A Note on the Separation of Natural Mixtures of Bacterial Ubiquinones using Reverse-phase Partition Thin-layer Chromatography and High Performance Liquid Chromatography

Natural mixtures of bacterial ubiquinones (coenzyme Q) were separated according to the length of the polyisoprenyl side-chain using reverse-phase thin-layer chromatography and high performance liquid chromatography. The chromatographic systems described afford a rapid and sensitive means of ubiquinone characterization.     

Effects of Exogenous Thyroxine on Statolith Synthesis and Resorption in Aurelia

Aurelia ephyrae which were maintained in thyroxine during theirmetamorphosis from the polyp state and another group of ephyraewhich were in thyroxine forfour and eight days of starvation,had significantly reduced numbers of statoliths as comparedwith control ephyrae in equimolar concentrations of iodine andin artificial sea water. We conclude, therefore, that thyroxinesignificantly affects the mineralization and demineralizationof statocytes resulting in changes in statolith numbers. A mineralization role of thyroxine in other invertebrates hasnot been reported in spite of the fact that thyroxine and itsprecursors, monoiodotyrosine and diiodotyrosine, have been locatedin numerous invertebrates, particularly in mineralizing areassuch as developing shells. On the other hand, an important roleof thyroxine in mineralization and demineralization of bonesand teeth of vertebrates including humans, has been known forsome time. The specific role of thyroxine in affecting mineralizationin vertebrates is not known, due perhaps to the presence ofmany other hormones and second messengers which also affectmineralization. The use of the relatively simple Aurelia statolithtest systems and the exploration for other invertebrate mineralizingsystems which respond to thyroxine will hopefully lead to abetter understanding of the basic mechanisms of thyroxine actionin mineralizing systems in the future.     

Gymnodinium chukwanii n. sp. and Other Marine Dinoflagellates Collected in the Vicinity of Zanzibar

Thirty-five species of marine dinoflagellates are described and figured, including one new species, Gymnodinium chukwanii . These were collected by the author during the period February - March 1956. G. chukwanii has affinities to G. splendens and G. nelsoni and their group. The remainder of the paper is concerned with described species.     

Archaebacterial Relationships of the Phosphoenolpyruvate Carboxykinase Gene Reveal Mosaicism of Giardia intestinalis Core Metabolism

A gene encoding a putative GTP-specific phosphoenolpyruvate carboxykinase has been cloned and sequenced from the type I amitochondriate protist Giardia intestinalis. The deduced amino acid sequence is related most closely to homologs from hyperthermophilic archaebacteria and only more distantly to homologs from Eubacteria and Metazoa. Most enzymes of Giardia core metabolism, however, are related more closely to eubacterial and metazoan homologs. An archaebacterial relationship has been noted previously for the unusual acetyl-CoA synthetase (ADP-forming) of this organism. The results suggest that phosphoenolpyruvate carboxykinase and acetyl-CoA synthetase have been acquired from different sources than most enzymes of Giardia core metabolism.     

Time-Lapse Filming of Cellular Interactions within Living Tissues

By a further development of the technique for time-lapse filming of organ cultures, it has become possible to observe the internal structure of the living tissues and to study the dynamics of intercellular contacts within the tissue. This method has been applied to a study of the interaction between the tissues of the chick chorioallantoic membrane and non-malignant fibroblasts, polyoma virus-transformed fibroblasts, and Harding-Passey melanoma cells. The behaviour of these cells in the absence and in the presence of colcemid has been investigated. From these studies it is concluded that disturbances in cell shape brought about by colcemid do not affect the invasive properties whereas the surface polypodial activity shown by the malignant cells is a major factor in tumour invasion.