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Biomedical subjects

G M Smith

Publications and source records attributed to G M Smith.

282 records · Page 16Linked to original sources
PubMedDate not supplied

Effect of doses of protected polyunsaturated fatty acids on indicators of selenium status of sheep.

In monogastric animals, dietary polyunsaturated fatty acids (PUFA) have been shown to increase glutathione peroxidase (GSH-Px) activity in plasma and erythrocytes and to decrease plasma selenium concentration. Ruminants feeding on grass can have a high intake of PUFA. In this experiment, sheep were dosed orally with protected PUFA (Pr-PUFA) for five weeks at 5 g kg liveweight-1 three times per week for the first week and at 8 g kg-1 for the following four weeks. The Pr-PUFA did not affect GSHPx activity in erythrocytes or plasma or liver selenium concentration, but did reduce the selenium concentration in muscles by between 20 and 30 per cent. In addition, liver iron concentration was reduced by about 42 per cent. The results suggest that dietary PUFA may affect the distribution of selenium rather than its absorption.

Administration, Oral↗
PubMedDate not supplied

Investigation of human enamel wear against four dental ceramics and gold.

OBJECTIVES: This in vitro study compared the wear of enamel against aluminous porcelin, bonded porcelain, low fusing hydrothermal ceramic, feldspathic machinable ceramic, and cast gold. METHODS: Fifty pairs of tooth-material specimens were tested in a dental wear machine, under a standard load (40 N), rate (80 cycles min-1) and for 25,000 cycles in distilled water. The amount of wear was determined by measuring the height loss of the tooth, and the depth of wear track of the restorative materials. RESULTS: There was a significant difference in wear among the groups for both enamel and materials (p < 0.001). Follow-up comparisons (95% CI significance level) showed that gold caused significantly less enamel wear than all ceramics tested. The amount of enamel wear in the aluminous and bonded porcelain groups was significantly higher than with the hydrothermal and machinable ceramic groups. There was no significant difference between the amount of enamel wear produced by the aluminous and bonded porcelains nor between that produced by the hydrothermal and machinable ceramics. Furthermore, the wear of the aluminous and bonded porcelains was significantly greater than that of the hydrothermal ceramic, the machinable ceramics and gold. No significant difference in wear was found between aluminous and bonded porcelains, hydrothermal and machinable ceramics, or between machinable ceramic and gold. However, the hydrothermal ceramic had significantly greater wear than gold. CONCLUSIONS: It was concluded that the hydrothermal and the machinable ceramics were significantly less abrasive and more resistant to wear than the conventional aluminous and bonded porcelains. Gold was the least abrasive material and most resistant to wear, although the difference in wear between the machinable ceramic and gold was not statistically significant.

Aluminum Oxide↗
PubMedDate not supplied

Evaluation of in vitro drug release, pH change, and molecular weight degradation of poly(L-lactic acid) and poly(D,L-lactide-co-glycolide) fibers.

Biodegradable fibers of poly(L-lactic acid) (PLLA) and poly(D,L-lactide-co-glycolide) (PLGA) that encapsulated a water-soluble drug were created by a patented technique consisting of wet-spinning a water-in-oil emulsion. These fibers are 2.4% by mass drug, which is slowly released, making these fibers potential candidates for implantation as drug delivery devices and/or tissue-engineering substrates. Drug release kinetics and changes in molecular weight were investigated over time. This study demonstrated that drug release rates and molecular weight degradation are a function of the amount of aqueous phase added as an emulsion during fabrication. The type of polymer used (PLLA or PLGA) determines the molecular weight degradation rates, but has little effect on drug release kinetics.

Absorbable Implants↗
PubMedDate not supplied

Burn-induced cosmetic disfigurement: can it be measured reliably?

Cosmetic disfigurement was measured reliably by averaging the ratings of four or more viewers of color slide photographs of severely burned children and young adults. Raters were clinical and nonclinical staff at a burn hospital. Reliability for four-person rating of overall cosmetic disfigurement (unclothed) was .94; for overall disfigurement (clothed) it was .86; for irregularity, thickness, and discoloration it was .78, .79, and .72, respectively. Profession, sex, and years of contact with burned patients did not influence inter-rater agreement. Any randomly selected panel of four raters produced reliable average ratings. The effect of impaired skin texture on overall ratings of cosmetic disfigurement (both clothed and unclothed) was three to five times as important as the effect of impaired color. Despite its subjectivity, cosmetic disfigurement can be measured reliably. This report describes a formal procedure for such measurement and discusses ways of using that procedure to improve patient care.

Adolescent↗
PubMedDate not supplied

Body image, self-esteem, and depression in burn-injured adolescents and young adults.

The present study was conducted to clarify the effects of burn-related variables (specifically, age at time of burn, years elapsed since burn, locus of burn, and percent of total body surface area burned), demographics, and perceived social support variables on psychological adjustment after injury within a well-defined sample. Subjects were 121 patients, currently 14 to 27 years old, burned within the past 10 years. They completed the following: Semantic Differential Measure of Body Image, Rosenberg Self-Esteem Scale, Beck Depression Inventory, Perceived Social Inventory--Friends, and Perceived Social Inventory--Family. The mean age of the subjects was 17.8 years; the mean percent total body surface area burned was 27.3%, with 75% of the subjects having burns on a visible or socially sensitive area. Correlational and multiple regression analyses showed that subjects perceiving more social support (friends more than family) had more positive body images (p less than 0.01), greater self-esteem (p less than 0.01), and less depression (p less than 0.01) than others, with a significant impact from difference in subjects' gender.

Adolescent↗
PubMedDate not supplied

Effect of water temperature on the accuracy of stone casts recovered from addition-reaction elastomeric impression materials.

This study investigated the accuracy of casts produced by mixing dental stone with water at different temperatures. Consecutive impressions of an acrylic resin model of the mandibular arch, on which the occlusal surfaces of three teeth had been indented with reference points, were made in two poly(vinyl siloxane) impression materials using a one-stage technique. After 1 hour these were cast in one of two stones using water at temperatures of 18 degrees C, 20 degrees C, or 24 degrees C. Five impressions were cast for each material at each temperature. The distances between the points were measured using a reflex microscope, and the difference between each cast and the model was calculated. Analysis of variance of the mean differences showed that there was no significant interaction between the temperature of the water and the accuracy of casts (P greater than 0.05).

Calcium Sulfate↗
PubMedDate not supplied

The abrasive effect of glazed, unglazed, and polished porcelain on the wear of human enamel, and the influence of carbonated soft drinks on the rate of wear.

The abrasive effect of various porcelain surfaces on human enamel was studied in vitro. Sixty pairs of tooth-porcelain specimens were tested under a standard load and rate in distilled water and with and without intermittent exposure to a carbonated beverage. The amount of wear of enamel and porcelain specimens was determined after 5,000, 15,000, and 25,000 cycles. After 25,000 cycles there was no significant difference in the enamel wear between glazed and polished groups, but wear produced by the unglazed groups was significantly higher (P < .05). Overall, exposure to a carbonated beverage significantly increased the amount of enamel wear produced by all porcelain surfaces (P < .001). The finish of the porcelain surface did not influence its wear.

Aluminum Oxide↗