The cryptonephridial system in the mealworm Tenebrio molitor: Transport of radioactive potassium,thallium and sodium; a functional and structural study

Larvae of the mealworm Tenebrio molitor were injected with radioactive potassium, sodium or thallium solution. It was found that the rectal complex of the animal was labelled with potassium and thallium, but not with sodium. Potassium and thallium labelled the complex to the same level as if the two ions were tracers for each other. Ramsay has found that potassium is actively transported to the complex from the hemocoel and there are reasons to believe that T1+ follows the same pathway. Therefore animals injected with thallium were investigated both by light and electron microscopy. The results suggest that thallium spreads from the hemocoel through the leptophragma to the neighbouring ordinary tubular cells, and in moist mealworms thallium is further found in the perirectal space. Due to diffusion and washing out of thallium during fixation it can not be determined whether T1+ and K+ follow identical pathways, but it is possible to determine how far thallium has penetrated during the experiments.     

Thallium(I) starchate

Thallium(I) starchates of various degrees of substitution were prepared from potato, corn and hydrogen starch by reaction with either thallium(I) hydroxide or with thallium ethanolate. After thallation, hydrogen and potato starch exhibited typical characteristics of gelation whereas that of corn starch did not. The chemical structure of the products was investigated using X-ray photoelectron spectroscopy. Potato starch was thallated and contained chemically bound thallium whereas corn starch formed complexes with thallium(I) hydroxide and ethoxide.     

Thallium as an industrial poison (review of literature).

The presented reports on cases of occupational thallium poisoning clearly demonstrate that the possibility of their occurrence in industrial plants is very real. The number of such intoxications is much higher than that of non-industrial poisonings, but this is predominantly due to the less pronounced clinical picture and to the fact that specific tests for thallium are not performed. As a result, these cases partly escape registration altogether and partly are wrongly diagnosed. Thallium and its compounds belong to the first class of poisons, their dangerousness being enhanced by their easy permeability through the skin. Industrial thallium poisoning can be either acute or chronic, but in all cases, it is characterized by a long duration and severity of its course. Strict hygienic demands on the organization of the technological process and the measures of protection of persons working with thallium are indispensable. Compulsory examination of the urine of those working with thallium for the presence of this substance should also be introduced.     

Thallium poisoning. Diagnosis may be elusive but alopecia is the clue.

Thallium is a heavy metal whose salts are used in some rodent poisons and in the manufacture of optical lenses, semiconductors, scintillation counters, low temperature thermometers, and switching devices, green coloured fireworks, and imitation jewelery, and as chemical catalysts. In clinical practice thallium isotopes are used in cardiac scanning, but the use of thallium salts to treat scalp ringworm was abandoned earlier this century because of their toxicity. The sale of thallium in Britain is strictly licensed because of its toxicity and potential for use in murder, which is helped by the fact that thallous salts are colourless, tasteless, and odorless. The more water soluble salts (such as thallium sulphate, acetate, or carbonate) have higher toxicity, and although the toxic dose is variable most deaths occur after the ingestion of 10-15 mg/kg of soluble salt. Most cases of thallium toxicity occur after oral ingestion but severe toxicity has been reported after inhalation of contaminated dust from pyrite burners, in zinc and lead smelting, and in the manufacture of cadmium, after dermal absorption through protective rubber gloves, and after snorting what was thought to be cocaine. The elimination half time of thallium is between 1.7 and 30 days depending on the time since, and chronicity of, ingestion. The elimination time phases are apparent and because of the long terminal elimination half time thallium may act as a cumulative poison. We present two cases of thallium poisoning with intent to kill.     

Protective effect of thallium against the formation of selenium cataract in rats

A simultaneous administration of thallium and cataractogenic dose of selenite to young rats protects the animals against the development of selenium cataract but does not prevent the transient epilation caused by thallium.     

Colistin sulfate as a suitable substitute of thallium acetate in culture media intended for mycoplasma detection and culture.

Thallium acetate in concentrations of 500 to 1000 mg/l is tolerated in the culture by the most mollicutes of the orders Mycoplasmatales and Acholeplasmatales and by this reason it is added in the culture media as a selective element for the detection and propagation of mycoplasmas and acholeplasmas. Because of the high toxicity of thallium acetate and its accumulation in the environment, thallium acetate is not biodegradable, an alternative was searched. The results and analysis of tests with nine mollicute species are presented here. It is recommended to replace thallium acetate in the formulations where it is used and colistin sulfate is proposed as its substitute.     

Relationship between pore occupancy and gating in BK potassium channels

Permeant ions can have significant effects on ion channel conformational changes. To further understand the relationship between ion occupancy and gating conformational changes, we have studied macroscopic and single-channel gating of BK potassium channels with different permeant monovalent cations. While the slopes of the conductance-voltage curve were reduced with respect to potassium for all permeant ions, BK channels required stronger depolarization to open only when thallium was the permeant ion. Thallium also slowed the activation and deactivation kinetics. Both the change in kinetics and the shift in the GV curve were dependent on the thallium passing through the permeation pathway, as well as on the concentration of thallium. There was a decrease in the mean open time and an increase in the number of short flicker closing events with thallium as the permeating ion. Mean closed durations were unaffected. Application of previously established allosteric gating models indicated that thallium specifically alters the opening and closing transition of the channel and does not alter the calcium activation or voltage activation pathways. Addition of a closed flicker state into the allosteric model can account for the effect of thallium on gating. Consideration of the thallium concentration dependence of the gating effects suggests that the flicker state may correspond to the collapsed selectivity filter seen in crystal structures of the KcsA potassium channel under the condition of low permeant ion concentration.     

Identification of novel KCNQ4 openers by a high-throughput fluorescence-based thallium flux assay

To develop a real-time thallium flux assay for high-throughput screening (HTS) of human KCNQ4 (Kv7.4) potassium channel openers, we used CHO-K1 cells stably expressing human KCNQ4 channel protein and a thallium-sensitive dye based on the permeability of thallium through potassium channels. The electrophysiological and pharmacological properties of the cell line expressing the KCNQ4 protein were found to be in agreement with that reported elsewhere. The EC₅₀ values of the positive control compound (retigabine) determined by the thallium and ⁸⁶rubidium flux assays were comparable to and consistent with those documented in the literature. Signal-to-background (S/B) ratio and Z factor of the thallium influx assay system were assessed to be 8.82 and 0.63, respectively. In a large-scale screening of 98,960 synthetic and natural compounds using the thallium influx assay, 76 compounds displayed consistent KCNQ4 activation, and of these 6 compounds demonstrated EC₅₀ values of less than 20 μmol/L and 2 demonstrated EC₅₀ values of less than 1 μmol/L. Taken together, the fluorescence-based thallium flux assay is a highly efficient, automatable, and robust tool to screen potential KCNQ4 openers. This approach may also be expanded to identify and evaluate potential modulators of other potassium channels.     

Thallium(III) chloride in organic solvents: Synthesis, solutions and solvates. The crystal structures of trichlorobis(dimethylsulfoxide)thallium(III) and tribromobis(dimethylsulfoxide)thallium(III)

The synthesis of thallium(III) chloride and bromide was performed in solution by chlorination and bromination, respectively, of the suspensions of the corresponding thallium(I) halides in acetonitrile. Crystalline compounds TlX₃(CH₃CN)₂ (X = Cl⁻, Br⁻) were prepared from the acetonitrile solutions. Thallium(III) chloride and bromide in dimethylsulfoxide solution were obtained by dissolving the corresponding solid compounds TlX₃(CH₃CN)₂ (Cl⁻, Br⁻) in DMSO. Both acetonitrile and dimethylsulfoxide solutions of thallium(III) chloride were studied by UV-Vis and ²⁰⁵Tl NMR spectroscopy. The UV-Vis study of the TlCl₃-CH₃CN system showed presence of at least two thallium(III) chloride species. Only one signal arising from the thallium(III) species was, however, detected by the ²⁰⁵Tl NMR in the solution because of the fast chemical exchange. The ²⁰⁵Tl NMR study of thallium(III) chloride in dimethylsulfoxide showed three separate signals assigned to the solvated , TlCl₃ and species. The crystalline compounds of trichlorobis(dimethylsulfoxide)thallium(III) and tribromobis(dimethylsulfoxide)thallium(III) were prepared and their crystal structures were solved by single-crystal X-ray analysis. The thallium atom in the complexes has a trigonal bipyramidal environment built by three halide ions occupying equatorial positions of the polyhedron and two oxygen atoms of the DMSO molecules in the apical positions.     

The Phytoremediation Potential of Thallium-Contaminated Soils Using Iberis and Biscutella Species

Biscutella laevigata and Iberis intermedia were sampled from sites near St Laurent le Minier, Southern France, and B. laevigata was also sampled from Rocca San Silvestro, Tuscany, Italy. Soils associated with the rhizosphere of each plant were also sampled. Both Biscutella laevigata and Iberis intermedia accumulate inordinately high concentrations of thallium (1.94 and 0.4%, respectively) in their above-ground dry tissue. The levels of thallium accumulated by both species were strongly correlated with both the total and extractable concentrations of thallium in the soils. Concentrations of zinc, cadmium, and lead were below the threshold for hyperaccumulation. It is proposed that B. laevigata and/or I. intermedia could be used for phytoremediation or phytomining of thallium-contaminated soils. Such an operation would involve the repeated cropping of either species, until an acceptable level of thallium in the soils was reached. Additionally, the harvested plant material could be burnt and the resulting ash smelted to produce an economically viable ‘crop’ of thallium.     

Critical periods during development as assessed by thallium-induced inhibition of growth of embryonic chick tibiae in vitro

In ovo application of thallium sulfate has been shown to produce a characteristic shortening and angulation of the tibia of the embryonic chick. The critical period for susceptibility to thallium-induced inhibition of tibial growth ends at 8 2/3 days of incubation, a time when the growth rate of the embryo declines by 55%. The aim of the present study was to expose tibiae to thallium in vitro to determine whether this response was intrinsic to the tibia. A 4-hour exposure to 400 micrograms thallium was found to be most effective. Growth of tibiae from 8-day-old embryos was inhibited, growth of tibiae from 9-day-old embryos was not, and the response of tibiae isolated from embryos of 8 2/3 days of incubation was intermediate. Therefore, the response of the tibia to thallium represents an intrinsic property and is not secondary to inhibited nerve growth as has been suggested. The critical period and its termination is also an intrinsic property of the tibia. Tibiae were exposed to thallium for 4 hours at various times after the tibiae had been established in vitro. Susceptibility to growth inhibition was shown to decline as tibiae developed beyond the critical period, a decline that could be correlated with a declining growth rate. Emphasis is placed upon critical events during development as a more useful concept than critical periods for explaining susceptibility to teratogens.     

Removal of thallium by combining desferrioxamine and deferiprone chelators in rats

The hypothesis that two known chelators deferiprone (1,2-dimethy1-3-hydroxypyrid-4-one, L₁) and desferrioxamine (DFO) might be more efficient as combined treatment than as monotherapies in removing thallium from the body was tested in rats. Six-week-old male Wistar rats received chelators: L₁ (p.o.), DFO (i.p.) or L₁ + DFO as 110 or 220 mg/kg dose half an hour after a single i.p. administration of 8 mg Tl/kg body weight in the form of chloride. Serum thallium concentration, urinary thallium and iron excretions were determined by graphite furnace atomic absorption spectrometry. Both chelators were effective only at the higher dose level, while DFO was more effective than L₁ in enhancing urinary thallium excretion, L₁ was more effective than DFO in enhancing urinary iron excretion. In the combined treatment group, L₁ did not increase the DFO effect on thallium and DFO did not increase the effect of L₁ on iron elimination. Our results support the usefulness of this animal model for preliminary in vivo testing of thallium chelators. Urinary values were more useful because of the high variability of serum results. Result of combined chelators treatment should be confirmed in a different experimental model before extrapolation to other systems.     

Effect of Monovalent Thallium Ions on Differentiation and Multiplication of Acanthamoeba castellanii

The vegetatively multiplying Acanthamoeba castellanii cells are transformed into cysts under unfavourable feeding conditions. The cyst formation may also be induced by treatment of the cells with DNA-synthesis inhibitors or by placing the cells into special ionic medium containing magnesium and calcium at pH 9, with aeration. During Acanthamoeba encystment the morphology of the cells changes significantly, namely a cellulose-protein cyst wall appears which is easily seen under the light and electron microscope. The process of encystment in Acanthamoeba castellanii is considered as a useful simple model of cytodifferentiation of eukaryotic cells.
This communication describes the effects of monovalent thallium ions on the differentiation and multiplication of Acanthamoeba cells growing in optimal feeding conditions. Thallium ions being potassium analogues are readily accumulated by cells. On the other hand, thallium ions, unlike potassium ions, are able to form complexes with some anions, which results in disturbances of some cellular functions.
Thallium ions, added to the growth medium of 2–3-days old Acanthamoeba culture at a concentration of 0.05–1.0 mM inhibit the population growth inducing the differentiation of cells into cysts. The increase of the thallium ion concentration up to 5 or 10 mM in the growth medium causes the very fast multiplication of Acanthamoeba cells. However, at these thallium ion concentrations no cysts can be observed.
Thus, on the basis of the experimental data it seems likely that thallium ions play some role in increasing the rate of multiplication and in switching on the differentiation process (encystment) in Acanthamoeba cells.     

Toxicity and accumulation of thallium in bacteria and yeast

Thallium sulphate inhibited microbial growth, withBacillus megaterium KM, more sensitive to the metal thanSaccharomyces cerevisiae andEscherichia coli. Inhibition ofB. megaterium KM andS. cerevisiae, but not ofE. coli, was alleviated by increasing the potassium concentration of the medium; inhibition of respiration ofS. cerevisiae, but not ofE. coli, was similarly alleviated. Thallium was rapidly bound, presumably to cell surfaces, byS. cerevisiae andE. coli, and was progressively accumulated by energy-dependent transport systems (probably concerned primarily with potassium uptake) with both organisms. Thallium uptake kinetics suggested more than one transport system operated in yeast, possibly reflecting a multiplicity of potassium transport systems. ApparentK _m andK _i values for competitive inhibition of thallium uptake by potassium indicatedS. cerevisiae to have a higher affinity for thallium uptake than for potassium, whileE. coli had a transport system with a higher affinity for potassium than for thallium. The likely systems for thallium transport are discussed. A mutant ofE. coli with tenfold decreased sensitivity to thallium was isolated and apparently effected surface binding of thallium in amounts equivalent to the wild type organism, but showed no subsequent uptake and accumulation of the metal from buffer, even though it was able to accumulate potassium to normal intracellular concentrations during growth. Abbreviations: Metal are referred to by their recognised atomic symbols (e.g. TI = Thallium; K = potassium; Co = cobalt)     

Silver and thallium(I) complexation with dibenzo-16-crown-4.

Dibenzo-16-crown-4 (1) indicates high silver and thallium(I) ion selectivity over sodium, potassium, and rubidium ion evaluated from the solvent extraction of metal picrates, while its cation-binding ability is lower than those of dibenzo-18-crown-6 (2) and dibenzo-22-crown-6 (3). Taking account of the highest thallium(I) ion selectivity for 1 obtained from extraction experiments, PVC membrane thallium(I)-selective electrodes based on 1 are prepared. The electrode shows the best potentiometric selectivity coefficients for thallium(I) over potassium and rubidium than those of 2 and 3, and commercially available bis(crown ether)s (4).     

Examining of Thallium in Cigarette Smokers

Smoking is one of the sources of thallium which is considered as a toxic heavy metal. The aim of this study was to determine urinary thallium levels and related variables in smokers, compared to a control group. The study was conducted on 56 participants who had smoked continuously during the year before they were referred to Kashan Smoking Cessation Clinic. Fifty-three nonsmokers who were family members or friends of the smokers were selected as the control group. Urinary thallium was measured in both groups (n = 109) using atomic absorption spectrophotometry. The mean value (with SD) for urinary thallium in the smokers (10.16 ± 1.82 μg/L) was significantly higher than in the control group (2.39 ± 0.63 μg/L). There was a significant relationship between smoking duration and urinary thallium levels (P = 0.003). In a subgroup of smokers who was addicted to opium and opium residues (n = 9), the mean level of thallium (37.5 ± 13.09 μg/L) was significantly higher than in the other smokers (4.93 ± 4.45; P = 0.001). Multiple regression analysis showed opioid abuse, insomnia, and chronic obstructive pulmonary disease (COPD), together were strong predictors of urinary thallium levels in smokers. There was no significant difference in thallium level in hookah smokers (P = 0.299) or in those with COPD compared to other smokers (P = 0.375). Urinary thallium levels of smokers with clinical signs of depression, sleep disorders, memory loss, and sweating were higher than those of smokers without these signs. Since thallium, as other toxic metals is accumulated in the body, and cigarette smoking also involves carcinogenic exposures and health hazards for passively exposed people, the need for cigarette control policies is emphasized.     

Electrostatic calculations for an ion channel. II. Kinetic behavior of the gramicidin A channel.

A theoretical model of the gramicidin A channel is presented and the kinetic behavior of the model is derived and compared with previous experimental results. The major assumption of the model is that the only interaction between ions in a multiply-occupied channel is electrostatic. The electrostatic calculations indicate in a multiply-occupied channel is electrostatic. The electrostatic calculations indicate that there will be potential wells at each end of the channel and, at high concentrations, that both wells can be occupied. The kinetics are based on two reaction steps: movement of the ion from the bulk solution to the well and movement between the two wells. The kinetics for this reaction rate approach are identical to those based on the Nernst-Planck equation in the limit where the movement between the two wells is rate limiting. The experimental results for sodium and potassium are consistent with a maximum of two ions per channel. To explain the thallium results it is necessary to allow three ions per channel. It is shown that this case is compatible with the electrostatic calculations if the presence of an anion is included. The theoretical kinetics are in reasonable quantitative agreement with the following experimental measurements: single channel conductance of sodium, potassium, and thallium; bi-ionic potential and permeability ratio between sodium-potassium and potassium-thallium; the limiting conductance of potassium and thallium at high applied voltages; current-voltage curves for sodium and potassium at low (but not high) concentrations; and the inhibition of sodium conductance by thallium. The results suggest that the potential well is located close to the channel mouth and that the conductance is partially limited by the rate going from the bulk solution to the well. For thallium, this entrance rate is probably diffusion limited.     

Metal-ion oxidation reactions of monosaccharides: A kinetic study

The kinetics of oxidation of hexoses, pentoses hexitols, and a pentitol by vanadium(V), cerium(IV), manganese(III), and thallium(III) in aqueous acidic media are best explained by a free-radical mechanism. Oxidation reactions of alditols produces the corresponding aldoses, which are further oxidised in the presence of an excess of oxidant to lower monosaccharides and thence to formaldehyde, formic acid, and even to carbon dioxide. All of the reactions except that of thallium(III) are acid-catalysed. Other kinetic data are summarised and the rate laws are given.     

Thallium (I) interactions in biological fluids: a potentiometric investigation of thallium(I) complex equilibria with some sulphur-containing amino acids

Formation constants for thallium(I) complexes of L-cysteine (CysH2), DL-penicillamine (PenH2), N-acetyl-L-cysteine (AcyH2), and N-acetyl-DL-penicillamine (ApeH2) in aqueous solution have been determined in 150 mmol dm-3 NaCl medium at 37 degrees C by potentiometric titrations using a glass electrode. Glycine has been used as a model for simple amino acids. The experimental data may be explained by the formation of the complexes T1(Cys)-, T1(Cys)H, T1(Pen)-, T1(Pen)H, T1(Acy)-, and T1(Ape)- with log formation constants 3.26, 11.28, 3.60, 12.05, 2.27, and 2.45, respectively. Analysis of the results obtained and comparison of thallium(I) complexing ability with that of dimethyl-thallium(III) seem to indicate that thallium(I) toxicity does not directly stem from its interference with the metabolism of sulphur-containing compounds.     

Criticality of Seven Specialty Metals

Evaluating metal criticality is a topic that addresses future metals supply and that has inspired research in corporations, academic institutions, and governments. In this article, we apply a comprehensive criticality methodology to seven specialty metals—scandium (Sc), strontium (Sr), antimony (Sb), barium (Ba), mercury (Hg), thallium (Tl), and bismuth (Bi)—at the national and global levels for 2008. The results are presented along with uncertainty estimates in a three‐dimensional “criticality space” comprised of supply risk (SR), vulnerability to supply restriction (VSR), and environmental implications (EI) axes. The SR score is the highest for antimony over the medium term (i.e., 5 to 10 years), followed very closely by bismuth and thallium; for the long term (i.e., a few decades), the highest SR is for thallium, followed very closely by antimony. Strontium and barium, followed very closely by mercury, have the lowest SR over the medium term, and mercury has the lowest SR over the long term. Mercury has the highest EI score. For VSR, thallium is the most vulnerable at both the national level (for the United States) and global level, followed by strontium at both levels. In general, specialty metals are found to possess a unique mix of sparse data, toxicity concerns (in some cases), and inadequate or nonexistent substitutes for a number of specialized uses, a situation that would seem to demand increased effort in acquiring the information needed to characterize specialty metal criticality with more rigor and transparency than is currently possible.