Brain CSF barrier

Siegal, T., Sandbank, U., Gabizon, A., Mizrachi, R., Ben-David, E., and Catane, R., Alteration of blood-brain-CSF barrier in experimental meningeal carcinomatosis. A morphologic and adriamycin-penetration stndy, J. NeurooncoL, 4(3), 233, 1987. 

Barrier Transport Pathways across the Blood Brain Barrier Brain CSF Barrier... 

The vascular barrier system in the brain consists of the blood-brain barrier (BBB) and the blood-cerebrospinal fluid (CSF) barriers. There is another barrier, the brain-CSF barrier, between brain tissue and the CSF. The locations of these barriers are demonstrated in Figure i4.i [3]. The blood-brain barrier is the name for the wall of the cerebral microvessels in the brain parenchyma. At the surface of the brain parenchyma, microvessels running in the pia mater are called pial microvessels, which are often used as in vivo models for studying the BBB permeability. Owing to its unique structure that wiUbe discussed in the next section, the BBB maintains very low permeability to water and solutes. In the middle of the brain parenchyma, there are ventricular cavities (ventricles) filled with CSF secreted by the epithelial cells of choroid plexus [4]. The choroid plexus is a highly vascular tissue with leaky, fenestrated capillaries covered with ependymal epithelium, which has relatively tight junctions. The multiceU layer between the blood and the CSF in the choroid plexuses is called the blood-CSF barrier. 

FIGURE 14.5 Circulation of the cerebrospinal fluid (CSF) and the brain-CSF barrier. (Modified from Abbott NJ etal. 2010. Neurobiol Dis. 37 13.)... 

Florfenicol concentrations in the brain, cerebrospinal fluid (CSF), and aqueous humor were one-fourth to one-half the corresponding semm concentrations. Concentrations in these tissues and fluids did not decrease as rapidly, maintaining a low, but fairly constant value. Because the brain, CSF, and aqueous humour are separated from the blood by specialized barriers, florfenicol can seemingly only cross these barriers to a limited extent. 

The blood-CSF barrier is relatively permeable to hydrophilic macromolecules, (i.e., ai-macroglobulin and IgM). In addition, the passage of smaller molecules, which are larger than 500 Da, is facilitated by lipophilicity (i.e., by antibiotics and cytostatic drugs). The composition of the extracellular fluid of the brain parenchyma is unknown. It resembles CSF only in a narrow margin of a few millimeters adjacent to the free CSF space, a zone where a limited diffusion of water-soluble molecules is possible (F2). The composition of CSF is well known because the subarachnoid space can be tapped at its lowest point. Despite the great distance from the site of production, the choroid plexus, it shows all of the characteristics of a filtrate, even in the lumbar sac. 

The CSF/serum ratio of IgG eliminates the individual variation of serum IgG. The quotient of IgG (CSF/serum) to albumin (CSF/serum) eliminates the variation of the IgG quotient by the individual blood-CSF barrier function. Intrathecal IgG is total CSF IgG minus transudative IgG. The first formulas were based on a linear relationship between Q ib and Qigo (Cl, K3, LI, S4). More recent formulas make use of a hyperbolic or exponential function. The application of the latter two formulas reduces the number of false-positive results in the cases of blood-brain barrier disturbances, while sensitivity is maintained. Soeverijn compared Reiber s hyperbolic formula to five other formulas and showed that Reiber s formula produced the best agreement with the lEF gold standard (LI). For the latest modification of the IgG, IgA, and IgM subclasses of immunoglobulins, see Section 3.2.3. 

F2. Felgenhauer, K., The filtration concept of the blood-CSF barrier as basis for the differentiation of CSF proteins. In New Concepts of Blood-Brain Barrier (L. Greenwood, D. J. Begley, M. B. Segal, and S. Lightman, eds.), pp. 209-217. Rlenum Rress, London, 1995. 

The result of this anatomical characteristic of endothelial cells in the CNS is an increased resistance to water-soluble and ionized drugs entering the brain, and cerebrospinal fluid (CSF), from capillary blood. However, in a few areas of the brain the barrier is absent. These areas include the lateral nuclei of the hypothalamus, the area postrema of the fourth ventricle, the pineal body, and the posterior lobe of the hypophysis. Highly lipophilic compounds can cross the barrier. Tranquilizers such as diazepam and its analogs are known to gain access rapidly to the CSF with a half-life (tm) entry time of less than 1 minute. 

Al-Sarraf H, Phillip L (2003) Effect of hypertension on the integrity of blood brain and blood CSF barriers, cerebral blood flow and CSF secretion in the rat. Brain Res 975 179-188. 

Increased Permeability. The permeability of the blood-CSF barrier to plasma proteins is increased by high intracranial pressure resulting from a brain tumor, intracerebral hemorrhage, or traumatic injury. In addition, increased permeability to proteins is seen with inflammation associated with bacterial or viral meningitis, encephalitis, or... 

The blood—brain barrier and the blood—cerebrospinal fluid (CSF) barrier often preclude or slow the entrance of drugs into the CNS. Therefore, when local and rapid effects on the meninges or cerebrospinal axis are desired, drugs sometimes are injected directly into the spinal subarachnoid space. Brain tumors may be treated by direct intraventricular drug administration. 

CENTRAL NERVOUS SYSTEM AND CEREBROSPINAL ELUID Brain capiUary endothelial cells have continuous tight junctions therefore, drug penetration into the brain depends on transcellular rather than paracellular transport. The unique characteristics of brain capillary endothelial cells and pericapillary glial cells constitute the blood-brain barrier. At the choroid plexus, a similar blood-CSF barrier is present based on epithelial tight junctions. The... 

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