Objective To elucidate the mechanisms of interface disruption between the actin filament and membrane of the cell pseudopodium that occurs during the breakage of the pseudopodium.Methods Time-lapse images of the behavior of actin filaments and membranes during the rupture process of cell pseudopodia were captured using the confocal microscopy.A theoretical model of the fracture of a cylindrical interface was developed to analyze the interface damage between the actin filament and the membrane during the breakage of the cell pseudopodium.Molecular dynamics simulations were employed to simulate the breaking process of the cell pseudopodium for comparison with the theoretical results.A finite element model considering the coupling of the tensile and torsional deformation of actin filaments was developed to simulate the torsional deformation of actin filaments under tension,both in the presence and absence of a membrane.Results The theoretical results indicated an exponential relationship between the critical load for the broken interface and crack length.The critical load increased with the interfacial strength.The effect of the fiber diameter on the critical load depended on the crack length,exhibiting different effects for small and large crack lengths.Finite element analysis suggested that the membrane substantially constrained torsional movement when the actin filament was extended.Conclusions This study revealed the breaking process of cell pseudopodia and the mechanical aspects underlying the disruption of the interface between the actin filament and the membrane.These results provide theoretical support for exploring cellular behaviors associated with pseudopodium breakage,such as the release of extracellular vesicles.

Objective:To investigate the efficacy of 99Tc m-pyrophosphate (PYP) SPECT imaging for the differential diagnosis of transthyretin-related cardiac amyloidosis (ATTR-CA) and hypertrophic cardiomyopathy (HCM). Methods:Data of patients who were definitively diagnosed with ATTR-CA (35 patients (28 males, 7 females); age 62.5(58.6, 64.3) years) or HCM (14 patients (13 males, 1 female); age 60.5(57.3, 68.7) years) by extracardiac biopsy and echocardiography in the Second Xiangya Hospital of Central South University between June 2020 and March 2023 were retrospectively analyzed. All patients underwent planar and SPECT imaging 1 h after injection of 370-720 MBq 99Tc m-PYP. Visual scoring was performed (0-1 was negative, 2-3 was positive), and heart-to-contralateral lung uptake ratio (H/CL) was calculated based on planar images. The χ2 test was used to compare the difference in visual scores between ATTR-CA and HCM groups, and the diagnostic efficacy of the visual score was calculated. The H/CL differences between ATTR and HCM groups were compared with Mann-Whitney U test, and the ROC curve was used to analyze the efficacy of H/CL for the differential diagnosis of ATTR-CA and HCM. Results:There were 34 patients with visual scores≥2 and 1 patient with visual score<2 in the ATTR-CA group, 6 patients with visual scores =2 and 8 patients with visual scores <2 in HCM group, and there were significant differences between the 2 groups ( χ2=16.20, P<0.001). The diagnostic sensitivity of the visual score was 97.1%(34/35), and the specificity was 8/14. The H/CL in the ATTR-CA group was significantly higher than that in the HCM group (2.08(1.97, 2.20) vs 1.26 (1.17, 1.35), z=-5.09, P<0.001). The ROC curve analysis suggested that the optimal cut-off value was 1.45 (AUC: 0.980, 95% CI: 0.946-1.000; P<0.001); the sensitivity of H/CL differential diagnosis between HCM and ATTR-CA was 97.1%(34/35), and the specificity was 14/14. Conclusion:99Tc m-PYP SPECT imaging is useful in differentiation of ATTR-CA and HCM, and the optimal cut-off value of H/CL for differential diagnosis of these 2 diseases is 1.45.

Carcinogenesis ; Cell Transformation, Neoplastic ; Hepatoblastoma ; Humans ; Liver ; Liver Neoplasms ; Organoids ; YAP-Signaling Proteins