Durch Seitenwurzelbildung induzierte und spontane Mitosen in den Dauergeweben der Wurzel

Ohne ZusammenfassungDie wesentlichen Untersuchungsergebnisse wurden im Rahmen einer Doktorarbeit am Botanischen Institut der Universität Wien gewonnen. Für Anregung und förderliche Kritik danken wir Herrn Prof. Dr. L.Geitler bestens.     

Spontane und induzierte Polyploidie bei Reben

Ohne Zusammenfassung     

Direkt induzierte Farbanpassungen und deren Vererbung

Ohne ZusammenfassungMit Tafel III, IV, V.     

Das Problem der Genomsonderung in den Mitosen unbehandelter Rattenlebern

Ohne Zusammenfassung     

Die Verteilung der Chromosomen auf die Tochterzellkerne multipolarer Mitosen in euploiden Gewebekulturen von Microtus agrestis

In kidney epithelial cultures from female Microtus agrestis, 3,55% of all mitoses are multipolar, 94% of them tripolar. Feulgen photometric measurements of 21 tripolar mitoses reveal a total DNA amount corresponding to the mitotic diploid value (4c) in 5 cases, and to the tetraploid value (8c) in 16 cases, Diploid tripolar mitoses divide into one daughter nucleus with a diploid DNA value (2c) and two nuclei each with a haploid DNA value (1c). Most tetraploid tripolar mitoses divide into one daughter nucleus with a diploid DNA value (2c) and two nuclei with a triploid DNA value (3c). Also the sex chromosomes are distributed to the daughter nuclei in the relation of 2∶3∶3. This can be seen in anaphase figures as well as in interphase nuclei presumably derived from tripolar mitoses, showing chromocenters according to the number of X-chromosomes. In two cases of tripolar tetraploid mitoses the resulting nuclei have a haploid, a triploid and a tetraploid DNA value. The DNA replication pattern is always identical in the daughter nuclei of diploid and tetraploid tripolar mitoses. — Our observations suggest segregation and distribution of haploid chromosome sets or multiples of haploid sets to the daughter nuclei of multipolar mitoses. They also show a possible way of formation of haploid and triploid cells in a basically diploid tissue. Presumably triploid nuclei (with 3 chromocenters) are capable of DNA synthesis.     

ATP und Ca2+ induzierte actomyosinartige Kontraktion glycerinisierter Makronuklei

Summary The addition of 2 mM-3 mM ATP to macronuclei ofParamecium bursaria suspended in a glycerol buffer medium causes a decrease in their volume up to 23% within 3 minutes. The infiltration medium must not only contain Ca²⁺, but must also be of low ionic strength for ATP to be effective. A slow, careful exchange of the glycerol medium for the contraction solution is also necessary. Ca²⁺ present alone in the standard contraction buffer can likewise induce a limited volume decrease; in the presence of low concentrations of Ca²⁺, Mg²⁺ shows no detectable effect on glycerinated nuclei. When the nuclear volume has been reduced by ATP in the presence of Ca²⁺, the addition of EGTA induces a reexpansion of the nuclei. Salyrgan, an organic mercurial, either prevents or abolishes the ATP-induced contraction. Other nucleotide triphosphates such as guanosine triphosphate (GTP), inosine triphosphate (ITP) or uridine triphosphate (UTP) likewise induce a volume decrease of the glycerinated macronuclei, but to a distinctly lesser extent than ATP.The results indicate that the volume decrease caused by the ATP-contraction solution is not a passive osmotic process. The resemblance to actomyosin contractions suggests that the volume decrease reported here might also be the result of the reaction of nuclear actomyosin and ATP.