Effects of light intensity on membrane differentiation in Rhodopseudomonas capsulata

Cells of Rhodopseudomonas capsulata, strain 37b4, leu-, precultivated anaerobically under low light intensity, were exposed to high light intensity (2000 W.m-2). The cells grew with a mass doubling time of 3 h. The synthesis of bacteriochlorophyll (BChl) began after two doublings of cell mass. Reaction center and light-harvesting BChl I (B-875) were the main constituents of the photosynthetic apparatus incorporated into the membrane. The size of the photosynthetic unit (total BChl/reaction center) decreased and light-harvesting BChl I became the dominating BChl species. Concomitant with the appearance of the different spectral forms of BChl the respective proteins were incorporated into the membrane, i.e. the three reaction center polypeptides, the polypeptide associated with light-harvesting BChl I, the two polypeptides associated with BChl II. A polypeptide of an apparent molecular weight of 45 000 was also incorporated. A lowering of the light intensity to 7 W.m-2 resulted in a lag phase of growth for 6 h. Afterwards, the time for doubling of cell mass was 11 h. The concentration of all three BChl complexes (reaction center, light-harvesting BChl I and II complexes)/cell and per membrane protein increased immediately. Also the size of the photosynthetic unit and the amount of intracytoplasmic membranes/cell increased. The activities of photophosphorylation, succinate dehydrogenase, NADH dehydrogenase and NADH oxidation (respiratory chain)/membrane protein are higher in membrane preparations isolated from cells grown at high light intensities than in such preparations from cells grown at low light intensities.

[Transferrin types in the Dama (Southwest Africa)]

The transferrin type of 238 Dama serums was determined and an estimate made of the gene frequencies. Using the SANGHVI method, the distribution of the transferrin types of the Dama was compared with 53 African populations south of the Sahara. The comparison demonstrates the great dissimilarity of the Dama to the Khoisanide tribes and confirms--at least in part--the results of polysymptomatic affinity comparisons of the Dama with other African populations.

[Morphological studies of the virus etiology of hepatosplenitis infectiosa strigum]

Das Virus der Hepatosplenitis infectiosa strigum (HSiS) wurde elektronen-optisch in verschiedenen Organen einer experimentell infizierten Waldohreule und mehrerer als Kulturmedium für das Virus verwendeter Hühnerembryonen nachgewiesen. Seine Entwicklung beginnt im Kern von Retikulum- und Leber-zellen mit der Bildung eines Nukleoids. Noch innerhalb des Zellkernes wird um dieses herum eine erste Schale (Capsid) gebildet. In diesem Stadium wird das Virus aus dem Zellkern in den perinukleären Raum ausgeschleust und erhält dabei eine von der inneren Kernmembran abstammende zweite Schale (Envelope oder Aussenhülle). Das ausgereifte durchschnittlich 140 mμ grosse Virus findet sich im Zytoplasma meist innerhalb von Vakuolen lagernd. Ein elektronenoptisches Äquivalent für die lichtoptisch nachweisbaren Kerneinschlusskörperchen vom Typ A nach Cowdry war nicht sicher nachweisbar. Die hierfür in Frage kommen-den Gründe werden ausführlich diskutiert. Wenn auch auf Grund der angestellten morphologischen Untersuchungen eine Klassifizierung des Virus nicht vorgenommen werden kann, sprechen die erhobenen Befunde doch am ehesten für seine Zugehörigkeit zur Herpes-Gruppe.