Monoisoamyl meso-2,3-dimercaptosuccinate: interaction with metallothionein-bound cadmium in vitro and evidence of active transport into renal and hepatic cells in vivo

Monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) and the unesterified 2,3-dimercaptosuccinic acid (DMSA) were evaluated for relative reactivities against metallothionein (MT)-bound cadmium (Cd) in vitro by elution of the reaction products through Sephadex G-75 gel. After 3 hr of incubation, Mi-ADMS removed about 70% of the Cd from Cd-MT, and a new peak emerged which corresponded to that obtained by elution of a 2:1 molar mixture of Mi-ADMS and Cd. Only about 15% of the Cd was removed from Cd-MT by DMSA. After 24 hr of incubation with Mi-ADMS, no evidence remained of the presence of Cd-MT; all of the Cd was recovered in a very high molecular weight fraction and in a fraction corresponding to Cd ion. In contrast, after 24 hr of incubation with DMSA, 25% of the Cd was still present as Cd-MT, while the remainder eluted in a fraction corresponding to a 2:1 molar complex of DMSA and Cd. When Mi-ADMS was administered to Cd-bearing mice which had received an inhibitor of organic anion transport, probenecid (PBC) or sulfinpyrazone (SPZ), prior to administration of the monoester, there was a marked attenuation of the Cd mobilizing actions of Mi-ADMS as reflected in whole body Cd levels. Analysis of organ Cd concentrations revealed that PBC blocked primarily the mobilization of renal Cd by Mi-ADMS, while the principal action of SPZ in antagonizing the action of Mi-ADMS was on hepatic Cd mobilization. It was concluded that Mi-ADMS has a higher affinity for Cd in Cd-MT than does DMSA, and that the access of Mi-ADMS to intracellular Cd is, at least in part, mediated by the organic anion transport system.

Cadmium mobilization in vivo by intraperitoneal or oral administration of monoalkyl esters of meso-2,3-dimercaptosuccinic acid in the mouse

The relative activities of a series of nine monoalkyl esters of meso-2,3-dimercaptosuccinic acid have been examined as agents for the mobilization of cadmium from mice one week after intraperitoneal administration of cadmium chloride. Eight of these are newly synthetized; all are of the type ROOCCH(SH)CH(SH)COOH, were R = Me, MMDMS; R = C2H5, MEDMS; R = (CH2)2CH3, Mn-PDMS; R = CHMe2, Mi-PDMS; R = (CH2)3CH3, Mn-BDMS; R = CH2CHMe2, Mi-BDMS; R = (CH2)4CH3, Mn-ADMS; R = (CH2)2CHMe2, Mi-ADMS; and R = (CH2)5CH3, Mn-HDMS. All are soluble in dilute sodium bicarbonate solutions and can be administered as aqueous solutions. Cadmium mobilization data were collected on each compound using mice previously loaded with cadmium; the monoesters were administered at a level of 0.40 mmol/kg intraperitoneally daily for five days. Data on whole body cadmium mobilization indicated that the monoester with the isoamyl group was the most effective under the conditions used. The relative whole body cadmium mobilization increased with the number of carbon atoms in the alkyl group of the monoester up to C5 and then decreased for the C6 compound. Cadmium removal from the kidneys and liver was also measured. It was found that the monoisoamyl ester was the most effective in removing cadmium from both the liver and the kidneys. The monoisoamyl ester also proved to be very effective in mobilizing cadmium from both the liver and the kidneys when given orally. This is the first compound which is reported capable of mobilizing cadmium in vivo from aged deposits after oral administration.

Compressibility of M3C60 Fullerene Superconductors: Relation Between Tc and Lattice Parameter

X-ray diffraction and diamond anvil techniques were used to measure the isothermal compressibility of K(3)C(60) and Rb(3)C(60), the superconducting, binary alkali-metal intercalation compounds of solid buckminsterfullerene. These results, combined with the pressure dependence of the superconducting onset temperature T(c) measured by other groups, establish a universal first-order relation between T(c) and the lattice parameter a over a broad range, between 13.9 and 14.5 angstroms. A small secondorder intercalate-specific effect was observed that appears to rule out the participation of intercalate-fullerene optic modes in the pairing interaction.

Identification and characterization of an Onchocerca volvulus cDNA clone encoding a microfilarial surface-associated antigen

The identification and characterization of a recombinant cDNA clone (OV103) expressing a microfilarial surface-associated antigen of Onchocerca volvulus is described. OV103 was identified and isolated from a lambda gt11 cDNA expression library derived from adult O. volvulus mRNA using a chimpanzee antiserum, taken 2 years after infection with third-stage larvae of O. volvulus. The cDNA clone encodes a 12.5-kDa protein that corresponds to a 15-kDa parasite protein present in microfilariae and adult female worms. The antigen encoded by this clone is located in the basal layer of the cuticle and the hypodermis of the female adult worm, and on the surface of microfilariae. OV103 fusion polypeptide is recognized only by some sera from onchocerciasis infected subjects (57%), but more significantly (89%) by sera from individuals that have low levels of patent infection. In addition, the antibody response to this protein developed before appearance of microfilariae in the skin of chimpanzees that had developed non-patent or low level patent infections, while the antibody response in chimpanzees with high levels of microfilariae appeared later at the time of appearance of microfilariae. Preliminary experiments indicated that affinity purified antibodies directed against OV103 fusion polypeptide mediated killing of nodular microfilariae in vitro in the presence of normal peripheral blood granulocytes.

Enhanced mobilization of hepatic cadmium in mice upon coadministration of an N, N-disubstituted dithiocarbamate and an alkyl monoester of dimercaptosuccinate

Oral (po) administration of mono-iso-amyl (2,3-dimercapto) succinate (Mi-ADMS), 0.5 mmol/kg for three consecutive days, to mice previously injected with cadmium (Cd) chloride reduced the whole body Cd burden 34%. Intraperitoneal (ip) administration of N-iso-amyl-N-glucaminedithiocarbamate (i-AmGDTC) by the same regimen reduced total body Cd 41%. Coadministration of the two compounds reduced the whole body Cd burden 60% (p less than 0.05). The liver Cd concentration was reduced 56% and 50%, respectively, by Mi-ADMS given po and i-AmGDTC given ip, each at 0.5 mmol/kg for three consecutive days. Coadministration of the two chelators reduced the liver Cd concentration 90% (p less than 0.05). The kidney Cd concentration was reduced 10% by Mi-ADMS alone, and 60% by i-AmGDTC alone, but there was only a 47% reduction when the two chelators were coadministered, probably as a result of redistribution of mobilized hepatic Cd to the kidneys. As 50-55% of the administered Cd is sequestered in the liver in this mouse model, it is concluded that coadministration of the two chemical classes of Cd complexing agents may offer a therapeutic advantage over administration of either agent alone.

Orientational Disorder in Solvent-Free Solid C 70

The high-temperature structure of solvent-free C(70) has been determined with high-resolution x-ray powder difraction and electron microscopy. Samples crystallized from solution form hexagonal close-packed crystals that retain an appreciable amount of residual toluene, even after prolonged heating. Samples prepared by sublimation, which contain no detectable solvent, are primarily face-centered cubic with some admixture of a hexagonal phase. The relative volume of the hexagonal phase can be further reduced by annealing. The structures of both phases are described by a model of complete orientational disorder. The cubic phase contains an appreciable density of stacking faults along the [111] direction.

Structure-activity relationships for in vivo cadmium mobilization by dithiocarbamates derived from lactose and maltotriose

The relationships between chemical structure and the relative ability to mobilize cadmium in vivo from its aged renal and hepatic deposits have been examined in a series of newly synthesized dithiocarbamates derived from lactose and maltotriose. The results suggest that, in the selection of hydrophobic groups to counter the hydrophilicity contributed by the disaccharides, aromatic groups provide compounds which have a superior efficacy to compounds containing aliphatic groups. The compounds derived from trisaccharides are much less effective than those derived from disaccharides, suggesting that there is a practical size limit to the hydrophilic groups which can be used in the structures of such compounds. With both di- and trisaccharides, aliphatic derivatives with straight chains containing more than eight carbon atoms tend to be less effective than the ones with seven or fewer carbon atoms in the alkyl chain. The three compounds prepared from lactose which contain a benzyl or a methyl-substituted benzyl group are the most effective compounds reported to date for the reduction of whole-body cadmium levels.

X-Ray Diffraction Evidence for Nonstoichiometric Rubidium-C 60 Intercalation Compounds

Powder x-ray diffraction at 300 K on equilibrated samples of several nominal compositions chi in Rb(chi)C(60) is reported. In addition to the face-centered cubic (fcc) (chi = 3, superconducting), body-centered tetragonal (chi = 4), and body-centered cubic (bcc) (chi = 6) stoichiometric phases, direct evidence for a dilute fcc doped phase, 0 x c </= 1, and for a substoichiometric bcc phase, chi approximately 5, is presented. In contrast, chi = 3 and chi = 4 appear to be line phases with nearly zero solubility of Rb vacancies and interstitials at 300 K. These results are summarized in a provisional binary phase diagram.

Comparative iron mobilizing actions of deferoxamine, 1,2-dimethyl-3-hydroxypyrid-4-one, and pyridoxal isonicotinoyl hydrazone in iron hydroxamate-loaded mice

A comparison was made of the actions of deferoxamine (DFX), 1,2-dimethyl-3-hydroxypyrid-4-one (L1), and pyridoxal isonicotinoyl hydrazone (PINH) in mobilizing and promoting excretion of iron in mice loaded with iron-acetohydroxamic acid complex. DFX was given ip, while L1 and PINH were given po. Each was given daily for four days at 300 mg/kg/day, and total excreta were collected 24 hr after each administration. Total iron excreted over the 4-day period, expressed as micrograms/mouse, were: Controls, 26; PINH-treated, 31; DFX-treated, 162; and L1-treated, 208. Measurements of iron in selected organs 96 hr after the last administration of each compound revealed that treatment with L1 and DFX induced significant reductions of iron concentrations in kidneys (16% and 17%, respectively) and in pancreas (18% and 19%, respectively). In addition, L1 treatment led to a significant reduction in the liver iron burden (11%), an action not seen after treatment with DFX. None of the compounds reduced iron concentrations in heart, the most critical organ for toxicity of transfusional siderosis. The synthetic routes for preparation of L1 and PINH are described in detail.

Structure-activity relationships for intracellular cadmium mobilization by N-alkyl-4-O-(beta-D-galactopyranosyl)-D-glucamine-N-carbodithioates+ ++

An examination of a group of dithiocarbamate chelating agents derived from various alkylamines and lactose reveals that the relative potencies in the mobilization of intracellular cadmium from renal and hepatic deposits in mice are highly dependent upon the size and nature of the alkyl groups. For those compounds containing straight-chain alkyl groups, the potency drops off as the number of carbon atoms is increased beyond seven. Branched-chain alkyl groups are more effective in promoting the removal of cadmium than straight-chain alkyl groups with the same number of carbon atoms. The fact that these compounds are effective in the mobilization of intracellular cadmium deposits suggests that the size and shape of the alkyl group are important in the determination of the facility with which the compound can pass through cellular membranes. Straight-chain derivatives with 10 or more carbon atoms were more toxic than those with nine or fewer carbon atoms. Of the new compounds, four (the n-hexyl, n-heptyl, n-octyl, and 2-ethylhexyl derivatives) are more effective than the corresponding benzyl derivative in inducing a reduction of hepatic cadmium levels from animals given cadmium at least 1 week previously. The results obtained indicate that modest modifications in the groups on the basic dithiocarbamate structure can produce agents of significantly enhanced effectiveness for the removal of cadmium from its hepatic deposits.

Compressibility of Solid C60

Room-temperature powder x-ray diffraction profiles have been obtained at hydrostatic pressures P = 0 and 1.2 gigapascals on the solid phase of cubic C(60) ("fullerite"). Within experimental error, the linear compressibility d(ln a)/dP is the same as the interlayer compressibility d(ln c)/dP of hexagonal graphite, consistent with van der Waals intermolecular bonding. The volume compressibility -d(ln V)/dP is 7.0 +/- 1 x 10(-12) square centimeter per dyne, 3 and 40 times the values for graphite and diamond, respectively.

Chirality, charge, and chain branching effects on dithiocarbamate-induced mobilization of cadmium from intracellular deposits in mice

The effects of three major structural features on the intracellular cadmium mobilizing potency of dithiocarbamates have been examined. These features, the chirality of the groups, the total ionic charge of the chelating agent, and the extent of chain branching, would be expected to affect the pharmacological properties of these chelating agents but to have little effect on the stability constants of the cadmium complexes involved. A total of 25 compounds (including 21 new ones) was prepared and used in animal studies designed to evaluate these effects. These included a series of amphipathic dithiocarbamates of the general type R1N(R2)CS2-Na+, where R1 is a relatively nonpolar organic group and R2 is derived from a reducing hexose. All of the factors examined influenced the potency of dithiocarbamates in the mobilization of cadmium from intracellular deposits. The compounds with R2 = galactose or mannose and R1 = benzyl were both more effective than the corresponding glucose derivatives in inducing the removal of cadmium from the liver and the whole body. Increases in the net negative charge of the chelating agent uniformly decreased the observed potency in the mobilization of hepatic and renal cadmium deposits. The replacement of a normal alkyl group by a branched-chain group of the same molecular weight also led to an increase in potency for the two pairs of compounds examined. Dithiocarbamates which are not amphipathic because of the presence of similar polar substituents for both R1 and R2, such as sodium diarabitylamine carbodithioate, were relatively ineffective as agents for the mobilization of intracellular cadmium.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of elemental mercury exposure at a thermometer plant

This study compares 84 mercury-exposed workers at a thermometer manufacturing facility with 79 unexposed workers for evidence of chronic mercury toxicity. Personal breathing-zone air concentrations of mercury ranged from 25.6 to 270.6 micrograms/m3 for thermometer workers. Urinary mercury levels in the study population ranged from 1.3 to 344.5 micrograms/g creatinine, with eight (10%) participants exceeding 150 micrograms/g creatinine and three workers exceeding 300 micrograms/g creatinine, which indicates increased absorption of mercury among the thermometer workers. All urine mercury levels in the comparison group were compatible with normal background levels in unexposed adults (less than 10 micrograms/g creatinine). Thermometer plant workers reported more symptoms than did controls; in general, these differences were not statistically significant and could not be specifically associated with mercury exposure. Static tremor, abnormal Romberg test, dysdiadochokinesia, and difficulty with heel-to-toe gait were more prevalent among thermometer workers than control workers, which could not be associated with recent mercury exposure; there was some suggestion of an association with chronic exposure. There were no intergroup differences for the standard clinical tests of renal function except for a significantly higher mean specific gravity among the thermometer workers. A positive correlation was found, however, between urinary N-acetyl-b-D-glucosaminidase (NAG) and urinary mercury. There was no consistent evidence for intergroup differences in proximal renal tubule function, as measured by urinary beta 2-microglobulin (B2M) or retinol binding protein (RBP).

The mobilization of intracellular cadmium by alkoxyethyl esters of meso-2,3-dimercaptosuccinic acid

The cadmium mobilizing properties of two newly synthesized esters of meso-2,3-dimercaptosuccinic acid in mice have been examined. They are: di(2'-methoxyethyl) meso-2,3-dimercaptosuccinate ([-CH(SH)COOCH2CH2OR]2, R = CH3; MEDMS), and di(2'-ethoxyethyl) meso-2,3-dimercaptosuccinate ([-CH(SH)COOCH2CH2OR]2, R = CH2CH3; EEDMS), conveniently prepared from dimercaptosuccinate acid with 2-methoxyethanol and 2-ethoxyethanol, respectively. Mobilization studies in mice of aged in vivo cadmium deposits using five ip injections of 0.40 mmol/kg of each chelator in peanut oil clearly indicate that both compounds, MEDMS and EEDMS, are significantly superior to 2,3-dimercaptopropan-1-ol (BAL) in depleting the whole body burden of cadmium. The reductions caused by MEDMS and EEDMS were approximately 20 and 26%, respectively, whereas under similar dosage regimens BAL effected about only a 12% reduction. The esters were neither equal nor superior to BAL for the reduction of renal cadmium levels, MEDMS being the least effective. For the mobilization of hepatic cadmium deposits, both were quite promising (MEDMS, 20%; EEDMS, 34% reduction) compared to BAL (only 2% reduction). There was no accumulation of cadmium with either MEDMS or EEDMS in any of the other organs examined--spleen, testes, pancreas, and particularly the brain. These compounds enhance the fecal excretion of cadmium by a factor of 25- to 40-fold but have very little effect on the urinary excretion of this element. The present study reveals that the order of overall efficacy is EEDMS greater than MEDMS greater than BAL, considering the liver and whole body burdens of cadmium, but BAL greater than EEDMS greater than MEDMS in terms of the efficacy in reducing cadmium levels in the kidneys.

Structural influences on intracellular cadmium mobilization by dithiols

An examination of 5 dithiols, N-(2,3-dimercaptopropyl)phthalamidic acid (DMPA), benzene-1,2-dithiol (BDT), toluene-3,4-dithiol (TDT), alpha, alpha'-dimercapto-o-xylene (DOX), and 4,5-dimethyl-alpha,alpha'-dimercapto-o-xylene (DDOX), reveals that these compounds are all inferior to previously reported compounds as agents for the in vivo mobilization of cadmium from its intracellular sites, although all possess sulfhydryl groups capable of reacting with cadmium. The results demonstrate the considerable importance of those parts of the molecule which do not participate directly in the formation of chelate rings in the determination of the ultimate behavior of such compounds in vivo.

Evaluation of occupational asthma from airborne egg protein exposure in multiple settings

We previously reported IgE-mediated occupational asthma among workers exposed to airborne egg protein at a plant that produces liquid and dried powdered egg products. To demonstrate that our original observations are generalizable to other facilities that process eggs, and to estimate the prevalence of IgE-mediated occupational asthma among egg-exposed workers, we conducted surveys at two additional plants. We administered a questionnaire to 188 employees to identify workers with symptoms suggestive of occupational asthma. We further evaluated 88 workers with and without symptoms by a clinical examination by a physician blinded to results of other tests, serial peak expiratory flow rate (PEFR) determinations every three hours while awake for one week, and skin prick tests and serum specific IgE levels to extracts of factory egg products, commercial egg test reagents, and egg white protein fractions. Fourteen workers had work-related asthmalike symptoms by questionnaire, a physician diagnosis of occupational asthma, and evidence of IgE-mediated sensitization to one or more egg proteins. Workers exposed exclusively to liquid egg aerosol, as well as workers exposed primarily to dried airborne egg protein, developed occupational asthma. This study replicated our original observations and demonstrated that workers in all areas of liquid and powdered egg production are at risk of developing occupational asthma from exposure to airborne egg proteins.

Schedule dependency of a cadmium-complexing dithiocarbamate analog in mice

A number of dosing regimens was assessed to determine the optimum schedule of administration of N-(4-methoxybenzyl)-N-dithiocarboxy-D-glucamine (MeOBDCG) in depleting whole-body, renal and hepatic levels of metallothionein-bound cadmium (Cd) in mice. A comparison of 4.0 mmol/kg given as a single injection versus 0.5 mmol/kg given as 8 hourly injections revealed the latter regimen to be superior in reducing renal Cd levels, but less effective than a bolus dose in lowering hepatic Cd concentrations. Administration of 1.33 mmol/kg for 3 consecutive days or 0.8 mmol/kg for 5 days effected a more extensive depletion of renal Cd concentrations than did a single injection of 4.0 mmol/kg. Three injections of 1.0 mmol/kg given at 4- to 7-day intervals were generally more effective in reducing renal Cd concentrations than were 3 consecutive daily injections in mice which had low or moderately high total Cd burdens. The lowest effective dose of MeOBDCG in lowering whole-body, liver and kidney Cd levels when given repetitively was about 0.2 mmol/kg. While schedule variations did not alter appreciably the whole-body Cd reductions at any given total dose of MeOBDCG, repetitive dosing schedules in which injections were given at intervals of several days rather than daily were typically more effective in reducing renal Cd levels. Based upon consideration of pharmacological response as influenced by body surface area, it was calculated that doses of MeOBDCG of the order of 2.0 g/d may be effective in reducing renal Cd levels in individuals with chronic renal dysfunction secondary to chronic Cd intoxication.

Selective removal of cadmium from aged hepatic and renal deposits: N-substituted talooctamine dithiocarbamates as cadmium mobilizing agents

The preparation and examination of three dithiocarbamates derived from N-substituted D-gluco-L-talooctamine reveals that the 4-methoxybenzyl derivative (MeOBGD) is superior to any previously prepared dithiocarbamates as an agent for the mobilization of aged intracellular hepatic cadmium deposits from mice. All of these compounds are also quite effective in reducing whole body burdens of cadmium. The use of these compounds does not result in any increase in the cadmium content of the brain. The selection of these chelating agents for synthesis was suggested by an analysis of the log dose-response curves for the mobilization of renal cadmium by previously studied dithiocarbamates. This revealed that the slope of the percentage renal cadmium mobilized vs the log dosage curve is determined to a considerable extent by the sum of the Hansch pi parameters for the substituents, while the intercept is largely determined by the molecular weight of the compound. The implication of such a correlation is that the ability of a chelating agent to remove cadmium from its aged deposits is determined to some extent by its molecular weight, provided the polarity of the overall molecule is appropriate.