Expression and characterization of Gag protein of HIV-1（CN） in Pichia pastoris

To express the core protein of HIV-1 of Chinese prevalent strain （HIV-1 （CN）） in Pichia pastoris, the fulllength gag gene was inserted into the secretory expression vector pHILS1. Linearized recombinant plasmid pHILGAG by Sail was electrotransformed into the yeast strain GS115, and the yeast transformants were identified by PCR. To induce the interest protein to be expressed, the PCR positive transformants were inoculated in the medium of BMGY and BMMY, mRNA of the strain was detected by RT-PCR, and the expressed protein was analyzed by SDS-PAGE, Western blotting and thin layer scanning. mRNA （1.3 kb） was amplified by RT-PCR. SDS-PAGE and Western blotting analysis showed that the molecular mass of the expressed protein was 55 kD, which was similar to the expected value, and the expressed protein could react with McAb to HIV-1 p24. Thin layer scanning analysis demonstrated that the whole amount of the expressed protein was approximately 13 % of the soluble protein in the supernatant. The recombinant yeast had good genetic stability. The optimal expression conditions of the engineering yeast were as follows： BMMY medium, 80-90% of dissolved oxygen, 1% methanol, and 3-day-cultivation course. Gag proteins were expressed under the optimal expression condition and purified via gel filtration chromatography. The purity of the interest protein was up to 85 %. After the purified proteins were inoculated into BALB/c mice, the anti-HIV-1 antibodies in the immunized mice could be detected by Western blotting.     

The combination of purified recombinant human platelet-derived growth factor-BB and equine particulate bone graft for periodontal regeneration

Background: The objective of this study is to evaluate the potential for periodontal regeneration of a critical‐sized defect with the application of recombinant human platelet‐derived growth factor (rhPDGF‐BB) combined with either a particulate equine or a β‐tricalcium phosphate (β‐TCP) matrix. Methods: Critical‐sized intrabony 2‐wall defects were created bilaterally on the distal surface of the second premolar and the mesial surface of the first molar in nine hounds. Twelve defects received rhPDGF‐BB/equine treatment, 12 defects received rhPDGF‐BB/β‐TCP treatment, and the remaining 12 sites served as sham‐surgery controls. The animals were sacrificed after a 10‐week healing period. Results: Clinical healing was uneventful without obvious signs of overt gingival inflammation. Histologic and histomorphometric analyses revealed statistically that there were differences among the three groups in terms of new bone formation (P <0.001). The amount of test material for both rhPDGF‐BB/equine and rhPDGF‐BB/β‐TCP groups was comparable, but the amount of newly formed bone was significantly higher (P <0.01) in favor of the rhPDGF‐BB/equine group. The amount of new cementum formed for the rhPDGF‐BB/equine group (4.8 ± 1.3 mm) was significantly higher (P =0.001) than the sham‐surgery control group (1.7 ± 1.9 mm). Conclusion: Both rhPDGF‐BB/equine and rhPDGF‐BB/β‐TCP have the potential to support the regeneration of the periodontal attachment apparatus.     

Vertical ridge augmentation using an equine bone and collagen block infused with recombinant human platelet-derived growth factor-BB: a randomized single-masked histologic study in non-human primates

Background: This study tests the effectiveness of hydroxyapatite and collagen bone blocks of equine origin (eHAC), infused with recombinant human platelet‐derived growth factor‐BB (rhPDGF‐BB), to augment localized posterior mandibular defects in non‐human primates (Papio hamadryas). Methods: Bilateral critical‐sized defects simulating severe atrophy were created at the time of the posterior teeth extraction. Test and control blocks (without growth factor) were randomly grafted into the respective sites in each non‐human primate. Results: All sites exhibited vertical ridge augmentation, with physiologic hard‐ and soft‐tissue integration of the blocks when clinical and histologic examinations were done at 4 months after the vertical ridge augmentation procedure. There was a clear, although non‐significant, tendency to increased regeneration in the test sites. As in the first two preclinical studies in this series using canines, experimental eHAC blocks infused with rhPDGF‐BB proved to be a predictable and technically viable method to predictably regenerate bone and soft tissue in critical‐sized defects. Conclusion: This investigation supplies additional evidence that eHAC blocks infused with rhPDGF‐BB growth factor is a predictable and technically feasible option for vertical augmentation of severely resorbed ridges.     

语言刺激的功能性MR成像在自闭症诊断中的潜在应用价值

目的对自闭症病人给予被动性语言刺激,评价采用功能性磁共振(MR)成像作为判断病人有无语言缺陷的客观指标的可行性。材料与方法本研究为前瞻性研究,研究方     

Problem-based learning and research at the Harvard School of Dental Medicine: a ten-year follow-up

Dental students at the Harvard School of Dental Medicine (HSDM) are required to pursue and complete research projects in order to obtain the doctor of dental medicine (D.M.D.) degree. The purpose of this study was to evaluate the effect of curriculum changes on a set of measurable outcomes related to research pursuits. This study was designed as a retrospective analysis of outcomes data from the period 1992-2002. The predictor variable was program format (non-PBL vs. PBL); the outcome variables were the percentage of students listed as authors on an IADR/AADR abstract during their tenure at HSDM and the percentage of students listed as first and/or presenting authors. Univariate statistics were computed for each class, and independent samples t-tests were used to compare the study groups with regard to our outcomes. For the majority of our outcomes, there was no statistically significant difference between the PBL and non-PBL groups, possibly due to sample size limitations. While the implementation of PBL at HSDM has not universally increased student productivity in research, it has not had an adverse effect either. It is possible that students in the PBL curriculum are nurturing other interests, such as community service, while retaining productivity in research.     

The effect of aspirin intake on bleeding on probing in patients with gingivitis

BACKGROUND: Bleeding indices are used as a screen for periodontal disease activity, a measure of disease prevalence, and a measure of effectiveness in clinical trials. Bleeding on probing (BOP) is widely interpreted as a sign of disease activity whereas its absence is interpreted as both a sign and predictor of health. Aspirin use has become increasingly common in the prevention of cerebrovascular and cardiovascular diseases. Because of its anti-platelet activity, aspirin is a non-disease factor that has the potential to affect the appearance of BOP. The hypothesis being tested is that short-term aspirin use in doses of 81 mg and 325 mg will increase the number of bleeding sites in a population with gingivitis. METHODS: Fifty-four subjects were screened initially, those subjects with 20% to 30% whole mouth BOP were randomly assigned to one of three arms: placebo group, 81 mg aspirin group, or 325 mg aspirin group. Before and after exposure to the respective regimens, clinical parameters were measured on all the teeth: the plaque index was recorded at four sites per tooth, and probing depth and BOP were evaluated at six sites per tooth using an automated pressure-sensitive probe. RESULTS: The data obtained in this clinical trial were analyzed utilizing a linear regression analysis to control for confounding variables. The primary measure of interest was BOP in patients clinically demonstrating naturally occurring gingivitis. The results of this study indicate that while controlling for age, gender, and plaque, "low dose" 81 mg and "regular dose" 325 mg of aspirin demonstrated a statistically significant 5.30 (P = 0.001) and 4.13 (P = 0.010) increase from baseline, respectively, in percent BOP. CONCLUSION: Failure to consider the effects of aspirin on BOP could impair proper diagnosis and treatment planning for clinicians and introduce a significant confounding variable in research situations.     

The effect of aspirin on the periodontal parameter bleeding on probing

BACKGROUND: The absence or presence of bleeding on probing (BOP) is a sign of periodontal health or disease, but the presence of BOP is not an accurate predictor of disease progression. Aspirin is increasingly used in the prevention of cerebrovascular and cardiovascular diseases and is a non-disease factor that may modify bleeding indices given its antithrombolytic activity. The purpose of this double-blind placebo-controlled randomized clinical trial was to study the effect of short-term daily aspirin ingestion on the clinical parameter BOP. METHODS: A total of 46 periodontally healthy subjects were included in this study: 16 received placebo, 15 low-dose aspirin (81 mg), and 15 regular dose (325 mg) aspirin. Clinical parameters assessed included plaque index, periodontal probing depth, and BOP using an automated pressure-sensitive probe. Measurements were recorded before and after 7-day exposure to placebo and aspirin regimens. RESULTS: A statistically significant difference in BOP was found in patients with > or = 20% of bleeding sites during the visit prior to placebo or aspirin exposure (n = 11). The group treated with 325 mg aspirin exhibited a moderate yet statistically significant increase in BOP (12.4%) compared to the placebo group (there was no significant difference between the 81 mg aspirin group and placebo). The tendency to bleed was not statistically significant in the group which exhibited <20% (n = 35) of bleeding sites during the visit prior to exposure. CONCLUSION: Aspirin intake of 325 mg daily for 7 days moderately increased the appearance of bleeding on probing in a population that had > or = 20% BOP sites.     

Comparison of clinical productivity of senior dental students in a dental school teaching clinic versus community externship rotations

The aim of this study was to report on the clinical and monetary productivity of fourth-year dental students at community-based clinical sites and school-based clinics at the Harvard School of Dental Medicine (HSDM). This study included forty-seven students from the graduating classes of 2006, 2007, and 2008. These fourth-year students were required to spend twelve weeks at one of several participating community health centers throughout Massachusetts and New Hampshire. Students also treated their patient pool in the teaching practice at HSDM in the fourth year. The most common sixty American Dental Association procedure codes were compared, and variables were created by grouping them by specialty or type of service. HSDM dental students completed 8,365 procedures at an externship site during their community experience. An average of 178 procedures was completed per student, and mean revenue of $17,486 was produced. In comparison, the same students completed 3,640 procedures during an equal amount of time spent (normalized for this study) at the school teaching practice clinic, where each student completed an average of seventy-seven procedures and generated $16,802 in revenue. The results of this study show that fourth-year dental students at the community health centers, working under the supervision of adjunct faculty, completed more than double the number of procedures they did in the HSDM teaching practice clinic. However, the revenue generated was very similar at the two sites. In addition, the types of procedures performed by students at externship sites were simpler than the complex and specialized procedures performed at the HSDM clinic, which include fixed and removable prosthetics, periodontal surgery, and implantology.