Fluorescence and Electron Microscopic Localization of F-actin in the Ependymocytes

The organization of F-actin in the ventricular system has been reported to display pronounced regional differences with respect to shape, size, and development. However, the real roles played by F-actin in these cells cannot be understood unless the precise localization of F-actin is defined. In the present study, we used double-fluorescence labeling to further examine the localization of F-actin in the ependymocytes and its spatial relation to the other two cytoskeletal components, microtubules and intermediate filaments. Then we converted fluorescence signals for F-actin to peroxidase/DAB reaction products by use of a phalloidin-based FITC-anti-FITC system. This detection technique provided an overview of the distribution of F-actin in the ependymocytes at the ultrastructural level, and has been proven to be helpful in correlating light and electron microscopic investigations. (J Histochem Cytochem 57:741–751, 2009)     

Some physiological aspects of the autecology of the suspension-feeding protozoanTetrahymena pyriformis

Feeding, growth, and reproductive responses of the suspension-feeding protozoanTetrahymena pyriformis to shifts up or down of the density of its bacterial food were observed. The rates of feeding, growth, and reproduction were determined by measuring the rates of uptake of viable bacterial cells, of change of mean volume of the protozoan cells, and of change of number of protozoan cells, respectively. The effects of the nutritional status of the protozoans at the time of shifting were observed also. Results are interpreted in terms of the limited polymorphism exhibited in the life cycle of this organism. Responses in all cases seem to reflect a strategy for exploiting a patchy, transient environment, a conclusion already reached by several earlier investigators.     

Temperature shift-up leads to simultaneous and continuous plasmid DNA relaxation and induction of DnaK and GroEL proteins in anaerobically growing Escherichia coli cells

Abstract We previously reported that plasmid DNA in Escherichia coli cells growing under aerobic conditions relaxed immediately and transiently after heat shock (Mizushima, T., Natori, S. and Sekimizu, K., Mol. Gen. Genet. (1993) 238, 1–5). We next examined DNA relaxation and induction of heat shock proteins after heat shock in cells growing under anaerobic conditions. DNA in these cells relaxed rapidly (2 min) after heat shock (42°C), as was the case with aerobically growing cells, but full superhelicity was not recovered. The relaxed state of DNA topology was maintained for 60 min after heat shock. Induction of DnaK and GroEL proteins, which was transient in aerobically growing cells, was continuous in anaerobically growing cells. Therefore, induction of heat shock proteins correlated with DNA relaxation in both aerobic and anaerobic conditions.     

Binding of a histidine-rich peptide to Porphyromonas gingivalis

Porphyromonas gingivalis 381 cells were incubated with 125I-histidine-rich polypeptide (histatin) 5 in the presence or absence of unlabeled histatin 5, to evaluate the histatin-binding capacity of the cells. The binding of histatin 5 was rapid, reversible, saturable and specific. The number of histatin 5-binding sites per cell was 3,600, and the dissociation constant (Kd) was in the order of 10(-6) M. These findings suggest that histatin interacts with certain bacterial cells through specific binding sites on their surface, and will allow the development of a histatin radioreceptor assay.