Detection of Botulinum Neurotoxin Serotype B at Sub Mouse LD50 Levels by a Sandwich Immunoassay and Its Application to Toxin Detection in Milk

Botulinum neurotoxin (BoNT), the causative agent of botulism, a serious neuroparylatic disease, is produced by the anaerobic bacterium Clostridium botulinum and consists of a family of seven serotypes (A-H). We previously reported production of high-affinity monoclonal antibodies to BoNT serotype A.Recombinant peptide fragments of the light chain, the transmembrane and receptor-binding domains of the heavy chain of botulinum neurotoxin type B (BoNT/B) were expressed in Escherichia coli as GST-fusion proteins and purified. These proteins were used to immunize BALB/cJ mice for the generation of monoclonal antibodies (mAbs). Antibody-producing hybridomas were detected using either a direct binding ELISA binding to plate-immobilized BoNT/B, or with a capture-capture ELISA whereby the capacity of the antibody to capture BoNT/B from solution was tested. A total of five mAbs were selected, two of which bound the toxin light chain and three bound the receptor-binding domain of BoNT/B heavy chain. MAb MCS6-27 was identified via capture-capture ELISA and was the only mAb able to bind BoNT/B in solution under physiological conditions. MAbs F24-1, F26-16, F27-33 and F29-40 were identified via direct binding ELISA, and were able to capture BoNT/B in solution only in the presence of 0.5-0.9 mM sodium dodecyl sulphate (SDS). MAb MCS6-27 and an anti-BoNT/B polyclonal antibody were incorporated into a sandwich ELISA that did not require SDS.We report here the generation of monoclonal antibodies to serotype B and the subsequent development of a sensitive sandwich immunoassay. This immunoassay has a detection limit of 100 fg BoNT/B, fifty times more sensitive than the mouse bioassay detection limit of 5 pg BoNT/B. Additionally, this assay detected as little as 39 pg/mL of toxin in skim, 2% and whole milk

Characterization of primary neurospheres generated from mouse ventral rostral hindbrain

Serotonergic (5-HT) neurons of the reticular formation play a key role in the modulation of behavior, and their dysfunction is associated with severe neurological and psychiatric disorders, such as depression and schizophrenia. However, the molecular mechanisms underlying the differentiation of the progenitor cells and the specification of the 5-HT phenotype are not fully understood. A primary neurosphere cell-culture system from mouse ventral rostral hindbrain at embryonic day 12 was therefore established. The generated primary neurospheres comprised progenitor cells and fully differentiated neurons. Bromodeoxyuridine incorporation experiments in combination with immunocytochemistry for neural markers revealed the proliferation capacity of the neural multipotent hindbrain progenitors within neurospheres and their ability to differentiate toward the neuronal lineage and serotonergic phenotype. Gene expression analysis by reverse transcription with the polymerase chain reaction showed that the neurospheres were regionally specified, as reflected by the expression of the transcription factors Gata2 and Pet1. Treatment of dissociated primary neurospheres with exogenous Shh significantly increased the number of 5-HT-immunopositive cells compared with controls, whereas neutralization of endogenous Shh significantly decreased the number of 5-HT neurons. Thus, the primary neurosphere culture system presented here allows the expansion of hindbrain progenitor cells and the experimental control of their differentiation toward the serotonergic phenotype. This culture system is therefore a useful model for in vitro studies dealing with the development of 5-HT neurons

Expression, Purification and Characterization of Arginase from Helicobacter pylori in Its Apo Form

Arginase, a manganese-dependent enzyme that widely distributed in almost all creatures, is a urea cycle enzyme that catalyzes the hydrolysis of L-arginine to generate L-ornithine and urea. Compared with the well-studied arginases from animals and yeast, only a few eubacterial arginases have been characterized, such as those from H. pylori and B. anthracis. However, these enzymes used for arginase activity assay were all expressed with LB medium, as low concentration of Mn2+ was detectable in the medium, protein obtained were partially Mn2+ bonded, which may affect the results of arginase activity assay. In the present study, H. pylori arginase (RocF) was expressed in a Mn2+ and Co2+ free minimal medium, the resulting protein was purified through affinity and gel filtration chromatography and the apo-form of RocF was confirmed by flame photometry analysis. Gel filtration indicates that the enzyme exists as monomer in solution, which was unique as compared with homologous enzymes. Arginase activity assay revealed that apo-RocF had an acidic pH optimum of 6.4 and exhibited metal preference of Co2+>Ni2+>Mn2+. We also confirmed that heat-activation and reducing regents have significant impact on arginase activity of RocF, and inhibits S-(2-boronoethyl)-L-Cysteine (BEC) and Nω-hydroxy-nor-Arginine (nor-NOHA) inhibit the activity of RocF in a dose-dependent manner

Mining Virulence Genes Using Metagenomics

When a bacterial genome is compared to the metagenome of an environment it inhabits, most genes recruit at high sequence identity. In free-living bacteria (for instance marine bacteria compared against the ocean metagenome) certain genomic regions are totally absent in recruitment plots, representing therefore genes unique to individual bacterial isolates. We show that these Metagenomic Islands (MIs) are also visible in bacteria living in human hosts when their genomes are compared to sequences from the human microbiome, despite the compartmentalized structure of human-related environments such as the gut. From an applied point of view, MIs of human pathogens (e.g. those identified in enterohaemorragic Escherichia coli against the gut metagenome or in pathogenic Neisseria meningitidis against the oral metagenome) include virulence genes that appear to be absent in related strains or species present in the microbiome of healthy individuals. We propose that this strategy (i.e. recruitment analysis of pathogenic bacteria against the metagenome of healthy subjects) can be used to detect pathogenicity regions in species where the genes involved in virulence are poorly characterized. Using this approach, we detect well-known pathogenicity islands and identify new potential virulence genes in several human pathogens

Serum uri acid: neuroprotection in thrombolysis. The Bergen NORSTROKE study

<p>Abstract</p> <p>Background</p> <p>A possible synergic role of serum uric acid (SUA) with thrombolytic therapies is controversial and needs further investigations. We therefore evaluated association of admission SUA with clinical improvement and clinical outcome in patients receiving rt-PA, early admitted patients not receiving rt-PA, and patients admitted after time window for rt-PA.</p> <p>Methods</p> <p>SUA levels were obtained at admission and categorized as low, middle and high, based on 33° and 66° percentile values. Patients were categorized as patients admitted within 3 hours of symptom onset receiving rt-PA (rt-PA group), patients admitted within 3 hours of symptom onset not receiving rt-PA (non-rt-PA group), and patients admitted after time window for rt-PA (late group). Short-term clinical improvement was defined as the difference between NIHSS on admission minus NIHSS day 7. Favorable outcome was defined as mRS 0 - 3 and unfavorable outcome as mRS 4 - 6.</p> <p>Results</p> <p>SUA measurements were available in 1136 patients. Clinical improvement was significantly higher in patients with high SUA levels at admission. After adjustment for possible confounders, SUA level showed a positive correlation with clinical improvement (r = 0.012, 95% CI 0.002-0.022, p = 0.02) and was an independent predictor for favorable stroke outcome (OR 1.004; 95% CI 1.0002-1.009; p = 0.04) only in the rt-PA group.</p> <p>Conclusions</p> <p>SUA may not be neuroprotective alone, but may provide a beneficial effect in patients receiving thrombolysis.</p

Synthesis, Characterization, and Microwave Absorption Property of the SnO2Nanowire/Paraffin Composites

In this article, SnO2nanowires (NWs) have been prepared and their microwave absorption properties have been investigated in detail. Complex permittivity and permeability of the SnO2NWs/paraffin composites have been measured in a frequency range of 0.1–18 GHz, and the measured results are compared with that calculated from effective medium theory. The value of maximum reflection loss for the composites with 20 vol.% SnO2NWs is approximately −32.5 dB at 14 GHz with a thickness of 5.0 mm

Efficient control of atmospheric sulfate production based on three formation regimes

The formation of sulfate (SO₄²⁻) in the atmosphere is linked chemically to its direct precursor, sulfur dioxide (SO₂), through several key oxidation paths for which nitrogen oxides or NO_x (NO and NO₂) play essential roles. Here we present a coherent description of the dependence of SO₄²⁻ formation on SO₂ and NO_x under haze-fog conditions, in which fog events are accompanied by high aerosol loadings and fog-water pH in the range of 4.7–6.9. Three SO₄²⁻ formation regimes emerge as defined by the role played by NO_x. In the low-NO_x regime, NO_x act as catalyst for HO_x, which is a major oxidant for SO₂, whereas in the high-NO_x regime, NO₂ is a sink for HO_x. Moreover, at highly elevated NO_x levels, a so-called NO₂-oxidant regime exists in which aqueous NO₂ serves as the dominant oxidant of SO₂. This regime also exists under clean fog conditions but is less prominent. Sensitivity calculations using an emission-driven box model show that the reduction of SO₄²⁻ is comparably sensitive to the reduction of SO₂ and NO_x emissions in the NO₂-oxidant regime, suggesting a co-reduction strategy. Formation of SO₄²⁻ is relatively insensitive to NO_x reduction in the low-NO_x regime, whereas reduction of NO_x actually leads to increased SO₄²⁻ production in the intermediate high-NO_x regime

The Dog Mite, Demodex canis: Prevalence, Fungal Co-Infection, Reactions to Light, and Hair Follicle Apoptosis

Infection rate, reaction to light, and hair follicle apoptosis are examined in the dogmite, Demodex canis Leydig (Prostigmata: Demodicidae), in dogs from the northern area of Taiwan. An analysis of relevant samples revealed 7.2% (73/1013) prevalence of D. canis infection. Infection during the investigation peaked each winter, with an average prevalence of 12.5% (32/255). The infection rates significantly varied in accordance with month, sex, age, and breed (p < 0.05). Most of the lesions were discovered on the backs of the infected animals, where the infection rate was 52.1% (38/73) (P < 0.05). The epidemiologic analysis of infection based on landscape area factor, found that employing a map-overlapping method showed a higher infection rate in the eastern distribution of Taiwan's northern area than other areas. Isolation tests for Microsporum canis Bodin (Onygenales: Arthrodermataceae) and Trichophyton mentagrophyte Robin (Blanchard) on the D. canis infected dogs revealed prevalence rates of 4.4% (2/45) and 2.2% (1/45), respectively. Observations demonstrated that D. canis slowly moved from a light area to a dark area. Skin samples were examined for cellular apoptosis by activated caspase3 immunohistochemical staining. Cells that surrounded the infected hair follicles were activated caspase3-positive, revealing cell apoptosis in infected follicles via the activation of caspase3