Biomedical subjects

X Jiang

Publications and source records attributed to X Jiang.

At least 73 records · Page 4Linked to original sources

PubMed2002

Effects of aluminum on physiological metabolism and antioxidant system of wheat (Triticum aestivum L.).

The Al-tolerant cultivar TAM202 and the Al-sensitive cultivar TAM 105 of winter wheat (Triticum aestivum L.) were exposed to 0, 50, 75, 100 or 150 microM of Al. The absorption of Al by wheat, the growth of root, several key enzymes concerned with C, N and P metabolism, as well as key constituents of antioxidant system, were investigated. The results showed that TAM105 absorbed more Al than TAM202 and its root growth (presented by the length) was inhibited more severely. The root growth was most closely related to mononuclear Al (Ala) activity. The metabolic enzymes (presented by glucose-6-phosphate dehydrogenase, nitrate reductase and acid phosphatase) in TAM202 were Al-tolerant. Presented by superoxide dimutase (SOD) and the content of reduced glutathione (GSH) and malondialdehyde (MDA), antioxidant system in TAM202 indicated lower oxidative stress and greater ability to protect the cultivar.

Absorption↗

PubMed2002

A large hotel outbreak of Norwalk-like virus gastroenteritis among three groups of guests and hotel employees in Virginia.

A large outbreak of acute gastroenteritis occurred among three different groups of guests and the employees of a Virginia hotel within a 2-week period in November 2000. At least 76 of the hotel's guests and 40 hotel employees had acute gastroenteritis during this period. All tested ill persons were infected with the same strain of Norwalk-like virus, as shown by cloning and sequencing of virus detected in stool specimens from the three guest groups and the employees. Epidemiologic investigation suggested food as the probable source for the guests. Most of the employees, including those sick, did not eat in the hotel, suggesting that environmental contamination and person-to-person transmission could have contributed to the outbreak. The disease continued to spread in the hotel, passing from one guest group to another, by food, environmental contamination, and/or by person-to-person transmission through infected employees and guests. The study describes procedures implemented to control the outbreak and makes recommendations for future outbreak control.

Adult↗

PubMed2002

Elucidating critical mechanisms of deregulated stem cell turnover in the chronic phase of chronic myeloid leukemia.

Chronic myeloid leukemia (CML) has been studied intensively for many years; yet its treatment remains problematic and its biology remains elusive. In chronic phase, the leukemic clone appears to be maintained by a small number of BCR-ABL-positive hematopoietic stem cells that differentiate normally and amplify slowly. In contrast, as these cells enter the intermediate stages of lineage restriction, their progeny are selectively expanded and generate an enlarged pool of neoplastic progenitors. Recent analyses of purified subsets of primitive CML cells have provided a coherent explanation for this dichotomous behavior of BCR-ABL-positive stem and progenitor cells based on the discovery of an unusual autocrine IL-3/G-CSF mechanism activated in them. This only partially counteracts in vivosignals that maintain normal stem cells in a quiescent state but, when active in CML stem cells, promotes their differentiation in favor of their self-renewal. In more differentiated CML progenitors, the same mechanism has a more potent mitogenic effect which is then extinguished when the cells enter the terminal stages of differentiation. Thus, further expansion of the clone is limited until inevitably additional mutations are acquired that further distort or override the regulatory mechanisms still operative in the chronic phase.

Adolescent↗

PubMed2002

Analysis of Helicobacter pylori and nonsteroidal anti-inflammatory drug-induced gastric epithelial injury.

BACKGROUND: Helicobacter pylori and nonsteroidal anti-inflammatory drugs (NSAIDs) are important factors in gastric mucosal injury. However, the relationship between H. pylori and NSAID-related gastroduodenal mucosal injury has not been clarified. AIM: To determine the role of H. pylori in NSAID-induced gastric mucosal injury and to examine the effects of H. pylori, indomethacin and sofalcone on gastric epithelial cells in culture, as a useful model to study gastric mucosal injury. In addition, we studied the effect of sofalcone, a gastric mucosal protection agent, on H. pylori and NSAID-induced gastric mucosal injury. METHODS: Cytotoxic and noncytotoxic strains of H. pylori were used, each with an inoculum of 10(7) cfu/mL. The effect on the growth of RGM-1 cells (a rat gastric epithelial cell line) was studied by MTT assay, and levels of prostaglandin E2 in culture supernatants were measured by EIA. RESULTS: Both cytotoxic and noncytotoxic strains of H. pylori tended to induce cell injury in RGM-1 cells at 48 h after inoculation. Indomethacin alone induced gastric epithelial injury in a dose-dependent manner, but did not augment cell injury induced by H. pylori. In addition, sofalcone (10(-5) mol/L) showed a suppressive effect on indomethacin-induced gastric epithelial injury. CONCLUSION: These findings indicate that indomethacin induces gastric mucosal injury regardless of H. pylori infection, and suggests that sofalcone may be a useful drug in the treatment of NSAID-induced mucosal injury.

Animals↗

PubMed2002

Additional evidence that the sympathetic nervous system regulates the vessel wall release of tissue plasminogen activator.

It is established that sympathetic neurons can synthesize, transport and store tissue plasminogen activator (t-PA) within axon terminals in the smooth muscle of vessel walls. Moreover, sympathetic excitations (e.g. physical and mental stress) are known to induce an acute release of t-PA into the circulation. However, relatively little is known about the nature and extent of sympathetic nervous system involvement in the release process. We inquired whether a chemical sympathectomy will alter the release of t-PA into the blood, and the intrinsic release of stored t-PA from isolated whole vessel explants. A long-term sympathectomy was induced in adult Sprague-Dawley rats by injection of guanethidine during a 5-week course. The destruction of ganglion neurons and vessel wall axons was verified immunohistochemically. t-PA release was assayed as the free activity in hind limb plasma and explant culture medium. Following sympathectomy: (i) the basal t-PA activity in plasma was 70% less than controls (2.92 +/- 1.96 versus 9.33 +/- 1.72 IU/ml; </= 0.001); (ii) the acute release from isolated vessels induced by bradykinin or phenylephrine was comparably reduced; and (iii) the greatest reductions occurred in densely innervated small vessel explants. The results provide new support for an autonomic regulation of neural t-PA release into the vessel wall matrix and blood of densely innervated thin-walled microvessels.

Animals↗

PubMed2002

Nanocrystalline sensor-grade Sn1-xInxO2 (0 < or = x < or = 0.2).

Nanocrystalline Sn1-xInxO2 (0 < or = x < or = 0.2) has been successfully prepared by a solution chemical route. High-resolution transmission electron microscopy studies show that the average grain size of Sn0.8In0.2O2 heated at 310 degrees C, 500 degrees C, and 800 degrees C for 12 h is about 3-4 nm, 5-6 nm, and 7-10 nm, respectively. The corresponding values for pure SnO2 are 3-4 nm, 7-10 nm, and 50-90 nm, respectively. Powder X-ray diffraction and electron diffraction studies confirm the existence of solid solution only in the nanocrystalline state (the average particle size is in the range of 5-10 nm) with the solubility limited to 20% of In2O3. Indium ions stabilize the nanocrystalline nature of Sn1-xInxO2 (0 < or = x < or = 0.2) and prevent the grain growth by entering the SnO2 lattice. The thermal characteristics of nanocrystalline Sn1-xInxO2 (0 < or = x < or = 0.2) investigated by thermogravimetric (TG) and differential thermal analysis (DTA) show that the solid solution decomposes at 820 degrees C into SnO2 and In2O3, which is accompanied by a rapid crystal growth. The electrical conductivity and activation energy of Sn1-xInxO2 (0 < or = x < or = 0.2) undergo significant changes when the average grain size is less than or equal to 2 x the Debye length, LD.

Crystallization↗

PubMed2001

The V122I cardiomyopathy variant of transthyretin increases the velocity of rate-limiting tetramer dissociation, resulting in accelerated amyloidosis.

The transthyretin (TTR) amyloid diseases are of keen interest, because there are >80 mutations that cause, and a few mutations that suppress, disease. The V122I variant is the most common amyloidogenic mutation worldwide, producing familial amyloidotic cardiomyopathy primarily in individuals of African descent. The substitution shifts the tetramer-folded monomer equilibrium toward monomer (lowers tetramer stability) and lowers the kinetic barrier associated with rate-limiting tetramer dissociation (pH 7; relative to wild-type TTR) required for amyloid fibril formation. Fibril formation is also accelerated because the folded monomer resulting from the tetramer-folded monomer equilibrium rapidly undergoes partial denaturation and self-assembles into amyloid (in vitro) when subjected to a mild denaturation stress (e.g., pH 4.8). Incorporation of the V122I mutation into a folded monomeric variant of transthyretin reveals that this mutation does not destabilize the tertiary structure or alter the rate of amyloidogenesis relative to the wild-type monomer. The increase in the velocity of rate-limiting tetramer dissociation coupled with the lowered tetramer stability (increasing the mol fraction of folded monomer present at equilibrium) may explain why V122I confers an apparent absolute anatomic risk for cardiac amyloid deposition.

Biopolymers↗

PubMed2001

Precision measurement of the spin-dependent asymmetry in the threshold region of 3He(e, e').

We present the first precision measurement of the spin-dependent asymmetry in the threshold region of 3He(e,e') at Q2 values of 0.1 and 0.2 (GeV/c)2. The agreement between the data and nonrelativistic Faddeev calculations which include both final-state interactions and meson-exchange current effects is very good at Q2 = 0.1 (GeV/c)2, while a small discrepancy at Q2 = 0.2 (GeV/c)2 is observed.

Journal Article↗

PubMed2001

Absence of gender differences in clinical outcomes in patients with cardiogenic shock complicating acute myocardial infarction. A report from the SHOCK Trial Registry.

OBJECTIVES: The aim of this study was to assess the impact of gender on clinical course and in-hospital mortality in patients with cardiogenic shock (CS) complicating acute myocardial infarction (AMI). BACKGROUND: Previous studies have demonstrated higher mortality for women compared with men with ST elevation myocardial infarctions and higher rates of CS after AMI. The influence of gender and its interaction with various treatment strategies on clinical outcomes once CS develops is unclear. METHODS: Using the SHould we emergently revascularize Occluded Coronaries for cardiogenic shocK? (SHOCK) Registry database of 1,190 patients with suspected CS in the setting of AMI, we examined shock etiologies by gender. Among the 884 patients with predominant left ventricular (LV) failure, we compared the patient demographics, angiographic and hemodynamic findings, treatment approaches as well as the clinical outcomes of women versus men. This study had a 97% power to detect a 10% absolute difference in mortality by gender. RESULTS: Left ventricular failure was the most frequent cause of CS for both gender groups. Women in the SHOCK Registry had a significantly higher incidence of mechanical complications including ventricular septal rupture and acute severe mitral regurgitation. Among patients with predominant LV failure, women were, on average, 4.6 years older, had a higher incidence of hypertension, diabetes and a lower cardiac index. The overall mortality rate for the entire cohort was high (61%). After adjustment for differences in patient demographics and treatment approaches, there was no significant difference in in-hospital mortality between the two gender groups (odds ratio = 1.03, 95% confidence interval of 0.73 to 1.43, p = 0.88). Mortality was also similar for women and men who were selected for revascularization (44% vs. 38%, p = 0.244). CONCLUSIONS: Women with CS complicating AMI had more frequent adverse clinical characteristics and mechanical complications. Women derived the same benefit as men from revascularization, and gender was not independently associated with in-hospital mortality in the SHOCK Registry.

Aged↗

PubMed2001

Relativistic effects and two-body currents in (H)((-->)e(')p)n using out-of-plane detection.

Measurements of the (2)H((-->)e,e(')p)n reaction were performed with the out-of-plane magnetic spectrometers (OOPS) at the MIT-Bates Linear Accelerator. The longitudinal-transverse, f(LT) and f(')(LT), and the transverse-transverse, f(TT), interference responses at a missing momentum of 210 MeV/c were simultaneously extracted in the dip region at Q2 = 0.15 (GeV/c)(2). In comparison to models of deuteron electrodisintegration, the data clearly reveal strong effects of relativity and final-state interactions and the importance of two-body meson-exchange currents and isobar configurations. We demonstrate that such effects can be disentangled by extracting these responses using the novel out-of-plane technique.

Journal Article↗

PubMed2001

Anion shielding of electrostatic repulsions in transthyretin modulates stability and amyloidosis: insight into the chaotrope unfolding dichotomy.

The balance between stabilizing forces and the localized electrostatic repulsions destabilizing the transthyretin (TTR) tetramer is tunable via anion shielding. The two symmetrical anion interaction sites in TTR are comprised of residues Lys15 and Lys15' from opposing subunits on the periphery of the two thyroxine binding sites. These epsilon-ammonium groups repel one another and destabilize the tetramer, unless an appropriate anion is present, which stabilizes the tetramer. Chaotrope denaturation of TTR exhibits unusual behavior in that urea appears to be a stronger denaturant than GdmCl (guanidinium chloride), even though GdmCl is typically twice as powerful as a denaturant. The shift in the midpoint of the urea denaturation curve to higher concentrations as well as the increase in the mole fraction of tetramer that is highly resistant to denaturation with increasing KCl concentration provides strong evidence that anion shielding stabilizes the TTR tetramer. A consequence of tetramer stabilization is folding hysteresis, because the high GdmCl concentrations required to denature the anion-stabilized tetramer do not allow refolding of the unfolded monomers. The formation of amyloid fibrils by TTR requires that its normal tetrameric structure dissociate to alternatively folded monomers, a process mediated by acidification (pH 5-4). This process is inhibited by Cl(-) ions in a concentration-dependent fashion. Chloride ion may not be the relevant physiological TTR stability modulator, but it is the main focus of these studies explaining the hysteresis observed in the denaturation and refolding studies with GdmCl.

Amino Acid Substitution↗

PubMed2001

An engineered transthyretin monomer that is nonamyloidogenic, unless it is partially denatured.

Transthyretin (TTR) is a soluble human plasma protein that can be converted into amyloid by acid-mediated dissociation of the homotetramer into monomers. The pH required for disassembly also results in tertiary structural changes within the monomeric subunits. To understand whether these tertiary structural changes are required for amyloidogenicity, we created the Phe87Met/Leu110Met TTR variant (M-TTR) that is monomeric according to analytical ultracentrifugation and gel filtration analyses and nonamyloidogenic at neutral pH. Results from far- and near-UV circular dichroism spectroscopy, one-dimensional proton NMR spectroscopy, and X-ray crystallography, as well as the ability of M-TTR to form a complex with retinol binding protein, indicate that M-TTR forms a tertiary structure at pH 7 that is very similar if not identical to that found within the tetramer. Reducing the pH results in tertiary structural changes within the M-TTR monomer, rendering it amyloidogenic, demonstrating the requirement for partial denaturation. M-TTR exhibits stability toward acid and urea denaturation that is nearly identical to that characterizing wild-type (WT) TTR at low concentrations (0.01-0.1 mg/mL), where monomeric WT TTR is significantly populated at intermediate urea concentrations prior to the tertiary structural transition. However, the kinetics of denaturation and fibril formation are much faster for M-TTR than for tetrameric WT TTR, particularly at near-physiological concentrations, because of the barrier associated with the tetramer to folded monomer preequilibrium. These results demonstrate that the tetramer to folded monomer transition is insufficient for fibril formation; further tertiary structural changes within the monomer are required.

Amino Acid Substitution↗

PubMed2001

Measurement of the high energy two-body deuteron photodisintegration differential cross section.

The first measurements of the d(gamma,p)n differential cross section at forward angles and photon energies above 4 GeV were performed at the Thomas Jefferson National Accelerator Facility (JLab). The results indicate evidence of an angular dependent scaling threshold. Results at straight theta(cm) = 37 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 4 GeV, while those at 70 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 1.5 GeV.

Journal Article↗

PubMed2001

Dynamic, self-assembled aggregates of magnetized, millimeter-sized objects rotating at the liquid-air interface: macroscopic, two-dimensional classical artificial atoms and molecules.

This paper describes self-assembly of millimeter-sized, magnetized disks floating on a liquid-air interface, and rotating under the influence of a rotating external magnetic field. Spinning of the disks results in hydrodynamic repulsion between them, while the rotating magnetic field produces an average confining potential acting on all disks. The interplay between hydrodynamic and magnetic interactions leads to the formation of patterns. Theoretical analysis of hydrodynamic and magnetic forces indicates that the interactions in this system are similar to those acting in systems of finite numbers of particles behaving classically ("classical artificial atoms"). Macroscopic artificial atoms and molecules are described, and the rules governing their morphologies outlined.

Journal Article↗

PubMed2001

Measurement of the elastic magnetic form factor of (3)He at high momentum transfer.

New electron scattering measurements have been made that extend data on the (3)He elastic magnetic form factor up to Q(2) = 42.6 fm(-2). These new data test theoretical conjectures regarding non-nucleonic effects in the three-body system. The very small cross sections, as low as 10(-40) cm(2)/sr, required the use of a high-pressure cryogenic gas target and a detector system with excellent background rejection capability. No existing theoretical calculation satisfactorily accounts for all the available data.

Journal Article↗

PubMed2001

Adrenergic regulation of ion transport across adult alveolar epithelial cells: effects on Cl- channel activation and transport function in cultures with an apical air interface.

The effect of beta-adrenergic receptor stimulation on Cl- channel activation was investigated in alveolar epithelial cells grown in monolayer culture and in freshly isolated cells. Monolayers cultured under apical air interface conditions exhibited enhanced amiloride-sensitive Na+ transport compared to apical liquid interface monolayers. Amiloride or benzamil inhibited most (66%) of the basal short circuit current (Isc) with half-maximal inhibitory concentration (IC50) values of 0.62 microm and 0.09 microm respectively. Basolateral addition of terbutaline (2 microm) produced a rapid decrease in Isc followed by a slow recovery that exceeded the basal Isc. When Cl- was replaced with methanesulfonate in either intact monolayers or basolateral membrane permeabilized monolayers, the response to terbutaline (2 microm) was completely inhibited. No effect of terbutaline on amiloride-sensitive Na+ current was detected. beta-Adrenergic agonists and 8-chlorothiophenyl cyclic adenosine monophosphate (8-ctp cAMP) directly stimulated a Cl- channel in freshly isolated alveolar epithelial cells. The current was blocked by glibenclamide (100 microm) and had a reversal potential of -22 mV. No increase in amiloride-sensitve current was detected in response to terbutaline or 8-cpt cAMP stimulation. These data support the conclusion that beta-adrenergic agonists produce acute activation of apical Cl- channels and that monolayers maintained under apical air interface conditions exhibit increased Na+ absorption.

Adrenergic Agents↗

PubMed2001

Matrix metalloproteinase inhibitor KB-R7785 attenuates brain damage resulting from permanent focal cerebral ischemia in mice.

Matrix metalloproteinases (MMPs) are proteolytic enzymes that can degrade the extracellular matrix. MMP-9 and MMP-2 have been implicated in brain injury formation. The authors examined the effect of MMP inhibitor KB-R7785 on brain infarct formation resulting from permanent focal cerebral ischemia in mice. Ischemia was induced by intraluminal middle cerebral artery occlusion (MCAO) in mice under halothane anesthesia. Zymography was conducted to measure the MMPs activity in ischemic brain tissues. Injection of KB-R7785 (100 mg/kg) 30 min before MCAO significantly decreased both MMP-9 activity and infarct volume determined at 24 h. In addition, KB-R7785 injected twice at 1 and 4.5 h after MCAO significantly decreased infarct volume. These results indicate that KB-R7785 has a protective efficacy against focal cerebral ischemia, and our data provide further evidence that MMP-9 contributes to brain infarct formation.

Animals↗

PubMed2001

[Prognosis of patients with bleeding caused by rupture of esophageal and gastric varices: a cohort study].

OBJECTIVES: To determine the factors of long-term survival in patients with bleeding caused by rupture of esophageal and gastric varices and evaluate the effects of surgical treatment, endoscopic treatment, TIPS, and combined therapy on the long-term survival. METHODS: Retrospective cohort study was used to analyze 202 patients with bleeding caused by rupture of esophageal and gastric varices who were admitted to Zhongshan Hospital from 1992 to 1999. All of the patients were divided into several groups according to the intervention they received: no-intervention group, surgery group, endoscopy group, TIPS group, and combined treatment group. The survival curves of different groups were compared. Multivariate analysis was conducted. RESULTS: Kaplan-Meier curves demonstrated that the combined treatment group and surgery group had better prognosis than the endoscopy group and control group (P < 0.01). There was no statistically significant difference in survival rate between the combined treatment group and surgery group and between the endoscopy group and control group. Child-Pugh stratification showed that the results were the same for patients in Child-Pugh A class and B class. Multivariate analysis based on Cox proportional hazard model showed that there were four independent variables associated with prognosis: prothrombin time, HBV-DNA, ascites, and operation. CONCLUSIONS: Surgery, sometimes combined with other treatment, may improve the prognosis of patients with bleeding caused by rupture of esophageal and gastric varices. The four factors associated with the prognosis of patients with bleeding caused by rupture of esophageal and gastric varices are: prothrombin time, HBV-DNA, ascites, and operation.

Adult↗