1.From blood transfusion to blood use
Zonglong LI ; Chen HOU ; Yu SI ; Delong QIN ; Xiaoliang ZHOU ; Zhaohui TANG
Chinese Journal of Blood Transfusion 2026;39(1):8-15
The promulgation of the Technical Specifications for Clinical Use of Blood (2025 Edition) signifies that China's clinical blood transfusion management has transitioned from mere technical operations to a new stage centered on patient blood management (PBM). Through an in-depth comparison of the new and old specifications, this paper analyzes the core transformations regarding conceptual reconstruction, legal alignment, technological upgrades, and closed-loop management. The new specifications establish PBM principles, reinforce legal safeguards for informed consent and emergency treatment, and construct a comprehensive, refined quality control system by specifying compatibility testing standards and introducing a post-transfusion evaluation system. Medical institutions should seize this opportunity to update management protocols and information systems, deepen multidisciplinary collaboration, and drive the profound transformation of clinical blood use from focusing solely on safety assurance to placing equal emphasis on science and value.
2.Correlation Analysis of Huanglian Jiedu Wan on Syndrome Improvement and Clinical Biomarkers of "Excess Heat-Toxicity" Based on Machine Learning Model
Qi LI ; Keke LUO ; Baolin BIAN ; Hongyu YU ; Mengxiao WANG ; Mengyao TIAN ; Wen XIA ; Yuan MA ; Xinfang ZHANG ; Pengyue LI ; Nan SI ; Hongjie WANG ; Yanyan ZHOU
Chinese Journal of Experimental Traditional Medical Formulae 2026;32(8):162-173
ObjectiveThis paper aims to find the identified and validated clinical biomarker data building upon a clinical study of early-phase phase Ⅱ and investigate the correlation analysis of Huanglian Jiedu Wan on syndrome improvement and clinical biomarkers in the treatment of "excess heat-toxicity" based on a machine learning model. Additionally, the effective prediction of clinical biomarker values for the main symptoms of the "excess heat-toxicity" syndrome was assessed. MethodsA total of 229 patients meeting the inclusion criteria for "excess heat-toxicity" syndrome were randomly divided into the Huanglian Jiedu Wan group and the placebo group. Syndrome score transition matrices were constructed for the Huanglian Jiedu Wan group and the placebo group based on three main symptoms of "excess heat-toxicity" syndrome, such as oral ulcers, sore throat, and gum swelling and pain. Data from the patients with these three syndromes were also integrated for an overall analysis. The corresponding syndrome score transition matrices were further constructed to visualize symptom change trends of the patients in the two groups via heatmaps. Based on the identified and validated clinical biomarkers related to inflammation, oxidative stress, and energy metabolism in the early phase, Spearman correlation analysis was employed to analyze and evaluate the associations between clinical biomarkers and syndrome improvement. Key clinical biomarkers reflecting the effect of Huanglian Jiedu Wan were screened through the comparison of differences between groups. An extreme gradient boosting (XGBoost) algorithm was used to develop a prediction model for main symptom classification, with classification performance evaluated through 10-fold cross-validation. Feature importance analysis was applied to identify variables with the greatest contribution to the prediction result. ResultsThe syndrome transition matrix results indicated that the Huanglian Jiedu Wan group showed a superior effect to the placebo group in improving oral ulcers, sore throat, and overall symptoms, with significant effects observed especially in sore throat and overall symptom analyses (P<0.01). Spearman correlation analysis revealed that several clinical biomarkers positively correlated with "excess heat-toxicity" syndrome and its main symptom improvement, were also called "heat-related biomarkers", including succinic acid, α-ketoglutaric acid, glycine, lactic acid, adenosine monophosphate (AMP), tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), and so on. Conversely, clinical biomarkers negatively correlated with symptom severity, were also called "heat-clearing related biomarkers" after administration of Huanglian Jiedu Wan, including malic acid, fumaric acid, cis-aconitic acid, adrenocorticotropic hormone (ACTH), IL-1β, IL-4, IL-8, succinic acid, and citric acid. The XGBoost classification model using all 52 biomarkers as variables achieved an average test accuracy of 0.754 and an average F1 score of 0.777. Feature importance analysis identified the scores of glutamic acid in saliva and IL-6 were the highest in all the variables, with importance scores of 0.081 and 0.080, respectively. After screening out 14 key variables and optimizing the parameters, model performance improved to an average accuracy of 0.758 and an F1 score of 0.798. Feature importance analysis further determined that the glutamic acid in saliva and IL-6 showed obvious changes after screening the variables, confirming the good syndrome prediction ability of the model constructed by these key clinical biomarkers. ConclusionThis study systematically elucidates the correlation between syndrome improvement and clinical biomarkers of Huanglian Jiedu Wan in the treatment of "excess heat-toxicity" syndrome. An XGBoost classification model based on key clinical biomarkers is successfully established, achieving effective prediction of the symptoms related to the "excess heat-toxicity" syndrome such as oral ulcers and sore throat and providing a new insight for objective identification of traditional Chinese medicine syndromes.
3.Correlation Analysis of Huanglian Jiedu Wan on Syndrome Improvement and Clinical Biomarkers of "Excess Heat-Toxicity" Based on Machine Learning Model
Qi LI ; Keke LUO ; Baolin BIAN ; Hongyu YU ; Mengxiao WANG ; Mengyao TIAN ; Wen XIA ; Yuan MA ; Xinfang ZHANG ; Pengyue LI ; Nan SI ; Hongjie WANG ; Yanyan ZHOU
Chinese Journal of Experimental Traditional Medical Formulae 2026;32(8):162-173
ObjectiveThis paper aims to find the identified and validated clinical biomarker data building upon a clinical study of early-phase phase Ⅱ and investigate the correlation analysis of Huanglian Jiedu Wan on syndrome improvement and clinical biomarkers in the treatment of "excess heat-toxicity" based on a machine learning model. Additionally, the effective prediction of clinical biomarker values for the main symptoms of the "excess heat-toxicity" syndrome was assessed. MethodsA total of 229 patients meeting the inclusion criteria for "excess heat-toxicity" syndrome were randomly divided into the Huanglian Jiedu Wan group and the placebo group. Syndrome score transition matrices were constructed for the Huanglian Jiedu Wan group and the placebo group based on three main symptoms of "excess heat-toxicity" syndrome, such as oral ulcers, sore throat, and gum swelling and pain. Data from the patients with these three syndromes were also integrated for an overall analysis. The corresponding syndrome score transition matrices were further constructed to visualize symptom change trends of the patients in the two groups via heatmaps. Based on the identified and validated clinical biomarkers related to inflammation, oxidative stress, and energy metabolism in the early phase, Spearman correlation analysis was employed to analyze and evaluate the associations between clinical biomarkers and syndrome improvement. Key clinical biomarkers reflecting the effect of Huanglian Jiedu Wan were screened through the comparison of differences between groups. An extreme gradient boosting (XGBoost) algorithm was used to develop a prediction model for main symptom classification, with classification performance evaluated through 10-fold cross-validation. Feature importance analysis was applied to identify variables with the greatest contribution to the prediction result. ResultsThe syndrome transition matrix results indicated that the Huanglian Jiedu Wan group showed a superior effect to the placebo group in improving oral ulcers, sore throat, and overall symptoms, with significant effects observed especially in sore throat and overall symptom analyses (P<0.01). Spearman correlation analysis revealed that several clinical biomarkers positively correlated with "excess heat-toxicity" syndrome and its main symptom improvement, were also called "heat-related biomarkers", including succinic acid, α-ketoglutaric acid, glycine, lactic acid, adenosine monophosphate (AMP), tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), and so on. Conversely, clinical biomarkers negatively correlated with symptom severity, were also called "heat-clearing related biomarkers" after administration of Huanglian Jiedu Wan, including malic acid, fumaric acid, cis-aconitic acid, adrenocorticotropic hormone (ACTH), IL-1β, IL-4, IL-8, succinic acid, and citric acid. The XGBoost classification model using all 52 biomarkers as variables achieved an average test accuracy of 0.754 and an average F1 score of 0.777. Feature importance analysis identified the scores of glutamic acid in saliva and IL-6 were the highest in all the variables, with importance scores of 0.081 and 0.080, respectively. After screening out 14 key variables and optimizing the parameters, model performance improved to an average accuracy of 0.758 and an F1 score of 0.798. Feature importance analysis further determined that the glutamic acid in saliva and IL-6 showed obvious changes after screening the variables, confirming the good syndrome prediction ability of the model constructed by these key clinical biomarkers. ConclusionThis study systematically elucidates the correlation between syndrome improvement and clinical biomarkers of Huanglian Jiedu Wan in the treatment of "excess heat-toxicity" syndrome. An XGBoost classification model based on key clinical biomarkers is successfully established, achieving effective prediction of the symptoms related to the "excess heat-toxicity" syndrome such as oral ulcers and sore throat and providing a new insight for objective identification of traditional Chinese medicine syndromes.
4.Effects of key molecules in m6A methylation modification on the replication and proliferation of Japanese encephalitis virus
Zhi-rong CHENG ; Min YAO ; Xue-yun LI ; Chao-jie CHAI ; Pin-xiang DANG ; Si-yu WANG ; Fang-lin ZHANG ; Xin LYU
Chinese Journal of Zoonoses 2025;41(2):150-157
This study was aimed at investigating the effects of demethylase fat mass and obesity-associated protein(FTO)and methyltransferase methyltransferase like protein 3(METTL3),key molecules in N6-methyladenosine(m6A)modification,on the replication and proliferation of Japanese encephalitis virus(JEV).Recombinant lentiviruses were generated by packaging the FTO and green fluorescent protein into lentiviral vectors.Neuro2a cells,a mouse neuroblastoma cell line,were infected with the lentivirus,and stable FTO-expressing cell lines were obtained through puromycin selection.Successful overexpression of FTO was confirmed through fluorescence microscopy,real-time quantitative PCR,and western blot analysis.When Neuro2a cells overexpressing FTO were infected with JEV,the overexpression of FTO decreased JEV replication in the cells,and increased the expression of interferon(IFN)and related molecules.Additionally,treatment of JEV-infected Neuro2a cells with the METTL3-specific inhibitor STM2457 resulted in a dose-dependent decrease in JEV replication and viral protein expression.These findings suggested that lowering m6A methylation levels inhibits JEV replication,thus shedding light on the regulatory role of methylation modification in JEV replication.
5.Transcriptome sequencing analysis of the mechanism by which cold water swimming regulates inflammatory response in rats
Juncheng SI ; Lina PENG ; Lili SUN ; Yu WANG ; Lei SHI ; Wenhui SHEN ; Mengqi LI ; Wanli ZANG
Chinese Journal of Tissue Engineering Research 2025;29(29):6205-6211
BACKGROUND:When exercising in a cold environment,the body's inflammatory response is affected by both low temperature and exercise intervention,and its impact and mechanism remain to be explored.OBJECTIVE:To explore the effects and mechanisms of cold water swimming on inflammatory response of rats based on transcriptome sequencing technology.METHODS:40 male SD rats were randomly divided into room temperature control group,room temperature swimming group,cold water control group,and cold water swimming group,with 10 rats in each group.The room temperature control group had no intervention and was free to eat.The room temperature swimming group received swimming at 30 min/time,6 times/week,for 5 weeks;the water temperature was(28±2)℃,and the water depth was 35 cm.In the cold water control group,the rats were placed in a water tank with a depth of 3 cm;the water temperature was(18±2)℃,and they were free to move.The cold water swimming group received swimming at 30 min/time,6 times/week,for 5 weeks;the water temperature was(18±2)℃,and the water depth was 35 cm.Enzyme-linked immunosorbent assay was used to detect the levels of serum interleukin-6,tumor necrosis factor-α,and high-sensitivity C-reactive protein.Based on the transcriptome sequencing results,differentially expressed genes were screened to draw Venn diagrams and heat maps,and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis were performed.The protein-protein interaction network was used to screen core genes.RT-qPCR was used to detect the mRNA expression of IRF7,OAS2,and OASL in rat spleen tissue.RESULTS AND CONCLUSION:(1)The ELISA results showed that compared with the room temperature control group,the levels of various inflammatory indicators in the room temperature swimming group and the cold water swimming group were significantly increased(P<0.05),and there was no significant difference in the cold water control group.Compared with the room temperature swimming group,there was no significant difference in the expression of inflammatory indicators in the cold water swimming group.Compared with the cold water control group,the expressions of interleukin-6 and tumor necrosis factor-α in the cold water swimming group showed an upward trend,and high-sensitivity C-reactive protein increased significantly(P<0.05).(2)Transcriptome analysis:Venn diagram showed that there were 39 differentially expressed genes affected by the dual factors of temperature and exercise intervention.Cluster heat map analysis results showed that the overall gene expression trends of the room temperature swimming group and the cold water swimming group were similar,and the cold water control group showed an opposite trend.Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis results showed that differentially expressed genes were enriched in the immune system,locomotion,nucleic acid-binding transcription factor activity,NOD-like receptor signaling pathways and other pathways.The number of genes enriched in the NOD-like receptor signaling pathway was relatively large,and the q value was small,which may be a key pathway.The protein-protein interaction network screened out IRF7,OAS2,OASL,IFIT2,IFIT3 and other core genes.(3)RT-qPCR verification results showed that compared with the room temperature control group,the expressions of IRF7,OAS2 and OASL were significantly increased in the room temperature swimming group and the cold water swimming group(P<0.01),and there was no significant difference in the cold water control group.Compared with the cold water control group,the expression of each gene was significantly increased in the cold water swimming group(P<0.01).(4)It is concluded that cold water swimming can promote inflammatory response,and its mechanism may be regulated through the NOD-like receptor signaling pathway.
6.Structural challenges and development pathways of the disease control supervisor system:A SWOT-CLPV integrated analysis
Yan-ling HAN ; Quan WANG ; Si-qi LIU ; Yu-meng LYU ; Yi-xin QIN ; Ying-ming SONG ; Jia-kun WANG ; Li YANG
Chinese Journal of Health Policy 2025;18(6):26-33
Objective:This study applies an integrated SWOT-CLPV framework combined with stakeholder analysis to systematically assess the strengths,weaknesses,opportunities,and threats of China's disease control inspector system,while identifying its control factors,leverage points,key problems,and vulnerabilities.Methods:Drawing on literature review,policy document analysis,and expert interviews with seven public health professionals,we extracted and categorized SWOT elements.A CLPV interaction analysis was conducted alongside stakeholder mapping to evaluate internal dynamics and systemic risks.Results:The inspector system demonstrates strengths in policy innovation and medical-public health integration,with external opportunities stemming from rising public health awareness and digital health advancements.However,the system faces weak endogenous momentum,limited leverage,and prominent control constraints and problem-prone areas,especially among grassroots institutions and inspectors themselves.Cross-sectoral coordination barriers and uneven local implementation contribute to significant institutional vulnerabilities.Conclusion:To enhance implementation and resilience,the system requires capacity building for key actors,improved governance structures,incentive and evaluation reforms,and strengthened coordination mechanisms to support the sustained and adaptive development of public health supervision.
7.Construction and validation of a mouse model for optically activation of oligodendrocyte precursor cells
Shu-yue WANG ; Bei-na SHENYANG ; Nan-xin HUANG ; Si-wei LI ; Bin YU ; Yu-xin WANG ; Lan XIAO
Acta Anatomica Sinica 2025;56(5):507-514
Objective To develop and validate a transgenic mouse model enabling specific and inducible optogenetic activation of oligodendrocyte precursor cells(OPCs).Methods A conditional allele for the photosensitive opsin chicken opsin 5(cOpn5)(Rosa26-LSL-cOpn5)was generated using CRISPR/Cas9 technology.These mice were subsequently crossed with NG2-CreERT transgenic mice to produce NG2-CreERT;cOpn5 animals.In this model,tamoxifen administration induces Cre-mediated recombination,leading to specific expression of cOpn5 in NG2-positive OPCs.The specificity and efficiency of cOpn5 expression in OPCs were confirmed by immunofluorescent staining.Functional validation of light-induced OPC activation was performed by using calcium imaging in acute brain slices after stimulation with 470 nm blue light.Results Immunofluorescence analysis confirmed robust and specific expression of cOpn5 within NG2-positive OPCs in the brains of tamoxifen-treated NG2-CreERT;cOpn5 mice.Crucially,calcium imaging of acute brain slices from these mice demonstrated a significant increase in intracellular calcium levels in cOpn5-expressing OPCs upon stimulation with 470 nm blue light,indicating successful optogenetic activation.Conclusion We have successfully generated and validated a novel transgenic mouse model(NG2-CreERT;cOpn5)that permits specific and inducible optogenetic activation of OPCs.This model provides a novel tool for subsequent in vivo studies of the role and regulating mechanisms of OPCs in the central nervous system.
8.Analysis of completion rate of tumor evaluation at initial assessment and after neoadjuvant therapy for mid and low rectal cancer : a national multicenter real-world study
Kexuan LI ; Tixian XIAO ; Xiaodong WANG ; Bin WU ; Guole LIN ; Yuchen GUO ; Ming QU ; Si WU ; Xiaodong YANG ; Yinshengbo′er BAO ; Baohua WANG ; Fan ZHANG ; Xiangwang YU ; Beizhan NIU ; Junyang LU ; Lai XU ; Guannan ZHANG ; Zhen SUN ; Guoyou ZHANG ; Yan SHI ; Hong JIANG ; Yongjing TIAN ; Yongxiang LI ; Hongwei YAO ; Jun XUE ; Quan WANG ; Lie YANG ; Qian LIU ; Yi XIAO
Chinese Journal of Digestive Surgery 2025;24(1):113-119
Objective:To investigate the completion rate of tumor evaluation at initial assessment and after neoadjuvant therapy for mid and low rectal cancer patients in the national multicenter real-world database.Methods:The prospective real-world study was conducted. The clinicopathological data of 1 074 patients who underwent surgical treatment for mid and low rectal cancer in 47 national medical institutions, including Peking Union Medical College Hospital et al, from May 12,2023 to May 11,2024 were collected. Observation indicators: (1) clinical characteristics of patients with mid and low rectal cancer; (2) initial colonoscopy and pathologic evaluation of tumors in patients with mid and low rectal cancer; (3) initial imaging evaluation of patients with mid and low rectal cancer; (4) imaging evaluation after neoadjuvant therapy for patients with mid and low rectal cancer. Measurement data with normal distribution were represented as Mean± SD, and measurement data with skewed distribution were represented as M( Q1, Q3). Count data were described as absoluter numbers and/or percentages. Results:(1) Clinical characteristics of patients with mid and low rectal cancer. Of the 1 074 patients, there were 713 males and 361 females, aged 63(56,70)years. The body mass index of 1 074 patients was 24(21,26)kg/m 2.For American Society of Anesthesiologists classification, there were 147 cases of stage Ⅰ, 641 cases of stage Ⅱ, 157 cases of stage Ⅲ, 2 cases of stage Ⅳ, and there were 127 cases missing data. (2) Initial colonoscopy and pathologic evaluation of tumors in patients with mid and low rectal cancer. Of the 1 074 patients, there were 787 cases (73.28%) undergoing complete colonoscopy, and there were only 197 cases (18.34%) undergoing immunohistochemical evaluation of all four mismatch repair proteins. (3) Initial imaging evaluation of patients with mid and low rectal cancer. Of the 1 074 patients, there were 842(78.40%) patients completing magnetic resonance imaging (MRI) or ultrasound evaluation, and there were 914(85.10%) patients completing chest, abdomen, and pelvis enhanced computed tomography (CT) evaluation. In the 149 patients completing rectal ultrasound evaluation, there were 122 cases (81.88%) comple-ting T staging evaluation, and there were 81 cases (54.36%) completing N staging evaluation. In the 808 patients completing rectal MRI evaluation, there were 708 cases (87.62%) completing T staging evaluation, and there were 590 cases (73.02%) completing N staging evaluation. (4) Imaging evalua-tion after neoadjuvant therapy for patients with mid and low rectal cancer. Of the 388 patients with neoadjuvant therapy, there were 332 patients (85.57%) completing MRI or ultrasound evaluation, and there were 327 patients (84.28%) completing chest, abdomen, and pelvis enhanced CT evalua-tion. In the 70 patients completing rectal ultrasound evaluation, there were 65 cases (92.86%) com-pleting T staging evaluation, and there were 49 cases (70.00%) completing N staging evaluation. In the 327 patients completing rectal MRI evaluation, there were 246 cases (75.23%) completing T staging, and there were 228 cases (69.72%) completing N staging evaluation. Conclusion:The com-pletion rate of tumor imaging evaluation at initial assessment and after neoadjuvant therapy for mid and low rectal cancer patients on a national scale is relatively good.
9.Research progress of hydrogen sulfide in ferroptosis-mediated neurodegenerative diseases
Lin-cen XIAO ; Yu-si-han ZENG ; Jia HONG ; Ke-ting LIU ; Li XIAO
Journal of Regional Anatomy and Operative Surgery 2025;34(10):923-928
Ferroptosis is a programmed cell death depends on iron and lipid peroxidation,which has been recognized as the key pathogenic factor for the occurrence of various diseases in recent years,especially playing a significant role in neurodegenerative diseases.Ferroptosis triggers lipid peroxidation and oxidative stress in neuronal cells,leading to neuronal damage and death,thereby accelerating disease progression.Hydrogen sulfide,as an endogenous gaseous signaling molecule,exhibits multiple protective effects,including anti-inflammatory,antioxidant,and anti-ferroptosis properties.Hydrogen sulfide can effectively inhibit the occurrence of ferroptosis through various mechanisms,such as regulating iron metabolism,inhibiting lipid peroxidation,and enhancing the activity of antioxidant enzymes,thereby slowing down the progression of neurodegenerative diseases.This article reviews the related research progress on hydrogen sulfide and ferroptosis and ferroptosis-mediated neurodegenerative diseases,and analyzes the underlying mechanisms,aims to provide new insights and theoretical foundations for the treatment of neurodegenerative diseases.
10.Impact of suture configuration and fixation type on biomechanical strength of rotator cuff repair:A factorial design study
Yinzhe CUI ; Zheng YAN ; Jia MA ; Zhefeng JIN ; Jiawen ZHAN ; Minshan FENG ; Guangwei LIU ; Jie YU ; Xu WEI ; Jiangtao SI ; Minghui ZHUANG ; Tao HAN ; Jianguo LI ; ZHANGKAIRUI ; Liguo ZHU
Chinese Journal of Sports Medicine 2025;44(9):729-737
Objective To explore the impact of suture configuration and fixation type on the biome-chanical strength of rotator cuff repair,using a factorial design study.Methods Sixteen fresh-frozen porcine shoulder samples were randomized into an anchorless double-row suture bridge transosseous su-tures(DS)group,an anchored double-row suture bridge transosseous-equivalent(DE)group,an an-chorless X-BOX construct transosseous sutures(XS)group,and an anchored X-BOX construct transos-seous-equivalent(XE)group,each of four,according to suture configuration(double-row suture bridge,traditional X-BOX construct)and fixation type(suture anchors,transosseous sutures).Then,their fatigue resistance(first-cycle excursion,gap length difference ratio,and the percentage of ex-posed footprints)and the failure strength(the maximum failure load and the re-tear type)were mea-sured using a biomechanical material testing machine.Results Different suture configurations affected failure strength(F=39.559,P<0.001),with the double-row suture bridge groups(693.07±58.35 N,746.76±138.57 N)showing significantly higher failure strength,compared to the traditional X-BOX groups(462.90±18.91 N,421.43±90.76 N).However,the fixation type did not significantly im-pact failure strength(F=1.161,P=0.302).Moreover,the suture configuration influenced the gap differ-ence ratio(F=7.781,P=0.016),but had no significant correlation with other fatigue resistance indica-tors(P>0.05).Meanwhile,failure strength and fatigue resistance were not correlated with fixation type,and the interaction between suture and fixation type(P>0.05).The incidence of failure types for the four suture configurations was as follows:Type I tendon tear:XS>XE>DS=DE;type II tendon tear:DS>XE>XS=DE;fixing material-related failure:DE>DS=XE=XS.Conclusion The failure strength and gap formation ratio in rotator cuff repair under fatigue loading are influenced by suture configuration,whereas no significant association has been observed with respect to fixation method,whether using transosseous sutures or suture anchors.

Result Analysis
Print
Save
E-mail