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C S Tang

Publications and source records attributed to C S Tang.

158 records · Page 9Linked to original sources
PubMed1986

[Pulse oximeter].

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Anesthesia↗
PubMed1982

Collection and Identification of Allelopathic Compounds from the Undisturbed Root System of Bigalta Limpograss (Hemarthria altissima).

Collection of allelopathic chemicals from the undisturbed plant root system is difficult because of their low concentrations and the high level of contaminants in growth media such as soil. A new approach for the continuous trapping of quantities of extracellular chemicals from donor plants is described. Bigalta limpograss (Hemarthria altissima), a tropical forage with allelopathic activities, was established in sand culture. Nutrient solution was circulated continuously through the root system and a column containing XAD-4 resin. Extracellular hydrophobic metabolites were selectively adsorbed by the resin, while inorganic nutrients were recycled to sustain plant growth. Columns were eluted with methanol and the eluate separated into neutral, acidic, and basic fractions. Bioassays of trapped root exudates using lettuce seed combined with paper and thin layer chromatography showed that the inhibitors were mainly phenolic compounds. The active neutral fraction was methylated and analyzed by gas chromatography-mass spectrometry. Twelve compounds were identified, with two additional compounds tentatively identified. 3-Hydroxyhydrocinnamic, benzoic, phenylacetic, and hydrocinnamic acids were the major rhizospheric compounds with known growth regulatory activities.Inasmuch as the root system was undisturbed and the recovery of exudates was highly efficient compared to conventional solvent extraction methods, this trapping system should be useful for a wide range of studies that relate to the chemistry of the rhizosphere.

Journal Article↗
PubMed1976

Inhibition of papain by isothiocyanates.

During the tapping of papaya latex for papain (EC 3.4.22.2), benzyl isothiocyanate is enzymatically produced from benzylglucosinolate, a major component of the latex fluid. Benzyl isothiocyanate inhibits papain hydrolysis of alpha-N-benzoyl-L-arginine ethyl ester (Bz-Arg-OEt). Since tha availability of the papain sulfhydryl group to 5,5'-dithiobis-2-nitrobenzoid acid (Nbs2) is inversely related to the extensiveness of the isothiocyanate inhibition, and treatment by benzyl isothiocyanate reduces the affinity of activated papain to a mercurial-Sepharose column, it is proposed that the papain sulfhydryl reacts with the electrophilic functional group of this inhibitor. Fifteen isothiocyanates were selected and both the chemical reactivity antors are involved in the isothiocyanate-papain inhibition: (1) chemical reactivity of isothiocyanates, (2) presence or absence of an aromatic substitution, and (3) the spatial relationship of the aromatic moiety to the -N = C = S group of isothiocyanates. These data further suggest the presence of an 'aromatic site' near the Cys-25 sulfhydryl group of activated papain. Based on the existing model of papain molecule, the imidazole group of His-159 coincides well with our proposed aromatic site. The prospects of using isothiocyanates as chemical probes for the study of chemical environment of active sites in other enzymes are briefly discussed.

Binding Sites↗
PubMed1974

Inhibition of ethylene evolution in papaya pulp tissue by benzyl isothiocyanate.

Papaya (Carica papaya L.) pulp tissue disks in an incubation medium composed of 0.4 m sucrose evolve ethylene at an optimum pH of 5.25 at 30 C. Disks of young preclimacteric fruit evolve the gas linearly with fruit age until fruit age reaches 4 months. Disks from 5-month-old postclimacteric fruit produce approximately 5-fold more ethylene than disks from 4-month-old fruit. Ethylene evolution by unaged papaya disks is inhibited potently by benzyl isothiocyanate. The compound inhibits production of ethylene by approximately 60% at a concentration of 0.046 mm. However, in aged papaya disks benzyl isothiocyanate causes no inhibition of ethylene production indicating that the compound inhibits the induction of the ethylene-producing system rather than the evolution of the gas per se. Even at a 2-fold higher concentration benzyl isothiocyanate has no effect on respiration of unaged papaya disks. It is proposed that benzyl isothiocyanate may act as an endogenous regulator of ethylene evolution in papaya fruit.

Journal Article↗
PubMed1972

Bacterial degradation of benzyl isothiocyanate.

Bacteria that degrade benzyl isothiocyanate to benzylamine and hydrogen sulfide were isolated from papaya pulp homogenate by enrichment culture techniques. These organisms were identified as members of Enterobacter cloacae.

Bacteriological Techniques↗
PubMedDate not supplied

Effect of active oxygen species on intimal proliferation in rat aorta after arterial injury.

Proliferation and migration of vascular smooth-muscle cells (VSMCs) are essential events in neointimal hyperplasia. Recent findings that active oxygen species induce pro-oncogene expression, and stimulate VSMC DNA synthesis and cell division, suggest that active oxygen species may play an important role in intimal proliferation after arterial injury. To determine how the redox state of the artery was altered by injury, the levels of thiobarbituric-acid-reactive substances (TBARs, markers of lipid oxidation) and glutathione peroxidase (GSH-PX, the enzyme responsible for the production of glutathione, a major intracellular antioxidant) were measured in the rat aorta after balloon injury. There was an inverse relationship between the level of TBARs, which increased significantly to a maximum 17% greater than normal at 10 days after injury (p<0.05, n=7), and the activity of GSH-PX, which decreased significantly to a minimum 36.5% less than normal at 10 days after injury (p<0.05, n=7). To determine whether maintaining a more reduced vessel environment would inhibit intimal proliferation, L-cysteine was administered by intraperitoneal injection from 3 days before to 14 days after balloon injury. At 14 days after the arterial injury, the aorta was harvested for histological and morphometric measurements of TBARs and GSH-PX. At 7 and 14 days after balloon injury, the aorta was harvested for [3H]thymidine incorporation studies. Efficacy of therapy was demonstrated by a significant decrease in the level of TBARs and an increase in the activity of GSH-PX (p<0.05 vs. the control group, n=7). In the L-cysteine group, all parameters of intimal proliferation were significantly reduced compared to the controls, including the intima:media ratio (0.091 vs. 0.253, p<0.05); the cross-sectional area of the neointima (0.0563 compared to 0.140 mm2, p<0.05), coverage of the internal elastic lamina by the neointima (23.44 compared to 43.27%, p<0.05), and [3H]thymidine incorporation (at 7 days 240.58 vs 350.68 cpm/mg tissue, p<0.05; at 14 days 181.71 vs. 275.30 cpm/mg tissue, p<0.05). These results demonstrate dynamic alterations in the vessel redox state after arterial injury, and suggest that maintaining a more reduced environment (e.g. administration of L-cysteine) will reduce intimal proliferation after arterial injury.

Animals↗
PubMedDate not supplied

Alcoholic carbowax prefixation and formal alcohol fixation. A new technique for urine cytology.

OBJECTIVE: To compare the cellular yield and sensitivity of cancer detection by urine cytology using alcoholic carbowax as a prefixative and formal alcohol as a final fixative with the conventional centrifugation-and-smearing method. STUDY DESIGN: Four hundred seventeen voided urine specimens were examined. Each specimen was divided into two equal portions. One portion was centrifuged and wet fixed (CS). The other was treated with alcoholic carbowax as a prefixative and then fixed in formal alcohol (CW). The smears were studied for cellular yield, morphology, cancer detection rate and typing. RESULTS: The CW method yielded significantly more cells with excellent morphology. It detected 25 more abnormal cases out of a total of 86, including 5 more transitional cell carcinomas, as compared to the CS method. This finding was statistically significant (P < .0000003). CONCLUSION: The CW method is simple and enhances cellular yield and the cancer detection rate as compared to the conventional centrifuge-and-smear technique.

Alcohols↗
PubMedDate not supplied

Sensitivity of sputum cytology after homogenization with dithiothreitol in lung cancer detection. Two years of experience.

OBJECTIVE: To compare the sensitivity of sputum cytology using the dithiothreitol homogenization method (DTT) with that of the standard pick-and-smear (PS) method in lung cancer detection. STUDY DESIGN: In a two-year period, 2,428 sputum specimens were examined. Standard PS smears were prepared as controls; the remainder of the specimens were homogenized with DTT before smears were prepared. The sensitivity of the two methods in detecting positive cases was compared. RESULTS: Among 260 positive cases, the DTT method detected 256, while the PS method detected only 212, representing a difference of 17%. The DTT method also detected 28 more suspicious cases and permitted definitive typing of the tumor in a further 11 cases. CONCLUSION: Homogenization of sputum with DTT is not only a simple and versatile method but also a more sensitive method as compared to the PS method in lung cancer detection.

Dithiothreitol↗
PubMedDate not supplied

Homogenization of sputum with dithiothreitol for early diagnosis of pulmonary malignancies.

Homogenization of sputum with dithiothreitol (DTT) has not been used in cytology for the detection of malignant cells. We examined the efficacy of this method as compared to the conventional "pick and smear" (PS) method. Smears were prepared from sputum samples using the PS technique to act as the control. The remaining sputum was digested with an equal volume of 0.3% DTT in 70% ethanol at room temperature. The cells were washed with 35% ethanol and smears prepared. The DTT-treated specimens gave a much higher concentration of evenly distributed cells. The background was clear and the morphology comparable to that of the control. More positive cases were detected with the DTT than the conventional PS technique. Homogenization of sputum with DTT is a simple and effective method of screening for pulmonary malignancies.

Cytological Techniques↗