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The expression of the larvicidal Bacillus thuringiensis subsp. israelensis cryIVB gene in cyanobacteria has been suggested to be an effective means of controlling mosquito populations. Using a variety of cryIVB constructs, in this study we have examined the effect of Synechococcus PCC 7942 culture age on intracellular toxin levels and have attempted to determine the mechanisms by which cryIVB gene expression is regulated. The data suggest that specific degradation of the cryIVB mRNA limits toxin production; however, the addition of cyanobacterial 3' untranslated DNA sequences to the cryIVB gene did not improve mRNA stability or toxin levels. An analysis of the cryIVB sequence and comparison of codon usage patterns with highly expressed cyanobacterial genes suggest that inefficient translation and intragenic ribosomal binding sites impede protein synthesis and result in rapid turnover of the toxin mRNA.

In order to study the ability of freshwater algae and cyanobacteria to form extracellular fibrils, a screening test using ruthenium red (RR) staining was carried out on 28 species. Five of these were examined for growth and production of fibrillar material in culture media of different phosphate (P;) contents. RR-staining and uronic acid determinations at various stages of algal growth were complemented by electron microscopy of the cells and of fibrillar material released into the medium. The lower Pi concentrations enhanced growth of Micrasterias radiata, Eremosphaera sp., and Microcystis aeruginosa, and had little or no effect on growth of a Xanthidium sp. and Scenedesmus quadricauda. Extracellular uronic acid production, which was higher in low Pi medium in M. radiata, M. aeruginosa, and Xanthidium sp., could reach levels of 50 mg/liter or more. Algae with high proportions of RR-positive cells (M. radiata, Eremosphaera sp., Xanthidium sp., and M. aeruginosa) produced high levels of slime-like material and distinct fibrils that were often seen attached to the cell surface and only slowly released into the medium. No such material was found in cultures (or supernatants) of Sc. quadricauda, which also produced relatively low amounts of polyuronic acids. Specific types of filaments, often forming "fascicles" with rectangular arrays of globular particles were observed by negative staining electron microscopy of some algal cultures. RR-positive material was also observed in the cytoplasm and on the cell walls and surfaces of M. radiata and M. aeruginosa.

A combination of previously known techniques for retrograde opacification of ileostomies and colostomies has been used successfully in neonates and infants. This combination of techniques used on very small stomas allows easy retrograde opacification of bowel. The technique uses a small feeding tube, a larger Foley catheter with an inflatable balloon, and a Lucite compression device, the construction and use of which are discussed here.