Radioactive Form Research Articles

Binding of the nucleoside transport inhibitor 4-nitrobenzylthioinosine to erythrocyte membranes.

4-Nitrobenzylthioinosine (NBMPR), a potent nucleoside transport inhibitor, was prepared in two radioactive forms and the binding of these to erythrocyte ghosts was studied. Similar binding data were obtained with inhibitor containing 14C in the purine 8-position or in the benzyl 7-position, suggesting that the entire inhibitor molecule was bound. A saturable high-affinity mode of NBMPR binding was apparent; NBMPR bound in this way was not removed by washing, but was displaced by a related inhibitor of nucleoside transport, 2-hydroxy-5-nitrobenzylthioguanosine (HNBTGR). It is postulated that the high-affinity binding sites are the nucleoside transport elements of the erythrocyte membrane. From ghosts treated with 14C-NBMPR under conditions which assured binding of the high affinity type, 14C was recovered by extractions in the form of NBMPR. Thus, this mode of NBMPR binding is reversible and covalent linkages do not appear to be involved. A low affinity mode of NBMPR binding was also demonstrated; this appeared to be a partition of NBMPR between the medium and the membrane substance. This component of bound NBMPR was not displaced by HNBTGR and was removed by washing.

Hormone metabolism and action: Testosterone and metabolites in prostate organ culture

Summary Explants of ventral prostate glands from intact rats were incubated for 24 hours in culture medium with 3H-testosterone and the radioactive metabolites in the medium and tissue analysed. At all testosterone concentrations (50-0.1 M), 4 metabolites averaging 22 p. 100 of incubated testosterone were identified. Among them, the main compound was 17β-hydroxy-5α-androstan-3-one (androstanolone). Androstanolone formed the greatest proportion of total radioactivity in the nuclei and was also the most abundant identified metabolite in the cytoplasmic fraction and in the medium. The highest androstanolone/testosterone ratio was observed in the cytoplasm. 5α-androstane-3α,17β-diol (androstanediol), 5α-androstane-3β,17β-diol (3β-androstanediol) were also identified, but neither 5β-derivatives nor 19-nor- compounds or estrogens were observed. Unknown non-polar radioactive compounds were found and partially characterized. The metabolism of metabolites prepared in radioactive form was also studied. Androstanolone was not converted to testosterone, but otherwise the pattern of metabolites in cytoplasm and nuclei was similar to that of testosterone. Androstanediol was largely converted to androstanolone and androsterone and to a smaller extent to 3β-androstanediol. In contrast, 3β-androstanediol was not converted to androstanolone, androsterone or androstanediol; its only metabolite identified in cytoplasma and nuclei was 3β-hydroxy-5α-androstan-17-one (epiandrosterone). The activity of testosterone and its metabolites was tested in organ cultures grown for 6 days in the presence of these compounds at concentrations ranging from 3.5 to 70 M. Testosterone maintained epithelial height and secretory activity, and kept the stroma at a minimum. Androstanolone was more active than testosterone and also provoked epithelial hyperplasia which was seen only after high doses of testosterone. Androstanediol was less active in preserving epithelial differentiation and increased epithelial proliferation to a slight degree. 3β-androstanediol fully maintained epithelial height and stimulated secretory activity but there was no hyperplasia. The corresponding 17-oxo-steroids showed weak activity, and 5β-androstane steroids were inactive. The results indicate that testosterone action may be related to its conversion to different active metabolites, and particularly to androstanolone and 3β-androstanediol.

The preparation of alcohol dehydrogenase and glyceraldehyde 3-phosphate dehydrogenase from baker's yeast.

A procedure has been developed for the preparation of alcohol dehydrogenase and glyceraldehyde 3-phosphate dehydrogenase from the same sample of baker's yeast. The two enzymes were obtained in good yield in a pure crystalline form. The method minimizes the work involved in preparing the two enzymes and would be of particular advantage for preparing the enzymes in radioactive form from yeast grown in a radioactive medium.

Biosynthesis of ponasterone A and ecdysterone from cholesterol in Podocarpus macrophyllus

Administration of cholesterol-4- 14C to Podocarpus macrophyllus seedlings resulted in the formation of the insect-metamorphosing substances ponasterone A and ecdysterone in radioactive form.

Location and Measurement of Enzymes in Single Cells by Isotopic Methods : Part I. Principles and Light Microscope Applications

The labeled inhibitor method has the advantage of quantitative capability. Isotopic disintegration is a nuclear event, entirely uninfluenced by the conditions and the molecular environment. Unlike the measurement of light absorption, it is independent of the packing of the labeled molecules, their polar or nonpolar milieu, and the distribution of the sites across the field measured. The inhibitor is attached to the enzyme active center in a 1:1 stoichiometry, and the errors attributable to the rate of deposition of the marker and to adsorption to various sites are absent. The basis of measurement is physically simple, and has been validated by independent measurements. A limitation of the method is the range of inhibitors available for it. These compounds must be specific or capable of high specificity by the use of associated reactions and must be available in highly radioactive form. Thus, the labeled inhibitor method is not regarded as a replacement for color reaction enzyme cytochemistry. It is, rather, a complementary method for the quantitative localization of enzymes that may often be localized sharply, and more spectacularly, by a color method.

Product Induction in Pseudomonas acidovorans of a Permease System Which Transports l -Tryptophan

Growth of Pseudomonas acidovorans in the presence of l-tryptophan resulted in the appearance of a tryptophan transport system which was extremely sensitive to sodium azide or 2,4-dinitrophenol. Asparagine-grown cells possessed no detectable tryptophan "permease" activity. Substitution of l-kynurenine for l-tryptophan in the growth medium also induced the tryptophan permease activity, along with tryptophan oxygenase and kynurenine formamidase. This is the first reported example of the product induction of a permease activity. Irrespective of whether Pseudomonas cells are grown in the presence of d- or l-tryptophan, the resulting induced tryptophan permease activity is specific for the l-isomer. In addition, the radioactive compounds l-leucine, l-phenylalanine, or dl-5-hydroxytryptophan are not transported. When dl-5-fluorotryptophan is a component of the inducing medium (with l-tryptophan), induction of tryptophan permease activity, as well as tryptophan oxygenase, is inhibited. In the permease assay system, using normally induced cells, the fluoroanalogue inhibited strikingly tryptophan transport. Therefore, this analogue may inhibit induction by blocking inducer transport into the cell. When added to the l-tryptophan-inducing medium, dl-7-azatryptophan markedly enhanced induction of tryptophan oxygenase, but the level of tryptophan permease activity was not further elevated. The mechanism of this analogue is unclear at present. Invariant tryptophan permease activity levels are found in cells grown with 5 or 15 mml-tryptophan or 5 mml-kynurenine, whereas the respective tryptophan oxygenase levels are greatly different. Together with other results, these results indicate that the synthesis of tryptophan permease activity is not coordinate with that of tryptophan oxygenase. Tryptophan transport is strongly inhibited by l-formylkynurenine and by l-kynurenine. These two metabolites were prepared in radioactive form, and they are actively transported following bacterial growth on l-tryptophan or l-kynurenine. Preliminary results suggest the tryptophan permease activity may be distinct from the permease(s) activity for l-formylkynurenine and l-kynurenine. Kynurenine, then, is capable of inducing tryptophan permease and kynurenine permease activities.

Ecdysterone biosynthesis in Podocarpus elata

The insect molting hormone ecdysterone was isolated in radioactive form after administration of cholesterol-4- 14C to Podocarpus elata seedlings. Cholestenone-4- 14C, however, was not significantly incorporated into ecdysterone by this plant. The biosynthetic implications of these results are discussed.

曹灰長石に対するDodecylammonium Chlorideの吸着に関する研究

The adsorption isotherms of dodecylammonium chloride on silica and labradorite at natural pH and for various pH values were determined using a radioactive form of the reagent. The effect of Ca ion and Na ion on the adsorption of dodecylammonium chloride on silica and labradorite was also investigated.The results of adsorption tests of dodecylammonium chloride on both silica and labradorite indicated that there is a significant difference between both adsorption mechanisms. Namely, dodecylammonium ions adsorb at Stern layer on quartz surface as counter ions, on the other hand, dodecylammonium ions mainly adsorb on the labradorite surface by ion exchange, viz, by exchanging Na ions or Ca ions which are lattice cations of labradorite.The effect of pH on the adsorption of dodecylammonium ion on both silica and labradorite showed a similar tendency, however, the mechanisms differ from each other. On silica surface, H ion is potential determining ion and so controls adsordtion of dodecylammonium ion as counter ion in the Stern Layer. On the other hand, since Na ion and Ca ion which are lattice cations of labradorite are exchanged easily by H ion in acldic side, H ion is a competitor to the dodecylammonium ion for labradorite surface.The effect of Ca ion on the adsorption of dodecylammonium chloride on silica and labradorite was less than the effecf of H ion, but it was signmcant.

Laboratory studies of intrathecal radiogold with a new rationale for its use.

Cells from certain intracranial neoplasms frequently disseminate via the cerebrospinal fluid (CSF) and grow after implantation in remote sites. Metastases of this kind are most commonly seen in tumors of childhood which arise in the posterior fossa, notably the medulloblastoma. The leptomeninges at the lower levels of the spinal subarachnoid space are the most common location for such metastatic implants. Retrograde ventricular dissemination is less common (12), the floor of the third ventricle being most frequently involved in this manner. Irradiation of the entire central nervous system (CNS) in patients with medulloblastoma is therefore advocated by many authorities, notably Paterson and his colleagues (9). Most investigators report limited success in achieving cures: 70 to 75 per cent of patients die before the fifth post-treatment year (7). In a few centers, this figure is reduced to 60 per cent (9, 10). The medulloblastoma thus is radiosensitive and subject to long-term control, but seldom radiocurable with the doses employed to date. Higher doses entail a great risk of producing permanent CNS damage (4). A therapeutic dilemma clearly arises: external irradiation at doses sufficiently high to insure complete eradication of the tumor causes irreversible damage to the spinal cord and medulla; lower doses are ineffectual for cure. Another approach is possible: (a) irradiation from external sources given in doses sufficient to reduce the tumor mass, followed by (b) dose augmentation with a beta-ray emitter introduced into the CSF. The latter permits high doses to be delivered to thin sheets of residual neoplasm remaining at or near the surface of the brain and spinal cord while the underlying normal structures are spared. Alternatively, antineoplastic chemotherapeutic agents introduced intrathecally might achieve a similar end. Accurate dosimetry and the short- and long-term neural effects of the inert and radioactive forms of the nuclide employed must be determined before large-scale clinical trials are undertaken. Some of the requisite data regarding radiogold has already been reported by Lewis (5) and by Kerr and his colleagues (2, 3). Our studies are designed to confirm and extend their observations. Radioactive Au198 has advantageous physical properties, and is low in cost. Therefore, we too selected this radionuclide to study the feasibility of the method described. Au198 is readily available in a sterile aqueous colloidal suspension which is stable and can be diluted with water, normal saline, or CSF. The isotope has a half-life of 2.7 days, and on decay emits a beta particle of 0.97 MeV and three gamma rays. Numerically, the most important of these latter has an energy of 0.41 MeV. This makes possible external monitoring of the flow and distribution of the isotope.

Natural acetylenes. Part XXI. The biosynthesis and transformation of some polyacetylenic metabolites of Merulius lacrymans Fr. and Clitocybe rhizophora velen

The triacetylenic acid (II; RH), the major polyacetylenic metabolite of the fungus Merulius lacrymans, has been biosynthesised on a medium containing either [14C]-acetate or [14C]-malonate. Degradation of the radioactive metabolite by selective copper-catalysed decarboxylation has revealed that the αβ-acetylenic carboxylic acid group is derived from an acetate-methyl group. The acid (II; RH) is probably an intermediate in the catabolism of some C10 to C9 polyacetylenic metabolites.The two diacetylenic metabolites (VII and VIII) of Clitocybe rhizophora have been obtained in a radioactive form by addition of [14C]-acetate to the culture medium. Degradation of the triol (VII) revealed that the terminal hydroxylated carbon atom was generated from an acetate-methyl group. By adding the radioactive metabolites separately to cultures of Clitocybe rhizophora it was possible to demonstrate that the diacetylenic ketone (VIII) is very probably the precursor of the triol (VII).

Radioisotope Tracer Elements in Nutrition Studies with Microorganisms

Research Article| August 01 1965 Radioisotope Tracer Elements in Nutrition Studies with Microorganisms Clarence T. Lange Clarence T. Lange Search for other works by this author on: This Site PubMed Google Scholar The American Biology Teacher (1965) 27 (6): 464–471. https://doi.org/10.2307/4441011 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Clarence T. Lange; Radioisotope Tracer Elements in Nutrition Studies with Microorganisms. The American Biology Teacher 1 August 1965; 27 (6): 464–471. doi: https://doi.org/10.2307/4441011 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe American Biology Teacher Search This content is only available via PDF. Copyright 1965 National Association of Biology Teachers Article PDF first page preview Close Modal You do not currently have access to this content.

Tritium-Labeling of Griseofulvin

The recent observation that griseofulvin is a fungistatic agent has stimulated much interest in the biological properties of this substance. A radioactive form of griseofulvin would be of great aid in studying these properties. The present report concerns our experiences with griseofulvin which had been exposed to tritium in an attempt to produce tritium-labeled griseofulvin by exchange of hydrogen for tritium atoms.

Synthesis of Carboxy-Labeled C14-N,N-Diethyl-m-Toluamide, an Insect Repellent2

For Studies of the various properties of N, N -diethyl- m -toluamide, an outstanding all-purpose insect repellent, this compound was prepared in radioactive form. The molecule was labeled in the carboxy position by carbonating m -toluene magnesium bromide with C14O2 to give C14- m -toluic acid. The m -toluic acid chloride was then combined with diethylamide to give the final product, of which the specific activity was 5.7 × 107 disintegrations per second per gram.

Synthesis and metabolism of a histamine metabolite, 1-methyl-4-(β-aminoethyl)-imidazole

A new synthesis is described for 1-methyl-4-(β-aminoethyl)-imidazole, a major metabolite of histamine. This compound was also prepared in radioactive form by biosynthesis and by chemical synthesis. When 1-methyl-4-(β-aminoethyl)-imidazole is injected into mice, a major portion is oxidized to 1-methylimidazole-4-acetic acid. Both compounds were determined quantitatively in urine using isotope dilution procedure. A study of the effect of inhibitors on this oxidation in intact mice indicated that diamine oxidase plays little or no role. The enzyme involved was inhibited by a monoamine oxidase inhibitor.

A PROGRESSIVE REACTION OCCURRING WITH A RADIOACTIVE HEMOLYSIN, SODIUM OLEATE-I131

Sodium oleate reacts progressively with human red cells at pH 7. By progressive is meant a reaction which is not adequately described as reversible or irreversible; such reactions cannot be stopped once they are under way, and are probably associated with a more or less stable "internal" lysin phase at the cell surfaces. The uptake of the lysin and the effect of dilution on the uptake can be studied by converting sodium oleate into the radioactive form, sodium oleate-I(131). The uptake is a parabolic function of the lysin initially present in the system, and the effect of a tenfold dilution of systems in which red cells have remained in contact with the lysin for 2 minutes is to reduce the lysin taken up at the cell surfaces twofold. The lysin rapidly forms a relatively stable layer at the cell interfaces, and this layer is little affected by the dilution of the system as a whole.

The Effect of X-Irradiation on the Absorption of Plutonium in the Gastrointestinal Tract

A large body of experimental evidence has accumulated which indicates that many of the rare earth and transuranic elements are poorly absorbed from the gastrointestinal tract and are rapidly excreted in the feces. Consequently, the ingestion of radioactive forms of these elements is generally not considered a hazard, at least not nearly so severe a hazard as the intake of similar quantities of such materials parenterally. It is of interest to know whether this holds true for certain special conditions, in particular the situation wherein the individual receives a large dose of external irradiation concomitantly with the ingestion of the radioactive material, i.e., exposure during radioactive fallout. Conceivably, external irradiation would alter the rate of absorption of such metals across the gastrointestinal tract and increase their hazard. The following experiment was set up to determine this, using Pu239 as representative of this group of elements.

Inherited Defects in Cattle

skeletons have always contained an amount of of the weakly radioactive forms of natural potassium and carbon, yielding about five times this amount in a lifetime. ~ In addition, there are areas on earth where natural deposits of radium yield up to five rads in a lifetime for large populations in those areas--and these groups have not shown evidence of harmful effects. Add all this to the seven to 15 rads in a lifetime from cosmic rays and other sources and you find that we humans are exposed to quite a bit more radiation from other sources than we are from bomb fall-out. And the talk about strontium-90 being found in our milk supply in increasing amounts has been singularly related to radioactive fall-out from bomb tests. From the foregoing information, it would seem we have a long way to go before the presence of strontium-90 in milk and other foods can catch up with the amounts of radioactivity to which we have long been exposed through natural sources. This does not mean that the finest scientific talent in America will not continue to be very alert to all possible human danger from radioactivity. What it does mean, however, is that any uninformed hue and cry about strontium-90 in our food supply should be answered with the facts as we know them.

Diffusion of Impurities in Germanium

A method is described for the study of diffusion of impurities in semiconductors; results are obtained by the observation of the $p\ensuremath{-}n$ junction formed as the diffusing impurity penetrates the specimen. Studies have been made upon germanium using this technique, and comparisons with the radioactive tracer method have shown the $p\ensuremath{-}n$ junction method to give valid results. Measurements on indium, gallium, aluminum, arsenic, boron, phosphorus, antimony, and zinc are described. The diffusion coefficients of these elements in germanium range, at 900\ifmmode^\circ\else\textdegree\fi{}C, from ${10}^{\ensuremath{-}12}$ ${\mathrm{cm}}^{2}$/sec to ${10}^{\ensuremath{-}9}$ ${\mathrm{cm}}^{2}$/sec. The activation energy for bulk diffusion in germanium is about 2.5 ev, or 57 000 cal/mole. Applications are given for the study of the $p\ensuremath{-}n$ junction method to the study of surface and grain-boundary diffusion. The method has also been applied to the study of new elements and their electrical activity in germanium. It is concluded that the rapidity with which results can be obtained by the junction method, and its applicability to elements not conveniently available in radioactive form make it a valuable adjunct to the radioactive tracer method for studying diffusion.

Metabolic studies with I131 labeled thyroid compounds: distribution and excretion of radiodiiodotyrosine in human beings.

PREVIOUS studies of the metabolism of labeled thyroidal substances (1, 2, 3, 4, 5) have suggested that thyroxine is slowly metabolized to at least two substances—inorganic iodide and diiodotyrosine. The further fate of the inorganic iodide liberated from the catabolism of thyroxine is well known, but that of diiodotyrosine is not. Earlier studies dealing with large doses of diiodotyrosine in human subjects indicated that it was decomposed to iodide, since urinary excretion of iodide rose greatly after the administration of diiodotyrosine (6). On the other hand, Salter (7) listed values for the concentration of diiodotyrosine in both erythrocytes and serum of normal persons and of those having various thyroid disorders. The possibilities that diiodotyrosine may exist as a free amino acid in the blood or that it may be accumulated or secreted by the thyroid, merit a reinvestigation of the metabolism of diiodotyrosine in man. We have, therefore, prepared diiodotyrosine in radioactive form (labeled with I131)...

Decomposition of radioactive octamethyl-pyrophosphoramide in living plants.

Gardiner and Kilby have described1,2 the synthesis of the systemic insecticide bis (bis-dimethylaminophosphonous) anhydride (octamethylpyrophosphoramide) in radioactive form (with phosphorus-32) and its application to the study of its uptake by living plants2. We also have experimented along these lines, but have extended our investigations to the study of the chemical fate of the substance, using for this purpose activities of about 400 µC./gm. to obtain the necessary sensitivity in analysis. Preparative details will be published elsewhere.