ObjectiveChronic atrophic gastritis (CAG) is usually diagnosed by gastroscopy and histopathological biopsy. These procedures remain the reference standard, but their invasive nature and resource requirements may limit their use in large-scale population screening and repeated follow-up. A convenient and reproducible method for noninvasive auxiliary screening may help identify individuals who require further endoscopic assessment. Fingertip photoplethysmography (PPG) provides a noninvasive recording of peripheral pulse waves and allows harmonic features to be extracted from the signal. In this study, the so-called meridian-related variables were defined as PPG-derived harmonic parameters labelled according to meridian nomenclature, rather than as direct measurements of meridian physiology. This study aimed to compare these harmonic parameters between patients with CAG and non-CAG controls, identify parameters that remained different after age adjustment, and develop a multivariable model for noninvasive auxiliary screening and pre-endoscopic risk stratification of CAG. MethodsA total of 343 participants were included, comprising 171 patients with CAG and 172 non-CAG controls. CAG diagnosis was established using gastroscopy and histopathology as the reference standard. Fingertip PPG signals were collected using a PPG-based pulse acquisition device. Eight PPG-derived harmonic parameters labelled according to meridian nomenclature were extracted for analysis. Between-group differences were first assessed using nonparametric tests. Age-adjusted analyses were then performed to reduce potential confounding by age. The false discovery rate (FDR) method was applied for multiple-comparison correction. A multivariable logistic regression model integrating age and multiple harmonic parameters was constructed. Model performance was evaluated using receiver operating characteristic (ROC) analysis and the area under the curve (AUC). Internal validation performance was assessed using stratified five-fold cross-validation and bootstrap optimism correction. Threshold performance was examined using both a high-specificity strategy and a Youden index-based cutoff. Decision curve analysis was used to evaluate the model’s net clinical benefit across a range of threshold probabilities. ResultsAll eight harmonic parameters were non-normally distributed. In the univariate analysis, the stomach-labelled harmonic parameter (ST), bladder-labelled harmonic parameter (BL), and liver-labelled harmonic parameter (LR) differed between the CAG and non-CAG groups. After age adjustment and FDR correction, only ST and BL remained statistically significant. Compared with non-CAG controls, patients with CAG showed higher ST values and lower BL values. This finding indicates an associated differential harmonic pattern that was not fully explained by age distribution. However, the discriminative ability of a single harmonic parameter was limited. The best-performing single indicator was ST, with an AUC of 0.652 (95% CI: 0.595-0.707). The multivariable model integrating age and multiple harmonic parameters achieved an AUC of 0.791 (95% CI: 0.743-0.835), representing an improvement of 0.139 over ST alone. In internal validation, stratified five-fold cross-validation yielded a mean AUC of 0.753 (95% CI: 0.715-0.781), and the bootstrap optimism-corrected AUC was 0.748. These results suggest that the model retained moderate discriminative performance after internal validation.At a specificity of at least 95%, the model achieved a sensitivity of only 40.4% (95% CI: 25.7%-49.7%). This high-specificity cutoff may be suboptimal as the preferred threshold for an initial screening setting because of the potential risk of missed CAG cases. The Youden index-based optimal cutoff was 0.419, corresponding to a sensitivity of 80.7% and a specificity of 62.8%. This threshold may better match the practical aim of noninvasive auxiliary screening, where sensitivity is usually prioritized to reduce missed cases. Decision curve analysis showed that, within a threshold probability range of 10%-55%, the model provided higher net clinical benefit than the reference strategies of recommending gastroscopy for all participants or for none. ConclusionPatients with CAG showed associated harmonic differences in fingertip PPG-derived features, mainly characterized by higher ST and lower BL values after age adjustment and FDR correction. Compared with a single harmonic parameter, the multivariable model showed better overall discrimination and retained moderate internal validation performance. These findings suggest that PPG-derived harmonic parameters labelled according to meridian nomenclature may provide auxiliary information for noninvasive auxiliary screening and front-line triage before gastroscopic confirmation in CAG. The present results support further validation rather than immediate clinical implementation. External validation in independent, multicenter, and preferably prospective screening cohorts is needed to assess the model’s generalizability, screening performance, and potential clinical utility.

ObjectiveChronic atrophic gastritis (CAG) is usually diagnosed by gastroscopy and histopathological biopsy. These procedures remain the reference standard, but their invasive nature and resource requirements may limit their use in large-scale population screening and repeated follow-up. A convenient and reproducible method for noninvasive auxiliary screening may help identify individuals who require further endoscopic assessment. Fingertip photoplethysmography (PPG) provides a noninvasive recording of peripheral pulse waves and allows harmonic features to be extracted from the signal. In this study, the so-called meridian-related variables were defined as PPG-derived harmonic parameters labelled according to meridian nomenclature, rather than as direct measurements of meridian physiology. This study aimed to compare these harmonic parameters between patients with CAG and non-CAG controls, identify parameters that remained different after age adjustment, and develop a multivariable model for noninvasive auxiliary screening and pre-endoscopic risk stratification of CAG. MethodsA total of 343 participants were included, comprising 171 patients with CAG and 172 non-CAG controls. CAG diagnosis was established using gastroscopy and histopathology as the reference standard. Fingertip PPG signals were collected using a PPG-based pulse acquisition device. Eight PPG-derived harmonic parameters labelled according to meridian nomenclature were extracted for analysis. Between-group differences were first assessed using nonparametric tests. Age-adjusted analyses were then performed to reduce potential confounding by age. The false discovery rate (FDR) method was applied for multiple-comparison correction. A multivariable logistic regression model integrating age and multiple harmonic parameters was constructed. Model performance was evaluated using receiver operating characteristic (ROC) analysis and the area under the curve (AUC). Internal validation performance was assessed using stratified five-fold cross-validation and bootstrap optimism correction. Threshold performance was examined using both a high-specificity strategy and a Youden index-based cutoff. Decision curve analysis was used to evaluate the model’s net clinical benefit across a range of threshold probabilities. ResultsAll eight harmonic parameters were non-normally distributed. In the univariate analysis, the stomach-labelled harmonic parameter (ST), bladder-labelled harmonic parameter (BL), and liver-labelled harmonic parameter (LR) differed between the CAG and non-CAG groups. After age adjustment and FDR correction, only ST and BL remained statistically significant. Compared with non-CAG controls, patients with CAG showed higher ST values and lower BL values. This finding indicates an associated differential harmonic pattern that was not fully explained by age distribution. However, the discriminative ability of a single harmonic parameter was limited. The best-performing single indicator was ST, with an AUC of 0.652 (95% CI: 0.595-0.707). The multivariable model integrating age and multiple harmonic parameters achieved an AUC of 0.791 (95% CI: 0.743-0.835), representing an improvement of 0.139 over ST alone. In internal validation, stratified five-fold cross-validation yielded a mean AUC of 0.753 (95% CI: 0.715-0.781), and the bootstrap optimism-corrected AUC was 0.748. These results suggest that the model retained moderate discriminative performance after internal validation.At a specificity of at least 95%, the model achieved a sensitivity of only 40.4% (95% CI: 25.7%-49.7%). This high-specificity cutoff may be suboptimal as the preferred threshold for an initial screening setting because of the potential risk of missed CAG cases. The Youden index-based optimal cutoff was 0.419, corresponding to a sensitivity of 80.7% and a specificity of 62.8%. This threshold may better match the practical aim of noninvasive auxiliary screening, where sensitivity is usually prioritized to reduce missed cases. Decision curve analysis showed that, within a threshold probability range of 10%-55%, the model provided higher net clinical benefit than the reference strategies of recommending gastroscopy for all participants or for none. ConclusionPatients with CAG showed associated harmonic differences in fingertip PPG-derived features, mainly characterized by higher ST and lower BL values after age adjustment and FDR correction. Compared with a single harmonic parameter, the multivariable model showed better overall discrimination and retained moderate internal validation performance. These findings suggest that PPG-derived harmonic parameters labelled according to meridian nomenclature may provide auxiliary information for noninvasive auxiliary screening and front-line triage before gastroscopic confirmation in CAG. The present results support further validation rather than immediate clinical implementation. External validation in independent, multicenter, and preferably prospective screening cohorts is needed to assess the model’s generalizability, screening performance, and potential clinical utility.

Objective To gain insights into the biological characteristics of different populations of Culex tritaeniorhynchus within and around the Yellow Sea wetland from the perspective of the occurrence of resistance, we investigated the levels of resistance to deltamethrin and kdr gene mutation in the wetland and its peripheral areas. Methods Specimens were collected from Cx. tritaeniorhynchus populations at two monitoring sites in the Rare Bird National Nature Reserve and Tiaozi Ni Wetland Scenic Area, and also from two populations in Yancheng City and the Liuhe District of Nanjing, and the resistance of these mosquitoes to deltamethrin was determined using the CDC biotest bottle method. For each concentration of deltamethrin assessed, a random subset of exposed specimens was selected for amplification of the kdr gene fragment, followed by Sanger sequencing to identify and analyze resistance-associated mutations. Results The LC50 levels of deltamethrin among mosquitoes from the four populations in Luhe, Yancheng, the Rare Bird National Nature Reserve and the Tiaozi Ni Wetland Scenic Area were 2.048 5, 7.798 2, 3.473 3, and 17.695 5 mg/mL, respectively, with corresponding concentrations of deltamethrin ranging from 0.005 to 5.000,0.050 to 50.000,0.050 to 25.000 and 0.050 to 50.000 mg/mL, respectively. Furthermore, the ranges of the KT50 values were 11.76-107.43, 67.05-216.30,29.77-107.43 and 28.40-329.51 min; the 1-h knockdown rates were 34.58%-99.15%, 9.52%-43.80%, 55.09%-73.01%, and 10.09%-68.07%; and the 24-h mortality rates were 12.15%-67.52%,9.52%-79.56%,13.17%-82.21%, and 11.01%-78.99%, respectively. With respect to kdr gene mutation, we assayed a total of 63,70,59, and 57 mosquitoes for the four populations, for which we detected L1014F mutation frequencies of 14.29%, 35.00%, 20.34%, and 31.58%, respectively, with a majority of these mutations being heterozygous for resistance. In addition, five adult mosquitoes were identified has having synonymous mutations at site 1011[i. e. , AAT(asparagine)mutation to AAC(asparagine)]. Conclusions Our findings revealed the clear resistance of Cx. tritaeniorhynchus to deltamethrin in the Yancheng region of the Yellow Sea wetland, and the resistance phenotype and kdr frequency of Cx. tritaeniorhynchus in the wetland environment were comparable to those of Cx. tritaeniorhynchus in the wetland environment, thereby indicating that the resistance of different populations of Cx. tritaeniorhynchus was homogeneous under the pressure of different insecticide selection within and around the wetland. However, the underlying mechanisms need to be further studied.

Objective: To analyze the trends in the burden of mental disorders attributable to bullying among adolescents aged 10-24 years in China from 1990 to 2023, so as to provide evidence to inform the prevention and control of school bullying and adolescent mental health interventions. Methods: Data were obtained from the Global Burden of Disease Study 2023 database. Disability adjusted life years (DALYs) of mental disorders attributable to bullying among Chinese adolescents aged 10-24 years were selected as the primary indicator. Data from 1990 to 2023 were extracted and stratified by gender and age groups. Joinpoint regression model was used to analyze temporal trends, and the annual percent change (APC) and average annual percent change (AAPC) were calculated. Results: The DALYs of mental disorders attributable to bullying among Chinese adolescents aged 10-24 years decreased from 515 981.6 person years in 1990 to 414 240.5 person years in 2023, reaching the lowest level in 2015 ( 373 292.8 person years). Joinpoint regression analysis showed that the overall AAPC was -0.67% (95% UI =-0.90% to -0.44%, P <0.01), with the overall trend characterized by "decline-stabilization-increase-decline-further decline-increase". Sex stratified analysis showed that DALYs decreased from 305 892.8 to 244 842.8 person years among males and from 210 088.7 to 169 397.7 person years among females between 1990 and 2023. The DALY levels were consistently higher in males than in females, and the AAPCs for both genders were -0.67% (both P <0.01). Age stratified analysis indicated that DALYs in the 10-14 years age group increased from 160 434.7 person years in 1990 to 170 773.2 person years in 2023, with an AAPC of 0.20%. DALYs in the 15-19 years age group decreased from 197 359.5 to 147 494.0 personyears, with an AAPC of -0.91 %; while those in the 20-24 years age group declined from 158 187.3 to 95 973.2 personyears, with an AAPC of -1.50% (all P <0.05). Conclusion From 1990 to 2023, the burden of mental disorders attributable to bullying among Chinese adolescents shows an overall downward trend; however, a recent rebound is observed among younger adolescents, with notable age and sex specific differences.

Objective To compare the differences in dosimetry and treatment efficiency of three radiotherapy plans after left-sided breast-conserving surgery,including modified intensity-modulated radiation therapy(IMRT),cross-field volume-modulated arc therapy(VMAT)or improved VMAT,so as to provide references for clinical practice.Methods Three radiotherapy plans of modified IMRT,cross-field VMAT and improved VMAT were designed for 12 patients after left-sided-breast-conserving surgery.The modified IMRT with five irradiation fields and the improved VMAT with two arcs were modified by not setting cross-fields while determining the start and end angles with the rays passing through the least lung area.The cross-field VMAT had its start and end angles set based on the cross-fields.The doses to the target areas,peripheral organs at risk,heart and its substructures were evaluated,and dose verification was carried out.The three plans were compared in terms of treatment efficiency and gamma pass rate.SPSS 22.0 was used for statistical analysis.Results All the three plans behaved well in dose distribution.In terms of planning gross tumor volume dosimetry dosimetry,the improved VMAT and modified IMRT gained advantages than others in CI and D50,respectively,with the differences being significant(all P<0.05).In terms of planning target volume dosimetry,the modified IMRT had the V107 and D50 lower than those of the others,with the differences being significant(P<0.05).In terms of the protection of peripheral organs at risk,V5 of the left lung,Dmean of the right lung and Dmean of the healthy breast were lower in the modified IMRT plan than in the other 2 plans,with statistically significant differences(P<0.05);V20,V30,V35 and V40 of the left lung were lower in the modified VMAT plan than in the other 2 plans,with statistically significant differences(P<0.05).In terms of protection of heart and its substructures,the left ventricle V20,V30 and Dmean of the improved VMAT plan behaved better than those of other 2 plans,and the difference was statistically significant(all P<0.05).In terms of treatment efficiency,the cross-field VMAT plan had the lowest MU while highest treatment efficiency;the improved VMAT plan had the MU higher while the treatment efficiency lower than the cross-field VMAT plan;the modified IMRT plan had the highest MU while the lowest gamma pass rate,and the differences in the MUs and gamma pass rates among the three plans were statistically significant(P<0.05).Conclusion Under the same standard conditions,the cross-field VMAT and improved VMAT plans show technical advantages.Though the improved VMAT plan has the treatment efficiency lower than the cross-field VMAT,it decreases the possibility of radiocardiac injury in terms of dosimetry and thus can be used for radiotherapy after left-sided breast-conserving surgery.[Chinese Medical Equipment Journal,2025,46(4):45-51]

Aim To investigate the effect of linarin on improving cognitive behavior of APP/PS1 mice,and to explore the therapeutic effect of linarin on A β deposi-tion and neuroinflammation and its correlation.Meth-ods APP/PS1 transgenic mice were randomly divid-ed into the model group,high-dose group,medium-dose group,low-dose group and positive control group.C57BL/6J mice were set as the normal group.Morris water maze was used to evaluate the learning and mem-ory abilities of mice.TUNEL staining was used to de-tect the apoptosis of neurons in the CA1 region of mice.IHC was used to detect the expression levels of Aβ42 and GFAP.Western blot was used to detect the expression levels of BACE1 and PS-1.Results Com-pared with the normal group,mice of the model group showed lower NCP,shorter target quadrant travel,less target quadrant residence time percentage(all P＜0.01),higher apoptosis rate of neurons in the CA1 re-gion(P＜0.01),significantly higher protein expres-sion levels of A β42 and GFAP(all P＜0.01),and significantly higher protein expression levels of BACE1 and PS-1(all P＜0.01).Compared with the model group,the medium-dose group,high-dose group and positive control group showed higher NCP,longer tar-get quadrant travel,more target quadrant residence time percentage(all P＜0.05),lower apoptosis rate of neurons in the CA1 region(P＜0.01),significantly lower protein expression levels of A β42 and GFAP(all P＜0.01),and significantly lower protein expression levels of BACE1 and PS-1(all P＜0.01).Conclu-sions Linarin can inhibit two key enzymes to reduce the decomposition of APP and the generation of A β42,thereby inhibiting the activation of astrocytes,allevia-ting neuroinflammation,improving the core pathologi-cal features of AD,and thus significantly improving learning and memory impairment in APP/PS1 mice.

Objective:To investigate the relationship between 18F-fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography(18F-FDG PET/CT)and tumor markers and the prognosis of patients with differentiated thyroid cancer(DTC)treated with surgery combined with iodine-131,and to construct a nomogram prediction model.Methods:The clinical data of 134 patients with DTC who underwent surgery combined with iodine-131 treatment in our hospital from January 2021 to January 2023 were retrospectively analyzed.According to the prognosis after 1 year of treatment,they were divided into a good prognosis group(n=106)and a poor prognosis group(n=28).The general data,18F-FDG PET/CT related parameters[maximum standardized uptake value(SUVmax),metabolic volume(MTV),total lesion gly-colysis(TLG)]and serum tumor markers[thyroglobulin(Tg),thyroglobulin antibody(TgAb)]levels were compared between the two groups.Pearson correlation coefficient was used to analyze the correlation between the related parameters and the tumor marker levels.Logistic multivariate analysis was used to analyze the influencing factors of DTC prognosis.Re-ceiver operating characteristic curve(ROC)was used to analyze the predictive efficacy of related parameters combined with tumor markers on poor prognosis.Anomogram prediction model for poor prognosis was constructed and the predic-tive efficacy of the model was evaluated.Results:The proportion of stage Ⅲ-Ⅳ,the proportion of total resection and the levels of thyroid stimulating hormone(TSH),SUVmax,MTV,TLG,Tg and TgAb in the poor prognosis group were higher than those in the good prognosis group,and the differences were statistically significant(P<0.05).Pearson correlation co-efficient showed that SUVmax,MTV,TLG and Tg,TgAb levels were positively correlated with tumor markers(P<0.05).Lo-gistic analysis showed that after adjusting for confounding variables,SUVmax,MTV,TLG,Tg and TgAb were independent influencing factors for the poor prognosis of DTC(P<0.05).ROC analysis showed that the combination of SUVmax,MTV,TLG,Tg and TgAb was significantly better than each parameter alone in predicting poor prognosis(P<0.05).The nomo-gram prediction model was constructed.ROC evaluation showed that the model had good prediction performance.K-fold cross validation showed that the model had stable performance and good generalization ability.Conclusion:The 18F-FDG PET/CT related parameters SUVmax,MTV,TLG and tumor markers Tg and TgAb are all independent factors affecting the poor prognosis of DTC patients treated with surgery combined with iodine-131.The prognostic nomogram prediction model based on the above factors has good predictive efficacy and can be used to guide clinical decision-making.

Objective To explore the long-term efficacy of percutaneous pulmonary valve implantation(PPVI)and the durability of the domestic self-expanding Venus P valve.Methods A total of 8 patients with post-surgical right ventricular outflow tract(RVOT)dysfunction,who were admitted to hospital from October 2014 to July 2016 and deemed anatomically suitable for PPVI with self-expanding valve,were included prospectively.Clinical,imaging,procedural and follow-up data were analyzed.The survival rates,perioperative and long-term complication rates,long-term efficacy of PPVI,and long-term function of Venus P in 8 patients were evaluated.The immediate procedural results were evaluated by clinical implant success rate,which is defined as successful valve implantation with echocardiography-assessed pulmonary regurgitation＜moderate and peak trans-pulmonary pressure gradient＜40 mmHg.Results A total of 8 patients were included,with 7 females,aged 14 to 36 years.The initial diagnosis included post-surgical Tetralogy of Fallot(5 cases),post-surgical Trilogy of Fallot(1 case),post-surgical Quadricuspid pulmonary valve stenosis(1 case)and post-surgical Double-Outlet Right Ventricle(1 case).The indications of PPVI included RVOT-pulmonary obstruction and regurgitation(1 case)and isolated regurgitation(7 cases).Clinical implant success was achieved in all of the 8 patients with firmly fixed valve,and there were no such complications as valve detachment,displacement or stent fracture.All patients experienced significant symptom relief after the procedure.The right ventricular end-diastolic volume index(RVEDVi)measured by CMR 6 months after PPVI showed a significant decrease compared to preprocedural values[(89.99±13.85)ml/m2 vs.(144.93±11.28)ml/m2,P=0.001].Postoperative pulmonary regurgitation were significantly improved or disappeared in all patients,and there was no statistically significant difference in the average peak pressure gradient measured by echocardiogram between preoperative and the latest follow-up[(23.25±8.39)mmHg vs.(18.75±6.28)mmHg,P=0.210].Over an average follow-up period of(9.25±0.71)years,1 case of infective endocarditis occurred 5 years after PPVI.During the follow-up,no death,deterioration of heart failure,malignant arrhythmia or other serious complications were observed.All patients completed 8-year follow-up,and 3 completed 10-year follow-up.All patients were graded as NYHA functional class one at the latest follow-up.Conclusions PPVI using the domestically produced self-expanding Venus P is safe and feasible for the treatment of patients with post-surgical RVOT dysfunction and suitable anatomy.Our study confirms the long-term efficacy and durability of Venus P from multiple perspectives,and no severe stent fracture occurred without pre-stent implantation in the native RVOT.

Objective This study investigated feasible cases and their significance in promoting the"generalized"development of inspection through digital-intelligent equipment.Methods A qualitative research approach was used,involving interviews conducted between February 2025 and March 2025 with experts in traditional Chinese medicine diagnostics,clinical research methodology,medical engineering integration,and related disciplines,using both online and offline methods.In accordance with the Consolidated Criteria for Reporting Qualitative Research,feasible cases involving the specific application of digital equipment in various parts of observation were collected through item enrichment.The significance of extending observation capabilities via these cases was analyzed,along with the overall implications of integrating digital technologies with traditional inspection method.Results Interviews were completed with 11 experts from domestic universities and research institutes in the fields of traditional Chinese medicine diagnosis,medical engineering integration,and related disciplines.A total of 78 feasible cases of digital-intelligent inspection were identified,along with 69 insights regarding the significance of enhancing the inspection capabilities.These insights were synthesized into two dimensions and 23 holistic meanings.The first dimension is to expand the scope of inspection,including obtaining internal environmental characteristics,observing external environmental characteristics,expanding thermodynamic characteristic data,and crossing time and space.The second dimension is to improve the quality of observation and diagnosis information collection and analysis,including 19 specific meanings,such as standardized collection environment,objective quantification,and refined observation.Conclusion Digital-intelligent equipment plays a significant role in expanding the scope of inspection content and achieving high-quality acquisition and analysis of extensive inspection information.These advancements extend and enrich the capabilities of traditional inspection method in traditional Chinese medicine.

Objective:To evaluate the clinical efficacy of Tianma Xionglin Zhixuan Tablets in treating hypertension patients with liver yang hyperactivity or comorbid phlegm-stasis syndrome and explore its therapeutic mechanisms through plasma metabolomics.Methods:Thirty-six hypertension patients(4 dropouts)diagnosed with liver yang hyperactivity or phlegm-stasis syndrome were enrolled as the treatment group from June 2022 to September 2023 at the First Affiliated Hospital of Hunan University of Chinese Medicine,while 30 healthy volunteers with balanced constitutions were recruited as the blank group.Plasma samples were collected from patients pre-and post-treatment and from healthy volunteers.Clinical outcomes,including syndrome scores,office blood pressure(BP),and 24-hour ambulatory BP,were recorded.Plasma metabolomic profiling was performed using liquid chromatography-mass spectrometry(LC-MS).Results:Compared with baseline,Tianma Xionglin Zhixuan Tablets significantly reduced traditional Chinese medicine syndrome scores(P＜0.01),office systolic/diastolic BP(P＜0.01),and 24-hour ambulatory BP parameters(24-hour mean BP,daytime/nighttime mean BP;all P＜0.01).Metabolomic analysis identified 45 differential metabolites between the blank group and pretreatment patients,and 64 metabolites altered post-treatment(VIP＞1,P＜0.05).Enrichment analysis of 16 overlapping endogenous metabolites revealed that Tianma Xionglin Zhixuan Tablets primarily modulated arachidonic acid metabolism and sphingolipid metabolism pathways.Conclusion:Tianma Xionglin Zhixuan Tablets demonstrates significant clinical efficacy in hypertension patients with liver yang hyperactivity or phlegm-stasis syndrome,potentially mediated through regulation of arachidonic acid and sphingolipid metabolism.