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Biomedical subjects

K Dunlap

Publications and source records attributed to K Dunlap.

59 records · Page 4Linked to original sources
PubMedDate not supplied

GTP-binding proteins mediate transmitter inhibition of voltage-dependent calcium channels.

The modulation of voltage-dependent calcium channels by hormones and neurotransmitters has important implications for the control of many Ca2+-dependent cellular functions including exocytosis and contractility. We made use of electrophysiological techniques, including whole-cell patch-clamp recordings from dorsal root ganglion (DRG) neurones, to demonstrate a role for GTP-binding proteins (G-proteins) as signal transducers in the noradrenaline- and gamma-aminobutyric acid (GABA)-induced inhibition of voltage-dependent calcium channels. This action of the transmitters was blocked by: (1) preincubation of the cells with pertussis toxin (a bacterial exotoxin catalysing ADP-ribosylation of G-proteins); or (2) intracellular administration of guanosine 5'-O-(2-thiodiphosphate) (GDP-beta-S), a non-hydrolysable analogue of GDP that competitively inhibits the binding of GTP to G-proteins. Our findings provide the first direct demonstration of the G-protein-mediated inhibition of voltage-dependent calcium channels by neurotransmitters. This mode of transmitter action may explain the ability of noradrenaline and GABA to presynaptically inhibit Ca2+-dependent neurosecretion from DRG sensory neurones.

Action Potentials↗
PubMedDate not supplied

Activation of a calcium-dependent photoprotein by chemical signalling through gap junctions.

In the hydrozoan coelenterate Obelia geniculata, epithelial cell action potentials trigger light emission from photocyte effector cells containing obelin, an endogenous calcium-activated photoprotein. As this luminescence is blocked by the removal of extracellular calcium it seemed likely that calcium entry via voltage-gated channels in the photocyte membrane would account for the light emission. However, no inward calcium current was detected in whole cell recordings from dissociated photocytes and depolarization of isolated photocytes produced no luminescence. In contrast, a voltage-dependent calcium current was recorded from non-luminescent support cells, and activation of this current triggered luminescence in an adjacent photocyte. Surprisingly, light emission was abolished when the gap junctions between the photocyte and support cell were blocked. We conclude that calcium entry into support cells leads to light emission from neighbouring photocytes via chemical signalling through intercellular gap junctions.

Action Potentials↗
PubMedDate not supplied

The practice of nursing theory in the operating room.

Nursing theory is a set of ideas, experiences, or observations regarding how and why nurses engage in certain activities and exhibit various behavioral attributes in providing patient care. The individualized caregiving activities perioperative nurses express during all phases of the surgical experience are supported by nursing theory.

Empathy↗