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Biomedical subjects

A D Bangham

Publications and source records attributed to A D Bangham.

At least 19 recordsLinked to original sources
PubMed1993

Liposomes: the Babraham connection.

A chronological history is given of the experimental work carried out at The Institute of Animal Physiology, Babraham, Near Cambridge (UK) prior to and after the first description of liposomes in 1965. A convergence of worldwide interest in membrane structure and function coupled with the coexistence of physiologists, biochemists and electron microscopists provided a unique opportunity for the development of a useful model system. As well as defining their properties, such as composition, dimensions, perm-selectivity, permeating pathways and response to solutes (oil and/or water soluble), temperature and pressure, attention is drawn to a number of ideas investigated over the years relating to in vivo 'invisibility' of foreign particles, the trapping of ions in small vesicles the origins of life, to the mechanisms of anaesthesia and formulation of an effective lung surfactant.

Anesthetics↗
PubMed1992

Liposomes: realizing their promise.

Thirty years of study have proved that these artificial organelles are versatile tools for learning about the cell membrane. Researchers are now actively investigating their potential for some interesting practical uses as vehicles for gene transfer, as artificial erythrocyte surrogates, as a lubricant for degenerated joint surfaces, and most imminently as "targeted carriers" of pharmacologic agents.

Blood Substitutes↗
PubMed1988

Randomized trial of artificial surfactant (ALEC) given at birth to babies from 23 to 34 weeks gestation.

Artificial surfactant (ALEC) composed of dipalmitoylphosphatidylcholine and unsaturated phosphatidylglycerol in a ratio of 7:3 (w/w) and a dose of 50-100 mg was suspended in 1 ml of cold saline and used at birth as a prophylaxis against the respiratory distress syndrome and its complications in a two centre randomized prospective trial involving 341 babies from 23 to 34 weeks gestation regardless of their antenatal problems. The surfactant had little effect in babies above 29 weeks gestation and was most beneficial in babies under 30 weeks gestation (67 controls and 69 surfactant treated babies). In this subgroup the artificial surfactant significantly reduced the inspired oxygen and peak ventilator pressure requirements during the first 96 h, the incidence of intraventricular haemorrhages from 40% to 19% (P less than 0.01), the overall mortality from 36% to 17% (P less than 0.02), the mortality due to RDS from 31% to 9% (P less than 0.01), the need for more than 28 days oxygen from 37% to 21% (P = 0.05) and the use of pancuronium in ventilated babies from 52% to 27% (P less than 0.01). There were no apparent side effects. This protein free, artificial surfactant should be a useful addition to the therapy of babies under 30 weeks gestation to reduce the severity of their RDS and the incidence of serious complications.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1982

Effects of poly(ethylene glycol) on liposomes and erythrocytes. Permeability changes and membrane fusion.

Poly(ethylene glycol) 6000 induced a concentration-dependent, time-dependent decrease in the latency of the reaction between Arsenazo III sequestered in liposomes and extraliposomal Ca2+. This was mediated by a gross change in liposomal permeability, i.e. by a release of Arsenazo III from liposomes rather than simply by an entry of Ca2+. The loss of latency was strongly temperature-dependent, and it was markedly diminished on increasing the cholesterol content of the liposomes. It was apparently not due to an osmotic stress of the polymer. The high activation energy found (63 kJ . mol-1) is thought to indicate that the loss of latency resulted from local discontinuities in the lipid bilayers, caused by dehydration, rather than from partial or total lysis. Related microscopy experiments indicated that the polymer also caused the liposomes to fuse, and it is suggested that membrane fusion may have occurred at the sites of dehydration-induced discontinuities in adjacent bilayers. In addition, the polymer was found to enhance the permeability of hen erythrocytes of Ca2+ in a manner that was comparable to its effect on liposomal latency, and it is proposed that gel fusion induced by poly(ethylene glycol) may occur at the sites of similarly induced discontinuities in the phospholipid bilayers of two closely adjacent cells.

Animals↗
PubMed1981

Dry artificial lung surfactant and its effect on very premature babies.

Artificial lung surfactant prepared with pure dipalmitoylphosphatidylcholine and phosphatidylglycerol in a ratio of 7:3 was made as a dry powder and then blown down an endotracheal tube into the lungs of 22 very premature babies at birth. Only one dose was given. The treated babies did better than their 33 controls. Fewer needed ventilation, and those who did required lower pressures in the first six hours of life. None of the treated babies died, compared with 8 of the controls.

Clinical Trials as Topic↗
PubMed1981

The therapeutic effect of amphotericin in acrodermatitis enteropathica: hypothesis and implications.

A nine year-old girl with acrodermatitis enteropathica developed typical clinical and biochemical features of zinc deficiency on two occasions while on an oral zinc supplement. On both occasions, these features responded immediately when she was treated with amphotericin B lozenges. Studies in vitro showed that amphotericin increases the permeability to zinc of pure lipid membranes containing cholesterol. We suggest that the antibiotic enhanced zinc absorption from the oral supplement thereby effecting resolution of the patient's zinc deficiency.

Acrodermatitis↗
PubMed1980

Fusion of liposome membranes by the n-alkyl bromides.

It has been found that the n-alkyl bromides are capable of inducing the fusion of unilamellar liposomes. These compounds can bring about fusion of liposomes composed of either pure phosphatidylcholine or phosphatidycholine+phosphatidic acid. Fusion of unilamellar liposomes gives rise to multilamellar structures, the morphology of which has been examined by negative staining and freeze-fracture techniques. It has been shown by microelectrophoresis that the n-alkyl bromides have no effect on the surface charge of liposomes, and fusion has been further characterized by use of light scattering and differential scanning calorimetry, the latter indicating that true mixing of the fatty acyl chains occurs upon fusion. Finally, fusion occurs at n-alkyl bromide levels below that required to saturate the aqueous phase of the system.

Calorimetry, Differential Scanning↗
PubMed1980

Measurement of net proton-hydroxyl permeability of large unilamellar liposomes with the fluorescent pH probe, 9-aminoacridine.

The fluorescent probe 9-aminoacridine was used to measure the rate of decay of experimentally established pH gradients across liposome membranes. From the rate of decay, separate permeability coefficients for protons (PH) and hydroxyls (POH) were calculated and summed to yield the net proton-hydroxyl permeability (Pnet). The net permeability of protons and hydroxyls was found to be approximately 10(-4) cm/s, six orders of magnitude greater than that measured for sodium and pyrophosphate ions under similar conditions. This suggests that protons and/or hydroxyls cross lipid bilayers by a different mechanism than do other monovalent cations and anions. In addition, the measurements provide a standard for net proton-hydroxyl permeability in pure phospholipid bilayers for comparison with biological membranes.

Aminoacridines↗
PubMed1979

The physical properties of an effective lung surfactant.

It is suggested that the phospholipids at the alveolar/air interface exhibit both thermodynamic (equilibrium) and kinetic forces during the course of a respiratory cycle. The alveolae are kept open at full expiration by a residue of nearly pure dipalmitoyl phosphatidylcholine which is condensed and therefore, incompressible at 37 degrees C.

Chemical Phenomena↗
PubMed1979

The effect of some general anaesthetics on the surface potential of lipid monolayers.

1 This study sought to investigate the report by Ginsberg (1978) that 0.7 M ethanol brought about a + 100 mV change (DeltaDeltaV) in the surface potential of glyceryl monooleate (GMO) monolayers formed on KCl, although he predicted that a DeltaDeltaV of -10 mV should have been found.2 The effect of general anaesthetics such as n-alkyl alcohols and pentobarbitone on surface potential (DeltaV) and surface tension (gamma) of lipid monolayers formed on 145 mM KCl from either glyceryl monooleate (GMO) or phosphatidyl choline (PC) was examined with an Americium-241 air electrode assembly (DeltaV) and a platinized platinum dipping plate and force balance (gamma).3 It was found that, as predicted by Ginsberg (1978), addition of 0.7 M ethanol to the aqueous phase bathing either PC or GMO monolayers brings about a negative-going change in interfacial potential (DeltaDeltaV).4 The magnitude of DeltaDeltaV is dependent in a linear fashion on ethanol concentration.5 Longer chain length alcohols up to n-decanol also bring about a negative going change in DeltaDeltaV, and the dependence of DeltaDeltaV on anaesthetic activity, with respect to increasing chain length of anaesthetic, is consistent with Traube's law.6 Pentobarbitone added to the aqueous phase bathing the monolayer also elicits a negative DeltaDeltaV, a finding which rules out the possibility of adsorption of the volatile alcohols to the measuring electrode.7 The findings are discussed in terms of the proposition that increasing disorder in an array of fixed dipoles, such as might occur in a bilayer exposed to anaesthetic, would result in a lowering of the electrostatic barrier to the predominantly impermeable cation.

Anesthetics↗