Myosin turnover controls actomyosin contractile instability.

Actomyosin contractile force produced by myosin II molecules that bind and pull actin filaments is harnessed for diverse functions, from cell division by the cytokinetic contractile ring to morphogenesis driven by supracellular actomyosin networks during development. However, actomyosin contractility is intrinsically unstable to self-reinforcing spatial variations that may destroy the actomyosin architecture if unopposed. How cells control this threat is not established, and while large myosin fluctuations and punctateness are widely reported, the full course of the instability in cells has not been observed. Here, we observed the instability run its full course in isolated cytokinetic contractile rings in cell ghosts where component turnover processes are absent. Unprotected by turnover, myosin II merged hierarchically into aggregates with increasing amounts of myosin and increasing separation, up to a maximum separation. Molecularly explicit simulations reproduced the hierarchical aggregation which precipitated tension loss and ring fracture and identified the maximum separation as the length of actin filaments mediating mechanical communication between aggregates. In the final simulated dead-end state, aggregates were morphologically quiescent, including asters with polarity-sorted actin, similar to the dead-end state observed in actomyosin systems in vitro. Our results suggest the myosin II turnover time controls actomyosin contractile instability in normal cells, long enough for aggregation to build robust aggregates but sufficiently short to intercept catastrophic hierarchical aggregation and fracture.

A temporally relaxed theory of physically or chemically non-equilibrium solute transport in heterogeneous porous media.

Groundwater constitutes a critical component in providing fresh water for various human endeavors. Never-theless, its susceptibility to contamination by pollutants represents a significant challenge. A comprehensive understanding of the dynamics of solute transport in groundwater and soils is essential for predicting the spatial and temporal distribution of these contaminants. Presently, conventional models such as the mobile-immobile (MIM) model and the rate-limited sorption (RLS) model are widely employed to describe the non-Fickian behavior of solute transport. In this research, we present a novel approach to solute transport that is founded on the temporally relaxed theory of Fick's Law. Our methodology introduces two relaxation times to account for solute particle collisions and attachment, leading to the derivation of a new advection-dispersion equation. Our findings indicate that the relaxation times possess similar properties to the transport parameters in the MIM and RLS models, and our solution can be applied to accurately predict transport parameters from soil column experiments. Additionally, we discovered that the relaxation times are proportional to the magnitude of Peclet number. This innovative approach provides a deeper insight into solute transport and its impact on groundwater contamination.

Analytical solutions for contaminant fate and transport in parallel plate fracture-rock matrix systems with poiseuille flow.

Modeling contaminant transport in fractured-rock matrix systems often approximates the effect of the parabolic flow field in the fractures (i.e., Poiseuille flow) on transport by adding a dispersion term to the uniform flow field. In this study, an analytical solution is derived to model contaminant transport in a parallel-plate fractured-rock matrix that explicitly simulates Poiseuille flow in the fractures, eliminating the need for the dispersion approximation. In addition to simulating Poiseuille flow in the fracture, the contaminant transport model developed here includes: (1) two-dimensional contaminant diffusion in the fractures and matrix, (2) first-order decay in the aqueous phase, and (3) rate-limited sorption onto matrix solids. It should be noted, however, that this model, much like the commonly employed Taylor dispersion approximation, neglects macro dispersion, thereby limiting the model's applicability to systems having wide fracture apertures with extremely high flow velocities (P e > 104). Model equations are analytically solved in the Laplace domain and numerically inverted. In addition, analytical expressions for the zeroth, first, and second spatial moments of the concentration profiles along the fractures are derived for both the new Poiseuille flow model as well as a model that approximates the effect of Poiseuille flow on transport by using a dispersion term. The first and second moment expressions are used to quantify how well the dispersion term approximates the effect of Poiseuille flow. Simulations confirm that the dispersion approximation will be adequate for natural fractures at long times. However, if a modeler is concerned with short-time transport behavior or transport behavior in systems with relatively wide-aperture fractures and high groundwater velocities where macro dispersion can be ignored, such as may be found at engineered geothermal systems and carbon capture and storage sites, there may be significant differences between model simulations that explicitly incorporate Poiseuille flow and those that approximate Poiseuille flow with a dispersion term. The model presented here allows the modeler to analytically quantify these differences, which, depending on the modeling objective, may cause the dispersion approximation to be inadequate. Simulations were also run to examine the effect of adsorption rate on remediation of fractured-rock matrix systems. It was shown that moderate adsorption rate constants could lead to very long remediation times, if remediation success is quantified by achieving low concentrations within the fracture.

Analytical Model for Volatile Organic Compound Transport in the Coupled Vadose Zone-Groundwater System.

A 3D mathematical model that describes transport of volatile organic compounds in a coupled vadose-saturated zone system is proposed. The subsurface processes incorporated in the model include advection, dispersion, interphase mass transfer, and diffusive mass exchange between two horizontal porous media formations, as well as the time-dependent mass loading from a source zone. The analytical solutions are derived subject to the specific initial and boundary conditions. The solutions are evaluated by numerical Laplace inverse transform. The model solutions can be used to study the fate and transport in subsurface formations composed of a vadose zone and a water table aquifer, where the volatile organic compound is released from entrapped nonaqueous phase liquid in the vadose zone, or the dissolved volatile organic compound transports with groundwater accompanied by diffusive mass transfer into the overlying soil formations. Mass transfer between two layers is demonstrated to have back-diffusion characteristics, which results in secondary contamination and retains low levels of contaminant concentrations over a prolonged period of time. The model solutions are specifically useful in assessing the vapor intrusion process in a contaminated site where a vadose zone is underlain by a water table aquifer contaminated with volatile organic compounds.

Strategies for Managing Risk due to Back Diffusion.

Back diffusion of contaminants from secondary sources may hamper site remediation if it is not properly addressed in the remedial design. A review of all reported technologies and strategies that have been or could be applied to address plume persistence due to back diffusion as published in the peer-reviewed literature is provided. We classify these into four major categories. The first category consists of those approaches that do not include active measures to specifically address contamination in the low permeable zones (LPZs) and can therefore be considered passive LPZ management approaches. A disadvantage of these approaches is the long duration that may be required to meet acceptable endpoints; however, this allows degradation to potentially play a significant part even at modest rates. The remaining three categories all use approaches to specifically address contaminants in the LPZ. The second category consists of strategies that promote contaminant destruction through the forward diffusion of amendments into the LPZ. A variety of laboratory tests indicate concentration or flux reductions range from no improvement, to reductions as high as four orders-of-magnitude depending on the evaluation metric. The third category consists of strategies that alter physical characteristics of the secondary source, and includes viscosity modification, fracturing, and soil mixing. Each of these offer unique advantages and are often used to deliver one or more amendments for contaminant treatment. The final category consists of thermal and electrokinetic remediation, both less susceptible to permeability contrast limitations. However, they are not routinely used for secondary-source treatment.

A study of dry eye after cataract surgery in MGD patients.

OBJECTIVE: To investigate the dry eye symptoms after cataract surgery in MGD patients and their relationships METHODS: The study included 115 patients (115 eyes) with age-related cataract that underwent uncomplicated cataract surgery, and the patients were divided into two groups according to the MGD diagnostic criteria: group A (MGD group) and group B (control group). Schirmer I test (ST-I), tear breakup time (TBUT), and corneal fluorescein staining (CFS) were performed preoperatively and at 3 days, 7 days, 14 days, and 30 days postoperatively. We also measured eyelid meibomian gland morphology, meibomian gland expression, and meibum character scores before and after the cataract surgery. RESULTS: Postoperatively, in group A, TBUT decreased and CFS scores increased significantly. ST-I increased in the early postoperative course but decreased later. The eyelid margin morphology scores and meibomian gland expression scores of group A significantly increased after the cataract operation. Thus, patients with MGD may have a greater chance of developing the dry eye disease after cataract surgery. Cataract surgery may aggravate the signs of MGD, and the severity of MGD may positively correlate with TBUT, CFS, and corneal lesions after surgery. CONCLUSIONS: The characteristics of dry eye after cataract surgery in patients with MGD are different from common cataract patients, changes in the early postoperative phase to the ocular surface were caused by surgical factors, and the damages to epithelial function in the later postoperative phase were mainly associated with the inflammation of the meibomian gland and eyelid.

Integrated analysis of a competing endogenous RNA network reveals key long noncoding RNAs as potential prognostic biomarkers for hepatocellular carcinoma.

Growing evidence has revealed that long noncoding RNAs (lncRNAs) have an important impact on tumorigenesis and tumor progression via a mechanism involving competing endogenous RNAs (ceRNAs). However, their use in predicting the survival of a patient with hepatocellular carcinoma (HCC) remains unclear. The aim of this study was to develop a novel lncRNA expression-based risk score system to accurately predict the survival of patients with HCC. In our study, using expression profiles downloaded from The Cancer Genome Atlas database, the differentially expressed messenger RNAs (mRNAs), lncRNAs, and microRNAs (miRNAs) were explored in patients with HCC and normal liver tissues, and then a ceRNA network constructed. A risk score system was established between lncRNA expression of the ceRNA network and overall survival (OS) or recurrence-free survival (RFS); it was further analyzed for associations with the clinical features of patients with HCC. In HCC, 473 differentially expressed lncRNAs, 63 differentially expressed miRNAs, and 1417 differentially expressed mRNAs were detected. The ceRNA network comprised 41 lncRNA nodes, 12 miRNA nodes, 24 mRNA nodes, and 172 edges. The lncRNA expression-based risk score system for OS was constructed based on six lncRNAs (MYLK-AS1, AL359878.1, PART1, TSPEAR-AS1, C10orf91, and LINC00501), while the risk score system for RFS was based on four lncRNAs (WARS2-IT1, AL359878.1, AL357060.1, and PART1). Univariate and multivariate Cox analyses showed the risk score systems for OS or RFS were significant independent factors adjusted for clinical factors. Receiver operating characteristic curve analysis showed the area under the curve for the risk score system was 0.704 for OS, and 0.71 for RFS. Our result revealed a lncRNA expression-based risk score system for OS or RFS can effectively predict the survival of patients with HCC and aid in good clinical decision-making.

Let-7e inhibits TNF-α expression by targeting the methyl transferase EZH2 in DENV2-infected THP-1 cells.

Tumor necrosis factor α (TNFα), an important inflammatory cytokine, is associated with dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), a severe pathological manifestation of dengue virus (DENV) infection. However, the regulatory mechanism of microRNA on TNFα is currently unknown. Our study showed that the TNFα expression increased immediately and then later decreased, while a marked increase for the miRNA let-7e was detected in dengue virus type 2 (DENV2)-infected peripheral blood mononuclear cells (PBMCs). From this study, we found that let-7e was able to inhibit TNFα expression, but bioinformatics analysis showed that the enhancer of zeste homolog 2 (EZH2) was the potential direct target of let-7e instead of TNFα. EZH2 methyl transferase can produce H3K27me3 and has a negative regulatory role. Using a dual-luciferase reporter assay and Western blotting, we confirmed that EZH2 was a direct target of let-7e and found that siEZH2 could inhibit TNFα expression. In the further study of the regulatory mechanism of EZH2 on TNFα expression, we showed that siEZH2 promoted EZH1 and H3K4me3 expression and inhibited H3K27me3 expression. More importantly, we revealed that siEZH2 down-regulated NF-κB p65 within the nucleus. These findings indicate that the let-7e/EZH2/H3K27me3/NF-κB p65 pathway is a novel regulatory axis of TNFα expression. In addition, we determined the protein differences between siEZH2 and siEZH2-NC by iTRAQ and found a number of proteins that might be associated with TNFα.

The multidisciplinary treatment of osteosarcoma of the proximal tibia: a retrospective study.

BACKGROUND: Survival and reconstruction constitute important challenges in multimodal treatment of osteosarcoma of the proximal tibia. The purpose of this study was to assess the efficacy and prognosis of neoadjuvant chemotherapy and custom-designed endoprosthetic arthroplasty. METHODS: A total of 69 patients with osteosarcoma of the proximal tibia were evaluated, including 43 males and 26 females, treated with multidisciplinary limb-salvage remedy from October 2003 to December 2013. They were at least 12 years old (mean, 20 years; range, 12-57 years). The gap between tumor and main artery/nerve was showed in MRI. Mean follow up was 69.5 months (range, 9-144 months). Kaplan-Meier survival curves were generated to assess prognosis and relapse rate. The initial symptoms and disease duration for each patient were recorded. Correlation analyses were performed for the association of various parameters with prognosis. Functional outcomes were evaluated using the Musculoskeletal Tumor Society (MSTS) guidelines after 6 months postoperatively, to analyze the relation between bone excision size and function recovery. RESULTS: The resection lengths measured intraoperatively ranged from 80 to 230 mm, and contained 3 cm of normal bone around the tumor. A total of 3 courses of preoperative chemotherapy were administered to all cases. At final follow-up, 1 case showed recurrence. Meanwhile, 8 patients (11.6%) died from lung metastasis. Post-operative infection occurred in 3 patients; 1 case was maintained with revision surgery. Two cases underwent amputation. The mean MSTS system score was 21.6. CONCLUSIONS: The multidisciplinary treatment result in an overall positive outcome, with improved function.

Analytical solutions for a soil vapor extraction model that incorporates gas phase dispersion and molecular diffusion.

To greatly simplify their solution, the equations describing radial advective/dispersive transport to an extraction well in a porous medium typically neglect molecular diffusion. While this simplification is appropriate to simulate transport in the saturated zone, it can result in significant errors when modeling gas phase transport in the vadose zone, as might be applied when simulating a soil vapor extraction (SVE) system to remediate vadose zone contamination. A new analytical solution for the equations describing radial gas phase transport of a sorbing contaminant to an extraction well is presented. The equations model advection, dispersion (including both mechanical dispersion and molecular diffusion), and rate-limited mass transfer of dissolved, separate phase, and sorbed contaminants into the gas phase. The model equations are analytically solved by using the Laplace transform with respect to time. The solutions are represented by confluent hypergeometric functions in the Laplace domain. The Laplace domain solutions are then evaluated using a numerical Laplace inversion algorithm. The solutions can be used to simulate the spatial distribution and the temporal evolution of contaminant concentrations during operation of a soil vapor extraction well. Results of model simulations show that the effect of gas phase molecular diffusion upon concentrations at the extraction well is relatively small, although the effect upon the distribution of concentrations in space is significant. This study provides a tool that can be useful in designing SVE remediation strategies, as well as verifying numerical models used to simulate SVE system performance.

XAF1 contributes to dengue virus-induced apoptosis in vascular endothelial cells.

The mechanism of vascular leakage in severe dengue infection remains unclear. Here, we used primary human umbilical vein endothelial cells (HUVECs) and the EA.hy926 cell line to study the molecular events that occur after dengue virus serotype 2 (DENV2) infection. DENV2-induced apoptosis was confirmed using nuclear staining, TUNEL assay, and electron microscopy. A genome-wide transcriptome analysis was performed using a microarray of DENV2-infected HUVECs. Notably, interferon-inducible genes were differentially expressed after DENV2 infection. Prominent among these genes was the X chromosome-linked inhibitor of apoptosis protein (XIAP)-associated factor 1 (XAF1; up-regulated 1.2-fold in the microarray analysis and ∼8-fold by qRT-PCR after DENV2 infection). XAF1 protein levels were up-regulated after DENV2 infection in both HUVECs and EA.hy926 cells. Evidence indicated interaction between XAF1 and XIAP during DENV2 infection based on their cellular localization, as observed by confocal microscopy and the coimmunoprecipitation of XIAP with an anti-XAF1 antibody. Next, recombinant EA.hy926 cell lines in which XAF1 was either knocked down or overexpressed were constructed. The expression levels of the apoptosis-related genes caspase 3, caspase 8, caspase 9, and poly-(ADP-ribose) polymerase (PARP) were down-regulated in the XAF1 knockdown (24-48 h postinfection) but were up-regulated in XAF1 overexpressing cells (36 h postinfection). This is the first study of the role of XAF1 in promoting apoptosis in vascular endothelial cells after DENV2 infection.

Coordinated regulation of autophagy and apoptosis determines endothelial cell fate during Dengue virus type 2 infection.

Dengue is the most prevalent mosquito-borne viral disease in tropical regions. Severe cases may progress to Dengue hemorrhagic fever, suggesting vascular endothelial dysfunction in disease pathogenesis. In our previous study, we found that Dengue virus type 2 (DENV2) induced apoptosis of vascular endothelial cells via FasL/Fas- and XIAP-associated factor 1 (XAF1)-dependent pathways. In this paper, we demonstrate that DENV2 can induce autophagy in primary human umbilical vein endothelial cells (HUVECs) and the human umbilical vein endothelial cell line EA.hy926. Inhibition of autophagy with 3-methyl adenine promoted apoptosis, while inhibition of apoptosis with Z-VAD-FMK facilitated autophagy in DENV2-infected HUVECs and EA.hy926 cells. Interferon-alpha-inducible protein 6 (IFI6), a putative apoptosis regulator, inhibited DENV2-induced autophagy in EA.hy926 cells, while XAF1, an inhibitor of anti-apoptotic XIAP, facilitated autophagy. Molecular regulators of apoptosis and autophagy interact at multiple levels to determine cell fate. Our data suggest that XAF1 and IFI6 are involved in regulating the balance between autophagy and apoptosis in DENV2-infected endothelial cells.

[Delay in formalin fixation and HER2 testing in gastric cancer].

OBJECTIVE: To evaluated HER2 status using immunohistochemistry (IHC) assay and fluorescence in situ hybridization (FISH) at two different time points of tissue fixation after surgical resection of gastric cancer, emphasizing the importance of standard operation and quality control in HER2 testing. METHODS: Forty-one resection specimens of advanced gastric cancer were collected with tissue fixation periods of < 30 min or > 30 min after surgical resection. HER2 status was evaluated by immunohistochemistry (IHC) assay and fluorescence in situ hybridization (FISH). RESULTS: The frequency of HER2 expression by IHC in the samples with fixation time of < 30 min was higher than that in those of > 30 min (P < 0.05). However, no significant difference was observed by FISH (P > 0.05) between the two groups. Samples of < 30 min fixation time had high concordant results between IHC and FISH (100.0% for both positive and negative cases, Rho = 0.724, P < 0.05). In addition, HER2 expression by IHC was significantly correlated with Lauren classification, histologic differentiation, TNM stage and gender (P < 0.05). CONCLUSION: The time to tissue fixation after surgical resection of more than 30 min has deleterious effect on the detection of HER2 by IHC although FISH testing is not affected.

Simulation Study on Temperature Control Performance of Lithium-Ion Battery Fires by Fine Water Mist in Energy Storage Stations.

The combustion of lithium-ion batteries is characterized by fast ignition, prolonged duration, high combustion temperature, release of significant energy, and generation of a large number of toxic gases. Fine water mist has characteristics such as a high fire extinguishing efficiency and environmental friendliness. In order to thoroughly investigate the temperature control effect of fine water mist on lithium-ion battery fires. This study employs numerical simulation methods, utilizing PyroSim software to simulate the fire process in lithium-ion battery energy storage compartments. First, we focus on the variation patterns of flame, changes in combustion temperature, and heat release rate over time at environmental temperatures of 10, 25, and 35 °C. Subsequently, the suppression of flame, reduction in temperature, and changes in heat release rate are simulated for water mist in lithium-ion battery fires. The simulation results indicate that the environmental temperature has a considerable impact on the flame but a lesser effect on the heat release rate. Fine water mist effectively impedes the spread of thermal runaway between internal battery core cells, leading to a reduction in the flame size and a significant decrease in the maximum temperature and heat release rate. The numerical simulation results can provide scientific guidance for the prevention and control of fires in lithium-ion battery energy storage compartments.

Multi-scale representation of surface-enhanced Raman spectroscopy data for deep learning-based liver cancer detection.

The early detection of liver cancer greatly improves survival rates and allows for less invasive treatment options. As a non-invasive optical detection technique, Surface-Enhanced Raman Spectroscopy (SERS) has shown significant potential in early cancer detection, providing multiple advantages over conventional methods. The majority of existing cancer detection methods utilize multivariate statistical analysis to categorize SERS data. However, these methods are plagued by issues such as information loss during dimensionality reduction and inadequate ability to handle nonlinear relationships within the data. To overcome these problems, we first use wavelet transform with its multi-scale analysis capability to extract multi-scale features from SERS data while minimizing information loss compared to traditional methods. Moreover, deep learning is employed for classification, leveraging its strong nonlinear processing capability to enhance accuracy. In addition, the chosen neural network incorporates a data augmentation method, thereby enriching our training dataset and mitigating the risk of overfitting. Moreover, we acknowledge the significance of selecting the appropriate wavelet basis functions in SERS data processing, prompting us to choose six specific ones for comparison. We employ SERS data from serum samples obtained from both liver cancer patients and healthy volunteers to train and test our classification model, enabling us to assess its performance. Our experimental results demonstrate that our method achieved outstanding and healthy volunteers to train and test our classification model, enabling us to assess its performance. Our experimental results demonstrate that our method achieved outstanding performance, surpassing the majority of multivariate statistical analysis and traditional machine learning classification methods, with an accuracy of 99.38 %, a sensitivity of 99.8 %, and a specificity of 97.0 %. These results indicate that the combination of SERS, wavelet transform, and deep learning has the potential to function as a non-invasive tool for the rapid detection of liver cancer.

Prevalence and molecular characteristics of ceftazidime-avibactam resistance among carbapenem-resistant Pseudomonas aeruginosa clinical isolates.

OBJECTIVES: Resistance against ceftazidime-avibactam (CZA) in carbapenem-resistant Pseudomonas aeruginosa (CRPA) is emerging. This study was aimed at detecting the prevalence and molecular characteristics of CZA-resistant CRPA clinical isolates in Guangdong Province, China. METHODS: The antimicrobial susceptibility profile of these strains was determined. A subset of 16 CZA-resistant CRPA isolates was analysed by whole-genome sequencing (WGS). Genetic surroundings of carbapenem resistance genes and pan-genome-wide association analysis were further studied. RESULTS: Of the 250 CRPA isolates, CZA resistance rate was 6.4% (16/250). The minimum inhibitory concentration (MIC) of CZA range was from 0.25 to >256 mg/L. MIC50 and MIC90 were 2/4 and 8/4 mg/L, respectively. Among the 16 CZA-resistant CRPA strains, 31.3% (5/16) of them carried class B carbapenem resistance genes, including blaIMP-4, blaIMP-45, and blaVIM-2, located on IncP-2 megaplasmids or chromosomes, respectively. Pan-genome-wide association analysis of accessory genes for CZA-susceptible or -resistant CRPA isolates showed that PA1874, a hypothetical protein containing BapA prefix-like domain, was enriched in CZA-resistant group significantly. CONCLUSIONS: Class B carbapenem resistance genes play important roles in CZA resistance. Meanwhile, the PA1874 gene may be a novel mechanism involving in CZA resistance. It is necessary to continually monitor CZA-resistant CRPA isolates.

Probing Lipid Peroxidation in Ferroptosis: Emphasizing the Utilization of C11-BODIPY-Based Protocols.

Ferroptosis is a form of regulated cell death that relies on iron and is characterized by the accumulation of lipid peroxides, resulting in oncotic cell swelling and eventual disruption of cellular membranes. Lipid peroxidation, a hallmark of ferroptosis, refers to the oxidative deterioration of lipids that contain carbon-carbon double bonds, particularly polyunsaturated fatty acids (PUFAs). Understanding the molecular mechanisms underlying the interplay between ferroptosis and lipid peroxidation and identifying reliable techniques for assessing lipid peroxidation levels are crucial for further advancements in this field of research. Various methods have been developed to detect lipid peroxidation levels, including C11-BODIPY (BODIPY™ 581/591 C11), liperfluo, 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), Click-iT LAA (linoleamide alkyne), and liquid chromatography-mass spectrometry (LC-MS)-based epilipidomics (redox lipidomics). Currently, one of the most commonly used and effective methods is the C11-BODIPY assay, which utilizes a fluorescent probe that selectively sensitizes lipid peroxidation in cell membranes. Incorporating advanced techniques such as flow cytometry and fluorescence microscopy with C11-BODIPY dye is essential for accurate assessment of lipid peroxidation levels in ferroptosis. This chapter aims to provide comprehensive experimental protocols for detecting lipid peroxidation levels indicative of ferroptosis using C11-BODIPY staining and subsequent detection via flow cytometry and fluorescence microscopy.

Neoadjuvant Chemotherapy and Expandable Prosthesis Reconstruction to Treat Osteosarcoma around the Knee in Children.

OBJECTIVE: Survival and reconstruction in osteosarcoma is quite challenging. The study aimed to investigate the prognosis in patients treated with neoadjuvant chemotherapy and determine the clinical outcomes of expandable endoprosthesis reconstruction in children. METHODS: From January 2009 to December 2014, we retrospectively analyzed 29 skeletally immature children (mean age, 10.5 years; range, 6-15 years) with osteosarcoma around the knee. Of the 29 patients who underwent neoadjuvant chemotherapy and limb salvage surgery, an expandable prosthesis was implanted for reconstruction. No patients were missed during follow-up. The evaluation index involved follow-up time, complication, functional results, and lengthening procedures. The survivorship and recurrence were assessed by GraphPad Software, and the function was evaluated by the Musculoskeletal Tumor Society (MSTS) scoring system. RESULTS: A mean follow-up time was 8.9 years (range, 6-12 years), and the overall 5-year survival was 89.1% based on Kaplan-Meier analysis. Three patients suffered a relapse and one underwent amputation. Lung metastasis developed in one patient. At 6 months after the operation, patients had a mean MSTS score of 27 points (range, 24-29). Two patients underwent revision surgery, one for implant infection and one for aseptic loosening. Prognosis is correlated with alkaline phosphatase change after treatment. CONCLUSIONS: Chemotherapy scheme and limb salvage can achieve high survival rates. This expandable prosthesis was associated with good function and low complication rates. The character of expandability could be a method to overcome discrepancies in the growth period.

[Effectiveness analysis of resection and reconstruction of primary bone tumor in pelvic zone â ¡].

Objective: To investigate the effectiveness of complete resection of bone tumor in pelvic zone Ⅱ and reconstruction with allogeneic pelvis, modular prosthesis, and three-dimensional (3D) printing prosthesis. Methods: The clinical data of 13 patients with primary bone tumor in pelvic zone Ⅱ who underwent tumor resection and acetabular reconstruction between March 2011 and March 2022 were retrospectively analyzed. There were 4 males and 9 females with an average age of 39.0 years ranging from 16 to 59 years. There were 4 cases of giant cell tumor, 5 cases of chondrosarcoma, 2 cases of osteosarcoma, and 2 cases of Ewing sarcoma. The Enneking classification of pelvic tumors showed that 4 cases involved zone Ⅱ, 4 cases involved zone Ⅰ and zone Ⅱ, and 5 cases involved zone Ⅱ and zone Ⅲ. The disease duration ranged from 1 to 24 months, with an average of 9.5 months. The patients were followed up to observe the recurrence and metastasis of the tumor, and the imaging examination was performed to observe the status of implant in place, fracture, bone resorption, bone nonunion, and so on. The improvement of hip pain was evaluated by visual analogue scale (VAS) score before operation and at 1 week after operation, and the recovery of hip function was evaluated according to the Musculoskeletal Tumor Society (MSTS) scoring system after operation. Results: The operation time was 4-7 hours, with an average of 4.6 hours; the intraoperative blood loss ranged from 800 to 1 600 mL, with an average of 1 200.0 mL. There was no reoperation or death after operation. All patients were followed up 9-60 months (mean, 33.5 months). No tumor metastasis was found in 4 patients receiving chemotherapy during follow-up. Postoperative wound infection occurred in 1 case, and prosthesis dislocation occurred in 1 case at 1 month after prosthesis replacement. One case of giant cell tumor recurred at 12 months after operation, and the puncture biopsy showed malignant transformation of giant cell tumor, and hemipelvic amputation was performed. The postoperative hip pain significantly relieved, and the VAS score was 6.1±0.9 at 1 week after operation, which was significantly different from the preoperative score (8.2±1.3) ( t=9.699, P<0.001). At 12 months after operation, the MSTS score was 23.0±2.1, including 22.8±2.1 for patients with allogenic pelvis reconstruction and 23.3±2.3 for patients with prosthsis reconstruction. There was no significant difference in the MSTS score between the two reconstruction methods ( t=0.450, P=0.516). At last follow-up, 5 patients could walk with cane assistance and 7 patients could walk without cane assistance. Conclusion: The resection and reconstruction of primary bone tumor in pelvic zone Ⅱ can obtain satisfactory hip function, and the interface of allogeneic pelvis and 3D printing prosthesis have better bone ingrowth, which is more in line with the requirements of biomechanics and biological reconstruction. However, pelvis reconstruction is difficult, the patient's condition should be evaluated comprehensively before operation, and the long-term effectiveness needs further follow-up.

Dynamic evolution of ceftazidime-avibactam resistance due to interchanges between blaKPC-2 and blaKPC-145 during treatment of Klebsiella pneumoniae infection.

Background: The emergence of ceftazidime-avibactam (CZA) resistance among carbapenem-resistant Klebsiella pneumoniae (CRKP) is of major concern due to limited therapeutic options. Methods: In this study, 10 CRKP strains were isolated from different samples of a patient with CRKP infection receiving CZA treatment. Whole-genome sequencing (WGS) and conjugation experiments were performed to determine the transferability of the carbapenem resistance gene. Results: This infection began with a KPC-2-producing K. pneumoniae (CZA MIC = 2 µg/mL, imipenem MIC ≥ 16 µg/mL). After 20 days of CZA treatment, the strains switched to the amino acid substitution of T263A caused by a novel KPC-producing gene, blaKPC-145, which restored carbapenem susceptibility but showed CZA resistance (CZA MIC ≥ 256 µg/mL, imipenem MIC = 1 µg/mL). The blaKPC-145 gene was located on a 148,185-bp untransformable IncFII-type plasmid. The subsequent use of carbapenem against KPC-145-producing K. pneumoniae infection led to a reversion of KPC-2 production (CZA MIC = 2 µg/mL, imipenem MIC ≥ 16 µg/mL). WGS analysis showed that all isolates belonged to ST11-KL47, and the number of SNPs was 14. This implied that these blaKPC-positive K. pneumoniae isolates might originate from a single clone and have been colonized for a long time during the 120-day treatment period. Conclusion: This is the first report of CZA resistance caused by blaKPC-145, which emerged during the treatment with CZA against blaKPC-2-positive K. pneumoniae-associated infection in China. These findings indicated that routine testing for antibiotic susceptibility and carbapenemase genotype is essential during CZA treatment.