The functional realization of proteins and other biological macromolecules depends on conformational dynamics and allosteric regulation, and elucidating their molecular mechanisms is an important foundation for understanding life processes. Molecular dynamics simulations are a powerful tool for investigating conformational evolution at the atomic level. However, traditional methods are limited by simulation timescales and high free-energy barriers, making it difficult to effectively capture rare conformations and their transition pathways. As a result, the development of enhanced sampling techniques has become key to overcoming this bottleneck. As a classical enhanced sampling technique, metadynamics suffers from several shortcomings, including strong dependence on collective variables and significant errors caused by bias potential accumulation. This article reviews three major improvement strategies. The first combines stochastic resetting with metadynamics, using trajectory-resetting mechanisms to improve sampling efficiency while avoiding the difficulty of optimizing collective variables. The second, SinkMeta, employs a “sinking” bias effect to enable efficient exploration of specific regions and paths. The third, OPES-based hybrid methods, improve the stability of free-energy estimation by optimizing the target distribution or the way the bias is constructed. These methods provide new ideas for characterizing free-energy landscapes and studying conformational transitions in complex biological systems, while also promoting the continued development of enhanced sampling methodologies.

Objective To develop a hypoxia endurance testing system for aviation physiological training of pilots.Methods The hypoxia endurance testing system comprised a low-oxygen mixed gas generator,a pressurization system for low-oxygen mixed gas and a personal breathing apparatus.The low-oxygen mixed gas generator consisted of a main unit composed of an air compressor,a filter,a buffer tank,polymer membrane,a control module,sensors and regulators,wire cables,supporting hoses,etc.;the pressurization system for low-oxygen mixed gas was made up of a protective box,a cooling fan,a motor and a driver,a control module,a solenoid valve,a convergence block,a pressure gauge,etc.;the personal breating apparatus was composed of a gas cylinder,a pressure reducer,an oxygen supply regulator,etc.Forty-eight subjects were selected for hypoxia exposure tests to verify the effectiveness of the system.Results The system developed had the functions of low-oxygen gas preparation,pressurized filling and hypoxia experiment,and the experimental results indicated the acute hypoxia exposure by the system significantly caused signs and symptoms of hypoxia and weakened physiological functions.Conclusion The system developed gains advantages in high accuracy of gas volume fraction control,safety and remarkable effect of simulated hypoxia,and can be an effective tool for acute high-altitude hypoxia testing and training of pilots.[Chinese Medical Equipment Journal,2025,46(10):23-28]

Objective To develop a hypoxia endurance testing system for aviation physiological training of pilots.Methods The hypoxia endurance testing system comprised a low-oxygen mixed gas generator,a pressurization system for low-oxygen mixed gas and a personal breathing apparatus.The low-oxygen mixed gas generator consisted of a main unit composed of an air compressor,a filter,a buffer tank,polymer membrane,a control module,sensors and regulators,wire cables,supporting hoses,etc.;the pressurization system for low-oxygen mixed gas was made up of a protective box,a cooling fan,a motor and a driver,a control module,a solenoid valve,a convergence block,a pressure gauge,etc.;the personal breating apparatus was composed of a gas cylinder,a pressure reducer,an oxygen supply regulator,etc.Forty-eight subjects were selected for hypoxia exposure tests to verify the effectiveness of the system.Results The system developed had the functions of low-oxygen gas preparation,pressurized filling and hypoxia experiment,and the experimental results indicated the acute hypoxia exposure by the system significantly caused signs and symptoms of hypoxia and weakened physiological functions.Conclusion The system developed gains advantages in high accuracy of gas volume fraction control,safety and remarkable effect of simulated hypoxia,and can be an effective tool for acute high-altitude hypoxia testing and training of pilots.[Chinese Medical Equipment Journal,2025,46(10):23-28]

BACKGROUND: Postoperative pulmonary complications (PPCs) are major adverse events in neurosurgical patients. This study aimed to develop and validate machine learning models predicting PPCs after neurosurgery. METHODS: PPCs were defined according to the European Perioperative Clinical Outcome standards as occurring within 7 postoperative days. Data of cases meeting inclusion/exclusion criteria were extracted from the anesthesia information management system to create three datasets: The development (data of Huashan Hospital, Fudan University from 2018 to 2020), temporal validation (data of Huashan Hospital, Fudan University in 2021) and external validation (data of other three hospitals in 2023) datasets. Machine learning models of six algorithms were trained using either 35 retrievable and plausible features or the 11 features selected by Lasso regression. Temporal validation was conducted for all models and the 11-feature models were also externally validated. Independent risk factors were identified and feature importance in top models was analyzed. RESULTS: PPCs occurred in 712 of 7533 (9.5%), 258 of 2824 (9.1%), and 207 of 2300 (9.0%) patients in the development, temporal validation and external validation datasets, respectively. During cross-validation training, all models except Bayes demonstrated good discrimination with an area under the receiver operating characteristic curve (AUC) of 0.840. In temporal validation of full-feature models, deep neural network (DNN) performed the best with an AUC of 0.835 (95% confidence interval [CI]: 0.805-0.858) and a Brier score of 0.069, followed by Logistic regression (LR), random forest and XGBoost. The 11-feature models performed comparable to full-feature models with very close but statistically significantly lower AUCs, with the top models of DNN and LR in temporal and external validations. An 11-feature nomogram was drawn based on the LR algorithm and it outperformed the minimally modified Assess respiratory RIsk in Surgical patients in CATalonia (ARISCAT) and Laparoscopic Surgery Video Educational Guidelines (LAS VEGAS) scores with a higher AUC (LR: 0.824, ARISCAT: 0.672, LAS: 0.663). Independent risk factors based on multivariate LR mostly overlapped with Lasso-selected features, but lacked consistency with the important features using the Shapley additive explanation (SHAP) method of the LR model. CONCLUSIONS: The developed models, especially the DNN model and the nomogram, had good discrimination and calibration, and could be used for predicting PPCs in neurosurgical patients. The establishment of machine learning models and the ascertainment of risk factors might assist clinical decision support for improving surgical outcomes. TRIAL REGISTRATION ChiCTR 2100047474; https://www.chictr.org.cn/showproj.html?proj=128279 .
Adult ; Aged ; Female ; Humans ; Male ; Middle Aged ; Algorithms ; Lung Diseases/etiology* ; Machine Learning ; Neurosurgical Procedures/adverse effects* ; Postoperative Complications/diagnosis* ; Risk Factors ; ROC Curve

Objective To construct an aptamer-functionalized carboxylated graphene oxide(CGO)fluo-rescent sensor to achieve highly sensitive and specific detection of ketamine(KET)and its metabolite norketamine(NK)using an aptamer capable of simultaneously recognizing KET and NK.Methods A specific aptamer for simultaneous recognition of KET and NK was screened using graphene oxide-sys-tematic evolution of ligand by exponential enrichment(GO-SELEX)and molecular docking tech-niques.The aptamer,labeled with Cy5 fluorescence,was chemically conjugated to CGO to construct an aptamer-functionalized CGO fluorescent sensor.By optimizing detection conditions,including the mass concentration of CGO,aptamer concentration,reaction temperature,and incubation time,quantita-tive analysis of the target analytes was achieved using the ratio of fluorescence intensity changes be-fore and after target addition.The stability of the sensor in biological matrices was evaluated by moni-toring fluorescence intensity changes over incubation time in blank blood and urine,in comparison with the traditional physical adsorption-based CGO fluorescent sensor.Spiked recovery experiments in blank blood and urine were conducted to compare performance with that of HPLC-MS/MS.Results A specific aptamer A5 was selected and chemically conjugated with CGO to construct the aptamer-functionalized CGO fluorescent sensor.Under optimized conditions,the proposed fluorescent sensor ex-hibited a linear detection range of 1.0-5.0 ng/mL for KET,with a limit of detection(LOD)of 0.86 ng/mL;while for NK,the linear detection range was 1.0-5.0 ng/mL,with an LOD of 0.70 ng/mL.Com-pared with the CGO fluorescent sensor constructed via physical adsorption,this sensor demonstrated greater stability in blood and urine.The spiked recovery rates of KET and NK in blank blood and urine ranged from 81.50%to 110.03%,exhibiting detection performance comparable to that of HPLC-MS/MS.Conclusion The aptamer screening method offers a novel approach for selecting aptamers tar-geting drugs and their metabolites.The constructed aptamer-functionalized CGO fluorescent sensor pro-vides an efficient and reliable strategy for the high-performance detection of KET and NK.

BACKGROUND: Non-invasive computed tomography angiography (CTA)-based fractional flow reserve (CT-FFR) could become a gatekeeper to invasive coronary angiography. Deep learning (DL)-based CT-FFR has shown promise when compared to invasive FFR. To evaluate the performance of a DL-based CT-FFR technique, DeepVessel FFR (DVFFR). METHODS: This retrospective study was designed for iScheMia Assessment based on a Retrospective, single-center Trial of CT-FFR (SMART). Patients suspected of stable coronary artery disease (CAD) and undergoing both CTA and invasive FFR examinations were consecutively selected from the Beijing Anzhen Hospital between January 1, 2016 to December 30, 2018. FFR obtained during invasive coronary angiography was used as the reference standard. DVFFR was calculated blindly using a DL-based CT-FFR approach that utilized the complete tree structure of the coronary arteries. RESULTS: Three hundred and thirty nine patients (60.5 ±10.0 years and 209 men) and 414 vessels with direct invasive FFR were included in the analysis. At per-vessel level, sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of DVFFR were 94.7%, 88.6%, 90.8%, 82.7%, and 96.7%, respectively. The area under the receiver operating characteristics curve (AUC) was 0.95 for DVFFR and 0.56 for CTA-based assessment with a significant difference (P < 0.0001). At patient level, sensitivity, specificity, accuracy, PPV and NPV of DVFFR were 93.8%, 88.0%, 90.3%, 83.0%, and 95.8%, respectively. The computation for DVFFR was fast with the average time of 22.5 ± 1.9 s. CONCLUSIONS The results demonstrate that DVFFR was able to evaluate lesion hemodynamic significance accurately and effectively with improved diagnostic performance over CTA alone. Coronary artery disease (CAD) is a critical disease in which coronary artery luminal narrowing may result in myocardial ischemia. Early and effective assessment of myocardial ischemia is essential for optimal treatment planning so as to improve the quality of life and reduce medical costs.

AIM To investigate the effects of Yunpi Tongchang Formula on intestinal mucosal barrier damage in rats with opioid-induced constipation(OIC)of Spleen-Kidney Yang Deficiency Syndrome.METHODS In contrast to the 10 rats of the blank group,the 50 rats of the modeling group were induced into models of OIC of Spleen-Kidney Yang Deficiency Pattern by 7 days consecutive administration of both subcutaneous loperamide injection and alternating gavage of activated carbon ice water and vinegar.Following successful modeling,rats were randomly allocated into the model group,the mosapride citrate tablet group(1.35 mg/kg),and the high-dose,medium-dose,and low-dose Yunpi Tongchang Formula groups(15.12,7.56,3.78 g/kg),with 8 mice in each group.Upon the completion of the 14 days treatment,the rats had their TCM Syndrome scores assessed;their fecal water content,initial black stool excretion time,and small intestine propulsion rate measured;their colon tissue morphology observed by HE staining;their serum levels of IL-6,TNF-α,and IL-1β detected by ELISA;their expressions of occludin and zonula occludens-1(ZO-1)in colon tissues detected by immunohistochemistry;their mRNA expressions of MyD88,TLR4 and NF-κB p65 in the colon tissues detected by RT-qPCR;and their protein expressions of MyD88,TLR4 and NF-κB p65 in the colon tissues detected by Western blot.RESULTS Compared to the blank group,the model group had higher TCM Syndrome scores(P＜0.01);lower fecal water content and small intestine propulsion rate(P＜0.05,P＜0.01);longer initial black stool excretion time(P＜0.01);more mucosal edema in colon tissue,obvious inflammatory infiltration,and glandular disorder;increased serum levels of IL-6,TNF-α and IL-1 β(P＜0.05);decreased colon expressions of ZO-1 and occludin(P＜0.01);and increased mRNA and protein expressions of TLR4,MyD88 and NF-κB p65(P＜0.01).Compared to the model group,both the medium-dose Yunpi Tongchang Formula group and the mosapride citrate tablet group demonstrated effectively reduced TCM syndrome scores(P＜0.01);increased fecal water content and small intestine propulsion rate(P＜0.05,P＜0.01);and shorter initial black stool excretion time(P＜0.01);improved colon mucosal edema and inflammatory infiltration;decreased serum levels of IL-6,TNF-α and IL-1β(P＜0.01);upregulated protein expressions of ZO-1 and occludin(P＜0.01);and downregulated mRNA and protein expressions of TLR4,MyD88 and NF-κB p65(P＜0.05,P＜0.01).CONCLUSION Yunpi Tongchang Formula significantly ameliorates constipation symptoms in OIC rat models of Spleen-Kidney Yang Deficiency Syndrome because of its efficacy in attenuating intestinal inflammation and preserving the integrity of intestinal epithelial barrier structure,with its mechanistic action in downregulating TLR4/MyD88/NF-κB signaling pathway activation.

AIM To investigate the effects of Yunpi Tongchang Formula on intestinal mucosal barrier damage in rats with opioid-induced constipation(OIC)of Spleen-Kidney Yang Deficiency Syndrome.METHODS In contrast to the 10 rats of the blank group,the 50 rats of the modeling group were induced into models of OIC of Spleen-Kidney Yang Deficiency Pattern by 7 days consecutive administration of both subcutaneous loperamide injection and alternating gavage of activated carbon ice water and vinegar.Following successful modeling,rats were randomly allocated into the model group,the mosapride citrate tablet group(1.35 mg/kg),and the high-dose,medium-dose,and low-dose Yunpi Tongchang Formula groups(15.12,7.56,3.78 g/kg),with 8 mice in each group.Upon the completion of the 14 days treatment,the rats had their TCM Syndrome scores assessed;their fecal water content,initial black stool excretion time,and small intestine propulsion rate measured;their colon tissue morphology observed by HE staining;their serum levels of IL-6,TNF-α,and IL-1β detected by ELISA;their expressions of occludin and zonula occludens-1(ZO-1)in colon tissues detected by immunohistochemistry;their mRNA expressions of MyD88,TLR4 and NF-κB p65 in the colon tissues detected by RT-qPCR;and their protein expressions of MyD88,TLR4 and NF-κB p65 in the colon tissues detected by Western blot.RESULTS Compared to the blank group,the model group had higher TCM Syndrome scores(P＜0.01);lower fecal water content and small intestine propulsion rate(P＜0.05,P＜0.01);longer initial black stool excretion time(P＜0.01);more mucosal edema in colon tissue,obvious inflammatory infiltration,and glandular disorder;increased serum levels of IL-6,TNF-α and IL-1 β(P＜0.05);decreased colon expressions of ZO-1 and occludin(P＜0.01);and increased mRNA and protein expressions of TLR4,MyD88 and NF-κB p65(P＜0.01).Compared to the model group,both the medium-dose Yunpi Tongchang Formula group and the mosapride citrate tablet group demonstrated effectively reduced TCM syndrome scores(P＜0.01);increased fecal water content and small intestine propulsion rate(P＜0.05,P＜0.01);and shorter initial black stool excretion time(P＜0.01);improved colon mucosal edema and inflammatory infiltration;decreased serum levels of IL-6,TNF-α and IL-1β(P＜0.01);upregulated protein expressions of ZO-1 and occludin(P＜0.01);and downregulated mRNA and protein expressions of TLR4,MyD88 and NF-κB p65(P＜0.05,P＜0.01).CONCLUSION Yunpi Tongchang Formula significantly ameliorates constipation symptoms in OIC rat models of Spleen-Kidney Yang Deficiency Syndrome because of its efficacy in attenuating intestinal inflammation and preserving the integrity of intestinal epithelial barrier structure,with its mechanistic action in downregulating TLR4/MyD88/NF-κB signaling pathway activation.

Through molecular identification of the ITS2 gene of Aedes albopictus in Hainan Island,we analyzed the genetic diversity,haplotype characteristics,and phylogenetic relationships,to characterize the genetic structure of the local Aedes al-bopictus population.Aedes albopictus samples were collected from 18 administrative cities and counties in Hainan Island.Ge-nomic DNA was extracted,and the 1TS2 gene was amplified.The base composition was analyzed in MEGA 11 software.The genetic distances were calculated,and the phylogenetic relationships were constructed.DnaSP6 and Pop Art 1.7 software were used to calculate the number of haplotypes,draw a haplotype topology network diagram,and analyze haplotype diversity.A to-tal of 360 ITS2 genes were obtained from Aedes albopictus in 18 cities and counties in Hainan Island,with sequence lengths ranging from 536 to 586 bp;GC content ranging from 51.29％to 55.31％;average intraspecies genetic distances ranging from 0.015 4;a total of 251 haplotypes and a haplotype diversity index of 0.987 0,indicating rich genetic diversity and intricate kin-ship relationships,the phylogenetic relationship between Aedes albopictus in Hainan Island and in Honduras was the closest.The existence of extensive gene exchange and rich genetic diversity within the Aedes albopictus population in Hainan Island provided sufficient genetic resources for the evolution and adaptation of the population.

Through molecular identification of the ITS2 gene of Aedes albopictus in Hainan Island,we analyzed the genetic diversity,haplotype characteristics,and phylogenetic relationships,to characterize the genetic structure of the local Aedes al-bopictus population.Aedes albopictus samples were collected from 18 administrative cities and counties in Hainan Island.Ge-nomic DNA was extracted,and the 1TS2 gene was amplified.The base composition was analyzed in MEGA 11 software.The genetic distances were calculated,and the phylogenetic relationships were constructed.DnaSP6 and Pop Art 1.7 software were used to calculate the number of haplotypes,draw a haplotype topology network diagram,and analyze haplotype diversity.A to-tal of 360 ITS2 genes were obtained from Aedes albopictus in 18 cities and counties in Hainan Island,with sequence lengths ranging from 536 to 586 bp;GC content ranging from 51.29％to 55.31％;average intraspecies genetic distances ranging from 0.015 4;a total of 251 haplotypes and a haplotype diversity index of 0.987 0,indicating rich genetic diversity and intricate kin-ship relationships,the phylogenetic relationship between Aedes albopictus in Hainan Island and in Honduras was the closest.The existence of extensive gene exchange and rich genetic diversity within the Aedes albopictus population in Hainan Island provided sufficient genetic resources for the evolution and adaptation of the population.