3D printed PLGA scaffold with nano-hydroxyapatite carrying linezolid for treatment of infected bone defects.

BACKGROUND: Linezolid has been reported to protect against chronic bone and joint infection. In this study, linezolid was loaded into the 3D printed poly (lactic-co-glycolic acid) (PLGA) scaffold with nano-hydroxyapatite (HA) to explore the effect of this composite scaffold on infected bone defect (IBD). METHODS: PLGA scaffolds were produced using the 3D printing method. Drug release of linezolid was analyzed by elution and high-performance liquid chromatography assay. PLGA, PLGA-HA, and linezolid-loaded PLGA-HA scaffolds, were implanted into the defect site of a rabbit radius defect model. Micro-CT, H&E, and Masson staining, and immunohistochemistry were performed to analyze bone infection and bone healing. Evaluation of viable bacteria was performed. The cytocompatibility of 3D-printed composite scaffolds in vitro was detected using human bone marrow mesenchymal stem cells (BMSCs). Long-term safety of the scaffolds in rabbits was evaluated. RESULTS: The linezolid-loaded PLGA-HA scaffolds exhibited a sustained release of linezolid and showed significant antibacterial effects. In the IBD rabbit models implanted with the scaffolds, the linezolid-loaded PLGA-HA scaffolds promoted bone healing and attenuated bone infection. The PLGA-HA scaffolds carrying linezolid upregulated the expression of osteogenic genes including collagen I, runt-related transcription factor 2, and osteocalcin. The linezolid-loaded PLGA-HA scaffolds promoted the proliferation and osteogenesis of BMSCs in vitro via the PI3K/AKT pathway. Moreover, the rabbits implanted with the linezolid-loaded scaffolds showed normal biochemical profiles and normal histology, which suggested the safety of the linezolid-loaded scaffolds. CONCLUSION: Overall, the linezolid-loaded PLGA-HA scaffolds fabricated by 3D printing exerts significant bone repair and anti-infection effects.

Local autocrine plasticity signaling in single dendritic spines by insulin-like growth factors.

The insulin superfamily of peptides is essential for homeostasis as well as neuronal plasticity, learning, and memory. Here, we show that insulin-like growth factors 1 and 2 (IGF1 and IGF2) are differentially expressed in hippocampal neurons and released in an activity-dependent manner. Using a new fluorescence resonance energy transfer sensor for IGF1 receptor (IGF1R) with two-photon fluorescence lifetime imaging, we find that the release of IGF1 triggers rapid local autocrine IGF1R activation on the same spine and more than several micrometers along the stimulated dendrite, regulating the plasticity of the activated spine in CA1 pyramidal neurons. In CA3 neurons, IGF2, instead of IGF1, is responsible for IGF1R autocrine activation and synaptic plasticity. Thus, our study demonstrates the cell type-specific roles of IGF1 and IGF2 in hippocampal plasticity and a plasticity mechanism mediated by the synthesis and autocrine signaling of IGF peptides in pyramidal neurons.

Dual Regulation of Spine-Specific and Synapse-to-Nucleus Signaling by PKCδ during Plasticity.

The activity-dependent plasticity of synapses is believed to be the cellular basis of learning. These synaptic changes are mediated through the coordination of local biochemical reactions in synapses and changes in gene transcription in the nucleus to modulate neuronal circuits and behavior. The protein kinase C (PKC) family of isozymes has long been established as critical for synaptic plasticity. However, because of a lack of suitable isozyme-specific tools, the role of the novel subfamily of PKC isozymes is largely unknown. Here, through the development of fluorescence lifetime imaging-fluorescence resonance energy transfer activity sensors, we investigate novel PKC isozymes in synaptic plasticity in CA1 pyramidal neurons of mice of either sex. We find that PKCδ is activated downstream of TrkB and DAG production, and that the spatiotemporal nature of its activation depends on the plasticity stimulation. In response to single-spine plasticity, PKCδ is activated primarily in the stimulated spine and is required for local expression of plasticity. However, in response to multispine stimulation, a long-lasting and spreading activation of PKCδ scales with the number of spines stimulated and, by regulating cAMP response-element binding protein activity, couples spine plasticity to transcription in the nucleus. Thus, PKCδ plays a dual functional role in facilitating synaptic plasticity.SIGNIFICANCE STATEMENT Synaptic plasticity, or the ability to change the strength of the connections between neurons, underlies learning and memory and is critical for brain health. The protein kinase C (PKC) family is central to this process. However, understanding how these kinases work to mediate plasticity has been limited by a lack of tools to visualize and perturb their activity. Here, we introduce and use new tools to reveal a dual role for PKCδ in facilitating local synaptic plasticity and stabilizing this plasticity through spine-to-nucleus signaling to regulate transcription. This work provides new tools to overcome limitations in studying isozyme-specific PKC function and provides insight into molecular mechanisms of synaptic plasticity.

Effects of single and combined exposure to zinc and two tetracycline antibiotics on zebrafish at the early stage.

Tetracycline antibiotics (TCs) and heavy metals are commonly used in livestock and poultry farming, leading to their coexistence in the aquatic environment. This coexistence causes combined toxicity to aquatic organisms. Here, zebrafish embryos were exposed to chlortetracycline (CTC), oxytetracycline (OTC), zinc chloride (ZnCl2), and their combinations for 120 h to evaluate their adverse effects on the growth, antioxidant system, immune system, and endocrine system during the early stage of life. OTC/ZnCl2 combined exposure significantly reduced the body weight, whereas the TCs/ZnCl2 combination significantly increased the heart rate of zebrafish larvae, suggesting growth impairment induced by TCs and ZnCl2. Further, combined groups showed more prominent toxicity to the antioxidant system than single groups, as revealed by related levels of enzyme activity and gene expression. In addition, the levels of most pro-inflammatory genes were downregulated, and those of NF-κB-related genes were upregulated in all treatment groups, indicating an immunosuppressive response and the potential role of NF-κB signaling, while the combined treatment was not more toxic than TCs or ZnCl2 alone. Similarly, hormone and endocrine related gene levels were determined. Although both single and combined exposures caused certain endocrine-disrupting effects, the combined exposure did not result in higher toxicity than a single exposure. Our findings showed that a mixture of TCs and ZnCl2 might exert greater toxic effects as compared to a single compound on some systems, providing fundamental data on the toxic effects of single and combined TC and ZnCl2 exposure on aquatic organisms, although studies are needed to explore the underlying mechanisms.

Rac1 is a downstream effector of PKCα in structural synaptic plasticity.

Structural and functional plasticity of dendritic spines is the basis of animal learning. The rapid remodeling of actin cytoskeleton is associated with spine enlargement and shrinkage, which are essential for structural plasticity. The calcium-dependent protein kinase C isoform, PKCα, has been suggested to be critical for this actin-dependent plasticity. However, mechanisms linking PKCα and structural plasticity of spines are unknown. Here, we examine the spatiotemporal activation of actin regulators, including small GTPases Rac1, Cdc42 and Ras, in the presence or absence of PKCα during single-spine structural plasticity. Removal of PKCα expression in the postsynapse attenuated Rac1 activation during structural plasticity without affecting Ras or Cdc42 activity. Moreover, disruption of a PDZ binding domain within PKCα led to impaired Rac1 activation and deficits in structural spine remodeling. These results demonstrate that PKCα positively regulates the activation of Rac1 during structural plasticity.

[Impacts of high-volume hemofiltration on hemodynamics and vascular endothelial permeability in children with septic shock].

OBJECTIVE: To investigate the effects of high-volume hemofiltration (HVHF) on hemodynamics, vasoactive factors, and vascular endothelial permeability in children with septic shock by a comparative analysis. METHODS: Thirty-six children who were diagnosed with septic shock between January 2013 and September 2014 were randomly divided into control and observation groups (n=18 each). Children in the control group were treated with the standard-volume hemofiltration (SVHF), while children in the observation group were treated with HVHF. The hemodynamic indices and levels of vasoactive factors including 6-keto-prostaglandin F1α (6-keto-PGF1α), thromboxane B2 (TXB2), soluble E-selectin (sE-selectin), and endothelium-derived relaxing factor (EDRF) were determined before and after treatment. In addition, the effects of ultrafiltrate on endothelial cell permeability were assessed. RESULTS: Compared with the control group, the observation group had significantly higher mean arterial pressure, significantly higher blood oxygen saturation, and a significantly lower heart rate after treatment (P<0.05). The levels of TXB2 and sE-selectin were significantly lower in the observation group than in the control group (P<0.05), while the levels of 6-keto-PGF1α and EDRF were significantly higher in the observation group than in the control group (P<0.05). Compared with the control group, the ultrafiltrate significantly attenuated the transepithelial electrical resistance in the observation group (P<0.05). CONCLUSIONS: Compared with SVHF, HVHF is a more effective approach for improving the hemodynamics and levels of vasoactive factors and reducing the vascular endothelial permeability in children with septic shock.

Silencing of Livin inhibits tumorigenesis and metastasis via VEGF and MMPs pathway in lung cancer.

Livin, an inhibitor of apoptosis protein (IAP), is overexpressed in various cancers and decreases tumor sensitivity to chemotherapy and radiotherapy. However, the effect of Livin on lung adenocarcinoma metastasis and the specific mechanism involved remain unclear. RNAi technology was used to stably silence Livin in A549 cells in the present study. The effect of Livin on tumor growth and invasion was investigated in lung cancer cells in vitro and animal models were established to determine the anti-metastasis ability of Livin silencing in vivo. The results indicated that Livin knock-down suppressed cell proliferation and inhibited cell invasion, accompanied by downregulation of VEGF and MMP-2/-9. Silencing of Livin resulted in the prevention of xenograft tumor formation. Seventy-five immunodeficient male BALB/C nude mice were randomly divided into three groups, the relative ratio of the areas with pulmonary nodules in the experimental group decreased from 46.71±7.27% to 11.07±2.94% compared with the negative control group (P<0.001), indicating the interaction between Livin, VEGF and MMPs. The xenograft tumor model of intravenous injection of tumor cells were successfully established and applied for the analysis of lung cancer tumorigenesis and metastasis in a time-dependent manner for the first time. Based on the reliable and reproducible animal model, our findings indicate that knock-down of Livin inhibits cell growth and invasion through blockade of the VEGF and MMPs pathways in lung cancer cells in vitro, and inhibits tumorigenesis and metastasis of lung cancer in vivo, suggesting that Livin is a promising antitumor target.

Influence of Sedation and Analgesia on Stress Reaction of Post-Operation Infants with Congenital Heart Disease / 实用儿科临床杂志

ObjectiveTo investigate influence of sedation and analgesia on stress reaction of post-cardiac surgery in infants with congenital heart disease.MethodsForty children with congenital heart disease were randomly divided into 2 groups after cardiac surgery.The analgesia group was given 0.5-2.0 ?g/(kg?h) fentanyl intravenous infusion in 20 children undergoing cardiovascular surgery.The control group was given 5-8 mg/(kg?dose) lbuprofen orally.Midaiolam 0.01-0.20 mg/(kg?h) was used in 2 groups for sedation by intravenous infusion or 0.05-0.10 mg/(kg?dose)by intravenous push intermittently.The effects and adverse effects of sedation and analgesia were observed on 2,8,24,48 h after surgery in each group.The levels of cortisol,growth hormone,insulin and blood glucose were measured,respectively.ResultsThere were significant differences in Ramsay,Comfort value on 2,8,24 h(Pa