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Biomedical subjects

J Chen

Publications and source records attributed to J Chen.

At least 685 records · Page 38Linked to original sources
PubMed2001

[Surface stress analysis of distal extension removable partial denture retained with two types of semi-precision attachments].

OBJECTIVE: The aims of this study are to analyze the surface stress of the periodontal supporting bone of the bilateral distol extension removable partial denture which is retained by using intra-coronal or extra-coronal semi-precision attachment, and to characterize the biomechanics of these two designs by using a strain gauge. METHODS: A fresh human mandible specimen with 76|67 missing and six bilateral partial removable denture retained with six semi-precision attachments were made, including three attachments with intra-coronal studs and three attachments with extra-coronal vertical bars. A total of six 45 degrees rosette strain gauges were bonded at six prepared points on the surface of the mandible to measure the surface stress, including the middle point between 76 of the buccal edentulous alveolar crest area under the denture base verge(point 1), the distal buccal cervix of 5 (point 2), the buccal apical area of 5 (point 3), the buccal middle area of 34 roots (point 4, 5), the lingual middle area of 5 root (point 6). The static loads of 14N, 28N and 42N were applied vertically, buccally 45 degrees, lingually 45 degrees at the middle point of the 6|6 occlusal surface. The micro-strain was recorded, and the maximal/minimal principle stresses were calculated for each RPD and each point. The stress characteristics of these two types of attachments were compared and analyzed. RESULTS: In most situations, the stress of these two semi-precision attachments showed significant differences. The vertical load: The stress values of these intra-coronal and extra-coronal attachments at points 1, 2, 3, 4, 6 differed significantly(P < 0.05), including points 1, 2, (sigma intra < sigma extra) and points 3, 4, 6(sigma intra > sigma extra). Buccal loads: The stress values of these intra-coronal and extra-coronal attachments at points 1, 2, 3, 4, 5 differed significantly(P < 0.05), including points 1, 2(sigma intra < sigma extra) and points 3, 4, 5(sigma intra > sigma extra). Lingual loads: The stress values of these intra-coronal and extra-coronal attachments at points 2, 3, 4, 6 differed significantly (P < 0.05, sigma intra > sigma extra). The intra-coronal attachment generally produced higher stress at the site of the alveolar bone around the abutment than the extra-coronal attachment, but extra-coronal attachment produced higher stress at the edentulous alveolar crest and the distal cervical alveolar bone of the distal abutment than the intra-coronal attachment. CONCLUSION: The intra-coronal attachment is suggested to be applied in some cases that the periodontal condition of distal abutment was good, and the extra-coronal attachment is suggested to be used in some cases that the condition of the edentulous alveolar crest is fairly good, while the periodontal condition of the distal abutment was relatively weak.

Adult↗
PubMed2001

[Expression of vascular endothelial growth factor in oral squamous cell carcinoma].

OBJECTIVE: The aim of this study was to estimate the expression of vascular endothelial growth factor(VEGF) and intratumoral microvessel density (IMVD) in oral squamous cell carcinoma(SCC). METHODS: A total of 60 cases of oral squamous carcinoma were immunohistochemically stained with a SP method by using monoclonal antibodies of VEGF and CD34. RESULTS: There was no significant difference in the expression of VEGF in different TNM stages and lymphe node metastases of oral squamous cell carcinoma. The expression of VEGF showed no relation with pathologic grades, but IMVD expression differed significantly in SCC. The carcinoma in grade I and IV of IMVD differed significantly in expression of VEGF. CONCLUSION: It indicates the change of IMVD may resulted from the change of VEGF in oral SCC.

Adult↗
PubMed2001

[The influences upon the passive tensile of the masticatory muscles and ligaments by Herbst appliance under various bite reconstruction--a three dimensional finite element analysis].

OBJECTIVE: This study aimed to provide some biomechanical references for the clinical use and improvement of Herbst appliance. METHODS: The three-dimensional model of the 'Temporomandibular joint mandible Herbst appliance system' was set up by SUPER SAP software (version 9.3). On this model, the passive tensile in the masticatory muscles and ligaments were analyzed under various bit reconstruction designed according to specified advanced displacement and vertical bite opening. RESULTS: When Herbst appliance drove the mandible forward, there was not any tensile in the medial, lateral pterygoid and the collateral ligament, while the temporalis, the deep paret of masseter, the stylomandibular ligament, and the sphenomandibular ligament were passively drawn. Under various bite reconstruction, the passive tensile in the medial temporalis, the posterior temporalis, the stylomandibular ligament and the sphenomandibular ligament increased with the amount of the advancement of the mandible; The passive tensile in the posterior temporalis and the deep part of masseter increased with the amount of vertical bite opening of the mandible. CONCLUSION: The StL, SpL, PT and AT played an important role in functional reconstruction of mandible by Herbst. All five group of bite reconstruction (3-7 mm advancement, 4-2 mm vertical bite opening of the mandible) designed by this study can be selected in clinic according to the patient's capability of adaptation, the extent of malocclusion and the potential and direction of growth.

Finite Element Analysis↗
PubMed2001

[The influences of the stress distribution on the condylar cartilage surface by Herbst appliance under various bite reconstruction--a three dimensional finite element analysis].

OBJECTIVE: The distribution of stress on the surface of condylar cartilage was investigated. METHODS: Three-dimensional model of the 'Temporomandibular joint mandible Herbst appliance system' was set up by SUPER SAP software (version 9.3). On this model, various bite reconstruction was simulated according to specified advanced displacement and vertical bite opening. The distribution of maximum and minimum principal stress on the surface of condylar cartilage were computerized and analyzed. RESULTS: When Herbst appliance drove the mandible forward, the anterior condyle surface was compressed while the posterior surface was drawn. The trend of stress on the same point on the condyle surface was consistent in various reconstruction conditions, but the trend of stress on various point were different in same reconstruction conditions. CONCLUSION: All five groups of bite reconstruction (3-7 mm advancement, 4-2 mm vertical bite opening of the mandible) designed by this study can be selected in clinic according to the patient's capability of adaptation, the extent of malocclusion and the potential and direction of growth.

Cartilage, Articular↗
PubMed2001

[One stage otoplasty treatment for congenital malformations of the auricle and middle ear].

OBJECTIVE: To investigate the application of one stage otoplasty for congenital atresia of the external acoustic canal and malformations of the middle ear and the auricle. METHOD: Patients with the ear malformations were given surgical reconstruction of one stage otoplasty. The auricle was reconstructed with the rib which was encapsulated with the superthin temporal flap. According to the malformations of the middle ear in patients, I style tympanoplasty and III style tympanoplasty were carried out respectively. All patients were performed myringoplasty with temporal fascia and reconstructed the external acoustic canal with full thickness skin-grafting. RESULT: A long term follow-up (4-6 years) demonstrated that 11 ears were survival of which 8 ears figuration were ideal. The hearing improvement was observed in all patients. CONCLUSION: One stage otoplasty is effective for treatment of the congenital malformations of the external and middle ear.

Adult↗
PubMed2001

[Clinical analysis of 62 cases laryngeal papilloma in children].

OBJECTIVE: To investigate the clinical features of laryngeal papilloma in children. METHOD: In a group of 62 patients with laryngeal papilloma in children, the tumors of 28 patients were cut under the direct laryngoscope, 34 patients were treated with laryngeal micro-laser operation. RESULT: The post-operation followup ranged from 2 to 5 years, the cure rate of 2 years was 51.61%. CONCLUSION: The clinical features of this disease include rapid development, a large lesion, and it is often found in the infraglottic cavity. Furthermore, we believe that in order to eliminate the tumors more accurately and decrease recurrence, micro-laser surgery and the use of interferon is very necessary.

Adolescent↗
PubMed2001

[Analysis of chlorogenic acid in sunflower cake by thin-layer chromatography].

The analytical method of chlorogenic acid in sunflower cake by thin-layer chromatography(TLC) was developed. With 36% acetic acid as mobile phase and on the polyamide film plate, the Rf value of chlorogenic acid was 0.61. The calibration curve was linear in the range of 0.05 microgram-0.6 microgram of chlorogenic acid with the detection limit of 0.025 microgram and the average recovery of 97.53%. The inter-plate accuracy of chlorogenic acid was 2.57%. With 70% ethyl alcohol as extracting solvent and 30 min of extraction time, the amount of chlorogenic acid in the extract, the residue amount of chlorogenic acid in the sunflower cake and the extraction rate were determined and calculated by applying this method. The optimal time of extraction was found.

Calibration↗
PubMed2001

[The study on the occult metastases to cervical lymph node in squamous cell carcinoma of the larynx and hypopharynx].

OBJECTIVE: To study the metastastic regularity of cervical lymph node in squamous cell carcinoma of the larynx and hypopharynx, which will provide some theoretical basis for surgeon to use selective neck dissection (SND) in some patients with carcinoma above. METHOD: Sixty-nine originally cN0 staged neck dissection specimens from 40 patients were evaluated using mutipl-level sectioning in 4 microns intervals, which were respectively processed by H&E-staining and immunostaining with an antibody to cytokeratin (CK AE3). These patients weren't given any treatment (radiotherapy or chemotherapy or surgery in neck) before surgery. All cases had been followed up 1 year or more. RESULT: The examination of lymph nodes from 40 patients revealed 31 (0.59% 31/2219) occult metastases in 14 (35% 14/40) patients. Among them, six patients with supraglottic cancer, 1 patient with transglottic cancer and 7 patients with hypopharyngeal cancer. There were no occult metastases to cervical lymph node among 9 patients with glottic cancer. All occult metastases mainly located in ipsilateral level II and/or level III. Occult metastases weren't found in nodes from level I, level IV and level V. CONCLUSION: The study further prove that metastases to cervical lymph node mainly occur in the ipsilateral level II and level III among patients with carcinoma of the larynx and hypopharynx. According to the risks of occurring occult metastases to cervical lymph node, we suggest applying to ipsilateral or bilateral SND (level II and level III be dissected) among patients with carcinoma of the larynx and hypopharynx which staged T2-T4 N0M0 clinically.

Adult↗
PubMed2001

[Diagnosis and surgical treatment of carotid body tumor].

OBJECTIVE: To promote the rate of diagnosis and successful rate of operation for carotid body tumor. METHOD: 26 cases of the 30 patients with carotid body tumor were performed by DSA and 5 cases of them, feeding arteries of tumor were embolized with gelfoam through superlective catheterization, preoperativelly. The tumor was resected under carotid adventitial plane in 12 cases, with extracervical artery in 8 cases and with tumor-carotid segment block in 10 cases. RESULT: Of the 30 cases, no one died from operation or cerebral vascular complications. DSA plays a significant role in diagnosis of the tumor. Intraoperative bleeding can be remarkably reduced if feeding arteries were embolized preoperativelly. The tumor fixed to segment of the carotid arteries block was resected and the reconstruction of vasculature was unnecessary as soon as candidates were certified to be qualified by carotid training and DSA or/and TCD tests. Follow up of these 30 patients revealed that 25 of them survived free from cerebrovascular complications and tumor recurrence for 5 months-10 years. 1 of them died from traffic accident 2 year after operation, 4 of them had lost communication. CONCLUSION: DSA is a most authritative approach for diagnosis of carotid body tumor, DSA and TCD tests play a key role to resect carotid artery without reconstruction. Successful operation based on a precise preoperative evaluation, choice of operative ways and proper procedure.

Adult↗
PubMed2001

[Determination of rutin and quercetin in mulberry leaves by high performance capillary electrophoresis].

Rutin and quercetin are the main effective components of mulberry leaves with the functions of controlling the increase of fat in serum and controlling the formation of arterio-sclerosis. In this article a high performance capillary electrophoretic(HPCE) method was used to separate and determine rutin and quercetin in mulberry leaves collected from different periods, different places and different kinds in Xinjiang. Electrophoretic conditions were as follows: a capillary tube (75 microns i.d. x 57 cm (effective length, 50 cm)), with 10 mmol/L dihydrogen sodium phosphate-20 mmol/L sodium borate containing 15% methanol as the running buffer (pH 8.62) and an applied voltage of 20 kV, at 25 degrees C, detected at a wavelength of 245 nm. Under the optimum conditions, rutin and querctin were separated successfully from other components within 12 minutes. The corrected peak areas of rutin and quercetin increased linearly with the increase of their concentrations in the range of 4.4 mg/L-28.8 mg/L and 1.8 mg/L-145.8 mg/L respectively. The corresponding regression equations for rutin and quercetin were Y = 71.60 rho + 30.51 (r = 0.9991) and Y = 315.17 rho - 929.70 (r = 0.9949) respectively, and the recoveries were 95.64% and 99.36%. The analytical results demonstrate the method is simple, quick and well reproducible, and can be used as a reliable tool for the quality control of mulberry leaves.

Drugs, Chinese Herbal↗
PubMed2001

[Knocking out of CEK2 and CSK1 affect the phenotype of Candida albicans].

We have cloned two novel mitogen-activated protein kinase (MAPK) genes CEK2 and CSK1 from Candida albicans strain SC5314. The heterozygous and homozygous cek 2 and csk 1 mutants were obtained by homologous recombination. The cek2 and csk1 null mutant strains CAJ3 and CAJ6 grew as wrinkled clonis on solid YPD medium. Expression of CEK2 gene in strain CAF3-1 repressed the filamentous growth of the strain weakly. Two-hybrid results showed Cek2 and Csk1 could not interact with Cph1 and Hst7 directly. Cek2 and Csk1 might cooperate with the filamentous transcriptional repressor Tup1.

Candida albicans↗
PubMed2001

[Biosynthesis of glutathione: construction of ATP regeneration system between recombinant E. coli and S. cerevisiae].

An ATP regeneration system between two microorganisms, in which recombinant E. coli II-1 and S. cerevisiae WSH-J702 were used as the biosynthesis enzymes source of glutathione and ATP, respectively, was constructed by using glucose as an energy substrate. Yeast cells after permeable treatment could hardly consume glucose. The glycolysis pathway of yeast was started by adding 1.0 mmol/L AMP and 0.05 mmol/L NADH simultaneously. GSH biosynthesis in the coupling system was improved with increasing glucose concentration to 400 mmol/L, where the concentration of GSH reached 10.4 mmol/L (3.2 g/L). Both the coupling system and the non-coupling system with ATP added could hardly produce GSH under the absence of magnesium. The low efficiency of ATP regeneration system constructed was probably caused by the chelation between magnesium and ATP. By adding magnesium to the coupling system, a final concentration of GSH, 14.3 mmol/L (4.4 g/L), was achieved at 6 h of reaction.

Adenosine Triphosphate↗
PubMed2001

[Construction of recombinant E. coli with high glutathione biosynthetic activity and the biosynthetic process].

A recombinant strain E. coli II-1, which exhibited high glutathione (GSH) biosynthetic activity and high stability, was constructed by transforming plasmid pGH501 which contains gene gsh I and gsh II into a wild type strain E. coli II. 4 g/L GSH accumulated extracellularly by using toluene-treated cell. In GSH biosynthetic system, GSH production was improved by increasing the concentration of L-glutamate, while inhibited by L-cysteine if it's concentration was beyond 20 mmol/L. In GSH biosynthetic reaction, the apparent little consumption of L-glutamate and glycine was concluded experimentally to be that toluene-treated E. coli II-1 cells still contained high concentration of L-glutamate and glycine. According to the change of energy cofactor in the GSH biosynthetic process, a possible GSH biosynthetic mechanism controlled by E. coli II-1, was proposed: the energy donator of reaction catalyzed by glutathione synthetase (GSH-II) was ADP but not ATP, the reaction was rate-limited step within the whole GSH biosynthetic process, high concentration of ADP might inhibit the activity of GSH-II. Further degradation of GSH was prevented by the addition of 100 mmol/L L-serine and potassium borate mixture. In such case, 23.0 mmol/L (about 7.1 g/L) GSH accumulated at 3 h.

Adenosine Diphosphate↗
PubMed2001

[Construction of the full-length cDNA clone of Chinese virulent strain--F114].

Seven subclones covered the complete genome of classical swine fever virus Chinese virulent strain F114 were obtained by reverse transcription PCR. The complete nucleotide sequence of the genome of strain F114 was determined by sequencing. The cDNA fragments were then assembled and inserted downstream of a T7 promoter in pBluescript II sk+ plasmid vector to obtain the full-length cD-NA clone sk-12297. Homology comparison of the nucleotide and amino acid sequence of strain F114 with the known sequences of HCLV, Brescia and Alfort showed 95.70%, 96.80%, 86.03% identity in nucleotide and 97.41%, 98.54%, 93.33% identity in amino acid respectively.

Animals↗
PubMed2001

[Studies on antimicrobial activity of extracts from thyme].

The extracts from thyme by water and ethanol, thyme essential oil, thymol and carvacrol were used as antimicrobial agents in this paper. The results show that all antimicrobial agents used have strong inhibition activity against Staphalococcus aureus, Bacillus subtilis, Escherichia coli.

Anti-Bacterial Agents↗
PubMed2001

[Studies on the determination of serum thymic factor by capillary zone electrophoresis].

The determination of serum thymic factor (FTS) by capillary zone electrophoresis was described. The optimum ionic concentration and the pH value of buffer system was examined through orthogonal analysis. The optimum conditions found to be 0.05 mol/L sodium tetraborate, 0.01 mol/L phosphate buffer at pH 8.70, working voltage at 12 kV and wavelength at 200 nm. The recoveries for FTS standards added to the bovine serum albumin and serum samples were measured. The values of the relative standard deviation(RSD), recovery and detection limit were 7.62%, 80.28% and 40 ng/ml respectively. The development of this method provide another way for studying the relations of zinc and thymic factor and investigating the effect of zinc on immune function.

Electrophoresis, Capillary↗
PubMed2001

[Tissue interaction with bioglass ceramic implanted in the rabbit cornea].

PURPOSE: To evaluate the biocompatibility and 'healing' of Bioglass Ceramic(BGC) in the cornea. METHODS: BGC dicks (8 mm in diameter, 0.5 mm thick, 20-70 microns pore diameter, 37-62% porosity, 7.8 mm radius of curvature) were implanted in 11 New Zealand albino rabbits after a free-hand intralamellar dissection. The eyes were examined by slit-lamp biomicroscope up to seven months postoperatively. The corneas were removed at seven month (one eye at eight month), then were examined by light microscope. RESULTS: Five of 11 dicks of BGC were extruded. All implant of BGC with 51-62% porosity were broken and then extruded. A large part of implants led to markedly edematous with severe degrees of corneal neovascularization within one month postoperatively. The corneal lamella before implants became not clear in all eyes after two months. Lipid deposits occurred in four eyes. It is difficulty to observe the 'healing' process of BGC in the cornea because the BGC is too hard to be cut in spite of being soft by 4% hydrochloric acid for four to ten days before cutting. CONCLUSION: Our findings suggest that BGC with above parameters is not suitable as peripheral keratoprosthetic materials because of its rough, hard, thick and breakable.

Animals↗