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 1,531 records · Page 85Linked to original sources
PubMed1978

Temperature-induced changes of spin-labelled radioactive lipids in isolated guinea pig liver microsomal membranes before and in mitochondrial membranes after their translocation.

Lipids of isolated guinea pig liver microsomal membranes were labelled biosynthetically with isomeric doxyl stearic acid and temperature-induced changes of these membranes were studied by electron spin resonance. A noticeable discontinuity was detected at 10--12 degree C with 12- or 16-doxyl stearic acid containing membrane lipids which was attributed to the spin-labelled lipid--microsomal membrane protein interactions since no such discontinuity was detected in liposomes prepared from total lipid extracts of microsomal membranes. When microsomal membranes containing radioactive isomeric spin-labelled lipids were incubated with unlabelled mitochondria, reisolated mitochondrial membranes contained translocated radioactive isomeric spin-labelled lipids. Temperature-induced changes in these membranes showed no discontinuity with either isomeric doxyl stearic acid derivative, establishing a difference in the environment of translocated lipids in the membrane donor compared with that in the membrane acceptor. Microsomal membranes recovered from translocation experiments showed the same behaviour as the original membranes and exhibited the same discontinuity at 10--12 degree C, establishing that the translocation incubation itself did not alter the spin-labelled lipid interaction within these membranes. Studies of the loss of paramagnetism of spin-labelled lipids in microsomal membranes before and in mitochondrial membranes after their translocation showed a significant difference and suggested that both the outer and the inner mitochondrial membranes might have been involved.

Animals↗
PubMed1986

The effects of pH, buffers, and fatty acid concentration on the incorporation of radioactive arachidonate into endogenous neuronal nuclear lipids.

Using neuronal nuclei (N1) isolated from cerebral cortices of 15-day-old rabbits the incorporation of [3H]arachidonate into N1 lipids was followed in vitro. Arachidonate was principally incorporated into triacylglycerol and phosphatidylinositol. When low concentrations (32 mM) of Tris-HC1 (pH 7.4) were used, rates of total arachidonate incorporation were small and phosphatidylinositol received the bulk (greater than 84%) of the arachidonate. When the concentration of Tris-HC1 (pH 7.4) or, in certain cases, the concentration of arachidonate was increased, there was a rise in total arachidonate incorporation into N1, with an increasing proportion of radioactivity entering triacylglycerol until it was the predominantly labelled lipid. Using other buffers (phosphate, imidazole, HEPES, pH 7.4), the shift from phosphatidylinositol to triacylglycerol as principal labelled lipid, with buffer concentration, was not as marked as with Tris-HC1 (pH 7.4). When the buffer concentration was maintained at 107 mM and the pH was lowered to 6.5, the three amine-containing buffers showed a sizeable decline in arachidonate incorporation into N1 lipids and a corresponding decrease in triacylglycerol labelling. The proportion of the total radioactivity in N1 phosphatidylinositol rose as the pH declined. Of the buffers used, Tris-HC1 showed the greatest changes over the pH range. Based upon pK values for the amine buffers, it is suggested that an increased proportion of the protonated amine may be inhibitory to arachidonate incorporation in N1. Studies of acyl-CoA synthetase in N1 indicated this enzyme as the site of the inhibition.

Animals↗
PubMed1985

Time course of the total and radioactive carbon dioxide production by piglets receiving dietary [14C]phenylalanine.

The influence of experimental protocol (i.e., timing of feeding and of the collection of expired carbon dioxide) upon the sensitivity of using the oxidation of a labelled amino acid as an indicator of the adequacy of the dietary amino acid balance was investigated using 2.5-kg piglets confined in ventilated chambers. In the first experiment it was shown that consumption of two meals, each of 20 g and separated by 2 h, after an overnight fast resulted in a rapid rise in carbon dioxide concentration in the air withdrawn from the chamber. The concentration peaked 12 min after the second meal and remained elevated for 50 min. In the second experiment the piglets received two meals containing three levels of either lysine (8, 10, and 12 g/kg) or tryptophan (1.3, 1.8, and 2.0 g/kg) plus 10 microCi L-[alanine-1-14C]phenylalanine (1 Ci = 37 GBq) in each meal. Radioactivity released as 14CO2 peaked in the second hour following the last meal, but there was such great variation in the mean for the three diets that they were not statistically different. However, in the third hour following the second meal both the means and their variances had decreased with the differences between the diets being statistically significant for this time period. An experiment with varying levels of tryptophan showed a similar effect of meal consumption on 14CO2 release. The third experiment confirmed the effect of time of collection upon the statistical significance of the dietary amino acid balance measured by the release of radioactivity from [14C]phenylalanine.

Animals↗
PubMed1975

Patterns of excretion of radioactive chelates in obstructive uropathy.

Radioactive chelates such as 99mTc-DTPA are advantageous in ranal imaging, particularly in defining functional and morphological abnormalities of the excretory tract. In a review of more than 200 studies, 19 cases of lower-tract disease were diagnosed by the gamma camera image alone. In 16 of them, the diagnosis was confirmed by excretory urography. Normal radionuclide patterns are described and compared with the characteristic findings in caliectasis, hydronephrosis, and hydroureter. By facilitating evaluation of renal perfusion, renal glomerular function, and gross renal structure as well as good difinition of excretory function, radioactive chelate imaging is ideally suited for use as general screening test.

Adult↗
PubMed1983

A simple device for loading radioactive seeds into absorbable sutures.

Radioactive I-125 seeds that are loaded into absorbable sutures are convenient for permanent or removable interstitial-implantation. A simple device for loading radioactive seeds into commercially available sutures is described. This loader permits fast placement of seeds in the suture with minimal exposure to the involved personnel. Variable spacing is accomplished either by absorbable spacers or by minor manipulation of the loaded suture.

Brachytherapy↗
PubMed1983

Work in progress: transcatheter embolization of renal cell carcinoma with radioactive infarct particles.

Treatment by radioactive infarct implant is advocated for patients who have renal cell carcinoma with distant metastases. The radioactive infarct implants were placed into the primary tumor, and when feasible into metastases, by transcatheter embolization. Metastases to the skeleton, liver, lungs, adrenals, and retroperitoneal muscles were also seeded; metastases to the central nervous system, pancreas, and spleen, as well as most pulmonary metastases, proved inaccessible to this approach. The effectiveness of this treatment modality was shown by improved cumulative survival rates (59% for patients with metastases and at risk at two years and 50% for those at risk at five years). The best results were obtained when treating patients who had skeletal metastases (90% survival of those at risk at two years and 60% at five years). Measurable palliation factors, such as decrease in the size of the primary lesion, weight gain, and control of bleeding and pain, were indicators of treatment response and were observed in the majority of patients. Remissions were signaled by weight gain, normalization of the erythrocyte sedimentation rate, and disappearance or decrease of tumor markers. Some evidence suggests that the salutary results may be based on significant reduction of tumor burden, temporary local control of tumor, and improved general immunocompetence.

Adenocarcinoma↗
PubMed1993

Malignant tumors invading chest wall: treatment with CT-directed implantation of radioactive seeds.

Computed tomography (CT) was used to direct permanent implantation of radioactive iodine-125 seeds in two patients with unresectable lung cancer and in one with recurrent breast cancer invading the chest wall. An average of 60 seeds were implanted, with a mean total radioactivity of 35.6 mCi (1,317 MBq). Tumor coverage was adequate and pain relief was good in all patients. One patient had histologically documented complete response and another had CT-documented partial response.

Aged↗
PubMed1990

Splanchnic and systemic hemodynamics in mice using a radioactive microsphere technique.

Mice are commonly used for the study of human disease processes. However, techniques for measuring systemic and hepatic blood flow in mice have not been developed. We attempted the conventional technique of radiolabeled microsphere injection into the left ventricle, but difficulties were encountered, including unsuspected ventricular perforation and outflow obstruction in 68% of the animals. We therefore evaluated whether an injection into the carotid artery close to the aortic arch can fulfill the criteria (approximately or greater than 300 microspheres in femoral blood or tissues, adequate mixing of microspheres with blood, and no significant alteration of blood pressure during microsphere injection) required for accurate measurement of systemic and regional hemodynamics. Carotid artery injection resulted in adequate mixing and number of microspheres in tissues in 78 and 91% of the animals, respectively. Portal venous inflow was 1.8 +/- 0.3 ml.min-1.g liver tissue-1 and renal blood flow was 5.1 +/- 0.75 ml.min-1.g tissue-1. Compared per unit weight, these values are quite similar to those reported in rats. Cardiac output was 12.1 +/- 1.2 ml/min and cardiac index was 462 +/- 47 ml.min-1.kg body wt-1. The reliability of cardiac output determination is improved if whole body radioactivity is taken into account. Five of 22 animals had to be excluded because of either a low number of microspheres in tissues or inadequate mixing of microspheres with blood (shown by asymmetrical distribution of microspheres between left and right kidney). With modifications, the radioactive microsphere technique can be adapted to the hemodynamic study of mice.

Animals↗
PubMed1978

Dextran as a radioactive microsphere suspending agent: severe hypotensive effect in rat.

The effects of different commercially available radioactive microsphere suspending solutions were studied on the cardiovascular hemodynamics of male, Sprague-Dawley rats. Single left ventricular injections of carbonized radioactive microspheres (15 +/- 5 micron diam) totaling 850,000 spheres, suspended in 10% dextran (mol wt, 73,000) solution with Tween, caused reductions in arterial pressure (control, 101; postinjection, 74 mmHg; P less than 0.001), with no change in heart rate. Identical injections made with isotonic saline solution plus Tween had no effect on either heart rate or arterial pressure. Independent studies were conducted to examine the effects of 1-ml injections of four suspending solutions without microspheres on the cardiovascular hemodynamics of rats. Isotonic saline had no hemodynamic effect, and isotonic saline plus Tween decreased only heart rate. Ten percent dextran soluton with Tween decreased arterial pressure, heart rate, peak left ventricular systolic pressure, and left ventricular end-diastolic pressure. Similar changes occurred when dextran solution without Tween was administered. These data demonstrate that 10% dextran solution used as a microsphere suspending agent induces a severe hypotensive response in rats. Furthermore, injections of up to 850,000 microspheres in isotonic saline solution do not alter arterial pressure in the rat.

Animals↗
PubMed1980

Quantitative microautoradiography of arteries: comparison of radioactivity to silver.

The local concentration of silver in developed aortic transmural microautoradiographs was compared to the corresponding 125I-labeled albumin radioactivity concentration [ci(x)] in the subjacent tissue. Silver [s(x)] was measured by electron probe X-ray microanalysis (EPA) and the corresponding ci(x) by direct gamma-ray counting. The results show 1) that the relationship between volume-averaged values of radioactivity (ci) and EPA signal (s) is adequately described by ci = Ks, where K is a proportionality constant, and 2) that ci(x) measured by EPA [i.e., Ks(x)] agrees closely with ci(s) measured direcly from en face microtomy slices of corresponding unfixed tissue specimens.

Animals↗
PubMed1992

Reproductive organ blood flow measured using radioactive microspheres in diestrous and estrous mice.

Blood flow is a primary mechanism controlling reproductive organ functions. In the present study, radioactive microsphere techniques were adapted to measure ovarian, uterine, and vaginal blood flow levels in C57BL mice. Anesthetized animals were tracheostomized and the left carotid artery was cannulated. The heart was exposed and 113Sn-labeled spheres (15 microns size, 2 microCi, 0.1 ml) were injected via the left ventricle. Reference sample was obtained by carotid artery blood "free flowing" into a tared microfuge tube for 1 min. The animal was killed, and selected tissues were excised for weighing and radioactivity measurement to determine flow. Absence of differences in flow levels (ml.min-1.g-1) to paired nonreproductive organs (adrenals and kidneys) validated the procedure. Blood flow levels were significantly higher in the ovaries, but not in the uterus and vagina of estrous mice vs. diestrous mice. Comparison of left vs. right ovaries suggested consistent blood flow distribution during diestrus. Ovarian blood flow level is enhanced during estrus and, in addition, is highly nonuniform regarding right-left flow distribution. Nonuniform ovarian blood flow distribution in estrous mice leads us to speculate that alternating right-left (i.e. nonuniform) ovulation predominates during each murine estrous cycle.

Animals↗
PubMed1975

Measurement of gastric blood flow with radioactive microspheres.

The validity of using radioactive microspheres (15 +/- 5-mum diameter) to measure gastric blood flow and its partition between gastric wall layers was investigated in anesthetized dogs with a chambered segment of gastric corpus. Total flow measured by a venous effluent technique demonstrated close correlation with microsphere-measured flow (r = 0.98, slope = 0.95) in 12 dogs given histamine, gastrin, or isoproterenol. In 12 histamine-stimulated dogs, mucosal flow measured by aminopyrine clearance and by microspheres also showed good agreement (r = 0.96, slope = 0.83). No evidence was found to indicate that microspheres altered hemodynamic or gastric function. In all experiments less than 1% of the total gastric radioactivity passed through arteriovenous shunts. The mucosa always contained a statistically adequate number of spheres (greater than 400), but the submucosa and muscularis frequently did not. Microspheres of all sizes mixed adequately in large arteries, but a significant difference was found in the distribution of 16- and 26 mum spheres between mucosa and submucosa, presumably because of streaming of the larger spheres past mucosal arteries. It was concluded that, with the techniques developed in our laboratory, microspheres could be a highly useful tool for quantitating gastric regional blood flow under a variety of experimental conditions.

Aminopyrine↗
PubMed1995

Cerebral blood flow measured with intracerebral laser-Dopplerflow probes and radioactive microspheres.

We have measured cerebral blood flow with intracerebral laser-Doppler microprobes in pentobarbital-anesthetized pigs. We compared the results with measurements from laser-Doppler probes placed on the surface of the brain and with blood flow estimation by the radioactive microsphere method. The cerebral blood flow was varied by alterations in inspired carbon dioxide, hemorrhagic hypotension, and high cerebrospinal fluid pressure. The intracerebral probes and the surface probes showed parallel responses to variations in cerebral blood flow. The correlation was closest between surface probes and the intracerebral probes measuring from the cerebral cortex (r = 0.46; P < 0.005). The r value between laser-Doppler flowmetry and radioactive microspheres was 0.41 (P < 0.0005) for all measurements. The correlation to microspheres was best for the probes located 3 or 10 mm into the brain and poorest for the surface probe. In conclusion, intracerebral laser-Doppler flow measurements reflect changes in blood flow, and the technique appears useful for continuous estimates of cerebral blood flow.

Animals↗
PubMedDate not supplied

Comparison of regional blood flow values measured by radioactive and fluorescent microspheres.

Fluorescent microspheres (FM) have become an attractive alternative to radioactive microspheres (RM) for the measurement of regional blood flow (RBF). The aim of the present study was to investigate the comparability of both methods by measuring RBF with FM and RM. Eight anaesthetised pigs received simultaneous, left atrial injections of FM and RM with a diameter of 15 microm at six different time points. Blood reference samples were collected from the descending aorta. RBF was determined in tissue samples of the myocardium, spleen and kidneys of all 8 animals. After radioactivity of the tissue samples was determined, the samples were processed automatically for measuring fluorescence using a recently developed filter device (SPU). RBF was calculated with both the isotope and spectrometric data of both methods for each sample resulting in a total of 10,512 blood flow values. The comparison of the RBF values yielded high linear correlation (mean r(2) = 0.95 +/- 0.03 to 0.97 +/- 0.02) and excellent agreement (bias 5.4-6.7%, precision 9.9- 16.5%) of both methods. Our results indicate the validity of MS and of the automated tissue processing technique by means of the SPU.

Animals↗
PubMed1981

An introduction to the measurement of the cerebral oxygen uptake rate by inhalation of 15O2; analysis of the contribution of 15O2 and H2 15O in brain radioactivity.

This paper introduces a model for the computation of the regional cerebral metabolic rate of oxygen from the data of cerebral regional radioactivity collected after inhalation of 15O2. A method was devised for the differential determination of the respective contribution of radiooxygen and of radiowater in the inflow and the outflow of radioactivity in the brain after or during such on inhalation. The results demonstrate the feasability of such a model and outline some of the methodological to be taken into account in the numerical analysis of the data.

Animals↗
PubMed1988

Animal experiments for estimating the radiation exposure of human subjects by radioactive drugs.

The radiation exposure of human subjects is extrapolated from the elimination rate of radioactivity from the plasma and a single determination of the tissue distribution of radioactivity in rats. With an interval of 3-4 half-lives between administration and determination, the radiation exposure of an organ is underestimated only if the elimination rate from the organ is 5.5-12.9 times lower than from the plasma. Determining the elimination rate from the relevant organs is recommendable only if the radiation exposure calculated for the commonly used dose of 100 microCi per volunteer approaches the official yearly limit.

Animals↗
PubMed1987

In vitro secretion and uptake of radioactive vitamin A in rats fed different dietary proteins.

Generally, protein energy malnutrition is accompanied with vitamin A deficiency. The present study was undertaken to evaluate the importance of the quality and the quantity of dietary proteins on the in vitro secretion and uptake of vitamin A in growing rats. The results show that the in vitro release of radioactive vitamin A was greater in rats fed Bengal gram diets as compared to those fed casein diets. However, this relationship between the two groups of rats was reversed for the in vitro uptake of radioactive vitamin A from plasma by various extrahepatic tissues. Thus the vitamin A status of the animal is profoundly influenced by the quality and the quantity of dietary proteins.

Animals↗
PubMed1994

Blood volume determination with sodium fluorescein and radioactive chromium--a clinical comparison of methods.

OBJECTIVE: There exists no method so far for the determination of circulating blood volume as an important parameter of circulatory function widely usable under clinical conditions. Therefore, the present study was designed to investigate whether identical distribution spaces could be measured by two methods for blood volume determination using sodium fluorescein (SoF) and radioactively labelled red blood cells (51Cr*). DESIGN: Comparative study. SETTING: Operating theatre, recovery room, or intensive care unit of a university hospital. PATIENTS: 35 patients undergoing abdominal, urological or vascular surgery. INTERVENTIONS: Simultaneous determinations of blood volume using SoF and 51Cr* in the intra- and postoperative period. RESULTS: There were no significant differences between the calculated means of blood volume (4,445 vs. 4,407 ml), red cell volume (1,554 vs. 1,540 ml), and plasma volume (2,891 vs. 2,807 ml) for 51Cr*-vs. SoF-stained red blood cells. The coefficient of correlation between the two methods was r = 0.95. The mean percentage error was -0.6% between the two methods, the precision 5.6%. CONCLUSIONS: SoF-stained erythrocytes allow a determination of the same distribution space as the well-established radioactive method using 51Cr*. Therefore, SoF-staining may replace 51Cr* labelling of red blood cells for the determination of blood volume in patients.

Adult↗