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Biomedical subjects

J McNeil

Publications and source records attributed to J McNeil.

52 records · Page 3Linked to original sources
PubMed1988

Measurement of choroidal melanomas: a comparison of methods.

The prognosis for death from metastatic choroidal melanoma following enucleation has been shown to be strongly correlated with a number of risk factors of which the most important are age of onset, aggressive cell types and tumour volume. The advantages of enucleation for the treatment of choroidal melanomas are put into question by the singular lack of a parallel increase in life expectancy following this treatment, and evidence that it may promote the development of metastatic disease. Alternative forms of treatment have been introduced including observation of small and asymptomatic tumours. We are using a computer-aided system for serial measurement and statistical analysis of area and volume of choroidal melanomas. A comparison of results using our method and the conventional method of estimating volume by the product of basal area and height for 51 measurements on 15 eyes over a 6-month period showed an overestimation of volume by conventional methods which could be corrected by applying a "shape constant" determined by linear regression. Calculation of tumour growth rates is also shape-dependent, and a slowing in growth rate or even a reduction in melanoma size is possible.

Choroid Neoplasms↗
PubMed1986

Is orally-derived epidermal growth factor beneficial following premature birth or intestinal resection?

Epidermal growth factor (EGF), a major growth factor in human milk, may stimulate growth and development of crucial infant tissues, particularly in conditions where the infant's growth is compromised. Here, we provide evidence of a role for EGF in two such conditions, premature birth and intestinal resection. Compared with women delivering at term, mothers of premature infants produce milk containing higher concentrations of EGF, an effect that is probably maintained throughout lactation. The increased EGF in milk could not be accounted for by a decrease in the volume of milk production or by events surrounding birth, but may instead represent a maternal compensatory mechanism to accelerate growth in pre-term infants. A role for EGF in stimulating adaptive intestinal regrowth following gut resection was identified using weanling rats. Following removal of 50% of the small intestine of weanling rats, inclusion of EGF (20 micrograms/100 g per day) in the diet (S-26 infant formula) significantly accelerated intestinal growth, as determined by wet weight, protein and sucrase activity per unit length. These studies support the concept that administration of EGF could prove beneficial to infants in which crucial, EGF-responsive tissues are poorly developed, e.g. following premature birth or intestinal resection.

Animals↗
PubMed1982

Interaction of lipids with intestinal brush border membrane preparations.

Conditions for uptake of lipids by rabbit intestinal brush border membrane preparations were investigated. A variety of lipids were found to be incorporated, including choline and ethanolamine phosphatides as well as cholesterol, diglyceride, and fatty acid. The incorporation of those lipids tested was enhanced by Ca2+ and other divalent cations but not by monovalent cations. The optimal Ca2+ concentration was approximately 10 mM. The uptake varied with lipid and membrane protein concentration and proceeded at rates which were too rapid to measure under several assay conditions tried. Incorporations were decreased substantially outside the pH range of 6.5-8.0. The effect of one lipid, phosphatidylcholine, on the structural appearance of the membrane fraction was examined by electron microscopy. No free or surface-bound lipid structures could be detected and the membrane fractions appeared to be unchanged after uptake.

Animals↗
PubMed1981

Combined high-performance liquid chromatographic procedure for measuring 4-hydroxypropranolol and propranolol in plasma: pharmacokinetic measurements following conventional and slow-release propranolol administration.

An assay is described for the simultaneous determination of propranolol and its active metabolite, 4-hydroxypropranolol, in human plasma. Both compounds were separated from an ethereal extract by high-performance liquid chromatography employing a C18 bonded-phase column. Detection of the effluent was by fluorescence. Suitable fluorescent spectrometers and wavelength settings that allow optimum detection of both compounds have been described. The limit of sensitivity was 2 ng/ml for both propranolol and 4-hydroxypropranolol. Mean peak plasma levels of propranolol and 4-hydroxypropranolol in six patients receiving a single dose of a slow-release 160-mg formulation of propranolol were 28 and 6 ng/ml, respectively. These levels were about one-tenth the level obtained following a single conventionally prepared dose of propranolol (160 mg). Peak levels were delayed and plasma levels of propranolol persisted for a longer period with the slow-release formulation. Area under the curve estimates suggested that the bioavailability of the slow-release formulation following single-dose administration was about one-third that of the conventional preparation.

Adult↗
PubMed1975

Juvenile hormone analogs: detrimental effects on the development of an endoparasitoid.

A high incidence of mortality of the endoparasitoid Aphidius nigripes was observed when its host. Macrosiphum euphorbiae, was treated with juvenile hormone analogs. Larval and pupal stages of the parasitoid were susceptible. Off-target effects on natural enemies may seriously limit the use of juvenile hormone analogs, especially in integrated control programs.

Animals↗
PubMedDate not supplied

Termite control and other determinants of high body burdens of cyclodiene insecticides.

Breast milk fat concentrations of three cyclodiene insecticides--dieldrin, heptachlor epoxide, and oxychlordane--were measured in 797 primiparous women, and sources of exposure that contributed significantly to high body burdens were investigated. All three distributions were highly skewed to the right, with median concentrations falling between 0.007 and 0.039 mg/kg. Termite control of residence was associated consistently with being in the high-body-burden group for all three compounds, but the association was greatest for heptachlor. Age, socioeconomic status, residential area, smoking, and home use of insecticides were also associated with high body burden of one or more of the compounds, but the odds ratios were lower than those for termite control; the findings were inconsistent for the three compounds. The results for termite control remained statistically significant when we adjusted for the other factors; therefore, termite control of residence is an important risk factor for cyclodiene insecticide absorption.

Adipose Tissue↗
PubMedDate not supplied

Relationship among health habits, social assets, psychologic well-being, life change, and alterations in health status.

To examine variables which may temper life change and enable individuals to withstand high degrees of life change without developing illness, a questionnaire was mailed to a systematically selected sample of the residents of Renton, Washington, of which 548 (57 percent) were returned. The major statistical analysis was linear correlation and multiple regression. When relationships between the major variables--health habits, social assets, psychologic well-being, and life change--and the dependent variable-alterations in health status--were examined, the single best predictor of subsequent alterations in health status for respondents in this study was found to be the magnitude of the life change. As the life changes increased, the risk of becoming ill also increased. The notion that health habits, psychologic well-being, and social assets might temper life change and make it possible to avoid a change in health status was not borne but strongly in the results of the analysis of data. These variables were weakly associated, however, with maintenance of health status.

Adaptation, Psychological↗