Biomedical subjects

Raquel Garcia

Publications and source records attributed to Raquel Garcia.

8 recordsLinked to original sources

PubMed2006

Learned preferences induced by electrical stimulation of a food-related area of the parabrachial complex: effects of naloxone.

Electrical stimulation of the External Lateral Parabrachial Subnucleus (LPBe), a food-related area, induced behavioral preferences for associated stimuli in a taste discrimination learning task. Although this stimulation appeared to be ineffective to elicit standard lever press self-stimulation, it induced place preference for one of two training compartments of a rectangular maze in which animals (adult male Wistar rats) received concurrent electrical brain stimulation. In subjects that consistently showed a preference behavior in different trials, administration of the opioid antagonist naloxone (4 mg/ml/kg) blocked concurrent learning when the test was made in a new maze but not in the same maze in which animals had learned the task. These results are discussed in terms of the possible participation of the LPBe subnucleus in different natural and artificial brain reward systems.

Animals↗

PubMed2006

Synthesis and biological evaluation of tricarbonyl Re(I) and Tc(I) complexes anchored by poly(azolyl)borates: application on the design of radiopharmaceuticals for the targeting of 5-HT1A receptors.

The building blocks fac-[(99m)Tc{kappa(3)-HB(tim(Me))(3)}(CO)(3)] and fac-[(99m)Tc{kappa(3)-R(mu-H)B(tim(Me))(2)}(CO)(3)] [R is H (4a), Ph (5a); tim(Me) is 2-mercapto-1-methylimidazolyl] were obtained almost quantitatively by reacting fac-[(99m)Tc(CO)(3)(H(2)O)(3)](+) with the corresponding scorpionate. These compounds cross the intact blood-brain barrier in mice, with significant retention in the case of 4a and 5a. Using 4a as the lead structure, we have synthesized the functionalized complexes fac-[M{kappa(3)-H(mu-H)B(tim(Bu-pip))(2)}(CO)(3)] [M is Re (8), (99m)Tc (8a); tim(Bu-pip) is methyl[4-((2-methoxyphenyl)-1-piperazinyl)butyl](2-mercapto-1-methylimidazol-5-yl)methanamide] and fac-[M{kappa (3)-H(mu-H)B(tim(Me))(tim(Bu-pip))}(CO)(3)] [M is Re (9), (99m)Tc (9a)] and evaluated their potential as radioactive probes for the targeting of brain 5-HT(1A) serotonergic receptors. The Re complexes exhibit excellent affinity [IC(50)=0.172 +/- 0.003 nM (8); IC(50)=0.65 +/- 0.01 nM (9)] for the 5-HT(1A) receptor. The radioactive congeners ((99m)Tc) have shown an initial brain uptake of 1.38 +/- 0.46%ID g(-1) (8a) and 0.43 +/- 0.12%ID g(-1) (9a), but suffer from a relatively fast washout.

Animals↗

PubMed2004

Efficiency of the cross-over design: an empirical estimation.

The aim of the present study is to estimate the relative efficiency of cross-over clinical trials as compared to the corresponding parallel designs. A MEDLINE 'full text' search covering years 2000-2003 over the word 'cross-over' identified 40 true cross-over studies with the parametric approach published in leading medical journals. A parallel design is expected to need, in order to achieve the same power, between 4 and 10 times more subjects than the corresponding cross-over design, meaning that cost of a parallel design can be between 2 and 5 times higher. There is a high proportion (18/40 = 45.0 per cent) of cross-over studies recently published in leading medical journals that, disregarding the CONSORT recommendations, does not provide estimates for the effect size and its standard error, hence, not allowing for the posterior use of the data in a meta-analysis.

Cross-Over Studies↗

PubMed2003

The distribution of visual objects on the retina: connecting eye movements and cone distributions.

Experimental data on the accuracy and frequency of saccades are incorporated into a model of the visual world and eye movements to determine the spatial distribution of visual objects on the retina. Visual scenes are represented as sequences of discrete small objects whose positions are initially uniformly distributed and then moved toward the center of the retina by eye movements. We then use this model to investigate whether the distribution of cones in the retina maximizes the information transferred about object position. Assuming for simplicity that a single cone is activated by the object, the rate of information transfer is maximized at the receptor stage if the probability that a target lies at a position on the retina is proportional to the local cone density. Although qualitatively it is easy to understand why the cone density is higher at the fovea, by linking the cone density with eye movements through information sampling theory, we provide an explanation for its quantitative variation across the retina. The human cone distribution and the object distribution in our model visual world are shown to have the same general form and are in close agreement between 5- and 30-deg eccentricity.

Fovea Centralis↗

PubMed2002

Reactivity of [Re[kappa(3)-H(mu-H)B(tim(Me))(2)](CO)(3)] (tim(Me) = 2-mercapto-1-methylimidazolyl) toward neutral substrates.

The complex [Re[kappa(3)-H(mu-H)B(tim(Me))(2)](CO)(3)] (2a) (tim(Me) = 2-mercapto-1-methylimidazolyl) reacts with a variety of neutral substrates to afford new complexes featuring the dihydrobis(2-mercapto-1-methylimidazolyl)borate coordinated in a bidentate or unidentate fashion. By treating 2a with unidentate ligands, the mononuclear complexes [Re[kappa(2)-H(2)B(tim(Me))(2)](CO)(3)(L)] (L = imidazole (5), 4-(dimethylamino)pyridine (6), tert-butylisonitrile (7), triphenylphosphine (8)) were formed, upon replacement of the agostic B-H...Re bond by the correspondent unidentate ligand. With potentially bidentate substrates, 2a is transformed into mononuclear or dinuclear complexes, depending on the atom donor set of the reacting substrates. Reaction of compound 2a with ethylenediamine (en) gave the complex [Re[kappa(1)-H(2)B(tim(Me))(2)](CO)(3)(en)] (9), because of cleavage of the agostic interaction, dechelation of one mercaptoimidazolyl ring, and bidentate coordination of the amine. By contrast, 1,2-bis(diphenyl)phosphinoethane (dppe) is not able to replace the mercaptoimidazolyl ring, and the dimer [Re[kappa(2)-H(2)B(tim(Me))(2)](CO)(3)](2)(mu-dppe) (10) was formed. The novel Re(I) tricarbonyl complexes (5-10) have been fully characterized, including by X-ray diffraction analysis in the case of 6, 8, 9, and 10. The X-ray diffraction study confirmed the unprecedented unidentate coordination mode of the dihydrobis(2-mercapto-1-methylimidazolyl)borate in complex 9.

Journal Article↗

PubMedDate not supplied

Air pollution and brain damage.

Exposure to complex mixtures of air pollutants produces inflammation in the upper and lower respiratory tract. Because the nasal cavity is a common portal of entry, respiratory and olfactory epithelia are vulnerable targets for toxicological damage. This study has evaluated, by light and electron microscopy and immunohistochemical expression of nuclear factor-kappa beta (NF-kappaB) and inducible nitric oxide synthase (iNOS), the olfactory and respiratory nasal mucosae, olfactory bulb, and cortical and subcortical structures from 32 healthy mongrel canine residents in Southwest Metropolitan Mexico City (SWMMC), a highly polluted urban region. Findings were compared to those in 8 dogs from Tlaxcala, a less polluted, control city. In SWMMC dogs, expression of nuclear neuronal NF-kappaB and iNOS in cortical endothelial cells occurred at ages 2 and 4 weeks; subsequent damage included alterations of the blood-brain barrier (BBB), degenerating cortical neurons, apoptotic glial white matter cells, deposition of apolipoprotein E (apoE)-positive lipid droplets in smooth muscle cells and pericytes, nonneuritic plaques, and neurofibrillary tangles. Persistent pulmonary inflammation and deteriorating olfactory and respiratory barriers may play a role in the neuropathology observed in the brains of these highly exposed canines. Neurodegenerative disorders such as Alzheimer's may begin early in life with air pollutants playing a crucial role.

Air Pollutants↗

PubMedDate not supplied

Intermittent total pedicular clamping in hepatic resections in non-cirrhotic patients.

BACKGROUND/AIMS: Evaluation of intermittent total pedicular clamping in hepatic resections in non-cirrhotic patients. METHODOLOGY: A prospective study was made of 72 patients submitted to hepatic resections using intermittent total pedicular clamping. Patients were placed in 5 groups for analysis according to the duration of liver ischemia (each 20 minutes). Tolerance of liver ischemia was assessed by analysis of postoperative morbimortality and biochemical test. RESULTS: Five patients (6.9%) died during the postoperative period and sixteen patients (23.8%) developed specific complications, however, none of the variables analyzed in this study proved to be an independent risk factor for the development of postoperative morbimortality. The transaminases presented a statistically significant relationship with duration of ischemia (P < 0.002), while the late rise was influenced by postoperative mortality (P < 0.009). Prothrombin time was influenced by the duration of ischemia and by postoperative mortality (P = 0.014) but, on the other hand, the bilirubin levels only showed the influence of mortality (P < 0.002). CONCLUSIONS: Immediate postoperative liver function was better preserved in patients submitted to less than 80 minutes of clamping. The late rise of bilirubin and transaminases and the drop in prothrombin time could be considered indicators of a bad postoperative course.

Adolescent↗

PubMedDate not supplied

Peripartum cardiomyopathy: a case report.

Peripartum cardiomyopathy (PPCM) is a specific form of dilated cardiomyopathy, characterized by the development of systolic heart failure in the period between the last month of pregnancy and five months after delivery. It is a rare clinical condition of variable prognosis that occurs in the absence of identifiable cause or prior known heart disease. The authors report a clinical case of a previously healthy 33-year-old woman who developed de novo symptoms of progressively worsening heart failure in the 33rd week of gestation, that ended after two weeks in the development of cardiogenic shock and the need for emergency delivery.

Adult↗