Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RADIOACTIVITY”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47Linked to original sources
PubMed1985

Enzymatic lactate-specific radioactivity determination in biological samples.

A method for the measurement of specific lactate radioactivity in biological samples is presented. It is based on the following steps: (a) enzymatic conversion of lactate to pyruvate, (b) pyruvate conversion to 2,4-dinitrophenylhydrazone, (c) concentration-separation of the latter in reusable Amberlite XAD-7 polymeric adsorbent columns, and finally (d) estimation of the radioactivity thus retained compared with that of enzymatically untreated aliquots of the same samples. Specificity was ensured by the use of lactate dehydrogenase as specific recognizing agent for lactic acid. No interference from glucose, lactate, or amino acids was observed. The method presented is simple and can be applied in routine multiple estimations of lactic acid radioactivity in conjunction with the enzymatic measurement of lactate in biological samples in tracer metabolic studies.

Animals↗
PubMed1992

Radioactive assay of 2,4-dienoyl-coenzyme A reductase.

A radioactive method for assaying 2,4-dienoyl-CoA reductase, also referred to as 4-enoyl-CoA reductase (EC 1.3.1.34), is described. The assay measures the incorporation of tritium from [4B-3H]NADPH into 2-trans,4-cis-decadienoyl-CoA or 2-trans,4-trans-decadienoyl-CoA which, after cleavage of the thioester bond with hydroxylamine, can be separated from the radioactive coenzyme by extraction with toluene. This assay is at least 30 times more sensitive than the spectrophotometric assay, even though rates determined by the radioactive method are 10 times lower than rates obtained spectrophotometrically due to a primary kinetic isotope effect. The linearity of this assay with respect to time and protein concentration is sufficient for determining 2,4-dienoyl-CoA reductase activities in extracts from small samples of human fibroblasts, which were found to contain reductase activities between 1.8 and 5.8 mU/mg of protein.

Animals↗
PubMed1978

Distribution of radioactivity in myelin lipids following subcutaneous injection of [14C]stearate.

Blood fatty acids are an important parameter for the synthesis of brain myelin as exogenous stearic acid is needed: after subcutaneous injection to 18-day-old mice this labelled stearic acid is transported into brain myelin and incorporated into its lipids. However the acid is partly metabolized in the brain by elongation (thus providing very long chain fatty acids, mainly lignoceric acid) or by degradation to acetate units (utilized for synthesis of medium chain fatty acids as palmitic acid, and cholesterol). These metabolites are further incorporated into myelin lipids. The myelin lipid radioactivity increases up to 3 days; most of the activity is found in phospholipids; their fatty acids are labelled in saturated as well as in polyunsaturated homologues but sphingolipids, especially cerebrosides, contain also large amounts of radioactivity (which is mainly found in very long chain fatty acids, almost all in lignoceric acid). The occurrence of unesterified fatty acids must be pointed out, these molecules unlike other lipids, are found in constant amount (expressed in radioactivity per mg myelin lipid).

Animals↗
PubMed1981

Extensive radioactive labeling of glycolipids in cultured hamster fibroblasts by incubation of whole cells with UDP-[14C]glucose and UDP-[14C]galactose.

NIL 2cl cells, a cloned hamster cell line, are known to have seven classes of neutral glycosphingolipids in addition to hematoside. In this paper, I examined the participation of cell surface glycosyltransferases in the glycolipid synthesis in NIL cells. The cells, harvested from culture bottles by the use of chelating agents of divalent cations, incorporated radioactive glucose and galactose from labeled UDPglucose and UDPgalactose into endogenous glycolipid acceptors to form all eight classes of glycosphingolipids and dolichyl phosphate glucose. The major part of the incorporation occurred by glycosyltransferase reactions from nucleotide sugars, as indicated by a slight inhibition of the incorporation observed in the presence of a large excess of sugars or sugar phosphates. Acid hydrolysis of the glycolipid products showed that 91.4% of the 14C label was in the galactose and glucose moieties of the glycolipids. Exogenously added lactosylceramide stimulated the synthesis of trihexosylceramide in the absence of detergents. Th results presented in this paper suggest that incubation of whole cells with an equilibrium mixture of radioactive UDPglucose and UDPgalactose is a useful radioactive labeling method to determine the glycolipid composition of a cultured cell.

Animals↗
PubMed1991

A monoclonal antibody to the phosphorylated form of glial fibrillary acidic protein: application to a non-radioactive method for measuring protein kinase activities.

Monoclonal antibody YC10 showed specificity for the phosphorylated form of human, bovine and porcine glial fibrillary acidic proteins (GFAPs) and negligible reactivity towards the dephosphorylated form of the GFAPs. Analysis of species specificity and of the epitope, determined using synthetic phosphopeptides, indicated that this antibody recognized the local phosphorylation-site sequence Thr-phosphoSer-Ala-Ala-Arg-Arg (residues 7-12 of GFAP). Making use of this antibody we developed a non-radioactive method to measure protein kinase activities. After incubation of a protein kinase with non-radioactive ATP in ninety-six wells coated with the synthetic peptide Arg-Arg-Arg-Val-Thr-Ser-Ala-Ala-Arg-Arg-Ser-Cys (residues 3-13 of GFAP), the phosphorylated product was detected by using this mouse antibody and peroxidase-labeled goat anti-mouse IgG. This method proved to be equally as sensitive as the radioactive method for the measurement of protein kinase activities and was less affected by concentrations of ATP present in the reaction mixture.

Amino Acid Sequence↗
PubMed1976

Time course and disposition of fucose radioactivity in rat hippocampus. A biochemical and microautoradiographic study.

Male adult rats were injected intraventricularly with L-[1-3H]fucose. At various intervals, ranging between 30 min and 11 days, one-half of the brain was prepared for microautoradiography, and the hippocampus from the other side was prepared for biochemical investigations. The TCA-precipitable proteins from the hippocampus homogenate were maximally labeled at between 8 and 24 h and remained at a high radioactivity level even 11 days after [3H]-fucose injection, the labeling being predominantly present in the solubilized insoluble proteins. Using gel electrophoretic separation, study of Tris-soluble material indicated a rapid turnover of soluble fucose-containing glycoproteins, whereas several slow-migrating bands of solubulized proteins revealed a time course suggesting the presence of fucose-containing glycoproteins with slower turnover rates. Using microautoradiography, a rapid labeling of neuronal cell bodies of the hippocampus was found, whereas the nuclei were not labeled. Perikarya were maximally labeled 4 h after [3H]fucose application. The radioactive material was continuously transported from the soma into the corresponding fiber layers, the latter being maximally labeled at a pulse interval of one day; even 10 days later a considerable amount of radioactivity could be detected in the neuropil.

Animals↗
PubMed1976

Distribution of protein-bound radioactivity in brain slices of the adult rat incubated with labelled leucine.

The distribution of protein-bound labelled leucine in brain cortex slices, prepared from adult rats by various methods and incubated with [14C]- or [3H]leucine, was investigated by autoradiography. In the first and second slices a marked gradient of incorporated radioactivity from the cut surface to the slice interior was observed. Very high labelling of leptomeningeal cells and vessels enhanced further the inhomogeneity of radioactivity distribution. Light microscopic examination of incubated slices revealed morphological alterations of neurones, especially in the vicinity of the cut surface. The comparison of grain density over neurones and their satellite glia indicated markedly higher incorporation into the latter. The ATP level in slices at the end of incubation reflected the method of slice preparation and morphological integrity. Inhomogeneity of incorporated radioactivity distribution in brain slices contrasted with the uniform labelling of cortical cells in vivo, and may represent at least one reason for the low estimates of protein synthesis rate in brain cortex slices.

Adenosine Triphosphate↗
PubMedDate not supplied

Incorporation of radioactivity from labeled Di-(2-ethylhexyl)phthalate into DNA of rat liver in vivo.

Di-(2-ethylhexyl)phthalate (DEHP), when fed at high levels in the diet for two years, is reportedly an hepatocarcinogen to rats and mice. Radioactivity from ethylhexyl-labeled, but not from phthalate-labeled, [14C]-DEHP is associated with highly purified DNA from the livers of treated rats and this radioactivity is not accounted for by assumptions of adsorption, intercalation, attachment to RNA or histones, an impurity in the labeled DEHP, or artifactual binding during sample workup. Spontaneous binding of radioactivity to DNA from either ethylhexyl-labeled DEHP or its total urinary metabolites could not be detected. Although rat liver slices generated all of the known metabolites of DEHP in vitro, no binding to DNA occurred. Administration of dual 3H/14C-labeled DEHP to rats yielded liver DNA whose 3H/14C ratio was inconsistent with the attachment of any reasonable multi-carbon fragment from the ethylhexyl portion to the DNA. The observation that roughly 100 times as high a percentage of the 14C administered was found in urea as in total DNA suggests that the 14C entered DNA through carbamyl phosphate, a precursor of both urea and pyrimidine bases. If this is the case, the association of C-1 from the ethylhexyl portion of DEHP with DNA may not involve alteration of the DNA or genetic damage.

Animals↗
PubMed1986

Biosynthetic preparation of radioactively labelled ethanolamine plasmalogen (1-O-[1'-14C]octadec-1'-enyl-2-acyl-sn-glycero-3-phosphoethanola mine) using a protozoan cell culture.

Ethanolamine plasmalogen radiolabelled mainly in the O-alkenyl moiety was prepared from cell suspension cultures of the flagellate Leishmania donovani previously incubated with [1-14C]octadecanol over one growth period. The optimal concentration of [1-14C]octadecanol for labelling was shown to be 1 microM, when 60% of total lipid radioactivity appeared in the 1,2-diradyl-sn-glycero-3-phosphoethanolamine fraction, with an overall yield of approx. 35%. Analysis of this fraction revealed that 93% of the label was present in O-octa-dec-1-enyl, 3% in O-alkyl and 4% in acyl moieties. A specific radioactivity of approx. 14 mCi/mmol was determined. Raising the culture medium concentration of [1-14C]octadecanol to 2 microM yielded a product with a specific radioactivity of 25 mCi/mmol.

Animals↗
PubMed1980

Computer programs for the radioactive microsphere technique. Determination of regional blood flows and other haemodynamic variables in different experimental circumstances.

Computer programs in FORTRAN IV have been designed to calculate regional blood flow values from injections of gamma radiation-emitting radioactive microspheres. The first program PRSO constitutes a file containing the names of organs, organ groups and systemic haemodynamic variables and data about the isotopes in use. The second program PRSI transfers the data of the particular experiment concerning protocol, systemic haemodynamic variables, organ weights, number of vials belonging to each organ and the radioactivity from each vial into a data file that is subsequently analyzed by the third program PRSII. One of 5 data conditions which later directs calculations in PRSII is determined by PRSI. PRSII deducts background radioactivity, decomposes the spectrum from the mixture of up to 6 nuclides using the "stripping' method, and corrects for isotope decay during the counting period. Depending upon the data condition, PRSII calculates one or more of the following variables: (i) cardiac output (CO); (ii) the distribution of CO; (iii) regional blood flow values and tissue vascular resistances; (iv) the distribution of blood flow within an arterial bed; (v) arteriovenous anastomotic blood flow; (vi) some specified systemic haemodynamic variables; and (vii) blood flow ratios. The systemic and regional haemodynamic data belonging to experiments are saved for later statistical analyses (e.g., mean, standard error of the variables, changes from the base line, comparison between two groups of experiments) by other programs. PRSO, PRSI and PRSII can be operated by investigators with little or no special training in computer use.

Animals↗
PubMed1991

Measurement of antigen specific lymphocyte proliferation using 5-bromo-deoxyuridine incorporation. An easy and low cost alternative to radioactive thymidine incorporation.

The classical in vitro assay for the determination of cell mediated immune responses is the lymphocyte transformation test (LTT) in which cell proliferation is measured by incorporation of radioactive labeled thymidine (3H-TdR). The LTT assay using 3H-TdR is less suited for modestly equipped laboratories as it is costly, laborious and involves the need to handle radioactive isotopes and specialized equipment. Here we describe an improved alternative LTT method which is capable of detecting specific cellular immune reactions (CMI) against (mycobacterial) antigens in vitro. This assay, the bromodeoxyuridine-ELISA LTT test, is simple, less expensive, reproducible and is as sensitive as the 3H-TdR test. The specific advantages of the test are a simple denaturation step and the fact that no radioactive isotopes are needed. The test is specifically suited for research laboratories in tropical countries which study CMI in those human infectious diseases where this arm of the immune response plays a pivotal role in the generation of immunity, e.g., in tuberculosis, leprosy and leishmaniasis.

Antigens, Bacterial↗
PubMed1995

Non-radioactive method to measure CD45 protein tyrosine phosphatase activity isolated directly from cells.

Preparation of radioactive phosphorylated substrates is laborious, yields a limited amount of substrate with a short half-life and generates a low percentage of phosphorylated product which then has to be separated from non-phosphorylated material. These factors limit the usefulness of radioactive phosphorylated substrates in phosphatase assays and prohibit their use for kinetic analysis, which often requires large amounts of substrate. An alternative method for the kinetic analysis of purified or recombinant soluble phosphatases uses the malachite green reagent which can detect nanomoles of phosphate released from chemically synthesized phosphorylated peptides. In this report we describe a rapid and sensitive non-radioactive method that can be used to measure protein tyrosine phosphatase (PTP) activities of both transmembrane and soluble phosphatases immunoprecipitated directly from cells. This colorimetric microassay is performed in 96 well microtitre plates and can reliably detect 100 pmol of free phosphate released, using a standard microplate reader. The phosphatase activity of CD45, a transmembrane PTP, was determined from as few as 1 x 10(4) lymphoid cells. The development of this colorimetric assay to measure immunoprecipitated CD45 PTP activity isolated from very small numbers of cells has general applicability for other PTPs and will help identify the cellular situations and conditions that result in changes in PTP activity.

Amino Acid Sequence↗
PubMed1995

A novel non-radioactive cellular cytotoxicity test based on the differential assessment of living and killed target and effector cells.

Monocyte/macrophage-mediated cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC) are slow processes, requiring cocultivation of effector and target cells for up to several days. Because of the high spontaneous release and possible reutilization of isotopic labels, the conventional radioactive release assays are unsuited for measuring long term cytotoxicity. We developed a non-radioactive flow cytometric assay for the quantitative analysis of cell-mediated cytotoxicity. Because dead cells can dissolve and disappear during the incubation period (lysis, phagocytosis), we determined the absolute numbers of living cells in the well. Prior to incubation the effector cells are stained with the red lipophilic fluorescent dye PKH26 and the target cells with the green fluorescent dye PKH2. At the end of the incubation (1-6 days) a defined number of bright fluorescent cell standards and propidium iodide for staining of dead cells was added to each well. Using flow cytometric analysis, we determined the ratio of targets to standards and calculated the absolute target cell number by multiplication with the known number of standards added. The main advantages of the assay are the possibility of extended incubation periods, the avoidance of radioactivity and its potential applicability to autologous culture systems, where effector and tumor cells are derived from the same patient. The assay opens new avenues for preclinical testing of tumor therapeutics such as monoclonal antibodies and/or cytokines.

Antibodies, Monoclonal↗
PubMed1983

Tumor selective enhancement of radioactivity uptake in mice treated with alpha-difluoromethylornithine prior to administration of 14C-putrescine.

A group of EMT6 tumor bearing male BALB/c mice which had been treated with alpha-difluoromethylornithine (DFMO, a specific, irreversible inhibitor of ornithine decarboxylase, the enzyme which catalyzes the biosynthesis of putrescine), 8 mg/mouse, ip, 20 and 5 hrs before the 14C-putrescine dose, and a group of control animals were administered 14C-putrescine (0.5 muCi, 0.1 mCi/mmol, iv) 60 min prior to sacrifice. Radioactivity uptake data was obtained for the tumor and 13 major normal organs. In the control animals the tumor exhibited one of the highest uptakes of radioactivity. For DFMO-pretreated mice the radioactivity distribution among most of the normal tissues was not very different from that obtained for the control animals. However, the uptake into the tumor was enhanced by a factor of approximately 4. So, high tumor-to-tissue ratios (3.8, lung to 38, brain) were attained as a result of DFMO treatment.

Animals↗
PubMed1986

Retention of radioactive substances in the hypothalamus, anterior pituitary, and reproductive organs of male rats after 3H-melatonin administration.

Radioactive concentrations were determined in serum, lung, hypothalamus, anterior pituitary, testis, and accessory sex organs of adult male rats at 2, 20, 30 and 60 min after intravenous 3H-melatonin administrations. The retention patterns of 3H-melatonin and other radioactive substance (3H-non-melatonin) in these tissues were compared. The anterior pituitary demonstrated best tissue retention with highest concentration of 3H-melatonin. The testis and prostate gland accumulated 3H-non-melatonin in an increasing manner from 2 to 60 min. The radioactive substances were also preferentially and progressively located in the nuclear fraction of the anterior pituitary, hypothalamus, testis, and prostate gland. This study leads to the following suggestions: the anterior pituitary is another target organ of melatonin; melatonin is converted into other active material which exerts its action in the testis and prostate gland; melatonin and its active derivative exert their action through the nuclei of their respective cells.

Animals↗
PubMed1986

Localization of radioactivity from 2-methoxy[1,2-14C]ethanol in maternal and conceptus compartments of CD-1 mice.

2-Methoxyethanol (ME) induces paw malformations in CD-1 mice when given by gavage on gestation day (gd) 11 (vaginal plug + day = gd 0). The distribution of radioactivity originating from 2-methoxy[1,2-14C]ethanol ([14C]ME) was examined by liquid scintillation spectrophotometry and whole body autoradiography in pregnant (gd 11) CD-1 mice from 5 min to 48 hr after oral administration. Each dam received either a trace dose of [14C]ME (0.92 mumol; 13 muCi) combined with an unlabeled teratogenic dose (187 mumol). By 5 min after the trace dose was administered, 14C had distributed throughout the maternal and conceptus compartments. Radioactivity in the maternal compartment was most concentrated in the liver, blood and gastrointestinal tract. Conceptus 14C was associated with the placenta, yolk sac, and embryonal structures such as limb buds, somites, and neuroepithelium. The concentration of blood 14C plateaued within 30 min after administration of the trace or combined trace/teratogenic dose. It remained stable for 1.5 hr and then gradually declined, reaching 2 to 10% of the maximal concentration by 48 hr. 14C content in the maternal liver, conceptuses, and embryos per se was always greater than that of the blood and was inversely related to ME dose at 6 hr but not 48 hr. At 6 hr after administration of the trace dose, 69% of total liver and 33% of embryonal 14C were acid insoluble. Tissue-specific interaction with [14C]ME was demonstrated by the distribution of acid insoluble radioactivity among various cellular components of the maternal liver and embryo. The findings indicate that the embryo is readily susceptible to blood borne ME and/or its metabolites. In addition, the chemical characteristics of the labeled molecule(s) apparently favored label incorporation into macromolecules by the liver and embryo.

Animals↗
PubMed1989

Uptake and distribution of 14C during and following inhalation exposure to radioactive toluene diisocyanate.

Inhalation of toluene diisocyanate (TDI) results in toxic responses ranging from pulmonary irritation to immunological sensitization. The use of radioactively labeled isocyanate has made it possible to follow the initial uptake of the compound into the bloodstream independent of the final fate of the isocyanate. This study shows that the rate of uptake into the blood is linear during exposure to concentrations ranging from 0.00005 to 0.146 ppm and that the uptake continues to increase slightly postexposure. It also demonstrates that the radioactivity clears from the bloodstream to a level corresponding to approximately a 100 nM concentration of tolyl group after 72 hr and persists at a nanomolar level even 2 weeks following the exposure. This is similar to the response previously reported by this group for radioactively labeled methyl isocyanate. The initial rate of 14C uptake is also a linear function of the concentration of TDI when expressed either as concentration (ppm) or as concentration multiplied by duration of exposure (ppm.hr). This is discussed in comparison with the toxic responses as a function of both ppm and ppm.hr. Finally, the inclusion of the data on methyl isocyanate indicates that the uptake into arterial blood is a function of exposure concentration, independent of isocyanate structure.

Administration, Inhalation↗
PubMed1983

Incorporation of radioactive precursors into glycosaminoglycans by rat muscle fibroblasts exposed to a solubilized rat bone matrix fraction.

Confluent cultures of rat muscle fibroblastic cells respond by increased glycosaminoglycan (GAG) synthesis when cultured in medium containing a solubilized bone matrix fraction (SBM) at a concentration of 100 micrograms/ml. The metabolism of the GAG associated with the cell pellet, the cell surface and the tissue culture medium fractions was studied, in the presence and absence of SBM, by measuring the incorporation of radioactivity from [3H]glucosamine and [35S]SO4 into the isolated GAG. Net synthesis of hyaluronic acid and of chondroitin sulfate in the medium fraction increased more rapidly in cultures containing SBM compared to controls, and the accumulation of labelled GAG in the medium of the treated cultures was approximately linear with respect to the length of incubation. The addition of SBM also resulted in increased incorporation of 3H and of 35S into the GAG of the cell surface and cell pellet fractions. In these fractions, stimulation of incorporation of radioactivity occurred in two waves: an early, relatively minor increase and a later relatively major increase. The relatively major stimulation of radioactivity into the GAG of the cell surface fraction occurred between 24 and 48 h and was independent of any apparent effect of serum.

Animals↗