Induction of uncoiled chromosomes by vibration

Summary Chromatin condensation during metaphase can be removed by simple vibration of metaphase cells prior to fixation. Uncoiled chromosome arms consist of long threads with dense regions at irregular distances each from the other.Acknowledgment. This work is supported by the Hellenic Anticancer Institute.     

C-band differentiation between the chromosomes of two subspecies of the chironomid midge Chironomus thummi

The metaphase chromosomes of Chironomus th. thummi contain approximately 17% more pericentric C-band heterochromatin than the chromosomes of Chironomus th. piger with 11% heterochromatin. In Ch. th. thummi, the proportion of heterochromatin appeared to be much larger in metaphase chromosomes than in polytene chromosomes. This discrepancy is interpreted as being due to the specific chromosome organization and not as the result of an underreplication of heterochromatin during polytenization.     

Increased incidence of unpartnered single chromatids in metaphase II oocytes in 39,X(XO) mice

Since rare cases of sex chromosome anomalies such as XXX and XXY were observed in the offspring of our XO breeder mice, we performed a cytogenetic analysis of metaphase II oocytes of XO mice to determine whether any changes in chromosomal configurations occur. We found a significantly increased incidence of unpartnered single chromatids in metaphase II oocytes of XO mice. Such single chromatids may contribute to embryonic aneuploidy. In addition, the tendency of the X-chromosome to segregate non-randomly to the oocyte rather than to the polar body was confirmed.     

C-band differentiation between the chromosomes of two subspecies of the chironomid midgeChironomus thummi

Summary The metaphase chromosomes ofChironomus th. thummi contain approximately 17% more pericentric C-band heterochromatin than the chromosomes ofChironomus th. piger with 11% heterochromatin. InCh. th. thummi, the proportion of heterochromatin appeared to be much larger in metaphase chromosomes than in polytene chromosomes. This discrepancy is interpreted as being due to the specific chromosome organization and not as the result of an underreplication of heterochromatin during polytenization.     

Position of the Y-chromosome at somatic metaphase in patients with chronic myelogenous leukemia (CML)

Summary A random distribution of the Y-chromosome at somatic metaphase was found in 50 patients with Ph' positive chronic myelogenous leukemia (CML). Thus, it is concluded that the positive of the Y-chromosome at somatic metaphase does not appear to influence the loss from bone marrow cells.     

Die Genomsonderung in den Mitosen der Rattenleber

Summary Model squashes with gelatine cubes containing 8 files like the chromosomes ofBellevalia romana (2n=8) showed the chromosomes only in groupings that correspond to the original position of metaphase chromosomes. The metaphase chromosomes in root tip cells ofBellevalia romana are arranged at random; there is neither somatic pairing nor genome segregation (= grouping of metaphase chromosomes into two complete chromosome sets). In contradiction to these results, the chromosomes in the regenerating liver cells (2n=42) show a certain precentage of grouping into complete genomes. It is concluded that in rat liver cells a mechanism exists which, starting with the genome segregation, may produce a change in chromosome number. Thus these same euploid or aneuploid chromosome numbers can be explained which are really observed in normal and treated rat liver. 4 possibilities of such mechanism are discussed.

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Nach einem Vortrag, gehalten anlässlich des IV. Symposium histologicum internationale Lausanne (Suisse), 5.–8. September 1961.     

Supercontraction of conifer chromosomes under the action of alkylating nitrosocompounds

Summary After treatment of seeds of the Norway spruce and of the Scotch pine with alkylating nitrosocompounds, an extremely strong contraction effect on mitotic metaphase chromosomes was observed in the first cell-cycles of the posttreatment period.     

Increased silver stainability of metaphase chromosomes from rat hepatocytes during in vivo hepatocarcinogenesis

Summary Silver stainability of metaphase chromosomes was studied in hepatocytes obtained from rats exposed or not to a partial or complete carcinogenic treatment with diethylnitrosamine and phenobarbital. An increased hyperstaining is reported in the carcinogen-treated animals.     

Feulgen-DNA amounts and karyotype lengths of three planarian species of the genusDugesia

Summary Genome sizes of the planariansD. lugubris (2n=8),D. polychroa (2n=8) andD. benazzii (2n=16) were evaluated on metaphase plates by measuring both the Feulgen-DNA contents and the karyotype lengths. In the three species, genome sizes are significantly different; this finding rules out the possibility of a karyotype evolution through simple chromosome rearrangements betweenD. lugubris andD. polychroa. A different Feulgen-DNA content per unit length of karyotype in the three species studied was also found, which suggests that DNA could be differently packed along metaphase chromosomes.     

Increased silver stainability of metaphase chromosomes from rat hepatocytes during in vivo hepatocarcinogenesis

Silver stainability of metaphase chromosomes was studied in hepatocytes obtained from rats exposed or not to a partial or complete carcinogenic treatment with diethylnitrosamine and phenobarbital. An increased hyperstaining is reported in the carcinogen-treated animals.     

Mitostatic action of 4,6-dimethyl-2-amino-3,4,5-trimethoxyphenyl-pyrimidine on mammalian cells

Summary 4, 6 dimethyl-2-amino-3, 4, 5-trimethoxyphenylpyrimidine arrests the mitotic cycle of mammalian cells in metaphase, both in vitro and in vivo. The mitostatic effect is promptly reverted by interruption of drug treatment.     

The differential banding pattern produced by Actinomycin-D/Acridine-Orange counterstaining in metaphase chromosomes ofDrosophila melanogaster

Summary A longitudinal differentiation is found in fixed metaphase chromosomes ofDrosophila melanogaster after treatment with Actinomycin-D and subsequent Acridine-Orange staining. We postulate that our findings are strictly related to the presence of AT-rich DNA in specific chromosomal areas of this species.     

An ammoniacal silver staining technique for mitotic chromosomes ofTriturus (Urodela: Salamandridae)

Summary An ammoniacal silver staining technique was applied to mitotic metaphase chromosomes of 2 species of Newts (Triturus). The method is useful for identifying nucleolar organizer regions. In addition, it reveals other sites of unknown significance.With financial support of the Consiglio Nazionale delle Ricerche, Rome.     

Réarrangements chromosomiques induits par les rayons X chez les Souris de race AKR/Tr

Summary A spontaneous translocated strain of mice (AKR/Tr.) with 36 acrocentric and 2 metacentric chromosomes received 400 R of whole-body X-irradiation. Cytological examination of dividing primary spermatocytes at the diakinesis-first metaphase stage of meiosis showed 6% of cells with chromosomal rearrangements.     

Giemsa centromere staining ofHumulus lupulus L. Metaphase chromosomes

Summary Giemsa staining of hop (Humulus lupulus L.) chromosomes at metaphase revealed kinetochore-like structures in the centromeric region.The authors are grateful to Dr C. K. Atal, for his keen interest and constant encouragement in the present study.     

High resolution of heterochromatin of Drosophila melanogaster by distamycin A

A DNA-binding AT-specific antibiotic, distamycin A, was used as inhibitor of the condensation process of the heterochromatic regions in Drosophila melanogaster embryonic cells. By this treatment the structural organization of heterochromatin at interphase is preserved until metaphase. The different patterns observed are interpreted as chronological steps in the condensation process.     

Acetaldehyde induces mature endoreduplicatedAllium cepa root cells to divide

Summary InAllium cepa root tips treated with acetaldehyde, metaphase cells showing diplochromosomes are occasionally observed. The short treatment time excludes the possibility that the endoreduplication has been induced by the chemical. Instead, it seems that acetaldehyde is able to stimulate, directly or indirectly, the division of mature cells previously endoreduplicated.     

Methods for determining ploidy in amphibians: Nucleolar number and erythrocyte size

Summary Diploid and triploidXenopus can be easily and reliably distinguished by the size of their erythrocytes. This method has several advantages over other methods, such as counting metaphase chromosomes and counting nucleoli. One problem with the latter method is the reduction in cells with a full complement of nucleoli when regenerating tissue is used.Research supported by NIH grant EY 01662.     

A combination of sister chromatid differential staining and giemsa banding.

We report a procedure for combining sister chromatid differential staining and G banding in the same metaphase plate. Mammalian cells in culture are grown in medium containing 5-bromodeoxyuridine for two cell cycles, and conventional air-dried preparations are made. The slides are treated with a trypsin or a urea solution the same way as for regular G banding. This method is simple and fast and provides additional information for cytogeneticists.     

Ultrastructural identification of the nucleolus organizer by the silver staining technic]

The nucleolus organizer regions can be selectively stained in metaphase chromosome preparations by the Goodpasture and Bloom's technique which was adapted to electron microscopy analysis of cells during interphase. Using this technique, a selective accumulation of silver grains was observed over nucleolus light areas. This selective accumulation allows the identification of the interphase fibrillar centers as the nucleolus organizer regions. Ultrastructural relationships between fibrillar centers and dense fibrillar component are discussed.