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PubMed2006

Competitive effect of iron(III) on metal complexation by humic substances: characterisation of ageing processes.

Aiming at an assessment of counteractive effects on colloid-borne migration of actinides in the event of release from an underground repository, competition by Fe(III) in respect of metal complexation by dissolved organic matter was investigated for the example of Eu(III) as an analogue of trivalent actinides. Complexation with different humic materials was examined in cation exchange experiments, using (59)Fe and (152)Eu as radioactive tracers for measurements in dilute systems as encountered in nature. Competitive effects proved to be significant when Fe is present at micromolar concentrations. Flocculation as a limiting process was attributed to charge compensation of humic colloids. Fe fractions bound to humic acids (HA) were higher than 90%, exceeding the capacity of binding sites at high Fe concentrations. It is thus concluded that the polynuclear structure of hydrolysed Fe(III) is maintained when bound to HA, which is also inferred from UV-Vis spectrometry. The competitive effect was found to be enhanced if Fe and HA were in contact before Eu was added. Depending on the time of Fe/HA pre-equilibration, Eu complexation decreased asymptotically over a time period of several weeks, the amount of bound Fe being unchanged. Time-dependent observations of UV-Vis spectra and pH values revealed that the ageing effect was due to a decline in Fe hydrolysis rather than structural changes within HA molecules. Fe polycations are slowly degraded in contact with humic colloids, and more binding sites are occupied as a consequence of dispersion. The extent of degradation as derived from pH shifts depended on the Fe/HA ratio.

Benzopyrans↗

PubMed1995

Real-time monitoring of antigen-antibody recognition on a metal oxide surface by an optical grating coupler sensor.

Real-time monitoring of intermolecular interactions can provide a direct and rapid estimate of the affinity and kinetics of interactions between biomolecules. Optical methods based on the measurement of changes of refractive index in the immediate vicinity of a liquid-solid interface are particularly convenient because they require no radioactive, fluorescent or other labelling of the molecules under study. In the present work we have followed the specific interaction of protein molecules on a SiO2/TiO2 surface with the help of the optical grating coupler sensor instrument BIOS-1. This instrument allows the determination of the absolute mass of protein adsorbed to the sensor surface and, therefore, the calculation of the molar ratio of the components partaking in an intermolecular interaction. For example, about 3 ng avidin/mm2 surface area could be adsorbed. This amount closely corresponds to a monolayer composed of densely packed globular avidin molecules. A dimeric, biotinylated leucine zipper peptide was bound to this avidin layer at a molar ratio of 1:1 (1 peptide molecule/4 biotin binding sites of tetrameric avidin). An average of 1/2.6 peptides was recognized by a peptide-specific monoclonal antibody. Even though avidin was not covalently bound to the sensor surface, the avidin-coated chip could be used repeatedly to measure the time course of antibody binding as a function of the concentration of the antibody. From such measurements it was possible to calculate the association and dissociation rate constants assuming that the interaction of the antibody with the surface-bound antigen can be described by a simple Langmuir binding model. The limits of the Langmuir model are discussed. The same antigen-antibody reaction was also analyzed by a surface plasmon resonance biosensor (BIAcoreTM, Pharmacia). The results obtained with the two instruments, which register different optical phenomena and employ different surface chemistry, were in good agreement.

Amino Acid Sequence↗

PubMed1997

Generation of putative intrastrand cross-links and strand breaks in DNA by transition metal ion-mediated oxygen radical attack.

Generation of putative intrastrand cross-links and strand breaks was investigated in salmon sperm DNA exposed to Fenton-type oxygen radical-generating systems. 32P-Postlabeling analysis of DNA treated with hydrogen peroxide and either copper(II), chromium(VI), cobalt(II), iron(II), nickel(II), or vanadium(III) resulted in the detection of between four and eight radioactive TLC spots that are probably hydroxyl radical-mediated oxidative DNA lesions. The copper Fenton system generated the highest total yield of these DNA lesions (75.6 per 10(8) nucleotides), followed by cobalt (47.5), nickel (26.2), chromium (25.1), iron (21.7), and vanadium (17.1). Two spots, common to all these Fenton systems, were the major oxidation products in each case. Similar Fenton-type treatment of the purine dinucleotides dApdG and dApdA resulted in products that were chromatographically identical on anion-exchange TLC and on reverse-phase HPLC to the two major products generated in DNA. These results extend our earlier studies suggesting that these products were the result of a free radical-mediated intrastrand cross-linking reaction. Incubations involving cadmium(II), chromium(III), or zinc(II) ions with hydrogen peroxide did not generate DNA oxidation products at levels greater than in incubations with hydrogen peroxide alone. Generation of the putative intrastrand cross-links increased in a concentration-dependent manner up to 1 mM cobalt, nickel, or chromium(VI) ions. However, in experiments with copper, iron, or vanadium ions, maximum levels were obtained at 250, 150, and 150 microM, respectively, and the yield declined with higher concentrations of these three metal ions. Agarose gel electrophoresis demonstrated extensive DNA strand breakage with copper, iron, chromium(III), or vanadium, but not with nickel, chromate(VI), cobalt, cadmium, or zinc Fenton systems. The results demonstrate that generation of the putative intrastrand cross-links and strand breaks in DNA, mediated by Fenton reactions, occurs by independent mechanisms.

Animals↗

PubMed1980

The effect of metal salts on the distribution of iron-59 in rats: Manganese (II), nickel (II) and tin (II).

The disappearance and reappearance of iron-59 in plasma and blood at various time intervals has been studied in control, manganese, nickel and tin administered and anaemic rats after a single intravenous injection of an aqueous solution of radioactive iron (III) citrate. Significant difference was observed in the rate of reappearance of iron-59 in the circulation between control and manganese treated animals. The disappearance of iron-59 from the plasma of control and treated animals however did not show any appreciable difference. A significant increase in the radio-iron content was observed in bone marrow, liver and kidney of treated animals as compared to control group forty eight hours after Fe-59.

Anemia↗

PubMed1998

Radioautographology: the proposal of a new concept.

A new concept termed "radioautographology" is advocated. This term was synthesized from "radioautography" and "ology", expressing a new science derived from radioautography. The concept of radioautographology (RAGology) is that of a science whose objective is to localize radioactive substances in the biological structure of objects and to analyze and study the significance of these substances in the biological structure. On the other hand, the old term radioautography (RAG) is the technique used to demonstrate the pattern of localization of various radiolabeled compounds in specimens. The specimens used in biology and medicine are cells and tissues. They are fixed, sectioned and placed in contact with the radioautographic emulsions, which are exposed and developed to produce metallic silver grains. Such specimens are designated as radioautographs and the patterns of pictures made of silver grains are named radioautograms. The technicians who produce radioautographs are named radioautographers, while those who study RAGology are scientists and should be called radioautographologists. The science of RAGology can be divided into two parts, general RAGology and special RAGology, as most natural sciences usually can. General RAGology is the technology of RAG which consists of three fields of science, i.e., physics concerning radioactivity, histochemistry for the treatment of cells and tissues, and photochemistry dealing with the photographic emulsions. Special RAGology, on the other hand, consists of applications of general RAGology. The applications can be classified into several scientific fields, i.e., cellular and molecular biology, anatomy, histology, embryology, pathology and pharmacology. Studies carried out in our laboratory are summarized and reviewed. All the results obtained from such applications should be systematized as a new field of science in the future.

Autoradiography↗

PubMed2000

Natural transfer of viable microbes in space.

The possibility and probability of natural transfer of viable microbes from Mars to Earth and Earth to Mars traveling in meteoroids during the first 0.5 Ga and the following 4 Ga are investigated, including: --radiation protection against the galactic cosmic ray nuclei and the solar rays, dose rates as a function of the meteorite's radial column mass (radius x density), combined with dose rates generated by natural radioactivity within the meteorite; and survival curves for some bacterial species using NASA's HZETRN transport code --other factors affecting microbe survival: vacuum; central meteorite temperatures at launch, orbiting, and arrival; pressure and acceleration at launch; spontaneous DNA decay; metal ion migration --mean sizes and numbers of unshocked meteorites ejected and percentage falling on Earth, using current semiempirical results --viable flight times for the microbe species Bacillus subtilis and Deinococcus radiodurans R1 --the approximate fraction of microbes (with properties like the two species studied) viably arriving on Earth out of those ejected from Mars during the period 4 Ga BP to the present time, and during the 700 Ma from 4.5 to 3.8 Ga. Similarly, from Earth to Mars. The conclusion is that if microbes existed or exist on Mars, viable transfer to Earth is not only possible but also highly probable, due to microbes' impressive resistance to the dangers of space transfer and to the dense traffic of billions of martian meteorites which have fallen on Earth since the dawn of our planetary system. Earth-to-Mars transfer is also possible but at a much lower frequency.

Bacillus subtilis↗

PubMed1987

In vivo cytotoxicity assays with 111In-labeled tumor cells: comparison with [125I]iododeoxyuridine-labeled cells and effects of chelators and inoculation site.

The fate of cells inoculated in nude mice can be determined using human tumor cells prelabeled with 111In oxine (111InOx). To facilitate elimination of extracellular 111In released from killed cells, an appropriate metal chelating agent is administered to the host mice. With calcium disodium edetate administered by various routes, highly significant differences in the rates of 111In loss were observed for viable compared to killed cells after i.p. or i.m. inoculation. Radioactivity was eliminated at similar rates for mice bearing viable cells labeled with 111In or with [125I]iododeoxyuridine (125IUdR). For killed cells, 111In was eliminated somewhat less efficiently than 125I. The 111In-prelabeling method allows facile and sensitive determination of host-mediated cytotoxicity for inoculated tumor cells.

Animals↗

PubMed1988

Sensitive non-radioactive dot-blot hybridization using DNA probes labelled with chelate group substituted psoralen and quantitative detection by europium ion fluorescence.

A new labelling method for cloned DNA probes used in hybridization assays is described. The DNA insert of recombinant plasmid DNA was made partially single-stranded for the labelling reaction by a restriction enzyme digest, followed by a controlled exonuclease III incubation. A thiol-containing psoralen derivative was covalently bound through irradiation with UV-light to the remaining double-stranded region of the plasmid DNA. The psoralen-SH groups were labelled with a large number of metal chelators (diethylentriamine pentaacetic acid, DTPA) using poly-L-lysine as a macromolecular carrier. The main advantage of the labelling procedure is that a high degree of labelling is achieved without modification of the single-stranded DNA hybridizing sequences. The specific hybrids were labelled after filter hybridization with europium ions through the chelating groups of DTPA. The europium ions were quantitatively detected by time-resolved fluorometry. The sensitivity of the assay for target DNA detection was in the low picogram range, comparable to radioactively labelled DNA probes.

Chelating Agents↗

PubMed1985

Can a sponge fractionate isotopes?

The study has unequivocally demonstrated that siliceous sponges Spirastrella cuspidifera and Prostylyssa foetida from the same microecological niche exhibit a high degree of species specificity, while accumulating a host of heavy metal ions (Ni, Cr, Cd, Sn, Ti, Mo, Zr). S. cuspidifera accumulated, in addition, 60Co and 63Ni, showing discrimination against other radionuclides, 137Cs and 131I, present in the ambient waters receiving controlled low level waste discharges from a B.W.R. nuclear power station. P. foetida, on the other hand, accumulated only 131I and showed discrimination against other radionuclides including 60Co, although the stable iodine concentrations in both the sponges were the same. The specific activity of 60Co (in becquerels per gram of 59Co) in S. cuspidifera and 131I (in becquerels per gram of 127I) in P. foetida were at least two orders of magnitude greater than in the ambient sea water. That of 63Ni (in becquerels per gram of 62Ni) in S. cuspidifera, on the other hand, was lower by two orders of magnitude than in either abiotic matrices from the same environment. Thus, not only did both the species show bioaccumulation of a specific element, but also preferential uptake of isotopes of the same element, though they were equally available for intake. Such differential uptake of isotopes can possibly be explained in terms of two quite different mechanisms operating, each applicable in a particular case. One is that the xenobiotic isotope enters the environment in a physicochemical form or as a complex different from that of its natural counterpart. If equilibration with the latter is slow, so that the organism acquires the xenobiotic in an unfamiliar chemical context, it may treat it as a chemically distinct entity so that its concentration factor differs from that of stable isotope, thus changing the specific activity. Alternatively, if the xenobiotic is present in the same chemical form as the stable isotope, the only way in which specific activities can be modified is by fractionation on the basis of mass of isotope. In view of the remarkable concentration factors observed for stable and radioactive isotopes of the same element and the specific activities reached, it is desirable that species of sponges, especially from the coastal and estuarine environments, be monitored to detect levels of pollution due to anthropogenic substances.

Animals↗

PubMed1979

In vitro sensitivity test of stomach cancer tissues by the use of metal grid method.

Ninety-nine specimens obtained from 53 patients with stomach cancer were cultured for about 3 days by means of the stainless steel grid method. In vitro effects of antitumor drugs on the cancer cells were evaluated autoradiographically or biochemically using a liquid scintillation counter to measure the uptake of 3H-thymidine. The radioactivity of the labeled tumor cells of both control fragments and fragments affected by drugs varied greatly among individual tumors. Therefore, the in vitro efficacy of antitumor drugs was represented as a comparison with that of control fragments. Positive correlation between in vitro tests and the clinical effects of antitumor drugs was observed in the specimens of 18 cases.

Antineoplastic Agents↗

PubMed2001

The 2,3-bisphosphoglycerate-independent phosphoglycerate mutase from Trypanosoma brucei: metal-ion dependency and phosphoenzyme formation.

Recombinant cofactor-independent phosphoglycerate mutase from Trypanosoma brucei was inactivated by EDTA, and reactivated by Co(2+) much more than by Mn(2+) or Fe(2+). It displayed a minor phosphoglycerate phosphatase activity, which was stimulated by Mn(2+) more than by Co(2+). Upon incubation with [(32)P]phosphoglycerate, radioactivity was incorporated into the enzyme, most particularly in the presence of Mn(2+) or Fe(2+). The phosphorylated residue was identified by tandem mass spectrometry as Ser74, a residue homologous to the phosphorylated serine in alkaline phosphatase. However, the rates of formation and of disappearance of this phosphoenzyme were quite low compared to the mutase reaction. This and other properties indicated that the observed phosphoenzyme is an intermediate in the minor phosphatase activity rather than in the phosphomutase reaction.

2,3-Diphosphoglycerate↗

PubMed1996

Nickel incorporation into hydrogenase 3 from Escherichia coli requires the precursor form of the large subunit.

A mutant derivative of hycE, the gene for the large subunit of hydrogenase 3 from Escherichia coli, was constructed that lacks the 3'-terminal part encoding the C-terminal portion of the HycE polypeptide, which is proteolytically removed during maturation of the hydrogenase. The truncated gene was transferred to the in situ position on the chromosome. Although the mutant possessed HycE in its "mature" form, it was devoid of hydrogenase 3 activity. The activity was not restored by high nickel concentrations in the medium. The mutated HycE was not associated with detectable radioactivity when the strain was grown in the presence of 63Ni2+. These results indicate that the C-terminal extension in the precursor form of the large subunit keeps the protein in a conformation required for the coordination of the metal.

Base Sequence↗

PubMed1982

[Uranium concentration by crustacea: A structural, ultrastructural and microanalytical study by secondary ion emission and electron probe X ray microanalysis].

Experimental intoxications were performed on the Crayfish Pontastacus leptodactylus using hydrosoluble uranium nitrate. Investigations demonstrate that Crustacea are able to concentrate both uranium main radioactive isotopes 238U and 235U within the cuticle, gill epithelium, midgut gland (= hepatopancreas) and macrophagic hemocytes. The storage occurs within nucleus and lysosomal system where uranium is precipitated in the form of an unsoluble phosphate. The proposed hypothesis for the metal extrusion is the following: residual bodies containing the uranium precipitates are extruded into the extracellular space where they are absorbed, by phagocytosis, by the macrophagic hemocytes.

Animals↗

PubMed1999

Radiolabelling of parenteral O/W emulsions by means of neutron activation.

Parenteral O/W emulsions containing lanthanide fatty acid derivatives were prepared. With regard to enhancing the incorporation efficiency of the neutron activatable excipients, the addition of the non-ionic co-emulsifier Solutol HS 15 proved to be most suitable. Comparing the different chain lengths of the fatty acids, the long chain fatty acid derivative lanthanide(tri)stearate seemed to be superior in strengthening the interfacial layer. After neutron activation, the physical and chemical stability of the irradiated formulations was evaluated. The chemical stability, indicated by the concentration of lyso phosphatidylcholine as the degradation product of the main emulsifier, was shown to be dependent on the irradiation time. By applying a neutron flux of 2.1 x 10(13) neutrons/cm2 per s, the maximum should not rise above 60 s. The physical stability indicated by the particle size distribution was affected by the presence of the non-ionic co-emulsifier. Concerning the amount of radiation necessary for in vivo biodistribution studies the maximum load of Samarium fatty acid derivatives did not yield sufficient radioactivity levels. However, Europium derivatives could be shown to be suitable for in vivo studies.

Emulsions↗

PubMed1976

Metal chelates of L-DOPA for improved replenishment of dopaminergic pools.

An exploratory study consisting of physiochemical and animal experiments was undertaken with the objective of developing one or more metal-L-DOPA chelate systems for an improved transport of L-DOPA into the brain. This approach is based on a theoretical speculation that the pyridoxal-dependent decarboxylation of L-DOPA in the precerebral areas might be obviated by an appropriate metal chelation of the aminocarboxylate end of the L-DOPA molecule. Equilibium studies on the interactions of L-DOPE with Cu2+,Zn2+, Co2+, Mg2+ and Fe2+ ions and their ATP chelates were carried out in order to examine the conditions for the selective binding of the terminal amine group. Metal chelate systems for in vivo transport experiments were selected viz., Cu2+ or Zn2+-L-DOPA (1:2) and Cu2+ or Zn2+-ATP-L-DOPA (1:1:1) which contained the amine-bound metal ion in a completely coordinated form. Results of in vivo studies involving the intraperitoneal administration of 14C-and 3H-LABELED L-DOPA compounds have shown a 100-150% increase in the transport of L-DOPA into the brain by using the Cu2+ and Zn2+ chelates over that effected by using the unchelated L-DOPA. A chromatographic analysis of the brain homogenates showed that only 6% of the overall radioactivity of the brain could be attributed to 3-methoxytyrosine, and the remaining activity was due to DOPA, dopamine and norepinephrine. The transport effectiveness was also compared with that obtained by using the combination drug, RO4-4602 + L-DOPA.

Animals↗

PubMed1991

Olfactory primary neurons as a route of entry for toxic agents into the CNS.

Reports in the literature suggest that the primary sensory neurons of the olfactory system may provide a direct route of entry for agents into the central nervous system (CNS). To investigate whether cadmium, a heavy metal which is normally excluded from the CNS by the blood-brain barrier, can enter the CNS via the olfactory system, rats were exposed either intranasally (unilaterally) or ip to 109Cd (1 mumol Cd labeled with 1 microCi 109Cd). Rats were allowed to survive 7 days, at which point they were euthanized and the kidneys, livers, right and left forebrains, right and left olfactory bulbs, and right and left olfactory epithelia were removed. Tissues were placed in scintillation vials and radioactivity counted. In rats exposed by intranasal instillation, Cd levels were significantly elevated in the kidney, liver and ipsilateral olfactory bulb and epithelium, but not in the contralateral bulb and epithelium or forebrain areas. With the ip exposure, Cd levels were only elevated in the kidney and liver. In a second study the protocol was repeated (without ip exposure), but the olfactory bulbs and epithelium were washed in EDTA before counting. Cd was still present in the bulbs after washing, suggesting that the metal was internal and not bound to the external membrane. In the final experiment, both time course and dose effect of this phenomenon were explored. Rats were exposed either intransally to 1 mumol Cd labeled with 109Cd (1 microCi) and then sacrificed after 1, 3, 7, or 14 days or were exposed to 0.01, 0.1, or 1.0 mumol Cd labeled with 1 microCi 109Cd and sacrificed after 7 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1976

Inhibition and stimulation of rapid axonal transport in vitro by sulfhydryl blockers.

The effects of sulfhydryl blocking agents have been studied on the rapid axonal transport in vitro of [3H]leucine-labelled proteins in the frog sciatic nerve. The transport was inhibited in the presence of low concentrations of N-ethylmaleimide (NEM) (greater than or equal to 10(-5) M), p-chloromercuribenzene sulfonic acid (PCMBS) (greater than 10(-5) M) or ions of heavy metals, Cd2+ (greater than or equal to 5 X 10(-5) M), Hg2+ (greater than or equal to 5 X 10(-6) M) and Cu2+(greater than or equal to 10(-4) M). Both the amount and the rate of transported radioactivity were reduced. Transport inhibiting concentrations of these agents also inhibited the binding of colchicine in rat brain or frog nerve supernatants. The amount of transported proteins was increased at an unchanged transport rate by a very low concentration of NEM (10(-6) M), PCMBS (10(-6) M) and Cd2+ (10(-6)M), which did not affect the binding of colchicine. The present results suggest that stimulation of axonal transport can be achieved through an interaction with sulfhydryl groups.

4-Chloromercuribenzenesulfonate↗

PubMed1995

Innocuity of agents for radiocontrast enhancement of urinary tract stones.

OBJECTIVES: Mineral kidney stones are frequently difficult to detect due to their radiotranslucency. We have recently developed a method that enhances the visibility of such stones by retrograde infusions of certain heavy metal salt solutions such as cesium or lanthanide gadolinium. This report describes toxicologic studies carried out on the use of those contrast agents to introduce this technique eventually into clinical trials. METHODS: Systemic absorption was assessed in dogs through infusion of radioactive contrast agent into the renal pelvis with or without ureteral obstruction. Radioactivity in urine and blood was monitored. Local toxicity was studied in animals infused with the contrast agent at intervals up to 4 weeks. RESULTS: Reabsorption studies under high intrapelvic pressures (70 cm H2O or higher), demonstrated reabsorption of cesium. However, at normal intrapelvic pressures, only a moderate reabsorption of cesium was observed. No gadolinium reabsorption was detected even at high intrapelvic pressures. Histopathologic studies showed no major urothelial lesions but only a transient inflammatory reaction that was undetectable 4 weeks following exposure to gadolinium salts. CONCLUSIONS: Gadolinium salt solutions are good positive radiocontrast agents for mineral kidney stones without having serious toxic effects or systemic reabsorption.

Absorption↗