Research is currently being conducted in two areas: excitation-contraction coupling in mammalian heart, and the role of intracellular calcium ions (Ca2+) in post-synaptic responses of neurons of the mammalian brain (cortex).
Excitation-contraction coupling: The laboratory has acquired a Bio-rad confocal microscope which we are using to examine the sub-cellular changes in [Ca2+]i that occur in small volumes (~2.0 cubic micrometers) of heart cells as a result of electrical depolarization. The cells are micro-injected with a fluorescent Ca2+-indicator substance (dye). The images obtained with the microscope are analyzed using digital image analysis. Confocal microscopy has revealed that [Ca2+]i is not released from internal storage sites uniformly in the cell after electrical depolarization (voltage-clamp). The high spatial and temporal resolution afforded by the confocal microscope provides the opportunity to observe new details about the release of Ca2+ from internal stores, and to study in new ways the mechanisms that are involved in signalling for such release. Since contraction of the mammalian heart depends mainly on the amount of Ca2+ released from the intracellular Ca2+-storage sites, these studies can provide fundamental new information on the contraction of the mammalian heart. Our initial results were published recently in Science (Lopez-Lopez, et al. 1995, 268, pp. 1042-1045) and The Journal of Physiology (Lopez-Lopez, et al. 1994, Vol. 480.1, pp. 21-29).
Neurophysiology: In these studies we have used fluorescent Ca2+-indicator dyes in cultured Gil Wier, continued neurons, derived originally from cortex of rat brains. We were able to observe, for the first time, spontaneous miniature synaptic [Ca2+]i-transients (MSCTs) within individual dendritic spines (Murphy et al, 1994, Science 263, pp. 529-532). In current work, we ar attempting to correlate miniature synaptic currents (MSCs) with the MSCTs. This would provide a way, for the first time, to observe the activity at a single dendritic spine, and to assign particular miniature synaptic currents to particular synapses. This may be a valuable technique in the study of phenomena such as long term potentiation (LTP), in which the activity of synapses is altered, presumably in association with phenomena such as learning and memory.
Parker, I., Zang, W-J, and Wier, W.G. "Ca2+ sparks involving multiple release sites along Z-lines in rat heart cells." 1996 Journal of Physiology, 497-1, 31-38.
Parker, I., Callamaras, N., and Wier, W.G. "A high-resolution, confocal laser scanning microscope and flash photolysis system for physiological studies." 1997, Cell Calcium, 21(6), 441-453.