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PubMed1992

Characterization of the defect in a variant of HL-60 promyelocytic leukemia cells with reduced transferrin receptor expression.

The mechanism by which a clone of HL-60 human promyelocytic leukemia cells designated Tf-Gel-1 expresses reduced levels of the transferrin receptor (TfR) was investigated. Tf-Gel-1 was developed by continuous exposure of HL-60 cells to human iron-saturated transferrin covalently linked to the plant toxin gelonin (Tf-Gel); this variant was five- to sixfold more resistant to Tf-Gel than parental HL-60 cells. The amount of cell surface, as well as of solubilized, TfR and the cycling pools of TfR in Tf-Gel-1 cells, as measured by the binding of [125I]Tf, were all decreased to 20-30% of the levels present in parental cells. The growth of Tf-Gel-1 cells was independent of exogenous Fe3+ and was comparable to that of parental HL-60 cells. Despite the lower levels of TfRs, the Tf-Gel-1 clone retained the capacity to alter receptor expression, depending upon the phase of growth and the intracellular iron concentration, and to down-regulate TfRs in response to inducers of differentiation. Southern hybridization of cellular DNA with TfR cDNA did not reveal differences between parental and Tf-Gel-1 cells in the level and arrangement of the TfR gene. Basal and inducible (repressible) levels of TfR mRNA from Tf-Gel-1 cells, as measured by northern hybridization of cellular RNA with TfR cDNA, were comparable to those of parental cells. Metabolic labeling of cells with [35S]methionine, followed by immunoprecipitation of TfRs, demonstrated that the amount of radioactivity incorporated into TfRs in Tf-Gel-1 cells was reduced to a degree that approximated the decrease in [125I]Tf binding. Cell surface TfRs prepared from exponentially growing parental cells labeled with 125I by the solid-phase lactoperoxidase-glucose oxidase method existed as a doublet, with one form being phosphorylated and the other not phosphorylated. In contrast, Tf-Gel-1 cells not only contained diminished amounts of TfRs but also contained only the phosphorylated form of TfRs in the surface membrane. The decrease in the surface membrane concentration of the TfR in Tf-Gel-1 cells was specific for this glycoprotein, since the levels of other cell surface antigens, such as CD13, CD15 and CD45, were normal in Tf-Gel-1 cells. A reduction in the incorporation of [3H]mannose into the acid-insoluble fraction of cells and an increase in sensitivity to ricin suggested that Tf-Gel-1 cells possessed an aberration in carbohydrate metabolism.

Antigens, Surface↗

PubMed2001

Functional fragments of ingested lactoferrin are resistant to proteolytic degradation in the gastrointestinal tract of adult rats.

Pharmaceutical and food-related applications of lactoferrin, an 80-kDa iron-binding glycoprotein found predominantly in milk, have attracted interest lately, but the process of digestion of lactoferrin has been poorly characterized. The digestive fate of bovine lactoferrin in adult rats after oral administration of a single dose and after dietary supplementation was studied by (125)I-labeling and by surface-enhanced laser desorption/ionization (SELDI) affinity mass spectrometry. The latter method was designed to detect multiple forms of degraded lactoferrin as simple molecular ion peaks corresponding to one of the core regions of lactoferrin, namely, the lactoferricin region (Phe17-Ala42). Radioactive fragments with molecular masses of 42, 36, 33 and 29 kDa were observed at 20, 60 and 180 min postingestion in the contents of the lower small intestine. Rats were given free access to milk enriched with lactoferrin at 482 micromol/L (40 mg/mL). The concentrations of lactoferrin fragments in the contents of the stomach, small intestine and lower small intestine as determined by SELDI affinity mass spectrometry were approximately 200, 20 and 1 micromol/L, respectively. These data indicate that functional fragments of LF such as fragments containing glycosaminoglycan-binding site(s), as well as large fragments with a mass >20 kDa, indeed survive proteolytic degradation in the small intestine of adult rats.

Administration, Oral↗

PubMed1979

Neutron activation analysis for the demonstration of amphibolite rock-weathering activity of a yeast.

Neutron activation analysis was employed in a survey of weathering abilities of rock surface microorganisms. A yeast isolated from an amphibolite of a megalithic grave was found actively to concentrate, in media and in or on cells, iron and other elements when grown in the presence of ground rock. This was demonstrated by comparing a spectrum of neutron-activated amphibolite powder (particle size, 50 to 100 mum) with the spectra of neutron-activated, lyophilized yeast cells which had grown with or without amphibolite powder added to different media. The most active yeast (IFAM 1171) did not only solubilize Fe from the rock powder, but significant amounts of Co, Eu, Yb, Ca, Ba, Sc, Lu, Cr, Th, and U were also mobilized. The latter two elements occurred as natural radioactive isotopes in this amphibolite. When the yeast cells were grown with neutron-activated amphibolite, the cells contained the same elements. Furthermore, the growth medium contained Fe, Co, and Eu which had been solubilized from the amphibolite. This indicates the presence, in this yeast strain, of active rockweathering abilities as well as of uptake mechanisms for solubilized rock components.

Journal Article↗

PubMed2003

Rapid identification and analysis of airborne plutonium using a combination of alpha spectroscopy and inductively coupled plasma mass spectrometry.

Recent wildland fires near two U.S. nuclear facilities point to a need to rapidly identify the presence of airborne plutonium during incidents involving the potential release of radioactive materials. Laboratory turn-around times also need to be shortened for critical samples collected in the earliest stages of radiological emergencies. This note discusses preliminary investigations designed to address both these problems. The methods under review are same day high-resolution alpha spectroscopy to screen air filter samples for the presence of plutonium and inductively coupled plasma mass spectrometry to perform sensitive plutonium analyses. Thus far, using modified alpha spectroscopy techniques, it has been possible to reliably identify the approximately 5.2 MeV emission of 239Pu on surrogate samples (air filters artificially spiked with plutonium after collection) even though the primary alpha-particle emissions of plutonium are, as expected, superimposed against a natural alpha radiation background dominated by short-lived radon and thoron progeny (approximately 6-9 MeV). Several processing methods were tested to prepare samples for analysis and shorten laboratory turn-around time. The most promising technique was acid-leaching of air filter samples using a commercial open-vessel microwave digestion system. Samples prepared in this way were analyzed by both alpha spectroscopy (as a thin-layer iron hydroxide co-precipitate) and inductively coupled plasma mass spectrometry. The detection levels achieved for 239Pu--approximately 1 mBq m(-3) for alpha spectroscopy screening, and, < 0.1 mBq m(-3) for inductively coupled plasma mass spectrometry analysis--are consistent with derived emergency response levels based on EPA's Protective Action Guides, and samples can be evaluated in 36 to 72 h. Further, if samples can be returned to a fixed-laboratory and processed immediately, results from mass spectrometry could be available in as little as 24 h. When fully implemented, these techniques have the potential to provide useful information and improved operational flexibility to emergency planners and first-responders during radiological emergencies.

Air Pollution, Radioactive↗

PubMed1991

[Uptake and intracellular metabolism of ferritin by primary cultured rat hepatocytes].

The uptake and intracellular metabolism of radiolabeled ferritin in rat hepatocytes were investigated. A receptor assay performed by incubating isolated hepatocytes with 125I-labeled ferritin at 37 degrees C for 1 h revealed 37,000 ferritin binding sites/cell with an affinity constant (Ka) of 1.8 X 10(9) M-1. The hepatocytes preincubated with 125I-labeled ferritin at 37 degrees C for 1 h were further incubated in a ligand-free medium at 37 degrees C for 4 h, and then the distribution of the label in the subcellular fractionations of hepatocytes was analyzed by 30% Percoll density gradient centrifugation. The label was transported from the plasma membrane fraction to the lysosome/mitochondria fraction and the cytosol fraction. Meanwhile, both of trichloroacetic acid (TCA)-soluble and TCA-precipitable 125I in the incubation medium increased with the incubation time. In order to study the intracellular metabolism of endocytosed ferritin, the hepatocytes preloaded with 59Fe-125I-double labeled ferritin were incubated at 37 degrees C for 4 h in the ligand-free medium containing 100 mumol/l chloroquine (a lysosomal metabolic inhibitor) or 10 mmol/l sodium cyanide (a mitochondrial metabolic inhibitor). Chloroquine increased TCA-precipitable 125I in the medium with a corresponding decrease in TCA-soluble 125I. However, no effect with sodium cyanide was observed. Radioactivities in the incubation medium were then divided into two components by HPLC gel filtration. One had a molecular weight similar to intact ferritin, 98% of which reacted to an anti-rat liver ferritin antiserum, while the other had a molecular weight of less than 1,000, 25% of which reacted to the antiserum. Chloroquine increased the amounts of intact ferritin released into the medium and decreased the degraded fragments. These results suggest two pathways of the endocytosed ferritin in hepatocytes; one is a degradation of ferritin in lysosome, which results in a storage of iron in the cells and an excretion of degraded peptides outside the cells, and the other is exocytosis of intact ferritin from the cells by a similar mechanism to "diacytosis" proposed for asialoglycoprotein.

Animals↗

PubMed2000

Nucleosynthesis and Mixing in Cassiopeia A.

We present results from the first light observations of the Cassiopeia A supernova remnant (SNR) by the Chandra X-Ray Observatory. Based on representative spectra from four selected regions, we investigate the processes of nucleosynthesis and mixing in Cas A. We make the first unequivocal identification of iron-rich ejecta produced by explosive silicon burning in a young Galactic SNR. Elsewhere in the remnant, we see silicon-rich ejecta from explosive oxygen burning. The Fe-rich ejecta lie outside the Si-rich material, indicating that bulk motions were extensive and energetic enough in Cas A to cause a spatial inversion of a significant portion of the supernova core. It is likely that this inversion was caused by "Fe"-rich ejecta emerging in plumes from the rising bubbles in the neutrino-driven convection layer during the supernova explosion. In addition, the radioactive decay energy from 56Ni may have contributed to the subsequent evolution of the material. We have also discovered faint, well-defined filaments with featureless X-ray spectra that are possibly sites of cosmic-ray acceleration in Cas A.

Journal Article↗

PubMed1992

Effects of complexed iron and aluminium on brain calcium.

Ferric lactate increases Ca(2+)-uptake by Ehrlich carcinoma ascites cells as well as in vitro and in vivo Ca(2+)-uptake by the liver. Iron and aluminium are increased in the substantia nigra of patients with Parkinson's disease and aluminium is suspected to be involved in the pathophysiology of Alzheimer's disease. This study was conducted to determine if there is any relationship between iron and aluminium uptake and a possible calcium influx into brain tissue. Groups of Swiss mice were injected in the tail vein with 100 microliters of 0.05 M ferric lactate plus 2 microCi45CaCl2, or 100 microliters of 0.05 M aluminium lactate plus 2 microCi45CaCl2, or 100 microliters of saline plus 2 microCi45CaCl2. Twenty-four hr later they were sacrificed by decapitation. Samples of blood and the total brain were weighed and ashed. The ashes were dissolved and the solution transferred to counting vials evaporated to dryness. A scintillation solution was added to the vials and the radioactivity was counted. To accurately assess brain uptake in each animal the value of brain specific activity was related to blood specific activity. When compared to those of control animals, these values gave the 24 hr increase of 45Ca-uptake by brain of ferric lactate or aluminium lactate-treated animals. A significant increase of 45Ca-uptake was observed for ferric lactate (136% of control value, p less than 0.005), which is more important for aluminium lactate (163% of control value, p less than 0.001). The nature of the complexed metal-brain tissue interaction is not known, several mechanisms are discussed.

Animals↗

PubMed2005

Biological and chemical interactions with U(VI) during anaerobic enrichment in the presence of iron oxide coated quartz.

Microcosm experiments were performed to understand chemical and biological interactions with hexavalent uranium (U(VI)) in the presence of iron oxide bearing minerals and trichloroethylene (TCE) as a co-contaminant. Interactions of U(VI) and hydrous iron oxide moieties on the mineral oxide surfaces were studied during enrichments for dissimilatory iron reducing (DIRB) and sulfate reducing bacteria (SRB). Microbes enriched from groundwater taken from the Test Area North (TAN) site at the Idaho National Laboratory (INL) were able to reduce the U(VI) in the adsorption medium as well as the iron on quartz surfaces. Early in the experiment disappearance of U(VI) from solution was a function of chemical interactions since no microbial activity was evident. Abiotic removal of U(VI) was enhanced in the presence of carbonate. As the experiment proceeded, further removal of U(VI) from solution was associated with the fermentation of lactate to propionate and acetate. During later phases of the experiment when lactate was depleted from the growth medium in the microcosm containing the DIRB enrichments, U(VI) concentrations in the solution phase increased until additional lactate was added. When additional lactate was added and fermentation proceeded, U(VI) concentrations in the liquid phase again returned to near zero. Similar results were shown for the SRB enrichment but lower uranium concentrations were seen in the liquid phase, while in the enrichment with carbonate a similar increase in uranium concentration was not seen. Chemical and biological interactions appear to be important on the mobilization/immobilization of U(VI) in an iron oxide system when TCE is present as a co-contaminant. Interestingly, TCE present in the microcosm experiments was not dechlorinated which was probably an effect of redox conditions that were unsuitable for reductive dechlorination by the microbial culture tested.

Adsorption↗

PubMed2003

Immobilization of iodide on copper(I) sulfide minerals.

In the goal of finding efficient scavengers for radioiodide in conditions (pH, pE) close to those encountered in deep geological sites, sorption of iodide ions on cuprous sulfide minerals (especially roxbyite, Cu(1.75)S) has been studied. Surface analysis by X-ray photoelectron spectroscopy has shown that commercial cuprous sulfides are covered by an oxidized overlayer (mainly in the form of CuSO(4)). Therefore, a synthetic procedure to get roxbyite (typically by mixing Na(2)S with an aqueous suspension of commercial Cu(2)O) was applied to produce pure samples with clean surfaces. Batch equilibration of cuprous sulfide particles suspended in aqueous solutions containing iodide species has revealed significant consumption of iodide. The sorption mechanism involves the formation of a surface complex via the exchange of surface hydroxyl groups by iodide anions, as highlighted by a transient pH increase during the immobilization process. Other copper and mixed copper-iron sulfides (e.g. CuS, CuFeS(2)), which are stable over wide pH and potential ranges are also likely to accumulate iodide species. Because of the specific interaction between iodide and copper(I) centers on the minerals, high distribution coefficients (>1000 ml/g) were observed.

Adsorption↗

PubMed1988

On the origin of intestinal transferrin.

The incorporation of 35S-L-methionine (35S-Met) into TCA-precipitable protein is used to measure protein synthesis in isolated non-vascular perfused jejunal segments and in isolated liver cells under steady-state conditions in rats. 10(5) X g supernatants of homogenates from jejunal segments and from liver cells as well as the jejunal absorbate were processed immuno-electrophoretically. Incorporation of 35S-Met radioactivity into precipitin lines with sera against transferrin, IgG and plasma proteins were autoradiographed and compared semiquantitatively with each other. Calculated on a wet-weight basis this system is sensitive enough to detect transferrin synthesis down to a level of 1% of that in the liver. Still, no transferrin synthesis was found in the jejunal mucosa, while 35S-Met incorporation into TCA precipitates and into IgG continued in isolated jejunal segments for over 2 h. A good correlation was found (r = 0.88, P less than 0.01) between mucosal and plasma transferrin in normal as well as in iron deficient rats. A complete immunologic cross-reactivity could be demonstrated between different plasma transferrins and the transferrin in three different preparations of the intestinal mucosa. Immunoblots of electropherograms after isoelectric focussing showed no distinct differences between transferrin in the plasma, bile, and in the mucosal epithelium.

Animals↗

PubMed1995

Gender does not influence acute myocardial infarction in adult dogs.

Mechanisms responsible for the well-documented "protection" against myocardial ischemia and infarction in young women and subsequent loss of protection after menopause remain speculative. One possibility is that gender-related variables (such as endogenous hormone levels or regular loss of stored iron) alter the susceptibility of the heart to ischemia: if so, then premenopausal women when compared with men may manifest endogenous protection against acute myocardial ischemic injury. Using the canine model we therefore sought to determine whether gender influences acute myocardial ischemia and infarction. Retrospective analysis was performed on data compiled from 60 mature adult dogs subjected to 1 hour of coronary artery occlusion and > or = 4 hours of reperfusion. We first compared the incidence of lethal ventricular fibrillation in the male and female cohorts and then for survivors compared collateral blood flow during coronary occlusion (by injection of radioactive microspheres), infarct size (assessed by tetrazolium staining and expressed as a percentage of the myocardium at risk), and regional wall motion (by somomicrometry) in the infarct-related area. The incidence of lethal ventricular fibrillation was 23% in the male dogs and 19% in the female dogs (p = 0.70, difference not significant). For survivors, the area at risk of infarction was comparable in males and females (23 +/- 2% and 22% +/- 1% of the total left ventricular weight), and the groups were equally ischemic during coronary occlusion, with collateral blood flow to the ischemic subendocardium averaging 0.05 +/- 0.02 and 0.07 +/- 0.01 ml/min/g tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Metabolic fate of 14C-camostat mesylate in man, rat and dog after intravenous administration.

1. The metabolic fate of N,N-dimethylcarbamoylmethyl 4-(4-guanidino[14C]benzoyloxy)phenylacetate methanesulphonate (14C-camostat mesylate) was investigated after i.v. administration to man (12-h infusion), and to rat and dog (bolus injection). 2. Renal excretion (mainly in 24 h) accounted for at least 80% dose in all three species, and the only two important metabolites were identified as 4-(4-guanidinobenzoyloxy)phenylacetic acid (GBPA) and 4-guanidinobenzoic acid (GBA). 3. Parent drug was not detected in human plasma either during or after infusion of 14C-camostat mesylate owing to rapid hydrolysis of the side-chain ester group (t1/2 < 1 min). Steady-state levels of both GBPA and GBA in plasma were apparently attained by the end of the infusion period. Mean terminal half-life, systemic clearance and apparent volume of distribution at steady-state of GBPA in man were 1.0 h, 6.4 ml/min per kg and 0.38 l/kg, respectively, and the corresponding values for GBA were 2.4 h, 4.7 ml/min per kg and 1.01/kg respectively. 4. Radioactivity was rapidly distributed to most tissues after bolus i.v. doses of 14C-camostat mesylate to rats and dogs, with highest levels being associated with the liver and kidney, the two main organs of drug elimination. Concentrations in the pancreas, a possible site for drug action, were generally lower than those in plasma.

Adult↗

PubMed1992

Development of a simple antioxidant screening assay using human skin fibroblasts.

The purpose of this study was to develop a simple antioxidant screening assay for quantifying the protective effects of antioxidant enzymes, inhibitors and scavengers against extracellularly generated oxygen species on human skin fibroblast cytotoxicity. Different in vitro oxidative stresses have been studied: xanthine oxidase-hypoxanthine, flavin mononucleotide-NADH, and hydrogen peroxide. Cytotoxicity and protection were evaluated by two procedures: evaluation of the living cells using a colorimetric method (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT), and ability of the viable cells to adherate and proliferate. Hypoxanthine-xanthine oxidase and H2O2 induced a dose dependent cytotoxicity only when we considered the delayed toxicity. The influence of the cell density was also investigated. The delayed toxicity was higher when cell density increased. One hundred percent protection against free radical cytotoxicity induced by the three systems were obtained with catalase (500 U/ml). When the oxidative stress used was H2O2 90-96% protection was obtained with deferoxamine an iron chelating agent that prevents iron catalysed radical reactions. Using the colorimetric method no significant protection was obtained when SOD was added before and during the stresses. Using the fibroblasts ability to proliferate SOD (10-150 micrograms/ml) reduced xanthine oxidase (20 U/l)-hypoxanthine (0.10-0.30 mM) or H2O2 (1-6 mM) cytotoxicity by 15-20%. SOD did not act as antioxidant when the applied stress was mediated by flavin. In this study we showed a paradoxical effect and the cytotoxicity of flavin-NADH system increased when we added SOD to the cell medium. This simple and reliable antioxidant screening assay required no costly or radioactive equipment.

Catalase↗

PubMed1987

Levels and patterns of 125I-labeled transferrin binding in mouse embryonic teeth and kidneys at various developmental stages.

The iron-transporting serum glycoprotein, transferrin, is necessary for the cell proliferation, morphogenesis, and differentiation of mouse embryonic teeth and kidneys in organ culture. The stimulatory effect of transferrin is mediated by the binding of transferrin to its specific cell-surface receptor and by receptor-mediated endocytosis. Since, in both teeth and kidneys, the requirement for and responsiveness to transferrin depend on the developmental stage of the organ, we studied the binding of transferrin at various stages of tooth and kidney development by incubating tissues with 125I-labeled transferrin. The amount of bound transferrin was determined by measuring the tissue-incorporated radioactivity, and the binding sites were localized by autoradiography. During tooth development in vitro, the requirement for exogenous transferrin is lost as the teeth proceed from the early cap stage to the bell stage. The level of transferrin binding was found to decrease simultaneously, and in bell-stage teeth, the transferrin receptors were concentrated in the areas of most active cell proliferation. In kidneys, the number of transferrin receptors was highest at the stage during which the undifferentiated kidney mesenchyme becomes responsive to transferrin. These receptors were located in both the ureter epithelium and the metanephric mesenchyme, and they dramatically decreased in number with advancing kidney differentiation. The results of the present study indicate that, during the embryonic development of teeth and kidneys, the amount and localization of transferrin binding are correlated with cell proliferation. The number of transferrin receptors is highest during the developmental stages when cell proliferation is most active, and decreases with advancing differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1999

Positron emission tomography and radioimmunotargeting--general aspects.

To optimize radioimmunotherapy, in vivo information on individual patients, such as radionuclide uptake, kinetics, metabolic patterns and optimal administration methods, is important. An overriding problem is to determine accurately the absorbed dose in the target organ as well as critical organs. Positron Emission Tomography (PET) is a superior technique to quantify regional kinetics in vivo with a spatial resolution better than 1 cm3 and a temporal resolution better than 10 s. However, target molecules often have distribution times of several hours to days. Conventional PET nuclides are not applicable and alternative positron-emitting nuclides with matching half-lives and with suitable labelling properties are thus necessary. Over many years we have systematically developed convenient production methods and labelling techniques of suitable positron nuclides, such as 110In(T(1/2) = 1.15 h), 86Y(T(1/2) = 14 h), 76Br(T(1/2) = 16 h) and 124I(T(1/2) = 4 days). 'Dose planning' can be done, for example, with 86Y- or 124I-labelled ligands before therapy, and 90Y- and 131I-labelled analogues and double-labelling, e.g. with a 86Y/90Y-labelled ligand, can be used to determine the true radioactivity integral from a pure beta-emitting nuclide. The usefulness of these techniques was demonstrated in animal and patient studies by halogen-labelled MAbs and EGF-dextran conjugates and peptides chelated with metal ions.

Bromine Radioisotopes↗

PubMed1998

Geographical distribution of radiation risks in The Netherlands.

Risk assessment of exposure to sources of radiation is an important tool for national governments in regulating radionuclide emissions and thus reducing radiation doses for the general public. For this reason radiation doses from sources throughout The Netherlands have been analyzed. For sources with well-defined locations and doses that were thought to vary significantly throughout The Netherlands, radiation dose maps were produced. Average dose values were calculated or derived from the literature for doses considered to be evenly distributed throughout the country or for which no information on the geographical distribution of dose was available. Emission, dispersion, and individual dose were modeled for each source using various pathways and exposure routes. Indoor radon and gamma radiation from building materials generate the highest dose values. The highest human induced radiation doses for industries of which the doses showed to be geographically distributed are found in the cement industry, elemental phosphorus production, phosphoric acid production, and iron and steel production. Radiation dose from some of these sources has a very local peak and decreases rapidly with distance. The elemental phosphorus production causes relatively high radiation doses throughout a large part of The Netherlands. Cumulation of doses from various sources occurs, but these are often masked by doses from a few large industries.

Eating↗

PubMed1999

Microbial mineralization of diisopropanolamine.

Diisopropanolamine (DIPA) is a "sweetening agent" used to remove hydrogen sulfide from sour natural gas, and it is a contaminant at some sour gas treatment facilities in western Canada. To investigate the biodegradation of this alkanolamine, 14C-DIPA was used in anaerobic and aerobic mineralization studies. Between 3 and 78% of the radioactivity from this compound was released as 14CO2 in sediment-enrichment cultures incubated under nitrate-reducing conditions. Similarly, 12-78% of the label was converted to 14CO2 in sediment-enrichment cultures incubated under Mn(IV)-reducing conditions. These activities were observed at 8 degrees C, a typical groundwater temperature in western Canada, and at 28 degrees C. In contrast, DIPA-degrading activity was difficult to sustain under Fe(III)-reducing conditions, and < 25% of the radioactive label from 14C-DIPA was liberated as 14CO2. Two mixed cultures and two isolates (both irregular, non-sporeforming, Gram-positive rods) were used to assess aerobic mineralization of 14C-DIPA. The aerobic mixed cultures released 73 and 79% of the radioactive label as 14CO2, whereas the pure cultures liberated only 39 and 47% as 14CO2. Between one-third and one-half of the nitrogen from DIPA was found as ammonium-N in aerobic batch cultures. These results clearly demonstrate that DIPA is mineralized under a variety of incubation conditions.

Aerobiosis↗

PubMed1996

A modified device for the differentiated study of intestinal transfer in isolated intestinal segments from mice and suckling rats in vitro.

An increasing number of mice with genetic variation of intestinal transfer properties is becoming available. A luminal perfusion system for small intestinal segments, therefore, was adapted for the use in mice and rat pups to investigate longitudinal differences in intestinal drug and toxin transfer and to explore the adaptation of transfer properties during maturation under standardized conditions in vitro. At present, cell cultures are inadequate for this goal. The perfusator consists of an upper reservoir and a lower moist chamber to accommodate the intestinal segment. The luminal perfusion fluid is oxygenized and circulated by a gas lift. It is directed through the segment by two three-way taps. For safe and easy decontamination of radioactive substrates, the system is made entirely of glass. To perfuse fragile segments from small animals such as mice and rat pups in vitro, the perfusion pressure had to be reduced to 15 cm H2O column. Therefore, the design of the perfusator was changed, and the gas lift and the three-way taps were moved to the side. With segments from adult rats, the modified perfusor yielded the same transfer data for 59Fe, glucose, and water as did the standard device. Experiments with proximal and distal segments from mice and rat pups showed a longitudinal pattern of adaptation during maturation as well as due to iron deficiency that was in accordance with expectations extrapolated from literature.

Aging↗