylcholine or dioleyl phosphatidylcholine had an osmotic permeability coefficient of approx. 35--40 micrometer/s at 25 degrees C; with sphingomyelin as the membrane lipid, the permeability was an order of magnitude lower than that for phosphatidylcholine. It is suggested that the water permeabilities of biological membranes might be partly controlled by the types of lipid present.

Glycerides↗
PubMed1977

Effects of spontaneous and artificial membrane rupture in labour upon fetal heart rate.

This study reports the effects of spontaneous rupture of membranes and artificial rupture of membranes on fetal heart rate patterns during labour in 87 normal and 25 complicated pregnancies. The incidence of early deceleration patterns following membrane rupture was 6.25 per cent during the first 15 minutes and 1.78 per cent after 45 minutes, regardless of whether the pregnancy was normal or complicated. It is concluded that rupture of membranes does not significantly increase the incidence of early deceleration patterns. However, the occurrence of other heart rate alterations such as late decelerations, loss of beat-to-beat variability, changes in base line and tachycardia, need to be investigated further in larger collaborative studies.

Extraembryonic Membranes↗
PubMed1976

Simultaneous measurements of optical and electrical properties of artificial membranes composed of mitochondrial lipids and their interaction with cytochrome c.

A newly constructed cell, which allows simultaneous measurements of optical and electrical properties, was used to study bimolecular black membranes composed of beef heart mitochondrial lipids and their interaction with cytochrome c. The results show that these highly charged membranes are stable only in relatively limited ranges of boundary conditions. In 0.1 n KCl their maximum direct current (dc) resistance is 7 X 10(8) Ohm cm2 +/- 10%; the series capacity at 1 kHz is 0.43 muF/cm2 +/- 3%; the entire thickness, determined by optical reflectivity, is 5.8 +/- 0.2 nm. The interaction between oxidized cytochrome c and these lipid membranes is primarily of electrostatic nature, and dependent on the presence of highly charged phospholipids, such as diphosphatidyl glycerol (cardiolipin) and phosphatidyl ethanolamine. The attachment of cytochrome c maximally causes a 2.5-fold increase in reflectivity, without any noticeable change in the capacity. This leads to a subsequent instability of the membrane (i.e., rupture) preceded by a rapid increase of the dc conductivity. This behavior is far less pronounced with reduced cytochrome c.

Animals↗
PubMed1978

Interaction of fluorinated ether anesthetics with artificial membranes.

Fluorine-19 nuclear magnetic resonance spectroscopy is applied to the study of the environment of dipalmitoyl phosphatidylcholine-bound fluorinated ether anesthetics (enflurane, fluoroxene and methoxyflurane) both below and above the lipid gel to liquid crystal phase transition temperature. Line widths and spin-lattice relaxation time (T1) measurements are consistent with substantial immobilization of the lipid-bound anesethetic molecules. Heating anesthetic/lipid mixtures above the lipid transition temperature leads to narrowing of the lipid-bound anesthetic fluorine resonances accompanied by little or no change in anesthetic fluorine-19 chemical shifts, suggesting that although the mobility of the bound anesthetic increases at the higher temperature, the nature of the anesthetic-lipid interaction changes little as a result of this phase change. Differential scanning calorimetric studies of the effects of these anesthetics on the phase transition behavior of the phospholipid indicate that the regions of the bilayer in which volatile anesthetics partition at lower concentrations are different from the regions in which they partition at higher concentrations.

Anesthetics↗
PubMed1977

Fluorescence energy transfer between Ca2+ transport ATPase molecules in artificial membranes.

The purified ATPase of sarcoplasmic reticulum was covalently labeled with N-iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine (1,5-IAEDANS) or with iodoacetamidofluorescein (IAF). In reconstituted vesicles containing both types of ATPase molecules fluorescence energy transfer was observed from the IAEDANS (donor) to the IAF (acceptor) fluorophore as determined by the ratio of donor and acceptor fluorescence intensities, and by nanosecond decay measurements of donor fluorescence in the presence or absence of the acceptor. The observed energy transfer may arise by random collisions between ATPase molecules due to Brownian motion or by formation of complexes containing several ATPase molecules. Experimental distinction between these two models of energy transfer is possible based on predictions derived from mathematical models. Up to tenfold dilution of the lipid phase of reconstituted vesicles with egg lecithin had no measurable effect upon the energy transfer, suggesting that random collision between ATPase molecules in the lipid phase is not the principal cause of the observed effect. Addition of unlabeled ATPase in five- to tenfold molar excess over the labeled molecules abolished energy transfer. These observations together with electron microscopic and chemical cross-linking studies support the existence of ATPase oligomers in the membrane with sufficiently long lifetimes for energy transfer to occur. A hypothetical equilibrium between monomeric and tetrameric forms of the ATPase governed by the membrane potential is proposed as the structural basis of the regulation of Ca uptake and release by sarcoplasmic reticulum membranes during muscle contraction and relaxation.

Adenosine Triphosphatases↗
PubMed1977

Differential effects of cholesterol and lanosterol on artificial membranes.

The effects of cholesterol, 4,4-dimethylcholesterol, and lanosterol (4,4',14alpha-trimethyl-delta8,24-cholestadiene-3beta-ol) on some properties of lecithin vesicles have been compared. Unlike cholesterol, lanosterol retards the exit of trapped glucose from phospholipid vesicles only slightly. The 13C nuclear magnetic resonance spectrum of cholesterol/lecithin vesicles shows no resonances attributable to the sterol. By contrast, several resonances attributable to quaternary carbon atoms or methyl groups are seen in the 13C nuclear magnetic resonance spectrum of lanosterol/lecithin vesicles, indicating that lanosterol is much less immobilized than cholesterol. Because the membrane behavior of 4,4-dimethylcholesterol is closely similar to that of cholesterol, it is concluded that the axial 14-alpha-methyl group is responsible for the lessened membrane immobilization of lanosterol. The results emphasize the importance of a planar sterol alpha-face for interaction with phospholipid acyl chains.

Cholesterol↗
PubMed1979

A phenomenologic evaluation of CO2-diffusion restriction in kidney tubules studied in an artificial membrane system.

The chemical course in a multi-membrane system with interacting H+ and HCO3 ions has been described phenomenologically as an analogy of the neutralisation reaction between secreted H+ and filtered HCO-3 ions in the proximal tubules of the kidney. It was shown that the produced CO2 gave the highest PCO2 in the asymmetrically placed reaction centre, which favours a build-up of a high intratubular PCO2. The CO2 transport was dependent on the rate-limiting permeation of the reacting ions, and the permeation could be increased by the influence of solutions of macromolecules such as carbonic anhydrase, albumin and dextran.

Bicarbonates↗