Biomedical subjects

J Zhang

Publications and source records attributed to J Zhang.

At least 91 records · Page 5Linked to original sources

PubMed2005

The enhancement of cell adherence and inducement of neurite outgrowth of dorsal root ganglia co-cultured with hyaluronic acid hydrogels modified with Nogo-66 receptor antagonist in vitro.

Hyaluronic acid hydrogels modified with polyclonal anti-Nogo-66 receptor antibody were developed in order to promote regeneration in the injured CNS. These modified hydrogels were intended not only to deliver antibodies, but also to serve as a scaffold for neural regeneration following their implantation into injured tissue. Since unmodified hyaluronic acid-hydrogels do not support cell attachment, the gels were modified with polyclonal anti-Nogo-66 receptor with the aim of altering the surface properties of the gels in such a way as to improve neuronal adherence and survival. After evaluating the immobilization efficiency of the system, chicken dorsal root ganglia and dorsal root ganglia cells were planted on the surface of the modified gels to determine cell viability. Dorsal root ganglia were also cultured close to the gels in order to assay the inducement of neurite outgrowth. In dorsal root ganglia and cell viability assay, dorsal root ganglia and neuron cells could adhere to the modified hydrogels and survive well, but it did not happen to unmodified hydrogels. After 72 h, these attached cells were stained positively with immuno-staining for neurofilament. Neurite outgrowth inducement assay showed that the number and length of dorsal root ganglia neurites on the side toward modified hydrogels were significantly more than that on the opposite side (both P<0.01). The results reveal that hyaluronic acid-hydrogels modified with anti-Nogo-66 receptor can support neural cell attachment and survival in vitro. Furthermore, this system can greatly induce neurite outgrowth. The results also indicate that this modified hydrogels have potential to repair injury in the CNS.

Animals↗

PubMed2005

Adsorption of polyelectrolyte/surfactant mixtures at the air-solution interface: poly(ethyleneimine)/sodium dodecyl sulfate.

Neutron reflectivity and surface tension have been used to characterize the adsorption of the polyelectrolyte/ionic surfactant mixture of poly(ethyleneimine) (PEI) and sodium dodecyl sulfate (SDS) at the air-water interface. The surface tension behavior and adsorption patterns show a strong dependence upon the solution pH. However, the SDS adsorption at the interface is unexpectedly most pronounced when the pH is high (when the polymer is essentially a neutral polymer) and when the polymer architecture is branched rather than linear. For both the branched and the linear PEI polymer/surfactant complex formation results in a significant enhancement of the amount of SDS at the interface, down to surfactant concentrations approximately 10(-6) M. For the branched PEI a transition from a monolayer to a multilayer adsorption is observed, which depends on surfactant concentration and pH. In contrast, for the linear polymer, only monolayer adsorption is observed. This substantial increase in the surface activity of SDS by complexation with PEI results in spontaneous emulsification of hexadecane in water and the efficient wetting of hydrophobic substrates such as Teflon. In regions close to charge neutralization the multilayer adsorption is accentuated, and more extensively ordered structures, giving rise to Bragg peaks in the reflectivity data, are evident.

Journal Article↗

PubMed2005

Direct acceleration of solid-density plasma bunch by ultraintense laser.

The interaction of a petawatt laser with a small solid-density plasma bunch is studied by particle-in-cell simulation. It is shown that when irradiated by a laser of intensity >10(21) W/cm2, a dense plasma bunch of micrometer size can be efficiently accelerated. The kinetic energy of the ions in the high-density region of the plasma bunch can exceed ten MeV at a density in the 10(23)-cm(-3) level. Having a flux density orders of magnitude higher than that of the traditional charged-particle pulses, the laser-accelerated plasma bunch can have a wide range of applications. In particular, such a dense energetic plasma bunch impinging on the compressed fuel in inertial fusion can significantly enhance the nuclear-reaction cross section and is thus a promising alternative for fast ignition.

Journal Article↗

PubMed2005

Measurements of the branching fraction and polarization in B+ --> rho+ K*0 decays.

We present the results of a study of the charmless vector-vector decay B+ --> rho+ K*0, based on 253 fb(-1) of data collected with the Belle detector at the KEKB asymmetric-energy e+ e- collider. We obtain the branching fraction B(B+ --> rho+ K*0) = [8.9 +/- 1.7(stat) +/- 1.2(syst)] x 10(-6). We also perform a helicity analysis of the rho and K* vector mesons, and obtain the longitudinal polarization fraction f(L)(B+ --> rho+ K*0) = 0.43 +/- 0.11(stat)(-0.02)(+0.05) (syst).

Journal Article↗

PubMed2005

Maxillofacial Injury Severity Score: proposal of a new scoring system.

In this study a new injury severity score system, the Maxillofacial Injury Severity Score (MFISS), was developed to evaluate the characteristics of injury from maxillofacial trauma. Nine hundred and two cases of maxillofacial trauma were included in this study to evaluate injury severity using the MFISS, which was designed on the basis of Abbreviated Injury Scale, 1990 revision (AIS-90), and defined as the product of the sum of the three highest maxillofacial AIS scores and the sum of the injury severity scores for three maxillofacial functional parameters, malocclusion (MO), limited mouth opening (LMO), and facial deformity (FD). The correlation analysis was undertaken with the dependent factor of cost and number of days of stay in hospital. The results demonstrated a significant difference (P < 0.01) between bone and soft-tissue injuries and among various regional fractures. There was correlation (P < 0.01) between the MFISS and the cost of treatment and days of stay in hospital. The newly established MFISS thus characterizes maxillofacial injury severity while reflecting the management costs and treatment complexity.

Adolescent↗

PubMed2005

Conductance of ion channels and nanopores with charged walls: a toy model.

We consider ion transport through protein ion channels in lipid membranes and water-filled nanopores in silicon films. It is known that, due to the large ratio of dielectric constants of water and the surrounding material, an ion placed inside the channel faces a large electrostatic self-energy barrier. The barrier leads to an exponentially large resistance of the channel. We study reduction of the electrostatic barrier by immobile charges located on the internal walls of the channel. We show that the barrier practically vanishes already at relatively small concentration of wall charges.

Biophysics↗

PubMed2005

Intrapallidal lipopolysaccharide injection increases iron and ferritin levels in glia of the rat substantia nigra and induces locomotor deficits.

Increasing evidence suggests that abnormal iron handling may be involved in the pathogenesis of Parkinson's disease. The present study investigates the role of iron and the iron-storage protein ferritin in inflammation-induced degeneration of dopaminergic neurons of the substantia nigra pars compacta. Injection of lipopolysaccharide into the globus pallidus of young and middle-aged rats substantially decreased tyrosine hydroxylase immunostaining in substantia nigra pars compacta four weeks after injection. Loss of tyrosine hydroxylase expression was accompanied by increased iron and ferritin levels in glial cells of the substantia nigra pars reticulata. Despite greater increases in nigral iron levels, ferritin induction was less pronounced in older rats, suggesting the regulation of ferritin was compromised with age. Automated movement tracking analyses showed that young rats recovered from LPS-induced locomotor deficits within four weeks, yet older rats failed to improve on measures of speed and total distance moved. Intrapallidal lipopolysaccharide injection also increased expression of alpha-synuclein and ubiquitin in tyrosine hydroxylase-positive neurons of the substantia nigra pars compacta. These results suggest that pallidal inflammation significantly increases stress on dopamine-containing neurons in the substantia nigra pars compacta. Alterations in nigral iron levels and protein handing may increase the vulnerability of nigral neurons to degenerative processes.

Aging↗

PubMed2005

Quantitative assessments of the effect of bilateral subthalamic stimulation on multiple aspects of sensorimotor function for patients with Parkinson's disease.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is effective for the treatment of advanced Parkinson's disease. Most studies have evaluated the effectiveness of DBS of the STN using clinical motor scores or simple timed tests of motor function. There have been few studies that quantitatively assessed the outcome of STN DBS using multiple testing paradigms. In the current study, 11 patients who had bilateral STN DBS were quantitatively evaluated under four conditions using gait, postural control, and gait initiation. The four conditions included the medication on/stimulation on (M_on/S_on), medication on/stimulation off (M_on/S_off), medication off/stimulation on (M_off/S_on), and medication off/stimulation off (M_off/S_off) conditions. DBS of the STN significantly increased walking speed with and without levodopa, but had no influence on the cadence. The addition of levodopa had a minimal additional effect on walking speed. The effect of STN DBS on gait initiation approached the significant level. The mean values of lateral body sway during quiet standing increased moderately with medication and/or DBS, but the changes were not statistically significant. Future studies need to determine whether or not there is a potential negative effect of STN DBS on the postural control.

Adult↗

PubMed2005

Lines of dense nanoparticle colloidal suspensions evaporating on a flat surface: formation of non-uniform dried deposits.

Line evaporation of dense nanoparticle suspensions is studied theoretically and experimentally. The 2-D lines are drawn by a pen-like nozzle continuously dispensing a commercially available concentrated organic suspension (50 wt%; 4.3 vol%) of 5 nm gold nanoparticles in toluene solvent. Such particle-containing lines show promise for industrial applications where circuits are inkjet-printed and heat-treated to dry off the organic solvent and sinter the nanoparticles, thus producing a continuous electrically conducting path. The employed nanosuspension displays spontaneous thickening upon contact with a solid surface in the ambient atmosphere, and thus does not dry according to the well-established coffee-stain forming mechanism applicable to dilute particle suspensions. In the present work, model lines ( approximately 1 mm width) are studied to elucidate the drying peculiarities of such nanoparticle slurries. These scaled-up lines allow detailed spatial measurements of their topography throughout their prolonged evaporation period, and make possible direct comparisons between experiment and theory. The results show the particle deposits formed by evaporative drying of these lines to be of non-uniform thickness with a dent in the middle of the lateral cross-section. Formation of this practically undesirable landscape is attributed to the highly non-uniform evaporative character of sessile or pendent liquid lines, which results in a non-uniform consolidation of the porous phase formed upon contact with the solid surface. The formulated description of the shape changing process, as done in the framework of the consolidation theory, yields predicted deposit speck shapes that compare favorably with the temporally resolved experimental data.

Journal Article↗

PubMed2005

Chain dynamics in a chiral C phase by deuteron spin relaxation study.

Molecular reorientations and internal conformational transitions of an aligned chiral liquid crystal (LC) 10B1M7 are studied by means of deuterium spin-lattice relaxation in its smectic A (SmA) and smectic C* (SmC*) phase. The motional model which is applicable to uniaxial phases of many LCs is found to be adequate even when the phase is a tilted SmC* phase. The deuterium NMR spectrum in this phase cannot discern rotations of the molecular director about the pitch axis. The basic assumption is that the phase biaxiality is practically unobservable. However, the relaxation rates can be accounted for by the tilt angle between the molecular director and the layer normal in the SmC* phase. The tumbling motion appears to show a higher activation energy upon entering from the uniaxial SmA into the SmC* phase.

Journal Article↗

PubMed2005

Bilateral subthalamic stimulation improves gait initiation in patients with Parkinson's disease.

Impaired gait initiation is one of the typical sign of advanced Parkinson's disease (PD). This is the first study to examine quantitatively the effect of deep brain stimulation of the subthalamic nucleus on the performance of gait initiation for patients with advanced PD. A total of 11 patients after surgery of bilateral deep brain stimulation of the subthalamic nucleus (STN) were tested in both the deep brain stimulation (DBS) ON and OFF conditions and/or in both the medication ON (i.e., with the usual dosage of antiparkinsonian medications administered) and OFF (i.e., with the usual dosage of antiparkinsonian medications withheld) conditions. DBS had no effect on the onset of anticipatory postural adjustment (APA). The effect of DBS approached significant level for the onset of swing foot lifting, but reached significant level for the delay of swing foot lifting. DBS significantly increased the amplitude of the APA, amplitude of reactive shear forces on both feet, and amplitude of COP in both anterior-posterior and medial-lateral directions. It is concluded that DBS significantly improved the performance of patients with advanced PD in gait initiation.

Adult↗

PubMed2005

Evidence for hydrogen desorption through both interdimer and intradimer paths from Si(100)-(2 x 1).

Despite intensive work there are still controversial issues about desorption and adsorption of hydrogen on Si(100)-(2 x 1). In particular, the relative importance of the various interdimer- and intradimer-desorption paths is not clear. Nanosecond-pulse-laser desorption data have been used to argue that the 4H interdimer path is important, while data from thermal-desorption time-of-flight measurements suggest a large translationally hot contribution which cannot arise from the 4H interdimer path. The observation of a translationally hot desorption fraction at low to medium coverage can be accounted for by including the 2H interdimer path in quantum dynamical calculations. In this paper we investigate this issue further and present evidence that supports the inclusion of the intradimer path. Specifically, our results show that the intradimer and 3H interdimer paths provide the major contributions to the translationally hot fraction in the desorbate. Our conclusions are based on density-functional calculations of hydrogen translational excitation, mean-field analysis of thermal-desorption experiments over a range of ramp rate, and Monte Carlo simulations of nanosecond-pulse-laser experiments.

Journal Article↗

PubMed2005

From Al4B2O9 nanowires to BN-coated Al18B4O33 nanowires.

A novel route was proposed to completely coat aluminum borate nanowires by in situ providing the precursor for BN coating. Uniformly BN-coated Al18B4O33 nanowires could be obtained by the reaction of Al4B2O9 nanowires with ammonia at high temperature. The high-temperature unstable Al4B2O9 nanowires were converted into Al18B4O33 nanowires, simultaneously evaporated boron oxide. The reaction between the in situ generated vapors and ammonia ensures that the BN layers are attached tightly on the surface of the as-formed Al18B4O33 nanowires.

Letter↗

PubMed2005

Premelting at defects within bulk colloidal crystals.

Premelting is the localized loss of crystalline order at surfaces and defects at temperatures below the bulk melting transition. It can be thought of as the nucleation of the melting process. Premelting has been observed at the surfaces of crystals but not within. We report observations of premelting at grain boundaries and dislocations within bulk colloidal crystals using real-time video microscopy. The crystals are equilibrium close-packed, three-dimensional colloidal structures made from thermally responsive microgel spheres. Particle tracking reveals increased disorder in crystalline regions bordering defects, the amount of which depends on the type of defect, distance from the defect, and particle volume fraction. Our observations suggest that interfacial free energy is the crucial parameter for premelting in colloidal and atomic-scale crystals.

Journal Article↗

PubMed2005

Adiabatic molecular-dynamics-simulation-method studies of kinetic friction.

An adiabatic molecular-dynamics method is developed and used to study the Muser-Robbins model for dry friction (i.e., nonzero kinetic friction in the slow sliding speed limit). In this model, dry friction between two crystalline surfaces rotated with respect to each other is due to mobile molecules (i.e., dirt particles) adsorbed at the interface. Our adiabatic method allows us to quickly locate interface potential-well minima, which become unstable during sliding of the surfaces. Since dissipation due to friction in the slow sliding speed limit results from mobile molecules dropping out of such unstable wells, our method provides a way to calculate dry friction, which agrees extremely well with results found by conventional molecular dynamics for the same system, but our method is more than a factor of 10 faster.

Journal Article↗

PubMed2005

Thomson scattering measurements of heat flux from ion-acoustic waves in laser-produced aluminum plasmas.

Thomson scattering (TS) measurements are performed at different locations in a laser-produced aluminum plasma. Variations of the separation, wavelength shift, and asymmetric distribution of the two ion-acoustic waves are investigated from their spectral-time-resolved TS images. Detailed information on the space-time evolution of the plasma parameters is obtained. Electron distribution and variation of the heat flux in the plasma are also obtained for a steep temperature gradient.

Journal Article↗

PubMed2005

Cardioprotective effects of peroxisome proliferator activated receptor gamma activators on acute myocarditis: anti-inflammatory actions associated with nuclear factor kappaB blockade.

OBJECTIVE: To test the hypothesis that activation of peroxisome proliferator activated receptor gamma (PPAR-gamma) reduces experimental autoimmune myocarditis (EAM) associated with inhibitor kappaB (IkappaB) alpha induction, blockade of nuclear factor kappaB (NF-kappaB), and inhibition of inflammatory cytokine expression. METHODS: EAM was induced in Lewis rats by immunisation with porcine cardiac myosin. PPAR-gamma activators 15-deoxy-Delta(12,14)-prostaglandin J2 (15d-PGJ2) and pioglitazone (PIO) were administered to rats with EAM. RESULTS: Enhanced PPAR-gamma expression was prominently stained in the nuclear and perinuclear regions of infiltrating inflammatory cells. Administration of 15d-PGJ2 and PIO greatly reduced the severity of myocarditis and suppressed myocardial mRNA and protein expression of inflammatory cytokines in rats with EAM. In addition, treatment with PPAR-gamma activators enhanced IkappaB concentrations in the cytoplasmic fractions and nuclear fractions from inflammatory myocardium. Concurrently, NF-kappaB was greatly activated in myocarditis; this activation was blocked in the 15d-PGJ2 treated and PIO treated groups. CONCLUSIONS: PPAR-gamma may have a role in the pathophysiology of EAM. Because an increase in IkappaB expression and inhibition of translocation of the NF-kappaB subunit p65 to the nucleus in inflammatory cells correlated with the protective effects of PPAR-gamma activators, these results suggest that PPAR-gamma activators act sequentially through PPAR-gamma activation, IkappaB induction, blockade of NF-kappaB activation, and inhibition of inflammatory cytokine expression. These results suggest that PPAR-gamma activators such as 15d-PGJ2 and PIO may have the potential to modulate human inflammatory heart diseases such as myocarditis.

Acute Disease↗

PubMed2005

In vitro mutation and selection of doubled-haploid Brassica napus lines with improved resistance to Sclerotinia sclerotiorum.

This paper describes a new protocol to develop doubled-haploid (DH) Brassica napus lines with improved resistance to Sclerotinia sclerotiorum. In this protocol, haploid seedlings derived from microspore cultures of B. napus were used to produce haploid calli for in vitro mutation-selection. For routine screening, mutation was induced by EMS (ethylmethane sulfonate) or occurred spontaneously, and screening for resistant mutants occurred on media with added oxalic acid (OA) as a selection agent. In tests with selected lines, the optimal concentration of EMS for mutation was determined to be 0.15%, and the optimal concentration of OA for in vitro screening was 3 mmol/l (half lethal dose was 3.1 mmol/l) for the first cycle of screening. There was an accumulated effect of OA toxicity on calli over two cycles of screening, but the growth and capacity of the surviving calli for regenerating seedlings were not affected by OA. Of the 54 DH lines produced from the in vitro mutation-selection, two DH lines of resistant mutants, named M083 and M004, were selected following seedling and glasshouse tests. The resistance of M083 and M004 to S. sclerotiorum following tests with both mycelial inoculum and OA was greater than that of their donor lines and the resistant control Zhongyou 821. In both glasshouse and field disease nurseries, disease indices on M083 and M004 were less than 50% of those of the control. The time required for M083 and M004 to mature was 14 days and 10 days shorter, respectively, than that of their donor lines. Furthermore, M083 had more pods per inflorescence, a greater 1,000 seed weight and higher yield than its donor line. Random amplified polymorphic DNA characterisation showed that M083 had DNA band patterns that differed from its donor line.

Ascomycota↗