This report describes hemochromatosis associated with chronic parenteral iron dextran administration in 2 female olive baboons (Papio anubis). These baboons were enrolled on an experimental protocol ...that induced and maintained anemia by periodic phlebotomy for use in studying
potential treatments for sickle cell anemia. The 2 baboons both presented with clinical signs consistent with iron overload, including decreased appetite, weight loss, elevated liver enzymes, and hepatosplenomegaly. Histopathologic findings supported a morphologic diagnosis of systemic hemosiderosis,
as evidenced by the overwhelming presence of iron in the reticuloendothelial system and liver after the application of Prussian blue stain. This finding, combined with the clinical presentation, lead to a final diagnosis of hemochromatosis. This case report suggests that providing anemic patients
with chronic parenteral iron supplementation in the absence of iron deficiency can result in iatrogenic iron overload and subsequent systemic toxicity. Furthermore, these subjects may present with hemochromatosis and its associated clinical signs many years after cessation of iron supplementation.
The intestinal microbiota is the largest source of microbial stimulation that exerts both harmful and beneficial effects on human health. The interaction between probiotic and enterocytes is the ...initiating event in immunomodulation and merits particular attention. The effects of probiotic is strain dependent and for each new probiotic strain, profiles of cytokines secreted by lymphocytes, enterocytes or dendritic cells that come in contact with the strain should be systematically established. To evaluate the effects of probiotics on the immune system, models that mimic the mucosa, and thus the physiological reality, should be preferred whenever it is possible. Then, the in vitro observed effects should be backed up by properly conducted randomized double bind clinical studies. More detailed studies are needed to determine the precise action mode of probiotics on both mucosal and systemic immunity.
A method is proposed to improve the numerical dispersion characteristics for simulations of the scalar wave equation in 3D using the FDTD method. The improvements are realized by choosing a ...face-centered-cubic (FCC) grid instead of the typical Cartesian (Yee) grid, which exhibits non-physical distortions of the wavefront due to the FD stencil. FCC grids are the logical extension of hexagonal grids in 2D, and have been shown previously to provide optimal sampling of space based on close packing of spheres (highest density). The difference equations are developed for the wave equation on this alternative grid, and the dispersion relationship and stability for grids of equal and non-equal aspect ratios are derived. A comparison is made between FCC and Cartesian formulations, based upon having an equal volume density of gridpoints in each method (i.e. the computational storage requirements of each method would be the same for the same simulated space). The comparison shows that the FCC grid exhibits a much more isotropic dispersion relation than the Cartesian grid of equivalent density. Furthermore, for an equivalent density, the FCC method has a more relaxed stability criterion by a factor of approximately 1.35, resulting in a further reduction in computational resources.
The ability to predict accumulation levels of sediment‐sorbed hydrophobic organic contaminants (HOCs) by depositfeeding organisms based on sediment concentrations is limited in part by an incomplete ...understanding of the chemistry that controls assimilation efficiency. This study was designed to test the hypothesis that desorption is an important process that controls the bioavailability of HOCs to deposit‐feeding organisms; we planned to do so by conducting desorption and bioavailability experiments with field‐contaminated sediments collected from New York Harbor, New York, USA. Three classes of organic contaminants, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and linear alkylbenzenes (LABs) were studied. In order to address the effects of contaminant aging, we compared the contaminant desorption rates from sediments collected from surface and at depth in an area of known high‐sediment accumulation to retarded intraparticle model predictions. Measured desorption rates of the LABs and the most hydrophobic PCBs compare well with model predictions. However, the PAH and less hydrophobic PCB desorption rates range from one to four orders of magnitude slower than model predictions. We postulate that these compounds are present in a resistant sedimentary phase and may represent only a small fraction of what was originally sorbed. The fraction of PCBs, PAHs, and LABs desorbed after 48 h correlate well with measured biota‐sediment factors (BSFs) in Yoldia limatula that were exposed to the same sediments, indicating that desorption rate‐limited assimilation. Several studies have related field BSFs with log Kow and have observed a maximum at intermediate Kows (∼6.0‐6.5). This maximum may be due to predictably slow desorption of high‐Kow compounds and may be lower than predicted rates and extent of desorption of the low‐Kow compounds because of association with resistant phases.
Solubilization of sediment-bound hydrophobic contaminants (HOCs) by gut fluids of deposit-feeding polychaetes greatly exceeds solubilization by seawater. We present evidence that digestive ...surfactants exert a central role in HOC desorption, and that the degree ofin vitrosolubilization by gut fluids is an excellent predictor of HOC absorption efficiency (AE) by the respective worm species. We comparedin vitrosolubilization of sediment-bound14C-hexachlorobenzene (HCB) and14C-tetrachlorobiphenyl (TCBP) by gut fluids of 2 deposit-feeding polychaete species,Nereis(Neanthes)succineaandPectinaria(Cistenides)gouldii, to AEs measured in live worms by pulse-chase methodology.N. succineadesorbed 72% HCB and 79% TCBPin vitro(during 6 h incubations), and absorbed both compounds with 73% efficiency, whileP. gouldiidesorbed only 37% HCB in 6 h, and analogously absorbed only 37% HCB. Higher desorption and absorption efficiencies ofN. succineawere accompanied by greater gut-fluid surfactancy and higher micelle concentration (determined by drop contact angle) compared toP. gouldii. Calibration of desorption efficiencies with a synthetic surfactant, sodium dodecyl sulfate (SDS), showed thatN. succineagut fluid desorbed a similar amount of HOC as a 1% (ca 3.5 mM) SDS solution, whereasP. gouldiigut fluid was equivalent to a 0.25% (ca 0.9 mM) SDS solution. Detailed analysis of the kinetics of HOC desorption (after 1, 45 and 360 min) showed that gut fluids from both polychaetes desorbed more than two-thirds of the bioavailable HOC within the first minute, suggesting that digestive desorption occurs rapidly and that gut-residence time has only minor influence on the degree of desorption or absorption of sediment-bound HOCs.
Purpose:
Factor analysis has been pursued as a means to decompose dynamic cardiac PET images into different tissue types based on their unique temporal signatures to improve quantification of ...physiological function. In this work, the authors present a novel kinetic model-based (MB) method that includes physiological models of factor relationships within the decomposition process. The physiological accuracy of MB decomposed
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cardiac PET images is evaluated using simulated and experimental data. Precision of myocardial blood flow (MBF) measurement is also evaluated.
Methods:
A gamma-variate model was used to describe the transport of
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in arterial blood from the right to left ventricle, and a one-compartment model to describe the exchange between blood and myocardium. Simulations of canine and rat heart imaging were performed to evaluate parameter estimation errors. Arterial blood sampling in rats and
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11
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blood pool imaging in dogs were used to evaluate factor and structure accuracy. Variable infusion duration studies in canine were used to evaluate MB structure and global MBF reproducibility. All results were compared to a previously published minimal structure overlap (MSO) method.
Results:
Canine heart simulations demonstrated that MB has lower root-mean-square error (RMSE) than MSO for both factor (0.2% vs 0.5%,
p
<
0.001
MB vs MSO, respectively) and structure (3.0% vs 4.7%,
p
<
0.001
) estimations, as with rat heart simulations (factors: 0.2% vs 0.9%,
p
<
0.001
and structures: 3.0% vs 6.7%,
p
<
0.001
). MB blood factors compared to arterial blood samples in rats had lower RMSE than MSO (1.6% vs 2.2%,
p
=
0.025
). There was no difference in the RMSE of blood structures compared to a
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blood pool image in dogs (8.5% vs 8.8%,
p
=
0.23
). Myocardial structures were more reproducible with MB than with MSO (
RMSE
=
3.9
%
vs 6.2%,
p
<
0.001
), as were blood structures (
RMSE
=
4.9
%
vs 5.6%,
p
=
0.006
). Finally, MBF values tended to be more reproducible with MB compared to MSO (
CV
=
10
%
vs 18%,
p
=
0.16
). The execution time of MB was, on average, 2.4 times shorter than MSO
(
p
<
0.001
)
due to fewer free parameters.
Conclusions:
Kinetic model-based factor analysis can be used to provide physiologically accurate decomposition of
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dynamic PET images, and may improve the precision of MBF quantification.
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