The unrecognized occupational relevance of the interaction between engineered nanomaterials and the gastro-intestinal tract: a consensus paper from a multidisciplinary working group

Background

There is a fundamental gap of knowledge on the health effects caused by the interaction of engineered nanomaterials (ENM) with the gastro-intestinal tract (GIT). This is partly due to the incomplete knowledge of the complex physical and chemical transformations that ENM undergo in the GIT, and partly to the widespread belief that GIT health effects of ENM are much less relevant than pulmonary effects.However, recent experimental findings, considering the role of new players in gut physiology (e.g. the microbiota), shed light on several outcomes of the interaction ENM/GIT. Along with this new information, there is growing direct and indirect evidence that not only ingested ENM, but also inhaled ENM may impact on the GIT. This fact, which may have relevant implications in occupational setting, has never been taken into consideration.This review paper summarizes the opinions and findings of a multidisciplinary team of experts, focusing on two main aspects of the issue: 1) ENM interactions within the GIT and their possible consequences, and 2) relevance of gastro-intestinal effects of inhaled ENMs. Under point 1, we analyzed how luminal gut-constituents, including mucus, may influence the adherence of ENM to cell surfaces in a size-dependent manner, and how intestinal permeability may be affected by different physico-chemical characteristics of ENM. Cytotoxic, oxidative, genotoxic and inflammatory effects on different GIT cells, as well as effects on microbiota, are also discussed.Concerning point 2, recent studies highlight the relevance of gastro-intestinal handling of inhaled ENM, showing significant excretion with feces of inhaled ENM and supporting the hypothesis that GIT should be considered an important target of extrapulmonary effects of inhaled ENM.

Conclusions

In spite of recent insights on the relevance of the GIT as a target for toxic effects of nanoparticles, there is still a major gap in knowledge regarding the impact of the direct versus indirect oral exposure. This fact probably applies also to larger particles and dictates careful consideration in workers, who carry the highest risk of exposure to particulate matter.

     

Age-related changes in glycerolipid formation in lean and obese zucker rats

Age-related changes in hepatic and adipose glycerolipid formation have been described in Zucker rats. Glycerolipid formation was measured in vitro in the presence of [¹⁴C]glycerol-3-phosphate, palmitate, ATP, CoA, and Mg²⁺ by using liver and adipose tissue homogenates derived from various age groups of animals. Hepatic glycerolipid formation increased after birth to reach a peak value at 1 day of age. This period was followed by a decline in the rates of glycerolipid formation. Hepatic glycerolipid formation increased again at the time of weaning and continued to rise up to 32 days in lean rats and 42–44 days in obese rats. Obesity in rats was recognizable at the age of 32 days and was associated with increased rates of glycerolipid formation in both liver and adipose tissue. As far as the changes in hepatic glycerolipid formation and triglyceride accumulation are concerned, obese rats showed more resemblance to 1-day-old rats than to lean animals of similar age groups. Glycerolipid formation decreased in liver and increased in adipose tissue with age in both lean and obese rats. These studies suggest that hepatic and adipose tissue glycerolipid formation is significantly influenced by age and obesity in Zucker rats.     

塔河油田4区奥陶系古地貌恢复研究

塔河油田奥陶系油藏储集空间以碳酸盐岩岩溶孔洞缝为主,古岩溶发育程度对奥陶系油气成藏有重要的控制作用。古岩溶发育受多种因素影响,其中古地貌形态是控制古岩溶发育及分布的主要因素之一。因此研究古岩溶分布规律,应先进行古地貌恢复。本文以塔河油田4区奥陶系油藏为例,总结了一套应用三维地震资料及钻井资料进行古地貌恢复的方法和技术,并恢复、描述了塔河4区奥陶系在石炭系沉积前的古地貌形态及特征。     

Salting out of elements Mg and Ca by clay in physiological gastro-intestinal mediums physicochemically simulated

Edible clays from West Africa (Sénégal, Côte d’Ivoire, Guinée) are characterized by XRD, IR, TGA and ICP. The major component is kaolinite and silica is the main impurity while illite is found in some of them. Kinetic analysis of salting out of Ca²⁺ and Mg²⁺ were studied by Ionic Chromatography in physicochemically simulated physiological mediums (SPM). Raw and heated (110 °C) materials have been studied. Cations releasing from both materials was higher for Ca²⁺ than Mg²⁺. Stomachal SPM (1 < pH < 2) is the most favourable to this behaviour. Cations exchange is the most probable process involving Na⁺ (0.102 nm) (SPM) and Ca²⁺ (0.100 nm), Mg²⁺ (0.072 nm) (Clay).     

Crystallisation processes in aluminium hydroxide gels. IV. Factors influencing the formation of the crystalline trihydroxides

The formation of crystalline aluminium trihydroxides from aqueous suspensions of pseudoboehmite, obtained by the hydrolysis of aluminium s-butoxide, has been examined by X-ray diffractometry, nitrogen adsorption and dilatometry. The results obtained have been interpreted in terms of a mechanism involving dissolution of the pseudoboehmite. For those suspensions with which the recrystallisation was followed dilatometrically, first-order kinetics were found, suggesting that random nucleation of trihydroxide crystals is involved. The rate of recrystallisation was decreased by the addition of organic solvents to the aqueous suspension and also, initially, by an increase in temperature. At the same time the proportion of gibbsite produced in admixture with bayerite was reduced and that of nordstrandite increased. It is concluded that the retardation is due, at least in part, to an increase in the crystallinity of pseudoboehmite which has been found to accompany the introduction of the organic solvents. The increased crystallinity must result in a decrease in the solubility and rate of solution of pseudoboehmite; under these conditions nordstrandite formation appears to be promoted. Neutron activation and spectroscopic analysis of hydroxide samples showed that storage of aqueous suspensions in glassware resulted in pick-up of sodium and silica at the ppm level. The changes in these levels as recrystallisation occurred suggested that retention of the products of glass dissolution was occurring in a way which depended on the surface area of the hydroxide. No variation related to the phase composition of the trihydroxide mixtures was observed.     

Studies in estolides. I. Kinetics of estolide formation and decomposition

A study has been made of the rate of formation of estolides from castor oil fatty acids and of their decomposition at different temps. Estolide formation appears to be optimum at the end of 5 hr at about 220C, beyond which estolides start decomposing, giving rise to DCO fatty acids. At about 300C, estolide decomposition is complete within an hour. During estolide formation there is a linear increase in optical rotation which again decreases linearly, although at a different rate, during estolide decomposition. At optimum estolide formation, the optical rotation is as high as 25.5. Part of the thesis submitted by S. N. Modak to the University of Bombay for the degree of Ph.D.     

Thiuram-accelerated sulfur vulcanization. I. The formation of the active sulfurating agent

Mixtures of tetramethylthiuram disulfide (TMTD)/sulfur/ZnO were heated in a DSC to various temperatures. Zinc dimethyldithiocarbamate (Zn₂(dmtc)₄ formed only in undried TMTD/ZnO mixes, the reaction being catalyzed by water on the ZnO surface. The presence of ZnO delays the decomposition of TMTD by adsorbing thiuram sulfenyl radicals, which are needed to initiate tetramethylthiuram monosulfide (TMTM) and tetramethylthiuram polysulfide (TMTP) formation. Increased amounts of TMTM are formed in mixes where ZnO is present, and TMTP are detected prior to TMTM formation. Zn₂(dmtc)₄ does not react with sulfur under conditions where labile hydrogen atoms are not available. © 1996 John Wiley & Sons, Inc.     

Sphingomyelinase and ceramidase in the intestinal tract

Sphingomyelin (SM) has emerged as an important source of lipid messengers affecting cell proliferation, differentiation and apoptosis. SM is present in mammalian cell membranes as a lipid constituent and also found as a component of dietary products such as milk, egg and meat. Digestion of SM has been found to have important implications in colon cancer development, gut maturation, and cholesterol absorption. SM in the intestine is sequentially digested by alkaline sphingomyelinase and neutral ceramidase before absorption. In the last decade, rapid progress has been made in many aspects of these two enzymes. The review intends to provide a short summary of the current knowledge on the properties, functions and the pathological changes of the enzymes in the intestinal tract.     

Electrochemical reactions of halohydrins. II. Olefins formation

2-Bromoethanol was reduced to ethylene, 1-bromo-2-propanol to propylene, and 2-bromo-l-indanol to indene on Pb or Cu electrodes with R₄N⁺ electrolytes, in DMF with and without addition of water. Material and current efficiencies were high. Hydrogen was the only by-product in all cases. It is suggested that this represents a general method for the conversion of bromohydrins to olefins.     

Interference between reactants in simultaneous interpenetrating polymer network formation. II. Influence of the presence of a free‐radical initiator on polyurethane formation

Polyether polyurethane networks were prepared in solution at 25 and 60°C, using various organotin catalysts. The presence of a free‐radical initiator [viz. azobisisobutyronitrile (AIBN)] in the reaction media has no effect on the catalytic efficiency of organotin(IV) compounds, whereas it causes severe deactivation of organotin(II) compounds. This effect was explained by the following mechanism: formation of a cyclic 1 : 1 complex by coordination of the nitrile groups of AIBN with the tin(II) atom, which both reduces the effective catalyst concentration and allows the early decomposition into radicals, as previously seen, leading to tin oxidation. The addition of a free‐radical scavenger such as 3‐tert‐butyl pyrocatechol allows the maintenance of the catalyst efficiency of organotin(II) compounds at their reference level. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1929–1937, 2002     

Chemistry of methane formation in hydrogasification of aromatics. 1. Non-substituted aromatics

The chemistry of the formation of methane in hydrogasification of such unsubstituted aromatics as benzene, naphthalene, phenanthrene, anthracene and biphenyl was studied using a flow tube. Temperatures varied between 800 and 1000 °C. Gases and benzene were analysed by on-line gas chromatography, the tar products being analysed by mass spectrometry. At short residence times up to 10 s, methane yields increase with decreasing stability of the aromatics; that is from benzene to naphthalene, phenanthrene and anthracene. As decreasing thermal stability also promotes carbon formation as a competitive reaction, the methane yields from the less reactive aromatics may exceed those of the reactive aromatics if the residence time is prolonged. In addition to thermal stability the position of the primary bond rupture is important because it determines the structure of intermediate products.