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Biomedical subjects

C Dai

Publications and source records attributed to C Dai.

At least 37 records · Page 2Linked to original sources
PubMed2000

[Repairing peripheral nerve defects by tissue engineering techniques:an experimental study].

OBJECTIVE: To develop a novel effective substitute material or technique to repair peripheral nerve gap. METHODS: We inoculated expanded Schwann cells (SCs) at re-arranged bio-absorbable polymer polyglycolic acid (PGA) fiber and incubated for two weeks, then we developed a novel tissue-engineered scaffolds. The scaffolds were used as cellular isografts to bridge 15 mm long gap of sciatic nerve in inbred strains of Wistar rats. In an autologous and pure PGA fiber control group, the same surgical procedure was used. Evaluation included general observation, electromyographic examination, muscle measurement, and histological observation of serial sections at 12 weeks after surgery. The total number and density of reinnervation and thickness of myelin sheath was measured by computerized image analysis. RESULTS: SCs put out a long and thin prominence and migrated along the PGA fibers in spirality or parallel when they divided and finally rank into a cell-chain formation similar to Büngner's band. TEM/SEM and immunohistochemical survey demonstrated that the SCs at PGA fiber also secreted a great deal of ECMs included laminin, which play a very important role in peripheral nerve regeneration. Non-tubular scaffold comprised SCs and laminin (LN) channel in three-dimensional longitudinal rank. Animal transplantation study indicated the sensory and motor functional results of hindlimbs of experimental group rats reached to similar level of those found in nerve autograft control group. The number of reinnervation in the experimental group rats was slightly fewer than that in nerve autograft control group; but the axonal density was just reversal between the two groups because of a large area ischemic necrosis in the center of nerve autografts. CONCLUSION: This new paradigm offers a potential solution to repairing a long gap of peripheral nerve.

Animals↗
PubMed2000

[A comparative study of fatty acids in human dental plaque and whole saliva].

This study was intended to carry out qualitative and quantitative analyses of fatty acids in plaque and saliva. Samples of plaque and saliva from 10 volunteers were analyzed for fatty acids by gas-chromatography and gas-chromatography/mass spectrometry. The sample preparation procedure allowed specimens from individual volunteers to be analyzed. The results showed the plaque contained C14.0, C15.0, C16.0, C16.1, C18.0, C18.1, C18.2, C20.0 acids and the saliva contained C16.0, C18.0, C20.0, C16.1, C18.1, C18.2 acids. The concentration of fatty acids in plaque was 35.17 +/- 7.723 micrograms/mg (dry weight); and that in saliva was 13.23 micrograms/ml. Quantitatively, C18.1 and C16.0 acids were the largest fatty acids. These findings imply that the origin and role of the fatty acids in plaque and saliva may be different.

Adolescent↗
PubMed2000

[Establishment of a GC and GC/MS method for analysis of fatty acids in human dental plaque].

OBJECTIVE: To study the composition of fatty acids in human dental plaque, a Gas Chromatography (GC) and Gas Chromatography/Mass Spectrometry (GC/MS) method was developed. METHODS: The C17:0 was internal standard and the C16:0 was test standard. Samples of plaque were methanolysis to be fatty acids methyl ester before detection. GC with OV-1 separated the sample for a quantitative analysis. The column size was 25 m x 25 mm. The temperature program was from 80 degrees C to 260 degrees C with 12 degrees C/min. The sample separation was carried out at fused silica capillary column with OV-1 for qualitative analysis by GC/MS. The column size was 23 m x 0.23 mm. The temperature program was from 40 degrees C to 240 degrees C at 6 degrees C/min. RESULTS: The linear regression equation was y = 0.0138X-0.1182, r = 0.9945, recovery was 90.18%-103.6%, CV intro-day was 2.60, 1.61, 2.20; CV inter-day was; 2.71, 1.69, 1.61. The lowest limit of detection was 0.6 ug. The GC and GC/MS diagram showed that internal standard and fatty acids of plaque have good separation. CONCLUSION: The method is simple, rapid accurate, and is useful to carry out qualitative and quantitative analyses of fatty acids in dental plaque.

Chromatography, Gas↗
PubMed2000

[Effects of epidermal growth factor on wound healing of penetrating keratoplasty in rabbits].

OBJECTIVE: To observe the effects of epidermal growth factor (EGF) on wound healing of the penetrating keratoplasty(PKP) in rabbits. METHODS: Twelve rabbits (24 eyes) were stratified randomly divided into 6 groups and underwent penetrating keratic autoplasy. Liquid scintillation counter was used to measure the incorporation rate of 3H-TdR. Pressure-detector was used to survey the intensity of keratic wound healing. AgNORs staining was used to count the fibroblast cells at keratic wound. HE staining, VG staining, AgNORs staining and transmission electron microscopy were used to observe the morphological changes of keratic wound. RESULTS: 1 The intensity of EGF group on 8 days, 14 days and 21 days after PKP was significantly higher than that of the control group(P < 0.01). 2. The incorporation rate of 3H-TdR in wound healing the EGF group on 14 days and 21 days was obviously higher than that of the control group(P = 0.01). 3. The number of fibroblast cells of EGF were more than that of the control group(P < 0.01) in 8 days. CONCLUSION: EGF can promote the wound healing in rabbits after PKP.

Animals↗
PubMed2000

[Construction of plasmids expressing hepatitis E virus antigen fragments and their combinations].

OBJECTIVE: Several different regions of the HEV antigen were expressed in Escherichia coli and their immunological characteristics were simply evaluated. METHODS: Three coding sequences of immunodominant antigenic regions in structural protein of the hepatitis E virus (ORF2.1: 6287-6403nt, ORF2.2: 6743-7126nt, ORF3: full length of ORF3) were amplified by RT-PCR from the fecal supernatants of macaques experimentally infected with HEV. These three fragments were inserted into the pThioHisC expression vector separately or fused in line by (Gly)n short arms. After identified by DNA sequence analysis, these six recombinant plasmids were transformed into Escherichia coli, and immunology characteristics of expressed antigen fragments were evaluated by Western blotting. RESULTS: All six genes were successfully expressed in Escherichia coli. Western blotting assay showed that the recombinant proteins specifically reacted with the serum antibody from hepatitis E patient in various degrees. CONCLUSION: Artificial antigen based on strung epitopes provides a promising strategy for detection and prevention of HEV infection.

Antigens, Viral↗
PubMed2000

[Expression and glycosylation of rotavirus strain SA11 VP4 protein in a recombinant adenovirus].

OBJECTIVE: A modified VP4 gene of rotavirus SA11 strain was expressed by a recombinant human adenovirus. METHODS: A whole VP4 gene was obtained with PCR and induced the signal peptide at the gene N terminal. The chimera gene was cloned into pCMV plasmid that consist of human cytomagolovirus promoter and then cloned the gene to transfer human adenovirus type 5 vector. Homologues recombinant was performed by co-transfection to 293 cell line with recombinant plasmid and viral genome using CaPO4 precipitation. RESULTS: VP4 gene is 2,362 base pair in length mutation was not found in whole VP4 gene sequence. Expressed product in recombinant adnovirus was confirmed to be specific and more antigenicity by indirect immunofluorescence assay. Both Western blot and immunoprecipitation assays showed that expressed protein molecular weight was higher than wild type VP4 protein and that modified product was corresponding to a glycosylation of VP4 protein. CONCLUSIONS: It may be a effective method to modify interested gene for enhancing stability, antigenicity and immunogenicity of expressive product.

Adenoviruses, Human↗
PubMed1999

Activation of

Reversible C(6)F(5) transfer takes place between the boron centers in the anion formed by methide abstraction from [MeZr{N(SiMe(3))(2)}(3)] or [Cp(2)ZrMe(2)] (L(n)M-CH(3) in the reaction scheme) by the perfluorinated diborane 1. The solution chemistry of the metallocenium ion pairs formed from 1 and [Cp(2)ZrMe(2)] is correlated with the observed ethylene polymerization behavior of 1 in comparison to the monoborane B(C(6)F(5))(3), the related diborane 1,2-C(6)H(4)[B(C(6)F(5))(2)](2), and the 9,10-diboraanthracene compound 9,10-(C(6)F(5))(2)C(12)B(2)F(8).

Journal Article↗
PubMed1999

Interferon gamma induces upregulation and activation of caspases 1, 3, and 8 to produce apoptosis in human erythroid progenitor cells.

Interferon gamma (IFNgamma) induces apoptosis in purified human erythroid colony-forming cells (ECFC) and inhibits cell growth. Fas (APO-1; CD95) and Fas ligand (FasL) mediate apoptosis induced by IFNgamma, because Fas is significantly upregulated by IFNgamma, whereas Fas ligand is constitutively present in the ECFC and neutralization of FasL greatly reduces the apoptosis. Because conversion of caspases from their dormant proenzyme forms to active enzymes has a critical role in transducing a cascade leading to apoptosis, we performed further studies of the expression and activation of caspases in normal human and IFNgamma-treated day-6 ECFC to better understand the mechanism of IFNgamma action in producing this cell death. RNase protection assays showed that the caspase-1, -2, -6, -8, and -9 mRNAs were upregulated by IFNgamma, whereas the caspase-5 and -7 mRNAs were not increased. Western blots showed that FLICE/caspase-8 was upregulated and activated by 24 hours of incubation with IFNgamma. FADD was not similarly altered by incubation with IFNgamma. Western blots of ICE/caspase-1, which might be required for amplification of the initial FLICE activation signal, showed that pro-ICE expression significantly increased after treatment with IFNgamma for 24 hours and cleavage of pro-ICE also increased. CPP32/apopain/caspase-3, responsible for the proteolytic cleavage of poly (ADP) ribose polymerase (PARP), was also studied and treatment of ECFC with IFNgamma resulted in an increased concentration of caspase-3 by 24 hours and a clear induction of enzyme activation by 48 hours, which was identified by the appearance of its p17-kD peptide fragment. The cleavage of PARP was demonstrated by an obvious increase of the 89-kD PARP cleavage product, which was observed at almost the same time as caspase-3 activation in the IFNgamma-treated cells, whereas untreated ECFC showed little change. Peptide inhibitors of the caspase proteins, DEVD-fmk, DEVD-cho, YVAD-cho, and IETD-fmk, were incubated with the ECFC to obtain further evidence for the involvement of caspases in IFNgamma-induced apoptosis. The activation of FLICE/caspase-8 and CPP32/caspase-3 and cleavage of PARP clearly were inhibited, but the reduction of cell growth due to apoptosis, induced by IFNgamma, was only partially blocked by the presence of the inhibitors. These results indicate that IFNgamma acts on ECFC not only to upregulate Fas, but also to selectively upregulate caspases-1, -3, and -8, which are activated and produce apoptosis, whereas the concentrations of FasL and FADD are not demonstrably changed.

Apoptosis↗
PubMed1999

"Skin-CNS-bladder" reflex pathway for micturition after spinal cord injury and its underlying mechanisms.

PURPOSE: A "skin-CNS-bladder" reflex pathway for inducing micturition after spinal cord injury has been established in cat. This reflex pathway which is basically a somatic reflex arc with a modified efferent limb that passes somatic motor impulses to the bladder, has been designed to allow spinal cord injured patients to initiate voiding by scratching the skin. MATERIALS AND METHODS: The skin-CNS-bladder reflex was established in the cat by intradural microanastomosis of the left L7 ventral root (VR) to the S1 VR while leaving the L7 dorsal root (DR) intact to conduct cutaneous afferent signals that can trigger the new micturition reflex arc. After allowing 11 weeks for axonal regeneration, urodynamic, pharmacological and electrophysiological studies were conducted in pentobarbital or chloralose anesthetized animals. RESULTS: A detrusor contraction was initiated at short latency by scratching the skin or by percutaneous electrical stimulation in the L7 dermatome. Maximal bladder pressures during this stimulation were similar to those activated by bladder distension in control animals. Electrophysiological recording revealed that single stimuli (0.3 to 3 mA, 0.02 to 0.2 msec duration) to the left L7 spinal nerve in which the efferent axons had degenerated evoked action potentials (0.5 to 1 mV) in the left S1 spinal nerve distal to the anastomosis. In addition, increases in bladder pressure were elicited by trains of the stimuli (5 to 20 Hz, 5 seconds) applied to the L7 spinal nerve. Urodynamic studies including external sphincter EMG recording demonstrated that the new reflex pathway could initiate voiding without detrusor-external urethral sphincter dyssynergia. Atropine (0.05 mg./kg., i.v.) or trimethaphan (5 mg./kg., i.v.), a ganglionic blocking agent, depressed the bladder contractions elicited by skin stimulation. The skin-CNS-bladder reflex could also be elicited after transecting the spinal cord at the L2-L3 or L7-S1 levels. CONCLUSION: The cross-wired somato-autonomic bladder reflex is effective in initiating bladder contractions and coordinated voiding in cats with an intact neuraxis and can also induce bladder contractions after acute transection of the lumbar spinal cord. The new pathway is mediated by cholinergic transmission involving both nicotinic and muscarinic receptors. It is concluded that somatic motor axons can innervate bladder parasympathetic ganglion cells and thereby transfer somatic reflex activity to the bladder smooth muscle.

Anastomosis, Surgical↗
PubMed1999

The theory of "expelling pathogens regardless of hard stool", a significant contribution of Wu Youke.

Though there are famous theories of "assorted Qi", "membranous origin", the contribution of Wu Youke's Wen yi lun (On Warm Pestilence) of the theory of " expelling pathogens regardless of hard stool" (EPRHS) is even more important. The main points of this theory includes: it is essential to expel pathogens at an early stage, while for attacking therapy, expelling pathogens with rhubarb is essential. EPRHS elucidates the significance of expelling pathogens in attacking therapy theoretically, and elevates the efficacy clinically with profound influence in later ages. In the past 2 decades, the early application of rhubarb to elevate the therapeutic effect for the treatment of pneumonia, epidemic meningitis, and Bencephalitis even in the absence of hard constipated stool marks the significance of Wu's such theory.

Catharsis↗
PubMed1999

[Establishment of animal model for ischemic facial palsy in rat].

OBJECTIVE: In order to establish animal model for ischemic facial nerve palsy in rats and to observe the intrinsic vascular network of facial nerve in the fallopian canal. METHOD: Selective vascular embolization of the external carotid artery was performed in rats. The animals were killed at 1 and 30 days after operation respectively. 10% gelatin solution with fluorescent dye were injected into their left ventricles. The changes intrinsic vascular network were observed under inverted fluorescent microscopy. RESULT: Facial palsy was presented within 5 to 15 min following arterial embolization, the intrinsic capillaries of facial nerve appeared to be thinner and some of them were blocked by microspheres, especially in the labyrinthine segment. Facial palsy almost recovered after 30 days postoperatively. The capillaries returned to be almost normal shape and only few of them were thinner. CONCLUSION: The establishment of animal model for ischemic facial palsy will make contribution to experimental research and clinical treatment for facial palsy.

Animals↗
PubMed1999

[Analysis of organic acids in human dental plaque by means of gas chromatography/mass spectrometry].

The purpose of this study was to investigate the composition of plaque fatty acids in the healthy population. The study was made on 10 volunteers over the age of 18 who were divided into three sub-groups (3-4 individuals). Neither subject exhibited clinical evidence of salivary gland disorder and any medication affecting salivary functions were not used. A sensitive GC/MS method with VG7070E mass spectrometer was developed in our study. The sample separation was carried out on a fused silica capillary column with OV-1. The column size was 23 m x 0.23 mm. The temperature program was as follows: from 40 degrees C to 120 degrees C fast, then from 120 degrees C to 240 degrees C at 6 degrees C/min. The results showed that there were 14 organic acids and isomers present in plaque. They were C12:0, C14:0, C15:0, C16:0, C16:1, C18:0, C18:1, C18:2, C20:0 and phenylacetic acid, phenylpropionic acid. The higher content of fatty acids in the sample were C16:0, C18:0, and C18:1. The aromatic acids were detected only in some samples. The odd-numbers fatty acids and aromatic acids were for the first time detected. The origin of organic acids in plaque is an ongoing area of research. Our data clearly identify the bacterial contribution to the organic acids of plaque matrix, which may have a special relationship with bacteria metabolism. The research will help us to understand fatty acids metabolism of dental plaque and to determine their role in the microbial homeostasis of dental plaque.

Adult↗
PubMed1998

Isolation of the Aspergillus nidulans sudD gene and its human homologue.

We have been studying the heat-sensitive bimD6 mutation of Aspergillus nidulans. At a restrictive temperature, the chromosomes of bimD6 mutant strains fail to attach properly to the spindle microtubules, and the mutant also displays a high rate of chromosome loss. We previously cloned the sudA gene, an extragenic suppressor of the heat-sensitive bimD6 mutation and showed that it coded for a DA-box or SMC protein. SMC proteins have been demonstrated to function in chromosome condensation, segregation and global gene regulation. We have now cloned the sudD gene, another of the extragenic suppressor genes of the bimD6 mutation. The predicted SUDD protein is the founding member of a widely expressed protein family. Similar proteins are found in sequence databases for Saccharomyces cerevisiae, Caenorhabditis elegans, mammals and four species of archaebacteria. We have also cloned and sequenced a human cDNA that encodes the human homologue of SUDD and mapped the gene to 18q11.2. The predicted SUDD proteins from A. nidulans, Homo sapiens and S. cerevisiae all share a variety of features. The predicted proteins are approximately 60000Da in mass and have a serine-plus-threonine content of about 11%. The evolutionary conservation of the proteins suggests an ancient origin and conserved function for these proteins.

Alleles↗
PubMed1998

[Synthesis of hirudin variant 1 (HV1) gene and primary study of expression in yeast].

OBJECTIVE: Hirudin is an extremely efficient and specific thrombin inhibitor. It is clinically used to prevent the formation of thrombus. In this research the hirudin gene was put into yeast system for expression to evaluate the feasibility of artificially synthesized gene expressed in eukaryotic system and study the factor affecting expression level. METHODS: According to the amino acid sequence of hirudin variant 1 (HV1), the genetic code saccharomyces cerevisiae was used to design and synthesize the HV1 gene. Amplified by PCR, it was inserted into cloning vector pBS-SK(+) and sequenced. Ligation with the signal peptide gene of yeast alpha factor the correct HV1 gene was inserted into yeast expression vector pYC-DE. The recombinant plasmid was transformed into the cell of S. cerevisiae BJ1990 to carry out the primary expression experiment. RESULTS: In cultured supernatant of screened positive clone the hirudin activity was detected to be 30 ATU/ml. The expression level was higher than HV2 in yeast and HV1 in prokaryotic system. The N terminal amino acid sequence completely matches with natural hirudin. CONCLUSIONS: It was proved by this study that the synthesized hirudin gene had been expressed in yeast successfully. This result showed that it was a better way to carry out the expression in yeast using synthesized HV1 gene and a stronger promoter.

Base Sequence↗
PubMed1997

[Peak shape distribution rule of high performance liquid chromatography in the end of column under linear and nonideal conditions].

The central moments of chromatographic elution curve are important parameters for describing the column efficiency and chromatographic peak shape. According to the equation of chromatographic dynamics, we can get the second central moment and the third central moment of elution curve of HPLC under linear nonideal conditions. In our work, we investigated the relationships between second central moment, third central moment, coefficient of skewness of components distribution in the end of column and chromatographic column parameters, operation conditions, such as diameter of packing particle, desorption constant, diffusion coefficient in mobile phase, linear velocity of mobile phase, effect of extra column and so on. By means of computer, we discovered that there are no significant differences the second central moment, third central moment and coefficient of skewness for different components with different distribution coefficients. In the column end, therefore, different components have similar peak shape if there exist no obvious extra column effects. The column extra effect which stems from joint line and/or dead volume of detector is an important factor, causing column efficiency lower and peak shape tailing.

English Abstract↗
PubMed1996

Distinct regulatory roles of lymphocyte costimulatory pathways on T helper type-2 mediated autoimmune disease.

We assessed the role of CD40-CD40L, cytotoxic T lymphocyte (CTL)A4/CD28-B7s, and CD2-CD48/CD58 lymphocyte costimulatory pathways in the development of mercury chloride (HgCl2)-induced autoimmune disease in mice, which is believed to be mediated by T helper (Th) subset Th2. Inhibition of CD40-CD40-L and CTLA4/CD28-B7s interactions by anti-CD40-L antibody and soluble CTLA4-immunoglobulin (Ig) fusion protein, respectively, abrogated the autoimmune disease without affecting interleukin 4 (IL-4) production, showing the importance of physical contact between T and B lymphocytes in the Th2-mediated process. In contrast, two anti-CD2 antibodies that have been shown to induce immunosuppression of Th1-mediated events exacerbated the autoantibody response and augmented IgG1, IgE, and IL-4 production, transforming a mild mesangial glomerulopathy into a severe systemic immune complex disease. These observations demonstrate that manipulation of lymphocyte accessory counterreceptor interactions may affect the course of Th2-associated autoimmune disease and suggest that signals resulting from CD2 engagement play an essential role in the regulation of the Th1-Th2 effector equilibrium.

Animals↗