The effect of dissolved organic matter (DOM) on sodium transport and nitrogenous waste excretion of the freshwater cladoceran (Daphnia magna) at circumneutral and low pH.

Dissolved organic matter (DOM), a heterogeneous substance found in all natural waters, has many documented abiotic roles, but recently, several possible direct influences of DOM on organism physiology have been reported. However, most studies have been carried out with a limited number of natural DOM isolates or were restricted to the use of commercial or artificial humic substances. We therefore employed three previously characterized, chemically-distinct natural DOMs, as well as a commercially available humic acid (Aldrich, AHA), at circumneutral (7-8) and acidic pH (~5), to examine DOM effects on whole-body Na(+) concentration, unidirectional influx and efflux rates of Na(+), and ammonia and urea excretion rates in Daphnia magna. Whole-body Na(+) concentration, Na(+) influx, and Na(+) efflux rates were all unaffected regardless of pH, suggesting no influence of the various natural DOMs on active uptake and passive diffusion of Na(+) in this organism. Ammonia and urea excretion rates were both increased by low pH. Ammonia excretion rates were reduced at circumneutral pH by the most highly colored, allochthonous DOM, and at low pH by all three natural DOMs, as well as by the commercial AHA. Urea excretion rates were not influenced by the presence of the various DOMs in circumneutral solutions, but were attenuated by the presence of two allochthonous DOM sources (isolated from Bannister Lake and Luther Marsh) at acidic pH. The observed reductions may be attributed partially to the higher buffering capacities of natural DOM sources, as well as their ability to interact with biological membranes as estimated by a new measure calculated from their acid-base titration characteristics, the Proton Binding Index (PBI).

Rapid immune reconstitution after a reduced-intensity conditioning regimen and a CD3-depleted haploidentical stem cell graft for paediatric refractory haematological malignancies.

The main obstacles to successful haploidentical haematopoietic stem cell transplantation from a mismatched family member donor are delayed immune reconstitution, vulnerability to infections and severe graft-versus-host disease (GvHD). We designed a reduced-intensity conditioning regimen that excluded total body irradiation and anti-thymocyte globulin in order to expedite immune reconstitution after a CD3-depleted haploidentical stem cell transplant. This protocol was used to treat 22 paediatric patients with refractory haematological malignancies. After transplantation, 91% of the patients achieved full donor chimaerism. They also showed rapid recovery of CD3(+) T-cells, T-cell receptor (TCR) excision circle counts, TCRbeta repertoire diversity and natural killer (NK)-cells during the first 4 months post-transplantation, compared with those results from a group of patients treated with a myeloablative conditioning regimen. The incidence and extent of viremia were limited and no lethal infection was seen. Only 9% of patients had grade 3 acute GvHD, while 27% patients had grade 1 and another 27% had grade 2 acute GvHD. This well-tolerated regimen appears to accelerate immune recovery and shorten the duration of early post-transplant immunodeficiency, thereby reducing susceptibility to viral infections. Rapid T-cell reconstitution, retention of NK-cells in the graft and induction of low grade GvHD may also enhance the potential anti-cancer immune effect.

Cidofovir for the treatment of adenoviral infection in pediatric hematopoietic stem cell transplant patients.

BACKGROUND: Adenovirus (ADV) infections are associated with significant morbidity and mortality after hematopoietic stem cell transplantation (HSCT). The virus is endemic in the general pediatric population and frequently causes severe disease in immunocompromised patients, especially children. We report our experience with cidofovir (CDV) for treatment of ADV infection in 57 HSCT patients, median age 8 years (range 0.5-26). METHODS: Peripheral blood was prospectively screened weekly on all patients for ADV by quantitative real-time PCR for the first 100 days post-HSCT or longer if clinically indicated. Cultures for viral pathogens were performed from other involved sites. Upon detection of ADV by PCR, culture or tissue histopathology, CDV was given intravenously at 5 mg/kg weekly for 2 consecutive weeks, then every 2 weeks until 3 consecutive ADV-negative samples were documented from all previously invoved sites. RESULTS: The clinical manifestations of ADV infection were: diarrhea (53%), fever (21%), hemorrhagic cystitis (12%), and pneumonitis (11%). Eight patients (14%) presented with disseminated disease. CDV treatment resulted in complete resolution of clinical symptoms in 56 (98%) patients in whom the virus became undetectable by all methods. One patient died due to ADV pneumonitis. No cases of dose-limiting nephrotoxicity were observed. CONCLUSIONS. Cidofovir appeared safe and effective for the treatment of ADV infection in this predominantly pediatric HSCT population. Vigilant surveillance and early treatment with CDV can prevent the poor outcomes associated with ADV disease. A larger prospective study is needed to further determine the role of CDV in the treatment of ADV after HSCT.

Outcome of hematopoietic stem cell transplantation for pediatric patients with therapy-related acute myeloid leukemia or myelodysplastic syndrome.

BACKGROUND: Therapy-related myelodysplastic syndrome (t-MDS) and acute myeloid leukemia (t-AML) carry a poor prognosis. We analyzed the results of allogeneic HSCT in 38 children to determine which factors, if any, affected outcome. PROCEDURE: The effects of demographic, donor, and disease-related factors were analyzed to determine their effects on overall and disease-free survival (OS, DFS), relapse, and non-relapse mortality (NRM). RESULTS: OS and DFS for t-AML and t-MDS were similar. Three-year OS and EFS were the same (15.4 +/- 5.8%) and the 3-year NRM was 59.6 +/- 8.4%. The 1-year cumulative risk of grade III-IV acute graft-versus-host disease (GVHD) and relapse were 23.7 +/- 7.0% and 18.7 +/- 6.5%, respectively. The percentage of pre-transplant bone marrow (BM) blasts was positively associated with relapse (P = 0.05), while the percentage of BM blasts at diagnosis of therapy-related disease tended to associate with NRM (P = 0.07). Alternative donor and matched sibling donor grafts had similar outcomes. NRM was higher among patients who did not develop acute GVHD as compared to those with grade 1-2 acute GVHD (69.2 +/- 14.2% vs. +/- 12.7%, respectively), while NRM was 100% in patients with grade III-IV acute GVHD (P = 0.007). CONCLUSIONS: The percentage of BM blasts is associated with relapse in these disorders. High rates of NRM negatively impact the outcome of allogeneic HSCT for children with t-AML and t-MDS. Future studies should focus on reducing NRM.

Etiology and outcome of graft failure in pediatric hematopoietic stem cell transplant recipients.

PURPOSE: To determine the incidence, etiology and outcome of graft failure in pediatric allogeneic bone marrow transplant (BMT) recipients. PATIENTS AND METHODS: Patients with primary or secondary graft failure were identified by database review. A retrospective chart review was performed. Etiologic factors were identified and assessed for statistical significance. RESULTS: 309 children underwent allogeneic BMT during the time interval studied. Four cases of primary graft failure and 7 cases of secondary graft failure occurred. Nonmalignant diagnosis, lower total nucleated cell (TNC) dose, and conditioning without total body irradiation were associated with a higher incidence of graft failure. Donor source, donor/recipient CMV status, CD34+ cell dose, and alloimmunization were not associated with graft failure. CONCLUSIONS: Graft failure is a relatively uncommon occurrence in pediatric patients. Autologous reinfusion may allow time to prepare the patient for a second transplant and decrease complications associated with aplasia. More immunosuppressive conditioning regimens may decrease the incidence of graft failure, particularly in patients with non-malignant diseases or those with lower stem cell doses. More frequent monitoring of chimerism by VNTR analysis may detect late graft failure earlier and allow for more rapid intervention.