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Biomedical subjects

T W Wong

Publications and source records attributed to T W Wong.

At least 19 recordsLinked to original sources
PubMed1992

Identification and characterization of a cytosolic protein tyrosine kinase of HeLa cells.

Fractionation of a cytosolic extract of HeLa cells revealed the existence of a highly active protein tyrosine kinase. Chromatographic fractionation of the extract resulted in partial purification of a single enzymatic activity that coeluted with a 94-kDa polypeptide. In vitro phosphorylation of the isolated enzyme showed that p94 was the only polypeptide phosphorylated and only the tyrosine residue(s) was (were) modified. The fractionated enzyme (p94 kinase) also phosphorylated a number of other nonspecific substrates exclusively on tyrosine residues. Unlike other protein tyrosine kinases that have been characterized, p94 kinase is relatively insensitive to inhibition by the isoflavone genistein. Using two different antisera, we provided evidence that the HeLa p94 kinase is most likely the FER gene product, which was previously shown to be expressed in a wide variety of cell types. These results represent the first biochemical characterization of the cellular FER gene product and also provide a basis for studying the biochemistry of tyrosine kinase function in HeLa cells.

Amino Acid Sequence↗
PubMed1992

Purification and identification of subunit structure of the human mitochondrial DNA polymerase.

The mitochondrial DNA polymerase of HeLa cells was purified 18,000-fold to near homogeneity. The purified polymerase cofractionated with two polypeptides that had molecular mass of 140 and 54 kDa. The 140-kDa subunit was specifically radiolabeled in a photoaffinity cross-linking assay and is most likely the catalytic subunit of the mitochondrial DNA polymerase. The purified enzyme exhibited properties that have been attributed to DNA polymerase gamma and shows a preference for replicating primed poly(pyrimidine) DNA templates in the presence of 0.5 mM MgCl2. As in the case of mitochondrial DNA polymerases from other animal cells, human DNA polymerase gamma cofractionated with a 3'----5' exonuclease activity. However, it has not been possible to determine if the two enzymatic activities reside in the same polypeptide. The exonuclease activity preferentially removes mismatched nucleotides from the 3' end of a duplex DNA and is not active toward DNA with matched 3' ends. These properties are consistent with the notion that the exonuclease activity plays a proofreading function in the replication of the organelle genome.

Base Sequence↗
PubMed1991

A manual sequencing method for identification of phosphorylated amino acids in phosphopeptides.

We describe a simple and inexpensive method for determining the location of phosphoamino acids in an isolated phosphopeptide. Phosphopeptides are immobilized on arylamine membrane discs using water-soluble carbodiimide, and the immobilized peptides are subjected to manual Edman degradation. The use of a membrane disc resulted in excellent recovery (65 to 80%) of radiolabeled phosphate following Edman degradation. Furthermore, interference from carryover and peptide washout is reduced to a minimum. The methodology should therefore be able to generate reliable results when used to analyze phosphopeptides that contain multiple phosphorylation sites. In addition to its advantage in sensitivity, the manual sequencing method is easy to perform and does not entail any sophisticated instrumentation.

Amino Acid Sequence↗
PubMed1991

In vitro replication of heavy strand DNA in permeabilized human mitochondria.

We have characterized some of the experimental conditions that are essential for initiation of human mitochondrial DNA synthesis. Mitochondria were purified from HeLa cells and were permeabilized with Triton X-100. When supplied with rNTPs and dNTPs, the permeabilized mitochondria synthesized nucleic acids that ranged in size from about 600 to 2000 nucleotides. In vitro DNA synthesis occurred on endogenous DNA templates and required a continuous supply of ATP. Analyses of the synthetic products revealed that almost all of them were of heavy-strand sequence and included authentic 7S DNA. Most of the synthetic products had 5' ends that mapped to similar locations as those previously identified for nascent heavy-strand DNA. Identification of these parameters should facilitate our efforts to achieve in vitro replication of heavy-strand mitochondrial DNA.

Base Sequence↗
PubMed1991

Acupuncture: from needle to laser.

Acupuncture has been used in the treatment of a variety of illnesses for more than 2000 years. The practice of acupuncture is based on a theoretical system different from our understanding of human anatomy and physiology, and has developed through experience and observation. Stimulation of selective acupoints (situated along 'meridians' in the body) by inserting needles is believed to restore bodily functions by promoting the flow of 'vital energy', throughout the system. Other forms of stimulation which have been developed are heat, electrical stimulation, magnetism and, recently, laser. Laser acupuncture offers distinct advantages over the traditional method because the procedure is pain-free and non-traumatic. Clinical applications include the control of pain in osteoarthritis, lumbago and migraine, and anaesthesia for certain surgical procedures, as well as other ailments of the cardiovascular, respiratory and nervous systems. The technique is easy to learn and there is no need for sophisticated instruments. Thus it is especially useful in developing countries where health resources are limited.

Acupuncture Therapy↗
PubMed1991

Prevalence of human T-cell lymphotropic virus type I infection in Singapore: a preliminary report.

Human T-cell lymphotropic virus type I (HTLV-I) infection is endemic in southwestern Japan, the Caribbean basin, Colombia, Africa and in several isolated populations in Papua New Guinea, the Solomon Islands and Vanuatu. To determine the seroprevalence of HTLV-I infection in Singapore, we tested sera from 115 hospitalized patients with acute nephritis, 50 patients with suspected leptospirosis, 34 patients with non-A, non-B hepatitis, and from 28 healthy volunteers for IgG antibodies against HTLV-I using an enzyme-linked immunosorbent assay. Antibodies were detected in sera from 6 of the 199 patients and from 3 of the 28 healthy volunteers, but these positives could not be confirmed by Western immunoblotting. Our data are consistent with other reports of low seroprevalence of HTLV-I infection despite extensive Japanese contact in Korea, Taiwan, the People's Republic of China and Micronesia. Further studies on a larger sample size, however, are necessary to confirm the absence of any focus of infection in the Singapore population.

Adolescent↗
PubMed1990

Driving experience and the risk of traffic accident among motorcyclists.

In a case-control study on the risk of traffic accidents among motorcyclists in Singapore, we demonstrated an inverse monotonic relationship between accident risk and driving experience. As compared to drivers with less that 1 yr of driving experience, the odds ratios (adjusted for race, age and frequency of riding) for those with driving experience of 1-4, 5-9 and 10 yr or more were 0.60, 0.50 and 0.36, respectively. We propose that intensive in-circuit training of learner motorcyclists should replace the conventional on-the-road training on the basis that the former serves to increase their driving experience without subjecting the learner motorcyclists to the risk of sustaining road accident.

Accidents, Traffic↗
PubMed1990

The use of personal cassette players among youths and its effects on hearing.

To assess the prevalence of use of Personal Cassette Players (PCP) among youths in a residential community in Hong Kong, we interviewed 487 youths aged 15-24 years who attended various activities in eight Youth Centres in Shatin, Hong Kong. 394 (81%) reported using the Personal Cassette Player regularly. The mean duration of PCP use was 2.8 years with a median of 2 years. The mean time of listening to PCP was 4.5 hours per week. We further examined 124 subjects by otoscopy and of the 103 otoscopically normal individuals, audiometric tests were performed. Among the 78 PCP users and 25 non-users, no significant difference in the mean hearing threshold was observed for the frequencies tested. The mean ear canal sound level was 70.4 dBA. Four subjects were habitually exposed to sound levels higher than 85 dBA. One was exposed to 116 dBA and was found to have a 4000 Hz dip on his audiogram, suggestive of noise-induced hearing loss. In general, despite the high prevalence of PCP use, most youths used their PCP at relatively safe sound levels with low risk of hearing loss. However, education directed towards the youth with respect to the potential hazard on hearing due to improper and prolonged use of PCP is still warranted.

Adolescent↗
PubMed1990

Effects of overweight on lung function.

Spirometric data from 1586 healthy children, who did not smoke, were analysed to examine the effects of overweight as measured by the body mass index (weight/height2) on lung function. Overweight (72 boys, 88 girls) was defined as on or above the 90th percentile weight for height. After having controlled for the confounding variables of height and age, there were positive partial correlations between body mass index and lung function in girls whose weight was normal, in overweight girls, and in boys whose weight was normal, but not in overweight boys. In contrast to adults, body mass index has a positive effect on lung function in girls, whatever their weight. No such correlation between body mass index and lung function was seen in overweight boys. The observations may be accounted for by distinct sex dependent patterns of fat distribution in children.

Adolescent↗
PubMed1990

Properties and clinical implications of body mass indices.

The properties of body mass indices were evaluated in a cross sectional study of the weights and heights of 5016 Chinese boys and girls aged between 3 and 18 years. Of the indices examined (weight/height (W/H), weight/height2 (W/H2), weight/height3 (W/H3) and weight/heightp (W/Hp], W/Hp was the only one that consistently showed least correlation with height, and so could be regarded as the optimal body mass index by the criterion of independence of the index from height. The exponent 'p' of W/Hp is, however, highly dependent on age; the value increases steadily between the age of 3 and 7-9 years, and then varies considerably around puberty. Only the age specific exponent ensures a lack of correlation between body mass index (W/Hp) and height. Age specific W/Hp should therefore be used in intrapopulation studies of weight or problems associated with obesity in children. Interpopulation comparison of weight and adiposity by W/H, W/H2, or W/H3 may give misleading results because of their dependence on height. Our results also suggest that the conventional weight for height charts may not be accurate enough for clinical use.

Adolescent↗
PubMed1990

Reliability of the Dinamap non-invasive monitor in the measurement of blood pressure of ill Asian newborns.

Four hundred thirty-one paired sets of readings of systolic and diastolic blood pressure and 438 paired sets of readings of mean arterial BP from 49 ill newborns, including 21 very low birth weight infants, were analyzed for the extent and pattern of agreement and the linear relationship between the Dinamap oscillometric monitor and the direct intraarterial blood pressure readings. Agreement between the two methods was measured by the intraclass correlation, whereas the linear relationship was assessed by the product-moment correlation. The intraclass correlations for systolic, diastolic and mean blood pressures were 0.696, 0.766, and 0.781, respectively. The product-moment correlations for systolic, diastolic and mean blood pressures were 0.706, 0.768, and 0.786, respectively. BP measurements by the Dinamap monitor showed reasonably close agreement to those obtained by the intraarterial mean arterial pressure ranges above 40 mmHg. For mean arterial pressure of 40 mmHg and lower, BP readings by the Dinamap monitor tended to be higher than those obtained by the intraarterial method. These findings appeared to be consistent regardless of the birth weight of the newborn.

Asian People↗
PubMed1990

Motorcyclist traffic accidents and risk factors: a Singapore study.

Motorcyclist accidents cause significant morbidity and mortality in Singapore. To elucidate personal and environmental factors associated with such accidents, we studied 198 motorcyclists who were hospitalized in Singapore General Hospital between April 1986 and June 1987. The patients were mostly young and almost exclusively male with a high proportion of Malays. Most accidents occurred on Sundays and at night. Ten percent of the victims took alcohol before the accident. Most had low injury severity scores (ISS). Less experienced drivers had a significantly higher ISS than those with one year or longer of driving experience. Vigorous control of drunken driving, through public education and intensive breath testing, should reduce the incidence of traffic accidents.

Accidents, Traffic↗
PubMed1979

The nucleotide sequence of the major glutamate transfer RNA from Schizosaccharomyces pombe.

The nucleotide sequence of glutamate tRNA1 from Schizosaccharomyces pombe was determined to be pU-C-C-G-U-U-G-U-m1G-G-U-C-C-A-A-C-G-G-C-D-A-G-G-A-U-U-C-G-U-C-G-C-U-U-U*-C-A-C-C-G-A-C-G-G-G-A-G-m5C-G-G-G-G-T-psi-C-G-A-C-U-C-C-C-C-G-C-A-A-C-G-G-A-G-C-C-AOH. The sequence differs markedly from that of S. cerevisiae tRNAGlu. S. pombe glutamate tRNA1 can be aminoacylated by the homologous glutaminyl-tRNA synthetase as well as by the corresponding enzyme from S. cerevisiae.

Amino Acyl-tRNA Synthetases↗
PubMed1978

Pathological aspects of the infertile testis.

In this review, the pathological findings from testicular biopsies of men suffering from various types of infertility are presented. The causes of male infertility are divided into three major categories: pretesticular, testicular, and post-testicular causes. The pre-testicular causes of infertility may be defined as extra-gonadal endocrine disorders, such as those originating in the hypothalamus, pituitary, or adrenals, which have an adverse effect on spermatogenesis. The testicular causes of infertility are primary defects of the testes. The post-testicular causes of infertility consist primarily of obstructions of the ducts leading away from the testes. Cases in which the spermatozoa are normal in number but greatly impaired in motility, presumably due to faulty maturation or improper preservation of the spermatozoa during their sojourn in the epididymides, or due to biochemical abnormalities of the seminal plasma, are also included in the postesticular category.

Androgens↗
PubMed1977

Alleviation of separation distress in 3 breeds of young dogs.

Twenty-four puppies (8 each of Shetland sheepdogs, Telomians, and beagles) served as subjects in this experiment which was designed to examine the effectiveness of 12 stimulus conditions (food, toys, canine contact, and human contact) on alleviation of separation-induced distress vocalization. Testing consisted of a prestimulus trial, stimulus trial, and post-stimulus trial each session 3 times a week from 4 to 8 weeks after birth. Overall results showed human contact to be the most effective, followed by canine contact, toys, and food. Breed differences were significant in only 2 of the stimulus conditions. In the typical case of effective treatment, the vocalization rate declined from the prestimulus trial to a low point in the stimulus trial and then increased again in the post-stimulus trial.

Age Factors↗
PubMed1976

Glomiform and fibrillar cytoplasmic inclusions.

Glomiform inclusions, also called tubular arrays in endoplasmic reticulum, are found in the epithelial cells of glandular tissues of a patient with systemic lupus erythematosus, a patient with Reye's syndrome, and a dog. Their three dimensional structure is interpreted as a skein of contorted tubules of endoplasmic reticulum. Fibrillar inclusions found in the pancreatic acinar cells of two patients are believed to represent altered zymogen granules.

Adult↗