Mechanistic insights into cardiovascular effects of ultrafine particle exposure: A longitudinal panel study.

BACKGROUND: Ultrafine particle (UFP) has been linked with higher risks of cardiovascular diseases; however, the biological mechanisms remain to be fully elucidated. OBJECTIVES: This study aims to investigate the cardiovascular responses to short-term UFP exposure and the biological pathways involved. METHODS: A longitudinal panel study was conducted among 32 healthy, non-smoking young adults in Shanghai, China, who were engaged in five rounds of follow-ups between December 2020 and November 2021. Individual exposures were calculated based on the indoor and outdoor real-time measurements. Blood pressure, arterial stiffness, targeted biomarkers, and untargeted proteomics and metabolomics were examined during each follow-up. Linear mixed-effect models were applied to analyze the exposure and health data. The differential proteins and metabolites were used for pathway enrichment analyses. RESULTS: Short-term UFP exposure was associated with significant increases in blood pressure and arterial stiffness. For example, systolic blood pressure increased by 2.10 % (95 % confidence interval: 0.63 %, 3.59 %) corresponding to each interquartile increase in UFP concentrations at lag 0-3 h, while pulse wave velocity increased by 2.26 % (95 % confidence interval: 0.52 %, 4.04 %) at lag 7-12 h. In addition, dozens of molecular biomarkers altered significantly. These effects were generally present within 24 h after UFP exposure, and were robust to the adjustment of co-pollutants. Molecular changes detected in proteomics and metabolomics analyses were mainly involved in systemic inflammation, oxidative stress, endothelial dysfunction, coagulation, and disturbance in lipid transport and metabolism. DISCUSSION: This study provides novel and compelling evidence on the detrimental subclinical cardiovascular effects in response to short-term UFP exposure. The multi-omics profiling further offers holistic insights into the underlying biological pathways.

Evaluating the Impact of Maternal Exposure to Ozone on Twin Fetal Growth in China.

Unlike singletons, twins require attention not only to the birth weight of the fetuses but also to discordance (i.e., the differences between weights) because twin growth discordance is a significant factor contributing to perinatal mortality and morbidity in twin pregnancies. However, the impact of maternal air pollution exposure on twin growth discordance has rarely been investigated. We examined the association of long-term ozone exposure during preconception and pregnancy with the birth weight of twins and twin growth discordance among 35,795 twins from the National Free Preconception Health Examination Project between January 2010 and December 2019. Linear mixed-effect models and random-effect logistic regression models were used to examine the associations of ozone exposure with the birth weight-related outcomes (i.e., birth weight of twins and within-pair birth weight difference) and risk of twin growth discordance, respectively, after adjustment for demographic characteristics and lifestyle. We found that an interquartile range (IQR) increase (15 µg/m3) in ozone exposure during the entire pregnancy was associated with a reduction (-28.96g, 95% confidence interval [CI]: -46.37, -11.56) in the total birth weight of twins, and ozone had a more pronounced impact on the birth weight of the smaller fetuses (-18.28 g, 95% CI: -27.22, -9.34) compared to the larger fetuses (-9.88 g, 95% CI: -18.84, -0.92) in twin pregnancies. An IQR increase in ozone exposure during the entire pregnancy was associated with a significant increase (8.41 g, 95% CI: 4.13, 12.69) in the within-pair birth weight difference; the odds ratio (OR) of twin growth discordance related to ozone exposure increased by 9% (OR = 1.09, 95% CI: 1.01, 1.18). However, no consistently significant associations were observed for ozone exposure during prepregnancy. Male-male twin pairs and those who were born prematurely appeared to be more susceptible to ozone exposure than their counterparts. Long-term ozone exposure during pregnancy was associated with twin growth discordance, and our findings provide reference data for future studies.

Time-restricted feeding's effect on overweight and obese patients with chronic kidney disease stages 3-4: A prospective non-randomized control pilot study.

Background: Time-restricted feeding (TRF) has become a popular weight loss method in recent years. It is widely used in the nutritional treatment of normal obese people and obese people with chronic diseases such as diabetes mellitus and hypertension, and has shown many benefits. However, most TRF studies have excluded chronic kidney disease (CKD) patients, resulting in a lack of sufficient evidence-based practice for the efficacy and safety of TRF therapy for CKD. Therefore, we explore the efficacy and safety of TRF in overweight and obese patients with moderate-to-severe stage CKD through this pilot study, and observe patient compliance to assess the feasibility of the therapy. Methods: This is a prospective, non-randomized controlled short-term clinical trial. We recruited overweight and obese patients with CKD stages 3-4 from an outpatient clinic and assigned them to either a TRF group or a control diet (CD) group according to their preferences. Changes in renal function, other biochemical data, anthropometric parameters, gut microbiota, and adverse events were measured before the intervention and after 12 weeks. Results: The change in estimated glomerular filtration rate (eGFR) before and after intervention in the TRF group (Δ = 3.1 ± 5.3 ml/min/1.73m2) showed significant improvement compared with the CD group (Δ = -0.8 ± 4.4 ml/min/1.73m2). Furthermore, the TRF group had a significant decrease in uric acid (Δ = -70.8 ± 124.2 µmol/L), but an increase in total protein (Δ = 1.7 ± 2.5 g/L), while the changes were inconsistent for inflammatory factors. In addition, the TRF group showed a significant decrease in body weight (Δ = -2.8 ± 2.9 kg) compared to the CD group, and body composition indicated the same decrease in body fat mass, fat free mass and body water. Additionally, TRF shifted the gut microbiota in a positive direction. Conclusion: Preliminary studies suggest that overweight and obese patients with moderate-to-severe CKD with weight loss needs, and who were under strict medical supervision by healthcare professionals, performed TRF with good compliance. They did so without apparent adverse events, and showed efficacy in protecting renal function. These results may be due to changes in body composition and alterations in gut microbiota.

Machine learning algorithms' accuracy in predicting kidney disease progression: a systematic review and meta-analysis.

BACKGROUND: Kidney disease progression rates vary among patients. Rapid and accurate prediction of kidney disease outcomes is crucial for disease management. In recent years, various prediction models using Machine Learning (ML) algorithms have been established in nephrology. However, their accuracy have been inconsistent. Therefore, we conducted a systematic review and meta-analysis to investigate the diagnostic accuracy of ML algorithms for kidney disease progression. METHODS: We searched PubMed, EMBASE, Cochrane Central Register of Controlled Trials, the Chinese Biomedicine Literature Database, Chinese National Knowledge Infrastructure, Wanfang Database, and the VIP Database for diagnostic studies on ML algorithms' accuracy in predicting kidney disease prognosis, from the establishment of these databases until October 2020. Two investigators independently evaluate study quality by QUADAS-2 tool and extracted data from single ML algorithm for data synthesis using the bivariate model and the hierarchical summary receiver operating characteristic (HSROC) model. RESULTS: Fifteen studies were left after screening, only 6 studies were eligible for data synthesis. The sample size of these 6 studies was 12,534, and the kidney disease types could be divided into chronic kidney disease (CKD) and Immunoglobulin A Nephropathy, with 5 articles using end-stage renal diseases occurrence as the primary outcome. The main results indicated that the area under curve (AUC) of the HSROC was 0.87 (0.84-0.90) and ML algorithm exhibited a strong specificity, 95% confidence interval and heterogeneity (I2) of (0.87, 0.84-0.90, [I2 99.0%]) and a weak sensitivity of (0.68, 0.58-0.77, [I2 99.7%]) in predicting kidney disease deterioration. And the the results of subgroup analysis indicated that ML algorithm's AUC for predicting CKD prognosis was 0.82 (0.79-0.85), with the pool sensitivity of (0.64, 0.49-0.77, [I2 99.20%]) and pool specificity of (0.84, 0.74-0.91, [I2 99.84%]). The ML algorithm's AUC for predicting IgA nephropathy prognosis was 0.78 (0.74-0.81), with the pool sensitivity of (0.74, 0.71-0.77, [I2 7.10%]) and pool specificity of (0.93, 0.91-0.95, [I2 83.92%]). CONCLUSION: Taking advantage of big data, ML algorithm-based prediction models have high accuracy in predicting kidney disease progression, we recommend ML algorithms as an auxiliary tool for clinicians to determine proper treatment and disease management strategies.

Association of residential noise exposure with maternal anxiety and depression in late pregnancy.

BACKGROUND: Noise is one of the most important environmental risk factors that adversely affects human health. Residential noise exposure has been associated with increased risk of anxiety and depression in the general population. However, limited study has been conducted in pregnant women. OBJECTIVE: To examine the associations of residential noise exposure with prenatal anxiety and depression. METHODS: Self-Rating Anxiety Scale (SAS) and Center for Epidemiological Survey Scale (CES-D) were used to assess the status of prenatal anxiety and depression for 2,018 pregnant women in Shanghai, China. Residential noise exposure was represented by a land use regression model. Multivariate logistic regression model was used to estimate the associations of noise exposure with prenatal anxiety and depression. RESULTS: The prevalence rates of prenatal anxiety and depression were 7.5 % and 8.1 %, respectively. The mean (±standard deviation) residential noise exposure during the whole pregnancy was 60.69 (±3.31) dB (A). Higher residential noise exposure was associated with increased odds of both prenatal anxiety and depression. Compared with low level of noise exposure group (<65 dB(A)), the odds of prenatal anxiety and depression increased 69 % (OR = 1.69, 95 % CI, 1.01-2.82) and 71 % (OR = 1.71, 95 % CI, 1.05-2.80) in higher noise exposure group (≥65 dB(A)), respectively. Stratified analyses showed that the associations were stronger among pregnant women with lower socioeconomic status. CONCLUSION: Residential noise exposure during pregnancy might be a risk factor for prenatal anxiety and depression.

Self-management program for patients with chronic kidney disease (SMP-CKD) in Southern China: protocol for an ambispective cohort study.

BACKGROUND: Chronic kidney disease (CKD) is a major global health problem. Short-term self-management has been considered to effect some renal and psychological endpoints. However, there are currently very few studies about self-management for CKD that a) have been scientifically designed by a theory-based framework and b) that evaluate the long-term effects and working mechanism. This study presents the rationale and design of a theory-based cohort study to explore how this self-management intervention works and its effectiveness on the Chinese CKD population. METHODS: In this ambispective intervention cohort study,1,200 patients with CKD stages 1-5 will be recruited from July 2015 to July 2024 in 3 branches of Guangdong Provincial Hospital of Chinese Medicine (GPHCM) in Guangdong province, China. The patients in the self-management cohort will choose to receive an intervention that consists of education, nutrition/diet modification, lifestyle change recommendation, medication review, and psychology support based on Social Cognition Theory (SCT). The patients in the control cohort will do regular follow-ups based on the clinic rules. All the patients will be followed up for 5 years, or until the occurrence of a primary outcome. Detailed clinical, laboratory markers, nutritional status, psychological exposures and outcome questionaries will be collected semiannually in CKD stage 1-2 and trimonthly in stage 3-5 patients. The primary outcome is the occurrence of composite clinical endpoints (doubling of serum creatinine level, ESKD, loss of renal function (≥ 40% decline in GFR from baseline), death, major cardiovascular or cerebrovascular events). The main secondary outcomes include the absolute change and slope of eGFR, absolute changes of urinary protein creatinine ratio, 24-h urine proteinuria, intact parathyroid hormone level, and self-management adherence rate and quality of life from baseline to end of the study. The effectiveness of self-management will be analyzed and the association between longitudinal trajectories of self-management and renal outcomes will be evaluated. DISCUSSION: This study aims to provide further evidence for the effectiveness of theory-based self-management in CKD patients and to improve the lives of patients with CKD by slowing progression, improving psychological well-being and overall quality of life. TRIAL REGISTRATION: Chinese Clinical Trial Register (ChiCTR1900024633). 19 July, 2019. http://www.chictr.org.cn/showproj.aspx?proj=38378.

Application of land use regression to map environmental noise in Shanghai, China.

BACKGROUND: Urban environment noise has been linked with wide adverse effects on health; however, noise epidemiological researches are hindered by the lack of large-scale population-based exposure assessment. OBJECTIVE: We aimed to measure noise levels over multiple seasons and to establish an LUR model to assess the spatial variability of intra-urban noise and identify its potential sources in Shanghai, China. METHODS: Forty-minute (LAeq, 40 min) measurements of environmental noise were collected at 144 fixed sites, and each was visited three times (morning, afternoon, and evening) in winter, spring, and summer in 2019. Noise measurements were then integrated with land-use types, road networks, socioeconomic variables, and geographic information systems to construct LUR models. Ten-fold cross-validation was used to test the model performance. RESULTS: A total of 1296 measurements and 29 predicting variables were used to estimate the spatial variation in environmental noise. The annual mean (±standard deviation) of LAeq, 40min, was 62 ± 8 dB (A). Significant variations were observed among monitoring sites but not between seasons or time of day. The LUR model explained 79% of the spatial variability of the noise, and the R2 of the ten-fold cross-validation was 0.75. The most contributory predictors of noise level were road-related variables all within the 50-m buffers, followed by urban area within a 50-m buffer, total area of buildings within a 1000-m buffer, and number of restaurant clusters within a 50-m buffer. Farmland area within a 100-m buffer was the only negative variable in the model. A 50-m resolution noise prediction map was produced and suggested high noise level in urban areas and near traffic arteries. CONCLUSION: LUR can be a robust method for reflecting noise variability in megacities such as Shanghai and may provide an efficient solution for noise exposure assessment in areas where noise maps are not available.

High spatial resolution land-use regression model for urban ultrafine particle exposure assessment in Shanghai, China.

BACKGROUND: Little is currently known about long-term health effects of ambient ultrafine particles (UFPs) due to the lack of exposure assessment metrics suitable for use in large population-based studies. Land use regression (LUR) models have been used increasingly for modeling small-scale spatial variation in UFPs concentrations in European and American, but have never been applied in developing countries with heavy air pollution. OBJECTIVE: This study developed a land-use regression (LUR) model for UFP exposure assessment in Shanghai, a typic mega city of China, where dense population resides. METHOD: A 30-minute measurement of particle number concentrations of UFPs was collected at each visit at 144 fixed sites, and each was visited three times in each season of winter, spring, and summer. The annual adjusted average was calculated and regressed against pre-selected geographic information system-derived predictor variables using a stepwise variable selection method. RESULT: The final LUR model explained 69% of the spatial variability in UFP with a root mean square error of 6008 particles cm-3. The 10-fold cross validation R2 reached 0.68, revealing the robustness of the model. The final predictors included traffic-related NOx emissions, number of restaurants, building footprint area, and distance to the nearest national road. These predictors were within a relatively small buffer size, ranging from 50 m to 100 m, indicating great spatial variations of UFP particle number concentration and the need of high-resolution models for UFP exposure assessment in urban areas. CONCLUSION: We concluded that based on a purpose-designed short-term monitoring network, LUR model can be applied to predict UFPs spatial surface in a mega city of China. Majority of the spatial variability in the annual mean of ambient UFP was explained in the model comprised primarily of traffic-, building-, and restaurant-related predictors.

Increasing CCL5/CCR5 on CD4+ T cells in peripheral blood of oral lichen planus.

Oral lichen planus (OLP) is a T cell-mediated autoimmune disease of oral mucosa, in which T helper 1 (Th1) cells are greatly involved. Chemokine CCL5 is required for T cells infiltration and activation. CCR5, one of its receptors, specifically expressed on Th1 cells among CD4(+) T cells, can be up-regulated by Th1 cytokines like interleukin2 (IL-2) and interferon-gamma (IFN-γ), and down-regulated by Th2 cytokines like IL-4. The present study aimed to determine whether CCL5 and CCR5 had effects on the immune response of OLP. We analyzed the proportion of CCR5(+)CD4(+) T cells in CD4(+) T cells using flow cytometry and the serum levels of CCL5, IL-2, IFN-γ, and IL-4 with ELISA. MicroRNA-125a (miR-125a), a blocker of CCL5, was examined with RT-PCR. The results showed both the serum CCL5 and the percentage of CCR5(+)CD4(+) T cells elevated in OLP patients. Serum IL-2 and IFN-γ increased in OLP patients, but IL-4 decreased. MiR-125a was down-regulated in OLP patients, and there was a negative correlation between miR-125a content and the OLP severity which was measured with a RAE (reticular, atrophic and erosive lesion) scoring system. In conclusion, increasing CCl5/CCR5 might participate in the immune response of OLP. Th1-type cytokines environment presented in OLP probably performed as a magnifier for the CCR5. Moreover, miR-125a might be a candidate biomarker to estimate the severity of OLP.

Increased B7-H1 expression on peripheral blood T cells in oral lichen planus correlated with disease severity.

BACKGROUND: Oral lichen planus (OLP) is a chronic and T cell-mediated autoimmune disease whose immunopathogenesis may involve antigen-presentation, T cells activation and migration as well as keratinocytes apoptosis. PD-1/B7-H1 pathway may have a unique function in regulating self-reactive T cells associated with inflammatory response and maintaining tolerance in peripheral tissues. In this study, we aimed to explore the contribution of PD-1/B7-H1 pathway to OLP. METHODS: We determined the expression of PD-1 and B7-H1 on peripheral blood T cells from OLP cases and analyzed their association with disease severity assessed by RAE (reticular, atrophic and erosive lesion) scoring system. In addition, interferon-γ, interleukin (IL)-2, IL-4, IL-10 and soluble PD-1 concentrations in serum were measured using ELISA. Then, we explored the regulation of PD-1/B7-H1 pathway on T cells immune response in OLP by blockade of PD-1 or B7-H1. RESULTS: We found that PD-1 and B7-H1 were up-regulated on peripheral blood T cells from OLP patients and B7-H1 expression positively correlated with disease severity of OLP. It is suggested that Th1 dominant inflammatory situation might contribute to the high expression of PD-1 and B7-H1 in OLP. Blockade of PD-1/B7-H1 pathway significantly increased the proliferation, and IFN-γ and IL-2 production of T cells. CONCLUSIONS: PD-1/B7-H1 pathway may play an important role in negatively modulating T cell-mediated immune response in OLP, and provide the rationale to employ B7-H1 expression on peripheral blood T cells as a marker of severity of OLP and to develop agonists targeting PD-1/B7-H1 pathway as a promising immunotherapeutic strategy for OLP.

[A multiple three-dimensional interactive teaching mode in teaching diseases of oral mucosa].

Diseases of oral mucosa are characterized by complex etiology, diverse and confused clinical manifestations, as well as lack of special therapeutic drugs and methods. So it has always been a non-evasive teaching conundrum. This paper explored a multiple three-dimensional interactive teaching mode, a combination of problem-based learning (PBL), case-based learning (CBL), multimedia, internet and evidence-based medicine. It is hoped that its application in the teaching of the diseases of oral mucosa will arouse the students' learning interest, broaden their professional perspective, cultivate their self-learning ability to find, ask, analyze and solve problems, and strengthen their clinical practice capacity.

Efficacy and safety of dexamethasone ointment on recurrent aphthous ulceration.

OBJECTIVE: Recurrent aphthous ulceration is the most common oral mucosal lesion and may be associated with many systemic diseases. Topical corticosteroids are used frequently for recurrent aphthous ulceration; however, the number of high-quality clinical experiments available is insufficient, and no reports exist on the blood level of corticosteroids after topical usage in the oral mucosa. The objective was to determine the efficacy and safety of dexamethasone ointment in the treatment of recurrent aphthous ulceration and detect serum dexamethasone concentrations in the patients. METHODS: A randomized, double-blinded, placebo-controlled, parallel, multicenter clinical trial was conducted in 5 centers to compare the efficacy and safety of dexamethasone ointment with placebo. There were 810 patients with minor recurrent aphthous ulcerations screened for study eligibility, and 240 patients were enrolled at 5 centers from March 1, 2009 to April 30, 2010; 120 were assigned randomly to the treatment group and 120 to a control group. Patients were instructed to apply the given agent to the identified ulcer 3 times a day (after meals) for 5 days. The size, pain level, healing ratio, and average duration of ulcers and the safety of the agents were evaluated. The serum concentration of dexamethasone was detected using a high-performance liquid chromatography/mass spectrometry assay. RESULTS: The results showed that baseline characteristics were similar (P>.5). At day 6 ± 2 after treatment, there was significant difference in the variation of ulcer size between the treatment group (7.167 ± 6.3415 mm(2)) and the control group (4.346 ± 7.0666 mm(2); P = .000); and in the variation of pain level between the treatment group (5.623 ± 1.9570) and the control group (4.940 ± 2.2449; P = .001). The healing ratio was 83.33% in the treatment group and 54.70% in the control group (P = .000). No severe adverse reactions were observed. No serum dexamethasone was detected before or after the use of the agents (<0.502 ng/mL). CONCLUSION: Dexamethasone ointment was efficient in the treatment of recurrent aphthous ulceration and was safe as evaluated using clinical assessment and serum level detection.

Biologics, an alternative therapeutic approach for oral lichen planus.

Oral lichen planus (OLP) is generally accepted as a chronic and T-cell-mediated autoimmune disease, whose immunopathogenesis may involve antigen presentation, T-cell activation and migration as well as, possibly, tumor necrosis factor-alpha (TNF-α)-induced keratinocytes apoptosis. However, present treatment options for OLP are far from being satisfactory. Recent advances in understanding the pathogenesis of OLP, progress in biologics, and the success of biologic therapies in OLP indicate that biologic agents are facing expanding indications in OLP. In this review, we mainly discuss the role of T cells in the pathogenesis of OLP and several biologic therapies that directly and/or indirectly target T cells to treat OLP.

Expression of T-bet and GATA-3 in peripheral blood mononuclear cells of patients with oral lichen planus.

OBJECTIVE: Oral lichen planus (OLP) is a T-cell-mediated chronic inflammatory oral disease of unknown aetiology. Imbalanced cytokine production by Th1 and Th2 probably contributes to the pathogenesis of OLP. Growing evidence has suggested that two Th1/Th2-specific transcription factors, T-bet and GATA-3, may play a critical role in the development of Th1 and Th2 immunity. The aim of the present study was to investigate the mRNA expressions of T-bet and GATA-3 in the peripheral blood mononuclear cells of OLP subjects, and their expression patterns in relation to several clinical features. DESIGN: Expressions of T-bet and GATA-3 mRNA in peripheral blood mononuclear cells isolated from twenty-eight OLP subjects and sixteen controls were detected by real-time reverse transcription-polymerase chain reaction. RESULTS: When OLP subjects were regarded as a whole group, T-bet mRNA level and the ratio of T-bet/GATA-3 mRNA in OLP subjects were significantly higher (P<0.05) than those in controls. When the OLP subjects were divided according to different clinical forms, genders or age groups, T-bet, but not GATA-3, mRNA levels in reticular (P<0.01), female (P<0.05) and elder (age>55, P<0.05) OLP patients were significantly higher than those in control subjects. T-bet/GATA-3 mRNA ratio only in reticular (P<0.05) OLP subjects was significantly higher than that in control subjects. CONCLUSIONS: The results implicate a predominant role of Th1-type immune response in pathogenesis of OLP. Different gene expressions of T-bet in different clinical features may indicate different immunoregulatory mechanisms of OLP.

Activation of nuclear factor-kappa B correlates with tumor necrosis factor-alpha in oral lichen planus: a clinicopathologic study in atrophic-erosive and reticular form.

BACKGROUND: Nuclear factor-kappa B (NF-kappaB) is believed to be involved in the pathogenesis of various inflammatory diseases, including oral lichen planus (OLP). The objective of the present study was to investigate the possible relationship between NF-kappaB activation and expression of tumor necrosis factor-alpha (TNF-alpha) in OLP and their expression pattern in relation to several clinical features. METHODS: Thirty OLP cases were divided into atrophic-erosive form (14 cases) and reticular form (16 cases) according to their clinical manifestations. The expression of NF-kappaB p65 and TNF-alpha of both two groups were investigated by immunohistochemical staining, and the percentage of positive cells was calculated in each case. Biopsies of 10 normal oral mucosa (NOM) also underwent the same procedure as controls. RESULTS: Nuclear factor-kappa B p65 nuclear staining was found in nuclei of basal and suprabasal epithelial keratinocytes in OLP, however, no positive staining was found in NOM. Positive TNF-alpha staining was detected in cytoplasm of basal epithelial keratinocytes in OLP, and only scattered staining was detected in NOM. Expression of NF-kappaB p65 and TNF-alpha were significantly different with respect to clinical forms and lesion sites (P < 0.05), except for genders (P > 0.05) in 30 OLP cases. NF-kappaB nuclear staining positively correlated (r = 0.676, P < 0.01) with TNF-alpha overexpression in OLP. CONCLUSIONS: Nuclear factor-kappa B activation and its correlation with overexpression of TNF-alpha may play an important role in pathogenesis of OLP. There might be a positive regulatory loop between NF-kappaB and TNF-alpha, which may contribute to inflammation in OLP; NF-kappaB may also protect epithelial keratinocytes from excessive apoptosis.