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R Yuste

Publications and source records attributed to R Yuste.

50 records · Page 3Linked to original sources
PubMed1995

[Gastrointestinal hemorrhage secondary to heterotopic jejunal pancreas].

A case of heterotopic pancreas located in the small intestine is herewith presented. The 19-years male patient had been admitted three times since 1991 for an anemic syndrome secondary to melena. The origin of the hemorrhage was not determined with the studies performed (intestinal transit, opaque enema, esophagogastroscopy, colonoscopy and gammagraphy with technetium 99). On the last admission a vascular lesion low flow was observed on arteriography of the upper mesenteric artery on the mesenteric edge of the proximal jejunum. Following laparotomy a small tumor was found in the jejunum and 5 cm of the intestine including the tumor was resected. The anatomic pathologic results demonstrated a heterotopic pancreas.

Adult↗
PubMed1994

Anatomical and functional imaging of neurons using 2-photon laser scanning microscopy.

Light scattering by brain tissue and phototoxicity are major obstacles to the use of high-resolution optical imaging and photo-activation ('uncaging') of bioactive compounds from inactive ('caged') precursors in intact and semi-intact nervous systems. Optical methods based on 2-photon excitation promise to reduce these obstacles (Denk, 1994; Denk et al., 1990, 1994). Here we show a range of imaging modes based on 2-photon laser scanning microscopy (TPLSM) as applicable to problems in neuroscience. Fluorescence images were taken of neurons labeled with ion-sensitive and voltage-sensitive dyes in invertebrate ganglia, mammalian brain slices, and from the intact mammalian brain. Scanning photochemical images with whole-cell current detection (Denk, 1994) show how the distribution of neurotransmitter receptors on the surface of specific cells can be mapped. All images show strong optical sectioning and usable images can be obtained at depths greater than 100 microns below the surface of the preparation.

Animals↗
PubMed1994

Ca2+ accumulations in dendrites of neocortical pyramidal neurons: an apical band and evidence for two functional compartments.

Apical dendrites constitute a prominent feature of the microcircuitry in the neocortex, yet their function is poorly understood. Using fura-2 imaging of layer 5 pyramidal neurons from slices of rat somatosensory cortex, we have investigated the Ca2+ influx into dendrites under intracellular, antidromic, synaptic, and receptor-agonist stimulation. We find three spatial patterns of Ca2+ accumulations: an apical band in the apical dendrite approximately 500 microns from the soma, an accumulation restricted to the basal dendrites, soma, and proximal apical dendrite, and a combination of both of these. We show that the apical band can be activated antidromically and synaptically and that, under blocked Na+ and K+ conductances, it generates Ca2+ spikes. Thus, the apical band may serve as a dendritic trigger zone for regenerative Ca2+ spikes or as a current amplifier for distal synaptic events. Our results suggest that the distal apical dendrite should be considered a separate functional compartment from the rest of the cell.

Animals↗
PubMed1993

Extensive dye coupling between rat neocortical neurons during the period of circuit formation.

A low molecular weight intracellular tracer, Neurobiotin, was injected into single neurons in living slices of rat neocortex made at postnatal days 5-18. Between days 5 and 12, 66% of single-neuron injections labeled clusters of up to 80 neurons surrounding the injected cell. Coupling between neurons occurred primarily through dendrites. Injections done in the presence of halothane, a gap junction blocker, abolished the spread of tracer to surrounding neurons, implying that gap junctions mediate coupling. Injections done after day 16 resulted in little or no dye coupling. We conclude that transient local coupling via gap junctions in developing cortex may provide a pathway for communicating intercellular signals, including subthreshold electrical activity, and thereby enable temporal coordination of local neuronal ensembles during circuit formation.

Aging↗
PubMed1992

Neuronal domains in developing neocortex.

The mammalian neocortex consists of a mosaic of columnar units whose development is poorly understood. Optical recordings of brain slices labeled with the fluorescent calcium indicator fura-2 revealed that the neonatal rat cortex was partitioned into distinct domains of spontaneously coactive neurons. In tangential slices, these domains were 50 to 120 micrometers in diameter; in coronal slices they spanned several cortical layers and resembled columns found in the adult cortex. In developing somatosensory cortex, domains were smaller than, and distinct from, the barrels, which represent sensory input from a single vibrissa. The neurons within each domain were coupled by gap junctions. Thus, nonsynaptic communication during cortical development defines discrete multicellular patterns that could presage adult functional architecture.

Action Potentials↗
PubMed1992

[Dubin-Johnson syndrome. Presentation of 3 cases. Review of the national literature].

Three patients, two male and one female, 42, 64 and 20 years old respectively, with a Dubin-Johnson syndrome are reported. Both men referred jaundice since several years and in the woman's case, the onset of the illness took place during the last term of her second pregnancy. In two patients, liver aspect and it's biopsy were diagnostic. In the other, who was hospitalized because of a myocardial infarction, a hepatic gammagraphy with Tc 99 HIDA was made. No case was associated with biliary lithiasis and only one patient had other members in his family with the illness.

Adult↗
PubMed1991

Control of postsynaptic Ca2+ influx in developing neocortex by excitatory and inhibitory neurotransmitters.

We assessed the pathways by which excitatory and inhibitory neurotransmitters elicit postsynaptic changes in [Ca2+]i in brain slices of developing rat and cat neocortex, using fura 2. Glutamate, NMDA, and quisqualate transiently elevated [Ca2%]i in all neurons. While the quisqualate response relied exclusively on voltage-gated Ca2+ channels, almost all of the NMDA-induced Ca2+ influx was via the NMDA ionophore itself, rather than through voltage-gated Ca2+ channels. Glutamate itself altered [Ca2+]i almost exclusively via the NMDA receptor. Furthermore, synaptically induced Ca2+ entry relied almost completely on NMDA receptor activation, even with low-frequency stimulation. The inhibitory neurotransmitter GABA also increased [Ca2+]i, probably via voltage-sensitive Ca2+ channels, whereas the neuromodulator acetylcholine caused Ca2+ release from intracellular stores via a muscarinic receptor. Low concentrations of these agonists produced nonperiodic [Ca2+]i oscillations, which were temporally correlated in neighbouring cells. Optical recording with Ca2(+)-sensitive indicators may thus permit the visualization of functional networks in developing cortical circuits.

Acetylcholine↗
PubMedDate not supplied

Role of calcium electrogenesis in apical dendrites: generation of intrinsic oscillations by an axial current.

Dendrites are covered with conductances whose function is still mysterious. Using intracellular recording and calcium imaging, we describe an electrogenic band of calcium channels in distal apical dendrites of layer 5 pyramidal neurons (Yuste et al., 1994). We now explore the functional consequences of this distal electrogenic area with multicompartmental numerical simulations. A calcium imaging and electrophysiological database from a single neuron, recorded under blocked sodium and potassium conductances, is replicated by simulations having increased dendritic calcium current. In these models a significant axial current flows from the apical dendrite into the somatic region, activating low-threshold calcium channels and generating oscillations similar to those seen in the electrophysiological data. We propose that the distal electrogenic area in apical dendrites serves to inject current into the soma and produce intrinsic oscillatory dynamics.

Animals↗
PubMedDate not supplied

Gap junctional communication and the development of local circuits in neocortex.

In the neocortex, as well as in many other brain regions, neurons responding to similar stimulus features are usually found close to one another. Here we examine the possible role of gap junctional communication in forming and defining these local neuronal groupings, examples of which may be the columns found in the neocortex of virtually all mammalian species. We have approached this question experimentally in cortical brain slices using calcium imaging to visualize multicellular activity patterns, and tracer injections to identify the anatomical pattern of gap junction coupling in the developing neocortex. Our results suggest that dendrodendritic gap junctional communication may be involved in the formation of local connectivity, most likely by synchronizing electrical or biochemical activity among neighboring neurons.

Animals↗
PubMedDate not supplied

[On the function of dendritic filopodia].

INTRODUCTION: Dendritic spines were first described by Ramón y Cajal in 1888, and considered by him to be the major sites of axo dendritic apposition and therefore of synaptic input in the CNS. Although a considerable wealth of information has been gathered over the last few decades about the function of spines in the mature nervous system, much less is known about how spines first appear on the otherwise smooth dendritic shafts. DEVELOPMENT: The earliest dendritic appendages, known as filopodia, are long and thin protrusions that occur predominantly during early postnatal development of the mammalian CNS. It is tempting to consider filopodia simply as precursors to spines because at first glance their overall shape is similar to that of mature spines and because their expression during development precedes that of spines. However, the elongated shape of dendritic filopodia (reminiscent of that of axonal filopodia and filopodia in non-neuronal cells) suggests an exploratory function, so that their role may be to contact axons in order to establish early synapses, independently of the eventual formation of spines. CONCLUSIONS: Here we review the literature on dendritic filopodia in an attempt to resolve this issue regarding these two distinct (though potentially overlapping) roles of filopodia in development: spinogenesis vs synaptogenesis. We summarize what is known about the physical characteristics and developmental time course of filopodia expression, as well as the mechanisms of growth and motility of these early dendritic protrusions, both in the intact nervous system and in pathologic settings. Throughout this review we present evidence that supports two hypotheses: that filopodia and spines are two inherently different types of protrusions, and that the role of dendritic filopodia is to capture axons and make early synapses, rather than transform into spines. Finally, we also discuss the potential role of filopodia in the sculpting of the dendritic tree. We also postulate that filopodia have additional important roles in regeneration and repair, in developmental plasticity and in the elaboration of dendritic arbors. These functions may not be limited to a specific developmental period, but probably extend into adulthood. We end by discussing specific experiments that could serve to test these hypotheses.

Animals↗