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Biomedical subjects

P Bessou

Publications and source records attributed to P Bessou.

At least 55 records · Page 3Linked to original sources
PubMed1969

Spindle secondary ending responses elicited by stimulation of static fusimotor axons.

1. Indirect evidence on the time course of intrafusal events associated with stimulation of a static fusimotor axon was obtained by analysis of the responses from muscle spindle secondary endings of the cat.2. In many instances, a single impulse in a single static fusimotor axon to a muscle spindle evoked a transient increase in discharge of the secondary ending the duration of which ranged from 30 to 60 msec with a rising phase of 6-20 msec. Increasing the length of the muscle increased the slope of the rising phase and augmented the magnitude of the response.3. Different static fusimotor axons produced different effects upon secondary endings. A single impulse in some fusimotor axons did not produce an effect while repetitive stimulation produced a smooth increase in discharge frequency. When efficacious, a single fusimotor impulse evoked approximately a similar duration of increased discharge from a secondary ending and a primary ending of the same muscle spindle. The relative magnitude of effects of a given fusimotor axon on primary and secondary endings of a spindle varied.4. During partial curarization the changes in the discharges of a secondary ending evoked by stimulation of a single static fusimotor axon occurred in a step-like fashion.5. These results are interpreted as supporting the idea that static fusimotor axons induce twitch-like contractions of intrafusal elements (nuclear chain) through the intermediary of propagated action potentials.

Action Potentials↗
PubMed1968

A method of analysing the responses of spindle primary endings to fusimotor stimulation.

1. The superposition of records of ;instantaneous' frequency of discharge of spindle primary endings after stimulation of single fusimotor fibres leads to the construction of graphs called ;frequencygrams'.2. The superposition is made on the screen of a storage oscilloscope, the time base of which is synchronized with the stimulus. It is essential that the stimulus be delivered at all possible intervals with respect to the impulse of the resting discharge which precedes it.3. Frequencygrams obtained by stimulating some static fusimotor fibres by single stimuli display a response with a fast rising phase, a pause, and a slower decreasing phase.4. Frequencygrams may give some information on the time course of the contraction of intrafusal muscle fibres elicited by stimulating their motor axons.

Action Potentials↗
PubMed1968

Frequencygrams of spindle primary endings elicited by stimulation of static and dynamic fusimotor fibres.

1. Frequencygrams of cat spindle primary endings, obtained by the method described by Bessou, Laporte & Pagès (1968), were elicited by the stimulation of single static and dynamic fusimotor fibres.2. Stimulation of static fibres by single stimuli may elicit: (i) no response, (ii) responses of small amplitude, (iii) responses of large amplitude with a pause after the rising phase.3. Stimulation of static fibres by repetitive stimuli gives frequencygrams resembling records of tetanic contraction of skeletal muscle. At a frequency of stimulation of 180-200/sec periodic oscillations are perceptible on the plateau of the frequencygram.4. Stimulation of dynamic fibres by single stimuli may elicit: (i) no response, (ii) responses smaller and longer than the responses given by static fibres.5. When the muscle is stretched the amplitude of the responses elicited by dynamic fibres decreases whereas the amplitude of the responses given by static fibres increases.6. Frequencygrams obtained by repetitive stimulation of dynamic fibres show periodic oscillations only at low rates of stimulation. At rates of stimulation higher than the minimal rate giving frequencygrams with a smooth contour, the amplitude of the frequencygram increases.

Animals↗
PubMed1966

Amovement receptor of the small intestine.

1. The characteristics of a mechanoreceptor of the small intestinal region of the cat were studied by recording potentials from single afferent fibres in filaments dissected from mesenteric nerves. Forty-six fibres were examined in detail. Each of these was excited by light mechanical stimulation of the mesentery or small bowel, but none responded to sinusoidal vibration at frequencies above 100/sec. A ;spontaneous' discharge was regularly observed and it appeared to be related to peristaltic intestinal activity. On the other hand, non-propulsive motor contractions of the intestinal musculature were poorly correlated with discharge frequency.2. The region of maximal sensitivity of each fibre was determined by light pressure applied with a fine probe. Under these conditions the receptive field always resolved itself into 1-5 sensitive points (smaller than 1 mm in diameter). Each such point lay upon or immediately adjacent to a branch of the mesenteric artery supplying the area. Commonly, one or more sensitive spots were located at the place where a mesenteric artery entered the intestinal musculature. Localized pressure to one sensitive spot evoked a low frequency discharge (under 30/sec) which adapted within several seconds. A movement of the mesentery or the intestine distorting the region near one of the sensitive points regularly evoked a near maximal response. The dynamic phase of distension of the intestine by an intraluminal ballon also evoked a response. During inflation or deflation of the intestinal balloon, the frequency of discharge was positively correlated with both the rate of inflation and the pressure reached at the end of the dynamic phase. There was little relation between static distension and the discharge frequency.3. The conduction velocity of each afferent fibre was determined by electrical stimulation of its mesenteric nerve. The majority of the fibres studied had conduction velocities between 5 and 10 m/sec, the range being 2-21 m/sec. These figures were taken to indicate that the fibres were myelinated and of small diameter. Histological determination of myelinated fibre diameter in the mesenteric nerves from which the recordings were taken suggested that the numerical factor relating fibre diameter in mu to conduction velocity in m/sec was under 6.4. It was concluded that these receptors signalled movement of the intestine, regardless of its origin.

Animals↗
PubMed1966

Action of static and dynamic fusimotor fibres on secondary endings of cat's spindles.

1. The effects exerted on secondary endings by repetitive stimulation of single static or single dynamic fusimotor fibres were studied in nine tenuissimus spindles in cats.2. The discharge of each secondary ending was recorded simultaneously with the discharge of the primary ending belonging to the same spindle.3. All the nineteen static fusimotor fibres studied activated secondary endings.4. Of eight dynamic fusimotor fibres, seven had no action on secondary endings. One dynamic fibre activated an atypical secondary ending which displayed some phasic sensitivity.5. No difference in conduction velocity was found between static and dynamic fibres.6. The implications of these observations for the mechanism of action of static and dynamic fusimotor fibres are discussed.

Animals↗