Search PubMed⌕ Search

Biomedical subjects

V Chernick

Publications and source records attributed to V Chernick.

At least 73 records · Page 4Linked to original sources
PubMed1982

Naloxone reverses neonatal depression caused by fetal asphyxia.

Pregnant near-term rabbits were given an intravenous dose of saline or the opiate antagonist naloxone and then asphyxiated. The fetuses were delivered by cesarean section and evaluated for respiration, color, muscle tone, response to stimulation, and general activity at 1, 3, 5, 10, 15, and 30 minutes of age. The naloxone-treated pups had significantly better scores during the first 15 minutes after birth than the saline-treated pups. Naloxone did not adversely affect the scores of nonasphyxiated pups. These data suggest that endogenous opiates worsen the neonatal depression caused by intrauterine asphyxia and that this effect can be reversed by naloxone.

Animals↗
PubMed1982

Influence of sleep state on the response to hypercapnia in fetal lambs.

The effect of sleep state on the respiratory response to hypercapnia was studied in 14 chronic fetal sheep, 125-140 days gestation. Fetal PaCO2 was raised by 11 to 34 Torr by gradually increasing the maternal FICO2 to 0.09. Fetal sleep state was monitored. Fetal breathing (FB) was analysed in terms of frequency (f), tracheal pressure (TP) and ventilation equivalent (VEq) = sigma TP /min. In 16 out of 17 experiments on apneic fetuses in NREM sleep, the fetuses switched to REM sleep and in 14 instances began to breathe within 2 1/2 min thereafter. The PaCO2 at which apneic fetuses started breathing was 54.8 +/- 8.4 Torr (mean +/- SD). In 4 out of 10 trials on breathing fetuses in REM sleep the fetuses switched to NREM sleep and stopped breathing before removal of the CO2 stimulus. During REM sleep hypercapnia stimulated FB by an increase in TP and by a reduction in the number and duration of apneic pauses. It is concluded that in the fetal lamb CO2 stimulates breathing only during REM sleep and that this stimulus is superimposed on the basic mechanism that stimulated spontaneous FB during this sleep state.

Animals↗
PubMed1982

Cranial blood volume changes during mechanical ventilation and spontaneous breathing in newborn infants.

We derived a noninvasive method to compare changes in cranial blood volume during mechanical ventilation with changes occurring during spontaneous breathing in newborn infants. In ten infants receiving mechanical ventilation, cranial blood volume increased during inspiration by a mean of 8.3%. We found a consistent relationship between clinical estimation of lung compliance and the amount of cranial volume expansion. During spontaneous breathing in ten infants cranial blood volume decreased during inspiration by a mean of 5.8%. The findings indicate the need for careful monitoring during periods of rapid changes in lung compliance.

Blood Volume↗
PubMed1982

Adenovirus bronchiolitis in Manitoba: epidemiologic, clinical, and radiologic features.

We reviewed our experience with 41 children hospitalized from 1974 to 1978 for adenovirus (ADV) bronchiolitis. Thirty-two patients (78 percent) were native Indians between four and 12 months old. In 18 of the 41 patients (43.9 percent) acute complications developed. The five fatal cases (12.2 percent) were confined to native children. The initial chest roentgenograms showed lobar consolidation in 35 patients (85.4 percent). Atelectasis developed in five (12.2 percent) during hospitalization. Sixteen of 25 patients (64 percent) with adequate radiologic follow-up examination had subsequent pneumonias or showed residual chronic changes. The reasons for the predilection of ADV bronchiolitis in native Indian children and the precise effect on subsequent airway function in survivors are unknown and require further study. We emphasize the importance of ADV as a cause of bronchiolitis in native Indian children. Furthermore, this report focuses attention on the contribution of this disease to the spectrum of chronic pulmonary disorders in the pediatric group.

Adenoviridae Infections↗
PubMed1981

Regular fetal breathing induced by pilocarpine infusion in the near-term fetal lamb.

We report that pilocarpine, a cholinergic drug, stimulated regular sustained breathing movements in 10 near-term fetal lambs with chronically implanted catheters in the carotid artery, jugular vein, and trachea. With increasing doses of pilocarpine (0.1-5.9 mg), there was an enhanced respiratory response as measured by the duration of continuous breathing movements (14 +/- 12 min, increasing to 82 +/- 50 min; mean +/- SD), and the mean tracheal pressure per breath at end inspiration during the first 2 min after drug infusion (18 +/- 5, increasing to 38 +/- 12 mmHg). The mean pressure per breath during the control periods was 8 +/- 3 mmHg. There was no significant change in the breath frequency with increasing drug dose. A similar breathing response was not seen with epinephrine, suggesting that pilocarpine does not act by stimulating release of endogenous catecholamines. There was no fetal breathing response to pilocarpine infusion in atropine-pretreated fetal lambs, suggesting tha pilocarpine acts through a muscarinic mechanism. In eight acute experiments on exteriorized fetal lambs, we measured responses to pilocarpine before and after carotid sinus nerve ligation. The response to pilocarpine was abolished by sinus nerve section, suggesting possible mechanisms whereby pilocarpine may stimulate fetal breathing: the drug may increase peripheral chemoreceptor output, may sensitized the central respiratory centers to peripheral chemoreceptor input, of both.

Animals↗
PubMed1981

Effect of carotid chemoreceptor denervation on breathing in utero and after birth.

The influence of the carotid bodies on fetal breathing activity in utero and on the establishment of postnatal breathing was studied. The electrocorticogram, the electromyogram of the lateral rectus and postural muscles, and tracheal and arterial pressures were monitored on chronically prepared intact and carotid sinus-denervated fetal lambs. The denervated fetuses required a longer time for recovery from the operation, but thereafter the sleeping and breathing behavior was similar to that of the control group. Four of the carotid sinus-denervated fetuses were allowed to be delivered spontaneously, and all established regular postnatal respiration despite conclusive evidence of nonfunctional carotid bodies. These experiments indicate that the fetal carotid chemoreceptors are not essential for the spontaneous intrauterine breathing activity during rapid-eye-movement sleep nor for the establishment of effective breathing at birth.

Animals↗
PubMed1981

Effect of feeding on the chemical control of breathing in the newborn infant.

To examine the influence of feeding on the chemical control of breathing in neonates, we studied the ventilatory response to 3% CO2 in air in nine bottle fed (BOT) and eight breast fed (BR) term infants during feeding while the infants were alert. Control responses were obtained either before or after feeding, VE, respiratory frequency, tidal volume, inspiratory time, expiratory time, and sum of inspiratory and expiratory time, VT/Ti/Ttot, PACO2 and slope (S) of CO2 response (liter/min/kg/mmHg) were determined. During 3% CO2 while resting BR had a lower VE, VT, VT/Ti than BOT and S in BR was 40% of BOT (P less than 0.05). During feeding and CO2 when compared to resting and CO2 there was no difference in either BR or BOT in VT/Ti but Ti/Ttot decreased in both groups. During feeding, S in BOT was reduced from 0.049 +/- 0.012 (mean +/- S.E.) to 0.013 +/- 0.002 (74% reduction) and in BR from 0.020 +/- 0.002 to 0.009 +/- 0.002 (55%). Thus, behavioral activity (either BR or BOT) markedly depresses the ventilatory response to chemical stimuli (CO2). This modification is primarily related to changes in "effective" respiratory timing (Ti/Ttot) rather than mean inspiratory flow (VT/Vi).

Bottle Feeding↗
PubMed1980

Respiratory response to somatic stimulation in fetal lambs during sleep and wakefulness.

1. The respiratory response to electrical stimulation of the nose, tail, gum and fibular nerve (nonspecific somatic stimulation) was tested in chronically instrumented fetal lambs during sleep and wakefulness. 2. The respiratory response to somatic stimulation was greatest during REM sleep, lowest during NREM sleep, and intermediate during the awake state (AW). 3. Respiratory responses could follow electrical somatic stimulation up to 2 Hz in any sleep state without changing sleep state. 4. The fetal breathing (FB) response to repetitive stimulation depended on the initial sleep state and whether or not the sleep state was affected by the stimulation. Five patterns of response were seen: a) NREM leads to NREM (initial sleep state and sleep state at end of stimulation)--FB was initiated and did not continue beyond the duration of the stimulation. b) NREM leads to REM sleep--FB was initiated and continued beyond the time of stimulation. c) REM leads to REM sleep--spontaneous FB was enhanced and continued beyond the time of stimulation. d) REM leads to NREM sleep--spontaneous FB was enhanced but did not continue beyond the time of stimulation. e) NREM, REM sleep, Awake leads to Awake--FB was initiated or enhanced and continued beyond the time of stimulation until the onset of NREM sleep.

Animals↗
PubMed1980

Sleep, wakefulness and the monosynaptic reflex in fetal and newborn lambs.

1. Electrocorticogram (ECoG), electromyogram (EMG) of the lateral rectus and antigravity muscles (neck and masseter) and breathing activity (FB) were monitored in chronically prepared fetal sheep of 125-140 days gestation and in newborn lambs up to 11 days postnatal age. 2. Awake state (AW), non-rapid eye movement sleep (NREM) and rapid eye movement sleep (REM) were defined using standard criteria for ECoG, eye movements and postural muscle tone. 3. The percentage of time the fetuses spent in each state was: NREM sleep 53%, REM sleep 41.4%, and AW 5.6%. 4. Spontaneous intrauterine breathing activity occurred only during REM sleep, but 35% of REM sleep was not associated with FB. 5. Gasps (isolated deep inspirations) appeared occasionally throughout the recording and were not related to any specific sleep state or wakefulness. 6. In the fetus, the monosynaptic reflex (MSR) induced by direct electrical stimulation of the fibular nerve was enhanced by about 75% during REM sleep compared to NREM and AW. In the newborn lamb the adult pattern of suppression of MSR during REM sleep was not seen until several days after birth.

Animals↗
PubMed1980

Endogenous opiates and chemical control of breathing in humans.

Endogenous opiates are found in large concentrations in the brainstem of vertebrate animals, suggesting that they play a possible role in the central control of breathing. To examine this possible role in human ventilatory control we evaluated the effect of nalozone, a specific opiate antagonist, on the ventilatory and mouth occlusion pressure (P0.1) responses to hypercapnia and hypoxia in 6 normal men 22 to 48 yr of age. In a random double-blind crossover study, each subject received both an intravenous infusion of 50 mg of naloxone and a placebo infusion of normal saline. Ventilatory responses were measured before and 5 min after each infusion. Ventilatory responses to hypercapnia and hypoxia were more marked after both the saline and naloxone infusions, but there was no significant difference in the responses between the 2 infusions. Similarly there was no significant difference in respiratory timing or mean inspiratory flow between the 2 infusions at an arterial oxygen saturation (SaO2) > 95%. We concluded that endogenous opiates have no major influence on the chemical control of breathing in normal humans.

Adult↗
PubMed1980

Naloxone decreases the duration of primary apnea with neonatal asphyxia.

Naloxone, a specific opiate antagonist with no agonist properties, in doses of 0.4 and 4.0 mg/kg was found to markedly reduce the duration of primary apnea in asphyxiated newborn rabbits. There was no effect on the duration of the hyperpneic phase (time to primary apnea) or on survival time (time to last gasp). It is suggested that endogenous opiate-like peptides are released during asphyxia and are the major factor in the suppression of medullary inspiratory neuronal discharge during primary apnea.

Animals↗