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Biomedical subjects

R W Phillips

Publications and source records attributed to R W Phillips.

At least 181 records · Page 10Linked to original sources
PubMed1978

Stability of plasma metabolites and hormones in lactating dairy cows.

Plasma concentration stability of glucose, free fatty acids, ketone bodies, growth hormone, insulin were determined in lactating dairy cows. Concentrations of these metabolites and hormones were measured during a 36- to 48-hour period in 3 normal, mature dairy cows in the 2nd month of lactation. Samples were taken at 30-minute intervals; also, intensive sampling (every 10 minutes) was done at varying times in relation to feeding and milking. Of the 5 components measured, glucose concentration was the most stable, easiest to assay, and most reliable for use as a diagnostic aid in assessing metabolic carbohydrate disturbances in dairy cattle.

Animals↗
PubMed1978

Stability of plasma metabolites and hormones in parturient dairy cows.

Metabolic changes that accompany the transition from parturition to lactation in dairy cows were studied. To measure these changes, plasma samples were obtained from 20 mature Holstein-Friesian dairy cows 10 days before through 10 days after parturition. They were analyzed for glucose, free fatty acids (FFA), lactic acid, ketone bodies, glucocorticoids, insulin, and growth hormone concentration. Lactic acid and glucocorticoids remained constant during the experiment, except for the day of parturition itself. In the prepartum period, changes were not detected in concentrations of hormones (glucocorticoids, insulin, and growth hormone), whereas, plasma metabolites began changing prior to parturition. Most evident were prepartum increased in FFA, ketones, and glucose. Postpartum plasma glucose concentration rapidly returned to prepartum concentrations. Plasma concentration of FFA and ketone bodies remained elevated for longer periods.

Animals↗
PubMed1978

Effect of fasting on plasma metabolites and hormones in lactating dairy cows.

Metabolic and pathophysiologic changes of secondary ketosis were studied. Plasma samples were obtained from a group of 8 mature, lactating dairy cows before, during, and after a 48-hour fast. These samples were analyzed for glucose, free fatty acids (FFA), lactic acid, ketone bodies, glucocorticoids, insulin, and growth hormone concentrations. In the prefasting period, metabolites and hormones remained constant. Lactic acid and glucocorticoids also remained stable during the entire experiment, except on the 1st day after termination of the fast, when glucocorticoids increased significantly (P less than 0.05). Glucose values decreased significantly (P less than 0.01) with the onset of fasting, began to rise halfway through the fast, and were elevated following termination of the fast. Plasma glucose concentration returned to normal by the end of the experiment. Plasma FFA concentrations increased during the early portions of the fast and decreased thereafter. Plasma ketone body concentration responded similarly, but the change occurred approximately 12 hours after the plasma FFA changes. A value determined as ketotic was reached during the fast (14.6 +/- 1.3 mg/dl). Insulin concentrations remained low during the fast and increased after fasting. Plasma growth hormone concentration increased to a new plateau in response to fasting and then decreased somewhate after fasting was ended.

Animals↗
PubMed1978

The Yucatan minature pig as a laboratory animal.

Parent stock for a minature pig herd was obtained from the progeny of pigs imported from the Yucatan Peninsula of Mexico. The Yucatan miniature pig is slate-gray, essentially hairless, and has a docile temperament. The tractable nature of this pig minimized risks for animal handlers as well as researchers. With regular human contact, these pigs became amenable to handling and tolerated restraint well. The mean birth weight was 0.74 kg, and the mean weaning weight at 60 days was 6.47 kg. The mean weight of mature nonobese boars was 83 kg while mature sows averaged 70 kg. The height and length for mature pigs of both sexes averaged 57 cm and 76 cm, respectively. The mean range of plasma glucose was 86-117 mg/dl during the first 8 weeks of life. The Yucatan miniature pig is native to tropical regions. The Colorado cold winter weather caused life-threatening stress to animals housed outside; therefore, intensive management procedures were required during the winter months.

Animals↗
PubMed1977

Testing of pit and fissure sealants in the monkey.

A pilot study was conducted employing the Macaca speciosa monkey to determine the retention and sealing ability of pit and fissure sealants in vivo. Several problems were encountered in the use of this animal model for this type of evaluation. Without doubt, the conditions to which the sealants were subjected in the monkey were more rigorous than those found in man. This is attested to by the lower rate of retention of sealants as compared to that found in studies on human beings. To increase the usefulness of animal studies of this type, additional research should be done to better establish the correlation between the behavior of sealants in the animal and in man. Nevertheless, certain pertinent observations were made, one of which is that in some instances where the sealant was retained on the teeth, the sealant-tooth interface was readily penetrated by an isotope solution.

Acrylic Resins↗
PubMed1977

An evaluation of silicophosphate as an orthodontic cement.

In a laboratory and clinical evluation, when used for the cementation of orthodontic bands, a zinc silicophosphate cement has proved to be comparable to zinc phosphate cement in its bond strength to enamel. This was demonstrated in laboratory tests by higher values being required to break the mechanical bond and in the clinical study by the slightly smaller percentage of bands which became loose during orthodontic treatment. In both the laboratory and clinical studies it was found that silicophosphate remained attached to the enamel in higher percentages after a band had become loose. It also was found that the remaining cement was often quite difficult to remove from the enamel. Probably the greatest advantage of using silicophosphate is that no decalcification of enamel was found under bands which had become loose during orthodontic treatment. This may be attributable to the higher bond strength and/or the presence of fluoride in the cement. Further clinical studies of this nature appear warranted.

Dental Bonding↗
PubMed1977

Recrystallization of compacted gold foil specimens.

Gold foil specimens were compacted by a technique commonly used in preparing dental restorations. Their recrystallization behavior for temperatures between 100 and 300 C was followed by the associated decrease in hardness, discontinuous increase in grain size, and disappearance of X-ray line broadening. The empirical dependence of time, t, (in minutes) for 50% recrystallization on annealing temperature (in K), T, is approximately log10 t=-12.3+6.5X1,000/T, indicating a recrystallization time greater than 100 years.

Crystallization↗
PubMed1976

Three-year clinical comparison of three amalgam alloy types emphasizing an appraisal of the evaluation methods used.

Five different evaluation techniques were used to measure the marginal breakdown of three-year-old amalgam restorations. The most useful method appeared to be one in which photographs of all restorations were ranked in descending order starting with the restoration that had the least marginal breakdown and ending with the restoration that had the greatest deterioration. Three different alloys were evaluated and the results confirm those of previous studies; the alloy having the lowest creep was superior whereas restorations placed with the alloy having the highest creep displayed the greatest marginal breakdown.

Dental Amalgam↗
PubMed1976

Future role of biomaterials in dentistry and dental education.

It is possible to make predictions on materials research and on its impact if one understands the background of materials science and appraises the constraints on research and practice. In the past ten years some significant advances have been implemented in dental practice. On the basis of these advances, some very optimistic predictions can be made for the next ten years. However, in some areas, little progress was made, and there are some reasons to believe that this limited success will continue. Planning in research and dental education must be based on realistic appraisals of research productivity.

Biocompatible Materials↗