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R Gallego

Publications and source records attributed to R Gallego.

At least 55 records · Page 3Linked to original sources
PubMed1996

Thalamic relay of spontaneous retinal activity prior to vision.

Before vision, retinal ganglion cells produce spontaneous waves of action potentials. A crucial question is whether this spontaneous activity is transmitted to lateral geniculate nucleus (LGN) neurons. Using a novel in vitro preparation, we report that LGN neurons receive periodic barrages of postsynaptic currents from the retina that drive them to fire bursts of action potentials. Groups of LGN neurons are highly correlated in their firing. Experiments in wild-type and NMDAR1 knockout mice show that NMDA receptor activation is not necessary for firing. The transmission of the highly correlated retinal activity to the LGN supports the hypothesis that retinal waves drive retinogeniculate synaptic remodeling. Because LGN neurons are driven to fire action potentials, this spontaneous activity could also act more centrally to influence synaptic modification within the developing visual cortex.

2-Amino-5-phosphonovalerate↗
PubMed1996

Cellular distribution of prolactin receptors in human digestive tissues.

In the present study we analyzed the expression of prolactin receptors (PRLR) in human digestive tissues by immunohistochemistry. PRLR immunoreactivity was primarily localized in the cytoplasm. However, in some organs (liver and salivary glands) a nuclear positivity was also found. The liver was used as control and showed a diffuse immunostaining in the parenchymal cells. In the gastrointestinal tract, PRLR immunoreactivity was observed in the mucosa, muscularis layer, and nervous plexuses. The more intense immunostaining in the mucosa of the different segments was as follows: esophagus, superficial layers of the stratified squamous epithelium and mucous glands; stomach, parietal cells; small intestine, absorptive and Paneth cells; and colon, surface epithelium and superficial half of the crypts of Lieberkühn. In the salivary glands, immunoreactivity was strong in the mucous tubules, moderate in the ducts, and weak in the serous cells. Endocrine pancreas showed a more intense immunoreactivity than the pancreatic acini. By serial sections of the islets of Langerhans we showed that immunostaining was confined to B cells. These findings demonstrate the widespread distribution of PRLR in human digestive tissues and its localization both in cytoplasms and nuclei.

Cell Nucleus↗
PubMed1996

S-100 immunoreactivity in pulmonary neuroendocrine cells of newborn infants.

S-100 protein was demonstrated by immunohistochemical techniques in occasional solitary neuroendocrine cells of the lungs of newborn infants. The S-100 immunoreactivity was located in both the nucleus and the cytoplasm; its distribution in the cytoplasm was diffuse, there being no differences in staining intensity between the apical and basal poles. This homogeneus distribution of immunoreactivity argues against the S-100 being located in the dense-core granules, since these organelles are concentrated towards the basal pole. Double immunohistochemical techniques revealed that S-100 immunoreactive cells were also chromogranin A immunoreactive. Our results indicate that the S-100 positive population is a subset of the chromogranin A positive neuroendocrine cells. S-100 immunoreactivity was not detected in neuroepithelial bodies.

Female↗
PubMed1995

Neural cell adhesion molecule immunoreactivity in Merkel cells and Merkel cell tumours.

We have analysed the expression of the neural cell adhesion molecule (NCAM) in normal Merkel cells of pig and human skin, and in nine neuroendocrine carcinomas of the skin (Merkel cell carcinomas). NCAM immunoreactivity was observed in virtually all Merkel cells, both in epidermis and vibrissae of pig snout skin and in human epidermis. Immunostaining surrounded the entire surface of Merkel cells and was not restricted to the contact areas between Merkel cells and nerve terminals. All Merkel cell carcinomas studied were also positive for NCAM. The immunostaining pattern of the tumour cells was similar to that observed in normal Merkel cells; the immunoreactivity was confined to the cell membranes. These results suggest that NCAM may be used as an immunohistochemical marker for both Merkel cells and Merkel cell tumours.

Animals↗
PubMed1995

Effects of postganglionic nerve section on synaptic transmission in the superior cervical ganglion of the guinea-pig.

In sympathetic neurons, axotomy induces a marked depression in synaptic transmission. We asked whether the decrease in synaptic efficacy observed in a given axotomized cell is more severe if most of the postsynaptic neurons are also injured. Accordingly, we studied if the synaptic depression induced by axotomy in neurons with axons running in a postganglionic nerve is influenced by section of other postganglionic nerves. The excitatory postsynaptic potentials evoked by preganglionic stimulation were recorded intracellularly in an in vitro preparation of the superior cervical ganglion. Eight days after cutting the inferior postganglionic nerve, postsynaptic potentials recorded from neurons projecting through this nerve were smaller (median = 6 mV, n = 62) than the controls (median = 34 mV, n = 89), but were similar to those found after sectioning the inferior nerve plus most postganglionic nerves (median = 5 mV, n = 70). If the inferior nerve was left intact, but most postganglionic branches were cut, the synaptic potentials recorded from inferior nerve neurons were normal (median = 33 mV, n = 77). It is concluded that the synaptic depression induced by axotomy in a sympathetic neuron is not affected by axotomy of nearby ganglion cells, even if they share part of their presynaptic axons. This suggests that the effect of axotomy is restricted to the synaptic terminals on the injured neuron.

Animals↗
PubMed1994

Calcium-dependent chloride current induced by axotomy in rat sympathetic neurons.

1. Seven to ten days after sectioning their axons, rat sympathetic neurons were studied using intracellular recording techniques in an in vitro preparation of the superior cervical ganglion. 2. In 75% of axotomized cells, an after-depolarization (ADP) was observed following spike firing or depolarization with intracellular current pulses. Discontinuous single-electrode voltage-clamp techniques were employed to study the ADP. When the membrane potential was clamped at the resting level just after an action potential, a slow inward current was recorded in cells that showed an ADP. 3. In the presence of TTX and TEA, inward peaks and outward currents were recorded during depolarizing voltage jumps, followed by slowly decaying inward tail currents accompanied by large increases in membrane conductance. The inward peak and tail currents activated between -10 and -20 mV and reached maximum amplitudes around 0 mV. With depolarizing jumps to between +40 and +50 mV, net outward currents were recorded during the depolarizing jumps but inward tail currents were still activated. 4. In the presence of the Ca2+ channel blocker cadmium, or when Ca2+ was substituted by Mg2+, the ADP disappeared. In voltage-clamped cells, cadmium blocked the inward tail currents. The reversal potential for the inward tail current was approximately -15 mV. Substitution of the extracellular NaCl by sucrose or sodium isethionate increased the amplitude of the inward tail current, and displaced its equilibrium potential to more positive values. Changes in extracellular [K+] did not appreciably affect the inward tail current amplitude or equilibrium potential. Niflumic acid, a blocker of chloride channels activated by Ca2+, almost completely blocked the tail current. 5. No ADPs were observed in non-axotomized neurons, and when depolarizing pulses were applied while in voltage clamp no inward tail currents were evoked in these normal cells. 6. It is concluded that axotomy of sympathetic ganglion cells produces the appearance of a Ca(2+)-dependent chloride current responsible for the ADP observed following spike firing.

Animals↗
PubMed1994

Axotomy-induced changes in Ca2+ homeostasis in rat sympathetic ganglion cells.

Some of the marked biochemical and electrophysiological changes provoked by section of the axon in mature neurons suggest that the intracellular calcium concentration ([Ca2+]i) may be increased. We have measured the [Ca2+]i using the fluorescent indicator Indo-1 microinjected into rat superior cervical ganglion neurons. No differences in resting [Ca2+]i levels were found between control neurons and cells which had been axotomized 7-10 days before. However, the rise in [Ca2+]i evoked by orthodromic or antidromic stimulation and the recovery after the stimulating train were considerably slower in axotomized neurons than in control cells. We also found that the number of calbindin-D28k-immunopositive cells in the ganglion increases after axotomy, which could be related to the observed differences in calcium homeostasis.

Action Potentials↗
PubMed1994

Distribution of prothymosin alpha in rat and human adrenal cortex.

BACKGROUND: Prothymosin alpha (ProT) is a polypeptide widely distributed in the organism and expressed by cell types with a high proliferative capacity. The aim of the current work was to investigate if ProT was localized in the progenitor compartment of the adrenal cortex which, following the cell migration theory, corresponds to the zona glomerulosa. METHODS: We studied by immunohistochemical and in situ hybridization methods the distribution of ProT in rat and human adrenal cortex. Immunohistochemical techniques for the study of the proliferating cell nuclear antigen (PCNA) and incorporation of 5-bromo-2'-deoxyuridin during DNA synthesis were also done. Immunoelectron microscopic procedures were performed to determine the exact subcellular localization of ProT. RESULTS: ProT was found in the zona glomerulosa cells, but not in the cells of the remaining cortical layers (zonae fasciculata and reticularis). Glomerulosa cells showed immunostaining for ProT only in the nuclei, excluding the nucleoli. Variability in immunostaining intensity was found between different glomerulosa cells. In situ hybridization of ProT mRNA confirmed that ProT synthesis in adrenal cortex occurs only in the zona glomerulosa. The results obtained for proliferating cell nuclear antigen and incorporation of 5-bromo-2'-deoxyuridin confirmed that adrenocortical proliferation occurs in the zona glomerulosa. Ultrastructural immunocytochemistry showed labelling for ProT over the euchromatin, but not on the heterochromatin aggregations nor the nucleoli. CONCLUSIONS: The results presented here: 1) support the migration theory for the adrenocortical cell renewal, 2) demonstrate that ProT is present in the nuclei of proliferating cells (being associated with euchromatin), and 3) suggest that the study of ProT expression would be useful in distinguishing cycling from resting cells.

Adrenal Cortex↗
PubMed1993

Evolution of prothymosin alpha and proliferating cell nuclear antigen (PCNA) immunoreactivity through the development of rat ovarian follicles.

The cellular distribution of prothymosin alpha (ProT) was studied in ovarian follicles of adult cycling rats. We found positive granulosa and theca cells throughout follicular maturation. When both ProT and proliferating cell nuclear antigen (PCNA) immunoreactivity was studied, we observed that both proteins were expressed in the same granulosa and theca cells, although sometimes ProT immunoreactivity was weak or absent in the mitotic (M) phase. Moreover, both peptides share the nuclear distribution, but ProT immunoreactivity was never seen in nucleoli. Therefore, we conclude that in mitotic cells ProT is expressed only in actively proliferating cells, since all ProT-positive cells were also positive for PCNA. ProT and PCNA immunoreactivities during the meiotic division were studied in oocytes. The presence of PCNA was, unlike ProT, constant throughout follicle development (except atretic oocytes). Oocytes expressed ProT from primordial follicles to the eighth generation, but more developed oocytes and atretic oocytes were not immunoreactive. In hypophysectomized rats, all oocytes were immunoreactive. Interestingly, in hypophysectomized rats treated with follicle stimulating hormone (FSH) that promoted follicle development, the more developed oocytes did not show ProT immunoreactivity. Since hypophysectomized rats were not treated with luteinizing hormone we conclude that ProT expression is not required to complete meiotic division I.

Animals↗
PubMed1993

Effects of axotomy or target atrophy on membrane properties of rat sympathetic ganglion cells.

1. The electrical properties of rat superior cervical ganglion cells were examined in vitro with intracellular microelectrodes after axotomy or atrophy of the submandibular salivary gland. 2. Membrane time constant, input resistance and excitatory synaptic potentials (EPSPs) were decreased to about 50% of their control values 7-10 days after axotomy. 3. Axotomized ganglion cells also showed reduced action potentials and after-hyperpolarizations (AHPs). The AHP duration was reduced to 40% of the control value. 4. In 25% of the axotomized cells, the action potential was followed by an after-depolarization (ADP) instead of the AHP that was always present in control cells. In eleven out of seventeen axotomized cells with ADP, preganglionic stimulation failed to evoke an EPSP, whereas the failure of the synaptic response was never observed in control cells and occurred only in two of fifty-three axotomized cells with AHP. 5. In some axotomized cells with AHP, a depolarizing potential developed after a train of action potentials. This was never observed in control cells. 6. Sympathetic neurones innervating the submandibular gland in control animals had membrane properties similar to those observed in other ganglion cells. 7. The properties of neurones innervating the submandibular gland remained unaltered after the experimentally induced atrophy of the gland. 8. It is concluded that the marked effects of short-term axotomy on membrane properties of sympathetic ganglion cells are not reproduced by long-term atrophy of the target tissue.

Action Potentials↗
PubMed1992

Fos expression in the trigeminal sensory nuclei after a chemical lesion of the lower lip mucosa.

C-fos containing neurons were investigated in the trigeminal sensory nuclear complex and in the dorsal horns of the cervical spinal cord (C1-C2) of the rat after a chemical noxious stimulus was applied to the lower lip mucosa. Numerous labelled neuronal nuclei were detected in the dorsolateral area of the caudal half of the trigeminal nucleus interpolaris, and in Rexed's laminae I-IIo of the dorsomedial area of the trigeminal nucleus caudalis and rostral C1. A few c-fos-labelled neurons were observed in laminae IIi and V. No Fos expression was detected in the trigeminal oral and principal nuclei.

Acetates↗
PubMed1992

Blockade by calcium antagonists of chemical excitation and sensitization of polymodal nociceptors in the cat's cornea.

1. The possibility that a modified Ca2+ channel mediates chemical and thermal excitation of nociceptors was examined in single polymodal nociceptive fibres of the cat's cornea. 2. Ca2+ channel blockers cadmium (2.5 mM) and diltiazem (1 mM), and high external [Ca2+] (40 mM), markedly reduced nociceptive responses to topical acidic solutions (pH 4.5). 3. Decreasing the pH to 6.5 did not cause excitation, but reduced the subsequent response to pH 4.5 buffer. 4. Diltiazem (1 mM), applied after repeated stimulation with stepped heating pulses (35 to 47-49 degrees C in 2 degrees C steps) decreased the impulse responses elicited by heat. The decrease in threshold to thermal stimulation produced by repeated heating was blocked by diltiazem. 5. Mechanical threshold and mechanical responsiveness of corneal polymodal nociceptors was not modified by Ca2+ antagonists or by a high-Ca2+ solution. 6. These results offer indirect evidence that proton-activated Ca2+ channels mediate stimulation of nociceptors by acidic solutions. The same type of ionic channel appears to be involved in the response of nociceptors to heat and in sensitization, but not in their responsiveness to mechanical stimulation. The blockade of nociceptive responses by Ca2+ antagonists opens the possibility of using Ca2+ blockers as selective analgesic drugs.

Animals↗
PubMed1992

Prothymosin alpha expression in lymph nodes and tonsils: an optical and ultrastructural study.

Prothymosin alpha (ProT alpha) distribution in human and rat lymph nodes and human tonsils was studied by means of immunohistochemical methods, using specific antibodies raised against thymosin alpha 1. We observed ProT alpha immunoreactivity in lymphoid cells of the germinal centers both in humans and rats. In human tonsils, positive cells were also seen in the basal layer of the surface epithelium. These results support the hypothesis that ProT alpha expression is restricted to actively proliferating cells. Immunoelectron microscopy revealed that ProT alpha was located in the nucleus, mainly in the border between euchromatin and heterochromatin.

Animals↗
PubMed1992

Reduced junctional permeability at interrhombomeric boundaries.

Intercellular communication is considered to have a role during pattern specification processes in early embryonic development. This report analyzes the changing gap junctional communication properties of chick neuroepithelial cells depending on their position relative to the segmental partitions of the rhombencephalon. Intercellular electrical coupling and dye transfer were studied with microelectrode techniques. Neuroepithelial cells were electrically coupled irrespective of their location relative to interneuromeric boundaries. Iontophoretic injection of biocytin or Lucifer Yellow into single cells inside the rhombomeres was followed by transjunctional diffusion to the surrounding cells. In contrast, dye transfer was strictly limited when the diffusion zone contacted the cells forming the interneuromeric limits. Label injected into the boundary cells did not spread to other cells at all. Avian interrhombomeric boundaries are thus sites of reduced junctional permeability during early morphogenesis.

Animals↗
PubMed1990

Axotomy decreases conduction velocity of unmyelinated sensory fibres.

We have examined the effect of axotomy on the conduction velocity of unmyelinated sensory fibres in the vagus nerve of the rabbit. In an in vitro preparation of the nodose ganglion, conduction velocity was calculated for each cell from the latency of the intracellularly recorded action potential evoked by vagus nerve stimulation. The average velocity of sensory fibres conducting at less than 1.1 m/s, was 0.53 m/s in 287 control cells and 0.45 m/s in 269 neurones recorded 10 days after cutting the vagus nerve. Therefore, peripheral axotomy decreases conduction velocity in mammalian unmyelinated sensory axons.

Action Potentials↗
PubMed1990

Prothymosin alpha expression is associated to cell division in rat testis.

Using immunohistochemical methods, we have investigated the cellular distribution of prothymosin alpha (ProT) in adult rat testis. A policlonal antibody raised against thymosin alpha 1 conjugated to keyhole limpet hemocyanin was used. ProT immunoreactivity was observed in the cytoplasm and nucleus of spermatogonia and primary spermatocytes in initial phases of the first meiotic division, preleptotene, leptotene and zygotene. However, in pachytene phase they already showed a weak or negative staining. On the other hand, secondary spermatocytes, spermatids, spermatozoa and Sertoli cells were not stained. Based on this fact we suggest that ProT is present in the proliferative cycle in the final steps of G1 phase, throughout the S and G2 phases and in initial steps of the prophase.

Animals↗