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Biomedical subjects

D Marlot

Publications and source records attributed to D Marlot.

At least 37 records · Page 2Linked to original sources
PubMed1984

Developmental changes in ventilation and breathing pattern in unanesthetized kittens.

Ventilation and the breathing pattern of 12 intact, unanesthetized, unrestrained kittens, were recorded at intervals from the second postnatal day to the end of the eighth month. Five of the animals were also studied at 12 months of age. Ventilation (VE) became stable by the 5th month, whereas body weight was still increasing. The relationship between tidal volume (VT) and breathing rate (BR) changed with age. During the 1st month, BR fell and VT increased, VE increasing slowly. From 1 to 5 months, BR remained nearly constant while VT increased. Finally, from 5 to 12 months, BR decreased slightly, VT increased slightly, and VE did not change. The results are compared with relevant data from the literature, especially those derived from interspecific analyses.

Aging↗
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

Positive- and negative-pressure breathing in newborn rat before and after anesthesia.

We have examined the effects of changes in functional residual capacity (FRC), determined by positive and negative body surface pressures, on the breathing pattern of intact newborn rats, before and after barbiturate anesthesia. With distending pressures (between 1 and 4 cmH2O) minute ventilation decreased mainly due to a prolongation of the expiratory time. This response was more marked after anesthesia and accompanied by a fall in tidal volume. The time of peak expiratory flow (TE'), an index of expiratory flow resistance, was not changed before anesthesia and only slightly decreased after anesthesia. With collapsing pressures between 1 and 2 cmH2O only small changes in breathing pattern occurred, whereas the TE' increased in all cases and the flow profile indicated a maintenance of lung volume during expiration. These data indicate that tonic vagal information is present in the newborn rat and is substantially enhanced after barbiturates. The result that changes in breathing pattern are not fully matched by the changes in TE' and expiratory flow profile may indicate that the receptors which control the respiratory pattern are not the same as those involved in the regulation of the expiratory flow. The pressure-volume curve of the respiratory system was similar before and after anesthesia, and the intercept was close to the zero pressure value, indicating that the FRC of the newborn rat, differently from the human baby, is not actively maintained above the resting volume of the system.

Anesthesia↗
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

Respiratory effects of stimulation of intercostal muscles and saphenous nerve in kittens.

Effects of intercostal muscle stimulation were studied in 2- to 7-day-old kittens under ketamine-acepromazine anesthesia. Animals were vagotomized, paralyzed, and artificially ventilated. Stimuli applied during inspiration (TI) inhibited this phase. Stimulus strength necessary for TI inhibition decreased with time. However, an all-or-nothing effect was not always observed. Stimulation during expiration (TE) prolonged this phase. The responsiveness increased with increasing stimulus delay. The effects of intercostal muscle stimulation were compared with those recorded during saphenous nerve stimulation. Stimulation during TI prolonged this phase. Phrenic activity increased after a short-lasting decrease in the on-going activity. Stimulation during the first 50% of TE had variable effects, whereas stimulation with longer delay shortened this phase. Our results indicated that the pattern of breathing in newborns can be affected by both intercostal muscle and other somatic efferents. However, the mechanisms controlling respiratory timing may differ in newborns and in adults. Different effects of respiratory muscle and saphenous nerve stimulation suggest different transmitters involved or different sites of interaction of these inputs with the medullary respiratory rhythm generator.

Animals↗
PubMed1983

Active and passive respiratory mechanics and control of breathing in kittens.

In five spontaneously breathing kittens (12-13 days old), anesthetized with pentobarbital sodium, we measured the passive and active elastances and resistances of the respiratory system and the decay of inspiratory muscle pressure (PmusI) during expiration. When normalized for body weight (BW), passive resistance (Rrs . BW) was smaller in kittens than in adult cats, whereas passive elastance (Ers . BW) did not differ significantly. As a result, passive time constant (tau rs = Rrs/Ers) was shorter in kittens (mean +/- SE: 0.073 +/- 0.011 s) than in cats (0.121 +/- 0.008 s). This, associated with a faster decay in PmusI in kittens, results in 2-3 times higher flows per kilogram body weight during spontaneous tidal expirations in kittens than in cats. As in the adult cats, the average values of active elastance and resistance were higher than the passive, the average percentage increase amounting to 59 and 49%, respectively. The greater active impedance reflects force-length and force-velocity properties of inspiratory muscles. Its price is higher work of breathing; its advantage is greater intrinsic load compensation.

Airway Resistance↗
PubMed1982

Spinal localization of the intercostal motoneurones innervating the upper thoracic spaces.

At the rostral level of the thorax, the intercostal muscles participate both in postural and respiratory functions to a variable degree depending upon the considered muscle: external intercostal, intercartilaginous, internal intercostal, and triangularis sterni. In order to determine if these physiological properties are related to a special organization at the spinal cord level, we have used the retrograde transport of horseradish peroxidase as a tool for studying the spinal distribution of intercostal motor cells in the adult cat. Results suggest that the intercostal motoneurones could be distributed, in the ventral grey horn, among two areas according to the respiratory or postural muscle specialization.

Animals↗
PubMed1982

Functional localization of pulmonary stretch receptors in the tracheobronchial tree of the kitten.

Seven kittens age 5 to 8 days were anaesthetized with ketamine, tracheotomized, cannulated just below the larynx, paralyzed, and ventilated. The thorax was widely opened and an expiratory load equal to the transpulmonary pressure at functional residual capacity (PLFRC) added. Single vagal fibers were dissected from the peripheral cut end of the right vagus nerve. Thirty-eight receptor discharges modulated during the respiratory cycle (pulmonary stretch receptors, PSR) were studied; 4 (10.5%) were tonically active at PLFRC while the remaining 34 had a mean threshold at 3.2 cmH2O. All the receptors progressively increased their discharge frequency with higher pressures reaching a plateau between 8-10 cmH2O. By occluding the airways at different levels of the tracheobronchial tree 32 PSR were functionally localized: none were found in the extrathoracic trachea; 3 (9.5%) were located in the intrathoracic trachea, 12 (37.5%) at the carina, main bronchi, and lobar bronchi, and 17 (53%) inside the lobes. All three tracheal receptors were tonic PSR. Previously obtained data from adult mammals indicate that 27-60% of PSR are tonically active and most of these are located in the trachea. The low incidence of tonically active PSR in the kitten may suggest a delayed functional maturation of the tracheal receptors.

Animals↗
PubMed1982

Anatomical organization of cat intercostal motor nuclei as demonstrated by HRP retrograde labelling.

1. Intercostal muscles participate both in postural and respiratory functions to a variable degree dependent upon the specific interspace or muscle. In order to determine if these physiological properties are related to a special organization at the spinal cord level, we have used the retrograde transport of HRP as a tool for studying the spinal distribution and morphology of intercostal motor cells in the adult cat. 2. Results obtained after intramuscular injections of the enzyme suggest that the intercostal motor columns could be distributed, in thoracic spinal segments, among two areas according to the respiratory or postural muscle specialization. Moreover, it appears that both postural and respiratory muscles are innervated by motor cells whose size is not related to histological or functional characteristics of the muscle.

Animals↗
PubMed1981

Postnatal development of the discharge pattern of phrenic motor units in the kitten.

The postnatal change of the mean frequency (F), the maximal frequency (FM) and the onset frequency (FO) of discharge of kitten phrenic motor units was studied and compared to adult values. The latency (recruitment time) and duration of discharge of phrenic units were also analyzed. In kittens less than 3 weeks old, there were relatively few early units (latency less than or equal to 10% of phrenic discharge duration), TI). The duration of discharge of early and late units, expressed in percentage of TI, was the same in kittens and adult cats, and the duration of discharge of the early units was greater than that of the late units. In kittens, F, FM and FO of the early and late units were always greater than in adult cats. In adult cat, as in Kittens, F, FM and FO of early units were not significantly greater than those of late units. In conclusion, the relatively small number of early units in kittens may reflect either a small number of active early bulbo-spinal neurons or may be linked to the electrical and morphological properties of phrenic motoneurons in the kitten.

Action Potentials↗
PubMed1980

The non-myelinated fibers of the phrenic and the intercostal nerves in the cat.

The aim of this work was obtaining quantitative data relative to the non-myelinated fibers of some thoracic nerves of the cat. The study has been done both through the utilization of the light and the electron microscope. A comparative analysis of the results obtained from the muscle nerves (external intercostal nerve and phrenic nerve), cutaneous nerve (lateral collateral branch of the internal intercostal nerve) and mixed nerves (internal intercostal) has been made. The C muscle fibers have a smaller diameter than the C cutaneous fibers. Some of the non-myelinated fibers of the phrenic nerve are probably involved in the innervation of the pleura or of the peritoneum. The relative number of non-myelinated fibers varies according to the nerves. The factor linking the diameter of the non-myelinated fibers to their conduction velocity is approximately equal to 0.7.

Animals↗
PubMed1979

Segmental motor innervation of the cat diaphragm.

In ten anaesthetized adult cats, bipolar recording electrodes were inserted in different muscular bundles of each hemi-diaphragm. Both stimulation and section of the phrenic cervical branches were made. The upper phrenic cervical branch innervates both the sternal and lateral portions of the diaphragm whereas the lower phrenic cervical branch innervates both the lateral and dorso-caudal portions.

Animals↗
PubMed1979

Somatotopy in the phrenic motor nucleus of the cat as revealed by retrograde transport of horseradish peroxidase.

Cats received unilateral or bilateral horseradish peroxidase (HRP) injections into various portions of the diaphragm. In two experiments one of the cut cervical roots of the phrenic nerve was immersed in HRP. The phrenic motoneurons located in the fifth and occasionally the fourth cervical segment send their axons, via the upper phrenic root, to pars sternalis and pars costalis of the diaphragmatic dome whereas the neurons of the sixth segment innervate preferentially the dorsal portion both crura and dome. No evidence of contralateral innervation of the diaphragm was obtained.

Animals↗
PubMed1979

Postnatal maturation of phrenic, vagus, and intercostal nerves in the kitten.

In the present work, we have compared the histological maturation of the phrenic nerve, the internal and external intercostal nerves of the 8th space and the vagus nerve. At least three nerves from each category have been taken from different kittens each week during the first 2 months of postnatal life, and each month for kittens aged between 2 and 8 months. Compared to references obtained in the adult animal, the development of the number and diameter of myelinated fibers has been studied for each nerve. Moreover, the maturation of unmyelinated fibers of the phrenic nerve has been studied with the electrom microscope. There is a possibility of a cephalo-caudal maturation in the somatic nerves. Important differences exist between somatic nerve maturation and that of the vagus nerve.

Animals↗
PubMed1979

Postnatal development of vagal control of breathing in the kitten.

At birth, the number of vagal myelinated fibers represents about 10% of the corresponding adult value. Their diameters range between 1 micron and 5 micron. The conduction velocities, calculated from the bimodal vagus nerve action potential, are 20 m.sec--1 (range 16--30 m.sec--1) and 6 m.sec--1 (range 1--10 m.sec--1) respectively. The discharge patterns of the vagal afferent units are similar to those described in adult cat for the various pulmonary mecano receptors. The proportion (9%) of low threshold broncho-pulmonary stretch receptors is smaller than that given by Paintal (1973) for the adult cat (50%). Nevertheless, the inhibitory action of the pulmonary stretch receptors is very potent at birth. Various experimental procedures (bivagotomy, vagal stimulation and lung deflation) which reinforce the central inspiratory activity in the adult cat provoke essentially a lengthening of expiration in the newborn. The predominance of expiratory activity can be seen as part of the general motor behaviour which in the newborn is essentially characterized by activation of flexor muscles.

Animals↗