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PubMed2007

Deep-inspiration breath-hold PET/CT of the thorax.

UNLABELLED: The goal of this study was to describe our initial experience with the deep-inspiration breath-hold (DIBH) technique in combined PET/CT of the thorax. This article presents particular emphasis on the technical aspects required for clinical implementation. METHODS: In the DIBH technique, the patient is verbally coached and brought to a reproducible deep inspiration breath-hold level. The first "Hold" period, which refers to the CT session, is considered as the reference. This is followed by 9- to 20-s independent breath-hold PET acquisitions. The goal is to correct for respiratory motion artifacts and, consequently, improve the tumor quantitation and localization on the PET/CT images and inflate the lungs for possible improvement in the detection of subcentimeter pulmonary nodules. A physicist monitors and records patient breathing during PET/CT acquisition using a motion tracker. Patient breathing traces obtained during acquisition are examined on the fly to assess the reproducibility of the technique. RESULTS: Data from 8 patients, encompassing 10 lesions, were analyzed. Visual inspection of fused PET/CT images showed improved spatial matching between the 2 modalities, reduced motion artifacts especially in the diaphragm, and increased the measured standardized uptake value (SUV) attributed to reduced motion blurring, as compared with the standard clinical PET/CT images. CONCLUSION: The practice of DIBH PET/CT is feasible in a clinical setting. With this technique, consistent lung inflation levels are achieved during PET/CT sessions, as judged by both motion tracker and verification of spatial matching between PET and CT images. Breathing-induced motion artifacts are significantly reduced using DIBH compared with free breathing, enabling better target localization and quantitation. The DIBH technique showed an increase in the median SUV by 32.46%, with a range from 4% to 83%, compared with SUVs measured on the clinical images. The median percentage reduction in the PET-to-CT lesions' centroids was 26.6% (range, 3%-50%).

Adult↗
PubMed1995

Determination of 3D imaging geometry and object configurations from two biplane views: an enhancement of the Metz-Fencil technique.

We present a new technique based on the method developed by Metz and Fencil for estimation of the 3D imaging geometry and 3D object configurations from biplane angiographic acquisitions. The new method employs the 3D configuration of points calculated by the Metz-Fencil technique as an initial estimate. A 3D Procrustes algorithm is employed to translate, rotate, and scale the configuration until it aligns optimally with the set of lines that connects a focal spot with the corresponding set of image points. This alignment procedure is applied independently for each view. The rotation and translation that relate the two aligned data sets are then determined by an additional 3D Procrustes calculation. These steps are applied iteratively. Evaluations were based on Monte Carlo simulation and phantom studies. With this new technique, the mean absolute errors in magnification, in the relative position of the points, and in the angles defining the rotation and translation matrices were approximately 3.0%, 1.5 mm, and 5 degrees and 3 degrees, respectively, for rms input errors in the image data up to 2.0 pixels (0.7 mm). Errors in the results can be as small as 0.5%, 0.16 mm, 0.6 degrees, and 0.3 degrees, respectively, if input image-data error is 0.035 mm. The improvement of the Metz-Fencil technique described here may provide a basis for precise estimation of the biplane imaging geometry and the 3D positions of vessel bifurcation points.

Algorithms↗
PubMed2000

Computerized tomographic ureteroscopy for diagnosing ureteral tumors.

PURPOSE: Helical computerized tomography (CT) image acquisition has led to the availability of improved data sets for CT endoscopic imaging that represent virtual endoscopy using CT. We assessed the usefulness of CT ureteroscopic imaging for diagnosing ureteral tumors. MATERIALS AND METHODS: A total of 16 patients with ureteral stenosis underwent surface rendering CT ureteroscopy after the intravenous administration of contrast material and furosemide. To distinguish ureteral tumors from ureteral strictures 2 observers blinded to other patient history and evaluation data independently and prospectively evaluated CT ureteroscopy with reformatted CT ureterograms in these 16 patients. CT ureteroscopic images were then correlated with surgical and pathological findings, which served as the gold standard. RESULTS: Surgical and pathological findings in the 16 patients revealed 16 ureteral tumors, including carcinoma in 10 (carcinoma in situ in 1, fibroepithelial polyps in 2 and hyperplastic polypoids in 4), inflammatory intrinsic stricture in 2 and extrinsic stricture in 4 caused by retroperitoneal fibrosis in 2 and lymph node metastasis in 2. CT ureteroscopy correctly detected all lesions except 1 carcinoma in situ, 1 polypoid carcinoma and 1 hyperplastic polypoid. The sensitivity and specificity of CT ureteroscopy for detecting ureteral tumors and carcinoma were 81% and 100%, and 80% and 75%, respectively, when tumors without stalks were considered carcinoma. CONCLUSIONS: CT ureteroscopy is useful for visualizing the complex morphology of ureteral tumors and distinguishing tumor from ureteral stricture.

Adult↗
PubMed2004

Nuclear export of the oncoprotein v-ErbA is mediated by acquisition of a viral nuclear export sequence.

v-ErbA, an oncogenic derivative of the thyroid hormone receptor alpha (TRalpha) carried by the avian erythroblastosis virus, contains several alterations including fusion of a portion of avian erythroblastosis virus Gag to its N terminus, N- and C-terminal deletions, and 13 amino acid substitutions. Nuclear export of v-ErbA occurs through a CRM1-mediated pathway. In contrast, nuclear export of TRalpha and another isoform, TRbeta, is CRM1-independent. To determine which amino acid changes in v-ErbA confer CRM1-dependent nuclear export, we expressed a panel of green and yellow fluorescent protein-tagged mutant and chimeric proteins in mammalian cells. The sensitivity of subcellular trafficking of these mutants to leptomycin B (LMB), a specific inhibitor of CRM1, was assessed by fluorescence microscopy. Our data showed that a nuclear export sequence resides within a 70-amino acid domain in the C-terminal portion of the p10 region of Gag, and in vitro binding assays demonstrated that Gag interacts directly with CRM1. However, a panel of ligand-binding domain mutants of v-ErbA lacking the Gag sequence exhibited greater nuclear localization in the presence of LMB, suggesting that the various amino acid substitutions/deletions may cause a conformation shift, unmasking an additional CRM1-dependent nuclear export sequence. In contrast, the altered DNA-binding domain of the oncoprotein did not contribute to CRM1-dependent nuclear export. Heterokaryon experiments revealed that v-ErbA did not undergo nucleocytoplasmic shuttling when the CRM1 export pathway was blocked by LMB treatment, suggesting that the ability to follow the export pathway used by TRalpha has been lost by the oncoprotein during its evolution. Our findings thus point to the intriguing possibility that acquisition of altered nuclear export capabilities contributes to the oncogenic properties of v-ErbA.

Active Transport, Cell Nucleus↗
PubMed1997

Development and evaluation of a fully automated monophasic action potential analysis program.

A fully automated program has been developed for analysing digitised cardiac monophasic action potentials (MAPs) of several animal species. Under diverse conditions, the program's performance is evaluated by comparison with high-resolution manual analysis of action potential duration, MAP detection, baseline and plateau determination. For each variable, the differences between both forms of analysis are categorised according to species (rabbit, dog or baboon), intervention (control, sematilide or LY-190147), rhythm source (sinus or paced), and rates. They are then examined using ANOVA (null hypothesis: no difference between methods for any category). Intra-group differences are significant for baseline selection (p < 0.05), and treatment effects are significant (p < 0.05) for one species (baboon). However, the differences found are negligible when compared with expected measurement errors. Thus the program reliably detects and accurately analyses MAPs, independent of species, drug or pacing. The program's strength is its use of simple heuristic algorithms to identify and profile MAP signals while rejecting spurious transients. These algorithms focus on the procedural aspects of automatic MAP detection and validation, with minimum use of complex mathematics. The program's estimated throughput exceeds 8200 MAPs min-1 on a 50 MHz 1486 DX machine. With available data format conversion packages, signals from almost any data-acquisition source can be analysed.

Action Potentials↗
PubMed2004

Virtual endoscopy of the tracheo-bronchial system: sub-millimeter collimation with the 16-row multidetector scanner.

The purpose of this study was to evaluate the scope of sub-millimeter collimation reconstruction parameters using 16-row computer tomography and ECG triggering on image quality in virtual bronchoscopy. Thirty-two patients (5 women, 27 men, mean age 66.6+/-1.4) who had been admitted for coronary artery bypass graft surgery underwent CT examination of the thorax (Sensation 16, Siemens, Inc., Forchheim, Germany). All patients were examined with 16x0.75-mm collimation. Image reconstruction was performed for two groups. In group A ( n=32), slice thickness of 1.5 mm and an overlap of 0.75 mm were used. In group B ( n=32), slice thickness of 0.75 mm and an overlap of 0.4 mm were applied. Retrospective ECG triggering was performed in all patients. The maximum order of recognizable bronchi was determined in each data set. In addition to assessing the maximum order of bronchial bifurcation, bronchial diameter was determined in truly perpendicular sections in each patient. For every segment proximal to a bifurcation, image quality was subjectively graded as poor (grade 1), moderate (grade 2) or good (grade 3). The observers were asked to identify the minimum cardiac movement ECG-triggered image sets assuming that they would be of better quality than the maximum cardiac movement ECG-triggered image sets. The Mann-Whitney U-test and the Fisher's Exact Test were used for statistical evaluation. In group A, a mean of 4.8+/-0.2 bifurcations was ascertained vs. 6.5+/-0.3 bifurcations in group B [ P<0.0003]. For bronchial diameters in group A, a mean of 7.5+/-0.4 mm was determined vs. 4.6+/-0.4 mm in group B [ P<0.0001]. In group B, two independent radiologists observed a significant shift to better image quality in all segments evaluated [ P<0.006 to P<0.000001]. Motion artifacts were judged as being significantly reduced by minimum cardiac movement ECG-triggering in group B [observer 1: P=0.0007 (20/32); observer 2: P=0.008 (18/32)], but not in group A [observer 1: P=0.286 (13/32); observer 2: P=0.123 (16/32)]. Sub-millimeter collimation and minimum cardiac movement ECG-triggered data acquisition allow deeper penetration into the tracheo-bronchial system allowing visualization of the bronchial surface down to diameters below 5 mm in certain cases up to the eighth bifurcation. Along with an enhanced visualization as such, better image quality is acquired in all segments evaluated. Trade off between better image quality, of doubtful diagnostic consequence, and much higher irradiation dose must be made.

Aged↗
PubMed2005

Quantitative data generation for systems biology: the impact of randomisation, calibrators and normalisers.

Systems biology is an approach to the analysis and prediction of the dynamic behaviour of biological networks through mathematical modelling based on experimental data. The current lack of reliable quantitative data, especially in the field of signal transduction, means that new methodologies in data acquisition and processing are needed. Here, we present methods to advance the established techniques of immunoprecipitation and immunoblotting to more accurate and quantitative procedures. We propose randomisation of sample loading to disrupt lane correlations and the use of normalisers and calibrators for data correction. To predict the impact of each method on improving the data quality we used simulations. These studies showed that randomisation reduces the standard deviation of a smoothed signal by 55% +/- 10%, independently from most experimental settings. Normalisation with appropriate endogenous or external proteins further reduces the deviation from the true values. As the improvement strongly depends on the quality of the normaliser measurement, a criteria-based normalisation procedure was developed. Our approach was experimentally verified by application of the proposed methods to time course data obtained by the immunoblotting technique. This analysis showed that the procedure is robust and can significantly improve the quality of experimental data.

Algorithms↗
PubMed1987

Comparative studies on estrogen receptors between a pregnancy-dependent mouse mammary tumor (TPDMT-4) and related autonomous tumors.

TPDMT-4 is a pregnancy-dependent mouse mammary tumor line characterized by progressive growth in pregnant, but dormancy in virgin, hosts and by significant estrogen (ER) and progesterone receptor (PR) levels. Three sublines, T4-OR26, T4-0I96, and T4-0I320, were established from sporadic outgrowths in virgins of TPDMT-4 pieces passaged long in breeding and estradiol (E2)- plus progesterone-treated mice and of enzymatically dissociated TPDMT-4 cells, respectively. T4-OR26 tumors produced ovarian-responsive growth and maintained the parent levels of ER and E2-dependent PR. T4-OI320 and T4-OI96 tumors were ovarian independent or autonomous. The former had ER, but not E2-dependent PR, and the latter had neither. To clarify the mechanism of acquisition of autonomy by hormone-dependent neoplastic cells, comparative ER studies were conducted between TPDMT-4 and T4-OI320 tumors. Although cytosolic, microsomal, and nuclear translocated ER levels were generally lower in T4-OI320 tumors, the dissociation constants, determined by the dextran-charcoal technique, steroid specificity, sedimentation data in sucrose gradients, and activation studies using DNA binding, molecular transformation from 4S to 5S, and [3H]E2 dissociation from [3H] E2-ER complexes as markers, revealed no autonomy-specific changes in cytosolic ER. Small but significant differences in the affinity of [3H]E2 to nuclear ER and the [3H]E2 dissociation rate from nuclear bound [3H]E2-ER complexes were found between both tumors. Hormone-dependent tumors may progress toward autonomy with different receptor statuses in different environments, and lack of E2-dependent PR synthesis in ER-positive tumors may be due to defects at postreceptor or nuclear levels involving subtle changes in interaction between activated ER and nuclei.

Animals↗
PubMed2003

[Advantage of virtual endoscopy in the evaluation of the ossicular chain].

PURPOSE: Our study consists of a comparison of traditional computed tomography (CT) data sets with 2 views of virtual endoscopy in the preoperative evaluation of various diseases of the middle ear. MATERIALS AND METHODS: We studied 59 patients, all sent for conductive hearing loss with normal eardrum who underwent a complete CT examination: axial helical acquisition and coronal incremental acquisition: virtual endoscopy with selection of two reproducible views: an external one of the auditory canal and a lower one of the hypotympanum. Reading was performed by 2 independent radiologists. All patients were subsequently operated by the same surgeon. Results were compared with surgical reports. RESULT: Virtual endoscopy is valuable for the evaluation of ossicular and prosthesis dislocations, morphological anomalies of the malleus, incus, and stapes superstructure. Nevertheless, standard axial and coronal CT images remain necessary as confirmed by the poor results of virtual endoscopy in cases of attic obstruction, cholesteatomas and otospongiosis. CONCLUSION: Virtual endoscopy is a valuable technique of the evaluation of some ossicular chain pathologies but it cannot be used alone.

Adolescent↗
PubMed2003

Risk factors for initial acquisition of Pseudomonas aeruginosa in children with cystic fibrosis identified by newborn screening.

The objective of this study was to identify risk factors for initial detection of Pseudomonas aeruginosa (P. aeruginosa) in children with cystic fibrosis (CF) identified by newborn screening. Life history data on 180 patients, collected prospectively in a follow-up study of infants and children diagnosed with CF, were examined for factors associated with the initial detection of P. aeruginosa ascertained by oropharyngeal cultures. Univariate and multivariate Cox proportional hazards regression analyses were used to assess the effect of baseline and time-varying covariates on age at first positive culture for P. aeruginosa. Seventy-nine patients (44%) had at least one culture positive for P. aeruginosa during the study. The median age of detection was 8.1 years (95% CI, 7.0, 10.0). Median length of follow-up was 4.1 years, ranging from 0.2-15.5 years. Multivariate Cox regression analysis identified female gender (RR, 1.85; 95% CI, 1.14, 3.01), the DeltaF508 homozygous genotype (RR, 2.23; 95% CI, 1.30, 3.80), and S. aureus isolations (RR, 1.30; 95% CI, 1.11, 1.52) to be independently associated with acquisition of P. aeruginosa. Other marginally independent associations were found with days hospitalized and increased height. We conclude that female gender, homozygous DeltaF508 mutation, and S. aureus isolations are important risk factors for early P. aeruginosa detection in children with CF identified through newborn screening.

Child↗
PubMed1996

On-line evaluation of systolic performance by densitometry in digital left ventriculography.

The angiocardiographic evaluation of left ventricular end-diastolic (LVEDV) and end-systolic (LVESV) volumes and ejection fraction (EF) is routinely performed by the area-length method (ALM) but may lead to erroneous results. Digital imaging in real time allows densitometric procedures of determining left ventricular (LV) performance to be applied alternatively. In this study, we present densitometric algorithms for the analysis of LVEDV, LVESV, and EF from digital image data, establish accuracy and reproducibility, and determine value and limitations in comparison with ALM in single-plane 30 degrees right anterior oblique (RAO) projection. A linear relationship between iodine depth and measured densities is mainly burdened with scatter radiation and beam hardening which reduce primary radiation and suppress iodine depth. However, facilities such as deconvolution and correction algorithms are capable of reducing these sources of error. In the present study, computer-analyzed contrast images of iodine-filled wedges and spheres showed a near-linear relationship between iodine depth between 50-100 mg/cm2 and measured densities. Contrast images of heart casts and LV angio-grams of 54 patients were obtained with a digital image acquisition and processing system, and evaluated by two independent observers. The phantom study resulted in significantly (p < or = 0.01) better densitometric standard errors of estimate for volumes [3.3 ml densitometry (DENS) vs. 8.9 ml (ALM)] and simulated EF [4.3% (DENS) vs. 7.8% (ALM)] than ALM. The standard error of estimate for the comparison between both methods was 8.4 ml for volumes and 7.5% for EF. Densitometric volumes tended to underestimate volumes calculated by ALM. The angiographic study of patients demonstrated significant correlations between both methods (LVEDV r = 0.78, LVESV r = 0.83, total volumes: r = 0.89; EF r = 0.88). The standard errors of estimate can be ascribed to systematic, method-related errors of both DENS and ALM (LVEDV +/- 28.9 ml, LVESV +/- 23.4 ml, total volumes (EDV and ESV) +/- 27.1 ml; EF +/- 8.1%). The intra- and interobserver variability, respectively, exhibited significantly smaller (p < or = 0.01 and p < or = 0.05, respectively) standard errors of estimate for densitometric EF [4.6% (DENS) vs. 8.5% (ALM) and 7.1% (DENS) vs. 10.3% (ALM), respectively]. Inclined but not significant differences were found for LVEDV and LVESV. In conclusion, the data presented indicate that the calculation of LV volumes and EF in digital left ventriculography may be performed accurately by densitometric calculation in single-plane 30 degrees RAO projection. Minor underestimations in densitometric volume determination may be anticipated in the evaluation of LV geometry.

Adult↗
PubMed1997

AAEM minimonograph #47: normative data in electrodiagnostic medicine. ff.

This article reviews, without mathematics, the important principles governing the acquisition and use of normative data in electrodiagnostic medicine. Common flaws in neurophysiological normative data include vague clinical criteria for establishing freedom from disease, samples that are too small and inadequately stratified, and application of Gaussian statistics to non-Gaussian variables. Other problematic issues concern the trade-off between permissible false-positivity and false-negativity in defining the limits of normative from sample data, test-retest variability, and the use of multiple independent test measurements in each electrodiagnostic examination. The following standards for normative data are proposed: (1) standardized objective determination of freedom from disease; (2) appropriately large sample of normal subjects; (3) proportional statification of normal subjects for known relevant variables; (4) test of Gaussian fit for application of Gaussian statistics; and (5) data presentation by percentiles when Gaussian fit is in doubt. Many existing normative studies in clinical neurophysiology do not meet these standards. High-quality normative data, readily accessible, is essential for the accurate electrodiagnosis of neuromuscular diseases.

Electromyography↗
PubMed1995

Developmental exposure to ozone induces subtle changes in swimming navigation of adult mice.

Following exposure to ozone (O3, 0.6 ppm) from the beginning of neonatal life until weaning, adult CD-1 mice were tested in swimming navigation, a sensitive indicator for hippocampal damage. Control mice received a sham exposure. All mice were tested at 12-13 weeks of age for their ability to find a submerged platform in a fixed location (acquisition: 18 trials, six trials per day) and for capacity to re-orient towards a new platform position (reversal: 12 trials, six trials per day). Exposure to O3 did not produce any significant impairment of swimming navigation during the acquisition phase while it slightly increased the swimming paths during the last day of the reversal phase. Mice exposed to O3 showed a slightly but significantly higher swimming speed during all the days, which was unrelated to differences in body weight and to navigational performances. Moreover, mice exposed to O3 (with the exception of one animal) had a strong tendency to make turns to the left while the controls, independent of sex, preferred clockwise turns. Data are discussed with respect to possible implications with early CNS and immune alteration leading to behavioral asymmetries at adulthood.

Animals↗
PubMed2006

IL-4R signaling is required to induce IL-10 for the establishment of T(h)2 dominance.

The requirement for IL-4 to promote differentiation of naive CD4(+) T cells into T(h)2 effector cell populations was established by classical in vitro studies. More recent in vivo data, however, indicate that signaling through the IL-4R is not essential for acquisition of the T(h)2 phenotype. In order to reconcile these seemingly contradictory conclusions, we have taken advantage of the ability of the excretory/secretory antigens of the gastrointestinal nematode Nippostrongylus brasiliensis to down-regulate T(h)1 cell development and drive T(h)2 cell expansion. We show that the initial development of IL-4-producing T cells is independent of IL-4R signaling but that the subsequent expansion of IL-4-producing CD4(+) T cells in a competitive environment that also contains T(h)1 potential is positively influenced by IL-4R signaling. We find that the production of IL-10 is the key IL-4R-dependent factor required to maintain T(h)2 dominance and that in the absence of IL-4R signaling, T(h)2 expansion can only be achieved by neutralization of T(h)1 cytokines. Moreover, in the absence of IL-4R signaling, reduced IL-10 production is due to the lack in expansion of an IL-10(+) T(h)2 population, rather than a global defect in the production of IL-10 by CD4(+) T cells. Thus, the evolution of T(h)2 dominance is achieved at the expense of T(h)1 cell development, normally restrained by IL-10 in an IL-4R-dependent manner. We conclude that T(h)2 cell development in response to N. brasiliensis antigen requires both IL-4 and IL-10 to act in concert on incipient populations of both T(h)1 and T(h)2 types.

Animals↗
PubMed2004

Contrast-enhanced three-dimensional pulmonary perfusion magnetic resonance imaging: intraindividual comparison of 1.0 M gadobutrol and 0.5 M Gd-DTPA at three dose levels.

RATIONALE AND OBJECTIVES: To compare 1.0 M gadobutrol and 0.5 M Gd-DTPA for contrast-enhanced three-dimensional pulmonary perfusion magnetic resonance imaging (3D MRI). MATERIALS AND METHODS: Ten healthy volunteers (3 females; 7 males; median age, 27 years; age range, 18-31 years) were examined with contrast-enhanced dynamic 3D MRI with parallel acquisition technique (FLASH 3D; reconstruction algorithm: generalized autocalibrating partially parallel acquisitions; acceleration factor: 2; TE/TR/alpha: 0.8/1.9 milliseconds/40 degrees; FOV: 500 x 375 mm; matrix: 256 x 86; slab thickness: 180 mm; 36 partitions; voxel size: 4.4 x 2 x 5 mm; TA: 1.48 seconds). Twenty-five consecutive data sets were acquired after intravenous injection of 0.025, 0.05, and 0.1 mmol/kg body weight of gadobutrol and Gd-DTPA. Quantitative measurements of peak signal-to-noise ratios (SNR) of both lungs were performed independently by 3 readers. Bolus transit times through the lungs were assessed from signal intensity time curves. RESULTS: The peak SNR in the lungs was comparable between gadobutrol and Gd-DTPA at all dose levels (15.7 vs. 15.5 at 0.1 mmol/kg bw; 12.9 vs. 12.5 at 0.05 mmol/kg bw; 7.6 vs. 8.9 at 0.025 mmol/kg bw). A dose of 0.1 mmol/kg achieved the highest peak SNR compared with all other dose levels (P < 0.05). A higher peak SNR was observed in gravity dependent lung (P < 0.05). Despite different injection volumes, transit times of the contrast bolus did not differ between both agents. CONCLUSION: Higher concentrated gadolinium chelates offer no advantage over standard 0.5 M Gd-DTPA for contrast-enhanced 3D MRI of lung perfusion.

Adolescent↗
PubMed2006

Target antigen, age, and duration of antigen exposure independently regulate immunoglobulin G subclass switching in malaria.

The isotype/subclass of immunoglobulin determines antibody function, but rather little is known about factors that direct class switching in vivo. To evaluate factors that might influence the maturation of the antibody response during infection, we conducted a seroepidemiological study of the immunoglobulin G (IgG) subclass response to four merozoite-associated antigens of Plasmodium falciparum in a mountainous region of northeastern Tanzania, where malaria endemicity declines with increasing altitudes. We found that IgG1/IgG3 class switching is independently affected by the nature of the antigen, cumulative exposure to the antigen, and the maturity of the immune system (i.e., the age of the individual). These observations provide insights into the effects of immune system maturity, the duration and intensity of antigen exposure, and inherent characteristics of individual antigens on the process of class switching in human B cells. Our data also throw light on the consequences of class switch decisions on the gradual acquisition of antimalarial immunity.

Adolescent↗
PubMedDate not supplied

New legal standards for trustee performance.

Until recently, trustees who acted "in good faith" were not held personally liable for mistakes in judgment. But in two recent cases--Smith v. Van Gorkom and Hanson Trust PLC v. MLSCM Acquisition, Inc.--the courts found directors liable for making hasty, ill-informed decisions regarding ownership issues. The rulings said that when boards make major decisions, they must be able to demonstrate that they approved a fair transaction. They can do this by consulting with senior management and corporate counsel and, if needed, with independent authorities. Boards should obtain pertinent documents to review before making a decision and should have ample time to obtain necessary data. Meeting minutes should document these precautions. In their rulings, the courts did not second-guess the boards' business judgment. Rather, they found that the unprepared directors acted so quickly that they could not have made an intelligent decision. The rulings convey a commonsense message: Trustees who exercise authority without adequate information risk damaging the corporation and its services. As trustees attempt to fulfill their legal obligation to probe and question before approving major actions, tensions with management may arise. Boards and corporate officers, however, must find ways to reach corporate consensus on important decisions while maintaining an appropriate division of authority.

Delaware↗
PubMed2005

Liver regeneration in humans is characterized by significant changes in cellular phosphorus metabolism: assessment using proton-decoupled 31P-magnetic resonance spectroscopic imaging.

In the present study we applied proton-decoupled 31P magnetic resonance spectroscopic imaging (MRSI) to noninvasively assess liver metabolism in patients who had undergone a partial hepatectomy (PH). Proton-decoupled 31P chemical shift imaging was performed in 47 patients 2-28 days following major hepatectomy, and the results were compared with those from eight control subjects. All studies were performed on a 1.5T MR imager (General Electric, Milwaukee, WI) equipped with a stand-alone proton decoupler. A 31P-1H resonator pair was used for data acquisition, and 31P data were obtained in 34 min. Liver regeneration was characterized by increases in phosphoethanolamine (PE), and decreases in nucleoside triphosphates (NTP), glycerophosphoethanolamine (GPE), and glycerophosphocholine (GPC). These alterations were most marked 48-72 hr after hepatectomy and returned to baseline within 3 weeks. The level of PE measured by MRSI was also found to depend on the percentage of liver that was removed, while changes in levels of cellular high energy phosphates were independent of the size of liver resection. Implementation of proton-decoupling was critical for assessing individual phosphomonoester and phosphodiester components. This study demonstrates that 31P MRSI can be used to assess metabolic changes in humans during liver regeneration, and may be useful for assessing derangement of the regenerative process or guiding adjuvant chemotherapies.

Female↗