[Transpedicular bone graft for the treatment of thoracolumbar vertebral fractures through Wiltse approach].

OBJECTIVE: To explore methods and therapeutic effects of transpedicular bone graft in treating thoracolumbar fractures through Wiltse approach. METHODS: From March 2009 to February 2012,56 patients with thoracolumbar fractures were treated by transpedicular bone graft through Wiltse approach. Among them, there were 36 males and 20 females, ranging in age from 14 to 55 years old (mean, 41 years old). The time from injury to operation from 2 to 15 d (mean,3 d). Twenty-five cases were caused by falling down, 7 cases were caused by slipping, 20 cases were caused by car accident and 4 cases were caused by crush trauma. MRI was performed before operation to exclude pathological fracture. The distance between multifidus muscle and longissimus to midcourt line was measured. Self-made trocar was applied in operation. According to AO classification,there were 33 cases with type A1 compression fracture,5 cases with type A2 cleavage fracture and 18 cases with type A3 burst fracture. Sixteen cases of the 56 cases combined with spinal cord injury. Based on Frankel neurologic grading system, preoperative neurological function was grade B in 5 cases, grade C in 2 cases, gade D in 9 cases. Preoperative Denis gading were P5. Frankel and lumbago Denis clssification were used to evaluate neurological function and lumbago. The imaging data before, after operation and the latest follow-up were used to evaluate correction vision. RESULTS: All patients were followed up over 24 months. At the time of the latest follow-up, Frankel B were 3 cases, Frankel C were 2 cases, Frankel D were 4 cases and Frankel E were 7 cases. According to lumbago Denis clssification, P1 (painlessness) were 32 cases, P2 ( slight pain without treatment) were 18 cases, P3 ( moderate pain and taking medicine occasionally) were 6 cases. The anterior vertebral height improved from preoperative (13.38 +/- 4.72)mm to postoperative (22.18 +/- 1.44)mm. The Cobb's angle decreased from preoperative (28.39 +/- 2.64) degrees to (10.07 +/- 3.05) degrees. There were no nails broken, rod broken, internal fixation lossen and vertebral body recompression. CONCLUSION: Transpedicular bone graft for thoracolumbar fractures through Wiltse approach can reduce intraoperative blood loss and postoperative complications, and aviod "eggshell" vertebral body. Mastering revealed way, drafting detailed preoperative plan and eariler exercise is the key to the success of treatment.

A simple RP-HPLC method for the simultaneous determination of curcumin and its prodrug, curcumin didecanoate, in rat plasma and the application to pharmacokinetic study.

A high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of curcumin and its prodrug, curcumin didecanoate (CurDD), in rat plasma. The analytes were extracted by ethyl acetate following the addition of sodium dodecyl sulfate, and separated on a reverse-phase C(18) column using a gradient mobile phase system of acetonitrile-tetrahydrofuran-water containing 0.1% formic acid. Detection by UV absorption at 425 nm gave a lower limit of quantitation (LLOQ) of 5 and 10 ng/mL for curcumin and CurDD in 50 µL of plasma, respectively. Intra- and inter-day precisions of quality control samples except those at LLOQ were within 15% for curcumin and CurDD, respectively, and the accuracies for both compounds were between 93.9 and 108%. The method was successfully applied to determine plasma concentration-time curves of curcumin and CurDD in rats following intravenous (i.v.) administration of curcumin or CurDD at doses of 1 mg/kg (calculated as curcumin). The results suggested that i.v. dosed CurDD provided sustained plasma levels of curcumin.

The proline-rich domain of tau plays a role in interactions with actin.

BACKGROUND: The microtubule-associated protein tau is able to interact with actin and serves as a cross-linker between the microtubule and actin networks. The microtubule-binding domain of tau is known to be involved in its interaction with actin. Here, we address the question of whether the other domains of tau also interact with actin. RESULTS: Several tau truncation and deletion mutants were constructed, namely N-terminal region (tauN), proline-rich domain (tauPRD), microtubule binding domain (tauMTBD) and C-terminal region (tauC) truncation mutants, and microtubule binding domain (tauDeltaMTBD) and proline-rich domain/microtubule binding domain (tauDeltaPRD&MTBD) deletion mutants. The proline-rich domain truncation mutant (tauPRD) and the microtubule binding domain deletion mutant (tauDeltaMTBD) promoted the formation of actin filaments. However, actin assembly was not observed in the presence of the N-terminal and C-terminal truncation mutants. These results indicate that the proline-rich domain is involved in the association of tau with G-actin. Furthermore, results from co-sedimentation, solid phase assays and electron microscopy showed that the proline-rich domain is also capable of binding to F-actin and inducing F-actin bundles. Using solid phase assays to analyze apparent dissociation constants for the binding of tau and its mutants to F-actin resulted in a sequence of affinity for F-actin: tau >> microtubule binding domain > proline-rich domain. Moreover, we observed that the proline-rich domain was able to associate with and bundle F-actin at physiological ionic strength. CONCLUSION: The proline-rich domain is a functional structure playing a role in the association of tau with actin. This suggests that the proline-rich domain and the microtubule-binding domain of tau are both involved in binding to and bundling F-actin.

Tubulin assembly is disordered in a hypogeomagnetic field.

Although the effect of a magnetic field on functions of many proteins has been reported, tubulin assembly in a hypogeomagnetic field (HGMF) has not yet been characterized. Here, we show disorder in tubulin self-assembly in an HGMF. Absorbance at 350 nm, commonly used to monitor tubulin self-assembly, was altered in the HGMF, providing evidence for the effects of HGMF on tubulin. Measurements of intrinsic fluorescence (335 nm) also revealed a disordered change in tubulin conformation during assembly in the HGMF. Under the same conditions, microtubule-like filaments were not observed by electron microscopy, with the exception of amorphous oligomers. Incubation of tubulin with tau in the natural geomagnetic field (GMF) yielded microtubule-like filaments, while only amorphous oligomers were observed following the incubation in the HGMF. This distinction suggests that tubulin assembly depends upon the GMF, and that elimination of the GMF induces disorder in tubulin organization.

Binding to the minor groove of the double-strand, tau protein prevents DNA from damage by peroxidation.

Tau, an important microtubule associated protein, has been found to bind to DNA, and to be localized in the nuclei of both neurons and some non-neuronal cells. Here, using electrophoretic mobility shifting assay (EMSA) in the presence of DNA with different chain-lengths, we observed that tau protein favored binding to a 13 bp or a longer polynucleotide. The results from atomic force microscopy also showed that tau protein preferred a 13 bp polynucleotide to a 12 bp or shorter polynucleotide. In a competitive assay, a minor groove binder distamycin A was able to replace the bound tau from the DNA double helix, indicating that tau protein binds to the minor groove. Tau protein was able to protect the double-strand from digestion in the presence of DNase I that was bound to the minor groove. On the other hand, a major groove binder methyl green as a negative competitor exhibited little effect on the retardation of tau-DNA complex in EMSA. This further indicates the DNA minor groove as the binding site for tau protein. EMSA with truncated tau proteins showed that both the proline-rich domain (PRD) and the microtubule-binding domain (MTBD) contributed to the interaction with DNA; that is to say, both PRD and MTBD bound to the minor groove of DNA and bent the double-strand, as observed by electron microscopy. To investigate whether tau protein is able to prevent DNA from the impairment by hydroxyl free radical, the chemiluminescence emitted by the phen-Cu/H(2)O(2)/ascorbate was measured. The emission intensity of the luminescence was markedly decreased when tau protein was present, suggesting a significant protection of DNA from the damage in the presence of hydroxyl free radical.

Amyloid-like aggregates of neuronal tau induced by formaldehyde promote apoptosis of neuronal cells.

BACKGROUND: The microtubule associated protein tau is the principle component of neurofibrillar tangles, which are a characteristic marker in the pathology of Alzheimer's disease; similar lesions are also observed after chronic alcohol abuse. Formaldehyde is a common environmental contaminant and also a metabolite of methanol. Although many studies have been done on methanol and formaldehyde intoxication, none of these address the contribution of protein misfolding to the pathological mechanism, in particular the effect of formaldehyde on protein conformation and polymerization. RESULTS: We found that unlike the typical globular protein BSA, the natively-unfolded structure of human neuronal tau was induced to misfold and aggregate in the presence of ~0.01% formaldehyde, leading to formation of amyloid-like deposits that appeared as densely staining granules by electron microscopy and atomic force microscopy, and bound the amyloid-specific dyes thioflavin T and Congo Red. The amyloid-like aggregates of tau were found to induce apoptosis in the neurotypic cell line SH-SY5Y and in rat hippocampal cells, as observed by Hoechst 33258 staining, assay of caspase-3 activity, and flow cytometry using Annexin V and Propidium Iodide staining. Further experiments showed that Congo Red specifically attenuated the caspase-3 activity induced by amyloid-like deposits of tau. CONCLUSION: The results suggest that low concentrations of formaldehyde can induce human tau protein to form neurotoxic aggregates, which could play a role in the induction of tauopathies.

Human protein tau represses DNA replication in vitro.

Here, in the experiments of both PCR and real-time PCR, a repression of DNA amplification was observed in the presence of protein tau. Furthermore, a strong repression appeared when an in vitro DNA replication assay was performed at the physiological temperature (37 degrees C). The incorporation of dNTP was markedly decreased to approximately 12% of control by the presence of tau23 and to approximately 15% by tau40. In the competitive experiments, the PCR product could be restored when the competitor DNA was added, indicating that the association of tau with the template gave rise to the repression. However, tau did not repress the yield of RNA in transcription, suggesting that tau was replaced or ejected from the template by the elongating T7 RNA polymerase.