Relationship of the frequency of acrocentric chromosome associations and the immune response in children primarily vaccinated against smallpox]

The frequency of acrocentric chromosomes associations in the lymphocytes of periferal blood decreased on the 7th and 30th day after vaccination. The rate of the decrease was in direct dependence on the intensity of the immunological response, that probably was due to shortening the length of the interphase of the lymphocytes induced for immunopoiesis. Frequency of the acrocentric chromosomes associations did not differ from the control level 6 months after vaccination.     

Genetic determination of NOR activity in human lymphocytes from twins

Summary Activity of nucleolar organizer regions (NORs) was studied in cultured blood lymphocytes from 20 monozygotic (MZ) and 20 dizygotic (DZ) twin pairs. The number of Agstained NORs, the degree of staining, and the frequency of acrocentric associations were used as criteria of the NOR activity, the acrocentric chromosomes being identified by G-banding. Analysis of intrapair concordance as well as of intrapair variance showed the number of Ag+NORs and the size of Ag-deposits to be highly heritable traits. Intrapair differences in acrocentric association frequency were not significantly higher in DZ compared with MZ twins.     

Frequency of Ag-stained nucleolus organizer regions in the acrocentric chromosomes of man

Summary The Ag-stainability of the nucleolus organizer region (NOR) was studied in the acrocentric chromosomes identified by Q-banding of cultured lymphocytes in 51 karyotypically normal persons (31 males and 20 females). A consistent pattern of Ag-positive NORs was found in each individual. Ninety percent of the individuals have a modal number of 8–10 Ag-positive NORs per cell. The frequency of Ag-positive NORs is similar in all five acrocentrics. A statistically nonsignificant lower frequency is found in chromosome 22. Ag-negative NORs on both homologues were found in four cases. The observed frequency distribution of individuals with homozygous NOR-positive, heterozygous, and homozygous negative acrocentric chromosomes was in accordance with the Hardy-Weinberg law in all five pairs of the acrocentric chromosomes as well as in total. No sex difference was observed in our material.A.-V. Mikelsaar is visiting exchange scientist of the Österreichische Bundesministerium für Wissenschaft und Forschung     

Quantitative studies on the arrangement of human metaphase chromosomes

Summary The association pattern was studied in 2715 mitoses of 90 meningiomas with different numbers of acrocentric chromosomes. In cells with monosomy 22, a significant increase of mitoses with associations was observed in comparison to cells with a normal karyotype. The number of associating acrocentric chromosomes was highly significantly increased. This surplus was not only caused by a highly significant increase of associating G chromosomes but also of D chromosomes. The loss of further acrocentric chromosomes had no significant influence on the number of mitoses with associations or the number of associating chromosomes. Based on the well-known correlations between the nucleolus organization and the association pattern, the results seem to indicate a compensation mechanism among the nucleoles organizing regions (NOR's) which keeps the supply of nucleolar material constant and simultaneously causes a higher association tendency between the remaining acrocentric chromosomes. The increase of associations in the 22 monosomic cells was interpreted as a overcompensation after the loss of only one NOR.     

Polymorphisms of Ag-stained nucleolar organizer regions in man

Summary Polymorphisms of the NORs as tested by Ag-staining of metaphase G-banded chromosomes were investigated in cultured blood lymphocytes of karyotypically normal individuals from the Moscow population.The study of cell-to-cell variability in the number of Ag-stained NORs carried out on 14 monozygotic twin pairs showed the phenomenon to have some features of real intercellular variation.In 40 unrelated individuals the individual acrocentric chromosomes were compared by the number of Ag-stained NORs, their degree of staining, and their participation in acrocentric association. Chromosome 21 was found to be significantly more active than four others by all the criteria, and chromosome 15 was less active compared with the others by the size of the Ag deposits and the frequency of participation in NOR associations. The frequency distribution of homozygotes and heterozygotes for Ag-stained NORs in the same group of 40 individuals was in accordance with the Hardy-Weinberg law.     

Differential associative behaviour of mitotic and meiotic acrocentric chromosomes

Summary A comparative study of the association of mitotic acrocentric chromosomes and acrocentric bivalents at the pachytene stage shows that at least two factors can act in the associative behaviour of these chromosomes: (1) Nor activity and (2) the presence of satellite DNA in the short arms of these chromosomes. These factors do not act with the same intensity in the two cell lines studied. In lymphocytes, Nor activity prevails, whereas satellite DNA plays the main role in the association of acrocentric chromosomes in germ cells at the pachytene stage.     

Frequency of acrocentric chromosome associations in human blood lymphocytes when using different methods for its assessment

The indeces of frequency of associations of acrocentric chromosomes in lymphocytes of human peripheral blood were compared with the help of different criteria of their estimation: by argentofile connections and by specific location of acrocentrics in metaphase plate. It was shown by the methods of variation statistics that the specificity of orientation of associative acrocentric chromosomes towards each other by short arms to the distance equal to the length of G-chromosome long arm is not accidental. Therefore, the method elaborated on the basis of the estimation criteria reflects participation of acrocentric chromosomes association in the formation of general nucleus in interphase more completely than the Ag-method, as preservation of Ag-material depends on the extent of its resorbtion in mitosis.     

Methylation status of ribosomal RNA gene clusters in the flow-sorted human acrocentric chromosomes

Southern blot analysis of the human acrocentric chromosomes that were flow-sorted from B-lymphoblastoid cell line GM130B revealed that the sensitivity of the ribosomal RNA (rDNA) gene clusters to the restriction enzyme NotI differs among these rDNA-containing chromosomes: the rDNA clusters of Chromosomes (Chr) 13, 14, and 15 are much more sensitive to NotI digestion than those of Chrs 21 and 22 in this particular cell line. Detailed analysis by use of methylation-sensitive enzymes HpaII and HhaI and methylation-insensitive enzyme MspI confirmed the significant variation in the methylation status of rDNA clusters among these chromosomes. Quantitative analysis by fluorescent in situ hybridization (FISH) indicated that copy number of rDNA varies among individual chromosomes, but the average copy number in the acrocentric Chrs 21 and 22 is significantly greater than that of the Chrs 13, 14, and 15 in GM130B cells. Similar analysis reveals that the methylation status of rDNA clusters in another B-lymphoblastoid cell line GM131 was different from that of GM130B. These data together indicate that the copy number and methylation patterns of rDNA clusters differ among individual acrocentric chromosomes in a given cell line, and they are different among cell lines.     

Frequent occurrence of translocations of the short arm of chromosome 15 to other D-group chromosomes

Summary The presence of DA/DAPI (distamycin A/ 4,6-diamino-2-phenyl-indole) heteromorphism on the short arm of human acrocentric chromosomes was investigated in 127 individuals. In 7 cases, a DA/DAPI signal was observed on an acrocentric chromosome other than 15. Subsequently, in situ hybridization (ISH) with a pericentromeric probe specific for chromosome 15 was carried out. In all 7 cases, three ISH signals were present in every metaphase, i.e., on both chromosomes 15 and on the third DA/DAPI-fluorescence-positive acrocentric chromosome (a chromosome 13 or 14), indicating that a chromosome 15 short arm was also present on these chromosomes. Therefore, we conclude that translocations of short arm sequences from chromosome 15 onto other D-group chromosomes occur frequently. Moreover, it appears that DA/DAPI staining remains specific for the short arm of chromosome 15, despite a number of recent papers suggesting otherwise.     

The quantity of associated acrocentric chromosomes in human lymphocytes passing through 1st, 2d and 3d mitoses in culture

The reproductive ability of lymphocytes of peripheral blood with the usage of 5-bromine-deoxyuridine has been studied in 8 healthy children at the age of 5-6 years. Single second mitoses occurred in 48 hour cultures (6.5%), in 72 hour cultures the frequency of the first, second and third mitoses was equal, in 96 hour cultures the third mitoses dominated. Consequent divisions of lymphocytes were accompanied by a decrease in associative acrocentric chromosome, in average by 25%, within one mitotic cycle, while in mitoses of a given ordinal number the frequency of associations did not depend on the duration of cultivation. The fixation of the culture at the 48th hour of cultivation makes it possible to take into account the frequency of associations of acrocentric chromosomes without calculation of the ordinal number of mitosis because of an significant amount of second mitoses at this time, and of a sufficient value of the mitotic index (4.6 +/- 0.5%) necessary for cytogenetic analysis.     

Quantitative studies on the arrangment of human metaphase chromosomes

Summary The pattern of association of acrocentric chromosomes was examined in ten and five carriers of a 15/21 and a 13/14 Robertsonian translocation, respectively, and was compared with that of the same numbers of relatives with normal karyotypes. In the carriers of 15/21 translocation, the number of large associations (involving more than two acrocentrics) and the association frequencies for individual acrocentric chromosomes, were significantly higher than in the control group. The mean number of associations of the single homologs of the translocation chromosomes was much higher than that of the other acrocentrics. In the carriers of 13/14 translocations, only the association frequency for chromosome 13 was higher than in the normal relatives. The uninvolved chromosomes homologous to those involved in translocations showed an insignificant increase in associations in comparison with the other acrocentrics. These results suggest that some mechanism within the cells compensates for the effect of missing acrocentrics or of acrocentrics lacking NORs on the number of associations. The possible relations of this phenomenon to the activity of the nucleolus organizing regions are discussed.     

Spontaneous and induced aneuploidy in peripheral blood lymphocytes of patients with Alzheimer’s disease

This study was aimed at assessing whether peripheral blood lymphocytes of patients with Alzheimer’s disease (AD) show significant levels of aneuploidy and high percentages of cytogenetic events in vitro, indicating a predisposition to aneuploidy spontaneously, or after chemical treatment in vitro. A group of affected individuals and a group of unaffected, age-, sex- and smoking-habit-matched controls were identified. Lymphocytes were cultured for analysis of the following cytogenetic parameters: premature centromere division (PCD), satellite associations of acrocentric chromosomes (SA) and micronuclei (MN). In a subset of subjects, the fluorescence in situ hybridization (FISH) technique was combined with the MN assay, by means of a pancentromeric DNA probe for the detection of the presence of centric material. To evaluate the sensitivity to aneuploidogenic agents, in vitro treatment of lymphocytes of affected individuals was performed by adding griseofulvin, a chemical whose supposed target is microtubule-associated protein(s). Both the spontaneous frequency of MN and the frequency of PCD was significantly higher in patient cells than in controls. Furthermore, after application of the FISH technique, we found that the majority of MN were composed of whole chromosomes (because of the phenomenon of chromosome loss). Metaphase analysis for the detection of associative events between satellite regions of acrocentric chromosomes showed no differences between the two groups under study. Analysis of sensitivity to the aneuploidogen griseofulvin showed that the patient group was characterized by lower levels of MN induction compared with controls. Our data confirm that peripheral blood lymphocytes of AD patients are prone to undergo aneuploidy spontaneously in vitro and support the hypothesis that microtubule impairment might be associated with the disease. Received: 13 January 1997 / Accepted: 30 July 1997     

Constitutive heterochromatin variation in two species of rattus with apparently similar karyotypes

Rattus blanfordi and R. cutchicus medius both have a chromosome complement of 2n=36 and all chromosomes except the submetacentric Y of R. blanfordi are acrocentric. The apparently similar karyotypes of the two species, however, show variations in the nature and quantity of C-band-positive constitutive heterochromatin (C-heterochromatin) as revealed by C- and G-banding and Hoechst 33258 fluorescence. R. blanfordi with large-sized X and Y chromosomes and conspicuously larger centromeric heterochromatin in all the autosomes as compared to that of R. cutchicus medius has much more C-heterochromatin in its genome than the latter. The variation in the quantity of C-heterochromatin has been accomplished without altering the morphology of the acrocentric chromosomes unlike other mammals in which variations have been reported to result generally in the addition or deletion of a totally heterochromatic second arm.     

Increased satellite association induced by 5′ Bromodeoxyuridine treatment of Phytohemaglutinin-stimulated blood lymphocytes

5'-Bromodeoxyuridine (BrdU) present in the course of late S and G2 phases of the cell cycle in PHA-stimulated human lymphocyte cultures causes the despiralization and elongation of some chromosome regions, including short arms of acrocentric chromosomes. BrdU present at a concentration of 250 microM during the last 10 h in lymphocyte cultures from 19 healthy subjects did not affect the number of silver-stained NORs, but raised significantly the number of satellite associations of acrocentric chromosomes. The mere substitution of thymine by BrdU in DNA strands as a reason for increased number of satellite associations seems a less plausible explanation than the modification of DNA-protein complexes of NOR regions, which could alter the degree of their spiralization and cause the increased tendency of acrocentric chromosomes to associate in the subsequent metaphase.     

Preferential association of nucleolar organizing human chromosomes as revealed by silver staining technique at mitosis

Summary The frequency of different types of satellite associations of nucleolar organizing human chromosomes (i.e. acrocentric chromosomes; 13, 14, 15, 21, and 22) is reported using 10 normal individuals by Ag-staining technique. The preferential involvement of acrocentric chromosomes in satellite association is suggested. Only acrocentric chromosomes with active NORs (i.e. Ag-stained) were found in association while unstained (inactive NORs) chromosomes were never seen in satellite association. In general as number of NORs expression increase, the frequency of association per cell was also increased. A possible mechanism and the clinical consequences of such an unusual phenophenon is described.     

Cytogenetic characterization and description of an XX/XY1Y2 sex chromosome system in catfish Harttia carvalhoi (Siluriformes, Loricariidae)

Karyotypic and cytogenetic characteristics of catfish Harttia carvalhoi (Paraíba do Sul River basin, S?o Paulo State, Brazil) were investigated using differential staining techniques (C-banding, Ag-staining) and fluorescent in situ hybridization (FISH) with 18S and 5S rDNA probes. The diploid chromosome number of females was 2n = 52 and their karyotype was composed of nine pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric and four pairs of acrocentric chromosomes. The diploid chromosome number of males was invariably 2n = 53 and their karyotype consisted of one large unpaired metacentric, eight pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric, four pairs of acrocentric plus two middle-sized acrocentric chromosomes. The differences between female and male karyotypes indicated the presence of a sex chromosome system of XX/XY1Y2 type, where the X is the largest metacentric and Y1 and Y2 are the two additional middle-sized acrocentric chromosomes of the male karyotype. The major rDNA sites as revealed by FISH with an 18S rDNA probe were located in the pericentromeric region of the largest pair of acrocentric chromosomes. FISH with a 5S rDNA probe revealed two sites: an interstitial site located in the largest pair of acrocentric chromosomes, and a pericentromeric site in a smaller metacentric pair of chromosomes. Translocations or centric fusions in the ancestral 2n = 54 karyotype is hypothesized for the origin of such multiple sex chromosome systems where females are fixed translocation homozygotes whereas males are fixed translocation heterozygotes. The available cytogenetic data for representatives of the genus Harttia examined so far indicate large kayotype diversity.     

Satellite association patterns in postpartum women and in newborn infants

Different features of the satellite associations between the acrocentric chromosomes of 100 postpartum mothers, between 14 and 43 years of age, and 100 neonates (51 males and 49 females) from Puriscal, Costa Rica, were compared (400 cells were examined, 2 from each individual). Several types of satellite associations showed higher frequencies in the mothers than in the neonates. The associations most frequently found in the two groups were those of two chromosomes, followed by those of three chromosomes. The D/G ratio was 1.43 in the children and 1.40 in the mothers. The number of associations per cell in the mothers was almost twice that of the children. The mean number of acrocentric chromosomes per association was 2.2 in the children and 2.35 in the mothers. No significant difference was found between observed and expected values of D and G chromosomes in the two groups. Thus, the probable factors responsible for the increase of satellite associations in the mothers similarly influenced the two types of acrocentric chromosomes.     

Inheritance of Ag-stainability of nucleolus organizer regions

Summary The Ag-stainability of the nucleolus organizer region (NOR) was studied in the acrocentric chromosomes identified by Q-banding in cultured lymphocytes from seven children with trisomy 21 and their parents. The observed Ag-NOR patterns were in accordance with chromosomal inheritance except for a slight intraindividual variation which might be explained mainly by technical causes. In two cases the meiotic nondisjunction could be attributed to one of the parents, once to the father, and once to the mother. It is concluded that the Ag-stainability of the NORs is in general a heritable characteristic of the acrocentric chromosomes in maximally activated cells as, e.g., cultured lymphocytes. It may reflect individual differences in the amount of rDNA as well as differences in the capacity for NOR activation.     

Chromosomes of the Black Sea Gobiidae--Gobius melanostomus (Pallas) and Gobius batrachocephalus (Pallas) ]

The chromosome set of G. melanostomus (Pallas) consists of 46 acrocentric chromosomes (2n-46). There are 30 chromosomes in the caryotype of G. batrachocephalus (Pallas): 16 metacentric and 14 acrocentric. The equal number of arms in the chromosome sets of the studied fish (FN-46) evidences for phylogenetic relationships of these species.     

Physical mapping of the 5S ribosomal RNA genes in Arabidopsis thaliana by multi-color fluorescence in situ hybridization with cosmid clones

The 5S ribosomal RNA genes were mapped to mitotic chromosomes of Arabidopsis thaliana by fluorescence in situ hybridization (FISH). In the ecotype Landsberg erecta, hybridization signals appeared on three pairs of chromosomes, two of which were metacentric and the other acrocentric. Hybridization signals on one pair of metacentric chromosomes were much stronger than those on the acrocentric and the other pair of metacentric chromosomes, probably reflecting the number of copies of the genes on the chromosomes. Other ecotypes, Columbia and Wassilewskija, had similar chromosomal distribution of the genes, but the hybridization signals on one pair of metacentric chromosomes were very weak, and detectable only in chromosomes prepared from young flower buds. The chromosomes and arms carrying the 5S rDNA were identified by multi-color FISH with cosmid clones and a centromeric 180 bp repeat as co-probes. The metacentric chromosome 5 and its L arm carries the largest cluster of the genes, and the short arm of acrocentric chromosome 4 carries a small cluster in all three ecotypes. Chromosome 3 had another small cluster of 5S rRNA genes on its L arm. Chromosomes 1 and 2 had no 5S rDNA cluster, but they are morphologically distinguishable; chromosome 1 is metacentric and 2 acrocentric. Using the 5S rDNA as a probe, therefore, all chromosomes of A. thaliana could be identified by FISH. Chromosome 1 is large and metacentric; chromosome 2 is acrocentric carrying 18S-5.8S-25S rDNA clusters on its short arm; chromosome 3 is metacentric carrying a small cluster of 5S rDNA genes on its L arm; chromosome 4 is acrocentric carrying both 18S-5.8S-25S and 5S rDNAs on its short (L) arm; and chromosome 5 is metacentric carrying a large cluster of 5S rDNA on its L arm.