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PubMed2004

The reactions of tellurium tetrahalides with triphenylphosphine under ambient conditions.

The reactions of tellurium tetrahalides and triphenylphosphine in tetrahydrofuran have been carried out under ambient conditions and afford [(Ph(3)PO)(2)H](2)[Te(2)X(10)] [X = Cl (1), Br (2)] and [(Ph(3)PO)(3)(OH(3)])(2)[TeI(6)] (4). The X-ray structures of 1 and 2 show that they are isostructural and contain discrete [Te(2)X(10)](2-) anions exhibiting octahedral coordination around both tellurium atoms with one shared edge and [Ph(3)POH...OPPh(3)](+) cations that show strong hydrogen bonds (the O...O distances are 2.399 and 2.404 A for 1 and 2, respectively). The compound 4 is built up with discrete octahedral hexaiodotellurate anions and [(Ph(3)PO)(3)(OH(3))](+) cations. The reaction of TeBr(4) and PPh(3) also results in the formation of formally zwitterionic Ph(3)PO(CH(2))(4)TeBr(4) (3). This reaction involves an unprecedented THF ring opening in which the oxygen atom becomes bonded to the phosphorus atom of triphenylphosphine and the carbon atom at the other end of the five-atomic chain becomes bonded to the tellurium atom of TeBr(4). The ring opening of the solvent THF is also taking place in the reaction involving tellurium tetraiodide, as indicated by the formation of C(4)H(8)TeI(2) (5). The reaction may initially lead to Ph(3)PI(2) that reacts with THF yielding Ph(3)PO and ICH(2)(CH(2))(2)CH(2)I. The latter species reacts with elemental tellurium producing 5. Depending on the conditions upon crystallization, two polymorphs of C(4)H(8)TeI(2) (5a and 5b) are observed. While the molecular structures of the two forms are virtually identical, their packing and intermolecular contacts are different. Two further minor products (6a and 6b) were isolated in the reaction of TeI(4) and PPh(3): Both are formally 1:1 adducts of 5 and TeI(4), but they differ considerably in their structures. 6a can be formulated as [C(4)H(8)TeI(+)](2)[Te(2)I(10)(2-)] and 6b as [C(4)H(8)TeI(+)](2)(TeI(3)(+))(2)(I(-))(4). The latter compound exhibits framework similar to that of the tetramers in gamma- and delta-TeI(4).

Journal Article↗
PubMed1990

Tellurium-induced neuropathy: a model for reversible reductions in myelin protein gene expression.

Inclusion of 1.1% tellurium in the diet of developing rats causes a highly synchronous primary demyelination of peripheral nerves, which is followed closely by a period of rapid remyelination. The demyelination is related to the inhibition of squalene epoxidase activity, which results in a block in cholesterol synthesis and accumulation of squalene. We now report that the demyelination resulting from this limiting of the supply of an intrinsic component of myelin (cholesterol) leads to repression of the expression of mRNA for myelin-specific proteins. Tellurium exposure resulted in an increase in total RNA (largely rRNA) in sciatic nerve, which could not be accounted for by cellular proliferation; these increased levels of rRNA may be a reactive response of Schwann cells to toxic insult and may relate to the higher levels of protein synthesis required during remyelination. In contrast, steady-state levels of mRNA, determined by Northern blot analysis, for P0 and myelin basic protein were markedly decreased (levels after 5 days of tellurium exposure were only 10-15% of control levels as a fraction of total RNA and 25-35% of control levels when the increased levels of total RNA were taken into account). Message levels increased during the subsequent period of remyelination and reached near-normal levels 30 days after beginning tellurium exposure. Although message levels for the myelin-associated glycoprotein showed a similar temporal pattern, levels did not decrease as greatly and subsequently increased sooner than did levels for P0 and myelin basic protein. The coordinate alterations in message levels for myelin proteins indicate that Schwann cells can down-regulate and then up-regulate the synthesis of myelin in response to alterations in the supply of membrane components.

Animals↗
PubMed1982

Return of axonal and glial membrane specializations during remyelination after tellurium-induced demyelination.

We have studied remyelination of rat peripheral nerves after tellurium-induced demyelination using thin section and freeze-fracture techniques. In rats fed a 1% tellurium diet, regions of demyelination were readily identified by myelin debris and the presence of large denuded axons. Remyelination occurred despite continued tellurium ingestion. However, the demyelinated axons underwent a more rapid remyelination if tellurium was removed from the diet. Remyelination proceeded as described for myelination in the normal developing animal. Sites destined to become nodes of Ranvier were identified as patches of intramembranous particles in the axonal E-face. Early terminal loops of the remyelinating Schwann cell were found adjacent to these particle patches. As wrapping proceeded, terminal loops of myelin, along with associated rows of dimeric-particles characteristic of the axonal P-face, were wound into a paranodal location. This winding of the membrane specializations and associated terminal loops resulted in the reformation of morphologically normal paranodes. The size of the nodal E-face particle patch increased in concordance with increases in the number of paranodal loops until an annulus of particles was obtained as seen in the normal node. The thin section and freeze-fracture morphology of remyelinated fibres was indistinguishable from the morphology of control fibres. These observations are discussed with respect to proposed functions of membrane specializations in myelination and nerve conduction.

Animals↗
PubMed2000

Catalytic determination of ultra trace amounts of tellurium by 2.5-order differential oscillopolarography.

A highly sensitive and selective catalytic method with 2.5-order differential oscillopolarographic detection is described for the determination of tellurium, based on its activation effect on the slow Pd(II)-catalyzed reaction of sodium hypophosphite and methyl red in hydrochloric acid medium at 100 degrees C. Methyl red exhibited a sensitive 2.5-order differential polarographic wave at -0.35 V (vs. SCE) in the supporting electrolyte of pH 5.0 acetate buffer solution and was chosen as the indicating component for the indirect determination of tellurium. A calibration curve of tellurium in the range of 0.02-2.0 ng mL(-1) was obtained by the fixed-time procedure. The detection limit was 0.007 ng mL(-1). Possible interferences by co-existing substances were examined. The new method has been used to analyze trace tellurium in organs of white mice with satisfactory results. RSD was 0.54% to 2.10%, recovery 98.4% to 95.7%. The mechanism is also discussed.

Azo Compounds↗
PubMed2005

Influence of rainfall characteristics on elimination of aerosols of cesium, strontium, barium and tellurium deposited on grassland.

This work is aimed at quantifying foliar transfer of cesium, strontium, barium and tellurium under the influence of rainfall characteristics (intensity, frequency and time elapsed between contamination and first rainfall). Grassland boxes were contaminated by dry deposition of multi-element aerosols of (137)Cs, (85)Sr, (133)Ba and (123m)Te. They were grown in a greenhouse under controlled conditions. The treatments consisted of mowing and applying rainfalls (8 and 30 mmh(-1)) at different times after the contamination. At a leaf area index of 5.9+/-1.9, interception of the aerosols was similar for the 4 radionuclides (83.8+/-5.9%). Dew produced significant radionuclide accumulation in the base of the vegetation and transfer to the soil. For moderate intensity, an early (2 days after contamination) first rainfall was as efficient, in terms of leaf wash-off, as a longer rainfall occurring later (6 days after contamination). For early rainfalls, eliminated activities were comparable because the influence of rain intensity was compensated by rain duration. However, for late rainfalls, wash-off efficiency increased with rainfall intensity. Total transfer factors (TTF) were determined on whole grass immediately after 4 rainfalls and at harvest. After 4 medium intensity rainfalls, rain frequency did not influence total transfer factors (TTF) of strontium, barium and tellurium (about 0.2, 0.3 and 0.35 Bq kg(fresh weight)(-1) by Bq m(-2), respectively). Cesium TTF value was lower in the case of a weekly rain (0.1 against 0.2 Bq kg(fresh weight)(-1) by Bqm(-2)). TTF values were similar for twice-a-week rainfalls, whatever their intensity. They were higher for weekly rains of high intensity (between 0.3 and 0.75 Bq kg(fresh weight)(-1) by Bqm(-2) against 0.1-0.35 Bq kg(fresh weight)(-1) by Bq m(-2), depending on the radionuclides). TTF values attested that wash-off was more efficient when rainfalls lasted longer. Field loss on the top of the leaves was well described by an offset exponential model. The half-lives varied with rainfall characteristics from 4 days for cesium, strontium and barium to 20 days for tellurium. The offset value varied between 0% for tellurium (high intensity rainfalls) and 14% for cesium (medium intensity rainfalls).

Aerosols↗
PubMed2005

Syntheses, crystal structures, and properties of six new lanthanide(III) transition metal tellurium(IV) oxyhalides with three types of structures.

Solid-state reactions of lanthanide(III) oxide (and lanthanide(III) oxyhalide), transition metal halide (and transition metal oxide), and TeO(2) at high temperature lead to six new lanthanide transition metal tellurium(IV) oxyhalides with three different types of structures, namely, DyCuTe(2)O(6)Cl, ErCuTe(2)O(6)Cl, ErCuTe(2)O(6)Br, Sm(2)Mn(Te(5)O(13))Cl(2), Dy(2)Cu(Te(5)O(13))Br(2), and Nd(4)Cu(TeO(3))(5)Cl(3). Compounds DyCuTe(2)O(6)Cl, ErCuTe(2)O(6)Cl, and ErCuTe(2)O(6)Br are isostructural. The lanthanide(III) ion is eight-coordinated by eight oxygen atoms, and the copper(II) ion is five-coordinated by four oxygens and a halide anion in a distorted square pyramidal geometry. The interconnection of Ln(III) and Cu(II) ions by bridging tellurite anions results in a three-dimensional (3D) network with tunnels along the a-axis; the halide anion and the lone-pair electrons of the tellurium(IV) ions are oriented toward the cavities of the tunnels. Compounds Sm(2)Mn(Te(5)O(13))Cl(2) and Dy(2)Cu(Te(5)O(13))Br(2) are isostructural. The lanthanide(III) ions are eight-coordinated by eight oxygens, and the divalent transition metal ion is octahedrally coordinated by six oxygens. Two types of polymeric tellurium(IV) oxide anions are formed: Te(3)O(8)(4)(-) and Te(4)O(10)(4)(-). The interconnection of the lanthanide(III) and divalent transition metal ions by the above two types of polymeric tellurium(IV) oxide anions leads to a 3D network with long, narrow-shaped tunnels along the b-axis. The halide anions remain isolated and are located at the above tunnels. Nd(4)Cu(TeO(3))(5)Cl(3) features a different structure. All five of the Nd(III) ions are eight-coordinated (NdO(8) for Nd(1), Nd(2), Nd(4), and Nd(5) and NdO(7)Cl for Nd(3)), and the copper(I) ion is tetrahedrally coordinated by four chloride anions. The interconnection of Nd(III) ions by bridging tellurite anions resulted in a 3D network with large tunnels along the b-axis. The CuCl(4) tetrahedra are interconnected into a 1D two-unit repeating (zweier) chain via corner-sharing. These 1D copper(I) chloride chains are inserted into the tunnels of the neodymium(III) tellurite via Nd-Cl-Cu bridges. Luminescent studies show that ErCuTe(2)O(6)Cl and Nd(4)Cu(TeO(3))(5)Cl(3) exhibit strong luminescence in the near-IR region. Magnetic measurements indicate the antiferromagnetic interactions between magnetic centers in these compounds.

Crystallography, X-Ray↗
PubMed1983

New myocardial imaging agents: stabilization of radioiodine as a terminal vinyl iodide moiety on tellurium fatty acids.

To determine the myocardial uptake and retention properties of radioiodinated tellurium fatty acids, we prepared two new tellurium fatty acids in which iodine-125 has been chemically stabilized by attachment as a trans-vinyl iodide (I-CH = CH-R-Te-R'-COOH) and evaluated them in rats. Fabrication of 18-iodo-13-tellura-17-octadecenoic acid was accomplished by coupling 1,5-diiodo-1-pentene with sodium 12-(methoxycarbonyl)-n-dodecan-1-yl telluride. The [5-125I]-1,5-diiodo-1-pentene was prepared by an organoborane technique involving 125I+ treatment of 5-iodo-1-penten-1-ylboronic acid [I(CH2)3CH = CHB(OH)2]. The absolute heart uptake of this agent was moderate (1.47-2.52% dose/g after 60 min), but the heart/blood ratios were low (approximately 2.6:1). Only marginal in vivo deiodination occurred, since the thyroid uptake was low (15-18% dose/g after 60 min). The effect of tellurium in position 13 was unexpected. To determine if the low heart specificity and low heart/blood ratios were dependent upon the position of the tellurium, we prepared an analogue with the same chain length, 18-[125I]iodo-7-tellura-17-octadecenoic acid, in the same manner by reaction of [11-125I]-1,11-diiodo-1-undecene with sodium 6-(methoxycarbonyl)-n-hexan-1-yl telluride. This agent showed pronounced heart uptake (2.47-3.94% dose/g after 60 min) and prolonged retention (1.76-3.14% dose/g after 4 h) in rats. Furthermore, the heart/blood ratios remained high for several hours (13:1 after 60 min; 9:1 after 4 h). Iodine-123 labeled 18-iodo-7-tellura-17-octadecenoic acid is an attractive new compound for evaluation as a myocardial imaging agent.

Animals↗
PubMed1991

Tellurium-induced alterations in 3-hydroxy-3-methylglutaryl-CoA reductase gene expression and enzyme activity: differential effects in sciatic nerve and liver suggest tissue-specific regulation of cholesterol synthesis.

The demyelination of peripheral nerves that results from exposure of developing rats to tellurium is due to inhibition of squalene epoxidase, a step in cholesterol biosynthesis. In sciatic nerve, cholesterol synthesis is greatly depressed, whereas in liver, some compensatory mechanism maintains normal levels of cholesterol synthesis. This tissue specificity was further explored by examining, in various tissues, gene expression and enzyme activity of 3-hydroxy-3-methylglutaryl-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis. Exposure to tellurium resulted in pronounced increases in both message levels and enzyme activity in liver, the expected result consequent to up-regulation of this enzyme in response to decreasing levels of intracellular sterols. In contrast to liver, levels of mRNA and enzyme activity in sciatic nerve were both decreased during the tellurium-induced demyelinating period. The temporal pattern of changes in 3-hydroxy-3-methylglutaryl-CoA reductase message levels in sciatic nerve seen following exposure to tellurium was similar to the down-regulation seen for mRNA specific for PNS myelin proteins. Possible mechanisms for differential control of cholesterol biosynthesis in sciatic nerve and liver are discussed.

Animals↗
PubMed1992

Primary demyelination induced by exposure to tellurium alters Schwann cell gene expression: a model for intracellular targeting of NGF receptor.

Exposure of developing rats to tellurium results in a highly synchronous segmental demyelination of peripheral nerves with sparing of axons; this demyelination is followed closely by a period of rapid remyelination. Demyelination occurs subsequent to a tellurium-induced block in the synthesis of cholesterol, the major myelin lipid. We utilized the techniques of Northern blotting, in situ hybridization, and immunocytochemistry to examine temporal alterations in Schwann cell gene expression related to demyelination and remyelination. Tellurium-induced demyelination is associated with downregulation of myelin protein expression and a corresponding upregulation of NGF receptor (NGF-R) and glial fibrillary acidic protein (GFAP) expression. Steady-state mRNA levels (expressed on a "per nerve" basis) for P0, the major myelin protein, were decreased by about 50% after 5 d of tellurium exposure, while levels of mRNA for NGF-R and GFAP were markedly increased (about 15-fold). In situ hybridization of teased fibers suggested that the increase in steady-state mRNA levels for NGF-R was primarily associated with demyelinated internodes and not with adjacent unaffected internodes. Although P0 message was almost totally absent from demyelinating internodes, it was also reduced in normal-appearing internodes as well. This suggests that limiting the supply of a required membrane component (cholesterol) may lead to partial downregulation of myelin gene expression in all myelinating Schwann cells. In partially demyelinated internodes, NGF-R and GFAP immunofluorescence appeared largely confined to the demyelinated regions. This suggests specific targeting of these proteins to local areas of the Schwann cell where there is myelin loss. These results demonstrate that demyelination is associated with reversion of the affected Schwann cells to a precursor cell phenotype. Because axons remain intact, our results suggest that these changes in Schwann cell gene expression do not require input from a degenerating axon, but instead may depend on whether concerted synthesis of myelin is occurring.

Animals↗
PubMed2005

A novel ultrasonic-assisted solution-phase approach for the fabrication of tellurium bundles of nanowhiskers.

An ultrasonic-assisted solution-phase approach to tellurium bundles of nanowhiskers has been successfully established. It is a convenient and efficient process for the formation of Te nanowhiskers and their simultaneous assembly into tellurium bundles without using any templates. It was found that the transformation from Te powder to Te nanowhiskers involved the reversible disproportionation of tellurium. Sonication played a critical role for the formation of the Tellurium bundles of nanowhiskers. The bandgap of the Te nanowhiskers was calculated to be about 3.8 eV based on the UV-visible spectrum. The simplicity and rapidity of the procedure, and the newly discovered uniform morphology of the products made this synthesis promising and potential for related future applications.

Journal Article↗
PubMed2005

Quasirelativistic theory for the magnetic shielding constant. III. Quasirelativistic second-order Møller-Plesset perturbation theory and its application to tellurium compounds.

The quasirelativistic (QR) generalized unrestricted Hartree-Fock method for the magnetic shielding constant [R. Fukuda, M. Hada, and H. Nakatsuji, J. Chem. Phys. 118, 1015 (2003); R. Fukuda, M. Hada, and H. Nakatsuji, J. Chem. Phys.118, 1027 (2003)] has been extended to include the electron correlation effect in the level of the second-order Møller-Plesset perturbation theory (MP2). We have implemented the energy gradient and finite-perturbation methods to calculate the magnetic shielding constant at the QR MP2 level and applied to the magnetic shielding constants and the NMR chemical shifts of 125Te nucleus in various tellurium compounds. The calculated magnetic shielding constants and NMR chemical shifts well reproduced the experimental values. The relations of the chemical shifts with the natures of ligands, and the tellurium oxidation states were investigated. The chemical shifts in different valence states were explained by the paramagnetic shielding and spin-orbit terms. The tellurium 5p electrons are the dominant origin of the chemical shifts in the Te I and Te II compounds and the chemical shifts were explained by the p-hole mechanism. The tellurium d electrons also play an important role in the chemical shifts of the hypervalent compounds.

Journal Article↗
PubMed1962

Reduction of inorganic compounds with molecular hydrogen by Micrococcus lactilyticus. I. Stoichiometry with compounds of arsenic, selenium, tellurium, transition and other elements.

Woolfolk, C. A. (University of Washington, Seattle) and H. R. Whiteley. Reduction of inorganic compounds with molecular hydrogen by Micrococcus lactilyticus. I. Stoichiometry with compounds of arsenic, selenium, tellurium, transition and other elements. J. Bacteriol. 84:647-658. 1962.-Extracts of Micrococcus lactilyticus (Veillonella alcalescens) oxidize molecular hydrogen at the expense of certain compounds of arsenic, bismuth, selenium, tellurium, lead, thallium, vanadium, manganese, iron, copper, molybdenum, tungsten, osmium, ruthenium, gold, silver, and uranium, as well as molecular oxygen. Chemical and manometric data indicate that the following reductions are essentially quantitative: arsenate to arsenite, pentavalent and trivalent bismuth to the free element, selenite via elemental selenium to selenide, tellurate and tellurite to tellurium, lead dioxide and manganese dioxide to the divalent state, ferric to ferrous iron, osmium tetroxide to osmate ion, osmium dioxide and trivalent osmium to the metal, uranyl uranium to the tetravalent state, vanadate to the level of vanadyl, and polymolybdate ions to molybdenum blues with an average valence for molybdenum of +5. The results of a study of certain other hydrogenase-containing bacteria with respect to their ability to carry out some of the same reactions are also presented.

Arsenic↗
PubMed1996

Biochemistry of tellurium.

Tellurium (Te) demonstrates properties similar to those of elements known to be toxic to humans, and has applications in industrial processes, which are rapidly growing in importance and scale. It is relevant, therefore, to consider the tellurium physiology, toxicity, and methods for monitoring the element in biological and environmental specimens. Animal studies suggest that up to 25% of orally administered tellurium is absorbed in the gut. There is a biphasic elimination from the circulation with loss of about 50% within a short period, t1/2 = 0.81 d, and slower elimination of the residual Te, t1/2 = 12.9 d. Following a single ip, injection the largest proportion is in the kidney and bone, but with repeated oral administration, Te is found in the heart > > kidney, spleen, bone, and lung. Formation of dimethyl telluride is a characteristic feature of exposure, and gives a pungent garlic-like odor to breath, excreta, and the viscera. The main target sites for Te toxicity are the kidney, nervous system, skin, and the fetus (hydrocephalus). Te can be reliable measured in different specimens by several analytical techniques. Recent work has employed hydride generation atomic absorption spectrometry. Topics for further investigation are proposed.

Administration, Oral↗
PubMed1984

Interactions between tellurium and mercury in murine lung and other organs after metallic mercury inhalation: a comparison with selenium.

Selenium is known to form complexes with heavy metals in the blood and thus increase the retention time of the metals in several organs, especially in the reticulo-endothelial system. Selenium may similarly cause retention of mercury in the lung after metallic mercury (Hg0) inhalation. This study, comparing the effects of tellurium with those of selenium (both in group '6b' of the periodical system), showed that Te(IV) was as effective as Se(IV) and Se(VI) (all given in a dose of 10 mumol/kg body wt.) in retaining inhaled 203Hg0 (1.5 mumol/kg body wt.) in the lung (presumably 203Hg2+ after oxidation). Te(VI) had to be given in a dose of 100 mumol/kg body wt to produce the same effect. As in the lung, also in other organs tellurium caused a dose-dependent increase in mercury retention. At a dose level of 10 mumol Te(IV) per kg body wt. the mercury retention ratios (treated/control) were 140 for the lung and 8.6 for the whole body. The corresponding figures for Te(VI) (10, 30 and 100 mumol/kg body wt.) were 10, 73 and 120 and 3.7, 3.9 and 4.3, respectively. Retention of i.v. injected 203HgCl2 was increased by pre-administration of tellurium, again in a dose-dependent manner and Te(IV) being 3-10 times more effective than Te(VI). The kidney and the spleen were the dominant organs, as is the case after Se pretreatment. Anions of other elements, arsenite, arsenate, chromate, molybdate and wolframate (30 mumol/kg body wt.), did not affect the retention of 203Hg in lung or any other organ, or in the whole body after inhalation of 203Hg0. It is suggested that Te(IV) may easily be reduced to Te2- (in analogy with selenium) which may complex with Hg2+. The liability for Te(VI) to be reduced to Te2- appears to be approx. 10 times lower.

Administration, Intranasal↗
PubMed2005

Kinetics study on separation of cadmium from tellurium in acidic solution media using ion-exchange resins.

The feasibility of using ion-exchange resins to separate cadmium from tellurium in acidic solutions of the two metals was investigated. We studied the competitive adsorption of cadmium and tellurium in such resins under varying acid strengths and contact time. We found that low sulfuric acid strength (i.e., 0.5 M) was most effective in removing cadmium from solutions. Different ion-exchange resins were tested for their affinity for cadmium and tellurium ions. In the selected systems, the ion-exchange rate of cadmium was rapid in the first 20 min, and reached equilibrium within 2 h. The Lagergren first-order model described the kinetic data with high coefficient of determination and correlation values. At room temperatures the ion-exchange for cadmium onto the resin followed the Freundlich isotherm model. The maximum removal of cadmium obtained from batch studies using resin A was 91%. Column studies with the same resin showed a removal of cadmium of 99.99% or higher.

Adsorption↗
PubMed2004

Organotellurium compound toxicity in a promyelocytic cell line compared to non-tellurium-containing organic analog.

Two substituted aryl organotellurium compounds and a tellurium-free analog of one of these were evaluated for in vitro cytotoxicity using human promyelocytic (HL-60) cells as an experimental system. Both tellurium-containing toxicants (2,2(')-dimethoxydiphenyl ditelluride and 2,2(')-diamino-3,3('),5,5(')-tetramethyldiphenyl ditelluride) were cytotoxic at concentrations as low as 5 x 10(-6) M and the dimethoxydiphenyl compound produced significant numbers of apoptotic cells at a concentration of only 1 x 10(-6) M after 8 h. Data indicate that 2,2(')-dimethoxydiphenyl ditelluride and 2,2(')-diamino-3,3('),5,5(')-tetramethyldiphenyl ditelluride induce apoptosis in both a time and dose dependent manner; however, 2,2(')-dimethoxybiphenyl, structurally comparable to the first of these but without the tellurium bridge, did not produce apoptosis under the concentrations and time course studied. Therefore the telluride moiety was apparently an important factor in the apoptotic effect.

Apoptosis↗
PubMed1998

Role of organotellurium species in tellurium neuropathy.

Exposure of weanling rats to a diet containing 1% elemental tellurium causes segmental demyelination of peripheral nerve, and an inhibition of squalene epoxidase. This inhibition is thought to be the mechanism of action leading to demyelination. Tellurite appears to be the active inhibitory species in a cell-free system but the active species in vivo is unknown. We examined potassium tellurite (K2TeO3) and three organotellurium compounds for their ability to inhibit squalene epoxidase in Schwann cell cultures and to induce demyelination in weanling rats. K2TeO3 had no effect on squalene epoxidase activity in cultured Schwann cells and caused no demyelination in vivo. All three organotellurium compounds caused inhibition of squalene epoxidase in vitro and caused demyelination in vivo. (CH3)2TeCl2 was the most potent of these compounds and its neuropathy most resembled that caused by elemental tellurium. These data are consistent with the hypothesis that tellurium-induced demyelination is a result of squalene epoxidase inhibition and suggest that a dimethyltelluronium compound may be the neurotoxic species presented to Schwann cells in vivo.

Animals↗
PubMed1975

Determination of beryllium, cadmium, and tellurium in animal tissues using electronically excited oxygen and atomic absorption spectrophotometry.

A method using electronically excited oxygen for destruction of organic matter and atomic absorption spectrophotometry for the determination of beryllium, cadmium and tellurium in animal tissues is presented. Samples are solubilized in dilute aqua regia after being subjected to an oxygen plasma, low-temperature (less than 190 degrees C) ashing system for 20 to 30 hours. Recovery data from spiked NBS freeze-dried bovine liver indicate a quantitative determination for the three elements. Limits of detection in micrograms of element per milliliter of solubilized sample solution are: beryllium, 0.05; cadmium 0.05; and tellurium, 0.50. Beryllium, cadmium, and tellurium assay data are reported for the fresh tissues of albino rats exposed to inorganic chemicals by oral or intraperitoneal routes. The tissues analyzed include: adrenal, brain, femur, heart, kidney, liver, lung, mesenteric lymph node, pancreas, prostate, seminal vesicle, spleen, testicle, and tracheal-bronchial lymph node.

Adrenal Glands↗