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Biomedical subjects

B Duron

Publications and source records attributed to B Duron.

At least 55 records · Page 3Linked to original sources
PubMed1987

Inhibitory and excitatory effects on respiration by phrenic nerve afferent stimulation in cats.

Respiratory effects of electrical stimulation of phrenic nerve afferents were studied in anesthetized cats, either spontaneously breathing or paralyzed and ventilated. The type of phrenic afferent fibers activated was controlled by recording the evoked action potentials from dorsal root fibers. In both preparations, stimulation at a strength sufficient to activate small diameter myelinated phrenic nerve afferents induced a biphasic response. The first phase lasted a few respiratory cycles and was inhibitory and consisted of a decrease in tidal volume (VT) or phrenic activity (NA), inspiratory time (TI), respiratory duty cycle (TI/Ttot) and instantaneous ventilation (VE) or minute phrenic activity (NMA). Expiratory time (TE) increased and breathing frequency (f) and mean inspiratory flow (VT/TI) or mean inspiratory neural activity (NA/TI) did not change. This short-term response was suppressed in animals pretreated with bicuculline. The second phase was a long-term excitation in which VT or NA, f, VE or NMA and VT/TI increased whereas both TI and TI/Ttot decreased and TE did not change. Unlike published data, our results suggest that small-diameter myelinated phrenic nerve afferents are involved in these responses. These phrenic fibers, like afferents from other muscles, affect respiratory output and may play a role in the control of breathing.

Afferent Pathways↗
PubMed1986

[Involvement of motor fibers in the ulnar nerve syndrome at the elbow].

In order to improve the diagnosis of the ulnar nerve neuropathy at the elbow, we have retrospectively analysed the data obtained in the course of the electrophysiological examinations of the ulnar nerve motor component in three groups of adult subjects of both sexes (210 control subjects; 111 patients with more or less marked clinical symptoms suggestive of ulnar nerve neuropathy; 21 patients who after our investigation have undergone an operation for an ulnar nerve neuropathy at the elbow). The comparison of the data obtained in the three groups permits us to propose the following parameters as signs of ulnar neuropathy at the elbow: the proximal conduction time (stimulation in the axilla) greater than or equal to 12 msec for males and greater than or equal to 11 msec for females; motor conduction velocity of ulnar motor nerve fibers at the arm comprise in the range of normal values and similar to that measured on the contralateral ulnar nerve; conduction velocity of ulnar nerve motor fibers when it is measured on all the length of the upper limb less than 45 m/sec-1 (males) or less than 50 m/sec-1 (females).

Adolescent↗
PubMed1986

[Non-participation of bulbar inspiratory neurons in the esophago-diaphragmatic inhibitory reflex].

The effects of the distension of the lower oesophageal sphincter were studied on the inspiratory activity of 96 medullary neurons located either in the dorsal or in the ventral respiratory groups and on the inspiratory activity of the costal and crural parts of the diaphragm in barbiturate anaesthetized cat. Inhibition of the inspiratory activity of the crural part of the diaphragm during oesophageal distension was never associated with significant changes of the medullary inspiratory neuron discharge. These results suggest that the observed crural inhibition is due to reflex loop that does not include the inspiratory neurons belonging to the dorsal and the ventral respiratory groups.

Animals↗
PubMed1985

Identification of phrenic afferents to the external cuneate nucleus: a fluorescent double-labeling study in the cat.

In the cat, C5-C6 dorsal root ganglion cells related to phrenic afferents projecting directly to the ipsilateral external cuneate nucleus (ECN) were submitted to a double-labeling procedure using anterogradely transported Fast Blue and retrogradely transported Nuclear yellow. These afferents, certainly related to muscle spindles and/or Golgi tendon organs, are very few and terminate preferentially in the intermediate and rostral parts of the ECN. Our results confirm previous electrophysiological and histological studies on the participation of phrenic afferents to the spino-cuneo-cerebellar pathway ascending through the dorsal columns.

Afferent Pathways↗
PubMed1985

Projection of phrenic afferents to the external cuneate nucleus in the cat.

The present study, performed on anesthetized, spontaneously breathing cats, deals with the projection of group I and II muscle afferents of the phrenic nerve (PN) to the external cuneate nucleus (ECN). Stimulation of the central end of the PN evoked a complex response in the ipsilateral ECN. Two principal components could be distinguished in this potential from the respective absolute refractory periods (ARP) and from the effect of antidromic stimulation in the ECN. Thus, the early group of waves may correspond to recordings of direct fibers and the later group to postsynaptic activations within the ECN. Similar to the forelimb nerves and intercostal nerves of the upper intercostal spaces, the larger muscle afferents of the PN project to the ECN.

Animals↗
PubMed1985

Phrenic afferent input to the lateral medullary reticular formation of the cat.

The afferent inputs from phrenic nerve stimulation to the lateral reticular formation of the lower brain stem were studied in anesthetized spontaneously breathing cats. The activity of reticular neurons was recorded by means of extracellular tungsten microelectrodes. Electrical stimulation of the central end of the right phrenic nerve evoked excitatory or inhibitory responses in the lateral reticular nucleus (LRN), in the nucleus ambiguus (AMB) and in a region dorsal to the AMB of ipsi- and contralateral sides. Phrenic afferents belonging to the flexor reflex afferent group were involved in these responses. The discharge pattern of the respiratory related units (RRU) of the AMB were exceptionally affected by phrenic nerve stimulations. It is concluded that high threshold phrenic afferents relay in the LRN before projecting to the cerebellar cortex. The overlapping of respiratory and non-respiratory afferents in the reticular formation may participate to the adaptations of respiratory and somatomotor functions during specific behaviors.

Afferent Pathways↗
PubMed1984

Identification of phrenic afferents in the dorsal columns: a fluorescent double-labeling study in the cat.

In this study in the cat, the tracer combination of the anterogradely transported Fast Blue and the retrogradely transported Nuclear Yellow was used to label dorsal root ganglion cells related to phrenic afferents running up through the ipsilateral dorsal column. These afferents are few; some of them leave the dorsal column near their segment of entry. Their localization in the dorsal column suggests that they are related to tendon and muscle receptors, which confirms previous electrophysiological studies.

Animals↗
PubMed1984

Are the external and internal intercostal muscles synergist or antagonist in the cat?

The electrical activity of the external and internal intercostal muscles was recorded in decerebrated cats during eupnea and in the course of dyspnoea artificially induced to reinforce the inspiratory or expiratory central drive. In the cephalic part of the thorax (1st-5th ribs) the lateral part of the external and internal intercostal muscles are synergist and inspiratory. In the caudal part of the thorax (9th-13th ribs) these muscles are also synergist but expiratory. In the intermediate part (5th-9th ribs) the intercostal muscles are antagonist, the external ones are inspiratory and the internal ones are expiratory.

Animals↗
PubMed1984

Absolute refractory period of the ulnar nerve motor fibers in the human newborn.

The absolute refractory period (ARP) of the most excitable motor fibers of the human ulnar nerve was measured in 12 full-term newborns (1-8 days old) and 15 adults. The mean calculated diameter (Hursh's equation) of the adult motor fibers was twice as large as that of the newborn fibers. The inverse relationship demonstrated in cat between the fibers' conduction velocity and the ARP is not confirmed in the present results. ARP, independently of the myelination process could be a specific membrane property of any given fiber with respect to the expected adult diameter.

Adult↗
PubMed1984

Projections of phrenic afferences to the cat cerebellar cortex.

Evoked phrenic potentials were recorded on the cerebellar cortex of anesthetized adult cats after electrical stimulation of both cervical branches (C5 and C6) of the right phrenic nerve. In this case phrenic stimulation evoked a surface positive response with a mean amplitude (+/- S.D.) of 13.4 +/- 5.2 microV. The mean latency and the mean duration of this phase were, respectively, 9.5 +/- 1.2 ms and 19.4 +/- 2.1 ms. This response was found only in the ipsilateral intermediate cortex and in the ipsilateral and, to a less extent, in the contralateral vermis of the posterior part of the anterior lobe (Larsell's lobule V); these areas corresponding to the forelimb projection zones. The phrenic afferences projecting to the cerebellar cortex were essentially conducted in the contralateral ventro-lateral spinal tracts.

Afferent Pathways↗
PubMed1984

An HRP study of the cat's spinal respiratory motoneurones during postnatal development.

The localization and morphology of spinal respiratory motoneurones (phrenic and intercostal) were studied in the cat by retrograde labelling using Horseradish Peroxidase (HRP), at different stages of postnatal development. At birth, the distribution of the phrenic and intercostal motoneurones in the cervical and thoracic ventral horn, respectively, is similar to that observed in adult animals. At birth, the phrenic and intercartilaginous motoneurone somata have respectively 60% and 40% of their adult volume, appearing much more developed than the motoneurones involved in the motor control of limbs. During postnatal development, the phrenic and intercartilaginous motoneurones undergo a characteristic sagittal elongation without evident modification along their transverse axes. From birth, the ratio of the somatic volume to that of its corresponding motor column markedly decreases inside of the phrenic column compared to the data obtained in the limb's muscle motor columns by other authors. Similar determinations in intercostal motor columns give intermediate values between those obtained from the phrenic column and from the motor system. These results indicate that the motoneurones innervating the respiratory muscles have some specific features of development.

Animals↗
PubMed1984

[Prognostic value of EEG abnormalities observed during sleep in epilepsy with rolandic spikes (RSE)].

The aim of this study is the quantitative analysis of the interictal discharges during nocturnal sleep in 6 children with rolandic spikes on the awake EEG, before and during treatment. During treatment, whatever it may be, these interictal discharges (diffuse spike and wave complexes and rolandic spikes) have no prognostic value and only the generalized paroxysmal ones, which are observed solely in sleep, decrease. Moreover, if the number of spikes of a slow irritative focus secondary to an organic cerebral lesion keeps steady during wakefulness and all sleep stages, the number of rolandic spikes is modulated by the type of sleep (REM or NREM). This modulation may be in favour of the benignity of this childhood epilepsy. Finally, in spite of the great number of interictal discharges during the whole night, sleep organization is not disturbed and only the advent of an epileptic seizure can interfere with sleep rhythms, depleting the REM phase.

Child↗
PubMed1984

Postnatal maturation of ventilation and breathing pattern in kittens: influence of sleep.

Ventilation and breathing pattern were studied in kittens at 1, 2, 3, 4, and 8 wk of life during quiet wakefulness (W), quiet sleep (QS), and active sleep (AS) with the barometric method. Tidal volume (VT), respiratory frequency (f), ventilation (VE), inspiratory time (TI), expiratory time (TE), mean inspiratory flow (VT/TI), and respiratory "duty cycle" (TI/TT) were measured. VT, VE, TI, TE, and VT/TI increased; f decreased and TI/TT remained constant during postnatal development in wakefulness and in both sleep states. No significant difference was observed between AS and QS for all the ventilatory parameters except TI/TT, which was greater in QS than in AS at 2 wk. VE was larger in W than in both AS and QS at all ages. This was mainly due to a greater f, TI/TT remaining constant. VT/TI, which represents an index of the central inspiratory activity, was larger in W than in sleep, VT not being significantly different whatever the stage of consciousness. The results of this study show that in the kitten 1) unlike in the adult cat, ventilation and breathing pattern are similar in QS and in AS; 2) in sleep, the central inspiratory drive appears to be independent of the type of sleep; and 3) in wakefulness, the increase of the central inspiratory activity could be related to important excitatory inputs.

Animals↗
PubMed1984

Effects of hypoxia on ventilation during postnatal development in conscious kittens.

Effects of steady-state hypoxia (inspired O2 fraction = 0.11) on ventilation and breathing pattern were studied during postnatal development in unanesthetized kittens. Studies were done from 2 days to 8 mo of age, every week during the first month and every month thereafter. During the first 2 months, states of consciousness were determined. In the first month, minute ventilation (VE) was depressed in hypoxia compared with control values in air, whereas in the older kittens VE was increased in hypoxia, as in adult cats. The inhibitory effect of hypoxia was observed in all three states of consciousness in 7- and 14-day-old kittens. In the 21- and 28-day-old kittens, VE could not be reliably related to the state of consciousness. In the 2-mo-old kittens, VE increased in all states. Tidal volume (VT) was markedly decreased in kittens up to 14 days of age, and respiratory frequency increased. In the 21- and 28-day-old kittens, changes in breathing pattern were variable. In the oldest, the increase of VE was mainly due to an increase of VT. We conclude that in unanesthetized kittens, the ventilatory response to hypoxia is mature at 2 mo of age. The hypoxic tachypnea observed at 7 and 14 days resembles that previously seen in adult carotid-denervated cats, and may be due to a low level of carotid chemoreceptor drive and to a central excitatory effect of hypoxia on respiratory frequency. The complex response observed during the first month of life must reflect the development of peripheral and central mechanisms and their interactions.

Aging↗
PubMed1984

[Possible inspiratory or expiratory synergism between various external and internal intercostal muscles in cats].

The electrical activities of the lateral parts of the external and internal intercostal muscles were recorded in decerebrated cats during eupnea and in the course of artificially induced dyspnoea, elicited in order to reinforce the inspiratory or expiratory central drive. Our results indicate that in the cephalic spaces (1st to 5th rib), external and internal intercostals are synergists during inspiration. In the caudal spaces (9th to 13th rib), the same muscles are activated during expiration only. In the intermediate part of the thorax (5th to 9th rib), external intercostals are inspiratory muscles, internal intercostals are expiratory muscles.

Animals↗
PubMed1983

Quantitative morphological changes in phrenic and intercostal motor columns and their respective spinal cord segments during postnatal development in the kitten.

In newborn kittens, the nervous control of breathing appears more mature than that of motricity which follows a cephalo-caudal evolution. In order to determine if the different postnatal evolutions of the respiratory and the motor function have an anatomical support at the spinal cord level, we made morphometric comparisons of the postnatal development of the spinal segments including motor columns sustaining both limb and respiratory movements (cervical and thoracic segments), with the postnatal development of segments containing only motoneurones involved in locomotion (lumbar segments). Furthermore, we used horseradish peroxidase to label cervical and thoracic groups of inspiratory motoneurones, i.e. the phrenic and the intercartilaginous motor nuclei at several postnatal ages. The present study suggests that the development of the white matter is the same at every spinal level and that it is delayed compared to the maturation of the grey matter. Overall evaluations of grey matter areas showed that the thoracic grey matter is more mature at birth but, further, has a slower rate of growth than the cervical and lumbar ones. This observation may be related to the maturity of the respiratory phasic activities within the early postnatal life. The phrenic and intercartilaginous motor nuclei have different patterns of development. These results suggest that the spinal postnatal functional maturation is not strictly related to its quantitative macroscopic changes.

Animals↗
PubMed1983

[Ventilatory disorders and sleep anomalies in severe chronic obstructive respiratory insufficiency. Effects of nocturnal oxygen therapy].

The influence of nocturnal oxygen therapy on ventilatory disorders and sleep abnormalities was evaluated in 5 male, non-obese patients with advanced chronic obstructive pulmonary disease (COPD). All had hypoxia, severe airway obstruction (FEV1 less than 1 l) and pulmonary arterial hypertension at rest; 3 had PaCO2 values above 50 mmHg. Polygraphic recordings were taken throughout the night, the patients breathing either air or oxygen, they included EEG, electromyography of chin muscles, eye movements, O2sat., thoraco-abdominal mechanics and nasal flow. Improvement in the quality of sleep under oxygen was observed in all patients, with an increase from 6.1% (air) to 14.6% (oxygen) in the R.E.M. (Rapid Eye Movement) sleep phase duration to total sleep duration ratio, and an increase from 8 to 12 in the number of episodes of apnoea (arrest of nasal flow greater than 10 sec). Oxygen also had a favourable influence on the number and amplitude of O2 desaturation phases (delta O2sat. greater than 4%) and on the time spent in desaturation, which decreased from 5.12% (air) to 3.7% (oxygen). Correction of the hypoxaemic episodes was partial in those R.E.M. sleep phases when these episodes were most severe and occurred in the absence of apnoea.

Aged↗