Search PubMed⌕ Search

Biomedical subjects

Y Tang

Publications and source records attributed to Y Tang.

At least 343 records · Page 19Linked to original sources
PubMed1996

[Detection of hepatitis B virus DNA and hepatitis C virus RNA in human hepatocellular carcinoma by polymerase chain reaction].

In order to study the relationship between hepatitis B virus DNA (HBV DNA), hepatitis C virus RNA (HCV RNA) and liver cell carcinoma, HBV DNA and HCV RNA from the tumor tissue of 42 liver cell carcinoma cases were studied by polymerase chain reaction (PCR) and nested-PCR respectively. The results were as follows: one case of cholangiocarcinoma was positive for both HBV DNA and HCV RNA, and one case of biliary cystadenoma positive only for HBV DNA. Among the 40 cases of hepatocellular carcinoma (HCC), 29 were positive for HBV DNA and 13 positive for HCV RNA. There was no relationship obtained between HBV or HCV infection and the histological types of HCC, and HCV infection in HCC was not interrelated with HBV. It's considered that although HBV is still to be the leading cause of HCC in China, HCV may play an important role in hepatic carcinogenesis because of its high positive rate and increasing incidence.

Adult↗
PubMed1996

[Effect of tetrandrine on intraacinar pulmonary arterial structural remodelling and pulmonary hypertension].

Rat's pulmonary hypertension was induced by a single subcutaneous injection of monocrotaline. The influences of tetrandrine (Tet) upon the structure of intraacinar pulmonary arteries (IAPA) was studied by light and electron microscopy. The results indicated that Tet reduced the thickness of IAPA medial membrane, the ratio of the thickness of IAPA medial membrane to the diameter of IAPA, the number of circular muscular artery and partially muscular artery about 16.4%, 30.5%, 24.3% and 16.4% respectively, and Tet increased the number of nonmuscular artery about 24.7%. It also decreased the degeneration of IAPA, collagen of medial membrane, prolife-ration and myoid differentiation of the pericyte, and it increased the number of IAPA. The authors discussed why Tet caused such changes.

Alkaloids↗
PubMed1996

[Clinical applications of China-made saline-filled breast implants--a report of 62 cases].

To evaluate the China-made saline-filled breast implants, we observed 62 patients (123 sides of breasts) who received augmentation mammaplasty from March 1994 to May 1995. The implants of 200 to 450 ml were manufactured in Shanghai. All the implants were placed beneath the pectoralis major muscle and a transient over-inflation was used. Fifty-nine patients had satisfactory results. One case developed breast shrinking postoperatively due to possible damage to the implant. Another two cases were not quite satisfactory because of associated breast ptosis. Thirty-two cases were followed up for 3 months and demonstrated nice-looking and soft breasts. We conclude that (1) the quality of the China-made saline-filled breast implant is good. And (2) transient over-inflation of the implant during the operation is advantageous and is worth recommending.

Adult↗
PubMed1996

[Study of electrophysiological properties of large conductance K(+)-channels in outer hair cells from the guinea pig with patch-clamp technique].

The basic electrophysiological characteristics of large conductance K(+)-channels in the basolateral cell membrane of outer hair cells (OHC) from the guinea pig cochlea were studied with patch-clamp technique. Acutely isolated OHC preparations were obtained by enzymatic digestion and excised patches were made in cell-attached configuration to record single-channel currents led by patch-clamp micropipette and fed to patch-clamp amplifier. Data were sampled and analyzed on-line with a computer. The result showed that the typical properties of single channels of large conductance K(+)-channels were: 1. The channel was activated by depolarization of membrane and it showed a marked voltage-dependence. The channel had a unitary conductance of about 133 pS and the channel current reversed at about -30mV under asymmetrical K+ concentration gradient. 2. Tetraethylammonium (TEA, > 10 mmol/L), a potassium channel blocker, dose-dependently abolished the outward current. 3. The open probability (Po) and mean open time of this channel was markedly increased with elevation of cytoplasmic Ca2+ concentration. These results suggest that a population of voltage-dependent and Ca(2+)-activated K+ channel exists in the basolateral membrane of OHC of the guinea pig; it is characterized by a very high unitary conductance and high sensitivity to Ca2+ and is blocked by K+ channel blocker. This work provided valuable basic materials for further study on the regulation and drug influence of the type of single channels.

Animals↗
PubMed1996

[Compatibility of toxic Chinese medicines].

This article expounds the suitable compatibility and incompatibility in using toxic Chinese medicines in respects of reducing toxicity, raising curative effect, enhancing toxicity and reducing curative effect. Meanwhile it discusses the compatibility mechanism of toxic Chinese medicines in combination with the studies of clinical and modern experiments.

Drug Incompatibility↗
PubMed1996

Molecular modeling of mu opioid receptor and its interaction with ohmefentanyl.

AIM: To build up the structure model of mu opioid receptor, then combined with the receptor model, to investigate the action mechanism of ohmefentanyl on the receptor. METHODS: Using the three-dimensional structure of bacteriorhodopsin as a template, we constructed mu opioid receptor model on computer. Ohmefentanyl was then docked into the supposed receptor binding sites. RESULTS: A good ligand-receptor interaction model was achieved. The possible binding sites were found to be Asp147 and His319. The protonated N atom of ohmefentanyl form potent electrostatic and hydrogen-bonding interactions with residue Asp147 of the receptor, the O atom of the carbonyl group form weak electrostatic and hydrogen-bonding interactions with residue His319, and the two phenyl groups form pi-pi interactions with some aryl residues of the receptor around ligand. CONCLUSION: The ligand-receptor interaction model should be helpful for rational design of novel analgesic.

Amino Acid Sequence↗
PubMed1995

Interference of PR-bound RNA polymerase with open complex formation at PRM is relieved by a 10-base pair deletion between the two promoters.

Bacteriophage lambda promoters PR and PRM direct RNA synthesis in divergent orientations from start sites 82 base pairs apart. We had previously determined that the presence on the same DNA fragment of a wild type PR promoter interfered with the utilization of the PRM promoter. The results reported here concern the effects of changing the distance between the start sites by insertion or deletion of 5 or 10 base pairs. Three different techniques (run-off transcription, gel mobility shift, and permanganate probing) were employed to monitor complex formation at PRM. Unexpectedly we find that deletion of 10 base pairs between the start sites abolishes the interference, whereas insertion of 10 base pairs does not. Deletion of 5 base pairs, however, essentially prevents joint complex formation at PR and PRM. These findings suggest several ways in which for the wild type separation of the two promoters the utilization of PRM could be affected by an RNA polymerase at PR. In addition to direct steric interference, these include the obstruction of access to DNA sites necessary for optimal contact with the RNA polymerase.

Bacteriophage lambda↗
PubMed1995

Contribution of B cell subsets to delayed development of MAIDS in xid mice.

C57BL/6 (B6) mice develop a syndrome of progressive lymphoproliferation and immunodeficiency, murine AIDS (MAIDS), when infected with an etiologic replication-defective virus termed BM5def. Induction of MAIDS requires the presence of CD4+ T cells and B cells. B6 mice with altered conventional B cell function and a deficit in CD5+ B cells due to the xid mutation develop disease with a greatly prolonged latency. The association of this mutation with resistance to MAIDS was confirmed in studies of P.xid mice. To test the hypothesis that conventional B cells are required for rapid induction of disease, B6.xid mice were injected with spleen cells from nude mice or were given bone marrow from aged donors. Both sets of recipients developed advanced disease by 10 weeks post infection, suggesting that resistance to MAIDS in xid mutants may be due to effects of B cells other than the CD5+ subset.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1995

Genetic analysis of the terminal 8-bp inverted repeats of transposon Tn7.

Mutations in the terminal 8-bp (5'-T1G2T3G4G5G6C7G8-3') of the inverted repeats of the bacterial transposon, Tn7, were analysed by measuring Tn7 transposition to the attachment site, attTn7. The mutation, C2, present at either end of Tn7 reduces transposition only threefold, but in the double mutant, with C2 at both ends of Tn7, no transposition is detected. C6 mutations have no effect on transposition frequency. Replacement with 5'-A3C4G5C6G7C8-3' at the right end of Tn7 apparently abolishes transposition; yet in the double mutant, where the inverted repeats are restored by substituting this sequence at both ends of Tn7, transposition is partially rescued. This suggests that the mechanism of Tn7 transposition requires communication between the two ends. Tn7 transposition has always been seen to generate a 5-bp target duplication. This is presumed to result from a staggered cut, plus repair synthesis during transposition. We found that two of our right-end mutants, C2 and C6, sometimes yielded a 6-bp target duplication. This observation implies that cleavage of the target site might also involve interaction with the donor ends which, when mutant, relax the specificity for target-site cleavage.

Bacteriophage M13↗
PubMed1995

Excitation, oscillations and wave propagation in a G-protein-based model of signal transduction in Dictyostelium discoideum.

In an earlier paper (Tang & Othmer 1994 Math. Biosci 120, 25-76), we developed a G-protein-based model for signal transduction in the cellular slime mould Dictyostelium discoideum and showed that it can account for the results from perfusion experiments done by Devreotes and coworkers (Devreotes et al. 1979 J. Cell. 80, 300-309; Devreotes & Steck 1979 J. Cell Biol. 80, 300-309; Dinauer et al. 1980 J. Cell Biol. 86, 537-561). The primary experimental observables are the amounts of cAMP secreted and the time scale of adaptation in response to various stimuli, and we showed that the predictions of the model agree well with the observations. Adaptation in the model arises from dual receptor-mediated pathways, one of which produces a stimulatory G protein Gs and the other of which produces an inhibitory G protein Gi. In this paper we use the model to simulate the suspension experiments of Gerisch & Wick (1975 Biochem. biophys. Res. Commun. 65, 364-370) and the experiments done in cell cultures on Petri dishes (Tomchik & Devreotes 1981 Science, Wash. 212, 443-446). The model predicts excitation to cAMP stimuli, sustained oscillations, or spiral waves and target patterns, depending on the developmental stage of the cells and experimental conditions. The interaction between different pacemakers is also studied.

Animals↗
PubMed1995

Frequency encoding in excitable systems with applications to calcium oscillations.

A number of excitable cell types respond to a constant hormonal stimulus with a periodic oscillation in intracellular calcium. The frequency of oscillation is often proportional to the hormonal stimulus, and one says that the stimulus is frequency encoded. Here we develop a theory of frequency encoding in excitable systems and apply it to intracellular calcium oscillations that results from increases in the intracellular level of inositol 1,4,5-triphosphate.

Animals↗
PubMed1995

Studies on crystal structures, active-centre geometry and depurinating mechanism of two ribosome-inactivating proteins.

Two ribosome-inactivating proteins, trichosanthin and alpha-momorcharin, have been studied in the forms of complexes with ATP or formycin, by an X-ray-crystallographic method at 1.6-2.0 A (0.16-0.20 nm) resolution. The native alpha-momorcharin had been studied at 2.2 A resolution. Structures of trichosanthin were determined by a multiple isomorphous replacement method. Structures of alpha-momorcharin were determined by a molecular replacement method using refined trichosanthin as the searching model. Small ligands in all these complexes have been recognized and built on the difference in electron density. All these structures have been refined to achieve good results, both in terms of crystallography and of ideal geometry. These two proteins show considerable similarity in their three-dimensional folding and to that of related proteins. On the basis of these structures, detailed geometries of the active centres of these two proteins are described and are compared with those of related proteins. In all complexes the interactions between ligand atoms and protein atoms, including hydrophobic forces, aromatic stacking interactions and hydrogen bonds, are found to be specific towards the adenine base. The relationship between the sequence conservation of ribosome-inactivating proteins and their active-centre geometry was analysed. A depurinating mechanism of ribosome-inactivating proteins is proposed on the basis of these results. The N-7 atom of the substrate base group is proposed to be protonated by an acidic residue in the active centre.

Amino Acid Sequence↗
PubMed1995

A new protein folding recognition potential function.

On the study of protein inverse folding problem, one goal is to find simple and efficient potential to evaluate the compatibility between structure and a given sequence. We present here a novo empirical mean force potential to address the importance of electrostatic interactions in protein inverse folding study. It is based on protein main chain polar fraction and constructed in a way similar with Sippl's from a database of 64 known independent three-dimensional protein structures. This potential was applied to recognize the protein native conformations among a conformation pool. Calculated results show that this potential is powerful in picking out native conformations, in addition it can also find structure similarity between proteins with low sequence similarity. The success of this new potential clearly shows the importance of electrostatic factors in protein inverse folding studies.

Electrochemistry↗