Biomedical subjects

Miguel A Pozo

Publications and source records attributed to Miguel A Pozo.

11 recordsLinked to original sources

PubMed2005

Accuracy of helical computed tomography and [18F] fluorodeoxyglucose positron emission tomography for identifying lymph node mediastinal metastases in potentially resectable non-small-cell lung cancer.

PURPOSE: Computed tomography (CT) and [18F] Fluorodeoxyglucose positron emission tomography (FDG-PET) are considered suitable methods for the noninvasive staging of the mediastinum. Our study was intended to estimate the efficacy of contrast-enhanced helical CT (hCT) and FDG-PET, alone and combined, in the diagnosis of lymph node mediastinal metastases. METHODS: This study was a prospective and blind comparison of the efficacy of hCT and FDG-PET with two alternative reference standards, mediastinoscopy, and mediastinoscopy plus thoracotomy plus a 6-month follow-up to diagnose lymph node mediastinal metastases in 132 consecutive patients with potentially resectable non-small-cell lung cancer (NSCLC). The metastatic disease was assessed histopathologically. Further clinical information was obtained postoperatively after a median follow-up of 42 months. RESULTS: The prevalence of cN2,3 is 0.28. For hCT the sensitivity and specificity are 0.86 (95% CI, 0.70 to 0.93) and 0.67 (95% CI, 0.56 to 0.75), for PET 0.94 (95% CI, 0.81 to 0.98) and 0.59 (95% CI, 0.49 to 0.68), and for hCT and PET combined in-parallel 0.97 (95% CI, 0.84 to 0.99) and 0.44 (95% CI, 0.34 to 0.53), which translate into a negative predicted probability of 0.98 (95% CI, 0.88 to 1.00). The crude diagnostic odds ratio of PET in the total sample studied is 13.1, in the subgroup hCT+ 11.04 (3.0 to 40 0.1), and in the hCT- 3.5 (0.5 to 21.5). Similar results were obtained for hCT stratified by PET. CONCLUSION: hCT and PET perform similarly in the mediastinal staging of NSCLC, both tests are conditionally dependent and provide complementary information, and their diagnostic value mainly resides on the negative results.

Aged↗

PubMed2005

Cholinergic modulation of status epilepticus in the rat barrel field region of primary somatosensory cortex.

Status epilepticus (SE) represents a serious medical emergency that can produce long-lasting brain damage as well as cognitive and memory deficits. However, the mechanisms that determine the emergence of SE from a single seizure and the prolonged duration of SE are unknown. Therefore, we used pharmacological tools to investigate the cellular mechanisms that underlie this prolonged epileptic activity in the rat barrel field region of somatosensory cortex (S1BF). Electrocortical and unitary extracellular field recording in the rat S1BF region was used to assess abnormal epileptiform activity induced by intracerebral application of 4-aminopyridine (4-AP). Simultaneously, electromyographic (EMG) activity was recorded from mystacial pad musculature. Intracerebral injection of 4-AP induced an SE that was paralleled by an increase of whisker activity that was not synchronized with the electrocortical recording. The seizures were originated ipsilaterally in the cortex of the injected hemisphere and propagated to the contralateral cortex with lower amplitude. The application of the glutamatergic NMDA receptor antagonist D (-)-2-amino-5-phosphonopentanoic acid (AP5) strongly increased the seizure-onset latency. The muscarinic receptor antagonist atropine changed the continuous rapid spiking pattern of SE to periodic discharges, while glutamatergic or GABAergic antagonist did not modify the electrographic features of SE. Our data suggest that the muscarinic cholinergic system plays an important role in the seizure modulation during SE in the somatosensory cortex, while their emergence is controlled, in part, by glutamatergic NMDA receptors.

4-Aminopyridine↗

PubMed2005

Anxiolytic-like effect of a serotonergic ligand with high affinity for 5-HT1A, 5-HT2A and 5-HT3 receptors.

S-(-)-2-[[4-(napht-1-yl)piperazin-1-yl]methyl]-1,4-dioxoperhydropyrrolo[1,2-alpha]-pyrazine (CSP-2503) is a serotonin (5-HT) receptor ligand with selectivity and high affinity for 5-HT1A, 5-HT2A and 5-HT3 receptors. CSP-2503 reduced rectal temperature and 5-HT neuronal hypothalamic activity in mice, decreased electrical activity of raphe nuclei cells in rats and blocked the enhancement of adenylate cyclase activity induced by forskolin in HeLa cells transfected with the human 5-HT1A receptor. This compound also blocked head-twitches induced by the 5-HT(2A/2C) receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI). Contractions of guinea pig ileum induced by the 5-HT3 receptor agonist 2-methyl-5-HT were prevented by CSP-2503. Moreover, it reduced the bradycardia reflex induced by 2-methyl-5-HT in anaesthetized rats. In the light/dark box and social interaction tests, CSP-2503 presented anxiolytic activity, an action shared by 5-HT1 agonists and 5-HT3 antagonists. Taken together, these results suggest that CSP-2503 is a new 5-HT1 receptor agonist with 5-HT2A and 5-HT3)receptor antagonist activities that might be useful in a number of conditions associated with anxiety.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2005

Syntactic expectancy: an event-related potentials study.

Although extensive work has been conducted in order to study expectancies about semantic information, little effort has been dedicated to the study of the influence of expectancies in the processing of forthcoming syntactic information. The present study tries to examine the issue by presenting participants with grammatically correct sentences of two types. In the first type the critical word of the sentence belonged to the most expected word category type on the basis of the previous context (an article following a verb). In the second sentence type, the critical word was an unexpected but correct word category (an article following an adjective) when a verb is highly expected. Event-related potentials (ERPs) were measured to critical words in both sentence types. Brain waves evoked by the correct but syntactically unexpected word revealed the presence of a negativity with a central distribution around 300-500 ms after stimuli onset, an N400, that was absent in the case of syntactically expected words. No differences were present in previous time windows. These results support models that differentiate between the processing of expected and unexpected syntactic structures.

Adult↗

PubMed2005

Higher-order activity beyond the word level: cortical dynamics of simple transitive sentence comprehension.

Slow electrophysiological effects, which fluctuate throughout the course of a sentence, independent of transient responses to individual words, have been reported. However, this type of activity has scarcely been studied, and with only limited use of electrophysiological information, so that the brain areas in which these variations originate have not been clearly identified. To improve this state of affairs, a principal component analysis and a modern source analysis algorithm (LORETA) were applied to the slow activity underlying transitive sentence reading. Four components explained 97.3% of the variance. Of key interest was a slow variation that occurred throughout the entire sentence but peaked with the appearance of the verb. The main solution for this component was localized in prefrontal and temporal regions presumably involved in semantic sentence processing. This constitutes empirical evidence for cortical activity--related to semantic processes thought to be involved in thematic role assignment--developing throughout the sentence but presenting a conspicuous maximum with the appearance of the verb. This finding also highlights the central role of verb information in the understanding of transitive sentences.

Adult↗

PubMed2004

Valproate reduced excitatory postsynaptic currents in hippocampal CA1 pyramidal neurons.

Valproate (VPA) is one of the most widely used antiepileptic drugs, and it is also increasingly used for the treatment of neuropsychological disorders and neuropathic pain, as well as migraine prophylaxis. However, the underlying cellular mechanisms of VPA on the synaptic physiology remain unclear. We investigated the effects of VPA on synaptic transmission using the in vitro rat hippocampal slice technique and whole-cell patch clamp recordings from CA1 pyramidal neurons. Perfusion with VPA, at therapeutically attainable concentrations, decreased the amplitude of excitatory postsynaptic currents (EPSCs) evoked by Schaffer collateral stimulation, without modifying inhibitory postsynaptic currents (IPSCs). Furthermore, VPA induced a significant reduction of the non-NMDA EPSC (non-NMDA(EPSC)) component, without modifying the NMDA EPSC (NMDA(EPSC)) component. Paired pulse facilitation and EPSC variance were not significantly affected by VPA, indicating that VPA did not decrease transmitter release probability, which suggests a postsynaptic mechanism of action. We therefore conclude that VPA decreases excitatory synaptic activity through the modulation of postsynaptic non-NMDA receptors, without modifying synaptic inhibition, and that this reduction of excitation is, at least in part, responsible for the effects of VPA.

Animals↗

PubMed2004

Electrophysiological evidence of automatic early semantic processing.

This study investigates the automatic-controlled nature of early semantic processing by means of the Recognition Potential (RP), an event-related potential response that reflects lexical selection processes. For this purpose tasks differing in their processing requirements were used. Half of the participants performed a physical task involving a lower-upper case discrimination judgement (shallow processing requirements), whereas the other half carried out a semantic task, consisting in detecting animal names (deep processing requirements). Stimuli were identical in the two tasks. Reaction time measures revealed that the physical task was easier to perform than the semantic task. However, RP effects elicited by the physical and semantic tasks did not differ in either latency, amplitude, or topographic distribution. Thus, the results from the present study suggest that early semantic processing is automatically triggered whenever a linguistic stimulus enters the language processor.

Adolescent↗

PubMed2004

Valproate reduced synaptic activity increase induced by 4-aminopyridine at the hippocampal CA3-CA1 synapse.

PURPOSE: We investigated the effects of valproate (VPA) on excitatory synaptic transmission changes induced by 4-aminopyridine (4-AP) to determine whether the antiepileptic effects shown by VPA can be ascribed to a modulation of spontaneous excitatory postsynaptic currents (sEPSCs) in the CA3-CA1 synapse. METHODS: Rat hippocampal slices were prepared and maintained in vitro with standard methods. Whole-cell current and voltage-clamp recordings were obtained from CA1 pyramidal neurons by using the "blind" patch-clamp technique in an immersion recording chamber. Increase in the spontaneous excitatory synaptic activity was induced by addition of 4-AP to the medium. RESULTS: Perfusion with VPA significantly counteracted the increase of frequency and amplitude of the sEPSCs induced by application of 4-AP and suppressed the epileptiform activity. CONCLUSIONS: We conclude that VPA decreases the 4-AP-induced enhancement of excitatory synaptic activity at the CA3-CA1 synapse, and that this reduction of excitation input to CA1 contributes to the anticonvulsant effects of VPA.

4-Aminopyridine↗

PubMed2003

Valproate suppresses status epilepticus induced by 4-aminopyridine in CA1 hippocampus region.

PURPOSE: We investigated the effects of valproate (VPA) on an in vivo model of status epilepticus (SE) induced by intrahippocampal application of 4-aminopyridine (4-AP). METHODS: To induce continuous epileptiform activity without a clinical component, 4-AP (100 mM) was slowly injected in the hippocampus of adult rats. Extracellular field potential from the CA1 region of the rat hippocampus was recorded to assess abnormal epileptiform activity. Once the SE seizures were induced by 4-AP, the test drug was injected. In some experiments to test the ability of a drug to prevent the induction of SE, the drug was administered before 4-AP injection. RESULTS: Intrahippocampal injection of 4-AP induced continuous epileptic activity without a clinical component that lasted >60 min. The intravenous injection of 400-600 mg/kg VPA rapidly (approximately 100 s) abolished the SE, and this effect persisted for >/=4 h in our experimental model. The intravenous injection of 100-300 mg/kg VPA did not abolish previously induced SE, but prevented the appearance of SE when applied before the induction of SE. The intravenous injection of 80 mg/kg phenytoin or carbamazepine did not abolish or prevent SE. CONCLUSIONS: We conclude that 4-AP-induced SE was suppressed by VPA at 400-600 mg/kg, whereas minor doses (100-300 mg/kg) only prevent the 4-AP-induced SE. Present results suggest the revisiting of VPA as a useful drug for the treatment of SE.

4-Aminopyridine↗

PubMed2002

The recognition potential and repetition effects.

The recognition potential (RP) is an electrical brain response peaking at 250 ms that appears when subjects view meaningful stimuli. Previous RP research was conducted in experimental conditions in which repetition effects could not be totally ruled out as influencing the generation of the RP response. The present study aims to elucidate whether repetition effects affect the topography and waveform of this component. For this purpose semantically correct, orthographically correct, strings of random letters, control and background stimuli were presented to 20 subjects following the rapid stream stimulation procedure and without repetition of any test stimulus. As previously, the RP showed its maximal amplitude at the PO7 electrode. It showed sensitivity to all levels of lexical processing, its response being maximal for semantically correct stimuli, and its topographical distribution was similar for all types of stimulus. Direct statistical comparisons with the data of a previous study where repetition effects could not be disregarded were performed, confirming the similarity between the results obtained in both experiments. The neural generators of the RP were placed again, as in previous studies, within the lingual gyrus. Although repetition effects have been reported to affect other semantic-related components such as the N400, they do not seem to affect either the topography or the waveform of the RP.

Adult↗

PubMed1992

Selective changes of receptive field properties of spinal nociceptive neurones induced by noxious visceral stimulation in the cat.

This study was designed to examine the central changes in the receptive field properties of dorsal horn neurones induced by a period of visceral noxious stimulation. The aim of this investigation was to establish whether noxious stimulation of the visceral input to the spinal cord could influence transmission of cutaneous information through dorsal horn neurones. Single-unit electrical activity was recorded in the lower thoracic spinal cord of anaesthetized cats from dorsal horn neurones with a somatic receptive field in the ipsilateral flank. Changes in the properties of these receptive fields induced by reversible spinalization (by means of a cold block 4 or 5 segments rostral to the recording electrodes) and by a conditioning noxious stimulation of the biliary system (3 successive distensions of the gall bladder for 30 sec at 65-80 mm Hg at 1-min intervals) were analysed. Nineteen neurones have been studied, 10 of which could be driven by stimulation of the gall bladder. All of these 10 cells showed increases in the size of their cutaneous receptive fields following conditioning noxious stimulation of the biliary system. The increases were large and lasted for at least 20 min. None of the 9 spinal cord neurones without an input from the gall bladder were affected by the conditioning visceral stimulus even though 7 showed changes in receptive field size when the animals were spinalised. These results show that noxious stimulation of viscera can evoke increases in the somatic receptive fields of spinal cord neurones but only of those neurones which are also driven by the visceral stimulus.

Anesthesia↗