CHANGES IN ULTRASTRUCTURE AND FUNCTION OF THE SHEEP PIGMENT EPITHELIUM AND RETINA INDUCED BY SODIUM IODATE 1

The electroretinogram (ERG) was recorded in 15 ICR albino mice before and 2, 4 and 24 h after injection of 40 mg/kg of NaIO3 and the results were compared with the corresponding ultrastructural findings. Both a- and b-wave amplitudes decreased at 2 h after injection and increased at 4 h to the levels before injection and further increased at 24 h after injection. The b-wave threshold intensity increased by 2.1 log units at 2 h after injection. Thereafter, it decreased once at 4 h and significantly increased at 24 h by 3.4 log units. Electron microscopic examination showed swollen cytoplasmic organelles of the retinal pigment epithelial cells at 4 h after injection. It was thus demonstrated that an early effect of NaIO3 on the electrical response of the mouse retina was more conspicuous than histopathological changes.

Section: Discussionmentioning

confidence: 84%

“…Little information has been gathered on chan-ges of a-and b-waves of the ERG within the first hour of recording (Nilsson et al 1977).…”

mentioning

confidence: 99%

Early effects of sodium iodate injection on ERG in mice

Hosoda

Adachi‐Usami

Mizota

et al. 1993

“…This may explain the transient increase in c-wave amplitude. Histopathological studies in sheep (Nilsson et al 1977) indicated that the earliest ultrastructural change after intravenous injection of 30 mg/kg of NaI03 was the destruction of the basal membrane and a less extent of the apical membrane of the pigment epithelium. Textorius & Welinder (198 1) reported that injection of 30 mg/kg of NaI03 increased the standing potential (SP), whereas injection of 40 mg/'kg NaI03 decreased it in rabbits.…”

Section: Discussionmentioning

confidence: 99%

“…C previously to abolish the c-wave (Noel1 1953(Noel1 , 1954(Noel1 , 1958(Noel1 , 1959(Noel1 , 1963Nilsson et al 1977). This observation was similar for both pigmented and albino rabbits, suggesting that pigmentation is not involved in the drug induced ERG changes.…”

mentioning

confidence: 85%

Paradoxical enhancement of the ERG c‐wave by a small dose of sodium iodate

Nao‐i

Kim

Honda

1986

The early effects of sodium iodate (NaIO3) on the ERG c- and b-waves were studied in rabbits. When 30 mg NaIO3/kg body weight was administered intravenously, the c-wave amplitude decreased and was replaced by a potential of opposite polarity. However, the administration of 20 mg/kg of NaIO3 enhanced the c-wave remarkably. Twenty min after administration, the mean c-wave amplitude significantly increased (P less than 0.001) to 211 +/- 6.2% of the pre-administration amplitude, whereas that of the control was 108 +/- 13.0%. The b-wave amplitude showed no significant changes. When 10 mg/kg of NaIO3 was administered, the enhancement of the c-wave was not remarkable. These effects were similar in both pigmented and albino rabbits. A lower blood concentration of NaIO3 applied to the basal side of the retinal pigment epithelium (RPE) may initially affect only the basal membrane of the RPE resulting in the decrease in the basal membrane resistance (Rba). This would explain the transient increase in the c-wave amplitude with 20 mg NaIO3/kg.

“…The morphology investigated by light microscopy 4 days later showed severe damage to the pigment epithelium, and Noell suggested that the c-wave of the 'on-ERG and the slow negative off-response were related phenomena and that they were generated mainly across the pigment epithelium. Later, Nilsson et al (1977a) observed severe ultrastructural damage to the pigment epithelium 2 h after the injection of NaIO3.…”

mentioning

confidence: 95%

EARLY EFFECTS OF SODIUM IODATE ON THE SLOW OFF‐EFFECTS, PARTICULARLY THE h‐WAVE, AND ON THE c‐WAVE OF THE DC RECORDED ELECTRORETINOGRAM IN RABBIT

Welinder

Textorius

1982

The early effects of intravenously administered sodium iodate (NaIO3) on the slow, negative 'off-effect', the h-wave, and on the slow, positive 'on-effect', the c-wave, of the DC recorded electroretinogram were studied in 8 rabbits. Both the h- and c-waves disappeared gradually after NaIO3 administration and were replaced by potentials of opposite polarity. These results strongly support the assumption that the h-wave originates in the pigment epithelium and represents the reversal of events underlying the c-wave. The slow, positive 'off-effect', the g-wave, elicited by 'dark flashes' was seen to pass into the potential replacing the h-wave after NaIO3 treatment.