Specific Activity Tritium Research Articles

Fabrication of deuterated–tritiated polystyrene shells for laser fusion experiments by means of an isotope exchange reaction

Deuterated–tritiated polystyrene shells with a silicon dopant for use in laser fusion experiments were fabricated by means of an isotope exchange method. In order to increase the isotope exchange rate, deuterated polystyrene shells in a tritium atmosphere were exposed by ultraviolet (UV) radiation from a mercury lamp. The specific activity of tritium in the shells were 92 Ci/g for partially deuterated polystyrene and 150 Ci/g for fully deuterated polystyrene, respectively. The isotope exchange rate with UV irradiation was 230 times as fast as that without the UV irradiation. The tritium in the shell was found to be strongly localized at the outer surface.

In the rat, intestinal lymph carries a significant amount of ingested glucose into the bloodstream.

Intestinal lymph flow in rats receiving an oral load of 3 mmoles of glucose was determined by measuring the amount of tritiated gavage water entering via the portal route [computed differential arterio-venous tritium water concentrations multiplied by portal blood flow) and measuring the total amount of tritium transferred from the intestinal lumen to the rest of the rat in a given time [from the blood tritium specific activity and the water space (795 ml.kg-1) of the rat]. The approximate figure obtained (79.8 ml.kg-1.h) was used for the evaluation of the amount of glucose (from 14C-labelled glucose in the gavage) transfer via intestinal lymph from the label present in the lymph and its flow. Lymph glucose concentration (c. 11 mM) and specific radioactivity were higher than those of blood. The amount of glucose actually taken up from the intestinal lumen was determined measuring the remaining label in the alimentary canal. The portal contribution to label distribution was measured as for tritium water transfer. Most glucose label passed through in the form of glucose, with much smaller proportions as CO2 and even smaller as lactate and other labelled compounds. The results suggest that the contribution of lymph circulation to dietary glucose incorporation into the bloodstream may be significant, amounting to values higher than 10% of the glucose actually incorporated.

A potential radioiodinated ligand for androgen receptor: 7.alpha.-methyl-17.alpha.-[2'-(E)-iodovinyl]-19-nortestosterone

The presence of androgen receptor (AR) in prostate cancer has been linked to the androgen-dependent nature of the tumor and has also been shown to have prognostic significance; it also appears to be a positive prognostic indicator in breast cancer. However, due to the relatively low AR concentrations in most tumors and the inherently low specific activity of tritium, the assay of AR based on available 3H-ligands is not sensitive enough to measure accurately the amount of receptor in small specimens. A 125I-ligand like those available for the estrogen and progesterone receptors would be helpful, but development of such a ligand for AR has not been very successful. Although several androgen analogues containing iodine, bromine, or selenium have been synthesized specifically as potential probes for AR, none have shown any significant affinity or specificity for the receptor. We therefore undertook the synthesis of new potential AR ligands which could be radioiodinated, and determined their affinities for AR (from rat uterus and MCF-7 human breast cancer cells) by using a competition assay. We have examined both 5 alpha-dihydrotestosterone (5 alpha-DHT) and 19-nortestosterone analogues and have identified two such compounds which showed high AR affinity: (17 alpha,20E)-17 beta-hydroxy-21-iodo-5 alpha-pregn-20-en-3-one (17 alpha-[E)-iodovinyl)-5 alpha-DHT, 9) and 17 beta-hydroxy-7 alpha-methyl-(17 alpha,20E)-21-iodo-19-norpregna-4,20-dien-3- one (7 alpha-methyl-17 alpha-[E)-iodovinyl)-19-nortestosterone, 11). In fact, the affinity of the latter for human AR was found to be superior to that of 5 alpha-DHT itself. These iodovinyl analogues could be easily prepared in the radioiodinated form, and should prove to be extremely useful in assaying low levels of AR in small specimens.

Technogenic Tritium in Central European Precipitations

An overview of environmental aspects of the tritium method is given. Temporal and local variations of the specific tritium activity of precipitations, particularly the decay of the bomb peak as well as the continential and latitude effects, are used to subdivide the tritium content of precipitations in bomb tritium and technogenic tritium for the example of the measurement series of Freiberg. Technogenic tritium is shown to have prevailed from the beginning of the eighties, whereas the emission of technogenic tritium has strongly decreased in Europe since the middle of the seventies.

In vivo fixation of atmospheric tritium gas in pine and zelkova trees and their surroundings.

In vivo laboratory experiments on tritium gas (HT) fixation in pine trees were conducted using one-way circuit inhalation apparatus and dwarf pine trees. After 2 hours of exposure to HT, tritium distribution in pine needles, branches, trunk, roots and soil was measured. The specific activity of tritium in pine needles was almost the same as that in the branches and about one fiftieth that in the small roots or soil. To eliminate the contribution of HT oxidation in the soil from the plants, a dwarf pine tree, washed and with its root system sealed, was exposed to HT. Oxidation activity of HT was also determined in in vitro experiments for each part from a dwarf pine tree. Oxidation activity of plant parts above the ground was quite low. In vivo and in vitro experiments were also conducted on dwarf zelkova trees and similar results were obtained.

Release of tritium, protium and helium from neutron-irradiated Li-Al alloy

Release of hydrogen gases (H 2 , HT, T 2 ) and helium from highly neutron-irradiated Li-Al alloy on heating was investigated as functions of 6 Li burnup and temperature. Tritium gas (T 2 , HT) was released abruptly from the alloy at about 650 K. H 2 gradually above about 670 K, and He near the melting point of the alloy. The fraction of T 2 increased with 6 Li burnup. The highest specific activity of tritium in the gases obtained for the alloy of 65% 6 Li burnup was 1.98 PBq mol 1 , which nearly equals to a specific activity of pure tritium gas (2.14 PBq mol −1 ). The abrupt release of tritium at about 650 K may be owing to recovery of defects accompanied by recrystallization of the alloy. Negligible release of He below the melting point of the alloy is likely attributed to trapping of He at vacancies of the alloy.

Radiolabeled allylic isoprenoid pyrophosphates: Synthesis, purification, and determination of specific activity

A new procedure for the preparation of [1- 3H]allylic isoprenoid pyrophosphates is reported. Tritium is introduced into dimethylallyl alcohol, geraniol, and farnesol by oxidation to the corresponding aldehydes followed by reduction with sodium [1- 3H]borohydride. The alcohols are phosphorylated by conversion to allylic halides and treatment of the halides with tris-tetra- n-butylammonium hydrogen pyrophosphate. The pyrophosphates are purified by chromatography on cellulose. Specific activities are determined from the corresponding naphthoate esters whose concentrations can be measured accurately by ultraviolet spectroscopy. Alternatively, the specific activity of tritium is determined for the naphthoate esters prepared with [ 14C]naphthoic acid of known specific activity by measurement of 3H 14C ratios. The methods described should prove advantageous over existing procedures for radiochemical preparations of this class of metabolites.

Global Environmental Transport Models for Tritium

In this paper we discuss some of the obstacles to the construction of credible models of global tritium transport for use in dose assessments. We illustrate these difficulties by comparing model predictions of environmental tritium levels with measurements. Monitoring of tritium has shown that specific activities in precipitation over land are typically higher by a factor of three to four than those in precipitation over the oceans. Experience with modeling CO/sub 2/ turnover in the oceans has led to the conclusion that two-box reservoir models of the ocean often give unsatisfactory representations of transient solutions. Failure to consider these factors in global models can lead to distorted estimates of collective dose and create difficulties in validation of the model against real data. We illustrate these problems with a seven-box model recommended by the National Council on Radiation Protection and Measurements in which we forced the atmospheric compartment to reproduce an exogenous function based on historic observations of HTO in precipitation at 50/sup 0/N. The fresh water response underestimates data from the Ottawa River by a factor of about five, and the ocean surface response overestimates tritium data from the surface waters of the Northern Pacific by nearly an order ofmore » magnitude. Revision of the model to include (1) separate over-land and over-ocean compartments of the atmosphere and (2) a box-diffusion model of the subsurface ocean brings the discrepant responses into good agreement with the environmental data. In a second exercise, we used a latitudinally disaggregated model and replaced a tropospheric compartment in the northern hemisphere by historic precipitation data. The model's response greatly underestimates the tritium specific activity in the southern hemisphere. These exercises lead us to doubt that a proper global transport model for tritium is available at present for collective dose assessment. 12 refs., 3 figs.« less

Global environmental transport models for tritium

In this paper we discuss some of the obstacles to the construction of credible models of global tritium transport for use in dose assessments. We illustrate these difficulties by comparing model predictions of environmental tritium levels with measurements. Monitoring of tritium has shown that specific activities in precipitation over land are typically higher by a factor of three to four than those in precipitation over the oceans. Experience with modeling CO/sub 2/ turnover in the oceans has led to the conclusion that two-box reservoir models of the ocean often give unsatisfactory representations of transient solutions. Failure to consider these factors in global models can lead to distorted estimates of collective dose and create difficulties in validation of the model against real data. We illustrate these problems with a seven-box model recommended by the National Council on Radiation Protection and Measurements in which we forced the atmospheric compartment to reproduce an exogenous function based on historic observations of HTO in precipitation at 50/sup 0/N. The fresh water response underestimates data from the Ottawa River by a factor of about five, and the ocean surface response overestimates tritium data from the surface waters of the Northern Pacific by nearly an order ofmore » magnitude. Revision of the model to include (1) separate over-land and over-ocean compartments of the atmosphere and (2) a box-diffusion model of the subsurface ocean brings the discrepant responses into good agreement with the environmental data. In a second exercise, we used a latitudinally disaggregated model and replaced a tropospheric compartment in the northern hemisphere by historic precipitation data. The model's response greatly underestimates the tritium specific activity in the southern hemisphere. These exercises lead us to doubt that a proper global transport model for tritium is available at present for collective dose assessment. 12 refs., 3 figs.« less

Measurement of tritium in natural water

A detergent-scintillation liquid mixture applied to measure low specific activity of tritium in natural water was studied. The DYS-1 low level liquid scintillation counter designed and manufactured by our institute was employed. In comparing the Triton X-100 scintillation liquid mixture with the dioxane-based-scintillation liquid, a better formula for Triton X-100 scintillation liquid mixture was determined, the mixture possesses the quality of high water content; high efficiency and low back-ground in measuring tritium in water. Chemiluminescence of the Triton X-100 scintillation liquid mixture can be totally de-excited in short time. It can be employed at ambient temperature 11–28°C. For 20ml sample in quartz vials, counting efficiency is 15% with a background 2.17 cpm, Y=31 TU (t=30 min).

Magnesium chloride supported high mileage catalyst for olefin polymerization. VII. Determinations of concentrations of titanium–polymer and aluminum–polymer bonds

AbstractTwo methods were used in an attempt to determine by radioquenching the active site concentration, [Ti*], in a MgCl2 supported high activity catalyst. For the reactions of tritium labelled methanol, the kinetic isotope effects were first determined: kH/kT = 1.63 for the total polymer and 1.67 for the isotactic polypropylene fraction. Polymerizations were quenched with an excess of isotopic CH3OH after various lengths of time, at different A/T (amount of AlEt3 with 0.33 equivalent of methyl‐p‐toluate to amount of Ti in the catalyst) ratios, and temperatures. From the known specific activity of tritium in CH3OH and radioassay of the polymer, value of the total metal polymer bond, [MPB], can be obtained. [MPB] increases linearly with polymerization time. Extrapolation to t = 0 gives [MPB]0, which should be close to [Ti*] because chain transfer with aluminum alkyls to produce Al–P bonds is negligible during very early stage of the polymerization. The values of [MPB]0 range from 7–30% of the total Ti; the number of MPB is nearly equally distributed in the amorphous and isotactic fractions of polypropylene in most runs. The rate of incorporation of radioactive CO into polymers produced by the MgCl2 supported high mileage catalyst is far slower than that claimed by some investigators for TiCl3 type catalysts. There is an initial rapid phase of incorporation of CO which lasts for about 1 hr of contact time. The subsequent rate of CO incorporation steadily declines, yet there is no constant maximum value of radioactivity even after 48 h of reaction in the absence of monomer. Radioquenching of polymerizations with CO was also performed at several temperatures and A/T ratios. In all cases, the maximum [Ti–P] was reached after 30–40 min of polymerization, whereas the maximum rates of polymerization, Rp,m, occurred within 3–10 min. In fact, the rate of polymerization decays to a small fraction of Rp,m after 30–40 min. Furthermore, this maximum value of [Ti–P] remains constant until the end of polymerization (t = 90 min). Therefore, isotopic CO is not reacting with the initially formed active sites Ti1*, but only with those sites, Ti2*, which predominate during the later stage of polymerization.

The Distribution of Tritium among the Amino Acids of Proteins Obtained from Mice Exposed to Tritiated Water

The distribution of tritium among the amino acids of serum proteins in mice chronically exposed to tritiated water was determined by ion exchange chromatography of the protein hydrolysate. The specific activity of nonexchangeable tritium in these amino acids relative to the specific activity of tritium in the tissue water of mice ranged from 0.04 for phenylalanine and threonine to 1.0 for glycine and alanine. Since tritium from tissue water can enter the nonexchangeable positions of amino acids only as the result of metabolic processing, the relative specific activity of tritium in each amino acid is an indicator of the extent of such processing. The tritium content of tyrosine and all the amino acids required in the diet for survival is quite low, except for histidine, and can be entirely accounted for by transamination or, in the case of methionine, by transmethylation. The tritium content of the other amino acids is too high to result from such minor processing and must reflect primarily the fraction synthesized de novo. The implications of these findings with respect to the radiobiological consequences of a diet containing tritiated proteins are discussed.

CO 2 laser isotope separation in ternary mixture of H/D/T compounds

Selective decomposition of trifluoromethane-D (CDF 3) in the presence of CHF 3 and CTF 3 was achieved by laser-induced multiphoton dissociation. A TEA CO 2 laser was tuned to 00°1–10°0 transition line R(12) at 970.5 cm −1. More than 60% of CDF 3 in the photolysis cell was decomposed in 10 min irradiation while CHF 3 and CTF 3 remained virtually unchanged: the tritium specific activity increased remarkably in the residual gas. This is the first successful separation of the middle component from ternary isotopic mixture with single-step separation factors exceeding 10.

Chemical forms and specific activity of tritium extracted from neutron-irradiated Li−Al alloys

When neutron-irradiated Li(1 wt%)-Al alloys were heated under vacuum at temperatures above 770 K, more than 95% of tritium was extracted in the gas phase within 1 h. The predominant species of extracted tritium were HT and HTO, although the distribution of both species varied depending upon the extraction temperature. The specific activity of the HT fraction was found to change within wide limits also depending upon the extraction temperature. The phenomenon was attributed to the difference in the release behaviour between tritium produced by the6Li(n, α) T reaction and protium contained as impurity in the alloy.

Migration and keratinization of cells in wool follicles.

Migration of cells in wool follicles of an adult Merino sheep was studied autoradiographically in skin samples taken at intervals after an intravenous injection of [3H]thymidine. Fibre and inner root sheath cells incorporated [3H]thymidine in a cone-shape region of the follicle bulb. Labelled inner sheath cells migrated out of the bulb ahead of contemporaneous cells in the fibre and remained in advance, although to a progressively lesser extent, until the inner sheath cells sloughed into the follicle lumen. Outer root sheath cells incorporated [3H]thymidine along the length of the follicle. Cells in the proximal half of the outer sheath migrated inwards and distally and sloughed into the follicle lumen before contemporaneous inner sheath cells. Other cells in the distal half of the outer sheath migrated past the level where cells from the proximal population were shed and also sloughed into the lumen. In the most distal part of the outer sheath, which formed the epidermis-like lining of the follicle canal, little migration of cells was observed during 8 days of observation. The specific activity of tritium in fibres plucked from the same sheep at intervals after the intravenous injection of [3H]thymidine was determined by scintillation counting and assessed in terms of cell migration and hardening of the fibres. The time which the specific activity of solvent-degreased fibres reached a maximum was found to give an estimate of the time for cells in the fibre to migrate to the upper limit of the keratogenous zone. When the plucked fibres were extracted with 8 M urea the times of the maximum specific activities of the urea-dispersible and urea-insoluble material provided respectively estimates of the times at which hardening of the fibres began and ended. The effects of different planes of nutrition were examined in two other Merino sheep by radioassay of fibres plucked after intravenous injections of [3H]thymidine given after equilibration period of at least 2 months on each level of feeding. A high plane of nutrition the rate of cell migration and hastened the onset of hardening of the fibres, but prolonged the hardening process. The prolongation of the hardening process was confirmed by the specific activities of fibres plucked after intravenous injections of [35S]cystine.

Difference in the specific activity of tritium labelled water in blood, urine and evaporative water in rabbits

1. 1. After a single injection of tritium labelled water (THO) into rabbits the specific activity was measured in blood, urine and evaporative water. 2. 2. The specific activity in urine was similar to that in blood, the specific activity in pulmocutaneous evaporate was 5–8% below that of blood. 3. 3. The permeability coefficient of the urinary bladder wall for THO was 44 ± 11 cm/sec × 10 −6. 4. 4. Maximum differences in the specific activity between blood and urine due to the accumulation of urine in the bladder were calculated as up to 1.8%. 5. 5. In the state of equilibrium the specific activity in urine water, but not in evaporative water. can be used for the estimation of total body water.

Tritium fractionation in plants

Alfalfa plants were hydroponically grown in environmental growth chambers in which they were continually exposed to tritium throughout growth. All segments of the environment were in equilibrium with respect to the specific activity of tritium. The tritium content in plant organic matter was about 22% lower than in the plant free water or rooting solution. Under conditions of low transpiration, there was a higher concentration (about 1·8%) of tritium in the leaves than in the stems and rooting solution. This is thought to represent the result of fractionation during transpiration.

“Fallout Tritium” Distribution in the Environment

It is evident that fallout tritium has been incorporated into all hydrogen-containing materials throughout the biosphere. We have analyzed the tritiated water content, available by freeze drying (loose water fraction), and the additional tritium available by complete combustion (organic bound fraction); in soil, vegetation, food, and animal and human tissues. Up until 1973 the tritium specific activity in the organic bound fraction is higher than that found in the loose water fraction. The ratio of specific activities decreased by a factor of 2 from each trophic level: soil 6–8, vegetation 3–4, and man 1.5–2. The lowest ratio observed in this study was 1.2 for the animal metabolite, milk.

Further Evidence for the Relative Immobility of Water in Sieve Tubes of Willow

AbstractGradients of tritiated water, 35S‐sulphate and 32P‐phosphate, were established in isolated segments of willow stems. Sieve tube exudate was collected as honeydew from the high activity end of the segment. After girdling the stem a few centimetres from the site of sieve tube puncture, the specific activity of 35S and 32P in the honeydew rose, whilst the specific activity of tritium remained constant.These findings indicate that prior to girdling, unlabelled sulphates and phosphates were contributing to the honeydew, whilst there had been no detectable contribution by unlabelled water from the low activity end of the segment.The data support the conclusions drawn from previous experiments by Peel et al. (1969), that water is relatively immobile in sieve tubes of willow when compared to solutes.

Tritium in the Equatorial Atlantic Current System

An improved sampling and analytical technique for ultra-low specific activities of tritium, as HTO, in sea water, is described. Tritium data, together with salinity and temperature from the Equalant III expedition in 1964 are presented and discussed. Negligible penetration of HTO below the thermocline is found in this area. Tritium-salinity relations support the concept that molecular exchange constitutes a major portion of the air to sea flux of HTO. A time scale of a few years seems reasonable for the transfer of distant surface water to the salinity and current cores of the Equatorial Atlantic Undercurrent.