High levels of transition metals in dinoflagellate chromosomes

Summary X-ray microanalysis of fixed, sectioned chromosomes of the dinoflagellatesGlenodinium foliaceum, Prorocentrum micans andAmphidinium carterae has revealed high levels of iron, nickel, copper and zinc. We report high levels of these transition metals in association with chromosomes in intact eukaryote cells.L.P.K. gratefully acknowledges the financial support of the SRC.     

Chromatin ofh regions of human chromosomes at high resolution

Summary Segmentation of the secondary constriction region (h) of human chromosomes 1, 9 and 16 is demonstrated by a high resolution banding technique. Based on these staining properties, it is suggested that the composition of theh region in human chromosomes is heterochromatic as well as euchromatic.     

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.     

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.     

Adriamycin-induced chromosome damage: elevated frequencies of isochromatid aberrations in G2 and S phases.

Analysis of chromosomes from cells treated with adriamycin during G2 and S phases showed a high frequency of isochromatid-type of breaks, in addition to the expected chromatid breaks. These are interpreted as independent breaks on sister chromatids because of preferential effects of the drug in specific chromosome regions. The break points are likely to be different, but morphologically such breaks would be indistinguishable from isochromatid or chromosome breaks.     

Larvale und imaginale Mitteldarmchromosomen vonDrosophila repleta

Summary In certain tissues ofD. repleta-flies, it is possible to observe the interphase chromosomes that are either of larval origin or that occur in imaginal tissues. The imaginal interphase chromosomes from the midgut are similar to the small larval midgut chromosomes in the early phases of their development.     

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.     

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.     

Variation in chromosome number in the sheep headflyHydrotaea irritans (Fallen) (Diptera: Muscidae)

Summary Variation in the number of chromosomes was found in sheep headflies, ranging from 12 to 15 chromosomes. Of these, five pairs were common among all individuals. Among 9 larvae no males were identified.     

Bau und Funktion der Nukleolen

Summary In previous years the composition and function of chromosomes have been analyzed to a considerable extent, in contrast to the small number of investigations that have been made on nucleoli. There exist at present many conflicting opinions about the structure and function of the nucleolus, and therefore a critical survey of the facts and theories about the nucleolar substance appears necessary.The structure, chemical composition and metabolism of the nucleoli of various cells are described in this publication. The regulation of the size and function of the nucleolus is also discussed.It is concluded that the size and structure of the nucleolus is organ- and species-specific. A rapid synthesis of RNA and proteins occurs in the nucleolus. After a short interval, this disappears; and it is therefore concluded that the nucleolus must have a high turnover of these substances. The size and function of the nucleoli depends on the energy state of the cytoplasm.It appears that the nucleolus can synthesize proteins which can be utilized by the chromosomes during their genetic function.     

Spontaneous robertsonian fusion leading to karyotype variation in the house mouse — First report from Asia

Summary The occurrence of spontaneous Robertsonian fusion leading to 2n=39 chromosomes (NF=40) in the house mouse (Mus musculus domesticus) has been reported for the first time from Asia. 3 phenotypically normal female mice collected from 2 distantly located populations of India (Tripura and Calcutta) show centric fusion in somatic chromosomes between pairs 2 and 16, and 8 and 14 respectively. C-banding analysis revealed that the (sub) metacentric has been originated by fusion between the broken/eroded centromeres of 2 telocentric chromosomes.     

Trends of karyological evolution in Pelobatoid frogs

Summary The Pelobatids have a basal karyotype of 26 chromosomes, with 6 pairs of large and 7 of small chromosomes (6+7). From this karyotype, shown byLeptobrachium, Pelobates andScaphiopus, those ofMegophrys andSpea (5+8) may be derived, as well as that ofL. pelodytoides, with only 24 chromosomes.Pelodytes has 24 chromosomes and a karyotype 7+5 differing from that of typical Pelobatids under several respects.Research supported by a contribution from the Italian C. N. R.     

Possible target of Abelson virus phosphokinase in cell transformation

By fusing interphase cells to cells undergoing mitosis, the interphase chromosomes can be visualized. When analyzed in this way, chromosomes of normal mouse cells show characteristic undercondensed centromeric regions. We have found that the centromeric regions of chromosomes from Abelson virus-transformed cells are fully condensed. Abelson virus transforms mouse cells by introducing into them a virally encoded phosphokinase that is expressed constitutively. Thus, we propose that the condensation of centromeric chromatin is a result of overphosphorylation by the Abelson virus phosphokinase, and that the centromeric region is the relevant target of overphosphorylation in transformed cell growth.     

A simple one-step procedure for staining the nucleolus organizer regions.

A simple silver staining technique for routine use is described by which the nucleolus organizer regions of mammalian chromosomes, including those of mouse chromosomes, are stained selectively.     

Supernumerary chromosomes in Drosophila nasuta albomicana

Supernumerary chromosomes have been detected in the karyotype of D.n.albomicana. Their number varies from one to three. They are the smallest elements in the karyotype. Karyotypes of D.n.albomicana with and without supernumerary chromosomes have been presented.     

Age-G staining, a rapid technique for producing combined silver staining and Giemsa banding in mammalian chromosomes

A combination of the silver staining method with a Giemsa banding technique is described for mammalian chromosomes. This double staining simultaneously shows silver-stained NORs and a G-band pattern, and thus allows a rapid identification of the NOR-bearing chromosomes.     

The mitotic chromosomes of the lampreyMordacia mordax (agnatha: Petromyzonidae)

Résumé L'étude des chromosomes somatiques de la lamproie de l'hémisphère sud,Mordacia mordax (Richardson), montre que l'équipement chromosomique diploïde de cette espèce est composé de 76 chromosomes très petits. La plupart des chromosomes sont métacentrique ou bien submétacentrique. Ces chromosomes sont différents en nombre de ceux décrits pour les lamproies de l'hémisphère nord.     

Ag-G staining,a rapid technique for producing combined silver staining and Giemsa banding in mammalian chromosomes

Summary A combination of the silver staining method with a Giemsa banding technique is described for mammalian chromosomes. This double staining simultaneously shows silver-stained NORs and a G-band pattern, and thus allows a rapid identification of the NOR-bearing chromosomes.     

Additional chromosome duplication in female meiotic prophase ofSipyloidea sipylus Westwood (Insecta,Phasmida), and its absence in male meiosis

Summary In the parthenogenetic stick insectSipyloidea sipylus, an additional chromosome duplication takes place in the primary oocytes immediately after pachytene. After duplication, the chromosomes again appear in a pachytene configuration, and oogenesis proceeds with twice the somatic number of chromosomes. Additional duplication does not occur during prophase of primary spermatocytes.     

Karyotype of the Japanese salamander,Hynobius abei

Summary A primitive representative of the Caudata endemic to Japan,Hynobius abei Sato (Caudata: Hynobiidae) has 2n=56 chromosomes, with 9 large, 4 medium and 15 small-sized homologous pairs. The morphology of the large-sized chromosomes is similar to that of the knownHynobius species, but the presence of a pair of acrocentrics in the medium-sized group and 5 pairs of biarmed chromosomes in the small-sized group characterized the karyotype ofH. abei.We thank A. Itoi, S. Segawa, K. Ban, T. Hikida and O. Murakami for their assistance in collecting specimens.