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M Carrasco

Publications and source records attributed to M Carrasco.

At least 55 records · Page 3Linked to original sources
PubMed1997

Effect of cholecystokinin and gastrin on human peripheral blood lymphocyte functions, implication of cyclic AMP and interleukin 2.

The effects in vitro of sulphated and desulphated cholecystokinin (CCK)-8, and of gastrin-17 and gastrin-34 were studied at concentrations from 10(-14) M to 10(-6) M on several functions of human peripheral blood lymphocytes, i.e.: adherence to substrate, mobility (spontaneous and directed by a chemical gradient or chemotaxis), and spontaneous and phytohaemagglutinin (PHA)-mediated proliferation. All peptides, at concentrations from 10(-10) M to 10(-8) M, inhibited significantly the mobility capacity and PHA-induced proliferation, and increased the adherence and spontaneous proliferation. A dose-response relationship was observed, with a maximum response of lymphocyte functions at 10(-10) M. These peptides induced a significant increase of intracellular cAMP levels at 30 and 60 sec. Because lymphoproliferation requires production of interleukin 2 (IL-2) by lymphocytes, we also measured the IL-2 production in the presence of the CCK and gastrin peptides, finding that this production was higher than in the respective controls. When peptides were added to samples containing PHA, the IL-2 production was significantly decreased with respect to samples incubated with PHA alone. These results suggest that the CCK and gastrin peptides are negative modulators of lymphocyte mobility (spontaneous mobility and chemotaxis), causing an inhibition of these activities through an increase of intracellular cAMP levels, and of PHA-induced lymphoproliferation, which is mediated by a diminution of the IL-2 production by lymphocytes.

Adult↗
PubMed1997

Oronasopharyngeal suction at birth: effects on arterial oxygen saturation.

The effect of oronasopharyngeal suction (ONPS) on arterial oxygen saturation (SaO2) is described in a controlled study of 30 normal term newborn infants. In 15 of them, ONPS was performed immediately after birth. The SaO2 value was recorded through a pulse oximeter. The ONPS group had a significantly lower SaO2 between the first and the sixth minutes of life and took longer to reach 86% and 92% saturation. According to this study, ONPS should not be performed as a routine procedure in normal, term, vaginally born infants.

Delivery, Obstetric↗
PubMed1997

Cortical magnification neutralizes the eccentricity effect in visual search.

We report two visual search experiments that explain an eccentricity effect previously found: detection of both feature and conjunction targets becomes increasingly less efficient as the orientation target appears at more distant field eccentricities (Carrasco et al., 1995). By cortically magnifying the stimuli we flattened out this effect for both feature and conjunction tasks. We conclude that spatial resolution factors affect visual search findings that have hitherto been attributed to covert attention. We stress the importance of analyzing data by target position to minimize the confound of the set size effect and retinal/field eccentricity. An alternative theory of orientation asymmetries is offered.

Analysis of Variance↗
PubMed1997

Inhibition of human neutrophil functions by sulfated and nonsulfated cholecystokinin octapeptides.

The effects of CCK-8s and desulfated CCK-8 at concentrations ranging from 10(-14) to 10(-6) M were studied in vitro on several functions of human peripheral neutrophils: adherence to substrate, mobility (spontaneous and directed by a chemical gradient or chemotaxis), ingestion of inert particles (latex beads) or cells (Candida albicans), and production of superoxide anion measured by the nitroblue tetrazolium reduction test. The effect of CCK-8s on intracellular levels of cAMP was investigated as well as the implication of calcium in the action of CCK-8s on phagocytic function using stimulants and inhibitors of both intracellular and extracellular calcium channels. The two peptides, at concentrations from 10(-12) to 10(-8) M, inhibited significantly both mobility and ingestion capacities and increased adherence to substrate. A dose-response relationship was observed with a maximum inhibition of neutrophil functions at 10(-10) M, CCK-8s and desulfated CCK-8 induced in these cells a significant, but transient, increase of cAMP levels at 60 s. Moreover, CCK-8s was found to inhibit completely the stimulation of latex bead phagocytosis in neutrophils produced by the calcium ionophore A23187. These results suggest that CCK-8 is a negative modulator of several neutrophil functions and that the inhibition of these activities could be carried out through an increase of the intracellular cAMP levels and a decrease of the extracellular calcium input.

Adult↗
PubMed1997

Methylating activity in ovarian membranes changes during the estrous cycle.

The aim of this study was to characterize the methylation system of phosphatidylethanolamine (PE) in the ovarian membranes and identify their possible role on the ovarian physiology. The presence of two methylating activities was found, by using S-adenosyl-L-[methyl-3H] methionine (SAM) as methyl donor. One of them (Met I) uses PE as substrate, and the other one, (Met II), catalyses the two successive methylations of phosphatidyl-N-monomethylethanolamine (PME) to phosphatidylcholine (PC). Met I shows a Km value of 5.71 microM and a Vm of 1.53 pmol/mg protein x min, working at pH 6.5, which seems to be the optimum. Met II exhibits low affinity for SAM, a Km of 50 microM, a Vm of 1.2 pmol/mg protein x min and it works an optimum pH of 9.5. Those enzymatic properties are in agreement with the amount of monomethylated and trimethylated products found working at pH 6.5 and 9.5, respectively. In order to investigate whether this enzyme system is affected or not by the hormonal environment influencing the ovary during the estrous cycle, the methylating activity was measured at its different stages. Both methylating activities were induced on proestrus but only Met I on diestrus. The total methylating activity increases when the ovarian membranes were obtained from rats injected with pregnant mare serum gonadotrophin (PMSG). Those results suggest that phospholipid methylation could be regulated by the hormonal environment during the estrous cycle.

Animals↗
PubMed1997

Modulation of human neutrophil function in vitro by gastrin.

We have studied the effects in vitro of gastrin-17 and gastrin-34, at concentrations from 10(-14) M to 10(-6) M, on several of the functions of peripheral blood human neutrophils, i.e. adherence to substrate, mobility (spontaneous and directed by a chemical gradient or chemotaxis), ingestion of inert particles (latex beads) and cells (Candida albicans) and superoxide anion production. Both gastrins inhibited several steps of the phagocytic process of human neutrophils, such as mobility and ingestion. By contrast, these peptides increased adherence and had no effect on superoxide anion production. In general, these effects were significant at peptide concentrations between 10(-12) M and 10(-8) M with a maximal effect at 10(-10) M. In addition, gastrin peptides induced a significant increase in intracellular cAMP levels at 30, 60 and 120 s. Moreover, the inhibitory effect of gastrin-17 on the ingestion capacity of neutrophils (latex bead phagocytosis) was similar to that obtained with EGTA, a well-known extracellular calcium chelating compound. Gastrin-17 was found to inhibit completely the stimulation of latex bead phagocytosis in neutrophils caused by the calcium ionophore A23187. These results suggest that gastrin is a negative modulator of the phagocytic process of human neutrophils, and that this effect might involve an increase in intracellular cAMP levels and a decrease in calcium entry into the cells.

Adult↗
PubMed1997

c-fos expression in the rat hypothalamic paraventricular nucleus induced by LiCl: descending projections to the dorsal vagal motor nucleus.

Anorexia inducing lithium chloride is believed to involve descending projections from hypothalamus to preganglionic autonomic output neurons. A multiple-labelling technique has presently been used to analyze the anatomical projections of lithium chloride sensitive neurons in the hypothalamus. Immunolabelling of c-fos was performed to stain neurons activated after LiCl administration, while neurons projecting toward vagal parasympathetic preganglionic levels were identified by injection of diamidino yellow in the dorsal motor nucleus of the vagus. Perikarya of descending neurons were mainly observed in the ventral and lateral areas of the paraventricular hypothalamic nucleus. In contrast, lithium chloride activated neurons were observed mainly in the magnocellular division of the paraventricular nucleus and supraoptic nucleus. Double-labelled neurons were not observed. These data provide evidence that lithium chloride sensitive neurons in the paraventricular nucleus are clearly different from those descending toward preganglionic vagal outflow neurons.

Animals↗
PubMed1996

Hypothalamic neuron projection to autonomic preganglionic levels related with glucose metabolism: a fluorescent labelling study in the rat.

The location of hypothalamic paraventricular neurons projecting to sympathetic preganglionic levels and related to the autonomic regulation of various organs involved in glucose metabolism (OGM) was determined by ipsilateral injections of two fluorescent tracers, Diamidino Yellow into the left dorsal motor nucleus of the vagus and Fast Blue into the left intermediolateral cell column of the T8-T9 spinal cord. Hypothalamospinal neurons were mainly located in the dorsal part of the paraventricular hypothalamic nucleus (PVH) and the hypothalamobulbar neurons were most abundant in the ventral, medial and extreme lateral parts of the PVH. No double-labelled neurons were found in the hypothalamus. These results can help the knowledge of the neural hypothalamic network related with the autonomic hypothalamic control.

Animals↗
PubMed1996

Modulation of murine peritoneal macrophage functions by gastrin.

The effect in vitro of gastrin-17 and gastrin-34 was studied at concentrations from 10(-12) to 10(-6) M on several functions of resting peritoneal macrophages from BALB/c mice: adherence to substrate, mobility (spontaneous and directed by chemical gradient or chemotaxis), and ingestion of inert particles (latex beads) or cells (Candida albicans). Both gastrins, at concentrations from 10(-10) to 10(-8) M, inhibited significantly all functions studied with the exception of adherence, which was increased. A dose-response relationship was observed, with a maximum inhibition of macrophage functions found at 10(-9) M. These peptides induced in murine macrophages a significant increase of cAMP levels at 60 and 120 s. Adenosine, an adenylate cyclase inhibitor, significantly increased the ingestion of latex beads, whereas the combined presence of adenosine and either G-17 or G-34 produced similar values to those of control samples without adenosine or gastrin. These results suggest that gastrin is a negative modulator of several macrophage functions, and that the inhibition of these activities is carried out through an increase of intracellular cAMP levels.

Adenosine↗
PubMed1995

Instability of the CGG repeat at the FRAXA locus and variable phenotypic expression in a large fragile X pedigree.

Fragile X syndrome is the major cause of inherited mental retardation. The molecular basis for the expression of the fragile X phenotype is the expansion of an unstable CGG repeat element which inhibits transcription of the FMR1 gene. The fragile X syndrome shows great diversity in its phenotype as well as in its cytogenetic and molecular status. We have studied, in a large fragile X family, the correlation between the molecular data and the phenotypic expression of the syndrome. We report two brothers who carry identical unmethylated premutated alleles but present different clinical phenotypes. We also suggest that reductions in allele size from one generation to another may be, as in other diseases, because of triplet amplifications, more common at the FRAXA locus than previously thought.

Alleles↗
PubMed1995

The interaction of objective and subjective organizations in a localization search task.

We investigated how both objective and subjective organizations affect perceptual organization and how this perceptual organization, in turn, influences observers' performance in a localization search task. Two groups of observers viewing exactly the same stimuli (objective organization) performed in significantly different ways, depending on how they were induced to parse the display (subjective organization). In Experiments 1 and 2, the observers were asked to describe the location of a tilted target among a varying number of vertical or horizontal distractors. Subjective organization was induced by instructing observers to parse the display into either three horizontal regions (rows) or three vertical regions (columns). The position of the target was critical: location performance, as assessed by reaction time and errors, was consistently impaired at the locations adjacent to the boundaries defining the regions, producing what we refer to as the subjective boundary effect. Furthermore, the extent of this effect depended on whether the stimulus-driven and conceptually driven information concurred or conflicted. This made location information more or less accessible. In Experiment 1, the strength of objective grouping was a function of the proximity of the items (near or far conditions) and their orientation in a 6 x 6 matrix. In Experiment 2, the strength of objective grouping was a function of similarity of color (items were color coded by rows or by columns) and the orientation of the items in a 9 x 9 matrix. The subjective boundary effect was more pronounced when the display promoted grouping in the direction orthogonal to that of the task (e.g., when observers parsed by rows but vertical distractors were closer together [Experiment 1] or color coded [Experiment 2] to induce global columns). In contrast, this effect decreased when the direction of both objective and subjective organizations was parallel (e.g., when observers parsed by rows and horizontal distractors were closer together [Experiment 1] or were color coded [Experiment 2] to induce global rows). A localization search task proved to be an ideal forum in which objective and subjective organizations interacted. We discuss how these results indicated that observers' performance in a localization task was determined by the interaction of objective and subjective organizations, and that the resulting perceptual organization constrained coarse location information.

Adult↗
PubMed1995

The eccentricity effect: target eccentricity affects performance on conjunction searches.

The serial pattern found for conjunction visual-search tasks has been attributed to covert attentional shifts, even though the possible contributions of target location have not been considered. To investigate the effect of target location on orientation x color conjunction searches, the target's duration and its position in the display were manipulated. The display was present either until observers responded (Experiment 1), for 104 msec (Experiment 2), or for 62 msec (Experiment 3). Target eccentricity critically affected performance: A pronounced eccentricity effect was very similar for all three experiments; as eccentricity increased, reaction times and errors increased gradually. Furthermore, the set-size effect became more pronounced as target eccentricity increased, and the extent of the eccentricity effect increased for larger set sizes. In addition, according to stepwise regressions, target eccentricity as well as its interaction with set size were good predictors of performance. We suggest that these findings could be explained by spatial-resolution and lateral-inhibition factors. The serial self-terminating hypothesis for orientation x color conjunction searches was evaluated and rejected. We compared the eccentricity effect as well as the extent of the orientation asymmetry in these three conjunction experiments with those found in feature experiments (Carrasco & Katz, 1992). The roles of eye movements, spatial resolution, and covert attention in the eccentricity effect, as well as their implications, are discussed.

Adult↗
PubMed1993

Olfactory perception and olfactory imagery: a multidimensional analysis.

Whether a system of imagery for olfaction exists is currently an unsettled issue. Moreover, the dimensions underlying odor perception have eluded researchers for many years. Two experiments bearing on these issues are presented. In one experiment, a group of 32 undergraduates rated the similarity of pairs of 16 commonplace odorants (e.g., chocolate and leather) they perceived using scratch and sniff stimuli; in another, a different group of 44 undergraduates was asked to imagine and then rate the similarity of the same pairs of odors. Multidimensional scaling of the data suggests that three-dimensional solutions with similar stimulus dimensions, such as fruitiness, strength, and familiarity, underlied the ratings of both perceived and imagined odors. By finding that similar dimensions define the psychological space of both the imagery and the perception tasks, this study suggests that imagery does indeed exist for olfaction.

Adult↗
PubMed1993

An unreported size illusion.

A previously unreported size illusion in some commonly used stimuli--a large (global) letter made up of small (local) letters (eg a large H made up of small Es) is described: the size of the local letters forming the horizontal component of the global letter appears to be over-estimated. Global and local letters made up of horizontal and vertical components (E, F, T, and H) were employed as stimulus material. The first experiment showed that the illusion was consistently perceived, and was present for most of the stimuli tested; ie for all global letters and for all local letters except H. A second experiment showed that the size distortion is not specific to a particular dimension: instructing observers to focus on the height or the width of the local letters did not affect the extent of the illusion. The effect of some stimulus manipulations was also investigated.

Adult↗