Induction of chromosome crossbanding by treating cells with chemical agents before fixation

Chromosome preparation and high resolution banding techniques. A review

High resolution banding techniques enable detection of chromosome rearrangements even within major bands. Banded chromosomes prepared for light microscopic studies of intact metaphase plates are, however, highly modified structures compared with native chromosomes, and the high resolution banding techniques only seem possible because the following methods were standardized and combined. The use of colcemid, which prevents formation of the spindle and thereby collects cells at the metaphase-anaphase border, is routinely used for chromosome preparations. For high resolution banding studies, short exposure time and concentrations near the threshold value have been recommended by several authors. Several agents interfere with chromosome contraction processes, but only a few have had a lasting influence on high resolution banding studies. The most used agents are ethidium bromide, actinomycin D, and Hoechst 33258, which all partially inhibit chromosome contraction. Treatment with hypotonic solutions induces swelling of animal cells, and the methanol in the fixative denatures and precipitates protein by dehydration. The acetic acid coagulates nucleoproteins and causes swelling of the cells. The fixative penetrates the cells rapidly and preserves the chromosome structure. To obtain long segmented chromosomes suitable for high resolution banding hypotonic treatment with .075 M KCl, frequent changes of fixative and overnight fixation at 4 degrees C have been recommended. The use of cell synchronization, 5-bromodeoxyuridine incorporation into DNA, and fluorochrome-photolysis Giemsa (FPG)-staining have improved the quality of high resolution banding. Synchronization techniques, which select for lymphocyte populations in early divisions, provide excellent materials for chromosome preparations and induction of high resolution banding. The banding techniques seem to enhance differences already present in the chromosomes, and the differential Giemsa staining has recently been explained by interactions between the hydrophobic dye complex, the supercoiled DNA helix, and the denaturated histone core of the nucleosomes.

Improvements in the premature chromosome condensation technique for cytogenetic analysis

In this paper we report a combination of procedures that serve to improve the usefulness of the technique of premature chromosome condensation in cytogenetic investigations. The mitotic inducer population was preincubated in high concentrations of BrdU, and the duration of fusion was increased to yield more discrete prematurely condensed chromosomes (PCC). After fusion, chromosome preparations were treated with a combination of G- or C-banding techniques and differential staining techniques. This combination of procedures allowed unequivocal distinction between the PCC and mitotic inducer chromosomes and yielded banded G1 and G2 PCC suitable for routine cytogenetic investigations.

Different reactivity of Z-DNA antibodies with human chromosomes modified by actinomycin D and 5-bromodeoxyuridine

Antibodies against Z-DNA react with fixed metaphase chromosomes of man and other mammals. Indirect immunofluorescence staining shows that chromosomal segments corresponding to R- and T-bands preferentially fix Z-DNA antibodies. In this work Z-DNA antibodies were used as a probe for DNA conformation in euchromatin of fixed human chromosomes whose condensation or staining were modified by actinomycin D (AMD) and by 5-bromodeoxyuridine (BrdU). Treatments with AMD and BrdU were performed to induce a G-banding by modification of chromosomal segments corresponding to R- and T-bands. Long BrdU treatments were used to induce asymmetrical and partially undercondensed chromosomes by substitution of thymidine in one or both DNA strand. Our results show a clear difference of Z-DNA antibodies reactivity after AMD or BrdU treatment. The G-banding obtained after AMD treatment is not reversed by Z-DNA antibodies staining since these antibodies bind very weakly to the undercondensed R-bands. On the other hand, the G-banding obtained by BrdU is completely reversed giving typical R-banding, as on untreated chromosomes. For asymmetrical chromosomes an R-, T-banding pattern is always observed but there is a decrease of the fluorescence intensity proportional to the degree of BrdU incorporation. We conclude that AMD treatment greatly disturbs Z-DNA antibodies binding suggesting a change in DNA conformation, whereas BrdU treatments do not suppress but only weaken the specific binding of Z-DNA antibodies on R- and T-bands. The direct involvement of thymidine substitution in DNA sequences recognized by Z-DNA antibodies is discussed.

Actinomycin D effects on termite chromosomes: induction of high resolution banding patterns with silver staining in mitotic stages

The treatment of termite male spermatogonia with actinomycin D induces highly elongated and finely banded late prophase and prometaphase chromosomes as evidenced by the silver staining method. Actinomycin D suppresses the silver staining of nucleolar organizing regions in prometaphase and reduces it in metaphase chromosomes.

Chromosome aberrations induced by 9-aminoacridine derivatives

The induction of chromosomal aberrations by 5 derivatives of nitro-9-aminoacridine in V79 Chinese hamster cells was observed. The clastogenic activity of the compounds tested depended on the position of the NO2 group in the acridine ring. The strongest clastogens were derivatives with NO2 in position 1. The remaining derivatives placed in decreasing order of clastogenic activity were: 3-nitro, 4-nitro and 2-nitro. In addition, 2-nitro and 3-nitro derivatives produced hyperdiploid/polyploid metaphases.

The technique of premature chromosome condensation to study the leukemic process: review and speculations

The technique of premature chromosome condensation involves the fusion of mitotic cells with interphase cells resulting in the immediate condensation of the interphase chromatin into discrete chromosome units, the prematurely condensed chromosomes (PCC). The ability to visualize the interphase chromosomes of bone marrow and blood cells by this technique has proved useful in the study of human leukemia. This article describes how the PCC technique has been used to predict clinical outcome as well as gain insight into the biology of leukemia.

Evaluation of chromosomal diagnosis for hereditary adenomatosis of the colorectum

Hereditary adenomatosis, particularly familial polyposis coli (FPC) and Gardner's syndrome (GS), has been investigated from family pedigrees and chromosomal markers for precancer and cancer. FPC and GS are much alike in phenotypes. Studies are in progress to determine if the two adenomatous diseases are controlled by the same DNA sequence. Chromosome numerical and structural instability is a good diagnostic criterion for hereditary adenomatous diseases where risk factors are already determined to the level of 0.5 probability from pedigree analysis. This has been applied successfully at the pediatric age level to identify family members who carry the gene but have no adenomas in the colorectum. Sister chromatid exchange (SCE) did not distinguish plasma samples from FPC, GS, or solitary adenoma patients form each other or from controls with no adenomas. SCE did distinguish invasive from recurrent and noninvasive cancer. The chromosome #2 polymorphism observed at 2q-21.3 has not been confirmed as a deletion, but is under investigation with more refined methods.

Clastogenic action of a dimethyl p-benzoquinone of animal origin

The cytogenetic action of a volatile dimethyl p-benzoquinone found in the natural secretion of an arachnid (Acanthopachylus aculeatus Kirby) was studied in cultured human peripheral leukocytes and in mouse bone-marrow cells. Continuous and pulse treatments carried out in vitro, as well as experiments performed in vivo, induced different chromatid and chromosome aberrations suggesting that this chemical has clastogenic properties. The biology of the animal and the possible role of one of the components of its secretion as a natural mutagenic agent are discussed.

Numerical and structural chromosome aberrations in cultured lymphocytes and cutaneous fibroblasts of patients with multiple adenomas of the colorectum

Excessive random loss and gain of simple chromosomes at the diploid and tetraploid levels, and numerous chromosomal aberrations, have been observed in lymphocytes and fibroblasts, cultured from Gardner syndrome and familial polyposis coli patients and children at risk for multiple adenomas. This increase in numerical and structural aberrations seems to represent a general instability of chromosomes in the lymphocyte and fibroblast nuclei of patients with multiple adenomas in the colorectum. A consistent heteromorphism of chromosome No. 2 homologous tentatively identified as a deletion was observed in all 17 patients with multiple adenomas in the colorectum, and two younger people of 13 and six years of age who are at risk for Gardner syndrome but do not have colorectal polyps. The chromosome No. 2 aberration was not observed in two symptomatic patients with occasional discrete colorectal adenomas.Eighteen controls who did not have Gardner syndrome nor familial polyposis coli did not show the structural aberration in chromosome No. 2 nor chromosome instability.

Effects of the antibiotic netropsin on mouse ascites tumour chromosomes in vitro

The antibiotic netropsin was found to induce an increase of the aberration frequency of up to 10% and a decondensation and elongation of centromeric regions of the chromosomes in mouse ascites tumour cells cultivated in vitro.

Cytogenetic effect of some anti-tuberculosis drugs in vitro

The comparative cytogenetic effects of some widely used anti-tuberculosis drugs (PAS Na, PRA, RMA) were estimated depending on the in vitro administered concentrations, in human peripheral blood cultures. The structural chromosomal lesions were randomly distributed between the different chromosome groups of the human karyotype; nearly 10 to 30% of affected cells had more than one lesion per metaphase. In the treatements with PAS Na and PRA the analysis of the frequencies of the cell carring chromosomal aberrations and of the chromosomal lesion types indicated a dose-response correlation. The significance of the results obtained in vitro on the chromosome-breaking effects of anti-tuberculosis agents and the genetic peril is pointed out.

Characterization of Drosophila heterochromatin. I. Staining and decondensation with Hoechst 33258 and quinacrine

A number of preliminary experiments have shown that the fluorescence pattern of Hoechst 33258, as opposed to that of quinacrine, varies with the concentration of dye. The metaphase chromosomes of D. melanogaster, D. simulans, D. virilis, D. texana, D. hydei and D. ezoana have therefore been stained with two concentrations of H 33258 (0.05 and 0.5 mug/ml in phosphate buffer at pH 7) and with a single concentration of quinacrine (0.5% in absolute alcohol). The three fluorescence patterns so obtained were shown to be somewhat different in some of the species and the coincide in others. All three stainings gave an excellent longitudinal differentiation of heterochromatin while euchromatin fluoresced homogeneously. Living ganglion cells of the six species mentioned above were treated with quinacrine and H 33258. Quinacrine induced a generalized lengthening and swelling of the chromosomes and H 33258 the decondensation of specific heterochromatic regions. A correlation of the base composition of the satellite DNAs contained in the heterochromatin of the species studied with the relative fluorescence and decondensation patterns showed that: 1) the extremely fluorochrome bright areas and those decondensed are present only in species containing AT rich satellite DNA; 2) the opposite is not true since some AT-rich satellite DNAs are neither fluorochrome bright nor decondensed; 3) there is no good correspondence between Hoechst bright areas and the decondensed ones. AT richness therefore appears to be a necessary but not sufficient condition both for bright fluorescence and decondensation. Some cytological evidence suggests that similarly AT rich satellite DNAs respond differently in fluorescence and decondensation because they are bound to different chromosomal proteins. A combination of the results of fluorescence and decondensation revealed at least 14 types of heterochromatin; 4-7 of which are simultaneously present in the same species. Since closely related species (i.e. D. melanogaster and D. simulans; D. virilis and D. texana) show marked differences in the heterochromatic types they contain, it can be suggested that within the genus Drosophila qualitative variations of heterochromatin have played an important role in speciation.

Laser microbeam irradiation of rat kangaroo cells (PTK2) following selective sensitization with bromodeoxyuridine and ethidium bromide

Ethidium bromide (10 mug/ml) and bromodeoxyuridine (25 mug/ml) were used to sensitize selective cell organelles to visible wavelengths of an argon ion laser (488 and 514 nanometers). Ethidium bromide was shown to be selective in sensitizing nucleoli, chromosomes, and the centriolar region of PTK2 cells to the laser microbeam. Similarly, BrDU sensitized chromosomes to the microbeam irradiation. The lesions produced on the chromosomes when either agent was used appeared as a phase paling of the irradiated segment. Nucleolar lesions also appeared as a phase paling, and the centriolar region alteration appeared either as a phase paling or a phase darkening.

An in vivo giemsa chromosome banding technique

An in vivo chromosome banding technique has been developed. Swiss albino mice were injected with the DNA alkylating agents ethyl methanesulfonate, methyl methanesulfonate, or methyl ethanesulfonate 12, 24, 48 or 72 hours prior to cell harvesting. After harvesting, the cells were fixed with 3:1 methanol-acetic acid and slides were prepared by air drying. The slides were stained 2 1/2 minutes in 3% Giemsa in pH 6.8 Sorensen's buffer. All three alkylating agents induced chromosome bands similar to the Giemsa bands induced by other banding techniques which involve postfixation treatments.

Differential fluorescent staining of human chromosomes with daunomycin and adriamycin--the d-bands

Human chromosome preparations were treated with a group of anthracycline antibiotics. Well-defined, orange-red fluorescent bands were observed on chromosomes after the slide was stained with daunomycin and adriamycin but not with nogalamycin. The characteristic differential bands appeared to be similar to the banding patterns obtained by the quinacrine techniques. Interaction of these antibiotics with DNA could provide information on the general mechanism of fluorescent banding. Further, these bands (D-bands) appeared to be more stable than the Q-bands and may have some usefulness for routine clinical cytogenetic analysis.

Actinomycin D effects on mitosis and chromosomes: sticky chromatids and localized lesions

When Indian muntjac and Chinese hamster cells in culture were treated with Actinomycin D (1 micron/ml) for 1-2 hours, the sister chromatids, especially the distal segments, appeared to have difficulty separating in anaphase. The separated proximal segments progressively became stretched. The nucleolus organizer regions seemed to be most susceptible to stretching, and breaks in these regions were frequently observed. Electron microscopic observations showed that the sticky chromatids (and less frequently sticky chromosomes) contain connecting submicroscopic chromosome strands. When the treated cells were allowed to grow in a drug-free medium for several days, a high frequency of endoreduplicated mitotic figures was found. Chromosome and chromatid breaks and other aberrations were common, mainly localized at G band negative areas particularly nucleolus organizer regions.

Chromosome bands induced in human and Syrian hamster cells by chemical carcinogens

After 24 hours of treatment of human peripheral leucocyte cultures or Syrian hamster embryonic secondary cultures with some known chemical carcinogens at concentrations that produce transformation in vitro of hamster cells, the chromosomes of both types of cells exhibited typical G banding. Chromosome bands did not result with urethane, a compound which does not produce cytotoxicity or cause transformation by direct exposure of cells. Non-carcinogenic chemicals which do not inhibit cell multiplication also failed to produce bands. Cytogenetic analysis following removal of the carcinogens from the cultures indicated non-banded uniformly stained chromosomes. It is concluded that metaphases with chromosome bands are more likely to be the result of nonspecific toxicity rather than being related to the carcinogenic properties of the chemicals.