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Biomedical subjects

W C Wang

Publications and source records attributed to W C Wang.

At least 73 records · Page 4Linked to original sources
PubMed1997

Recurrent Streptococcus pneumoniae sepsis in children with sickle cell disease.

Streptococcus pneumoniae sepsis is the most common invasive infection among patients with sickle cell disease. The risk of a recurrent episode of sepsis and subsequent death in those patients who have had a previous septic event is much higher. Patients with sickle disease who have had pneumococcal sepsis should continue penicillin prophylaxis indefinitely and should not be candidates for out-patient management of febrile episodes.

Anemia, Sickle Cell↗
PubMed1997

Orbital compression syndrome in sickle cell disease.

BACKGROUND: Orbital complications are an uncommonly reported finding in sickle cell disease. METHODS: The authors review the reported orbital manifestations of sickle cell disease and discuss a patient with hemoglobin sickle beta(0) thalassemia in whom rapidly progressive bilateral orbital compression developed. RESULTS: Computed tomography of the orbits in a patient with fever, headache, orbital swelling, and optic nerve dysfunction displayed bilateral superior subperiosteal cystic masses. Surgical exploration showed bilateral liquefied hematomas, which were evacuated. Recovery was complete 13 days after surgery. A mild recurrence 14 months later resolved with conservative treatment. The literature contains 11 reports of 16 young patients with sickle cell disease (15 sickle cell disease [Hb SS] and 1 hemoglobin sickle cell disease [Hb SC]) with rapidly developing findings ranging from frontal headache, fever, and eyelid edema to bilateral complete orbital compression syndrome. Including our patient, 60% had orbital hemorrhage on computed tomography. Ten of 12 patients tested were found to have orbital bone marrow infarctions. Sixteen of 17 patients had complete recovery; 13 were treated conservatively and 4 surgically. Only 2 of 17 had recurrence. CONCLUSIONS: Orbital complications in sickle cell disease are unusual manifestations in which a vaso-occlusive process in the marrow space around the orbit results in frontal headache, fever, eyelid edema, and often orbital compression syndrome. Subperiosteal hematomas are common and appear to result from bone marrow infarctions. Appropriate management requires a thorough evaluation to exclude other hemorrhagic, infectious or neoplastic processes, as well as vigilant ophthalmic monitoring. Supportive care is effective, unless optic nerve dysfunction or large hematomas are present, which would indicate that surgical evacuation is warranted to prevent loss of vision and to speed recovery.

Anemia, Sickle Cell↗
PubMed1997

Myelodysplastic syndrome in children: differentiation from acute myeloid leukemia with a low blast count.

To evaluate diagnostic criteria, disease characteristics, and the clinical course of pediatric myelodysplastic syndrome (MDS), we reviewed 327 consecutive cases diagnosed with de novo acute myeloid leukemia (AML) or MDS at St Jude Children's Research Hospital between February 1980 and January 1993. Among 49 cases with <30% marrow blasts (consistent with FAB criteria and common diagnostic practice for MDS), eight had karyotypes associated with de novo AML (four with t(8;21)(q22;q22) and one each with inv(16)(p13q22), t(11;17)(q23;q21), t(9;11)(p22;q13), and i(1)(ql0)). We termed these cases AML with a low blast count (AML-LBC) and compared their clinical and morphologic features with those of the remaining 41 cases. AML-LBC cases had little or no hematopoietic dysplasia. MDS cases consisted of refractory anemia (RA, n=6), RA with ring sideroblasts (n=2), RA with excess blasts (RAEB, n=4), RAEB in transformation (n=14), and chronic myelomonocytic leukemia (n=15). Most had moderate/severe or multilineage hematopoietic dysplasia, with significantly higher dysplasia scores than AML-LBC cases (P=0.007). Only 30% of patients with MDS achieved complete remission (CR) after two cycles of AML-directed therapy, compared with 88% of patients with AML-LBC (P=0.0001); MDS patients tended to experience prolonged severe cytopenias with chemotherapy. The 4-year survival for MDS patients was 23% +/- 7% (s.e.), vs 50% +/- 18% (s.e.) for AML-LBC (P=0.048). AML-LBC patients frequently had chloromas; none were seen in MDS patients. We conclude that the 30% blast threshold is ineffective for separation of AML and MDS in pediatric patients, and that genetic data should be included in this decision process. AML-LBC, defined by <30% blasts in bone marrow and cyto- (or molecular) genetic abnormalities associated with de novo AML, and characterized by absent or mild marrow dysplasia, is biologically and clinically distinct from MDS and should be treated as de novo AML. Outcome in pediatric MDS remains poor, and new treatment strategies are needed for these patients.

Acute Disease↗
PubMed1997

Nasopharyngeal carriage of penicillin-resistant Streptococcus pneumoniae in children with sickle cell disease.

OBJECTIVE: We studied the prevalence of nasopharyngeal (NP) carriage, antimicrobial susceptibilities, and serotypes of Streptococcus pneumoniae (SP) in children with sickle cell disease (SCD) in the Mid-South. In addition, we examined risk factors for NP carriage of penicillin-resistant SP (PRSP). STUDY DESIGN: Between July 1994 and December 1995, we obtained NP cultures from 312 children with SCD followed at the Mid-South Sickle Cell Center, 208 (67%) of whom were receiving penicillin prophylaxis. RESULTS: Among the 312 patients, colonization with SP occurred in 42 (13%), 30 (71%) of whom were receiving penicillin prophylaxis. Twenty-three of the 42 SP isolates (55%) were resistant to penicillin; 5 of the 23 (22%) were highly resistant. PRSP organisms were also resistant to cefotaxime (43%), trimethoprim-sulfamethoxazole (57%), and erythromycin (22%). Serotypes 6A, 6B, 14, 19A, and 23F accounted for 19 (90%) of 21 resistant strains. Children who were treated with antibiotics during the preceding month were more likely to carry PRSP than children who were not treated. CONCLUSIONS: There is a high prevalence of NP carriage of PRSP in children with SCD in the Mid-South, which raises concerns regarding the continued effectiveness of penicillin prophylaxis in these children. Further studies on the antimicrobial susceptibilities of resistant organisms and the relationship between NP carriage of SP and invasive disease are needed before developing new recommendations for prophylaxis and treatment.

Adolescent↗
PubMed1997

Genetic analysis of the cytotoxin-associated gene and the vacuolating toxin gene in Helicobacter pylori strains isolated from Taiwanese patients.

OBJECTIVE: Two virulence factors encoded by the cytotoxin-associated (cagA) gene and the vacuolating toxin (vacA) gene of Helicobacter pylori are known to be associated with gastroduodenal pathologic conditions. In this report, nucleotide sequence of cagA and vacA and the serum antibody response to the CagA antigen in H. pylori isolates from Taiwanese patients were studied. METHOD: cagA and vacA were characterized in 173 H. pylori strains by polymerase chain reaction and DNA hybridization analyses. The presence of serum IgG antibodies against CagA was assessed by Helico-blot Western blot system. Sequence analysis of polymerase chain reaction-amplified vacA and cagA was performed for two strains. RESULTS: cagA was detected in all the isolates with peptic ulcers and gastric cancer. Of 54 strains with non-ulcer dyspepsia, 51 were found to be cagA+. Serum antibodies to CagA were detected for 99.2% of cagA+ strains compared with 0% of strains lacking cagA. vacA was detected in all isolates. Sequence analysis of vacA and cagA indicated that sequences of two Taiwanese strains were closely related to each other (95.9% and 97% nucleotide identity, respectively) but less homologous to the published strains (90.9% and 91.4% mean nucleotide sequence identity, respectively). CONCLUSIONS: The strong association (98%) of cagA+ strains with Taiwanese patients suggests that the cagA+ phenotype could not be used as a single marker of high-risk patients in Taiwan. Moreover, sequence analysis indicates that Taiwanese strains contain different genetic sequences from those in other geographic regions.

Adolescent↗
PubMed1996

Characterization of a CD43/leukosialin-mediated pathway for inducing apoptosis in human T-lymphoblastoid cells.

The monoclonal antibody (mAb) J393 induces apoptosis in Jurkat T-cells. NH2-terminal amino acid sequence analysis identified the 140-kDa surface antigen for mAb J393 as CD43/leukosialin, the major sialoglycoprotein of leukocytes. While Jurkat cells co-expressed two discrete cell-surface isoforms of CD43, recognized by mAb J393 and mAb G10-2, respectively, only J393/CD43 signaled apoptosis. J393/CD43 was found to be hyposialylated, bearing predominantly O-linked monosaccharide glycans, whereas G10-2/CD43 bore complex sialylated tetra- and hexasaccharide chains. Treatment with soluble, bivalent mAb J393 killed 25-50% of the cell population, while concomitant engagement of either the CD3.TcR complex or the integrins CD18 and CD29 significantly potentiated this effect. Treatment of Jurkat cells with mAb J393 induced tyrosine phosphorylation of specific protein substrates that underwent hyperphosphorylation upon antigen receptor costimulation. Tyrosine kinase inhibition by herbimycin A diminished J393/CD43-mediated apoptosis, whereas inhibition of phosphotyrosine phosphatase activity by bis(maltolato)oxovanadium-IV enhanced cell death. Signal transduction through tyrosine kinase activation may lead to altered gene expression, as J393/CD43 ligation prompted decreases in the nuclear localization of the transcriptional regulatory protein NF-kappaB and proteins binding the interferon-inducible regulatory element. Since peripheral blood T-lymphocytes express cryptic epitopes for mAb J393, these findings demonstrate the existence of a tightly regulated CD43-mediated pathway for inducing apoptosis in human T-cell lineages.

Antibodies, Monoclonal↗
PubMed1996

Arylsulfatase A pseudodeficiency in Chinese.

Arylsulfatase A (ASA) pseudodeficiency was found to be much rarer in Taiwan than in most western countries (2.5% versus 7.3%-20% carrier rate). The linkage of two mutations (A2725G and A1788G) in the pseudodeficiency allele was preserved in Chinese, and A2725G did not occur alone. This unusual linkage of mutations has not been fully explained previously because the frequency of A2725G alone was not clear (as low as 4% in the only report). However, A1788G was found in 55 of 160 (34.4%) DNA samples tested in this study. These data suggest that the A2725G mutation occurred in DNA that already contained the A1788G change, at an ancient time in one of our common ancestors.

Asian People↗
PubMed1996

Serotype-specific immunoglobulin G antibody responses to pneumococcal polysaccharide vaccine in children with sickle cell anemia: effects of continued penicillin prophylaxis.

OBJECTIVES: (1) To determine serotype-specific IgG antibody responses to reimmunization with pneumococcal polysaccharide vaccine at age 5 years in children with sickle cell anemia and (2) to determine whether continued penicillin prophylaxis had any adverse effects on these responses. STUDY DESIGN: Children with sickle cell anemia, who had been treated with prophylactic penicillin for at least 2 years before their fifth birthday, were randomly selected at age 5 years to continue penicillin prophylaxis or to receive placebo treatment. These children had been immunized once or twice in early childhood with pneumococcal polysaccharide vaccine and were reimmunized at the time of randomization. RESULTS: Serotype-specific IgG antibody responses to reimmunization varied according to pneumococcal serotype but in general were mediocre or poor; the poorest response was to serotype 6B. The antibody responses were similar in subjects with continued penicillin prophylaxis or placebo treatment, and in subjects who received one or two pneumococcal vaccinations before reimmunization. The occurrence of pneumococcal bacteremia was associated with low IgG antibody concentrations to the infecting serotype. CONCLUSIONS: Reimmunization of children with sickle cell anemia who received pneumococcal polysaccharide vaccine at age 5 years induces limited production of serotype-specific IgG antibodies, regardless of previous pneumococcal vaccine history. Continued penicillin prophylaxis does not interfere with serotype-specific IgG antibody responses to reimmunization.

Adult↗
PubMed1996

Antibiotic-resistant pneumococcal infection in children with sickle cell disease in the United States.

OBJECTIVE: The purpose of this report is to examine the increasing problem of antibiotic-resistant pneumococcal infection in children with sickle cell disease in the United States. PATIENTS AND METHODS: In this retrospective review, 16 children with sickle cell disease and penicillin-resistant pneumococcal invasive infection were identified. They had a median age of 2 years (range 1-15) and were treated in Memphis, Dallas, Los Angeles, and five other cities between 1987 and early 1995. RESULTS: At presentation, patients frequently had high fever (> or 40.0 degrees C in 75%) and a toxic appearance (44%). Meningitis was present initially in two and diagnosed on days 4 and 5 in two. All were treated with an intravenous cephalosporin and nine received vancomycin. The clinical course was variable: two died within 36 h of presentation. In 20-86% of cases the organisms were resistant to cephalosporins, chloramphenicol, trimethoprim/sulfamethoxazole, erythromycin, and clindamycin; none were resistant to vancomycin. CONCLUSIONS: (a) The increasing prevalence of antibiotic-resistant Streptococcus pneumoniae infection in the United States poses special problems for patients with sickle cell disease. (b) Prompt antibiotic susceptibility testing of pneumococcal isolates should be performed. (c) Initial antibiotic management for patients suspected of sepsis/meningitis should include intravenous cephalosporin and vancomycin. (d) No alternative to penicillin prophylaxis is currently available. (e) An effective conjugated pneumococcal vaccine is needed.

Adolescent↗
PubMed1996

Outpatient therapy with ceftriaxone and oral cefixime for selected febrile children with sickle cell disease.

PURPOSE: Children with sickle cell disease are at increased risk for bacterial sepsis and, when febrile, are usually hospitalized for intravenous antibiotic therapy pending results of blood cultures. In this study, we prospectively identified a group of febrile patients with sickle cell disease who were at low risk for sepsis and treated them with outpatient therapy. PATIENTS AND METHODS: Children identified as low risk for sepsis were treated with an initial dose of intravenous ceftriaxone, followed by outpatient therapy with oral cefixime, and were monitored for 14 days after the initial visit. Compliance was assessed by phone calls to parents and by analysis of urine samples. RESULTS: In 107 eligible febrile episodes (80 patients) over a 21-month period, no patient developed sepsis. One child developed bacteremia 3 days after completing the course of cefixime, and one had splenic sequestration on the fourth study day. Both patients did well. Side effects of cefixime were modest, and overall compliance was excellent (approximately 95%), although urine samples were returned by only 56% of parents. CONCLUSION: We conclude that outpatient therapy is safe and effective in febrile patients with sickle cell disease who meet the criteria for a low risk of sepsis.

Administration, Oral↗
PubMed1996

Transdermal fentanyl administration in children and adolescents with sickle cell pain crisis.

PURPOSE: The purpose of this study was to determine the dose-concentration relationship and clinical effect of transdermal fentanyl (TF) in patients with sickle cell pain crisis (SCPC). PATIENTS AND METHODS: Ten patients aged 9-16 years were studied. Patients initially received a TF dose of 25 (n = 7) or 50 (n = 3) micrograms/h if morphine use was > 2.5 mg/h. Supplemental morphine usage via patient-controlled analgesia (PCA), sedation status, pain status, respiratory rate, pulse rate, oxygen saturation, and blood pressure were monitored. RESULTS: The average TF dose was 0.77 +/- 0.37 micrograms/kg/h on day 1 and 1.17 +/- 0.46 micrograms/kg/h on day 2. Fentanyl concentrations measured at 24 and 48 h were 0.60 +/- 0.31 and 1.18 +/- 0.44 ng/ml, respectively. A significant relationship existed between TF dose and fentanyl concentration (r2 = 0.56, p < 0.01). There was no difference in any of the clinical monitoring parameters between day 1 and day 2. However, 7 of 10 patients reported subjective improvement in pain control over that achieved with PCA alone. No adverse effects were noted. CONCLUSIONS: Improved understanding of the dose-effect relationship for TF in children and adolescents is necessary before adequate pain control can be achieved with this delivery system.

Administration, Cutaneous↗
PubMed1996

The spectrum of brain MR abnormalities in sickle-cell disease: a report from the Cooperative Study of Sickle Cell Disease.

PURPOSE: To define the spectrum of abnormalities in sickle-cell disease, including infarction, atrophy, and hemorrhage, that are identified by brain MR imaging. METHODS: All MR studies included T1, T2, and intermediate pulse sequences. Images were interpreted without knowledge of the clinical history or neurologic examination findings. Brain MR imaging was performed in 312 children with sickle-cell disease. RESULTS: Seventy patients (22%) had infarction/ischemia and/or atrophy, infarction/ischemia was noted in 39 children (13%) who had no history of a stroke (the "silent" group). The prevalence rates for silent lesions were 17% for sickle-cell anemia and 3% for hemoglobin sickle-cell disease. For patients with sickle-cell anemia and a history of cerebrovascular accident, infarction/ischemia lesions typically involved both cortex and deep white matter, while silent lesions usually were confined to deep white matter. Within the age range studied, the prevalence of infarction/ischemia did not increase significantly with age, although older patients with lesions had more lesions than did younger patients with lesions. CONCLUSIONS: Brain MR imaging showed infarction/ischemia in the absence of a recognized cerebrovascular accident in 13% of patients. The prevalence of these lesions did not increase significantly between the ages of 6 and 14 years, suggesting that lesions are present by age 6. However, the increase in the average number of lesions per patient with age may indicate progressive brain injury.

Adolescent↗
PubMed1995

Cloning, mapping, and characterization of activated leukocyte-cell adhesion molecule (ALCAM), a CD6 ligand.

Antibody-blocking studies have demonstrated the role of CD6 in thymocyte-thymic epithelial (TE) cell adhesion. Here we report that CD6 expressed by COS cells mediates adhesion to TE cells and that this interaction is specifically blocked with an anti-CD6 monoclonal antibody (mAb) or with a mAb (J4-81) that recognized a TE cell antigen. We isolated and expressed a cDNA clone encoding this antigen and show that COS cells transfected with this cDNA bind a CD6 immunoglobulin fusion protein (CD6-Rg). This antigen, which we named ALCAM (activated leukocyte-cell adhesion molecule) because of its expression on activated leukocytes, appears to be the human homologue of the chicken neural adhesion molecule BEN/SC-1/DM-GRASP. The gene was mapped to human chromosome 3q13.1-q13.2 by fluorescence in situ hybridization of cDNA probes to metaphase chromosomes. We prepared an ALCAM-Rg fusion protein and showed that it binds to COS cell transfectants expressing CD6, demonstrating that ALCAM is a CD6 ligand. The observations that ALCAM is also expressed by activated leukocytes and that both ALCAM and CD6 are expressed in the brain suggest that ALCAM-CD6 interactions may play a role in the binding of T and B cells to activated leukocytes, as well as in interactions between cells of the nervous system.

Activated-Leukocyte Cell Adhesion Molecule↗
PubMed1995

Penicillin- and cephalosporin-resistant strains of Streptococcus pneumoniae causing sepsis and meningitis in children with sickle cell disease.

OBJECTIVE: We investigated the possibility that antimicrobial-resistant pneumococci were causing invasive disease in children with sickle-cell disease (SCD). STUDY DESIGN: Records of all children with SCD observed at the Mid-South Sickle Cell Center (MSSCC) at LeBonheur Children's Medical Center were reviewed from January 1990 to June 1994. Children with SCD and pneumococcal sepsis were identified. The Streptococcus pneumoniae isolates from these children were examined for serotype and antimicrobial susceptibilities. Two additional children not observed in the MSSCC had pneumococcal sepsis caused by penicillin-resistant isolates and were also included. RESULTS: Antimicrobial susceptibility testing of the six penicillin-resistant isolates revealed that four were resistant to trimethoprim-sulfamethoxazole, two to erythromycin, and one to clindamycin. The two isolates that were resistant to ceftriaxone also were multiply resistant. From the MSSCC, 26 children had pneumococcal sepsis during the 4 1/2-year period studied. Five of these children (19%) died. Four (15%), including one who died, were infected with penicillin-resistant strains. CONCLUSION: Pneumococcal sepsis, meningitis, and infections of other foci in children with SCD may be caused by S. pneumoniae that is resistant to one or more antimicrobial agents, including penicillin. The addition of vancomycin to the antibiotics currently used for initial management should be considered in areas where the antibiotic resistance of S. pneumoniae is prevalent.

Anemia, Sickle Cell↗
PubMed1995

Serum selenium, zinc and copper in Swedish and Finnish orienteers. A comparative study.

Serum selenium, zinc and copper concentrations of 127 highly-trained Swedish orienteers have been analysed and compared with the corresponding values of 30 elite Finnish orienteers, and those of 111 healthy Finnish medical students. The mean serum selenium levels of Finnish orienteers, 1.35 mumol l-1, and students, 1.38 mumol l-1, were statistically significantly higher than those of Swedish orienteers, 1.09 mumol l-1. The serum levels of selenium were lower than 1.0 mumol l-1 in 27% of Swedish orienteers. This is obviously due to the lower selenium intake of the population in Sweden, where the soil selenium content is known to be low. Serum levels of zinc were within the reference interval in both Swedish and Finnish orienteers (mean values 14.8 and 14.1 mumol l-1, respectively). However, Finnish students had significantly lower serum levels of zinc, 12.5 mumol l-1. The mean serum concentration of copper was statistically significantly higher in females than in males.

Adolescent↗
PubMed1995

Effect of nationwide selenium supplementation in Finland on selenium status in children with juvenile rheumatoid arthritis. A ten-year follow-up study.

A study was performed on the effect of increased selenium intake on the serum selenium level of 212 children with juvenile rheumatoid arthritis (JRA) and of 214 controls in a follow-up study during the Finnish nationwide selenium fertilization programme, which was started in 1984. The mean serum level of selenium increased from 0.90 mumol l-1 in 1985 to 1.56 mumol l-1 in 1990 in the children with JRA. The corresponding selenium levels in the controls were 0.87 mumol l-1 in 1985 and 1.33 mumol l-1 in 1990. Boys had slightly higher selenium levels in all the age groups among the patients and the controls. During the entire 10-year observation period, the patients with JRA had slightly higher mean levels of selenium than the controls. The age of the children did not have any significant effect on the selenium level in either group. The present study shows that the main factor affecting the serum level of selenium was the dietary intake of selenium both in patients and in healthy controls.

Adolescent↗
PubMed1995

Magnetic resonance imaging for evaluation of childhood aplastic anemia.

PURPOSE: We prospectively evaluated the ability of magnetic resonance imaging (MRI) of the thoraco-lumbar vertebrae to determine the relative amount of red and fatty marrow in children with aplastic anemia. PATIENTS AND METHODS: Twenty pediatric patients (ages 1-19 years) with aplastic anemia underwent T1-weighted (T1W, n = 31) and short T1 inversion recovery (STIR, n = 30) MRI of the midline sagittal thoraco-lumbar spine. Bone marrow (BM) biopsies from the posterior iliac crest (n = 29) were also performed. All studies were evaluated by blinded observers; MR grading was based on visual inspection of signal intensity. Biopsy-estimated cellularity was compared with T1W and STIR grading when these were performed within 14 days of each other (n = 16). All studies were compared to a simultaneous absolute neutrophil count (ANC), absolute reticulocyte count (ARC), and platelet count. RESULTS: BM cellularity estimated by BM biopsy was significantly associated with STIR grading (p = 0.032, Jonckheere-Terpstra test), as were peripheral ANC (p = 0.044), ARC (p = 0.007), and platelet count (p = 0.003). T1W grade was significantly associated with ANC (P = 0.011) but not ARC (p = 0.053) or platelet count (p = 0.377). Biopsy-estimated cellularity was associated with ANC (p = 0.032) and ARC (p = 0.036), but not platelet count (p = 0.282). CONCLUSION: In childhood aplastic anemia patients, STIR (and, to a lesser extent, T1W) MRI of the thoraco-lumbar spine reflects BM activity, as measured by peripheral blood ANC, ARC, and platelet count, and BM cellularity, as measured by BM biopsy. MRI may thus provide a noninvasive measure of hematopoietic status.

Adolescent↗