M J Pujante | PubMed Health

PubMed2000

Stimulus frequency affects c-fos expression in the rat visual system.

We have characterised the c-fos expression patterns in various centers of the visual pathway of adult rats monocularly stimulated either by continuous or flickering light at different frequencies. Results show different immunocytochemical patterns in all centers studied, the geniculate lateral complex (LGC), superior colliculus (SC) and primary visual cortex (Oc1), depending on the physical characteristics of the stimulus (blinking frequency and light wavelength). After stimulation of the left eye, the ipsilateral pathway presents a substantial density of immunoresponsive cells, which is greater than expected with respect to the number of fibers that project ipsilaterally from the retina to the LGC and the superficial layers of the SC. A surprisingly high positive immunoresponsiveness is obtained in all cases with coherent light stimulation in the red spectrum (634 nm).

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PubMed1990

Tectorial membrane changes in hypothyroid rats during postnatal development.

The morphological changes of the tectorial membrane (TM) during the postnatal development (0, 3, 6, 12 and 25 day old) of the organ of Corti were studied by light microscopy in 20 control and hypothyroid rats. Hypothyroidism was induced by daily administration of propylthioruracil (PTU) until the end of lactation. The auditive receptor in the cochlea of the hypothyroid animals shows serious structural alterations compared with those of normal ones: abnormal persistence of Kölliker's organ, immaturity of sensory cells and supporting cells and a specific distortion of the TM. Differences with controls were first observed on the sixth postnatal day of the hypothyroid rats. The inner spiral sulcus was not shaped and the TM was attached to the Kölliker's organ. In older stages (12 and 25 days), Kölliker's organ was still present. The TM acquired a shap hump with an abnormal fibrillar arrangement in its middle part. It was still attached to the outer supporting cells by a remnant of the marginal net. It was suggested that the TM is secreted by the inner spiral limbus and Kölliker's organ. An abnormal persistence of these structures in the hypothyroidism results in a retardation of Corti's organ development. However, this conclusion does not explain the absence of the outer portion of the TM. Our study confirms the hypothesis that the secretion of any components of the marginal zone of TM is made by outer supporting cells which in PTU-treated animals appear very immature and with hypoplasia.

Animals↗