1.Pathogenesis Evolution and Stage-based Treatment of Gout: An Exploration Based on Theory of ''Endogenous Dampness Leading to Bi Syndrome''
Yingjie ZHANG ; Fan YANG ; Ruifang YANG ; Zhuoming ZHENG ; Siwei PENG ; Yan XIAO ; Peng CHEN ; Youxin SU ; Jiemei GUO
Chinese Journal of Experimental Traditional Medical Formulae 2026;32(7):74-83
Gout is a crystal-associated arthropathy caused by the deposition of monosodium urate crystals and is closely related to purine metabolic disorders and impaired uric acid excretion. It is clinically characterized by hyperuricemia, recurrent joint swelling and pain, and tophus formation. The disease course is divided into three stages: The hyperuricemia stage, acute attack stage, and chronic gouty arthritis stage. Modern medicine has reached a consensus on its pathology, but traditional Chinese medicine (TCM) lacks a systematic stage-specific understanding of gout pathogenesis and its underlying mechanisms, making it difficult to guide precise syndrome differentiation and treatment. By integrating classical TCM theory, clinical practice, and modern medical understanding, and drawing upon descriptions of Bi syndrome caused by endogenous dampness and turbidity in classical texts such as Huangdi Neijing·Ling Shu and Synopsis of the Golden Chamber, our team proposes the pathogenic concept of gout as ''endogenous dampness leading to Bi syndrome'' and the core pathogenesis of ''spleen deficiency with internal retention of dampness-turbidity''. We systematically elucidate the evolution of pathogenesis across different stages and corresponding therapeutic strategies. This study posits that metabolic byproducts such as urate fall under the category of ''endogenous pathogenic dampness-turbidity''. When genetic or dietary factors lead to metabolic abnormalities, it manifests as ''spleen deficiency with impaired transport and transformation'', resulting in ''internal retention of pathogenic dampness-turbidity''. When damp-turbidity stagnates in the blood vessels, serum uric acid levels rise. When it stagnates in the viscera and limbs, monosodium urate crystals deposit in the joints. Triggered by precipitating factors, this leads to gout attacks—the core pathological process of ''endogenous dampness leading to Bi syndrome''. Based on this theory, the stage-specific pathogenic characteristics of gout are proposed: The hyperuricemia stage is characterized by ''spleen deficiency with impaired transport and transformation, internal retention of pathogenic dampness-turbidity'', the acute attack stage is primarily marked by ''dampness-turbidity and static heat obstructing the limbs and joints'', while the chronic stage is defined by ''spleen deficiency with internal retention of pathogenic dampness-turbidity, intermingled with phlegm-stasis binding''. The treatment principle centers on ''strengthening the spleen and draining dampness'' throughout all stages. During the hyperuricemia stage, treatment focuses on ''strengthening the spleen, draining dampness, and eliminating turbidity''. In the acute attack stage, the treatment should "strengthen the spleen, drain dampness, clear heat, eliminate turbidity, alleviate swelling, and relieve pain''. In the chronic stage, the treatments emphasizes to ''strengthen the spleen, drain dampness, transform turbidity, clear heat, resolve phlegm, and activate blood circulation''. This approach has yielded favorable therapeutic outcomes in clinical practice. This theoretical system clarifies the nature of gout as ''spleen deficiency being the root, dampness-turbidity being the secondary manifestation'' and systematically analyzes its pathogenesis evolution process and characteristics. The constructed stage-based treatment protocol has been validated through clinical and basic research, providing systematic theoretical guidance and a practical framework for the precise TCM management of gout, thereby promoting the modernization of TCM pathogenesis theory related to gout.
2.Effect and Action Mechanism of Huazhuo Sanjie Chubi Prescription on Gouty Bone Erosion Model Rats Based on PI3K/Akt Signaling Pathway
Zhuoming ZHENG ; Jun LIU ; Meiling WANG ; Xiaohua CHEN ; Yuwan LI ; Siwei PENG ; Yingjie ZHANG ; Ruifang YANG ; Youxin SU ; Yan XIAO ; Jiemei GUO
Chinese Journal of Experimental Traditional Medical Formulae 2026;32(7):105-117
ObjectiveThis paper aims to observe the effect of Huazhuo Sanjie Chubi prescription (HSCD) on the gouty bone erosion model rats and investigate its action mechanism. MethodsThirty-six two-month-old male SD rats were randomly divided into the blank group with nine rats and the modeling group with 27 rats. The rats in the modeling group were administered hypoxanthine solution at 300 mg·kg-1·d-1 and potassium oxonate solution at 250 mg·kg-1·d-1, combined with intra-articular injection of 200 μL monosodium urate (MSU) crystal suspension at 25 g·L-1 into the right ankle joint (joint injection once every three days), so as to induce the gouty bone erosion model. After four weeks of modeling, three rats were selected from these two groups to validate the model. The modeled 24 rats were randomly divided into the model group, HSCD group (10.35 g·kg-1·d-1), allopurinol group (20 mg·kg-1·d-1), and inhibitor group (LY294002, 10 mg·kg-1·d-1), with six rats per group. Except for the blank group, rats in all other groups continued to receive hypoxanthine solution at 300 mg·kg-1 and potassium oxonate solution at 250 mg·kg-1 via gavage concurrently with administration to maintain modeling intervention. The rats in the HSCD group and allopurinol group received administration by gavage at the above doses. The rats in the inhibitor group received an intraperitoneal injection at the above dose. The rats in the blank group and model group received saline (10.35 g·kg-1·d-1) by gavage for four consecutive weeks. After administration, ankle joint swelling of the rats in all groups was observed, and the diameters were measured. Bone volume fraction (BV/TV) and bone surface area to bone volume (BS/BV) were observed and quantitatively analyzed by Micro-CT. Histopathological changes in the ankle joint were observed by hematoxylin-eosin (HE) staining and safranin O-fast green staining. The uric acid in the rats' serum was determined by enzyme colorimetry. The levels of inflammatory factors, including tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA). The protein expressions of receptor activator of nuclear factor-κB ligand (RANKL) and phosphorylated (p)-phosphatidylinositol-3-kinase (PI3K) in ankle joint tissues of rats were detected by immunofluorescence staining. The mRNA levels of the proteins related to the bone erosion, including RANKL, tartrate-resistant acid phosphatase
3.Analysis of Changes on Volatile Components of Ligusticum sinense cv. Chaxiong Rhizome Before and After Wine Processing Based on Electronic Nose and HS-GC-MS
Wen ZHANG ; Peng ZHENG ; Jiangshan ZHANG ; Xiaolin XIAO ; Zaodan WU ; Li XIN ; Wenhui GONG ; Jinlian ZHANG
Chinese Journal of Experimental Traditional Medical Formulae 2025;31(2):173-181
ObjectiveBy comparing the composition and content of volatile components in raw products, wine-washed products and wine-fried products of Ligusticum sinense cv. Chaxiong rhizome(LSCR), to investigate the influence of wine processing on the volatile components of LSCR, in order to provide a basis for the development of quality standards for LSCR and its processed products. MethodsElectronic nose was used to identify the odors of LSCR, wine-washed and wine-fried LSCR, and their volatile components were detected by headspace gas chromatography-mass spectrometry(HS-GC-MS), and the relative mass fractions of these components were determined by peak area normalization method. Principal component analysis(PCA) and orthogonal partial least squares-discriminant analysis(OPLS-DA) were performed on the obtained sample data by SIMCA 14.1 software, and the differential components of LSCR, wine-washed and wine-fried LSCR were screened according to the variable importance in the projection(VIP) value>1. Pearson correlation analysis was used to explore the relationship between volatile differential flavor components and electronic nose sensors. ResultsElectronic nose detection results showed that there were significant differences in the odors of LSCR, wine-washed and wine-fried LSCR, mainly reflected in the sensors S2, S4, S5, S6, S11, S12, S13. And a total of 62 compounds were identified from LSCR and its wine-processed products, among which 46, 50 and 51 compounds were identified from LSCR, wine-fried and wine-washed LSCR, respectively. There were 21 differential components between the raw products and wine-fried products, of which 10 components were increased and 11 were decreased after processing. There were 20 differential components between the raw products and wine-washed products, of which 11 constituents increased and 9 decreased after processing. There were 17 differential components between the wine-wash products and wine-fried products. Compared with the wine-washed products, the contents of 13 components in the wine-fried products increased, and the contents of 4 components decreased. The increasing trend of the content of phthalides in the wine-washed products was more obvious than that in the wine-fried products, but the content of total volatile components was higher in the wine-fried products than the wine-washed products. Correlation analysis showed that there were different degrees of correlation between the 7 differential sensors of electronic nose and 24 differential volatile components, mainly phthalides and olefins. ConclusionThe odor and the content of volatile components in LSCR changed obviously after wine processing, and n-butylphthalide, Z-butylidenephthalide and E-ligustilide can be used as the candidate differential markers of volatile components in LSCR before and after wine processing.
4.Evaluation on repeatability and accuracy of iCare IC100 tonometer in measuring intraocular pressure
Yue PENG ; Ping ZHAO ; Juan TAN ; Rui LIU ; Yiping ZHENG ; Jiangping HUANG
International Eye Science 2025;25(3):494-498
AIM: To evaluate the repeatability and accuracy of iCare IC100 tonometer in measuring intraocular pressure(IOP)by comparing the correlation and difference with Goldmann applanation tonometry(GAT)and non-contact tonometer(NCT), and to compare the correlation of the three types of IOP measurement with the central corneal thickness(CCT).METHODS: Prospective study. A total of 90 outpatients(90 eyes)in Liaoning Aier Eye Hospital from March 2019 to May 2019 were randomly selected as study subjects. All patients were measured IOP using iCare IC100, NCT, and GAT. The interclass correlation coefficient(ICC)was used to evaluate the repeatability of IOP measured 3 times consecutively using an intraocular tonometer. The correlation and consistency of iCare IC100, GAT and NCT were compared by one-way ANOVA, Pearson linear correlation analysis and Bland-Altman analysis. The linear regression analysis was used to analyze the correlation of the three tonometers with CCT.RESULTS: The mean IOP measured with iCare IC100, GAT and NCT was 19.74±6.90, 19.88±7.07 and 18.47±6.31 mmHg, respectively(F=1.180, P=0.309). The measurements of iCare IC100 with GAT, iCare IC100 with NCT and GAT with NCT were all positively correlated(r=0.930, 0.946, 0.918, all P<0.05), the Bland-Altman analysis showed that the mean differences between iCare IC100 and GAT, iCare IC100 and NCT, GAT and NCT were -0.142±2.61, 1.27±2.24, and 1.41±2.81 mmHg, respectively, with 97%(87/90), 96%(86/90), and 97%(87/90)IOP differences distributed within their 95% confidence intervals. The IOP measured with iCare IC100 and CCT, GAT and CCT and NCT and CCT were all positively correlated(r=0.426, 0.353, 0.451, all P<0.01). The linear regression equations between iCare IC100, GAT and NCT measurement and CCT were iCare IC100 IOP=-19.62+0.074×CCT; GAT IOP=-13.54+0.063×CCT; NCT IOP=-19.65+0.072×CCT; that is, for every 10 μm increase in CCT, iCare IC100 measurement increased by 0.74 mmHg, GAT measurement increased by 0.63 mmHg, and NCT measurement increased by 0.72 mmHg.CONCLUSION: The iCare IC100 tonometer has good repeatability and accuracy in measuring IOP, and the CCT has a greater impact on the measurement of iCare IC100 than the GAT and NCT.
5.Evaluation on repeatability and accuracy of iCare IC100 tonometer in measuring intraocular pressure
Yue PENG ; Ping ZHAO ; Juan TAN ; Rui LIU ; Yiping ZHENG ; Jiangping HUANG
International Eye Science 2025;25(3):494-498
AIM: To evaluate the repeatability and accuracy of iCare IC100 tonometer in measuring intraocular pressure(IOP)by comparing the correlation and difference with Goldmann applanation tonometry(GAT)and non-contact tonometer(NCT), and to compare the correlation of the three types of IOP measurement with the central corneal thickness(CCT).METHODS: Prospective study. A total of 90 outpatients(90 eyes)in Liaoning Aier Eye Hospital from March 2019 to May 2019 were randomly selected as study subjects. All patients were measured IOP using iCare IC100, NCT, and GAT. The interclass correlation coefficient(ICC)was used to evaluate the repeatability of IOP measured 3 times consecutively using an intraocular tonometer. The correlation and consistency of iCare IC100, GAT and NCT were compared by one-way ANOVA, Pearson linear correlation analysis and Bland-Altman analysis. The linear regression analysis was used to analyze the correlation of the three tonometers with CCT.RESULTS: The mean IOP measured with iCare IC100, GAT and NCT was 19.74±6.90, 19.88±7.07 and 18.47±6.31 mmHg, respectively(F=1.180, P=0.309). The measurements of iCare IC100 with GAT, iCare IC100 with NCT and GAT with NCT were all positively correlated(r=0.930, 0.946, 0.918, all P<0.05), the Bland-Altman analysis showed that the mean differences between iCare IC100 and GAT, iCare IC100 and NCT, GAT and NCT were -0.142±2.61, 1.27±2.24, and 1.41±2.81 mmHg, respectively, with 97%(87/90), 96%(86/90), and 97%(87/90)IOP differences distributed within their 95% confidence intervals. The IOP measured with iCare IC100 and CCT, GAT and CCT and NCT and CCT were all positively correlated(r=0.426, 0.353, 0.451, all P<0.01). The linear regression equations between iCare IC100, GAT and NCT measurement and CCT were iCare IC100 IOP=-19.62+0.074×CCT; GAT IOP=-13.54+0.063×CCT; NCT IOP=-19.65+0.072×CCT; that is, for every 10 μm increase in CCT, iCare IC100 measurement increased by 0.74 mmHg, GAT measurement increased by 0.63 mmHg, and NCT measurement increased by 0.72 mmHg.CONCLUSION: The iCare IC100 tonometer has good repeatability and accuracy in measuring IOP, and the CCT has a greater impact on the measurement of iCare IC100 than the GAT and NCT.
6.Research and Application of Scalp Surface Laplacian Technique
Rui-Xin LUO ; Si-Ying GUO ; Xin-Yi LI ; Yu-He ZHAO ; Chun-Hou ZHENG ; Min-Peng XU ; Dong MING
Progress in Biochemistry and Biophysics 2025;52(2):425-438
Electroencephalogram (EEG) is a non-invasive, high temporal-resolution technique for monitoring brain activity. However, affected by the volume conduction effect, EEG has a low spatial resolution and is difficult to locate brain neuronal activity precisely. The surface Laplacian (SL) technique obtains the Laplacian EEG (LEEG) by estimating the second-order spatial derivative of the scalp potential. LEEG can reflect the radial current activity under the scalp, with positive values indicating current flow from the brain to the scalp (“source”) and negative values indicating current flow from the scalp to the brain (“sink”). It attenuates signals from volume conduction, effectively improving the spatial resolution of EEG, and is expected to contribute to breakthroughs in neural engineering. This paper provides a systematic overview of the principles and development of SL technology. Currently, there are two implementation paths for SL technology: current source density algorithms (CSD) and concentric ring electrodes (CRE). CSD performs the Laplace transform of the EEG signals acquired by conventional disc electrodes to indirectly estimate the LEEG. It can be mainly classified into local methods, global methods, and realistic Laplacian methods. The global method is the most commonly used approach in CSD, which can achieve more accurate estimation compared with the local method, and it does not require additional imaging equipment compared with the realistic Laplacian method. CRE employs new concentric ring electrodes instead of the traditional disc electrodes, and measures the LEEG directly by differential acquisition of the multi-ring signals. Depending on the structure, it can be divided into bipolar CRE, quasi-bipolar CRE, tripolar CRE, and multi-pole CRE. The tripolar CRE is widely used due to its optimal detection performance. While ensuring the quality of signal acquisition, the complexity of its preamplifier is relatively acceptable. Here, this paper introduces the study of the SL technique in resting rhythms, visual-related potentials, movement-related potentials, and sensorimotor rhythms. These studies demonstrate that SL technology can improve signal quality and enhance signal characteristics, confirming its potential applications in neuroscientific research, disease diagnosis, visual pathway detection, and brain-computer interfaces. CSD is frequently utilized in applications such as neuroscientific research and disease detection, where high-precision estimation of LEEG is required. And CRE tends to be used in brain-computer interfaces, that have stringent requirements for real-time data processing. Finally, this paper summarizes the strengths and weaknesses of SL technology and envisages its future development. SL technology boasts advantages such as reference independence, high spatial resolution, high temporal resolution, enhanced source connectivity analysis, and noise suppression. However, it also has shortcomings that can be further improved. Theoretically, simulation experiments should be conducted to investigate the theoretical characteristics of SL technology. For CSD methods, the algorithm needs to be optimized to improve the precision of LEEG estimation, reduce dependence on the number of channels, and decrease computational complexity and time consumption. For CRE methods, the electrodes need to be designed with appropriate structures and sizes, and the low-noise, high common-mode rejection ratio preamplifier should be developed. We hope that this paper can promote the in-depth research and wide application of SL technology.
7.Construction and practice of the theory of “turbid toxin pathogenesis” and related prevention and treatment strategies for hepatic encephalopathy in traditional Chinese medicine/Zhuang medicine
Zhipeng WU ; Yuqin ZHANG ; Chun YAO ; Minggang WANG ; Na WANG ; Mengru PENG ; Ningfang MO ; Yaqing ZHENG ; Rongzhen ZHANG ; Dewen MAO
Journal of Clinical Hepatology 2025;41(2):370-374
Hepatic encephalopathy is a difficult and critical disease with rapid progression and limited treatment methods in the field of liver disease, and it is urgently needed to make breakthroughs in its pathogenesis. Selection of appropriate prevention and treatment strategies is of great importance in delaying disease progression and reducing the incidence and mortality rates. This article reviews the theory of “turbid toxin pathogenesis” and related prevention and treatment strategies for hepatic encephalopathy in traditional Chinese medicine/Zhuang medicine, proposes a new theory of “turbid toxin pathogenesis”, analyzes the scientific connotations of “turbid”, “toxin”, and the theory of “turbid toxin pathogenesis”, and constructs the “four-step” prevention and treatment strategies for hepatic encephalopathy, thereby establishing the new clinical prevention and treatment regimen for hepatic encephalopathy represented by “four prescriptions and two techniques” and clarifying the effect mechanism and biological basis of core prescriptions and techniques in the prevention and treatment of hepatic encephalopathy, in order to provide a reference for the prevention and treatment of hepatic encephalopathy.
8.Analysis and evaluation of platelet bank establishment strategy from the perspective of donor loss
Zheng LIU ; Yamin SUN ; Xin PENG ; Yiqing KANG ; Ziqing WANG ; Jintong ZHU ; Juan DU ; Jianbin LI
Chinese Journal of Blood Transfusion 2025;38(2):238-243
[Objective] To analyze the loss rate of platelet donors and evaluate the strategies for establishing a platelet donor bank. [Methods] A total of 1 443 donors who joined the HLA and HPA gene donor bank for platelets in Henan Province from 2018 to 2020 were included in this study. Data on the total number of apheresis platelet donations, annual donation frequency, age at enrollment, donation habits (including the number of platelets donated per session and whether they had previously donated whole blood), and enrollment location were collected from the platelet donor information management system. Donor loss was determined based on the date of their last donation. The loss rates of different groups under various conditions were compared to assess the enrollment strategies. [Results] By the time the platelet bank was officially operational in 2022, 421 donors had been lost, resulting in an loss rate of 29% (421/1 443). By the end of 2023, the overall cumulative loss rate reached 52% (746/1 443). The loss rate was lower than the overall level in groups meeting any of the following conditions: total apheresis platelet donations exceeding 50, annual donation frequency of 10 or more, age at enrollment of 40 years or older, donation of more than a single therapeutic dose per session, or a history of whole blood donation two or more times. Additionally, loss rates varied across different enrollment locations, with higher enrollment numbers generally associated with higher loss rates. [Conclusion] Through a comprehensive analysis of donor loss, our center has adjusted its strategies for establishing the donor pool. These findings also provide valuable insights for other blood collection and supply institutions in building platelet donor banks.
9.Clinical characteristics and risk factors for adverse outcomes in omphalocele
Wei SHI ; Mingyu HAN ; Zheng CHEN ; Xiaoying CHENG ; Junjin CHEN ; Peng WANG ; Jinfa TOU ; Liping SHI ; Xiaolu MA
Chinese Journal of Pediatrics 2025;63(1):43-49
Objective:To investigate the clinical characteristics of omphalocele, and to assess the risk factors associated with adverse outcomes.Methods:A retrospective cohort study was conducted. Clinical data of 224 patients diagnosed with omphalocele, who were hospitalized at Children′s Hospital, Zhejiang University School of Medicine from January 2013 to December 2022, were collected. Based on their discharge outcomes, the patients were classified into 2 groups: favorable outcomes and unfavorable outcomes. Chi-square test or continuity correction χ2 test or Fisher exact probability method, and Mann-Whitney U test were used for intergroup comparisons. Logistic regression analysis was performed to identify risk factors associated with adverse outcomes in omphalocele. Results:Among the 224 patients with omphalocele, 126 were male. A total of 208 patients (92.9%) had favorable outcomes, while 16 patients (7.1%) had unfavorable outcomes. In the unfavorable outcomes group, 14 patients had giant omphaloceles, while 100 patients had giant omphaloceles in the favorable outcomes group. The rates of herniation of more than two intra-abdominal organs in the hernial sac, congenital heart defects, patent ductus arteriosus, pulmonary hypertension, sepsis and infection of the hernial sac, were all higher in the unfavorable outcomes group compared to the favorable outcomes group (all P<0.05). Patients with unfavorable outcomes had longer mechanical ventilation time, duration of oxygen use, duration of parenteral nutrition, hospital stays, and higher rates of parenteral nutrition-associated cholestasis compared to those with favorable outcomes (all P<0.01). Multivariate Logistic regression analysis indicated that pulmonary hypertension ( OR=9.39, 95% CI 1.20-73.32), sepsis ( OR=8.59, 95% CI 1.32-55.86), and congenital heart defects ( OR=6.55, 95% CI 1.11-38.73) were all independent risk factors for adverse outcomes in omphalocele (all P<0.05). Conclusions:Infants with omphalocele are prone to complications such as cardiovascular malformations, infections, and pulmonary hypertension. Adverse outcomes in omphalocele are associated with pulmonary hypertension, sepsis, and congenital heart defects.
10.Associations of adipokine with diabetic retinopathy among patients with type 2 diabetes mellitus
SUN Xia ; DAN lingying ; ZHENG Peng ; CHEN Xinyi
Journal of Preventive Medicine 2025;37(3):248-252
Objective:
To examine the associations between three adipokines (omentin-1, nesfatin-1 and apelin) and diabetic retinopathy (DR) among patients with type 2 diabetes mellitus (T2DM), so as to provide the basis for the prevention and control of DR.
Methods:
The T2DM patients hospitalized in Lishui TCM Hospital from August 2021 to May 2023 were selected and divided into three groups: no diabetic retinopathy (NDR) group, non-proliferative diabetic retinopathy (NPDR) group, and proliferative diabetic retinopathy (PDR) group based on fundus fluorescein angiography. Data on gender, age, and course of T2DM were collected through questionnaires, and serum omentin-1, nesfatin-1, apelin, and related blood biochemical indicators were measured. The associations of omentin-1, nesfatin-1 and apelin with DR were analyzed using a multinomial logistic regression model.
Results:
A total of 150 T2DM patients were enrolled, including 58 cases in the NDR group, 60 cases in the NPDR group, and 32 cases in the PDR group, with males accounting for 60.34%, 45.00% and 68.75%, respectively. The mean ages were (54.79±14.40), (57.03±12.20) and (57.72±10.70) years, respectively. The median (interquartile range) courses of T2DM were 7.00 (7.75), 10.00 (8.00) and 10.00 (5.00) years, respectively. Compared with the NDR group, the NPDR group had lower levels of omentin-1 and nesfatin-1 and higher level of apelin, while the PDR group had higher level of omentin-1 and lower level of apelin (all P<0.05). Compared with the NPDR group, the PDR group had higher levels of omentin-1 and nesfatin-1 and lower level of apelin (all P<0.05). Multinomial logistic regression analysis showed that omentin-1 level was statistically associated with NPDR (OR=0.503, 95%CI: 0.291-0.871) and PDR (OR=7.862, 95%CI: 2.956-20.910); nesfatin-1 (OR=0.971, 95%CI: 0.953-0.989) and apelin (OR=3.266, 95%CI: 1.817-5.868) levels were statistically associated with NPDR.
Conclusion
Serum levels of omentin-1, nesfatin-1 and apelin were associated with different stages of DR among T2DM patients.


Result Analysis
Print
Save
E-mail