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Biomedical subjects

Wei Zhu

Publications and source records attributed to Wei Zhu.

At least 37 records · Page 2Linked to original sources
PubMed2006

Keyhole approach surgery for petroclival meningioma.

BACKGROUND: In China, the feasibility of keyhole approach in surgical treatment of petroclival meningioma has not been well evaluated. This report summarized our experience in 25 patients with petroclival meningioma who had been treated with keyhole approach surgery. METHODS: From July 2000 to July 2005, 25 patients with petroclival meningioma were subjected to resection via subtemporal, retrosigmoid or combined keyhole approaches. The extent of tumor resection was evaluated by MRI 3 months after surgery, and postoperative complications were investigated. RESULTS: The maximum diameter of tumors ranged from 2 to 7 cm (mean, 4.5 cm). Gross total resection (GTR) was achieved in 14 patients, giving a GTR rate of 56%. Subtotal resection (STR) was carried out in 8 patients and partial resection in 3. Thirteen patients kept normal neurological status, whereas others suffered from cranial nerve deficits (VII, VII, III and lower CN). One patient died in the postoperative period. CONCLUSIONS: Keyhole approach surgery, especially the combined keyhole approach is suitable for the treatment of petroclival meningioma. It provides easy and quick access to the supra- and infratentorial juxta-clival region without drilling of the petrous bone. Complications related to the approach can be minimized.

Adult↗
PubMed2006

Shape evolution and size-controllable synthesis of Cu2O octahedra and their morphology-dependent photocatalytic properties.

Octahedral Cu(2)O crystals with tunable edge length were synthesized by reducing copper hydroxide with hydrazine without using any surfactant. Systematic experiments were carried out to investigate the factors which impact on the morphology and size of the products. The molar ratios of the reagents (NH(3):Cu(2+) and OH(-):Cu(2+)) determined the morphology and size of the corresponding products via affecting the coordination between NH(3) and Cu(2+). It is demonstrated that the ratio of growth rate along 111 versus 100 was varied by adjusting the molar ratio of NH(3) to Cu(2+), thus Cu(2)O crystals with different morphologies such as spheres, cubelike, and octahedra were obtained. The edge lengths of octahedra can be easily tuned from 130 to 600 nm by adjusting the molar ratio of OH(-) to Cu(2+). It is an effective and facile method for the controlled synthesis of octahedral Cu(2)O. The obtained octahedral Cu(2)O particles show improved ability on adsorption and photodegradation of methyl orange compared with cubic Cu(2)O particles.

Journal Article↗
PubMed2006

Ab initio and molecular dynamics studies of crystalline TNAD (trans-1,4,5,8-tetranitro-1,4,5,8-tetraazadecalin).

The structural and electronic properties of the energetic crystal TNAD (trans-1,4,5,8-tetranitro-1,4,5,8- tetraazadecalin) have been studied using plane-wave ab initio calculations based on the density function theory method with the ultrasoft pseudopotentials. It is found that the predicted crystal structure is in good agreement with experimental data and there are strong inter- and intramolecular interactions in bulk TNAD. Band structure calculations indicate that TNAD is an insulator with the band gap of ca. 3.3 eV. The hydrostatic compression effect on TNAD has been studied in the pressure range of 0-600 GPa. The results show that a pressure less than 10 GPa does not significantly change the geometric parameters, charge distributions, and electronic bands. When the pressure is over 10 GPa, increasing the pressure determines significant changes of the geometrical and electronic structures and large broadening of the electronic bands together with a sharp decrease of the band gap. Isothermal-isobaric molecular dynamics simulations at atmospheric pressure were further performed on the TNAD crystal in the temperature range 5-500 K. Average equilibrium lattice parameters and elastic properties as functions of temperature were determined. The thermal expansion coefficients calculated for the crystal indicate anisotropic behavior with the largest expansion along the b axis.

Journal Article↗
PubMed2006

A reverse cation-exchange route to hollow PbSe nanospheres evolving from Se/Ag2Se core/shell colloids.

A reverse cation-exchange approach for the synthesis of hollow PbSe nanospheres is successfully established. This route involves a new strategy of a stepwise, in-situ template-based evolution from spherical amorphous Se colloids to Se/Ag(2)Se core/shell colloids, then to hollow PbSe nanospheres. Se colloids are prepared as the initial product by utilizing the chelation of ethylenediamine to bulk Se. They are converted into Se/Ag(2)Se core/shell colloids through the reaction with Ag(+) in ethylene glycol. During the conversion from Ag(2)Se shell to PbSe shell, a small amount of tributylphosphine is crucial as the capping agent. The characterization results, including XRD, SEM, TEM, HRTEM, and EDX, reveal that hollow PbSe nanospheres with polycrystalline and cubic structure are prepared. The corresponding optical band gap is calculated to be 0.56 eV. This conformation is potentially beneficial to the improvement concerning the applications of PbSe nanostructures.

Journal Article↗
PubMed2006

Intron gain and loss in segmentally duplicated genes in rice.

BACKGROUND: Introns are under less selection pressure than exons, and consequently, intronic sequences have a higher rate of gain and loss than exons. In a number of plant species, a large portion of the genome has been segmentally duplicated, giving rise to a large set of duplicated genes. The recent completion of the rice genome in which segmental duplication has been documented has allowed us to investigate intron evolution within rice, a diploid monocotyledonous species. RESULTS: Analysis of segmental duplication in rice revealed that 159 Mb of the 371 Mb genome and 21,570 of the 43,719 non-transposable element-related genes were contained within a duplicated region. In these duplicated regions, 3,101 collinear paired genes were present. Using this set of segmentally duplicated genes, we investigated intron evolution from full-length cDNA-supported non-transposable element-related gene models of rice. Using gene pairs that have an ortholog in the dicotyledonous model species Arabidopsis thaliana, we identified more intron loss (49 introns within 35 gene pairs) than intron gain (5 introns within 5 gene pairs) following segmental duplication. We were unable to demonstrate preferential intron loss at the 3' end of genes as previously reported in mammalian genomes. However, we did find that the four nucleotides of exons that flank lost introns had less frequently used 4-mers. CONCLUSION: We observed that intron evolution within rice following segmental duplication is largely dominated by intron loss. In two of the five cases of intron gain within segmentally duplicated genes, the gained sequences were similar to transposable elements.

Amino Acid Sequence↗
PubMed2006

Norlaudanosoline and nicotine increase endogenous ganglionic morphine levels: nicotine addiction.

1. Given the presence of morphine, its metabolites and precursors, e.g., norlaudanosoline, in mammalian and invertebrate tissues, it became important to determine if exposing normal excised ganglia to norlaudanosoline would result in increasing endogenous morphine levels. 2. Mytilus edulis pedal ganglia contain 2.2 +/- 0.41 ng/g wet weight morphine as determined by high pressure liquid chromatography coupled to electrochemical detection and radioimmunoassay. 3. Incubation of M. edulis pedal ganglia with norlaudanosoline, a morphine precursor, resulted in a concentration- and time-dependent statistical increase in endogenous morphine levels (6.9 +/- 1.24 ng/g). 4. Injection of animals with nicotine also increased endogenous morphine levels in a manner that was antagonized by atropine, suggesting that nicotine addiction may be related to altering endogenous morphine levels in mammals. 5. We surmise that norlaudanosoline is being converted to morphine, demonstrating that invertebrate neural tissue can synthesize morphine.

Animals↗
PubMed2006

Molecular dynamics simulations for pure epsilon-CL-20 and epsilon-CL-20-based PBXs.

Molecular dynamics has been employed to simulate the well-known high energy density compound epsilon-CL-20 (hexanitrohexaazaisowurtzitane) crystal and 12 epsilon-CL-20-based PBXs (polymer bonded explosives) with four kinds of typical fluorine polymers, i.e., polyvinylidenedifluoride, polychlorotrifluoroethylene, fluorine rubber (F(2311)), and fluorine resin (F(2314)) individually. The elastic coefficients, isotropic mechanical properties (tensile moduli, bulk moduli, shear moduli, and poission's ratios), and bonding energy are first reported for epsilon-CL-20 crystal and epsilon-CL-20-based polymer bonded explosives (PBXs). The mechanical properties of epsilon-CL-20 can be effectively improved by blending with a small amount of fluorine polymers, and the whole effect of the adding fluorine polymers to improve mechanical properties of PBXs along the three crystalline surfaces of epsilon-CL-20 is found to be (100) approximately (001) > (010). The interaction between each of the crystalline surfaces and each of the fluorine polymers is different, and the ordering of binding energy for the three surfaces is (001) > (100) > (010); F(2314) always has the strongest binding ability with the three different surfaces. F(2314) can best improve the ductibility and tenacity of PBX when it is positioned on epsilon-CL-20 (001) crystal surface. The calculations on detonation performances for pure epsilon-CL-20 crystal and the four epsilon-CL-20-based PBXs show that adding a small amount of fluorine polymer into pure epsilon-CL-20 will lower detonation performance, but each detonation parameter of the obtained PBXs is still excellent.

Journal Article↗
PubMed2006

Interaction of SH2-Bbeta with RET is involved in signaling of GDNF-induced neurite outgrowth.

RET receptor signalling is essential for glial-cell-line-derived neurotrophic factor (GDNF)-induced survival and differentiation of various neurons such as mesencephalic neurons. To identify proteins that mediate RET-dependent signaling, yeast two-hybrid screening was performed with the intracellular domain of RET as bait. We identified a new interaction between RET and the adapter protein SH2-Bbeta. Upon GDNF stimulation of PC12-GFRalpha1-RET cells (that stably overexpress GDNF receptor alpha1 and RET), wild-type SH2-Bbeta co-immunoprecipitated with RET, whereas the dominant-negative SH2-Bbeta mutant R555E did not. RET interacted with endogenous SH2-Bbeta both in PC12-GFRalpha1-RET cells and in rat tissues. Mutagenesis analysis revealed that Tyr981 within the intracellular domain of RET was crucial for the interaction with SH2-Bbeta. Morphological evidence showed that SH2-Bbeta and RET colocalized in mesencephalic neurons. Furthermore, functional analysis indicated that overexpression of SH2-Bbeta facilitated GDNF-induced neurite outgrowth in both PC12-GFRalpha1-RET cells and cultured mesencephalic neurons, whereas the mutant R555E inhibited the effect. Moreover, inhibition of SH2-Bbeta expression by RNA interference caused a significant decrease of GDNF-induced neuronal differentiation in PC12-GFRalpha1-RET cells. Taken together, our results suggest that SH2-Bbeta is a new signaling molecule involved in GDNF-induced neurite outgrowth.

Adaptor Proteins, Signal Transducing↗
PubMed2006

[Early-mid-phase microsurgery for ruptured cerebral anterior circulating aneurysm].

OBJECTIVE: To evaluate clinical strategy and effect of early-mid-phase microsurgery for ruptured cerebral anterior circulating aneurysm. METHODS: Seventy-five patients presenting with anterior circulating aneurysmal subarachnoid hemorrhage (SAH) underwent early-mid-phase (within 3 days or 3-10 days) microsurgical clipping at Huashan Hospital between January 2001 and August 2004. Glasgow outcome scale (GOS) was conducted to evaluate patients' outcomes. RESULTS: Of 81 intracranial aneurysms, 77 lesions were clipped successfully, and 4 were wrapped. Good outcome was achieved in 53 cases, mild disability in 9 cases, severe disability in 7 cases, persistent vegetative state in 3 cases, and 3 patients (4%) died after surgery. The difference of GOS was statistically significant between patients in Hunt and Hess Grade I-III and Grade IV-V. However, there was no significant difference between early surgery and metaphase surgery. CONCLUSIONS: Early-mid-phase microsurgery for ruptured cerebral anterior circulating aneurysm is considered the feasible opinion.

Acute Disease↗
PubMed2006

Noggin regulation of bone morphogenetic protein (BMP) 2/7 heterodimer activity in vitro.

Bone morphogenic proteins (BMPs) are growth factors important for skeletal development and bone growth. Noggin, one of the soluble BMP antagonists, regulates the action of BMPs on mesenchymal precursor cells, partially through a feedback type of inhibition. In this study, we constructed a novel BMP2/7 'fusion gene' that encodes both BMP2 and BMP7 genes in tandem by a linker. Polymerase chain reaction (PCR) and Western blotting showed that the BMP2/7 fusion gene construct led to the production of BMP2/7 heterodimers in A549 'producer' cells. When applied to C2C12 myoblastic cells, BMP2/7 heterodimers increased alkaline phosphatase (ALP) activity and osteocalcin (OCN) expression (markers of osteoblastic differentiation) more effectively than either BMP2 or BMP7 homodimers. Moreover, this heterodimer induced significantly lower levels of Noggin expression in C2C12 cells than respective homodimers at similar doses. The addition of Noggin did not affect the heterodimer's activities in increasing osteoblastic differentiation in C2C12 cells. In contrast, BMP2 and BMP7 homodimers were largely inhibited by Noggin. Our finding suggests that the 'fusion gene' construct led to the production of bioactive BMP2/7 heterodimers, which were not antagonized by Noggin as effectively as it to BMP homodimers. The weaker Noggin antagonism on BMP heterodimers compared to homodimers may contribute to increased osteogenic potency of heterodimers in vitro and in vivo.

Alkaline Phosphatase↗
PubMed2006

Restoration of thumb opposition by transposing the flexsor pollicis brevis muscle: thirteen-year clinical application.

BACKGROUND: To repair late median nerve injury, many methods have been used in the past years. The aim of this study was to review a thirteen-year experience in restoration of thumb opposition by transposing flexor pollicis brevis muscle. METHODS: From July 1992 to August 2005, 63 patients without thumb opposition because of late median never injury were treated by transposing the flexor pollicis brevis muscle. All the patients had received primary nerve repair after the jnjury. The interval between the injury and the second operation was (1.87 +/- 2.31) years (6 months to 4.2 years). The patients were followed up for 3 to 48 [months mean (22.93 +/- 2.31) months]. A functional evaluation system designed in 1992 were used to estimate the outcomes of the patients. RESULTS: All the patients gained excellent functional results without complications and disabilities during follow-up. CONCLUSIONS: Restoration of thumb opposition by transposing flexsor pollicis brevis muscle has the following advantages: 1. Operative trauma is minimal; 2. It is not necessary to transpose other tendons; 3. Except for the thumb in opposition, movements of other fingers and the wrist are not restricted postoperatively.

Adolescent↗
PubMed2006

Feature extraction in the analysis of proteomic mass spectra.

Feature extraction or biomarker selection is a critical step in disease diagnosis and knowledge discovery based on protein MS. Many studies have discussed the classification methods applied in proteomics; however, few could be found to address feature extraction in detail. In this paper, we developed a systematic approach for the extraction of mass spectrum peak apex and peak area with special emphasis on noise filtration and peak calibration. Application to a head and neck cancer data generated at the Eastern Virginia Medical School [Wadsworth, J. T., Somers, K. D., Cazares, L. H., Malik, G. et al.., Clin. Cancer Res. 2004, 10, 1625-1632] revealed that the new feature extraction method would yield consistent and highly discriminatory biomarkers.

Biomarkers, Tumor↗
PubMed2006

Preservation of mitochondrial structure and function after cardioplegic arrest in the neonate using a selective mitochondrial KATP channel opener.

BACKGROUND: Mitochondrial dysfunction may contribute to early postoperative neonatal heart dysfunction. Diazoxide, a mitochondrial-selective adenosine triphosphate-sensitive potassium-channel opener, is associated with mitochondrial preservation after cardioplegic arrest. We evaluated the mitochondrial-protective effect of diazoxide in terms of mitochondrial structure and function after neonatal cardioplegic arrest. METHODS: Newborn piglets (age, approximately 14 days) underwent cardiopulmonary bypass and 60 minutes of cardioplegic arrest using cold crystalloid cardioplegic solution (CCP, n = 5) or cold crystalloid cardioplegic solution with diazoxide (CCP+D, n = 5). After 6 hours of recovery, myocardium was harvested. Control myocardium from piglets that did not undergo cardiopulmonary bypass (non-CPB, n = 5) was obtained. RESULTS: Cardioplegic arrest was associated with translocation of Bax to the mitochondria, which was not prevented by diazoxide. Nevertheless, by electron microscopy, CCP-associated remodeling of mitochondrial structure was subjectively diminished in CCP+D hearts. In addition, CCP-associated mitochondrial permeabilization and cytochrome c release into the cytosol were prevented with CCP+D (p < 0.05). In vitro oxygen consumption of isolated mitochondria demonstrated deficient function of mitochondrial complex I in CCP, but it was preserved in the CCP+D myocardial mitochondria (p < 0.05). Complex II and IV activity was not different among groups. In parallel with impaired complex I function, the cardiac adenosine triphosphate content was diminished in CCP hearts, but well maintained in CCP+D hearts (p < 0.05). CONCLUSIONS: Although early apoptotic signaling events (Bax translocation) are not prevented by diazoxide, addition of the mitochondrial-selective adenosine triphosphate-sensitive potassium-channel opener to the cardioplegic solution is associated with protection of mitochondrial structural and functional integrity in a clinically relevant model of neonatal cardiac surgery. The mitochondrial-protective effects of diazoxide may contribute to improved postoperative myocardial function in the neonate.

Adenosine Triphosphate↗
PubMed2006

Nuclear and cytoplasmic mRNA quantification by SYBR green based real-time RT-PCR.

Measurement of the steady-state abundance of nuclear and cytoplasmic RNA requires efficient subcellular fractionation and RNA recovery coupled with accurate quantification of individual RNA species. Detergent lysis of tissue culture cells provides a simple fractionation procedure that can be optimized to individual cell lines. The large dynamic range, extreme sensitivity, high sequence-specificity, and fast turn-around time has allowed real-time reverse transcription polymerase chain reaction (real-time RT-PCR) to become a standard tool for mRNA quantification. Among the different chemistries used for PCR product detection during amplification, DNA binding dyes such as SYBR Green I are simple, versatile, and yet highly reliable and least expensive. With attention to primer design and cycling conditions, virtually any mRNA species can be accurately quantified from even minute quantities of starting RNA. This method provides an accurate and efficient procedure for estimating the relative ratios of nuclear and cytoplasmic RNA concentrations.

Benzothiazoles↗
PubMed2006

Studies on biodegradation of nicotine by Arthrobacter sp. strain HF-2.

A nicotine-degrading bacterium, strain HF-2, was isolated from tobacco waste-contaminated soil and identified as a member of Arthrobacter sp. based on morphology, physiological tests, 16S rDNA sequence and phylogenetic characteristics. At thermal denaturation test indicated that the G + C mol% of strain HF-1 was 63.5. The relationship between the growth of the isolate and the nicotine degradation suggested that strain HF-2 could utilize nicotine as sole sources of carbon, nitrogen and energy. Blue pigment was observed during the nicotine degradation by strain HF-2. The isolate grew well at 20 to 33 degrees C, initial pH 6.5 to 8.0 and 0.5 to 2.0 g L-1 of nicotine concentration in the nicotine inorganic salt media. The maximum growth and nicotine degradation occurred at 30 degrees C, initial pH 7.0 and 0.7 g.L-1 of nicotine concentration in media under natural incubation condition. Strain HF-2 could degrade 100% of nicotine under the optimized incubation conditions for 43 h. The concentrations of nicotine were monitored by high performance liquid chromatography. This study demonstrates Arthrobacter sp. strain HF-2 had a great ability to degrade nicotine, and it may be available for the application to the bioremediation of environments contaminated by tobacco waste.

Arthrobacter↗
PubMed2006

Bayesian optimal designs for a quantal dose-response study with potentially missing observations.

In a dose-response study, there are frequently multiple goals and not all planned observations are realized at the end of the study. Subjects drop out and the initial design can be quite different from the final design. Consequently, the final design can be inefficient. Single- and multiple-objective Bayesian optimal designs that account for potentially missing observations in quantal response models were recently proposed in Baek (2005). In this work, we investigate the efficiencies of the conventional optimal designs that do not incorporate potential missing information relative to our proposed designs. Furthermore, we examine the impact of restricted dose range on the resulting optimal designs. As an application, we used missing data information from a study by Yocum et al. (2003) to design a study for estimating dose levels of tacrolimus that will result in a certain percentage of rheumatoid arthritis patients having an ACR20 response at 6 months.

Algorithms↗
PubMed2006

Modern biologics used in orthopaedic surgery.

PURPOSE OF REVIEW: In this review we summarize some of the most recent research in the area of local bone regeneration. These innovations may be relevant in the orthopaedic treatment of patients with rheumatoid arthritis, or other inflammatory arthridities, as such patients often present with inadequate bone stock. RECENT FINDINGS: Bone grafting remains the standard treatment for bone deficiency. Several new approaches, such as the use of concentrated blood products or osteoprogenitor cells in conjunction with grafts, have been developed but remain to be tested clinically. Experimental studies have elucidated important aspects of the biology of bone graft remodeling and osteoprogenitor cell differentiation. Materials that can serve as graft alternatives continue to be developed. Positive experimental findings have resulted from combinations of such materials with osteoprogenitor cells or osteoinductive factors such as bone morphogenetic proteins. SUMMARY: While few studies to date have examined the specific use of these new strategies in the setting of rheumatoid arthritis, many hold promise for patients with rheumatoid arthritis and other inflammatory and metabolic conditions that affect bone quality and quantity.

Arthritis↗