五种常用口腔修复材料对细菌滞留影响的临床研究

目的:评价不同修复材料对牙周组织的潜在危害.方法:采用临床实验的方法观察了5种常用口腔修复材料在体内戴用2个月后的细菌粘附量及其种类.结果:(1)树脂粘附的微生物最多,其次为钴铬合金和镍铬合金,纯钛和Ⅲ型金合金最少;(2)G-杆菌在树脂组明显多于钴铬合金和镍铬合金组,在纯钛和Ⅲ型金合金上粘附最少.对于G-球菌,树脂组明显多于钴铬合金、镍铬合金和纯钛组,Ⅲ型金合金组最少.白色念珠菌在树脂组有少量粘附,但在4种牙科金属上粘附量极少.结论:从对牙周组织的危害程度看,纯钛和Ⅲ型金合金应为临床医生的首选材料,其次为钴铬合金和镍铬合金.     

In vivo chromium-enhanced MRI of the retina

Chromium (Cr) has been used histologically to stabilize lipid fractions in the retina and is suggested to enhance oxidizable lipids in brain MRI. This study explored the feasibility, sensitivity, and specificity of in vivo chromium‐enhanced MRI of retinal lipids by determining its spatiotemporal profiles and toxic effect after intravitreal Cr(VI) injection to normal adult rats. One day after 3 μL Cr(VI) administration at 1–100 mM, the retina exhibited a dose‐dependent increase in T₁‐weighted hyperintensity until 50 mM. Time‐dependently, significant T₁‐weighted hyperintensity persisted up to 2 weeks after 10 mM Cr(VI) administration. Three‐dimensional chromium‐enhanced MRI of ex vivo normal eyes at isotropic 50‐μm resolution showed at least five alternating bands across retinal layers, with the outermost layer being the brightest. This agreed with histology indicating alternating lipid contents with the highest level in the photoreceptor layer of the outer retina. Although Cr(VI) reduction may induce oxidative stress and depolymerize microtubules, manganese‐enhanced MRI after chromium‐enhanced MRI showed a dose‐dependent effect of Cr toxicity on manganese uptake and axonal transport along the visual pathway. These results potentiated future longitudinal chromium‐enhanced MRI studies on retinal lipid metabolism upon further optimization of Cr doses with visual cell viability. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

The Microstructure and Pitting Corrosion Behavior of K-TIG Welded Joints of the UNS S32101 Duplex Stainless Steel

In this paper, the microstructure and pitting corrosion resistance of {"type":"entrez-protein","attrs":{"text":"S32101","term_id":"422005","term_text":"pir||S32101"}}S32101 duplex stainless steel keyhole tungsten inert gas welded joints with different heat inputs were studied. The electrochemical experiments were conducted in a 1 mol/L NaCl solution at room temperature. The pitting rupture potential of the heat affected zone and the weld metal zone under different heat inputs were tested. The research showed that with the increase of heat inputs, more ferrite was converted to austenite and the number and size of intragranular austenite grains in the weld metal zone increased. The austenite content of the heat affected zone and the weld metal zone increase with the increase of heat inputs, and the CrN and Cr₂N in the heat affected zone and the weld metal zone were mainly precipitated in the ferrite, in the austenite and ferrite/austenite interfaces. The pitting rupture potential value of the heat affected zone and the weld metal zone were increased with the increase of heat inputs, and the pitting corrosion resistance of the heat affected zone and weld metal zone were also increased with the increase of heat inputs. The relationship between the position CrN and Cr₂N, the austenite content and the pitting corrosion resistance were elucidated, and the initiation mechanism of the pitting was investigated. Additionally, in this work, the heat affected zone and weld metal zone made at 2.46 kJ/mm heat inputs had the best pitting corrosion resistance. The research results provided useful information for improving the pitting corrosion resistance of {"type":"entrez-protein","attrs":{"text":"S32101","term_id":"422005","term_text":"pir||S32101"}}S32101 duplex stainless steel keyhole tungsten inert gas welded joints.     

Effect of chromium supplementation on hair chromium concentration and diabetic status

Thirty-nine diabetic and 39 non-diabetic subjects matched for age and sex were given torula yeast (placebo) or brewer's yeast (68 μg chromium/day) in a double blind experiment. Hair chromium concentration was determined on all subjects before and after the 90 day yeast supplementation period. An overnight fasting blood sample was drawn from all diabetic subjects before and after yeast supplementation. The blood was analyzed for glycosylated hemoglobin and for serum glucose, insulin, total cholesterol, HDL cholesterol, and triglycerides. Mean initial hair chromium concentration of the non-diabetic subjects was 383±75 ppb, which was greater than that of the diabetic subjects (317±74 ppb) (p<0.001). Hair chromium concentration increased 111±78 ppb in subjects who received high chromium yeast compared with 17±80 ppb in those who received the placebo (p<0.001). The amount of increase in hair chromium concentration was similar between non-diabetic and diabetic subjects who received the high chromium yeast (p<0.05). No significant effect of chromium supplementation occurred in diabetic subjects as measured by any of the blood parameters (p>0.05).     

微量元素铬镉与白内障

用20Gy~(60)Coγ射线一次性照射新西兰幼兔双眼,复制电离辐射白内障动物模型。于辐射前1天及辐射后1、7、21及77天动态观察血清,晶体、房水及虹膜睫状体中铬、镉含量的变化。发现除辐射后早期晶体、房水及虹膜睫状体中铬增加外,其余各期血清、晶体、房水及虹膜睫状体中铬和镉含量均降低,与白内障形成呈负相关。提示微量元素铬镉在电离辐射白内障的发生机理中起一定作用。     

Detection of genotoxic effects in human gastric and nasal mucosa cells isolated from biopsy samples

To assess genotoxic burdens from chemicals, it is necessary to relate observations in experimental animals to humans. The success of this extrapolation would be increased by including data on chemical activities in human tissues. Therefore, we have developed techniques to assess DNA damage in human gastric and nasal mucosa (GM, NM) cells. Biopsy samples were obtained during gastroscopy from macroscopically healthy tissue of the stomach or from healthy nasal epithelia during surgery. The specimens were incubated for 30–45 min at 37°C with a digestive solution. We obtained 1.5–8 × 10⁶ GM cells and 5–10 × 10⁵ NM cells per donor, both with viabilities of 80–95%. The cells were incubated in vitro for 1 hr at 37°C with the test compounds added in their appropriate solvents. In GM cells, we studied N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), sodium dichromate (Na₂Cr₂O₇), nickel sulphate (NiSO₄), cadmium sulphate (CdSO₄), and lindane. In NM cells, lindane was investigated. Each compound was assessed for DNA damaging activity in cells of at least three different human donor samples using the microgel single cell assay. Similar studies were performed with GM and NM cells obtained from Sprague-Dawley rats. We have found human GM cells to be more sensitive to the genotoxic activity of MNNG than rat GM cells (low effective concentration [LEC] = 0.16 and 0.625 μg/ml for human and rat, respectively). Human cells were also more sensitive to the cytotoxic/genotoxic activity of NiSO₄ (LEC = 5 and 19 μmoles/ml for human and rat, respectively). CdSO₄ was genotoxic in human GM cells (LEC = 0.03–0.125 μmoles/ml), whereas no dose-related genotoxicity was observed in rat GM at concentrations up to 0.5 μmoles/ml. In contrast, approximately equal responses regarding genotoxicity and cytotoxicity were observed in rat and human GM for Na₂Cr₂O₇ (0.25–1 μmoles/ml). Lindane, however, was genotoxic in three out of four rat GM but not in human GM cells (0.5–1 μmoles/ml), whereas it was active in both rat and human NM cells. Together with other recently published in vivo findings, our results with lindane can be interpreted according to a parallelogram approach. In view of possible human exposure situations and the sensitivities of the two target tissues from both species, the data imply that lindane will pose a health risk to humans by inhalation but not by ingestion. © 1994 Wiley-Liss, Inc.     

Reduction of carcinogenic chromium(vi) on the skin of living rats

The reduction of chromate (Cr(VI)) on the skin of living rats was investigated using the technique of in vivo electron paramagnetic resonance (EPR) spectroscopy with a surface coil resonator. Topical application of aqueous solution of Cr(VI) on the skin of rats generated the transient species, Cr(V). Partial removal of the stratum corneum increased the rates of formation and decay of Cr(V), as well as Cr(V) signal intensity. The results demonstrate that skin represents one route for chromium to enter into animals and humans. The generation of reactive Cr(V) species in the reduction of Cr(VI) by the skin may play an important role in the mechanism of Cr(VI)-induced skin cancer. These findings indicate the potential for in vivo EPR spectroscopy for studying the metabolism of paramagnetic reactive species in chemical and biochemical reactions occurring in/on the skin of both small and large animals, and possibly humans.     

Autoradiographic study of distribution patterns of metals which occur as corrosion products from dental restorations

Abstract – Radioactive chromium, cobalt, gold and mercury, all of which may occur as corrosion products from dental restorations, were injected in single doses via the tail vein of mice and an in vivo analysis of their distribution was performed using whole-body autoradiography. Gold seemed to be inert and went mainly to the liver and bones. The other elements studied were distributed widely in the body and remained for a long period of time in specific target organs and tissues.