Hidehiro Tokunaga

In vivo protection of a water-soluble derivative of vitamin E, Trolox, against methylmercury-intoxication in the rat

Methylmercury (MeHg) is a well-known neurotoxicant. MeHg-intoxication causes a disturbance in mitochondrial energy metabolism in skeletal muscle and apoptosis in cerebellum. We report the first in vivo effectiveness of antioxidant Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carhoxylic acid), a water soluble vitamin E analog, against the MeHg-induced cellular responses. Treatment with Trolox (6-hydroxy-2.5,7,8-tetramethylchroman-2-carboxylic acid) clearly protects MeHg-treated rat skeletal muscle against the decrease in mitochondrial electron transport system enzyme activities despite the retention of MeHg. Tdt-mediated dUTP nick-end-labeling method clarified that Trolox is effective for protecting cerebellum from MeHg-induced apoptosis. These data indicate that MeHg-mediated oxidative stress plays an important role in the in vivo pathological process of MeHg intoxication. Trolox may prevent some of clinical manifestations of MeHg-intoxication in humans.

An Autopsy Case of Minamata Disease (Methylmercury Poisoning)—Pathological Viewpoints of Peripheral Nerves

The outbreak of methylmercury poisoning in the geographic areas around Minamata Bay, Kumamoto, Japan in the 1950s has become known as Minamata disease. Based on earlier reports and extensive pathological studies on autopsied cases at the Kumamoto University School of Medicine, destructive lesions in the anterior portion of the calcarine cortex and depletion predominantly of granular cells in the cerebellar cortex came to be recognized as the hallmark and diagnostic yardstick of methylmercury poisoning in humans. As the number of autopsy cases of Minamata disease increased, it became apparent that the cerebral lesion was not restricted to the calcarine cortex but was relatively widespread. Less severe lesions, believed to be responsible for the motor symptoms of Minamata patients, were often found in the precentral, postcentral, and lateral temporal cortices. These patients also frequently presented with signs of sensory neuropathy affecting the distal extremities. Because of few sufficiently comprehensive studies, peripheral nerve degeneration has not been universally accepted as a cause of the sensory disturbances in Minamata patients. The present paper describes both biopsy and autopsy findings of the peripheral nerves in a male fisherman who died at the age of 64 years and showed the characteristic central nervous system lesions of Minamata disease at autopsy. A sural nerve biopsy with electron microscopy performed 1 month prior to his death showed endoneurial fibrosis and regenerated myelin sheaths. At autopsy the dorsal roots and sural nerve showed endoneurial fibrosis, loss of nerve fibers, and presence of Büngners bands. The spinal cord showed Wallerian degeneration of thefasciculus gracilis (Golls tract) with relative preservation of neurons in sensory ganglia. These findings support the contention that there is peripheral nerve degeneration in Minamata patients due to toxic injury from methylmercury.

A fetal type of minamata disease. An autopsy case report with special reference to the nervous system

Our knowledge concerning the pathology of fetal cases of human Minamata disease (methylmercury poisoning) is relatively limited. We report here a case with description of the distribution of mercury in the systemic organs, and the ultrastructural changes of the nervous system after a survival of 29 yr. The patient was a female born in 1957, with a body wt of 3000 g, who died in 1987. She carried a diagnosis of cerebral palsy, and had a convulsion at age 3 yr. Mercury levels in her mothers hair were 101 micrograms/g at the time of examination in 1959. At autopsy, the body measured 43 cm and weighed 23 kg. The brain weighed 920 g and showed marked cerebral atrophy, mild neuronal loss in the calcarine, postcentral and precentral cortices, cerebellar atrophy, and segmental demyelination of peripheral nerves. Mercury granules were present in the brain, kidney, and liver. Ultrastructural examination of the calcarine, post- and precentral cortices, and cerebellar cortices, showed severe atrophy of nerve cells, with a decrease in rough ER and an increase in nuclear chromatin and preservation of mitochondria. Autophagosomes were increased in number. In addition, high electron density, globular and dense bodies, measuring 0.3-1.8 microns in diameter, were found, surrounded by limited membrane, within both cerebral and cerebellar neurons. In the cellebellum, synapses were well-preserved.

Differential Diagnosis between Organic and Inorganic Mercury Poisoning in Human Cases-The Pathologic Point of View

Differences in pathology were found between acute and chronic exposure to methylmercury, mercury vapor, and inorganic mercury. Characteristic pathologic changes produced by organic mercury in the brain have previously been described in patients with Minamata disease. The brains of patients who presented with acute onset of symptoms and died within 2-mo showed loss of neurons with reactive proliferation of glial cells, microcavitation, vascular congestion, petechial hemorrhage, and edema in the cerebral cortices, predominantly in the calcarine, pre- and postcentral, and transverse temporal cortices and in the cerebellar cortex. The neuropathologic changes in the patients with acute onset of symptoms who survived for a long period (> 10 yr) were also included neuronal loss with reactive proliferation of glial cells in similar anatomic locations. The neuropathologic changes in patients with inorganic mercury poisoning are quite different. Autopsies performed on 3 individuals with fatal cases of acute inorganic mercury poisoning who were exposed to mercury vapor for about 2 wk revealed diffuse organized pneumonia, renal cortical necrosis, disseminated intravascular coagulopathy, and infarctions in the brain and kidneys. In 2 other patients who worked in mercury mines for about 10 yr and who suffered from chronic inorganic poisoning, no specific lesions were demonstrated in the brain. However, the assay and the histochemistry of mercury revealed that inorganic mercury was present in the brain in all 3 groups irrespective of the brain lesions and the duration of clinical signs.

Extensive intraoperative peritoneal lavage and chemotherapy for gastric cancer patients with peritoneal free cancer cells.

Abstract.The effects of extensive intraoperative peritoneal lavage (EIPL) for gastric cancer patients with peritoneal free cancer cells were investigated. This study was based on 22 consecutive patients with peritoneal free cancer cells, among 663 patients who underwent curative surgical treatment for advanced gastric cancer. The 22 patients were followed up for 2 years or until death. These patients were divided into three groups: group 1, patients with no additional intraoperative therapy (from 1989 to 1992; n = 8); group 2, patients with intraoperative intraperitoneal chemotherapy alone (from 1992 to 1995; n = 7); and group 3, patients with EIPL followed by intraoperative intraperitoneal chemotherapy (from 1996 to 1999; n = 7). Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed that viable cancer cells were not detected after the eighth EIPL in a gastric cancer patient with numerous intraperitoneal free cancer cells. In group 3, 4 of the 7 patients survived for more than 2 years, including 3 with cancer-free status, whereas no patient survived cancer-free in groups 1 and 2. The peritoneal recurrence rates and cancer-specific 2-year survival rates in groups 1, 2, and 3 were 100%, 85.7% and 42.9%; and 0%, 14.3%, and 57.1%, respectively. The 2-year survival rate of group 3 was significantly higher than that of group 1 (P = 0.017) and that of group 2 (P = 0.025). In a subset analysis, patients with peritoneal free gastric cancer cells but no macroscopic dissemination showed a statistically significant improvement in survival those treated with EIPL compared with those not treated with EIPL.

Methylmercury Poisoning in Common Marmosets—A Study of Selective Vulnerability Within the Cerebral Cortex

Neuropathological lesions found in chronic human Minamata disease tend to be localized in the calcarine cortex of occipital lobes, the pre- and postcentral lobuli, and the temporal gyri. The mechanism for the selective vulnerability is still not clear, though several hypotheses have been proposed. One hypothesi s is vascular and postulates that the lesions are the result of ischemia secondary to compression of sulcal arteries from methylmercury-induced cerebral edema. To test this hypothesis, we studied common marmosets because the cerebrum of marmosets has 2 distinct deep sulci, the calcarine and Sylvian fi ssures. MRI analysis, mercury assays of tissue specimens, histologic and histochemical studies of the brain are reported and discussed. Brains sacrifi ced early after exposure to methylmercury showed high contents of methylmercury and edema of the cerebral white matter. These results may explain the selective cortical degeneration along the deep cerebral fi ssures or sulci.

Methylmercury Poisoning in Common Marmosets—MRI Findings and Peripheral Nerve Lesions

Common marmosets were used as model animals for methylmercury (MeHg) poisoning. Six marmosets were given MeHg of 5 ppm Hg in drinking water. The animals were divided into 3 groups of 2 each. The first group was examined for acute symptomatic MeHg poisoning. They were given MeHg for 70 and 90 days, respectively, to manifest severe symptoms. The second group was sacrificed after 38 days of MeHg exposure, when they had acute-subclinical MeHg poisoning. The third group of animals was exposed for 21 days, and then observed for 2.5 years without MeHg exposure. One of them showed typical symptoms of MeHg poisoning after MeHg exposure had ended, but the other one showed only slight symptoms without ataxia. This experiment demonstrated that MeHg causes pathological changes in neural tissues including the peripheral nerves in common marmosets. Furthermore, common marmosets were found to show MeHg-induced pathological changes similar to those in humans in the cerebrum and cerebellum.