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Y M Yao

Publications and source records attributed to Y M Yao.

At least 19 recordsLinked to original sources
PubMed2006

Sensitive and selective liquid chromatography-mass spectrometry method for the quantification of rosiglitazone in human plasma.

A sensitive and selective high-performance liquid chromatography-electrospray ionisation-tandem mass spectrometry (HPLC-ESI-MS-MS) method for determination of rosiglitazone in human plasma has been developed. After the addition of the internal standard, plasma samples were precipitated by acetonitrile. The compounds were separated on a proC18 column using a mixture of ammonium acetate buffer (0.02 M, pH 6.5) and acetonitrile (in the ratio of 47:53, v/v) as mobile phase. A Finnigan LCQdeca plus ion trap mass spectrometer connected to a Finnigan Surveyor HPLC was used to develop and validate the method. Linearity was established for the range of concentrations 1-1000 ng/ml with a coefficient of determination (r(2)) of 0.999. The intra-day accuracy for rosiglitazone ranged from 110.0 to 99.2% at low, medium and high levels. The inter-day accuracy was less than 15%. The lower limit of quantitation (LLOQ) was identified reproducible at 1.0 ng/ml with a precision of 5.7%. After validation, the method was used to study the pharmacokinetic profile of rosiglitazone in five healthy volunteers after administration of a single oral dose (4.0mg). The proposed method enabled the unambiguous evaluation and quantitation of rosiglitazone for pharmacokinetic, bioavailability or drug-drug interaction studies. A possible chromatography peak (m/z 121, its parent ion m/z 344) of N-demethyl rosiglitazone was observed at 3.49 min during determining rosiglitazone. This may be also a potential method for simultaneous determination of rosiglitazone and its metabolite N-demethyl rosiglitazone concentrations in plasma.

Administration, Oral↗
PubMed2001

Upconverting phosphor reporters in immunochromatographic assays.

Immunochromatographic assays have become popular diagnostic tools in a variety of settings because they are sensitive, fast, and easy to use. Here, we describe the use of a novel reporter, upconverting phosphors (UCP), in this assay format. UCP are submicron-sized, inorganic crystals that are excited with infrared light and that emit photons in the visible range depending on the ion composition of the crystal. Using human chorionic gonadotropin (hCG) as a model analyte to describe the properties of phosphors in immunochromatographic assays, a detection limit of 10 pg hCG in a 100-microl sample has been achieved on a regular basis, with occasional detection of 1 pg hCG. This represents at least a 10-fold improvement over conventional reporter systems such as colloidal gold or colored latex beads. Quantitation of analytes is possible over at least 3 orders of magnitude. Furthermore, an example is given of how UCP can be used for analyte multiplexing using a two-plexed wick for the detection of mouse IgG and ovalbumin. Thus, UCP lateral flow assays can be used for applications that are currently limited by assay sensitivity, and they can increase the probability of a diagnosis by verifying the presence of several analytes in the same sample.

Chorionic Gonadotropin↗
PubMed2001

Effect of recombinant bactericidal/permeability-increasing protein on endotoxin translocation and lipopolysaccharide-binding protein/CD14 expression in rats after thermal injury.

OBJECTIVE: To investigate the potential mechanisms underlying the in vivo effect of recombinant bactericidal/permeability-increasing protein (rBPI21) on endogenous bacteria or endotoxin translocation and lipopolysaccharide-binding protein/CD14 expression secondary to thermal injury. DESIGN: Prospective, randomized, controlled animal study. SETTING: College hospital animal research laboratory. SUBJECTS: Thirty-six male Wistar rats weighing 250-300 g. INTERVENTIONS: The rats were anesthetized, and a 35% total body surface area full-thickness burn was created. Animals were randomized to receive treatment with either rBPI21 or the control protein (albumin). rBPI21 (2 mg/kg body wt, BPI group) or a protein control preparation (burn group) in the same dose was administered in an intravenous bolus at 30 mins and 4 hrs after thermal injury. All animals were killed at 12 and 24 hrs postburn (six to ten rats for each interval). In addition, eight rats were taken as normal controls. MEASUREMENT AND MAIN RESULTS: Our data showed that treatment with rBPI21 was effective in preventing endotoxin translocation secondary to severe burns. Meanwhile, tissue lipopolysaccharide-binding protein, CD14, and tumor necrosis factor-alpha mRNA expression in various organs were inhibited markedly by rBPI21 secondary to acute insults (p <.05-.01). Furthermore, significant reduction in serum aminoleucine transferase concentrations and elevation in intestinal diamine oxidase activities in the rBPI21-treated group were found compared with controls (p <.05-.01). CONCLUSIONS: These findings indicate that endotoxin accumulated in local sites after thermal injury can markedly up-regulate lipopolysaccharide-binding protein/CD14 and tumor necrosis factor-alpha mRNA expression in various organs. Meanwhile, up-regulation of lipopolysaccharide-binding protein/CD14 expression would be the major molecular mechanism of increasing sensitivity to endogenous endotoxin response after burns. Early treatment with rBPI21may be effective in attenuating multiple organ damage resulting from gut-origin endotoxin translocation. This might be associated with the down-regulation effects of tissue lipopolysaccharide-binding protein and CD14 gene expression by the use of rBPI21.

Acute-Phase Proteins↗
PubMed1999

High sensitivity immunoassays using particulate fluorescent labels.

The use of polystyrene fluorescent microspheres as sensitive labels in direct-detection (not enzymatically amplified) heterogeneous equilibrium "sandwich" immunoassays in 96-well plates is described. With mouse IgG as a model antigen, a fluorescent particulate label is more sensitive than a corresponding soluble reporter. The limit of detection of mouse IgG in the multiparametrically optimized assay was 0.2 ng/ml (7.6 x 10(8) antigens/ml) for the particulate reporter and 50 ng/ml (1.9 x 10(11) antigens/ml) for the soluble reporter. The sensitivities of assays using the particulate label were dependent on the surface densities of the capture and reporter antibodies and the concentration of reporter beads. Sensitivity was improved by adding the preformed reporter antibody/fluorescent microsphere complex to trapped antigen on the well surfaces instead of sequentially adding the reporter antibody and then the fluorescent microspheres. Maximal (equilibrium) binding of the particulate reporter to captured antigen occurred after 20 h with a concentration of 1.4 x 10(9) reporter beads/ml. Thus, particulate fluorescent labels provide high sensitivity in direct-detection immunoassays.

Animals↗
PubMed1999

[The biological effect of tetrahydrobiopterin and its potential role in sepsis].

It is well known that overproduction of nitric oxide (NO) is the final common pathway in septic shock. Tetrahydrobiopterin (BH4), a low molecular weight pterdine, is an essential cofactor required for the activity of NO synthase (NOS). Existing evidences show that lipopolysaccharide and proinflammatory cytokines can cause significant rises in bipoterin levels, which in turn augments the synthesis of NO. Also inhibition of biosynthesis of BH4 can decrease NO formation, implying that BH4 may be involved in the pathophysiological alterations of sepsis. However, the precise mechanisms of BH4 in regulating NO formation are not yet fully understood. In this review, we focus on the biological effects and regulation of BH4, as well as its potential role in sepsis. The therapeutic significance of biopterin synthesis inhibitors in septic symptoms is also discussed.

Biopterins↗
PubMed1998

The inflammatory basis of trauma/shock-associated multiple organ failure.

Multiple alterations in inflammatory and immunologic function have been demonstrated in clinical and experimental situations after trauma and hemorrhage, in particular the activation of various humoral (e.g. complement, coagulation) and cellular systems (neutrophils, endothelial cells, macrophages). As a consequence of this activation process there is synthesis, expression and release of numerous mediators (toxic oxygen species, proteolytic enzymes, adherence molecules, cytokines), which may produce a generalized inflammation and tissue damage in the body. Mediators are responsible for ongoing interactions of different cell types and for amplification effects through their networks and feedback cycles, finally leading to a sustained inflammation and multiple organ damage in the body. In the setting of trauma/shock, many activators including bacterial as well as non-bacterial factors may be present that will induce local and systemic inflammatory responses. Although the potential role of bacteria/endotoxin translocation and its clinical relevance remains controversial, many lines of evidence support the concept that the gut may be the reservoir for systemic sepsis and subsequent MOF in a number of pathophysiologic states.

Bacterial Translocation↗
PubMed1997

IL-6 release after intestinal ischemia/reperfusion in rats is under partial control of TNF.

Although there is much evidence to substantiate the view that tumor necrosis factor (TNF) plays a pivotal role in the pathogenesis of multiple organ injury subsequent to intestinal ischemia/reperfusion (I/R), it is still unclear whether TNF is involved in triggering the release of other inflammatory mediators in this condition. The current study was designed to determine the potential effects of TNF blockade, by means of monoclonal antibody (TNF MoAb) treatment, on plasma interleukin 6 (IL-6) in rats after acute intestinal I/R injury. Anesthetized rats underwent 75-min occlusion of superior mesenteric artery followed by 6 hr of reperfusion. The animals were treated with TNF MoAb or control protein at a dose of 20 mg/kg i.v. 30 min before the onset of I/R. Similar IL-6 responses in both the portal and the systemic circulation were observed in animals subjected to intestinal I/R, who showed a progressive increase in plasma IL-6 concentration upon release of the clamp. In animals receiving TNF MoAb before I/R, the subsequent IL-6 release following reperfusion was significantly blunted compared to the levels in controls (P < 0.05). The present study demonstrates that the activation and/or release of IL-6 in the setting of acute gut I/R may, at least in part, be mediated via TNF-dependent mechanisms, providing further evidence that a complex interaction exists between TNF and IL-6.

Animals↗
PubMed1997

Monoclonal antibody to endotoxin attenuates hemorrhage-induced lung injury and mortality in rats.

OBJECTIVES: To determine the possible role of enteric bacteria-derived endotoxin in the pathogenesis of the lung injury and mortality in rats following hemorrhagic shock and resuscitation. DESIGN: Prospective, randomized study. SETTING: Animal laboratory of an institute for research traumatology. SUBJECTS: Male Sprague-Dawley rats, weighing 450 to 480 g. INTERVENTIONS: Anesthetized rats were subjected to a prolonged hemorrhagic shock (mean arterial pressure of 30 to 35 mm Hg for 180 mins) followed by resuscitation. A murine monoclonal antibody to lipopolysaccharide from Escherichia coli and Salmonella, WN1 222-5, was administered at a total dose of 5 mg/kg i.v., starting at the onset of shock (WN1 group). The control group was treated similarly to the WN1 group but received saline at the same volume as WN1 222-5. MEASUREMENTS AND MAIN RESULTS: The 48-hr mortality rate was significantly reduced by WN1 222-5 treatment (28.6% in the treatment group vs. 78.6% in the control group; p = .0169). The characteristic lung injury in this model was significantly reduced in the WN1 group, as assessed by microscopic histopathologic examination increase in lung wet weight (7.60 +/- 0.47 g/kg in the control group vs. 5.14 +/- 0.31 g/kg in the WN1 group; p = .0002), and pulmonary neutrophilic infiltration (myeloperoxidase activity: 1835 +/- 567 mU/g wet weight in the control group vs. 891 +/- 212 mU/g wet weight in the WN1 group). CONCLUSIONS: These data suggest that a) endotoxin derived from enteric bacteria might play an important role in the pathogenesis of lung injury; and b) antiendotoxin agents, such as WN1 222-5, appear to protect against endogenous bacterial endotoxin-related disorders in severe hemorrhagic shock in rats.

Animals↗
PubMed1997

Influence of selective decontamination of the digestive tract on cell-mediated immune function and bacteria/endotoxin translocation in thermally injured rats.

OBJECTIVE: To determine the influence of pretreatment with selective decontamination of the digestive tract (SDD) on systemic immunosuppression, and the relationship between bacteria/endotoxin translocation and abnormalities of immune function in thermally injured rats. DESIGN, MATERIALS, AND METHODS: Animals were subjected to a 40% full-thickness scald injury, and divided into SDD-treated and control groups. The treatment group received SDD (polymyxin E, tobramycin, and 5-flucytosine) by gavage twice daily for 3 days before the experiment and continued for 5 days after thermal injury. The control group was given the same amount of water. The parameters reflecting cell-mediated immunity, including splenocyte proliferation in response to mitogens, interleukin 2 (IL-2) production, and lymphocyte subpopulation, were measured before injury and 1 and 5 days after burn, respectively. MEASUREMENTS AND MAIN RESULTS: Thermal injury resulted in marked reduction in splenocyte proliferative response to T-cell mitogens, IL-2 production, and T-helper/suppressor cells (CD4/CD8) ratio. Prophylactic treatment with SDD significantly decreased the incidences of bacterial translocation and endotoxemia, prevented suppressive mitogenic response and inadequate IL-2 production (p < 0.05-0.01) but did not affect the abnormal ratio of CD4 to CD8 T lymphocytes in blood (p > 0.05). CONCLUSIONS: These results suggest that bacteria/endotoxin translocation from the gut appears to be involved in cell-mediated immune dysfunction as a consequence of thermal injury. Pretreatment with SDD might attenuate postburn immunosuppression by preventing translocation events.

Animals↗
PubMed1997

Significance of TNF in hemorrhage-related hemodynamic alterations, organ injury, and mortality in rats.

To evaluate the role of tumor necrosis factor-alpha (TNF-alpha) in hemodynamic alterations, multiple organ damage, and mortality caused by hemorrhagic shock, we employed a monoclonal antibody to TNF-alpha (TNF-alpha MAb) in anesthetized rats subjected to prolonged hemorrhagic shock (mean arterial pressure of 30-35 mmHg for 180 min) followed by resuscitation over 50 min. Treatment of rats with 20.0 mg/kg TNF-alpha MAb 15 min after the end of resuscitation significantly decreased the total peripheral resistance index (P = 0.031) and provided remarkable protection from multiple organ damage compared with controls. The 48-h survival rate was significantly higher in the treatment group (73.3%) than in the control group (26.7%; P = 0.029). The results suggest that TNF-alpha induced by hemorrhagic shock in rats is an important mediator of pathophysiological alterations associated with cardiovascular abnormalities, multiple organ injury, and even lethality. Postresuscitation treatment with TNF-alpha MAb, even after an initial TNF-alpha formation had occurred, significantly attenuated the cardiovascular consequences and improved the survival rate. Thus monoclonal antibodies to TNF-alpha might provide new prospects in the treatment of hemorrhage-related disorders.

Animals↗
PubMed1996

Animal models as the basis of pharmacologic intervention in trauma and sepsis patients.

With limited resources and the current concerns about using animals for research purposes, the needs must be clear when setting up trauma and sepsis experiments for pharmacologic interventions. Such interventions are performed typically for four reasons: (1) to study the pathophysiologic role of certain mediators (which can be influenced by pharmacologic agents); (2) to study the therapeutic efficacy of treatment strategies; (3) to study the overall safety of new drugs under trauma/sepsis conditions, which are adjunct studies to standard toxicology; (4) to test new diagnostic procedures in a defined trauma or sepsis setting. Intervention in the inflammatory response may be performed at several levels: (1) at the primary induction site (e.g., by antilipopolysaccharide or by preventing complement activation); (2) at the intermediate mediator level (e.g., by antitumor necrosis factor); (3) at the final mediator level (e.g. , by block of polymorphonuclear neutrophil elastase, and (4) at the target (e.g., by membrane stabilization or enhanced antioxidant defense).

Animals↗
PubMed1996

Elevated serum neopterin level: its relation to endotoxaemia and sepsis in patients with major burns.

The present study was conducted to determine the relationship between levels of neopterin and endotoxin in the circulation, and whether the neopterin level was related to the development of severe sepsis after extensive burns. This prospective study included 35 patients with burn size greater than 30% (30-98%), and 22 healthy volunteers who served as a comparison group. Neopterin levels increased in most patients on day 3 post-burn, but they were not significantly correlated with the extent of the burn surface (P > 0 center dot 05). A high serum neopterin level was found in patients with sepsis (n = 15), and a marked elevation persisted throughout the observation period. The difference between septic and non-septic patients (n = 20) became significant on 14 and 28 days post-burn. Although the presence of early endotoxaemia did not influence the alterations in serum neopterin, patients with endotoxaemia had much higher neopterin values than those who showed no endotoxaemia from the second week onward (P < 0 center dot 05-0 center dot 01). In addition, circulating endotoxin and neopterin levels were positively correlated in patients who developed endotoxaemia on day 14 (r = 0 center dot 368, P < 0 center dot 05) and day 21 (r = 0 center dot 439, P < 0 center dot 01) after major burns. These results suggest that thermal injury can lead to an elevation of serum neopterin independent of the burn surface area. The initial increase in the neopterin level may be a part of the acute-phase response to tissue injury itself, whereas the endotoxin release in the circulation may be responsible for the continuous induction of neopterin during the late stage. In addition, the presence of a constant high neopterin level is associated with a critical event in the development of severe burn sepsis.

Adolescent↗
PubMed1996

Monoclonal antibody to tumor necrosis factor-alpha attenuates hemodynamic dysfunction secondary to intestinal ischemia/reperfusion in rats.

OBJECTIVE: To evaluate the effects of monoclonal antibody to tumor necrosis factor (TNF)-alpha on the hemodynamic alterations and survival rate in rats subjected to intestinal ischemia/reperfusion. DESIGN: Prospective, randomized study. SETTING: Animal laboratory of an institute for research in traumatology. SUBJECTS: Male Sprague-Dawley rats, weighing 430 to 460 g. INTERVENTIONS: Anesthetized rats underwent 75 mins of superior mesenteric artery occlusion followed by 6 hrs of reperfusion. The animals were treated intravenously with either TNF-alpha monoclonal antibody (TN3, 20 mg/kg) or the control protein (albumin, 20 mg/kg) 30 mins before the onset of ischemia. MEASUREMENTS AND MAIN RESULTS: Pretreatment with TNF-alpha monoclonal antibody significantly attenuated the decreases in blood pressure and cardiac index (p < .01) compared with controls, for < or = 6 hrs after reperfusion. Stroke volume remained stable in the TNF-alpha monoclonal antibody-treated group and was significantly higher than in the control group at 0.5, 5, and 6 hrs after reperfusion (p < .05 at 0.5 and 5 hrs and p < .01 at 6 hrs). No differences in vascular resistance index values were observed between the two groups at any point in time (p > .05). After intestinal ischemia/reperfusion injury, both the portal and systemic TNF concentrations in the control animals were completely neutralized by TNF-alpha monoclonal antibody treatment. The 72-hr survival rate was significantly (p < .01) better in the treatment group (90%, 9/10) than in the control group (20%, 2/10). CONCLUSIONS: These results suggest that intestinal ischemia/reperfusion injury can lead to increased TNF release into both the portal and the systemic circulation, which may be an important factor contributing to the development of hemodynamic dysfunction. Pretreatment with TNF-alpha monoclonal antibody significantly attenuates the cardiovascular consequences and improves the survival rate after acute intestinal ischemia/reperfusion injury.

Animals↗
PubMed1996

Reduction of circulating prostaglandin E2 level by antiserum against core lipopolysaccharide in a rabbit model of multiple organ failure.

OBJECTIVE: To determine the potential role of prostaglandin E2 (PGE2) in the development of multiple organ dysfunction or failure (MOF), the possible effects of antiserum directed against Re chemotype lipopolysaccharide (LPS, from Re mutant of Escherichia coli F515) on circulating PGE2 level and survival rate, and whether there is an elevation in the plasma LPS concentration that could account for the induction of arachidonic acid metabolite in a rabbit model of MOF caused by acute hypovolemic insult. DESIGN, MATERIALS, AND METHODS: An animal model of MOF in rabbits, engendered by feeding live Escherichia coli O111:B4 before hemorrhagic shock (35-40 mm Hg for 60 min), was used in the present study. Re-LPS antiserum was given intravenously in the treatment group at the onset of hemorrhage and 4 hours after resuscitation. The animals that received equal volumes of normal rabbit serum and antiserum served as the control group. MEASUREMENTS AND MAIN RESULTS: The circulating PGE2 level was not increased at the end of shock (p > 0.05), but it was found to be significantly elevated 24 hours after hemorrhage and resuscitation in both groups. However, Re-LPS antiserum administration markedly decreased peak PGE2 level (p < 0.05) and attenuated multiple organ damage caused by acute insult. Concomitantly, there were also lower LPS concentrations in the treatment group as compared with the control group (p < 0.05-0.01). The survival rate was significantly increased in antiserum-treated rabbits 96 hours postinjury (treatment vs. control: 58.0% vs. 11.1%, p < 0.01). CONCLUSIONS: The results suggest that an excessive generation and release of PGE2 may be involved in the pathogenesis of immunosuppression and MOF following hemorrhage and resuscitation. Re-LPS antiserum has an inhibitory effect on overproduction of circulating PGE2 and the ability to improve survival with MOF. Gut-derived endotoxemia, bacterial translocation, or both, could account, at least in part, for the PGE2 formation and release in animals response to acute hypovolemic insult.

Animals↗
PubMed1996

Comparison of the efficacy of pentoxifylline and albifyllin (HWA 138) on endotoxin-induced cytokine production, coagulation disturbances, and mortality.

We have evaluated two different xanthine derivatives, pentoxifylline (POF) and albifyllin (HWA), in rat endotoxemia for their ability to reduce 1) cytokine formation, 2) coagulation disturbances, and 3) mortality. The animals were injected with lipopolysaccharide (LPS) (15 mg/kg i.p.) and received HWA or POF (25, 50, or 100 mg/kg) or saline 30 min before LPS administration. The plasma tumor necrosis factor levels were significantly reduced and in a similar manner by pretreatment with HWA or POF in vivo as well as in vitro. Neither the coagulation disturbance nor the characteristic leukopenia that follow an LPS challenge were significantly influenced by the xanthine derivatives. At a dose of 100 mg/kg, the 6 day mortality was significantly reduced by HWA to 36% but only attenuated by POF to 55% as compared to 80% in the control group. The similar effect of both agents on cytokine formation and coagulation disturbances indicate that, at least to a substantial degree, other mechanisms may account for the significant protection of rats against endotoxin-induced mortality by HWA only. HWA 138 may, therefore, be a new powerful agent against endotoxin-related disorders and mortality.

Animals↗