8-Hydroxydeoxyguanosine (8-OHdG) is a typical form of oxidative DNA damage which causes mutation in vitro and in vivo. We investigated potential factors confounding 8-OHdG determination and, based on the results, then determined the 8-OHdG levels in human peripheral blood leukocytes. 8-OHdG was detected electrochemically after extraction of DNA from the cells without the use of phenol by a DNA extractor under helium. In the preliminary experiments, the mononuclear leukocytes (MN) in blood samples obtained from 19 laboratory workers and students were separated from the polymorphonuclear leukocytes (PMN) with Mono-Poly resolving medium. The 8-OHdG in the MN (1.157 +/- 0.414 molecules per 10(5) deoxyguanosine) did not differ significantly from that in PMN (1.131 +/- 0.418). The effect of red blood cells (RBC) on 8-OHdG formation during DNA extraction was then examined by adding RBC to the human lymphoblastoid cell line FA72. Addition of RBC at ratios of up to 4 RBC per FA72 cell did not increase 8-OHdG levels, while addition at a RBC/FA72 cell ratio of 20 increased the 8-OHdG level 1.43-fold over that without RBC. The potential effect of histidine, a scavenger of both hydroxyl radicals and singlet oxygen, on reduction of artificial 8-OHdG formation during DNA extraction was examined during DNA extraction in the human promyelocytic leukemia cell line HL60. Addition of His decreased the 8-OHdG level dose-dependently (30% reduction at 30 mM His concentration). Based on these results, we determined the 8-OHdG levels in human leukocyte samples obtained from 79 healthy male factory workers aged 24-59 years. The leukocyte fraction containing both MN and PMN was separated from RBC with Mono-Poly resolving medium and DNA was extracted from the leukocytes in the presence of 30 mM His. The mean 8-OHdG level in these samples was 1.072 +/- 0.230. To evaluate the reliability of the assay, FA72 was used as a standard sample in all assay determinations and the 8-OHdG levels of both the leukocyte samples and the FA72 sample(s) were measured in each determination. The inter- and intra-assay coefficients of variation (CV) were calculated to be 14.4% (n = 14) and 3.9-13.5% (n = 3-5 per assay) respectively. The 8-OHdG level was measured twice in 19 leukocyte samples; the value at the first determination was not correlated with that at the second determination. The range of 8-OHdG levels in the samples was relatively small compared with the CV of the assay.(ABSTRACT TRUNCATED AT 400 WORDS)

We investigated the association between incidental cerebral hyperintensities (CH) found by magnetic resonance imaging (MRI) and cognitive functions in neurologically normal, nondemented subjects. Semiquantitative scores for MRI lesions and those for brain atrophy were compared with the results of extensive cognitive examinations using multivariate analysis. There was no correlation between CH and cognition, except that periventricular hyperintensities, especially those in posterior locations, were associated with reduced performance in the Stroop test. Overall cognitive functions were associated with age, and age was a predominant factor in the prefrontal functions. Brain atrophy was associated more with decline of the posterior and dorsolateral frontal brain functions. We suggest that disturbances in attention and speed may initially result from incidental CH, while other cognitive functions remain unaffected.

Using multivariate analysis, we investigated the influence on cognitive functions of aging, brain atrophy, incidental cerebral hyperintensities (CHs), medication, and severity, duration and the inital symptoms of the disease in 53 patients with idiopathic Parkinson’s disease (PD). We semiquantitatively assessed the degree of brain atrophy and CHs based on previously established methods. Cognitive functions were significantly and diffusely impaired in PD when compared with controls who were matched for age as well as for the degree and location of CHs. Patients with PD, however, had larger ventricles. Prefrontal dysfunctions were associated with a variety of predictors such as CHs, brain atrophy, severity of PD and medication whereas dorsolateral frontal functions were related simply to age and CHs in the periventricular region. Posterior brain functions had association with severity of illness, ventricular dilatation and total CH score. Clinically observed cognitive impairments in PD may consist of cognitive defects intrinsic to the disease which are variously modified by these factors. It is essential to consider all these predictors simultaneously in any discussion of cognitive functions in PD.