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Biomedical subjects

J L Fox

Publications and source records attributed to J L Fox.

At least 73 records · Page 4Linked to original sources
PubMed1998

Combined effects of laser irradiation/solution fluoride ion on enamel demineralization.

OBJECTIVE: The effects of CO2 laser irradiation of dental enamel were evaluated in enamel demineralization experiments in partially saturated solutions (i.e., solutions containing both calcium and phosphate ions) with and without fluoride ions. SUMMARY BACKGROUND DATA: Previous studies had shown that a continuous-wave CO2 laser at an energy density of around 130 J/cm2 may induce an increased acid resistance in human dental enamel as assessed by exposure to severe demineralization conditions (0.1 mol/L acetate buffer, pH 4.5 and ionic strength 0.5 mol/L). METHODS: Enamel blocks were irradiated with a continuous-wave CO2 laser at a wavelength of 10.6 microns using energy densities of from 42.5 to 170.0 J/cm2. The blocks were then exposed to a partially saturated demineralizing solution with or without 0.2 ppm fluoride at a temperature of 30 degrees C for 24 hours. The demineralization was examined both qualitatively by light microscopy and quantitatively by microradiography. RESULTS: A comparison between the lased and the unlased portions of enamel showed increased acid-resistance with increasing laser energy density and, at the highest energy density of 170.0 J/cm2, there was little or no lesion development in the fluoride-free dissolution medium. The demineralization of enamel was reduced dramatically in the presence of 0.2 ppm fluoride for both lased and unlased enamel; there was only modest lesion development observed for unlased enamel and, at an energy density as low as 85.0 J/cm2, the surface of enamel was found to be completely protected. CONCLUSIONS: These findings are consistent with the mechanism that laser irradiation of dental enamel results in significant reduction of the effective solubility of enamel mineral and that there is a significant synergism between laser irradiation and solution fluoride with regard to this effect.

Carbon Dioxide↗
PubMed1998

The spectrum of respiratory disease associated with exposure to metal working fluids.

Occupational respiratory diseases have been reported following exposure to metal working fluids. We report a spectrum of respiratory illnesses occurring in an outbreak in 30 workers of an automobile parts engine manufacturing plant. Workers presented with respiratory complaints and, after clinical and laboratory evaluations, were classified as those having hypersensitivity pneumonitis, occupational asthma, or industrial bronchitis, or those without occupational lung disease. Hypersensitivity pneumonitis affected seven workers, with six exhibiting serum precipitins to Acinetobacter Iwoffii. Occupational asthma and industrial bronchitis affected 12 and six workers, respectively. Oil-mist exposures were below current recommendations. Gram-negative bacteria, but no fungi, Thermophiles, or Legionella, were identified. Although specific agents responsible for each individual case could not be identified, probably both specific sensitizing agents and non-specific irritants from metal working fluids, additives, or contaminants contributed to this spectrum of occupational respiratory illness.

Adult↗
PubMed1998

Effect of a dual-lumen peripheral catheter on the delivery of known incompatible medications.

OBJECTIVE: To determine the degree to which a dual-lumen peripheral catheter prevented precipitation of solutions known to be incompatible due to pH during simultaneous infusion in an in vitro model. METHODS: An in vitro model was devised to simulate peripheral venous blood flow from an antecubital source to systemic circulation. Ondansetron was simultaneously infused with fluorouracil, aminophylline, sodium bicarbonate, and ampicillin sodium in concentrations reflective of clinical conditions into the Twin Cath 20/22 (the dual-lumen catheter used in this experiment). Study solutions were primed with the prepared drug solution and administered for 15 minutes. Phase I used Normosol-R as the diluent to gather preliminary data; phase II used human plasma. All samples were obtained immediately before the start of the infusion and at 5, 10, and 15 minutes during the infusion, and 5 minutes after the infusion. Samples were visually inspected at each time point for precipitation and analyzed in duplicate by the appropriate stability-indicating HPLC method (except for sodium bicarbonate). Compatibility was defined as no visual evidence of precipitation and no more than 15% mean change in final versus initial concentration. RESULTS: Phase I experiments showed immediate precipitation in Normosol-R within the venous flow. However, in phase II, because of the buffering capacity that plasma proteins add to plasma, no precipitation occurred. All the drug combinations used in this study have been reported to be incompatible at the concentrations tested; however, we detected no incompatibilities. CONCLUSIONS: The results of this study indicate that using a dual-lumen peripheral catheter, such as the Twin Cath, may allow solutions incompatible due to pH to be administered simultaneously.

Aminophylline↗
PubMed1997

Mechanism of long-range Ca2+ signalling in the nucleus of isolated rat hepatocytes.

Ca2+ regulates a wide range of cell proteins, in both the cytosol and nucleus. It enters the nucleus from stores along the nuclear envelope, but how it then spreads through the nuclear interior is unknown. Here we used high-speed confocal line-scanning microscopy to examine the propagation of Ca2+ waves across nuclei in isolated rat hepatocytes. Nuclear Ca2+ waves began at the nucleus/cytosol border as expected, then spread across the nucleus at less than half the speed of cytosolic Ca2+ waves. High concentrations of caffeine slowed Ca2+ waves in the cytosol but not in the nucleus. We developed a mathematical model based on diffusion to analyse these data, and the model was able to describe the nuclear but not cytosolic Ca2+ waves that were experimentally observed. These findings suggest that Ca2+ waves cross the nucleus by simple diffusion, which is distinct from the reaction-diffusion mechanism by which Ca2+ waves propagate across the cytosol. Since the range of messenger action for Ca2+ in the cytosol is much smaller than the distance across the nucleus, this also suggests that the unique environment and geometry of the nuclear interior may permit this simple mechanism of Ca2+ wave propagation to control Ca2+-mediated processes in a relatively large region despite Ca2+ release pools that are spatially limited.

Animals↗
PubMed1997

Stability of sumatriptan succinate in extemporaneously prepared oral liquids.

The stability of sumatriptan succinate in extemporaneously prepared oral liquids was studied. Suspensions of sumatriptan (as the succinate salt) in Ora-Sweet, Ora-Sweet SF, and Syrpalta syrups (Paddock Laboratories and Humco Laboratory) were extemporaneously compounded to produce a sumatriptan concentration of 5 mg/mL. Each suspension was prepared in triplicate. The suspensions were stored at 4 degrees C in amber glass bottles for 60 days. Two 1-mL samples were removed from each bottle initially and on days 2, 7, 14, 21, 28, 35, and 60. Sumatriptan concentrations were determined by high-performance liquid chromatography. The samples also underwent visual inspection and microbial testing. The mean concentration of sumatriptan in all suspensions remained above 90% of the initial concentration for up to 21 days. By day 28, the sumatriptan concentration of all suspensions had decreased to less than 90% of the initial concentration. None of the suspensions had microbial growth up to day 28, and there were no visible changes in the suspensions throughout the study period. Sumatriptan 5 mg/mL (as the succinate salt) in three oral suspensions was stable for up to 21 days when stored without light at 4 degrees C.

Administration, Oral↗
PubMed1997

Effect of sodium bicarbonate amount on in vitro indomethacin release from self-setting carbonated-apatite cement.

PURPOSE: In the present study, to develop a drug delivery system with higher bioactivity in hard tissues by using the self-setting bioactive carbonate apatite cement, we have investigated the effects of sodium bicarbonate content on the in vitro drug release from a self-setting bioactive carbonate apatite cement containing indomethacin (IMC). METHODS: The cement powder systems constituted an equimolar mixture of tetracalcium phosphate (Ca4(PO4)2O) and dicalcium phosphate dihydrate (CaHPO4.2H2O), hydroxyapatite (HAP, Ca10(PO4)6(OH)2) seed crystals and sodium bicarbonate. Two types of 2% IMC loaded-cements were prepared as follows, one containing 0% HAP seed crystal and 0-10% sodium bicarbonate, and the other containing 40% HAP seed crystal and 0-10% sodium bicarbonate. The drug release profiles from 2% IMC loaded-cements were measured in simulated body fluid at pH 7.25 and 37.0 degrees C. RESULTS: The drug release profiles from the cement matrix systems with or without seed crystals were estimated using a moment analysis computer program. The mean drug release time (MDT) and the time required for 50% drug release of the cement containing 0 and 40% seed crystal decreased with an increase of sodium bicarbonate. Furthermore, after the drug release the total pore volume of the cement matrix, as measured by mercury porosimetry, increased with an increase of sodium bicarbonate. CONCLUSIONS: MDT and T50's were a function of adding the amount of sodium bicarbonate. The results of the relationship between the micropore distribution, total volume of pores after drug release and drug release supported the hypothesis that the variation in drug release from the cements resulting from the addition of sodium bicarbonate was mainly due to an increase in the diffusion of the drug in the micropores of the cement by dissolution or erosion of the cement matrix.

Anti-Inflammatory Agents, Non-Steroidal↗