Maria del Pilar Gomez

Maria del Pilar Gomez
National University of Colombia | UNAL · Departamento de Biología (Bogotá)

Doctor of Philosophy

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50
Publications
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615
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Publications

Publications (50)
Article
Full-text available
Although lithium has long been one of the most widely used pharmacological agents in psychiatry, its mechanisms of action at the cellular and molecular levels remain poorly understood. One of the targets of Li ⁺ is the phosphoinositide pathway, but whereas the impact of Li ⁺ on inositol lipid metabolism is well documented, information on physiologi...
Article
Full-text available
It has been known for a long time that inositol-trisphosphate (IP 3 ) receptors are present in the axon of certain types of mammalian neurons, but their functional role has remained unexplored. Here we show that localized photolysis of IP 3 induces spatially constrained calcium rises in Purkinje cell axons. Confocal immunohistology reveals that the...
Article
Full-text available
Channelopsins and photo-regulated ion channels make it possible to use light to control electrical activity of cells. This powerful approach has lead to a veritable explosion of applications, though it is limited to changing membrane voltage of the target cells. An enormous potential could be tapped if similar opto-genetic techniques could be exten...
Article
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The two basic animal photoreceptor types, ciliary and microvillar, use different light-transduction schemes: their photopigments couple to G t versus G q proteins, respectively, to either mobilize cyclic nucleotides or trigger a lipid signaling cascade. A third class of photoreceptors has been described in the dual retina of some marine invertebrat...
Article
Full-text available
Melanopsin, the photopigment of the "circadian" receptors that regulate the biological clock and the pupillary reflex in mammals, is homologous to invertebrate rhodopsins. Evidence supporting the involvement of phosphoinositides in light-signaling has been garnered, but the downstream effectors that control the light-dependent conductance remain un...
Preprint
The discovery of melanopsin-expressing, intrinsically photosensitive ganglion cells in the mammalian retina has shaken the long-standing belief that rods and cones are the only photoreceptor cells of the vertebrate eye. Exploration of melanopsin orthologs in other vertebrate species revealed that in birds this photopigment is not confined to a few...
Conference Paper
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The discovery of melanopsin-expressing intrinsically photoresponsive retinal ganglion cells (ipRGCs) paved the way for understanding light regulation of non-visual functions, like the pupillary reflex and circadian rhythms entrainment. The scarcity of mammalian ipRGCs, however, is a hurdle for studying melanopsin signaling. In the avian retina mela...
Article
Full-text available
Melanopsin, a photopigment related to the rhodopsin of microvillar photoreceptors of invertebrates, evolved in vertebrates to subserve nonvisual light-sensing functions, such as the pupillary reflex and entrainment of circadian rhythms. However, vertebrate circadian receptors display no hint of a microvillar specialization and show an extremely low...
Conference Paper
In mammals, the discovery of melanopsin and intrinsic light responsiveness in a small population of retinal ganglion cells (ipRGCs) paved the way for understanding light regulation of nonvisual functions, like the pupillary reflex or the entrainment of circadian rhythms. The scarcity of ipRGCs, however, is a hurdle for investigating melanopsin sign...
Article
Full-text available
Melanopsin, the receptor molecule that underlies light sensitivity in mammalian 'circadian' receptors, is homologous to invertebrate rhodopsins and has been proposed to operate via a similar signaling pathway. Its downstream effectors, however, remain elusive. Melanopsin also expresses in two distinct light-sensitive cell types in the neural tube o...
Article
Full-text available
Two types of microvillar photoreceptors in the neural tube of amphioxus, an early chordate, sense light via melanopsin, the same photopigment as in "circadian" light detectors of higher vertebrates. Because in amphioxus melanopsin activates a G(q)/phospholipase C cascade, like phototransduction in arthropods and mollusks, possible commonalities in...
Article
Full-text available
Arrestin was identified in ciliary photoreceptors of Pecten irradians, and its role in terminating the light response was established electrophysiologically. Downstream effectors in these unusual visual cells diverge from both microvillar photoreceptors and rods and cones; the finding that key regulatory mechanisms of the early steps of visual exci...
Article
Full-text available
In microvillar photoreceptors, light stimulates the phospholipase C cascade and triggers an elevation of cytosolic Ca2+ that is essential for the regulation of both visual excitation and sensory adaptation. In some organisms, influx through light-activated ion channels contributes to the Ca2+ increase. In contrast, in other species, such as Lima, C...
Article
Full-text available
The two fundamental lineages of photoreceptor cells, microvillar and ciliary, were long thought to be a prerogative of invertebrate and vertebrate organisms, respectively. However evidence of their ancient origin, preceding the divergence of these two branches of metazoa, suggests instead that they should be ubiquitously distributed. Melanopsin-exp...
Article
Full-text available
Spatial vision in different organisms is mediated by 2 classes of photoreceptors: microvillar and ciliary. Recently, additional photosensitive cells implicated in nonvisual light-dependent functions have been identified in the mammalian retina. A previously undescribed photopigment, melanopsin, underlies these photoresponses, and it has been propos...
Article
Full-text available
The hyperpolarizing receptor potential of ciliary photoreceptors of scallop and other mollusks is mediated by a cGMP-activated K conductance; these cells also express a transient potassium current triggered by depolarization. During steady illumination, the outward currents elicited by voltage steps lose their decay kinetics. One interesting conjec...
Article
Full-text available
In microvillar photoreceptors the pivotal role of phospholipase C in light transduction is undisputed, but previous attempts to account for the photoresponse solely in terms of downstream products of phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis have proved wanting. In other systems PIP2 has been shown to possess signaling functions of it...
Article
Full-text available
Calcium is thought to be essential for adaptation of sensory receptor cells. However, the transduction cascade of hyperpolarizing, ciliary photoreceptors of the scallop does not use IP3-mediated Ca release, and the light-sensitive conductance is not measurably permeable to Ca2+. Therefore, two typical mechanisms that couple the light response to [C...
Article
The mechanisms by which Ca2+ regulates light adaptation in microvillar photoreceptors remain poorly understood. Protein kinase C (PKC) is a likely candidate, both because some sub-types are activated by Ca2+ and because of its association with the macromolecular 'light-transduction complex' in Drosophila. We investigated the possible role of PKC in...
Article
Full-text available
The hyperpolarizing receptor potential of scallop ciliary photoreceptors is attributable to light-induced opening of K(+)-selective channels. Having previously demonstrated the activation of this K(+) current by cGMP, we examined upstream events in the transduction cascade. GTP-gamma-S produced persistent excitation after a flash, accompanied by de...
Article
Full-text available
The light-dependent K conductance of hyperpolarizing Pecten photoreceptors exhibits a pronounced outward rectification that is eliminated by removal of extracellular divalent cations. The voltage-dependent block by Ca(2+) and Mg(2+) that underlies such nonlinearity was investigated. Both divalents reduce the photocurrent amplitude, the potency bein...
Article
Full-text available
The light-dependent K conductance of hyperpolarizing Pecten photoreceptors exhibits a pronounced outward rectification that is eliminated by removal of extracellular divalent cations. The voltage-dependent block by Ca2+ and Mg2+ that underlies such nonlinearity was investigated. Both divalents reduce the photocurrent amplitude, the potency being si...
Article
Full-text available
Visual excitation in rhabdomeric photoreceptors is thought to be mediated by activation of a light-regulated phospholipase C (PLC) and the consequent hydrolysis of phosphatidylinositol bisphosphate. Whereas much attention has been devoted to inositol trisphosphate (IP3) production and intracellular Ca2+ release, little is known about the possible r...
Article
1. Hyperpolarizing scallop photoreceptors, like vertebrate rods, use cGMP as an internal messenger and their light-sensing structure is also of ciliary origin. To ascertain possible functional similarities between the light-sensitive conductances in the two classes of visual cells, we examined in scallop photoreceptors the effects of several antago...
Article
Full-text available
The ability of scallop hyperpolarizing photoreceptors to respond without attenuation to repetitive flashes, together with their low light sensitivity, lack of resolvable quantum bumps and fast photoresponse kinetics, had prompted the suggestion that these cells may be constitutively in a state akin to light adaptation. We here demonstrate that thei...
Article
Full-text available
The ability of scallop hyperpolarizing photoreceptors to respond without attenuation to repetitive flashes, together with their low light sensitivity, lack of resolvable quantum bumps and fast photoresponse kinetics, had prompted the suggestion that these cells may be constitutively in a state akin to light adaptation. We here demonstrate that thei...
Article
Full-text available
The receptor potential of rhabdomeric photoreceptors is mediated primarily by a Na influx, but other ions must also permeate through light-dependent channels to account for some properties of the photoresponse. We examined ion conduction in macroscopic and single-channel light-induced currents of slug and scallop photoreceptors. In the absence of N...
Article
The activation of light-dependent K+ channels in ciliary photoreceptors from Pecten was investigated using intracellular dialysis of putative messengers and modulators. Neither elevated [Ca2+] nor BAPTA changed the membrane current in the dark or the light response. IP3 and the antagonists heparin and decavanadate were similarly ineffective, indica...
Article
Full-text available
The tight-seal whole-cell recording technique was used to examine the effect of tetraethylammonium (TEA) and 4-aminopyridine (4-AP) on the photocurrent of hyperpolarizing ciliary photoreceptors isolated from the distal retina of the bay scallop (Pecten irradians). In these cells, light causes an increase in a conductance that is highly selective to...
Article
Full-text available
Tight-seal recording was employed to investigate membrane currents in hyperpolarizing ciliary photoreceptors enzymatically isolated from the eyes of the file clam (Lima scabra) and the bay scallop (Pecten irradians). These two organisms are unusual in that their double retinas also possess a layer of depolarizing rhabdomeric cells. Ciliary photorec...
Article
1. Whole-cell and perforated-patch tight-seal recording techniques were used to characterize the voltage-dependent membrane conductances of the Y-79 cells, a human retinoblastoma line composed of pluripotential retinal precursor cells. 2. Membrane resistance and capacitance were measured under current clamp, yielding approximate average values of 1...
Article
1. Neuronlike differentiation of Y-79 retinoblastoma was chemically induced in vitro, by plating the cells onto a poly-D-lysine and laminin substrate. The changes in voltage-dependent conductances after 48-72 h were examined with the whole-cell tight-seal and the perforated-patch recording techniques. 2. Although outward currents carried by potassi...
Article
Full-text available
Retinas from the scallop Pecten irradians were enzymatically dispersed, yielding a large number of isolated photoreceptors suitable for tight-seal recording. Whole-cell voltage clamp measurements demonstrated that the phototransducing machinery remained intact: quantum bumps could be elicited by dim illumination, while brighter flashes produced lar...
Article
A protocol was developed to isolate enzymatically photoreceptors from the retina of the squid, Loligo pealei. The procedure routinely results in a high yield of intact cells. Examination of solitary photoreceptors under Nomarski optics revealed that the fine morphological features described in anatomical studies of retinal sections are retained. Th...
Article
Previous studies have demonstrated that brief fasting augments and refeeding a complete diet diminishes the breakdown of myofibrillar proteins in rat skeletal muscle. The purpose of the present study was to determine which dietary component(s) was responsible for this effect and to determine the role of insulin and amino acids. Myofibrillar proteol...
Article
Full-text available
A B S T R A C T Retinas from the scallop Pecten irradians were enzymatically dispersed, yielding a large number of isolated photoreceptors suitable for tight-seal recording. Whole-cell voltage clamp measurements demonstrated that the phototransducing machinery remained intact: quantum bumps could be elicited by dim illumination, while brighter flas...
Article
Thesis (Ph. D.)--Boston University, 1991. Vita. Includes bibliographical references (leaves 78-96).

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