[Exploration and practice of Peking University Model to improve the clinical teaching effect of clinical postgraduates majoring in periodontology].

The number of patients with periodontal disease in China is large, and the ratio of doctors to patients is seriously imbalanced, especially in the insufficient number of periodontal specialists and periodontal teachers. Strengthening the cultivation of professional postgraduates in periodontology can effectively solve this problem. This paper summarizes the experiences of Peking University School and Hospital of Stomatology in the teaching of periodontal postgraduate students for more than 30 years, in cluding teaching objectives formulation, teaching resources allocation and enhancement of the quality control system of clinical teaching, for ensuring that the periodontal professional postgraduates could reach the expected level after training. This formed the current "Peking University Model". There are both opportunities and challenges in clinical teaching of periodontal postgraduates in domestic stomatology community. The authors hope that the continuous exploration and improvement of this teaching system will promote the vigorous development of clinical teaching for the postgraduates majoring in periodontology in China.

[Comparison of two training protocols in periodontal surgery teaching for undergraduate students].

Objective: To compare the efficacies of two training protocols, i.e. the multimedia instruction and the conventional method, in periodontal surgery teaching for undergraduate students. Methods: One hundred and twenty-three dental undergraduates in their pre-clinical training course were recruited and divided into two groups according to the learning grade matching principle: the experimental group (multimedia instruction, 60 students) and the control group (conventional method, 63 students). The teaching aim was to train the students gingivectomy and periodontal flap surgery by using the pig jaws. The conventional teaching method of teacher-demonstrating and student-practicing was used in the control group, and the practice time of the students' for each surgery was 45 minutes. A standardized teaching video combined with the teachers' explanations of the key steps was used in the experimental group. The students' practice time for each surgery was 60 minutes. The efficacy of teaching protocol was evaluated by the teachers according to the scoring criteria set by the teaching group. Results: In gingivectomy training, accuracy of fixed points, angle of postoperative gingival margin and morphology of gingiva of the experimental group were better than those of the control group. The experimental group also had more complete and continuous excised gingivae and more thorough adjacent gingival removal. The total scores of the experimental group were significantly higher than those of the control group (92.8±2.6 vs. 89.9±3.7, P<0.05). In periodontal flap surgery training, the experimental group operated the blade around the shape of the tooth better in internal bevel incision than the control group. Additionally, the incision position of internal bevel incision, periosteal integrity after flapping and flap depth of the experimental group were better than those of the control group. Besides, the experimental group had smoother flap edge and more thorough debridement. The total scores of the experimental group were significantly higher than those of the control group (92.2±4.1 vs. 89.2±4.4, P<0.05). Conclusions: The teaching efficacy of multimedia instruction was better than that of the conventional method. Its value needs to be further tested in future teaching practice.

[Influence of vitamin D receptor FokI polymorphism on expression of CYP24A1 in periodontal cells].

OBJECTIVE: There is asingle nucleotide polymorphism (SNP) in the exon 2 of the vitamin D receptor (VDR) gene that can be distinguished using the restriction endonuclease FokI, and accordingly divided into three genotypes: FF, Ff and ff. VDR-FokI polymorphism was the only known SNP that could alter the protein structure of VDR. CYP24A1 is the gene encoding vitamin D 24 hydroxylase and is a vitamin D responsive gene. The influence of rs2228570 on transcriptional activation by VDR in human gingival fibroblasts (hGF) and periodontal ligament cells (hPDLC) was investigated in this study. METHODS: hGF and hPDLC of 12 donors' were primarily cultured and genomic DNA was extracted. A part of genomic DNA with the length of 267 bp was obtained using PCR, which contained the SNP. VDR-Fok I genotypes were determined according to the results of restriction fragment length polymorphism. hGF and hPDLC were stimulated with 10 nmol/L 1α,25 dihydroxy vitamin D3 (1,25OH2D3) or 1 000 nmol/L 25 hydroxy vitamin D3 (25OHD3) for 48 h before RNA was extracted. Then VDR antagonist ZK159222 was used or not used during 1,25OH2D3 or 25OHD3 stimulation with hGF and hPDLC. After 1,25OH2D3 stimulation for 48 h, the proteins in hGF and hPDLC were also collected. The protein expressions of CYP24A1 and VDR were detected using Western blot. RESULTS: Among the 12 donors' cell cultures, the number of FF, ff and Ff genotypes was 4, 3 and 5, respectively.After stimulation with 1,25OH2D3 or 25OHD3 for 48 h,CYP24A1 mRNA levels in FF-hGF were significantly higher than those in other hGF genotypes(1,25OH2D3: F=31.147, P<0.01; 25OHD3: F= 32.061,P <0.01), as was in FF-hPDLC (1,25OH2D3: F=23.347, P<0.01; 25OHD3: F=32.569,P<0.01). When ZK159222 was used before 1,25OH2D3 stimulation, this statistically significant difference disappeared (hGF: F=0.246, P=0.787; hPDLC: F=0.574, P=0.583). When ZK159222 was used before 25OHD3 stimulation, the trend was similar (hGF: F=1.636, P=0.248; hPDLC: F=0.582, P=0.578).After stimulation with 1,25OH2D3 for 48 h, CYP24A1 protein levels in FF-hGF were significantly higher than those in the other hGF genotypes (F=12.368, P <0.01), as was in FF-hPDLC (F=15.749, P <0.01). In hGF and hPDLC, the mRNA or protein expression of VDR of different genotypes was not significantly different under different stimulation conditions.The paired comparison showed that there was no statistically significant difference between the expression of CYP24A1 in hGF and that in hPDLC under all the stimulation conditions, as was the expression of VDR. CONCLUSION: In hGF and hPDLC, the FF-VDR genotype is associated with the more remarkable up-regulation of CYP24A1than the other genotypes, indicating that transcriptional activation of FF-VDR might be higher than those of other vitamin D receptors.

[Exploration of training pattern on periodontal probing during pre-clinical periodontal practice of undergraduate students].

Objective: To explore the training pattern of periodontal probing practice so as to improve the accuracy of probing depth measurements of undergraduate students. Methods: Sixty-two undergraduate dental students in their pre-clinical training course were divided into two groups (31 students in each group): the reform group and the control group. The students in reform group learned and practiced periodontal probing by using transparent gingiva models for 30 minutes, and using conventional periodontal probing models for further 90 minutes in two sessions. The total practicing time was 2 hours. The students in control group learned and practiced periodontal probing using conventional periodontal probing models only for 1 hour of practicing time. After the training, new conventional periodontal probing models were used to evaluate the accuracy of probing depth measurements of the students in the two groups. The probing depths of Ramfjord index teeth were recorded by the students and were compared with the results of an experienced teacher's measurements. Results: The percentage of absolutely consistent sites in the reform group (63.4% [708/1 116]) was significantly higher than that of the control group (60.0% [670/1 116]) (P=0.012). In both reform group and control group, the percentages of absolutely consistent sites of the incisors (reform group: 69.1% [257/372], control group: 65.9% [245/372]) were significantly higher than those of the molars (reform group 58.9% [219/372], control group 54.3% [202/372])(P< 0.01), meanwhile, the percentages of absolutely consistent sites of the buccal-lingual sites (reform group: 88.7% [330/372], control group: 80.4% [299/372]) were significantly higher than those of the interproximal sites (reform group: 50.8% [378/744], control group: 49.9% [371/744])(P<0.01). Conclusions: The comprehensive reform of periodontal probing training could improve the accuracy of probing depth measurement of the undergraduate students. During the pre-clinical practice, probing training in the molar areas and the interproximal sites should be reinforced.

[An modified culture method of primary human gingival epithelial cells].

OBJECTIVE: To establish a stable primary culture method of human gingival epithelial cells, with a higher successful rate and shorter culture time. METHODS: Nine patients who received "crown-lengthening surgery" with relatively healthy periodontal conditions were selected (n=9). Gingival samples were collected from the 9 donors during gingivectomy. Gingival epithelial cells were isolated and cultured by both an advanced enzyme digestion method and a tissue explant method. In the advanced enzyme digestion culture process, 2.5 g/L DispaseIIwas used to separate the epithelial tissue part from the connective tissue part, which lasted for one night. Then the epithelial tissues were digested by 0.025% trypsin without EDTA for 10 minutes, and centrifuged by keeping the digested epithelial tissues that remained. This advanced method not only decreased the concentration and digesting time of the two above-mentioned enzymes, but also simplified the centrifugel process. The tissue explant method was not changed too much compared with the original method. Growing processes of the primary cells cultured by the two methods were observed and recorded respectively, and indirect immunocytochemical staining was used to identify the type of cultured cells. At the same time, successful rates and cell culture time were also compared between the two methods. RESULTS: Human gingival epithelial cells with typical morphology could be cultured within a shorter period by the advanced enzyme digestion method with a successful rate of 88.9%, and proliferated rapidly as sheets. After 10-14 d cells could be passaged, gradually turned to be like fibroblasts when passaged to the third generation, and eventually went to apoptosis. The primary culture time was longer by using the tissue explant method, and approximately after 17-22 d cells could be passaged, although the successful rate was the same as the enzyme digestion method. Cytokeratin staining was both positive by indirect immunocytochemical staining of cells. CONCLUSION: Primary human gingival epithelial cells cultured by the advanced enzyme digestion method could grow faster and be passaged to the second generation successfully, which could supply a stable origin for cellular experiments.

[An modified culture method of primary human gingival epithelial cells].

OBJECTIVE: To establish a stable primary culture method of human gingival epithelial cells, with a higher successful rate and shorter culture time. METHODS: Nine patients who received "crown-lengthening surgery" with relatively healthy periodontal conditions were selected (n=9). Gingival samples were collected from the 9 donors during gingivectomy. Gingival epithelial cells were isolated and cultured by both an advanced enzyme digestion method and a tissue explant method. In the advanced enzyme digestion culture process, 2.5 g/L DispaseIIwas used to separate the epithelial tissue part from the connective tissue part, which lasted for one night. Then the epithelial tissues were digested by 0.025% trypsin without EDTA for 10 minutes, and centrifuged by keeping the digested epithelial tissues that remained. This advanced method not only decreased the concentration and digesting time of the two above-mentioned enzymes, but also simplified the centrifugel process. The tissue explant method was not changed too much compared with the original method. Growing processes of the primary cells cultured by the two methods were observed and recorded respectively, and indirect immunocytochemical staining was used to identify the type of cultured cells. At the same time, successful rates and cell culture time were also compared between the two methods. RESULTS: Human gingival epithelial cells with typical morphology could be cultured within a shorter period by the advanced enzyme digestion method with a successful rate of 88.9%, and proliferated rapidly as sheets. After 10-14 d cells could be passaged, gradually turned to be like fibroblasts when passaged to the third generation, and eventually went to apoptosis. The primary culture time was longer by using the tissue explant method, and approximately after 17-22 d cells could be passaged, although the successful rate was the same as the enzyme digestion method. Cytokeratin staining was both positive by indirect immunocytochemical staining of cells. CONCLUSION: Primary human gingival epithelial cells cultured by the advanced enzyme digestion method could grow faster and be passaged to the second generation successfully, which could supply a stable origin for cellular experiments.

A controlled study of reverse transcriptase in serum and CSF of HIV-negative patients with ALS.

Reverse transcriptase has been detected in the serum of HIV-negative patients with amyotrophic lateral sclerosis (ALS). An ALS-like disorder in HIV-positive patients can remit with antiretroviral therapy. Using the product enhanced assay technique, we measured reverse transcriptase activity in the serum and CSF of 23 HIV-negative patients with ALS and 21 neurologic disease controls. Results for CSF were not significant, whereas reverse transcriptase was detected in 56% of ALS sera vs 19% of controls.

[Determination of micro amounts of iodide in dairy products by ion chromatography with direct amperometric detector].

A method was developed for the determination of micro amounts of iodide in dairy products by ion chromatography with direct amperometric detection. The eluent used was 0.04 mol/L NaOH. The relative standard deviations of retention times and peak heights for 1 mg/L and 2 micrograms/L iodide solutions were 0.67%, 3.9% (n = 8) and 0.97%, 1.8% (n = 8), respectively. Calibration curves showed good linearity with r = 0.9991 (n = 8, from 10 micrograms/L to 160 micrograms/L), and with r = 0.9986 (n = 8, from 400 micrograms/L to 5 mg/L). The detection limit of iodide by this method was 1 microgram/L. The method has been used to analyse two kinds of milk powder and a kind of fresh milk. The recoveries were 89.0%, 86.0% and 84.1% for infant formula milk powder, mother's milk powder and fresh milk, respectively.

Simplified column-switching technology for the determination of traces of anions in the presence of high concentrations of other anions.

A binary eluent model was proposed to study the retention behavior of trace anions in the presence of high concentrations of co-eluent anions. According to this model, the effect of the matrix on the retention of trace anions can be suppressed by using a high-concentration eluent. Based on the model, a simplified 'heart-cut' column-switching technology was proposed, in which the column-switching time window can be determined directly by standard solution of the analyte. By using this technology, a detection limit of 50 microg/l was obtained for nitrate in the presence of 5,000 mg/l chloride and 250 mg/l sulfate. The effect of the matrix on the concentration efficiency of weak acid anions was studied according to the result of phosphate. The possibility of the determination of weak acid anion by the 'heart-cut' technology was also discussed. The technology has been applied for the determination of nitrate in high salinity sea water, the spike recovery is in the range of 89.2-101.3%.

Determination of aspartame by ion chromatography with electrochemical integrated amperometric detection.

In this paper, the separation and determination of the sweetener aspartame by ion chromatography coupled with electrochemical amperometric detection is reported. Sodium saccharin, acesulfame-K and aspartame were separated using 27.5 mmol/l NaOH isocratic elution on a Dionex IonPac AS4A-SC separation column. Aspartame can be determined by integrated amperometric detection without interference from the other two sweeteners. The method can be applied to the determination of aspartame in powered tabletop, fruit juice and carbonated beverage samples, and the results obtained by integrated amperometry were in agreement with those obtained using a UV detection method. A method for determining analytes with an NH2 group by ion chromatography with integrated amperometry was developed.

Ion chromatographic determination of taurine in medicine, nutrient capsule and human urine with electrochemical detection.

A very simple and sensitive method for the determination of taurine by ion chromatography with electrochemical integrated pulsed amperometry is firstly described. Taurine was determined using 160 mmol/l NaOH as eluent and a Dionex CarboPac PA1 separation column (250x4 mm I.D.) without the interference with ten kinds of common amino acids. The peak area response of taurine was linear in the range 0.1-20 microg/ml, the detection limit was 0.034 microg/ml. The method has been applied successfully in the determination of taurine in medicinal granule, nutrient capsule and human urine. The content determined in medicinal granule is consistent with that marked by the manufacturer.

Evidence that tumor necrosis factor alpha converting enzyme is involved in regulated alpha-secretase cleavage of the Alzheimer amyloid protein precursor.

The amyloid protein, Abeta, which accumulates in the brains of Alzheimer patients, is derived by proteolysis of the amyloid protein precursor (APP). APP can undergo endoproteolytic processing at three sites, one at the amino terminus of the Abeta domain (beta-cleavage), one within the Abeta domain (alpha-cleavage), and one at the carboxyl terminus of the Abeta domain (gamma-cleavage). The enzymes responsible for these activities have not been unambiguously identified. By the use of gene disruption (knockout), we now demonstrate that TACE (tumor necrosis factor alpha converting enzyme), a member of the ADAM family (a disintegrin and metalloprotease-family) of proteases, plays a central role in regulated alpha-cleavage of APP. Our data suggest that TACE may be the alpha-secretase responsible for the majority of regulated alpha-cleavage in cultured cells. Furthermore, we show that inhibiting this enzyme affects both APP secretion and Abeta formation in cultured cells.

A comparison of lidocaine, fentanyl, and esmolol for attenuation of cardiovascular response to laryngoscopy and tracheal intubation.

BACKGROUND: Laryngoscopy and tracheal intubation are known to increase sympathetic activity that may be detrimental to patients with pre-existing ischemic or hypertensive heart diseases. In order to alter the hyperdynamic consequences resulting from intubation during induction of general anesthesia, we chose esmolol, an ultra-short acting cardioselective beta-adrenergic blocker, to attenuate the cardiovascular responses during tracheal intubation in patients undergoing elective surgery. The efficacy of esmolol in this regard was carefully evaluated. METHODS: Eighty ASA physical status class I or II patients undergoing elective, non-cardiac procedures were included in a randomized, single-blinded study consisting of 4 groups with each group receiving a designated drug: group A received normal saline as control, while group B, group C and group D received lidocaine 2 mg/kg, fentanyl 3 micrograms/kg and esmolol 2 mg/kg, respectively. Monitoring included EKG, pulse oximetry, capnometry and arterial pressure. All patients were premedicated with diazepam 0.1 mg/kg 30 min before induction of general anesthesia. Each designated drug was given upon induction of anesthesia (time zero). Anesthesia was induced with thiopental 5 mg/kg and succinylcholine 1.5 mg/kg, and maintained with N2O, 1% isoflurane in 50% O2 and vecuronium. Intubation was carried out 3 min after the designated drug was given. Heart rate (HR) and systolic arterial blood pressure (SBP) were obtained every min for 10 min after induction. Either chi-square test or analysis of variances (ANOVA) was used for statistical comparison. A p value less than 0.05 was considered statistically significant. RESULTS: There was no difference in the demographic data among the four groups. After intubation, the incidence of tachycardia (HR > 100/min) was found in 3 of 20 (15%) patients in esmolol group, significantly lower than 17 of 20 (85%) patients in the control group, 15 of 20 (75%) patients in lidocaine group, and 11 of 20 (55%) patients in fentanyl group, respectively (p < 0.05). The incidence of hypertension (SBP > 180 mmHg) was found in 4 of 20 (20%) patients in esmolol group, significantly lower than 16 of 20 (80%) patients in control group and 14 of 20 (70%) patients in lidocaine group, respectively (p < 0.05), but not in 8 of 20 (40%) patients in fentanyl group. Besides, the incidence of hypertension in fentanyl group (40%) was significantly lower than control group (80%; p < 0.05), but not in lidocaine group (70%). CONCLUSIONS: Results of this study showed that only esmolol could reliably offer protection against the increase in both HR and SBP, low dose of fentanyl (3 micrograms/kg) prevented hypertension but not tachycardia, and 2 mg/kg lidocaine had no effect to blunt adverse hemodynamic responses during laryngoscopy and tracheal intubation.

Virologic, immunologic, and clinical evaluation of human immunodeficiency virus antibody status of symptom-free children born to infected mothers.

STUDY OBJECTIVE: To determine the prevalence of infection by the human immunodeficiency virus (HIV) in a population of symptom-free children who were born to HIV-infected mothers and who subsequently underwent seroreversion from an HIV antibody-positive to an HIV antibody-negative status. DESIGN: Cohort. SETTING: Pediatric HIV program in a community setting. PATIENTS: We used HIV DNA polymerase chain reaction (PCR) and coculture to detect the presence or absence of HIV in peripheral blood mononuclear cells of 134 children aged 6 to 53 months. All children had HIV antibody at birth and underwent a subsequent seroreversion to antibody-negative status. RESULTS: In 134 children with HIV antibody-negative status, 219 of 220 culture results and 242 of 247 HIV-1 DNA PCR assay results were negative. Six positive laboratory results were obtained for six different children, each of whom had negative results on multiple assays. For HIV-infected children, 56 of 62 cultures and 99 of 104 PCR evaluations showed positive results. There was no clinical or laboratory evidence of HIV infection in the group with HIV antibody-negative status. CONCLUSION: We were unable to find evidence of latent HIV type 1 infection in this cohort of symptom-free children who underwent seroreversion to HIV antibody-negative status. The loss of maternal HIV antibody in these children indicates the absence of HIV infection. False-positive PCR and culture results occurred sporadically, indicating that repeated analysis of HIV seropositivity in infants and children is necessary.

Neurinoma of the spinal accessory nerve: report of a case.

We report a patient with neurinoma of the spinal accessory nerve, who complained of intermittent occipital headaches, nausea, vomiting, blurred vision and unsteady gait. Neurological examination revealed papilledema, bilateral horizontal nystagmus and right cerebellar signs. Computed tomography revealed mild hydrocephalus, a low-attenuated lesion with a faint capsule after enhancement and partial compression of the 4th ventricle in the right posterior fossa. Vertebral angiography revealed no definite tumor vessels or stains. Under the impression of a posterior fossa tumor, a suboccipital craniectomy with a C1 and C2 laminectomy was performed. A 4 x 4 x 2.5 cm3 dumbbell tumor arising from the left spinal accessory nerve at the C2 level was found 4 x 4 x 2.5 cm3. The tumor extended upward through the foramen magnum with upward displacement of both tonsils to the right jugular foramen with slight adhesion to the right IX, X and XI cranial nerves. The left spinal accessory nerve was severed from the pedicle at the C2 level, and the tumor was totally removed. Diagnosis was made during the operation. The pathological examination showed neurinoma with cystic degeneration. During the following year, atrophy of the left sternocleidomastoid and trapezius muscles were noticed. Up to the time of this writing, there had been no clinical recurrence.

Facilitated ERG recovery in taurine-treated bovine eyes, an ex vivo study.

Excorporal bovine eye with stable ERG patterns were used in this study to examine the possible antihypoxic property of the taurine. Taurine (1 mM) given prior to or after the on-set of hypoxia facilitated the retinal recovery as indicated by the B-wave amplitude changes. This observation is consistent with previous observations in hippocampal slice and other tissues which suggests an antihypoxic function of this sulfur-containing amino acid.

Isolated, perfused bovine eye a model for acute retinal toxicity screening.

Excorporal bovine eye has been resuscitated and sustained with an aim of its development as an alternative to whole animal in evaluating acute retinal toxicity of xenobiotics. As indicated by the stable ERG response, such preparation is functionally reactive to photic stimuli over a span of 6-12 h. Moreover, after experienced a 20 min hypoxia the reperfused eyes recovered fully. This functionally responsive preparation was used to evaluate the influence of a highly purified bacterial collagenase (Nucleolysin) on the integrity of vitreoretinal junction. Nucleolysin at concentrations between 120-600 U/ml was injected into the posterior chamber for 15 min. Retinal surfaces were irrigated and eyes were perfusion fixed with glutaraldehyde. Ultrastructural analysis indicated that thinning of the internal limiting membrane occurred when enzyme exceeded 480 U. At 600 U concentration, the principle subcellular change involved the end-foot region of the Muller cells. These studies suggest that the isolated, perfused bovine eye is a suitable model for evaluating acute retinal toxicity of xenobiotics.