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PubMed1980

Temperature-mediated hyperinduction of fatty acid desaturation in pre-existing and newly formed fatty acids synthesized endogenously in Bacillus megaterium.

3H-labedeled fatty acids synthesized endogenously by Bacillus megaterium ATCC 14581 growing at 35 degrees C in the presence of L-[G-3H]valine exhibited the same time-course of hyperinduced desaturation following a temperature decrease to 20 degrees C as was observed previously with exogenously supplied 14C-labeled fatty acids. Radioactive fatty acids synthesized in the presence of [U-14C]glucose during hyperinduction at 20 degrees C following a shift-down from 35 degrees C were desaturated at the same relative rate as 14C-labeled fatty acids synthesized previously at 35 degrees C, suggesting that the newly synthesized fatty acids equilibrate with a large portion of the preexisting moieties before becoming susceptible to desaturation.

Bacillus megaterium↗

PubMed2003

Metabolism of fungicide diethofencarb in grape (Vitis vinifera L.): definitive identification of thiolactic acid conjugated metabolites.

The metabolic fate of diethofencarb (isopropyl 3,4-diethoxycarbanilate) separately labeled with (14)C at the phenyl ring and 2-position of the isopropyl moiety was studied in grape (Vitis vinifera L.). The acetonitrile solution of (14)C-diethofencarb at a rate of 500 g a.i. ha(-)(1) was once applied topically to fruits or leaves at the maturity stage of fruits (PHI 35 days), and the plants were grown in the greenhouse until harvest. In the grape plants, diethofencarb was scarcely translocated to the untreated portion and was degraded more in the fruit as compared to the leaf. For the fruit, diethofencarb primary underwent O-deethylation at the 4-position of the phenyl ring to form the phenolic derivative, isopropyl 3-ethoxy-4-hydroxycarbanilate (0.9% of the total radioactive residue, TRR). This metabolite was successively transformed via conjugation with glucose at the phenolic hydroxy group (8.1-18.1% TRR) or with thiolactic acid at the 5-position of the phenyl ring (1.5-1.7% TRR). The thiolactic acid conjugate was further metabolized mainly to two different types of glucose conjugates at the 4-position of the phenyl ring (8.7-13.5% TRR) and the hydroxy group in the thiolactic acid moiety (6.4-7.3% TRR), as evidenced by (1)H NMR and atmospheric pressure chemical ionization-liquid chromatography-mass spectrometry together with cochromatographies with synthetic standards.

Carbamates↗

PubMed2002

Ligation of arabinogalactan to peptidoglycan in the cell wall of Mycobacterium smegmatis requires concomitant synthesis of the two wall polymers.

To study the late events of cell wall assembly in Mycobacterium smegmatis, specific in vivo radiolabelling of exponentially growing liquid cultures over periods of less than one cell generation were carried out. N-Acetyl-[(14)C]glucosamine was used to label peptidoglycan and [(14)C]glucose to label arabinogalactan and arabinomannan. Over periods of several generations, radioactive cell wall material was turned over as soluble autolysis products into the culture fluid. However, turnover of newly synthesized and labelled cell wall was delayed for about one cell generation, implying inside-to-outside growth of the wall as observed in Bacillus. Little radioactive wall material was released into the culture fluid during the first generation of labelling in growing cultures, but the addition of amoxicillin plus the beta-lactamase inhibitor clavulanic acid, at the minimum inhibitory concentration of amoxicillin, led to the release of radioactive peptidoglycan that could be isolated by gel filtration chromatography and contained nearly 3 mol alanine per glutamic acid residue, indicating that it was linear, un-crosslinked peptidoglycan that had never been substantially cross-linked to the cell wall due to inhibition of transpeptidation by amoxicillin. This peptidoglycan had no covalently attached arabinogalactan. Radioactive arabinogalactan was synthesized and released from the amoxicillin-treated bacteria without attachment to peptidoglycan. The results indicate that during growth, incorporation of arabinogalactan into the cell wall requires its ligation to newly synthesized peptidoglycan and that the peptidoglycan must be undergoing concomitant cross-linking to the inner surface of the cell wall. Inhibition of peptidoglycan transpeptidation prevents ligation of arabinogalactan to peptidoglycan and its consequent incorporation into the wall.

Amoxicillin↗

PubMed1978

Metabolic Studies on Intermediates in the myo-Inositol Oxidation Pathway in Lilium longiflorum Pollen: I. Conversion to Hexoses.

The myo-inositol oxidation pathway was investigated in regard to its role as a source of carbon for products of hexose monophosphate metabolism in germinated pollen of Lilium longiflorum Thunb., cv. Ace. myo-[2-(14)]Inositol and d-[1-(14)C]glucuronate had similar distributions of radioactivity, contributing about three times more label to polysaccharide-bound glucose than myo-[2-(3)H]inositol. In the course of glucogenesis label from the latter appeared as tritiated water in the medium. This exchange could be enhanced by supplying d-[5R,5S-(3)H]xylose instead of myo-[2-(3)H]inositol. When the former was administered, [(3)H]glucose was the only labeled sugar residue found in polysaccharide products. The soluble constituents of d-[5R,5S-(3)H]xylose-labeled pollen contained no traces of labeled xylose despite massive uptake and utilization.l-[1-(14)C]- and l-[5-(14)C]Arabinose produced similar labeling patterns in germinated pollen including incorporation of arabinosyl units into pollen tube polysaccharides and substantial glucogenesis which led to utilization of arabinose for respiration and further incorporation of labeled glucosyl units into pollen tube polysaccharides.d-[5-(3)H]Galacturonate was rapidly taken up by germinated pollen but slowly utilized, without conversion to other sugars, for incorporation into pollen tube polysaccharides. l-[6-(14)C]Gulonate was not taken up by pollen.Results strongly support a scheme of conversion from myo-inositol to hexose monophosphate and subsequent products of glucose metabolism that involves the myo-inositol oxidation pathway.

Journal Article↗

PubMed1983

Translocation of [C]sucrose in wheat.

Flag leaves of wheat plants (Triticum aestivum L. em. Thell. cv ;Duke') were supplied with (14)C(glucosyl)sucrose. Translocated [(14)C]sucrose was isolated, then hydrolyzed. Label appeared in both the hexose moieties indicating that some randomization of label had occurred. However, near the radioactive front essentially all of the (14)C was in the glucose moiety, suggesting that randomization occurred after unloading, supporting the conclusion that sucrose was taken up intact by phloem and translocated unaltered.

Journal Article↗

PubMed1991

Acetate uptake by intestinal brush border membrane vesicles.

The mechanism of acetate absorption in the small intestine is not yet established. One possible mechanism is by carrier mediated Na(+)-acetate cotransport since acetate, like glucose, stimulates intestinal Na+ and water absorption in vivo. Uptake of radioactive carbon acetate by small intestinal brush border membrane vesicles was not saturable or Na+ dependent and did not respond to osmotic shrinkage of the vesicles. This suggests that acetate binds to the membranes but is not transported into the intravesicular space and argues against carrier mediated Na+ acetate cotransport. These results are consistent with acetate absorption by a non-mediated diffusion and suggest that the stimulation of water and Na+ absorption by acetate in vivo is largely due to osmotic forces and solvent drag.

Acetates↗

PubMedDate not supplied

Insulinotropic response to enterally administered succinic and glutamic acid methyl esters.

Both the monomethyl and dimethyl esters of succinic acid, administered enterally to fasted rats, caused a rapid increase in plasma insulin. Such was not the case, however, after enteral administration of either succinic acid or the dimethyl ester of glutamic acid. The time course for the appearance of radioactive material in plasma was also vastly different after enteral administration of either [1,4-14C]succinic acid or its dimethyl ester. In the latter case, the separation of acidic and nonacidic radioactive metabolites and the measurement of 14C-labelled D-glucose indicated that, after enteral administration of succinic acid dimethyl ester (2 mmol), its initial appearance rate in plasma averaged 45 +/- 9 microM/min resulting, after 120 min, in a plasma concentration of 1.34 +/- 0.14 mM.

Animals↗

PubMed1977

Radiopharmaceuticals XXVII. 18F-labeled 2-deoxy-2-fluoro-d-glucose as a radiopharmaceutical for measuring regional myocardial glucose metabolism in vivo: tissue distribution and imaging studies in animals.

18F-2-Deoxy-2-fluoro-D-glucose (18FDG) is rapidly extracted by the mouse heart, and the radioactivity in heart (3-4% per organ) remains relatively constant for 2 hr post injection. The brain uptake (2-3% per organ) remained relatively constant throughout the time course of the study. Liver, lungs, kidneys, small intestine, and blood all showed a rapid clearance of radioactivity after injection of 18FDG. At 120 min the heart-to-lung ratio was 12 and heart-to-liver ratio was 32. Urinary excretion of activity was approximately 16% of the injected dose at 60 min. The uptake of radioactivity by dog heart following the intravenous administration of 18FDG was 2.8-4.1% at 60 min and 2.4% at 135 min; it was regionally distributed, the areas of highest activity being the left ventricle and the interventricular septum. The brain activity was 2.1-3.5% at 120 min, with a ratio of gray matter-to-white matter of 2-3:1. Urinary excretion in dogs was 16% and 50% of the injected dose at 60 and 135 min. The chemical form of the activity in the urine, although unidentified, was not 18F-. Cross-sectional images of the myocardium of the dog after intravenous injection of 18FDG were obtained using emission tomography.

Animals↗

PubMed1984

[Keypoints and compositions of total parenteral nutrition for patients with low glucose tolerance levels].

Management of total parenteral nutrition (TPN) in depressed glucose metabolism was investigated clinically and experimentally in view of insulin control and/or new component of carbohydrate solution. Fifty TPN cases out of 837 for 9 years were successfully performed insulin control, while 17 patients were unable to get sufficient calory in spite of insulin administration. Cumulative expired CO2 after injection of radioactive carbohydrate in rats showed that each carbohydrate was utilized in the order of glucose, fructose, maltose, sorbitol and xylitol even in depressed glucose metabolism and that depressed carbohydrate metabolism was improved by adequate insulin injection. Combined use of glucose, fructose and xylitol at 4:2:1 (GFX) was was experimentally revealed to be superior to glucose alone as carbohydrate source of TPN in depressed glucose metabolism. Compared with conventional TPN (C-TPN), GFX-TPN showed lower blood glucose and insulin level in rabbits of sepsis and rats of streptozotocin diabetes. Contents of fructose 2,6 bisphosphate and triglyceride and activities of fructose 6 phosphate 2 kinase, acetyl CoA carboxylase and fatty acid synthetase in liver of these animals supported that GFX had favourable effects on glucose and fat utilization in depressed glucose Blood glucose of early postoperative patients was lower in GFX-TPN than in C-TPN.

Animals↗

PubMed1977

Xylitol infusion and oxalate formation in rabbits.

Oxalate levels in the plasma and urine fractions of fasted normal, oxythiamin treated (20 mg/kg) and 4-deoxypyridoxine treated (300 mg/kg) rabbits were determined following infusion with either xylitol or glucose at a dose of 2 g/kg body weight. Biochemical determinations showed that transient thiamin or pyridoxine deficient states had been induced in the antivitamin treated rabbits. In the first 24 hour following infusion with either carbohydrate, urinary oxalate levels remained within the normal range for all groups. Oxythiamin hastened the appearance of the transient, elevation in plasma oxalate concentrations seen in rabbits after infusion with glucose. After xylitol infusion, the elevation of plasma oxalate was not significnatly above normal. 4-Deoxypyridoxine enhanced peak plasma oxalate levels above those of controls for both sugars. Glucose, at an equivalent dose to xylitol, resulted in higher plasma oxalate levels than xylitol for all groups. Infusions of [U-14C]xylitol and [U-14C]glucose solutions into 4-deoxypyridoxine treated rabbits demonstrated a conversion of the administered radioactive carbon into 14C oxalate of 0.01% with a high dilution of the specific activity. The results suggest that oxalate production from xylitol is negligible; any toxicity related to xylitol administration is not a consequence of oxalate production.

Animals↗

PubMed1985

Luminal secretion of myo-inositol by the rat epididymis perfused in vitro.

A technique for perfusing the lumen of rat epididymal tubules maintained in vitro showed that [3H]inulin was largely excluded from the lumen of unravelled tubules from the cauda and tubules from the corpus if the connective tissue capsule was removed. The preparation transported [3H]inositol from the bath fluid for 3 h against a concentration gradient in both regions with activity rising (16-29% of bath fluid values) in the cauda and reaching a plateau (18%) in the corpus epididymidis. HPLC showed that radioactivity was solely associated with inositol and its movement to the lumen was reduced by raising inositol in the bath fluid from 50 microM (plasma levels) to 10 mM, but not affected by reducing the glucose concentration in the bath fluid or introducing physiological concentrations of inositol (30 mM) into the lumen. Secretion into the caudal lumen of unlabelled inositol measured by g.l.c. was maintained for 3 h at concentrations (300 microM) greater than those in the bath fluid and was not reduced when glucose or inositol were removed from the bath. In contrast, glucose was only detectable in the lumen when it was present in the bathing medium, reaching 1% of this concentration. Radioactivity appeared in the epididymal lumen reaching a plateau (19% of bath fluid values) in the corpus and cauda when [3H]glucose was added to the bath fluid, but no radiolabelled inositol was found in the lumen. We conclude that epididymal tissue is a major source of secreted inositol.

Animals↗

PubMed1976

125I-labelling = 125I-Labelling.

Erythropoietin, the hormone that regulates erythropoiesis in mammals, was 125I-labelled by using the catalytic properties of lactoperoxidase and the H2O2-generating properties of glucose oxidase. This methodology, both rapid and simple, not only produced hormone preparations with high specific radioactivity but also did not substantially alter the biological integrity of erythropoietin when it was assayed in vivo.

Animals↗

PubMed1993

Enzyme-to-enzyme tunnelling between phosphoglucoisomerase and phosphofructokinase.

1. Cross-linked and permeabilized rat erythrocytes were incubated for 2-5 min at 37 degrees C in the presence of ATP and either D-[U-14C]glucose 6-phosphate (3 mM) mixed with unlabelled D-fructose 6-phosphate (1 mM) or D-[U-14C]fructose 6-phosphate (1 mM) mixed with unlabelled D-glucose 6-phosphate (3 mM). 2. The contribution of molecules derived from the radioactive ketohexose ester relative to the total amount of newly formed D-fructose 1,6-bisphosphate was lower than the time-related average value for such a relative contribution in the pool of D-fructose 6-phosphate. 3. From such a difference, it was calculated that, under the present experimental conditions, 13.1 +/- 2.0% of the molecules of D-fructose 1,6-bisphosphate formed during incubation are directly derived from D-glucose 6-phosphate by a process of enzyme-to-enzyme channelling between phosphoglucoisomerase and phosphofructokinase, rather than originating from the free pool of D-fructose 6-phosphate. 4. A comparable value of 13.2 +/- 3.2% was reached when the process of enzyme-to-enzyme tunnelling was judged from the 3H/14C ratio in D-fructose 1,6-bisphosphate formed by permeabilized erythrocytes exposed for 5-15 min to D-glucose 6-phosphate (3 or 5 mM) mixed with tracer amounts of both D-[1-14C]glucose 6-phosphate and D-[2-3H]glucose 6-phosphate.

Animals↗

PubMed1987

Lactate production and absence of gluconeogenesis from placental transferred substrates in fetuses from fed and 48-H starved rats.

Fed and 48-h starved rats were infused on day 21.5 of gestation for 20 min through the left uterine artery with [U-14C-]-D-glucose, [U-14C]-glycerol, or [U-14C]-L-alanine. The mother and fetuses from both uterine horns were processed separately for radioactivity measurements in plasma and liver. Differences in radioactivity values between fetuses from the left and the right sides are used as indexes of placental transference of the infused tracers prior to their distribution and transformation in the maternal circulation. After infusion of [U-14C]-D-glucose, [U-14C]-glycerol, or [U-14C]-L-alanine, plasma radioactivity values and specific activities corresponding to the respective infused tracer appeared much higher in fetuses from the left than the right uterine side. Plasma 14C-lactate values also were higher in the left than the right fetuses indicating that fetoplacental structures produced lactate from those placentally transferred 14C-metabolites. No difference in plasma 14C-glucose between left and right uterine horn fetuses was observed after maternal infusion with either [U-14C]-glycerol or [U-14C]-L-alanine, either in fed or 48-h starved rats. In the mother both [U-14C]-glycerol and [U-14C]-L-alanine were efficiently converted to 14C-glucose, and this process was significantly enhanced with starvation. 14C-fatty acids present in fetal liver after maternal infusions with either [U-14C]-D-glucose or [U-14C]-glycerol were decreased by starvation whereas no fatty acid synthesis from [U-14C]-L-alanine was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗

PubMed1979

Investigation by luminal perfusion of the transfer of compounds into the epididymis of the anaesthetized rat.

Controlled perfusion through the lumen of the distal cauda epididymidis in the anaesthetized rat has been explored as a means of examining physiological exchanges from blood across the epididymal epithelium. The mean length of the perfused, sperm-free, tubule was 14.5 cm (+/- 1.5 s.e.m., n = 9). No cholesterol, protein or sialic acid was detected in the perfusate at flow rates exceeding 10 microliters/min, but at rates of 0.4--1.2 microliters/min, protein appeared at concentrations of 0.21--0.55 mg/ml (i.e. secretion rates of 0.21--0.83 micrograms/min; 3 rats). Glucose was detected at all perfusion rates (3--27 microliters/min) at concentrations of 0.06--0.58 mM (0.8--6.8% blood levels). During intravenous infusions of 3H2O, radioactivity in the perfusate rapidly attained 87% blood plasma concentrations; no radioactivity was detected when carboxy-E114C]dextran or methoxy-[3H]inulin were infused. Radioactivity appeared in the epididymal perfusate to 1--7% of blood levels during intravenous infusions of D-E1U-1RC]glucose or 3-O-methyl[1-3H]glucose. This evidence suggests that the preparation is physiological and could be used to explore the dynamics of exchanges between blood and epididymis.

Animals↗

PubMed1965

THE INCORPORATION OF CARBON DIOXIDE INTO MILK CITRATE IN THE ISOLATED PERFUSED GOAT UDDER.

1. Isolated perfused goat udders supplied with glucose, acetate and amino acids were infused for several hours with NaH(14)CO(3). 2. Lactose, milk-fat fatty acids and glycerol had very little radioactivity. The specific radioactivity (counts./min./mg. of C) of milk citrate was 9-16% that of the carbon dioxide in the perfusion fluid and 19% that estimated for tissue carbon dioxide. The specific radioactivity of tissue citrate resembled that of milk citrate. 3. The radioactivity in citrate was predominantly in C-6, suggesting some carboxylation of alpha-oxoglutarate in addition to carboxylation of C(3) compounds. 4. [1-(14)C]Glutamate was infused in a similar experiment, and milk citrate radioactivity was predominantly in C-1+C-5. 5. The results are discussed in relation to the contribution of glucose and acetate carbon to citrate. The implications of the carboxylation of alpha-oxoglutarate are considered.

Acetates↗

PubMed1986

Compartmentation and regulation of acetylcholine synthesis at the synapse.

Acetylcholine and choline release was measured by using an automated and modified version of the chemiluminescence technique of Israel & Lesbats [(1981) Neurochem. Int. 3, 81-90]. A comparison of acetylcholine and choline release from synaptosomes demonstrated that acetylcholine release was K+-stimulated and inhibited by the Ca2+ ionophore A23187 and cyanide. Choline release, however, did not vary markedly under different conditions, suggesting that it is not associated with acetylcholine release at the nerve ending. Total acetylcholine synthesis in synaptosomal preparations was measured concurrently with the incorporation of [14C]acetyl and [3H]choline moieties by using the chemiluminescence method. Under sub-optimal glucose concentrations or in the absence of treatment of the synaptosomes with the acetylcholinesterase inhibitor phospholine, the incorporation of radioactivity exceeded total synthesis, indicating that cycling between acetylcholine and its precursors may occur. After treatment with phospholine, acetyl-group incorporation from D-[U-14C]glucose occurred without dilution of the precursor at optimal (1.0 mM) and low (0.1 mM) glucose concentrations; however, at very low (0.01 mM) glucose concentrations, dilution by a small endogenous pool occurred. [14C]Acetyl incorporation into acetylcholine was compared with various metabolic parameters. A closer correlation was observed between [14C]acetyl-group incorporation into acetylcholine and the calculated acetyl-carrier efflux from the mitochondria than with the calculated pyruvate-dehydrogenase-complex flux. The results are discussed with respect to the regulation of acetylcholine concentrations at the synapse and the mechanism whereby turnover occurs.

Acetylcholine↗

PubMed1996

Models of metabolism in Rhizopus oryzae.

A flux analysis of glucose metabolism in Rhizopus oryzae was achieved using [14C]-labeled glucose and acetate. The rates of glucose utilization and end product production were estimated, and metabolite pool sizes and specific radioactivities were determined. These data were analysed using a specific radioactivity curve-matching program called TFLUX. The analysis is consistent with the existence of separate mitochondrial and cytosolic pools of pyruvate, malate and fumarate.

Acetates↗