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Biomedical subjects

J L Peña

Publications and source records attributed to J L Peña.

At least 19 recordsLinked to original sources
PubMed2003

Functional outcome and subset identification in RA patients from meridional Europe: analysis of a Spanish cohort.

The aim of this study was to study the short-term functional and anatomical prognosis of rheumatoid arthritis (RA) in a series of Spanish patients and to identify different subsets of patients as well as possible baseline factors associated with specific outcomes. All patients seen in our division who met the ACR criteria for RA and with disease duration between 2 and 7 years were eligible for the study. Available patients were further evaluated at the clinic for disease activity using biological tests and joint indices as joint counts and Thompson's index, functional capacity using the ACR functional classification (ACR-FC) and the modified Health Assessment Questionnaire (M-HAQ) and radiologic damage by the Sharp's radiologic scoring method. Cluster analysis was used to identify different clinical subsets of patients. One hundred and sixty-three patients were eligible for the study, 13 could not be located or refused to participate and 12 had died. Mean (+/-SD) age at disease onset and mean disease duration were, respectively, 56(+/-14) years and (55+/-20) months. Median (interquartile range) of M-HAQ was 0.4 (0.1-1.1) and 41% of patients were in III or IV ACR-FC. The majority of patients (93%) showed radiologic lesions and 65% had erosions. Cluster analysis identified three subsets: cluster I (70% of patients) was characterised by a good prognosis, cluster II (13%) by a high level of disease activity, and cluster III (17%) by a greater anatomic damage and longer disease duration. No baseline predictive markers were found for these different outcomes. We concluded that RA portends an overall poor short-term prognosis in a relative large percentage of our patients with significant anatomic and functional sequelae. Aggressive management is specially indicated in this subgroup of patients, although definitive prognostic markers for its early identification are still lacking.

Adult↗
PubMed2003

n-3 Fatty acids plus oleic acid and vitamin supplemented milk consumption reduces total and LDL cholesterol, homocysteine and levels of endothelial adhesion molecules in healthy humans.

BACKGROUND AND AIMS: Numerous studies suggest n -3 polyunsaturated fatty acids (n -3 PUFA) and oleic acid intake have beneficial effects on health including risk reduction of coronary heart disease. The purpose of this study was to evaluate the effect of a commercially available skimmed milk supplemented with n -3 PUFA, oleic acid, and vitamins E, B(6), and folic acid (Puleva Omega3) on risk factors for cardiovascular disease. (CVD). METHODS: Thirty volunteers were given 500 ml/day of semi-skimmed milk for 4 weeks and then 500 ml/day of the n -3 enriched milk for 8 further weeks. Plasma and LDL lipoproteins were obtained from volunteers at the beginning of the study (T(pre)), and at 4, 8 and 12 weeks. RESULTS: The consumption of n -3 enriched milk produced a significant decrease in plasma concentration of total and LDL cholesterol accompanied by a reduction in plasma levels of homocysteine. Plasma and LDL oxidability and vitamin E concentration remained unchanged throughout the study. A significant reduction in plasma levels of vascular cell adhesion molecule 1, and an increase in plasma concentration of folic acid were also observed. CONCLUSION: Daily intake of n -3 PUFA and oleic acid supplemented skimmed milk plus folic acid and B-type vitamins has favourable effects on risk factors for CVD.

Adult↗
PubMed2003

Photoacoustic determination of iron in corn meal.

We report here on the use of the photoacoustic technique for the determination of low concentrations of total iron in corn meal samples. The determination of this element in food is of considerable interest because several foods are currently enriched with it at proper levels in order to increase the resistance of people, after consumation, to several diseases, such as anemia. The proposed technique is based on an open photoacoustic cell configuration in conjunction with a suitable colorimetric method. We applied it to a measurement of the total iron concentration in corn meal samples. The results agree very well with those obtained using a conventional spectrophotometric method, showing the possibilities of new experimental methodologies based on photothermal methods to perform this kind of study, with the advantage of a higher sensitivity and increment of the range of appreciable absorbance.

Acoustics↗
PubMed2001

Auditory spatial receptive fields created by multiplication.

Examples of multiplication by neurons or neural circuits are scarce, although many computational models use this basic operation. The owl's auditory system computes interaural time (ITD) and level (ILD) differences to create a two-dimensional map of auditory space. Space-specific neurons are selective for combinations of ITD and ILD, which define, respectively, the horizontal and vertical dimensions of their receptive fields. A multiplication of separate postsynaptic potentials tuned to ITD and ILD, rather than an addition, can account for the subthreshold responses of these neurons to ITD-ILD pairs. Other nonlinear processes improve the spatial tuning of the spike output and reduce the fit to the multiplicative model.

Acoustic Stimulation↗
PubMed2000

Cellular mechanisms for resolving phase ambiguity in the owl's inferior colliculus.

Both mammals and birds use the interaural time difference (ITD) for localization of sound in the horizontal plane. They may localize either real or phantom sound sources, when the signal consists of a narrow frequency band. This ambiguity does not occur with broadband signals. A plot of impulse rates or amplitude of excitatory postsynaptic potentials against ITDs (ITD curve) consists of peaks and troughs. In the external nucleus (ICX) of the owl's inferior colliculus, ITD curves show multiple peaks when the signal is narrow-band, such as tones. Of these peaks, one occurs at ITDi, which is independent of frequency, and others at ITDi +/- T, where T is the tonal period. The ITD curve of the same neuron shows a large peak (main peak) at ITDi and no or small peaks (side peaks) at ITDi +/- T, when the signal is broadband. ITD curves for postsynaptic potentials indicate that ICX neurons integrate the results of binaural cross-correlation in different frequency bands. However, the difference between the main and side peaks is small. ICX neurons further enhance this difference in the process of converting membrane potentials to impulse rates. Inhibition also appears to augment the difference between the main and side peaks.

Acoustic Stimulation↗
PubMed1999

Sleep and wakefulness modulation of the neuronal firing in the auditory cortex of the guinea pig.

Sleep-related changes-including modification in sensory processing-that influence brain and body functions, occur during both slow wave and paradoxical sleep. Our aim was to investigate how cortical auditory neurons behave during the sleep/waking cycle, and to study cell firing patterns in relation to the processing of auditory information without the interference of anesthetic drugs. We recorded single cells in the A region of the auditory cortex in restrained, chronically-implanted guinea pigs, and compared their evoked and spontaneous activity during sleep stages and quiet wakefulness. A new classification of the unit's responses to simple sound during wakefulness is presented. Moreover, a number of the neurons in the primary auditory cortex exhibited significant quantitative changes in their evoked or spontaneous firing rates. These changes could be correlated to sleep stages or wakefulness in 42.2% to 58.3% of the sampled neurons. A similar population did not show behavioral related changes in firing rates. Our results indicate that the responsiveness of the auditory system during sleep may be considered partially preserved. An important result was that spontaneous and evoked activity may vary in opposite directions, i.e. , the evoked activity could increase while the spontaneous activity decrease or vice versa. Then, a general question was proposed: is the increased spontaneous activity in the auditory cortex, particularly during PS, related to auditory hypnic 'images'? The studied cortical auditory neurons exhibit changes in their firing rates in correlation to stages of sleep and wakefulness. This is consistent with the hypothesis that a general shift in the neuronal networks involved in sensory processing occurs during sleep.

Acoustic Stimulation↗
PubMed1997

Effects of interaural intensity difference on the processing of interaural time difference in the owl's nucleus laminaris.

Interaural time and intensity differences (ITD and IID) are processed independently in the owl's auditory system. This paper examines whether this independence is established in nucleus laminaris (NL), the first site of ITD processing. A plot of discharge rate against time difference (ITD curve) is sinusoidal in NL. The ITDs that produce the peaks are called the most favorable ITDs, and those that produce the troughs are called the least favorable ITDs. IID had little effect on the discharge rates of laminaris neurons for the most and least favorable ITDs. The degree of peak-trough modulation changed slightly with variation in IID. In contrast, IID in tonal stimuli affected the temporal aspect of ITD curves depending on the difference between the stimulus frequency and the neuron's best frequency (BF). For frequencies below BF, IID caused large and systematic shifts in ITD toward the ear in which the sound was louder, whereas for frequencies above BF, IID caused small shifts in ITD toward the opposite ear. IID had little effect on ITD curves taken with BF or broadband noise. These results can be largely accounted for by the effects of frequency and intensity on the timing of impulses at the level of the cochlear nuclei. Thus, the processing of ITD by NL neurons is independent of IID for behaviorally relevant stimuli, because the timing of impulses is insensitive to sound level when the signal is broadband.

Acoustic Stimulation↗
PubMed1997

Auditory deprivation modifies sleep in the guinea-pig.

After destruction of both cochleae, a significant enhancement of both paradoxical sleep and slow wave sleep together with decreased wakefulness, were observed for up to 45 days. The sleep augmentation consisted of an increment in the number of episodes of both slow wave and paradoxical sleep rather than in the duration of single episodes. The partial isolation provoked by deafness is postulated as explanation. We suggest that the suppression of one input to a complex set of networks related to the sleep-waking cycle, introduce an imbalance that leads to sleep enhancement.

Animals↗
PubMed1997

[Spontaneous acquired localized neuropathies in childhood].

Acquired non-surgical, non-traumatic localized neuropathies, excluding cranial nerve disorders, are rare in infancy. We review the clinical histories of six children, studied for this disorders amongst a total of 2,105 children seen in the Neuropediatric Department of the Hospital Miguel Servet in Zaragoza. Two were diagnosed as familial neuropathy with pressure sensitive paralysis. Two plexopathies were considered to be familial brachial plexopathy with minor dysmorphic features. One case was diagnosed as idiopathic radial neuropathy and a further case as idiopathic lumbosacral plexopathy. We emphasize that although rare in pediatrics, spontaneous localized neuropathies often show constitutional pathology, frequently hereditary. Idiophatic cases may also be hereditary, and it may be difficult to confirm the diagnosis if there is no family history or phenotypic characteristics. Diagnosis depends on the personal and family history, physical examination, neurophysiological study, absence of abnormal neuroimaging findings and awareness of the possibility of this diagnosis. These disorders probably occur more often than is generally believed.

Brachial Plexus↗
PubMed1996

Tolerance to sound intensity of binaural coincidence detection in the nucleus laminaris of the owl.

Neurons of the owl's nucleus laminaris serve as coincidence detectors for measurement of interaural time difference. The discharge rate of nucleus laminaris neurons for both monaural and binaural stimulation increased with sound intensity until they reached an asymptote. Intense sounds affected neither the ratio between binaural and monaural responses nor the interaural time difference for which nucleus laminaris neurons were selective. Theoretical analysis showed that high afferent discharge rates cause coincidence detectors with only excitatory input to lose their selectivity for interaural time difference when coincidence of impulses from the same side becomes as likely as that of impulses from the two sides. We hypothesize that inhibitory input whose strength increases with sound intensity protects nucleus laminaris neurons from losing their sensitivity to interaural time difference with intense sounds.

Acoustic Stimulation↗
PubMed1996

Firing of inferior colliculus auditory neurons is phase-locked to the hippocampus theta rhythm during paradoxical sleep and waking.

The activity of 52 single auditory units in the central nucleus of the inferior colliculus (IC) was recorded along with cortical and hippocampal (CA1) electrograms and neck muscle electromyograms in behaving, head-restrained guinea pigs during paradoxical sleep (PS) and wakefulness. Sixteen (30%) of the IC auditory units showed positive correlation with the hippocampal theta (theta) rhythm: 8 (15%) were theta rhythmic with theta phase-locking (type 1), 8 (15%) showed only theta phase-locking with no rhythmicity (type 2), while 70% did not show any correlation to hippocampal theta rhythm (type 3). During wakefulness IC neurons (4 of 13) showed a higher synchrony with hippocampal theta when sound-stimulated at the unit's characteristic frequency. During PS all IC auditory neurons recorded presented some hippocampal theta correlation: 40% were rhythmic and phase-locked to the theta frequency and 60% were nonrhythmic maintaining the theta phase-locking. Shifts in the angle of phase-locking to the theta rhythm were observed during PS. It is suggested that the hippocampal theta rhythm may play the part of an internal clock, adding a temporal dimension to the processing of auditory sensory information.

Animals↗
PubMed1994

alpha-L-arabinofuranosidase production by Aspergillus nidulans.

The effects of some physico-chemical parameters on production of extracellular alpha-L-arabinofuranosidase by Aspergillus nidulans were examined. Highest levels of alpha-L-arabinofuranosidase were generated with cultures grown on 1% (w/v) purified beet pulp arabinan at 30 degrees C and at an initial pH of 7.0. The enzyme was shown to be very sensitive to the action of proteases. Zymogram overlay of a protein profile obtained by SDS-PAGE revealed the occurrence of a band (M(r) 36,000) exhibiting alpha-L-arabinofuranosidase activity. The isoelectric pH of the enzyme lay near 4.3. Temperature and pH optima for the activity of crude alpha-L-arabinofuranosidase preparations were 55 degrees C and 5.5, respectively. Enzyme activity was greatly reduced by thiol reagents such as Hg2+ and p-hydroxymercuribenzoate and showed a Km value of 2.7 mM on p-nitrophenyl alpha-L-arabinofuranoside as substrate.

Aspergillus nidulans↗
PubMed1994

Internally-generated sound stimulates cochlear nucleus units.

The body generates many physiological sounds. One of the most prominent is that produced by the blood flowing inside the vessels with each heart beat. On the other hand, the cochlea is a very sensitive receptor with a low threshold. Given the anatomical close proximity of the carotid artery and other vessels to the inner ear, the possibility of its being stimulated is very high. Cochlear nucleus spontaneous as well sound-responding auditory units were studied. A close relationship between the heart beat, that is the blood flow, and the cochlear nucleus firing was demonstrated, in anesthetized and awake guinea-pigs. Temporary mechanical interruption of the blood flow through the ipsilateral carotid artery abolished firing increments at the cochlear nucleus time-locked to the heart beat. We conclude that one component of the so called 'spontaneous' firing in the auditory system is actually evoked activity due to normal body-generated sounds or noises.

Acoustic Stimulation↗
PubMed1994

Effects of sleep on the responses of single cells in the lateral superior olive.

The effects of behavioral shifts on auditory lateral superior olive neurons were analyzed in guinea-pigs during the sleep-waking cycle with single unit extracellular recordings at the unit characteristic frequency and with low sound intensity. Shifts in the number of spikes in response to pure tones and in spontaneous firing proved to be closely related to waking, slow wave and paradoxical sleep. All of the recorded lateral superior olive (LSO) auditory neurons showed sleep-related firing shifts. Moreover, changes in the pattern of discharge over time were observed in 15% of the LSO cells on passing from waking to sleep. Sleep may determine either an increase or a decrease of the firing number in response to sound. The most important change observed in decreasing firing units was the near-absence of units responding to sound in the paradoxical sleep phase during the last 40 ms of the response. The waking cues for binaural detection, studied with our experimental paradigm, disappeared during slow wave sleep. We thus conclude that the binaural function of some lateral superior olive neurons (11.5%) was impaired during this sleep period in the present experimental conditions. Auditory efferent pathways are postulated to impinge on the auditory processing at LSO nucleus level during the sleep-waking cycle. Thus, auditory unitary activity appears to be dependent on both incoming information, and a CNS descending action closely related to the waking and sleep periods. Functional interactions between pontine sleep-related groups of neurons and auditory system units are suggested.

Acoustic Stimulation↗
PubMed1992

Single unit activity in the guinea-pig cochlear nucleus during sleep and wakefulness.

The effects of waking and sleep on the response properties of auditory units in the ventral cochlear nucleus (CN) were explored by using extracellular recordings in chronic guinea-pigs. Significant increases and decreases in firing rate were detected in two neuronal groups, a) the "sound-responding" and b) the "spontaneous" (units that do not show responses to any acoustic stimuli controlled by the experimenter). The "spontaneous" may be considered as belonging to the auditory system because the corresponding units showed a suppression of their discharge when the receptor was destroyed. The auditory CN units were characterized by their PSTH in response to tones at their characteristic frequency and also by the changes in firing rate and probability of discharge evaluated during periods of waking, slow wave and paradoxical sleep. The CNS performs functions dependent on sensory inputs during wakefulness and sleep phases. By studying the auditory input at the level of the ventral CN with constant sound stimuli, it was shown that, in addition to the firing rate shifts, some units presented changes in the temporal probability of discharge, implying central actions on the corresponding neurons. The mean latency of the responses, however, did not show significant changes throughout the sleep-waking cycle. The auditory efferent pathways are postulated to modulate the auditory input at CN level during different animal states. The probability of firing and the changes in the temporal pattern, as shown by the PSTH, are thus dependent on both the auditory input and the functional brain state related to the sleep-waking cycle.

Acoustic Stimulation↗
PubMed1991

A search for a mesencephalic periaqueductal gray-cochlear nucleus connection.

Horseradish peroxidase placed into the ventral mesencephalic periaqueductal gray (PAG) and in the lateral superior olivary complex region demonstrated indirect paths towards the cochlear nucleus (CN). Because no direct connections could be observed, a pathway throughout the auditory efferent system was proposed. The results suggest three possibilities: 1) The PAG is connected to the lateral superior peri-olivary complex synapsing with known efferent fibers that reach the CN; 2) Neurons located at the dorsal PAG were demonstrated to be connected to the inferior colliculus (IC). The possibility of synapses with known neurons that run from IC to the CN is postulated; 3) Neurons in the trapezoid body, which are partially associated with a system that communicates with the CN, are also connected to and from the PAG. The present results anatomically support an extracellular study (1) describing PAG actions on CN units.

Animals↗
PubMed1990

Periaqueductal gray influence on anteroventral cochlear nucleus unitary activity and naloxone effects.

The effect of periaqueductal gray (PAG) electrical stimulation on the response properties of auditory and 'spontaneously' firing units (abolished when the cochlea is destroyed) in the anteroventral cochlear nucleus (AVCN) was explored using extracellular recordings in acute guinea-pigs. Significant increases and decreases in firing rate were detected in both neuronal groups: only 4% of the sound-responding units were insensitive to PAG stimulation while the 'spontaneous' units showed significantly smaller changes in firing rate in response to PAG stimulation. The auditory AVCN neurons were categorized both by their sound post stimulus time (PST) histograms at their characteristic frequency (CF) and the changes in the probability of discharge after PAG stimulation while the tone burst was maintained constant. PAG was implicated in pain input modulation through enkephalin actions. Because enkephalins have been also observed at the CN level, a pharmacological approach administering naloxone was carried out. We observed that 1) naloxone abolished the unit discharge shifts observed after PAG stimulation and 2) when the drug was injected without PAG stimulation, it produced changes in the firing, increasing or decreasing, and shifts in the probability of discharge versus time, even in cases in which the firing rate was not altered. An involvement of the auditory efferent pathways to CN is postulated and a possible enkephalinergic factor is suggested as a modulator of the auditory input at this level. The probability of discharge observed in the PSTH at the AVCN is dependent on the auditory input plus the central efferent action to its neurons.

Acoustic Stimulation↗