The accumulation of uremic toxins such as urea nitrogen, blood creatinine, and uric acid of patients with renal failure in vivo would lead to aggravated kidney damage. In this study, coated aldehyde oxy-starch (CAO) was used as an adsorbent to investigate its in vitro adsorption performance on renal failure indexes for urea, indoxyl sulfate (INS), monomethylamine (MMA), dimethylamine (DMA), uric acid (UA), and creatinine (Cr). The effects of variables such as pH, temperature, concentration, dosage, and time on the adsorption capacity of CAO were systematically investigated, employing analytical techniques of high-performance liquid chromatography (HPLC) and gas chromatography (GC). The results revealed that CAO exhibited a strong adsorption capacity for urea, INS, and MMA, alongside a moderate adsorption capacity for DMA, UA, and Cr. The adsorption kinetics and thermodynamic studies indicated that the adsorption of urea and UA by CAO were fitted in pseudo-first-order kinetics, and the adsorption isotherm aligned with the Freundlich adsorption model. The enthalpy change ΔH of urea in adsorption was in the range of 40 to 60 kJ·mol^-1, which demonstrated the presence of strong adsorption force due to the interactions of coordinating groups. The ΔH of UA was greater than 80 kJ·mol^-1, indicating the generation of chemical bonds during the adsorption. Both of them, Gibbs free energy ΔG was less than 0, within the range of -20 to 0 kJ·mol^-1, suggested that the adsorption of urea and UA by CAO occurred spontaneously as physical adsorption process. The adsorption entropy ΔS of urea and UA was > 0, which indicated an increase in entropy throughout the adsorption. The infrared spectroscopygram showed the formation of a chemical bond, specifically the imine bond, following the adsorption of urea by CAO, thereby indicating a chemical reaction during the adsorption. This study elucidates the adsorption mechanism of CAO on various indexes of renal failure, providing a scientific basis for its clinical usage.

ObjectiveTo study the changing law of appearance color and physicochemical properties of Angelicae Sinensis Radix Carbonisata（ASRC） during the processing by color space method combined with statistical analysis， so as to provide reference for determining the processing endpoint and evaluating the quality of the decoction pieces. MethodsTaking processing time（4， 8， 12， 16 min） and temperature（180， 200， 220， 240 ℃） as factors， ASRC decoction pieces with different processing degrees were prepared in a completely randomized design. Then， the brightness value（L^*）， red-green value（a^*）， yellow-blue value（b^*）， and total chromaticity value （E^*ab） of the decoction pieces were determined by spectrophotometer， the color difference value（ΔE） was calculated， and the data of colorimetric values were analyzed by discriminant analysis. At the same time， the pH， charcoal adsorption， and contents of tannins， 5-hydroxymethylfurfural（5-HMF）， tryptophan， chlorogenic acid， ferulic acid， senkyunolide I， senkyunolide H and ligustilide of ASRC with different processing degrees were determined by pH meter， ultraviolet and visible spectrophotometry and ultra-high performance liquid chromatography（UPLC）. Principal component analysis（PCA） was used to analyze the data of physicochemical indexes， after determining the processing technology of ASRC， the canonical discriminant function was established to distinguish the decoction pieces with different processing degrees， and leave-one-out cross validation was conducted. Finally， Pearson correlation analysis was used to explore the correlation between various physicochemical indexes and chromaticity values. ResultsWith the prolongation of the processing time， L^*， a^*， b^* and E^*ab all showed a decreasing trend， and the established discriminant model based on color parameters was able to distinguish ASRC with different processing degrees. The pH showed an increasing trend with the prolongation of processing time， and the charcoal adsorption， and the contents of tannins， 5-HMF， and tryptophan all showed an increasing and then decreasing trend. Among them， the charcoal adsorption， contents of tannin and 5-HMF reached their maximum values successively after processing for 8-12 min. While the contents of chlorogenic acid， ferulic acid， senkyunolide I， senkyunolide H and ligustilide decreased with the increase of processing time， with a decrease of 60%-80% at 8 min of processing. Therefore， the optimal processing time should be determined to be 8-12 min. PCA could clearly distinguish ASRC with different processing degrees， while temperature had no significant effect on the processing degree. The 12 batches of process validation results（10 min， 180-240 ℃） showed that except for 3 batches identified as class Ⅱ light charcoal， all other batches were identified as class Ⅲ standard charcoal， and the chromaticity values of each batch of ASRC were within the reference range of class Ⅱ-Ⅲ sample chromaticity values. The correlation analysis showed that the chromaticity values were negatively correlated with pH and charcoal adsorption， and positively correlated with contents of tryptophan， chlorogenic acid， ferulic acid， senkyunolide I， senkyunolide H， and ligustilide. And both pH and charcoal adsorption were negatively correlated with the contents of the above components， but the charcoal adsorption was positively correlated with the content of 5-HMF. ConclusionThe chromaticity values and the contents of various physicochemical indicators of ASRC undergo significant changes with the prolongation of processing time， and there is a general correlation between chromaticity values and various physicochemical indicators. Based on the changes in color and physicochemical indicators， the optimal processing time for ASRC is determined to be 8-12 min. This study reveals the dynamic changes of the relevant indexes in the processing of ASRC， which can provide a reference for the discrimination of the processing degree and the quantitative study of the processing endpoint.

Periodontal disease is a chronic infectious disease characterized by chronic inflammation and progressive destruction of the periodontal tissue. Ferroptosis, an iron-dependent form of programmed cell death, is primarily characterized by altered iron homeostasis, weak antioxidant defense, and accumulation of lipid peroxides and plays an important role in a variety of diseases. Recent research has shown the correlation between ferroptosis and the occurrence and development of periodontal disease. Through in-depth research of relevant literature on periodontal ligament fibroblasts, periodontal ligament stem cells, human immortalized oral epithelial cells, human gingival fibroblasts, dental pulp stem cells, MLOY4 cells, mouse mandibular osteoblast, and macrophages, we found that ferroptosis is widely suppressed in periodontal disease. This phenomenon is primarily related to lipid metabolism, iron metabolism, cysteine/glutamate transporter system xc-/glutathione/glutathione peroxidase 4, nicotinamide adenine dinucleotide phosphate/ferroptosis suppressor protein 1/coenzyme Q10, kelch-like ECH-associated protein-1/nuclear factor E2 related factor 2, and p53. Current research indicates that ferroptosis plays an important role in regulating the destruction of periodontal soft and hard tissues, inflammatory response, and periodontopathogen-induced progression of systemic diseases. Although there are several studies on the mechanism of ferroptosis in periodontal disease, there are many uncertainties in the application of ferroptosis in periodontal therapy. Therefore, further studies are required to explore and develop ferroptosis-related drugs for the treatment of periodontal disease.

ObjectiveTo investigate the efficacy and underlying mechanisms of Gynostemma pentaphyllum alcohol extract in improving glucose and lipid metabolism disorders in db/db mice through transcriptomics and gut microbiota analysis. MethodsEighteen db/db mice were randomly assigned to the model（DM） group， metformin（MET） group， and G. pentaphyllum alcohol extract（GP） group， with six mice in each group， based on stratification of fasting blood glucose and body weight. An additional six db/m mice were selected as the normal control（NC） group. Mice in the NC and DM groups were administered deionized water （10 mL·kg^-1） daily. The MET group received metformin （0.195 g·kg^-1） by gavage. The GP group was treated with G. pentaphyllum alcohol extract （3.9 g·kg^-1） by gavage for six weeks. Fasting blood glucose was measured every two weeks. After six weeks of intervention， serum levels of total cholesterol （TC）， triglycerides （TG）， low-density lipoprotein cholesterol （LDL-C）， high-density lipoprotein cholesterol （HDL-C）， aspartate aminotransferase （AST）， alanine aminotransferase （ALT）， creatinine （CREA）， and blood urea nitrogen （BUN） were assessed. Enzyme-linked immunosorbent assay （ELISA） was used to measure insulin （FINS）， adiponectin （ADP）， and tumor necrosis factor-α （TNF-α）. Hematoxylin-eosin （HE） staining was used to observe liver histomorphology， periodic acid-Schiff （PAS） staining was employed to assess hepatic glycogen synthesis， and Oil Red O staining was used to detect hepatic lipid deposition. Liver transcriptomic data were used to identify differentially expressed genes in the liver and conduct enrichment analysis. Real-time PCR was employed to verify the expression levels of adiponectin gene （Adipoq）， peroxisome proliferator-activated receptor gamma coactivator-1α （PGC-1α）， AMP-activated protein kinase （AMPK）， peroxisome proliferator-activated receptor α （PPARα）， glucokinase （GCK）， forkhead box （Fox）O1， FoxO3， phosphoenolpyruvate carboxykinase （PEPCK）， and glucose-6-phosphatase （G6PC）. Metagenomic sequencing was conducted to analyze changes in gut microbiota composition. ResultsCompared with the NC group， the DM group exhibited significantly elevated fasting blood glucose （P<0.01）， serum AST， ALT， TC， TG， LDL-C， and HDL-C （P<0.01）. FINS， homeostatic model assessment for insulin resistance （HOMA-IR）， and the inflammatory cytokine TNF-α were significantly increased （P<0.01）， while ADP was significantly decreased （P<0.05）. Histological analysis confirmed severe hepatic steatosis and excessive lipid accumulation in the DM group， along with markedly reduced glycogen synthesis. Compared with the DM group， the GP group showed significantly decreased fasting blood glucose （P<0.01）， reduced serum TC， LDL-C， and HDL-C levels （P<0.05）， significantly decreased serum TG and AST levels （P<0.01）， significantly reduced FINS， HOMA-IR， and TNF-α levels （P<0.01）， and significantly increased ADP （P<0.01）. Hepatic steatosis and lipid deposition were significantly alleviated， while glycogen synthesis was markedly enhanced. Transcriptomic differential and enrichment analyses suggested that the mechanisms by which G. pentaphyllum alcohol extract improved hepatic glucose and lipid metabolism in db/db mice may involve regulation of the AMPK and FoxO signaling pathways. Real-time PCR results confirmed that expression of PGC-1α， PEPCK， G6PC， FoxO1， and FoxO3 was significantly downregulated following treatment with G. pentaphyllum alcohol extract （P<0.05， P<0.01）， whereas mRNA expression of Adipoq， PPARα， GCK， and AMPK was significantly upregulated （P<0.05， P<0.01）. Metagenomic analysis showed that the relative abundance of Lactobacillus， Alistipes， and Akkermansia species was higher in the GP group than in the DM group. ConclusionG. pentaphyllum alcohol extract may improve glucose and lipid metabolism disorders in db/db mice by regulating the hepatic AMPK/PPARα pathway to suppress lipid deposition and alleviate hepatic steatosis， by inhibiting gluconeogenesis through the AMPK/PGC-1α and FoxO pathways to lower fasting blood glucose， and by increasing the abundance of beneficial gut bacteria such as Lactobacillus， Alistipes， and Akkermansia to restore gut microbiota balance.

ObjectiveTo investigate the efficacy and underlying mechanisms of Gynostemma pentaphyllum alcohol extract in improving glucose and lipid metabolism disorders in db/db mice through transcriptomics and gut microbiota analysis. MethodsEighteen db/db mice were randomly assigned to the model（DM） group， metformin（MET） group， and G. pentaphyllum alcohol extract（GP） group， with six mice in each group， based on stratification of fasting blood glucose and body weight. An additional six db/m mice were selected as the normal control（NC） group. Mice in the NC and DM groups were administered deionized water （10 mL·kg^-1） daily. The MET group received metformin （0.195 g·kg^-1） by gavage. The GP group was treated with G. pentaphyllum alcohol extract （3.9 g·kg^-1） by gavage for six weeks. Fasting blood glucose was measured every two weeks. After six weeks of intervention， serum levels of total cholesterol （TC）， triglycerides （TG）， low-density lipoprotein cholesterol （LDL-C）， high-density lipoprotein cholesterol （HDL-C）， aspartate aminotransferase （AST）， alanine aminotransferase （ALT）， creatinine （CREA）， and blood urea nitrogen （BUN） were assessed. Enzyme-linked immunosorbent assay （ELISA） was used to measure insulin （FINS）， adiponectin （ADP）， and tumor necrosis factor-α （TNF-α）. Hematoxylin-eosin （HE） staining was used to observe liver histomorphology， periodic acid-Schiff （PAS） staining was employed to assess hepatic glycogen synthesis， and Oil Red O staining was used to detect hepatic lipid deposition. Liver transcriptomic data were used to identify differentially expressed genes in the liver and conduct enrichment analysis. Real-time PCR was employed to verify the expression levels of adiponectin gene （Adipoq）， peroxisome proliferator-activated receptor gamma coactivator-1α （PGC-1α）， AMP-activated protein kinase （AMPK）， peroxisome proliferator-activated receptor α （PPARα）， glucokinase （GCK）， forkhead box （Fox）O1， FoxO3， phosphoenolpyruvate carboxykinase （PEPCK）， and glucose-6-phosphatase （G6PC）. Metagenomic sequencing was conducted to analyze changes in gut microbiota composition. ResultsCompared with the NC group， the DM group exhibited significantly elevated fasting blood glucose （P<0.01）， serum AST， ALT， TC， TG， LDL-C， and HDL-C （P<0.01）. FINS， homeostatic model assessment for insulin resistance （HOMA-IR）， and the inflammatory cytokine TNF-α were significantly increased （P<0.01）， while ADP was significantly decreased （P<0.05）. Histological analysis confirmed severe hepatic steatosis and excessive lipid accumulation in the DM group， along with markedly reduced glycogen synthesis. Compared with the DM group， the GP group showed significantly decreased fasting blood glucose （P<0.01）， reduced serum TC， LDL-C， and HDL-C levels （P<0.05）， significantly decreased serum TG and AST levels （P<0.01）， significantly reduced FINS， HOMA-IR， and TNF-α levels （P<0.01）， and significantly increased ADP （P<0.01）. Hepatic steatosis and lipid deposition were significantly alleviated， while glycogen synthesis was markedly enhanced. Transcriptomic differential and enrichment analyses suggested that the mechanisms by which G. pentaphyllum alcohol extract improved hepatic glucose and lipid metabolism in db/db mice may involve regulation of the AMPK and FoxO signaling pathways. Real-time PCR results confirmed that expression of PGC-1α， PEPCK， G6PC， FoxO1， and FoxO3 was significantly downregulated following treatment with G. pentaphyllum alcohol extract （P<0.05， P<0.01）， whereas mRNA expression of Adipoq， PPARα， GCK， and AMPK was significantly upregulated （P<0.05， P<0.01）. Metagenomic analysis showed that the relative abundance of Lactobacillus， Alistipes， and Akkermansia species was higher in the GP group than in the DM group. ConclusionG. pentaphyllum alcohol extract may improve glucose and lipid metabolism disorders in db/db mice by regulating the hepatic AMPK/PPARα pathway to suppress lipid deposition and alleviate hepatic steatosis， by inhibiting gluconeogenesis through the AMPK/PGC-1α and FoxO pathways to lower fasting blood glucose， and by increasing the abundance of beneficial gut bacteria such as Lactobacillus， Alistipes， and Akkermansia to restore gut microbiota balance.

[摘 要] 目的：评估放疗作为原位疫苗的联合治疗模式在晚期软组织肉瘤（STS）患者中的有效性和安全性。方法：回顾性分析2020年12月至2024年9月期间在南京大学医学院附属鼓楼医院肿瘤中心接受联合治疗模式的12例晚期STS患者的临床资料。12例患者均接受了联合治疗。放疗主要以大分割为主。靶向治疗：安罗替尼10例、阿帕替尼2例。免疫治疗以PD-1抗体为主。主要研究终点为疾病控制率（DCR），次要研究终点为客观有效率（ORR）及安全性。结果：接受联合治疗的12例STS患者中有0例CR，4例PR，7例SD，1例PD。ORR为33%，DCR为91.7%，其中靶病灶的DCR为100%。12例患者中，9例出现Ⅰ~Ⅱ级不良反应。最常发生的血液学不良反应是贫血（6例）、肝功能检查结果异常（3例）。最常发生的非血液学不良反应是尿蛋白（5例）、高血压（4例）、甲状腺功能异常（3例）、厌食（3例）、恶心呕吐（2例）；仅2例发生Ⅲ级血液毒性，有1例发生Ⅲ级气胸。结论：放疗作为原位疫苗的联合治疗模式在晚期STS患者中展现出较高的DCR，且未出现严重不良反应。该联合治疗模式具有良好的有效性与安全性。

Objective To investigate the changes in eosinophil counts and the activation of microglial cells in the brain tissues of mice at different stages of Angiostrongylus cantonensis infection, and to examine the role of microglia in regulating the progression of angiostrongyliasis and unravel the possible molecular mechanisms. Methods Fifty BALB/c mice were randomly divided into the control group and the 7-d, 14-d, 21-day and 25-d infection groups, of 10 mice in each group. All mice in infection groups were infected with 30 stage III A. cantonensis larvae by gavage, and animals in the control group was given an equal amount of physiological saline. Five mice were collected from each of infection groups on days 7, 14, 21 d and 25 d post-infection, and 5 mice were collected from the control group on the day of oral gavage. The general and focal functional impairment was scored using the Clark scoring method to assess the degree of mouse neurological impairment. Five mice from each of infection groups were sacrificed on days 7, 14, 21 d and 25 d post-infection, and 5 mice from the control group were sacrificed on the day of oral gavage. Mouse brain tissues were sampled, and the pathological changes of brain tissues were dynamically observed using hematoxylin and eosin (HE) staining. Immunofluorescence staining with eosinophilic cationic protein (ECP) and ionized calcium binding adaptor molecule 1 (Iba1) was used to assess the degree of eosinophil infiltration and the counts of microglial cells in mouse brain tissues in each group, and the morphological parameters of microglial cells (skeleton analysis and fractal analysis) were quantified by using Image J software to determine the morphological changes of microglial cells. In addition, the expression of M1 microglia markers Fcγ receptor III (Fcgr3), Fcγ receptor IIb (Fcgr2b) and CD86 antigen (Cd86), M2 microglia markers Arginase 1 (Arg1), macrophage mannose receptor C-type 1 (Mrc1), chitinase-like 3 (Chil3), and phagocytosis genes myeloid cell triggering receptor expressed on myeloid cells 2 (Trem2), CD68 antigen (Cd68), and apolipoprotein E (Apoe) was quantified using real-time quantitative reverse transcription PCR (RT-qPCR) assay in the mouse cerebral cortex of mice post-infection. Results A large number of A. cantonensis larvae were seen on the mouse meninges surface post-infection, and many neuronal nuclei were crumpled and deeply stained, with a large number of bleeding points in the meninges. The median Clark scores of mouse general functional impairment were 0 (interquartile range, 0), 0 (interquartile range, 0.5), 6 (interquartile range, 1.0), 14 (interquartile range, 8.5) points and 20 (interquartile range, 9.0) points in the control group and the 7-d, 14-d, 21-d and 25-d groups, respectively (H = 22.45, P < 0.01), and the median Clark scores of mouse focal functional impairment were 0 (interquartile range, 0), 2 (interquartile range, 2.5), 7 (interquartile range, 3.0), 18 (interquartile range, 5.0) points and 25 (interquartile range, 6.5) points in the control group and the 7-d, 14-d, 21-d and 25-d groups, respectively (H = 22.72, P < 0.01). The mean scores of mice general and focal functional impairment were all higher in the infection groups than in the control group (all P values < 0.05). Immunofluorescence staining showed a significant difference in the eosinophil counts in mouse brain tissues among the five groups (F = 40.05, P < 0.000 1), and the eosinophil counts were significantly higher in mouse brain tissues in the 14-d (3.08 ± 0.78) and 21-d infection groups (5.97 ± 1.37) than in the control group (1.00 ± 0.28) (both P values < 0.05). Semi-quantitative analysis of microglia immunofluorescence showed a significant difference in the counts of microglial cells among the five groups (F = 17.66, P < 0.000 1), and higher Iba1 levels were detected in mouse brain tissues in 14-d (5.75 ± 1.28), 21-d (6.23 ± 1.89) and 25-d infection groups (3.70 ± 1.30) than in the control group (1.00 ± 0.30) (all P values < 0.05). Skeleton and fractal analyses showed that the branch length [(162.04 ± 34.10) μm vs. (395.37 ± 64.11) μm; t = 5.566, P < 0.05] and fractal dimension of microglial cells (1.30 ± 0.01 vs. 1.41 ± 0.03; t = 5.266, P < 0.05) were reduced in mouse brain tissues in the 21-d infection group relative to the control group. In addition, there were significant differences among the 5 groups in terms of M1 and M2 microglia markers Fcgr3 (F = 48.34, P < 0.05), Fcgr2b (F = 55.46, P < 0.05), Cd86 (F = 24.44, P < 0.05), Arg1 (F = 31.18, P < 0.05), Mrc1 (F = 15.42, P < 0.05) and Chil3 (F = 24.41, P < 0.05), as well as phagocytosis markers Trem2 (F = 21.19, P < 0.05), Cd68 (F = 43.95, P < 0.05) and Apoe (F = 7.12, P < 0.05) in mice brain tissues. Conclusions A. cantonensis infections may induce severe pathological injuries in mouse brain tissues that are characterized by massive eosinophil infiltration and persistent activation of microglia cells, thereby resulting in progressive deterioration of neurological functions.

Objective: To explore the relationship of physical exercise behavior with mobile phone addiction and mental health of college students, so as to provide evidence for interventions to improve mobile phone addiction and mental health of college students. Methods: From October 8 to December 20 in 2024, 896 college students from 4 colleges in Beijing were selected using a combination of convenience sampling and stratified random cluster sampling method. Physical Activity Rating Scale (PARS-3), Mobile Phone Addiction Tendency Scale (MPATS), Adolescence Mental Health Diathesis Questionnaire (AMHDQ) and Symptom Checklist 90 (SCL-90) were used. The correlation of mobile phone addiction and mental health on physical exercise behavior of college students were analyzed by multivariable Logistic regression and linear regression. Results: Among the surveyed college students, 504 (56.25%) students had low exercise, 262 (29.24%) had moderate exercise, 130 (14.51%) had high exercise, and 392 (43.75%) had sufficient exercise. The total score of PARS-3 was 18.00 ( 15.00 , 33.00) points. Logistic regression analysis showed that the total score of MPATS ( OR=1.022, 95%CI =1.008-1.036), the total score of SCL-90 ( OR=1.010, 95%CI = 1.005 -1.015), the total AMHDQ score ( OR=0.995, 95%CI =0.992-0.998) were significantly associated with insufficient exercise among college students ( P <0.05). Linear regression analysis showed that the scores of MPATS, AMHDQS and SCL-90 were significantly correlated with physical exercise behavior ( B=-0.20, 0.04, -0.07, P <0.05). Conclusion The physical exercise behavior of college students is related to mobile phone addiction and mental health.

Purpose: The aim of this study was to investigate the feasibility of an intelligent handheld ultrasound (US) device for assisting non-expert general practitioners (GPs) in detecting carotid plaques (CPs) in community populations. Methods: This prospective parallel controlled trial recruited 111 consecutive community residents. All of them underwent examinations by non-expert GPs and specialist doctors using handheld US devices (setting A, setting B, and setting C). The results of setting C with specialist doctors were considered the gold standard. Carotid intima-media thickness (CIMT) and the features of CPs were measured and recorded. The diagnostic performance of GPs in distinguishing CPs was evaluated using a receiver operating characteristic curve. Inter-observer agreement was compared using the intragroup correlation coefficient (ICC). Questionnaires were completed to evaluate clinical benefits. Results: Among the 111 community residents, 80, 96, and 112 CPs were detected in settings A, B, and C, respectively. Setting B exhibited better diagnostic performance than setting A for detecting CPs (area under the curve, 0.856 vs. 0.749; P<0.01). Setting B had better consistency with setting C than setting A in CIMT measurement and the assessment of CPs (ICC, 0.731 to 0.923). Moreover, measurements in setting B required less time than the other two settings (44.59 seconds vs. 108.87 seconds vs. 126.13 seconds, both P<0.01). Conclusion Using an intelligent handheld US device, GPs can perform CP screening and achieve a diagnostic capability comparable to that of specialist doctors.

Metabolites produced as intermediaries or end-products of microbial metabolism provide crucial signals for health and diseases, such as metabolic dysfunction-associated steatotic liver disease (MASLD). These metabolites include products of the bacterial metabolism of dietary substrates, modification of host molecules (such as bile acids [BAs], trimethylamine-N-oxide, and short-chain fatty acids), or products directly derived from bacteria. Recent studies have provided new insights into the association between MASLD and the risk of developing chronic kidney disease (CKD). Furthermore, alterations in microbiota composition and metabolite profiles, notably altered BAs, have been described in studies investigating the association between MASLD and the risk of CKD. This narrative review discusses alterations of specific classes of metabolites, BAs, fructose, vitamin D, and microbiota composition that may be implicated in the link between MASLD and CKD.