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J Tang

Publications and source records attributed to J Tang.

At least 595 records · Page 33Linked to original sources
PubMed1983

Involvement of a cytosolic carrier protein fraction in the microsomal metabolism of benzo(a)pyrene in rat liver.

Rat liver cytosol contains two protein fractions capable of serving as benzo(a)pyrene (BP) carrier in in vitro oxidation of BP (O. Hanson-Painton, M.J. Griffin, and J. Tang, Biochem. Biophys. Res. Commun., 101: 1364-1371, 1981). The role of the smaller carrier fraction in in vitro BP transport and oxidation was studied. Using Sephadex G-100 chromatography, [14C]BP bound to the carrier was shown to preferentially transfer to the microsomes. In the presence of excess BP in suspension, the carrier protein fraction transferred levels of BP many-fold in excess of its BP-binding capacity. The carrier fraction delivered BP to liposomes prepared from microsomal lipids. However, incubation of fresh liver homogenate with protein-bound BP resulted in the transfer of over 80% of the BP to the microsomes, indicating that BP is transferred selectively. Isolated microsomes containing [14C]BP oxidized bound BP upon the addition of NADPH. Sephadex G-100 chromatography and high-performance liquid chromatography analysis of bound radioactivity indicated that oxidized products of BP were preferentially transferred back to the carrier protein fraction. Thus, the carrier fraction is capable of both transferring BP to the microsomes and accepting oxidized BP from microsomes. The transfer of oxidized BP from microsomes to the carrier fraction was inhibited by an epoxide hydrolase inhibitor, alpha-bromo-4-nitroacetophenone.

Aldehyde Dehydrogenase↗
PubMed1982

Complete amino acid sequence of streptokinase and its homology with serine proteases.

The complete amino acid sequence of streptokinase has been determined by automated Edman degradation of its cyanogen bromide and proteolytic fragments. The protein consists of 415 amino acid residues. Sequence microheterogeneity was found at two positions. The NH2-terminal 245 residues of streptokinase are homologous to the sequences of several serine proteases including bovine trypsin and Streptomyces griseus proteases A and B. The sequence alignment suggests that the active-site histidine-57 has changed to a glycine in streptokinase. The other active-site residues, aspartyl-102 and serine-195, are, however, present at the expected positions. Streptokinase also contains internal sequence homology between the NH2-terminal 173 residues and a COOH-terminal 162-residue region between residues 254 and 415. Moderate homology in predicted secondary structures also exists between these two regions. Although streptokinase is not a protease, these observations suggest that it has evolved from a serine protease by gene duplication and fusion. A COOH-terminal region of about 80 residues is apparently deleted from the second half of the duplicated structures. These observations further suggest that the three-dimensional structure of streptokinase likely contains two independently folded domains, each homologous to serine proteases.

Amino Acid Sequence↗
PubMed1982

Liquid culture of Rhizopus chinensis for the production of acid protease rhizopuspepsin.

1. Culture conditions for the production of rhizopuspepsin in liquid medium by Rhizopus chinensis have been investigated. 2. Optimum production was achieved in 24 hr shaking culture in 1% bovine serum albumin, 1% corn starch, 0.1% yeast extract and a salt mixture, pH 5. 3. Levels at 24 hr compared in isozyme pattern and in quantity to conventional solid culture on wheat bran.

Aspartic Acid Endopeptidases↗
PubMed1982

Purification and characterization of rhizopuspepsin isozymes from a liquid culture of Rhizopus chinensis.

1. Rhizopuspepsin has been purified from liquid cultures of Rhizopus chinensis. 2. Purification by ammonium sulfate precipitation, affinity chromatography on pepstatin Sepharose and low/high resolution isoelectric focusing produced five isoelectric forms. 3. The two major isozymes pI 5.1 and 5.8 did not differ significantly in amino acid composition, molecular weight and enzyme activity. 4. Three minor isozymes were partially purified as pI 7.35, 7.41 and 7.9.

Aspartic Acid Endopeptidases↗
PubMed1982

Distribution of met-enkephalin-Arg6-Phe7 in various tissues of rats and guinea pigs.

A specific and sensitive radioimmunoassay coupled with gel filtration and HPLC was used to demonstrate the presence and to measure MEAP content in stomach, doudenum, ileum, myenteric plexus, colon, heart, lung, pancreas, liver, adrenal and superior cervical sympathetic ganglia of rat and guinea pig. The highest content was found in various parts of intestine, lung and superior cervical sympathetic ganglia, pancreas and liver were practically devoid of immunoreactivity. In these tissues we found that the distribution of MEAP is not parallel to that of metenkephalin (ME). Our assay excludes interferences by high molecular weight MEAP-like peptides, the cardioexcitatory tetrapeptide (Phe-Met-Arg-Phe NH2) and the correspondent acid Phe-Met-Arg-Phe.

Adrenal Glands↗
PubMed1982

Magnetic characterization of the primary state of bacterial photosynthesis.

The results of reaction yield-detected magnetic resonance (RYDMR) experiments carried out on modified bacterial photosynthetic reaction centers (RCs) are interpreted in terms of a model that assigns the initial charge-separated radical ion-pair state, P(F), as the carrier of the spectrum. The radical pair theory, which has been invoked to explain magnetic field effects in RCs, was significantly expanded to take into consideration the electron dipole-dipole interaction. It is shown that this is the largest interaction between the components of the radical ion pair. Quantum statistical calculations are described simulating the RYDMR spectra and low-field effects in quinone-depleted RCs. The experimental data on which the simulations are based are (i) the magnitude of the field effect at 3,000 G, (ii) the field at which 0.5 of the maximal field effect is observed, (iii) the P(F) population as a function of time at zero magnetic field, (iv) the RYDMR linewidth for low microwave field strength, (v) the RYDMR intensity and width as a function of microwave field, and (vi) the maximum RYDMR intensity at H(I) approximately 2J. With this information it was found possible to characterize P(F) in terms of four parameters, two containing structural information and two with kinetic implications. These are the dipole-dipole interaction, D = -47 +/- 10 x 10(-4) cm(-1); the exchange interaction, J = -7.5 +/- 1.9 x 10(-4) cm(-1); and the inverse rate constants of the decay of the radical pair states with singlet and triplet spin functions, respectively, k(S) (-1) = 15 +/- 4 nsec and k(T) (-1) = 1.8 +/- 0.2 nsec. The structural and dynamic implications of these parameters are discussed.

Journal Article↗
PubMed1982

The implication of central serotonin in electro-acupuncture tolerance in the rat.

Electro-acupuncture (EA) applied to both legs for 30 min raised the tail flick latency of the rat significantly. This effect of EA analgesia became attenuated and finally disappeared after repeated EA stimulations, which was termed EA tolerance. EA tolerance and its cross tolerance to morphine analgesia were found to be partially reversed by intracerebro-ventricular injection of 5-hydroxytryptophan (5-HTP), the precursor of 5-hydroxytryptamine (5-HT). However, there was no depletion in cerebral 5-HT, nor was there decrease of the number of 5-HT receptors in the brain of the EA tolerant animals. Results obtained from different lines of analysis point to the conclusion that development of tolerance to profoundly released 5-HT during prolonged EA stimulation may constitute one of the mechanisms for EA tolerance.

5-Hydroxytryptophan↗
PubMed1980

Central neurotransmitters and acupuncture analgesia.

The role played by central neurotransmitters in acupuncture analgesia was evaluated by correlating neurochemical changes in central nervous system with the acupuncture effect, as well as modification of the acupuncture effects by pharmacological manipulations of central neurotransmitters. The results of experimental studies which were performed mainly on rats and rabbits indicated that central serotonin and endogenous opiate-like substances (OLS) seem to be the most important substrates for mediation of acupuncture analgesia while central catecholamines, especially norepinephrine through alpha receptors, may exert an antagonistic effect. It was also found that prolonged and repeated acupuncture resulted in a gradual decrease of the acupuncture effects. The development of some endogenous anti-opiate substrates (AOS) in central nervous system was tentatively implicated.

Acetylcholine↗