C. H. Hill

In vivo interactions of cadmium with copper, zinc and iron.

The chemical similarities between copper, zinc, and cadmium led to the speculation that there existed a copper component of cadmium toxicity in addition to the previously shown zinc component. Cadmium was found to be toxic to chicks at dietary levels of 25 to 400 ppM in a copper- and iron-deficient diet. The toxicity resulted in a reduced growth rate, mortality, microcytic hypochromic anemia, and atony and elongation of the gizzard. The growth depression and gizzard abnormality were corrected by increased dietary zinc. The mortality was reversed by added copper indicating that the speculation which prompted the study was valid. Increased dietary iron partially corrected both the mortality and the growth depression, indicating a previously unsuspected iron component of cadmium toxicity. 13 references, 6 tables.

Multiple Roles for Elastic Fibers in the Skin

Dermal elastic fibers are believed to have a primary role in providing elastic stretch and recoil to the skin. Here we compare the structural arrangement of dermal elastic fibers of chick skin and different animal species. Most elastic fibers in chick skin are derived from cells that line the feather follicle and/or smooth muscle that connects the pterial and apterial muscle bundles to feather follicles. Elastic fibers in the dermis of animals with single, primary hair follicles are derived from cells lining the hair follicle or from the ends of the pili muscle, which anchors the muscle to the matrix or to the hair follicle. Each follicle is interconnected with elastic fibers. Follicles of animals with primary and secondary (wool) hair follicles are also interconnected by elastic fibers, yet only the elastic fibers derived from the primary follicle are connected to each primary follicle. Only the primary hair follicles are connected to the pili muscle. Human skin, but not the skin of other primates, is significantly different from other animals with respect to elastic fiber organization and probably cell of origin. The data suggest that the primary role for elastic fibers in animals, with the possible exception of humans, is movement and/or placement of feathers or hair.

Isolation and characterization of induced ceruloplasmin from chicken serum

Abstract Stree-induced ceruloplasmin was isolated from the serum of chicks infected with Salmonella gallinarum. The purified protein had a molecular weight of 158 000, a ratio of absorbance (A160mμ/A280mμ) of 0.072, and contained 0.20% copper. This indicates 5 atoms of copper per mole of enzyme. Amino acid composition and electrophoretic mobility were similar to those reported for human ceruplasmin. Kinetic studies with p-phenylenediamine as the substrate indicated a Km value of 1.1 mM.

Antibody Raised to AKAAAKAAAKA Sequence on Tropoelastin Recognizes Tropoelastin but not Mature Crosslinked Elastin: A New Tool in Metabolic and Structural Studies of Elastogenesis

Tropoelastin, which is secreted from the cell in a soluble form, contains specific alanine rich repeat domains that are destined to form covalent desmosine and isodesmosine crosslinks in mature insoluble elastin. We raised a monospecific polyclonal antibody to a AKAAAKAAAKA synthetic peptide (AKA) which represents this alanine rich region of tropoelastin. The antibody was reactive with the original peptide antigen and purified tropoelastin, but not with mature crosslinked elastin isolated from several animal species. Conditioned media from chick aorta smooth muscle cells in culture reacted in an ELISA with the AKA antibody, but only in the presence of BAPN to block the conversion of the epsilon-amino groups to aldehydes. Immunofluorescence demonstrated that the AKA antibody decorated newly deposited tropoelastin assembled in fine fibrils in matrix produced by cultured human skin fibroblasts. EM-immunogold specifically localized this antibody to the immature elastic fibers present in fetal sheep ductus arteriosus. Moreover, immunohistochemistry demonstrated that the antibody recognized nonpolymerized tropoelastin assembled on the periphery of elastic fibers in the aorta of chicks raised on copper deficient and BAPN containing diets. These studies demonstrate that this new anti-tropoelastin antibody can be used as a useful tool to investigate elastin metabolism where it is important to distinguish between tropoelastin and mature crosslinked elastin.

ELASTIN DEFECTS IN THE LUNGS OF AVIAN AND MURINE MODELS OF HOMOCYSTEINEMIA

Homocysteinemia in animals is associated with disruption of the elastic fiber component of the extracellular matrix, resulting in vascular complications. The authors have utilized both avian and murine models to investigate the effects of homocysteinemia on lung development and repair following injury. Days old chicks were fed a diet containing 2% methionine for 3 weeks. Pregnant mice were given 2% methionine in the diet and feeding continued for up to 6 weeks after birth. The lungs were removed and examined for defects in elastin fiber formation. Methionine levels were elevated 20-fold in the serum from chicks receiving the methionine and 10-fold in pregnant mice. The elastic fibers in the parabronchi and air capillaries of chicks receiving methionine were thin and clearly disrupted. In the 2% methionine neonatal pups, normal lung development was prevented and the alveoli were significantly enlarged. However, after the pups reached 10 days of age the 2% methionine lungs did not differ histologically from the normal controls. Fetal mice reflected the same serum methionine levels as the dams fed the 2% methionine diet, yet after birth the serum levels of the neonates returned to control levels within 3 days. The authors found that the high serum methionine levels of the dams were not transferred to the milk, allowing the pups to reverse the histopathology observed early and then develop normally. The ability of the lung to replace elastin following elastase injury was not different in mice raised on the 2% methionine diet compared to controls. The studies show that continuous exposure of the developing lung to high circulating levels of methionine/homocysteine can result in major disruptions of elastic fibers and lung architecture. However, young mammals such as the mouse are protected from extended lung pathology because toxic levels of methionine are not transferred through the mothers milk.

Studies on the role of iron in the reversal of cadmium toxicity in chicks.

The interaction of dietary iron levels on vanadium toxicity was studied in chicks. Dietary iron levels ranged from a deficiency, ca. 10 ppm, to an adequacy, 100 ppm supplemental iron. to an excess, 1000 ppm supplemental iron. Vanadium was fed at 10, 20, and 40 ppm. Vanadium toxicity as measured by chick growth was more severe in the iron-deficient animals than in those receiving supplemental iron. The increase in degree of toxicity in the iron-deficient animals was accompanied by an increase in the liver vanadium, both total and concentration. The addition, of vanadium to the diet did not influence the iron concentration of the liver or kidney. Radioisotope, studies with48V revealed that the absorption of vanadium was not influenced by the iron concentration of the diet, but that the iron-deficient animals retained more vanadium in the blood and liver and less in the bone than did the iron supplemented animals. It is proposed that the degree of iron saturation of transferrin and ferritin to which vanadium can bind is a possible explanation for the results obtained.

Relationship between serum somatomedin C levels and tissue selenium content among adults living in a seleniferous area

Abstract Depressed serum somatomedin C levels have been suggested by others as an early indicator of selenium (Se) toxicity. In both human and animal studies, somatomedin C levels were lower in Se supplemented as compared to control subjects. The present study examined Se and somatomedin C levels in 44 adult long-term residents of seleniferous areas in South Dakota. Serum Se (SSe) and whole blood Se (WBSe) levels were analyzed by GC/MS. Toenail Se (TSe) was measured by neutron activation analysis. Somatomedin C was analyzed by RIA assay. Subjects were divided into 3 groups based on the following criteria: group I, SSe 240, WBSe >400 ng/ml. Data were pooled across gender (20 males, 24 females). Somatomedin C levels were not different despite greater than 50% differences in SSe, WBSe, and TSe levels among the groups. In these subjects, somatomedin C was not a sensitive index of elevated Se exposure.

The effect of dietary mercury on vanadate toxicity in the chick.

Three experiments were conducted investigating the interaction of dietary vanadate and mercury on the growth of chicks. The growth-retarding effect of 30 mg vanadium/kg diet was completely overcome by the inclusion of 500 mg mercury/kg diet. Restricting the feed intake of the mercury-supplemented animals to approximately those receiving vanadate alone still resulted in an amelioration of the growth retarding effect of vanadate. Analyses of femurs and kidneys revealed that mercury added to a vanadium-containing diet increased the vanadate concentration of the femur and had no effect on the vanadium concentration in the kidney. As little as 25 mg mercury/kg diet significantly reduced the growth retarding effect of vanadium. The inclusion of 100 mg mercury/kg in the diet resulted in a significant increase in renal glutathione concentration.

Effect of dietary copper on vanadate toxicity in chicks.

The addition of copper to a corn-soybean diet at levels of 200 mg/kg and above lessened the growth-retarding effect of vanadate for chicks. This interaction between vanadate and copper was evident in bothad libitum-fed chicks and chicks in which feed consumption was restricted to approximately equal amounts. The ameliorating effect of copper was not accompanied by changes in the femur levels of vanadium nor by changes in the hepatic or renal glutathione concentrations. Zinc added at 515 mg/kg of diet had no effect on the toxicity of vanadium. Sodium sulfate added at a level to supply the same amount of sulfate, as supplied by 500 mg/kg copper sulfate, was without effect on the vanadate-induced growth depression. The underlying mechanism of the interaction of copper and vanadium is not known, but it does not lie in changes in feed consumption or organ burdens of vanadium, as represented by the femur vanadium concentrations.

Interaction of vanadate and chloride in chicks

Six experiments have been conducted examining the interaction of dietary sodium chloride levels and vanadate toxicity in chicks. Increasing the dietary supplement of NaCl from 0.5 to 2.0% resulted in amelioration of vanadate toxicity, as measured by growth rate. The amelioration was found to reside in the chloride ion. Hepatic, renal, and femur vanadium concentrations were usually reduced at the higher levels of NaCl supplementation, but there was little correlation between these reductions and the reversal of vanadate toxicity.