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Biomedical subjects

J C Price

Publications and source records attributed to J C Price.

At least 19 recordsLinked to original sources
PubMed1992

Complications and early outcome of anterior craniofacial resection.

OBJECTIVE: To evaluate the complications of anterior craniofacial resection and correlate their impact with tumor control status. DESIGN: We conducted a retrospective review of 32 consecutive, operable patients' records seen over a 6-year period, requiring 35 procedures. SETTING: Academic tertiary referral medical center. PARTICIPANTS: Twenty-six patients (81%) had malignant lesions (esthesioneuroblastoma, squamous cell carcinoma, and a group of miscellaneous malignant tumors). Six patients had various benign neoplasms. INTERVENTION: The surgical approach involved bifrontal craniotomy coupled with lateral rhinotomy in 19 cases (61%), facial degloving in 10 cases (32%), a total rhinectomy in one case, and endoscopic sinusectomy without facial incision in two cases. OUTCOME MEASURE: Clinically noted complications and oncologic outcome. RESULTS: There was one avoidable perioperative death indirectly associated with the patient's procedure. Nine patients suffered significant intracranial neurological complications such as tension pneumocephalus and delayed epidural abscess. All of these complications were managed successfully. Of patients with malignant tumors, 13 (52%) are alive with no evidence of disease and one is alive with recurrence after a mean follow-up period of 28.9 months. The 10 patients who succumbed to disease had a mean postoperative survival of 22.9 months. CONCLUSIONS: In contrast to the perspective of only a decade ago, we conclude that craniofacial resection is a relatively safe, versatile, and effective procedure for surgical management of tumors involving the anterior skull base.

Adult↗
PubMed1992

Pharmacokinetics of progesterone in ovariectomized rats after single dose intravenous administration.

The pharmacokinetics of progesterone were characterized in ovariectomized female rats. Progesterone was administered intravenously at a dose of 500 micrograms kg-1. Serum progesterone concentrations were determined by radioimmunoassay. Serum concentrations of progesterone were best described by a two-compartment model with elimination from the central compartment. The distribution and elimination phase half-lives were 0.13 +/- 0.024 (mean +/- SD) and 1.21 +/- 0.21 h, respectively. Elimination of the steroid was rapid with a total clearance of 2.75 +/- 0.42 l h-1 kg-1. Progesterone was widely distributed in the rat with a steady state volume of distribution of 2.36 +/- 0.23 l kg-1, a volume of the central compartment of 0.86 +/- 0.24 l kg-1 and a volume of the peripheral compartment of 1.50 +/- 0.19 l kg-1. The results of this study suggest that the ovariectomized female rat is a suitable animal model for examining the pharmacokinetics of progesterone.

Animals↗
PubMed1991

Iodine-125 seed implantation as an adjunct to surgery in advanced recurrent squamous cell cancer of the head and neck.

Survival for extensive recurrent squamous cell carcinomas of the head and neck remains poor, with the major cause of death being local recurrence. Surgical implantation of iodine-125 interstitial seeds allows tumoricidal doses of radiation to be delivered to residual tumor while minimizing radiation doses to the surrounding tissues. From 1978 to 1988, 39 implantations were performed on 35 patients for extensive recurrent squamous cell carcinoma of the head and neck. The decision for implantation was based on positive margins or close to resection margins from frozen sections after salvage resection. The determinate 5-year disease-free survival was 41%, with both the overall and no evidence of disease 5-year survivals being 29%. Significant complications occurred in 36% of all cases. This figure increased to 56% when flap reconstruction was required. Possible reasons for this seemingly high complication rate are discussed. Considering the advanced nature of these recurrent carcinomas, surgical resection with iodine-125 seed implantation appears to be an effective method of managing disease that might otherwise be judged unresectable and treated for palliation only.

Actuarial Analysis↗
PubMed1991

Effect of drug loading and molecular weight of cellulose acetate propionate on the release characteristics of theophylline microspheres.

Microspheres with 40, 50, and 60% drug loading of anhydrous theophylline core material were prepared by the emulsion-solvent evaporation method. Three different molecular weights of cellulose acetate propionate were used as encapsulating polymers. The geometric mean diameter of the microspheres increased with drug loading for all polymers. Dissolution rate for a given particle size fraction also increased with drug loading for all polymers. Higuchi/Baker-Lonsdale spherical matrix dissolution kinetics were followed by narrow particle size fractions of the microspheres. A linear relationship between the T-50% (time required for 50% of the drug to be released) and the square of microsphere diameter was observed with all three molecular weights of the encapsulants. The slowest drug release was obtained with the high molecular weight polymer, which also produced the smoothest microspheres.

Capsules↗
PubMed1991

Development and evaluation of sustained-release ibuprofen-wax microspheres. I. Effect of formulation variables on physical characteristics.

A congealable disperse phase encapsulation method was used to prepare sustained-release ibuprofen-wax microspheres. Microspheres prepared with paraffin wax, such as ceresine and microcrystalline waxes, using polyvinylpyrrolidone (PVP) as dispersant had a tendency to aggregate, but the addition of wax modifiers (stearyl alcohol and glyceryl monostearate) greatly reduced aggregation. Optimum modifier and dispersant concentrations were 20% (w/w) and 5% (w/v), respectively. The particle size distribution of the microspheres was log-normal. An increase in modifier, dispersant concentration, emulsification stirring speed, or temperature shifted the size distribution toward finer particles. Microcrystalline wax required a higher emulsification temperature and produced finer particles than ozokerite wax. The recovery of drug from the different microsphere formulations varied between 71 and 92%. Differential scanning calorimetry (DSC) of the single components and physical mixtures showed endothermic peaks at the respective melting-point ranges. The DSC of the ceresine and microcrystalline wax microspheres was similar to rescans of ternary mixtures of components of the microspheres with less prominent and lower melting temperatures than individual components or physical mixtures.

Delayed-Action Preparations↗
PubMed1991

Effect of moisture content on compression properties of two dextrose-based directly compressible diluents.

Moisture sorption characteristics and the effect of moisture content on the compression properties of two dextrose-based directly compressible diluents, namely, Emdex (diluent A) and Sweetrex (diluent B) were studied. Both diluents sorbed moisture rapidly at relative humidities greater than 60%. For both the diluents, pressures required to compress tablets to the same relative density decreased with increasing moisture content. Yield pressures calculated from linear Heckel plots obtained from the compression data of both diluents reflected decreasing values with increasing moisture content. Three-way surface profile graphs of moisture content versus tablet parameters such as crushing force, relative density, and compression pressure give a unique overall picture of the compression properties of a diluent and offer the tablet formulator a useful tool for diluent comparison.

Chemical Phenomena↗
PubMed1991

Quantification of human opiate receptor concentration and affinity using high and low specific activity [11C]diprenorphine and positron emission tomography.

[11C]Diprenorphine, a weak partial opiate agonist, and positron emission tomography were used to obtain noninvasive regional estimates of opiate receptor concentration (Bmax) and affinity (Kd) in human brain. Different compartmental models and fitting strategies were compared statistically to establish the most reliable method of parameter estimation. Paired studies were performed in six normal subjects using high (769-5,920 Ci/mmol) and low (27-80 Ci/mmol) specific activity (SA) [11C]diprenorphine. Two subjects were studied a third time using high SA [11C]diprenorphine after a pretreatment with 1-1.5 mg/kg of the opiate antagonist naloxone. After the plasma radioactivity was corrected for metabolites, the brain data were analyzed using a three-compartment model and nonlinear least-squares curve fitting. Linear differential equations were used to describe the high SA (low receptor occupancy) kinetics. The k3/k4 ratio varied from 1.0 +/- 0.2 (occipital cortex) to 8.6 +/- 1.6 (thalamus). Nonlinear differential equations were used to describe the low SA (high receptor occupancy) kinetics and the curve fits provided the konf2 product. The measured free fraction of [11C]diprenorphine in plasma (f1) was 0.30 +/- 0.03, the average K1/k2 ratio from the two naloxone studies was 1.1 +/- 0.2, and the calculated free fraction of [11C]diprenorphine in the brain (f2) was 0.3. Using the paired SA studies, the estimated kinetic parameters, and f2, separate estimates of Bmax and Kd were obtained. Bmax varied from 2.3 +/- 0.5 (occipital cortex) to 20.6 +/- 7.3 (cingulate cortex) nM. The average Kd (eight brain regions) was 0.85 +/- 0.17 nM.

Adult↗
PubMed1991

Effect of aspartame-derived phenylalanine on neutral amino acid uptake in human brain: a positron emission tomography study.

The possible effects of elevation of the plasma phenylalanine level secondary to the ingestion of aspartame on brain amino acid uptake in human subjects have been investigated by means of positron emission tomography (PET). 1-[11C]Aminocyclohexanecarboxylate [( 11C]ACHC) is a poorly metabolized synthetic amino acid that crosses the blood-brain barrier by the same carrier that transports naturally occurring large neutral amino acids. Quantitative test-retest PET studies were performed on 15 individuals. Seven received two identical baseline scans, whereas eight received a baseline scan followed by a scan performed approximately 40-45 min following ingestion of an orange-flavored beverage containing 34 mg/kg of body weight of the low-calorie sweetener aspartame, a dose equivalent to the amount in 5 L of diet soft drink consumed all at once by the study subjects, weighing an average of 76 kg. The 40-45-min interval was selected to maximize the detection of possible decreases in ACHC uptake resulting from increased competition for the carrier, because the plasma phenylalanine level is known to peak at this time. We observed an 11.5% decrease in the amino acid transport rate constant K1 and a smaller decrease in the tissue distribution volume of ACHC (6%). Under conditions of normal dietary use, aspartame is thus unlikely to cause changes in brain amino acid uptake that are measurable by PET.

Amino Acids↗
PubMed1990

Esophageal reflux and secondary malignant neoplasia at laryngoesophagectomy.

Pathologic evidence of gastroesophageal reflux demonstrated by either Barrett's esophagus or esophagitis was present in 33% of patients undergoing laryngopharynoesophagectomy, while secondary esophageal squamous cell carcinomas were present in 25% of the specimens. Overall, 54% of all the patients undergoing laryngopharyngoesophagectomy had esophageal disease. This incidence of reflux and secondary esophageal malignant neoplasia is higher than in the general population. Careful assessment of the patient's preoperative history for gastroesophageal reflux, contrast swallowing studies, and esophagoscopies correctly diagnosed most but not all of the esophageal lesions found on pathologic examination. Interestingly, all of the esophageal carcinomas removed in the laryngopharyngoesophagectomy specimens were small and sometimes not evident clinically. Although gastroesophageal reflux has been postulated as an additional etiologic agent in the development of laryngeal carcinoma, all the patients in our study had heavy alcohol and tobacco consumption, and therefore reflux could not be evaluated separately as a risk factor.

Adult↗
PubMed1990

Estimated fetal radiation dose from multislice CT studies.

It is often necessary to estimate the dose of radiation to a fetus from a series of CT scans. To assist in making this process easier and more accurate, we measured fetal doses in an adult anthropomorphic phantom for four CT scanners: Picker 1200, Siemens DRH, GE 9800, and GE 8800. Measurements were made at four kilovoltages (100, 120, 130, and 140 kVp), for 2-, 5-, 8-, and 10-mm thicknesses, for two scanning angles (360 degrees and 398 degrees) and for two patient orientations (prone and supine). The fetal-dose estimates are based on the CT dose index measured by using a pencil ionization chamber at the center position of a 16-cm-diameter cylindrical phantom. Comparison with data from other investigators shows reasonable agreement when phantom differences, X-ray tube output, and equipment calibration are considered.

Female↗
PubMed1989

Effect of drug (core) particle size on the dissolution of theophylline from microspheres made from low molecular weight cellulose acetate propionate.

Three particle sizes (450, 120, and 5 microns) of theophylline were encapsulated in low molecular weight cellulose acetate propionate (intrinsic viscosity, 1.08 dl/g) by the solvent evaporation method. The theoretical drug content for all the batches of microspheres was 50% (w/w). Particle size analysis revealed that about 50% of the microspheres containing the large theophylline crystals (average length of 450 microns) were greater than 500 microns in diameter, whereas only about 35% of the microspheres containing the medium drug crystals (average length of 120 microns) were greater than 500 microns in diameter. The drug content of the larger microspheres prepared from the large drug crystals and the medium drug crystals was much greater than the theoretical drug content (50%, w/w); however, the drug content of all the batches of microspheres containing micronized drug was close to 50% (w/w). Release of the drug in simulated intestinal fluid was very rapid from microspheres containing large and medium drug crystals, while release was slower and more predictable from microspheres made from micronized drug.

Cellulose↗
PubMed1989

Modification of gelatin beadlets for zero-order sustained release.

A three-phase suspension process was used for the preparation of gelatin beadlets containing succinylsulfathiazole. When the beadlets were hardened with 10% formalin at 5 degrees C for varying periods of time up to 24 hr, the 6-hr hardening time gave the slowest release rate. Drug release rate from gelatin beadlets was slower in simulated gastric fluid (SGF) than in simulated intestinal fluid (SIF) but the sustained effect was too limited to be useful for most applications. When the hardened gelatin beadlets were coated with cellulose acetate butyrate (CAB) by an emulsion-solvent evaporation method, a more pronounced sustained effect and a nearly zero-order release were found in SIF. The effects of the amount of gelatin used, the amount of CAB employed, and the length of hardening time on drug release were investigated. The treatment of gelatin beadlets with formalin reduced the swelling action of gelatin in aqueous medium. A nonzero-order drug release rate was observed when the gelatin swelled sufficiently to rupture the CAB coating. The drug release rate can be adjusted by using different ratios of hardened gelatin beadlets and CAB coating in which the gelatin enhances the release rate and the CAB serves as a barrier.

Capsules↗
PubMed1988

The disaggregation of calcium-depleted casein micelles.

The effect of depletion of Ca2+ on the composition and size distribution of casein micelles in milk has been examined using chemical analysis, size exclusion chromatography, fast protein liquid chromatography, turbidimetry and photon correlation spectroscopy. Partial removal of Ca2+ by EDTA and subsequent dialysis resulted in disaggregation of some of the casein micelles; as the EDTA concentration increased, the proportions of Ca2+ and phosphate relative to protein in the micelles remaining intact decreased. However, the composition of the intact micelles, with respect to the different caseins, and the number-frequency size distribution were essentially unchanged.

Animals↗