Biomedical subjects

Gervasio Martín-Partido

Publications and source records attributed to Gervasio Martín-Partido.

9 recordsLinked to original sources

PubMed2006

Developmental changes in the fibre population of the optic nerve follow an avian/mammalian-like pattern in the turtle Mauremys leprosa.

The changes in the axon and growth cone numbers in the optic nerve of the freshwater turtle Mauremys leprosa were studied by electron microscopy from the embryonic day 14 (E14) to E80, when the animals normally hatch, and from the first postnatal day (P0) to adulthood (5 years on). At E16, the first axons appeared in the optic nerve and were added slowly until E21. From E21, the fibre number increased rapidly, peaking at E34 (570,000 fibres). Thereafter, the axon number decreased sharply, and from E47 declined steadily until reaching the mature number (about 330,000). These observations indicated that during development of the retina there was an overproduction and later elimination of retinal ganglion cells. Growth cones were first observed in the optic nerve at as early as E16. Their number increased rapidly until E21 and continued to be high through E23 and E26. After E26, the number declined steeply and by E40 the optic nerve was devoid of growth cones. These results indicated that differentiation of the retinal ganglion cells occurred during the first half of the embryonic life. To examine the correlation between the loss of the fibres from the optic nerve and loss of the parent retinal ganglion cells, retinal sections were processed with the TUNEL technique. Apoptotic nuclei were detected in the ganglion cell layer throughout the period of loss of the optic fibres. Our results showed that the time course of the numbers of the fibres in the developing turtle optic nerve was similar to those found in birds and mammals.

Age Factors↗

PubMed2006

Spatial and temporal patterns of proliferation and differentiation in the developing turtle eye.

Here we show for the first time different aspects of the pattern of neurogenesis in the developing turtle retina by using different morphological and molecular clues. We show the chronotopographical fashion of occurrence of three major aspects of retinal development: (1) morphogenesis of the optic primordia and emergence of the different retinal layers, (2) the temporal progression of neurogenesis by the cessation of proliferative activity, and (3) the apparition and cellular localization of different antigens and neuroactive substances. Retinal cells were generated in a conserved temporal order with ganglion cells born first, followed by amacrine, photoreceptor, horizontal and bipolar/Müller cells. While eventually expressed in many types of retinal neurons, Islet1 was permanently expressed in differentiating and mature ganglion cells. Calbindin-immunoreactive elements were found in the ganglion cell layer and the inner nuclear layer. Interestingly, at later stages the amount of expressing cells in these layers was reduced dramatically. On the contrary, the number of calbindin-immunoreactive photoreceptors increased as development proceeded. In addition, calretinin expressing cells were prominent in the horizontal cell bodies, and their processes extending into the outer plexiform layer were also strongly labeled. Finally, the synthesis of gamma-aminobutyric acid (GABA) was detected in developing and matured horizontal and amacrine cells. All these maturational features began in the dorso-central area, in a region slightly displaced towards the temporal retina.

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PubMed2006

Fgf19 expression patterns in the developing chick inner ear.

The inner ear is a complex sensorial structure with hearing and balance functions. A key aim of developmental biology is to understand the molecular and cellular mechanisms involved in the induction, patterning and innervation of the vertebrate inner ear. These developmental events could be mediated by the expression of regulating genes, such as the members of the family of Fibroblast Growth Factors (Fgfs). This work reports the detailed spatial and temporal patterns of Fgf19 expression in the developing inner ear from otic cup (stage 14) to 8 embryonic days (stage 34). In the earliest stages, Fgf19 and Fgf8 expressions determine two subdomains within the Fgf10-positive proneural-sensory territory. We show that, from the earliest stages, the Fgf19 expression was detected in the acoustic-vestibular ganglion and the macula utriculi. The Fgf19 gene was also strongly, but transiently, expressed in the macula lagena, whereas the macula neglecta never expressed this gene in the period analysed. The Fgf19 expression was also clearly observed in some borders of various sensory elements. These results could be useful from further investigations into the role of FGF19 in otic patterning.

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PubMed2005

Macrophages during retina and optic nerve development in the mouse embryo: relationship to cell death and optic fibres.

We compared the spatial and temporal patterns of distribution of macrophages, with patterns of naturally occurring cell death and optic fibre growth during early retina and optic nerve development, in the mouse. We used embryos between day 10 of embryogenesis (E10; before the first optic fibres are generated in the retina) and E13 (when the first optic fibres have crossed the chiasmatic anlage). The macrophages and optic axons were identified by immunocytochemistry, and the apoptotic cells were detected by the TUNEL technique, which specifically labels fragmented DNA. Cell death was observed in the retina and the optic stalk long before the first optic axons appeared in either region. Subsequently, specialized F4/80-positive phagocytes were detected in chronological and topographical coincidence with cell death, which disappeared progressively. As development proceeded, the pioneer ganglion cell axons reached the regions where the macrophages were located. As the number of optic fibres increased, the macrophages disappeared. Therefore, cell death, accompanied by macrophages, preceded the growth of fibres in the retina and the optic nerve. Moreover, these macrophages synthesized NGF and the optic axons were p75 neurotrophin receptor (p75(NTR))- and TrkA-positive. These findings suggest that macrophages may be involved in optic axon guidance and fasciculation.

Animals↗

PubMed2005

Expression of Fgf19 in the developing chick eye.

Fibroblast growth factor 19 (FGF19) is a new member of the FGF family of growth factors. Here, we describe the localization of Fgf19 mRNA in the developing chick retina and lens in stages from the Hamburger and Hamilton stage 15 (HH15) to postnatal day 30 (P30). Fgf19 was expressed in a transient manner in postmitotic neuroblasts during the migration from the ventricular surface to their final location. Moreover, from HH31 (embryonic day 7, E7) on, a subset of lined up Fgf19 expressing cells was distributed in the outer region of the presumptive INL. These cells were Pax6 immunoreactive horizontal cells. During the last third of embryogenesis, Fgf19 expression in the retina was progressively down-regulated and was not detected at P30. Also, it was transiently expressed in the equatorial region of the lens.

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PubMed2005

Pax2 expression patterns in the developing chick inner ear.

The fate specification of the developing vertebrate inner ear could be determined by complex regulatory genetic pathways involving the Pax2/5/8 genes. Pax2 expression has been reported in the otic placode and vesicle of all vertebrates that have been studied. Loss-of-function experiments suggest that the Pax2 gene plays a key role in the development of the cochlear duct and acoustic ganglion. Despite all these data, the role of Pax2 gene in the specification of the otic epithelium is still only poorly defined. In the present work, we report a detailed study of the spatial and temporal Pax2 expression patterns during the development of the chick inner ear. In the period analysed, Pax2 is expressed only in some presumptive sensory patches, but not all, even though all sensory patches show the scattered Pax2 expression pattern later on. We also show that Pax2 is also expressed in several non-sensory structures.

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PubMed2004

Otx2, Gbx2, and Fgf8 expression patterns in the chick developing inner ear and their possible roles in otic specification and early innervation.

The chick inner ear is a complex structure containing auditory and vestibular sensory organs innervated by neurons of the acoustic-vestibular ganglion. The molecular signals involved in the specification and initial innervation of the otic epithelium are poorly understood. Here, we present a detailed description of the Otx2, Gbx2, and Fgf8 gene expression patterns in the chick developing inner ear, comparing them with the Bmp4 expression, a putative sensory-organ marker. The Otx2 expression was detected in the ventro-lateral wall of the otic anlage and could play a role in the segregation of the saccule and utricle maculae. The relationship between Gbx2 and Fgf8 expression changed during inner ear development but was always related to the macula sacculi innervation and endolymphatic duct formation. Our results also suggest that the maculae of the saccule and lagena, and the medial portion of the macula utriculi could arise within a broad Fgf8-positive domain previously observed at the otocyst stage. The spatial and temporal relationships between these gene expression domains and the initial innervation of the epithelium by some subpopulations of otic axons suggest that expression domain boundaries could be involved in the specification and early innervation of presumptive sensory patches.

Animals↗

PubMed2004

Liver portal fibrosis in dioxin receptor-null mice that overexpress the latent transforming growth factor-beta-binding protein-1.

Mice lacking aryl hydrocarbon (dioxin) receptor (AhR) had variable degree of hepatic fibrosis and altered liver architecture. Transforming growth factor-beta (TGF-beta), a major profibrogenic molecule in the liver, is localized to the extracellular matrix by its association to the latent TGF-beta-binding protein-1 (LTBP-1). Very recently, LTBP-1 has been shown to be negatively regulated by the AhR. Embryonic fibroblasts from AhR-null (AhR(-/-)) mice overexpress LTBP-1 and secrete four times more active TGF-beta than wild-type fibroblasts. To test whether TGF-beta and LTBP-1 overexpression colocalize within the fibrotic nodule of AhR(-/-) liver, we have characterized this hepatic portal fibrosis using collagen protein staining, immunohistochemistry and in situ hybridization. LTBP-1 mRNA and protein were overexpressed in the fibrotic region and colocalized with other indicators of fibrosis such as collagen and fibronectin and the fibroblast marker proteins alpha-actin and vimentin. TGF-beta protein also colocalized with fibrosis, although in contrast, TGF-beta mRNA expression, rather than restricted to the fibrotic compartment, was present throughout the hepatic parenchyma and exhibited similar levels in wild-type and AhR(-/-) mice. These results suggest that LTBP-1 targets TGF-beta to specific areas of the liver and that the AhR could be a negative regulator of liver fibrosis, possibly through the control of LTBP-1 and TGF-beta activities.

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PubMedDate not supplied

Differential expression of Otx2, Gbx2, Pax2, and Fgf8 in the developing vestibular and auditory sensory organs.

The vertebrate inner ear is a complex organ with vestibular and auditory sensory functions, which derives from a single ectoderm structure, the otic placode. The development and regional patterning of the otic primordium is determined by the restricted expression of several genes. Here, we show the expression pattern of three transcription factors (Otx2, Gbx2, Pax2) and of a member of the fibroblast growth factor family (Fgf8) in the developing chick inner ear, and we correlate these patterns with the developing sensory and nonsensory elements.

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