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Biomedical subjects

J Montiel

Publications and source records attributed to J Montiel.

At least 19 recordsLinked to original sources
PubMed2003

One hundred million years of interhemispheric communication: the history of the corpus callosum.

Analysis of regional corpus callosum fiber composition reveals that callosal regions connecting primary and secondary sensory areas tend to have higher proportions of coarse-diameter, highly myelinated fibers than callosal regions connecting so-called higher-order areas. This suggests that in primary/secondary sensory areas there are strong timing constraints for interhemispheric communication, which may be related to the process of midline fusion of the two sensory hemifields across the hemispheres. We postulate that the evolutionary origin of the corpus callosum in placental mammals is related to the mechanism of midline fusion in the sensory cortices, which only in mammals receive a topographically organized representation of the sensory surfaces. The early corpus callosum may have also served as a substrate for growth of fibers connecting higher-order areas, which possibly participated in the propagation of neuronal ensembles of synchronized activity between the hemispheres. However, as brains became much larger, the increasingly longer interhemispheric distance may have worked as a constraint for efficient callosal transmission. Callosal fiber composition tends to be quite uniform across species with different brain sizes, suggesting that the delay in callosal transmission is longer in bigger brains. There is only a small subset of large-diameter callosal fibers whose size increases with increasing interhemispheric distance. These limitations in interhemispheric connectivity may have favored the development of brain lateralization in some species like humans.

Animals↗
PubMed2002

Behavioral effects of aminochrome and dopachrome injected in the rat substantia nigra.

The exact mechanism of cell death in neurodegenerative diseases remains obscure, although there is evidence that their pathogenesis may involve the formation of free radicals originating from the oxidative metabolism of catecholamines. The purpose of this study was to evaluate the degree of neurodegenerative changes and behavioral impairments induced by unilateral injection into the rat substantia nigra of cyclized o-quinones, aminochrome and dopachrome, derived from oxidizing dopamine and L-DOPA, respectively, with Mn(3+)-pyrophosphate complex. The behavioral changes were compared with those induced after selective lesions of dopaminergic neurons with 6-hydroxydopamine (6-OHDA). Intranigral injection of aminochrome and dopachrome produced impairment in motor and cognitive behaviors. The behavioral impairment was also revealed by apomorphine-induced rotational asymmetry. Apomorphine (0.5 mg/kg sc) significantly increased rotational behavior in rats injected with aminochrome and dopachrome. These rats presented a clear motor bias showing a significant contralateral rotation activity, similar but less vigorous that in rats injected with 6-OHDA. The avoidance conditioning was seriously impaired in rats injected with aminochrome and dopachrome although only dopachrome-injected rats showed a similar hypomotility to 6-OHDA-injected rats. The behavioral effects were correlated to the extent of striatal tyrosine hydroxylase (TH)-positive fiber loss. Rats receiving unilateral intranigral aminochrome and dopachrome injections exhibited a 47.9+/-5.1% and a 39.7+/-4.4% reduction in nigrostriatal TH-positive fiber density. In conclusion, this study provided evidence that oxidizing DA and L-DOPA to cytotoxic quinones, aminochrome and dopachrome appears to be an important mediator of oxidative damage in vivo.

Animals↗
PubMed2002

Critical steps in the early evolution of the isocortex: insights from developmental biology.

This article proposes a comprehensive view of the origin of the mammalian brain. We discuss i) from which region in the brain of a reptilian-like ancestor did the isocortex originate, and ii) the origin of the multilayered structure of the isocortex from a simple-layered structure like that observed in the cortex of present-day reptiles. Regarding question i there have been two alternative hypotheses, one suggesting that most or all the isocortex originated from the dorsal pallium, and the other suggesting that part of the isocortex originated from a ventral pallial component. The latter implies that a massive tangential migration of cells from the ventral pallium to the dorsal pallium takes place in isocortical development, something that has not been shown. Question ii refers to the origin of the six-layered isocortex from a primitive three-layered cortex. It is argued that the superficial isocortical layers can be considered to be an evolutionary acquisition of the mammalian brain, since no equivalent structures can be found in the reptilian brain. Furthermore, a characteristic of the isocortex is that it develops according to an inside-out neurogenetic gradient, in which late-produced cells migrate past layers of early-produced cells. It is proposed that the inside-out neurogenetic gradient was partly achieved by the activation of a signaling pathway associated with the Cdk5 kinase and its activator p35, while an extracellular protein called reelin (secreted in the marginal zone during development) may have prevented migrating cells from penetrating into the developing marginal zone (future layer I).

Animals↗
PubMed2001

Dendritic structure of single hippocampal neurons according to sex and hemisphere of origin in middle-aged and elderly human subjects.

The organization of basilar dendritic patterns in the CA1 hippocampal region obtained from 13 middle-aged and elderly human subjects was assessed using the Golgi method. Neurons were classified according to hemisphere of origin and the sex of the respective subjects. Three parameters were measured: total dendritic length (TDL), number of dendritic segments (NDS) and average segment length (ASL, which is TDL divided by NDS). Dendritic segments were classified into proximal (first to third order) and distal (fourth order and above). Sex differences were found in distal TDL and in proximal and distal NDS, neurons belonging to males having larger values than those belonging to females. In addition, a hemispheric difference was detected in distal TDL, in which neurons of the left hemisphere had larger values than those of the right hemisphere.

Aged↗
PubMed2001

The inverted neurogenetic gradient of the mammalian isocortex: development and evolution.

In this paper we review recent evidence on the molecular control of cell migration in the isocortex, and present an hypothesis for the evolutionary origin of the inside-out neurogenetic gradient of this structure. We suggest that there are at least two key factors involved in the acquisition of the inside-out gradient: (i) the expression of the protein reelin, which arrests the migration of cortical plate cells by detaching them from the radial glial fiber. This permits younger neurons to use the same fiber to migrate past the previous neurons; and (ii) the second factor is an intracellular signaling pathway dependent on a cyclin-dependent protein kinase (Cdk5). Cdk5 may work by inhibiting N-cadherin mediated cell aggregation as young cells cross the cortical plate, permitting them to move to the more superficial layers. Interestingly, the mutation in Cdk5 affects the migration of only those cells belonging to superficial layers, which are considered to be an evolutionary acquisition of the mammalian isocortex.

Animals↗
PubMed2001

Integrated effects of the vasodilating beta-blocker nebivolol on exercise performance, energy metabolism, cardiovascular and neurohormonal parameters in physically active patients with arterial hypertension.

OBJECTIVE: The present study was designed to investigate the integrated effects of the beta-1-selective blocker with vasodilator properties, nebivolol, on systemic haemodynamics, neurohormones and energy metabolism as well as oxygen uptake and exercise performance in physically active patients with moderate essential hypertension (EH). DESIGN AND METHODS: Eighteen physically active patients with moderate EH were included: age: 46.9 +/- 2.38 years, weight: 83.9 +/- 2.81 kg, blood pressure (BP): 155.8 +/- 3.90/102.5 +/- 1.86 mm Hg, heart rate: 73.6 +/- 2.98 min(-1). After a 14-day wash-out period a bicycle spiroergometry until exhaustion (WHO) was performed followed by a 45-min submaximal exercise test on the 2.5 mmol/l lactate-level 48 h later. Before, during and directly after exercise testing blood samples were taken. An identical protocol was repeated after a 6-week treatment period with 5 mg nebivolol/day. RESULTS: Nebivolol treatment resulted in a significant (P < 0.01) decrease in systolic and diastolic BP and heart rate at rest and during maximal and submaximal exercise. Maximal physical work performance, blood lactate and rel. oxygen uptake (rel. VO(2)) before and after nebivolol treatment at rest and during maximal and submaximal exercise remained unaltered. Free fatty acid, free glycerol, plasma catecholamines, beta-endorphines and atrial natriuretic peptide (ANP) increased before and after treatment during maximal and submaximal exercise but remained unaltered by nebivolol treatment. In contrast, plasma ANP levels at rest were significantly higher in the presence of nebivolol, endothelin-1 levels were unchanged. CONCLUSIONS: Nebivolol was effective in the control of BP at rest and during exercise in patients with EH. Furthermore, nebivolol did not negatively affect lipid and carbohydrate metabolism and substrate flow. The explanation for the effects on ANP at rest remain elusive. This pharmacodynamic profile of nebivolol is potentially suitable in physically active patients with EH.

Adrenergic beta-Antagonists↗
PubMed2001

Species differences and similarities in the fine structure of the mammalian corpus callosum.

A cross-species ultrastructural study of the corpus callosum was performed in six domestic species: the rat, the rabbit, the cat, the dog, the horse and the cow. The results indicate cross-species conservatism in callosal fiber composition with a good interspecies relation between fiber number and brain size. Across species, increases in both brain size and callosal area indicate more callosal fibers, although less than expected from the estimated increase in cortical cell number. Within each species, the correlation between fiber number and brain weight tends to disappear, although in most cases a larger callosum implies a larger number of callosal fibers. The median fiber diameter was conservative across species (0.11-0.2 microm), indicating the maintenance of conduction velocity of most callosal fibers regardless of interhemispheric distance. Nevertheless, the maximal fiber diameters tended to be higher in species with larger brains. Therefore, there is a population of coarse-diameter fibers that tend to increase their diameter and conduction velocity with increasing brain size. However, allometric calculations suggest that the associated increase in velocity in these large fibers may not be sufficient to maintain a constant interhemispheric transmission time in different species.

Animals↗
PubMed2000

Multiple intracardiac lesions after blunt chest trauma.

Closed chest trauma can cause rupture of intracardiac structures. We report the case of a 17-year-old boy whose chest was trodden by a horse. He sustained rupture of tricuspid and aortic valve leaflets and rupture of the interventricular septum. He underwent surgical repair of these lesions, but aortic insufficiency developed 2 years later and the aortic valve was replaced with a mechanical prosthesis.

Adolescent↗
PubMed2000

[Traumatic rupture of tricuspid valve: report of 3 cases].

Tricuspide valve lesions due to non-penetrating trauma are rare and their diagnosis is difficult. Nevertheless, over 100 cases of post-traumatic valve regurgitation have been described in the last 35 years. We present 3 such cases diagnosed and operated at our center in the last 8 years.

Adolescent↗
PubMed1999

Expanding subintimal coronary dissection under a stent-covered arterial segment: serial intravascular ultrasound observations.

A patient with an angiographically unrecognized minor coronary dissection in a stent-covered coronary segment in which a type D spiral dissection extended submedially to the distal artery is described. This complication occurred 6 months after stent implantation and was ascribed to injury of the stented vessel wall during an intravascular ultrasound study.

Aortic Dissection↗
PubMed1999

Ministernotomy versus median sternotomy for aortic valve replacement: a prospective, randomized study.

BACKGROUND: Minimally invasive aortic valve replacement reduces surgical trauma and, supposedly, postoperative pain, blood loss, and length of stay. A prospective, randomized study was designed to prove these theoretical advantages. METHODS: Forty patients undergoing isolated, elective aortic valve replacement were randomized into two equal groups. Patients in group M underwent aortic valve replacement through a ministernotomy (reversed L or reversed C). In group S, a median sternotomy was used. The anesthetic and surgical protocol was identical for both groups. Pain was evaluated on a daily basis. Pulmonary function tests were performed preoperatively and before hospital discharge in all patients. RESULTS: There were two deaths in each group. Cross-clamp time was longer in group M: 70 +/- 19 minutes versus 51 +/- 13 minutes in group S (p = 0.005). There were no statistically significant differences between groups M and S in pump time (95 +/- 20 minutes versus 83 +/- 19 minutes), extubation time (9.9 hours in both groups), chest drainage (479 +/- 274 mL/L 24 hours versus 355 +/- 159 mL/24 hours), transfusion requirements (27% in both groups), pain evaluation (1.34 +/- 1.3 versus 2.15 +/- 1.5), length of stay (6.2 +/- 2.3 days versus 6.3 +/- 2.5 days), and cosmetic appraisal. Forced vital capacity decreased 26% from preoperative reference values in group M and 33% in group S (p = not significant). Forced expiratory volume in 1 second decreased 22% and 35%, respectively (p = not significant). CONCLUSIONS: This study has failed to prove the theoretical advantages of minimally invasive aortic valve replacement. With this technique, cross-clamp time is longer than with a median sternotomy.

Adult↗
PubMed1999

[Evaluation of the patency of left internal mammary artery graft by transcutaneous Doppler flow velocity analysis].

OBJECTIVE: To analyze the features of Doppler flow velocity curve of left internal mammary artery by-pass grafts in relation with their permeability as assessed by selective angiography. METHODS: Twenty-five consecutive patients with a left mammary artery graft were studied by angiography and transcutaneous Doppler technique. From the Doppler tracings, peak velocity and time-velocity integral of the systolic and diastolic components were determined. Patency of the graft and the characteristics of the distal native coronary artery were evaluated at angiography. RESULTS: Doppler flow signal was obtained in 23 (92%) of 25 analyzed patients. The graft was angiographically patent in 17 (68%) of 25 patients; in 15 (88%) of them the Doppler flow velocity signal was mainly diastolic and in only 2 (12%) it was predominantly systolic. In 8 (32%) of the 25 patients the graft was angiographically occluded, 6 (75%) of these patients showing a predominantly systolic Doppler signal, while the remaining 2 (25%) patients were those in whom the signal could not be elicited. Sensitivity and specificity of a predominantly diastolic Doppler flow pattern for the presence of graft patency was 88% and 100% respectively, with a predictive positive value of 100% and a negative one of 80%. CONCLUSIONS: Doppler flow velocity pattern of internal mammary artery by-pass grafts is related with patency of the graft, the presence of a predominantly diastolic curve being highly indicative of a patent graft.

Aged↗
PubMed1998

[Intramural hematomas of the ascending aorta].

We present four patients with intramural hematomas in the ascending aorta. Diagnostic suspicion was aortic dissection in two of them. Prompt surgical procedures were performed in all of them. After reviewing other series, we conclude that ascending aorta hematomas should be treated as true aortic dissections.

Aged↗
PubMed1998

[Transmyocardial revascularization with laser].

Patients with severe angina pectoris, refractory to medical treatment, in which conventional revascularization (PTCA or bypass surgery) is not possible because they present advanced coronary artery disease with a poor distal bed, account for an important clinical problem due to an increasing incidence, combined with poor quality of life, an elevated risk of severe complications, repeated hospital admissions and high mortality rate. Laser transmyocardial revascularization provides a new therapeutic alternative for these patients. Although up to now there are only a few published series, with a small number of patients, the results obtained in the two ongoing multicentric studies in Europe and the United States (including more than 500 patients at present) are quite promising. It is a simple surgical procedure, but its associated mortality is not to be dismissed (in the beginning 12% and currently 5%), because patients are in an advanced evolutionary stage. In Spain this procedure has been available since April 1996 and the results have been encouraging. In our small series we have noted a significant symptomatic improvement and better quality of life.

Aged↗
PubMed1996

[Peritoneal migration of defibrillator implanted behind the rectus abdominis].

Automatic Implantable Cardioverter Defibrillator (AICD) has become a therapeutic option to malignant ventricular tachyarrhythmias. Its bulky device responds for discomfort and the likelihood of generator extrusion or migration, when implanted under the subcutaneous tissue. Among alternative sites, pre-peritoneal location has several advantages but hides its own risks. We present a generator peritoneal migration from a pocket made behind the rectus abdominis.

Aged↗
PubMed1996

[Modified Takeuchi in adults].

Anomalous origin of left coronary artery from pulmonary artery is a rare congenital anomaly (0.25-0.46%). Mortality is high in the first months (65%). Paradoxically, some patients reach adulthood because of a net made of collaterals from the right coronary artery. Thus, we classify the entity in two ways of clinical onset: childhood and adulthood. Ideally, the best surgical approach is the arrangement of a double coronary system. The most well-known technique is the one described by Takeuchi, that links the aorta and the left coronary artery by a tunnel through the pulmonary artery, made from a pulmonary artery frontal wall flap (closing the defect with a pericardial patch). We present a case of anomalous origin of the left coronary artery in an adult, treated in our institution using a modified Takeuchi technique.

Adult↗
PubMed1994

Adenosine 5'-triphosphate (ATP), the neurotransmitter in the prostatic portion of the longitudinal muscle layer of the rat vas deferens.

Suramin (1-100 microM) and alpha, beta-methylene adenosine 5'-triphosphate (AMPCPP, 39 microM), antagonized the motor activity induced by exogenous adenosine 5'-triphosphate (ATP) but not exogenous noradrenaline (NA) in the longitudinal musculature of prostatic (P) and epididymal (E) segments of the rat vas deferens. Likewise, application of these drugs reduced the fast component of the nerve-stimulated contraction in response to a single transmural electrical pulse in E and P. Suramin also blocked in a concentration-dependent fashion, the contractile responses to trains of 1.5, 5, 15 or 30 Hz transmural electrical pulses in P, while it did not affect those in E. AMPCPP obliterated responses to trains of 1.5, 5, and 15 Hz in P, while reducing these responses in E to a significantly lesser extent. Present results strongly support that ATP is the motor transmitter in P, while in E, ATP and NA are likely the co-transmitters responsible for the motor tone.

Adenosine Triphosphate↗