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J Qian

Publications and source records attributed to J Qian.

At least 217 records · Page 12Linked to original sources
PubMed1994

[Detection of SOS response inhibitor with E. coli GW1104 and GW1107 and its mechanism].

E. coli GW1104 and GW1107 are temperature-sensitive strains carrying a fusion gene umu:: Mud(Ap,lac) with genotypes recA441 (tif-1) and recA441 (tif-1),lexA (Def) (spr), respectively. SOS response can be produced spontaneously at 32 degrees C in E. coli GW1107, and induced at 42 degrees C in both E. coli GW1107 and GW1104. To detect SOS response inhibitor and to study its mechanism, a quick-test-system was established based on their genetic characteristics of the two strains. It was found some kinds of Chinese herbal medicine, vegetables, and chemicals could inhibit SOS response in the strains to different extent with varied mechanisms. Shell of water chestnut could inhibit temperature-induced SOS response at 42 degrees C in E. coli GW1104, and spontaneously-produced one at 32 degrees C in E.coli GW1107. Chinese chives can only inhibit temperature-induced SOS response in E. coli GW1104. It suggested the former's inhibition effect on SOS response occurred at lexA gene or on the pathway of SOS response before lexA gene, and so did the latter's on the pathway after lexA gene.

Antimutagenic Agents↗
PubMed1994

Hearing shift and inner ear pathology of guinea pigs exposed to octave bands of noise centered at 63 Hz and 4 kHz.

Twenty-four guinea pigs with normal Preyer's reflex were exposed to the octave bands of noise centered at 63 Hz and 4 kHz, 110 dB SPL. The duration of exposure was 4 and 8 hours respectively. The permanent shift of the guinea pigs at the above two frequencies was at 4-8 kHz. As the duration of exposure were 4 hours, the threshold shift at 63 Hz was smaller than that at 4 kHz. But as the duration of exposure was 8 hours, the threshold shift at 63 Hz and 4 kHz was almost the same. No morphological change of the inner ear was observed in the guinea pigs exposed for 4 hours at the octave bands of noise centered at 63 Hz and 4 kHz, but ultrastructural abnormalities were noted. After the animals were exposed for 8 hours, morphological, ultrastructural changes in the inner ear were observed. The main pathologic changes were seen at the second turn of the cochlea. These changes in hearing physiology and pathology suggest that a high intensive low frequency noise can result in high frequency hearing loss and that the use of A-weighted levels of specific damage risk criteria for noise sources may be inappropriate.

Animals↗
PubMed1993

Light-induced reorientation in the purple membrane.

Reorientation of bacteriorhodopsin in the native purple membrane was studied by time-resolved linear dichroism spectroscopy (TRLD) over the millisecond time regime. The time responses observed in TRLD are distinctly different from the isotropic transient absorption (TA) at wavelengths in the range 550-590 nm, where the bacteriorhodopsin ground state absorbs. In contrast, the TA and TRLD responses have nearly identical time dependence at 410 and 690 nm, where the intermediates M and O, respectively, principally contribute. These results demonstrate ground-state bacteriorhodopsin reorientation triggered by the photocycle. The TRLD and TA data are analyzed to test models for reorientational motion. Rotational diffusion of ground-state bacteriorhodopsin cannot account for the details of the data. Rather, the results are shown to be consistent with a reversible reorientation of "spectator" (nonexcited) members of the bacteriorhodopsin trimer in the purple membrane in response to the photocycling member of the trimer. This response may be associated with cooperativity in the trimer.

Anisotropy↗
PubMed1992

Reduced susceptibility to HIV-1 infection of ethyl-methanesulfonate-treated CEM subclones correlates with a blockade in their protein kinase C signaling pathway.

We have described the isolation of chemically induced CEM subclones that express CD4 receptors and bind soluble gp120, yet show a markedly reduced susceptibility to infection with HIV-1. Two subclones were found to have an abnormal response to the protein kinase C (PKC) activator PMA. PMA treatment induced CD3 and CD25 (IL-2R) receptors on the parental line and on other ethyl-methanesulfonate-derived subclones, but not on these two mutants. Direct assays of PKC activity were conducted. Total cellular PKC enzymatic activity was found to be normal in these subclones. PMA-induced CD4 down-modulation occurred normally. In addition, activation of c-raf kinase was normal. Since HIV-1 long terminal repeat contains two functional nuclear factor kB (NF-kB) regulatory elements, we studied the ability of PMA to induce NF-kB binding activity by different assays. Chloramphenicol acetyl transferase (CAT) assays using the HIV-1 (-139)long terminal repeat-CAT construct showed no PMA induction of CAT activity in these subclones (unlike the parental line and other subclones). Okadaic acid, an inhibitor of phosphatases 1 and 2A, did not overcome the defect in these subclones. Gel retardation assays, using a 32P-probe containing the HIV-1 NF-kB probe and nuclear extracts from PMA-treated cells, showed significantly reduced induction of nuclear NF-kB binding proteins in these two subclones compared with wild type CEM and a control subclone. Deoxycholate treatment of cytoplasmic extracts from these subclones released much reduced NF-kB binding proteins from their cytoplasmic pools. Thus, reduced levels of PKC-induced nuclear NF-kB activity in two T cell subclones did not affect their normal cell growth, but correlated with a pronounced reduction in their susceptibility to HIV-1 infection.

Base Sequence↗
PubMed1992

[Catheter closure of patent ductus arteriosus without thoracotomy].

Transcatheter plugging of patent ductus arteriosus with modified Porstmann's method was performed in children of school age and adults (130 cases) in recent 10 years. We devised a set of instrument, self-made plastic Ivalon for tailoring the plugs, developed the technique of retrograde aortic angiography to measure the diameter of the ductus, and determined the criteria of definite lodgement of the plug. 3 cases failed because their femoral arteries were too small to have the catheter sheath introduced. The other 3 cases developed thrombosis of the femoral arteries after the procedure, and the thrombi were removed by surgery.

Adolescent↗
PubMed1992

A basic study on the hybridoma cell culture of microencapsulation.

We report here that the constitute component of Na alginate is a very important factor on microcapsular strength. We developed a method of estimating viable cell count in batch microcapsular process and the factors influencing the full loading rate in microcapsules. The physical integrity of microcapsule and full loading rate were greater than 95%. The cell line of C3 hybridoma was found to reach maximum intracapsule cell density of 8.8 x 10(6) - -2.1 x 10(7) cells/ml during static culture period of 6-10 days. During this period, the mouse monoclonal antibody accumulated in the intracapsular space to a final concentration of 379 micrograms/ml. Analysis of intracapsular protein by SDS gel electrophoresis during the culture period demonstrated that there was one band or two bands of protein which means its purity is relatively high.

Alginates↗
PubMed1991

Conformational motion in bacteriorhodopsin: the K to L transition.

By comparison of the time dependence of linear dichroism and transient absorption in light-adapted bacteriorhodopsin over the first 10 microseconds following excitation, conformational motion in the protein has been detected. Time-resolved linear dichroism and transient absorption scans are reported for several wavelengths that probe the K610 and L550 intermediates in the bacteriorhodopsin photocycle. The transient absorption scans are insensitive to conformational motion and yield the lifetimes of the K610 and L550 intermediates. In contrast, the time-resolved linear dichroism scans demonstrate orientational motion of the chromophore with a 1.7-microsecond rotational time. The wavelength dependence of the least-squares fitting parameters establishes that this motion is associated with L550. This motion is discussed in relation to a protein conformational change in the course of the bacteriorhodopsin photocycle. No evidence is observed for orientational motion on the time scale of the L550----M410 transition.

Bacteriorhodopsins↗
PubMed1991

Plasmid pSK1002-mediated mutator effect and SOS response and SOS mutagenesis of 2,5-dichloronitrobenzol in Salmonella typhimurium.

The plasmid pSK1002 (umuC'-'lacZ) could increase the number of revertants induced by methyl methanesulfonate (MMS) and 4-nitroquinoline-N-oxide (4NQO) in Salmonella typhimurium TA 1535 (his-). The values induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were not different irrespective of the presence or absence of plasmid. However, the plasmid pKM101-mediated mutagenesis-enhancing effect was much greater than that mediated by pSK1002 as induced by the 3 mutagens mentioned above. Moreover, the plasmid pSK1002 could induced umu-mediated SOS response in the presence of any of these 3 mutagens or of mitomycin C, and a dose-response relationship was evident. It shows that pSK1002 (umuC'-'lacZ) has a dual biological effect, namely a mutator effect and the effect of inducing the SOS response. Besides, this study has proved SOS mutagenesis of 2,5-dichloronitrobenzol (2,5-DCNB) because of the dual indicator nature of pSK1002. Therefore, it is probable that pSK1002 could be further developed and applied in studying the relation between the SOS response and mutagenesis and in identifying environmental SOS mutagens.

Mutagenesis↗
PubMed1991

The effect of temperature and oligonucleotide primer length on the specificity and efficiency of amplification by the polymerase chain reaction.

The polymerase chain reaction (PCR) is most effectively performed using a thermostable DNA polymerase such as that isolated from Thermus aquaticus. Since temperature and oligonucleotide length are known to control the specificity of oligonucleotide hybridization, we have investigated the effect of oligonucleotide length, base composition, and the annealing temperature on the specificity and efficiency of amplification by the PCR. Generally, the specificity of PCR is controlled by the length of the oligonucleotide and/or the temperature of annealing of the primer to the template. An empirical relationship between oligonucleotide length and ability to support amplification was determined. This relationship allows for the design of specific oligonucleotide primers. A model is proposed which helps explain the observed dependence of PCR on annealing temperature and length of the primer.

Base Sequence↗
PubMed1991

[Plasmid pSK1002-mediated mutator effect and SOS response in Salmonella typhimurium and its use for detection of mutagens].

The plasmid pSK1002 carrying the fused gene umuC'-'lacZ could increase the number of revertants induced by methyl methanesulfonate (MMS) and 4-nitroquinoline-1-oxide (4NQO) in S. typhimurium LT2 TA 1535(his-). Maximum revertants were 4.35 and 3.96 times that of the controls without the plasmid. The values induced by N-methyl-N'-nitrosoquanidine (MN-NG) were about the same with or without plasmid. However, the plasmid pKM101-mediated mutagenesis-enhancing effect was much greater than that through the mediation of pSK1002 as induced by the three mutagens mentioned above. Moreover, the plasmid pSK1002 could induce umu-mediated SOS response in the presence, of either mutagen stated above and mitomycin C(MMC). Maximum levels of beta-galactosidase (beta-gal) activity induced by four mutagens respectively were 4.56, 7.14, 4.94, and 3.42 times that of the controls, and a dose-response relationship was evident. The sensitivity of SOS response was superior to mutagenesis-enhancing effect. It showed that pSK1002 (umuC'-'lacZ) had a dual biological effect, namely, mutator effect and the effect of inducing SOS response. Besides, this study has proved SOS mutagenesis of 2,5-dichloronitrobenzol (2,5-DCNB). Because of the dual indicator nature of pSK1002, it is probable that pSK1002 would be further developed and applied in studying the relation between SOS response and mutagenesis, and monitoring environmental SOS mutagens.

Humans↗
PubMed1990

Rat liver NAD(P)H:quinone oxidoreductase: cDNA expression and site-directed mutagenesis.

Rat liver NAD(P)H:quinone oxidoreductase cDNA was cloned and expressed in a eukaryotic cell expression plasmid containing a cytomegalovirus (CMV) promoter. Transient expression of enzyme activity and RNA transcription were measured in COS7 cells. The expressed quinone reductase has kinetic properties similar to the rat liver enzyme and is inhibited by dicourmarol, a known inhibitor of NAD(P)H:quinone oxidoreductase. Site-directed mutagenesis experiments carried out using this expression system revealed possible regions involved in NAD(P)H binding.

Amino Acid Sequence↗
PubMed1987

Structural evidence for the authenticity of the human retinoblastoma gene.

The retinoblastoma (Rb) gene is the prototype for a class of recessive human cancer genes in which loss of activity of both normal alleles is thought to be associated with tumorigenesis. Sixteen of 40 retinoblastomas examined with a complementary DNA probe shown to be the Rb gene had identifiable structural changes of the Rb gene including in some cases homozygous internal deletions with corresponding truncated transcripts. An osteosarcoma also had a homozygous internal deletion with a truncated transcript. In addition, possible hot spots for deletion were identified within the Rb genomic locus. Among those tumors with no identifiable structural changes there was either absence of an Rb transcript or abnormal expression of the Rb transcript. Comparison of the structural changes in the tumor cells and fibroblasts of certain patients provided support for Knudson's two-hit hypothesis for the development of retinoblastoma at the molecular level. The ability to detect germline structural deletions in fibroblasts from some patients with bilateral retinoblastoma also indicates that the isolated gene is useful for diagnostic purposes.

Alleles↗
PubMed1985

Studies on the induction of tolerance to alloantigens. I. The abrogation of potentials for delayed-type-hypersensitivity response to alloantigens by portal venous inoculation with allogeneic cells.

The present study investigates the effect of portal venous (p.v.) administration of allogeneic cells on the capacity of delayed-type-hypersensitivity (DTH) reactivity to alloantigens. BALB/c mice were inoculated with C3H/He spleen cells via intravenous (i.v.) or p.v. route. Intravenous injection of C3H/He spleen cells into BALB/c mice resulted in appreciable DTH responses to C3H/He alloantigens. In contrast, p.v. inoculation of the same number of C3H/He cells not only failed to induce any significant anti-C3H/He DTH responses but also abolished the capability of the animals to develop DTH responses as induced by subcutaneous (s.c.) immunization with C3H/He spleen cells. Such suppression was alloantigen-specific, since p.v. inoculation of C3H/He spleen cells resulted in selective inhibition of anti-C3H/He DTH potential without suppressing DTH responses to C57BL/6 alloantigens. This tolerance was rapidly inducible and long-lasting. When spleen cells from tolerant mice were transferred i.v. into 600 R X-irradiated syngeneic recipient mice alone or together with normal BALB/c spleen cells, these tolerant spleen cells themselves failed to induce DTH responses but did not exhibit any suppressive effect on the generation of DTH responses induced by normal spleen cells co-transferred. These results indicate that tolerance was not necessarily associated with the induction of suppressor cell activity but rather was associated with the elimination or functional impairment of clones specific for alloantigens. The results are discussed in the context of a) the role of the liver in immune responses, b) cellular mechanisms underlying the tolerance induction, and c) potential application of this approach to the future transplantation immunology.

Animals↗
PubMed1985

[The augmentation of tumor-specific immunity by T-T cell interaction].

The present study establishes a tumor-specific immunotherapy model based on the principle of T-T cell interaction mechanism responsible for augmenting the induction of anti-tumor-specific effector T cells. In this model, high incidence of tumor regression was observed in hosts bearing transplantable or autochthonous tumors when these hosts, in which hapten-reactive helper T cells had been generated, received an injection of haptenic solution into the growing tumor mass. This indicated a role of hapten-reactive helper T cells in regressing the tumor. In consideration clinical application of this tumor-specific immunotherapy model, we have also tried to investigate the use of more appropriate haptenic compounds and have succeeded in synthesizing a noble haptenic compound cross-reactive with BCG, a haptenic muramyl dipeptide (MDP) derivative. The results demonstrated that prepriming of BCG and subsequent immunization with syngeneic tumor cells (mitomycin C-treated) modified with the haptenic MDP derivative resulted in the enhanced induction of tumor-specific immunity. Further investigation is in progress to establish a new tumor-specific immunotherapy model by utilizing this haptenic MDP derivative.

Animals↗