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Biomedical subjects

H Z Pan

Publications and source records attributed to H Z Pan.

At least 19 recordsLinked to original sources
PubMed2001

[The cause of brackets lost in fixed appliance].

OBJECTIVE: To discusses the causes of brackets lost in fixed appliance. METHODS: Thirty-eight patients received three kinds of adhesives, with a total of adhesive brackets 1,303, including 325 edgewise brackets and 978 Begg brackets. The three adhesives were JJ enamel adhesive, TF non mixed orthodontic adhesive and 3M light-cured composite. RESULTS: The overall rate of bracket lost was 54.3% (707/1,303), including 63.8% in mandibular teeth brackets, 36.2% of maxillary teeth brackets. On statistical analysis, there were significant differences between 3M light cured composite and other two adhesives (chi(2)=24.39, 8.63, P<0.01), but no significant difference between the JJ enamel adhesive and TF no-mixed orthodontic adhesive (chi(2)=1.48, P>0.05). CONCLUSION: There were many factors related to bracket lost. The lowest rate of bracket lost was noted in 3M light cured composite among three adhesives.

English Abstract↗
PubMed1993

Deficiency of phosphatidylinositol-linked membrane proteins on erythrocytes of different subpopulations in paroxysmal nocturnal hemoglobinuria.

The surface phosphatidylinositol (PI)-linked proteins on membrane of paroxysmal nocturnal hemoglobinuria (PNH) erythrocytes (PNHE) was analysed by a flowcytometer (FACS 420). It was found that the loss of acetylcholinesterase (AchE) and decay accelerating factor (DAF), two PI-linked proteins, from cell membrane of PNHE was not synchronous. The hemolysis rates of DAF (-) and AchE (-) PNHE were much higher than that of mixed population in cobra-venom factor (CoF) lysis test. Intact PNHE remaining after CoF lysis had relatively lower immunofluorescent labeling rate of AchE on membrane in comparison with normal erythrocytes. It implied that this subpopulation, in spite of being insensitive to complement lysis, was still abnormal in terms of the amount of PI-linked protein on cell membrane. When these intact PNHE remaining after CoF lysis were incubated with activated polymorphonuclear leukocytes (PMN) for three hours, immunofluorescent labeling of AchE on PNHE was prominently decreased. This indicated that reactive oxidants released from activated PMN might injure PI-linked proteins.

Acetylcholinesterase↗
PubMed1992

Activated oxygen generation by a primaquine metabolite: inhibition by antioxidants derived from Chinese herbal remedies.

Primaquine is an important antimalarial drug which causes hemolytic anemia in patients with glucose-6-phosphate dehydrogenase (G6PDH) deficiency, probably due to oxidant generation by its metabolites. One of primaquine's metabolites, 5,6-dihydroxy-8-aminoquinoline (AQD), was found to cause chemiluminescence (CL) in vitro when incubated in the presence of luminol. This CL is inhibited by catalase and deferoxamine, unaffected by mannitol, and stimulated by superoxide dismutase (SOD), suggesting that it is mediated by H2O2. Three antioxidants (daphnetin, ferulate, and maltol), derived from Chinese herbal remedies, inhibited AQD- and H2O2-mediated CL, whereas a fourth, anisodamine, had no effect. Daphnetin also potently inhibited H2O2-mediated lipid peroxidation as measured by the production of thibarbituric acid reacting substances (TBARS). Thus, the possibility is raised that an antioxidant might be able to mitigate the oxidant hemolytic effects of primaquine.

Aminoquinolines↗
PubMed1992

Daphnetin: a novel antimalarial agent with in vitro and in vivo activity.

Daphnetin is a dihydroxycoumarin that is being used in China for the treatment of coagulation disorders. It is also a chelator and an antioxidant. In vitro, daphnetin causes a 50% inhibition (IC50) of 3H-hypoxanthine incorporation by Plasmodium falciparum at concentrations between 25 and 40 microM. Several related compounds, such as scopoletin, 2, 3-dihydroxybenzoic acid and 3, 4-dihydroxybenzoic acid show no inhibitory activity. The antimalarial activity of daphnetin is inhibited by the addition of iron. Daphnetin does not appear to be an oxidant drug, since it does not spontaneously generate superoxide in vitro. However, it does alkylate bovine serum albumin when incubated in the presence of iron. In vivo, daphnetin significantly prolongs survival of P. yoelli-infected mice.

Animals↗
PubMed1991

Artemisinin (qinghaosu): the role of intracellular hemin in its mechanism of antimalarial action.

Artemisinin (qinghaosu), is a promising new antimalarial drug derived from an ancient Chinese herbal remedy. When [13-14C]artemisinin is added to cultures of Plasmodium falciparum, it is converted into a product with different solubility and chromatographic properties than the parent drug. Artemisinin reacts with hemin in aqueous solution to form an adduct with an apparent molecular weight of 914 which has identical chromatographic, solubility, and electrophoretic behavior to the parasite-derived product. The reaction between artemisinin and hemin, when carried out in the presence of red cell membranes, leads to the oxidation of protein thiols. Malarial parasites are rich in hemin; artemisinin's reactivity toward hemin may explain its selective toxicity to malarial parasites.

Animals↗
PubMed1990

Targeted anti-tumor agents and their cytotoxicity on gastric cancer cells in vitro.

Several chemotherapeutic drugs including methotrexate, daunomycin, mitomycin C and toxin such as ricin, A chain of ricin were chosen to conjugate with murine monoclonal antibodies MGb2 and MG11. The drugs were linked to antibody directly or through human serum albumin as intermediary. The ELISA results showed that the antibody retained well the antigen-binding capacity during conjugation. These conjugates showed highly selective cytotoxic effect on target cells. In chronic cytotoxicity tests, the cytotoxic effect of these conjugates on human gastric cancer cells KATOIII was quite similar to that of free drugs or ricin, but greater than that of irrelevant conjugates, while they had a little effect on non-target cells, suggesting that the selective cytotoxicity on target cells of the conjugates be mediated by antibodies.

Animals↗
PubMed1989

[Peroxidative antimalaria mechanism of sodium artesunate].

Peroxidative antimalaria action of sodium artesunate was studied in vitro. Under alkaline conditions, sodium artesunate could produce active oxygen species, including the superoxide anion (O2-) and hydrogen peroxide (H2O2), but no O2- or H2O2 was produced by the drug at pH 7.4. However, sodium artesunate could increase the concentration of O2- and H2O2 in erythrocytes by increasing membrane lipid peroxidation, with this action being more marked in infected than in normal erythrocytes.

Animals↗
PubMed1989

[Inhibitory effect of chemically and enzymatically treated erythrocytic membrane on the invasion of Plasmodium falciparum merozoites].

By treating chemically and enzymatically erythrocytic membrane to change its structure and properties, the recognition of merozoite to erythrocyte and the effect of erythrocyte skeleton protein on the invasion of P. falciparum (Fc c-1/HN) were studied. It was found that the invasion of merozoite into erythrocyte digested with trypsin was greatly decreased; merozoite invasion into the erythrocyte treated with neuraminidase or wheat germ agglutinin (WGA) was partially inhibited; erythrocytes treated with cross-linker diamide and depolymerizer colchicine, N-ethyl maleinimide (NEM) of skeleton protein had evident resistance to invasion; the invasion of merozoite into erythrocyte treated with 2.0 mM of NEM was completely blocked.

Animals↗
PubMed1989

[Changes in antioxidative system in erythrocytes infected with Plasmodium falciparum].

In order to probe into the redox state in erythrocytes infected with P. falciparum, parasites of Hainan strain (FCC-1/HN) were cultured in vitro and trophozoites and schizonts were obtained by Percoll gradient separation. The effects of P. falciparum infection on antioxidative system and active oxygen level in erythrocytes were studied. It was found that the activities of superoxide dismutase, catalase and the content of reduced glutathione in infected erythrocytes were markedly decreased, while the activities of glutathione peroxidase and glutathione reductase in infected erythrocytes remained unchanged. There was no evident increase in superoxide in infected erythrocytes. However, the level of hydrogen peroxide in infected erythrocytes was markedly increased.

Animals↗
PubMed1989

Effect of sodium artesunate on malaria infected human erythrocytes.

Oxidative stress in malaria infected human erythrocytes is augmented and the anti-oxidant system is attenuated as compared with normal RBC's. Exacerbation of intra-erythrocytic oxidative stress might provide a means to kill the parasites. Sodium artesunate (SA), an effective Chinese anti-malaria drug, markedly increased the levels of active oxygen species and production of malonyldialdehyde in normal red blood cells and, to a greater extent, in malaria infected red blood cells. SA caused a remarkable decrease of unsaturated fatty acids content in normal red blood cell membrane. These suggest that the anti-oxidative system in red blood cells infected with malaria is jeopardized. Certain active oxygen species generated and accumulated in such red blood cells might in turn kill the parasites. SA augmented intracellular O2-. and H2O2 production, and this may partly account for its antimalaria action.

Animals↗