ObjectiveTo systematically compare the differential regulation of the maternal-fetal interface cell lineages and communication networks in the CBA/J×DBA/2 mouse model of recurrent pregnancy loss （RPL） by the two classic therapeutic methods-tonifying the kidney to stabilize the fetus and invigorating the spleen to stabilize the fetus （Shoutai Wan， Juyuan Jian）-of traditional Chinese medicine （TCM） at the single-cell resolution and clarify their modern scientific connotations. MethodsFemale non-pregnant CBA/J mice were caged with male BALB/c （blank group） and DBA/2 （modeling group） mice separately. Pregnant mice in the modeling group were randomly grouped as follows： high/low-dose Shoutai Wan， high/low-dose Juyuan Jian， model （RPL）， and positive control （dydrogesterone）， with 10 mice in each group. Starting from the day after the detection of the vaginal plug， mice were administrated with drugs or an equal volume of normal saline by gavage for 10 consecutive days. After the intervention， the following indicators were measured. ① Macroscopic evaluation： general conditions， uterine wet weight， embryo loss rate， four coagulation parameters ［prothrombin time （PT）， activated partial thromboplastin time （APTT）， fibrinogen （FIB）， and thrombin time （TT）］， and peripheral blood estradiol （E₂） and progesterone （Pg） levels. The decidua with embryos was stained with hematoxylin-eosin （HE） and evaluated by transmission electron microscopy （TEM）. The expression of B-cell lymphoma-2 （Bcl-2）， vascular endothelial growth factor （VEGF）， angiotensin Ⅱ （AngⅡ）， matrix metalloproteinase-2 （MMP-2）， interleukin-6 （IL-6）， leukemia inhibitory factor （LIF）， CXC chemokine ligand 12 （CXCL12）， and microtubule-associated protein 1 light chain 3 homolog （LC3）Ⅰ/Ⅱ was quantified by Western blot. ② Mechanism analysis at the single-cell level： The decidua with embryos from the blank， model， high-dose Shoutai Wan， and high-dose Juyuan Jian groups （6 mice per group， with 3 single-cell samples per group， totaling 24 mice） were analyzed by the BD Rhapsody™ platform， and the whole-cell atlas was drawn by uniform manifold approximation and projection （UMAP） dimensionality reduction clustering combined with the single-cell mouse cell atlas （scMCA）. The differentially expressed genes （DEGs） and cell interaction networks were analyzed via Gene Ontology （GO）， Kyoto Encyclopedia of Genes and Genomes （KEGG）， and CellChat， and the protein-protein interaction （PPI） map of subtype cells was constructed. The CytoTRACE pseudo-temporal analysis was performed to explore the developmental trajectories of core immune cells （natural killer cells， NK cells） from maternal and fetal sources. Results① Pathological and Western blot results indicated that compared with the blank group， the RPL group showed an increase in the embryo loss rate （P<0.01）， down-regulated expression of Bcl-2， LIF， MMP-2， and Vegf in the decidua with embryos （P<0.05）， up-regulated protein levels of CXCL-12， AngⅡ， and IL-6 （P<0.05）， blocked angiogenesis， apoptosis-inflammation imbalance， and coagulation dysfunction. Both prescriptions dose-dependently reduced the abortion rate and restored the angiogenesis-inflammation balance， and Shoutai pill showed superior performance in restoring the E₂ level to the Pg level （P<0.05）. ② Single-cell transcriptome analysis indicated that compared with the blank group， the RPL group showed differences in multiple key cell populations such as decidual cells， trophoblast cells， endothelial cells， erythroblasts， NK cells， and macrophages at the maternal-fetal interface. Immunity and angiogenesis were the key links in RPL. Compared with the RPL group， high-dose Shoutai Wan reversed the changes of NK cells in the embryonic layer （upregulating the mRNA levels of 17 genes and downregulating the mRNA levels of 29 genes） and macrophages （upregulating the mRNA levels of 117 genes and downregulating the mRNA levels of 53 genes） through the regulation of gene expression. High-dose Shoutai pill regulated the immune cells to affect unfolded proteins， cell adhesion， and programmed cell death， thereby promoting decidualization and angiogenesis and modulating embryo-membrane development. High-dose Juyuan Jian regulated the key subgroups of NK cells （up-regulating the mRNA levels of 9 genes and down-regulating the mRNA levels of 17 genes） and macrophages （up-regulating the mRNA levels of 110 genes and down-regulating the mRNA levels of 81 genes）， which affected decidual inflammation and apoptosis and intervened in glycolysis. ③ The pseudo-temporal analysis and communication network indicated that the communication frequency of the RPL group decreased. High-dose Shoutai Wan restored maternal-fetal tolerance through pathways such as NKG2D， CDH5， GDF， and FASLG. High-dose Juyuan Jian enhanced the IL-6/LIFR/JAK/signal transducer and activator of transcription 3 （STAT3） and desmosome/SEMA6/tumor necrosis factor-like weak inducer of apoptosis （TWEAK） signaling to improve endometrial receptivity. The RPL group showed an increased proportion of toxic dNK7， a decreased proportion of reparative dNK4， and blocked embryo fNK1. High-dose Shoutai Wan down-regulated dNK7 and up-regulated dNK4. High-dose Juyuan Jian inhibited the terminal differentiation of dNK7 and up-regulated LILRB1， thus restoring the balance of cytotoxicity and repair. ConclusionBoth the kidney-tonifying and spleen-invigorating methods are effective in treating RPL. NK and macrophages are the key immune cells in the interaction between the embryo and the membrane. The kidney-tonifying method （Shoutai Wan） has an advantage in regulating the phenotypes of unfolded protein， cell adhesion， and programmed cell death， and shows expression characteristics closer to the physiological state in the regulation of NKG2D and CDH5 signals. The spleen-invigorating method （Juyuan Jian） has an advantage in regulating epithelial-mesenchymal transition （EMT）， angiogenesis， and glycolysis and shows higher communication intensity in the IL-6 and LIFR pathways.

Enhancer of zeste homolog 2(EZH2)is a histone methyltransferase It mediates trimethylation of lysine 27 on histone H3,thereby facilitating the epigenetic silencing of downstream genes.In conjunc-tion with SUZ12,EED,and other components,it constitutes the polycomb repressive complex 2(PRC2)complex.While EZH2 is intricately involved in cellular proliferation and cardiac development,the chan-ges in its expression during cardiac terminal differentiation remain elusive.In this study,we employed differential gene expression analysis of embryonic and adult myocardial cells using the GEO database,and found that EZH2 is highly expressed in embryonic myocardium,but is present at very low levels in adult myocardium(P＜0.0001).Conversely,the expression changes of PRC2 members SUZ12 and EED are not as pronounced.Online analysis through the Tabula Muris database indicates that under physiological conditions,various cell subpopulations in the adult mouse heart exhibit negligible expression of EZH2.Immunohistochemical staining of mouse cardiac tissues shows that EZH2 is highly expressed in embryonic and neonatal myocardium but declines progressively from the first day after birth(P＜0.0001),becoming almost undetectable by the third day.Western blotting further confirms the rapid disappearance of EZH2 expression post-birth(P＜0.05),with EZH1 compensating for the downregulation of EZH2 to maintain H3K27me3 modification levels.Additionally,using the P19 teratocarcinoma stem cell model for cardio-myocyte differentiation,it is observed that EZH2 is significantly upregulated during the transition from cardiac progenitor cells to spontaneously beating cardiomyocytes,correlating with the expression of the cardiomyocyte transcription factor Gata4(P＜0.01).Targeted degradation of EZH2 using the small mole-cule drug MS1943 significantly inhibits the proliferation of induced cardiomyocytes,as evidenced by 5-e-thynyl-2'-deoxyuridine(EdU)incorporation assays(P＜0.01),and RT-qPCR reveals a marked in-crease in the expression of the proliferation inhibitor CDKN1A(P＜0.01).In summary,the high expres-sion of EZH2 in embryonic myocardial cells is associated with enhanced cell proliferation.The rapid loss of EZH2 expression postnatally correlates with the loss of proliferative capacity in cardiomyocytes,mark-ing it as a key indicator of cardiac terminal differentiation.

Objective To propose an EBT3 film technology-based quality control measurement method for the INTRABEAM PRS500 intraoperative radiotherapy equipment to solve the problems of the traditional methods in cumbersome operation and setup error.Methods According to HJ 1198-2021 Requirements of radiation safety and protection for radiotherapy and GBZ 121-2020 Requirements for radiological protection in radiotherapy,the environmental radiation testing of the INTRABEAM PRS500 intraoperative radiotherapy equipment was carried out point by point by means of the radiation inspection instrument.The INTRABEAM PRS500 intraoperative radiotherapy equipment was characterized by a point X-ray source(XRS),and the XRS was detected in terms of the probe linearity,radiation dose,dynamic deviation,isotropy and dose rate.The EBT3 film technology was used to verify the symmetry and isotropy of the XRS planar dose of INTRABEAM PRS500 intraoperative radiotherapy equipment.Results The X-γ dose equivalent rate of each monitoring site of the INTRABEAM PRS500 intraoperative radiotherapy device was lower than the method detection limit(MDL).The results of SQA quality control showed that the INTRABEAM PRS500 intraoperative radiotherapy equipment XRS met the quality control requirements in terms of the probe linearity,radiation dose,dynamic deviation and etc,and the isotropy differences in the+X,-X,+Y,and-Y axis directions ranged from-1.40％to 1.79％,which were all within the allowable range of measurement tolerance(5.60％to 5.65％).The results of measuring the isotropy of the INTRABEAM PRS500 intraoperative radiotherapy equipment based on the EBT3 film technology showed that the dose distribution of the XRS in the directions of the+X,-X,+Y,and-Y axes at the same plane was well isotropic,and that the doses in the directions of the X and Y axes were symmetrically distributed,and that the maximum skewness value for the isotropy of the XRS in the XY plane was-1.581％,which met the requirements of AAPM TG61 report on the reference dosimetry of low-energy and medium-energy X-rays for radiotherapy and radiobiology of≤±5.3％.Conclusion The EBT3 film technology-based measurement method gains high simplicity and feasibility for the isotropy of the INTRABEAM PRS500 intraoperative radiotherapy equipment in the directions of the+X,-X,+Y,and-Y axes at the same planet,which realizes the dynamic monitoring of the dosimetric changes and facilitates the whole-process quality control management of the intraoperative radiotherapy equipment.[Chinese Medical Equipment Journal,2025,46(6):47-53]

Objective To propose an EBT3 film technology-based quality control measurement method for the INTRABEAM PRS500 intraoperative radiotherapy equipment to solve the problems of the traditional methods in cumbersome operation and setup error.Methods According to HJ 1198-2021 Requirements of radiation safety and protection for radiotherapy and GBZ 121-2020 Requirements for radiological protection in radiotherapy,the environmental radiation testing of the INTRABEAM PRS500 intraoperative radiotherapy equipment was carried out point by point by means of the radiation inspection instrument.The INTRABEAM PRS500 intraoperative radiotherapy equipment was characterized by a point X-ray source(XRS),and the XRS was detected in terms of the probe linearity,radiation dose,dynamic deviation,isotropy and dose rate.The EBT3 film technology was used to verify the symmetry and isotropy of the XRS planar dose of INTRABEAM PRS500 intraoperative radiotherapy equipment.Results The X-γ dose equivalent rate of each monitoring site of the INTRABEAM PRS500 intraoperative radiotherapy device was lower than the method detection limit(MDL).The results of SQA quality control showed that the INTRABEAM PRS500 intraoperative radiotherapy equipment XRS met the quality control requirements in terms of the probe linearity,radiation dose,dynamic deviation and etc,and the isotropy differences in the+X,-X,+Y,and-Y axis directions ranged from-1.40％to 1.79％,which were all within the allowable range of measurement tolerance(5.60％to 5.65％).The results of measuring the isotropy of the INTRABEAM PRS500 intraoperative radiotherapy equipment based on the EBT3 film technology showed that the dose distribution of the XRS in the directions of the+X,-X,+Y,and-Y axes at the same plane was well isotropic,and that the doses in the directions of the X and Y axes were symmetrically distributed,and that the maximum skewness value for the isotropy of the XRS in the XY plane was-1.581％,which met the requirements of AAPM TG61 report on the reference dosimetry of low-energy and medium-energy X-rays for radiotherapy and radiobiology of≤±5.3％.Conclusion The EBT3 film technology-based measurement method gains high simplicity and feasibility for the isotropy of the INTRABEAM PRS500 intraoperative radiotherapy equipment in the directions of the+X,-X,+Y,and-Y axes at the same planet,which realizes the dynamic monitoring of the dosimetric changes and facilitates the whole-process quality control management of the intraoperative radiotherapy equipment.[Chinese Medical Equipment Journal,2025,46(6):47-53]

IgA vasculitis is a common childhood vasculitis disorder.Its primary clinical manifestation is cutaneous purpura,which is often accompanied by gastrointestinal and joint symptoms.Renal involvement can present as hematuria or proteinuria.This condition is recurrent and protracted,significantly affecting the health of children.The pathogenic factors in pediatric IgA vasculitis are diverse."Wind-toxin damaging collaterals"is presented as the core pathogenesis based on clinical practice and theoretical exploration.This concept essentially entails the latent attack of wind-toxin,collateral damage leading to blood extravasation,and healthy qi deficiency and lingering toxins,with the disease primarily located in the collateral vessels.The disease course is divided into three stages:acute,lingering,and recovery.Clinical practice should adhere to the pathogenesis principles and apply stage-based pattern differentiation and treatment.The acute stage involves wind-toxin attacking collaterals with dampness-heat accumulation.Treatment focuses on dispersing wind,clearing heat,and eliminating dampness to expel wind-toxin from the muscular exterior.The self-prescribed Qufeng Xiaodian Formula is a frequently selected modified formula.The lingering stage features latent wind-toxin in the collaterals and congealed accumulations in the kidney collaterals.Treatment aims to resolve wind-toxin,disperse stasis,and eliminate accumulation to remove densely accumulated wind-toxin.A modified Taohong Siwu Decoction is selected.The recovery stage involves deficient healthy qi with persistent wind assault and lingering toxins.Emphasis should be placed on cultivating the fundamental,strengthening the root,and nourishing yin,as well as supporting the healthy qi to dispel wind and expel toxins,while conditioning the body to prevent recurrence.A modified Guomin Decoction is selected.Clinical application emphasizes the combination of characteristic medicines,such as wind medicines to expel pathogens,insect medicines to identify collaterals,and vine medicines to unblock the meridians,to enhance the effects of identifying wind,resolving toxins,unblocking collaterals,and dispersing congealed accumulations.This study aims to systematically elaborate on the stage-based treatment strategy from the perspective of"wind-toxin damaging collaterals,"providing a theoretical basis and clinical practice reference for the traditional Chinese medicine diagnosis and treatment of pediatric IgA vasculitis.

BACKGROUND:The pathogenesis of inflammatory bowel disease involves inflammation,immune activation,visceral hypersensitivity,and dysbiosis of the gut microbiota.Inflammation promotes the release of inflammatory mediators by immune cells,damaging the enteric nervous system.Enteric glial cells are an important component of the intestinal nervous system and are excellent cells for studying intestinal neuroinflammation.Primary enteric glial cells play a crucial role in exploring cell therapies for intestinal nervous system diseases.Currently,the methods for obtaining these cells are mostly cumbersome.Therefore,finding a convenient and fast method for extracting this cell is crucial.OBJECTIVE:To establish a method for optimizing the isolation,culture,and identification of mouse enteric glial cells.METHODS:0-7-day-old C57BL/6 neonatal mice were euthanized by excessive inhalation of isoflurane.After soaking in 75％alcohol for disinfection,the duodenum(1 cm below the pylorus to 1 cm above the Qu's ligament)was removed by laparotomy at the midline of the abdomen.A 1 mL syringe was filled with DPBS and the intestinal contents were repeatedly rinsed until the intestine became translucent,and the mesentery and blood vessels were peeled off.The duodenum was cut to a size of 1 mm and digested in 0.25％EDTA trypsin for 20 minutes.Then an equal amount of DMEM/F12 complete culture medium was added to terminate digestion.The liquid was filtered through a 100 μm cell filter,centrifuged,and the cells were resuspended in 1 mL of DMEM/F12 complete culture medium.When the cell adhesion growth density reached 80％,cells were digested for subculture.When cells were cultured to the third generation,glial fibrillary acid protein labeled with enteric glial cells was used for identification by immunofluorescence method.RESULTS AND CONCLUSION:The isolated and cultured cells were full of colloids,with protrusions extending outward and passable.Glial fibrillary acid protein staining was positive.This method can successfully isolate and culture enteric glial cells and is easy to operate,providing a stable model for the study of the pathophysiology of the enteric nervous system.

Enhancer of zeste homolog 2(EZH2)is a histone methyltransferase It mediates trimethylation of lysine 27 on histone H3,thereby facilitating the epigenetic silencing of downstream genes.In conjunc-tion with SUZ12,EED,and other components,it constitutes the polycomb repressive complex 2(PRC2)complex.While EZH2 is intricately involved in cellular proliferation and cardiac development,the chan-ges in its expression during cardiac terminal differentiation remain elusive.In this study,we employed differential gene expression analysis of embryonic and adult myocardial cells using the GEO database,and found that EZH2 is highly expressed in embryonic myocardium,but is present at very low levels in adult myocardium(P＜0.0001).Conversely,the expression changes of PRC2 members SUZ12 and EED are not as pronounced.Online analysis through the Tabula Muris database indicates that under physiological conditions,various cell subpopulations in the adult mouse heart exhibit negligible expression of EZH2.Immunohistochemical staining of mouse cardiac tissues shows that EZH2 is highly expressed in embryonic and neonatal myocardium but declines progressively from the first day after birth(P＜0.0001),becoming almost undetectable by the third day.Western blotting further confirms the rapid disappearance of EZH2 expression post-birth(P＜0.05),with EZH1 compensating for the downregulation of EZH2 to maintain H3K27me3 modification levels.Additionally,using the P19 teratocarcinoma stem cell model for cardio-myocyte differentiation,it is observed that EZH2 is significantly upregulated during the transition from cardiac progenitor cells to spontaneously beating cardiomyocytes,correlating with the expression of the cardiomyocyte transcription factor Gata4(P＜0.01).Targeted degradation of EZH2 using the small mole-cule drug MS1943 significantly inhibits the proliferation of induced cardiomyocytes,as evidenced by 5-e-thynyl-2'-deoxyuridine(EdU)incorporation assays(P＜0.01),and RT-qPCR reveals a marked in-crease in the expression of the proliferation inhibitor CDKN1A(P＜0.01).In summary,the high expres-sion of EZH2 in embryonic myocardial cells is associated with enhanced cell proliferation.The rapid loss of EZH2 expression postnatally correlates with the loss of proliferative capacity in cardiomyocytes,mark-ing it as a key indicator of cardiac terminal differentiation.

Objective To investigate the risk factors for ligamentum flavum hypertrophy(LFH)and its correlation with clinical symptoms in patients with degenerative lumbar spinal stenosis(DLSS).Methods The clinical and imaging data of 79 patients with DLSS were collected.Patients were divided into four groups based on LFH severity.Quantitative parameters,including lumbar lordosis(LL),sacral slope(SS),facet tropism,facet joint effusion,intervertebral height index,dural sac cross-sectional area(CSA),epidural fat area,and fat infiltration rate(FIR)of the paraspinal muscle were measured on imaging.One-way analysis of variance was used to compare the differences in these parameters among groups.Multiple linear regression analysis was performed to identify the risk fac-tors for LFH,and the correlation between LFH severity and clinical manifestations was analyzed.Results The results of one-way analy-sis of variance showed that there were statistically significant differences among the four groups of patients in terms of sex,body mass index(BMI),LL,epidural fat area and FIR of the multifidus(MF).Multiple linear regression analysis identified that BMI,LL,and epidural fat area as independent risk factors for LFH.Correlation analysis indicated a weak positive association between LFH and dis-ease duration(r=-0.231,P=0.041).Conclusion In DLSS patients,LFH is weakly correlated with disease duration,while BMI,LL,and epidural fat area are risk factors for LFH.

IgA vasculitis is a common childhood vasculitis disorder.Its primary clinical manifestation is cutaneous purpura,which is often accompanied by gastrointestinal and joint symptoms.Renal involvement can present as hematuria or proteinuria.This condition is recurrent and protracted,significantly affecting the health of children.The pathogenic factors in pediatric IgA vasculitis are diverse."Wind-toxin damaging collaterals"is presented as the core pathogenesis based on clinical practice and theoretical exploration.This concept essentially entails the latent attack of wind-toxin,collateral damage leading to blood extravasation,and healthy qi deficiency and lingering toxins,with the disease primarily located in the collateral vessels.The disease course is divided into three stages:acute,lingering,and recovery.Clinical practice should adhere to the pathogenesis principles and apply stage-based pattern differentiation and treatment.The acute stage involves wind-toxin attacking collaterals with dampness-heat accumulation.Treatment focuses on dispersing wind,clearing heat,and eliminating dampness to expel wind-toxin from the muscular exterior.The self-prescribed Qufeng Xiaodian Formula is a frequently selected modified formula.The lingering stage features latent wind-toxin in the collaterals and congealed accumulations in the kidney collaterals.Treatment aims to resolve wind-toxin,disperse stasis,and eliminate accumulation to remove densely accumulated wind-toxin.A modified Taohong Siwu Decoction is selected.The recovery stage involves deficient healthy qi with persistent wind assault and lingering toxins.Emphasis should be placed on cultivating the fundamental,strengthening the root,and nourishing yin,as well as supporting the healthy qi to dispel wind and expel toxins,while conditioning the body to prevent recurrence.A modified Guomin Decoction is selected.Clinical application emphasizes the combination of characteristic medicines,such as wind medicines to expel pathogens,insect medicines to identify collaterals,and vine medicines to unblock the meridians,to enhance the effects of identifying wind,resolving toxins,unblocking collaterals,and dispersing congealed accumulations.This study aims to systematically elaborate on the stage-based treatment strategy from the perspective of"wind-toxin damaging collaterals,"providing a theoretical basis and clinical practice reference for the traditional Chinese medicine diagnosis and treatment of pediatric IgA vasculitis.

Objective To establish a human monocytic THP-1 macrophage-derived foam cell model and analyze the role of the α subunit of coatomer protein Ⅰ(α-COP)in apolipoprotein A-1(apoA-1)-mediated cholesterol efflux from foam cells.Methods THP-1 cells were induced to adhere using PMA(PMA group),followed by treatment with acetylated low-density lipoprotein(Ac-LDL)to generate macrophage-derived foam cells(Ac-LDL group).Subsequent incubation with apoA-1 formed the apoA-1 group.Cholesterol efflux rates mediated by apoA-1 and intracellular lipid accumulation were quantified through liquid scintillation counting and oil red O staining.The expression patterns of α-COP were systematically analyzed using quantitative real-time PCR(qPCR),Western blotting,and laser scanning confocal microscopy.THP-1 macrophage-derived foam cells mediated by apoA-1 were transduced with scrambled shRNA(Scr group)or α-COP-specific shRNA lentivirus(α-COP shRNA group)to assess the effects of α-COP knockdown on cholesterol efflux efficiency and total cellular cholesterol content.Subcellular localization of adipopoilin(ADFP)and cholesterol probe Fil-ipin Ⅲ staining patterns were visualized via laser scanning confocal microscopy.Bioinformatics analysis of α-COP expression profiles in carotid atherosclerotic plaques was performed using datasets from the GEO data-base.Results Compared with the Ac-LDL group,the cholesterol efflux rate in the apoA-1 group was signifi-cantly increased[(9.77±0.79)%vs.(2.74±0.37)%,P＜0.001].Oil red O staining demonstrated reduced lipid accumulation in foam cells of the apoA-1 group compared with the Ac-LDL group.The relative mRNA expression level of α-COP in the apoA-1 group was significantly higher than that in the Ac-LDL group(P＜0.001),with corresponding elevation in protein expression(P＜0.001).Fluorescence intensity analysis re-vealed increased mean fluorescence intensity of α-COP in the apoA-1 group compared with the Ac-LDL group.Following α-COP knockdown by shRNA,the apoA-1-mediated cholesterol efflux rate was significantly de-creased(P＜0.05)and total intracellular cholesterol levels were increased(P＜0.001)in the α-COP shRNA group compared with the Scr group.The α-COP shRNA group exhibited enhanced red fluorescence intensity of ADFP(P＜0.05)and increased blue fluorescence intensity of Filipin Ⅲ(P＜0.01)compared with the Scr group.Database analysis indicated that α-COP mRNA expression was lower in carotid atherosclerotic plaques than in normal arterial tissues,with reduced expression in advanced-stage plaques compared with early-stage plaques(P＜0.05).Conclusion α-COP participates in apoA-1-mediated cholesterol efflux from foam cells,and interference with α-COP expression results in reduced cholesterol efflux and increased intracellular lipid accumulation.