An orally bioavailable small molecule antagonist of CRTH2, ramatroban (BAY u3405), inhibits prostaglandin D2-induced eosinophil migration in vitro

Ramatroban (Baynas, BAY u3405), a thromboxane A(2) (TxA(2)) antagonist marketed for allergic rhinitis, has been shown to partially attenuate prostaglandin (PG)D(2)-induced bronchial hyperresponsiveness in humans, as well as reduce antigen-induced early- and late-phase inflammatory responses in mice, guinea pigs, and rats. PGD(2) is known to induce eosinophilia following intranasal administration, and to induce eosinophil activation in vitro. In addition to the TxA(2) receptor, PGD(2) is known as a ligand for the PGD(2) receptor, and the newly identified G-protein-coupled chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2). To fully characterize PGD(2)-mediated inflammatory responses relevant to eosinophil activation, further analysis of the mechanism of action of ramatroban has now been performed. PGD(2)-stimulated human eosinophil migration was shown to be mediated exclusively through activation of CRTH2, and surprisingly, these effects were completely inhibited by ramatroban. This is also the first report detailing an orally bioavailable small molecule CRTH2 antagonist. Our findings suggest that clinical efficacy of ramatroban may be in part mediated through its action on this Th2-, eosinophil-, and basophil-specific chemoattractant receptor.     

Enhancement of human basophil histamine release by interleukin 5.

Substantial evidence indicates a close relationship between eosinophils and basophils. We examined whether interleukin 5 (IL-5), known to be eosinophilopoietic and capable of selectively regulating eosinophil functions, has an affect on basophil functions. IL-5 enhanced basophil histamine release evoked by anti-IgE, formyl-methionyl-leucyl-phenylalanine, or ionophore A23187 at picomolar concentrations. Direct action of IL-5 on human basophils was confirmed using highly purified basophil populations. These observations reveal the novel fact that IL-5 is able to modulate basophil functions as well as eosinophil functions, and suggest that normal human basophils possess functional receptors for IL-5.     

Localization of eosinophil granule major basic protein in human basophils

In experiments using an immunofluorescent method to localize human eosinophil granule major basic protein (MBP) in cells and tissues, a small number of cells stained for MBP that subsequently could not be identified as eosinophils. Because the Charcot-Leyden crystal protein, another eosinophil protein, was recently identified in basophils, we tested whether MBP might also be a constituent of blood basophils. Highly purified, eosinophil-free basophil suspensions were prepared using the fluorescence-activated cell sorter (FACS) to sort basophil-containing mononuclear cell preparations stained with fluorescein-conjugated sheep IgG anti-human IgE antibody. Using these FACS-purified basophils, we found that: (a) enrichment for surface IgE-positive cells (greater than 95% basophils) by FACS also enriched for cells staining for MBP by immunofluorescence; (b) MBP appeared to be localized in the histamine-, heparin-containing granules; (c) significant quantities of MBP were measurable by radioimmunoassay (RIA) in freeze-thaw detergent extracts of purified basophils; and (d) RIA dose-response curves for extracts of purified eosinophils and basophils had identical slopes. The MBP content of basophils from normal individuals averaged 140 ng/10(6) cells, whereas purified eosinophils from normal donors and patients with the hyper-eosinophilic syndrome averaged 4,979 and 824 ng/10(6) cells, respectively. MBP was also detected by immunofluorescence and RIA in cells obtained from a patient with basophil leukemia, although the MBP content for basophil leukemia cells was lower than that for normal basophils. We conclude that basophils contain a protein that is immunochemically indistinguishable from eosinophil granule MBP.     

Prostaglandin D2-induced eosinophilic airway inflammation is mediated by CRTH2 receptor

Mast cell-derived prostaglandin D(2) (PGD(2)) is one of the essential modulators of eosinophilic airway inflammation in asthma and allergic rhinitis. Two G protein-coupled receptors for PGD(2), prostaglandin D(2) receptor (DP) and chemoattractant receptor-homologous molecule expressed on Th(2) cells (CRTH2), are both expressed on the surface of eosinophils, and CRTH2 has been demonstrated to mediate PGD(2)-induced eosinophil mobilization in vitro. However, it has not yet been determined whether PGD(2) and its receptors mediate in vivo eosinophil trafficking into the airways or other organs. We demonstrated that intratracheal administration of PGD(2) in rats pretreated with systemic interleukin-5 (IL-5) injection induced marked airway eosinophilia, determined by the differential counts of cells in bronchoalveolar lavage (BAL) fluid and lung histology, within 2 h. Systemic IL-5 alone significantly increased the number of eosinophils in the peripheral blood but showed no effect on airway eosinophilia. Three CRTH2-specific agonists (13,14-dihydro-15-keto-PGD(2), 11-deoxy-11-methylene-15-keto-PGD(2), and indomethacin) demonstrated equivalent induction of BAL eosinophilia to that of PGD(2), but a DP agonist (BW 245C [5-(6-carboxyhexyl)-1-(3-cyclohexyl-3-hydroxypropyl)-hydantoin]) or a thromboxane A(2) receptor (TP) agonist ([1S-1alpha,2beta(5Z), 3alpha(1E,3R*),4alpha)]-7-[3-(3-hydroxy-4-(4'-iodophenoxy)-1-butenyl)-7-oxabicyclo-[2.2.1]heptan-2-yl]-5-heptenoic acid) showed no effect. PGD(2) or CRTH2 agonist-induced BAL eosinophilia was almost completely inhibited by pretreatment with a CRTH2/TP antagonist, ramatroban [BAY-u3405; (+)-(3R)-3-(4-fluorobenzenesulfonamido)-1,2,3,4-tetra-hydrocarbazole-9-propionic acid], whereas a TP-specific antagonist, SQ29,548 (5-heptenoic, 7-[3-[[2-[(phenylamino)carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1]-hept-2-yl]-[1S-[1alpha,2alpha(Z),3alpha,4alpha]]), or a DP-specific antagonist, BW A868C [3-benzyl-5-(6-carboxyhexyl)-1-(2-cyclohexy-2-hydroxyethylamino)-hydantoin], did not inhibit the effects of PGD(2). These results suggest that CRTH2 plays a significant role in the eosinophil trafficking from the bloodstream into the airways in PGD(2)-related airway inflammation.     

Prostaglandin D2 selectively induces chemotaxis in T helper type 2 cells, eosinophils, and basophils via seven-transmembrane receptor CRTH2

Prostaglandin (PG)D2, which has long been implicated in allergic diseases, is currently considered to elicit its biological actions through the DP receptor (DP). Involvement of DP in the formation of allergic asthma was recently demonstrated with DP-deficient mice. However, proinflammatory functions of PGD2 cannot be explained by DP alone. We show here that a seven-transmembrane receptor, CRTH2, which is preferentially expressed in T helper type 2 (Th2) cells, eosinophils, and basophils in humans, serves as the novel receptor for PGD2. In response to PGD2, CRTH2 induces intracellular Ca2+mobilization and chemotaxis in Th2 cells in a Galphai-dependent manner. In addition, CRTH2, but not DP, mediates PGD2-dependent cell migration of blood eosinophils and basophils. Thus, PGD2 is likely involved in multiple aspects of allergic inflammation through its dual receptor systems, DP and CRTH2.     

Formation of Charcot-Leyden crystals by human basophils

Charcot-Leyden crystals (CLC) are currently believed to be unique to the eosinophil and a hallmark of active eosinophilic inflammation or proliferation. The distinctiveness of the CLC to the eosinophil was questioned in 1965 by Archer and Blackwood (9), but their demonstration of CLC formation in basophils was ignored and later dismissed (1) as being the result of eosinophil contamination of basophil-enriched cell suspensions. We reexamined this question and showed that basophils obtained from the peripheral blood of normal individuals form CLC and that basophils contain a protein that is immunochemically indistinguishable from eosinophil CLC protein. These conclusions are based upon the findings that (a) crystal formation in basophils was demonstrated by specific histochemical staining of crystal-containing cells in highly enriched basophil suspensions prepared by fluorescence- activated cell sorter (FACS) purification of surface IgE-positive cells, (b) that enrichment for surface IgE-positive cells (primarily basophils) by the FACS also enriched for cells staining positively by immunofluorescence for eosinophil CLC protein, and (c) that CLC protein was measured by radioimmunoassay in cell extracts prepared from purified basophil suspensions containing 97-99% basophils and absolutely no contaminating eosinophils. These basophil extracts contained a protein immunochemically indistinguishable from eosinophil CLC protein. Based upon these findings, the CLC or the protein comprising the crystal (lysophospholipase) can no longer be considered as distinctive to the eosinophil. We must now consider the possibility that the presence of CLC in tissues, sputum, or stool may also represent basophil involvement in disease processes.     

Deletion of the NH2-terminal residue converts monocyte chemotactic protein 1 from an activator of basophil mediator release to an eosinophil chemoattractant

Chemotactic cytokines of the CC subfamily (CC chemokines) are considered as major mediators of allergic inflammation owing their actions on basophil and eosinophil leukocytes. The monocyte chemotactic protein (MCP) 1 is a potent inducer of mediator release from basophils but is inactive on eosinophils. To obtain information on the structural determinants of the activities of MCP-1, we have synthesized several NH2-terminally truncated analogues and tested their effects on basophils and eosinophils. Through deletion of the NH2-terminal residue, MCP-1(2-76) was obtained, which was a potent activator of eosinophils, as assessed by chemotaxis, cytosolic free Ca2+ changes, actin polymerization, and that induction of the respiratory burst. In contrast, the activity of MCP-1(2-76) on basophil leukocytes was dramatically decreased (50-fold) compared with that of full-length MCP- 1. Deletion of the next residue led to total loss of activity on eosinophil and basophil leukocytes. Analogues with three or four residue deletions, MCP-1(4-76) and MCP-1(5-76), were again active on both cells, whereas all further truncation analogues, MCP-1(6-76) through MCP-1(10-76), were inactive. Thus, a minimal structural modification can change receptor and target cell selectivity of MCP-1. Our observations indicate that the recognition sites of CC chemokine receptors on eosinophils and basophils are similar, although they discriminate between MCP-1 and MCP-1(2-76) and suggest NH2-terminal processing as a potential mechanism for the regulation of CC chemokine activities.     

Adhesion of human basophils, eosinophils, and neutrophils to interleukin 1-activated human vascular endothelial cells: contributions of endothelial cell adhesion molecules

Cytokines such as interleukin 1 (IL-1) promote adhesiveness in human umbilical vein endothelial cells for leukocytes including basophils, eosinophils, and neutrophils, and induce expression of adherence molecules including ICAM-1 (intercellular adhesion molecule-1), ELAM-1 (endothelial-leukocyte adhesion molecule-1), and VCAM-1 (vascular cell adhesion molecule-1). In the present study, blocking monoclonal antibodies (mAb) recognizing ICAM-1, ELAM-1, and VCAM-1 have been used to compare their roles in IL-1-induced adhesion of human basophils, eosinophils, and neutrophils. IL-1 treatment of endothelial cell monolayers for 4 hours induced a four- to eight-fold increase in adhesion for each cell type. Treatment of endothelial cells with either anti-ICAM-1 or anti-ELAM-1 mAb inhibited IL-1-induced adherence of each cell type. In contrast, treatment with anti-VCAM-1 mAb inhibited basophil and eosinophil (but not neutrophil) adhesion, and was especially effective in blocking eosinophil adhesion. The effects of these mAb were at least additive. Indirect immunofluorescence and flow cytometry demonstrated expression of VLA-4 alpha (very late activation antigen-4 alpha, a counter-receptor for VCAM-1) on eosinophils and basophils but not on neutrophils. These data document distinct roles for ICAM-1, ELAM-1, and VCAM-1 during basophil, eosinophil, and neutrophil adhesion in vitro, and suggest a novel mechanism for the recruitment of eosinophils and basophils to sites of inflammation in vivo.     

Aerosolized tachykinin antagonists inhibit pentamidine-induced bronchoconstriction in guinea pigs

Summary— To investigate the role of tachykinins in pentamidine-induced bronchoconstriction and airway microvascular leakage in the guinea pig, we examined the effects on bronchoconstriction and microvascular leakage of the nonpeptide antagonists of NK₁ and NK₂ tachykinin-receptors, respectively, CP-96,345 and SR 48968. Respiratory system resistance was measured by the occlusion method in anaesthetized, tracheotomized and mechanically ventilated guinea pigs. Airway microvascular permeability was evaluated by measuring the quantity of Evans blue dye in the trachea and main bronchi. Aerosolized CP-96,345 or SR 48968 partially abolished pentamidine-induced bronchoconstriction (at 5 to 30 mg/mL pentamidine; 60 breaths) whereas the combination of the two prevented it. In contrast, CP-96,345 and SR 48968 did not prevent the increase in airway microvascular permeability induced by pentamidine (50 mg/mL; 90 breaths) whether they were administered separately or together, by aerosol or intravenously. These results demonstrate that in the guinea pig, pentamidine-induced bronchoconstriction is mediated through both NK₁ and NK₂ tachykinin-receptor activation and that when directly administered into the airways, tachykinin antagonists effectively prevent pentamidine-induced bronchoconstriction.     

Interleukin 5 modifies histamine release and leukotriene generation by human basophils in response to diverse agonists

Human interleukin 5 (IL-5), known as a selective colony-stimulating factor of the eosinophil lineage and activator of mature eosinophils, also profoundly influences the mediator release profile of human basophils. IL-5 by itself triggers neither granule release nor de novo synthesis of lipid mediators. However, at low concentrations (0.1-10 ng/ml), IL-5 rapidly primes basophils for enhanced histamine release and leukotriene C4 (LTC4) generation in response to all established basophil agonists. LTC4 generation is more strongly affected by IL-5 than histamine release. In particular, IL-5 renders basophils capable of producing large quantities of LTC4 in response to C5a, which, without the cytokine, induces histamine release only. Finally, IL-5 renders basophils responsive to agonists (neutrophil-activating peptide 1 and C3a), which are otherwise inefficient triggers for basophil mediator release. The effects are similar to the recently established bioactivity of IL-3 on basophils, with the exception of its influence on IgE-dependent basophil activation, which is less pronounced. Thus, IL-5 strongly modulates the function not only of eosinophils but also of basophils, the two major effector leukocyte types involved in allergic inflammatory processes, e.g., in asthma.     

Thromboxane A2 and related prostaglandins in airways

Summary— Asthma is now thought to be a chronic inflammatory disease of the airways. The roles of prostanoids, thromboxane A₂ (TXA₂) and the prostaglandins (PGs) in the pathogenesis and pathophysiology of asthma have fostered a wealth of studies but remain controversial. TXA₂ and the bronchoconstrictor PGs, PGD₂ and PGF_2α, are generated in greater amounts in asthmatic than in normal subjects. TXA₂ is a potent constrictor of airway smooth muscle, an inducer of acetylcholine release and of airway microvascular leakage. It may participate in the thickening and the remodeling of the airway wall which may contribute to the airway hyperresponsiveness, a typical feature of asthma. Strategies for inhibition of TXA₂ effects include antagonism of the TXA₂ receptor (TP receptor) and inhibition of the thromboxane synthase. TP receptor antagonists could block the effects of all the bronchoconstrictor prostanoids because TXA₂ as well as the bronchoconstrictor PGs act through activation of lung TP receptor. The recent development of specific and potent TP receptor antagonists and inhibitors of thromboxane synthase has provided tools to assess the role of TXA₂ and bronchoconstrictor PGs in the pathophysiology of asthma.     

Low-oxygen and high-carbon-dioxide atmosphere improves the conservation of hematopoietic progenitors in hypothermia

BACKGROUND: During short-term storage of hematopoietic cells (HCs) at 4°C a substantial decline in number and in functional capacity of progenitors occurs after 3 days. We hypothesized that physiologic O₂ and CO₂ concentrations of hematopoietic tissue microenvironment (approx. 3% O₂ and approx. 6% CO₂) could improve cell viability and functionality during storage at 4°C.
STUDY DESIGN AND METHODS: Mobilized peripheral blood (PB) CD34+ cells from multiple myeloma or non-Hodgkin's lymphoma patients were stored in flasks containing air (approx. 20% O₂ and approx. 0.05% CO₂) or 3% O₂/6% CO₂ atmosphere, for 3, 5, and 7 days at 4°C. The total number of cells, the number of cells in G0 or G1 phase of cell cycle, and the apoptosis rate were determined. The functional capacity of stored cells was assessed by the capacity of progenitors to form colonies in methylcellulose (colony-forming cells [CFCs]) and of stem cells to repopulate the bone marrow (BM) of immunodeficient mice (SCID-repopulating cell [SRC] assay).
RESULTS: The total number of viable cells and cells in G1 phase as well as the number of total CFCs were significantly higher at 3% O₂/6% CO₂ than in air at all time points. Cells in G0 phase and SRC were equally preserved in both conditions.
CONCLUSION: Atmosphere with low O₂ and high CO₂ concentration (3% O₂/6% CO₂) in hypothermia (+4°C) during 7 days of storage prevents cell damage and preserves a high number of functional HSCs and progenitors mobilized in PB by granulocyte–colony-stimulating factor.     

Mixed-lineage eosinophil/basophil crisis in MDS: a rare form of progression

Background   Basophilic crisis and eosinophilia are well recognized features of advanced chronic myeloid leukaemia. In other myeloid neoplasms, however, transformation with marked basophilia and eosinophilia is considered unusual.
Design   We examined the long-term follow-up of 322 patients with de novo myelodysplastic syndromes (MDS) to define the frequency of basophilic, eosinophilic and mixed lineage (basophilic and eosinophilic) transformation.
Results   Of all patients, only one developed mixed lineage crisis (≥ 20% basophils and ≥ 20% eosinophils). In this patient, who initially suffered from chronic myelomonocytic leukaemia, basophils increased to 48% and eosinophils up to 31% at the time of progression. Mixed lineage crisis was not accompanied by an increase in blast cells or organomegaly. The presence of BCR/ABL and other relevant fusion gene products (FIP1L1/PDGFRA, AML1/ETO, PML/RARα, CBFβ/MYH11) were excluded by PCR. Myelomastocytic transformation/myelomastocytic leukaemia and primary mast cell disease were excluded by histology, KIT mutation analysis, electron microscopy and immunophenotyping. Basophils were thus found to be CD123+, CD203c+, BB1+, KIT- cells, and to express a functional IgE-receptor. Among the other patients with MDS examined, 4(1·2%) were found to have marked basophilia (≥ 20%) and 7(2·1%) were found to have massive eosinophilia ( ≥ 20%), whereas mixed-lineage crisis was detected in none of them.
Conclusions   Mixed basophil/eosinophil crisis may develop in patients with MDS but is an extremely rare event.     

Time to Equilibration of Oxygen Saturation Using Pulse Oximetry

Objective: To determine the time it takes for O₂, saturation measured by pulse oximetry to equilibrate after a change is made in supplemental O₂, administered by nasal cannula in patients with cardiac and pulmonary disease.
Methods: A prospective, observational study of a convenience sample of 51 patients treated in a university-affiliated ED with nasal cannula O₂. Patients were placed on and/or subsequently taken off O₂ via nasal cannula set at 2 or 4L/min based on clinical indications. Oxygen saturation was measured at l-minute intervals over a 30-minute period using finger-probe pulse oximetry. Of the 51 patients in the study, 43 were monitored while O₂, treatment was initiated and 18 were monitored when it was discontinued.
Results: Most (95%) of the patients placed on O₂, attained equilibration of O₂, saturation within 3.5 minutes. Most (95%) of the patients taken off supplemental O₂, attained equilibration of O₂, saturation within 4.5 minutes.
Conclusion: The interval to equilibration of O₂, saturation in patients receiving O₂ by nasal cannula is considerably shorter than the 20–30 minutes generally suggested. Adequacy of O₂, supplementation should be assessable much sooner than was previously taught.     

Ultrastructural analysis of the development of human basophils and mast cells in vitro

Summary The ultrastructural analysis of a variety of culture systems of human cord blood mononuclear cells (spanning a 10-year research effort) is reviewed. Human basophils, eosinophils and mast cells reliably developed from their agranular precursors that are present in human cord blood. Suspension cultures and cocultures with fibroblasts were used to examine the effects on differentiation and maturation of full (fibroblast), interleukin-2-depleted (human T cells), and murine inducer T cell culture supernatants, partially purified mouse fibroblast factor(s), recombinant human interleukins 3 and 5, and recombinant human and murine c-kit ligands (stem cell factor, mast cell growth factor). Together, these studies allowed us to define the differentiation and full maturation of the basophil and eosinophil lineages and provided evidence for the induction of a form of secretion (termed piecemeal degranulation) of the basophil and eosinophil lineages in interleukin-3- or-5-supplemented cultures. Mast cells were absent from interleukin-3- or-5-containing cultures. The development of fully mature mast cells occurred regularly in fibroblast-containing cocultures; partially mature mast cells developed in fibroblast culture supernatant-, partially purified mouse fibroblast factors(s)-, and either recombinant human or murine c-kit ligand-supplemented suspension cultures. Small numbers of basophils and eosinophils were present in the suspension cultures the received c-kit ligand in its recombinant or naturally occurring forms. Ultrastructural immunogold analyses confirmed that basophils and eosinophils contained the Charcot-Leyden crystal protein (in different subcellular locations) but that mast cells did not. In both cocultures and suspension cultures, the primary event recorded for mast cells was that of differentiation and maturation, with the ultrastructural correlates of synthetic activity and granule building prevailing. Spontaneous secretory events, recognizable by ultrastructural analysis, were not evident, in either mature or partially mature mast cells developing in these cultures.     

Inhibitory effect of the 4-aminotetrahydroquinoline derivatives, selective chemoattractant receptor-homologous molecule expressed on T helper 2 cell antagonists, on eosinophil migration induced by prostaglandin D2

Prostaglandin (PG) D2, a major cyclooxygenase metabolite generated from immunologically stimulated mast cells, is known to induce activation and chemotaxis in eosinophils, basophils, and T helper 2 (Th2) lymphocytes via a newly identified PGD2 receptor, chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2). CRTH2 is hypothesized to play an important role in the outcome of allergic responses. However, the absence of selective CRTH2 antagonists has prevented the elucidation of the role of CRTH2 in pathogenesis of allergic diseases. We now report compounds discovered as selective CRTH2 antagonists, (2R*,4S*)-N-(1-benzoyl-2-methyl-1,2,3,4-tetrahydroquinolin-4-yl)-N-phenylisobutyramide (K117) and (2R*,4S*)-N-(1-benzoyl-2-methyl-1,2,3,4-tetrahydroquinolin-4-yl)-N-phenylcyclopropanecarboxamide (K604). K117 and K604 have inhibitory effects on human CRTH2 with Ki values of 5.5 and 11 nM, respectively. The effect of these compounds is CRTH2-specific with no cross-reactivity against 15 other receptors and four arachidonic acid-metabolizing enzymes. K117 and K604 has no effect on the basal Ca2+ level and inhibited the Ca2+ response induced by PGD2 in 293EBNA cells expressing human CRTH2. Also, K117 and K604 inhibit PGD2-induced human eosinophil chemotaxis with IC50 values of 7.8 and 42.2 nM, respectively, but they do not inhibit the CC-chemokine receptor 3 agonist eotaxin-induced chemotaxis. These results indicate that K117 and K604 are highly potent and selective antagonists for human CRTH2. These compounds have possibilities to become useful tools to explore CRTH2 functions in allergic diseases.     

Electrocardiogram-Based Algorithm to Predict the Left Ventricular Lead Position in Recipients of Cardiac Resynchronization Systems

Introduction: Biventricular pacing is associated with various electrocardiographic patterns depending on the position of the left ventricular (LV) lead. We aimed to develop an electrocardiogram-based algorithm to predict the position of the LV lead.
Methods: The algorithm was developed in 100 consecutive recipients of cardiac resynchronization therapy (CRT) systems. QRS axis, morphology, and polarity were analyzed with a view to define the specific electrocardiographic characteristics associated with the various LV lead positions . The algorithm was prospectively validated in 50 consecutive CRT device recipients.
Results: The first analysis of the algorithm was the QRS morphology in V₁. A positive R wave in V₁ suggested LV lateral or posterior wall stimulation. A QS pattern was specific of anterior LV leads. In the presence of an R wave in V₁, V₆ was analyzed to distinguish between an inferior and anterior LV lead. Inferior leads were never associated with a positive V₆. To differentiate between lateral and posterior positions, we analyzed the pattern in V₂. Lateral leads were associated with an R morphology in V₁ and a negative V₂. Posterior leads were associated with an R morphology in V₁ and V₂. The algorithm allowed a reliable distinction between an inferior or anterior and a lateral or posterior lead position in 90% of patients. Inferior, anterior, lateral, and posterior positions were reliably distinguished in 80% of patients.
Conclusion: This algorithm predicted the position of the LV lead with a high sensitivity and predictive value.     

Evaluation of Pre- and Posttreatment Pulse Oximetry in Acute Childhood Asthma

Objectives : To evaluate the utility of pre- and posttreatment O₂ saturation (SpO₂) for prediction of admission or relapse after ED release in acute asthma exacerbations using a standardized treatment protocol.
Design : A prospective, double-blind, observational study was performed at a pediatric ED. Children with acute asthma were enrolled upon ED presentation. SpO₂ was measured prior to treatment and after disposition decision. Two experienced physicians determined disposition based on history and physical examination alone, while blinded to SpO₂. Relapse of released patients was determined by telephone follow-up.
Results : A pretreatment room-air SpO₂ of ≤91% had a sensitivity of 0.24, a specificity of 0.86, and a likelihood ratio of 1.77 to predict admission/relapse. A posttreatment room-air SpO₂ of ≤91% had a sensitivity of 0.34, a specificity of 0.98, and a likelihood ratio of 16.43 to predict admission/relapse.
Conclusions : As opposed to some previous studies, this study found pretreatment SpO₂ to be a relatively poor predictor of admission. A posttreatment SpO₂ of ≤91% occurred in a minority (32%) of patients, but increased the odds of admission 16-fold and may be used as an adjunct to objectively confirm the need for admission.     

The selective eosinophil chemotactic activity of histamine

Histamine diphosphate was shown to selectively attract human eosinophils from mixed granulocyte populations when over 20% eosinophils were used in a modified Boyden chamber chemotactic assay system. This effect of histamine is abolished by incubation with diamine oxidase (histaminase) and was generated by decarboxylation of L-histidine. A linear dose dependent increase in eosinophil migration was observed between 3 X 10(-7) M and 1.25 X 10(-6) M, while higher concentrations of histamine inhibited the migration of eosinophils. The attractant activity of histamine was not inhibited by H-1 or H-2 receptor antagonists, however, the inhibition of migration observed at higher histamine concentrations was reversed by metiamine, an H-2 receptor antagonist. The effects of histamine upon eosinophil migration were demonstrable using three different assays: (a) counting cells that had traversed 5-mum pore, 12-mum thick polycarbonate filters, (b) counting cells that had migrated various distances into a 3-mum pore, 145-mum cellulose nitrate filters, or (c) measuring the number of cells that had traversed an upper polycarbonate filter and migrated into a lower cellulose nitrate filter using 15Cr-labeled cells. The ability of histamine to enhance eosinophil migration was shown to be dependent upon the presence of a concentration gradient; histamine did not cause a dose-dependent increase in random motility. Furthermore, preincubation of the eosinophils with histamine deactivate the cells to further stimulation by histamine or by C5a. It is concluded that in low doses histamine is a chemoattractant for human eosinophils, while in higher doses histamine inhibits eosinophil migration. These observations may relate to the influx and localization of eosinophils in immediate hypersensitivity reactions.