Correlative study between reading, laterality, mobility, and binocularity.

Under certain circumstances, Navy divers breathe 100% O2 when working underwater. Serious symptoms of central nervous system (CNS) O2 toxicity can develop from hyperbaric O2 exposure; immersion and exercise are also known to exacerbate toxicity. We developed risk models for quantitative prediction of the probability of developing symptoms using a large set of human data in which occupational exposure conditions were simulated. Exposures were 5 to 265 min at PO2 levels from 20 to 50 feet of sea water (fsw) (1 fsw = 3.06 kPa). Approximately half of the exposures were to a single PO2, while the remainder were more complicated consisting of exposures to multiple levels of hyperbaric O2. In 688 trials, there were 42 exposure-stopping symptoms. We used maximum likelihood to estimate parameters, likelihood ratios to compare model fits, and chi 2 tests to judge goodness-of-fit of model predictions to observations. The modeling shows that risk has a steep PO2 dependence. A model with autocatalytic features fits the data as well as a simpler model: when PO2 is elevated beyond 34 fsw, risk accumulates rapidly without bound while accumulating toward an asymptote at lower PO2 levels. This autocatalytic feature of risk accumulation implies a testable hypothesis that substantial protection from human CNS O2 toxicity can be obtained from intermittent exposure (periodic exposure to lower PO2). The models predict that the probability of O2 toxicity is less than 7% with current Navy limits while breathing 95% O2. Probability of symptoms is < 1% if FIO2 is maintained at the United States Navy recommended level of 75%.

Central Nervous System↗

PubMed1995

Multiple sclerosis: a unique immunopathological syndrome of the central nervous system.

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Central Nervous System↗

PubMed1995

Stress proteins: their role in the normal central nervous system and in disease states, especially multiple sclerosis.

Stress proteins are constitutively expressed in normal CNS tissues, in a variety of cell types (oligodendrocytes, astrocytes and neurons). Their function is uncertain but they may be critical during nervous system development and may protect cells from various stresses, such as hypoxia, anoxia, and excessive excitatory stimulation. Increased amounts of stress proteins are expressed in various cells of the CNS during acute toxic-metabolic states and in more chronic degenerative diseases. Increased expression of stress proteins may constitute a sensitive marker of cell injury. Antibodies to mycobacterial stress proteins bind to normal human myelin and to oligodendrocytes in regions of MS demyelination. Cellular immune responses to stress proteins occur with increased frequency and magnitude in persons with MS, especially those with recent onset of disease. In addition, there are populations of T cells expressing gamma/delta T cells in the brains and CSF of persons with MS, suggesting an in situ immune response to hsp. Humoral immune responses to stress proteins are found in CSF, but no disease specificity has been documented. Some myelin proteins have sequence homology with particular stress proteins. One instance is the homology between a peptide of mycobacterial hsp65 and the myelin protein CNP. Preliminary observations suggest that immune responses to such cross-reactive epitopes modify the course of EAE. All in all, these data support the hypothesis that an immune response to the stress proteins of an infectious agent could result in a cross-reactive immune response to CNS myelin, resulting in demyelination. This may be an especially important mechanism in MS.

Central Nervous System↗