Which one of the following is true regarding collagen?
Every third amino acid in collagen is glycine, the others usually being proline and hydroxyproline. Collagen is derived from the Greek kolla (glue) and gennao (to produce) because when boiled, collagen forms glue. The fibrillar collagens, Type 1 and 3, are the most abundant types in skin. Type 1 is comprised of polypeptide chains which are arranged in a triple helix. Two of the chains making up Type 1 collagen are identical (alpha-1 chain), while the third chain is distinct (alpha-2 chain). Every third amino acid in the collagen molecule is glycine, resulting in the pattern Gly-X-Y with the X and Y positions occupied by proline and hydroxyproline. Stability is due to disulphide bonds and also cross-links formed as a result of de-amination of lysyl and hydroxylysyl residues. Type 3 collagen is expressed in greater quantities in scar and healing tissue, and Type 4 collagen is found in the basement membrane.
With regards to anticoagulants in microsurgery:
Unfractionated and fractionated heparins have different proportions of anti-Factor Xa and antithrombin activity. Heparin exerts its anticoagulant activity principally by binding antithrombin III. This causes increased exposure of the antithrombin III active site that, in turn, inactivates the coagulation enzymes, Factor IIa, IXa and Xa. Fractionated heparins also bind antithrombin III but have greater anti-Factor Xa activity rather than greater antithrombin activity. The frequency of heparin-induced thrombocytopenia varies greatly depending on, amongst other factors, the type of heparin administered and the patient population receiving it. In a large clinical trial, serologically-confirmed heparin-induced thrombocytopenia was approximately 1% at 7 days and 3% at 14 days in patients receiving prophylactic unfractionated heparin and 0% in patients receiving prophylactic fractionated heparin. Aspirin is contraindicated in patients under the age of 16 years when used other than as an antiplatelet agent (due to the risk of Reye’s syndrome).
1. Warkentin TE, Levine MN, Hirsh J, Horsewood P, Roberts RS, Gent M, Kelton JG. Heparin-induced thrombocytopenia in patients treated with low-molecular-weight heparin or unfractionated heparin. N Engl J Med 1995; 332: 1330.
Which landmark publication related to free tissue transfer is correct?
Cobbett performed the first successful free great toe-to-hand transfer in humans in 1968. Komatsu and Tamai performed the first known successful thumb replantation in 1965 and published their accomplishment in 1968. Nakayama published the first clinical series of free tissue transfers in 1964 (16 of 21 were successful; all were performed without a surgical microscope). Although it has been published that toe-to-hand free tissue transfer in humans was first performed in China in 1967, this was of the second toe; Cobbett was the first to perform free great toe-to-hand transfer in humans. McLean and Buncke performed the first free omentum flap in 1969 for scalp reconstruction and published their achievement in 1972.
Concerning composite tissue allotransplantation, which of the following is true?
All of the above. The ultimate goal, and thus the focus of transplant immunology research, is to effectively suppress rejection while minimising toxic side effects. In clinical practice this is achieved through a balance of multiple drugs that interfere with the immune response at various sites by blocking the formation, stimulation, proliferation, and differentiation of lymphocytes. These drugs are administered immediately after transplanting the organ or tissues (induction therapy) and regularly thereafter ‘for life’ (maintenance therapy) and in response to rejection episodes (treatment or rescue therapy). The above drugs are often used following composite tissue allotransplantation.
1. Whitaker IS, Duggan EM, Alloway RR, Brown CS, McGuire S, Woodle ES, Hsiao EC, Maldonado C, Banis JC, Jr., Barker JH. Composite tissue allotransplantation: a review of relevant immunological issues for plastic surgeons. J Plast Reconstr Aesthet Surg 2008; 61(5): 481-92.
In relation to free tissue transfer, which one is true?
None of the above is true. The skin of the anterolateral thigh can be based on any appropriate underlying pedicle, which may or may not arise from the descending branch of the lateral circumflex femoral artery. The superficial inferior epigastric artery was absent in 35% of cadaveric dissections and in 40% of patients in a clinical study. Although the skin paddle of the fibula osteoseptocutaneous free flap was widely believed to be unreliable during the 1970s and 1980s, this has been refuted by several clinical studies from different centres. Microsurgery is, by definition, performed with the aid of a surgical microscope.
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