Endogenous iron excretion

The effects of supplemental oral (0, 40, and 400 ppm) and parenteral iron (0 and 2.72 mg Fe iv given initially as a single dose) on iron absorption, excretion, and retention were determined in 30 rats. Endogenous fecal iron excretion was determined by the radioisotope dilution technique after im injection of 80 kBq Fe-59, using blood and certain body tissues as reference sources for the estimation of the specific activity (Bq Fe-59/micrograms Fe) of endogenous iron. The basal diet contained 3.6 ppm Fe. Fe(III)-hydroxide-polymaltose was used as the sole iron source in oral, iv, and im iron treatments. Iron balance as determined from day 14 to 20 of the experiment was not significantly affected by iv iron administration. Nevertheless, a temporarily reduced retention should have occurred, since differences in final body iron contents were lower than 2.72 mg, as compared to the respective untreated groups. Apparent iron absorption and iron retention increased with surplus oral iron, and the efficiency rates were highest with adequate iron supply (40 ppm). True absorption rates of iron were similar without any, and with 40 ppm Fe amounting 40 to 50% of the intake. In the iron deficient rats, half of the actually absorbed iron (about 16 micrograms/d) was lost by endogenous fecal re-excretion, and another 3 micrograms/d by the urinary route. Endogenous loss with feces and with urine increased with further oral iron supply, but at a considerably lower rate as total fecal excretion. Parenterally administered iron did not affect endogenous loss at all. The results indicate that endogenous excretion cannot be regarded as a means to eliminate excessive iron, and might actually be an inevitable loss.     

Bioactive carbohydrates—In chemistry,biochemistry, and biology: By J. F. Kennedy and C. A. White,Halsted Press,New York, 1983, 331 pp. $79.95

A method for analysis of plasma adenosine which combines the principles of radioisotope dilution and enzymatic catalysis is presented. Plasma from venous heparinized blood containing the adenosine deaminase inhibitor 2′-deoxycoformycin is mixed with a small amount of [³H]adenosine and extracted with perchloric acid. Using highly purified enzyme and [γ-³²P]GTP as the phosphate donor, the neutralized extract then serves as substrate for adenosine kinase, and the AMP product is purified by high-performance liquid chromatography. Adenosine concentrations in plasma are linearly proportional to ${}^{32}\text{P}{}^3\text{H}$ ratios in the enzymatically synthesized AMP and are calculated from a standard curve. The advantages of the method are: ease of sample preparation; sensitivity of 20 nm in as little as 0.3 ml plasma; 20 samples per day can be analyzed by a single operator. Care must be used when obtaining plasma since cellular contamination will affect results. Using this assay, human plasma adenosine levels are 0.121 ± 0.054 μm for males and 0.101 ± 0.067 μm for females.     

Models for the analytical ultracentrifuge behavior of Helix pomatia alpha-hemocyanin. II. Simulations of reacting microheterogeneous hemocyanin

Simulations for the moving-boundary ultracentrifuge behavior of Helix pomatia alpha-hemocyanin have been developed, based on modification of published models. In the present treatment, it has been assumed that the protein system is extensively microheterogeneous, with respect to its whole-half molecule reactivity. It has also been assumed that all such association and dissociation reactions can proceed to equilibrium in a time appreciably shorter than that which would be required to separate nonreacting half molecules from nonreacting whole molecules. Predictions based on this model agree well with reported experimental findings of nonequilibration of fractionated material, apparent independence of whole-to-half molecule concentration ratios on total concentration in sedimentation experiments, and stopped-flow dilution reactivity over a wide range of sedimentation coefficients.     

Proposal for an integrated approach for the assessment of cross-media aspects relevant for the determination of “best available techniques” bat in the european union

The EC Directive concerning integrated pollution prevention and control (IPPC Directive 96/61/EC) obliges all Member States to make an integrated assessment of the impacts on the environment “as a whole”, as regards granting permission for and the operation of environmentally relevant industrial installations. The determination of “Best Available Techniques” BAT plays an essential role in the material transformation of the IPPC-Directive. An integrated approach for the assessment of cross-media aspects of techniques for the determination of BAT is outlined in this paper, which is grounded on the basic concept of Life Cycle Assessment (LCA), emphasising the need for decision support. The proposed assessment approach is applied to a case study sinter production in an integrated iron and steel works, which forms the base for several recommendations concerning further research.     

Nippostrongylus brasiliensis: effect of dexamethasone upon anthelmintic efficacy

A study has been made to determine the chemotherapeutic susceptibility of natural and “steroid sustained” Nippostrongylus brasiliensis infections in rats. Dexamethasone in the drinking water (2.5 × 10^?4 mg/ml) aided establishment of greater parasite populations but restricted growth of young rats. Comparison trials with thiabendazole, cambendazole, and parbendazole, as well as 10 candidate drugs, showed that the parasiticidal activity of these materials was not significantly altered between the 10-day-old naturally maintained and the 17-day-old steroid-treated parasitic infections. As expected, 17-day-old naturally maintained parasite populations were highly susceptible to the anthelmintic action of these materials. In one instance, the toxic response elicited by a candidate drug was apparently potentiated by dexamethasone.     

Modified silver staining of nucleolar organizer regions to improve the accuracy of image analysis

Silver staining of nucleolar organizer regions (NORs) and their subsequent quantification by image analysis are used increasingly in human pathological specimens and experimental models. Because certain conditions determined by the type of tissue and/or its fixation render AgNOR segmentation for image analysis difficult due to insufficient contrast or nonspecific silver precipitation, we propose three improvements to the original technique to overcome these difficulties. Pretreatment with 7% nitric acid produced very distinct dark brown images of AgNORs on a yellow background. The gradient of background colors allowed easy discrimination of nucleolar, nuclear and cytoplasmic structures. Seven morphometric parameters related to number, size and shape of AgNORs were evaluated quantitatively by image analysis on sections pretreated with nitric acid and on adjacent sections treated with citrate buffer in a wet autoclave according to the most widely accepted method for image analysis of AgNOR. Both methods yielded similar results. A second improvement was achieved by coating the slides with 7% celloidin solution in ethyl alcohol-ether prior to AgNOR staining and acid pretreatment. This coating prevented nonspecific silver deposition on argyrophilic bacteria and other tissue debris in human vaginal smears that could make visualizing AgNOR sites difficult. Finally, placing sections face down on the staining solution prevents the formation of nonspecific silver precipitates. These procedures can be applied together or separately according to the requirements of the material to be evaluated.     

Food consumption and utilization responses to dietary dilution with cellulose and water by velvetbean caterpillars, Anticarsia gemmatalis

Abstract Dilution of an artificial diet with water or cellulose to nutrient levels of 32% (undiluted), 19% and 10% fresh weight (fw) resulted in increased fw and dry weight (dw) food consumption (both absolute amounts and weight-relative rates) by velvetbean caterpillars, Anticarsia gemmatalis Hübner. Despite these increases, the absolute amount and relative rate of nutrient intake by the caterpillars declined with dilution, as did their dw gain and dw (% fw) and lipid (% dw) contents. The proportion of consumed food (dw, including cellulose) that was digested and absorbed declined with increased dietary cellulose; however, the proportion of consumed nutrients (dw, excluding cellulose) that was digested and absorbed was not affected by the presence of cellulose, although it increased slightly (but significantly) with dietary water. The efficiency with which the absorbed nutrients were converted to biomass energy showed a negative relationship with the various measures of food consumption and thus a positive relationship with dietary nutrient level.
The compensatory increases in feeding mitigated the deleterious impact of dietary dilution on growth, which would have declined further without the increased feeding. These data suggest that food consumption is regulated primarily through an evaluation of food nutrient level, and that the metabolic costs associated with the increased consumption and processing of food may be substantial, especially on the most diluted diets. Another hypothesized cost of increased feeding, reduced efficiency of digestion and absorption as food presumably passes more rapidly through the gut, was not detected.     

Characterization of dominant cultivable lactobacilli and their antibiotic resistance profiles from faecal samples of weaning piglets

AIMS: To examine the lactic acid bacteria flora of weaning piglets, to define the distribution of different lactobacilli species in piglet faecal samples, and to determine the susceptibility phenotype to 11 antibiotic of different families. METHODS AND RESULTS: The faecal samples were taken from piglets with good herd status at 11 and 28 days after weaning. The Lactobacillus isolates (n = 129) from 78 animals housed in pairs in 39 pens were preliminarily identified by their morphology and biochemical characteristics. Partial 16S ribosomal DNA (16S rDNA) was used to identify the isolates to the species level, and RAPD (randomly amplified polymorphism DNA) profiles to differentiate Lactobacillus isolates to the strain level. Based on these studies, 67 strains were selected for antibiotic resistant tests. The most numerous Lactobacillus species found in the piglets was Lactobacillus reuteri (n = 43). Other lactobacilli were L. salivarius (n = 15), L. agilis (n = 4), L. johnsonii (n = 2), L. vaginalis (n = 1), L. mucosae (n = 1) and L. gallinarum (n = 1). All the strains were susceptible to chloramphenicol, ampicillin and gentamicin. Two L. salivarius isolates and two L. reuteri isolates were found to be multiresistant. CONCLUSIONS: This study indicates that the faecal Lactobacillus flora in piglets consists mainly of L. reuteri, L. salivarius and L. acidophilus group lactobacilli, and the distribution of lactobacilli is similar between individuals of the same age and with the same diet. Most of the Lactobacillus isolates tested were sensitive to the antibiotics used in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: Valuable information on Lactobacillus species distribution and their antibiotic resistance profiles in piglets is obtained.     

Evolution of virulence in heterogeneous host communities under multiple trade-offs

Many pathogens and parasites are transmitted through hosts that differ in species, sex, genotype, or immune status. In addition, virulence (here defined as disease-induced mortality) and transmission can vary during the infectious period within hosts of different state. Most models of virulence evolution assume that transmission and virulence are constant over the infectious period and that the host population is homogenous. Here, we examine a multispecies susceptible-infected-recovered (SIR) model where transmission occurs within and between species, and transmission and virulence varied during the infectious period. This allows us to understand virulence evolution in a broader range of situations that characterize many emerging diseases. Because emerging pathogens are by definition new to their host populations, they should be expected to rapidly adapt after emergence. We illustrate these evolutionary effects using the framework of adaptive dynamics to examine how virulence evolves after emergence in response to the relative strength of selection on pathogen fitness and mutational variance for virulence. We illustrate the role of evolution by simulating adaptive walks to an evolutionarily stable virulence. We found that the magnitude of between-species transmission and the relative timing of transmission and mortality across species were of primary importance for determining the evolutionarily stable virulence.