Some effects of methyl mercury salts on the rabbit nervous system

Abstract

Young adult rabbits have been given methyl mercury salts by subcutaneous injections or by gastric intubation. After 3 daily doses of 7.5 mg/kg by the 8th day moderate to severe ataxia developed, and after 4 doses, severe ataxia. Some of these latter animals might die. This species, therefore, seems to be about twice as sensitive to the neurotoxic properties of methyl mercury salts as the laboratory rat. With the light microscope extensive degenerative changes were seen in primary sensory ganglion cells, in both Purkinje and granule cells of the cerebellum, and in certain cells in several regions of the forebrain. The earliest changes became visible microscopically about the fourth day after commencing dosing, and reached a maximum of severity from the 7th to 10th day. The pattern of neuronal damage more closely resembled that found in the cat and in man than that seen in the rat. No evidence of changes vascular permeability was detected.

Widespread calcium deposits, as detected using the alizarin red S technique, in the nervous system of rats treated with dimethyl mercury

“…In the present study, although neuronal cell death was distributed widely in the central and peripheral nervous systems, calcium deposits, as detected by staining with von Kossa's method, were restricted to the cerebellum from day 32 onward. In contrast calcium deposition has never been reported, even in chronic cases of human MeHg intoxication 12 or in experimental MeHg intoxication in the mouse, 16 rabbit 15 or cat. 14 It is likely that cerebellar calcification (detected by von Kossa's method) following MeHg intoxication and dimethyl mercury exposure is specific to the rat.…”

“…It is well known that the nervous system displays regional and cellular differences in its sensitivity to MeHg. 7,8 The cerebellar granule cells, calcarine cortical neurons, and the dorsal root ganglion (DRG) neurons in humans [9][10][11][12] and in other animals [13][14][15][16][17][18][19][20] are the most vulnerable to MeHg. Previous histopathologic studies using von Kossa's staining method have shown that deposition of calcospherites occurs in the granular layer of the cerebellum in rats that have survived for a long time following MeHg administration.…”

Changes in the Distribution of Histochemically Localized Mercury in the CNS and in Tissue Levels of Organic and Inorganic Mercury During the Development of Intoxication in Methylmercury Treated Rats

“…Some primates in the study of Garman et al., (1975) showed a similar distribution. It is possible that the granular layer neurones, which are known to be particularly sensitive to the toxic effects of methylmercury, (Carmichael, Cavanagh & Rodda 1975;Jacobs, Carmichael & Cavanagh, 1977;Cavanagh, 1977) succumbed to mercury concentrations that were below the detection limit of the staining technique used in this study. Alternatively, mercury in the larger neurones and glial cells may have undergone a chemical transformation essential for the precipitation of silver by the technique used or which prevents its loss from the cells during tissue preparation.…”

Effects of methylmercury chloride on rat incisor odontoblasts and dentinogenesis

“…In man, sensory and motoric dysfunction including paresthesia, constriction of the visual field, impairment of fine coordination, and ataxia have been described (1 1-14). Similar neurological disturbances are found after administration of organomercurial compounds in the rat, rabbit, mink, and cat (15)(16)(17)(18). Histomorphologically, the earliest signs of experimental intoxication are dispersion of rough endoplasmic reticulum in neurons (19), followed by diminished protein synthesis in the same cells (20).…”

“…Histomorphologically, the earliest signs of experimental intoxication are dispersion of rough endoplasmic reticulum in neurons (19), followed by diminished protein synthesis in the same cells (20). Later, degenerative and necrotic changes are seen, especially in primary sensory ganglion cells and in Purkinje and granule cells of the cerebellum (15,18).…”