17 research outputs found
The Heat of Nervous Conduction: A Thermodynamic Framework
Early recordings of nervous conduction revealed a notable thermal signature
associated with the electrical signal. The observed production and subsequent
absorption of heat arise from physicochemical processes that occur at the cell
membrane level during the conduction of the action potential. In particular,
the reversible release of electrical energy stored as a difference of potential
across the cell membrane appears as a simple yet consistent explanation for the
heat production, as proposed in the "Condenser Theory." However, the Condenser
Theory has not been analyzed beyond the analogy between the cell membrane and a
parallel-plate capacitor, i.e. a condenser, which cannot account for the
magnitude of the heat signature. In this work, we use a detailed electrostatic
model of the cell membrane to revisit the Condenser Theory. We derive
expressions for free energy and entropy changes associated with the
depolarization of the membrane by the action potential, which give a direct
measure of the heat produced and absorbed by neurons. We show how the density
of surface charges on both sides of the membrane impacts the energy changes.
Finally, considering a typical action potential, we show that if the membrane
holds a bias of surface charges, such that the internal side of the membrane is
0.05 C m more negative than the external side, the size of the heat
predicted by the model reaches the range of experimental values. Based on our
study, we identify the change in electrical energy of the membrane as the
primary mechanism of heat production and absorption by neurons during nervous
conduction
STARDUST (Spatial and Temporal Assessment of high Resolution Depth profiles Using novel Sampling Technologies): Final Report
België en Antarctica: ontdekking, wetenschap en leefmilieu = La Belgique et l’Antarctique: exploration, science et environnement
Eupalinilide E Inhibits Erythropoiesis and Promotes the Expansion of Hematopoietic Progenitor Cells
Eupalinilide E Inhibits Erythropoiesis and Promotes the Expansion of Hematopoietic Progenitor Cells
Small Molecule Mediated Proliferation of Primary Retinal Pigment Epithelial Cells
Retinal pigment epithelial (RPE)
cells form a monolayer adjacent
to the retina and play a critical role in the visual light cycle.
Degeneration of RPE cells results in retinal disorders such as age-related
macular degeneration. Cell transplant strategies have potential therapeutic
value for such disorders; however, risks associated with an inadequate
supply of donor cells limit their therapeutic success. The identification
of factors that proliferate RPE cells <i>ex vivo</i> could
provide a renewable source of cells for transplantation. Here, we
report that a small molecule (WS3) can reversibly proliferate primary
RPE cells isolated from fetal and adult human donors. Following withdrawal
of WS3, RPE cells differentiate into a functional monolayer, as exhibited
by their expression of mature RPE genes and phagocytosis of photoreceptor
outer segments. Furthermore, chemically expanded RPE cells preserve
vision when transplanted into dystrophic Royal College of Surgeons
(RCS) rats, a well-established model of retinal degeneration