In Escherichia coli, MutS scans the DNA, recognizing mismatches from the distortion they cause in the DNA backbone. 

MutS has an ATPase activity that is required for mismatch repair and recruits MutL, a second protein component of the repair system. MutL, in turn, activates MutH, an enzyme that causes an incision or nick on one strand near the site of the mismatch. Nicking is followed by the action of a specific helicase (UvrD) helicase unwinds the DNA, starting from the incision and moving in the direction of the site of the mismatch, and the filled in by DNA polymerase III

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#Unit 7. System Physiology – Animal

Astrocytes, which are found throughout the brain, are of two subtypes:

Fibrous astrocytes

Protoplasmic astrocytes

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#Unit 7. System Physiology – Animal

Fibrous astrocytes, contain many intermediate filaments are found primarily in white matter.Protoplasmic astrocytes are found in gray matter and have a granular cytoplasm.

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#Unit 7. System Physiology – Animal

Both Astrocytes

send processes to blood vessels, where they induce capillaries to form the tight junctions making up the blood–brain barrier send processes that envelop synapses and the surface of nerve cells.

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#Unit 7. System Physiology – Animal

Protoplasmic astrocytes produce substances that are tropic to neurons, & they help maintain the appropriate concentration of ions & neurotransmitters by taking up K+ & neurotransmitters glutamate & γ-aminobutyrate (GABA)

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#Unit 7. System Physiology – Animal

Ependymal cells are ciliated-epithelial glial cells that develop from radial glia along the surface of the ventricles of the brain and the spinal canal & play a critical role in cerebrospinal fluid homeostasis, brain metabolism, and the clearance of waste from the brain.

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#Id: 5419

#Unit 7. System Physiology – Animal

Neurons generally have four important zones:

A dendritic zone, where multiple local potential changes generated by synaptic connections are integrated. a site where propagated action potentials are generated. an axonal process that transmits propagated impulses to the nerve endings the nerve endings, where action potentials cause the release of synaptic transmitters.