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PubMed1986

Protection against alcohol-induced gastric mucosal injury by aluminum-containing compounds--sucralfate, antacids, and aluminum sulfate.

Previously, we demonstrated that both antacids and sucralfate can protect the gastric mucosa against alcohol injury. Since these compounds contain aluminum, we studied whether other aluminum compounds have cytoprotective properties as well. Fasted rats were pretreated intragastrically with A) 0.9% NaCl, B) sucralfate, C) aluminum-magnesium antacid gel, D) Al2(SO4)3, E) Al(OH)3, and 1 h later they received 2 ml 100% ethanol by gavage. The stomach was removed and assessed for injury 3 h after ethanol administration. Control (group A) rats had 39 +/- 3% gross mucosal injury, which was reduced to 5 +/- 1% with sucralfate, 7 +/- 1% with Al2(SO4)3, 12 +/- 2% with Al(OH)3, and 16 +/- 2% with aluminum-magnesium antacid gel pretreatment. Microscopic surface epithelial injury and submucosal edema were seen in all five groups, while deep mucosal necrosis was largely prevented by pretreatment in groups B to E. These findings indicate that aluminum in a wide variety of molecular forms can protect the gastric mucosa against alcohol injury.

Alum Compounds↗
PubMed1987

Haemophilus influenzae type b: the search for a vaccine.

In adults Hib CPS protein conjugates are much more immunogenic than the polysaccharide alone; further studies have shown that they induce a booster response in children. The antibodies produced in response to the conjugates have the same biologic properties, isotype and IgG subclass composition as those elicited by Hib CPS alone or those present in serum after convalescence from Hib disease. More recently attempts have been made to make the conjugates compatible with DTP vaccine. In this procedure DTP is absorbed onto aluminum compounds (aluminum hydroxide or phosphate), with the effect of significantly prolonging diphtheria and tetanus antibody synthesis. Adsorption of the Hib CPS conjugate under controlled conditions does not alter the total amount of antibody elicited in infant rhesus monkeys after the third or final injection. The appearance of Hib CPS antibodies after the first injection, however, is accelerated with conjugate that has been adsorbed. This is an encouraging finding, because it means that more polysaccharide conjugates can be compatible with existing DTP vaccine.

Antibodies, Bacterial↗
PubMed1990

Experimental aluminum pathology in rabbits: effects of hydrophilic and lipophilic compounds.

Aluminum lactate [Al(lact)3] (hydrophilic, hydrolytically unstable) and aluminum acetylacetonate [Al(acae)3] (lipophilic, hydrolytically stable) were tested as potential toxicants to rabbits upon IV administration both as aqueous solutions and as liposome suspensions. Both chemicals behaved as cardiotoxic agents when administered as aqueous solutions, but Al(acae)3 was at least two orders of magnitude more active than Al(lact)3. Al(acae)3, but not Al(lact)3, caused myocardial infarcts resembling those in humans (with contraction bands) at doses as low as 0.24 mg/kg body weight, as well as a prominent acanthocytosis. Al(lact)3, when administered as a liposome suspension, was about 300 times more toxic than in aqueous solution, although cardiac damage was not infarctual in character. Both chemical and physical speciation of aluminum(III) thus play an essential role in determining the toxicity of the metal.

Aluminum↗
PubMed1990

Phosphate and pepsin adsorptions by a new boehmite compound and aluminum hydroxide.

A new microcrystalline compound of aluminum oxide hydroxide (tentatively named PT-A) was synthesized in the hope of providing a better phosphate adsorbent for future clinical use than the currently marketed aluminum hydroxide gels (ALG). An X-ray diffraction study demonstrated a boehmite structure in PT-A but an amorphous structure in ALG. PT-A was more stable in pH change than ALG; in elution tests in artificial gastric and intestinal solutions, aluminum ion eluted from PT-A was maximally 10% of the amount from ALG at pH 1.2; and was undetectable at pH 6.8, at which point ALG still showed some aluminum elution. Phosphate-adsorbing efficacy of PT-A and ALG in vitro was about the same at pH 1.2; however, it was four times greater in PT-A than in ALG at pH 6.8, indicating that PT-A will be effective in the intestine. PT-A also adsorbed pepsin but the amount was at most the same or much less than that adsorbed by ALG, which depended on pH in solution.

Adsorption↗
PubMed1995

Adjuvant properties of aluminum and calcium compounds.

It is likely that aluminum compounds will continue to be used with human vaccines for many years as a result of their excellent track record of safety and adjuvanticity with a variety of antigens. For infections that can be prevented by induction of serum antibodies, aluminum adjuvants formulated under optimal conditions are the adjuvants of choice. It is important to select carefully the type of aluminum adjuvant and optimize the conditions of adsorption for every antigen since the degree of adsorption of antigens onto aluminum adjuvants markedly affects immunogenicity. The mechanism of adjuvanticity of aluminum compounds includes formation of a depot at the site of injection from which antigen is released slowly; stimulation of immune-competent cells of the body through activation of complement, induction of eosinophilia, and activation of macrophages; and efficient uptake of aluminum-adsorbed antigen particles by antigen-presenting cells because of their particulate nature and optimal size (< 10 microns). Limitations of aluminum adjuvants include local reactions, production of IgE antibodies, ineffectiveness for some antigens, and inability to elicit cell-mediated immune responses especially cytotoxic T-cell responses. Calcium phosphate, which has adjuvant properties similar to aluminum adjuvants, has the potential advantages of being a natural component of the body and of not increasing IgE production. There is a need for alternative adjuvants, particularly for diseases in which cell-mediated immune responses are important for prevention or cure.

Adjuvants, Immunologic↗
PubMed2006

A new binary compound for the production of 124I via the 124Te(p,n)124I reaction.

The binary compound, aluminum telluride (Al(2)Te(3)), was investigated as a target material for the production of (124)I by way of the (124)Te(p,n)(124)I reaction on a low-energy cyclotron. The high melting point and formation of a glassy matrix upon heating provided a stable target material at irradiations up to 20 microA of 11 MeV protons. The 87% tellurium mass fraction and 95% iodine separation yield led to significantly higher quantities of iodine compared to traditional TeO(2)/6%Al(2)O(3) admixtures. Radiochemical analysis of distilled samples using ion chromatography showed that the product remained in the iodide form while supported in weak buffer solutions. Stable Te impurities in the radioiodine product were less than 0.5 microg following purification by ion exchange chromatography. Average thick target yields of 229+/-18 microCi/microAh were achieved, and typical production runs at 18 microA for three hours yielded 12 mCi at the end-of-bombardment. Total losses of the target material after each irradiation and distillation cycle were approximately 2%.

Aluminum Compounds↗
PubMed2006

Insertion, reduction, and carbon-carbon coupling induced by monomeric aluminum hydride compounds bearing substituted pyrrolyl ligands.

A monomeric aluminum hydride complex bearing substituted pyrrolyl ligands, AlH[C(4)H(3)N(CH(2)NMe(2))-2](2) (1), was synthesized and structurally characterized. To further confirm the presence of Al--H bonds, the compound AlD[C(4)H(3)N(CH(2)NMe(2))-2](2) ([D]1) was synthesized by reacting LiAlD(4) with [C(4)H(4)N(CH(2)NMe(2))-2]. Compound 1 and [D]1 react with phenyl isothiocyanate yielding Al[C(4)H(3)N(CH(2)NMe(2))-2](2)[eta(3)-SCHNPh] (2) and Al[C(4)H(3)N(CH(2)NMe(2))-2](2)[eta(3)-SCDNPh] ([D]2) by insertion. The reactions of 1 with 9-fluorenone and benzophenone generated the unusual aluminum alkoxide complexes 3 and 4, respectively, through intramolecular proton abstraction and C-C coupling. A mechanistic study shows that 9-fluorenone coordinates to [D]1 and releases one equivalent of HD followed by C-C coupling and hydride transfer to yield the final product. Reduction of benzil with 1 affords aluminum enediolate complex 5 in moderate yield. Mechanistic studies also showed that the benzil was inserted into the aluminum hydride bond of [D]1 through hydroalumination followed by proton transfer to generate the final product [D]5. All new complexes have been characterized by (1)H and (13)C NMR spectroscopy and X-ray crystallography.

Journal Article↗
PubMed2004

F2Al(mu-eta2:eta2-O2)AlF2: an unusual, stable aluminum peroxo compound.

The oxidation processes in the industrial production of aluminum from cryolite melts are not fully understood. Oxidation of AlOF2- leads initially to AlOF2 radicals. The structure of the AlOF2 dimer and several oxidized and reduced forms of this compound are investigated by theoretical methods and compared to analogous boron and gallium compounds. The thermodynamic stability of these compounds is investigated. It is shown that the dimeric compound of AlOF2 contains a symmetric peroxo bridge and is unexpectedly stable toward decomposition.

Journal Article↗
PubMed2002

Mechanisms of stimulation of the immune response by aluminum adjuvants.

Aluminum adjuvants are widely used in human and veterinary vaccines. They are appropriate adjuvants for vaccines that confer protection by inducing antibodies via the induction of a type 2 immune response, but they do not induce cytotoxic T cell and cell-mediated immunity. The mechanisms by which aluminum adjuvants selectively enhance the immune response are poorly understood. Following exposure to interstitial fluid in vitro and in vivo, most antigens are rapidly desorbed from aluminum adjuvants, suggesting that sustained release of antigen from a depot does not significantly contribute to the adjuvant effect of aluminum compounds. However, the adsorption of antigens onto aluminum salts may result in a high local concentration of antigen at the injection site and enhance the uptake by antigen-presenting cells. Aluminum compounds can further enhance the immune response by direct or indirect stimulation of dendritic cells, activation of complement and by inducing the release of chemokines. The relative importance of these mechanisms remains to be determined.

Adjuvants, Immunologic↗
PubMed2004

Interaction of anhydride and carboxylic acid compounds with aluminum oxide surfaces studied using infrared reflection absorption spectroscopy.

The chemical bonding of three different anhydride and carboxylic acid based compounds with a set of differently prepared aluminum substrates has been investigated using infrared reflection absorption spectroscopy. The compounds were selected to model typically used adhesives, coatings, and self-assembling monolayers. The purpose of the investigation was to study the interaction of these functional groups with the aluminum oxide surface and to determine whether this interaction is influenced by the changes in chemistry and composition of the oxide layer. The extent to which the compounds resisted disbondment in water was also investigated. The oxide layers on the differently prepared substrates were all found to be capable of hydrolysis of the anhydride group, resulting in the formation of two carboxylic acid groups. Subsequently, both of the carboxylic acid groups became deprotonated, to form a coordinatively bonded carboxylate species. The same behavior was also observed for monofunctional carboxylic acids. For all different oxides layers, the carboxylate was found to be coordinated in a bridging bidentate way to two aluminum cations in the oxide layer. The oxide layers showed however clear differences in the amount of molecules being chemisorbed. A relation was established with the amount of hydroxyls present on their surfaces, as determined from X-ray photoelectron spectroscopy measurements. The coordinative bonding of a monofunctional carboxylic acid group to the oxide surface was found to be not stable in the presence of water, while a bifunctional carboxylic acid group could resist displacement by water for a prolonged period of time.

Journal Article↗
PubMed2003

Molecular recognition of alpha,beta-unsaturated carbonyl compounds using aluminum tris(2,6-diphenylphenoxide) (ATPH): structural and conformational analysis of ATPH complexes and application to the selective vinylogous aldol reaction.

Various alpha,beta-unsaturated carbonyl compounds were coordinated with aluminum tris(2,6-diphenylphenoxide) (ATPH) to give the corresponding Lewis acid-base complexes in a distinctive coordination fashion (selective coordination). ATPH recognizes carbonyl substrates and subsequently orients itself as it forms a stable complex through selective coordination with the carbonyl oxygen. Selective coordination also confers a conformational preference to each carbonyl compound under the steric and electronic influence of ATPH, which enables the vinylogous aldol reaction of alpha,beta-unsaturated carbonyl compounds to give the corresponding gamma-aldol products with different regio- and stereoselectivities.

Journal Article↗