Earth's gravity exerts relatively weak forces in the range of 10-100 pN directly on cells in biological systems. Nevertheless, it biases the orientation of swimming unicellular organisms, alters bone cell differentiation, and modifies gene expression in renal cells. A number of methods of simulating different strength gravity environments, such as centrifugation, have been applied for researchi...

Paramecium caudatum cells were pulse-chased in horseradish peroxidase (HRP) using pulses of 30 s to follow endosome (endocytotic vesicle) formation from defaecating digestive vacuoles and 3-min pulses to follow the movement and fate of these vesicles in the cell. Endosomes formed during the 30 s in HRP are heavily labelled with HRP reaction product and are mostly flattened. Some align along mic...

Although acidification of phagocytic vacuoles has received a broadened interest with the development of pH-sensitive fluorescent probes to follow the pH changes of vacuoles and acidic vesicles in living cells, the mechanism responsible for the acidification of such vacuoles still remains in doubt. In previous studies of the digestive vacuole system in the ciliate Paramecium caudatum we observed...

In Paramecium primaurelia surface antigen (SAg) expression can be experimentally controlled by temperature-shift-induced antigenic variation. As only one SAg is usually expressed at the cell surface under stable environmental conditions, we used the temperature-shift-induced change in SAg to follow the newly expressed antigen and the disappearing one, by both immunofluorescence and immunogold e...

In Paramecium, the differentiation of a highly polyploid macronucleus from a diploid nucleus is accompanied by an extensive reorganization of the genome, involving reduction in chromosome size and formation of new telomeres at heterogeneous, but reproducible, positions. The results presented here, as well as work by others, indicate that telomere addition regions are not strictly determined by ...

1. Irradiation with three short ultraviolet (UV) wave lengths, 226, 233, and 239 mmicro rapidly immobilizes Paramecium caudatum, the dosage required being smaller the shorter the wave length. 85 per cent of paramecia immobilized with wave length 226 mmicro recover completely. Recovery from immobilizing doses is less the longer the wave length. 2. Irradiation continued after immobilization kills...