Theoretical Study of a Two-Photon Fluorescent Probe Based on Nile Red Derivatives with Controllable Fluorescence Wavelength and Water Solubility.

Hypochloric acid (HOCl) plays a vital role in the natural defense system, but abnormal levels of it can cause cell damage, accelerated human aging, and various diseases. It is of great significance to develop new probes for detecting HOCl in biosystems nondestructively and noninvasively. The purpose of this work is to explore new chemical modification strategies of two-photon excitation fluorescence (TPEF) probes to improve the poor water solubility and low efficiency in imaging applications. Nil-OH-6 has a two-photon absorption cross-section value as high as 243 GM and attains a good quantum yield of 0.49. In addition, the modification of terminal groups with different azetidine-heterospirocycles or N,N-dialkyl fused amino groups to Nile Red can effectively improve the fluorescence efficiency as well as increase the solubility to some extent. This study provides some strategies to simultaneously improve the fluorescence performance and solubility of these two-photon probes and, hence, reliable guidance and a foundation for the subsequent synthesis of TPEF probes based on Nile Red.

Psychometric properties of the Chinese version of the aging transformation scale for older adults with dementia.

BACKGROUND: The key part of home care services is the assessment of the needs of the home environment for older adults with dementia. The present study was conducted to evaluate the psychometric properties of a newly adapted Chinese version of an instrument designed to measure aging transformation needs among older adults with dementia. METHODS: A sample of 175 older adults with dementia was selected from ten communities in China. The 55-item aging transformation needs scale was answered by the participants. Content validity, Cronbach's alpha, item-to-total correlation, and exploratory factor analysis were used to assess the reliability and validity of the instrument. RESULTS: The aging transformation needs scale has a good surface validity, content validity, and structural validity. The content validity was 0.965; 55 items had large factor loads on their corresponding principal components (≥0.5). There was a significant correlation between the aging transformation needs scale and each component (r = 0.897-0.973, all P< 0.01), and 9 components also had a high correlation (r = 765~0.977, all P< 0.01); the total table Cronbach's α was 0.993, the Cronbach's α of each constituent factor was 0.944~0.990, and the correlation coefficient between factor and content was > 0.40 (all P< 0.01). CONCLUSIONS: Evidence was found to support the reliability and validity of the aging transformation needs scale that measures the quality of the aging transformation needs for older adults with dementia from an aging transformation needs perspective.

Metabolic profiling of cold adaptation of a deep-sea psychrotolerant Microbacterium sediminis to prolonged low temperature under high hydrostatic pressure.

The most wide-spread "hostile" environmental factor for marine microorganisms is low temperature, which is usually accompanied by high hydrostatic pressure (HHP). Metabolic mechanisms of marine microorganisms adapting to prolonged low temperature under HHP remain to be clarified. To reveal the underlying metabolic mechanisms, we performed NMR-based metabolomic analysis of aqueous extracts derived from a psychrotolerant Microbacterium sediminis YLB-01, which was isolated from deep-sea sediment and possess great biotechnology potentials. The YLB-01 cells were firstly cultivated at the optimal condition (28 °C, 0.1 MPa) for either 18 h (logarithmic phase) or 24 h (stationary phase), then continually cultivated at either 28 °C or 4 °C under HHP (30 MPa) for 7 days. The cells cultivated at low temperature, which experienced cold stress, were distinctly distinguished from those at normal temperature. Cold stress primarily induced metabolic changes in amino acid metabolism and carbohydrate metabolism. Furthermore, the logarithmic and stationary phase cells cultivated at low temperature exhibited distinct metabolic discrimination, which was mostly reflected in the significantly disturbed carbohydrate metabolism. The logarithmic phase cells displayed suppressed TCA cycle, while the stationary phase cells showed decreased pyruvate and increased lactate. In addition, we performed transcriptome analysis for the stationary phase cells to support the metabolomic analysis. Our results suggest that the cold adaptation of the psychrotroph YLB-01 is closely associated with profoundly altered amino acid metabolism and carbohydrate metabolism. Our work provides a mechanistic understanding of the metabolic adaptation of marine psychrotrophs to prolonged low temperature under HHP.

New ß-Lactone with Tea Pathogenic Fungus Inhibitory Effect from Marine-Derived Fungus MCCC3A00957.

Fusarium solani H915 (MCCC3A00957), a fungus originating from mangrove sediment, showed potent inhibitory activity against tea pathogenic fungus Pestalotiopsis theae. Successive chromatographic separation on an ethyl acetate (EtOAc) extract of F. solani H915 resulted in the isolation of five new alkenoic diacid derivatives: fusarilactones A-C (1-3), and fusaridioic acids B (4) and C (5), in addition to seven known compounds (6-12). The chemical structures of these metabolites were elucidated on the basis of UV, IR, HR-ESI-MS, and NMR spectroscopic data. The antifungal activity of the isolated compounds was evaluated. Compounds with a ß-lactone ring (1, 2, and 7) exhibited potent inhibitory activities, while none of the other compounds show activity. The ED50 values of the compounds 1, 2, and 7 were 38.14 ± 1.67, 42.26 ± 1.96, and 18.35 ± 1.27 µg/mL, respectively. In addition, inhibitory activity of these compounds against 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase gene expression was also detected using real-time RT-PCR. Results indicated that compounds 1, 2, and 7 may inhibit the growth of P. theae by interfering with the biosynthesis of ergosterol by down-regulating the expression of HMG-CoA synthase.

Relative telomere length and gene expression of shelterin complex proteins among vinyl chloride monomer-exposed workers in China.

Vinyl chloride monomer (VCM) is a confirmed carcinogen. The effects of VCM on telomeres and the gene expression of telomere complex proteins, shelterin, have not been well studied but could be of potential relevance to the carcinogenic mechanism of VCM and the health surveillance of VCM-exposed workers. A group of 241 VCM-exposed workers and 101 internal controls from the same plant in Shandong, China were recruited and quantitative polymerase chain reaction was preformed to measure relative telomere length (RTL) and gene expression of shelterin proteins. VCM cumulative exposure dose (CED) was estimated for the exposed workers. The differences in RTL and gene expression between groups were compared by Wald test fitted with robust regression. Shorter RTL was observed in VCM-exposed workers than in the controls (P < 0.001) and was related to CED of VCM. Shortened RTL was also significantly related to increasing age (P = 0.012) and high blood pressure (P = 0.056). Levels of gene expression of shelterin components in exposed workers were all lower than in controls except increased TIN2 expression, and the gene expression differences in TIN2 and POT1 among exposed and control groups were significant (P = 0.014 for TIN2 and P < 0.001 for POT1, respectively). VCM exposure is found associated with altered telomere length and gene expression of shelterin components. This provides new insights into the potential carcinogenic mechanisms of VCM and could be helpful for the health surveillance for VCM-exposed workers. Environ. Mol. Mutagen. 60:361-367, 2019. © 2018 Wiley Periodicals, Inc.

Hypermethylation of CpG islands is associated with increasing chromosomal damage in chinese lead-exposed workers.

Lead is a widely existing environmental pollutant with potential carcinogenicity. To investigate the association of blood lead level (B-Pb) with potential chromosomal damage and cancer, we analyzed micronucleus (MN) frequency of peripheral blood lymphocytes (PBLs) and the methylation status of six human tumor suppressor genes (TSGs) post lead exposure. In the study, 147 lead-exposed workers were divided into two groups according to their B-Pb P50 value, with other 50 lead-unexposed workers as a control group. The cytokinesis-blocked micronucleus (CBMN) assay was performed to detect chromosomal damage of PBLs of both lead-exposed and -unexposed workers. The methylation-specific polymerase chain reaction (MSP-PCR) was further used to examine the methylation status of six TSGs (GSTP1, hMLH1, MGMT, p14, p15, and p16). Results showed that MN frequencies of high B-Pb workers 8.1 ± 3.1‰ and low B-Pb workers 5.7 ± 2.3‰ were significantly higher than that of control group 2.8 ± 1.9‰ (P < 0.01), while the MN frequency of high B-Pb workers was also higher than that of the low B-Pb workers (P < 0.01). The MN frequency in PBLs of lead-exposed group with the methylated TSGs was significantly higher than that in PBLs with the unmethylated TSGs (P < 0.05). Notably, the CpG island methylator phenotype (CIMP) correlated with chromosome damage (P < 0.05). Additionally, workers with high B-Pb had higher chromosome damage than those with low B-Pb (P < 0.05). Taken altogether, the results suggest that lead-exposed workers with CIMP positive and high B-Pb have a higher risk of being vulnerable to tumorigenesis. Environ. Mol. Mutagen. 59:549-556, 2018. © 2018 Wiley Periodicals, Inc.

Association of Telomere Length With Chromosomal Damage Among Chinese Workers Exposed to Vinyl Chloride Monomer.

OBJECTIVE: To explore the relationship between relative telomere length (RTL) and chromosomal damage represented by micronucleus (MN) frequencies among vinyl chloride monomer (VCM) -exposed workers. METHODS: A group of 126 VCM-exposed workers, 60 internal controls, and 25 external controls were examined for RTL by Quantitative polymerase chain reaction and MN frequencies by cytokinesis-block micronucleus test. Cumulative exposure dose was used to estimate the exposure of VCM-exposed workers. RESULTS: The RTL were significantly shorter in exposed workers and internal controls than in external controls. The exposed workers had significantly increased MN frequencies than both control groups. Additionally, MN frequencies were negatively associated with RTL in VCM-exposed group. CONCLUSIONS: VCM exposure may alter telomere length, which could be a potential biomarker of susceptibility to chromosomal damage.

Integrated Supported Employment for People With Schizophrenia in Mainland China: A Randomized Controlled Trial.

OBJECTIVE: In this randomized controlled trial, we investigated the effectiveness of integrated supported employment (ISE) compared with individual placement and support (IPS) and traditional vocational rehabilitation (TVR) for people with schizophrenia in mainland China. METHOD: One hundred and sixty-two participants with schizophrenia were randomly assigned to ISE (n = 54), IPS (n = 54), or TVR (n = 54). Blinded assessments of employment status, job tenure, and psychological outcomes were conducted at admission; completion of the 3-mo program; and follow-up at 7, 11, and 15 mo. RESULTS: Significantly higher employment rate and longer job tenure were found in the ISE group (63.0%, 29.56 wk) compared with the IPS group (50.0%, 25.47 wk) and TVR group (33.3%, 9.91 wk). The ISE group also attained the most positive psychological outcomes. CONCLUSION: Work-related social skills training embedded in ISE with generalization strategies can enhance vocational and nonvocational outcomes for people with schizophrenia in mainland China.

Comparison of carotid and lower limb atherosclerotic lesions in both previously known and newly diagnosed type 2 diabetes mellitus.

AIMS/INTRODUCTION: To compare carotid and lower limb atherosclerotic lesions, and examine if carotid atherosclerotic lesions are in line with lower limb atherosclerotic lesions, and can reflect generalized atherosclerosis in inpatients with type 2 diabetes. MATERIALS AND METHODS: This was an observational study carried out in 867 Chinese inpatients with type 2 diabetes, including 573 previously known and 294 newly diagnosed patients. Ultrasonographic assessments of intima-media thickness (IMT), plaques, and stenosis in the carotid and lower limb arteries were evaluated. Atherosclerotic lesions between the carotid and lower limb arteries were compared in both previously known and newly diagnosed diabetes, respectively. RESULTS: In both the known (77.3% vs 49.4%, P < 0.001) and the newly diagnosed diabetes (55.4% vs 29.9%, P < 0.001), the prevalence of atherosclerotic plaques was significantly higher in the lower limb arteries than in the carotid arteries. Likewise, the prevalence of stenosis was also significantly higher (P < 0.001) in the lower limb arteries (16.9%) than in the carotid arteries (4.2%) in the established diabetes patients. However, there was no significant difference in the mean IMT between common carotid and common femoral arteries in both the previously known (0.90 ± 0.24 mm vs 0.89 ± 0.20 mm, P = 0.675) and the newly diagnosed diabetes patients (0.86 ± 0.22 mm vs 0.85 ± 0.16 mm, P = 0.436). CONCLUSIONS: Carotid plaques might underestimate generalized plaques in inpatients with type 2 diabetes, as shown by its significantly lower prevalence compared with that of the lower extremity arteries. A combined carotid and lower limb ultrasound examination can improve the detection of atherosclerotic lesions in inpatients with type 2 diabetes.

[Detection rates of atherosclerosis by carotid versus lower limb ultrasonography in newly diagnosed type 2 diabetics].

OBJECTIVE: To compare the detection rates of atherosclerosis by carotid versus lower limb ultrasound in newly diagnosed type 2 diabetics and analyze the relationship between atherosclerosis and cardio-cerebrovascular events. METHODS: A total of 148 newly diagnosed type 2 diabetics were recruited. Both carotid and lower extremity atherosclerosis were assessed by Doppler ultrasound. Diabetic atherosclerosis was defined as the presence of either carotid or lower extremity plaques in any of the above-mentioned arterial segments. A kappa value was computed to document the agreement between isolated carotid (or lower limb) atherosclerosis and diabetic atherosclerosis. The prevalence of cardio-cerebrovascular events was compared among different distribution types of atherosclerosis. RESULTS: According to the diagnostic criteria, the prevalence of diabetic atherosclerosis was 66.2% in the newly diagnosed type 2 diabetes. Based on carotid or lower extremity ultrasound, the prevalence of diabetic atherosclerosis was 27.0% and 62.2% respectively in newly diagnosed type 2 diabetes. The kappa values for the agreement between carotid/lower limb atherosclerosis and diabetic atherosclerosis were 0.32/0.91 (95% confidence interval 0.22-0.42 for carotid vs 0.84-0.98 for lower extremity). The combination of carotid and lower extremity arterial atherosclerosis was associated with a significantly increased detection rate of cardio-cerebrovascular events (26.5%) versus those with either carotid or lower extremity arterial atherosclerosis (0% and 10.3% respectively). CONCLUSION: The combination of carotid and lower extremity ultrasonography can more accurately reflect the atherosclerotic lesions in type 2 diabetes. Due to a higher prevalence of cardio-cerebrovascular events, type 2 diabetics with both carotid and lower extremity atherosclerosis should be managed more aggressively to reduce the risk of cardio-cerebrovascular events.

Low-grade albuminuria is associated with early but not late carotid atherosclerotic lesions in community-based patients with type 2 diabetes.

BACKGROUND: Low-grade albuminuria is associated with cardiovascular risk factors and mortality. Our aim was to investigate the association between low-grade albuminuria and carotid atherosclerotic lesions in community-based patients with type 2 diabetes. METHODS: A cross-sectional study was performed in 475 community-based patients with type 2 diabetes (190 males and 285 females) with normal urinary albumin-to-creatinine ratios (UACR) (< 3.5 mg/mmol) from Shanghai, China. The subjects were stratified into tertiles based on UACR levels (the lowest tertile was UACR ≤ 1.19 mg/mmol, and the highest tertile was UACR ≥ 2 mg/mmol). Carotid intima-media thickness (CIMT), carotid atherosclerotic plaque formation and stenosis were assessed and compared among the three groups based on ultrasonography. The urinary albumin excretion rate was determined as the mean of the values obtained from three separate early morning urine samples. RESULTS: Compared with the subjects with UACR in the lowest tertile, the subjects with UACR in the middle and highest tertiles had greater CIMT values (0.88 ± 0.35 mm, 0.99 ± 0.43 mm and 1.04 ± 0.35 mm, respectively; all p < 0.05) and a higher prevalence of carotid atherosclerotic plaques (25.3%, 39.0% and 46.2%, respectively; all p < 0.05) after adjusting for sex and age. Fully adjusted multiple linear regression and logistic regression analyses revealed that UACR tertiles were significantly associated with elevated CIMT (p = 0.007) and that, compared with the subjects in the first tertile of UACR, those in the second and third tertiles had 1.878- and 2.028-fold risk of carotid plaques, respectively. However, there was no statistical association between UACR tertile and the prevalence of carotid stenosis. CONCLUSIONS: Higher UACR within the normal range was independently associated with early but not late carotid atherosclerotic lesions in community-based patients with type 2 diabetes. Low-grade albuminuria contributes to the risk of carotid atherosclerosis and may be used as an early marker for the detection of atherosclerosis in patients with type 2 diabetes.

Prevalence and clinical characteristics of carotid atherosclerosis in newly diagnosed patients with ketosis-onset diabetes: a cross-sectional study.

BACKGROUND: The features of carotid atherosclerosis in ketosis-onset diabetes have not been investigated. Our aim was to evaluate the prevalence and clinical characteristics of carotid atherosclerosis in newly diagnosed Chinese diabetic patients with ketosis but without islet-associated autoantibodies. METHODS: In total, 423 newly diagnosed Chinese patients with diabetes including 208 ketosis-onset diabetics without islet-associated autoantibodies, 215 non-ketotic type 2 diabetics and 79 control subjects without diabetes were studied. Carotid atherosclerosis was defined as the presence of atherosclerotic plaques in any of the carotid vessel segments. Carotid intima-media thickness (CIMT), carotid atherosclerotic plaque formation and stenosis were assessed and compared among the three groups based on Doppler ultrasound examination. The clinical features of carotid atherosclerotic lesions were analysed, and the risk factors associated with carotid atherosclerosis were evaluated using binary logistic regression in patients with diabetes. RESULTS: The prevalence of carotid atherosclerosis was significantly higher in the ketosis-onset diabetic group (30.80%) than in the control group (15.2%, p=0.020) after adjusting for age- and sex-related differences, but no significant difference was observed in comparison to the non-ketotic diabetic group (35.8%, p=0.487). The mean CIMT of the ketosis-onset diabetics (0.70±0.20 mm) was markedly higher than that of the control subjects (0.57±0.08 mm, p<0.001), but no significant difference was found compared with the non-ketotic type 2 diabetics (0.73±0.19 mm, p=0.582) after controlling for differences in age and sex. In both the ketosis-onset and the non-ketotic diabetes, the prevalence of carotid atherosclerosis was markedly increased with age (both p<0.001) after controlling for sex, but no sex difference was observed (p=0.479 and p=0.707, respectively) after controlling for age. In the ketosis-onset diabetics, the presence of carotid atherosclerosis was significantly associated with age, hypertension, low-density lipoprotein cholesterol and mean CIMT. CONCLUSIONS: The prevalence and risk of carotid atherosclerosis were significantly higher in the ketosis-onset diabetics than in the control subjects but similar to that in the non-ketotic type 2 diabetics. The characteristics of carotid atherosclerotic lesions in the ketosis-onset diabetics resembled those in the non-ketotic type 2 diabetics. Our findings support the classification of ketosis-onset diabetes as a subtype of type 2 diabetes.

Combined effects of all-trans-retinoic acid and trichostatin A on the induction of differentiation of thyroid carcinoma cells.

BACKGROUND AND OBJECTIVE: The effectiveness rate of all-trans-retinoic acid (RA) is only about 30% in the clinical application of inducing thyroid carcinoma differentiation. In addition, there are severe toxic side effects, which limit its clinical application. Phase I-III clinical studies have been conducted on the combined application of two or more kinds of inductors in tumors. Nevertheless, the combination of RA with histone deacetylase inhibitors is rarely reported. This article studied the effects of differentiation for papillary thyroid carcinoma and follicular thyroid carcinoma cell lines induced by RA combined with trichostatin A (TSA), enhancing the effect of induction, while reducing the toxic side effects of a single drug, to provide a theoretical basis for preclinical trials. METHODS: After incubation with RA combined with TSA, K1 and FTC-133 were grouped into Group 1 (RA 10(-4) mol/L plus TSA 1.65 x 10(-7) mol/L), Group 2 (RA 1 x 10(-4) mol/L plus TSA 3.31 x 10(-7) mol/L), Group 3 (RA 10(-5) mol/L plus TSA 1.65 x 10(-7) mol/L), Group 4 (RA 1 x10(-5) mol/L plus TSA 3.31 x 10(-7) mol/L) by four varied concentrations and three time points (12 h, 24 h, and 48 h). The cell proliferation, conformation, toxic effect, and induced differentiation on K1 and FTC-133 cell lines were studied microscopically with hematoxylin-eosin (HE) to observe cell quantity and morphology, methyl-thiazolyl-tetrazolium (MTT) to calculate cell survival rates, and electrochemiluminescence analysis measuring in vitro thyroglobulin (Tg) levels. RESULTS: The research showed that K1 and FTC-133 cells had cell spacing increases, with an outer edge of smooth, nuclear chromatin condensation after RA combined TSA. Survival rate were assessed by an analysis of variance (ANOVA) by concentration and time point, F values of K1 and FTC-133 were 23.52 and 170.14, and 57.09 and 224.35, respectively. There were significant differences for both cells (P < 0.01). The SNK analysis indicated that survival rates were in the order of Group 2 < Group 1 < Group 4 < Group 3. Tg was also assessed by ANOVA, F values of K1 were 69.63 and 101.07, and F values of FTC-133 were 79.77 and 81.72 (P < 0.01). Group 1 was compared with Group 3 of K1 and FTC-133 by the least significant difference (LSD) method, and there was no statistical difference between the two group (P = 0.06, 0.2, respectively; P > 0.05), yet a significant difference was seen between the other Groups. CONCLUSIONS: Lower concentrations of RA combined with lower concentrations of TSA have both inhibited cell proliferation, decreased toxicity of the drugs, and increased the effect of K1 and FTC-133 cell differentiation. The mechanism of action may be that TSA has pretranscription DNA regulation and that RA has posttranscriptional signal regulation to enhance the effects of inhibited proliferation and differentiation of cells by transcription systems.

[Inhibitive effect of ursolic acid on the invasion and metastasis of ovarian carcinoma cells HO-8910PM].

OBJECTIVE: To study the effects of ursolic acid (UA) on the invasion and metastasis of ovarian carcinoma cell HO-8910PM and its underlying mechanism. METHODS: MTT assay was performed to examine the effects of UA on the proliferation of ovarian carcinoma cells HO-8910PM in vitro. The effects of UA on the invasion and migration of HO-8910PM were evaluated using Transwell chambers attached with polycarbonate filters and reconstituted basement membrane. Gelatin zymography was performed to detect the activity of gelatinase in the HO-8910PM cells. The expressions of MMP-2 and MMP-9 in the HO-8910PM cells were measured by Western blot. RESULTS: UA inhibited the proliferation of HO-8910PM cells in a time- and dose-dependent manner. There was a statistically significant difference in the invasion and migration of HO-8910PM cells between the UA treated cells and the controls (P < 0.01, P < 0.05). UA inhibited the activity of gelatinase of the treated cells. CONCLUSION: UA downregulated the expressions of MMP-2 and MMP-9. UA inhibits the invasion and metastasis of HO-8910PM cells, probably through inhibiting the activity of gelatinase and the expressions of MMP-2 and MMP-9.

Effect of a nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester on invasion of human colorectal cancer cell line SL-174T.

AIM: To investigate the effect and mechanism of action of the nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME) on invasion and metastasis of human colorectal cancer cell line SL-174T. METHODS: Human colorectal cancer cell line SL-174T was cultured and treated separately with four different dosages of L-NAME for 72 h. Nitric oxide (NO) production was measured with Griess reagent. The effect of L-NAME on invasion and migration of SL-174T cells were evaluated by using Transwell chambers attached with polycarbonate filters and reconstituted basement membrane (Matrigel). RT-PCR was performed to determine the mRNA levels of matrix metalloproteinase-2 (MMP-2) and tissue inhibitor metalloproteinase-2 (TIMP-2). RESULTS: L-NAME could significantly inhibit NO production of SL-174T in a dose-dependent manner. After being treated for 72 h with 0.2, 0.4, 0.8, and 1.0 mmol/L L-NAME, respectively, the ability of the L-NAME treated SL-174T cells to invade the reconstituted basement membrane decreased significantly (t = 8.056, P< 0.05; t = 14.467, P< 0.01; t = 27.785, P< 0.01; and t = 29.405, P< 0.01, respectively) and the inhibition rates were 10.29%, 19.62%, 34.08%, and 42.23%, respectively. Moreover, L-NAME could inhibit migration of SL-174T cells, and the inhibition rates were 20.76%, 24.95%, 39.43%, and 46.85% for L-NAME at 0.2, 0.4, 0.8, and 1.0 mmol/L, respectively (t= 15.116, P< 0.01). In addition, after treatment with L-NAME, expression of MMP-2 mRNA was significantly decreased (t = 71.238, P< 0.01) and that of TIMP-2 mRNA was markedly increased (t = -13.020, P< 0.01). CONCLUSION: L-NAME exerts anti-invasive and anti-metastatic effects on SL-174T cell line via downregulating MMP-2 mRNA expression and upregulating TIMP-2 mRNA expression.