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PubMed2004

Pulsed discharge detector: theory and applications.

The pulsed discharge detector (PDD) is a significant advancement in gas chromatography (GC) detector design which can be operated in three different modes: pulsed discharge helium ionization (He-PDPID), pulsed discharge electron capture (PDECD) and helium ionization emission (PDED). The He-PDPID can detect permanent gases, volatile inorganics and other compounds which give little or no response with the flame ionization detector (FID) and has significantly better limits of detection (minimum detectable quantities (MDQs) in low picogram range) than can be achieved with a thermal conductivity detector (typically not lower than 1 ng). The PDECD has similar or better sensitivity (MDQs of 10(-15) to 10(-12) g) than radioactive source ECD but does not require licensing, wipe tests and other administrative or safety requirements which have increased over security concerns. The PDED shows promise as an extremely selective and sensitive elemental detector but a commercial unit is not presently available. In this report, the theory of operation, applications of the PDD and the practical aspects of using this novel detector are presented.

Animals↗
PubMed1982

A phosphorylated basic vaccinia virion polypeptide of molecular weight 11,000 is exposed on the surface of mature particles and interacts with actin-containing cytoskeletal elements.

A phosphorylated vaccinia virus structural polypeptide of an apparent molecular weight of 11,000 (p11K) was isolated by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and used for antibody induction. After purification by antigen affinity chromatography, the immunoglobulins detected only one target of a rather basic nature in two-dimensional immune blotting procedures of total virion proteins. By use of a combination of biological, biochemical, and microscopic techniques, p11K could be located on the surface of those vaccinia virus particles, with "classical" morphology and a buoyant density of 1.27 g/cm3. Upon immunoprecipitation from radioactively labeled infected cells, p11K appeared to be complexed to two additional virus structural proteins, which could be tentatively identified by their molecular weights as precursors for the two major core constituents. When virus assembly was inhibited by rifampin treatment of infected cells, a great part of p11K, either free or in complexed form, was found associated with actin-containing cytoskeletal elements. The ability of p11K to interact with a not-yet-identified, microfilament-associated cellular protein may be related to previous findings showing that assembled vaccinia particles in situ are found in connection with microfilaments. A possible role for the structures precipitated by p11K-specific antibodies in early stages of particle assembly is discussed.

Animals↗
PubMed2002

Rat vasopressin mRNA: a model system to characterize cis-acting elements and trans-acting factors involved in dendritic mRNA sorting.

The genes encoding the vasopressin (VP) and oxytocin (OT) precursors are expressed in magnocellular neurons of the hypothalamo-neurohypophyseal system. The neuropeptides have a dual function: (1) they are secreted from the nerve terminals into the systemic circulation to act as hormones on various peripheral target organs; and (2) VP and OT are also released from the dendrites into the central nervous system where they presumably play a role as either neurotransmitters or as modulators of the classical transmitters. Substantial amounts of VP and OT mRNAs are sorted to both axons and dendrites. Since the latter are equipped with components of the translation machinery, the peptide hormone precursors are likely to be locally synthesized in dendrites of magnocellular neurons. Evidence for axonal precursor synthesis, on the other hand, has not been obtained. Subcellular mRNA localization is a complex pathway. It is determined by sequences (cis-acting elements) within the RNA and proteins (trans-acting factors) which interact with these elements in order to guide the molecules to their ultimate destination. We have investigated the mechanisms involved in mRNA targeting in neurons by using VP mRNA as a model system. Recombinant eukaryotic expression vectors harboring the VP cDNA have been microinjected into the cell nuclei of cultured superior cervical ganglion (SCG) neurons. The subcellular distribution of the vector-expressed mRNAs was determined by non-radioactive in situ hybridization techniques. This revealed transport of VP mRNA to the dendrites, but not to the axonal compartment of SCG neurons. A complex dendritic localizer sequence (DLS) that spans part of the coding region as well as the 3'-untranslated region was identified by microinjecting constructs encoding partial sequences of the VP mRNA. In order to characterize trans-acting factors interacting with this element, protein/RNA binding experiments with radiolabeled in vitro synthesized VP RNA probes and proteins extracted from rat brain have been carried out. A protein specifically interacts with the DLS of the VP mRNA but not with sequences that obviously lack a role in subcellular RNA transport. Biochemical purification revealed that this protein is the multifunctional poly(A)-binding protein (PABP). It is well known for its ability to bind with high affinity to poly(A) tails of mRNAs, prerequisite for mRNA stabilization and stimulation of translational initiation, respectively. With lower affinities, PABP can also associate with non-poly(A) sequences. The physiological consequences of these PABP/RNA interactions include functions such as translational silencing. The translational state of mRNAs subject to dendritic sorting is most likely influenced by external stimuli. Consequently, PABP could represent one of several components necessary to regulate local synthesis of the VP precursor and possibly of other proteins.

Animals↗
PubMed1996

Induction of phloem unloading in Arabidopsis thaliana roots by the parasitic nematode Heterodera schachtii.

Phloem unloading of both the fluorescent probe carboxyfluorescein (CF) and 14C-labeled solutes was induced in Arabidopsis thaliana L. roots by the parasitic nematode Heterodera schachtii Schmidt. Confocal laser scanning microscopy demonstrated that anomalous unloading of CF from the sieve element companion cell complexes occurred specifically into the syncytium, the nematode-induced feeding structure located within the stele of the root. From this syncytial complex of modified root cells, both fluorescent and radioactive labels were withdrawn by feeding nematodes. Movement of CF was unidirectional from the phloem to the syncytium. A range of low-molecular-weight fluorescent probes (including CF) microinjected into the syncytium stayed in this structure, demonstrating that it is symplastically isolated from the surrounding root tissue. The mechanism of unloading in this host-pathogen relationship therefore appears to be apoplastic. Our results provide unequivocal evidence that sedentary cyst-forming nematodes have direct access to phloem-derived solutes.

Animals↗
PubMed1996

DNA damage induction by 125I-estrogen.

DNA damage induced by the radioactive decay of 125I-estrogen (125I-VME2) in an estrogen receptor expressing CHO cell line, CHO-ER, was measured. 125I-VME2 targeted 125I atoms proximal to DNA estrogen response elements (EREs). 125I decays were accumulated at -135 degrees C, and thereafter assayed by alkaline and neutral filter elution techniques to measure DNA single strand break (ssb) and double strand break (dsb) induction respectively. Increasing DNA damage (both ssbs and dsbs) was detected after exposure of cells to increasing concentrations of 125I-VME2. DNA ssb and dsb dose-response curves for 125I-VME2 were multiphasic. The rates of DNA damage induction by the decay of 125I-VME2 was determined by comparing slopes of all data or by comparing initial slopes. DNA ssb induction per 125I-VME2 decay was approximately 2 times greater compared with DNA dsb induction. 125I-VME2 decay induced approximately 4-8 times more DNA dsbs than 125IUdR decay.

Animals↗
PubMedDate not supplied

[Bone marrow hematopoiesis in those who worked in the cleanup of the aftermath of the accident at the Chernobyl Atomic Electric Power Station with a history of acute radiation sickness (based on myelogram data)].

On the basis of myelograms an evaluation was done of medullary hemopoiesis in 15 subjects who had been taken ill with acute radiation sickness (ARS) as a result of Chernobyl accident in 1986. 6-12 years following the exposure to ionizing radiation the bone marrow of ARS convalescents still shows a tendency toward hypocellularity (the number of myelokaryocytes in the examinus ranged from 40 to 80 x 10(9)/l), high index of neutrophil maturation (0.99) was recordable, which fact was related to depletion of granulocyte reserve and increase among the elements of granulopoiesis of share of proliferating cells, together with a rise in the number of lymphoid elements (19%).

Acute Disease↗
PubMed1999

Targeted delivery of radiolabeled imaging and therapeutic agents: bifunctional radiopharmaceuticals.

Clinical application of radioactive diagnostic and therapeutic agents constitutes one of the great advances in noninvasive medicine, nuclear medicine. The radioactive agents used in the nuclear medical field are called "radiopharmaceuticals," and are required to exhibit high and specific localization of radioactivity into target tissue. Among radionuclides used in radiopharmaceuticals, radiometals such as 99mTc and (111)In have received much attention because of their nuclear physical characteristics and widespread availability. However, since these metallic elements are not constituents of bioactive molecules, they cannot simply replace common constituent atoms in biologically interesting compounds. Thus, demand for biospecific radiopharmaceuticals constitutes a great challenge in rational design of biologically active molecules labeled with metallic radionuclides, and evolves into a generation of bifunctional radiopharmaceuticals. Molecules contain both a biologically active site and a chelating group for binding the metallic radionuclide in which attachment of a chelating group does not affect the inherent biospecificity of the mother compound. This paper describes recent progress in research of macro- and small-molecular bifunctional radiopharmaceuticals for targeted diagnosis and therapy.

Animals↗
PubMed1978

Potentiation by substance P of contractions of the isolated vas deferens of the mouse elicited by electric field stimulation and by drugs.

1 Isolated vasa deferentia from the mouse were opened longitudinally and suspended in Krebs solution at 37 degrees C in an organ bath. Contractions of the muscle were elicited by electric field stimulation, noradrenaline (10(-6) M) and acetylcholine (10(-6) M). Continued transmural stimulation evoked a biphasic response comprising a rapid twitch followed about 10 s later by a smaller, sustained rise in muscle tone.2 The amplitudes of nerve-mediated and drug-induced responses were considerably potentiated by substance P (SP) in the dose range 10(-12) to 10(-7) M. Higher concentrations of SP were directly spasmogenic. The sensitizing property of SP was dose-dependent and was usually well maintained, but always disappeared quickly on washing the preparation. In some experiments SP facilitated the twitch, but not the subsequent phase of the electrically-induced contraction or the response to externally applied noradrenaline.3 Phentolamine (10(-6) M) failed to block this effect of SP, but itself potentiated the nerve-mediated twitch, and completely abolished the sustained secondary contraction.4 Desmethylimipramine (10(-6) M) enhanced the delayed contraction but not the immediate contraction.5 The uptake of tritiated noradrenaline (3 x 10(-7) M) by vasa was inhibited by desmethylimipramine (10(-6) M) and increased by nialamide (3 x 10(-5) M), but was not modified by SP (10(-6) M).6 Nerve-mediated release of accumulated radioactivity was accelerated by phentolamine, but not by SP or desmethylimipramine.7 These findings suggest that SP sensitizes the muscle cells to depolarizing stimuli but that it has no facilitatory effect on sympathetic neural elements.

Animals↗
PubMed1990

Accumulation of radiocaesium in fungi.

The accumulation of radioactive Cs by fungi was studied by analysis of fruit bodies (n (total) = 205, n greater than or equal to 5 for 22 species) collected in 1988 in a Norwegian mountain area with high deposition of radiocaesium from the Chernobyl accident. To account for site variation, the radiocaesium content of soil and plants was determined for each sampling spot. The soil contained 5-600 kBq/m2 (median = 50 kbq/m2, 134Cs + 137Cs). The plant content ranged from 0.25 to 23 Bq/g dry weight (median = 3.1 Bq/g) and was positively correlated with radiocaesium concentration in the soil (r = 0.56) and negatively correlated with soil pH (r = -0.28). The ratio between radiocaesium content in fungi and that in plants at the same spot (F/P) differed among species: 25 species had F/P values between 30 and 270, 12 species had F/P values between 10 and 30, and the rest (16 species) had F/P values below 10 (only four samples had values below 1). The concentration of nonradioactive Cs in fruit bodies was positively correlated with their radiocaesium content. Certain species selectively accumulated one or several trace elements (V, Cd, Hg, Pb, Th).

Accidents↗
PubMed1986

Temperature-sensitive steps in the transport of secretory proteins through the Golgi complex in exocrine pancreatic cells.

The effect of temperature on secretory protein transport was studied by cell fractionation of rat pancreatic lobules, pulse-labeled in vitro with [35S]methionine and chased for 60 min at 16, 20, or 37 degrees C. Chase at 37 degrees C allowed secretory proteins to reach a zymogen granule fraction, whereas chase at 16 or 20 degrees C led to their extensive retention in a total microsomal fraction. To pinpoint the sites of transport inhibition, total microsomes were subfractionated by flotation in a sucrose density gradient. Five bands were resolved, of which the heaviest or B1 (density = 1.20 g/ml) consisted primarily of rough microsomes. The lighter fractions, B2 (1.17 g/ml), B3 (1.15 g/ml), and B4 (1.14-1.13 g/ml), consisted primarily of smooth vesicles derived from Golgi elements. B4 had the highest specific activity for galactosyltransferase, a trans Golgi cisternal marker; B2, B3, and B4 are assumed to represent cis, middle, and trans Golgi subcompartments, respectively. At the end of a 2-min pulse, a single peak of labeled proteins colocalized with B1. During subsequent 60-min chases, labeled proteins advanced to B2 at 16 degrees C and to B3 at 20 degrees C. At 37 degrees C the radioactivity remaining in the total microsomal fraction was distributed among four peaks (B1-B4). The results indicate that transport from the endoplasmic reticulum to the Golgi complex is strongly inhibited below 20 degrees C. At 16 degrees C, the bulk of the cohort of labeled secretory proteins is still in the rough endoplasmic reticulum, but its advancing front reaches cis Golgi elements. At 20 degrees C, the front advances to a middle Golgi compartment, and at 37 degrees C most of the cohort (approximately 70%) reaches condensing vacuoles and zymogen granules. It is concluded that transport steps along the endoplasmic reticulum-plasmalemma pathway have distinct temperature requirements.

Animals↗
PubMed1996

Differentiation by magnesium ions of affinities of nuclear proteins for consensus core nucleotide element of the transcription factor c-Myc in murine brain.

The addition of divalent cations such as Mg(2+) and Ca(2+) ions markedly reduced binding of a radiolabeled double stranded oligonucleotide probe for the transcription factor c-Myc in the presence of 100 mM KCl in nuclear extracts of the mouse whole brain. Irrespective of the addition of MgCl(2), binding was selectively competed with the unlabeled probe for c-Myc having a double stranded conformation. Treatment with V8 protease differentially modulated binding of the probe for c-Myc determined in the presence and absence of added MgCl(2). Introduction of irreversible covalent bonding between the radiolabeled probe and nuclear proteins led to retarded mobility of the radioactive probe/protein complex in the presence of MgCl(2) on sodium dodecyl sulfate electrophoresis regardless of treatment with DNase. However, an antibody against the c-Myc protein affected neither mobility nor intensity of the radioactive band on gel retardation electrophoresis. Moreover, regional distribution was different from each other in mouse brain when determined in the presence and absence of added MgCl(2). These results suggest that magnesium ions may have an ability to differentiate between nuclear c-Myc family proteins with different affinities for the consensus core nucleotide element CACGTG in murine brain.

Animals↗
PubMed1996

[Wilhelm Conrad Röntgen and the discovery of X-rays].

W.C. Röntgen reported the discovery of X-rays in December 1895 after seven weeks of assiduous work during which he had studied the properties of this new type of radiation able to go through screens of notable thickness. He named them X-rays to underline the fact that their nature was unknown. The news of this discovery immediately aroused an immense interest in the public and also initiated intense research in several directions. Physicians and physicists began as early as January 1896 to use X-rays on patients to investigate the skeleton and subsequently the lung and other organs. This was the birth or radiology. Rapidly they observed skin erythema, which led to the idea of using X-rays against a variety of lesions. In June 1896 the first patient was treated by radiotherapy. J.J. Thomson (Cambridge, U.K.) showed that X-rays were able to ionize gaz and the study of this phenomenon led to the discovery of electrons in 1897. In order to understand the emission of X-rays, H. Becquerel (Paris) investigated the role of the phosphorescence of the glass of the tube and while doing so discovered radioactivity in March 1896. X-rays and radioactivity were at the origin of the scientific revolution at the end of the 19th and the beginning of the 20th centuries. Research on radioactive materials demonstrated the existence of atoms which had been till then only a convenient hypothesis for explaining chemical reactions, but whose reality was considered as dubious by most physicists. Moreover, interaction of particles emitted by radionuclides and atoms enabled first the study of the structure of the atom and subsequently its nucleus. Matter, elements which were thought to be immutable were found to be transmutable, and eventually to disintegrate. The origin of the energy transferred to the radiation which was emitted appeared as a mystery and in order to explain it the physicist had to accept that matter could convert energy. In 1903 Einstein established the equivalence between matter and energy. Matter, energy, electricity, light which were formerly considered as continuous quantities were found to be discrete: there are particles of matter (elementary particles), energy (quanta, Planck 1905), electricity (electron), light (photons). Radioactive decay, particle interactions imposed a probabilistic physics which progressively replaced classic deterministic physics. Radioactivity can be used as a clock to measure time in the universe. Datations were made for fossils, art masterpieces and also for the earth, the solar system and universe. X-rays diffraction proved to be a powerful tool for studying crystals and molecules, in particular protein, and in 1953 enabled to demonstrate the DNA double helix. Hence X-rays and radioactivity originated a revolution in physics and science and in the vision of nature. The imperceptible and yet so powerful rays demonstrated the deficiencies of our senses. Mathematical entities and instrumentation must complement our sensations. The huge increment in our knowledge is accompanied by a divorce between the scientist and the layman who now often has great difficulties understanding new concepts not only in physics but also in biology.

Germany↗
PubMed1993

Chemical methods to reduce the radioactive contamination of animals and their products in agricultural ecosystems.

After major nuclear accidents the most effective action to reduce activity levels in animal products is to provide uncontaminated feed or feed diluted with uncontaminated material. However, uncontaminated feed may not always be available in such situations. Therefore other effective procedures are needed to reduce activity levels which must be easy to apply, low in cost and have no side effects on animals and their products. Chemical substances administered as feed additive to housed or grazing animals act by influencing gut absorption or increasing the rate of excretion from blood and organs. The main chemical methods used are: (1) dilution of radionuclides by stable isotopes or analogous inactive elements; and (2) natural or artificial binding agents. In this paper a summary and critical review of the different chemical methods described in the literature is given.

Accidents↗
PubMed1987

Transport of iron and transferrin synthesis by the seminiferous epithelium of the rat in vivo.

The transport of radioactive iron across the seminiferous tubules was analyzed in vivo by light-microscope quantitative radioautography. At 5 min after a single intratesticular injection of 55Fe-transferrin, a strong labeling of the basal aspect of the seminiferous epithelium was observed. Between 30 min and 2 h, the labeling on the basal aspect of the seminiferous epithelium decreased. This decrease was accompanied by a substantial increase of the radioautographic reaction over the cellular elements in the adluminal compartment. These results were consistent with the demonstration of 59Fe associated with meiotic spermatocytes and differentiating spermatids isolated by velocity sedimentation from testes injected with 59Fe-transferrin. Furthermore, after a single intratesticular injection of 59Fe-labeled human transferrin, radiolabeled rat transferrin was immunoprecipitated from homogenates of isolated tubules with a specific antibody and appeared as a single radioactive band on fluorographs of urea/polyacrylamide gels. Similarly, 59Fe-labeled rat transferrin but not 125I-transferrin was immunoprecipitated from rete testis fluids of testes infused with either 59Fe- or 125I-labeled human transferrin. Finally, the synthesis of testicular transferrin in vivo was demonstrated in fluorographs of immunoprecipitated transferrin after an intratesticular injection of 35S-methionine in rats whose livers were excluded from the general circulation by ligation of both the hepatic artery and the portal vein. Thus, our results demonstrated a unidirectional system of iron transport from the basal compartment of the seminiferous epithelium to the germ cells in the adluminal compartment involving two distinct transferrins, i.e., a serum transferrin and a testicular transferrin synthesized by the seminiferous epithelium.

Animals↗
PubMed1984

Natural cytotoxicity in lymphatic metastasis. II. In vivo studies with BSp73 variants differing in metastatic capacity.

The survival of cloned variants of the BSp73 tumor differing in susceptibility to natural killer (NK) and macrophage-mediated cytotoxicity in vitro was evaluated in syngeneic animals. The cytocidal effect was assayed by whole-body determination of (125I)5-iodo-2'-deoxyuridine (125IUdR) retention in intact animals and in animals depleted of phagocytes and/or radiation-sensitive lymphocytes. The following results were obtained: (1) In the peritoneal cavity, survival of the susceptible tumor cells (variant AS) was significantly higher in rats pretreated with radiation and silica than in untreated rats. (2) Cold target competition, response modification by C. parvum, and correlation of label excretion with survival of animals supported the notion that excretion rates of radioactivity were in fact determined by natural cytotoxicity in vivo. (3) Tumor cells resistant to natural cytotoxicity in vitro (variant ASML) were nevertheless killed in vivo (IP) by NK cells and macrophages. (4) Additional elements of tumor cell destruction were active upon IV injection of both AS- and ASML-derived cells, since rapid label excretion was observed irrespective of irradiation and silica treatment or addition of excess unlabeled competitor cells. The apparent increase in susceptibility of ASML cells in vivo might be due to a shift in phenotype induced by microenvironmental factors. No evidence was gained that differences in metastatic capacity exhibited by the variants might relate to differential action of natural cytotoxicity on these cells.

Animals↗