Search PubMed⌕ Search

Biomedical subjects

R Stevenson

Publications and source records attributed to R Stevenson.

At least 91 records · Page 5Linked to original sources
PubMed1983

Corneal transparency changes resulting from osmotic stress.

Corneal thickness and transparency changes were measured following exposure of the cornea to various levels of osmotic stress. Bathing the cornea in hypotonic solutions of NaCl caused an increase in corneal thickness and light scatter within the cornea. Transparency changes with hypotonicity were determined by comparing the relative brightness of haloes around a bright lamp source for the various concentrations of NaCl solutions. Corresponding corneal thickness changes were determined by pachometry. A nearly linear relationship was found between solution hypotonicity and the degree of corneal swelling, whilst an exponential relationship was found between hypotonicity and relative halo brightness. The rate of corneal recovery from osmotic stress was found to be constant with different degrees of tonicity, although the rate of thickness recovery was much slower than the recovery from haloes.

Cornea↗
PubMed1981

Measuring corneal recovery from osmotic and anoxic stress.

Halos indicate an important change in vision performance which can occur in contact lens wearers. Experimentally, halos occur when the cornea id deprived of atmospheric oxygen or bathed with hypotonic solutions. Pachometry is the accepted technique for measuring changes in the cornea, yet there is little evidence that measurement of overall corneal thickness is a sensitive indicator of structural changes in the epithelium, such as those causing halos. There is a need for a technique which is responsive to changes in the epithelium. This paper describes a new technique for quantifying changes in the epithelium by measuring halo brightness. Halos were produced by osmotic and anoxic stress, and recovery was monitored using measurements of corneal thickness and halo brightness. We found that the time course of halo recovery could be measured successfully on a naive subject. The technique provides information not available from pachometry and should be of considerable value in studies on the human cornea of factors which alter the optical integrity of the epithelium.

Contact Lenses↗
PubMed1980

Further studies on histamine release from rat mast cells in vitro induced by peptides. Characteristics of a synthetic intermediate with potent releasing activity.

Previous studies on histamine release by corticotropin peptides and melittin peptides were extended, leading to the identification of a synthetic peptide intermediate, Lys(Z)-Arg(NO2)-Arg(NO2)OMe, (I) as an active non-cytolytic histamine releaser from rat mast cells. However, significant differences in the releasing capacity of optical isomers of this compound, and of Lys-Lys-Arg-ArgOMe [methyl ester of corticotropin-(15-18)-tetrapeptide; 'basic core'] were observed, with the L-forms being markedly more active. A study of various analogues of the tripeptide compound (I) indicated that the structural basis for mast-cell triggering by such peptidic agents was highly specific. The relevance of these observations to the immunologically induced histamine-release processes is discussed.

Adrenocorticotropic Hormone↗
PubMed1979

Protection of the eyes against damage by light activated psoralen.

It is current practice to order eye protection while patients are under treatment with psoralen. There is considerable variation in the protection against long wave light provided by different sunglasses, therefore, it is necessary to write a specific prescription for sunglasses for these patients. We have found Noir Model 102 or 109 with side flaps or the Rayban dark green glass to be the most effective.

Eye Injuries↗