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Biomedical subjects

E Murphy

Publications and source records attributed to E Murphy.

At least 325 records · Page 18Linked to original sources
PubMed1979

Regulation of airway smooth muscle tone in sleeping dogs.

We examined the influence of sleep state on airway smooth muscle tone in 4 unanesthetized dogs that were trained to sleep in the laboratory. The dogs had been prepared with a permanent side-hole tracheostomy and bilateral cervical vagal loops. During the studies, the dogs breathed through a cuffed endotracheal tube inserted through the tracheostomy. To monitor changes in tracheal smooth muscle tone, we measured the pressure in the water-filled cuff of the endotracheal tube. The technique was validated by examining changes in cuff pressure after administration to the dogs of a series of chemical agents and physiologic stimuli known to constrict or relax tracheobronchial smooth muscle. Sleep state of the dogs was determined by behavioral, electroencephalographic, and electromyographic criteria. During quiet wakefulness, tracheal smooth muscle tone was stable. With the onset and progression of sleep through the nonrapid-eye movement stages, airway smooth muscle tone relaxed (decrease in cuff pressure of 20 to 40 cm H2O), reaching a new steady level during slow-wave sleep. In contrast, during rapid-eye-movement sleep, tracheal smooth muscle tone fluctuated markedly and erratically, as reflected by changes in cuff pressure as large as 90 cm H2O. Partial blockade of the vagus nerves, by cooling the exteriorized cervical vagal loops, decreased or abolished the fluctuations in tracheal smooth muscle tone during rapid-eye-movement sleep at temperatures that did not abolish resting tone, demonstrating that the changes in tone during rapid-eye-movement sleep were related to variability in neural control of airway smooth muscle.

Animals↗
PubMed1979

Severity of psychiatric disorder and the 30-item general health questionnaire.

The 30-item General Health Questionnaire misclassified 26 per cent of respondents in two samples of women who were interviewed by a psychiatrist using the Present State Examination. False negatives were likely to be women with chronic disorders, particularly anxiety states. False positives were likely to be distressed by severe physical illness, a recent adverse life event, or loneliness. Applying a higher threshold score to their GHQ responses would help to separate those with a diagnosable psychiatric disorder from those in states of distress.

Adult↗
PubMed1979

A study of media effectiveness for sickle cell anemia education in a rural community.

A study was done in Orangeburg County, South Carolina, in order to determine the relative effectiveness of the various mass media (television, radio, and newspaper) in delivering an educational message about sickle cell anemia. The study also focused on different subpopulations. It was found that subpopulations varied in the extent to which they were reached by the message through a given medium. This indicates that any plan for media utilization in a campaign for sickle cell anemia education should take into consideration the subpopulation at which the message is aimed.

Adult↗
PubMed1978

Ventilatory and waking responses to hypoxia in sleeping dogs.

We examined waking and ventilatory responses to acute hypoxia in four dogs during natural sleep. Progressive hypoxia was induced by a rebreathing technique in which alveolar CO2 pressure (PACO2) was held at the eucapnic level. Arterial O2 saturation (SaO2) was measured with an ear oximeter, and sleep stage was determined by electroencephalographic and behavioral criteria. Arousal from eucapnic hypoxia occurred at a SaO2 of 87.5 +/- 2.6% (mean +/- SE) during slow-wave sleep (SWS), and at a SaO2 of 70.5 +/- 3.4% during rapid-eye-movement (REM) sleep (P less than 0.005). The irregular pattern of breathing typical of REM sleep persisted during hypoxia. However linear regression analysis of breath-by-breath instantaneous minute volume of ventilation (VI) against SaO2 revealed regression coefficients in REM sleep that were similar to those found in SWS and wakefulness. This finding contrasts with earlier observations of a decreased response of VI to CO2 during REM sleep. The results indicate that although waking responses to hypoxia are delayed in REM sleep, ventilatory responses remain intact and therefore may be of importance in maintaining adequate ventilation during this stage of sleep.

Animals↗
PubMed1978

Primary role of respiratory afferents in sustaining breathing rhythm.

We studied the effects on breathing rhythm of suppressing the major respiratory stimuli (wakefulness, vagal, peripheral and central chemoreceptors) in healthy, unanesthetized dogs. Respiratory frequency (f) was obtained with a pneumotachograph; the state of wakefulness (W) or sleep was determined by EEG and behavioral criteria. During quiet W, f averaged 17 breaths/min and minute volume of ventilation (VI), 8.4 l/min. In slow-wave sleep (SWS), f slowed to 14 breaths/min, and VI decreased to 6.8 l/min. Afferent vagal blockade during SWS slowed f to 4 breaths/min, due primarily to prolongation of expiratory duration (Te) to 13.3 s, and decreased VI to 4.8 l/min. One breath of 100% O2 prolonged Te further to 27.4 s. Central chemoreceptor sensitivity was then reduced by inducting a metabolic alkalosis that combined with SWS, vagal blockade, and hyperoxia prolonged Te to as long as 57 s and reduced f to as low as 1 breath/min. The results demonstrate that afferent respiratory stimuli are essential for sustaining adequate ventilation.

Animals↗
PubMed1978

Waking and ventilatory responses to laryngeal stimulation in sleeping dogs.

We studied waking and ventilatory responses to laryngeal stimulation during sleep in three dogs. The dogs breathed through an endotracheal tube inserted caudally into the trachea through a tracheostomy. Laryngeal stimulation was produced either by inflating a small balloon that was positioned in the rostral tracheal segment, or by squirting water onto the larynx through a catheter inserted through the tracheostomy. Airflow was measured with a pneumotachograph, and sleep state was determined by behavioral, electroencephalographic, and electromyographic criteria. We found that the degree of laryngeal stimulation required to produce arousal and coughing was higher in rapid-eye-movement (REM) sleep than in slow-wave sleep (SWS). Stimuli that failed to cause arousal from SWS often produced a single expiratory effort, or brief apnea (1--2 s) and bradycardia. In contrast, during REM sleep subarousal stimuli often resulted in prolonged apnea (greater than 10 s) and marked bradycardia. We conclude that during REM sleep arousal responses to laryngeal stimulation are depressed, but ventilatory and cardiac responses are intact.

Animals↗
PubMed1978

Adenosine deaminase activity in human diploid skin fibroblasts varies with the age of the donor.

Activities of adenosine deaminase, adenosine kinase and purine nucleoside phosphorylase were determined in extracts prepared from human skin fibroblast strains derived from 7 normal newborn males and 4 normal adult males. All strains were harvested between passages 9 and 12. Adenosine deaminase activity in adult strains, 40.80 +/- 1.76 (mean +/- S.E.) nanomoles/min per mg protein, was almost twice the activity in neonatal strains, 22.40 +/- 3.02. This difference was significant at the 99.5% confidence level. Moreover, there was no overlap between the adult and neonatal activities. In contrast, adenosine kinase and purine nucleoside phosphorylase activities did not differ with the age of the donor.

Adenosine Deaminase↗
PubMed1978

Survival in patients with intraventricular conduction defects.

All 42,000 electrocardiograms taken at the University of Oregon Health Sciences Center from 1969 through 1971 were reviewed; 325 patients (0.77%) had left bundle-branch block (LBBB) or right bundle-branch block (RBBB) with axis deviation (AD). In December 1974, 90% were contacted or found to be dead. The five-year survival rate (actuarial technique) (mean +/- SE) was 45.5 +/- 2.9%. It was significantly worse than that of age- and sex-matched "controls." In most patients the cause of death could not be determined. Survival of 164 LBBB patients (40.7 +/- 4.1%) at five years was not significantly worse than that of 161 RBBB and AD patients (49.5 +/- 4.2%). Those with syncope did no worse in terms of survival than did those without. The five-year survival in coronary artery disease patients was 33.7 +/- 4.4%, in those with primary conduction system disease (20% of patients), it was 50.6 +/- 6.6%. It will be necessary to know the causes of death and of syncope in conduction disease patients before it can be determined whether or not pacemakers can prevent either.

Adult↗
PubMed1977

Ventilatory and waking responses to CO2 in sleeping dogs.

We examined ventilatory and waking responses to hyperoxic hypercapnia in 3 dogs during natural sleep. Progressive hypercapnia was induced by a rebreathing technique, and sleep was determined by electroencephalographic and behavioral criteria. In non-rapid eye movement sleep (high-voltage, slow-frequency electroencephalography) rebreathing continued for 0.99 +/- 0.05 min (mean +/- SE) before arousal occurred, and the alveolar PCO2, at arousal was 54.2 +/- 3.4 mm Hg. In contrast, during rapid eye movement sleep, rebreathing lasted for 1.71 +/- 0.27 min (P less than 0.05) before arousal occurred and the alveolar PCO2 at arousal was 60.3 +/- 4.2 mm Hg (P less than 0.05). Linear regression analysis of breath-by-breath instantaneous minute volume of ventilation, tidal volume, and respiratory frequency against alveolar PCO2 revealed regression coefficients in rapid eye movements sleep that were 14 to 33 per cent of those found in non-rapid eye movement sleep, and correlation coefficients of 0.26 to 0.46, compared to 0.71 to 0.91 in non-rapid eye movement sleep. Thus, the link between CO2 and ventilation appeared to be strong in non-rapid eye movement sleep but considerably disrupted during rapid eye movement sleep. We conclude that centers involved in both waking and ventilatory responses to hypercapnia behave as if they are less aware of or responsive to CO2 in rapid eye movement sleep than in non-rapid eye movement sleep.

Animals↗
PubMed1976

Regulation of respiration in sleeping dogs.

We have examined the respiratory changes that occur during physiological sleep in three dogs with exteriorized cervical vagal loops. Sleep stage was determined by behavioral and EEG criteria. During non-REM (NREM) sleep breathing was slower (mean change, 23%),deeper (mean change, 18%), and less variable (coefficients of variation, 0.05-0.10) than during wakefulness (W); minute volume of ventilation (Ve) decreased (mean change, 14%) and alveolar CO2 pressure (PAco2) increased slightly (mean change, 1.3 mmHg). In addition, the rate of O2 consumption and ventilatory response to hypercapnia were decreased. In contrast, REM sleep was characterized by rapid, shallow, and considerably more irregular (coefficients of variation, 0.18-0.30) breathing; Ve increased markedly and PAco2 decreased (mean change, 5.2 mmHg). Blockade of both cervical vagus nerves produced comparable changes in each stage of sleep (W, NREM, REM): breathing became slower and deeper, but the differences between stages and the marked irregularity in REM sleep persisted. In contrast, the Hering-Breuer inflation reflex (HBIR) was strong in W and NREM sleep, but weak in REM sleep. The results indicate that changes in respiratory control and stability during sleep are not due to fluctuations in vagal influence despite the fact that one vagal reflex (HBIR) was sleep-state dependent.

Animals↗
PubMed1976

Respiratory load compensation in awake and sleeping dogs.

We have investigated immediate and progressive ventilatory responses to external elastic loads in five dogs with cervical vagal loops. Three dogs were studied while awake (W) and during non-REM sleep (S); the other two during barbiturate anesthesia (A). Elastic loads were applied at the end expiration for 1-6 breaths by having the dogs breathe from a rigid container (partial load) or against an occluded airway (infinite load). "Effective" elastance (EE) was determined from the tidal volume (VT)-tracheal pressure relationships of the unloaded, partially loaded, and infinitely loaded breaths. Passive thoracic elastance during W and S averaged 16.7 cmH2O/1. EE averaged 55.8 cmH2O/1 during W, 54.7 during S, and 59.5 during A. Vagal blockade (VB) induced large changes in VT but no change in EE in W or S; during A, EE decreased 37.5%. With sustained loading (partial) there was a progressive increase in VT but a corresponding increase in chemical (primarily hypoxic) respiratory drive, so that EE remained constant during five loaded breaths. VB augmented the progressive increase in VT during W or S but virtually abolished the increase in A. Thus the responses to elastic loads in W and S are similar and independent of conscious reactions or vagal influence; responses during A differ considerably. "Progressive load compensation" is a reflection of increasing of increasing chemical drive and not of progressive changes in EE.

Animals↗