G-Protein Pathway

Receptor-Mediated Endocytosis

Schematic representation of the endocytic pathway and membrane trafficking. Ligands, such as hormones and growth factors, bind to specific surface receptors and are internalized in pinocytotic vesicles coated with clathrin and other proteins. After the liberation of the coating molecules, the pinocytotic vesicles fuse with the endosomal compartment, where the low pH causes the separation of the ligands from their receptors. Membrane with receptors is returned to the cell surface to be reused. The ligands typically are transferred to lysosomes. The cytoskeleton with motor proteins is responsible for all vesicle movements described.

Receptor-Mediated Endocytosis

Internalization of low-density lipoproteins (LDL) is important to keep the concentration of LDL in body fluids low. LDL, which is rich in cholesterol, binds with high affinity to its receptors in the cell membranes. This binding activates the formation of pinocytotic vesicles from coated pits. The vesicles soon lose their coating, which is returned to the inner surface of the plasmalemma: the uncoated vesicles fuse with endosomes. In the next step, the LDL is transferred to lysosomes for digestion and separation of their components to be utilized by the cell.

A 76-year-old man presents to the emergency department (ED) complaining of a sudden onset of abdominal pain.

A 76-year-old man presents to the emergency department (ED) complaining of a sudden onset of abdominal pain. The pain started about 4 hours before presentation to the ED and has been persistent; it is present in the upper abdomen and is centered in the epigastrium. He describes the pain as deep and burning. There is no associated nausea or vomiting. He does not report any changes in his bowel habits and has not experienced any recent fevers. The review of systems is also negative for any recent unintended weight loss or trauma. The patient also reports having had "indigestion" in the past that caused pain similar to what he is currently experiencing, though much less in intensity. His past medical history is significant for coronary artery disease and hypertension. He takes two medications, both for his high blood pressure, but does not drink excessively and does not smoke.
http://cme.medscape.com/viewarticle/727247?src=emed_case_nl_0&uac=149212BX

X-Ray of pneumopertoneum

Numerous signs are described for diagnosing pneumoperitoneum on plain radiographs. One of the best known, the Rigler sign (also known as the double-wall or bas-relief sign), is a visualization of the outer surface of a bowel loop wall resulting from free air in the peritoneal cavity. The intraluminal gas provides negative contrast and outlines the internal wall. The cupola sign, typically seen on supine radiographs, is an inverted cup-shaped arcuate lucency overlying the lower thoracic spine and projecting caudally to the heart. This sign is formed as air accumulates anteriorly in the median subphrenic space under the central leaf of the diaphragm. The umbilical ligaments, the urachus, and particularly the falciform ligament are sometimes identified as linear radiopaque structures in the presence of free air.[1,3,5,7]

cAMP dependent pathway Mechanism

http://en.m.wikipedia.org/wiki/Redox

Pancreatic artery