The T cell antigen receptor complex expressed on normal peripheral blood CD4-, CD8- T lymphocytes. A CD3-associated disulfide-linked gamma chain heterodimer.

IL-2-dependent cell lines were established from normal peripheral blood T lymphocytes that express neither CD4 nor CD8 differentiation antigens. CD3+,4-,8- cell lines from 15 different donors failed to react with WT31, an mAb directed against the T cell antigen receptor alpha/beta heterodimer. Anti-Leu-4 mAb was used to isolate the CD3/T cell antigen receptor complex from 125I-labeled CD3+,4-,8- (WT31-) T cells. Using detergent conditions that preserved the CD3/T cell antigen receptor complex, an approximately 90 kD disulfide-linked heterodimer, composed of approximately 45- and approximately 40- (or approximately 37-) kD subunits, was coimmunoprecipitated with the invariant 20-29-kD CD3 complex. Analysis of these components by nonequilibrium pH gradient electrophoresis indicated that the approximately 40-kD and approximately 37-kD subunits were similar, and quite distinct from the more basic approximately 45-kD subunit. None of these three subunits reacted with an antibody directed against a beta chain framework epitope. Heteroantiserum against a T cell receptor gamma chain peptide specifically reacted with both the approximately 37- and approximately 40-kD CD3-associated proteins, but not with the approximately 45-kD subunit. CD3+,4-,8- cells failed to transcribe substantial amounts of functional 1.3-kb beta or 1.6-kb alpha mRNA, but produced abundant 1.6-kb gamma mRNA. Southern blot analysis revealed that these CD3+,4-,8- cell lines rearranged both gamma and beta genes, and indicated that the populations were polyclonal. The expression of a CD3-associated disulfide-linked heterodimer on CD3+,4-,8- T cell lines established from normal, adult peripheral blood contrasts with prior reports describing a CD3-associated non-disulfide-linked heterodimer on CD3+/WT31- cell lines established from thymus and peripheral blood obtained from patients with immunodeficiency diseases. We propose that this discrepancy may be explained by preferential usage of the two C gamma genes in T lymphocytes

The expansion field: The value of H_0

Any calibration of the present value of the Hubble constant requires recession velocities and distances of galaxies. While the conversion of observed velocities into true recession velocities has only a small effect on the result, the derivation of unbiased distances which rest on a solid zero point and cover a useful range of about 4-30 Mpc is crucial. A list of 279 such galaxy distances within v<2000 km/s is given which are derived from the tip of the red-giant branch (TRGB), from Cepheids, and from supernovae of type Ia (SNe Ia). Their random errors are not more than 0.15 mag as shown by intercomparison. They trace a linear expansion field within narrow margins from v=250 to at least 2000 km/s. Additional 62 distant SNe Ia confirm the linearity to at least 20,000 km/s. The dispersion about the Hubble line is dominated by random peculiar velocities, amounting locally to <100 km/s but increasing outwards. Due to the linearity of the expansion field the Hubble constant H_0 can be found at any distance >4.5 Mpc. RR Lyr star-calibrated TRGB distances of 78 galaxies above this limit give H_0=63.0+/-1.6 at an effective distance of 6 Mpc. They compensate the effect of peculiar motions by their large number. Support for this result comes from 28 independently calibrated Cepheids that give H_0=63.4+/-1.7 at 15 Mpc. This agrees also with the large-scale value of H_0=61.2+/-0.5 from the distant, Cepheid-calibrated SNe Ia. A mean value of H_0=62.3+/-1.3 is adopted. Because the value depends on two independent zero points of the distance scale its systematic error is estimated to be 6%. Typical errors of H_0 come from the use of a universal, yet unjustified P-L relation of Cepheids, the neglect of selection bias in magnitude-limited samples, or they are inherent to the adopted models.Comment: 44 pages, 4 figures, 6 tables, accepted for publication in the Astronony and Astrophysics Review 15

A Neutrophil Phenotype Model for Extracorporeal Treatment of Sepsis

Neutrophils play a central role in eliminating bacterial pathogens, but may also contribute to end-organ damage in sepsis. Interleukin-8 (IL-8), a key modulator of neutrophil function, signals through neutrophil specific surface receptors CXCR-1 and CXCR-2. In this study a mechanistic computational model was used to evaluate and deploy an extracorporeal sepsis treatment which modulates CXCR-1/2 levels. First, a simplified mechanistic computational model of IL-8 mediated activation of CXCR-1/2 receptors was developed, containing 16 ODEs and 43 parameters. Receptor level dynamics and systemic parameters were coupled with multiple neutrophil phenotypes to generate dynamic populations of activated neutrophils which reduce pathogen load, and/or primed neutrophils which cause adverse tissue damage when misdirected. The mathematical model was calibrated using experimental data from baboons administered a two-hour infusion of E coli and followed for a maximum of 28 days. Ensembles of parameters were generated using a Bayesian parallel tempering approach to produce model fits that could recreate experimental outcomes. Stepwise logistic regression identified seven model parameters as key determinants of mortality. Sensitivity analysis showed that parameters controlling the level of killer cell neutrophils affected the overall systemic damage of individuals. To evaluate rescue strategies and provide probabilistic predictions of their impact on mortality, time of onset, duration, and capture efficacy of an extracorporeal device that modulated neutrophil phenotype were explored. Our findings suggest that interventions aiming to modulate phenotypic composition are time sensitive. When introduced between 3–6 hours of infection for a 72 hour duration, the survivor population increased from 31% to 40–80%. Treatment efficacy quickly diminishes if not introduced within 15 hours of infection. Significant harm is possible with treatment durations ranging from 5–24 hours, which may reduce survival to 13%. In severe sepsis, an extracorporeal treatment which modulates CXCR-1/2 levels has therapeutic potential, but also potential for harm. Further development of the computational model will help guide optimal device development and determine which patient populations should be targeted by treatment

Validating Arterial Spin Labelling Cerebral Blood Flow measure with perfusion phantom

Introduction The maintenance of cerebral functions strongly depends on the sustained supply of blood and the ability to adapt cerebral blood flow (CBF) to its metabolic demands. Occlusion of afferent vessels bears a risk for ischemic stroke and permanent cerebral damage. Arterial spin labeling (ASL) technique [1] can be used to quantify CBF. However, the CBF measure extracted by this technique may contain artifacts [2] and moreover may be affected by large within-subject, between-subject and regional variability [3]. An unambiguous and reliable description of physiological features by this method may therefore represent a “mission impossible”. It is therefore mandatory to validate and optimize the CBF measure by independent methods. Validation via a perfusion phantom is the aim of the present study. Methods A perfusion phantom was constructed with 125cm3 volume filled with SiO2 spheres of different diameters [e.g. 0.01 mm 0.05 mm and 0.1 mm]. Due to this set of diameters an average pore size of 0.0138 mm was achieved. With this average pore size, we are a factor 2 larger than average diameter of capillaries of ~ 6 m. A pump (Harvard Apparatus Pulsatile Blood pump for hemodynamic studies) provides a circular flow into the phantom via the input- and output tubes. The pump allows exact setting of flow volume and flow rate. MR imaging was conducted in a 3T Siemens Prisma Scanner. The pseudo CASL sequence [1] were set with the following paramerters: TE = 30 ms, TR = 2 s, 3 mm 3 mm 3 mm voxel dimension, 64 64 matrix size, FOV 192 mm, 38 slices, and slice thickness = 3 mm. In order to assess variability and precision of CBF measure estimate we systematically changed the following ASL parameters [4]: Post-labeling delay [100 ms:200:ms:1500ms], Bolus duration # RF [ 20, 60, 80]; and the following pump parameters: flow ratio [0.5, 1, 1.5] and Flow volume*Flow rate [20:20:200]. Results The perfusion phantom is operating (Fig 1.A and B). Due to the large amount of different sequence and pump settings we present a limited set only. Setting the pump Flow volume*Flow rate at 200 [ml/min], a flow ratio of 1, post labeling delay of 500 ms revealed an extraordinary high precision of CBF estimation by the perfusion phantom: 198.3029 ± 0.76 [ml/100g/min] (Fig 1.C and Fig. 2). The signal to noise ratio (SNR) was 4.2. The 0expected value of CBF was therefore underestimated by 1.7 [ml/100g/min]. The error in CBF estimation is 0.5 % which is at same level as the accuracy of the pulsatile pump. Conclusion The perfusion phantom with the pulsatile pump showed high accuracy of CBF estimation that were reliable and reproducible. The observed CBF values showed high precision (i.e. low standard deviation) that allows to draw conclusion about the variance of the CBF measure originated by the ASL sequence only. Uncertainty in CBF estimation by ASL technique may therefore be assessed. This novel approach will finally allow clinicians, physicians and researchers to unambiguously estimate disease-related CBF effects. Therefore, it is relevant for patients as well as for socioeconomic aspects. The perfusion phantom will be generalized to be used within other institutions to enable quality controls on different scanners with different ASL sequences and different field strengths: since the phantom is stable and easy to send. References [1] Dai, W., et al., Continuous flow-driven inversion for arterial spin labeling using pulsed radio frequency and gradient fields. Magn Reson Med, 2008. 60(6): p. 1488-97

Quantification of network perfusion in ASL cerebral blood flow data with seed based and ICA approaches.

Independent component analysis (ICA) or seed based approaches (SBA) in functional magnetic resonance imaging blood oxygenation level dependent (BOLD) data became widely applied tools to identify functionally connected, large scale brain networks. Differences between task conditions as well as specific alterations of the networks in patients as compared to healthy controls were reported. However, BOLD lacks the possibility of quantifying absolute network metabolic activity, which is of particular interest in the case of pathological alterations. In contrast, arterial spin labeling (ASL) techniques allow quantifying absolute cerebral blood flow (CBF) in rest and in task-related conditions. In this study, we explored the ability of identifying networks in ASL data using ICA and to quantify network activity in terms of absolute CBF values. Moreover, we compared the results to SBA and performed a test-retest analysis. Twelve healthy young subjects performed a fingertapping block-design experiment. During the task pseudo-continuous ASL was measured. After CBF quantification the individual datasets were concatenated and subjected to the ICA algorithm. ICA proved capable to identify the somato-motor and the default mode network. Moreover, absolute network CBF within the separate networks during either condition could be quantified. We could demonstrate that using ICA and SBA functional connectivity analysis is feasible and robust in ASL-CBF data. CBF functional connectivity is a novel approach that opens a new strategy to evaluate differences of network activity in terms of absolute network CBF and thus allows quantifying inter-individual differences in the resting state and task-related activations and deactivations

Interhemispheric cerebral blood flow balance during recovery of motor hand function after ischemic stroke--a longitudinal MRI study using arterial spin labeling perfusion.

BackgroundUnilateral ischemic stroke disrupts the well balanced interactions within bilateral cortical networks. Restitution of interhemispheric balance is thought to contribute to post-stroke recovery. Longitudinal measurements of cerebral blood flow (CBF) changes might act as surrogate marker for this process.ObjectiveTo quantify longitudinal CBF changes using arterial spin labeling MRI (ASL) and interhemispheric balance within the cortical sensorimotor network and to assess their relationship with motor hand function recovery.MethodsLongitudinal CBF data were acquired in 23 patients at 3 and 9 months after cortical sensorimotor stroke and in 20 healthy controls using pulsed ASL. Recovery of grip force and manual dexterity was assessed with tasks requiring power and precision grips. Voxel-based analysis was performed to identify areas of significant CBF change. Region-of-interest analyses were used to quantify the interhemispheric balance across nodes of the cortical sensorimotor network.ResultsDexterity was more affected, and recovered at a slower pace than grip force. In patients with successful recovery of dexterous hand function, CBF decreased over time in the contralesional supplementary motor area, paralimbic anterior cingulate cortex and superior precuneus, and interhemispheric balance returned to healthy control levels. In contrast, patients with poor recovery presented with sustained hypoperfusion in the sensorimotor cortices encompassing the ischemic tissue, and CBF remained lateralized to the contralesional hemisphere.ConclusionsSustained perfusion imbalance within the cortical sensorimotor network, as measured with task-unrelated ASL, is associated with poor recovery of dexterous hand function after stroke. CBF at rest might be used to monitor recovery and gain prognostic information