OBJECTIVE The double transgenic mouse model (APPswe/PS1dE9) of Alzheimer's disease (AD) has been widely used in experimental studies. β-Amyloid (Aβ) peptide is excessively produced in AD mouse brain, which affects synaptic function and the development of central nervous system. However, little has been reported on characterization of this model. The present study aimed to characterize this mouse AD model and its wild-type counterparts by biochemical and functional approaches. METHODS Blood samples were collected from the transgenic and the wild-type mice, and radial arm water maze behavioral test was conducted at the ages of 6 and 12 months. The mice were sacrificed at 12-month age. One hemisphere of the brain was frozen-sectioned for immunohistochemistry and the other hemisphere was dissected into 7 regions. The levels of Aβ1-40, Aβ1-42 and 8-hydroxydeoxyguanosine (8-OHdG) in blood or/and brain samples were analyzed by ELISA. Secretase activities in brain regions were analyzed by in vitro assays. RESULTS The pre-mature death rate of transgenic mice was approximately 35% before 6-month age, and high levels of Aβ(1-40) and Aβ(1-42) were detected in these dead mice brains with a ratio of 1:10. The level of blood-borne Aβ at 6-month age was similar with that at 12-month age. Besides, Aβ(1-40) level in the blood was significantly higher than Aβ(1-42) level at the ages of 6 and 12 months (ratio 2.37:1). In contrast, the level of Aβ(1-42) in the brain (160.6 ng/mg protein) was higher than that of Aβ(1-40) (74 ng/mg protein) (ratio 2.17:1). In addition, the levels of Aβ(1-40) and Aβ(1-42) varied markedly among different brain regions. Aβ(1-42) level was significantly higher than Aβ(1-40) level in cerebellum, frontal and posterior cortex, and hippocampus. Secretase activity assays did not reveal major differences among different brain regions or between wild-type and transgenic mice, suggesting that the transgene PS1 did not lead to higher γ-secretase activity but was more efficient in producing Aβ(1-42) peptides. 8-OHdG, the biomarker of DNA oxidative damage, showed a trend of increase in the blood of transgenic mice, but with no significant difference, as compared with the wild-type mice. Behavioral tests showed that transgenic mice had significant memory deficits at 6-month age compared to wild-type controls, and the deficits were exacerbated at 12-month age with more errors. CONCLUSION These results suggest that this mouse model mimics the early-onset human AD and may represent full-blown disease at as early as 6-month age for experimental studies.

No abstract

Human hemoglobin was reacted with five dicarboxylic acid bis(methyl phosphate) reagents under different ligand conditions. The bis(methyl phosphate) reagents tested were derived from fumaric, isophthalic, terephthalic, trans-stilbene-3,3'-dicarboxylic, and trans-stilbene-4,4'-dicarboxylic acids. These acyl phosphate mixed anhydrides are anionic electrophiles and will react with N-terminal amino and lysyl epsilon-amino groups to form amides. The major and many of the minor reaction products that result have been isolated and structurally characterized by globin chain and peptide analysis. Products which are not cross-linked, intrachain linked, and interchain singly and doubly cross-linked occur in proportions which depend upon the reaction conditions and reagent. Modifications of the beta chains were limited to the amino groups of beta 1Val, beta 82Lys, and, to a minor extent, beta 144Lys. In the case of the smaller reagents, the amino groups of alpha 1Val, alpha 99Lys, and, to a minor extent, alpha 139Lys were modified. The oxygen binding affinities of most of the major modified hemoglobins have been measured and are characterized by P50 values from about 1/2 to over 5 times that of unmodified human hemoglobin. Most show strong cooperativity with Hill coefficients (n) of 2.0 or greater. Several of the products that are cross-linked between the beta 1Val of one chain and the beta 82Lys of the other chain have oxygen affinities in a physiologically useful range for oxygen transport and delivery. An inverse linear correlation has been found between the log of P50 and bridging distances for the hemoglobins cross-linked between beta 1Val of one chain and the beta 82Lys of the other chain.(ABSTRACT TRUNCATED AT 250 WORDS)

The symmetrical trifunctional cross-linking reagent trimesoyl tris(methyl phosphate) (3), reacts selectively with amino groups (beta 1Val and beta 82Lys) in the diphosphoglycerate binding site of human hemoglobin A, producing cross-linked tetrameric species in good yield. A major species is triply linked, alpha alpha beta 1(82) greater than B beta 82, where B symbolizes benzene-1,3,5-tricarbonyl. Both this triply linked species and the doubly linked species, alpha alpha beta 1B beta 82, produced from deoxyhemoglobin have a considerably lower oxygen affinity than does native hemoglobin while maintaining a high degree of cooperativity (n50 = 2.4), making them potentially useful as red cell substitutes, in principle delivering twice as much oxygen as whole blood between pO2 = 100 and = 40 Torr. The yield of products indicates that triply and doubly linked species form in parallel so that there are independent routes to each. It is proposed that differences in routes are due to stereoisomerism about the amide bonds which form from reaction of the reagent with the protein.

No abstract