PubMed Health⌕ Search

Biomedical subjects

M D Crapon de Caprona

Publications and source records attributed to M D Crapon de Caprona.

8 recordsLinked to original sources
PubMed2001

Development of the ear and of connections between the ear and the brain: is there a role for gravity?

This paper outlines the development of the gravistatic sensory system of the ear. First, evidence is presented that a genetic program, for which major transcription factors have already been identified using gene expression studies and targeted mutagenesis, governs the initial development of this system. Second, the formation of sensory neurons and their connections to the brain is described as revealed by tracing studies and genetic manipulations. It is concluded that the initial development of the connections of sensory neurons with mechanosensory transducers of the ear (the hair cells) and the targets in the brainstem (vestibular nuclei) is also dependent on fairly rigid genetic programs. During late embryonic and early postnatal development, however, sensory input appears to be used to fine-tune connections of these sensory neurons with the hair cells in the ear as well as with second order vestibular neurons in the brainstem. This phase is proposed to be critical for a proper calibration of the gravistatic information processing in the brain.

Animals↗
PubMed1990

Development of two morphological types of retinopetal fibers in chick embryos, as shown by the diffusion along axons of a carbocyanine dye in the fixed retina.

Centrifugal fibers to the retinas of chick embryos and hatched chicks have been examined and traced following staining by diffusion along their axonal membranes of the carbocyanine dye DiI in fixed tissue. In the older embryos and hatched chicks, the report of Dogiel (Arch. Mikrosk. Anat. 44:622-648, 1895) has been confirmed that there are two very different morphological types of centrifugal fiber. The restricted type ends as a relatively thick fiber, lacking varicosities, that runs for a short distance in the most sclerad level of the inner plexiform layer before terminating in a pericellular nest overlying the flask-shaped body of a single amacrine cell. Thin filaments occasionally leave the pericellular net, apparently to terminate on adjacent cells. The widespread type also runs in the most sclerad level of the inner plexiform layer, but it is thin, varicose, and highly branched, and its terminal arbor may span more than 1 mm, remaining at the same level. Both types of terminal arbor issue from parent axons in the optic fiber layer of the retina. A single parent axon gives either a single terminal fiber of the restricted type or several terminals of the widespread type, but never a mixture of the two. It is argued that the restricted and widespread types originate respectively from the neurons of the contralateral isthmo-optic nucleus and from the "ectopic" neurons scattered outside the isthmo-optic nucleus. In development, the centrifugal fibers reach the retina between E9 and E10 and initially run radially in the optic fiber layer, parallel to the retinofugal fibers but avoiding the dorsal retina. They dive into the inner plexiform layer at about E12. By E13, the terminal arbors are forming, and the widespread and restricted types can already be distinguished. The widespread type continues to increase its territory until about E18, and then appears to remain stable, whereas the restricted type attains its maximum ramification between E13 and E15 and then contracts. Prior to the retraction, the terminal territories of the restricted type fibers overlap, which may provide the anatomical basis for the interaxonal competition that apparently contributes to neuronal death in the isthmo-optic nucleus between E13 and E16. Axons of ganglion cells exhibit transient side branches between E11 and E13; these never reach as deep as the level where the centrifugal fibers run.

Animals↗
PubMed1987

Ipsilateral retinofugal and retinopetal projections in normal and monocular cichlid fish.

A previously unknown ipsilateral retinotectal projection in juvenile and adult cichlid fishes is revealed by anterograde labelling with horseradish peroxidase (HRP). Enucleation results in an enlarged ipsilateral projection from the intact eye; after 4 months this projection may cover the tectum almost completely. These data are interpreted as an increase in the normally occurring ipsilateral projection of newly differentiated ganglion cells due to the absence of interocular competition. Conversely, after enucleation cells of the homolateral thalamoretinal nucleus seem, on the basis of retrograde HRP staining to develop a new connection with the remaining eye.

Animals↗
PubMed1985

Visual projections in larval Ichthyophis kohtaoensis (Amphibia: gymnophiona).

The visual projection patterns of retinal efferents were studied in larval Ichthyophis kohtaoensis by means of anterogradely transported HRP. Our results show in all larvae a projection contralateral to a thalamic terminal field, a pretectal terminal field, and a basal optic neuropil, but only a sparse innervation of the contralateral tectum. In addition, all larvae possess an uncrossed projection to a thalamic and a pretectal terminal field. The fibers are bilaterally almost confined to the medial optic tract with only a few fibers running in the marginal and basal optic tract. The ipsilateral and contralateral tracts and terminal fields seem to enlarge during larval life. Comparison with other amphibian orders reveals that larval Ichthyophis are unique in that they develop the medial optic tract and the related thalamic and pretectal terminal fields very early in larval life. In addition they possess only a very sparse tectal projection, though it is the largest projection in larval urodeles and anurans. This suggests a selective phylogenetic loss of those ganglion cells or collaterals which project mainly to the tectum in other amphibian orders and a change in the ontogenetic program leading to an earlier development of the medial optic tract in Ichthyophis as compared to urodeles and anurans.

Amphibians↗
PubMed1983

The development of the retinopetal nucleus olfacto-retinalis of two cichlid fish as revealed by horseradish peroxidase.

Adult patterns and the development of the nucleus of origin of centrifugal innervation of the retina, the nucleus olfacto-retinalis (NOR), were studied with horseradish peroxidase in 2 cichlid fish species. In the adults large and small cells within the nuclear boundaries can be distinguished by their cytoarchitecture and their HRP-labelling. The NOR is already formed at hatching (5.5 days post-spawning) but cannot be filled by HRP injections into one eye until 2 days later. The number of labelled neurons increases steadily until adult cell density is reached. Later larval stages show that the NOR neurons also increase in size. The two cell types found in the adult can first be distinguished at around 30 days post-spawning. Early unilateral enucleation reduces the density of the small cells in the contralateral NOR. In spite of different environmental constraints on the growth of the larvae, the NOR develops in a similar way in both species but always somewhat later in the substrate-spawner than in the mouth-brooder. The centrifugal innervation of bird (isthmo-optic nucleus, ION) and fish (NOR) retinae starts at comparable developmental stages of the retina, but no cell death as found in the developing ION in birds occurs in the developing NOR in fish. It is suggested that this is due to the constant adjustment of the NOR to the ever increasing cell numbers in the fish retina. The NOR is thus the only known centrifugally projecting nucleus in vertebrates which lacks extensive degenerating patterns during early development. The known LH-RH immunoreactivity, the two cell types, the early development, and the projection to the retina of the NOR in cichlid fish resemble closely characteristics of the ganglion of the terminalis nerve of other piscine species.

Animals↗
PubMed1980

Olfactory communication in a Cichlid fish, Haplochromis burtoni.

Part I: The responses of adult male Haplochromis burtoni to chemical stimuli produced by conspecifics in a reproductive state are tested. The different chemical substances presented to the test fish are described in terms of their short and long-term effects on particular behavior patterns. The responses of intact, anosmic and sham-operated fish are compared to determine whether these substances are perceived through olfaction (as opposed to gustation). Part II: Some aspects of the relative importance of visual and chemical cues from gravid female on the reproductive behavior of conspecific male Haplochromis burtoni are analysed.

Animals↗
PubMedDate not supplied

Neuroanatomical evidence for electroreception in lampreys.

The patterns of the anterior lateral-line afferents of Lampetra fluviatilis as revealed by transganglionic transport of horseradish peroxidase are described. The afferents form two roots in entering the rhombencephalon. Fibers of the dorsalmost root can be traced to a short dorsal fascicle which runs along the dorsal nucleus. The ventral roots form two fascicles adjacent to the nucleus intermedius. Comparison with urodeles indicates that lampreys, like urodeles and other anamniotic vertebrates are electroreceptive.

Afferent Pathways↗