心房扑动患者的下腔静脉-三尖瓣环峡部和房间隔缓慢传导的电生理意义

目的　用电 解剖标测方法标测右心房 ,然后比较心房扑动 (AFL)和房室结折返性心动过速(AVNRT)患者在下腔静脉 三尖瓣环峡部 (CTI)和心房间隔部 (AS)的电冲动传导速度 ,以便确定AFL患者除了解剖结构上的异常外 ,是否伴有心房电生理方面的异常变化。方法　 1 0例AFL患者 ,男性 7例 ,女性 3例 ,平均 (53± 1 0 )岁 ;1 3例AVNRT患者 ,男性 5例 ,女性 8例 ,平均 (51± 1 1 )岁。对这两组患者进行了详细的电 解剖标测、电生理检查和射频消融术。分别以周长为 60 0、40 0、和 30 0ms在冠状静脉窦 (CS)起搏的情况下测量AFL和AVNRT患者的CTI和AS的冲动传导速度 ,并将两组患者在CTI和AS的冲动传导速度进行比较。结果　与AVNRT患者相比 ,AFL患者在各个起搏周长 (PCL)时CTI和AS的冲动传导速度都明显减慢 (P <0 0 5)。另外 ,在AFL组 ,AS的冲动传导速度在起搏周长 60 0、40 0ms时低于CTI,但在 30 0ms时差异无显著性 (P >0 0 5)。因为在AFL组 ,PCL为 30 0ms时的冲动传导速度明显低于 60 0和 40 0ms时的冲动传导速度 ,致使PCL为 30 0ms时CTI和AS的冲动传导速度差异无显著性。结论　与CTI相比 ,AS的冲动传导速度在所有患者都较慢 ,而AFL患者在CTI和AS的冲动传导速度减低更明显 ,并且在CTI的冲动传导速度减慢具有频率依     

Stem cell factor modulates avidity of alpha 4 beta 1 and alpha 5 beta 1 integrins expressed on hematopoietic cell lines

Interactions between hematopoietic cells and bone marrow (BM) stroma, composed of extracellular matrix and stromal cells, are crucial for hematopoiesis. Integrins facilitate these interactions by mediating adherence of hematopoiesis. Integrins facilitate these interactions by mediating adherence of hematopoietic cells to both the extracellular matrix and stromal cells. Marrow stromal cells secrete a variety of growth factors, including stem cell factor (SCF). Because treatment with SCF in vivo mobilizes primitive hematopoietic cells from the BM, we investigated the effect of the growth factor SCF of hematopoietic cell adhesion. These studies show that SCF modulates adhesive function in a dose- and time-dependent manner, but does not modulate expression of the integrins alpha 4 beta 1 and alpha 5 beta 1 in the SCF- responsive cell line MO7E. Treatment of MO7E cells with SCF (200 ng/mL) produced a transient increase in adherence to cytokine-activated human umbilical vein endothelial cells (HUVECs) or to vascular cell adhesion molecule 1 (VCAM-1)-transfected Chinese hamster ovary (CHO) cells with peak adhesion at 30 minutes and return to baseline by 60 to 90 minutes. This increase in adhesion was paralleled by increased binding of the beta 1 activation-dependent monoclonal antibody (MoAb) 15/7, as determined by flow cytometry. However, prolonged incubation of MO7E with SCF induced a marked decrease in integrin-mediated adherence, with maximal inhibition by 24 hours. No change in expression of integrins, as determined by flow cytometry, was observed with short- or long-term incubation with SCF. SCF-treated cells were still able to respond to phorbol esters and to the activating beta 1 MoAb 8A2 with increased adherence, but not to the level seen in control cells. This suggests that a subpopulation of expressed alpha 4 beta 1 and alpha 5 beta 1 integrins is disengaged by prolonged incubation with SCF.     

Factors in the liquid portion of stored blood inhibit the proliferative response in mixed lymphocyte cultures

The transfusion of blood may suppress the immune responses of patients with renal transplants and with malignant disorders. To study the in vitro suppressive effects of banked blood, 4 units of blood were stored in CPDA-1 and ADSOL at 4 degrees C for 14 days. Lymphocytes and plasma or ADSOL supernatants were harvested on Days 0, 4, 7, 10, and 14. Subpopulations of lymphocytes were enumerated by flow cytometry. Recalcified and heat-treated plasma and supernatants from the units of blood were added to mixed lymphocyte cultures (MLC) composed of cells from normal individuals. No significant changes were noted in the proportions of T or B cells from blood stored under these conditions. A 60 +/− 3 percent inhibition in the proliferative response was observed when plasma from CPDA-1 units was added to MLCs (p less than 0.02). Supernatants from ADSOL units demonstrated a 29 +/− 4 percent inhibition (p less than 0.10) of the proliferative response, and this inhibition of response was observed on all 14 days of the study. When appropriate concentrations of dextrose or adenine were added to other MLCs, adenine (at the concentration found in ADSOL) caused a significant inhibition of the proliferative response. This inhibition was not, however, as marked as that observed with recalcified, heat- treated plasma from CPDA-1 units. We conclude that adenine plus some additional factor(s) found in the liquid portion of stored blood inhibits the proliferative response of normal lymphocytes. It is possible that these factors contribute to the immune suppression observed in vivo in some patients who receive blood transfusions.     

Protein A adsorption of acute myelogenous leukemia serum induces in vitro blast lysis

We studied cytotoxic activity of acute myelogenous leukemia (AML) sera for AML blasts before and after immunoadsorption with Staphylococcus aureus, Cowan I (SAC), which contains protein A. We found in vitro that incubation with treated AML sera reduced viability to 42.7% of control (p less than 0.01) for autologous and 21.0% of control (p less than 0.01) for allogeneic blasts. Normal peripheral blood cells were not killed by treated AML sera. Wood 46 strain of Staphylococcus aureus, which does not contain protein A, did not significantly reduce AML blast viability (94.8%, p greater than 0.4), while Sepharose-bound protein A reduced viability to 63.8% (p less than 0.01). Cytotoxicity does not appear to be complement-mediated, byt cytotoxic activity is trypsin-sensitive and is contained in the immunoglobulin fraction. This model for study of the tumoricidal action of protein A adsorption should be useful for predicting utility of plasma adsorption as a therapeutic adjunct in the future.     

Human umbilical vein endothelial cells display high-affinity c-kit receptors and produce a soluble form of the c-kit receptor

Stem cell factor (SCF) is a hematopoietic growth factor produced by fibroblasts and endothelial cells that stimulates the growth of primitive hematopoietic cells. SCF triggers cell growth by binding to the c-kit receptor. Because endothelial cells can respond to certain hematopoietic growth factors, we tested human umbilical vein endothelial cells for display of the c-kit receptor and examined the effect of SCF on endothelial cell proliferation, adhesion molecule expression, and production of tissue factor. Quantitative binding experiments with 125I-SCF showed both high-affinity (Kd = 42 pmol/L) and low-affinity (Kd = 1.7 nmol/L) c-kit receptors. There were approximately 1,100 high-affinity c-kit receptors, and 5,400 low- affinity c-kit receptors per endothelial cell. Enzyme immunoassays showed that endothelial cells released soluble c-kit receptor and SCF. The transmembrane form of SCF was detected by indirect immunofluorescence analysis using monoclonal or polyclonal anti-SCF receptor antibodies. The addition of SCF (100 ng/mL) did not alter endothelial cell proliferation over a 7-day period. Similarly, there was no change in the release of tissue factor or expression of inducible endothelial adhesion molecules (intercellular adhesion molecule-1, endothelial-leukocyte adhesion molecule-1, and vascular cell adhesion molecule-1) measured by enzyme-linked immunosorbant assay at 4 and 24 hours after SCF addition. The neutralizing anti-c-kit receptor monoclonal antibody SR-1 blocked binding of 125I-SCF to the c- kit receptor by 98% but did not alter endothelial cell proliferation or adhesion-molecule expression. c-kit receptors were also detected on adult endothelial cells lining small blood vessels in normal human lymph nodes. These data indicate that normal human endothelial cells produce SCF and show high-affinity c-kit receptors that have the capacity to dimerize. The lack of response to exogenous SCF may be because of intracellular activation of the c-kit receptor via autocrine production of SCF. Alternatively, SCF and c-kit may play a role other than stimulation of proliferation, adhesion-molecule display, or tissue factor production by endothelial cells. The production of soluble c-kit receptors by normal human endothelial cells may serve to regulate the bioactivity of SCF within the bone marrow microenvironment.     

FLT3 receptor expression on the surface of normal and malignant human hematopoietic cells

FLT3 ligand is a hematopoietic growth factor that plays a key role in growth of primitive hematopoietic cells. FLT3 receptor mRNA is found in early hematopoietic progenitors and in human myeloid leukemia blasts. Much less is known about the surface expression of FLT3 receptor on human hematopoietic cells. Using human 125I-FLT3 ligand, we have identified and characterized surface FLT3 receptors on normal and malignant human hematopoietic cells and cell lines. Our results showed that surface display of FLT3 receptor was greatest in fresh myeloid leukemia blast cells and myeloid leukemia cell lines. Erythroleukemic and megakaryocytic leukemia cell lines (n = 5) bound little to no 125I- FLT3 ligand. Scatchard analysis of 125I-FLT3 ligand binding data shows that three myeloid leukemia cell lines, ML-1, AML-193, and HL-60, as well as normal human marrow mononuclear cells, exhibit high affinity FLT3 receptors. Crosslinking of 125I-FLT3 ligand to FLT3 receptors on the surface of ML-1 myeloid leukemia cells indicates that the FLT3 ligand. The rates of FLT3 ligand internalization and degradation were determined by binding 125I-FLT3 ligand to ML-1 cells and acid stripping to distinguish surface bound from internalized ligand. Internalized 125I-FLT3 ligand was detected within 5 minutes after binding to ML-1 cells. In addition, we evaluated the effect of FLT3 ligand on megakaryocytic colony growth and nuclear endoreduplication, alone or in the presence of thrombopoietin. FLT3 ligand did not promote colony forming unit megakaryocyte (CFU-Meg) colony growth or megakaryocyte nuclear maturation, nor did FLT3 ligand augment the effects of thrombopoietin on these measures of megakaryopoiesis. These data indicate that the FLT3 receptor shares several characteristics with the c-kit receptor including dimerization and rapid internalization. However, the more restricted cellular distribution of the FLT3 receptor may target the effects of FLT3 ligand to primitive hematopoietic cells and to myeloid and lymphoid progenitor cells, in contrast to the pleiotropic effects of the c-kit receptor ligand, stem cell factor.     

Reasons given for disclosure of maternal HIV status to children

The purpose of this investigation was to ascertain the reasons given by mothers diagnosed with AIDS (acquired immunodeficiency syndrome) for disclosing or not disclosing their HIV (human immunodeficiency virus) status to their children, a dilemma faced by most HIV-infected parents and those who counsel them. We interviewed 29 mothers residing in one of two New York City facilities that provide housing and medical treatment for adults with AIDS. The majority of these mothers do not live with their children, but all had recent face-to-face contact with them. The two reasons most frequently considered important for disclosing to children were that disclosure was the “right thing to do” and the need to make arrangements for children's future in case of maternal death or incapacity. The reason most frequently considered important for not disclosing was maternal concern about discussing death and dying with children. These findings have significant implications for counseling of HIV-positive parents.     

Comparison of hematopoietic progenitor cells in human umbilical cord blood collected from neonatal infants who are small and appropriate for gestational age

BACKGROUND: Cord blood has been used for transplantation. The purpose of this study was to compare numbers of hematopoietic progenitors in cord blood collected from neonatal infants who are small for their gestational age and those who are normal. STUDY DESIGN AND METHODS: Sixteen pregnant women diagnosed with intrauterine growth restriction were prospectively identified. Cord blood was collected at delivery. Fourteen cord blood samples were obtained from gestational age-matched, appropriately grown newborns. In vitro assays for hematopoietic progenitors were performed and results of the two compared. Comparisons were also made with numbers of hematopoietic progenitor cells previously found by this laboratory in samples collected with the possibility of use for transplantation. RESULTS: Gestational age, the women's pregnancy and delivery histories, maternal risk factors for intrauterine growth restriction, maternal age, delivery method, umbilical cord blood gases, and 5-minute Apgar scores were similar in the two groups. Newborns who were small for their gestational age had significantly lower birth weights and longer stays in the neonatal intensive care unit with no evidence for viral infections in the immediate neonatal period. The mean number of progenitors per collection of cord blood in the small newborns was about half that per collection from appropriately grown newborns, but in most cases, these differences were not significant in the two groups, and many numbers in the small newborns fell within the range associated with successfully engrafting cord blood collections. CONCLUSION: Hematopoietic progenitor cells in the small newborns may be adequate for transplantation purposes in many cases. Their possible use in this context should, however, involve careful consideration of the numbers of progenitors collected as well as of possible viral or other contamination.