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C Luo

Publications and source records attributed to C Luo.

At least 55 records · Page 3Linked to original sources
PubMed2001

[A study of the acting mechanism of aspirin for resistance to oxidative damage].

OBJECTIVE: To explore the mechanism of aspirin for resistance to oxidative damage in endothelial cells. METHODS: Using cultured endothelial cells, we measured the levels of aspirin induced ferritin expression on resistance to hydrogen peroxide toxicity toward cells in the presence of the iron chelator desferrioxamine added to FeCl3. RESULTS: Aspirin at low concentration (0.1 mmol/L) induced significant increase of ferritin expression in a time- and concentration-dependent fashion up to 25% over basal levels(P < 0.05). Preincubating the cells for 8 h with aspirin (0.1 mmol/L) reduced lactate dehydrogenase(LDH) release rate by 50%, toxicity reduction by 40%, and significant decrease of malondialdehyde (MDA) production. Aspirin induced cytoprotection from H2O2 damage was also in a concentration- and time-dependent fashion. However, in the presence of the iron chelator desferrioxamine, aspirin enhanced ferritin synthesis was abrogated, in contrast, FeCl3 increased aspirin induced ferritin synthesis in cells. CONCLUSION: The study suggested that the antioxidation of aspirin was brought into action by affecting the cellular iron metabolism pathway to induce ferritin synthesis.

Antioxidants↗
PubMed2001

[Randomized controlled trial for the effect of amrinone and aprotinin on proinflammatory cytokine release in patients with prosthetic valve replacement during perioperative period].

OBJECTIVE: To explore the effect of amrinone and aprotinin on whole-body inflammatory response in the patients with prosthetic valve replacement during perioperative period. METHODS: 24 patients undergoing prosthetic valve replacement were randomized to control group (group A, n = 8), aprotinin group (group B, n = 8) and amrinone combined with aprotinin group (group C, n = 8). In the aprotinin group, 3 x 10(6) of aprotinin was added to the priming solution of the extracorporeal circulation (ECC). In the amrinone combined with aprotinin group 3 x 10(6) of aprotinin was added to the priming solution of the ECC and amrinone began with a bolus of 1 mg/kg followed by a maintenance infusion of 8 micrograms/(kg.min). The control group received an equivalent prime volume without aprotinin. Venous blood samples were drawn before the operation, at the end of ECC, 1 hour after the end of ECC, and one day after the operation respectively. Enzyme-linked immunosorbent assay techniques were used to measure each of the cytokines. RESULTS: Before ECC, there were no differences of the levels of IL-6 and IL-8 among groups (P > 0.05). After ECC, the levels of IL-6 and IL-8 increased significantly in all groups (P < 0.05). The levels on day one after the operation were still higher than those before the operation in all groups (except the level of IL-8 in group C), but no statistical significance was observed. (P > 0.05). At 1 hour after the end of ECC, the level of IL-6 in group B was lower than that in group A, and the level of IL-6 in group C was lower than that in group B, but there was no statistically significant difference (P > 0.05); At the end of ECC, the level of IL-8 in group B was lower than that in group A and the level of IL-8 in group C was lower than that in group B, but no significant difference was noted (P > 0.05). It was also observed that the level of IL-8 was lower in group C than group A or B at 1 hour after the end of ECC. CONCLUSION: Although amrinone and aprotinin have antiinflammatory activity, but pump prime only aprotinin or aprotinin combined with amrinone may fall in preventing proinflammatory cytokine release (IL-6, IL-8) completely in patients with prosthetic valve replacement during ECC perioperative period.

Adult↗
PubMed2001

[Spectral analysis on self-assembly ultrathin film of polyaminobenzonitrile].

Poly(p-amino benzonitrile) (PABN) was synthesized by the method of plasma polymerization. With the self-assembly techniques, an ultrathin film of PABN and NaPSS (sodium polystyrene sulfonate) was successfully prepared. UV-Visible absorption spectra revealed that the film is very regular. This is a new method to prepare ultrathin film of PABN.

Macromolecular Substances↗
PubMed2000

A new photoactive and highly soluble C(60)-TTF-C(60) dimer: charge separation and recombination

The covalent linkage of two [60]fullerene cores to a tetrathiafulvalene (TTF) donor affords a soluble and photoactive C(60)-TTF-C(60) triad. Spectroscopic and photophysical characterization of the C(60)-TTF-C(60) triad are given. Although the cyclic voltammetry measurements reveal no notable interaction between the chromophores in the ground state, photophysical data show that in the excited state an intramolecular electron transfer, evolving from the TTF donor to the singlet state of C(60), prevails, yielding a long-lived charge separated radical pair.

Journal Article↗
PubMed2000

Recognition and incision of site-specifically modified C8 guanine adducts formed by 2-aminofluorene, N-acetyl-2-aminofluorene and 1-nitropyrene by UvrABC nuclease.

Nucleotide excision repair plays a crucial role in removing many types of DNA adducts formed by UV light and chemical carcinogens. We have examined the interactions of Escherichia coli UvrABC nuclease proteins with three site-specific C8 guanine adducts formed by the carcinogens 2-aminofluorene (AF), N:-acetyl-2-acetylaminofluorene (AAF) and 1-nitropyrene (1-NP) in a 50mer oligonucleotide. Similar to the AF and AAF adducts, the 1-NP-induced DNA adduct contains an aminopyrene (AP) moiety covalently linked to the C8 position of guanine. The dissociation constants for UvrA binding to AF-, AAF- and AP-DNA adducts, determined by gel mobility shift assay, are 33 +/- 9, 8 +/- 2 and 23 +/- 9 nM, respectively, indicating that the AAF adduct is recognized much more efficiently than the other two. Incision by UvrABC nuclease showed that AAF-DNA was cleaved approximately 2-fold more efficiently than AF- or AP-DNA (AAF > AF approximately AP), even though AP has the largest molecular size in this group. However, an opened DNA structure of six bases around the adduct increased the incision efficiency for AF-DNA (but not for AP-DNA), making it equivalent to that for AAF-DNA. These results are consistent with a model in which DNA damage recognition by the E. coli nucleotide excision repair system consists of two sequential steps. It includes recognition of helical distortion in duplex DNA followed by recognition of the type of nucleotide chemical modification in a single-stranded region. The difference in incision efficiency between AF- and AAF-DNA adducts in normal DNA sequence, therefore, is a consequence of their difference in inducing structural distortions in DNA. The results of this study are discussed in the light of NMR solution structures of these DNA adducts.

2-Acetylaminofluorene↗
PubMed2000

Donor/Acceptor fulleropyrrolidine triads

New C(60)-based triads, constituted by a fulleropyrrolidine moiety and two different electroactive units [donor 1-donor 2 (10, 15a,b), or donor 1-acceptor (17, 21)], have been synthesized by 1,3-dipolar cycloaddition reaction of azomethyne ylides to C(60) and further acylation reaction on the pyrrolidine nitrogen. The electrochemical study reveals some electronic interaction between the redox-active chromophores. Triads bearing tetrathiafulvalene (TTF) and ferrocene (Fc) (10) or pi-extended TTFs and Fc (15a,b) show reduction potentials for the C(60) moiety which are cathodically shifted in comparison to the parent C(60). In contrast, triads endowed with Fc and anthraquinone (AQ) (17) or Fc and tetracyanoanthraquinodimethane (TCAQ) (21) present reduction potentials for the C(60) moiety similar to C(60). Fluorescence experiments and time-resolved transient absorption spectroscopy reveal intramolecular electron transfer (ET) processes from the stronger electron donor (i.e., TTF or extended TTF) to the fullerene singlet excited state, rather than from the poorer ferrocene donor in 10, 15a,b. No evidence for a subsequent ET from ferrocene to TTF(*)(+) or pi-extended TTF(*)(+) was observed.

Journal Article↗
PubMed2000

Synthesis, cyclic voltammetry, and photophysical properties of a bridged o-phenylenediamine-C(60) dyad.

The synthesis, complete spectroscopic characterization, cyclic voltammetry, and photophysical measurements of a new o-phenylenediamine-C(60) dyad are described. By using a tether strategy, only a single regioisomer was obtained. Cyclic voltammetry measurements indicate that the two electroactive groups do not interact in their singlet ground states. Photophysical investigations reveal a rapid photoinduced electron transfer between the singlet excited state of the fullerene acceptor and the o-phenylenediamine donor, yielding a charge-separated radical pair.

Journal Article↗
PubMed2000

The 1.7 A crystal structure of human cell cycle checkpoint kinase Chk1: implications for Chk1 regulation.

The checkpoint kinase Chk1 is an important mediator of cell cycle arrest following DNA damage. The 1.7 A resolution crystal structures of the human Chk1 kinase domain and its binary complex with an ATP analog has revealed an identical open kinase conformation. The secondary structure and side chain interactions stabilize the activation loop of Chk1 and enable kinase activity without phosphorylation of the catalytic domain. Molecular modeling of the interaction of a Cdc25C peptide with Chk1 has uncovered several conserved residues that are important for substrate selectivity. In addition, we found that the less conserved C-terminal region negatively impacts Chk1 kinase activity.

Catalytic Domain↗
PubMed2000

Independent evolution of Toll and related genes in insects and mammals.

Toll and Toll-related proteins play an important role in antibacterial innate immunity in insect, plants, and mammals. We present the first comprehensive phylogenetic analyses of Toll-related genes from both insects and mammals. Drosophila melanogaster contains Toll and a highly homologous gene, Tehao. The protein, Dm Tehao, comprises 795 amino acid residues and its cytoplasmic domain shares a striking 61% identity with Dm Toll. Two Toll homologues were found in another dipteran of medical importance, Anopheles gambiae, a vector for human malaria. One Toll-like gene each was identified from Aedes aegypti and Glossina palpalis palpalis, vectors for yellow fever and trypanosomiasis, respectively. Phylogenetic analyses revealed separate clustering of Toll and related proteins from insects and mammals, suggesting independent evolution of the Toll family of proteins and of innate immunity in arthropods and vertebrates. These results also provide new avenues to understanding the function of Toll proteins in insect innate immunity against bacteria, fungi, and protozoans.

Aedes↗
PubMed2000

Expression of insulin-receptor substrate-1 and -2 in ovaries from women with insulin resistance and from controls.

OBJECTIVE: To evaluate the role of insulin-receptor substrate (IRS)-1 and -2 in ovary dysfunction in women with insulin resistance. DESIGN: Immunoblotting and immunohistochemical analyses of the localization and staining intensity of IRS-1 and IRS-2 in the ovaries of women with the polycystic ovary syndrome (PCOS) and gestational diabetes mellitus. SETTING: Department of Obstetrics and Gynecology, Turku University Central Hospital. PATIENT(S): Sections of ovary were obtained at the time of cesarean section from five volunteers without medical complications and three patients with gestational diabetes mellitus. Paraffin-embedded ovary sections were selected from those on file from the department of pathology; four were from women with a histologic diagnosis of PCOS and seven were from women with endometriosis (controls). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Protein expression of IRS in human ovary samples. RESULT(S): Immunoblotting with specific monoclonal and polyclonal antibodies showed the presence of 165-kDa and 183-kDa proteins that corresponded to the size of IRS-1 and IRS-2, respectively, in normal pregnant ovaries and human cultured follicles. Immunohistochemical staining showed that positive IRS-2 expression in antral follicles was restricted to theca internal cells in ovulatory ovaries but was distributed widely in all compartments of follicles in different stages in polycystic ovaries. Compared with follicles at a similar stage of development in ovulatory ovaries, follicles in polycystic ovaries showed decreased staining for IRS-1 in granulosa cells but increased staining for IRS-2 in theca internal cells. These features of IRS-1 and -2 expression were also noted in preantral and atretic follicles from patients with gestational diabetes mellitus compared with those who had uncomplicated pregnancy. CONCLUSION(S): This study highlights a shift of the follicular insulin signal protein from IRS-1 to IRS-2 in insulin-resistant states and suggests an association between this change and ovarian abnormality in PCOS and gestational diabetes mellitus.

Adult↗
PubMed2000

Strategies for prevention of mother-to-child transmission of HIV.

Over 90 per cent of paediatric HIV infections are maternally acquired, most of these in sub-Saharan Africa. Mortality trends underscore the humanitarian and ethical obligation for urgent global action to protect children from HIV. With the adoption of anti-retroviral therapy in pregnancy, mother-to-child transmission rates have declined to 4-6 per cent in the USA and other industrialised countries. In low-resource settings, where most of the children are continuously being exposed to HIV, the cost of anti-retroviral therapy is prohibitive. Very few developing countries apart from Botswana, Thailand and Brazil have national policies for integration of preventive anti-retroviral therapy in antenatal clinics. This paper reviews anti-retroviral and non-anti-retroviral interventions for prevention of mother-to-child transmission of HIV. To support the health of mothers as well, it supports the implementation of a comprehensive package of care in pregnancy and post-partum, such as access to antenatal and delivery services; anti-retroviral preventive therapy; malaria treatment; family planning; multivitamin, iron and folate supplementation; counselling on feeding options; post-natal care for the child and post-partum care for the mother, and calls for a strategy for advocacy, programme communication and community mobilisation.

AIDS Serodiagnosis↗
PubMed2000

Comparison between the comet assay and pimonidazole binding for measuring tumour hypoxia.

Pimonidazole is finding increasing use in histochemical analyses of hypoxia in tumours. Whether it can identify every hypoxic cell in a tumour, and whether the usual subjective criteria used to define 'positive' cells are optimal, are less certain. Therefore, our aim was to develop an objective flow cytometry procedure for quantifying pimonidazole binding in tumours, and to validate this method by using a more direct indicator of radiobiologic hypoxia, the comet assay. SCCVII tumours in C3H mice were analysed for pimonidazole binding using flow cytometry and an iterative curve-fitting procedure, and the results were compared to the comet assay for the same cell suspensions. On average, cells defined as anoxic by flow analysis (n = 43 tumours) bound 10.8 +/- 0.95 times more antibody than aerobic cells. In samples containing known mixtures of aerobic and anoxic cells, hypoxic fractions as low as 0.5% could easily be detected. To assess the flow cytometry assay under a wider range of tumour oxygen contents, mice were injected with hydralazine to reduce tumour blood flow, or allowed to breathe various gas mixtures during the 90 min exposure to pimonidazole. Hypoxic fraction estimated by the pimonidazole binding method agreed well with the hypoxic fraction measured using the comet assay in SCCVII tumours (r2 = 0.87, slope = 0.98), with similar results in human U87 glioma cells and SiHa cervical carcinoma xenografts. We therefore conclude that this objective analysis of pimonidazole labelling by flow cytometry gives a convenient and accurate estimate of radiobiological hypoxia. Preliminary analyses of biopsies from 3 patients given 0.5 g m-2 pimonidazole also suggest the suitability of this approach for human tumours.

Animals↗
PubMed2000

Achievable standard of care in low-resource settings.

The gap between rich and resource-poor countries has continued to grow as reproductive care providers integrate interventions to limit mother-to-child transmission (MTCT) of HIV in a manner consistent with existing information. There are two major reasons for this difference: access to prophylactic antiretroviral therapy (ARV) for HIV-infected pregnant mothers and availability of alternative feeding for babies. In resource-poor settings, these options are beyond reach for the majority of the women. Infant and under-five mortality rates from other infections are high in these settings and breastfeeding remains the norm. Answering the question, What is an achievable standard of care in resource-poor settings? still remains a major challenge today. Dialogue has begun in most resource-poor settings to address the key elements in the package of interventions to reduce MTCT of HIV. These elements include the following: (1) overall prevention of HIV in mothers and fathers; (2) provision of good-quality voluntary testing and counseling (VCT) in antenatal clinics; (3) a comprehensive package of interventions during pregnancy, during labor, and after delivery, including screening for sexually transmitted diseases (STDs), family planning, and--where possible--ARVs; (4) provision of infant and maternal nutrition within the socioeconomic realities; (5) advocacy and program communication; and (6) other supportive measures, including community mobilization to address issues such as stigmatization of and violence against HIV-infected women. This paper discusses the challenges faced by most resource-poor settings in integrating some of these activities into reproductive care services.

Anti-HIV Agents↗
PubMed2000

[Genes of micrometastasis in bone marrow of patients with colorectal cancer].

OBJECTIVE: To detect the gene of micrometastasis in bone marrow of patients with colorectal cancer. METHODS: PCR-SSCP/silver stain technique was used to find out the metastatic cancer cells in 51 bone marrow samples in different time. RESULTS: The total positive rate of mutations of p53 and K-ras in bone marrow was 37.25% before operation. The incidence of mutations was obviously correlated with Duke's stage and lymphatic metastasis. After postoperative chemotherapy mutation in 11 patients turned to be negative. CONCLUSIONS: Detection of micrometastasis in bone marrow may contribute to early diagnosis of blood stream metastasis of colorectal cancer.

Bone Marrow Neoplasms↗
PubMed2000

[The study of RDS gene mutation and clinical phenotype in a family with primary retinitis pigmentosa].

OBJECTIVE: To investigate retinal degeneration slow (RDS) gene mutation in a Chinese family with primary retinitis pigmentosa (RP) and the association of the mutation with clinical phenotypes and to explore the pathogenesis of RP. METHODS: Blood DNA from 2 patients in the same family with RP and 2 normal persons was analyzed by molecular genetic methods. RDS gene mutation was screened out by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis. The mutant RDS gene fragment was cloned, then sequenced with an automatic DNA sequencer using a dideoxy chain termination protocol. The phenotype of the patients with the gene mutation were examined and determined by clinical ophthalmologic examinations. RESULTS: The PCR-RFLP analysis of the RDS gene in 2 patients with RP revealed codon 216 mutation of RDS gene. The mutation was heterozygous, and not found in 2 normal persons as controls. The alteration in the DNA sequence was identified as a heterozygous transversional change of C to T at the second nucleotide in codon 216 of RDS gene, resulting in the amino acid replacement of proline residue with leucine residue (Pro216Leu). The ocular finding of the patients with Pro216Leu mutation of RDS gene included severe visual loss and diffuse distribution of pigmentary changes with macular degeneration. CONCLUSIONS: The Pro216Leu mutation of RDS gene is found in Chinese patients with RP. The gene mutation is associated with the ocular phenotype, diffuse RP with macular degeneration.

Adult↗