Highest Concentrations Of 14C Research Articles

Anthropogenic Releases of Radiocarbon and its Concentration Burden in Environment

: The radiocarbon (14C) concentrations in air and vegetation samples around a nuclear research reactor were studied. Objective: 14C concentrations in the air and vegetation samples around the nuclear research reactor were measured to assess its 14C burden on the environment. Methods: Air samples were collected by converting CO2 into Na2CO3 by using a specified system. Leaf samples were carbonized to convert organic carbon into inorganic carbonates. The samples were converted into carbamate through carbosorb systems with 74% efficiency. The fractionation of 14C for each sample was corrected and normalized to a 13C composition of -25‰ Pee Dee Belemnite. Results: 14C concentrations in the air and vegetation samples around the nuclear research reactor were found to range from 158 to 406 Bq/Kg and 162 to 339 Bq/kgC, respectively. The highest concentrations of 14C were found in the samples close to the reactor and along the prevailing wind direction. The specific activities of the samples decreased with an increase in the distance from the reactor and in the opposite to prevailing wind direction. In addition to the distance from the reactor and wind direction, the local Suess effect was an additional factor affecting the 14C activities in the air and vegetation samples. Conclusion: One can conclude that other than the 14C emissions from the nuclear reactor, local Suess effects and climatic factors (wind directions) dilute and disperse 14C concentrations in the atmosphere and consequently decrease its availability for uptake and accumulation by plants at 4-5 km aerial distance from the point of release in prevailing wind direction.

Groundwater flow system under a rapidly urbanizing coastal city as determined by hydrogeochemistry

In the Jakarta area (Indonesia), excessive groundwater pumping due to the rapidly increasing population has caused groundwater-related problems such as brackish water contamination in coastal areas and land subsidence. In this study, we adopted multiple hydrogeochemical techniques to demonstrate the groundwater flow system in the Jakarta area. Although almost all groundwater existing in the Jakarta basin is recharged at similar elevations, the water quality and residence time demonstrates a clear difference between the shallow and deep aquifers. Due to the rapid decrease in the groundwater potential in urban areas, we found that the seawater intrusion and the shallow and deep groundwaters are mixing, a conclusion confirmed by major ions, Br −:Cl − ratios, and chlorofluorocarbon (CFC)-12 analysis. Spring water and groundwater samples collected from the southern mountainside area show younger age characteristics with high concentrations of 14C and Ca–HCO 3 type water chemistry. We estimated the residence times of these groundwaters within 45 years under piston flow conditions by tritium analysis. Also, these groundwater ages can be limited to 20–30 years with piston flow evaluated by CFCs. Moreover, due to the magnitude of the CFC-12 concentration, we can use a pseudo age indicator in this field study, because we found a positive correlation between the major type of water chemistry and the CFC-12 concentration.

Effects of Vegetation Switch and Subsequent Change in Soil Invertebrate Composition on Soil Carbon Accumulation Patterns, Revealed by Radiocarbon Concentrations

Vegetation types strongly affect soil organic carbon (SOC) accumulation in the terrestrial ecosystem through multiple factors such as litter quality and soil biodiversity. However, the roles of soil fauna in SOC accumulation remain unclear. The objectives of this study were to (1) examine how changes in litter types and soil animal communities affect SOC accumulation in continuously forested or vegetation-switched forest areas; and (2) discuss the role of soil animals in SOC accumulation in forest ecosystems. We focused on soils that have accumulated on top of a volcanic ash layer in the 268 yr since a volcanic eruption in 1739. The radiocarbon “bomb spike”' in the late 1950s and early 1960s provides a unique isotopic signature of soil carbon age. We investigated the combined effects of litter quality and soil invertebrate function on soil14C accumulation patterns. To determine the effects of vegetation types on SOC accumulation, we selected 4 types of cool temperate forests, 2 of which had undergone a vegetation switch in about 1960 (conifer to broadleaved forest, CB; broadleaved forest to conifer, BC), and 2 that had continuous forests (conifer forest, CC; broadleaved forest, BB). The Δ14C values at depth intervals in CC were consistent with the expected bomb-14C profile. In contrast, Δ14C patterns in BB, BC, and CB differed from that of CC. Compared to CC, Δ14C values of the other sites showed relatively high14C concentrations even in deeper soil layers, which suggests the bomb-induced14C has been transported to a greater depth by soil animals. Current broadleaved forests (BB and CB) had higher biomass of litter-feeding invertebrates than in current coniferous forests (CC and BC). These results suggest that carbon from leaf litter was vertically translocated to deeper soil layers by the abundant soil invertebrates in broad-leaved forests. Disagreement with the expected soil profile in BC suggests that past vegetation (broadleaved forest) has affected the present SOC accumulation pattern.

Conversion of cropland into grassland: Implications for soil organic‐carbon stocks in two soils with different texture

AbstractSoil organic‐carbon (SOC) stocks are expected to increase after conversion of cropland into grassland. Two adjacent cropland and grassland sites—one with a Vertisol with 23 y after conversion and one with an Arenosol 29 y after conversion—were sampled down to 60 cm depth. Concentrations of SOC and total nitrogen (Ntot) were measured before and after density fractionation in two light fractions and a mineral‐associated fraction with C adsorbed on mineral surfaces. For the soil profiles, SOC stocks and radiocarbon (14C) concentrations of mineral associated C were determined.Carbon stocks and mineral‐associated SOC concentrations were increased in the upper 10 cm of the grassland soil compared to the cropland. This corresponded to the root‐biomass distribution, with 59% and 86% of the total root biomass at 0–5 cm soil depth of the grasslands. However, at the Arenosol site, at 10–20 cm depth, C in the mineral‐associated fraction was lost 29 y after the conversion into grassland. Over all, SOC stocks were not significantly different between grassland and cropland at both sites when the whole profile was taken into account. At the Arenosol site, the impact of land‐use conversion on SOC accumulation was limited by low total clay surface area available for C stabilization. Subsoil C (30–50 cm) at cropland of the Vertisol site comprised 32% of the total SOC stocks with high 14C concentrations below the plowing horizon. We concluded that fresh C was effectively translocated into the subsoil. Thus, subsoil C has to be taken into account when land‐use change effects on SOC are assessed.

Pharmacokinetics and metabolism of intravenous pirfenidone in sheep

Pirfenidone, a promising antifibrotic agent, was administered intravenously to six female sheep at 30 mg/kg. Four sheep received 14C-pirfenidone simultaneously. Plasma and urine were obtained for assay of pirfenidone and its metabolites over two days, and tissues were obtained via necropsy. Samples were analysed for pirfenidone and metabolites using HPLC-MS and flow scintillation spectrometry. Plasma pirfenidone disappeared with first order kinetics with a clearance of 1.2 l/kg/h, half-life of 24 min, and distribution volume of 0.71 l/kg. After 48 h, the organs containing the largest quantity of 14C were lungs, liver and intestinal wall. Tissues with the highest concentration of 14C were lung, kidney, brain, liver, lymph node and adipose. Metabolites found in plasma and urine were hydroxypirfenidone (half-life of 44 min) and carboxypirfenidone. Additional metabolites found in urine were hydroxypirfenidone glucuronide and acetoxypirfenidone. Approximately, 80% of the tracer eventually appeared in the urine, and approximately 50% of it was in the form of identifiable metabolites. Less than 1% of the dose appeared in the urine in the form of the parent drug. Quantitatively, most of the metabolites appeared in the urine within 2 h. Thus, the drug is rapidly and completely metabolized.

Variable use of plant- and soil-derived carbon by microorganisms in agricultural soils

In this study we used compound specific 13C and 14C isotopic signatures to determine the degree to which recent plant material and older soil organic matter (SOM) served as carbon substrates for microorganisms in soils. We determined the degree to which plant-derived carbon was used as a substrate by comparison of the 13C content of microbial phospholipid fatty acids (PLFA) from soils of two sites that had undergone a vegetation change from C3 to C4 plants in the past 20–30 years. The importance of much older SOM as a substrate was determined by comparison of the radiocarbon content of PLFA from soils of two sites that had different 14C concentrations of SOM. The 13C shift in PLFA from the two sites that had experienced different vegetation history indicated that 40–90% of the PLFA carbon had been fixed since the vegetation change took place. Thus PLFA were more enriched in 13C from the new C4 vegetation than it was observed for bulk SOM indicating recent plant material as preferentially used substrate for soil microorganisms. The largest 13C shift of PLFA was observed in the soil that had high 14C concentrations of bulk SOM. These results reinforce that organic carbon in this soil for the most part cycles rapidly. The degree to which SOM is incorporated into microbial PLFA was determined by the difference in 14C concentration of PLFA derived from two soils one with high 14C concentrations of bulk SOM and one with low. These results showed that 0–40% of SOM carbon is used as substrate for soil microorganisms. Furthermore a different substrate usage was identified for different microorganisms. Gram-negative bacteria were found to prefer recent plant material as microbial carbon source while Gram-positive bacteria use substantial amounts of SOM carbon. This was indicated by 13C as well as 14C signatures of their PLFA. Our results find evidence to support ‘priming’ in that PLFA indicative of Gram-negative bacteria associated with roots contain both plant- and SOM-derived C. Most interestingly, we find PLFA indicative of archeobacteria (methanothrophs) that may indicate the use of other carbon sources than plant material and SOM to a substantial amount suggesting that inert or slow carbon pools are not essential to explain carbon dynamics in soil.

Regulation of root anaerobiosis and carbon translocation by light and root aeration in Isoetes alpinus

ABSTRACTThe activity of alcohol dehydrogenase (ADH) was measured in corms and roots of the submerged freshwater macrophyte Isoetes alpinus Kirk. growing in situ, and related to its capacity for internal oxygen transport and to carbohydrate translocation. ADH activity was present in roots but not corms at uniform activity (0.15–0.35 × 10−6 mol g−1 fresh weight s−1) over the entire plant depth range (3–7 m depth), and was intermediate to that developed in excised roots after 1‐week exposure to either dissolved oxygen at air‐saturation or to anoxia. Responses of photosynthesis and root oxygen release to light intensity confirmed that shoot‐to‐root oxygen transport saturated at similar light intensities to photosynthetic oxygen evolution, but was positive in the dark and at irradiances below the compensation point for photosynthesis, due to contributions to transport by oxygen diffusion from the external medium. Transport of 14C‐labelled photo‐assimilates to roots nevertheless ceased when intact plants were exposed to a combination of leaf darkness and root external anoxia, even when high 14C concentrations were present in shoots, but remained high when the roots were provided with external oxygen. The lack of any control over permeability of the root surface to gases in this species suggested that ADH activity and reduced translocation is most likely caused by development of hypoxic tissues in the apical tissue. These results suggest that reductions in ambient light intensity may have indirect effects on I. alpinus viability by increasing the degree of root hypoxia and impairing carbon partitioning.

14C Sources and Distribution in the Vicinity of La Hague Nuclear Reprocessing Plant: Part Ii—Marine Environment

Carbon dioxide partial pressure and radiocarbon activity were measured in air and seawater in the Bay of Seine and around the COGEMA-La Hague nuclear reprocessing plant (northwest France) during 3 cruises in 2000 and 2002. Results clearly show that the sea is a source of CO2 and 14C to the atmosphere. High 14C concentrations in air and water related to the La Hague liquid waste are clearly recorded. For the restricted area of the Bay of Seine, CO2 carbon and 14C fluxes were estimated, indicating that less than 3% of the liquid 14C release is introduced in the atmosphere.

Measurement of Radiocarbon Content in Leaves from Some Japanese Sites

We have measured radiocarbon contents in leaves collected from 15 sites in Japan, including mountain areas and big city areas for last three years. Comparing the radiocarbon contents in various areas, high 14C concentrations (80–100‰ as δ14C) are seen for the leaves from the mountain and country sites. On the contrary, low concentrations (5–40‰) were observed for the leaves from city region, especially near the road with heavy traffic. These results indicate that the atmosphere of the mountain and country sites in Japan is still clean but the CO2 gas coming from fossil non-radioactive carbon significantly pollutes the atmosphere of the city sites. The value of δ14C for the mountain areas implies that 14C produced by nuclear bomb test in 1960s still remains. The decrease of δ14C at heavy traffic sites in Tokyo is consistent with the increase of CO2 concentration in the atmosphere assuming that almost all CO2 gas in this region originates from the fossil fuel.

Pentachlorophenol Dermal Absorption and Disposition from Soil in Swine: Effects of Occlusion and Skin Microorganism Inhibition

Residue of the environmentally relevant biocide pentachlorophenol (PCP) is found mainly in soil, making dermal contact one of the primary routes for PCP exposure. To quantify exposure effects on dermal absorption and systemic disposition, [ 14C-UL]PCP was dosed nonocclusively or occlusively at 40 μg/cm 2in a soil-based mixture in an in vivoswine model. Additionally, antibiotics were also codosed with occlusive PCP in soil to examine the impacts of skin microbial PCP biodegradation on total dermal absorption. Under nonocclusive, occlusive, and occlusive-antibiotic conditions, total radiolabel absorption by 408 hr was 29.08, 100.72, and 86.21% dose, respectively. Tissue accumulation of PCP and its labeled metabolite(s) was very significant in swine since one-half to two-thirds of the absorbed dose was still present in tissues by 17 days after PCP dermal exposure. High 14C concentrations were found in liver, kidney, lung, ovary, and uterus. Urine and fecal routes were equally important for label excretion from the body. Occlusion enhanced total dermal absorption and changed the shape of the absorption profiles in the blood and plasma. Skin microorganism inhibition retarded 14C dermal absorption, altered local and systemic tissue distribution, and increased plasma/blood concentration ratios, suggesting skin microbial PCP degradation might play an important role in the altered absorption and disposition by occlusion. This study demonstrated significant dermal absorption and extensive tissue persistence of PCP after soil exposure. Occlusion and skin microflora growth may greatly impact dermal absorption, cutaneous disposition, and systemic toxic input. Therefore, exposure-specific PCP absorption and disposition profiles must be taken into consideration in risk analysis.

Effects of ionizing radiation on the boreal forest: Canada's FIG experiment, with implications for radionuclides

The Field-Irradiator Gamma (FIG) experiment chronically irradiated a section of the Canadian boreal forest over a period of 14 years. Forest trees were affected at dose rates > 0.1 gGy·h −1, but a herbaceous plant community thrived at dose rates up to 65 mGy·h −1. Irradiation resulted in the establishment of four zones of vegetation: a herbaceous community, a shrub community, a narrow zone of dying trees, and a zone with no apparent impacts. Concentrations of 14C, 99Tc, 129I, 137Cs and 226Ra that could cause a dose rate of 0.1 mGy·h −1 within vegetation were calculated. Chemical toxic effects on plants would be caused by 99Tc and 129I before radiological effects are predicted to occur. The calculated 226Ra concentration is about a factor of 10 greater than that measured at some natural sites. Sufficiently high concentrations of 14C and 137Cs to cause an impact are unlikely unless a site is severely contaminated.

Disposition of parathion after dermal application in pigs*

Pharmacokinetic parameters of parathion were studied in pigs after intravenous (i.v.) and dermal administration of unlabelled and 14C-parathion. Plasma concentration-time data were subjected to non-compartmental analysis. Intravenous injection studies showed a mean residence time (MRT) of 2.15 h, a body clearance (ClB) of 4.4 l/kg/h and a volume of distribution (Vss) of 9.8 l/kg. Dermal application led to a mean absorption time (MAT) of 78 h, and a bioavailability of 9.9%. Plasma levels of 14C-parathion (parathion + metabolites) were much higher and more persistent than those of parathion itself. After i.v. administration, recovery of 14C-parathion from urine plus faeces was almost 100% within 3 d, while it was less than 20% after dermal application. Ten days after dermal application high 14C concentrations remained in the back skin, i.e. the application area. In skin samples from areas where contamination from the application area could not have occurred, the 14C-parathion concentration was as low as 2 micrograms/g. It is concluded that in view of the low dermal bioavailability for organophosphorus insecticides it is unlikely that pour-on preparations containing these insecticides reach the ectoparasites through absorption and systemic distribution, but rather that this happens after spreading on the surface of the skin.

Disposition of Parathion in Neonatal and Young Pigs

Pharmacokinetics, metabolism (in vivo and in vitro), elimination and tissue distribution of 14C-parathion was studied after intravenous administration of 0.5 mg/kg to newborn, 1 week and 8 weeks old piglets. Body clearance increased from 7 ml/min./kg in newborn to 35 and 121 ml/min./kg in 1 and 8 weeks old piglets, respectively. Urinary excretion during the first 3 hr rose from 18 to 48 and 82% of the dose in newborn, 1 and 8 week old piglets. The main metabolite of parathion was p-nitrophenyl-glucuronide making up 85% of the urinary 14C excretion. About 6% was excreted as p-nitrophenyl-sulfate and only 1% as free (non-conjugated) p-nitrophenol. Unchanged parathion or paraoxon was not detectable in urine from any of the age groups. The in vitro experiments showed that biotransformation of parathion took place only when cofactors for oxidative reactions were present, indicating that oxidation is the first and necessary metabolic step and that hydrolysis does not contribute significantly to the elimination of parathion. The highest concentration of 14C 3 hr after administration was found in kidney and liver. In newborn piglets the 14C-concentration in tissues was higher than or equal to the plasma concentration. The 14C tissue/plasma ratio decreased with age for all tissues except kidney. Parathion was present in high concentrations in plasma, liver and kidney from newborn piglets, whereas the level just exceeded the detection limit in the 8 week old ones. Paraoxon was clearly detectable in plasma and liver from newborn piglets, while only traces were found in the older groups.

Absorption and metabolism of [U-14C] acetic acid in growing pigs

ABSTRACTBy tracing14C after an injection of [U-14C] sodium acetate into the caecum of pigs, it was found that proportionately 0·93 of the acetate injected was absorbed. About 0·25 of the administered acetate was recovered in the body 96 h later. It is assumed that the remainder was oxidized during this period and exhaled as carbon dioxide.The14C initially predominated in plasma lipids, but it progressively shifted over the 96 h to plasma proteins. In the lipid fraction of blood plasma there was a continuous shift of14C from triglycerides and free cholesterol to cholesterol esters over the 96-h period of measurement.In the body most of the14C was recovered in the fat, liver and intestinal wall. The highest concentration of14C was in the bile, especially in glycine-conjugated bile acids.It was shown that the absorbed acetate was a source of energy to the pigs and it was recycled and metabolized into more complex components in the body during 96 h.

Absorption, distribution, excretion and metabolism of a single oral dose of [formula omitted] phosphate (TOCP) in the male rat

A single oral dose of 50 mg/kg of [ 14C]TOCP was administered in corn oil to male rats. Three animals were sacrificed at each of 2, 6 and 12 h and 1,2 and 5 days following dosing, and tissues and excreta were analyzed for 14C. Within 5 days, 63 and 36% of the dose were recovered in the urine and feces, respectively. Initially, the highest concentrations of radioactivity were observed in the gastrointestinal tract, its contents, the urinary bladder, liver and kidneys. Appreciable concentrations of 14C were detected in plasma, red blood cells, lungs and adipose tissues, while neural tissues, muscle, spleen and testes contained lower concentrations of radioactivity. Among neural tissues, the sciatic nerve contained the highest concentrations of 14C at all time points studied. The concentration of TOCP in plasma was at maximum by 6 h then declined biexponentially with terminal half-life of 46 h. The predominant metabolites in plasma were o-cresyl dihydrogen phosphate, di-ocresyl hydrogen phosphate and o-hydroxybenzoic acid (salicylic acid). Small concentrations of the neurotoxic metabolite of saligenin cyclic- o-tolyl phosphate, were detected in plasma at all but the last time point analyzed. Most of the radioactivity extracted from the livers of rats sacrificed at 2 and 4 h were metabolites. No TOCP was detected in the urine or feces collected within 3 days after dosing. The major metabolite in the urine and feces was o-cresyl dihydrogen phosphate followed by di- o-cresyl hydrogen phosphate, salicylic acid, o-hydroxybenzyl alcohol and o-cresol. This study supports the hypothesis that the insensitivity of the rat to TOCP-induced delayed neurotoxicity may be attributed, in part, to the disposition and metabolism of this chemical.

Absorption, distribution, metabolism and excretion of a new iminodibenzly derivative Y-516 in rats.

ラットに14C-Y-516を経口投与した際の吸収，分布，代謝，排泄について検討し，以下の成績を得た．1．本品のラット消化管からの吸収は速やかであり，かつ良好である．吸収に関する性差はみられなかった．雄ラットにおいて，高用量で吸収速度の低下がみられたが，吸収率の低下はなかった．2．5mg/kgを雄ラットに経口投与すると，投与後30分以内にCmaxに達し，以後T1/2が3および15時間の2相性で消失した．50mg/kgを経口投与した場合にも同様の消失推移を示した．血液中14C濃度に著しい性差はみられなかった．3．5mg/kgを雄ラットに経口投与すると，肝臓中に最も高濃度の14Cが移行し，ついで，肺，腎臓，脾臓副腎，甲状腺および唾液腺が比較的高かった．4．5mg/kgを経口投与後1，6時間における血清中14Cの蛋白との結合率は，それぞれ72%および77%であった．また，14Cの血球への移行は少なかった．5．Y-516のラットにおける主代謝経路は，iminodibenzyl核8位への水酸化反応であり，その他2，10および11位の水酸化反応も認められた・また，Y-516および水酸化された代謝物の一部はスピロアミソ部で脱水素化され，対応するdehydro体を生成した．これらY-516およびdehydroY-516の水酸化体はいずれもグルクロン酸抱合を受けて，胆汁を介して糞中に排泄された．また，代謝に性差や用量差はみられなかった．6．5mg/kgを雄ラットに経口投与すると，投与後4日以内の尿中に投与した14Cの6.5%，糞中に96.0%が排泄された．雄ラットに50mg/kgを経口，5mg/kgを腹腔内，雌ラットに5mg/kgを経口投与した場合にも同様の成績が得られた．7．5mg/kgを経口投与後24時間以内の胆汁中に投与した14Cの雄ラットで62.0%，雌ラットで75.0%が排泄された．

Lung, liver, and kidney as potential target organs after exposure to 1-nitropyrene, as determined by the time course of covalently bound material.

Previous studies in which rats were exposed to [14C]-1-nitropyrene by inhalation indicated that lung, liver, and kidney consistently accumulated the highest concentrations of 14C after exposure. The purpose of the study described here was to determine the extent to which this 14C was covalently bound to macromolecules. Male F344/N rats were exposed to 360 ng [14C]-1-nitropyrene/l air for 1 h resulting in an average of 2.2 micrograms 1-nitropyrene deposited per rat. An additional group of rats was given 4.2 micrograms [14C]-1-nitropyrene by gavage. Total 14C in 23 tissues was determined for up to 96 h after inhalation exposure and up to 30 d after gavage. Lung, liver, and kidney contained the highest concentrations of 14C. Samples of these tissues were exhaustively extracted to determine the amount of radioactivity covalently bound to macromolecules. Regardless of the route of administration, the kidneys had the highest concentrations of covalently bound 14C. At 96 h after exposure kidneys had overall mean concentrations of 2.7 pmol bound/g tissue.micrograms nitropyrene administered. The overall mean concentration in liver was 0.18 pmol bound/g.microgram and the overall mean concentration in lung was 0.06 pmol/g.microgram at 96 h after exposure. Covalently bound material persisted in kidneys for the duration of the study (30 d postexposure). The calculated half-time for removal of bound 14C from kidneys was 150 d. These data suggest that kidney should be considered as one of the organs at risk after exposure to nitropyrene by inhalation or ingestion.

Absorption, distribution and excretion of L-DOPS in animals.

The absorption, distribution and excretion of (−)-(2 S, 3 R)-2-amino-3-hydroxy-3-(3, 4-dihydroxyphenyl) propionic acid (L-DOPS), an unphysiological amino acid and the precursor of norepinephrine, were investigated in mice, rats, dogs and Rhesus monkeys after oral or intravenous administration of 14C-L-DOPS labelled at C-3 position. 1. When 14C-L-DOPS (10 mg/kg) was administered orally to male animals, the maximal concentration (Cmax) in the serum was obtained within 1 hr after administration. Cmax levels were 9.5, 4.4, 3.6 and 2.7 μg eq/ml in dogs, Rhesus monkeys, mice and rats, respectively. The serum levels decreased rapidly with halflives of 1.3 to 4.2 hr. 2. After single oral administration of 10, 100 or 1000 mg/kg of 14C-L-DOPS to male rats, the maximal serum concentration of radioactivity for all doses appeared within 1 hr and then decreased rapidly. The area under the serum concentration-time curve for 14C was closely correlated with the administered dose. 3. There was no difference in 14C serum levels between male and female rats. 4. The radioactivity was distributed throughout organs and tissues after single oral administration of 14C-L-DOPS (10 mg/kg) to animals. Then the 14C levels rapidly decreased and 24 hr after administration only tracer concentrations were observed in the tissues. No particular accumulation in specific tissues was found. Relatively high concentrations of 14C were found in the kidney and liver of every species, and in the pancreas of mice and rats. 5. When 14C-L-DOPS (10 mg/kg) was administered orally to male animals, the excretion of a radioactivity to urine and feces was 60 ?? 72 % and 9 ?? 20 % of administered dose, respectively. Male rats excreted 14 % of the administered dose with expired air. The male rats excreted with bile 2.8 % of the dose during 48 hr.

Metabolism of n-Alkanes and their incorporation into lipids in the rainbow trout

The metabolic utilization by fish of n-alkanes was investigated in Salmo gairdneri R. receiving per os a single dose of [14C]heptadecane. This alkane was largely absorbed and radioactivity in the intestinal content was entirely in heptadecane. No elimination of the hydrocarbon was observed in urine. One week after dosing, ca. 50% of the ingested radioactivity was stored in the carcass and two-thirds of this radioactivity was due to heptadecane. The highest concentration of 14C was found in adipose tissue and liver, in which 77 and 22%, respectively, of the radioactivity originated from hydrocarbon. The rest was omega-oxidized to heptadecanoic acid. This fatty acid was incorporated into neutral lipids (mainly as free fatty acid) and phospholipids.

Loading of assimilates in wheat leaves. II. The path from chloroplast to vein

Abstract. An improved method is described for micro‐autoradiography of water‐soluble substances alter freeze‐substitution of plant tissue in which water is rigorously excluded. Resin sections are cut and flattened dry, and dry photographic emulsion is mounted on them. When the location of 14C in wheat leaves after assimilation of 14CO2 was studied with this method, it was found that 14C entered the intermediate veins before the laterals and entered both types of veins along the flanks of the veins adjacent to the phloem. High concentrations of 14C were found in small spaces in the cells of mesophyll and vein parenchyma; these spaces coincide with the nuclei. The concentration of 14C in these nucleus‐associated spaces was as high as that reached at later times in the sieve tubes. Water washed the 14C out of these spaces of the sections and the label in the washings was predominantly in sucrose. The high 14C concentrations of the nucleus‐associated spaces were particularly easily leached. It is concluded that the raising of the sugar concentration to the high levels found in sieve tubes can take place in these leaves in a special space in each mesophyll cell not, or not only, at the boundary of the sieve tubes.