The extracellular space(ECS) of brain is defined as an irregular channel which is located in the interstitial tissue outside the plasma membranes of neurons,and occupied by interstititial fluid(ISF).Diffusion in ECS i...The extracellular space(ECS) of brain is defined as an irregular channel which is located in the interstitial tissue outside the plasma membranes of neurons,and occupied by interstititial fluid(ISF).Diffusion in ECS is described by a modified diffusion equation from which several parameters can be calculated,such as the diffusion coefficient(D),the tortuosity(λ),the volume fraction(α) and the clearance of molecules.Radiolabeled tracers were used for early diffusion measurements.Presently,the real-time iontophoresis(RTI) method is employed for small ions,whereas the integrative optical imaging(IOI) and the magnetic resonance diffusion weighted imaging(DWI) are developed for macromolecules tracers.Extensive experimental studies with such methods show that in normal brain tissue,the volume fraction of ECS typically is about 20% and the tortuosity is 1.6,although there are regional variations.These parameters change with the brain development and in various pathophysiological states.Knowledge of ECS diffusion properties help us to understand extrasynaptic volume transmission to the development of paradigms for drug delivery in brain.展开更多
The respiratory burst of neutrophils is an important response in inflammation. The alterations in extracellular pH per se is not a sufficient trigger to the respiratory burst in neutrophils. While neutrophils in respo...The respiratory burst of neutrophils is an important response in inflammation. The alterations in extracellular pH per se is not a sufficient trigger to the respiratory burst in neutrophils. While neutrophils in respose to conventional agonists, the respiratory burst in neutrophils is affected by the alterations in extracellular pH, and there is a direct relationship between intracellular and extracellular pH. O-· 2 production in neutrophils is decreased while H 2O 2 production is increased at acidic pH. O-· 2 release in neutrophils is enhanced at weak alkaline pH. Na+/H+ exchanger plays an important role in the regulation of the respiratory burst of neutrophils.展开更多
文摘The extracellular space(ECS) of brain is defined as an irregular channel which is located in the interstitial tissue outside the plasma membranes of neurons,and occupied by interstititial fluid(ISF).Diffusion in ECS is described by a modified diffusion equation from which several parameters can be calculated,such as the diffusion coefficient(D),the tortuosity(λ),the volume fraction(α) and the clearance of molecules.Radiolabeled tracers were used for early diffusion measurements.Presently,the real-time iontophoresis(RTI) method is employed for small ions,whereas the integrative optical imaging(IOI) and the magnetic resonance diffusion weighted imaging(DWI) are developed for macromolecules tracers.Extensive experimental studies with such methods show that in normal brain tissue,the volume fraction of ECS typically is about 20% and the tortuosity is 1.6,although there are regional variations.These parameters change with the brain development and in various pathophysiological states.Knowledge of ECS diffusion properties help us to understand extrasynaptic volume transmission to the development of paradigms for drug delivery in brain.
文摘The respiratory burst of neutrophils is an important response in inflammation. The alterations in extracellular pH per se is not a sufficient trigger to the respiratory burst in neutrophils. While neutrophils in respose to conventional agonists, the respiratory burst in neutrophils is affected by the alterations in extracellular pH, and there is a direct relationship between intracellular and extracellular pH. O-· 2 production in neutrophils is decreased while H 2O 2 production is increased at acidic pH. O-· 2 release in neutrophils is enhanced at weak alkaline pH. Na+/H+ exchanger plays an important role in the regulation of the respiratory burst of neutrophils.
