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Biomedical subjects

J Y Lim

Publications and source records attributed to J Y Lim.

31 records · Page 2Linked to original sources
PubMed1997

Delayed internal capsule infarctions following radiofrequency pallidotomy. Report of three cases.

The authors report on a series of patients with idiopathic Parkinson's disease (IPD) who underwent stereotactic radiofrequency (RF) pallidotomies, three of whom suffered delayed postoperative strokes. These three belonged to a group consisting of 42 patients with medically intractable IPD in whom 50 pallidotomies were performed. All three patients had significant previous vascular disease and were in a high-risk group for cerebral infarction. A postoperative magnetic resonance (MR) image was obtained immediately after the pallidotomy was performed to document the placement of the RF lesion and to rule out any hematoma. The delayed strokes occurred on postoperative Days 10, 51, and 117 in patients with previous vascular disease (Group 1, 11 patients). No strokes occurred in the group with the vascular disease risk factor (Group 2, 11 patients) or in the group with no risk factors for vascular disease (Group 3, 20 patients). This observation is statistically significant (p < 0.05). The T2-weighted MR images showed the lesions as high-intensity signals extending to the posterior limb of the internal capsule ipsilateral to the pallidotomy site. The poststroke T1-weighted images obtained in two patients showed persistent contrast enhancement of the RF lesion and no enhancement around the stroke lesion. Clinically and radiographically, these discrete new lesions represent delayed infarctions, suggesting that RF lesioning can induce delayed injury in adjacent tissue. Patients with previously identified vasculopathy may be at risk for delayed capsular infarction following RF pallidotomy.

Adult↗
PubMed1996

Structure of catechol 2,3-dioxygenase gene encoded in chromosomal DNA of Pseudomonas putida KF715.

A catechol 2,3-dioxygenase gene in chromosomal DNA of P. putida KF715 was cloned and its nucleotide sequence analyzed. The enzyme gene was composed of 924 base pairs with ATG initiation codon and TGA termination codon, which can encode a polypeptide of molecular weight 35 kDa containing 307 amino acids. A promoter-like sequence and a ribosome-binding sequence were identified upstream the enzyme gene. A deduced amino acid sequence of the catechol 2,3-dioxygenase exhibited 94% identity with that of corresponding enzyme in TOL plasmid and 25% identity with that of 2,3-dihydroxybiphenyl 1,2-dioxygenase from the same strain. Furthermore, sequence comparison of the catechol 2,3-dioxygenase with other extradiol-type dioxygenases has led to identify evolutionally conserved amino acid residues whose possible catalytic roles are proposed.

Amino Acid Sequence↗
PubMed1995

Cloning of salicylate hydroxylase gene and catechol 2,3-dioxygenase gene and sequencing of an intergenic sequence between the two genes of Pseudomonas putida KF715.

The salicylate hydroxylase can convert the salicylate to catechol, and catechol 2,3-dioxygenase catalizes the conversion of catechol to 2-hydroxymuconic semialdehyde. A salicylate hydroxylase gene and a catechol 2,3-dioxygenase have been cloned from chromosomal DNA of P. putida KF715. The two genes have different promoters. An open reading frame with 339 nucleotides preceded by a putative ribosome-binding sequence (GGAGG) was identified in the intergenic sequence between salicylate hydroxylase gene and catechol 2,3-dioxygenase gene of P. putida KF715 and its sequence analyzed. This open reading frame can encode a polypeptide of molecular weight 13 kDa containing 112 amino acids, whose sequence exhibited 87% homology with that of ferredoxin encoded in NAH7 of P. putida PpG7 and significant homology with those of redox components in phenol hydroxylase, benzoate 1,2-dioxygenase, toluate 1,2-dioxygenase, xylene monooxygenase, and toluene 4-monooxygenase.

Amino Acid Sequence↗
PubMed1994

An economic analysis of AIDS--towards a proposed model of costing: a Singapore experience.

With the increasing prevalence of HIV infection/AIDS and the extending range of care and treatment, the economic implications of the various prevention and control strategies, and of treatment, have become the subject of interest to policy-makers, public health specialists and health economists. This paper presents an overview of the methods used for the economic analysis of AIDS/HIV infection. It proposes an activity-oriented, cost center-based model for the costing of the economic impact of AIDS, using cost figures in Singapore since 1985, when the National AIDS Control Program was started. Priorities for future research are also identified.

Acquired Immunodeficiency Syndrome↗
PubMed1993

The attenuation of GABA sensitivity in the maturing myelin-deficient rat optic nerve.

GABA (gamma-aminobutyric acid) can modulate axonal excitability by activating GABAA receptors on some central nervous system axons. The effects of GABA on optic nerve axons decrease significantly during the course of myelination, suggesting that myelination may influence changes in GABA sensitivity. To test this hypothesis, we compared the depolarizing effect of GABA and the GABAA-receptor agonist, muscimol, on optic nerves of myelin-deficient (MD) rats and their unaffected siblings using a modified sucrose-gap technique. Optic nerves from both control and MD rats displayed relatively large GABA-induced depolarizations when studied at an early postnatal period. In both the control and MD rats, the GABA uptake inhibitor nipecotic acid led to a distinct depolarization suggesting endogenous release of GABA. Although the GABA-induced depolarization in the MD rat was significantly greater than that in the control rat at the third postnatal week, the response in the MD rat attenuated with maturation. These results demonstrate that the attenuation of the depolarization induced by GABA and nipecotic acid seen in the normal optic nerve also occurs in the MD rat optic nerve. This suggests that the attenuation of optic nerve sensitivity to GABA is not the result of myelination or interaction with myelin-associated proteins.

Action Potentials↗
PubMed1993

Transient presence of GABA in astrocytes of the developing optic nerve.

Immunostaining and high-pressure liquid chromatography (HPLC) were used to study the developmental time course of astrocytic gamma-aminobutyric acid (GABA) expression in rat optic nerve. GABA immunostaining was carried out on cultured astrocytes, and on whole optic nerve. Confocal scanning laser microscopy was used to obtain optical sections in excised whole tissue in order to localize the cellular origins of GABA within the relatively intact optic nerve. GABA immunoreactivity was localized in astrocytes identified by GFAP staining; GABA staining was most intense in early neonatal optic nerve and attenuated over 3 weeks of postnatal development. The staining was pronounced in the astrocyte cell bodies and processes but not in the nucleus. There was a paucity of GABA immunoreactivity by postnatal day 20, both in culture and in whole optic nerve. A biochemical assay for optic nerve GABA using HPLC indicated a relatively high concentration of GABA in the neonate, which rapidly attenuated over the first 3 postnatal weeks. Immunoreactivity for the GABA synthesis enzyme glutamic acid decarboxylase (GAD) was pronounced in neonates but also attenuated with development. These results indicate that GABA and the GABA synthesis enzyme GAD are localized in astrocytes of optic nerve, and that their expression is transient during postnatal development.

Animals↗
PubMed1993

The effects of extraction versus nonextraction orthodontic treatment on the growth of the lower anterior face height.

The effect of orthodontic treatment on the lower anterior face height (ANS-Me) is of fundamental importance to the orthodontist. However, the choice between the two main methods of treatment, extraction versus nonextraction, is not clear cut. It is believed that the extraction method decreases ANS-Me, whereas nonextraction methods result in an increase in ANS-Me. This study examined the effects of both methods on ANS-Me for a sample of 174 subjects divided equally between Class I and II malocclusions. Most studies controlled for growth by using subjects in the same age group. However, we controlled for the effects of growth by normalizing ANS-Me measurements to the Michigan Growth Standard. With this method, we can compare subjects who differ in terms of the age at which treatment was started, as well as subjects whose treatments were of different duration, thereby enlarging the sample size. In addition to growth and duration of treatment, other factors like the effects of treatment choice and treatment mechanics were considered. The results obtained show that nonextraction treatment in Class I and II subjects is associated with a significant increase in the lower anterior face height. However, extraction treatment is not associated with any significant change in ANS-Me.

Adolescent↗
PubMed1993

Condom knowledge, attitudes and use among patients attending the public STD clinic in Singapore.

Three hundred patients (255 males and 45 females) attending the public STD clinic in Singapore were interviewed regarding their frequency of condom use, attitudes towards condoms, problems related to condom use and places of purchase of the condoms. Among respondents with regular partners, 55.2% of males and 48.8% of females never used condoms, only 12.4% of males and 16.3% of females used condoms consistently. Among respondents with non-regular partners, only 2.2% of males used condoms consistently. The commonest reasons why male respondents did not use condoms consistently were that condoms decreased sensation, condoms made sex mechanical, the use of other forms of contraception, no condoms were available, and the perception that there was no risk of contracting STD/AIDS. Condoms were most commonly obtained from sex partners, supermarkets, roadside sundry shops and the Maternal & Child Health Clinics (MCHCs). About 8% of both males and females had experienced some problems with condoms before. Greater efforts to promote the practice of protected intercourse among the STD patient population as well as in the general population are required in order to control the spread of STD and AIDS in Singapore.

Adult↗
PubMedDate not supplied

Acute sensory neuronopathy: identified with electrodiagnosis and magnetic resonance imaging.

We report on a 13-year-old female with idiopathic acute sensory neuronopathy mimicking a sensory form of Guillain-Barré syndrome, which was identified by using electrodiagnosis and spine magnetic resonance imaging. Motor conduction results were normal, but no sensory nerve action potentials were seen in the four limbs. On magnetic resonance imaging of the whole spine, the diffuse gadolinium enhancement of the dorsal roots in the spinal canal was detected, without evidence of intramedullary lesions. The clinical symptoms and electrodiagnostic findings had persisted for more than 18 months of follow-up.

Adolescent↗
PubMedDate not supplied

Factors associated with sexually transmitted diseases among prostitutes in Singapore.

From June to December 1990, 806 prostitutes registered with the STD programme in Singapore for regular screening for sexually transmitted diseases (STD) were investigated for factors associated with STD incidence in the preceding year. The majority were foreigners (92.7% Malaysians and 3.1% Thais). Anal sex (0.4%) and intravenous drug use (0.9%) were rare. The overall STD incidence rate was 47.7 per 100. None was human immunodeficiency virus (HIV) positive. The crude and age-adjusted risk of STD was found to increase significantly with client load. An inverse relationship between condom use and STD risk was also observed. Mean condom use among clients was reported as 56.1% for spontaneous use and estimated as 75.4% following negotiation for condom use by prostitutes. Although the prostitutes negotiated for condom use with majority of the clients (85.5%) who did not use condoms spontaneously, they were successful with only about half of them (54.4%). Health education should be targeted at clients on the protective effects of condom use and at the prostitutes on skills in negotiating condom use.

Adult↗
PubMedDate not supplied

Bone marrow necrosis: an entity often overlooked.

Bone marrow necrosis is a poorly understood and frequently an unrecognized finding in routine bone marrow biopsies. Previous reports indicate the incidence of bone marrow necrosis ranges from 0.5 percent (rare) to approximately one-third of all bone marrow biopsies examined. Our studies indicate that the presence of bone marrow necrosis depends on the clinical condition of the patient. Overall, our incidence of bone marrow necrosis was 37 percent of the bone marrow biopsies examined. Of these, 26.4 percent was mild. 7.5 percent moderate, and 3.1 percent severe necrosis. The mechanism in most cases had an identifiable underlying etiology such as a malignancy, or vascular or cytotoxic damage, with a small percentage being unexplained. Bone marrow necrosis is seen across a wide range of conditions, including sickle cell diseases, AIDS, leukemia, lymphoma, metastatic carcinoma, anemia, sepsis, and other systemic diseases. Patients at the extremes of age, less than 20 years and greater than 70 years, usually demonstrate only small foci of necrosis (Grade I). Moderate (Grade II) and severe (Grade III) bone marrow necrosis are often associated with life threatening illnesses, with most of these being hematologic malignancies or bone marrow metastases. The prognosis associated with bone marrow necrosis seems to be dependent on the underlying primary clinical condition regardless of the degree of necrosis observed.

Adult↗