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Biomedical subjects

G Benchetrit

Publications and source records attributed to G Benchetrit.

At least 55 records · Page 3Linked to original sources
PubMed1983

Simulation of a biological oscillator: the respiratory system.

Several models of oscillators defined by a system of non-linear differential equations have been built which simulate quite well some entrainment characteristics of the respiratory system: the range of entrainment, positioning of the stimulus at entrainment and the variation of inspiratory duration with entrainment periods. The construction of the model has been guided by consideration of the isochron configuration and the phase response curve of the system, which may yield a good qualitative fit between simulation and experimental results.

Animals↗
PubMed1980

Ventilatory CO2 drive in the tortoise Testudo horsfieldi.

1. Ventilation was recorded by pneumotachography, before and after bilateral vagotomy, in conscious tortoises (Testudo horsfieldi) (breathing 0, 2, 3 or 4% CO2 in air or oxygen). 2. Each breath consists of expiratory and inspiratory phases and an apneic plateau (absence of air flow). Inhalation of hypercapnic mixtures led to increased ventilatory flow, augmentation of tidal volume, and an increase in respiratory frequency through the shortening of the apneic plateau. 3. Intact tortoises breathing hypercapnic-hyperoxic mixtures hyperventilated less than with hypercapnic-normoxic mixtures. 4. In bivagotomized animals, the respiratory frequency decreased, the expiratory and inspiratory durations lengthened, and the apneic plateau was prolonged. The tidal volume was increased, but ventilation, nevertheless, decreased slightly. 5. Bivagotomized animals breathing hypercapnic-normoxic or hypercapnic-hyperoxic mixtures hyperventilated, but less than intact animals under the same conditions. 6. It is concluded that in tortoises there are: (1) peripheral chemoreceptors which are innervated by branches of the vagus nerves, and are sensitive to CO2; and (2) an extrathoracic, probably central, ventilatory CO2 drive.

Animals↗
PubMed1979

Liver heat production and temperature regulation in the anesthetized dog.

Liver heat production (LHP) was measured in the anesthetized dog by a new calorimetric method. Blood flows and temperatures were measured at the same points. The method avoided damage of liver innervation and vascularization. Changes of LHP were investigated under different thermal conditions. Measurements at controlled arterial temperatures within the physiological range showed changes of LHP when arterial temperature was randomly increased or decreased. When measured LHP was compared in experiments carried out at different ambient temperatures, a negative linear correlation was found between LHP and the ambient temperature. It was concluded that liver heat production may be a factor in temperature regulation.

Animals↗
PubMed1975

A short-term memory in the respiratory centres: statistical analysis.

It has been observed previously that the successive values of depth and duration of respiratory cycles recorded in man are not independent random variable. The present study has been performed in order to test whether a serial dependence of the characteristics of the respiratory cycles results from an inherent property of the central respiratory oscillator. In the "isolated respiratory centre" preparation of the cat (spinalized, bivagotomized, curarized and artificially ventilated) the following respiratory data have been studied: the value of integrated phrenic discharge per breath (S), inspiratory duration (TI), expiratory duration (TE) and total cycle duration (T), at rest and during hypercapnia and hyperthermia. Each recording in a steady-state condition provided a set of four series of data; using statistical analysis of time series the following results were obtained: 1. In each series the successive values are not independent random variables. This suggests that a cycle may be considered as an event whose characteristics condition those of the following cycle. 2. TE is not independent of the preceding TI, and TI is not independent of the immediately preceding TE. However, this last relation cannot be asserted in hypercapnia and hyperthermia. 3. A positive correlation exists between S and TI. This result indicates that a simultaneous adjustment of S and TI, in terms of one another, does exist in absence of the vagal mechanism.

Animals↗