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T Tang

Publications and source records attributed to T Tang.

103 records · Page 6Linked to original sources
PubMed1968

Mixed chelates of Ca(II)-pyridine-2,6-dicarboxylate with some amino acids related to bacterial spores.

The high resistance of bacterial spores to heat has been repeatedly postulated to be due to stabilization of spore biopolymers by metal chelate compounds. Binding of calcium dipicolinic acid (Ca(II)-DPA) with spore proteins and amino acids has been discussed in the literature, but equilibrium data are generally lacking. By means of potentiometric pH titrations at 25 degrees C and an ionic strength of 1.0 (KNO(3)), the formation of Ca(II)-DPA (1:1 and 1:2) chelates and the interactions of Ca(II)-DPA chelate with a mole of each of three typical amino acids viz., cysteine, alanine, and glycine has been investigated. Analysis of the potentiometric data indicates that calcium and DPA forms 1:1 and 1:2 chelates with log K(ML1) = 4.39 +/- 0.01 and log K(ML2) = 2.25 +/- 0.01. In the presence of an equimolar amount of each of the amino acids under consideration, the Ca(II)-DPA chelate forms mixed ligand (ternary) chelate yielding the following stepwise stability constants: log K(1) = 4.17 +/- 0.01, log K(2) = 0.78 +/- 0.01 for cysteine, log K(1) = 4.06 +/- 0.01, log K(2) = 0.65 +/- 0.01 for alanine, and log K(1) = 4.30 +/- 0.02, log K(2) = 0.11 +/- 0.01 for glycine. Methods for calculating the stability constants of the mixed ligand system have been developed. On the basis of the potentiometric equilibrium data, possible structures for the various calcium chelate species are discussed. The data suggest that the differences in heat resistance of various strains of bacterial spores may conceivably be related to the differences in composition and stability of coordination complexes in the spore.

Alanine↗
PubMedDate not supplied

Heterogeneity of endothelial cell function for angiotensin conversion in serial-arranged arterioles.

The involvement of the endothelial cell in the vasoconstriction induced by angiotensin I and II (AI, AII), and norepinephrine (NE) was studied in microvessels of the hamster cheek pouch before and after the following procedures: endothelial impairment by light-dye treatment, inhibition of angiotensin-converting enzyme (ACE), blockade of endothelium-derived relaxing factor (EDRF) and inhibiting prostaglandin (PG) synthesis. The results showed that in large 2nd-order arterioles, endothelial impairment did not affect the vasoconstrictor activity of AII and NE, nor did it alter ACE activity. However, in small 4th-order arterioles, endothelial impairment significantly reduced angiotensin conversion without altering the vasoconstrictor responses to either AII or NE. Thus, the endothelium plays differential roles in the modulation of local angiotensin conversion in these distinct segments of serial-arranged arterioles. Furthermore, it is unlikely that the vasoconstrictor response to AII in these arterioles is modulated by the endothelium through a pathway involving the release of EDRF or PGs.

Angiotensin II↗
PubMedDate not supplied

Effects of N-nitrosodiethylamine on murine hepatic mixed-function-oxidase activities.

Administration of N-nitrosodiethylamine (diethylnitrosamine, DEN) to mice caused a loss of cytochrome P-450 and a corresponding depression in the activities of aminopyrine demethylase and aniline hydroxylase. Maximum effects were achieved 24 hr. after a single dose of 100 mg/kg. In chronic experiments, similar effects were achieved after animals had been drinking water containing 50 ppm of DEN for 12 weeks. The effects of DEN on aminopyrine demethylase could not be reproduced by collecting microsomes, from homogenates which had been treated with DEN in vitro. Homogenates prepared from livers of mice treated chronically with DEN were used to activate compounds to mutagens in the Salmonella/microsome test of Ames. Activation by these homogenates was not lower than activation by homogenates prepared from control animals. In fact, activation of aflatoxin B1 was enhanced by use of homogenates from DEN-treated animals as source of activating enzymes.

Aminopyrine N-Demethylase↗
PubMedDate not supplied

Effects of phenobarbital and methylcholanthrene on hepatic mixed-function-oxidase activities in hamsters.

The effects of the inducers phenobarbital (PB) and 3-methylcholanthrene (MC) on hamster liver mixed-function-oxidase activities were studied. Both inducers increased to content of cytochrome P-450 in the microsomes, aminopyrine demethylase activity, and biphenyl 4-hydroxylase activity when given for 8 days. The ability of liver homogenates from treated animals to activate compounds to mutagens was tested using the Salmonella/microsome test. Neither inducer appreciably altered mutagenicity of 2-acetylaminofluorene, benzidine, benzo(a)pyrene, aflatoxin B1, or sterigmatocystin. Mutagenicity of MC was increased when homogenates from MC-treated hamsters were used as a source of activating enzymes, and this mutagenicity could be correlated with increased biphenyl 2-hydroxylase activity.

Animals↗