Synthesis and structure-activity relationship of 2-(aminoalkyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives: a novel series of 5-HT(2A/2C) receptor antagonists. Part 2.

Following the programme started at Janssen Research Foundation searching for 5-HT(2A/2C) antagonists, we now report on the synthesis of a series of substituted 2-(Dimethylaminomethyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives. The 5-HT(2A), 5-HT(2C) and H(1) receptor affinities as well as the mCPP antagonistic activity of the compounds synthesised is described.     

Molecular characterization of a fourth isoform of the catalytic subunit of protein phosphatase 2A from Arabidopsis thaliana

We have recently reported the existence of multiple isoforms of the catalytic subunit of protein phosphatase 2A (PP2A) in Arabidopsis thaliana and the molecular cloning of cDNAs encoding three of these proteins (PP2A-1, PP2A-2, PP2A-3). The reported cDNA encoding PP2A-3 was truncated at the 5 terminus, lacking a short fragment of the N-terminal coding sequence. We have now isolated a near full-length cDNA encoding the entire PP2A-3 protein (313 residues). The clone includes 188 nucleotides of 5-untranslated region, where a 44 bp long poly(GA) track is found. We also describe the cloning of a cDNA encoding a fourth isoform of PP2A (PP2A-4). The polypeptide contains 313 residues being 98% identical to PP2A-3 and only 80% identical to both PP2A-1 and PP2A-2. The mRNA for PP2A-4 is 1.4 kb in length and, although predominantly expressed in roots, it is also found in other organs. It is concluded that in A. thaliana the isoforms of PP2A can be grouped in two extremely conserved subfamilies.     

Field methods to study the spatial root density distribution of individual plants

Plant and Soil - The ecological study of root systems lags behind the understanding of the aboveground components of plant communities, mainly due to methodological challenges. As ecological root...     

Fine Mapping and Functional Analysis of the Multiple Sclerosis Risk Gene CD6

CD6 has recently been identified and validated as risk gene for multiple sclerosis (MS), based on the association of a single nucleotide polymorphism (SNP), rs17824933, located in intron 1. CD6 is a cell surface scavenger receptor involved in T-cell activation and proliferation, as well as in thymocyte differentiation. In this study, we performed a haptag SNP screen of the CD6 gene locus using a total of thirteen tagging SNPs, of which three were non-synonymous SNPs, and replicated the recently reported GWAS SNP rs650258 in a Spanish-Basque collection of 814 controls and 823 cases. Validation of the six most strongly associated SNPs was performed in an independent collection of 2265 MS patients and 2600 healthy controls. We identified association of haplotypes composed of two non-synonymous SNPs [rs11230563 (R225W) and rs2074225 (A257V)] in the 2^nd SRCR domain with susceptibility to MS (P _{max(T) permutation} = 1×10⁻⁴). The effect of these haplotypes on CD6 surface expression and cytokine secretion was also tested. The analysis showed significantly different CD6 expression patterns in the distinct cell subsets, i.e. – CD4⁺ naïve cells, P = 0.0001; CD8⁺ naïve cells, P<0.0001; CD4⁺ and CD8⁺ central memory cells, P = 0.01 and 0.05, respectively; and natural killer T (NKT) cells, P = 0.02; with the protective haplotype (RA) showing higher expression of CD6. However, no significant changes were observed in natural killer (NK) cells, effector memory and terminally differentiated effector memory T cells. Our findings reveal that this new MS-associated CD6 risk haplotype significantly modifies expression of CD6 on CD4⁺ and CD8⁺ T cells.     

The high diversity of <Emphasis Type="Italic">Lotus corniculatus</Emphasis> endosymbionts in soils of northwest Spain

The diversity of rhizobia that establish symbiosis with Lotus corniculatus has scarcely been studied. Several species of Mesorhizobium are endosymbionts of this legume, including Mesorhizobium loti, the type species of this genus. We analysed the genetic diversity of strains nodulating Lotus corniculatus in Northwest Spain and ten different RAPD patterns were identified among 22 isolates. The phylogenetic analysis of the 16S rRNA gene showed that the isolated strains belong to four divergent phylogenetic groups within the genus Mesorhizobium. These phylogenetic groups are widely distributed worldwide and the strains nodulate L. corniculatus in several countries of Europe, America and Asia. Three of the groups include the currently described Mesorhizobium species M. loti, M. erdmanii and M. jarvisii which are L. corniculatus endosymbionts. An analysis of the recA and atpD genes showed that our strains belong to several clusters, one of them very closely related to M. jarvisii and the remanining ones phylogenetically divergent from all currently described Mesorhizobium species. Some of these clusters include L. corniculatus nodulating strains isolated in Europe, America and Asia, although the recA and atpD genes have been sequenced in only a few L. corniculatus endosymbionts. The results of this study revealed great phylogenetic diversity of strains nodulating L. corniculatus, allowing us to predict that even more diversity will be discovered as further ecosystems are investigated.     

Evidence of an American origin for symbiosis-related genes in Rhizobium lusitanum

Randomly amplified polymorphic DNA (RAPD) analysis was used to investigate the diversity of 179 bean isolates recovered from six field sites in the Arcos de Valdevez region of northwestern Portugal. The isolates were divided into 6 groups based on the fingerprint patterns that were obtained. Representatives for each group were selected for sequence analysis of 4 chromosomal DNA regions. Five of the groups were placed within Rhizobium lusitanum, and the other group was placed within R. tropici type IIA. Therefore, the collection of Portuguese bean isolates was shown to include the two species R. lusitanum and R. tropici. In plant tests, the strains P1-7, P1-1, P1-2, and P1-16 of R. lusitanum nodulated and formed nitrogen-fixing symbioses both with Phaseolus vulgaris and Leucaena leucocephala. A methyltransferase-encoding nodS gene identical with the R. tropici locus that confers wide host range was detected in the strain P1-7 as well as 24 others identified as R. lusitanum. A methyltransferase-encoding nodS gene also was detected in the remaining isolates of R. lusitanum, but in this case the locus was that identified with the narrow-host-range R. etli. Representatives of isolates with the nodS of R. etli formed effective nitrogen-fixing symbioses with P. vulgaris and did not nodulate L. leucocephala. From sequence data of nodS, the R. lusitanum genes for symbiosis were placed within those of either R. tropici or R. etli. These results would support the suggestion that R. lusitanum was the recipient of the genes for symbiosis with beans from both R. tropici and R. etli.     

Pollination of Euphorbia dendroides by lizards and insects: Spatio-temporal variation in patterns of flower visitation

The patterns of flower visitation by lizards (Podarcis lilfordi, Lacertidae) and insects (mainly flies, bees and wasps) on the shrub Euphorbia dendroides, were studied in the island of Cabrera (Balearic Islands) during the flowering seasons of 1995 and 1996. Lizards act as true pollinators of the plant, moving large quantities of pollen within and among shrubs. To our knowledge, this is the first time that pollination by lizards has been empirically demonstrated. Variation in the quantitative component of pollination (frequency of visits × flower visitation rate) by the two groups of pollinators (lizards and insects) is documented at both spatial (within a plant population) and temporal scales (throughout the flowering season and between seasons). Variation in lizard density on a small spatial scale (within c. 200 m), presumably due to differences in vegetation cover, strongly affected their frequency of flower visitation. Insects were rather scarce, mainly because the plant flowers at a time (mid-March) when temperatures are still low. At the site where lizards were abundant, their frequency of flower visits was more than 3 times that of insects, they stayed on the shrubs about 3 times longer and visited about 8 times more cyathia per minute than did insects. Fruit and seed set were greater at this site, and this is attributed to the different frequency of flower visits by lizards, as shrubs are similar in size and produce similar amounts of cyathia in the two sites compared. Both, lizards and insects went more frequently to plants with large flower crops. However, flower crop was not associated with seed viability. We found no evidence for pollinator-mediated selection on plant traits related to fitness. Received: 28 August 1996 / Accepted: 26 February 1997     

Shedding of Infectious Borna Disease Virus-1 in Living Bicolored White-Toothed Shrews

Background

Many RNA viruses arise from animal reservoirs, namely bats, rodents and insectivores but mechanisms of virus maintenance and transmission still need to be addressed. The bicolored white-toothed shrew (Crocidura leucodon) has recently been identified as reservoir of the neurotropic Borna disease virus 1 (BoDV-1).

Principal Findings

Six out of eleven wild living bicoloured white-toothed shrews were trapped and revealed to be naturally infected with BoDV-1. All shrews were monitored in captivity in a long-term study over a time period up to 600 days that differed between the individual shrews. Interestingly, all six animals showed an asymptomatic course of infection despite virus shedding via various routes indicating a highly adapted host-pathogen interaction. Infectious virus and viral RNA were demonstrated in saliva, urine, skin swabs, lacrimal fluid and faeces, both during the first 8 weeks of the investigation period and for long time shedding after more than 250 days in captivity.

Conclusions

The various ways of shedding ensure successful virus maintenance in the reservoir population but also transmission to accidental hosts such as horses and sheep. Naturally BoDV-1-infected living shrews serve as excellent tool to unravel host and pathogen factors responsible for persistent viral co-existence in reservoir species while maintaining their physiological integrity despite high viral load in many organ systems.     

Scaffold hopping from pyridones to imidazo[1,2-a]pyridines. New positive allosteric modulators of metabotropic glutamate 2 receptor

Imidazo[1,2-a]pyridines were identified via their shape and electrostatic similarity as novel positive allosteric modulators of the metabotropic glutamate 2 receptor. The subsequent synthesis and SAR are described. Potent, selective and metabolically stable compounds were found representing a promising avenue for current further studies.