“Pubic grooming has led to a severe depletion of crab louse populations,” said Ian F. Burgess, a medical entomologist with Insect Research & Development Ltd. in Cambridge, England. “Add to that other aspects of body hair depilation, and you can see an environmental disaster in the making for this species.”
There is, however, no evidence to indicate that the transmission of D. medinensis to humans has ever been reintroduced in any formerly endemic country (e.g. Uzbekistan, Iran, India, Pakistan, Yemen and Senegal) as the result of canine or other, non-human infections. Humans are the principle host of this infection.
two lines of published evidence suggest that the parasite alters neurotransmitter signal transduction: the disruption of the parasite-induced behavioral changes with medications used to treat psychiatric disease (specifically dopamine antagonists) and identification of a tyrosine hydroxylase encoded in the parasite genome. In this study, infection of mammalian dopaminergic cells with T. gondii enhanced the levels of K+-induced release of dopamine several-fold, with a direct correlation between the number of infected cells and the quantity of dopamine released. Immunostaining brain sections of infected mice with dopamine antibody showed intense staining of encysted parasites. Based on these analyses, T. gondii orchestrates a significant increase in dopamine metabolism in neural cells. Tyrosine hydroxylase, the rate-limiting enzyme for dopamine synthesis, was also found in intracellular tissue cysts in brain tissue with antibodies specific for the parasite-encoded tyrosine hydroxylase. These observations provide a mechanism for parasite-induced behavioral changes. The observed effects on dopamine metabolism could also be relevant in interpreting reports of psychobehavioral changes in toxoplasmosis-infected humans.
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