Biomedical subjects

B Duron

Publications and source records attributed to B Duron.

At least 19 recordsLinked to original sources

PubMed1992

Influence of trigeminal nasal afferents on bulbar respiratory neuronal activity.

This study examined the influence of nasal trigeminal afferents, the anterior ethmoidal nerve (AEN) and posterior nasal nerves (PNN) on the spike discharges of respiratory-related neurons recorded in the ventral respiratory group (VRG) (2.6-3.5 mm lateral to the midline, from 1 mm rostral to 3 mm caudal to the obex and at depth of 2-4 mm below the dorsal surface). Electrical stimulations to the AEN and PNN were administered to 10 pentobarbital anaesthetized cats and to 8 ketamine anaesthetized, vagotomized, curarized and ventilated cats. Single shock stimulations of either nerve evoked transient and total inhibition of inspiratory activities. Expiratory-related neurons of the VRG presented three patterns of activity in response to stimulation:excitation, inhibition or inhibition followed by excitation. More generally, expiratory units are activated with a short latency. In the course of repetitive stimulation of the AEN and PNN we observed a prolongation of the spontaneous inspiratory discharge which presented transient, short inhibition in response to each shock. Most expiratory units presented a short activation which was synchronous with the transient inhibition of inspiratory activities. When repetitive stimulation provoked a sneeze-like response, we observed a progressive increase in the duration of transient inspiratory inhibition first, associated with a progressive reinforcement of transient expiratory activation. Secondarily, just before the expiratory thrust, we noted a stronger inhibition of the inspiratory activity which preceded a high-frequency (400 Hz) expiratory discharge. Nasal afferents exert a forceful excitatory effect on bulbospinal (BS) and non-bulbospinal-non-vagal (NBS-NV) expiratory cells of the VRG. The effects due to vagotomy and curarization are discussed.

Action Potentials↗

PubMed1992

A comparative HRP study of the neuronal supply to the inferior and superior nasal meatus in the cat.

Neurons supplying the nasal mucosa in the cat were retrogradely labelled with horseradish peroxidase. Sensory trigeminal neurons to the inferior and superior nasal meati are somatotopically organized, according to the ophthalmic or maxillary origin of the afferents studied. Whatever their relative location, the cell bodies from nasal afferents were, on average, smaller than the overall cell population in the ganglion, in keeping with the high proportion of nasal receptors innervated by thin fibers. Postganglionic neurons from parasympathetic origin could be labelled in the sphenopalatine ganglion. These neurons probably supply mucosal secretory glands. They are in the same size range as the bulk of neurons in the same ganglia.

Animals↗

PubMed1992

[Postnatal development of central motor pathways. An electrophysiological study].

The percutaneous electrical stimulation of the brain and spinal cord has been used to study the central motor pathways in 19 healthy full-term newborns and in 19 infants. The evoked compound muscle action potential were recorded by bipolar surface electrodes fixed on the skin overlying the thenar eminence muscles and the tibialis anterior muscle. In full-term newborns, the responses of lower limb muscles to cortical stimulation are more difficult to obtain that those of upper limb muscles. At birth, the conduction velocity of central motor fibres along the spinal cord are around 10 m/s, 4 or 5 times lower that the lowest values published for adult subjects. Thus, as has been demonstrated in animals, there seems to exist in man a very clear dissociation between myelination of central motor pathways and that of peripheral motor fibres.

Action Potentials↗

PubMed1992

[Electrophysiological aspects of peripheral nervous system development].

Different aspects of the maturation of the peripheral nervous system have been studied in infants, essentially during the first year of postnatal life. Absolute refractory periods which enable indirect estimation of excitability have been measured in both nerve and muscle fibers. It appears that already at birth, the absolute refractory period is characteristic for a given group of nerve fibres. In each group of nerve fibres, the absolute refractory period is not correlated to conduction velocity (ie fibre diameter) and remains rather constant during development. However, the absolute refractory period of the most excitable fibres is smaller than the absolute refractory period of motor fibres independent of the subject's age. On the other hand, the absolute refractory period of muscle fibres is slightly higher in premature in comparison with full-term neonates and adults. The diameter growth of different categories of nerve, fibers (motor--IA--non nociceptive cutaneous) is assessed by measurement of conduction velocities. At each age the IA fibre conduction velocities are the highest. The marked difference which exists between length development and postnatal increase of the fibre diameter explains the particular evolution of conduction times.

Adult↗

PubMed1992

[Effect of acute administration of acamprosate on the risk of encephalopathy and on arterial pressure in patients with alcoholic cirrhosis].

To evaluate the risk of hepatic encephalopathy and arterial hypotension in cirrhotic patients after acute administration of acamprosate, a GABA mimetic drug used in the weaned alcoholic, a randomized double-blind trial was conducted in 24 cirrhotic patients with low or moderate hepatic insufficiency (Pugh grade A or B). Twelve patients received 666 mg (2 tablets) of acamprosate and 12 received placebo. The 2 groups were similar before treatment, except for a male predominance in the acamprosate group. Tested parameters were the P100 latency of visual evoked potentials using a checkerboard pattern reversal as stimulus, the number connection test and the arterial blood pressure in upright and recumbent positions. The two first parameters were studied before and 2 hours after treatment. Blood pressure was recorded every half hour during 6 hours. No significant effect on the development of subclinical hepatic encephalopathy was noted. Nevertheless, even if some authors disagree with the GABA hypothesis of hepatic encephalopathy, it is possible that the dose was too low to induce subclinical hepatic encephalopathy. A study with more prolonged treatment could be necessary to be sure of the drug's safety in these patients. On the other hand, a transient decrease of diastolic arterial blood pressure was observed without significant systolic blood pressure modification. These results suggest that a moderate dose of acamprosate does not induce subclinical encephalopathy, but transient diastolic hypotension.

Acamprosate↗

PubMed1991

The post-potential excitability modulation of alpha nerve and muscle fibers in human newborn and adult.

In order to assess indirectly the excitability of human motor units, the absolute refractory period of the ulnar nerve alpha motor fibers and the absolute irresponsive period of the abductor digiti minimi fibers were measured in 8 premature, 10 fullterm newborns and 10 adults. Results indicate that absolute refractory period of alpha motor nerve fibers appears to be a specific functional property of the membrane, independent of postnatal development. Moreover the maturation of muscle membrane seems slightly delayed in comparison to that of nerve fibers. Indeed the absolute irresponsive period of muscle fibers is slightly higher in premature in comparison with fullterm newborn and adult.

Adult↗

PubMed1991

Trigeminal afferences implied in the triggering or inhibition of sneezing in cats.

The aim of this study was to precise the role of the different trigeminal nerve branches involved in innervation of the nostril in triggering the sneeze reflex. Electrical stimulation of the anterior ethmoidal, posterior nasal and infraorbital nerves was performed in anaesthetized cats. Stimulation of these 3 nerves produced sneezing identical to that induced by mechanical stimulation. Our results emphasize inhibition of the sneeze reflex related to stimulation of the anterior ethmoidal or the posterior nasal nerves by stimulation of the infraorbital nerve.

Afferent Pathways↗

PubMed1991

Postnatal development of small and large dorsal root ganglion neurons in the cat. A study on cervical levels (C5-C6) and on phrenic afferents.

During feline postnatal development, the size of phrenic afferent neurons labelled by horseradish peroxidase was evaluated in comparison to that of the bulk of counterstained neurons located in the same cervical dorsal root ganglia (DRG) (C5-C6). From age 1 week to maturity, small and large cell components were individualized from experimental size distributions using a mathematical approach. The analysis of data in adult indicated a close correspondence between small cells and unmyelinated afferents and between large cells and myelinated afferents, respectively. From age 1 week to adulthood, mean increases in cell diameter ranged between 10 microns (small cells from phrenic afferents) and 29.5 microns (large counterstained cells). In each population, the ratio of small/large cells remained constant during growth. In contrast to data in adults, at 1 week, large phrenic neurons were bigger than the counterstained ones. At 19 weeks, the cat DRG cells had not yet reached their adult size.

Animals↗

PubMed1991

Trigeminal nasal receptors related to respiration and to various stimuli in cats.

In twenty adult cats of either sex under nembutal anaesthesia, we aimed at delineating the sensitive territory of trigeminal nerves innervating the nasal mucosa. The different trigeminal nerves (anterior ethmoidal, posterior nasal and infraorbital nerves) were dissected in the orbit. Activity of these nerves was recorded during spontaneous nasal and tracheal breathing and in response to various stimuli: mechanical (manual probing and air jets) and irritants (ammonia vapours). Multiple and unitary activity recorded in nerve filaments enabled a classification of the receptors on the basis of their discharge pattern as rapidly-, intermediately- or slowly adapting receptors, and as drive or non-drive nasal receptors depending on whether or not the respiratory modulation was preserved during tracheal breathing.

Afferent Pathways↗

PubMed1991

Postnatal development of descending motor pathways studied in man by percutaneous stimulation of the motor cortex and the spinal cord.

Using the percutaneous electrical stimulation of the brain and spinal cord, we have determined central motor pathway conduction velocities in a group of 19 healthy fullterm newborns (average post-conceptional age 39.8 weeks) and in 19 infants between 2 months and 8 years of age. The newborns were examined during the first postnatal week. The percutaneous stimulation of the motor cortex and of the cervical and lumbar enlargements of the spinal cord was made by means of bipolar electrodes. The evoked compound muscle action potentials were recorded by bipolar surface electrodes fixed on the skin overlying the thenar eminence muscles and the tibialis anterior muscle. In fullterm newborns, the responses of lower limb muscles to cortical stimulation were more difficult to obtain than those of upper limb muscles. Conduction velocities of central motor fibres along the spinal cord (between vertebrae C7 and L4) were around 10 m/sec in fullterm newborns and 38 m/sec at the age of 4 years. These values are considerably lower than those described for adult man (48-60 m/sec). The adult values are established around the age of 8 years.

Child↗

PubMed1991

Absolute refractory period of human nerve fibres during postnatal myelination.

In order to study the absolute refractory period of a given group of nerve fibres during development we measured absolute refractory periods and conduction velocities of motor fibres and the most excitable fibres in the human ulnar nerve of newborns, children and adults. In each group of nerve fibres absolute refractory period was not correlated to conduction velocity (i.e. fibre diameters) and was rather constant during development. However, absolute refractory period of the most excitable fibres was smaller than absolute refractory period of motor fibres independently of the subject's age. Thus, it appears that already at birth, absolute refractory period is characteristic for a given group of nerve fibres.

Adolescent↗

PubMed1990

The cat cervical dorsal root ganglia: general cell-size characteristics and comparative study of neck muscle, neck cutaneous and phrenic afferents.

Sizes of neuronal somata in the cat cervical dorsal root ganglia were determined at different levels (C1-C8). The average value and class distribution of mean cell diameter were analyzed. The ganglia from C1 to C5 could be clearly distinguished from those at levels of brachial plexus afferents (C6-C8) with respect to cell size range, distribution and average. The size distribution, most often limited to 70 microns from C1 to C5, skewed to more than 90 microns from C6 to C8. Cells in the 35-50 microns range of diameter constituted the main portion of the cell population (49-52%) at the C1-C5 levels, whereas from C6 to C8 51-77% of the ganglion cell bodies were more than 50 microns in diameter. The cell size distribution of afferents projecting from C1 to C5 and supplying different muscle or cutaneous targets was studied following retrograde labeling with horseradish peroxidase conjugated to wheatgerm agglutinin. Sizes of cell bodies of biventer cervicis (postural muscle), phrenic (purely respiratory muscle) and cutaneous afferents were all similar. The labelled cell bodies were in the majority (51-64%) less than 35 microns in diameter and ranged towards smaller diameters than counterstained cells in the corresponding ganglia. In spite of similarities in cell size distribution it was estimated from the fiber caliber spectra of the labelled afferents that both unmyelinated and myelinated cutaneous afferents originate from larger cell bodies than muscle afferents in the same diameter range.

Adolescent↗

PubMed1989

[Chronic obstructive bronchopneumopathies. Changes in carbon dioxide pressure during sleep in environmental air and with oxygen].

The effects of oxygen administration were studied in 10 patients with severe obstructive lung disease. Sleep variable and gas exchanges were measured during two nights: one when they were breathing environmental air, the other when they were receiving oxygen. Carbon dioxide saturation and partial pressure measured by the transcutaneous method were continuously recorded. Sleep was perturbed in all patients, but despite wide interindividual variations its amount and quality were improved by oxygen. None of the patients had sleep apnoea syndrome. Oxygen administration was accompanied by a nocturnal increase in carbon dioxide pressure that was about twice as high as that observed under environmental air. Thus, in patients with chronic obstructive lung disease without concomitant infection suppression of the hypoxic stimulus by oxygen therapy seems to result in an increase in carbon dioxide partial pressure identical with the increase produced by sleep alone. Correlations between diurnal and nocturnal oxygen saturation and carbon dioxide partial pressure indicate that patients with the highest degree of hypoxia and hypercapnia in daytime have the most severe nocturnal blood gas disorders.

Blood Gas Monitoring, Transcutaneous↗

PubMed1989

Evolution of motor, IA and cutaneous nerve-fibre conduction velocities in premature and fullterm newborns.

The conduction velocities of motor, IA and non-nociceptive cutaneous sensory fibres have been studied in the ulnar and median nerves of 145 healthy fullterm neonates and in 77 preterm neonates (postconceptional age-range 28 to 42 weeks). The posterior tibial-nerve motor and IA fibres were studied: the sural nerve cutaneous-fibre conduction velocities were measured in fullterm neonates only. At each age the IA fibre conduction velocities were the highest. There was no difference between the conduction velocity increase per week of postconceptional age in motor and cutaneous fibres. Except for the cutaneous-nerve fibres, conduction velocities were higher in the upper than in the lower limbs.

Electric Stimulation↗

PubMed1988

Phrenic-to-phrenic inhibition and excitation in spinal cats.

In decerebrate, C2-spinalized cats, stimulation of the C6-phrenic root produces a weak activation of phrenic motoneurons in the adjacent C5 segment in a few animals (23%). When phrenic motoneurons are electrically excited by testing stimulation applied to the spinal cord or internal intercostal nerve, the evoked responses recorded in a cervical phrenic root are partly inhibited by conditioning stimulation applied to another ipsilateral or contralateral cervical phrenic root. We therefore conclude that phrenic fibers exert both inhibitory and excitatory effects on adjacent phrenic motoneurons in the cervical spinal cord.

Animals↗

PubMed1988

Effects of ipsilateral and contralateral cervical phrenic afferents stimulation on phrenic motor unit activity in the cat.

The phrenic-to-phrenic inhibitory reflex has been analyzed using recordings of activity of single C5-phrenic motor units (PMUs). After ipsilateral or contralateral stimulation of the C6-phrenic root, early and late PMUs exhibit a similar inhibition. After contralateral stimulation, the duration of the inhibition is smaller and the threshold stimulus is higher than the corresponding values observed after ipsilateral stimulation. The latency of the inhibition is similar for both stimulations. Hemispinalization, contralateral to the recording site, affects weakly the phrenic-to-phrenic reflex. We conclude that early and late PMUs receive a similar inhibitory input from phrenic afferents and that the inhibition observed after cervical phrenic nerve stimulation may involve spinal cord circuits.

Action Potentials↗

PubMed1988

Morphometrical study of the cat thoracic dorsal root ganglion cells in relation to muscular and cutaneous afferent innervation.

The sizes of neuronal somata in cat dorsal root ganglia were determined at the different thoracic segmental levels (T1-T13). The intersegmental variations in the average value and class distribution of diameters were analysed. The maximal and minimal average mean cell diameters were 51.1 and 43.3 microns at the T1 and T2 levels, respectively. Caudally, this value gradually increased from T2 to T8 (47.8 microns) and thereafter decreased progressively to T12 (44.7 microns). At T1, large cells (greater than 50 microns in diameter) were 3.3-fold in excess compared to small ones (less than 35 microns in diameter). The proportion of large to small cells strongly decreased to a 0.9 ratio from T1 to T2, then increased again from T2 (0.9) to T8 (2.3). The size distributions of the overall cell populations were compared to those of neurones supplying muscular targets via the external intercostal nerves or cutaneous targets via the lateral branch of the internal intercostal nerves, identified following the retrograde transport of horseradish peroxidase. The size distribution of cells serving cutaneous nerves was similar to that exhibited by the overall population of ganglion cells. In contrast, the size distributions of cells giving rise to muscle afferents tended towards smaller values. In the thoracic dorsal root ganglia, the cell body sizes of the muscular primary afferents were close to those previously reported for the visceral primary afferents.

Animals↗

PubMed1988

[Conduction velocities of motor, cutaneous sensory, and IA proprioceptive fibers in normal newborn infant at term].

Conduction velocities of non-nociceptive cutaneous and IA afferent fibres and alpha-motor fibres from ulnar, median, deep peroneal, posterior tibial and sural nerves have been measured in healthy full-term newborns, using surface electrodes. There is an overlapping in the distribution of the individual values of conduction velocities for the different types of fibres. The conduction velocities of cutaneous afferent fibres are not different in the upper or lower limbs. The conduction velocities of motor and IA fibres are higher in the upper than in the lower limb. In the upper limb, conduction velocities of IA fibres are higher than those of motor fibres, as they are in the lower limb for the posterior tibial nerve. Moreover, conduction velocities of motor fibres do not differ in males and females.

Humans↗