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PubMed1985

Microanalyses of beta-cyclodextrin in plasma by high-performance liquid chromatography.

Procedures for the micro-determination of beta-cyclodextrin (beta-CyD) in plasma were investigated by four methods using high-performance liquid chromatography (HPLC). In methods A and B, underivatized beta-CyD was detected with a refractive index detector and determined by the absolute calibration graph method. An NH2-bonded silica/acetonitrile-water system was used in A and a C18-bonded silica/methanol-water system in B. In method C, the percarbanilate of beta-CyD was separated on a C8-bonded silica column with acetonitrile-water and determined using gamma-CyD as the internal standard with a UV detector at 231 nm. In method D, the per[1-14C]acetate of beta-CyD was fractionated on a silica column with n-hexane-ethanol containing 1% of water and the radioactivity of each fraction was measured with a liquid scintillation counter. gamma-CyD was used as the internal standard. Interfering plasma proteins were removed by centrifugal ultrafiltration with an MPS-1 micro-partition system. Method B was superior to the other methods with respect to ease of sample preparation, sensitivity and time required for analysis. The cumulative amount of beta-CyD in the mesenteric vein absorbed from the rat intestinal lumen after administration of phenobarbital-beta-CyD complex in a closed loop method was determined by the use of method B.

Acetylation↗

PubMed1985

Monitoring radioactive compounds in high-performance liquid chromatographic eluates: fraction collection versus on-line detection.

This study compared two methods of monitoring radioisotopes in high-performance liquid chromatographic eluates (on-line radioactivity detector versus fraction collection and counting). Testing was accomplished by pumping solutions of tritiated water in acetonitrile--water mixture through the detector or to the fraction collector. At most solvent compositions, the detector's counting efficiency and detection limits were poorer than those of the scintillation counter. However, the reproducibility of the detector data was superior at acetonitrile concentrations of less than 50%. This was attributed to the difficulty in collecting fractions of small equal volumes at the lower organic solvent concentrations in short time intervals. We conclude that on-line monitoring with homogeneous detection is the preferred method for detecting radiolabeled compounds in high-performance liquid chromatographic eluates.

Chromatography, High Pressure Liquid↗

PubMed2003

Determination of simvastatin-derived HMG-CoA reductase inhibitors in biomatrices using an automated enzyme inhibition assay with radioactivity detection.

A robust, automated enzyme inhibition assay method was developed and validated for the determination of HMG-CoA reductase inhibitory activities in plasma and urine samples following simvastatin (SV) administration. The assay was performed on Tecan Genesis 150 and 200 systems equipped with 8-probe and 96-well plates. Plasma samples containing HMG-CoA reductase inhibitors were treated with acetonitrile for protein precipitation before being incubated with HMG-CoA reductase, [14C]-HMG-CoA, and NADPH for a fixed length of time at a fixed temperature. The product, [14C]-mevalonic acid, was lactonized and separated from excess substrate via a small ion exchange resin column, and radioactivity was counted on a scintillation counter. HMG-CoA reductase inhibitors were measured before and after base hydrolysis. The two values obtained for each sample are referred to as 'active' and 'total' HMG-CoA reductase inhibitor concentrations. Simvastatin acid (SVA), the beta-hydroxy acid of SV, was used as a standard to generate a calibration curve of HMG-CoA reductase activity versus SVA concentration (ng/ml). Three calibration ranges, 0.4-20, 2-50, and 50, 100 ng/ml, in human and animal plasma and urine were validated. The assay precision was less than 8.5%, CV in plasma and less than 10.4% in urine. The assay accuracy was 93.6-103.0 and 98.1-103.9% for the 0.4 20 and 2-50 ng/ml calibration ranges, respectively, in human plasma, and was 97.3-105.1, 94.4- 105.2, and 90.2-95.7%, for calibration range 5-100 ng/ml in rat plasma, dog plasma and human urine, respectively.

Animals↗

PubMed1997

A modified HPLC method for monensin analysis in liposomes and nanocapsules and its comparison with spectrophotometric and radioactive methods.

Monensin is a carboxylic ionophore which can potentiate the immunotoxin activity against human tumors in vitro and in vivo. Currently monensin is being encapsulated in liposomes and nanocapsules in our laboratory. The reported methods for monensin analysis by spectrophotometric and HPLC lack the required sensitivity. We have developed a sensitive HPLC method for analysis on monensin. Separation was achieved on a Beckman C18 reverse phase column with methanol-acetonitrile-methylene chloride-water-acetic acid (45:20:25:9.5: 0.5) as the mobile phase. The eluent was reacted with vanillin reagent in the post column reactor at 70 degrees C. The reagent reacted with monensin and formed a pink color, which was detected at 520 nm. The retention time of monensin was found to be 6 min. By using this method it was possible to quantify monensin down to 100 ng ml-1, with a signal to noise ration of > 17:1. Linearity was observed within the range of 10 to 100 ng (r2 > 0.99). Inter-day standard deviations for monensin samples of 20, 50 and 80 ng were 0.675, 0.543 and 0.736 respectively. Alternative methods of analysis include using radioactive [3H]monensin in liposomes which can be quantified by scintillation counter. The results from the HPLC, spectrophotometric and radioactive method were compared and were found to be within acceptable limits. The HPLC method is being utilized in our laboratory for quantitative analysis of monensin in liposomes and nanocapsules.

Capsules↗

PubMed2002

Determination of transport in the Caco-2 cell assay of compounds varying in lipophilicity using LC-MS: enhanced transport of Leu-enkephalin analogues.

PURPOSE: To synthesize a number of analogues of Leu-enkephalin with different lipophilicities and to develop an LC-MS method for determining the Caco-2 cell permeability values of these compounds. METHODS: A number of sugar and sugar plus lipoamino acid analogues of Leu-enkephalin were synthesized by solid-phase and solution methods. An LC-MS method was developed for analyzing the Caco-2 cell assay samples and validated against the traditional method using radiolabelled compounds. RESULTS: A sensitive and specific LC-MS assay was developed. Standard curves were linear in the range of 0.025-5 microM. Apparent permeability values determined by LC-MS and liquid scintillation counter were identical, for both a hydrophilic drug, cephalexin and a lipophilic Leu-enkaphalin analogue. Caco-2 permeability values for the analogues of Leu-enkephalin were determined and it was found that attachment of sugar or sugar and lipoamino acid to the Leu-enkephalin peptide resulted in an increase in the apparent permeability values compared to the native peptide, which was not transported across the Caco-2 cell monolayers. CONCLUSIONS: A rapid, generic LC-MS method for analyzing a range of compounds was developed. Attachment of a sugar or sugar and lipoamino acid to Leu-enkephalin improves the apparent permeability across Caco-2 cell monolayers.

Absorption↗

PubMedDate not supplied

Comparison of five antisecretory agents acting via gastric H+/K+-ATPase.

Lansoprazole(L), pantoprazole (P), rabeprazole and RO-18-5364 (RO) are new benzimidazole derivatives which rival omeprazole (O) as proton pump inhibitors (PPIs) for treatment of ulcer disease. In this study, we compared the effects of these compounds on acid secretion and determined their relative potencies in relation to their effect on [14C]-aminopyrine (AP) accumulation in isolated gastric glands. Inhibition of AP (1.2 microCi x mL(-1)) accumulation was measured in rabbit isolated gastric glands. dbcAMP (1 mmol; stimulant of acid secretion) and Ro 20-1724 (0.1 mmol; a phosphodiasterase inhibitor) were added to the Eppendorf tubes containing the PPIs and AP and dose-response curves were done for each drug after incubating for 5, 10 and 20 min at 37 degrees C and AP accumulation was determined using a scintillation counter. All the PPIs significantly (P < 0.001) inhibited acid secretion as demonstrated by the inhibition of AP accumulation in the isolated gastric glands. Minimum inhibition occurred at a concentration of 0.001 micromol for lansoprazole and omeprazole, 0.01 micromol for rabeprazole and RO 18-5364 and 0.02 micromol for pantoprazole. No differences were observed between PPIs with regards to the maximum inhibition they produce. When expressed as a percentage inhibition of control at 10-min incubation and at concentrations of 1 micromol, L showed 85.6 +/- 0.5, O 87 +/- 0.5, P 83.2 +/- 1.1, R 86.4 +/- 1.1 and RO 87.8 +/- 1.9 inhibition respectively. When comparing the IC50 values, their relative potencies were different. Maximum potency was shown by L (0.007 micromol) > O (0.012 micromol) > R (0.018 micromol) > RO (0.034 micromol) > P (0.050 micromol). All the new PPIs showed different potencies as inhibitors of acid secretion as evident from their IC50s. Extensive ulcer healing trials demonstrated comparable efficacy with a number of studies indicating that symptoms relief are more rapid with P and L, while in this study L appeared to be the most potent in inhibiting AP accumulation in the isolated gastric glands.

Aminopyrine↗

PubMed1989

Radio-immunoscintigraphy and intraoperative tumour detection by means of anti-tumour antibodies in patients with ovarian cancer.

A hand-held gamma-ray detection probe was developed by us to circumvent the problems of conventional radio-immunoscintigraphy (RIS). The intraoperative use of this probe in terms of radionuclide-assisted surgery (RAS) should help to overcome problems associated with insufficient accumulation by the tumour of the radio-active antibodies, unfavourable localization of tumour sites, collimation problems, etc., in patients with ovarian cancer. The probe was designed as a scintillation counter. Twelve patients were operated upon and investigated by RAS. It could be shown that RAS is able to detect tumour tissue intraoperatively, although we have already seen that improvements in the probe are necessary to make the method of real clinical value.

Antibodies, Monoclonal↗

PubMed2000

A multi-sample liquid scintillation counting system for weak beta-emitting samples with single phototube detectors

The relative merits of low-level liquid scintillation counters with one and two phototubes, respectively, are discussed and an analysis of their background components is presented. A simple and compact system with manual sample changing is described. It counts four samples simultaneously, and it is based on the single-phototube arrangement where conical vials sit on the top of 28 mm diameter phototubes. A PC computer collects and processes the pulses from a specially designed electronic unit. The system is operated in a small underground counting room, a closet in the wall of a road tunnel under a fjord. Its performance is described.

Journal Article↗

PubMed2001

Simultaneous measurement of 89Sr and 90Sr in aqueous samples by liquid scintillation counting using the spectrum unfolding method.

Two radiostrontium isotopes, 89Sr and 90Sr, were measured simultaneously by liquid scintillation counter coupling with a full spectrum DPM counting protocol. Strontium was separated from the aqueous media by extraction chromatography using Sr-spec resin. Individual count rates were evaluated from quench correlation curves for 89Sr and 90Sr related with SIS and tSIE quench indicators. The method exhibited a counting efficiency of 95% for 89Sr and 92% for 90Sr within their full energy channels and gave highly precise results when the sample was counted within 4 h after strontium separation. Lower limits of detection were 37 mBq/l for 90Sr and 32 mBq/l for 89Sr with a 60 min counting time.

Journal Article↗

PubMed2003

Coincidence system for standardization of radionuclides using a 4pi plastic scintillator detector.

A coincidence system using a plastic scintillator detector in 4pi geometry has been developed and applied for the standardization of radionuclides. The scintillator shape and dimensions have been optimized for maximum charge particle detection efficiency, while keeping background low and a nearly constant gamma-ray efficiency for different points from the radioactive source. The gamma-ray events were measured with a NaI(Tl) scintillation counter. The electronic system for processing pulses consisted of logic gates and delay modules feeding a time-to-amplitude converter with output to a multichannel analyzer. The alpha detection efficiency measured with 241Am was around 95% and the beta detection efficiency for 60Co was around 67%. Activity measurements of 241Am and 60Co were performed and the results showed good agreement when compared with a conventional coincidence system employing a 4pi proportional counter.

Journal Article↗

PubMed1997

Activity concentrations and population dose from radium-226 in food and drinking water in Taiwan.

The purpose of this study was to determine the radioactivity of 226Ra in environmental samples in Taiwan. Fish, pork, rice, flour, chicken, vegetable, milk, fruit, egg and water samples were collected and pretreated by radiochemical procedure to extract the 226Ra, and the activity concentrations of 226Ra were determined using a liquid scintillation counter. The 226Ra content of groundwater was 12.0 mBq l-1. The 226Ra contents of the food ranged from 0.02 Bq kg-1 fresh to 0.17 Bq kg-1 fresh. The annual internal dose from ingestion of 226Ra from food and drinking water per caput was evaluated to be 7.5 microSv.

Environmental Exposure↗

PubMed1998

Measurement standards for strontium-89 for use in bone palliation.

Strontium-89 standards have been prepared for use in calibrating instruments in the measurement chain from production in reactors to administration in the clinic or radiopharmacy. Alternate reactor production schemes were evaluated to yield high purity 89Sr with minimum 85Sr impurity. Following purification to remove radionuclidic impurities, samples of 89Sr were standardized by high-efficiency liquid-scintillation counting with a relative expanded uncertainty (intended to approximate two standard deviations) of 0.48%. A Standard Reference Material, SRM 4426A, was prepared and distributed to radiopharmaceutical manufacturers and other customers. The standard sources of 89Sr were used in different geometries to calibrate high purity Ge semiconductor detectors, re-entrant ionization chambers and commercial radionuclide calibrators. The latter included Capintec dose calibrators and the Capintec beta C NaI(Tl) scintillation counter.

Bone Diseases↗

PubMed1999

Distribution pattern of 90Sr and 137Cs in the Nile delta and the adjacent regions after Chernobyl accident.

Strontium and cesium contents in surface soil samples across the Nile Delta and the north coast of Egypt after the Chernobyl accident have been investigated. The concentration of 137Cs and 90Sr was determined using a high resolution gamma spectrometer based on hyperpure germanium detector (HPGe) and a liquid scintillation counter (LSC) respectively. 90Sr was determined through its decay product 90Y using Cerenkov counting. The determination of 90Sr was based on tributylphosphate (TBP) extraction of yttrium from nitric acid extract of ashed samples. The radioactivity of soils ranged between 18.5 and 2175 Bq/m2 with a mean of 652 Bq/m2 and 234 and 3129 Bq/m2 with a mean of 760 Bq/m2 for 137Cs and 90Sr respectively. An estimated absorbed dose equivalent due to the measured deposit of 137Cs was found to be 0.062 murem/h.

Cesium Radioisotopes↗

PubMed2002

Biodistribution study of [(123)I] ADAM in mice: correlation with whole body autoradiography.

Iodine-123 labeled 2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine ([(123)I] ADAM) has been suggested as a promising serotonin transporter (SERT) imaging agent. Much research has been accomplished, mainly focusing on the SERT binding sites in the central nervous system (CNS). However, the biodistribution of [(123)I] ADAM using whole body autoradiography (WBAR) has never been previously described, to the best of our knowledge. In this study, we assayed the biodistribution of [(123)I] ADAM in tissues/organs removed from mice, and measured their radioactivity with a scintillation counter (SC). The results showed that the liver has the highest uptake. On the other hand, the WBAR clearly demonstrated that [(123)I] ADAM was bound to SERT-rich sites including those in the brain stem, lung, adrenal glands and intestinal mucosa. This radiotracer also accumulated in the liver, kidney, and thyroid. The results from both methods were compared; each has its own complementary role in the biodistribution studies. The SC method revealed the total amount of radiotracer accumulation in each organ, and the WBAR demonstrated more anatomical details of the radiotracer's distribution. The whole body distribution results of the radioligand using both methods explore the usage of this novel radioligand for most possible SERT binding sites, not only in the CNS but also in the peripheral nervous system and neuroendocrine tissues. These findings suggest that [(123)I] ADAM is a potentially useful imaging agent for SERT.

Animals↗

PubMed2002

Effects of intrathecal injection of diatrizoate on dopamine receptors.

RATIONALE AND OBJECTIVES: The authors performed this study to determine whether adverse reactions similar to those that occur in patients receiving antipsychotic medication may occur after inadvertent intrathecal injections of some contrast material. MATERIALS AND METHODS: Recombinant human dopamine-2 (D-2) receptors were incubated together with tritiated (hydrogen 3) spiperone, a D-2 receptor agonist commonly used in binding studies, and three types of contrast material (sodium/meglumine diatrizoate; meglumine iothalamate; and iohexol) in different concentrations to determine competitive binding potentials. Nonspecific binding was also assessed. Membranes were washed, filtered, and counted in a scintillation counter. RESULTS: At several different concentrations, diatrizoate demonstrated a potential to displace the binding of spiperone to the D-2 receptors, whereas the other two contrast materials tested (iothalamate meglumine and iohexol) showed only weak binding potentials. CONCLUSION: Diatrizoate, which has been incriminated in most adverse reactions resulting from the inadvertent intrathecal injection of a contrast material, may produce symptoms similar to those of the neuroleptic malignant syndrome by blocking neurotransmission through dopamine receptors. Although antipsychotic drugs produce this parkinsonism-like effect only after prolonged use, it is probable that diatrizoate produces the effect immediately by virtue of the high concentrations that may accumulate at the base of the brain after myelography. Also worthy of note is the fact that the two other contrast materials that have produced a number of reported adverse reactions share a molecular similarity to diatrizoate that is not found with other contrast materials.

Animals↗

PubMed2001

Neutron dosimetric measurements in shuttle and MIR.

Detector packages consisting of thermoluminescence detectors (TLD), nuclear emulsions and plastic track detectors were exposed at identical positions inside MIR space station and on shuttle flights inside Spacelab and Spacehab during different phases of the solar cycle. The objectives of the investigations are to provide data on charge and energy spectra of heavy ions, and the contribution of events with low-energy deposit (protons, electrons, gamma, etc.) to the dose, as well as the contribution of secondaries, such as nuclear disintegration stars and neutrons. For neutron dosimetry 6LiF (TLD600) and 7LiF (TLD700) chips were used both of which have almost the same response to gamma rays but different response to neutrons. Neutrons in space are produced mainly in evaporation and knock-on processes with energies mainly of 1-10 MeV and up to several 100 MeV, respectively. The energy spectrum undergoes continuous changes toward greater depth in the attenuating material until an equilibrium is reached. In equilibrium, the spectrum is a wide continuum extending down to thermal energies to which the 6LiF is sensitive. Based on the difference of absorbed doses in the 6LiF and 7LiF chips, thermal neutron fluxes from 1 to 2.3 cm-2 s-1 are calculated using the assumption that the maximum induced dose in TLD600 for 1 neutron cm-2 is 1.6 x 10(-10) Gy (Horowitz and Freeman, Nucl. Instr. and Meth. 157 (1978) 393). It is assumed that the flux of high-energy neutrons is at least of that quantity. Tissue doses were calculated taking as a mean ambient absorbed dose per neutron 6 x10(-12) Gy cm2 (for a10 MeV neutron). The neutron equivalent doses for the above-mentioned fluxes are 52 micro Gy d-1 and 120 micro Gy d-1. In recent experiments, a personal neutron dosimeter was integrated into the dosimeter packages. First results of this dosimeter which is based on nuclear track detectors with converter foils are reported. For future measurements, a scintillator counter with anticoincidence logic is under development.

Cosmic Radiation↗

PubMed1997

A high-speed gated baseline restorer and its implementation in a blood cell volume analyser.

Accurate measurement of the height of individual pulses in a signal that is a.c.-coupled is dependent upon correcting a changing baseline to a constant value. A new fast baseline restorer, using internally triggered gated feedback with gain, has been designed and a version optimized for Gaussian-shaped pulses. Performance is dependent on the magnitudes of both the forward and the feedback gains. The design presented can achieve a 0.5% accuracy in pulse height for a minimum pulse width of 2.5 microseconds or for 5 microseconds overlapping pulses as long as the overlap is less than 50%. Typical applications for the baseline restorer include blood cell volume measurement systems, scintillation counters and radiation spectroscopy.

Biomedical Engineering↗

PubMed1980

Levels and location of adenosine 5'-triphosphate in bovine milk.

Bovine milk systems were analysed for adenosine 5'-triphosphate (ATP) using the luciferase-ATP reaction in a liquid scintillation counter. Approximately 0.2 mumol ATP/l milk serum were evident both in whole milks and the corresponding skim-milks. ATP was not detectable in skim-milk ultrafiltrates. These findings indicated that ATP was present in a non-dialysable portion of skim-milk. Centrifugation of whole milks from individual cows at 5500 g for 15 min at 10 degrees C yielded skim-milks essentially devoid of somatic cells and bacteria. However, the ATP in the skim-milks decreased by less than 20% compared with the whole milks indicating that the calcium phosphate-citrate (CPC)--caseinate micelles were the source of the ATP. ATP was not detectable in colloidal phosphate-free milk, from which CPC had been removed, confirming that the ATP was sequestered in the constituent CPC. Likewise, the occurrence of significant amounts of Mg, another potent stabilizer of amorphous calcium phosphate (ACP) in other biological systems, was confirmed in the colloidal phosphate of milk. From 0.13 to 0.31 mumole ATP/1 (mean 0.23) was found in the 9 milk samples studied. The discovery of small but appreciable levels of ATP in the CPC of milk provides further evidence for the analogy previously shown to exist between the CPC complex of milk and the ACP which accumulates in mitochondria. The latter has been postulated to provide an essential precursor for crystalline bone salts to form in ordered calcification processes. The implications of these findings in the biosynthesis of milk are briefly discussed.

Adenosine Triphosphate↗