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Neurodevelopmental

Effect of thimerosal on the neurodevelopment of premature rats.
Published: 2013
SYNOPSIS

An animal model of early life exposure to thimerosal finds it adversely impacts learning and memory and may be associated with the development of autism in susceptible individuals.

CITATION

Chen YN, Wang J, Zhang J, Li SJ, He L, Shao DD, Du HY. World J Pediatr. 2013 Nov;9(4):356-60. doi: 10.1007/s12519-013-0443-z. Epub 2013 Nov 14.

SUMMARY

Thimerosal is a preservative used in vaccines and contains approximately 49% mercury. This animal model study was undertaken to investigate the neurodevelopmental effect of exposure to thimerosal in premature rats. Four groups of premature rats received four different doses of thimerosal (32.8, 65.6, 98.4 or 131.2 μg/kg) injected into the gluteus maximus on postnatal day 1. A fifth group served as a control and received a saline injection. Tests were performed 44-48 days post injection to determine spatial learning and memory function. On day 49 the animals were euthanized and prepared for immunohistochemical staining to determine the expression of the dopamine D4 receptor (DRD4), serotonin 2A receptor (5-HT2AR) and apoptosis (programmed cell death) in the prefrontal cortex. The DRD4 receptor is associated with memory function while the 5-HT2AR receptor correlates with episodic memory. Previous rat studies have demonstrated that early life exposure to thimerosal alters the dopamine and serotonin systems. Similarly, this study found a significant decrease in the expression of DRD4, 5-HT2AR and learning at the highest dose of thimerosal. The decrease in receptor expression correlated with increased levels of apoptosis. In all but the lowest exposure group, memory function was significantly decreased when compare to the control group. The authors close by saying, “In conclusion, our results are consistent with previous studies in mice, rats, rhesus macaques, and humans, demonstrate that exposure to mercury from thimerosal- containing vaccines in susceptible populations, such as premature infants, may be associated with neurodevelopmental disorders like autism.”

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Maternal Thimerosal Exposure Results in Aberrant Cerebellar Oxidative Stress, Thyroid Hormone Metabolism, and Motor Behavior in Rat Pups; Sex- and Strain-Dependent Effects
Published: 2011
SYNOPSIS

Harvard researchers find vaccine mercury impacts neurodevelopment in rats.

CITATION

Z. L. Sulkowski & T. Chen & S. Midha & A. M. Zavacki & Elizabeth M. Sajdel-Sulkowska. Cerebellum, (2012) 11:575–586.

SUMMARY

“Our data indicate that maternal TM exposure results in a delayed auditory maturation and impaired motor learning in rat pups. Factors that may contribute to these abnormalities include increased cerebellar oxidative stress and decreased D2 activity resulting local intracerebellar T3 deficiency and altered TH-dependent gene expression. Indeed, provided here is the first evidence of altered TH-dependent gene expression following TM exposure. Our data thus demonstrate a negative neurodevelopmental impact of perinatal TM exposure, which appears to be both strain- and sex-dependent. Although, additional studies are needed, data derived from TM exposure in rats may provide clues relevant to understanding neurodevelopmental consequences of TM exposure in humans.”

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Delayed acquisition of neonatal reflexes in newborn primates receiving a thimerosal-containing Hepatitis B vaccine: Influence of gestational age and birth weight
Published: 2009
SYNOPSIS

Newborn monkeys given a mercury-containing hepatitis b vaccine had significant delays in neonatal reflexes and neurological development.

CITATION

Laura Hewitson, Lisa A. Houser, Carol Stott, Gene Sackett, Jaime L. Tomko, David Atwood, Lisa Blue, E. Railey White, Andrew J. Wakefield. NeuroToxicology, 2009; doi:10.1016/j.neuro.2009.09.008.

SUMMARY

“In summary, this study provides preliminary evidence of abnormal early neurodevelopmental responses in male infant rhesus macaques receiving a single dose of Th-containing HB vaccine at birth and indicates that further investigation is merited.”

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Activation of methionine synthase by insulin-like growth factor-1 and dopamine: a target for neurodevelopmental toxins and thimerosal
Published: 2004
SYNOPSIS

Scientists identify vaccine mercury’s role in blocking crucial neurodevelopmental pathways.

CITATION

M Waly, H Olteanu, R Banerjee, S-W Choi, JB Mason, BS Parker, S Sukumar, S Shim,
A Sharma, JM Benzecry, V-A Power-Charnitsky and RC Deth. Molecular Psychiatry , (2004) 9, 358–370.

SUMMARY

“The ethylmercury-containing preservative thimerosal inhibited both IGF-1- and dopamine-stimulated methylation with an IC50 of 1nM and eliminated MS activity. Our findings outline a novel growth factor signaling pathway that regulates MS activity and thereby modulates methylation reactions, including DNA methylation. The potent inhibition of this pathway by ethanol, lead, mercury, aluminum and thimerosal suggest that it may be an important target of neurodevelopmental toxins.”

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