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Dipalmitoyl Phosphatidylcholine (dipalmitoyl + phosphatidylcholine)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Molecular dynamics simulation of the hydrocarbon region of a biomembrane using a reduced representation model

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 14 2001
Lewis Whitehead
Abstract The development of a coarse-grained reduced-representation model of the hydrocarbon region of a biological membrane is reported. The potential is based on the popular Gay,Berne model of liquid crystals, and involves the linking of individual Gay,Berne ellipsoids by harmonic springs to form each hydrocarbon chain. Diffusion coefficients and order parameters have been calculated by molecular dynamics computer simulations for a range of parameter sets. The results clearly demonstrate the presence of a phase transition from an ordered low-temperature solid phase reminiscent of the L,, phase of phospholipids, to a high-temperature disordered phase reminiscent of the L, phase. Order parameters calculated for each layer of the model are consistent with the experimental segmental order parameters reported for dipalmitoyl phosphatidylcholine. The application of this model to the study of small molecule diffusion within the membrane core is proposed. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1622,1633, 2001 [source]

SURGICAL ADHESIONS: EVIDENCE FOR ADSORPTION OF SURFACTANT TO PERITONEAL MESOTHELIUM

ANZ JOURNAL OF SURGERY, Issue 6 2000
Y. Chen
Background: It has been speculated that the formation of surgical adhesions must be preceded by physical adhesion of the two surfaces, a process normally prevented by a lining of adsorbed surface-active phospholipid (surfactant) acting as both a superb boundary (solid-to-solid) lubricant and a release (antistick) agent. Animal trials administering exogenous surfactant as a dry powder (ALECÔ) have previously demonstrated a reduction of 80% in abdominal adhesions. Methods: Incubation of rat peritoneum (both live and excised) with radiolabelled dipalmitoyl phosphatidylcholine (DPPC) has been used to demonstrate adsorption; while the normal lining of surfactant in the human abdominal cavity has been confirmed by epifluorescence microscopy using Phosphin E as the hydrophobic probe. Aims: The overall aim is to confirm that peritoneal mesothelium has a lining of surfactant known for its lubricating and release properties, and that this lining can be enhanced by the adsorption of exogenous material. Results: Adsorption of DPPC to peritoneal mesothelium was 470 ng/cm 2 (n = 8) ex vivo and 598 ng/cm 2 (n = 18) in vivo, these rates being enhanced by EggPG by 62%ex vivo and 47%in vivo to reach the equivalent of almost three close-packed monolayers. Conclusions: These results can explain the reduction in surgical adhesions previously reported in animals by administering ALECÔ (7:3 DPPC:EggPG) as a highly surface-active dry powder, although it is now used in saline suspension to treat respiratory distress syndrome in newborns, in whom it has no side-effects. These findings would appear to justify clinical trials for dry ALECÔ in suppressing surgical adhesions with minimal risk of an adverse reaction. The results of these trials are also discussed and found to be compatible with the known ability of surfactant to resist physical adhesion by fibronectin, the tacky ,glue' by which fibroblasts attach to surfaces as the first step in formation of fibrinous adhesions. [source]

Effects of Drug Hydrophobicity on Liposomal Stability

CHEMICAL BIOLOGY & DRUG DESIGN, Issue 1 2008
David R. Khan
A major obstacle in drug delivery is the inability to effectively deliver drugs to their intended biological target without deleterious side-effects. Delivery vehicles such as liposomes can minimize toxic side-effects by shielding the drug from reaction with unintended targets while in systemic circulation. Liposomes have the ability to accommodate both hydrophilic and hydrophobic drugs, either in the internal aqueous core or the lipid bilayer, respectively. In the present study, fluorescein and rhodamine have been used to model hydrophilic and hydrophobic drugs, respectively. We have compared the stabilities of liposomes encapsulating these fluorophores as a function of lipid content, time, and temperature. At 25 and 37 °C, liposomes containing distearoyl phosphatidylcholine as the major phospholipid component were found to be more stable over time than those containing dipalmitoyl phosphatidylcholine, regardless of the fluorophore encapsulated. Liposomes loaded with fluorescein were found to be more stable than those with rhodamine. Dipalmitoyl phosphatidylcholine liposomes that encapsulated rhodamine were the least stable. The results indicate that the physical properties of the drug cargo play a role in the stability, and hence drug delivery kinetics, of liposomal delivery systems, and desired drug release times can be achieved by adjusting/fine-tuning the lipid compositions. [source]

Suppression of neural activity of bronchial irritant receptors by surface-active phospholipid in comparison with topical drugs commonly prescribed for asthma

CLINICAL & EXPERIMENTAL ALLERGY, Issue 9 2000
Hills
Background Much indirect evidence has been put forward previously in support of the concept that surface-active phospholipid (SAPL) normally masks irritant receptors in the lungs and upper respiratory tract; but this physical barrier is deficient in asthmatics, imparting hyperresponsiveness of the bronchoconstrictor reflex. Objective To determine whether exogenous SAPL applied to bronchial mucosa reduces the sensitivity of irritant receptors to a standard challenge used clinically to diagnose asthma and to compare the effects with those of corticosteroids and ,-stimulation. Methods Nerve fibres in the vagi were monitored to record action potentials from irritant receptors identified in the upper airways of rat lungs in response to a methacholine challenge. SAPL in the form of dipalmitoyl phosphatidylcholine (PC) and phosphatidylglycerol (PG) , 7 : 3 PC:PG , was applied as a fine dry powder to enhance surface activity and, hence, chemisorption to epithelium. Comparison was also made with clinical doses of i.v. hydrocortisone and instilled salbutamol together with liquid or solid controls, as appropriate. Results Neural activity of irritant receptors was found to be significantly (P = 0.0018) decreased by topical SAPL by 35.8% in response to a methacholine challenge in contrast to an increase of 11.2% in response to a solid (lactose) control. Instilled salbutamol and i.v. hydrocortisone also decreased responses to the same challenge by 43.4% and 14.7%, respectively, in contrast to a liquid (saline) control which increased by 24.5%. Conclusions Surface-active phospholipid has an appreciable effect upon irritant receptors in rat airways, reducing neural response to a methacholine challenge by an amount comparable to that of Salbutamol. These results support the concept of SAPL masking bronchial irritant receptors and warrant placebo-controlled clinical trials of this dry powder as a means of controlling asthma without the side-effects of current medication. Other possible roles discussed for the SAPL epithelial barrier include the exclusion of viruses and allergens. [source]