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Träfflista för sökning "L773:0302 766X ;pers:(van Veen Theo)"

Sökning: L773:0302 766X > Van Veen Theo

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1.
  • Ekström, P., et al. (författare)
  • Ontogenetic development of the pineal organ, parapineal organ, and retina of the three-spined stickleback, Gasterosteus aculeatus L. (Teleostei) - Development of photoreceptors
  • 1983
  • Ingår i: Cell and Tissue Research. - 0302-766X. ; 233:3, s. 593-609
  • Tidskriftsartikel (refereegranskat)abstract
    • The ontogenetic developments of the pineal organ, parapineal organ, and retina were studied by the use of light and electron microscopy in embryos and fry of the teleost, Gasterosteus aculeatus, from 60 to 168 h after fertilization. Sixty to 66 h after fertilization, the primordium of the pineal complex is discernible in the diencephalic roofplate; the parapineal anlage is located rostral to the pineal anlage. Photoreceptor cells endowed with outer segments are present in the embryonic pineal organ already after 72 h, whereas outer segments of retinal photoreceptors could not be demonstrated before 144 h (hatching occurs between 120-144 h). Furthermore, neuropil formations with synaptic specializations are present in the rostral part of the pineal organ 108 h after fertilization. At 72 h, the embryonic parapineal parenchyma is already differentiated into parapinealocytes, which give rise to the parapineal tract, and glia-resembling elements. Although parapinealocytes carry cilia (9 × 2 + 0), only a single outer segment of the photoreceptor type could be demonstrated in the parapineal organ of one adult stickleback. Photoreceptors present in the pineal organ of unhatched embryos are hardly involved in visual functions, but may already at this early developmental stage serve as photoneuroendocrine transducers.
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2.
  • Johnson, Leif, et al. (författare)
  • Differential Akt activation in the photoreceptors of normal and rd1 mice.
  • 2005
  • Ingår i: Cell and Tissue Research. - : Springer Science and Business Media LLC. - 1432-0878 .- 0302-766X. ; 320:2, s. 213-222
  • Tidskriftsartikel (refereegranskat)abstract
    • Retinitis pigmentosa is a blinding disease in which unknown mechanisms cause the degeneration of retinal photoreceptors. The retinal degeneration (rd1) mouse is a relevant model for this condition, since it carries a mutation also found in some forms of retinitis pigmentosa. To understand the degenerative process in the rd1 mouse, we must identify the survival and apoptosis-related signaling pathways in its photoreceptors and determine whether signaling differs from that in normal mice. The phosphatidylinositol 3-kinase/Akt kinase pathway promotes survival in several different cell types. The purpose of the present study has been to compare Akt activity in retinal cells of normal and rd1 mice. We have found that, in normal mice, Akt becomes activated in the retina in a developmentally regulated and cell-type-specific fashion, encompassing essentially all retinal cells. In most cell types, once Akt activation has begun, it remains in this state throughout life. An exception is seen in the rod photoreceptors, in which Akt is activated only transiently during their development. The rd1 retina behaves identically in all but one respect, namely that the activation of Akt in rod photoreceptors persists until these cells undergo apoptosis. Thus, Akt may participate in constitutive survival processes in retinal neurons, except in rod photoreceptors in which the role of this pathway may be restricted to the developmental period. However, Akt activation in the rods may be part of a defense mechanism initiated in response to insults, such as the retinal degeneration seen in the rd1 mouse.
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3.
  • van Veen, Theo, et al. (författare)
  • Serotonin and opsin immunoreactivities in the developing pineal organ of the three-spined stickleback, Gasterosteus aculeatus L.
  • 1984
  • Ingår i: Cell and Tissue Research. - 0302-766X. ; 237:3, s. 559-564
  • Tidskriftsartikel (refereegranskat)abstract
    • 5-hydroxytryptamine (5-HT, serotonin)- and opsin-immunoreactive sites were studied in the developing pineal complex of the stickleback, Gasterosteus aculeatus L., by use of light-microscopic indirect immunoperoxidase techniques. 5-HT immunoreactivity first occurs in the pineal organ at the age of 80 h after fertilization and appears to be localized in cells of the photoreceptor type. The outer segments of a few pineal photosensory cells exhibit opsin immunoreactivity at the age of 84 h after fertilization. The number of cells seems to increase until the pineal organ is completely developed. The increase in the number of 5-HT immunoreactive perikarya runs parallel in time to that of the opsinimmunoreactive outer segments. The cells of the parapineal organ show neither opsin nor 5-HT immunoreactivity. The retina of the embryonic stickleback does not display opsin immunoreactivity until after hatching, which takes place about 144 h after fertilization. These results suggest, in the three-spined stickleback, an earlier light-perception capacity for the developing pineal organ than for the retina.
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  • Resultat 1-3 av 3

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