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S T Lee

Publications and source records attributed to S T Lee.

At least 19 recordsLinked to original sources
PubMed1995

A phylogenetic analysis of the genus Saccharomonospora conducted with 16S rRNA gene sequences.

Nearly complete sequences of 16S rRNA genes of representative strains of the genus Saccharomonospora were determined following the isolation and cloning of the amplified genes. The sequences were aligned with those of representatives of the family Pseudonocardiaceae, and a phylogenetic tree was inferred by the neighbor-joining method. The genus Saccharomonospora formed a distinct clade within the evolutionary radiation encompassed by the family Pseudonocardiaceae. The average nucleotide similarity value found between the type strains of the four validly described Saccharomonospora species was 97.5% +/- 1.0%. The most distant relationship was found between Saccharomonospora azurea and Saccharomonospora viridis K73 (96.3% similarity). In contrast, Saccharomonospora azurea K161 and "Saccharomonospora caesia" K163 had identical 16S rRNA gene sequences. The nucleotide sequence data suggest that the genus Saccharomonospora contains several new centers of variation.

Actinomycetales↗
PubMed1995

CD34 immunohistochemical staining of bone marrow biopsies in myelodysplastic syndromes.

Although it has been shown that the percentage of bone marrow blasts in myelodysplastic syndrome (MDS) constitute the only independent determinant of survival and progression to acute leukemia, the great variability in survival among patients with MDS of similar percentage of blasts has prompted us to investigate new objective, independent prognostic parameters for the selection of high-risk patients. It was suggested that CD34 antigen expression adversely affected the prognosis of acute myelogenous leukemia. However, no study has been published so far on clinical and prognostic significance of CD34 antigen expression in MDS. Bone marrow biopsies from 58 patients diagnosed as primary MDS were studied using QBEND/10, a monoclonal antibody which recognized the human progenitor CD34 antigen on routine aldehyde-fixed, paraffin-embedded samples. The high percentage of CD34-positive cells (above 3% of total bone marrow nucleated cells) was predominantly observed in cases with RAEB-T, CMML, and to a lesser degree in RAEB. But neither age, hemograms, bone marrow findings including percentage of blasts, ALIP, nor leukemic transformation correlated with the percentage of CD34-positive cells. The median actuarial survival time in the high positive group was significantly shorter (12.0 months) than that of the low group (30.0 months; p = 0.028). The high CD34 aggregate (> or = 3) was selectively found in cases with RAEB, RAEB-T, and CMML. The percentage of bone marrow blasts (p = 0.007) and ALIP (p = 0.030) significantly correlated with number of CD34 aggregates.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Differential responses of CD34-positive acute myelogenous leukemic blasts to the costimulating effects of stem cell factor with GM-CSF and/or IL-3.

Stem cell factor (SCF), a c-kit ligand, has a preferential effect on the proliferation of several classes of immature hematopoietic progenitor cells in combination with GM-CSF or IL-3. To analyze the costimulatory role of SCF in leukemic growth, we investigated the effect of SCF in the presence of GM-CSF and/or IL-3 on isolated CD34-positive (CD34+) leukemic blasts from 15 patients with acute myelogenous leukemia (AML). Cultures of CD34+ cells from normal bone marrow were used as controls. When the proliferation of CD34+ AML blasts in the presence of GM-CSF and/or IL-3 were evaluated in vitro for the effects of SCF, two patterns emerged. In one pattern, CD34+ AML blasts responded with a significant increase in DNA synthesis and/or colony formation when SCF was used with GM-CSF and/or IL-3 relative to the growth with SCF alone; This result is consistent with those CD34+ bone marrow cells from normal donors. Six patients (40%) were included in this category. The addition of SCF as a single factor resulted in colony formation in all six of these cases. In the other pattern, nine of the patients (60%) had CD34+ leukemic cells whose growth with SCF plus either GM-CSF, IL-3, or GM-CSF+IL-3, was not significantly different from the growth noted in the presence of SCF alone. Among them seven cases that did not form colonies in response to SCF alone, and one case showing autocrine, background growth were included. In the six cases in which the costimulating effects of SCF were documented, CD34+ c-kit+ blasts comprised 50.5 +/- 18.7% of the CD34+ leukemic blasts-higher than 21.8 +/- 19.4% of cases in which the costimulating effect of SCF was not documented. In the cases showing high c-kit antigen expression (> or = 40%), SCF had a costimulatory effect in 71% (5/7) of the patients. In conclusion, our data indicate that CD34+ leukemic blasts from a good proportion of patients with AML did not respond to the costimulating effects of SCF in the presence of GM-CSF adn/or IL-3, in contrast to those CD34+ bone marrow cells from normal donors. The possible use of SCF for acute leukemia must await further cytogenetic and molecular studies, which should clarify the preferential costimulating role of SCF in normal hematopoiesis.

Antigens, CD↗
PubMed1994

A YAC contig spanning a cluster of human type III receptor protein tyrosine kinase genes (PDGFRA-KIT-KDR) in chromosome segment 4q12.

We have mapped five genes encoding protein tyrosine kinases (PTKs) to the pericentromeric region of human chromosome 4. PTK4 and TYRO4, which encode nonreceptor intracellular PTKs, are located at 4p12 and 4q13, respectively. The other three genes, PDGFRA, KIT, and KDR, encode type III transmembrane receptor PTKs for known ligands. We have developed a contig of 29 yeast artificial chromosomes (YACs) spanning approximately 2 Mb of DNA at 4q12 that includes PDGFRA, KIT, and KDR, and we have used this YAC contig to map 12 different sequence-tagged sites in this region. PDGFRA, KIT, and KDR thus constitute a cluster of genes at 4q12 encoding closely related type III receptor PTKs. Mutations of the human KIT gene result in piebaldism, an autosomal dominant disorder of melanocyte development.

Base Sequence↗
PubMed1992

Deletion of the pro-alpha 1(I) N-propeptide affects secretion of type I collagen in Chinese hamster lung cells but not in Mov-13 mouse cells.

We have introduced two mutations into a full-length human pro-alpha 1(I) cDNA that delete 114 amino acids or the entire 139 amino acids of the N-propeptide domain. Wild-type and mutated versions of the cDNA were introduced into cultured Chinese hamster lung (CHL) cells, which do not produce endogenous type I collagen, and into Mov-13 mouse cells, which produce endogenous pro-alpha 2(I) chains but not pro-alpha 1(I) chains. As judged by resistance to proteases, neither mutation impaired intracellular triple helical assembly of human alpha 1(I) homotrimers in CHL cells, or of chimeric type I collagen comprised of human alpha 1(I) and mouse alpha 2(I) chains in Mov-13 cells. Thus, the N-propeptide is not necessary for intracellular assembly of the main helical collagen domain of type I collagen. In CHL cells the rate of secretion of the mutant homotrimers was greatly reduced as compared to wild type homotrimers, and by immunofluorescence and immunoelectron microscopy, the mutant chains were shown to be accumulated in large vesicular expansions of the rough endoplasmic reticulum. When such cells were retransfected with cDNA encoding wild-type human alpha 2(I) chains, mutant alpha 1(I) chains were not rescued and heterotrimers containing the mutant chains were also retained in the intracellular vesicles. By contrast, deletion of the N-propeptide did not affect secretion of heterotrimers containing mutant chains from Mov-13 cells. Thus, an intact N-propeptide appears necessary for efficient secretion of type I collagen from some but not all cell types.

Amino Acid Sequence↗
PubMed1992

Retention of C60 and C70 fullerenes on reversed-phase high-performance liquid chromatographic stationary phases.

The separation of C60 and C70 fullerenes on four different polysiloxane stationary phases was examined. It was determined that polar solvents can be used as mobile phases effectively for the separation of fullerene molecules. Unlike previously published work, a polymeric octadecyl siloxane (ODS) stationary phase provided higher separation factors for C70/C60 than did monomeric ODS stationary phases or phenyl substituted stationary phases. For example, for a methanol-diethyl ether (50:50, v/v) mobile phase and C60, k' approximately 5.0 separation factors, alpha = 3.3, were achieved with polymeric ODS compared to alpha = 2.2, with a monomeric ODS stationary phase. A linear solvation energy relationship (LSER) was used to model the importance of solvent interactions and stationary phase interaction to solute retention.

Carbon↗
PubMed1992

Characterization of sequence changes in kinetoplast DNA maxicircles of drug-resistant Leishmania.

We have compared kinetoplast DNA maxicircles of tunicamycin- and arsenite-resistant variants of repeatedly cloned Leishmania mexicana amazonensis showing DNA amplification with wild-type and arsenite-resistant variants of the same lineage that do not show DNA amplification. DNA restriction patterns and the degree of cross-hybridization between maxicircle DNA fragments of parasites displaying DNA amplification and those of parasites without amplification were examined. In addition, the nucleotide sequence of the cytochrome b (Cyb) gene from the coding region was compared between these two groups of parasites. Extensive changes were found in the nucleotide sequences and the amino acid sequences of the cytochrome gene of the maxicircles of variants with DNA amplification. The Cyb genes from both groups had much shorter open reading frames than the same gene from Leishmania tarentolae and Trypanosoma brucei. The simultaneous changes in maxicircles and minicircles of these variants suggest that they may confer the advantage of maintaining viable mitochondrial function under selective pressure.

Amino Acid Sequence↗
PubMed1992

Effects of exposure to carbon disulphide on low density lipoprotein cholesterol concentration and diastolic blood pressure.

The relation of carbon disulphide (CS2) exposure to risk factors for ischaemic heart disease was recently examined using data from a 1979 cross sectional study of 410 male textile workers, of whom 165 were exposed and 245 were unexposed to CS2. Average eight hour CS2 exposure concentrations ranged from 0.6 to 11.8 ppm by job title category among the exposed workers. A significant and positive linear trend in low density lipoprotein cholesterol concentration (LDLc) and diastolic blood pressure with increasing CS2 exposure was found after adjustment for potential confounders. When exposure was examined as a categorical variable (none, low, moderate, and high), the high exposure group had an adjusted mean LDLc that was 0.32 mmol/l greater than the non-exposed group (p = 0.02), and an adjusted mean diastolic blood pressure that was 3.16 mm Hg greater than the non-exposed group (p = 0.09). The effect of CS2 on diastolic blood pressure was strengthened in analyses limited to exposed workers: the high exposure group had an adjusted mean diastolic blood pressure that was 5 mm Hg greater than that of the low exposed group (p = 0.03). Triglyceride, high density lipoprotein cholesterol, and fasting glucose concentration, and systolic blood pressure were not affected by exposure. Blood lead concentration was positively associated with systolic and diastolic blood pressure. The results indicate that relatively modest exposure to CS2 may raise LDLc concentration and diastolic blood pressure and suggest mechanisms by which exposure to CS2 may influence risk of ischaemic heart disease. Also the results provide further support for the hypothesis of a possible association between blood lead concentration and blood pressure.

Adult↗
PubMed1992

Esophageal strictures: treatment with a new design of modified Gianturco stent. Work in progress.

To overcome the drawbacks of the modified Gianturco stent tube with barbs, a new barbless stent tube was constructed. Twenty-two barbless stent tubes 4.5-14.0 cm long were placed with a new introducing tube in 21 patients: 10 stent tubes in 10 patients with recurrent dysphagia after radiation therapy or chemotherapy, 10 in 10 patients with esophageal cancer in whom surgical management was contraindicated, and two in one patient with postoperative benign stricture. No technical failure or procedural complications occurred. After the procedure, all but two patients could ingest most or all foods. In two patients with an esophagorespiratory fistula and one patient with esophageal rupture, the barbless stent tube successfully occluded the fistula and rupture site. The stent tube migrated in one patient. Fifteen patients are surviving, with the stent tubes patent for 3-35 weeks (mean patency, 13 weeks); the six other patients died 7-24 weeks (mean, 16 weeks) after stent placement. It is concluded that barbless stent tubes show promise in the management of dysphagia caused by esophageal strictures.

Aged↗
PubMed1992

Bilateral multiple sclerosing hemangiomas of the lung.

A Chinese woman had bilateral coin lesions of the lung, which grew slowly. At pathologic examination, the lesions were considered to be multiple sclerosing hemangiomas. Multiplicity is rare, and bilaterality has not been previously reported.

Female↗
PubMed1992

Early seizures after mild closed head injury.

The authors review the seizure incidence in 4232 adult patients with mild closed head injury who did not receive prophylactic anticonvulsant agents. One hundred patients (2.36%) experienced seizures within 1 week after head injury; 43 of these (1.02% of the series) had seizures within 24 hours after trauma. Most of the seizures (84%) that developed during the 1st week after injury were of the generalized tonic-clonic type. The incidence of generalized tonic-clonic seizures was higher than that of partial seizures with motor symptoms both within 24 hours (91% vs. 9%) and during the Day 2 to 7 period (79% vs. 21%). No definite intracranial pathological findings were detected by computerized tomography (CT) in 53% of patients with early posttraumatic seizures; six patients had intracranial hemorrhage without intracranial parenchymal damage (three with epidural hematoma and three with subarachnoid hemorrhage). The most common positive CT findings in the early posttraumatic-seizure group were intracerebral hemorrhage (24%), followed by acute subdural hematoma with intracerebral hemorrhage (17%). Intracerebral parenchymal damage could be identified on CT scans in 41 (48.8%) of 84 patients with generalized tonic-clonic seizures and five (31%) of 16 patients with partial seizures with motor symptoms. The intracerebral parenchymal damage was most commonly detected in the frontal lobe (21%) and the temporal lobe (19%). Seven patients with early posttraumatic seizures received emergency craniotomy to remove an intracranial hematoma (epidural in three, subdural and intracerebral in four) because the mass effect resulted in significant midline shift as seen on CT scans. This review suggests that early posttraumatic seizures after mild closed head injury have a high incidence (53%) in patients with normal CT scan findings. Although the possibility of surgically correctable intracranial hemorrhage is low (7%), the condition may be devastating if not treated properly.

Adolescent↗
PubMed1992

Epidemiology and management of respiratory burns in National Burns Centre, Singapore.

Respiratory burns constitute one of the two leading causes of burns mortality today, the other being infection. When cutaneous burns are complicated by co-existent respiratory or inhalational injury, the mortality remains high in most reported series. We began our prospective study of respiratory burns in 1982 as a multi-disciplinary team effort involving respiratory physicians, anaesthetists and our burns physicians. Between 1982 until February 1990, we treated a total of 240 patients with respiratory burns. During the same period, a total of 4041 patients were admitted to our Burns Centre at Singapore General Hospital. Respiratory burns cases therefore constituted 5.4% of the total burns admissions. In our series, there were 44 deaths out of 240 patients, giving an overall mortality of 18.3%. The average size of burns in the patients who died was 57.4% BSA in Group A patients, 65.0% BSA in Group B and 57.7% BSA in Group C. Our management protocol has gradually evolved over the eight years of the study. Systemic antibiotics and steroids are no longer used routinely. Fiberoptic bronchoscopy is done early in the ward as a bedside procedure once a patient is clinically assessed to have suffered a respiratory burns and repeat bronchoscopic examination done when deemed necessary. An aggressive regime of respiratory support measures with early intubation and PEEP ventilation is recommended.

Adolescent↗
PubMed1992

Morbidity and mortality in respiratory burns--a prospective study of 240 cases.

A prospective study of 240 consecutive admissions with respiratory burns over an eight-year period beginning 1982 was carried out at the National Burns Centre, Singapore General Hospital. Diagnosis of respiratory burns was based on clinical criteria and a clinical score was then computed to grade the severity. Investigations included chest x-rays, blood gases, carboxyhaemoglobin level, lung scan and fibreoptic bronchoscopy. Treatment was carried out according to a standard protocol where a policy of early intervention in the form of endotracheal intubation was emphasised. Other respiratory support measures were chest physiotherapy, tracheobronchial suction, mucolytics and bronchoscopic lavage where indicated. We found that respiratory burns was a significant cause of mortality in burns patients. The influence on mortality was most marked in patients with large body surface area burns of more than 40%. Age was also an important determinant of survival with patients older than 50 years faring significantly worse. The routine steroids and prophylactic antibiotics did not influence the survival rate. Carbon monoxide poisoning was not a significant cause of mortality. We achieved an overall mortality rate of 18.3%, with 44 deaths out of 240 patients. The main causes of deaths at post-mortem were bronchopneumonia, septicaemia and extensive burns.

Adolescent↗
PubMed1992

Radionuclide lung scanning in the management of respiratory burns.

Soluble radioaerosols such as technetium-99m diethylene triamine pentacetate (DTPA) permit simple quantitative studies of alveolar-capillary permeability to be performed, since the submicronic aerosols are deposited mainly at the lung periphery and are cleared across the alveolar-capillary membrane. Regional alterations in permeability can also be noted using this radionuclide technique. We have measured the alteration in pulmonary epithelial permeability in normal subjects and in patients with inhalation burns using a computer-linked gamma-camera. In the normal volunteers, the time taken for 50% of inhaled Tc-99m DTPA to be cleared from the lungs (T1/2) was 66 minutes +/- 1sd of 12 minutes. In the 42 patients with inhalation burns, besides the T1/2, retention images of uncleared Tc-99m DTPA in the lungs were obtained to note regional differences, if any, in lung clearance arising from pulmonary epithelial damage; these patients showed increased rate of clearance (short T1/2) with mean T1/2 of 36 minutes +/- 1sd of 11 minutes, while the retention images revealed regional lung damage in moderately severe inhalation burns. In 18 patients with abnormal T1/2, 16 (89%) had abnormal bronchoscopy findings. Fifteen patients also had lung perfusion scans with Tc-99m MAA (macroaggregated albumin). The regional defects in perfusion when present were generally matched with the defects seen on ventilation scans. The Tc-99m DTPA lung clearance measurement and imaging has clinical usefulness in suspected inhalation burns.

Accidents, Occupational↗
PubMed1992

Emergence of a multiply-resistant strain of Acinetobacter in a burns unit.

Multiply-resistant Acinetobacter has emerged as an important organism in the Burns Unit of the Singapore General Hospital. From November 1990 onwards, a strain that was resistant to all antibiotics except Polymyxin B emerged in the Burns Unit. We present two cases where the Acinetobacter isolated was resistant to all antibiotics including Polymyxin B. These cases serve as an important reminder to adhere to strict infection control procedures.

Acinetobacter↗