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Biomedical subjects

Z Chen

Publications and source records attributed to Z Chen.

At least 721 records · Page 40Linked to original sources
PubMed1999

[Hair cell apoptosis and hearing loss of perilymphatic fistula].

OBJECTIVE: To investigate the effect of hair cell apoptosis on hearing loss of perilymphatic fistula (PLF) in guinea pig. METHOD: Twenty-five guinea pigs with light microscope and TdT mediated biotin dUTP nick-end labelling (TUNEL) techniques. The ECochG and ABR were measured and the data analyzed with statistics. RESULT: 1. The apoptosis of hair cell was not revealed in 0-hour-group and 2-hour-group of PLF. Following the time of PLF was longer, the apoptosis of hair cell was more increased. The apoptosis of hair cell was demonsted in 1-day-group (1 case, 17%), 2-day-group (4 case, 67%) and 7-day-group (4 case, 80%); 2. The amplication of AP was reduced after operation induced PLF. The CAP of experimental ear was significantly higher than that of control ear (P < 0.01) in 1-day-group, 2-day-group and 7-day-group. CONCLUSION: 1. Apoptosis of hair cell was appeared in PLF; 2. The apoptosis of hair cell may be one of morphological evidence in hearing loss of PLF.

Animals↗
PubMed1999

[C677T genetic polymorphism of methylenetetrahydrofolate reductase in premature coronary heart disease].

OBJECTIVE: Methylenetetrahydrofolate reductase (MTHFR) is an important factor responsible for hyperhomocysteinemia. The relation of MTHFR gene C677T polymorphism and premature coronary heart disease was studied. METHODS: MTHFR C677T genetic polymorphisms in 67 patients with premature coronary heart disease were detected by PCR-RFLP technique. RESULTS: In case group, the frequency of T homogenic type was 34.3% (23/67), heterogenic type 43.3% (29/67) and C homogenic type 22.4% (15/67). T allele frequency was 55.9% (75/134) while C allele frequency 44.1% (59/134) in case group. There were significant differences in MTHFR genotype and allele frequencies between cases and controls (chi 2 = 6.82 and 5.41 respectively, P < 0.05). CONCLUSIONS: It was suggested that MTHFR gene C677T mutation was a possible risk factor of Chinese premature coronary heart disease.

Adult↗
PubMed1999

[Application study of yangkang biological fertilizer on Panax notoginseng cultivation].

Yangkang Biological Fertilizer was sprayed on Panax notoginseng. The result indicated that the yield and the surviving rate can be raised 25.2% and 15.2% respectively. The best spraying practice were: in the unfolding stage of leaves (April) and bloom stage (July), with Yangkang Biological Fertilizer plus water (1:400), at four times every stage.

Fertilizers↗
PubMed1999

[Expanded polytetrafluoroethylene with different pore diameter for keratoprosthesis cell ingrowth and corneal metabolism].

PURPOSE: (1). To study the relationship between the different pore diameter of the expanded polytetrafluoroethylene, (ePTFE) and the rate of cellular ingrowth in cornea; (2). To evaluate the influence of implant on corneal metabolism. METHODS: Two kinds of ePTFE disk with 45 microns and 28 microns pore diameter were implanted after a free-hand intralamellar dissection. The eyes were examined by slit-lamp biomicroscopy up to 7 months postoperatively. The corneas were removed and examined by light and transmission electron microscopy. RESULTS: Stromal fibroblasts penetrate, proliferate, and synthesize collagen in the pore of these two kinds of ePTFE, while the rate of cellular ingrowth and collagen deposition was greater in the ePTFE with 45 microns pore than 28 microns pore. Lipid deposits occurred in 3 eyes with 45 microns pore and in 5 eyes with 28 microns pore (P > 0.05). Dicks remained in corneas for 7 months without any extrusion in all eyes. CONCLUSION: Stromal fibroblasts can penetrate, proliferate, and synthesize collagen in the pore of both two kind of ePTFE, while cells penetrate greatly in the larger pore. Dicks interfere corneal metabolism in some degree. The ePTFE with 45 microns pore diameter, 200 mm thick, 84% porosity is a suitable material for the skirt of the keratoprosthesis.

Animals↗
PubMed1999

[Determination of lead in tinplate by ICP-AES].

The determination of lead in tinplate by ICP-AES was presented in this paper. The tinplate samples were pretreated with NaOH-H2O2 for dissolving tin and lead,and the spectral interferences from iron could thus be avoided. The lead content in the sample was determined in the range of 0.14-0.38 microg/cm2. The recovery and the relative standard deviation (RSD) were in the ranges of 96.1%-103.2% and 2.6%-3.8%, respectively. The method was simple,rapid and efficient.

Food Packaging↗
PubMed1999

[Study on spectral emission characteristics of infrared lamps].

The spectral characteristics at wavelength ranges of 0.35-0.85 microm and 1.72-16.7 microm (5800-600 cm(-1)) for both domestic and imported infrared lamps used in scientific research, industry, medical service, home electrical appliance etc. have heen studied and compared. This paper has provided the theoreical and experimental bases for their applications and improvement in designs, technology of manufacture, quality and performance.

English Abstract↗
PubMed1999

[An algorithm for real-time quantitative analysis of remote detection spectrum of chemical vapor with passive Fourier-transform infrared spectroscopy].

The algorithm for quantitative analysis of passive Fourier-transform infrared spectum (FTIR) of a chemical vapor is given. It can be applied to both real-time processing for chemical vapor and quantitative measurements of chemical vapor column density. The algorithm simultaneously achieves quantitation of the vapor spectral transmission, background removal, real-time calibration for FTIR. Finally, we discuss in detail an example of the use of the algorithm to a simulant DMMP.

Air Pollutants↗
PubMed1999

[Prediction the octane number of gasoline by near infrared spectra analysis].

The feasibility of predicting the octane number by the near infrared spectra analysis technique in the quantitative analysis was investigated. 12 calibration gasoline samples and 4 prediction samples were collected and their absorption spectra were measured with a high precision model Lambda 19 scanning spectrophotometer. Based on the multivariate statistic model, stagewise regression and partial least squares were selected. A model of the correlation behavior between the spectra and octane number was established and calibrated, and then the prediction of octane number is made. The prediction error is +/-1.0 octane number in the best analysis results.

Gasoline↗
PubMed1999

[Analysis of carbon in low alloy steel by XRF].

In this paper optimum conditions for the analysis of carbon have been found and a new sampling method introduced. The detection limit is 0.0179% and the standard deviation is 0.0039% as C=0.18%. The method has been used for the determination of carbon in low alloy steel with satisfactory results.

English Abstract↗
PubMed1999

[Transmission grating spectrograph for soft X-ray spectrum measurements with a pre-optics].

A novel diffraction spectroscopic instrument consisting of a large area transmission grating and a grazing-incidence pre-optics comprising of a toroidal mirror, a slit and a cylindrical mirror has been implemented. A nearly perfect stigmatism and a medium spectral resolution are due to the separation of the focusing and dispersing function. The experimental results show that it is possible to construct large area transmission grating spectrograph with high collecting efficiency and good spatial resolution.

English Abstract↗
PubMed1998

Molecular basis for interprotein complex-dependent effects on the redox properties of amicyanin.

The quinoprotein methylamine dehydrogenase (MADH), type I copper protein amicyanin, and cytochrome c-551i form a complex within which interprotein electron transfer occurs. It was known that complex formation significantly lowered the oxidation-reduction midpoint potential (Em) value of amicyanin, which facilitated an otherwise thermodynamically unfavorable electron transfer to cytochrome c-551i. Structural, mutagenesis, and potentiometric studies have elucidated the basis for this complex-dependent change in redox properties. Positively charged amino acid residues on the surface of amicyanin are known to stabilize complex formation with MADH and influence the ionic strength dependence of complex formation via electrostatic interactions. Altering the charges of these residues by site-directed mutagenesis had no effect on the Em value of amicyanin, ruling out charge neutralization as the basis for the complex-dependent changes in redox properties. The Em value of free amicyanin varies with pH and exhibits a pKa value for the reduced form of 7.5. The crystal structure of reduced amicyanin at pH 4.4 reveals that His95, which serves as a ligand for Cu2+, has rotated by 180 degrees about the Cbeta-Cgamma bond relative to its position in oxidized amicyanin and is no longer in the copper coordination sphere. At pH 7.7, the crystal structure of reduced amicyanin contains an approximately equal distribution of two active-site conformers. One is very similar to the structure of reduced amicyanin at pH 4.4, and the other is very similar to the structure of oxidized amicyanin at pH 4.8. Potentiometric analysis of amicyanin in complex with MADH indicates that its Em value is not pH-dependent from pH 6.5 to 8.5, and exhibits an Em value similar to that of free amicyanin at high pH. The structure of reduced amicyanin at pH 4.4, with His95 protonated and "flipped", was modeled into the structure of the complex of oxidized amicyanin with MADH. This showed that in the complex, the redox-linked pH-dependent rotation of His95 is hindered because it would cause an overlap of van der Waals' radii with residues of MADH. These results demonstrate that protein-protein interactions profoundly affect the redox properties of this type I copper protein by restricting a pH-dependent, redox-linked conformational change of one of the copper ligands.

Bacterial Proteins↗
PubMed1998

Natural infection of a homozygous delta24 CCR5 red-capped mangabey with an R2b-tropic simian immunodeficiency virus.

A homozygous 24-bp deletion (Delta24) was found in the CC chemokine receptor 5 (CCR5) of 11 out of 15 red-capped mangabeys (RCMs), Cercocebus torquatus torquatus, both in Africa and in an American zoo. The CCR5 Delta24 defect encompassed eight amino acids in frame in the fourth transmembrane region. Unexpectedly, RCM-009, one of 11 homozygotes (Delta24CCR5/ Delta24CCR5), was found to be naturally infected with a divergent simian immunodeficiency virus (SIV) strain, which was not R5-tropic, but used CCR2b (R2b) as its major coreceptor. SIVrcmGab1 was the only R2b-tropic SIV among other divergent SIVs tested. Cells transfected with the Delta24 CCR5 did not support entry of R5-tropic SIVmac, SIVcpz, SIVmne, HIV-2, or HIV-1, and were also inactive in signal transduction mediated by beta-chemokines. At 86.6%, the Delta24 allelic frequency was significantly higher than that of the 32-bp deletion found in humans. The Delta24 frequency was 4.1% in 34 sooty mangabeys (SMs), a geographically isolated subspecies that was naturally infected with R5-tropic SIV. Finding identical deletions in two mangabey subspecies separated for 10,000 years or more dates the Delta24 CCR5 deletion as ancient. However, the source of the selective pressure for the high rate of CCR5 deletion in RCMs remains to be determined. The high allelic frequency of the Delta24 CCR5 in RCMs, in comparison to that of SMs, suggests that R2b-tropism may have been acquired by SIVrcm, as an adaptation to CCR5 genetic defects appeared in its host.

Amino Acid Sequence↗
PubMed1998

B cells malignantly transformed by human immunodeficiency virus are polyclonal.

The roles that human immunodeficiency virus (HIV) and Epstein-Barr virus (EBV) play in the genesis of acquired immune deficiency syndrome (AIDS)-related lymphomas are not understood. A human B cell line (B-HIV), developed to study AIDS-related lymphomagenesis, contains EBV and HIV genomes and is malignantly transformed. This line was produced by exposing B cells from an EBV-seropositive donor to HIV. To investigate the number of independent transformation events that took place at the time of HIV infection, we sought to determine how many transformed lineages are present in this cell line. B-HIV was found to have multiple different sites of HIV integration (> or = 25) as determined by fluorescence in situ hybridization. As a control, we analyzed a clonal cell line of HIV-infected human T cells, 8E5, and found HIV sequences located exclusively at band q22 in chromosome 13. We conclude that B-HIV is polyclonal, and viral sequences are located at multiple variable chromosomal sites in different B-HIV cells.

B-Lymphocytes↗
PubMed1998

Amplification of closed circular DNA in vitro.

The polymerase chain reaction is a powerful technique used to amplify nucleic acids in vitro. The reaction produces linear products, and as of yet, closed circular products have not been possible. Since the replicatively competent form of many DNA molecules is the closed circular form, it would be adventitious to amplify closed circular DNA as closed circular molecules. Until now, these molecules could only be amplified in vivo in appropriate host cells. Here, we describe an in vito procedure, ligation-during-amplification (LDA), for selective amplification of closed circular DNA using sequence-specific primers. LDA is useful for site-directed mutagenesis, mutation detection, DNA modification, DNA library screening and circular DNA production.

DNA Ligases↗