Neural mechanisms central nervous system

Spatial cooperation is a term coined to describe a situation when disease in one particular anatomic site is missed by one modality but is treated adequately by another. The essence of this is that radiation is a local therapy that will not impact on metastatic disease beyond the planned field borders. Systemic cytotoxic chemotherapy is traditionally used to address the potential distant spread of cancer. In the original description of this mechanism there is no assumption of an interaction between the drugs and radiation with the idea being that the best radiation and best chemotherapy be administered independently of toxicities. The classic example used in several textbooks to illustrate this is the treatment of childhood leukemia with systemic chemotherapy, while their central nervous system, a potential sanctuary site where disease is not treated adequately by chemotherapy, is treated by radiation (28). The reality of the interaction between radiation and chemotherapy is that the dose and timing of radiation are adjusted accordingly to minimize their impact on the neural tissues. 

Cebria, F., Kudome, T., Nakazawa, M., Mineta, K., Ikeo, K., Gojobori, T. and Agata, K. (2002) The expression of neural-specific genes reveals the structural and molecular complexity of the planarian central nervous system. Mechanisms of Development 11 6, 1 99-204. 

Our study was initiated because the mechanism of adaptation is still obscure, and much additional information is needed concerning the relationship between cholinesterase activity and the acetylcholine content of the central nervous system during the adaptation process. We also desired to investigate the possibility that adaptation might involve compensatory changes in the production or release of neural mediators, other than acetylcholine, capable of modifying the effects of high levels of the latter within the central nervous system. Norepinephrine was the first such mediator selected for study. 

Some trichothecene-induced effects may be due to neurotransmitter alteration in the central nervous system. Emesis or vomiting, which occurs with many of the trichothecenes when given at high doses, has been attributed to the stimulation of the chemoreceptor trigger zone in the area postrema of the medulla oblongata. However, studies with T-2 toxin in cats indicated that other mechanisms, such as the neural afferent pathways from the abdomen, implicated in radiation-induced emesis, may also be involved (Borison and Goodheart, 1989). DON alters serotonin activity in the central nervous system of swine which is important in... 

The mechanism by which the endocrine and metabolic response is activated has not been defined clearly. There is evidence that both neural impulses and tissue substances play a part in stimulating what is virtually a total increase in endocrine activity. Many of the hormones which are increased have metabolic functions which include the maintenance of blood glucose levels. This appears to be a fundamental biological defense mechanism whereby an essential energy source is preserved for the central nervous system. 

The exact mechanism of central nervous system (CNS) depression has not been determined, but the most plausible hypothesis is change in membrane fluidity that alters neural transmission. No significant histological damage has been noted in the brains of animals exposed to lethal concentrations. 

The mechanism by which 1,1,1-trichloroethane and other organic solvents depress the central nervous system is poorly understood, but is thought to involve interactions of the parent compound with lipids and/or proteinaceous components of neural membranes (Evans and Balster 1991). No known methods specifically counteract the central nervous system effects of 1,1,1-trichloroethane. Because the specific cellular or biochemical nature of central nervous system depression is poorly understood, it is difficult to propose any method to interfere with this effect of 1,1,1 -trichloroethane, other than to prevent further exposure to the compound so that it can be cleared from the body. 

A fundamental characteristic of the vertebrate central nervous system (CNS) is bilateral symmetry along the midline (Figure 3). This symmetrical structure divides neuronal projections into two types, uncrossed projections to ipsilateral targets and crossed projections to contralateral targets. Over the past decade, the mechanism involved in the formation of crossed projections has been extensively studied in spinal cord commissural projections. Spinal commissural axons, which derive from the dorsal part of the neural tube (alar plate), initially project ventrally along the circumferential axis and then cross the ventral midline [10]. These axons have been shown to be guided by a diffusible molecule released... 

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