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C Straznicky

Publications and source records attributed to C Straznicky.

At least 73 records · Page 4Linked to original sources
PubMed1983

Aberrant retinotectal projection induced by larval unilateral enucleation in Xenopus.

The left eye was removed at late larval stages in Xenopus and the optic fibre projections of the remaining right eye assessed from 2 weeks to 13 months past metamorphosis. [3H]Proline autoradiography and electrophysiological recording of the visual field projection showed an aberrant optic fibre projection from the peripheral ventral retina to the right ipsilateral tectum. It is suggested that optic fibres, arising from the retina formed after the time of the operation, reach the ipsilateral tectum by following the axon debris of the removed eye.

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PubMed1983

The patterns of innervation and movements of ectopic hindlimb supplied by brachial spinal cord segments in the chick.

Pools of motoneurons in the ventral horn of the brachial spinal cord segments 13-16, innervating muscles of an ectopic hindlimb were mapped in chicks with the use of retrograde axoplasmic transport of horseradish peroxidase (HRP). On the third day of incubation the right wing bud of the acceptor embryo was removed and replaced by either a right or left hindlimb bud of the donor embryo. HRP was injected into selected muscles of the ectopic and intact hindlimbs as well as into muscles of the intact left wing between 17-21 days of incubation and after hatching. The position of labelled motoneuron pools representing individual muscles was determined. In 19-21 day old embryos and in hatched chicks the movement of the ectopic limbs was also studied. HRP histochemistry showed that the ectopic limb muscles of dorsal and ventral embryonic muscle mass origin were innervated by motoneurons located in the lateral and medial parts of the ventral horn, respectively. This is similar to the innervation pattern of normal wing and hindlimb muscles. Despite the ordered motor nerve supply to the ectopic limbs they failed to display any co-ordinated movements characteristic of a normal hindlimb. These observations indicate specific target affinities between pools of motoneurons in the spinal cord segments and appropriate limb muscles, even when the motoneuron pools and the limb are inappropriately matched. Nevertheless, it is evident that the 'wing-like' motor activation pattern of the brachial spinal cord segments is unable to initiate co-ordinated movements of the ectopic hindlimb.

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PubMed1983

The localization of motoneuron pools innervating wing muscles in the chick.

Motoneuron pools supplying principal muscles of the shoulder girdle and wing were localized in the chicks 2-7 days post hatching with the use of retrograde axonic transport of horse radish peroxidase (HRP). HRP was injected into selected muscles and the animals sacrificed after 24 h survival. Labelled motoneuron pools representing individual muscles were found to be clustered in longitudinal columns along the brachial spinal cord segments 13-16. Muscles derived from the dorsal muscle mass were innervated by motoneurons located in the ventro-lateral portion of the horn, while those originating from the ventral muscle mass received innervation from neurons occupying the dorsomedial portion within the ventral horn of the spinal cord. The rostrocaudal extent of the motoneuron pools could be correlated with the proximodistal position of wing muscles. The observed orderly topographical relationships between clusters of motoneurons of the brachial spinal cord and the muscles they innervate will be used as baseline data for experiments where the limb innervation is perturbed.

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PubMed1982

Peripheral and central terminations of axons of the mesencephalic trigeminal neurons in Xenopus.

Following injection into masticatory and extraocular muscles, the peripheral and central distributions of the axonic processes of mesencephalic trigeminal neurons (MTC) were studied with the aid of retrograde and anterograde transport of horseradish peroxidase. Peripheral projections included the superior rectus, inferior rectus, superior oblique and the temporalis muscles. Central axonic processes of MTC terminated in the oculomotor--trochlear nuclear complex and in the motor nucleus of the trigeminal nerve.

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PubMed1982

Retinotectal map formation in dually innervated tecta: a regeneration study in Xenopus with one compound eye following bilateral optic nerve section.

Retinotectal map formation was studied during regeneration in young adult Xenopus. Right compound double-temporal eyes (TT) were formed in tailbud stage embryos by the fusion of two temporal halves of the eye blastema in the same orbit. In other animals right compound double-nasal eyes (NN) were prepared. In both combinations the left eye was kept intact. After metamorphosis the right and left optic nerves were sectioned to induce optic fiber regeneration from each eye to both tecta. The patterns of retinotectal projections from the compound and normal eyes were studied from 37 to 364 days after optic nerve section, using electrophysiological recording of the visuotectal projections and 3H-proline autoradiographic assay from one of the two eyes. The left normal eyes projected in a retinotopic fashion, across the entire extent of the right and left dually innervated tecta. In contrast, the right compound eye projections were confined to the rostrolateral or to the caudomedial part of the right and left tecta and TT and NN animals, respectively. These tectal areas corresponded to the termination of temporal and nasal hemiretinal fibers of the normal eye. Discontinuous, interdigitating projection patterns from the right and left eyes were found in parts of the tecta where the compound and the normal eye projections overlapped. These results indicate that the normal optic fiber projections caused the originally expanded compound eye projections to be restricted to the corresponding part of the dually innervated tecta. It is suggested that the orderliness and the extent of the retinotectal map are established by the competition and interaction of optic fibers based on stable positional programming of the retinal ganglion cells.

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PubMed1982

Temporo-nasal asymmetry in the accretion of retinal ganglion cells in late larval and postmetamorphic Xenopus.

The spatial pattern of cell production and retinal growth were studied in Xenopus between stage 60 and two months after metamorphosis using 3H-proline and 3H-thymidine autoradiography. The position and the number of the ganglion cells labelled with 3H-thymidine were determined. The area of the unlabelled retina due to growth since 3H-proline administration at stage 60 was measured. Both retinal area measurements and counts of labelled ganglion cells showed 30-40% higher values in the temporal than in the nasal retinal half. The greater cell production and area accretion were even more pronounced between the temporal and the nasal retinal quadrants. The results on the temporoventral crescentic retinal growth rule out the possibility that from midlarval stages onwards the retinal and the tectal growth patterns are matched.

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PubMed1982

The innervation of a virgin tectum by a double-temporal or a double-nasal eye in Xenopus.

In Xenopus embryos at stage 32/33 one eye anlage was removed and the other made into a compound double-nasal or double-temporal eye. At metamorphosis the optic nerve was cut and the compound eye was permitted to regenerate fibres both to its own contralateral tectum and to the ipsilateral 'virgin' tectum. One month later the projection from the compound eye to the virgin tectum was assessed autoradiographically by use of tritiated proline. Projections from double-temporal eyes were found to be restricted to rostrolateral tectum, whereas projections from double-nasal eyes covered the entire tectal surface. It was concluded that the results did not suggest that positional markers existed on the tectum before the arrival of the optic fibres.

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PubMed1981

Mapping retinal projections from double nasal and double temporal compound eyes to dually innervated tectum in Xenopus.

Right double nasal (NN) and left double temporal (TT) compound eyes were formed in the same animal by the fusion of two similar halves at early embryonic stages in Xenopus. After metamorphosis either the right or left optic nerve was sectioned to induce optic fiber regeneration from one of the two eyes to both tecta. Retinal projections from each eye to the monocularly and dually innervated tecta were later investigated by visuotectal mapping and by [3H]proline autoradiography. Visuotectal and autoradiographic maps from NN and TT eyes showed the restoration of typical compound eye projections where each of the hemiretinal projections extended across the entire contralateral (monocularly innervated) tectum. In contrast, the tectum ipsilateral to the optic nerve section was dually innervated by fibers from the TT and NN eyes. The rostral and caudal poles of the tectum were innervated by fibers from the TT and NN eyes respectively, whereas the middle third received partially overlapping projections from both eyes. Thus the full expansion of the hemiretinal projection across the dually innervated tectum was prevented by fiber-fiber interactions between optic fibers from the TT and NN eyes. It is concluded that tectal polarity cues determine the proper orientation, and fiber-fiber interaction the extent and orderliness of the retinotectal map. The formation of the latter two features of the retinotectal map does not require the existence of independent tectal positional markers.

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PubMed1981

Spreading of hemiretinal projections in the ipsilateral tectum following unilateral enucleation: a study of optic nerve regeneration in Xenopus with one compound eye.

Right compound eyes were formed in Xenopus embryos at stages 32-33 by the fusion of two nasal (NN), two ventral (VV) or two temporal (TT) halves. Shortly after metamorphosis the optic nerve from the compound eye was sectioned and the left intact eye removed. The retinotectal projections from the compound eye to the contralateral and ipsilateral tecta were studied by [3H]proline autoradiography and electrophysiological mapping between 6 weeks and 5 months after the postmetamorphic surgery. The results showed that NN and VV eyes projected to the entire extent of both tecta. In contrast, optic fibre projection from TT eyes, although more extensive than the normal temporal hemiretinal projection, failed to cover the caudomedial portion of the tecta. The visuotectal projections in all three combinations corresponded to typical reduplicated maps to be expected from such compound eyes, where each of the hemiretinae projected across the contralateral and ipsilateral tecta in an overlapping fashion. The rapid expansion of the hemiretinal projections of the compound eyes in the ipsilateral tectum following the removal of the resident optic fibre projection suggests that tectal markers may be carried and deployed by the incoming optic fibres themselves.

Action Potentials↗
PubMed1981

The development of the retinotectal projections from compound eyes in Xenopus.

The retinotectal projections from double-nasal (NN), double-temporal (TT) and double-ventral (VV) compound eyes in Xenopus were studied autoradiographically and electrophysiologically during development. Early TT projections were confined to rostrolateral tectum and spread with advancing age to cover most of the tectum by shortly after metamorphosis. Early VV projections showed a decreased density of label on lateral tectum. Early NN projections appeared to extend across the entire rostrocaudal length of the available tectum at all stages of development, but showed a decrease in label density on rostral tectum. The results are discussed in relation to various hypotheses about the formation of retinotectal connexions.

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PubMed1981

Interactions between compound and normal eye projections in dually innervated tectum: a study of optic nerve regeneration in Xenopus.

Right compound eyes were formed in Xenopus embryos at tailbud stages by the fusion of two nasal (NN), two temporal (TT) or two ventral (VV) halves. The left eye was kept intact. Two to four weeks after metamorphosis the optic nerve from the intact eye was severed to induced bilateral optic nerve regeneration. The contralateral retinotectal projections from the compound eye and the induced ipsilateral projections from the intact eye to the same (dually innervated) tectum were studied by [3H]proline autoradiography and visuotectal mapping from 3 to 6 months after the postmetamorphic surgery. The results showed that the NN, TT and VV projections, in the presence of optic fibres from the intact eye failed to spread across the whole extent of the dually innervated tectum. Unexpectedly the bulk of the regenerating projection from the intact eye was confined to the previously uninnervated parts of the dually innervated tecta, the caudomedial region in TT, the rostrolateral region in NN and the lateral region in VV eye animals. The partial segregation of the two populations of optic fibres in the dually innervated tectum has been taken as a further indication of the role of fibre-fibre and fibre-tectum interactions in retinotectal map formation.

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PubMed1980

The development of the nucleus isthmi in Xenopus: an autoradiographic study.

The time of origin of the neurons of the nucleus isthmi (NI) in Xenopus has been investigated with [3H] thymidine autoradiography. The first cells of the NI were formed at stage 20 and they continued to be formed until stage 62. The majority of the neurons of the NI were generated between stages 45 and 55. The cells in the NI were distributed in a spatiotemporal manner. Cells generated earliest were located in the rostroventral pole of the NI followed in a dorsocaudal sequence by neurons formed later.

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PubMed1980

Segregation of optic fibre projections into eye-specific bands in dually innervated tecta in Xenopus.

The restoration of the retinotectal projections following metamorphic bilateral optic nerve sections was studied in Xenopus 20 weeks after operation, using [3H]proline autoradiography and electrophysiological mapping. Optic fibre projections from each eye to both tecta segregated into eye-specific termination bands with some overlap at the borders. The bands were arranged rostrocaudally in the tecta such that each eye had an alternating representation. Despite the segregation of the optic fibres, each eye had a complete visual (retinal) projection with the normal nasotemporal and dorsoventral polarities of the visual field maintained. The results suggest competition for preferred terminal sites between the two sets of optic fibres in dually innervated tecta.

Animals↗
PubMed1980

Aberrant retinotectal pathways induced by larval unilateral optic nerve section in Xenopus.

Following unilateral optic nerve section in Xenopus tadpoles and toadlets, the reformation of visual pathways and retinotectal projections was analyzed using [3H]proline autoradiography. Bilateral retinotectal projections were found in 61% of the animals operated on between stages 42 and 58. In these animals, the projections were established through multiple aberrant pathways which included the oculomotor nerve, the trigeminal nerve and the posterior commissure. In contrast, in animals with optic nerve section at stage 62 or after metamorphosis, the regenerated optic fibres arrived at the contralateral and ipsilateral tecta through normal visual pathways.

Animals↗
PubMed1980

Regeneration of optic nerve fibres from a compound eye to both tecta in Xenopus: evidence relating to the state of specification of the eye and the tectum.

Xenopus with one double-nasal (NN), double-temporal (TT) or double-ventral (VV) eye were induced to regenerate optic fibres from the compound eye to both tecta after metamorphosis. The extent of the projection from the compound eye was then estimated autoradiographically at various intervals after nerve section. The regenerated projection covered the whole of the contralateral tectum but covered only a restricted part of the ipsilateral tectum; thus NN eyes innervated caudomedial tectum only, TT eyes innervated rostrolateral tectum only and VV eyes innervated medial tectum only. Since the tectum ipsilateral to the compound eye also received the projection from the normal eye these results are taken to indicate that NN, TT and VV eyes are unregulated systems in terms of the retinal positional markers that they carry; each such eye bears only the appropriate half-set of such markers.

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PubMed1980

Stable programming for map orientation in fused eye fragments in Xenopus.

Compound eyes were formed in Xenopus embryos at stages 32/33 by fusion in the right orbit of (1) two right naso-ventral halves, (2) two right ventral halves, (3) two right temporo-ventral halves, (4) one right and one left naso-ventral half and (5) one right and one left temporo-ventral half. The contralateral visuotectal projections from the operated eyes later showed abnormalities reflecting the anatomical arrangement of the fused fragments. The experiments thus revealed considerable stability of the developmental programme leading to the later development of map orientation, in the face of operative disturbance of the types used.

Animals↗
PubMed1980

Stable programming for map orientation in disarranged embryonic eyes in Xenopus.

In Xenopus embryos of stage 32/33 either the temporal or nasal half of the right eye anlage was replaced by a corresponding left half, giving a right eye in which the grafted half was inverted dorsoventrally. In other embryos either the dorsal or ventral half of the right eye anlage was replaced by a corresponding left half, giving an eye in which the grafted half was reversed nasotemporally. These foud types of operation were intended to produce eyes that were disarranged internally but which each had a complete range of positional values. The visuotectal projections from such eyes, recorded later in life, in most cases showed axial reversal of half of the map, reflecting the nature of the operation. The results thus demonstrate that the developmental programme in each of the fused retinal fragments is stable in relation to the eventual orientation of the map from that fragment. Operations to produce eyes with an inverted temporal half, if performed in operating solution of low ionic strength, may result in mirror reduplication and the formation of double nasal maps. It is suggested that this phenomenon may underlie previous reports of reprogramming of one eye fragment by another.

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