Environmental exposure to cadmium and factors affecting trace-element metabolism and metal toxicity

In the general population, food constitutes the major environmental source of cadmium (Cd) in nonsmokers. It is established that leafy vegetables, roots, and grains (wheat or rice) can accumulate relatively high amounts of Cd from the soil. Beef liver and kidney and shellfish are also major dietary sources of Cd. The daily intake of Cd in various parts of the world is different and depends on both the dietary habits and concentration of Cd in foodstuffs. Because of the long biological half-life of Cd in humans and absence of any specific indicators of its toxicity, the environmental exposure of Cd should be monitored in various countries. Although environmental Cd poisoning is rare, there are isolated reports on excessive exposure to Cd in Japan and Shipham, a zinc-mining town in England. The body retention and toxicity of Cd depends on various factors, such as daily intake, the form of Cd in food, its interactions with essential elements, and nutritional status of the population. Since kidney is considered a critical organ in Cd toxicity, the indicators of renal dysfunction have been widely used for evaluation of Cd poisoning in occupationally exposed people. It is unclear whether similar indicators can be used for monitoring environmental Cd exposure.     

Developmental changes in hepatic metallothionein, zinc, and copper levels in genetically altered mice.

Using mice that either overexpress metallothionein 1 (MT-1*) or do not express metallothionein 1 and 2 (MT-null) and a control strain (C57BL/6), the essential metal storage function of hepatic metallothionein and its subcellular localization were investigated during development. Hepatic metallothionein, zinc, and copper levels were measured in all groups from gestational day 20 to 60 days of age. Hepatic metallothionein levels were maximal during the perinatal period in both MT-1* and C57BL/6 mice with levels approximately three times higher in MT-1* mice. MT-null mice had no detectable hepatic metallothionein throughout development. Hepatic zinc levels were highest in the neonatal period of MT-1* and C57BL/6 mice and declined to adult levels by 30 days of age, while hepatic zinc levels in MT-null mice did not vary markedly throughout development. Hepatic copper profiles were very similar in MT-1* and MT-null mice as compared with the C57BL/6 mice. Correlation analysis showed a strong positive correlation between hepatic metallothionein and zinc levels in MT-1* mice, moderate correlation between hepatic metallothionein and metals in C57BL/6 mice, but only a very weak correlation between hepatic metallothionein and copper levels in MT-1* mice. Immunohistochemical localization showed specific nuclear staining in both MT-1* and C57BL/6 mice during the neonatal period with a gradual shift to the cytoplasm. The results show that hepatic metallothionein is a major determinant of zinc but not copper levels during murine development. Additionally, hepatic metallothionein levels and localization are regulated in a similar manner in MT-1* and C57BL/6 mice. The MT-null mice maintain a basel level of zinc sufficient for development, which was found to be 15.9 micrograms/g. This value was similar to the levels of hepatic zinc that was not bound to metallothionein in MT-1* and C57BL/6 mice during development.     

Change in acetylcholinesterase during early phase of experimental spinal cord trauma in primates

Specific activity of acetylcholinesterase has been shown to be decreased following experimental spinal cord trauma (200 gcm) in primates. The decrease in activity was evident at 8, 24, 48 hr and 1 week after injury to the traumatized segments of spinal cord.     

Fine structure and cytochemical evidence for the presence of polysaccharide surface coat of Dirofilaria immitis microfilariae

Cherian P. V., Stromberg B. E., Weiner D. J. and Soulsby E. J. L. 1980. Fine structure and cytochemical evidence for the presence of polysaccharide surface coat of Dirofilaria immitis microfilariae. International Journal for Parasitology10: 227–233. Cytochemical staining techniques were employed at the fine structural level using ruthenium red, ruthenium violet and Alcian blue-lanthanum nitrate to demonstrate the polysaccharide rich surface coat of Dirofilaria immitis microfilariae. The coat matrix present at the external surface of the cuticle of microfilariae stained densely with each of the polycationic dyes. The reaction products were restricted to the outer surface of the cuticle suggesting that the polycationic dyes did not penetrate the cuticle. The junctions of the cuticular annulations lacked surface coat matrix and reaction products which might be indicative of the absence of carbohydrate residues or the masking of reactive sugar molecules in these areas. The speciflcity of the reaction was indicated by the absence of reaction products in untreated organisms. These carbohydrate moieties probably represent glycoproteins as structural constituents of the parasite surface. Ultrastructural analysis of the surface of microfilariae is of signiflcance in elucidating both the molecular dynamics of the parasite surface and its immunological function in the host.