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At least 271 records · Page 15Linked to original sources
PubMed1993

PET imaging of non-small-cell lung carcinoma with carbon-11-methionine: relationship between radioactivity uptake and flow-cytometric parameters.

Carbon-11-methionine PET scans were obtained from 24 patients with non-small-cell lung carcinoma for whom surgical treatment was considered. The tumor mass was visualized with clear delineation. After PET scanning, the tumor was removed by lobectomy or pulmonectomy. The tumor tissue was first processed to yield tumor cell suspensions and then subjected to DNA flow cytometry. Comparison between 11C uptake rate and flow-cytometric data gave the following results: 11C uptake rate in the tumor correlated well with the cellular DNA content (DNA index) of tumor cells at the resting state of cell division (G0 + G1-phase) (r = 0.67). The correlation between 11C uptake rate and S-phase cell percentage was markedly high (r = 0.76), and the correlation between 11C uptake rate and S+G2/M-phase cell percentage was extremely high (r = 0.86). It was concluded that the tumor uptake rate of 11C-methionine was representative of tumor growth rate in this tumor type.

Aged↗
PubMed2004

Ionizing radiation attracts soil fungi.

During the last 15 years, about 2000 strains of 200 species of 98 genera of fungi have been isolated from around the Chernobyl Atomic Energy Station. Many of these microfungi are capable of growing into and decomposing 'hot particles'; carbon based radioactive graphite from the reactor and there are suggestions that some fungi actively direct their growth toward sources of radioactivity, possibly attracted to the carbon skeleton of these structures. In our experiments, we eliminated the confounding effects of carbon as a fungal resource, by developing experimental protocols that expose fungal spores and their germinating hyphae to directional sources of ionizing radiation allowing us to measure fungal response to ionizing radiation per se. We show that both beta and gamma radiation promote directional growth of hyphae towards the source of ionizing radiation.

Beta Particles↗
PubMed1975

Rapid determination of (carbon-14) glucose specific radioactivity for in vivo glucose kinetics.

Specific radioactivity of blood glucose was determined by use of a Dowex-1 anion-exchange column after (carbon-14) glucose was infused for in vivo kinetics. The first 20-ml eluate of protein-free blood filtrate from the column was discarded; then 10 ml was collected, lyophilized, and counted in a liquid-scintillation counter. Glucose concentration was determined and specific radioactivity calculated. Kinetic results were comparable to those obtained with the more laborious glucose-pentaacetate procedure.

Acetates↗
PubMed1974

Biosynthesis of fosfomycin by Streptomyces fradiae.

The antibiotic fosfomycin was produced as a secondary metabolite in a glucose-asparagine medium containing citrate, l-methionine, and l-glutamate. The citrate requirement for antibiotic synthesis was related to its requirement for growth. In contrast, l-methionine and l-glutamate caused a marked stimulation of fosfomycin production and had no effect on growth. l-Methionine had to be added early to effect maximal antibiotic synthesis later in the fermentation. The l-glutamate requirement was not specific, since several tricarboxylic acid cycle intermediates could replace this amino acid. l-Asparagine was the most effective nitrogen source for growth and production of fosfomycin. Glycine, an alternate nitrogen source, supported fosfomycin synthesis only when added in excess of that needed for growth. Cobalt and inorganic phosphate were required also for antibiotic production at concentrations exceeding those supporting maximal growth. Radioactive incorporation studies showed that the methyl carbon of methionine was the precursor of the methyl of fosfomycin. Carbon 1 of fosfomycin was derived from glucose carbons 1 and 6, whereas glucose-2-(14)C labeled fosfomycin carbon 2. Radioactivity from acetate-2-(14)C was distributed equally between fosfomycin carbons 1 and 2. No incorporation of acetate-1-(14)C, asparagine-U-(14)C, citrate-1,5-(14)C, or glutamate-U-(14)C occurred. The labeling pattern of fosfomycin carbons 1 and 2 was similar to that found in 2-aminoethylphosphonate from Tetrahymena.

Acetates↗
PubMed1976

Methionine metabolism and ethylene biosynthesis in senescent flower tissue of morning-glory.

In immature rib segments prepared from morning-glory (Ipomoea tricolor) flower buds, the major soluble metabolite formed from tracer amounts of l-methionine-U-(14)C was S-methylmethionine (SMM). In segments of senescing ribs, (14)C was progressively lost from SMM and appeared in free methionine. Immature segments contained about 4 nmoles of free methionine and about 16 nmoles of SMM per 30 segments. As the segments senesced, the methionine content increased about 10-fold while the SMM content remained unchanged; during this time about 0.8 nmole of ethylene was produced per 30 segments. Tracer experiments with l-methionine-U-(14)C, l-methionine-methyl-(3)H, and l-homocysteine thiolactone-(35)S indicated that SMM was capable of acting as a methyl donor, and that in senescent segments the methyl group was utilized for methionine production with homocysteine serving as methyl acceptor. Of the 2 molecules of methionine produced in this reaction, 1 was re-methylated to SMM, and the other contributed to the observed rise in the content of free methionine.Internal pools of methionine and SMM were prelabeled (but not significantly expanded) by overnight incubation on 10 mum l-methionine-U-(14)C. The specific radioactivity of the ethylene subsequently evolved during the senescence of the segments closely paralleled the specific radioactivity of carbon atoms 3 plus 4 of free methionine extracted from the tissue, demonstrating that methionine was the major precursor of ethylene in this system. The specific radioactivity of carbon atoms 3 plus 4 of extracted SMM was about twice that of the free methionine.Based on these results, a scheme for methionine biosynthesis in senescent rib tissue is presented. The operation of this pathway in the control of ethylene production is discussed.

Journal Article↗
PubMed1995

A new method of assessing rates of the futile cycle during glycolytic and gluconeogenic metabolism.

A method for assessing rates of the futile cycle is presented, and it is illustrated in vitro. Glycolytic- and gluconeogenic-type futile cycles are simulated for the reactions catalyzed by phosphofructokinase (EC 2.7.1.11) and fructose-1,6-bisphosphatase (EC 3.1.3.11) in assays systems in which the cycle rates in either direction can be varied and determined. While either system is sustaining a net flux of carbons in a given direction, the flux of radioactively labeled carbons in the opposite direction is determined. Different cycle rates are obtained by varying phosphofructokinase activity while keeping fructose-1,6-bisphosphatase activity constant in the "gluconeogenic" simulation and varying fructose-1,6-bisphosphatase while keeping phosphofructokinase activity constant in the "glycolytic" simulation. A direct, linear relationship was found between the cycle rate and the radioactive labeling of fructose 1,6-bisphosphate from [U-14C]glucose 6-phosphate during net gluconeogenic carbon flux. Also, a direct, linear relationship was found between cycle rate and radioactive labeling of fructose-6-P from [U-14C]fructose-1,6-bisP during net glycolytic carbon flux. The applicability, advantages, and problems of the method are discussed.

Animals↗
PubMed1977

Absorption, distribution, and excretion of [14C]patulin by rats.

Adult rats of both sexes were given a single oral dose of [14C] patulin and were sacrificed at various time intervals from 4 hr to 7 days following administration of the mycotoxin. Two groups of rats were employed; the treated group had been exposed to daily oral doses of unlabeled patulin (dissolved in pH 5.0 citrate buffer) in utero and for 41-66 wk after weaning, while the controls were given the buffer only throughout gestation and for 38-81 wk after weaning. Approximately 49% of the administered 14C radioactivity was recovered from feces and 36% from urine within 7 days after dosing. Most of the excretion of labeled material occurred within the first 24 hr. All of the 14C activity detected in the urine samples was either metabolites and/or conjugates of the original [14C]patulin. About 1-2% of the total radioactivity was recovered as 14CO2 from expired air. Carbon-14 radioactivity in various tissues and organs was determined throughout the 7 day period; the most significant retention site was the red blood cells.

Animals↗