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PubMed2004

Determination of choline and ethanolamine plasmalogens in human plasma by HPLC using radioactive triiodide (1-) ion (125I3-).

For the purpose of developing highly sensitive and convenient determination of plasmalogens, the high-performance liquid chromatography (HPLC) method using radioactive iodine ((125)I) was investigated. Radioactive triiodide (1-) ion ((125)I(3)(-)), which is an actual iodine form capable of reacting with vinyl ether bond ([bond]CH(2)[bond]O[bond]CH[double bond]CH[bond]) of plasmalogens, could be safely and efficiently produced by oxidizing a commercial radioactive sodium iodine (Na(125)I) with hydrogen peroxide (H(2)O(2)) under acid condition (pH 5.5-6.0), which is called iodine-125 reagent. I(3)(-) specifically reacted with plasmalogens at the molar ratio of 1:1 in methanol, and 1 or 2 mol of plasmalogens was involved in the binding with iodine per iodine atom, resulting in the formation of stable iodine-binding phospholipids. The HPLC system with Diol column and acetonitrile/water as a mobile phase was available for separating iodine-binding phospholipids from nonbinding free iodine and for separately eluting iodine-binding phospholipids derived from choline and ethanolamine plasmalogens. Using iodine-125 reagent (1.85 MBq/ml), plasmalogens were detectable at high sensitivity of 10,000-15,000 cpm/nmol, which is more than 1000-fold higher sensitivity than the classical determination with nonradioactive iodine. Plasmalogen concentrations in human plasma were measured with the HPLC system and determined as, on average, 129.1+/-31.3 microM (n=8) in a 1.2 content ratio of choline to ethanolamine plasmalogens, a concentration that nearly agrees with the value reported previously.

Choline↗

PubMed1984

Circulatory clearance, internalization, and degradation of muscle AMP aminohydrolase.

Chicken muscle AMP aminohydrolase is cleared rapidly from the circulation of chickens after intravenous injection of the purified enzyme (Husic, H. D., and Suelter, C. H. (1980) Biochem. Biophys. Res. Commun. 95, 228-235). After the intravenous injection of unlabeled, 125I-labeled, or [14C]sucrose-labeled AMP aminohydrolase, enzyme activity and radioactivity are cleared at the same rates and concentrate in the liver and spleen. After injection of the [14C]sucrose-labeled enzyme, 14C is retained in the liver and spleen and low molecular weight 14C is recovered primarily in a fraction which cosediments with lysosomes when tissue homogenates are sedimented on sucrose density gradients. When liver cells are fractionated after clearance of [14C]sucrose-labeled enzyme, 14C is recovered primarily in the parenchymal cells. The circulatory clearance of AMP aminohydrolase is inhibited by heparin and other sulfated polysaccharides, but not by compounds which inhibit previously described carbohydrate-mediated systems for the uptake of circulatory glycoproteins. Heparin injection after the clearance of AMP aminohydrolase causes the release of the enzyme from the liver and spleen into the circulation. When heparin is injected at various times after clearance, decreasing amounts of enzyme are released with time; these results show that the enzyme is internalized with a half-life of 0.98 h.

AMP Deaminase↗

PubMed1997

[125I]IPH, an epibatidine analog, binds with high affinity to neuronal nicotinic cholinergic receptors.

An analog of epibatidine (EB) was synthesized with an iodine atom in the 2 position of the pyridyl ring. This analog, (+/-)-exo-2-(2-iodo-5-pyridyl)-7-azabicyclo[2.2.1]heptane (IPH), as well as its two stereoisomers, displayed high affinity for neuronal nicotinic receptors; therefore, radioiodinated IPH, [125I]IPH, was synthesized with specific radioactivities consistently > 1000 Ci/mmol, and its properties as a radioligand for neuronal nicotinic receptors were evaluated. The characteristics of [125I]IPH binding in tissue homogenates appeared to be virtually identical to those reported for [3H]epibatidine binding; but the high specific radioactivity of [125I]IPH greatly facilitated measurements of nicotinic receptors in tissues with relatively low receptor densities and/or where tissues are in limited supply. Autoradiography with [125I]IPH provided clear localization of nicotinic receptors in brain and adrenal gland after film exposure times of < or = 2 days. We conclude that [125I]IPH will be a very useful radioligand for the study of neuronal nicotinic receptors in brain and in peripheral ganglia.

Animals↗

PubMed1997

Behavior of Na131I and meta(131I) iodobenzylguanidine (MIBG) in municipal sewerage.

Behavior of 131I activity in primary sludge at the Ann Arbor, Michigan, Municipal Waste Water Treatment Plant was studied in relation to known radioiodine therapy events at the University of Michigan Hospital complex. The principal compounds administered are Na131I, which has widespread use, and meta (131I) iodobenzylguanidine (MIBG), which is a compound unique to the University of Michigan, although labeled antibodies and other forms are also used in therapy and research. The objectives of the study were to determine the environmental fate of such discharges and to determine radiation exposures to workers and the public when sludges are incinerated. Approximately 17% of the MIBG activity administered in a therapy was found in the primary sludge, whereas only 1.1% of the Na131I was in sludge. When land applied, the short half life of 131I in the sludge presents few radiological health concerns; however, incineration, which is done in winter months, is assumed to release organically bound 131I to the atmosphere. Radiation doses due to incineration of sludge containing measured concentrations were calculated for a maximally exposed worker to be 1.7 microSv (0.17 mrem) of which 0.48 microSv (0.048 mrem) was due to a 2-d upset condition. For a more typically exposed worker, and a member of the public, the committed effective dose equivalents were 1.2 microSv (0.12 mrem) and 0.06 microSv (0.006 mrem), respectively, for a 22-wk incineration period with release of all radioiodine in the sludge. Transport time to the treatment plant for radioiodine was found to be much longer than that of normal sewage, possibly due to organic material in sewer lines that absorb iodine. The residence time of radioiodine in the sewer also appears to be longer than expected; whether other radioactive materials are held up the same way is not known but chemical form is surely a factor.

3-Iodobenzylguanidine↗

PubMed1993

Pharmacokinetics, absorption, distribution and disposition of [125I]-defibrotide following intravenous or oral administration in the rat.

Defibrotide (D) was labelled with 125I. The radiolabelled compound ([125I]-Defibrotide ([125I]-D)) retained the same profibrinolytic activity as the parent drug. Following single intravenous administration of [125I]-D the half lives of radioactivity associated with D components in plasma were 9.45 min and 11.27 h for alpha and beta phases respectively. Following single oral administration of [125I]-D the half life of radioactivity associated with D components in plasma was 12.83 h for the elimination phase. Bioavailability was apparently 58%. The areas under plasma total radioactivity versus time curves were dose-dependent following both intravenous and oral administration. No significant accumulation of total radioactivity in plasma was observed following multiple oral administration of [125I]-D. Following single intravenous administration of [125I]-D a larger proportion of administered radioactivity was excreted via urine than faeces while following single oral administration excretion via urine and faeces accounted for similar proportions of administered radioactivity. Following both single and oral administration the levels of total radioactivity in tissues and organs examined were generally highest in highly perfused organs and were very high in the thyroid despite pretreatment with non-radiolabelled potassium iodide. Radioactivity was also found to be associated with the aorta wall.

Absorption↗

PubMed1989

[The evaluation of split renal function in the experimentally induced transient renal vein obstruction].

The split renal function was measured in order to evaluate the alteration of renal function secondary from transient renal vein obstruction. Three microcuries of I-131 Hippuran and 7 microCi of Tc-99m DTPA were injected into the femoral vein of adult male rats 30 min, 3 hr, 6 hr, 2 days and 1 week after the renal vein obstruction for 30 min. Blood samples were taken from the tail vein 5, 10, 15, 20 and 30 min after injection. Immediately after taking blood sample at 30 min, both kidneys and urinary bladder with ureters were taken. The radioactivities of Tc-99m and I-131 of these samples were measured respectively using a well type scintillation counter at the energy ranges of 140 KeV +/- 25% and 360 KeV +/- 25%. In the obstructed side, the blood clearances of I-131 Hippuran (ERPF) and Tc-99m DTPA (GFR) were decreased at 30 min and 6 hr after the release of left renal vein obstruction. Therefore the filtration fraction was not significantly changed. In conclusion, the single study using either Tc-99m DTPA or I-131 Hippuran may be enough to evaluate the alteration of split renal function in a model of renal vein obstruction, although the combined study using both agents is more preferable.

Animals↗

PubMed2002

The synthesis and radiolabeling of 2-nitroimidazole derivatives of cyclam and their preclinical evaluation as positive markers of tumor hypoxia.

UNLABELLED: The cyclam ligand (1,4,8,11-tetraazacyclotetradecane) was condensed with various azomycin-containing synthons to produce chemical compounds that could chelate radioactive metals. It was expected that these radiolabeled markers would become bound selectively to hypoxic cells on the bioreduction of their azomycin substituent. METHODS: The markers were radiolabeled with (99m)Tc, (67)Cu, or (64)Cu. Their uptake and binding to tumor cells in vitro was characterized as a function of time and oxygen concentration. These data defined the hypoxia-specific factor, the ratio of the initial rate of marker binding to severely hypoxic relative to aerobic cells. In addition, the concentration of oxygen (in the equilibrium gas phase) that inhibited binding to 50% of the maximum rate was determined. The in vivo biodistribution and clearance kinetics of the favorable markers were investigated with severe combined immune deficiency mice bearing EMT-6 tumors whose radiobiologic hypoxic fraction (RHF) was approximately 40%. The specific activity (percentage injected dose per gram [%ID/g]) in normal and tumor tissue and the tumor-to-blood and tumor-to-muscle ratios of the optimal markers were also measured for Dunning prostate carcinomas of anaplastic (RHF = 15%-20%) and well-differentiated (RHF < 1%) histology growing in Fischer X Copenhagen rats. Planar images were acquired with some markers from these tumor-bearing rats. RESULTS: The tumor uptake of these cyclam-based markers is approximately 10 times higher when they are labeled with copper isotopes than when labeled with (99m)Tc. FC-327 and FC-334, di-azomycin-substituted cyclams, exhibited hypoxia-specific factors > or = 7.0. The oxygen concentration that inhibited their binding to 50% of the maximal rate was approximately 0.5% O(2), similar to that of the radiobiologic oxygen effect. The %ID/g of (64)Cu-FC-334 retained in EMT-6 tumors in mice and in the anaplastic and well-differentiated prostate tumors in rats 6 h after administration was approximately 6.5, 0.4, and 0.1, respectively. Marker activity in tumor was always less than that in liver and kidney. The tumor-to-blood and tumor-to-muscle ratios of (64)Cu-FC-327 and (64)Cu-FC-334 activity in R3327-AT tumor-bearing rats are higher than those observed for (64)Cu-di-acetyl-bis (N(4)-methylthiosemicarbazone) and approach those of beta-D-(125)I-iodinated azomycin galactopyranoside, the optimal hypoxia marker of the azomycin-nucleoside class. CONCLUSION: These data suggest that some azomycin-cyclams exhibit good hypoxia-marking potential to tumor cells in vitro and to animal tumors of known RHF. Both PET and SPECT could be used to image tumor hypoxia with markers labeled with (64)Cu and (67)Cu, respectively.

Animals↗

PubMed2002

Pharmacokinetics and brain distribution in non human primate of R(-)[123I]DOI, A 5HT(2A/2C) serotonin agonist.

Our goal was to synthesize with high specific activity R(-)-1-(2,5-Dimethoxy-4-[123I]iodophenyl)-2-aminopropane [R(-)[123I]DOI], an in vitro potent and selective 5-HT(2A/2C) serotonin agonist, and study in vivo its plasma pharmacokinetics and brain distribution in baboon by SPECT. The purpose was to evaluate this radiotracer as a potential tool in discerning the role of the agonist high affinity state of 5-HT(2) receptors in depression and other neurological disorders. The radiotracer was prepared by electrophilic radioiodination of the N-trifluoroacetyl precursor of R(-)-1-(2,5-Dimethoxyphenyl)-2-aminopropane [R(-)DMA-TFA] with high-purity sodium [123I]iodide in the presence of chloramine-T, followed by amino deprotection with KOH in isopropanol (labeling yield: 73%, radiochemical yield: 62%, radiochemical purity: 99%). In vivo studies in baboon showed high accumulation of radioactivity in thalamus, the frontoparietal cortex, temporal, occipital and the striatum regions, with slightly lower accumulation in the midbrain and cerebellum. Ketanserin did not displaced the radioactivity in any of these brain regions. Plasma metabolite analysis was performed using methanol protein precipitation, the methanol fractions contained from 68% to 92% of the mixture of a labeled metabolite and parent compound. The recovery coefficient of unmetabolized R(-)[123I]DOI was 68%. The percent parent compound present in the extracted fraction, measured by HPLC, decreased gradually with time from 99.8% to 0.3% still present after 4.7 hours post injection whereas the percentage of the only one detected metabolite increased conversely. Free fraction determination (f(1)), was 31 +/- 0.9% (n = 3). For comparison purposes, ex-vivo brain distribution, displacement and metabolite analysis was also carried out in rodents. Although R(-)[123I]DOI displayed good brain uptake and localized in serotonergic areas of the brain, its target to non target ratio and its insensitivity to ketanserin displacement suggest high nonspecific uptake, therefore non potentially useful as brain imaging radiotracer for visualization of the agonist high-affinity state of 5-HT(2A) receptors and for visualizing 5-HT(2C) receptors by SPECT.

Amphetamines↗

PubMed1994

Strategy for boron neutron capture therapy against tumor cells with over-expression of the epidermal growth factor-receptor.

PURPOSE: Gliomas, squamous carcinomas and different adenocarcinomas from breast, colon and prostate might have an increased number of epidermal growth factor (EGF) receptors. The receptors are, in these cases, candidates for binding of receptor specific toxic conjugates that might inactivate cellular proliferation. The purpose of this study was to evaluate whether it is reasonable to try ligand-dextran based conjugates for therapy. METHODS AND MATERIALS: EGF or TGF alpha were conjugated to dextran and binding, internalization, retention and degradation of eight types of such conjugates were analyzed in EGF-receptor amplified glioma cells. The conjugates were labelled with radioactive nuclides to allow detection and two of the conjugates were carrying boron in the form of carboranyl amino acids or aminoalkyl-carboranes. Comparative binding tests, applying 125I-EGF, were made with cultured breast, colon and prostate adenocarcinoma, glioma and squamous carcinoma cells. Some introductory tests to label with 76Br for positron emission tomography and with 131I for radionuclide therapy were also made. RESULTS: The dextran part of the conjugates did not prevent receptor specific binding. The amount of receptor specific binding varied between the different types of conjugates and between the tested cell types. The dextran part improved intracellular retention and radioactive nuclides were retained for at least 20-24 h. The therapeutical effect improved when 131I was attached to EGF-dextran instead of native EGF. CONCLUSION: The improved cellular retention of the ligand-dextran conjugates is an important property since it gives extended exposure time when radionuclides are applied and flexibility in the choice of time for application of neutrons in boron neutron capture therapy (BNCT). It is possible that ligand-dextran mediated BNCT might allow, if the applied neutron fields covers rather wide areas around the primary tumor, locally spread cells that otherwise would escape treatment to be inactivated.

Adenocarcinoma↗

PubMed1976

Organic cation uptake in vitro by the rabbit iris-ciliary body, renal cortex, and choroid plexus.

The uptake in vitro of radioactively labeled test substances was studied in tissues from albino rabbits. Choroid plexus, slices of outer renal cortex, and iris-ciliary body were incubated in a K-rich medium containing one of the cations 14C-Emepronium (Cetiprin), 14C-tetraethylammonium, 14C-choline, or 125I-o-iodobenzyltrimethylammonium and sometimes the anions 131I-o-iodohippurate and 125I-iodipamide. Choroid plexus and renal cortex accumulated all test substances, some to very high tissue-medium ratios. The iris-ciliary body preparation accumulated the anions well but the organic cations only weakly. The only convincing uptake was that of Emepronium. The affinity of this uptake system seemed to be similar to that in the kidney, half-saturating around 10(-4)M Emepronium.

Animals↗

PubMed1997

Synthesis and tissue distribution of substituted [125I]iodophenylamine derivatives: possible brain imaging agents.

The synthesis and brain uptake in mice of the radioiodinated derivatives of N,N-dimethyl-N'-(iododimethoxyphenyl)-1,3-propanediamine, as well as the N-substituted derivatives of (iodoalkylphenyl)isopropyl, iodoalkylphenylethylamine and 3,4-(methylenedioxy)phenyl-amphetamine (MDA) are described. These compounds contain structural features of both IMP and HIPDM, the cerebral perfusion agents currently in clinical use. The radiolabeled analogs were obtained via the [125I]I exchange method, or by [125I]NaI treatment of the iodo-free precursor in the presence of an oxidant. Following intravenous injection in mice, all compounds showed important radioactivity concentrations in the lungs and kidneys. The N-substituted (iodoalkylphenyl)isopropyl and iodoalkylphenyl-ethylamine derivatives displayed a high initial brain uptake (> 10% IDg-1) followed by a rapid clearance phase, resulting in lower brain-to-blood ratios as those reported for IMP and HIPDM. In contrast, N,N-dimethyl-N'-(iododimethyphenyl)-1,3-propanediamine derivatives featuring the iodo substituent on the benzene carbon adjacent to the methyl amine group and the methoxy substituents on the 2,5- or 2,4-positions, showed low but more persistant brain uptake. Combined with fast blood clearance, this resulted in high brain-to-blood ratios at later time points. Among all compounds tested, the highest brain-to-blood ratio was observed with compound N,N-dimethyl-N'-(6-iodo-3,4-dimethyoxyphenyl)-1,3-propanediamine (27e), reaching a maximum of > 20 at 12 h post-injection.

Aniline Compounds↗

PubMed2001

Characterization of novel kidney-specific delivery system using an alkylglucoside vector.

The alkylglucoside vector has been demonstrated to be a kidney-specific drug delivery system via cell surface-specific binding sites. In the present study, we examined the targeting efficiency of this vector derivatized with several types of ligand to determine the efficacy and limitations of this system. The tissue uptake clearance in the kidney (CL(uptake, kidney)) of alkylglucoside-acylated poly-L-lysine conjugates (Glc-S-C8-APL) with a mol. wt. of 4,500, 17,000, or 41,000 was greater than that accounted for by glomerular filtration and was reduced by coadministration of n-octyl-thioglucoside, which has an affinity for alkylglycoside binding sites. The mol. wt. distribution, assessed by gel filtration high-performance liquid chromatography, of the radioactivity associated with the kidney after intravenous administration of Glc-S-C8-APL41000 was shifted to a lower mol. wt. range compared with the authentic compound. The CL(uptake, kidney) and specific binding of Glc-S-C8-APL, fractionated based on mol. wt., to kidney membrane fractions was reduced as the mol. wt. of the fractionated Glc-S-C8-APL increased. These results suggest that the target efficiency of this vector depends on the size of the ligand that it delivers. Both the CL(uptake, kidney) and specific binding to kidney membranes of an alkylglucoside-tyrosine conjugate (Glc-S-C8-Tyr) with an acidic charge was much lower than that of Glc-S-C8-Tyr with cationic and neutral charges, suggesting that the anionic moiety could reduce the renal targeting efficiency. Thus, the targeting efficacy of the alkylglucoside vector seems to depend on, at least, the size and charge of the ligand that it delivers.

Animals↗

PubMed1988

Evaluation of cyclosporine nephrotoxicity in rats with various renal radioactive agents.

The efficacy of different radiodiagnostic agents for demonstrating the decline in renal function from cyclosporine (CyA) nephrotoxicity was assessed in rats receiving a standard dose of the drug for 2 wk, compared with control rats. The agents included [99mTc]DTPA, [131I]hippuran, [111In]lysozyme, [99mTc]glucoheptonate (GHA), [99mTc]dimercaptosuccinate (DMS) and [111In]aminated dextran (amdex). A small dose of [99mTc]- or [111In]DTPA was administered simultaneously to normalize the results for variations in drug response from one animal to another. There were statistically significant differences in the detectability of the renal functional impairment by plasma clearance, early and 2-hr renal uptake among the different agents. However, none was clearly superior to DTPA. This conclusion is consistent with previous studies which showed a parallel decline in glomerular filtration rate (GFR) and effective renal plasma flow in acute CyA toxicity probably due primarily to vasoconstriction.

Animals↗

PubMed2004

Abnormal retention of 99mTc-TF in a hamster model of cardiomyopathy analyzed by 99mTc-TF and 125I-BMIPP autoradiography.

OBJECTIVE: Enhanced washout of 99mTc-tetrofosmin (TF) has been reported in patients with hypertrophic cardiomyopathy (HCM). Here, using quantitative dual-autoradiography, the relationship between TF retention abnormality and metabolism depicted by 125I-BMIPP uptake was investigated quantitatively in a hamster model of cardiomyopathy. METHODS AND RESULTS: Early and delayed TF images were obtained at 5 min (7 cardiomyopathic and 5 normal hamsters) and 60 min (8 cardiomyopathic and 5 normal hamsters) after injection, respectively. BMIPP image was obtained 5 min after injection. Five cardiomyopathic and 5 normal hamsters were evaluated histologically. Percent uptake of TF and BMIPP in the heart was measured by an auto-well counter. The left ventricular wall was divided into 12 segments, and the relative regional uptake of TF and BMIPP was measured for each segment. Heterogeneity of radioactive distribution was determined by the standard deviation (SD) of radioactive counts in the left ventricular wall on autoradiogram. The uptake of early TF, delayed TF, and BMIPP in cardiomyopathic hamsters was 8.8%, 20.3%, and 25.3% lower than that in normal hamsters, p < 0.05, p < 0.01, and p < 0.001, respectively. In normal hamsters, distribution of radioactivity in all images was homogeneous, and the SD values were about 13. In cardiomyopathic hamsters, heterogeneous distribution was observed on all images, and the degree of heterogeneity was marked on delayed TF and BMIPP images. The SD was 19.7 +/- 1.2 for early TF image, 25.5 +/- 1.4 for delayed TF image, and 31.7 +/- 2.4 for BMIPP image, respectively. A weak linear correlation was observed between the relative regional uptake of the delayed TF and BMIPP in cardiomyopathic hamsters (r = 0.57). Electron microscopy demonstrated ultra-structural changes in mitochondria of cardiomyopathic hamsters. CONCLUSION: Degree of retention abnormality on delayed TF image corresponded to the metabolic abnormality, probably due to mitochondrial dysfunction, depicted on BMIPP imaging.

Animals↗

PubMed1996

Nonlinearity correction of brain perfusion SPECT based on permeability-surface area product model.

UNLABELLED: It is well known that many cerebral perfusion tracers underestimate cerebral blood flow in high flow range. A model has been proposed to correct nonlinear relationship of flow and uptake of the tracers that accounts for the permeability-surface area product (PS model). METHODS: We examined 43 patients in this study. To test the feasibility of this method for 123I-IMP, 99(m)Tc-HMPAO and 99(m)Tc-ECD, radioactivity ratios of cerebral regions to cerebellum (C/Cr) on SPECT images were compared with those of rCBF (F/Fr) measured by PET using the 15O CO2 steady-state method. Coefficient for correction in the PS model was estimated by the least squares method, and SPECT data were corrected using these coefficients. RESULTS: Estimated PS value by this method was highest in IMP (116 ml/min/100 g) followed by ECD (66 ml/min/100 g) and HMPAO (46 ml/min/100 g). The corrected SPECT data demonstrated an excellent linear relationship, which was close to unity, with rCBF. CONCLUSION: These results indicate that the PS model can be used for nonlinearity correction of brain perfusion SPECT.

Adult↗

PubMed2006

Differential BBB interactions of three ingestive peptides: obestatin, ghrelin, and adiponectin.

Endogenous compounds, including ingestive peptides, can interact with the blood-brain barrier (BBB) in different ways. Here we used in vivo and in vitro techniques to examine the BBB permeation of the newly described satiety peptide obestatin. The fate of obestatin in blood and at the BBB was contrasted with that of adiponectin. By the sensitive multiple time-regression method, obestatin appeared to have an extremely fast influx rate to the brain whereas adiponectin did not cross the BBB. HPLC analysis, however, showed the obestatin result to be spurious, reflecting rapid degradation. Absence of BBB permeation by obestatin and adiponectin was in contrast to the saturable transport of human ghrelin reported previously. As a positive control, ghrelin showed saturable binding and endocytosis in RBE4 cerebral microvessel endothelial cells. By comparison, obestatin lacked specific binding and endocytosis, and the small amount internalized showed rapid intracellular degradation before the radioactivity was released by exocytosis. The differential interactions of obestatin, adiponectin, and ghrelin with the BBB illustrate their distinctive physiological interactions with the CNS.

Adiponectin↗

PubMed2000

Development of a fluorescent ligand-binding assay using the AcroWell filter plate.

One of the most powerful tools for receptor research and drug discovery is the use of receptor-ligand affinity screening of combinatorial libraries. Early work involved the use of radioactive ligands to identify a binding event; however, there are numerous limitations involved in the use of radioactivity for high throughput screening. These limitations have led to the creation of highly sensitive, nonradioactive alternatives to investigate receptor-ligand interactions. Pall Gelman Laboratory has introduced the AcroWell, a patented low-fluorescent-background membrane and sealing process together with a filter plate design that is compatible with robotic systems. Taken together, these allow the AcroWell 96-well filter plate to detect trace quantities of lanthanide-labeled ligands for cell-, bead-, or membrane-based assays using time-resolved fluorescence. Using europium-labeled galanin, we have demonstrated that saturation binding experiments can be performed with low-background fluorescence and signal-to-noise ratios that rival traditional radioisotopic techniques while maintaining biological integrity of the receptor-ligand interaction. In addition, the ability to discriminate between active and inactive compounds in a mock galanin screen is demonstrated with low well-to-well variability, allowing reliable determination of positive hits even for low-affinity interactions.

Cell Line↗

PubMed1985

Measurement of absorbed dose from radionuclide solutions mixed intimately with the FBX dosimeter.

Chemical dosimeters are used widely for accurate measurement of large radiation doses due to external beam irradiation from radionuclide sources and from particle accelerators. Their use for measurement of absorbed doses from radioactive solutions mixed in the dosimeter solution was reported as early as 1952, but the large activities needed to produce suitable absorbance values in the relatively insensitive dosimeters of that time discouraged further work. This manuscript reports the results of an investigation into the suitability of the ferrous sulfate-benzoic acid-xylenol orange (FBX) dosimeter for measurement of small absorbed doses caused by radionuclide solutions mixed with the dosimeter solution. The FBX dosimeter exhibited a linear dose response as a function of activity for two common radiopharmaceuticals, 99mTc sodium pertechnetate and 131I sodium iodide. Conditions under which the FBX dosimeter may be used with radionuclide solutions were studied and were found to be amenable to routine use by laboratories possessing relatively unsophisticated instrumentation. That any radionuclide could be studied using this dosimeter appears likely.

Benzoates↗