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S Cullheim

Publications and source records attributed to S Cullheim.

At least 91 records · Page 5Linked to original sources
PubMed1987

The combined use of immunohistochemistry and intracellular staining with horseradish peroxidase for light and electron microscopic studies of transmitter-identified inputs to functionally characterized neurons.

Physiologically identified triceps surae alpha motoneurons in the cat were stained intracellularly with horseradish peroxidase (HRP). After fixation with 2% glutaraldehyde and treatment with sodium borohydride, spinal cord sections were incubated with rabbit antiserum against thyrotropin-releasing hormone (TRH) and rabbit peroxidase-antiperoxidase complex. Light microscopically detected close contacts between immunoreactive nerve terminals and intracellularly HRP-stained profiles were studied under the electron microscope. In this way, synaptic contacts between TRH-immunoreactive boutons and functionally characterized alpha motoneurons could be demonstrated.

Animals↗
PubMed1987

Thyrotropin-releasing hormone (TRH)-immunoreactive boutons and nerve cell bodies in the dorsal horn of the cat L7 spinal cord.

With the use of the peroxidase-anti-peroxidase (PAP) technique, thyrotropin-releasing hormone (TRH)-like immunoreactivity was found in axon terminals and cell bodies in the dorsal horn of the cat spinal cord L7 segment. In particular, a conspicuous band-shaped region of axon terminals was observed in laminae II and III, while the cell bodies were most frequent in lamina III. Electron microscopic analysis showed that the TRH-immunoreactive terminals made synaptic contacts with cell bodies and dendrites of various sizes.

Animals↗
PubMed1987

Membrane area and dendritic structure in type-identified triceps surae alpha motoneurons.

The size and branching structure of the dendritic tree were studied in nine type-identified triceps surae alpha-motoneurons that were labeled intracellularly with horseradish peroxidase and reconstructed from serial sections in the light microscope. The average total membrane area (AN) for motoneurons of type S (slow-twitch) motor units was about 22% smaller than AN for cells of type F units (including both FF and FR motor unit types in this category) (480.1 X 10(3) microns 2 vs. 617.7 X 10(3) microns 2, respectively). Systematic correlations were found between stem dendrite diameter and three measures of dendritic size: dendrite membrane area, combined dendritic length, and number of terminations. All of these correlations were significantly different for the dendrites of F and S motoneurons. Power-function relations between stem diameter and dendritic membrane area were used to estimate AN for a sample of 79 type-identified motoneurons. Mean estimated AN values were significantly different for the F and S motoneuron groups, despite a large overlap in AN values between these groups. The branching structure of dendrites of F and S motoneurons also showed clear differences. Type S motoneuron dendrites showed less-profuse branching and a more-even radial distribution of branch points than found in type F cells. Examination of two forms of the "3/2 power rule" for the relation between the diameters of parent and daughter dendritic branches at branch points showed that the dendrites of type S motoneurons conform less well with the anatomical constraints necessary to represent binary branching trees as equivalent cylinders than do dendrites of type F cells. There was no systematic difference between F and S motoneuron dendrites in the degree of asymmetry of first-order daughter trees. The results overall indicate that the dendrites of F and S motoneuron groups are structurally different, giving rise to a systematic difference in AN between these groups. Such structural differences suggest that the F and S groups of alpha-motoneurons can be viewed as intrinsically distinct cell types and not just large vs. small variants of the same cell species.

Animals↗
PubMed1987

Three-dimensional architecture of dendritic trees in type-identified alpha-motoneurons.

We have studied the spatial distribution of dendrites of type-identified triceps surae alpha-motoneurons, labeled intracellularly with HRP, using a variety of analytical approaches that were designed to quantify the ways in which dendrites occupy three-dimensional space. All of the methods indicated a strong tendency for motoneuron dendrites to project radially. However, regions dorsal and ventral to the somata contained fewer dendritic elements, and less membrane area, than expected for complete radial symmetry. Individual dendrites projecting into these regions tended to be smaller than those projecting rostrocaudally or mediolaterally. Nevertheless, the center of mass of membrane area for five of six fully analyzed cells was within 100 micron of the soma and, in all six cells, was located in the same dorsoventral plane as the cell soma. Maps of the projection of dendritic branches onto concentric shells at various radial distances from the soma showed that some regions have high concentrations of branches, sometimes with considerable overlap between branches arising from different stem dendrites, while other regions have relatively few branches, or none at all. Each motoneuron exhibited a different pattern of projection and there were no systematic differences between fast-twitch (type F, including both types FF and FR units) and slow-twitch (type S) motoneurons evident in the patterns of dendritic concentration. Assessment of the three-dimensional territories of individual dendrites showed that dendrites with larger numbers of terminal branches tended to have larger spatial territories. Despite considerable scatter, the results suggest that the density of branches tends to be approximately the same in large and small dendrites, and in F and S cell groups. The results are discussed in relation to the spatial location of synaptic input to motoneurons.

Animals↗
PubMed1987

An ultrastructural study of 5-hydroxytryptamine-, thyrotropin-releasing hormone- and substance P-immunoreactive axonal boutons in the motor nucleus of spinal cord segments L7-S1 in the adult cat.

The distribution and fine structure of 5-hydroxytryptamine-, thyrotropin-releasing hormone- and substance P-immunoreactive synaptic boutons and varicosities were studied in the motor nucleus of the spinal cord segments L7-S1 in the cat, using the peroxidase-antiperoxidase immunohistochemical technique and analysis of ultrathin serial sections. The 5-hydroxytryptamine-, thyrotropin-releasing hormone- and substance P-immunoreactive boutons had a similar ultrastructural appearance as judged from serial section analysis. The boutons could be classified into two types on the basis of their vesicular content, with one type containing a large number of small agranular vesicles together with only a few, if any large granular vesicles, while the other type contained a large number of large granular vesicles in addition to small agranular vesicles. The vesicles were spherical or spherical-to-pleomorphic. Postsynaptic dense bodies (Taxi bodies) were occasionally observed in relation to all three types of immunoreactive boutons, which almost invariably formed synaptic junctions with dendrites. Judged by the calibre of the postsynaptic dendrites, the boutons were preferentially distributed to the proximal dendritic domains of motoneurons. In one case, a substance P-immunoreactive bouton formed an axosomatic synaptic contact. In addition to synaptic boutons, 5-hydroxytryptamine-, thyrotropin-releasing hormone- and substance P-immunoreactive axonal varicosities containing a large number of large granular and small agranular vesicles but lacking any form of conventional synaptic contact were observed. Such varicosities were either directly apposing surrounding neuronal elements or separated from the neurons by thin glial processes. The origin of the immunoreactive boutons was not traced, but it was thought likely that the main source of the boutons was neurons with their cell bodies located in the medullary raphe nuclei.

Animals↗
PubMed1986

Electron microscopic observations on the synaptology of cat sciatic gamma-motoneurons after intracellular staining with horseradish peroxidase.

Four cat sciatic motoneurons with axon conduction velocities below 30 m/s, and thus considered to be of the gamma-type, were intracellularly labelled with horseradish peroxidase (HRP) and subsequently studied in the electron microscope. The labelled neurons were apposed by synaptic terminals with spherical (S-type) and flattened vesicles (F-type) but not by large terminals with spherical vesicles (M- and C-types) seen on alpha-motoneurons. Quantitative analysis of a complete series of ultrathin sections through one of the neurons showed that the synaptic covering on the cell body (24.2%) was considerably larger than what has been reported for triceps surae gamma-motoneurons, but within the range of values for gamma-motoneurons in the thoracic region of the spinal cord.

Animals↗
PubMed1986

Electron microscopic observations on recurrent axon collateral boutons of a triceps surae gamma-motoneuron in the cat.

Boutons from the recurrent axon collaterals of an adult cat gastrocnemius gamma-motoneuron were studied after intracellular labelling with horseradish peroxidase (HRP). Light and electron microscopic observations revealed that the studied gamma-motoneuron possessed 6 dendrites with 39 dendritic end branches totally and that its axon gave off two axon collaterals with together 8 synaptic boutons of either en passant or terminal type. Both collateral trees were confined to the ventral part of lamina VII. Four of the synaptic boutons were studied electron microscopically. They were all found to be S-type boutons containing spherical vesicles. In two cases the bouton could be further subclassified as a type T bouton. All of the studied boutons made synaptic contact with thin dendrites of unknown origin.

Animals↗
PubMed1985

'Dendraxons' in regenerating motoneurons in the cat: do dendrites generate new axons after central axotomy?

The intramedullary portions of motor axons in the spinal cord of adult cats were divided by longitudinal incisions in the ventral funiculus. After 7-11 weeks ventral horn neurons were injected intracellularly with horseradish peroxidase. Regenerating processes of the injected cells were studied with light- and electron-microscopical techniques. The results show that in some cases more than one axon-like myelinated regenerating process was found in a single neuron. Moreover, in such cases at least one of the processes seemed to be of dendritic origin.

Animals↗
PubMed1985

Dimensions and branching patterns of triceps surae alpha-motor axons and their recurrent axon collaterals in the spinal cord during the postnatal development of the cat.

Triceps surae alpha motoneurons in the cat were stained intracellularly with horseradish peroxidase (HRP) at different postnatal ages from birth to the adult stage. The motor axons and axon collaterals were studied with regard to length, diameter and branching pattern. The postnatal increase of internodal length, measured as the distance between two subsequent axon collateral origins, was about 100% which paralleled the total length increase of the main axon in the grey matter. The axon collaterals were unmyelinated at birth and branched exclusively dichotomously until after 3 weeks of age when a substantial fraction of the branching points gave off 3-5 daughter branches. This was interpreted as signs of a fusion between neighboring branching points during the period of myelination of the axon collaterals. The length analysis of the collaterals indicated that the postnatal elimination of collateral branches described previously is preferentially located in the distal parts of the collateral tree.

Animals↗
PubMed1985

Postnatal changes in the termination pattern of recurrent axon collaterals of triceps surae alpha-motoneurons in the cat.

alpha-Motoneurons innervating the triceps surae and short plantar muscles were stained intracellularly with horseradish peroxidase (HRP) in 0-44-day-old kittens and adult cats. The terminal arborizations of the recurrent axon collaterals in the spinal cord were studied in the light microscope (LM). The short plantar motoneurons lacked axon collaterals in all age groups. With a few exceptions in the youngest kittens (0-1 days of age), the projection field of the axon collaterals of triceps surae motoneurons did not change during development. The exceptional motoneurons had axon collaterals projecting ventromedial to the adult termination areas in Rexed's laminae VII and IX. Within all parts of the projection field, there was a substantial postnatal reduction in the number of axon collateral swellings, interpreted as synaptic terminals, and a total elimination of short and thin axonal processes without swellings. The findings are discussed in relation to earlier demonstrated loss of synaptic terminals on the motoneurons and elimination of polyneuronal innervation of muscle fibers postnatally.

Animals↗
PubMed1984

Direct monosynaptic contacts between type-identified alpha-motoneurons in the cat.

We have examined, at the light microscope level, putative direct synaptic interconnections, via motor axon collaterals, between type-identified triceps surae alpha-motoneurons labeled by intracellular injection of HRP. The results indicate that monosynaptic recurrent contacts can occur between synergist motoneurons (in this case, medial gastrocnemius to soleus, and vice versa), irrespective of motor unit type (type FF to type S, and vice versa).

Animals↗
PubMed1984

Invasion of the L7 ventral root and spinal pia mater by new axons after sciatic nerve division in kittens.

In young kittens the left sciatic nerve was divided followed by nerve suture, distal stump resection, or resection combined with proximal stump capping. The kittens were killed 2 to 3 months postoperatively. In other kittens bilateral L7 ventral rhizotomy or neuroma excision was carried out 80 to 90 days after nerve resection, followed by killing a few days later. Thin sections from the ventral root L7 were examined in the electron microscope. In all animals the average proportion of ventral root unmyelinated axon profiles (UAP) was above normal on the operated side, being highest in capped and resected animals and lower in sutured cases. The proportion of UAP was inversely related to the extent of functional calf muscle reinnervation. In cases with high proportions of UAP, numerous bundles of unmyelinated and small myelinated axons were present in juxtamedullary root fascicles and surrounding pia mater. After L7 ventral rhizotomy in resected animals few intact UAP occurred together with numerous signs of axon degeneration in the proximal root stump on the lesion side. After neuroma excision the proportion of ventral root UAP decreased. Therefore some proportion of the new axons should represent recurrent sprouts from peripheral sources.

Animals↗
PubMed1984

Conduction velocities of nerve fibers proximal to muscle nerve transection in kittens and adult cats.

The nerves to the medial gastrocnemius muscle (MG) and to the soleus muscle (S) were transected unilaterally, close to the muscles, in young kittens and in adult cats. About 1 year postoperatively, conduction velocities of the fastest efferent and afferent fibers were assessed above the lesion in those cut nerves, which showed signs of an appropriate muscular reinnervation. The velocities were found to be subnormal in animals operated as kittens but normal in animals operated as adults.

Animals↗
PubMed1983

Reinnervation of the ventral root L7 from ventral horn neurons following intramedullary axotomy in adult cats.

Through small longitudinal incisions in the ventral funiculus of the adult cat spinal cord the intramedullary portions of motoraxons forming the L7 ventral root were divided. The animals were sacrificed by glutaraldehyde-perfusion 1-15 weeks postoperatively. In some cases this was preceded by HRP injection into large L7 ventral horn neurons. Sections from the lesioned ventral funiculus and the denervated ventral root L7 were examined by light and electron microscopy. During the first postoperative month increasing numbers of unmyelinated and thinly myelinated large-diameter axons coursed through the lesion and entered the denervated ventral root. Occasional neuroma-like formations were also found in the lesion area. After 5 weeks survival clusters of regenerating axons reached the distal end of the L7 ventral root. Light microscopic examination of Vibratome sections from HRP-injected animals showed that at least some regenerated axons come from large neurons, presumably alpha-motoneurons, in the ventral horn motor nuclei. Most of the examined labeled regenerated axons reached the CNS/PNS junction of the ventral root but a few followed a grossly aberrant course and/or terminated within the lesion. These observations show that regeneration of large-diameter axons through a CNS-lesion is possible. Both the intrinsic regenerative capacity of the axotomized neurons and the presence of a denervated ventral root in the immediate vicinity are likely to be contributing factors with respect to this example of successful CNS axon regeneration.

Animals↗
PubMed1983

Electron microscopic observations on the synaptic contacts of group Ia muscle spindle afferents in the cat lumbosacral spinal cord.

After intra-axonal injection of horseradish peroxidase (HRP) into afferent fibers originating from muscle spindle primary endings of the cat gastrocnemius, group Ia boutons located in the ventral horn of the spinal cord were identified and studied electron microscopically. The Ia boutons were invariably found to contain spherical synaptic vesicles (S-type boutons), and a number of them were also postsynaptic to smaller P-type boutons (large S-type boutons with axo-axonic contacts). None of the present Ia-boutons belonged to the previously described M-type. The vast majority of the studied boutons were considered to be located at less than 500 microns distance from the alpha-motoneuron soma. The results are discussed in relation to previous light and electron microscopic data.

Animals↗
PubMed1982

Observations on the morphology and the axon conduction velocity of axotomized and regenerating sciatic motoneurons in the kitten.

In 1 week old kittens a 10 mm long segment of the sciatic nerve was removed distal to the hamstring branch point. After 70-85 days sciatic motoneurons were injected intracellularly with horseradish peroxidase (HRP). The cell body diameter, the summed diameter of the 1st order dendrites, the intramedullary axon diameter and the axon conduction velocity proximal to the lesion were determined in individual neurons and related to the conduction velocity of the regenerating segment of the axons. The lesioned neurons were compared with normal sciatic motoneurons in 7-8 and 77-92 days old kittens. In motoneurons which seemed to lack regenerating axons or had regenerating axon segments with a low conduction velocity there was a clear growth retardation of all studied parameters. In those neurons, however, which had regenerating axon segments conducting faster than 10 m/s, all parameters above the lesion, except for the conduction velocity of the axon, had attained normal values. The intramedullary part of the axon seemed to be less affected by the injury than all other studied parts of the neuron proximal to the lesion.

Animals↗
PubMed1982

Evidence for a postnatal elimination of terminal arborizations and synaptic boutons of recurrent motor axon collaterals in the cat.

Triceps surae alpha motoneurons in cats of different postnatal ages were stained intracellularly with horseradish peroxidase (HRP). The recurrent axon collateral trees of the neurons were studied light microscopically. A large reduction of the number of axon collateral end branches and swellings, interpreted as synaptic boutons, was found to occur during the first two weeks of postnatal life.

Aging↗