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 1,423 records · Page 79Linked to original sources
PubMed1972

Deletion of hapten-binding cells by a highly radioactive 125-I conjugate.

Exposure of normal mouse spleen cells in vitro to highly (125)I-labeled dinitrophenyl (DNP)-protein carrier conjugates specifically inactivated cells able to mount an immune response to that hapten after in vivo challenge. The deletion was hapten specific and independent of the radioactive carrier to which the hapten was bound. DNP-binding cells were inactivated by radioactivity that was not part of the hapten, but was solely confined to the carrier moiety. The deletion of the anti-DNP response lasted 2-3 wk and could be specifically inhibited.

Animals↗
PubMed1950

Age as effecting the osmotic and mechanical fragility of dog erythrocytes tagged with radioactive iron.

Radioactive iron was administered to three normal dogs, two of which had previously been bled, in order to tag a group of erythrocytes of approximately known age. The osmotic fragility of the newly formed tagged cells was significantly greater than that of the general cell population during the first few days after injection of the iron, while the mechanical fragility of the young cells was less than that of the general red cell population. As the cells aged and approached the end of their life span, their susceptibility to destruction by trauma inflicted by rolling glass beads exceeded that of the general cell population. The osmotic behavior of the old cells was not distinctive. The increased mechanical fragility of senescent cells suggests that the life span of erythrocytes may be limited at least in part by changes within the cell which render it more susceptible to destruction by mechanical wear and tear in the circulation. It is emphasized, however, that the trauma produced by rolling glass beads may be quite unlike that inflicted upon red cells in vivo. A decrease in circulating radioactive iron was observed in each experiment soon after the mechanical fragility of the tagged cells began to exceed that of the total cell population. The lowest point on the curve representing circulating radioiron was noted at 119, 119, and 122 days respectively after injection of iron in the three experiments. Estimates of the life span of dog erythrocytes obtained in this way agree with those provided by other methods.

Age Factors↗
PubMed1954

The combination between hemolysins and red cells or ghosts, as studied with a radioactive lysin and with new color reactions.

The quantity of a radioactive hemolysin, sodium dodecyl sulfonate-S(35), taken up by red cells from concentrations too small to produce hemolysis varies with the lysin concentration, and does so in a way which can be described by an adsorption isotherm. Attempts to use color reactions or surface tension measurements to determine the quantity of digitonin, saponin, and the bile salts taken up by red cells from hypolytic concentrations have failed, principally because chromogenic, and also surface-active, substances are liberated from the cells when the lysin is added. Color reactions with the anthrone reagent show that digitonin and saponin are both taken up by or fixed to red cell ghosts; the extent of the uptake, however, is uncertain, again because of the liberation of chromogenic substances. Comparison of the results of the various methods which measure the apparent amount of lysin fixed, or utilized in reactions between lysins and red cells or ghosts show discrepancies between results given by direct methods (measurement of radioactivity or of color) and indirect methods (addition of a second population after lysis of a first, and dependence of the position of the asymptote of the time-dilution curve on the number of red cells). The discrepancies are traceable to the inhibitory effects of substances liberated from the red cells or ghosts. The ease with which a lysin, once taken up by red cells, can be detached by diluting the system determines the extent to which the hemolytic reaction is "progressive," but has no observed connection with the quantity taken up in the first place. There is now ample evidence that lysis in systems containing simple hemolysins is a process involving two stages in time and two phases, and that it is usually complicated by reactions between the hemolysin and liberated inhibitory material.

Anthracenes↗
PubMed1955

Inactivation of bacteriophages by decay of incorporated radioactive phosphorus.

The inactivation of the phages T1, T2, T3, T5, T7, and lambda by decay of incorporated P(32) has been studied. It was found that these phages fall into two classes of sensitivity to P(32) decay: at the same specific activity of P(32) in their deoxyribonucleic acid (DNA), T2 and T5 are inactivated three times as rapidly as T1, T3, T7, and lambda. Since the strains of the first class were found to contain about three times as much total phosphorus per phage particle as those of the second) it appears that the fraction of all P(32) disintegrations which are lethal is very nearly the same in all the strains. This fraction alpha depends on the temperature at which decay is allowed to proceed, being 0.05 at -196 degrees C., 0.1 at +4 degrees C., and 0.3 at 65 degrees C. Decay of P(32) taking place only after the penetration of the DNA of a radioactive phage particle into the interior of the bacterial cell can still prevent the reproduction of the parental phage, albeit inactivation now proceeds at a slightly reduced rate. T2 phages inactivated by decay of P(32) can be cross-reactivated; i.e., donate some of their genetic characters to the progeny of a mixed infection with a non-radioactive phage. They do not, however, exhibit any multiplicity reactivation or photoreactivation. The fact that at low temperatures less than one-tenth of the P(32) disintegrations are lethal to the phage particle and the dependence of the fraction of lethal disintegrations on temperature can be accounted for by the double stranded structure of the DNA macromolecule.

Bacteriophages↗
PubMed1979

Radioactivity of building materials and the gamma radiation in dwellings.

Measurements of the radioactivity in some common building materials in Norway are reported, together with calculations of the gamma-ray exposure from walls of different materials. Model rooms are used in calculations of the mean exposure inside concrete, brick and light-weight expanded clay aggregate buildings. These calculations give very good agreement with previous experimental results. The radiological implications of using building materials with high concentrations of radioactivity are also discussed.

Background Radiation↗
PubMed2004

The use of molecular sieves to produce point sources of radioactivity.

We have used commercially available molecular sieves (zeolites) to adsorb radioactivity onto small (approximately 2.1 mm diameter) beads for use in various applications in nuclear medicine. Soaking the beads in [99mTc]-NaTcO4 solution of approximately 3 GBq ml(-1) for 1-2 min can produce point sources containing 3-6 MBq total. Radioactive uptake was strongly dependent on bead size. We have employed the sources for gamma camera uniformity and as point source markers for interactive identification of anatomical landmarks. Due to their small size (<< system spatial resolution), relatively high uptake and negligible scattering contribution they provide excellent devices with which to measure spatial resolution, detector uniformity and energy resolution. The molecular sieves are inexpensive and readily usable with both single photon and positron emitting radionuclides.

Absorption↗
PubMed1999

Doses to organs from exposure to gamma rays during immersion in a radioactive cloud.

Methods and parameters of different studies for calculating organ doses from immersion in a radioactive cloud are investigated. The effects of some factors such as the ground scattering, air density, phantom size and organ structure are analysed. Relationships are presented between the organ doses and the photon fluence in free air, the radionuclide concentration, and free-air absorbed dose respectively. These relationships can be used to evaluate the organ doses from immersion in a radioactive cloud.

Gamma Rays↗
PubMed2003

In situ electroporation of radioactive compounds into adherent cells.

We previously developed a technique, termed in situ electroporation, where nonpermeant molecules are introduced through an electrical pulse into adherent cells, while they grow on electrically conductive, optically transparent, indium-tin oxide (ITO). Careful control of the electric field intensity results in essentially 100% of the cells taking up the introduced material, without any detectable effect upon the physiology of the cell, presumably because the pores reseal rapidly so that the cellular interior is restored to its original state. Electroporation of radioactive material is faced with two important considerations: (1) potential for exposure of personnel to irradiation, and (2) the requirement for electroporation of a large number of cells. In this report, we describe a modification in the geometry of the slides and electrodes which permits the use of inexpensive ITO-coated glass of lower conductivity that can be discarded after use, to electroporate large numbers of cells using a minimum volume of radioactive nucleotide solution. The results demonstrate that, using this assembly, the determination of the Ras-bound GTP/GTP+GDP ratios through electroporation of [alpha32P]GTP can be conducted using approximately five times lower amounts of isotope than in previous designs. Moreover, this assembly permits efficient upscaling, which makes the determination of Ras-GTP binding in cells which are deficient in Ras activity possible. In addition, we demonstrate the labeling of two viral phosphoproteins--the Simian Virus 40 Large Tumor antigen, and Adenovirus E1A--through [gamma32P]ATP electroporation using this setup. In both cases, electroporation of the nucleotide can achieve a great increase in the efficiency and specificity of labeling compared to the addition of [32P]-orthophosphate to the culture medium, presumably because the immediate phosphate donor nucleotide itself is introduced, which can directly bind to the target proteins.

Adenovirus E1A Proteins↗
PubMed2003

Radioactive iodine and the salivary glands.

Radioactive iodine ((131)I) targets the thyroid gland and has been proven to play an effective role in the treatment of differentiated papillary and follicular cancers. Simultaneously, this radioisotope hones in on the salivary glands where it is concentrated and secreted into the saliva. Dose related damage to the salivary parenchyma results from the (131)I irradiation. Salivary gland swelling and pain, usually involving the parotid, can be seen. The symptoms may develop immediately after a therapeutic dose of (131)I and/or months later and progress in intensity with time. In conjunction with the radiation sialadenitis, secondary complications reported include xerostomia, taste alterations, infection, increases in caries, facial nerve involvement, stomatitis, candidiasis, and neoplasia. Prevention of the (131)I sialadenitis may involve the use of sialogogic agents to hasten the transit time of the radioactive iodine through the salivary glands. However, studies are not available to delineate the efficacy of this approach. Recently, amifostine has been advocated to prevent the effects of irradiation. Treatment of the varied complications that may develop encompass numerous approaches and include gland massage, sialogogic agents, duct probing, antibiotics, mouthwashes, good oral hygiene, and adequate hydration.

Amifostine↗
PubMed2005

Development of a non-radioactive, 384-well format assay to detect inhibitors of the mitogen-activated protein kinase kinase 4.

Mitogen-activated protein kinase (MAPK) kinases (MKKs, also called MAPK/extracellular signal-regulated kinase [ERK] kinase [MEK]) are constituents of numerous signal transduction pathways involved in growth, differentiation, and stress response. One of its members, MKK4, directly phosphorylates and activates the c-Jun terminal kinases (also called stress-activated protein kinase [SAPK]) in response to stress and pro-inflammatory cytokines. Recent evidence suggest that control of MKK4 activity may provide a novel approach for the treatment of cancer or as anti-inflammatory therapy. To screen for novel low-molecular-weight inhibitors of MKK4, we established a quantitative, non-radioactive in vitro kinase assay. Human MKK4 was expressed as fusion protein with glutathione S-transferase (GST) in Escherichia coli. Co-expression of a constitutive active fragment of the MAPK/ERK kinase kinase-1 yielded active GST-MKK4 using GST-SAPK alpha-kinase-negative (KN) mutant as substrate. We determined the kinetic constants for ATP and GST-SAPK alpha-KN. The apparent Km value for GST-SAPKalpha-KN was 3.7 microM, while the apparent Km value for ATP was 0.17 microM. Staurosporine inhibited GST-MKK4 with an IC50 of 70 nM. The kinase assay was adapted to a 384-well non-radioactive format. After the kinase reaction the phosphorylated product was captured onto a streptavidin-coated microtiter plate, and phosphorylation was detected with a europium-labeled anti-phosphotyrosine antibody, which allowed time-resolved fluorescence measurement.

Biological Assay↗
PubMed2006

Application of cryopreserved cells to HERG screening using a non-radioactive Rb+ efflux assay.

The aim of the present study was to test the use of cryopreserved cells for human ether-ago- go (hERG) channel screening. A stable Chinese hamster ovary-K1 cell line expressing hERG channels was used in a non-radioactive Rb+ efflux assay for screening hERG channel activity. Cells prepared from normal cultures and following cryopreservation were compared with regard to time course of Rb+ efflux response at different concentrations of KCl, overall cell morphology, signal-to noise assay window, assay robustness, and 50% inhibitory concentration (IC50) of the hERG blocker dofetilide. Our results showed that cryopreserved hERG-expressing cells at 1, 2, and 3 days following plating at different cell densities had no obvious morphological changes in comparison to the growing cells. The assay window, Z' factor, and IC50 of dofetilide were also very similar in all series of cells tested. It was concluded that the cryopreserved hERG cells prepared using the protocol described are as effective as growing hERG cells in the non-radioactive Rb+ efflux assay.

Animals↗
PubMed2004

Emergency communication and information issues in terrorist events involving radioactive materials.

With the threat posed by terrorism involving radioactive materials now high on the nation's agenda, local, state, and federal agencies are moving to enhance preparedness and response capabilities. Crucial to these efforts is the development of effective risk communication strategies. This article reports findings from an ongoing study of risk communication issues in nuclear/radiological terrorism situations. It is part of a larger CDC-funded effort that aims to better understand communication challenges associated with weapons of mass destruction terrorism incidents. Presented here are formative research findings from 16 focus groups (n = 163) in which a multi-part, hypothetical radioactive materials terrorism situation was discussed. Twelve of the focus groups were carried out with members of the general public (drawn from a variety of ethnic backgrounds and geographic locations), and four groups were composed of first responders, hospital emergency department personnel, and public health professionals. One aim of the focus groups was to elicit detailed information on people's knowledge, views, perceptions, reactions, and concerns related to a nuclear/radiological terrorism event, and to better understand people's specific information needs and preferred information sources. A second aim was to pretest draft informational materials prepared by CDC and NIOSH. Key findings for the public and professional groups are presented, and the implications of the research for developing messages in radiological/nuclear terrorism situations are explored.

Communication↗
PubMed2000

Accuracy of gamma probes in localizing radioactivity: in-vitro assessment and clinical implications.

BACKGROUND: Radioguided surgery (RGS) uses gamma probes to localize radioactive targets. We examined the in-vitro localizing properties of commercially available gamma probes for three common RGS radioisotopes: technetium-99m (99mTc), indium-111 (111In), and iodine-125 (125I). METHODS: The linear and angular localizing properties of five gamma probes were assessed. Radioactive counts in air were obtained at multiple energy threshold settings for each radioisotope. The full width half maximum (FWHM) and angular half maximum (AHM) were calculated to determine localizing accuracy. RESULTS: The FWHM of the five probes ranged from 1.2 to 3.4 cm for 99mTc, 1.8 to 2.7 cm for 111In and 1.6 to 2.8 cm for 125I. AHM of the probes ranged from 20 to 49 degrees for 99mTc, 14 to 35 degrees for 111In, and 18 to 47 degrees for 125I. The ranking of probe accuracy depended on the radioisotope studied. Absolute count rates varied with energy threshold settings for each probe and radioisotope. Probes required individualized energy threshold settings for optimal performance. CONCLUSIONS: The five probes varied in their characteristics for localizing the three radioisotopes. Each probe has particular detection characteristics that may change with different radioisotopes. Differences in radioisotope detection may explain intraoperative variation in localization during lymphatic mapping and sentinel lymph node dissection (LM/SL). Surgeons should be aware of probe performance characteristics before intraoperative use.

Gamma Rays↗
PubMed2006

Comparative renal, hepatic, and bone marrow toxicity of Cisplatin and radioactive Cisplatin (191Pt) in Wistar rats.

The aim of the study was to investigate the possibility to increase the therapeutic gain of the cytotoxic agent, cisplatin, by incorporation of radioactive platinum. In this study, we investigated how organs at risk (i.e., kidneys, bone marrow, and liver) are affected by treatment with 191Pt-cisplatin, compared to treatment with conventional cisplatin. Rats (total, n = 69) were divided into three groups and given 5 mg/kg 191Pt-cisplatin and 5 mg/kg nonradioactive cisplatin or saline. The weight of the animals and blood samples, including analysis of creatinine, bilirubin, alanine and aspartate aminotransferases and platelet count, was followed for 6 weeks after treatment. Histopathology examinations of kidney and liver tissues were performed. An initial decrease in weight gain was seen from 3 days after treatment with cisplatin and 191Pt-cisplatin and for 1 week onward; thereafter, the weight gain continued, following the same pattern as for the control group. Concentration of plasma creatinine was increased for both cisplatin groups but with no significant difference between treatment groups. No other significant differences in effect parameters were found. There was no increase in toxicity for radioactive cisplatin on liver, kidneys, and bone marrow, compared to conventional cisplatin. Further experimental and clinical studies on preparations of this type are thus warranted.

Animals↗
PubMed2000

Accounting for radioactivity before and after nebulization of tobramycin to insure accuracy of quantification of lung deposition.

The ability to predict drug deposition of inhaled drugs used in cystic fibrosis (CF) is important if there is a need to target specific doses of drug to the lungs of individual patients. The gold standard of measuring pulmonary deposition is the quantification of an aerosolized radiolabel either mixed with the drug solution or tagged directly to the compound of interest. Accuracy of the quantification could be assured if there is agreement between the amount of radioactivity before and after administration. Before administration, the radiolabel is concentrated in the well of the nebulizer, whereas after administration, it is distributed throughout the nebulizer, the expiratory filter and connectors, and the upper airway, stomach, trachea, and lung. Not only is the geometry of the distribution that is presented to the gamma camera different, but there are different attenuation factors for the various body tissues. The primary aim of this study was to evaluate the accuracy of the quantification of deposition. Secondary goals were to compare in vitro nebulizer performance with that measured in vivo during the deposition study. Eighty milligrams of tobramycin and technetium bound to human serum albumin was administered to 10 normal adults using a Pari LC Jet Plus (Pari Respiratory Equipment, Inc., Richmond, VA) breath-enhanced nebulizer. Techniques were developed that allowed for the accounting of 99 +/- 2% of the initial radioactivity. The fraction of the rate of lung deposition to total body deposition was the in vivo respirable fraction (0.62 +/- 0.07), which closely agreed with in vitro measurements of respirable fraction (0.62 +/- 0.04). Drug output measured from the change in weight and concentration in the nebulizer systematically overestimated drug output measured by the deposition study. The results indicate that 11.8 of the initial 80 mg would be deposited in the lungs. This technique could be adapted to accurately quantify the amount of deposition on any inhaled therapeutic agent, but caution must be used when extrapolating performance of a nebulizer on the bench to expected deposition in patients.

Adult↗
PubMed1981

Characterization of radioactive human fibroblast-derived beta interferon synthesized in vivo.

Radioactive human fibroblast-derived beta interferon has been synthesized in vivo after induction of human diploid fibroblast cells with poly I:C. The radioactive protein is not synthesized and secreted by uninduced cells. It reacts with antibody made against homogeneous human beta interferon and has the same N-terminal amino acid sequence as human beta interferon.

Amino Acid Sequence↗
PubMed2000

Use of thyroid ultrasound volume in calculating radioactive iodine dose in hyperthyroidism.

One hundred twenty-one patients treated with 131I had a thyroid ultrasound to measure thyroid volume precisely. This volume measurement was used to determine the radioactive iodine dose. The average size (+/-SEM) of the thyroid glands measured in this manner was 39.7 cm3 +/- 1.9 cc. A significant correlation was found in the estimated size of the gland by the endocrinologists and the ultrasound volume. Of the 121 patients, 89 patients had the same 131I microcurie per gram of tissue factor to determine the radioactive iodine dose. This group of patients was further evaluated in this study. The average 131I dose (+/-SEM) given was 13.2 mCi +/- 0.5 mCi. The average time until hypothyroidism was achieved 2.85 +/- 0.14 months. Ultrasound provides a safe and precise way to determine actual thyroid size when calculating 131I doses.

Dose-Response Relationship, Radiation↗
PubMed1982

32P-postlabeling analysis of non-radioactive aromatic carcinogen--DNA adducts.

A newly developed enzymatic 32P-postlabeling method was applied to the analysis of DNA's containing non-radioactive arylamine, arylamide, and polycyclic aromatic hydrocarbon adducts. DNA reacted in vitro with N-hydroxy-2-amino-fluorene, N-acetoxy-2-acetylaminofluorene, and 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, respectively, as well as DNA preparations from the liver of rats treated with N-hydroxy-2-acetylaminofluorene and benzo[a]pyrene, respectively, were enzymatically digested to deoxyribonucleoside 3'-monophosphates, which were then converted to [5'-32P]deoxyribonucleoside 3',5'-bisphosphates by T4 polynucleotide kinase-catalyzed [32P]phosphate transfer from [gamma-32P]ATP. The 32P-labeled nucleotides were resolved by anion-exchange t.l.c. on polyethyleneimine-cellulose and detected by autoradiography. Aromatic adduct nucleotides were found to be retained at the origin in aqueous electrolyte solutions, but to migrate as distinct spots in solvents containing 7-8.5 M urea. Advantage was taken of this observation to remove 32P-labeled normal DNA nucleotides from adduct nucleotides. This purification enabled the detection of a single adduct in 10(7)-10(8) normal nucleotides. The method appears applicable to the ultrasensitive detection of a large number of carcinogen--DNA adducts of diverse structure without requiring radioactive carcinogens or specific antibodies.

Animals↗