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Biomedical subjects

C S Tan

Publications and source records attributed to C S Tan.

35 records · Page 2Linked to original sources
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↗
PubMed1984

Pneumothorax and subcutaneous emphysema complicating endotracheal intubation.

We report subcutaneous emphysema and pneumothorax as immediate complications of endotracheal intubation in a patient with diffuse interstitial lung disease. We postulate increased intra-alveolar pressure during intubation leading to rupture of a subpleural bleb or cyst as a possible mechanism causing these complications.

Emphysema↗
PubMed1981

Effect of assisted ventilation on respiratory drive of normal anesthetized dogs.

We measured the diaphragm electromyogram (EMGd) and airway occlusion pressure (P100) of anesthetized dogs at the ends of 30-min of alternating spontaneous breathing and assisted mechanical ventilation (inspiratory positive pressure triggered by a minimal inspiratory effort; IPPB). Peak airway pressures (Paw) of 5, 10, 15, and 20 cm H2O were applied in random order during IPPB. The initial rate of rise of EMGd (4 experiments) and P100 (9 experiments) decreased during IPPB, both in proportion to the Paw. At Paw of 20 cm H2O, PaCO2, EMGd and P100 decreased on the average 5.2 Torr, 58% and 56%, respectively. When PaCO2 was kept the same during IPPB as during spontaneous breathing (8 experiments), IPPB reduced EMGd and P100 15% and 24% respectively, both statistically significant. During progressive cooling of both cervical vagi, the effect of IPPB (Paw=20 cm H2O) on EMGd and P100 decreased progressively, near maximal at 6--4 degrees C and after vagotomy. However, the decrease in PaCO2 during IPPB was not affected. These data suggest that increasing tidal volume during IPPB depresses respiratory drive (EMGd and P100), partially from decreased PaCO2 and partially from stimulating pulmonary stretch receptors. The drop in PaCO2 during IPPB does not appear to be vagally mediated.

Animals↗
PubMed1981

Supernormal maximal mid-expirartory flow rates in diffuse interstitial lung disease.

We studied the frequency of changes in maximal mid-expiratory flow rate (MMF) in 32 nonsmokers and 22 smokers with diffuse interstitial lung disease (DILD) and in 36 health nonsmoking control subjects. Supernormal MMF to total lung capacity (TLC) and MMF to forced vital capacity (FVC) ratios (greater than 120% of predicted) were significantly more common in nonsmokers with DILD than in healthy nonsmokers, but the prevalence of supernormal forced expired volume in 1 s (FEV1) to FVC ratios was similar. In non-smokers with DILD, a supernormal MF/TLC ratio was associated with a significantly greater static lung recoil pressure (Pst) and a tendency toward a higher maximal expiratory flow to Pst ratio than in normals, suggesting that the increased MMF is due to the combined effects of increased driving pressure for flow and reduced resistance in peripheral airways.

Adult↗
PubMedDate not supplied

Atypical transmural thoracic lipoma: CT diagnosis.

Two cases of transmural thoracic lipomas demonstrate a pattern of rib involvement that has not been previously reported. The lipomas presented with an otherwise characteristic appearance on plain radiography and CT.

Adult↗
PubMedDate not supplied

The spectrum of opportunistic filamentous fungi present in the CBS culture collection.

The mould collection of the Centraalbureau voor Schimmelcultures, Baarn, The Netherlands, was screened for isolates originating from warm-blooded animals. The range of species indicates that distribution of clinically relevant, pathogenic or opportunistic strains over the fungal kingdom is non-random. Some opportunistic fungi possess adaptations to life under hostile environmental conditions, enabling them to survive inside the human body. Presence of melanin or carotene seems to be an important virulence factor. Opportunistic fungi which sporulate in submersion are able to disseminate or cause severe local mycoses when the aspecific immune system of the host is impaired. Mycoses caused by a few dimorphic fungi, mostly in their natural ecological niche living in association with vertebrates, are promoted by specific immune deficiencies.

Animals↗
PubMedDate not supplied

Diagnostic problems with imported cases of mycetoma in The Netherlands.

Eight cases of imported mycetomata in The Netherlands are reviewed. Seven of these were cultured; only one isolate, Actinomadura madurae, belonged to a species commonly known as an agent of mycetoma. The remaining strains either belonged to very rare species, such as Phialophora cyanescens, or could not be identified at all. The list of possible agents of mycetoma apparently needs to be expanded. In addition, the concept of endemic occurrence of aetiological agents of eumycetoma needs revision. Divergent saprophytes may be involved which are able to survive in human tissue.

Adult↗
PubMedDate not supplied

Tillage, intercrop, and controlled drainage-subirrigation influence atrazine, metribuzin, and metolachlor loss.

Atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] have been found with increasing occurrence in rivers and streams. Their continued use will require changes in agricultural practices. We compared water quality from four crop-tillage treatments: (i) conventional moldboard plow (MB), (ii) MB with ryegrass (Lolium multiflorum Lam.) intercrop (IC), (iii) soil saver (SS), and (iv) SS + IC; and two drainage control treatments, drained (D) and controlled drainage-subirrigation (CDS). Atrazine (1.1 kg a.i. ha-1), metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazine-5(4H)-one] (0.5 kg a.i. ha-1), and metolachlor (1.68 kg a.i. ha-1) were applied preemergence in a band over seeded corn (Zea mays L.) rows. Herbicide concentration and losses were monitored from 1992 to spring 1995. Annual herbicide losses ranged from < 0.3 to 2.7% of application. Crop-tillage treatment influenced herbicide loss in 1992 but not in 1993 or 1994, whereas CDS affected partitioning of losses in most years. In 1992, SS + IC reduced herbicide loss in tile drains and surface runoff by 46 to 49% compared with MB. The intercrop reduced surface runoff, which reduced herbicide transport. Controlled drainage-subirrigation increased herbicide loss in surface runoff but decreased loss through tile drainage so that total herbicide loss did not differ between drainage treatments. Desethyl atrazine [6-chloro-N-(1-methylethyl)-1,3,5-triazine-2,4-diamine] comprised 7 to 39% of the total triazine loss.

Acetamides↗
PubMedDate not supplied

Runoff and drainage losses of atrazine, metribuzin, and metolachlor in three water management systems.

Rainfall can transport herbicides from agricultural land to surface waters, where they become an environmental concern. Tile drainage can benefit crop production by removing excess soil water but tile drainage may also aggravate herbicide and nutrient movement into surface waters. Water management of tile drains after planting may reduce tile drainage and thereby reduce herbicide losses to surface water. To test this hypothesis we calculated the loss of three herbicides from a field with three water management systems: free drainage (D), controlled drainage (CD), and controlled drainage with subsurface irrigation (CDS). The effect of water management systems on the dissipation of atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine), metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazine-5(4H)-one), and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] in soil was also monitored. Less herbicide was lost by surface runoff from the D and CD treatments than from CDS. The CDS treatment increased surface runoff, which transported more herbicide than that from D or CD treatments. In one year, the time for metribuzin residue to dissipate to half its initial value was shorter for CDS (33 d) than for D (43 d) and CD (46 d). The half-life of atrazine and metolachlor were not affected by water management. Controlled drainage with subsurface irrigation may increase herbicide loss through increased surface runoff when excessive rain is received soon after herbicide application. However, increasing soil water content in CDS may decrease herbicide persistence, resulting in less residual herbicide available for aqueous transport.

Acetamides↗
PubMedDate not supplied

Molecular taxonomy and GC/MS of metabolites of Scytalidium hyalinum and Nattrassia mangiferae (Hendersonula toruloidea).

ARDRA of ribosomal genes confirmed that the hyphomycete Scytalidium hyalinum is identical to the coelomycete Nattrassia mangiferae (Hendersonula toruloidea, with arthroconidial synanamorph Scytalidium dimidiatum). S. hyalinum may be just a melanin-less cultural mutant of S. dimidiatum. This explains why the two species are regularly found in the same patient population as agents of human dermatomycosis. Two strains from plant sources were found to be identical to the human strains in ITS-RFLP patterns. RFLP of SSU and LSU was hampered by the frequent occurrence of introns. Profiles of secondary metabolites were studied using TLC, GC and GC/MS. Production of metabolites varies considerably with the strain, but two naphthoquinone compounds were nearly always present. Selected-ion monitoring (SIM) of these compounds enabled the specific recognition of the taxon.

Animals↗