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Biomedical subjects

S McLaughlin

Publications and source records attributed to S McLaughlin.

135 records · Page 8Linked to original sources
PubMed1974

Phospholipid flip-flop and the distribution of surface charges in excitable membranes.

There is now good evidence that most of the lipids in a biological membrane are arranged in the form of a bilayer. Charged lipids in the membrane of an excitable cell are subject to a significant driving force, the gradient of the intramembrane potential, which will tend to redistribute the lipids between the two halves of the bilayer by a "phospholipid flip-flop" mechanism. We have calculated, by combining the Boltzmann relation from statistics and the Gouy equation from the theory of the diffuse double layer, the steady-state distribution of charged lipids in the bilayer. This distribution is completely determined, within the framework of the model, by three experimentally accessible variables; the percentage of charged lipid in the bilayer as a whole, the resting potential and the ionic strength. The known values for the percentage of anionic phospholipids in squid axons (10-15%), the membrane potential (50-100 mV) and ionic strength (0.5 M) imply that the charge density and double layer potential at the outer surface of the nerve will be substantially greater than the charge density and double layer potential at the inner surface, in agreement with the best available evidence from physiological measurements.

Mathematics↗
PubMedDate not supplied

Nutritional considerations for other complications of diabetes.

The long-term complications of diabetes can have a devastating effect on an individual's self-esteem and outlook on life. Some preliminary studies have suggested that normalization of blood glucose levels may prevent or reverse the complications of diabetes in some individuals. Nutrition and diabetes meal planning play a critical role toward achieving this normalization. It is our job as diabetes educators to fully assess a patient's eating and life-style habits, as well as to recognize any complications from diabetes that the patient may be coping with at this time. Depending on the type of complication, diet alterations may need to be made to meet the patient's current needs, ie, reducing fiber content of the diet temporarily in patients with mild gastroparesis, or increasing the protein content of the diet in patients with nephropathy and a foot ulcer. By setting positive, attainable goals, the individual with diabetes may lead a healthier, more productive life in which the complications from diabetes can be prevented, reduced, or better tolerated.

Diabetes Complications↗
PubMedDate not supplied

Pancreatic cancer and diabetes.

Whether having diabetes predisposes an individual to developing pancreatic cancer continues to be studied. At present, the greater challenge for diabetes educators is to help those individuals who have had surgical resection for pancreatic cancer and now have resultant IGT or frank diabetes to manage their condition to the best of their ability and make their quality of life the best it can be, given the circumstances.

Aged↗
PubMedDate not supplied

Does the binding of clusters of basic residues to acidic lipids induce domain formation in membranes?

Several proteins that are important components of the calcium/phospholipid second messenger system (e.g. phospholipase C, protein kinase C, myristoylated alanine-rich C kinase substrate (MARCKS) and pp60src) contain clusters of basic residues that can interact with acidic lipids on the cytoplasmic surface of plasma membranes. We have studied the membrane binding of MARCKS and pp60src, peptides that mimic the basic regions of these proteins, and simple model peptides. Specifically, we determined how the binding of these model peptides depends on (1) the number of basic residues in the peptide (2) the fraction of acidic lipids in the membrane (3) the ionic strength of the solution (4) the chemical nature of the basic residues (Arg versus Lys) and the acidic phospholipids [phosphatidylglycerol (PG) versus phosphatidylserine (PS)] (5) the pressure and (6) the temperature. The results are consistent with a simple theoretical model: each basic residue in a peptide binds independently to an acidic lipid with an intrinsic microscopic association constant of 1-10 M-1 (binding energy congruent to 1 kcal/mol). The binding is described with a mass action formalism and the non-specific electrostatic accumulation of the peptides in the aqueous diffuse double layer is described with the Gouy-Chapman theory. This Gouy-Chapman/mass action model accounts surprisingly well for the sigmoidal dependence of binding on the percentage of acidic lipids in the membrane (apparent co-operativity or Hill coefficient > 1); the model assumes that the multivalent basic peptides bind > 1 acidic lipids and thus induce or stabilize domain formation.

Amino Acid Sequence↗