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Biomedical subjects

K H Tan

Publications and source records attributed to K H Tan.

At least 19 recordsLinked to original sources
PubMed1995

Percutaneous transluminal coronary angioplasty of aorta ostial, non-aorta ostial, and branch ostial stenoses: acute and long-term outcome.

The acute and long-term outcome of 198 patients who underwent coronary angioplasty of ostial stenoses was evaluated. Procedural success was achieved in 85% of aorta ostial stenoses, 90% of non-aorta ostial stenoses, and 87% of branch ostial stenoses (P = 0.84). A major complication occurred in 5.9%, 6.3%, and 6.9% of patients who underwent aorta ostial, non-aorta ostial, and branch ostial stenosis angioplasty, respectively (P = 0.97). A greater residual stenosis (P = 0.005) resulted from angioplasty of aorta ostial lesions despite a greater inflation frequency (P < 0.001), inflation pressure (P < 0.001), and total inflation duration (P < 0.001). The restenosis rate was higher for aorta ostial lesions (71%) when compared to non-aorta ostial (60%) and branch ostial lesions (32%) (P = 0.01). However, since the denominator included only the 49% who returned for repeat coronary angiography, the exact angiographic restenosis rate cannot be determined. The cumulative probability of survival was 99% at 1 year and 93% at 3 years. The 1 and 3 year freedom from death, myocardial infarction, bypass surgery, and repeat angioplasty was 70% and 57%, respectively. At census, 57% were asymptomatic, and only 9% suffered severe angina. Coronary angioplasty of ostial stenoses can be carried out with an acceptable success and complication rate, and provides good symptomatic relief and favourable long-term outcome. Randomized trials to compare new angioplasty technology with balloon angioplasty will be necessary to select the best device therapy for ostial lesions.

Adult↗
PubMed1995

Percutaneous transluminal coronary angioplasty in patients 70 years of age or older: 12 years' experience.

OBJECTIVE: To evaluate the short and long term results of coronary angioplasty in patients aged 70 years and older and identify the determinants of long-term survival. DESIGN: A retrospective analysis of clinical, angiographic, and procedure related variables on a consecutive series of patients. PATIENTS: 163 patients aged 70 years and older (mean (range) age 73 (70-83) years; 63% men) who underwent a first coronary angioplasty procedure between 1981 and 1993. RESULTS: Procedural success was achieved in 82% of patients. Four patients (2%) died, three (2%) had a myocardial infarction, and five (3%) underwent emergency coronary artery bypass surgery. Complete follow up data were available for all patients (median (range) 35 (2-146) months). During the follow up period 16 patients (10%) died, two (1%) suffered non-fatal myocardial infarction, and 12 (7%) underwent elective coronary artery bypass surgery. A second angioplasty procedure was performed in 24 patients (15%). The cumulative probability of survival was 90.7% at 1 year and 83.4% at 5 years. Survival free from myocardial infarction, bypass surgery, and repeat angioplasty at 1 and 5 years was 68.2% and 56.0%, respectively. Proportional hazards regression analyses identified incomplete revascularisation as the only independent predictor of poorer overall survival (P = 0.04) and event free survival (P < 0.001). At census, of the 143 survivors, 75 (52%) were asymptomatic, 58 (41%) had mild angina, and only 10 (7%) complained of grade III or IV angina. Some 112 patients (78%) improved by at least two angina grades. CONCLUSION: Coronary angioplasty can be performed safely in the elderly and provides good symptomatic relief and favourable long-term outcome. Complete revascularisation may not be necessary if the primary goal is to achieve symptomatic relief, but incomplete revascularisation is associated with poorer long-term survival.

Aged↗
PubMed1995

The aetiology of postmenopausal bleeding--a study of 163 consecutive cases in Singapore.

OBJECTIVE: To study the aetiology and pattern of Postmenopausal Bleeding (PMB) in the local population. DESIGN: A retrospective study SUBJECTS: 163 consecutive patients who presented with postmenopausal bleeding (PMB) SETTING: Kandang Kerbau Hospital, Singapore RESULTS: Malignant causes were found in 42 (25.7%) patients. Cervical carcinoma was the most common malignancy (12.9% of the patients) followed by endometrial carcinoma (11%). Important benign causes are cervicitis (12.9%), atrophic vaginitis (12.3%) and cervical polyp (6.7%). Other benign causes include endometrial hyperplasia (3.1%), urethral caruncle (2.5%) and estrogen replacement therapy (1.8%). CONCLUSION: PMB is a symptom of varied aetiologies. The associated incidence of malignancy is high and a thorough diagnostic evaluation is mandatory.

Adult↗
PubMed1992

Kielland's forceps delivery: is it a dying art?

A retrospective study in the use of Kielland's Forceps for rotation of the foetal head and mid-cavity delivery in Kandang Kerbau Hospital, Singapore from 1987-1990 is presented. Out of a total of 53,889 singleton births during this period, Kielland's Forceps was used for delivery in 137 (0.25%) patients with an incidence of 0.65% in the primiparae and 0.07% in the multiparae. Primiparity, induction of labour and epidural analgesia were associated with a significantly higher incidence of rotational delivery by Kielland's forceps. The success rate of Kielland's forceps delivery was 93.4% (128 of 137). There was no maternal or perinatal mortality. About one-third of the mothers experienced postpartum morbidity, commonest being retention of urine, postpartum haemorrhage and vaginal lacerations. Traumatic injuries were present in about one-quarter of the babies and were minor. Out of a total of 306 mid-cavity deliveries for occipito-transverse malposition, Kielland's forceps accounted for 38.2% (117), vacuum extraction 30.7% (94), manual rotation followed by Neville-Barnes forceps 11.1% (34) and Caesarean section 20.0% (61). The junior specialists tended to use vacuum extraction for rotational delivery more than the senior specialists.

Birth Injuries↗
PubMed1991

Testicular biopsy and scrotal exploration in the management of male infertility.

Testicular biopsy findings in 52 subfertile men were correlated with the clinical findings, semen analyses and hormonal levels. Mild to moderate pathological changes were seen in 2/3 of cases while 1/3 had severe damage. Almost 3/4 of them had atrophic testicles while up to 1/2 had varicoceles. In most cases, routine examination, semen analyses and hormonal studies could not provide an accurate guide to the severity of the lesions. Size alone correlated well with worse changes in the smaller testes. Biopsy was more precise for assessing oligospermia and azoospermia in which the histology can vary considerably. The pattern with varicocele was not pathnognonomic but maturation arrest was common in younger patients while older men tend to have sclerosis and intraluminal sloughing irrespective of the grade of venous reflux. FSH and LH levels were only useful when either or both were raised more than 3 times. Normal FSH could be found in germinal aplasia or maturation arrest. In the latter, the testes were often of good size; thus diagnosis would not be made without biopsy. Examination of the testes, epididymis and the vasa was always done at the time of biopsy and when indicated, vasography helped elucidate the nature and site of the obstruction causing azoospermia. When a varicocele was present, biopsy of the testes at the time of ligation can provide assessment of the pathological change and provide a prognosis especially when additional hormonal treatment was being considered. The greatest value of biopsy was in cases confirmed beyond salvage by histology. This enabled appropriate action to be taken ie. AID or adoption, etc.

Adult↗
PubMed1990

A low dose oxytocin regime for induction and augmentation of labour.

A low dose oxytocin regime was used in Labour Ward, Alexandra Hospital for the induction and augmentation of labour. It utilised an oxytocin infusion administered in an arithmetic progression from 1 to 16 mU in a peristaltic infusion pump. A total of 100 patients (67 for augmentation and 33 for induction of labour) classified according to parity were studied. An overall vaginal delivery rate of 87% was obtained. The overall mean durations of labour for nulliparous and multiparous patients were 6.6 hours (S.D. +/- 2.9 hours) and 4.9 hours (S.D. +/- 2.8 hours) respectively. The mean induction delivery time for nulliparous patients was 6.4 hours (S.D. +/- 3.2 hours) and for multiparous patients it was 4.0 hours (S.D. +/- 2.2 hours). About 69% of the nulliparae and 94% of the multiparae who were induced delivered within 9 hours. All the induced patients delivered within 12 hours. Neonatal outcome was good as assessed by Apgar score.

Adult↗
PubMed1988

Detoxification of DNA hydroperoxide by glutathione transferases and the purification and characterization of glutathione transferases of the rat liver nucleus.

DNA peroxidized by exposure to ionizing radiation in the presence of oxygen is a substrate for the Se-independent GSH peroxidase activity of several GSH transferases, GSH transferases 5-5, 3-3 and 4-4 being the most active in the rat liver soluble supernatant fraction (500, 35 and 20 nmol/min per mg of protein respectively) and GSH transferases mu and pi the most active, so far found, in the human liver soluble supernatant fraction (80 and 10 nmol/min per mg respectively). Although the GSH transferase content of the rat nucleus was found to be much lower than that of the soluble supernatant, nuclear GSH transferases are likely to be more important in the detoxification of DNA hydroperoxide produced in vivo. Two nuclear fractions were studied, one extracted with 0.075 M-saline/0.025 M-EDTA, pH 8.0, and the other extracted from the residue with 8.5 M-urea. The saline/EDTA fraction contained subunits 1, 2, 3, 4 and a novel subunit, similar but not identical to 5, provisionally referred to as 5*, in the proportions 40:25:5:5:25 respectively. The 8.5 M-urea-extracted fraction contained principally subunit 5* together with a small amount of subunit 6 in the proportion 95:5 respectively. GSH transferase 5*-5* purified from the 8.5 M-urea extract has the highest activity towards DNA hydroperoxide of any GSH transferase so far studied (1.5 mumol/min per mg). A Se-dependent GSH peroxidase fraction from rat liver was also active towards DNA hydroperoxide; however, since this enzyme accounts for only 14% of the GSH peroxidase activity detectable in the nucleus, GSH transferases may be the more important source of this activity. The possible role of GSH transferases, in particular GSH transferase 5*-5*, in DNA repair is discussed.

Animals↗
PubMed1987

Lipid peroxidation in choline-methionine deficiency.

A deficiency of choline and methionine is hepatocarcinogenic and is associated with an apparent increase in lipid peroxidation. In this study the susceptibility of microsomes and nuclei to ferritin-dependent lipid peroxidation is examined together with the status of the peroxidation-protective systems. Choline-methionine deficiency caused an increase in Se-independent GSH peroxidases (GSH transferase subunit 2) and membrane vitamin E but a decrease in Se-dependent GSH peroxidase and microsomal GSH peroxidase activity. Choline-methionine deficient microsomes and nuclei were 4-fold more susceptible to lipid peroxidation induced in vitro by physiological concentrations of ferritin/ascorbate/ADP; and the peroxidation was less effectively inhibited by GSH and soluble GSH peroxidases than controls. The results indicate that a decreased level of Se-dependent and membrane GSH peroxidases is involved in the increase in lipid peroxidation observed in choline-methionine deficiency.

Choline Deficiency↗
PubMed1986

Thymine hydroperoxide, a substrate for rat Se-dependent glutathione peroxidase and glutathione transferase isoenzymes.

The thymine hydroperoxide, 5-hydroperoxymethyluracil, is a substrate for Se-dependent glutathione (GSH) peroxidase and the Se-independent GSH peroxidase activity associated with the GSH transferase fraction. These enzymes may contribute to repair mechanisms for damage caused by oxygen radicals. GSH transferases 1-1, 2-2, 3-3, 4-4, 6-6, and 7-7 [(1984) Biochem. Pharmacol. 33, 2539-2540] are shown to differ considerably in their ability to utilize this substrate. For example, high activity is found in GSH transferase 6-6 which is the major isoenzyme in spermatogenic tubules where DNA synthesis is so active and faithful DNA replication so important. The activity of the purified GSH transferase isoenzymes towards 5-hydroperoxymethyluracil is comparable with their activity towards other endogenous substrates related to cellular peroxidation such as linoleate hydroperoxide and 4-hydroxynon-2-enal or biologically important xenobiotic metabolites such as benzo(a)pyrene-7,8-diol-9,10-oxide.

Animals↗
PubMed1986

Long-term survey of prominent ear surgery: a comparison of two methods.

A retrospective study was undertaken of 191 patients under the age of 16, who underwent surgery during the period 1974 to 1978. Using questionnaires, acceptance of the 2 most used methods, the Mustardé technique (45 cases) and the anterior scoring (101 cases), was assessed and the case sheets of the involved patients were collected. Though there was no difference in the final acceptance of both methods, a significantly larger number of cases treated with the Mustardé technique needed re-operation. The use of non-absorbable material (white silk) was the cause of stitch complications in this method.

Adolescent↗
PubMed1985

Glutathione transferases in primary rat hepatomas: the isolation of a form with GSH peroxidase activity.

A previously uncharacterized glutathione (GSH) transferase which is not apparent in normal liver, accounts for at least 25% of the soluble GSH transferase content of primary hepatomas induced by feeding N,N-dimethyl-4-aminoazobenzene. This enzyme is readily isolated, has an isoelectric point of 6.8, is composed of two identical subunits of apparent Mr 26000 and has GSH transferase activity towards a number of substrates including benzo(a)pyrene-7,8-diol-9,10-oxide. It is unusual in that it has GSH peroxidase activity towards fatty acid hydroperoxides but not towards the model substrates, cumene hydroperoxide and t-butyl hydroperoxide. It has been shown by tryptic peptide analysis to be distinct from GSH transferases composed of subunits 1, 2, 3, 4 or 6 and has been designated GSH transferase 7-7.

Animals↗
PubMed1984

Inhibition of microsomal lipid peroxidation by glutathione and glutathione transferases B and AA. Role of endogenous phospholipase A2.

Lipid peroxidation in vitro in rat liver microsomes (microsomal fractions) initiated by ADP-Fe3+ and NADPH was inhibited by the rat liver soluble supernatant fraction. When this fraction was subjected to frontal-elution chromatography, most, if not all, of its inhibitory activity could be accounted for by the combined effects of two fractions, one containing Se-dependent glutathione (GSH) peroxidase activity and the other the GSH transferases. In the latter fraction, GSH transferases B and AA, but not GSH transferases A and C, possessed inhibitory activity. GSH transferase B replaced the soluble supernatant fraction as an effective inhibitor of lipid peroxidation in vitro. If the microsomes were pretreated with the phospholipase A2 inhibitor p-bromophenacyl bromide, neither the soluble supernatant fraction nor GSH transferase B inhibited lipid peroxidation in vitro. Similarly, if all microsomal enzymes were heat-inactivated and lipid peroxidation was initiated with FeCl3/sodium ascorbate neither the soluble supernatant fraction nor GSH transferase B caused inhibition, but in both cases inhibition could be restored by the addition of porcine pancreatic phospholipase A2 to the incubation. It is concluded that the inhibition of microsomal lipid peroxidation in vitro requires the consecutive action of phospholipase A2, which releases fatty acyl hydroperoxides from peroxidized phospholipids, and GSH peroxidases, which reduce them. The GSH peroxidases involved are the Se-dependent GSH peroxidase and the Se-independent GSH peroxidases GSH transferases B and AA.

Acetophenones↗