Influence of periconceptional zinc deficiency on embryonic plasma membrane function in mice

Brain-Delivery of Zinc-Ions as Potential Treatment for Neurological Diseases: Mini Review

Homeostasis of metal ions such as Zn(2+) is essential for proper brain function. Moreover, the list of psychiatric and neurodegenerative disorders involving a dysregulation of brain Zn(2+)-levels is long and steadily growing, including Parkinson's and Alzheimer's disease as well as schizophrenia, attention deficit and hyperactivity disorder, depression, amyotrophic lateral sclerosis, Down's syndrome, multiple sclerosis, Wilson's disease and Pick's disease. Furthermore, alterations in Zn(2+)-levels are seen in transient forebrain ischemia, seizures, traumatic brain injury and alcoholism. Thus, the possibility of altering Zn(2+)-levels within the brain is emerging as a new target for the prevention and treatment of psychiatric and neurological diseases. Although the role of Zn(2+) in the brain has been extensively studied over the past decades, methods for controlled regulation and manipulation of Zn(2+) concentrations within the brain are still in their infancy. Since the use of dietary Zn(2+) supplementation and restriction has major limitations, new methods and alternative approaches are currently under investigation, such as the use of intracranial infusion of Zn(2+) chelators or nanoparticle technologies to elevate or decrease intracellular Zn(2+) levels. Therefore, this review briefly summarizes the role of Zn(2+) in psychiatric and neurodegenerative diseases and highlights key findings and impediments of brain Zn(2+)-level manipulation. Furthermore, some methods and compounds, such as metal ion chelation, redistribution and supplementation that are used to control brain Zn(2+)-levels in order to treat brain disorders are evaluated.

The Embryo and Its Future1

The preimplantation mammalian embryo from different species appears sensitive to the environment in which it develops, either in vitro or in vivo, for example, in response to culture conditions or maternal diet. This sensitivity may lead to long-term alterations in the characteristics of fetal and/or postnatal growth and phenotype, which have implications for clinical health and biotechnological applications. We review the breadth of environmental influences that may affect early embryos and their responses to such conditions along epigenetic, metabolic, cellular, and physiological directions. In addition, we evaluate how embryo environmental responses may influence developmental potential and phenotype during later gestation. We conclude that a complex of different mechanisms may operate to associate early embryo environment with future health.

Role of zinc in plasma membrane function

The concentration of plasma zinc is the generally accepted index of zinc status. Although low plasma zinc is an essential criterion of deficiency, alone it is inadequate. To supplement this index, we sought to determine the first limiting biochemical defect in animals fed zinc-deficient diets and concluded that the limiting function is associated with a posttranslational change in plasma membrane proteins. Among the signs of zinc deficiency in rats is a bleeding tendency associated with failure of platelet aggregation, a phenomenon that correlates with impaired uptake of Ca(2+) when stimulated. Zinc-deficient guinea pigs exhibit signs of peripheral neuropathy, and their brain synaptic vesicles exhibit impaired Ca(2+) uptake when they are stimulated with glutamate. Red cells from zinc-deficient rats show increased osmotic fragility associated with decreased plasma membrane sulfhydryl concentration. Both phenomena are readily reversed (2 d) by dietary zinc repletion. Volume recovery is dependent on Ca-dependent K channels and the sulfhydryl redox state. Both the impaired aggregation and calcium uptake of zinc-deficient platelets are corrected by in vitro incubation of blood with glutathione. Considering the fact that plasma membranes from several cell types show impaired function that is associated with a decreased rate of calcium uptake, it is postulated that a defect in calcium channels is the first limiting biochemical defect in zinc deficiency. The calcium uptake defect and consequent impaired second-messenger function likely results from an abnormal sulfhydryl redox state in the membrane channel protein.

Cytogenetic effects of cadmium on unfertilized oocytes in short-term zinc deficiency in hamsters

Chromosomal mutagenic effects of cadmium were examined during oogenesis in hamsters fed a zinc-deficient diet in the short term. Although mild zinc deficiency per se decreased the number of oocytes recovered, other reproductive and cytogenetic effects were not observed. On the other hand, cadmium induced a high incidence of oocyte degeneration and diploidy, which did not differ between the zinc-deficient and control groups. The mutagenic activities of cadmium were not accentuated in metaphase II oocytes of zinc-deficient hamsters. However, it appears that zinc deficiency alters the effects of cadmium on the reproductive system in female hamsters.