Endothelial prostacyclin production is a late event in granulocyte migration into bovine pulmonary artery intimal explants

Whether migration of granulocytes across pulmonary vascular endothelium in the absence of structural evidence of endothelial injury causes increased production of thromboxane or prostacyclin is not known. Using bovine pulmonary artery intimal explants mounted in Boyden chambers and homologous separated granulocytes, concentrations of thromboxane B2 and 6-keto-PGF1 alpha in the upper-well fluid were measured by radioimmunoassay over a three-hour period under the following conditions: (1) granulocyte chemotaxis (zymosan-activated plasma in the lower well, granulocytes in the upper well); (2) unstimulated granulocyte migration (serum or plasma in the lower well, granulocytes in the upper well); (3) granulocyte activation without migration (zymosan-activated plasma and granulocytes in the upper well); (4) granulocyte chemotaxis in the absence of endothelium (identical to condition 1 above except that endothelium was scraped from the explant surface); and (5) explants incubated in the absence of granulocytes. Minimal increases in thromboxane B2 concentrations in upper-well fluid occurred under all conditions. In contrast, granulocyte chemotaxis was accompanied by large increases in concentrations of 6-keto-PGF1 alpha evident by two hours of incubation and increasing markedly by three hours, to 524.3 +/- 69.0 ng/mL (m +/- SEM). Unstimulated migration of granulocytes toward serum or plasma and granulocyte activation without migration were accompanied, at three hours, by more modest increases in 6-keto-PGF1 alpha (296.5 +/- 46.4; 128.0 +/- 38.6, and 236.7 +/- 47.0 ng/mL, respectively) and, in the absence of granulocytes or in the absence of endothelium, only minimal increases in this prostacyclin metabolite occurred (137.2 +/- 16.9 and 53.9 +/- 12.6 ng/mL, respectively). The large rises in prostacyclin metabolite occurred at a time when the majority of granulocytes had migrated through the endothelial layer rather than during their adherence or transendothelial passage. We conclude that chemotaxis of granulocytes through pulmonary vascular endothelium causes endothelial production of large amounts of prostacyclin, but this occurs late in the chemotactic process, after granulocytes have transversed the endothelium.     

Immature human cord blood progenitors engraft and proliferate to high levels in severe combined immunodeficient mice

Unseparated or Ficoll-Hypaque (Pharmacia, Piscataway, NJ)--fractionated human cord blood cells were transplanted into sublethally irradiated severe combined immunodeficient (SCID) mice. High levels of multilineage engraftment, including myeloid and lymphoid lineages, were obtained with 80% of the donor samples as assessed by DNA analysis, fluorescence-activated cell sorting (FACS), and morphology. In contrast to previous and concurrent studies with adult human bone marrow (BM), treatment with human cytokines was not required to establish high-level human cell engraftment, suggesting that neonatal cells either respond differently to the murine microenvironment or they provide their own cytokines in a paracrine fashion. Committed and multipotential myelo- erythroid progenitors were detected using in vitro colony assays and FACS analysis of the murine BM showed the presence of immature CD34+ cells. In addition, human hematopoiesis was maintained for at least 14 weeks providing further evidence that immature hematopoietic precursors had engrafted the murine BM. This in vivo model for human cord blood- derived hematopoiesis will be useful to gain new insights into the biology of neonatal hematopoietic cells and to evaluate their role in gene therapy. There is growing evidence that there are ontogeny-related changes in immature human hematopoietic cells, and therefore, the animal models we have developed for adult and neonatal human hematopoiesis provide useful tools to evaluate these changes in vivo.     

Asynchronous antigen expression in B lineage acute lymphoblastic leukemia

Cell surface phenotypes of 113 B lineage acute lymphocytic leukemia (ALL) cases, defined by the presence of HLA-DR and at least one B-cell- specific antigen (either CD19, CD20, or CD22), were compared with antigen-defined stages of normal B lymphocyte development. The cases were first evaluated for expression of HLA-DR, CD19, CD34, CD10, CD20, and CD22 by indirect one-color immunofluorescence. Pairwise comparisons of cell surface marker expression were performed for each leukemic sample: no correlations were observed for paired antigen expression on the leukemic samples using antigens expressed either early or late during normal B lymphoid development. Complete immunophenotypes of the cases were then compared with normal B-cell developmental stages. Sixteen different complete immunophenotypes were observed on the leukemias that were not found in normal marrow; at least 78% of the cases demonstrated such "asynchronous" combinations of B lymphoid- associated differentiation antigens. Several samples were subsequently studied by two-color immunofluorescence, and the presence of doubly labeled cells with "asynchronous" antigen combinations was confirmed. These results indicate that the majority of B lineage leukemias exhibit "developmental asynchrony," as compared with normal marrow B cells. The data further suggest that ALL cases do not accurately represent cells arrested at the stage where the leukemogenic event occurred. Rather, ALL appears to be a disease in which there may be maturation of leukemic blasts; but this maturation is "asynchronous" when compared with the normal developmental process.     

Progressive hearing loss and vestibular dysfunction caused by a homozygous nonsense mutation in CLIC5

In a consanguineous Turkish family diagnosed with autosomal recessive nonsyndromic hearing impairment (arNSHI), a homozygous region of 47.4 Mb was shared by the two affected siblings on chromosome 6p21.1-q15. This region contains 247 genes including the known deafness gene MYO6. No pathogenic variants were found in MYO6, neither with sequence analysis of the coding region and splice sites nor with mRNA analysis. Subsequent candidate gene evaluation revealed CLIC5 as an excellent candidate gene. The orthologous mouse gene is mutated in the jitterbug mutant that exhibits progressive hearing impairment and vestibular dysfunction. Mutation analysis of CLIC5 revealed a homozygous nonsense mutation c.96T>A (p.(Cys32Ter)) that segregated with the hearing loss. Further analysis of CLIC5 in 213 arNSHI patients from mostly Dutch and Spanish origin did not reveal any additional pathogenic variants. CLIC5 mutations are thus not a common cause of arNSHI in these populations. The hearing loss in the present family had an onset in early childhood and progressed from mild to severe or even profound before the second decade. Impaired hearing is accompanied by vestibular areflexia and in one of the patients with mild renal dysfunction. Although we demonstrate that CLIC5 is expressed in many other human tissues, no additional symptoms were observed in these patients. In conclusion, our results show that CLIC5 is a novel arNSHI gene involved in progressive hearing impairment, vestibular and possibly mild renal dysfunction in a family of Turkish origin.     

High-efficiency gene transfer and expression in normal human hematopoietic cells with retrovirus vectors

Retroviral vectors containing the selectable bacterial gene for G418 resistance (neo) were used to demonstrate gene transfer into primary human bone-marrow progenitor cells. To obtain populations of cells in which a high proportion of cells were expressing the neo gene, several important modifications were made to earlier procedures. Cells from normal donors were infected in vitro, were exposed to high concentrations of G418 for two days in liquid culture to enrich for cells expressing the neo gene, and were plated in semisolid medium. Gene transfer and expression were detected in colonies arising from progenitors of granulocyte-macrophage and erythroid lineages. Survival curves indicated that a high proportion of progenitor cells, approaching 100%, were G418 resistant. Furthermore, addition of growth factors contained in 5637-conditioned medium to the bone marrow improved the recovery of G418-resistant progenitors twofold to threefold. In addition to these biological measurements of gene expression in progenitor cells, significant levels of neo-specific RNA, similar to the levels of RNA expression in the virus-producing fibroblast cell line, were detected in the bone marrow cells after preselection. These results demonstrate that retrovirus vectors can be used successfully to transfer genes at high efficiency into progenitor cells in the human blood-forming system.     

Transferrin saturation and recovery from coma in cerebral malaria

To determine if the elevated transferrin saturations found in some patients with severe malaria are associated with an adverse outcome in cerebral malaria, we retrospectively measured baseline saturations in stored serum samples from 81 Zambian children with strictly defined cerebral malaria. The children had been treated with quinine, sulfadox- ine-pyrimethamine, and intravenous infusions of either placebo (n = 39) or the iron chelator, desferrioxamine B (n = 42), in a previously reported trial (Gordeuk et al, N Engl J Med 327:1473, 1992). More than one-third of children in both the placebo- and iron chelator-treated groups had transferrin saturations exceeding 43%, which is 3 standard deviations above the expected mean for age. Among children receiving quinine and placebo, those with elevated transferrin saturations had a delayed estimated median time to recover full consciousness (68.2 hours) compared with those with saturations < or = 43% (25.4 hours; P = .006). The addition of iron chelation to quinine therapy in children with high saturations appeared to hasten recovery (P = .046). We conclude that increased transferrin saturations may be associated with delayed recovery from coma during standard therapy for cerebral malaria and that serum iron and total iron binding capacity should be measured in future studies.     

The heritable nature of clonal characteristics in acute myeloblastic leukemia

Marked patient-to-patient variation is observed when blood or marrow from AML patients is examined using colony methods in culture. Concentrations of the progenitors of colonies change with time during the course of the disease. We asked whether blast progenitor properties were more stable. We measured blast cell self-renewal and drug sensitivity (adriamycin and cytosine arabinoside) repeatedly in the courses of seven AML patients. These properties were found to be stable or slowly evolving. We conclude that capacity for renewal and sensitivities to certain chemotherapeutic drugs are heritable characteristics in leukemic clones.