Interferon-gamma increases expression of chemokine receptors CCR1, CCR3, and CCR5, but not CXCR4 in monocytoid U937 cells

Chemokine receptors (CR), which can mediate migration of immune cells to the site of inflammation, also function as coreceptors for human immunodeficiency virus (HIV) entry into CD4+ T lymphocytes and antigen-presenting cells. We demonstrate here that interferon-gamma (IFN-gamma) increases the expression of chemokine receptors CCR1, CCR3, and CCR5 in monocytoid U937 cells as detected by cell surface molecule labeling and mRNA expression, as well as by intracellular calcium mobilization and cell migration in response to specific ligands. The increased expression of these chemokine receptors also results in an enhanced HIV-1 entry into cells. Our data provide evidence for a relationship of cellular pathways that are induced by IFN-gamma with those that regulate chemokine receptor expression.     

Structural polymorphism in a tubercidin analogue of the DNA double helix

The neurotoxic beta-amyloid (Abeta) peptide fragment Abeta(25-35) has been suggested to exert its deleterious effects on cells via production of hydrogen peroxide. In human platelets and in the presence of DMSO to prevent production of hydroxyl radicals from hydrogen peroxide, both Abeta(25-35) and hydrogen peroxide were found to increase intracellular calcium levels. Hydrogen peroxide in addition reduced the calcium response to thrombin, whereas this was not seen with Abeta(25-35). A similar pattern of effects to those seen with hydrogen peroxide were also seen with the neurotoxic aldehyde lipid peroxidation product 4-hydroxy-2-nonenal (HNE). The initial increase in calcium produced by hydrogen peroxide was not affected by EGTA, but was partially prevented by dithiothreitol. The calcium response to Abeta(25-35) [which was also seen with Abeta(1-40) and Abeta(1-42) but not with the inactive peptide Abeta(40-1)] consisted of an EGTA-sensitive and an EGTA-resistant component, of which the latter was also sensitive to DTT. Hydrogen peroxide increased basal phosphoinositide breakdown in rat brain miniprisms and decreased the responses to noradrenaline, carbachol and veratrine. The specific binding of [3H]inositol-1,4,5-trisphosphate ([3H]Ins(1,4,5)P3) to its receptor recognition site in human platelet membranes was increased by Abeta(25-35) but remained unchanged following hydrogen peroxide treatment. It is concluded that under conditions where production of hydroxyl radicals from hydrogen peroxide is blocked, hydrogen peroxide and Abeta(25-35) produce their effects on calcium by affecting the mobilisation of intracellular calcium. The qualitative differences in the calcium responses of these two agents can be explained (a) by an additional effect of Abeta(25-35) upon calcium entry and (b) by differences in their effects upon the Ins(1,4,5)P3 receptor.     

Sequential use of intravenous and oral acyclovir in the therapy of varicella in immunocompromised children

BACKGROUND: Immunocompromised children are at risk for disseminated varicella infections. Standard management involves hospitalization and intravenous acyclovir for 7 to 10 days. This approach is expensive, is inconvenient and may not be necessary. We undertook a pilot study to assess the safety and efficacy of an alternative approach that utilized a combination of intravenous (i.v.) followed by oral (p.o) acyclovir in a cohort of immunocompromised children. METHODS: The cohort consisted of 26 immunocompromised children between the ages of 1.5 and 12.7 years (mean, 6.3). Therapy was commenced with i.v. acyclovir (1500 mg/m2/day in 3 divided doses). Concurrent management included holding or reducing immunosuppressive therapy (by 50%) and administering varicella-zoster immunoglobulin in 69% (11 of 16) of cases where exposure to chickenpox was recognized. Patients were eligible to switch to p.o therapy after receiving a minimum of 48 h of i.v. acyclovir therapy provided they were afebrile; had no new lesions for 24 h; had no internal organ involvement and were able to tolerate oral medications. Patients were observed in hospital for a further 24 h and then discharged provided they remained well. Oral acyclovir was continued for a total of 7 to 10 days (i.v. plus p.o). RESULTS: Of the 26 patients 25 were successfully switched from i.v. to p.o after 4.1 +/- 1.2 days (mean +/- SD) (range, 2.3 to 6) Children had fever for a mean of 2.0 +/- 1.6 days (range, 0 to 5) and developed new lesions for 2.9 +/- 0.7 days (range, 2 to 4). All 25 patients switched to p.o therapy had resolution of their disease and no patient required resumption of i.v. therapy. CONCLUSIONS: The sequential use of i.v. followed by p.o acyclovir is feasible in the treatment of varicella in immunocompromised children and results in a reduction in duration of intravenous therapy and hospitalization.     

Hydrogen peroxide decreases pHi in human aortic endothelial cells by inhibiting Na+/H+ exchange

Postischemic endothelial dysfunction may occur as a result of the effects of endogenous oxidants like hydrogen peroxide. Since endothelium-dependent vasodilator function may be affected by pHi, the effect of hydrogen peroxide on endothelial pHi was examined. Hydrogen peroxide (100 micromol/L for 10 minutes) decreased pHi from 7.24+/-0.01 to 7.02+/-0.02 and inhibited recovery from an ammonium chloride-induced intracellular acid load in carboxy SNARF 1 (c-SNARF 1)-loaded human aortic endothelial cells in bicarbonate-free solution. Prior inhibition of Na+/H+ exchange with 5-(N-ethyl-N-isopropyl)amiloride (10 micromol/L), by removal of extracellular Na+, or by glycolytic inhibition with iodoacetic acid blocked the subsequent effect of hydrogen peroxide on pHi. A 2-minute exposure to 100 micromol/L H2O2 decreased intracellular ATP levels by approximately 40%; this was prevented by 3-aminobenzamide and nicotinamide (1 mmol/L each), inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase. Both 3-aminobenzamide and nicotinamide significantly inhibited the hydrogen peroxide-induced intracellular acidification and the effect of hydrogen peroxide on recovery from an intracellular acid load. Hydrogen peroxide decreases pHi in human endothelial cells by inhibiting Na+/H+ exchange. This appears to be mediated by activation of the DNA repair enzyme poly(ADP-ribose) polymerase and subsequent depletion of intracellular ATP. Since a decrease in pHi in this range may alter the activity of NO synthase or affect the synthesis of vasodilator prostaglandins, the effect of hydrogen peroxide on the endothelial Na+/H+ exchanger may be important in the pathogenesis of postischemic endothelial dysfunction.     

Stress response and mode of ventilation in preterm infants

AIM: To assess the change in stress response in preterm babies changed from patient triggered ventilation (PTV) to conventional mandatory ventilation (CMV) and vice versa; to determine outcome in relation to stress hormone concentrations. METHODS: A randomised controlled study was conducted in two district general hospital neonatal intensive care units. Thirty babies, treated initially with CMV, were randomly assigned to remain on CMV or to change to PTV. A second group of 29 babies, treated initially with PTV, were randomly assigned to remain on PTV or to change to CMV. The babies were less than 32 weeks of gestation, ventilated within 72 hours of birth, with clinical and radiological features compatible with respiratory distress syndrome (RDS). Stress hormone concentrations and clinical distress score were measured before and 20 minutes after allocation of mode of ventilation. RESULTS: Babies changed from CMV to PTV had significantly reduced adrenaline concentrations (median change -0.4 nmol/l) compared with those who remained on CMV. There was no increase in adrenaline in babies changed from PTV to CMV. There were no significant changes in noradrenaline concentrations or clinical distress score. Babies who died had significantly higher adrenaline and noradrenaline concentrations than those who survived. CONCLUSION: A change in mode of ventilation significantly reduces adrenaline concentrations. Raised catecholamine values are associated with a poor outcome.     

The effect of abdominal wall morphology on ultrasonic pulse distortion. Part II. Simulations

Wavefront propagation through the abdominal wall was simulated using a finite-difference time-domain implementation of the linearized wave propagation equations for a lossless, inhomogeneous, two-dimensional fluid as well as a simplified straight-ray model for a two-dimensional absorbing medium. Scanned images of six human abdominal wall cross sections provided the data for the propagation media in the simulations. The images were mapped into regions of fat, muscle, and connective tissue, each of which was assigned uniform sound speed, density, and absorption values. Propagation was simulated through each whole specimen as well as through each fat layer and muscle layer individually. Wavefronts computed by the finite-difference method contained arrival time, energy level, and wave shape distortion similar to that in measurements. Straight-ray simulations produced arrival time fluctuations similar to measurements but produced much smaller energy level fluctuations. These simulations confirm that both fat and muscle produce significant wavefront distortion and that distortion produced by fat sections differs from that produced by muscle sections. Spatial correlation of distortion with tissue composition suggests that most major arrival time fluctuations are caused by propagation through large-scale inhomogeneities such as fatty regions within muscle layers, while most amplitude and waveform variations are the result of scattering from smaller inhomogeneities such as septa within the subcutaneous fat. Additional finite-difference simulations performed using uniform-layer models of the abdominal wall indicate that wavefront distortion is primarily caused by tissue structures and inhomogeneities rather than by refraction at layer interfaces or by variations in layer thicknesses.     

A comparison of standardized and narrative letters of recommendation

OBJECTIVE: To compare the Council of Emergency Medicine Residency Directors' (CORD's) standardized letters of recommendation (SLORs) with traditional narrative letters of recommendation (NLORs) with regard to interrater reliability, consistency, and time of interpretation. METHODS: In part I of the study, four members of the residency selection committee each evaluated the same 20 SLORs and 20 NLORs from which all identifying characteristics had been deleted. Using Likert-type scales of the global assessment, each letter was assigned a numeric value from 1 to 7. The interrater reliability was calculated for both types of letters using the Kendall coefficient of concordance. Average time to interpretation of the letters was also determined. In part II, using the same numeric values as in part I, 207 single-author SLOR/NLOR pairs were evaluated to determine whether the global assessment of the SLOR was consistent with that of its partner NLOR. Interpretation of the NLOR was performed blinded to the SLOR. Statistical analysis was calculated using Spearman correlation coefficients. RESULTS: In part I of the study, the interrater reliability of the SLOR was 0.97, as compared with 0.78 for the NLOR. The average time to interpret the global assessment of the SLOR was 16 seconds, vs 90 seconds for the NLOR. In part II of the study, of the 207 SLOR/NLOR pairs, 112 (54%) were assigned the same numeric value, 80 (39%) differed by one, 13 (6%) differed by two, and two (1%) differed by three, for an overall correlation of 0.58. CONCLUSIONS: Compared with NLORs, the CORD SLOR offers better interrater reliability with less interpretation time. Single-author SLOR/NLOR pairs submitted for a single applicant do not correlate well. Residency selection committees must decide whether the added work of interpreting NLORs is beneficial.