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Sodium iodate selectively injuries the posterior pole of the retina in a dose-dependent manner: morphological and electrophysiological study.

Machalińska A, Lubiński W, Kłos P, Kawa M, Baumert B, Penkala K, Grzegrzółka R, Karczewicz D, Wiszniewska B, Machaliński B - Neurochem. Res. (2010)

Bottom Line: Sequential morphological and functional features of retinal damage in mice exposed to different doses (40 vs. 20 mg/kg) of sodium iodate (NaIO(3)) were analyzed.The peak of photoreceptor apoptosis was found on the 3rd day, but the lower dose induced more intense reaction within the central retina than in its peripheral region.In conclusion, these results indicate that peripheral area of the retina reveals better resistance to NaIO(3) injury than its central part.

View Article: PubMed Central - PubMed

Affiliation: Department of Histology and Embryology, Pomeranian Medical University, Szczecin, Poland. annam@sci.pam.szczecin.pl

ABSTRACT
Sequential morphological and functional features of retinal damage in mice exposed to different doses (40 vs. 20 mg/kg) of sodium iodate (NaIO(3)) were analyzed. Retinal morphology, apoptosis (TUNEL assay), and function (electroretinography; ERG) were examined at several time points after NaIO(3) administration. The higher dose of NaIO(3) caused progressive degeneration of the whole retinal area and total suppression of scotopic and photopic ERG. In contrast, the lower dose induced much less severe degeneration in peripheral part of retina along with a moderate decline of b- and a-wave amplitudes in ERG, corroborating the presence of regions within retina that retain their function. The peak of photoreceptor apoptosis was found on the 3rd day, but the lower dose induced more intense reaction within the central retina than in its peripheral region. In conclusion, these results indicate that peripheral area of the retina reveals better resistance to NaIO(3) injury than its central part.

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The regional pattern of retinal damage after the injection of the lower dose (20 mg/kg) of sodium iodate (a). TUNEL-stained sections visualizing apoptotic photoreceptors located in the central (b) and peripheral (e) parts of the retinal area on the 3rd day post NaIO3 exposure. (c, f) corresponding (central vs. peripheral part) H/E stained sections. (d, g) corresponding (central vs. peripheral part) whole eye flat mounts (FMs) with nuclei pseudocolored blue; green pseudocolor indicates RPE autofluorescence. The blackarrow (c) indicates a thin layer of melanin released along Bruch’s membrane. The graphs illustrate the difference in the number of apoptotic cells between the central and peripheral parts of the retina exposed to the lower (h) and higher (i) doses of NaIO3. Photoreceptor apoptosis shows the peak intensity on the 3rd day after NaIO3 administration regardless of the dose used. GCL ganglion cell layer, INL inner nuclear layer, ONL outer nuclear layer
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Fig2: The regional pattern of retinal damage after the injection of the lower dose (20 mg/kg) of sodium iodate (a). TUNEL-stained sections visualizing apoptotic photoreceptors located in the central (b) and peripheral (e) parts of the retinal area on the 3rd day post NaIO3 exposure. (c, f) corresponding (central vs. peripheral part) H/E stained sections. (d, g) corresponding (central vs. peripheral part) whole eye flat mounts (FMs) with nuclei pseudocolored blue; green pseudocolor indicates RPE autofluorescence. The blackarrow (c) indicates a thin layer of melanin released along Bruch’s membrane. The graphs illustrate the difference in the number of apoptotic cells between the central and peripheral parts of the retina exposed to the lower (h) and higher (i) doses of NaIO3. Photoreceptor apoptosis shows the peak intensity on the 3rd day after NaIO3 administration regardless of the dose used. GCL ganglion cell layer, INL inner nuclear layer, ONL outer nuclear layer

Mentions: When using the higher dose of NaIO3 (40 mg/kg) we observed progressive degeneration of the neurosensory retina along with widespread loss of RPE cells. These changes spread through the posterior pole and the peripheral region, indicating significant damage within the whole retinal area. On the first day after NaIO3 administration we discerned marked RPE damage with slight changes in the neurosensory retina in the form of some disorganization of the outer and inner segments of the photoreceptors (Fig. 1c). Individual RPE cells were flattened and most were devoid of nuclei, although they maintained their orientation and boundaries. On the third day after NaIO3 injection we detected complete destruction of the RPE, which had been replaced by a thin layer of melanin released along Bruch’s membrane (Fig. 2c). At this time point, the retinal pigment epithelium FMs revealed a discontinuous melanin sheet displaying empty spaces with nuclei present, possibly belonging to inflowing cells (Fig. 2d). Discontinuity of the RPE layer, macrophage infiltration, and disrupted structure of the outer and inner photoreceptor segments were observed in the retinal H-E stained sections (Fig. 2c). Moreover, TUNEL staining revealed the presence of massive apoptosis in the outer nuclear layer, which corroborated immense degeneration of the photoreceptors (Fig. 2b). By the 7th day after NaIO3 delivery, the thickness of the outer nuclear layer decreased significantly and the outer and inner photoreceptor segments were markedly shortened (Fig. 1e). The RPE flat mount obtained at this time point revealed an irregular network of melanin remnants spread along Bruch’s membrane (Fig. 1d). On the 18th and 28th days after NaIO3 administration we observed bumpy melanin clumping scattered along Bruch’s membrane with no apparent RPE cover. There were also features suggesting that glial cells might contribute to the phagocytosis of melanin remnants (Fig. 1f). The retinal thickness was drastically reduced, predominantly due to the progressive photoreceptor loss.Fig. 1


Sodium iodate selectively injuries the posterior pole of the retina in a dose-dependent manner: morphological and electrophysiological study.

Machalińska A, Lubiński W, Kłos P, Kawa M, Baumert B, Penkala K, Grzegrzółka R, Karczewicz D, Wiszniewska B, Machaliński B - Neurochem. Res. (2010)

The regional pattern of retinal damage after the injection of the lower dose (20 mg/kg) of sodium iodate (a). TUNEL-stained sections visualizing apoptotic photoreceptors located in the central (b) and peripheral (e) parts of the retinal area on the 3rd day post NaIO3 exposure. (c, f) corresponding (central vs. peripheral part) H/E stained sections. (d, g) corresponding (central vs. peripheral part) whole eye flat mounts (FMs) with nuclei pseudocolored blue; green pseudocolor indicates RPE autofluorescence. The blackarrow (c) indicates a thin layer of melanin released along Bruch’s membrane. The graphs illustrate the difference in the number of apoptotic cells between the central and peripheral parts of the retina exposed to the lower (h) and higher (i) doses of NaIO3. Photoreceptor apoptosis shows the peak intensity on the 3rd day after NaIO3 administration regardless of the dose used. GCL ganglion cell layer, INL inner nuclear layer, ONL outer nuclear layer
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2957578&req=5

Fig2: The regional pattern of retinal damage after the injection of the lower dose (20 mg/kg) of sodium iodate (a). TUNEL-stained sections visualizing apoptotic photoreceptors located in the central (b) and peripheral (e) parts of the retinal area on the 3rd day post NaIO3 exposure. (c, f) corresponding (central vs. peripheral part) H/E stained sections. (d, g) corresponding (central vs. peripheral part) whole eye flat mounts (FMs) with nuclei pseudocolored blue; green pseudocolor indicates RPE autofluorescence. The blackarrow (c) indicates a thin layer of melanin released along Bruch’s membrane. The graphs illustrate the difference in the number of apoptotic cells between the central and peripheral parts of the retina exposed to the lower (h) and higher (i) doses of NaIO3. Photoreceptor apoptosis shows the peak intensity on the 3rd day after NaIO3 administration regardless of the dose used. GCL ganglion cell layer, INL inner nuclear layer, ONL outer nuclear layer
Mentions: When using the higher dose of NaIO3 (40 mg/kg) we observed progressive degeneration of the neurosensory retina along with widespread loss of RPE cells. These changes spread through the posterior pole and the peripheral region, indicating significant damage within the whole retinal area. On the first day after NaIO3 administration we discerned marked RPE damage with slight changes in the neurosensory retina in the form of some disorganization of the outer and inner segments of the photoreceptors (Fig. 1c). Individual RPE cells were flattened and most were devoid of nuclei, although they maintained their orientation and boundaries. On the third day after NaIO3 injection we detected complete destruction of the RPE, which had been replaced by a thin layer of melanin released along Bruch’s membrane (Fig. 2c). At this time point, the retinal pigment epithelium FMs revealed a discontinuous melanin sheet displaying empty spaces with nuclei present, possibly belonging to inflowing cells (Fig. 2d). Discontinuity of the RPE layer, macrophage infiltration, and disrupted structure of the outer and inner photoreceptor segments were observed in the retinal H-E stained sections (Fig. 2c). Moreover, TUNEL staining revealed the presence of massive apoptosis in the outer nuclear layer, which corroborated immense degeneration of the photoreceptors (Fig. 2b). By the 7th day after NaIO3 delivery, the thickness of the outer nuclear layer decreased significantly and the outer and inner photoreceptor segments were markedly shortened (Fig. 1e). The RPE flat mount obtained at this time point revealed an irregular network of melanin remnants spread along Bruch’s membrane (Fig. 1d). On the 18th and 28th days after NaIO3 administration we observed bumpy melanin clumping scattered along Bruch’s membrane with no apparent RPE cover. There were also features suggesting that glial cells might contribute to the phagocytosis of melanin remnants (Fig. 1f). The retinal thickness was drastically reduced, predominantly due to the progressive photoreceptor loss.Fig. 1

Bottom Line: Sequential morphological and functional features of retinal damage in mice exposed to different doses (40 vs. 20 mg/kg) of sodium iodate (NaIO(3)) were analyzed.The peak of photoreceptor apoptosis was found on the 3rd day, but the lower dose induced more intense reaction within the central retina than in its peripheral region.In conclusion, these results indicate that peripheral area of the retina reveals better resistance to NaIO(3) injury than its central part.

View Article: PubMed Central - PubMed

Affiliation: Department of Histology and Embryology, Pomeranian Medical University, Szczecin, Poland. annam@sci.pam.szczecin.pl

ABSTRACT
Sequential morphological and functional features of retinal damage in mice exposed to different doses (40 vs. 20 mg/kg) of sodium iodate (NaIO(3)) were analyzed. Retinal morphology, apoptosis (TUNEL assay), and function (electroretinography; ERG) were examined at several time points after NaIO(3) administration. The higher dose of NaIO(3) caused progressive degeneration of the whole retinal area and total suppression of scotopic and photopic ERG. In contrast, the lower dose induced much less severe degeneration in peripheral part of retina along with a moderate decline of b- and a-wave amplitudes in ERG, corroborating the presence of regions within retina that retain their function. The peak of photoreceptor apoptosis was found on the 3rd day, but the lower dose induced more intense reaction within the central retina than in its peripheral region. In conclusion, these results indicate that peripheral area of the retina reveals better resistance to NaIO(3) injury than its central part.

Show MeSH
Related in: MedlinePlus