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Biomedical subjects

B Qin

Publications and source records attributed to B Qin.

At least 19 recordsLinked to original sources
PubMed2004

TEM study of the structural dependence of the epitaxial passive oxide films on crystal facets in polyhedral nanoparticles of chromium.

Nanocubes and partially truncated rhombic dodecahedral nanoparticles of Cr have been studied by electron diffraction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. It is found that the nanoparticles of Cr are enclosed by the epitaxial passive oxide films. The oxide films on 100% truncated nanocubes of Cr with only one kind of facets, (100) facets, are face-centered cubic (fcc) structured Cr(2)O(3) with a lattice constant of 0.407nm. There are two kinds of oxide films in partially truncated nanoparticles of Cr with two kinds of crystallographic facets, (100) and (110). The same fcc Cr(2)O(3) is found on the (100) facets while the rhombohedral [Formula: see text] -Cr(2)O(3) is found on the (110) facets. This is similar to the two kinds of oxides, fcc and rhombohedral Fe(2)O(3), which have also been observed in polyhedral nanoparticles of Fe. These passive Cr(2)O(3), found in nanoparticles of Cr which have remained unchanged in water for four years, may have important implications for protective oxide films involving Cr.

Journal Article↗
PubMed2004

Cinnamon extract prevents the insulin resistance induced by a high-fructose diet.

The aim of this study was to determine whether cinnamon extract (CE) would improve the glucose utilization in normal male Wistar rats fed a high-fructose diet (HFD) for three weeks with or without CE added to the drinking water (300 mg/kg/day). In vivo glucose utilization was measured by the euglycemic clamp technique. Further analyses on the possible changes in insulin signaling occurring in skeletal muscle were performed afterwards by Western blotting. At 3 mU/kg/min insulin infusions, the decreased glucose infusion rate (GIR) in HFD-fed rats (60 % of controls, p < 0.01) was improved by CE administration to the same level of controls (normal chow diet) and the improving effect of CE on the GIR of HFD-fed rats was blocked by approximately 50 % by N-monometyl-L-arginine. The same tendency was found during the 30 mU/kg/min insulin infusions. There were no differences in skeletal muscle insulin receptor (IR)-beta, IR substrate (IRS)-1, or phosphatidylinositol (PI) 3-kinase protein content in any groups. However, the muscular insulin-stimulated IR-beta and IRS-1 tyrosine phosphorylation levels and IRS-1 associated with PI 3-kinase in HFD-fed rats were only 70 +/- 9 %, 76 +/- 5 %, and 72 +/- 6 % of controls (p < 0.05), respectively, and these decreases were significantly improved by CE treatment. These results suggest that early CE administration to HFD-fed rats would prevent the development of insulin resistance at least in part by enhancing insulin signaling and possibly via the NO pathway in skeletal muscle.

Animals↗
PubMed2001

Constraints on the interaction between dark matter and Baryons from cooling flow clusters.

Other nongravitational heating processes are needed to resolve the disagreement between the absence of cool gas components in the centers of galaxy clusters revealed recently by Chandra and XMM observations and the expectations of conventional radiative cooling models. We propose that the interaction between dark matter and baryonic matter may act as an alternative for the reheating of intracluster medium (ICM) in the inner regions of clusters, in which kinetic energy of dark matter is transported to ICM to balance radiative cooling. Using the Chandra and XMM data, we set a useful constraint on the dark-matter-baryon cross section: sigma(xp)/m(x) approximately 1x10(-25) cm(2) GeV-1, where m(x) is the mass of dark matter particles.

Journal Article↗
PubMed2001

The L3 loop and C-terminal phosphorylation jointly define Smad protein trimerization.

Smad proteins mediate the transforming growth factor beta responses. C-terminal phosphorylation of R-Smads leads to the recruitment of Smad4 and the formation of active signaling complexes. We investigated the mechanism of phosphorylation-induced Smad complex formation with an activating pseudo-phosphorylated Smad3. Pseudo-phosphorylated Smad3 has a greater propensity to homotrimerize, and recruits Smad4 to form a heterotrimer containing two Smad3 and one Smad4. The trimeric interaction is mediated through conserved interfaces to which tumorigenic mutations map. Furthermore, a conserved Arg residue within the L3 loop, located near the C-terminal phosphorylation sites of the neighboring subunit, is essential for trimerization. We propose that the phosphorylated C-terminal residues interact with the L3 loop of the neighboring subunit to stabilize the trimer interaction.

Animals↗
PubMed2001

[Role of tumor necrosis factor receptor 1 and Fas antigen in hepatocellular apoptosis of viral hepatitis B patients].

OBJECTIVE: To evaluate the role of tumor necrosis factor receptor 1 (TNFR1) and Fas antigen in hepatocellular apoptosis and necrosis in viral hepatitis B. METHODS: Seventy paraffin sections from patients with HBV infection were studied. Five cases of normal liver tissues were studied as control. Apoptosis was detected by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL). TNFR1 and Fas antigen were determined by immunohistochemistry. RESULTS: Hepatocellular apoptosis and the expression of TNFR 1 and Fas antigen on hepatocytes were not detected in normal liver tissues. In contrast, there was a strong reaction in TUNEL assay and TNFR1 or Fas antigen expressed on hepatocytes in liver tissues infected with HBV. The degree of apoptosis and the expression of TNFR 1 or Fas antigen on hepatocytes had distinct difference in different hepatitis (P<0.005). There was a positive correlation between degrees of the expression of Fas and hepatic apoptosis (P<0.005), but the similar result was not observed in the expression of TNFR 1 and hepatocellular apoptosis. Our observations also showed that TNFR1 was detected in cytoplasm and cell membrane similarly, and Fas antigen was mainly detected in cytoplasm. There was not positive correlation between degrees of the expression of TNFR1 and Fas antigen on hepatocytes. It was showed that 60.9% (28/46) hepatocytes with strong reaction in TUNEL assay expressed both TNFR1 and Fas antigen. CONCLUSIONS: The degrees of hepatocellular apoptosis and necrosis induced by Fas antigen are stronger than that induced by TNF. The expression of Fas and TNFR 1 on hepatocytes simultaneously may enhance hepatocellular apoptosis in hepatitis B patients.

Apoptosis↗
PubMed2001

[Cloning and sequencing of Chinese squash leaf curl virus].

Sequence analysis of virus isolation DNA of Squash leaf curl disease shows that Squash Leaf Curl Virus (SLCH-CHI) contains 2741nt, which encode six Open Reading Frames (ORFs). Two of them are on virus sense strand: AV1 (256aa) and AV2 (140aa). AV1 encode coat protein. The other of ORFs are on complementary sense strand: AC1 (replicase gene, 243aa), AC2 (transactivtor, 134aa), AC3 (136aa) and AC4 (172aa). The virus belongs to one number of begomoviruses from old world.

Amino Acid Sequence↗
PubMed2000

Baryon Distribution in Galaxy Clusters as a Result of Sedimentation of Helium Nuclei.

Heavy particles in galaxy clusters tend to be more centrally concentrated than light ones according to the Boltzmann distribution. An estimate of the drift velocity suggests that it is possible that the helium nuclei may have entirely or partially sedimented into the cluster core within the Hubble time. We demonstrate this scenario using the Navarro-Frenk-White profile as the dark matter distribution of clusters and assuming that the intracluster gas is isothermal and in hydrostatic equilibrium. We find that a greater fraction of baryonic matter is distributed at small radii than at large radii, which challenges the prevailing claim that the baryon fraction increases monotonically with cluster radius. It shows that the conventional mass estimate using X-ray measurements of intracluster gas along with a constant mean molecular weight may have underestimated the total cluster mass by approximately 20%, which in turn leads to an overestimate of the total baryon fraction by the same percentage. Additionally, it is pointed out that the sedimentation of helium nuclei toward cluster cores may at least partially account for the sharp peaks in the central X-ray emissions observed in some clusters.

Journal Article↗
PubMed2000

Apolipoprotein E polymorphism and serum concentration in Alzheimer's disease in nine European centres: the ApoEurope study. ApoEurope group.

As part of the ApoEurope Project, apolipoprotein E (apo E) common polymorphism and serum concentration were determined in 489 Alzheimer's disease patients and 429 controls. Patients and controls were recruited through nine centres in eight European countries. Age, sex ratios and education levels of both case and control populations were similar, although discrete differences appeared between centres. The prevalence of the epsilon4 allele was higher in Alzheimer's disease than in controls (increased by 140%), while serum apo E concentration was lower by 11.2% (p<0.001). In addition, serum total cholesterol and triglyceride concentrations were lower in Alzheimer's disease (p<0.001), while that of apo Al was not affected. The decrease in serum apo E concentration was not accounted for by the epsilon4 allele, age or gender, suggesting that apo E concentration might represent an additional risk factor for Alzheimer's disease, complementary and independent of the epsilon4 allele. Further analysis will be aimed at determining whether the quantitative link between apo E concentration and Alzheimer's disease occurs through the effect of apo E genotype on lipid parameters or by other mechanisms.

Age Factors↗
PubMed2000

A trial of ademetionine in the treatment of intrahepatic biliary stasis viral hepatitis.

OBJECTIVE: To observe the efficacy and safety of ademetionine in the treatment of viral hepatitis with intrahepatic biliary stasis. METHODS: In this series, 110 patients with viral hepatitis associated intrahepatic biliary stasis were randomly divided into Groups A and B. Patients in Group A received ademetionine for four weeks. Patients in Group B received potassium magnesium aspartate for four weeks. RESULTS: In Group A, at the end of treatment, the effective rate for skin pruritus in patients with cholestatic hepatitis was 86.67% (13/15), and the effective rate for skin pruritus and anorexia were 88.24% (15/17) and 82.35% (14/17), respectively in patients with chronic hepatitis combining intrahepatic cholestasis, which were significantly higher than that in Group B (P<0.05). STB, SCB, TBA, ALT and AST were lower in Group A than Group B (P<0.05). The decrease of ALP and the increase of albumin after treatment were more significant in Group A than in Group B (P<0.05). CONCLUSION: Ademetionine has better efficacy than potassium magnesium aspartate in the treatment of patients with cholestatic viral hepatitis.

Adolescent↗
PubMed1999

Crystal structure of a transcriptionally active Smad4 fragment.

BACKGROUND: Smad4 functions as a common mediator of transforming growth factor beta (TGF-beta) signaling by forming complexes with the phosphorylated state of pathway-restricted SMAD proteins that act in specific signaling pathways to activate transcription. SMAD proteins comprise two domains, the MH1 and MH2 domain, separated by a linker region. The transcriptional activity and synergistic effect of Smad4 require a stretch of proline-rich sequence, the SMAD-activation domain (SAD), located N-terminal of the MH2 domain. To understand how the SAD contributes to Smad4 function, the crystal structure of a fragment including the SAD and MH2 domain (S4AF) was determined. RESULTS: The structure of the S4AF trimer reveals novel features important for Smad4 function. A Smad4-specific sequence insertion within the MH2 domain interacts with the C-terminal tail to form a structural extension from the core. This extension (the TOWER) contains a solvent-accessible glutamine-rich helix. The SAD reinforces the TOWER and the structural core through interactions; two residues involved in these interactions are targets of tumorigenic mutation. The solvent-accessible proline residues of the SAD are located on the same face as the glutamine-rich helix of the TOWER, forming a potential transcription activation surface. A tandem sulfate-ion-binding site was identified within the subunit interface, which may interact with the phosphorylated C-terminal sequence of pathway-restricted SMAD proteins. CONCLUSIONS: The structure suggests that the SAD provides transcriptional capability by reinforcing the structural core and coordinating with the TOWER to present the proline-rich and glutamine-rich surfaces for interaction with transcription partners. The sulfate-ion-binding sites are potential 'receptors' for the phosphorylated sequence of pathway-restricted SMAD proteins in forming a heteromeric complex. The structure thus provides a new model that can be tested using biochemical and cellular approaches.

Amino Acid Sequence↗
PubMed1998

Suppression of spinal cord motoneuron excitability correlates with surgical immobility during isoflurane anesthesia.

BACKGROUND: Recent evidence suggests that the spinal cord is an important site of anesthetic action that produces surgical immobility. Inhalation anesthetics depress the Hoffmann's reflex (H reflex) and F wave, indicating spinal motoneuron suppression. The aim of this study was to assess the correlation between isoflurane-induced immobility and H- and F-wave suppression. METHODS: The baseline H reflex and F wave were measured before anesthesia in 15 adult patients. After induction, 1% end-tidal isoflurane was maintained for 20 min before the H and F waves were reelicited. Using an electric stimulus applied to the forearm and grading the response as movement or no movement, the authors increased or decreased the isoflurane concentration in 0.1% steps, depending on the movement responses. The H and F waves were recorded 20 min after each change of isoflurane concentration. The correlation between H- and F-wave suppression and surgical immobility was analyzed using a paired t test with Bonferroni correction. RESULTS: H-reflex amplitude (2.74 +/- 1.63 mV) and F-wave persistence (70.69 +/- 26.19%) at the highest isoflurane concentration that allowed movement response to a stimulus are different (P < 0.01) from these (1.97 +/- 1.46 mV; 43.16 +/- 22.91%) at the lowest isoflurane concentration that suppressed response. At 0.8% isoflurane, the H-reflex amplitude was 3.69 +/- 1.83 mV with movement and 1.01 +/- 1.14 mV without movement (P < 0.01); F-wave amplitude was 0.29 +/- 0.15 mV with movement and 0.11 +/- 0.06 mV without movement (P < 0.01); F-wave persistence was 80 +/- 22.36% with movement and 34.9 +/- 25.75% without movement (P < 0.01). CONCLUSIONS: The degree of H- and F-wave amplitude and F-wave persistence suppression correlates with movement response, suggesting that isoflurane-suppressive action in the spinal cord plays a significant role in producing surgical immobility.

Adult↗
PubMed1993

Enhanced skin allograft survival after photodynamic therapy. Association with lymphocyte inactivation and macrophage stimulation.

It has been found previously that peritoneal exposure to hematoporphyrin derivative (HpD) photodynamic therapy (PDT) can induce systemic immunosuppression of contact hypersensitivity. We have now found that HpD-PDT also significantly prolongs survival of murine skin allografts. Normal A/J mice transplanted with BALB/c skin rejected the grafts within 10 +/- 0.9 days. Recipient mice treated 24 hr previously with HpD-PDT rejected skin allografts at 16 +/- 1.2 days. HpD alone or irradiation alone had no effect on skin graft survival, nor did HpD-PDT administered shortly after grafting. Flow cytometric analyses showed a nearly complete depletion of peritoneal lymphocytes 3 days after HpD-PDT. Lymphocyte levels were normal in the spleen, an organ not directly targeted by the PDT treatment, but the cells were totally unresponsive to Con A and LPS mitogens. Conversely, peritoneal HpD-PDT caused a striking enhancement in macrophage function as measured by phagocytosis of antibody-coated sheep erythrocytes. Humoral immunity to hen egg-white lysozyme was not significantly changed by HpD-PDT. These results demonstrate that HpD-PDT causes systemic immunosuppression of cellular immunity which, in turn, allows prolonged survival of allografts. Humoral immunity appears to remain largely unaffected by HpD-PDT and macrophages become activated, suggesting that this therapy might be more effective in specifically targeting T cell-mediated immunity than current immunosuppressive treatments.

Animals↗
PubMed1993

Pyrimidine metabolism by intracellular Chlamydia psittaci.

Pyrimidine metabolism was studied in the obligate intracellular bacterium Chlamydia psittaci AA Mp in the wild type and a variety of mutant host cell lines with well-defined mutations affecting pyrimidine metabolism. C. psittaci AA Mp cannot synthesize pyrimidines de novo, as assessed by its inability to incorporate aspartic acid into nucleic acid pyrimidines. In addition, the parasite cannot take UTP, CTP, or dCTP from the host cell, nor can it salvage exogenously supplied uridine, cytidine, or deoxycytidine. The primary source of pyrimidine nucleotides is via the salvage of uracil by a uracil phosphoribosyltransferase. Uracil phosphoribosyltransferase activity was detected in crude extracts prepared from highly purified C. psittaci AA Mp reticulate bodies. The presence of CTP synthetase and ribonucleotide reductase is implicated from the incorporation of uracil into nucleic acid cytosine and deoxycytidine. Deoxyuridine was used by the parasite only after cleavage to uracil. C. psittaci AA Mp grew poorly in mutant host cell lines auxotrophic for thymidine. Furthermore, the parasite could not synthesize thymidine nucleotides de novo. C. psittaci AA Mp could take TTP directly from the host cell. In addition, the parasite could incorporate exogenous thymidine and thymine into DNA. Thymidine kinase activity and thymidine-cleaving activity were detected in C. psittaci AA Mp reticulate body extract. Thus, thymidine salvage was totally independent of other pyrimidine salvage.

Animals↗