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Biomedical subjects

S F Kwok

Publications and source records attributed to S F Kwok.

At least 19 recordsLinked to original sources
PubMed1994

Urinary beta 2- and alpha 1-microglobulin levels in normal subjects in Singapore.

Differing normal values for urinary beta 2-microglobulin have been reported for different countries. In this study, we have attempted to establish the urinary beta 2- and alpha 1-microglobulin levels of apparently healthy subjects in Singapore. Urine samples collected from 271 subjects were analysed. The subjects ranged from 19 to 62 years old, with a mean age of 36.8 years. The majority (84.5%) were non-smokers. Urine samples with a pH level < 5.5 were excluded from the analysis. The urinary beta 2- and alpha 1-microglobulin values followed log normal distributions. Their 95th percentiles were 288 micrograms/g creatinine and 7.35 mg/g creatinine, respectively. Statistically significant differences were found between sexes and ethnic groups for urinary beta 2-microglobulin values. Both alpha 1- and beta 2-microglobulin values increased significantly with age. Smokers had significantly higher urinary alpha 1-microglobulin values.

Adult↗
PubMed1994

Arabidopsis COP8, COP10, and COP11 genes are involved in repression of photomorphogenic development in darkness.

Wild-type Arabidopsis seedlings are capable of following two developmental programs: photomorphogenesis in the light and skotomorphogenesis in darkness. Screening of Arabidopsis mutants for constitutive photomorphogenic development in darkness resulted in the identification of three new loci designated COP8, COP10, and COP11. Detailed examination of the temporal morphological and cellular differentiation patterns of wild-type and mutant seedlings revealed that in darkness, seedlings homozygous for recessive mutations in COP8, COP10, and COP11 failed to suppress the photomorphogenic developmental pathway and were unable to initiate skotomorphogenesis. As a consequence, the mutant seedlings grown in the dark had short hypocotyls and open and expanded cotyledons, with characteristic photomorphogenic cellular differentiation patterns and elevated levels of light-inducible gene expression. In addition, plastids of dark-grown mutants were defective in etioplast differentiation. Similar to cop1 and cop9, and in contrast to det1 (deetiolated), these new mutants lacked dark-adaptive change of light-regulated gene expression and retained normal phytochrome control of seed germination. Epistatic analyses with the long hypocotyl hy1, hy2, hy3, hy4, and hy5 mutations suggested that these three loci, similar to COP1 and COP9, act downstream of both phytochromes and a blue light receptor, and probably HY5 as well. Further, cop8-1, cop10-1, and cop11-1 mutants accumulated higher levels of COP1, a feature similar to the cop9-1 mutant. These results suggested that COP8, COP10, and COP11, together with COP1, COP9, and DET1, function to suppress the photomorphogenic developmental program and to promote skotomorphogenesis in darkness. The identical phenotypes resulting from mutations in COP8, COP9, COP10, and COP11 imply that their encoded products function in close proximity, possibly with some of them as a complex, in the same signal transduction pathway.

Arabidopsis↗
PubMed1993

Arabidopsis ethylene-response gene ETR1: similarity of product to two-component regulators.

Ethylene behaves as a hormone in plants, regulating such aspects of growth and development as fruit ripening, flower senescence, and abscission. Ethylene insensitivity is conferred by dominant mutations in the ETR1 gene early in the ethylene signal transduction pathway of Arabidopsis thaliana. The ETR1 gene was cloned by the method of chromosome walking. Each of the four known etr1 mutant alleles contains a missense mutation near the amino terminus of the predicted protein. Although the sequence of the amino-terminal half of the deduced ETR1 protein appears to be novel, the carboxyl-terminal half is similar in sequence to both components of the prokaryotic family of signal transducers known as the two-component systems. Thus, an early step in ethylene signal transduction in plants may involve transfer of phosphate as in prokaryotic two-component systems. The dominant etr1-1 mutant gene conferred ethylene insensitivity to wild-type Arabidopsis plants when introduced by transformation.

Amino Acid Sequence↗
PubMed1992

The TMK1 gene from Arabidopsis codes for a protein with structural and biochemical characteristics of a receptor protein kinase.

Genomic and cDNA clones that code for a protein with structural and biochemical properties similar to the receptor protein kinases from animals were obtained from Arabidopsis. Structural features of the predicted polypeptide include an amino-terminal membrane targeting signal sequence, a region containing blocks of leucine-rich repeat elements, a single putative membrane spanning domain, and a characteristic serine/threonine-specific protein kinase domain. The gene coding for this receptor-like transmembrane kinase was designated TMK1. Portions of the TMK1 gene were expressed in Escherichia coli, and antibodies were raised against the recombinant polypeptides. These antibodies immunodecorated a 120-kD polypeptide present in crude extracts and membrane preparations. The immunodetectable band was present in extracts from leaf, stem, root, and floral tissues. The kinase domain of TMK1 was expressed as a fusion protein in E. coli, and the purified fusion protein was found capable of autophosphorylation on serine and threonine residues. The possible role of the TMK1 gene product in transmembrane signaling is discussed.

Amino Acid Sequence↗
PubMed1989

Study on the health hazards of scrap metal cutters.

Scrap metal cutters seemed to be left out in most preventive programmes as the workers were mainly contract workers. The health hazards of scrap metal cutting in 54 workers from a foundry and a ship breaking plant were evaluated. Environmental sampling showed lead levels ranging from 0.02 to 0.57 mg/m3 (threshold limit values is 0.15 mg/m3). Exposure to lead came mainly from the paint coat of the metals cut. Metal fume fever was not reported although their main complaints were cough and rhinitis. Skin burns at all stages of healing and residual scars were seen over hands, forearms and thighs. 96% of the cutters had blood lead levels exceeding 40 micrograms/100 ml with 10 workers exceeding 70 micrograms/100 ml. None had clinical evidence of lead poisoning. The study showed that scrap metal cutting is a hazardous industry associated with significant lead exposure. With proper medical supervision, the blood lead levels of this group of workers decreased illustrating the importance of identifying the hazard and implementing appropriate medical surveillance programmes.

Adult↗
PubMed1988

Respiratory function in cadmium battery workers--a follow-up study.

The lung function status of workers in a cadmium-nickel battery factory was re-examined 3 years after an initial study which showed a mild restrictive effect. During this period, further measures were taken to reduce the cadmium exposure. Of the 44 'original' cadmium-exposed workers, 17 were still exposed to cadmium. Another 13 were transferred to non-cadmium work at least 6 months and 14 left the company at least 1 year before the present study. Blood and urine cadmium concentrations were considerably lower than previously, consistent with the decreased cadmium-in-air levels. The total lung capacity increased both in the workers who were still exposed to cadmium and those who ceased exposure. The latter group also had increased vital capacity and forced expiratory volume in one second. The prevalence of respiratory symptoms decreased particularly in the workers who were no longer exposed to cadmium.

Adult↗
PubMed1986

A simple method of qualitative analysis for musk ambrette, musk ketone and musk xylene in cologne.

Musk ambrette has become one of the commonest photosensitizers in many countries and is the cause of persistent light reactions in many patients. A simple method is presented for qualitative analysis for musk ambrette and other nitromusks in colognes using thin-layer chromatography with toluene as carrier solvent and visualization under UVL. It is useful for identifying such colognes so that proper recommendations can be given to patients sensitive to musk ambrette. 14 of 32 men's colognes, analysed by TLC and confirmed on GC/MS, were found to contain musk ambrette, the concentration varying from 0.02 to 0.39% w/v.

Chromatography, Gas↗
PubMed1986

Cobalt and nickel content of Asian cements.

The total cobalt and nickel concentration of 11 brands of Asian cement ranged from 8.1 to 14.2 micrograms/g and 14.9 to 28.5 micrograms/g, respectively. These metals exist mainly as insoluble salts; the water-soluble concentration of cobalt and nickel in the cements ranged from 0.39 to 0.65 micrograms/g and from 0-1.2 micrograms/g, respectively. 1.5% (4/272) of construction workers in a prefabrication construction factory had cobalt sensitivity. All had allergic contact dermatitis from chromate in cement. No worker had isolated cobalt sensitivity and cement dermatitis. It appeared that sensitization to cobalt in cement occurs only secondarily to an existing cement dermatitis. 1.8% (5/272) workers had nickel sensitivity: 2 with allergic contact dermatitis to nickel in their watches, 2 were asymptomatic and 1 had allergic contact dermatitis to chromate and cobalt in cement. The low prevalence of cobalt and nickel sensitivity from cement was probably related to the low concentration of soluble cobalt and nickel salts in the cement. However, these insoluble salts can form soluble complexes with body fluids on eczematous skin and sensitize the skin.

Asia↗
PubMed1986

The influence of temperature on the concentration homogeneity of patch test materials.

The concentration homogeneity of nickel sulphate 4.8% pet. and potassium dichromate 0.5% pet. in patch test materials appeared to become less homogeneous if stored at room temperature compared storage at 4 degrees C, after 2 months. The coefficient of variation of concentration for nickel sulphate after storage at 4 degrees C was 3.0883%, and at room temperature 25.3098%. The coefficient of variation for potassium dichromate after storage at 4 degrees C was 4.6324% and at room temperature 9.6334%. This indicates that patch test materials containing nickel sulphate and potassium dichromate should be kept refrigerated in the tropics.

Dermatitis, Contact↗
PubMed1985

Photosensitivity associated with carprofen (Imadyl).

Photodermatitis from Carprofen in 3 patients was reported. The absorbance spectrum of Carprofen revealed maximum absorbance at UVB range. The clinical presentation in the 3 patients suggested that a phototoxic mechanism may be responsible.

Aged↗
PubMed1984

Cross sensitivity in colour developers.

Colour developers are widely used and contact dermatitis and lichen planus-like eruptions from them are well-known. As a result of automation, there have been few recent reports of contact dermatitis from colour developers. We describe here 4 cases of dermatoses from Kodak CD4 colour developer and study their cross sensitivity to other colour developers and PPD. Attempts were made to determine the purity of the patch test allergens to ensure that cross sensitivity was not the result of contamination and decomposition of the allergens.

Adult↗
PubMed1984

Five cases of arsine poisoning.

Arsine is one of the most potent haemolytic agents found in industry. Four workers presented with abdominal pain, jaundice and passing tea-coloured urine. A fifth worker also passed dark urine but had no other symptoms. Investigation revealed that all five workers were from a tin smelting plant where they were involved in mixing tin ore with dross. They were exposed to arsine gas after mixing a particularly large quantity of dross with tin ore which was wet because of rain. Three of the cases developed renal impairment and also a mild sensory neuropathy. All survived with proper management in hospital which included exchange blood transfusions, and peritoneal dialysis where indicated. Prevention of such poisoning includes keeping dross away from all moisture, good ventilation in work areas, and adding dross directly to the furnace.

Acute Kidney Injury↗