Tissue Distribution and Metabolism of Aflatoxin B1-14C in Broiler Chickens

The effects of administering low levels of aflatoxin B(1)-(14)C by crop intubation daily for 14 days to broiler chickens were determined. Studies on the distribution of (14)C in the blood, selected organs, tissues, and excreta were conducted. No toxic effects were observed in broiler chickens during the 14 days of the experiment. The broiler chickens excreted 90.64% of the (14)C administered. Of the (14)C retained, 11.04, 9.83, 4.30, 12.52, 31.66, and 30.63% were detected in the blood, liver, heart, gizzard, breast, and leg, respectively. Chemical assay of those samples demonstrating radioactivity revealed that 81.2% of the radioactivity in these substrates was not extractable by classical extraction procedures while approximately 10% was extractable. Treatment of aqueous extracts for conjugated steroids by treatments with beta-glucuronidase revealed that 31.5% of the (14)C detected in the aqueous extract was a liberated glucuronide conjugate of aflatoxin M(1)-(14)C.     

Metabolism of [1-14C]glyoxylate, [1-14C]-glycollate, [1-14C]glycine and [2-14C]-glycine by homogenates of kidney and liver tissue from hyperoxaluric and control subjects

1. The metabolism of [1-(14)C]glyoxylate to carbon dioxide, glycine, oxalate, serine, formate and glycollate was investigated in hyperoxaluric and control subjects' kidney and liver tissue in vitro. 2. Only glycine and carbon dioxide became significantly labelled with (14)C, and this was less in the hyperoxaluric patients' kidney tissue than in the control tissue. 3. Liver did not show this difference. 4. The metabolism of [1-(14)C]glycollate was also studied in the liver tissue; glyoxylate formation was demonstrated and the formation of (14)CO(2) from this substrate was likewise unimpaired in the hyperoxaluric patients' liver tissue in these experiments. 5. Glycine was not metabolized by human kidney, liver or blood cells under the conditions used. 6. These observations show that glyoxylate metabolism by the kidney is impaired in primary hyperoxaluria.     

Long-term Metabolism of [14C]Sugars in Stored Potatoes

[¹⁴C]Sucrose, [¹⁴C]glucose and [¹⁴C]fructose were introducedinto potato tubers held at 10 °C and the redistributionof label chased over a 65 d period in storage. Respiratory losseswere identical in all treatments, as was the partitioning of¹⁴C between soluble and insoluble forms. Sucrose was the predominantlabelled sugar in the tubers after 20 h, regardless of the original[¹⁴C]sugar introduced, and was loaded and distributed throughoutthe tubers by the internal phloem system. After 20 h the proportionsof labelled sugars bore no relationship to those of the unlabelledendogenous sugars. However, with time the percentage of ¹⁴Cin sucrose fell while that in glucose increased and by 65 dthe proportions of the labelled sugars more closely resembledthe endogenous pools. Fructose represented a consistently lowproportion of both the labelled and unlabelled sugars. By 21d a considerable proportion of the soluble ¹⁴C had been convertedto starch (approx. 25% of the total tuber 14C), this value remainingrelatively constant for the remainder of the storage period.Sprouts which formed on the tubers contained up to 6% of thetotal tuber ¹⁴C but less than 0.2% of the tuber dry matter.It is suggested that the bulk of the translocated [¹⁴C]sucroseentered the symplast and exchanged slowly with the bulk of thesugars in the storage cell vacuoles. [¹⁴C]sugars, phloem loading, starch, potato tuber, Solunum tuberosum, cold storage     

Production of [14C]rubratoxin B

[¹⁴C]rubratoxin B was produced by culturing Penicillium rubrum Stoll for 13 days at 22 °C in medium containing [¹⁴C]glucose. The most efficient incorporation of glucose into rubratoxin occurred when Raulin-Thom medium enriched with 2.5% malt extract was supplemented with 2.5% added glucose. The presence of 1.0 mCi of radioactivity in 50 ml of medium with 2.5% added glucose resulted in the production of 38 mg of labeled, chromatographically pure rubratoxin with a specific activity of 0.47 Ci/mole.Rubratoxin B is a hepatotoxic mycotoxin produced by Penicillium rubrum Stoll. It was first isolated by Wilson and Wilson in 1962 (14, 15), and its structure was proposed by Moss in 1968 (11). A simplified procedure for obtaining rubratoxin B in good yield directly from liquid culture media has been described by Hayes and Wilson (6), and there have been numerous investigations of the biological effects of purified rubratoxin B (among others, 4, 7, 9, 12). However due to the insensitivity of the analytical technique for rubratoxin (5), little work has been done to determine the molecular basis of its activity. Determining metabolic products, identifying activated or inactivated toxin complexes or locating binding sites in tissues require a labeled toxin molecule. The purpose of this study was to produce radiolabeled rubratoxin for use in investigations of its various biological activities and also for use in techniques such as autoradiography of tissue sections and radioimmunoassay.Presented in partial fulfillment of the requirements for the degree Master of Science at Iowa State University, Ames, IA 50010.     

Metabolism of [14C] amitraz in larvae of Boophilus microplus

Amitraz, 1, 5-di(2, 4-dimethylphenyl)-3-methyl-1, 3, 5-triazapenta-1, 4-diene, labelled with 14C in the 2-methyl groups was applied to B. microplus larvae by an immersion technique. The chemical penetrated readily but never appeared in large amounts internally due to rapid cleavage to N-2, 4-dimethylphenyl-N'-methylformamidine. The expected complementary cleavage product 2, 4-dimethylformanilide was not produced in equivalent quantity. However, large amounts of polar metabolite(s) were produced. Small quantities of 2, 4-dimethylaniline and an unidentified non-polar metabolite were also produced. Of the identified chemicals only amitraz and N-2, 4-dimethylphenyl-N'-methylformamidine were toxic to larvae. Piperonyl butoxide applied simultaneously with amitraz had only a slight effect on metabolism but had a three-fold synergistic effect. SKF 525-A similarly applied had a negligible effect on both metabolism and toxicity.     

Metabolism of ent-kaurenol-[17-14C], ent-kaurenal-[17-14C] and ent-kaurenoic acid-[17-14C] by germinating Hordeum distichon grains

Subcellular fractions from germinated barley embryos, chloroplast preparations and whole germinating barley grains are able to carry out the conversions ent-kaurenol → ent-kaurenal → ent-kaurenoic acid → ent-hydroxykaurenoic acid, the initial steps of the biosynthetic pathway to gibberellins. Whole grains, and chloroplasts to a slight extent, incorporate radioactivity from ent-kaurenol-[17-¹⁴C] and ent-kaurenoic acid-[17-¹⁴C] into materials with similar but distinct properties from the gibberellins GA₁, GA₃, GA₄ and GA₇.     

A lipid-linked oligosaccharide intermediate in glycoprotein synthesis. Characterization of [Man-14C]glycoproteins labeled from [Man-14C]oligosaccharide-lipid and GDP-[14C]Man.

Endogenous proteins of cell-free preparations of hen oviduct labeled from GDP-[14C]Man or from [Man-14C]oligosaccharide-lipid have been compared by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Under the conditions tested, a polypeptide chain of molecular weight about 25,000 was the principle acceptor for the oligosaccharide moiety of exogenous [Man-14C]oligosaccharide-lipid. The product labeled by [Man-14C]oligosaccharide-lipid appeared identical with one of three glycoproteins formed when GDP-[14C]Man was incubated with a crude membrane fraction. These three proteins (apparent molecular weight of 75,000, 55,000, and 25,000) accounted for nearly two-thirds of the [14C]mannose-labeled glycoprotein products using GDP-[14C]Man and either the crude membrane fraction or a total oviduct homogenate. Thus, all of the mannose acceptor proteins present in the oviduct homogenate appear to be membrane-bound. Analyses of the [Man-14C]glycoproteins labeled from GDP-[14C]Man in membrane fractions from hen kidney, liver, brain, and oviduct indicated that a labeled polypeptide of apparent molecular weight 25,000 was the only major protein product common to the four preparations.     

Absorption, Distribution, Metabolism and Leaching of [14C] ABA during Culture of Apple Embryos

Barthe, Ph. and Bulard, C. 1987. Absorption, distribution, metabolismand leaching of [¹⁴C] ABA during culture of apple embryos.—J.exp. Bot. 38: 1002–1011. It has been known for some time that dormant embryos, laid flaton damp filter-paper one cotyledon only being in direct contactwith it (C/2M mode of culture), exhibit unequal growth and greeningof their cotyledons. The aim of this work was to investigatewhether this particular mode of culture led to detectable differencesbetween the two cotyledons in the distribution and metabolismof [¹⁴C] abscisic acid (ABA). Two different approaches wereused, the material in both cases being dormant embryos of Pyrusmalus L. cv. Golden Delicious cultured at 23°C in darkness.In a first experiment, the embryos were cultured directly inthe C/2M mode and in the presence of 10^–2 mol m^–3[¹⁴C] ABA. In these conditions marked differences in the distributionof radioactivity between the lower (LC) and upper (UC) cotyledonappear after 24 h of culture. After 5 d, amounts of total radioactivitywere four times higher in LC than in UC, and the level of ABAwas three times higher. Metabolism was extremely active in LC,since certain metabolites were found in relative percentages(percentages with respect to the total radioactivity of thecotyledon) equivalent to (esters, glucosides), or even higher(dihydrophaseic acid, DPA) than those found in UC. It is suggestedthat this high level of metabolism in LC limits the availabilityof the transportable molecule, that is to say ABA. In a secondexperiment double culturing was carried out. The embryos werefirst cultured in the presence of 10^–2 mol m^–3 [¹⁴C]ABA in conditions which ensured equal distribution of ABA andits metabolites between the two cotyledons. After 5 d they weretransferred to an ABA-free medium and cultured in the C/2M mode.After 2 d and 5 d of culture, dissymmetry between the two cotyledonswas again noted; UC this time containing greater amounts ofradioactivity than LC. The differences, however, were less markedthan in the first experiment. This dissymmetry is due to leachingof a certain amount of radioactivity from LC, which is onlypartially compensated for by migration from UC. Key words: ¹⁴C-ABA distribution, leaching and metabolism, embryo culture, embryo dormancy     

Thermophilic Anaerobic Biodegradation of [14C]Lignin, [14C]Cellulose, and [14C]Lignocellulose Preparations

Thermophilic (55°C) anaerobic enrichment cultures were incubated with [¹⁴C-lignin]lignocellulose, [¹⁴C-polysaccharide]lignocellulose, and kraft [¹⁴C]lignin prepared from slash pine, Pinus elliottii, and ¹⁴C-labeled preparations of synthetic lignin and purified cellulose. Significant but low percentages (2 to 4%) of synthetic and natural pine lignin were recovered as labeled methane and carbon dioxide during 60-day incubations, whereas much greater percentages (13 to 23%) of kraft lignin were recovered as gaseous end products. Percentages of label recovered from lignin-labeled substrates as dissolved degradation products were approximately equal to percentages recovered as gaseous end products. High-pressure liquid chromatographic analyses of CuO oxidation products of sound and degraded pine lignin indicated that no substantial chemical modifications of the remaining lignin polymer, such as demethoxylation and dearomatization, occurred during biodegradation. The polysaccharide components of pine lignocellulose and purified cellulose were relatively rapidly mineralized to methane and carbon dioxide; 31 to 37% of the pine polysaccharides and 56 to 63% of the purified cellulose were recovered as labeled gaseous end products. An additional 10 to 20% of the polysaccharide substrates was recovered as dissolved degradation products. Overall, these results indicate that elevated temperatures can greatly enhance rates of anaerobic degradation of lignin and lignified substrates to methane and low-molecular-weight aromatic compounds.     

In vitro oxidation of [U-14C] palmitate, [1-14C] and [6-14C] glucose in newborn and adult rats and pigs

Studies have been made on the intensity of oxidation of [U-14C]-palmitate, [1-14C]- and [6-14C]-glucose by slices of the liver and skeletal muscles of new-born, 1-day, 5-day and adult Wistar rats and domestic pigs. It was found that the level of 14CO2 production from these substrates is higher in tissues of rats than in those of pigs. At early stages of ontogenesis, in tissues of both species intensive oxidation of glucose is observed together with oxidation of fatty acids. In the course of ontogenetic development, the intensity of glucose utilization significantly decreases, whereas the level of fatty acid catabolism remains relatively unaffected.     

Metabolism of [14C]citrulline in the perfused sheep and goat udder

1. A lactating-sheep mammary gland was perfused for 12h in the presence of l-[2-(14)C]-citrulline and received adequate quantities of glucose, acetate and amino acids. Two lactating-goat udders were similarly perfused in the presence of either l-[carbamoyl-(14)C,-2-(14)C]citrulline or l-[carbamoyl-(14)C,1-(14)C]citrulline and l-[4-(3)H]arginine. 2. In these experiments, [(14)C]citrulline was substantially oxidized to CO(2) and converted into arginine and proline of casein. 3. The specific radioactivities of arginine, ornithine and proline of the plasma increased after passage through the udders, demonstrating that [(14)C]citrulline is metabolized by the mammary gland. 4. The presence of two unknown radioactive metabolites of [(14)C]citrulline was detected in the perfusate. These substances were not found after incubation in vitro of oxygenated blood in the presence of the radioactive precursor. 5. From these experiments, it is concluded that citrulline is metabolized in mammary tissue by way of arginine to urea, ornithine and proline.