Saturday, December 11, 2010

Basic Medical Biochemistry: A Clinical Approach

Dr. Dawn Marks and her coauthors cover human biochemistry in a reasonably comprehensive fashion for students, using case studies to show the relationship between biochemistry and clinical problems. Facts and pathways are presented to emphasize how the underlying biochemistry is related to the body's overall physiological functioning.

Publisher: Lippincott Williams & Wilkins | ISBN: 068305595X | edition 1996 | PDF | 806 pages | 53,6 mb

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establishment of The asymmetry of the cell membrane

The asymmetry of the cell membrane is established primarily by which of the following?
  • a.Membrane synthesis in the endoplasmic reticulum
  • b.Membrane modification in the Golgi apparatus
  • c.Presence of carbohydrates on the cytoplasmic surface
  • d.The distribution of cholesterol
  • e.Flipping proteins between the leaflets of the lipid bilayer

The answer is:  ( a ).
 Asymmetry of the lipid bilayer is established during membrane synthesis in the endoplasmic reticulum (answer a) before reaching the Golgi apparatus (answer b). Carbohydrates are associated with the N terminals of transmembrane proteins that extend from the extracellular surface, not the cytoplasmic surface (answer c).
Cholesterol is different from proteins and phospholipids that are asymmetrically distributed within the bilayer (answer d). Cholesterol is found on both sides of the bilayer. The small polar head group structure of cholesterol allows it to flip-flop from leaflet to leaflet and respond to changes in shape. In contrast to cholesterol, most proteins and phospholipids are capable of only rare flip-flop (answer e). For example, transbilayer movement of phospholipid is limited mostly to the endoplasmic reticulum.


Popliteal fossa Mnemonic

Popliteal fossa: muscles arrangement

The two Semi's go together, Semimembranosus and Semitendonosus.
The Membranosus is Medial and since the two semis go together, Semitendonosus is also medial.

Therefore, Biceps Femoris has to be lateral.
Of the semi's, to remember which one is superficial: the Tendonosus is on Top.

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Diplopia in a Patient with HIV Infection

A 25-year-old man with human immunodeficiency virus (HIV) infection who was receiving highly active antiretroviral therapy presented with a 1-week history of diplopia and headache. The CD4 count was 218 cells per cubic millimeter, and the viral load was 50,000 copies per milliliter.
The neurologic examination revealed an inability to abduct the right eye with horizontal gaze, a finding that was consistent with an isolated right abducens nerve palsy (rightward gaze, Panel A; leftward gaze, Panel B). The examination of other cranial nerves was normal. The remainder of the motor and sensory examination was within normal limits.
The patient reported having had low back pain and constipation for the previous week. There was no history of bowel or bladder incontinence. A gadolinium-enhanced magnetic resonance image of the brain showed a minimally enhancing mass filling and expanding the right cavernous sinus (Panel C, arrow). Lumbar-spine imaging showed a mass with similar radiographic characteristics involving the ventral epidural compartment.
Biopsy of the spinal lesion revealed diffuse large-B-cell lymphoma. A chemotherapeutic regimen of cyclophosphamide, doxorubicin, vincristine, and prednisolone, along with the monoclonal antibody rituximab (R-CHOP), was started. Progressive leg weakness from spinal involvement developed, and the patient had a poor response to corticosteroids and radiation therapy and died 3 months later.

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