Human myeloid alpha 3-fucosyltransferase is involved in the expression of the sialyl-Lewis(x) determinant, a ligand for E- and P-selectin

The sialyl-Lex determinant (NeuAc alpha 2-->3Gal beta 1-->4[Fuc alpha- 1-->3]GlcNAc) has been identified as a major ligand in the selectin- mediated adhesion of neutrophils and monocytes to activated endothelium or platelets. This carbohydrate epitope is formed by the sequential action of alpha 3-sialyltransferase and alpha 3-fucosyltransferase on N- acetyllactosamine (Gal beta 1-->4GlcNAc) disaccharide termini of glycoconjugates. We have addressed the role of the human myeloid alpha 3-fucosyltransferase in the expression of this epitope at the leucocyte surface by determining its activity in human-mouse leukemic cell hybrids (WEGLI), normal human granulocytes and chronic myeloid leukemia (CML) cells using sialylated and desialylated glycoproteins and oligosaccharides as acceptor substrates. In contrast to what has been reported for the myeloid-type enzyme, we found that the alpha 3- fucosyltransferase of the cells studied can use sialylated acceptors be it that the activity is several times lower than with asialo- substrates. Characterization of the product obtained with a sialylated oligosaccharide indicated that the enzyme can catalyze the formation of the sialyl-Le(x) structure. Flow cytometry of the WEGLI cells using a sialyl-Le(x)-specific monoclonal antibody (MoAb) showed that these cells indeed express sialyl-Lex at their surface, provided that they contain human chromosome 11. Earlier the presence of this chromosome had been correlated with the expression of alpha 3-fucosyltransferase activity. In addition to sialyl-Le(x), WEGLI cells containing chromosome 11 showed high-expression levels of related structures recognized by antibodies VIM-2 and VIM-8, suggesting that fucose addition can occur at both distal and proximal GlcNAc residues in poly- N-acetyl-lactosaminoglycan sequences. Based on the human chromosome contents it could be ruled out that the alpha 3-fucosyltransferase of WEGLI cells is a Lewis-type alpha 3/4- or plasma-type alpha 3- fucosyltransferase, the genes of which have been mapped to chromosome 19. It is concluded that the enzyme studied is of the myeloid-type and indeed is involved in the synthesis of sialyl-Le(x) (and also VIM-2 and VIM-8 structures) in leukocytes provided that its expression is at a sufficiently high level.     

Colon perforation following percutaneous nephrostomy and renal calculus removal

Two patients had colonic perforation as a result of percutaneous nephrostomy placement followed by track dilatation and renal calculus removal. We present the technical aspects of nephrostomy placement and stone removal, as well as the clinical diagnosis and management of these cases. Both patients recovered well with conservative therapy and required no surgical intervention. This report reviews the anatomic considerations for percutaneous nephrostomy in patients undergoing renal stone removal.     

Modeling of the naked facet sign in the thoracolumbar spine

On transverse computed tomographic (CT) scan cuts of the thoracolumbar spine, the naked facet sign occurs when the inferior articular facets of the cephalad vertebra do not appear adjacent to the superior facets of the subjacent caudal vertebra. The objective of this study was to determine the angles of rotation required for the naked facet sign to occur in the thoracolumbar spine, with the center of rotation located at various points in or anterior to the vertebral body. A commercial spinal model and visualization software were used to simulate various flexion injuries. Each functional spinal unit (FSU; T11-T12, T12-L1, and L1-L2) was examined separately. In the model, two CT scan slices (each 2 mm thick) were created parallel to the inferior end plate of the cephalad vertebra of each FSU. The cephalad vertebra was rotated in 0.5 degrees increments, and after rotation both modeled CT slices were examined for the presence of the naked facet sign. If the sign did not occur, the process was repeated, rotating the cephalad vertebra an additional 0.5 degrees until the naked facet sign occurred. The angle of rotation necessary for the sign to occur increases as the point of rotation of the vertebra moves from anterior to posterior and from superior to inferior. The naked facet sign occurred at a minimum rotation angle of 5 degrees (with respect to the anterior-superior point on T11) and at a maximum rotation angle of 16.5 degrees (with respect to the posterior-inferior point on L1). For rotations about a point located 3 cm anterior to the vertebral body, the minimum angles required for the sign decreased only 1 degrees for each FSU. These results suggest that the naked facet sign does not consistently imply the presence of posterior column vertebral instability. This will help clinicians to relate the mechanism of injury, radiographic findings (including the naked facet sign), and the implied injury pattern to the determination of stability, and ultimately the management options for the injury.     

Gamma-knife radiosurgery for trigeminal neuralgia

Gamma knife was installed at the PD Hinduja National Hospital and Medical Research Centre, Mumbai, India, in January 1997. In the first year of gamma-knife radiosurgery to January 1998, we treated 110 patients, of whom six had medically refractory trigeminal neuralgia. Seven treatments were administered to this group of six patients (one had bilateral neuralgia). This report evaluates the effectiveness of radiosurgery treatment in these patients. The median age of the patients was 56 years and there were five males and one female. Following Leksell stereotactic frame fixation, a magnetic resonance imaging scan was done in all. The Leksell gamma plan was used for planning. A radiosurgery dose of 70–80 Gy was delivered to the trigeminal root entry zone, 2–4 mm anterior to the junction of the pons and trigeminal nerve with a single 4 mm collimator helmet. Complete pain relief was achieved in four patients. Two had partial relief. No patient developed any radiosurgery related morbidity during the follow-up period of 5–16 months. Radiosurgery seems to be an effective approach for medically or surgically refractory trigeminal neuralgia.     

Hypoaldosteronism in three sibs due to 18-dehydrogenase deficiency

Three sibs all presented in the early neonatal period with a salt-losing syndrome. The salt-losing form of congenital adrenal hyperplasia was diagnosed and appropriate treatment with glucocorticosteroids, mineralocorticosteroids, and additional dietary salt started. Although early life was maintained with difficulty, with age all 3 children required decreasing amounts of replacement steroids to maintain normal plasma electrolyte balance. They were reinvestigated at the ages of 15 years and 8 years (twins), when cortisol synthesis and metabolism proved normal, but aldosterone synthesis was blocked by deficiency of 18-dehydrogenase. Rational treatment of these cases of a salt-losing syndrome in which aldosterone synthesis alone is blocked due to lack of the enzyme 18-dehydrogenase requires the administration of a mineralocorticosteroid drug only. Since deoxycorticosterone (acetate or pivalate) requires intramuscular administration, as life-long therapy oral fludrocortisone is preferable. Although fludrocortisone has glucocorticoid activity, the "hydrocortisone equivalent" effect of the small dosage used was unlikely to inhibit either pituitary corticotrophin or growth hormone production.     

Centrilobular emphysema: CT-pathologic correlation

Over a 5-year period, 25 patients who had undergone chest computed tomography (CT) died and were autopsied. Their lungs were fixed in the inflated state and were assessed for the presence and severity of centrilobular emphysema (CLE). Three radiologists independently evaluated the CT scans for nonperipheral low-attenuation areas, peripheral low-attenuation areas, pulmonary vascular pruning, pulmonary vascular distortion, and pulmonary density gradient. The CT criterion that best correlated with the presence and severity of CLE was the nonperipheral low-attenuation area. With this CT criterion, lung destruction was correctly identified in 13 of 15 cases. The absence of this criterion resulted in correct identification of eight of ten normal lungs. These preliminary data suggest that CLE can be reliably identified and quantified with current CT scanners.     

Pulmonary embolism after hip or knee replacement: postoperative changes on pulmonary scintigrams in asymptomatic patients

Serial pulmonary imaging has proved to be effective in the evaluation of patients undergoing total joint arthroplasty. A clinical dilemma arises in asymptomatic patients whose postoperative pulmonary images differ from the preoperative images. The authors prospectively evaluated 403 patients with serial imaging to determine the significance of changed postoperative images in asymptomatic patients undergoing total hip or knee arthroplasty. Twenty-two (5.5%) patients had significant changes on postoperative images. Seventeen were asymptomatic; all but one underwent pulmonary angiography. Documented pulmonary emboli were demonstrated in 100% of patients whose postoperative images changed to indicate a high probability of pulmonary embolism, 71% whose images changed to a moderate probability, and 0% whose images changed to indeterminate probability. Overall, pulmonary emboli occurred in 76% of all asymptomatic patients with significantly change postoperative images. Asymptomatic pulmonary embolism is a significant occurrence after total hip or knee repair, and a changed lung scan with appropriate clinical evaluation is an accurate indicator of pulmonary emboli in asymptomatic postarthroplasty patients.