Citrus limonoid effects on Colorado potato beetle larval survival and development

The effects of citrus limonoids, applied topically to potato (Solanum tuberosum L. var. Katahdin) foliage, on Colorado potato beetle (Leptinotarsa decemlineata) (Say) (Chrysomelidae) larval development, growth, and survival were quantified in laboratory assays and a small-plot field test. In laboratory assays, survival, development rate, and body weight decreased with increasing limonoid concentration, however these measures of larval response did not significantly differ among varying periods of limonoid exposure (three, six, or nine days). Significant limonoid application concentration and frequency effects on survival, development rate, and defoliation were observed in the field test. These results indicate the potential utility of lethal and non-lethal effects of citrus limonoids for management of the Colorado potato beetle.     

Analysis of a FliM-FliN flagellar switch fusion mutant of Salmonella typhimurium.

In the course of an analysis of the three genes encoding the flagellar motor switch, we isolated a paralyzed mutant whose defect proved to be a 4-bp deletion of the ribosome binding sequence of the fliN switch gene (V. M. Irikura, M. Kihara, S. Yamaguchi, H. Sockett, and R. M. Macnab, J. Bacteriol. 175:802-810,1993). This sequence lies just before the 3' end of the coding sequence of the upstream fliM switch gene, in the same operon. This mutant readily gave rise to pseudorevertants which, though much less motile than the wild type, did exhibit significant swarming. One such pseudorevertant was found to contain a compensating frameshift such that the fliM and fliN genes were placed in frame, coding for an essentially complete FliM-FliN protein fusion. Minicell analysis demonstrated that, as expected, the parental mutant synthesized an essentially full-length FliM protein but no detectable FliN. The pseudorevertant, in contrast, synthesized a protein with the predicted size for the FliM-FliN fusion protein and no detectable FliM or FliN. Immunoblotting of minicells with antibodies against FliM and FliN confirmed the identities of these various proteins. Immunoblotting of book-basal-body complexes from the wild-type strain gave a strong signal for the three switch proteins FliG, FliM, and FliN. Complexes from the FliM-FliN fusion mutant gave a strong signal for FliG but no signal for either FIiM or FliN; a moderately strong signal for the FliM-FliN fusion protein was seen with the anti-FliM antibody, and a weaker signal was seen with the anti-FliN antibody. The cytoplasmic C ring of the structure, which is seen consistently in electron microscopy of wild-type complexes and which is known to contain the FliM and FliN proteins, was much more labile in the FliM-FliN fusion mutant, giving a fragmented and variable appearance or being completely absent. Complementation data indicated that wild-type FliM had a mild dominant negative effect over the fusion protein, that wild-type FliN and the fusion protein work much better than the fusion protein alone, and that wild-type FliM and FliN together have no major positive or negative effect on the function of the fusion protein. We interpret these data to mean that the FliM-FliN fusion protein incorporates into structure but less stably than do the FliM and FliN proteins separately, that wild-type FliM tends to displace the fusion protein, and that wild-type FliN can supplement the FliN domain of the fusion protein without displacing the FliM domain. The data support, but do not prove, a model in which FliM and FliN in the wild-type switch complex are stationary with respect to each other.     

The prevalence of gentamicin 2'-N-acetyltransferase in the Proteeae and its role in the O-acetylation of peptidoglycan

Abstract The prevalence of aac(2')-Ia , a gene coding for gentamicin 2'-JV-acetyltransferase in Providenda stuartii , among species of the Proteeae was investigated to determine if it is a common resistance factor and whether the correlation observed in P. stuartii between its expression and the levels of peptidoglycan O -acetylation represents a general feature of bacteria producing this form of modified peptidoglycan. An evaluation of the MICs of gentamicin for each of the species of the Proteeae did not reveal any apparent relationship between resistance and the degree of O-acetylation of peptidoglycan. The entire aac(2')-Ia gene was used as a probe in Southern hybridization experiments against genomic DNA from each species of the Proteeae. A sequence with strong homology to aac(2')-Ia was present only in Proteus penneri while weak hybridization was also observed to the restriction digested DNA from Providenda rettgeri . Other bacteria that O -acetylate peptidoglycan were also screened with this probe and a homologous DNA sequence was only found in Neisseria subflava . These data suggest that AAC(2')-Ia may contribute to the rO -acetylation of peptidoglycan in P. stuartii , but a more specific enzyme must also be produced for this function.     

Complex repetitive arrangements of gene sequence in the candidate region of the spinal muscular atrophy gene in 5q13.

Childhood-onset proximal spinal muscular atrophy (SMA) is a heritable neurological disorder, which has been mapped by genetic linkage analysis to chromosome 5q13, in the interval between markers D5S435 and D5S557. Here, we present gene sequences that have been isolated from this interval, several of which show sequence homologies to exons of beta-glucuronidase. These gene sequences are repeated several times across the candidate region and are also present on chromosome 5p. The arrangement of these repetitive gene motifs is polymorphic between individuals. The high degree of variability observed may have some influence on the expression of the genes in the region. Since SMA is not inherited as a classical autosomal recessive disease, novel genomic rearrangements arising from aberrant recombination events between the complex repeats may be associated with the phenotype observed.     

SR141716A, a potent and selective antagonist of the brain cannabinoid receptor

SR141716A is the first selective and orally active antagonist of the brain cannabinoid receptor. This compound displays nanomolar affinity for the central cannabinoid receptor but is not active on the peripheral cannabinoid receptor. In vitro, SR141716A antagonises the inhibitory effects of cannabinoid receptor agonists on both mouse vas deferens contractions and adenylyl cyclase activity in rat brain membranes. After intraperitoneal or oral administration SR141716A antagonises classical pharmacological and behavioural effects of cannabinoid receptor agonists. This compound should prove to be a powerful tool for investigating the in vivo functions of the anandamide/cannabinoid system.