[Test battery for objective assessment and differential diagnosis in the early stage of suspected development of presenile dementia of the Alzheimer type]. / Testbatterie zur Objektivierung und Differentialdiagnostik im Frühstadium einer angenommenen präsenilen Demenzentwicklung vom Alzheimertyp.

The clinical diagnosis of organic brain syndromes (especially of primary degenerative dementia) in their early stages is uncertain or only tentative. We used a set of relatively simple tests to support the hypothesis that the disturbance of several operational brain functions precedes memory decline in primary degenerative dementia. Twenty-one patients with early stage, presenile onset of DAT, 14 patients with cardiovascular disease (CVD) and a questionable dementia, an age-matched control group (EC, n = 15), and a younger control group (YC, n = 16) were examined in the following tests: labyrinth learning test, tactile and visual pattern recognition, different reaction time tasks, eye-tracking, finger-tapping, alpha-EEG-blockade, photic driving, flicker fusion frequency, and interaction tasks. The test demonstrated that the patients performed more slowly for all tasks than did control subjects. The CVD patients performed better than the DAT group, but they were also significantly worse in the tests compared with healthy elder subjects. This test battery was found purposeful for early diagnosis of both primary degenerative and other forms of dementia, and may also be helpful to exclude other forms of organic brain syndromes.

Impaired tactile pattern recognition in the early stage of primary degenerative dementia compared with normal aging.

Tactile pattern recognition of ten different patterns which were engraved upon 4 x 4 cm plastic plaquettes with one hand and thereafter drawing with the other or the same hand was tested in 21 patients with a mild stage primary degenerative presenile onset dementia of Alzheimer type (DAT) and in 14 patients with a questionable dementia on the background of a chronic cardiovascular disease (CVD) in comparison to 15 healthy subjects of the same age (51 years old, elder controls, (EC)) and 16 younger subjects (22 years old, younger controls, (YC)). Patients made about four times more errors than the EC group. Duration from the begin of touching to the end of drawing was significantly longer in patients than in controls. In a second task the subjects had to recognize four subsequent patterns, then to perform a standard multiplication task and afterwards to draw all four patterns in their correct sequence. Patients made about ten times more errors in pattern recognition and series reproduction than age-matched controls.

Impaired eye tracking performance in patients with presenile onset dementia.

Smooth pursuit eye movements, saccades and eye blinks were electrooculographically recorded from 26 healthy subjects of different age and 35 patients with presumptive presenile onset dementia (mean age 54), who had to track a light spot which oscillated with different speeds. Older subjects (mean age 51) performed the eye tracking with less accuracy and more saccades than younger ones (mean age 22). 16 patients with stage CDR 1 according to Washington University Clinical Dementia Rating performed smooth pursuit eye movements significantly worse with increased saccade numbers than the healthy older subjects and lost attention significantly more often which was measured by omitted trackings to presented target oscillations. Their number of eye blinks was partly increased. The test is found suitable for early diagnosis of dementia onset, supporting clinical findings and presumptive diagnosis by objective parameters.

Duration of EEG alpha wave blockade by tone stimulation is prolonged in early stage of presenile onset dementia of the Alzheimer type.

The EEG alpha rhythm suppression by sudden unexpected tones in a relaxed wakefulness state (Berger response) was measured in four groups of patients and healthy control subjects. One patient group with early cognitive deficits probably caused by a mild stage of presenile onset primary degenerative dementia of the Alzheimer type (DAT), a second patient group with cardiovascular disease and a stage of questionable dementia, an age-matched group of older healthy control subjects and a younger control group. Only half of the DAT group in the mild stage had significantly prolonged Berger responses and a retarded or disturbed habituation. In agreement with other data of their cognitive deficits this indicated a weakening in focussing attention and selective inhibition.

Reaction time prolongation in the early stage of presenile onset Alzheimer's disease.

Simple reaction times (RT) to clicks, flashes and numerical signals were measured in four groups of subjects: 21 patients with mild presenile onset dementia of the Alzheimer type (PDAT, mean age 56 years), 14 patients with chronic cardiovascular disease and incipient cognitive deficit (mean age 55 years), 15 healthy older controls (mean age 53 years) and 16 younger controls (mean age 23 years). Both patient groups had significantly prolonged RTs, the PDAT group especially to the numerical signal (149%), compared with the age-matched controls.

Labyrinth learning impairment in patients with early symptoms of presenile dementia.

21 patients (54 +/- 7 years old) with early cognitive deficit (ECD) during the presenile stage of presumptive primary degenerative dementia (mild stage) and 14 patients (54 +/- 4 years old) with early cognitive deficit with a background of cardiovascular disease (CVD) were examined in a labyrinth learning test of Milner (modified by Roth). 15 patients in the ECD group made 3 times more errors to negative fields (p less than 0.01), about 10 times more errors to positive fields (p less than 0.01) and needed treble the amount of time for passing through the labyrinth (p less than 0.01) compared with a healthy control group (51 +/- 4 years). A further 6 patients of the ECD group had no success in performing the labyrinth test. The CVD group was not different from the control group in making errors, but slower (p less than 0.05). The labyrinth test is found suitable for a more precise diagnosis of early cognitive deficit in the early stage of a primary degenerative dementia of the Alzheimer type.

Active chromatin.

Active genes are packaged into an altered nucleosome structure forming a chromosomal domain defined by increased sensitivity to nucleases. This structure, reflecting a potential for transcription, contains sites hypersensitive to nuclease digestion adjacent to the coding regions and may also be distinguished by specific non-histone proteins, variant or modified histones or modified DNA. Its formation, by unfolding of a tightly packed chromatin fibre by factors which might affect DNA supercoiling, may be the first step in gene activation.

Properties of active nucleosomes as revealed by HMG 14 and 17 chromatography.

Nucleosomes from actively transcribed genes (active nucleosomes) contain nonhistone proteins HMG 14 and 17 and are preferentially sensitive to digestion by DNAse I. Active nucleosomes isolated by chromatography on an HMG 14 and 17 glass bead affinity column were analyzed with respect to overall structure, accessory nonhistone components and modifications to the DNA and histones. The experiments lead to the following conclusions: the DNA in the active nucleosome is undermethylated compared to bulk DNA; topoisomerase I is a non-stoichiometric component of the active nucleosome fraction; the level of histone acetylation is enriched in active nucleosomes, but the extent of enrichment cannot account for HMG binding; and the two histone H3 molecules in the active nucleosome can dimerize more readily and are, therefore, probably closer together than those in the bulk of the nucleosomes. Additionally it is shown that HMG 14 and 17 prefer to bind to single- vs. double-stranded nucleic acids. The role of HMG 14 and 17 in producing a highly DNAse I sensitive structure and correspondingly helping to facilitate transcription is discussed in terms of these properties.

Isolation of actively transcribed nucleosomes using immobilized HMG 14 and 17 and an analysis of alpha-globin chromatin.

Taking advantage of the known specificity of interaction of HMG 14 and 17 with actively transcribed chromatin, we have covalently cross-linked these proteins to agarose and used this HMG 14-17 column to purify active nucleosomes. The column has been used to map the DNA regions surrounding the chicken alpha-globin genes for their capacity to bind HMG 14-17. The results show that at a crude level the HMG binding region correlates with the major stable primary transcript and the region of DNAase I sensitivity. At a finer level of analysis, however, the correspondence between DNAase I sensitivity and HMG binding is preserved, yet this chromosomal domain is shown to extend about 1 kb beyond the known primary transcript for the two chicken alpha genes. Why HMG 14 and 17 bind specifically to active nucleosomes is still not known. Our experiments suggest that at least one additional chemical difference distinguishes them. This difference is not reflected in the DNA:protein ratio; in the electrophoretic mobility of the particles or associated DNA; in the inner histone stoichiometry; in a marked degree of histone modification as assayed on Triton-urea gels; or in the presence of nonhistone proteins. Active nucleosomes can be dissociated and reconstituted and their ability to bind to HMG 14-17 restored. The ability to reconstitute binding should make it possible to determine whether the specificity for the interaction resides in the protein or the DNA.

Interaction of HMG 14 and 17 with actively transcribed genes.

The interaction of HMG 14 and 17 with actively transcribed genes was studied by monitoring the sensitivity of specific genes to DNAase I after reconstitution of HMG-depleted chromatin with HMG 14 and 17. Our experiments lead to the following conclusions: most actively transcribed genes become sensitized to DNAase I by HMG 14 and 17; either HMG 14 or HMG 17 can sensitize most genes to DNAase I; genes transcribed at different rates have about the same affinity for HMG 14 and 17; HMG 14 and 17 bind stoichiometrically to actively transcribed nucleosomes; and HMG 14 and 17 can restore DNAase I sensitivity to purified nucleosome core particles depleted to HMGs. This last observation suggests that during reconstitution, low levels of HMG 14 and 17 can associate with the active nucleosomes in the presence of a 10--20 fold excess of inactive nucleosomes. Consequently, we conclude that besides their association with HMGs, active nucleosomes also have at least one other unique feature that distinguishes them from bulk nucleosomes and insures proper HMG binding during reconstitution.

Isolation of a subclass of nuclear proteins responsible for conferring a DNase I-sensitive structure on globin chromatin.

The globin gene is preferentially sensitive to digestion by DNase I in erythrocyte chromatin but not in brain, fibroblast, or oviduct chromatin. Elution of the erythrocyte chromatin with 0.35 M NaCl leads to no detectable change in the gross structure of individual nucleosomes; however, in this depleted chromatin the globin gene is no longer preferentially sensitive to DNase I. Reconstitution of the depleted chromatin with either the entire 0.35 M NaCl fraction or a subclass from this fraction greatly enriched in two high mobility group proteins (nos. 14 and 17) results in the successful reconstitution of DNase I sensitivity of the globin gene. For all of these preparations, the inactive ovalbumin gene exhibited no preferential sensitivity to DNase I. Reconstitution of the erythrocyte 0.35 M NaCl fraction with depleted brain chromatin resulted in no preferential sensitivity of the globin gene in brain chromatin; however, reconstitution of the brain 0.35 M NaCl fraction with depleted erythrocyte chromatin led to successful reconstitution of DNase I sensitivity of the globin gene. Thus, the eluted proteins responsible for conferring DNase I sensitivity are probably not tissue-specific and probably do not recognize specific DNA sequences.