Diuresis used to increase urine output and decrease extracellular fluid volume. Substances in the circulation can also increase the amount of circulating fluid by increasing the osmolarity of the blood. This has the effect of pulling water from the interstitial space, making more water available in the blood and causing the kidney to compensate by removing it as urine. In hypotension, often colloids are used intravenously to increase circulating volume in themselves, but as they exert a certain amount of osmotic pressure, water is therefore also moved, further increasing circulating volume. As blood pressure increases, the kidney removes the excess fluid
Blood–brain barrier more likely, aggravated) by a breakdown in the blood–brain barrier. Cerebral edema is the accumulation of excess water in the extracellular space of the brain, which can result when hypoxia causes the blood–brain barrier to open. Many neurodegenerative diseases including synucleinopathies such as Parkinson's, and tauopathies such as Alzheimer's are thought to result from seeded misfolding from pathological extracellular protein variants known as prions. This prion-like hypothesis is gaining support in numerous studies in vitro and involving in vivo intracerebral injection of brain lysates, extracted protein (tau, alpha-synuclein) and synthetically generated fibers in alpha-synucleinopathies. These proteins are also detectable in