Findings Consistent with Nonselective Feeding in Tetrahymena pyriformis

In amoeboid cells, food particles are engulfed only after receptors on the phagocytic cell’s membrane bind to ligands on a particle’s surface. Ciliates also feed via phagocytosis but, instead of enveloping particles, some ciliates take them up through a complex, permanent, funnel-shaped, feeding apparatus. It is unclear whether receptor-ligand interactions are needed to trigger the process. If ciliates were shown to feed selectively on certain particles over others, based on the particles’ surface properties, then receptor-ligand interactions would likely play a role in phagocytosis. The literature includes few reports of such selectivity. To further investigate this issue, we chose to study feeding preference in the ciliate Tetrahymena pyriformis. We fed Tetrahymena mixtures of orange and green, fluorescent, 3 µm, polystyrene beads at two concentrations. One of the two types of beads was coated with bovine serum albumin. Authors were blinded to experimental conditions. We found no evidence of a preference for coated or uncoated beads at either concentration. We also found no trend toward the development of selective feeding as cells acquired more beads over time. Although we cannot rule out the possibility that Tetrahymena feeds selectively, we did not find convincing evidence of such selectivity when T. pyriformis is given a choice between uncoated beads and those coated with albumin. Our results failed to demonstrate a role for molecular recognition when Tetrahymena engages in phagocytosis

Mitochondrial DNA Manipulations Affect Tau Oligomerization

Background:Mitochondrial dysfunction and tau aggregation occur in Alzheimer’s disease (AD), and exposing cells or rodents to mitochondrial toxins alters their tau. Objective:To further explore how mitochondria influence tau, we measured tau oligomer levels in human neuronal SH-SY5Y cells with different mitochondrial DNA (mtDNA) manipulations. Methods:Specifically, we analyzed cells undergoing ethidium bromide-induced acute mtDNA depletion, ρ0 cells with chronic mtDNA depletion, and cytoplasmic hybrid (cybrid) cell lines containing mtDNA from AD subjects. Results:We found cytochrome oxidase activity was particularly sensitive to acute mtDNA depletion, evidence of metabolic re-programming in the ρ0 cells, and a relatively reduced mtDNA content in cybrids generated through AD subject mitochondrial transfer. In each case tau oligomer levels increased, and acutely depleted and AD cybrid cells also showed a monomer to oligomer shift. Conclusion:We conclude a cell’s mtDNA affects tau oligomerization. Overlapping tau changes across three mtDNA-manipulated models establishes the reproducibility of the phenomenon, and its presence in AD cybrids supports its AD-relevance

AN EXAMINATION OF SELECTIVE FEEDING AND MOLECULAR RECOGNITION IN THE CILIATE, TETRAHYMENA PYRIFORMIS Ehrenberg, 1830

In amoeboid cells, food particles are engulfed only after receptors on the phagocytic cell’s membrane bind to ligands on a particle’s surface. Ciliates also feed via phagocytosis, but instead of enveloping particles the way amoebae do, ciliates take up particles through a complex, permanent, funnel-shaped feeding apparatus. It is unclear whether receptor-ligand interactions are needed to trigger the process. If ciliates were shown to prefer certain particles over others, based on the particles’ surface properties, then receptor-ligand interactions would likely play a role in phagocytosis. The literature includes few reports of such selectivity in ciliates. To further investigate this issue, we chose to study feeding selectivity in the ciliate Tetrahymena pyriformis Ehrenberg, 1830. We fed Tetrahymena mixtures of orange and green fluorescent, 3 μm, latex beads at two concentrations in which one type of bead was coated with bovine serum albumin through passive adsorption (BSA; 8–13 μg protein/mg beads). Authors were unaware of which beads were coated while collecting data. Treatment groups included the results of 12–16 trials. We found no evidence of a preference for either coated or uncoated beads at either concentration (coated vs. not coated, P = 0.131; bead concentration, P = 0.866; interaction, P = 0.294). In contrast, others have reported that T. pyriformis feeds more rapidly on BSA-coated beads than uncoated ones. We also found no trend toward the development of a preference as cells acquired more beads over time. The literature indicates that two species of nanoflagellates develop such a preference. Although we cannot rule out the possibility that Tetrahymena feeds selectively, we did not find convincing evidence of such selectivity when T. pyriformis is given a choice between uncoated beads and those coated with BSA. Our results failed to demonstrate a role for molecular recognition when Tetrahymena engages in phagocytosis