Biomedical subjects

F Walberg

Publications and source records attributed to F Walberg.

At least 37 records · Page 2Linked to original sources

PubMed1985

The cerebellar nucleo-olivary and olivo-cerebellar nuclear projections in the cat as studied with anterograde and retrograde transport in the same animal after implantation of crystalline WGA-HRP. II. The fastigial nucleus.

The bidirectional connections between the inferior olive and the fastigial nucleus were studied by means of anterograde and retrograde transport after implantation of crystalline wheat germ agglutinin-horseradish peroxidase (WGA-HRP) complex into the fastigial nucleus. The fastigio-olivary fibres terminate in the caudal half of the medial accessory olive, nucleus beta and the dorsal cap, and the olivo-fastigial projection has its origin within the same olivary regions. A topical arrangement is indicated for both pathways. The lateral part of the medial accessory olive appears to be connected with the lateral part of the fastigial nucleus, while the medial part of the medial accessory olive appears to be connected with more medial fastigial regions. Retrogradely labelled olivo-fastigial neurons were often located within the terminal field of anterogradely labelled fastigio-olivary fibres, indicating that the olivo-fastigial and fastigio-olivary projections are at least in part reciprocally organized. The findings are discussed and related to previous studies on the olivo-cerebellar nuclear and cerebellar nucleo-olivary pathways. Some methodological considerations are made, and comments are made concerning the active area for uptake and transport from the stained area at the WGA-HRP injection site.

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PubMed1985

A projection from the periaqueductal grey to the lateral reticular nucleus in the cat.

A projection from the periaqueductal grey (PAG) to the lateral reticular nucleus (NRL) in the cat was demonstrated by means of retrograde transport of the wheat germ agglutinin-horseradish peroxidase complex. The connection has its main origin ipsilaterally in the ventral part of the caudal PAG, but scanty projections from other parts of the PAG were also found. The neurons projecting to the NRL are of varying shapes and sizes, but most cells have a maximum diameter of less than 20 micron. The findings are discussed in relation to the other afferent and efferent connections of the NRL.

Afferent Pathways↗

PubMed1985

The cerebellar nucleo-olivary and olivo-cerebellar nuclear projections in the cat as studied with anterograde and retrograde transport in the same animal after implantation of crystalline WGA-HRP. I. The dentate nucleus.

The implantation technique described by Mori et al. has been modified for the implantation of crystalline wheat germ agglutinin-horseradish peroxidase (WGA-HRP) complex. This method permits a detailed analysis of the afferent and efferent connections of the cerebellar nuclei without the complication of uptake and transport of the tracer into passing fibres. We have used this method for studies of the olivo-dentate and dentato-olivary projections in the cat. After implantation of WGA-HRP into the dentate nucleus in all our cases, both anterogradely labelled terminal dentato-olivary fibres and retrogradely labelled olivo-dentate neurons were found in the contralateral inferior olive. It appears from our findings that both projections are topically organized. The dorsal part of dentate nucleus is bidirectionally connected with the rostral part of the principal olive, the ventrolateral part of the dentate is connected with the intermediate portion of the principal olive, while its ventromedial part is connected with the caudal portion of the principal olive. The olivo-dentate and dentato-olivary connections appear to be largely reciprocally organized. The advantages and drawbacks encountered with implantation of crystalline WGA-HRP are discussed, and our observations are considered in relation to previous studies on the olivo-cerebellar and cerebello-olivary connections.

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PubMed1984

On the morphology of the mesencephalic trigeminal cells. New data based on tracer studies.

Injections of free horseradish peroxidase in the masticatory muscles of the cat resulted in retrograde labeling of not only large and small so-called pseudounipolar cells but also of multipolar neurons within the ipsilateral mesencephalic trigeminal nucleus. The latter cell type was present only in the pontine part of the nucleus, and usually more faintly labeled than the other cells. Several of the so-called pseudounipolar cells showed cell processes similar to dendrites of other cells, a finding indicating that the afferent connections of these cells are much more complex than hitherto assumed. The observations are discussed also with reference to the problem whether the multipolar cells should be considered as displaced locus coeruleus neurons.

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PubMed1984

The medullary projection from the mesencephalic trigeminal nucleus. An experimental study with comments on the intrinsic trigeminal connections.

The medullary projection from the mesencephalic trigeminal nucleus has been studied in cats where the wheat germ agglutinin-horseradish peroxidase complex has been used as a retrograde and anterograde tracer. All injections were made at the level of the caudal pole of the inferior olive and show that it is especially the lateral part of nucleus parvicellularis of the reticular formation which is the main area for termination of the fibres. In addition, it can not be excluded that the descending fibres also reach the medialmost part of the spinal trigeminal sensory nucleus (pars magnocellularis and the adjoining pars gelatinosa). All three cell types of the mesencephalic trigeminal nucleus are labelled, the large globular, the small globular and the polygonal cells. Some of these cells are only faintly labelled. The observations confirm previous studies of the intrinsic trigeminal connections, but show that when the wheat germ agglutinin-horseradish peroxidase complex is used as a tracer, the origin as well as the termination for the intrinsic fibres (also the commissural) can be studied in the same section. The use of this sensitive tracer also shows new details within the intrinsic connections. The findings are discussed with special reference to the recent observations by Ruggiero et al. (1982). These authors found that in rabbit and rat there is a more restricted termination for the descending mesencephalic trigeminal fibres. The discrepancies between the observations seem to indicate that there are species differences as regards the connections between the mesencephalic trigeminal nucleus and the nuclei in the lower part of the brain stem.

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PubMed1984

An ipsilateral projection from the red nucleus to the lateral reticular nucleus in the cat.

Injections of the wheat germ agglutinin--horseradish peroxidase complex into the lateral reticular nucleus reveal that in addition to the well known contralateral rubroreticular connection, there is also a small but clear cut ipsilateral projection. Cells of various sizes participate in this ipsilateral pathway, and the retrogradely labelled neurons lie dispersed throughout the entire red nucleus.

Animals↗

PubMed1983

Is lectin-coupled horseradish peroxidase taken up and transported by undamaged as well as by damaged fibers in the central nervous system?

Uptake and transport of horseradish peroxidase-wheat germ agglutinin conjugate (HRP-WGA) in intact and damaged passing fibers were studied by injections of the medulla and pons in 11 cats. Injections with evidence of damage to olivocerebellar fibers and cranial nerve fibers invariably lead to retrograde labeling of neurons in the inferior olive and cranial motor nuclei. With staining around--but apparently no damage of--cranial nerve root fibers, no labeling was found in their motor nuclei. Injections limited to the medullary pyramid with slight fiber damage and limited staining lead to faint retrograde labeling of a small number of cells in the ipsilateral sensorimotor cortex. More extensive staining and fiber damage of the pyramid gave a higher number of labeled cells in the ipsilateral sensorimotor cortex. From these experiments we conclude that HRP-WGA is taken up and transported retrogradely with subsequent significant cell labeling in damaged but not in intact fibers. Anterograde transport of HRP-WGA in fibers passing through the injected area was found to take place only for a very short distance, as judged from cases with injections of either the pons or the medullary pyramid interrupting many corticospinal fibers.

Animals↗

PubMed1983

Cerebellar cortical afferents from the red nucleus in the cat.

A crossed projection from the red nucleus to the cerebellar cortex in the cat has been demonstrated by means of retrograde transport of the wheat germ agglutinin-horseradish peroxidase complex. The majority of projecting neurons are situated in the rostral part of the red nucleus and have a maximum diameter of more than 20 microns. The findings indicate that rubrocerebellar fibers terminate in intermediate parts of the anterior and posterior cerebellar cortical lobes.

Afferent Pathways↗

PubMed1983

The cerebellar corticovestibular projection in the cat as studied with retrograde transport of horseradish peroxidase.

The cerebellar corticovestibular projection in the cat was studied by means of retrograde transport of HRP. After injections confined to the vestibular nuclei retrogradely labelled Purkinje cells were found ipsilaterally in vermal lobules I through X, crus I, the ventral paraflocculus and flocculus. The neurons projecting to the vestibular nuclei are located in all parts of the cerebellar folia (bottom, side and top). Most of the vestibular projecting Purkinje cells are located within a sagittal band (corresponding to Voogd's B zone) in the lateral vermis. In some of our cats the width of this band exceeds 1 mm in lobule I, 800 microns in lobule II and 1.5 mm in lobule V. However, the sagittal band is not sharply demarcated, and some retrogradely labelled Purkinje cells were present almost in the midline while others were located more than 4 mm lateral to this. The findings are discussed with special emphasis on the cerebellar sagittal zonal arrangement and related to previous studies on the cerebellar corticovestibular projection.

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PubMed1983

A projection from the raphe nuclei to the lateral reticular nucleus in the cat.

By means of retrograde transport of the wheat germ agglutinin-horseradish peroxidase complex afferent fibres to the lateral reticular nucleus from the raphe nuclei were demonstrated in the cat. The projection is bilateral and has its main origin in nucleus raphe pallidus and magnus, but there appear to be contributions also from nucleus raphe obscurus, dorsalis and linearis rostralis.

Afferent Pathways↗

PubMed1982

Cerebellar afferent fibres from the dorsal motor vagal nucleus in the cat.

A bilateral cerebellar afferent projection from the dorsal motor vagal nucleus is described after injections of horseradish peroxidase in various parts of the cerebellar cortex and nuclei. The projection is scanty, but a topical arrangement is indicated: the rostral part of the dorsal motor vagal nucleus appears to project mainly to the cortex of the posterior lobe, the caudal part mainly to the cortex of the anterior lobe, and the fibres appear to reach also the fastigial and anterior interposite nuclei.

Afferent Pathways↗

PubMed1982

A re-evaluation of the question of ascending fibers in the pyramidal tract.

In 1952 we published a study in the cat with the Glees method, demonstrating the occurrence of degenerating fibers in the pyramidal tract rostral to transections of the tract in the spinal cord. These fibers were interpreted as spinocortical fibers, which have also been described in man. However, other authors have disputed the existence of such fibers. In an attempt to provide more information about this subject, multiple injections of horseradish peroxidase (free and lectin-labeled) were made in the sensorimotor cortex of 4 cats. No retrogradely labeled cells were found in the spinal cord in these cases. Our present and previously reported findings are discussed in the light of other studies of pathological changes in fiber tracts within the central nervous system. Although the present experiments were negative, the degenerating axons previously observed by us in silver sections from the pyramid, pons and internal capsule after lesions of the pyramidal tract in the spinal cord, can not be satisfactorily explained as evidence of retrograde, indirect Wallerian, degeneration of corticospinal fibers.

Animals↗

PubMed1982

The trigemino-olivary projection in the cat as studied with retrograde transport of horseradish peroxidase.

The trigemino-olivary projection was studied in cats which from a ventral approach were injected with horseradish peroxidase into various parts of the inferior olive. Retrogradely labelled cells of all sizes were present in all three divisions of the spinal sensory nucleus: nucleus caudalis, nucleus interpolaris and nucleus oralis. The projection is bilateral with the highest number of labelled cells on the contralateral side. No retrogradely labelled cells are found in the principal nucleus, but some cats showed a few retrogradely labelled cells within the ipsilateral mesencephalic nucleus. The findings are discussed and related to recent observations concerning the distribution of the direct trigemino-cerebellar fibres.

Afferent Pathways↗

PubMed1982

Olivary afferents from the brain stem reticular formation.

The projections from the brain stem reticular formation to the inferior olive have been studied in cats in which microinjections of horseradish peroxidase have been made into the inferior olive from a ventral approach. Retrogradely labelled cells were observed within the reticular formation proper of the medulla, pons and mesencephalon (within the nucleus reticularis parvicellularis, reticularis ventralis, reticularis gigantocellularis, reticularis lateralis, reticularis pontis caudalis, reticularis pontis oralis, cuneiformis and subcuneiformis). Labelled cells were also found within the lateral reticular nucleus (the nucleus of the lateral funiculus), the paramedian reticular and the perihypoglossal nuclei. The connections are bilateral (the projection from the lateral reticular nucleus is only contralateral). The observations demonstrate a more widespread origin for the reticulo-olivary fibres than has previously been shown and indicate that the medullary reticular formation is the area with the highest number of cells projecting to the olivary complex.

Afferent Pathways↗

PubMed1982

Olivary afferents from the raphe nuclei as studied with retrograde transport of horseradish peroxidase.

The afferent projection to the olive from the raphe nuclei in the cat has been studied in animals where microinjections of horseradish peroxidase have been made into the inferior olive from a ventral approach. Retrogradely labelled cells were present in the three caudal most raphe nuclei: the nucleus raphe pallidus, obscurus and magnus. The retrogradely labelled cells are of all sizes, and there appears to be a higher concentration of cells on the side ipsilateral to the injection. The observations demonstrate that all three major subdivisions of the olive--the medial accessory, the dorsal accessory and the principal olive--all receive efferent raphe fibres. No retrogradely labelled cells were present in the other raphe nuclei. The findings are discussed and related to other tracer studies dealing with olivary afferents from the raphe complex.

Animals↗

PubMed1982

The origin of olivary afferents from the central grey and its surroundings in the cat.

The olivary afferents from the mesencephalic central grey and its surroundings have been studied in cats in which microinjections of horseradish peroxidase have been made into the inferior olive from a ventral approach. Retrogradely labelled cells are present in the ventral part of the central grey, the nucleus of Darkschewitsch (especially its ventral part), the Edinger-Westphal nucleus, the interstitial nucleus of Cajal and the reticular formation between the red nucleus and the central grey. The projection is ipsilateral and the heaviest contribution of afferents is derived from the interstitial nucleus of Cajal. The findings indicate that the afferents from the mesencephalic reticular formation to the inferior olive probably are collaterals of fibres terminating dorsally to the olive or passing to the spinal cord. The observations are discussed and related to previous experimental studies in the cat.

Animals↗

PubMed1981

On retro- and anterograde transport of horseradish peroxidase in the pontocerebellar fibers as studied with the Mesulam TMB technique.

In cats where injections of HRP have been made in the cerebellar cortex, pontocerebellar fibers are visualized throughout their length. Likewise, injections of HRP into the pontine nuclei visualize the pontocerebellar fibers and these anterogradely stained axons can in fortunate sections be followed into the granular layer. A visualization of retrogradely filled pontocerebellar fibers was unexpected and its another example of the sensitivity of the Mesulam8 technique.

Afferent Pathways↗

PubMed1981

Olivary afferents from the pretectal nuclei in the cat.

The organization of the projection from the pretectal region to the inferior olive in the cat was studied by means of retrograde protein tracing and experimental degeneration. Small injections of horseradish peroxidase (HRP) were made into various parts of the inferior olive from a ventral approach. The number of nerve cells in the pretectal nuclei retrogradely labelled with HRP was counted and put in relation to the site of injection. Labelled cells were only found in the posterior pretectal nucleus (NPP), the nucleus of the optic tract (NOT) and the anterior pretectal nucleus (NPA). Most labelled cells were found in NPP and NOT in cases in which the rostral or caudal levels of the principal olive were labelled by the injection. NAP labelling occurred in one case with a very rostral injection of the inferior olive. Unilateral electrolytical destruction of the pretectal region produced terminal degeneration in the ipsilateral inferior olive. The heaviest ipsilateral degeneration was found in the upper half of the principal and dorsal accessory olives, and caudally in the ventrolateral outgrowth, the dorsal cap and nucleus beta with the adjacent part of the medial accessory olive. Some functional implications of the findings are discussed.

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