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Biomedical subjects

R Mercado

Publications and source records attributed to R Mercado.

At least 19 recordsLinked to original sources
PubMed2005

Microsurgical considerations of the anterior spinal and the anterior-ventral spinal arteries.

BACKGROUND: There are few data describing the microanatomy of the anterior-ventral spinal (AVSA) and anterior spinal arteries (ASA) and discussing their clinical and surgical implications. We describe the anatomical features of this arterial complex, and highlight their use when planning and performing surgical approaches to lesions involving the ventral aspect of the medulla and the foramen magnum. METHOD: The microsurgical anatomy and branching pattern of the AVSA and the ASA from fifty human cadaver brain stems is described using a surgical microscope. RESULTS: We found one anterior-ventral spinal artery at each side in 30 of the brain stems (60%). The ASA was a direct branch emerging from the left vertebral artery (VA) in 15 (30%), from the right VA in 4 (8%), and from the basilar artery (BA) in one brain stem (2%). The previously described as "typical pattern" of the junction of the AVS arteries from both sides, was observed only in 9 brain stems (18%). The anterior communicating spinal artery (ACoSA) was observed in 15 brain stems (30%). Also multiple ACoS arteries were described in one brain stem. Both, the AVSA and the ASA were observed to send long circumferential branches that supplied irrigation to the olive in 42 (84%) brain stems. CONCLUSIONS: This anatomical study gives important information for a better understanding of the clinical picture of ischemic lesions of the brain stem, such as the medial medullary syndrome, and highlights the remarkable role of the AVSA and ASA as anatomical landmarks during the surgical approaches to lesions involving the ventral aspect of the medulla and the foramen magnum.

Basilar Artery↗
PubMed2004

Vascular anatomy of the foramen of Vicq d'Azyr: a microsurgical perspective.

INTRODUCTION: The foramen of Vicq d'Azyr, is a triangular-shaped area located rostral to the ventral median fissure of the medulla oblongata. Its importance relies on the fact that it is penetrated by small vessels from the vertebrobasilar axis that nourish vital pontine nuclei and tracts. We described the microvascular anatomy of the perforating vessels of the foramen of Vicq d'Azyr (FVA). MATERIALS AND METHODS: The vertebrobasilar junction arteries and the perforating arteries of the foramen of Vicq d'Azyr were examined using a surgical microscope in 21 formalin-fixed brain stems. RESULTS: The total number of perforating branches found was 286 in the 21 brains, an average of 13.6 perforators per brain, range 7 to 22. They arose as distal branches of 73 main trunks, average of 3.5 per brain, range 2 to 5, originating mainly from the basilar artery in 41 (56.1 %); the left ventral spinal artery in 12 (16.4 %), and the left vertebral artery in 8 (11 %). The average outer diameters of the left and right vertebral arteries were 3.2 mm and 2.9 mm, 4.1 mm for the basilar artery, and 0.6 mm for the right and left ventral spinal arteries. The branching pattern and interesting anatomic variations of the main vessels of the vertebro-basilar junction are also described. DISCUSSION: The vascular anatomy of the infratentorial compartment is highly variable. These variations should be kept in mind to avoid pitfalls during vascular or tumor surgery. In contrast, the entering locations of perforating vessels remain constant, referring to these zones as key areas when planning or doing surgical procedures in this region.

Basilar Artery↗
PubMed2001

Human infection by Pseudoterranova decipiens (Nematoda, Anisakidae) in Chile: report of seven cases.

From 1997 to 1999, we identified seven human cases of infection by fourth stage larvae of Pseudoterranova decipiens in Chile. All identified larvae were coughed up by the patients. Subjects were 10-55 years old; five were female. Some patients complained of coughing, expectoration, pharyngeal pain, nausea or anal and nasal pruritus. Larvae of three patients were coughed up from 36 h to 7 days after having eaten raw (cebiche or sushi) or lightly fried fish. P. decipiens has a marine life cycle. Infective third stage larva develop to adult stage in pinniped mammals. The nematode eggs are voided with the host faeces and develop and hatch releasing third stage larvae. Some crustaceans and fish act as hosts of third stage larvae. Man is an accidental host for third or fourth stage larvae.

Adult↗
PubMed2000

Early programming of T cell populations responding to bacterial infection.

The duration of infection and the quantity of Ag presented in vivo are commonly assumed to influence, if not determine, the magnitude of T cell responses. Although the cessation of in vivo T cell expansion coincides with bacterial clearance in mice infected with Listeria monocytogenes, closer analysis suggests that control of T cell expansion and contraction is more complex. In this report, we show that the magnitude and kinetics of Ag-specific T cell responses are determined during the first day of bacterial infection. Expansion of Ag-specific T lymphocyte populations and generation of T cell memory are independent of the duration and severity of in vivo bacterial infection. Our studies indicate that the Ag-specific T cell response to L. monocytogenes is programmed before the peak of the innate inflammatory response and in vivo bacterial replication.

Adoptive Transfer↗
PubMed1999

MHC class I restricted T cell responses to Listeria monocytogenes, an intracellular bacterial pathogen.

Studies of the murine immune response to infection with the intracellular bacterial pathogen Listeria monocytogenes have provided a wealth of information about innate and acquired immune defenses in the setting of an infectious disease. Our studies have focused on the MHC class I restricted, CD8+ T cell responses of Balb/c mice to L. monocytogenes infection. Four peptides that derive from proteins that L. monocytogenes secretes into the cytosol of infected cells are presented to cytotoxic T lymphocyte (CTL) by the H2-Kd major histocompatibility complex (MHC) class I molecule. We have found that bacterially secreted proteins are rapidly degraded in the host cell cytosol by proteasomes that utilize, at least in part, the N-end rule to determine the rate of degradation. The MHC class I antigen processing pathway is remarkably efficient at generating peptides that bind to MHC class I molecules. The magnitude of in vivo T cell responses, however, is influenced to only a small degree by the amount of antigen or the efficiency of antigen presentation. Measurements of in vivo T cell expansion following L. monocytogenes infection indicate that differences in the sizes of peptide-specific T cell responses are more likely owing to differences in the repertoire of naive T cells than to differences in peptide presentation. This notion is supported by our additional finding that dominant T cell populations express a more diverse T cell receptor (TCR) repertoire than do subdominant T cell populations.

Animals↗
PubMed1999

Regulation of glial Na+/K+-ATPase by serotonin: identification of participating receptors.

The purpose of the present study was the characterization of the receptors participating in the regulatory mechanism of glial Na+/K+-ATPase by serotonin (5-HT) in rat brain. The activity of the Na+ pump was measured in four brain regions after incubation with various concentrations of serotoninergic agonists or antagonists. A concentration-dependent increase in enzyme activity was observed with the 5-HT1A agonist R (+)-2-dipropylamino-8-hydroxy-1,2,3, 4-tetrahydronaphthalene hydrobromide (8-OH-DPAT) in homogenates or in glial membrane enriched fractions from cerebral cortex and in hippocampus. Spiperone, a 5-HT1A antagonist, completely inhibited the response to 8-OH-DPAT but had no effect on Na+/K+-ATPase activity in cerebellum where LSD, a 5-HT6 agonist, elicited a dose-dependent response similar to that of 5-HT. In brainstem, a lack of response to 5-HT and other agonists was confirmed. Altogether, these results show that serotonin modulates glial Na+/K+-ATPase activity in the brain, apparently not through only one type of 5-HT receptor. It seems that the receptor system involved is different according to the brain region. In cerebral cortex, the response seems to be mediated by 5-HT1A as well as in hippocampus but not in cerebellum where 5-HT6 appears as the receptor system involved.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1998

Comparison in systemic hypertension of left ventricular mass and geometry with systolic and diastolic function in patients <65 to > or = 65 years of age.

Previous studies have differed on the independent effect of age and gender to left ventricular (LV) mass. Data on ventricular remodeling in hypertensive patients > or = 65 years of age is lacking. Similarly, the systolic and diastolic interaction in older hypertensives is not well defined. In a prospective study, we examined the relation of LV mass, relative wall thickness, and systolic and diastolic interaction in 508 hypertensive patients between 50 and 80 years of age who were divided according to age (<65 and > or = 65 years) and gender. LV mass, geometric classification, systolic wall stress, and Doppler filling were obtained according to standard Doppler echocardiographic criteria. In men, most measurements were similarly distributed. However, women > or = 65 years of age had smaller LV systolic dimensions, thicker ventricular septums, higher endocardial and midwall fractional shortenings, and lower end-systolic wall stress. Although LV mass was higher in men, there was no age difference within the same sex. The most common LV geometric remodeling was increased relative wall thickness in the form of concentric hypertrophy or concentric remodeled. The predominant mitral flow pattern was "impaired relaxation"; however, older patients had even shorter E waves, taller A waves, and lower E/A ratios. Thus, patients > or = 65 years of age had an even higher prevalence of this pattern (men, 89% vs 73%, p <0.001, and women, 91% vs 77%, p <0.001). Delayed LV relaxation with preservation of systolic ejection indexes is an early abnormality in essential hypertension, which lasts an undetermined time with further progression as patients aged. As a result, hypertensive patients > or = 65 years of age had the most pronounced structural and functional changes, an observation particularly noted in women. In those > or = 65 years, data from the Doppler E wave and A wave do not distinguish the physiologic process of aging from the pathologic changes of pressure overload.

Aged↗
PubMed1998

Regulated release of serotonin from axonal growth cones isolated from the fetal rat brain.

In the present work we propose an hypothetical model related to a molecular recognizing system for serotonin in isolated growth cone particles. This model is supported by previous results from our laboratory plus new ones which show that growth cones release serotonin tonically and such release can be stimulated by potassium in a calcium-dependent manner. The present results, together with other author's data, suggest a physiological basis for the putative role of serotonin as a trophic factor during nervous system development.

Animals↗
PubMed1998

Serotonin modulation of low-affinity ouabain binding in rat brain determined by quantitative autoradiography.

Previous results showed that Na+/K+-ATPase may have a functional relationship with the neurotransmitter serotonin which activates the glial sodium pump in the rat brain. Both the reaction rate (V) of Na+/K+-ATPase activity and [3H]ouabain binding were significantly increased in the presence of serotonin. It is not known, however, which alpha isoform is involved in the Na+/K+-ATPase response to serotonin and its regional distribution. Quantitative autoradiography of [3H]ouabain binding to rat brain slices was employed at different [3H]ouabain concentrations in order to gain information on both the distribution and the possible isoform involved. The results showed that 1500 nM [3H]ouabain binding was sensitive to serotonin 10(-3) M and significantly increased in the following brain regions: frontal cortex, areas CA1, CA2, and CA3 of the hippocampus, presubiculum, zona incerta, caudate putamen and the amygdaloid area, confirming and extending previous results. An effect of serotonin on brain but not kidney tissue at high, 1500 nM, and the lack of effect at low, 50 nM [3H]ouabain concentrations, strongly suggests the participation of the alpha2 isoform in the response of the pump to the neurotransmitter. Glial cells showed stimulation of ouabain binding by serotonin at ouabain concentrations above 350 nM. The present results open interesting questions related to the brain regions involved and the K+ handling by the glial alpha2 isoform of the pump.

Animals↗
PubMed1997

Pattern of deletions of the dystrophin gene in Mexican Duchenne/Becker muscular dystrophy patients: the use of new designed primers for the analysis of the major deletion "hot spot" region.

We have analyzed 59 unrelated Mexican Duchenne/Becker muscular dystrophy patients (DMD/BMD) using PCR analysis of the 2 prone deletion regions in the DMD gene. Thirty one (52%) of the patients had a deletion of one or several of the exons. Most of the alterations (87%) were clustered in exons 44-52, this being the highest percentage reported until now. In order to improve the molecular diagnosis in the Mexican population, we designed a new multiplex assay to PCR amplify exons 44-52. This assay allowed for the identification of a greater number of deletions in this region compared with the 9 and 5-plex assays previously described and to determine most of the deletion end boundaries. This is a reliable alternative for the initial screening of the DMD patients in the Mexican population.

Dystrophin↗
PubMed1997

Human case of gastric infection by a fourth larval stage of Pseudoterranova decipiens (Nematoda, Anisakidae).

Only three cases of human infection by anisakid nematodes have been reported in Chile since 1976. In the present case, an anisakid worm, identified as a fourth-stage Pseudoterranova decipiens larva, was removed with a gastroendoscopic biopsy clipper from the stomach of a 45 year-old man from southern Chile. The patient, who presented acute epigastric pain and a continuous sensation of having an empty stomach, reported having eaten smoked fish. The worm was fixed in 70% ethanol and cleaned in lactophenol for morphological study. The morphometric characteristics of the worm are described and drawn. Anisakid larvae in fish flesh can be killed by freezing or cooking.

Animals↗
PubMed1996

Carrier detection in Duchenne and Becker muscular dystrophy using dinucleotide repeat polymorphisms. A study in Mexican families.

In order to improve carrier detection of Duchenne and Becker muscular dystrophy, dinucleotide sequences repeats (CA) of introns 44, 45, 49 and 50 were used as well as two markers located at the 5' and 3' ends of the dystrophin gene. Haplotypes of the unaffected and affected persons of ten DMD/ BMD Mexican families were determined. Fifty eight females were studied, 30 of whom were at-risk STR haplotypes. Furthermore, it was possible to identify a recombination event in the dystrophin gene in one family, and a gonadal mosaicism was found in another family.

Genetic Carrier Screening↗
PubMed1995

[Annual frequency of Cryptosporidium parvum infections in children and adult outpatients, and adults infected by HIV].

We report the analysis of 4892 parasitological stool samples coming from outpatients and patients of a nutritional recuperation center of north Santiago. Cryptosporidium parvum was detected in 21 samples (0.4%). The protozoan was detected in 6 of 1203 samples from children of less than 2 years old, 3 of 1.727 samples from children between 6 and 15 years, none of 776 samples from healthy adults and 2 of 13 samples from HIV infected patients. Nine of 97 children of less than 2 years old, hospitalized in the nutritional recuperation center, were infected with Cryptosporidium; this frequency was significantly higher than that of outpatients of the same age. Most infections were detected from May to August, a rainy and mildly cold period. It is concluded that Cryptosporidium infections are infrequent in healthy outpatients and that its prevalence increased in hospitalized children and HIV infected adults.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Biochemical properties of Na+/K(+)-ATPase in axonal growth cone particles isolated from fetal rat brain.

Axonal growth cones (AGC) isolated from fetal rat brain have an important specific activity of N+/K(+)-ATPase. Kinetic assays of the enzyme in AGC showed that Km values for ATP or K+ are similar to those reported for the adult brain enzyme. For Na+ the affinity (Km) was lower. Vmax for the three substrates was several times lower in AGC as compared to the adult value. We also observed two apparent inhibition constants of Na+/K(+)-ATPase by ouabain, one of low affinity, possibly corresponding to the alpha 1 isoform and another of high affinity which is different to that described for the alpha 2 isoform of the enzyme. These results support an important role for the sodium pump in the maintainance of volume and cationic balance in neuronal differentiating structures. The functional differences observed also suggest that the enzymatic complex of Na+/K(+)-ATPase in AGC is in a transitional state towards the adult configuration.

Adenosine Triphosphate↗
PubMed1992

A molecular recognizing system of serotonin in rat fetal axonal growth cones: uptake and high affinity binding.

Axonal growth cone particles (AGCP) isolated from prenatal and postnatal rat brain had different high-affinity 5-HT uptake characteristics. In postnatal AGCP the uptake behaves as in the adult rat brain, while in the prenatal AGCP the uptake characteristics seem to be in a transitional stage. Also in prenatal AGCP we observed specific, high-affinity 5-HT binding sites. These results support the idea of an important role for 5-HT during axogenesis.

Animals↗
PubMed1992

Regulatory role of a neurotransmitter (5-HT) on glial Na+/K(+)-ATPase in the rat brain.

In the present work we studied the effect of serotonin (5-HT) on the kinetics of Na+/K(+)-ATPase in subcellular preparations of the cerebral cortex from male Wistar rats using various concentrations of ATP and K+ with and without added 5-HT. Also we studied the effect of 5-HT on the enzyme in glial or neuronal preparations. The results indicated that there was a significant increase (P < 0.05) of the Vmax in the presence of 5-HT in the whole tissue preparation (homogenate) but not in the subcellular fractions, suggesting that the interaction could be preferentially with the glial pump. Further results supported that this was the case since activation by 5-HT was mainly in the glial preparations. Kinetic data and the binding of [3H]ouabain supported that the enzyme is activated by 5-HT through the exposure of more enzymatic active sites.

Animals↗
PubMed1992

Effect of myotonia induced by anthracene-9-carboxylic acid on mitochondrial calcium, plasma creatinine-phosphokinase and aldolase activity in the rat.

The frequent association of myotonia with dystrophy and the knowledge that calcium is increased in injured skeletal muscle cells suggest a possible relationship between cell calcium and myotonic alterations. This investigation has been performed to study the role of calcium in experimental myotonia induced by anthracene-9-carboxylic acid (9-AC) in rats treated with several regimens of food and exercise. Thirty-two rats were divided into 4 groups of 8 rats each, one control and 3 experimental groups. The treatments included caffeine plus exercise (group 2), and a calcium-rich diet (group 3); these procedures were designed to increase intracellular calcium; another group was treated with 9-AC as a myotonia-inducer (group 4). The treatment for all groups lasted 60 days. No significant differences in plasma sodium, potassium, chloride and calcium between control and experimental groups were observed. Whole muscle calcium in wet tissue samples did no change with any treatment. On the contrary, mitochondrial calcium showed a significantly higher concentration in group 3 and 4. CPK and aldolase activities in groups 1, 2 and 3 were similar; but in group 4 these enzyme activities were significantly higher (p less than 0.05). The electrical and mechanical responses were not altered in any rat with any experimental treatment. Our data suggest that myotonia is a predisposing factor for an altered mitochondrial calcium homeostasis in this model; in addition, the enzyme activities of CPK and aldolase were increased in the rats of group 4 implicating that myotonia is a crucial factor in the development of enzymatic abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗