Effect of stretch frequency on osteogenesis of periodontium during periodontal ligament distraction.

OBJECTIVES: Periodontal ligament distraction (PDLD) can accelerate orthodontic tooth movement (OTM). However, the effect of stretch frequency on osseous formation during PDLD remains unclear. Here, we sought to identify the effect of PDLD frequency on the osteogenic remodelling of the periodontium. MATERIALS AND METHODS: (i) In vitro, five human periodontal ligament stem cell (PDLSC) cultures were randomized to either static conditions or exposure to a cyclic stretch force involving 12% deformation at frequencies of 0.3, 0.5, 0.7 or 1.0 Hz for 12 h, and the osteogenic differentiation of PDLSCs was assessed using Western blotting. (ii) In vivo, 18 beagle dogs underwent orthodontic distalization of bilateral maxillary first premolars. In the test groups, PDLD was performed at a frequency of two or six times/day, while Ni-Ti coil springs were applied to mimic traditional OTM in the control group. The amount of OTM and histological staining was estimated after force loading for 5, 10 and 15 days. RESULTS: (i) In vitro, the expression of osteogenic-specific markers (runt-related transcription factor 2 [Runx2], type I collagen [COL-I] and osteocalcin [OCN]) increased with the frequency of tensile force, to a peak at 0.7 Hz. (ii) In vivo, both PDLD groups displayed a greater rate of OTM and a higher bone metabolism than the control group. The expression of COL-I and OCN was significantly reinforced in the six times/day-PDLD group in comparison to the two times/day-PDLD group. CONCLUSIONS: The cyclic stretch force enhances osteogenesis of the periodontium in a frequency-dependent manner.

[Epidemiological and etiological characteristics of hand, foot and mouth disease among children aged 5 years and younger in Ningbo (2016 to 2019)].

OBJECTIVE: To describe the epidemiological and etiological characteristics of hand, foot and mouth disease (HFMD) among children aged 5 years and younger in Ningbo after the access of entero-virus-A71 vaccine (2016 to 2019). METHODS: A retrospective cohort study were performed in children aged 5 years and younger in Ningbo from 2016 to 2019. Data for incidence of HFMD was collected from the National Notifiable Disease Surveillance Reporting System and the Electronic Medical Records (EMRs) System, while the demographic information was derived from the Immunization Information System. Speci-mens were detected by real-time fluorescence quantitative PCR and the Wilson method was used to estimate the incidence rate and 95% confidence interval. RESULTS: From 2016 to 2019, a total of 1 044 800 residential children were observed in this population-based cohort. In the study, 102 471 cases of HFMD were diagnosed in 2 651 081 person-years, revealing an overall incidence density of 3 865.25/100 000 person-years. There was no significant decline in the number of the cases after the vaccine was available. The number of the patients of hand foot mouth disease during the four years was 93 421, of whom 84 875 (90.85%) had only one incident record, while 8 946 (9.15%) had 2 or more cases in this period; there were 69 771 (66.06%) patients who only needed to see a doctor once for each disease, 19.92% of the patients needed to be treated twice, and 14 801 (14.02%) patients needed to go to the hospital or clinic three times or more. The incidence of HFMD showed obvious seasonality and periodicity, which mainly concentrated in April to July each year, and the epidemic cycle was 2 years; most of the cases were 1 to 3-year old children, with more cases in male. The incidence density varied across the region, with the highest density observed in Ninghai (4 524.76/100 000 person-years), followed by Xiangshan (3 984.22/100 000 person-years). In 3 748 library-conformed cases, 2 834(75.61%) were detected positive, among which enterovirus-A71, Cox-A16 and other enteroviruses accounted for 9.03%, 31.55% and 59.42%, respectively. During the study period, the cumulative coverage of enterovirus-A71 vaccine increased year by year, with the proportion of enterovirus-A71 and severe cases both gradually decreasing. CONCLUSION: The current status of hand, foot and mouth disease in Ningbo is still serious. Children under 3-year old (especially male children aged 1 year) were the key population for prevention and control. Vaccination might lead to changes in major pathogenic virus type, of which more attention should be paid to the potential impact on disease surveillance, prevention and control.

Adverse events associated with mirabegron 50mg versus placebo: A systematic review and meta-analysis.

PURPOSE: The safety of mirabegron 50mg monotherapy was comprehensively assessed versus placebo for overactive bladder. METHODS: A systematic literature search was conducted up to June, 2020 using PUBMED, EMBASE and Cochrane Library. Randomized controlled trials evaluating safety of mirabegron in overactive bladder were collected, and safety was assessed according to 15 adverse events. Adverse events were widely selected to be assessed if they could be calculated. Heterogeneity among studies was assessed by using the χ2 test based on the Q and I2 tests. Pooled effect sizes were calculated using fixed model if I2<50%, otherwise a random-effects model was chosen. The outcomes were nasopharyngitis, dry mouth, hypertension, constipation, headache, dyspepsia, urinary tract infection, dizziness, blurred vision, nausea, cardiovascular events, influenza, electrocardiogram QT prolonged, upper respiratory tract infection and high blood pressure. RESULTS: In all, 10 peer-reviewed trials comprising 6135 patients were identified. Compared with placebo, mirabegron 50mg had an unfavorable safety profile resulting in nasopharyngitis (OR, 1.54[95% credible interval, 1.05-2.25]; P=0.03. No statistical difference was found between mirabegron 50mg and placebo groups in other 14 outcomes. CONCLUSION: Mirabegron 50mg is further confirmed to be nearly as safe as placebo, expect for nasopharyngitis. Nasopharyngitis is associated with mirabegron 50mg monotherapy for patients with overactive bladder.

[Cluster analysis and significance of clinical subtypes in patients with obstructive sleep apnea hypopnea syndrome].

Objective: To study the clinical subtypes of obstructive sleep apnea hypopnea syndrome (OSAHS) by cluster analysis, and to discuss the characteristics and clinical significance of these subtypes. Methods: A retrospective analysis was done among patients who were diagnosed with OSAHS in the Sleeping Center of the Second Affiliated Hospital of Soochow University from January 2010 to June 2018. In this cluster analysis, 16 main symptoms, 7 comorbidities and 3 assessment scales were included. After selecting the best model, the parameters and characteristics of different subtypes were compared and analyzed. Results: A total of 2 592 patients with complete data were included in this study. After cluster analysis, they were divided into 4 groups: sleep apnea group (1 173 cases, 45.3%), daytime sleepiness group (518 cases, 20.0%), insomnia and memory loss group (212 cases, 8.2%), mild symptom group (689 cases, 26.6%). In the sleep apnea group, the patients were found to be younger [(40.2±10.4) years old], with higher body mass index (BMI) [(27.7±3.7) kg/m(2)] when compared to the other groups. In addition, the prevalence of comorbidities of this group was found to be lower, whereas the probability of sleep apnea symptom was the highest (94.7%). In daytime sleepiness group, the Epworth Sleepiness Scale (ESS) score was the highest [(12.4±5.5) points], and the probability of daytime sleepiness symptom was also found to be the highest (88.0%). The age of patients in the insomnia and memory loss group was the highest [(51.1±13.0) points], with the highest percentage of women (19.3%). The probability of insomnia was found to be 70.3%, and memory loss symptoms was 88.2% which were the highest when compared to the other groups. The prevalence of comorbidities was the highest, and the scores of short mental state scale (MMSE) and Montreal cognitive assessment (MoCA) were the lowest with a mean of [(28.5±2.4) points] and [(25.4±3.2) points], respectively, among the 4 groups. The probability of most symptoms and comorbidities were found be the lowest in the mild symptom group. There were significant differences in the main symptoms among the 4 groups (P<0.05). Symptoms like sleep apnea, daytime sleepiness, insomnia, memory loss, headache and dry mouth upon awakening were found significantly different in pairwise comparisons among the groups (P<0.002). Conclusion: The patients with OSAHS can be divided into four clinical subtypes by cluster analysis, each of which is significantly heterogeneous, and this is helpful to evaluate the condition and guide individualized treatment.

Clinically Oriented CBCT Periapical Lesion Evaluation via 3D CNN Algorithm.

Apical periodontitis (AP) is one of the most prevalent disorders in dentistry. However, it can be underdiagnosed in asymptomatic patients. In addition, the perioperative evaluation of 3-dimensional (3D) lesion volume is of great clinical relevance, but the required slice-by-slice manual delineation method is time- and labor-intensive. Here, for quickly and accurately detecting and segmenting periapical lesions (PALs) associated with AP on cone beam computed tomography (CBCT) images, we proposed and geographically validated a novel 3D deep convolutional neural network algorithm, named PAL-Net. On the internal 5-fold cross-validation set, our PAL-Net achieved an area under the receiver operating characteristic curve (AUC) of 0.98. The algorithm also improved the diagnostic performance of dentists with varying levels of experience, as evidenced by their enhanced average AUC values (junior dentists: 0.89-0.94; senior dentists: 0.91-0.93), and significantly reduced the diagnostic time (junior dentists: 69.3 min faster; senior dentists: 32.4 min faster). Moreover, our PAL-Net achieved an average Dice similarity coefficient over 0.87 (0.85-0.88), which is superior or comparable to that of other existing state-of-the-art PAL segmentation algorithms. Furthermore, we validated the generalizability of the PAL-Net system using multiple external data sets from Central, East, and North China, showing that our PAL-Net has strong robustness. Our PAL-Net can help improve the diagnostic performance and speed of dentists working from CBCT images, provide clinically relevant volume information to dentists, and can potentially be applied in dental clinics, especially without expert-level dentists or radiologists.

Phosphoric acid-etching promotes bond strength and formation of acid-base resistant zone on enamel.

This study examined the effect of phosphoric acid (PA) etching on the bond strength and acid-base resistant zone (ABRZ) formation of a two-step self-etching adhesive (SEA) system to enamel. An etch-and-rinse adhesive (EAR) system Single Bond (SB) and a two-step SEA system Clearfil SE Bond (SE) were used. Human teeth were randomly divided into four groups according to different adhesive treatments: 1) SB; 2) SE; 3) 35% PA etching→SE primer→SE adhesive (PA/SEp+a); (4) 35% PA etching→SE adhesive (PA/SEa). Microshear bond strength to enamel was measured and then statistically analyzed using one-way analysis of variance and the Tukey honestly significant difference test. The failure mode was recorded and analyzed by χ( 2 ) test. The etching pattern of the enamel surface was observed with scanning electron microscope (SEM). The bonded interface was exposed to a demineralizing solution (pH=4.5) for 4.5 hours and then 5% sodium hypochlorite with ultrasonication for 30 minutes. After argon-ion etching, the interfacial ultrastructure was observed using SEM. The microshear bond strength to enamel of the SE group was significantly lower (p<0.05) than that of the three PA-etched groups, although the latter three were not significantly different from one another. The ABRZ was detected in all the groups. In morphological observation, the ABRZ in the three PA-etched groups were obviously thicker compared with the SE group with an irregular wave-shaped edge.

[A prospective randomized controlled study of antibiotic bone cement in the treatment of diabetic foot ulcer].

Objective: To investigate the clinical effects and related mechanism of antibiotic bone cement in treating diabetic foot ulcer (DFU). Methods: A prospective randomized controlled study was conducted. From August 2020 to August 2022, 24 patients with DFU who met the inclusion criteria were admitted to the First Affiliated Hospital of Air Force Medical University. According to the block randomization, the patients were divided into 2 groups, with 12 patients in each group. In antibiotic bone cement group, there were 7 male and 5 female patients, aged (64±8) years, with the ulcer area of (41±21) cm2. In silver sulfadiazine group, there were 8 male and 4 female patients, aged (62±8) years, with the ulcer area of (38±19) cm2. Under the condition of ensuring the patency of at least one main inferior genicular artery in each patient, the continuous vacuum sealing drainage was performed for 3-5 days after thorough debridement. Thereafter, the wounds in antibiotic bone cement group were treated with gentamicin-laden bone cement, and the wounds in silver sulfadiazine group were treated with silver sulfadiazine cream for dressing change. After 3 weeks of dressing change, the wound was covered with split-thickness skin graft from the lateral thigh on the affected side. Before debridement and after 3 weeks of dressing change, the blood flow intensities of wound tissue and normal skin tissue in foot were measured using laser Doppler flowmeter, and then, the percentage of relative blood flow intensity of wound and the change rate of blood flow intensity were calculated. After 3 weeks of dressing change, the wound margin tissue was taken, the number of CD31-positive neovascular and the vascular morphology were observed and detected by immunohistochemical staining, the morphology of blood vessels surrounded by CD31 and α-smooth muscle actin (α-SMA) double-positive cells was observed by immunofluorescence staining, the cell proliferation activity was evaluated by immunofluorescence staining (denoted as the ratio of Ki67 positive cells), and the protein expression of vascular endothelial growth factor receptor 2 (VEGFR2) was detected by Western blotting. The skin graft survival was observed 3-5 days after skin grafting, and the wound healing time was recorded. Data were statistically analyzed with independent sample t test and Fisher's exact probability test. Results: The percentages of relative blood flow intensity of wounds of patients before debridement were similar between the two groups (P>0.05). After 3 weeks of dressing change, the percentage of relative blood flow intensity of wounds and the change rate of blood flow intensity of patients in antibiotic bone cement group were (44.7±2.0)% and (129±12)%, respectively, which were significantly higher than (28.3±1.2)% and (41±8)% in silver sulfadiazine group (with t values of 24.15 and 20.97, respectively, P<0.05). After 3 weeks of dressing change, compared with those in silver sulfadiazine group, the number of CD31-positive neovascular in the wound margin tissue of patients in antibiotic bone cement group was significantly increased (t=33.81, P<0.05) with larger diameter and more regular arrangement, the vascular wall continuity surrounded by CD31 and α-SMA double-positive cells was better, and the ratio of Ki67 positive cells and protein expression of VEGFR2 were significantly increased (with t values of 40.97 and 47.38, respectively, P<0.05). On post skin grafting day 3-5, all the patients in antibiotic bone cement group and 8 patients in silver sulfadiazine group had good skin graft survival, while 4 patients in silver sulfadiazine group showed spotted/patchy skin graft necrosis, which were cured after corresponding treatment. The wound healing time of patients in antibiotic bone cement group was (47.1±2.9) d, which was significantly shorter than (58.8±2.3) d in silver sulfadiazine group (t=10.86, P<0.05). Conclusions: Compared with silver sulfadiazine, clinical application of antibiotic bone cement for treating DFU has the characteristics of accelerating wound healing and better reconstruction of local blood flow, which may be closely related to the fact that antibiotic bone cement promoted the local angiogenesis effectively in the wound through enhancing the expression of VEGFR2.

Prolonged exclusive breastfeeding, autumn birth and increased gestational age are associated with lower risk of fever in children with hand, foot, and mouth disease.

Epidemics of hand, foot, and mouth disease (HFMD) have been emerging and reemerging in recent years. This study aims to investigate whether breastfeeding and other factors may affect the profile of fever and disease course in children with HFMD. Three hundred seventy-two preschool children with HFMD were included. The demographics, environmental factors, and delivery- and feeding-associated factors in the children were obtained and their effects on the profile of fever and disease course were analyzed. Of the 372 children, 139 (37.37%) had fever during the disease course. Gender, breastfeeding pattern, birth season and gestational age were significantly different between the children with and without fever (p = 0.034, p < 0.0001, p = 0.035 and p = 0.013, respectively). After multivariate-adjusted analysis, prolonged exclusive breastfeeding (p = 0.001, OR 0.401, 95% CI 0.229-0.704), autumn birth (p = 0.007, OR 0.409, 95% CI 0.214-0.784) and higher gestational age (p = 0.029, OR 0.089, 95% CI 0.010-0.781) were protective factors for the incidence of fever.

Global prevalence, risk factors, and reporting practice of needlestick and sharps injuries among dental students: a systematic review and meta-analysis.

BACKGROUND: Dental students are vulnerable to needlestick injuries (NSIs) due to their inadequate training. However, the global prevalence of NSI among dental students is unknown. AIM: To determine the pooled prevalence among dental students, epidemiological profile, and risk factors for NSI. METHODS: A systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The review protocol was registered at the International Prospective Register of Systematic Reviews (CRD 42022312778). Eligible studies were identified from PubMed, Scopus, Web of Science, Embase, OVID, and EBSCO databases. A meta-analysis with a random effects model was performed to estimate the pooled prevalence, and meta-regression was conducted to explore heterogeneity among studies. FINDINGS: A total of 25 studies from 15 countries met the inclusion criteria. The estimated pooled prevalence of NSI among dental students was 44% (95% confidence interval: 38-51%). Local anaesthesia, tooth cleaning or scaling, and waste disposal were associated with highest risk for NSI. Most studies observed under-reporting of NSI. Dental students had inadequate knowledge regarding post-exposure management. CONCLUSION: Dental students had a high prevalence and low reporting rate of NSI exposure. Inadequate knowledge might increase the probability of NSI exposure.

[Combined detection of Helicobacter pylori 16S rRNA and cagA gene in saliva specimens using multiplex PCR].

OBJECTIVE: To establish a multiplex PCR-based method for detecting Helicobacter pylori (Hp) 16S rRNA gene and cagA gene in saliva samples for investigating the prevalence of Hp in the oral cavity of Hp-infected patients with digestive tract diseases. METHODS: Bioinformatics technique was used to design specific primers for Hp 16S rRNA and cagA genes for Hp detection using multiplex PCR, with recombinant cloning plasmids serving as the standard positive control. Oral saliva samples were collected from 156 patients with digestive tract diseases, and Hp 16S rRNA and cagA genes were detected using the established multiplex PCR system. RESULTS: The established multiplex PCR system showed a strong specificity and a high sensitivity for detecting Hp 16S rRNA gene and cagA gene, with the lowest detection limit of 103 copies/µL. The recombinant plasmids pGMT-16s and pGMT-cagA could be used as standard positive controls for the identification of Hp. Among the 156 saliva samples, 87.2% were positive for Hp 16S rRNA gene and 23.1% for Hp cagA gene. CONCLUSION: Hp is highly prevalent in saliva specimens of Hp-infected patients with digestive tract diseases. The presence of Hp in the oral cavity may importantly contribute to Hp infection in the digestive tract and recurrence after treatment.

Relapse rate after surgical treatment of maxillary hypoplasia in non-growing cleft patients: a systematic review and meta-analysis.

Maxillary hypoplasia in cleft lip and palate is a complex deformity. Despite surgical improvements, postoperative relapse persists. This systematic review was performed to determine the mean horizontal relapse rates for the surgical techniques used to treat maxillary hypoplasia: Le Fort I osteotomy with rigid fixation, Le Fort I distraction osteogenesis, and anterior maxillary distraction osteogenesis. This study followed the PRISMA statement. The PubMed, Embase, Science Direct, and Web of Science databases were searched through to June 2018. Studies on non-growing cleft lip and palate patients who had undergone one of the three surgical procedures and who had postoperative horizontal maxillary changes assessed at >6 months post-surgery were included. Stata SE was used to estimate pooled means, heterogeneity, and publication bias. The search strategy identified 326 citations, from which 24 studies were selected. Relapse rates following Le Fort I osteotomy with rigid fixation, Le Fort I distraction osteogenesis, and anterior maxillary distraction osteogenesis were 20%, 12%, and 12%, respectively. Relapse rates with and without bone grafting were 19% and 66%, respectively. The relapse rate following distraction osteogenesis with internal distraction was lower than that with external distraction. Study limitations were heterogeneity, which was above moderate, the low number of high-quality studies, and unidirectional assessment of postoperative maxillary movement.

[Analysis of functional speech sound disorder and related erroneous consonants in children].

Objective: To investigate the features and trends of functional speech sound disorder and related erroneous consonants in children, so as to provide evidence for clinical evaluation and rational intervention. Methods: Clinical data of 1 562 children diagnosed with functional speech sound disorder in the language-speech clinic of the Department of Child Health Care, Children's Hospital, Capital Institute of Pediatrics from January 2007 to December 2018 were analyzed retrospectively. By using the mandarin phonetic test table, the picture-naming method was adopted to test the word-level pronunciation. The Chi-square test was conducted to analyze the incidence of consonant errors in different age groups, gender and different places of articulation. The trend in incidence of the consonant errors in different age groups and during the last 12 years were analyzed by chi-square trend test. Results: A total of 1 562 cases were diagnosed with functional speech sound disorder, including 1 171 males and 391 females, the age was 4-17 years. The incidence of consonant errors in different places of articulation was 43.0% (672/1 562) for labial, 47.0% (734/1 562) for lingua-palatal, 63.7% (995/1 562) for velar, 77.7% (1 213/1 562) for linguo-alveolar, 78.9% (1 233/1 562) for apico-dental and 81.6% (1 274/1 562) for palatal. The incidence of consonant errors in males on labial, lingua-palatal, linguo-alveolar and palatal was higher than that in females (44.7% (523/1 171) vs. 38.1% (149/391), 49.1% (575/1 171) vs. 40.7% (159/391), 80.1% (938/1 171) vs. 70.3% (275/391), 82.8% (970/1 171) vs. 77.7% (304/391), χ²=5.138, 8.379, 16.126 and 5.042,all P<0.05). The incidence of consonant errors on labial, lingua-palatal, velar, linguo-alveolar, apico-dental and palatal decreased with age (χ²=27.023, 13.230, 20.579, 29.718, 26.390, and 17.887, all P<0.01). The incidence of consonant errors on labial, linguo-alveolar, apico-dental increased with years (χ²=9.030, 51.894 and 18.507, all P<0.01). Conclusions: The incidence of palatal errors is the highest in children with functional speech sound disorder. As part of the palatal errors could not be completely self-healing with growing, the phonological therapy for palatal errors should be carried out as early as possible. The incidence of consonant errors on labial, linguo-alveolar, and apico-dental presents an upward tendency with years, more attention should be paid to the factors related to the acquisition of these consonants.

Persistence with hepatitis C therapy in the Department of Veterans Affairs.

BACKGROUND: Persistence with Hepatitis C therapy has been identified as a key variable for predicting treatment success. The primary purpose of this study was to assess the persistence with therapy for patients undergoing hepatitis C treatment in the VA healthcare system with two forms of combination therapies: peginterferon alfa-2a with Ribavirin (peg-IFN alpha-2a/Rib) and peginterferon alpha-2b with Ribavirin (peg-IFN alpha-2b/Rib). METHODS: A retrospective cohort study design was used to analyse persistence in VA patients undergoing hepatitis C therapy during FY 2003-2004 using a large national VA data set. Stringent inclusion and exclusion criteria along with various defining variables were used to identify the inception cohort. Persistence rates were calculated for each of the two treatment groups at 3, 6, 9 and 11 months using the Kaplan-Meier method. Likelihood ratio test of equality between the two treatment groups was performed to detect any differences in persistence rates. RESULTS: A total of 5816 hepatitis C patients formed the inception cohort. Persistence rates for the overall duration showed significantly higher rates for patients on peg-IFN alpha-2a/Rib than peg-IFN alpha-2b/Rib. Cox regression analysis also showed favourable hazard ratio of persistence (0.88) for peg-IFN alpha-2a/Rib over peg-IFN alpha-2b/Rib. CONCLUSION: Peg alfa-2A/Rib showed slightly higher persistence rates for the overall duration of treatment as compared to Peg alfa-2B/Rib. However the differences, even though statistically significant, are small and not likely to translate into any substantial clinical advantage. Further research involving other approaches is required to confirm these findings.

Silica as a reference for laboratory dentifrice assessment methods: multiple site collaborative study.

OBJECTIVE: This collaborative study was designed to collect data from multiple laboratories, using recognized abrasion and cleaning power methods, to assess the functionality, stability, and suitability of three Sident silica abrasives for consideration as references for ISO (International Standards Organization) abrasion and other dentifrice assessment methods. METHODOLOGY: This study included ISO and other physicochemical methods to characterize the abrasive powders, as well as ISO and related abrasion methods--Radioactive Dentin Method, Profilometry, and Copper Gravimetric, and two Cleaning Power methods--to test the functionality of the silica abrasives with the current ISO abrasion reference calcium pyrophosphate. RESULTS: The outcomes demonstrated that the collaborative study to measure the physicochemical characteristics of three Sident silica abrasive materials, stored at ISO and tropical conditions, found no change in the functionality as measured by these methods over the two-year test period. CONCLUSION: The three Sident silica abrasives demonstrated suitability to be considered as references for use with calcium pyrophosphate in the ISO 11609 Toothpaste Specification.

Development of chitosan-based granular adsorbents for enhanced and selective adsorption performance in heavy metal removal.

Novel chitosan-based granular adsorbents were developed for enhanced and selective separation of heavy metal ions. The research included the synthesis of chitosan hydrogel beads, the cross-linking of the hydrogel beads with ethylene glycol diglycidyl ether (EGDE) in a conventional and a novel amine-shielded method, the functionalization of the chitosan beads through surface grafting of polyacrylamide via a surfaceinitiated atom transfer radical polymerization (ATRP) method, and the examination of the adsorption performance of the various types of chitosan beads in the removal of heavy metal ions. It was found that chitosan beads were effective in heavy metal adsorption, the conventional cross-linking method improved the acidic stability of the beads but reduced their adsorption capacity, the novel amine-shielded cross-linking method retained the good adsorption capacity while it improved the acidic stability of the beads, and the grafting of polyacrylamide on chitosan beads not only enhanced the adsorption capacity but also provided the beads with excellent selectivity for mercury over lead ions. XPS analyses indicated that the adsorption of metal ions on chitosan beads was mainly attributed to the amine groups of chitosan, the novel amine-shielded cross-linking method preserved most of the amine groups from being consumed by the cross-linking process and hence improved the adsorption capacity of the cross-linked chitosan beads, and the many amide groups from the polyacrylamide grafted on the chitosan beads increased the adsorption capacity and also made possible selective adsorption of mercury ions because the amide groups can form covalent bonds with mercury ions.

Characterization of genes encoding two manganese peroxidases from the lignin-degrading fungus Dichomitus squalens(1).

Genes encoding two manganese peroxidases from the white-rot basidiomycete Dichomitus squalens were cloned and sequenced. The mnp1 and mnp2 genes encode mature proteins of 369 and 365 amino acids, respectively. The amino acids involved in peroxidase function, those forming the Mn(II) binding site, and those forming the five disulfide bonds in other Mn peroxidases are conserved in these sequences. Both predicted D. squalens proteins contain multiple acidic residues in their C-terminal sequences, which may be involved in additional metal binding. Both genes contain seven small introns, the locations of which align with each other. The promoters of both D. squalens genes contain putative AP-2 sites, which may be involved in their regulation by nutrient nitrogen. Southern blot analysis of genomic PCR fragments suggests that these sequences represent separate genes rather than allelic variants.

Influences of fixatives on flow cytometric measurements of platelet P-selectin expression and fibrinogen binding.

Sample fixation is an important issue in flow cytometric platelet assays. However, previous reports were less than consistent regarding the influence of sample fixation on the assays. We evaluated the effects of formaldehyde and paraformaldehyde fixation on platelet P-selectin expression and fibrinogen binding using whole-blood flow cytometry and a Coulter EPICS XL-MCL cytometer. Fluorescent-labeled whole-blood samples were diluted with HEPES-buffered saline or fixed with formaldehyde (0.2, 0.5, and 1. 0%) or paraformaldehyde (0.5, 1.0, and 2.0%). Platelet P-selectin expression was 1.1+/-0.3% and 39.6+/-13.7% in unfixed resting and 10(-5) M ADP stimulated samples, respectively. Resting P-selectin expression was not significantly altered by 0.2 or 0.5% formaldehyde fixation, but was slightly decreased by 1.0% formaldehyde fixation or PFA fixation. Formaldehyde fixation caused small increases of P-selectin expression in ADP-stimulated samples. Compared to platelet fibrinogen binding of unfixed resting (4.5+/-2.1%) and ADP-stimulated (56.7+/-22.6%) samples, formaldehyde or paraformaldehyde fixation had no significant influence on resting samples, but mildly increased fibrinogen binding in stimulated samples. Unfixed samples were stable for 2 h. Fixed samples were generally stable for at least 6 h, but not thereafter. Thus, formaldehyde and paraformaldehyde have mild but complex influences on platelet P-selectin expression and fibrinogen binding measurements. To evaluate the stabilities of unfixed and fixed samples, samples were analyzed after different durations (0, 1, 2, 4, 6, 12, and 24 h) of storage at 4 degrees C in the dark. The results suggest that sample manipulation without fixation may be used when the samples are analyzed within 2 h, and that fixation with 0.5-1.0% formaldehyde or paraformaldehyde seems to be preferable when sample analysis is delayed. Effects of fixation should be carefully evaluated when establishing flow cytometric platelet assays in every laboratory.

[Effects of tea on DMBA-induced oral carcinogenesis in hamsters].

The preventive effects of green tea, tea pigments and mixed tea (a composite of whole water extract from green tea, tea polyphenols, and tea pigments) on 7, 12-dimethylbenz(a) anthracene(DMBA)-induced oral carcinogenesis in golden Syrian hamsters were studied. The hamsters were divided into five groups. i.e. the positive control group(the right buccal pouches of animal was topically treated with 0.5% DMBA in acetone three times per week for 15 weeks), three tea treated groups(1.5% green tea, 0.1% tea pigments and 0.5% mixed tea as the sole source of drinking water from two weeks before starting the DMBA treatment to the end of the experiment) and the negative control group(acetone applied topically). The results showed that in the 1.5% green tea, 0.1% tea pigments and 0.5% mixed tea groups, the inhibitory rates of the average number of tumor per hamster were 42.6%, 50.8% and 67.2% respectively, and the mean tumor burdens were 79% 89% and 95% respectively, compared with the positive control group. In the three tea groups, the frequency of micronucleated cells, the number of silver-stained nucleolar organizer regions (AgNOR), labeling index of proliferating cell nuclear antigen(PCNA) and the level of epidermal growth factor receptor(EGFR) expression in the oral mucosa cells were also less than those in the positive control group. These results clearly indicated that the mixed tea could effectively inhibit DMBA-induced oral carcinogenesis in hamsters. The mixed tea was more effective than green tea or tea pigments in this animal model. Protection of DNA from damage by carcinogen and suppression of cell proliferation was considered as important mechanisms of the anticarcinogenic effects of the mixed tea preparations.

[Biological mechanism of macrophage activation by wear particles at the bone-implant interface].

OBJECTIVE: To observe the response of membrane Ca(2+) channel of macrophage-like cells (MCs) to wear particles and analyze the cytoplasmic [Ca(2+)]i change in macrophage activation at the bone-implant interface. METHODS: The synoviocyte system of normal hip joint was established in vitro. Immunohistochemical technique (SABC) with CD68 Mab was used to differentiate MCs and fibroblast-like cells (FCs) in the system, and the time when MCs begin to perform phagocytosis was determined by SEM. 1.5 mg/ml (W/V) Ti alloy, Co-Cr alloy or UHMWPE particles suspension was added into the system to monitor the [Ca(2+)]i change in the MCs by confocal laser scanning microscope (CLSM). RESULTS: Phagocytosis of MCs happened after 6 hours, but within 1 hour the Ca(2+) channel of their cell membrane opened for 1 - 6 times and caused rapid and transient pulses of [Ca(2+)]i in cytoplasm after different period of incubation. There was no significant difference between times or range of the [Ca(2+)]i pulse (P > 0.05). The group of UHMWPE particles had the longest incubation period (P < 0.05), but the interval of pulses was shorter than that in the group of Co-Cr alloy particles (P < 0.05). [Ca(2+)]i pulses still appeared when MCs were incubated by indomethecin (P > 0.05), but the phenomenon could be blocked by nimodipin. CONCLUSIONS: Activation of macrophages at the bone-implant-interface could happen before they phagocytose wear particles. The primary switch-on mechanism of osteolysis mediated by cytokines at the bone-implant interface may be the opening of membrane Ca(2+) channel and pulse-like Ca(2+) influx of macrophages when stimulated by wear particles.

[Effect of wear particles on cell-to-cell communication of synoviocyte system in vitro and its significance in aseptic loosening of prosthesis].

OBJECTIVE: To study the biological reason of abnormal fiber proliferation at bone-implant interface of aseptically loosened prosthesis by observing cell-to-cell communication of synoviocyte system in vitro under the stimulation of wear particles. METHODS: The synoviocyte system of normal human hip joint was established in vitro and the change of cell-to-cell communication was monitored by fluorescence redistribution after photobleaching technique (FRAP) and confocal laser scanning microscope (CLSM) after Ti alloy, CoCr alloy or UHMWPE particles suspension (1.5 mg/ml, W/V) was added into the system. RESULTS: Cell-to-cell communication of synoviocyte system significantly decreased under the stimulation of three kinds of particles (P < 0.01). he decreased degree was maximal in UHMWPE group and minimal in Ti alloy group (P < 0.01). The cell-to-cell communication level of fibroblast-like-cells (FCs) was significantly lower than that of macrophage-like-cells (MCs) (P < 0.05). CONCLUSIONS: Besides the effect of cytokines promoting fiber proliferation, the great amount of fibrous granuloma at bone-implant interface which has relations with aseptic loosening may be caused by the decrease of cell-to-cell communication of fibroblast under direct stimulation of wear particles.