Role Of Aluminum Research Articles

Effects of Acute Exposure to Aluminum on Cognition in Humans

There is epidemiological evidence suggesting an association between aluminum in drinking water and Alzheimer's disease (AD), and between aluminum in dialysate and dialysis dementia. The exact role of aluminum in the pathogenesis of these and other dementias is not clear. This study examined the acute effects of aluminum on cognitive function in patients with AD and related dementias and in age-matched and younger volunteers with normal cognitive function. Whether individuals with AD and/or the APOE ϵ4 genotype had enhanced gastrointestinal absorption of aluminum was tested, and whether individuals with elevated blood aluminum concentrations exhibited acute cognitive effects was determined. Subjects were randomized to receive a single dose of aluminum orally (Amphojel plus citrate) for 3 d followed by a 3-wk washout, and then 3 d ofmatched placebo administration, or vice versa. Serum aluminum levels were measured and the daily dose of Amphojel was adjusted to a target aluminum level between 50 and 150 μg/L. Neuropsychological tests were administered at baseline and 90 min after the third dose of Amphojel or placebo. There was a large interindividual variation in aluminum serum levels in all study groups after the same initial dose of Amphojel. There were no significant differences in neuropsychological test scores after aluminum ingestion in normal volunteers or in patients with cognitive impairment. There was no association between APOE ϵ4 genotype and aluminum absorption. The results did not support the hypothesis that aluminum ingested at these doses produces acute effects on cognition or adverse effects, nor did they reveal that AD patients are more vulnerable to such outcomes. Further inquiry is required to explore any possible association between aluminum and cognition, but controlled trials may be limited by safety concerns.

Thulium environment in a silica doped optical fibre

Thulium-doped optical fibre amplifiers (TDFA) are developed to extend the optical telecommunication wavelength division multiplexing (WDM) bandwidth in the so-called S-band (1460–1530nm). The radiative transition at 1.47μm (3H4→3F4) competes with a non-radiative multi-phonon de-excitation (3H4→3H5). The quantum efficiency of the transition of interest is then highly affected by the phonon energy (Ep) of the material. For reliability reasons, oxide glasses are preferred but suffer from high phonon energy. In the case of silica glass, Ep is around 1100cm−1 and quantum efficiency is as low as 2%. To improve it, phonon energy in the thulium environment must be lowered. For that reason, aluminium is added and we explore three different core compositions: pure silica, and silica slightly modified with germanium or phosphorus. The role of aluminium is studied through fluorescence decay curves, fitted according to the continuous function decay analysis. From this analysis, modification of the thulium local environment due to aluminium is evidenced.

The role of aluminium and silicon in the setting chemistry of glass ionomer cements

A model of the setting chemistry of glass-ionomer cements (GICs) is proposed based on 27Al and 29Si solid state nuclear magnetic resonance spectroscopy data on three GICs. All the precursor glasses are found to contain three aluminium species viz.: four, five and six-coordinate aluminium environments as well as four-bridging silicate tetrahedra. Upon cement formation, Al3+ ions in the glass are leached out from the surface layer of the glass. On entering the cement matrix, these ions adopt six-coordination and crosslink the polymer chains as part of the setting reaction. The remaining four-coordinate aluminium is distributed between two species: one in the inert core of the glass particles; and a second, less concentrated, in the surface layer of the glass particles, modified by the curing reactions. There is some evidence for residual five and six coordinate aluminium species in the final cement in some of the systems. In the case of the silicate tetrahedra, the curing reactions result in a decrease in the number of aluminium atoms in the second coordination sphere, with a subsequent recondensation of silicate network of the glass.

Further evidence of centrophenoxine mediated protection in aluminium exposed rats by biochemical and light microscopy analysis

The environmental agent aluminium has been intensively investigated in the initiation and progression of various neurological disorders and the role of oxidative stress in these disorders is a widely discussed phenomenon. In this light, the present study is focused on the role of aluminium in mediating oxidative stress, which may help in better understanding its role in neuronal degeneration. Further, we have exploited a known anti-aging drug centrophenoxine to explore its potential in the conditions of metal induced oxidative damage. Aluminium was administered orally at a dose level of 100 mg/kg b.wt./day for a period of 6 weeks followed by a post treatment of centrophenoxine at a dose level of 100 mg/kg b.wt./day for another 6 weeks. Following aluminium exposure, a significant increase in lipid peroxidation levels (estimated by MDA) were observed which was accompanied by a decrease in reduced glutathione content in both cerebrum and cerebellum of rat brain. Post treatment of centrophenoxine significantly reduced the lipid peroxidation levels and also increased the reduced glutathione content in both the regions. Histologically observed marked deteriorations in the organization of various cellular layers in both cerebrum and cerebellum were observed after aluminium administration. Centrophenoxine treated animals showed an appreciable improvement in the histoarchitecture of the cellular layers. Our results indicate that centrophenoxine has an antioxidant potential and should be examined further in aluminium toxic conditions.

The role of aluminum in slow sand filtration

Engineering enhancement of slow sand filtration has been an enigma in large part because the mechanisms responsible for particle removal have not been well characterized. The presumed role of biological processes in the filter ripening process nearly precluded the possibility of enhancing filter performance since interventions to enhance biological activity would have required decreasing the quality of the influent water. In previous work, we documented that an acid soluble polymer controls filter performance. The new understanding that particle removal is controlled in large part by physical chemical mechanisms has expanded the possibilities of engineering slow sand filter performance. Herein, we explore the role of naturally occurring aluminum as a ripening agent for slow sand filters and the possibility of using a low dose of alum to improve filter performance or to ripen slow sand filters.

Role of aluminum in hot-rolled ultra-low-carbon Nb-interstitial-free steels

The role of aluminum was investigated in the hot-rolled ultra-low-carbon Nb-interstitial-free (IF) steels containing aluminum ranging from 0.055 to 0.16 wt pct. As aluminum content increased, the yield and tensile strengths decreased and the elongation increased. The softening effect of the aluminum is related to the decrease in the fine NbC precipitates and increase in the coarse AIN precipitates, resulting in the coarse and uniform equiaxed grain structures.

The role of aluminum and copper on neuroinflammation and Alzheimer's disease

Metals such as aluminum (Al), copper (Cu), zinc and iron have been implicated in the pathogenesis of Alzheimer's disease (AD). Because trace amounts of metals are present in the drinking water, there is a possibility for low-dose chronic exposure. Since the presence of Al and Cu in drinking water has been shown to adversely affect the progression of AD, these two metals may aggravate some of the events associated with the disease process. The main focus of this review will be on the effects of Al and Cu in initiating or propagating an inflammatory response within the aging brain. Since inflammatory events are reported to be upregulated in the AD brain, this may be one of the mechanisms by which the metals potentiate neurodegeneration.

The Role of Aluminum in Bacterial‐induced Colitis in Young IL‐10‐deficient Mice

The Role of Aluminum in Bacterial‐induced Colitis in Young IL‐10‐deficient Mice

Supplementation of the diet with silicic acid to reduce body burden of aluminum: A miracle cure or useless treatment for Alzheimer's disease?

The study reported in this present issue of the Journal of Alzheimer’s Disease [4] from the research group headed by Dr. Exley, resurrects a decades-long debate as to a possible role of aluminum in neurodegenerative disorders, particularly Alzheimer’s disease. Perhaps the perception that aluminum is not a health hazard stems from the fact that it is only in the fairly recent past that applications of aluminum in society have been introduced. There was no “aluminum age” in antiquity as there was an iron age or bronze age. Since aluminum is the most common metal in the Earth’s crust and the third most common element after silicon and oxygen, it is has not been a trivial matter to assess whether exposure to aluminum is detrimental to health since it is so abundant in the environment. Aluminum is highly prevalent in the earth’s crust but is complexed so that the bioavailability of its toxic species is limited.

Neurofilament phosphorylation and disruption: A possible mechanism of chronic aluminium toxicity in Wistar rats

The present study was designed to investigate the possible effects of chronic aluminium exposure on neurofilament phosphorylation and its subsequent disruption in various regions of the rat brain. An intra-gastric dose of aluminium (10 mg/kg bw for 12 weeks) resulted in a marked enhancement of Ca 2+/CaM dependent protein kinase activity as compared to cAMP dependent protein kinase. The levels of phosphoprotein phosphatase were found to be significantly depleted only in the cerebral cortex. After in vitro phosphorylation using [ 32γ-P] ATP, various proteins were resolved on one-dimensional 8% SDS-PAGE, stained with Coomassie Blue and autoradiographed. The amount of 32P-incorporated was quantified using ADOPE PHOTOSHOP (7.0). The 200 kDa neurofilament protein was identified using immunoblotting. Finally, the extent of phosphorylation induced neurofilamentous damage was assessed using immunocytochemical studies. The cytoskeletal proteins were found to be aggregated and disrupted in all the three neuronal regions following 12 weeks of aluminium treatment. This study lends further support to the possible role of aluminium as a potent neurotoxic agent and in the etiopathogenisis of various neurodegenerative diseases.

Aluminium Mediated Oxidative Stress : Possible Relationship to Cognitive Impairment of Alzheimer's Type

Aluminum (Al) is a trivalent cation that does not undergo redox change and it may cause a variety of neurological disorders. In this review, we discuss evidence for a significant role of aluminum in Alzheimer's disease (AD). Al has been implicated as a potential risk factor in AD and for elderly cognitive impairment by epidemiological studies of drinking water, food, medicine as well as natural resources. Neurotoxicity from excess brain exposure to aluminum is documented from both clinical observations and animal experiments. The pathology of Alzheimer's disease is related to the alteration in neurotransmission, beta amyloid production, plaques formation and cytoskeletal abnormalities. The exact mechanism of Al toxicity is still unclear; however accumulating evidences suggested that Al could potentiate oxidative and inflammatory events leading to tissue damage. In conclusion it is proposed that a combination of anticholinergic drugs and micronutrients including antioxidants may be more effective than the individual agents in prevention and treatment of Alzheimer's disease. doi: 10.5214/ans.0972.7531.2006.130104

Irreversible Adsorption of an Aztec Dye on Fractal Surfaces

Carminic acid was adsorbed into amorphous silicas prepared by the sol−gel process. While cromophore is gradually released in silica when put in contact with water, irreversible adsorption takes place when silica is doped with aluminum. The role of aluminum on effective retention of carminic acid by aluminic silicas is described. A fractal geometry approach was employed to describe changes in silica samples when they are doped with aluminum and when chromophore is incorporated. Inclusion of chromophore provokes aggregates to form interconnected fractal surfaces.

Mechanism of Hierarchical Porosity Development in MFI Zeolites by Desilication: The Role of Aluminium as a Pore‐Directing Agent

The role of the concentration and the nature of aluminium in the creation of hierarchical porosity in both commercial and synthesized MFI zeolites have been investigated through controlled mesoporosity development by desilication in alkaline medium. Framework aluminium controls the process of framework silicon extraction and makes desilication selective towards intracrystalline mesopore formation. An optimal molar Si/Al ratio in the range 25-50 has been identified; this leads to an optimal mesoporosity centred around 10 nm and mesopore surface areas of up to 235 m(2) g(-1) while preserving the intrinsic crystalline and acidic properties. At lower framework Si/Al ratios the relatively high Al content inhibits Si extraction and hardly any mesopores are created, while in highly siliceous ZSM-5 unselective extraction of framework Si induces formation of large pores. The existence of framework Al sites in different T positions that are more or less susceptible to the alkaline treatment, and the occurrence of re-alumination, are tentative explanations for the remarkable behaviour of Al in the desilication process. The presence of substantial extra framework Al, obtained by steam treatment, inhibits Si extraction and related mesopore formation; this is attributed to re-alumination of the extraframework Al species during the alkaline treatment. Removal of extraframework Al species by mild oxalic acid treatment restores susceptibility to desilication, which is accompanied by formation of larger mesopores due to the enhanced Si/Al ratio in the acid-treated zeolite.

The role of aluminium and titanium in the point defects of gamma irradiated natural quartz

In this work, the origin of the smoky colour acquired by quartz when exposed to extremely high doses (20 kGy) of ionising radiation is studied. Five paramagnetic centres were detected in the electron paramagnetic resonance (EPR) spectrum of irradiated quartz: [AlO4]0, [TiO4–/Li+]0A, [GeO4–/Na+]0A, [GeO4–/Li+]0C, and E′1. Optical absorption revealed a complex spectrum with superposition of bands. With the technique of thermoluminescence, at least three peaks at around 180, 260 and 320 °C were detected. The peak at around 180 ºC has maximum emission at 470 nm and the peaks at around 260 and 320 °C have maximum emissions at 450 nm. Through correlations between the obtained results with these techniques, it was possible to confirm previous results from the literature, i.e., that the smoky colour of quartz is strongly related to the centre [AlO4]0. Besides, it was verified an excellent correlation between the thermal decay of [AlO4]0 and [TiO4–/Li+]0A, suggesting that at a temperature around 200 ºC the Li leaves the Ti centre and recombines with the aluminium centre destroying the smoky colour of irradiated quartz. On the other hand and differently from the literature this process does not correlate to any of the thermoluminescence peaks. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Vaccine adjuvants: current state and future trends.

The problem with pure recombinant or synthetic antigens used in modern day vaccines is that they are generally far less immunogenic than older style live or killed whole organism vaccines. This has created a major need for improved and more powerful adjuvants for use in these vaccines. With few exceptions, alum remains the sole adjuvant approved for human use in the majority of countries worldwide. Although alum is able to induce a good antibody (Th2) response, it has little capacity to stimulate cellular (Th1) immune responses which are so important for protection against many pathogens. In addition, alum has the potential to cause severe local and systemic side-effects including sterile abscesses, eosinophilia and myofascitis, although fortunately most of the more serious side-effects are relatively rare. There is also community concern regarding the possible role of aluminium in neurodegenerative diseases such as Alzheimer's disease. Consequently, there is a major unmet need for safer and more effective adjuvants suitable for human use. In particular, there is demand for safe and non-toxic adjuvants able to stimulate cellular (Th1) immunity. Other needs in light of new vaccine technologies are adjuvants suitable for use with mucosally-delivered vaccines, DNA vaccines, cancer and autoimmunity vaccines. Each of these areas are highly specialized with their own unique needs in respect of suitable adjuvant technology. This paper reviews the state of the art in the adjuvant field, explores future directions of adjuvant development and finally examines some of the impediments and barriers to development and registration of new human adjuvants.

On the role of aluminum in the selective oxidation of benzene to phenol by nitrous oxide over iron-containing MFI zeolites: an in situ Fe XANES study

In situ Fe K-edge XANES experiments point to a distinct difference in reducibility of iron in Fe-silicalite (without aluminum) and FeZSM-5 (with aluminum) upon dehydration. Whereas a noticeable part of Fe 3+ is reduced to ferrous ions in the iron-containing aluminosilicalite, the ferric species in the ferrosilicalite maintain their oxidation state. The ability to selectively oxidize benzene to phenol with nitrous oxide in ferroaluminosilicalite relates to these Fe 2+ centers. It is proposed that the large difference in reactivity between ferroaluminosilicalite and ferrosilicalite is due to the chemical difference of iron in Fe O Al and Fe O Fe adducts. A new preparation method is introduced which leads to more selective and stable catalysts.

Investigations on the selective oxidation of benzonitrile using nitrous oxide catalyzed by modified ZSM-5 zeolites

The direct oxidation of benzonitrile to hydroxybenzonitriles using nitrous oxide as oxidant has been studied on ZSM-5 type zeolites as catalyst. The influence of catalyst properties as well as of reaction conditions on the conversion and on the selectivity of the reaction has been investigated systematically. It has been found that catalysts prepared without addition of iron gives up to 73% selectivity to hydroxybenzonitriles at a benzonitrile conversion of 10%. The three isomers of hydroxybenzonitrile have been found with an o: m: p ratio of 1:6:3. At higher reaction temperatures a higher benzonitrile conversion of up to 22% has been obtained, and the decomposition of nitrous oxide is increased. An excess of nitrous oxide is beneficial for higher conversions. However, with increasing conversion the selectivity to hydroxybenzonitriles is decreased. The role of aluminum and iron in the ZSM-5 zeolite has been investigated. The initial activity of the catalyst is increased by decreasing the Si/Al ratio. The lower the amount of Al, generating acid sites, the higher the selectivity to hydroxybenzonitriles. The catalyst activity is increased by addition of iron, but the higher activity results in a strong loss of selectivity caused by stronger total oxidation and a more rapid deactivation of the catalyst. Moreover, it seems possible that both components, aluminum and iron, are responsible for the catalytic activity of the zeolite. A reaction network for selective benzonitrile oxidation has been developed which includes the oxidation to hydroxybenzonitrile as well as competitive and consecutive reaction steps.

Pulsed laser-ablated MoS 2-Al films: friction and wear in humid conditions

The application of MoS 2 as a solid lubricant in dry conditions is well established, but the presence of humidity degrades the tribological behavior of MoS 2 films. There has been much progress toward increasing the efficiency of MoS 2 films in humid environments by using various additives. In our work, aluminum is evaluated as an additive because of its affinity for O 2 and (OH) compared to Mo and its potential to modify transfer film formation. The MoS 2 films examined here were deposited on 440C steel substrates by laser ablation along with simultaneous magnetron sputtering of Al. The friction and wear studies were made on a ball on disc tribometer. Films containing Al outperformed pure MoS 2. Under optimal conditions, 1–2-μm-thick films with ∼8% aluminum had a wear life of 150 to 250 K cycles in 25% humidity. Micro-Raman and X-ray photoelectron spectroscopy (XPS) were used to analyze chemistry and scanning electron microscopy (SEM) was used to study the morphology and film cross-section. Nanoindentation showed that Al addition did not increase film hardness. The role of aluminum in increasing the wear life of laser-ablated MoS 2 films in humid conditions is discussed. The mechanism controlling the increased wear life is partially explained by showing that Al is gradually turned into alumina, creating an adhesive and lubricating mix of wear debris under tribostress in humid surroundings.

Formation of Colloidal Silica and Alumina During Experimental Granodiorite Weathering

The role of aluminum and silica in the formation of colloids during granodiorite weathering was studied on the basis of long-term experiments in batch reactors. Rock samples were dissolved in un-buffered solutions of initial pH ∼ 3.2, 5.4, and 9.9 at ambient conditions for 500 days. During weathering, extremely high supersaturation with respect to various secondary solids was attained in the solutions. Consequently, new solids, part of which was conserved in solutions as colloids, condensed. The mean concentrations of colloidal Si reached values of 70, 50, and 48 μmol 1−1 in the alkaline, neutral, and acid solutions, respectively. The mean concentrations of colloidal Al, reached values of 34, 22, and 12 μmol 1−1 in the alkaline, neutral, and acid solutions, respectively. The concentration of colloids gradually decreased after 200-400 days of experiment. This phenomenon was interpreted as being due to the competition between homogeneous nucleation and crystal growth. At the initial stages of the experiments, the colloidal species (predominantly colloidal Al) comprised a large proportion of the total amounts of aqueous species. Their share, however, decreased with time. The molar Al/Si-ratios of colloids were as high as 2–2.5 at the early stages of the experiment. After 250–300 days of experiments, on the other hand, these ratios decreased to values of about 0.5 in both the neutral and alkaline solutions and to a value of 0.15 in the acid solution. The evolution of colloids was consistent with the evolution of secondary solids in the sequence Al-hydroxides – clay minerals (illite, chlorite), in both the neutral and alkaline solutions. In acid solutions, the evolution of Al/Si-colloids was influenced by the presence of sulfate ion and Al-sulfate precipitation. Besides Al and Si, other elements, in particular Ca or Mg as a major component and Na, K, P, S, and Cl as minor components, readily participated in the formation of colloids.

Parenteral nutrition-associated cholestasis in neonates: the role of aluminum.

Parenteral nutrition (PN) is an essential component in the care of premature and ill infants. The incidence of parenteral nutrition-associated cholestasis (PNAC) ranges from 7.4 to 84%. One substance in PN solutions that has been implicated in PNAC is aluminum. Aluminum loading in animals and humans causes hepatic accumulation and damage. The degree of aluminum contamination of PN solutions has decreased over time, but contamination still significantly exceeds levels that are safe for human neonates. Further study into the relationship between aluminum contamination in neonatal PN solutions and the development of PNAC is necessary.