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Biomedical subjects

T Ling

Publications and source records attributed to T Ling.

33 records · Page 2Linked to original sources
PubMed1988

Percutaneous absorption of nicardipine and ketorolac in rhesus monkeys.

Vehicle effects on the percutaneous absorption of nicardipine base, nicardipine hydrochloride, ketorolac acid, and ketorolac tromethamine were determined using the rhesus monkey as an in vivo model for human skin penetration. Vehicles investigated included blends of propylene glycol, trimethylene glycol, ethanol, Azone, Tween 20, water, and long-chain fatty acids. Formulations were prepared such that the compound dose, application area, and percentage saturation of the compound in the vehicle were held constant. Variations in absorption of the compounds were therefore attributable to vehicle effects. Each formulation was applied to three monkeys for a period of 24 hr using 10 Hill Top Chambers. Plasma samples were taken at appropriate intervals for 36 to 48 hr. The results indicated that trimethylene glycol and Tween 20 did not enhance absorption of the test compounds despite claims by other investigators. Azone and ethanol provided moderate enhancement of both the rate and the extent of absorption, while long-chain fatty acids in combination with propylene glycol significantly enhanced penetration. In general, higher fluxes were observed with the more lipophilic compounds nicardipine base and ketorolac acid as compared to the hydrochloride and tromethamine salts.

Animals↗
PubMed1988

Susceptibility of Hong Kong isolates of methicillin-resistant Staphylococcus aureus to antimicrobial agents.

Two hundred and sixty-six non-replicate Hong Kong isolates of methicillin-resistant Staphylococcus aureus were tested for their susceptibility to various anti-staphylococcal agents. Multiple resistance was common. More than 95% of patient isolates were resistant to both gentamicin and tetracycline, 68% to erythromycin, 37% to chloramphenicol, 10% to trimethoprim, 5% to rifampicin and 2% to fusidic acid. No isolate was resistant to all these agents, but nineteen different patterns of resistance were identified. Selected gentamicin-resistant isolates were tested against other aminoglycosides, and were sensitive to amikacin and netilmicin. The pattern of aminoglycoside resistance indicated that all isolates produced the aminoglycoside-modifying enzymes APH-(2") and AAC-(6')-I. All isolates were sensitive to vancomycin and teicoplanin. A single strain was resistant to three of the five quinolones tested, but resistance to all the quinolones could be induced easily in vitro by exposure to increasing subinhibitory concentrations of norfloxacin in broth.

Anti-Bacterial Agents↗
PubMed1987

Osmotically induced central and peripheral corneal swelling in the cat.

A number of factors have been suggested to account for the reduced swelling response of the peripheral cornea. The osmotic swelling was determined in 25 adult cats by dripping deionized water onto the cornea for 30 min. The central cornea swelled 62 +/- 19 microns compared to 32 +/- 21 microns for the peripheral cornea. Before treatment, the cat was found to have a very uniform thickness profile, measuring 592 +/- 42 microns centrally, and 585 +/- 46 microns peripherally. The difference in central and peripheral swelling was therefore not due to topographical differences in baseline thickness. Endothelial cell density (ECD) determined with specular microscopy was 2920 cells/mm2 centrally, compared to 3,185 cells/mm2 peripherally. Differences in cell density between the center and periphery are not responsible for the reduced swelling response of the corneal periphery inasmuch as swelling response was not correlated with cell density either in the center of the cornea or in the periphery (r = 0.179 and r = 0.221, respectively). By selecting an animal with a uniform thickness profile and by using an osmotic stimulus, this study has shown that the most likely cause for the reduced swelling response near the limbus is a difference in structural and/or hydration characteristics of the cornea at the limbus.

Animals↗
PubMed1986

Tinted contact lenses for treatment of retinal degeneration in a Greyhound.

The owner of a Greyhound reported photophobia and disturbance of vision in the dog's left eye. Racing performance, previously excellent, had become erratic under bright lighting. An irregular area of retinal degeneration was observed in the left eye. We used a flush-fitting scleral (haptic) lens made of tinted lucite with visible transmission of 9% to enhance rod function. Behavioral indications and racing performance improved after the fitting of this lens. The report describes a method of contact lens manufacturing, which will help veterinarians solve vision-related problems in domestic animals.

Animals↗
PubMed1986

Method of evaluating ultrasonic pachometers.

Although many ultrasonic pachometers are commercially available, little has been reported about their performance. We outline a technique for evaluating the accuracy of ultrasonic pachometers by simulating corneal thickness measurements using hydrogel contact lenses. On-eye contact lens thickness is determined using ultrasonic and optical pachometry. Absolute lens thickness is determined using a thickness gauge. Comparisons are made between measurements from the ultrasonic pachometer and measurements from the thickness gauge and optical pachometer. We used this technique to evaluate the performance of the Vida-55 ultrasonic pachometer. This technique was also used to determine the ultrasonic velocity for cat corneal tissue and two hydrogel lens materials. We determined the velocity of ultrasound in cat corneal tissue to be 1590 m/s at 33 degrees C. The velocity of ultrasound in hydroxyethyl methacrylate (HEMA) was 1740 +/- 24 m/s and 1700 +/- 40 m/s in Snoflex 50. We found the Vida-55 pachometer measured corneal thickness accurately when the appropriate ultrasound velocity was used (SEM = 6 microns).

Animals↗
PubMed1984

Pharmacokinetics of nicardipine following oral and intravenous administration in man.

The pharmacokinetics of nicardipine have been studied following oral and intravenous administration in man and the effects of food on nicardipine kinetics investigated. Following intravenous administration of nicardipine as an infusion plasma levels declined in a biphasic manner and plasma clearance values were of the same order as hepatic plasma flow. Following oral administration in the starved state nicardipine was rapidly absorbed but subject to presystemic elimination. Maximal plasma concentrations were achieved typically between 20 minutes and 2 hours after administration. The oral bioavailability of nicardipine determined by reference to a co-administered intravenous radiolabelled dose was found to be non-linearly related to dose. Bioavailability ranged from 15-45% approximately over the dose range 10-40 mg. Administration of nicardipine following a meal reduced the bioavailability of nicardipine.

Administration, Oral↗
PubMed1983

Plasma levels and pharmacokinetics of norethindrone and ethinylestradiol administered in solution and as tablets to women.

Twenty-four normal adult female volunteers were dosed orally with a solution and tablet formulation containing the contraceptive combination of norethindrone (NET, 1.0 mg) and ethinylestradiol (EE2, 0.12 mg) in a crossover bioequivalence study. Blood was sampled sequentially following single oral doses and the plasma separated for analysis of NET and EE2 by specific radioimmunoassays. Comparisons of both drugs following a dose in solution and tablets were made with respect to the following parameters: (a) plasma concentrations at each sample time; (b) maximum plasma concentration (Cpmax); (c) time to maximum plasma concentration (Tmax); (d) total area under the plasma concentration vs. time curve (AUC), and (e) plasma half-life (t1/2). It was found that the tablet and solution doses were bioequivalent with respect to EE2 absorption. However, absorption of NET from solution and tablet doses exhibited significant differences with respect to plasma levels at certain time points as well as AUC (which were higher following the tablet dose), but Cpmax, Tmax and t1/2 were not significantly different. Pharmacokinetic analysis of both drugs following the tablet dose was carried out using a two-compartment open model. The absorption rate constant (ka) and peripheral to central compartment transfer rate constant (k21) were similar for NET and EE2, but statistically significant differences were observed with respect to the distribution rate constant (alpha), the central to peripheral transfer rate constant (k12), the overall elimination rate constant (ke1), and volume of distribution (V1/F). The elimination rate constant (beta) for both drugs showed a difference of borderline statistical significance.

Adolescent↗
PubMedDate not supplied

Clinical pharmacokinetics of ganciclovir in patients with normal and impaired renal function.

The pharmacokinetics of ganciclovir was evaluated in 21 patients with life- or sight-threatening cytomegalovirus infections. Thirteen patients had normal renal function and eight patients had various degrees of renal insufficiency. Most patients received 5 mg of ganciclovir/kg as a 1-hour intravenous infusion twice daily for periods of up to 2 weeks. Quantification of ganciclovir was assessed by high-performance liquid chromatography and radioimmunoassay. In patients with normal renal function, a biexponential decay of ganciclovir from plasma was observed, with an initial distribution half-life (t1/2) of 0.76 +/- 0.67 hour and a terminal elimination t1/2 of 3.60 +/- 1.40 hours. A large fraction of the administered dose was excreted in urine, and total clearance of ganciclovir correlated well with creatinine clearance. In patients with renal insufficiency who were receiving 5 mg of ganciclovir/kg, the terminal elimination t1/2 of ganciclovir was markedly increased (11.50 +/- 3.90 hours), as compared with values obtained in patients with normal renal function. Hemodialysis efficiently reduced levels of ganciclovir in plasma by approximately 53.0% +/- 11.5%, a finding that indicates this drug should be administered after dialysis.

Acyclovir↗
PubMedDate not supplied

Smoking behavior among adolescents in the city, suburbs, and rural areas of Shanghai.

PURPOSE: The study was designed to investigate differences in predisposing factors, enabling factors, reinforcing factors, and smoking behavior among middle school students living in the city, suburbs, and rural areas of Shanghai. DESIGN: A one-time cross-sectional survey design was applied in this study. SETTING: The study was conducted in 11 schools in three areas. SUBJECTS: A total number of 1116 students from these three areas participated in this study. The response rates were 92, 88, and 84% for city, suburbs, and rural areas, respectively. MEASURE: A PRECEDE instrument including predisposing, enabling, and reinforcing factors was employed to collect data. A Multivariate Analysis of Variance (MANOVA) and Multiple Regression Analysis were used to analyze the data. RESULTS: Smoking was reported by 39.8% of boys and 5.14% of girls. Students in the city of Shanghai had the best (against smoking) predisposing factors, but students in rural areas had the best (against smoking) enabling and reinforcing factors and consumed the fewest cigarettes. CONCLUSION: Results indicated that smoking behavior in students was affected strongly by enabling factors and reinforcing factors that were related to socioeconomic, cultural, and environmental influences in China.

Adolescent↗