Effect of Maternal Age on DNA and RNA Content of <Emphasis Type="Italic">Drosophila</Emphasis> Eggs

THE influence of maternal age on the characteristics of offspring may appear quite early where egg size and the time of first larval hatching are concerned^1–4. We have therefore investigated the DNA and RNA content of eggs produced by ageing Drosophila melanogaster females (Nettlebed inbred strain). We used virgin eggs, which do not degenerate even several hours after laying⁵ and which therefore do not require immediate collection. We have measured DNA content by a fluorometric technique⁶ and RNA content by the orcinol method.     

Primary Structure of Lysozymes from Man and Goose

The primary structure of goose egg white lysozyme seems to be distinct from that of hen egg white and human leukaemia lysozymes.     

The histones of the ciliated protozoan Stylonychia mytilus

Histones were extracted from pure macronuclei, micronuclei and macronucleus anlagen and from chromatin which was isolated from these different nuclear fractions. Analysis of these preparations by polyacrylamide gel electrophoresis showed differences in electrophoretic patterns between the histones of these nuclei.     

Photochemical disproportionation of sulfur into sulfide and sulfate byChlorobium limicola formathiosulfatophilum

The anaerobic bacteriumChlorobium assimilates carbon dioxide in the light with various sulfur compounds as electron donors. The well-known metabolic pathway proceeds from the oxidation of sulfide via sulfur to sulfate. In the dark the reaction is partially reversed when sulfur is reduced to hydrogen sulfide. The fermenting cells thereby release an excess of reductant. We have now found a hydrogen sulfide production from sulfur, which is light-dependent. It is more than ten times faster than the dark reaction. This appears in experiments where the cell suspension is illuminated in absence of CO₂ and flushed continuously with H₂ or Ar. The H₂S is trapped with ZnCl₂ and the S^2- titrated with iodine. The total amount of H₂S evolved in the light increases proportionally with the amount of sulfur added, and about one-half of the added sulfur is converted to H₂S. Another part of the metabolized sulfur appears at the same time as sulfate, but all the sulfur oxidized to sulfate does not account for the larger amount of sulfur reduced to hydrogen sulfide. Very likely other unanalyzed oxidized sulfur compounds must also have been produced. Use of H₂ instead of Ar as the anaerobic gas phase does not increase the amount of H₂S produced, nor does the addition of thiosulfate; sulfur itself is the preferred electron donor for the sulfur reduction. Up to a light intensity of 10000 ergs cm^-2sec^-1 CO₂ does not affect H₂S production. Without CO₂, saturation of the light-dependent evolution of H₂S is reached at about 40000 ergs cm^-2sec^-1. In contrast, presence of CO₂ at this light intensity makes the sulfide production disappear completely. On application of mass spectrometry to the gas exchange upon illumination, at high light intensity a H₂S gush is found during the first 3 min. This is followed by CO₂ fixation, while simultaneously the reductant H₂S is now taken up. WithRhodospirillum rubrum, the addition of sulfur leads to a moderate evolution of H₂S. In contrast toChlorobium this reaction inR. rubrum is not light-sensitive, nor does it produce detectable amounts of sulfate. After addition of malate the rate of H₂S evolution does increase in the light, since the cells use malate as an electron donor during their photochemical metabolism.