Biomedical subjects

Lei Yu

Publications and source records attributed to Lei Yu.

At least 73 records · Page 4Linked to original sources

PubMed2004

[The characteristics of polymorphism and gene structure of DYF155S1 locus in Y-specific minisatellite from Chinese Uygur population].

The study is to reveal the diversity and gene structure of 5' and 3' end of DYF155S1 locus in Y-chromosome minisatellite among Chinese Uygur population. Fluorescent MVR-PCR(minisatellite variant repeat by PCR), Amp-FLP(Amplified fragment length polymorphism) and DNA sequencing methods were used respectively to detect 106 unrelated males among Chinese Uygur population. The polymorphisms of DYF155S1 locus could be revealed in three aspects: (1) polymorphic length: the sizes of amplified fragments ranged from 1405 to 2505 bp. There are 37 types found among the 106 unrelated males. (2) polymorphism at 5' end of DYF155S1 locus, 68 types found among the 106 unrelated males. (3) polymorphism at 3' end of DYF155S1 locus, 23 types found among the 106 unrelated males. In combination of these three aspects of polymorphism, none of the 106 unrelated males tested had the same allele, and the gene diversity (h) was over 0.9999. Seven and two types of modular structure were founded in the 5' and 3' end of DYF155S1 locus, respectively, by DNA sequencing. The alleles at DYF155S2 locus showed yes/no dimorphism and the rate of deletion was 4.7%. The polymorphisms of DYF155S1 locus were fully revealed by using combination of MVR-PCR, Amp-FLP and DNA sequencing methods, and we suggested the nomenclature for alleles of MVR loci. These methods are useful tools and provide basic data for the study of human genetics and forensic medicine.

Alleles↗

PubMed2004

[Application of fluorescent real-time reverse transcriptase-polymerase chain reaction in detecting influenza viruses].

OBJECTIVE: To apply fluorescent real-time reverse transcriptase-polymerase chain reaction (RT-PCR) in detecting influenza viruses. METHODS: A total of 207 oral swab samples were obtained in 16 collections from SARS patients and suspected influenza outbreak cases. They were subjected to influenza virus detection by fluorescent real-time RT-PCR, MDCK cell culture, and hemagglutinin inhibition assay. RESULTS: Out of 207 samples, 79 (38.16%) were positive for influenza viruses when tested by fluorescent real-time PCR, and 62 (29.95%) positive when tested by MDCK cell culture. There was a statistically significant difference between them (chi square=8.64, P less than 0.005). From 104 cases in 9 collections dual serum samples were obtainable. When tested with hemagglutinin inhibition assay, 64 cases (61.54%) showed a 4-fold increase against H3N2 antigen. CONCLUSION: This study showed that fluorescent real-time PCR is a reliable, sensitive, and fast method for detecting influenza viruses.

Cell Culture Techniques↗

PubMed2003

Synthesis, electrochemistry and self-assembled monolayers of novel tetrathiafulvalene (TTF) and pi-extended TTF (exTTF) disulfides.

The synthesis of a new series of tetrathiafulvalene (TTF) and pi-extended TTF (exTTF) disulfides and the electrochemical properties of self-assembled monolayers derived from these compounds are described. When the intermediate bromides 3 and 7 were reacted with thiourea, followed by basic hydrolysis, the expected thiol formation was not observed and only disulfides were obtained. A mechanism is proposed to explain the self-oxidation process of these compounds. For the first time SAMs of exTTF derivatives were prepared. Electrochemical data for SAMs of 6 and 8 reveal a single two-electron chemically reversible oxidation process to form a dicationic state, typical of the exTTF system. The SAMs are stable over extended periods of time and show electrochemical stability upon repeated potential scans.

Journal Article↗

PubMed2003

Function of gamma-aminobutyric acid receptor/channel rho 1 subunits in spinal cord.

gamma-Aminobutyric acid (GABA) receptor/channel rho 1 subunits are important components in inhibitory pathways in the central nervous system. However, the precise locations and roles of these receptors in the central nervous system are unknown. We studied the expression localization of GABA receptor/channel rho 1 subunit in mouse spinal cord and dorsal root ganglia (DRG). The immunohistochemistry results indicated that GABA receptor/channel rho 1 subunits were expressed in mouse spinal cord superficial dorsal horn (lamina I and lamina II) and in DRG. To understand the functions of the GABA receptor/channel rho 1 subunit in these crucial sites of sensory transmission in vivo, we generated GABA receptor/channel rho 1 subunit mutant mice (rho 1-/-). GABA receptor/channel rho 1 subunit expression in the rho 1-/- mice was eliminated completely, whereas the gross neuroanatomical structures of the rho 1-/- mice spinal cord and DRG were unchanged. Electrophysiological recording showed that GABA-mediated spinal cord response was altered in the rho 1-/- mice. A decreased threshold for mechanical pain in the rho 1-/- mice compared with control mice was observed with the von Frey filament test. These findings indicate that the GABA receptor/channel rho 1 subunit plays an important role in modulating spinal cord pain transmission functions in vivo.

Animals↗

PubMed2003

Insulin signaling inhibits the 5-HT2C receptor in choroid plexus via MAP kinase.

BACKGROUND: G protein-coupled receptors (GPCRs) interact with heterotrimeric GTP-binding proteins (G proteins) to modulate acute changes in intracellular messenger levels and ion channel activity. In contrast, long-term changes in cellular growth, proliferation and differentiation are often mediated by tyrosine kinase receptors and certain GPCRs by activation of mitogen-activated protein (MAP) kinases. Complex interactions occur between these signaling pathways, but the specific mechanisms of such regulatory events are not well-understood. In particular it is not clear whether GPCRs are modulated by tyrosine kinase receptor-MAP kinase pathways. RESULTS: Here we describe tyrosine kinase receptor regulation of a GPCR via MAP kinase. Insulin reduced the activity of the 5-HT2C receptor in choroid plexus cells which was blocked by the MAP kinase kinase (MEK) inhibitor, PD 098059. We demonstrate that the inhibitory effect of insulin and insulin-like growth factor type 1 (IGF-1) on the 5-HT2C receptor is dependent on tyrosine kinase, RAS and MAP kinase. The effect may be receptor-specific: insulin had no effect on another GPCR that shares the same G protein signaling pathway as the 5-HT2C receptor. This effect is also direct: activated MAP kinase mimicked the effect of insulin, and removing a putative MAP kinase site from the 5-HT2C receptor abolished the effect of insulin. CONCLUSION: These results show that insulin signaling can inhibit 5-HT2C receptor activity and suggest that MAP kinase may play a direct role in regulating the function of a specific GPCR.

Animals↗

PubMed2003

Phospholipid membrane interactions of saposin C: in situ atomic force microscopic study.

Saposin C (Sap C) is a small glycoprotein required for hydrolysis of glucosylceramidase in lysosomes. The full activity of glucosylceramidase requires the presence of both Sap C and acidic phospholipids. Interaction between Sap C and acidic phospholipid-containing membranes, a crucial step for enzyme activation, is not fully understood. In this study, the dynamic process of Sap C interaction with acidic phospholipid-containing membranes was investigated in aqueous buffer using atomic force microscopy. Sap C induced two types of membrane restructuring: formation of patch-like structural domains and the occurrence of membrane destabilization. The former caused thickness increase whereas the latter caused thickness reduction in the gel-phase membrane bilayer, possibly as a result of lipid loss or an interdigitating process. Patch-like domain formation was independent of acidic phospholipids, whereas membrane destabilization is dependent on the presence and concentration of acidic phospholipids. Sap C effects on membrane restructuring were further studied using synthetic peptides. Synthetic peptides corresponding to the amphipathic alpha-helical domains 1 (designated "H1 peptide") and 2 (H2 peptide) of Sap C were used. Our results indicated that H2 contributed to domain formation but not to membrane destabilization, whereas H1 induced neither type of membrane restructuring. However, H1 was able to mimic Sap C's destabilization effect in conjunction with H2, but only when H1 was present first and H2 was added afterwards. This study provides an approach to investigate the structure-function aspects of Sap C interaction with phospholipid membranes, with insights into the mechanism(s) of Sap C-membrane interaction.

Glycoproteins↗

PubMed2003

[Morphological observation of mesenchymal stem cells cultured with allogenic decalcified bone matrix].

OBJECTIVE: To investigate the feasibility of using decalcified bone matrix loaded with mesenchymal stem cells (MSCs) derived from adult human bone marrow as scaffolds for bone tissue engineering. METHODS: Allogenic decalcified bone matrix was prepared. MSCs were isolated from adult human bone marrow with monocyte-separating medium and then cultured in basic medium of mesenchymal stem cells (MSC). The third generation of the cultured cells were identified by FITC-antiCD105, seeded onto allogenic decalcified bone matrix followed by observation under scanning electron microscope and invert microscope a week later. RESULTS: Rapid proliferation of both primary and subcultured MSCs was observed, and CD105-positive cells reached 64.1% among the third generation of the cells. MSCs also grew well and proliferated rapidly after being cultured with decalcified bone matrix. CONCLUSION: Naive MSCs are ideal seeding cells for bone tissue engineering, and the allogenic decalcified bone matrix loaded with MSCs may be used as a good scaffold.

Bone Matrix↗

PubMed2003

[Morphological study on three-dimensional culture of rat muscle satellite cells under cyclic mechanical stretch].

OBJECTIVE: To study the effect of mechanical stretch on the morphologic change of rat muscle satellite cell in the three-dimensional culture. METHODS: Based on the apparatus for three-dimensional cell cultures under a cyclic mechanical strain, a specific stretch pattern (10% elongation, 10 stretches/min for 10 min of each hour 48 h total) was applied to cell-scaffolding composites. RESULTS: Under the stretch pattern, the shape of satellite cells changed to oblate and spread to the direction of the stretch. Furthermore, the myotube was observed. On the contrary, the satellite cells spread to the all direction, and the formation of the myotube was not been found in the control group. CONCLUSION: Cyclic mechanical stretch is helpful for the formation of the ideal directivity and these results are compatible with a significant role for the stretch in tissue-engineered muscle construction.

Animals↗

PubMed2003

[Mechanical strength and in vivo degradation of human hair keratin-polylactic acid composite rods].

OBJECTIVE: To test the mechanical strength and observe the in vivo degradation of self-made human hair keratin-polylactic acid (HHK-PLA) composite rods designed for use in internal fixation. METHODS: Twenty such HHK-PLA composite rods were tested for shear strength, bending strength and bending modulus using the material testing system MTS-858 Mini Bionix. A total of 36 samples of HHK-PLA composite rods designed for internal fixation of bone fracture were randomly implanted in dorsal subcutaneous tissue of 18 SD rats, and weight losses of these rods were measured 1, 2, 4, 8, 12, 16, 20, 24 and 28 weeks after the implantation to evaluate the in vivo degradation of the material. RESULTS: The initial shear strength of HHK-PLA rod was 241 MPa, bending strength 358 MPa, and bending modulus 13 GPa. The test demonstrated a slower rate of degradation in SD rats in earlier period following implantation than in later period. CONCLUSION: HHK-PLA composite rods have good initial mechanical strength and tolerable degradation in vivo, and may be used potentially for internal fixation of the weigh-bearing bones of the limbs.

Animals↗

PubMed2003

[Studying the polymorphism at DYF155S1 locus in Chinese Han population by MVR-PCR marked with fluorescence].

The simple and useful genotyping methods of DYF155S1 locus by silver staining and fluorescence detection have been established. The blood samples from 155 unrelated males in Chinese Han population were typed by these two methods respectively and the same results were obtained. Among the 155 samples 66 alleles were found, out of them 38 were observed once only. The most frequent alleles named 18 or 22, which frequency was 0.065, the size of their first DNA fragments was 180 bp and the number of fragments was 16 or 17. The gene diversity (h) was 0.9789. Out of the 155 samples, 25 samples had one or two bands lost (null repeat) among the successive bands. It was demonstrated by sequencing that the position of the lost bands corresponded to type 3 repeats. Our results indicated that the method, which revealed the 5' end diversity of DYF155S1 locus, was a technique that could obtain the most Y-specific polymorphic information only by one PCR reaction. The allele frequencies of DYF155S1 locus in Chinese Han population provided the basic data for the study of population genetics and forensic practices.

Alleles↗

PubMed2003

[Amplification of brain-derived neurotrophic factor receptor trkB gene and construction of its eukaryotic expression vector].

OBJECTIVE: To construct a recombinant eukaryotic expression vector of rat brain-derived neurotrophic factor receptor trkB gene. METHODS: Using the total RNA extracted from rat brain tissue as the template, the trkB gene was amplified by reverse transcription-polymerase chain reaction (RT-PCR) with a pair of specific primers containing the restriction sites of EcoRI and BamHI. The amplified fragment of trkB gene was digested with EcoRI and BamHI, and then subcloned into cloning vector pMD18-T and then expression vector pEGFP-C2. The recombinant plasmid was identified by restriction endonuclease analysis and PCR. RESULTS: The amplified DNA fragment was about 1 461 bp in length, and enzyme digestion and PCR analysis showed that trkB gene had been successfully cloned into the vectors pMD18-T and pEGFP-C2. CONCLUSION: The trkB gene of rat has been successfully amplified and cloned into the eukaryotic expression vector pEGFP-C2.

Animals↗

PubMed2003

[Sequence variation of D12S391 and D11S554 loci in Guangzhou han population].

To study the core sequence of the hypervariable short tandom repeats, we sequenced the alleles of D12S391 and D11S554 loci which show high mutation rate in Guangzhou Han population. The D12S391 locus has the basic sequence structure (AGAT)8-17 (AGAC)6-10 (AGAT)0-1. The smaller alleles (15-18) at D12S391 locus have variation limited to the number of the first repeat (AGAT), whereas the larger alleles (19-27) have more complex variation in the number not only of the first repeat but also of the other two repeats (AGAC) and (AGAT). Four new alleles named 22", 23", 24"' and 27 respectively were found. The D11S554 locus has more complex core sequence classified into five sequence types. Three of them have the same basic sequence structure (AAAGG) (AAAG)4 (AAAGG)2-3 (AAAG)13-19. In the larger alleles (219-249), there are four and five nucleotide repeats. Some of the larger alleles(219-249) have one base variation, bases insert or deletion. The two loci all have sequence heterogeneity. Our results indicated that the two loci D12S391 and D11S554 belong to complex repeats and this adds difficulty to their correctly typing. It is essential to construct allelic ladder in each population.

Alleles↗

PubMed2003

[Typing for HLA-DR DNA by polymerase chain reaction with sequence-specific primers].

AIM: To type the HLA-DR DNA for renal transplantation by PCR with sequence specific primers (PCR-SSP). METHODS: According to nucleotide sequences of HLA-DR, 16 pairs of specific primers and a pair of positive control primers were designed and synthesized for PCR-SSP. Then HLA-DR sites of 52 donors and recipients for renal transplantation were typed by the PCR-SSP. RESULTS: All the samples were successfully typed by PCR-SSP with the synthesized primers. The results were available within 3 hours after sampling and the accuracy and reproducibility were 100%. CONCLUSION: Genotyping for HLA-DR sites by PCR-SSP with primers reported herein was a simple and accurate technique suitable for clinical application.

Adolescent↗

PubMed2002

Artery wall binding peptide-poly(ethylene glycol)-grafted-poly(L-lysine)-based gene delivery to artery wall cells.

Artery wall binding peptide (AWBP; Cys-Gly-Arg-Ala-Leu-Val-Asp-Thr-Leu-Lys-Phe-Val-Thr-Gln-Ala-Glu-Gly-Ala-Lys), a specific targeting peptide, was conjugated to poly(ethylene glycol)-grafted-poly(L-lysine) (PEG-g-PLL) to enhance the gene transfer to artery wall cells. AWBP-PEG-PLL was synthesized by the reaction between the vinylsulfone group of PEG-g-PLL and the thiol group of cysteine in AWBP. 1H-NMR analysis confirmed the composition of the obtained polymer and indicated that four mol of AWBP were reacted to one mole of VS-PEG-PLL. The particles of AWBP-PEG-PLL/pDNA complexes were determined spherical with a size of approximately 100 nm by dynamic light scattering (DLS) and atomic force microscopy (AFM). Agarose gel retardation assay indicated that AWBP-PEG-PLL was able to condense plasmid DNA and reach complete complexation at and above a charge ratio 1/1 (+/-). Transfection efficiency of AWBP-PEG-PLL/pDNA complexes was 150-180 times higher than that of control systems, such as PEG-g-PLL/pDNA and PLL/pDNA, in both bovine aorta endothelial cells and smooth muscle cells. Luciferase activities of AWBP-PEG-PLL depended on the amount of free AWBP, while those of the control carriers such as PLL and PEG-g-PLL were not affected by free AWBP. These results supported that gene transfer of AWBP-PEG-PLL/pDNA complexes to bovine aorta wall cells was mediated by specific artery wall cell receptor-mediated endocytosis.

Amino Acid Sequence↗

PubMed2002

[Study on the mutation of human short tandem repeats at three loci].

OBJECTIVE: To understand the mutational patterns and mechanism of short tandem repeats(STRs). METHODS: The DNA samples of 19 parent-child pairs with mutations in three loci (FGA, D12S391, and D11S554) were genotyped by silver staining on STR. Alleles to be sequenced were excised from gels, reamplified by PCR, and purified. Sequencing was performed by use of cycle sequencing. RESULTS: There were 18 out of 19 pedigrees in which the 'new' alleles gained or lost a single repeat (8 gains, 7 losses, and 3 being indistinguishable). Only one pedigree lost two repeats. In the 19 pedigrees, there were 13 pedigrees whose 'new' alleles came from fathers, 3 from mothers, 3 from either father or mother. The ratio was 4 1 between fathers and mothers. The mutation of three STR loci occurred in the long, uninterrupted tetranucleotide repeat regions ('CTTT' in FGA, 'AGAT' in D12S391, and 'AAAG' in D11S554). CONCLUSION: Single- step mutations accounted for 95% of STR mutation events in these three loci: FGA, D12S391, and D11S554. The rest were double step mutations. There was no insertion or deletion of an incomplete repeat in any of the pedigrees. The mutation was mainly caused by fathers. The long, uninterrupted tetranucleotide repeats in these three loci might be susceptible to mutation.

Alleles↗

PubMed2002

Changes in content of macrophage migration inhibitory factor secreted by Schwann cells after peripheral nerve injury.

OBJECTIVE: To investigate whether Schwann cells can secrete macrophage migration inhibitory factor (MIF) after peripheral nerve injury. METHODS: Two kinds of infant rat Schwann cells(which were derived from intact and injured nerves respectively) were cultured in 10% newborn calf serum (NCS) DMEM/F12 medium for 72 h. Then the level of MIF in the conditioned media was determined by an enzyme-linked immunoadsordent assay (ELISA). As control,MIF level was also determined in 10% NCS DMEM/F12 medium without any cells. RESULTS: The concentration of MIF in the conditioned medium of Schwann cells derived from injured nerves was significantly higher than that of control samples (P<0.05), while the concentration of MIF in the conditioned medium of Schwann cells from intact nerves was not elevated. CONCLUSION: After peripheral nerve injury, Schwann cells can secrete MIF which may play an important role as an immunomodulatory cytokine for macrophage activation, inflammatory reactions and immune responses.

Animals↗

PubMed2002

Clinical anatomy of the fibrous capsule of human lumbar facet joint.

OBJECTIVE: To describe the anatomical and histological characteristics of the fibrous capsule of human lumbar facet joints. METHODS: Specimens of the facet joint capsules were obtained from 5 embalmed cadavers for macroscopic investigation, and microscopic observation of L5 facet joint capsules obtained from 2 fresh cadavers was performed after the specimens were stained by way of resorzinoroseine-van Gieson method. RESULTS: The outer layer of the fibrous capsule was constituted by dense regular connective tissue that was in turn composed of parallel bundles of collagenous fibers. In the superior part of the joint capsules, the fibers were arranged in the direction different from that taken by the fibers in the inferior part. In the middle layer of the joint capsules, large quantities of elastic fibers were identified in the roots of the capsule. CONCLUSIONS: The anatomical and histological complexities adapt the lumbar facet joint to better withstand loads from various directions. Immoderate rotatory manipulations may result in capsule injuries, which may aggravate low back pain in some cases.

Adolescent↗

PubMed2002

In vitro culture and study of the biological characteristics of rabbit keratocytes.

OBJECTIVE: To improve the technique for culturing rabbit keratocytes in vitro and investigate the biological characteristics of these cells. METHODS: Fresh rabbit corneas were obtained and the epithelial and endothelial cells were removed after digestion with trypsin. The stroma was rinsed, minced, and incubated in DMEM/F12 medium supplemented with 10% fetal bovine serum and the biological characteristics of the keratocytes were observed with MTT assay and compared with those of the cells in serum-free culture media. RESULT: On about the third day of incubation, some keratocytes germinated from the stromal tissues and migrated onto the flask surface presenting fibroblast-like arrangement with spindle-shaped appearance. The keratocytes became confluent after 10 day's incubation and the peak of cell proliferation occurred on day 8 in the presence of serum in the media, while in the absence of serum, the peak took place on day 10. CONCLUSION: The method improved for in vitro keratocyte culture is convenient and effective, and the presence of serum in the media may to some degree affect the growth of the keratocytes.

Animals↗