The epidemiology of dental caries in relation to environmental trace elements

This paper reviews the influence of the geochemical environment on the epidemiology of human dental caries. The best documented association is that between water borne fluoride and reduced caries prevalence. The influence of fluoride was first reported during the early decades of this century in Colorado, USA, and led to the fluoridation of some public water supplies in several countries. In all cases, fluoridation has been followed by significant improvements in dental health and no adverse effects in general health. Other trace elements in food and water have now been linked with dental caries. Molybdenum has been associated with reduced caries prevalence whereas selenium and lead appear to have adverse effects. Cavity formation in teeth probably involves a localised dissolution of the enamel surface by the products of bacterial activity. It is possible that the incorporation of trace metals into the apatite microcrystals of enamel may alter their physical properties, especially solubility, and hence their susceptibility to degradation.     

Distribution of metals in annual rings of the beech (Fagus sylvatica) as an expression of environmental changes

Summary Annual rings of 140–160-year-old beeches (Fagus sylvatica) from St. Ingbert, Saarland (FRG) were prepared and analyzed for 14 metals by atomic absorption spectroscopy. According to the chronological variations of their concentrations, the elements could be divided into three groups: 1) Metals without any tendency for chronological changes. This was established for Na, K, Cu, Cr, Co, Ni, Pb, and Cd. 2) Metals with a recent decrease of their concentrations, appropriate for Ca, Mg, Mn, and Zn. 3) Metals with a recent tendency to increase, e.g. Fe and Al. These variations are discussed in connection with the industrial history of the Saarland region and the influence of acid immissions which may alter the soil and thereby the trace element metabolism of the trees with consequences for the vitality of the plants.     

The in vitro antiapoptotic effect of dehydroepiandrosterone sulfate in mouse thymocytes and its relation to caspase-3/caspase-6

The effects of dehydroepiandrosterone sulfate (DHEAS) on thymocyte apoptosis induced by dexamethasone (DEX) were investigated. Apoptosis was measured by using agarose gel electrophoresis of DNA, the terminal deoxynucleotidyltransferase (TdT)- mediated dUTP nick end labeling (TUNEL) assay and flow cytometry. Our results showed that preincubation with 1×10⁻⁴ M DHEAS protected thymocytes from DEX-induced apoptosis in vitro. Moreover, we found no blocking effect on the DEX-induced activation of caspase-3 and caspase-6 by the preincubation of thymocytes with DHEAS. This may be interpreted to mean that the antagonism of DHEAS to DEX-induced apoptosis is not related to the activation of these downstream caspases which play a critical role in the execution of apoptosis. Received 25 June 1999; received after revision 1 September 1999; accepted 13 September 1999     

从博弈论谈南水北调西线工程的四川对策

南水北调西线工程,从博弈论的角度考虑,属于非零和博弈,各方效益的和大于零,从而具有南北两利的可能.四川的最佳策略,应根据西北的优势策略和中央的决策而选择,应坚持有偿调水,有偿调水可以实现南水北调博弈的纳什均衡.在西线工程中,应将调水藏区的可持续发展和民族区域的稳定作为四川的重点战略选择,借机推动藏区社会经济的跨越式发展.