Tritiated substances

The preparation of multilabeled compounds representsse a difficult synthetic problem, owing to the high specific activity of tritium, ca. 58,250 Curie per mole, which causes a fast self-radiolytic decomposition of the pime tritiated substances and the formation of isotopic byproducts, containing only one T atom per molecule. 

Thin-layer chromatograms of tritiated substances usually need more than a week s exposure, whereas compounds containing and often yield good autoradiographs within 30 min and generally in less than 6 hours [89, 426]. 

The difficulties of the Wilzbach procedure arise in the working up of the tritiated substances and the purification of the compounds which suffer radiolysis during prolonged storage. TLC can be used successfully for this purification purpose also (see Fig. 93). 

Water tracers were tested for use in carbonate reservoirs. Seven substances were tested tritiated water (HTO) and the ions S CN, Cl ,... 

To ascertain whether tritium could have entered the polyisobutylenes by a process other than the hydrolysis of a carbon-aluminium bond, we tested the reaction of suitable polymers with aluminium bromide. The polyisobutylenes were dissolved in ethyl bromide, and phials of aluminium bromide were crushed into these solutions, which were subsequently kept at 0 °C for ca. 15 minutes, and then hydrolysed in the usual way with tritiated water. The three substances examined in this way were polyisobutylenes of high and low DP, and nonadecane. The polyisobutylenes contain approximately one double bond per molecule. The results in... 

Maleuric acid (A -carbamoylmaleamic acid, XVIII), when injected into mice bearing Ehrlich ascites tumours, can produce cytoplasmic abnormalities in all phases of mitosis. This acid also inhibits the incorporation of tritiated thymidine into DNA, and prevents the progression of premitotic cells into mitosis [217]. This substance, which is an open-chain analogue of orotic acid, may possibly be an antimetabolic of this pyrimidine or related compounds. 

Know the physical properties of the substances with which you are working. Keep in mind that some compounds (such as acetaldehyde and tritiated water) have low boiling points. Again, keep in mind that some gloves do not offer an adequate barrier to certain chemicals. Some compounds enter the body with such facility that special care must be exercised when they are in use. One example is dimethyl sulfoxide, which as a solvent facilitates the entry of many solutes into the body. There are many known cases where radiolabeled compounds contaminated individuals who failed to consider this power of DMSO as a solute vehicle. 

In this experiment, tritiated water is purified by simple distillation, and the tritium beta particles in the condensate are measured with a liquid scintillation (LS) counter. Such distillation also can collect tritiated water samples from solids. Tritium in other forms must be processed before it can be counted like tritium in water for example, tritiated hydrogen gas and tritiated organic substances can be oxidized to form water. Additional separations may be needed if the liquid or solid sample contains radioactive gases or volatile substances other than tritium that may be collected with the distilled tritiated water. Such radioactive impurities can be identified in the data output from the LS counter of an energy spectrum that differs from that of pure tritium, or of counts in energy regions where tritium counts are not found. 

The working substance of the ITEP-group /9 source was a doubly tritiated crystalline amino acid, DL-valine (Mallikarjunan and Rao, 1969), which is a molecular crystal. As a result of decay, during the time 10 18 sec the valine molecule transforms into the corresponding helium-containing ion (RHe)+. Since the translational symmetry of the crystal is disturbed, no exciton states are produced, and only molecular states of the complex (RHe)+ are excited. Since in molecular crystals the intermolecular interactions are considerably weaker than the intramolecular ones, one can neglect the influence of the valine crystalline surrounding on the /S-decay process and consider only an isolated valine molecule. 

A number of isotopically different forms of water can be prepared, which greatly facilitates experimental studies. Replacing both of the usual hydrogen atoms with deuterium (2H) results in heavy water, or deuterium oxide, with a molecular weight of 20. The role of water in chemical reactions can then be studied by analyzing the deuterium content of substances involved as reactants or products. Tritium (3H), a radioactive isotope with a half-life of 12.4 years, can also be incorporated into water. Tritiated water has been used to measure water diffusion in plant tissues. Another alternative for tracing the pathway of water is to replace the usual 160 isotope with lsO. This labeling of water with lsO helped determine that the O2 evolved in photosynthesis comes from H20 and not from CO2 (Chapter 5, Section 5.5A). 

Investigating metabolism or stability of prostanoids, radiolabeled precursors or analytes are often used. The tritiated or -labeled compounds can easily be detected without any further derivatization using online or off-line liquid scintillation, which is not impaired by any interferences derived from matrix components. Efficient but less sensitive PG analysis is possible by UV detection (190-210 nm) of underivatized substances demanding the remove of interfering contaminants or simple sample matrices like buffers or some cell supernatants. 

CF3COOD, and so forth) and tritiated (HTO) substances, combined with mass spectrometry, IR spec- ... 

Oldendorf, W.H., 1970. Measurement of brain uptake of radiolabeled substances using a tritiated water internal standard. Brain Research, 24(2), pp. 372-376. 

The microinjection technique described by Gottschalk, Morel and Mylle (5) was applied with some minor modifications. Known volumes (10 to 25 nl) of a colored solution of buffered saline containing tritiated inulin and urate labeled with 14c were injected with a calibrated pipette into proximal or distal surface convolutions. Inulin was used as the reference substance (6) and was totally recovered in the urine of the punctured kidney after technically satisfactory microinjections. It was assumed that the injected inulin remained solely within the lumen of the tubule, i.e. the liaihinal membrane was impeinneable to inulin. It was further assumed that labeling of urate did not impair its physiological properties and that excreted 14c represented urate. 

Fig. 93 shows the separation of tritiated steroids on silica gel G. The distribution of activity was measured on the plate with a special coimting tube, the active zones scraped off and the individual substances eluted [617]. 

Several authors have reported the analysis and purification by TLC, of substances which had been tritiated according to the Wilzbach procedure. Thus glycerol ethers [262], the insect hormone ecdysone [338], vitamin Dg [501] and other steroids [501, 513, 617] (see Fig. 93, p. 170) and cardiac glycosides [551] have been purified on silica gel G layers. Unsaturated fatty acids have been isolated by TLC on silver nitrate-impregnated silica gel layers [425, 628]. 

In recent years, the mouse local lymph node assay (LLNA) has been approved as an alternative to the guinea pig test. It is based on the proliferation of lymphocytes (a type of immune cell) in lymph nodes draining the site of contact with the chemical. In the LLNA, the substance is applied to the mouse s ear on days 1-3 of the test but withheld on days 4 and 5 to give the immune system a chance to respond. On day 6, the mouse is injected in its tail vein with a small amount of a radioactive DNA base such as H-thymidine (tritiated thymidine) to label newly formed immune cells. The mouse is sacrificed, its auricular lymph nodes (located near the ears) are cut out, and their radioactivity is measured. Increased radioactivity in the lymph nodes of treated animals compared with controls indicates that the test chemical sensitizes the immune system and can cause contact dermatitis. The LLNA is more objective than the traditional guinea pig test because the amount of immune cell proliferation can be determined as a function of dose. 

In vivo, glycerol, similarly to succinate and lactate, shows comparatively better incorporation of these tritiated precursors into fatty acids of liver than of carcass. The incorporation of these hydrogenated precursors into fatty acids and insaponifiable fraction has also been compared to that of C-acetate at 3 and 30 minutes after intravenous injection of radioactive tracer (Rous et al., 1968). It appeared that the incorporation of all these precursors into fatty acids increases between 3 and 30 minutes. The rate of the incorporation is not identical for all these substances but occurs in the same direction. 

From the mycelium of R, leguminicola cultured on [ Hjpipecolate, two previously unrecognized tritiated basic substances, named compounds I and... 

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