TRANSFORMATION RULES: A CROSS-DOMAIN DIFFICULTY

The learning of a symbolic system such as algebra relies on the learning of the use of transformation rules. The implementation of rules in a CAS (Computer Algebra System) for students' modelling has pointed out some questions that are at the junction of three research fields: informatics, mathematics and didactics. Each of these communities has its own perception of algebraic objects, founded on models or practices. The implementation of objects that live in school has questioned object reliability. In this paper, a parallel is proposed between difficulties of informatics implementation of transformation rules and novices' difficulties

Nadroparine-induced skin necrosis on a patient with essential thrombocythaemia: a case report

Skin necrosis is a rare but serious complication of subcutaneously administered low-molecular-weight heparin. We report a case of a 53-year-old female patient with skin necrosis induced by subcutaneous administration of nadroparine. The patient suffered from essential thrombocythaemia on a background of chronic myeloproliferative disease. She was admitted to our clinic with a subacute ileus due to endometriosis of the rectosigmoid junction. She underwent a high anterior resection and she received pre- and postoperative antithrombotic prophylaxis with subcutaneous nadroparine on a daily basis. On the 6th and 7th postoperative days, two skin necroses occurred at two injection sites

Lipoprotein [a] is cleared from the plasma primarily by the liver in a process mediated by apolipoprotein [a]

The cellular and molecular mechanisms responsible for lipoprotein [ a] (Lp[a]) catabolism are unknown. We examined the plasma clearance of Lp[ a] and LDL in mice using lipoproteins isolated from human plasma coupled to radiolabeled tyramine cellobiose. Lipoproteins were injected into wild-type, LDL receptor-deficient (Ldlr(-/-)), and apolipoprotein E-deficient (Apoe(-/-)) mice. The fractional catabolic rate of LDL was greatly slowed in Ldlr(-/-) mice and greatly accelerated in Apoe(-/-) mice compared with wild-type mice. In contrast, the plasma clearance of Lp[ a] in Ldlr(-/-) mice was similar to that in wild-type mice and was only slightly accelerated in Apoe(-/-) mice. Hepatic uptake of Lp[ a] in wild-type mice was 34.6% of the injected dose over a 24 h period. The kidney accounted for only a small fraction of tissue uptake (1.3%). To test whether apolipoprotein [ a] (apo[a]) mediates the clearance of Lp[a] from plasma, we coinjected excess apo[a] with labeled Lp[ a]. Apo[a] acted as a potent inhibitor of Lp[ a] plasma clearance. Asialofetuin, a ligand of the asialoglycoprotein receptor, did not inhibit Lp[ a] clearance. In summary, the liver is the major organ accounting for the clearance of Lp[ a] in mice, with the LDL receptor and apolipoprotein E having no major roles. Our studies indicate that apo[a] is the primary ligand that mediates Lp[a] uptake and plasma clearance