Biomedical subjects

Hong Xu

Publications and source records attributed to Hong Xu.

137 records · Page 8Linked to original sources

PubMed2002

Theoretical studies on the mechanism of primary electron transfer in the photosynthetic reaction center of Rhodobacter sphaeroides.

The mechanism of the primary electron transfer (ET) process in the photosynthetic reaction center (PRC) of Rhodobacter sphaeroides has been studied with quantum chemistry method of ab initio density functional theory (DFT) (B3LYP/6-31G) based on the optimized X-ray crystallographic structure. The calculation was carried out on different structural levels. The electronic structure of pigment molecules was first studied, and then the influence of the neighboring protein was taken into account at three approximation levels: (a) the surrounding proteins were treated as a homogeneous medium with a uniform dielectric constant (SCRF); (b) both the influence of axial coordination of His to the special pair P and ABChl as, and the hydrogen bonds between related residues and P and also BPhas were included; and (c) the influence of the electronic structure of the protein subunit chains as a whole was studied. The results suggest that: (1) according to the composition of the HOMO and LUMO of P, there might be a charge-separated state of (BChl(L) (+)BChl(M) (-)) for the excited state of P; (2) to treat the protein surroundings as a homogeneous medium is not sufficient. Different interactions between pigment molecules and related residues play different roles in the ET process; (3) the axial coordination of His to P raises the E (LUMO) of P greatly, and it is very important for the ET process to occur in the PRC of wild-type bacterium; the axial coordination of His to ABChl as also raises their E (LUMO) significantly; (4) the hydrogen-bonds between amino acid residues and P and also BPh as depress the E (LUMO) of the pigment molecules to some extent, which makes the E (LUMO) of P lower than those of ABChlas, and the E (LUMO) of BPh a (L) lower than that of BPh a (M). Consequently, the ET process from P to BPh a (L) does not, according to our calculation model, occur via ABChl a (L). The possibility of the ET pathway from P to BPh a (L) via ABChl a (L) was discussed; (5) the frontier orbitals of protein subunit chains L and M are localized at the random coil area and the alpha-helix areas, respectively. Results mentioned above support the fact that the ET process proceeds in favourable circumstances along the branch L.

Journal Article↗

PubMed2002

Authentication of stems of Dendrobium officinale by rDNA ITS region sequences.

The rDNA ITS regions of five Dendrobium species were sequenced. Each Dendrobium species was found to have a unique sequence in the ITS region, so that they could be easily distinguished at the DNA level. The aligned 644 bp of the ITS region includes 235 bp ITS1, 163 bp 5.8S, and 246 bp ITS2. One hundred and eighty-nine sites are variable. The sequences of D. officinale could be easily distinguished from the other four adulterant species according to the sequence variation at 11 sites, 7 in ITS1, 1 in 5.8S, and 3 in ITS2. These could be used as molecular characters to distinguish the stems of D. officinale from the adulterants.

China↗

PubMed2002

[Expression and characterization of envelope protein 2 gene of hepatitis G virus in Pichia pastoris].

A cDNA fragment locating at the putative envelop protein 2(E2) region of GBV-C/HGV fused with Schistosoma japonicum, glutathione S-transferase(GST) was amplified with PCR from plasmid pGEX-E2. The amplified DNA fragment was inserted into plasmid pGEX-5X-1, at the downstream of the coding sequences of GST, in the same reading frame with the gene of GST. The fusion gene fragment of GST-E2 was amplified with PCR, using the recombinant plasmid pGEX-5X-1-E2 as the template. The amplified 1324 bp DNA fragment of GST-E2 was inserted into Pichia pastoris expression vector pPIC9K in reading frame with alpha-factor secreting signal peptide. The plasmid pPIC9K-GST-E2 was transformed into Pichia pastoris GS115 with electroporation. The transformants (His+ Muts) were selected and induced to express the 54kD GST-E2 fusion protein, which could be specially recognized by both the antisera directed against E2 and against GST. The GST-E2 fusion protein was purified with Sepharose 4B glutathione affinity chromatography to a purity of 95%. The expression was optimized to achieve the highest expression level of GST-E2 fusion protein which was accumulated up to 50% of total proteins in the culture supernatant. The GST-E2 protein derived from the recombinant Pichia pastoris was proved possessing antigenicity and high specificity by ELISA, probed with sera from the patients infected by GBV-C/HGV.

Animals↗

PubMed2002

Expression profile and genome location of cDNA clones from an infant human trabecular meshwork cell library.

PURPOSE: To delineate the profile of genes expressed in infant human trabecular meshwork and identify candidate genes for glaucoma. METHODS: Human trabecular meshwork cell cultures were established from six young donors. A cDNA library was made from the combined trabecular meshwork mRNA. The end-sequence of random clones was determined by direct sequencing. These sequences were then analyzed by a National Center for Biotechnology Information (NCBI, Bethesda, MD) database search. Nucleotide searches were performed using the BLASTN (ver. 2.1.3; against the nonredundant nucleic acid sequence) and dbEST databases (both provided by NCBI in the public domain at www.ncbi.nlm.nih.gov). RESULTS: Sequences from 1118 clones from this nonamplified trabecular meshwork cDNA library were categorized. Of these, 877 expressed sequence tags (ESTs) (78.7%) were known genes. One hundred thirty-nine ESTs (12.5%) showed close identity to EST sequences reported in the public domain database (dbEST). Thirteen ESTs (1.2%) showed no significant similarity to known genes or ESTs in the public databases and were thus defined as novel ESTs. The most abundant genes expressed by the human trabecular meshwork included ferritin H, eukaryotic translation elongation factor 1-alpha, ferritin L, fibronectin, and TIMP-1. Ferritin H was the most abundant transcript, making up more than 4% of the genes expressed by the human trabecular meshwork. Extracellular matrix proteins were also highly expressed. The chromosome location of the trabecular meshwork ESTs is reported. CONCLUSIONS: A profile of genes expressed by human trabecular meshwork is presented. Thirteen novel ESTs were identified. The combined information obtained from expression analysis and chromosomal localization of trabecular meshwork cDNAs should be valuable in identifying candidate genes for glaucoma.

Cells, Cultured↗

PubMed2002

[Expression and clinical significance of matrix metalloproteinase-9 and vascular endothelial growth factor in oral squamous cell carcinomas].

BACKGROUND & OBJECTIVE: Matrix metalloproteinase-9 (MMP-9) is closely associated with the metastasis and infiltration of tumor. It was recently discovered that it is also associated with angiogenesis of tumor. This study was designed to investigate the expressions of MMP-9 and vascular endothelial growth factor (VEGF) in oral squamous cell carcinoma (OSCC) tissue and their association with metastasis and infiltration of OSCC. METHODS: The expressions of MMP-9 and VEGF were detected on paraffin-embedded samples from 51 cases of OSCC, 10 cases of oral squamous cell papilloma, and 10 of normal oral mucosa by immunohistochemistry. RESULTS: MMP-9 and VEGF showed negative or weak positive expression in normal oral mucosa and oral squamous cell papilloma. The positive expression rate of MMP-9 and VEGF in OSCC were 78.4% (40/50) and 82.4% (42/51); the coexpression of MMP-9 and VEGF was 66.7% (34/51). CONCLUSION: There was difference between the expression of MMP-9 and VEGF in OSCC tissue. The infiltration of tumor cell is closely associated with the expression of MMP-9 (P < 0.01). Cervical lymph node metastasis closely correlates to the expression level of VEGF (P < 0.01). MMP-9 and VEGF could be used as biological indices for clinically evaluating infiltrative and metastatic potential of OSCC.

Carcinoma, Squamous Cell↗

PubMed2002

[Study on sequence difference and SNP pheomenon of rDNA ITS region in F type and H type population of Dendrobium officinale].

OBJECTIVE: To study rDNA ITS sequence differences between F type and that of H type of Dendrobium officinale in main habitat of China. METHOD: The population differences of the rDNA ITS region (including ITS1, ITS2, 5.8S) sequences of D. officinale were studied by the method of DNA sequences analysis. RESULT: There were two different sites between the rDNA ITS sequence of F type and that of H type. One was in ITS1 region, and the other was in 5.8S region. It was proved that there was some relativity between the character of rDNA ITS region and the life type of the populations. The phenomenon of single nucleotide polymorphism (SNP) existed in 5.8S region of rDNA ITS region between F type and H type. The sequences of rDNA ITS region of D. officinale were reported for the first time, and the sequences of ITS region ranged 634 bp (ITS1 231 bp, ITS2 240 bp, 5.8S 163 bp). CONCLUSION: The analysis of rDNA ITS of D. officinale deeply reveal the population differences of D. officinale of F type and H type.

Base Sequence↗

PubMed2002

[Molecular authentication of Dendrobium chrysanthum from its allied species of Dendrobium].

OBJECTIVE: To define molecular characters to distinguish D. chrysanthum from its allied species D. primulinum, D. lituiflorum, D. aphyllum, D. crepidatum. METHOD: The molecular characteristics of D. chrysanthum and its allied species were compared. The sequences of rDNA ITS regions were exploited to explore the evidence for authentication D. chrysanthum and its allied species. RESULT: Although the morphological difference was slight, the sequence difference of ITS regions among five rDNAs was obvious and stable. Fifteen sites of ITS region were defined as DNA character to identify D. chrysanthum from the other four allied species. CONCLUSION: The difference of rDNA ITS sequences can be used to authenticate accurately D. chrysanthum from three allied species of Dendrobium.

Base Sequence↗

PubMed2002

[Database establishment of the whole rDNA ITS region of Dendrobium species of "fengdou" and authentication by analysis of their sequences].

AIM: To establish the whole rDNA ITS region sequence database of various Dendrobium species of "Fengdou" and to authenticate exactly the inspected species of "Fengdou". METHODS: The rDNA ITS regions of various Dendrobium species of "Fengdou" were amplified and sequenced. The database of their rDNA ITS regions was established in order to authenticate the inspected species by means of the softwares of CLUSTRAL and MEGA which were used to analyze the rDNA ITS region. RESULTS: A database of the rDNA ITS sequences of 21 species of Dendrobium has been established. The notable and stable differences of the interspecies of the rDNA ITS regions have been demonstrated. The numbers of transitions and transversions among 21 species are 11-122. The variable sites are 341 while the informative sites are 195. The ITS sequence differences between the outgroup species (Pholidota yunnanensis) and species of "Fengdou" are obvious. The numbers of transitions and transversions are 131-161. The population differences of the rDNA ITS region of various species of "Fengdou" are very small (0-6). CONCLUSION: On the basis of the database of various Dendrobium species of "Fengdou" and two genetics software, the botanical origin of the inspected species of "Fengdou" has been authenticated successfully by sequencing the rDNA ITS regions.

Base Sequence↗

PubMed1999

Effect of bactericidal/permeability-increasing protein on sepsis induced by intra-abdominal infection in rats.

OBJECTIVE: To investigate the effect and mechanism of bactericidal/permeability-increasing protein (BPI) on sepsis induced by intra-abdominal infection in rats. METHODS: Cecal ligation and puncture (CLP) was made on 20 rats with sepsis induced by intra-abdominal infection. BPI or equal volume of physiological saline (PS) was intra-abdominally given immediately and 12 h after CLP, respectively (2.5 mg/kg of BPI each time). Plasma endotoxin levels were determined with limulus amebocyte chromogenic assay. RESULTS: (1) The survival time in BPI group was significantly higher than that in PS group. (2) The values of the mean arterial pressure (MAP), the left ventricular systolic pressure (LVSP), the isovolumic ventricular pressure (IP), and the maximal change of left intraventricular pressure (+/-dp/dtmax) in BPI group, although decreasing, were markedly higher than those in PS group. (3) Plasma glutamic-pyruvic transaminase (GPT) and urea nitrogen levels in BPI group, though increasing, were obviously lower than those in PS group. (4) There was no significant change of plasma endotoxin levels in BPI group, while plasma endotoxin levels markedly increased in PS group. CONCLUSIONS: BPI has obvious protective effect on sepsis induced by intra-abdominal infection, which might be related to its neutralization of endotoxin.

Journal Article↗

PubMed1999

The dynamic response of heart and its injury involving chest impact.

OBJECTIVE: The dynamic response of the heart during chest impact and the characteristics of heart injuries were investigated to further understand the mechanisms of heart impact injuries. METHODS: Eleven dogs and thirty-four rabbits were subjected to front thoracic impact with different impact velocities and compression response. The accelerated movement of thoracic wall during the impact period was monitored. The pathological examination of the injured heart was done and the dynamic responses and mechanisms of injuries were analyzed with mathematics models. RESULTS: The analysis of mathematics model and experimental results showed that the injury severity of heart was well correlated with the viscous criterion. The thoracic wall was involved in bi-directional movement of compression and expansion. The injured heart showed spotty or stripy hemorrhages in the ventricle endocardium. Light microscopic examination showed interstitial bleeding and rupture of the myocardial fibers in the contusion area. The biomechanical analysis indicated that there was a large deformation caused by the stress concentration on the lateral ventricle wall. CONCLUSIONS: There is a high speed and excessive deformation of the heart during the impact period, which might be the key mechanism of heart injury. The strong impact and press coming from both sternum and vertebral column and the rapid elevation of pressure in the ventricle are the main cause of deformation.

Journal Article↗

PubMedDate not supplied

Inhibition and enhancement by organic compounds of luminol-KIO4-H2O2 chemiluminescence.

The effects of 36 organic compounds on luminol-KIO(4)-H(2)O(2) chemiluminescence (CL) were studied. It was found that most of the tested compounds could inhibit or enhance the CL intensity. The activities of such inhibitors or enhancers were related to the pH of the CL system and the number and position of functional groups such as -OH and -NH(2) on aromatic rings. The mechanism of the CL inhibition and enhancement was considered. Based on the CL inhibition or enhancement, the possibility of analytical applications was explored. The results demonstrated that numerous compounds were detectable at the ng/mL level using the CL system.

Hydrogen Peroxide↗