Search PubMed⌕ Search

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.

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

At least 577 records · Page 32Linked to original sources
PubMed2000

Hematin polymerization assay as a high-throughput screen for identification of new antimalarial pharmacophores.

Hematin polymerization is a parasite-specific process that enables the detoxification of heme following its release in the lysosomal digestive vacuole during hemoglobin degradation, and represents both an essential and a unique pharmacological drug target. We have developed a high-throughput in vitro microassay of hematin polymerization based on the detection of (14)C-labeled hematin incorporated into polymeric hemozoin (malaria pigment). The assay uses 96-well filtration microplates and requires 12 h and a Wallac 1450 MicroBeta liquid scintillation counter. The robustness of the assay allowed the rapid screening and evaluation of more than 100, 000 compounds. Random screening was complemented by the development of a pharmacophore hypothesis using the "Catalyst" program and a large amount of data available on the inhibitory activity of a large library of 4-aminoquinolines. Using these methods, we identified "hit" compounds belonging to several chemical structural classes that had potential antimalarial activity. Follow-up evaluation of the antimalarial activity of these compounds in culture and in the Plasmodium berghei murine model further identified compounds with actual antimalarial activity. Of particular interest was a triarylcarbinol (Ro 06-9075) and a related benzophenone (Ro 22-8014) that showed oral activity in the murine model. These compounds are chemically accessible and could form the basis of a new antimalarial medicinal chemistry program.

Animals↗
PubMed1978

Effect of chemoattractants on chemiluminescence.

Upon ingestion of particulate matter, polymorphonuclear leukocytes produce a chemiluminescence that can be measured in a liquid scintillation counter. In the experiments reported here, the influence of three chemoattractants and three chemotactic modulators upon the chemiluminescence induced by opsonized zymosan was studied. The chemoattractants investigated (including bacterial factor derived from Escherichia coli, the simple peptide formylmethionylalanine, and activated human complement), which initiate directed movement when presented to cells in a concentration gradient, significantly enhanced zymosan-induced chemiluminescence. In the absence of opsonized zymosan, however, they had no effect on the chemiluminescence response. In contrast, the chemotactic modulators studied (including carbamylcholine, phenylephrine, and cyclic guanosine 5'-monophosphate, which are not chemotactic by themselves but can enhance or depress the movement of polymorphonuclear leukocytes initiated by chemoattractants) produced no enhancement of chemiluminescence. Other experiments were carried out in which neutrophils were pretreated with cytochalasin D, a compound that inhibits phagocytosis by interacting with microfilaments. Under these conditions, the chemiluminescence induced by opsonized zymosan was markedly reduced, but the response resulting from the addition of a chemoattractant to the leukocyte/zymosan mixture was not. This indicates that the chemiluminescence in response to chemoattractants is not dependent on phagocytosis per se. Neutrophils were also pretreated with dinitrofluorobenzene, a compound that binds amino groups and can be expected to react with proteins on the cell membrane. In these experiments, the chemiluminescence induced by opsonized zymosan and the pronounced spike of activity produced by the addition of a chemoattractant were completely abolished. These results suggest that the polymorphonuclear leukocyte chemiluminescence response to chemoattractants is mediated by cell surface proteins. Thus, chemoattractants may have a dual role in the acute inflammatory response: (i) the initiation and maintenance of directed cell movement, and (ii) enhancement of metabolic steps mediated at the cell membrane, resulting in microbicidal activity.

Bacterial Physiological Phenomena↗
PubMed2001

Adherence properties of Staphylococcus aureus under static and flow conditions: roles of agr and sar loci, platelets, and plasma ligands.

Global regulatory genes in Staphylococcus aureus, including agr and sar, are known to regulate the expression of multiple virulence factors, including cell wall adhesins. In the present study, the adherence of S. aureus RN6390 (wild type), RN6911 (agr), ALC136 (sar), and ALC135 (agr sar) to immobilized fibrinogen, fibronectin, von Willebrand factor (vWF), extracellular matrix (ECM), and human endothelial cells (EC) EAhy.926 was studied. Bacteria grown to postexponential phase were subjected to light oscillation (static condition) or to shear stress at 200 s(-1) (flow condition) on tissue culture polystyrene plates coated with either protein ligands, ECM, or EC. Adherence of nonlabeled bacteria to immobilized ligands was measured by an image analysis system, while adherence of [(3)H]thymidine-labeled S. aureus to ECM and EC was measured by a beta-scintillation counter. The results showed increased adherence of agr and agr sar mutants to immobilized fibrinogen and higher potential of these mutants to induce platelet aggregation in suspension, decreased adherence of sar and agr sar mutants to immobilized fibronectin and vWF as well as to ECM and EC, increased adherence of both S. aureus wild type and sar mutant to EC treated with platelet-rich plasma (PRP) compared to platelet-poor plasma (PPP) and to EC treated with PPP compared to the control, and increased adherence of S. aureus wild type to EC coated with PRP in which platelets were activated with phorbol 12-myristate 13-acetate compared to intact PRP. This finding paralleled the increased adherence to EC of activated compared to intact platelets. It is suggested that platelet-mediated S. aureus adherence to EC depends on platelet activation and the number of adherent platelets and available receptors on the platelet membrane. In conclusion, the agr locus downregulates S. aureus adherence to fibrinogen, while the sar locus upregulates S. aureus adherence to fibronectin, vWF, ECM, and EC. The effect of both agr and sar on S. aureus adherence properties develops primarily under flow conditions, which suggests different adhesion mechanisms in static and flow conditions.

Animals↗
PubMed1971

Microbial life at 90 C: the sulfur bacteria of Boulder Spring.

The physiology of the bacteria living in Boulder Spring (Yellowstone National Park) at 90 to 93 C was studied with radioactive isotope techniques under conditions approximating natural ones. Cover slips were immersed in the spring; after a fairly even, dense coating of bacteria had developed, these cover slips were incubated with radioactive isotopes under various conditions and then counted in a gas flow or liquid scintillation counter. Uptake of labeled compounds was virtually completely inhibited by formaldehyde, hydrochloric acid, and mercuric bichloride, and inhibition was also found with streptomycin and sodium azide. The water of Boulder Spring contains about 3 mug of sulfide per ml. Uptake of labeled compounds occurs only if sulfide or another reduced sulfur compound is present during incubation. The pH optimum for uptake of radioactive compounds by Boulder Spring bacteria is 9.2, a value near that of the natural spring water (8.9). Many experiments with a variety of compounds were performed to determine the temperature optimum for uptake of labeled compounds. The results with all the compounds were generally similar, with broad temperature optima between 80 and 90 C, and with significant uptake in boiling (93 C) but not in superheated water (97 C). The results show that the bacteria of Boulder Spring are able to function at the temperature of their environment, although they function better at temperatures somewhat lower. The fine structure of these bacteria has been studied by allowing bacteria in the spring to colonize glass slides or Mylar strips which were immediately fixed, and the bacteria were then embedded and sectioned. The cell envelope structure of these bacteria is quite different from that of other mesophilic or thermophilic bacteria. There is a very distinct plasma membrane, but no morphologically distinct peptidoglycan layer was seen outside of the plasma membrane. Instead, a rather thick diffuse layer was seen, within which a subunit structure was often distinctly visible, and connections frequently occurred between this outer layer and the plasma membrane. The thick outer layer usually consisted of two parts, the outer part of which was sometimes missing. Within the cells, structures resembling ribosomes were seen, and regions lacking electron density which probably contained deoxyribonucleic acid were also visible.

Acetates↗
PubMed1984

Etiological diagnosis of influenza A virus by enzymatic radioimmunoassay.

An enzymatic radioimmunoassay for influenza A virus was developed by using polystyrene beads coated with rabbit immunoglobulin G to capture viral hemagglutinins (H1 and H3). Captured hemagglutinin was detected with goat immunoglobulin G followed by affinity-purified rabbit anti-goat immunoglobulin G labeled with alkaline phosphatase. [3H]AMP was added to quantify alkaline phosphatase activity, and free [3H]adenosine was measured with a scintillation counter. The assay detected as little as 0.1 ng of purified hemagglutinin. It was specific for hemagglutinin subtype and, depending on the source of the goat immunoglobulin G used, detected either H1 or H3. There was no reaction with neuraminidase or core antigens of influenza strain WSN-33. The clinical efficacy of the assay was evaluated with sequential nasal washes from 33 patients with naturally acquired H1N1 influenza. In the first 3 days of infection, the assay was consistently less sensitive than the viral culture, although detectable antigen persisted in secretions longer than did the infectious virus. Testing of multiple samples greatly increased the number of individuals in whom an etiological diagnosis could be made by immunoassay (81% of patients were positive for viral antigens at some point in their illness), and such testing was necessary to achieve the sensitivity of a single culture. Mean antigen levels were highest in nasal washes with the highest titers of infectious virus.

Animals↗
PubMed1996

Effects of the cytokines on the proliferation of and collagen synthesis by human cataract lens epithelial cells.

AIMS: To assess the effects of the cytokines, interleukin-1 (IL-1), IL-1 receptor antagonist (IL-1ra), transforming growth factor-beta 2 (TGF-beta 2) and basic fibroblast growth factor (b-FGF), on the mitosis of and collagen synthesis by lens epithelial cells (LECs) of human cataracts. METHODS: The anterior lens capsule with attached LECs was obtained by capsulotomy during cataract surgery and cultured. The cultures at 2 to 3 weeks before confluency were used for the experiments. To quantify the mitosis and collagen synthesis, the incorporation of 3H-thymidine and 3H-proline, respectively, into the LECs was measured by a scintillation counter at 48 hours and 24 hours, respectively, after addition of the cytokine at various concentrations into the incubation medium. RESULTS: IL-1 and b-FGF increased the mitosis and collagen synthesis significantly, but IL-1ra significantly decreased the mitosis while leaving the collagen synthesis intact. TGF-beta 2 decreased the mitosis significantly, but increased the collagen synthesis significantly. CONCLUSION: These cytokines may play an important role in an autocrine or paracrine pathway in the proliferation of residual LECs after cataract surgery. Elucidation of the role of these cytokines may lead to the development of new therapies for the prevention of secondary cataract.

Adult↗
PubMed2001

Effect of ABO blood group mismatching on corneal epithelial cells: an in vitro study.

AIM: To determine, in vitro, the effects of blood group ABO mismatching on corneal epithelial cells. METHODS: Corneal epithelial cell cultures were established from 32 human cadaver donor eyes. Epithelial cells (100 microl of 4 x 10(2) cells per microl) were incubated for 4 hours with antibodies against blood group antigens A, B, and AB, with and without complement. Cell lysis was assayed by a chemiluminescent assay using Cytolite reagent. Live cells, remaining after incubation, were counted in a scintillation counter. The blood group of the donors was determined retrospectively, in a blinded manner. RESULTS: Retrospective tracing of donor blood groups was possible for 20 donors. In all cases the blood group corresponded with that suggested by the cell lysis assay. Significant cell lysis was observed when known A group cells were incubated with anti-A and anti-AB antibody, B group cells were incubated with anti-B and AB antibody, and AB group cells were incubated with anti-AB antibody. Lysis occurred only in the presence of complement. No lysis of O group cells was observed with any of the antibodies. In all cases, lysis was observed only with neat (serum) antibody concentrations. CONCLUSIONS: Blood group ABO mismatching results in significant lysis of corneal epithelial cells. The antibody concentration required for lysis equals that found in serum. Such levels of antibody are unlikely to be achieved in tears and/or aqueous. This may offer an explanation for the conflicting reports of the studies on the effect of blood group matching on corneal grafts. The variability in the outcome may reflect the levels of antibodies gaining access to the corneal cells and not the mismatching alone.

ABO Blood-Group System↗
PubMed1970

Use of radioactive fibrinogen for detecting rejection of human renal transplants.

Radioactive (125)I-labelled human fibrinogen was given to 11 recipients of cadaveric renal transplants and the radioactivity of the transplant was measured with a scintillation counter. In the six patients with no increase in radioactivity over the transplants there was no evidence of rejection. The five patients with an increased transplant radioactivity all had other evidence of rejection at that time. In one patient the test detected rejection in the absence of any other signs, and this result was afterwards confirmed by renal biopsy. The test in one patient was invalidated by haemorrhage occurring from the site of a renal biopsy, and other possible errors in the test may arise.It is suggested that the technique may have particular value in recipients with delayed function of their transplants, but may also be useful in patients with functioning transplants in helping to confirm the diagnosis of rejection suspected on other grounds.

Adolescent↗
PubMed1969

Simplified placental localization.

Localization of the placenta by means of technetium-99m and a portable scintillation counter and ratemeter proved to be both simple and accurate. It could be performed by resident obstetric staff with minimal technical knowledge, and the radiation dosage was low.

Female↗
PubMed1993

Thallium poisoning. Diagnosis may be elusive but alopecia is the clue.

Thallium is a heavy metal whose salts are used in some rodent poisons and in the manufacture of optical lenses, semiconductors, scintillation counters, low temperature thermometers, and switching devices, green coloured fireworks, and imitation jewelery, and as chemical catalysts. In clinical practice thallium isotopes are used in cardiac scanning, but the use of thallium salts to treat scalp ringworm was abandoned earlier this century because of their toxicity. The sale of thallium in Britain is strictly licensed because of its toxicity and potential for use in murder, which is helped by the fact that thallous salts are colourless, tasteless, and odorless. The more water soluble salts (such as thallium sulphate, acetate, or carbonate) have higher toxicity, and although the toxic dose is variable most deaths occur after the ingestion of 10-15 mg/kg of soluble salt. Most cases of thallium toxicity occur after oral ingestion but severe toxicity has been reported after inhalation of contaminated dust from pyrite burners, in zinc and lead smelting, and in the manufacture of cadmium, after dermal absorption through protective rubber gloves, and after snorting what was thought to be cocaine. The elimination half time of thallium is between 1.7 and 30 days depending on the time since, and chronicity of, ingestion. The elimination time phases are apparent and because of the long terminal elimination half time thallium may act as a cumulative poison. We present two cases of thallium poisoning with intent to kill.

Adult↗
PubMed1985

Increase in mucociliary clearance in normal man induced by oral high frequency oscillation.

Data on the effect on mucociliary clearance of oral high frequency oscillation is conflicting. By means of a technique to superimpose high frequency oscillation on tidal breathing, changes in mucociliary clearance during high frequency oscillation were studied in seven normal non-smokers by monitoring the clearance of inhaled radiolabelled aerosol from the lungs. After inhalation of 5 microns technetium 99m labelled particles under controlled conditions, whole lung clearance was monitored by scintillation counters half hourly for six hours with a final count at 24 hours, from which tracheobronchial deposition and clearance could be calculated. Control and high frequency oscillation studies were performed on separate days in random order. Oral high frequency oscillation was applied by a bass loudspeaker through a mouthpiece to superimpose sinewave oscillations (RMS input pressure 1.2 cm H2O, mean pressure zero) on normal breaths. On high frequency oscillation days 30 minutes of oscillation alternated with 30 min of rest. Between 3 and 4.5 hours mucociliary clearance with high frequency oscillation exceeded control by about 10% (p less than 0.05). The mean time taken to eliminate 90% of deposited radioaerosol from the tracheobronchial tree fell from 4 hours 50 minutes (range 1 h 52 min-6 h 50 min) during control to 3 hours 43 minutes (range 2 hr 28 min-5 hr 54 min) during the high frequency oscillation run (p less than 0.05). Possibly this comfortable, simple technique would be of therapeutic benefit to patients with chronic sputum retention and merits further investigation.

Adult↗
PubMed1992

Acute effect of inhaled bradykinin on tracheobronchial clearance in normal humans.

BACKGROUND: Bradykinin, a nonapeptide that contributes as a mediator to the pathogenesis of asthma, may affect lung mucociliary clearance, as it has been shown to be a potent secretagogue in canine airways and in human nasal mucosa in vivo. To evaluate this possibility the effect of inhaled bradykinin on mucociliary clearance has been studied in 10 healthy volunteers. METHODS: Subjects attended the laboratory on two occasions to take part in tracheobronchial clearance studies using a non-invasive radioisotopic technique. Inhalation of radioaerosol was followed 30 minutes later by inhalation of either bradykinin (8 mg/ml) or vehicle placebo in a randomised, double blind fashion. After each inhalation the number of coughs was recorded. Whole lung radioactivity was measured every half hour for six hours with two collimated scintillation counters, and a tracheobronchial clearance curve was plotted for each subject on each occasion. RESULTS: Mucociliary clearance, expressed as the area under the tracheobronchial radioaerosol retention curve calculated for the first six hours (AUC0-6h), was greater in nine out of 10 subjects after inhalation of bradykinin than after placebo. The median values (range) for AUC0-6h were significantly reduced from 126% (78-232%)/h with placebo to 87% (51-133%)/h with bradykinin. CONCLUSION: It is concluded that acute exposure to inhaled bradykinin accelerates tracheobronchial clearance in normal human airways.

Administration, Inhalation↗
PubMed1976

A noninvasive technique for the study of cardiac hemodynamics utilizing C15-O2 inhalation.

A new technique for the study of cardiac hemodynamics is described which utilizes single-breath inhalation of C15O2 (T 1/2 = 124 sec.) and the recording of activity vs. time curves with scintillation counters placed externally over the left ventricle and right lung. The results from 10 normal volunteers and 28 patients with acquired or congenital heart disease have been compared to the findings at cardiac catheterization. The technique is safe, rapid, and nontraumatic, and yielded no false positives or negatives in this series.

Aortic Valve↗
PubMed1975

Hematocrit of the fetal rabbit placenta.

51Cr-labeled erythrocytes and [125I]RISA were used simultaneously to measure the fetal rabbit whole-body and placental hematocrits (Hct) and to find the ratio of placental transit times of erythrocytes and plasma. The levels were injected into the heart of 21 fetal rabbits of 26--28 days gestation, and about 60 s mixing time, the placenta and a fetal blood sample were assayed with a gamma well-type scintillation counter. Erythrocyte and plasma activity per milliliter were determined from a standard dilution of the isotopes. Large-vessel Hct was measured as the corrected packed erythrocyte percentage in capillary tubes. Large-vessel Hct was 37.3 (+/- 3.7 SD) %, whole-body Hct was 31.3 (+/- 3.5) %, and the placental Hct was 25.3 (+/- 4.0) %. The placental/large-vessel Hct ratio was 0.676. The ratio may be estimated as 0.765 when corrected for the loss of albumin in time. The transit time of erythrocytes in the placenta was calculated to be 0.682 of that for plasma. The shorter erythrocyte transit time implies that there is less time for O2 and CO2 exchange than previously thought.

Animals↗
PubMed1976

Washout kinetics of red cells and plasma from the spleen.

Radioiodinated (125I) serum albumin was injected inttravenously in cats and allowed to equilibrate in the circulation. Red cell and plasma washout from the isolated spleens were enrom the isolated spleens were then compared during perfusion with oxygenated Ringer solution, the respective concentrations in the outflow being measured by celloscope and scintillation counters. Washout kinetics yielded three exponential components for cells (perfusate volumes for 50% washout (V1/2) being 0.067, 4.70, and 97 ml/g spleen) but only two for plasm (V1/2, 0.14 and 2.40 ml/g). There is no plasma counterpart to the slowly released cells, i.e., they do not represent a separate vascular space. This is an accord with a previous view that these are immature cells, delayed through adherence to fine structures of the red pulp. Compartment analysis indicates that the plasma and two remaining cell components represent washout from two separate vascular spaces, containing 0.09 ml/g blood at arterial hematocrit 37% and 0.42 ml/g blood at hematocrit 75%, perfused by 0.9 and 0.1 of the arterial inflow respectively. Evidence suggests these spaces are i) blood vessels, and ii) red pulp.

Animals↗
PubMed1991

Relative contribution of gravity to pulmonary perfusion heterogeneity.

We designed a series of experiments and analyses to quantify the contribution of gravity to pulmonary perfusion heterogeneity. Regional pulmonary perfusion was measured in five anesthetized and ventilated dogs in both supine and prone positions by use of radiolabeled microspheres injected during apnea at functional residual capacity. Measurements of flow were repeated in each position, and the sequence of positions was prospectively designed to nullify any effect of order. The lungs of each animal were excised, perfused with saline until clear, dried at an inflation pressure of 25 cmH2O, and cut into 1.9-cm3 pieces. Each piece was weighed and the radioactivity determined in a scintillation counter. Measurement errors were minimized by excluding lung pieces that had greater than 25% airway and weighed less than 10 mg or greater than 60 mg. Weight-normalized flows in each position and repetition were determined for each lung piece. An analysis of variance model was used to identify the percentage of variation in regional flow that was due to position (supine vs. prone), to random error and time (measurement and repetition), and to structure, where structure was defined as the component of flow that remained constant across position and replication. The contributions of position, error/time, and structure to the total variability of flow across the five dogs were 7.8 +/- 0.6, 8.4 +/- 8.3, and 83.8 +/- 8.4%, (SD), respectively. Because the contribution of position represents the additive effect of gravity between two opposite positions, the contribution of gravity to perfusion heterogeneity in one position may be as little as 4%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Validation of fluorescent-labeled microspheres for measurement of regional organ perfusion.

Estimations of dog lung, pig heart, and pig kidney regional perfusion by use of fluorescent-labeled microspheres were compared with measurements obtained with standard radiolabeled microspheres. Pairs of radio- and fluorescent-labeled microspheres (15 microns diam, 6 colors) were injected into a central vein of a supine anesthetized dog and the left ventricle of three supine anesthetized pigs while reference blood samples were simultaneously withdrawn from a femoral artery in the pigs. The lungs were cubed into approximately 2 cm3 pieces (n = 1,510). Each pig heart and kidney was cubed into approximately 1-g pieces (total n = 192 and 120, respectively). The radioactivity of each organ piece and reference blood sample was determined using a scintillation counter with count rates corrected for decay, background, and spillover. Tissue samples and reference blood samples were digested with KOH and filtered and the fluorescent dye was extracted with a solvent, or the dye was extracted from lung tissue without filtering. The fluorescence of each sample was determined for each color by use of an automated spectrophotometer. Perfusion was calculated for each organ piece from both the radioactivity and fluorescence. Correlation between flow determined by radio- and fluorescent-labeled microspheres was as follows: r = 0.96 +/- 0.01 (SD) (lung, filtered, n = 588), r = 0.99 +/- 0.00 (lung, nonfiltered, n = 710), r = 0.95 +/- 0.02 (heart, filtered), and r = 0.96 +/- 0.02 (kidney, filtered). Compared with colored microspheres, methods for quantitating fluorescent-labeled microspheres are more sensitive, less labor intensive, and less expensive. Fluorescent-labeled microspheres provide a new nonradioactive method for single and repeated measurement of regional organ perfusion.

Animals↗
PubMed1998

Pulmonary blood flow distribution during partial liquid ventilation.

Regional pulmonary blood flow was investigated with radiolabeled microspheres in four supine lambs during the transition from conventional mechanical ventilation (CMV) to partial liquid ventilation (PLV) and with incremental dosing of perfluorocarbon liquid to a cumulative dose of 30 ml/kg. Four lambs supported with CMV served as controls. Formalin-fixed, air-dried lungs were sectioned according to a grid; activity was quantitated with a multichannel scintillation counter, corrected for weight, and normalized to mean flow. During CMV, flow in apical and hilar regions favored dependent lung (P < 0.001), with no gradient across transverse planes from apex to diaphragm. During PLV the gradient within transverse planes found during CMV reversed, most notably in the hilar region, favoring nondependent lung (P = 0.03). Also during PLV, flow was profoundly reduced near the diaphragm (P < 0.001), and across transverse planes from apex to diaphragm a dose-augmented flow gradient developed favoring apical lung (P < 0.01). We conclude that regional flow patterns during PLV partially reverse those noted during CMV and vary dramatically within the lung from apex to diaphragm.

Animals↗