Teratogenic effects of a chelating agent and their prevention by zinc.

Ingestion of a chelating agent (ethylenediaminetetraacetic acid) by female rats during pregnancy impaired reproduction and resulted in congenitally malformed young. When ethylenediaminetetraacetic acid was fed from days 6 to 21 of gestation, all of the full-term young had gross congenital malformations. These effects were prevented by simultaneous supplementation with 1000 parts per million of dietary zinc.

Zinc-deficient embryos: reduced thymidine incorporation.

The 12-day-old embryos of rats with a deficiency of zinc showed a reduced uptake of tritiated thymidine when compared with controls, as shown by liquid scintillation and autoradiography. The high incidence of gross congenital malformations resulting from zinc deficiency may thus be caused by DNA impaired DNA synthesis.

Neurological defect: manganese in phenocopy and prevention of a genetic abnormality of inner ear.

A specific congenital ataxia may be caused by presence of mutant genes and by manganese deficiency during prenatal development in normal mice. Supplementation of the diet of mutant mice with manganese during prenatal development rectifies the aberrant development, resulting in normal behavior. The congential ataxa results from defective development of the the otoliths.

Copper supplementation in quaking mutant mice: reduced tremors and increased brain copper.

Mice homozygous for the mutant gene quaking (qk) with a high frequency of axial tremors had a low concentration of copper in the brain. Supplementation during pregnancy and lactation with a high level of dietary copper greatly reduced the frequency of tremors and brought brain copper level to normal in the off-spring. It is suggested that qk affects copper metabolism.

Liver mitochondria from manganese-deficient and pallid mice: function and ultrastructure.

Oxidative phosphorylation was studied in isolated liver mitochondria from manganese-deficient mice and in those from a mutant strain, pallid. In mitochondria from manganese-deficient mice, ratios of adenosine triphosphate formed to oxygen consumed were normal, but oxygen uptake was reduced. Electron microscopy of these mitochondria revealed ultrastructural abnormalities including elongation and reorientation of cristae. No biochemical or structural abnormalities were found in mitochondria from pallid mice.

Gestational zinc deprivation in mice: persistence of immunodeficiency for three generations.

Pregnant Swiss Webster mice were fed a diet moderately deficient in zinc from day 7 of gestation until parturition. Offspring of these mice showed depressed immune function through 6 months of age. In addition, the second and third filial generations, all of which were fed only the normal control diet, continued to manifest reduced immunocompetence, although not to the same degree as in the first generation.

Zinc binding: a difference between human and bovine milk.

Gel chromatography indicated that most of the zinc in cow's milk was associated with high-molecular-weight fractions, whereas zinc in human milk was associated with low-molecular-weight fractions. A species difference in zinc-binding ligands may explain why symptoms of the genetic disorder of zinc metabolism, acrodermatitis enteropathica, can be alleviated by feeding human but not cow's milk.

A mutation influencing the transportation of manganese, L-dopa, and L-tryptophan.

Transportation of manganese, L-dopa, and L-tryptophan was slower through the tissues, of intact pallid mice than through those of black C57Bl/6J mice, presumably because of the influence of the gene pallid.

Evaluation of negative staining technique for determination of CN--insensitive superoxide dismutase activity.

The different forms of superoxide dismutase (superoxide-superoxide oxidoreductase, EC 1.15.11) have been studied, in tissues of rat, mouse and chicken, by the ectrophoresis-nitro blue tetrazolium technique proposed by Beauchamp. Similar enzyme patterns were evident in every tissue. A fast migrating CN--sensitive form of dismutase activity was present in isolated liver mitochondria of each species. Chicken and mouse liver mitochondria, as well as whole homogenate of every tissue of these two species, showed two additional slow-migrating bands of CN--insensitive activity. In contrast, such bands were not detectable in mitochondria isolated from rat liver or in any of the rat tissues analyzed by this technique. Prior to their electrophoretic separation, the samples were analyzed for CN--insensitive superoxide dismutase activity by a spectrophotometric assay; by this assay it was possible to demonstrate and quantitate a CN--insensitive superoxide dismutase activity in every preparation. Two units of CN--insensitive activity were applied to the gels for each sample. These results indicate that the electrophoresis-nitro blue tetrazolium technique is unsuitable for the detection of the rat CN--insensitive form of superoxide dismutase in crude preparations such as whole tissue homogenates or isolated mitochondria.

Hematologic and trace element alterations following chronic maternal ingestion of propylthiourea.

Rats with diets containing 0.2% propylthiouracil (PTU) throughout gestation had progeny with persistent cyanosis and high neonatal mortality. Histological and histochemical studies failed to reveal lung abnormalities in these pups. Studies of the blood of PTU-fed dams demonstrated that hemoglobin, packed cell volume, and numbers of erythrocytes were significantly reduced. In their 21-day fetal young, erythrocytopenia was accompanied by an elevated mean corpuscular volume and a reduced mean corpuscular hemoglobin concentration. Imprints of marrow from dams and of liver and spleens of the young showed normoblastic erythropoiesis. A granulocytic leucocytosis was present in the blood of the PTU-fed dams, whereas their progeny had a granulocytopenic leucopenia. Tissue concentrations of copper, zinc, manganese, magnesium and iron were determined. The most striking changes observed were the significant elevations of copper in the dams' brain, liver and kidneys. No changes in the concentration of any of the trace minerals were found in the livers of the pups. Food restriction to the dam failed to significantly alter maternal or fetal hematologic or trace element concentrations as compared with controls. It is evident that PTU, when fed to pregnant rats, has demonstrable effects on erythropoiesis, granulocytopoiesis, and maternal trace element distribution. It is not presently known whether these phenomena are interrelated.

Dynamics of insulin and glucagon release in rats: influence of dietary manganese.

The effect of manganese on endocrine pancreatic function was examined in manganese-sufficient (control) and manganese-deficient (Mn-) Sprague-Dawley rats. Pancreatic insulin release was lower (P less than 0.05) in Mn- rats than in controls in response to both a 300 mg/dl and a 100 mg/dl glucose stimulus. The 300 mg/dl glucose stimulus induced the synthesis of 19.4 micrograms insulin/g pancreas in control rats. Additionally, no appreciable intracellular degradation of insulin occurred over an 80-min perfusion period. By contrast, in Mn- rats, there occurred an intracellular insulin degradation amounting to 7.8 micrograms/g pancreas. This enhanced degradation was partially compensated by a net insulin synthesis of only 3.4 micrograms insulin/g pancreas. Initial (min 1-3) insulin release by Mn- rats in response to 10 mM arginine was lower (P less than 0.05) than that observed in controls. Pancreatic glucagon release in response to 10 mM arginine was not affected by manganese deficiency. These findings demonstrate that manganese deficiency results in depressed pancreatic insulin synthesis and enhanced degradation. These factors may be responsible for the abnormal carbohydrate metabolism observed in Mn- animals.

Effect of large amounts of vitamin E during pregnancy and lactation.

The effects of excessive intake of vitamin E during gestation and lactation on female rats and their progeny were studied. Pregnant rats receiving large doses of vitamin E (22.5 to 2252 mg/kg per day) had larger livers, higher levels of lipids and vitamin E in plasma, and higher concentrations of vitamin E in the livers than did controls. These deviations from normal were not, however, observed for all levels of supplementation. No obvious teratogenic effects were observed in the newborn young of the vitamin E-supplemented rats. Some eye abnormalities were seen in the older pups of rats given extremely high amounts of the vitamin. The survival rate, weight of the pups, and litter size were unaffected. However, the pups of the mothers who had received 500 mg of vitamin E per day (2252 mg/kg per day) during gestation and lactation had a much higher concentration of vitamin E in their livers and plasma than did controls. This study also confirmed the observation that vitamin E transfer across the placenta is negligible and that mammary transfer of this vitamin is quite efficient.

Zinc absorption through skin: correction of zinc deficiency in the rat.

The therapeutic effect of topical administration of zinc was tested in pregnant rats consuming a diet deficient in the element. Four groups of rats were fed a zinc-deficient diet for 24 hr. Half of the animals were treated during this period with a topical application of oil saturated with zinc chloride, for the full 24 hr in one group, and for the last 8 hr in the other. In the two remaining groups, oil without zinc chloride was applied under the same conditions as described above, and in all cases oral ingestion of the supplement was prevented. At the end of the 24-hr period, the animals were killed and plasma zinc was determined. An additional group of animals consuming a diet adequate in zinc was killed without any treatment to provide control values of normal plasma zinc. Rats consuming the deficient diet and without topical zinc supplementation had plasma zinc values significantly lower than all other groups after 24 hr. Animals receiving zinc supplementation for 8 hr had plasma levels similar to those of the control group fed an adequate zinc diet and significantly higher than those of rats that received no zinc application to the skin. In animals in which zinc was applied for 24 hr, plasma zinc values were significantly higher than in any other group, including normal controls. The results indicate that percutaneous transport of zinc may be of sufficient magnitude to be clinically significant and that topical application of this element may be useful in cases of dietary zinc deficiency or diseases producing a zinc deficiency state.

Zinc and copper binding proteins in human milk.

The proteins binding zinc and copper in human milk have been fractionated and identified, and the distribution of these trace elements among the different binding compounds has been determined. Casein was separated by ultracentrifugation and was found to contain 14% (range 5 to 21%) of the total zinc content in the milk and 28% (range 7 to 48%) of the total copper. Another zinc- and copper-binding protein was isolated by gel filtration and ion-exchange chromatography and identified as serum albumin by gel electrophoresis. Serum albumin in breast milk binds 28% of total zinc and 39% of total copper. The remainder of Zn and Cu was found to be in a low molecular weight form (29% (range 24 to 36%) of Zn; 24% (range 15 to 47%) of Cu) or associated to the fat (29% (range 20 to 45%) of Zn; 9% (range 1 to 21% of Cu). It is hypothesized that association constants of the different binding compounds as well as their concentrations will determine the relative distribution of zinc and copper among them and may affect bioavailability of these elements for the infant.

Copper nitrilotriacetate: a potent therapeutic agent in the treatment of a genetic disorder of copper metabolism.

Copper nitrilotriacetate (NTA) was evaluated for its ability to ameliorate effects of the recessive mutant gene crinkled (cr) in mice. Copper-NTA was superior to copper sulfate in increasing postnatal survival and body copper content of offspring of dams supplemented during pregnancy and lactation. Feeding of NTA alone during these periods had no effect on survival. Postnatal supplementation with copper did not increase survival of the mutants. The therapeutic use of copper-NTA, and the necessity for prenatal intervention for successful treatment of the mutant, are discussed in relation to Menkes' syndrome.

Manganese binding proteins in human and cow's milk.

Manganese nutrition in the neonatal period is poorly understood, due in part to a lack of information on the amount of manganese in infant foods and its bioavailability. Since the molecular localization of an element in foods is one determinant of its subsequent bioavailability, we have studied the binding of manganese in human and cow's milk. An extrinsic label of 54Mn was shown to equilibrate isotopically with native manganese in milks and formulas. Milk samples were separated into fat, casein and whey by ultracentrifugation. In human milk, the major part (71%) of manganese was found in whey, 11% in casein and 18% in the lipid fraction. In contrast, in cow's milk, 32% of total manganese was in whey, 67% in casein and 1% in lipid. Within the human whey fraction, most of the manganese was bound to lactoferrin, while in cow's whey, manganese was mostly complexed to ligands with molecular weights less than 200. The distribution of manganese in formulas was closer to that of human milk than of cow's milk. The bioavailability of manganese associated with lactoferrin, casein and low molecular weight complexes needs to be assessed.

Picolinic acid in milk, pancreatic juice, and intestine: inadequate for role in zinc absorption.

Picolinic acid (PA) was measured by high pressure liquid chromatography in human milk and other fluids and tissues. Skimmed human milk, intestinal homogenates from human infants and rats, and human and rat pancreatic juice were ultrafiltered and analyzed by high pressure liquid chromatography using an anion-exchange column. Identity of sample components was verified by comparing retention times with those of pure nicotinic acid and PA. The detection limit for PA was 2.5 microM. Human milk contained less than 3.7 microM PA. PA was undetectable in human infant or rat intestine or in human or rat pancreatic juice. The extremely low concentration of PA in milk and its apparent absence in pancreatic juice and intestine provide additional evidence that PA is not the low molecular weight zinc binding ligand of human milk and that it does not have an important physiological role in intestinal zinc absorption.

Dietary superoxide dismutase does not affect tissue levels.

The effects of dietary supplementation of superoxide dismutase on tissue superoxide dismutase levels were examined in mice. Mice were divided into two groups; the control received a complete purified diet, and the supplemented group received the same diet containing 0.004% superoxide dismutase. There were no differences in the activity of CuZn superoxide dismutase or Mn superoxide dismutase in intestine, liver, kidney, or blood. These data show that oral supplementation of superoxide dismutase does not affect tissue superoxide dismutase activity.

Persistent immunological consequences of gestation zinc deprivation.

Recent work has shown that offspring of outbred mice deprived of adequate dietary zinc during the latter two-thirds of gestation exhibited a defective direct plaque-forming cell response to immunization with heterologous erythrocytes, as well as impaired ontogenesis of serum IgM. Moreover, such aberrant immunological measurements continued to be observed, although to a lesser degree, in F2 and F3 progeny. We now demonstrate that offspring of mice moderately deprived of zinc (5 ppm zinc diet) between days 7 and 20 of gestation also show an aberrant pattern of development of serum levels of IgG2a and IgA, despite complete nutritional rehabilitation beginning at birth. Only by 6 months of age were concentrations of these serum immunoglobulins similar to those in offspring of control dams. In contrast, levels of IgG1 and IgG2b were within normal ranges by 6 wk of age. Cross-fostering of zinc-deprived offspring to dams adequately nourished during pregnancy did little to ameliorate their aberrant pattern of serum immunoglobulin development. Defective maturation of serum IgG2a and IgA did not persist in F2 and F3 progeny. Nonetheless such 2nd and 3rd generation offspring continued to have higher than normal perinatal mortality. The alterations of immune ontogenesis in these mice could not be attributed to the persistence of abnormal plasma zinc levels, as these were within normal ranges. It would appear that zinc deficiency during gestation may alter the basic mechanism of development of immunological competence.

A prospective study of serum copper and zinc levels in patients receiving total parenteral nutrition.

Weekly determinations of serum copper (Cu) and zinc (Zn) were made in eight adult patients receiving total parenteral nutrition (TPN) for 3 to 13 weeks. Serum Cu decreased in all eight patients. Five of eight patients had hypocupremia lasting at least 2 consecutive weeks and three of the five had Cu levels of 30 mug/dl or lower. Low levels of serum ceruloplasmin provided supportive evidence of Cu deficiency in the three patients with the lowest Cu levels. Two patients who had Cu less than or equal to 20 mug/dl demonstrated declines in hemoglobin which were probably due to Cu deficiency. The mean rate of decline in serum Cu was 10.8 mug/dl/week. After resumption of oral feedings in five patients, the mean rate of increase in Cu was 14 mug/dl/week. The sharpest rise in Cu was seen during the 2nd week after oral feedings were resumed in four of the five patients. Three of eight patients had serum Zn levels less than 70 mug/dl for at least 2 consecutive weeks. Serum Zn decreased at a mean rate of 6.6 mug/dl/week. There was a further decline in serum Zn in three of five patients in whom measurements were made after resumption of oral intake. Concentrations of Zn in TPN solutions varied between 0.63 and 1.0 mg/liter. Cu was undetectable in TPN solutions.