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Biomedical subjects

R Duclaux

Publications and source records attributed to R Duclaux.

At least 73 records · Page 4Linked to original sources
PubMed1976

Conduction velocity along the afferent vagal dendrites: a new type of fibre.

1. We systematically calculated the conduction velocity along the peripheral extensions of sensory vagal neurones in cats (the dendrites). In addition, a study of excitability cycle and light microscopic investigation were also conducted on these neurones. 2. The conduction velocity of the three known types of fibres (A, B and C) remains uniform along the dendrites. 3. Another mixed type of fibres exists with a C conduction velocity (mean value 1-5 m/sec) along its distal pathway and a B conduction velocity (mean value 6 m/sec) along its proximal pathway. The change in conduction velocity progressively occurs in the thoraco-cervical portion of the vagus nerve at least 20 mm from the receptor and at least 40 mm from the T cell. 4. The mixed fibres exhibited a C type excitability cycle in their peripheral pathway and a B type excitability cycle in their central pathway. 5. The histological study using the teasing method demonstrated the existence of unmyelinated fibres, in the thoraco-cervical region of the vagus nerve, becoming progressively myelinated from the periphery to the nodose ganglion. These fibres are likely to be the ones showing mixed electrophysiological properties. They represent (approximately) 10% of the vagal nerve population. 6. We propose to call the mixed fibres BC because they present electrophysiological and morphological properties of C fibres in their distal part and properties of B fibres in their proximal part.

Action Potentials↗
PubMed1976

The thermal sensitivity of the polymodal nociceptors in the monkey.

1. The static and dynamic sensitivities to thermal and mechanical stimuli of polymodal nociceptors in hairy skin of the anaesthetized monkey have been investigated by recording activity in their primary nerve fibres. 2. Polymodal nociceptors responded to skin pricking, pinching and heating to temperatures higher than 40 degrees C. They did not respond to touch, stretch or cold. The conduction velocity of their axons was from 0.6 to 1.1 m/sec. 3. Three types of cutaneous receptive fields have been observed: single spot-like areas of 1-2 mm2; multiple spot-like areas of 1-2 mm2; and larger areas up to 25 mm2 with heterogeneous sensitivity. 4. Polymodal nociceptors were subjected to heat stimuli that commenced from a 33 or 37 degrees C adapting temperature. A series consisted of heating their receptive fields to 43, 45, 47 and 50 degrees C from one or the other adapting temperatures at a constant rate of 0.2 degrees C/sec. Each heat stimulus intensity was maintained for 4 min after which the skin was returned to the adapting temperature. Immediately after the first series the identical series was repeated in order to determine the effect of prior heating upon the dynamic responses to re-heating. The dynamic responses were characterized by three phases: an initiation of a discharge at a threshold level of skin temperature; a dynamic discharge during the suprathreshold change, that reached a peak frequency when the temperature reached its maximum; and an adaptation phase while the temperature remained at the high intensity. Adaptation was rapid initially, and then slowed during the final minutes at the high intensity. 5. Adapting the receptive field to either 33 degrees C or to 37 degrees C before the heat stimuli did not affect the sensitivity and the discharge pattern of the polymodal nocicpetors. 6. During the first series of stimulations, the threshold at which the individual polymodal nociceptors began to discharge to heat stimuli varied from 40 to 46.5 degrees C. The mean threshold of the population was 42.5 degrees C. 7. No change in the threshold was observed when responses to 0.2 and 1.5 degrees C/sec rates of heating were compared...

Action Potentials↗
PubMed1976

[Methods for measurement and analysis of human dietary behavior].

Food intake in humans may be studied by the measurement of the quantity of food ingested, by the estimate of sensations evoked by food, and by recordings of the motor and secretory activities of the digestive tract. These methods may be used to study normal as well as pathologic food intake in humans.

Diet↗
PubMed1972

The temperature sensitivity of the type I slowly adapting mechanoreceptors in cats and monkeys.

1. The sensitivity of Type I slowly adapting mechanoreceptors in cat and monkey skin to temperature and changes in temperature was investigated.2. Multiple receptors innervated by a single axon appeared to be more frequent in the monkey than in the cat skin.3. The responses of these receptors to thermal stimulation at static skin temperatures from 27 to 40 degrees C were similar in cats and monkeys. At 43 degrees C the monkey receptors showed a higher steady-state activity than the cat receptors.4. A maximum steady-state frequency of 5.5 impulses/sec occurred in both the cat and monkey receptors at a static skin temperature of 37 degrees C.5. The maximum dynamic response to cooling occurred at a skin temperature of 40 degrees C. The response was near its maximum at 2 degrees C cooling and increased but little with further increases in the intensity of cooling.6. Dynamic responses to cooling disappeared after the skin had been heated to 51 degrees C for 35 sec and to mechanical stimulation after heating to 53 degrees C for 35 sec. Excitation by either mechanical or thermal stimulation did not reappear within 1-2 hr.7. The response characteristics of the Type I slowly adapting mechanoreceptors to temperature and temperature changes differ from those of specific cold receptors.

Action Potentials↗