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Biomedical subjects

Xu Chen

Publications and source records attributed to Xu Chen.

At least 37 records · Page 2Linked to original sources
PubMed2005

Crooked tail (Cd) model of human folate-responsive neural tube defects is mutated in Wnt coreceptor lipoprotein receptor-related protein 6.

A cranial neural tube defect in Crooked tail (Cd) mice is prevented with prenatal dietary folic acid Cd positional cloning reveals a missense mutation of a highly conserved amino acid in the low density lipoprotein receptor-related protein 6 (Lrp6), a coreceptor required for Wnt canonical signaling. Molecular modeling predicts that Lrp6(Cd) alters a hinge region of the second YWTD beta-propeller domain. Mutant LRP6 binds to Wnt and Dickkopf1 (Dkk1) but not Mesd1, and Dkk1 cannot antagonize Wnt in Cd/Cd cells, resulting in hyperactivity. NIH 3T3 cells transfected with a mutant Lrp6 plasmid resist Dkk1 antagonism much like Cd/+ cells, confirming the significance of the mutation. The Lrp6 mutation in Cd mice provides evidence for a functional connection between Wnt signaling and folate rescue of neural tube defects.

Amino Acid Sequence↗
PubMed2005

Increased resting heart rate following radiofrequency catheter ablation for atrial fibrillation.

AIM: Sinus tachycardia has been observed following radiofrequency (RF) catheter ablation for various kinds of supraventricular tachycardia. This study is aimed at determining the occurrence of changes in sinus-rhythm heart rate (HR) after pulmonary vein (PV) isolation in patients with paroxysmal/persistent atrial fibrillation (AF), prospectively. METHODS: Patients with a history of AF underwent segmental or circumferential isolation of the PVs. A total of 62 consecutive patients, mean age 55 +/- 10, was included. Clinical evaluation was performed before and one, three, six, nine, and 12 months following the procedure. RESULTS: Following PV isolation, the mean HR significantly increased from 58 +/- 10 bpm at baseline to 67 +/- 12 bpm at one month, 71 +/- 13 bpm at three months, 69 +/- 12 bpm at six months, 69 +/- 13 at nine months, and 70 +/- 13 at 12 months follow-up. The ablation success significantly correlated with the increase in HR at one month follow-up. In three patients the mean HR increased > 25 bpm resulting in symptoms necessitating therapy with rate-controlling drugs. CONCLUSION: PV isolation in patients with AF may result in increased HR, which positively correlated with the ablation success. This change does not seem to resolve spontaneously after a follow-up of 12 months. Approximately 5% of patients may develop symptoms due to an increased HR, necessitating treatment with rate-controlling drugs.

Atrial Fibrillation↗
PubMed2005

[Preliminary study on the improvement of wound microcirculation and retrospection on several methods of the management of deep partial thickness burn wound].

OBJECTIVE: To analyze several methods of wound repair for deep partial thickness burn wounds retrospectively, so as to evaluate the significance of improvement of wound microcirculation on wound healing. METHODS: (1) 2,976 burn patients admitted to our department were enrolled in the study, among them 614 undertook tangential excision, 32, eschar abrasion, 86 allo-skin coverage after debridement, 1836 tropical application of silver sulfadiazine and 408 with traditional Chinese medicine (Jing Wan Hong ointment) with gauze bandage. The results of the management with different methods were compared. (2) Rat model with deep partial thickness burn was reproduced and topical application of silver sulfadiazine was given. The rats were randomly divided into control (n = 10, with normal saline injected via caudal vein within 5 minutes postburn), and treatment (n = 10, with batroxobin injected via caudal vein within 5 minutes postburn) groups. The blood flow perfusion unit in the wound skin was measured before burn and at 0.5 to 72 postburn hours by Laser Doppler. The wound healing rate, contraction rate and wound healing time in each group were calculated on 14 and 18 postburn days (PBDs). The number of hair follicles after wound healing was observed by histological method. RESULTS: (1) The burn wound treated by tangential excision healed within 2 to 3 post operation weeks (POWs), with the healing rate of 94.8% in patients with burn covering 50% - 70% TBSA and 93.4% in those with burn of 80% approximately 98% TBSA. The healing time of patients with allo-grafts coverage after eschar abrasion was 13.8 +/- 2.1 days without scar formation. The wound healing time was 18.0 +/- 2.3 day in 82 patients with allo-graft coverage after debridement, and it was 26.0 +/- 3.2 days with subeschar healing in 1658 patients with topical application of silver sulfadiazine. Infection in burn wound was encountered in most patients undergoing traditional Chinese medicine bandage treatment with wound healing time of 26.0 +/- 2.8 days in the lower extremities. (2) The blood flow perfusion unit of the rats in the treatment group was significantly higher than that in the control group (P < 0.01). The wound healing rate in treatment group on 14 and 18 PBD was obviously higher than that in the control group (P < 0.01). But the wound contraction rate in the two groups was similar (P > 0.05). The wound healing time in treatment group was much shorter than that in control group (P < 0.01). A few hair follicles remained in the dermis of the rats in the control group on 30 PBD, and the number was evidently smaller than that in the treatment group (P < 0.01). CONCLUSION: Early tangential excision and eschar abrasion remained better methods in the management of deep partial thickness burn wounds, as they could ameliorate burn wound infection, shorten treatment period, raise wound healing rate and quality. Application of batroxobin could accelerate wound healing rate by improving wound microcirculation in deep partial thickness burn wound.

Adult↗
PubMed2005

[A practical method for the calculation of wound water loss in burn patients].

OBJECTIVE: To evaluate a calculating method of wound water loss (WWL) in hospitalized burn patients. METHODS: Eighty-five adult burn patients with total burn area over 50% were enrolled in the study. The WWL formula after shock stage (after 3rd postburn day) was given as: WWL (ml/%/kg/24 h) = [input (ml/24 h)-urine output (ml/24 h)-500 ml] / actual burn wound area(%) / body weight (kg). The result was compared with that determined by other formulas such as Davies, S.M.S.P and Lamke and palm rule. RESULTS: The calculated daily WWL in burn patients after shock stage was found out to be 0.9 +/- 0.1 ml/%/kg/24 h by this method. This figure is comparable with that calculated by several different methods. Palm rule could be simply applied in the patients with body weight around 60 kg. CONCLUSION: This method and palm rule were proved to be simple and practical for the calculation of WWL in burn patients, which could be applied in clinical work.

Adolescent↗
PubMed2005

[Biological effect of WO-1 on human embryonic osteoblasts].

OBJECTIVE: To investigate the effect of WO-1 on the proliferation and differentiation of human embryonic osteoblasts (HEO) and to provide research methods of bone tissue engineering. Methods HEO were isolated from periosteum and calvaria and then cultured in vitro. The dose-effect relationship between WO-1 concentration and biological effect of HEO was evaluated by growth curve and 3H-TdR count. The effect of WO-1 on cell activity and proliferation was investigated by cloning efficiency, cell cycle analysis was determined by flow cytometer and morphological was examined through transmission electron microscope. Moreover, the effect of WO-1 on osteoblastic function was evaluated at protein and mRNA levels by ALP activity, 3H-proline incorporation, osteocalcin secretion (RIA) and mRNA expression of type I collagen and osteocalcin (RT-PCR). Results The proliferation of HEO was inhibited in high concentration of WO-1, while it was promoted in low concentration of WO-1. The optimal dose was 8 microg/ml, and there was dose-effect relationship in the certain range of WO-1 concentration (0.25 microg/ml to 8 microg/ml). In 8 microg/ml of WO-1, the cloning efficiency and cloning volume of HEO were increased, population doubling time was decreased. All indexes of osteoblastic function including ALP activity, type I collagen synthesis and osteocalcin secretion were increased, the more sufficed cell organs were observed under transmission electron microscope than control group (P < 0.05). CONCLUSION: WO-1 can promote the cell activity and proliferation of HEO cultured in vitro in low concentration, enhance the synthesis of extracellular matrix, such as type I collagen and osteocalcin, and accelerate the mineralization of osteoid. WO-1 can be used as a stimulant of proliferation and differentiation of HEO in the research of bone tissue engineering, which provide the theoretical basis in clinical application.

Bone Substitutes↗
PubMed2005

[Detection of Porphyromonas gingivalis in the subgingival plaque of puberty gingivitis].

PURPOSE: To detect the presence of Porphyromonas gingivalis (Pg) in the subgingival plaque of puberty gingivitis and to investigate its relationship with gingival health. METHODS: The subjects of 14- to 17-year-old children in this study were divided into two groups, puberty gingivitis group and gingival healthy group, with 36 in each group. Periodontal parameters were recorded. A 16S rRNA-based polymerase chain reaction (PCR) detection method was used to determine the prevalence of Pg in the subgingival plaque samples. The AVG of positive band in the agarose gel electrophoresis was analyzed using the automatic gel documentation and image analyzer software. The relative quantity of Pg was determined. The data were statistically analyzed using SPSS11.5 software. Chi-square test was used to compare the prevalence of Pg in the two groups. Wilcoxon rank sum test was used to analyze the relative quantity of Pg and the severity between the Pg-positive and the Pg-negative subjects. Spearman correlation analysis was used to test the relationship between the relative quantity of Pg and periodontal parameters. RESULTS: The prevalence of Pg in the puberty gingivitis group and gingival healthy group was 47.22% and 25.00%, respectively (P<0.05). The relative quantity of Pg in the two groups was 48.02% and 21.46%, respectively(P<0.01). In all the Pg-positive subjects of puberty gingivitis group, there was positive correlation between the relative quantity of Pg and the gingival index (GI),sulcus bleeding index (SBI) and the probe depth (PD). There were statistically differences between them. The GI and SBI index of the Pg-positive subjects were statistically higher than that of the Pg-negative subjects in the puberty gingivitis group (P<0.01). CONCLUSION: Periodontal pathogens can colonize in the subgingival plaque in puberty subjects and colonization of Pg is relevant to the status of gingival health.

Adolescent↗
PubMed2004

Characteristics of structure, composition, mass spectra, and iron release from the ferritin of shark liver (Sphyrna zygaena).

The ferritin consists of a protein shell constructed of 24 subunits and an iron core. The liver ferritin of Sphyrna zygaena (SZLF) purified by column chromatography is a protein composed of eight ferritins containing varying iron numbers ranging from 400+/-20 Fe3+/SZLF to 1890+/-20 Fe3+/SZLF within the protein shell. Nature SZLF (SZLFN) consisting of holoSZLF and SZLF with unsaturated iron (SZLFUI) to have been purified with polyacrylamide gel electrophoresis (PAGE) exhibited five ferritin bands with different pI values ranging from 4.0 to 7.0 in the gel slab of isoelectric focusing (IEF). HoloSZLF purified by PAGE (SZLFE) not only had 1890+/-20 Fe3+/SZLFE but also showed an identical size of iron core observed by transmission electron microscopy (TEM). Molecular weight of approximately 21 kDa for SZLFE subunit was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Four peaks of molecular ions at mass/charge (m/z) ratios of 10611.07, 21066.52, 41993.16, and 63555.64 that come from the SZLFE were determined by matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF MS), which were identified as molecular ions of the ferritin subunit (M+) and its polymers, namely, [M]2+, [M]+, [2M]+, and [3M]+, respectively. Both SZLFE and a crude extract from shark liver of S. zygaena showed similar kinetic characteristics of complete iron release with biphasic behavior. In addition, a combined technique of visible spectrometry and column chromatography was used for studying ratio of phosphate to Fe3+ within the SZLFE core. Interestingly, this ratio maintained invariable even after the iron release, which differed from that of other mammal ferritins.

Animals↗
PubMed2004

Single-wall carbon nanotube-based voltammetric sensor and biosensor.

The pH-sensitive property of the single-wall carbon nanotube modified electrode based on the electroactive group on the single-wall carbon nanotube was explored by differential pulse voltammetry technique. In pH range 1-13 investigated in Britton-Robinson (B-R) buffer, the anodic peak shifted negatively along with the increase of pH exhibiting a reversible Nernstian response. Experiments were carried out to investigate the response of the single-wall carbon nanotube (SWNT) modified electrode to analytes associated with pH change. The response behavior of the modified electrode to ammonia was studied as an example. The potential response could reach equilibrium within 5 min. The modified electrode had good operational stability. Voltammetric urease and acetylcholinesterase biosensors were constructed by immobilizing the enzymes with sol-gel hybrid material. The maximum potential shift could reach 0.130 and 0.220 V for urea and acetylthiocholine, respectively. The methods for preparing sensor and biosensor were simple and reproducible and the range of analytes could be extended to substrates of other hydrolyases and esterases. This broadened the biosensor application of carbon nanotube in electrochemical area.

Acetylcholine↗
PubMed2004

Acute fatal pulmonary vein occlusion after catheter ablation of atrial fibrillation.

BACKGROUND: In treatment of atrial fibrillation (AF) catheter radiofrequency isolation of the pulmonary veins (PVs) has proved to be highly successful. There have been several case reports regarding PV stenosis, however none of these have reported a fatal outcome. METHODS AND RESULTS: A 31-year-old man was referred to us for treatment of complications related to catheter ablation. According to the documentation from the hospital, the patient underwent segmental ostial PV isolation for treatment of AF. A few hours after the procedure, the patient developed dyspnoea, hemoptysis, and a high fever. The patient was first diagnosed as having pneumonia but five days later transesophageal echocardiography and pulmonal angiography revealed total occlusion of the left superior and inferior PVs. When we received the patient he underwent open-heart surgery, which showed thrombi in the orifices of the left sided PVs protruding into the left atrium. In each of the left sided PVs severe stenosis was seen in the bifurcation area. Thrombus material was removed followed by placement of two stents in each of the left sided pulmonary veins at the first bifurcations. However, the patient died 14 days after the ablation procedure. Selective autopsy of the left lung revealed diffuse alveolar damage, disseminated intravascular coagulation, multiple thrombi formation, and haemorrhagic infarctions. CONCLUSIONS: PV stenosis may occur very early after the ablation procedure. Delayed diagnosis can be fatal. The early stenosis may result in thrombus formation in the left atrium and PVs and in this case surgery should be considered.

Adult↗
PubMed2004

[Expression of basic fibroblast growth factor in dental pulp during root development of permanent teeth].

OBJECTIVE: The purpose of this study was to investigate the changes of basic fibroblast growth factor (bFGF) expressed in normal human dental pulp at different root development stages of permanent teeth. METHODS: Based on the teeth root development status, the pulp tissues were classified into three groups: root just starting development, being in development and apical closed. The pulps were immunohistochemically examined by use of bFGF antibody. RESULTS: Staining was strongly positive in immature permanent teeth, especially at the stage of root just starting development. Image analysis indicated that the gray values of positive reaction in three groups were statistically different (P < 0.001). For the first group, the gray value of the outer pulp was higher than that of the pulp core. For the second group, the pulp core has a higher gray value in the coronal pulp, while a lower value in root pulp compared to the outer pulp. CONCLUSION: With the development of root formation, the expression of bFGF in dental pulp shows different characteristics. bFGF may play a role in dental pulp development and maturation.

Dental Pulp↗
PubMed2003

Sol-gel-derived titanium oxide/copolymer composite based glucose biosensor.

A new type of sol-gel-derived titanium oxide/copolymer composite material was developed and used for the construction of glucose biosensor. The composite material merged the best properties of the inorganic species, titanium oxide and the organic copolymer, poly(vinyl alcohol) grafting 4-vinylpyridine (PVA-g-PVP). The glucose oxidase entrapped in the composite matrix retained its bioactivity. Morphologies of the composite-modified electrode and the enzyme electrode were characterized with a scanning electron microscope. The dependence of the current responses on enzyme-loading and pH was studied. The response time of the biosensor was < 20 s and the linear range was up to 9 microM with a sensitivity of 405 nA/microM. The biosensor was stable for at least 1 month. In addition, the tetrathiafulvalene-mediated enzyme electrode was constructed for the decrease of detection potential and the effect of three common physiological sources that might interfere was also investigated.

Adsorption↗
PubMed2003

Co-immobilized microbial biosensor for BOD estimation based on sol-gel derived composite material.

A novel type of biochemical oxygen demand (BOD) biosensor was developed for water monitor, based on co-immobilizing of Trichosporon cutaneum and Bacillus subtilis in the sol-gel derived composite material which is composed of silica and the grafting copolymer of poly (vinyl alcohol) and 4-vinylpyridine (PVA-g-P(4-VP)). Factors that influence the performance of the resulting biosensor were examined. The biodegradable substrate spectrum could be expanded by the co-immobilized microorganisms. The biosensor prepared also exhibited good reproducibility and long-term stability. Good agreement was obtained between the results of the sensor BOD measurement and those obtained from conventional BOD(5) method for water samples.

Bacillus subtilis↗
PubMed2003

[An observation of the effects of Tiopronin on the oxygen free radicals in severely scalded rats receiving delayed fluid resuscitation].

OBJECTIVE: To observe the harmful effects of oxygen free radicals and the protective roles of Tiopronin in severely scalded rats after delayed fluid resuscitation. METHODS: Rats inflicted with 30% III degree scald on the back were employed as the model. They were divided into delayed resuscitation (D) and Tiopronin treatment (T) groups. The changes in superoxide dismutase (SOD) and malonyldialdehyde (MDA) in plasma and subeschar fluid were determined at 24 to 48 postburn hours (PBHs) by means of electron spin resonance (ESR) technique and other routine methods. And the pathomorphological changes in the heart, liver, kidneys and small intestine, and changes in the blood biochemical indices were simultaneously determined. Normal rats were taken as control group (N). RESULTS: The plasma SOD level was was lower than that in N group, while the MDA content in plasma and subeschar fluid in D group was much higher than that in N group. Changes in all the blood biochemical and internal organ pathomorphology were more obvious in the D group. on the other hand, the rat plasma SOD level in T group increased obviously (P < 0.01) while the MDA contents was decreased in T group (P < 0.05) when compared with those rats of D group. In addition, the internal organ pathomorphology and blood biochemical indices were improved evidently in T group. CONCLUSION: Oxidative stress injury was evoked in severely scalded rats after delayed fluid resuscitation, and it could be protected to some extent by Tiopronin.

Animals↗
PubMed2003

[Relationship of caries experience between primary teeth and the first permanent molars in 100 children of 6-year-old].

OBJECTIVE: To investigate the correlation of caries experience between primary teeth and the first permanent molars. METHODS: A total of 100 school children 6 years old were surveyed. The caries diagnosis criteria defined by WHO were employed. The data were statistically analyzed by use of SAS. RESULTS: Fisher's exact test showed that there was association between the caries experience of primary teeth and that of the first permanent molars in 6-year-old children. The average dmft of primary teeth was in positive correlation with DMFT of the first permanent molars(r = 0.5629). The results were statistically significant. CONCLUSION: The primary tooth caries experience may play an important role in predicting permanent tooth caries. More attention was suggested to pay to the children with more primary teeth decayed.

Child↗
PubMed2003

[Expression of basic fibroblast growth factor in dental pulp of immature permanent teeth].

OBJECTIVE: To investigate the expression of basic fibroblast growth factor (bFGF) in normal human dental pulp of immature permanent teeth. METHODS: The teeth root development has been completed 1/3-3/4. Their pulps were immunohisto-chemically examined by use of bFGF antibody and image analysis techniques were used for evaluation. RESULTS: Staining was strongly positive in immature permanent teeth pulp. Image analysis indicated that in the coronal pulp, the gray value of the pulp core was higher than that of the outer pulp, while in the root pulp was the opposite (P < 0.05). CONCLUSION: bFGF may play a role in dental pulp development and maturation.

Adolescent↗
PubMed2003

[Characteristics and sources of trace elements in ambient PM2.5 in Beijing].

To understand concentration levels and sources of trace elements in PM2.5(particulate matter with aerodynamic diameters less than 2.5 microns) concentration and composition in the ambient air of Beijing, weekly samples were simultaneously collected for one year in Chegongzhuang and Qinghuayuan. Trace elements exhibited similar significant weekly variations. The strongest weekly shift occurred in winter, which reached as high as a factor of 1.6 for two consecutive weeks. No obvious seasonal pattern was found for trace elements except for that their average concentrations were much higher in winter. The EFs of trace elements were lowest in spring, probably due to frequent dust storms resulting in reduced contribution of anthropogenic sources and increased contribution of soil dust. The ambient concentrations of Se, Br, and Pb were about 1000-8000 times higher than those expected from the crustal soil in Beijing. Se was most enriched in PM2.5, reflecting the characteristics of fine particles from coal burning in Beijing. The annual mean concentration of Pb of 0.31 microgram.m-3 did not exceeded the WHO annual standard, but was at very high level compared to those measured in Los Angles and Brisbane. Comparison analysis of Pb with Br and Se shows that coal burning is probably another major source of Pb in PM2.5 other than vehicle emission.

Air↗
PubMed2003

[An epidemiological survey on fusion of deciduous teeth of 4286 kindergarten children in Shenyang city].

OBJECTIVE: To clarify the occurrence and distribution of the fusion of deciduous teeth in Shenyang. METHODS: By using cross-sectional study, 4286 children were examined, who aged from 2 to 6 years in 37 kindergartens. RESULTS: Of 4286 children investigated, fusion of the deciduous teeth were detected in 65 children (1.52 percent) without sex predilection. The fused teeth typically occurred unilaterally (68.75 percent), and mainly located in the anterior region, more frequently in the mandibular (91.25 percent) than that in the maxillary arch. 12 cases were bilaterally symmetrical (18.46 percent). Two rare cases were found with fused teeth, one occurred in central incisor, lateral incisor and canine, the other occurred between two molars with two incisors fused in the same side. Fused teeth in two cases had caries. CONCLUSION: The occurrence of the fused teeth may cause some complications. Pediatric dentists should pay attention to the fused teeth occurred in preschool children.

Child↗