Biomedical subjects

H Dai

Publications and source records attributed to H Dai.

At least 37 records · Page 2Linked to original sources

PubMed2001

[Stress response of Nilaparvata lugens at high temperature and activities of its protective enzyme systems].

The nymphae and different wing-form adults of Brown Planthopper (BPH) were treated intermittently at 34 degrees C, 36 degrees C and 38 degrees C. During the process of heat shock treatment, the variation of the activities of the endogenous enzymes of protective system and the content of lipid peroxides (LPO) in BPH were researched. The results showed that the effect of heat shock treatments on CAT activity in 4th instar of nymphae was higher than that in 3rd and 5th instar. The CAT activity in BPH adults increased with the day-age, and 36 degrees C was the suitable temperature at which H2O2 was scavenged by CAT. The GSH-px activity was higher in old than that in young nymphae, and the ability of GSH-px to scavenge H2O2 was higher in old adults than in those adults emerged early. The activity of SOD had a positive correlation with the treated temperatures, and decreased with the increase of nymphae instar and the day-age of adults after emergence at the same temperature. The activities of CAT, GSH-px, and SOD in macropterous adults were higher than those in brachypterous adults. There were no significant difference for the activities of CAT, GSH-px and SOD between female and male adults (alpha > 0.05). The content of LPO in BPH increased with the rise of treated temperature, and also increased with the increase of instars in nymphae and day-age after emergence in adults at the same temperature. The LPO content was higher in brachypterous than in macropterous adults.

Animals↗

PubMed2001

[Validation and comparison of ISO standard method for the examination of fluoride in drinking water].

The validation of ISO standard method for the examination of fluoride in drinking water was introduced. The test for compensating interference, standard curves, accuracy, precision and the minimum detection limit etc were included. The comparison between ISO method and others was made. The results indicated that the ISO method was better in anti-interference, wider linear range and higher precision. The points designed were reasonable. The method is superior to other methods in the same kind, and it should be adopted and extended.

Fluorides↗

PubMed2001

[Detection of telomerase activity in laryngeal carcinoma and the association between telomerase activity and lymphatic metastasis].

OBJECTIVE: To investigate the telomerase activity in human laryngeal squamous cell carcinomas (LSCC) and the association between telomerase activity and lymphatic metastasis. METHOD: Telomerase activity was determined in 47 specimens of LSCC and 10 specimens of laryngeal inflammatory polyps using PCR-ELISA. RESULT: Telomerase activity was detected in 39 of 47 (83%) LSCC, but was not detected in all 10 laryngeal inflammatory polyps. There were significant differences between them (P < 0.01). Telomerase activation in LSCC with positive cervical lymph node involvement appeared to be higher (13 out of 13 cases, 100%) than in LSCC with negative cervical lymph node involvement (26 out of 34, 76.47%), (P < 0.05). CONCLUSION: Telomerase is activated frequently in LSCC and may become a biomarker of LSCC. The detection of telomerase activity in LSCC may have some value for predicting metastasis potential and prognosis and can guide the clinical practices applying selective neck dissection.

Adult↗

PubMed2001

[Study on the elimination of bacterial endotoxins by ultrafiltration device].

An external-pressed polysulfone hollow fiber UF membrane, was made by phase inversion method. The cutoff molecular weight was 6000. The water permeation rate of this membrane module (psi 90 x 500 mm) is more than 150 L/hr.atm. The operating results show that the elimination of bacterial endotoxins by this membrane has reached the national standard in pharmacopoeia, and this technology is worthy to be extended over to medical industry. In addition, the essence of pyreotogen, the quantification units and measure methods for pyreotogen, and the operating conditions of UF device in the process of eliminating pyreotogen are introduced. Some critical points in operation was discussed.

Animals↗

PubMed2001

[Immunological classification of 112 adult acute leukemia patients].

OBJECTIVE: To explore the criteria and significance of immunological classification in adult acute leukemias. METHODS: One or two color monoclonal antibodies directly labeled with immunofluorescence were used to analyse the surface and cytoplasma antigens by flow cytometry, and an antibody integral system was developed for the immunologic classification. RESULTS: One hundred and twelve adult acute leukemia cases were detected. (1) The undifferentiated phenotype account for 0.9%, simple 51.8%, variant 38.4% and mixed lineage 8.9%. (2) The abnormal expressions of antigen in variant and mixed lineage phenotype were CD7, CD33, CD10, CD13, CD19 and CD20, by order of decreased level. CONCLUSION: The strict, numerical diagnostic criteria was very convenient and useful for immunophenotyping of adult acute leukemia.

Acute Disease↗

PubMed2000

Modulated chemical doping of individual carbon nanotubes.

Modulation doping of a semiconducting single-walled carbon nanotube along its length leads to an intramolecular wire electronic device. The nanotube is doped n-type for half of its length and p-type for the other half. Electrostatic gating can tune the system into p-n junctions, causing it to exhibit rectifying characteristics or negative differential conductance. The system can also be tuned into n-type, exhibiting single-electron charging and negative differential conductance at low temperatures. The low-temperature behavior is manifested by a quantum dot formed by chemical inhomogeneity along the tube.

Journal Article↗

PubMed2000

The zinc finger protein schnurri acts as a Smad partner in mediating the transcriptional response to decapentaplegic.

In Drosophila, a BMP-related ligand Decapentaplegic (Dpp) is essential for cell fate specification during embryogenesis and in imaginal disc development. Dpp signaling culminates in the phosphorylation and nuclear translocation of Mothers against dpp (Mad), a receptor-specific Smad that can bind DNA and regulate the transcription of Dpp-responsive genes. Genetic analysis has implicated Schnurri (Shn), a zinc finger protein that shares homology with mammalian transcription factors, in the Dpp signal transduction pathway. However, a direct role for Shn in regulating the transcriptional response to Dpp has not been demonstrated. In this study we show that Shn acts as a DNA-binding Mad cofactor in the nuclear response to Dpp. Shn can bind DNA in a sequence-specific manner and recognizes sites within a well-characterized Dpp-responsive promoter element, the B enhancer of the Ultrabithorax (Ubx) gene. The Shn-binding sites are relevant for in vivo expression, since mutations in these sites affect the ability of the enhancer to respond to Dpp. Furthermore we find that Shn and Mad can interact directly through discrete domains. To examine the relative contribution of the two proteins in the regulation of endogenous Dpp target genes we developed a cell culture assay and show that Shn and Mad act synergistically to induce transcription. Our results suggest that cooperative interactions between these two transcription factors could play an important role in the regulation of Dpp target genes. This is the first evidence that Dpp/BMP signaling in flies requires the direct interaction of Mad with a partner transcription factor.

Animals↗

PubMed2000

Functional discovery via a compendium of expression profiles.

Ascertaining the impact of uncharacterized perturbations on the cell is a fundamental problem in biology. Here, we describe how a single assay can be used to monitor hundreds of different cellular functions simultaneously. We constructed a reference database or "compendium" of expression profiles corresponding to 300 diverse mutations and chemical treatments in S. cerevisiae, and we show that the cellular pathways affected can be determined by pattern matching, even among very subtle profiles. The utility of this approach is validated by examining profiles caused by deletions of uncharacterized genes: we identify and experimentally confirm that eight uncharacterized open reading frames encode proteins required for sterol metabolism, cell wall function, mitochondrial respiration, or protein synthesis. We also show that the compendium can be used to characterize pharmacological perturbations by identifying a novel target of the commonly used drug dyclonine.

Cell Wall↗

PubMed2000

Reversible electromechanical characteristics of carbon nanotubes under local-probe manipulation

The effects of mechanical deformation on the electrical properties of carbon nanotubes are of interest given the practical potential of nanotubes in electromechanical devices, and they have been studied using both theoretical and experimental approaches. One recent experiment used the tip of an atomic force microscope (AFM) to manipulate multi-walled nanotubes, revealing that changes in the sample resistance were small unless the nanotubes fractured or the metal-tube contacts were perturbed. But it remains unclear how mechanical deformation affects the intrinsic electrical properties of nanotubes. Here we report an experimental and theoretical elucidation of the electromechanical characteristics of individual single-walled carbon nanotubes (SWNTs) under local-probe manipulation. We use AFM tips to deflect suspended SWNTs reversibly, without changing the contact resistance; in situ electrical measurements reveal that the conductance of an SWNT sample can be reduced by two orders of magnitude when deformed by an AFM tip. Our tight-binding simulations indicate that this effect is owing to the formation of local sp3 bonds caused by the mechanical pushing action of the tip.

Journal Article↗

PubMed2000

Intrinsic electrical properties of individual single-walled carbon nanotubes with small band gaps

Individual single-walled carbon nanotubes (SWNT) exhibiting small band gaps on the order of 10 meV are observed for the first time in electron transport measurements. Transport through the valence or conduction band of a small-gap semiconducting SWNT (SGS-SWNT) can be tuned by a nearby gate voltage. Intrinsic electrical properties of the Ohmically contacted SGS-SWNT are elucidated. An SGS-SWNT exhibits metal- or semiconductorlike characteristics depending on the Fermi level position in the band structure.

Journal Article↗

PubMed2000

Controllable reversibility of an sp(2) to sp(3) transition of a single wall nanotube under the manipulation of an AFM tip: A nanoscale electromechanical switch?

A simulation of the deflection of a single wall nanotube under the manipulation of an atomic force microscope tip revealed the key feature characterizing the deformation at relatively small bending angles to be a reversible transition from sp(2) to sp(3) bonding configurations in the bending region, leading to a 2 orders of magnitude reduction in conductance consistent with our most recent experimental observation. A local analysis elucidating the underlying physics of the findings is also discussed.

Journal Article↗

PubMed2000

Signaling and circuitry of multiple MAPK pathways revealed by a matrix of global gene expression profiles.

Genome-wide transcript profiling was used to monitor signal transduction during yeast pheromone response. Genetic manipulations allowed analysis of changes in gene expression underlying pheromone signaling, cell cycle control, and polarized morphogenesis. A two-dimensional hierarchical clustered matrix, covering 383 of the most highly regulated genes, was constructed from 46 diverse experimental conditions. Diagnostic subsets of coexpressed genes reflected signaling activity, cross talk, and overlap of multiple mitogen-activated protein kinase (MAPK) pathways. Analysis of the profiles specified by two different MAPKs-Fus3p and Kss1p-revealed functional overlap of the filamentous growth and mating responses. Global transcript analysis reflects biological responses associated with the activation and perturbation of signal transduction pathways.

Cell Cycle Proteins↗

PubMed2000

Nanotube molecular wires as chemical sensors

Chemical sensors based on individual single-walled carbon nanotubes (SWNTs) are demonstrated. Upon exposure to gaseous molecules such as NO(2) or NH(3), the electrical resistance of a semiconducting SWNT is found to dramatically increase or decrease. This serves as the basis for nanotube molecular sensors. The nanotube sensors exhibit a fast response and a substantially higher sensitivity than that of existing solid-state sensors at room temperature. Sensor reversibility is achieved by slow recovery under ambient conditions or by heating to high temperatures. The interactions between molecular species and SWNTs and the mechanisms of molecular sensing with nanotube molecular wires are investigated.

Journal Article↗

PubMed2000

PSM, a mediator of PDGF-BB-, IGF-I-, and insulin-stimulated mitogenesis.

PSM/SH2-B has been described as a cellular partner of the FcepsilonRI receptor, insulin receptor (IR), insulin-like growth factor-I (IGF-I) receptor (IGF-IR), and nerve growth factor receptor (TrkA). A function has been proposed in neuronal differentiation and development but its role in other signaling pathways is still unclear. To further elucidate the physiologic role of PSM we have identified additional mitogenic receptor tyrosine kinases as putative PSM partners including platelet-derived growth factor (PDGF) receptor (PDGFR) beta, hepatocyte growth factor receptor (Met), and fibroblast growth factor receptor. We have mapped Y740 as a site of PDGFR beta that is involved in the association with PSM. We have further investigated the putative role of PSM in mitogenesis with three independent experimental strategies and found that all consistently suggested a role as a positive, stimulatory signaling adapter in normal NIH3T3 and baby hamster kidney fibroblasts. (1) PSM expression from cDNA using an ecdysone-regulated transient expression system stimulated PDGF-BB-, IGF-I-, and insulin- but not EGF-induced DNA synthesis in an ecdysone dose-responsive fashion; (2) Microinjection of the (dominant negative) PSM SH2 domain interfered with PDGF-BB- and insulin-induced DNA synthesis; and (3) A peptide mimetic of the PSM Pro-rich putative SH3 domain-binding region interfered with PDGF-BB-, IGF-I-, and insulin- but not with EGF-induced DNA synthesis in NIH3T3 fibroblasts. This experiment was based on cell-permeable fusion peptides with the Drosophila antennapedia homeodomain which effectively traverse the plasma membrane of cultured cells. These experimental strategies independently suggest that PSM functions as a positive, stimulatory, mitogenic signaling mediator in PDGF-BB, IGF-I, and insulin but not in EGF action. This function appears to involve the PSM SH2 domain as well as the Pro-rich putative SH3 domain binding region. Our findings support the model that PSM participates as an adapter in various mitogenic signaling mechanisms by linking an activated (receptor) phospho-tyrosine to the SH3 domain of an unknown cellular partner.

3T3 Cells↗

PubMed2000

Frequency of SCA1, SCA2, SCA3/MJD, SCA6, SCA7, and DRPLA CAG trinucleotide repeat expansion in patients with hereditary spinocerebellar ataxia from Chinese kindreds.

OBJECTIVE: To assess the frequency of SCA1 (spinocerebellar ataxia type 1), SCA2, SCA3/MJD (spinocerebellar ataxia type 3/Machado-Joseph disease), SCA6, SCA7, and DRPLA (dentatorubropallidoluysian atrophy) CAG trinucleotide repeat expansions [(CAG)n] among persons diagnosed with hereditary SCA from Chinese families. PATIENTS AND METHODS: Spinocerebellar ataxia type 1, SCA2, SCA3/MJD, SCA6, SCA7, and DRPLA (CAG)n mutation were detected with the polymerase chain reaction, highly denaturing polyacrylamide gel electrophoresis, and silver staining technique in 167 patients with autosomal dominant SCA from 85 Chinese families and 37 patients with sporadic SCA. RESULTS: Spinocerebellar ataxia type 1 (CAG)n mutation in 7 patients from 4 kindreds (4.70%) was expanded to 53 to 62 repeats. Spinocerebellar ataxia type 2 (CAG)n mutation in 12 patients from 5 kindreds (5.88%) was expanded to 42 to 47 repeats. Spinocerebellar ataxia type 3/Machado-Joseph disease (CAG)n mutation in 83 patients from 41 kindreds (48.23%) was expanded to 68 to 83 repeats. Sixty-five patients from 35 kindreds (41.19%) and 37 patients with sporadic SCA did not test positive for SCA1, SCA2, SCA3/MJD, SCA6, SCA7, or DRPLA. There was a predictable inverse relationship between the number of CAG repeats and the age at onset for SCA3/MJD and SCA2. Clinically, dementia and hyporeflexia were more frequent in patients with SCA2, while spasticity, hyperreflexia, and Babinski signs were more frequent in patients with SCA3/ MJD, and those might be helpful in clinical work to primarily distinguish patients with SCA3/MJD and SCA2 from others with different types of SCA. CONCLUSIONS: The frequency of SCA3/MJD is substantially higher than that of SCA1 and SCA2 in patients with autosomal dominant SCA from Chinese kindreds, who are non-Portuguese. Clinical expressions of the various types of SCAs overlap one another; therefore, for clinical study it is important to make a gene diagnosis and genetic classification for patients with SCA.

Adolescent↗

PubMed2000

Probing the roles of the only universally conserved leucine residue (Leu122) in the oligomerization and chaperone-like activity of Mycobacterium tuberculosis small heat shock protein Hsp16.3.

To understand the role of the only universally conserved hydrophobic residue among all the members of the sHsp family, this extremely well conserved Leu122 residue in Hsp16.3 was replaced by valine, alanine, asparigine, or aspartate residues. Only very small amounts of the L122D and L122N mutant Hsp16.3 proteins were expressed in the transformed E. coli; however, both the L122V and L122A were readily expressed. The L122V and L122A mutant proteins had similar oligomeric structures to the wild-type protein at room temperature. Examination of the L122A mutant protein by native pore gradient PAGE and CD spectroscopy, however, revealed a smaller oligomeric size and different secondary structure at 37 degrees C. Both L122V and L122A mutant proteins exhibited significantly lowered chaperone activities. Observations reported here suggest a very important role of this only universally conserved Leu residue in both the formation of specific oligomeric structures and the molecular chaperone activities of Hsp16.3.

Bacterial Proteins↗

PubMed2000

Widespread aneuploidy revealed by DNA microarray expression profiling.

Expression profiling using DNA microarrays holds great promise for a variety of research applications, including the systematic characterization of genes discovered by sequencing projects. To demonstrate the general usefulness of this approach, we recently obtained expression profiles for nearly 300 Saccharomyces cerevisiae deletion mutants. Approximately 8% of the mutants profiled exhibited chromosome-wide expression biases, leading to spurious correlations among profiles. Competitive hybridization of genomic DNA from the mutant strains and their isogenic parental wild-type strains showed they were aneuploid for whole chromosomes or chromosomal segments. Expression profile data published by several other laboratories also suggest the use of aneuploid strains. In five separate cases, the extra chromosome harboured a close homologue of the deleted gene; in two cases, a clear growth advantage for cells acquiring the extra chromosome was demonstrated. Our results have implications for interpreting whole-genome expression data, particularly from cells known to suffer genomic instability, such as malignant or immortalized cells.

Aneuploidy↗

PubMed2000

On the relative influence of individual harmonics on pitch judgment.

Spectral weighting functions were estimated in a pitch-comparison task to assess the relative influence of individual harmonics on listeners' pitch judgment. The stimuli were quasi-harmonic complex tones composed of the first 12 components, with fundamental frequencies ranging from 100 to 800 Hz. On each stimulus presentation the frequency of each harmonic was randomly jittered by a small amount. The perceptual weight for each harmonic was calculated as the correlation coefficient between the binary responses of the listener and the frequency jitters for that harmonic. Although in general the present results conform to previous ones showing the predominant role of several low-ranked harmonics, discrepancies exist in details. Contrary to some previous reports that the dominant harmonics were of fixed harmonic ranks regardless of their frequencies, the current results showed that the dominant harmonics were best described as close to a fixed absolute frequency of 600 Hz.

Humans↗