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Biomedical subjects

Y Laporte

Publications and source records attributed to Y Laporte.

At least 73 records · Page 4Linked to original sources
PubMed1970

Skeleto-fusimotor fibres in the rabbit.

1. In rabbits, repetitive stimulation of single motor axons to lumbrical muscles elicits both a contraction of extrafusal muscle fibres and an increase in the discharge frequency of spindle primary endings.2. This activation of the sensory endings can be attributed to the contraction of intrafusal muscle fibres because it persists after the contraction of extrafusal muscle fibres has been suppressed by selective curarization of their neuromuscular junctions.3. In non-curarized preparations the frequency of most of the afferent discharges continues to increase when rates of stimulation of motor fibres exceed the tetanic fusion frequency of the extrafusal muscle fibres.4. The effect of repetitive stimulation of motor fibres that supply extrafusal and intrafusal muscle fibres was studied on the responses of primary endings to phasic stretch. Of twelve fibres, eight were found to exert a dynamic effect and four a static one.5. Selective curarization of the extrafusal neuromuscular junctions does not modify the nature of the static and dynamic effects.

Action Potentials↗
PubMed1969

Frequencygrams of rabbit spindle primary endings elicited by stimulation of fusimotor fibres.

1. Frequencygrams of rabbit spindle primary endings elicited by stimulation of single fusimotor axons were obtained by the method described by Bessou, Laporte & Pagès (1968a) which gives indirect information on the contraction of intrafusal muscle fibres.2. Repetitive stimulation of the majority of static axons (twenty out of twenty-five axons studied) gave frequencygrams showing discrete large peaks corresponding to each stimulus, even for rates of stimulation as high as 300-500/sec.3. Large responses to single stimuli were elicited by thirteen of these axons. The responses consisted of a fast-rising phase lasting 5-10 msec and declining phase lasting 30-50 msec.4. Repetitive stimulation of some static axons (five out of twenty-five) gave frequencygrams displaying a smooth contour with no sign of individual responses to single stimuli and with a slow rising and declining phase.5. Both kinds of ;static' frequencygrams may be obtained from the same spindle.6. Repetitive stimulation of dynamic axons gave frequencygrams of small amplitude with a slow rising and declining phase and no sign of individual responses, even at low rates of stimulation.7. Although rabbit spindles lack nuclear chain muscle fibres (Barker & Hunt, 1964), rabbit's frequencygrams were essentially similar to those of cat spindles. The functional implications of this similarity are discussed.

Animals↗
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

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↗