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101.
Summary Application of a granular formulation of hexachlorocyclohexane (HCH) to the potted soil at flooding decreased the concentration
of iron and. to some extent, manganese in rice plants, especially at concentrations above 3 ppm active ingredient (a.i.) Likewise,
HCH, applied to rice fields at transplanting (several days after submergence) caused a significant decrease in the concentration
of iron, and not manganese, in the rice plant but only at concentrations above 12.5 kg a.i./ha despite high levels of reduced
iron in the soil. Inhibition of iron reduction by HCH was more pronounced when applied at flooding than at several days after
flooding. 相似文献
102.
The influence of light and nutrient addition upon the sediment chemistry of iron in an arctic lake 总被引:1,自引:1,他引:0
The geochemical response of sediments to increased nutrient input to an Alaskan, arctic lake was examined using direct measurements
of sediment-water chemical fluxes. An unexpected increase in Fe flux occurred when sediments were exposed to high incident
radiation and nutrient concentrations. Correlation between light and acid-soluble Fe concentrations suggests that photoreduction
of Fe(III) oxides may occur, but nutrient addition enhanced the effect indicating that primary productivity was also important.
The processes controlling the flux of Fe from sediments in this lake were complex and included the redox potential (dissolved
oxygen concentration) of the water, quality of organic matter present in the sediment, light, and nutrients supplied from
the sediments and/or water column. These four factors together with the possibility of direct uptake of Fe by phytoplankton
and the possible release of algal reductants may contribute to Fe cycling in this lake. 相似文献
103.
In a laboratory experiment using full-sibs, 60% of the variation in pupal weight of the monophage Tyria jacobaeae L. (Lepidoptera, Arctiidae) could be explained by variation in the nitrogen concentration of the food plant, Senecio jacobaea L. and only 4% by variation in sugar concentration. Larval weight and growth rates of young and old larvae were also positively correlated with nitrogen and sugar concentration. Developmental time was negatively correlated with nitrogen concentration. In a second experiment full-sib families differed significantly in larval weight at day 7, mortality, growth rate and developmental time. Pupal weight did not differ significantly among families, but was positively correlated with nitrogen concentration of Senecio. Larval performance was not significantly influenced by concentrations of sugars or alkaloids. We conclude that larval performance of Tyria during most of the larval period is mainly determined by genetic factors, but pupal weights are primarily determined by nitrogen concentration of the food plant. 相似文献
104.
Nutritional indices, development rates, percent dry weights and total lipids were determined in gypsy moth larvae (Lymantria dispar L.) reared on a high wheat germ (HWG) diet or diets prepared from lyophilized, ball-milled oak or pine foliage as the only source of dietary nitrogen (N). With regard to both total and proteinaceous N content, HWG diet>oak diet>pine diet. All nutritional indices measured were significantly lower in second instars fed pine diet vs. oak diet. Protein supplementation of pine diet with either casein or ovalbumin to bring total N up to the level present in oak diet resulted in small increased in approximate digestibility (AD) and effciency of conversion of ingested food (ECI), but relative growth rate (RGR) remained unaffected. The low RGR of larvae fed pine diet (unsupplemented or protein supplemented), as compared to those fed HWG or oak diet, was accompanied by significantly lower larval percent dry weight and percent total lipid. In contrast, RGR, larval percent dry weight and total lipid values were comparable in second instars fed HWG or oak diet. Insects reared from the first through the final instar on oak diet exhibited lower pupal weights compared to those reared on HWG. Casein addition to oak diet generally resulted in even more extended larval development times and further reduced pupal weights, but wheat germ addition to oak diet did not alter development rates and caused an increase in pupal weights. 相似文献
105.
Collaborative experiments were conducted to determine whether microbial populations associated with plant roots may artifactually
affect the rates of Fe uptake and translocation from microbial siderophores and phytosiderophores. Results showed nonaxenic
maize to have 2 to 34-fold higher Fe-uptake rates than axenically grown plants when supplied with 1 μM Fe as either the microbial siderophore, ferrioxamine B (FOB), or the barley phytosiderophore, epi-hydroxymugineic acid (HMA).
In experiments with nonsterile plants, inoculation of maize or oat seedlings with soil microorganisms and amendment of the
hydroponic nutrient solutions with sucrose resulted in an 8-fold increase in FOB-mediated Fe-uptake rates by Fe-stressed maize
and a 150-fold increase in FOB iron uptake rates by Fe-stressed oat, but had no effect on iron uptake by Fe-sufficient plants.
Conversely, Fe-stressed maize and oat plants supplied with HMA showed decreased uptake and translocation in response to microbial
inoculation and sucrose amendment. The ability of root-associated microorganisms to affect Fe-uptake rates from siderophores
and phytosiderophores, even in short-term uptake experiments, indicates that microorganisms can be an unpredictable confounding
factor in experiments examining mechanisms for utilization of microbial siderophores or phytosiderophores under nonsterile
conditions. 相似文献
106.
The etiology of selenium-vitamin E (Se-E) deficiency diseases may be complex. Many of the syndromes involve combined deficiency
of selenium and vitamin E. Selenium moves into the animal and human food chain from soil and plants, which may contain inadequate
amounts of the nutrient in many areas of the world. Vitamin E may be in low concentration in many animal feeds unless supplements
are added. Some syndromes, such as steatitis in cats, result from an increased requirement of vitamin E in diets that contain
large amounts of polyunsaturated fatty acids, and these diseases will only respond to vitamin E administration. Deficiency
syndromes in animals owing to pure Se deficiency are infrequent and have been produced mainly by laboratory studies utilizing
extreme deficiency conditions. Other factors that may affect the occurrence of these deficiency diseases are concurrent dietary
deficiency of S-containing amino acids, bioavailability of different forms of dietary Se, intake of compounds that antagonize
Se (e.g., silver salts), and exposure to various prooxidant substances (e.g., iron compounds, oxygen, ozone, and various drugs).
A wide variety of pathologic alterations occur in animals and humans with Se-E deficiency. Myocardial lesions are seen most
frequently in calves, lambs, pigs, turkey poults, and ducklings. In humans, Keshan disease, an endemic cardiomyopathy in China,
is attributed to Se deficiency. Necrosis of skeletal muscle is the most frequent lesion observed in animal species. Necrosis
of smooth muscle of the gizzard and intestine may be a prominent lesion in turkey poults, ducklings, and quail. Other Se-E
deficiency lesions include hepatic necrosis, gastric ulceration, intestinal and uterine lipofuscinosis, pancreatic damage,
steatitis, exudative diathesis, encephalomalacia, and testicular necrosis. Selenium toxicosis is well characterized in animals
and humans by neurological, hoof, and hair alterations. 相似文献
107.
Roles of iron in neoplasia 总被引:5,自引:0,他引:5
Eugene D. Weinberg 《Biological trace element research》1992,34(2):123-140
Research and clinical observations during the past six decades have shown that: 1. Iron promotes cancer cell growth; 2. Hosts attempt to withhold or withdraw iron from cancer cells; and 3. Iron is a factor in prevention and in therapy of neoplastic disease. Although normal and neoplastic cells have similar qualitative requirements for iron, the neoplastic cells have more flexibility in acquisition of the metal. Excessive iron levels in animals and humans are associated with enhanced neoplastic cell growth. In invaded hosts, cytokine-activated macrophages increase intracellular ferritin retention of the metal, scavenge iron in areas of tumor growth, and secrete reactive nitrogen intermediates to effect efflux of nonheme iron from tumor cells. Procedures associated with lowering host intake of excess iron can assist in prevention and in management of neoplastic disease. Chemical methods for prevention of iron assimilation by neoplastic cells are being developed in experimental and clinical protocols. The antineoplastic activity of a considerable variety of chemicals, as well as of radiation, is modulated by iron. The present article focuses on recent findings and suggests directions for further cancer-iron research. 相似文献
108.
A. M. Rofe J. C. Philcox D. R. Haynes M. W. Whitehouse P. Coyle 《Biological trace element research》1992,34(3):237-248
The early changes in hepatic metallothionein (MT) and plasma zinc (Zn), copper (Cu), and iron (Fe) were investigated during
the induction of adjuvant (AJ) arthritis in rats in conjunction with cyclosporin (CSA) treatment. Plasma Zn decreased after
AJ injection (60% of control values at 8 h), and this was associated with a 4.5-fold increase in hepatic MT at 8 h. Plasma
Zn was lowest at 16 h (40% of control), whereas hepatic MT concentrations increased to a maximum of 20-fold at 16 h. Changes
in plasma Fe paralleled those of Zn, whereas plasma Cu levels were increased. Plasma metal and hepatic MT concentrations returned
toward normal from d 1–7. At d 14, when marked paw swelling was apparent, hepatic MT and plasma Cu were again increased and
plasma Zn decreased.
Administration of CsA decreased MT induction in rats injected with AJ and also caused a marked recovery in plasma Zn and Fe
levels. These changes were small but significant even in the early stages (up to 24 h) after AJ injection and were followed
by a sustained improvement in all parameters, corresponding to the nonappearance of clinical arthropathy in CsA-treated rats.
TNF-α and IL-6 production by peritoneal macrophages isolated from AJ-injected rats was significantly decreased by CsA treatment
at d 7 and 14. The inhibition of hepatic MT induction during acute and chronic inflammation by cyclosporin emphasizes the
role of the immune system in altered metal homeostasis in inflammation. 相似文献
109.
Pilar Galan Helene Thibault Paul Preziosi Serge Hercberg 《Biological trace element research》1992,32(1-3):421-426
The relationship between iron status and capacity for IL-2 production by lymphocytes was assessed in 81 children from 6 mo
to 3 yr of age selected at random from a population with low socioeconomic status, undergoing free systematic examination
in four children's health centers in the Paris area. Iron deficiency was defined by the existence of at least two abnormal
values among the three indicators of iron status: serum ferritin level ≤12 μg/L, transferrin saturation <12%, and erythrocyte
protoporphyrin concentration >3 μg/g hemoglobin. According to this definition, 53 children were classified as iron deficient
and 28 as iron sufficient. No differences were observed between the iron-deficient and iron-sufficient groups in terms of
the IL-2 concentration without stimulation by PHA. IL-2 production by lymphocytes stimulated with PHA, as well as the stimulation
index (ratio of IL-2 concentration following stimulation by PHA to that of IL-2 concentration without stimulation by PHA)
were significantly lower in iron-deficient children. The reduction in IL-2 production by activated lymphocytes observed in
our study of iron-deficient children may be responsible for impairments in immunity found by other authors, particularly in
cell-mediated immunity. 相似文献
110.
The inorganic formulations of fourteen common plant tissue culture basal media were examined from the primary literature. Inaccuracies and errors were found for molecular formulae, chemical hydrations, and molar equivalences for iron/EDTA complexation. A comparison with published basal medium formulations from six commercial suppliers uncovered additional inaccuracies, modifications, and errors, thereby emphasizing the need for investigators to examine and describe medium formulations precisely in future publications. 相似文献