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Biomedical subjects

R W Phillips

Publications and source records attributed to R W Phillips.

At least 73 records · Page 4Linked to original sources
PubMed1986

Evaluation of materials and techniques for restoration of erosion areas.

The data indicate that the two dentin bonding agents, used in conjunction with enamel acid etching, provided a superior seal of the cavity compared to the respective resins alone or with either the dentin bond agent or acid etching used alone. The seal of resin restorations placed with the total system (acid etch and dentin bond agent) were comparable to the seal of the glass ionomer cement restorations. Compared with the 2-week specimens, there was no increase in leakage of the 6-month resin restorations when inserted with dentin bond agents and acid etch. The sealing ability of the resin restorations in conservatively prepared cavities was superior to comparable resin restorations in cavities that had not been prepared. This did not appear to be true for glass ionomer cement restorations. Data obtained to compare the bond strength of resins as used in the study with that of glass ionomer cements do not indicate a precise correlation between bond strength and sealing ability. The exact role of dentin bonding agents await further evaluation of their stability over a prolonged period of time, particularly in clinical investigations.

Acid Etching, Dental↗
PubMed1986

Report of Committee on Scientific Investigation of the American Academy of Restorative Dentistry.

A few personal points seem appropriate in summary. It is axiomatic that while research solves problems, it also creates them. As an example, it is an accepted fact that dentistry more than any other profession has made serious inroads into putting itself out of business through research. Each year this report takes note of the reduction in dental caries in children, which has thus triggered a change in the nature of general practice. Be this as it may, it is well to acknowledge that major dental diseases are not disappearing, but their patterns in the population are changing, accompanied by an expansion of other services. Despite the optimistic picture painted earlier in this report, it is grossly premature to acclaim the elimination of caries, and thereby a significant segment of restorative dentistry. Of course the younger age groups have been the major beneficiaries of caries reduction. As the child ages from 9 to 16 years, the percentage of mouths free of caries drops by one half. In addition, the disease pattern in the adult population is being altered because of a longer life span and loss of fewer teeth. Unquestionably what we will, and are already seeing, is not an elimination of restorative dentistry but a different target and changes in procedures because of new materials, therapy, and expanded scope of services. There is yet another subtle change in the trend of dental research and it deals with the reduction in the number of dental schools worldwide and smaller class sizes in those schools. Dental research thereby suffers because of the traditional link between education and research. Thus the potential pool of researchers becomes smaller and research monies for training programs for dental investigators, particularly in clinical research, decreases. This year a surprising number of articles are concerned with manpower as it relates to research priorities. So, it is indeed a time that both the profession and the scientific community find filled with controversy and frustration. Yet never has there been a time that offers more in challenges and rewards.

Combined Modality Therapy↗
PubMed1986

Effects of sodium dichloroacetate in awake, healthy, Yucatan miniature swine.

Four healthy, fully conscious, 50- to 80-kg Yucatan miniature swine were fitted with carotid artery and jugular, portal, and hepatic vein catheters and hepatic artery and portal vein flow cuffs to determine transhepatic kinetics and insulin secretion. Three days later, after a 3-hour control period, the pigs were given IV sodium dichloroacetate (30 mg/kg of body weight as a bolus and 30 mg/kg/hr, as an infusion) for 6 hours. Arterial lactate concentrations decreased during the dichloroacetate infusion, but pyruvate concentrations were unaltered. The whole body rate of appearance and disappearance of glucose decreased, but plasma glucose concentrations did not change markedly. Limb skin surface temperatures increased, indicating a peripheral vasodilatory effect. Dichloroacetate had little effect on mean arterial pressure and hepatosplanchnic blood flow. Dichloroacetate may be effective as a hypolactatemic agent for lactic acidosis in pigs.

Acetates↗
PubMed1986

Metabolic effects of glucagon in endotoxemic minipigs.

A treatment group of four 50-80-kg Yucatan minipigs was fitted with jugular, portal, hepatic vein, and carotid artery catheters, and hepatic artery and portal vein flow cuffs to quantitate transhepatic kinetics of glucose, lactate, and insulin. Three days later, they were placed in slings, and a primed-continuous intravenous infusion of 3-tritiated glucose was initiated to monitor whole body glucose kinetics. Following a 3-hour control period, an intravenous infusion of E. coli endotoxin was administered at 15 micrograms/kg/hr for 6 hours. After 1 hour of endotoxin infusion, glucagon was administered as a primed (50 micrograms/kg)-continuous (50 micrograms/kg/hr) intravenous infusion for 5 hours. These results were compared statistically to a control group of eight minipigs given endotoxin only. Glucagon caused a transient (less than 1 hour) peak elevation of arterial glucose levels due to increased hepatic glycogenolysis immediately following initiation of the glucagon infusion. Despite enhanced extrahepatic (renal) gluconeogenesis, plasma glucose concentrations decreased to the hypoglycemic levels of the control group, as glucagon was unable to overcome the relative endotoxic inhibition of hepatic gluconeogenesis. Pancreatic output of insulin increased sixfold resulting in threefold increments in transhepatic uptake and arterial serum insulin levels. Arterial lactate and pyruvate concentrations were elevated due to increased peripheral production and hepatic output. Survivability in the treatment group (75%) improved over the control group (33%).

Animals↗
PubMed1986

Metabolic effects of sodium dichloroacetate in endotoxemic minipigs.

Lactic acidosis is significant in the pathophysiology of endotoxicosis. By increasing the activity of pyruvate dehydrogenase, sodium dichloroacetate (DCA) decreases lactate production and may be useful as a therapy for endotoxic shock. Five (n = 5) 50-80-kg Yucatan minipigs were fitted with jugular, portal, hepatic vein, and carotid artery catheters, and hepatic artery and portal vein flow cuffs to quantitate transhepatic kinetics of glucose, lactate, and insulin. Three days later, they were placed in slings, and a primed-continuous intravenous infusion of 3-tritiated glucose was initiated to monitor whole body glucose kinetics. Following a 3-hour control period, an intravenous infusion of E. coli endotoxin (LPS) was administered at 15 micrograms/kg/hr for 6 hours. After 1 hour of LPS infusion, DCA was administered as a primed (30 mg/kg)-continuous (30 mg/kg/hr) intravenous infusion for 5 hours. These DCA-treated endotoxemic minipigs (group DE) were compared statistically to a group (n = 8) of minipigs given endotoxin only (group E). Group DE arterial lactate concentrations eventually decreased (19.2 +/- 1.0 mg/dl) significantly (P less than or equal to 0.05) below group E (39.3 +/- 7.7 mg/dl) in the last hour of DCA infusion. The progressive hypoglycemia of group DE decreased below that of group E and became significantly (P less than or equal to 0.05) lower in the last hour of the experiment (33.6 +/- 11.5 vs 50.6 +/- 10.0 mg/dl, respectively) due to decreased hepatic gluconeogenesis as evidenced by a lower relative rate of appearance (%Ra) of glucose and decreased hepatic glucose output and lactate extraction. A large relative decrease in pancreatic output of insulin in group DE contributed to the lower serum insulin levels than group E throughout the treatment period. Lethality in group DE (60%) was unaltered from that of group E (67%). Despite its ability to decrease arterial lactate concentrations, DCA alone does not appear to be an effective treatment for endotoxicosis.

Acetates↗
PubMed1986

The Yucatan miniature pig: characterization and utilization in biomedical research.

Yucatan miniature swine have a variety of applications in biomedical research. Sublines developed from the primary population at Colorado State University have been characterized genetically with special attributes. This report describes this unique laboratory animal, genetic selection programs, and its utilization in biomedical research.

Animal Husbandry↗
PubMed1986

Methylprednisolone and gentamicin effects on hepatosplanchnic blood flow and carbohydrate metabolism in endotoxemic Yucatan miniature pigs.

Conjoint therapy of a glucocorticoid and aminoglycoside antibiotic have been recommended for septic shock. These studies examined the hemodynamic and metabolic effects of methylprednisolone sodium succinate (MPSS) with and without gentamicin sulfate in a nonanesthetized model of nonseptic endotoxemia in Yucatan miniature pigs. Methylprednisolone sodium succinate alone had no effect on endotoxin-induced systemic hypotension. Endotoxemic pigs treated with MPSS in combination with gentamicin sulfate had lower mean arterial pressures than did MPSS-treated and nontreated endotoxemic pigs. Methylprednisolone sodium succinate alone and with gentamicin sulfate improved portal and hepatic venous blood flows moderately. Net hepatic lactate extraction, glucose production, and whole body [6-3H]glucose-derived rates of glucose appearance were also improved, but [6-3H]glucose-derived rates of glucose disappearance and blood lactate concentrations were increased, leading to no improvement in plasma glucose concentration. Pancreatic insulin secretion was higher in treated groups, which may have contributed to greater glucose utilization rates. Hepatic oxygen extraction efficiency was not affected by treatment, but increased in all groups to maintain hepatic oxygenation at base-line values. Although a calcium-antagonistic activity of gentamicin has been reported to synergize with endotoxin, thereby adversely affecting cardiovascular function, such effects did not complicate the metabolic response to steroid in the present studies.

Animals↗
PubMed1986

Diarrhea and malabsorption in calves associated with therapeutic doses of antibiotics: absorptive and clinical changes.

Of 28 healthy, nondiarrheal, colostrum-fed neonatal calves, 22 developed diarrhea after they were given (orally) for 3 to 5 days maximally recommended doses of chloramphenicol, neomycin, ampicillin, or tetracycline. Ampicillin-, neomycin-, or tetracycline-treated calves had significantly (P less than 0.05) decreased and delayed glucose absorption during oral glucose tolerance tests. Chloramphenicol-treated calves had significantly (P less than 0.05) higher base-line plasma glucose concentrations during the non-test period and had no significant increase in blood glucose concentrations during the tolerance tests compared with those in control calves.

Ampicillin↗
PubMed1986

Age-related changes in carbohydrate tolerance in healthy neonatal calves.

Calves at 3 to 4 days of age had higher plasma glucose concentrations during glucose and lactose tolerance tests (orally administered glucose and lactose) than when the calves were 8 to 9 days old. These observations may be accounted for by decreased insulin secretion and/or insulin sensitivity of the target tissues. Lower hepatic glucokinase activity in neonates also may allow increased passage of splanchnic glucose to the system circulation.

Aging↗
PubMed1985

Comparison of four thermocycling techniques.

This investigation revealed no significant difference among the four thermocycling techniques. The use of a dye or an isotope was equally effective and penetrated the tooth/restoration interface to a similar degree. The extent of tracer penetration appeared to be independent of the dwell time in the thermal baths. All procedures involving thermal changes were more potent in demonstrating leakage than the noncycled method.

Acid Etching, Dental↗