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Biomedical subjects

K H Ho

Publications and source records attributed to K H Ho.

At least 37 records · Page 2Linked to original sources
PubMed1999

Intraocular pressure variation following retrobulbar anaesthesia among the different sex, age and ethnic groups in Malaysia.

A total of 114 patients (48 Chinese, 34 Malay and 32 Indian) undergoing extracapsular cataract extraction (ECCE) with intraocular lens implantation, were enrolled. All were given 3 ml of local anaesthetic (combination of equal amounts of lignocaine 2% and bupivacaine 0.5%) using retrobulbar technique. Intraocular pressure (IOP) was measured at different time intervals; before, immediately after and 5 minutes after injection with Honan balloon compression. Mean IOP increased by 5.0 mmHg immediately after injection (p < 0.001) and reduced to baseline level after 5 minutes of external compression. Although there were no statistical difference in terms of IOP variation between sex and age groups, Chinese patients demonstrated the highest IOP rise following retrobulbar anaesthesia. This is the first study to demonstrate the influence of race in the IOP response with Chinese subjects having the highest IOP rise.

Adult↗
PubMed1998

Covariation between human intrinsic hand muscles of the silent periods and compound muscle action potentials evoked by magnetic brain stimulation: evidence for common inhibitory connections.

Transcranial magnetic stimuli at different stimulus intensities were applied in six healthy subjects to test the hypothesis that, in different intrinsic hand muscles, the duration of the resultant cortically evoked silent periods (C-SPs) from each stimulus would be positively correlated between muscles, indicating a common inhibitory mechanism. A figure-of-eight coil discharging through a Magstim 200 stimulator delivered 25 stimuli at each stimulus intensity at a minimum of five intensities ranging from 55% to 160% of the individual resting motor threshold. In each subject, simultaneous surface recordings from pairs of muscles were made from the first dorsal interosseous (FDI), opponents pollicis (OP), abductor pollicis brevis (APB) and abductor digiti minimi (ADM). The C-SP durations within all three muscle pairs tested were highly correlated (P<0.001). The amplitude of the preceding compound-muscle action potentials (CMAPs) was positively correlated between FDI and OP, but not between APB and ADM or FDI and ADM. C-SP duration was linearly related to stimulus intensity, but did not correlate with the latency or amplitude of the preceding CMAP. SPs elicited by peripheral nerve stimuli in pairs of hand muscles did not co-vary significantly. The results provide evidence that inhibitory influences of cortical origin are distributed widely to intrinsic hand muscles. In contrast, covariation of excitatory effects only appears between muscles synergistically involved in a motor task.

Action Potentials↗
PubMed1998

Dual effect of cobra cardiotoxin on vascular smooth muscle and endothelium.

AIM: To assess the cytotoxic effects of cobra cardiotoxin (CTX) on rat aorta. METHODS: Measure of contractility of aortic rings with or without endothelium. RESULTS: In endothelium-intact rings, CTX 10 mumol.L-1 induced a transient relaxation followed by a sustained contraction. Removal of the endothelium or pre-incubation of the rings with NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) abolished the transient relaxation but did not affect the magnitude of the contractile response induced by CTX. CTX itself induced contraction of vascular smooth muscle but also reduced contractions induced by phenylephrine (PhE) or KCl stimulation in a concentration-dependent manner. Contraction induced by CTX was dependent on the external Ca2+ concentration. Maximal contractile response to CTX was obtained in medium containing Ca2+ 1 mmol.L-1. This response decreased with higher Ca2+ concentration and disappeared when Ca2+ 7 mmol.L-1, organic and inorganic calcium channel blockers were present in the external solution before CTX addition. In preparations with the endothelium intact and incubated with CTX, relaxation by acetylcholine (ACh) stimulation of the tension induced by PhE was decreased. Endothelium-dependent relaxation to ACh was preserved when Ca2+ 5 mmol.L-1 was added to the medium prior to CTX. CONCLUSION: CTX first triggers the release of NO from the endothelium which results in muscle relaxation, and then causes smooth muscle contraction, Ca2+ and Ca2+ channel blockers prevented the effect of CTX.

Animals↗
PubMed1998

The effect of enteral fibre-containing feeds on stool parameters in the post-surgical period.

BACKGROUND/AIM OF STUDY: Specialised nutritional support includes both enteral and parenteral routes. When oral intake is not an option, but gastro-intestinal function is present, enteral tube feeding should be considered. However, one of the complications of enteral feeding access is diarrhoea. The aim of this study was to test the effect of fibre on a local population, in a prospective, single-blinded trial to determine whether the presence of fibre in enteral feeds reduced the incidence of diarrhoea in Asian patients. METHODS: Sixteen post-surgical candidates were randomly assigned to receive a fibre-supplemented (FSF) enteral formula or a fibre-free formula (FFF) for 10 days post-surgery to assess the usefulness of FSF in reducing the incidence of diarrhoea in tube-fed patients. Differences in stool consistency, stool frequency, capillary blood glucose and serum albumin levels between the two groups were determined. Antibiotic usage in both groups was noted. RESULTS: Patients in the FSF group had more bowel movements throughout the 10-day period and firmer stools than the FFF group, but this difference was not statistically significant (p = 0.39). There were no significant differences in daily mean glucose levels between both groups. CONCLUSION: We conclude that there is insufficient evidence that fibre-containing enteral formulae reduce the incidence of diarrhoea in tube-fed patients in the short term. However, these products could inherently be included for patients on tube-feeds during extended periods, with the prospect of maintaining gut function integrity and flora.

Adult↗
PubMed1997

Headache and self-assessed depression scores in Singapore University undergraduates.

A self-administered questionnaire covering the diagnostic criteria of the International Headache Society was completed by 1208 undergraduates of the National University of Singapore to determine the prevalence and characteristics of headaches in this population. The relationship between headaches and depressive illness was investigated with the Zung Self-assessed Depression Scale. The mean age of respondents was 20.9 +/- 1.6 years; 50.3% were men and 46.4%, women. Ten point nine percent had migraine without aura, 29.8% had tension-type headaches, 1.1% had headaches consistent with migraines with aura, and in 56.3% the headaches could not be classified. The lifetime prevalence of headache in this population was 98.1%. Significantly higher mean Zung scores were found in subjects who had more intense and frequent headaches than in those without headaches and less severe symptoms, although the clinical relevance of this finding is uncertain. Zung scores did not differ significantly with diagnostic group, sex, or race.

Adolescent↗
PubMed1997

Neurocysticercosis--case report and literature review.

A 30-year-old Indian migrant worker presented with seizures at the National University Hospital. A CT-scan of the brain showed multiple calcifications and cysts consistent with neurocysticercosis. Plain radiographs of the humeri and femora also revealed multiple soft tissue calcifications. He was given a course of anti-helminthic therapy and started on anti-epileptics. Neurocysticercosis is a common cause of seizures in endemic areas and must be considered in the differential diagnosis of epilepsy involving the members of the large community of migrant workers in Singapore.

Adult↗
PubMed1996

A model of blast overpressure injury to the lung.

Despite decades of animal experiments, data on blast injury to the lung cover only a limited number of circumstances and are in a fragmented form. This paper develops a mathematical model of the chest wall dynamics and the subsequent generation of strong pressure waves within the lung, which have been hypothesized as the mediator of injury. The model has been compared to an extensive database of observed pathologies from animal tests. The incidence of injury and lethality is found to follow a log-normal correlation with the computed total energy in these waves and, when the energy is normalized by the lung volume, the lethality correlation applies to all large animal species. Small animals also correlate with the normalized energy, but at a different value, and it is speculated that structural differences, other than lung volume, may be involved. This relatively simple model allows the potential for blast injury to the lung to be determined from measured or computed pressure traces without additional animal testing. Improved occupational exposure criteria should follow from this methodology.

Animals↗
PubMed1996

Hyporesponsiveness to Ca2+ of aortic smooth muscle in endotoxin-treated rats: no-dependent and -independent in vitro mechanisms.

The aim of this study was to assess the nature of vascular hyporeactivity to vasopressor agents in rats with endotoxemia. Endotoxemia was induced in rats by bacterial endotoxin (E. Coli lipopolysaccaharide, LPS). In LPS-treated rats, the reactivity of endothelium-denuded aortic rings to phenylephrine (PE) and potassium chloride (KCl) was characterized by a decreased magnitude of contraction, a slower onset of contraction and a faster rate of relaxation when compared to the control aortic rings. Addition of L-arginine (L-arg), the substrate of nitric oxide synthase (NOS), but not D-arginine (D-arg), reduced further PE-induced contraction in rings from LPS-treated rats. Inhibition of contraction in rings of LPS-treated rats was partially antagonized by the inhibitor of NOS, N omega-nitro-L-arginine methyl ester (L-NAME). Thus, production of non-endothelial nitric oxide (NO) was in part responsible for the hyporesponsiveness to PE. Rings from LPS-treated rats also displayed hyporeactivity and decreased sensitivity to Ca2+ in depolarizing medium (60 mM K+). Hyporeactivity and hyposensitivity to Ca2+ could only be partially reversed by L-NAME. The inhibitory effects of LPS-treatment on both PE-and KCl-induced aortic responses and the reversal effects of L-NAME confirm the contention that NO formation is involved in vascular hyporesponsiveness in endotoxic shock. The partial reversal by L-NAME of the hyporesponsiveness to KCl- and PE-induced contraction, and hyposensitivity to Ca2+ in depolarized aorta suggest that factors other than the action of nonendothelial source of NO formation in vitro from L-arg also contribute to endotoxin-induced vascular hyporesponsiveness to vasopressor agents.

Acetylcholine↗
PubMed1996

The bulbocavernosus reflex in the assessment of neurogenic impotence in diabetic and non-diabetic men.

The results of a 6-year review of bulbocavernosus reflex (BCR) latencies in 300 men are presented. The relationship of BCR latency to potency, diabetic status and age was examined. The mean BCR latency in 32 normal men aged 22 to 78 years (x = 44.9 +/- 14.4) was 40.6 +/- 8.9 ms. A significant trend towards increasing BCR latency with age was evident. BCR latency was not found to be significantly associated with potency, the mean measurable BCR latency in impotent men being 43.0 +/- 11.6 ms. Diabetic men were more likely to have a prolonged measurable BCR latency (x = 46.2 +/- 11.2) and impotence, but even in this subset no significant correlation between BCR latency and impotence was detectable. Our results suggest that detectable pudendal neuropathy is unrelated to impotence in non-diabetic and diabetic men and does not usefully distinguish between neurologic and non-neurologic causes of impotence. With the advent of newer objective techniques to assess organic impotence, the value of BCR latency in the routine assessment of impotent subjects is questionable.

Adult↗
PubMed1996

Headache characteristics in university undergraduates presenting to medical attention.

A 78-point self-administered questionnaire relating to headaches was completed by 1208 undergraduates of the National University of Singapore. The management and characteristics of the study population that had sought medical consultation for their headaches was studied. The lifetime prevalence of headaches in the study population was 98.1%. One hundred and six (8.8%) had visited a doctor for their headache. These had more severe symptoms and required more pharmacotherapy. They also tended to have migraines rather than tension headaches. Malays were more likely than non-Malays to seek medical attention. No significant gender predisposition was found. Eight of the 106 (7.5%) had been given prophylactic/interval therapy. A significant proportion of the study population responds well to non-prescription medication, suggesting that the purpose of many medical consultations may be to relieve anxieties regarding the diagnosis rather than to obtain symptomatic relief.

Adolescent↗
PubMed1994

Hemangioma of the ethmoidal sinuses.

A report of a rare case of hemangioma of the ethmoidal sinuses with erosion of bony orbital wall and anterior cranial fossa. An outline of the management is presented.

Adult↗
PubMed1993

Langerhans cell histiocytosis presenting as a goitre: a case report.

We report a case of Langerhans cell histiocytosis (histiocytosis X) in a 36-year-old female with an euthyroid nodular goitre as the rare initial presentation. She subsequently developed a pathological fracture of the lumbar spine which was initially thought to be due to malignant infiltration, possibly from metastatic thyroid carcinoma. Open vertebral biopsy and total thyroidectomy were performed. Histological features of histiocytic proliferation with erythrophagocytosis were found in both the thyroid gland and in the involved vertebral body. The diagnosis of histiocytosis X was made on the basis of the positive immunoperoxidase staining of the histiocytic cells with S-100 and peanut agglutinin (PNA) as well as the clinical picture. Despite systemic chemotherapy with low dose corticosteroids and vinblastine, diabetes insipidus with a suprasellar mass occurred three years post thyroidectomy. Successful management of this uncommon disease is difficult to conduct and evaluate at the present time.

Adult↗
PubMed1992

Retrieval of the resilient element in an osseointegrated implant system.

A fractured apical fragment of the resilient intramobile element within the IMZ dental implant cylinder is difficult to remove. The continued usefulness of the implant will be compromised if the fractured intramobile element is not removed. Two methods of retrieving the apical fragment without causing damage to the internal threads of the implant cylinder are described.

Dental Abutments↗
PubMed1992

Soft-tissue cephalometric norms in Chinese adults with esthetic facial profiles.

Using a double selection process comprised of professional and lay judges, the cephalometric tracings on a final sample of 48 Chinese adults with esthetically pleasing profiles were analyzed. The soft-tissue cephalometric norms and standard deviations of two widely accepted soft-tissue analyses, the Legan and Burstone analysis and the Holdaway analysis, were determined. In comparison with white norms, the Chinese nose was less prominent (P < .01), the nasolabial angle was less obtuse (P < .01), both the upper and lower lips were more protrusive (P < .05), the upper lip curvature was greater (P < .01), and the soft-tissue chin thickness was less (P < .05). This variance between racial types emphasizes the need to recognize that soft-tissue lateral cephalometric norms are specific for the racial group and cannot always be applied across different racial types.

Adolescent↗
PubMed1990

Pituitary surgery--a report of 46 cases.

Resection of pituitary adenomas, by the transcranial, or more commonly, by the transsphenoidal approach is an established operation in Singapore. The authors review the results of pituitary surgery in 46 patients over a 7 year period. Forty patients had transsphenoidal surgery. Six patients had transcranial resection of their tumours. There was only one operative mortality and low morbidity. Total macroscopic resection was achieved in all but 7 patients. Eighteen of 21 patients with non-secretory adenomas had radiological evidence of cure. Normalisation of growth hormone levels was achieved in 6 out of 9 acromegalics. Three out of 6 patients with Cushing's disease had normal ACTH following surgery. Only 1 out of 6 patients was cured of her prolactinoma. Vision improved in 16 out of 25 patients with decreased vision preoperatively.

Adenoma↗