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Biomedical subjects

E H Goh

Publications and source records attributed to E H Goh.

At least 19 recordsLinked to original sources
PubMed1990

Analysis of cholesterol and desmosterol in cultured cells without organic solvent extraction.

Cultured cell sterols such as cholesterol and desmosterol are usually extracted into organic solvents before they are quantified with cholesterol esterase and oxidase. A method to quantify these cultured cell sterols using cholesterol enzymes without prior organic solvent extraction is described. In this method, a suspension or monolayer of cultured L-M, U-937, or PC-12 cells is digested with 0.1% sodium dodecyl sulfate (SDS), and the digest treated with microbial cholesterol enzymes. The quantity of oxidized sterols produced by the reaction can be measured easily with high-pressure liquid chromatography, when a mixture of sterols is present, or by the production of hydrogen peroxide when only one sterol is present. This method is easier and safer to use than solvent extraction and can greatly expedite the quantitation of cultured cell sterols. Preliminary data show that other lipids such as choline phospholipids, triglycerides, and fatty acids can also be directly quantified in SDS cell digest by using specific enzymes to transform these lipids into hydrogen peroxides.

Acetonitriles↗
PubMed1989

HPLC analysis of desmosterol, 7-dehydrocholesterol, and cholesterol.

A simple and sensitive method to analyze mixtures of desmosterol, 7-dehydrocholesterol and cholesterol is described. The method involves the oxidative conversion of the sterols with cholesterol oxidase, followed by high performance liquid chromatographic (HPLC) analysis. A C18 reversed phase column (3 microns, 75 X 4.6 mm) and a mixture of methanol and acetonitrile (1:1, v/v) at a rate of 1 ml/min are used to separate the sterols. The eluted sterols are quantified by measuring UV absorption at 240 nm. As little as 10 pmoles of sterol can be quantified under these conditions.

Cholestadienols↗
PubMed1983

Transfer of exogenous cholesterol to microsomes of hepatocytes investigated with [3H]desmosterol tracer.

The feasibility of using exogenous [3H]desmosterol as a mass metabolic tracer for exogenous non-esterified cholesterol in hepatocytes is investigated with albumin-bound non-esterified cholesterol containing [3H]desmosterol and [14C] cholesterol tracers. The amounts of uptake and metabolism of exogenous cholesterol monitored by either tracer are the same. In addition, the conversion of [3H]desmosterol into [3H]cholesterol by the delta 24-sterol reductase in the microsomes can be used as an estimate for the mass transfer of exogenous cholesterol to the microsomes. The results obtained indicate that only a small fraction of exogenous cholesterol that was transferred to the microsomes was metabolized into bile acids and steryl esters. The technique of estimating the mass transfer of exogenous cholesterol to the microsomes with [3H]desmosterol may be of importance in investigations dealing with the effect of exogenous plasma cholesterol on changes in the physiological functions of the endoplasmic reticulum in the cells.

Animals↗
PubMed1981

Presenting symptoms of patients with active pulmonary tuberculosis in Singapore.

A prospective study of 1,258 new cases of active pulmonary tuberculosis was conducted to identify their mode of presentation. About 70% of the patients were symptomatic. Symptom frequency increased with rising age, was higher among females and among those with more extensive disease. A higher proportion of symptomatics was found among the bacillary (83.5%) than among the abacillary (59.4%) cases. Differences in interview technique and composition of the two groups could not account for this large difference. It was suggested that this was due to some of the abacillary cases not being cases of tuberculosis at all. Cough was the most common presenting symptom and was present in 66.1% of bacillary cases. This finding contrasted with that of the 1975 prevalence survey where cough was reported in 24% of bacillary cases. The reasons for this difference was discussed and it was suggested that the proportion of bacillary cases with cough symptoms would be higher than what was previously reported. Cough of more than two weeks duration, weight loss, blood stained sputum and chest pain were more prevalent among tuberculosis patients than in other patients seen by private medical practitioners. It was suggested that a case detection programme based upon this set of symptoms would help identify the epidemiologically more important cases of tuberculosis. Such a programme should complement existing case detection programmes as it would be expected to miss a sizeable proportion of the abacillary cases with minimal pulmonary lesions.

Adolescent↗
PubMed1981

The detection of active pulmonary tuberculosis in Singapore.

A prospective study was carried out to identify the services which were responsible for detection of pulmonary tuberculosis in Singapore. It was found that the public health services were the sources of 58.8% of cases. Among them the Tuberculosis Control Department detected the largest proportion (25.8%) of cases. These formed the majority of the asymptomatic and a large proportion of the abacillary cases detected. It was suggested that this reflected the result of the Department's active case-finding programme. The private practitioners identified 30% of patients. More than half of them were bacillary cases and they were a significant proportion of all infectious cases detected. Thus while the Department of Tuberculosis Control detected most of the patients with early tuberculosis disease, the bulk of the infectious cases with extensive disease were diagnosed by the private practitioners. Both sectors complement each other in the detection of tuberculosis cases in the country. An improvement and expansion of the existing case detection programme among patients attending the clinics of private practitioners and the Outpatient Service Department's dispensaries was recommended. The way in which this could be done and some of the problems that might be encountered were discussed.

Bacteriological Techniques↗
PubMed1981

Hydrolysis of guinea pig nascent very low density lipoproteins catalyzed by lipoprotein lipase: activation by hjman apolipoprotein C-II.

Very low density lipoproteins isolated from guinea pig liver perfusate (VLDLp) lack the equivalent of human apolipoprotein C-II (apoC-II), the activator of lipoprotein lipase (LpL). These lipoproteins are therefore ideal substrates with which to investigate the mechanism by which apoC-II activates the enzyme. VLDLp binds apoC-II, and apoC-II associated with VLDLp markedly increases the rate of lipoprotein lipase-catalyzed hydrolysis of VLDLp-triglycerides. The activator potency of apoC-II is independent of the method of enrichment of VLDLp with apoC-II: delipidated human apoC-II and apoC-II transferred from human high density lipoproteins activate lipoprotein lipase to equal extents. ApoC-II causes pH-dependent changes in both apparent Km and VmaX of LpL-catalyzed hydrolysis of VLDLp-triglycerides. At pH l7.4--7.5, the major effects of apoC-II is to decrease the apparent Km by 3.3--4.0 fold. The apparent Vmax is increased 1.3-fold. At pH 6.5 and 8.5, the decrease of apparent Km is less marked, 1.6-fold and 1.4-fold, respectively. At pH 6.5, apoC-II increases the apparent Vmax ty 1.3-fold, while at pH 8.5 the primary effect of apoC-II is a 1.6-fold increase of apparent Vmax. Based on a simple kinetic model, the data suggest that apoC-II favors direct interaction between enzyme and triglyceride within the lipoprotein particle, as well as subsequent catalytic turnover.

Animals↗
PubMed1981

A dynamic model of tuberculosis epidemiology for Singapore.

An epidemiological model was used to estimate the size of the tuberculosis problem in Singapore from 1975 to 2025. It was shown that even without any control activities after 1979 there would be a reduction of the tuberculosis indices in the country. If the present control programme was pursued unchanged, a reduction of the tuberculosis problem by 10.0% and 14.5% would be expected in 2000 and 2025 respectively. Tuberculosis would be expected to remain a major public health problem over the next fifty years. In Singapore's context increased case finding and treatment of bacteriologically positive cases of tuberculosis would be the most effective ways of further reducing the tuberculosis problem over the next fifty years. Practical methods of implementing this were suggested. Reduced BCG coverage of infants was not expected to increase the tuberculosis problem to any significant extent over this period. Treatment relapse rates were shown not to be a sensitive variable that would affect the tuberculosis problem in Singapore.

Adolescent↗
PubMed1981

Selective area tuberculosis surveys in Singapore 1978.

A random population sample survey in Singapore 1975 revealed that a relatively high proportion of active pulmonary tuberculosis patients remained undiagnosed, mainly in the older age groups. Previous studies disclosed the cause to the lack of symptoms of concern in these patients. A new programme was devised to discover hidden elderly patients by mass chest X-ray screening of population aged 45 years and older living in areas with known high incidence of tuberculosis. The yield of cases was less than expected mainly due to the dislocation and dispersion of population from recent extensive urban re-development in Singapore. Nevertheless the results were comparable to the most productive case finding programme carried out in this department.

Aged↗
PubMed1979

Relationship between activity of hepatic 3-hydroxy-3-methylglutaryl-coenzyme A reductase and secretion of very-low-density-lipoprotein cholesterol by the isolated perfused liver and in the intact rat.

The hepatic output of triacylglycerol and cholesterol from very-low-density lipoprotein (VLD lipoprotein), and the activity of 3-hydroxy-3-methylglutaryl-coenzyme A reductase were compared in the isolated perfused rat-liver preparation and in the intact rat. The output of triacylglycerol and cholesterol from VLD lipoprotein by the perfused liver was stimulated by oleate concomitant with stimulation of hepatic microsomal hydroxymethylglutaryl-coenzyme A reductase activity. In the intact animal treated with Triton WR-1339, the magnitude of secretion of triacylglycerol and cholesterol from VLD lipoprotein coincided with the diurnal rhythm of hepatic hydroxymethylglutaryl-coenzyme A reductase activity, which was maximal at 24:00 h and minimal at 12:00 h. These observations suggest that the stimulation of the reductase and of the secretion of cholesterol from VLD lipoprotein by non-esterified fatty acids, as observed with the isolated perfused rat liver preparation in vitro, may also be an important physiological mechanism in vivo. Hepatic cholesterogenesis may be stimulated under conditions conductive to the secretion of the VLD lipoprotein, the primary transport form for triacylglycerol in the postabsorptive state.

Animals↗
PubMed1979

A comparison of the prognostic value of antibody-dependent lymphocyte cytotoxicity and other EBV antibody assays in Chinese patients with nasopharyngeal carcinoma.

Antibody titres to EBV-associated antigens in Chinese NPC patients were analysed according to length of survival after diagnosis and to disease stage. Geometric mean titres of ADLC antibody were highest in the long-term survivors, whereas VCA, EA and EBNA antibody titres showed an inverse relationship to survival. High VCA, EA and EBNA titres were less frequent, and high ADLC titres were more frequent in long-term survivors than in intermediate or short-term survivors. The association of geometric mean titres of EBV antibodies with prognosis could not be entirely explained by stage of disease. A functional role for the ADLC antibody is suggested by the association of a high ADLC antibody titre with a good prognosis regardless of stage of disease.

Antibodies, Viral↗
PubMed1978

General immunological status of nasopharyngeal carcinoma patients in Singapore.

Newly diagnosed NPC patients were found to have impaired general T-cell functions, as determined in vivo by the Mantoux test and in vitro by the PHA response assay. Treated remission patients were as hyporesponsiveness as newly diagnosed patients. PHA hyporesponsiveness was associated with the HLA profile of A2-B Sin 2 and with high antibody titres to EBV-related antigens, in particular to the early antigen. Impaired responses in the Mantoux or PHA tests were associated with poor survival. The impaired response could be partially or totally restored by in vitro treatment of the hyporesponsive lymphocytes with levamisole.

Antigens, Viral↗
PubMed1978

Etiological factors in nasopharyngeal carcinoma: a hospital-based, retrospective, case-control, questionnaire study.

A total of 379 Singapore Chinese patients with NPC were interviewed by use of a questionnaire covering the following items: occupation, level of education, language medium of education, personal and family history of nasal illnesses, types of medicines used, use of Chinese medicines for the nose and throat, use of soya sauce, Chinese tea, cooling drinks and alcohol, cigarette smoking (number and duration), cooking fuels and use of incense (frequency and duration) and of anti-mosquito coils. The same questionnaire was given to two groups of controls: 595 patients with diseases of the ear, nose and throat other than NPC and 1 044 patients with diseases other than cancer or otorhinolaryngeal disease. NPC patients differed significantly from both groups of controls in that they showed stronger associations with personal history of nasal illnesses, family history of nasal illnesses, use of Chinese medicines for the nose and throat and exposure to smoke from anti-mosquito coils.

Adolescent↗
PubMed1978

Nasopharyngeal carcinoma and histocompatibility antigens.

New data are presented concerning the relationship between NPC and HLA antigens among Chinese. When attention is confined to newly diagnosed cases, it can be shown that, apart from the increased risk associated with the joint occurrence of A2 and B-Sin 2, there is also an increased risk associated with BW17 and a decrease in risk associated with A11. Among long-term survivors, however, BW17 is appreciably decreased, whereas A2 in the absence of B-Sin 2 or BW17 is increased. Among Malays, a non-Chinese group, there is an excess among NPC patients of a locus A blank, a blank which is probably associated with the AW19 complex.

Carcinoma↗