[Arterial complications of arthroscopic meniscectomies. Apropos of three cases]

The authors report three exceptional cases of vascular lesions occurring during arthroscopic meniscectomies involving the posterior horn of the lateral meniscus. These lesions consisted of false aneurysms of the popliteal artery detected early (1 month) or later (5 months and 3 years) after the procedure, one of which formed a fistula with the accompanying vein. This later case resulted in intermittent claudication of the calf and the other two cases presented with painful flexion deformity of the knee. In the case diagnosed after 1 month, the false aneurysm arose from a punctate injury to the artery and was treated by direct arterial suture. In the other two cases, treatment consisted of excision of the false aneurysm and restoration of arterial continuity by an autologous saphenous vein graft. The quality of the clinical result was confirmed angiographically in all three cases. The anatomy predisposes to this complication which can be avoided by respecting a few simple precautions. The surgeon must be avoided by respecting a few simple precautions. The surgeon must be aware of and look for signs of this complication in order to allow early diagnosis.

[Response to hepatic intra-arterial chemotherapy for metastases of colorectal cancer. Anatomo-pathological evaluation apropos of 3 cases of secondary hepatic excision]

Following intra-arterial chemotherapy (5-fluorouracil), wide hepatic resection was performed in three patients with metastases from colorectal cancer. These surgical procedures had been considered to be unfeasible before chemotherapy in two of the three cases because of the extension of the metastases. In contrast to the results of preoperative imaging techniques (CT scan, ultrasonography), the histologic response of tumors to chemotherapy was found to be significant (1/3) or complete (2/3). Since after chemotherapy these imaging procedures are unable to determine whether the observed lesions are tumoral, fibrotic or necrotic, a laparotomy after hepatic intra-arterial chemotherapy is proposed to obtain specimens for histopathologic examination and an assessment of resectability. This procedure should be reserved for patients in whom substantial benefit can be expected considering the extension of primary and metastatic disease.

The effect of tri-N-acetylglucosamine on hydrogen exchange in hen egg white lysozyme

Tritium-hydrogen isotope exchange techniques have been employed to study the effect of tri-N-acetylglucosamine binding on the conformational dynamics of hen egg white lysozyme. Numerical Laplace inversion of the data provides exchange rate probability density functions that reveal three overlapping peaks for both the free enzyme and (GlcNAc)3-enzyme complex. Binding of (GlcNAc)3 decreases the exchange rates of all protons to some extent with by far the largest effect being observed for the slow exchanging protons. These have been located, by comparison with neutron diffraction results (Mason, S. A., Bentley, G. A., and McIntyre, G. J. (1984) in Neutrons in Biology (Schoenborn, B. P., ed) pp. 323-334, Plenum Press, New York), within the beta-sheet structure and on helices (8-13), (28-34), and (89-97), that define the edges of the so-called "hydrophobic box" in lysozyme. The regions of the protein that are most affected by binding (GlcNAc)3, as revealed by hydrogen exchange, are found to be quite distinct from the regions observed to undergo conformational changes by x-ray diffraction. Most of these segments of the protein are located at some distance from the (GlcNAc)3-binding site itself. Two segments (the beta-sheet and helix (28-34)) are closely associated with the two active-site carboxylate groups. These results suggest that exchange-stable regions having strong, highly organized hydrogen bonding may have an important role in catalytic function and the differential propagation of conformational and dynamic perturbations caused by ligand binding at distant sites on the protein.