SEARCH · Search PubMed

Results for “SCINTILLATION COUNTER”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources

PubMed1982

Determination of oxidative deterioration of milk powder and reconstituted milk by measurement of chemiluminescence.

A scintillation counter was used to measure chemiluminescence (CL) from milk powder and reconstituted milk. Only a small amount of CL, just above the background level, was observed from powders, but reconstituted milks emitted easily measurable CL. CL from milk was stimulated by exposure to light and found to decline gradually but non-exponentially after the exposure ceased. CL was at a maximum immediately after the milk was reconstituted from milk powder. Without light exposure, CL then declined gradually but non-exponentially over several hours to reach a constant value related to the level of oxidation of the powder. When determined under standard conditions 60 min after reconstitution, CL of milk reconstituted from stored milk powders correlated well with peroxide values and oxidized flavour as assessed by a taste panel.

Animals↗

PubMed2005

Measurement of cosmogenic 35S activity in rainwater and lake water.

Although cosmogenic 35S (t(1/2) = 87 d) has been found to be a unique and excellent radioactive tracer for stable S in atmospheric and aqueous environments, its application has been very limited because an analytical method for its detection has not been well-documented. Here, we report a rapid and robust method for analyzing extremely low levels of 35S in rainwater and lake water samples. About 20-L water samples were preconcentrated using an anion exchange column. The purified 35S was precipitated as BaSO4, and the precipitates were collected using a GF/B filter. The 35S in precipitates on the filter was directly counted using a super-low-background liquid scintillation counter with cocktail. We successfully measured 35S in precipitation and lake water samples using this method, which promises future diverse applications of the 35S tracer to S cycling in the environment and to age determination of lake water and shallow groundwater.

Journal Article↗

PubMed2006

Coating of poly(p-xylylene) by PLA-PEO-PLA triblock copolymers with excellent polymer-polymer adhesion for stent applications.

Poly(p-xylylene) (PPX) was deposited by chemical vapor deposition (CVD) on stainless steel substrates. These PPX films were coated by solution casting of poly(lactide)-poly(ethylene oxide)-poly(lactide) triblock copolymers (PLA-PEO-PLA) loaded with 14C-labeled paclitaxel. Adhesion of PLA-PEO-PLA on PPX substrate coatings was measured using the blister test method. Excellent adhesion of the block copolymers on PPX substrates was found. Stress behavior and film integrity of PLA-PEO-PLA was compared to pure PLA on unexpanded and expanded stent bodies and was found to be superior for the block copolymers. The release of paclitaxel from the biodegradable coatings was studied under physiological conditions using the scintillation counter method. Burst release of paclitaxel was observed from PLA-PEO-PLA layers regardless of composition, but an increase in paclitaxel loading was observed with increasing content of PEO.

Adhesiveness↗

PubMed2004

Absorption, distribution, and excretion of [14C]-3-chloro-4-methylaniline hydrochloride in two species of birds following a single oral dose.

Ring-labeled [14C]-3-chloro-4-methylaniline hydrochloride (250 microg per bird) was delivered to 21 red-winged blackbirds (Agelaius phoeniceus) and 21 dark-eyed juncos (Junco hyemalis) via oral gavage, and the distribution and excretion of radioactivity were determined at 15 and 30 min and 1, 4, 8, 12, and 24 h (n = 3 per time point). Direct measurement of radioactivity as well as measurement following combustion was accomplished using a liquid scintillation counter. Elimination from most tissues followed a two-compartment model, with very rapid elimination occurring between time 0 and 4 h and a much slower elimination phase occurring after that. The average half-life of elimination for the initial phase in most tissues examined was 0.16 h for juncos and 0.62 h for blackbirds. The average for the slower second phase of elimination was 3.4 h for juncos and 5.4 h for blackbirds. The radioactivity in blackbird kidney tissues did not change significantly for the duration of the test, pointing toward the kidney as a possible site of action for this important agricultural chemical.

Absorption↗

PubMed2002

An improved method to evaluate secretory activity of isolated gastric glands and cells.

The accumulation of [14C]aminopyrine (AP) is a valuable and widely used method to probe acid secretion of gastric glands and parietal cells. Usually, the dry weight of glands is used to normalize the AP accumulation ratio, and since the nonhomogeneity of the suspension makes it impossible to evenly distribute glands by simple pipetting, it is necessary to scrupulously dry and weigh each and every experimental sample. Thus, massive, time-consuming procedures of tube drying and weighing are involved. Moreover, the weighing of approximately 1 mg dried gland samples in a 1-g Eppendorf tube introduces considerable sample variance. Here, we present a modified protocol to simplify the AP accumulation method by introducing a generic 3H labeling of protein for normalization. Freshly isolated glands were treated with high specific activity 3H-labeled succinimidyl propionate (3H-succ, 60 Ci/mmol) for 10 min at room temperature during the normal isolation/washing procedure. This reagent reacts with primary amines, and even at normal cell pH the efficiency of reaction (25-30%) is more than adequate. The 3H-labeled glands are then processed normally with simultaneous monitoring of 3H (representing gland amount) and AP (representing the extent of acid accumulation) in separate energy windows of a liquid scintillation counter. Dose- and time-dependent efficiency of 3H labeling were evaluated. The relations between labeling and gland protein and dry weight were linear. No detrimental effects of reagent were noted in the useful range of 1-3 nM 3H-succ. Although some limited sample weighing or protein determination must be made for each batch of 3H-labeled glands, this method avoids massive tube weighings and provides the convenience of double label counting with a highly reproducible method for normalizing data.

Aminopyrine↗

PubMed2000

Effects of propofol on desipramine-sensitive [3H]-noradrenaline uptake kinetics in rat femoral artery.

BACKGROUND: The intravenous anaesthetic propofol inhibits the neuronal uptake of noradrenaline (uptake1) from the vascular sympathetic neuromuscular junction, resulting in an enhancement of the sympathetic neurotransmission. This could be important for maintenance of blood pressure during propofol anaesthesia. The aim of the present study was to determine how propofol influences the kinetics of uptake1. METHODS: Isolated segments of rat femoral arteries were incubated with [3H]-noradrenaline in the presence or absence of propofol and the radioactivity taken up was measured in a scintillation counter. The uptake1 inhibitor, desipramine, was used to delineate the specific neuronal uptake. RESULTS: Desipramine and 10 microM propofol significantly reduced the uptake in segments incubated with 0.1 microM [3H]-noradrenaline. Propofol at 1 microM and 100 microM did not affect the uptake. Non-linear regression analysis of specific uptake yielded Km 0.50 microM, Vmax 1.6 pmol mg(-1) 15 min(-1) and Hill coefficient 1.1. Propofol (1-10 microM) increased the Km value and propofol (10-100 microM) increased the Vmax value concentration-dependently, while the Hill coefficient was not affected. CONCLUSION: Propofol seems to have a biphasic effect on the uptake of noradrenaline in the vascular sympathetic neuromuscular junction. At lower propofol concentrations there is a decrease in the affinity of the noradrenaline transporters. The resulting uptake inhibition is counteracted at higher propofol concentrations by an increase in the efficacy of the uptake.

Adrenergic Uptake Inhibitors↗

PubMed2002

Acetylcholine receptor density in human cricopharyngeal muscle and pharyngeal constrictor muscle.

BACKGROUND: Upper esophageal sphincter resting tone is reduced during partial neuromuscular block, whereas contraction of the pharyngeal constrictor muscle is only slightly affected. We hypothesized that this difference may arise from differential nicotinic acetylcholine receptor (nAChR) density, the density supposedly being lower in the more sensitive cricopharyngeal muscle than in the resistant pharyngeal constrictor muscle. The aim of this study was to determine the density of nAChR in the main component of the upper esophageal sphincter, the cricopharyngeal muscle, and in the pharyngeal constrictor muscle. METHOD: After approval by the institutional ethics committee and informed consent, muscle specimens were obtained from five patients undergoing surgery with laryngectomy for malignancies of the larynx or thyroid gland. None had received radiation therapy to the affected area. The nAChR from these tissue specimens were solubilized and incubated with 125I-alpha-bungarotoxin. The quantity of radioligand-receptor complex was measured by radioactive decay in a liquid scintillation counter. The receptor density was expressed as femtomoles per milligram of protein (fmol/mg protein). RESULTS: The nAChR density was determined to 6.8 (3.5) fmol/mg protein (mean (SD)) in the cricopharyngeal muscle and 5.6 (2.1) fmol/mg protein in the pharyngeal constrictor muscle (P = 0.22). Although we could not find any difference in mean nAChR density, contrary to our hypothesis, the density in four of the five patients was higher in the cricopharyngeal muscle than in the pharyngeal constrictor muscle. CONCLUSION: Our results indicate that the density of nicotinic acetylcholine receptors is similar in the cricopharyngeal muscle and in the pharyngeal constrictor muscle. Nicotinic acetylcholine receptor density, as determined by 125I-alpha-bungarotoxin assay, cannot explain the difference in response to neuromuscular blocking drugs between the investigated muscles.

Humans↗

PubMed1999

Adherence of periodontopathic bacteria to bioabsorbable and non-absorbable barrier membranes in vitro.

Guided tissue regeneration (GTR) techniques are increasingly used for the treatment of periodontal defects, or in conjunction with dental implant procedures. As adhesion of bacteria to barrier membranes used in these techniques may lead to failure, a prerequisite for treatment success is an infection-free healing process. The present study examined the adhesion of 3 periodontal pathogenic bacteria: Actinobacillus actinomycetemcomitans, Treponema denticola and Porphyromonas gingivalis, to 3 barrier membranes: Collagen, (Biomend) PTFE, (TefGen-FD) and e-PTFE, (Gore-Tex). The membranes were incubated with 3[H]-thymidine labeled bacteria, and the number of adherent bacteria was calculated using a scintillation counter. The effect of albumin coating on bacterial adherence to the membranes was also studied. Bacterial adherence to the membranes was further examined by scanning electron microscopy (SEM). The results show that the adherence of all bacterial strains to collagen membranes was significantly higher than to the other membranes tested. Precoating of the membranes with albumin did not change the bacterial adherence significantly. These findings are of importance in evaluating the ability of periodontal bacteria to colonize and infect different types of barrier membranes.

Absorbable Implants↗

PubMed2002

Glutamate uptake is inhibited by tamoxifen and toremifene in cultured retinal pigment epithelial cells.

The systemic drugs chloroquine and tamoxifen have caused retinal defects in human eye. The aim of our study was to investigate the effects of the amphiphilic drug tamoxifen, of its homologue toremifene, and of chloroquine on the glutamate uptake in retinal pigment epithelial (RPE) cells. Cultured human RPE cell line D407 and pig RPE cells were used in the study. Glutamate uptake was characterised and the glutamate transporters of pig RPE cells and the human RPE cell line D407 were compared to each other. The uptake of glutamate was studied using L-[3H]glutamate as a tracer. The radioactivity in the solubilised RPE was measured with a liquid scintillation counter. In the uptake experiments, the cells were exposed to the test drugs, to the selected glutamate receptor antagonists, and to the glutamate transporter inhibitors. Both RPE cell types exhibited a high-affinity transport system for glutamate. The glutamate transporter in RPE exhibited features characteristic of the uptake systems of neurotransmitters. The transport was Na+-dependent, and L- and D-aspartate were transported into the cell by the same transporter. Chloroquine had no effect on glutamate uptake, but tamoxifen and toremifene decreased the glutamate uptake of RPE cells dose-dependently both in pig RPE cells and in human RPE cell line. The IC50 values of tamoxifen and toremifene were lower for pig RPE cells, compared to the human RPE cell line D407. The glutamate uptake was a sensitive target for the effects of tamoxifen and toremifene, and disturbances in this function could be considered as one of the possible mechanisms of retinal defects.

Animals↗

PubMed1992

Hydrated clearance of gadolinium-DTPA as a measurement of glomerular filtration rate.

Technetium (99mTc)-diethylene triamine pentaacetic acid (DTPA) hydrated clearance studies are accurate for determining GFR but require special facilities for handling and measuring samples. We investigated the potential of a non-radioactive paramagnetic analog, Gadolinium (Gd)-diethylene triamine pentaacetic acid (DTPA), an approved NMR contrast agent, as a glomerular filtration marker. Instead of relying on the radioactivity of technetium, this test is based on the fact that gadolinium induces alterations in the NMR T1 relaxation times in blood and urine samples. Ninety patients underwent simultaneous determinations of GFR using 1 mCi of Tc-DTPA and 0.05 mmol/kg Gd-DTPA (Berlex Labs) IV. The patients were hydrated with oral and intravenous fluid. Following a one hour equilibrium period, three or four consecutive urine collections were obtained; plasma samples were acquired at the beginning and end of each approximately 20-minute interval. 99mTc-DTPA radioactivity was determined with a scintillation counter. T1 relaxation times were measured on a 10 MHz NMR spectrometer. These were converted to Gd-DTPA concentration by comparison with standard solutions. The Gd-DTPA derived GFR closely approximated the 99mTc-DTPA derived GFR which ranged from 15 to 147 ml/min. The equation and correlation coefficient of the regression line is y = 1.04 x -2.2, r = 0.94. Thus, Gd-DTPA is a safe, non-radioactive indicator of GFR that may provide an alternative renal clearance method for clinical studies of progressive renal disease and nephrotoxicity.

Contrast Media↗

PubMed1983

Body composition comparison in two elite female wheelchair athletes.

It was the purpose of this study to determine body composition by two methods in two excellent female athletes. One sportswoman (SRH) was national wheelchair marathon champion in 1977 in 3 hours, 40 minutes on the Boston course. She still competes internationally and has won three gold medals and set three world records in the last Olympiad for the handicapped in 1980. The second woman athlete (LSJ) competes in wheelchair basketball and track on a national level. Body density was determined by the standard underwater weighing procedure and residual volume determination. A second method to calculate cellular body mass was the measure of potassium 40 (40K) activity by whole body scintillation counter. The characteristics of these athletes are listed as follows: (formula; see text) The results show that both methods of determining adiposity produce results differing by only one percentage point. It is important to determine body composition in these wheelchair athletes since their cellular body mass is decreased because of their disability.

Adipose Tissue↗

PubMed2002

Uptake and localisation of mTHPC (Foscan) and its 14C-labelled form in normal and tumour tissues of the hamster squamous cell carcinoma model: a comparative study.

The aim of this study was to evaluate the pharmacokinetics of meta(tetrahydroxyphenyl)chlorin (mTHPC) on different tissues of interest in a hamster tumour model and to confirm our earlier animal studies on semi-quantitative fluorescence microscopy. The results obtained by three different evaluation methods were compared: in vivo spectrofluorometry, ex vivo fluorescence microscopy and chemical extraction of (14)C-labelled mTHPC. Following intracardiac injection of 0.5 mg kg(-1) mTHPC, groups of five tumour-bearing animals were used for in situ light-induced fluorescence spectroscopy. Afterwards, the biopsies were taken and snap frozen for fluorescence microscopy. The presence of radioactivity in serum and tissues was determined after chemical digestion in scintillation fluid using a scintillation counter. For each analysed tissue, a good correlation was observed between the three evaluation methods. The highest fluorescence intensity and quantities of mTHPC were observed between 12 and 24 h in liver, kidney, serum, vascular endothelium and advanced neoplasia. The majority of mTHPC was found at around 48 h in smooth muscle and at 96 h in healthy cheek pouch mucosa and early malignant lesions. The lowest level of mTHPC was noted in striated muscle at all times. No selectivity in dye localisation was observed between early squamous cell carcinoma and healthy mucosa. Soon after the injection, a significant selectivity was noted for advanced squamous cell carcinoma as compared to healthy cheek pouch mucosa or striated muscle. A significant difference in mTHPC localisation and quantity was also observed between striated and smooth muscle during the first 48 h following the injection. Finally, this study demonstrated the usefulness of non-invasive in situ spectroscopic measurements to be performed systematically prior to photodynamic therapy as a real-time monitoring for each treated patient in order to individualise and adapt the light dosimetry and avoid over or under treatments.

Animals↗

PubMed1999

Stimulation of collagen production in an in vitro model for Peyronie's disease.

AIMS OF THIS STUDY: This study evaluated whether human cavernosal myofibroblasts in cell culture is a viable model for the study of the role of oxygen free radicals in the production of collagen types I and III, as observed in Peyronie's disease. METHOD: Human cavernosal cells in primary culture were incubated with 3H-proline in the absence or presence of (i) glyceraldehyde; (ii) alpha-tocopherol (vitamin E); (iii) a combination of the two; or (iv) gamma interferon alone or in combination with glyceraldehyde. Collagen production was monitored after precipitation by specific monoclonal antibody and quantitated using a scintillation counter. RESULTS: Collagen type III was stimulated to higher than baseline values after doses of 10 and 100 microM glyceraldehyde was added and showed suppression of stimulation with incorporation of alpha-tocopherol. There was a 40% increase in collagen type III production as compared to baseline values in glyceraldehyde-treated cells. Collagen type I showed no consistent stimulation or suppression. In glyceraldehyde-stimulated transformed caveronsal cells, alpha-tocopherol treatment caused a 10-60% decrease in collagen type I and III production. With the addition of 100,000 IU/ml gamma interferon, a significant reduction of both collagen types I and III was observed. CONCLUSIONS: The generation of oxygen radicals is associated with the stimulation of collagen production in cavernosal cells. Transformed fibroblasts from cavernosal cells in culture can be utilized to explore possible etiologies of Peyronie's disease and to further evaluate potential medical therapies for this pathological condition.

Cells, Cultured↗

PubMed1990

Determination of low-energy beta-emitter radionuclides deposited on surfaces by attapulgite treatment.

A method for the determination of surface contamination of various materials by 3H and 99Tc is reported. Both 3H and 99Tcm are widely used in chemical and clinical applications. The isotopes 99Tc, the decay product of 99Tcm, and 3H are soft beta-emitter radionuclides and the use of unsealed sources can frequently produce contamination and excessive internal dosing for workers. The removal of radionuclides from surfaces was effected with attapulgite, a clay with a high absorption capacity for many organic and inorganic substances. The determination was carried out by extracting the absorbed radionuclide from the clay and then measuring it in a beta-scintillation counter. The determination limits of the method, 20 Bq cm-2 for 3H and 100 Bq cm-2 for 99Tc, are below the "derived working limits" for these radionuclides.

Magnesium↗

PubMed1994

Investigation of Charm Test II receptor assays for the detection of antimicrobial residues in suspect meat samples.

Charm Test II receptor assays for beta-lactams, sulfonamides, (dihydro)streptomycin and erythromycin were applied to 257 bovine muscle and kidney samples, and 215 porcine muscle and kidney samples collected from animals suspected to contain antimicrobial residues. The assays were run in conjunction with Agriculture and Agri-food Canada's routine diagnostic confirmation analyses for suspect samples collected at federally inspected packing plants. All samples were subjected to the Charm Test II receptor assays and thin layer chromatography-bioautography (TLC-BA). Selected samples were quantitatively analysed using a liquid chromatographic method for penicillin G and a thin layer chromatography-fluorescence densitometry (TLC-FD) method for sulfonamides. The Charm Test II assays for beta-lactams, (dihydro)streptomycin and erythromycin were an acceptable alternative to the TLC-BA screen for laboratory confirmation of the presence of these compounds, with enhanced sensitivity for (dihydro)streptomycin and erythromycin. In addition, the Charm Test II provided a sensitive screen for sulfonamides as confirmed by the standard TLC-FD procedure. The analysis time, laboratory space and analyst time required to complete the Charm Test II assays is less than that for TLC-BA. Operating costs are similar for both analyses, but the Charm Test II does require capital expenditure for a scintillation counter.

Agriculture↗

PubMed2002

The effect of sevoflurane on glutamate release and uptake in rat cerebrocortical presynaptic terminals.

BACKGROUND: Volatile anaesthetics exert their effect in the brain mainly by reducing synaptic excitability. Isoflurane abates excitation by reducing the release and increasing the uptake of transmitter glutamate into the presynaptic terminal. The exact molecular mechanisms exerting these effects, however, are not clear. Voltage-gated calcium channels have been proposed as the pharmacological target. The present study examines the effect of sevoflurane on synaptic glutamate release and free cytosolic calcium and the effect on high- and low-affinity uptake of L-glutamate using isolated presynaptic terminals prepared from rat cerebral cortex. METHODS: Released glutamate was measured fluorometrically in a spectrophotometer as the fluorescence of NADPH and calcium as the fluorescence of fura-2. 4-aminopyridine was used to induce membrane depolarization. Glutamate uptake was measured in a series of different concentrations of L-glutamate corresponding to the high- and the low- affinity uptake systems adding a fixed concentration og radiolabelled glutamate. The labelling was measured by counting disintegrations per min in a beta-scintillation counter. RESULTS: Sevoflurane reduced the calcium-dependent glutamate release in a dose-dependent manner as sevoflurane 1.5, 2.5 and 4.0% reduced the release by 58, 69 and 94%, respectively (P<0.05). Membrane depolarization induced an increase in free cytosolic calcium by 25%. Sevoflurane did not affect this increase. Neither the high- nor the low-affinity uptake transporter systems are affected by the anaesthetic. CONCLUSION: These results indicate that different volatile anaesthetics may act differently on the presynaptic terminal. The exact modes of action have to be further investigated.

Anesthetics, Inhalation↗

PubMed1998

In vitro bacterial adherence onto pellicle-coated aesthetic restorative materials.

Adhesion of oral bacteria to teeth and restorative materials plays an important role in the pathogenesis of oral diseases. This study investigated the initial adhesion of Streptococcus mutans to enamel and restorative materials. Three types of composites and two types of glass ionomer cements were used. The specimens were coated with freshly collected human parotid saliva. The salivary coated samples were incubated with cell-free glucosyltransferase, and further incubated with sucrose solution. Finally, the specimens were incubated with 3H-thymidine labelled bacteria. Adhesion of the bacteria to the specimens was measured by scintillation counter. SEM observations were performed on each sample. The results showed no significant differences among the materials and the control. These findings can be explained by the pellicle which coated all the specimens. This biofilm, to which the bacteria were adhered and proved to probably masked existing surface properties of the specimens resulting in similar bacterial adhesion.

Adult↗

PubMed2003

Concentration gradient of oxalate from cortex to papilla in rat kidney.

BACKGROUND: The kidney eliminates the major fraction of plasma oxalate. It is well known that oxalate is freely filtered by glomeruli and secreted by the proximal tubules. However, the renal handling of oxalate in distal nephrons, which is considered as playing an important role in stone formation, remains obscure. METHODS: At 15-180 min after intravenous injection of 14C-oxalate to rats, the intrarenal localization of radioactivity was quantitatively measured by the radioluminographic method using a bioimaging analyzer. Tissue radioactivity was compared with plasma, and urinary radioactivities were measured by a liquid scintillation counter. The control study was conducted with 14C-inulin. RESULTS: The radioactivity of 14C-oxalate in the papilla was 10 times greater than in the cortex and eight times greater than in the medulla 180 min after injection when almost no radioactivity was present in the urine. In contrast, the radioactivity of 14C-inulin was nine times less in the papilla than in the cortex at the same time. CONCLUSION: Oxalate remains in the renal papilla for an extended period. This accumulation of oxalate may be attributed to calcium oxalate crystal fixation along the deep nephron which is considered to be the first step of stone formation.

Animals↗