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Biomedical subjects

B Ulfhake

Publications and source records attributed to B Ulfhake.

At least 73 records · Page 4Linked to original sources
PubMed1989

Altered levels of calcitonin gene-related peptide (CGRP)-like immunoreactivity of cat lumbar motoneurons after chronic spinal cord transection.

In cats subjected to total spinal cord transection at the lower thoracic level, the calcitonin gene-related peptide (CGRP)-like immunoreactivity (LI) was studied in motoneuron cell bodies in the L6-L7 segments. In transected animals, the CGRP-immunoreactive labeling of the motoneurons was virtually absent. When combining the spinal cord transection with a unilateral rhizotomy of all dorsal roots below the transection, however, an apparently normal labelling pattern of CGRP-LI of the motoneurons was displayed on both sides. Thus, surgical interventions which affect afferent pathways to the motoneurons may have influence on the levels of CGRP-LI in otherwise intact motoneurons.

Animals↗
PubMed1989

Motoneurons reinnervate skeletal muscle after ventral root implantation into the spinal cord of the cat.

By use of intracellular recording and staining with horseradish peroxidase it was found that alpha and probably also gamma motoneurons were able to reinnervate ventral root implants after an avulsion of ventral roots at the spinal cord surface in the cat. The reinnervation of the implant was achieved after an initial growth of new axons in central nervous system tissue. Reinnervating neurons could be excited or inhibited by segmental reflex activity and their axons could conduct nerve impulses. The character of muscle twitch responses elicited by electrical stimulation of implanted roots strongly indicated that denervated muscles were reinnervated by new motor axons via the implant.

Action Potentials↗
PubMed1989

Nerve fibre regeneration across the PNS-CNS interface at the root-spinal cord junction.

Root-spinal cord regeneration was investigated in immature and adult rats. The elongation in the dorsal root of regrowing dorsal root axons, rerouted ventral root nerve fibres (cholinergic neurons) or hypogastric nerve fibres (catecholaminergic neurons) is impeded as they meet the astrocyte dominated CNS tissue of the root. The establishment of synaptoid nerve terminals as the regrowing axons encounter astrocytes indicates a mechanism for growth inhibition other than a physical impediment in the CNS environment. The glial cells of the CNS segment in the root are influenced by the type of regenerating nerve fibres in terms of maintenance, multiplication and phenotypic expression. After a dorsal root lesion in the neonatal rat several root axons may reinnervate the spinal cord. In these rats, the normal establishment of a CNS root segment has been disrupted and the PNS-CNS border is situated central to the root-spinal cord junction. Implantation of cut dorsal roots into the spinal cord of adult rats results in the extension of processes from intrinsic spinal cord neurons out into the root. After implantation of avulsed ventral roots into the ventro-lateral aspect of the cord, axonal regrowth and functional restitution of alpha-motoneurons could be demonstrated by intracellular recordings and injections with horseradish peroxidase. These results show that regeneration can occur across a PNS-CNS interface that has been established secondary to a trauma in the mature animal and in the immature animal before the astrocyte-rich CNS root segment has been developed.

Age Factors↗
PubMed1989

Distribution of TRH-like immunoreactivity with special reference to coexistence with other neuroactive compounds.

During the last years, several important advancements have been made that are of importance for our understanding of the distribution and localization of neurons and cells producing TRH-LI. As detailed in other chapters in this volume, the precursor for TRH has been characterized that has allowed production of antibodies raised against specific sequences of this precursor. This, in turn, has provided new tools for the immunohistochemical elucidation of TRH systems in the CNS. The TRH precursor has also been cloned, leading to possibilities for studying the localization of TRH mRNA with in situ hybridization. Finally, as shown in this paper, improvement of the fixation technique has made it possible to visualize extensive TRH-immunoreactive cell body and fiber systems with antiserum raised against the TRH tripeptide. The results from the latter studies and those with antisera directed to the TRH precursor and in situ hybridization are in good agreement, with some minor exceptions. It should be pointed out that some of the systems described here, for example TRH positive-cell bodies in cortical areas and the hippocampal formation, contain only a very weak immunoreactivity. As always with immunohistochemical techniques, the possibility of crossreactivity with TRH-like peptides or TRH-like sequences within larger proteins must be considered. The present results confirm the presence of TRH-LI in the insulin-producing beta cells of the pancreas, which with the improved technique can be demonstrated also in early adulthood in rats and guinea pigs. Moreover, it could be established that TRH-LI is present in neurons in the gastrointestinal tract as well as in a population of endocrine cells in the antrum of the stomach of the guinea pig. These cells seem at least partly to be identical to the well-known gastrin-producing cells. TRH-LI has been observed to occur in neurons already containing a classical transmitter and/or other peptides. Of particular importance here seems to be a descending bulbospinal system that in addition to TRH co-contains 5-HT, substance P-LI, galanin-LI, human growth hormone immunoreactive material, and proctolin-like material. The significance of this coexistence is not well understood, but interesting interactions have been observed. Attempts to manipulate the TRH phenotype in these medullary neurons by transplantation to other sites in the brain has so far shown that the expression of this peptide seems fairly stable.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Postnatal development of cat hind limb motoneurons. I: Changes in length, branching structure, and spatial distribution of dendrites of cat triceps surae motoneurons.

The postnatal development of length, branching structure, and spatial distribution of dendrites of triceps surae motoneurons, intracellularly stained with horseradish peroxidase, was studied from birth up to 44-46 days of postnatal (d.p.n.) age in kittens and compared with corresponding data from adult cats. The number of dendrites of a triceps surae motoneuron was about 12, and the arborization of each dendrite generated an average of 12-15 terminal branches. There was no net change in the number of dendrites of a neuron or in the degree of branching of the dendrites despite the occurrence of both a transient remodeling of the dendritic branching structure and changes of the spatial distribution of the dendritic branches during postnatal development. The perisomatic territory in the transverse plane occupied by the dendritic branches of a motoneuron increased in parallel with the overall growth of the spinal cord. Thus, the relative size of the dendritic territory in this plane was kept almost constant, whereas dendritic branches projecting in the rostrocaudal direction grew much faster than the spinal cord and also became more numerous. At birth the rostro-caudal dendritic span of individual motoneurons bridged 1:6 to 1:5 of the L7 spinal cord segment length; this figure was 1:3 at 22-24 d.p.n. Hence, in this direction, the growing dendritic branches invaded novel dendritic territories. The change in dendritic branch length from birth to 6 weeks of age corresponded to an average growth rate of 2 to 4 microns per dendritic branch and day, which implies that the total increase in length of the dendrites of a neuron could amount to 1 mm/day. The increase in branch length did not occur in a uniform or random manner; instead, it followed a spatiotemporal pattern with three phases: From birth to 22-24 d.p.n., growth was particularly prominent in greater than or equal to 3rd order preterminal and 2nd through 6th order terminal branches. From 22-24 to 44-46 d.p.n., a large increase in branch length confined to terminal branches of greater than or equal to 3rd branch orders was observed. As indicated by topological analysis, this length increase was probably due in part to a resorption of peripheral dendritic branches during this stage of development. From 44-46 d.p.n. to maturity, the increase of dendritic branch length was restricted to preterminal branches of low (less than or equal to 4th) branch order.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Postnatal development of cat hind limb motoneurons. II: In vivo morphology of dendritic growth cones and the maturation of dendrite morphology.

The maturation of dendrite morphology was studied by light and electron microscopy in cat spinal alpha-motoneurons intracellularly labeled with horseradish peroxidase. Alpha-motoneurons supplying the triceps surae (TS) and the intrinsic foot sole (SP) muscles were investigated in kittens from birth to 44-46 days of postnatal (d.p.n.) age. At birth, a large number of dendritic branches displayed growth cones, filopodia, and fusiform processes. The growth cones were of lamellipodial and filopodial types, but intermediate forms also occurred. The growth cones shared several morphological features with the neuritic growth cones studied in vitro. It was suggested that the occurrence of different types of growth cones--even in the same dendrite--may reflect their transformation from one type to the other and the level of growth activity could be inferred from the number and form of the growth cones. About 50-70% of the terminal branches in the dendrites of newborn kittens possessed growth cones, filopodia, and/or fusiform processes. The corresponding figure for preterminal branches was 20-30%, with a clear decrease in incidence when approaching the soma. During the period under study, most of these growth-associated processes disappeared from the dendrites so that at 44-46 d.p.n. of age only about 10% of the terminal and less than 1% of the preterminal branches had growth-associated processes. Analysis of the three-dimensional distribution of dendritic branches with such processes disclosed that they were relatively more frequent in the medial, rostral, and caudal dendritic territories. It was concluded that the pattern of distribution and disappearance of growth cones, filopodia, and fusiform processes coincided with postnatal longitudinal dendritic growth and the development of the adult dendritic territories described in a preceding paper (Ulfhake et al., '88). Dendritic growth, with respect to length and caliber, also occurred in the absence of growth cones and filopodia. It is suggested that the important role of these processes may be to act as a steering device in establishing the adult distribution and synaptology of the dendrites. Comparison of TS and SP alpha-motoneuron dendrite morphology at birth and at 22-24 d.p.n. age showed that the SP neurons lagged in the maturation process. Light and electron microscopic observations indicated that postnatally direct contacts might exist between dendrites and fine blood vessels in the neuropil without any interposing glial sheath. The number of such suspected contacts diminished during the period under study, indicating that the glial ensheathment of the blood vessel takes place, in part, postnatally.

Animals↗
PubMed1988

Postnatal development of cat hind limb motoneurons. III: Changes in size of motoneurons supplying the triceps surae muscle.

The postnatal changes of neuronal dimensions were studied in cat triceps surae motoneurons intracellularly labeled with horseradish peroxidase. Systematic correlations were observed in the analysis of single dendrites at each studied stage, from birth to 44-46 days post natum (d.p.n.) age, between size parameters intrinsic to the dendrites as the diameter of a 1st-order dendrite, the combined dendritic length, the dendritic membrane area, and the degree of branching. Some variability among samples was evident in each studied age group. The correlations were, however, sufficiently close to permit indirect estimations of both combined dendritic length and dendritic membrane area for larger samples of neurons from data on dendritic stem caliber. The total postnatal increase in dendritic membrane area was, on the average, 400%, i.e., from close to 100 X 10(3) microns2 to about 500 X 10(3) microns2. The corresponding increase in soma area amounted to 100%. Analysis revealed that there was a time lag between the increase in somatic and dendritic size. Thus, adult somatic dimensions were attained at age 44-46 d.p.n.; however, at this stage, the mean total dendritic membrane area was only about half of the adult value. The postnatal increase in size appeared to vary among neurons, yielding a wider neuronal size spectrum in the adult cat than that observed in kittens. The measured increase in size corresponded to a calculated average addition of dendritic membrane area of 3700 microns2/day from birth to 22-24 d.p.n. and from that stage to 44-46 d.p.n. of 2700 microns2 per day. Likewise, the increase in combined dendritic length could initially be as large as 1 mm/day down to 0.4 mm/day between 22-24 and 44-46 d.p.n., with a mean growth during the first 44-46 d.p.n. of 0.5 to 0.6 mm/day. The ratios of daughters to parent branch diameters (sigmadd1.5: dp1.5) and the dendritic trunk parameter (sigma d1.5) recorded along the proximodistal dendritic path distance revealed transient changes that might impact on the electrotonic properties of the dendrites during postnatal development. Computations from the measured changes in dendritic branch lengths and calibers indicated that if membrane and internal resistivity remain unaltered during postnatal development, the dendritic domain is electrotonically more compact in the newborn kitten than in the adult cat.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

The effects of tenotomy and overload on the postnatal development of muscle fibre histochemistry in the cat triceps surae.

Five to seven day-old kittens were subjected to partial tenotomy of the Achilles (triceps surae) tendon. The effects of tenotomy and overload on the development of muscle fibre histochemistry and fibre sizes were investigated when the cats had reached the adult stage. The examined muscles were the uniform soleus and the mixed medial gastrocnemius. Tenotomized muscles of both types had lower weights than their controls. Tenotomized soleus showed a redistribution of succinic dehydrogenase (SDH) activity, together with signs of muscle fibre death. Tenotomized medial gastrocnemius muscles displayed more severe degenerative signs than the soleus, together with signs of fibre death. The fibre death seemed to affect mainly fibres of type IIb. Moreover, a less distinct differentiation in histochemical staining pattern between muscle fibre types was found in these muscles. Overloaded soleus muscles had greater weights than their controls, while no difference could be shown for the overloaded medial gastrocnemius. The overloaded medial gastrocnemius showed a uniform hypertrophy of all fibre types. Also, overloaded soleus showed a uniform hypertrophy. Both types of muscle showed a normal histology as well as normal staining characteristics (SDH and AcATPase). It is concluded that both soleus and medial gastrocnemius are sensitive to loss of muscle tension during development. The basic features of muscle morphology and histochemistry were normal, though, and it is suggested that other factors account for most of the normally occurring development and differentiation.

Achilles Tendon↗
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

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↗
PubMed1987

Ultrastructural observations on beaded alpha-motoneuron dendrites.

Beaded dendrites of alpha-motoneurons intracellularly labelled with horseradish peroxidase (HRP) were studied ultrastructurally in eight adult cats. For comparison, adjacent unlabelled beaded dendrites of unknown origin were also included in the study. Electron microscopy revealed no signs of degeneration or poor fixation according to common criteria. With the exception of the HRP-reaction product no difference in structure was observed between labelled and unlabelled beaded dendrites. Both the beads and their interconnecting segments were postsynaptic to boutons of normal appearance containing spherical (S-type boutons) or flattened vesicles (F-type boutons). The values for synaptic covering and synaptic packing density of the beaded dendritic regions, which usually were located in the periphery of the dendritic trees, were clearly lower than values obtained previously for cell bodies and proximal dendrites of alpha-motoneurons.

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↗
PubMed1986

The effects of tenotomy and compensatory hypertrophy on the postnatal development of soleus motor units in the cat.

Kittens, 5-7 days old, were subjected to tenotomy of either the soleus muscle or all its Achilles tendon synergists. When the cats had reached the adult stage, the physiological properties of the soleus motor units were investigated in both the atrophic and hypertrophic situations. Tenotomy resulted in a marked muscle weight loss and overload due to tenotomy of synergists in a marked gain in muscle weight compared to the contralateral side. The motor units of the tenotomized soleus muscles exhibited a moderate shortening of the twitch contraction time, and also a change in twitch shape, related to the degree of atrophy. In the motor units of the hypertrophic soleus muscles, an increased fatiguability could be demonstrated. Further, in this group, there was a tendency towards differentiation of the normally uniform motor units into two groups with different features. The functional implications of this process are discussed. The development of motor units in both the tenotomized and the hypertrophic muscles were only marginally influenced by the operations, and it is concluded that the basic features of their development are largely unaffected by the functional manipulations imposed in the present study.

Animals↗
PubMed1986

The effects of tenotomy and overload on the postnatal development of medial gastrocnemius motor units in the cat.

Five-to 7-day-old kittens were subjected to tenotomy of either the medial gastrocnemius muscle (MG) or its synergists within the Achilles tendon. The effects of these operations on the postnatal differentiation of MG motor units were investigated when the cats had reached the adult stage. The MG tenotomy produced a substantial weight loss, while tenotomy of synergists induced only a minor weight gain of the MG muscle. Tenotomy of the MG synergists induced a marked prolongation of motoneuronal AHP durations in the overloaded MG. This prolongation affected equally motoneurones of the S and F types. The twitches of the tenotomized motor unit group showed a relatively slower relaxation than those of the overloaded group. The muscle unit properties of the tenotomized MG muscles showed a less distinct differentiation than those of the overloaded muscles. The basic features of the various motor unit types were, however, normal in both groups, and there was no evidence of a major shift in the proportions of different motor unit types. It is concluded that the postnatal differentiation of all types of MG motor units is largely unaffected by the abnormal situations introduced in the present study.

Achilles Tendon↗
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↗