Author
Catherine M. O’Reilly
Bio: Catherine M. O’Reilly is an academic researcher from University of Massachusetts Medical School. The author has contributed to research in topics: Membrane potential & Depolarization. The author has an hindex of 3, co-authored 3 publications receiving 240 citations.
Papers
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TL;DR: Nearly all mitochondria flickered, and they did so independently of one another, indicating that mitochondria function as independent units in the myocytes employed here, and a new method to determine the amplitude of flickers in terms of millivolts of depolarization.
116 citations
Journal Article•
TL;DR: In this paper, the amplitude of flicker in terms of millivolts of depolarization was measured using high-speed, high-sensitivity three-dimensional imaging to track individual mitochondria in freshly dissociated smooth muscle cells.
Abstract: Spontaneous transient depolarizations in mitochondrial membrane potential (Δψ m ), mitochondrial flickers, have been observed in isolated mitochondria and intact cells using the fluorescent probe, tetramethylrhodamine ethyl ester (TMRE). In theory, the ratio of [TMRE] in cytosol and mitochondrion allows Δψ m to be calculated with the Nernst equation, but this has proven difficult in practice due to fluorescence quenching and binding of dye to mitochondrial membranes. We developed a new method to determine the amplitude of flickers in terms of millivolts of depolarization. TMRE fluorescence was monitored using high-speed, high-sensitivity three-dimensional imaging to track individual mitochondria in freshly dissociated smooth muscle cells. Resting mitochondrial fluorescence, an exponential function of resting Δψ m , varied among mitochondria and was approximately normally distributed. Spontaneous changes in mitochondrial fluorescence, indicating depolarizations and repolarizations in Δψ m , were observed. The depolarizations were reversible and did not result in permanent depolarization of the mitochondria. The magnitude of the flickers ranged from 100 mV with a mean of 17.6 ′ 1.0 mV (n = 360) and a distribution skewed to smaller values. Nearly all mitochondria flickered, and they did so independently of one another, indicating that mitochondria function as independent units in the myocytes employed here.
104 citations
TL;DR: High-speed three-dimensional imaging was used to monitor DeltaPsi(m) in freshly dissociated myocytes from toad stomach that were simultaneously voltage clamped at 0 mV to ensure the cytosolic TMRE concentration was constant and equal to the low level in the bath (2.5 nM).
Abstract: The mitochondrial membrane potential (ΔΨm) underlies many mitochondrial functions, including Ca2+ influx into the mitochondria, which allows them to serve as buffers of intracellular Ca2+. Spontane...
29 citations
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TL;DR: A "two-hit" hypothesis is developed, in which Ca(2+) plus another pathological stimulus can bring about mitochondrial dysfunction, and the delicate balance between the positive and negative effects of Ca( 2+) and the signaling events that perturb this balance is highlighted.
Abstract: The mitochondrion is at the core of cellular energy metabolism, being the site of most ATP generation. Calcium is a key regulator of mitochondrial function and acts at several levels within the organelle to stimulate ATP synthesis. However, the dysregulation of mitochondrial Ca(2+) homeostasis is now recognized to play a key role in several pathologies. For example, mitochondrial matrix Ca(2+) overload can lead to enhanced generation of reactive oxygen species, triggering of the permeability transition pore, and cytochrome c release, leading to apoptosis. Despite progress regarding the independent roles of both Ca(2+) and mitochondrial dysfunction in disease, the molecular mechanisms by which Ca(2+) can elicit mitochondrial dysfunction remain elusive. This review highlights the delicate balance between the positive and negative effects of Ca(2+) and the signaling events that perturb this balance. Overall, a "two-hit" hypothesis is developed, in which Ca(2+) plus another pathological stimulus can bring about mitochondrial dysfunction.
2,265 citations
TL;DR: Additional potential mechanisms for which ΔΨm is essential for maintenance of cellular health and viability are proposed and recommendations how to accurately measure ΔΩm in a cell are provided and potential sources of artifacts are discussed.
1,024 citations
TL;DR: In this review, recent developments in knowledge of basic aspects of mitochondrial biology are considered as an essential step in developing understanding of the contributions of mitochondria to disease.
673 citations
TL;DR: Basic concepts about PTP structure, function and regulation within the framework of intracellular death signalling, and its role in disease pathogenesis are reviewed.
Abstract: Current research on the mitochondrial permeability transition pore (PTP) and its role in cell death faces a paradox. Initially considered as an in vitro artifact of little pathophysiological relevance, in recent years the PTP has received considerable attention as a potential mechanism for the execution of cell death. The recent successful use of PTP desensitizers in several disease paradigms leaves little doubt about its relevance in pathophysiology; and emerging findings that link the PTP to key cellular signalling pathways are increasing the interest on the pore as a pharmacological target. Yet, recent genetic data have challenged popular views on the molecular nature of the PTP, and called into question many early conclusions about its structure. Here we review basic concepts about PTP structure, function and regulation within the framework of intracellular death signalling, and its role in disease pathogenesis.
493 citations
TL;DR: The emphasis here is on isolated mitochondria and on general mitochondrial properties in order to focus on how mitochondria alone may function to fulfill their physiological roles even though the interactions of mitochondria with other organelles, particularly with endoplasmic and sarcoplasmsic reticulum, may also influence this story.
399 citations