Structure of Langmuir-Blodgett Films of Disk-Shaped Molecules Determined by Atomic Force Microscopy

Monolayer Langmuir-Blodgett films of a discotic mesogen have been studied with atomic force microscopy (AFM). These measurements confirm the "edge on" arrangement for the disk-shaped molecules suggested by surface pressure-area isotherms and show that the molecules form columns that are separated by 17.7 angstroms +/- 10 percent. Column alignment is found to be predominantly along the film deposition direction, with an angular spread of 35 degrees . The AFM images also show that the mean disk separation within the columns is 5.1 +/- 1.3 angstroms, in good agreement with x-ray diffraction (XRD) results. Roomtemperature XRD measurements on bulk samples of the same material indicate a disordered-hexagonal liquid crystalline mesophase, with a column-to-column spacing of 19.9 +/- 0.2 angstroms.

Effect of cromakalim on micturition function in rats

Although many studies investigating the effect of cromakalim on bladder contractility exist, thus far, there are no published studies investigating its effect on micturition function in conscious rats. We measured the effect of cromakalim i.v. on urine output, frequency, volume of each micturition, and blood pressure in saline-diuresed and non-diuresed rats. In saline-diuresed rats cromakalim produced significant decreases in urine output (0.1 mg/kg, 32%; 0.3 mg/kg, 46%; 1.0 mg/kg, 68%) and average frequency (0.1 mg/kg, 36%; 0.3 mg/kg, 51%; 1.0 mg/kg, 70%) in the first 3 hours. At 3-6 hours after administration of cromakalim there were rebound increases in both urine output (0.1 mg/kg, 290%; 0.3 mg/kg, 373%; 1.0 mg/kg, 538%), and frequency (0.1 mg/kg, 147%; 0.3 mg/kg, 181%; 1.0 mg/kg, 314%) and by 6-12 hours the effects of cromakalim on micturition function were gone. Mean arterial pressure dropped to 50% of control immediately after cromakalim administration in saline-diuresed rats and began to return to control levels after 3 hours. Cromakalim produced similar results in non-diuresed rats. The decrease in urine output 0-3 hours after cromakalim administration may have been a consequence of cromakalim's profound decrease in blood pressure that occurred during that time.

N-benzyl-N-lactyl dithiocarbamate treatment of mice after chronic cadmium administration

Administration of N-benzyl-N-lactyl dithiocarbamate (BLDTC) to mice after chronic cadmium (Cd) administration evoked a prompt, dose-dependent reduction of the whole body burden; 75% of the retained Cd was mobilized and excreted after 20 i.p. injections of BLDTC at 1.0 mmol/kg/injection. This same dose regimen produced 71% and 98% reductions of the renal and hepatic Cd concentrations, respectively. There was no reduction by BLDTC of the endogenous level of any of seven other metals measured: iron, magnesium, selenium, copper, calcium, zinc, and manganese. Renal proximal tubular damage in mice which received Cd followed by BLDTC was much less than that observed in kidneys from mice which received Cd alone. Chronic Cd administration led to substantial epithelial vacuolar damage to renal distal tubules, and this process was not apparently reversed or antagonized by BLDTC treatment to the extent observed in proximal tubules.

Evidence of active transport of cadmium complexing dithiocarbamates into renal and hepatic cells in vivo

A study was made of the effects of certain inhibitors of transport systems on the actions of four cadmium (Cd) complexing N,N-disubstituted dithiocarbamates (DTCs) in mobilizing murine renal and hepatic Cd in vivo. Probenecid, the prototypical antagonist of organic anion transport in the kidney, when given 1 hr prior to each DTC, sharply suppressed the DTC-induced reduction of renal Cd but was virtually without effect on mobilization of Cd from liver. Sulfinpyrazone, which blocks tubular reabsorption of uric acid and also inhibits transport of a variety of organic acids, inhibited markedly the mobilization of both renal and hepatic Cd by DTCs. Phlorizin, an inhibitor of tubular sugar reabsorption, did not affect the Cd mobilizing actions of DTCs in any consistent fashion. We propose that the high degree of selectivity of DTCs in mobilizing renal and hepatic Cd is dependent, at least in part, upon active transport of DTCs into these tissues via the organic anion transport systems. This report presents the first evidence that compounds of the (R)2NCSS- class may gain access to intracellular space by an active, carrier-mediated process.

Mobilization of lead in mice by administration of monoalkyl esters of meso-2,3-dimercaptosuccinic acid

The following six monoalkyl esters of meso-2,3-dimercaptosuccinic acid (DMSA) were synthesized and evaluated for relative activities in mobilizing lead from kidneys and brains of lead-bearing mice: n-propyl (Mn-PDMS), i-propyl (Mi-PDMS), n-butyl (Mn-BDMS), i-butyl (Mi-BDMS), n-amyl (Mn-ADMS) and i-amyl meso-2,3-dimercaptosuccinate (Mi-ADMS). DMSA was used as a positive control. When each was administered intraperitoneally (i.p.) as a single dose of 2.0 mmol/kg, DMSA lowered the kidney lead concentration 52%, while the monoesters effected reductions of 54-75%. Mn-ADMS was toxic at this dose. DMSA lowered the brain lead level 20% when given as a single dose, while the monoesters conferred reductions of 64-87%. When given as 5 daily i.p. injections at 0.5 mmol/kg, DMSA reduced the kidney lead concentration 45%, while the monoesters caused reductions of 56-73%. DMSA lowered the brain lead concentration 35% on the 5-day treatment regimen, while the monoesters evoked reductions of 59-75%. Mi-ADMS was equally effective when given orally or i.p. The i.p. LD50 value of this analog in mice is 3.0 mmol/kg, a value which lies between the reported LD50 doses of DMSA (16.0 mmol/kg) and dimercaprol (1.1 mmol/kg). It is suggested that the ability of these monoesters to cross cell membranes may account for their superiority to DMSA in mobilizing brain lead in this animal model.

Mortality among workers exposed to polychlorinated biphenyls

On the basis of evidence from animal studies, polychlorinated biphenyls (PCBs) are considered potentially carcinogenic to humans. However, the results of studies in human populations exposed to PCBs have been inconsistent. The authors conducted a retrospective cohort analysis (1957-1986) comparing the mortality of 3,588 electrical capacitor manufacturing workers with known exposure to PCBs with age-, sex-, and calendar time-specific mortality rates for all whites in the United States. Proportional hazards modeling was also performed to examine the association between cumulative PCB exposure and site-specific cancer mortality. All-cause mortality (192 deaths observed, 283.3 expected) and total cancer mortality (54 deaths observed, 63.7 expected) were lower than expected. More deaths were observed than expected for malignant melanoma (8 observed, less than 2.0 expected) and cancer of the brain and nervous system (5 observed, 2.8 expected). The average estimated cumulative dose for the cases of brain cancer (22.9 units) was greater than for other workers (12.9 units), but the 95% confidence intervals around this difference were broad. The risk of malignant melanoma was not related to cumulative PCB exposure. These results provide some evidence of an association between employment at this plant and malignant melanoma and cancer of the brain. The possibility that the results are due to chance, bias, or confounding cannot be excluded.

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.

Effect of chelating agent structure on the mobilization of cadmium from intracellular deposits

An examination of the efficacy of several structural types of chelating agents in the removal of cadmium from its intracellular deposits in mouse liver and kidneys reveals that of the structural types examined, only dithiocarbamates and a vicinal dithiol were able to mobilize cadmium from such intracellular sites. Esters of L-cysteine, a macrocyclic thioether, and a disulfide of a dithiocarbamate were unable to cause any appreciable decrease in either renal or hepatic cadmium levels. Charged groups such as carboxylic acid groups reduce the efficacy as well as the toxicity of the structural types that can otherwise mobilize such cadmium. It was also found that the administration of a cadmium-binding polymer ip leads to only a very slight net excretion of cadmium, while the po administration of this polymer leads to no net additional cadmium excretion. Of the compounds newly reported here, some are approximately equal in cadmium-mobilizing efficacy to the most effective of previously reported compounds.

Half-life of polychlorinated biphenyls in occupationally exposed workers

In 1977 and 1985, serum polychlorinated biphenyl (PCB) concentrations were determined for 58 workers in a Bloomington, Indiana, factory that used polychlorinated biphenyls (PCBs) in capacitor manufacture until 1977. Less chlorinated PCBs were quantitated as Aroclor 1242, and more highly chlorinated PCBs were quantitated as Aroclor 1254. The median half-life was 2.6 y for Aroclor 1242 and 4.8 y for Aroclor 1254. However, the half-life varied inversely with the initial serum concentration. This pattern may be a result of continued low-level exposure, variation in the time of exposure, or enzyme induction by PCBs.

The rate of the in vivo dithiocarbamate-induced mobilization of hepatic and renal cadmium deposits

The dithiocarbamate-induced removal of aged cadmium from intracellular sites in the kidneys and liver of mice has been followed as a function of time. The processes are quite rapid with the entire course of the cadmium-removal process being completed in 60-90 min. An examination of the rates at which a dithiocarbamate removes cadmium from hepatic and renal deposits in vivo and from metallothionein in vitro, suggests strongly that the processes are similar. A common mechanism is proposed for both processes which involves the direct attack by the dithiocarbamate on cadmium ion incorporated into metallothionein. Such a mechanism is consistent with the similarities in rates and the degree of overall mobilization of cadmium by the same dithiocarbamate both in vitro and in vivo. The administration of 1 mmol/kg of sodium N-(4-methoxybenzyl)-D-glucamine dithiocarbamate (MeOBDCG) to cadmium-loaded mice leads to a reduction of in vivo renal and hepatic cadmium levels of 45% and 30%, respectively, over a period of only 1 h. Previously the incubation of metallothionein in vitro in the presence of 1 mmol/l of MeOBDCG was found to lead to the reduction of the cadmium content of metallothionein of approximately 60% over a period of 1 h. The administration of higher doses of this compound (2 mmol/kg and 4 mmol/kg) to cadmium-loaded mice led to an even more rapid and more extensive removal of cadmium from both the liver and the kidney. The major factors which limit the ability of dithiocarbamates to mobilize cadmium from in vivo sites appear to be molecular structural features which hinder or prevent the access of the dithiocarbamates to the intracellular sites at which the majority of aged cadmium deposits are held.

Mobilization of lead by esters of meso-2,3-dimercaptosuccinic acid

An examination was made of the relative efficacies of 2,3-dimercapto-1-propanol (BAL) and three diesters ( [CH(SH)COOR]2; DMDMS, R = CH3; DEDMS, R = C2H5; and Di-PDMS, R = CH(CH3)2] of meso-2,3-dimercaptosuccinic acid (DMSA) in mobilizing freshly injected lead from mice. These diesters, like BAL, reduced the lead levels resulting from freshly injected lead in both the soft tissues (liver, kidneys, spleen, and brain) and the bone (tibia). After treatment with the dimethyl (DMDMS), the diethyl (DEDMS), and the diisopropyl (Di-PDMS) esters the lead content of each of the organs was significantly less than that present in the untreated controls. Each of the diesters reduced lead levels in the kidneys, liver, and spleen significantly below those levels found after BAL treatment. The action of the diesters in reducing brain lead levels was comparable to that of BAL. Di-PDMS was the most effective of these compounds and was significantly superior to BAL. Each of the esters was also significantly more effective than BAL in reducing the whole body level of lead.

N,N-disubstituted dithiocarbamates as cadmium antagonists: N-(4-methoxybenzyl)-N-dithiocarboxy-D-glucamine

The newly synthesized dithiocarbamate analog, N-(4-methoxybenzyl)-N-dithiocarboxy-D-glucamine (MeOBDCG) reduced whole-body cadmium levels 66% in cadmium-laden mice when given as 3 injections at 1.0 mmol/kg. Renal and hepatic Cd concentrations were reduced 78 and 85%, respectively. After 6 injections, the whole-body cadmium burden was reduced 71%, while renal and hepatic levels were lowered 84% and 91%, respectively. Mobilized cadmium was excreted almost exclusively by the fecal route. There was no evident toxicity consequent to treatment as judged by mouse body weights and by gross appearance of organs upon dissection. On a molar dose basis, MeOBDCG was more effective than N-benzyl-N-dithiocarboxy-D-glucamine (BDCG) in removing cadmium from both renal and hepatic deposits. An in-vitro assessment of the interaction of MeOBDCG, BDCG and N-methyl-N-dithiocarboxy-D-glucamine with murine cadmium-metallothionein (Cd-MT) revealed a direct relationship between the extent of cadmium depletion from Cd-MT and the relative in-vivo efficacies of the 3 analogs.

Mechanistic aspects of the dithiocarbamate-induced mobilization of cadmium

The examination of some of the species involved in the in vivo processes in which dithiocarbamates mobilize cadmium from its intracellular deposits indicates that several competing reactions occur. Rates of hydrolytic decomposition of a series of dithiocarbamates capable of mobilizing cadmium in vivo have been determined, and the solubility behavior and nuclear magnetic resonance (NMR) spectra of their cadmium complexes have been examined. Some of the dithiocarbamates most effective in this mobilization process are shown to undergo slow conversion to oxazolidine-2-thiones in the presence of cadmium. All of the cadmium complexes involved in the mobilization process are shown to undergo rapid ligand exchange. While dissociative mechanisms based on the turnover of metallothionein are inconsistent with the experimental data, at least two associative mechanisms are possible. These involve attack on the metallothionein by the dithiocarbamate itself or by a compound derived from it by known metabolic processes.

The mobilization of intracellular cadmium by butyl and amyl esters of meso-2,3-dimercaptosuccinic acid

The esters of the general structure, [CH(SH)COOR]2, i.e., Di-BDMS, R = CH2CH(CH3)2; Ds-BDMS, R = CH(CH3)CH2CH3; Di-ADMS, R = CH2CH2CH(CH3)2; and D3-ADMS, R = CH(CH2CH3)2 from the reaction of meso-2,3-dimercaptosuccinic acid with isobutyl, sec-butyl, isoamyl, and 3-amyl alcohols, respectively, have been prepared, characterized, and examined as chelating agents for the removal of cadmium from its aged intracellular deposits. All of these compounds depleted cadmium from such deposits and significantly reduced the whole body levels of cadmium. In the case of three (Ds-BDMS, Di-BDMS, and Di-ADMS) of these compounds, the reductions achieved are equal to or greater than that produced by 2,3-dimercapto-1-propanol (BAL) under similar circumstances. None of these compounds caused any redistribution of cadmium to the brain, and two of them (Di-BDMS and Di-ADMS) caused a very much larger reduction in the liver levels of cadmium than BAL. None was as effective as BAL in reducing kidney levels of cadmium. These compounds are not soluble in water and are administered as solutions in peanut oil. A comparison of the behavior of these compounds with others which have been reported to be effective in reducing body burdens of cadmium in chronic cadmium intoxication reveals that they are among the most effective. An analysis of the manner in which mobilizing efficacy changes with structure indicates that higher, purely alkyl analogs are not expected to be superior to these compounds, though other structural variations may be.

Reducing knee morbidity among carpetlayers

Carpetlayers have a high prevalence of occupational knee morbidity, partly attributable to their use of the knee kicker to stretch carpet for wall-to-wall installation. While a mechanical alternative "power stretcher" is available, knee kickers are still widely used. A questionnaire survey indicated that unavailability of the mechanical stretcher at installation sites was a major factor for continued use of the knee kicker. Strategies to reduce use of the knee kicker are discussed.

Khoikhoi susceptibility to virgin soil epidemics in the 18th century

It has long been assumed that the devastation caused by European epidemic diseases on aboriginal populations was due to their lack of immunity to these diseases. It is argued here, from data on modern Third-World aboriginal people, that this has not been proven, thus it is likely that smallpox epidemics played only a minor role in the disappearance of the Khoikhoi at the Cape in the early 18th century. Increasing usurpation of their pasture land by the colony and loss of livelihood through livestock epidemics and drought, resulting in their subjugation and a downward spiral of anomie, had a much greater effect.

Mobilization of cadmium in mice by combined treatment with N-benzyl-N-dithiocarboxy-D-glucamine and diesters of meso-2, 3-dimercaptosuccinic acid

Mice which had received a non-lethal injection of cadmium (Cd) as CdCl2 nine days prior to therapy were treated with N-benzyl-N-dithiocarboxy-D-glucamine (BDCG) alone or in combination with either di(iso-butyl)dimercaptosuccinate (DiBDMS) or di(iso-amyl)-dimercaptosuccinate (DiADMS). Seven injections of BDCG (1.0 mmole/kg), DiBDMS (0.4 mmole/kg), and DiADMS (0.4 mmol/kg) reduced whole body Cd burdens 50%, 54% and 37%, respectively; coadministration of BDCG + DiBDMS and BDCG + DiADMS produced respective reductions of 65% and 61%. Seven injections of BDCG lowered renal Cd concentrations an average of 82%, but reduced hepatic Cd concentrations only 53%. The DMSA diesters were more effective in lowering hepatic Cd than in reducing the levels of Cd in the kidneys. The respective hepatic and renal Cd reductions were 50% and 20% after treatment with DiADMS, and were 73% and 30% after treatment with DiBDMS. Coadministration of BDCG with DiADMS reduced hepatic and renal Cd concentrations 74% and 82%, respectively, while BDCG co-administered with DiBDMS yielded respective reductions of 80% and 82%. It is suggested that combined use of these newer Cd complexing agents in studies of experimental Cd poisoning may now permit resolution of the issue of reversibility of Cd-induced nephrotoxicity.

Dithiocarbamate treatment of chronic cadmium intoxication in mice

The dithiocarbamate analogs, N-benzyl-N-dithiocarboxy-D-glucamine (BDCG) and N-cyclohexyl-N-(2-hydroxy-3-sulfonatopropyl)dithiocarbamate (CAPSO-DTC), were evaluated as cadmium (Cd) antagonists in mice which had received repetitive injections of Cd to effect accumulation of substantial levels of metallothionein-bound Cd in kidneys and livers. BDCG was highly effective in lowering whole body Cd stores and renal Cd concentrations. While the percent of renal Cd mobilized decreased with increasing Cd concentrations, the total amount of Cd mobilized increased. CAPSO-DTC was also effective in reducing whole body Cd levels, but appeared to have less affinity for renal Cd than did BDCG. Treatment of Cd-laden mice with BDCG provoked only a modest elevation of serum creatinine levels, suggesting that the complex of Cd with BDCG may be less nephrotoxic than the complex of Cd with EDTA or dimercaprol. The log of the percent reduction of renal Cd by BDCG was found to be a linear function of the pretreatment renal Cd concentration, and reductions of whole body Cd burdens correlated closely with reductions of liver and kidney Cd concentrations. It was suggested that a Cd complexing agent of the dithiocarbamate class may have ultimate application in a provocative methodology to estimate body or organ Cd stores based upon the amount of Cd excreted following a standard dose of the chelator.

Esters of meso-dimercaptosuccinic acid as cadmium-mobilizing agents

The dimethyl, diethyl, di-n-propyl, diisopropyl (Di-PDMS), and di-n-butyl esters of meso-2,3-dimercaptosuccinic acid were prepared by esterification of the parent acid and were subsequently purified and characterized. Their relative ability to mobilize cadmium from its aged (greater than 30 days) deposits was evaluated in mice in comparison with 2,3-dimercapto-1-propanol (BAL). All but the dimethyl ester were superior to BAL in reducing the hepatic cadmium levels, though none was superior in reducing renal cadmium levels. Their efficacy in reducing hepatic cadmium levels had the result that all except the dimethyl ester were significantly more effective than BAL in reducing total cadmium body burdens in mice. The most effective of these compounds, Di-PDMS, caused a reduction of whole body cadmium of 59% (i.e., to 41% of control values) under conditions where the corresponding reduction found for BAL was only 18% (i.e., to 82% of control value). The predominant route of excretion of cadmium subsequent to administration of these compounds is via the fecal route (greater than 99%). A synergistic effect was found in the reduction of whole body and kidney cadmium burdens when Di-PDMS was used in combination with trisodium calcium diethylenethriaminepentaacetate.

Interaction of caffeine with acetaminophen in mice: schedule dependency of the antagonism by caffeine of acetaminophen hepatotoxicity and the effects of caffeine metabolites, allopurinol, and diethyl ether

Administration of caffeine (CAF) to mice as early as 6 hr prior to injection of a hepatotoxic but nonlethal dose of acetaminophen (ACM) significantly antagonized the hepatotoxic action of ACM as judged by serum levels of alanine aminotransferase (ALT) activity. Administration of CAF after ACM produced complete antagonism only when CAF was given no later than 1 hr after ACM. Administration of CAF daily for 3 days prior to injection of ACM enhanced ACM toxicity markedly, but little or no toxicity ensued when CAF-pretreated mice received ACM followed immediately by CAF. The four primary metabolites of CAF, 1,3-dimethylxanthine (theophylline), 3,7-dimethylxanthine (theobromine), 1,7-dimethylxanthine (paraxanthine), and 1,3,7-trimethyluric acid were effective and virtually complete antagonists of ACM-induced hepatotoxicity when given immediately after ACM, as were the secondary metabolites, 1-methylxanthine and 1,3-dimethyluric acid. Allopurinol, which reduces theophylline clearance, increases the rate of oxidative N-demethylation of theophylline to 1-methylxanthine, and inhibits conversion of 1-methylxanthine to 1-methyluric acid, was also a dose-dependent antagonist of ACM-induced hepatotoxicity. The hepatotoxic response of mice to ACM is exaggerated by a brief period of diethyl ether anesthesia; CAF given immediately after ACM to previously anesthetized mice suppressed this response and maintained serum ALT levels at control values. It is suggested that CAF and its primary metabolites compete with ACM for biotransformation by the cytochrome P-450 mixed function oxidase system, thereby reducing the rate of formation of the hepatotoxic ACM metabolite.

Dermatitis from plastic tote boxes impregnated with an antistatic agent

An outbreak of dermatitis occurred among employees of a microelectronics firm. In a cross-sectional epidemiologic investigation, we found that dermatitis of the hands or arms had occurred among 14 of 29 (48.3%) employees of the incoming inspection department where plastic tote boxes recently purchased from one manufacturer had been used, compared to only one case among 17 (5.9%) employees in another department which had not used these boxes. Affected workers could detect an oily film on the surfaces of these new boxes, but not on older ones. We identified the oily film to be a surface accumulation of bis-hydroxyethyl-tallow amine (BHETA), an antistatic agent with which the tote boxes had been impregnated. Subsequent toxicologic investigation established that BHETA could provoke both follicular and nonfollicular irritant dermatitis, and was also a potential skin sensitizer. Antistatic agents should be considered as potential causes of dermatitis among employees who handle electrical parts transported in plastic boxes, particularly when affected employees can detect an oily film on the box surfaces.