Chromatolysis of A-cells of dorsal root ganglia is a primary structural event in acute acrylamide intoxication

To test the hypothesis that a somatofugal wave of atrophy moving distally in the axon of primary sensory neurons leads to loss of myelinated nerve fibers in acrylamide neuropathy, rats (N = 18) were intoxicated with an initial dose of 75 mg acrylamide per kg body weight followed by daily treatment with 30 mg/kg for three, six and 12 days. Ten age matched saline treated rats served as controls. Numbers and mean volumes of A- and B-cell perikarya of the L5 dorsal root ganglion, numbers of myelinated axons and the mean cross sectional myelinated axon area 3 and 18 mm from the ganglion in the dorsal root and in the sural nerve were estimated using stereological techniques. After three days no changes in the number or size of primary sensory perikarya or myelinated axons were observed. However, after six days 11% of the A-cell perikarya showed signs of chromatolysis (P < 0.001). After 12 days the rats showed signs of ataxia and 23% (P < 0.001) of A-cell perikarya were chromatolytic. There was a tendency for atrophy of the mean perikaryal volume of A-cells (2P = 0.059). The size-frequency distributions of axonal area of myelinated fibers in the dorsal root 3 mm from the ganglion were displaced to the left towards smaller sizes (25–50% quartile: 2P < 0.005 and 75–100% quartile: 2P < 0.05). In conclusion, the primary structural event in acute acrylamide intoxication is chromatolysis of A-cells of the dorsal root ganglion without the occurrence of somatofugal axonal atrophy.     

Bacterial polysaccharides suppress induced innate immunity by calcium chelation

Bacterial pathogens and symbionts must suppress or negate host innate immunity. However, pathogens release conserved oligomeric and polymeric molecules or MAMPs (Microbial Associated Molecular Patterns), which elicit host defenses [1], [2] and [3]. Extracellular polysaccharides (EPSs) are key virulence factors in plant and animal pathogenesis, but their precise function in establishing basic compatibility remains unclear [4], [5], [6] and [7]. Here, we show that EPSs suppress MAMP-induced signaling in plants through their polyanionic nature [4] and consequent ability to chelate divalent calcium ions [8]. In plants, Ca2+ ion influx to the cytosol from the apoplast (where bacteria multiply [4], [5] and [9]) is a prerequisite for activation of myriad defenses by MAMPs [10]. We show that EPSs from diverse plant and animal pathogens and symbionts bind calcium. EPS-defective mutants or pure MAMPs, such as the flagellin peptide flg22, elicit calcium influx, expression of host defense genes, and downstream resistance. Furthermore, EPSs, produced by wild-type strains or purified, suppress induced responses but do not block flg22-receptor binding in Arabidopsis cells. EPS production was confirmed in planta, and the amounts in bacterial biofilms greatly exceed those required for binding of apoplastic calcium. These data reveal a novel, fundamental role for bacterial EPS in disease establishment, encouraging novel control strategies.     

Long-term acrylamide intoxication induces atrophy of dorsal root ganglion A-cells and of myelinated sensory axons

We have examined the effects of acrylamide on primary sensory nerve cell bodies and their myelinated axons in chronic acrylamide intoxication. The numbers and sizes of dorsal root ganglion cell bodies (L5) and myelinated nerve fibers were estimated with sterelogical techniques in severely disabled rats which had been treated with 33.3 mg/kg acrylamide twice a week for 7.5 weeks. There was no loss of dorsal root ganglion cells or myelinated nerve fibers in the roots, the sciatic nerve, sural nerve, and a tibial nerve branch. The mean perikaryal volume of A-cells was reduced by 20% (2P < 0.001) from 50000 μm³ in controls (CV = 0.13) to 40000 μm³ (0.12), whereas B-cell volume was unchanged. All size-frequency distribution curves of myelinated axon area of peripheral nerves and sensory roots were shifted to the left towards smaller values in rats exposed to acrylamide. In the L5 sensory root 3 mm from the ganglion, there was a significant reduction of mean cross sectional area of myelinated axons by 14% (2P < 0.05) from 7.6 μm² (0.11) in controls to 6.5 μm² (0.13) in intoxicated rats. The mean cross sectional area of myelinated sural nerve axons was reduced by 22% (2P < 0.001) from 8.6 μm² (0.08) in controls to 6.7 μm² (0.17) in intoxicated rats. We conclude that chronic intoxication with acrylamide leads to selective atrophy of type A dorsal root ganglion cell bodies and simultaneous atrophy along their peripheral axons, whereas neuronal B-cell bodies and motor axons are spared. It is suggested that the neuronal atrophy might well represent a defect of neurofilament synthesis and transport.     

Cellular response of Campylobacter jejuni to trisodium phosphate

The highly alkaline compound trisodium phosphate (TSP) is used as an intervention to reduce the load of Campylobacter on poultry meat in U.S. poultry slaughter plants. The aim of the present study was to investigate the cellular responses of Campylobacter jejuni NCTC11168 when exposed to sublethal concentrations of TSP. Preexposure of C. jejuni to TSP resulted in a significant increase in heat sensitivity, suggesting that a combined heat and TSP treatment may increase reduction of C. jejuni. A microarray analysis identified a limited number of genes that were differently expressed after sublethal TSP exposure; however, the response was mainly associated with ion transport processes. C. jejuni NCTC11168 nhaA1 (Cj1655c) and nhaA2 (Cj1654c), which encode orthologues to the Escherichia coli NhaA cation/proton antiporter, were able to partially restore TSP, alkaline, and sodium resistance phenotypes to an E. coli cation/proton antiporter mutant. In addition, inhibition of resistance-nodulation-cell division (RND) multidrug efflux pumps by the inhibitor PaβN (Phe-Arg β-naphthylamide dihydrochloride) decreased tolerance to sublethal TSP. Therefore, we propose that NhaA1/NhaA2 cation/proton antiporters and RND multidrug efflux pumps function in tolerance to sublethal TSP exposure in C. jejuni.     

An antagonist of lipid A action in mammals has complex effects on lipid A induction of defence responses in the model plant Arabidopsis thaliana

Lipopolysaccharides, the ubiquitous part of the outer membrane of Gram-negative bacteria, and their derivatives are recognised by plants to trigger or potentiate particular defence responses such as induction of genes encoding pathogenesis-related proteins. The molecular mechanisms of LPS perception that underpin these effects in plants are, however, unknown. Here, lipid A from Halomonas magadiensis, which is an antagonist of lipid A action in human cells, was used to investigate lipid A action in plants. Our findings offer an insight into the different structural requirements for direct induction and potentiation of plant defences by lipid A.     

Unbiased estimates of number and size of rat dorsal root ganglion cells in studies of structure and cell survival

For quantitative studies of rat dorsal root ganglion (DRG) in experimental models stereological principles offer a number of different techniques. The application, however, requires knowledge of the anatomy and cytology of the ganglion, considerations of sampling and choosing between the many estimators available. For number and volume estimates in thick glycolmethacrylate sections the optical fractionator and the vertical planar rotator technique in most cases provide sufficient efficiency and are simple to use. Classification of the neurons in the DRG into A- and B-cells is of value in experimental conditions where the two cell types can react differently. Studies on development and subclassification of neuronal DRG cells will gain from application of stereological methods, also. Until now the methods have mainly been applied in studies of axotomy and in a few intoxication models where the time course of cell loss and changes in perikarya volume are important parameters. Further quantitative studies providing better understanding of distribution and expression of neuropeptides, cytokines, apoptotic molecules etc. will provide insight for future therapeutic approaches in neurodegenerative disorders. The more demanding staining techniques require less restrictive embedding media, but unbiased principles are available for almost all the stereological techniques applied to tissue only deformed after sectioning.     

Distinct proteome pathology of circulating microparticles in systemic lupus erythematosus

Background

The pathogenesis of systemic lupus erythematosus (SLE) is poorly understood but has been linked to defective clearance of subcellular particulate material from the circulation. This study investigates the origin, formation, and specificity of circulating microparticles (MPs) in patients with SLE based on comprehensive MP proteome profiling using patients with systemic sclerosis (SSc) and healthy donors (HC) as controls.

Methods

We purified MPs from platelet-poor plasma using differential centrifugation of samples from SLE (n = 45), SSc (n = 38), and two sets of HC (n = 35, n = 25). MP proteins were identified and quantitated after trypsin digestion by liquid chromatography-tandem mass spectrometry. The abundance of specific proteins was compared between the groups using univariate statistics and false discovery rate correction for multiple comparisons. Specific proteins and protein ratios were explored for diagnostic and disease activity information using receiver-operating characteristic curves and by analysis of correlations of protein abundance with disease activity scores.

Results

We identify and quantitate more than 1000 MP proteins and show that a subpopulation of SLE-MPs (which we propose to call luposomes) are highly specific for SLE, i.e. not found in MP preparations from HC or patients with another autoimmune, systemic disease, SSc. In SLE-MPs platelet proteins and mitochondrial proteins are significantly diminished, cytoskeletal proteins deranged, and glycolytic enzymes and apoptotic proteins significantly increased.

Conclusions

Normal MPs are efficiently removed in SLE, but aberrant MPs, derived from non-lymphoid leukocytes, are less efficiently removed and abundantly produced leading to an altered MP proteome in SLE. The data suggest that an abnormal generation of MPs may partake in the pathology of SLE and that new diagnostic, monitoring, and treatment strategies targeting these processes may be advantageous.