ALBERT

Notes: Summary 1. Currently available data on chromosome elimination in Cecidomyiidae are still inadequate to support any definite conclusions regarding its immediate causes. It seems that some evidence on the mechanism of elimination could be obtained from observation of the behavior of E chromosomes in complete absence of spindle. To bring about such absence of spindle, ultraviolet microbeams would appear promising, since they have already been used to destroy spindles in cells of other organisms. 2. For irradiation the embryos of Rhabdophaga batatas Walsh were chosen. It was established that in this species 2 S+E=40 and 2 S (for female)=8. Elimination of 30-odd chromosomes regularly occurs in the fifth cleavage. Embryos were irradiated with 8μ and 16μ heterochromatic ultraviolet microbeams not only in this fifth cleavage but also in the fourth, in which elimination was never observed. The irradiated regions were small parts of somatic cytoplasm or small parts of germ cells. 3. The effects of irradiation were multifold: complete degeneration of nuclei in the vicinity of irradiated cytoplasm; disappearance of spindle and formation of quasi-rosettes; multipolar mitosis. The polar substance present in germ cells was often severely damaged and fragmented. All these effects are evidently indirect. 4. In mitoses thus deprived of spindles, the separation of chromosomes into daughter chromatids was suppressed but some of their active movements persisted. All chromosomes were gathered into a quasirosette, which afterwards divided into two quasi-rosettes. The daughter quasi-rosettes moved apart and formed telophase nuclei. In both irradiated divisions (fourth and fifth) E chromosomes behaved in exactly the same manner as S chromosomes; they showed the same kind of peculiar movement and were incorporated into telophase nuclei. Suppression of elimination of E chromosomes in the fifth division can be regarded as one more indirect effect of irradiation to be added to the list above. 5. These results show that elimination of E chromosomes does not result from failures in chromosomal spindle fibers or from intrinsic morphological defects in the centromeres. The fact that elimination can be suppressed by indirect action of ultraviolet light strongly supports the assumption that elimination occurs because of chemical changes in adjacent cytoplasm that are injurious to the centromeres of E chromosomes. Most probably the indirect action of ultraviolet interferes with the production of some substance that is normally injurious to the centromeres in the fifth division. 6. Since in Cecidomyiidae the general features of the metabolism are known to be stable up to the mid-blastoderm stage, it would appear that the chemical changes involved in elimination cleavage are probably quite specific.

Notes: Zusammenfassung Beryllium gibt mit Chromazurol S auf Filtrierpapier einen charakteristischen hellblauen Fleck. Der störende Einfluß anderer Kationen kann durch Zugabe von Oxalat und ÄDTA behoben werden. Es lassen sich noch 4,5μg Beryllium in 0,05 ml Lösung nachweisen. Bei zehnfachem Überschuß einiger Kationen wird die Empfindlichkeit der Reaktion verringert.

Notes: Zusammenfassung Aus einem Natriumaluminiumsilicat-Glas mit der Synthese-Zusammensetzung (Mol-%) 27% Na2O, 8% Al2O3 und 65% SiO2 (NAS 27-8) wurden Glaselektroden hergestellt, deren Eignung zur Indizierung der Kaliumtitration mit Zn[SiF6] in methanoliseher Lösung untersucht wurde. In reinen, schwach sauren Kaliumsalzlösungen erhält man gut auswertbare Titrationskurven. Die Glaselektrode versagt in stark saurer Lösung. Außer den Ionen, die mit Hexafluorosilicat schwerlösliche Salze bilden, stören auch Ca2+, Mg2+ und Al3+, die mit den im Gleichgewicht vorliegenden Fluoridionen reagieren.

Notes: Zusammenfassung Stark salzsaure Wolframatlösungen lassen sich mit Zinkstaub quantitativ zu WIII reduzieren. Auf dieser Grundlage wird ein schnelles und genaues volumetrisches Verfahren zur Wolframbestimmung entwickelt. Bei geeigneter Arbeitsweise ist die Ausschaltung des Luftsauerstoffes nicht erforderlich. Die Titration erfolgt mit Cer(IV)-sulfat.