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This study presents an experimental investigation of the effect of sand particle size on the shear behaviour of bio-cemented sand-steel structure interface, with sand treated by microbially induced calcite precipitation (MICP). Five sand groups were involved with different median particle sizes. The MICP treatment followed the surface percolation method featuring bacterial suspensions with a fixed optical density (linearly related to active cell concentration or urease activity). Scanning electron microscopy was used to identify the microstructure of the samples, while interface shear test was performed to observe the macroscale mechanical behaviour. The testing results indicated that smaller sand particle size was associated with a relatively larger effective calcium carbonate bonding area, providing a more significant bonding effect. Thus, smaller sand particle sizes in the treated samples were associated with higher values for the interface cohesion and a more pronounced increase in the interface friction angle at the peak state (compared to the corresponding untreated samples). By contrast, because the bonding effect broke close to the interface during shearing, the bottom of the treated samples became planar and smooth. Hence, a lower interface friction angle at the ultimate state was identified for a treated sample, compared to the corresponding untreated one. Key words: Bio-cemented sand-structure interface, microbially induced calcite precipitation (MICP), sand particle size, interface shear behaviour, 1. Introduction Microbially induced calcite precipitation (MICP), a novel sustainable treatment approach for weak soils, has developed rapidly over the last two decades. In general, the MICP process entails the [...]

Oxidative stress can lead to nucleus pulposus cell (NPC) apoptosis, which is considered to be one of the main contributors to intervertebral disc degeneration (IVDD). Procyanidin B2 is a natural antioxidant that protects against oxidative stress. However, whether procyanidin B2 protects NPCs from oxidative stress remains unknown. In this study, we demonstrated that procyanidin B2 could reduce tert‐butyl hydroperoxide‐induced reactive oxygen species in rat NPCs and attenuate rat NPC apoptosis. Further experiments revealed that procyanidin B2 upregulated the expression of both nuclear factor erythroid 2‐related factor 2 (Nrf2) and phosphorylation of protein kinase B (Akt). We then used silencing of Nrf2 and LY294002 to silence Nrf2 expression and block the phosphatidylinositol 3‐kinase (PI3K)/Akt pathway, respectively, and found that the protective roles of procyanidin B2 in NPCs were inhibited. Therefore, we demonstrated that procyanidin B2 alleviated rat NPC apoptosis induced by oxidative stress by upregulating Nrf2 via activation of the PI3K/Akt signaling pathway. This study provides a potential therapeutic approach for procyanidin B2 in IVDD, which might help in the development of new drugs for IVDD treatment. [ABSTRACT FROM AUTHOR]

OBJECTIVE To investigate the characteristics of left ventricular layer-specific strain in patients with chronic kidney disease (CKD). METHODS Eighty-five patients of chronic kidney disease in the Department of Nephrology of our hospital from March 2020 to August 2021 were selected and divided into three groups according to the estimated GFR: Group A (CKD stage 1–2), Group B (CKD stage 3–4), and Group C (CKD stage 5), 40 hypertensive patients without renal insufficiency were gathered as hypertension (HT) group and 40 gender and age-matched healthy volunteers were selected as the control group. Then, (i) Routine echocardiographic parameters: left ventricular diameter, left atrium diameter, wall thickness, LVEF. (ii) Myocardial strain: global longitudinal strain (GLS), longitudinal strain in endocardium (SL-endo), longitudinal strain in average (SL-ave), longitudinal strain in epicardium (SL-epi), global circumferential strain (GCS), global circumferential strain in endocardium (SC-endo), global circumferential strain in average (SC-ave), global circumferential strain in epicardium (SC-epi), and global radial strain (GRS) were analyzed. RESULTS (i) Compared with the control group, the structure of the left heart and LVEF in groups A and B had no significant changes, left ventricular remodeling appeared, and diastolic function declined in HT group and group C, LVEF decreased in group C (all P  < 0.05). (ii) Only SL-endo decreased in the HT group. All of SL-endo, SL-ave, and SL-epi were reduced in the CKD group and were lowest in group C. Radial strain decreased only in group C (all P < 0.05). (iii) The global and layer-specific longitudinal strain were correlated with estimated glomerular filtration rate (eGFR) (r  = 0.541–0.559, all P < 0.05), LVEF was correlated with longitudinal and circumferential strain (r  = 0.406–0.424, all P < 0.05). Multiple linear regression analysis showed that longitudinal strain in different layers were independently correlated with different stages of CKD and the occurrence of secondary hypertension or not (β = −0.251 to −0.443, all P < 0.05). Circumferential strain in all layers were independently correlated with the appearance of secondary hypertension or not (β = −0.255 to −0.31, all P < 0.05). CONCLUSIONS The degree and range of the impairment of left ventricular strain in CKD patients are related to the stage of eGFR and secondary hypertension, which may affect the global systolic pump function by involving the circumferential strain. [ABSTRACT FROM AUTHOR]