Central nervous system blood-brain barrier, alterations

This approach has been explored in attempts to treat progressive multifocal leukoencephalopathy/ a rapidly fatal disease caused by the JC virus and characterized by regions of central nervous system demyelination and markedly altered neuroglia. The virus is known to be sensitive in vitro to the action of cytosine arabi-noside (ARA-C) concentrations of 40 M (10 pg/mL) or more (12). Because the agent crosses the blood-brain barrier slowly Hall et al. (13) designed a study to test whether intraventricular/intrathecal administration of ARA-C could successfully treat JC virus in humans. ARA-C was administered as a bolus into the cerebrospinal fluid (CSF) space at the initial rate of 50 mg every 7 days. This ARA-C regimen was found to be... 

Proteases are crucial enzymes induced by HIV to alter the physiology of the central nervous system. Indeed, proteases participate in brain infection, helping infected peripheral cells to cross the blood-brain barrier, as well as in the viral neuropathogenesis as will be later discussed. We will first describe examples of... 

The pharmacodynamics are affected due to altered levels of neurotransmitters and receptors in the central nervous system with age. The blood-brain barrier may be less effective, hence the brain may be exposed to higher drug and toxin levels in elderly subjects (Toornvliet et al. 2006). 

Another hypothesis is that environmental chemicals gain access to the central nervous system via the olfactory and limbic pathways. The absence of a blood-brain barrier in the olfactory system could permit direct access of environmental chemicals through the nasal mucosa to the olfactory bulb. The olfactory and limbic systems are anatomically linked and participate directly and indirectly in the regulation of cognitive, endocrine, and immune functions. In this hypothesis, chemical exposure could induce lasting changes in limbic and neuronal activity and alter a broad spectrum of behavioral and physiological functions. 

There is a blood-brain barrier that protects the central nervous system (CNS) by excluding large molecules from contacting CNS neurons. It has been reported (Brodie, 2006) that infection or stress can allow certain large molecules access to specific parts of the brain. Bacterial endotoxin or adrenaline have both been shown to breach the blood-brain barrier and permit access to brain nerve cells by autoimmune antibodies. These antibodies normally cause such autoimmune diseases such as lupus, rheumatoid arthritis, or multiple sclerosis (a disease of the peripheral nervous system), but have no effect on brain function. Infections or stress can change that and result in alterations to memory or emotions. This underscores the connections between the body and the brain. 

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