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Biomedical subjects

Qi Li

Publications and source records attributed to Qi Li.

At least 91 records · Page 5Linked to original sources
PubMed2005

Molecular and conformational basis of a specific and high-affinity interaction between AlbA and albicidin phytotoxin.

The albA gene of Klebsiella oxytoca encodes a protein of 221 amino acids that binds the albicidin phytotoxin with a high affinity (dissociation constant = 6.4 x 10(-8) M). For this study, circular dichroism (CD) spectrometry and an alanine scanning mutagenesis approach were used in combination to investigate the molecular and conformational mechanisms of this high-affinity protein-ligand interaction. CD analysis revealed that AlbA contains a high-affinity binding site, and binding of the albicidin ligand to AlbA in a low-ionic-strength environment induced significant conformational changes. The ligand-dependent conformational changes of AlbA were specific and rapid and reached a stable plateau within seconds after the addition of the antibiotic. However, such conformational changes were not detected when AlbA and albicidin were mixed in the high-ionic-strength buffer that is required for maximal binding activity. Based on the conceptual model of protein-ligand interaction, we propose that a threshold ion strength allows AlbA to complete its conformational rearrangement and resume its original stable structure for accommodation of the bound albicidin. Mutagenesis analysis showed that the replacement of Lys106, Trp110, Tyr113, Leu114, Tyr126, Pro134, and Trp162 with alanine did not change the overall conformational structure of AlbA but decreased the albicidin binding activity about 30 to 60%. We conclude that these residues, together with the previously identified essential residue His125, constitute a high-affinity binding pocket for the ligand albicidin. The results also suggest that hydrophobic and electrostatic potentials of these key amino acid residues may play important roles in the AlbA-albicidin interaction.

Amino Acid Sequence↗
PubMed2005

bcl2, bax, and nestin in the brains of patients with neurodegeneration and those of normal aging.

This study was conducted by employing specimens from the frontal cortices of Alzheimer, multiple-infarct dementia patients, and those of normal aging (age matched to patients). The objective was to evaluate and compare the bcl2, bax, and nestin patterns in these three groups. Using immunocytochemistry, it was observed that bcl2 and bax active sites were colocalized in 45% of cells in Alzheimer, 52% of cells in multiple infarct, and 30% of cells in normal aging. bcl2 and bax could also be separately located in cells of all three groups. bax cells were most prominent in number in Alzheimer patients and least prominent in normal aging. nestin was found in all three groups but was most prominent in the multiple-infarct patients. Both astrocytes and neurons demonstrated positive nestin sites. The difference in pattern between groups will lead to further understanding of cellular changes in neurodegenerative patients and those of normal aging.

Aged↗
PubMed2005

[Apoptosis-inducing ligand TRAIL can be recruited to lipid rafts].

AIM: To investigate the relationship between tumor necrosis factor-related apoptosis-inducing ligand(TRAIL) and cell membrane microdomain lipid rafts. METHODS: The expression of TRAIL on K562 cells was detected by indirect immunofluorescence staining and flow cytometry. The lipid rafts on K562 cells were detected with FITC-labeled cholera toxin B subunit (CTx-FITC) which bound to the GM1 glycosphingolipid in lipid rafts. The lipid rafts were then cross-linked with an anti-FITC mAb after binding with CTx-FITC. The localization of TRAIL on K562 cells was analyzed with rabbit anti-TRAIL antibody, Cy3-labeled goat-anti-rabbit IgG (Cy3-labeled GAR) and laser scanning confocal microscope. RESULTS: The cross-linking of lipid rafts appeared at 20 minutes, reached peak at 30 minutes, and weakened around 40 minutes. After the cells were labeled with CTx-FITC and anti-FITC mAb TRAIL was aggregated in the cross-linked lipid rafts. CONCLUSION: The anti-FITC mAb could be used for cross-linking of lipid rafts. TRAIL can be recruited to lipid rafts.

Animals↗
PubMed2005

Effect of free-air CO2 enrichment on nematode communities in a Chinese farmland ecosystem.

At a rice-wheat rotational free-air CO2 enrichment( FACE) platform, the effect of elevated atmospheric CO2 on soil nematode communities in a farmland ecosystem was studied. Wheat plots were exposed to elevated atmospheric CO2 (ambient 370 microl/L + 200 microl/L). 32 families and 40 genera of nematode were observed in soil suspensions during the study period. Under FACE treatment, the numbers of total nematodes, bacterivores and fungivores exhibited an increasing trend. Because of the seasonal variation of soil temperature and moisture, the effect of elevated atmospheric CO2 on soil nematodes was only observed under favorable conditions. The response of nematode communities to elevated atmospheric CO2 may indicate the change of soil food web.

Agriculture↗
PubMed2005

[Mutation analysis of gene CX31.1 in the hereditary hearing loss pedigrees].

OBJECTIVE: To make clear of the relation between CX31.1 and hereditary hearing loss by the mutation detect of gene CX31.1 in nonsyndromic hearing loss pedigrees. METHOD: Thirty-seven pedigrees of autosomal recessive inheritance hereditary hearing loss and twenty-four pedigrees of autosomal dominant inheritance hereditary hearing loss were collected from decades provinces of China. By using polymerase chain reaction and direct sequence, we screened the members of this pedigrees for the mutations of gene CX31.1. RESULT: One polymorphism and one synonymous mutation of gene CX31.1 and two absent pieces in the introns of CX31.1 were found. CONCLUSION: Though we have not found mutations of CX31.1 which can induce corresponding hereditary deafness of the pedigrees inspected before, we don't think we can deny gene CX31.1 is a nosogenesis gene of hereditary hearing loss, and what we can do is to collect enough pedigrees to continue our research.

Connexins↗
PubMed2005

[The pulmonary protective effects of leukocyte depletion with a modified filter located at the cardiopulmonary bypass (CPB) venous line in canine].

OBJECTIVE: To investigate the pulmonary protective effects of short-term leukocyte depletion with a modified filter located at the CPB venous line in canine. METHODS: Sixteen healthy hybrid canines were randomly allocated to the LD-1 group, with an LD-1 filter installed in the CPB venous-line for a 5-minute leukocyte depletion at the beginning of the CPB, and to the control group. Blood samples were taken for routine test respectively at 9 time-points, namely pre-CPB, at 5, 10, 40, 70 min of the CPB, 5 min after aortic cross-clamp being off, at the discontinuation of the CPB, 5 min after protamine being administered, and 2 h after the CPB. Oxygen index (OI), pulmonary pathology and levels of interleukin-6 (IL-6) and interleukin-8 (IL-8) in plasma were measured at pre-CPB, 5 min after protamine being administered and 2 h after the CPB respectively. The levels of IL-6 and IL-8 in the bronchial alveolar lavage fluid (BALF) were measured at 2 h after the CPB. RESULTS; In LD-1 group, white blood cell (WBC) counts were significantly less than those in control group at 5 min of the CPB (P < 0.05), the filtration rate of WBC was (65.72 +/- 9.36)%. The WBC counts showed no significant difference in either group from 40 min of the CPB to 2 h after the CPB. OI was higher in LD-1 group than that in control group (P < 0.05) at 5 min after protamine being administered and 2 h after the CPB. There was significantly less WBC infiltration and alveolar edema of the lung in LD-1 group than that in control group at 5 min after protamine being administered and 2 h after the CPB. There were no significant differences of IL-6 and IL-8 in plasma between the two groups at 5 min after protamine being administered (P > 0.05), but the levels of IL-6 and IL-8 were much lower in the LD-1 group than those in the control group at 2 h after CPB. At 2 h after the CPB, IL-6 level in the BALF showed no significant difference in each group (P > 0.05); however, the level of IL-8 was lower in LD-1 group than that in control group (P < 0.05). CONCLUSION: The LD-1 filter in the CPB venous-line in canine model used for short-term leukocyte depletion filtration could reduce WBC counts significantly, decrease the levels of IL-6 and IL-8 in plasma, attenuate inflammatory response in the lung after CPB, so it has protective effect on canine lung.

Animals↗
PubMed2005

[Software and hardware design for the temperature control system of quantitative polymerase chain reaction].

A temperature control system for quantitive polymerase chain reaction (PCR) is presented in the paper with both software and hardware configuration. The performance of the control system has been improved by optimizing the software and hardware design according to the system's properties. The control system has been proven to have a good repeatability and reliability as well as high control precision.

Equipment Design↗
PubMed2005

[Expression of aquaporin-1,3 in the cochlea and endolymphatic sac of guinea pig].

OBJECTIVE: To detect the expression of Aquaporin-1,3 in the cochlea and endolymphatic sac of guinea pig. METHOD: Two-step immunohistochemical method and immunofluorescence was used to examine the expression of Aquaporin-1,3. RESULT: Aquaporin-1 was expressed on the basilar part of spiral ligament, basal membrane of Corti's organ and epithelialis of scala tympani, and basilar part under the cellular epithelialis in endolymphatic sac. Aquaporin-3 was expressed on stria vascularis, spiral ligament, Corti's organ, spiral ganglion and, the basilar part and the cellular epithelialis in endolymphatic sac. CONCLUSION: Aquaporin-1,3 were widely expressed in the cochlea and endolymphatic sac of guinea pig.

Animals↗
PubMed2005

Workflow analysis in primary care: implications for EHR adoption.

Within busy practice settings, it is difficult to provide adequate provider training on evolving electronic health record (EHR) functionality. As a result, providers may not reap the full benefits of EHR. This poster presents a systematic workflow study conducted to enhance the adoption of advanced EHR features. This study led us to develop new adoption and training strategies, which resulted in statistically significant (p<0.03) improvement in the adoption of advanced results management features.

Computer User Training↗
PubMed2004

Primary care physician time utilization before and after implementation of an electronic health record: a time-motion study.

Despite benefits associated with the use of electronic health records (EHRs), one major barrier to adoption is the concern that EHRs may take longer for physicians to use than paper-based systems. To address this issue, we performed a time-motion study in five primary care clinics. Twenty physicians were observed and specific activities were timed during a clinic session before and after EHR implementation. Surveys evaluated physicians' perceptions regarding the EHR. Post-implementation, the adjusted mean overall time spent per patient during clinic sessions decreased by 0.5 min (p=0.86; 95% confidence interval [-5.05, 6.04]) from a pre-intervention adjusted average of 27.55 min (SE=2.1) to a post-intervention adjusted average of 27.05 min (SE=1.6). A majority of survey respondents believed EHR use results in quality improvement, yet only 29% reported that EHR documentation takes the same amount of time or less compared to the paper-based system. While the EHR did not require more time for physicians during a clinic session, further studies should assess the EHR's potential impact on non-clinic time.

Attitude of Health Personnel↗
PubMed2004

Enhancement of the superconducting transition temperature of MgB2 by a strain-induced bond-stretching mode softening.

We report a systematic increase of the superconducting transition temperature T(c) with a biaxial tensile strain in MgB2 films to well beyond the bulk value. The tensile strain increases with the MgB2 film thickness, caused primarily by the coalescence of initially nucleated discrete islands (the Volmer-Weber growth mode.) The T(c) increase was observed in epitaxial films on SiC and sapphire substrates, although the T(c) values were different for the two substrates due to different lattice parameters and thermal expansion coefficients. We identified, by first-principles calculations, the underlying mechanism for the T(c) increase to be the softening of the bond-stretching E(2g) phonon mode, and we confirmed this conclusion by Raman scattering measurements. The result suggests that the E(2g) phonon softening is a possible avenue to achieve even higher T(c) in MgB2-related material systems.

Journal Article↗
PubMed2004

Ultrafast photoinduced reflectivity transients in doped manganite.

The temperature and magnetic field dependence of ultrafast photoinduced spin and quasiparticle relaxation dynamics is reported in La(0.67)Ca(0.33)MnO(3) and LaMnO(3) single crystals and thin films. Both manganites reveal an unusually slow ( approximately 10 micros) carrier relaxation process attributed to the spin-lattice relaxation in localized states. The quasiparticle dynamics is governed by the temperature- and magnetic field-dependent pseudogap in La(0.67)Ca(0.33)MnO(3), and by the temperature-independent Jahn-Teller gap in LaMnO(3). The loss of spectral weight near the Fermi level in La(0.67)Ca(0.33)MnO(3) strongy affects the quasiparticle relaxation dynamics as temperature increases from below T(C). Our results show that the coupled dynamics of charge, spin and lattice is strongly correlated with the distinct gap structures in these manganites.

Journal Article↗
PubMed2004

The allograft defines the type of rejection (acute versus chronic) in the face of an established effector immune response.

Transplanted organs fail due to either acute or chronic rejection. The prevailing view is that the nature or magnitude of the recipient's immune response to donor Ags determines the type of rejection. In variance with this view, we show in this study that the status of the graft itself plays a dominant role in defining the type of rejection even in the face of an established alloimmune response. Using adoptive transfer mouse models in which the graft is exposed to a constant number of effector lymphocytes, we found that newly transplanted heart allografts are rejected acutely, while healed-in allografts undergo chronic rejection. Acute rejection of healed-in allografts was largely recapitulated by subjecting the grafts to ischemia-reperfusion injury similar to that present in newly transplanted organs. Ischemia-Reperfusion injury altered the outcome of rejection by enhancing the accumulation of effector T cells within the graft. The accumulation of effector T cells in the graft was dependent on the presence of both ischemia-reperfusion injury (inflammation) and alloantigens. These findings demonstrate that the graft plays a dominant role in shaping the outcome of rejection by controlling the trafficking of effector T cells.

Acute Disease↗
PubMed2004

Paracrine and autocrine functions of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in brain-derived endothelial cells.

Brain-derived neurotrophic factor (BDNF) is expressed by endothelial cells. We investigated the characteristics of BDNF expression by brain-derived endothelial cells and tested the hypothesis that BDNF serves paracrine and autocrine functions affecting the vasculature of the central nervous system. In addition to expressing TrkB and p75NTR and BDNF under normoxic conditions, these cells increased their expression of BDNF under hypoxia. While the expression of TrkB is unaffected by hypoxia, TrkB exhibits a base-line phosphorylation under normoxic conditions and an increased phosphorylation when BDNF is added. TrkB phosphorylation is decreased when endogenous BDNF is sequestered by soluble TrkB. Exogenous BDNF elicits robust angiogenesis and survival in three-dimensional cultures of these endothelial cells, while sequestration of endogenous BDNF caused significant apoptosis. The effects of BDNF engagement of TrkB appears to be mediated via the phosphatidylinositol (PI) 3-kinase-Akt pathway. Modulation of BDNF levels directly correlate with Akt phosphorylation and inhibitors of PI 3-kinase abrogate the BDNF responses. BDNF-mediated effects on endothelial cell survival/apoptosis correlated directly with activation of caspase 3. These endothelial cells also express p75NTR and respond to its preferred ligand, pro-nerve growth factor (pro-NGF), by undergoing apoptosis. These data support a role for neurotrophins signaling in the dynamic maintenance/differentiation of central nervous system endothelia.

Animals↗
PubMed2004

Induction of haploid androgenesis in Pacific oyster by UV irradiation.

Androgenesis, development from paternal but not maternal chromosomes, can be induced in some organisms including fish, but has not been induced previously in mollusk. In this study we investigated the induction of haploid androgenesis in the Pacific oyster by ultraviolet irradiation and observed nuclear behavior in the androgenetic eggs. Irradiation for 90 seconds at a UV intensity of 72 erg/mm2 per second (6480 erg/mm2) was the optimal dose to achieve haploid androgenesis. The fertilization and development rates of D-shaped larvae decreased with increasing exposure time, and the development of the genetically inactivated eggs terminated before reaching the D-shaped stage. Cytologic observations showed that UV irradiation did not affect germinal vesicle breakdown or chromosomal condensation but caused various nuclear behavioral patterns during meiosis and first mitosis: 21.7% of eggs extruded all maternal chromosomes as 2 or 3 polar bodies, and 59.1% of eggs formed one female pronucleus. The maternally derived nucleus did not participate, or partially participated, in the first karyokinesis. The cytologic evidence demonstrates that the male genome is directing development in haploids produced by UV irradiation.

Animals↗
PubMed2004

A syntaxin 1, Galpha(o), and N-type calcium channel complex at a presynaptic nerve terminal: analysis by quantitative immunocolocalization.

Presynaptic Ca(V)2.2 (N-type) calcium channels are subject to modulation by interaction with syntaxin 1 and by a syntaxin 1-sensitive Galpha(O) G-protein pathway. We used biochemical analysis of neuronal tissue lysates and a new quantitative test of colocalization by intensity correlation analysis at the giant calyx-type presynaptic terminal of the chick ciliary ganglion to explore the association of Ca(V)2.2 with syntaxin 1 and Galpha(O). Ca(V)2.2 could be localized by immunocytochemistry (antibody Ab571) in puncta on the release site aspect of the presynaptic terminal and close to synaptic vesicle clouds. Syntaxin 1 coimmunoprecipitated with Ca(V)2.2 from chick brain and chick ciliary ganglia and was widely distributed on the presynaptic terminal membrane. A fraction of the total syntaxin 1 colocalized with the Ca(V)2.2 puncta, whereas the bulk colocalized with MUNC18-1. Galpha(O,) whether in its trimeric or monomeric state, did not coimmunoprecipitate with Ca(V)2.2, MUNC18-1, or syntaxin 1. However, the G-protein exhibited a punctate staining on the calyx membrane with an intensity that varied in synchrony with that for both Ca channels and syntaxin 1 but only weakly with MUNC18-1. Thus, syntaxin 1 appears to be a component of two separate complexes at the presynaptic terminal, a minor one at the transmitter release site with Ca(V)2.2 and Galpha(O), as well as in large clusters remote from the release site with MUNC18-1. These syntaxin 1 protein complexes may play distinct roles in presynaptic biology.

Animals↗
PubMed2004

Technique for retransplanting heterotopic heart grafts in mice.

Removal of a transplanted organ from its original recipient and retransplanting it into a new host is an important method to study the role of the graft in the rejection process. Here we describe a novel technique of heart retransplantation in the mouse. In this technique, a primarily vascularized heart graft is anastomosed to the abdominal aorta and inferior vena cava of a syngeneic or immunodeficient allogeneic mouse, using standard techniques. Either 10 or 70 days later, the same graft is retransplanted into the abdomen of a second mouse by end-to-side anastomosis of the donor (first recipient) aortic and inferior vena cava's cuffs to the second recipient's abdominal aorta and inferior vena cava, respectively. A greater than 90% success rate was achieved by using this microsurgical technique. This method should be useful for studying intragraft factors, such as ischemia-reperfusion injury and donor antigen-presenting cells, on the outcomes of transplantations.

Anastomosis, Surgical↗