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Biomedical subjects

L Jami

Publications and source records attributed to L Jami.

At least 55 records · Page 3Linked to original sources
PubMed1980

Glycogen depletion of bag1 fibers elicited by stimulation of static gamma axons in cat peroneus brevis muscle spindles.

1. The distribution of static fusimotor axons to intrafusal muscle fibres in cat peroneus brevis spindles has been studied with the glycogen depletion method. 2. In each of six experiments three to seven static axons were stimulated. The muscle was subsequently quick-frozen and cut in serial transverse sections that were stained for glycogen. In each muscle, nearly all the spindles were examined for depletion. 3. Intrafusal muscle fibres displaying zones of complete glycogen depletion were observed in fifty-two whole spindles and seven half-spindles. Chain fibres were depleted in forty-eight (92%) of the whole spindles, bag2 fibres in thirty-five spindles (67%) and bag1 fibres in nineteen spindles (36%). 4. Seven other experiments were performed to test whether small amplitude sinusoidal stretching (30--100 Hz) of the muscle might produce glycogen depletion in bag1 fibres. Two hundred and seven spindles were examined. In nearly all of them the glycogen content of the intrafusal muscle fibres was normal. Two muscles had limited atrophic portions within which a few depleted spindles were found. 5. These experiments show that the intrafusal distribution of static gamma axons is not restricted to chain and bag2 fibres but that in a significant number of spindles the bag1 fibres are also supplied by static gamma axons.

Animals↗
PubMed1980

Glycogen-depletion method of intrafusal distribution of gamma-axons that increase sensitivity of spindle secondary endings.

1. The glycogen-depletion method was used in cat tenuissimus muscles to investigate whether the action of static gamma-axons that increase the sensitivity of spindle secondary endings to muscle length is associated with a specific pattern of distribution of these axons to intrafusal muscle fibers. 2. In each experiment, a single gamma-axon acting on a secondary ending of a precisely located spindle was repetitively stimulated, and subsequently the intrafusal muscle fibers of that spindle were examined for glycogen depletion. 3. The gamma-axons whose repetitive stimulation increased the length sensitivity of secondary endings depleted all the chain fibers in one or both poles of the spindle, with the bag fibers being inconstantly involved. The gamma-axons whose stimulation did not exert this effect produced much more restricted patterns of glycogen depletion. 4. The length sensitivities of two secondary endings belonging to the same spindle were similarly affected by a single gamma-axon, whereas a gamma-axon could increase the sensitivity of a secondary ending without altering that of the primary ending of the same spindle. 5. The action exerted by single gamma-axons on secondary endings appears related to their intrafusal distribution since enhancement of the secondary endings sensitivity was observed only when all the chain fibers of at least one spindle pole were activated. 6. If several static gamma-axons supplying a given spindle are firing together, an increase in the length sensitivity of the secondary endings of that spindle can be expected since probably all chain fibers are activated.

Animals↗
PubMed1979

Histophysiological observations on fast skeleto-fusimotor axons.

In three instances, repetitive stimulation of a single fast skeleto-fusimotor axon supplying cat tenuissimus muscle was observed to activate a secondary ending belonging to a precisely located spindle. Prolonged repetitive stimulation of these beta-axons elicited glycogen depletion in the intrafusal muscle fibres of the located spindles and in extrafusal fibres. The intrafusal depletion affected the longest of the chain fibres in two instances, and the bag1 and bag2 fibres in the third instance. In one experiment, the discharge from the primary ending of the located spindle was also recorded. The fast beta-axon (it supplied the longest chain fibre in the spindle) had a static action on the primary ending. The extrafusal muscle fibres of the 3 fast beta-motor units belonged to the fast oxidative-glycolytic type.

Animals↗
PubMed1978

"Fast" and "slow" skeleto-fusimotor innervation in cat tenuissimus spindles; a study with the glycogen-depletion method.

The glycogen-depletion method was used to investigate the motor supply to tenuissimus with respect to the presence of fast beta axons and to assess the total proportion of both fast and slow beta-innervated spindles in this muscle. In a first series of 5 expts., groups of motor axons with conduction velocities higher than 85 m/s were repetitively stimulated so as to produce glycogen depletion in the muscle fibres they innervated. The whole muscle was then quick-frozen, serially cut, stained to demonstrate glycogen and examined for intrafusal glycogen depletion. Zones of glycogen depletion were found in 16 of the 46 examined spindles; they were most frequently located in the longest of the chain intrafusal muscle fibres. Since it is known that there are no purely fusimotor axons to tenuissimus with conduction velocities above 50 m/s, it was concluded that beta axons are present among the fastest axons to this muscle. In a second series of 5 expts. as many motor axons as possible with conduction velocities above 60 m/s were stimulated. Zones of glycogen depletion were found in 19 of the 47 examined spindles. They affected chain fibres in about half of the instances and bag1 fibers in the others. As this latter location is characteristic of slow dynamic beta axons, it was concluded that both slow and fast beta axons occur regularly in the motor supply to tenuissimus. beta-innervation is present in at least 40% of tenuissimus spindles with almost no convergence of fast and slow beta axons onto the same spindle.

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PubMed1977

Types of intra- and extrafusal muscle fibre innervated by dynamic skeleto-fusimotor axons in cat peroneus brevis and tenuissimus muscles, as determined by the glycogen-depletion method.

1. The types of intra- and extrafusal muscle fibre innervated by dynamic skeleto-fusimotor (beta) axons were determined by using a modification of the glycogen-depletion method of Edström & Kugelberg (1968) combined with histochemical tests for various enzyme reactions. A single beta axon was prepared in each of the experiments, which were carried out on six peroneus brevis and two tenuissimus muscles. 2. The intrafusal distribution of dynamic beta axons is almost exclusively restricted to bag1 fibres. The bags fibre was depleted in each of twenty-four beta-innervated spindle poles; the only fibres of a different type depleted intrafusally were a bag2 fibre in one pole and a long chain in another. 3. Depletion in the bag1 fibres was usually restricted to one zone in one pole, generally in a mid-polar location. 4. The extrafusal muscle fibres depleted by dynamic beta axons belong to the slow oxidative type as defined by Ariano, Armstrong & Edgerton (1973). The number of such fibres in each motor unit could not be accurately determined, but is almost certainly small. 5. The slow oxidative muscle fibres innervated by dynamic beta axons were not depleted over their entire length. Since there is no reason to assume that they are not twitch fibres, it would seem that the localized depletions result from the conditions required to obtain glycogen depletion, i.e. long periods of motor stimulation applied during the occlusion of the muscle's blood supply. Under similar experimental conditions depletion of glycogen was also restricted to portions of fibres in fast oxidative-glycolytic motor units, but extended over most of the length of the fibres in fast glycolytic units.

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PubMed1977

Fast-conducting skeletofusimotor axons supplying intrafusal chain fibers in the cat peroneus tertius muscle.

1. In six experiments on cat peroneus tertius muscle, from 12 to 23 motor axons with conduction velocities above 85 m/s were repetitively stimulated so as to produce glycogen depletion in the muscle fibers they innervated. 2. The whole muscle was then quick-frozen, serially cut, stained to demonstrate glycogen, and examined for intrafusal glycogen depletion. 3. Zones of glycogen depletion were found in 27 of the 99 examined spindles: they were almost invariably located on chain fibers and specifically on the longest of the chain fibers in affected spindles. 4. Since it was shown that there are no purely fusimotor fast axons in the motor supply to peroneus tertius, it is concluded that skeletofusimotor axons are present among the fastest motor axons to this muscle.

Animals↗
PubMed1976

Heterogeneity of motor units activating single Golgi tendon organs in cat leg muscles.

The aim of this study was to investigate whether an individual Golgi tendon organ can signal the contraction of motor units with different physiological properties. The axonal conduction velocity and tetanic tension of motor units were examined in four muscles of the cat leg (peroneus brevis, peroneus longus, tibialis anterior and soleus). The motor units which were found to activate a given tendon organ had contractile properties dispersed over the same range as those of the whole muscle population. The proportion of tendon organ-activating motor units found in the studied samples suggests that altogether, the Golgi tendon organs of a muscle monitor the contraction of every motor unit in this muscle.

Animals↗
PubMed1976

Distribution of fusimotor axons to intrafusal muscle fibres in cat tenuissimus spindles as determined by the glycogen-depletion method.

1. The distribution of fusimotor axons to bag1, bag2 and chain muscle fibres in cat tenuissimus spindles has been studied using a modification of the glycogen-depletion technique of Edstrrom & Kugelberg (1968). Single fusimotor axons were stimulated intermittently at 40-100/sec for long periods (30-90 sec) during blood occlusion. Portions of muscle containing the activated spindles were quick-frozen, fixed in absolute ethanol during freeze-substitution, and then embedded in paraffin wax. Serial transverse sections were stained for glycogen using the periodic acid-Schiff method, and examined for depletion. 2. Dynamic gamma axons (i.e. those that increase the dynamic index of primary-ending responses to ramp stretches of large amplitude) depleted bag1 fibres almost exclusively. 3. Static gamma axons (i.e. those that reduce or abolish the dynamic index) depleted both bag and chain fibres. Bag1 and bag2 fibres were depleted about equally. 4. A single static gamma axon may activate both bag and chain fibres in one spindle (the most common pattern), chain fibres only in another, and bag fibres only in a third spindle. 5. Static gamma axons with conduction velocities less than 25 m/sec also had a non-selective distribution, but no depletion was observed in bag2 fibres. 6. The zones of depletion produced by dynamic gamma axons were distributed more or less equally in the intra- and extracapsular parts of spindle poles, whereas those produced by static gamma axons were mainly intracapsular. 7. The results are compared with the glycogen-depletion studies of Brown & Butler (1973, 1975) and our own study of the distribution of static gamma axons to spindles in which all other motor axons had degenerated (Barker, Emonet-Dénand, Laporte, Proske & Stacey, 1973). The implications of the finding that both static gamma and dynamic gamma axons activate bag1 fibres are discussed.

Animals↗
PubMed1976

Frequency of tendon organ discharges elicited by the contraction of motor units in cat leg muscles.

1. The responses elicited in individual tendon organs by the contraction of single motor units were studied in peroneus longus, peroneus brevis, tibialis anterior and soleus muscles. 2. No simple relation was found between the discharge frequency of a tendon organ and the tension produced in the muscle tendon by the contraction of individual motor units. 3. The sensitivity of a given tendon organ to contractile tension was not the same for each of the motor units which elicited its discharge. There was no correlation between the sensitivity of the receptor and the strength of the motor units. 4. Upon repetitive stimulation of a tendon-organ-activating motor unit at increasing rates, the frequency of the receptor sustained discharge reached a maximal value for rates of stimulation eliciting submaximal tetanic tension. Higher rates only produced an increase in the dynamic component of the tendon organ response. 5. These observations show that the contractile tension sensed by a tendon organ is not a simple fraction of the tension which appears at the muscle tendon. They might be accounted for as consequences of the fine structure of tendon organs and of variations in the number of muscle fibres contributed by different motor units to the bundle inserted on each receptor. The location of most tendon organs at musculo-aponeurotic junctions rather than in the tendon proper, could also be responsible for some of the observed discrepancies.

Action Potentials↗
PubMed1975

Skeleto-fusimotor axons in the hind-limb muscles of the cat.

1. Motor axons supplying various hind-limb muscles of the cat (flexor hallucis lingus, peroneus brevis, peroneus digiti quinti, tibialis anterior, soleus and tenuissimus) were identified as skeleto-fusimotor or beta axons because their repetitive stimulation elicited both the contraction of extrafusal muscle fibres and an increase in the rate of discharge of spindle primary endings which perisited after selective blockade of extrafusal neuromuscular junctions. 2. The conduction velocity of these axons ranged from 39 to 92 m/sec. 3. Of seventy-six beta axons, seventy-two had a dynamic action on the sensitivity to velocity of stretching of primary endings, four had a static action. 4. The dynamic action of six beta axons was observed only after the contraction of extrafusal muscle fibres was selectively suppressed. 5. Tendon organs can be activated by beta motor units.

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