Biomedical subjects

V Dascalu

Publications and source records attributed to V Dascalu.

5 recordsLinked to original sources

PubMed1991

Fever in young lambs: temperature, metabolic and cardiorespiratory responses to a small dose of bacterial pyrogen.

Experiments were done on ten lambs ranging in age from 15 to 25 days to define the temperature, metabolic and cardiorespiratory responses to intravenous administration of a small dose of bacterial pyrogen (SAE). Administration of SAE but not normal saline produced a short-lived fever of about 0.7 degrees C. The increase in body-core temperature was preceded by a surge in total body oxygen consumption and the onset of shivering which was influenced by behavioral state (ie, shivering was inhibited during active sleep). The increase in total body oxygen consumption was initially met by an increase in total body oxygen extraction and then by an increase in systemic oxygen delivery. Systemic arterial blood pressure did not change significantly during the febrile response; however, pulmonic arterial blood pressure increased significantly. Thus, our experiments provide new data on oxygen supply and demand during the development of fever and that shivering thermogenesis is inhibited in active sleep following the administration of bacterial pyrogen in young lambs. The influence of active sleep on the overall febrile response, and whether or not there is a shift from shivering thermogenesis to non-shivering thermogenesis remains to be determined.

Animals↗

PubMed1990

Influence of carotid denervation on the arousal and cardiopulmonary responses to upper airway obstruction in lambs.

Experiments were done on five lambs to determine if carotid denervation influences the arousal and cardiopulmonary responses to upper airway obstruction during sleep. Each lamb was anesthetized and instrumented for recordings of electrocorticogram, electro-oculogram, nuchal and diaphragm electromyograms, and measurements of arterial blood pressure and arterial Hb oxygen saturation. A tracheotomy was done and a fenestrated tracheotomy tube placed in the trachea. During the study, a 5 F balloon-tipped catheter was inserted into the tracheotomy tube so that air flow could be obstructed by inflating the balloon. No sooner than 3 d after surgery, measurements were made in quiet sleep and active sleep during control periods when the animal was breathing room air and during experimental periods of upper airway obstruction. Carotid denervation significantly affected the arousal response to upper airway obstruction. Arousal occurred during 14 of 14 epochs in quiet sleep and during 12 of 13 epochs in active sleep before the arterial Hb oxygen saturation decreased to 30%. However, the time to arousal was increased and the arterial Hb oxygen saturation at arousal was decreased in carotid-denervated lambs compared with what we have previously observed in carotid-intact lambs. These data provide evidence that the carotid chemoreceptors and/or carotid baroreceptors play a major role in causing arousal from sleep during upper airway obstruction in lambs. Our results may have implications for sudden infant death syndrome, because it is possible that alterations in the arousal response to respiratory stimuli play a role in sudden infant death.

Airway Obstruction↗

PubMed1990

Influence of sleep on the cardiovascular and metabolic responses to a decrease in ambient temperature in lambs.

Experiments were done on seven lambs between the ages of 10 and 24 days to investigate the effects of sleep on the cardiovascular and metabolic responses to a decrease in ambient temperature. Each lamb was anesthetized and instrumented for recordings of electrocorticogram, electro-oculogram, and nuchal electromyograms and measurements of cardiac output, systemic and pulmonic pressures and hemoglobin oxygen saturations as well as body core temperature. No sooner than three days after surgery, measurements were made during periods of quiet wakefulness, quiet sleep and active sleep at ambient temperatures of 25 degrees C and 18 degrees C. Decreasing the environmental temperature from 25 degrees C to 18 degrees C elicited a similar thermogenic response during quiet wakefulness, quiet sleep and active sleep as evidenced by an increase in total body oxygen consumption. The increased metabolic oxygen demand was met by an increase in systemic oxygen transport as well as by an increase in total body oxygen extraction. Since shivering was absent during active sleep, it is likely that nonshivering thermogenesis played a major role in the metabolic response. Our data provide evidence that sleep does not significantly alter the cardiovascular and metabolic responses to a modest decrease in ambient temperature in young lambs.

Animals↗

PubMed1989

Influence of carotid denervation on the arousal and cardiopulmonary response to rapidly developing hypoxemia in lambs.

Experiments were done on five lambs to determine if carotid denervation influences the arousal and cardiopulmonary responses to rapidly developing hypoxemia during sleep. Each lamb was anesthetized and instrumented for recordings of electrocorticogram, electrooculogram, nuchal and diaphragm electromyograms, and measurements of arterial blood pressure and arterial hemoglobin oxygen saturation. The carotid chemoreceptors and baroreceptors were denervated, a tracheostomy was done, and a fenestrated tracheostomy tube was placed in the trachea so that the inspired oxygen mixture could be changed quickly. No sooner than 3 d after surgery, measurements were made in quiet sleep and active sleep during control periods when the animal was breathing 21% oxygen and during experimental periods of rapidly developing hypoxemia when the animal was breathing 5% oxygen. Rapidly developing hypoxemia was terminated during each epoch by changing the inspired gas mixture back to 21% oxygen once the animal aroused from sleep or once the arterial Hb oxygen saturation decreased to 30%. Arousal occurred during only 4 of 11 epochs in quiet sleep and during only 3 of 14 epochs in active sleep before the arterial IIb oxygen saturation decreased to 30%. These data provide evidence that the carotid chemoreceptors and/or carotid baroreceptors play a major role in causing arousal from sleep during rapidly developing hypoxemia in lambs.

Animals↗

PubMed1989

Influence of carotid-denervation on the arousal and cardiopulmonary responses to alveolar hypercapnia in lambs.

Experiments were done on five lambs to determine if carotid-denervation influences the arousal and cardiopulmonary responses to alveolar hypercapnia during sleep. Each lamb was anaesthetized and instrumented for recordings of electrocorticogram, electro-oculogram, nuchal and diaphragm electromyograms and measurements of systemic arterial blood pressure and arterial haemoglobin oxygen saturation. The carotid chemoreceptors and baroreceptors were denervated, a tracheostomy was done and a fenestrated tracheostomy tube placed in the trachea so that the inspired gas mixture could be changed quickly. No sooner than three days after surgery, measurements were made in quiet sleep and active sleep during control periods when the animal was breathing room air and during experimental periods of alveolar hypercapnia when the lamb was breathing 10% carbon dioxide in air. Alveolar hypercapnia was terminated during an experimental period by changing the gas mixture back to room air once the animal aroused from sleep. If an animal did not arouse within 2 min, the gas mixture was changed back to room air. Arousal occurred during only 6 of 12 epochs in quiet sleep and during only 2 of 10 epochs in active sleep. These data provide evidence that the carotid chemoreceptors and/or carotid baroreceptors play a major role in causing arousal from sleep during alveolar hypercapnia in lambs.

Animals↗