Biomedical subjects

Y Duan

Publications and source records attributed to Y Duan.

At least 37 records · Page 2Linked to original sources

PubMed2001

[The ultrastructure changes of nerve fibers in pressure side of periodontal ligament during orthodontic tooth movement in rats].

OBJECTIVE: To observe the ultrastructure changes of nerve fibers in pressure side of periodontal ligament during orthodontic tooth movement (OTM) in rats. METHODS: The left maxillary of fifteen rats molar was moved mesially by an appliance for 2 days, 1 week, 2 weeks and 3 weeks. The ultrastructure changes of nerve fibers in pressure side of the periodontal ligament in rats were observed with electron microscope. RESULTS: The thick myelinated axon was degenerated after 2 days of OTM and not recovered after 3 weeks of OTM; the number of thin unmyelinated axons was increased after 2 days of OTM. It reached a maximum after 1 week of OTM and recovered after 3 weeks of OTM. Only part of thin unmyelinated was slightly degenerated. At the same time, some of the thin myelinated axons were slightly degenerated and partly demyelinated. CONCLUSION: The nerve fibers were involved in periodontal tissue remodelling.

Animals↗

PubMed2001

[Effect of SP on intracellular free calcium concentration in cultured osteoblast].

OBJECTIVE: To investigate the effect of SP on intracellular free calcium concentration (Ca2+)i in cultured osteoblast. METHODS: Effect of SP on intracellular free calcium was measured using cell culturing and laser scanning confocal microscopy with fluo-3/AM as a fluorescence probe. RESULTS: After treated with SP(10(-4) mol/L), 70% of the cells responded to it; the intracellular (Ca2+)i increased markedly [fluorescence intensity increased by (90 +/- 18)%]. CONCLUSIONS: These results suggested that calcium may have a role as a intracellular secondary messenger in the action of SP in osteoblast.

Animals↗

PubMed2001

[Relation of plasma glucose levels to serum lipids and apolipoproteins levels in middle and old age males].

OBJECTIVE: To gain an insight into the relation of plasma glucose levels to lipids and apolipoproteins levels. METHODS: Fasting 12-14 h blood glucose (BG), high density lipoprotein cholestrol(LDL-C), apolipoproteins(apo) A I, A II, B100, C II, C III and E levels were measured in 735 men aged 40-70 in Chengdu area. The subjects studied were divided into three groups by the plasma glucose levels: 1. normal group (S1), 2. decreased glucose tolerance group (S2), 3. diabetes mellitus (DM) group (S3). RESULTS: Among 735 cases studied, groups S2 and S3 had more hyperlipidemia than group S1 (64%, 45% and 32.2% respectively). The fasting serum mean TG levels in groups S2 (3.62 +/- 2.52 mmol/L) and S3 (4.45 +/- 3.82 mmol/L) group were significantly higher than that in group S1 (1.92 +/- 1.39 mmol/L) (P < 0.01 and P < 0.01), and the mean TG levels in groups S2 (5.68 +/- 1.15 mmol/L) and S3 (5.68 +/- 1.12 mmol/L) were higher than that in group S1 (5.13 +/- 1.06 mmol/L) (P < 0.05, P < 0.05). The serum apo B100, C II, C III and E levels in groups S2 and S3 were significantly higher as compared with that in the normal group (P < 0.01, P < 0.05). The correlation analysis indicated that there was a positive correlation of BG with serum TG in groups S1, S2 and S3 whose correlation coefficients (r) were 0.1800, 0.1436 and 0.3212 respectively (P < 0.001); and a negative correlation with HDL-C levels in groups S2 and S3 (r = -0.2534 and -0.1477, P < 0.001). The plasma glucose levels were positively correlated with apo B100, C III and E levels in groups S1, S2 and S3, P < 0.001), with apo C II in groups S1 and S2 (P < 0.001, P < 0.01); and negatively correlate to apoA I only in group S2 (r = -0.1182, P < 0.01). CONCLUSION: The results suggest that serum TG, TC, HDL-C, apoB100, C II, C III and E levels be the main factors that related to plasma glucose levels.

Aged↗

PubMed2001

[Orthodontic diagnosis and treatment of unilateral posterior cross-bite].

OBJECTIVE: The aim of this study is to investigate the clinical diagnosis and treatment of unilateral posterior cross-bite and to provide information for correct treatment of this disease. METHODS: The X-ray examination of patients' heads in the posterior-anterior position, analysis of pantomorphic films and model measurement were used for the diagnosis of unilateral cross-bite. According to these data, three types of unilateral posterior cross-bite would be classified, and different orthodontic appliances would be applied in the following treatment, including separate plate removable expansion appliances, Quad-helix appliances, narrowing dental arch and inter-arch elastics. RESULTS: A total of 78 cases of unilateral posterior cross-bite were treated by different techniques in a manner consistent with the classification. All of the clinical results of treatment were satisfactory and successful. CONCLUSION: If diagnosis is correct, and suitable treatment methods are chosen, unilateral cross-bite can be treated successful.

Activator Appliances↗

PubMed2001

[Changes of soft tissue profile in operated unilateral cleft lip and palate patients after maxillary protraction].

OBJECTIVE: The aim of this study is to investigate effects of maxillary protraction on soft tissue profile in operated operated unilateral cleft lip and palate (UCLP) patients. METHODS: A total of 10 growing UCLP patients (male 7, female 3), age from 8.2 to 12 years old (Average: 10.4 years old), were selected to be treated with maxillary protraction using head gear-chin cap-long hook protraction appliance. The appliance was worn 12-14 hours per day, and the protraction force was 400-500 g each side. The protraction direction was forward and slightly downward. The treatment period was 4.7 months (Average: 5.8 months). Cephalometrics were taken before and after treatment. The changes of soft-tissue profile were studied using the computer-aid X-ray cephalometric analysis. RESULTS: After protraction, the points of Prn, Sn and Ls moved forward significantly. The distance from points Ls to E plane changed significantly from 0.46 mm before treatment to 1.18 mm after treatment. The angle G-Prn-Pg' decreased significantly, and G-Sn-Pg' changed significantly from -0.30 before treatment to 6.260 after treatment. The anterior-posterior position of mandible and lower lip did not change significantly, the changes of angles Cm-Sn-Ls, A'ls/SiLi had no statistical significance. The results indicated that maxillary protraction could make maxilla and upper lip move forward, and the convexity of soft tissue profile improve significantly. CONCLUSION: Maxillary protraction is an effective way to improve the facial deformity of operated UCLP patients. UCLP patients should have early interrupted treatment.

Cephalometry↗

PubMed2000

Development and evaluation of a glow discharge microwave-induced-plasma tandem source for time-of-flight mass spectrometry.

In this work, a new glow discharge, microwave-induced-plasma (GDMIP), tandem ion source was developed, characterized, and used in conjunction with time-of-flight mass spectrometry. This tandem source was designed to be simple and compact The GD and the MIP unit are independent and demountable, providing flexibility in tuning and operating. The microwave plasma can be formed with very low power (a few watts) and overlapped with the glow discharge. The discharge current increased with the addition of microwave discharge when the GD was operated in constant-voltage mode, and the amplitude of the current increase was found to be related to microwave power, discharge pressure, and sampling distance. With the addition of microwave discharge, significant signal enhancement was achieved under a discharge pressure of 2.0 Torr and a discharge voltage of 500 V with 2.0-mm sampling distance. Enhanced factors of analyte signals ranging from approximately 1 to nearly 10 could be obtained with MIP boosting, while no significant change in noise level was observed. This new tandem source provides improved performance in direct solid sample analysis.

Journal Article↗

PubMed2000

Helium plasma source time-of-flight mass spectrometry: off-cone sampling for elemental analysis

In this paper, an atmospheric pressure, helium microwave-induced plasma (MIP) ion source coupled with an orthogonal acceleration time-of-flight mass spectrometer (TOFMS) is explored for elemental analysis. Studies of the relationship between ion signals and sampling distance of the MS reveal that background signals can be suppressed dramatically without sacrificing the signal intensities of analytes when the microwave plasma plume is off the tip of the sampler orifice. This "off-cone" ion sampling mode provides a technique to obtain nearly "clean" background spectra and, thus, eliminates the spectral interference from entrainment air and the working-gas species, making it possible to sensitively determine isotopes that suffered from spectral interference in ICPMS and MIPMS (such as 40Ca, 52Cr, 55Mn, and 56Fe). On the other hand, since the high-temperature plasma is kept away from the sampler aperture, off-cone sampling places little demand on the cooling device and the lifetime of the sampler plate can be extended. The instrumental system can provide a fairly good mass resolution of 1100 (fwhm). The detection limits (3sigma) in the tens of picograms per milliliter level for the elements studied can be achieved with a digital oscilloscope. These detection limits can be easily improved with an advanced detection system, which is currently available in commercial markets.

Journal Article↗

PubMed2000

Use of MM-PB/SA in estimating the free energies of proteins: application to native, intermediates, and unfolded villin headpiece.

We investigated the stability of three different ensembles of the 36-mer villin headpiece subdomain, the native, a compact folding intermediate, and the random coil. Structures were taken from a 1-micros molecular dynamics folding simulation and a 100-ns control simulation on the native structure. Our approach for each conformation is to first determine the solute internal energy from the molecular mechanics potential and then to add the change resulting from solvation (DeltaG(solv)). Explicit water was used to run the simulation, and a continuum model was used to estimate DeltaG(solv) with the finite difference Poisson-Boltzmann model accounting for the polarization part and a linearly surface area-dependent term for the non-polar part. We leave out the solute vibrational entropy from these values but demonstrate that there is no statistical difference among the native, folding intermediate, and random coil ensembles. We find the native ensemble to be approximately 26 kcal/mol more stable than the folding intermediate and approximately 39 kcal/mol more stable than the random coil ensemble. With an experimental estimate for the free energy of denaturation equal to 3 kcal/mol, we approximate the non-native degeneracy to lie between 10(16) and 10.(25) We also present a possible scheme for the mechanism of folding, first-order exponential decay of a putative transition state, with an estimate for the t(1/2) of folding of approximately 1 micros.

Carrier Proteins↗

PubMed2000

A field-portable plasma source monitor for real-time air particulate monitoring

In this research, a novel portable instrument for on-site, real-time air particulate monitoring was developed. It is highly desirable to use microwave plasmas for on-site, real-time environmental and occupational hazard monitoring because they can be sustained with various gases at relatively low power and possess excellent detection capabilities for both metal and nonmetal air pollutants. In the new instrument design, a microwave plasma was selected as an excitation source and was used in conjunction with atomic emission spectrometry. A small, integrated spectrometer with a charge-coupled detector (CCD) was used for optical signal detection. An efficient, in situ air-sampling system was developed for direct sampling of air particles into the plasma. Characterization and calibration of the new instrument were achieved with an in-house-fabricated high-efficiency nebulization-desolvation system. Tolerance of the microwave argon plasma source to air introduction was tested, and the operational parameters were optimized. Analytical performance and the feasibility of the newly developed portable instrument for aerosol particle analysis were evaluated. Some advantages and possible applications of the new instrument are discussed. The instrument provides an innovative tool for rapid environmental and occupational hazard monitoring.

Journal Article↗

PubMed2000

Novel gain-of-function mechanism in K(+) channel-related long-QT syndrome: altered gating and selectivity in the HERG1 N629D mutant.

The N629D mutation, adjacent to the GFG signature sequence of the HERG1 A K(+) channel, causes long-QT syndrome (LQTS). Expression of N629D in Xenopus oocytes produces a rapidly activating, noninactivating current. N629D is nonselective among monovalent cations; permeation of K(+) was similar to that of Na(+) or Cs(+). During repolarization to potentials between -30 and -70 mV, N629D manifested an inward tail current, which was abolished by replacement of extracellular Na(+) (Na(+)(e)) with extracellular N-methyl-D-glucamine (NMG(e)). Because LQTS occurs in heterozygous patients, we coexpressed N629D and wild type (WT) at equimolar concentrations. Heteromultimer formation was demonstrated by analyzing the response to 0 [K(+)](e). The outward time-dependent current was nearly eliminated for WT at 0 [K(+)](e), whereas no reduction was observed for homomultimeric N629D or for the equimolar coexpressed current. To assess physiological significance, dofetilide-sensitive currents were recorded during application of simulated action potential clamps. During phase 3 repolarization, WT manifested outward currents, whereas homomultimeric N629D manifested inward depolarizing currents. During coexpression studies, variable phenotypes were observed ranging from a reduction in outward repolarizing current to net inward depolarizing current during phase 3. In summary, N629D replaces the WT outward repolarizing tail current with an inward depolarizing sodium current, which is expected to delay later stages of repolarization and contribute to arrhythmogenesis. Thus, the consequences of N629D resemble the pathophysiology seen in LQT3 Na(+) channel mutations and may be considered the first LQTS K(+) channel mutation that exhibits gain of function.

Action Potentials↗

PubMed2000

Calculating structures and free energies of complex molecules: combining molecular mechanics and continuum models.

A historical perspective on the application of molecular dynamics (MD) to biological macromolecules is presented. Recent developments combining state-of-the-art force fields with continuum solvation calculations have allowed us to reach the fourth era of MD applications in which one can often derive both accurate structure and accurate relative free energies from molecular dynamics trajectories. We illustrate such applications on nucleic acid duplexes, RNA hairpins, protein folding trajectories, and protein-ligand, protein-protein, and protein-nucleic acid interactions.

Base Sequence↗

PubMed2000

Bone size and volumetric density in women with anorexia nervosa receiving estrogen replacement therapy and in women recovered from anorexia nervosa.

Anorexia nervosa is associated with bone loss during adulthood, but may also delay skeletal growth and mineral accrual during growth. We asked the following questions. 1) Is anorexia nervosa associated with reduced bone size and reduced volumetric bone mineral density (vBMD)? 2) Is estrogen replacement therapy (ERT) or recovery from anorexia nervosa associated with normal bone size and vBMD? Using dual-energy x-ray absorptiometry, we measured bone size and vBMD of the third lumbar vertebra and femoral neck in a cross-sectional study of 161 female patients: 77 with untreated anorexia nervosa, 58 with anorexia nervosa receiving ERT, 26 recovered from anorexia nervosa, and 205 healthy age-matched controls. Results were expressed as the SD or z-score (mean +/- SEM). Deficits in vertebral body and femoral neck width in untreated women were -1.0 +/- 0.1 and -0.3 +/- 0.1 SD (P < 0.001 and P < 0.05, respectively). Deficits in bone width were less in the ERT-treated women than in untreated women at the vertebral body (-0.6 +/- 0.1 SD; P < 0.001), but not at the femoral neck (-0.4 +/- 0.2 SD; P < 0.05). There were no significant deficits in vertebral body and femoral neck width in recovered women (both -0.3 +/- 0.2 SD; P = NS). In untreated women, vertebral and femoral neck vBMD were -1.6 +/- 0.1 and -1.1 +/- 0.1 SD, respectively (both P < 0.001), less severely reduced in ERT-treated women (-1.2 +/- 0.2 and -0.6 +/- 0.2 SD, respectively; both P < 0.001), and least reduced in recovered women (-0.6 +/- 0.1 and -0.5 +/- 0.2 SD; P < 0.01 and P < 0.05, respectively). After adjusting for differences in fat and lean mass, vertebral body and femoral neck width were no longer reduced in untreated, ERT-treated, and recovered women. Adjustment for body composition had little effect on group difference in vBMD. Bone fragility in anorexia nervosa is due to reduced bone size and reduced vBMD. Although causality cannot be inferred in cross-sectional studies, the data are consistent with the view that malnutrition may contribute to reduced bone size, whereas estrogen deficiency may reduce vBMD. The use of ERT early in disease is a reasonable component of management if the chance of recovery appears remote.

Absorptiometry, Photon↗

PubMed2000

Heterogeneity in the growth of the axial and appendicular skeleton in boys: implications for the pathogenesis of bone fragility in men.

Men with spine fractures have reduced vertebral body (VB) volume and volumetric bone mineral density (vBMD). Men with hip fractures have reduced femoral neck (FN) volume and vBMD, site-specific deficits that may have their origins in growth. To describe the tempo of growth in regional bone size, bone mineral content (BMC), and vBMD, we measured bone length, periosteal and endocortical diameters, BMC, and vBMD using dual-energy X-ray absorptiometry in 184 boys aged between 7 and 17 years. Before puberty, growth was more rapid in the legs than in the trunk. During puberty, leg growth slowed while trunk length accelerated. Bone size was more advanced than BMC in all regions, being approximately 70% and approximately 35% of their predicted peaks at 7 years of age, respectively. At 16 years of age, bone size had reached its adult peak while BMC was still 10% below its predicted peak. The legs accounted for 48%, whereas the spine accounted for 10%, of the 1878 g BMC accrued between 7 and 17 years. Peripubertal growth contributed (i) 55 % of the increase in leg length but 78% of the mineral accrued and (ii) 69% of the increase in spine length but 87% of the mineral accrued. Increased metacarpal and midfemoral cortical thickness was caused by respective periosteal expansion with minimal change in the endocortical diameter. Total femur and VB vBMD increased by 30-40% while size and BMC increased by 200-300%. Thus, growth builds a bigger but only slightly denser skeleton. We speculate that effect of disease or a risk factor during growth depends on the regions maturational stage at the time of exposure. The earlier growth of a regions size than mass, and the differing growth patterns from region to region, predispose to site-specific deficits in bone size, vBMD, or both. Regions further from their peak may be more severely affected by illness than those nearer completion of growth. Bone fragility in old age is likely to have its foundations partly established during growth.

Absorptiometry, Photon↗

PubMed2000

On exposure to anorexia nervosa, the temporal variation in axial and appendicular skeletal development predisposes to site-specific deficits in bone size and density: a cross-sectional study.

Skeletal development is heterogeneous. Throughout growth, bone size is more maturationally advanced than the mineral being accrued within its periosteal envelope; before puberty, appendicular growth is more rapid than axial growth; during puberty, appendicular growth slows and axial growth accelerates. We studied women with differing age of onset of anorexia nervosa to determine whether this temporal heterogeneity in growth predisposed to the development of deficits in bone size and volumetric bone mineral density (vBMD), which varied by site and severity depending on the age at which anorexia nervosa occurred. Bone size and vBMD of the third lumbar vertebra and femoral neck were measured using dual-energy X-ray absorptiometry in 210 women aged 21 years (range, 12-40 years) with anorexia nervosa. Results were expressed as age-specific SDs (mean +/- SEM). Bone width depended on the age of onset of anorexia nervosa; when the onset of anorexia nervosa occurred (1) before 15 years of age, deficits in vertebral body and femoral neck width did not differ (-0.77+/-0.27 SD and -0.55+/-0.17 SD, respectively); (2) between 15 and 19 years of age, deficits in vertebral body width (-0.95+/-0.16 SD) were three times the deficits in femoral neck width (-0.28+/-0.14 SD; p < 0.05 comparing the deficits), (3) after 19 years of age, deficits in the vertebral body width (-0.49+/-0.26 SD; p = 0.05) were half that in women with earlier onset of anorexia nervosa. No deficit in bone width was observed at the femoral neck. Deficits in vBMD at the vertebra and femoral neck were independent of the age of onset of anorexia nervosa but increased as the duration of anorexia nervosa increased, being about 0.5 SD lower at the vertebra than femoral neck. We infer that the maturational development of a region at the time of exposure to disease, and disease duration, determine the site, magnitude, and type of trait deficit in anorexia nervosa. Bone fragility due to reduced bone size and reduced vBMD in adulthood is partly established during growth.

Adolescent↗

PubMed2000

Molecular determinant of high-affinity dofetilide binding to HERG1 expressed in Xenopus oocytes: involvement of S6 sites.

This study reports that the affinity of HERG1 A for dofetilide is decreased from 0.125 +/- 0.003 microM for wild-type (WT) channels to 15 +/- 3 microM for F656V, a mutation in the COOH-terminal half of the S6. Similarly, the IC(50) for quinidine was increased from 8 +/- 4 microM for WT to 219 +/- 65 microM for the F656V mutation, whereas affinity for external tetraethylammonium was similar for WT (51 +/- 10 mM) and F656V (36 +/- 10 mM, NS). Kinetics of onset of inactivation of F656V was similar to WT but kinetics of deactivation, activation, and recovery from inactivation differed from WT. However, mutations in nearby amino acids in the S6 more strikingly altered deactivation, activation, and recovery from inactivation but had little effect on affinity for dofetilide. To assess the effects of disruption of inactivation, the S631A mutation was made. The S631A mutation altered the IC(50) for dofetilide to 20 +/- 3 microM, but the IC(50) for quinidine was unchanged at 8 +/- 4 microM for WT and 10 +/- 1 microM for S631A. To address whether the F656V mutation alters the IC(50) for dofetilide in a channel that does not inactivate, the double mutation S631A/F656V was made. The IC(50) for dofetilide of the double mutation was 32 +/- 3 microM, which is not substantially different than that of S631A. These data support the notion that allosteric changes occurring during the process of inactivation are necessary for high-affinity dofetilide binding. In conclusion, the Phe-656 residue of HERG is a molecular determinant of high-affinity dofetilide binding.

Amino Acid Motifs↗

PubMed2000

[Modification of surface of Dacron materials by UV irradiation for prevention of microbial adhesion].

UV irradiation grafting method was used to modify the surface of Prosthetic Valve materials (Dacron) for prevention of bacteria-adhesion, and PEG was introduced to the surface of Dacron by this method. The result showed that the chemical magnifying effect of PEG improved the grafting of heparin on the material surface. This method can obviously reduce the number of adherent bacteria.

Bacterial Adhesion↗

PubMed2000

[Study of covalently immobilizing heparin to polyetherurethane surface].

In this paper an approach of covalently immobilizing heparin to the surface of polyetherurethane without functional groups was studied. By quantitation of amino groups on PEU surface, the appropriate hydrolysis condition to PEU was determined. The assays of the heparin content heparinized PEU and the time of recalcification proved the above approach comparatively ideal.

Heparin↗

PubMed2000

[Researches on surface modification for prevention of bacterial adhesion to implanting biomaterials].

The failure of operation caused by biomaterials centered infections (BCI) has seriously restricted the clinical application of biomaterials. Two mechanisms of bacterial adhesion and the relationship between surface free energy of bimaterials and bacterial adhesion are introduced and discussed in this paper. Increasing the surface free energy can improve (decrease) the adhesion of some kinds of bacteria. At last, some methods of the surface modification are reviewed.

Bacterial Adhesion↗