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Biomedical subjects

C S Tan

Publications and source records attributed to C S Tan.

At least 19 recordsLinked to original sources
PubMed2002

Two case reports on incessant left ventricular tachycardia: curative therapy with radiofrequency ablation.

INTRODUCTION: Incessant ventricular tachycardia is a rare arrhythmia which can be life threatening. Treatment with anti-arrhythmic agents may occasionally fail. CLINICAL PICTURE: We report 2 cases of incessant ventricular tachycardia. The first case was a young man with idiopathic left ventricular tachycardia who was in incessant ventricular tachycardia despite treatment with multiple anti-arrhythmic drugs and developed dilated cardiomyopathy. The second case was an asymptomatic girl with the incidental finding of an incessant ventricular tachycardia which originated from the left ventricular outflow tract. TREATMENT AND OUTCOME: Both patients underwent electrophysiologic study and radiofrequency ablation with complete termination of the tachycardia. CONCLUSION: Radiofrequency catheter ablation in experienced centres should be the first-line therapy for incessant ventricular tachycardia.

Adolescent↗
PubMed2000

Toward the differentiation of trust in supervisor and trust in organization.

Trust in supervisor and trust in organization are argued to be distinct but related constructs, each with its own set of antecedents and outcomes. Empirical field results supported the proposition. Although trust in supervisor and trust in organization were positively and significantly correlated, trust in supervisor was more strongly associated with proximal variables (ability, benevolence, and integrity of supervisor), whereas trust in organization was more strongly correlated with global variables (perceived organizational support and justice). This conclusion held despite the inclusion of proximal variables in the regression on trust in organization and the inclusion of global variables in the regression on trust in supervisor. In addition to the differential antecedents of trust in supervisor and trust in organization, the outcomes for both variables were different. Trust in supervisor was related to increased innovative behavior and satisfaction with supervisor, and trust in organization was related to higher organizational commitment and lower intention to leave. Therefore, the authors provide clear preliminary data on the distinctiveness of trust in supervisor and trust in organization. One implication of this set of results is that organizations should adopt a more holistic approach in building trust, which can be achieved by focusing on the various constituents of the organization and the various levels (e.g., the supervisor level and the organizational level).

Humans↗
PubMed2000

Initial experience with an autocapture pacemaker system.

INTRODUCTION: Autocapture management aims to extend pacemaker longevity without compromising on patient safety by automatically monitoring the pacing threshold and adjusting the pacemaker output for consistent capture. This paper describes our initial experience with the Pacesetter Regency pacemaker with autocapture management. MATERIALS AND METHODS: Nineteen patients were implanted with single chamber pacemakers with autocapture management. Autocapture was programmed "ON" the day after implantation if Evoked Response (ER) amplitude was at least 2.8 mV. The patients were followed up at 2 weeks, 2 months and 6 months. At each visit, pacing threshold and lead impedance were measured. Autocapture was turned "ON" during follow-up if it had not been done previously. RESULTS: In 16 out of 19 patients, autocapture could be turned "ON" the day after implantation. One patient had an ER signal that was less than 2.8 mV and 2 patients were in fast atrial fibrillation of more than 120 beats per minute which precluded ER signal testing. These patients could not have autocapture programmed "ON". CONCLUSION: The benefits of autocapture management can only be realised if an ER signal of at least 2.8 mV is obtained. This requires intraoperative testing of the ER signal. Since there is no commercially available pacing system analyser presently that can measure this, modification of the standard implantation procedure with some prolongation of procedure time is needed.

Aged↗
PubMed1997

Reassessing the organization of the UL42-UL43 region of the human cytomegalovirus strain AD169 genome.

A polymorphism in the UL42-UL43 region of the human cytomegalovirus genome has been characterized by nucleotide sequence analysis, revealing a 929-bp insertion following nt 54,612 relative to the published strain AD169-UK genome sequence (M.S. Chee et al., 1990, Curr. Top. Microbiol Immunol. 154, 125-170). Although AD169-UK exhibited polymorphism in this genomic region, other CMV strains (Towne, Toledo, and AD169-ATCC) carried only the newly characterized longer form. The additional sequence altered the assignment of UL42 and UL43 open reading frames. UL42 decreased in size from 157 to 125 codons, retaining 76 of the previously reported carboxyl terminal codons, and UL43 increased in size from 187 to 423 codons, retaining 185 of the previously reported amino terminal codons. This additional sequence makes UL43 a more conserved betaherpesvirus US22 family member. Only AD169-UK exhibited restriction fragment length polymorphism in this region, suggesting that a deletion occurred during the propagation of this strain in cell culture. The additional sequence should be considered a bona fide part of the cytomegalovirus genome and the AD169 genome size should be corrected to 230,283 bp.

Amino Acid Sequence↗
PubMed1996

[Fungi and yeasts isolated in mycological studies in skin and nail infections in The Netherlands, 1992-1993].

OBJECTIVE: To describe fungi and yeasts isolated from skin and nail infections in the Netherlands. DESIGN: Retrospective. SETTING: Centraalbureau voor Schimmelcultures (CBS), Baarn, the Netherlands. METHOD: Results of mycological investigation of skin and nail samples in the period 1992-1993 were analysed. After a clinical diagnosis of mycosis, performed by dermatologists and general practitioners, material was sent to the CBS for mycological research. RESULTS: The clinical diagnosis of onychomycosis was rather accurate, especially if made performed by dermatologists. Mycoses of the skin were sometimes confused with other skin diseases. When microscopical observation showed a positive result, 93% of the cultures were positive as well. The main agent of onychomycosis was Trichophyton rubrum; T. mentagrophytes was more frequently isolated from tinea manuum/pedis and T. tonsurans from tinea corporis/cruris. Epidermophyton floccosum was only isolated from skin lesions and Microsporum canis, T. soudanense and T. verrucosum only from tinea corporis/cruris. The most important yeasts isolated were Trichosporon mucoides, Candida guilliermondii, C. parapsilosis, C. famata and Malassezia furfur. Other fungi isolated were either pigmented (melanin, carotene), thermophilic or belonged to the order of the Onygenales. CONCLUSION: Mycological research to confirm the clinical diagnosis of a skin mycosis is advisable. Species isolated differed in their predilection for different parts of the human body. Yeasts were mainly isolated as double infections. Apart from the dermatophytes there is a special group of fungi which can cause mycoses.

Dermatomycoses↗
PubMed1994

Structural and functional properties of human and mouse apolipoprotein A-I.

Mouse and human plasma apolipoprotein A-I (apo A-Im and apo A-Ih, respectively) were investigated to compare their molecular properties in solution, their incorporation into palmitoyloleoylphosphatidylcholine-apo A-I (POPC-apo A-I) discoidal complexes; their structural stability in discoidal complexes and high-density lipoproteins (HDL), and their effect on structural rearrangement of discoidal complexes upon interaction with low-density lipoproteins (LDL). Unlike apo A-Ih, only minimal concentration-dependent self-association was observed for apo A-Im. While both apo A-Im and apo A-Ih formed discoidal complexes of distinct composition and size that reflected reassembly molar ratios of POPC/apo A-I, apo A-Im demonstrated specific deficiencies in formation of larger-sized complexes. Denaturation of both apo A-Im- or apo A-Ih-containing complexes and HDL with guanidine hydrochloride (GuHCl) indicated significantly reduced stabilization of apo A-Im by lipid in these particles. Interaction of apo A-Im- or apo A-Ih-containing discoidal complexes with human plasma LDL revealed a more extensive conversion of apo A-Im-complexes to smaller species. Mean hydrophobicities and mean hydrophobic moments of amphipathic helical segments in apo A-Im and apo A-Ih were compared; differences potentially contributing to differential lipid-binding properties between apo A-Im and apo A-Ih were identified. Our results demonstrate differences between apo A-Im and apo A-Ih that may contribute to the major changes in plasma HDL distribution and function observed in apo A-Ih transgenic mice.

Animals↗
PubMed1992

[Shifts in the species spectrum of mycoses in The Netherlands from 1970-1990].

A review is presented of yeast and mould infections occurring in humans in the Netherlands. The occurrence of the dermatophytes Trichophyton rubrum and T. mentagrophytes tends to increase, while Microsporum canis and particularly Epidermophyton floccosum have become less common. The yeast Candida glabrata is particularly often involved in infections of the urinary tract. Candida krusei, C. parapsilosis and C. tropicalis have become less significant. Remarkable differences are found between the spectra of Aspergillus species causing infections in lungs and in ears; an entirely different pathogenesis is to be presumed. The number of systemic mycoses in the Netherlands is underestimated. The possibility of hundreds of cases each year cannot be excluded.

Dermatomycoses↗
PubMed1991

[Little known mycoses caused by dematiaceous opportunists].

The mycoses caused by melanized hyphomycetes are reviewed. Agents of superficial, (sub)cutaneous, paranasal, and systemic mycoses are listed, putting the emphasis on species isolated in Germany. Adaptations to survive in extreme environments may be considered as virulence factors of these fungi. Survival inside human tissue is more or less successful depending on the immune status of the host. Several neurotropic fungi are possibly real pathogens in that they are capable of invading immunocompetent individuals.

Brain Diseases↗
PubMed1989

Fractionation of Sumatran pit viper (Trimeresurus sumatranus sumatranus) venom by DEAE-Sephacel ion exchange chromatography and some biological properties of the fractions.

Sumatran pit viper (Trimeresurus sumatranus sumatranus) venom was fractionated by DEAE-Sephacel ion exchange chromatography into seven fractions. Fractions 4, 5 and 6 were lethal to mice and exhibited strong hemorrhagic activity, as well as some enzymatic activities. Fraction 6 also exhibited potent anticoagulant and thrombin-like activities. Analysis of the biological and enzymatic properties of the three lethal fractions suggests that the major lethal component of fractions 4 and 5 may be the hemorrhagic principle, and that the lethality of fraction 6 may be due to the hemorrhagic principle and/or the anticoagulant principle.

Chromatography, Ion Exchange↗
PubMed1989

The lethal and biochemical properties of Bungarus candidus (Malayan krait) venom and venom fractions.

Bungarus candidus venom exhibited high hyaluronidase, acetylcholinesterase and phospholipase A activities; low proteinase, 5'-nucleotidase, alkaline phosphomonoesterase and phosphodiesterase activities and moderately high L-amino acid oxidase activity. SP-Sephadex C-50 ion exchange chromatographic fractionation of the venom and Sephadex G-50 chromatography of the major lethal venom fractions indicate that the venom contains at least two highly lethal, basic phospholipases A with LD50 (i.v.) values of 0.02 micrograms/g (F6A) and 0.18 micrograms/g (F4A), respectively; as well as two polypeptide toxins with LD50 (i.v.) values of 0.17 micrograms/g and 0.83 micrograms/g, respectively. The major lethal toxin is the basic lethal phospholipase A, F6A, which accounts for approximately 13% of the venom protein and has a mol. wt of 21,000.

Animals↗
PubMed1989

The enzymatic activities and lethal toxins of Trimeresurus wagleri (speckled pit viper) venom.

Trimeresurus wagleri (speckled pit viper) venom exhibited the usual set of enzyme activities occurring in pit viper venoms but the content of alkaline phosphomonoesterase was unusually high, whereas the proportions of protease and arginine ester hydrolase were very low. The venom also exhibited weak thrombin-like activity but did not exhibit hemorrhagic or anticoagulant activity. Analysis of the Sephadex G-200 gel filtration fractions of the venom indicated that the lethal fraction was a low mol.wt protein, and that fractions exhibiting phosphodiesterase, phosphomonoesterase, arginine ester hydrolase, thrombin-like enzyme, L-amino acid oxidase and phospholipase A activities were not lethal. Two lethal toxins, designated as wagleri toxins 1 and 2, were isolated from the venom using Sephadex G-50 gel filtration chromatography followed by SP-Sephadex C-25 ion exchange chromatography. The mol.wts of the two toxins were 8900 by gel filtration. The LD50 (i.v.) values in mice for wagleri toxins 1 and 2 are 0.17 microgram/g and 0.19 microgram/g, respectively.

Animals↗
PubMed1989

A comparative study of the enzymatic and toxic properties of venoms of the Asian lance-headed pit viper (Genus Trimeresurus).

1. The lethalities, anticoagulant effects, hermorrhagic, thrombin-like enzyme, hyaluronidase, protease, arginine ester hydrolase, 5'-nucleotidase, L-amino acid oxidase, alkaline phosphomonoesterase, phosphodiesterase and phospholipase A activities of twenty-three samples of venoms from twelve species of Asian lance-headed pit vipers (genus Trimeresurus) were examined. 2. The results indicate that notwithstanding individual variations in venom properties, the differences in biological properties of the Trimeresurus venoms can be used for the differentiation of venoms from different species of Trimeresurus. 3. The results also suggest that differences in the biological properties of snake venoms are useful parameters in the classification of snake species. 4. Our results indicate that venoms from the species T. okinavensis exhibited biological properties markedly different from other Trimeresurus venoms examined. This observation supports the recently proposed reclassification of T. okinavensis as a member of the genus Ovophis, rather than the genus Trimeresurus.

5'-Nucleotidase↗
PubMed1988

Acidimetric assay for phospholipase A using egg yolk suspension as substrate.

A convenient acidimetric assay for phospholipase A using egg yolk suspension as substrate has been developed. The substrate mixture consists of 1 part egg yolk, 1 part 8.1 mM sodium deoxycholate, and 1 part 18 mM calcium chloride. Phospholipase A activity is measured by following the initial rate of pH change, which is linear between pH 8.0 and 7.75 and is proportional to enzyme concentration over a wide range. The assay is highly reproducible, with a coefficient of variation of 3%, and as sensitive as most established assays for phospholipase A. The assay uses inexpensive and easily available substrate and is simple to perform. It is particularly useful for monitoring phospholipase A activity in chromatography fractions.

Animals↗
PubMed1988

Partial purification of acetylcholinesterase from the venom of the shore pit viper (Trimeresurus purpureomaculatus).

Trimeresurus purpureomaculatus venom acetylcholinesterase has been partially purified by Sephadex G-200 gel filtration chromatography and DEAE Sephacel ion exchange chromatography. The enzyme has a mol. wt of 58,600. It was strongly inhibited by physostigmine salicylate and edrophonium chloride and exhibited substrate inhibition at high substrate concentration. The content of acetylcholinesterase in Trimeresurus purpureomaculatus venom was estimated to be much less than 0.3%.

Acetylcholinesterase↗
PubMed1988

A comparative study of cobra (Naja) venom enzymes.

1. The L-amino acid oxidase, hyaluronidase, alkaline phosphomonoesterase, protease, phosphodiesterase, acetylcholinesterase, phospholipase A and 5'-nucleotidase activities of 47 samples of venoms from all the six species of cobra (Naja), including five subspecies of Naja naja, were examined. 2. The results demonstrated interspecific differences in the venom contents of phospholipase A, acetylcholinesterase, hyaluronidase and phosphodiesterase. These differences in venom enzyme contents can be used for the differentiation of species of the genus Naja. 3. Thus, our results revealed a correlation between the enzyme composition of venom and the taxonomic status of the snake at the species level for the genus Naja.

5'-Nucleotidase↗
PubMed1987

Enzymatic activities of Malayan cobra (Naja naja sputatrix) venoms.

The enzymatic activities of four samples of Malayan cobra venom were investigated. There was significant variation in the contents of L-amino acid oxidase, alkaline phosphomonoesterase, acetylcholinesterase, phospholipase A, 5'-nucleotidase and hyaluronidase. The phosphodiesterase content was, however, constant. Storage of the lyophilized venom powder at 25 degrees C for 1 month did not affect the enzymatic activities. The venom enzymatic activities were generally also stable at 4 degrees C in 0.85% saline solution. After incubation at 37 degrees C for 39 days in 0.85% saline solution, the venom still retained considerable amounts of enzymatic activities. SP-Sephadex C-25 ion-exchange chromatography of the venom showed that the phospholipase A, L-amino acid oxidase, 5'-nucleotidase, phosphodiesterase and alkaline phosphomonoesterase exist in multiple forms.

Animals↗
PubMed1986

Enzymatic activities of Calloselasma rhodostoma (Malayan pit viper) venom.

The enzyme contents of four venom samples of Calloselasma rhodostoma were analyzed. The venoms contained phosphodiesterase, alkaline phosphomonoesterase, 5'-nucleotidase, protease, phospholipase A, L-amino acid oxidase, hyaluronidase, arginine ester hydrolase, arginine amidase, fibrinogenase and coagulant enzyme activities. There is significant variation in the contents of coagulant enzyme, arginine ester hydrolase, hyaluronidase, protease, phosphodiesterase, alkaline phosphomonoesterase and L-amino acid oxidase. DEAE-Sephacel ion exchange chromatography of the venom resolved it into eight major protein fractions. The eight fractions were heterogeneous and exhibited more than one type of enzymatic activity. The 5'-nucleotidase, alkaline phosphomonoesterase, protease, coagulant enzyme, arginine ester hydrolase, arginine amidase and fibrinogenase exist in multiple forms.

Aminopeptidases↗