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Biomedical subjects

Tao Xiang

Publications and source records attributed to Tao Xiang.

11 recordsLinked to original sources
PubMed2007

Aberrant branch of the superior laryngeal artery passing through the thyroid foramen.

This study examines the microsurgical anatomy of the aberrant superior laryngeal artery (ASLA) which passes through the thyroid foramen. It defines the location of the ASLA and its main branches. The aberrant superior thyroid artery was looked for in 20 randomly selected Chinese adult cadavers, and when found, was dissected and measured under an operating microscope (7-30x magnification). The ASLA passed through the thyroid foramen, which only occurred in the presence of the artery. The foramen was observed in six of the 20 cadavers: one on the right, three on the left, and two on both sides. The study provides detailed information concerning the ASLA, which we hope will help explain the arterial bleeding that may occur during laryngeal surgery. The results might be helpful in improving surgery to the larynx and other neck operations. Incidental intraoperative injury of the aberrant artery could be avoided by understanding details of its course in relation to surrounding anatomic landmarks.

Arteries↗
PubMed2006

[Isolation and purification of BMScs of GFP transgenic mouse using the method of adhering to cuture plastic in different time].

OBJECTIVE: To adopt the method of adhering to culture plastic in different time for cultivating and purifying BMSCs of green fluorescent protein (GFP) transgenic mice. METHODS: Bone marrow cells isolated from GFP transgenic mice are directly planted in culture flask and an exchange of the total volume medium is made at different time. Then the cells adhering to culture plastic are differently counted according to the cell types and are examined by immunohistochemistry using the antibodies of CD44, CD45 and CD54 in three days. Moreover, the cells after the exchange of the total volume medium in 4 hours, 8 hours and 24 hours are selected and successively subcultured down to the fifth passage. Then the result of amplification is calculated and the cells are examined by immunohistochemistry using the antibodies of CD44, CD45 and CD54. RESULTS: With the extending of the time for the first exchange of medium, the density of cells adhering to culture plastic increased accordingly, but the BMSCs proportion decreased. The cells after first exchange of medium in 4 hours had high BMSCs proportion but low BMSCs density, and the cells in 24 hours had high BMSCs density and low BMSCs proportion. However, the cells in 8-10 hours had high BMSCs density and also high BMSCs proportion. The subcultured BMSCs could stably express GFP. CONCLUSION: The method of adhering to culture plastic in different time for cultivating and purifying BMSCs of GFP transgenic mice is effective. It is suitable to make the first exchange of total volume medium in 8-10 hours. The subcultured cell has the capacity for amplification and will probably be a seed cell for the research of tissue engineering and gene therapy.

Animals↗
PubMed2005

Midgap states in antiferromagnetic Heisenberg chains with a staggered field.

We study low-energy excitations in antiferromagnetic Heisenberg chains with a staggered field which splits the spectrum into a longitudinal and a transverse branch. Bound states are found to exist inside the field induced gap in both branches. They originate from the edge effects and are inherent to spin-chain materials. The sine-Gordon scaling h(2/3)(s)[log(h(s)](1/6) (h(s), the staggered field) provides an accurate description for the gap and midgap energies in the transverse branch for S=1/2 and the midgap energies in both branches for S=3/2 over a wide range of magnetic field; however, it can fit other low-energy excitations only at much lower field. Moreover, the integer-spin S=1 chain displays scaling behavior that does not fit this scaling law. These results reveal intriguing features of magnetic excitations in spin-chain materials that deserve further investigation.

Journal Article↗
PubMed2005

[Preliminary analysis of retinal gene expression profile of diabetic rat].

OBJECTIVE: Establishing the retinal gene expression profiles of non-diabetic rat and diabetic rat and comparing the profiles in order to analyze the possible genes related with diabetic retinopathy. METHODS: The whole retinal transcriptional fragments of non-diabetic rat and 8-week diabetic rat were obtained by restriction fragments differential display-PCR (RFDD-PCR). Bioinformatic analysis of retinal gene expression was performed using soft wares, including Fragment Analysis. After comparison of the expression profiles, the related gene fragments of diabetic retinopathy were initially selected as the target gene of further approach. RESULTS: A total of 3639 significant fragments were obtained. By means of more than 3-fold contrast of fluorescent intensity as the differential expression standard, the authors got 840 differential fragments, accounting for 23.08% of the expressed numbers and including 5 visual related genes, 13 excitatory neruotransmitter genes and 3 inhibitory neurotransmitter genes. At the 8th week, the expression of Rhodopsin kinase, beta-arrestin, Phosducinìrod photoreceptor cGMP-gated channel and Rpe65 as well as iGlu R1-4 were down-regulated. mGluRs and GABA-Rs were all up-regulated, whereas the expression of GlyR was unchanged. CONCLUSION: These results prompt again that the changes in retinal nervous layer of rat have occurred at an early stage of diabetes. The genes expression pattern of visual related genes and excitatory and inhibitory neurotransmitters in rat diabetic retina have been involved in neuro-dysfunctions of diabetic retina.

Animals↗
PubMed2004

Crystal structure of a heat-resilient phytase from Aspergillus fumigatus, carrying a phosphorylated histidine.

In order to understand the structural basis for the high thermostability of phytase from Aspergillus fumigatus, its crystal structure was determined at 1.5 A resolution. The overall fold resembles the structure of other phytase enzymes. Aspergillus niger phytase shares 66% sequence identity, however, it is much less heat-resistant. A superimposition of these two structures reveals some significant differences. In particular, substitutions with polar residues appear to remove repulsive ion pair interactions and instead form hydrogen bond interactions, which stabilize the enzyme; the formation of a C-terminal helical capping, induced by arginine residue substitutions also appears to be critical for the enzyme's ability to refold to its active form after denaturation at high temperature. The heat-resilient property of A.fumigatus phytase could be due to the improved stability of regions that are critical for the refolding of the protein; and a heat-resistant A.niger phytase may be achieved by mutating certain critical residues with the equivalent residues in A.fumigatus phytase. Six predicted N-glycosylation sites were observed to be glycosylated from the experimental electron density. Furthermore, the enzyme's catalytic residue His59 was found to be partly phosphorylated and thus showed a reaction intermediate, providing structural insight, which may help understand the catalytic mechanism of the acid phosphatase family. The trap of this catalytic intermediate confirms the two-step catalytic mechanism of the acid histidine phosphatase family.

6-Phytase↗
PubMed2003

Nogo-A at CNS paranodes is a ligand of Caspr: possible regulation of K(+) channel localization.

We report Nogo-A as an oligodendroglial component congregating and interacting with the Caspr-F3 complex at paranodes. However, its receptor Nogo-66 receptor (NgR) does not segregate to specific axonal domains. CHO cells cotransfected with Caspr and F3, but not with F3 alone, bound specifically to substrates coated with Nogo-66 peptide and GST-Nogo-66. Binding persisted even after phosphatidylinositol- specific phospholipase C (PI-PLC) removal of GPI-linked F3 from the cell surface, suggesting a direct interaction between Nogo-66 and Caspr. Both Nogo-A and Caspr co-immunoprecipitated with Kv1.1 and Kv1.2, and the developmental expression pattern of both paralleled compared with Kv1.1, implicating a transient interaction between Nogo-A-Caspr and K(+) channels at early stages of myelination. In pathological models that display paranodal junctional defects (EAE rats, and Shiverer and CGT(-/-) mice), distances between the paired labeling of K(+) channels were shortened significantly and their localization shifted toward paranodes, while paranodal Nogo-A congregation was markedly reduced. Our results demonstrate that Nogo-A interacts in trans with axonal Caspr at CNS paranodes, an interaction that may have a role in modulating axon-glial junction architecture and possibly K(+)-channel localization during development.

Amino Acid Sequence↗
PubMed2003

Low-resolution molecular replacement using a six-dimensional search.

A parallel-aware program MPI_FSEARCH has been implemented to perform molecular replacement using an exhaustive six-dimensional search. In particular, the program can be used to deal with diffraction data at very low resolution (d > 10 A) that would normally not be appropriate for other molecular-replacement programs such as AMoRe and CNS. Although an envelope constructed from a PDB (Protein Data Bank) file was tested in the present study, the program can be used to perform low-resolution molecular replacement with an envelope derived from various sources such as electron microscopy or small-angle solution X-ray scattering.

6-Phytase↗
PubMed2003

Expression of vascular endothelial growth factor and matrix metalloproteinase-2 correlates with the invasion and metastasis of hepatocellular carcinoma.

To investigate the relationship of the expression of vascular endothelial factor (VEGF) and matrix metalloproteinase-2 (MMP-2) with the recurrence and metastasis of hepatocellular carcinoma (HCC), the expression of VEGF and MMP-2 in HCC tissue(n = 50) and in normal liver tissue(n = 30) were examined by immunochemistry. The results showed that the positive rates of VEGF and MMP-2 in HCC tissue were 86% and 60% respectively, and in normal liver tissue were 53.3% and 30% respectively. The positive rates of VEGF and MMP-2 in HCC were significantly higher than those in normal liver tissue. The positive rates of VEGF and MMP-2 in HCC with intra- or extra-hepatic metastasis were higher than those of HCC without metastasis. VEGF and MMP-2 play important roles in the invasion and metastasis of HCC.

Adult↗
PubMed2003

[Three-dimensional structure of collagen fibril of pigskin].

OBJECTIVE: To probe deply into the three-dimensional structure of pigskin collagen fibril and provide the basic data for using the pigskin tissue as tissue engineering material. METHODS: Scanning Probe Microscope (SPM) and Transmission Electron Microscope (TEM) were employed to study the three-dimensional structure of collagen fibril in pigskin tissue. RESULTS: Microscopy revealed that pigskin collagen fibril had periodic transverse groove (i.e. D-periodicity) which was about 67 nm. The diameter of fibril ranged from 57 to 135 nm, showing much difference among the papillary layer, reticular layer and infra-reticular layer. The length of fibril varied from 5 to 13 microns. Both ends of fibril were rotund and slightly bulgy. The fibrils assembled and the D-periodicities were homologous in flank. In axial direction fibrils were found staggered end by end. CONCLUSION: The data obtained in this study on the three-dimensional structure of pigskin collagen fibril are of significance to researches in tissue engineering materials.

Animals↗
PubMed2002

The Methanobacterium thermoautotrophicum MCM protein can form heptameric rings.

Mini-chromosome maintenance (MCM) proteins form a conserved family found in all eukaryotes and are essential for DNA replication. They exist as heteromultimeric complexes containing as many as six different proteins. These complexes are believed to be the replicative helicases, functioning as hexameric rings at replication forks. In most archaea a single MCM protein exists. The protein from Methanobacterium thermoautotrophicum (mtMCM) has been reported to assemble into a large complex consistent with a dodecamer. We show that mtMCM can assemble into a heptameric ring. This ring contains a C-terminal helicase domain that can be fit with crystal structures of ring helicases and an N-terminal domain of unknown function. While the structure of the ring is very similar to that of hexameric replicative helicases such as bacteriophage T7 gp4, our results show that such ring structures may not be constrained to have only six subunits.

Amino Acid Motifs↗