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Biomedical subjects

S T Lim

Publications and source records attributed to S T Lim.

At least 19 recordsLinked to original sources
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↗
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↗
PubMed1985

Evaluation of the posterior approach for subfascial ligation of perforating veins.

A posterior midline incision was used for subfascial ligation of incompetent medial and lateral perforating veins in 32 patients. The indications for surgery were recurrent ulceration in 31 limbs and stasis dermatitis in six limbs. Incompetent perforating veins were found on the medial aspect of the leg in all cases and lateral aspect of the leg in 69% of cases. Postoperative mild skin edge necrosis and wound infection each occurred in seven limbs. Follow-up of these patients from 5 months to 4 years showed that there were 11 recurrent ulceration, 10 mild leg oedema and three recurrent varices. This operation was successful in preventing further leg ulceration in 70% of patients, and a further 21.6% had benefited from the operation in that ulcers which recurred in the follow-up period were small in size compared to the original ones, and healed quickly.

Adult↗
PubMed1984

Micturition after cystoplasty.

In patients with advanced carcinoma of the bladder not involving the trigone, radical total cystectomy with bladder replacement (replacement cystoplasty) using either the colon, ileum or stomach can be performed. In male patients, the prostatic urethra is always included in the resection so that the extent of radical surgery is not compromised. Thus the neobladder is anastomosed to the membranous urethra in these patients. In patients with contracted tuberculous bladder, the neobladder is anastomosed to the trigone after subtotal cystectomy (augmentation cystoplasty). The pattern of micturition is studied in 32 patients with cystoplasty after cystectomy. Emptying of the neobladder is achieved and completed mainly by abdominal straining rather than by the spontaneous contraction of the gastrointestinal segment, as evidenced by cystometric studies. The stomach generates high pressures during its peristaltic contractions but this could be a disadvantage during the early postoperative period particularly in the females, as urinary incontinence may result. In the majority of patients, micturition takes place every 2 to 3 hours with full urinary continence during the waking hours. However, in patients after radical total cystectomy, incontinence of urine during deep sleep is inevitable. No differences of voiding pattern, bladder capacity and residual urine volume are noted when either the colon, ileum or stomach is used for cystoplasty.

Adult↗
PubMed1983

Effects of gastrocystoplasty on serum gastrin levels and gastric acid secretion.

Hypersecretion of gastric acid and hypergastrinaemia occur when the antrum of the stomach is transposed as a diverticulum to the colon. Thus, when an antral pouch is transposed to increase bladder capacity or to replace the bladder as a gastrocystoplasty, similar pathophysiological disturbances can be anticipated. However, previous studies in our laboratories in dogs have shown that acid overproduction and stomal ulcerations do not occur. This paper reports the results of gastrocystoplasty in 13 patients followed up from 1 to 6 years. Gastric acid hypersecretion and hypergastrinaemia did not occur.

Adult↗
PubMed1983

Disseminated tuberculosis in a renal transplant recipient.

A case of disseminated tuberculosis in a renal transplant recipient is presented. Tuberculosis can occur in the early postoperative period and is potentially curable. It should be vigilantly looked for in every case of post-transplant infection.

Humans↗
PubMed1982

Intrathoracic gastric bypass for carcinoma of oesophagus found unresectable at exploration.

Assessment of the resectability of carcinoma of the oesophagus or cardia may be inaccurate. At exploration, 8 patients in whom resection was contemplated were found to have unresectable lesions. An intrathoracic oesophagogastric bypass was performed without further change of position. Five patients were discharged from hospital and survived between 3 and 20 months before they finally succumbed to metastases. Each of them was able to take an ordinary diet. The aims of palliation were achieved.

Adenocarcinoma↗