Let us look at a model of a phosphoglyceride, such as phosphatidyl choline. Its overall shape is roughly rectangular ( Figure ). The two hydrophobic fatty acid chains are approximately parallel to each other, whereas the hydrophilic phosphoryl choline moiety points in the opposite direction. Sphingomyelin has a similar conformation, as does the archaeal lipid depicted. Therefore, the following shorthand has been adopted to represent these membrane lipids: the hydrophilic unit, also called the polar head group , is represented by a circle, whereas the hydrocarbon tails are depicted by straight or wavy lines ( Figure ).
Epidural steroid injections are commonly prescribed for patients with a disc injury or spinal arthritis causing nerve irritation, and generally consist of local anesthetic (numbing medication such as lidocaine) and cortisone (a steroid that reduces inflammation and pain). Lidocaine is often injected initially so patients experience minimal, if any, pain during the procedure. The injection may be performed by placing the needle posteriorly between the spine bones (Translaminar or interlaminar) and injecting the medicine into the space around the spinal nerves. A transforaminal ESI means the injection is placed slightly to one side of the spine, and the medicine is injected near the ruptured disc and inflamed spinal nerve. A caudal ESI is performed by placing the needle near the tailbone, and injecting the medicine into the region of the sacral nerves and lower lumbar spinal nerves. Epidural steroid injections, as well as most spinal injections, are performed using a special x-ray guidance system called fluoroscopy. This allows the doctor to immediately see an x-ray image on a television screen and inject the medicine precisely into the right spot. The procedure time is often less than 10-15 minutes.
A very typical case of severe cholestasis due to anabolic steroid use. Because the steroids were being used without medical supervision, the dose and actual duration of use of each preparation was unclear, but cholestasis usually arises within 4 to 12 weeks of starting a C-17 alkylated androgenic steroid. The jaundice can be severe and prolonged and accompanied by severe pruritus and marked weight loss. The serum enzymes are typically minimally elevated except for a short period immediately after stopping therapy. The pattern of enzyme elevations can be hepatocellular, cholestatic or mixed. Liver biopsy shows a “bland” cholestasis with minimal inflammation and hepatocellular necrosis. Ma Huang has also been implicated in cases of drug induced liver injury, but is associated with an acute hepatocellular pattern of injury.