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The distribution of three DNA polymorphisms (XbaI, EcoRI, and I/D) of the apolipoprotein B (APOB) gene, and of the I/D polymorphism of the angiotensin I-converting enzyme (ACE) gene was investigated in 53 patients with vascular dementia, in 80 patients with late-onset sporadic Alzheimer's disease, and in 153 age-matched control subjects. Furthermore, plasma total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides were measured in the three groups and the involvement of the genetic variation at APOB locus on lipid levels was determined. Major findings of this work are (1) no genotype or allele of the polymorphisms examined here seemed to be associated with vascular dementia or with Alzheimer's disease, (2) total cholesterol and LDL cholesterol levels were lower in Alzheimer's disease patients than in vascular dementia patients and in elderly controls, and (3) the dementia patients with APOB EcoRI R+R- genotype had higher total cholesterol and LDL cholesterol levels than R+R+ homozygotes.

The somatostatin (SST) gene was analyzed to detect possible molecular variations in subjects with familial isolated growth hormone deficiency type I (IGHD I). No gross alterations in restriction fragments were observed with 18 used enzymes. The association with two RFLPs closely linked to the SST gene was also negative, adding weight to the evidence that the SST gene is not involved in the etiology of IGHD I. The nucleotide variability of a 23-kb DNA segment containing the SST gene and its flanking sequences was studied by restriction analysis of a sample of 19 Italians. The data suggest that approximately 1 in 400 bp is variant in this region.

Five Italian samples were examined for an EcoRI restriction fragment length polymorphism associated with a DNA sequence of unknown function, located on chromosome 5. No significant difference was observed between the samples. The allele frequencies in Italy were D5S4ES = 0.697, D5S4EF = 0.303.

Three Italian populations were examined for a multiple restriction fragment length polymorphism tightly linked to the human somatostatin gene. No difference was observed between the three samples. The haplotype frequencies in Italy were found to be: SST ESBS = 0.836, SST ESBF = 0.072, SST EFBS = 0.091 and SST EFBF = 0.001.

Three Italian populations were examined for a restriction fragment length polymorphism probing with a DNA sequence of unknown function located on chromosome 1. No difference was observed between the samples. The allele frequencies in Italy were: D1S1 BS = 0.82, D1S1 BF = 0.18.

Four Italian populations were examined for a HindIII RFLP associated with the human insulin-like growth factor I gene. No differences were observed among the four samples. The allele frequencies in Italy were: IGF-I HF = 0.834; IGF-I HS = 0.166. The polymorphism appears to be due to a 400-bp sequence insertion-deletion mechanism.

The effect of three thiol reagents on erythrocyte adenosine deaminase (ADA) activity has been studied. Oxidized glutathione and iodoacetate do not alter ADA activity, while the treatment with p-chloromercuribenzoate at similar concentrations results in a reduction of enzymatic activity which is statistically significant only for ADA 1, but not ADA 2-1 phenotype haemolysates.