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Biomedical subjects

R W Phillips

Publications and source records attributed to R W Phillips.

At least 145 records · Page 8Linked to original sources
PubMed1981

Metabolic alterations related to reverse portal vein flow in an endotoxic pig.

Chronic hepatic artery and portal vein flowcuffs, in concert with hepatic vein and portal vein catheters, were placed in a Yucatan miniature pig. One week following surgery an endotoxin infusion was initiated. During endotoxemia there was a period of reverse portal vein flow while hepatic artery flow continued. This aberration resulted in unusual portal vein substrate and hormone concentrations. As endotoxemia progressed, the pig became hypoglycemic and hyperlactemic. Specific activity of [6-3H] - glucose was constant during developmental hypoglycemia, while insulin secretion rate was minimal indicating a significant endotoxin-induced, insulin-like activity. Hepatocytes isolated from the pig's liver at termination had inhibited gluconeogenic capacity.

Animals↗
PubMed1981

Genetic selection for small body size in Yucatan miniature pigs.

Yucatan miniature swine exhibiting smaller than average size and weight were selected as foundation stock for a miniaturization program. The F1 progeny from four matings of parent stock were evaluated based on weight through 24 months of age. Those animals with a mature weight at least 20% below the average of the population were selected as breeding stock for the succeeding generations. The selected F1 boars, when compared in size to the mean weight of unselected adult boars, were significantly lighter (p less than 0.01). Selected F1 sows were significantly lighter (p less than 0.001) compared to unselected sows of a comparable age.

Animals↗
PubMed1981

A method for quantitation of hepatic, pancreatic, and intestinal function in conscious Yucatan miniature swine.

A right laparotomy was performed in anesthetized miniature swine. A hepatic vein was catheterized through the diaphragmatic surface of the left lateral lobe of the liver or through the cut surface of the right lateral lobe following a partial lobectomy. Continuous wave Doppler flow cuffs were applied to the hepatic artery and portal vein. Portal vein catheterization was accomplished through a stab incision made through the center of a preplaced purse string suture. Catheters and flow cuff wires exited the abdomen at the dorsal limit of the incision and were placed in nylon packs. Sterile surgery of the right ventro-lateral cervical region allowed catheterization of the right external jugular vein and carotid artery. These catheters were passed subcutaneously to the dorsum of the neck and inserted into another nylon pack. This method allowed repetitive experiments on conscious miniature swine after recovery from surgery. It allowed accurate quantitative determination of hepatic extraction of hormones as well as extraction of production of metabolites. Rates of intestinal absorption and pancreatic hormone secretion also could be assessed.

Animals↗
PubMed1980

In vivo measurements of thermal diffusion through restorations of various materials.

Temperature diffusion was monitored through in vivo restorations with and without bases 0.5 and 1 mm thick. Temperature diffusion was highest through amalgam restorations and slowest through unfilled resin restorations. The rate of diffusion through composite resins and silicate cement fell between the extremes. Bases of both zinc phosphate cement and zinc oxide-eugenol cement reduced the rate of temperature change on the floor of the cavity beneath amalgam restorations. The temperature change was generally less under the 1 mm base than the 0.5 mm base. Bases used beneath the nonmetallic restorations did not reduce the magnitude of temperature change on the cavity floor.

Acrylic Resins↗
PubMed1980

The effects of alloxan diabetes on Yucatan miniature swine and their progeny.

Alloxanization as a method to induce diabetes has been successfully undertaken in several laboratory animal models. The genetic transmissibility of the alloxan-diabetic condition has been investigated and confirmed by several studies in rodents. The Yucatan miniature pig is a potential laboratory animal model for diabetes. Studies were conducted to investigate the possibility that alloxan diabetes could be transmitted to subsequent generations in these animals. Diabetic pigs were produced directly with alloxanization, but the genetic transmissibility of this trait was not substantiated through the F2 generation. On the basis of these data, alloxan diabetes is not transmissible in Yucatan pigs in the same way that it is in rats.

Alloxan↗
PubMed1980

Rheology of luting cements.

A rheometer has been developed to simulate the extrusion of luting cement from beneath a full crown during seating using clinically realistic shear rates. Five luting cements were studied, and differences in rheological behavior were illustrated. These measurements demonstrate the importance of consideration of the effects of shear rate on viscosity when evaluating a cement for optimal clinical utilization.

Cold Temperature↗
PubMed1980

Fluoride distribution in teeth using a silicate model.

The fluoride determinations were done on enamel biopsies taken before and after restoration of extracted teeth with silicate cement. Two sites, one near the restoration and one 3 mm or more away from the restoration, were assayed. No difference was noted in pre- and post-restoration biopsies when teeth were restored with a fluoride-free silicate. Post-restoration biopsies at sites near and away from the restoration were significantly higher in fluoride as compared to pre-restoration biopsies when the teeth were restored with a fluoride-containing silicate.

Dental Cements↗
PubMed1980

Physiological and urinary metabolite responses to cold shock and confinement of sheep.

Fourteen 15-kg hand-raised lambs were subjected to a control treatment or to one 3-hr, -5 C cold shock each day for 4 days. The greatest increase in heart rate occurred at the second hour of cold shock, when ambient temperatures were lowest. This increase became successively smaller each day. The greatest rectal temperature decreases occurred after 3 hr of cold shock, 1 hr after the minimum ambient temperature had been reached. This rectal temperature decrease became successively greater each day as the lambs habituated to the cold shocks. Urinary calcium excretion was 67% higher (P less than .05) in the cold-shocked lambs than in the controls during the 18-hr intervals following the shock. Urinary cortisol excretion was different only on day 2, when the control group showed higher (P less than .05) values. A confinement stress was induced by the placing of four lambs in metabolic cages 5 days after they were removed from a range environment. These lambs were compared to four other lambs in metabolic cages which had been reared in the laboratory. Confinement stress increased urinary cortisol excretion (P less than .05) above that of the laboratory-reared lambs for the first 3 days. A mean urinary cortisol excretion of 41 ng.MBS-1.mr-1 or 20 ng.mg.creatine-1 was found in lambs in the range and laboratory groups over the remainder of the study. The range lambs' nitrogen retention, measured after cortisol excretion returned to baseline, was greater (P less than .05) than that of the laboratory lambs.

Animals↗
PubMed1980

Altered metabolism, acute shock, and therapeutic response in a calf with severe coronavirus-induced diarrhea.

Acute shock and metabolic failure appeared in a diarrheic calf being studied intensively to determine kinetics of glucose and lactate metabolism. Intravenous therapy significantly improved its condition. During metabolic failure, the rapid increase in blood lactate and concomitant decrease in glucose were due to inhibited gluconeogenesis, as glucose entry and lactate oxidation were not modified. Therapy restored metabolic activity and decreased the severe hyperkalemia.

Animals↗
PubMed1980

Lactic acid and glucose metabolism in healthy, lactic acid-infused, and diarrheic calves.

Kinetics of glucose and lactate metabolism were measured in healthy (normal) calves, healthy calves infused with lactate, and in calves which had received an enteropathogenic coronavirus inoculum and had become diarrheic. Lactate utilization was positively correlated with blood lactate concentration in the healthy calves, but its turnover was markedly reduced in diarrheic animals. The decreased turnover was not due to inhibition of lactate oxidation, but appeared to relate to decreased gluconeogenesis. Glucose entry rate was not affected by diarrhea, but was a function of glucose concentration.

Animals↗
PubMed1979

Availability of oral carbohydrates to neonatal calves.

Four experiments were conducted to determine the availability of 3 carbohydrate sources given orally to 1- to 3-week-old clinically normal calves. In terms of effect on plasma glucose concentration, commercial fruit pectin was equivalent to glucose, corn syrup was less effective (P less than 0.05) than glucose, and sucrose was totally unavailable. The addition of 80 mM NaCl to a 10% glucose solution enhanced glucose absorption (P less than 0.01). Increasing the glucose concentration of a commercial product from 1% to 3% resulted in a significant (P less than 0.01) increase in plasma glucose concentration. Lactose availability from suckled fluids was greater (P less than 0.01) than that from fluids given by stomach tube.

Administration, Oral↗
PubMed1979

The effect of relining on the accuracy and stability of maxillary complete dentures--an in vitro and in vivo study.

A technique was developed for evaluating in vitro the accuracy or fit of experimental denture bases using a low-viscosity impression material for determining the space between the master die and the processed denture base. These measurements indicated that relining heat-cured maxillary denture bases with autopolymerizing acrylic resin improved their adaptation to the ridges. Interestingly, if no teeth were present in the heat-cured denture base, markedly less distortion occurred after processing. Limited clinical measurements on the stability of maxillary dentures in function showed no statistically significant change in stability after relining, but the trend was toward increased stability with the relined denture.

Acrylic Resins↗
PubMed1979

Heat-released stress in acrylic dentures.

Dimensional changes in an acrylic resin denture blank that are sufficient to cause changes in fit on a gypsum cast occur primarily when the dentures are heated in water to a temperature of 90 degrees C or more. The poor correlation between observed fit and the intermolar distance change indicates that the dimensional change of dentures is much more complex than suggested previously and may be the product of factors that are not as yet fully understood. Enough heat to cause distortion of the denture can be produced during the process of grinding the denture. It should be recognized by the dentist, the dental assistant, and the dental laboratory technician that denture resins are sensitive to the techniques that are used in finishing. Overheating even small regions may allow localized dimensional changes that result in distortion of the denture.

Acrylic Resins↗
PubMed1979

Effect of composite resin bond agent on microleakage and bond strength.

A study was conducted to evaluate the efficacy of the bonding agents supplied with three composite resins in improving the sealing ability of the materials to tooth structure and the bond of the resins to enamel. When the enamel was not etched prior to insertion of the resin, the use of the bonding agents did not improve marginal seal. Little or no marginal leakage was detected when the restorations were placed by means of the acid etch technique, either with or without use of the respective bonding agents. A slight improvement in the bond of the resins to unetched enamel was secured by use of the bonding agents; however, this advantage was lost when the specimens were thermal cycled. Acid etching of the enamel significantly improved the bond of the strength of all three resins, both when the specimens were thermal-cycled and when stored at a constant temperature. Only one of the commercial bond agents enhanced the bond of its respective composite resin to etched enamel subjected to cycling.

Acid Etching, Dental↗