Allergic reactions following contrast material administration: nomenclature, classification, and mechanisms

In forensic pathology routine, fatal cases of contrast agent exposure can be occasionally encountered. In such situations, beyond the difficulties inherent in establishing the cause of death due to nonspecific or absent autopsy and histology findings as well as limited laboratory investigations, pathologists may face other problems in formulating exhaustive, complete reports, and conclusions that are scientifically accurate. Indeed, terminology concerning adverse drug reactions and allergy nomenclature is confusing. Some terms, still utilized in forensic and radiological reports, are outdated and should be avoided. Additionally, not all forensic pathologists master contrast material classification and pathogenesis of contrast agent reactions. We present a review of the literature covering allergic reactions to contrast material exposure in order to update used terminology, explain the pathophysiology, and list currently available laboratory investigations for diagnosis in the forensic setting.

Transition from hemifusion to pore opening is rate limiting for vacuole membrane fusion.

Fusion pore opening and expansion are considered the most energy-demanding steps in viral fusion. Whether this also applies to soluble N-ethyl-maleimide sensitive fusion protein attachment protein receptor (SNARE)- and Rab-dependent fusion events has been unknown. We have addressed the problem by characterizing the effects of lysophosphatidylcholine (LPC) and other late-stage inhibitors on lipid mixing and pore opening during vacuole fusion. LPC inhibits fusion by inducing positive curvature in the bilayer and changing its biophysical properties. The LPC block reversibly prevented formation of the hemifusion intermediate that allows lipid, but not content, mixing. Transition from hemifusion to pore opening was sensitive to guanosine-5'-(gamma-thio)triphosphate. It required the vacuolar adenosine triphosphatase V0 sector and coincided with its transformation. Pore opening was rate limiting for the reaction. As with viral fusion, opening the fusion pore may be the most energy-demanding step for intracellular, SNARE-dependent fusion reactions, suggesting that fundamental aspects of lipid mixing and pore opening are related for both systems.

Estrogen-dependent in vitro transcription from the vitellogenin promoter in liver nuclear extracts.

One approach to analyzing the molecular mechanisms of gene expression in vivo is to reconstitute these events in cell-free systems in vitro. Although there is some evidence for tissue-specific transcription in vitro, transcriptionally active extracts that mimic a steroid hormone-dependent enhancement of transcription have not been described. In the study reported here, nuclear extracts of liver from the frog Xenopus laevis were capable of estrogen-dependent induction of a homologous vitellogenin promoter that contained the estrogen-responsive element.

Peroxisome proliferator-activated receptors: a nuclear receptor signaling pathway in lipid physiology.

Peroxisome proliferator-activated receptors (PPARs) are lipid-activated transcription factors that belong to the steroid/thyroid/retinoic acid receptor superfamily. All their characterized target genes encode proteins that participate in lipid homeostasis. The recent finding that antidiabetic thiazolidinediones and adipogenic prostanoids are ligands of one of the PPARs reveals a novel signaling pathway that directly links these compounds to processes involved in glucose homeostasis and lipid metabolism including adipocyte differentiation. A detailed understanding of this pathway could designate PPARs as targets for the development of novel efficient treatments for several metabolic disorders.

Proton NMR of (15)N-choline metabolites enhanced by dynamic nuclear polarization.

Chemical shifts of protons can report on metabolic transformations such as the conversion of choline to phosphocholine. To follow such processes in vivo, magnetization can be enhanced by dynamic nuclear polarization (DNP). We have hyperpolarized in this manner nitrogen-15 spins in (15)N-labeled choline up to 3.3% by irradiating the 94 GHz electron spin resonance of admixed TEMPO nitroxide radicals in a magnetic field of 3.35 T during ca. 3 h at 1.2 K. The sample was subsequently transferred to a high-resolution magnet, and the enhanced polarization was converted from (15)N to methyl- and methylene protons, using the small (2,3)J((1)H,(15)N) couplings in choline. The room-temperature lifetime of nitrogen polarization in choline, T(1)((15)N) approximately 200 s, could be considerably increased by partial deuteration of the molecule. This procedure enables studies of choline metabolites in vitro and in vivo using DNP-enhanced proton NMR.

Nuclear factor I-C regulates TGF-{beta}-dependent hair follicle cycling.

Skin appendages such as teeth and hair share several common signaling pathways. The nuclear factor I C (NFI-C) transcription factor has been implicated in tooth development, but a potential role in hair growth had not been assessed. In this study we found that NFI-C regulates the onset of the hair growth cycle. NFI-C(-/-) mice were delayed in the transition from the telogen to anagen phase of the hair follicle cycle after either experimental depilation or spontaneous hair loss. Lack of NFI-C resulted in delayed induction of the sonic hedgehog, Wnt5a, and Lef1 gene expression, which are key regulators of the hair follicle growth initiation. NFI-C(-/-) mice also showed elevated levels of transforming growth factor β1 (TGF-β1), an inhibitor of keratinocyte proliferation, and of the cell cycle inhibitor p21 at telogen. Reduced expression of Ki67, a marker of cell proliferation, was noted at the onset of anagen, indicating impaired activation of the hair progenitor cells. These findings implicate NFI-C in the repression of TGF-β1 signaling during telogen stage, resulting in the delay of progenitor cell proliferation and hair follicle regeneration in NFI-C-deficient mice. Taken together with prior observations, these findings also designate NFI-C as a regulator of adult progenitor cell proliferation and of postnatal tissue growth or regeneration.

A nuclear factor I-like activity and a liver-specific repressor govern estrogen-regulated in vitro transcription from the Xenopus laevis vitellogenin B1 promoter.

A hormone-controlled in vitro transcription system derived from Xenopus liver nuclear extracts was exploited to identify novel cis-acting elements within the vitellogenin gene B1 promoter region. In addition to the already well-documented estrogen-responsive element (ERE), two elements were found within the 140 base pairs upstream of the transcription initiation site. One of them, a negative regulatory element, is responsible for the lack of promoter activity in the absence of the hormone and, as demonstrated by DNA-binding assays, interacts with a liver-specific transcription factor. The second is required in association with the estrogen-responsive element to mediate hormonal induction and is recognized by the Xenopus liver homolog of nuclear factor I.

Chemical probes that differentially modulate peroxisome proliferator-activated receptor alpha and BLTR, nuclear and cell surface receptors for leukotriene B(4).

Peroxisome proliferator-activated receptor alpha (PPARalpha)is a nuclear receptor for various fatty acids, eicosanoids, and hypolipidemic drugs. In the presence of ligand, this transcription factor increases expression of target genes that are primarily associated with lipid homeostasis. We have previously reported PPARalpha as a nuclear receptor of the inflammatory mediator leukotriene B(4) (LTB(4)) and demonstrated an anti-inflammatory function for PPARalpha in vivo (Devchand, P. R., Keller, H., Peters, J. M., Vazquez, M., Gonzalez, F. J., and Wahli, W. (1996) Nature 384, 39-43). LTB(4) also has a cell surface receptor (BLTR) that mediates proinflammatory events, such as chemotaxis and chemokinesis (Yokomizo, T., Izumi, T., Chang, K., Takuwa, Y., and Shimizu, T. (1997) Nature 387, 620-624). In this study, we report on chemical probes that differentially modulate activity of these two LTB(4) receptors. The compounds selected were originally characterized as synthetic BLTR effectors, both agonists and antagonists. Here, we evaluate the compounds as effectors of the three PPAR isotypes (alpha, beta, and gamma) by transient transfection assays and also determine whether the compounds are ligands for these nuclear receptors by coactivator-dependent receptor ligand interaction assay, a semifunctional in vitro assay. Because the compounds are PPARalpha selective, we further analyze their potency in a biological assay for the PPARalpha-mediated activity of lipid accumulation. These chemical probes will prove invaluable in dissecting processes that involve nuclear and cell surface LTB(4) receptors and also aid in drug discovery programs.

Integrating nuclear receptor mobility in models of gene regulation.

The mode of action of nuclear receptors in living cells is an actively investigated field but much remains hypothetical due to the lack, until recently, of methods allowing the assessment of molecular mechanisms in vivo. However, these last years, the development of fluorescence microscopy methods has allowed initiating the dissection of the molecular mechanisms underlying gene regulation by nuclear receptors directly in living cells or organisms. Following our analyses on peroxisome proliferator activated receptors (PPARs) in living cells, we discuss here the different models arising from the use of these tools, that attempt to link mobility, DNA binding or chromatin interaction, and transcriptional activity.

Phylogenetics of Olea (Oleaceae) based on plastid and nuclear ribosomal DNA sequences: tertiary climatic shifts and lineage differentiation times.

BACKGROUND AND AIMS: The genus Olea (Oleaceae) includes approx. 40 taxa of evergreen shrubs and trees classified in three subgenera, Olea, Paniculatae and Tetrapilus, the first of which has two sections (Olea and Ligustroides). Olive trees (the O. europaea complex) have been the subject of intensive research, whereas little is known about the phylogenetic relationships among the other species. To clarify the biogeographical history of this group, a molecular analysis of Olea and related genera of Oleaceae is thus necessary. METHODS: A phylogeny was built of Olea and related genera based on sequences of the nuclear ribosomal internal transcribed spacer-1 and four plastid regions. Lineage divergence and the evolution of abaxial peltate scales, the latter character linked to drought adaptation, were dated using a Bayesian method. KEY RESULTS: Olea is polyphyletic, with O. ambrensis and subgenus Tetrapilus not sharing a most recent common ancestor with the main Olea clade. Partial incongruence between nuclear and plastid phylogenetic reconstructions suggests a reticulation process in the evolution of subgenus Olea. Estimates of divergence times for major groups of Olea during the Tertiary were obtained. CONCLUSIONS: This study indicates the necessity of revising current taxonomic boundaries in Olea. The results also suggest that main lines of evolution were promoted by major Tertiary climatic shifts: (1) the split between subgenera Olea and Paniculatae appears to have taken place at the Miocene-Oligocene boundary; (2) the separation of sections Ligustroides and Olea may have occurred during the Early Miocene following the Mi-1 glaciation; and (3) the diversification within these sections (and the origin of dense abaxial indumentum in section Olea) was concomitant with the aridification of Africa in the Late Miocene.

A high-efficiency HeLa cell nuclear transcription extract.

A HeLa cell nuclear transcription extract that is approximately 20 times more efficient than standard HeLa cell transcription extracts was developed. Transcription of the strong adenovirus II major late promoter by this extract results in the synthesis of 1.5-4 molecules of product RNA per molecule of template, indicating that the extract is capable of multiple rounds of initiation. Standard HeLa cell nuclear extracts transcribe closed circular and linear adenovirus major late promoter templates with equal efficiency. In contrast, the new extract exhibits an increase of approximately twofold on transcription of a closed circular, as opposed to a linear, major late promoter template.

Intravitreous injection of PLGA microspheres encapsulating GDNF promotes the survival of photoreceptors in the rd1/rd1 mouse.

PURPOSE: To evaluate the potential delay of the retinal degeneration in rd1/rd1 mice using recombinant human glial cell line-derived neurotrophic factor (rhGDNF) encapsulated in poly(D,L-lactide-co-glycolide) (PLGA) microspheres. METHODS: rhGDNF-loaded PLGA microspheres were prepared using a water in oil in water (w/o/w) emulsion solvent extraction-evaporation process. In vitro, the rhGDNF release profile was assessed using radiolabeled factor. In vivo, rhGDNF microspheres, blank microspheres, or microspheres loaded with inactivated rhGDNF were injected into the vitreous of rd1/rd1 mice at postnatal day 11 (PN11). The extent of retinal degeneration was examined at PN28 using rhodopsin immunohistochemistry on whole flat-mount retinas, outer nuclear layer (ONL) cell counting on histology sections, and electroretinogram tracings. Immunohistochemical reactions for glial fibrillary acidic protein (GFAP), F4/80, and rhodopsin were performed on cryosections. RESULTS: Significant delay of rod photoreceptors degeneration was observed in mice receiving the rhGDNF-loaded microspheres compared to either untreated mice or to mice receiving blank or inactivated rhGDNF microspheres. The degeneration delay in the eyes receiving the rhGDNF microspheres was illustrated by the increased rhodopsin positive signals, the preservation of significantly higher number of cell nuclei within the ONL, and significant b-wave increase. A reduction of the subretinal glial proliferation was also observed in these treated eyes. No significant intraocular inflammatory reaction was observed after the intravitreous injection of the various microspheres. CONCLUSIONS: A single intravitreous injection of rhGDNF-loaded microspheres slows the retinal degeneration processes in rd1/rd1 mice. The use of injectable, biodegradable polymeric systems in the vitreous enables the efficient delivery of therapeutic proteins for the treatment of retinal diseases.

Changes in nuclear 3,5,3'-triiodothyronine receptor expression in rat dorsal root ganglia and sciatic nerve during development: comparison with regeneration.

The action of the thyroid hormones on responsive cells in the peripheral nervous system requires the presence of nuclear triiodothyronine receptors (NT3R). These nuclear receptors, including both the alpha and beta subtypes of NT3R, were visualized by immunocytochemistry with the specific 2B3 monoclonal antibody. In the dorsal root ganglia (DRG) of rat embryos, NT3R immunoreactivity was first discretely revealed in a few neurons at embryonic day 14 (E14), then strongly expressed by all neurons at E17 and during the first postnatal week; all DRG neurons continued to possess clear NT3R immunostaining, which faded slightly with age. The peripheral glial cells in the DRG displayed a short-lived NT3R immunoreaction, starting at E17 and disappearing from the satellite and Schwann cells by postnatal days 3 and 7 respectively. In the developing sciatic nerve, Schwann cells also exhibited transient NT3R immunoreactivity restricted to a short period ranging from E17 to postnatal day 10; the NT3R immunostaining of the Schwann cells vanished proximodistally along the sciatic nerve, so that the Schwann cells rapidly became free of detectable NT3R immunostaining. However, after the transection or crushing of an adult sciatic nerve, the NT3R immunoreactivity reappeared in the Schwann cells adjacent to the lesion by 2 days, then along the distal segment in which the axons were degenerating, and finally disappeared by 45 days, when the regenerating axons were allowed to re-occupy the distal segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Monte Carlo simulation of a clearance box monitor used for nuclear power plant decommissioning.

When decommissioning a nuclear facility it is important to be able to estimate activity levels of potentially radioactive samples and compare with clearance values defined by regulatory authorities. This paper presents a method of calibrating a clearance box monitor based on practical experimental measurements and Monte Carlo simulations. Adjusting the simulation for experimental data obtained using a simple point source permits the computation of absolute calibration factors for more complex geometries with an accuracy of a bit more than 20%. The uncertainty of the calibration factor can be improved to about 10% when the simulation is used relatively, in direct comparison with a measurement performed in the same geometry but with another nuclide. The simulation can also be used to validate the experimental calibration procedure when the sample is supposed to be homogeneous but the calibration factor is derived from a plate phantom. For more realistic geometries, like a small gravel dumpster, Monte Carlo simulation shows that the calibration factor obtained with a larger homogeneous phantom is correct within about 20%, if sample density is taken as the influencing parameter. Finally, simulation can be used to estimate the effect of a contamination hotspot. The research supporting this paper shows that activity could be largely underestimated in the event of a centrally-located hotspot and overestimated for a peripherally-located hotspot if the sample is assumed to be homogeneously contaminated. This demonstrates the usefulness of being able to complement experimental methods with Monte Carlo simulations in order to estimate calibration factors that cannot be directly measured because of a lack of available material or specific geometries.