Biological Half-life Values Research Articles

Analysis of Tc99m MDP Radiopharmaceuticals in the Spinal Areas of Breast Cancer Patients

The aim of this study was to obtain doses in the spine of breast cancer patients. This dose is very important in pharmacy to determine the distribution of drugs in the body's organs, especially the spine. The data of this study came from the results of bone scintigraphy examinations which had known the value of the injection dose and the percentage of absorption in the spine. This research was conducted by simulating the biological half-life values for 3 hours, 4 hours, 5 hours, 6 hours, and 7 hours to find the total half-life which will produce a total decay constant that will be used in calculating spinal dose. The results obtained were the lowest mean dose in the spinal 0.680 ± 0.160 mCi when the decay constant had the highest value (biological half-life 3 hours) and the largest mean dose in the spinal 1.011 ± 0.238 mCi when the decay constant had the lowest value (biological half-life 7 hours). In the spine, the thoracic region is the area with the highest dose because it is located closest to the breast organs (breast cancer) so it will experience the highest damage/metastasis. Then the Tc99m MDP radiopharmaceutical absorbed into the thoracic region will be higher. By simulating the biological half-life, it is hoped that we can find the exact biological half-life for the absorbed dose

Bio-kinetics of cesium-137 in Mediterranean mussel (Mytilus galloprovincialis) and sea snail (Rapana venosa) via seawater exposure

Accumulation and depuration kinetics in the samples of mussel (Mytilus galloprovincialis L. 1758) and sea snail (Rapana venosa (Valenciennes, 1846)) exposed to 137Cs radioisotope via seawater exposure were investigated under laboratory conditions. Accumulation and depuration kinetics were monitored for 49 and 59 days, respectively. Concentration factor and biological half-life values were calculated from the accumulation and depuration kinetics of mussel and sea snail samples. Concentration factors at equilibrium were 16.25 ± 4.41 and 19.50 ± 1.17 for large and small mussels, respectively, while 16.34 ± 0.70 and 14.31 ± 0.63 for large and small snails, respectively. The biological half-lives at slow components were 38.50 and 77.00 days for large and small mussels, respectively, while 49.50 and 57.75 days for large and small snails, respectively. Compared to the literature, the slightly higher concentration factor and biological half-life values obtained in this study for both mussel and snail samples may help to identify these species as bio-indicators of the 137Cs radioisotope in the marine environment. In addition, it was statistically determined that body size is an important parameter for both living organisms in bioaccumulation experiments unlike the depuration experiments. In the light of all these results, it has been determined that mussel and sea snail organisms are extremely valuable indicators in terms of reflecting radioactive pollution in the sea in monitoring the 137Cs radioisotope for possible inputs of any radioactive pollution in the marine environment.

BIOKINETIC MODEL DEVELOPMENT OF RADIOIODINE-131 VIA IN VIVO GAMMA CAMERA/8-SLICE CT TECHNIQUE: CASE-CONTROL STUDY OF FELINE HYPERTHYROIDISM

Objectives: A biokinetic model of iodine in the thyroid was developed and applied to a case-control study of hyperthyroid cat undertaken the NaI-131 dose administration using a gamma camera/8-slice CT with the in vivo study. Methods: The case-control hyperthyroid cats were administered 55.5 or 3.7[Formula: see text]MBq of I-131 radioactive solution and continuously surveyed by a gamma camera. The scan schedule was preset as 5- or 10-min counting per each hour from the initial time to the sixth hour, then on the 24th, 48th and 72nd hours, respectively. An in-house developed program run in the MATLAB was applied to evaluate the biokinetic model of iodine in the thyroid, in compliance with the ICRP-30 report regulations. The model was defined by five compartments (namely: stomach, body fluid, thyroid, whole body, and excretion) and allowed one to simulate the variations of time-dependent I-131 radioactive concentration among various compartments of each study subject. The numerical simulation via MATLAB was compiled with the empirical evaluation to optimize the time-dependent concentration of I-131 within the above compartments. Results: The derived biological half-life values for stomach, body fluid, thyroid, whole body, and excretion, respectively, were as follows: 17, 3, 10, 5 and 140[Formula: see text]h for hyperthyroid cat, 18, 1, 8, 2, and 40[Formula: see text]h for control #1 cat, and 22, 2, 12, 4, and 20[Formula: see text]h for control #2 cat. The cumulative radioactive doses from both gamma-ray and beta particles were assessed via a simplified algorithm as 0.135, 0.0082, and 0.005 Gy, for hyperthyroid cat, control #1, and control #2 ones, respectively. Conclusion: The derived biokinetic model was found to be helpful in the evaluation of the metabolic mechanism in case of feline hyperthyroidism. The revealed deviations from available human biomodels can be used for refining the radioiodine treatment of pets with hyperthyroidism.

Radionuclide biological half-life values for terrestrial and aquatic wildlife

The equilibrium concentration ratio is typically the parameter used to estimate organism activity concentrations within wildlife dose assessment tools. Whilst this is assumed to be fit for purpose, there are scenarios such as accidental or irregular, fluctuating, releases from licensed facilities when this might not be the case. In such circumstances, the concentration ratio approach may under- or over-estimate radiation exposure depending upon the time since the release. To carrying out assessments for such releases, a dynamic approach is needed. The simplest and most practical option is representing the uptake and turnover processes by first-order kinetics, for which organism- and element-specific biological half-life data are required. In this paper we describe the development of a freely available international database of radionuclide biological half-life values. The database includes 1907 entries for terrestrial, freshwater, riparian and marine organisms. Biological half-life values are reported for 52 elements across a range of wildlife groups (marine = 9, freshwater = 10, terrestrial = 7 and riparian = 3 groups). Potential applications and limitations of the database are discussed.

Estimating the biological half-life for radionuclides in homoeothermic vertebrates: a simplified allometric approach

The application of allometric, or mass-dependent, relationships within radioecology has increased with the evolution of models to predict the exposure of organisms other than man. Allometry presents a method of addressing the lack of empirical data on radionuclide transfer and metabolism for the many radionuclide-species combinations which may need to be considered. However, sufficient data across a range of species with different masses are required to establish allometric relationships and this is not always available. Here, an alternative allometric approach to predict the biological half-life of radionuclides in homoeothermic vertebrates which does not require such data is derived. Biological half-life values are predicted for four radionuclides and compared to available data for a range of species. All predictions were within a factor of five of the observed values when the model was parameterised appropriate to the feeding strategy of each species. This is an encouraging level of agreement given that the allometric models are intended to provide broad approximations rather than exact values. However, reasons why some radionuclides deviate from what would be anticipated from Kleiber's law need to be determined to allow a more complete exploitation of the potential of allometric extrapolation within radioecological models.

Proceedings: Apparent biological half-life values determined by administration of drug by methods other than rapid intravenous injection.

Proceedings: Apparent biological half-life values determined by administration of drug by methods other than rapid intravenous injection.

Effects of Cardiopulmonary Bypass on Propofol Pharmacokinetics and Bispectral Index During Coronary Surgery

PURPOSECardiopulmonary bypass is known to alter propofol pharmacokinetics in patients undergoing cardiac surgery. However, few studies have evaluated the impact of these alterations on postoperative pharmacodynamics. This study was designed to test the hypothesis that changes in propofol pharmacokinetics increase hypnotic effects after cardiopulmonary bypass.METHODSTwenty patients scheduled for on-pump coronary artery bypass graft (group, n=10) or off-pump coronary artery bypass graft (group, n=10) coronary artery bypass grafts were anesthetized with sufentanil and a propofol target controlled infusion (2.0 μg/mL). Depth of hypnosis was monitored using the bispectral index. Blood samples were collected from the induction of anesthesia up to 12 hours after the end of propofol infusion, at predetermined intervals. Plasma propofol concentrations were measured using high-performance liquid chromatography, followed by a non-compartmental propofol pharmacokinetic analysis. Data were analyzed using ANOVA, considering p<0.05 as significant.RESULTSAfter cardiopulmonary bypass, despite similar plasma propofol concentrations in both groups, bispectral index values were lower in the on-pump coronary artery bypass graft group. Time to extubation after the end of propofol infusion was greater in the on-pump coronary artery bypass graft group (334 ± 117 vs. 216 ± 85 min, p = 0.04). Patients undergoing cardiopulmonary bypass had shorter biological (1.82 ± 0.5 vs. 3.67 ± 1.15h, p < 0.01) and terminal elimination (6.27 ± 1.29 vs. 10.5h ± 2.18, p < 0.01) half-life values, as well as higher total plasma clearance (28.36 ± 11.40 vs.18.29 ± 7.67 mL/kg/min, p = 0.03), compared to patients in the off-pump coronary artery bypass graft group.CONCLUSIONAside from the increased sensitivity of the brain to anesthetics after cardiopulmonary bypass, changes in propofol pharmacokinetics may contribute to its central nervous system effects.

Radiocesium contamination behavior and its effect on potassium absorption in tropical or subtropical plants

The accumulation and long-term decline of radiocesium contamination in tropical plant species was studied through measurements of gamma-ray spectra from pomegranate ( Punica granatum) and chili pepper ( Capsicum fructescens) trees. The plants were originally grown at a 137Cs contaminated site (where a radiological accident occurred in the city of Goiânia, Brazil, in 1987), and transplanted to uncontaminated soil, so that the main source of contamination of the new leaves and fruits would be the fraction of the available radiocesium in the body of the plants. Measurements of 137Cs and 40K concentrations along the roots, main trunk, twigs, leaves and fruits before and after the transplant process of both plant species indicated a direct competition between Cs and K ions, suggesting that these elements could have a common accumulation mechanism. Cesium transfer factors from soil to pomegranate, green and red chili pepper fruits were evaluated as 0.4 ± 0.1, 0.06 ± 0.01 and 0.05 ± 0.01, respectively. Biological half-life values due to 137Cs translocation from the tree reservoir (BHL T) were calculated as 0.30 years for pomegranate, 0.12 years and 0.07 years for red and green peppers, respectively.

Urinary mandelic acid as an exposure test for ethylbenzene.

Absorption of ethylbenzene and excretion of mandelic acid were investigated under controlled conditions in six volunteers, exposed at concentrations of 18, 34, 80, and 200 mg/m3. Retention of ethylbenzene vapours in the lungs was 49 +/- 5%. Elimination of mandelic acid was found to be biphasic, with biological half-life values of 3.1 and 24.5 h. Total excreted mandelic acid accounts for 55 +/- 2% of retained ethylbenzene. The results obtained were applied to devise an exposure test for ethylbenzene, which would enable the precise evaluation of exposure at low ethylbenzene, vapour concentrations (+/- 13%). Exposures, carried out dermally, gave a rationale for the exclusion of the skin as a route of entry of ethylbenzene vapours into the body.

Accumulation of cobalt by cephalopods-I. Uptake and excretion of cobalt-60 taken up from seawater by Octopus vulgaris.

For a part of the study on the accumulation of cobaly by cephalopods, uptake and excretion of innic 60Co taken up from seawater by Octopus vulgaris was exanined under labortory cinditions. Coblat-60 from seawater was accumlated remarkably in branchial heart that is a specific organ for cephalopods and the concentration factor of the nuclode by the organ attained to 33, 000 at 25th day in the uptake experiment at 20°C. Muscle showed the lowest concentration factor among the organs and tissues measered and the value was about 40 at 25th day. The 60Co ertention curve for whole body of the octopus was composed of two exponentail rate functions with biological half-life values of 1.2 (22%) and 190 days (78%). The Sephadex gel chromatograms of 60Co extracted from seceral tissues and organs of the octopus suggest that the nuclide bound to different constituents on the respective tissues and organs. In muscle and liver, most of the muclide seems to be bound to the protein with low milecular weight (about several thousands MW). On the other hand, the nuclide in blood, internal medium, associated with a constituent with more than 80, 000 MW.

The labeling of pulmonary surfactant phosphatidylcholine in newborn and adult sheep.

The labeling of the saturated phosphatidylcholine from surfactant with radiolabeled palmitic acid was characterized in seven newborn and seven adult sheep using a repetitive sampling technique. Each animal had a small cannula placed surgically in the trachea. Following the intravenous injection of (3H) palmitic acid, surfactant samples in saline were recovered from the distal airways of each animal with fine plastic catheters over a period of 10 days. The change in specific activity of the saturated phosphatidylcholine (cpm/mumol) was used to define the kinetics of secretion and then disappearance of the labeled saturated phosphatidylcholine. Labeled saturated phosphatidylcholine accumulated in a linear fashion without an apparent initial delay for 27 hr in adult and 44 hr in newborn sheep. The labeled saturated phosphatidylcholine then decayed with mean apparent biological half-life values of 45 hr and 54 hr in adult and newborn sheep, respectively. However, these half-life estimates are compromised by the long secretory phase of the labeling curves. The characteristics of the labeling of surfactant saturated phosphatidylcholine in sheep may be more representative of surfactant metabolism in large mammals than previous studies in small rodents.

Distribution of 23 elements in the kidney, liver and lungs of workers from a smeltery and refinery in north Sweden exposed to a number of elements and of a control group

The levels of antimony, arsenic, cadmium, caesium, chromium, cobalt, copper, gold, iron, lanthanum, lead, manganese, mercury, molybdenum, phosphorus, rubidium, scandium, selenium, silver, tellurium, tin, tungsten and zinc in the kidney, liver and lungs of autopsy specimens from exposed workers in North Sweden, as well as from a control group, have been assayed quantitatively. The workers had been exposed to several elements and their compounds, e.g. lead, mercury, arsenic and cadmium, for long periods in arsenic, lead or selenium plants and in a lead or copper smelter. The chemical analysis was by neutron activation analysis and atomic absorption spectrophotometry. Median levels of antimony, arsenic, cadmium, chromium, cobalt, lanthanum, lead or selenium in kidney, liver or lungs in the exposed worker group were found to be about 2 to 16 times as great as the corresponding levels for the control group. Long biological half-life values were observed for these elements, especially in lung tissue.

Disposition kinetics of cyclohexanone in beagle dogs

The disposition kinetics of cyclohexanone, a commonly used industrial solvent, was studied in beagle dogs following intravenous administration of a 284 mg/kg dose at various rates for 18 or 21 days. The major metabolite of cyclohexanone was identified as cyclohexanol. Plasma and urine concentrations of the compound and the metabolite were determined using a newly developed gas chromatographic procedure. A two-compartment open model was used to analyze plasma concentration-time data of cyclohexanone. The distribution half-life, biological half-life, and clearance values for cyclohexanone were 6.6 ± 3.6 min, 81.0 ± 22.5 min, and 27.4 ± 4.3 ml/kg/min, respectively. Between 74 and 100% of the administered dose of cyclohexanone was converted to cyclohexanol and approximately 60% of the dose was excreted in the urine as the glucuronide conjugate of cyclohexanol. Peak cyclohexanol concentrations in plasma following intravenous bolus administrations of 284 mg/kg of cyclohexanone ranged from 140 to 220 μg/ml and occurred between 5 and 30 min after cyclohexanone administration. Apparent plasma elimination half-life of the metabolite was 99 min. Urinary excretion data suggested that less than 1% of the dose was excreted as cyclohexanol and cyclohexanone. Under the dosage schedule employed in the present study, there was neither any accumulation of cyclohexanone nor any evidence of enzyme induction on repeated administrations. The data gathered in the present investigation are useftul in calculations of cyclohexanone peak or steady-state levels during comparative toxicological studies involving different dosage regimens.

The labeling and biological half-life of phosphatidylcholine in subcellular fractions of rabbit lung

Rabbits were given [ 14C]palmitic acid, [ 3H]choline and ortho[ 32P]phosphate to label lung phosphatidylcholine. The rabbit lungs were lavaged to obtain an alveolar wash phosphatidylcholine sample, and subsequently samples of phosphatidylcholine were obtained from the lung parenchyma, and from microsomal and lamellar body fractions. The specific activity of the phosphatidylcholine in each fraction was determined. The labeling of phosphatidylcholine and the biological half-life values for the labeled phosphatidylcholine in each lung fraction are presented. Phosphatidylcholine labeled with palmitic acid or choline reached a maximal specific activity rapidly in microsomal fractions. Maximal specific activity of lamellar body phosphatidylcholine and alveolar phosphatidylcholine was achieved by 2 h and 6 h, respectively. The labeling of lecithin with phosphate was quite slow in all lung fractions relative to the other precursors. The decay curves for parenchymal and microsomal phosphatidylcholine had two exponential components while the disappearance of lamellar body and alveolar wash phosphatidylcholine was described by simple decay curves. The biological half-life values of palmitic acid-labeled and choline-labeled alveolar wash phosphatidylcholine were 16 and 30 h, respectively. Total phosphatidylcholine and disaturated phosphatidylcholine decay rates in the parenchyma and alveolar wash were similar. The labeling of phosphatidylcholine in subcellular lung fractions indicated that the precursors did not cleanly pulse label the phosphatidylcholine of the lamella bodies and alveolar wash. The labeling patterns of the subcellular fractions were consistent with previous anatomical descripitions of surfactant synthesis and secretion.

IMPLICATIONS OF NEWBORN LUNG LECITHIN METABOLISM

Premature and term newborn and adult rabbit lungs were pulse labeled in vivo with lecithin precursors choline, palmitic acid, and phosphate. Lecithin was isolated from parenchyma, alveolar wash, lamellar bodies and microsomes from the lungs of each group of animals. Time of appearance and biological half-life of lecithin in each fraction was monitored by changes in lecithin specific activity with time. All animals rapidly incorporated isotopic precursors into microsomal lecithin. Radioactive lecithin appeared after a 3 hour delay in premature and term newborn lamellar bodies; no delay was noted in appearance of labeled lecithin in lamellar bodies isolated from adult lung. Maximal specific activity in alveolar lecithin was reached by 6 hours in adult rabbits and in about 20 hours in premature and term newborns. Biological half-life values for lecithin in the lung fractions of premature and term newborn rabbits were greater than 3 times longer than comparable half-life values determined for the adult. The long delay (3 hours) before de novo synthesized lecithin begins to reach the alveolar space suggests that synthesis does not contribute to alveolar stability until many hours after birth. Significant lecithin synthesized de novo is not present at the alveolar space of the newborn for at least 20 hours. Premature and term newborn rabbits must rely on lecithin stored in anticipation of birth to maintain alveolar stability at birth. The prolonged half-life argues against lecithin degradation contributing to RDS.

EFFECTS OF DIETARY IODINE ON THE UTILIZATION OF RADIOACTIVE IODIDE BY THE RAT

Sprague–Dawley rats were fed on diets ranging from 40 μg I/kg to 3885 μg I/kg. Single doses of iodide-131 were injected intraperitoneally into each of the rats. In vivo measurements of radioisotope levels were made at intervals for 11 to 15 days over the neck and thorax. Thyroidal I131 curves were obtained by using a fraction of the thoracic counts to correct for the extrathyroidal component of the neck counts. Animals on low-iodine diets concentrated I131 in their thyroids more rapidly and to greater peak values, had lower protein-bound iodine (I127) concentrations, and lower total thyroidal iodide (I127) content than did rats in the high-iodine groups. An attempt was made to compensate the thyroidal counts for the continuing decrease in the concentration of iodide-131 in the plasma. From this attempt was derived the "thyroidal index", a parameter which may be related to the rate of exchange of the total thyroidal iodine stores. Biological half-life values (I131 in thyroid gland) for the low-iodine groups were larger than those for the high-iodine animals. The hypothesis is advanced that, at least for the conditions reported here, the biological half-life does not adequately reflect thyroidal activity; exchange of iodine between the rat and its environment is considered to be the more important factor in controlling the numerical value of this parameter.

EFFECTS OF DIETARY IODINE ON THE UTILIZATION OF RADIOACTIVE IODIDE BY THE RAT

Sprague–Dawley rats were fed on diets ranging from 40 μg I/kg to 3885 μg I/kg. Single doses of iodide-131 were injected intraperitoneally into each of the rats. In vivo measurements of radioisotope levels were made at intervals for 11 to 15 days over the neck and thorax. Thyroidal I131 curves were obtained by using a fraction of the thoracic counts to correct for the extrathyroidal component of the neck counts. Animals on low-iodine diets concentrated I131 in their thyroids more rapidly and to greater peak values, had lower protein-bound iodine (I127) concentrations, and lower total thyroidal iodide (I127) content than did rats in the high-iodine groups. An attempt was made to compensate the thyroidal counts for the continuing decrease in the concentration of iodide-131 in the plasma. From this attempt was derived the "thyroidal index", a parameter which may be related to the rate of exchange of the total thyroidal iodine stores. Biological half-life values (I131 in thyroid gland) for the low-iodine groups were larger than those for the high-iodine animals. The hypothesis is advanced that, at least for the conditions reported here, the biological half-life does not adequately reflect thyroidal activity; exchange of iodine between the rat and its environment is considered to be the more important factor in controlling the numerical value of this parameter.

Effects of hypothalamic lesions and of cold on thyroid activity in the rat.

ABSTRACT The effect was studied of an electrolytic basal midline lesion in the anterior part of the hypothalamus on thyroid activity of rats exposed to environmental temperatures of 24° C and 4° C. The index of thyroid function used was the biological half-life of thyroidal 131I calculated from the amount of radioactivity released by the gland in seven days. In one experiment, thyroid function was studied at 24° C one month after the placement of a lesion and at 4° C a month later. In another experiment hypothalamic lesions were made in the middle of a release study, during which some of the animals were kept at 24° C and others at 4° C. The two experiments yielded comparable results; the biological half-life values were approximately 7½ days at 24° C and 4 days at 4° C in intact or blank-operated rats, and approximately 13 days at 24° C and 7 days at 4° C in rats with a hypothalamic lesion. Thyroid 127I contents of various groups were identical. It appears that the biological half-life was reduced to approximately half the normal value by exposure to cold, that a lesion caused doubling of the half-life and that summation of the two effects was produced, when a lesioned rat was exposed to cold or when a cold-exposed animal was lesioned. The basal midline region of the hypothalamus destroyed by the lesions, whilst appearing to be essential for the maintenance of »spontaneous« thyroid activity, does not seem to be essential for the thyroid response to cold. Observations on so-called goitre-block lesions are discussed in the light of these findings.

The biological half-life of K42 in the cow and the obese pig.

Potassium-42 was used as a tracer of the total exchangeable body potassium in six cows and five large sows. One millicurie of K42 solution was injected intravenously into each animal and samples of urine and faeces were collected in 8-liter plastic pails, at intervals, for 70 hours. The radioisotope content of the samples was determined by dipping an unshielded sodium iodide scintillometer into the pails to a constant depth. Background error was reduced by setting the discriminator levels to accept only pulses corresponding to the photopeak of the K42 emission. The rate of excretion of K42 decreased for approximately 16 hours, then appeared to remain constant for the rest of the experiment. Means of biological half-life values, as calculated for the period from 22 to 70 hours, were 10.5 days for the cows and 45.6 days for the pigs. Percentages by weight of total potassium in the animals were 0.21 for the cows and 0.24 for the pigs, as estimated from flame photometric determinations of urinary potassium and biological half-life values. These results are compared with caesium and potassium studies reported by other investigators.