Behavioral Effects of Aluminum

Numerous mechanistic studies of aluminum neurotoxicity have been performed, but the main sites of action have not been discerned as discussed in Section 2.4.2 and by Strong et al. (1996). Additional studies could help identify a single unifying mechanism that can explain and reconcile the wide variety of pathological, neurochemical, and behavioral effects of aluminum induced by oral exposure and in various model systems (e.g., intracerebral and intracistemal administration), but these kinds of studies are unlikely to better characterize neurotoxicity NOAELs and LOAELs relevant to MRL assessment. The relationship between aluminum exposure and neurotoxicity is an active area of research. 

Bowdler NC, Beasley DS, Fritze C, et al. 1979. Behavioral effects of aluminum ingestion on animal and human subjects. Pharmacol Biochem Behav 10 509-512. 

The behavioral effects of aluminum have not been extensively studied. Crapper and Dalton described a number of behavioral changes in cats after infusion of aluminum chloride into the brain. 

Other intermediate-duration oral studies in rats evaluated effects of aluminum on brain chemistry as well as neurobehavioral performance. Rats that consumed 51 mg Al/kg/day as aluminum chloride in drinking water for 180 days had alterations in behavior (reduced spontaneous locomotor activity, impaired learning, extinction and relearning of an active avoidance task, impaired maze relearning ability) and brain chemistry (increased lipid peroxidation, decreased activity of Na+-, K+-, and Mg2+-ATPases) (Lai et al. 1993). Ingestion of 490 mg Al/kg/day as aluminum sulfate in drinking water for 4-12 weeks caused reduced retention of a learned passive avoidance task and changes in brain chemistry (e.g., increased cyclic adenosine monophosphate levels, decreased concentrations of MAP-2 and other structural... 

Domingo JL, Llorens J, Sanchez DJ, et al. 1996. Age-related effects of aluminum ingestion on brain aluminum accumulation and behavior in rats. Life Sci 58 1387-1395. 

Han B, Golub MS, Keen CL. 1997. Effects of aluminum exposure over the life span on brain and behavior of mice. Toxicologist 36 64-65. 

Misawa T, Shigeta S. 1992. Behavioral effects of repeated aluminum administration in the rat. Tokai J Exp Clin Med 17 155-159. 

Struys-Ponsar C, Kerkhofs A, Gauthier A, et al. 1997. Effects of aluminum exposure on behavioral parameters in the rat. Pharmacol Biochem Behav 56 643-648. 

Effects of aluminum in low pH solutions on aquatic biota, especially fish, and on land plants growing in acidic soil have been studied by various investigators (35-38). Although much of the work has assigned the observed toxicity to monomeric dissolved forms of Al, the behavior of polymeric species in biochemical systems is probably in need of more careful study than it has so far received. Schindler (39) in a review of the topic of environmental impacts of acid rain noted that aluminum is highly toxic to fish and quoted literature references to the effect that polymeric and colloidal aluminum hydroxide species may physically obstruct gill membranes and cause asphyxiation. The maximal pH range for this effect was reported as 5.2 to 5.4. 

Release waves for the elastic-plastic regime are dominated by the strength effect and the viscoplastic deformations. Here again, quantitative study of the release waves requires the best of measurement capability. The work of Asay et al. on release of aluminum as well as reloading, shown in Fig. 2.11, demonstrates the power of the technique. Early work by Curran [63D03] shows that limited time-resolution detectors can give a first-order description of the existence of elastic-plastic behavior on release. 

An overview of the superplastic behavior of aluminum alloys to demonstrate the grain-size effect is depicted in Fig. 1, in which the quantitative relation between the logarithm of the optimum strain rate for superplastic flow and the grain size (plotted as the logarithm of reciprocal grain size) is clearly shown [4]. The slope of the curve in Fig. 1 is noted to be about 3. 

Most commercial uses of aluminum require special properties that the pure metal cannot provide. The addition of alloying elements imparts strength, improves formability characteristics, and influences corrosion resistance properties. The general effect of several alloying elements on the corrosion behavior of aluminum has been reported by Godard et al. (2) as follows ... 

The behavior of aluminum in neutral and weakly alkaline solutions resembles the behavior of magnesium, but the negative difference effect is much less pronounced at aluminum. The steady-state potential of aluminum is approximately 1V more positive than the thermodynamic value. Yet unlike magnesium, aluminum will not passivate in strongly alkaline solutions, but undergoes fast dissolution to soluble aluminates. 

A consideration of the electrochemical behavior of the large variety of aluminum alloys used in practice surpasses by far the scope of this chapter. Nevertheless, we consider it useful to review here the effect of some elements that have a profound effect on this behavior. 

The microcalorimetry of NH3 adsorption coupled with infrared spectroscopy was used to study the effect of the synthesis medium (OH or F ) on the nature and amount of acid sites present in Al,Si-MFl zeolites [103]. Both techniques revealed that H-MFl (F ) with Si/Al < 30 contained extra-framework aluminum species. Such species were responsible for the presence of Lewis acid sites and poisoning of the Brpnsted acidity. In contrast, MFl (F ) characterized by Si/Al > 30 presented the same behavior as H-MFl (OH ). 

The rate of the second reaction is quite low as long as there is enough free sulfonyl chloride to react with additional amounts of aluminum chloride. Once this is no longer true, further additions of catalyst enormously increase the reaction rate (27). The recently discovered swamping catalyst effect in the halogenation of aromatic donor species (35) probably exhibits analogous kinetic behavior. The basic rate expression found by Olivier consisted of only one term for reaction when a relatively small amount of aluminum chloride was present ... 

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