PubMed Health⌕ Search

Biomedical subjects

E Sabbioni

Publications and source records attributed to E Sabbioni.

At least 109 records · Page 6Linked to original sources
PubMed1980

Relationships between iron and vanadium metabolism: the exchange of vanadium between transferrin and ferritin.

The study of possible relationships between iron and vanadium metabolism (E. Sabbioni and E. Marafante, Proc. XIth Int. Conf. Biochem., 13-5-R122, Toronto, Canada) was extended to the vanadium in the biochemical mechanisms which involve the exchange of iron between transferrin and ferritin. The transfer of vanadium between transferrin and ferritin was investigated using 48V radiotracer and gel filtration technique. 48V labeled human transferrin and horse spleen ferritin, 48V plasma from rats injected with 48VO2+, unlabelled rat liver cytosol, and plasma were used as sources of the two proteins for their incubation under different conditions. The results show that the equilibrium: V - transferrin in equilibrium V - ferritin occurs in vitro at physiological pH under the conditions of this experiment. No transfer of vanadium between the two proteins, however, occurs when they are incubated simply in a buffer at pH = 7.4. The maximum transfer was observed when transferrin and ferritin were mixed in their natural environments such as plasma and liver cytosol. This suggests that the exchange of the vanadium between the two proteins is affected by biochemical factors which are present in the body. A brief evaluation of the significance on the very low amounts of the element exchanged between the two proteins is also presented.

Animals↗
PubMed1978

Similarity in metabolic patterns of different chemical species of vanadium in the rat.

To gain information about the influence of the oxidation state of vanadium on its metabolic behavior, different 48V-labeled vanadium compounds, such as cationic VO2+(V), VO2+(IV), V3+(III), and anionic V4O12(3-)(V), VS4(3-)(V) species were prepared and intravenously injected into rats. The 48V radioactivity was measured in whole tissues as well as in nuclei, mitochondria, lysosomes, microsomes, and cytosols from liver and kidney homogenates. The distribution of 48V radioactivity between the plasma components was investigated using gel filtration of the 48V-labeled plasma. The findings indicate that there are common pathways of the different chemical forms of vanadium in animals. The similarities are referred to the distribution in different tissues and their intracellular distribution as well as to the transport in the blood, in which 48V was always found in the plasma bound to transferrin. The results obtained tend to exclude a possible influence of the oxidation state of vanadium on its metabolism and support the existence in the body of two mechanisms of conversion of different chemical forms of vanadium ions to one with the same valence.

Animals↗
PubMed1978

Cadmium toxicity studies under long term-low level exposure (LLE) conditions. I. Metabolic patterns in rats exposed to present environmental dietary levels of Cd for two years.

A long term-low level exposure (LLE) experiment was conducted on rats to determine the metabolic patterns for realistic environmental dietary levels of cadmium. Male rats fed with 61 ppb of cadmium ad libitum, 50 labelled with 109 Cd radiotracer as cadmium chloride via drinking mineral water and 11 unlabelled via food for 2 years. The diet was characterized in its metal content by neutron activation analysis to obtain the total dietary intake of different elements. The kidney was found to be the tissue with the major concentration of cadmium which accumulated continuously during the experiment. The variation of the accumulation pattern of Cd concentration in the liver and intestine indicated an itiial rapid increase of Cd during the first 100 days. After this period an apparent equilibrium was attained in both these tissues until the end of the study. The intracellular distribution of cadmium in kidneys, liver, intestine and pancreas were similar, the cytosol fractions containing about 80% of the cellular cadmium. Dialysis experiments indicated that significant amounts of cadmium were able to be associated with cellular organelles, the mitochondria representing the most important organelle capable of binding cadmium. The cytoplasmatic Cd-profiles obtained at various stages of the experiment showed that the metal was only bound to a low-molecular-weight component, cadmium-binding protein (CdBP), which represents the specific cellular-binding component for cadmium under the long term-low level exposure (LLE) conditions. No significant variations in the concentrations of the elements in different organs were observed in animals supplemented with 109Cd untreated controls.

Animals↗
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↗
PubMed1976

Replacement of metal in metalloenzymes. A lead-alkaline phosphatase.

Lead ions can interact with calf intestine alkaline phosphatase. Experiments using 203Pb-labeled Pb2+ ions showed that Pb2+ ions bind the native protein in a molar ratio of Pb/protein of 1:5 with moderate inhibition of its biochemical activity. The 4 g-atoms of Zn per mol present in the native enzyme may be removed by dialysis against EDTA. The inactive apoenzyme is capable of incorporating Pb2+ ions in a Pb/protein molar ratio of 2:1, giving a lead-protein complex still enzymatically active also when genetic material, such as nucleotides or DNA, has been used a a substrate. The reconstituted lead-protein is capable of binding Zn2+ ions without any release of the Pb2+ ions and with an increase in the catalytic activity of only 10-15%. The absence of Zn in the inactive apoenzyme as well as in the reconstituted lead-protein, the incorporation of Pb2+ ions in stoichiometric amounts in the apoenzyme, and the weak influence of the Zn2+ ions on the enzymatic assay of the lead-enzyme suggest that lead ions partially reactivate the calf intestine alkaline phosphatase apoenzyme.

Alkaline Phosphatase↗
PubMed1976

Identification of lead-binding components in rat liver: in vivo study.

In vivo experiments using 203Pb and radioactively labelled precursors such as [14C] arginine and [3H] tryptophan were performed to identify lead binding components in rat liver. The distribution of lead in 9 tissues and the intracellular distribution in liver and kidney was also investigated. Male rats were injected intravenously with 18 mug of 203Pb/rat and the 203Pb radioactivity was measured in whole tissues as well as in nuclei, mitochondria, lysosomes, microsomes and soluble fractions obtained by centrifugation of liver and kidney homogenates. The subcellular fractions from liver were purified and fractionated into macromolecular components by ultracentrifugation, gel filtration, ion exchange chromatography and solvent extraction. Nuclei were fractionated into membranes, chromatin proteins (histone and residual non-histone proteins) and DNA. Most of the lead was detected in the nuclear membrane fraction bound exclusively to membrane proteins and absent in phospholipids. The intranuclear lead was associated with histone fractions and other basic or very weakly acid proteins as indicated by the incorporation of [14C] arginine and [3H] tryptophan. Lead was present in the chromatographically purified DNA fraction but whether lead was really bound to the nucleic acid was not determined. Mitochondria were fractionated into heavy, soluble and light subfractions representing the inner membranes, the intramitochondrial matrix and the outer membranes respectively. These subfractions contained appreciable quantities of lead. No appreciable lead was present in lipids of the mitochondrial membranes. Significant quantities of lead were associated with the endoplasmic reticulum. Fractionation of microsomes into rough and smooth membranes showed that lead was almost exclusively bound to membranes of rough-surfaced microsomes associated with the heavy rough membrane subfraction. No significant lead was present in the free polysome subfraction or in lipids from the endoplasmic reticulum. More than one lead binding site was identified in the soluble fraction, the high molecular weight components representing the most important lead binding site.

Animals↗
PubMed1975

Inhibition of enzymatic hydrolysis of end-phosphate DNA by iridium chlorocomplexes.

The enzymatic hydrolysis of end-phosphate DNA by calf intestine alkaline phosphatase is inhibited by iridium chlorocomplexes. The inhibitory effect is strongly influenced by the chemical form of iridium. While hexachloroiridate (IV) and hexachloroiridite (III) strongly inhibit the enzymatic activity of calf intestine alkaline phosphatase no inhibitory effect was observed when these chlorocomplexes were previously irradiated by light and transformed to their photochemical reaction products. Evidence is presented which suggests that the noncompetitive and irreversible inhibitory effect was due to an effective interaction of iridium with the protein without release of its metal constituent at a very low concentration of enzyme. The protective effects of various chemicals on the inhibitory action was also briefly investigated.

Alkaline Phosphatase↗
PubMed1975

Heavy metals in rat liver cadmium binding protein.

The simultaneous determination of heavy metals in microsamples of chromatographically isolated cadmium-binding protein (Cd-BP) from rat liver was performed by neutron activation analysis. The results suggested that metals other than those already reported (Cd, Zn, Cu, and Hg) can bind the protein. These observations were confirmed by in vivo radiotracer experiments by injecting i.p. 21 labelled metal ions in cadmium-treated rats. Of the metals tested, 109Cd, 65Zn, 64Cu, 203Hg, 106Ag and 113Sn were found incorporated in the Cd-BP. The incorporation of 35S-cysteine, used as an indicator of Cd-BP biosynthesis, was increased in rats exposed to cadmium as compared to untreated animals. In order to establish the influence of other metal ions on the biosynthesis of Cd-BP and the incorporation of cadmium in the protein, in vivo experiments were carried out by i.p. injection of 109Cd and 35S-cysteine. In the presence of 42 metal ions no influence was observed on the incorporation of the two radioisotopes in the Cd-BP. These observations tend to support the hypothesis that cadmium can act as a highly specific inducer of Cd-BP and that this protein might be involved in the metabolism of several heavy metals.

Animals↗
PubMed1975

Accumulation of cadmium in rat liver cadmium binding protein following single and repeated cadmium administration.

The accumulation of cadmium in rat liver cadmium binding protein induced by single and repeated intraperitoneal injections of CdCl2 and the de novo biosynthesis of CdBP were studied by using 109Cd to measure cadmium binding in the CdBP and 35S incorporation as indicator of protein synthesis. The biosynthesis of CdBP is controlled by the cadmium concentrations. For single doses up to 1 mg Cd2+/Kg b.w. about 50% of the cadmium is present in the soluble fraction of liver bound to CdBP and the incorporation of 35S-cysteine is linear with the cadmium concentration. When single doses ranging from 1 to 3 mg Cd2+/Kg b.w. are administered the fractions of both 35S-cysteine and cadmium incorporated into de novo synthesized CdBP gradually decrease. For single doses higher than 3 mg Cd2+/Kg b.w. the biosynthesis capability is maximum and 20 mug Cd/g liver can be incorporated into the de novo biosynthesized CdBP. When rats are treated every day with amounts of cadmium of about 0.8 mg Cd2+/Kg b.w. for up to 8 days a dose-proportional increase in both Cd incorporation and CdBP biosynthesis are observed. This shows a cumulative incorporation of cadmium in the de novo biosynthesized CdBP. Experiments carried out by injecting 65ZnCl2 and 203HgCl2 every day showed that they are not accumulated like cadmium and do not induce the biosynthesis of rat liver CdBP after repeated administration over 7 days.

Animals↗
PubMedDate not supplied

Induction of the human growth hormone gene placed under human hsp70 promoter control in mouse cells: a quantitative indicator of metal toxicity.

An in vitro test method for general metal toxicity screening was designed, based on the cellular response to stress. The expression of a transfected human growth hormone gene sequence driven by the human heat-shock protein 70 promoter in NIH/3T3 cells was used as marker of noxious contact with metal compounds. Out of a series of 31 metals, 17 were competent for inducing this stress response system. According to the effective concentration and to the intensity of the response, three different clusters of positive compounds emerged and were ranked as strong, intermediate strength and weak inducers. These results correlated well with data from other in vivo and in vitro metal toxicity studies, including LD50 in mice. Apparently the positive/negative compounds also fitted well with data from genotoxicity and carcinogenesis studies on metal salts.

3T3 Cells↗
PubMedDate not supplied

Vanadate as an inhibitor of plant and mammalian peroxidases.

Vanadate ions are shown to inhibit horseradish, squash, and rat intestinal peroxidases by following the reaction spectrophotometrically in a wide range of vanadate concentrations. I50 in phosphate buffer were 43, 9.4, and 535 microM, respectively. No inhibitory effect was found on cow milk lactoperoxidase and beef liver catalase. Gel filtration of peroxidases in the presence of vanadate, as carried out by radioactive 48V for horseradish peroxidases (either in aerobic or anoxic conditions) and neutron activation analysis (NAA) for squash peroxidase, demonstrated a binding of vanadium to these enzymes in stoichiometric amounts. Electron paramagnetic resonance spectra of the eluted peaks for the former peroxidase indicated that vanadium is in the +5 oxidation state, but an equilibrium between V (V) and V (IV) in the assay conditions cannot be discarded. Although the inhibitory mechanism remains obscure, some hypotheses are considered. The potential implications that the inhibitory effect of vanadium might have on plant and animal metabolism are also discussed.

Animals↗
PubMedDate not supplied

Fluorine concentrations in bone biopsy samples determined by proton-induced gamma-ray emission and cyclic neutron activation.

Fluorine concentrations in bone biopsy samples taken from the iliac crest of subjects, divided into four groups depending on the length of dialysis treatment, and aluminium levels in blood and bone pathology, in terms of osteoporosis, were determined by two instrumental methods. Proton-induced gamma-ray emission (PIGE), making use of the resonance reaction of 19F(p, alpha gamma)16O at 872 keV, and cyclic neutron activation analysis (CNAA), using the 19F(n, gamma)20F reaction in a reactor irradiation facility, were employed. Rutherford backscattering (RBS) was used to calculate the volume, and, hence, mass of the sample excited in PIGE by determining the major element composition of the samples in order to express results in terms of concentration. From this preliminary investigation, a relationship is suggested between fluorine concentrations in bone and aluminium levels in the system.

Aluminum↗
PubMedDate not supplied

Inductively coupled atomic emission spectrometry and neutron activation analysis for the determination of element reference values in human lung tissue.

An investigation was undertaken in order to assess the performance of neutron activation analysis and inductively coupled plasma atomic emission spectrometry techniques for determining reference values for minor and trace elements in human lungs of urban subjects. Results show that in both instances experimental conditions must be carefully optimized to guarantee reliability of experimental data. Strict criteria for tissue sampling and pretreatment also had to be set. Provisional reference values for ca. 50 elements could thus be established.

Animals↗