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Biomedical subjects

S Lam

Publications and source records attributed to S Lam.

At least 145 records · Page 8Linked to original sources
PubMed1988

High-performance liquid chromatography of hydroxysteroids detected with post-column immobilized enzyme reactors.

Assaying the low concentrations of steroid hormones in extracts of body fluids requires detectors that are both highly sensitive to the steroid and relatively insensitive to interfering compounds usually present in much higher concentrations. To explore the use of moderately specific enzymes in post-column reactors, we immobilized 3 alpha- and beta-hydroxysteroid dehydrogenase on controlled pore glass beads, 37 microns in diameter, and constructed 4.6-mm diameter reactor columns, 3-cm long, packed with one of the two kinds of these beads. Hydroxysteroids eluted from the analytical column were mixed with the coenzyme, nicotinamide adenine dinucleotide (NAD), before passing through the reactor. The effluent from the reactor was passed through the 70-microliters flow cell of a fluorometer in which the fluorescence of the NADH produced in the enzyme-catalyzed oxidation of the hydroxysteroid was monitored. At the conventional high-performance liquid chromatography flow-rates used, oxidation of the steroids was almost complete. The yield depended on both the residence time of steroids in the reactor column and the concentration of organic modifier in the reaction mixture. Maximal yield was obtained with buffer having a low organic solvent concentration and passing through the reactor slowly. In assays of mixtures of epimeric hydroxysteroids, the 3 alpha-hydroxysteroids were detected with the 3 alpha-hydroxysteroid dehydrogenase reactor; the beta-hydroxysteroids were not, confirming the specificity of the enzymatic detection. With the fluorometer used, picomole quantities of steroids could easily be distinguished from noise.

3-Hydroxysteroid Dehydrogenases↗
PubMed1988

Release of leukotrienes in patients with bronchial asthma.

To investigate whether leukotrienes (LTs) are released into the bronchial fluid of patients with symptomatic asthma, bronchial lavage was carried out in 17 patients with mild to severe asthma and nine healthy subjects without asthma. LTE4 was detected in 15 of the 17 patients with asthma with reverse-phase high-performance liquid chromatography. The identify of LTE4 was confirmed by ultraviolet spectrometry and by positive ion fast atom-bombardment mass spectrometry. LTD4 was found in two patients and 20-OH-LTB4 in 12 patients. No LTs were detectable in the lavage fluid from any of the healthy subjects without asthma. The finding of LTs in bronchial lavage fluid from the patients with asthma despite bronchodilator and/or corticosteroid therapy suggests that these compounds may be important in asthma. However, the presence of significant quantities of LTE4 in patients with mild asthma requiring only intermittent bronchodilator therapy for control and the lack of correlation between LTE4 and pulmonary function also suggests that other factors may be important in determining the net end organ response. The present study points to the importance of studying the whole spectrum of mediators that are released. Analysis of bronchial lavage fluid may be useful in determining the relative role of these mediators and the effect of pharmacologic intervention.

Adult↗
PubMed1988

The effect of concurrent aspirin upon plasma concentrations of tenoxicam.

1. The effect of chronic, high-dose aspirin therapy upon the disposition of a single dose and multiple doses of tenoxicam was examined in normal volunteers. 2. Aspirin caused a 24% drop in the t1/2 (P less than 0.005), a 49% rise in the volume of distribution (P less than 0.0003) and a 98% increase in the clearance (P less than 0.0001) of tenoxicam after a single dose of the tenoxicam. 3. Steady-state concentrations of tenoxicam decreased significantly from 10.4 +/- 1.5 to 4.5 +/- 1.6 micrograms ml-1 in the presence of chronic, high-dose aspirin treatment. 4. Tenoxicam percentage free measured in plasma from a normal volunteer was 0.56 +/- 0.05% over the tenoxicam concentration range 1-20 micrograms ml-1 and rose to 1.24 +/- 0.07% in the presence of aspirin 150 micrograms ml-1. 5. The effect of aspirin upon the disposition of tenoxicam was consistent with a competitive protein binding interaction.

Adult↗
PubMed1988

Comparison of cellular and protein changes in bronchial lavage fluid of symptomatic and asymptomatic patients with red cedar asthma on follow-up examination.

Seventeen patients with occupational asthma due to western red cedar had bronchial lavage during follow-up examination after removal from exposure for at least 1 year. Seven patients were asymptomatic while ten continued to have symptoms of asthma requiring treatment. Symptomatic patients had evidence of airway inflammation, as reflected by a significantly higher total cell count, neutrophils and eosinophils, as well as an increase in protein and albumin in their bronchial lavage fluid compared to those without symptoms. Asymptomatic patients had no evidence of airway inflammation in the lavage fluid. There was no correlation between the degree of non-specific bronchial hyperresponsiveness and the number or percentage of inflammatory cells to suggest that cellular infiltration is the sole cause of persistent bronchial hyperresponsiveness.

Adult↗
PubMed1988

Bronchial leukocyte proteinase inhibitor levels in bronchial washings in asthma patients.

To evaluate whether epithelial damage of airways in asthma could be related to diminished levels of the low molecular weight bronchial leukocyte proteinase inhibitor (BLPI) in airways, we determined BLPI in bronchial washings of 13 asthma patients and 13 healthy subjects, using a sensitive enzyme-linked immunoassay. The patients had asthma due to western red cedar and had bronchial washings done 24 to 48 hours after a mild to moderate asthmatic reaction induced by inhalation challenge. We did not find significant differences in BLPI concentrations in lavage fluid of asthma patients and healthy control subjects. The ratios of BLPI to albumin levels in bronchial washings appeared to be lower among asthmatic patients, but this difference was mainly due to an increase in albumin levels in lavage fluid in asthma. In addition, there were no significant differences in BLPI levels in washings obtained from main and segmental bronchi in both control subjects and asthma patients.

Adult↗
PubMed1987

Laser treatment of obstructive endobronchial tumors: factors which determine response.

To investigate whether computerized tomography (CT) and radionuclide quantitative ventilation-perfusion lung scan add any useful information to a carefully performed endoscopic examination in determining the response of patients with obstructive endobronchial tumors to laser treatment, the findings in 40 patients treated with photodynamic therapy (PDT) or the Nd:YAG laser were analysed. Endoscopic laser treatment was found to be most effective when the tumor was polypoid in appearance bronchoscopically, with little or no submucosal invasion or peribronchial extension seen on CT. When bronchoscopy and CT showed increasing submucosal and/or peribronchial disease, the immediate and long-term response to treatment was poorer. CT provided valuable information regarding the extent of the peribronchial involvement and airway distortion which were often underestimated by bronchoscopy alone. Reduction of regional perfusion out of proportion to ventilation on scintigraphy in the involved lung zone was found to be associated with extensive peribronchial involvement. We conclude that the addition of CT and radionuclide quantitative ventilation-perfusion lung scan to bronchoscopic examination is useful in predicting the response of patients with obstructive endobronchial tumors to laser treatment. Whether PDT or YAG laser is more effective in relieving endobronchial obstruction by tumor awaits a randomized controlled trial.

Aged↗
PubMed1987

Cyclosporin-induced gingival overgrowth: correlation with dental plaque scores, gingivitis scores, and cyclosporin levels in serum and saliva.

Gingival overgrowth, dental plaque, and gingivitis were assessed by means of standardized semiquantitative indices in thirty renal transplant patients undergoing immunosuppression with cyclosporin-A (Cy-A). Radioimmunoassay techniques were used to determine Cy-A in serum samples and in parotid, submandibular, and whole saliva samples from each patient. A significant positive correlation was found between gingival overgrowth scores and both dental plaque and gingivitis scores. A significant positive correlation was found between whole-saliva Cy-A and both plaque and gingival overgrowth scores. No such correlation was found when parotid Cy-A or submandibular Cy-A was considered. This was attributed to differences in saliva-collection methods, and a possible role of dental plaque as a local reservoir of Cy-A is proposed.

Adult↗
PubMed1987

Epidemiological characteristics of an institutional outbreak of cholera.

An outbreak of cholera caused by Vibrio cholerae 01, biotype El Tor, serotype Inaba, phage type 4, occurred in an institution for the aged in Singapore in August and September 1984. 96 inmates were infected (21 symptomatic and 75 asymptomatic) and 5 died. The index case was a 72-year-old male inmate who continued to assist in food preparation in the kitchen from the time of onset of diarrhoea until he was seriously ill and hospitalized 4 days later. Another kitchen helper was found to have asymptomatic V. cholerae 01 infection. The infection rate for males was significantly higher than that for females (P less than 0.025), associated with the use of unsanitary toilets. The main mode of transmission was through food contaminated by the 2 kitchen helpers who probably accounted for most of the infections, while poor personal hygiene of the inmates helped to sustain person-to-person spread. The outbreak was confined within the institution as the result of the prompt and effective implementation of control measures.

Aged↗
PubMed1987

Cellular and protein changes in bronchial lavage fluid after late asthmatic reaction in patients with red cedar asthma.

To investigate the sequence of cellular and protein changes after a late asthmatic reaction (LAR), bronchial lavage was carried out in 44 patients with red cedar asthma at different time intervals after bronchial challenge with plicatic acid. The results were compared to five patients with red cedar asthma who became asymptomatic after removal from exposure to red cedar for more than 2 months and 31 healthy subjects without asthma. The LAR was found to be associated with an increase in eosinophils in the lavage fluid, an increase in sloughing of bronchial epithelial cells, and an increase in degenerated cells consisting mainly of degenerated epithelial cells and alveolar macrophages. There was an increase in vascular permeability as reflected by an increase in albumin in the lavage fluid. Although there was a slight but significant increase in neutrophils 48 hours after bronchial challenge, neutrophil infiltration was not a prominent feature earlier. The potential role of loss of epithelial cells to account for an increase in nonspecific bronchial hyperresponsiveness after an LAR was discussed.

Adult↗
PubMed1987

Effect of food and various antacids on the absorption of tenoxicam.

1 Twelve healthy volunteers received a single oral dose of tenoxicam 20 mg on six occasions separated by 3 weeks. 2 The six occasions were: fasted overnight; postprandial; fasting and 15 ml aluminium hydroxide gel; postprandial and 15 ml aluminium hydroxide gel; fasting and 15 ml aluminium and magnesium hydroxide gel; postprandial and 15 ml aluminium and magnesium hydroxide gel. 3 Twenty plasma samples were collected over 15 days following dosing with tenoxicam. 4 The following kinetic parameters for plasma tenoxicam were compared: peak concentrations, time taken to reach peak concentrations, area under the plasma concentration-time curve (AUC) and half-life of elimination. 5 Food lengthened the time taken to reach peak tenoxicam concentrations (5.82 +/- 4.6 vs 1.84 +/- 1.0 h in the fasting state; P less than 0.02) and marginally reduced the peak concentrations achieved. AUC was not affected by any of the different regimens. 6 These effects of food on tenoxicam bioavailability are unlikely to be of clinical significance during chronic dosing with the drug.

Adult↗
PubMed1987

Cavernous sinus syndrome as the initial manifestation of multiple myeloma.

A 76-year-old man developed a cavernous sinus syndrome as the initial manifestation of multiple myeloma. Although clinically the patient had stage IA disease, which is typically associated with a favorable response to therapy, his disease was rapidly fatal. This case emphasizes a weakness of the traditional staging system because it does not take into account certain clinical and histopathologic aspects of myeloma relevant to extramedullary plasmacytomas. Since disorders of ocular motility are more likely to be associated with extramedullary myeloma than myeloma confined to the marrow, clinicians need to be aware of the limitations in the clinical staging system and the potential problems associated with anaplastic plasmacytomas.

Aged↗
PubMed1987

Aetiology of diarrhoea in Singapore.

Stools from acute diarrhoea were investigated for bacterial and viral pathogens. In one study involving 63 young children in a paediatric ward, 70% of the stools were positive for the pathogens looked for of which 37% contained bacteria, 22% viruses and 11% mixed cultures of bacteria and viruses. In another study in which 130 watery stools from routine specimens of patients of all ages were investigated, 36% were positive for pathogens with 11% bacteria, 18% viruses and 7% mixed pathogens. The high incidence of bacterial diarrhoea in young children was attributed to gastroenteritis caused by Salmonella species. Salmonella and rotavirus were found the most common pathogens in bacterial and viral diarrhoeas, and the most susceptible age group was under 5 years-old.

Acute Disease↗
PubMed1986

Predicting the response of obstructive endobronchial tumors to photodynamic therapy.

To investigate the usefulness of bronchoscopic examination, computerized tomography (CT), and radionuclide quantitative ventilation-perfusion lung scan to determine the response of patients with obstructive endobronchial tumors to photodynamic therapy (PDT), the findings in 24 patients treated with PDT were analyzed. PDT was found to be most effective when the tumor was bronchoscopically polypoid in appearance, with little or no submucosal invasion or peribronchial extension seen on CT scans. With increasing submucosal and/or peribronchial extension, the immediate response to treatment was poorer. Patients who had 50% or more of the airway obstruction due to mucosal tumor had no evidence of local tumor recurrence for a median interval of 22 weeks after treatment. In patients with predominant submucosal and/or peribronchial tumor, the duration of response was 7 weeks. Response to treatment did not correlate with the degree of airway obstruction. CT provided valuable information regarding the extent of the peribronchial involvement and airway distortion, which was often underestimated by bronchoscopy alone. Absent perfusion or reduction of regional perfusion out of proportion to ventilation on scintigraphy in the involved lung zone was found to be associated with extensive peribronchial involvement and a poor outcome. The authors conclude that the addition of CT and radionuclide quantitative ventilation-perfusion lung scan to bronchoscopic examination is useful in predicting the response of patients with obstructive endobronchial tumors to PDT.

Adult↗
PubMed1986

L-pipecolaturia in Zellweger syndrome.

Purified rat peroxisomes have been reported to oxidize D-pipecolic acid and the pipecolaturia of Zellweger syndrome has been attributed to the absence of peroxisomes. The logical consequences would be excesses of D-pipecolic acid in the urine of patients with Zellweger syndrome. The urine of two patients with Zellweger syndrome has been analyzed by complexing the pipecolic acid to copper-aspartame to separate the L- and D-isomers. L-Pipecolic acid constituted 100% and 78% of the total pipecolic acid in the two urines. The possibility of preferential retention of D-pipecolic acid was excluded by measuring renal excretion in two control subjects following administration of each isomer. The clearance of L-pipecolic acid was 1.1 and 0.2 ml/min and of D-pipecolic acid was 36.4 and 43.6 ml/min. These results do not support the contention that the pipecolaturia of Zellweger syndrome is the direct result of peroxisomal deficiencies.

Brain Diseases↗