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Biomedical subjects

W Chen

Publications and source records attributed to W Chen.

At least 253 records · Page 14Linked to original sources
PubMed2001

[Fabrication of cartilage in predetermined shapes from human nasoseptal chondrocytes with tissue engineering method].

OBJECTIVE: To investigate the feasibility of fabricating a new cartilage in predetermined shapes with tissue engineering methods. METHODS: Human nasoseptal chondrocytes were seeded onto a nonwoven mesh of polyglycolic acid(PGA) to form a cell-PGA construct. The construction was then configured in sheet and tube shapes, and implanted subcutaneously into the dorsa of 11 athymic mice. The specimens were harvested 4, 6, 8 weeks after implantation and subjected to gross morphologic and histologic analysis. RESULTS: Gross observation showed that the predetermined sheet and tube shapes of new cartilage were formed. Histological observation demonstrated that new mature cartilages were formed in 6-week. A Masson's trichrome stain showed the interwining bands of collagen at the periphery of the cartilage. Staining of Safranin O evaluated that the new cartilage was bound of glycosaminoglycan. In the control group, the PGA of the specimens were completely absorbed at 6 weeks. CONCLUSION: Human nasoseptal chondrocytes-PGA construct could develop into a new cartilage in predetermined shapes in athymic mice.

Animals↗
PubMed2001

[Surgery of substernal goiter].

OBJECTIVE: To study the surgical approaches and operative techniques for substernal goiter. METHOD: A retrospective study of 27 cases with substernal thyroid nodules was made in our hospital. RESULT: The operations on 27 patients with substernal nodules have been successfully carried out. Among them, 10 were goiters, 9 adenomas, 4 malignancy and 4 were thyroid cancer metastasizing to paratracheal or substernal nodes. Resection via cervical collar incision was adequate in 23 cases. Three thyroid cancers with paratracheal node metastasis were completely resected by sternotomy and only one thyroid cancer with paratracheal and substernal nodes metastasis was resected by combined thoracotomy and cervical collar incision. CONCLUSION: Resection via cervical collar incision for all retrosternal thyroid nodules were advised. The preliminary experience with this procedure suggests that it has some advantages in the management of substernal goiter, including: 1. ease of operation compared to both sternotomy and thoracotomy; 2. relatively low morbidity; 3. safe and reliable.

Adult↗
PubMed2001

[Fabrication of allogeneic cartilage with tissue engineering technique and repair of laryngeal cartilage defects in rabbits].

OBJECTIVE: To investigate the fabrication of allogeneic tissue engineered cartilage in predetermined shapes and its ability to repair laryngeal cartilage defects. METHODS: Tissue engineering technique was used to make allogeneic tissue engineered cartilage in predetermined shapes, and then some of them were utilized to repair cartilage defects in the rabbit larynges(n = 12). Finally, the chondrogenesis and reparative effect were studied grossly and histologically at various periods. RESULTS: 1. The gross specimens of 4 weeks after implantation revealed the presence of new hyaline cartilage of approximately the same shapes as original predetermined shapes, which had fair elasticity and support ability. Histological evaluation showed the characteristics of cartilage tissue. 2. Laryngeal cartilage defects were well repaired using allogeneic tissue engineered cartilage in different periods after operation. A few chondrocytes were observed between the reparative areas with tissue engineered cartilage and normal cartilage. Abundant matrices were also detected in the reparative and interfacial areas. No inflammatory cells were found. CONCLUSION: It is possible to regenerate new cartilage in predetermined shapes using tissue engineering technique in allograft animals with immunity. Allogeneic tissue engineered cartilage can be used as reparative material to repair cartilage defect of rabbit larynx.

Animals↗
PubMed2001

[Study on the absorption spectrum analysis for increasing the productivity of C60].

Absorption spectrum analysis of arc discharge products on graphite electrode and arc discharge experiment with mixing metallic elements (Fe) show that oxygen is one of the important factors that affect the C60 productivity. Moreover, enlarging the area of electric arc also plays an important role in increasing the C60 productivity. Normally, if an amount of Fe has been added into the graphite electrode, the productivity of C60 can be raised to 40%. At same time, the derivative of cholesterol, as part of yield discharging electricity, can be found.

Cholesterol↗
PubMed2001

[A cephalometric investigation on Shanghainese with normal occlusion using Ricketts analysis].

OBJECTIVE: To provide a database for orthodontic diagnosis, treatment planning and treatment evaluation. METHODS: Cephalograms taken from 121 Shanghainese (57 adolescents and 64 adults) with normal occlusion were traced and examined using Ricketts analysis. RESULTS: (1) In adolescent group, the angle of mandibular arc and facial contour were larger in male than in female. (2)In adults group, the angle of mandibular arc and genial angle were larger in male than in female, whilst the lower facial height and the convexity of lower incisor were smaller in male than in female. (3) The angle of mandibular arc, the convexity of lower incisor and the position of upper first molar were larger in adults than in adolescents,whilst the convexity of A was smaller in adults than in adolescents. CONCLUSION: In adolescents, the ramus and maxilla grow more in male than in female. In adults, chin and ramus grow more in male than those in female.

English Abstract↗
PubMed2000

Enhanced bioaccumulation of heavy metals by bacterial cells displaying synthetic phytochelatins.

A novel strategy using synthetic phytochelatins is described for the purpose of developing microbial agents for enhanced bioaccumulation of toxic metals. Synthetic genes encoding for several metal-chelating phytochelatin analogs (Glu-Cys)(n)Gly (EC8 (n = 8), EC11 (n = 11), and EC20 (n = 20)) were synthesized, linked to a lpp-ompA fusion gene, and displayed on the surface of E. coli. For comparison, EC20 was also expressed periplasmically as a fusion with the maltose-binding protein (MBP-EC20). Purified MBP-EC20 was shown to accumulate more Cd(2+) per peptide than typical mammalian metallothioneins with a stoichiometry of 10 Cd(2+)/peptide. Cells displaying synthetic phytochelatins exhibited chain-length dependent increase in metal accumulation. For example, 18 nmoles of Cd(2+)/mg dry cells were accumulated by cells displaying EC8, whereas cells exhibiting EC20 accumulated a maximum of 60 nmoles of Cd(2+)/mg dry cells. Moreover, cells with surface-expressed EC20 accumulated twice the amount of Cd(2+) as cells expressing EC20 periplasmically. The ability to genetically engineer ECs with precisely defined chain length could provide an attractive strategy for developing high-affinity bioadsorbents suitable for heavy metal removal.

Bacterial Outer Membrane Proteins↗
PubMed2000

Novel mutations in spastin gene and absence of correlation with age at onset of symptoms.

Autosomal dominant hereditary spastic paraplegia is genetically heterogeneous, with at least five loci identified by linkage analysis. Recently, mutations in spastin were identified in SPG4, the most common locus for dominant hereditary spastic paraplegia that was previously mapped to chromosome 2p22. We identified five novel mutations in the spastin gene in five families with SPG4 mutations from North America and Tunisia and showed the absence of correlation between the predicted mutant spastin protein and age at onset of symptoms.

Adenosine Triphosphatases↗
PubMed2000

The use of enzyme therapy to regulate the metabolic and phenotypic consequences of adenosine deaminase deficiency in mice. Differential impact on pulmonary and immunologic abnormalities.

Adenosine deaminase (ADA) deficiency results in a combined immunodeficiency brought about by the immunotoxic properties of elevated ADA substrates. Additional non-lymphoid abnormalities are associated with ADA deficiency, however, little is known about how these relate to the metabolic consequences of ADA deficiency. ADA-deficient mice develop a combined immunodeficiency as well as severe pulmonary insufficiency. ADA enzyme therapy was used to examine the relative impact of ADA substrate elevations on these phenotypes. A "low-dose" enzyme therapy protocol prevented the pulmonary phenotype seen in ADA-deficient mice, but did little to improve their immune status. This treatment protocol reduced metabolic disturbances in the circulation and lung, but not in the thymus and spleen. A "high-dose" enzyme therapy protocol resulted in decreased metabolic disturbances in the thymus and spleen and was associated with improvement in immune status. These findings suggest that the pulmonary and immune phenotypes are separable and are related to the severity of metabolic disturbances in these tissues. This model will be useful in examining the efficacy of ADA enzyme therapy and studying the mechanisms underlying the immunodeficiency and pulmonary phenotypes associated with ADA deficiency.

Adenosine↗
PubMed2000

Scavenger receptor-BI inhibits ATP-binding cassette transporter 1- mediated cholesterol efflux in macrophages.

Scavenger receptor BI (SR-BI) facilitates the efflux of cellular cholesterol to plasma high density lipoprotein (HDL). Recently, the ATP-binding cassette transporter 1 (ABC1) was identified as a key mediator of cholesterol efflux to apolipoproteins and HDL. The goal of the present study was to determine a possible interaction between the SR-BI and ABC1 cholesterol efflux pathways in macrophages. Free cholesterol efflux to HDL was increased ( approximately 2.2-fold) in SR-BI transfected RAW macrophages in association with increased SR-BI protein levels. Treatment of macrophages with 8-bromo-cAMP (cAMP) resulted in a 4.1-fold increase in ABC1 mRNA level and also increased cholesterol efflux to HDL (2.2-fold) and apoA-I (5.5-fold). However, in SR-BI transfected RAW cells, cAMP treatment produced a much smaller increment in cholesterol efflux to HDL (1.1-fold) or apoA-I (3.3-fold) compared with control cells. In macrophages loaded with cholesterol by acetyl-LDL treatment, SR-BI overexpression did not increase cholesterol efflux to HDL but did inhibit cAMP-mediated cholesterol efflux to apoA-I or HDL. SR-BI neutralizing antibody led to a dose- and time-dependent increase of cAMP-mediated cholesterol efflux in both SR-BI transfected and control cells, indicating that SR-BI inhibits ABC1-mediated cholesterol efflux even at low SR-BI expression level. Transfection of a murine ABC1 cDNA into 293 cells led to a 2.3-fold increase of cholesterol efflux to apoA-I, whereas co-transfection of SR-BI with ABC1 blocked this increase in cholesterol efflux. SR-BI and ABC1 appear to have distinct and competing roles in mediating cholesterol flux between HDL and macrophages. In nonpolarized cells, SR-BI promotes the reuptake of cholesterol actively effluxed by ABC1, creating a futile cycle.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2000

Characterization of halotolerant rhizobia isolated from root nodules of Canavalia rosea from seaside areas.

Twelve nodule isolates from Canavalia rosea, an indigenous leguminous halophyte growing in the seaside areas of southern Taiwan, were effective symbionts for the original host and able to grow at NaCl concentrations up to 3-3.5% (w/v). The taxonomy of these isolates was investigated using a polyphasic approach, including phenotypic characteristics, banding patterns of total proteins from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), genomic fingerprint patterns from random amplified polymorphic DNA (RAPD) analysis, pulsed-field gel electrophoresis (PFGE) analysis, amplified 16S rDNA restriction analysis (ARDRA), 16S rRNA gene sequencing, and nifH gene sequencing. Based on the SDS-PAGE, RAPD, PFGE and ARDRA results, the 12 isolates are highly diverse. The 16S rRNA and nifH gene sequences were determined for isolates with distinct ARDRA patterns and compared with other members of the rhizobial species. We propose these isolates should be classified into the genus Sinorhizobium and distinguished from the current species of this genus.

Journal Article↗
PubMed2000

The rat arylalkylamine N-acetyltransferase E-box: differential use in a master vs. a slave oscillator.

The rat arylalkylamine N-acetyltransferase (AA-NAT) gene encodes the key enzyme whose rhythmic expression drives the nocturnal production of melatonin. It is of interest that this enzyme is expressed virtually exclusively in two phylogenetically related tissues: retinal photoreceptors, which harbor an endogenous clock, and pinealocytes which, in higher vertebrates, function strictly in response to the master oscillator in the suprachiasmatic nucleus (SCN). While much is known about AA-NAT transcriptional regulation in the rat pineal gland (a slave oscillator), a full understanding of the mechanisms controlling AA-NAT gene expression in the retina by the clock is lacking. In the present study we have identified a functional E box in the first intron of the rat AA-NAT gene which is capable of mediating transcriptional upregulation via the action of a bMAL/CLOCK heterodimer. This is the first report to characterize the AA-NAT gene as a possible direct transcriptional target of the biological clock loop in a master oscillator.

Animals↗
PubMed2000

An approach to probe some neural systems interaction by functional MRI at neural time scale down to milliseconds.

In this paper, we demonstrate an approach by which some evoked neuronal events can be probed by functional MRI (fMRI) signal with temporal resolution at the time scale of tens of milliseconds. The approach is based on the close relationship between neuronal electrical events and fMRI signal that is experimentally demonstrated in concurrent fMRI and electroencephalographic (EEG) studies conducted in a rat model with forepaw electrical stimulation. We observed a refractory period of neuronal origin in a two-stimuli paradigm: the first stimulation pulse suppressed the evoked activity in both EEG and fMRI signal responding to the subsequent stimulus for a period of several hundred milliseconds. When there was an apparent site-site interaction detected in the evoked EEG signal induced by two stimuli that were primarily targeted to activate two different sites in the brain, fMRI also displayed signal amplitude modulation because of the interactive event. With visual stimulation using two short pulses in the human brain, a similar refractory phenomenon was observed in activated fMRI signals in the primary visual cortex. In addition, for interstimulus intervals shorter than the known latency time of the evoked potential induced by the first stimulus ( approximately 100 ms) in the primary visual cortex of the human brain, the suppression was not present. Thus, by controlling the temporal relation of input tasks, it is possible to study temporal evolution of certain neural events at the time scale of their evoked electrical activity by noninvasive fMRI methodology.

Animals↗
PubMed2000

Expression, immobilization, and enzymatic characterization of cellulose-binding domain-organophosphorus hydrolase fusion enzymes.

Bifunctional fusion proteins consisting of organophosphate hydrolase (OPH) moieties linked to a Clostridium-derived cellulose-binding domain (CBD) were shown to be highly effective in degrading organophosphate nerve agents, enabling purification and immobilization onto different cellulose materials in essentially a single step. Enzyme kinetics studies were performed for the CBD-OPH fusions using paraoxon as the substrate. The kinetics values of the unbound fusion enzymes were similar to OPH with a modest increase in K(m). Immobilization of the enzymes onto microcrystalline cellulose resulted in a further increase in the K(m) values of approximately twofold. The pH profile of the cellulose-immobilized enzymes was also only minimally affected. The CBD-OPH fusion proteins could be immobilized onto a variety of cellulose matrixes, and retained up to 85% of their original activity for 30 days. The durability of the bound fusions increased with the amount of Avicel used, suggesting that protein/cellulose interactions may have a dramatic stabilizing effect. Repeated hydrolysis of paraoxon was achieved in an immobilized enzyme reactor with 100% degradation efficiency over 45 days. These fusion proteins should prove to be invaluable tools for the development of low cost, OPH-based cellulose materials for the simultaneous adsorption and degradation of stored or spilled organophosphate wastes.

Aryldialkylphosphatase↗
PubMed2000

Dual-specific Cdc25B phosphatase: in search of the catalytic acid.

Cdc25 is a dual-specificity phosphatase that catalyzes the activation of the cyclin-dependent kinases, thus causing initiation and progression of successive phases of the cell cycle. Although it is not significantly structurally homologous to other well-characterized members, Cdc25 belongs to the class of well-studied cysteine phosphatases as it contains their active site signature motif. However, the catalytic acid needed for protonation of the leaving group has yet to be identified. To elucidate the role and identity of this key catalytic residue, we have performed a detailed pH-dependent kinetic analysis of Cdc25B. The pK(a) of the catalytic cysteine was found to be 5.6-6.3 in steady state and one-turnover burst experiments using the small molecule substrates p-nitrophenyl phosphate and 3-O-methylfluorescein phosphate. Interestingly, Cdc25B does not exhibit the typical bell-shaped pH-rate profile with small molecule substrates seen in other cysteine phosphatases and indicative of the catalytic acid because it lacks pH dependence between 6.5 and 9. Reactions of Cdc25B with the natural substrate Cdk2-pTpY/CycA, however, did yield a bell-shaped pH-rate profile with a pK(a) of 6.1 for the catalytic acid residue. Recent structural studies of Cdc25 have suggested that Glu474 [Fauman, E. B., et al. (1998) Cell 93, 617-625] or Glu478 [Reynolds, R. A., et al. (1999) J. Mol. Biol. 293, 559-568] could function as the catalytic acid in Cdc25B. Using site-directed mutagenesis and truncation experiments, however, we found that neither of these residues, nor the unstructured C-terminus, is responsible for the observed pH dependence. These results indicate that the catalytic acid does not appear to lie within the known structure of Cdc25B and may lie on its protein substrate.

Amino Acid Substitution↗
PubMed2000

A role for serine-175 in modulating the molecular conformation of calponin.

Calponin is an actin filament-associated protein found in smooth muscle and non-muscle cells. Calponin inhibits actin-myosin interaction in a manner that is prevented by protein kinase C (PKC)-catalysed phosphorylation of serine-175. To investigate the molecular basis of serine-175-mediated regulation, we examined the effect of phosphorylation on the conformation of calponin using monoclonal antibody (mAb) epitope analysis. Eight mAbs against different epitopes on chicken gizzard calponin were developed to monitor the conformational changes in calponin induced by PKC-mediated phosphorylation or serine-175-->alanine (S175A) substitution. The relative affinities of the mAbs for calponins immobilized on microtitre plates or bound to actin-tropomyosin thin filaments were determined, and epitope competitions between free and immobilized calponins were carried out. The changes in binding affinity between mAb paratopes and calponin epitopes demonstrate several serine-175 modification-induced conformational effects: (a) structures of calponin are reconfigured by serine-175 modification, supporting the regulatory function of serine-175; (b) there are submolecular structures unaffected by modification of serine-175 in both free and thin filament-associated calponins, suggesting that the serine-175-based conformational modulation is a targeted allosteric effect; (c) significant conformational changes are detected between free and thin filament-associated calponins, indicating two functional states of the molecular conformation; and (d) the different epitope characteristics between thin filament-bound and free calponins suggest that calponin is a flexible molecule, and the modifications of serine-175 may also determine the structural flexibility to increase the epitope accessibility. These results provide novel information concerning the structure-function relationships of calponin and its regulation by phosphorylation.

Actins↗
PubMed2000

Inhibition of C-raf expression by antisense oligonucleotides extends heart allograft survival in rats.

BACKGROUND: C-raf is a well-characterized serine/ threonine (Ser/Thr) protein kinase that is involved in the transduction of multiple signals of T cells. We demonstrate that the inhibition of C-raf mRNA expression prolongs heart allograft survival. METHODS: Three 20-mer C-raf antisense oligonucleotides, each with identical sequences, were synthesized with different chemical modifications: one as a uniform phosphorothioate oligodeoxynucleotide (PS oligo), a second with a PS backbone and 2'-methoxyethyl (ME) substitutions at the 2'-sugar positions in the first and last five nucleotides, and a third with a mixed PS and phosphodiester (PD) backbone and ME modifications on the first and last five nucleotides. RESULTS: Both ME-modified C-raf antisense oligos were at least 5-fold more effective than the PS C-raf antisense oligo in blocking C-raf mRNA expression in two cell lines. Similarly, each of the ME C-raf antisense oligos produced better heart allograft survival rates than did PS C-raf oligo. Furthermore, although the combination of PS C-raf antisense oligo with sirolimus (SRL) acted synergistically to extend heart allograft survival, the effect was potentiated by either of the ME-modified oligos. CONCLUSIONS: C-raf inhibition extends heart allograft survival, and ME-modification potentiates antisense activity.

Animals↗
PubMed2000

Ischemic preconditioning activates phosphatidylinositol-3-kinase upstream of protein kinase C.

The present study is designed to test whether phosphatidylinositol 3-kinase (PI3-kinase) has a role in the signaling pathway in ischemic preconditioning (PC) and whether it is proximal or distal to protein kinase C (PKC). Before 20 minutes of global ischemia, Langendorff-perfused rat hearts were perfused for 20 minutes (control); preconditioned with 4 cycles of 5-minute ischemia and 5-minute reflow (PC); treated with either wortmannin (WM) or LY 294002 (LY), each of which is a PI3-kinase inhibitor, for 5 minutes before and throughout PC; treated with 1,2-dioctanoyl-sn-glycerol (DOG), an activator of PKC for 10 minutes (DOG); treated identically to the DOG group except with WM added 10 minutes before and during perfusion with DOG; or treated with either WM or LY for 25 minutes. Recovery of left ventricular developed pressure (LVDP; percentage of initial preischemic LVDP), measured after 30 minutes of reflow, was improved by PC (72+/-2% versus 36+/-4% in control; P<0.001), and this was blocked by WM and LY (41+/-4% and 43+/-5%, respectively; P<0.05 compared with PC). DOG addition improved postischemic LVDP (67+/-6%; P<0.001 compared with control), but in contrast to its effect on PC, WM did not completely eliminate the protective effect of DOG (52+/-4%; P>0.05 compared with DOG; P<0.05 compared with control). PC induced phosphorylation of protein kinase B and translocation of PKC epsilon, and it increased NO production, and these effects were blocked by WM, which suggests a role for PI3-kinase in PC upstream of PKC and NO.

Adenosine Triphosphate↗