Risk factors for acute chest syndrome in children with sickle cell disease undergoing abdominal surgery

BACKGROUND/PURPOSE

The reported incidence of acute chest syndrome (ACS) in children with sickle cell disease (SCD) is 15% to 20%. Our current objective was to assess risk factors and morbidity associated with ACS.

METHODS

The authors reviewed the outcome of children with SCD undergoing abdominal surgery over a 10-year period.

RESULTS

From 1991 to 2003, 60 children underwent laparoscopic cholecystectomy (LC; n = 29), laparoscopic splenectomy (LS; n = 28), or both (LB; n = 3). Mean age was 8.6 (0.7 to 20) years, and 35 (58%) were boys. Fifty-four (90%) had a preoperative hemoglobin greater than 10 g/dL, but only 22 (37%) received routine oxygen after surgery. No surgery was converted to an open procedure. Four children (6.6%), all of whom underwent either LS or LB, had ACS associated with an increased length of stay (7.4 +/- 2.4 days) but no mortality. Factors associated with the development of ACS were age (3.0 +/- 1.7 v 9.4 +/- 5.7 years; P =.03), weight (12.1 +/- 3.0 v 32.6 +/- 18.2 kg; P =.04), operative blood loss (3.2 +/- 0.5 v 1.4 +/- 1.2 mL/kg; P =.03), and final temperature in the operating room (OR; 36.2 +/- 0.4 v 37.6 +/- 0.4 degrees C; P =.01). ACS was not significantly related to duration of surgery, OR fluids, or oxygen usage.

CONCLUSIONS

Younger children with greater blood and heat loss during surgery appear more prone to ACS. Splenectomy also seems to increase the risk of ACS. The authors' current incidence (6.6%) of ACS in children with SCD undergoing abdominal surgery is much lower than previously reported. This may be explained by the aggressive use of preoperative blood transfusion or more routine use of laparoscopy.

Biochemical characterization and intracellular localization of the Menkes disease protein

Menkes disease is a fatal neurodegenerative disorder of childhood due to the absence or dysfunction of a putative copper-transporting P-type ATPase encoded on the X chromosome. To elucidate the biosynthesis and subcellular localization of this protein, polyclonal antisera were generated against a bacterial fusion protein encoding the 4th to 6th copper-binding domains in the amino terminus of the human Menkes protein. RNA blot analysis revealed abundant Menkes gene expression in several cell lines, and immunoblotting studies utilizing this antiserum readily detected a 178-kDa protein in lysates from these cells. Pulse-chase studies indicate that this protein is synthesized as a single-chain polypeptide which is modified by N-linked glycosylation to a mature endoglycosidase H-resistant form. Sucrose gradient fractionation of HeLa cell lysates followed by immunoblotting of individual fractions with antibodies to proteins of known intracellular location identified the Menkes ATPase in fractions similar to those containing the cation-independent mannose-6-phosphate receptor. Consistent with this observation, confocal immunofluorescence studies of these same cells localized this protein to the trans-Golgi network and a vesicular compartment with no expression in the nucleus or on the plasma membrane. Taken together, these data provide a unique model of copper transport into the secretory pathway of mammalian cells which is compatible with clinical observations in affected patients and with recent data on homologous proteins identified in prokaryotes and yeast.

Expression of the Wilson disease gene is deficient in the Long-Evans Cinnamon rat

Long-Evans Cinnamon rats develop a necrotizing hepatitis characterized by excessive hepatic copper accumulation, defective holoceruloplasmin biosynthesis and impaired biliary copper excretion. To elucidate the molecular basis of this defect, a cDNA clone encoding the rat Wilson disease gene was isolated and used to examine gene expression in selected tissues from normal and Long-Evans Cinnamon rats. Although this cDNA readily detects Wilson transcripts in liver and other tissues from normal rats, such transcripts are entirely absent from tissues derived from the Long-Evans Cinnamon rat strain. These data therefore identify the Long-Evans Cinnamon rat as the first bona fide animal model of Wilson disease and suggest that this rat strain may be a valuable resource in the study of this genetic disorder.

Isolation and characterization of a human liver cDNA as a candidate gene for Wilson disease

The putative copper and ATP-binding domains of the human Menkes disease gene were used as probes to screen a human liver cDNA library at reduced stringency. Sixty-five clones which remained positive after tertiary screening were subcloned and sequenced. One of these cDNA clones contains an open reading frame with 65% amino acid homology to the Menkes protein. Southern blot analysis localizes this cDNA to the region of the Wilson disease locus on chromosome 13. This cDNA detects a 7.5 kB transcript which is present in human liver and cell lines devoid of the Menkes transcript and which is absent in liver from a patient with Wilson disease. These data suggest that this cDNA is a candidate gene for Wilson disease and that the protein encoded at this locus is a member of the P-type ATPase family.

Purification of hemopexin and its domain fragments by affinity chromatography and high-performance liquid chromatography

A method is described for the preparation of apohemopexin from Cohn Fraction IV-4 of human serum by one-step affinity chromatography on a heme-agarose column and separation of its tryptic domain fragments by high-performance liquid chromatography (HPLC). Limited tryptic digestion cleaved human apohemopexin after Arg-216 into half molecules and the N-terminal half was degraded very rapidly, whereas heme-saturated hemopexin was cleaved after Lys-101. These results suggest that hemopexin is composed of two domains that are connected by an exposed histidine-rich hinge-like region in apohemopexin which becomes inaccessible to trypsin in heme-saturated hemopexin. Also described is the preparation of apohemopexin from whole rabbit serum in two steps, heme-affinity chromatography and ion-exchange HPLC, and separation of its tryptic domain fragments by HPLC. Limited tryptic digestion also cleaves rabbit apohemopexin into half-molecules but the N-terminal half is more stable than the C-terminal half in this case. This lends support to the idea of functional differences between domains.