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S T Lee

Publications and source records attributed to S T Lee.

At least 145 records · Page 8Linked to original sources
PubMed1997

Inter- and intraspecific genetic analysis of the genus Saccharomonospora with 16S to 23S ribosomal DNA (rDNA) and 23S to 5S rDNA internally transcribed spacer sequences.

In order to clarify interspecific relationships and to investigate the intraspecific phylogenetic structure of the genus Saccharomonospora, 16S to 23S ribosomal DNA (16S-23S) and 23S to 5S ribosomal DNA (23S-5S) internally transcribed spacers (ITSs) were used for sequence analyses. The 16S-23S and 23S-5S ITSs from 22 Saccharomonospora strains were amplified by PCR and directly sequenced. The average levels of nucleotide similarity of the 16S-23S and 23S-5S ITSs for the four valid species were 87.6% +/- 3.9% and 83% +/- 2.2%, respectively. For the most part, intraspecific sequence differences were not found in the two ITSs; the only exception was Saccharomonospora glauca K194, which differed from other S. glauca strains by 1 bp in the 23S-5S ITS. The Saccharomonospora viridis strains had a smaller 16S-23S ITS region than the other strains, which may be useful for differentiating these organisms from other Saccharomonospora species. The characteristics of the two ITS regions make them more useful than 16S rRNA sequences as a tool for defining and identifying Saccharomonospora strains. However, Saccharomonospora azurea K161T had two types of 23S-5S ITSs; rrnB, separated by XhoI digestion, had two additional nucleotides inserted between positions 52 and 55. Most of the 16S-23S and 23S-5S ITS sequences of S. azurea K161T and strains of "Saccharomonospora caesia" were identical; the only exception was rrnB in S. azurea K161T. The lengths and levels of sequence divergence of the two ITSs of Saccharomonospora sp. strain K180 were different from the lengths and levels of sequence divergence of the ITSs of other species. These findings suggest that a taxonomic revision of the genus Saccharomonospora is necessary. Two trees based on 16S-23S and 23S-5S ITS sequences revealed distinct interspecific relationships in the genus Saccharomonospora.

Actinomycetales↗
PubMed1997

Reclassification of Nocardioides simplex ATCC 13260, ATCC 19565, and ATCC 19566 as Rhodococcus erythropolis.

Our phylogenetic analysis based on 16S ribosomal DNA (rDNA) sequences and chemotaxonomic analyses showed that Nocardioides simplex ATCC 13260, ATCC 19565, and ATCC 19566 are more closely related to the genus Rhodococcus, especially Rhodococcus erythropolis, than to the genus Nocardioides. N. simplex ATCC 13260 and N. simplex ATCC 19565 and ATCC 19566 exhibited levels of 16S rDNA similarity of 99.4 and 100%, respectively, to R. erythropolis DSM 43066T. Strains ATCC 13260, ATCC 19565, and ATCC 19566 had mesodiaminopimelic acid in their peptidoglycan and MK-8(H2) as their predominant menaquinone. These three strains produced cellular fatty acid patterns similar to those of R. erythropolis strains rather than those of Nocardioides species. Therefore, N. simplex ATCC 13260, ATCC 19565, and ATCC 19566 should be reclassified as strains of R. erythropolis Gray and Thornton 1928.

DNA, Bacterial↗
PubMed1997

Nocardioides pyridinolyticus sp. nov., a pyridine-degrading bacterium isolated from the oxic zone of an oil shale column.

A bacterial strain which is able to degrade pyridine was previously isolated from the oxic zone of an oil shale column and described as Pimelobacter sp. strain OS4T. However, Pimelobacter species have been transferred to the genera Nocardioides and Terrabacter. Strain OS4T was identified as a member of the genus Nocardioides on the basis of chemotaxonomic analysis and phylogenetic inference based on 16S ribosomal DNA (rDNA) sequence analysis. The G+C content of strain OS4T is 72.5 mol%. The cell wall peptidoglycan contains LL-diaminopimelic acid as the diamino acid. The predominant menaquinone is MK-8(H4). The cellular fatty acid profile of strain OS4T is similar to that of the genus Nocardioides. The 16S rDNA similarity of strain OS4T with previously described Nocardioides species is 94.5% +/- 0.7%, and a phylogenetic tree based on 16S rDNA sequences revealed a distinct lineage for strain OS4T within the evolutionary radiation enclosed by the genus Nocardioides. Therefore, on the basis of our data, we propose that strain OS4T should be placed in the genus Nocardioides as a member of a new species, Nocardioides pyridinolyticus. The type strain of the new species is strain OS4 (= KCTC 0074BP).

Base Composition↗
PubMed1997

Complementation of hypopigmentation in p-mutant (pink-eyed dilution) mouse melanocytes by normal human P cDNA, and defective complementation by OCA2 mutant sequences.

Mutations in the P gene of humans and the homologous p-locus of mice, respectively, result in the homologous disorders oculocutaneous albinism type 2 (OCA2) and pink-eyed dilution. Although clearly required for melanin biosynthesis, the specific function of the P gene product, a melanosomal transmembrane protein expressed in melanocytes of the skin, hair, and eyes, is not yet known. Here we describe lines of immortal melanocytes and melanoblasts from mice of the null genotype p(cp)/p(25H). These p-null melanocytes were severely hypopigmented, although they and the melanoblasts expressed mRNAs for a number of melanosomal proteins. Proliferation of the p-null melanoblasts was normal. Both diploid and immortal p-null melanocytes grew more slowly than wild-type melanocytes, however, and were unusually susceptible to the antibiotic G418; these abnormalities were corrected by culture in high concentrations of L-tyrosine. Transfection of the p-null melanocytes with full-length normal human P cDNA resulted in complementation of deficient melanin biosynthesis and hypopigmentation. In contrast, transfection with mutant human P cDNAs containing amino acid substitutions (A481T, V443I) found in patients with OCA2 resulted in minimal or partial correction, consistent with the corresponding pigmentation phenotypes in patients with these mutations. These results demonstrate the utility of this model system for distinguishing true OCA2 mutations from nonpathologic polymorphisms and for quantitating the effect of these mutations on P function.

Albinism, Oculocutaneous↗
PubMed1997

Anaerobic and aerobic degradation of pyridine by a newly isolated denitrifying bacterium.

New denitrifying bacteria that could degrade pyridine under both aerobic and anaerobic conditions were isolated from industrial wastewater. The successful enrichment and isolation of these strains required selenite as a trace element. These isolates appeared to be closely related to Azoarcus species according to the results of 16S rRNA sequence analysis. An isolated strain, pF6, metabolized pyridine through the same pathway under both aerobic and anaerobic conditions. Since pyridine induced NAD-linked glutarate-dialdehyde dehydrogenase and isocitratase activities, it is likely that the mechanism of pyridine degradation in strain pF6 involves N-C-2 ring cleavage. Strain pF6 could degrade pyridine in the presence of nitrate, nitrite, and nitrous oxide as electron acceptors. In a batch culture with 6 mM nitrate, degradation of pyridine and denitrification were not sensitively affected by the redox potential, which gradually decreased from 150 to -200 mV. In a batch culture with the nitrate concentration higher than 6 mM, nitrite transiently accumulated during denitrification significantly inhibited cell growth and pyridine degradation. Growth yield on pyridine decreased slightly under denitrifying conditions from that under aerobic conditions. Furthermore, when the pyridine concentration used was above 12 mM, the specific growth rate under denitrifying conditions was higher than that under aerobic conditions. Considering these characteristics, a newly isolated denitrifying bacterium, strain pF6, has advantages over strictly aerobic bacteria in field applications.

Aerobiosis↗
PubMed1997

Structure of the musculus uvulae: functional and surgical implications of an anatomic study.

OBJECTIVE: The role of the musculus uvulae in velopharyngeal function, its morphologic status in cleft palate, and its fate in palatoplasty procedures are subjects of controversy. The aims of this investigation were to re-examine this velar muscle to clarify its anatomic characteristics, to analyze its role in speech physiology, and to study the surgical implications of this information for cleft palate repair. METHODS: Its attachments, morphology, and relations were examined in 18 fresh human adult cadavers by detailed dissection under 3.2x magnification and light microscopy. RESULTS: The musculus uvulae was observed to be a paired midline muscle extending between the tensor aponeurosis anteriorly and the base of the uvula posteriorly along the nasal aspect of the velum. It had no attachments to the hard palate. CONCLUSIONS: These findings suggest that its action is to increase midline bulk on the nasal aspect of the velum, thus contributing to the levator eminence. It may also have an extensor effect on the nasal aspect of the velum, displacing it toward the posterior pharyngeal wall. Both of these actions would serve to maximize midline velopharyngeal contact. One clinical application of this anatomic information is that the muscle should be preserved in the dissection performed during intravelar veloplasty. Furthermore, it should be recognized that the musculus uvulae is invariably divided and reoriented incorrectly in the Furlow double opposing Z-plasty.

Adult↗
PubMed1997

Joint lectureship of the Royal College of Surgeons of Edinburgh and the Academy of Medicine, Singapore--accurate long-term documentation in surgical audit and evaluation of outcomes.

The purpose of a surgical audit is to allow a critical assessment of patient care, carried out among peers and in an atmosphere of learning, open discussion, free of recriminations. The results of a surgical unit will hopefully lead to improvement in the quality of care of our patients by reducing the preventable causes of mortality and morbidity. Data from surgical audit can also be used to monitor the teaching programme in a department. It may even allow us to study the cost effectiveness of certain procedures which is obviously very important in this era of diminishing resources and cost containment.

Cleft Lip↗
PubMed1997

Combined use of stereotactic aspiration and intracerebral streptokinase infusion in the surgical treatment of hypertensive intracerebral hemorrhage.

Stereotactic aspiration is well known for its simplicity and safety in the surgical treatment of hypertensive intracerebral hemorrhage. Postoperative fibrinolytic infusion with urokinase or recombinant tissue plasminogen activator and drainage of liquified hematoma are often used to improve the removal of hematoma. We evaluated the safety and effectiveness of streptokinase in this treatment modality in patients with hypertensive intracerebral hemorrhage or cerebellar hemorrhage. Twelve patients with hypertensive intracerebral hemorrhage underwent stereotactic aspiration using streptokinase as a fibrinolytic agent. There were six cases of putaminal hemorrhage, three of thalamic hemorrhage, and three of cerebellar hemorrhage. All but one patient had a large hematoma and presented with intracranial hypertension. Stereotactic aspiration was undertaken to remove the hematoma. Postoperatively, streptokinase was infused into the residual hematoma every 6 to 12 hours via a catheter implanted during the operation. Liquified hematoma was aspirated by syringe manually just before each infusion of streptokinase. The average duration of the entire treatment was 6 days (range 1-7). The residual hematoma at the end of treatment was less than 10 mL in all patients. Intracranial hypertension also subsided significantly in all patients. Only one patient had aspiration-induced bleeding during the operation. We conclude that stereotactic aspiration of hypertensive intracerebral hemorrhage is relatively safe and simple. Streptokinase can be infused intracerebrally to drain residual hematoma without severe side-effects.

Adult↗
PubMed1997

The pattern of burn infection in the Singapore National Burns Centre.

As part of the multi-pronged strategy in the fight against burn infection, we conducted a retrospective study of the pattern of infection in our burn patients for a period of 15 months from January 1993 to March 1994. We studied culture and sensitivity reports to determine the incidence of each organism, their antibiotic sensitivity patterns and the time interval between the burns injury and the appearance of these organisms. Organisms like methicillin-resistant Staphylococcus aureus (MRSA) and multiply-resistant Acinetobacter baumannii constituted a problem in our patients. Other organisms that were isolated from our patients included Pseudomonas aeruginosa, Enterobacter species and Klebsiella species. The infection control measures in our burns centre are aimed at combating the spread of gram-positive and gram-negative organisms. This study has helped to influence our antibiotic administration policy for treating infection in our centre based on the sensitivity patterns of the prevailing flora.

Adolescent↗
PubMed1996

Biodegradation of 4-chlorophenol via a hydroquinone pathway by Arthrobacter ureafaciens CPR706.

A newly isolated Arthrobacter ureafaciens, strain CPR706, could degrade 4-chlorophenol via a new pathway, in which the chloro-substituent was eliminated in the first step and hydroquinone was produced as a transient intermediate. Strain CPR706 exhibited much higher substrate tolerance and degradation rate than other strains that degraded 4-chlorophenol by the hydroxylation at the second carbon position to form chlorocatechol. Strain CPR706 could also degrade other para-substituted phenols (4-nitro-, 4-bromo-, 4-iodo-, and 4-fluoro-phenol) via the hydroquinone pathway.

Arthrobacter↗
PubMed1996

Prolonged circulatory arrest in moderate hypothermia with retrograde cerebral perfusion. Is brain ischemic?

BACKGROUND: Circulatory arrest (CA), which provides a bloodless field and good visualization without the need of aortic cross-clamp, is commonly used to facilitate repair of aortic lesions. However, extended periods of CA may impair cerebral metabolism and cause ischemic injury. Studies were performed to evaluate the efficacy of retrograde cerebral perfusion (RCP) in protecting the brain from ischemic injury during a prolonged period of CA in moderate hypothermia. METHODS AND RESULTS: Twenty-three patients (18 men and 5 women) were operated on for aortic lesions (17 acute type A aortic dissection and 6 chronic type A aortic dissection with Marfan's syndrome). The aortic operations were performed with CA (58 to 104 minutes; mean +/- SD, 75 +/- 12 minutes) at a rectal temperature of 23.3 +/- 0.5 degrees C (21 degrees C to 25 degrees C). For RCP, cold (14 degrees C to 18 degrees C) oxygenated blood (300 mL/min) was pumped to the superior vena cava with internal jugular venous pressure of 15 +/- 5 mm Hg. The cardiopulmonary bypass time was 157 +/- 18 minutes. Cortical blood flow during RCP detected by subdural laser Doppler probe was 10 +/- 5% of baseline. Percent oxygen extraction and pyruvate and lactate levels (26 +/- 2% and 0.43 +/- 0.17 and 45 +/- 16 mg/dI) were insignificantly different from those before CA (28 +/- 3% and 0.71 +/- 0.08 and 62 +/- 20 mg/dL, P > .05). Creatine kinase-BB isoenzyme was undetectable. All but 1 patient survived the operation (95.5%) and woke up without neurological deficit. Follow-up (mean, 13 months) was complete in all survivors. There were no late deaths. Cerebral functional studies performed 3 months after discharge showed results insignificantly different from those of the normal control subjects. CONCLUSIONS: There is no evidence of ischemia of the brain during prolonged moderate hypothermic CA with the aid of RCP. Retrograde cerebral perfusion effectively extends the safe time of CA. Deep hypothermia during CA seems unnecessary.

Adult↗
PubMed1996

Chemopreventive effect of chlorophyllin on mutagenicity and cytotoxicity of 6-sulfooxymethylbenzo[a]pyrene.

The chemopreventive activity of chlorophyllin (CHL) was monitored by using 6-sulfooxymethylbenzo[a]pyrene (SMBP) which is an ultimate metabolite of benzo[a]pyrene (B[a]P). CHL was quite effective in reducing both cytotoxicity and mutagenicity for SMBP in dose dependent manner up to 12.5 mM CHL in Chinese hamster V79 cells. The inhibitory patterns of CHL for SMBP were also confirmed in Salmonella typhimurium strains TA98 and TA100. Mutation frequency caused by SMBP was diminished almost to a control level at a 50 nmol CHL. A similar but less effective prevention of CHL was indicated in the mammalian and the bacterial mutagenicity assays with 6-hydroxymethylbenzo[a]pyrene (HMBP). The inhibitory effect of CHL against assault of SMBP on V79 cells was found to be related to the reduced cellular uptake of SMBP and further the remarkably lowered DNA adducts.

Animals↗
PubMed1996

p53 gene mutation in cerebral primitive neuroectodermal tumor in Taiwan.

p53 mutation has been rarely reported in cerebral primitive neuroectodermal tumors (PNET). To determine the significance of p53 mutations in the development of cerebral PNET, we studied cerebral PNET samples from 14 patients, 8 females and 6 males with a mean age of 38 years (range 10 months to 77 years) who had total or subtotal surgical resection. Histological typing of PNET with neuronal (N) and non-neuronal (NN) differentiation groups revealed 8 and 6 cases, respectively. Six (43%) of the 14 patients had p53 mutation. The p53(+) and p53(-) groups had an age range of 19-77 with a mean of 49 years and 10 months to 57 years with a mean of 30 years, respectively. p53 expression between the PNET-N and PNET-NN groups was 5 of 8 (62.5%) and 1 of 6 (16.7%), respectively. The mutations contained 3 transitions, 2 transversions and 1 frameshift; none of them occurred at the site of 'hot-spot' residues (codons 175, 248, 273). The results suggest that: (1) p53 mutation in cerebral PNET tends to show a higher incidence of neuronal differentiation and occurs in the older age group in Taiwan, (2) there was no difference in survival time between the PNET-N and PNET-NN groups (7 months and 6 months) (P = 0.54), and between p53(+) and p53(-) groups (6 months and 7 months) (P = 0.57), and (3) PNET may be an entity of a heterogenous group of tumors with different genetic mechanisms controlling their trends of differential lineage. Further studies are needed to determine the significance of p53 mutations in PNET development, especially the role of carcinogens in the genesis of PNET in Taiwan.

Adolescent↗
PubMed1996

Influence of a supplementary carbon source on biodegradation of pyridine by freely suspended and immobilized Pimelobacter sp..

The effect of the presence of supplementary glucose or acetate on the growth and pyridine-degrading activity of freely suspended and calcium-alginate-immobilized Pimelobacter sp. was investigated. Although the supplementary carbon sources could be degraded simultaneously with pyridine, Pimelobacter sp. exhibited a preference for pyridine over supplementary carbon sources. Thus, the pyridine-degrading activity of the freely suspended cells was not decreased significantly by the addition of either glucose (1.5-6 mM) or acetate (6-24 mM) to the pyridine (6-24 mM). In the semi-continuous immobilized cell culture, immobilized cells also exhibited a preference for pyridine over supplementary carbon sources and did not switch their substrate preference throughout the culture. Owing to a high cell concentration, the volumetric pyridine degradation rate at 24 mM pyridine in the immobilized cell culture was approximately six times higher than that in the freely suspended cell culture. Furthermore, the immobilized cells could be reused 16 times without losing their pyridine-degrading activity during the culture period tested. Taken together, the use of immobilized Pimelobacter sp. for the degradation of pyridine is quite feasible because of the preference for pyridine over supplementary carbon sources, the high volumetric pyridine degradation rate, and the reusability of immobilized cells.

Acetates↗