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Biomedical subjects

S T Lim

Publications and source records attributed to S T Lim.

At least 55 records · Page 3Linked to original sources
PubMed2000

Technetium-99m MDP bone scintigraphic findings of hypercalcemia in accelerated phase of chronic myelogenous leukemia.

Hypercalcemia in accelerated phase of chronic myelogenous leukemia (CML) is very rare. Its pathogenesis is considered humoral hypercalcemia of malignancies mediated by parathyroid hormone-related protein (PTHrP). In severe hypercalcemia, calcifications in kidneys, skin, vessels, heart, and stomach may occur. Our two cases were admitted because of severe hypercalcemia in accelerated phase of CML. On Tc-99m methylene diphosphonate (MDP) bone scintigraphies, a marked tracer accumulation was seen in the lung, heart, stomach and kidney. We report increased tracer accumulation of multiple organs on Tc-99m MDP bone scintigraphy in two rare hypercalcemic patients with CML.

Adult↗
PubMed1999

Interstitial deletion of chromosome 5 in a neonate due to maternal insertion, ins(8;5)(p23;q33q35).

We describe an infant girl with an interstitial deletion of chromosome bands 5q33 to 5q35 inherited from a maternal interchromosomal insertion ins(8;5)(p23;q33q35) which was demonstrated by fluorescent in situ hybridization with whole chromosome paints. Physical anomalies included hypertonicity, microcephaly, short neck, apparently low-set ears, micrognathia, camptodactyly, mild rocker bottom feet, and hammer toe. Cardiac anomalies included a large ventricular septal defect, patent ductus arteriosus, pulmonary hypertension and hypoplastic right ventricle. She died at age 3 months.

Abnormalities, Multiple↗
PubMed1999

Changes in refraction and axial length according to the viscosity of intraocular silicone oil.

We performed this study to evaluate the changes in refraction and axial length induced by intraocular silicone oil, and to compare with various clinical parameters between 1,000 and 5,000 cSt silicone oil. The refraction length was measured with an autorefractometer, and the axial length was measured with A-scan ultrasonography. These measurements were performed before and after removal of the silicone oil, using a clear cornea technique in which the silicone oil was injected in combination with pars plana vitrectomy. The mean age of the 25 patients was 38.73 years. On average the intraocular retention after the removal of the silicone oil lasted 5.13 months, and the follow-up time following silicone oil removal was 4.37 months. The changes in refraction and axial length were 6.32 diopters and 12.02 mm, respectively. Eyes injected with 5,000 cSt (11 eyes) tended to have higher changes in the refraction (5.84 vs 6.86 diopters) and axial length (11.70 vs 12.34 mm) than did eyes injected with 1,000 cSt silicone oil (14 eyes). Statistically significant differences were shown for the changes in refraction (p = 0.010) and intraocular pressure (0.63 vs 2.00 mmHg; p = 0.006), whereas but not for the changes in axial length (p = 0.306) and visual acuity (14/100 vs 15/100; p = 0.125). Intraocular silicone oil induced changes in refraction and axial length, and these changes seemed to vary with different viscosities.

Adolescent↗
PubMed1999

Uvulo-palatoglossal junctional ulcers--an early clinical sign of exanthem subitum due to human herpesvirus 6.

A provisional clinical diagnosis of exanthem subitum was made in six febrile infants seen in the Paediatric Unit of Assunta Hospital, Petaling Jaya, Malaysia with uvulo-palatoglossal junctional ulcers prior to the eruption of maculopapular rash. On follow-up, all six infants developed maculopapular rash with the subsidence of fever at the end of the fourth febrile day. Human herpesvirus 6 was isolated from the peripheral blood mononuclear cells during the acute phase of the illness and HHV 6 specific genome was also detected in these cells by nested polymerase chain reaction. All the six infants showed seroconversion for both specific IgG and IgM to the isolated virus. This study suggests that the presence of uvulo-palatoglossal junctional ulcers could be a useful early clinical sign of exanthem subitum due to human herpesvirus 6.

Exanthema Subitum↗
PubMed1998

A spheroplast rate assay for determination of cell wall integrity in yeast.

The rate of formation of spheroplasts of yeast can be used as an assay to study the structural integrity of cell walls. Lysis can be measured spectrophotometrically in hypotonic solution in the presence of Zymolyase, a mixture of cell wall-digesting enzymes. The optical density of the cell suspension decreases as the cells lyse. We optimized this assay with respect to enzyme concentration, temperature, pH, and growth conditions for several strains of Saccharomyces cerevisiae. The level of variability (standard deviation) was 1-5% between trials where the replications were performed on the same culture using enzyme prepared from the same lot, and 5-15% for different cultures of the same strain. This assay can quantitate differences in cell wall structure (1) between exponentially growing and stationary phase cells, (2) among different S. cerevisiae strains, (3) between S. cerevisiae and Candida albicans, (4) between parental and mutated lines, and (5) between drug- or chemically-treated cells and controls.

Anti-Bacterial Agents↗
PubMed1998

Syndecan-4 proteoglycan cytoplasmic domain and phosphatidylinositol 4,5-bisphosphate coordinately regulate protein kinase C activity.

Phosphatidylinositol 4,5-bisphosphate (PIP2) is involved in the organization of the actin cytoskeleton by regulating actin-associated proteins. The transmembrane heparan sulfate proteoglycan syndecan-4 also plays a critical role in protein kinase C (PKC) signaling in the formation of focal adhesions and actin stress fibers. The cytoplasmic domain of syndecan-4 core protein directly interacts with and potentiates PKCalpha activity, and it can directly interact with the phos- phoinositide PIP2. We, therefore, investigated whether the interaction of inositol phosphates and inositol phospholipids with syndecan-4 could regulate PKC activity. Data from in vitro kinase assays using purified PKCalpha beta gamma show that in the absence of phosphatidylserine and diolein, PIP2 increased the extent of autophosphorylation of PKCalpha beta gamma and partially activated it to phosphorylate both histone III-S and an epidermal growth factor receptor peptide. This activity was dose-dependent, and its calcium dependence varied with PKC isotype/source. Addition of the cytoplasmic syndecan-4 peptide, but not equivalent syndecan-1 or syndecan-2 peptides, potentiated the partial activation of PKCalpha beta gamma by PIP2, resulting in activity greater than that observed with phosphatidylserine, diolein, and calcium. This study indicates that syndecan-4 cytoplasmic domain may bind both PIP2 and PKCalpha, localize them to forming focal adhesions, and potentiate PKCalpha activity there.

Amino Acid Sequence↗
PubMed1998

Cloning and sequencing of the celA gene encoding CMCase of Erwinia carotovora subsp. carotovora LY34.

The phytopathogenic Erwinia carotovora subsp. carotovora LY34 secretes multiple isozymes of the plant cell wall-disintegrating enzyme, endoglucanases. Genomic DNA from Ecc LY34 was digested with Sau3AI and ligated into the BamHI site of pBluescript II SK+. One of the E. coli clones containing a Sau3AI fragment of Ecc genomic DNA hydrolyzed carboxymethyl cellulose and was shown to contain the 2.2 kb BamHI restriction fragment, which was subcloned to generate pLYCA100 named as celA. The structural organization of a celA gene encoding 387 amino acids consists of an open reading frame (ORF) of 1161 bp starting with an ATG start codon and followed by a TAA stop codon. CelA protein contained a typical catalytic domain, interdomain, cellulose binding domain, and prokaryotic signal peptide of 32 amino acids. Since the deduced amino acid sequences of CelA protein was very similar to those of CelV of Erwinia carotovora subsp. carotovora SCC3193 enzyme and to those of CelN of Erwinia atroceptica enzyme, it belongs to the cellulase family 5. The apparent molecular mass of CelA protein was calculated to be 39 kDa by carboxymethylcellulose-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (CMC-SDS-PAGE). Activity staining of carboxymethyl cellulase (CMCase) in sodium dodecyl sulfate polyacrylamide gel containing 0.1% CMC revealed that the cloned isozyme comigrated with a corresponding isozyme produced by Ecc LY34. The CelA had a calculated pI of 5.42. The optimum pH was 7 and the optimum temperature was about 45 degrees C.

Amino Acid Sequence↗
PubMed1998

What constitutes a normal seminal analysis? Semen parameters of 243 fertile men.

A cross-sectional study was conducted to determine the semen parameters (i.e. volume, concentration, motility, viability and normal morphology) of proven fertile males in Singapore and compare it with the World Health Organization (WHO) recommended normal values and to examine some factors that may affect spermatogenesis. A total of 243 men, whose wives were pregnant at the time of collection of semen, provided a semen sample each after sexual abstinence for 3 days. A questionnaire was used to elicit occupational exposure, alcoholic consumption, smoking history and past significant medical history. Most subjects had normal sperm volume (56.4%), concentration (79.8%), motility (69.5%) and viability (53.5%) based on WHO criteria. However, fertile men had a low mean percentage of normal sperm morphology (20.0%), although they were normally distributed. Cigarette smoking was associated with significantly lower semen volumes even after adjusting for alcohol consumption. The sperm parameters (i.e. volume, density, motility, viability and normal morphology) were not significantly associated with ethnic differences. The WHO criterion for normal sperm morphology is too stringent, and should be adopted with caution. Normal sperm morphology is but one of many parameters for assessment of fertility. Social alcohol consumption, cigarette smoking, and 'recent fever' did not appear to affect sperm quality in this group of fertile men.

Adult↗
PubMed1997

Characterization of Erwinia carotovora subsp. carotovora LY34 endo-1,4-beta-glucanase genes and rapid identification of their gene products.

Genomic DNA of the phytopathogenic Erwinia carotovora subsp. carotovora LY34 was partially digested with Sau3AI, ligated into the BamHI site of pBlue-script II SK+, and introduced into E. coli. Two clones that were able to hydrolyse carboxymethylcellulose were selected. 1.5 kb and 1.2 kb fragments containing the celA and celB genes, respectively, were subcloned and sequenced. The celA and celB genes had open reading frames of 1,161 bp and 792 bp encoding 487 and 264 amino acid residues with calculated molecular weights of 42,003 Da and 29,890 Da, respectively. Each, CelA and CelB, carried a typical prokaryotic signal peptide of 32 and 36 amino acid residues, respectively. The apparent molecular masses of the proteins when expressed in E. coli cells were approximately 39 kDa (CelA) and 26 kDa (CelB) as assessed by CMC-SDS-PAGE. Activity staining of CMCase in an SDS-PAGE gel containing 0.1% CMC revealed that the cloned endoglucanase isozymes comigrated with the corresponding ones present in Erwinia carotovora subsp. carotovora LY34.

Amino Acid Sequence↗
PubMed1997

Percutaneous transluminal coronary angioplasty in Singapore General Hospital in 1995: a medical audit.

BACKGROUND: There are few reports which describe the outcomes of unselected groups of patients undergoing percutaneous transluminal coronary angioplasty (PTCA) locally. This study has undertaken to audit the outcome of patients undergoing elective PTCA at Singapore General Hospital. METHODS: Procedural data and acute outcomes were recorded prospectively in all patients undergoing PTCA over a 12 month period. A retrospective casenotes review of all patients were carried by independent observers to determine out-of-lab complications. RESULTS: Seven hundred and eight-two patients underwent PTCA in 1995. Acute angiographic success rate was 90.9% and early clinical success rate was 89% ie excluding death, coronary bypass surgery and non fatal myocardial infarction. There were only two deaths in the series (0.26%). CONCLUSION: The audit confirms the importance of a high volume PTCA cases to achieve excellent results. The data serve as a useful background for future comparison of outcomes.

Aged↗
PubMed1996

An unusual case of ruptured aneurysm of sinus of Valsalva.

Ruptured congenital aneurysms of the noncoronary aortic sinus shunting into both the right atrium and right ventricle are extremely rare. We present here such an anomaly in a 40-year-old man, focusing on the diagnostic reliability of echocardiography and the unusual angiographic features of the aortic sinus aneurysm in this patient.

Adult↗
PubMed1995

Oxidative cell wall damage mediated by bleomycin-Fe(II) in Saccharomyces cerevisiae.

Bleomycin mediates cell wall damage in the yeast Saccharomyces cerevisiae. Bleomycin treatments in the presence of Fe(II) increased the rate of spheroplast formation by lytic enzymes by 5- to 40-fold. Neither Fe(III) nor other tested ions caused significant cell wall damage in the presence of bleomycin. The effect of bleomycin-Fe(II) on the cell wall mimicked the characteristics of bleomycin-Fe(II)-mediated DNA damage in dependence on aeration, inhibition by ascorbate, and potentiation by submillimolar concentrations of sodium phosphate. Bleomycin-mediated cell wall damage was time and dose dependent, with incubations as short as 20 min and drug concentrations as low as 3.3 x 10(-7)M causing measurable cell wall damage in strain CM1069-40. These times and concentrations are within the range of effectiveness for bleomycin-mediated DNA damage and for the cytotoxicity of the drug. Although Fe(III) was inactive with bleomycin and O2, the bleomycin-Fe(III) complex damaged walls and lysed cells in the presence of H2O2. H2O2 causes similar activation of bleomycin-Fe(III) in assays of DNA scission. These results suggest that an activated bleomycin-Fe-O2 complex disrupts essential cell wall polymers in a manner analogous to bleomycin-mediated cleavage of DNA.

Bleomycin↗
PubMed1994

A novel strong promoter of the groEx operon of symbiotic bacteria in Amoeba proteus.

Gram- symbiotic bacteria (called X-bacteria), present in the xD strain of Amoeba proteus as required cell components, contain a large amount of a 67-kDa protein, a GroEL analog. The complete nucleotide (nt) sequence of the groEx operon of X-bacteria has been determined and it has a high degree of nt identity with those of other bacterial groE operons. The groELx gene is expressed in transformed Escherichia coli and has a novel and potent promoter (P2) in addition to the heat-shock consensus promoter (P1). This is shown by the production of GroELx in Escherichia coli transformed with modified DNA clones lacking P1 and by an enhanced production of a GroELx::beta-galactosidase fusion protein when a portion of groEx containing P2 is linked to the lacZ gene. Primer-extension analyses revealed the presence of possible P2 sequences within the open reading frame of the groESx gene. It is suggested that the presence of a potent P2 in the X-bacterial gene is an adaptation for the endosymbiotic bacteria to survive within a potentially hostile intracellular environment.

Amino Acid Sequence↗
PubMed1993

Rapid detection of cymbidium mosaic virus by the polymerase chain reaction (PCR).

A direct, simple and sensitive method was developed for the detection of cymbidium mosaic virus (CyMV), based on the polymerase chain reaction (PCR). Two oligonucleotide primers were selected from regions that are homologous to potexviruses and CyMV, and used to hybridize with purified viral RNA and particles. This resulted in the amplification of a 313 bp fragment after 30 cycles of PCR in all samples. A less prominent fragment of 227 bp was also obtained due to mispriming of the second primer. The amplified fragments were easily seen in an agarose gel when stained with ethidium bromide. As little as 1 fg of viral RNA (about 200 target copies) or 10 fg of purified virus (approximately 130 viral particles) were detectable. For CyMV infected orchid leaf tissues, 10 microliters aliquots of 1 mm3 tissue homogenate in 1 ml could be detected routinely. All reverse transcription and amplification reactions were carried out in a single tube and results can be obtained within 5 h.

Base Sequence↗
PubMed1993

Long-term results of antral gastrocystoplasty.

Long-term results of gastrocystoplasty had not been reported in the literature. The results of 10 patients (7 augmentation and 3 replacement) during 15 years were reviewed. All patients voided spontaneously and achieved daytime continence. Enuresis occurred in 3 patients. Median peak flow rate and post-void residual urine were 16.0 ml. per second and 10 ml., respectively. Average cystometric capacity was 554 ml. and median pressure at full capacity was 46 cm. water. Phasic contractions resulted in pressures higher than 50 cm. water in 4 patients. Small capacity, absence of bladder sensation and high pressure were identified as risk factors for a poor result. Routine urine culture was positive in 20.5%. Urine mucus content remained low. Electrolyte disturbance, histopathological abnormalities and ulcer syndrome related to hypergastrinemia were absent. The data showed that antral gastrocystoplasty is superior because of the low infective complication rate, ability to empty and absence of metabolic disturbance.

Adult↗
PubMed1993

Bleomycin affects cell wall anchorage of mannoproteins in Saccharomyces cerevisiae.

Bleomycin induces strand breakage in DNA through disruption of glycosidic linkages. We investigated the ability of bleomycin to damage yeast cell walls, which are composed primarily of carbohydrate. Bleomycin treatment of intact yeast cells facilitated enzymatic conversion of yeasts to spheroplasts. Bleomycin treatment also altered anchorage of mannoproteins to the cell wall matrix in intact cells or isolated cell walls. Cell surface mannoproteins were labelled with 125I, and their solubilization was monitored. Seventeen hour treatments with bleomycin released some of the label directly into treatment supernatants and facilitated extraction of mannoproteins by dithiothreitol and lytic enzymes. Bleomycin treatments as short as 10 min caused changes in extraction of mannoproteins from intact cells. Specifically, cell wall anchorage of several mannoproteins was affected by the drug. There were drug-induced changes in extractability of mannoproteins with apparent molecular weights of 96,000, 80,000, 61,000, 41,000, 31,500, and 21,000 (determined after deglycosylation with endo-N-acetylglucosaminidase H). The similarity of results obtained in the presence and absence of cycloheximide, the appearance of cell wall effects after only 10 min of treatment, and the similarity of effects in intact cells and isolated cell walls are consistent with direct drug-induced damage and inconsistent with a mechanism dependent on expression of bleomycin-damaged genes or other intracellular mediators. The results are consistent with bleomycin-mediated increases in cell wall permeability through disruption of glycosidic cross-linking structures in the cell wall.

Bleomycin↗
PubMed1991

A preliminary report on ABO incompatible bone marrow transplant.

Between September 1985 and June 1990, five patients with major and six patients with minor ABO blood group incompatibility between donor and recipient underwent allogeneic bone marrow transplantation (BMT) in the Singapore General Hospital. The period to engraftment, rate of recovery of peripheral blood leukocytes, granulocytes, and platelets and the incidence of graft versus host disease (GVHD) was similar to that observed following ABO blood group compatible marrow transplant. Erythroid development and reticulocytosis were, however, significantly delayed in patients receiving major ABO incompatible marrow transplant.

ABO Blood-Group System↗