Pattern Of 14C Distribution Research Articles

Effects of Temperature and Light on the Carbon Budget of Young Cucumber Plants Studied by Steady-State Feeding with14CO2

cucumber seedlings was studied at irradiances of either 30 or 75 W m 2 (PAR) with a daylength of 8 h. The irradiance did not affect the relative distribution of 14C. assimilated by the source leaf between growth, respiration and export. In the range 15-30 °C rises in temperature generally increased the proportion of carbon exported. The average rate of carbon exported during the night was about half the rate in the day. About 45% of the exported carbon was lost by respiration. The distribution pattern of carbon exported during the day differed considerably from that of carbon exported during the night. The intensity of irradiance did not affect the proportion of labelled carbon recovered from the roots. Thus the decreased shoot/root ratio generally observed with increased irradiance is not directly controlled by carbohydrate supply. We found that the distribution patterns of exported 14C do not necessarily represent the real carbon distribution, due to differences in specific activity of imported carbon of individual organs. Consequently distribution patterns of 14C observed in experiments with one source leaf have to be considered with caution.

Lipogenesis in isolated human sebaceous glands

Lipogenesis in isolated human sebaceous glands from [U- 14C]glucose, [U- 14C]leucine, [U- 14C]isoleucine, and [U- 14C]valine has been determined by thin-layer chromatography. Total lipogenesis from 2 mmol l [U- 14C]glucose was 114.8 ± 22.3 pmol gland per h (mean ± SE), with 53.8% being incorporated into triglycerides, 20.2% into squalene, 12.8% into phospholipids, 2.1% into cholesterol and 7.1% into wax monoester and cholesterol ester and 5% into di- and monoglycerides and free fatty acids. Total lipogenesis from 2 mmol l [U- 14C]leucine, 2 mmo mmol l [U- 14C]isoleucine, and 2 mmol l [U- 14C]valine in the presence of 2 mmol l glucose was 26, 29 and 9%, respectively, of that seen with 2 mmol l glucose alone. The pattern of 14C distribution in the various lipid classes from the three U- 14C-labelled branched-chain amino acids was not significantly different from that seen with [U- 14C]glucose.

Hydrolysis and Absorption of Pantothenate and Its Coenzymes in the Rat Small Intestine

The transport of pantothenate by the rat small intestine occurs by simple diffusion. There was no significant difference in the rate of in the upper, middle or lower sections of the intestine. Coenzyme A was hydrolyzed to pantetheine and pantothenate in the intestinal lumen via the following series of reactions: coenzyme A → phosphopantetheine → pantetheine → pantothenate. Intestinal tissue, which contains high levels of pantetheinase, quickly degrades pantetheine to pantothenate, which is then transported to the blood and thence to other tissues. Tissue distribution patterns of 14C 5 hours after intraluminal administration of 14C-labeled coenzyme A or [14C]pantothenate were similar; approximately 40% of the 14C was present in muscle and 10% in liver.

DISTRIBUTION OF CARBON AMONG PHOTOSYNTHETIC END‐PRODUCTS IN PHYTOPLANKTON OF THE EASTERN CANADIAN ARCTIC1

ABSTRACTThe distribution of 14C among photosynthetic end‐products was examined in eastern Canadian arctic phytoplankton, with particular emphasis on the synthesis of lipids. The pattern of 14C distribution for phytoplankton at each of three depths was generally similar among populations from 12 stations. About 18% of the total 14C fixed was incorporated into lipids. At one station, phytoplankton were experimentally subjected to temperature and light conditions different from those in situ: lipid‐14C did not exceed 30% of total 14C fixed within the temperature range ‐1.0 to 6.0° C and irradiance range 1 to 700 W · m−2. It is suggested that low temperatures and low light intensities, even when, maintained for prolonged periods, are not fully sufficient conditions for eliciting high relative rates of 14C incorporation into lipids. It is possible that differences in species composition may be a factor accounting for different patterns of 14C distribution between north and south polar phytoplankton under apparently similar environmental conditions.

Significance of atretic follicles as the site of androgen production in polycystic ovaries.

To examine androgenic potential of polycystic ovaries (PCO), slices of follicular and stromal tissues from the same ovary obtained by wedge resection from two markedly, two moderately and one slightly enlarged PCO were incubated separately with [1-14C] acetate. Incorporation into progestins, androgens and estrogens was assessed by reverse dilution technique with recrystallization to constant specific activity. Although the greatest incorporation into androstenedione with much lesser incorporation into testosterone and dehydroepiandrosterone was observed with all the five follicles, the amount of incorporation into the three steroids increased gradedly with histologically defined magnitude of thecal cell hyperplasia in atretic follicles. Only the stromal tissues from two markedly enlarged PCO produced androgens with a similar pattern of 14C distribution among the steroids, thereby incorporation into the three androgens remaining 5.5% or less of that by the follicles from the same ovary. Preoperative levels of plasma androstenedione and urinary 17-ketosteroids were shown to increase in four patients with PCO containing atretic follicles with thecal cell hyperplasia, but not in one patient with slightly enlarged PCO containing atretic follicles without thecal cell hyperplasia. It is inferred that atretic follicles with thecal cell hyperplasia is a significant source of androgen overproduction by PCO.

Cytokinin activity in Lupinus albus

The distribution and metabolism of {8‐14C}zeatin incorporated into the transpiration stream of fruiting white lupin plants (Lupinus albus L.) has been studied. The distribution pattern of 14C in the different aerial organs suggests that the amount of cytokinin being incorporated into any one organ may have been a function of its transpiration rate. Once in these organs, particularly the leaves, zeatin was rapidly metabolised and or utilised. This resulted in the formation of a number of labelled compounds that did not give a response with the soybean callus bioassay. Substances co‐eluting with zeatin glucoside and ribosylzeatin appeared to be the principal biologically active metabolites. From the present evidence it can be concluded that the leaf and side shoots received a major proportion of the applied labelled cytokinin. However, the presence of a small amount of radioactivity co‐eluting with zeatin and ribosylzeatin in the fruits indicates that the high levels of cytokinins normally associated with these organs need not necessarily all have been synthesised in situ.

Excretion and disposition of [14C]carbaryl in pregnant, non-pregnant and foetal tissues of the rat after acute administration.

1. Non-pregnant or pregnant Sprague-Dawley rats on the 18th and 19th days of gestation were injected i.p. with a tracter dose (2.8 microCi/kg) of either [ring-14C]carbaryl or [carbonyl-14C]carbaryl. Distribution of total 14C was examined in foetal, maternal and non-pregnant rat tissues. Pregnancy alters the disposition and excretion of carbaryl. 2. Carbaryl crossed the placenta and was rapidly distributed in all foetal tissues. Highest concentrations were seen in foetal kidney. At 8 h after injection, foetal brain, heart and lung all contained more 14C, on a weight basis, than their maternal organ counterparts. Elimination from the whole foetus was biphasic, and after 8 h approx. 3% of the dose was still present in the whole foetus. 3. Significantly more 14CO2 was exhaled by the pregnant rat during 8 h than by non-pregnant. Urinary excretion of 14C after dosage with [ring-14C]carbaryl was significantly less in pregnant than in non-pregnant rats. 4. Kinetically, the tissue distribution of 14C from carbaryl or metabolites was biphasic in pregnant and non-pregnant animals. [14C]carbaryl concn. declined rapidly for 1 to 2 h. After 2 h the 14C levels from animals dosed with [ring-14C]carbaryl declined more slowly. 5. The pattern of 14C distribution was more complicated after injection of [carbonyl-14C]carbaryl. The 14C activity increased in the animal tissues after 2 h, in contrast to animals dosed with [ring-14C]carbaryl. Non-pregnant animals treated with [carbonyl-14C]carbaryl did not show a similar pattern of distribution. Carbamylated tissue proteins may, after time, release some bound carbonyl-14C label, causing the increase in 14C activity seen between 2 and 8 h. However, this does not necessarily imply uptake of the intact carbamate.

Tricarboxylic acid cycle operation at the kinetoplast-mitochondrion complex of Trypanosoma cruzi

Culture of Trypanosoma cruzi (Tulahuen strain) in the presence of ethidium bromide (1–20 μg/ml) resulted in dyskinetoplasty and inhibition of growth, to an extent depending on the dye concentration and the medium composition. The ethidium bromide-induced dyskinetoplasty caused a decrease of (a) the cytochrome content of epimastigotes ( a,a 3 and b species); (b) the rate of respiration (endogenous or supported by D-glucose); and (c) the rate of production of 14CO 2 from [2- 14C]acetate and [1- 14C]glucose. [2- 14C]Acetate oxidation to 14CO 2 was affected by dyskinetoplasty more than [1- 14C]glucose oxidation, particularly at the exponential growth phase. With dyskinetoplastic epimastigotes, diminution of 14CO 2 production from [2- 14C]acetate largely exceeded that of oxygen uptake, while with [1- 14C]glucose, 14CO 2production and respiration were affected to about the same extent. Dyskinetoplasty also decreased the incorporation of [2- 14C]acetate carbon into intermediates of the tricarboxylic acid cycle and related amino acids, and modified the distribution pattern of 14C in accordance with the decrease of respiration. Reduction of cytochrome content of epimastigotes by restriction of heme compounds during growth decreased 14CO 2 production from [2- 14C]acetate, like the ethidium-induced dyskinetoplasty. The same occurred after inhibition of electron transfer by antimycin and cyanide, though to a much more significant extent, thus confirming the functional association of electron transport at the mitochondrial cytochrome system of T. cruzi and the enzymatic reactions of the tricarboxylic acid cycle.

Transport and Distribution of 14CO2 Assimilate in Lolium perenne in Response to Varying Nitrogen Supply to Halves of a Divided Root System

AbstractThe movement of 14C assimilate from shoots to roots and its subsequent metabolism in the root of Lolium perenne L. was studied using variable N nutrition supplied to halves of a divided root system. Half of the N‐deficient root system was supplied with either high NO3‐N or high NH4‐N for 16 hours or 6 days before 14CO2 labeling of the shoots.The distribution of 14C in sugars, ethanol‐soluble nitrogen and organic acids in roots appeared to be related to the N content of the tissue. Supply of high NO3‐N for 6 days resulted in significant internal translocation of N into the low N supplied root half. Both root halves also had similar patterns of 14C distribution among soluble and insoluble metabolites. However, NH4‐N supply for 6 days did not result in a significant increase of N in the low N supplied roots, thus only the high NH4‐N supplied roots displayed stimulated sugar metabolism, similar to that in both root halves in the high NO3‐N supply treatment.Percent transport of 14C assimilates from shoot to root was influenced by form and level of N supplied to root halves. Root halves supplied with either high N source for 6 days accumulated greater amounts of 14C assimilate than the corresponding low N root half. However NH4‐N supply appeared to make roots stronger sinks since NH4 supply resulted in significantly greater 14C accumulation in both the high NH4 supplied and the low N root halves than did NO3‐N supply in corresponding root halves.The data suggest that factors other than root metabolism, such as N mediated metabolism in the shoot, may also influence the percent transport of assimilates to the root. Internal distribution of the incoming assimilate within the root system could be regulated by the metabolic activity or assimilate demand of the roots.

Photoassimilation of CO2 by Isolated Bundle‐Sheath Strands of Zea mays

AbstractThe role of malate decarboxylation as a source of CO2 and NADPH for the evolution of photosynthesis of isolated maize bundle‐sheath strands has been investigated. The bundle‐sheath cells were supplied with malate plus NADP, in the presence of intermediates of the Calvin cycle to increase the rate of CO2 fixation.The effects of malate addition on the rate of 3 phospoglycerate synthesis, with non‐saturating concentrations of bicarbonate, can be explained by an increase of the cellular pool of CO2 in the cells due to malate decarboxylation. The CO2 reacting with RuDP to give phosphoglycerate corresponds effectively to carbon atom 4 of malate. Malate addition produces an enhancement of the rate of CO2 incorporation which is much more important when the reducing power is the limiting process for the evolution of the Calvin cycle (with phosphoglycerate as added substrate and/or in the presence of DCMU. These results demonstrate the utilization of NADPH produced by malate decarboxylation for the regeneration of RuDP. NADPH can also reverse the reaction of malate decarboxylation and gives rise to a synthesis of malate by carboxylation of pyruvate.In contrast, the pattern of 14C distribution among compounds is not strongly modified by malate addition. This result suggests that PGA reduction in the whole leaf must occur also in mesophyll cells to allow correctregeneration of the reduced compounds of the photosynthetic cycle.

Studies on effects of certain quinones: III. Photosynthetic 14CO 2 incorporation by Rhodospirillum rubrum

Substituted naphthoquinones, 2,3,-dichloro-1,4-naphthoquinone, and 2-methyl-1,4-naphthoquinone produced marked changes in the pattern of 14C-distribution during 14CO 2-fixation by photosynthetic bacterium Rhodospirillum rubrum. The most obvious change in the labeling pattern during photoautotrophic 14CO 2-fixation was a several-fold increase in 3-phosphoglyceric acid accompanied with a decrease in the amount of glutamate. In photoheterotrophic cells, quinones caused an appreciable increase in 14C-glycolic acid and concomitant decrease, although not proportional, in the amount of 14C-sugar phosphate. The level of 14C-incorporated in poly-β-hydroxybutyrate and ether-extractable lipids was considerably decreased in photoautotrophic and photoheterotrophic cells treated with quinones. The ability of quinones to interfere with the synthesis of NADH and ATP, and their ability to interact with sulfhydryl enzymes and coenzymes appears to be responsible for the changes observed.

Photosynthetic and translocation pattern in contrasting winter wheat varieties

SUMMARYThe rates of photosynthesis and patterns of translocation of 14C from the flag leaves of tall and semi‐dwarf wheat varieties, with and without awns, were compared in a field experiment. The rates of photosynthesis of the awnless varieties fell during the 14 days after anthesis but those of the awned varieties did not change. Wide differences in translocation pattern of 14C supplied at anthesis were also found between varieties, but the differences in distribution pattern of 14C supplied 14 days later were less. At anthesis, the high yielding semi‐dwarf selection translocated most carbohydrate to the ears and awned selections least. It is suggested that varietal differences in translocation pattern are determined by differences in the capacity of the grain to store carbohydrate.

Effects of Nitrogen and Phosphorus Nutrition on [14C]-Sucrose Translocation in Hibiscus esculentus

Summary The influence of nitrogen (N) and phosphorus (P) nutrition on the retention of [14C]-sucrose by fed leaves and the distribution patterns of 14C were investigated in vegetative okra plants at the 4-leaf stage. When the oldest leaf 1 was fed, medium and high levels of N and P (20 and 200 mg/1, compared with 2 mg/l) enhanced the outflow of assimilates in a 48 h period. High levels of N enhanced [14C]-distribution to the leaves but decreased that to the stem and the root. The high level of P decreased the distribution to the leaves but enhanced that to the root. When the youngest leaf 4 was fed, high levels of N again enhanced while high levels of P decreased 14C export. The high level of N generally had no significant effect on 14C distribution patterns. The high level of P decreased 14C distribution to leaves, at it did when leaf 1 was fed, but decreased that to the stem while it had no significant effect on 14C imported by the root. The effects o N were, therefore, generally opposite to those of P in terms of both the distribution of 14C to the leaves, stem and root, and the direction of transport.

Distribution and metabolism in vivo of 14C-tetrahydrocannabinol in the rat

14C-Tetrahydrocannabinol (THC) was injected i.v. into a total of 92 adult Wistar rats. At 14 times ranging from 2 min to 48 hr afterwards, groups of animals were examined for total 14C activity and thin-layer chromatographic (TLC) pattern of 14C distribution in blood, brain, heart, kidney, liver, lung, muscle, spleen and perirenal fat. The time course of rise and fall of radioactivity in the various organs and tissues closely resembled that of thiopental and other strongly lipophilic substances. Relatively high levels persisted in fat 48 hr, but levels in brain were quite low. TLC analysis showed the early appearance of 7-hydroxy-THC in all tissues, followed by increasing amounts of more polar compounds and disappearance of THC, except in fat. Levels were much lower after i.p. injection, and whole body autoradiography showed most of the activity remaining in the peritoneal cavity.

Effect of Cytoplasmic Male Sterility on Accumulation and Translocation of 14C‐labelled Assimilates in Corn1

A male‐sterile corn (Zea mays L.) hybrid and its fertile counterpart were grown under field conditions for 3 years. In each year one upper leaf of plants of both types was allowed to assimilate 14CO2 in photosynthesis at both tassel emergence and silking. The plants were harvested after either 1 or 8 days, and distribution patterns of 14C were measured. Less upper leaf assimilates were distributed to male‐sterile tassels than to fertile tassels. More of the labelled assimilates accumulated in developing ears and husks of male‐sterile plants. Increased tolerance in male‐sterile corn lines to stresses caused by high plant populations and other environmental factors appears to occur at least partly because of reduced intraplant competition for assimilates by tassels during early ear development.

Translocation and Metabolism of Atrazine in Canada Thistle

Canada thistle (Cirsium arvense L.) plants containing one elongated and one recently emerged shoot from the same root segment were treated with14C-ring labeled atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine]. Fourteen days after atrazine application to the elongated shoot 98% of the recovered activity remained in this shoot. The distribution pattern of14C suggested movement with the transpiration stream. Of the14C in the treated shoot, 82% was in the form of unaltered atrazine at 14 days after application. Greenhouse studies with nonlabeled atrazine indicated that this herbicide had only an indirect effect on portions of the plant located basipetally to the area of application.

The mechanism of acetate and pyruvate oxidation by Trypanosoma cruzi.

SYNOPSISThe epimastigote or culture form of Trypanosoma cruzi oxidizes [3‐14C] pyruvate and [2‐14C] acetate to 14CO2 without an apparent increase in overall respiration. This oxidation takes place through the tricarboxylic acid cycle as shown by (a) the incorporation of substrate 14C into cycle intermediates; (b) the earlier liberation of acetate carboxyl carbon as CO2; and (c) the characteristic intramolecular distribution of pyruvate and acetate carbon atoms in the skeletal carbon of aspartic and glutamic acids. Upon oxidation of [3‐14C] pyruvate and [2‐14C] acetate, two of the products, alanine and glutamic acid, are found to account for more than 50% of incorporated 14C; labeling of alanine predominates with [3‐14C] pyruvate while labeling of glutamic acid predominates with [2‐14C] acetate. Using [1‐ or 6‐14C] glucose as substrate, the pattern of 14C distribution in soluble metabolites closely resembles that obtained with [3‐14C] pyruvate, in accordance with the joint operation of the Embden‐Meyerhof pathway and Krebs cycle. The cycle operation depends on electron transport through the mitochondrial respiratory chain, since antimycin A, at a relatively low concentration, inhibits the oxidation of [2‐14C] acetate to 14CO2, to the same extent as the parasite respiration. Though functional in T. cruzi epimastigotes, the oxidative role of the Krebs’ cycle is apparently limited by the absence of an efficient oxidative apparatus. The cycle operation does, however, constitute an important source of skeletal carbon for the biosynthesis of amino acids and can contribute to the process of glycogenesis.

Distribution Patterns of 14C in the Labelled Vitamin B6 Prepared with the Cell-suspension of Achromobacter cycloclastes

Distribution Patterns of 14C in the Labelled Vitamin B6 Prepared with the Cell-suspension of Achromobacter cycloclastes

Studies on Effects of Certain Quinones

The effects of various quinone herbicides and fungicides on the photosynthetic (14)CO(2) fixation and the incorporation of (14)C among the products of photosynthesis in Chlorella pyrenoidosa was investigated. Addition of 30 mum 2,3-dichloro-1,4-naphthoquinone (dichlone), 2-amino-3-chloro-1,4-naphthoquinone (06K-quinone), or 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil) inhibited CO(2) fixation, whereas 1,4-benzoquinone had no effect. Treatment with 3 mum or higher concentrations of dichlone, 06K-quinone or 1,4-benzoquinone also produced marked changes in the pattern of (14)C distribution. A noticeable effect was an increase in the proportion of (14)C in sucrose and glycine accompanied by a reduction in (14)C lipids and glutamic acid. These changes appear to occur as a result of shifts in the flow of carbon along various biosynthetic pathways of photosynthetic CO(2) fixation. It is suggested that inactivation of coenzyme A and shortage of reduced triphosphopyridine nucleotide in the quinone-treated cells inhibited the synthesis of lipids and glutamic acid, thereby diverting more carbon into sucrose and glycine.

Absorption and Translocation of Bioxone in Cotton

Absorption and translocation of the 14C-labeled herbicide 2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione (bioxone) in cotton (Gossypium hirsutum L. ‘Acala 4-42-77′) were studied using autoradiography and counting. Foliar penetration and acropetal distribution of 14C occurred within 3 hr and increased with time. No basipetal translocation of 14C out of treated leaves was detected 6 days after treatment. Radioactivity first occurred in the leaf veins, then more generally in interveinal tissues distally from the point of application. Absorption into roots of 30-day-old plants via nutrient solution was rapid; translocation into stem and leaves occurred 12 to 24 hr after treatment. Translocation of 14C was more rapid in 40-day plants. Radioactivity in leaves of root-treated plants was first located in the veins, then distributed throughout with accumulation of 14C in lysigenous glands and leaf margins. Little 14C moved into young growing points; most accumulated in older leaves. Plants treated with heterocyclic ring-labeled and phenyl ring-labeled bioxone-14C had similar distribution patterns of 14C, characteristic of compounds which move only in the apoplast.