Definition of a new alpha satellite suprachromosomal family characterized by monomeric organization.

We have analyzed more than 500 alphoid monomers either sequenced in our laboratory or available in the literature. Most of them belonged to the well studied suprachromosomal families 1, 2 and 3 characterized by dimeric (1 and 2) and pentameric (3) ancestral periodicities. The sequences that did not belong to the previously known families were subjected to further analysis. About a half of them formed a relatively homogenous family. Its members were on average 80.5% identical and 89.5% homologous to the M1 consensus sequence derived from this group (39 monomers). In the genome they do not form any ancestral periodicities other than a monomeric one, and are found at least in chromosomes 13, 14, 15, 21, 22 and Y. The newly defined family was termed suprachromosomal family 4. Comparison of all 10 alphoid monomeric groups identified so far showed that the M1 sequence is closely related to the J1-D2-W4-W5 homology grouping. Notably the African Green Monkey alpha satellite, also characterized by monomeric construction, appears to be a member of the same group.

Chromosome-specific alpha satellites: two distinct families on human chromosome 18.

Two types of human chromosome 18-specific alpha satellite fragments have been cloned and sequenced. They represent closely related but distinct alphoid families formed by two different types of the higher-order repeated units (1360-bp EcoRI and 1700-bp HindIII fragments) that do not alternate in the genome. The individual repeats within each family are 99% identical and interfamily homology is about 78%. Sequence analysis shows that both repeats belong to alphoid suprachromosomal family 2, but their homology is not higher than that of family members located on different chromosomes. Therefore, the two repeats shared a common origin in the recent past, although they are not the direct offspring of one ancestral sequence. Our data indicate that these two 18-specific domains have appeared as a result of two separate amplification events. Despite the high degree of homology, they are not undergoing intrachromosomal homogenization, although some variation of this process might take place within each domain.

[Clinical heterogeneity of dementia of the Alzheimer type]. / O klinicheskoi geterogennosti dementsii al'tsgeimerovskogo tipa.

Using clinico-psychopathological, clinico-neuropsychological and computer-aided tomography approaches, material differences were ascertained between groups of patients with Alzheimer's disease (AD) and senile dementia (SD) in terms of the clinical parameters, including the age at which the disease sets in; the disease standing; the build-up features of the patients; the frequency of diverse exogenous and environmental actions at the premorbid stage and at the disease debut; the psychopathological structure of dementia and the initial disease manifestations. The clinical differences indicated were in agreement with different structures of the neuropsychological syndrome marked by the impairment of higher mental functions in AD and SD and with different structures and topography of alterations in the medulla, discovered by means of computer-aided studies. The differences in the clinical and morphofunctional characteristics of AD and SD allow a conclusion that AD and SD are clinically independent disease entities within the framework of the common group of the Alzheimer's type dementias.