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Biomedical subjects

L Chen

Publications and source records attributed to L Chen.

At least 289 records · Page 16Linked to original sources
PubMed2001

[Preliminary study on apoptosis of human leukemic cells induced by bufalin].

OBJECTIVE: To study the mechanism of inhibiting actions of bufalin on human leukemic cells (HL60). METHODS: HL60 cells were incubated with bufalin at different concentrations and growth inhibition was analyzed by trypan-blue staining. Cell apoptosis was evaluated by phase contrast microscopy, transmission eletron microscopy and agarose gel electrophoresis. RESULTS: Bufalin remarkably inhibited the growth of HL60 cells. Apoptosis of HL60 cells could be effectively induced by bufalin at concentration of 0.01 mumol.L-1 or higher, showing the apoptotic changes in morphology, including cell shrinkage, chromatin agglutination and formation of apoptotic corpuscula; DNA cleavage was observed with agarose gel electrophoresis. CONCLUSION: Bufalin can effectively induce apoptosis of HL60 cells, which is possibly one of the mechanisms for anti-cancer of bufalin.

Antineoplastic Agents↗
PubMed2001

[Study on HIV DNA of epidemic HIV-1 strains].

OBJECTIVE: To study the characteristics of variation of HIV DNA in prevalent HIV-1 strains. METHODS: HIV DNA, extracted from peripheral blood mononuclear cell(PBMC) in 63 patients infected with HIV, was investigated by reverse-transcript PCR (RT-PCR), Long-Distance PCR(LD-PCR), molecular cloning hybridization and sequencing, respectively. RESULTS: The subtypes were identified in 57 samples. Subtype B was identified in 43 cases, subtype C in 5 and subtype E in 9. It was found that both full-length and defective HIV DNA in 31 out of 57 cases, defective HIV DNA in 19 cases and full-length HIV DNA in 7 cases. The deleted regions of genome were from 71 to 7,759 nucleotides. CONCLUSION: The variation of gene segments of HIV DNA plays an important role in the infection and epidemic of HIV.

Adult↗
PubMed2001

[An experimental study on the implantation of a biomaterial with electro-activity for replacement of hard tissue in bone].

OBJECTIVE: To assess the effects of a piezoelectric biological ceramic on osteogenesis. METHODS: Hydroxyapatite (HA) and piezoelectric biological ceramics (hydroxyapatite and barium titanate, HABT) were implanted in the jawbones of 5 dogs, and for sample collection, the dogs were killed separately at 1 week, 2 weeks, 1 month, 2 months and 3 months after implantation. The samples from a rhesus monkey and a blank control were collected 34 months after implantation. The implanted samples and surrounding tissues were subjected to histological observations using light microscopy (LM) and scanning electronmicroscopy (SEM) were made. RESULTS: Compared with the control groups, the HABTs promoted osteogenesis significantly. One week after implantation, new bone tissues were found on the surface vertical to the longitudinal direction of HABT; more bone tissues were found after 2 weeks. HABTs induced the bone tissues to arrange orderly. After two years and ten months of implantation, the piezoelectric bioceramic and bone became monolithic, and the structure of bone was normal. CONCLUSION: HABTs could promote osteogenesis.

Animals↗
PubMed2001

[Study on the expression of fibronectin after cerebral contusion in rats for timing of injuries].

An experimental model of reproducible focal cerebral contusions in rats was made by a free-drop impacting right hemisphere. The expression of fibronectin and its mRNA after cerebral contusion were detected respectively by immunohistochemical staining and in situ hybridization. Results indicated that the expression of fibronectin and its mRNA increased after injury, and there existed a relationship between increased fibronectin and its mRNA and different intervals after brain injury. It is inferred that the expression of fibronectin and its mRNA can be used for timing of brain injuries and distinguishing antemortem and postmortem brain contusions.

Animals↗
PubMed2001

[Extraction of residual formaldehyde in polymer complex and high performance liquid chromatographic analysis].

This paper presents a simple and accurate method for analyzing formaldehyde in polymer complex by headspace extraction derivatization and HPLC analysis. The sample preparatio of formaldehyde in polymer complex was based on a simple thermodynamic equilibrium in a closed and thermostat jar, and the gaseous formaldehyde in equilibrium could be absorbed and extracted by the liquid in the bottom of the jar. The formaldehyde was derivatized with 2,4-dinitrophenyl hydrazine before chromatography. The influences of temperature, equilibrium time, sample quantity and geometric form on the extraction efficiency were studied. The extraction and HPLC conditions were optimized. The limit of detection (LOD) was 0.1 mg/kg, and the relative standard deviation (RSD) was below 5%, and the recoveries were between 96%-103%. As a result, this method would meet the demands for analyzing microamounts of residual formaldehyde in polymer complex.

Chromatography, High Pressure Liquid↗
PubMed2001

[The location of new porcine microsatellites by means of PRINS and somatic cell hybrid panel].

In this study, two new microsatellites HAU02 and HAU06, which are screened and cloned. HUA02 and HAU06 are repectively mapped in lq23-27 and 6q11-21 by means of PRINS (primed in situ labeling) and somatic cell hybrid (SCH) panel techniques, we discussed their advantage and disadvantage in gene mapping. These two means provide us more techniques in gene mapping, and the locations of these new microsatellites accumulate more resource for Porcine Physical Map.

Animals↗
PubMed2001

A study on the preservation of fresh amniotic membrane.

OBJECTIVE: To establish the standard preservation methods of fresh amniotic membrane for clinical use. METHODS: Human placentas were collected aseptically from selective caesarean sections in normal women in time. Amniotic or placental membrane were peeled and preserved in N. S, P. B. S or DMEM at 4 degrees C or cultured in DMEM at 37 degrees C, 5% CO2. Trypan-blue staining, light and electronic microscopy were observed every six hours after preservation. RESULTS: Seventy percent of amniotic epithelial cells survived after preservation in N.S for 6 hours, PBS 12 hours, DMEM 24 hours and 1 week in tissue culture. The amount of living epithelial cells maintained in placental membrane preservation was less than that in amniotic membrane preservation at the same time (t-test, P < 0.01). No collagen degeneration was found during preservation. CONCLUSION: Preservative solution and time will affect the maintenance time of fresh amniotic membrane greatly. Fresh amniotic membrane should be preserved within 6 hours in N. S, 12 hours in P. B. S, 24 hours in DMEM at 4 degrees C and 1 week in tissue culture for clinical use.

Adult↗
PubMed2001

[Studies on the triterpenoidal saponins from flowers of Eriobotrya japonica].

OBJECTIVE: To investigate the chemical composition of the flowers of Eriobotrya japonica. METHODS: Four constituents were isolated from the ethanolic extracts of flowers of Eriobotrya japonica (Thunb) Lindl and were identified by chemical methods and spectroscopic (IR, MS, 1HNMR, 13CNMR). RESULTS: The structures were identified as: Oleanolic acid (I), Ursolic acid(II), 2 alpha, 3 alpha, 19 alpha-Trihydroxyurs-5,12-dien-28-acid (III) and 2 beta, 3 beta, 23 alpha-Trihydroxyolean-12-en-28-acid (IV). CONCLUSION: The compounds I, II, III and IV were obtained from the flowers of Eriobotrya japonica for the first time.

Eriobotrya↗
PubMed2001

[Study on the photoluminescence spectrum of nickel passivation treatment of porous silicon].

A new method for electrolysis passivation treatment of porous silicom (PS) in NiCl2 is reported in this paper. The photoluminescence (PL) spectra of PS treated in different time is observed, the spectra show that peak intensity is 2.5 times stronger than that without treatment, peak wavelength is 33 nm blue shift when PS is treated properly. The phenomenon caused is that the results of the SiHx change into SiNix when replaced H by Ni on surface of PS.

Chemical Phenomena↗
PubMed2001

[Study on the reaction mechanism and application of eldest amine basic dye with nitrite].

In this paper, the reaction of eldest amine basic dye with nitrite in hydrochloric acid medium by ultraviolet-visible spectrometry, electrochemistry analysis, Fourier transform infrared spectrometer and nuclear magnetic resonance was studied systematically. The reaction of its structure and effect was preliminarily understood. It is realized that there is diazotization-coupling or diazo-reaction mechanism, generating triazene or diazo-compound. It has magnificent meaning for perfecting, applying this kind of basic dye and instituting a ultraviolet-visible spectrometry or electrochemistry analysis new method of measuring nitrite.

Amines↗
PubMed2001

[Determination of enthalpy change of coordinating color reaction by UV-Vis absorption spectrum method].

In this paper, a simple experimental method for the determination of enthalpy change of coordinating color reaction has been proposed and a relation formula between absorption and temperature has been deduced. Using coordinating color reaction of cobalt(II) thiocyanate in Tween-80 medium, the linear relation of this formula has been validated: r = 0.9957 and delta H = -44.7 kJ.mol-1, which is accordant with the result obtained from Van't Hoff equation.

Cobalt↗
PubMed2001

[Optical parameters of Tm3+ in oxyfluoride glass ceramic].

Optical-absorption spectrum of Tm3+ ions in oxyfluoride glass ceramic was measured, from which the measured oscillator strengths were obtained. The Judd-Ofelt intensity parameters omega t (t = 2, 4, 6) were determined by a best fit of the calculated and measured oscillator strengths, the rms deviation was 3.9 x 10(-7). Some predicted spectroscopic parameters of the excited states, like the spontaneous radiative transition rate, radiative lifetime, branching ratio and integrated emission cross section were given using the intensity parameters. The spectroscopic parameters were comparable with some laser materials, and some of them were better.

Ceramics↗
PubMed2001

[FTIR studies of compounds of 2-D networks].

Recently, there is increasing interest in the study of 2-D square network materials which have inner cavities as zeolites, expected to find applications in catalysis, sensor and absorbent. Here, the synthesis of two compounds of [[Cd(4,4'-bpy)2.2H2O](NO3)2.4H2O] and [[Cd(4,4'-bpy)2NO3H2O].NO3.(C13H11NO)2] have been reported. The FTIR spectra of those clusters and the structure-sensitive bands are studied.

English Abstract↗
PubMed2001

[FTIR studies on two compounds containing cyanide].

Two compounds containing cyanide [Ni(1,10-phen)2O2MoS2(CuCN)]n and [ZnCu4 (CN)6(dmf)4]n have been synthesized. The FTIR spectra and the crystal structure of those clusters have also been deal with. The stretching frequency of cyanide is alterable with the different coordinated environments.

Crystallization↗
PubMed2000

Oxidation of nitric oxide in a two-stage chemical scrubber using dc corona discharge.

The dc corona was studied as an alternative for NO oxidation in a two-stage chemical scrubber. The dc corona plasma reactor completely oxidized 150ppm of NO to NO2 in an air stream. The NO2 was further oxidized at a higher voltage. For some cases, the NO2 in the effluents of the plasma reactor was absorbed quantitatively by a caustic sodium sulfite aqueous solution in a 2l bubble column gas absorber. The outlet concentrations of both NO and NO2 from the plasma-scrubber combination system (corona-induced chemical scrubber) were below the detection limit of the chemiluminescent NOx analyzer.

Air Pollutants↗
PubMed2000

Temperature-sensitive mutants of p53 homologs.

Two homologs of the p53 tumor suppressor, p63 and p73 have recently been discovered. These proteins have activities similar to p53 in cell culture but have distinct developmental functions in vivo. We found that temperature-sensitive mutants of certain p63 and p73 isoforms can be created by single amino acid substitutions of an alanine residue corresponding to alanine 135 of murine p53. The mutants (p63gamma-Pro167, p73alpha-Leu156 and p73beta-Ile156) can be controlled by temperature shift between 32 degrees C and 39 degrees C. They can be stably expressed in p53-null H1299 cells at 39 degrees C, become transcriptionally activated at 32 degrees C, and induce expression of p53-responsive genes MDM2 and p21WAF1. Activation of p73beta-Ile156 in H1299 cells inhibits cell division but induces significant increase in cell size (hypertrophy), whereas activation of p73alpha-Leu156 and p63gamma-Pro167 induces apoptosis. These mutants may be useful tools for gaining further insight to the functions of p53 homologs.

Amino Acid Sequence↗
PubMed2000

Activation of atypical protein kinase C zeta by caspase processing and degradation by the ubiquitin-proteasome system.

Atypical protein kinase C zeta (PKCzeta) is known to transduce signals that influence cell proliferation and survival. Here we show that recombinant human caspases can process PKCzeta at three sites in the hinge region between the regulatory and catalytic domains. Caspase-3, -6, -7, and -8 chiefly cleaved human PKCzeta at EETD downward arrowG, and caspase-3 and -7 also cleaved PKCzeta at DGMD downward arrowG and DSED downward arrowL, respectively. Processing of PKCzeta expressed in transfected cells occurred chiefly at EETD downward arrowG and DGMD downward arrowG and produced carboxyl-terminal polypeptides that contained the catalytic domain. Epitope-tagged PKCzeta that lacked the regulatory domain was catalytically active following expression in HeLa cells. Induction of apoptosis in HeLa cells by tumor necrosis factor alpha plus cycloheximide evoked the conversion of full-length epitope-tagged PKCzeta to two catalytic domain polypeptides and increased PKCzeta activity. A caspase inhibitor, zVAD-fmk, prevented epitope-tagged PKCzeta processing and activation following the induction of apoptosis. Induction of apoptosis in rat parotid C5 cells produced catalytic domain polypeptides of endogenous PKCzeta and increased PKCzeta activity. Caspase inhibitors prevented the increase in PKCzeta activity and production of the catalytic domain polypeptides. Treatment with lactacystin, a selective inhibitor of the proteasome, caused polyubiquitin-PKCzeta conjugates to accumulate in cells transfected with the catalytic domain or full-length PKCzeta, or with a PKCzeta mutant that was resistant to caspase processing. We conclude that caspases process PKCzeta to carboxyl-terminal fragments that are catalytically active and that are degraded by the ubiquitin-proteasome pathway.

Animals↗