THE FATE OF MITOCHONDRIA DURING AGING IN TETRAHYMENA PYRIFORMIS

Abstract

During the growth cycle of Tetrahymena pyriformis the mitochondria undergo changes in position, number, and structure. Ciliates in the logarithmic growth phase possess elongated mitochondria which are aligned along the plasma membrane and are closely associated with the kinetosomes and kinetodesmata. Mitochondria appear to divide across the long axis at this time, resulting in two or more products. Throughout this phase of growth mitochondrial divisions keep pace with cytokinesis so that the population of mitochondria remains at essentially the minimal level. As the ciliates enter the stationary growth phase the mitochondria increase in number, become oval to spherical in shape, and some migrate into the cytoplasm. Intramitochondrial masses of various configurations appear at this time. Some of the mitochondria lying in the cytoplasm become incorporated into vacuoles. Within these vacuoles either a single mitochondrion appears or several mitochondria may be seen along with other cytoplasmic structures. Later in the stationary growth phase the contained mitochondria are dense and the tubules are more compact than normal. Various stages in disorganization of the mitochondria are observed in a single large vacuole. Cytochemical tests reveal the presence of acid phosphatase, suggesting that hydrolysis of the vacuolar contents occurs. Lipid droplets increase in number during the middle and late stationary phase of growth. These events are interpreted as being associated with the normal process of aging in T. pyriformis.

Living unicellular eukaryote Tetrahymena pyriformis as a model for study

“…Close contacts between lipid droplets and mitochondria were clearly detected in hepatocytes of the hibernating animals (see Fig 1B in [2]) and in T. pyriformis cells during stationary growth phase (see Fig. 17 in [9]). …”

“…Hepatocytes during hibernation and T. pyriformis cells use lipid droplets as a fuel source [ 2,9,10]. Close contacts between lipid droplets and mitochondria were clearly detected in hepatocytes of the hibernating animals (see Fig 1B in [2]) and in T. pyriformis cells during stationary growth phase (see Fig.…”

“…Calcium was probably bound during the stationary growth phase of T. pyriformis cells; the inclusions found in these cells were tentatively identified as Ca 2+ complex with other substances [9].…”

“…For example, the autophagy of mitochondria is probably activated in Tetrahymena pyriformis during later growth phase; some mitochondria are incorporated into vacuoles containing acid phosphatase [9]. The moderate autophagy facilitates surviving of the cells under the metabolic depression; it defends mitochondria from apoptosis ( [15] and references within).…”

Age changes in the canine pancreas: histomorphological, electron microscopic, and biochemical study

“…A pronounced fall in the concentration of acyl ester bonds into mitochondrial lipid, characterized by a decrease in lecithin and a concomitant rise in lysolecithin,was demon strated. In addition, it has been shown in Tetrahymena that mitochondria undergo changes in position, number, and structure (Elliot and Bak, 1964). The mitochondria changed from elon gated to oval structures, increased in number, and some became incorporated into vacuoles as the ciliates go from a logarith mic growth phase to a stationary growth phase.…”