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Biomedical subjects

J Y Huang

Publications and source records attributed to J Y Huang.

At least 19 recordsLinked to original sources
PubMed2006

Kink formation and motion in carbon nanotubes at high temperatures.

We report that kink motion is a universal plastic deformation mode in all carbon nanotubes when being tensile loaded at high temperatures. The kink motion, observed inside a high-resolution transmission electron microscope, is reminiscent of dislocation motion in crystalline materials: namely, it dissociates and multiplies. The kinks are nucleated from vacancy creation and aggregation, and propagate in either a longitudinal or a spiral path along the nanotube walls. The kink motion is related to dislocation glide and climb influenced by external stress and high temperatures in carbon nanotubes.

Journal Article↗
PubMed2006

AFM study of the effect of metronidazole on surface structures of sulfate-reducing bacteria.

The effect of metronidazole (ME) on sulfate-reducing bacteria (SRB) was studied by atomic force microscopy (AFM) in this paper. Topography images of SRB cell show that after exposure to ME individual cell shape is sharply modified. Topography and phase images of SRB cell wall show that after exposure to ME not only the roughness of the cell wall increases but also the physical performance of SRB surface is changed to be uniform. AFM frictional loops show that after exposure to ME, SRB surface friction is increased remarkably.

Anti-Infective Agents↗
PubMed2006

Superplastic carbon nanotubes.

The theoretical maximum tensile strain--that is, elongation--of a single-walled carbon nanotube is almost 20%, but in practice only 6% is achieved. Here we show that, at high temperatures, individual single-walled carbon nanotubes can undergo superplastic deformation, becoming nearly 280% longer and 15 times narrower before breaking. This superplastic deformation is the result of the nucleation and motion of kinks in the structure, and could prove useful in helping to strengthen and toughen ceramics and other nanocomposites at high temperatures.

Journal Article↗
PubMed2006

Real-time observation of tubule formation from amorphous carbon nanowires under high-bias Joule heating.

The tubule formation process from amorphous carbon nanowires under high-bias-caused Joule heating was observed in real time in a high-resolution transmission electron microscope. The crystallization of the amorphous carbon nanowires occurred in two distinct ways: the formation of tubular graphitic basal planes parallel to the nanowire axis on the surface and the formation of nano-onions in the interior of the nanowire. The tubule formation mechanism is a process of solid-state atom diffusion at high temperatures. Energetically, the tubule formation is caused by the exceptionally low surface energy of the (0002) plane of graphite. Higher input power to the amorphous nanowires generally leads to improved graphitization and, in turn, to increased conductance. The results suggest that nanotube formation in the arc-discharge growth process may involve the formation and crystallization of amorphous carbon.

Computer Systems↗
PubMed2006

Shape evolution of lead telluride and selenide nanostructures under different hydrothermal synthesis conditions.

Face-open nanoboxes of lead telluride and selenide have been synthesized by a simple hydrothermal method. Nano- and microcrystals of various morphologies, including microflowers, semi-microflowers, cubic nanoparticles, etc., have also been observed at different synthesis conditions. Temperature, time, and concentrations of various reactants play a major role in controlling the morphology and shape evolution of the product. This simple synthesis technique for the growth of various nano- and microstructures opens a new route to prepare hierarchical structures of a variety of binary semiconducting materials in a large quantity. A possible growth mechanism of such nano- and microstructures has been proposed.

Crystallization↗
PubMed2005

Observation of anomalously large spectral bandwidth in a high-gain self-amplified spontaneous emission free-electron laser.

Observation of ultrawide bandwidth, up to 15% full-width, high-gain operation of a self-amplified spontaneous emission free-election laser (SASE FEL) is reported. This type of lasing is obtained with a strongly chirped beam (deltaE/E approximately 1.7%) emitted from the accelerator. Because of nonlinear pulse compression during transport, a short, high current bunch with strong mismatch errors is injected into the undulator, giving high FEL gain. Start-to-end simulations reproduce key features of the measurements and provide insight into mechanisms, such as angular spread in emitted photon and electron trajectory distributions, which yield novel features in the radiation spectrum.

Journal Article↗
PubMed2005

Atomic-scale imaging of wall-by-wall breakdown and concurrent transport measurements in multiwall carbon nanotubes.

We report the atomic-scale imaging with concurrent transport measurements of the breakdown of individual multiwall carbon nanotubes inside a transmission electron microscope equipped with a piezomanipulator. We found unexpectedly three distinct breakdown sequences: namely, from the outermost wall inward, from the innermost wall outward, and alternatively between the innermost and the outmost walls. Remarkably, a significant amount of current drop was observed when an innermost wall is broken, proving unambiguously that every wall is conducting. Moreover, the breakdown of each wall in any sequence initiates in the middle of the nanotube, not at the contact, proving that the transport is not ballistic.

Journal Article↗
PubMed2001

Activation or detoxification of mutagenic and carcinogenic compounds in transgenic Drosophila expressing human glutathione S-transferase.

Sensitivity of transgenic Drosophila melanogaster with expression of a human gene encoding the glutathione S-transferase alpha subunit (GSTA1-1) to 1,2:5,6-dibenzanthracene (DBA) and 1,2-dichloroethane (DCE) was investigated in the somatic mutation and recombination test (SMART). We performed the same assay in control transgenic flies expressing the bacterial lacZ gene. Three types of transgenic Drosophila strains carrying GSTA1-1 were used: two transgenic strains homozygous for the second chromosome with a single-copy transgene insertion and one strain with two transgene insertions. Larvae carrying the lacZ gene were significantly more sensitive to genotoxic effects of DBA than those carrying three copies of the GSTA1-1 gene. The larvae with lacZ expression showed significantly lower sensitivity to DCE compared with those expressing GSTA1-1. Finally, a pretreatment with buthionine-sulphoximine (BSO) in experiment with DCE significantly decreased the frequency of mutation events in larvae with three GSTA1-1 copies in comparison with others.

Animals↗
PubMed2001

Crossings and writhe of flexible and ideal knots.

The data of ideal knots [Nature, 384, 142 (1996)] are reanalyzed and the average crossing number of the ideal knots (ideal) shows a nonlinear behavior with the essential crossing number C. Supplemented with our Monte Carlo simulations using the bond fluctuation model on flexible knotted polymers, our analysis indicates that (ideal) varies nonlinearly with both C and the corresponding average crossing number of the flexible knot, which is contrary to previous claims. Our extensive simulation data on the average crossing number of flexible knots suggest that it varies linearly with the square root of C. Furthermore, our data on the average writhe number indicate that various knots are classified into holonomous groups, and has a quantized linear increment with C in all four knot groups in our study.

Journal Article↗
PubMed2001

The EMOTIF database.

The EMOTIF database is a collection of more than 170 000 highly specific and sensitive protein sequence motifs representing conserved biochemical properties and biological functions. These protein motifs are derived from 7697 sequence alignments in the BLOCKS+ database (released on June 23, 2000) and all 8244 protein sequence alignments in the PRINTS database (version 27.0) using the emotif-maker algorithm developed by Nevill-Manning et al. (Nevill-Manning,C.G., Wu,T.D. and Brutlag,D.L. (1998) Proc. Natl Acad. Sci. USA, 95, 5865-5871; Nevill-Manning,C.G., Sethi,K.S., Wu,T. D. and Brutlag,D.L. (1997) ISMB-97, 5, 202-209). Since the amino acids and the groups of amino acids in these sequence motifs represent critical positions conserved in evolution, search algorithms employing the EMOTIF patterns can identify and classify more widely divergent sequences than methods based on global sequence similarity. The emotif protein pattern database is available at http://motif.stanford.edu/emotif/.

Amino Acid Motifs↗
PubMed2001

The effect of an iron supplement on serum aluminum level and desferrioxamine mobilization test in hemodialysis patients.

BACKGROUND: The serum aluminum (Al) measurement with desferrioxamine (DFO) mobilization is a screening test for uremic patients with an Al overload. In these patients, body iron status is one of the factors affecting the serum Al level. This study is designed to elucidate the effects of iron supplements on the serum Al and the DFO mobilization test. METHODS: Our study featured ten hemodialysis patients with iron deficiency anemia. The iron supplement was given intravenously with saccharated ferric oxide, 40 mg three times weekly, at the end of each hemodialysis. The total amount of iron supplement was 1,000 mg. All the patients underwent a DFO test at a dose of 5 mg/kg. The same test was repeated two weeks after completion of the iron supplement. RESULTS: After the iron supplement, patients' iron deficiency anemia improved with a serum ferritin elevation from 312.4 +/- 589.5 to 748.2 +/- 566.2 microg/L (p < 0.01), and iron saturation from 21.6 +/- 20.3 to 41.1 +/- 21.7% (p = 0.06). The basal serum Al level decreased from 34.3 +/- 13.8 to 21.8 +/- 8.5 microg/L (p = 0.01). In the DFO mobilization test, the peak serum Al level decreased from 63.4 +/- 19.3 to 50.7 +/- 20.5 microg/L (p < 0.01). The amount of Al increment (deltaAl) in DFO test was not changed (29.1 +/- 12.0 vs. 28.9 +/- 15.9 microg/L, p = 0.86). The change in basal Al level tended to negatively correlate with the percentage of increment in iron saturation (r = -0.628, p = 0.05). CONCLUSION: Results in this study suggest that iron supplements may significantly reduce the basal serum Al and peak Al in DFO mobilization test, without significant change of the mean deltaAl. The data presented indicate that in the interpretation of serum aluminum levels the iron status should be taken into account.

Adult↗
PubMed2001

Serum interleukin-6 (IL-6), IL-10, tumor necrosis factor (TNF) alpha, soluble type II TNF receptor, and transforming growth factor beta levels in human immunodeficiency virus type 1-infected individuals with Mycobacterium avium complex disease.

To characterize changes in serum cytokine levels in human immunodeficiency virus type 1 (HIV-1)-infected persons with Mycobacterium avium complex (MAC) bacteremia, the levels of IL-1alpha (interleukin-1alpha), IL-6, IL-10, tumor necrosis factor alpha (TNF-alpha), soluble type II TNF receptor (sTNF-RII), and transforming growth factor beta (TGF-beta) in serum were measured in two cohorts of HIV-1-infected persons with MAC bacteremia. The first cohort was part of a MAC prophylaxis study. Patients with bacteremia were matched with controls without bacteremia. Elevated IL-6, IL-10, TNF-alpha, sTNF-RII, and TGF-beta levels were noted at baseline for all subjects, a result consistent with advanced HIV-1 disease. IL-1alpha was not detected. No differences in cytokine levels in serum were noted at baseline and at the time of bacteremia between patients with MAC and controls. In the second cohort, subjects had serum samples collected at the time of MAC bacteremia and thereafter while on macrolide therapy. Serum samples at time of bacteremia were collected from HIV-1-infected persons at a time when neither highly active antiretroviral therapy (HAART) nor MAC prophylaxis was used routinely. MAC treatment resulted in decreased levels of IL-6 and TNF-alpha in serum, which were evident for IL-6 by 4 to 6 weeks and for TNF-alpha by 8 to 16 weeks. Thus, antibiotic treatment for MAC results in decreased levels of IL-6 and TNF-alpha in serum in HIV-1-infected persons who are not on HAART.

AIDS-Related Opportunistic Infections↗
PubMed2000

Centrosomes have a role in regulating the destruction of cyclin B in early Drosophila embryos.

We reported previously that the disappearance of cyclin B at the end of mitosis in early Drosophila embryos starts at centrosomes and spreads into the spindle [1]. Here, we used a novel mutation, centrosome fall off (cfo), to investigate whether centrosomes are required to initiate the disappearance of cyclin B from the spindle. In embryos laid by homozygous cfo mutant mothers, the centrosomes co-ordinately detached from the mitotic spindle during mitosis, and the centrosomeless spindles arrested at anaphase. Cyclin B levels decreased on the detached centrosomes, but not on the arrested centrosomeless spindles, presumably explaining why the spindles arrest in anaphase in these embryos. We found that the expression of a non-degradable cyclin B in embryos also caused an anaphase arrest, but most centrosomes remained attached to the arrested spindles, and non-degradable cyclin B levels remained high on both the centrosomes and spindles. These findings suggest that the disappearance of cyclin B from centrosomes and spindles is closely linked to its destruction, and that a connection between centrosomes and spindles is required for the proper destruction of the spindle-associated cyclin B in early Drosophila embryos. These results may have important implications for the mechanism of the spindle-assembly checkpoint, as they suggest that unattached kinetochores may arrest cells in mitosis, at least in part, by signalling to centrosomes to block the initiation of cyclin B destruction.

Anaphase↗
PubMed2000

A study of secondary cutaneous amyloidosis in basal cell carcinoma in Chinese patients: lack of correlation with bcl-2 or p53 protein expression.

Pigmented basal cell carcinoma (BCC) is an uncommon form of BCC among Caucasians. In contrast, the majority of BCC in Orientals are pigmented BCC. To assess the occurrence of secondary amyloid deposits in BCC among Chinese patients, a retrospective study was conducted on 53 BCC specimens. We used a terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling method for detecting the apoptotic cells. In addition, immunohistochemical staining was performed to examine the expression of the B-cell leukemia/lymphoma-2 gene (bcl-2) and p53 protein. Of the 53 BCC specimens, 37 (69.8%) were pigmented BCC and 31 (58.5%) showed amyloid deposits in the stroma of the tumor cells. The mean percentage of apoptotic tumor cells was 0.29%. Immunostaining of bcl-2 and p53 was detected in 33 BCCs (62.3%) and 19 BCCs (35.8%), respectively. No relationship between amyloid deposition and the number of apoptotic cells was found. In addition, there was no correlation between amyloid deposition and bcl-2 protein expression or between amyloid deposition and p53 protein expression. Our results indicate that the frequency of secondary amyloidosis in BCC among Chinese patients is not higher than that reported in the West. Although no correlation could be detected between amyloid deposition and bcl-2/p53 protein expression, the possible role of apoptosis in the pathogenesis of amyloid deposition in BCC still needs further investigation.

Adult↗
PubMed2000

Differential interaction of Cbl with Grb2 and CrkL in CD2-mediated NK cell activation.

Natural killer (NK) cells participate in both innate and adoptive immunity by their prompt secretion of cytokines and by their ability to lyse virally infected cells or tumor cells. CD2 is surface glycoprotein receptors and crucial for NK cell activation. However, molecular events involved in CD2-mediated NK cell activation have not been fully elucidated. Cbl-Grb2 and Cbl-CrkL interactions have been implicated in T cell and B cell receptor, and cytokine receptor signaling. Here we analyzed tyrosine phosphorylation and interactions of Cbl with adapter proteins, Grb2 and CrkL, in NK3.3 cells. CD2 crosslinking results in the marked tyrosine phosphorylation of Cbl in an antibody concentration- and time-dependent manner. Immunodepletion studies reveal that Grb2-associated tyrosine phosphorylated p120 kDa protein is Cbl. In vitro binding studies using GST-fusion proteins demonstrate that Cbl constitutively associates with the SH3 domains of Grb2, with a preference for the amino-terminal domain. In addition, we demonstrate that CrkL associates with a large portion of tyrosine phosphorylated Cbl after CD2 stimulation of NK3.3 cells. In contrast to constitutive Cbl association with Grb2, tyrosine phosphorylated Cbl interacts with CrkL via its SH2 domain only after CD2 stimulation. Although the precise roles of interactions of Cbl with Grb2 and CrkL in NK cell activation remains to be elucidated, their tyrosine phosphorylation, in addition to the multiple protein interactions described here, strongly suggest that interactions of Cbl with Grb2 and CrkL may play pivotal roles in CD2-mediated NK cell activation.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Total creatinine appearance as indicator of risk of infectious complication in peritoneal dialysis.

Peritonitis and exit-site infections are the main causes of complications in peritoneal dialysis. Death due to infectious complication is also one of the major causes of drop-out. The underlying cause of infection may include malnutrition. Total creatinine appearance (TCA) may reflect overall nutritional status. We determined TCA from the daily dialysate, urine, and estimated gut creatinine of patients and normalized it to actual body weight (nTCA). We examined the relationship between nTCA and the incidence of infection, and between nTCA and infection-related survival. The study included 323 adult patients in a single dialysis center. The mean nTCA of all patients was 19.73 +/- 4.75 mg/kg/day. The patients with an nTCA below 1 standard deviation from the mean (nTCA < 14.98 mg/kg/day) had a significantly higher peritonitis and exit-site infection rate (p < 0.01) and a higher chance of drop-out owing to infection-related complications (p < 0.0001). Our study concluded that the adult patient with malnutrition (nTCA < 14.98 mg/kg/day) has higher risk of infection.

Bacterial Infections↗
PubMed1999

Beta2-integrin, LFA-1, and TCR/CD3 synergistically induce tyrosine phosphorylation of focal adhesion kinase (pp125(FAK)) in PHA-activated T cells.

Complete T cell activation requires not only a first signal via TCR/CD3 engagement but also a costimulatory signal through accessory receptors such as CD2, CD28, or integrins. Focal adhesion kinase, pp125(FAK) (FAK), was previously shown to be localized in focal adhesions in fibroblasts and to be involved in integrin-mediated cellular activation. Although signaling through beta1- or beta3-integrins induces tyrosine phosphorylation of FAK, there has been no evidence that activation of T cells through the beta2-integrin, LFA-1, involves FAK. We report here that crosslinking of LFA-1 induces tyrosine phosphorylation of FAK in PHA-activated T cells. Moreover, cocrosslinking with anti-LFA-1 mAb and suboptimal concentration of anti-CD3 mAb markedly increases tyrosine phosphorylation of FAK in an antibody-concentration-dependent and time-kinetics-dependent manner compared with stimulation through CD3 alone, which correlates well with enhanced proliferation of PHA-activated T cells. Furthermore, LFA-1beta costimulation with CD3 induces tyrosine phosphorylation of Syk associated with FAK. These results indicate, for the first time, that signals mediated by LFA-1 can regulate FAK, suggesting that LFA-1-mediated T cell costimulation may be involved in T cell activation at least partially through FAK.

CD18 Antigens↗