False positives in plasma ammonia measurement and their clinical impact in a pediatric population

OBJECTIVE: Plasma ammonia measurement is greatly influenced by pre-analytical conditions, which may lead to false positives. We wanted to evaluate the prevalence and clinical impact of plasma ammonia false positives in a pediatric population. DESIGN AND METHODS: Over a 28-month period, charts of patients with elevated ammonemia were retrospectively reviewed to identify false positives defined as elevated concentrations that subsequently normalized without plausible explanation for the elevations. RESULTS: 1880 Ammonia measurements were available in 479 patients. Elevated results that subsequently normalized were found in 86 patients. Forty-one (48%) of these patients had most likely falsely elevated ammonemia. Additional blood sampling and laboratory testing were the most frequent consequences of false positives. CONCLUSION: There is a high proportion of false positives among elevated plasma ammonia measurements. Capillary samples and delay between sampling and centrifugation are possible contributing factors. Clinical consequences of false positives were most often limited.     

Left atrial size,pressure, and v wave height in patients with isolated,severe, pure mitral regurgitation

In recent years, some concepts regarding the etiology and hemodynamics present in the syndrome of mitral regurgitation have changed. Coronary artery disease and mitral valve prolapse have replaced rheumatic heart disease as the most frequent cause of mitral regurgitation. Hemodynamic studies have shown that tall V waves in the pulmonary capillary wedge tracings are neither specific nor sensitive in detecting the presence of mitral regurgitation. In this study, we evaluated the role of various clinical, echocardiographic, and hemodynamic findings with regard to left atrial (LA) size, pressure, and V wave height. We found that the mean pulmonary capillary wedge pressure (PCW) and V wave height for the subset of patients with acute mitral regurgitation (PCW = 24.1 ± 10.9; V = 41.2 ± 20.7 mm Hg) was similar to the subset with chronic mitral regurgitation (PCW = 17.9 ± 7.5; V = 32.0 ± 18.2 mm Hg). In addition, we found that there was a significant logarithmic relationship between the LA size and the duration of the mitral regurgitation (y = 1.404 [log X] + 3.948; R = 0.678; p < 0.0005). Lastly, we found that LA size, compliance, regurgitant volume, and regurgitant valve orifice area all increase with time.     

Maturation of the hippocampal formation and amygdala in Macaca mulatta: A volumetric magnetic resonance imaging study

Malformations of the hippocampal formation and amygdala have been implicated in several neurodevelopmental disorders; yet relatively little is known about their normal structural development. The purpose of this study was to characterize the early developmental trajectories of the hippocampus and amygdala in the rhesus macaques (Macaca mulatta) using noninvasive MRI techniques. T1‐weighted structural scans of 22 infant and juvenile monkeys (11 male, 11 female) were obtained between 1 week and approximately 2 yrs of age. Ten animals (five males, five females) were scanned multiple times and 12 monkeys (six males, six females) were scanned once between 1 and 4 weeks of age. Both structures exhibited significant age‐related changes throughout the first 2 yrs of life that were not explained by overall brain development. The hippocampal formation increased 117.05% in males and 110.86% in females. No sex differences were evident, but the left hemisphere was significantly larger than the right. The amygdala increased 86.49% in males and 72.94% in females with males exhibiting a larger right than left amygdala. For both structures, the most substantial volumetric increases were seen within the first month, but the hippocampal formation appeared to develop more slowly than the amygdala with the rate of hippocampal maturation stabilizing around 11 months and that of amygdala maturation stabilizing around 8 months. Differences in volumetric developmental trajectories of the hippocampal formation and amygdala largely mirror differences in the timing of the functional development of these structures. The current results emphasize the importance of including early postnatal ages when assessing developmental trajectories of neuroanatomical structures and reinforces the utility of nonhuman primates in the assessment of normal developmental patterns. © 2009 Wiley‐Liss, Inc.     

A comparative transmission electron microscopy study of titanium dioxide and carbon black nanoparticles uptake in human lung epithelial and fibroblast cell lines

Several studies suggest that the biological responses induced by manufactured nanoparticles (MNPs) may be linked to their accumulation within cells. However, MNP internalisation has not yet been sufficiently characterised. Therefore, the aim of this study was to compare the intracellular uptake of three different MNPs: two made of carbon black (CB) and one made of titanium dioxide (TiO(2)), in 16HBE bronchial epithelial cells and MRC5 fibroblasts. Transmission electron microscopy was used to evaluate the intracellular accumulation. Different parameters were analysed following a time and dose-relationship: localisation of MNPs in cells, percentage of cells having accumulated MNPs, number of aggregated MNPs in cells, and the size of MNP aggregates in cells. The results showed that MNPs were widely and rapidly accumulated in 16HBE cells and MRC5 fibroblasts. Moreover, MNPs accumulated chiefly as aggregates in cytosolic vesicles and were absent from the mitochondria or nuclei. CB and TiO(2) MNPs had similar accumulation patterns. However, TiO(2) aggregates had a higher size than CB aggregates. Intracellular MNP accumulation was dissociated from cytotoxicity. These results suggest that cellular uptake of MNPs is a common phenomenon occurring in various cell types.     

Phenotypic characterization and functional analysis of human tumor immune infiltration after mechanical and enzymatic disaggregation

Multi-parametric flow cytometry analysis is a reliable method for phenotypic and functional characterization of tumor infiltrating immune cells (TIIC). The isolation of infiltrating leukocytes from solid tumors can be achieved through various methods which can be both enzymatic and mechanical; however, these methods may alter cell biology. The aim of this study was to compare the effects of three tissue disaggregation techniques on TIIC biology in breast, kidney and lung tumor specimens. We therefore compared two enzymatic treatments using either collagenase type IA alone or in combination with collagenase type IV and DNase I type II, and one mechanical system (Medimachine?). We evaluated the impact of treatments on cell viability, surface marker integrity and proliferative capacity. We show that cell viability was not significantly altered by treatments. However, enzymatic treatments decreased cell proliferation; specifically collagenases and DNase provoked a significant decrease in detection of surface markers such as CD4, CD8, CD45RA and CD14, indicating that results of phenotypic studies employing these techniques could be affected. In conclusion, mechanical tissue disaggregation by Medimachine? appears to be optimal to maintain phenotypic and functional TIIC features.     

Perilipin deficiency and autosomal dominant partial lipodystrophy

Perilipin is the most abundant adipocyte-specific protein that coats lipid droplets, and it is required for optimal lipid incorporation and release from the droplet. We identified two heterozygous frameshift mutations in the perilipin gene (PLIN1) in three families with partial lipodystrophy, severe dyslipidemia, and insulin-resistant diabetes. Subcutaneous fat from the patients was characterized by smaller-than-normal adipocytes, macrophage infiltration, and fibrosis. In contrast to wild-type perilipin, mutant forms of the protein failed to increase triglyceride accumulation when expressed heterologously in preadipocytes. These findings define a novel dominant form of inherited lipodystrophy and highlight the serious metabolic consequences of a primary defect in the formation of lipid droplets in adipose tissue.     

Estimation of urinary stone composition by automated processing of CT images

The objective of this article was developing an automated tool for routine clinical practice to estimate urinary stone composition from CT images based on the density of all constituent voxels. A total of 118 stones for which the composition had been determined by infrared spectroscopy were placed in a helical CT scanner. A standard acquisition, low-dose and high-dose acquisitions were performed. All voxels constituting each stone were automatically selected. A dissimilarity index evaluating variations of density around each voxel was created in order to minimize partial volume effects: stone composition was established on the basis of voxel density of homogeneous zones. Stone composition was determined in 52% of cases. Sensitivities for each compound were: uric acid: 65%, struvite: 19%, cystine: 78%, carbapatite: 33.5%, calcium oxalate dihydrate: 57%, calcium oxalate monohydrate: 66.5%, brushite: 75%. Low-dose acquisition did not lower the performances (P < 0.05). This entirely automated approach eliminates manual intervention on the images by the radiologist while providing identical performances including for low-dose protocols.     

Anti-Nogo-A antibody treatment enhances sprouting of corticospinal axons rostral to a unilateral cervical spinal cord lesion in adult macaque monkey

After injury, regrowth of axons in mammalian adult central nervous system is highly limited. However, in monkeys subjected to unilateral cervical lesion (C7-C8 level), neutralization of an important neurite outgrowth inhibitor, Nogo-A, stimulated axonal sprouting caudal to the lesion, accompanied by enhanced functional recovery of manual dexterity, compared with lesioned monkeys treated with a control antibody (Freund et al. [2006] Nat. Med. 12:790-792). The present study aimed at comparing the same two groups of monkeys for axonal sprouting rostral to the cervical lesion. The corticospinal tract was labeled by injecting the anterograde tracer biotinylated dextran amine into the contralesional motor cortex. The corticospinal axons were interrupted at the level of the lesion, accompanied by retrograde axonal degeneration (axon dieback), reflected by the presence of terminal retraction bulbs. The number of terminal retraction bulbs was lower in anti-Nogo-A antibody treated monkeys, and, when present, they were found closer to the lesion than in control-antibody treated monkeys. Compared with control antibody treated monkeys, the anti-Nogo-A antibody treated monkeys exhibited an increased cumulated axon arbor length and a higher number of axon arbors going in the medial direction from the white to the gray matter. Higher in the cervical cord (at C5 level), the anti-Nogo-A treatment enhanced the number of corticospinal fibers crossing the midline, suggesting axonal sprouting. Thus, the anti-Nogo-A antibody treatment enhanced axonal sprouting rostral to the cervical lesion; some of these fibers grew around the lesion and into the caudal spinal segments. These processes paralleled the observed improved functional recovery.