Subject(s)
Agriculture , Carbon Dioxide , Carbon , Forestry , Agriculture/economics , Animals , Climate , Conservation of Natural Resources/economics , Costs and Cost Analysis , Crops, Agricultural/economics , Fertilizers , Forestry/economics , Greenhouse Effect , Models, Theoretical , Soil , Trees , United StatesABSTRACT
Fixed aliquots of both radiolabeled [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and hepatic Ah receptor from C57BL/6J mice were incubated competitively at 4, 23, and 30 degrees C with mixtures of 2,3,7,8-TCDD and several polychlorinated biphenyls (PCBs). The production of the radiolabeled receptor-ligand complex changed if the ligands were added sequentially, demonstrating that the competition between PCBs and TCDD for the Ah receptor in vitro is principally a kinetic rather than an equilibrium phenomenon and is irreversible on the time scale of our in vitro experiments. Examination of previous reports on the ability of TCDD, PCBs, and their mixtures to induce cleft palate in fetal mice suggests that the potency of receptor-ligand complexes is ligand-dependent. Receptor occupancy is not a sufficient condition for toxicity, and protection by one ligand against the toxic effect of a second, more potent one is only possible when a significant fraction of receptors is occupied.
Subject(s)
Liver/metabolism , Polychlorinated Biphenyls/metabolism , Polychlorinated Dibenzodioxins/metabolism , Receptors, Aryl Hydrocarbon/metabolism , Animals , Binding, Competitive , Cytosol/metabolism , In Vitro Techniques , Male , Mice , Mice, Inbred C57BL , Structure-Activity RelationshipABSTRACT
Generally, implants give rise to toxic reactions and favour the formation and propagation of local infections. Adherance of the soft tissue to the implant prevents the development of fluid filled cavities, thus being of particular interest as a prophylactic measure in arresting spread of infections. Teflon cylinders with an etched surface have been investigated by optical and electron microskopic means following subcutane implantation in mice. We were able to demonstrate closed tissue contact. Signs of toxic tissue reactions were completely absent.
Subject(s)
Foreign-Body Reaction/prevention & control , Polytetrafluoroethylene/toxicity , Prostheses and Implants , Skin/cytology , Animals , Biocompatible Materials , Mice , Microscopy, Electron , Skin/immunology , Skin/ultrastructure , Surgical Wound Infection/prevention & controlSubject(s)
Bone and Bones/anatomy & histology , Stress, Mechanical , Tibia/physiology , Animals , Female , Male , Pressure , Sheep , Tibia/pathologyABSTRACT
The availability of iron in metabolism was determined in dependence on the performance after lactation had finished and on the level of Fe-supply of a total of 56 rats. The availability of iron of those animals which had reared young was, according to the increased requirement, high and decreased from 87 to 54% after increased doses of iron. The values of full-grown control animals were considerably lower and had a falling tendency from 52 to 36% after an increasing supply with iron. Because of the reduced utilization of iron after increased supply the gross requirement must be increased over-proportionally when the net requirement rises.
Subject(s)
Iron/metabolism , Lactation , Animals , Biological Availability , Dose-Response Relationship, Drug , Female , Iron/administration & dosage , Nutritional Requirements , Pregnancy , RatsSubject(s)
Iron/metabolism , Pregnancy, Animal , Absorption , Animals , Diet , Female , Iron/administration & dosage , Pregnancy , RatsABSTRACT
Enhanced retention of nutrients in the gravid organism, which exceeds the normal deposition in the reproductive organs and in fetuses, is called 'pregnancy anabolism'. For zinc this superretention could be established only in the liver which was enlarged in gravid rats, too. In all other tissues of gravid animals, zinc contents were lower compared with nongravid rats. After lactation, these changes in zinc status were equalized, and gravid and nongravid animals showed the same values.
Subject(s)
Pregnancy, Animal , Zinc/metabolism , Animals , Bone and Bones/metabolism , Female , Lactation , Liver/metabolism , Mammary Glands, Animal/metabolism , Muscles/metabolism , Pregnancy , Rats , Tissue Distribution , Uterus/metabolismABSTRACT
Enhanced retention of nutrients in the gravid organism, which exceeds the normal deposition in the reproductive organs and in fetuses, is called 'pregnancy anabolism'. For zinc this superretention could be established only in the liver which was enlarged in gravid rats, too. In all other tissues of gravid animals, zinc contents were lower compared with nongravid rats. After lactation, these changes in zinc status were equalized, and gravid and nongravid animals showed the same values.
Subject(s)
Pregnancy, Animal , Zinc/metabolism , Animals , Female , Liver/metabolism , Mammary Glands, Animal/metabolism , Muscles/metabolism , Placenta/metabolism , Pregnancy , Rats , Tissue Distribution , Uterus/metabolism , Zinc/bloodSubject(s)
Fetus/analysis , Iron/metabolism , Pregnancy, Animal , Zinc/metabolism , Animals , Body Weight , Female , Growth , Litter Size , Nutritional Requirements , Pregnancy , RatsABSTRACT
In the livers of pregnant rats an anabolic effect was found for zinc which, however, developed analogously to the enlargement of the organ. Femur and muscle did not reveal any super-retention of zinc during pregnancy. In the whole organism, a 10% increased zinc storage was found being attributable to stronger accumulation in the reproductive organs (3%) and in the liver (1%) and in other organs (6%) that were not under study. Higher Zn supply did not allow to increase this additional zinc storage during pregnancy. After lactation, the anabolic effect in the livers had declined, the Zn values of the lactating rats remaining, on the whole, at the same level as those of the pregnant animals. The Zn-serum concentrations as well as the alkaline phosphatase and carboxy peptidase A activities of the pancreatic gland were reduced during pregnancy, whilst the alkaline phosphatase activity in the femur increased. This finding is discussed in relation to Zn-supply and Zn-mobilisation.
