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PubMed1963

ULTRASTRUCTURAL STUDIES ON THE BLUE-GREEN ALGAL SYMBIONT IN CYANOPHORA PARADOXA KORSCHIKOFF.

Studies conducted on the ultrastructure of Cyanophora paradoxa Korschikoff (a cryptomonad) have shown that its intracellular symbiont is closely related to unicellular blue-green algae. Due to its peculiar habitat, the intracellular symbiont lacks the characteristic cyanophycean double-layered cell wall, but is surrounded by a thin protoplasmic membrane. The protoplasm itself is differentiated into a lamellated chromatoplasm containing photosynthetic pigments, polyphosphate granules, and possible oil droplets, and a non-lamellar centroplasm with a large centrally located electron-opaque body surrounded by a fibril-containing halo. This halo-central body complex may be nuclear in nature. Binary fission of the organism is described. Since this cyanelle has not yet been classified, we name it Cyanocyta korschikoffiana nov. gen. nov. sp.; and because of its structural peculiarities, we find it necessary to create a new family for it, Cyanocytaceae, in the order Chroococcales.

Animals↗
PubMed1965

THE FINE STRUCTURE AND FUNCTION OF THE CONTRACTILE AXOSTYLES OF CERTAIN FLAGELLATES.

The axostyles of the flagellates Oxymonas, Saccinobaculus, and Notila are large ribbon-shaped structures which undulate actively in the cytoplasm. The form of their movements is described and illustrated. Axostyles consist of regular arrays of longitudinal fibres, the number of which varies between 100 and 5000 in different species. The fibres are about 240 A in diameter, apparently hollow, regularly cross-banded with a periodicity of about 150 A, and connected by delicate cross-links, also at regular intervals of about 150 A. They resemble very closely the central fibres of cilia and flagella. No other structural components are present, except at the anterior end, where the fibres are attached to one or more basal bodies, and at the posterior tip, where they are anchored to the plasma membrane. The relevance of the findings to an understanding of the mechanism of ciliary and flagellar movements is discussed.

Adenosine Triphosphatases↗
PubMed1953

Chlorophyll monolayers in chloroplasts.

1. The data on the fine structure of the chloroplasts and the chlorophyll analyses, in two algal flagellates, Euglena gracilis and Poteriochromonas stipitata, are consistent with the assumption that the chlorophyll molecules are arranged in monomolecular layers at the interfaces between the lipid (dense) and the aqueous protein complex layers. 2. The cross-sectional area available to each chlorophyll molecule in the chloroplasts of Euglena and Poteriochromonas was found to be 222 x 10(-16) cm(2). and 246 x 10(-16) cm(2). By comparison, the cross-sectional area of the hydrophilic head of the chlorophyll molecule is approximately 240 x 10(-16) cm(2). 3. The model of the molecular network depicted in Text-fig. 1 is purely speculative. It predicts a lower limit for the number ratio of chlorophyll to other pigment molecules of about 1:1 and a weight ratio of 2:1. A loose packed structure such as that shown in Text-fig. 1 predicts a weight ratio of 4:1 to 6:1. These values bracket the large majority of experimental values found for this ratio. The relative constancy of the number of chlorophyll molecules per chloroplast and the volume of the chloroplast indicated by the data in Table III suggest that chloroplasts probably possess a similar structural arrangement in a variety of photosynthetic microorganisms and plants.

Chlorophyll↗
PubMed1963

THE EFFECTS OF INHIBITORS OF MACROMOLECULAR BIOSYNTHESIS UPON THE PERSISTENT RHYTHM OF LUMINESCENCE IN GONYAULAX.

Certain inhibitors of nucleic acid and protein synthesis, namely actinomycin D, mitomycin C, and puromycin, have been found to block the expression of a persistent daily rhythm of bioluminescence. The action does not inhibit luminescence per se but rather the rhythmicity. Exposure of the cells to these inhibitors for only a few hours, which might be expected to thereby delay the rhythm by a few hours, does not in fact have this effect. Chloramphenicol and amethopterin do not inhibit the rhythm. It is proposed that the functioning of the clock-like rhythmic mechanism depends upon the cell's normal ability to synthesize RNA.

Anti-Bacterial Agents↗