Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ISOTOPES, RADIOACTIVE”

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 1,657 records · Page 92Linked to original sources
PubMed2004

Competition for attachment of aquaculture candidate probiotic and pathogenic bacteria on fish intestinal mucus.

Probiotics for aquaculture are generally only selected by their ability to produce antimicrobial metabolites; however, attachment to intestinal mucus is important in order to remain within the gut of its host. Five candidate probiotics (AP1-AP5), isolated from the clownfish, Amphiprion percula (Lacepéde), were examined for their ability to attach to fish intestinal mucus and compete with two pathogens, Aeromonas hydrophila and Vibrio alginolyticus. Two different radioactive isotopes were used to quantify competition between pathogens and probionts. Attachment of the pathogens was enhanced by the presence of the candidate probiotics. However, the addition of the candidate probiotics after the pathogens resulted in reduced pathogen attachment. Only AP5 caused lower attachment success of V. alginolyticus when added before the pathogen. When AP5 was added first, the average attachment change was 41% compared with 72% when added after V. alginolyticus, suggesting that the probiotic is displaced but that enhanced attachment of the pathogen does not occur. Conversely, when V. alginolyticus was added first, followed by AP5, attachment change was 37% while AP5 had 92% attachment change when added second. This implies that the pathogen was displaced by the candidate probiotic and therefore it appeared that, based on the ability of probiont AP5 to attach to mucus, the growth of the pathogen in the digestive tract might be suppressed by the candidate probiont's presence.

Aeromonas hydrophila↗
PubMed1992

Calcium absorption and calcium bioavailability.

Calcium is important for bone health. It has been customary to focus on dietary calcium intake, but of central importance for the body needs in the individual patient is the actual calcium absorption. This absorption consists of an active vitamin D-mediated component and a passive diffusional component. A number of different methods are available for the evaluation of calcium absorption. At present the calcium absorption tests using calcium isotopes (radioactive or stable) appear to be the most reproducible way of determining calcium absorption. The major nutrient sources for calcium are milk and milk products, whereas some of the green vegetables have a low bioavailability of calcium. When deciding whether an increased calcium intake is advisable, the following questions must be answered. What is the calcium absorptive status of the patient? How should the calcium supplement be dispensed? What calcium salt should be used? When should calcium supplements be taken? What is the compliance of the patient? When should the treatment be evaluated? The calcium supplement might be taken as milk (or milk products) or, in patients with lactose intolerance, as calcium supplements. Quite a number of calcium supplements are available on the market, and many of them are marketed without proper knowledge of the bioavailability of the actual preparation. For the benefit of our patients it is now reasonable to demand such investigations before marketing calcium supplements.

Biological Availability↗
PubMed1990

The effects of dentine bonding agents on marginal leakage of composite restorations.

The aim of this study was to compare the effects upon marginal leakage of a number of dentine bonding agents: Gluma, Scotchbond, Topaz and an experimental material when used with a posterior composite resin, Occlusin. The results were also compared with composite used without a dentine bonding agent and with a glass ionomer, Chemfil II. Class V cavities with or without a bevelled cavo-surface margin were prepared in the buccal surfaces of extracted premolar teeth. Following restoration, the teeth were stored for periods of up to 3 months and then thermally cycled. Marginal leakage was subsequently determined using a radioactive isotope containing 45Ca, and an autoradiographic technique. Image analysis was used to determine the total amount of linear leakage for each specimen. The results showed that some leakage occurred for all materials at each time interval. The bevelled design of cavity allowed significantly less leakage than the non-bevelled type. The use of dentine bonding agents did not improve the marginal seal of the composite restorations, and the glass ionomer restorations showed significantly less leakage than the composite resin and dentine bonding agent combinations.

Adhesives↗
PubMed1993

The effects of dentine bonding agents on marginal leakage of composite restorations--long-term studies.

The aim of this study was to compare the effects upon marginal leakage of a number of dentine bonding agents when used with a posterior composite resin, Occlusin, after storage for periods of up to 2 years. The bonding agents used were Gluma, Scotchbond, Topaz and an experimental material. The results were compared with a glass ionomer, Chemfil II. Class V cavities with or without a bevelled cavo-surface margin were prepared in the buccal surfaces of extracted premolar teeth. Following restoration, the teeth were stored for periods of up to 2 years and then thermally cycled. Marginal leakage was subsequently demonstrated using a radioactive isotope containing 45Ca, and an auto-radiographic technique. Image analysis was used to determine the total amount of linear leakage for each specimen. The results showed that some leakage occurred for all materials at each time interval. The bevelled design of cavity allowed significantly less leakage than the unbevelled cavity. Overall, there was little difference between the various dentine bonding agents. The glass ionomer restorations showed significantly less leakage than the composite resin and dentine bonding agent combinations in unbevelled cavities.

Composite Resins↗
PubMed1994

NarK is a nitrite-extrusion system involved in anaerobic nitrate respiration by Escherichia coli.

Escherichia coli can use nitrate as a terminal electron acceptor for anaerobic respiration. A polytopic membrane protein, termed NarK, has been implicated in nitrate uptake and nitrite excretion and is thought to function as a nitrate/nitrite antiporter. The longest-lived radioactive isotope of nitrogen, 13N-nitrate (half-life = 9.96 min) and the nitrite-sensitive fluorophore N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide have now been used to define the function of NarK. At low concentrations of nitrate, NarK mediates the electrogenic excretion of nitrite rather than nitrate/nitrite exchange. This process prevents intracellular accumulation of toxic levels of nitrite and allows further detoxification in the periplasm through the action of nitrite reductase.

Anaerobiosis↗
PubMed1991

Radiospirometry V/Q.

Single photon emission computerized tomography (SPECT) of the lungs was used for topographical determination of V/Q ratios in anaesthetized-paralyzed subjects. Ventilation and perfusion were estimated from the distribution of an inhaled aerosol containing a radioactive isotope and injected macroaggregates of human albumin tagged with another isotope. There was a prominent gradient of V/Q ratios in the vertical direction. In the horizontal plane there were marked gradients of both ventilation and perfusion of similar appearance with maxima in central lung regions, resulting in only small gradients of V/Q ratios.

Anesthesia, Inhalation↗
PubMed1987

Evidence for a delta pH-driven Ca2+ uptake in EGTA-treated bovine spermatozoa.

Calcium efflux from ejaculated bovine spermatozoa occurred upon incubation in Ca2+/EGTA buffers with Ca2+ ion concentrations ranging from 0.1 microM to 1 nM. Both total cellular calcium and cytosol free Ca2+ concentrations, the latter measured with Quin 2, were inversely correlated with the Ca2+ activity of the medium. An influx of radioactive 45Ca2+ parallel to a net efflux of calcium took place in spermatozoa incubated in 45Ca2+/EGTA buffers with 45Ca2+ activity of 0.01 microM or 0.1 microM. The uptake of the radioactive isotope was higher in spermatozoa incubated at pH 7.8 than that found at pH 6.8, increased in the presence of acetate or amiloride but decreased when ammonium chloride or monensin was added to the incubation mixture. Addition of acetate produced a decrease of the cytoplasmic pH, determined with the indicator carboxyfluorescein, whereas addition of NH4Cl or monensin caused a pH increase. Addition of either nigericin or monensin to spermatozoa suspended in a choline medium containing low concentrations of Na+, K+ and Ca2+ produced a cytosolic acidification, the subsequent addition of Ca2+ caused a cytosolic alkalinization parallel to an increase of the cytosolic free Ca2+. Addition of CaCl2 to EGTA-pretreated spermatozoa resuspended in a poorly buffered medium induced an evident decrease of extracellular pH suggesting a cellular proton extrusion. Both monensin and nigericin caused an increase of the calcium transport in spermatozoa suspended in a choline medium containing a physiological concentration of 1.5 mM CaCl2. Taken together the present results indicate that, under the experimental conditions used, a delta pH-driven Ca2+ uptake occurs in ejaculated bovine spermatozoa and suggest that Ca2+ is taken up in exchange with H+.

Acetates↗
PubMed1991

Polyamide-oligonucleotide hybrid molecules.

1. Recent experience with polyamide-oligonucleotide hybrids shows the versatility of this approach for replacement of radioactive isotopes for detection of hybridization on gels and for hybridization histochemistry. 2. These molecular hybrids also show great promise as antisense inhibitors.

Molecular Probe Techniques↗
PubMed2004

Evaluation of the 13C-triolein breath test for fat malabsorption in adult patients with cystic fibrosis.

BACKGROUND AND AIMS: A simple non-invasive test not requiring the use of radioactive isotopes is required to assess fat malabsorption in adult cystic fibrosis (CF) patients. Breath tests using substrates labeled with 13C meet these conditions. The 14C-triolein breath test is sensitive and specific for measuring fat malabsorption, but involves radiation exposure. The aim of this study was to examine the utility of a test using a 13C label and to determine whether pancreatic replacement therapy would return the test to the values of a normal control group. METHODS: 13CO2 recovery was assessed after an overnight fast in six adult patients with CF, both with and without pancreatic enzyme replacement therapy (PERT) in the usual dose for a light snack, in a randomized order, on different days. Studies were also performed in eight healthy volunteers after oral ingestion. Subjects drank 50 mL of a liquid meal mixed with 200 microL 13C-triolein and breath samples were collected by blowing through a straw into collection tubes every 30 min for 6 h. The effect of gastric emptying was assessed by comparison of oral ingestion with intraduodenal infusion. Intra-individual variability was assessed in nine volunteers by repeating the breath test after drinking the test meal on a separate day. RESULTS: Compared with healthy subjects there was virtually no recovery of 13CO2 in CF patients without PERT. The median (interquartile range) cumulative percentage dose recovery (cPDR) at 6 h was 3% (0-8) in CF patients compared with 28% (22-41) in healthy controls (P < 0.01). Fat absorption was normalized (37%) (36-43) after ingestion of PERT. Gastric emptying delayed the peak in 13CO2 recovery, but there was no difference in the cPDR at 6 h. There was no difference in recovery between days 1 and 2. CONCLUSIONS: The 13C-triolein breath test is a simple and reproducible method to measure fat malabsorption. The test provides a screening technique for fat malabsorption in adult CF patients and may be useful for monitoring the lowest effective dose of PERT.

Administration, Oral↗
PubMed1994

A case of bacterial meningitis complicated by post-traumatic cerebrospinal fluid rhinorrhea.

This paper reports an 11 year old boy with bacterial meningitis accompanied by post-traumatic cerebrospinal fluid (CSF) rhinorrhea. Streptococcus pneumoniae was cultured from CSF. The clinical course was very rapid before admission and his age relatively high for usual bacterial meningitis. Consequently, we examined the cause in detail. Immunological findings were within normal limits. Although routine graphic examinations, such as cranial X-ray photography, horizontal cranial computed tomography (CT) and magnetic resonance imaging, could not demonstrate a bone defect, both coronal thin-section cranial CT scanning and radioactive isotope counting by means of cotton packed into the nasal cavity were useful for detecting CSF rhinorrhea. In a case of atypical meningitis, the past history should be examined with caution and coronal thin-section CT should be performed.

Cerebrospinal Fluid Rhinorrhea↗
PubMed1980

The intraarterial infusion of chemotherapeutic agents as "basal" treatment of cancer: evidence of increased drug activity in regionally infused tissues.

There is evidence from a number of centres that some forms of locally advanced and aggressive cancers which are difficult to eradicate by standard means can be reduced by the use of "basal" chemotherapy and/or surgery. Clinicians have been divided as to whether there is an advantage in giving the chemotherapeutic agents directly into a regional artery of supply where this is feasible, as opposed to their systemic administration. This paper documents supportive evidence that some and possibly many chemotherapeutic agents are more effective if given regionally into an artery of supply. There is a higher incidence of local side-effects in the region infused, including loss of hair, inflammatory changes, and ulceration of the skin or mucosa of the region infused. After intraarterial infusion of tagged bleomycin (indium-III bleomycin) into a limb, the radioactive isotope remained more concentrated in the limb infused than in the opposite limb for at least 24 hours. Systemic side-effects, including bone-marrow depression, are less frequent and less severe in patients given chemotherapeutic agents by intra-arterial infusion than if the same doses of agents are given intravenously. There is now sufficient evidence of the value of basal chemotherapy used in this way to make it mandatory that medical oncologists and surgeons, working together, should plan controlled studies to determine the most appropriate applications of this technique of management.

Antineoplastic Agents↗
PubMed2002

Evaluating acceptance and understanding of risk in the emergency department: are all risk statements created equally?

OBJECTIVE: To determine whether mathematically equivalent but conceptually different presentations of risk from radioactive isotope exposure might affect the rate of agreement to participate in a hypothetical research study. METHODS: This was a prospective study of consenting English-speaking subjects more than 18 years of age who were asked whether they would agree to participate in a mock study when presented with six mathematically equivalent statements of research-related risk. Participants were classified as recognizing the equivalence of the risk statements if they accepted all or refused all of the risk statements. RESULTS: Three hundred forty-six subjects were enrolled. There were 55 subjects (16%; 95% CI = 12% to 20%) who refused all of the six risk statements, and 23 participants (6.7%; 95% CI = 4% to 9%) who accepted all of the given risk statements. Most of the participants (77%; 95% CI = 73% to 82%) did not recognize that the six risk statements were equivalent and agreed to some, or did not understand some of the risk statements. In stepwise multivariate logistic regression, being white, being of older age, and having higher education were associated with a higher likelihood of accepting or rejecting all six of the risk statements. CONCLUSIONS: Ethnicity, age, and education affected whether patients recognized the equivalence of six risk statements for a hypothetical study of low-dose radiation. Risk acceptance may be more likely when familiar concepts are used to express research risks. Researchers must focus on strategies that enhance the understanding of research risks and address the reasons for nonparticipation by subjects who are younger, of different ethnic or cultural background, or of lower education.

Adolescent↗
PubMed1977

Association of some enterobacteria with the intestinal mucosa of mouse in relation to their partition in aqueous polymer two-phase systems.

The association of enterobacteria with mouse intestinal mucosa has been investigated by pumping heat-killed, radioactively-labelled bacteria through the gut lumen in vitro. Approximately 20 cm of the small intestine proximal to the ileo-caecal valve was rinsed, excised and maintained in an organ bath. By using two different bacteria labelled with different radioactive isotopes, the relative association of the two bacterial pumped through the same piece of gut was determined. Cross-labelling showed that choice of isotope did not affect the association. Salmonella typhimurium 395 MR10 was used as reference and the other bacteria investigated related to it. S. typhimurium MR10 and Escherichia coli O 14 K7, which are relatively lipophilic, showed greater association than S. typhimurium 395 MS and E. coli O 111 K58, which are more hydrophilic. Prolonged incubation of bacteria with the length of intestine in vitro leading to damage of the brush border of the mucosal epithelium enhanced the association of the bacteria. These data suggest that similar physico-chemical surface properies govern the association certain enterobacteria to the intestinal mucosa as in phagocytosis with professional phagocytes.

Acetylglucosaminidase↗
PubMedDate not supplied

Technique for construction of dental molds for high-dose-rate remote brachytherapy.

High-dose-rate remote (HDR) brachytherapy eliminates radiation exposure hazard to personnel, allows for optimum dosage planning (dosimetry), and delivers high radiation dose close to the tumor in only a few minutes. The catheters can be incorporated into a fixed geometry within a mold, allowing for repeated treatments without the need for repeated implantation of radioactive isotopes or repeated dosimetry. This article presents the use of HDR brachytherapy in three patients to illustrate the advantages of HDR brachytherapy for the treatment of head and neck cancers in the following circumstances: (a) for outpatient therapy, (b) as an addition to or potentiation of external beam irradiation, (c) for preservation of function of regional structures, (d) for optimization of dosimetry, and (e) for palliation. It requires close interaction among the radiation oncologist, head and neck surgeon, and the dental oncologist and/or maxillofacial prosthodontist in order for optimum benefit for the patient to be achieved.

Acrylic Resins↗
PubMed1978

The influence of parathyroidectomy upon calcium and phosphate homeostasis in adult sheep.

The absorption and secretion of Ca and PO4 were measured with the use of radioactive isotopes in 4 adult sheep before and after parathyroidectomy. Secretion of Ca and PO4 into the stomach and intestines was measured separately. Parathyroidectomy resulted in a negative balance for Ca and PO4 and an accompanying fall in plasma Ca and PO4 concentrations. In the case of PO4 this response was attributed primarily to a reduced intestinal absorption, but for Ca increases in urinary excretion and intestinal secretion also contributed significantly. Secretion of PO4 to the stomach was reduced but endogenous PO4 excretion in the faeces was unchanged which indicated a reduced reabsorption of secreted PO4 by the intestines.

Animals↗
PubMed1969

Calculation of the membrane potential in smooth muscle cells of the guinea-pig's taenia coli by the Goldman equation.

1. The intracellular K(+), Cl(-) and Na(+) concentrations in the taenia coli cells of the guinea-pig have been estimated from the total ion content or the extrapolated intracellular tracer content, the sorbitol space and the dry wt./wet wt. ratio.2. The exchange of K(+), Cl(-) and Na(+) was studied by following the uptake and the efflux of these ions with radioactive isotopes. The following efflux values have been calculated: m(K), 4 p-mole.cm(-2).sec(-1); m(Cl), 8.4 p-mole.cm(-2).sec(-1) and m(Na), 7.2 p-mole.cm(-2).sec(-1). These flux values agree well with the influx values, obtained under the same experimental conditions.3. The slowness of diffusion in the extracellular space reduces the Na flux by about 2.5% and the K flux by about 30%. A correction factor of 1.3 has to be introduced to obtain the true K flux.4. The values for the permeability constants calculated by the constant field assumptions are for P(K), 11 x 10(-8) cm/sec; P(Cl), 6.7 x 10(-8) cm/sec and for P(Na), 1.8 x 10(-8) cm/sec. The introduction of these values and of the ion concentrations in the Goldman equation gives a resting potential of -37 mV.5. One of the possible explanations for the discrepancy between the measured resting potential and the calculated one, is that the resting potential of these smooth muscle cells is partly a diffusion potential and partly due to the operation of an electrogenic Na pump.

Animals↗
PubMed2004

Geochemical precursors to volcanic activity at Mount St. Helens, USA.

The importance of the interplay between degassing and crystallization before and after the eruption of Mount St. Helens (Washington, USA) in 1980 is well established. Here, we show that degassing occurred over a period of decades to days before eruptions and that the manner of degassing, as deduced from geochemical signatures within the magma, was characteristic of the eruptive style. Trace element (lithium) and short-lived radioactive isotope (lead-210 and radium-226) data show that ascending magma stalled within the conduit, leading to the accumulation of volatiles and the formation of lead-210 excesses, which signals the presence of degassing magma at depth.

Journal Article↗
PubMed2006

Rubidium-rich asymptotic giant branch stars.

A long-debated issue concerning the nucleosynthesis of neutron-rich elements in asymptotic giant branch (AGB) stars is the identification of the neutron source. We report intermediate-mass (4 to 8 solar masses) AGB stars in our Galaxy that are rubidium-rich as a result of overproduction of the long-lived radioactive isotope (87)Rb, as predicted theoretically 40 years ago. This finding represents direct observational evidence that the (22)Ne(alpha,n)(25)Mg reaction must be the dominant neutron source in these stars. These stars challenge our understanding of the late stages of the evolution of intermediate-mass stars and would have promoted a highly variable Rb/Sr environment in the early solar nebula.

Journal Article↗