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At least 415 records · Page 23Linked to original sources
PubMed2002

[Noninvasive detection of dynamics of various elements in the upper abdomen of selenium-deficient rat using multitracer analysis technique].

The advantages of a technique as a diagnostic tool for examining the distribution of bio-trace elements in the living body are discussed. Time courses of the distribution of Be, V, Mn, Fe, Co, Zn, As, Se, Rb, Sr, and Y in the upper abdomen of living selenium-deficient rats were examined using the in vivo multitracer analysis technique. The dynamics of the elements were estimated by comparison with the distribution of As. Almost all As was taken up by red blood cells. The present findings of a decrease in Se and increase in Co in the liver of Se-deficient rats are in good agreement with the previous data that showed a decrease in Se and increase in Co uptake into the liver cell fraction of Se-deficient rats. Although the normalized uptake rate and the relative distribution of Co 48 h after administration increased in Se-deficient rats, the early level of the relative distribution of Co was not lower compared with that in the normal group. This suggests that the high level of the normalized uptake rate and the relative distribution of Co in Se-deficient rats were affected by the decreasing excretion rate rather than by the increasing uptake rate of Co. The plateau level of relative distribution of Se in the Se-deficient rats is lower than that in normal rats, suggesting that the lower levels of the normalized uptake rate and relative distribution of Se in Se-deficient rats were due to the decreased uptake rate of the element.

Abdomen↗
PubMed2001

Distribution of trace elements in normal and tumor-bearing mice using the multitracer technique.

A multitracer solution obtained from the nuclear reaction of selenium with 25-MeV/nucleon 40Ar ions was orally administered to normal and tumor-bearing Balb/c male mice. After 96 h, the mice were sacrificed and the elemental distribution was determined in various tissues, organs, and blood. The uptake of Na, Rb, Ga, Sc, V, Cr, Mn, Co, Fe, Zn, Y, Zr, Tc, Ru, Ag, and In in normal and, except for zinc, in tumor-bearing mice was simultaneously detected. Most elements were distributed in about the same manner in the skin and liver of animals in both groups. The distribution of Rb, Ga, V, Cr, Tc, and In showed little or no significant differences between the two study groups. The distribution of Na, Mn, Fe, Ag, Sc, and Co showed significant differences between normal and tumor-bearing mice. In the blood, spleen, and kidney of the normal mice, there was good absorption of Na, Mn, Fe, Ag, Co, and Zn. In the heart, these elements were well absorbed, except for Na and Mn.

Animals↗
PubMed2004

Verification of mid-ocean ballast water exchange using naturally occurring coastal tracers.

We examined methods for verifying whether or not ships have performed mid-ocean ballast water exchange (BWE) on four commercial vessels operating in the Pacific and Atlantic Oceans. During BWE, a ship replaces the coastal water in its ballast tanks with water drawn from the open ocean, which is considered to harbor fewer organisms capable of establishing in coastal environments. We measured concentrations of several naturally occurring chemical tracers (salinity, six trace elements, colored dissolved organic matter fluorescence and radium isotopes) along ocean transects and in ballast tanks subjected to varying degrees of BWE (0-99%). Many coastal tracers showed significant concentration changes due to BWE, and our ability to detect differences between exchanged and unexchanged ballast tanks was greatest under multivariate analysis. An expanded dataset, which includes additional geographic regions, is now needed to test the generality of our results.

Atlantic Ocean↗
PubMed2002

Sampling and analyses of colloids at the Drigg low level radioactive waste disposal site.

Water samples have been extracted from inside (from standpipes) and from outside (from boreholes) of the trenches at the low level radioactive waste disposal site at Drigg in Cumbria, UK. The samples were taken anaerobically from between 8.5 and 10.0 m below the surface using a submersible pump at low flow rates to ensure that the waters in the standpipes and boreholes were maintained at constant levels. To ensure representative samples, the Eh, pH. conductivity, temperature, iron and dissolved oxygen concentrations of the waters were taken during initial purging and during sampling. The gross tritium, gross non-tritium beta, gross alpha and gamma activities of each sample were determined using suitable sample preparation and counting techniques. Samples were then anaerobically, sequentially filtered through 12 microm, 1 microm, 30 kDa and 500 Da filter membranes. The filtrates were analysed for gross alpha, gross non-tritium beta and gamma activities. SEM and STEM analyses were used to determine the colloid population. An energy dispersive analyser on the SEM was used to determine the major elements present in the colloids. UV-visible spectrophotometry, fluorescence spectrophotometry and high performance size exclusion liquid chromatography were used to analyse the waters before and after treatment with ion exchange materials to determine whether natural organic matter was present in the waters. Results showed that two major types of colloids (iron containing colloids and silicon containing colloids) were present in the waters. There were also a small number of other colloids that contain, as major elements, aluminium, calcium and chromium. Organic colloids were also present. The majority of the radioactivity in the waters was due to tritium. Waters taken from outside the trenches contained low levels of non-tritium beta activities and alpha activities which were lower than the minimum detectable amount. Waters taken from the trenches contained non-tritium beta activities and low levels of alpha emitters. Filtration of the trench waters showed that some of the alpha activity was retained by the 30 kDa and 500 Da membranes suggesting that this activity was associated with small colloids. Radioactivity was not found to be associated with colloids present in the waters taken from outside the trenches. Possible reasons for this observation could be that radionuclide bearing colloids have not yet reached the far-field or that the radionuclide concentration is diluted to below the minimum detectable amount. After concentrating two of the samples by factors of x20 and x 16 respectively, 2.4+/-0.1 and 0.6+/-0.1 Bq dm(-3) of 137Cs were measured.

Colloids↗
PubMed1989

Radiochemical neutron activation analysis of zinc isotopes in human blood, urine, and feces for in vivo tracer experiments.

Enriched stable isotopes are being increasingly used for study of trace element nutrition in humans who cannot be studied by use of in vivo radioactive tracers (e.g., subjects under age 18 and pregnant women). Zinc metabolism in these subjects can be evaluated by administration of Zn enriched to 65% in the minor isotope, 70Zn (0.6% natural abundance). The enhanced 70Zn is detected later in red blood cells, plasma, urine, and feces by measuring 70Zn/64Zn or 70Zn/68Zn ratios. Stable isotope concentrations are measured by neutron activation of the samples and observation of their products: 244-day 65Zn, 14-h 69mZn, and 4-h 71mZn. Zinc-65 can be observed in these samples without chemical separations 3 weeks after irradiations, but large amounts of 24Na and other short-lived species preclude direct observation of the short-lived Zn activities. Preirradiation chemistry was developed to remove most interferences, the major steps being to place the sample on Chelex resin, elute alkali metals and alkaline earths from it, and irradiate the resin containing the Zn. gamma-Rays of 69mZn can be observed on the irradiated resin, but additional precipitation and solvent extraction steps are needed to remove 56Mn and 64Cu for clear observation of 71mZn and 65Zn within hours after irradiation. Yields for pre- and postirradiation separations are typically 85% and 70%, respectively. The stable isotope tracer method was validated by simultaneous in vivo tracing with radioactive 65Zn in four subjects.

Feces↗
PubMed1989

Electron microscopic localization of neurotensin binding sites in the midbrain tegmentum of the rat. I. Ventral tegmental area and the interfascicular nucleus.

The distribution of specifically labeled neurotensin (NT) binding sites was examined by light and electron microscopic radioautography in the ventral tegmental area (VTA) and nucleus interfascicularis of the rat following incubation of lightly prefixed midbrain slices with the monoiodinated ligand, 125I-(Tyr3)-NT. Film radioautograms of whole 125I-NT-incubated slices exhibited intense NT displaceable binding throughout the VTA and interfascicular nucleus. In light microscopic radioautographs from 1-microns-thick sections taken from the surface of the slices, the label was found to be present both inside and outside neuronal perikarya. Probability circle analysis of silver grain distribution in electron microscopic radioautographs confirmed that a significant proportion (greater than 20%) of the specifically labeled binding sites was intraneuronal. The frequent association of these sites with profiles of rough endoplasmic reticulum or Golgi apparatus suggested that they corresponded in part to receptors undergoing synthesis and/or glycosylation. The remainder was associated with neuronal and/or glial plasma membranes, as attested by comparing the distribution of grains overlying apposed cellular elements with the distribution of hypothetical grains originating from randomly distributed membrane bound radioactive sources. Although the resolution of the technique did not make it possible to ascribe labeled membrane-bound receptors to either one of the apposed plasma membranes, their frequent association with interfaces involving the plasmalemma of perikarya and dendrites, together with the occurrence of silver grain alignments along the membrane of certain somata and dendrites suggested that a proportion of them was associated with the perikarya and dendrites of a subpopulation of ventral tegmental neurons. Interestingly, these perikaryal and dendritic receptors were not exclusively present on, or even concentrated opposite, abutting axon terminals but instead were more or less evenly distributed along the plasma membrane. Only an exceedingly small proportion was found to be associated with synaptic junctions. Such a low incidence makes it unlikely that only the synapse-linked binding sites correspond to functional receptors. On the contrary, the dispersion of labeled receptors seen here along the plasma membrane of presumptive dopamine neurons suggests that NT acts mainly in a paracrine or parasynaptic fashion in the ventral midbrain tegmentum.

Animals↗
PubMed1979

Medical applications of the radioisotope X-ray fluorescence analysis.

The X-ray fluorescence, induced by small, sealed-off radioactive sources, can be applied as very sensitive method of analysis of trace elements in biological specimens. The preparation and technique for the analysis of small (0.1 to 0.5 ml) or larger (more than several milliters) volumes of liquid samples will be described, and the principal patss of the devices for analyzing only one element or a series of them are presented. The measuring time for typical analysis ranges between 10(2) and 10(4) seconds. For a simple X-ray fluorescence analysis the sensitivity of the method is varying between 10 ppm and 100 ppm when measuring during 100 seconds. A large number of applications of this method in the medical field is listed, concerning the analysis of trace elements naturally present in biological samples, and the analysis of elements employed as "stable tracers" in order to follow a dynamic process, or in order to label blood components, such as erythrocytes, leukocytes and platelets.

Blood Cells↗
PubMed2004

Determination of thorium, uranium and potassium elemental concentrations in surface soils in Cyprus.

A comprehensive study was conducted to determine thorium, uranium and potassium elemental concentrations in surface soils throughout the accessible area of Cyprus using high-resolution gamma-ray spectrometry. A total of 115 soil samples was collected from all over the bedrock surface of the island based on the different lithological units of the study area. The soil samples were air-dried, sieved through a fine mesh, sealed in 1000-ml plastic Marinelli beakers, and measured in the laboratory in terms of their gamma radioactivity for a counting time of 18 h each. From the measured gamma-ray spectra, elemental concentrations were determined for thorium (range from 2.5 x 10(-3) to 9.8 microg g(-1)), uranium (from 8.1 x 10(-4) to 3.2 microg g(-1)) and potassium (from 1.3 x 10(-4) to 1.9%). The arithmetic mean values (A.M. +/- S.D.) calculated from all samples are: (1.2+/-1.7 microg g(-1)), (0.6+/-0.7) microg g(-1), and (0.4+/-0.3%), for thorium, uranium and potassium, respectively, which are by a factor of three-six lower than the world average values of 7.4 microg g(-1) (Th), 2.8 microg g(-1) (U) and 1.3% (K) derived from all data available worldwide. The best-fitting relation between the concentrations of Th and K versus U and also of K versus Th, is essentially of linear type with a correlation coefficient of 0.93, 0.84 and 0.90, respectively. The Th/U, K/U and K/Th ratios (slopes) extracted are equal to 2.0, 2.8 x 10(3) and 1.4 x 10(3), respectively.

Cyprus↗
PubMed1997

Estimation of radioactive calcium absorption based on expanding Ca-exchangeable space.

Anthropological interest in calcium metabolism is partially connected with the genetic basis of skeletal metabolism that could provide additional optimism for people suffering from osteoporosis. The present investigation is aimed at deal with a of model describing Ca intestinal absorption, suitable for other descriptions currently investigated in anthropology (migration and gene flow). The purpose of this investigation was to establish features of the reflection of the Ca isotopic absorption tests in serum using the concept of an expanding Ca-space and to assess the reliability of the estimation of absorption (ABS) from one serum sample. Double tracer method, using 85Sr as the iv tracer, was used as the referent. The study included 100 subjects (49 females, 51 males) of which 34 were considered healthy. The mean value of ABS was 68 (+/-17.45 SD) % of dose. Serum radioactivity during the 24 hours following oral administration of 47Ca (together with 100 mg elemental Ca), o.s(t), from five blood samples was determined. The relationship between o.s(t) and ABS was found to be connected to an expanding Ca-space, V(t): ABS = o.s(t)V(t) = 26 + 11.8t0.35 o.s(t). After the absorption process was finished, an approximate value of V(t) is (100/S1)(t-x)b. The constants "S1" and "b" describe power function of iv s(t), whereas parameter "x" represents delay of V(t) Ca-space at oral administration in comparison to the iv administration. Statistical models selected on the basis of their low values of the SEE (from 8.71 to 8.90% of dose) include body surface index or body weight index (BW0.425). The CV expressed as (SEE/mean x ABS(Ca/Sr) x 100 were about 13% and the observed greatest difference between the estimated and measured ABS(Ca/Sr) was 20% of dose. The authors believe that models presented permit, to a limited extent, comparison of results obtained by different procedures. The results, according to variability of the sample of subjects, permit judgment on upper limits of error at estimation of absorption from one blood sample radioactivity.

Adult↗
PubMed1989

Identification of rat ovarian nuclear factors that interact with the cAMP-inducible lactate dehydrogenase A subunit promoter.

Utilizing the gel electrophoresis/DNA binding assay and a new technique of direct binding of radioactive DNA to protein blots, we have investigated putative factors selective for the cAMP-responsive element (CRE) of the lactate dehydrogenase A subunit promoter in rat ovary nuclear extracts. Analysis of linker-scanning mutants of lactate dehydrogenase A subunit promoter fragments by DNA binding assay identified DNA binding activity selective for the 11-nucleotide sequence 5' TCTGACGTCAG 3' located between positions -51 and -41 relative to the transcription initiation site. This sequence contains the previously identified CRE 5' TGACGTCA 3'. Probing of protein blots with radioactive promoter fragments containing the CRE demonstrated that ovarian nuclear extracts contain a protein of relative molecular mass 47,000 (Mr 47,000) which exhibits selective binding affinity for the CRE. The 47-kDa CRE binding protein was found to be present in comparable levels in the ovaries of normal and hypophysectomized rats. Furthermore, our data suggest the presence of a 37,000-dalton (Mr 37,000) protein which possesses selective binding affinity for part of the CRE sequence. The binding activity/level of the 37-kDa CRE binding protein appeared to be modulated by short-term hypophysectomy/follicle-stimulating hormone administration. These results provide evidence for the presence of CRE binding factors in rat ovarian nuclei, which may be involved in the molecular events responsible for transcriptional regulation of ovarian cAMP-inducible genes.

Animals↗
PubMed2000

Antioxidant defense and trace element imbalance in patients with postradiation syndrome: first report on phase I studies.

More than 6000 residents of Latvia were involved in recovery work in Chernobyl. They were healthy men exposed to substantial ionizing radiation (0.01-0.5 Gy). Now, these recovery workers suffer from "postradiation syndrome": dizziness and poor memory, headache, local pains, and so forth. The biochemical mechanism of "postradiation syndrome" has not been completely established. In this Phase I study, we have investigated how exposure to radiation impacts antioxidative defense and trace element concentrations in the blood of recovery workers. Thirty-five patients with postradiation syndrome (men, age range 33-50 yr) and 15 healthy men similar in age as control subjects were studied for the effects on plasma chemiluminescence, the activity of antioxidant enzymes, and the concentration of ceruloplasmin and concentrations of selenium (Se), zinc (Zn), and copper (Cu) in blood. The results revealed that plasma chemiluminescence was significantly increased (3.5-fold to 5.5-fold), the activity of catalase in erythrocytes was significantly elevated, and the activity of glutathione peroxidase in plasma was significantly reduced in examined patients. Concentrations of Zn and Cu were significantly higher and the concentration of Se was lower in these patients. We conclude that the patients exposed to ionizing radiation have diminished blood antioxidant defense associated with pronounced Se deficiency and imbalance of Zn and Cu.

Adult↗
PubMed2002

252Cf: the potential for activation analysis of selected medium-weight and heavy elements in the limited neutron flux of a partially depleted 50 microg source.

A 50 microg 252Cf source, depleted by about 2 orders of magnitude from its original neutron output, was used to examine the sensitivity of neutron activation analysis for a selection of 20 pure materials and compounds containing elements with atomic numbers greater than 40. Generally speaking, the sensitivity is seriously restricted by the neutron flux of the source, but in certain specific cases the nuclear properties of the elements concerned, such as thermal absorption cross-section, isotopic abundance and half-life of the radioactive product were considered for the production of a practicable gamma-ray yield. A description of the irradiation assembly and the conditions of activation are presented. Detection limits varied between 30 microg g(-1) to 8.2 mg g(-1) based on the most suitable gamma-ray of the radionuclide of interest. For purposes of determining trace and minor concentrations of selected elements, a source of this nature could be acquired at a nominal cost especially in developing countries that do not have access to a nuclear reactor.

Journal Article↗
PubMed1977

Biochemical characterization of RNA and protein synthesis in erythrocyte development.

Newts (Triturus cristatus) made anemic with acetylphenylhydrazine (APH) fail to regenerate erythrocytes (RBC's) immediately and exhibit a latent period of 1.5-2 wk during which animals lack RBC's and are aplastic. With the establishment of erythroid regeneration at 10-14 days, relatively homogeneous populations of successive erythropoietic stages occur in the blood. This feature makes possible biochemical analyses of events in early, intermediate, and late developmental stages, respectively, each of which can be obtained in vivo with minimal contamination by other stages. Previous studies have described a primitive cell population referred to as "erythroid precursor cells" (EPC's) which precedes the appearance of definitive erythroid elements. The present studies show that EPC's and early erythroid cells are engaged mainly in ribosomal production, including synthesis of rRNA and ribosomal proteins. Moreover, EPC's and early erythroid cells also synthesize tRNA and a presumed Hb-mRNA which has been identified by its sedimentation rate at 9-12 s and its content of polyadenylic acid. In intermediate stages, there occurs a fourfold decrease in the level of RNA synthesis and, while rRNA continues to be formed, there is a disproportionate accumulation of the two major cytoplasmic rRNA species in favor of the large ribosomal subunit RNA. In late developmental stages, the level of RNA synthesis is markedly diminished with little or no evidence of formation of defined RNA classes. Correlated radioautographic and biochemical studies with radioactive delta-aminolevulinic acid and leucine indicate that EPC's and other early erythroid elements synthesize not only hemoglobin but also ferritin and ribosomal proteins. It is concluded that: (a) erythroid RNA synthesis is most pronounced in the early developmental stages, being manifested predominantly by rRNA production but including tRNA and Hb-mRNA; (b) intermediate developmental stages show both "ribosomal wastage" and decreased growth rate, marking a pivotal point between the transcriptional activities of early stages and translational activities of late stages; (c) EPC's represent a cell population already committed to RBC formation and are excluded from a role as the pluripotential stem cell.

Animals↗
PubMed1991

Kinetic analysis.

With the aid of positron emission tomography the concentration of radioactivity labeled ligands can be measured as a function of time in small parts of the human body in vivo. The use of short lived isotopes enables repeated studies to be performed on the same subject within reasonable time. A basic tool in the analysis of such data is a tracer kinetic model which relates the time course of the radioligand in plasma to the time course of the radioligand in the tissue. The model takes into account transport between the blood and the tissue, specific binding and release from the receptors, and non-specific binding. From a fit of the model to the measured time course of the radioligand, the receptor density, the association rate constant, and the dissociation rate constant can be determined in small volume elements of the tissue.

Humans↗
PubMed1977

Metallobiochemistry of heavy metal pollution: nuclear and radiochemical techniques for long term--low level exposure (LLE) experiments.

The chronic exposure of man to increasing amounts of heavy metals as a consequence of environmental pollution, requires accurate knowledge of how much the homeostatic control of trace elements can stand increased exposure to abnormal amounts of metal pollutants without alteration of the biochemical functions. This topic includes the study of the accumulation of metal pollutants in the body with the identification of metal biocomplexes under long term-low level exposure (LLE) conditions. Extremely sensitive analytical techniques are required for experimentation at the heavy metal levels which are typical of a polluted environment in order to assess the limits of physiological homeostatic controls. The possiblity of applying nuclear and radiochemical techniques, such as neutron activation analysis, multiple tracing, high resolution gamma-ray spectrometry and Cerenkov counting, coupled with biochemical techniques, such as gel filtration, ion-exchange chromatography, polyacrylamide gel electrophoresis and differential centrifugation, has been demonstrated in various typical applications in metallobiochemistry. The subject of the first part of this paper is the development and improvement of the techniques, dealing with potential metal binding components, such as metalloenzymes and nucleic acids chosen as models. The developments refer to: preparation of labelled metal pollutants with very high specific activity to label in vivo nanogram or subnanogram amounts of pollutant metals; neutron activation analysis of enzymes and nucleic acids with the aim of analyzing concentrations of many metal pollutants in the identified metal binding components of the microsamples; radiochemical methods including radiobiochemical techniques for multielement tracer experiments and for studying the interaction of heavy metas and metal binding components; development of complementary counting techniques. The in vivo applications are centered on biochemical studies on cadmium, in particular on the long term-low exposure experiment, which is under investigation at present, with the identification of both critical organs of accumulation and of the cadmium binding components. Results are given for biochemical mechanisms involving cadmium such as the stimulation of the "de novo" biosynthesis of rat liver and intestine cadmium binding proteins (CdBP) and on the systematic study of the interaction of metal pollutants and rat liver cadmium binding proteins itself. Preliminary data are also given for short term experiments dealing with the identification of cellular metal binding components for V, Se, Cd and Pb.

Alkaline Phosphatase↗