HLM1, an essential signaling component in the hypersensitive response,is a member of the cyclic nucleotide-gated channel ion channel family

The hypersensitive response (HR) in plants is a programmed cell death that is commonly associated with disease resistance. A novel mutation in Arabidopsis, hlm1, which causes aberrant regulation of cell death, manifested by a lesion-mimic phenotype and an altered HR, segregated as a single recessive allele. Broad-spectrum defense mechanisms remained functional or were constitutive in the mutant plants, which also exhibited increased resistance to a virulent strain of Pseudomonas syringae pv tomato. In response to avirulent strains of the same pathogen, the hlm1 mutant showed differential abilities to restrict bacterial growth, depending on the avirulence gene expressed by the pathogen. The HLM1 gene encodes a cyclic nucleotide-gated channel, CNGC4. Preliminary study of the HLM1/CNGC4 gene pro-duct in Xenopus oocytes (inside-out patch-clamp technique) showed that CNGC4 is permeable to both K(+) and Na(+) and is activated by both cGMP and cAMP. HLM1 gene expression is induced in response to pathogen infection and some pathogen-related signals. Thus, HLM1 might constitute a common downstream component of the signaling pathways leading to HR/resistance.     

A new species of Thecadactylus from Sint Maarten, Lesser Antilles (Reptilia, Squamata, Gekkonidae)

We describe a new species of Thecadactylusfrom the Caribbean island of Sint Maarten. The new species differs from all other species in the genus by having a distinct dorsal pattern of numerous irregular but sharply deliminated black spots and blotches on an otherwise almost patternless background.     

Exotic Pine Plantations in Victoria, Australia: A Threat to Epigaeic Beetle (Coleoptera) Assemblages?

Ground-dwelling invertebrates were sampled by pitfall traps over a 14 week period in parent eucalypt forest and three stages of exotic Pinus radiata plantations established after forest clearance in central Victoria. The four treatments each yielded numerous beetle morphospecies, and the assemblages corresponded only partially with the understorey vegetation. More than 200 beetle morphospecies were captured during this short survey, with 30 found in all four treatments; few morphospecies were abundant (only five with >100 individuals in a total of 3382 beetles). Each treatment had unique morphospecies, but all were rich, with the lowest diversity being 91 morphospecies (young pines). These data confirm that beetle diversity can remain substantial in exotic softwood plantations, but considerable care is needed to interpret this apparent diversity in relation to forest management and the effect of replacement of native forests by exotic taxa.     

Heterogeneity in the density of spotted hyaenas in Hluhluwe-iMfolozi Park,South Africa

Animal population sizes and trends, as well as their distributions, are essential information to the understanding and conservation of ecosystems. During this study in Hluhluwe-iMfolozi Park, South Africa, a spotted hyaena Crocuta crocuta Erxleben, 1777 (Hyaenidae) population was surveyed by attracting individuals with pre-recorded sounds. The hyaena population (excluding cubs) is substantially larger (321 individuals) than the previous estimate of 200 and this population is the second largest protected population in South Africa. Average hyaena density, at 0.357 individuals/km², was relatively high compared to other southern African conservation areas, and range from 0 to 1.25 individuals/km² across sampling stations. For short periods, spatial heterogeneity in density was marked at small and large spatial scales, but decreased when averaged over a longer period. This heterogeneity may be important in promoting the coexistence of other large and mobile carnivores in Hluhluwe-iMfolozi Park by creating potential dynamic competition refugia in space and time. Furthermore, heterogeneity of hyaena density at smaller scales should influence studies investigating the avoidance of hyaenas by competitively inferior carnivores.     

Early-Onset and Robust Amyloid Pathology in a New Homozygous Mouse Model of Alzheimer's Disease

Background

Transgenic mice expressing mutated amyloid precursor protein (APP) and presenilin (PS)-1 or -2 have been successfully used to model cerebral β-amyloidosis, one of the characteristic hallmarks of Alzheimer''s disease (AD) pathology. However, the use of many transgenic lines is limited by premature death, low breeding efficiencies and late onset and high inter-animal variability of the pathology, creating a need for improved animal models. Here we describe the detailed characterization of a new homozygous double-transgenic mouse line that addresses most of these issues.

Methodology/Principal Findings

The transgenic mouse line (ARTE10) was generated by co-integration of two transgenes carrying the K670N/M671L mutated amyloid precursor protein (APP_swe) and the M146V mutated presenilin 1 (PS1) both under control of a neuron-specific promoter. Mice, hemi- as well as homozygous for both transgenes, are viable and fertile with good breeding capabilities and a low rate of premature death. They develop robust AD-like cerebral β-amyloid plaque pathology with glial inflammation, signs of neuritic dystrophy and cerebral amyloid angiopathy. Using our novel image analysis algorithm for semi-automatic quantification of plaque burden, we demonstrate an early onset and progressive plaque deposition starting at 3 months of age in homozygous mice with low inter-animal variability and 100%-penetrance of the phenotype. The plaques are readily detected in vivo by PiB, the standard human PET tracer for AD. In addition, ARTE10 mice display early loss of synaptic markers and age-related cognitive deficits. By applying a γ-secretase inhibitor we show a dose dependent reduction of soluble amyloid β levels in the brain.

Conclusions

ARTE10 mice develop a cerebral β-amyloidosis closely resembling the β-amyloid-related aspects of human AD neuropathology. Unifying several advantages of previous transgenic models, this line particularly qualifies for the use in target validation and for evaluating potential diagnostic or therapeutic agents targeting the amyloid pathology of AD.     

Novel B-ring modified allocolchicinoids of the NCME series: design,synthesis, antimicrotubule activity and cytotoxicity

Two new series of allocolchicinoids mimicking the structure of (-)-N-acetylcolchinol O-methyl ether (2, NCME) were synthesized and evaluated for their abilities to inhibit tubulin assembly. Possible antitumor properties resulting thereof were evaluated in vitro on the human MCF-7 breast cancer cell line. The first series of NCME-derivatives was brought about by extending the seven membered B-ring to novel semisynthetic variations with a nitrogen containing eight-membered B-ring similar, for example, to the artificial, potent steganacin aza-analogue 3. In the second series the seven-membered B-ring of NCME (2) was modified by annulation with a heterocyclic ring system. The racemic ketone 7a serving as key precursor involved in the syntheses of all the target NCME variants 9-13 and 15, 16 was easily transformed into the eight-membered B-ring lactams 9 and 10 via a Beckmann rearrangement of the corresponding E-oxime 8. The tetrazole annulated congener 11 was prepared via azidotrimethylsilane-mediated Schmidt rearrangement. Treatment of educt 7a with Bredereck's reagent led to the enamino ketone 14, which was easily converted into the pyrazole- or pyrimidine-annulated allocolchicinoids 15 and 16. Remarkably, all the allocolchicinoids 9-13 with an azocin-B-ring affected the tubulin/microtubule equilibrium only moderately. In contrast, the novel heterocycle annulated seven membered B-ring variants 15 and 16 proved to be highly potent tubulin-inhibitory, antimitotic agents. Interaction with tubulin occured at concentrations similar to those observed for colchicine (1) or the lead NCME (2). In all cases the antiproliferative effects correlated roughly with the inhibition of tubulin assembly.     

Halogenated and isosteric cytisine derivatives with increased affinity and functional activity at nicotinic acetylcholine receptors

A series of pyridone ring-modified derivatives of (7R,9S)-(-)-cytisine were evaluated for affinity and functional activity at neuromuscular alpha1beta1gammadelta, ganglionic alpha3beta4, and central neuronal alpha4beta2 subtypes of nicotinic receptors. Halogenation at the 3-position improved affinity and functional activity, while substitution at the 5-position led to modest decreases in both, and disubstitution led to near abolition of functional activities and could be correlated with the electron-withdrawing ability of the halogen. Subtype selectivities of the halogenated derivatives were altered relative to cytisine in a substitution-dependent manner. Caulophylline methiodide was less potent than cytisine, but retained significant activity. Thiocytisine was relatively weak in potency and efficacy, but was significantly selective for the alpha4beta2 subtype.     

RIG-I Detects Triphosphorylated RNA of Listeria monocytogenes during Infection in Non-Immune Cells

The innate immune system senses pathogens by pattern recognition receptors in different cell compartments. In the endosome, bacteria are generally recognized by TLRs; facultative intracellular bacteria such as Listeria, however, can escape the endosome. Once in the cytosol, they become accessible to cytosolic pattern recognition receptors, which recognize components of the bacterial cell wall, metabolites or bacterial nucleic acids and initiate an immune response in the host cell. Current knowledge has been focused on the type I IFN response to Listeria DNA or Listeria-derived second messenger c-di-AMP via the signaling adaptor STING. Our study focused on the recognition of Listeria RNA in the cytosol. With the aid of a novel labeling technique, we have been able to visualize immediate cytosolic delivery of Listeria RNA upon infection. Infection with Listeria as well as transfection of bacterial RNA induced a type-I-IFN response in human monocytes, epithelial cells or hepatocytes. However, in contrast to monocytes, the type-I-IFN response of epithelial cells and hepatocytes was not triggered by bacterial DNA, indicating a STING-independent Listeria recognition pathway. RIG-I and MAVS knock-down resulted in abolishment of the IFN response in epithelial cells, but the IFN response in monocytic cells remained unaffected. By contrast, knockdown of STING in monocytic cells reduced cytosolic Listeria-mediated type-I-IFN induction. Our results show that detection of Listeria RNA by RIG-I represents a non-redundant cytosolic immunorecognition pathway in non-immune cells lacking a functional STING dependent signaling pathway.