Is activation of the granulocyte by concanavalin-A a reversible process?

The stimulation of granulocyte O2- production by concanavalin-A can be reversed with alpha-methylmannoside. Such cells can be reactivated to generate O2- by adding phorbol myristate acetate or N-formyl-methionyl- leucyl-phenylalanine. Opsonized zymosan, however, is not an effective stimulant to these cells. alpha-Methylmannoside prevents, but does not reverse, depolarization of granulocytes by concanavalin-A. Previously activated cells have a shorter lag time for reactivation by phorbol myristate acetate. Incubation in 2-deoxyglucose of cells previously treated with concanavalin-A and alpha-methylmannoside prevents reactivation. EGTA prevents concanavalin-A-stimulated O2- production only when added prior to the stimulant. EGTA has only a slight effect on reactivation. alpha-Methylmannoside prevents concanavalin-A- stimulated release of lysozyme only when added prior to the stimulant. Prior treatment of cells with concanavalin-A and alpha-methylmannoside inhibits subsequent ingestion of complement-coated particles. We conclude that although the O2--generating system can be reversibly activated with concanavalin-A followed by alpha-methylmannoside, these cells are different from untreated cells. Cells treated in such a way do not respond to all stimuli, remain depolarized, have shortened lag times, no longer require calcium for activation, continue to degranulate, and do not ingest well. Thus, although some changes that accompany the interaction of stimuli with granulocytes are reversible, some are not, and the previously activated cell does not return to a true resting state.     

Generation of natural killer cells from Thy 1.1+ bone marrow precursor cells in the rat

We have recently described a long-term bone marrow culture (LTBMC) system in the rat for the generation of natural killer (NK) cells from bone marrow (BM) precursors in the presence of interleukin-2 (IL-2). We found that the LTBMC-conditioned medium was essential to render the NK precursor cells responsive to IL-2. In this report, we isolated by flow cytometric cell sorting Thy 1.1+ BM cells, which have been shown to contain pluripotent stem cells and early precursor cells of various hematopoietic lineages. These Thy 1.1+ immature BM precursors did not generate any detectable NK activity when cultured for 7 days with IL-2 alone. However, when the cells were cultured with IL-2 in the presence of LTBMC-conditioned medium, NK cells were generated as demonstrated by cytolytic activity against NK-sensitive tumor targets, large granular lymphocyte (LGL) morphology, and the acquisition of NK cell-associated phenotype (72% of the cells were 3.2.3+/OX41-/CD5-). This study demonstrates the existence of an IL-2 unresponsive Thy 1.1+ NK precursor in the BM of the rat, that can differentiate to a mature NK cell in the presence of LTBMC-conditioned medium and IL-2.     

Synthesis of cobalamin coenzymes by human lymphocytes in vitro and the effect of folates and metabolic inhibitors

The uptake of 57Co-cyanocobalamin (CN-Cbl) and its conversion to 5- deoxyadenosylcobalamin (Ado-Cbl), methylcobalamin (Me-Cbl), and hydroxocobalamin (OH-Cbl) has been studied in phytohemagglutinin (PHA)- transformed lymphocytes from normal subjects and patients with patients with pernicious anemia. Uptake and conversion were much greater by PHA- stimulated lymphocytes than by mature non-transformed lymphocytes. In normal cells, uptake of 57Co-CN-Cbl and synthesis of the cobalamin coenzymes were approximately linear between 3 and 48 hr incubation. Ado- Cbl was the major cobalamin formed, and after 72 hr the cells contained about twice as much Ado-Cbl as Me-Cbl. Uptake by lymphocytes from patients with untreated pernicious anemia (PA) was greater than that by normal lymphocytes, but the proportions of Ado-Cbl and Me-Cbl synthesized by each were similar. Folic acid and methyltetrahydrofolate enhanced synthesis of Me-Cbl both in normal and in PA cells, while methotrexate and 5-fluorouracil depressed it. This depression was overcome by 5-formyltetrahydrofolate, suggesting that an uninterrupted folate cycle may play an important role in Me-Cbl synthesis.     

The acute chest syndrome in sickle cell disease: incidence and risk factors. The Cooperative Study of Sickle Cell Disease

The acute chest syndrome (ACS), a pneumonia-like illness in sickle cell patients, is one of the most frequent causes of their morbidity and hospitalizations. Repeated ACS events may predict the development of chronic lung disease. ACS is reported as a frequent cause of death in these patients. We examine here the incidence and risk factors of ACS in 3,751 patients with sickle cell disease who were observed prospectively for at least 2 years (19,867 patient-years [pt-yrs]) as part of a multicenter national study group. The ACS, defined by a new pulmonary infiltrate on x-ray, occurred at least once in 1,085 patients (2,100 events). ACS incidence was higher in patients with homozygous sickle cell disease (SS; 12.8/100 pt-yrs) and in patients with sickle cell-beta(0) -thalassemic (9.4/100 pt-yrs), and lower in patients with hemoglobin (Hb) SC disease (5.2/100 pt-yrs) and patients with sickle cell-beta(+) thalassemia (3.9/100 pt-yrs). alpha-Thalassemia did not affect the rate of ACS incidence in SS patients. Within each Hb type the incidence was strongly but inversely related to age, being highest in children 2 to 4 years of age (25.3/100 pt-yrs in SS) and decreasing gradually to its lowest value in adults (8.8/100 pt-yrs in SS). In SS children (< 10 years of age), we documented an age-related within- person reduction in ACS attack rates. Adults with a higher ACS rate had a higher rate of mortality (from all causes) than those with low ACS rates. This increased rate of mortality might also have contributed to the decline in ACS rate with age. In multivariate analysis, other factors affecting incidence in SS patients were degree of anemia (lower ACS rates in patients with lower steady-state Hb levels) and fetal Hb (lower rates in patients with high fetal Hb). There was also a positive association between ACS rate and steady-state leukocyte count. The relationship of ACS rate to higher steady-state Hb levels in SS patients is unexplained but might be caused by increased blood viscosity.     

A randomized comparison between rasburicase and allopurinol in children with lymphoma or leukemia at high risk for tumor lysis

Standard therapy in the United States for malignancy-associated hyperuricemia consists of hydration, alkalinization, and allopurinol. Urate oxidase catalyzes the enzymatic oxidation of uric acid to a 5 times increased urine soluble product, allantoin. Rasburicase is a new recombinant form of urate oxidase available for clinical evaluation. This multicenter randomized trial compared allopurinol to rasburicase in pediatric patients with leukemia or lymphoma at high risk for tumor lysis. Patients received the assigned uric acid-lowering agent for 5 to 7 days during induction chemotherapy. The primary efficacy end point was to compare the area under the serial plasma uric acid concentration curves during the first 96 hours of therapy (AUC(0-96)). Fifty-two patients were randomized at 6 sites. In an intent-to-treat analysis, the mean uric acid AUC(0-96) was 128 +/- 70 mg/dL.hour for the rasburicase group and 329 +/- 129 mg/dL.hour for the allopurinol group (P <.0001). The rasburicase versus allopurinol group experienced a 2.6-fold (95% CI: 2.0-3.4) less exposure to uric acid. Four hours after the first dose, patients randomized to rasburicase compared to allopurinol achieved an 86% versus 12% reduction (P <.0001) of initial plasma uric acid levels. No antirasburicase antibodies were detected at day 14. This randomized study demonstrated more rapid control and lower levels of plasma uric acid in patients at high risk for tumor lysis who received rasburicase compared to allopurinol. For pediatric patients with advanced stage lymphoma or high tumor burden leukemia, rasburicase is a safe and effective alternative to allopurinol during initial chemotherapy.     

Human HL-60 myeloid leukemia cells transport dehydroascorbic acid via the glucose transporters and accumulate reduced ascorbic acid

The cellular accumulation of vitamin C, a substance critical to human physiology, is mediated by transporters located at the cell membrane, and is regulated in a cell-specific manner. Neoplastic cells may have special needs for vitamin C. Therefore, we investigated the transport of vitamin C in a human myeloid leukemia cell line (HL-60). The HL-60 cells lacked the capacity to transport the reduced form of vitamin C, ascorbic acid, but they showed a remarkable ability to transport the oxidized form of vitamin C, dehydroascorbic acid (DHA). Uptake- accumulation studies indicated that the HL-60 cells accumulated ascorbic acid when provided with DHA. Kinetic analysis showed the presence of two functional activities involved in the uptake of DHA, one with low affinity and one with high affinity. Cytochalasin B and phloretin, which inhibit the passage of glucose through the facilitative glucose transporters, also inhibited the transport of DHA by HL-60 cells. Transport of DHA was completed by D- but not L-hexoses, and was sensitive to D-hexose-dependent counter transport acceleration. These data support the concept that HL-60 myeloid leukemic cells transport DHA through the facilitative hexose transporters (glucose transporters) and accumulate the reduced form of ascorbic acid.     

A pattern of 5-1-1 and c100-3 only on hepatitis C virus (HCV) recombinant immunoblot assay does not reflect HCV infection in blood donors

Current criteria for a reactive (positive) interpretation on hepatitis C virus (HCV) recombinant immunoblot assay (RIBA) require > or = 1+ reactivity to at least two of the four HCV antigens present in the assay. Given that 5-1-1 is a subcomponent of c100-3, there is concern that donor samples reacting only with these two antigens (and not with c22-3 or c33c) could be incorrectly classified as positive on the basis of limited reactivity to only one HCV gene product. It is determined that 0.23 to 0.44 percent of HCV enzyme immunoassay-repeatably reactive donor sera demonstrate a pattern of 5-1-1 and c100-3 only on RIBA. Evaluation of six such donor sera using peptide enzyme immunoassays spanning the c100-3 antigen showed highly restricted reactivity to the 5-1-1 N-terminal region of c100-3, in contrast to broad 5-1-1 and c100- 3 C-terminal peptide reactivity observed in the majority of donor sera with other positive RIBA patterns. HCV polymerase chain reaction and follow-up serologic evaluations of four of these donors indicated the absence of viremia or evolving seroconversion in all cases. It is concluded that, in the blood donor setting, a pattern of only 5-1-1 and c100-3 reactivity is typically not indicative of HCV infection. To avoid overinterpretation, it is recommended that RIBA grading criteria be revised to require reactivity to two or more HCV-encoded gene products.     

热塑矫形支具治疗青少年特发性脊柱侧凸：疗效及材料和宿主反应随访

目的:回顾性分析支具矫正的青少年特发性脊柱侧凸适应证及临床效果。方法:对2003-01/2005-12在解放军第211医院骨科收治的106例未做过治疗的生长发育期青少年特发性脊柱侧凸患者,给予热塑矫形支具治疗。男21例,女85例;年龄8～19岁,平均(13.1±3.6)岁。单胸凸49例,双胸凸8例,胸和腰双凸37例,胸腰段或腰凸12例。原发Cobb角20°～42°,平均(±6.4)°。Risser征0度51例,Ⅰ度33例,Ⅱ度19例,Ⅲ度3例。支点29.5弯曲位时的矫正率≥50%的柔软性侧凸57例,<50%的僵硬性侧凸49例。每3～6个月复查1次,摄站立位全脊柱正侧位X射线片。结果:①全部病例随访24～72个月,平均36个月,79例(74.5%)治疗有效(原发性侧凸Cobb角增加≤5°,或是胸腰双主弯中继发侧凸超过原发侧凸≤5°),27例(25.5%)出现脊柱侧凸进展,治疗无效。②柔软性侧凸57例,支具矫正有效是48例;僵硬性侧凸49例,有效是37例,柔软性侧凸的矫正效果优于僵硬性侧凸。③脊柱侧凸Cobb角在20°°者63例,有效是54例,～2930～40°者43例,有效是25例,Cobb角20°°组的矫正效果优于Cobb角30°°组。③未出现特殊的材料和宿主的明显～29～40不良反应和负性事件,但腰、髋部骨密度明显下降。结论:①热塑矫形支具矫正青少年特发性脊柱侧凸能够取得良好疗效。②骨骼正处于生长发育期者,侧凸柔软性好者,Cobb角较小者,矫正效果好。③支点弯曲位时的矫正率可以预测支具矫正效果。④随访中发现应用支具后患者腰、髋部骨密度明显下降。