Hydrogen Peroxide Might Bleach Natural Dentin by Oxidizing Phosphoprotein.

Recent studies suggested that bleaching agents may whiten teeth by oxidizing the fluorescent materials, which are the proteins located in the organic-inorganic interface. Therefore, we postulated that fluorescence of dentin came from dentin phosphoprotein (DPP) and that bleaching agents might bleach dentin by oxidizing DPP. Fifty-six specimens were randomly divided into 4 groups and exposed to distilled water, hydrogen peroxide (HP), ethylenediamine tetraacetic acid disodium salt (EDTA), and acetic acid for 24 h. After measuring the organic and inorganic components, fluorescence, and color characteristics of dentin before and after exposure, we found that when DPP was removed from dentin by EDTA, fluorescent intensity declined proportionally with the reduction in Raman relative intensity, and dentin was whitened considerably, with an Δ E value 6 times higher than that of the distilled water group. On the contrary, due to the incapability of acetic acid to dissolve DPP during decalcification, fluorescent intensity values and tooth color remained nearly unchanged after exposure to acetic acid. Dentin exposed to neutral HP showed no obvious morphologic and organic/inorganic component changes except for the destruction of DPP. Similarly, dramatically decreased fluorescent intensity and lightened color were found in the HP group. Moreover, DPP solution of the HP group exhibited decreased ultraviolet absorbance, especially between 250 and 300 nm, which arose from aromatic amino acids. The results indicated that DPP was responsible for the fluorescent properties of dentin and that HP might bleach dentin by the oxidization of aromatic amino acids in DPP. These findings are of great significance in promoting our further understanding of the mechanism of tooth bleaching and the fluorescent property of normal dentin.

New Insights into Effects of Aromatic Amino Acids on Hydroxyapatite.

Biomimetics inspired by superstructures and extraordinary properties of teeth have resulted in tooth repair and the generation of novel materials. However, little attention has been paid to tooth color, whose origin remains unknown. Based on recent studies, fluorophores-mainly aromatic amino acids (AAAs) in proteins-might be responsible for tooth color. We synthesized carbonated hydroxyapatite (HA; the mineral phase of teeth) in the presence of different amino acids (AAs; the basic units of protein matrix of teeth) as a simplified model of teeth to explore the color source at the AA level. After measuring the fluorescence and color characteristics of HA-AAs before and after bleaching treatment, we found that only HA, synthesized in the presence of AAAs, exhibited remarkable fluorescence and color property. Furthermore, linearly increased fluorescence intensity and deeper color were observed with an increase in AAA content in HA-AAAs. Similarly, significantly decreased absorbance of HA-AAAs between 250 and 300 nm in ultraviolet spectra, declined fluorescence intensity, and decolored performance of HA-AAAs were observed after bleaching treatment. The results showed that AAAs contributed to the fluorescence and color properties of HA and that hydrogen peroxide might whiten HA-AAAs by oxidizing the benzene ring in AAAs. These findings are of great significance in promoting the synthesis of advanced tooth-colored materials and furthering our understanding of the possible mechanisms of hydrogen peroxide. Moreover, our study shed light on the importance of AAAs and might provide new ideas for investigations of biomineralization and biomimetics.

[Immune response to one booster dose of inactivated hepatitis A vaccine in college students].

Objective: To evaluate the safety and immunogenicity of one booster dose of inactivated hepatitis A vaccine in young adults. Methods: The subjects were selected from participants in the clinical trial of immunogenicity of inactivated and attenuated live hepatitis A vaccine in young adults. Eligible subjects were those who had received one dose of inactivated or attenuated hepatitis A vaccine, could be contacted and were sero-negative before primary vaccination. All qualified subjects were immunized with one booster dose of inactivated hepatitis A vaccine. The blood samples were collected before booster dose vaccination and 28 days after the immunization. Anti-HAV antibody titer ≥20 mIU/ml was considered to be sero-protected against hepatitis A virus. Results: The GMCs in the inactivated HAV vaccine group and attenuated live vaccine group before booster dose vaccination were 70.80 mIU/ml and 50.12 mIU/ml, respectively, and the sero-protection rates were 94.7% and 65.0%, respectively. After the vaccination of the booster dose, the sero-protection rates in both groups were 100.0%, and the GMCs were 2 816.09 mIU/ml and 2 654.55 mIU/ml, respectively. Conclusion: The GMCs and sero-protection rates of anti-HAV antibody in young adults declined after three years of the primary vaccination. However, the higher GMC and sero-protection rate were observed in the inactivated vaccine group than in the attenuated live vaccine group. Significant increases of GMC levels were observed in both groups after one booster dose vaccination.

Nanoscale spheroidized cementite induced ultrahigh strength-ductility combination in innovatively processed ultrafine-grained low alloy medium-carbon steel.

We describe here innovative processing of low alloy medium-carbon steel with a duplex microstructure composed of nanoscale spheroidized cementite (Fe3C) in an ultrafine-grained (UFG) ferritic steel. After multi-pass rolling and intermittent annealing at 550 °C for 300 s, the obtained UFG-1 steel showed an average ferrite grain size of ~430 nm, containing nanoscale spheroidized cementite (Fe3C) particles with an average size of ~70 nm. On annealing at 600 °C for 300 s, the average size of ferritic grains was increased to ~680 nm and the average size of spheroidized Fe3C particles increased to ~90 nm, referred as UFG-2 steel. Tensile tests indicated that UFG-1 steel had high yield strength (σ y) of 1260 MPa, and ultimate tensile strength (σ UTS) of 1400 MPa. These values are higher than that of UFG-2 steel (σ y = 1080 MPa and σ UTS = 1200 MPa), suggesting that the strengthening contribution is a cumulative effect of decrease in ferrite grain size and nanoscale cementite. The incoherent interfaces between nanosized particles and the matrix acted as a strong barrier to dislocation motion. The study underscores that nanosized precipitates not only provide strength but also contribute to ductility, which is very encouraging for improving the ductility of medium-carbon steels.

Successful treatment of larynx-tracheobronchial-pulmonary aspergillosis in an immunocompetent host.

Immunocompromised individuals are susceptible to pulmonary Aspergillus infections, whereas invasive Aspergillus infection is extremely rare in the presence of normal immunity. A case of larynx-tracheobronchial-pulmonary aspergillosis in an immunocompetent 57-year-old female host who was successfully treated with amphotericin-B and voriconazole is reported here.

Comparative pharmacokinetics and bioavailability of tylosin tartrate and tylosin phosphate after a single oral and i.v. administration in chickens.

The pharmacokinetics and oral bioavailability of tylosin tartrate and tylosin phosphate were carried out in broiler chickens according to a principle of single dose, random, parallel design. The two formulations of tylosin were given orally and intravenously at a dose level of 10 mg/kg b.w to chicken after an overnight fasting (n = 10 chickens/group). Serial blood samples were collected at different time points up to 24 h postdrug administration. A high performance liquid chromatography method was used for the determination of tylosin concentrations in chicken plasma. The tylosin plasma concentration's time plot of each chicken was analyzed by the 3P97 software. The pharmacokinetics of tylosin was best described by a one-compartmental open model 1st absorption after oral administration. After intravenous administration the pharmacokinetics of tylosin was best described by a two-compartmental open model, and there were no significant differences between tylosin tartrate and tylosin phosphate. After oral administration, there were significant differences in the Cmax (0.18 ± 0.01, 0.44 ± 0.09) and AUC (0.82 ± 0.05, 1.57 ± 0.25)between tylosin phosphate and tylosin tartrate. The calculated oral bioavailability (F) of tylosin tartrate and tylosin phosphate were 25.78% and 13.73%, respectively. Above all, we can reasonably conclude that, the absorption of tylosin tartrate is better than tylosin phosphate after oral administration.

Prevalence of obesity and associated risk factors in Northeastern China.

AIM: To investigate the prevalence of obesity and associated risk factors in the Northeastern Chinese city of Dehui. METHODS: A cross-sectional study involving random sampling methods generated 3598 completed questionnaires by permanent residents of Dehui. Binary multivariate logistic regression analysis was used to identify factors that were significantly associated with obesity. RESULTS: Based on the 2000 WHO diagnostic criterion regarding populations in the Asia-Pacific region, the prevalence of obesity was 37.71% (34.77% of females; 41.11% of males). Elevated body mass index (BMI) was significantly associated with cardiovascular disease (CVD)-associated conditions (P<0.05), and increased prevalence of abnormally high transaminase levels (P<0.05). Binary logistic regression analysis demonstrated the following variables were associated with obesity: increased age (odds ratio [OR]: 1.01, 95% confidence interval [CI]: 1.0-1.02), high total cholesterol (TC) (OR: 1.26, 95% CI: 1.03-1.54), high triglycerides (TG) (OR: 1.38, 95% CI: 1.16-1.64), hypertension (OR: 1.62, 95% CI: 1.39-1.90), fatty liver (OR: 2.91, 95% CI: 2.41-3.49), living in an urban setting (OR: 2.84, 95% CI: 2.39-3.38), and advanced education (OR: 1.22, 95% CI: 1.06-1.40). CONCLUSIONS: Obesity is prevalent among the adult population in Northeastern China and is significantly associated with CVD risk factors such as hypertension, dyslipidemia, as well as transaminase abnormalities.

Epidemiological investigation of metabolic syndrome and analysis of relevant factors in north-eastern China.

This epidemiological study was conducted to investigate the prevalence of metabolic syndrome and associated risk factors in Chinese subjects from Dehui in north-eastern China. Using a random sampling method, a questionnaire was completed by 3785 permanent residents aged 18 - 72 years and relevant clinical data were collected from each subject. Binary multivariate logistic regression analysis was used to identify factors that were significantly associated with metabolic syndrome. Based on the International Diabetes Federation definition, the prevalence of metabolic syndrome was 22.4%, which is higher than that of the general Chinese population. Metabolic syndrome occurred more frequently in females and the prevalence gradually increased with age. Living in an urban setting and being female, > 50 years old, overweight, having total cholesterol > or = 5.18 mmol/l, low-density lipoprotein cholesterol > or = 3.1 mmol/l, and a fatty liver were significant risk factors associated with metabolic syndrome.

Proteomic analysis of differentially expressed proteins in rat liver allografts developed acute rejection.

BACKGROUND: Acute rejection (AR) after liver transplantation is a cell-mediated immune response that takes place within the allograft and results in graft dysfunction and failure, but the molecular mechanisms about hepatocyte dysfunction remain poorly understood. Here we characterized global protein expression changes in liver allograft during AR. METHODS: The effect of an alloantigen-dependent immunological response was evaluated by syngeneic and allogeneic rat orthotopic liver transplantation (OLT). Using a combination of two-dimensional gel electrophoresis and mass spectrometry, we identified 18 differentially expressed proteins in AR allograft compared with matched tolerance allograft. Serum chemistry and allograft histology were determined. RESULTS: Allogeneic OLT recipients exhibited elevated plasma levels of liver injury markers, progressive portal and venous inflammation and cellular infiltration in liver allograft compared with syngeneic OLT. 18 protein expressions altered by AR play important roles in metabolism, oxidative stress defense, signal transduction, biotransformation and transport. Decreased expression of protein disulfide isomerase in AR allograft was confirmed by Western blotting and immunohistochemistry. CONCLUSIONS: This study uncovered new mechanistic insights into graft dysfunction in AR of liver allograft. Several significantly altered protein expressions act coordinately in hepatocyte dysfunction by depressed energy, enhanced oxidative stress-induced molecular damage and restrained biotransformation. The present findings may open new avenues for the understanding and prevention of graft dysfunction and failure during AR.

Donor apoptotic lymphocyte transfusion-induced liver allograft tolerance by up-regulation of CD4(+)CD25(+) regulatory T cells in peripheral blood.

Uptake of apoptotic cells by antigen-presenting cells (APC) may be involved in tolerance maintenance with an immunoregulatory role. The aim of this study was to evaluate the consequences of preoperative transfusion of donor apoptotic lymphocytes on survival of orthotopic liver transplantations (OLT). OLT was performed between Lewis (donor) and Brown Norway (BN recipient) inbred rats using a double-cuff technique. Apoptotic splenic lymphocytes induced by ultraviolet-C (UVC) irradiation were infused intravenously at 7 days before OLT. Changes in regulatory T cells in blood were determined using flow cytometry. UVC irradiated lymphocytes were sensitive and effective, as evidenced by increased peripheral blood CD4(+)CD25(+) T cells compared with recipients that received infusion of untreated donor lymphocytes or a control. Apoptotic lymphocyte transfusion prolonged hepatic allograft survival, with significantly lower histological stages of inflammation and cellular infiltration than in untreated allografts. Our results demonstrated that donor apoptotic cells promoted allograft acceptance and up-regulated CD4(+)CD25(+) regulatory T cells (Treg) in blood.

The role of toll-like receptors 2 and 4 in acute allograft rejection after liver transplantation.

Toll-like receptors (TLRs) are germline-encoded receptors expressed on antigen-presenting cells (APCs) that identify a variety of microbial and endogenous ligands and activate the innate immune responses to the presence of danger. However, their role in the development of allograft rejection after liver transplantation remains unknown. In this study, we used flow cytometry to assess TLR-4 and TLR-2 expression among circulating CD14+ monocytes in 64 liver transplant patients and 24 healthy volunteers. We demonstrated significantly higher TLR-2 and TLR-4 expression on circulating monocytes among conditioned liver transplantation recipients with acute rejection compared with those in clinically stable with normal liver function. Steroid pulse therapy significantly reduced the expression of TLR-4 and TLR-2 on the monocytes of recipients with acute rejection. Based on these data, we have suggested that activation of innate immunity in liver transplant recipients through TLR-4 and TLR-2 contributes to the development of acute allograft rejection after liver transplantation. The reduced expression of TLR-4 and TLR-2 may be one of the mechanisms by which steroid pulse therapy inhibits the development of acute rejection. Estimation of TLR expression on APCs may be predictive of in acute rejection after liver transplantation.

[DNA damage induced by fotemustine in cultured HL60 cells].

AIM: To detect DNA damage caused by fotemustine (Fot). METHODS: DNA damage in HL60 cells was evaluated by modified alkaline elution technique. DNA interstrand crosslink (ISC) and DNA-protein crosslink (DPC) were determined. Carmustine (Car) was used as control. Drug treatment time was 1 h. RESULTS: After treatment with Fot 300 mumol.L-1, ISC and DPC index were 5.4 and 6.1 at 6 h, 2.7 and 1.2 at 12 h, respectively. ISC reached the maximum at about 6 h. For Fot 100 mumol.L-1, ISC and DPC index at ISC peak time were 2.1 +/- 0.9 and 3.55 +/- 0.23, 5.0 +/- 0.5 and 7.7 +/- 1.1 for Car 100 mumol.L-1, respectively. Single strand break (SSB) was induced by Fot. CONCLUSION: Fot caused HL60 cell DNA ISC, DPC, and SSB. ISC was formed more quickly by Fot than that by Car.

Effects of Rehmannia glutinosa polysaccharide b on T-lymphocytes in mice bearing sarcoma 180.

AIM: To study immuno-antitumor action mechanism of RGP-b. RGP-b (Rehmannia glutinosa polysaccaride b) is a new component isolated from the herb, had an average molecular mass of 160 kDa and 5 kinds of monosaccharides as acid-splitting products. Its HPLC showed a main sharp peak at 162 kDa. METHODS: The kinetic effects of RGP-b on IL-2 secretion, cytotoxic T-lymphocyte (CTL) activities and L3T4+, lyt-2+ T-lymphocyte subset in mice bearing S180 were observed. RESULTS: RGP-b 10 or 20 mg kg-1 ip obviously attenuated the decrease of CTL cytotoxity caused by excessive tumor growth on d 9 after the administration, but only partly ameliorated the descent of IL-2. Its effect on lyt-2+ subset was quite parallel with that on CTL cytotoxity. RGP-b kept the ratio of L3T4+ to lyt-2+ subset lower than that of control. CONCLUSION: Improving the production of lyt-2+ CTL and its cytotoxity were an essential immuno-antitumor mechanisms of RGP-b.

Design of a scanning ellipsometer by synchronous rotation of the polarizer and analyzer.

We have designed and constructed a new type of spectroscopic ellipsometer to study the optical properties of materials in the 3500-8000-Å wavelength range. In the system, the analyzer and polarizer are driven 10(4) steps/revolution by two stepping motors that have hollow shafts and rotate synchronously with a speed ratio of 2:1, i.e., A = 2P. Both the polarizer and analyzer are mounted directly on the shafts to avoid mechanical transmission and vibration problems entirely and make the system simple and reliable. An additional source polarizer was placed in the optical path to reduce the slight polarization effects of the light source. The light intensity finally received by the detector contained five components, one dc and four ac, with frequencies of ω(0), 2ω(0), 3ω(0), and 4ω(0), respectively. One can independently obtain the ellipsometric parameters of ψ and Δ as well as the optical constants by calculating any one of the two sets of ac signals, with a raw data self-consistency of better than 0.5%. The incident angle, aligned precisely by a laser beam, was continuously variable through a mechanical system with a computercontrolled resolution of 0.001° or a visual resolution of 0.005°. The system operations, including data acquisition and reduction, high-voltage control of the photomultiplier, incident angle, as well as wavelength setting and scanning, were fully and automatically controlled by a 386-based microcomputer. We self-calibrated the system by adjusting and setting precisely the initial azimuthal angles of the prisms. The results from the measured spectra of the complex refractive index for a gold-film sample are presented, and we show that the data obtained at three different incident angles of 65°, 70°, and 75° are remarkably consistent with one another. A comparison of the two results from the ellipsometry and reflectance measurements is given. The experimental skills and system error reduction are discussed in detail.

Impaired antigen-presenting capability of monocytes correlated with their decreased expression of HLA-II antigens in patients with myeloid leukemia.

Antigen-presenting capability and expression of HLA-II antigens on peripheral blood monocytes were analyzed by isotope incorporation technique and indirect immunofluorescence assay with monoclonal antibodies Tü 22, Tü 36 and anti-Leu-M2 in patients with acute and chronic myeloid leukemias (AML, CML). All patients (17 AML and 13 CML) demonstrated impaired antigen-presenting capability of monocytes (P < 0.001), when compared with simultaneously studied controls, which were HLA-identical normal siblings of the patients. These patients also showed a markedly decreased proportion of MAC-120- and HLA-DQ-positive monocytes as compared with the controls (P < 0.001), while the percentage of HLA-DR-positive monocytes in the patients was similar to that observed in the controls (P > 0.05). These findings suggested, therefore, that impaired antigen-presenting capability of monocytes correlated with their decreased expression of HLA-DQ in patients with acute and chronic myeloid leukemias.