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 1,495 records · Page 83Linked to original sources
PubMed1984

Effect of age on vitamin E concentrations in various regions of the brain and a few selected peripheral tissues of the rat, and on the uptake of radioactive vitamin E by various regions of rat brain.

The concentrations of tocopherols in selected areas of the brains and a few peripheral tissues of 3-, 14-, and 30-month-old male Fischer 344 rats were determined by a high-performance liquid chromatographic method. Throughout the time period studied, alpha-tocopherol was the only tocopherol detected in the brain. Concentrations of alpha-tocopherol increased significantly with age in medulla and spinal cord whereas no such change was seen in other brain areas. Among the peripheral tissues, total tocopherol concentrations increased with age in the liver and adipose tissue while no significant changes were observed in the heart. The pattern of uptake of radioactive alpha-tocopherol from the serum by the various areas of the brain was similar for the 3- and 14-month-old animals even though the brains from the 14-month-old animals took up less of the radioactive compound. Measurable amounts of tocopherol esters were not present in the tissues of the 30-month-old animals.

Adipose Tissue↗
PubMed1969

An uptake of radioactivity from (plus or minus)-3H-isoprenaline and its inhibition by drugs which potentiate the responses to (minus)-isoprenaline in the guinea-pig isolated trachea.

1. The uptake of radioactivity derived from (+/-)-(3)H-isoprenaline by the guinea-pig isolated trachea has been measured, and the assumption is made that all the radioactivity is due to isoprenaline.2. 40% of the total (+/-)-(3)H-isoprenaline taken up was loosely bound to the tissue while 25% was firmly bound.3. The firmly bound component of the uptake was more susceptible to inhibition by drugs than the loosely bound component.4. Desipramine and cocaine did not reduce the accumulation of firmly bound isoprenaline.5. Cooling to 23 degrees C, guanethidine and phentolamine caused a moderate reduction in the accumulation of firmly bound isoprenaline.6. Phenoxybenzamine and (+/-)-metanephrine caused a highly significant reduction in the accumulation of firmly bound isoprenaline.7. These findings are discussed in relation to previous studies of the uptake of isoprenaline and of other processes which may be related.8. The inhibition of uptake by the agents examined correlated with their potentiation of the action of (-)-isoprenaline found previously.9. It is suggested that a tissue uptake can significantly modify the pharmacological response to isoprenaline in vitro.

Animals↗
PubMedDate not supplied

Radioactive 131I use in end-stage renal disease: nightmare or nuisance?

Patients with end-stage renal disease (ESRD) are at risk of prolonged radiation exposure during therapy with radioactive iodine (131I) because it is normally renally excreted. However, 131I is dialyzable and exposure can be monitored with a standard Geiger counter during dialysis. We present two cases of thyroid carcinoma in patients with ESRD who were treated successfully with 131I while continuing chronic hemodialysis (HD). In each case, single HD treatments of 3 and 4 hours performed approximately 20 hours after the administration of 131I resulted in an 80% and 70% reduction in total body radiation levels, respectively. In both cases, Geiger counter measurements after HD following 131I administration revealed levels less than 3 mR/hr, allowing safe discharge from the hospital in a timely manner. All contaminated waste was disposed of by the hospital's Department of Radiation Safety. Postdialysis monitoring revealed no residual radiation contamination of the HD machine or radiation exposure to the dialysis staff. Hemodialyzer reuse was suspended until monitoring demonstrated no appreciable evidence of radioactivity in these spent supplies. HD is a critical aspect in the treatment of patients with ESRD receiving 131I and can safely be administered with close planning between the HD staff and the staff of radiation safety.

Adult↗
PubMed1979

Regional blood flow in canine myocardium as determined by local washout of a freely diffusable radioactive indicator.

The aim of this study has been to examine the utility of the washout of a freely diffusable radioactive indicator as a measure of regional myocardial blood flow in open-chest anesthetized dogs. The method employed was direct intramyocardial injection of Xenon-133 followed by measurement of its gamma-radiation. The experimental washout curves show, after a short acceleration period, monoexponential washout of the indicator over two decades. We found indications of insignificant veno-arterial shunting by diffusion of the blood flow level measured, insignificant arterial recirculation of the indicator, and minimal radioactive contribution to precordial residue versus time curves arising from right heart or non-myocardial tissue. We suggest that diffusion equilibrium between the tissue in the counting field and the blood leaving it is maintained during the linear down slope of two decades of the clearance curve, and that local blood flow can be calculated from washout rate constant obtained from this part of the curve. The method employing intramyocardial injection of Xenon-133 was found to give the same results as atraumatic epicardial labelling indicating negligible effect of the injection trauma and supporting the validity of the local injection method using small volumes (2-10 microliter).

Animals↗
PubMed1981

Regional differences in skin blood flow as measured by radioactive microspheres.

Regional skin blood flows in the trunk were measured by means of radioactive labeled microspheres in anesthetized rats and monkeys. Mean arterial pressure, heart rate, cardiac output and arterial pH, pO2 and pCO2 were registered and body and ambient air temperature were kept constant for the duration of the experiments. The blood flows were determined on a total of 6 skin samples, 2 samples each from the thoracic, lumbar and sacral regions. The reproducibility of the microsphere technique for measurements were given with a 10 min interval. The coefficient of variation varied with the region from 10.3 to 22.7%. In both species the skin blood flows in the thoracic regions were significantly higher than in the lumbar and sacral regions (P less than 0.05). The skin blood flows in the thoracic region of the rat ranged from 39-45 ml.min-1.100 g-1, in the lumbar region from 32-33 and in the sacral region from 29-30. In the monkeys the corresponding values for the different regions were: thoracic: 7-9, lumbar 5-7 and sacral: 4-7 ml.min-1.100 g-1, respectively. Our results support the use of radioactive microspheres for skin blood flow measurements, and demonstrate the existence of regional differences in the skin blood flow of the trunk. We suggest that this may be an important consideration during the development, and interpretation of data from experimental models in which skin blood flow is important.

Animals↗
PubMed1977

Effect of oxotremorine and sodium pentobarbitone on the pharmacokinetics of intravenous tracer doses or radioactive choline.

The present study explains for the previous findings that oxotremorine increases and sodium pentobarbitone decreases the initial brain uptake of intravenously injected radioactive choline (3H-Ch). The effects are explained by haemodynamic changes since a corresponding increase and decrease in the plasma concentrations of 3H-Ch were found. This is important to know when 3H-Ch is used for estimation of aceytlcholine turnover in the brain. The drugs did not affect the distribution of radioactivity (3H) between plasma and erythrocytes.

Animals↗
PubMed1966

The uptake and release of radioactive noradrenaline by the splenic nerves of cats.

1. DL-[(3)H]noradrenaline was infused close-arterially into the spleens of chloralosed cats at rates of 0.625 or 1.25 mug/min for 10 or 20 min and the recovery of noradrenaline and its metabolites in the venous blood measured during the infusion and after nerve stimulation at various times after the infusion.2. During the infusion 41% of the noradrenaline was recovered in the blood as such and 11% as metabolites. The remaining 48% was retained within the spleen.3. The noradrenaline retained in the spleen was slowly released to appear as metabolites in the blood stream. In normal animals the rate of loss from the spleen was 0.22% per minute. In animals given phenoxybenzamine after the end of the infusion this rate was several times greater.4. Splenic nerve stimulation in normal animals or in animals treated with phenoxybenzamine resulted in an increase in the radioactivity of the blood leaving the spleen. Paper chromatography showed this to be radioactive noradrenaline.5. In normal animals the specific activity of the transmitter liberated by nerve stimulation was less than that of the stores of noradrenaline within the spleen. In animals treated with phenoxybenzamine these two values were similar.6. It is suggested that the infused noradrenaline retained in the spleen is largely taken up into nerve fibres and is available for subsequent release by nervous activity.

Animals↗
PubMed1993

[Detection and identification of HBV DNA and DNA subtypes of HBs-antigen by the use of the polymerase chain reaction and non-radioactive probes].

A technique of nested polymerase chain reaction (PCR) and hybridization with non-radioactive probes was developed for the detection and identification of HBV DNA and HBs-subtypes in very small volumes of human sera. Four oligonucleotide primers (20 mer) complementary to DNA sequences in the S region of HBV and probes (18 or 20 mer) conjugated to alkaline phosphatase were used for the present PCR assay. The results of the PCR assay coincide with those of enzyme immunoassay (EIA) in 14 HBe-positive and 59 HBe-negative samples with 98.6% of specificity. The HBV subtypes adr and adw were identified using an 18-mer DNA probe in 30 samples with an accuracy of 100%. Further, the DNA subtypes were clearly demonstrated in 3 samples where HBs-antigen was undetectable. These results indicate that amplification of HBV DNAs by PCR and their detection with non-radioactive probes is a reliable tool for diagnosis of HBV infection in clinical laboratories.

Base Sequence↗
PubMed1996

A CT assisted method for absolute quantitation of internal radioactivity.

A method is described for the determination of radioactivity (microCi or MBq) at an organ site within an object or patient. Using both anatomic image data (CT or MRI scans) and planar gamma camera images, activity at depth is determined using a matrix inversion method based on least squares. The result of the inversion analysis was the unknown set of n linear (uniform) activity densities representative of each organ within the phantom or patient. The problem was overdetermined since the number of unknown activity densities (microCi/cm) was much less than the number of analysis points (N) within the nuclear image. This method, defined as the CT assisted matrix inversion (CAMI) technique, was accurate to within 15% for a three "organ" plastic phantom, wherein the organs were right circular cylinders having activities of 74 to 508 microCi (or 2.74 MBq to 18.8 MBq). This accuracy included image quantitation effects, particularly assumptions concerning attenuation correction. The average absolute percent error of the estimated activity in four distinct radioactive volumes in the phantom was 9.8%. It was found that the background activity within the phantom was estimated to be too high if sampling regions near strong sources were used in the analysis (scatter effect). This was minimized by going at least 2 cm away from such sources. By applying the method to a monoclonal antibody clinical study, activities within the patient's major organs such as liver, spleen, and kidney could be estimated, even in cases where the organ could not be visualized. Here, the CAMI algorithm gave internally consistent results for the patient's left and right lung linear activity concentrations. The CAMI technique resolves the problem of tissue superimposition using depth information from 3-D CT and is applicable in cases where a number of organs overlap in the gamma camera image. Thus, the method should be generally useful to nuclear image quantitation and the estimation of absorbed radiation doses in patients. One particular application is the estimation of radiation doses in radioimmunotherapy (RIT).

Algorithms↗
PubMed1999

Combined use of transverse and scout computed tomography scans to localize radioactive seeds in an interstitial brachytherapy implant.

Various techniques have been developed to localize radioactive sources in brachytherapy implants. The most common methods include the orthogonal film method, the stereo-shift film method, and recently, direct localization from a series of contiguous CT transverse images. The major advantage of the CT method is that it provides the seed locations relative to anatomic structures. However, it is often the case that accurate identification and localization of the sources become difficult because of partial source artifacts in more than one transverse cut and other artifacts on CT images. A new algorithm has been developed to combine the advantages of using a pair of orthogonal scout views with the advantages of using a stack of transverse cuts. In the new algorithm, a common reference point is used to correlate CT transverse images and two orthogonal scout CT scans (AP and lateral). The radioactive sources are localized on CT transverse images. At the same time, the sources are displayed automatically on the two CT scout scans. In this way, the individual sources can be clearly distinguished and ambiguities arising from partial source artifacts are resolved immediately. Because of the finite slice thickness of transverse cuts, the longitudinal coordinates are more accurately obtained from the scout views. Therefore, the longitudinal coordinates of seeds localized on the transverse cuts are adjusted so that they match the position of the seeds on scout views. The algorithm has been tested on clinical cases and has proved to be a time saving and accurate method.

Adult↗
PubMed1971

Transneuronal transfer of radioactivity in the central nervous system.

After injection of tritiated amino acid into the mouse eye, radioactivity appeared in the contralateral visual cortex, indicating that some material had been transferred from optic axons to lateral geniculate neurons. The radioactivity in the cortex was about 2 percent of that arriving in the geniculate, and most of it was contained in material that appeared to be protein.

Animals↗
PubMed1982

Gut reactions of radioactive nitrite after intratracheal administration in mice.

Intratracheal administration to mice of radioactive nitrite labeled with nitrogen-13 (13NO2-) (half-life, 9.96 minutes) in dosages that do not cause pharmacological perturbation reveals that oxidative and reductive reactions occur in different organs. Oxidation of 13NO2- to radioactive nitrate (13NO3-) predominates in the blood and liver. Reduction of 13NO2- occurs in those mice that harbor intestinal microflora; this reduction does not occur in germ-free mice. The intestinal reduction products include ammonium, glutamate, glutamine, and urea. With a detection limit of about 0.01 percent of the instilled nitrogen-13, no labeled nitrosamines were detected within 30 minutes. Reduced nitrogen-13 is transported out of the intensive into the circulatory system and appears in the urine along with 13NO3-. The biological half-period for 13NO2- destruction is about 7 minutes, and both oxidation and reduction products are formed.

Animals↗
PubMed1983

Inhibition by alcohols of the localization of radioactive nitrosonornicotine in sites of tumor formation.

Oral administration of ethanol, n-butanol, or t-butanol to mice 20 minutes before injection of carbon-14-labeled nitrosonornicotine inhibited the localization of radioactivity in bronchial and salivary duct epithelium and in the liver. Localization of radioactivity in the nasal epithelium and esophagus was not significantly reduced. These alcohols therefore may selectively inhibit tumor formation in three of the five sites where this carcinogen typically acts.

1-Butanol↗
PubMed1981

Radioactivity measurements of former military personnel exposed to weapon debris.

Sixteen former military personnel who were present at the "Smoky" atmospheric nuclear weapon test have been investigated for internal deposits of radioactivity. Whole-body and thorax gamma-ray measurements, thorax and skeletal actinide measurements, and urinalyses for plutonium-239 and strontium-90 indicated no evidence of radioactivity in excess of that found in the general population.

Adult↗
PubMed1978

Isolation and identification of the cytoplasmic membrane from Saccharomyces carlsbergensis by radioactive labeling.

The cytoplasmic membrane of Saccharomyces carlsbergensis was isolated by enzymatic digestion of the yeast cell wall, followed by lysis of the protoplasts and fractionation by ultracentrifugation in a discontinuous sucrose density gradient. Location of the cytoplasmic membrane fraction on the sucrose gradient was made by labeling intact protoplasts with [G-3H]dansyl chloride, and was settled at the 50% (wt/vol) sucrose gradient (d = 1.186 g/cm3). Approximately 80% of the radioactivity was found in the membrane fraction prepared in the presence of Mg2+ ions. However, when protease inhibitors were used in the preparation step, the membrane fraction contained over 90% of the total radioactivity. The presence of Mg2+ ions during membrane isolation and purification enhanced the aggregation of membrane components but, at higher concentrations, as well as in the prolonged presence of Mg2+ ions in the membrane suspension, it caused the breakdown of membrane components. The membrane preparation contained Mg2+-adenosine triphosphatase, which was insensitive to oligomycin and ouabain. The distribution of Mg2+-adenosine triphosphatase in different fractions during sucrose gradient is reported.

Adenosine Triphosphatases↗
PubMed1979

Measuring radioactive methane with the liquid scintillation counter.

Although a gas proportional counter is the most convenient method of measuring the radioactivity of fixed gases such as methane, it cannot be used when high nonradioactive concentrations of methane are present in the gas phase, due to quenching. If only methane and carbon dioxide are present in radioactive form in the gas phase, a liquid scintillation method for measuring these substances can be used. The procedure is described in detail, and the solubility of methane in liquid scintillation cocktails is determined.

Journal Article↗
PubMed1981

Rapid chemotaxis assay using radioactively labeled bacterial cells.

A rapid chemotaxis assay is described in which radioactively labeled cells of the assay organism are used to detect the number of cells trapped in capillaries containing attractant. The sensitivity and reproducibility of the radioactive technique is comparable to that of the dilution plating procedure of Adler (J. Adler, J. Gen. Microbiol. 17:77-91, 1973), but is faster and also permits the results of the assay to be determined on the day that the assay is run. The method could be particularly useful for environmental studies and for field experiments, since it does not rely on sterile techniques for dilution plating.

Bacteriological Techniques↗
PubMed1997

Development of a radioactive protein A-based assay for analysis of surface protein expression in gram-positive bacteria.

This paper describes an immunochemical method which uses radioactive protein A for the detection and analysis of streptococcal M6 protein epitopes on the surface of recombinant Streptococcus gordonii. With this assay, recombinant S. gordonii cells expressing a portion of the M6 protein on their surfaces show a 75-fold increase in bound radioactivity over cells of the control S. gordonii parental strain. Furthermore, use of the assay to monitor the amount of M6 protein present on the surface of the S. gordonii recombinant during growth in culture demonstrated that expression is highest at late log phase, with the protein being sloughed off during stationary phase. This simple assay allows analysis of surface protein without any protein purification or sophisticated instrumentation. As such, it should be broadly applicable to following the expression of most surface-accessible bacterial proteins.

Antigens, Bacterial↗