Chloroplast and Cytoplasmic Ribosomes of Euglena: Selective Binding of Dihydrostreptomycin to Chloroplast Ribosomes

Dihydrostreptomycin binds preferentially to chloroplast ribosomes of wild-type Euglena gracilis Klebs var. bacillaris Pringsheim. The K(diss) for the wild-type chloroplast ribosome-dihydrostreptomycin complex is 2 x 10(-7) M, a value comparable with that found for the Escherichia coli ribosome-dihydrostreptomycin complex. Chloroplast ribosomes isolated from the streptomycin-resistant mutant Sm(1) (r)BNgL and cytoplasmic ribosomes from wild-type have a much lower affinity for the antibiotic. The K(diss) for the chloroplast ribosome-dihydrostreptomycin complex of Sm(1) (r) is 387 x 10(-7) M, and the value for the cytoplasmic ribosome-dihydrostreptomycin complex of the wild type is 1,400 x 10(-7) M. Streptomycin competes with dihydrostreptomycin for the chloroplast ribosome binding site, and preincubation of streptomycin with hydroxylamine prevents the binding of streptomycin to the chloroplast ribosome. These results indicate that the inhibition of chloroplast development and replication in Euglena by streptomycin and dihydrostreptomycin is related to the specific inhibition of protein synthesis on the chloroplast ribosomes of Euglena.     

The origin and structure of the secondary coat of the egg of Drosophila melanogaster

Summary The techniques of light and electron microscopy have been employed in a study of the protective coverings of the egg of Drosophila melanogaster. Data obtained during this investigation suggest the involvement of the follicle cells, in the production of one of these coverings and justify its classification as a secondary coat. The secondary coat of D. melanogaster is highly organized and has been divided into three Zones (I, II, IIII). The follicle cells enveloping the oocyte exhibit two phases of secretory activity each involving hypertrophy of the Golgi complex and rough endoplasmic reticulum, and the production of protein and polysaccharide components. The first phase concerns the elaboration of the material which gives rise to the homogeneous lamina referred to as Zone I. The second results in the release of an electron dense component which becomes organized into two laminae separated by struts or pillars; this construction is referred to as Zone II. At the completion of this secretory phase, the follicle cells assume a squamous morphology and a third Zone, composed of a homogeneous substance, appears between the follicle cells and Zone II.This investigation was supported by grant GM-08776 to one of us (EA) from the National Institutes of Health, United States Public Health Service.     

Assimilation of Alkanes and Alkenes by Fungi

A group of filamentous fungi were assayed for their ability to utilize a series of n-alkanes and 1-alkenes as the sole source of carbon. Although strains of Cunninghamella exhibited profuse growth on most of the hydrocarbons tested, the majority of fungi tested were able to produce definite growth on one or more of the compounds. The hydrocarbons with a 14-carbon chain length appeared to be more consistently utilized than any other. Strains of Aspergillus appeared to differ in their capacity to utilize individual members of the hydrocarbon series. Thin-layer chromatographic analyses of ether extracts from C. blakesleeana grown on n-tetradecane and 1-tetradecene were similar and revealed the presence of a monocarboxylic acid, a primary alcohol, and a secondary alcohol.     

Studies with cyanidium caldarium,an anomalously pigmented chlorophyte

Summary Cyanidium caldarium, an alga found in acid hot springs troughout the world, has a morphology and developmental history resembling those of Chlorella, but contains C-phycocyanin and no chlorophyll other than chlorophyll a. The reasons for considering it to be a member of the Chlorophyta are reviewed. Cyanidium is also remarkable for its thermal and acid tolerance. It grows readily in the dark on sugar media. However, light is required for the formation of chlorophyll and phycocyanin except in occasional variant cells which can form limited amounts of these pigments in the dark. Light-grown Cyanidium carries out normal green plant photosynthesis but resembles the red and some of the blue-green algae in that chlorophyll-absorbed light is used with lower efficiency than that absorbed by phycocyanin.The possible significance of the unusual pigmentation of Cyanidium is discussed.Contribution no.23 from the Laboratory of Comparative Physiology and Morphology of The Kaiser Foundation.     

Cerebrovascular Occlusive Disease—Experience with Panarteriography in 300 Consecutive Cases

Three hundred patients with cerebrovascular occlusive disease have had cerebral angiographic examination at the Veterans Administration Hospital, San Francisco, in the last five years. The present technique consists of preliminary visualization of the aortic arch and the major extracranial branches, followed by selective study of the subclavian and carotid arteries as necessary for evaluation of the intracranial circulation.Nine major complications occurred (an over-all incidence of 3 per cent). Two patients died after angiography and seven had major neurologic deficits persisting for more than 24 hours. Three of these patients had permanent damage, but four recovered completely.One-third of the patients had extracranial disease and one-third had intracranial disease. No significant lesion was found in the remainder. In the 212 patients with lesions, multiple lesions were common, the average number being three. Six patients had brain tumors and five had aneurysms.The mechanism of the stroke could be ascertained readily in most of the patients, but the extent of the disease and the resulting symptoms varied considerably. Several patients with occlusion of most of the cerebral vessels had minimal symptoms, while others had catastrophic symptoms but only minimal findings at arteriography.