Giemsa banding, quinacrine fluorescence and DNA-replication in chromosomes of cattle (Bos taurus)

Investigation of hycanthone binding to DNA in chromatin with different supra-organization, composition, and function

Hycanthone is a drug used for the clinical treatment of schistosomiasis, although inducing chromosomes breaks and mutagenesis when it enters the DNA double helix. Based on visual observation of characteristics of basophilia and anisotropy after toluidine blue staining, a preferential binding of hycanthone to heterochromatin could be demonstrated for the nuclei of the Malpighian tubules of Triatoma infestans. In other cellular systems like cattle kidney cells in culture, plant cells, and mouse lymphocytes, the drug could be demonstrated to bind heterochromatin and euchromatin, irrespective of the packing state of the latter. When penetrating the various heterochromatin types (with the exception of T. infestans), the drug induced a chromatin loosening that could favor incidence of chromatin breaks. The variation of hycanthone binding to DNA in different cell types is possibly related to differences in composition, stereo-arrangement and stability of the DNA-protein complexes involved.

C- and G-banding patterns and chromosomal morphology of some breeds of Australian cattle

A cytogenetical study using metaphase chromosomes from cultured lymphocytes, was made of 2 Banteng (Bibos banteng) steers and 218 bulls representing 13 purebreeds (Bos taurus type, Bos indicus type and Sanga) and 7 cross-breeds. Studies were made of photographic karyotypes of Giemsa stained and C-banded chromosomes of bulls of each breed and of B-banded chromosomes from 3 breeds of Bos indicus and one cross-breed Australian Friesian Sahiwal) cattle. The relative lengths of chromosomes of Bos taurus and Bos indicus bulls were compared and significant difference in relative lengths of the X chromosomes were noted between these two species. There was a differences in morphology of the Y chromosomes; Sanga, Banteng and Bos taurus type breeds had a small submetacentric Y chromosome, except for the Jersey which had a metacentric Y chromosome. All Bos indicus type bulls had an acrocentric Y chromosome but the Droughtmaster breed had two forms of the Y chromosome (submetacentric and acrocentric). The C-banding patterns of the autosomes and X chromosomes were similar for all breeds while those of the Y chromosomes of Bos indicus type cattle allowed their accurate identification. G-banding patterns of Bos indicus resembled those of Bos taurus and enabled pairing of homologous chromosomes. Centromeres of the autosomes were unstained but those of the sex chromosomes were darkly stained.

A Robertsonian translocation and its effect upon fertility in Brown Swiss cattle

Metaphase chromosomes derived from leukocyte cultures of peripheral blood were observed in 299 head of Brown Swiss cattle. A Robertsonian translocation (centric fusion) was found in 31 of the animals. Estimated from this small sample 2.4% of animals of the Brown Swiss breed carry the translocation. Chromosome measurements and analysis of G-banded chromosomes proved inconclusive in identification of the homologue to the short arm of the translocation chromosome. The long arm was homologous to the longest acrocentric autosome. By C-banding, a single, small area of centromeric constitutive heterochromatin on the translocation chromosome indicated a single centromere. The translocation in Brown Swiss may be homologous to the 1/29 Robertsonian translocation in many other breeds of cattle. The translocation chromosome appeared to have segregated normally from its homologues. Aneuploid karyotypes were not observed. Analyses of breeding data failed to detect any decrease in fertility of translocation heterozygous females as compared to females of the normal karyotype. It would be premature to recommend a selection program against this translocation in Brown Swiss, but widespread use of sires heterozygous for the translocation should not be encouraged.

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.

Mechanisms of chromosome banding. IX. Are variations in DNA base composition adequate to account for quinacrine, Hoechst 33258 and daunomycin banding?

Prior studies on subfractions of mouse and Kangaroo rat DNA have suggested that variations in base concentration within a given genome may not be great enough to account for Q-banding. To examine this with another species, calf DNA was subfractionated by CsCl ultracentrifugation into GC-rich satellites and the main band DNA was further fractionated into AT-rich, intermediate and GC-rich portions. The effect of varying concentrations of these DNAs on quinacrine and Hoechst 33258 fluorescence was examined. Although with both compounds there was less fluorescence in the presence of the GC-rich satellites than main band fractions, these results per se did not answer the question of whether the variation in base composition alone was adequate to account for chromosome banding. To answer this the fluorescence observed in the presence of DNA of a given base composition was related to the fluorescence observed in the presence of DNA of 40% GC content (F/F40). This allowed the derivation of a term B which indicated the relative change in fluorescence per 1% change in base composition of DNA. To determine the percent change in fluorescence observed in Q-banding, the photoelectric recordings of Caspersson et al. (1971) were used. From these data we conclude: 1. Quinacrine is twice as sensitive to changes in base composition as Hoechst 33258. 2. Variation in the base content of DNA along the base content of DNA along the chromosome is sufficient to account for most Q-banding, except possibly for some of the extremes of quinacrine fluorescence. This was further examined with daunomycin. Even though daunomycin gives good fluorescent banding, DNAs varying in base composition from 100 to 40% GC content all resulted in the same relative fluorescence of 0.03. However, in the presence of poly (dA-dT) the relative fluorescence was 0.85, indicating a great sensitivity to very AT-rich DNA. This suggests that with daunomycin and possibly other fluorochromes, stretches of very AT-rich DNA may be more important in fluorescent banding than simple variation in mean base composition.

5-methylcytosine in heterochromatic regions of chromosomes in Bovidae

The centromeric regions of cattle, goat and sheep chromosomes bind anti-5-MeC as revealed by immunofluorescence technique, indicating concentration of 5-MeC at these heterochromatic regions. The centromere of the submetacentric X of cattle remains nearly unstained and so do the centromeres of the acrocentric X chromosomes in goat and sheep. The short arm of the cattle Y exhibits strong anti-5-MeC binding whereas the tiny Y chromosomes of goat and sheep contain no brightly fluorescent material.

[Simple chromosome banding technique for farm animal investigations]

For routine cytogenetic investigations, a simple banding technique on chromosomes is described. Used on different cell material, a visible banding appearance is produced which makes the typing of chromosomes precise and fast. On 2 examples of cattle and rabbit chromosomes, the identification of a centric fusion and a trisomic is shown.

Giemsa banding of the chromosomes of the domestic sheep (Ovis aries)

A Giemsa banding procedure was used to construct a basic G-band idiogram for the domestic sheep. The idiogram is labelled in a systematic manner according to the routine recommended for human chromosomes. This pattern based on NaOH treatment, provides a standard of comparison for further studies on intra- and interspecific chromosome homologies in addition to identification of chromosomal abnormalities.Late replicating regions of chromosomal DNA were detected with tritiated thymidine. Partial homologies between G-bands and these late replicating areas were found. Previously reported areas of prevalent secondary constrictions were seen to coincide with late replicating, G-positive regions on the metacentric and X chromosomes.