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Biomedical subjects

J Sun

Publications and source records attributed to J Sun.

At least 361 records · Page 20Linked to original sources
PubMed1998

[The food habit and its affecting factors of preschool children in Guangzhou].

A survey of nutritional knowledge-attitude-practice was conducted among 1300 preschool children, their parents, 203 teachers and nurses in Kindergarten in 1997. Results showed that the food habit of preschool children was unsuitable. Most preschool children rejected eating animal liver, peanut product and animal blood, but often ate snacks. From statistic analysis among affecting factors, the mother's and teachers' nutritional knowledge and the food habit of parents had significant effect on food habit of preschool children. The family income did not significantly affect food habit of preschool children. Moreover, there was little nutrition education involved in the preschool children courses in 4 kindergartens. The result suggested that the nutrition education plan should be done.

Adult↗
PubMed1998

Determination of gene usage by differential polymerase chain reaction product hybridization.

All swine VH genes belong to a highly homologous family and have identical leader sequences, and the swine VH locus contains a single JH. The small number of VH genes used by the fetus and neonate in the first 6 weeks have unique CDR1 and CDR2 sequences, permitting each to be identified using specific oligonucleotide probes. We have used this system as a model for the development of a rapid method for determining the proportional usage of closely related genes based on differential polymerase chain reaction (PCR) product hybridization (DPPH). The validity of the method is demonstrated using mixtures of PCR product containing known amounts of VH gene DNAs and by comparing data obtained by this method with those obtained by enumeration of individual hybridizing clones from lymphoid tissue and peripheral blood B cells. Since DPPH is at least 100-fold more efficient than the enumeration of individual hybridizing clones, it is especially useful for analyzing large numbers of samples in population studies. The possible extension of this method to the usage of other genes is discussed.

Animals↗
PubMed1998

Ligand-induced changes in periplasmic loops in the lactose permease of Escherichia coli.

N- and C-terminal halves of lactose permease, each with a single-Cys residue in a periplasmic loop, were coexpressed, and cross-linking was studied in the presence or absence of ligand. A Cys residue at position 36 between transmembrane helices I and II (loop I/II) forms a disulfide spontaneously with a Cys residue at position 253, 254, 255, or 256 in loop VII/VIII. Moreover, in the presence of o-phenanthroline-copper, a Cys residue at position 42 in loop I/II forms a disulfide with a Cys residue at position 253, 254, 257, or 258 in loop VII/VIII. Changes in the rate of cross-linking are also observed in the presence of substrate, suggesting that ligand binding induces movement between loops I/II and VII/VIII such that positions 253-256 are brought closer to position 36 or 42, while positions 257 and 258 move away from position 42.

Amino Acid Substitution↗
PubMed1998

Sulfhydryl oxidation of mutants with cysteine in place of acidic residues in the lactose permease.

To examine further the role of charge-pair interactions in the structure and function of lactose permease, Asp237 (helix VII), Asp240 (helix VII), Glu126 (cytoplasmic loop IV/V), Glu269 (helix VIII), and Glu325 (helix X) were replaced individually with Cys in a functional mutant devoid of Cys residues. Each mutant was then oxidized with H2O2 in order to generate a sulfinic and/or sulfonic acid at these positions. Due to the isosteric relationship between aspartate and sulfinate, in particular, and the lower pKa of the sulfinic and sulfonic acid side chains, oxidized derivatives of Cys are useful probes for examining the role of carboxylates. Asp237-->Cys or Asp240-->Cys permease is inactive, as shown previously, but H2O2 oxidation restores activity to an extent similar to that observed when a negative charge is reintroduced by other means. Glu126-->Cys, Glu269-->Cys, or Glu325-->Cys permease is inactive, but oxidation does not restore active lactose transport. The data are consistent with previous observations indicating that Asp237 and Asp240 are not critical for active lactose transport, while Glu126, Glu269, and Glu325 are irreplaceable. Although Glu269-->Cys permease does not transport lactose, the oxidized mutant exhibits significant transport of beta,D-galactosylpyranosyl 1-thio-beta,D-galactopyranoside, a property observed with Glu269-->Asp permease. The observation supports the idea that an acidic residue at position 269 is important for substrate recognition. Finally, oxidized Glu325-->Cys permease catalyzes equilibrium exchange with an apparent pKa of about 6.5, more than a pH unit lower than that observed with Glu325-->Asp permease, thereby providing strong confirmatory evidence that a negative charge at position 325 determines the rate of translocation of the ternary complex between the permease, substrate, and H+.

Amino Acid Substitution↗
PubMed1998

Kinetics of intragraft cytokine expression, cellular infiltration, and cell death in rejection of renal allografts compared with acceptance of liver allografts in a rat model: early activation and apoptosis is associated with liver graft acceptance.

BACKGROUND: Liver transplants in the rat strain combination PVG-to-Dark Agouti are spontaneously tolerated, whereas kidney transplants in the same strain combination are rejected in 7-9 days. METHODS: To identify organ-specific differences that might yield further information about the mechanism of tolerance induction in this strain combination, liver or kidney grafts, spleen, and draining lymph nodes were harvested at days 1, 3, 5, and 7, and examined by immunohistochemistry, terminal deoxynucleotide transferase-mediated dUTP nick end labeling assay, and reverse transcriptase-polymerase chain reaction for interferon-gamma, interleukin (IL)-2, IL-4, and IL-10. RESULTS: Renal allograft rejection was associated with the progressive development of an intense mononuclear cell infiltrate. Markers of lymphocyte activation and cytokine up-regulation appeared from day 3, and many apoptotic parenchymal cells were noted on days 5-7, at the peak of rejection. Conversely, liver allograft tolerance was associated with more rapid infiltration by activated T cells and earlier increases in cytokine expression, but with a more limited degree of cellular infiltration. Concurrent with the early activation, high levels of apoptosis were found in areas of leukocyte infiltrate, paralleling the disappearance of activated T cells from the graft between days 3 and 5. CONCLUSIONS: Apoptosis of infiltrating leukocytes in liver allografts may represent an important process in the induction of spontaneous liver transplant tolerance and may underlie the abortive nature of the effector response observed within tolerated livers. In contrast, activated cells in renal allografts in the same strain combination survive and proliferate, express high levels of cytokines, and are efficient in bringing about graft destruction.

Animals↗
PubMed1998

Bradykinin stimulates the tyrosine phosphorylation and bradykinin B2 receptor association of phospholipase C gamma 1 in vascular endothelial cells.

Bradykinin (BK) B2 receptor signaling involves activation of phospholipase C (PLC). PLC activation by other receptors consists of either allosteric activation of PLC beta isoforms by G-proteins or tyrosine phosphorylation of PLC gamma isoforms. Because the B2 receptor is a G-protein-coupled receptor, it has been assumed that the receptor signals through PLC beta. In the present study, however, we have found that BK stimulation of IP3 production and the Ca2+ signal in endothelial cells is dependent on tyrosine phosphorylation. Furthermore, stimulation of B2 receptors in these cells is accompanied by a transient tyrosine phosphorylation of PLC gamma 1. Phosphorylation is correlated with increased IP3 production and association of PLC gamma 1 with the C-terminal intracellular domain of the B2 receptor. The B2 receptor can thus physically associate with intracellular proteins other than G-proteins. Activation of PLC gamma isoforms, rather than PLC beta isoforms, may, therefore, be primarily responsible for BK-stimulated IP3 generation in endothelial cells.

Animals↗
PubMed1998

Long-term T cell memory requires the surface expression of self-peptide/major histocompatibility complex molecules.

How memory T cells are maintained in vivo is poorly understood. To address this problem, a male-specific peptide (H-Y) was identified and used to activate female anti-H-Y T cells in vitro. Anti-H-Y T cells survived in vivo for at least 70 days in the absence of antigen. This persistence was not because of the intrinsic ability of memory T cells to survive in vivo. Instead, the survival and function of adoptively transferred memory cells was found to require transporter of antigen protein 1-dependent expression of self-peptide/major histocompatibility complex class I molecules in recipient animals. Therefore, it appears that the level of T cell receptor engagement provided by transporter of antigen protein 1-dependent, self-peptide/major histocompatibility complexes is sufficient to maintain the long-term survival and functional phenotype of memory cells in the absence of persistent antigen. These data suggest that positive selection plays a role not only in T cell development but also in the maintenance of T cell memory.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Role of antioxidant enzymes on ionizing radiation resistance.

Exposure of cells to ionizing radiation leads to formation of reactive oxygen species (ROS) that are associated with radiation-induced cytotoxicity. The antioxidant enzymes manganese superoxide dismutase (MnSOD), copper-zinc superoxide dismutase (CuZnSOD), and glutathione peroxidase (GPx), are key intracellular antioxidants in the metabolism of ROS. We investigated the potential role of the three antioxidant enzymes in radioresistance by analyzing cell morphology, cell viability, and cellular radioresistance in stably transfected CHO cell lines overexpressing MnSOD, CuZnSOD, and GPx, respectively. We found that overexpression of human MnSOD substantially protected cells from ionizing radiation injury. Relative to MnSOD, GPx could slightly reduce the radiation sensitivity while the radioresistance in CuZnSOD expressing cells did not change significantly. The results suggested that MnSOD may play a central role in protecting cells against reactive oxygen species injury during ionizing radiation exposure among MnSOD, CuZnSOD, and GPx.

Animals↗
PubMed1998

Capture-ELISA based on recombinant PR3 is sensitive for PR3-ANCA testing and allows detection of PR3 and PR3-ANCA/PR3 immunecomplexes.

Proteinase 3 (PR3), a constituent of azurophil granules of neutrophils (polymorphonuclear cells, PMNs), is the target antigen for most anti-neutrophil cytoplasmic antibodies (c-ANCA) in Wegener's granulomatosis (WG). We have recently developed an expression system for recombinant PR3 (rPR3) that is recognized by c-ANCA. Here, we report on the development and characterization of two monoclonal antibodies (moABs) and a rabbit polyclonal antiserum generated against this rPR3. Epitope competition analysis indicates that the moABs MCPR3-1 and MCPR3-2 recognize overlapping epitopes on the PR3 molecule that are distinct from the ones recognized by moABs 4A5 and 6A6 developed by others. Since MCPR3-2 does not appear to compete for epitopes recognized by a sizable proportion of PR3-ANCA, we used it to develop a sensitive capture enzyme linked immunosorbent assay (ELISA) for clinical PR3-ANCA testing. Both purified PMN PR3 and crude human mast cell line (HMC-1)/PR3-S176A cell lysates were used as sources of PR3 target antigen in this assay with equal analytical sensitivity and specificity. Of 109 patients with ANCA-associated disease, 91 (83.5%) and 90 (82.6%) were PR3-ANCA positive by capture ELISA when PMN-PR3 and HMC-1/PR3-S176A cell lysates were used as antigen, respectively. When HMC-1/PR3 and HMC-1/PR3-S176A cells were used as indirect immunofluorescence (IIF) substrate, 88 (80.7%) and 92 (84.4%) were PR3-ANCA positive, respectively. These differences were not statistically significant. Only 1 of 151 controls without defined ANCA-associated disease tested positive by capture ELISA with either target antigen (both negative by PR3-ANCA specific IIF). The capture ELISA can also be used to detect of PR3-ANCA immunecomplexes and, in combination with the rabbit antiserum, for the quantitative measurement of PR3 in biological fluids.

Animals↗
PubMed1998

Conversion of pancreas allograft rejection to acceptance by liver transplantation.

BACKGROUND: Liver allografts of PVG(RT1c)-->DA(RT1a) are spontaneously accepted, whereas pancreas, heart, and kidney allografts are rejected. Our previous studies have shown that simultaneous liver and pancreas transplantation prevents pancreas allograft rejection. The aim of this study was to examine the effect of liver transplantation on subsequent pancreas allografts and on ongoing pancreas rejection. METHODS: Heterotopic, duct-ligated segmental pancreas grafts were transplanted into streptozotocin-induced diabetic recipients (60 mg/kg body weight i.p.) with or without orthotopic liver grafting at different times. Experimental design was as follows. Group 1 received PVG-->PVG pancreas syngrafts (n=6); group 2, PVG-->DA pancreas allografts (n=7); groups 3-5, PVG-->DA pancreas allografts followed by liver transplantation on day 2 (n=6), on day 4 (n=5), and on day 6 (n=5), respectively, group 6, PVG-->DA pancreas allografts after liver transplantation at 4 weeks (n=6). RESULTS: The results showed that pancreas allografts in group 2 were rejected from postoperative day 7 to 13. Liver transplantation prevented subsequent pancreas allograft rejection in group 6. Ongoing pancreas rejection was reversed by liver transplantation with subsequent graft acceptance in groups 3-5. Significant graft-infiltrating lymphocyte apoptosis was demonstrated at 2 weeks in pancreas transplants associated with liver grafting. Graft-versus-host disease was not detected in the pancreas recipients. CONCLUSIONS: We conclude that pancreas allografts in the PVG-->DA combination are rejected rapidly with median survival time of 9 days. Liver transplantation can protect subsequent pancreas grafts from rejection and reverse ongoing pancreas graft rejection with subsequent pancreatic acceptance. Graft-infiltrating lymphocyte apoptosis may be associated with the process of graft acceptance.

Animals↗
PubMed1998

Three-dimensional 87Rb imaging of isolated pig hearts: effects of regional ischemia.

The aim of this work was to investigate whether 1) Rb uptake is reduced in ischemic myocardium, and 2) 87Rb three-dimensional (3D) imaging can detect the ischemic area. Hearts of domestic pigs (n = 8, 20-30 kg) were perfused retrogradely with Krebs-Henseleit buffer in a 7-T, 40-cm horizontal bore magnet interfaced with Bruker MSLX spectrometer. Control (C) and ischemic (I) (45 min ligation of the left anterior descending coronary artery (LAD)) hearts were loaded with Rb+ by perfusion with a Rb(+)-containing solution (2-4.7 mM, 30-100% of K+ substitution) for 35 min and 87Rb (C) or 31P (ischemic area in I) spectra were acquired. After mechanical arrest with 0.6-0.9 mM lidocaine, 87Rb images (7 min each, 1 cm3 resolution) were acquired (30-40 min) in the presence of Rb(+)-containing perfusate. Subsequently, the hearts were stained with Evans blue (EB) and samples taken for measurements of Rb+ content. In the Group C, distribution of Rb+ in the left ventricle and the intensities of the 3D 87Rb images were uniform. In the ischemic area (Group I), verified by the lack of EB staining and changes in 31P spectra, the images showed a reduced intensity, which corresponded to decreased Rb+ content (33 +/- 11% of the normal). Thus, 87Rb imaging reveals damaged cells detecting reduced Rb+ content in the ischemic area.

Animals↗
PubMed1998

Determination of the amino acid requirements for a protein hinge in triosephosphate isomerase.

We have determined the sequence requirements for a protein hinge in triosephosphate isomerase. The codons encoding the hinge at the C-terminus of the active-site lid of triosephosphate isomerase were replaced with a genetic library of all possible 8,000 amino acid combinations. The most active of these 8,000 mutants were selected using in vivo complementation of a triosephosphate isomerase deficient strain of E. coli, DF502. Approximately 3% of the mutants complement DF502 with an activity that is above 70% of wild-type activity. The sequences of these hinge mutants reveal that the solutions to the hinge flexibility problem are varied. Moreover, these preferences are sequence dependent; that is, certain pairs occur frequently. They fall into six families of similar sequences. In addition to the hinge sequences expected on the basis of phylogenetic analysis, we selected three new families of 3-amino-acid hinges: X(A/S)(L/K/M), X(aromatic/beta-branched)(L/K), and XP(S/N). The absence of these hinge families in the more than 60 known species of triosephosphate isomerase suggests that during evolution, not all of sequence space is sampled, perhaps because there is no neutral mutation pathway to access the other families.

Amino Acid Sequence↗
PubMed1998

Pyruvate potentiates beta-adrenergic inotropism of stunned guinea-pig myocardium.

UNLABELLED: This study tested the hypotheses that the sensitivity of stunned myocardium to beta-adrenergic stimulation is diminished, and that metabolic intervention with pyruvate can restore beta-adrenergic responsiveness to pre-ischemic levels. Isolated working guinea-pig hearts metabolizing 10 mM glucose were stunned by 45 min of low flow ischemia, and pyruvate and/or isoproterenol treatments were initiated 15 and 30 min after reperfusion, respectively. The dose: response for cardiac power from 0.1-100 nM isoproterenol was significantly shifted to the right in stunned hearts: EC50 (nm) increased from 0.3 +/- 0.06 to 5.2 +/- 1.86. Pyruvate (5 mM) largely restored isoproterenol responsiveness of stunned myocardium, lowering EC50 to 1.1 +/- 0.34 nM. Maximum power was similar in each group. Additional stunned hearts were treated with intermediate (2 nM) or high (30 nM) isoproterenol concentrations with or without pyruvate. Combining treatments produced a significant interaction at the low dose of isoproterenol, increasing cardiac power (mJ x min(-1) x g(-1)) to 149 +/- 20, twice the sum of the individual treatments (2 nM isoproterenol: 34 +/- 11; pyruvate: 33 +/- 8). Cyclic AMP content was unaltered by isoproterenol or pyruvate alone but was increased 41% by the combination. Power was maximized by 30 nM isoproterenol, which tripled cyclic AMP content; pyruvate did not augment these responses, but lessened the isoproterenol-induced decline in cytosolic phosphorylation potential. CONCLUSIONS: Beta-adrenergic inotropism is attenuated in stunned myocardium, although the maximal response is unchanged. Pyruvate potentiated the effects of sub-maximal doses of isoproterenol without depleting cellular energy reserves further, and attenuated energy depletion by high doses of isoproterenol. Pyruvate may allow restoration of contractile performance with lower, energetically less costly doses of beta-adrenergic agents.

Animals↗
PubMed1998

Effects of biliary tract pressure on dynamics of the Oddi's sphincter and its nerve mechanism.

In order to explore the effect of biliary tract pressure on Oddi's sphincter and the mechanism of development of high pressure of biliary tract during acute obstructive and suppurative cholangitis (AOSC), house rabbits were used to establish model of high biliary pressure in acute biliary duct caecus. It was observed that when the pressure of the acute biliary tract was increased to 8 kPa, the electric activity of Oddi's sphincter was obviously enhanced, the pressure of Oddioes sphincter increased remarkably (P < 0.05), and even constant spasm appeared with accompanying increase of discharge frequency of the right greater splanchnic nerves (P < 0.05) and progressive decrease of mean arterial pressure. However, when lidocaine of 0.6% was used to block the right celiac plexus, no above-mentioned reaction happened when the biliary tract pressure was increased again. The results indicated that the acute biliary tract obstruction might induce the contraction or spasm of Oddi's sphincter and bring about a vicious cycle. Its mechanism is related to splanchnic nerves reflection and it is one of important factors in the development of AOSC course.

Acute Disease↗
PubMed1998

The role of vague nerve in the hemodynamic changes induced by acute biliary tract pressure increase.

In order to explore the mechanism of hemodynamic changes caused by high biliary tract pressure, we established an animal model of high biliary tract pressure, in which the disturbance of hemodynamics developed. The cervical or abdominal vague nerve was then blocked. It was observed that when the biliary tract pressure was increased to 16 kPa and kept for 1 h, the arterial blood pressure and cardiac output decreased immediately and parallelly (P < 0.05). When the cervical or abdominal vague nerve were blocked or the pressure of the biliary tract was decreased to zero, both indices returned to normal immediately (P > 0.05). The change of cardiac output lags a little behind that of arterial blood pressure. It suggests that the signal of biliary tract pressure increase can be sent to the cardiovascular center through vague nerve, and the balance between sympathic and parasympathic nerve was broken, which led to the weakening of cardiac contraction and decrease of cardiac output. Due to the peripheral effects of vague nerve, hemodynamic resistance of vessels decreased, which brought about redistribution of peripheral blood flow. Both were the causes of hemodynamic disturbances. After the blood pressure decreased markedly, it showed a jump to normal state when cervical vague nerve was blocked. And the amplitude of diastolic blood pressure restored more than that of systolic blood pressure. This suggests that the cardiac output and peripheral blood resistance are important factors that cause the decrease of blood pressure.

Animals↗
PubMed1998

Effect of basic fibroblast growth factor on angiogenesis in the infarcted porcine heart.

Administration of growth factors is emerging as a new therapeutic approach for the enhancement of collateral vessel formation in the ischemic heart. We have investigated the effects of intramyocardial delivery of FGF-2 in the presence and absence of heparin on angiogenesis in a porcine model of myocardial infarction. Yorkshire pigs were subjected to myocardial infarction by the placement of an embolization coil in the left anterior descending artery (n = 5). Four to five weeks after creation of an infarct, FGF-2 (10 micrograms) alone or in complex with heparin, heparan sulfate, or heparin agarose beads was injected either into the normal myocardium or along the infarct border area. Histologic evaluation of each injection site was performed 4 to 5 weeks post-injection. The effect of FGF-2 on angiogenesis was evaluated by determining the number of capillaries (diameter < 20 microns (and arterioles (> 20 microns with tunica media) in each area observed. The number of capillaries were not affected by the treatment of FGF-2 both in normal myocardium and infarct border area. However, in the normal myocardium, the number of arterioles were increased with the treatment of FGF-2 alone (85 +/- 59%, P < 0.04), FGF-2 plus heparin (281 +/- 193%, P < 0.004) and FGF-2-coated heparin beads (241 +/- 141%, P < 0.01), as compared to control. Delivery of FGF-2 into the infarct border area, also increased the number of arterioles when FGF-2 was given with heparin (736 +/- 154%, P < 0.001) or heparin beads (700 +/- 109%, P < 0.001), as compared to control. FGF-2 administered with heparin was the most effective method of enhancing angiogenesis as compared to FGF-2 alone, FGF-2 plus heparan sulfate, or FGF-2 coated heparin agarose beads.

Affinity Labels↗
PubMed1998

Does simultaneous antegrade/retrograde cardioplegia improve myocardial perfusion in the areas at risk? A magnetic resonance perfusion imaging study in isolated pig hearts.

OBJECTIVE: This study was designed to determine whether simultaneous antegrade/retrograde cardioplegia improves myocardial perfusion in areas supplied by occluded vessels. METHODS: Isolated pig hearts placed in a Langendorff preparation were divided into two groups. The left anterior descending coronary artery was occluded at its origin. In group 1 (n = 7), simultaneous antegrade/retrograde cardioplegia was conducted with use of a single perfusion unit with tubing in a Y-shaped configuration at the end, joined to the aorta and the coronary sinus. In group 2 (n = 8) simultaneous antegrade/retrograde cardioplegia was performed with two separate units, one for antegrade delivery of cardioplegic solution and the other for retrograde cardioplegic solution delivery. Myocardial perfusion in the region supplied by the left anterior descending artery and the region not supplied by this artery was assessed by magnetic resonance imaging, with use of a magnetic resonance contrast agent. The contrast agent was introduced into the common perfusion line in group 1 and into the aortic line only in group 2. RESULTS: Magnetic resonance images showed that the myocardium in the region supported by the left anterior descending artery could not be perfused with antegrade cardioplegic solution because of occlusion of the artery. During simultaneous antegrade/retrograde cardioplegia, however, the myocardium in the left anterior descending region was perfused by approximately 40% to 50% (group 1) or 20% to 30% (group 2) of the degree of perfusion in the region not perfused by the left anterior descending artery (100%). Almost no cardioplegic solution was delivered to the heart through the coronary sinus route during simultaneous antegrade/retrograde cardioplegia in both groups of hearts. Myocardial perfusion in the region supported by the left anterior descending artery was heterogeneous during simultaneous antegrade/retrograde cardioplegia. CONCLUSIONS: Simultaneous antegrade/retrograde cardioplegia significantly improved myocardial perfusion in jeopardized areas of the myocardium. The jeopardized myocardium was mainly perfused by the solution drained from the adjacent normal tissue. Elevated pressure at the coronary sinus during simultaneous antegrade/retrograde cardioplegia is responsible for the redistribution of antegradely delivered cardioplegic solution.

Animals↗