Correcting Fan-Beam Magnification in Clinical Densitometry Scans of Growing Subjects

As children grow, body and limb girths increase. For serial densitometric measurements, growth increases the distance between the bone region of interest and X-ray source over time, thereby increasing fan-beam magnification. To isolate bone accrual from magnification error in growing subjects, we developed a correction method based on waist girth, a common anthropometric measure. This correction was applied to dual-energy X-ray absorptiometry output obtained in a cohort of premenarcheal gymnasts and nongymnasts. After correcting for magnification, results for projected area and bone mineral content (BMC) increased by 0.4–1.1% at the lumbar spine and 8–16% at the femoral neck, decreasing areal bone mineral density (aBMD) by 0.4–2.3% at both sites. The effects of magnification correction were similar in magnitude to BMC and aBMD gains previously reported in longitudinal studies of normoactive children. Because of body size differences, the effect of correction for BMC and aBMD was 10–20% greater in nongymnasts than in gymnasts, which increased the observed aBMD differential between gymnasts and nongymnasts. Fan-beam magnification distorts true changes in bone mineral measures in growing premenarcheal girls and, therefore, may obscure additional activity-related changes during growth. Our correction technique may enhance detection of skeletal adaptation, particularly in pediatric populations.     

Life-long follow-up in congenitally corrected transposition

A male patient with congenitally corrected transposition, with no associated cardiac malformations, was diagnosed in childhood and followed until his death at age 28. He underwent two cardiac gated single photon emission computed tomographies over a two year period, which demonstrated progression of ischaemia and reduction of systolic function. The findings suggest that, when the systemic ventricle is perfused by the morphologically right coronary artery, there may be inadequate perfusion to supply any subsequent extensive hypertrophy.     

The design and performance of the exubera pulmonary insulin delivery system

The Exubera system (Pfizer, New York, NY/Nektar Therapeutics, San Carlos, CA) is an integration of five major new technologies: protein formulation, powder processing, powder filling, drug packaging, and delivery device. The product provides a simple interface, where the patient interacts only with the delivery device and powder packaging. These components were designed together to assure repeatable dosing when used by a wide range of patients under real-world life-style and handling conditions. The device design is purely mechanical, using patient-generated compressed air as the energy source. Upon actuation, a sonic discharge of air through the novel release unit reproducibly extracts, de-agglomerates, and disperses the inhalation powder into a respirable aerosol. A clear holding chamber allows for patient feedback via dose visualization and separates aerosol cloud generation from the inspiratory effort. The Exubera product was tested under a wide range of typical use conditions and potential misuse scenarios and following long-term usage in clinical trials. These comprehensive characterization programs demonstrated robust aerosol and mechanical performance, confirming the design intent of the inhaler. These studies provide assurance of consistent and reliable dose delivery in a real-world use of the product.     

Expectancy of impaired neuropsychological test scores in a non-clinical sample

Two methods were addressed to evaluate the incidence of false positive impairment on tests in neuropsychological evaluation. One method used a mathematical model based on the binomial theory (Ingraham & Aiken, 1996) to offer predictions based on probability. The model sets boundaries to determine when score variations would occur by chance and is therefore useful for identifying when cases exceed established boundaries. In addition, the present study examined test performance in a non-clinical sample of 94 college students via the Halstead Reitan Neuropsychological Test Battery. Results found that 15% of the sample had impairments suggested by the Halstead Impairment Index, using criteria established by Reitan and Wolfson (1993). In addition, one-half of the sample obtained impaired scores on one or two tests. These results are consistent with what the binomial model predicted. The model would therefore serve as a useful resource for clinicians when considering the probability of impaired test performance.     

Changes in the subcellular distribution of NADPH oxidase subunit p47phox in dendrites of rat dorsomedial nucleus tractus solitarius neurons in response to chronic administration of hypertensive agents

NADPH oxidase-generated superoxide can modulate crucial intracellular signaling cascades in neurons of the nucleus tractus solitarius (NTS), a brain region that plays an important role in cardiovascular processes. Modulation of NTS signaling by superoxide may be linked to the subcellular location of the mobile NADPH oxidase p47(phox) subunit, which is known to be present in dendrites of NTS neurons. It is not known, however, if hypertension can produce changes in the trafficking of p47(phox) in defined NTS subregions, particularly the preferentially barosensitive dorsomedial NTS (dmNTS), or preferentially gastrointestinal medial NTS (mNTS). We used immunogold electron microscopy to determine if p47(phox) localization was differentially affected in dendritic profiles of neurons from these NTS subregions of the rat in response to distinct models of hypertension, namely chronic 7-day subcutaneous administration of angiotensin II (AngII), or phenylephrine. In small (<1 microm) dendritic processes, both AngII and phenylephrine produced a decrease in intracellular p47(phox) labeling selectively in dmNTS neurons. In intermediate-size (1-2 microm) dendritic profiles in the dmNTS region only, there was an increase in p47(phox) labeling in response to each hypertensive agent, although these changes occurred in different subcellular compartments. There was an increase in non-vesicular labeling in response to AngII, but an increase in surface labeling with phenylephrine. Moreover, each of the changes in p47(phox) targeting mentioned above occurred in dendritic profiles with, or without immunoperoxidase labeling for the AngII AT-1A receptor subtype (AT-1A). These results indicate that chronic administration of agents that induce hypertension can also produce changes in the subcellular localization in p47(phox) in dmNTS neurons. Thus, systemic hypertension may produce alterations in the trafficking of proteins associated with superoxide production in central autonomic neurons, thus revealing a potentially important neurogenic component of free radical production and systemic blood pressure elevation.     

Alterations in QT dispersion in the surface electrocardiogram of female adolescents diagnosed with restricting-type anorexia nervosa

OBJECTIVE: QT dispersion (QTd), defined as the difference between the longest interval and the shortest interval in the 12-lead electrocardiogram (ECG), is a measure of myocardial repolarization inhomogeneity. We assessed QTd in malnourished anorexia nervosa (AN) inpatients and following weight restoration. METHODS: QTd analysis, anthropometric evaluations, and laboratory tests were carried out in 30 malnourished female adolescent AN restricting-type (AN-R) inpatients and following weight restoration. RESULTS: A significant increase was found in weight/height ratio and body mass index from malnourished stage to weight restoration, paralleled by a significant decrease in QTd (70+/-16 vs. 47+/-16 ms; P<.0001). No correlations were found between ECG indices and anthropometric and laboratory measures. CONCLUSION: Elevated QTd in malnourished AN-R inpatients may indicate possible cardiac autonomic imbalance and/or myocardial damage, likely corrected following weight restoration.