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Biomedical subjects

L A Mackenzie

Publications and source records attributed to L A Mackenzie.

11 recordsLinked to original sources
PubMed1999

A mechanism for branchial acid excretion in marine fish: identification of multiple Na+/H+ antiporter (NHE) isoforms in gills of two seawater teleosts.

Both Na+/H+ exchange and the electrogenic extrusion of H+ via an H+-ATPase have been postulated to drive acid excretion across the branchial epithelium of fishes. While the H+-ATPase/Na+ channel system appears to be the predominant mechanism in some freshwater species, it may play a reduced role in seawater and brackish-water animals, where high external Na+ concentrations may thermodynamically favor Na+/H+ exchange driven by a Na+/H+ antiporter (NHE). In this study, we used molecular and immunological methods to assess the role of NHE isoforms in the branchial epithelium of the marine long-horned sculpin (Myoxocephalus octodecimspinosus) and the euryhaline killifish (Fundulus heteroclitus). Northern blot analysis of RNA probed with the human NHE-1 BamHI fragment suggested the presence of homologous gill NHE mRNA in sculpin. RT-PCR on gill RNA isolated from sculpin recovering from metabolic acidosis provided evidence for two distinct NHE isoforms; one with 76 % amino acid homology to mammalian NHE-2, and another 92 % homologous to trout erythrocytic beta-NHE. Killifish also have transcripts with 91 % homology to beta-NHE. Immunological detection using monoclonal antibodies for mammalian NHE-1 revealed a protein antigenically similar to this isoform in the gills of both species. Metabolic acidosis caused an approximately 30-fold decrease in expression of the NHE-1-like protein in sculpin. We speculate that beta-NHE in the gills plays the intracellular 'housekeeping' roles described for mammalian NHE-1. During systemic acidosis, apical gill NHE-2 (which is sensitive to external amiloride and low [Na+]) in parallel with a dramatic suppression of basolateral NHE-1 activity enhances net capdelta H+ transfers to the water.

Acidosis↗
PubMed1985

UV radiometry in dermatology.

UV radiometry in photodermatology remains in an unsatisfactory state, which has been highlighted and, in some respects, worsened by improvements in UV detector technology. Complex, fundamental problems are involved, but matters have not been helped by a failure to recognize the clear distinction between those UV measurements which aim at accurate radiometry, and those which aim only at long-term consistency in a particular irradiation technique within a department.

Dermatology↗
PubMed1983

The analysis of the ultraviolet radiation doses required to produce erythemal responses in normal skin.

When the abnormality of a skin response to sunlight is expressed in terms of a decreased minimum erythemal dose (MED) on photo-testing, it is essential to know the range of response in normal skin. In any homogeneous population, the statistical distribution of the MED is skewed and is not Gaussian (normal), but a Gaussian distribution can be fitted to the logarithm of the MED. Using established methods of probit analysis, such 'lognormal' distributions have been fitted to the observed proportions of erythemal responses to a series of test exposure doses of UV radiation (250-365 nm), thus providing estimates of the average log MED for normal skin, the standard deviations of the distributions and associated confidence limits. These estimates, in arithmetical terms, are available for quantitative comparison with the results of other test exposures on skin which may be abnormal.

Dose-Response Relationship, Radiation↗
PubMed1983

The destruction of peripheral-blood lymphocytes by extracorporeal exposure to ultraviolet radiation.

Venous blood from healthy adult human donors was circulated through a wholly extracorporeal circuit for periods up to 140 min without apparent damage to the lymphocytes. However, when the blood was exposed to short-wave ultraviolet radiation (UVC; lambda, 254 nm), separated mononuclear cells showed a depressed response to mitogen stimulation: the magnitude of this effect was related to the duration of exposure. This depression cannot be attributed to change in blood pH, partial pressures of oxygen and carbon dioxide, temperature of cell trauma. Plasma from irradiated blood was less satisfactory than non-irradiated plasma for the support of growth of phytohaemagglutinin-stimulated lymphocytes in culture, probably because of depletion of essential nutrients, and there was little evidence for the generation of growth-inhibitory humoral factors. The UVC-irradiated lymphocytes had normal ultrastructure when removed from the extracorporeal circuit, but underwent apoptosis and necrosis during the first day of tissue culture with or without mitogen stimulation.

Adult↗
PubMed1977

Photochemotherapy in the treatment of psoriasis.

This article describes the satisfactory clinical improvement obtained in the majority of a group of 72 patients with psoriasis of various types as a result of the oral and/or topical administration of 8-methoxypsoralen followed by long wavelength ultraviolet irradiation. The irradiation source used was that of conventional longwave UV fluorescent tubes mounted in a specially constructed cubicle. Until such time as the long term effect of this form of photochemotherapy on the cell has been evaluated and the most appropriate regime worked out, it would seem to be important to restrict the amount of irradiation used to that required to produce acceptable maintained clinical improvement.

Adolescent↗