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Biomedical subjects

W Cao

Publications and source records attributed to W Cao.

At least 73 records · Page 4Linked to original sources
PubMed2000

[Study on the mortality of injury in Chinese population in urban and rural areas from 1990 to 1997].

OBJECTIVE: To describe the characteristics and trend of injuries among urban and rural Chinese population. METHODS: Data from annual Chinese national health statistics (1990 - 1997) were analyzed. RESULTS: The overall mortality of injury in China increased from 36.8/10(6) to 76.7/10(6) from 1990 to 1997. Injury was the forth leading causes of death in urban areas and the fifth in rural areas. The death rate of injury declined in the urban while increasing in the rural areas. The rural death rate of injury was about two times of that in urban and the difference was increasing over time. The death rate of men was higher than that of women and the ratio was 1.3 - 1.9. Children below 4 years old and people above 60 years old showed the highest rates. The first three leading causes of death of injuries in urban areas were traffic accident, suicide and fall, while in rural areas were suicide, traffic accident and drowning. The death rate caused by suicide was 6.5/10(6) - 27.1/10(6) and the rate in rural areas was 2.7 to 4.0 times of that in urban areas. The mortality of suicide declined in urban while increased in rural areas. The mortality of traffic accidents had a tendency of increase in both urban and rural areas. CONCLUSION: Injury has been one of the leading cause of death but without effectively control programs for population in Urban and Rural areas in China, special in rural areas.

Accidents, Traffic↗
PubMed2000

[Phenotypic features and genetic diversity of strains of Rhodopseudomonas].

14 strains of purple non-sulfur bacteria and 3 type strains of Rhodopseudomonas were investigated by phenotypic characterizing, DNA-DNA hybridizing and DGGE analyzing. The characteristics of their morphology, structure and physiology show that 14 strains of isolates have the features of the genus Rhodopseudomonas: dividing asymmetrically by budding, lamellar intracytoplasmic membranes, presence of bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series. On the base of their differences in morphology, growth, carbon sources 14 strains can be divided into 2 groups: g-c group, T group. Parts of 16S rRNA gene were amplified by using a pair of primers: 341f-906r. Denaturing gradient gel electrophoresis(DGGE) of PCR-amplified fragment of rDNA indicated that they have 3 genetic types: 1 of them, including 6 of 8 strains of T groups is similar to that of Rps. rutila R1, the other 2 types, represented separately by 2 of T group or all the g-c group, were different from that of either of 3 type strains The Data of the DNA-DNA hybridization of 8 representative strains indicated that the differences between different types were enough to separate them into different species including 2 possible new species.

DNA, Bacterial↗
PubMed2000

[Two-dimensional surface Raman imaging of a roughened iron electrode in saline solution].

By using a confocal microprobe Raman system and proper surface roughening procedure for iron, the pit corrosion behavior of bare iron electrode in 3.4% NaCl (saline solution) solution has been investigated. The surface-enhanced Raman scattering (SERS) spectra of the corrosion products due to the pit corrosion at positive potential was obtained with high ratio of signal to noise. The application of SERS technique has been extended successfully to the study of iron corrosion. The two-dimensional surface Raman imaging acquired at 660 cm-1 was obtained also with the utility of surface Raman image technique. Results show that different iron oxides should coexist in the pit corrosion region and the distribution of the corrosion products was not uniform.

Chemical Phenomena↗
PubMed2000

[Fluorescence quenching method for the determination of trace copper with DBH-PF].

A fluorescence quenching method for the determination of trace Cu(II) was developed. The method was based on the fluorescence quenching effect of DBH-PF and Triton X-100 due to the formation of a non-fluorescent ternary complex in pH 6.2-8.2 KH2PO4-Na2HPO4 medium. The excitation and emission wavelengths are 530 and 560 nm, respectively. The linear range is 0-80 micrograms.L-1 and the detection limit is 0.20 microgram.L-1 for Cu(II). The method has been used to determine trace amounts of Cu(II) in hair, tea and water. The recovery is 98%-104%, and the relative standard deviation is less than 6.9% with satisfactory results.

Copper↗
PubMed2000

[Fluoride-oxide glass for high efficiency upconversion from IR to green].

In this paper, the fluoride-oxide glass doped with Er3+ for upconversion from IR to green was report. The component of sample in experiment is 60TeO2-8PbF2-10AlF3-10BaF2-10NaF-2ErO3/2, and the prepared method is obtained. The absorption spectrum was measured at room temperature. Intense green upconversion emissions from Er3+ doped the sample were observed under 808 nm and 970 nm excitation, and the upconversion emissions spectra under 808 nm and 970 nm LD excitation were measured at room temperature. The upconversion mechanics was discussed. The relationship between working currents of LD and intensity of upconversion emissions has been studied. The results was improved that needs of two photons for upconversion process under 808 nm and 970 nm excitation respectively.

English Abstract↗
PubMed1999

Pigment epithelium-derived factor protects cultured retinal neurons against hydrogen peroxide-induced cell death.

Pigment epithelium-derived factor (PEDF) is a neurotrophic protein synthesized and secreted by retinal pigment epithelial (RPE) cells in early embryogenesis and has been shown to be present in the extracellular matrix between the RPE cells and the neural retina. It induces neuronal differentiation and promotes survival of neurons of the central nervous system from degeneration caused by serum withdrawal or glutamate cytotoxicity. Because the role of PEDF in the retina is still unknown, we examined its ability to protect cultured retinal neurons against hydrogen peroxide (H(2)O(2))-induced cell death. Retinas of 0-2-day-old Sprague-Dawley rats were isolated and dissociated, and the neurons were maintained for 2 weeks in a synthetic serum-free medium. Immunocytochemical labeling showed that 50-60% of the cultured cells were rod photoreceptors. Treatment with H(2)O(2) induced significant death of retinal neurons in a dose- and time-dependent manner. Pretreatment with PEDF prior to insult greatly attenuated H(2)O(2)-induced cytotoxicity, and its effect was shown to be dose dependent. Cytotoxicity was determined by 3,(4,5-dimethylthiazol-2-yl)2, 5-diphenyl-tetrazolium bromide and lactate dehydrogenase assays, and apoptotic cell death was evaluated by the TdT-mediated digoxigenin-dUTP nick-end labeling assay. The present study also showed that H(2)O(2)-induced retinal neuron death was by apoptosis that could be inhibited by PEDF. Combination of PEDF with basic fibroblast growth factor, brain-derived neurotrophic factor, or ciliary neurotrophic factor improves the protection. These data strongly suggest that PEDF is a potential neuroprotective agent in the treatment of retinal degeneration.

Animals↗
PubMed1999

Anti-recoverin antibodies cause the apoptotic death of mammalian photoreceptor cells in vitro.

We developed an in vitro model to study the effect of anti-recoverin antibodies on retinal cells and the mechanism(s) by which they kill photoreceptors in cancer-associated retinopathy (CAR). Rat retinal cells were grown in a defined medium, and cell types were identified by using antibodies against rhodopsin, recoverin, syntaxin, and thy-1. Purified immunoglobulin (IgG) against recoverin was added to the cultures at different concentrations for 24, 48, or 72 hr, and the survival of the cells was determined by fluorescence microscopy. Preimmune IgG and normal medium were used as controls. The cell death detection enzyme-linked immunosorbent assay and the terminal deoxyuridine triphosphate nick-end labeling assay were used to demonstrate cells undergoing apoptosis. Double labeling was used to visualize cell types and apoptotic death. Rods, amacrine cells, and ganglion cells were identified in the cultures. Rod cells, but not ganglion cells and amacrine cells, markedly decreased in the presence of 200 microg/ml of anti-recoverin IgG for 24, 48, and 72 hr. Anti-recoverin antibodies caused apoptosis in rod cells but not in amacrine cells. Almost all cells were shown to take up IgG from the medium. In conclusion, our retinal cell cultures provide a system for investigating antibody-mediated photoreceptor cell death and demonstrate that anti-recoverin antibodies cause the apoptotic death of rod cells, with no effect on amacrine cells. The results suggest that anti-recoverin antibodies play a key role in the apoptotic death of photoreceptors in CAR.

Animals↗
PubMed1999

A thermodynamic study on the formation and stability of DNA duplex at transcription site for DNA binding proteins GCN4.

Using isothermal titration calorimetry (ITC), we studied the thermodynamic parameters of the 15-mer duplex dsDNA [d(GAGATGACTCATCTC)].[d(GAGATGAGTCATCTC)] formation from its two complementary single strands (S1 and S2) over a range of temperatures. The two complementary single strands d(GAGATGACTCATCTC) (herein called S1) and d(GAGATGAGTCATCTC) (herein called S2) containing palindromic sequences may assume ordered structures at low temperatures, which made the duplex dsDNA formation rather complicated. The thermodynamic parameters for the duplex formation, such as the binding constants (Kb), the enthalpies (delta H0), the free energies (delta G0), the entropies (delta S0) are strongly temperature-dependent. The thermally-induced disruptions of the duplex and its two complementary single strands, S1 and S2, were measured using differential scanning calorimetry (DSC) and CD spectroscopy, the results demonstrate that the DNA duplex is very stable, and its component single strands have an ordered structure at low temperature. This 15-mer specific sequence DNA may act as recognition site for DNA binding proteins GCN4 and plays a key role in transcription regulation of gene expression. Our analyses of the thermodynamic data suggest that the duplex formation is a coupled process between conformational transitions in the two single strands and their binding to form duplex dsDNA.

Binding Sites↗
PubMed1999

Binding kinetics and footprinting of TaqI endonuclease: effects of metal cofactors on sequence-specific interactions.

Restriction endonucleases achieve sequence-specific recognition and strand cleavage through the interplay of base, phosphate backbone, and metal cofactor interactions. In this study, we investigate the binding kinetics of TaqI endonuclease using the wild-type enzyme and a binding proficient, catalysis deficient mutant TaqI-D137A both in the absence of a metal cofactor and in the presence of Mg2+ or Ca2+. As demonstrated by gel mobility shift analyses, TaqI endonuclease requires a metal cofactor for achieving high-affinity specific binding to its cognate sequence, TCGA. In the absence of a metal cofactor, the enzyme binds all DNA sequences (TaqI cognate site, star site, and nonspecific site) with essentially equal affinity, thereby exhibiting little discrimination. The dissociation constant of the cognate sequence in the presence of Mg2+ at 60 degrees C is 0. 26 nM, a value comparable to our previously reported Km of 0.5 nM measured under steady-state conditions. The TaqI-TCGA-Mg2+ complex is stable, with a half-life of 21 min at 60 degrees C. The boundary of the protein-DNA interface is approximated to be about 18 bp as determined by DNase I footprinting. Data from this study support the notion that a metal cofactor plays a critical role for achieving sequence-specific discrimination in a subset of nucleases, including TaqI, EcoRV, and others.

Base Sequence↗
PubMed1999

The beta3-adrenergic receptor activates mitogen-activated protein kinase in adipocytes through a Gi-dependent mechanism.

Promiscuous coupling between G protein-coupled receptors and multiple species of heterotrimeric G proteins provides a potential mechanism for expanding the diversity of G protein-coupled receptor signaling. We have examined the mechanism and functional consequences of dual Gs/Gi protein coupling of the beta3-adrenergic receptor (beta3AR) in 3T3-F442A adipocytes. The beta3AR selective agonist disodium (R, R)-5-[2[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino]propyl]-1, 3-benzodioxole-2,2-dicarboxylate (CL316,243) stimulated a dose-dependent increase in cAMP production in adipocyte plasma membrane preparations, and pretreatment of cells with pertussis toxin resulted in a further 2-fold increase in cAMP production by CL316,243. CL316,243 (5 microM) stimulated the incorporation of 8-azido-[32P]GTP into Galphas (1.57 +/- 0.12; n = 3) and Galphai (1. 68 +/- 0.13; n = 4) in adipocyte plasma membranes, directly demonstrating that beta3AR stimulation results in Gi-GTP exchange. The beta3AR-stimulated increase in 8-azido-[32P]GTP labeling of Galphai was equivalent to that obtained with the A1-adenosine receptor agonist N6-cyclopentyladenosine (1.56 +/- 0.07; n = 4), whereas inclusion of unlabeled GTP (100 microM) eliminated all binding. Stimulation of the beta3AR in 3T3-F442A adipocytes led to a 2-3-fold activation of mitogen-activated protein (MAP) kinase, as measured by extracellular signal-regulated kinase-1 and -2 (ERK1/2) phosphorylation. Pretreatment of cells with pertussis toxin (PTX) eliminated MAP kinase activation by beta3AR, demonstrating that this response required receptor coupling to Gi. Expression of the human beta3AR in HEK-293 cells reconstituted the PTX-sensitive stimulation of MAP kinase, demonstrating that this phenomenon is not exclusive to adipocytes or to the rodent beta3AR. ERK1/2 activation by the beta3AR was insensitive to the cAMP-dependent protein kinase inhibitor H-89 but was abolished by genistein and AG1478. These data indicate that constitutive beta3AR coupling to Gi proteins serves both to restrain Gs-mediated activation of adenylyl cyclase and to initiate additional signal transduction pathways, including the ERK1/2 MAP kinase cascade.

3T3 Cells↗
PubMed1999

Interaction of Diphenylamine Diazonium Salt with Sodium Dodecyl Sulfate in Aqueous Solution.

The interaction of diphenylamine-4-diazonium salt (DDS) with sodium dodecyl sulfate (SDS) in aqueous solution was investigated. The results show that in a 2.1-2.3 molar ratio of SDS/DDS, the solution viscosity increases suddenly to a thousand times the original and then drops rapidly as the ratio beyond the region. The dramatic increase in the viscosity was proposed to be due to aggregated micelles that form in solution due to the interaction of diphenylamine diazonium salt and micelles formed from SDS, and when further SDS was added drops rapidly, because the aggregated micelles were separated by the electrostatic repulsion force originated from the overfeeding of SDS. It is interesting that the viscosity of the solution is very susceptible to UV light, i.e., the increased viscosity decreases gradually when the solution was exposed under UV light because the irradiation decomposes the diazonium group. The influence of [SDS] and the ratio of SDS/DDS on the viscosity of the solution were also investigated. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Biochemical properties of a high fidelity DNA ligase from Thermus species AK16D.

NAD+-dependent DNA ligases from thermophilic bacteria Thermus species are highly homologous with amino acid sequence identities ranging from 85 to 98%. Thermus species AK16D ligase, the most divergent of the seven Thermus isolates collected worldwide, was cloned, expressed in Escherichia coli and purified to homogeneity. This Thermus ligase is similar to Thermus thermophilus HB8 ligase with respect to pH, salt, NAD+, divalent cation profiles and steady-state kinetics.However, the former is more discriminative toward T/G mismatches at the 3'-side of the ligation junction, as judged by the ratios of initial ligation rates of matched and mismatched substrates. The two wild-type Thermus ligases and a Tth ligase mutant (K294R) demonstrate 1-2 orders of magnitude higher fidelity than viral T4 DNA ligase. Both Thermus ligases are active with either the metal cofactor Mg2+, Mn2+or Ca2+but not with Co2+, Ni2+, Cu2+or Zn2+. While the nick closure step with Ca2+becomes rate-limiting which results in the accumulation of DNA-adenylate intermediate, Ni2+only supports intermediate formation to a limited extent. Both Thermus ligases exhibit enhanced mismatch ligation when Mn2+is substituted for Mg2+, but the Tsp. AK16D ligase remains more specific toward perfectly matched substrate.

Amino Acid Sequence↗
PubMed1999

Unique retina cell phenotypes revealed by immunological analysis of recoverin expression in rat retina cells.

Among retina-specific proteins, recoverin is unique with respect to its cellular regulation in that it is found in rods, cones, some bipolar cells, and a rare population of cells in the ganglion cell layer. Recoverin is a calcium-binding protein which inhibits rhodopsin kinase from phosphorylating rhodopsin. Because cells in the inner layers of the retina do not contain rhodopsin kinase, arrestin, or other phototransduction proteins, it seems likely that recoverin has a different function in those cell types. To study this protein more fully, antibodies were generated against the entire mouse recoverin protein, as well as against peptides from the amino and from the carboxyl termini. These antibodies confirmed the localization of recoverin in vivo and clearly demonstrated, in culture, cells which were recoverin positive and rhodopsin negative. Surprisingly, two unique cell phenotypes were seen in cell culture which are not found in vivo. These cells are [rhodopsin(+), recoverin(-)] and [arrestin(+), recoverin(-)]. These phenotypes appear to represent the same population of cells and suggest that the recoverin gene can be regulated independent of genes for other phototransduction proteins. This cell culture system will be useful for investigating environments and factors which participate in the expression of the recoverin gene, and may identify regulatory features of the recoverin gene which cause it to be illicitly expressed in small-cell lung carcinomas in cancer-associated retinopathy (CAR).

Amino Acid Sequence↗
PubMed1999

Multiplex PCR/LDR for detection of K-ras mutations in primary colon tumors.

Point mutations in codons 12, 13, and 61 of the K-ras gene occur early in the development of colorectal cancer and are preserved throughout the course of tumor progression. These mutations can serve as biomarkers for shed or circulating tumor cells and may be useful for diagnosis of early, curable tumors and for staging of advanced cancers. We have developed a multiplex polymerase chain reaction/ligase detection reaction (PCR/LDR) method which identifies all 19 possible single-base mutations in K-ras codons 12, 13, and 61, with a sensitivity of 1 in 500 wild-type sequences. In a blinded study, 144 paraffin-embedded archival colon carcinomas were microdissected and K-ras mutations determined by both dideoxy-sequencing and multiplex PCR/LDR. Results were concordant for 134 samples. The ten discordant samples were re-evaluated using higher sensitivity uniplex PCR/LDR, and the original multiplex PCR/LDR result was confirmed in nine of these ten cases. Multiplex PCR/LDR was able to identify mutations in solid tumors or paraffin-embedded tissues containing a majority of wild-type stromal cells, with or without microdissection. The technique is well suited for large scale studies and for analysis of clinical samples containing a minority population of mutated cells.

Colorectal Neoplasms↗
PubMed1999

Basic FGF-induced down-regulation of IGF-I mRNA in cultured rat Müller cells.

Interactions among growth factors are important in a variety of physiological and pathological processes. The regulation of IGF-I mRNA expression by bFGF was investigated in cultured rat Müller cells and the mechanism of regulation studied. Müller cells from 1- to 3-day-old Sprague-Dawley rats were isolated and cultured with Eagle MEM+10% FCS. Cultured cells were identified by immunocytochemistry using antibodies against vimentin, carbonic anhydrase C, and glutamine synthetase. Cells of passage 1-4 were treated with bFGF, the PKC inhibitor H-7, calphostin C, the PKC activator PMA or the PKA inhibitor H-89, as well as the adenylate cyclase activator forskolin, or adenylate cyclase inhibitor SQ22536. IGF-I and bFGF expression levels were assessed by Northern blot analysis. The addition of bFGF to culture medium down-regulated IGF-I expression in a dose- and time-dependent manner. Decrease of IGF-I expression started at a bFGF concentration of 1 ng ml-1. IGF-I mRNA level declined to 44% of baseline level at 10 ng ml-1 of bFGF, and reached a trough of 40% at 50 ng ml-1. At 10 ng ml-1 of bFGF, down-regulation of IGF-I expression was observed as early as 4 hr (60%) after treatment, and reached a trough of 42% by 8 hr. The temporal and concentration dependence of IGF-I expression by addition of the PKC activator PMA, to culture medium was similar to that due to the addition of bFGF. The down-regulation of IGF-I expression by bFGF (10 ng ml-1) and PMA (0.1 microM) was blocked by the PKC inhibitors H-7 (30 microM) and calphostin C (1 microM). Forskolin (5 microM), an adenylate cyclase activator, had activator, had no effect on IGF-I expression. SQ22536 (100 microM), an adenylate cyclase inhibitor, and H-89, a PKA inhibitor, had no inhibitory effect on bFGF-induced down-regulation of IGF-I expression. These results indicate that bFGF down-regulates IGF-I expression in cultured rat M uller cells through PKC activation.

Animals↗
PubMed1999

Search for a human homologue of the mouse Ped gene.

The Ped gene influences the rate of cleavage division of preimplantation mouse embryos and subsequent embryonic survival. The mouse Ped gene product is a major histocompatibility complex (MHC) class Ib protein called Qa-2. Studies from many human in-vitro fertilization (IVF) clinics suggest that the mouse Ped gene has a human homologue because embryos fertilized at the same time have different cleavage rates, and those embryos that cleave at a faster rate are more likely to result in a viable pregnancy. Candidates for the human homologue of the mouse Ped gene include the MHC class Ib genes HLA-E, HLA-F, and HLA-G. The presence of mRNA for these three genes was tested in 108 spare day 3 human preimplantation embryos from 25 couples by using reverse transcription-polymerase chain reaction (RT-PCR). Of the 86 embryos tested for HLA-E mRNA, 72 were positive (84%), and of the 88 embryos tested for HLA-G mRNA, 39 were positive (44%). None of the 17 embryos tested for HLA-F mRNA were positive (0%). Studies of expression of HLA-G protein were undertaken to ascertain whether HLA-G was attached to the cell membrane via a glycosylphosphatidylinositol (GPI) linkage similar to that found in Qa-2 protein. Treatment of JEG-3 cells, an HLA-G expressing cell line, with phospholipase C did not result in removal of HLA-G showing that HLA-G, unlike Qa-2, is not GPI linked to the cell surface. The pros and cons of HLA-E, HLA-F, and HLA-G as candidates for the human Ped gene are discussed.

Animals↗