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S Cullheim

Publications and source records attributed to S Cullheim.

102 records · Page 6Linked to original sources
PubMed1981

A quantitative light microscopic study of the dendrites of cat spinal gamma -motoneurons after intracellular staining with horseradish peroxidase.

By use of intracellular staining with horseradish peroxidase (HRP), the dendritic systems of spinal gamma-motoneurons of the adult cat were studied with a light microscope. The dendrites extended in various directions up to 1.5 mm from the cell body. The dendritic branching was sparse and even unbranched dendrites were occasionally seen. The number and combined diameter of the first-order dendrites increased in parallel with the mean cell body diameter. The number of dendritic end branches, the combined dendritic length, the membrane surface area, and the volume of the entire dendrite correlated positively with the diameter of the parent first-order dendrite. In comparison with the alpha -motoneurons (Ulfhake and Kellerth, '81) the gamma -motoneurons had smaller values for mean cell body diameter and mean diameter of the first-order dendrites and they also had a smaller number of first-order dendrites. The dendrites of the gamma-motoneurons were also found to have fewer branching points and larger values for combined dendritic length. The relation between the diameter of the first-order dendrite and the surface area of the entire dendrite was almost identical for the two types of motoneurons.

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PubMed1981

An ultrastructural study of the synaptic contacts of alpha 1-motoneuron axon collaterals. II. Contacts in lamina VII.

Horseradish peroxidase (HRP) was injected intracellularly in triceps surae alpha-motoneurons. The axons and axon collaterals of these neurons were traced light and electron microscopically. Synaptic boutons of collaterals in the ventral part of Rexed's lamina VII were studied ultrastructurally. The boutons exhibited spherical synaptic vesicles and made synaptic contacts with cell bodies and proximal dendrites of neurons assumed to be Renshaw cells and with dendrites of unknown origin. The observations are discussed in relation to earlier qualitative and quantitative studies on the other known synaptic contacts of the alpha-motor axons, both in the central and peripheral nervous system.

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PubMed1981

An ultrastructural study of the synaptic contacts of alpha-motoneurone axon collaterals. I. Contacts in lamina IX and with identified alpha-motoneurone dendrites in lamina VII.

Horseradish peroxidase (HRP) was injected intracellularly in triceps surae alpha-motoneurones. The axons and axon collaterals of these neurones were traced light and electron microscopically. Synaptic boutons of collaterals, in Rexed's lamina IX or in synaptic contact with HRP-stained motoneurone dendrites in lamina VII, were studied ultrastructurally. The boutons exhibited spherical synaptic vesicles and made synaptic contacts of two different types with HRP-stained alpha-motoneurone dendrites in lamina IX and VII, dendrites and cell bodies of large neurones in lamina IX, dendrites of unknown origin in lamina IX and with one cell body of a medium size neurone in lamina IX. The observations are discussed in relation to earlier qualitative and quantitative studies on the synaptology of cat spinal alpha-motoneurones.

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PubMed1981

Two kinds of recurrent inhibition of cat spinal alpha-motoneurones as differentiated pharmacologically.

1. The effects of i.v. administration of the glycine-antagonist strychnine nitrate and the GABA-antagonists bicuculline hydrochloride and picrotoxin on the recurrent inhibition of lumbosacral alpha-motoneurones were studied in cats anaesthetized with pentobarbitone sodium. 2. As revealed from both monosynaptic reflex experiments and intracellular recordings, each of the drugs generally reduced, but rarely abolished, the recurrent inhibition. The amount of reduction was more or less identical for bicuculline and picrotoxin. 3. By applying de- and hyperpolarizing currents intracellularly it could be shown that both the strychnine-resistant and bicuculline/picrotoxin-resistant recurrent inhibitory potentials were genuinely post-synaptic in nature. 4. The strychnine-resistant part of the recurrent inhibition had a later maximum and a longer duration than the part which was resistant to bicuculline/picrotoxin. 5. The time course of the strychnine-resistant recurrent inhibition was more or less identical to that of the bicuculline/picrotoxin-sensitive recurrent inhibition. 6. The bicuculline/picrotoxin-resistant recurrent inhibition was blocked by strychnine and, vice versa, the strychnine-resistant recurrent inhibition was blocked by bicuculline/picrotoxin. The combined administration of strychnine and bicuculline/picrotoxin always resulted in a virtual abolition of the recurrent inhibitory effects. 7. The values for central delay suggested that both the strychnine-resistant and bicuculline/picrotoxin-resistant inhibitions were mediated via disynaptic pathways. 8. The results suggest that both glycine and GABA act as transmitter substances of Renshaw cells in mediating recurrent inhibition to alpha-motoneurones. 9. No organizational pattern of the two types of recurrent inhibition based on motor pool category or motor unit type could be detected.

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PubMed1979

Relations between cell body size, axon diameter and axon conduction velocity of triceps surae alpha montoneurons during the postnatal development in the cat.

Triceps surae alpha-motoneurons in cats of different postnatal ages were stained intracellularly with horseradish peroxidase (HRP) and studied light microscopically. In individual neurons, the mean diameter of the cell body and the intramedullary axon diameter were measured and related to the axon conduction velocity. The mean diameter of the cell body grew from 39.6 micrometer at birth to 57.6 micrometer in the adult cat, while the corresponding figures for the intramedullary axon diameters were 2.4 micrometer and 6.7 micrometer. During the same period of time, the axon conduction velocity increased from 11.3 m/s to 93.5 m/s, and the ratio between the conduction velocity and the intramedullary diameter of the axon (CV/d ratio) increased from 4.6 to 14.1. The results indicate that the growth of the cell body is smaller and completed earlier than the growth in diameter of the intramedullary and, in particular, the peripheral parts of the axon. The considerable change of the CV/d ratio during the postnatal development may be explained by previously described immature morphological properties of the axons in very kittens, and by a changing relation between the dimensions of the intramedullary and peripheral parts of the axon.

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PubMed1979

Observations on the morphology of intracellularly stained gamma-motoneurons in relation to their axon conduction velocity.

Hindlimb gamma-motoneurons of adult cats were stained intracellularly with horseradish peroxidase. The gamma-motor-axons had intramedullary diameters between 2.0 micron and 2.4 micron and lacked recurrent collaterals. The conduction velocity of the gamma-motor-axons (20-29 m/sec) was close to what could be predicted from the relationship between conduction velocity and intramedullary diameter of much thicker adult alpha-motor-axons. However, the gamma-motor-axons were conducting much faster than alpha-motor-axons of 1-week-old kittens in spite of the fact that these two types of axons had about the same dimensions intramedullarly.

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PubMed1978

A morphological study of the axons and recurrent axon collaterals of cat sciatic alpha-motoneurons after intracellular staining with horseradish peroxidase.

Utilizing the centrifugal neuronal transport of intracellularly injected horseradish peroxidase (HRP), we have performed a light microscopic (LM) investigation of the intramedullary parts of the axons and axon collaterals of sciatic alpha-motoneurons in the adult cat. The intramedullary parts of the alpha-motor axons had comparatively short internodes (down to 75 microns) and were thinner than reported in earlier studies on the ventral root. Positive correlations were obtained when relating nodal diameters (2.8-7.8 micron) or the mean diameters of the motor axons in the white matter (4.4-9.0 micron) to the diameters of the initial axonal segments (2.3-4.9 micron). Eighty percent of the motor axons gave off one to five collaterals. There was no correlation between the numbers of collaterals and the lengths of the parent motor axons in the gray matter. The branching patterns of the axon collaterals showed considerable variation and the number of end branches from a single collateral ranged between 1 and 39. The rostro-caudal distribution of the collateral end branches was arranged symmetrically within a narrow space (+/- 300 micron) around the origins of the first order collaterals. Outbulgings of the motor axon collaterals, interpreted as synaptic terminals, were found along (59%) or at the ends (41%) of the collateral branches, and were located 200-700 micron away from the origin of the first order collateral. No characteristic LM feature of the outbulgings was distinguished.

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PubMed1978

A morphological study of the axons and recurrent axon collaterals of cat alpha-motoneurones supplying different hind-limb muscles.

1. Intracellular injections with horseradish peroxidasewere performed in cat alpha-motoneurones supplying various hind-limb muscles. 2. Ten alpha-motoneurones from each of the quadriceps, posterior biceps, gastrocnemius-soleus and anterior tibial pools as well as from the pool supplying the short plantar muscles were collected for morphological analysis of the intramedullary axonal systems including the recurrent axon collaterals. 3. The diameter of the alpha-motor axons showed considerable variation within each motoneurone pool, the total range being from 4.6 to 9.0 micrometer. No significant difference in mean axon diameter was obtained between the different pools. 4. All alpha-motoneurones supplying the short plantar muscles and one single alpha-motoneurone supplying the quadriceps muscle lacked collaterals completely, while the remaining motoneurones gave off one to five collaterals. 5. The number of axon collateral outbulgings, interpreted as synaptic boutons, wihch originated from a single alpha-motoneurone showed large variation within each pool that possessed axon collaterals, the total range being from seventeen of 158. The mean number varied from forty-four (quadriceps) to eighty-two (anterior tibial). 6. The axon collateral outbulgings were distributed not only in the Renshaw cell area ventromedial to the main motor nuclei but also in those parts of the motor nuclei which were located in the vicinity of the parent cell bodies. In the rostrocaudal direction, the outbulgings were distributed within a distances of less than 1 mm around the position of the parent cell bodies. 7. Some physiological implications of the lack of axon collaterals from alpha-motoneurones supplying the short plantar muscles were discussed in relation to the functional characteristics of plantar muscles and motor units.

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PubMed1978

A morphological study of the axons and recurrent axon collaterals of cat alpha-motoneurones supplying different functional types of muscle unit.

1. Cat alpha-motoneurones supplying muscle units of the soleus S type and gastrocnemius S, FR and FF types were injected intracellularly with horseradish peroxidase. 2. Ten alpha-motoneurones of each motor unit type were collected for morphological analysis of the intramedullary parts of their axonal systems including the recurrent axon collaterals. 3. The alpha-motor axon diameters in the spinal cord white matter were significantly smaller for the soleus motor units (mean = 5.2 micrometer) than for the gastrocnemius S units (mean = 6.4 micrometer), which in turn differed significantly from those of the gastrocnemius FR (mean 7.4 micrometer) and FF (mean = 7.3 micrometer types. 4. The number of axon collateral outbulgings, interpreted as synaptic terminals, which originated from the soleus motor axons (mean = 27.8) was significantly smaller, white that of the gastrocnemius FF motor axons (mean = 98.1) was significantly larger, than the number of outbulgings from the gastrocnemius S (mean = 44.4) and FR (mean = 53.8) motor axons. The latter two types were not significantly different. 5. In transverse sections the axon collateral outbulgings were found not only in the classical Renshaw cell area ventromedial to the main motor nuclei but also within the homonymous motor nucleus. However, only some of the neurones projected to the latter area. Rostrocaudally, the outbulgings were distributed within a distance of less than 1 mm around the position of the parent cell bodies. 6. Some physiological implications of the observed differences between axon collateral systems of various functional types of alpha-motoneurones were discussed in relation to the present knowledge of the effects of the recurrent axon collaterals during different types of involuntary and voluntary activation of the alpha-motoneurones.

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PubMed1977

Evidence for direct synaptic interconnections between cat spinal alpha-motoneurons via the recurrent axon collaterals: a morphological study using intracellular injection of horseradish peroxidase.

By using intracellular injection of horseradish peroxidase into cat triceps surae alpha-motoneurons we have been able to trace the motor axons as well as the recurrent motor axon collaterals with their synaptic terminals both with the light and electron microscope. In addition to the expected projection to the 'Renshaw cell area', the triceps surae motor axon collaterals were frequently found to terminate within the motor nuclei, where at least some of the terminals made direct synaptic contact with triceps surae alpha-motoneurons.

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