Biomedical subjects

H T Ong

Publications and source records attributed to H T Ong.

33 records · Page 2Linked to original sources

PubMed1998

Association of infantile convulsions with paroxysmal dyskinesias (ICCA syndrome): confirmation of linkage to human chromosome 16p12-q12 in a Chinese family.

We have studied one family of Chinese origin, in which benign infantile convulsions and paroxysmal choreoathetosis (of the dystonic form) were co-inherited as a single autosomal dominant trait. This association is specific to ICCA syndrome, which we have recently described in four French families. Some patients in the new family also exhibit recurrence of epileptic seizures at a much later age, making the ICCA syndrome in this family atypical. DNA samples isolated from this family of 22 members (9 affected) have been tested with genetic markers at chromosome 16p12-q12, in which region the ICCA syndrome has previously been linked. Confirmation of linkage to this pericentromeric region of human chromosome 16 has been obtained and no critical meiotic recombination event has been detected in the ICCA region. This result suggests that, in contrast to marked clinical heterogeneity, the association of infantile convulsions with paroxysmal dyskinetic movements could be genetically homogeneous.

China↗

PubMed1997

Semi-automated extraction of brain contours from MRI.

We compared brain volumes computed by trained operators using the BRAIN-MAP algorithm, which automatically extracts the contours of the brain from gradient-echo magnetic resonance images. The images of 19 subjects randomly selected from a group of normals and a group of patients with dementia were included. BRAIN-MAP found brain perimeters that were on the average ca. 3% tighter than those obtained by two experienced operators. Between-operator and within-operator reproducibility of the analyses were also estimated and found to be (-0.13 +/- 0.51)% and (-0.63 +/- 0.08)%, respectively. Replicate volume measurement by the computer alone provided a reproducibility of (0.44 +/- 0.46)%.

Adult↗

PubMed1996

Molecular diagnosis of Duchenne muscular dystrophy in Singapore.

Duchenne muscular dystrophy (DMD) is a common lethal sex-linked recessive disorder. Seventy percent of the cases are inherited and 30% are due to mutations. The mainstay of prevention is detection of female carriers and antenatal diagnosis of affected foetuses. Before the era of molecular diagnosis, DMD has been clinically defined. Serum creatine kinase (CK) has also been used to screen women at risk for carrier status. With the isolation and sequencing of the DMD gene at Xp21 and the identification of the DMD gene-product dystrophin, DNA technology can be applied for the diagnosis of the affected, for the detection of carriers and in antenatal diagnosis. The multiplex polymerase chain reaction (PCR) technique offers a rapid and simple screening method for deletions of the gene. We were able to detect partial deletions which account for 58.3% of gene defects in our patients. This direct demonstration of the gene defect that causes DMD gives a 100% assurance of accuracy and specificity of the diagnosis. Linkage analysis is especially useful for prenatal diagnosis and carrier detection in the remaining 41.7% of families without detectable deletions or duplications. This approach however is indirect and is dependent on information on genotypes from affected males and key family members. With the availability of increasingly more restriction fragment length polymorphisms (RFLPs), it has become practical to use the haplotype method for accurate carrier detection and prenatal diagnosis.

DNA↗

PubMed1994

Comparison of the precision of two standardized co-ordinate systems for the quantitation of brain anatomy: preliminary results.

We assessed reproducible definition of two standardized co-ordinate systems for intersubject analysis of brain images. The baselines in the two co-ordinate systems were a modification of the canthomeatal (mCM) line and the anterior-posterior commissural (AC-PC) line. Axial spin-echo MR images of four subjects at 1.5T were used. Operator error was computed from the replicate analyses of two operators. The mCM line was determined by the lens of the eye and the internal auditory canal, and the AC-PC line was determined by the intersection of AC and PC with the interhemispheric fissure. Reproducibility of the mCM markers (SD = 0.59 mm) did not differ significantly from that of the AC-PC line (SD = 0.68 mm). The measurement error of the angle of the baseline (delta alpha), however, was more than 7 times as large for the AC-PC line as for the mCM line. An additional error affecting the rostrocaudal rotation of the co-ordinate systems, attributable to the distance between the anatomic markers, was 2.1 and 3.6 degrees (3 mm and 5 mm slice thickness) for the mCM co-ordinate system and 8.2 and 11.0 degrees (3 mm and 5 mm slice thickness) for the AC-PC system. The AC-PC line based co-ordinate system is therefore, less reproducible than the mCM line based system. This could be improved if a combination of axial and sagittal images were used for the definition of the AC-PC line.

Brain↗

PubMed1993

Reliability of computerised electrocardiographic reports.

The aim of this study is to assess the reliability of computerised reporting of electrocardiograms (ECG). Fifty ECG performed consecutively at the outpatient department of the Penang Adventist Hospital on the Marquette 12SL-SC were studied. Two physicians independently reviewed the ECG and the manual readings were compared with each other and to the computer reports. There was no significant difference in the measurement of rate. The PR and QT intervals measured by the two physicians were similar but each was significantly different from the computer reading. The QRS duration assessed by Physician 1 was similar to the computer reading but each was significantly different from that of Physician 2. The overall diagnosis was the same between the two physicians in 76%, between Physician 1 and the computer in 68%, and between Physician 2 and the computer in 78%. No ECG was reported as normal by the computer and said to be abnormal by either physician. Thus, the computer programme is reasonably reliable in ECG reporting with computer-physician variability being comparable to inter-physician variability.

Diagnosis, Computer-Assisted↗

PubMed1993

Cholesterol reduction therapy: a double-edged knife.

Cholesterol reduction reduces ischaemic cardiovascular morbidity and mortality in the asymptomatic healthy population as well as in those with known coronary artery disease. Angiographic studies have also demonstrated regression of atherosclerotic plaques as well as retardation of new atheroma formation with such therapy. Yet, there is a consistent inability to reduce overall mortality in cholesterol-lowering drug trials. An excess of suicide, homicide and violence has been attributed to cholesterol reduction interfering with membrane lipids and receptors, leading to aggressive behaviour. The risk and benefits of cholesterol reduction must thus be weighed in the individual patient; it is more useful in those with known coronary artery disease who are at high risk of subsequent ischaemic cardiovascular events.

Anticholesteremic Agents↗

PubMed1991

Cholesterol atheroembolism: an increasingly frequent complication of cardiac catheterisation.

Cholesterol atheroembolisation is increasingly encountered as a complication of cardiac catheterisation. We report three cases seen recently in our unit. Autopsy and histological evidence confirmed cholesterol atheroembolism in one case, while the other two patients presented with classical clinical features of this condition. All three patients were elderly with extensive atheromatous disease. No excessive difficulty was encountered at catheterisation. Embolisation involved the gastrointestinal tract, the skin and extremities, and the kidneys. Despite anticoagulation, dialysis and surgical intervention all our patients died. With investigative and therapeutic catheterisation being increasingly performed in the setting of severe atherosclerosis, the need for continued scrutiny for catheter-induced complications is emphasised.

Age Factors↗

PubMed1991

Early management of myocardial infraction: a report from the Waikato Hospital, New Zealand.

A retrospective review was made of the early management of 50 consecutive patients admitted with an acute myocardial infarction to assess the potential suitability and actual application of thrombolysis, intravenous beta-blockade and aspirin therapy. Thrombolysis was indicated for 15 patients (30%), of whom 14 actually did receive intravenous streptokinase. Thus, 93.3% of all eligible patients received thrombolysis. The main contraindication to thrombolysis was a presentation more than six hours from onset of symptoms in 26 patients (52%). Intravenous beta-blockade was indicated for 17 patients (34%), six patients were actually treated resulting in a therapeutic coverage of 35.3%. Heart failure in 21 patients (42%) was the main contraindication. Aspirin was indicated for 48 patients (96%). However, only 14 were treated giving a therapeutic coverage of 29.2%. A large majority of our patients with an acute myocardial infarction were eligible to receive aspirin which has been a neglected therapeutic modality.

Administration, Oral↗

PubMed1991

Syndrome X: an uncommon cause of angina.

A 61-year old lady presented clinically in unstable angina with ST-segment depression typical of myocardial ischemia. However, coronary arteries were completely normal at angiography. Exercise testing reproduced symptoms and ST-segment depression. A diagnosis of Syndrome X was made, an uncommon disorder of myocardial ischemia with normal coronary anatomy and excellent prognosis.

Angina Pectoris↗

PubMed1989

Digoxin toxicity: clinical and laboratory assessment.

A prospective study to correlate clinical digoxin toxicity with serum digoxin levels was carried out in 67 patients of whom 24 were clinically toxic and 43 were asymptomatic. The patients were clinically diagnosed to be toxic based on typical cardiac arrhythmias (n = 11) or non-cardiac symptoms (n = 13). Blood samples were collected at least six hours after the last digoxin dose and the sera assayed for digoxin using a radioimmunoassay method. The mean serum digoxin level in the toxic group (x1 = 2.09 +/- 1.28 ng/ml) was significantly higher than in the non-toxic group (x2 = 1.20 +/- 0.75 ng/ml), p less than 0.01. All the non-toxic patients had serum digoxin levels below 3 ng/ml. However, there was a considerable overlap of serum digoxin levels between the two groups of patients. Serum level cannot be the sole criterion in diagnosing digoxin toxicity. Nevertheless, raised serum digoxin levels especially above 3 ng/ml, in the presence of suggestive clinical features is strongly suggestive of toxicity.

Adolescent↗

PubMed1977