Cockayne syndrome can be caused by mutations in either of two genes (CSA and CSB), both of whose products appear to be part of or bound to TFIIH, and can also be caused by specific mutations in XPB or XPD.

TLS Online TPP Program

#Id: 5528

#Unit 7. System Physiology – Animal

Late proximal tubule reabsorbs primarily NaCl

TLS Online TPP Program

#Id: 5529

#Unit 7. System Physiology – Animal

In late proximal convoluted tubule High tubular fluid Cl− concentration is the driving force for reabsorption

TLS Online TPP Program

#Id: 5530

#Unit 7. System Physiology – Animal

Function of the two exchangers is to transport NaCl from the lumen into the cell:

Na+-H+ exchanger

Cl−-formate− anion exchanger

TLS Online TPP Program

#Id: 5531

#Unit 7. System Physiology – Animal

Transepithelial Voltage 

Cl− diffusion establishes a Cl− diffusion potential, making the lumen positive with respect to blood.

TLS Online TPP Program

#Id: 5532

#Unit 7. System Physiology – Animal

Thin descending and thin ascending segments, have thin epithelial membranes with no brush borders, few mitochondria, & minimal levels of metabolic activity.

TLS Online TPP Program

#Id: 5533

#Unit 7. System Physiology – Animal

Descending part of the thin segment is highly permeable to water and moderately permeable to most Solutes (urea and sodium)