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Biomedical subjects

M Andersen

Publications and source records attributed to M Andersen.

At least 163 records · Page 9Linked to original sources
PubMed1977

Van der Waals interactions between cell surfaces.

Van der Waals energies of interaction between model cell surfaces are calculated for various distances of separation, layer thicknesses and compositions of cell surfaces and intercellular media. In these calculations the cell peripheries are considered to consist of two layers: (1) A phospholipid-cholesterol-protein plasma membrane and (2) a surface coat, which consists of protein, sugar and water. The required Van der Waals parameters of sugars, phospholipids and cholesterol are derived from refractive indices of their solutions in the visible and ultraviolet regions. Polarizabilities and Van der Waals parameters of these substances are determined and shown to be almost independent of concentration of solutions. Resulting isotropic polarizabilities differ by less than five percent from values obtained by the addition of bond polarizabilities. The magnitude of Van der Walls interactions between cell surfaces has been found to vary with composition according to the following sequence: water less than phospholipid less than cholesterol, protein less than sugar. A decrease in the concentration of a given substance in the cell surface at the expense of a corresponding increase in the concentration of a substance preceding it in this sequence lowers the magnitude of attractive interactions, whereas a similar change in the extracellular medium would have an opposite effect. A consideration of experimentally found variations in composition of cell surfaces results in calculated values of Hamaker's coefficients between 8 X 10(-15) ergs and 6 X 10(-14) ergs at 50 A distance of separation, which corresponds to free energies per unit area of 210-1600 kT/mu2.

Carbohydrates↗
PubMed1976

The natural history of small atrial septal defects; long-term follow-up with serial heart catheterizations.

Thirty-nine patients with a small ASD of the secundum type were followed clinically for 5 to 21 years (mean 11.6 years); no evidence of deterioration was found. In 26 of these cases recatheterization was carried out with a mean follow-up period of 9.8 years. No significant changes were found in most patients; in four patients, however, the left-to-right shunt had increased significantly. Our recommendations are that we will continue to advise surgery in patients with large ASD's, whereas we still do not recommend surgery in patients with small ASD's; the latter patients should be followed for longer periods to ensure that no deterioration occurs. The decision as to whether an ASD should be regarded as large or small in our opinion not only should be based on a chosen limit of pulmonary-to-systemic flow ratio, but clinical factors such as diastolic flow murmurs, ECG changes, the heart size, and the pulmonary vascular markings should also be taken into consideration.

Adolescent↗
PubMed1975

Sinoatrial block during lithium treatment.

Lithium is known to produce T wave changes in the ECG, whereas effect upon the conducting system of the heart has not been described. In our patient lithium produced sinoauricular block and possibly tachycardia. The correlation between lithium treatment and tachyarrhythmias is discussed. When during lithium treatment block is found, the treatment should preferably be stopped, but if this is not possible it is important to realize that digitalis should not be used as a prophylactic drug against tachycardia, as it worsens the block and therefore increases the frequency of arrhythmia, even leading to Adams-Stokes attacks.

Depression↗