Abnormal fat distribution and use of protease inhibitors.
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Adipose Tissue↗
Biomedical subjects
K C Chan
Publications and source records attributed to K C Chan.
Capillary electrophoresis analysis of isomeric truxillines and other high molecular weight impurities in illicit cocaine.
The analysis of by-products and impurities in illicit cocaine, including the isomeric truxillines, is important for derivation of both strategic and tactical intelligence. In the present study, various capillary electrophoresis techniques were investigated for this purpose. The use of the anionic beta-cyclodextrin sulfobutyl ether IV as a run buffer additive at pH 8.6 gave a good separation of the truxillines and similar high molecular weight impurities in less than eight minutes. These impurities were first isolated from the bulk cocaine matrix using liquid-liquid extraction and size-exclusion high performance liquid chromatography. There was a red shift in the UV spectra obtained for the truxillines using photodiode array (PDA) UV detection during CE analysis. This anomalous behavior is attributed to photo-degradation of the truxillines during the PDA-UV irradiation process. Laser-induced fluorescence detection using a UV krypton/fluoride laser provided greater selectivity and sensitivity versus UV detection for certain uncharacterized high molecular weight impurities.
Cocaine↗
Cyclic vomiting syndrome in South-East Asian children.
OBJECTIVE: To describe the clinical features, management and outcome of children with cyclic vomiting syndrome (CVS) from South-East Asia. METHODOLOGY: Retrospective review of all children who fulfilled the diagnostic criteria of CVS and who were seen at Department of Paediatrics, University of Malaya Medical Centre, Kuala Lumpur and Paediatric Unit, Penang Hospital, Penang, Malaysia from 1987 to 1997. RESULTS: Eight children with CVS were seen at the two units during the study period, five girls and three boys. All had cyclical, self-limited episodes of nausea and vomiting with symptom-free intervals. The mean age of onset was 5.9 years. The clinical features were similar to other series described in the literature. Only two of the eight children were described as 'perfectionist'. Two children identified stress as precipitating factors. Therapy to reduce the number of emeses during acute attacks and to prevent subsequent attacks had been ineffective. CONCLUSION: There are similarities and differences in CVS from South-East Asian children as compared to those described in the literature.
Age of Onset↗
Intermittent intussusception caused by colonic lipoma.
Colonic lipomas are rare, usually small, and occur most often in the right colon, particularly in the cecum. They are most common in elderly women. Intermittent episodes of intussusception are not uncommon in patients with colonic lipoma, but they are usually caused by larger pedunculated lipomas. We report a 43-year-old woman with a large colonic submucosal lipoma that induced intermittent colocolic intussusception. The patient presented with symptoms of peptic ulcer, including intractable upper abdominal pain, which did not resolve with treatment. Abdominal sonography showed typical findings of intussusception caused by a lipoma, but the manifestations on barium enema and computed tomography mimicked a malignant colonic tumor. The patient's abdominal pain disappeared after right hemicolectomy and the tumor was demonstrated to be a lipoma. The postoperative course was uneventful; there was no evidence of recurrence at follow-up 6 months later. Physicians should be aware that surrounding organs should also be evaluated in cases of chronic peptic ulcer with intractable upper abdominal pain.
Adult↗
Pediatric mucoepidermoid carcinoma of the minor salivary glands.
Carcinoma of the minor salivary glands is an uncommon lesion in children. However, due to the greater proportion of malignancies in salivary gland masses of children as compared to adults, a high degree of suspicion is warranted. Questionable lesions should be biopsied, and a diagnosis aggressively pursued. Wide local excision is the treatment of choice for mucoepidermoid carcinoma of the minor salivary glands, and radiation therapy should be considered in select cases.
Carcinoma, Mucoepidermoid↗
Redefining AIDS: case exemplified by Penicillium marneffei infection in HIV-infected people in Hong Kong.
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AIDS-Related Opportunistic Infections↗
Absent pulmonary valve syndrome with intact ventricular septum: role of ductus arteriosus revisited.
We report two patients (four and twelve days old respectively) with heart failure due to absent pulmonary valve and patent ductus arteriosus. The ductus arteriosus in both patients had unusual course arising early from the aortic arch and maintaining an acute angle with the aortic arch. The etiology of absent pulmonary valve syndrome is still not clear. We speculate on the role of arterial duct in the development of absent pulmonary valve syndrome.
Ductus Arteriosus, Patent↗
High-speed electrophoretic separation of DNA fragments using a short capillary.
Capillary electrophoresis using a replaceable gel buffer was applied to the separation of DNA fragments. A short effective length capillary (1-2 cm) at low electric field allowed the separation of a 20-1000 bp ladder in 1 min. Although similar separation speed was achieved with a longer capillary at high field, the resolution of larger fragments was degraded. The short effective length capillaries were able to separate the wildtype and mutant PCR products of the TGF-beta1 gene in under 45 s.
DNA↗
The effect of column length, applied voltage, gel type, and concentration on the capillary electrophoresis separation of DNA fragments and polymerase chain reaction products.
This work examines the effect of different parameters on migration time, resolution, and speed of analysis of DNA fragments and PCR products. These parameters include column length, applied voltage, gel type and concentration, and buffer ionic strength. Our results indicate that 1 cm capillary at an applied voltage of 185 V/cm, filled with commercial gel, was adequate for the separation of small DNA fragments in under 1 min. Resolution of large fragments is directly proportional to column length at the same field strength. Also, resolution of large fragments is higher (better) at lower field strength at constant column length. Analysis is fastest (high throughput) using a short capillary and moderate field strength (200 v/cm). CE using a single short capillary (2-7 cm) is comparable to slab gel in throughput, but more economical. The Sigma DNA buffer and hydroxyethyl cellulose liquid gel gave equivalent results in terms of resolution and reproducibility. The Sigma DNA replaceable gel gave reproducible results when used as received or diluted at 60%. In our hands hydroxyethyl cellulose gave more reproducible results than polyacrylamide gel.
Buffers↗
Absorbable pulmonary artery band.
Absorbable pulmonary artery banding may be a useful method of avoiding further operation or angioplasty in patients whose underlying lesion has a natural history of resolution. We report 2 cases of absorbable pulmonary artery banding using braided Dexon. In both cases the bands functioned well initially and were completely resorbed after 2 years and 6 months, respectively.
Absorption↗
5- to 18-year follow-up study of cemented total knee arthroplasty for patients 55 years old or younger.
Seventy-two cemented total knee arthroplasties were performed on 52 patients who were 55 years old or younger. Results on 68 knees in 50 patients with an average follow-up period of 9.92 years are reported. The average age of the patients was 50.7 years (range, 30-55) at the time of surgery. The diagnosis was osteoarthritis in 37 knees, rheumatoid arthritis in 29 knees, and ankylosing spondylitis in 2 knees. The average preoperative Knee Society knee score was 23 and the average follow-up knee score was 97. All knees were rated as good or excellent for knee score. The average latest function score was 75 (preoperative, 36). Both knees in one patient required revision for loose components. This review demonstrates that cemented total knee arthroplasty in younger patients with osteoarthritis and rheumatoid arthritis can attain results comparable to the excellent results obtained in the older age groups.
Age Factors↗
Low dietary protein impairs blood coagulation in BHE/cdb rats.
The influence of dietary protein on blood coagulation tests was evaluated in BHE/cdb rats. Three experiments were conducted in order to compare effects of diets with low (8 g/100 g diet) or high (38 g/100 g diet) protein, to establish values for coagulation tests at intermediate (12-30 g/100 g diet) concentrations of dietary protein, and to compare feeding identical quantities of diets with 8 g protein/100 g diet vs. 18 g protein/100 g diet. After 4 wk of feeding the semipurified diets, bleeding time exceeded 15 min in the groups fed low protein diets, compared to a range of 3-6 min for the groups fed high protein diets. Several in vitro tests of coagulation were abnormal in the rats fed low protein diets. For example, prothrombin time averaged 27 +/- 8 s in rats fed 8 g protein/100 g diet plus beef tallow, but 17 +/- 1 s in rats fed 38 g protein/100 g diet plus tallow. The coagulation deficit in rats fed low protein was not affected by fat source (tallow vs. menhaden oil), but fibrinogen was elevated in rats fed diets with menhaden oil. Conversely, no differences in coagulation tests were observed among rats fed 12-30 g protein/100 g diet. Bleeding times ranged from 7 to 9 min, and prothrombin time was 17-18 s. Significant differences in plasma fibrinogen concentration and prothrombin time were observed in rats fed 8 vs. 18 g protein/100 g diet at a fixed rate of 6 g/100 g body weight. Platelet and blood cell numbers were unaffected by dietary protein. The evidence for multiple deficits in the coagulation system suggests that hepatic function in BHE/cdb rats may become impaired when the rats are fed low protein diets of the composition used here.
Animals↗
Dislodgment of catheter during arterial cannulation: a case report.
Invasive blood pressure monitoring is important in medical practice, especially for hemodynamic monitoring of the critically ill. Catheter dislodgment is a rarely reported complication. We herein report a catheter dislodgment complication during the procedure of arterial cannulation.
Catheterization, Peripheral↗
High-speed screening of polymerase chain reaction products by capillary electrophoresis.
In an effort to develop capillary electrophoresis (CE) for high-throughput polymerase chain reaction (PCR) molecular diagnostics, a method was developed to rapidly screen small PCR products of similar molecular weights. The assay of interest required the separation of two PCR products (375 and 400 bp) in an assay of TGF-beta 1 knockout mice to determine the genotype of neonates. Using a commercially available CE instrument, the two PCR products were separated in 12 min with a replaceable gel buffer, a 20-cm effective length DB-17 capillary, and 185 V/cm field strength. With the coinjection of a 20-bp ladder, the sizes of the PCR products were determined from the electropherogram without using a calibration plot and curve-fitting program. Faster separation was obtained using the combination of a short effective length capillary and high field strength. The two PCR products were separated in 82 s with a 7-cm effective length capillary and 556 V/cm. A 60% buffer further reduced the separation time in about a minute. This high-speed separation, with minimum postrun data processing, is highly desirable for the high-throughput screening of PCR products using a single-capillary CE system.
Animals↗
Calculated stress-shielding in the distal femur after total knee replacement corresponds to the reported location of bone loss.
This study sought to determine the similarities between features of calculated stress-shielding and observed bone loss in the distal femur after total knee replacement. Stress-shielding was determined by comparing the magnitudes and distributions of strain energy density, calculated using three-dimensional finite element models of the intact bone, the bone after total knee replacement with bonding assumed at all prosthesis-bone interfaces, and the bone after total knee replacement with bonding assumed only at the distal interface. The loading condition simulated static lifting with the knee flexed at 45 degrees, producing tibiofemoral and patellofemoral joint reactions of 900 and 450 N, respectively. The maximum magnitudes of strain energy density calculated using the total knee replacement models were less than 15% of the corresponding magnitudes from the intact bone model. The greatest difference was found to occur at the anterior distal corner of the femur, suggesting this location as the one most vulnerable to stress-shielding. Clinically observed bone loss after total knee replacement frequently occurs at this location. At the anterior distal corner, the calculated magnitudes for the two total knee replacement models were similar, suggesting that stress-shielding at this location was not reduced by limiting fixation only to the distal interface. Although the study corresponded to one loading condition and one geometry of the total knee replacement femoral component with the inherent limitations of model calculations, the results suggest a possible scenario for stress-shielding.
Bone Resorption↗
Separation of tryptophan and related indoles by micellar electrokinetic chromatography with KrF laser-induced fluorescence detection.
Micellar electrokinetic chromatography (MEKC) was applied for the separation of tryptophan and related indoles. Using a 5 mM sodium borate buffer (pH 9.2) containing 50 mM sodium dodecyl sulfate and 5% acetonitrile, eleven indoles were baseline separated in under 17 min. Most of the indoles were detected at the nM level by native fluorescence using KrF laser-induced fluorescence (LIF), which was approximately 100 times more sensitive than UV absorption detection at 200 nm. Preliminary results show that the MEKC-LIF with direct sample injection is a feasible method for assessing indole profiles in diluted urine and serum.
Electrophoresis, Capillary↗
Separation and detection of acidic and neutral impurities in illicit heroin via capillary electrophoresis.
The separation and detection of acidic and neutral impurities in illicit heroin using capillary electrophoresis (CE) is described. Separations were achieved using charged cyclodextrin modified micellar electrokinetic capillary chromatography. The use of the anionic beta-cyclodextrin sulfobutyl ether 1V in combination with sodium dodecyl sulfate significantly increased resolution. Improved selectivity and/or sensitivity in detection was obtained using photodiode array ultraviolet and laser-induced fluorescence detection. The phenanthrene-like heroin impurities exhibit high native fluorescence under krypton-fluoride laser excitation (248 nm). The limit of detection by laser-induced fluorescence detection for one of these solutes (acetylthebaol) is 1.8 ng/ml, 500 times more sensitive than UV. This methodology is applicable to analysis of both crude and refined heroin.
Drug Contamination↗
Separation of estrogens by micellar electrokinetic chromatography.
Capillary electrophoresis of the sex hormone estrogens using different buffer components was investigated. Free zone electrophoresis with 10 mM phosphate buffer (pH 11.5) or 10 mM phosphate buffer with 10-20% methanol was not effective in separating the ten estrogens used in this study. However, nine estrogens were resolved by micellar electrokinetic chromatography using a 10 mM borate buffer (pH 9.2) containing 100 mM sodium cholate. In addition, some estrogens were partially separated using sodium dodecyl sulfate (SDS) micellar buffers; however, the addition of modifiers such as organic solvents or cyclodextrins improved resolutions significantly. Using a 10 mM phosphate buffer (pH 7.0) containing 50 mM SDS and 20% methanol, or a 10 mM borate buffer (pH 9.2) containing 50 mM SDS and 20 mM gamma-cyclodextrin, all ten of the tested estrogens were separated. However, the cyclodextrin-modified buffer allowed faster separation.
Chromatography, Liquid↗