The elution and breakdown behavior of constituents from various light-cured composites

Objectives

Constituents of dental composites can be released from dental fillings after polymerization. The aim of this study was to examine the time-related elution and breakdown of separable constituents of polymerized composites using deuterated solvents.

Method

Elution and breakdown of constituents were investigated with deuterated solvents methanol and water by gas chromatography/mass spectrometry of following composites for 180 days: Filtek™ Supreme XT, Filtek™ Supreme XT Flow, Tetric Ceram^®, Tetric Flow^®, Grandio^®, Grandio^® Flow.

Results

Within 180 days no compounds were formed as the products of breakdown. 19 compounds were identified as elution products: Bis-EMA, TEGDMA, DDDMA, EGDMA, MAA, BPA, CQ, HQME, DMABEE, CSA, BL, TEG, BHT, TINP, TPP, TPSB, DEDHTP, DCHP, ß-PHEA.The highest concentration of Bis-EMA was measured for Tetric Flow^® in deuterated methanol on day 90 at 36.993 mmol/l and in deuterated water also on day 90 at 0.031 mmol/l.The highest TEGDMA concentrations were measured for Grandio^® Flow in deuterated methanol on day 60 at 1.322 mmol/l and for Filtek™ Supreme XT Flow in deuterated water on day 3 at 0.689 mmol/l. The highest BPA concentration was measured for Tetric Flow^® in deuterated methanol on day 90 at 1.469 mmol/l. The highest BPA concentration was measured for Grandio^® in deuterated water on day 180 at 0.007 mmol/l.Significance Examination of time-related elution indicates that various elution products (e.g. Bis-EMA, BPA) were only released in small quantities during the first 90 days, but in high quantities between day 90 and day 180.     

Dictyostelium cytokinesis: from molecules to mechanics

Cytokinesis is the mechanical process that allows the simplest unit of life, the cell, to divide, propagating itself. To divide, the cell converts chemical energy into mechanical energy to produce force. This process is thought to be active, due in large part to the mechanochemistry of the myosin-II ATPase. The cell's viscoelasticity defines the context and perhaps the magnitude of the forces that are required for cytokinesis. The viscoelasticity may also guide the force-generating apparatus, specifying the cell shape change that results. Genetic, biochemical, and mechanical measurements are providing a quantitative view of how real proteins control this essential life process.     

一氧化氮外源性供体L-arginine对破骨细胞骨吸收功能的影响

目的:一氧化氮在维持机体多个系统的生理功能中起重要作用,许多慢性疾病可造成一氧化氮产生减少,此时一氧化氮供体是一种必要的补充。观察一氧化氮外源性供体L-arginine对体外培养破骨细胞增殖及骨吸收功能的影响。方法:实验于2005-06/2006-05在四川大学华西医院生物治疗国家重点实验室干细胞与组织工程研究室完成。选择出生1d的清洁级SD大鼠乳鼠,采用骨髓诱导法体外培养破骨细胞,培养液内分别加入0.3,0.6,1.0g/L不同浓度的L-arginine,并以等体积三蒸水作为对照。培养7d后,以抗酒石酸酸性磷酸酶染色观察破骨细胞数目、形态,MIAS-2000图像分析仪检测骨片上骨吸收陷窝的数目和面积,并用扫描电镜观察不同浓度L-arginine对骨吸收陷窝的影响。结果:①破骨细胞的一般形态:破骨细胞较其他细胞大,形态不规则,呈油煎蛋形、长条形、腊肠形或漏斗形等,细胞内可见几个至几十个核不等。抗酒石酸酸性磷酸酶染色酶活性部分酒红色,颗粒状。②抗酒石酸酸性磷酸酶阳性细胞数:各组破骨细胞数目随着L-arginine浓度增加而减少(P<0.05)。③骨吸收陷窝的面积和数目:骨片培养7d,吸收陷窝计数的结果显示,0.3g/L以上浓度L-arginine对破骨细胞吸收功能均有明显抑制作用,并呈剂量相关性。0.3g/LL-arginine组陷窝面积为对照组的91%(P<0.05),0.6g/LL-arginine组为对照组的80%(P<0.05),1.0g/LL-arginine组为对照组的69%(P<0.01)。结论:采用骨髓诱导法培养的破骨细胞数量多、纯度高,且具有明显的骨吸收功能。L-arginine抑制破骨细胞增殖,抑制破骨细胞骨吸收功能,并呈剂量相关性。     

Effect of Various Antidotes on Biliary Excretion of Arsenic in Isolated Perfused Livers of Guinea Pigs after Acute Experimental Poisoning with As2O3*

Abstract: The effect of the dithiols British Anti-Lewisite (BAL), dimercaptopropanesulfonic acid (DMPS), dimercaptosuc-cinic acid (DMSA) and a new metal binding agent 2, 3–bis-(acetylthio)-propanesulfonamide (BAPSA) on the biliary excretion of arsenic in perfused livers of guinea pigs after acute experimental poisoning with As₂O₃ was investigated. Guinea pigs received As₂O₃, 10.0 mg/kg subcutaneously at 9 a. m. as a single injection. One hour after the injection the livers were perfused (2.5 mix min.^–1 x g^–1 liver) with Krebs-Henseleit buffer and glucose for 80 min. After 40 min. of saline perfusion (control) 0.1 or 0.7 mmol/1 BAL, DMSA, DMPS, or BAPSA were added to the perfusate and arsenic elimination in the bile and effluent perfusate was measured. The biliary excretion of arsenic in control livers between 40 and 80 min. was 0.7% of the total arsenic liver content before perfusion (= arsenic liver content after perfusion + portion excreted in the bile + perfusate). After antidote addition (0.1 mmol/l) the excretion was 0.2% for livers perfused with BAL, 6.8% for DMSA, 10.6% for DMPS, and 11.1% for BAPSA, respectively. After 0.7 mmol/l antidote the excretion of arsenic was 0.1% in livers perfused with BAL, 9.6% for DMSA, 12.3% for DMPS, and 13.3% for BAPSA, respectively. Except BAL, all compounds and most effectively BAPSA increased biliary excretion of arsenic. This indicates that excretion of arsenic which normally is mainly renal is shifted towards faecal excretion by the dithiols.     

Effect of dental materials on gluconeogenesis in rat kidney tubules

The effect of dental composite components triethyleneglycoldimethacrylate (TEGDMA) and hydroxyethylmethacrylate (HEMA) as well as mercuric chloride (HgCl₂) and methylmercury chloride (MeHgCl) on gluconeogenesis was investigated in isolated rat kidney tubules. From starved rats kidney tubules were prepared and isolated by digestion with collagenase. Every 10 min up to 60 min 1-ml samples were drawn from the cell suspension for quantitating the glucose content. Glucose formation in controls was 3.3 ± 0.2 nmol/mg · per min (mean ± SEM, n=21). Relative rates of glucose formation were obtained by expressing individual rates as a percentage of the corresponding control. X–Y concentration curves (effective concentration, EC) of the substances were calculated by fitting a four-parametric sigmoid function to the relative rates of glucose formation at various test concentrations. At the end of the incubation period cell viability was assessed by trypan blue exclusion. Cell viability decreased within the 60 min interval from 90 to approx. 80% (controls), <25 (HEMA), <20 (TEGDMA), <10 (MeHgCl), and <10% (HgCl₂). Values of 50% effective concentration (EC₅₀) were calculated from fitted curves. EC₅₀ values were (mmol; mean ± SEM; n=4): HEMA, 17.7 ± 2.9; TEGDMA, 1.8 ± 0.2; MeHgCl, 0.018 ± 0.0005; and HgCl₂, 0.0016 ± 0.0005. The toxic effect of HgCl₂ was ∼1000 or 10 000 higher than that of the dental composite components TEGDMA or HEMA, respectively. Received: 7 April 1999 / Accepted: 25 June 1999     

Lack of effectiveness of D-penicillamine in experimental arsenic poisoning

Based on some anecdotal case reports D-penicillamine (DPA) has been advocated for the treatment of arsenic poisoning. Experimental evidence, however, supporting that recommendation is lacking. In the present experiments the effectiveness of DPA was compared with dimercaprol (British Antilewisite, BAL), dimercaptopropanesulfonate (DMPS), and dimercaptosuccinic acid (DMSA) using different controlled experimental settings. In one study mice received As2O3 (9-14 mg/kg sc). Treatment with DMSA after 30 min afforded almost complete protection against the lethal effects of arsenic whereas DPA was not effective. In a second study, mice and guinea pigs were injected sc with 8.4 mg/kg As2O3 (containing a tracer dose of 74As). Thirty min later 0.7 mmol/kg of DPA or one of the other antidotes was injected ip. As determined 4 and 12 h after the arsenic injection, DPA was unable to reduce the 74As content in any of the organs investigated (blood, liver, kidneys, lungs, heart, brain, testes, spleen, skeletal muscle, and skin). On the other hand, BAL, DMPS, and DMSA markedly reduced the tissue content of 74As with respect to controls. Finally, the ability of the antidotes to reverse biochemical effects of arsenic was investigated in vitro using suspensions of incubated renal tubulus cells. The marked inhibition of gluconeogenesis induced by 30 mumol/L As2O3 was almost completely reversed upon addition of 90 mumol of either BAL, DMPS, or DMSA. In this experimental model, too, DPA was ineffective. It was concluded that the use of DPA in arsenic poisoning needs to be reevaluated.     

Efficacy of various dithiol compounds in acute As2O3 poisoning in mice

The efficacy ofdl-dimercaptopropanol (British Anti-Lewisite, BAL),dl-dimercaptopropanesulfonate (DMPS), and meso-dimercaptosuccinic acid (DMS A) was compared in reducing the acute As₂O₃ toxicity in mice. Mice were treated with a single equimolar dose of a dithiol compound (0.7 mmol/kg i.p.) 0.5 or 30 min after the s.c. injection of various doses of As₂O₃. Both DMPS and DMSA were significantly (p<0.05) more effective in mice treated 0.5 min after the poisoning if compared to BAL on an equimolar level. The highest potency ratio (PR) (LD50 with treatment/LD5o without treatment) was found in animals injected with DMSA (PR=8.6). The corresponding value for DMPS was 4.2, and for BAL 2.1, respectively. In animals treated 30 min after poisoning the efficacy of DMPS (PR = 2.6) was similar to the efficacy of DMSA 2.4, both being only slightly superior to BAL 2.O. DMPS and DMSA were found to be much less toxic than BAL. The LD₅₀ of arsenic was 0.057 mmol/kg. The efficacy of BAL, DMPS, and DMSA in reducing the tissue content of arsenic following acute As₂O₃ poisoning was investigated in mice (n=6/group) and guinea pigs (n=3-4/group). The animals were injected s.c. with 0.043 mmol/kg As₂O₃ (containing a tracer dose of⁷⁴As(III)). Thirty minutes later the antidotes were administered A were more effective in reducing the arsenic content of tissues than BAL. Moreover, BAL caused accumulation of the toxicant in the brain. It is concluded that the recommendation of BAL as drug of choice in acute arsenic poisoning needs to be carefully re-evaluated.     

Analysis of two new leukemia-associated antigens detected on human T- cell acute lymphoblastic leukemia using monoclonal antibodies

Two monoclonal antibodies (anti-3-3 and anti-3-40) were produced, which identify two new leukemia-associated antigens. Both antibodies reacted with most cell lines derived from patients with T lymphoblastic leukemia (T-ALL), but were not detected on suspensions of normal hematopoietic cells (including thymocytes) by cytotoxicity, absorption, or indirect immunofluorescence assays. Analysis of fresh leukemic cells indicated that anti-3-3 only reacted with T-ALL cells, while anti-3-40 also reacted with some non-T, non-B ALL cells and a few acute myelocytic leukemia (AML) cells. The 3-40 antigen was also found histopathologically in frozen sections of several normal tissues, including the epithelial cells and a few lymphoid cells of the thymus, and some malignant tissues. The 3-3 antigen was not found in any tissue studied. A "double absorption"assay provided additional serologic evidence that the two antibodies identify different antigenic determinants. Biochemical analysis indicated that the molecules immunoprecipitated by anti-3-3 and anti-3-40 have molecular weights of 35,000-40,000 daltons. This study demonstrated that the 3-3 and 3-40 antigens are markers for human T-ALL and can be used along with the normal T-lymphocyte antigen, 3A1, to discriminate T-ALL from cutaneous T-cell lymphoma (CTCL), adult T-cell leukemia (ATL), and T-cell chronic lymphocytic leukemia (T-CLL).     

Effects of starvation and plasma exchange on lecithin: Cholesterol acyltransferase activity and cholesterol efflux in cholesterol-fed pigs

The effects of starvation and of plasma exchange with a cholesterol-free substitute on efflux of tissue cholesterol and on lecithin: cholesterol acyltransferase (LCAT) activity in plasma and peripheral lymph were investigated in two pigs fed a cholesterol diet for 3-4 months. The pigs were labelled with i.v. [14C]cholesterol before plasma exchange or starvation. The cholesterol diet increased plasma total cholesterol concentration and LCAT activity in plasma and lymph, but had little effect on the rate of esterification of cholesterol in plasma or lymph. During cholesterol feeding, and when the animals were fed a normal diet, cholesterol esterification rates in plasma and lymph were much lower than the maximum rates achieved when LCAT was saturated with substrate, suggesting that LCAT in normal pig plasma and lymph is not saturated with substrate. Plasma exchange, carried out when the specific activity of tissue cholesterol exceeded that of plasma cholesterol, was followed by a brief rise in the specific activity of plasma cholesterol to a maximum value between the specific activities of muscle and adipose-tissue cholesterol, reflecting the transfer of radioactive cholesterol from tissue to plasma. During the rise in plasma total cholesterol specific activity there were no differences between the specific activities of low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol in plasma or lymph. Starvation had no effect on the plasma-cholesterol specific-activity curve. From about day 14 after labelling, cholesterol-specific activity decreased in the order: tissues greater than lymph greater than plasma. This suggests that the transfer of cholesterol from tissues to plasma was mediated by lipoproteins in the interstitial fluid.