The multiple mechanisms of Ca2+ signalling by listeriolysin O, the cholesterol-dependent cytolysin of Listeria monocytogenes

Cholesterol-dependent cytolysins (CDCs) represent a large family of conserved pore-forming toxins produced by several Gram-positive bacteria such as Listeria monocytogenes, Streptococcus pyrogenes and Bacillus anthracis. These toxins trigger a broad range of cellular responses that greatly influence pathogenesis. Using mast cells, we demonstrate that listeriolysin O (LLO), a prototype of CDCs produced by L. monocytogenes, triggers cellular responses such as degranulation and cytokine synthesis in a Ca(2+)-dependent manner. Ca(2+) signalling by LLO is due to Ca(2+) influx from extracellular milieu and release of from intracellular stores. We show that LLO-induced release of Ca(2+) from intracellular stores occurs via at least two mechanisms: (i) activation of intracellular Ca(2+) channels and (ii) a Ca(2+) channels independent mechanism. The former involves PLC-IP(3)R operated Ca(2+) channels activated via G-proteins and protein tyrosine kinases. For the latter, we propose a novel mechanism of intracellular Ca(2+) release involving injury of intracellular Ca(2+) stores such as the endoplasmic reticulum. In addition to Ca(2+) signalling, the discovery that LLO causes damage to an intracellular organelle provides a new perspective in our understanding of how CDCs affect target cells during infection by the respective bacterial pathogens.     

Cranial anatomy,taxonomic implications and palaeopathology of an Upper Jurassic Pliosaur (Reptilia: Sauropterygia) from Westbury,Wiltshire, UK

Abstract: Complete skulls of giant marine reptiles of the Late Jurassic are rare, and so the discovery of the 1.8‐m‐long skull of a pliosaur from the Kimmeridge Clay Formation (Kimmeridgian) of Westbury, Wiltshire, UK, is an important find. The specimen shows most of the cranial and mandibular anatomy, as well as a series of pathological conditions. It was previously referred to Pliosaurus brachyspondylus, but it can be referred reliably only to the genus Pliosaurus, because species within the genus are currently in need of review. The new specimen, together with another from the same locality, also referred to P. brachyspondylus, will be crucial in that systematic revision, and it is likely that the genus Pliosaurus will be found to include several genera. The two Westbury Pliosaurus specimens share many features, including the form of the teeth, but marked differences in the snout and parietal crest suggest sexual dimorphism; the present specimen is probably female. The large size of the animal, the extent of sutural fusion and the pathologies suggest this is an ageing individual. An erosive arthrotic condition of the articular glenoids led to prolonged jaw misalignment, generating a suite of associated bone and dental pathologies. Further damage to the jaw joint may have been the cause of death.     

On the existence of a gradient of sensitivity to the lack of sodium in the spinal roots of the bullfrog

The Et class of fibers includes fibers of Gasser's d.r. C group. The fibers of the dorsal root are more sensitive to the effect of lack of sodium than are the fibers of the ventral root. In the two roots there is a gradient of sensitivity to the lack of sodium, which is such that in all the root fibers the sensitivity decreases with increasing distance from the spinal cord. The gradient continues in the trunk up to about 10 to 12 mm. peripheral to the trunk-roots margin. No comparable gradient of sensitivity to the lack of sodium has been observed in the rest of the nerve trunk. The gradient of sensitivity to the lack of sodium has no relationship to the anatomical distribution of the epineurium. As a working hypothesis it is suggested that the gradient of sensitivity to the lack of sodium is one aspect of a transitional gradient that serves to establish a gradual change between the properties that the axons have inside the spinal cord and the properties that they have inside the nerve trunks. Details are given of the temporal course of the loss of excitability by root fibers deprived of sodium. It is suggested that sodium is present in the nerve fibers, in 2 forms, loosely and tightly bound sodium and that loss of loosely bound sodium is sufficient to render the nerve fibers unable to conduct impulses. If the rate of loss of loosely bound sodium is decreased, conversion of tightly bound into loosely bound sodium may temporarily restore the excitability of the nerve fibers.     

Mast cells initiate early anti-Listeria host defences

The Gram-positive bacterium Listeria monocytogenes ( L. m. ) is the aetiological agent of listeriosis. The early phase listeriosis is characterized by strong innate host responses that play a major role in bacterial clearance. This is emphasized by the fact that mice deficient in T and B cells have a remarkable ability to control infection. Mast cells, among the principal effectors of innate immunity, have largely been studied in the context of hyper-reactive conditions such as allergy and autoimmune diseases. In the present study, we evaluated the significance of mast cells during the early phase of listeriosis. Compared with controls, mice depleted of mast cells showed hundred-fold higher bacterial burden in spleen and liver and were significantly impaired in neutrophil mobilization. Although L. m. interacts with and triggers mast cell degranulation, bacteria were hardly found within such cells. Mainly neutrophils and macrophages phagozytosed L. m . Thus, mast cells control infection not via direct bacterial uptake, but by initiating neutrophils influx to the site of infection. We show that this is initiated by pre-synthesized TNF-α, rapidly secreted by mast cell upon activation by L. m . We also show that upon recruitment, neutrophils also become activated and additionally secrete TNF-α thus amplifying the anti- L. m. inflammatory response.     

Bacteria Induce Prolonged PMN Survival via a Phosphatidylcholine-Specific Phospholipase C- and Protein Kinase C-Dependent Mechanism

Polymorphonuclear leukocytes (PMNs) are essential for the human innate immune defense, limiting expansion of invading microorganisms. PMN turnover is controlled by apoptosis, but the regulating signaling pathways remain elusive, largely due to inherent differences between mice and humans that undermine use of mouse models for understanding human PMN biology. Here, we aim to elucidate signal transduction mediating survival of human peripheral blood PMNs in response to bacteria, such as Yersinia pseudotuberculosis, an enteropathogen that causes the gastro-intestinal disease yersiniosis, as well as Escherichia coli and Staphylococcus aureus. Determinations of cell death reveal that uninfected control cells undergo apoptosis, while PMNs infected with either Gram-positive or -negative bacteria show profoundly increased survival. Infected cells exhibit decreased caspase 3 and 8 activities, increased mitochondrial integrity and are resistant to apoptosis induced by a death receptor ligand. This bacteria-induced response is accompanied by pro-inflammatory cytokine production including interleukin-8 and tumor necrosis factor-α competent to attract additional PMNs. Using agonists and pharmacological inhibitors, we show participation of Toll-like receptor 2 and 4, and interestingly, that protein kinase C (PKC) and phosphatidylcholine-specific phospholipase C (PC-PLC), but not tyrosine kinases or phosphatidylinositol-specific phospholipase C (PI-PLC) are key players in this dual PMN response. Our findings indicate the importance of prolonged PMN survival in response to bacteria, where general signaling pathways ensure complete exploitation of PMN anti-microbial capacity.     

Evolution of the Zfx and Zfy genes: rates and interdependence between the genes

A phylogenetic analysis of sex-chromosomal zinc-finger genes (Zfx and Zfy) indicates that the genes have not evolved completely independently since their initial separation. The sequence similarities suggest gene conversion in the last exon between the duplicated Y-chromosomal genes Zfy-1 and Zfy-2 in the mouse. There are also indications of conversion (or recombination) between the X- and Y-chromosomal genes in the crab- eating fox and in the mouse. The method for estimating synonymous and nonsynonymous substitutions is modified by incorporating the substitutions in the twofold-degenerate sites in a novel way. The estimates of synonymous substitutions support the generation-time hypothesis in that the obtained rates are higher in mice (by a factor of 4.7) than in humans and higher in the Y-chromosomal genes (by a factor of 1.9) than in the X-chromosomal genes.      

INFLUENCE OF EDUCATION/PROFESSION OF MEXICAN CONSUMERS ON ACCEPTANCE AND PURCHASE INTENT OF CORN TORTILLA

Influence of education/profession of Mexican consumers on acceptance and purchase intent of corn tortillas was evaluated. Two groups of 150 Mexican consumers each (faculty/graduate students [A] versus field laborers [B]) rated sensory acceptability of corn tortillas. Acceptance and purchase intent were rated using a binomial scale. Group B had higher expectations towards corn tortillas as indicated by lower acceptability ratings. Both groups used rollability, resistance-to-tearing, and chewiness to differentiate tortilla samples, but group B paid more attention to these attributes as indicated by higher canonical correlation values. Acceptance was influenced by overall liking for both groups; chewiness and taste were also significant for group B. Purchase intent was influenced by overall liking and taste for both groups, but color for group A, and appearance and chewiness for group B were also critical. This study demonstrated that education/profession of Mexican consumers affected their acceptance and purchase intent of corn tortillas.

PRACTICAL APPLICATIONS

This study revealed that education/profession of Mexican consumers affected acceptance and purchase intent of corn tortillas. Two groups of consumers with different levels of education had different expectation toward tortillas when making purchase decision. Understanding how each consumer segment differently perceives about the tortilla product will give marketers and manufacturers a better direction for developing tortilla products with expected sensory qualities.     

Use of a crude extract or purified antigen from first‐instar cattle grubs,Hypoderma lineatum,for the detection of anti‐Hypoderma antibodies in free‐ranging cervids from southern Spain

During the 2003–2005 hunting seasons, a total of 120 Cervidae, including 39 red deer (Cervus elaphus hispanicus) and 81 fallow deer (Dama dama), were examined for subcutaneous myiasis. Animals were shot from January to June in southern Spain. Specific antibodies against Hypodermatinae (Diptera: Oestridae) were detected by indirect enzyme‐linked immunosorbent assay (iELISA) using a crude larval extract (CLE) and a purified antigen [hypodermin C (HC)] obtained from first instars of Hypoderma lineatum (De Villers) (Diptera: Oestridae). Hypoderma actaeon Brauer was the only species detected in this study, which represents the first confirmation of this species in fallow deer from Spain. The overall prevalence of animals presenting subcutaneous larvae (14.2%) was considerably lower than the prevalences determined by iELISA with CLE (43.3%) and HC (40.0%). Red deer showed a higher prevalence of Hypoderma than fallow deer. The concordance between larval examination during the hunting season and iELISA using both antigens was low, whereas the concordance between the CLE and HC ELISAs was good. Larval antigens obtained from H. lineatum constitute a good tool for the diagnosis of H. actaeon in Cervidae, especially when the hunting season does not coincide with the maximum presence of larvae on the back.     

Evaluation of neem seed powder for Fusarium wilt and Meloidogyne control on tomato

Fusarium wilt and root-knot are important diseases of tomato. The use of chemical is becoming less appealing because of the health implications. Also, the chemicals required are often not within the reach of farmers in most of the developing part of the world. This research is aimed at finding an alternative mode of control. Tomato variety Roma VF inoculated with Meloidogyne and Fusarium were treated with 2 g/kg soil neem seed powder in the screenhouse and 2 Mg ha ^{? 1} in the field. An untreated and Furadan treated plot in the field served as control. Neem seed powder significantly reduced the disease severity of Fusarium and root-knot in both screenhouse and field. Results suggest the possible use of neem seed powder for control of the root-knot nematodes - Fusarium wilt disease complex.