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Biomedical subjects

K H Lim

Publications and source records attributed to K H Lim.

At least 73 records · Page 4Linked to original sources
PubMed1997

Improvements in visual acuity following limbal lensectomy for subluxated lenses in children.

BACKGROUND AND OBJECTIVE: To report the surgical results of limbal lensectomy using an automated vitrectomy instrument for the treatment of subluxated lenses in children. PATIENTS AND METHODS: The authors reviewed the charts of children who underwent surgery for subluxated lenses. Limbal lensectomies with an "in the bag" technique were performed on 18 eyes of 10 patients. The indications for surgery were a best-corrected visual acuity of less than 20/60, bisection of pupil by the lens, or both. RESULTS: Best-corrected visual acuity improved in all 18 eyes (paired t test, P < .01). In 1 eye, transient anterior chamber hyphema occurred during the early postoperative period. No other significant complications were found during an average follow-up of 19.6 months. CONCLUSION: Limbal lensectomy for subluxated lenses in children improved visual acuity without severe complications.

Adolescent↗
PubMed1996

Spectroscopic and elemental investigation of microbial decomposition of aquatic fulvic acid in biological process of drinking water treatment.

As humic substances left in treated water tend to form trihalomethans during chlorination, their removal in water treatment processes is a significant concern for drinking water supplies. One of the removal technologies, the biofilm reactor is studied for the microbial decomposition of aquatic fulvic acid (AFA). The AFA is characterized by elemental analysis. UV-Vis, 13C-NMR, and IR spectroscopic methods. The spectroscopic and elemental investigation was capable of characterizing the microbial decomposition of AFA. Biologically treated fulvic acid was in a more oxidized state; its spectra displayed a higher degree of condensation of aromatic constituents than influent fulvic acid. Microbial degradation of AFA was more active in the low molecular weight fractions and intensively occurred in the aliphatic fraction.

Benzopyrans↗
PubMed1996

Surgical management for persistent pupillary membrane with vitreous scissors.

Persistent pupillary membranes are common congenital disorders. To reduce the surgical complications, we used vitreous scissors instead of conventionally used Vannas scissors to remove the membrane and reviewed the surgical results. Five eyes of 4 children with persistent pupillary membrane were treated by surgery. Through the 1.5 mm limbal incision, the membrane was removed by using vitreous scissors after intracameral sodium hyaluronate. After 22.6 months follow-up, all pupils of operated eyes were round and no complications associated with the surgery were found. Three eyes showed improved visual acuities after the operation. We suggest that the surgery with vitreous scissors is better than with Vannas scissors.

Anterior Chamber↗
PubMed1996

Simulated bleeding--a forgotten disease in a land of plenty.

The human body is unable to synthesise Vitamin C and a diet deficient in Vitamin C leads to scurvy. Scurvy may mimic other medical conditions, like bleeding diasthesis or deep vein thrombosis, leading to delay in diagnosis and treatment, thus prolonging sufferings of patients. Often, scurvy could have been diagnosed if it is thought of and features of scurvy carefully looked for. Scurvy is easily treated with high dose of oral vitamin C. Recurrences may occur. Education of care providers cannot be overemphasised. We report three local cases of scurvy to highlight the existence of the disease in our modern society.

Adult↗
PubMed1996

Global blindness and the nation.

In this presentation, the major causes of blindness and blindness according to geographical regions are considered. World blindness has become a global problem and is different in various regions of the Third World. The problems of the developing countries require individual solutions. Prevention of blindness in Singapore and around the region is considered from a local perspective. A national consciousness that involves every ophthalmologist is required, just as every individual has a contribution to make towards the prevention of blindness.

Blindness↗
PubMed1995

Human placental HLA-G expression is restricted to differentiated cytotrophoblasts.

Human placental trophoblasts lie at the maternal-fetal interface, a position in which they could play an important role in maternal tolerance of the fetal semi-allograft. Central to this hypothesis is their unusual MHC class I expression: they suppress class Ia production while expressing HLA-G, a class Ib molecule. We investigated human trophoblast HLA-G protein production in vivo and in vitro. We first used a synthetic peptide corresponding to the variable sequence of the alpha 1 domain to produce mAbs that recognized HLA-G. Ab specificity was demonstrated by immunoaffinity purification of a single protein with the same molecular mass (38 kDa) as HLA-G from choriocarcinoma cells. Use of these Abs to stain tissue sections of the maternal-fetal interface containing cytotrophoblasts in all stages of differentiation showed that HLA-G is expressed only by cytotrophoblasts that invade the uterus. Our previous in vitro studies showed that when early-gestation cytotrophoblast stem cells are cultured, they differentiate rapidly along the invasive pathway, as demonstrated by their expression of stage-specific markers. Here we show they also up-regulate HLA-G production. Cytotrophoblasts from term placentas, which have reduced invasive capacity in vitro, also had decreased ability to up-regulate HLA-G protein expression. We detected high levels of HLA-G mRNA in cytotrophoblasts isolated from first- and second-trimester placentas, but only trace amounts in term cells. Taken together, these results suggest that HLA-G production is a critical component of cytotrophoblast differentiation along the invasive pathway.

Amino Acid Sequence↗
PubMed1995

Plasma type II phospholipase A2 levels are elevated in severe preeclampsia.

OBJECTIVE: Our purpose was to compare plasma concentrations of type II phospholipase A2 in normal and preeclamptic pregnancies and to determine whether plasma from preeclamptic patients increases endothelial cell secretion of type II phospholipase A2. STUDY DESIGN: We compared the plasma levels of type II phospholipase A2 in 23 patients with normal pregnancies and 25 patients with strictly defined preeclampsia. Plasma samples were collected throughout pregnancy and stored at -80 degrees C. Patients with preeclampsia were matched closely as possible with controls for maternal age, race, gestational age at blood sampling, and parity. Plasma levels of type II phospholipase A2 were measured by enzyme immunoassay. To investigate endothelial cell type II phospholipase A2 production, we measured levels of prostacyclin and type II phospholipase A2 in conditioned media from cultured human umbilical vein endothelial cells exposed to plasma from preeclamptic and normal pregnant patients. RESULTS: The mean plasma type II phospholipase A2 level in the mild preeclampsia group (6.1 +/- 3.0 ng/ml, n = 6) was not different from that in control patients (6.0 +/- 3.2 ng/ml, n = 23). However, the mean type II phospholipase A2 level in patients with severe preeclampsia (19.9 +/- 12.3 ng/ml, n = 19) was significantly higher when compared with the other two groups (p < 0.001). Prostacyclin concentrations in conditioned media of endothelial cells exposed to plasma from patients with preeclampsia were elevated compared with cells incubated with control plasma (8.6 +/- 1.7 vs 4.0 +/- 5.0 ng/ml, p < 0.05). However, the concentration of type II phospholipase A2 in conditioned medium was not significantly different (1.6 +/- 0.3 vs. 1.8 +/- 1.0 ng/ml, p = 0.40). CONCLUSIONS: Plasma concentrations of type II phospholipase A2 are elevated in preeclampsia and correlate well with the severity of disease. Plasma from preeclamptic women increased secretion of prostacyclin, but not type II phospholipase A2 by endothelial cells in culture.

Case-Control Studies↗
PubMed1995

Aqueous shunts: single-plate Molteno vs ACTSEB.

A retrospective study was done to compare the results of the single-plate Molteno implant surgery with those of the anterior chamber tube shunt to an encircling band procedure in eyes with refractory glaucoma. Both Molteno implant and anterior chamber tube shunt to an encircling band are made of silicone. There were 19 eyes in the Molteno group, 17 eyes in the anterior chamber tube shunt to an encircling band group, with at least 6 months of follow-up. Preoperative intraocular pressure in the Molteno group and anterior chamber tube shunt to an encircling band group was 47.5 +/- 11.4 and 46.5 +/- 10.3 mmHg, respectively. Intraocular pressure at 6 months postoperatively was 20.4 +/- 15.1 and 15.5 +/- 10.4 mmHg, respectively. The difference in pressure reduction between the two groups was not significant statistically. Serious complication rate for 6 months was 11% and 47%, respectively.

Anterior Chamber↗
PubMed1994

MDR1 gene expression: its effect on drug resistance to doxorubicin in human hepatocellular carcinoma cell lines.

BACKGROUND: Hepatic tumors are resistant to many chemotherapeutic agents. Although elevated MDR1 (also known as PGY1) gene expression has been shown in such tumors, no direct association has been established between the gene expression and multidrug resistance. PURPOSE: To evaluate the role of the MDR1 gene in the drug resistance of hepatoma, we tested nine human hepatoma cell lines for their expression of the MDR1 gene. METHODS: We measured the MDR1 messenger RNA (mRNA) expression by RNA slot-blot analysis and by immunocytochemical staining with a P-glycoprotein-specific monoclonal antibody, MRK16. The in vitro chemosensitivity of these cell lines to fluorouracil, doxorubicin, mitomycin C, cisplatin, and etoposide (VP-16) was determined using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) colorimetric assay. For doxorubicin cytotoxicity, we also tested the potentiating effect of several multidrug resistance-reversing agents. RESULTS: Slot-blot analysis and immunocytochemistry showed that two cell lines expressed high levels of MDR1 mRNA, one expressed an intermediate level, and all others were low expressors. The MTT assay results showed that all cell lines tested were generally resistant to chemotherapeutic agents. The assay area under the curve (AUC) was within a clinically achievable range only for VP-16 in one of nine cell lines. When the IC50 values were compared among the cell lines, the results revealed a close association with the MDR1 gene expression only for doxorubicin resistance. Verapamil and quinidine lowered the IC50 values of doxorubicin for MDR1-positive cell lines. The lowered assay AUC levels for both reversing agents, however, were still higher than the clinically achievable range. CONCLUSION: These results indicate that the MDR1 gene probably has a role in doxorubicin resistance in hepatocellular carcinoma and that the resistance can be overcome by some multidrug resistance-reversing agents. IMPLICATIONS: Some widely used anticancer agents might be ineffective for treating hepatocellular carcinoma in clinical situations even when combined with reversing agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Integrin switching regulates normal trophoblast invasion.

Cells invade extracellular matrices in a regulated manner at specific times and places during normal development. A dramatic example is trophoblast invasion of the uterine wall. Previous studies have shown that differentiation of trophoblasts to an invasive phenotype is accompanied by temporally and spatially regulated switching of their integrin repertoire. In the first trimester human placenta, alpha 6 integrins are restricted to cytotrophoblast (CTB) stem cells and downregulated in invasive CTBs, whereas alpha 5 beta 1 and alpha 1 beta 1 integrins are upregulated in differentiating and invasive CTBs. The goal of the present study was to determine whether these changes have functional consequences for CTB invasiveness. Using an in vitro invasion model, we determined first that aggregates of invading first trimester CTBs in vitro undergo the same pattern of integrin switching as was observed in situ, thereby validating the utility of the model. We then showed that antibody perturbation of interactions involving laminin or collagen type IV and their integrin alpha 1/beta 1 receptor inhibited invasion by CTBs, whereas perturbing interactions between fibronectin and the alpha 5/beta 1 fibronectin receptor accelerated invasion. Finally, we report that later gestation CTBs, which display greatly decreased invasive capacity, are also unable to upregulate alpha 1 beta 1 complexes, providing further evidence that this integrin is critical for CTB invasion. This gestational regulation is transcriptional. These data indicate that integrin switching observed during differentiation in situ has significant functional consequences for CTB invasion. The data suggest further that differentiating CTBs upregulate counterbalancing invasion-accelerating and invasion-restraining adhesion mechanisms. We propose that this contributes to regulating the depth of CTB invasion during normal implantation.

Blotting, Northern↗
PubMed1993

Phenytoin versus magnesium sulfate in preeclampsia: a pilot study.

A randomized clinical trial was designed to determine whether there are clinically demonstrable advantages of phenytoin over magnesium sulfate in preeclamptic patients because of the latter drug's uterine relaxant properties. An intravenous infusion, immediately after randomization, of either phenytoin or magnesium sulfate, with subsequent measurement of serum concentrations and maintenance of therapeutic levels was given to 103 preeclamptic and two eclamptic women. Observed were the rate of cervical dilation during active labor and change in hematocrit between predelivery and 24-hour postdelivery values and the incidence of side effects ascertained by interview. Compared with those receiving magnesium sulfate, patients receiving phenytoin had more rapid cervical dilation (3.3 cm/hr versus 1.5 cm/hr, p = 0.016) and a smaller fall in hematocrit after delivery (-4.7% versus -7.6%, p = 0.034). A significantly lower incidence of hot flushes (15% versus 46%, p < 0.005) and a trend toward less dyspnea and weakness were reported by phenytoin-treated patients. Our phenytoin regimen produced acceptable serum phenytoin levels (10 to 25 micrograms/ml) in 96% of patients.

Adult↗
PubMed1993

Massive haemothorax as a complication of primary lung cancer--a case report.

A 58-year-old man was admitted with a massive haemothorax. At thoracotomy, the cause was found to be due to a bleeding primary lung cancer, the cell type of which was adenocarcinoma. A literature search revealed that this complication of lung cancer has not previously been described. Reasons as to the infrequency of this complication are discussed.

Adenocarcinoma↗
PubMed1993

Poisons information in Singapore.

The Poisons Information Centre (PIC) provides viral and timely information to prevent and manage poisoning episodes. Comprehensive information on household, agricultural and industrial chemicals, natural toxins, pharmaceuticals, local antidote stocks and local poisons experts is retrieved from the Centre's computerised information system and printed literature. Public subscribers can obtain poisons information through Teleview.

Adult↗
PubMed1993

Hypertension in pregnancy.

Selected articles on hypertensive diseases in pregnancy from the past year are highlighted. The concept that endothelial cell dysfunction plays an important role in the pathogenesis of preeclampsia has been strengthened. The initial inciting event is still unclear, but inadequate implantation and decreased antioxidant activity may play a role. Magnesium sulfate is still the anticonvulsant of choice for seizure prophylaxis, but the exact mechanism of its action remains controversial. The ideal screening test to identify those patients likely to develop preeclampsia is still lacking, and the side effects and risks of aspirin prophylaxis are not yet known. The results from the National Institutes of Health-sponsored multicenter trial on this subject should be forthcoming.

Female↗
PubMed1991

Analysis of T cell reactivities to phosphorylcholine-conjugated hen egg lysozyme in C57BL/6 mice: hapten-conjugate specificity reflects an altered expression of a major carrier epitope.

We have selected several different T cell hybridoma clones reactive to hen egg lysozyme (HEL) conjugated to phosphorylcholine (PC) after fusion of PC-HEL-primed C57BL/6 lymphocytes with BW5147 parent cells. These hybridoma clones preferentially recognize PC-HEL over unconjugated HEL, but not other carrier molecules conjugated with the same hapten. All the PC-HEL-reactive clones are similarly responsive to not only p-azobenzenearsonate (ABA)-conjugated HEL (ABA-HEL) but also to a variety of other diazotized hapten-HEL conjugates. However, these clones are not stimulated by fluoresceinated or dinitrophenylated HEL beyond the level of HEL carrier alone. Therefore, the type of hapten linkage (diazonium) to the carrier molecule appears to affect T cell recognition. The hybridoma clones apparently recognize the carrier molecule alone, although the level of stimulation is relatively low compared to that induced by either PC-HEL or ABA-HEL. Interestingly, HEL unfolded by S-carboxymethylation is capable of stimulating the hybridomas to a level comparable to that obtained with PC-HEL. T cell recognition of the unfolded HEL is independent of antigen processing, which is different from that of PC-HEL. The peptide sequence corresponding to the amino acids 81-93 of HEL appears to contain the epitope region for the hybridoma clones based on testing stimulation activity with synthetic peptides. Previously, the peptides including this region (81-96) have been reported as the determinant recognized by T cells derived from C57BL/6 mice after immunization with an HEL peptide (HEL 13-105) but not with native HEL. These results suggest that a hapten conjugation via diazonium linkage modifies antigen presentation and consequently the presentation of the major T cell epitopes similar to that of the HEL fragment.

Animals↗
PubMed1991

Hemangiopericytoma of the lacrimal sac.

Hemangiopericytomas are soft tissue tumors composed of pericapillary pericytes. These tumors are rare in the lacrimal sac. To the author's knowledge, only four previous cases of these tumors occurring in the lacrimal sac have been reported. A primary hemangiopericytoma of the lacrimal sac in a 34-year-old female is reported. Total excision with the surrounding tissue appears to be the treatment of choice for this tumor.

Adult↗