Rapid and Sensitive Chemiluminescent Enzyme Immunoassay for the Determination of Neomycin Residues in Milk / 生物医学与环境科学（英文）

Immunoassays greatly contribute to veterinary drug residue analysis. However, there are few reports on detecting neomycin residues by immunoassay. Here, a rapid and sensitive chemiluminescent enzyme immunoassay (CLIEA) was successfully developed for neomycin residue analysis. CLIEA demonstrated good cross-reactivity for neomycin, and the IC50 value was 2.4 ng/mL in buffer. The average recovery range was 88.5%-105.4% for spiked samples (10, 50, and 100 μg/kg), and the coefficient of variation was in the range of 7.5%-14.5%. The limit of detection of CLEIA was 9.4 μg/kg, and this method was compared with the liquid chromatography-tandem mass spectrometry method using naturally contaminated samples, producing a correlation coefficient of >0.95. We demonstrate a reliable CLIEA for the rapid screening of neomycin in milk.

The Benefit Risk Assessment of Consumption of Marine Species Based on Benefit-Risk Analysis for Foods (BRAFO)-tiered Approach / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To assess the net health effect caused by the consumption of specific marine species based on Benefit-Risk Analysis for Foods (BRAFO)-tiered approach.</p><p><b>METHODS</b>Twenty species were collected from the Zhoushan Archipelago, China. Concentrations of n-3 long-chain polyunsaturated fatty acids, methyl mercury (MeHg), and dioxin-like compounds (DLCs) in the samples were analyzed for benefit risk assessment based on BRAFO-tiered approach.</p><p><b>RESULTS</b>Based on the BRAFO-tiered approach, reference scenario (no intake) and alternative scenario (intake of specific species of 200 g/week) were determined. The exposure to MeHg/DLCs via alternative scenario of all studied species did not exceed provisional tolerable weekly/monthly intake. However, the adult population with high DLCs exposure in China would significantly exceed the upper limit of DLCs via an additional alternative scenario of some species such as Auxis thazard. The results of deterministic computation showed that alternative scenario of all studied species generated clear net beneficial effects on death prevention and child IQ gain.</p><p><b>CONCLUSION</b>The alternative scenario of all studied species could be recommended to population with average DLCs exposure, and the reference scenario of species with relatively high DLCs concentration could be recommended to population exposed to high DLCs.</p>

Determination of enantiomeric impurity in levocetirizine tablets by capillary electrophoresis / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To determine enantiomeric impurity in levocetirizine tablets by using capillary electrophoresis.</p><p><b>METHODS</b>The effects of pH and the concentrations of sulfated-Β-cyclodextrin (S-Β-CD) and buffer salt on chiral resolution were examined with S-Β-CD as chiral selector.</p><p><b>RESULTS</b>A good enantioseparation of cetirizine was achieved with 30 mmol/L NaH2PO4 buffer solution (pH 7.0) containing 20 g/L of S-Β-CD.</p><p><b>CONCLUSION</b>The method developed in the study is sensitive and reliable for determination of enantiomeric impurity in levocetirizine tablets.</p>

The human body burden of polychlorinated dibenzo-p-dioxins and dibenzofurans and dioxin-like polychlorinated biphenyls in residents' human breast milk from Beijing in 2007 / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate contamination levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in human breast milk from Beijing residents, and evaluate the human body burden of PCDD/Fs and dl-PCBs of general population.</p><p><b>METHODS</b>A total of 110 human milk samples were collected from 11 regions in Beijing in 2007. After 11 pooled samples were made, concentrations of PCDD/Fs and dl-PCBs in breast milk pooled samples were measured by a high resolution gas chromatography - high resolution mass spectrometry (HRCG-HRMS) with isotope dilution.</p><p><b>RESULTS</b>For congeners of PCDD/Fs and dl-PCBs in human breast milk from Beijing, the highest content of congeners was octachlorodibenzo-p-dioxin (OCDD), polychlorinated biphenyl (PCB)-118, and PCB-105 with the median of 20.6 pg/g fat, 4.07 ng/g fat and 1.63 ng/g fat, respectively. The concentration median of total dioxins in 11 pooled human milk samples from Beijing was 7.4 pg TEQ/g fat. The highest was 13.5 pg TEQ/g fat from Tongzhou, and the lowest was 4.3 pg TEQ/g fat from Pinggu.</p><p><b>CONCLUSION</b>The contamination level of PCDD/Fs and dl-PCBs in human milk from Beijing is relatively low. However, with the rapid industrialization in China, the human body burden of PCDD/Fs and dl-PCBs will be likely to rise. Thus, further studies should be conducted to continuously monitor the trend of contamination level.</p>

Dietary exposure of the Chinese population to acrylamide / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To assess the current status of the acrylamide in the Chinese food supply, the dietary acrylamide exposure in the Chinese population and to estimate the public health risks of the current consumption.</p><p><b>METHODS</b>The acrylamide content in the total diet study (TDS) food samples was analyzed using an LC-MS/MS method. Based on the analytical results, the dietary exposure calculations were performed using a deterministic method, combining mean acrylamide concentrations from the food group composite with their associated food consumptions.</p><p><b>RESULTS</b>Acrylamide was detected in 43.7% of all samples collected and acrylamide concentration varied from ND to 526.6 µg/kg. The estimated dietary intakes of acrylamide among Chinese general population given as the mean and the 95th percentile (P95) were 0.286 and 0.490 µg•kg(-1) bw•day(-1), respectively. The margins of exposure (MOEs) for the population calculated using both benchmark dose lower confidence limit for a 10% extra risk of tumors in animals (BMDL10) 0.31 and 0.18 µg•kg(-1) bw•day(-1), were 1069 and 621 for the mean dietary exposure, and 633 and 367 for the high dietary exposure respectively.</p><p><b>CONCLUSION</b>These MOE values might indicate a human health concern on acrylamide for Chinese population. Efforts should continue to reduce acrylamide levels in food in order to reduce the dietary risks to the human health.</p>

Development of an enzyme-linked immunosorbent assay for determination of the furaltadone etabolite, 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ) in animal tissues / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To determine 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ) residues released from protein bound AMOZ in animal tissues.</p><p><b>METHODS</b>Polyclonal and monoclonal antibodies were produced in this study. A rapid, sensitive, and specific competitive direct enzyme-linked immunosorbent assay (cdELISA) was developed.</p><p><b>RESULTS</b>Rabbit polyclonal antibodies were used in the optimized cdELISA method, and exhibited negligible cross-reactivity with other compounds structurally related to AMOZ. The IC(50) of the polyclonal antibody was 0.16 ng/mL. The method limit of detection in four different types of animal and fish tissues was less than 0.06 μg/kg. Recoveries ranged from 80% to 120% for fortified samples with the coefficient of variation values less than 15%. The results of the cdELISA method were in good agreement with the results from an established liquid chromatography-tandem mass spectrometry confirmatory method used for AMOZ residues.</p><p><b>CONCLUSION</b>The cdELISA method developed in the present study is a convenient practical tool for screening large numbers of animal and fish tissue samples for the the detection of released protein bound AMOZ residues.</p>

Advances in functional studies of nonstructural proteins and development of antiviral agents for enterovirus 71 / 药学学报

Human enterovirus 71 (EV71) is one of the major etiological agents for the hand, foot, and month disease (HFMD) and is causing frequent, widespread occurrence in the mainland of China. The single positive-stranded RNA genome of EV71 is translated into a single polyprotein which is autocleavaged into structural and nonstructural proteins. The functions of many nonstructural proteins characterized in the life cycle of virus are potential targets for blocking viral replication. This article reviews the studies of the structures and functions of nonstructural proteins of EV71 and the anti-enterovirus 71 drugs targeting on these nonstructural proteins.

Polybrominated diphenyl ethers load in human serum of Taiyuan city in 2010 / 中华预防医学杂志

<p><b>OBJECTIVE</b>This study was conducted to characterize polybrominated diphenyl ethers (PBDEs) load in human serum of Taiyuan city in 2010.</p><p><b>METHODS</b>A total of 42 blood samples were collected in Taiyuan city, 2010. Solid-phase extraction (SPE)-gas chromatography-negative chemical ionization-mass spectrometry method was used to measure the concentration of brominated diphenyl ethers (BDE)-17, BDE-28, BDE-47, BDE-66, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183 and BDE-209 and ΣPBDEs was calculated.</p><p><b>RESULTS</b>Of the tested serum samples, ΣPBDEs ranged from 2.09 to 66.74 ng/g of lipid weight (lw), the median and mean was 6.32 ng/g lw and 9.84 ng/g lw, respectively. BDE-209 was the main source of ΣPBDEs and its concentration ranged from no detection to 64.99 ng/g lw, the median was 4.11 ng/g lw, accounting for 67.6% of ΣPBDEs. Second source was BDE-153 and its concentration ranged from 0.29 to 4.92 ng/g lw, the median was 0.62 ng/g lw accounting for 10.1% of ΣPBDEs.</p><p><b>CONCLUSION</b>The overall load of PBDEs in the serum of local residents was low in 2010.</p>

Effect of ecdysterone on the proliferation of human mesenchymal stem cells in vitro / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of ecdysterone (EDS) on the proliferation of human bone marrow mesenchymal stem cells (hMSCs) in vitro.</p><p><b>METHODS</b>hMSCs were isolated from human bone marrow cell suspension by density gradient centrifugation. The expression of integrins CD44, CD105, CD34 and CD29 were examined by immunocytochemical method. EDS at 10, 25, 50 or 100 microg/ml were added in hMSC culture system, using the routine culture medium for hMSCs as control. The cell viability were analyzed by MTT assay and the cell cycle changes were examined by flow cytometry.</p><p><b>RESULTS</b>The optical density (OD) differed significant between the EDS treatment groups and the control group (P<0.01), and 25 microg/ml EDS group showed the highest OD value (P<0.01) without significant differences among 10, 50 and 100 microg/ml EDS groups (P>0.05). Flow cytometry showed that treatment of the cells with 25 microg/ml EDS significantly increased the cell percentages in S and G(2)M phases and the proliferation index (PI) of the cells as compared with the control group.</p><p><b>CONCLUSION</b>Within a given concentration range, EDS can promote the proliferation of hMSCs in vitro, and this effect can be the most obvious at the concentration of 25 microg/ml. The effect of EDS in promoting the proliferation of hMSCs does not positively correlate to EDS concentration administered.</p>

Smoking status or age impact on urinary 8-hydroxy-2'-deoxyguanosine in electrical and electronic equipment waste dismantling workers / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate the smoking or age impact on occupational workers in electrical and electronic equipment waste (e-waste) dismantling procedure, using 8-Hydroxy-2'-deoxyguanosine (8-OHdG) in the urine as a biomarker for oxidative damage to DNA.</p><p><b>METHODS</b>The pre-workshift and post-workshift urinary samples of 64 male workers in e-waste dismantling procedure were detected by solid-phase extraction-high performance liquid chromatography-electrochemical detector (SPE-HPLC-ECD). The data were statistically analyzed by two factors, age or smoking status.</p><p><b>RESULTS</b>The 8-OHdG levels in non-smokers' urines (n = 42) were higher than those in smokers' urines (n = 22). The levels in pre-workshift urines were detected at (8.25 +/- 4.23) micromol/mol creatinine in non-smokers, while the values were (5.44 +/- 1.18) micromol/mol in smokers. And, the levels in post-workshift were detected at (43.12 +/- 16.19) micromol/mol creatinine in non-smokers, while the values were (14.82 +/- 2.51) micromol/mol in smokers. The 8-OHdG levels in pre-workshift urines were not different between non-smokers and smokers (t = -0.81, P = 0.42), however after 1 day exposure, urinary 8-OHdG levels were significantly increased in non-smokers than those in smokers (t = - 2.33, P < 0.05). On the other hand, the subjects were divided into five groups according to their age. The 8-OHdG levels in pre-workshift urines were (1.86 +/- 0.66), (3.57 +/- 0.54), (8.12 +/- 4.10), (11.39 +/- 3.70) micromol/mol creatinine in < 20 years group (n = 6), 20 -years group (n = 22), 30 - years group ( n = 23), 40 - 49 years group (n = 11) respectively. No effect of age was found on the pre-workshift urinary 8-OHdG levels (F = 0.98, t = 0.41). However, it was found that the post-workshift urinary 8-OHdG levels increased along with the e-waste workers' age (F = 4.81, P = 0.03), and they were (4.19 +/- 2.85), (19.89 +/- 5.26), (28.89 +/- 14.61), (34.94 +/- 12.50) micromol/mol creatinine in < 20 years group, 20 - years group, 30 - years group, 40 - 49 years group respectively.</p><p><b>CONCLUSION</b>The urinary 8-OHdG levels in the e-waste dismantling workers might be inhibited by smoking status. The post-workshift urinary 8-OHdG levels increased along with the e-waste workers' age.</p>

Simultaneous determination of melamine, ammelide, ammeline, and cyanuric acid in milk and milk products by gas chromatography-tandem mass spectrometry / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To develop an analytical method for simultaneously qualitative and quantitative determination of melamine and triazine-related by-products including ammelide, ammeline, and cyanuric acid in milk and milk products by gas chromatography-tandem mass spectrometry (GC-MS/MS).</p><p><b>METHODS</b>Melamine and triazine-related by-products namely ammelide, ammeline and cyanuric acid in the samples were extracted in a solvent mixture of diethylamine, water, and acetonitrile (10:40:50, V/V/V). After centrifugation, an aliquot of the supernatant was evaporated to dryness under a gentle stream of nitrogen gas, and then melamine and triazine-related by-products were derivatized using BSTFA with 1% TMCS. The derivatives of melamine and its analogues were determined by gas chromatography/tandem mass spectrometry using multiple reactional monitoring (MRM) with 2, 6-Diamino-4-chloropyrimidine (DACP) being used as an internal standard.</p><p><b>RESULTS</b>The linear detectable ranges were from 0.004 mg/kg to 1.6 mg/kg for melamine, ammelide, ammeline, and cyanuric acid with a correlation coefficient no less than 0.999. The recovery rates of the four compounds in spiked blank milk powder at concentrations 0.5, 1, 2 mg/kg were between 61.4%-117.2%, and the relative standard deviation was no more than 11.5% (n=6). The detection limits of melamine, ammelide, ammeline and cyanuric acid in milk powder were 0.002 mg/kg with a ratio of signal to noise of 3.</p><p><b>CONCLUSION</b>This GC-MS/MS method for simultaneous determination of melamine, ammelide, ammeline, and cyanuric acid in milk and milk products is sensitive and specific.</p>

A survey on occurrence of melamine and its analogues in tainted infant formula in China / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To investigate the occurrence and concentrations of melamine and its analogues in tainted infant formula and to identify the etiologic factors for the urinary stones epidemic in infants and young children in China in 2008.</p><p><b>METHODS</b>Sanlu infant formula samples were collected from families of the affected children in Gansu province, and markets in Gansu and Hebei provinces and Beijing city. Melamine and its analogues, including cyanuric acid, ammeline, and ammelide were measured by gas chromatography/tandem mass spectrometry.</p><p><b>RESULTS</b>High prevalence and concentrations of melamine were found in Sanlu infant formula samples, with low concentrations of cyanuric acid, ammeline and ammelide. Melamine were detected in 87 out of 111 Sanlu infant formula samples with a range of 118 to 4,700 mg/kg.</p><p><b>CONCLUSION</b>The results provide strong evidence for melamine as the etiological factor for the urinary stones epidemic in infants and young children in China in 2008.</p>

Assessment on dietary melamine exposure from tainted infant formula / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To estimate the dietary melamine exposure in Chinese infants and young children from the consumption of melamine adulterated Sanlu infant formula.</p><p><b>METHODS</b>Four age groups of infants and young children (3, 6, 12, and 24 months) were chosen as the assessed subjects and the maximum amount of infant formula consumption was estimated based on the recommended usage level in the package insert of Sanlu infant formula and other brands. Melamine was analyzed in 111 Sanlu infant formula samples collected from the markets in Beijing and Gansu province using the LC-MS-MS with a limit of quantification of 0.05 mg/kg. Four levels of melamine concentration were chosen to estimate the dietary intakes, including the mean, median, 90th percentile, and maximum.</p><p><b>RESULTS</b>The infants of 3 months had the highest intake of melamine, and with the increase of the age (month), the intake decreased. Based on the median melamine concentration (1,000 mg/kg) as an example, the melamine intakes for the infants of 3, 6, 12, and 24 months were 23.4, 21.4, 15.0, and 8.6 mg/kg bw/d, respectively.</p><p><b>CONCLUSION</b>Dietary melamine intakes from tainted Sanlu infant formula significantly exceeded the TDI level (0.2 mg/kg bw/d) recommended by the WHO Expert Meeting in 2008. However, the present assessment has some limitations including the poor representative samples, the varied melamine concentrations in the adulterated Sanlu infant formula, and other brand infant formula possibly consumed by these infants.</p>

A study on arsenic speciation analysis in animal origin seafood / 中华预防医学杂志

<p><b>OBJECTIVE</b>To develop a method for determining arsenobetaine (AsB), arsenite (AsIII), arsenate (AsV), Monomethylarsonic acid (MMA) and Dimethylarsenic acid (DMA) with liquid chromatography (LC), on-line UV-decomposition (UV), hydride generation (HG) and atomic fluorescence spectrometry (AFS) in animal origin seafood samples.</p><p><b>METHODS</b>Arsenic compounds were extracted in an ultrasonic bath with methanol-water (9:1) solvent from the animal origin seafood samples. The extracts were evaporated with N2 and dissolved in water. The solvent was extracted by hexane to remove lipids. And then, the aqueous solution was diluted to 10 ml. The extracts were filtered before analysis by LC-AFS. The mobile phase consisted of 0.5 mmol/L NH4H2PO4 (pH 9.0) and 20 mmol/L NH4H2PO4 (pH 6.0). Arsenic species were separated with an anion exchange column Hamilton PRPX-100 and gradient elution, detected by LC-UV-HG-AFS.</p><p><b>RESULTS</b>The established separation condition could achieve a better separation for five arsenic species. Detection Limits (LOD) were ranged from 0.0025 to 0.0032 mg/L, AsB was the predominant arsenic species in the animal origin seafood samples. AsIII and DMA were detected in certain shellfish samples at trace level. The accuracy of total arsenic measurement was tested by the analysis of NBS 1566 (Oyster Tissue). The accuracy of arsenic species measurement was tested by the analysis of BCR 627 (Tuna Fish). The data were tallied with the certified value.</p><p><b>CONCLUSION</b>Arsenic species were specifically detected by LC-UV-HG-AFS in the animal origin seafood samples.</p>

Study on the contamination level and intake of organotins of Chinese dietary / 中华预防医学杂志

<p><b>OBJECTIVE</b>To obtain the baseline data of organotins' pollution of Chinese meal in order to carry on primary danger analysis of the exposure.</p><p><b>METHODS</b>The samples of the third Chinese total diet study were determined by gas-chromatography pulsed flame photometric detector to estimate dietary intake of organotins. The dietary intake of organotins was estimated according to the contamination level of organotins and food consumption.</p><p><b>RESULTS</b>Only several kinds of organotin were founded in several foods and no organotins was found in fruit, sugar and alcoholic beverages. Dimethyltin (DMT) were detected in some samples from Southern 1 area, the content ranged from 1.5 microg/kg to 4.1 microg/kg. Butyltin compounds existed in seafoods from Southern 1 area, the contents of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MTB) being 0.9 microg/kg, 1.1 microg/kg, 1.4 microg/kg respectively. The lower limit and upper limit of exposure to tributyltin were from 0.003 microg x kg(-1) x d(-1) to 0.006 microg x kg(-1) x d(-1) and from 0.004 microg x kg(-1) x d(-1) to 0.019 microg x kg(-1) x d(-1) respectively. Comparing to ADI of tributyltin (WHO), the Chinese dietary intake of tributyltin only accounted for 2.5% and that of butyltin only accounted for 3.5%. To identify the contamination source of organotins in Southern 1 area, the individual samples of aquatic food from individual province were analyzed, revealing that Fujian province and Shanghai City were the main contributors of organotins pollution in this area. The belt fish and yellow croaker were typical pollution samples. Higher levels of DMT were detected in seafood samples from Shanghai.</p><p><b>CONCLUSION</b>The exposure level of Chinese dietary was relative low, however the sources of organotin pollution needs further investigation.</p>

Research on investing methods and mold cooling methods of the self-made investment for pure titanium castings / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To observe the influence of different investing methods and mold cooling methods on pure titanium castings invested in the self-made investment, and to provide theoretic base for the development for the investment.</p><p><b>METHODS</b>The influence of investing methods (one-step investing method and two-step investing method) on castability and crown fit of titanium castings were investigated, and the influence of cooling methods on reaction layers, mechanical properties and crown fit of titanium castings were investigated.</p><p><b>RESULTS</b>Both the investing methods exhibited good castability, but only the titanium full crowns by one-step investing method showed clinically acceptable fit. Although the quenching group showed thinner reaction layer(100 microm), lower strength and similar elongation rate, the titanium castings by bench cooling showed clinically acceptable full crown fit with 115 microm thick reaction layer as cast.</p><p><b>CONCLUSION</b>The one-step investing method and the bench cooling are recommended for the self-made investment.</p>

The study on strengthening of fluorophlogopite-based dental machinable ceramic / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To study the strengthening of fluorophlogopite-based dental machinable ceramic through developing a new type of calcium-mica-based ceramic.</p><p><b>METHODS</b>Based on the analysis of the crystal structure of the fluorophlogopite ceramic of Dicor MGC, the structure of a new type of calcium-mica-based ceramic was designed and the corresponding composition of the new material was experimented. And the new glass-ceramic was obtained through the treatment of glass preparation and nucleation. Then crystal content of the glass ceramic was analyzed by X-ray diffraction analysis (XRD) and the 3-point bending strength of the new ceramic was recorded.</p><p><b>RESULTS</b>A new type of calcium-mica-based glass ceramic was developed and had the 3-point bending strength of (210.2 +/- 14.7) MPa. Compared with the strength of fluorophlogopite-based dental machinable ceramic, such as Dicor MGC, which was reported in the range of 150 approximately 180 MPa within inclusive studies, the higher strength of the new ceramic was recorded.</p><p><b>CONCLUSIONS</b>The fluorophlogopite-based dental machinable ceramic could be reinforced through internal strengthening.</p>

Effect of camera control devices of Cerec 2 on the fit of CAD/CAM all-ceramic copyings of posterior tooth / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effect of camera control devices of Cerec 2 on the fit of CAD/CAM all-ceramic copyings of posterior tooth.</p><p><b>METHODS</b>24 all-ceramic copyings were made by Cerec 2 with camera control devices and that without camera control devices. Copyings were embed and sectioned, then SEM and image analyzer was used to measure the space between the copyings and dies at the marginal opening, the axial wall, and the occlusal adaptation at the measurement locations.</p><p><b>RESULTS</b>The marginal fit at buccal space of copyings with camera control devices group was smaller than that without camera control devices group (P < 0.05). The internal fit of of copyings had statistically significant difference at mesio-axial, disto-axial, bucco-axial, bucco-occlusal, linguo-occlusal and disto-occlusal space between camera control device group and without camera control devices group (P < 0.05). There was no statistical difference on the marginal fit and internal fit of copyings between Vita MK II and porous alumina oxide (P < 0.05).</p><p><b>CONCLUSION</b>The Cerec 2 with camera control devices reduced effectively the inaccuracy of inner space of copyings which contributed from the technical errors of the operator, and provided well-proportioned space for adhesive. Both the fit of copyings made of Vita MK II and porous alumina oxide satisfied the clinical demand.</p>

Study on of dietary pesticide residues in Chinese residents / 中华流行病学杂志

<p><b>OBJECTIVES</b>To investigate the change of pesticide residues in Chinese dietary through analysis on results of the pesticide residues in the Chinese total diet study carried out the first in 1990.</p><p><b>METHODS</b>Organochlorine, such as HCH and DDT of 9 groups and 15 organophosphorus pesticide residues of 3 groups in four regions of China were determined by gas chromatography-electron capture detector (GC-ECD) and gas chromatography-flame photometric detector (GC-FPD) respectively. According to the amount of pesticide residues in various foods and the amount of food consumption in different areas, we calculated the amount of dietary intake of pesticide residues, then compared with the acceptable daily intake (ADI) or provisional tolerable daily intake (PTDI). The contaminated samples were validated by gas chromatography-mass spectrometry (GC-MS).</p><p><b>RESULTS</b>Results showed that the total dietary daily intake of HCH per person was decreasing from 5.04 micro g in 1990 to 3.11 micro g in 2000, where as the total dietary daily intake of DDT per person was decreasing from 20.47 micro g in 1990 to 2.15 micro g in 2000. The result was less than 1 percent difference of PTDI (0.01 mg/kg bw) established by the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) in 2000. Compared to the results in 1990, the intake of HCH from animal foods increased a little, due to the contaminated of aquatic products by Lindan in the second Southern region and the first Northern region. None of the organophosphorous pesticide residues analyzed were detected in cereals, vegetables and fruits.</p><p><b>CONCLUSION</b>The intake level of pesticide residues in Chinese dietary in 2000 was considered to be low, and the abuse of organophosphorous pesticide seemed to be under effective control.</p>

The effect of tooth preparation design on the CAD/CAM all-ceramic coping crown's fitness / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To study the effect of tooth preparation design on fitness of CAD/CAM all-ceramic coping crown.</p><p><b>METHODS</b>The tooth preparation comprised 2 types of occlusal convergence (10 degrees, 20 degrees), 2 margin forms (shoulder, chamfer). The MC coping were milled by Cerec 2 CAD/CAM system, cemented, embedded, sectioned, and measured at 10 sites to obtain the data of margin, shoulder, axial surface, occlusal surface fitness.</p><p><b>RESULTS</b>The coping's fitness was influenced by convergence angle and margin form. The coping's fitness was very nice (101.7 approximately 127.9) microm when the coping with 20 degrees occlusal convergence angle. Those coping with 20 degrees occlusal convergence and chamfer margin in tooth preparation provided the best fitness, its cement film thickness in margin was (40.1 +/- 11.8) microm.</p><p><b>CONCLUSIONS</b>The 20 degrees occlusal convergence and chamfer margin can be used for CAD/CAM all-ceramic crown in clinical application.</p>