CD43 interaction with ezrin-radixin-moesin (ERM) proteins regulates T-cell trafficking and CD43 phosphorylation

CD43 interaction with ERM proteins regulates CD43 phosphorylation and T-cell migration. CD43 phosphorylation can also drive CD43 localization in T-cells independently of ERM association.

Cell polarization is a key feature of cell motility, driving cell migration to tissues. CD43 is an abundantly expressed molecule on the T-cell surface that shows distinct localization to the migrating T-cell uropod and the distal pole complex (DPC) opposite the immunological synapse via association with the ezrin-radixin-moesin (ERM) family of actin regulatory proteins. CD43 regulates multiple T-cell functions, including T-cell activation, proliferation, apoptosis, and migration. We recently demonstrated that CD43 regulates T-cell trafficking through a phosphorylation site at Ser-76 (S76) within its cytoplasmic tail. Using a phosphorylation-specific antibody, we now find that CD43 phosphorylation at S76 is enhanced by migration signals. We further show that CD43 phosphorylation and normal T-cell trafficking depend on CD43 association with ERM proteins. Interestingly, mutation of S76 to mimic phosphorylation enhances T-cell migration and CD43 movement to the DPC while blocking ERM association, showing that CD43 movement can occur in the absence of ERM binding. We also find that protein kinase Cθ can phosphorylate CD43. These results show that while CD43 binding to ERM proteins is crucial for S76 phosphorylation, CD43 movement and regulation of T-cell migration can occur through an ERM-independent, phosphorylation–dependent mechanism.

The effect of scatter and attenuation on aerosol deposition as determined by gamma scintigraphy

Gamma scintigraphy is often used to quantify deposition patterns from aerosol inhalers. The errors caused by scatter and tissue attenuation in planar Tc-99m gamma scintigraphy were investigated based on the data collected from four subjects in this study. Several error correction methods were tested. The results from two scatter correction methods, Jaszczak's method and factor analysis of dynamic sequences (FADS), were similar. Scatter accounted for 20% of raw data in the whole lung, 20% in the oropharynx, and 43% in the central airways and esophagus. Three attenuation correction methods were investigated and compared. These were: uniform attenuation correction (UAC), a known method used for inhalation drug imaging work; the broad-beam attenuation correction used for organ imaging in nuclear medicine; and a narrow-beam inhomogeneous tissue attenuation correction proposed in this study. The three methods differed significantly (p < 0.05), but all indicated that attenuation is a severe quantification problem. The narrow beam attenuation correction with scatter correction, showed that raw data underestimated tracer deposition by 44% in the lung, 137% in the oropharynx, and 153% in the trachea/esophageal region. To quantify aerosol lung deposition using planar scintigraphy even in relative terms, corrections are necessary. Much of the literature concerning quantified aerosol dose distributions measured by gamma scintigraphy needs to be interpreted carefully.

Iterative optimal design of PET experiments for estimating beta-adrenergic receptor concentration

To estimate in vivo myocardial beta-adrenergic receptor concentration with sufficient precision and to reduce the experimental complexities in positron emission tomography (PET), an iterative optimal design method is applied. An initial three-injection protocol, utilising [F-18]-labelled (R)- and (S)-fluorocarazolol and unlabelled (S)-fluorocarazolol, is optimised for ligand dosages and administration times to maximise the precision of all model parameters using the D-optimal criterion. Using this experimental protocol, PET data are collected in porcine studies, and model parameters are estimated. All model parameters are identified with satisfactory precision. The in vivo myocardial beta-receptor concentration is 7.5+/-0.6 pmol x ml(-1), which corresponds to the in vitro result of 10.1+/-1.3 pmol x ml(-1). With more accurate parameter values, a simplified two-injection protocol is optimally designed, utilising only radiolabelled and unlabelled (S)-fluorocarazolol, based on a new criterion to maximise the precision of the beta-receptor concentration. This revised optimum design predicts that the in vivo beta-receptor concentration can be estimated with good precision but reduced experiment complexity.

Polyploid evolution and biogeography in Chelone (Scrophulariaceae): morphological and isozyme evidence

Chelone is a genus of perennial herbs comprising three diploid species (C. cuthbertii, C. glabra, and C. lyonii) and a fourth species (C. obliqua) that occurs as tetraploid and hexaploid races. To assess patterns of isozyme and morphological variation, and to test hypotheses of hybridization and allopolyploidy, we analyzed variation among 16 isozyme loci from 61 populations and 16 morphological characters from 33 populations representing all taxa and ploidy levels. Based on morphological analyses using clustering (unweighted pair group method using an arithmetic average) and ordination (principal components analysis and canonical variance analysis) methods, we recognize three diploid species without infraspecific taxa. Polyploids in the C. obliqua complex were most similar morphologically to diploid populations of C. glabra and C. lyonii. Patterns of isozyme variation among polyploids, which included fixed heterozygosity and recombinant profiles of alleles present in diploids, suggested polytopic origins of tetraploids and hexaploids. Our data indicate independent origins of polyploids in or near the southern Blue Ridge, Interior Highlands and Plains, and Atlantic Coastal Plain regions from progenitors most similar to C. glabra and C. lyonii. Extant tetraploids were not implicated in evolution of hexaploids, and plants similar to C. cuthbertii appeared unlikely as diploid progenitors for polyploids. We propose multiple differentiation and hybridization/polyploidization cycles in different geographic regions to explain the pattern of allopatry and inferred polytopic origins among polyploids.

Simultaneous recovery of size and radioactivity concentration of small spheroids with PET data

Quantification of tumor activity is used to predict prognosis and discriminate benign from malignant lesions identified by PET. Accurate quantitation of small lesions requires correction for the partial volume effects. Such a correction is often based on the recovery coefficient (RC), which depends on the lesion size, the object-to-background ratio (OBR) and physical properties of the media. The purpose of this investigation was to determine whether a model-based optimization method to simultaneously recover the size and the activity concentration of small spheroids could improve estimates of lesion radioactivity when object size is unknown. For reference, we compared our method with a widely used approach, RC correction, that requires the object size to be known.

METHODS

A three-dimensional, spatially varying, object size- and contrast-dependent Gaussian model of the point spread function (PSF) of an ECAT EXACT was developed. The observed dependence of the PSF on random coincidences and measured-peak/background activity were included in the PSF using three adjusting factors. Size and radioactivity concentration of a spheroid were estimated by adjusting size and concentration until model output best matched the image data. Elliptic and circular phantoms both containing seven hot spheroids, with OBRs ranging from 5.6 to 0 background, were evaluated.

RESULTS

The proposed quantification method reduced the activity error by 11%-63% of the error obtained without correction. The greatest error reduction occurred for small spheroids. The average error in radius estimation ranged from 2% to 48%, wherein the smallest spheroid produced the largest errors. For spheroids with diameters from 8 to 22 mm, Student t test (paired, one-tail) showed the proposed method significantly improved accuracy (P < 0.05) in comparison with the RC method and also in comparison with optimization without the three adjusting factors.

CONCLUSION

The model-based optimization method improved estimation of radioactivity concentration over that corrected by the RC method and that made without any correction. It also provided accurate estimation of size for spheroids larger than 6 mm in diameter.

PET quantification of specific binding of carbon-11-nicotine in human brain

Previous work on the PET measured uptake of (S)-[11C]nicotine presents conflicting findings as to whether it reflects specific binding.

METHODS

We studied the uptake of (R)-[11C]nicotine and (S)-[11C]nicotine in normal volunteers at baseline conditions and after a challenge with unlabeled (S)-nicotine to decrease the concentration of free binding sites or with CO2 to increase perfusion. We analyzed the data using two- and three-compartment models.

RESULTS

We found tissue pharmacokinetics of (R)- and (S)-[11C]nicotine are adequately described by the two-compartment model. (S)-nicotine challenge induced small but statistically significant reductions in distribution volume (DV) of both (R)- and (S)-[11C]nicotine. The changes in DV could not be attributed to perfusion changes because DV was not affected by CO2 challenge. Although the reduction in DV indicates sensitivity of [11C]nicotine to status of nicotinic binding sites, the small magnitude of the reduction suggests that most nicotine uptake is nonspecific.

CONCLUSION

Although differences in DV attributable to specific binding were detected, (R)- and (S)-[11C]nicotine are relatively poor tracers for studying nicotinic binding sites using PET.

Global cerebral blood flow, blood volume, and oxygen metabolism in patients with migraine headache

OBJECTIVE

Migraine headaches with and without aura are representative of vascular headache states traditionally thought to be mediated by alterations in vascular tone. Validation of this theory has been hampered in part by technical difficulties inherent in the measurement of cerebral blood flow (CBF). The purpose of this study was to compare CBF measured during migraine and migraine-free states using PET.

METHODS

Patients with a minimum of one migraine headache without aura per month (International Headache Society [IHS] criteria) underwent measurement of CBF, cerebral blood volume (CBV), oxygen extraction, and metabolism during an episode of spontaneous migraine headache. Imaging was repeated during a migraine-free period of at least 48 hours. PET radiotracers used were: CBF, H(2)15O; CBV, C15O; oxygen metabolism, 15O2.

RESULTS

In nine patients (seven female and two male), global CBF (mL/min/100 g [SD]) was measured as 52.70 (6.9) during migraine and 59.65 (10.6) in the migraine-free state; p=0.028. CBV (mL/100 g [SD]) was 3.6 (0.43) during the symptomatic state and 3.8 (0.55) after the migraine; p=0.047. Oxygen metabolism (mL/min/100 g [SD]) was 3.68 (0.9) during migraine and 3.38 (1.02) without headache; p=0.211. The oxygen extraction ratio was 0.48 (0.15) and 0.41 (0.12) during migraine and migraine-free states, respectively; p=0.132.

CONCLUSIONS

In patients experiencing migraine without aura, CBF and CBV are reduced during the headache phase. Cerebral oxygen metabolism and oxygen extraction are not significantly affected.

A method to correct for scatter, spillover, and partial volume effects in region of interest analysis in PET

Scatter and spatial resolution effects degrade the accuracy of radioactivity concentration estimates obtained from positron emission tomography (PET) data. We present and evaluate a methodology for region quantification which accounts for these degradations. The method is based on analysis of sinogram data and does not require dynamic data sequences to be reconstructed. Moreover, estimates of region variance are also produced which may be used to define weights for model analyses that use weighted least squares minimization in order to obtain unbiased parameter estimates. We evaluate the method using both simulation and measured data and find that, with an appropriate model of scatter and spatial resolution effects, it is unbiased and capable of quantifying myocardial concentration with no more than a 5% error in accuracy for myocardium as thin as 10 mm.

A nonlinear spatially variant object-dependent system model for prediction of partial volume effects and scatter in PET

Accurate quantitation of small lesions with positron emission tomography (PET) requires correction for the partial volume effect. Traditional methods that use Gaussian models of the PET system were found to be insufficient. A new approach that models the non-Gaussian object-dependent scatter was developed. The model consists of eight simple functions with a total of 24 parameters. Images of line and disk sources in circular and elliptical cylinders, and an anthropomorphic chest phantom were used to determine the parameter values. Empirical rules to determine these parameter values for various objects based on those for a reference object, a 21.5-cm circular cylinder, were also proposed. For seven spheroids and a 3.4-cm cylinder, pixel values predicted by the model were compared with the measured values. The model-to-measurement-ratio was 1.03+/-0.07 near the center of the spheroids and 0.99+/-0.03 near the center of the 3.4-cm cylinder. In comparison, the standard single Gaussian model had corresponding ratios of 1.27+/-0.09 and 1.24+/-0.03, respectively, and the corresponding ratios for a double Gaussian model were 1.13+/-0.09 and 1.05+/-0.01. Scatter fraction (28.5%) for a line source in the 21.5-cm cylinder was correctly estimated by our model. Because of scatter, we found that errors in the measurement of activity in spheroids with diameters from 0.6 to 3.4 cm were more significant than previously appreciated.

A robust edge detection method for gated radionuclide ventriculograms

We present a myocardial edge detection technique that was developed for fast, reproducible measurements of left ventricular ejection fraction in the clinical setting.

METHODS

This myocardial edge detection method compares three edge parameters--count amplitude and first and second count derivatives--in three consecutive locations along a radius to a predetermined template of these values. Each of the radii, defined at 10-degree intervals, has different template values that permit accurate edge detection even though adjacent structures, such as the left atrium and the right ventricle, alter edge parameters. The template for edge detection is based on either the average edge parameters determined from manually defined edges in 15 patients (automatic method) or an operator-defined edge in the first frame (semiautomatic method).

RESULTS

The edge detection methods were tested in 100 patients, and intraobserver variabilities as well as comparison with clinically obtained ejection fractions were calculated. The standard error of the estimate was less than 3.1% for all observer comparisons. In 15 patients with both high-count (400,000 counts per image) and low count (50,000 counts per image) studies, the mean absolute difference in ejection fraction was 2.6% for intraobserver comparisons.

CONCLUSION

A robust myocardial edge detection technique was developed that is applicable for routine clinical use.

Optimal experiment design for PET quantification of receptor concentration

The mathematical models used to analyze positron emission tomography (PET) data obtained for receptor quantitation have many unknown parameters which must be estimated from the data. Obtaining unique and precise estimates of the model parameters from PET data is difficult as a result of the complex interdependence of the parameters. Here the authors address the task of estimating the concentration of myocardial beta-adrenergic receptors using unlabeled and (18)F-labeled S(-)-fluorocarazolol as the receptor ligand. For a three-injection study the authors have optimized the ligand injection times and dosages using the D-optimal criterion for estimating receptor concentration. They found that in optimizing a three-injection experimental design, the dose of ligand in the third injection approaches zero so that the optimal three-injection design is actually a two-injection experiment. Using this optimal experiment, the authors demonstrate estimates of receptor concentration that are almost five times as precise as compared to an empirically designed three-injection experiment.

Specific beta-adrenergic receptor binding of carazolol measured with PET

Carazolol is a promising high-affinity beta-adrenergic receptor ligand for the noninvasive determination of beta receptor status using PET. Earlier investigations demonstrated specific receptor binding of carazolol in mice. These PET studies with S(-)-[2"-11C]carazolol in pigs were performed to explore the utility of the tracer for PET receptor studies.

METHODS

Tracer uptake in the heart and lung was measured by PET as a function of time. Receptors were blocked with propranolol and different doses of ICI 118,551 to estimate specific binding. Fluorine-18-1"-Fluorocarazolol and the less active R-enantiomer of [11C]-carazolol were also studied.

RESULTS

Specific receptor binding was 75% of the total uptake in the heart, preventable and displaceable by propranolol. Dose-dependent competition showed that carazolol binds in vivo to beta 1 and to beta 2 subtypes. Uptake of the labeled R(+) enantiomer of carazolol was not receptor-specific.

CONCLUSIONS

Carazolol labeled with 11C or 18F is a strong candidate for use in receptor estimation with PET. The in vivo observations were consistent with its known high affinity and slow receptor dissociation rate. Its high specific receptor uptake and low metabolism allow existing kinetic models to be applied for receptor measurements. The 11C label is convenient for repeated administrations, though 18F allowed the long observation periods necessary for measurement of the receptor dissociation rate. If needed, nonspecific uptake can be estimated without pharmacologic intervention by using the labeled R enantiomer.

Noninvasive arterial monitor for quantitative oxygen-15-water blood flow studies

A noninvasive monitor has been developed for monitoring arterial radioactivity in quantitative PET studies of blood flow. The significance of this probe is that quantitative blood flow studies can be performed without the use of arterial catheterization. The method employed is based on the flux of photons emanating from the superior lobe of the right lung following an intravenous bolus of H2(15)O. Calibration of the monitor is obtained by measuring the relationship between lung monitor counts and arterial radioactivity after arterial and venous radioactivity levels have equilibrated following inhalation of C15O. To determine the accuracy of the lung probe as a measure of arterial radioactivity, 44 brain blood flow determinations were made in 11 volunteers using arterial radioactivity measures based both on the lung probe and continuous sampling from a radial artery. Repeated measures analysis of variance found no differences between invasive and noninvasive estimates of blood flow. These results suggest that the lung monitor enables quantitation of cerebral blood flow yet avoids the trauma of an arterial puncture.

Temporal alignment of tissue and arterial data and selection of integration start times for the H(2)(15)O autoradiographic CBF model in PET

A technique has been developed and tested that provides an automated method of temporally aligning the PET tissue activity curve with the arterial activity curve for quantification of cerebral blood flow using the H(2)(15)O autoradiographic model. This technique not only determines the relative time delay between the two curves, but also provides the start time of integration. Variability in computing global cerebral blood flow using this technique is shown to be less than that obtained by trained observers manually selecting parameters and at least as good as that obtained by using another automated alignment technique.

Tn4556 and luciferase: synergistic tools for visualizing transcription in Streptomyces

Progress in understanding genetic regulatory controls in the Actinomycetes has been rate limited by the properties of in vivo transcriptional probes. We have developed a set of plasmid- and transposon-based promoter-probe vectors that employ the Vibrio harveyi luciferase-encoding luxAB cassette as a reporter of transcription. The primary advantages of luciferase (Lux) over other reporter gene products are: (i) unsurpassed sensitivity; (ii) utility during stationary-phase gene expression; and (iii) the ability to localize promoter activity spatially within developing colonies. We have used these vectors to screen for Streptomyces coelicolor promoters that exhibit developmental phenotypes or that are induced by various environmental stimuli. The plasmid-based probes have proved invaluable for identifying cis- and trans-acting elements that are required for stationary-phase expression of the S. coelicolor sapA gene. A collection of novel bld and whi insertion mutants has been obtained by use of the Lux-encoding transposon, Tn5353.

A dual-radioisotope technique for the evaluation of penile blood flow during tumescence

A technique is described for concomitant study of both arterial and venous penile blood flow during tumescence. Dual-isotope acquisition is started after labeling red cells in vivo with 99mTc. Xenon-133 in saline is then injected into the corpus cavernosum followed with vasoactive drugs to induce an erection. The resulting xenon and technetium time-activity curves are inputs for a one-compartment model. In 14 subjects, the average peak arterial flow rate (PAF) for normal males was calculated as 13.0 +/- 1.28 ml/min (avg +/- s.d.) compared to 16.1 +/- 5.14 and 5.02 +/- 1.78 ml/min for patients with venous leak (VL) or arterial insufficiency (AI), respectively. Peak venous flows (PVF) were 4.25 +/- 1.17, 12.1 +/- 3.75, and 3.78 +/- 1.00 ml/min for normal, VL and AL respectively. Al patients have significantly lower PAF than normal (p = 0.002) or VL patients (p = 0.018), and VL patients had significantly higher PVF than normal (p = 0.012) or Al (p = 0.018). The technique may be helpful in the study of impotence.

Measurement of human cerebral blood flow with [15O]butanol and positron emission tomography

Although H2(15)O is widely used for CBF measurement by positron tomography, it underestimates CBF, especially at elevated flow rates. Several tracers, including butanol, overcome this problem, but the short half-life of 15O provides advantages that cause water to remain the tracer of choice. We report the first use and evaluation of 15O-labeled butanol for CBF measurement. Flow measurements made in a similar fashion with water and butanol at 10-min intervals were compared in normal volunteers under resting and hypercapnic conditions. Regional analysis showed good agreement between the tracers at low flows, and significant underestimation of flow by water relative to butanol in regions of elevated flow. The observed relationship between the tracers and the curve-fitted permeability-surface area product for water (133 ml.100 g-1.min-1) follow the known relationship between water and true flow. These observations indicate that [15O]-butanol provided accurate measurements of human regional CBF under conditions of elevated perfusion. We conclude that butanol is a convenient and accurate method for routine CBF determination by positron emission tomography.

Comparison of the effect of temafloxacin, ciprofloxacin, or placebo on cerebral blood flow, glucose, and oxygen metabolism in healthy subjects by means of positron emission tomography

STUDY OBJECTIVE

To determine the cause of the central nervous system effect of the fluorinated quinolones temafloxacin and ciprofloxacin by measuring cerebral blood flow and metabolism by use of positron emission tomography.

DESIGN

This was a prospective, randomized, double-blind, placebo-controlled study.

PATIENTS

The patients were 13 healthy, nonsmoking volunteers whose ages ranged from 18 to 40 years.

RESULTS

We measured brain blood flow and metabolism by use of positron emission tomography before and after a five-dose course of 750 mg ciprofloxacin, 600 mg temafloxacin, or placebo given every 12 hours. Quinolone administration produced no significant effect on visual (qualitative) reading of the positron emission tomography scans.

CONCLUSIONS

We conclude that short-term administration of temafloxacin, ciprofloxacin, or placebo does not significantly alter cerebral glucose or oxygen metabolism. Subjects treated with ciprofloxacin demonstrated a significant decrease in brain blood flow compared with baseline and with temafloxacin- or placebo-treated subjects.

Tn4563 transposition in Streptomyces coelicolor and its application to isolation of new morphological mutants

The Tn3-like transposon Tn4556 (and its derivatives Tn4560 and Tn4563) has been used for insertion mapping of genetic loci cloned on plasmids, but it has been difficult to obtain chromosomal insertions, largely because of the lack of a strong selection against transposon donor molecules. In this communication, we report two efficient selection techniques for transposition and their use in the isolation of chromosomal insertion mutations. A number of independent Streptomyces coelicolor morphological mutants (bld and whi) were obtained. Two of the bld mutations were mapped to locations on the chromosome by SCP1-mediated conjugation; at least one mutation, bld-5m1, appears to define a novel locus involved in control of S. coelicolor morphogenesis and antibiotic production.

An assessment of cerebral blood flow and metabolism after fleroxacin therapy

Cerebral blood flow (CBF), glucose (FDG), and oxygen metabolism (OM) were evaluated by positron emission tomography (PET) in 18 healthy volunteers who were randomized to a 72-hour course of either 600 mg/d of fleroxacin or placebo. Such studies attempted to assess potentially serious, yet unexplained, central nervous system adverse effects of the fluorinated quinolone class. Baseline and postplacebo values for CBF (mL/min/100 g) and FDG (mg/min/100 g) were: 53 +/- 6 and 5.7 +/- 1.8; and 49.6 +/- 4.4, and 5.2 +/- 1.2, respectively. Identical values for fleroxacin were: 53.9 +/- 4.8 and 6.3 +/- 1.1; and 54.4 +/- 2.2 and 6.8 +/- 1.5, respectively. The differences between fleroxacin and placebo were not significant. There was also no effect seen in OM between placebo and the active drug. The authors conclude that short-term administration of fleroxacin does not alter CBF, FDG, or OM in healthy volunteers.

Mathematical simplification of a PET blood flow model

The positron emission tomography (PET) H(2)(15)O bolus injection model for cerebral blood flow (CBF) requires calculation of a certain double integral that, when calculated, provides the pixel values of a reconstructed image (PET number) in terms of the tissue flow, the arterial input function, a decay constant for (15)O, the partition coefficient and a camera calibration constant that relates the flow-dependent integrated tissue activity to the measured PET number (cts/pixel). The tissue activity is assumed to be zero at the time of injection. A mathematical simplification, changing the order of integration, enabled the integration with respect to time to be performed analytically before the integration of the arterial input function. As a result of this simplification, only single integrals remain to be calculated numerically; cubic spline integration was used to calculate numerically these remaining integrals. This technique increases the accuracy and speed of evaluating blood flow without making simplifying assumptions. Similar simplifications may be applicable to other physiological models.

Pseudo-gating: elimination of periodic motion artifacts in magnetic resonance imaging without gating

This note explains and illustrates a technique of reducing artifacts produced by periodic motion without using physiologic gating. The method is simple and can be applied on any standard MRI unit. For periodic motion, effective gating can be attained by setting the product of the number of acquisitions (at each phase-encoding step), N, times the repeat time, TR, equal to the period of the motion, T. This pseudo-gating can be used with any TR but, if changes in the period occur, is most robust with short TR values. The method is also applicable to multislice and volume imaging. For fast field echo methods, the above rule can be used if the period of the motion is smaller than the total scan time. Otherwise, the scan need only be repeated N times to avoid artifacts and improve signal-to-noise. The method has been implemented to remove both respiratory and/or cardiac motion artifacts.