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Transfer learning is provided with potential research value and application prospect in motor imagery electroencephalography (MI-EEG)-based brain-computer interface (BCI) rehabilitation system, and the source domain classification model and transfer strategy are the two important aspects that directly affect the performance and transfer efficiency of the target domain model. Therefore, we propose a parameter transfer learning method based on shallow visual geometry group network (PTL-sVGG). First, Pearson correlation coefficient is used to screen the subjects of the source domain, and the short-time Fourier transform is performed on the MI-EEG data of each selected subject to acquire the time-frequency spectrogram images (TFSI). Then, the architecture of VGG-16 is simplified and the block design is carried out, and the modified sVGG model is pre-trained with TFSI of source domain. Furthermore, a block-based frozen-fine-tuning transfer strategy is designed to quickly find and freeze the block with the greatest contribution to sVGG model, and the remaining blocks are fine-tuned by using TFSI of target subjects to obtain the target domain classification model. Extensive experiments are conducted based on public MI-EEG datasets, the average recognition rate and Kappa value of PTL-sVGG are 94.9% and 0.898, respectively. The results show that the subjects' optimization is beneficial to improve the model performance in source domain, and the block-based transfer strategy can enhance the transfer efficiency, realizing the rapid and effective transfer of model parameters across subjects on the datasets with different number of channels. It is beneficial to reduce the calibration time of BCI system, which promote the application of BCI technology in rehabilitation engineering.
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Humanos , Algoritmos , Interfaces Cerebro-Computador , Electroencefalografía/métodos , Imaginación , Aprendizaje AutomáticoRESUMEN
Noninfectious uveitic macular edema (NIU-ME) is a major cause of visual impairment in patients with uveitis. Intravitreal route can control inflammation rapidly, reduce macular edema, and improve vision with relatively lower doses of the drug. Currently, several intravitreal injection drugs have been used for the treatment of NIU-ME. Cataract and elevated intraocular pressure are the major complications. Due to its efficacy and safety, intravitreal drugs have gradually become an effective alternative to systemic treatment, especially in patients with unilateral disease. However, more studies are needed on drug selection, timing of injection and combination therapy in clinical practice. There are various treatments for NIU-ME, and the ultimate treatment should be individualized based on the severity of the disease, the risk/benefit ratio of each therapy, and the patient's tolerance.
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Non-suicidal self-injury, which is especially common in depressed adolescents, has become an important public health issue of global concern.It’s an independent risk factor for suicide, which not only seriously affects the physical and mental health of individuals, but also brings a great burden to families and society.The research status of non-suicidal self-injury in adolescent depression were systematically evaluated, aiming to improve the understanding of non-suicidal non-suicidal self-injury in adolescent depression, and provide a basis for clinical treatment and prevention of serious suicidal behavior.
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Combining with the currently applied psychology teaching mode of medical colleges and universities, regarding the core curriculum, abnormal psychology, as the object, we have explored the new teaching mode of graduate students majoring in applied psychology based on massive open online courses (MOOC), and promoted the fusion of classroom theory teaching, hospital practice, and MOOC course, so as to guide teaching reform of applied psychology and improve the quality of personnel training.
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Objective To determine the impact of new methods in teaching and examination on students' learning of psychiatry by increasing the proportion of objective questions in the final exam papers through examination reform, so as to help students adapt to the Practitioner Examination. Methods A total of 483 students from grade 2011&2012 were selected as research subjects. Through the comparative study of the test scores under different teaching methods before and after the examination reform, the SPSS 22.0 statistical software was used to analyze the structure, reliability, difficulty and level of differentiation of the examine papers via t tests. Results Examination papers after the reform showed an increase in difficulty in all question types; some question types also had higher levels of differentiation. Students receiving PBL-based education had higher scores compared to those under traditional teaching methods. The difference was statistically significant. Conclusion PBL teaching mode is more conducive to the mastering of knowledge points and helps students improve grades in objective questions. Medical schools should increase the use of PBL teaching reform in psychiatry courses and conduct examination reform, so as to improve the teaching effect and the passing rate of Practitioners Examination.
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Objective To explore the correlation between polymorphisms (SNPs) of locus rs2269272 of glial high-affinity glutamate transporter (SLC1A3) gene and suicide attempt among Chinese adolescents.Methods iMLDRTM genotyping technology was used to detect the polymorphism of rs2269272 SLC1A3 gene loci in 55 suicide attempters and 112 healthy controls,and survival analysis was applied to analyze the relationship between allele (T) and the age of suicide attempt.Results The differences of rs2269272 locus allele distribution between two groups were statistically significant(x2=4.208,P=0.040),but genotype distribution of two groups had no significantly differences(x2 =4.011,P=0.135).Non-suicidal self-injury adolescents with locus rs2269272 (15.6 ± 0.4) were younger than adolescents without locus rs2269272(16.4±0.7),but the difference was not statistically significant.Conclusion Preliminary findings suggest that rs2269272 SLC1 A3 may be relevant to non-suicidal self-injury acts,and rs2269272 locus allele is not related to earlier suicide attempt.
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European psychiatric specialist training system has been maturely developed for 6 decades.The institutional framework for psychiatric training during specialization has been conformed to European standards,including training content,assessment and training base.In Europe,psychiatry specialist education lasts 5-7 years.Trainees should have experience of psychiatric internships and get assessed prospectively.After the training,trainees will receive the qualifications of the association for psychiatric training in Europe.While in China,the training time of psychiatrists is 3 years,the training of related departments is nearly 1 year,and psychiatric training is only 2 years.The training time of psychotherapy and clinical practice of psychiatry is still not enough.There is also a lack of consistency in the implementation of theoretical and practical training in all the bases in China.Therefore,by comparing the advantages and disadvantages of the Chinese and European psychiatry training system,this paper proposes optimizing the training program in China,increasing the students' humanistic cultivation and psychological care,and further improving the input of special training funds.
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AIM:To observe the concentration of RBP4 and IL-6 in vitreous of proliferative diabetic retinopathy (PDR). METHODS: A total of 65 patients (66 eyes) were enrolled in Department of Ophthalmology, Renmin Hospital of Wuhan University from February 2017 to July 2017 with the informed consent. The patients were divided into PDR group (23 cases) and NPDR group (16 cases). Twenty- six patients without diabetic mellitus (DM) served as control group. The demography was matched among the groups, but the course of DM, the blood glucose level and the HbA1c level were elevated in the PDR group and the NPDR group (all P<0.05). Vitreous samples were collected during the procedure of vitrectomy. RBP4,IL-6,TNF-α concentrations in vitreous specimens were detected by ELISA. The differences of vitreous RBP4, IL-6 and TNF-α in various groups were statistically analyzed by ANOVA, respectively. The correlations between RBP4 and IL - 6, TNF - α were calculated by Pearson correlation analysis. RESULTS:The concentration of RBP4 in PDR group,the NPDR group and control group were 13.68士2.66, 11 03士1 12,10.45士1.17μ g/Ml, and the concentration of IL-6 were 56.0士10.27, 20.92士5.77, 10.26士1.91pg/Ml. RBP4 and IL- 6 concentrations were elevated in PDR group compared with NPDR group and control group, with significant difference among three groups (F = 12. 135, 161.167; P < 0. 01). IL - 6 concentrations in vitreous increased in the NPDR group in comparison with control group(P<0.05). RBP4 concentrations had no significant difference between the NPDR group and the group(P>0 05). Pearson correlation coefficient was significant positive between RBP4 concentration and IL - 6 concentration(r=0.606,P=0.001). CONCLUSION: RBP4 is probability involved in the inflammation pathogenesis of PDR. These results indicate that RBP4 could be a new target for the diagnosis and treatment of PDR.
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Objective To improve the diagnosis and treatment of type Ⅰ autoimmune pancreatitis, a study was carried out to summarize the epidemiological characteristics, clinical manifestations and diagnosis of autoimmune pancreatitis (AIP).Methods This study retrospectively analyzed the clinical data of all the patients diagnosed with AIP from January 1998 to December 2016 in the ward of Peking union medical college hospital.Results 194 type 1 AIP patients were enrolled in this study.The M/F ratio of the disease was 3.51/1,with an average age of 57±15 years.The most common symptom is jaundice, abdominal pain and weight loss.The most common diseases of the pancreas are sclerosing cholangitis, salivary glands, IgG4 nephropathy.There are 36.68 percent of AIP patients with diabetes mellitus.IgG4, ANA, ESR, c-reactive protein and CA199 are all contribute to disease diagnosis and follow-up.Pathology, pet-CT and hormone therapy response all contribute to the diagnosis of AIP.Conclusions As a systemic disease, the type 1 AIP has special clinical features and laboratory profiles.The diagnosis of AIP can be applied in many ways.
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Objective To understand the occurrence situation of negative life events in the past year among college students with suicidal ideation and to explore the correlation between negative life events and suicidal ideation. Methods The stratified and cluster sampling method was applied to conduct the questionnaire survey on 12 114 students from 11 universities in Chongqing City. The questionnaire of general demographic information was used to learn sociodemographic characteristics;the perspective on personal life questionnaire was applied to evaluate the suicidal ideation within recent 1 month and the self-designed life event scale was used to investigate the occurrence of negative life events in the past 1 year. Results The report rate of suicidal ideation within 1 month was 9.6%, the occurrence rate of short term suicidal ideation was increased with experiencing more negative life events. The x2 test showed that there was statistically significant difference in the proportion of suicidal ideation occurrence between college students experiencing 1 negative life event and those without experiencing the negative life event (x2 = 37.72,P<0.01) ;besides, the occurrence proportion of recent suicidal ideation had statistical difference between the college students with experiencing two or more negative life events and those without experiencing negative life event (x2 = 65.46,P<0.01). The multivariate Logistic regression analysis showed that the conflict with other family members (OR=0. 295,95%CI 0. 017-0. 571),abuse (OR=7. 295, 95%CI 6. 049-9. 701) were independentrisk factor for the recent suicidal ideation in college students. Conclusion Experiencing more negative life events, conflicting with other family members and abused by others have a correlation with the appearance of short term suicidal ideation in college students.
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Objective To study the non-fastidous antibiotic-resistance bacteria pollution in tap water from a neighborhood in Tianjin.Methods Tap water samples were collected and bacteria were isolated by R2A agar,and 16S rRNA gene sequence for the identification of bacteria isolates was used.Antibiotic susceptibility testing was performed using the Kirby-Bauer disc diffusion method.Results Among the 39 non-fastidous bacteria isolates,the resistance rate of antibioticresistance bacteria was 79.49％,including Enterococcus,Staphylococcus,Acinetobacter and Pseudomonas.Some bacteria (28.21％) showed resistance against only one antibiotic.The others (51.28％) were multiple resistant bacteria.Trimethoprim/sulfamethoxazole resistance was most prevalent (53.85％),and sulfamethoxazole resistance was also widely distributed (28.21％).Conclusion Tap water from this neighborhood is heavily polluted by non-fastidous antibioticresistantance bacteria,which deserves more attention.
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Objective To sum up the experience in diagnosis of fungal esophagitis. Methods An analysis was per-formed on clinical data of 38 cases of fungal esophagitis diagnosed through gastroscopy in Peking Union Medical College Hospital from Jan. 2013 to Dec. 2015. Results Of 38 cases, 26 were males and 12 were females. The mean age was(54.0±1.5) years old.76.3% had at least one risk factor.7 patients had oral candidiasis and 10 pa-tients had typical symptom of fungal esophagitis. Endoscopic severity was classified according to Kodsi's grade:gradeⅠ6 cases,grade Ⅱ29 cases, grade Ⅲ 1 case,grade Ⅳ 2 cases. Most patients were treated with systemic antifungal therapy. However,one patient's fungal esophagitis resolved without any treatment. Conclusions Endos-copy with biopsy is a valuable definitive diagnostic method for fungal esophagitis, especially for asymptomatic pa-tients or those without oral candidiasis. Systemic antifungal treatment is recommended with fluconazole as the first choice. More evaluation is needed to determine if systemic antifungal therapy is necessary for asymptomatic and im-munocompetent patients with mild fungal esophagitis.
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Objective To sum up the experience in diagnosis of fungal esophagitis. Methods An analysis was per-formed on clinical data of 38 cases of fungal esophagitis diagnosed through gastroscopy in Peking Union Medical College Hospital from Jan. 2013 to Dec. 2015. Results Of 38 cases, 26 were males and 12 were females. The mean age was(54.0±1.5) years old.76.3% had at least one risk factor.7 patients had oral candidiasis and 10 pa-tients had typical symptom of fungal esophagitis. Endoscopic severity was classified according to Kodsi's grade:gradeⅠ6 cases,grade Ⅱ29 cases, grade Ⅲ 1 case,grade Ⅳ 2 cases. Most patients were treated with systemic antifungal therapy. However,one patient's fungal esophagitis resolved without any treatment. Conclusions Endos-copy with biopsy is a valuable definitive diagnostic method for fungal esophagitis, especially for asymptomatic pa-tients or those without oral candidiasis. Systemic antifungal treatment is recommended with fluconazole as the first choice. More evaluation is needed to determine if systemic antifungal therapy is necessary for asymptomatic and im-munocompetent patients with mild fungal esophagitis.
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Background Studies show that retinal neurodegeneration may precede retinal microvascular changes in diabetes mellitus.The apoptosis of retinal ganglion cells (RGCs) is an early finding in retinal neurodegeneration.Toll-like receptor 4 (TLR4) is proved to be up-regulated in diabetic rats retina.However,the impact of TLR4 on RGCs damage in retinal neurodegeneration is poorly understood.Objective The aim of this study was to investigate the expressing change of TLR4 induced by high glucose in RGCs in order to offer a basis for the prevention diabetic retinal neurodegeneration and the study on targeting drugs.Methods RGCs were isolated and purified from the retinas of SPF SD rats aged postnatal 1-3 days by using papain digestion method and then were identified by immunofluorescence technology to detect the expression of Brn3a,a specific marker of RGCs.The cells were divided into normal control group and 10,20,30 mmol/L glucose groups.The expressions of TLR4 mRNA and protein in the ceils were detected by real-time fluorescence quantitative PCR and Western blot analysis in 24 and 48 hours after addtion of glucose.All procedures performed in studies were in accordance with the Association for National Institutes of Health (NIH) Statement for the Care and Use of Laboratory Animals recommendations.The protocol was approved by the Ethics Committee of Renmin Hospital of Wuhan University.Every effort was made to minimize animal discomfort and stress.Results The normal cells grew well with the shape of near roundness after inoculaton.The cells were gradually enlarged and clustered with obvious axons and dendrites 24 hours after purifying.Brn3a showed the positive expression in cultured cells.At 24 hours and 48 hours after glucose culture,the cell structures were gradually invisible in most cells.The expressions of TLR4 mRNA in the cells were 0.945 ±0.237,1.180±0.193 and 0.827±0.213 at 24 hours and 1.509±0.422,2.433±0.617 and 1.435±0.410 at 48 hours after culture in the 10,20 and 30 mmol/L glucose groups,respectively,which were significantly higher than 0.600±0.099 and 0.724±0.302 in the normal control group (all at P＜0.01).The expressions of TLR4 protein in the cells were 0.442±0.147,0.626±0.128 and 0.330±0.153 at 24 hours and 0.464±0.121,0.930±0.441 and 0.394±0.158 at 48 hours after culture in the 10,20 and 30 mmol/L glucose groups,respectively,which were significantly higher than 0.090±0.050 and 0.094±0.070 in the normal control group (all at P＜0.01).Conclusions A large number of RGCs die in a high-glucose environment in vitro,meanwhile,the expression of TLR4 up-regulates in the cells,indicating that TLR4 maybe participate in the damage of RGCs induced by high glucose.
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Objective To study the effect of clinical nursing path with graph and text instructions (GTI) on health education to patients with complex retinal detachment.Methods Toally 76 inpatients with complex retinal detachment were enrolled in the study:38 of them hosptalized from March to August 2015 were put in the control group received routine treatment and the others hosptalized from September 2015 to March 2016 as the experiment group treated with GTI.The clinical outcomes were compared.Result The patients treated with GTI were better in the knowledge of the complex retinal detachment and moreover,they felt significantly more satisfied compared to that of the control group (P＜0.05).Conclusion It is beneficial to use GTI in the patients with complex retinal detachment.GTI is effective for improving their knowledge on the disease,and increasing their satisfaction with the clinical nursing.
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BACKGROUND:After cataract extraction and intraocular lens implantation, some patients stil appear to suffer from refractive errors to varying degrees. In this case, excimer laser epithelial keratomileusis or excimer laser in situ keratomileusis can be used for correction of refractive errors. OBJECTIVE:To observe the therapeutic effect of excimer laser epithelial keratomileusis on the treatment of residual refractive errors after cataract extraction and intraocular lens implantation. METHODS:Thirty-eight patients with refractive errors (45 eyes) who had received cataract extraction and intraocular lens implantation were enroled, including 22 males and 16 females. Patient’s age was 24-74 years, and the central corneal thickness ranged 490-590μm. Before laser epithelial keratomileusis, the uncorrected visual acuity and corrected visual acuity were 0.1-0.3 and 0.6-1.0, respectively. The uncorrected visual acuity, best corrected visual acuity, diopter, and intraocular pressure were observed at 12 months after correction. RESULTS AND CONCLUSION:Most of the patients had foreign body sensation, pain and other symptoms of eye irritation at 3-6 postoperative hours, and then presented with eye pain, photophobia, tearing and other symptoms of corneal irritation with 2 days after surgery. The corneal epithelium healed basicaly at 7 days after surgery, and the vision recovered to top after about 20 days. After 12 months, the uncorrected visual acuity was 0.6-1.2,≥ 0.6 in al eyes,≥ 1.0 in 26 eyes (58%) and reached or exceeded the preoperative best corrected visual acuity in 35 eyes (78%). After surgery, the spherical degree was decreased from -2.5 m-1 to 0.5 m-1, and the cylinder degree was reduced from-3.85 m-1 to -0.53 m-1. High intraocular pressure occurred in 12 eyes, and 0.5-level corneal haze formed in 5 eyes. The results demonstrate that the excimer laser epithelial keratomileusis is safe and effective for treatment of refractive errors after cataract extraction and intraocular lens implantation.
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BACKGROUND:Hydrophilic acrylic materials with good biocompatibility have been widely used in clinic. However, there are some problems about the biocompatibility and safety of hydrophilic acrylic intraocular lens after long-term clinical application. OBJECTIVE:To discuss the biocompatibility and stability issues and corresponding processing methods after hydrophilic acrylic intraocular lens implantation. METHODS:A computer-based search of Wanfang and PubMed database was performed for articles related to clinical application of hydrophilic acrylic intraocular lens published from 2005 to 2014. The keywords were “hydrophilic acrylic,intraocular lens” in Chinese and English, respectively. A total of 618 articles were initialy retrieved, and finaly 35 articles were included in result analysis. RESULTS AND CONCLUSION:As the hydrophilic acrylic intraocular lens is foldable, a smal incision is required for implantation and the operation is simple that cause less damage to the patients. In addition, the hydrophilic acrylic intraocular lens has poor bacterial and inflammatory cel adhesion, which leads to a low probability of infective endophthalmitis after implantation. But there is a high incidence of posterior capsule opacification as wel as some refractive errors and visual quality problems after implantation. Taken together, to solve these problems depends on the continuous improvements and updates of intraocular lens materials and designs.
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AlM: To compare the clinical efficacy of treatment on recurrent pterygium using different concentration mitomycin C ( MMC) in the pterygium excision operation combined with the corneal limbal stem cell autografting ( CLSCA) .METHODS: Sixty patients ( 65 eyes ) with recurrent pterygium were randomly divided into three groups. All cases were accepted CLSCA, 21 patients (22 eyes) were given 0. 15g/L MMC during operation, 20 patients ( 22 eyes) were given 0. 25g/L MMC during operation, 19 patients ( 21 eyes ) were given 0. 4g/L MMC during operation. The patients were followed up for 6mo to 2a.RESULTS:The recurrent rates of the three groups were 9%, 5%, 5% respectively. There was no statistically significant differences (P>0. 05). The complication rates of the three groups were 5%, 36%, 33% respectively. There were statistically significant differences (P<0. 05). CONCLUSlON: The treatment to the recurrent pterygium using low concentration MMC has the similar recurrence rates, but the complication rate was lower, it is an ideal operation method, and it is worth popularization and application.
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To evaluate the clinical efficacy of corneal lamellar debridement combined with sutureless amniotic membrane transplantation for the treatment of superficial fungal keratitis. ●METHODS:Totally 22 cases (22 eyes) with superficial fungal keratitis were referred to our hospital from April 2012 to October 2013. The patients with persistent cornea ulcer after treatment of local and systemic antifungal drugs underwent corneal lamellar debridement combined with sutureless amniotic membrane transplantation, and the recipient bed was covered with an amniotic membrane using fibrin sealant during the operation. All patients were still given topical antifungal therapy for 1 -2mo after operation. The followed- up time was 3mo or above. We observed the corneal healing and amniotic membrane adhesion by split lamp microscope, and investigated the transformation of amniotic membrane and fungal infection recurrence with confocal microscope. ●RESULTS: Corneal edema and anterior chamber reaction of 21 patients disappeared gradually, and no amniotic membrane graft dissolved and shed off within 1-2wk postoperatively. Two weeks after operation, the graft integrated into the corneal and the corneal wounds' thickness increased gradually, the corneal epithelium reconstructed and corneas became clear. Four weeks after operation, the corneal scarring developed gradually and fluorescence staining was negative. Nineteen cases' amniotic membranes that adhered with the cornea dissolved 4wk after operation. There were different degrees of corneal nebula or macula remained 3mo postoperatively. All patients' vision improved in varying degrees, except in 1 case with fungal keratitis who had been cured by lamellar keratoplasty. ●CONCLUSlON:Corneal lamellar debridement combined with sutureless amniotic membrane transplantation can effectively remove the foci of inflammation, improve the local efficacy, shorten the operation time, relieve the postoperative reaction, and promote cornea union, which is an effective way to treat superficial fungal keratitis.
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Background Researches showed that platelet-derived growth factor (PDGF) modulate the expression of matrix metalloproteinase/tissue inhibitor of metalloproteinase (MMP/TIMP) in cells,but the association of expression of MMP/TIMP in retinal pigment epithelial (RPE) cells and the dose and active time of PDGF is unclear.Objective This study was to observe the effects of PDGF on the expressions of MMP-2,MMP-9 and TIMP-1 in cultured RPE cells in vitro.Methods RPE cell line,ARPE-19,was calculated in vitro,and the cells were divided into 5 groups when they reached 70％-80％ confluence.Different concentrations (0,0.1,1,10,50 mg/L) of PDGF was added into the medium respectively for 36 hours,and the expressing levels of mRNA and protein of MMP-2,MMP-9 and TIMP-1 were detected by reverse transcription PCR (RT-PCR) and Western blot assay.In addition,RPE cells in PDGF group were treated with 10 mg/L PDGF for 24,36,48 hours respectively to detect the expressions of mRNA and protein of MMP-2,MMP-9 and TIMP-1 in the cells and to compare with the control group without PDGF.Results PDGF stimulated proliferation of RPE cells in a dose-and time-dependent manner.As the increase of the PDGF concentrations,the expression values of MMP-2 mRNA and MMP-9 mRNA in RPE cells were gradually elevated,with a statistically significant difference among various groups (MMP-2 mRNA:F=79.304,P=0.000;MMP-9 mRNA:F =8.465,P=0.003),and the expressions of MMP-2 mRNA and MMP-9 mRNA were significantly higher in the 1,10,50 mg/L PDGF groups compared with 0 mg/L PDGF normal control group (all at P＜0.05).Also,the expression values of MMP-2 and MMP-9 proteins in RPE cells were gradually elevated with the increase of PDGF concentrations,showing statistically differences among the groups (MMP-2:F=26.550,P=0.000;MMP-9:F=80.993,P=0.000).Compared with the 0 mg/L PDGF group,MMP-2 and MMP-9 expression levels in the 1,10,50 mg/L PDGF groups were significantly up-regulated (all at P＜ 0.05).However,the expression levels of TIMP-1 mRNA and protein group in the cells were not significantly different among various groups (mRNA:F =0.143,P =0.962 ; protein:F =1.955,P =0.178).The expression levels of M MP-2 mRNA,M MP-9 mRNA in the cells were increased in the PDGF group compared with the control group at different time points (MMP-2 mRNA:Ftime =83.250,P=0.002 ; MMP-9 mRNA:Ftime =6.785,P =0.019).Also,the expression values of MMP-2 and MMP-9proteins in RPE cells were increased in the PDGF group compared with the control group at different time points (MMP-2:Ftime =1 l.185,P =0.041 ; MMP-9:Ftime =968.413,P =0.000).The expression levels of MMP-2 and MMP-9 mRNAs and proteins were significant between the two groups at different time points (all at Pgroup =0.000;all at Ptime＜0.05).While the expression changes of TIMP-1 werc not significant between the two groups and among various time points (all at P＞0.05) Conclusions PDGF up-regulates MMP-2 and MMP-9 expressions in RPE cells in a dose-and time-dependent manner.But,PDGF dose not alter the expression of TIMP-1.These results indicate that PDGF disrupt the balance of MMP/TIMP,which may damage the extracellular matrix and therefore facilitate the migration of RPE cells in the pathogenesis of proliferative vitreoretinopathy.