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B L Lee

Publications and source records attributed to B L Lee.

At least 73 records · Page 4Linked to original sources
PubMed1997

High-performance liquid chromatographic determination of dehydroabietic and abietic acids in traditional Chinese medications.

In Asia, there is still a high usage of traditional Chinese medicament by the general population. Some patients with contact dermatitis to these medicaments have been found to be sensitive to colophony on patch testing. Dehydroabietic acid (DHAA) and abietic acid (AA) are the main components of colophony and believed to be the agents responsible for skin sensitization. This paper describes a reliable high-performance liquid-chromatographic method for determining these two resin acids in ointment samples. The samples were either pretreated with diethyl ether or treated with acetonitrile directly by ultrasonication for 30 min. One volume of this sample was added to an equal volume of water and purified by solid-phase extraction. The mobile phase used was methanol-water-phosphoric acid (87:13:0.02, v/v) and the flow-rate was 1 ml/min. DHAA and AA were detected at 4.3 and 6.3 men with ultraviolet detection at wavelength 200 and 239 nm, respectively. However, fluorimetric detection with an excitation wavelength of 225 nm and emission wavelength of 285 nm, provided more selective determination of DHAA. The detection limits for DHAA and AA were 1 ng. Analytical recovery generally exceeded 90%. We analyzed nine types of commonly used topical Chinese medicaments and two types of Western medical ointments in Singapore. The results showed that most of these medicaments contain colophony below 5 ppm (micrograms g-1). Only one Chinese medicament contained > 70 ppm of both allergens and one of the Western medical ointments contained 0.2% of DHAA and 2.2% of AA.

Abietanes↗
PubMed1997

Purification and characterization of prophenoloxidase from the hemolymph of coleopteran insect, Holotrichia diomphalia larvae.

Prophenoloxidase (pro-PO), a precursor of phenol oxidase (PO), was purified from the hemolymph of coleopteran Holotrichia diomphalia larvae. The enzyme was purified to apparent homogeneity, in six steps of chromatography, using Sephadex G-100, CM-52, Dextran-sulfate Sepharose CL-6B, Phenyl Sepharose CL-4B, Sephacryl S-200, and a Mono-Q column. The preparation exhibited a single band on SDS-PAGE. The proenzyme had a molecular weight of 158 kDa, as estimated by gel filtration. On SDS-PAGE under reducing conditions, it gave a 79 kDa band, indicating that it forms a dimer of the 79 kDa protein. On the other hand, the purified pro-PO gave two well-separated peaks, named pro-PO-1 and pro-PO-2, on reverse-phase HPLC. Amino acid compositions of both proteins were indistinguishable, thereby suggesting the presence of an allelic variant or an isoprotein. On dextran-sulfate Sepharose CL-6B chromatography, a fraction containing prophenoloxidase activating enzyme(s) (PPAE fraction), free from pro-PO, was also separated. In reconstitution experiments, the activation of purified pro-PO by PPAE fraction, was observed in the presence of 5 mM Ca2+, with a specific limited proteolysis. The NH2-terminal sequence of generated PO was determined to be NH2-Phe-Gly-Glu-Asp-Asp-. The activated PO oxidized o-diphenols but did not oxidize mono-phenol and p-diphenol substrates. The purified pro-PO was not activated by trypsin, alpha-chymotrypsin, and SDS.

Amino Acid Sequence↗
PubMed1997

Entoptic evaluation of diabetic retinopathy.

PURPOSE: Studies using optimized entoptic viewing of the parafoveal retinal vasculature have shown that normal subjects see their own capillaries with greater detail in the fovea than seen typically in fluorescein angiography. The authors have extended these investigations to persons with diabetes to evaluate the sensitivity, specificity, and accuracy with which they can detect and locate their own parafoveal retinal defects untrained. METHODS: A vascular entoptoscope using Maxwellian view optics creates a high-contrast entoptic view of retinal vasculature abnormalities in the parafoveal area. Using a double-masked protocol, 70 patients with diabetes and 29 control subjects described, drew, and quantified their entoptic image. These entoptic records were compared to angiograms and color photographs obtained immediately after the entoptic evaluation. RESULTS: Angiograms or color photographs or both showed that 61 of 70 patients with diabetes had retinal defects (e.g., microaneurysms or exudates or both) within the field of view of the Vascular Entoptoscope (8.1 degrees or 11.6 degrees circular field depending on the Vascular Entoptoscope used: parafoveal area subtends approximately 9.7 degrees). Of these 61 patients with diabetes, 51% (31) observed dark "spots" or "blobs" in the entoptic field corresponding to retinal defects in the angiograms or photographs or both. Seven (18%) of the 38 patients (9 patients with diabetes and 29 control subjects without defects in the entoptic field) said they saw something when angiograms or photographs or both showed nothing (false-positive). Thus, the sensitivity and specificity (using angiograms or photographs or both as the gold standard) with which untrained patients with diabetes detect their own parafoveal area defects are 51% and 82%, respectively. Superimposition of the entoptic image (as drawn by the patient) and the angiograms or color photography or both often showed excellent correspondence. Most (22 of 29) of the control subjects and more than half (40 of 70) the patients with diabetes were able to quantify the size of their foveal avascular zone (FAZ) from the entoptic view, whereas only 22 of 70 of the capillary loops defining the FAZ were visible in the optimal frame of the capillary phase of the fluorescein angiogram. As reported previously in a smaller sample, large FAZs often were associated with poor visual acuity. CONCLUSIONS: More than half the untrained patients with diabetes were able to visualize their own parafoveal retinopathy entoptically, and most untrained patients with diabetes and control subjects where able to quantify the size of their FAZ. Patients and control subjects without parafoveal defects rarely report defects not visible photographically. Patients can be trained to detect their defects. Clinical entoptic monitoring will require verification that patients can detect changes in their retinopathy. Entoptic testing is low cost, noninvasive, and can be performed as often as needed at no risk to the patient. It is, therefore, a promising research technique for subjective monitoring of the early natural history of parafoveal area disease processes.

Adolescent↗
PubMed1997

Hypopyon uveitis following panretinal photocoagulation.

The authors describe the rare complication of hypopyon uveitis following panretinal photocoagulation. A 55-year-old man with a history of diabetes mellitus and previous repair of a retinal detachment by scleral buckle and vitrectomy was referred to the authors after a hypopyon uveitis developed following supplemental panretinal photocoagulation. The patient was treated with frequent topical steroids in addition to periocular injection of steroids with resolution of the inflammation. Risk factors for anterior segment ischemia, such as a history of a scleral buckle, may predispose diabetic patients to the complication of hypopyon uveitis following panretinal photocoagulation.

Anterior Chamber↗
PubMed1996

Structure and expression of the tenecin 3 gene in Tenebrio molitor.

A genomic DNA fragment encoding tenecin 3, an antifungal protein was cloned from the genomic DNA library of Tenebrio molitor. The DNA sequence analysis showed that the coding region is divided into two exons by an intron of 49 bp in the middle of the putative leader peptide coding region. Southern blot analysis suggests that the gene is present as a single copy. The transcription initiation site was determined by primer extension analysis and S1 mapping. The TATA box and CCAAT box sequences were found at -30, and -121, respectively, from the transcription initiation site. Tenecin 3 mRNA is abundantly expressed in larvae and adults, while little was detected in RNAs from pupae, suggesting that the expression of the tenecin 3 gene is developmentally regulated.

Amino Acid Sequence↗
PubMed1996

Urinary homovanillic acid and vanillylmandelic acid in workers exposed to carbon disulfide.

Homovanillic acid (HVA) and vanillylmandelic acid (VMA), two end products of dopamine metabolism, were measured in 60 workers exposed to carbon disulfide (CS(2)) in a rayon factory and in 48 unexposed workers. The airborne CS(2) concentrations in eight major exposure zones of the plant were measured monthly over a period of 4 years, from 1990 to 1994. In addition, the exposure concentrations and exposure history of each worker were integrated to estimate the overall lifetime exposure. Industrial hygiene data showed that the geometric mean concentrations of CS(2) in the plant ranged from 2.68 to 20.19 ppm, and more than 15% of the studied population had been repeatedly exposed to CS(2) at concentrations exceeding the ACGIH recommended time-weighted average of 10 ppm. The results showed that there was a significantly lower level and a higher proportion of CS(2) workers with decreased HVA and VMA excretion. However, there were no statistical correlations between the two dopaminergic metabolites and the mean CS(2) concentration, and years of employment. In contrast, significant dose-effect relationships were observed between these two metabolites and the integrated cumulative exposure (ICE) variable. The correlation coefficients for ICE and HVA, and ICE and VMA were -0.35 (p < 0.01) and -0.20 (p <0.05), respectively. These data suggest that chronic exposure to CS(2) was associated with measurable reduction in catecholamine metabolite concentrations. This finding is compatible with the earlier observations in laboratory animals that CS(2) exposures interfere with neurochemical metabolism.

Adult↗
PubMed1996

Chiasmal infarction and sudden blindness caused by mucormycosis in AIDS and diabetes mellitus.

PURPOSE: To report rapidly progressive rhino-orbitocerebral mucormycosis in a 47-year-old woman with both diabetes mellitus and the acquired immunodeficiency syndrome (AIDS). METHOD: Case report including postmortem examination of the eyes, orbit, and brain of a patient with rhino-orbitocerebral mucormycosis, diabetes mellitus, and AIDS. RESULTS: Invasion by hyphae of the Rhizopus species produced an occlusive vasculitis and massive infarction of the optic chiasm. Fungal organisms were discovered in multiple granulomata of the optic nerve. CONCLUSION: Infarction at the optic chiasm probably caused sudden blindness in this patient.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Posterior segment neovascularization associated with optic nerve aplasia.

PURPOSE: To report the presence of posterior segment neovascularization in eyes with optic nerve aplasia. METHODS: Three eyes in two patients with clinical optic nerve aplasia were studied. RESULTS: Examination disclosed posterior segment neovascularization in one eye and progressive posterior segment neovascularization in two eyes. CONCLUSIONS: Posterior segment neovascularization may occur in association with optic nerve aplasia. Retinal ischemia or retinochoroidal anatomic disorganization, or both, may provide the stimulus for neovascularization in such eyes.

Coloboma↗
PubMed1996

Atovaquone inhibits the glucuronidation and increases the plasma concentrations of zidovudine.

The pharmacokinetic interaction between atovaquone, a 1,4-hydroxynaphthoquinone, and zidovudine was examined in an open, randomized, three-phase crossover study in 14 patients infected with human immunodeficiency virus. Atovaquone (750 mg every 12 hours) and zidovudine (200 mg every 8 hours) were given orally alone and in combination. Atovaquone significantly increased the area under the zidovudine concentration-time curve (AUC) (1.82 +/- 0.62 micrograms.hr/ml versus 2.39 +/- 0.68 micrograms.hr/ml; p < 0.05) and decreased the oral clearance of zidovudine (2029 +/- 666 ml/min versus 1512 +/- 464 ml/min; p < 0.05). In contrast, atovaquone tended to decrease the AUC of zidovudine-glucuronide (7.31 +/- 1.51 micrograms.hr/ml versus 6.89 +/- 1.42 micrograms.hr/ml; p < 0.1) and significantly decreased the ratio of AUC zidovudine-glucuronide/AUC zidovudine (4.48 +/- 1.94 versus 3.12 +/- 1.1; p < 0.05). The maximum concentration of zidovudine-glucuronide was significantly lowered by atovaquone (5.7 +/- 1.5 versus 4.57 +/- 0.97 micrograms/ml; p < 0.05). Zidovudine had no effect on the pharmacokinetic disposition of atovaquone. Atovaquone appears to increase the AUC of zidovudine by inhibiting the glucuronidation of zidovudine.

Adult↗
PubMed1996

Autosomal-dominant anomalies of the iris pigment epithelium.

PURPOSE: The authors document two families in which anomalies of the iris pigment epithelium occur as an autosomal dominant trait. METHODS: Eyes of members of two families were examined for the presence of anomalies of the iris pigment epithelium. RESULTS: In both families, anomalies characterized by iris pigment epithelial cysts and peripupillary ruffles were observed in successive generations. In one family, the proband was 3 months of age, and both cysts and ruffles were present in affected individuals. CONCLUSIONS: Anomalies of the iris pigment epithelium can be inherited in an autosomal-dominant pattern. The cystic and ruffled phenotypes represent variable expressivity and may be evident in infancy.

Cysts↗
PubMed1996

Ocular nail gun injuries.

PURPOSE: Penetrating ocular trauma resulting from nails can have disastrous visual consequences. Ocular nail gun injuries occur when a nail propelled at high velocity penetrates the globe. The authors report four consecutive patients with ocular injuries resulting from nail guns. METHODS: Four patients with ocular nail gun injuries are described: one with scleral penetrating injury, one with corneal penetrating injury, and two with perforating (through- and-through) injuries of the globe. RESULTS: Three of the four patients recovered good visual acuity after surgical intervention. CONCLUSION: Although dependent on the site of impact, the visual prognosis may be less severe than expected because the nail penetrates the eye at a high velocity such that there are less contusive forces. Adherence to safety precautions involving the use of nail guns as well as the obligatory use of safety glasses should reduce the incidence of these injuries.

Accidents, Occupational↗
PubMed1996

Determination of heterocyclic amines in flame-grilled fish patty by capillary electrophoresis.

A simple and reliable capillary zone electrophoretic (CZE) method for quantifying mutagenic and carcinogenic heterocyclic amines (HCAs) in cooked foods with UV-visible diode-array detection is described. The buffer system consisted of 50 mM disodium hydrogen phosphate, 30 mM sodium chloride, 20 mM citric acid and 26% methanol at pH 2.1. An uncoated silica tubing, 51 cm in length, was used for the CZE separation. The capillary tubing temperature was maintained at 25 degrees C with a constant voltage of 20 kV. The reproducibility of the method was over 95% for a five-replicate analysis of 10 micrograms/l-spiked 2-amino-3,4,7,8-tetramethylimidazo[4,5-f]quinoxaline (4,7,8-TriMeIQx) and the detection limit was in the low microgram/l range with coefficients of variation between 6 and 18%. An analytical run took only 15 min for 12 known HCAs. Using this procedure, up to 30 samples could be analysed in a single day. The method is reliable and can be used for screening of various HCAs. It has been applied to assess the concentrations of heterocyclic amines in otak-otak, a Malay-style grilled fish patty. The major mutagenic contaminant found in this foodstuff was 2-aminodipyrido[1,2-a:3',2'-d]imidazole (Glu-P-2) (286-1068 micrograms/kg), followed by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) (1.6-13.0 micrograms/kg) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) (14.0-87.5 micrograms/kg). Two co-mutagens norharman (NH) and harman (H) were also detected in otak-otak at levels of 2.0-13.0 micrograms/kg and 12.8-21.3 micrograms/kg, respectively. The substantial amount of Glu-P-2 detected in otak-otak is probably a result of the ingredients used and the high temperature grilling process.

Amines↗
PubMed1996

Clinicopathologic features of indocyanine green angiography-imaged, surgically excised choroidal neovascular membranes.

OBJECTIVE: The authors describe the clinicopathologic features of surgically excised choroidal neovascular membranes imaged by indocyanine green angiography (ICG). DESIGN: Fifteen eyes from 15 patients with surgically excised subfoveal choroidal neovascular membranes underwent preoperative and postoperative ICG angiography. All excised membranes were examined by light microscopy for overall configuration and the presence of cellular and extracellular constituents. One membrane was examined by transmission electron microscopy. RESULTS: Fourteen patients had age-related macular degeneration and one had ocular histoplasmosis syndrome. Constituents in more than 50% of membranes included retinal pigment epithelium (15/15), vascular endothelium (14/15), inflammatory cells (10/15), and basal laminar deposit (8/15). Basil laminar deposit was present only in membranes of patients with age-related macular degeneration. Eleven membranes were located primarily under the retinal pigment epithelium and four were located primarily under the neurosensory retina. There appeared to be no correlation between the ICG appearance and the histopathologic configuration of the membranes. CONCLUSION: Surgically excised ICG-imaged membranes correspond to subretinal pigment epithelium and subneurosensory retinal choroidal neovascularization.

Adult↗
PubMed1996

Zidovudine, trimethoprim, and dapsone pharmacokinetic interactions in patients with human immunodeficiency virus infection.

Zidovudine is widely prescribed for the treatment of human immunodeficiency virus (HIV) infection. Trimethoprim and dapsone are commonly used in the management of Pneumocystis carinii pneumonia in HIV-infected patients. To examine the pharmacokinetic interactions among these drugs, eight HIV-infected patients (26 to 43 years old) with a mean CD4 count of 524.4 +/- 405.7 cells per mm3 received zidovudine (200 mg), trimethoprim (200 mg), and dapsone (100 mg) as single agents and in two- and three-drug combinations. Blood and urine samples were collected at a specified time and analyzed for zidovudine, zidovudine-glucuronide, trimethoprim, dapsone, and monoacetyl-dapsone concentrations under single-dose and steady-state conditions. Zidovudine did not influence the pharmacokinetic disposition of dapsone or trimethoprim. Dapsone had no effect on the pharmacokinetic disposition of zidovudine. Trimethoprim significantly decreased the renal clearance of zidovudine by 58% (5.0 +/- 1.8 versus 2.1 +/- 0.5 ml/min/kg of body weight [P < 0.05]). There was a concurrent 54% decrease in the mean urinary recovery of zidovudine (11.7 +/- 3.5 versus 5.4 +/- 3.0 [P < 0.05]), and the metabolic ratio was decreased by 78% (0.32 +/- 0.4 versus 0.07 +/- 0.05 [P < 0.05]). The mean area under the concentration-time curve from 0 to 6 h of the zidovudine-glucuronide/ zidovudine ratio was unchanged. We conclude that zidovudine, trimethoprim, and dapsone can be coadministered to patients with AIDS without significant pharmacokinetic interaction. However, in AIDS patients with liver impairment and impaired glucuronidation, doses of zidovudine may need to be decreased.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Biomarkers of exposure to low concentrations of benzene: a field assessment.

OBJECTIVE: To carry out a comprehensive field investigation to evaluate various conventional and recently developed biomarkers for exposure to low concentrations of benzene. METHODS: Analyses were carried out on environmental air, unmetabolised benzene in blood and urine, urinary trans, transmuconic acid, and three major phenolic metabolites of benzene: phenol, catechol, and hydroquinone. Validations of these biomarkers were performed on 131 never smokers occupationally exposed to the time weighed average benzene concentration of 0.25 ppm (range, 0.01 to 3.5 ppm). RESULTS: Among the six biomarkers studied, unmetabolised benzene in urine correlated best with environmental benzene concentration (correlation coefficient, r = 0.76), followed by benzene in blood (r = 0.64). When urinary metabolites were compared with environmental benzene, trans, trans-muconic acid showed a close correlation (r = 0.53) followed by hydroquinone (r = 0.44), and to a lesser extent with urinary phenol (r = 0.38). No correlation was found between catechol and environmental benzene concentrations. Although unmetabolised benzene in urine correlates best with benzene exposure, owing to serious technical drawbacks, its use is limited. Among the metabolites, trans, trans-muconic acid seems to be more reliable than other phenolic compounds. Nevertheless, detailed analyses failed to show that it is specific for monitoring benzene exposures below 0.25 ppm. CONCLUSION: The overall results suggest that most of the currently available biomarkers are unable to provide sufficient specificity for monitoring of low concentrations of benzene exposure. If a lower occupational exposure limit for benzene is to be considered, the reliability of the biomarker and the technical limitations of measurements have to be carefully validated.

Air↗
PubMed1996

Determination of serum and urinary aluminum by HPLC with fluorometric detection of Al-lumogallion complex.

We describe a simple and sensitive HPLC method for quantifying aluminum (Al) in biological fluids by measuring the fluorescence of the Al-lumogallion complex (excitation wavelength 500 nm, emission wavelength 575 nm). Serum samples are deproteinized with 0.83 mol/L perchloric acid and centrifuged; the supernates are mixed with lumogallion reagent. Urine samples are pretreated with sodium hydroxide (2 mol/L) and methanol, kept for 1 h at -20 degrees C, and then centrifuged; the precipitate is resuspended in perchloric acid and mixed with lumogallion reagent, as for serum. The maximal fluorescence complex is formed after 1 h at pH 5 +/- 0.5. The HPLC mobile phase consists of (per liter) 100 mL, of 0.2 mol/L potassium hydrogen phthalate, 220 mL of acetonitrile, and distilled deionized water. The flow rate is 1 mL/min, and the injection volume is 5 microliters. The major aluminum species is eluted at 3.5 min, the lowest detection limit being 0.45 pg. We validated the method with samples collected from normal subjects and from workers occupationally exposed to aluminum. Comparing the results with those by traditional atomic absorption spectrometry of urinary aluminum suggests that the proposed method is reliable.

Adult↗