This almost-complete survey, conducted in a prefecture of Japan, revealed a high prevalence of dementia in centenarians. The ApoE epsilon 4 allele does not have an impact on the development of AD in centenarians.

Dimethyl disulfide (DMDS) adducts are prepared from fatty acid methyl esters to locate the double-bond position in monoenoic fatty acids by gas chromatography/ mass spectrometry. We improved our original procedure for preparing DMDS adducts with a simple device that can be made in any laboratory using a glass pipette and silica based packing material, Extelut NT.

The novel pathways of oleic acid formation from cis-vaccenic (cis-I 1-octadecenoic) acid and of cis-vaccenic acid formation from oleic acid by enzymatic positional isomerization have been proposed in higher plants, based on stable-isotope experiments using [2,2-Z&]cis-vaccenate or [2,2-ZH,]oleate as an immediate precursor. A pulp homogenate and also pulp slices prepared from developing kaki (Diospyros kakt> fruit could catalyze these hitherto unknown isomerizations. This suggests the presence of a new type of isomerase responsible for the double-bond shifting reaction without cis-tram isomerization in the middle of fatty acid carbon chains.

A gas chromatographic‐mass spectrometric method using [2,2‐2H2]fatty acids has been developed to trace the biosynthesis ofcis‐vaccenic (cis‐11‐octadecenoic) acid in higher plants. The deuterated fatty acids and other unlabeled fatty acids in the biosynthetic reaction mixture were converted into bis(methylthio) derivatives and analyzed by mass chromatography. The principle of this method was based on the shift of key fragment ions (containing two deuterium atoms) due to the cleavage between the methylthio‐substituted carbons. The labeled compounds were detected by the m/z values which shifted 2 mass units from those of the corresponding unlabeled compounds and estimated by a calibration curve based on the peak areas of the key fragment ions. For metabolic experiments, a homogenate fraction was prepared from the pulp part of maturing kaki (Diospyros kaki) fruit and incubated with ammonium [2,2‐2H2]palmitoleate (cis‐9‐hexadecenoate) or [2,2‐2H2]palmitoleoyl‐CoA. The incubation resulted in the formation of detectable amounts of isotopically‐labeledcis‐vaccenic acid containing two deuterium atoms at the carbon chain between the double bond and the carboxyl group. This experimental evidence proved thatcis‐vaccenic acid was formed from palmitoleic acid by chain elongation.

We have demonstrated an association between apolipoprotein E (apoE) gene polymorphisms and Alzheimer’s disease (AD) in 163 Japanese patients by means of PCR. We found a significant increase in risk of nonfamilial AD for apoE allele Ε4 in these individuals; this trend decreases with the increase in onset age. In centenarians, the distribution of apoE gene alleles is similar to that in the general population. The protective effect of allele Ε2 against the development of AD is not statistically significant in our analysis. This indicates that apoE polymorphism is associated with AD regardless of race and that the age of onset is related to the apoE gene in the development of AD.