Prevalence of aeroallergen sensitization and increased exhaled nitric oxide values in schoolchildren of different socioeconomic status

BACKGROUND

Screening for allergic diseases allows an early diagnosis to be made, thus reducing socioeconomic burden and enhancing quality of life. We determined the prevalence of elevated exhaled nitric oxide (eNO) levels and sensitization to common airborne allergens in schoolchildren from different socioeconomic backgrounds.

MATERIAL AND METHODS

The study population comprised 271 children (136 boys) aged between 8 and 12 years in whom we applied skin prick tests and determined eNO levels.

RESULTS

Thirty-five percent of the children were identified as atopic. There was a significantly higher prevalence of atopy in boys (43% vs. 27%). Among the children with a high socioeconomic status, 37% were atopic, compared with 30% of those with a low socioeconomic status. We observed a significantly lower prevalence of pollen sensitization in children of lower socioeconomic status (10% vs. 20%). In the atopic group, 51% had elevated eNO levels, while in the nonatopic group this value was 4%. The mean (SD) eNO level was 33.4 (26.6) ppb in the atopic group and 11.9 (6.4) ppb in the nonatopic group. No differences were found for eNO values in terms of gender or socioeconomic status.

CONCLUSIONS

Our results emphasize the high prevalence of atopy in our population and suggest that determination of eNO levels could help to provide an early diagnosis. We also observed the following: (a) a significant difference in mean eNO values between atopic and nonatopic children; (b) a significantly lower prevalence of pollen sensitization in children of lower socioeconomic status; and (c) a higher prevalence of atopy in boys.

Immediate hypersensitivity to penicillins with negative skin tests--the value of specific IgE

The determination of specific IgE in patients with history of penicillins hypersensitivity is simple, safe and widely available. The positive and negative predictive values of this determination, however, are not yet established. In order to evaluate them, we performed specific IgE determination and diagnostic drug challenges in a group of 22 patients with a clear history of immediate penicillins hypersensitivity but negative skin tests. In this sample, the positive and negative predictive values were 29% and 87%, respectively. This seems to indicate that a positive specific IgE is not enough to confirm the diagnosis, and further study is necessary.

Work up of patients with history of beta-lactam hypersensitivity

INTRODUCTION

Beta-lactam antibiotics are the most frequent cause of antibiotic hypersensitivity reactions. The study of all cases of suspected beta-lactam hypersensitivity is highly important, to avoid the use of less efficient or more expensive alternatives, for fear of a reaction.

MATERIALS AND METHODS

Sixty-seven consecutive patients with suspected beta-lactam hypersensitivity reactions were studied. Skin prick tests (SPT), intradermal tests (IDT) and specific IgE determination were performed. In non-immediate reactions, epicutaneous testing was also done. If all were negative, a drug challenge was performed.

RESULTS

Sixty-seven patients (54 female symbol), with a mean age + or - SD of 36.6 + or -19.3 years (4-78 years) were studied. The self-reported antibiotics were amoxicillin and amoxicillin/clavulanic acid in 30 (45%), penicillin in 24 (36%), cephalosporins in 11 (16%) and flucloxacillin in 2 (3%). SPT and IDT were positive in 6 patients (9%) and specific IgE in 11 (16%). Only one patient had both positive specific IgE and skin tests. Of the remaining 51 cases, 33 underwent a drug challenge with the culprit antibiotic, with a positive reaction in 2 (6%). In all positive cases and when a drug challenge with the suspected antibiotic was not indicated, a challenge with an alternative drug was done, all with negative results.

CONCLUSIONS

Of the 67 studied cases with history of beta-lactam hypersensitivity reactions, 18 (27%) were confirmed after testing. A combination of skin testing, specific IgE determination and drug challenge is necessary since none has sufficient sensitivity to be used alone.

Age-related reduction in microcolumnar structure correlates with cognitive decline in ventral but not dorsal area 46 of the rhesus monkey

The age-related decline in cognitive function that is observed in normal aging monkeys and humans occurs without significant loss of cortical neurons. This suggests that cognitive impairment results from subtle, sub-lethal changes in the cortex. Recently, changes in the structural coherence in mini- or microcolumns without loss of neurons have been linked to loss of function. Here we use a density map method to quantify microcolumnar structure in both banks of the sulcus principalis (prefrontal cortical area 46) of 16 (ventral) and 19 (dorsal) behaviorally tested female rhesus monkeys from 6 to 33 years of age. While total neuronal density does not change with age in either of these banks, there is a significant age-related reduction in the strength of microcolumns in both regions on the order of 40%. This likely reflects a subtle but definite loss of organization in the structure of the cortical microcolumn. The reduction in strength in ventral area 46 correlates with cognitive impairments in learning and memory while the reduction in dorsal area 46 does not. This result is congruent with published data attributing cognitive functions to ventral area 46 that are similar to our particular cognitive battery which does not optimally tap cognitive functions attributed to dorsal area 46. While the exact mechanisms underlying this loss of microcolumnar organization remain to be determined, it is plausible that they reflect age-related alterations in dendritic and/or axonal organization which alter connectivity and may contribute to age-related declines in cognitive performance.

Automated identification of neurons and their locations

Individual locations of many neuronal cell bodies (>10(4)) are needed to enable statistically significant measurements of spatial organization within the brain such as nearest-neighbour and microcolumnarity measurements. In this paper, we introduce an Automated Neuron Recognition Algorithm (ANRA) which obtains the (x, y) location of individual neurons within digitized images of Nissl-stained, 30 microm thick, frozen sections of the cerebral cortex of the Rhesus monkey. Identification of neurons within such Nissl-stained sections is inherently difficult due to the variability in neuron staining, the overlap of neurons, the presence of partial or damaged neurons at tissue surfaces, and the presence of non-neuron objects, such as glial cells, blood vessels, and random artefacts. To overcome these challenges and identify neurons, ANRA applies a combination of image segmentation and machine learning. The steps involve active contour segmentation to find outlines of potential neuron cell bodies followed by artificial neural network training using the segmentation properties (size, optical density, gyration, etc.) to distinguish between neuron and non-neuron segmentations. ANRA positively identifies 86 +/- 5% neurons with 15 +/- 8% error (mean +/- SD) on a wide range of Nissl-stained images, whereas semi-automatic methods obtain 80 +/- 7%/17 +/- 12%. A further advantage of ANRA is that it affords an unlimited increase in speed from semi-automatic methods, and is computationally efficient, with the ability to recognize approximately 100 neurons per minute using a standard personal computer. ANRA is amenable to analysis of huge photo-montages of Nissl-stained tissue, thereby opening the door to fast, efficient and quantitative analysis of vast stores of archival material that exist in laboratories and research collections around the world.

Role of electrostatic interactions in amyloid beta-protein (A beta) oligomer formation: a discrete molecular dynamics study

Pathological folding and oligomer formation of the amyloid beta-protein (A beta) are widely perceived as central to Alzheimer's disease. Experimental approaches to study A beta self-assembly provide limited information because most relevant aggregates are quasi-stable and inhomogeneous. We apply a discrete molecular dynamics approach combined with a four-bead protein model to study oligomer formation of A beta. We address the differences between the two most common A beta alloforms, A beta 40 and A beta 42, which oligomerize differently in vitro. Our previous study showed that, despite simplifications, our discrete molecular dynamics approach accounts for the experimentally observed differences between A beta 40 and A beta 42 and yields structural predictions amenable to in vitro testing. Here we study how the presence of electrostatic interactions (EIs) between pairs of charged amino acids affects A beta 40 and A beta 42 oligomer formation. Our results indicate that EIs promote formation of larger oligomers in both A beta 40 and A beta 42. Both A beta 40 and A beta 42 display a peak at trimers/tetramers, but A beta 42 displays additional peaks at nonamers and tetradecamers. EIs thus shift the oligomer size distributions to larger oligomers. Nonetheless, the A beta 40 size distribution remains unimodal, whereas the A beta 42 distribution is trimodal, as observed experimentally. We show that structural differences between A beta 40 and A beta 42 that already appear in the monomer folding, are not affected by EIs. A beta 42 folded structure is characterized by a turn in the C-terminus that is not present in A beta 40. We show that the same C-terminal region is also responsible for the strongest intermolecular contacts in A beta 42 pentamers and larger oligomers. Our results suggest that this C-terminal region plays a key role in the formation of A beta 42 oligomers and the relative importance of this region increases in the presence of EIs. These results suggest that inhibitors targeting the C-terminal region of A beta 42 oligomers may be able to prevent oligomer formation or structurally modify the assemblies to reduce their toxicity.

Molecular dynamics simulation of amyloid beta dimer formation

Recent experiments with amyloid beta (Abeta) peptide indicate that formation of toxic oligomers may be an important contribution to the onset of Alzheimer's disease. The toxicity of Abeta oligomers depends on their structure, which is governed by assembly dynamics. Due to limitations of current experimental techniques, a detailed knowledge of oligomer structure at the atomic level is missing. We introduce a molecular dynamics approach to study Abeta dimer formation. 1), We use discrete molecular dynamics simulations of a coarse-grained model to identify a variety of dimer conformations; and 2), we employ all-atom molecular mechanics simulations to estimate thermodynamic stability of all dimer conformations. Our simulations of a coarse-grained Abeta peptide model predicts 10 different planar beta-strand dimer conformations. We then estimate the free energies of all dimer conformations in all-atom molecular mechanics simulations with explicit water. We compare the free energies of Abeta(1-42) and Abeta(1-40) dimers. We find that 1), dimer conformations have higher free energies compared to their corresponding monomeric states; and 2), the free-energy difference between the Abeta(1-42) and the corresponding Abeta(1-40) dimer conformation is not significant. Our results suggest that Abeta oligomerization is not accompanied by the formation of thermodynamically stable planar beta-strand dimers.

In silico study of amyloid beta-protein folding and oligomerization

Experimental findings suggest that oligomeric forms of the amyloid beta protein (Abeta) play a critical role in Alzheimer's disease. Thus, elucidating their structure and the mechanisms of their formation is critical for developing therapeutic agents. We use discrete molecular dynamics simulations and a four-bead protein model to study oligomerization of two predominant alloforms, Abeta40 and Abeta42, at the atomic level. The four-bead model incorporates backbone hydrogen-bond interactions and amino acid-specific interactions mediated through hydrophobic and hydrophilic elements of the side chains. During the simulations we observe monomer folding and aggregation of monomers into oligomers of variable sizes. Abeta40 forms significantly more dimers than Abeta42, whereas pentamers are significantly more abundant in Abeta42 relative to Abeta40. Structure analysis reveals a turn centered at Gly-37-Gly-38 that is present in a folded Abeta42 monomer but not in a folded Abeta40 monomer and is associated with the first contacts that form during monomer folding. Our results suggest that this turn plays an important role in Abeta42 pentamer formation. Abeta pentamers have a globular structure comprising hydrophobic residues within the pentamer's core and hydrophilic N-terminal residues at the surface of the pentamer. The N termini of Abeta40 pentamers are more spatially restricted than Abeta42 pentamers. Abeta40 pentamers form a beta-strand structure involving Ala-2-Phe-4, which is absent in Abeta42 pentamers. These structural differences imply a different degree of hydrophobic core exposure between pentamers of the two alloforms, with the hydrophobic core of the Abeta42 pentamer being more exposed and thus more prone to form larger oligomers.

Health-Related Quality of Life in HIV Patients Switching to Twice-Daily Indinavir/Ritonavir Regimen or Continuing with Three-Times-Daily Indinavir-Based Therapy

Objective

To evaluate health-related quality of life (HRQoL) changes in patients treated with indinavir three-times daily after switching to a twice-daily indinavir/ritonavir regimen or continuing with the same regimen.

Methods

Patients on HAART including indinavir three-times-daily with undetectable viral load were randomly assigned to continue with this therapy or to change to a twice-daily indinavir/ritonavir (800/100 mg) regimen. The Medical Outcomes Study HIV Health Survey (MOS-HIV) questionnaire was used as the HRQoL measure.

Results

A total of 118 patients participated in the study, of which 59 (50%) were randomly assigned to continue with the three-times-daily regimen. Patients had a mean age of 39 years and 80% of them were male. At baseline, subjects included in the three-times-daily group presented a significantly greater number of symptoms than subjects in the twice-daily group, but no statistically significant differences were observed in MOS-HIV scores between the groups. In the intention-to-treat (ITT) analysis, a reduction in HRQoL scores was observed in both groups, which was greater in the twice-daily group. In the per protocol analysis, reduction of HRQoL was minimal.

Conclusions

A HRQoL deterioration, greater in the twice-daily group, was observed in this study in the ITT analysis, while HRQoL remained stable in both groups in patients who continued with and tolerated the allocated regimen.

Discrete molecular dynamics simulations of peptide aggregation

We study the aggregation of peptides using the discrete molecular dynamics simulations. Specifically, at temperatures above the alpha-helix melting temperature of a single peptide, the model peptides aggregate into a multilayer parallel beta-sheet structure. This structure has an interstrand distance of 4.8 A and an intersheet distance of 10 A, which agree with experimental observations. Our model explains these results as follows: hydrogen-bond interactions give rise to the interstrand spacing in beta sheets, while Gō interactions between side chains make beta strands parallel to each other and allow beta sheets to pack into layers. An important feature of our results is that the aggregates contain free edges, which may allow for further aggregation of model peptides to form elongated fibrils.

Neuron recognition by parallel Potts segmentation

Identifying neurons and their spatial coordinates in images of the cerebral cortex is a necessary step in the quantitative analysis of spatial organization in the brain. This is especially important in the study of Alzheimer's disease (AD), in which spatial neuronal organization and relationships are highly disrupted because of neuronal loss. To automate neuron recognition by using high-resolution confocal microscope images from human brain tissue, we propose a recognition method based on statistical physics that consists of image preprocessing, parallel image segmentation, and cluster selection on the basis of shape, optical density, and size. We segment a preprocessed digital image into clusters by applying Monte Carlo simulations of a q-state inhomogeneous Potts model. We then select the range of Potts segmentation parameters to yield an ideal recognition of simplified objects in the test image. We apply our parallel segmentation method to control individuals and to AD patients and achieve recognition of 98% (for a control) and 93% (for an AD patient), with at most 3% false clusters.

Neurotoxic effects of thioflavin S-positive amyloid deposits in transgenic mice and Alzheimer's disease

Despite extensive deposition of putatively neurotoxic amyloid-beta (Abeta) protein in the brain, it has not been possible to demonstrate an association of Abeta deposits with neuronal loss in Alzheimer's disease (AD), and neuronal loss is minimal in transgenic mouse models of AD. Using triple immunostaining confocal microscopy and analyzing the images with the cross-correlation density map method from statistical physics, we directly compared Abeta deposition, Abeta morphology, and neuronal architecture. We found dramatic, focal neuronal toxicity associated primarily with thioflavin S-positive fibrillar Abeta deposits in both AD and PSAPP mice. These results, along with computer simulations, suggest that Abeta develops neurotoxic properties in vivo when it adopts a fibrillar beta-pleated sheet conformation.

Plaque-induced abnormalities in neurite geometry in transgenic models of Alzheimer disease: implications for neural system disruption

Neurites that pass through amyloid-beta deposits in Alzheimer disease (AD) undergo 3 changes: they develop phosphorylated tau immunoreactivity; the density of SMI-32-positive dendrites diminishes; and they also develop a marked alteration in their geometric features, changing from being nearly straight to being quite curvy. The extent to which the latter 2 phenomena are related to phosphorylated tau is unknown. We have now examined whether amyloid-beta deposits in APP695Sw transgenic mice, which have only rare phosphorylated tau containing neurites. develop these changes. We found that dendritic density is diminished within the boundaries of amyloid-beta plaques, with the greatest loss (about 80%, p < 0.001) within the boundaries of thioflavine S cores. Remaining dendrites within plaques develop substantial morphological alterations quantitatively similar to those seen in AD. A statistically significant but smaller degree of change in geometry was seen in the immediate vicinity around plaques, suggesting a propagation of cytoskeletal disruption from the center of the plaque outward. We examined the possible physiological consequences of this change in dendritic geometry using a standard cable-theory model. We found a predicted delay of several milliseconds in about one quarter of the dendrites passing through a thioflavine S plaque. These results are consistent with previous observations in AD, and suggest that thioflavine S-positive amyloid-beta deposits have a marked effect on dendritic microarchitecture in the cortex, even in the relative absence of phosphorylated tau alterations.

Description of microcolumnar ensembles in association cortex and their disruption in Alzheimer and Lewy body dementias

The cortex of the brain is organized into clear horizontal layers, laminae, which subserve much of the connectional anatomy of the brain. We hypothesize that there is also a vertical anatomical organization that might subserve local interactions of neuronal functional units, in accord with longstanding electrophysiological observations. We develop and apply a general quantitative method, inspired by analogous methods in condensed matter physics, to examine the anatomical organization of the cortex in human brain. We find, in addition to obvious laminae, anatomical evidence for tightly packed microcolumnar ensembles containing approximately 11 neurons, with a periodicity of about 80 microm. We examine the structural integrity of this new architectural feature in two common dementing illnesses, Alzheimer disease and dementia with Lewy bodies. In Alzheimer disease, there is a dramatic, nearly complete loss of microcolumnar ensemble organization. The relative degree of loss of microcolumnar ensembles is directly proportional to the number of neurofibrillary tangles, but not related to the amount of amyloid-beta deposition. In dementia with Lewy bodies, a similar disruption of microcolumnar ensemble architecture occurs despite minimal neuronal loss. These observations show that quantitative analysis of complex cortical architecture can be applied to analyze the anatomical basis of brain disorders.

Dynamic feedback in an aggregation-disaggregation model

We study an aggregation-disaggregation model which is relevant to biological processes such as the growth of senile plaques in Alzheimer disease. In this model, during the aggregation each deposited particle has a probability of producing a new particle in its vicinity, while during disaggregation the particles are anihilated randomly. The model is held in a dynamic equilibrium by a feedback mechanism which changes the disaggregation probability in proportion to the change in the total number of particles. We also include surface diffusion which influences the morphology of growing aggregates and colonies. A colony includes the descendents of a single particle. We investigate the statistical properties of the model in two dimensions. We find that unlike the colonies, individual aggregates are fractals with a fractal dimension of D(f)=1.92+/-0.06 in the absence of surface diffusion. We show that the surface diffusion changes the fractal dimension of aggregates: at a small aggregation-disaggregation rate, D(f) is independent of the strength of the surface diffusion, D(f)=1.73+/-0.03. At larger aggregation-disaggregation rates and different strengths of surface diffusion, aggregates with fractal dimensions between D(f)=1.73 and 1.92 form. The steady-state distribution of aggregate sizes is shown to be power law if the aggregation-disaggregation process dominates over the surface diffusion. In the limit of weak aggregation-disaggregation and strong surface diffusion the size distribution is log-normal.

A bacterial single-chain Fv antibody fragment that inhibits binding of its parental anti-E-selectin monoclonal antibody to activated human endothelial cells

Using the polymerase chain reaction, we cloned, modified, and linked antibody variable (V) region coding genes from a mouse hybridoma, and produced a bacterial single-chain Fv (scFv) antibody fragment specific for E-Selectin. A vector of pBR322 origin, bearing the tryptophan promoter and the ompA bacterial signal peptide, was used to direct scFv expression to periplasm. The vector included a six-histidine coding sequence 5' to the scFv for the purification of the expressed protein using immobilized metal affinity chromatography (IMAC). We found that the VH-Linker-VL 32-33 kDa scFv remained insoluble after cellular fractionation, and transmission electron microscopy showed the new protein to be present in the periplasm as inclusion bodies. The scFv was solubilized using urea, purified using IMAC, and renatured to its active form. In a competitive enzyme-linked immunosorbent assay with activated human vein endothelial cells in the solid phase, the scFv competed for binding with the original monoclonal antibody.

Ingestion of chilli pepper (Capsicum annuum) reduces salicylate bioavailability after oral asprin administration in the rat

The bioavailabilities of aspirin (acetylsalicylic acid) and of salicylic acid were studied in male Wistar rats after acute and chronic administration of a Capsicum annuum extract, containing 100 mg of capsaicin per gram. With a single administration of 100 mg/kg of the extract, aspirin blood levels remained unchanged, but salicylic acid bioavailability was reduced in 44% compared with control animals. With a single administration of 300 mg/kg of the extract, aspirin blood levels were undetectable while salicylic acid bioavailability was reduced in 59%. Chronic administration once daily for 4 weeks of 100 and 300 mg/kg of the extract resulted in undetectable aspirin blood levels, while salicylic acid bioavailability was reduced in 63 and 76%, respectively, compared with controls. Results show that Capsicum ingestion reduces oral drug bioavailability, likely as a result of the gastrointestinal effects of capsaicin.

Plaque-induced neurite abnormalities: implications for disruption of neural networks in Alzheimer's disease

The brains of Alzheimer's disease patients contain extracellular Abeta amyloid deposits (senile plaques). Although genetic evidence causally links Abeta deposition to the disease, the mechanism by which Abeta disrupts cortical function is unknown. Using triple immunofluorescent confocal microscopy and three-dimensional reconstructions, we found that neuronal processes that cross through an Abeta deposit are likely to have a radically changed morphology. We modeled the electrophysiological effect of this changed morphology and found a predicted delay of several milliseconds over an average plaque. We propose that this type of delay, played out among thousands of plaques throughout neocortical areas, disrupts the precise temporal firing patterns of action potentials, contributing directly to neural system failure and dementia.

Dynamics of plaque formation in Alzheimer's disease

Plaques that form in the brains of Alzheimer patients are made of deposits of the amyloid-beta peptide. We analyze the time evolution of amyloid-beta deposition in immunostained brain slices from transgenic mice. We find that amyloid-beta deposits appear in clusters whose characteristic size increases from 14 microm in 8-month-old mice to 22 microm in 12-month-old mice. We show that the clustering has implications for the biological growth of amyloid-beta by presenting a growth model that accounts for the experimentally observed structure of individual deposits and predicts the formation of clusters of deposits and their time evolution.

Role of P-selectin expression in hepatic ischemia and reperfusion injury

BACKGROUND

Researchers have shown that reperfusion of ischemic tissues initiates a complex series of reactions that paradoxically injure tissues. Although several mechanisms have been proposed to explain the pathobiology of ischemic/reperfusion (I/R) injury, much attention has focused on adhesion molecules. Our research is intended to show the kinetics of P-selectin in the liver in response to I/R injury.

METHODS

Left-lobar hepatic ischemia was induced for 30 min in 35 C57BL-6 mice and 20 P-selectin-deficient (K-O) mice. P-selectin expression was measured in these mice at 20 min, 2, 5, 12 and 24 h reperfusion times, as well as in control and sham animals. The animals were injected with radio-labeled P-selectin monoclonal antibody and the organs were harvested for counts/g tissue, expressed as the percentage injected dose. Serum liver enzymes were measured and pathological sections of ischemic and control livers were performed. The unpaired t-test was used for statistical analysis.

RESULTS

P-selectin expression showed two peaks in this animal model. The first peak was at 20 min and the second peak at 5 h of reperfusion (p < 0.001). We documented an 8-fold increase in aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) levels 10 h following I/R injury. Pathological specimens showed periportal necrosis consistent with an ischemic event. P-selectin K-O mice showed no up-regulation as a separate control group, and the liver enzymes were significantly lower than the wild-type mice at 10 h (p < 0.001).

CONCLUSION

P-selectin has a bimodal expression following hepatic I/R injury. The first peak is attributed to the Weibel-Palade bodies and the second to new translational P-selectin. We noted no difference in the up-regulation of P-selectin in the ischemic and non-ischemic liver lobes in the same animal.