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Biomedical subjects

C K Lim

Publications and source records attributed to C K Lim.

At least 127 records · Page 7Linked to original sources
PubMed1984

Pseudoporphyria associated with consumption of brewers' yeast.

A case of pseudoporphyria associated with excessive consumption of brewers ' yeast was studied. Detailed analysis of the yeast tablets by high performance liquid chromatography showed the presence of dicarboxylic deuteroporphyrin , mesoporphyrin, and protoporphyrin; coproporphyrin I and III isomers; and uroporphyrin I and III isomers. The faecal porphyrin concentration of the patient taking yeast tablets was significantly increased, resembling the excretion pattern in variegate porphyria. Any patient showing an unusual porphyrin excretion pattern on high performance liquid chromatography should be investigated for a possible dietary cause.

Adult↗
PubMed1984

Urine and faecal porphyrin profiles by reversed-phase high-performance liquid chromatography in the porphyrias.

A novel reversed-phase system is described for the simultaneous separation of type I and type III isomers of uro-, heptacarboxylic-, hexacarboxylic -, pentacarboxylic - and copro -porphyrins and the dicarboxylic meso- and proto-porphyrins. The porphyrins were resolved on a Hypersil -SAS column eluted with 10% (v/v) acetonitrile in 1 mol/l ammonium acetate, pH 5.16 (solvent A) and 10% (v/v) acetonitrile in methanol (solvent B) with a linear gradient from 100% A (0%B) to 35% A (65%B) in 30 min followed by isocratic elution at 65% B for a further 10 min. The method is simple and reproducible and has been applied to the analysis of porphyrins in urine and faeces from patients with acute intermittent, variegate, hereditary copro , congenital erythropoietic, erythrohepatic proto and symptomatic porphyrias.

Chromatography, High Pressure Liquid↗
PubMed1983

High-performance liquid chromatography of naturally occurring 8-, 7-, 6-, 5- and 4-carboxylic porphyrin isomers.

Naturally occurring 8-, 7-, 6-, 5- and 4-carboxylic porphyrin isomers are separated on C18 reversed-phase columns with various proportions (13-31%, v/v) of acetonitrile in 1 M ammonium acetate buffer (pH 5.16) as the mobile phases. Hydrophobic interaction between the porphyrin side chain substituents and the C18 hydrophobic surface is the main retention mechanism. Ion-exchange behaviour is also observed, but this does not influence the relative retention of the isomers. All possible forms of the decarboxylation intermediates of uroporphyrinogen III are detected in normal and porphyric urine, and the results provide conclusive evidence for the existence of decarboxylation pathways other than the currently accepted clockwise sequence, starting at the ring D acetic acid group of uroporphyrinogen III.

Chemical Phenomena↗
PubMed1983

Simultaneous determination of hydroxymethylbilane synthase and uroporphyrinogen III synthase in erythrocytes by high-performance liquid chromatography.

A high-performance-liquid-chromatographic method is developed for the simultaneous determination of hydroxymethylbilane synthase and uroporphyrinogen III synthase activity in erythrocytes. Effective separation of uroporphyrin I and III isomers allows the accurate quantification of individual isomers and the total uroporphyrin concentration. Total uroporphyrin production is used to calculate hydroxymethylbilane synthase activity, and the amount of uroporphyrin III formed represents the activity of uroporphyrinogen III synthase. Normal ranges are established for the two enzymes.

Ammonia-Lyases↗
PubMed1983

Assay of blood and tissue aldehydes by HPLC analysis of their 2,4-dinitrophenylhydrazine adducts.

A new method for the assay of blood and tissue acetaldehyde is described. Samples are reacted with a methanolic solution of 2,4-dinitrophenylhydrazine (DNP) and the DNP-aldehyde adducts extracted into CHCl3. DNP-[14C]formaldehyde is added as internal standard. The CHCl3 extracts are washed with HCl and H2O and purified by aluminium oxide chromatography. The eluate is dried down, re-dissolved in methanol and subjected to quantitative analysis by HPLC. The acetaldehyde adduct was identified by co-chromatography with the authentic derivative and by mass spectrometry. Recoveries of added acetaldehyde were 85% and addition of 20 mmol ethanol to the sample gave no apparent increment in acetaldehyde content. This technique is suitable for assessment of acetaldehyde levels in clinical and experimental studies of ethanol metabolism.

Aldehydes↗
PubMed1983

Separation of porphyrin isomers by high-performance liquid chromatography.

A reversed-phase gradient elution system is described for the simultaneous separation of the type I and type III isomers of 8-, 7-, 6-, 5- and 4-carboxylated porphyrins and isocoproporphyrins. The method, adaptable for isocratic and stepwise separation of individual groups of isomers, is also suitable for preparative isolation of pure porphyrins. The analyses of porphyrin isomers in the urine and faeces of porphyric patients are examples of applications.

Acetates↗
PubMed1983

High-performance liquid chromatography of coproporphyrin isomers.

A reversed-phase system is described for the simultaneous isocratic separation of coproporphyrin I, II, III and IV isomers. The retention behaviour of coproporphyrin I and III is studied in detail. The method is suitable for both analytical and semi-preparative separation.

Acetonitriles↗
PubMed1983

Metabolic and drug profiling.

Over recent years, advances in analytical technology have greatly improved our ability to study the metabolism of compounds from either endogenous or erogenous sources. The application of gas-liquid chromatography, mass spectrometry, high-performance liquid chromatography and immunological approaches are discussed in relation to the analysis of steroids, bile acids, organic acids, prostaglandins, porphyrins and bile pigments, amino acids, proteins, nucleotides, catecholamines, vitamins and drugs.

Journal Article↗
PubMed1981

High-performance liquid chromatography of bile pigments: separation and characterization of the urobilinoids.

The detailed analysis of faecal bile pigments by high-performance liquid chromatography is described. Non-aqueous reversed-phase systems with acetonitrile-dimethyl sulphoxide or acetonitrile-dimethyl sulphoxide-methanol as the mobile phase on C1, C8 or C18-bonded silica are used for the group separation of verdinoids, violinoids and urobilinoids. A silica column, with acetonitrile-water-tetraethylene-pentamine as mobile phase, separates the laevorotatory stercobilin (C33H46N4O6) and half-stercobilin (C33H44N4O6) from the optically inactive urobilin (C33H42N4O6). The diastereoisomers are resolved by converting the urobilinoids into their dimethyl esters before chromatography on a silica column with n-heptane-methyl acetate-methanol containing 1% of diethylamine as the solvent system.

Anemia, Hemolytic↗
PubMed1981

Determination of delta-aminolaevulinic acid synthase activity in human bone marrow using high performance liquid chromatography.

A high performance liquid chromatographic (HPLC) method is described for the rapid and specific determination of the activity of the enzyme delta-aminolaevulinic acid synthase (ALA-S) in mitochondria prepared by sonication of human bone marrow cells. After incubation with 14C-alpha-ketoglutarate the 14C-delta-aminolaevulinic acid (ALA) formed is converted to a pyrrole derivative, 2-methyl-3-carbethoxy-4-(3-propionic acid) pyrrole. This is isolated by reversed-phase ion-pair chromatography on a Hypersil-SAS column with methanol-water (45:155, v/v) in the presence of 0.005 mol/l 1-heptanesulphonic acid (PIC B-7) as the mobile phase. The radioactivity of the isolated pyrrole is determined by scintillation counting. The optimal substrate concentration and pH were 0.17 mmol/l alpha-ketoglutarate and pH 7.4, with an optimal period of sonication of 18s. Under these conditions ALA production was proportional to the concentrations of erythroblasts in the initial sample and was linear with time up to 60 min. The addition of pyridoxal phosphate (PLP) did not affect ALA-S activity in normal subjects. The mean ALA-S activity in 10 haematologically normal control subjects was found to be 318.8 pmol.10-6 erythroblasts.h-1 (S.D. 125.8, range 193-444.6).

5-Aminolevulinate Synthetase↗
PubMed1981

High-performance liquid chromatography of bile pigments: application to the determination of unconjugated bilirubin in serum.

A rapid, sensitive and specific method for the determination of unconjugated bilirubin in serum is described. Reversed-phase chromatography on short-chain alkylsilica (C2) or octadecylsilica (C18) with acetonitrile--dimethylsulphoxide--water as eluent is used for the separation of bilirubin. The method is applied to the analysis of bilirubin in patients with disorders associated with jaundice.

Anemia, Hemolytic↗
PubMed1981

Corrosion of mild and stainless steel by four tropical Desulfovibrio desulfuricans strains.

The corrosion potential of four tropical Desulfovibrio desulfuricans isolates was determined using a semicontinuous batch culture technique in a 56-day test incubated at 37 degrees C. The corrosion potentials for mild and stainless steel of marine or brackish water isolates (0.55 and 0.0026 mg cm-2 day-1) were observed to be approximately twice those of freshwater isolates (0.23 and 0.0014 mg cm-2 day-1). Under comparable experimental conditions of severe anaerobic corrosion, stainless steel was found to be over 200 times more resistant than mild steel.

Alloys↗