Biomedical subjects

J Shu

Publications and source records attributed to J Shu.

At least 19 recordsLinked to original sources

PubMed2001

Nuclear inelastic x-ray scattering of FeO to 48 GPa.

The partial density of vibrational states has been measured for Fe in compressed FeO (wüstite) using nuclear resonant inelastic x-ray scattering. Substantial changes have been observed in the overall shape of the density of states close to the magnetic transition around 20 GPa from the paramagnetic (low pressure) to the antiferromagnetic (high pressure) state. The results indicate that strong magnetoelastic coupling in FeO is the driving force behind the changes in the phonon spectrum of FeO. The paper presents the first observation of changes in the density of terahertz acoustic phonon states under magnetic transition at high pressure.

Journal Article↗

PubMed2001

Phonon density of states of iron up to 153 gigapascals.

We report phonon densities of states (DOS) of iron measured by nuclear resonant inelastic x-ray scattering to 153 gigapascals and calculated from ab initio theory. Qualitatively, they are in agreement, but the theory predicts density at higher energies. From the DOS, we derive elastic and thermodynamic parameters of iron, including shear modulus, compressional and shear velocities, heat capacity, entropy, kinetic energy, zero-point energy, and Debye temperature. In comparison to the compressional and shear velocities from the preliminary reference Earth model (PREM) seismic model, our results suggest that Earth's inner core has a mean atomic number equal to or higher than pure iron, which is consistent with an iron-nickel alloy.

Journal Article↗

PubMed2001

A crossed molecular beam study of the O(1D) + C(3)H(8) reaction: multiple reaction pathways.

The O((1)D) + C(3)H(8) reaction has been reinvestigated using the universal crossed molecular beam method. Three reaction channels, CH(3) + C(2)H(4)OH, C(2)H(5) + CH(2)OH, and OH + C(3)H(7), have been observed. All three channels are significant in the title reaction with the C(2)H(5) formation process to be the most important, while the CH(3) formation and the OH formation channels are about equal. Product kinetic energy distributions and angular distributions have been determined for the three reaction channels observed. The oxygen-containing radicals in the CH(3) and C(2)H(5) formation pathways show forward-backward symmetric angular distribution relative to the O atom beam, while the OH product shows a clearly forward angular distribution. These results indicate that the OH formation channel seems to exhibit different dynamics from the CH(3) and C(2)H(5) channels.

Journal Article↗

PubMed2001

[Isolation, purification and identification of metallothionein from strain BD102 of Hansenula anomala].

Metallothionein (MTs) in Cu and Cd resistant strain BD102 of Hansenula anomala were induced by administration of Cu2+ and Cd2+. These proteins were isolated and purified by Sephadex G-50 and subsequent DEAE-Sepharose CL-6B, then Sephadex G-25 for desalation. There were two isoform MTs by Cu(Cu-MTs), one form induced by Cd (Cd-MT). The molecular weights of the Cu-MTs and the Cd-MT were about 7 kD and 7.5 kD respectively. Exposure of Hansenula anomala to copper salts stimulated formation of two isoform Cu-MTs with a cysteine content of 6.6-6.8% and had 60 amino acids. Exposure of Hansenula anomala to cadmium, stimulated formation of Cd-MT with a cystein content of 10% was synthesized and had 61 amino acids. 4 atom Cu or Cd/mole MTs.

Amino Acids↗

PubMed2001

[The reconstruction of laryngeal function in subtotal laryngectomy by pedicled flaps].

OBJECTIVE: To explore the possibility of subtotal laryngectomy in the treatment of advanced laryngeal cancer and selection of reconstruction. METHODS: Forty patients were treated surgically by subtotal laryngectomy with preservation of arytenoid cartilage and perichondrium. The pedicled flaps between cricoid cartilage and arytenoid cartilage were sewed up. The new larynx was reconstructed by suturing the cricoid or trachea to the hyoid bone or the tongue base. RESULTS: The 3 and 5 year survival rates were 85.0% and 76.2% respectively. Decannulation rate was 92.5%. CONCLUSION: The reconstruction of laryngeal function in subtotal laryngectomy by pedicled flaps not only is safe and beneficial to the patients with the cancers above the cricoid, but also improves the quality of patient's life.

Adult↗

PubMed2000

Transformations in methane hydrates.

Detailed study of pure methane hydrate in a diamond cell with in situ optical, Raman, and x-ray microprobe techniques reveals two previously unknown structures, structure II and structure H, at high pressures. The structure II methane hydrate at 250 MPa has a cubic unit cell of a = 17.158(2) A and volume V = 5051.3(13) A(3); structure H at 600 MPa has a hexagonal unit cell of a = 11.980(2) A, c = 9.992(3) A, and V = 1241.9(5) A(3). The compositions of these two investigated phases are still not known. With the effects of pressure and the presence of other gases in the structure, the structure II phase is likely to dominate over the known structure I methane hydrate within deep hydrate-bearing sediments underlying continental margins.

Journal Article↗

PubMed2000

Fossilized high pressure from the Earth's deep interior: the coesite-in-diamond barometer.

Mineral inclusions in diamonds provide an important source of information about the composition of the continental lithosphere at depths exceeding 120-150 km, i.e., within the diamond stability field. Fossilized high pressures in coesite inclusions from a Venezuela diamond have been identified and measured by using laser Raman and synchrotron x-ray microanalytical techniques. Micro-Raman measurements on an intact inclusion of remnant vibrational band shifts give a high confining pressure of 3.62 (+/-0.18) GPa. Synchrotron single-crystal diffraction measurements of the volume compression are in accord with the Raman results and also revealed direct structural information on the state of the inclusion. In contrast to olivine and garnet inclusions, the thermoelasticity of coesite favors accurate identification of pressure preservation. Owing to the unique combination of physical properties of coesite and diamond, this "coesite-in-diamond" geobarometer is virtually independent of temperature, allowing an estimation of the initial pressure of Venezuela diamond formation of 5.5 (+/-0.5) GPa.

Journal Article↗

PubMed2000

The plastic deformation of iron at pressures of the Earth's inner core

Soon after the discovery of seismic anisotropy in the Earth's inner core, it was suggested that crystal alignment attained during deformation might be responsible. Since then, several other mechanisms have been proposed to account for the observed anisotropy, but the lack of deformation experiments performed at the extreme pressure conditions corresponding to the solid inner core has limited our ability to determine which deformation mechanism applies to this region of the Earth. Here we determine directly the elastic and plastic deformation mechanism of iron at pressures of the Earth's core, from synchrotron X-ray diffraction measurements of iron, under imposed axial stress, in diamond-anvil cells. The epsilon-iron (hexagonally close packed) crystals display strong preferred orientation, with c-axes parallel to the axis of the diamond-anvil cell. Polycrystal plasticity theory predicts an alignment of c-axes parallel to the compression direction as a result of basal slip, if basal slip is either the primary or a secondary slip system. The experiments provide direct observations of deformation mechanisms that occur in the Earth's inner core, and introduce a method for investigating, within the laboratory, the rheology of materials at extreme pressures.

Journal Article↗

PubMed2000

Assessment of autonomic function in patients with acute myocardial infarction or diabetes mellitus by heart rate variability, ventricular late potential and QT dispersion.

To compare the efficacy and sensitivity of heart rate variability (HRV), QT dispersion (QTd) and ventricular late potential (VLP) examination in judging autonomic function. Thirty three patients with acute myocardial infarction (AMI) and 33 patients with diabetes mellitus (DM), all of whom were diagnosed with autonomic neuropathy determined by a standard test of cardiovascular autonomic function, were examined by HRV (timing domain methods), QTd and VLP. Thirty three normal individuals served as controls. The mean SD of the normal R-R interval (SDNN) in both the AMI and DM groups was significantly less than that in the control group (p< 0.01); and of course, the QTd of these groups was significantly greater than that of the controls (p< 0.01). The VLP positive rate of the AMI and DM groups were much higher than that of the control group (p< 0.001). SDNN was shown to be significantly negatively correlated to QTd (r= -0.45); and significantly negatively correlated to VLP (r= -0.47); QTd was shown to be positively, though not significantly, correlated to VLP (r=0.48). QTd could be looked as sieving index; HRV could be looked as routine examination of cardiovascular autonomic function, especially SDNN; the combination of HRV and VLP could improve the accuracy of diagnosis.

Adult↗

PubMed1999

NF-kappaB-mediated up-regulation of Bcl-x and Bfl-1/A1 is required for CD40 survival signaling in B lymphocytes.

Activation of CD40 is essential for thymus-dependent humoral immune responses and rescuing B cells from apoptosis. Many of the effects of CD40 are believed to be achieved through altered gene expression. In addition to Bcl-x, a known CD40-regulated antiapoptotic molecule, we identified a related antiapoptotic molecule, A1/Bfl-1, as a CD40-inducible gene. Inhibition of the NF-kappaB pathway by overexpression of a dominant-active inhibitor of NF-kappaB abolished CD40-induced up-regulation of both the Bfl-1 and Bcl-x genes and also eliminated the ability of CD40 to rescue Fas-induced cell death. Within the upstream promoter region of Bcl-x, a potential NF-kappaB-binding sequence was found to support NF-kappaB-dependent transcriptional activation. Furthermore, expression of physiological levels of Bcl-x protected B cells from Fas-mediated apoptosis in the absence of NF-kappaB signaling. Thus, our results suggest that CD40-mediated cell survival proceeds through NF-kappaB-dependent up-regulation of Bcl-2 family members.

Apoptosis↗

PubMed1999

Comparison of the breaking strength of polyglactin mesh in urine, serum, and cell culture media.

OBJECTIVES: This study was designed to determine the durability of polyglactin woven mesh in various in vitro environments, including urine, since polyglactin 901 mesh has been considered for implementation in urinary tract reconstruction. METHODS: Segments of 1 x 1-cm sterile woven and knitted polyglactin 910 mesh with and without collagen coating were exposed to the following conditions: dry (at room temperature and at 37 degrees C, humidified air), in porcine and human serum and urine, in porcine urine over a range of pH levels, in infected urine, in cell culture media (MCDB 105 with 5% fetal bovine serum), and in cell culture media with porcine bladder fibroblasts. The mesh breaking strength was measured at 0, 12, 21, 28, and 36 days. RESULTS: The mean breaking strength for dry, room temperature mesh segments measured 350 g for all time intervals. At day 21, the breaking strength for all mesh types in human and porcine serum, cell culture media, and cell culture media with bladder fibroblasts was less than 10% of the control, but the human and porcine urine maintained 12% to 24% of the control breaking strength (this difference did not reach statistical significance). There was no significant difference in the breaking strength in human and porcine urine or human and porcine serum. By day 38, the breaking strength for all mesh types in all solutions was less than 5% of the control breaking strength. The presence of fibroblasts increased the rate of degradation of the mesh compared with the urine, serum, and cell culture media alone. There was a significant prolongation of degradation with decreasing pH, as well as with infected urine. This prolongation was additive; in fact, all mesh types in low pH (5.0), infected urine showed minimal degradation at 38 days. CONCLUSIONS: In acidic infected urine, the durability of polyglactin 910 mesh is significantly prolonged compared with the other conditions tested. Therefore, when used in urinary tract reconstruction, as in other organ systems, the integrity of the polyglactin mesh should diminish rapidly after 3 weeks as long as the urine is kept sterile and a neutral to alkaline pH is maintained.

Animals↗

PubMed1999

Adenovirus-mediated gene transfer of dominant negative Ha-Ras inhibits proliferation of primary meningioma cells.

OBJECTIVE: Previous studies demonstrated that activation of receptor tyrosine kinases in human meningiomas by an autocrine or paracrine growth-stimulatory loop plays an important role in meningioma proliferation. Although it is well established that the proliferative signal from protein tyrosine kinase receptors is transduced through Ras proteins, the relevance of the Ras pathway in meningioma proliferation, to our knowledge, has not been studied. The purpose of this study was, therefore, to determine whether Ras proteins are functionally important in meningioma proliferation. METHODS: Meningioma cells of nine primary cell cultures were infected with the recombinant adenovirus Ad-rasN17 encoding the dominant negative Ras protein or control adenovirus Ad-pAC. Ras-N17 is a Ras mutant protein with substitution of asparagine for serine at position 17 in the cellular Ha-Ras protein that inhibits function of all endogenous cellular Ras proteins. Proliferation of meningioma cells was measured using [3H]thymidine or 5-bromo-2'-deoxyuridine labeling and detection assays. RESULTS: Infection of meningioma cells with Ad-rasN17 dramatically increased the expression levels of the Ras-N17 mutant protein and inhibited phosphorylation of the mitogen-activated protein kinases, compared with uninfected cells or cells infected with the control adenovirus. Suppression of Ras proteins inhibited proliferation of all exponentially growing and growth-arrested meningioma cells stimulated with serum. CONCLUSION: The obtained results suggest that proliferation of primary meningioma cells is dependent on the presence of functional Ras proteins. Therefore, inhibition of the Ras pathway may be important in preventing growth factor-stimulated meningioma proliferation.

Adenoviruses, Human↗

PubMed1999

TANK potentiates tumor necrosis factor receptor-associated factor-mediated c-Jun N-terminal kinase/stress-activated protein kinase activation through the germinal center kinase pathway.

Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) are mediators of many members of the TNF receptor superfamily and can activate both the nuclear factor kappaB (NF-kappaB) and stress-activated protein kinase (SAPK; also known as c-Jun N-terminal kinase) signal transduction pathways. We previously described the involvement of a TRAF-interacting molecule, TRAF-associated NF-kappaB activator (TANK), in TRAF2-mediated NF-kappaB activation. Here we show that TANK synergized with TRAF2, TRAF5, and TRAF6 but not with TRAF3 in SAPK activation. TRAF2 and TANK individually formed weak interactions with germinal center kinase (GCK)-related kinase (GCKR). However, when coexpressed, they formed a strong complex with GCKR, thereby providing a potential mechanism for TRAF and TANK synergy in GCKR-mediated SAPK activation, which is important in TNF family receptor signaling. Our results also suggest that TANK can form potential intermolecular as well as intramolecular interactions between its amino terminus and carboxyl terminus. This study suggests that TANK is a regulatory molecule controlling the threshold of NF-kappaB and SAPK activities in response to activation of TNF receptors. In addition, CD40 activated endogenous GCKR in primary B cells, implicating GCK family proteins in CD40-mediated B-cell functions.

Adaptor Proteins, Signal Transducing↗

PubMed1999

[Diagnostic value of ultrasonography in cervical lymph node metastasis].

OBJECTIVE: To research the accuracy of ultrasonography in the diagnosis of cervical lymph node metastasis and the value of that of cervical lymph node occult metastasis. METHOD: Fifty-five patients(61 sides) operated by neck dissection were double-blindedly studied by preoperation palpation and ultrasonography comparing with postoperating pathological examination. RESULT: Fifty-two sides were confirmed to be pathology lymph node metastasis from 61 sides. 40 and 48 sides were checked out by palpation and ultrasonography, respectively. The sensitivity, specificity and accuracy of palpation and ultrasonography were 76.9% and 92.3% (P < 0.05), 77.8% and 88.9%(P > 0.05) and 77.0% and 91.8%(P < 0.05), respectively. Six sides were checked out by ultrasonography (occult metastasis) in 12 sides of palpation negative. CONCLUSION: The accuracy of ultrasonography was prior to that of palpation in examining cervical lymph node metastsis. Ultrasonography could check out about half occult metastasis and should be regarded as a routine examining items in diagnosing cervical lymph node metastasis.

Adult↗

PubMed1999

[Improvements on radical neck dissection].

OBJECTIVE: To improve the surgery of radical neck dissection for a better curative effect. METHOD: Some improvements on incision, path to exploration and manipulation of operation were made in 65 patients with head and neck tumors while radical neck dissection were done. RESULT: The average surgical time was 110 minutes and the average amount of bleeding was 120 ml in the patients when radical neck dissection had been completed. The complications decreased to 1.54%. The surviual rates of 2 and 3 years are 86.2% (56/65) and 81.6 (31/38) respectively. CONCLUSION: With these improvements on radical neck dissection, the curative effect in the near future is improved.

Adolescent↗

PubMed1998

p21Waf1 inhibits the activity of cyclin dependent kinase 2 by preventing its activating phosphorylation.

Prostaglandin A2 (PGA2), a potent inhibitor of the growth of many cell types, inhibits G1 phase cyclin dependent kinases (cdk). Although PGA2 suppresses cyclin D1 and elevates p21Waf1 levels, it was the failure of cdk2 to become activated by phosphorylation which correlated best with growth inhibition. In kinetic studies, cdk2 activation was inhibited efficiently only if p21Waf1 levels increased prior to the activating phosphorylation; suggesting that p21Waf1 had blocked this phosphorylation. This model was confirmed in cells from p21Waf1 knockout mice where PGA2 was completely unable to block the activating phosphorylation of cdk2, or inhibit cdk2 activity. As expected, growth inhibition of p21Waf1(-/-) cells was not observed at PGA2 concentrations which inhibited cdk2 activity and growth of p21Waf1(+/+) cells.

3T3 Cells↗

PubMed1998

[A new way for neural transplantation: the grafted central neurons migration from the subarachnoid space into the spinal cord and cerebral cortex].

In the studies of neural transplantation, Chen and his colleagues observed that the grafted central neurons could migrate from the subarachnoid space into the spinal cord and cerebral cortex. This finding promises an attractive possibility that a lot of neurons might be introduced into a long distance of the spinal cord and the extensive superficial layer of the brain which has suffered neuronal loss and thus might reinnervate a wide range of denervated area. Female rats were used in the study. Neural tissues or cell suspension containing fetal monoaminergic or arginine vasopressin (AVP) neurons were implanted into the subarachnoid space of the transected spinal cord or the normal brain and spinal cord. The rats were treated in different ways: some were grafted and the spinal cord was cut at the same time; grafted one month later or before the spinal cord was cut; grafted but the brain and spinal cord remained intact. Immunohistochemical method was used to monitor the grafted neurons after these rats survived for one or nine months. The results showed that there were a few to hundreds of 5-HT, TH or AVP-immunoreactive neurons and fibers found in the spinal cord or cerebral cortex near the grafted region. These neurons grew well and displayed their capacity of adaptability and long-time survival in the host CNS. No neurons, however, were found in the subarachnoid space of the grafted rats which had survived for another month or longer. On the other side, grafted with tissue block, it was found that transplants left in the grafted region grew as a "nodule" attaching to the surface of the spinal cord. The "nodule" was also found occasionally when the cell suspension was centered heavily at one region of the subarachnoid space. In both cases, the pia mater between them disappeared. Immunoreactive neurons were found in the "nodule" and neighboring spinal cord, some fibers from the neurons in the "nodule" extended into the spinal cord. It is supposed that a part of cells in the suspension died after grafted in the subarachnoid space and released hydrolases which injured the near pia mater by hydrolysis. As a result, some neurons in the suspension had a chance to migrate into the spinal cord and cerebral cortex. After the transplant in the subarachnoid space was gradually cleaned out, the enzymatic hydrolysis to the pia mater became weaker and finally stopped, the lesioned pia mater was gradually repaired. If the transplant was not cleared timely, the pia mater could not withstand the persistent hydrolysis and collapsed finally, leading the transplant to be fused with the host CNS.

Animals↗

PubMed1998

[Chemical constituents of Drosera peltata Smith var. lunata (Buch.-Ham.) C.B. clarke collected in Tibet].

OBJECTIVE: To investigate the chemical constituents of the whole plant of Drosera peltata var. lunata collected in Tibet. METHOD: Compounds were separated by means of pH gradient extraction and rechromatography on silica gel, and the structures were determined by spectral analysis and physicochemical evidence. RESULT: Five crystalline compounds were obtained and elucidated as plumbagin(1), droserone(2), hydroxydroserone(3), beta-sitosterol(4) and stigmasterol(5) respectively. CONCLUSION: Compound 3 and 5 were isolated from the plant for the first time.

Drosera↗