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PubMed1995

The thiol reagent, thimerosal induces intracellular calcium oscillations in mature human oocytes.

The aim of this study was to investigate the effects of thimerosal on intracellular calcium in human oocytes related to the stage of nuclear maturity. A total of 20 oocytes from superovulated women undergoing gamete intra-Fallopian transfer (GIFT) were studied. The calcium-sensitive fluorescent dye Fura-2 was used to monitor intracellular calcium. Regular oscillations in the concentration of cytosolic calcium were observed in 13 out of 20 oocytes following exposure to thimerosal; five oocytes did not respond to thimerosal treatment, and spontaneous oscillations of cytosolic free calcium were recorded in two oocytes. Thimerosal induced oscillations of intracellular calcium in a significantly higher proportion of metaphase II oocytes (10/11) compared with metaphase I oocytes (3/8; P < 0.2). These findings demonstrate that thimerosal is a potentially useful agent for the study of the calcium signalling processes in human eggs and suggest that the underlying cellular mechanisms develop at a relatively late stage of oocyte maturation.

Calcium↗
PubMed1988

Prospective screening for thimerosal hypersensitivity: a pilot study.

This pilot study was conducted to determine if prospective patch-test screening could predict ocular tolerance to a thimerosal-preserved chemical disinfection system. Thirty patients were patch tested for thimerosal hypersensitivity before beginning soft contact lens wear. Only one patient exhibited a positive prospective patch test and subsequently developed an ocular thimerosal hypersensitivity. Two other patients with negative patch tests developed thimerosal hypersensitivity reactions over the 1-year study duration. Prospective patch testing for thimerosal hypersensitivity was neither clinically valuable nor sensitive in this particular sample.

Adolescent↗
PubMed1988

Thimerosal: a hidden allergen in ophthalmology.

We report 36 patients with thimerosal-induced follicular allergic contact conjunctivitis. 18 patients had follicular conjunctivitis without eyelid involvement, while 5 patients had follicular conjunctivitis associated with an allergic contact dermatitis of the eyelids; all these patients had been using thimerosal-containing eye drops. A further 13 patients were soft contact lens wearers who became sensitized to their own thimerosal-containing lens solutions. All 36 patients showed a positive patch test reaction to thimerosal, while only 1 of them reacted to an ophthalmic solution. Thimerosal sensitization appears to be clinically relevant in ophthalmic patients.

Adolescent↗
PubMed1991

Minimum eliciting patch test concentration of thimerosal.

Positive patch test reactions to thimerosal 0.1% pet. (40/690 subjects: 5.8%) were more common in younger age groups, in the allergic contact dermatitis group and in subjects who had used contact lens solutions. In the 40 thimerosal-positive patients, the minimum eliciting quantity of preservative was evaluated using different test concentrations: 0.05% and 0.01% pet. (patch testing) and 1:10,000 in saline (intradermal testing). Cross-reactions between thimerosal and other mercury compounds and sensitivity to thiosalicylic acid were also examined. The results of the investigation demonstrate that many of the reactions to 0.1% thimerosal are probably irritant, because only half the subjects studied had positive patch tests when allergen concentrations 5 to 10x lower than that conventionally used for patch testing, were utilized. In these subjects, the average strength of patch test reactions was higher, intradermal testing was more often positive and cross-reactions between mercurials more frequent. These data indicate that the optimal eliciting patch test concentration for studying thimerosal sensitivity is 0.05% pet.

Adolescent↗
PubMed2001

Impact of the Joint Statement by the American Academy of Pediatrics/US Public Health Service on thimerosal in vaccines on hospital infant hepatitis B vaccination practices.

OBJECTIVE: To determine the impact of the American Academy of Pediatrics/US Public Health Service (AAP/USPHS) joint statement on thimerosal in vaccines on hospital infant hepatitis B vaccination policies in Wisconsin. METHODS: The nurse managers of hospital newborn nurseries (n = 110) were surveyed by mail. Nonresponders were resurveyed. Twelve hospitals no longer provided obstetric services. Of the remaining 98 hospitals, 84 (86%) responded to the initial mailing and 14 (14%) responded to the second mailing. The number of hospitals that offered hepatitis B vaccine to infants before July 1999 was compared with that in March 2000. The number of hospitals that had policies in place to vaccinate infants whose mothers' hepatitis B surface antigen status (HBsAg) was positive or unknown during the thimerosal alert (July 1999 through November 1999) was compared with that in March 2000. RESULTS: Before July 1999, 81% of the hospitals representing 84% of reported Wisconsin births routinely offered hepatitis B vaccine to all infants. By March 2000, 50% of hospitals, representing 43% of births, had resumed routine infant hepatitis B vaccination. Physician decision to use a combination Haemophilus influenzae type b hepatitis B vaccine was the most frequently given reason for not reinstituting infant hepatitis B vaccination. During the thimerosal alert, 23% of hospitals did not have policies to vaccinate infants whose mothers were HBsAg-positive and 51% did not have policies to vaccinate infants whose mothers' HBsAg status was unknown. By March 2000, 6% of hospitals still did not have policies to vaccinate infants whose mothers were HBsAg-positive and 24% did not have policies to vaccinate infants whose mothers' HBsAg status was unknown. CONCLUSION: The AAP/USPHS joint statement on thimerosal in vaccines has resulted in a 38% decrease in the number of hospitals routinely offering infants hepatitis B vaccine. Although thimerosal-free hepatitis B vaccine is now available, some hospitals still do not have appropriate policies in place for vaccinating infants whose mothers' HBsAg status is positive or unknown. In the future, policymakers should include anticipated consequences that may result from changes in immunization policy in their recommendations.

Academies and Institutes↗
PubMed2004

Thimerosal exposure in infants and developmental disorders: a retrospective cohort study in the United kingdom does not support a causal association.

OBJECTIVE: After concerns about the possible toxicity of thimerosal-containing vaccines in the United States, this study was designed to investigate whether there is a relationship between the amount of thimerosal that an infant receives via diphtheria-tetanus-whole-cell pertussis (DTP) or diphtheria-tetanus (DT) vaccination at a young age and subsequent neurodevelopmental disorders. METHODS: A retrospective cohort study was performed using 109 863 children who were born from 1988 to 1997 and were registered in general practices in the United Kingdom that contributed to a research database. The disorders investigated were general developmental disorders, language or speech delay, tics, attention-deficit disorder, autism, unspecified developmental delays, behavior problems, encopresis, and enuresis. Exposure was defined according to the number of DTP/DT doses received by 3 and 4 months of age and also the cumulative age-specific DTP/DT exposure by 6 months. Each DTP/DT dose of vaccine contains 50 microg of thimerosal (25 microg of ethyl mercury). Hazard ratios (HRs) for the disorders were calculated per dose of DTP/DT vaccine or per unit of cumulative DTP/DT exposure. RESULTS: Only in 1 analysis for tics was there some evidence of a higher risk with increasing doses (Cox's HR: 1.50 per dose at 4 months; 95% confidence interval [CI]: 1.02-2.20). Statistically significant negative associations with increasing doses at 4 months were found for general developmental disorders (HR: 0.87; 95% CI: 0.81-0.93), unspecified developmental delay (HR: 0.80; 95% CI: 0.69-0.92), and attention-deficit disorder (HR: 0.79; 95% CI: 0.64-0.98). For the other disorders, there was no evidence of an association with thimerosal exposure. CONCLUSIONS: With the possible exception of tics, there was no evidence that thimerosal exposure via DTP/DT vaccines causes neurodevelopmental disorders.

Attention Deficit Disorder with Hyperactivity↗
PubMed2000

Summary of the joint statement on thimerosal in vaccines. American Academy of Family Physicians, American Academy of Pediatrics, Advisory Committee on Immunization Practices, Public Health Service.

In June 2000, a joint statement on thimerosal in vaccines was prepared by the American Academy of Family Physicians (AAFP), the American Academy of Pediatrics (AAP), the Advisory Committee on Immunization Practices (ACIP), and the Public Health Service (PHS) in response to 1) the progress in achieving the national goal declared in July 1999 to remove thimerosal from vaccines in the recommended childhood vaccination schedule, and 2) results of recent studies that examined potential associations between exposure to mercury in thimerosal-containing vaccines and health effects. In this statement, AAFP, AAP, ACIP, and PHS recommend continuation of the current policy of moving rapidly to vaccines that are free of thimerosal as a preservative. Until adequate supplies are available, use of vaccines that contain thimerosal as a preservative is acceptable.

Preservatives, Pharmaceutical↗
PubMed2006

An assessment of downward trends in neurodevelopmental disorders in the United States following removal of Thimerosal from childhood vaccines.

BACKGROUND: The US is in the midst of an epidemic of neurodevelopmental disorders (NDs). Thimerosal is an ethylmercury-containing compound added to some childhood vaccines. Several previous epidemiological studies conducted in the US have associated Thimerosal-containing vaccine (TCV) administration with NDs. MATERIAL/METHODS: An ecological study was undertaken to evaluate NDs reported to the Vaccine Adverse Event Reporting System (VAERS) from 1991 through 2004 by date of receipt and by date of vaccine administration. The NDs examined included autism, mental retardation, and speech disorders. Statistical trend analysis was employed to evaluate the effects of removal of Thimerosal on the proportion of NDs reported to VAERS. RESULTS: There was a peak in the proportion of ND reports received by VAERS in 2001-2002 and in the proportion of ND reports by date of vaccine administration in 1998. There were significant reductions in the proportion of NDs reported to VAERS as Thimerosal was begun to be removed from childhood vaccines in the US from mid-1999 onwards. CONCLUSIONS: The present study provides the first epidemiological evidence showing that as Thimerosal was removed from childhood vaccines, the number of NDs has decreased in the US. The analysis techniques utilized attempted to minimize chance or bias/confounding. Additional research should be conducted to further evaluate the relationship between TCVs and NDs. This is especially true because the handling of vaccine safety data from the National Immunization Program of the CDC has been called into question by the Institute of Medicine of the National Academy of Sciences in 2005.

Child Development Disorders, Pervasive↗
PubMedDate not supplied

[Contact sensitization to thimerosal in healthy subjects].

The aim of our study was to evaluate the prevalence of thimerosal allergy in subjects free of dermatitis. 256 recruits, selected by the Military Health Authorities as healthy subjects, without dermatitis or ocular defects, underwent allergological examination. The percentage of sensitization observed (6.25%) was compared to that found among 2150 patients, consecutively admitted to the Allergological Service of our Department, with suspected allergic dermatitis. Here we found 76 positivities (3.53%). Contact sensitization to ammoniated-mercury is lower among thimerosal-negative subjects (1.88%) than among both the healthy group of thimerosal-positive subjects (12.5%) and thimerosal-positive patients (11.84%). In the group of 76 positive patients it was not possible to relate the sensitization to thimerosal to either a particular clinical dermatological picture or to a specific exposure.

Adolescent↗
PubMed1983

Decomposition of thimerosal in aqueous solution and its determination by high-performance liquid chromatography.

Studies on the decomposition of thimerosal in aqueous solution have confirmed that thiosalicylic acid and ethylmercuric hydroxide are the initial products. On prolonged reaction, thiosalicylic acid was oxidized to 2,2'-dithiosalicylic acid, while ethylmercuric hydroxide was reduced to elemental mercury. As a result, a specific, reverse-phase high-performance liquid chromatographic assay has been developed for thimerosal in the presence of its decomposition products. By comparison, an existing colorimetric assay procedure employing dithizone was shown to be not fully specific. The presence of sodium chloride in the solution accelerated the decomposition of thimerosal. There was evidence that thimerosal was sorbed onto plastic containers on storage.

Benzoates↗
PubMed1984

Influence of isotonic agents on the stability of thimerosal in ophthalmic formulations.

Storage tests on the stability of thimerosal in trimethoprim-polymyxin B eyedrop formulations containing isotonic agents other than sodium chloride have been carried out. The HPLC assay of thimerosal in stored formulations containing boric acid and EDTA decreased with time and temperature, while formulations containing propylene glycol, glycerol, and mannitol showed no significant decrease in thimerosal assay compared with a formulation containing no isotonic agent. The latter group provide suitable alternatives to sodium chloride, which has been shown to have a seriously detrimental effect on thimerosal stability.

Boric Acids↗
PubMedDate not supplied

Thimerosal attenuates ischaemia-reperfusion arrhythmias in rats: no modification by anti-ischaemic agent trimetazidine or endothelin receptor antagonist bosentan.

The effects of acyl-coenzyme a: lysolecithin acyltransferase (LAT) inhibitor thimerosal (20, 30 and 40 mg kg-1), anti-ischaemic and free radical scavenging drug trimetazidine (10 mg kg-1) and endothelin ETA-ETB receptor blocker bosentan [30 mg kg-1) were investigated in an anaesthetized rat model of coronary artery ligation (7 min) and release (7 min) induced myocardial ischaemia-reperfusion arrhythmias. Neither of the drugs produced significant effects on blood pressure except thimerosal which induced a transient fall lasting 5-8 min. The total number of ectopic beats during occlusion (controls 141.8 +/- 73.5, n = 12) and reperfusion (controls 1151.1 +/- 199.1, n = 10) was not modified by either trimetazidine (occlusion 452.5 +/- 128.6, n = 10; reperfusion 1002.0 +/- 198.4, n = 6) or bosentan (occlusion 431.2 +/- 112.8, n = 10; reperfusion 1530.7 +/- 296.8, n = 9) while thimerosal attenuated them (occlusion 50.2 +/- 14.9, n = 10, P < 0.01 vs controls; reperfusion 345.1 +/- 83.8, n = 8, P < 0.01 vs controls). The durations (in seconds) of ventricular tachycardia (occlusion 33.9 +/- 6.1, n = 12; reperfusion 94.2 +/- 18.1, n = 10) were also shortened by thimerosal (occlusion 2.6 +/- 1.0, n = 10, P < 0.01; reperfusion 28.5 +/- 7.8, n = 8, P < 0.01) while trimetazidine or bosentan did not significantly modify them. The incidences of ventricular fibrillation or mortality were not significantly modified by either of the drugs. Besides the lack of any effect of trimetazidine, we conclude that endogenous endothelin has no pathophysiological significance in this experimental model while LAT inhibition does.

Animals↗
PubMed1991

Thimerosal causes calcium oscillations and sensitizes calcium-induced calcium release in unfertilized hamster eggs.

Calcium-induced-calcium-release (CICR) was assayed in unfertilized golden hamster eggs by injecting Ca2+ and monitoring Ca2(+)-dependent hyperpolarizing responses (HRs) and Ca2(+)-sensitive fluo-3 fluorescence. Incubating eggs in the sulfhydryl reagent thimerosal caused [Ca2+]i oscillations as monitored by Ca2(+)-dependent HRs and decreased approximately 10-fold the Ca2+ injection current required to generate an HR and cause a large intracellular Ca2+ increase. Thimerosal also enhanced the sensitivity of eggs to Ca2+ injection in a calcium-free medium. The effects of thimerosal on CICR were prevented by dithiothreitol and were not mimicked by injecting inositol 1,4,5-trisphosphate. The data suggest that thimerosal may be an alternative agent for studying CICR in caffeine-insensitive cells.

Animals↗
PubMed1996

Thimerosal modulates the agonist-specific cytosolic Ca2+ oscillatory patterns in single pancreatic acinar cells of mouse.

Modulation of the agonist-specific cytosolic Ca2+ oscillatory pattern by thimerosal has been investigated in single pancreatic acinar cells using patch-clamp perforated whole-cell recording to measure the calcium-dependent chloride current (I(C1)(Ca2+)). 1 microM thimerosal, which fails to evoke Ca2+ oscillation alone, clearly changed the pattern of Ca2+ oscillation from pulsatile spikes (evoked by low concentrations of activators) to sinusoidal or transient oscillations. The mimetic action of thimerosal was independent of extracellular Ca2+, was blocked by extracellular application of dithiothreitol or 10 mM caffeine, as well as by internal perfusion with heparin; but was unaffected by ruthenium red. We conclude that thimerosal modulates the agonist-specific cytosolic Ca2+ oscillatory patterns mediated by sensitizing the InsP3-induced Ca2+ release.

Acetylcholine↗
PubMed2005

Thimerosal neurotoxicity is associated with glutathione depletion: protection with glutathione precursors.

Thimerosol is an antiseptic containing 49.5% ethyl mercury that has been used for years as a preservative in many infant vaccines and in flu vaccines. Environmental methyl mercury has been shown to be highly neurotoxic, especially to the developing brain. Because mercury has a high affinity for thiol (sulfhydryl (-SH)) groups, the thiol-containing antioxidant, glutathione (GSH), provides the major intracellular defense against mercury-induced neurotoxicity. Cultured neuroblastoma cells were found to have lower levels of GSH and increased sensitivity to thimerosol toxicity compared to glioblastoma cells that have higher basal levels of intracellular GSH. Thimerosal-induced cytotoxicity was associated with depletion of intracellular GSH in both cell lines. Pretreatment with 100 microM glutathione ethyl ester or N-acetylcysteine (NAC), but not methionine, resulted in a significant increase in intracellular GSH in both cell types. Further, pretreatment of the cells with glutathione ethyl ester or NAC prevented cytotoxicity with exposure to 15 microM Thimerosal. Although Thimerosal has been recently removed from most children's vaccines, it is still present in flu vaccines given to pregnant women, the elderly, and to children in developing countries. The potential protective effect of GSH or NAC against mercury toxicity warrants further research as possible adjunct therapy to individuals still receiving Thimerosal-containing vaccinations.

Acetylcysteine↗
PubMed2006

Cultured lymphocytes from autistic children and non-autistic siblings up-regulate heat shock protein RNA in response to thimerosal challenge.

There are reports suggesting that some autistic children are unable to mount an adequate response following exposure to environmental toxins. This potential deficit, coupled with the similarity in clinical presentations of autism and some heavy metal toxicities, has led to the suggestion that heavy metal poisoning might play a role in the etiology of autism in uniquely susceptible individuals. Thimerosal, an anti-microbial preservative previously added routinely to childhood multi-dose vaccines, is composed of 49.6% ethyl mercury. Based on the levels of this toxin that children receive through routine immunization schedules in the first years of life, it has been postulated that thimerosal may be a potential triggering mechanism contributing to autism in susceptible individuals. One potential risk factor in these individuals may be an inability to adequately up-regulate metallothionein (MT) biosynthesis in response to presentation of a heavy metal challenge. To investigate this hypothesis, cultured lymphocytes (obtained from the Autism Genetic Resource Exchange, AGRE) from autistic children and non-autistic siblings were challenged with either 10 microM ethyl mercury, 150 microM zinc, or fresh media (control). Following the challenge, total RNA was extracted and used to query "whole genome" DNA microarrays. Cultured lymphocytes challenged with zinc responded with an impressive up-regulation of MT transcripts (at least nine different MTs were over-expressed) while cells challenged with thimerosal responded by up-regulating numerous heat shock protein transcripts, but not MTs. Although there were no apparent differences between autistic and non-autistic sibling responses in this very small sampling group, the differences in expression profiles between those cells treated with zinc versus thimerosal were dramatic. Determining cellular response, at the level of gene expression, has important implications for the understanding and treatment of conditions that result from exposure to neurotoxic compounds.

Anti-Infective Agents, Local↗
PubMed1981

Delayed hypersensitivity to thimerosal in soft contact lens wearers.

Thirty-eight patients were examined because of ocular redness, irritation, and corneal changes apparently related to soft contact lens wear. The corneal changes were transient and ranged from faint epithelial opacities to a coarse, punctate epithelial keratopathy. Solutions containing thimerosal had been used by all of the patients for lens care, and 31 responded to an ocular challenge with a thimerosal-preserved lens lubricant. Twenty-seven of these 31 also reacted to thimerosal patch testing. The 31 resumed lens wear with relief of symptoms by using unit-dose, preservative-free saline for lens storage and thermal disinfection. A hypersensitivity to thimerosal was assumed responsible for the clinical findings.

Adolescent↗
PubMed2003

Determination of methylmercury, ethylmercury, and inorganic mercury in mouse tissues, following administration of thimerosal, by species-specific isotope dilution GC-inductively coupled plasma-MS.

Isotopically enriched HgO standards were used to synthesize CH3(200)Hg+ and C2H5(199)Hg+ using Grignard reagents. These species were employed for isotope dilution GC-ICPMS to study uptake and biotransformation of ethylmercury in mice treated with thimerosal, (sodium ethylmercurithiosalicylate) 10 mg L(-1) in drinking water ad libitum for 1, 2.5, 6, or 14 days. Prior to analysis, samples were spiked with aqueous solutions of CH3(200)Hg+, C2H5(199)Hg+, and 201Hg2+ and then digested in 20% tetramethylammonium hydroxide and extracted at pH 9 with DDTC/toluene. Extracted mercury species were reacted with butylmagnesium chloride to form butylated derivatives. Absolute detection limits for CH3Hg+, C2H5Hg+, and Hg2+ were 0.4, 0.2, and 0.6 pg on the basis of 3sigma of five separate blanks. Up to 9% of the C2H5Hg+ was decomposed to Hg2+ during sample preparation, and it is therefore crucial to use a species-specific internal standard when determining ethylmercury. No demethylation, methylation, or ethylation during sample preparation was detected. The ethylmercury component of thimerosal was rapidly taken up in the organs of the mice (kidney, liver, and mesenterial lymph nodes), and concentrations of C2H5Hg+ as well as Hg2+ increased over the 14 days of thimerosal treatment. This shows that C2H5Hg+ in mice to a large degree is degraded to Hg2+. Increased concentrations of CH3Hg+ were also observed, which was found to be due to impurities in the thimerosal.

Animals↗