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Biomedical subjects

M Escudero

Publications and source records attributed to M Escudero.

At least 37 records · Page 2Linked to original sources
PubMed1996

Discharge properties of brain stem neurons projecting to the flocculus in the alert cat. II. Prepositus hypoglossal nucleus.

1. The aim of this study was to characterize the signals transmitted by the neurons of the nucleus prepositus hypoglossal (NPH) to the middle zone of the flocculus of the cat. The methods, the behavioral testing, and the animals used in this study were the same as those used in the accompanying paper on medial vestibular nucleus neurons. 2. The rostral two-thirds of the NPH was explored in alert animals with microelectrodes during stimulation of the middle zone of both flocculi. Discharges of neurons were analyzed during spontaneous eye movements (head fixed) and during horizontal vestibuloocular reflex (VOR) activity elicited by sinusoidal stimulation (10, 20, 30, or 40 degrees at 0.1 Hz). Forty neurons were found to be antidromically activated from only one or the other of the two flocculi (latency: 0.99 +/- 0.17 ms, mean +/- SD): 37 from the contralateral flocculus and 3 from the ipsilateral one. None of the neurons could be activated antidromically from both flocculi. Floccular stimulation never resulted in direct inhibition of these NPH neurons. 3. Of the 37 units antidromically activated from the contralateral flocculus, 26 were recorded sufficiently long to allow full quantitative analysis. Most of these (20 neurons) were classified as burst-tonic (BT) neurons. The BT neurons exhibited during each saccade made in one direction (the ON direction) a burst of spikes, and during postsaccadic fixation a tonic activity that increased with gaze displacement in the ON direction. The mean sensitivity of the neurons to eye velocity during the "ON" saccades was 3.3 +/- 1.6 spikes.s-1.deg-1.s-1. During intersaccadic fixation, the mean sensitivity to eye position was 3.6 +/- 2.5 spikes.s-1.deg-1. During the VOR, the majority showed modulation in relation to both eye position and eye velocity. The mean sensitivity to eye position during the VOR was 3.4 +/- 2.6 spikes.s-1.deg-1 (range: 0.2-8.1 spikes.s-1.deg-1). The mean sensitivity to eye velocity during the VOR was 2.1 +/- 1.3 spikes.s-1.deg-1.s-1. The mean phase lead of with respect to eye position was 16.4 +/- 6.8 degrees (range: 6.0-28.9 degrees). Eighty percent of the BT neurons behaved as type I neurons. Forty-seven percent of the BT neurons also presented some head velocity sensitivity (1.48 +/- 0.6 spikes.s-1.deg-1.s-1, mean +/- SD). 4. Other NPH cells antidromically activated from the contralateral flocculus were classified in two groups: bidirectional burst (BB) neurons (n = 4) and burst-driving (BD) neurons (n = 2). The BB neurons were characterized by a burst discharge during every horizontal saccade or VOR quick phase, irrespective of the direction. The mean sensitivity of the BB neurons to eye velocity during saccades was 3.3 +/- 7.8 (SD) spikes.s-1.deg-1.s-1. Both BD neurons increased their firing rate during the slow VOR phases induced by an ipsilateral rotation (type I neurons) and exhibited high-frequency bursts in association with ipsilaterally directed quick phases. 5. The results indicate that the main projection of the NPH onto the middle zone of the flocculus comes from contralaterally located type I BT neurons. Signals transmitted in this path associate a high sensitivity for eye velocity with a high sensitivity for eye position. This type of input is consistent with the suggestion that the main function of the flocculus is to control the gain of downstream reflexes and to perform a fine adjustment of the gaze holding command.

Animals↗
PubMed1995

Comparison of the effects of nerve growth factor and superoxide dismutase on vascular extravasation in experimental burns.

Superoxide dismutase (SOD), a free-radical scavenger, inhibits the increase of vascular permeability in experimental burn lesions in rats. In this study the aim was to determine whether Nerve Growth Factor (NGF), which has been implicated in the modulation of some inflammatory reactions, behaves in an analogous way. The study compares the haematocrit (Ht) and haemoglobin (Hb) variations in three groups of rats treated respectively with saline solution, SOD and NGF, immediately after causing a 25 per cent dermal burn injury. Statistical comparison (Student's t test) of the Ht and Hb variations between the Control group (Ht and Hb increase) and the NGF group (Ht and Hb decrease), shows significant differences in the intervals between 15 and 60 min (P < 0.01) and between 60 and 120 min (P < 0.05). Although SOD is able to control extravasation in the immediate postburn period (basal-15 min), NGF has a comparable effect in subsequent periods. The overall action of NGF shows that this agent is able to maintain Ht and Hb values at basal levels even after 120 min postburn. These results seem to be the first evidence of an inhibitory effect of NGF on the vascular permeability in burn lesions.

Animals↗
PubMed1995

Hypoglossal nerve conduction study by transcranial magnetic stimulation in normal subjects.

The introduction of transcranial magnetic stimulation has allowed the study of conduction in the proximal portions and central pathways of the cranial nerves. A study is made of cranial nerve XII with transcranial magnetic stimulation at two levels, cortical and cisternal, registering the motor evoked potential by means of surface electrodes in contact with the upper face of the tongue. Motor evoked potentials were constantly observed on cortical stimulation, in a painless, easy, and reproducible way, with mean values of 10.84 +/- 1.14 milliseconds (latency) and 7.81 +/- 1.14 mV (amplitude). Motor evoked potentials were unconstant and showed reduced amplitudes on cisternal stimulation, with mean values of 4.72 +/- 0.62 milliseconds and 0.83 +/- 1.26 mV. The magnetic stimulation technique allows the study of the entire motor pathway of cranial nerve XII (motor cortex-medulla, motoneuron-muscle). The method is efficient, noninvasive, painless, and easily reproduced, and it comes close to being an ideal clinical conduction study technique for this cranial nerve.

Adult↗
PubMed1993

Saccadic eye movements and the horizontal vestibulo-ocular and vestibulo-collic reflexes in the intact guinea-pig.

The guinea-pig is an attractive model for investigating gaze stabilization because it is suitable for in vitro and in vivo studies. However, few data are available on its oculomotor performance. We therefore investigated spontaneous eye movements, horizontal vestibulo-ocular (HVOR) and vestibulo-collic reflexes (HVCR) in the alert head-fixed guinea-pig using the magnetic search coil method. First the characteristics of the spontaneous saccades in the light were analysed. They occurred with a mean frequency of 4.6/min and with a mean amplitude and duration of 7.41 +/- 3.57 deg and 30.9 +/- 9.5 ms, respectively (n = 340). Saccadic duration and velocity were linearly related to the amplitude of the eye movement. The HVOR was studied in response to sinusoidal rotations (0.01 Hz to 2 Hz, peak head velocity of 40 deg/s) in the dark. Vestibular responses were linear at 0.5 and 0.05 Hz for peak head velocities between 40 and 80 deg/s. As in other species, the gain increased and the phase lead decreased with increasing frequencies. The number of fast phases per second increased with peak head velocity and with increasing frequencies from 0.01 to 0.5 Hz, with a plateau between 0.2 and 0.5 Hz. The HVOR time constant, when measured in response to velocity steps, was 7.0 +/- 1.5 s and the latency of the vestibular responses averaged 21 +/- 4 ms. Finally, the HVCR was assessed in unrestrained guinea-pigs subjected to horizontal sinusoidal rotation in the frequency range of 0.05-2 Hz. Exploratory behaviour was prevalent and there were few head stabilization episodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

The horizontal vestibulo-ocular reflex in the hemilabyrinthectomized guinea-pig.

The horizontal vestibulo-ocular reflex (HVOR) in the alert guinea-pig elicited by sinusoidal rotations and by velocity steps was studied with scleral search coil measurement between 3 and 7 days (short term) and between 35 and 160 days (long term) after hemilabyrinthectomy. Animals of the short-term group were always tested after spontaneous nystagmus in darkness had disappeared. The HVOR gain in response to sinusoidal rotations (peak angular velocity: 40 deg/s) in the short-term group was bilaterally depressed compared to normal animals. The HVOR phase showed a shift towards larger phase leads over the whole frequency range tested (from 0.05 to 3 Hz). In addition, both the mean number of fast phases per half-cycle of sinusoidal rotation and the mean amplitude were reduced. HVOR responses to velocity steps at a constant acceleration of 300 deg/s2 up to final velocity (0 to 100 deg/s) and of 1000 deg/s2 up to final velocity (0 to 300 deg/s) were depressed bilaterally and asymmetrically such that the gain for rotation towards the intact side greatly exceeded that obtained for rotation towards the lesioned side. Finally, the latency of the vestibular responses was increased and the time constant reduced for both sides of rotation. The HVOR gain values for sinusoidal rotations in the long-term group were lower than normal but higher than in the short-term group: they were asymmetric as a result of a greater compensation for rotation towards the intact side. Neither the phase lead nor the HVOR latency and time constant recovered values close to normal. Finally, the mean number of fast phases per half-cycle remained depressed although the mean amplitude recovered. These results demonstrate that in the guinea-pig, the dynamic deficits show a certain degree of recovery after unilateral labyrinthectomy. However, compared to the compensation of the static deficits previously quantified, the rate of recovery is much lower. This suggests that different processes may be involved in the compensation of the static and dynamic deficits.

Animals↗
PubMed1993

Accessory nerve electroneurography by magnetic stimulation in normal subjects.

An electroneurographic study was made of the accessory nerve in 15 healthy subjects by conventional peripheral electrical stimulation and transcranial magnetic stimulation at three different levels: cortical contralateral (frontoparietal), homolateral occipital and at the base of the skull. The motor evoked potential (MEP) obtained by magnetic stimulation at the skull base exhibited greater latency and amplitude than that recorded by conventional peripheral electrical stimulation. The MEP obtained by stimulating at occipital level again exhibited a greater latency than that corresponding to skull base stimulation, but the amplitude was smaller. Finally, the MEP resulting from cortical stimulation failed to appear uniformly in all of the individuals studied. Its amplitude was smaller than in the previous cases, with a mean latency of 11.76 ms and a central conduction time of 7.5 ms. The magnetic stimulation technique allowed the efficient, painless, non-invasive and easily reproducible study of the motor pathway of the spinal nerve over its entire trajectory (motor cortex-motor neuron-muscle).

Accessory Nerve↗
PubMed1992

A physiological study of vestibular and prepositus hypoglossi neurones projecting to the abducens nucleus in the alert cat.

1. Vestibular and prepositus hypoglossi (PH) neurones projecting to the abducens (ABD) nucleus were recorded in the alert cat. Their discharge characteristics were analysed to ascertain the origin of the horizontal eye position signal present in ABD neurones. 2. Neurones were classified according to: their location with respect to the ABD nucleus; their antidromic activation from the ABD nucleus; the synaptic field potential they induced in the ABD nucleus with the spike-triggered averaging technique; and their activity during spontaneous and vestibularly induced eye movements. 3. Vestibular neurones projecting to the ABD nucleus were located in the rostral medial vestibular nucleus. They were excitatory on the contralateral and inhibitory on the ipsilateral ABD neurones. Both types of premotor vestibular neurone showed a firing rate weakly related to eye position, increasing for eye fixations in the contralateral on-direction, and decreasing with ipsilateral fixation. Position sensitivity during eye fixations was (means +/- S.D.) 1.8 +/- 0.9 spikes s-1 deg-1 for excitatory neurones and 2.2 +/- 1.3 spikes s-1 deg-1 for inhibitory neurones. Firing rate exhibited a high variability during eye fixations. Their responses during saccades in the off-direction were characterized by a pause that, although less defined, was occasionally present during saccades in the on-direction. Eye velocity sensitivity during spontaneous saccades in the on-direction was 0.17 +/- 0.15 spikes s-1 deg-1 s-1 for excitatory neurones and 0.15 +/- 0.07 spikes s-1 deg-1 s-1 for inhibitory vestibular neurones. During sinusoidal head stimulation at 0.2 Hz, vestibular neurones showed a type I discharge rate with a phase lead over eye position of 86.0 +/- 14.1 deg for excitatory and 80.2 +/- 12.5 deg for inhibitory neurones. Position sensitivity during vestibular stimulation did not differ significantly from values obtained for spontaneous eye movements. However, the velocity sensitivity of premotor vestibular neurones during head rotation was significantly higher (1.6 +/- 0.2 spikes s-1 deg-1 s-1 for excitatory and 1.5 +/- 0.3 spikes s-1 deg-1 s-1 for inhibitory neurones) than during spontaneous eye movements. 4. PH neurones projecting to the ABD nucleus were located in the rostral one-third of the nucleus. These neurones were excitatory on the ipsilateral and inhibitory on the contralateral ABD nucleus. Their firing rates were correlated mainly with eye position, increasing for abducting eye positions of the ipsilateral eye and decreasing with adduction movements.(ABSTRACT TRUNCATED AT 400 WORDS)

Abducens Nerve↗
PubMed1990

Changes in anti-idiotype antibodies against anti-HBs during recombinant interferon treatment of chronic hepatitis B.

To determine the possible changes in the presence and level of anti-idiotype (anti-Id) antibodies against anti-HBs induced by recombinant interferon (rIFN) therapy in chronic hepatitis B virus (HBV) infection, a study of patients under rIFN treatment has been carried out. A total of 62 (38 treated and 24 controls), HBeAg and HBV-DNA positive HBsAg carriers were tested serially for the presence of IgG and IgM anti-Id antibodies. According to serological evolution, treated patients were divided in responders (HBeAg and HBV-DNA became negative) (n = 18) and nonresponders (n = 20). Control patients were also classified as having spontaneous seroconversion (n = 11) and without changes (n = 13). Basally all patients had IgG and IgM anti-Id. At the end of the follow-up period (15th month), a significant decrease was observed in the percentage of cases positive to anti-Id among rIFN-responders (IgG, 67%, p less than 0.01; IgM, 44%, p less than 0.001). In contrast, only one nonresponder lost IgM anti-Id during the study. Among controls, only one with spontaneous loss of HBV-DNA and HBeAg clearance became negative to both IgG and IgM anti-Id. In addition, in the basal sample, the rIFN-responders had significantly lower anti-Id levels than the nonresponders (p less than 0.05). Similar results were obtained when comparing the controls with or without spontaneous response (p less than 0.05). Furthermore, a significant decrease in the anti-Id levels among the rIFN responders at the 9th month was detected (p less than 0.01). In summary, the anti-Id antibodies decreased significantly in patients who became HBV-DNA negative following rIFN administration. This result confirms the close relationship between HBV replication and the anti-idiotype against anti-HBs.

Adolescent↗
PubMed1990

Behavior of accessory abducens and abducens motoneurons during eye retraction and rotation in the alert cat.

1. The activity of both accessory abducens (Acc Abd) and abducens (Abd) motoneurons (Mns) was recorded in the alert cat during eye retraction and rotational eye movements. Cats were fitted with two scleral coils, one measured rotational eye movements directly and the other retraction by distinguishing the translational component. 2. Acc Abd and Abd Mns were identified following antidromic activation from electrical stimulation of the ipsilateral VIth nerve. 3. In response to corneal air puffs, bursts of spikes were produced in all (n = 30) Acc Abd Mns. The burst began 7.2 +/- 1.2 (SD) ms after onset of the air puff and 8.9 +/- 1.9 ms before eye retraction. 4. Acc Abd Mns were silent throughout all types of rotational eye movements, and tonic activity was not observed during intervals without air-puff stimulation. 5. In contrast, all (n = 50) identified Abd Mns exhibited a burst and/or pause in activity preceding and during horizontal saccades as well as a tonic activity proportional to eye position. 6. Only 10% of Abd Mns fired a weak burst of spikes in response to air-puff stimulation. 7. We conclude that Acc Abd Mns are exclusively involved in eye retraction in the cat and that only a few Abd Mns have an eye-retraction signal added to their eye position and velocity signals. Thus any rotational eye-movement response described in retractor bulbi muscle must result from innervation by Mns located in the Abd and/or the oculomotor nuclei. 8. The organization of the prenuclear circuitry and species variation are discussed in view of the nictiating membrane extension response measured in associative learning.

Abducens Nerve↗
PubMed1990

Lower serum osteocalcin levels in pregnant drug users and their newborns at the time of delivery.

Osteocalcin was evaluated by radioimmunoassay at the time of delivery in mothers and in the umbilical arteries of newborns in a group of pregnant drug users (eight heroin users and seven cocaine users) and compared with findings from a group of normal mothers and their newborns (N = 18). Drug users had lower osteocalcin values than did the normal women (1.3 +/- 0.7 versus 2.7 +/- 0.8 ng/mL, P less than .001); and infants of drug users had lower values than normal infants (14.1 +/- 3.8 versus 19.0 +/- 4.0 ng/mL, P less than .005). The birth weights of drug users' infants were smaller (3160 +/- 402 versus 3591 +/- 374 g, P less than .05) and there was a significant negative correlation (P less than .001) between osteocalcin and drug intake during pregnancy, but no changes in osteocalcin dependent on the type of drug used. These results suggest a toxic effect of these drugs on the osteoblast, which could account for the lower birth weights and skeletal alterations reported in the infants of drug users.

Adolescent↗
PubMed1989

Computer simulation of the neural discharge carried by the abducens nerve during eye fixation in the cat.

The neural signal carried by the abducens nerve during eye fixations was simulated. The neural discharge was defined by the number of spikes carried by the abducens nerve within each ms. Calculations were based on real neurophysiological data. The computed neural signal showed frequency histograms and variance/mean ratios typical of a Poisson distribution. A peak was obtained in the power spectral density function of the simulated neural signal. This peak appeared in the frequency range corresponding to the firing rate of single motoneurons for each eye position. It remained as a broad spectral peak after filtering by a second-order differential equation simulating the ocular mechanics. The obtained spectra are similar to the described power spectral density function of eye position recordings. Present results add evidence of a possible neural basis for ocular tremor.

Abducens Nerve↗
PubMed1989

Treatment of advanced ovarian cancer with cisplatin, adriamycin and cyclophosphamide (PAC).

Forty two ovarian cancer patients with residual disease after the first laparotomy were treated with the combination of cisplatin (80 mg/m2 day 1), adriamycin (50 mg/m2 i.v. day 2) and cyclophosphamide (500 mg/m2 i.v. day 2) (PAC). Forty women were considered evaluable for analysis, with an overall response rate (partial, plus complete responses) of 62.5%. Twelve patients (30%) obtained a complete response (histologically confirmed after second look surgery in 6 cases, surgical complete response, residual tumor completely resected in the second look-in 5 cases and maintained complete clinical remission without second look confirmation in 1 case). Main side effects were nausea and vomiting (90%), leukopenia (70%), mucositis (45%), and anemia (37%). Seventeen percent of the patients were free of disease at 60 months, after a median follow-up of 48 months. The prognostic factors that showed significant influence on survival were the Karnofski index (90-100 vs 80 or less), stage of the disease (II + III vs IV) and the volume of residual tumor after the first surgical procedure (less than or equal to 2 cms vs greater than 2 cms). Patients who achieved a complete remission have not reached the median 5 years survival, which was 10 months for the remaining patients. These results confirm the activity of PAC in ovarian cancer, mainly in those patients with residual tumor of less than 2 cms and good performance status.

Adult↗
PubMed1989

[Activity of premotor vestibular neurons in the alert cat].

The activity of medial vestibular nucleus neurons projecting to the contralateral abducens nucleus (premotor vestibular neurons) has been recorded during spontaneous and vestibular induced eye movements in the alert cat. Recorded neurons were identified by their antidromic activation from the abducens nucleus and by the post-synaptic field potential induced in this nucleus. The activity of identified medial vestibular neurons increased significantly with horizontal eye position and velocity toward the contralateral side, and decreased abruptly during ipsilateral saccades. The activity of these neurons was also related to head velocity toward the ipsilateral side. The functional role and origin of eye position and velocity signals present in these vestibular neurons are discussed.

Animals↗
PubMed1988

Behavioral and morphological effects of oculomotor nucleus lesion on abducens internuclear neurons in the cat.

The activity of identified control and injured abducens internuclear neurons was recorded during spontaneous eye movements in the alert cat. From 2 days following the electrocoagulation of the contralateral oculomotor nucleus, abducens internuclear neurons showed a quick fatigability during eye fixations not observed in controls. Discharge rate during saccades started after the beginning of the eye movement and showed a fast exponential-like decay. These abnormal responses were not further recorded from 20 days following the lesion. Morphological studies indicated that 90% of the abducens internuclear neuron population disappeared 2 months following the lesion and showed no sign of recovery one year later.

Abducens Nerve↗
PubMed1988

Behavior of reticular, vestibular and prepositus neurons terminating in the abducens nucleus of the alert cat.

The activity of pontomedullary reticular, vestibular, and prepositus neurons has been recorded in the alert cat during spontaneous and vestibular-induced eye movements. Neurons were identified by their antidromic activation from the abducens nucleus. Spikes of these neurons were used to trigger the recording of field potentials in the abducens nucleus. The analysis by post-spike averaging of the field potentials showed the presence of a trifold system of reciprocal (excitatory and inhibitory) direct projections that originated in the above nuclei and terminated in the abducens nucleus with a distinctly graded effectiveness. This trifold afferent system is involved in the generation of fast eye movements, slow compensatory movements of vestibular origin, and eye fixation, respectively.

Abducens Nerve↗
PubMed1987

Diminished natural killer activity in pregnancy: modulation by interleukin 2 and interferon gamma.

We investigated the alterations of natural killer (NK) cells in pregnancy, which led to decreased killing from the first trimester to the puerperium. We show that this phenomenon cannot be ascribed to a defective number of NK cells since the amounts of HNK-1+, CD16+ (Leu 11), and CD11b+ (OKM1) cells were within normal ranges. Recombinant interleukin 2 (rIL-2) corrects the functional defect in a dose and time-dependent manner, without modification in the surface phenotype of the population. Analysis of the pattern of target cell susceptibility to lysis, together with the similar ability of recombinant interferon gamma (rIFN-gamma) to correct the deficiency, and CD16+, CD3- phenotype of the precursor and effector lymphocytes, demonstrated that the induced cytotoxicity was mediated by NK cells. Inhibitors in pregnancy sera block IL-2 production by specific T cells, but we show that they do not influence either NK activity or its reconstitution by rIL-2. These findings place the deficiency at the level of NK cell maturation into cytotoxic effector lymphocytes. Thus, homeostasis of the NK activity of pregnant women may provide a biological model for clarifying the internal mechanisms regulating NK-cell activation in vivo. Present studies in vitro suggest that modulation of lymphokine production may play a role in the adaptive response of NK cells in pregnancy.

Cell Differentiation↗