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Biomedical subjects

Yu He

Publications and source records attributed to Yu He.

At least 37 records · Page 2Linked to original sources
PubMed2005

Studies on interaction of norfloxacin, Cu2+, and DNA by spectral methods.

The interactions of norfloxacin (NFA), DNA, and Cu2+ are studied by fluorescence and UV-spectra method. According to the experimental results, it can be concluded that NFA can form a steady binary complex with Cu2+. There is a linear relationship between the Fluorescence intensity of the norfloxacin-Cu2+-DNA system and the concentration of DNA. And when the concentration of the NFA is 1.95x10(-5) mol L-1, they possess a good linearity in the concentration of DNA ranged from 4.7x10(-6) to 2.8x10(-5) mol L-1. It is a good method due to the high sensitivity and selectivity.

Calibration↗
PubMed2005

Attribute capture in the precedence effect for long-duration noise sounds.

Listeners perceptually fuse the direct wave from a sound source with its reflections off nearby surfaces into a single sound image, located at or near the sound source (the precedence effect). This study investigated how a brief gap presented in the middle of either a direct wave or simulated reflection is incorporated into the fused image. For short (<9.5 ms) delays between the direct (leading) and reflected (lagging) waves, no sound was perceived from the direction of the lagging wave. For delays between 10 and 15 ms, both sounds were perceived, but the gap was heard only on the leading side. When the gap was only in the correlated lagging sound at short delays, it also was perceived as occurring on the leading side. Moreover, gap detection thresholds were the same for gaps in the leading and lagging sounds, suggesting that the perception of the gap was not suppressed, but rather incorporated into the leading sound. Finally, scalp event-related potentials were not associated with the precedence effect until the gap occurred. This suggests that cortical mechanisms are engaged to maintain fusion when attributes in direct or reflected waves change.

Adult↗
PubMed2005

Hearing two things at once: neurophysiological indices of speech segregation and identification.

The discrimination of concurrent sounds is paramount to speech perception. During social gatherings, listeners must extract information from a composite acoustic wave, which sums multiple individual voices that are simultaneously active. The observers' ability to identify two simultaneously presented vowels improves with increasing separation between the fundamental frequencies (f0) of the two vowels. Event-related potentials to stimuli presented during attend and ignore conditions revealed activity between 130 and 170 msec after sound onset that reflected the f0 differences between the two vowels. Another, more posterior and right-lateralized, negative wave maximal at 250 msec, and a central-parietal slow negativity were observed only during vowel identification and may index stimulus categorization. This sequence of neural events supports a multistage model of auditory scene analysis in which the spectral pattern of each vowel constituent is automatically extracted and then matched against representations of those vowels in working memory.

Acoustic Stimulation↗
PubMed2005

Effects of visual attentional load on low-level auditory scene analysis.

The sharing of processing resources between the senses was investigated by examining the effects of visual task load on auditory event-related brain potentials (ERPs). In Experiment 1, participants completed both a zero-back and a one-back visual task while a tone pattern or a harmonic series was presented. N1 and P2 waves were modulated by visual task difficulty, but neither mismatch negativity (MMN) elicited by deviant stimuli from the tone pattern nor object-related negativity (ORN) elicited by mistuning from the harmonic series was affected. In Experiment 2, participants responded to identity (what) or location (where) in vision, while ignoring sounds alternating in either pitch (what) or location (where). Auditory ERP modulations were consistent with task difficulty, rather than with task specificity. In Experiment 3, we investigated auditory ERP generation under conditions of no visual task. The results are discussed with respect to a distinction between process-general (N1 and P2) and process-specific (MMN and ORN) auditory ERPs.

Acoustic Stimulation↗
PubMed2005

[Capillary electrophoresis with end-column electrochemical detection for hydrochlorothiazide and triamterene diuretics].

A method based on capillary electrophoresis with end-column electrochemical detection (HPCE-ED) was developed for the determination of the diuretics of hydrochlorothiazide (HCT) and triamterene (TAT) simultaneously. The detection electrode was a 300 microm carbon disc electrode at a working potential of +1.1 V versus Ag/AgCl electrode. The two analytes could be well separated within 8 min in a 50 cm long capillary at a separation voltage of 24 kV with a 10 mmol/L phosphate buffer (pH 7.5). Under optimum conditions, the current response was linear over about two orders of magnitude with detection limits (S/N = 3) of 0.29 and 0.25 mg/L for triamterene and hydrochlorothiazide, respectively. The proposed method was successfully applied to determine the synthetic urine and real pharmaceuticals samples. The recoveries were found to be in the range of 93.5%-97.2%.

Diuretics↗
PubMed2005

[Study of phenotypes and functions of cord blood dendritic cells from fetuses whose mothers had chronic hepatitis B].

OBJECTIVE: To investigate the phenotypes and functions of cord blood dendritic cells of fetuses whose mothers are patients with chronic hepatitis B. METHODS: Peripheral blood and cord blood mononuclear cells (PBMC) were isolated from whole blood by density gradient centrifugation with Ficoll-Hypaque. The adherent cells were cultured in AIM-V medium containing recombinant human IL-4, TNF-alpha and GM-CSF. On day 9, mature DCs (mDC) were harvested and used for phenotype analysis. The amounts of IL-12 which dendritic cells produced were measured. The dendritic cells that were studied and compared were from cord blood of fetuses of both CHB positive and negative mothers and from CHC adult peripheral blood. RESULTS: The expression rate of CD80 and CD83 of chronic hepatitis B mother cord blood dendritic cells was low compared with that of the healthy cord blood, healthy adult peripheral blood, and chronic hepatitis B adult peripheral blood, P < 0.05. The amount of IL-12 produced by chronic hepatitis B mother cord blood dendritic cells was lower than that of healthy cord blood, healthy adult peripheral blood, chronic hepatitis B adult peripheral blood (P < 0.05). The T lymphocyte proliferation inducing ability of dendritic cells of healthy adult peripheral blood was higher in inducing cord blood T lymphocytes proliferation, which was greater than that of the healthy adult peripheral blood in inducing adult T lymphocytes and was greater than that of the healthy cord blood dendritic cells in inducing cord blood T lymphocytes, which was greater than that of the healthy cord blood in inducing adult T lymphocytes, which was greater than that of chronic hepatitis B mothers in inducing cord blood T lymphocytes, which was greater than that of chronic hepatitis B mother cord blood in inducing adult T lymphocytes. CONCLUSION: The maturation and functioning of CHB mother cord blood dendritic cells were lower than those of healthy cord blood, healthy adult peripheral blood and CHB adult peripheral blood.

Adult↗
PubMed2005

[Allelopathic effects of grafted eggplant root exudates].

By the methods of bioassay, this paper studied the allelopathic effects of different concentrations root exudates from the eggplants grafted with different stocks and at different growth stages. The results showed that compared with that of own-rooted eggplant, the root exudates from grafted eggplants promoted the seed germination and seedling growth of eggplants, and, in comparing with the control (water), they increased the germination rate and plant height by 29.1% and 37.1%, respectively. The seed germination and root length of eggplants was increased at lower concentrations root exudates, but decreased at higher concentrations. The germination rate was increased up to 50% above control at 0.04 g x ml(-1), and the inhibition of root length was up to 30.3% at 0.24 g x ml(-1). The promotion effect of the root exudates from late growth stage grafted eggplants on seed germination was less than that from other growth stage grafted eggplants. Own-rooted eggplant had an intensified inhibitory effect at its late growth stage. Grafting was one of the effective methods for relieving the continuous cropping obstacles caused by autotoxicity.

Pheromones↗
PubMed2005

[Simultaneous determination of 7-methylguanosine and mitomycin C by capillary electrophoresis with amperometric detection].

A method based on capillary electrophoresis with amperometric detection (CE-AD) has been developed for the simultaneous determination of 7-methylguanosine and mitomycin C. The detection electrode was a 0.3 mm carbon disc electrode at a working potential of 950 mV (versus Ag/AgCl electrode). A suitable electrolyte consists of 20 mmol/L phosphate buffer (pH 9.4), with the separation voltage of 18 kV, the injection time of 10 s, and the injection voltage of 18 kV. Under optimum conditions, the two analytes could be well separated within 10 min in a 60 cm length capillary. The current responses were linear over about two orders of magnitude (0.50 - 50 mg/L) with detection limits (S/N = 3) of 0. 050 and 0.025 mg/L for 7-methylguanosine and mitomycin C, respectively. The proposed method was successfully applied to determine the synthetic urine and serum samples. The recoveries were found in the range of 93.0% - 97.2%.

Alkylating Agents↗
PubMed2004

[Construction of HLA-A2-peptide tetramer and application in HBV/HCV infection].

OBJECTIVE: To construct HBV and HCV-specific HLA-A2-peptide tetramers, and to direct clinical therapy. METHODS: Recombinant class I HLA-A2 heavy chains and beta-2 M were produced in Escherichia coli cells transformed with pBV220 vectors. Only the extracellular domain of class I heavy chain was expressed, following modification by replacement of the C-terminal domain with a substrate sequence for BirA biotinylation. HLA-A2-BSP was folded in the presence of beta-2 microglobulin and a specific peptide to form a peptide-MHC complex. The MHC complexes were biotinylated using purified BirA enzyme. Biotinylated MHC-peptide complexes were purified. Tetramers were generated by mixing biotinylated protein complex with streptavidin-PE at a molar ratio of 4:1. Then analysis of stained PBMCs was performed using FACScan and CellQuest software. RESULTS: The expression levels of pBV220-HLA-A2-BSP and beta-2M were 46% and 48% of total bacterial proteins estimated from SDS - PAGE, respectively. And they were mainly located in the insoluble fraction of the cell as inclusion bodies and the proportion were about 85% and 90%, respectively. The purity of pBV220-HLA-A2-BSP and beta-2M was above 95% analyzed by SDS-PAGE, and the concentration of pBV220-HLA-A2-BSP and beta-2M was about 1.5 g/L and 1.2 g/L, respectively. Using the constructed HLA-A2-peptide tetramer to detect the HBV/HCV-specific CTL, the HBV-specific CD8(+) frequencies were 1.84% and 0.02% - 0.68% of the total CD8(+) T cells in acute and chronic HBV hepatitis, respectively. As an additional control, an HLA-A2/HCV tetramer was tested in the acute and chronic HBV hepatitis. The frequencies never exceeded 0.02% of the total CD8(+) T cell number. Similar low levels of background staining were also detected in the HLA-A2(+) or A2(-) healthy control. The HCV-specific CD8(+) frequency was 0.02 - 0.72% of the total CD8(+) T cells in chronic HCV hepatitis. The same frequencies of control were detected. CONCLUSION: High-efficient expressions of HLA-A0201-BSP and beta-2m proteins lay a good foundation for further expression and purification in prokaryotic system and constructing MHC class I-peptide tetramer complexes to study the function of CTLs. Especially, using these two HBV and HCV-specific tetramer can detect the frequencies of the HBV/HCV-specific CD8(+) T cells directly in vitro.

Cloning, Molecular↗
PubMed2004

Cloning, expression, and purification of HLA-A2-BSP and beta-2m in Escherichia coli.

Tetramer analysis is a novel technique in immunological research that has dramatically changed our knowledge of the immune response to pathogens, tumors and autoimmune disease. Through the formation of major histocompatibility complex (MHC)-peptide tetrameric complexes, it can provide accurate counts of antigen-specific T-cells and it allows their phenotypical and functional analysis. The tetramer is composed of the human leukocyte antigen (HLA) heavy chain, beta-2 microglobulin (beta-2m), the nominal peptide, and streptavidin. The HLA heavy chain and the beta-2m are expressed in Escherichia coli. But up to now, all laboratories have been expressing these two proteins by using isopropyl beta-d-thiogalactopyranoside IPTG. IPTG is very expensive, and it is tedious and laborious to induce expression protein. So it is difficult to scale up to express the objective protein. To address this problem, extracellular fractions of HLA-A0201 and beta-2m (absent signal peptide) genes were cloned from peripheral blood mononuclear cells (PBMCs) by RT-PCR. DNA coding for a Gly-Ser linker and a BSP (15-amino acid substrate peptide for BirA-dependent biotinylation) was added to the COOH-terminus of the extracellular fraction of HLA-A0201 by PCR, using an HLA-A0201 as the template. Then the HLA-A0201-BSP and beta-2m genes were cloned into pBV220 vector and expressed, respectively. The expressed proteins were purified and detected by ELISA and Western blot analyses. High-efficient expressions of HLA-A0201-BSP and beta-2m proteins lay a good foundation for further expression and purification in prokaryotic system and constructing MHC class I-peptide tetramer complexes to study the function of CTLs.

Base Sequence↗
PubMed2004

The interaction between levofloxacine hydrochloride and DNA mediated by Cu2+.

Levofloxacin (LEV) is a fluoroquinolone antimicrobial agent. LEV also inhibits DNA synthesis and is bactericidal. The mechanisms of the interaction among LEV, DNA and Cu2+ are studied by fluorescence method. In the paper, the results show that LEV and Cu2+ can form binary complex, and also LEV and DNA can form complex mediated by Cu2+. The composition of the complex is determined. The affects to the reaction are also found.

Animals↗
PubMed2004

[Study of the correlation between drug exposure and blood concentration during cyclosporine microemulsion absorption phase in Chinese adult liver transplant recipients].

OBJECTIVE: To analyze the correlation between drug exposure (AUC0-4) and blood concentration of different sample points during Neoral absorption phase in Chinese adult liver transplant recipients, and to evaluate the possibility of using post-dose 2 hour level (C2) as a surrogate marker of AUC0-4 for the therapeutic drug monitoring (TDM) of Neoral. METHODS: Neoral levels at 0, 1, 2, 3, and 4 hours (C1, C2, C3, C4) after morning dose of 22 de novo Chinese adult liver transplant recipients were monitored during different posttransplant periods. Liner regression was used to analyze the correlation between CsA concentration at different time points and the AUC0-4. RESULTS: The best correlation was found at C2, while the correlation of C0 was the lowest. During following-up, the correlation between C2 and AUC0-4 was very stable. CONCLUSION: C2 had the best correlation with drug exposure. This correlation is very stable. C2 may be used as a good surrogate marker of AUC0-4 for the TDM of Neoral.

Adult↗
PubMed2003

Perceptual learning modulates sensory evoked response during vowel segregation.

With practice, people become better at discriminating two similar stimuli, such as two sounds. The neural mechanisms that underlie this type of learning have been of interest to researchers investigating neural plasticity associated with learning and recovery of function following stroke. We utilized event related potentials (ERP) to study the neural substrates underlying auditory discrimination learning. Stimuli were five steady-state American English vowels. On each trial, participants were presented with a pair of vowels created by summing together the digital waveforms of two different vowels. Listeners were instructed to identify both vowels in the pair. ERPs were recorded during two sessions separated by 1 week. Half of the participants practised the discrimination task during the intervening week while the other half served as controls and did not receive any training. Trained listeners showed greater improvement in accuracy than untrained participants. In both groups, vowels generated N1 and P2 waves at the fronto-central and temporal scalp regions. The behavioral effects of training were paralleled by decreased N1 and P2 latencies as well as enhanced P2 amplitude in the trained compared with untrained listeners. The effects of training on sensory evoked responses are consistent with the proposal that perceptual learning is associated with changes in sensory cortices.

Adolescent↗
PubMed2002

Visual feature conjunction in patients with schizophrenia: an event-related brain potential study.

The neural mechanisms supporting performance during single feature and feature conjunction detection were investigated in patients with schizophrenia and age-matched controls using event-related brain potentials. In different blocks of trials, participants responded to visual targets defined by one of two colors, one of two orientations, or both color and orientation. All participants were faster and more accurate in detecting targets defined by a single feature than for targets defined by a conjunction of features. Relative to controls, patients made more errors and were slower in detecting targets defined by a combination of features. Patients also generated a smaller N2 wave to single and conjunctive targets, and showed greater P3b reduction over the right hemisphere for conjunctive targets than for targets defined by color only. In addition, target stimuli generated an increased negativity at the occipital sites that varied in scalp distribution with the attended features in controls but not in patients. Both behavioral and electrophysiological data provide converging evidence for deficits in integrating visual features in schizophrenia and suggest that processing features of visual objects in schizophrenia are partly supported by distinct functional networks.

Adult↗
PubMed2002

Neurophysiological evidence of error-monitoring deficits in patients with schizophrenia.

The present study was designed to investigate the time-course of neural activity underlying the disruption of response monitoring in patients with schizophrenia. Event-related brain potentials were recorded from 12 patients with schizophrenia and from 12 age-matched controls while they performed a computerized version of the Stroop color-naming task. In control participants, but not in patients with schizophrenia, intrusion errors elicited an error-related negativity (ERN) that peaked at approximately 40 ms after the response and was maximum over the central region of the scalp. Brain electrical source analysis revealed an anterior cingulate generator for the ERN. Patients also showed reduced error-related slowing of response time following intrusion errors. These findings provide neuro-physiological evidence indicating that deficits in error monitoring in schizophrenia arise from a disruption of error-detection processes, possibly attributable to anterior cingulate dysfunction.

Adult↗