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Biomedical subjects

C F Wong

Publications and source records attributed to C F Wong.

At least 55 records · Page 3Linked to original sources
PubMed1993

Correlation of serum ofloxacin concentration and serum creatinine level in patients on prolonged therapy.

Serum ofloxacin concentrations were assessed by high performance liquid chromatography 4 h after drug administration in 86 patients with pulmonary tuberculosis. All patients had multidose, once-daily drug administration (200 mg to 800 mg p.o.) for at least 3 weeks prior to assessment. The serum creatinine levels were simultaneously assessed for these patients. A positive correlation was found between serum ofloxacin (Y) and serum creatinine x dose of ofloxacin administered/body surface area (X). The correlation can be represented mathematically by the equation: Y = 0.87X + 0.68 (r = 0.80, p < 0.001).

Adolescent↗
PubMed1992

Preparation and properties of gem-dichlorocyclopropane derivatives of long-chain fatty esters.

Methyl oleate (18:1) and linoleate (18:2) were readily transformed to the corresponding gem-dichlorocyclopropane derivatives in high yield, using triethylbenzylammonium chloride as the phase-transfer catalyst in the presence of aqueous NaOH and CHCl3. Reaction of dichlorocarbene with methyl 12-hydroxystearate furnished methyl 12-chlorostearate (49%) and 12-O-formylstearate (19%). The hydroxy group in methyl ricinoleate was protected (O-tetrahydropyran-2'-yl) prior to dichlorocyclopropanation of the ethylenic bond. Removal of the protecting group allowed the hydroxy group to be converted to a chloride, O-acetyl, azido or O-formyl function. Treatment of methyl ricinoleate with thionyl chloride, followed by the reaction with dichlorocarbene gave the corresponding 12-chloro-dichlorocyclopropane derivative. The dichlorocyclopropane derivative of oleic acid was transformed to a C19 allenic fatty acid when treated with t-butyl lithium. However, the remaining dichlorocyclopropane derivatives containing an additional functional group in the alkyl chain, failed to yield the corresponding allenic derivatives. All derivatives were characterized by a combination of spectroscopic and chromatographic techniques, including infrared, 1H nuclear magnetic resonance (NMR), and 13C NMR spectroscopy.

Catalysis↗
PubMed1992

Measurement of human exposure to ultraviolet-B solar radiation using a CR-39 dosimeter.

CR-39 (allyl diglycol carbonate) dosimeters were tested for measurements of ultraviolet-B (erythemal dose) solar radiation with a rotating model head and a human survey during solar exposure. The ratio of summer dose to winter dose for the vertex is 3.3, and for the eye and lower face is greater than 1. A survey suggests the relation of the ultraviolet-B dose to outdoor activities.

Face↗
PubMed1992

Automatic counting of nuclear tracks.

Two software packages designed for automatic counting nuclear tracks are tested and compared. The image processing in the first package is divided into three parts segmentation, speckle elimination and removal of ill-formed track holes. The second package is also divided into three parts but the last part is modified such that the track holes with white centres are filled by the program. The processes in the second package are done by the use of mathematical morphology. From the test, it was found that the first package has severe limitations for the working range. The second package provides a greater working range but the running time of the program is longer than that of the first package.

Radioactivity↗
PubMed1991

The temperature for fusing blood vessels using a copper vapour laser.

Specimens of canine femoral or carotid artery were preserved at the temperature of liquid nitrogen and restored to room temperature before use. Fusing experiments were performed by repeatedly scanning along cuts of 1.0 cm long using a copper vapour laser at a power level of 500 mW. The laser was delivered via a 0.2 mm diameter optical fibre, 10 cm from the specimen, providing a beam spot area of 0.125 mm2 (a power density of 400 W cm-2). Drops of saline solution were applied to the irradiated areas for cooling at a rate of one drop every five seconds. At a scanning rate of 1 cm s-1, about 300 s were taken to successfully fuse a cut of 1 cm long with minimum tissue damage. Direct measurement of tissue temperatures whilst the beam was applied was not possible because of the interference of the laser, therefore the fusing temperature was estimated by the method of extrapolation. Time dependence of the surface temperature at the centre of the target area immediately after exposure and the spatial distribution of the surface temperature around the target area during exposures were measured using a thermocouple thermometer. The fusing temperature was estimated to be 62 degrees C by extrapolation of the time dependence and spatial distributions.

Anastomosis, Surgical↗
PubMed1991

Evaluation of a low-cost automatic counting system for nuclear track detectors.

This paper describes a low-cost automatic counting system for recognising and counting microscopic track holes in plastic nuclear track detectors. The hardware includes an Olympus BH2 microscope, (manufactured by the Olympus Optical Company, Japan) a Philips resistive gate sensor (RGS) board, (manufactured by the Philips Company, Netherlands) a frame-grabber board and an IBM PC compatible. The RGS board acts like a camera, sending analog video signals of the microscope's field image to the frame-grabber, which produces a digital image with a resolution of 256 x 256 pixels and 128 grey levels in about 20 ms. This is then stored in either one of two 64K on-board RAMs for processing by the PC. The software is menu-driven and allows image grabbing, saving, loading and processing. The image processing can be divided into three parts namely: segmentation, speckle elimination and the removal of ill-formed track holes. In this paper we will present the results of testing the system with sample images obtained from CR-39 plastic nuclear track detectors. The limitations of the system for counting track holes on these detectors will be discussed.

Evaluation Studies as Topic↗
PubMed1990

Determination of minor impurities in temafloxacin hydrochloride by high-performance liquid chromatography.

Minor impurities in the antibacterial agent temafloxacin hydrochloride were determined using high-performance liquid chromatography. Manufacturing impurities and degradation products were separated using a reversed-phase system with gradient elution. Detector response was linear for the individual impurities to approximately 50 micrograms/ml which represents 2.5% of the drug concentration. The procedure provides quantitation of impurities to approximately the 0.05% level with precision (relative standard deviations) of 4.7% to 29% in typical bulk drug lots. A variety of reversed-phase columns were evaluated for the assay method with optimum resolution achieved using a 5-microns Nucleosil C18 packing.

4-Quinolones↗
PubMed1989

Superoxide dismutase: fluctuations in the structure and solvation of the active site channel studied by molecular dynamics simulation.

The molecular dynamics (MD) simulation of superoxide dismutase (SOD) in water is carried out for a total of 23 ps. The simulation system is a 26 A sphere centered at the active site of SOD, including 1602 atoms from SOD and 1761 water molecules. There is no gross deviation from the x-ray structure for the average MD structure. The structure and potential fluctuations around the active site are examined. The results provide new insight to the interactions between SOD and its substrate superoxide.

Binding Sites↗
PubMed1988

Quantum simulation of ferrocytochrome c.

The dramatic progress in the understanding of the dynamics of biomolecules has been largely fuelled by computer simulations based on the law of classical mechanics. However in some respects biomolecules are at the borders of the domain of applicability of classical mechanics. The role of quantum mechanical effects in biomolecular structure and function is therefore worth investigating. Here we present preliminary results from a quantum simulation of a protein and contrast them with results from full classical simulations. The most significant differences are found in motions of high frequency, such as bond stretching or the torsional oscillation of groups that bear hydrogen atoms. The amplitudes of such motions are significantly increased by the penetration of atoms into classically forbidden regions. These differences will directly influence the rates of such processes as proton and electron transfer.

Cytochrome c Group↗
PubMedDate not supplied

Polymeric films as vehicle for buccal delivery: swelling, mechanical, and bioadhesive properties.

PURPOSE: To investigate the suitability of an SCMC (sodium carboxymethyl cellulose/polyethylene glycol 400/carbopol 934P) and an HPMC (hydroxypropylmethyl cellulose/polyethylene glycol 400/carbopol 934P) films as drug vehicle for buccal delivery. METHODS: The mechanical and in vitro bioadhesive strength properties of the films were investigated using texture analyzer equipment, while swelling behavior was studied in different media, namely, distilled water and simulated saliva solution. In addition, the in vivo bioadhesion of the film was studied by estimating the film residence time on buccal mucosa of human volunteers. RESULTS: Increase in carbopol 934P content was found to elevate the elasticity, softness and bioadhesive strength but decrease the strength and degree of swelling of both SCMC and HPMC films. SCMC films swelled more extensively in distilled water while HPMC films in simulated saliva solution. HPMC films exhibited greater in vivo bioadhesion although the in vitro bioadhesive strength was lower than SCMC films. Correlation existed between the in vivo and in vitro bioadhesion data within the polymer, but no rank correlation was observed between the two polymers. CONCLUSION: HPMC films may be preferred over SCMC films as drug vehicle for buccal delivery as the former was tougher, more elastic, more bioadhesive in vivo and swelled in a more tolerable manner in the oral cavity than the latter.

Adhesiveness↗