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Biomedical subjects

X M Jiang

Publications and source records attributed to X M Jiang.

At least 19 recordsLinked to original sources
PubMed2005

Body-centered-cubic Ni and its magnetic properties.

The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52+/-0.08 micro(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs x cm(-3), as opposed to -5.7x10(4) ergs x cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation.

Journal Article↗
PubMed2002

Photoinduced quantum interference antiresonances in pi-conjugated polymers.

We observed photoinduced quantum interference antiresonances between several discrete infrared-active vibrations and the lower-polaron continuous absorption band in a series of pi-conjugated polymer films having superior planar orders, where the polaron transition energy is relatively small. The photoinduced Fano-type antiresonances are well explained by extending the amplitude mode model beyond the adiabatic limit. The agreement between the data and the model confirms the presence of a continuous electronic band above the polaron state. We show that high frequency modes are strongly coupled to electrons, with implications for superconductivity.

Journal Article↗
PubMed2002

Conjugation-length dependence of spin-dependent exciton formation rates in pi-conjugated oligomers and polymers.

We have measured the ratio, r = sigma(S)/sigma(T) of the formation cross section, sigma of singlet and triplet excitons from polarons in pi-conjugated oligomer and polymer films, using a spectroscopic technique we developed recently. We discovered a universal relation between r and the conjugation length (CL): r(-1) depends linearly on CL-1, irrespective of the chain structure. Since r is directly related to the maximum possible electroluminescence quantum efficiency in organic light emitting diodes (OLED), our results indicate that polymers have an advantage over small molecules in OLED applications.

Journal Article↗
PubMed2001

Mechanism of transfer of NO from extracellular S-nitrosothiols into the cytosol by cell-surface protein disulfide isomerase.

N-dansylhomocysteine (DnsHCys) is quenched on S-nitrosation. The product of this reaction, N-dansyl-S-nitrosohomocysteine, is a sensitive, direct fluorogenic substrate for the denitrosation activity of protein disulfide isomerase (PDI) with an apparent K(M) of 2 microM. S-nitroso-BSA (BSA-NO) competitively inhibited this reaction with an apparent K(I) of 1 microM. The oxidized form of DnsHCys, N,N-didansylhomocystine, rapidly accumulated in cells and was reduced to DnsHCys. The fluorescence of DnsHCys-preloaded human umbilical endothelial cells and hamster lung fibroblasts were monitored as a function of extracellular BSA-NO concentration via dynamic fluorescence microscopy. The observed quenching of the DnsHCys fluorescence was an indirect measure of cell surface PDI (csPDI) catalyzed denitrosation of extracellular S-nitrosothiols as decrease or increase in the csPDI levels in HT1080 fibrosarcoma cells correlated with the rate of quenching and the PDI inhibitors, 5,5'-dithio-bis-3-nitrobenzoate and 4-(N-(S-glutathionylacetyl) amino)phenylarsenoxide inhibited quenching. The apparent K(M) values for denitrosation of BSA-NO by csPDI ranged from 12 microM to 30 microM. Depletion of membrane N(2)O(3) with the lipophylic antioxidant, vitamin E, inhibited csPDI-mediated quenching rates of DnsHCys fluorescence by approximately 70%. The K(M) for BSA-NO increased by approximately 3-fold and V(max) decreased by approximately 4-fold. These findings suggest that csPDI catalyzed NO released from extracellular S-nitrosothiols accumulates in the membrane where it reacts with O2 to produce N(2)O(3). Intracellular thiols may then be nitrosated by N2O3 at the membrane-cytosol interface.

Animals↗
PubMed2001

Efficacy trial of Vi polysaccharide vaccine against typhoid fever in south-western China.

OBJECTIVE: To test the efficacy of locally produced Vi vaccine over a time period of longer than one year. METHODS: A double-blinded, randomized field trial was performed in Guangxi Zhuang Autonomous Region in south-western China, using 30 micrograms doses of locally produced Vi. Enrolled subjects were 3-50 years of age, although the majority (92%) were school-aged children, who have the highest rate of typhoid fever in this setting. A total of 131,271 people were systematically allocated a single dose of 30 micrograms of Vi polysaccharide or saline placebo. The study population was followed for 19 months, with passive surveillance conducted in the Ministry of Health and the Regional Health and Anti-epidemic Centre (HAEC). Clinically suspected cases of typhoid fever were confirmed by blood culture, or by serological reaction with O-antigen (Widal tests). FINDINGS: After 19 months, there were 23 culture-confirmed cases of typhoid fever in the placebo group versus 7 cases in the Vi group (Protective efficacy (PE) = 69%; 95% CI = 28%, 87%). Most of the isolates were from school-aged children: 22 cases in the placebo group versus 6 in the Vi group (PE = 72%; 95% CI = 32%, 82%). No serious post-injection reactions were observed. The locally produced Vi polysaccharide vaccine showed levels of protective efficacy similar to those for Vi vaccine produced in industrial countries. CONCLUSION: The slightly higher dose of vaccine did not seem to alter efficacy significantly in China.

Adolescent↗
PubMed2000

Phosphoglycerate kinase acts in tumour angiogenesis as a disulphide reductase.

Disulphide bonds in secreted proteins are considered to be inert because of the oxidizing nature of the extracellular milieu. An exception to this rule is a reductase secreted by tumour cells that reduces disulphide bonds in the serine proteinase plasmin. Reduction of plasmin initiates proteolytic cleavage in the kringle 5 domain and release of the tumour blood vessel inhibitor angiostatin. New blood vessel formation or angiogenesis is critical for tumour expansion and metastasis. Here we show that the plasmin reductase isolated from conditioned medium of fibrosarcoma cells is the glycolytic enzyme phosphoglycerate kinase. Recombinant phosphoglycerate kinase had the same specific activity as the fibrosarcoma-derived protein. Plasma of mice bearing fibrosarcoma tumours contained several-fold more phosphoglycerate kinase, as compared with mice without tumours. Administration of phosphoglycerate kinase to tumour-bearing mice caused an increase in plasma levels of angiostatin, and a decrease in tumour vascularity and rate of tumour growth. Our findings indicate that phosphoglycerate kinase not only functions in glycolysis but is secreted by tumour cells and participates in the angiogenic process as a disulphide reductase.

Angiostatins↗
PubMed2000

The neuropeptides VIP and PACAP inhibit IL-2 transcription by decreasing c-Jun and increasing JunB expression in T cells.

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) act as macrophage and T-cell deactivators. Previously we established that VIP/PACAP limit T-cell activation directly, by inhibiting interleukin 2 (IL-2), and indirectly, by reducing the macrophage costimulatory functions. The nature of the IL-2 transcriptional factors affected by VIP/PACAP has not been elucidated. Here we investigate the effect of VIP on the AP-l complexes bound to several regulatory sites. VIP/PACAP downregulate c-Jun, and upregulate JunB mRNA and protein. The reduction in c-Jun correlates with the inhibition of the c-Jun N-terminal kinase (JNK). The effects of VIP/PACAP on c-Jun and JunB expression lead to changes in the composition of the AP-l complexes, from c-Jun/Fos to JunB/Fos dimers, with a subsequent decrease in DNA binding and loss of transactivating activity.

Animals↗
PubMed2000

Presence of closely spaced protein thiols on the surface of mammalian cells.

It has been proposed that certain cell-surface proteins undergo redox reactions, that is, transfer of hydrogens and electrons between closely spaced cysteine thiols that can lead to reduction, formation, or interchange of disulfide bonds. This concept was tested using a membrane-impermeable trivalent arsenical to identify closely spaced thiols in cell-surface proteins. We attached the trivalent arsenical, phenylarsenoxide, to the thiol of reduced glutathione to produce 4-(N-(S-glutathionylacetyl)amino)phenylarsenoxide (GSAO). GSAO bound tightly to synthetic, peptide, and protein dithiols like thioredoxin, but not to monothiols. To identify cell-surface proteins that contain closely spaced thiols, we attached a biotin moiety through a spacer arm to the primary amino group of the gamma-glutamyl residue of GSAO (GSAO-B). Incorporation of GSAO-B into proteins was assessed by measuring the biotin using streptavidin-peroxidase. Up to 12 distinct proteins were labeled with GSAO-B on the surface of endothelial and fibrosarcoma cells. The pattern of labeled proteins differed between the different cell types. Protein disulfide isomerase was one of the proteins on the endothelial and fibrosarcoma cell surface that incorporated GSAO-B. These findings demonstrate that the cell-surface environment can support the existence of closely spaced protein thiols and suggest that at least some of these thiols are redox active.

Animals↗
PubMed2000

[Determination of chiral purity of synthetic amino acids by high performance liquid chromatography].

A series of synthetic beta-heterocyclic and beta-naphthyl alanine and aromatic substituted phenylalanine were separated by reversed-phase HPLC as diastereomeric derivatives obtained after derivatization with (1-fluoro-2,4-dinitrophenyl)-5-L-valinamide (FDNP-Val-NH2). The separation was performed with gradient elution. The mobile phase A was acetonitrile containing 0.1% trifluoroacetic acid and mobile phase B was 0.1% trifluoroacetic acid. According to the hydrophobicity of the side chain of the amino acids, 6 different linear gradient programs were selected and all gradients completed in 20 minutes. Good resolution was obtained for neutral amino acids. All L-L diastereomer of neutral amino acids (the first letter refers to the configuration of amino acid) were eluted faster than the D-L diastereomer with retention times less than 16 minutes. In the same gradient eluting system, the hydrophobic parameter (pi value) and the position of the substituent in benzene ring of phenylalanine also influence the retention time of diastereomers. Usually the retention time of the phenylalanine with a large pi value was longer than that with a small one. Among the three phenylalanines containing the same substituent, compounds with the substituent in 2-postion gave the shortest retention time. In the case of basic amino acids, the D-L diastereomers eluted prior to the L-L diastereomers and showed rather poor resolution. The chiral purity (ee) of the optical active amino acids (synthetic DL-amino acids after resolution by different enzymes) were calculated with the equation as follows: ee = [[A(L- or D-) - A(D- or L-)]/[A(L-) + A(D-)]] x 100% (L- or D-), A: peak area; L-, D-: amino acid diastereomer.

Amino Acids↗
PubMed1999

Redox control of exofacial protein thiols/disulfides by protein disulfide isomerase.

Protein disulfide isomerase (PDI) facilitates proper folding and disulfide bonding of nascent proteins in the endoplasmic reticulum and is secreted by cells and associates with the cell surface. We examined the consequence of over- or underexpression of PDI in HT1080 fibrosarcoma cells for the redox state of cell-surface protein thiols/disulfides. Overexpression of PDI resulted in 3.6-4. 2-fold enhanced secretion of PDI and 1.5-1.7-fold increase in surface-bound PDI. Antisense-mediated underexpression of PDI caused 38-53% decreased secretion and 10-33% decrease in surface-bound PDI. Using 5,5'-dithio-bis(2-nitrobenzoic acid) to measure surface protein thiols, a 41-50% increase in surface thiols was observed in PDI-overexpressing cells, whereas a 29-33% decrease was observed in underexpressing cells. Surface thiol content was strongly correlated with cellular (r = 0.998) and secreted (r = 0.969) PDI levels. The pattern of exofacial protein thiols was examined by labeling with the membrane-impermeable thiol reactive compound, 3-(N-maleimidylpropionyl)biocytin. Fourteen identifiable proteins on HT1080 cells were labeled with 3-(N-maleimidylpropionyl)biocytin. The intensity of labeling of 11 proteins was increased with overexpression of PDI, whereas the intensity of labeling of 3 of the 11 proteins was clearly decreased with underexpression of PDI. These findings indicated that secreted PDI was controlling the redox state of existing exofacial protein thiols or reactive disulfide bonds.

Base Sequence↗
PubMed1997

Effect on infant mortality of iodination of irrigation water in a severely iodine-deficient area of China.

BACKGROUND: Hotien county in Xinjiang province, China, is an area of severe iodine deficiency and has a high infantmortality rate. We investigated whether iodine replacement through iodination of the irrigation water would decrease infant mortality. METHODS: We added potassium iodate to irrigation water over a 2 to 4 week period beginning in 1992 in certain areas of three townships (Tusala, Long Ru, and Bakechi). Logistic regression analysis was used to compare the odds ratios for infant and neonatal mortality in treated and intreated areas. FINDINGS: The median urinary iodine concentration significantly increased in women of child-bearing age from < 10 micrograms/L to 55 micrograms/L. Infant-mortality rates decreased in the treated areas of Long Ru (mean [SD] 58.2 [4.4] per 1000 births to 28.7 [7.1] per 1000 births), Tusala (47.4 [12.4] per 1000 births to 19.1 [1.5] per 1000 births), and Bakechi (106.2 [9.5] per 1000 births to 57.3 [7.3] per 1000 births). Similar results were also seen for neonatal mortality. On regression analysis iodine treatment and time were significant independent predictors of infant mortality. INTERPRETATION: Iodine supplementation of irrigation water in areas of severe iodine deficiency decreases neonatal and infant mortality. Iodine replacement has probably been an important factor in the national decrease in infant mortality in China.

Adult↗
PubMed1997

Fc gamma RIIA H/R 131 polymorphism, subclass-specific IgG anti-heparin/platelet factor 4 antibodies and clinical course in patients with heparin-induced thrombocytopenia and thrombosis.

The explanation why only a subset of patients with heparin-induced thrombocytopenia (HIT) develop clinically apparent thromboses (HITT) remains uncertain. It has been proposed that platelet activation induced by cross-linking of Fc gamma RIIA by anti-heparin/platelet factor 4 (PF4) antibodies is central to the pathogenesis of thrombosis. The observation that a common functional polymorphism of Fc gamma RIIA, involving either an arginine (R) or histidine (H) at amino acid 131, may underlie disease susceptibility prompted us to investigate the prevalence of receptor isoforms in patients with HIT and HITT. Furthermore, because these isoforms reportedly differ in their avidity for immune complexes containing human IgG2, we also analyzed sera from patients with HIT and HITT for the prevalence of various subclass-specific IgG anti-heparin/PF4 antibodies. No difference in the allele frequency of Fc gamma RIIA-H131 or R131 was identified among 13 patients with HIT or 23 with HITT compared with 102 controls (chi 2 = 1.21, P = .8). Furthermore, although most patients had IgG2 antibodies (62%), IgG, was the predominant subclass in 30 of the 34 patients with IgG anti-heparin/PF4 antibodies and in 12 was the exclusive subclass found. Also, there was no association between the concordance of IgG2 anti-heparin/ PF4 antibodies and the expression of Fc gamma RIIA-H131 in patients with HITT compared with patients with thrombocytopenia alone. These results make it unlikely that the Fc gamma RIIA-H131 isoform or IgG2 anti-heparin/PF4 antibodies are required to develop HITT, suggesting that factors in addition to cross-linking of Fc gamma RIIA receptors contribute to the pathogenesis of thrombosis in patients with heparin-dependent antiplatelet: antibodies.

Aged↗
PubMed1996

Rapid detection of the Fc gamma RIIA-H/R 131 ligand-binding polymorphism using an allele-specific restriction enzyme digestion (ASRED).

A polymorphism of the gene for Fc gamma RIIA, arginine (R) or histidine (H) at position 131, alters the ability of the receptor to bind certain IgG subclasses. Identification of the Fc gamma RIIA-H/R 131 genotype has assumed increasing importance in disorders of host defense, immunohematologic diseases and systemic autoimmune disorders. We report a new method for determination of this genotype in which an allele-specific restriction enzyme site is introduced into an Fc gamma RIIA PCR product from genomic DNA, and polymorphism assignment is determined by restriction enzyme digestion followed by agarose gel electrophoresis. This method is more rapid, more reliable and less expensive than currently available methods.

Alleles↗
PubMed1996

Regeneration of myelinated fiber after crush injury is retarded in sciatic nerves of mutant Japanese quails deficient in neurofilaments.

Regeneration of myelinated fibers in the sciatic nerve 2 weeks after crush injury was studied morphometrically in mutant Japanese quails deficient in neurofilaments and in normal quails (controls). There were fewer regenerated myelinated fibers per nerve at 10 mm (R1) and 20 mm (R2) distal to the crush site in mutants than in controls (P < 0.05). Both median and maximum diameters were smaller (P < 0.01) in mutants than in controls. On electron microscopy, transverse axonal area and axonal circumference were smaller (P < 0.001) at both R1 and R2 in mutants than in controls. The number of myelin lamellae was less (P < 0.01) in mutants than in controls at R1, but was similar at R2. There were fewer myelin lamellae in relation to axonal area in mutants than in controls at R1 (P < 0.0001) and R2 (P = 0.0032). The results indicate a retardation of both radial growth of axons and myelination around axons of the same size in mutants compared with controls. Such retardation may be explained by the deficiency of neurofilaments and the altered relationship between Schwann cell and axon in the mutant.

Animals↗
PubMed1996

[Study of depyrogen deactivation of syringes by using 3 efficacious pyrogen deactivator methods].

2% three-efficacious pyrogen deactivator (TEPD) was put into ultrasound washer for syringe washing. A total of 370 syringes were divided into three groups. Each group was washed by using a different program of sterilization, decontamination, and depyrogen. The results showed that the following program was not only effective for depyrogen but also convenient and inexpensive: (1)5 minutes' ultra-washing by using ultrasound washer with TEPD; (2)suspension over 1 hours; (3) another 5 minutes' ultra-washing; (4)ordinary washing and sterilization.

Equipment Contamination↗
PubMed1995

The effect of MS-818, a pyrimidine compound, on the regeneration of peripheral nerve fibers of mice after a crush injury.

One of the pyrimidine compounds, 2-piperadino-6-methyl-5-oxo-5,6- dihydro(7H)pyrrolo[3,4-d]pyrimidine (MS-818), has neurotropic effects in vitro. Therefore, we studied the effect of MS-818 on the regeneration of the peroneal nerve in C57BL/6J mice after a crush injury. Two test groups, which received a daily intraperitoneal injection of 5 mg/kg or 10 mg/kg MS-818, respectively, were compared with controls, which received daily intraperitoneal injections of physiological saline, over a 14-day period. The maximum foot-width ratio (crushed side/uncrushed side) was obtained on days 1, 8 and 14 after the crush injury, and the various morphometric parameters were evaluated at both 5 and 10 mm distal to the proximal portion of the crush site. The significant effects of MS-818 included a larger maximum foot width (P < 0.04) and a greater number of unmyelinated axons per nerve at both levels (P < 0.003) in both test groups than in controls. MS-818 had no significant effects on body weight, the increase of total transverse fascicular area after the crush injury, the total number of myelinated fibers with their size distributions, or the number of nuclei of Schwann cells and macrophages. Therefore, we conclude that MS-818 promotes axonal sprouting and elongation after a crush injury in mice.

Animals↗
PubMed1995

Downregulation of male-specific cytochrome P450s 2C11 and 3A2 in bile duct-ligated male rats: importance to reduced hepatic content of cytochrome P450 in cholestasis.

The effects of bile duct ligation (BDL) on the activity and content of individual hepatic mixed-function oxidases (MFOs) was examined. Five days after BDL, hepatic microsomal total cytochrome P450 (CYP) content and NADPH-cytochrome P450-reductase (P450-reductase) activity were reduced to 56% and 57% of control, respectively. MFO activities attributable to the sexually undifferentiated CYPs 1A, 2A1, 2C6, and 2E1 were decreased to 32% to 52% of control, but the activities of two male sex-specific CYPs, 2C11 and 3A2, were reduced to a significantly greater extent (P < .05). The microsomal contents of CYP proteins 2C6 and 2E1 were decreased after BDL to 61% and 63% of control, whereas 2C11 and 3A2 proteins were 21% and 45% of control. Corresponding reductions of the messenger RNA (mRNA) species for CYP 2C11 (9% of control) and 3A2 (37%) were detected, whereas there was no reduction of 2C6 mRNA. These findings are consistent with downregulation of the CYP 2C11 and 3A2 genes. Nuclear run-on studies performed 3 days after BDL showed that there was a generalized impairment of gene transcription after BDL, but a disproportionate reduction in transcription of CYPs 2C11 and 3A2. A possible explanation for downregulation of CYP 2C11 and 3A2 was provided by the observation that serum estradiol concentrations were threefold greater in BDL male rats, while serum testosterone was reduced; estradiol is known to downregulate CYPs 2C11 and 3A2. It is concluded that male sex-specific CYP enzymes are decreased to a greater extent than other microsomal proteins in BDL male rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗