Biomedical subjects

Qi Lu

Publications and source records attributed to Qi Lu.

47 records · Page 3Linked to original sources

PubMed2002

Fractional isolation and physico-chemical characterization of hemicelluloses by a two-stage treatment from Haloxylon ammodendron and Elaeagnus angustifolia.

The cell wall material of Chinese shrubs Haloxylon ammodendron and Elaeagnus angustifolia was fractionated by successive extractions with ethanol/H(2)O (60:40, v/v) under acidic conditions (0.2 N HCl) at 70 degrees C for 4 h, and 2% H(2)O(2) at pH 11.5 for 16 h, respectively. The sequential two-step treatment resulted in the dissolution of 83.9% and 87.6% of the original hemicelluloses from dewaxed H. ammodendron and E. angustifolia, respectively. Xylose, glucose, and galactose were the major sugar constituents in the two acidic organosolv-soluble hemicellulosic preparations. The two alkaline peroxide-soluble hemicellulosic fractions were shown to be composed primarily of xylose, comprising over 80% of the total sugars. The results also showed that the two alkaline peroxide-soluble hemicellulosic fractions were more linear and acidic, and had higher molecular mass and thermal stability than the two acidic organosolv-soluble hemicellulosic preparations. The 2% H(2)O(2) posttreatment did not result in any significant changes in the macromolecular structure of the isolated hemicelluloses. It is probable that lignin protects hemicelluloses and cellulose from being attacked by peroxide.

Cell Wall↗

PubMed2002

Apoptosis in organs of rats in early stage after polytrauma combined with shock.

OBJECTIVE: Apoptosis in organs of rats in early stage after polytrauma combined with shock was researched. METHODS: Sixty Sprague-Dawley rats were divided into six groups: normal control (A, n = 6), sham-operation (N, n = 6), single hemorrhagic shock (S, n = 6), two-site trauma/shock (B, n = 6), four-site trauma/shock (C, n = 6), and six-site trauma/shock (D, n = 30). Shock was kept 60 min by blood withdrawal. Polytrauma was performed by clamping different sites of limbs to make fractures according to different groups: B at both femurs; C at femurs and tibias; and D at femurs, tibias, and humeri. The animals of A were totally normal without any operation. The rats of N, S, B, and C were killed at 6 hours after resuscitation, and the rats of D were killed at 1, 3, 6, 12, and 24 hours, respectively. Then, DNA agarose gel electrophoresis, in situ end-labeling (ISEL), and light and electron microscopy were performed and the percentage of DNA fragmentation was detected to assess apoptosis. RESULTS: In B, C, and D, the special ladder patterns for apoptosis were seen in thymus, spleen, liver, lung, and intestine, but not in heart, kidney, and brain. However, positive responses were observed in all these eight organs by ISEL. At 6 hours after resuscitation, the percentages of DNA fragmentation in thymus, spleen, liver, lung, and intestine all increased together with the severity of trauma. In D, the percentages of DNA fragmentation in these five organs all increased significantly at 1 hour after resuscitation. At 3 hours, the percentages in spleen, liver, lung, and intestine reached peak, and declined gradually afterward, whereas those in thymus continued increasing after 3 hours and kept stable from 6 hours to 24 hours. It was shown by morphologic examination that the majority of apoptotic cells lay in cortex of thymus, in growth center of white pulp of spleen, in border area of hepatic lobule and portal area of liver, and at the base of crypts of intestine. In lung, multiple kinds of cells, including alveolar epithelial cells, vascular endothelial cells, and polymorphonuclear neutrophils, induced apoptosis. CONCLUSION: Apoptosis was induced in thymus, spleen, liver, lung, and intestine in early stage after polytrauma combined with shock, which may play partial roles in the development of multiple organ failure.

Animals↗

PubMed2002

Shock mesenteric lymph-induced rat polymorphonuclear neutrophil activation and endothelial cell injury is mediated by aqueous factors.

BACKGROUND: After trauma and hemorrhagic shock (T/HS), mesenteric lymph (ML) activates polymorphonuclear neutrophils (PMNs), injures endothelial cells (ECs), and predisposes to lung injury. The involved mediators, however, are unknown. We studied the ability of aqueous (AQ) and lipid (LIP) extracts of rat T/HS ML to activate PMNs and injure ECs. METHODS: ML was collected from male rats undergoing trauma (laparotomy) plus hemorrhagic shock (30 mm Hg, 90 minutes) or sham shock. AQ and LIP ML fractions were separated using the Bligh-Dyer technique. Human umbilical vein endothelial cells were incubated 18 hours in 5% LIP or AQ lymph fractions and viability was assessed using the MTT assay. Rat PMNs incubated 5 minutes with 3% LIP or AQ fractions were assessed for respiratory burst (RB) and cytosolic calcium ([Ca(2+)](i)) using dihydrorhodamine 123 and fura-2AM. Human PMN responses to AQ and LIP T/HS lymph were studied similarly. RESULTS: EC incubated in AQ showed 19 +/- 4% viability as compared with 65 +/- 11% in LIP (p < 0.001). Whole lymph affected ECs comparably to AQ T/HS lymph. Rat PMN basal [Ca(2+)](i) increased after exposure to AQ but not LIP T/HS lymph extracts. AQ T/HS lymph primed [Ca(2+)](i) responses to macrophage inflammatory protein-2 and platelet-activating factor; neither LIP T/HS nor any trauma and sham shock lymph fraction caused PMN priming. Rat PMN RB was elevated after AQ T/HS lymph incubation when compared with buffer (610 +/- 122 U/s vs. 225 +/- 38 U/s, p = 0.01). Rat PMN incubation in LIP T/HS lymph caused minimal activation (289 +/- 28 U/s, p = NS). Conversely, human PMN showed [Ca(2+)](i) and RB priming by rat T/HS LIP and not AQ extracts. CONCLUSION: T/HS mesenteric lymph contains multiple biologically active mediators. Both AQ and LIP extracts of T/HS lymph are toxic to human umbilical vein endothelial cells, with AQ more active than LIP. Only AQ T/HS lymph activates rat PMNs, although LIP rat lymph extract activates human PMNs. These findings demonstrate the complex nature of gut lymph-derived biologic factors as well as species-specific differences on PMN and EC physiology. Therapies directed at any one specific molecule or mediator are therefore unlikely to be successful.

Animals↗

PubMed2002

Nitric oxide directly impairs intestinal barrier function.

Excess production of nitric oxide (NO) has been implicated in endotoxin-induced loss of gut barrier function in vivo. Thus, we tested the direct effect of NO on the barrier function of intestinal mucosal membranes suspended ex vivo in Ussing chambers and on IEC-6 enterocyte monolayers. In these experiments, ex vivo-mounted ileal membranes or IEC-6 cell enterocyte monolayers were exposed to the NO donor, S-nitroso-N-acetyl-penicillamine (SNAP) over a dose range (10 microm to 2 mM) or medium. SNAP at concentrations of 1 or 2 mM, but not 10 or 100 microM, increased the rates of bacterial translocation (BT) across both the ileal membranes and the IEC-6 monolayers by >1 log (P < 0.05), as well as the permeability of the IEC-6 monolayers to phenol red (P < 0.05). The ileal membranes exposed to 1 or 2 mM SNAP for 3 h manifested histologic evidence of mucosal injury and decreases in electrical resistance and potential difference values (P < 0.05), while the IEC-6 cells exposed to SNAP for 18 h had increased levels of cell death (P < 0.05). Since NO produced locally by stimulated enterocytes could contribute to barrier dysfunction, NO production, iNOS mRNA levels, and monolayer permeability were measured in enterocytes (IEC-6 and Caco-2) exposed to medium, endotoxin (lipopolysaccharide [25 microg/mL]) or a cytokine mixture (IL-1beta 10 ng/mL, TNF-alpha 10 ng/mL, and INF-gamma 250 U/mL) for 6 or 24 h. Endotoxin increased NO production, iNOS mRNA expression, and monolayer permeability in the IEC-6, but not the Caco-2 cells, while exposure to the cytokine mixture increased both NO production, iNOS mRNA expression, and monolayer permeability in both the IEC-6 and Caco-2 cell lines. Based on the results of these studies it appears that NO can directly increase ileal mucosal membrane and enterocyte monolayer permeability and BT and that increased NO production and iNOS mRNA expression is associated with endotoxin- and/or cytokine-induced loss of enterocyte monolayer barrier function.

Animals↗

PubMed2002

Lipopolysaccharide-induced enterocyte-derived nitric oxide induces intestinal monolayer permeability in an autocrine fashion.

Studies indicate that endotoxin (LPS) causes intestinal injury, increases inducible nitric oxide synthase (iNOS) activity, leads to increased NO production, and promotes bacterial translocation (BT). To investigate the mechanism by which LPS causes gut injury and to test the hypothesis that NO produced by enterocytes promotes gut injury in an autocrine fashion, rat intestinal epithelial cell (IEC-6) monolayers were tested. IEC-6 monolayers grown in a bicameral system were incubated with media or with LPS (25 microg/mL) and tested for permeability to phenol red, BT, and nitrate/nitrite (NO2/NO3) production. To determine the direct effect of NO on permeability, monolayers were incubated with the NO donor S-nitroso-acetylpenicillinamide (SNAP; 1 mM) and tested for permeability. Next, the protective effects of two NOS inhibitors (L-NMMA and L-NIL) were tested. Finally, to determine if LPS-induced permeability occurs via a poly (ADP-ribose) synthetase- (PARS) dependent pathway, monolayers incubated with LPS alone or with the PARS inhibitor, INH2BP (100 microM) were tested. LPS significantly increased IEC-6 permeability to phenol red, as well as increased NO2/NO3 by 20-fold (P < 0.001) and increased BT 10-fold (P < 0.001). SNAP mimicked the effect of LPS and significantly increased both permeability to phenol red and BT. Inhibition of iNOS significantly decreased the LPS-induced increase in monolayer permeability and BT (P < 0.05). Monolayers incubated with INH2BP had significantly decreased permeability to phenol red and BT, suggesting that LPS-induced NO production increases monolayer permeability at least in part via a PARS-dependent mechanism. In summary, LPS-induced disruption of monolayer barrier function appears to be related, at least in part, to enterocyte produced NO. This supports the hypothesis that NO produced by LPS-stimulated enterocytes promotes injury in an autocrine fashion and highlights the fact that enterocytes can be a target as well as a producer of NO.

Animals↗

PubMed2002

Trauma/hemorrhagic shock mesenteric lymph upregulates adhesion molecule expression and IL-6 production in human umbilical vein endothelial cells.

Trauma/hemorrhagic shock (T/HS) is associated with significant lung injury, which is mainly due to an inflammatory process, resulting from the local activation and subsequent interaction of endothelial cells and leukocytes. Adhesion molecules expressed by both cell types play a crucial role in the process of neutrophil-mediated endothelial cell injury. We have previously shown that mesenteric lymph duct ligation prevents T/HS-induced lung leukocyte infiltration and endothelial injury, suggesting that inflammatory factors originating from the gut and carried in the lymph are responsible for the lung injury observed following T/HS. Based on these observations, we hypothesized that inflammatory substances in T/HS lymph trigger lung injury by a mechanism involving the upregulation of adhesion molecules. To test this hypothesis, we examined whether T/HS mesenteric lymph induces the expression of E-selectin, P-selectin, and intracellular adhesion molecule-1 (ICAM-1) in human umbilical vein endothelial cells (HUVECs). Furthermore, because the cytokine IL-6 is an important component of the endothelial inflammatory process, we investigated how T/HS lymph affects the production of IL-6 by HUVECs. Mesenteric lymph from T/HS rats increased both E- and P-selectin, as well as ICAM-1 expression on HUVECS, as compared to trauma/sham shock (T/SS) lymph or medium only groups. However, T/HS lymph failed to induce the shedding of E-selectin. In HUVECs treated with T/HS lymph, IL-6 concentrations were higher than HUVECs treated with T/SS lymph. These findings suggest that mesenteric lymph produced after hemorrhagic shock potentiates lung injury by the upregulation of endothelial cell adhesion molecule expression and IL-6 production.

Animals↗

PubMed2002

Hypertonic saline improves intestinal mucosa barrier function and lung injury after trauma-hemorrhagic shock.

Our objective was to test the hypotheses that small volume hypertonic saline (HTS) resuscitation protects against trauma-hemorrhagic shock (T/HS)-induced intestinal and lung injury better than standard volume resuscitation with Ringer's lactate (RL), and that the degree of lung injury correlates with the degree of gut injury after therapy. Male Sprague-Dawley rats were subjected to laparotomy (trauma) and 90 min of T/HS or sham shock (T/SS), and were then resuscitated with RL or 7.5% NaCl solution at an equivalent sodium load. Intestinal and lung injury was assessed at 3 and 24 h after resuscitation. Lung permeability, pulmonary myeloperoxidase (MPO) levels, and the bronchoalveolar lavage fluid (BALF) protein to plasma protein ratio were increased after T/HS, but were significantly lower in HTS-resuscitated than RL-treated rats. The incidence of bacterial translocation (BT) was not different between the groups, but the magnitude of BT after T/HS was less after HTS than RL resuscitation. Barrier function of intestinal segments was impaired only in the T/HS rats resuscitated with RL and histological analysis demonstrated fewer injured villi in the T/HS rats resuscitated with HTS than RL. Linear regression analysis revealed direct correlations between the percent of injured villi, increased lung permeability, and pulmonary neutrophil sequestration. Resuscitation with HTS ameliorated T/HS-induced gut and lung injury seen with RL resuscitation. These results, together with the direct correlation found between gut and lung injury, suggest that lung injury after T/HS may be mediated by gut injury.

Animals↗

PubMed2002

NHE blockade inhibits chemokine production and NF-kappaB activation in immunostimulated endothelial cells.

Na(+)/H(+) exchanger (NHE) activation has been documented to contribute to endothelial cell injury caused by inflammatory states. However, the role of NHEs in regulation of the endothelial cell inflammatory response has not been investigated. The present study tested the hypothesis that NHEs contribute to endothelial cell inflammation induced by endotoxin or interleukin (IL)-1beta. NHE inhibition using amiloride, 5-(N-ethyl-N-isopropyl)-amiloride, and 5-(N-methyl-N-isobutyl)amiloride as well as the non-amiloride NHE inhibitors cimetidine, clonidine, and harmaline suppressed endotoxin-induced IL-8 and monocyte chemoattractant protein (MCP)-1 production by human umbilical endothelial vein cells (HUVECs). The suppressive effect of amiloride on endotoxin-induced IL-8 production was associated with a decreased accumulation of IL-8 mRNA. NHE inhibitors suppressed both inhibitory (I)kappaB degradation and nuclear factor (NF)-kappaB DNA binding, suggesting that a decrease in activation of the IkappaB-NF-kappaB system contributed to the suppression of HUVEC inflammatory response by NHE blockade. NHE inhibition decreased also the IL-1beta-induced HUVEC inflammatory response, because amiloride suppressed IL-1beta-induced E-selectin expression on HUVECs. These results demonstrate that maximal activation of the HUVEC inflammatory response requires a functional NHE.

Adjuvants, Immunologic↗

PubMed2002

Detection of posttrauma apoptosis and necrosis of hepatocytes and its significance.

OBJECTIVE: To study the role of apoptosis and necrosis of hepatocytes in the pathogenesis of acute liver dysfunction following severe trauma in rats. METHODS: Rat models of multiple fractures complicated by shock were established, in which apoptotic and necrotic hepatocytes were detected by flow cytometry (FCM) via double-staining technique of Annexin-V-flous and propidium iodide (PI). Observation of the pathological changes in the hepatocytes was also conducted by means of light and electron microscopy and electronphoresis respectively, and the correlation of these changes with liver function were evaluated. RESULTS: Hepatocytes underwent both apoptosis and necrosis in rat models of severe trauma. The quantities of necrotic hepatocytes increased progressively in positive correlation with the degree of hepatic injury, reaching the peak at 3 h post trauma. A proportion of the apoptotic cells underwent secondary necrosis, the number of the necrotic cells positively correlated with liver dysfunction deterioration. CONCLUSIONS: Both necrosis and apoptosis are important factors responsible for liver function damages following severe trauma. Necrosis of hepatic cells directly causes liver function damages that are further aggravated by secondary necrosis among apoptotic hepatocytes.

Animals↗

PubMedDate not supplied

Inducible nitric oxide synthase knockout mice are resistant to diet-induced loss of gut barrier function and intestinal injury.

Loss of gut barrier function has been documented to occur in animals receiving total parenteral nutrition (TPN) and certain liquid diets. However, the mechanisms responsible for diet-induced gut barrier dysfunction remain to be fully determined. Thus we tested the hypothesis that increased intestinal nitric oxide production contributes to this phenomenon. To test this hypothesis, iNOS-deficient (iNOS -/-) mice and their wild-type littermates (iNOS +/+) were fed either chow or TPN solution for 14 days. Subsequently they were killed and gut barrier function was assessed by measuring bacterial translocation to the mesenteric lymph node (MLN) complex. Additionally, intestinal bacterial population levels, gut morphology, plasma and intestinal nitric oxide levels, as well as intestinal levels of the nitric oxide synthase (NOS) enzymes cNOS and iNOS, were measured. Bacterial translocation occurred in the iNOS +/+ but not the iNOS -/- mice receiving oral TPN solution. Oral TPN-induced bacterial translocation was associated with increased intestinal bacterial population levels as well as morphologic evidence of intestinal injury. Plasma and intestinal levels of the nitric oxide products, nitrite/nitrate, were increased in the iNOS +/+ mice fed the TPN solution but not in the chow-fed groups or the iNOS -/- mice receiving TPN solution. Last, intestinal iNOS, but not cNOS, activity was increased in the iNOS +/+ oral TPN-fed mice. These results implicate a role for increased intestinal nitric oxide production, through iNOS, in the pathogenesis of oral TPN-induced gut barrier dysfunction and injury.

Animals↗

PubMedDate not supplied

Chemical considerations and biological selectivity of protein nitrosation: implications for NO-mediated signal transduction.

Nitric oxide (NO) is a diatomic free radical that plays an important role in the homeostatic regulation of the central nervous, immune, and cardiovascular systems. In addition to its interaction with guanylate cyclase, which results in the production of the second messenger cyclic GMP, there is now a large body of literature indicating that many of the effects associated with the production of NO are due to the nitrosation of cysteine residues in proteins. In this review, we outline the primary chemical pathways that may account for protein nitrosation in cells and tissues. The functional implications of protein nitrosation are discussed by using the p21(ras) subfamily of small monomeric GTPases and the cysteine-containing aspartate-specific proteases (caspases) as prototypical examples. Overall, in addition to the well characterized NO/O(2) reaction, there may exist multiple pathways accounting for protein nitrosation in cells. These include acid- and free radical-mediated mechanisms. Although protein nitrosation may not be limited to cysteine residues, there is now ample evidence that nitrosation reactions, in a fashion similar to oxidative modifications, may modulate the structure, activity, association, and localization of a specific subset of proteins in cells and tissues.

Animals↗