Cisternal space

Formation of PTH begins with the synthesis of several precursor molecules. PreproPTH is the initial peptide that is synthesized within the parathyroid gland, and it serves as a precursor to both proPTH and PTH. PreproPTH is formed within the rough endoplasmic reticulum, transported into the cisternal space, and then cleaved to form proPTH. The proPTH polypeptide is transported into the cisternal space, where another proteolytic cleavage occurs, forming PTH. 

Another example of a situation in which distributed pharmacokinetics plays an important role is in the infusion of drug solutions into the lateral ventricles or cisternal space of the brain. Drugs that have been delivered this way include chemotherapeutic agents for the treatment of tumors antibacterial antifungal and antiviral agents for the treatment of infection and neurotrophic factors for the treatment of neurodegenera tive disease. 

When protein synthesis terminates, the initiator amino acid, Methionine, will have a free amino group. This end of the protein is the N terminus and the last amino acid of the chain has a free carboxy or C terminus. Protein synthesis thus initiates with the amino terminus and proceeds towards the C terminus. Proteins synthesized on the rough ER are transported across a membrane aiad into the cisternal spaces between the sheets of the ER where they are packaged for export. 

The endoplasmic reticulum (ER) is a system of interconnected membranous tubules, vesicles, and large flattened sacs. A hint of its importance in cell function is that it often constitutes more than half of a cell s total membrane. The repeatedly folded, continuous sheets of ER membrane enclose an internal space called the ER lumen. This compartment, which is often referred to as the cisternal space, is entirely separated from the cytoplasm by ER membrane. 

It is now clear from studies of the morphology of protein synthesis that this process originates in the cell nucleus and is effectuated on the rough endoplasmic reticulum. There is considerable evidence that proteins destined for export from the cell pass from the membrane-bound ribo.somes through the cisternal spaces of the smooth endoplasmic reticulum to the vesicles of the Golgi apparatus, where they accumulate in succesively larger vesicles before being finally extruded by exocytosis (reverse pinocytosis). 

One mechanism for the transfer of particular translation products across membrane barriers which has received extensive experimental support is the vectorial release of secretory proteins into the cisternal space of the endoplasmic reticulum. In this system, secretory proteins are synthesized selectively on polysomes attached to the rough endoplasmic reticulum and are subsequently released from the membrane-bound ribosomes through the adjacent membrane into the cisternum of the reticulum for later transport from the cell. ... 

The water-soluble iodopyracet was introduced for myelography in 1931 (870). Because of the extreme irritant effects as well as occasional production of some long-term disabilities, it never gained wide use. Iodized oil Lipi-odol was used for myelography with less irritation. Its aftereffects were avoided if the oily medium was removed by aspiration from the spinal canal (871). lophendylate was introduced by Ramsey et al. (872)for myelography in 1944 and proved to be an excellent contrast medium for the entire spinal canal and the basal cisterns. Like the iodized oil, it had to be aspirated to avoid aftereffects (873). Arachnoiditis did develop in some cases in the subarachnoid space because of the presence of residual iophendylate. 

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