Daniel K. Hartline

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The evolution of a character is better appreciated if examples of convergent emergence of the same character are available for comparison. Three instances are known among invertebrates of the evolution of axonal sheaths possessing the functional properties and many of the structural properties of vertebrate myelin. Comparison of these invertebrate myelins(More)
Significant error is made by using a point voltage clamp to measure active ionic current properties in poorly space-clamped cells. This can even occur when there are no obvious signs of poor spatial control. We evaluated this error for experiments that employ an isochronal I(V) approach to analyzing clamp currents. Simulated voltage clamp experiments were(More)
The evolutionary origins of glia are lost in time, as soft tissues rarely leave behind fossil footprints, and any molecular footprints they might have been left we have yet to decipher. Nevertheless, because of the growing realization of the importance glia plays in the development and functioning of the nervous system, lessons we can draw about(More)
The copepod crustacean Calanus finmarchicus plays a critical role in the ecology of the Gulf of Maine and other regions of the North Atlantic. To increase our understanding of the physiology of this species, a normalized, whole organism cDNA library was constructed, and expressed sequence tags (ESTs) of the clones were generated. Among these ESTs was one(More)
Nerve-impulse conduction is greatly speeded by myelin sheaths in vertebrates, oligochaete annelids, penaeid and caridean shrimp, and calanoid copepods. In the first three invertebrate cases, myelin arises from glial cells, as it does in vertebrates. The contribution of the glial cells to the layered structure of the myelin is clear: their nuclei are either(More)
The copepod Acartia tonsa exhibits a vigorous escape jump in response to rapid decreases in light intensity, such as those produced by the shadow of an object passing above it. In the laboratory, decreases in light intensity were produced using a fiber optic lamp and an electronic shutter to abruptly either nearly eliminate visible light or reduce light(More)
Peptides represent the largest class of signaling molecules used by nervous systems, functioning as locally-released paracrines and circulating hormones in both invertebrates and vertebrates. While many studies have focused on elucidating peptidergic systems in higher crustaceans, little is known about neuropeptides in the more primitive crustacean taxa.(More)
Almost 90 years ago, Lillie reported that rapid saltatory conduction arose in an iron wire model of nerve impulse propagation when he covered the wire with insulating sections of glass tubing equivalent to myelinated internodes. This led to his suggestion of a similar mechanism explaining rapid conduction in myelinated nerve. In both their evolution and(More)
Nerve impulse conduction is greatly increased by myelin, a multilayered membranous sheath surrounding axons. Best known from and most extensively investigated among vertebrates, a few invertebrates, including some superfamilies of copepod, have functionally and structurally similar myelin-like sheaths surrounding their axons. We examined the development of(More)