New ventures in the chemistry of avermectins

An overview is given on recent work towards new avermectin derivatives of extremely high insecticidal and acaricidal activity. These compounds were prepared from commercially available abamectin (avermectin B1) 1. For the synthesis, many novel entries have been opened up, making use of modern synthetic methods and applying them, for the first time, to the chemistry of avermectins. Several types of avermectin derivatives can be regarded as key innovations in the field. These are, in particular, 4″-deoxy-4″-(S)-amino avermectins 3, 4′-O-alkoxyalkyl avermectin monosaccharides 5, 4″-deoxy-4″-C-substituted 4″-amino avermectins 6 and 2″-substituted avermectins 7. 4″-Deoxy-4″-(S)-amino avermectins 3 were obtained by the consecutive application of the Staudinger and Aza-Wittig reaction. 4′-O-Alkoxyalkyl avermectin monosaccharides 5 were prepared by alkoxyalkylation of 5-O-protected avermectin monosaccharide. For the synthesis of 4″-deoxy-4″-C-substituted 4″-amino avermectins 6, several methods were used to construct the fully substituted 4″-carbon centre, such as a modified Strecker synthesis, the addition of organometallics to a 4″-sulfinimine and a modified Ugi approach. In order to prepare 2″-substituted avermectins 7, 5-O-protected avermectin monosaccharide was coupled with carbohydrate building blocks. An alternative synthesis involved the hitherto unknown enol ether chemistry of 4″-oxo-avermectin and the conjugate addition of a cuprate to an avermectin 2″,3″-en-4″-one. In addition, a number of other highly potent derivatives were synthesised. Examples are 4″-O-amino avermectins 8, as well as products arising from intramolecular rhodium catalysed amidations and carbene insertions. A radical cyclisation led to an intriguing rearrangement of the avermectin skeleton. Many of the new avermectins surpassed the activity of abamectin 1 against insects and mites.     

Multiple cyst formation in the liver and kidneys of a lion (<Emphasis Type="Italic">Panthera leo</Emphasis>): a case of polycystic kidney disease?

The present report describes the case of a 19-year-old male lion (Panthera leo) with polycystic lesions in liver and kidney. The animal suffered from inappetence and progressing hind limb weakness and was euthanized due to poor prognosis. Necropsy revealed multiple large, cystic cavities in the liver and numerous cysts in the renal cortex. Hepatic and renal cysts were lined by a flattened or cuboidal single-layered epithelium and derived from hepatic bile ducts and renal tubular structures, respectively, as confirmed by immunohistochemistry for the detection of different cytokeratins and carcinoembryonic antigen. Furthermore, a marked bile duct proliferation and fibrosis was found in the portal areas. Occasionally, renal cysts contained variable amounts of partly mineralized proteinaceous material, detached epithelial cells, and cellular debris. Additional findings included a moderate suppurative bronchopneumonia and other minor age-related degenerative changes. A mutation screen of exon 29 of the PKD1 gene did not reveal causative mutations like in domestic cats. This is the first report of polycystic kidney disease (PKD)-like lesions in a lion. The features of these lesions are similar to those of the adult-onset form of PKD in Persian cats.     

Characterization of Phleum pratense pollen extracts by 2-D DIGE and allergen immunoreactivity

The allergen content of standardized pollen material is crucial for an effective diagnosis and treatment. However, variations in IgE reactivities of allergic patients to different preparations of Phleum pratense pollen have been reported. In order to define and directly compare the allergen composition of pollen preparations provided by different suppliers, a comprehensive proteome analysis of three different timothy grass pollen extracts was performed. More than 140 proteins were annotated comprising the pollen proteome/allergome in a global 2-D map. With regard to the individual pollen preparations, several major differences in the overall protein composition were detected that also affected known Phleum allergens and their isoforms. Importantly, these differences were also reflected at the level of antibody reactivities in 1-D and 2-D immunoblots. As a consequence, it is suggested that the observed differences should be taken into consideration aiming for a standardized diagnosis and therapy of grass pollen allergies as recommended by international medical agencies.     

Identification of interaction partners of the cytosolic polyproline region of CD95 ligand (CD178)

The CD95/Fas/Apo-1 ligand (CD95L, CD178) induces apoptosis through the death receptor CD95. CD95L was also described as a co-stimulatory receptor for T-cell activation in mice in vivo. The molecular basis for the bidirectional signaling capacity and directed expression of CD95L is unknown. In the present study we identify proteins that precipitate from T-cell lysates with constructs containing fragments of the CD95L cytosolic tail. The determined peptide mass fingerprints correspond to Grb2, actin, beta-tubulin, formin binding protein 17 (FBP17) and PACSIN2. Grb2 had been identified as a putative mediator of T-cell receptor-to-CD95L signaling before. FBP17 and PACSIN2 may be associated with expression and trafficking of CD95L. When overexpressed, CD95L co-precipitates with FBP17 and PACSIN. Protein-protein interactions are mediated via Src homology 3 (SH3) domain binding to the polyproline region of CD95L and can be abolished by mutation or deletion of the respective SH3 domain.     

Monitoring the spatial and temporal dynamics of a community of the tree-root endophyte Phialocephala fortinii s.l

Phialocephala fortinii sensu lato was isolated from Picea abies roots that had been collected from the same 3 x 3-m forest plot in 2001 and 2004, to examine the spatial and temporal dynamics of this fungal community. RFLP analysis was used to define the multilocus haplotype (MLH) of each isolate. Pielou's measure of association and chi(2) tests of independence were employed to examine the randomness of patterns of spatial distribution of MLH observed in 2001 and 2004. Population differentiation between the two samplings was tested using the G(ST) statistic. In 2001, 144 strains of 28 MLH were isolated; in 2004, 139 strains of 29 MLH. Abundant MLH in 2001 also prevailed in 2004, and the same two cryptic species were dominant in both collections. The probability of being isolated in both years increased with increasing frequency of an MLH. The patterns of spatial distribution of most MLH did not differ between years. The G(ST) values indicated identity of the two collections. Communities of P. fortinii sensu lato remain spatially and genetically stable for at least 3 yr.