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PubMed1981

Turnover and uptake by organs of radioactive serum high-density lipoprotein cholesteryl esters and phospholipids in the rat in vivo.

The serum decay of rat serum high-density lipoprotein (HD lipoprotein), labelled biosynthetically with (32)P in the phospholipid or with (3)H in the cholesteryl ester moiety, was measured in rats after partial hepatectomy or sham operation. The serum decay of (3)H-labelled HD lipoprotein cholesteryl esters was biexponential. In sham-operated rats the t((1/2)) values for the rapid phase and the slow phase were 0.2+/-0.1h and 4.2+/-0.4h (means+/-s.e.m.) respectively. After removal of two-thirds of the liver the t((1/2)) value of the rapid phase did not change (0.1+/-0.1h), whereas the t((1/2)) value of the slow phase increased to 5.7+/-0.8h. Partial hepatectomy hardly changed extrahepatic tissue radioactivities, whereas the percentage of the injected dose recovered in the liver 6h after injection decreased from 34.0+/-1.9% before to 13.5+/-1.6% after partial hepatectomy. The (32)P-labelled HD lipoprotein phospholipids showed a rapid monoexponential decay from serum with t((1/2)) values of 0.71+/-0.3h and 1.48+/-0.11h after sham operation or partial hepatectomy respectively. The tissue (32)P radioactivities in the shamoperated rats, measured 1h after injection, were 46.0+/-1.7% (liver), 1.7+/-0.3% (adipose tissue), 3.7+/-1.2% (skeletal muscle) and 3.0+/-0.0% (erythrocytes) of the injected dose. Only the value for liver was affected by partial hepatectomy and decreased to 16.7+/-3.8%. In a previous publication [Van Tol, Van Gent, Van't Hooft & Vlaspolder (1978) Atherosclerosis29, 439-448] we showed in a highly comparable experimental setting that the turnover rates of HD apolipoproteins A and C in vivo are not influenced by removal of two-thirds of the liver. From the present study it is clear that the removal rates of radioactive HD lipoprotein cholesteryl esters and HD lipoprotein phospholipids from serum in vivo are decreased by partial hepatectomy. The results indicate the possibility of partly separate metabolic pathways of HD apolipoproteins A and C, HD lipoprotein cholesteryl esters and HD lipoprotein phospholipids. The phospholipids and cholesteryl esters of HD lipoprotein are metabolized predominantly by the liver. Possible mechanisms for the hepatic uptake and metabolism of HD lipoprotein cholesteryl (esters) and phospholipids are discussed.

Animals↗
PubMed1983

A simple assay method for determination of the specific radioactivity of the gamma-phosphate group of 32P-labelled ATP.

A simple and rapid assay method is described for determining the specific radioactivity of the gamma-phosphate group of 32P-labelled ATP. Labelled ATP is incubated with cyclic AMP, cyclic AMP-dependent protein kinase and histone H2A under conditions leading to maximum phosphorylation of the histone. The specific radioactivity of the gamma-phosphate group of the 32P-labelled ATP is calculated from the total amount of [32P]Pi incorporated into a standard amount of histone. This assay method uses inexpensive commercially available materials, and it yields an accurate specific radioactivity with as little as 0.25 nmol of 32P-labelled ATP.

Adenosine Triphosphate↗
PubMed1993

Receptor-mediated endocytosis of retinol-binding protein by liver parenchymal cells: interference by radioactive iodination.

Retinol-binding protein (RBP) was iodinated directly by radio-iodine substitution on the tyrosyl residues by the sodium hypochlorite (NaOCl) or the Enzymobead (EB) methods, or indirectly by linkage of 125I-tyramine-cellobiose (TC) or 125I-N-succinimidyl-3-(4- hydroxyphenyl)propionic acid ester (SHPP) adduct on to free amino residues of RBP. Binding, uptake and degradation of iodinated RBP were studied in isolated rat and rabbit liver parenchymal cells. The amount of ligand bound to cells at 4 degrees C was dependent on the type of labelling, in that the 125I-TC ligand was bound to a lesser extent than NaClO-labelled 125I-RBP, EB-labelled 125I-RBP and 125I-SHPP-RBP. At 37 degrees C, the 125I-SHPP-RBP and the EB-labelled 125I-RBP became cell-associated more rapidly than the other two ligands. The higher cell association at 37 degrees C than at 4 degrees C suggests that internalization of the ligand occurred at the higher temperature. The degradation of the ligands was also different. The EB-labelled 125I-RBP, the 125I-TC-RBP and the 125I-SHPP-RBP showed an apparent lag phase before a steady increase in acid-soluble radioactivity was observed. Much less of EB-labelled 125I-RBP and 125I-TC-RBP were degraded (about 6%) than of the other two ligands (about 16%) after 120 min. About 50% of the acid-soluble radioactivity in these experiments could be accounted for by degradation in the medium, suggesting that about half of the degradation observed was intracellular. The present study therefore shows that the different labelling techniques yield varying estimates of the cellular handling of RBP. In addition, a rapid release of RBP was observed in experiments where cells were pulsed with radioactive RBP at 4 degrees C, washed and incubated further at 37 degrees C. Between 50% and 70% was released after 5 min of incubation. By increasing the temperature during the pulse to 37 degrees C, or by lowering the temperature during the chase to 4 degrees C, much less RBP was released from the cells. These data suggest that the release process represents recycling of internalized ligand from an early endosome.

Animals↗
PubMed1981

A comparison of radioactive calcium absorption tests with net calcium absorption.

1. Four different methods of calculating calcium absorption by radioactive calcium procedures have been compared with each other and with net calcium absorption in calcium-balance studies in 100 consecutive studies on 71 patients. 2. All four isotope procedures yielded highly significant correlations with net calcium absorption derived from the balance studies, but there was little to choose between the validity of the double-isotope and single-isotope procedure judged by these criteria. 3. The rate of calcium absorption calculated from one or other isotope procedure correlated better with net calcium absorption than did the fraction of the radioactive calcium absorbed. 4. The measurement of plasma radioactivity 1 h after single-isotope administration, corrected for body weight, proved almost as useful as the more complex procedures but would be expected to underestimate calcium absorption in states of very high bone turnover.

Calcium↗
PubMed1992

Distribution of radioactivity of 14C-amino acids added to the medium in cells and metabolites in cultures of rumen fungi.

A mixture of L-(U-14C) amino acids was added to cultures of 11 strains of rumen anaerobic fungi belonging to Neocallimastix frontalis, Neocallimastix joyonii, Sphaeromonas communis and Piromonas communis. Fungi were grown in a complex medium with glucose for 4 days. The radioactivity was found in cellular protein (27.7-65.3% of the total radioactivity recovered), lactate (16.9-41.8%), volatile fatty acids (7.4-25.7%) and ethanol (4.6-10.5%). A small amount of radioactivity was recovered in lipids (0.2-1.8%) and CO2 (0.3-1.0%). The results suggest that the assimilation of amino acids by growing fungal cells was quantitatively comparable with their dissimilation to metabolites.

Amino Acids↗
PubMed1975

Chronic lymphocytic thyroiditis, thyrotoxicosis, and low radioactive iodine uptake. Report of four cases.

To characterize four patients with thyrotoxicosis and a low radioactive iodine uptake, thyroid biopsies were performed, and iodine metabolism was studied. Histologic examination showed the presence of chronic lymphocytic thyroiditis, with no features of Graves's disease, in all. Detailed studies in one patient revealed insufficient metabolism of iodine to account for the clinical and chemical features of thyrotoxicosis, which implies that release of stored hormone by the inflammatory process causes the thyrotoxic state. The thyrotoxicosis in this entity subsides spontaneously. Thus, this form of thyrotoxicosis differs from the usual form found in Graves's disease in that histologie features of Graves's disease are absent, the radioactive iodine uptake is low, and specific antithyroid therapy is contraindicated. The observations further demonstrate that the radioactive iodine uptake remains a valuable tool in the diagnosis of thyrotoxicosis and the differentiation of its various forms.

Adult↗
PubMed2002

Increasing the effectiveness of radioactive iodine therapy in the treatment of thyroid cancer using Trichostatin A, a histone deacetylase inhibitor.

BACKGROUND: Radioactive iodine is used to identify and treat recurrent and metastatic thyroid cancer of follicular cell origin. Between 30% and 40% of thyroid cancers are either resistant or become resistant to radioactive iodine. Increased sodium-iodide symporter (NIS) and decreased Pendrin (PDS) activity may be associated with increased radioactive iodine effectiveness. In this investigation the effects of Trichostatin A (TSA), a histone deacetylating inhibitor, on human thyroid NIS and PDS gene expression was investigated. METHOD: Cell lines from papillary, Hürthle, and follicular cell carcinomas were treated with TSA for 72 hours at concentrations up to 100 ng/mL. NIS and PDS gene expression was determined using quantitative RT-polymerase chain reaction. RESULTS: . NIS messenger RNA expression in cell carcinomas was increased 107- (1.8-307) and 217- (5.7-408) fold in papillary, 39- (20-63) and 58- (37-80) fold in Hürthle, and 459- (178-810) and 781- (412-1229) fold in follicular after treatment with 50 and 100 ng/mL of TSA, respectively. PDS messenger RNA expression in cell carcinomas was decreased 0.22- (0.05-0.45) and 0.27- (0.09-0.47) fold in papillary, 0.53- (0.46-0.60) and 0.54- (0.44-0.64) fold in Hürthle, and 0.32- (0.26-0.39) and 0.56- (0.47-0.64) fold in follicular, after the same treatment. CONCLUSIONS: In thyroid cancer cell lines, TSA dramatically increased NIS gene expression and reduced PDS expression. The increased NIS expression and reduced PDS expression may make radioiodine therapy more effective in patients with thyroid cancer, especially when the tumors have no or low uptake of radioiodine.

Carcinoma, Papillary↗
PubMed1986

Metabolic breakdown of [3H]thymidine and the inability to measure human lymphocyte proliferation by incorporation of radioactivity.

Quantitative measurement of the incorporation of tritiated thymidine into cultures of phytohemagglutinin-stimulated lymphocytes is routinely used as an indication of the immunocompetence of the cells and of their proliferation. The present experiments show that several components of human blood catabolize nucleosides, including thymidine, extensively. Most of the radioactivity from tritiated thymidine, for example, is quickly rendered unincorporable as the compound is metabolized to thymine and further breakdown products. Thus, cells continue to proliferate without incorporating radioactivity from the medium. Furthermore, variability in the degree of catabolism has been found from person to person, so that neither measurement of the depletion of radioactivity from the medium nor measurement of the amount of label incorporated into the cultures can be used as a quantitative indicator of cell proliferation or immunocompetence.

Animals↗
PubMedDate not supplied

Radioactive mercury distribution in biological fluids and excretion in human subjects after inhalation of mercury vapor.

The distribution of mercury in red blood cells (RBCs) and plasma, and its excretion in urine and feces are described in five human subjects during the first 7 days following inhalation of radioactive mercury vapor. A major portion (98%) of radioactive mercury in whole blood is initially accumulated in the RBCs and is transferred partly to the plasma compartment until the ratio of mercury in RBCs to plasma is about 2 within 20 hr. The cumulative urinary and fecal excretion of mercury for 7 days is about 11.6% of the retained dose, and is closely related to the percent decline in body burden of mercury. There is little correlation between either the urinary excretion and plasma radioactivity of mercury, or the specific activities of urine and plasma mercury, suggesting a mechanism other than a direct glomercular filtration involved in the urinary excretion of recently exposed mercury. These studies suggest that blood mercury levels can be used as an index of recent exposure, while urinary levels may be an index of renal concentration of mercury. Howver, there is no reliable index for mercury concentration in the brain.

Adult↗
PubMed1996

The measurement of radioactivity in people living near the Dounreay Nuclear Establishment, caithness, scotland.

In 1986, a statistically significant excess of leukaemia was reported in young people living near the Dounreay Nuclear Establishment in northern Scotland. The committee on Medical Aspects of Radiation in the Environment (COMARF) confirmed this finding and concluded that, based on conventional dose and risk estimates, the radioactive discharges from the plant could not be held responsible. However, COMARF, recognizing the uncertainties involved in the dose and risk calculations, recommended that levels of radioactivity should be measured in the general population living near the plant. Alpha-emitting contamination has been measured by urinary 239Pu analysis and 241Am in-vivo skull measurements in 66 subjects associated with the Dounreay area and in 42 subjects living remote from reprocessing plants. Whole-body counting was employed to check for gamma ray-emitting contamination. Urinary 90Sr and chromosome abnormality analyses were also carried out on subsets of the study group. No significant inter-group differences for measurements of contamination were demonstrated for groups of leukaemia cases, siblings, parents, matched local controls and controls living remote from reprocessing plants. The findings suggest that it is unlikely that the observed increased incidence in leukaemia is due to the single factor of personal radioactive contamination from the Dounreay Nuclear Establishment.

Adolescent↗
PubMed1975

[Resorption and incorporation of radioactive labeled amino acids during administration of various protein carriers in rats. 1. Resorption of 14C leucine and 3H glycine after intragastric administration].

Male Albino rats (90-100 g) were fed ad libitum (with limited periods of feeding) for 14 days. The diets were adjusted to a crude protein content of 10%. Powdered whole egg, fish meal, yeast and gelatine were used as protein sources. Additionally, one group of rats was fed a protein-free diet. On the 15th day of experiment the rats were fed a test diet at a level of 2 g per 100 g of body weight. 2 hrs after that the rats received 25 muCi of 3H glycine and 5 muCi of 14C-L-Leucine per 100 g of body weight administered by way of intragastric infusion. It was found that a large proportion of the radioactive amino acids were absorbed as early as after 0.5 hr. The highest rate of absorption was observed in animals fed dietary proteins of poor quality or a protein free diet, so that in animals receiving a gelatine diet or a protein-free diet only 68.4% or 56.4% of the administered amount of 14C activity were detected inside the gastro intestinal tract after 0.5 hr. Analogous data for the 3H activity were 52.4% and 25.3%. Maximum absorption occurred after 3-7 hrs. Following this the level of radioactivity in the intestinal contents again increased reaching a peak value after 14-24 hrs; in the case of 14C activity this peak value amounted to 25.4% of the administered dose in animals fed the gelatine diet and 32.8% in the group receiving the protein-free diet. It was established that the major proportion of the resecreted amount of 14C activity was present in leucine. Until 72 hrs after the intake of 14C activity the level of radioactivity was again found to decline, a processes which was induced by processes occurring in the large intestines. Moreover, evidence was obtained in confirmation of previous findings, indicating that the composition of faecal amino acids was constant and unaffected by dietary proteins.

Animal Feed↗
PubMed1956

Inactivation of bacteria by decay of incorporated radioactive phosphorus.

Cultures of Escherichia coli will not grow in media containing very high specific activities of radiophosphorus P(32), the inhibition of growth being due to the decay of assimilated P(32) atoms. Experiments with a differentially labeled thymineless strain of E. coli show that the P(32) disintegrations which occur in the bacterial deoxyribonucleic acid, i.e. in the nucleus, are mainly responsible for the inactivation of the cell. The kinetics with which radioactive bacterial populations are inactivated indicate that the function of several nuclei per bacterial cell must be eliminated by P(32) decay before the ability to generate a colony is lost. The efficiency with which each P(32) disintegration inactivates the nucleus in which it has occurred is calculated to be 0.02 (at -196 degrees ), i.e., similar in magnitude to the killing efficiency of P(32) decay in bacteriophages. P(32) decay and thymine starvation cooperate in bringing about the death of individuals of the thymineless strain, from which observation it is inferred that "thymineless death" is likewise a nuclear inactivation. The descendants of a non-radioactive bacterial culture grown for several generations in the presence of P(32) and the descendants of a radioactive culture grown in the absence of P(32) are inactivated by P(32) decay in a manner which indicates that the phosphorus atoms of bacterial nuclei are dispersed among the progeny nuclei in their line of descendance.

Bacteria↗
PubMed2006

Radioactive skin bandages incorporating 32P for treatment of superficial tumors.

Radioactive bandages incorporating 32P, a high-energy beta- emitter, were prepared with an aim to have a radiation source that can be used for the treatment of superficial tumors. 32P-Chromic phosphate particles were prepared and filtered through Millipore filters. Filter incorporating 32P activity was immobilized between nitrocellulose membranes and placed on an adhesive bandage. There was no leakage of radioactivity from the bandage when tested in saline. Efficacy of the radioactive bandage for treatment of superficial tumors was tested in melanoma-bearing C57BL/6 mice. A single dose of treatment with 74 MBq 32P bandage resulted in tumor growth delay, whereas multiple dose treatment with 74 MBq 32P bandage at twice-weekly intervals resulted in complete tumor regression when treatment was started, when the tumor was merely palpable. Histology sections from the treated animals showed absence of tumor.

Administration, Topical↗
PubMed2006

The diagnostic role of radioactivity in sentinel nodes in oral and oropharyngeal cancer.

Sentinel lymph node biopsy (SNB), using radioactive tracers, is a novel, interesting tool in the staging of patients with oral and oropharyngeal squamous-cell carcinoma (OOSCC), which could lead to a reduced rate of elective neck dissections. The aim of the study was to evaluate the ranking of measured radioactivity in the sentinel lymph nodes (SLNs) and to correlate these findings with histopathological results to assess the number of SLN being sufficient for exact staging of the neck. In 77 consecutive patients with T1-4 OOSCC clinically and positron emission tomography-staged N0, between 15 and 55 MBq of Tc- 99m-labeled albumin-microcolloids were injected peritumorally and 213 SLNs were excised by small skin incisions using a gamma probe 2-3 hours later. The counts per second (cps) were measured ex vivo and excised SLNs were ranked according to their cps defining the LN with the highest activity as primary SLN, followed by a 2nd, 3rd, and so forth, SLN. Elective neck dissections were not performed. Median activity was 213 cps. All levels harbored SLNs with a maximum (43%) in level II and a minimum in level V (1%). SLNs in level II had significantly higher tracer accumulation (median, 289 cps) than those in levels I (144 cps) and IV (149 cps), but distant levels did not have significantly lower counts, compared to proximal. Eight (8) pathologically positive SLNs in 7 patients (7/77 = 9%; median activity, 157 cps) were detected. The median counts of the positive SLNs were not significantly different from those of the 205 negative SLNs (235 cps). The positive SLN was the one with the highest tracer accumulation in 4 cases, with the second highest in 1 case, and with the third highest tracer accumulation in 2 cases. Three (3) positive SLN were in level IB, 4 in level IIA, and 1 in level III. One (1) patient had 2 positive SLNs: a SLN with the third highest activity in level IIB and a SLN with the fifth highest activity in level III. In OOSCC, excision of only 1 SLN is not feasible. The positive SLNs were not necessarily the hottest nodes. Utilizing radiotracer lymphatic mapping, the 3 SLNs with the highest activity should be excised for exact staging of the neck in patients with T1-3 tumors. Excision of all radioactive nodes is recommended until further studies will prove this result. Large T4a tumors should not be staged using SNB.

Adult↗
PubMed1993

Estimation of steady-state flux rates in metabolic systems by computer simulations of radioactive tracer experiments.

The dynamics of radioactive tracers in metabolic systems can be mathematically modelled by coupled systems of differential equations for both the concentrations and the specific radioactivities of the metabolites involved. Computer simulations, i.e. direct fitting of numerical solutions of these equations to observed time-courses of metabolites and specific radioactivities, enables one to estimate unknown kinetic parameters of the system. The theoretical fundamentals of this approach and the main steps towards the quantitative assessment of flux rates in stationary metabolic systems are outlined. An application of the method to the purine nucleotide metabolism of Ehrlich ascites tumor cells is given based on a simplified model of this pathway. The obtained steady-state flux rates indicate a marked increase in the metabolism of the adenine nucleotides during the proliferating phase in comparison to the resting phase of tumor growth.

Adenine Nucleotides↗
PubMedDate not supplied

Metabolite analysis, isolation and purity assessment using various liquid chromatographic techniques combined with radioactivity detection.

During the discovery of metabolic routes of a drug candidate, radioactively labeled substances are administered. This study reports the multidimensional application of overpressured layer chromatography (OPLC) and high-performance liquid chromatography (HPLC) coupled with online or off-line nondestructive radioactivity detection methods in metabolism studies. Among these methods, digital autoradiography and flow-cell radioactivity detectors (RD) using solid scintillators are used. In this study, the hyphenation of OPLC with RD is reported. The application of the OPLC-RD technique is demonstrated on a metabolism study as well as the multidimensional chromatographic selectivity using normal-phase OPLC for the separation in the first dimension, followed by reversed-phase HPLC-RD, which provides additional selectivity to the separation. Information regarding the identity of radiolabeled metabolites and data obtained from spectroscopic methods could be advantageously used during structure elucidation.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

A comparison of sodium hydroxide and sodium sulfide digestion of mouse hair in the recovery of radioactivity following systemic administration of [3H]-nicotine and [3H]-flunitrazepam.

Pigmented (C57BI) and nonpigmented (balb/c) mice, 25 days of age, were treated intraperitoneally with [3H]-nicotine (4 mg/kg, 555 dpm/ng) or [3H]-flunitrazepam (1 mg/kg, 2200 dpm/ng) daily for three days. After 21 days, shaved back hair was digested at 37 degrees C for 24 h with either 1 M sodium hydroxide or 1 M sodium sulfide. With both drugs, sodium sulfide extraction removed the same amount of radioactivity as sodium hydroxide from nonpigmented hair. However, sodium sulfide removed significantly more radioactivity from pigmented hair than did sodium hydroxide. In pigmented hair, sodium sulfide solubilized 35% and 74% of the flunitrazepam- and nicotine-associated radioactivity, respectively. Of this, 12% and 43%, respectively, could be partitioned into ethyl acetate. Microscopic examination of residual pellets after digestion demonstrated a more thorough dissolution of the hair shaft with sodium sulfide with only melanosomes remaining. The results demonstrate the significant interaction of flunitrazepam and nicotine with melanins and the utility of sodium sulfide in increasing drug recovery.

Acetates↗
PubMed1980

Binding of radioactivity after transplacental administration of tritiated N-nitrosodiethylamine to Syrian golden hamsters.

Tritiated N-nitrosodiethylamine (DEN) was administered to two groups of female Syrian golden hamsters on days 11 and 15 of pregnancy. Binding of radioactivity was measured in maternal and fetal organs after various intervals by liquid scintillation counting of dehydrated and combusted tissues. No bound activity was found in the fetal tracheas on day 11 of gestation, when transplacental administration of DEN is known to be noncarcinogenic for the offspring. On day 15, when DEN administration caused a 95% incidence of tracheal tumors in the offspring, bound radioactivity was found in the fetal tracheas. In the respiratory tracts of the mothers, the distribution of bound radioactivity correlated with the distribution of target cell types. Binding was high in segmental bronchi and bronchioles which contain numerous Clara cells, the major source of DEN-induced pulmonary tumors. No binding occurred in the main bronchi, which do not possess Clara cells.

Animals↗