[Modified QuEChERS method combined with ultra performance liquid chromatography-tandem mass spectrometry for detection of cyclopiazonic acid in feeds].

Mycotoxins are toxic secondary metabolites produced by fungal species that can cause acute, subacute, and chronic toxicity in humans and animals. Thus, these toxins pose a significant threat to health and safety. Owing to the lack of effective antimold measures in the agricultural industry, feed ingredients such as corn, peanuts, wheat, barley, millet, nuts, oily feed, forage, and their byproducts are prone to mold and mycotoxin contamination, which can affect animal production, product quality, and safety. Cyclopiazonic acid (CPA), which is mainly biosynthesized from mevalonate, tryptophan, and diacetate units, is a myotoxic secondary metabolite produced by Penicillium and Aspergillus fungi. CPA is widely present as a copollutant with aflatoxins in various crops. Compared with some common mycotoxins such as aflatoxins, fumonisins, ochratoxins, zearalenones, and their metabolites, CPA has not been well investigated. In the United States, a survey showed that 51% of corn and 90% of peanut samples contained CPA, with a maximum level of 2.9 mg/kg. In Europe, CPA was found in Penicillium-contaminated cheeses as high as 4.0 mg/kg. Some studies have shown that CPA can cause irreversible damage to organs such as the liver and spleen in mice. Therefore, the establishment of a rapid and efficient analytical method for CPA is of great significance for the risk assessment of CPA in feeds, the development of standard limits, and the protection of feed product quality and safety. The QuEChERS method, a sample pretreatment method that is fast, simple, cheap, effective, and safe, is widely used in the analysis of pesticide residues in food. In this study, a modified QuEChERS method combined with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to determine CPA levels in feeds. The chromatographic separation and MS detection of CPA as well as the key factors affecting the extraction efficiency of CPA, including the type of extraction solvent, type of inorganic salt, and type and dosage of adsorbent, were optimized in detail. During the optimization of the chromatographic-separation step, the acid and salt concentrations of the mobile phase affected the separation and detection of CPA. During the optimization of the QuEChERS method, the addition of a certain amount of acetic acid improved the extraction efficiency of CPA because of its acidic nature; in addition, GCB and PSA significantly adsorbed CPA from the feed extract. Under optimal conditions, the CPA in the feed sample (1.0 g) was extracted with 2 mL of water and 4 mL of acetonitrile (ACN) containing 0.5% acetic acid. After salting out with 0.4 g of NaCl and 1.6 g of MgSO4, 1 mL of the ACN supernatant was purified by dispersive solid-phase extraction using 150 mg of MgSO4 and 50 mg of C18 and analyzed by UPLC-MS/MS. The sample was separated on a Waters HSS T3 column (100 mm×2.1 mm, 1.8 µm) using 2 mmol/L ammonium acetate aqueous solution with 0.5% formic acid and ACN as the mobile phases and then analyzed by positive electrospray ionization in multiple reaction monitoring mode. CPA exhibited good linearity in the range of 2-200 ng/mL, with a high correlation coefficient (r=0.9995). The limits of detection and quantification of CPA, which were calculated as 3 and 10 times the signal-to-noise ratio, respectively, were 0.6 and 2.0 µg/kg, respectively. The average recoveries in feed samples spiked with 10, 100, and 500 µg/kg CPA ranged from 70.1% to 78.5%, with an intra-day precision of less than 5.8% and an inter-day precision of less than 7.2%, indicating the good accuracy and precision of the proposed method. Finally, the modified QuEChERS-UPLC-MS/MS method was applied to the analysis of CPA in 10 feed samples obtained from Wuhan market. The analysis results indicated that the developed method has good applicability for CPA analysis in feed samples. In summary, an improved QuEChERS method was applied to the extraction and purification of CPA from feeds for the first time; this method provides a suitable analytical method for the risk monitoring, assessment, and standard-limit setting of CPA in feed samples.

[Protective effects of salidroside on vascular endothelial cells in rats with frostbite after chronic hypoxia].

Objective: To investigate the protective effects of salidroside on endothelial cells in rats with frostbite after chronic hypoxia. Methods: Healthy male SD rats, randomly divided into 3 groups with 10 rats in each group, which included the sham injury group, the model group, and the model +salidroside group. The rats in each group were placed in a composite low-pressure chamber to simulate a environment with a pressure of 54.1 kpa and a temperature of 23~25°C. The rats were exposed to hypoxia under these conditions for 14 days, during the experimental time the rats in the model+salidroside group were treated with 50 mg/kg salidroside daily. After the rats were removed from the low-pressure chamber, except for the sham injury group, frozen iron sheets were applied tightly to the back of the rats for 30 s, supplemented with low temperature for frostbite modeling. Blood and skin tissues were collected at 12 hours after modeling for testing. The structural changes in tissue and vascular endothelial cells were observed in the frostbite region. Vascular endothelial cell particulate EMP levels were detected. The levels of ICAM-1, sEPCR, vWF, ET-1 and NO secretion were determined. The expression levels of HIF-1α, p-PI3K, p-Akt and VEGF were detected by Western blot. Results: Salidroside could effectively reduce skin collapse in frostbitten areas. It could reduce the injury of frostbitten tissues, and improve the subcutaneous tissue necrosis and inflammatory cell infiltration. The autophagy of vascular endothelial cells was reduced. Compared with the model group (0.250±0.165)%, the expression of EMPs in the model+salidroside group (2.453±0.196)% was increased significantly (P＜0.01). In addition, the contents of NO (2.622±0.219)pg/ml was also significantly higher than that of the model group (1.616±0.152)pg/ml (P＜0.01), and the content of vWF (233.50±13.43)pg/ml was lower than that of the model group (315.60±8.78)pg/ml (P＜0.05). There was no significant difference in the levels of ICAM-1, sEPCR and ET-1. Salidroside significantly decreased the expressions of p-PI3K, p-Akt, VEGF and HIF-1α protein in vascular endothelial cells of rats with frostbite (P＜0.01). Conclusion: Salidroside can reduce endothelial cell damage, reduce endothelial cell autophagy and promote endothelial cell regeneration. Based on the PI3K/Akt pathway, salidroside has a good protective effect on endothelial cells of rats with frostbite after chronic hypoxia.

Mixtures of aromatic compounds induce ligninolytic gene expression in the wood-rotting fungus Dichomitus squalens.

Heterologous production of fungal ligninolytic cocktails is challenging due to the low yields of catalytically active lignin modifying peroxidases. Production using a natural system, such as a wood-rotting fungus, is a promising alternative if specific or preferential induction of the ligninolytic activities could be achieved. Using transcriptomics, gene expression of the white-rot Dichomitus squalens during growth on mixtures of aromatic compounds, with ring structures representing the two major lignin sub-units, was compared to a wood substrate. Most of the genes encoding lignin modifying enzymes (laccases and peroxidases) categorised as highly or moderately expressed on wood were expressed similarly on aromatic compounds. Higher expression levels of a subset of manganese and versatile peroxidases was observed on di- compared to mono-methoxylated aromatics. The expression of polysaccharide degrading enzymes was lower on aromatic compounds compared to wood, demonstrating that the induction of lignin modifying enzymes became more specific. This study suggests potential for aromatic waste streams, e.g. from lignocellulose pretreatment, to produce a lignin-specific enzyme cocktail from D. squalens or other white-rot fungi.

Glucose-Mediated Repression of Plant Biomass Utilization in the White-Rot Fungus Dichomitus squalens.

The extent of carbon catabolite repression (CCR) at a global level is unknown in wood-rotting fungi, which are critical to the carbon cycle and are a source of biotechnological enzymes. CCR occurs in the presence of sufficient concentrations of easily metabolizable carbon sources (e.g., glucose) and involves downregulation of the expression of genes encoding enzymes involved in the breakdown of complex carbon sources. We investigated this phenomenon in the white-rot fungus Dichomitus squalens using transcriptomics and exoproteomics. In D. squalens cultures, approximately 7% of genes were repressed in the presence of glucose compared to Avicel or xylan alone. The glucose-repressed genes included the essential components for utilization of plant biomass-carbohydrate-active enzyme (CAZyme) and carbon catabolic genes. The majority of polysaccharide-degrading CAZyme genes were repressed and included activities toward all major carbohydrate polymers present in plant cell walls, while repression of ligninolytic genes also occurred. The transcriptome-level repression of the CAZyme genes observed on the Avicel cultures was strongly supported by exoproteomics. Protease-encoding genes were generally not glucose repressed, indicating their likely dominant role in scavenging for nitrogen rather than carbon. The extent of CCR is surprising, given that D. squalens rarely experiences high free sugar concentrations in its woody environment, and it indicates that biotechnological use of D. squalens for modification of plant biomass would benefit from derepressed or constitutively CAZyme-expressing strains.IMPORTANCE White-rot fungi are critical to the carbon cycle because they can mineralize all wood components using enzymes that also have biotechnological potential. The occurrence of carbon catabolite repression (CCR) in white-rot fungi is poorly understood. Previously, CCR in wood-rotting fungi has only been demonstrated for a small number of genes. We demonstrated widespread glucose-mediated CCR of plant biomass utilization in the white-rot fungus Dichomitus squalens This indicates that the CCR mechanism has been largely retained even though wood-rotting fungi rarely experience commonly considered CCR conditions in their woody environment. The general lack of repression of genes encoding proteases along with the reduction in secreted CAZymes during CCR suggested that the retention of CCR may be connected with the need to conserve nitrogen use during growth on nitrogen-scarce wood. The widespread repression indicates that derepressed strains could be beneficial for enzyme production.

Dichomitus squalens partially tailors its molecular responses to the composition of solid wood.

White-rot fungi, such as Dichomitus squalens, degrade all wood components and inhabit mixed-wood forests containing both soft- and hardwood species. In this study, we evaluated how D. squalens responded to the compositional differences in softwood [guaiacyl (G) lignin and higher mannan content] and hardwood [syringyl/guaiacyl (S/G) lignin and higher xylan content] using semi-natural solid cultures. Spruce (softwood) and birch (hardwood) sticks were degraded by D. squalens as measured by oxidation of the lignins using 2D-NMR. The fungal response as measured by transcriptomics, proteomics and enzyme activities showed a partial tailoring to wood composition. Mannanolytic transcripts and proteins were more abundant in spruce cultures, while a proportionally higher xylanolytic activity was detected in birch cultures. Both wood types induced manganese peroxidases to a much higher level than laccases, but higher transcript and protein levels of the manganese peroxidases were observed on the G-lignin rich spruce. Overall, the molecular responses demonstrated a stronger adaptation to the spruce rather than birch composition, possibly because D. squalens is mainly found degrading softwoods in nature, which supports the ability of the solid wood cultures to reflect the natural environment.

Spatial Organization in Protein Kinase A Signaling Emerged at the Base of Animal Evolution.

In phosphorylation-directed signaling, spatial and temporal control is organized by complex interaction networks that diligently direct kinases toward distinct substrates to fine-tune specificity. How these protein networks originate and evolve into complex regulatory machineries are among the most fascinating research questions in biology. Here, spatiotemporal signaling is investigated by tracing the evolutionary dynamics of each functional domain of cAMP-dependent protein kinase (PKA) and its diverse set of A-kinase anchoring proteins (AKAPs). Homologues of the catalytic (PKA-C) and regulatory (PKA-R) domains of the (PKA-R)2-(PKA-C)2 holoenzyme were found throughout evolution. Most variation was observed in the RIIa of PKA-R, crucial for dimerization and docking to AKAPs. The RIIa domain was not observed in all PKA-R homologues. In the fungi and distinct protist lineages, the RIIa domain emerges within PKA-R, but it displays large sequence variation. These organisms do not harbor homologues of AKAPs, suggesting that efficient docking to direct spatiotemporal PKA activity evolved in multicellular eukaryotes. To test this in silico hypothesis, we experimentally screened organisms with increasing complexity by cAMP-based chemical proteomics to reveal that the occurrence of PKA-AKAP interactions indeed coincided and expanded within vertebrates, suggesting a crucial role for AKAPs in the advent of metazoan multicellularity.

Biomechanical study of the funnel technique applied in thoracic pedicle screw replacement.

BACKGROUND: Funnel technique is a method used for the insertion of screw into thoracic pedicle. AIM: To evaluate the biomechanical characteristics of thoracic pedicle screw placement using the Funnel technique, trying to provide biomechanical basis for clinical application of this technology. METHODS: 14 functional spinal units (T6 to T10) were selected from thoracic spine specimens of 14 fresh adult cadavers, and randomly divided into two groups, including Funnel technique group (n = 7) and Magerl technique group (n = 7). The displacement-stiffness and pull-out strength in all kinds of position were tested and compared. RESULTS: Two fixed groups were significantly higher than that of the intact state (P < 0.05) in the spinal central axial direction, compression, anterior flexion, posterior bending, lateral bending, axial torsion, but there were no significant differences between two fixed groups (P > 0.05). The mean pull-out strength in Funnel technique group (789.09 ± 27.33) was lower than that in Magerl technique group (P < 0.05). CONCLUSIONS: The Funnel technique for the insertion point of posterior bone is a safe and accurate technique for pedicle screw placement. It exhibited no effects on the stiffness of spinal column, but decreased the pull-out strength of pedicle screw. Therefore, the funnel technique in the thoracic spine affords an alternative for the standard screw placement.

Plasma amyloid-ß oligomers and soluble tumor necrosis factor receptors as potential biomarkers of AD.

Amyloid beta (Aß), especially Aß oligomers, is important in early Alzheimer's disease (AD) pathogenesis. AD-associated inflammation has generally been considered as a secondary response to the pathological lesions evoked by Aß oligomers in the early stage of pathogenesis. We studied the levels of plasma Aß monomers, Aß oligomers, and soluble tumor necrosis factor α receptors (sTNFRs) in 120 controls, 32 amnestic mild cognitive impairment (aMCI) patients, and 90 mild AD patients. The plasma Aß monomer, oligomer and sTNFR levels were measured by ELISA. We observed that the Aß oligomer levels in mild AD patients were significantly higher than those in aMCI (200.8±83.8 versus 93.9±23.3, P<0.05) and healthy subjects (200.8±83.8 versus 70.0±60.9, P<0.05). The sTNFR levels in the plasma of aMCI and mild AD patients were significantly higher than the levels of control subjects. Moreover, the levels of both sTNFR1 and sTNFR2 were significantly correlated with Aß oligomer levels in aMCI (sTNFR1 : r= 0.376, P= 0.034; sTNFR2 : r= 0.367, P= 0.039) and mild AD patients (sTNFR1 : r= 0.471, P<0.001; sTNFR2 : r= 0.407, P< 0.001). More importantly, changes in Aß oligomer and sTNFR levels accurately differentiated mild AD patients from control subjects, supporting these levels might be potential diagnostic biomarkers for aMCI and AD.

Epidemiological study and control trial of taeniid cestode infection in farm dogs in Qinghai Province, China.

An epidemiological study and control trial were conducted to assess taeniid infection in farm dogs in Qinghai Province, China. To improve egg detection by fecal examination, a deworming step with praziquantel was incorporated into the sampling methodology. As a result, a marked increase in the number of egg-positive samples was observed in samples collected at 24 hr after deworming. Then, the fecal examination and barcoding of egg DNA were performed to assess the prevalence of taeniid species in dogs from Xinghai, Haiyan, Gangcha and Chengduo counties. Analysis of 277 dog feces revealed that taeniid cestodes, including Taenia spp. and Echinococcus granulosus, were highly prevalent in Xinghai (34.4%), but eggs were not found in Haiyan where a control trial on canine echinococcosis had been conducted 20 years previously. A control trial involving the administration of 5-10 mg/kg praziquantel to 90 farm dogs at 45-day intervals was conducted in Xinghai. The prevalence of taeniid cestodes in the dogs was reduced to 9.6% and 4.9% after one and two years, respectively, indicating that some dogs were not administered praziquantel properly. A questionnaire survey of farmers in Xinghai and Haiyan revealed that most farmers in Xinghai were not familiar with echinococcosis or the transmission route of the disease, while most farmers in Haiyan had a more thorough understanding of the disease. The findings implied that a program for educating local farmers would be important for efficiently controlling canine taeniid infection in the region.

Finding the same needles in the haystack? A comparison of phosphotyrosine peptides enriched by immuno-affinity precipitation and metal-based affinity chromatography.

Analysis of tyrosine (Tyr) phosphorylation by mass spectrometry (MS)-based proteomics remains challenging, due to the low occurrence of this post-translational modification compared to serine and threonine phosphorylation events in mammalian systems. Conventional metal-based affinity chromatography methods used to enrich phosphopeptides can nowadays isolate over 10,000 phosphopeptides. However, these approaches are not particularly suitable for the selective enrichment of low abundant Tyr phosphorylated peptides as the higher abundant co-enriched serine (Ser) and threonine (Thr) phosphorylated peptides typically obscure their detection. Therefore, a more targeted approach based on immuno-affinity precipitation at the peptide level has been introduced for the specific analysis of Tyr phosphorylated species. This method typically leads to the detection of a few hundreds of phosphopeptides, albeit typically over 70% of those are Tyr phosphorylated. Here, we evaluated and compared phosphotyrosine peptides enriched by a phospho-Tyr immuno-affinity enrichment (employing pY99 antibodies) and a multidimensional approach consisting of metal-affinity based enrichment (Ti(4+)-IMAC) followed by hydrophilic interaction liquid chromatography (HILIC) fractionation. Our aim was to assess differences and similarities in the set of Tyr phosphorylated peptides detected by each approach. Our data suggest that both strategies are not redundant but complementary and should ideally be combined for a more comprehensive view at phosphotyrosine signaling. BIOLOGICAL SIGNIFICANCE: Here we evaluated enabling tools for the global analysis of phosphotyrosine phosphorylation. Phosphotyrosine phosphorylation is a key protein modification driving cellular response also involved in disease/cancer molecular pathways.

Construction of flame retardant nanocoating on ramie fabric via layer-by-layer assembly of carbon nanotube and ammonium polyphosphate.

A new flame retardant nanocoating has been constructed by the alternate adsorption of polyelectrolyte amino-functionalized multiwall carbon nanotube (MWNT-NH2) and ammonium polyphosphate (APP) onto flexible and porous ramie fabric. Scanning electron microscopy indicates that the adsorbed carbon nanotube coating is a randomly oriented and overlapped network structure, which is a promising candidate for flame retardancy applications. Attenuated total reflection Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis confirm that the APP is successfully incorporated into the multilayers sequentially. Assessment of the thermal and flammability properties for the pristine and nanocoated ramie fabrics shows that the thermal stability, flame retardancy and residual char are enhanced as the concentration of MWNT-NH2 suspension and number of deposition cycles increases. The enhancements are mostly attributed to the barrier effect of intumescent network structure, which is composed of MWNT-NH2 and the absorbed APP.

Toward a comprehensive characterization of a human cancer cell phosphoproteome.

Mass spectrometry (MS)-based phosphoproteomics has achieved extraordinary success in qualitative and quantitative analysis of cellular protein phosphorylation. Considering that an estimated level of phosphorylation in a cell is placed at well above 100,000 sites, there is still much room for improvement. Here, we attempt to extend the depth of phosphoproteome coverage while maintaining realistic aspirations in terms of available material, robustness, and instrument running time. We developed three strategies, where each provided a different balance between these three key parameters. The first strategy simply used enrichment by Ti(4+)-IMAC followed by reversed chromatography LC-MS (termed 1D). The second strategy incorporated an additional fractionation step through the use of HILIC (2D). Finally, a third strategy was designed employing first an SCX fractionation, followed by Ti(4+)-IMAC enrichment and additional fractionation by HILIC (3D). A preliminary evaluation was performed on the HeLa cell line. Detecting 3700 phosphopeptides in about 2 h, the 1D strategy was found to be the most sensitive but limited in comprehensivity, mainly due to issues with complexity and dynamic range. Overall, the best balance was achieved using the 2D based strategy, identifying close to 17,000 phosphopeptides with less than 1 mg of material in about 48 h. Subsequently, we confirmed the findings with the K562 cell sample. When sufficient material was available, the 3D strategy increased phosphoproteome allowing over 22,000 unique phosphopeptides to be identified. Unfortunately, the 3D strategy required more time and over 1 mg of material before it started to outperform 2D. Ultimately, combining all strategies, we were able to identify over 16,000 and nearly 24,000 unique phosphorylation sites from the cancer cell lines HeLa and K562, respectively. In summary, we demonstrate the need to carry out extensive fractionation for deep mining of the phosphoproteome and provide a guide for appropriate strategies depending on sample amount and/or analysis time.

[Pedicle screw at the fracture level and vertebroplasty via paraspinal approach for the treatment of old thoracolumbar fractures].

OBJECTIVE: To investigate the feasibility and safety of the treatment for thoracolumbar fractures with pedicle screw at the fracture level and vertebroplasty via paraspinal approach. METHODS: From August 2007 to August 2010, 22 old patients with thoracolumbar fractures were treated with pedicle screw at the fracture level and vertebroplasty via paraspinal approach. There were 14 males and 8 females, ranging in age from 60 to 71 years (mean, 64.6 years). The time from injury to surgery varied from 1 to 4 d (mean,2.7 d). All the patients suffered from single thoracolumbar fractures and located at T11 in 2 cases, at T12 in 5 cases, at L1 in 11 cases and at L2 in 4 cases. According to the Denis fracture classification, there were 6 compression fractures and 16 burst fractures. The mean preoperative load-sharing classification of spine fractures was 5.4 score. The mean preoperative thoracolumbar injury classification and scoring was 5.2. Based on the ASIA neurologic grading system, preoperative neurological function was grade B in 2 cases,grade C in 3 cases, grade D in 7 cases and grade E in 10 cases. The neurological function, vertebral central and anterior height, kyphotic angle of the vertebral fractures by radiographs and visual analog scale were calculated pre-operatively, post-operatively and at the last follow-up. RESULTS: Median operating time was 60.8 min (ranged from 50 to 95 min) and median blood loss was 84 ml (ranged from 50 to 130 ml). The operative incisions were healed well. The duration of follow-up averaged 21.6 months (ranged from 12 to 48 months). The anterior vertebral body height was corrected from preoperative (52.3 +/- 10.3) % to postoperative (6.1 +/- 4.2) % and (6.8 +/- 5.4) % at the last follow-up. The central vertebral body height was corrected from preoperative (38.9 +/- 11.2) % to postoperative (8.3 +/- 4.7) % and (9.4 +/- 4.5)% at the last follow-up. The Cobbs angle of the injured vertebral segment was corrected from preoperative (19.5 +/- 9.5) degrees to postoperative (4.3 +/- 4.1) degrees and (6.2 +/- 4.7) degrees at the last follow-up. The VAS scores reduced from preoperative 8.56 +/- 0.88 to post-operative 3.48 +/- 0.91 and 3.20 +/- 0.92 at the last follow-up. The postoperative neurologic function of all 22 patients improved 1 to 2 degrees except 10 patients of grade E. There were no instances of instrumentation failure and no patient had persistent postoperative back pain. CONCLUSION: The pedicle screw at the fracture level and vertebroplasty via paraspinal approach has the advantages of less invasive and blood loss, and could prevent the development of kyphosis and offers improvement of the spinal cord function. Furthermore, it could decrease the risks of postoperative back pain and the failure of instrumentation.

[Surgical treatment of thoracolumbar fractures using reduction and short-segment pedicle screw at the fracture level with the approach through para-vertebral muscles].

OBJECTIVE: To evaluate the efficacy and clinical outcome of reduction and pedicle screws fixation at the fracture level with the approach through para-vertebral muscles in treating thoraeolumbar fractures. METHODS: From January 2007 to March 2010,27 patients with thoracolumbar fractures were treated with posterior open reduction and internal fixation with the approach through para-vertebral muscles. There were 19 males and 8 females with the mean age of 36.3 years old (ranged,21 to 57). According to Magerl type, type A2 was in 5 cases, A3 in 14, B1 in 3, B2 in 5. According to Frankel classification of spinal cord injury: grade D was in 6 cases and grade E in 21 cases. X-rays and CT scans were performed after operation. Cobb angle of the injured vertebral segment,the percentage of vertebral compression,and sagittal diameter stenosis rate of the injured spinal canal were observed by radiographic data. Neurological function was evaluated by the Frankel grade. RESULTS: All patients were followed up from 12 to 28 months with an average of 19.6 months. The percentage of vertebral compression, Cobb angle of the injured vertebral segment, spinal canal sagittal diameter stenosis rate were respectively corrected from (46.6 +/- 10.5)%, (18.3 +/- 7.2) degrees, (30.2 +/- 7.2)% to postoperative (5.2 +/- 3.7)%, (5.3 +/- 5.1) degrees, (6.3 +/- 4.2)% and (6.7 +/- 4.6)%, (7.1 +/- 3.1), (7.2 +/- 4.5)% at last follow-up. There were significant difference in above items between preoperation and postoperation (P < 0.05); and there was no significant difference in above items between postoperation and last follow-up (P > 0.05). In aspect of nerve function, 3 cases with Frankel grade D recovered to grade E. CONCLUSION: Using reduction and short-segment pedicle screws fixation at the fracture level through para-vertebral muscles approach is an effective method in treating thoracolumbar fractures. The method has advantages of simple operation,easy establishing screw, short operative time, less blood loss, which can obtain good reduction and stable, reliable fixation after operation.

Effects of reactive compatibilization on the morphological, thermal, mechanical, and rheological properties of intumescent flame-retardant polypropylene.

Flame-retardant polypropylene (PP) samples were in situ compatibilized with maleic anhydride grafted PP. Compatibilization reaction was verified by an IR spectrum and gel content measurements. Electron microscopy images showed that compatibilization could considerably reduce the size of the flame-retardant domains, control the phase morphology, and improve the interfacial adhesion between PP and intumescent flame retardant (IFR) with different IFR loading levels. The limiting oxygen index (LOI) of flame-retardant PP increased to different extents after compatibilization, indicating an improvement in the flame retardancy. Compatibilization enhanced the thermal stability to some extent and remarkably delayed thermal oxidative degradation of flame-retardant PP. For PP containing 20 wt % flame retardant, the temperature at which the maximum weight loss rate occurred was enhanced by about 99 degrees C after compatibilization. The storage modulus and glass transition temperatures were elevated to different extents. Tensile strengths of samples reduced in the presence of flame retardant alone but in the additional presence of compatibilizer were restored to levels similar to those of pure PP. Elongation-at-break values, however, showed IFR concentration-dependent reductions that were less for compatibilized samples. Furthermore, the complex viscosity of a compatibilized PP melt turned slightly smaller, which is favorable to melt processing.

Substrate effect on the formation of hydrogels with heterogeneous network structure.

It was found that when an aqueous solution of vinyl monomers is polymerized on a hydrophobic substrate, obvious heterogeneity occurs in the region of the interface. This substrate effect was observed on polytetrafluroethylene (Teflon), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyvinylchloride (PVC), but not on hydrophilic substrates. Compared with synthesis on hydrophilic surfaces, the surfaces of hydrogels synthesized on a hydrophobic substrate exhibit a larger degree of swelling, a lower surface coefficient of friction and elastic modulus, weaker interfacial adhesion, and reduced interaction with biological cells. This substrate effect has been observed for many types of aqueous monomer solutions. It was found that the above properties are related to the loosely cross-linked architecture, containing some graft-like polymer chains, that is formed on the gel surface when the gel is prepared on a hydrophobic substrate. To understand the mechanism of the substrate effect, two novel optical methods, electric speckle pattern interferometry (ESPI) and real-time laser sheet refraction (RT-LSR), were developed. It was found that oxygen trapped in the composite interface between the monomer solution and rough hydrophobic substrates played an important role in the substrate effect.