Erythrocyte adenosine deaminase overproduction in hereditary hemolytic anemia

A marked tissue-specific increase in erythrocyte adenosine deaminase (ADA) activity is associated with an autosomal dominantly inherited hemolytic anemia. We investigated the molecular basis of ADA overproduction by studying reticulocyte ADA mRNA from affected individuals. Analysis of proband reticulocyte ADA cDNA clones revealed normal sequence. RNase mapping demonstrated that the amount of ADA mRNA in affected reticulocytes was greater than the amount in normal B lymphoblasts, whereas ADA mRNA was undetectable in normal reticulocytes. The 5'- and 3'-untranslated regions of reticulocyte and B-lymphoblast ADA mRNAs from affected individuals were structurally indistinguishable from those of normal B lymphoblasts. Northern blot analysis performed under stringent hybridization and washing conditions confirmed a markedly increased amount of reticulocyte ADA mRNA in affected individuals as compared with controls. We conclude that the RBC-specific overexpression of ADA in this disorder occurs at the mRNA level.     

Complement sensitivity of paroxysmal nocturnal hemoglobinuria bone marrow cells

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired disorder in which erythrocytes, granulocytes, and platelets are defective, as shown by increased susceptibility of RBCs, WBCs, and platelets to complement- mediated lysis in vitro. The purpose of this study is to determine the sensitivity to complement lysis of PNH and non-PNH erythroid and myeloid precursors using the release of 59Fe and myeloperoxidase as specific markers to monitor the lytic action of complement on erythroid and myeloid cell precursors, respectively. Erythroid cell precursors in four of four PNH patients demonstrated increased sensitivity to complement-mediated lysis. Myeloid cell precursors in four of five PNH patients also exhibited increased sensitivity to complement and antibody. In addition, CFU-c growth was below normal in the marrow of seven PNH patients. These findings support the hypothesis that the defect in PNH occurs at the level of the hematopoietic stem cell.     

Thrombotic thrombocytopenic purpura and dose of plasma exchange

Four patients with thrombotic thrombocytopenic purpura (TTP) were treated by plasma-exchange transfusion, three of whom recovered completely. Because previous reports in the literature describing exchange transfusion as treatment for TTP have demonstrated variable success rates, particular attention was given to "dose" and frequency of plasma exchange. Evans blue dye studies established a measure of "dose" under conditions of varying efficiency. Serum LDH activity was found to be diminished by plasma exchange, and the rate of return of serum LDH activity reflected residual disease activity. The magnitude of LDH activity reduction correlated with the adequacy of dose of plasma exchange and was an indicator for the need of repeated daily exchanges. Failure to obtain a spontaneous increment in platelet count also suggested the need for additional exchanges and/or larger dose of exchange. There is a need for a standard expression of dose of plasma exchange. Utilizing these markers (LDH, platelet count), it may be possible to improve the survival in TTP if adequate dose and frequency of plasma exchange are used.     

Six point mutations that cause factor XI deficiency

We have identified six novel types of mutation that cause factor XI deficiency, an inherited bleeding disorder. Two are point mutations that interfere with the normal splicing of exons in the mRNA and four are point mutations that result in amino acid substitutions. One of these amino acid substitutions (Asp 16-->His) is near the amino terminal end of the protein. The other three amino acid substitutions (Leu 302-->Pro, Thr 304-->Ile, and Glu 323-->Lys) are in the fourth apple domain, a region that mediates dimerization of identical subunits of factor XI. All four amino acid substitutions cause a reduction in the amount of factor XI secreted from cells grown in vitro.     

Conversion of the active to latent plasminogen activator inhibitor from human endothelial cells

The plasminogen activator inhibitor from human endothelial cells (PAI- 1) exists in two forms in the culture medium: an active form that binds to and inactivates plasminogen activators and a latent form that in its native state has no anti-activator activity. Inhibitor activity associated with the latent form can be generated by treatment with protein denaturants and makes up more than 98% of the total inhibitor activity in conditioned medium. Plasminogen activator inhibitor activity is also found in cell cytosol. This inhibitor activity is stable to SDS-treatment but is not enhanced by it. We investigated the relationship between this active cell-associated inhibitor and the latent PAI-1 found in the conditioned medium. Both intracellular and extracellular inhibitors were immunoprecipitated by a monoclonal antibody produced against the latent inhibitor from HT1080 fibrosarcoma cells and electrophoresis on SDS gels of various acrylamide concentrations demonstrated that both forms had the same Mr. Incubation of cytosol inhibitor at 37 degrees C resulted in a decline in inhibitor activity with a half-life of approximately 4 hours, a rate of decline similar to that of the active PAI-1 in conditioned medium, with less than 10% of the original activity present after eight hours. This decline is accelerated at higher temperatures and is not affected by the presence of a variety of protease inhibitors. Approximately 90% of the activity can be regenerated after SDS treatment suggesting that the cell associated inhibitor, during incubation at 37 degrees C, converts to a form similar to that found in conditioned medium. Despite these similarities, the apparent Stoke's radii of the active intracellular inhibitor and the latent inhibitor in conditioned medium were significantly different with values of 2.77 nm and 2.40 nm for active and latent PAI-1, respectively. Incubation of the active form at 37 degrees C resulted in the shift of the Stoke's radius to that similar to the latent PAI-1 (2.45 nm). Thus, the active and latent PAI-1, while being immunologically similar and of the same apparent Mr, can be differentiated by their behavior on gel permeation columns. This suggests that the intracellular inhibitor is a precursor to the latent form.     

The effect of stem cell proliferation regulators demonstrated with an in vitro assay

Spleen colony formation after transplantation of bone marrow cells into irradiated mice has been used as an assay for hematopoietic stem cells (CFU-S), but has serious limitations intrinsic to an in vivo assay. In this report we describe experiments using an in vitro clonogenic assay that is especially suitable for studies of stem cell regulation as defined growth factors and normal untreated bone marrow can be used. We have demonstrated that the colony-forming cells have proliferative properties in common with CFU-S and respond to specific proliferation regulators previously detected using the spleen colony assay.     

Human bone marrow and peripheral blood T lymphocyte depletion: efficacy and effects of both T cells and monocytes on growth of hematopoietic progenitors

The efficacy of four separate methods of human bone marrow T lymphocyte depletion was assessed, and the effect of T cells and monocytes on in vitro growth of marrow (CFU-GEMM, BFU-E, and CFU-GM) and peripheral blood (BFU-E) hematopoietic progenitors was determined. Extent of T cell depletion was assessed by multiparameter fluorescent cell sorter (FACS) analysis and by functional studies. Cells staining positively by FACS analysis for one or more of three separate fluorescent pan-T cell monoclonal antibodies (MCAbs) comprised 8.4% to 9.5% of control marrow mononuclear cells (MNCs). T cells constituted 3.2% to 5.1% of marrow following single, sequential, or combination treatment with two different pan-T cell MCAbs (Leu 1 and TM1) plus complement, 1.5% to 2.2% of marrow following solid-phase immunoabsorption ("panning"), 0.2% of marrow after sheep cell rosetting, and only 0.05% of marrow after FACS selective cell sorting and gated separation. T cells made up 59% to 73% of control peripheral blood MNCs and 0.8% to 2.8% of peripheral MNCs following sheep cell rosetting plus treatment with Leu 1 MCAb and complement. Mitogen (PHA, Con A) and allogeneic MLC-induced blastogenic responses (stimulation indices, experimental/control or E/C) revealed a concordant decrement in marrow T cell function after MCAb plus complement (E/C of 3.9 to 9.0), after panning (E/C of 1.6 to 3.5) and after sheep cell rosetting (E/C of 0.7 to 1.3), compared with control marrow (E/C of 5.3 to 15.7). After T cell depletion, marrow BFU-E growth was 95% to 120% of control, CFU-GM growth was 90% to 108% of control, and CFU-GEMM growth was 89% to 111% of control. Marrow T cell and/or monocyte depletion did not alter erythropoietin-dependent BFU-E growth in the absence of Mo-conditioned medium (81% to 95% of control), and the addition of as many as 50 to 100 X 10(3) purified marrow monocytes or T cells to 10(5) autologous nonadherent T cell-depleted marrow target cells had a negligible (P greater than .1) effect on marrow BFU-E growth in vitro. Peripheral blood (PB) BFU-E/10(5) T- depleted target cells were 106% +/- 19% of expected; PB BFU-E growth was significantly diminished after monocyte depletion alone (7% +/- 6% of expected) or after monocyte plus T cell depletion (8% +/- 4% of expected).(ABSTRACT TRUNCATED AT 400 WORDS)     

Heart rate variability in the neonate and infant: analytical methods, physiological and clinical observations

Naturally occurring oscillations in heart rate have long been considered to reflect the modulating influences of the autonomic nervous system. Individual reports of heart rate variability in healthy and sick neonates and infants have provided valuable information as to pathophysiological changes in autonomic cardiovascular control. It is evident that prematurity and poor health are reflected in attenuated heart rate variability. However, at present, there are few standard criteria for the analysis of heart rate variability, preventing precise comparisons among the various studies. Until recommendations for standardized analytical methods are made, clinical application of heart rate variability in neonatal and infant prognosis and therapy remains premature.