Ground cover management does not influence densities of key Iridomyrmex species (Hym., Formicidae) in Australian citrus groves

Abstract:  Ants in the genus Iridomyrmex cause extensive problems for citrus producers in southern Australia by disrupting the biological control of honeydew-producing Hemiptera. We used baited pitfall traps to survey ant communities in 20 commercial citrus groves and test the hypothesis that populations of Iridomyrmex rufoniger gp spp. and Iridomyrmex purpureus can be reduced by conserving volunteer inter-row vegetation. Nine groves (five in the Murrumbidgee Irrigation Area, New South Wales, and four in the Sunraysia area, Victoria) were classified as 'bare' groves, where inter-row vegetation was routinely eliminated using herbicides and cultivation. The remaining 'grassed' groves (five in the MIA, six in Sunraysia) had inter-row vegetation controlled only by intermittent mowing. All groves had been managed consistently for between 9 and 22 years. MIA groves were trapped on three occasions (October 1997, January 1998 and April 1998), and Sunraysia groves once (March 1999). Over 190 000 ants were recovered, with I. rufoniger gp spp. accounting for 74% of overall captures and dominating collections in both 'bare' and 'grassed' groves. A linear mixed model analysis showed that ground cover management history had no significant effect (P > 0.05) on captures of I. rufoniger gp spp., I. purpureus , other Dolichoderinae, Ponerinae, Formicinae or Myrmicinae. High variability between ant populations in groves under the same management regime in each region suggests that aspects of grove management may be affecting ant community composition, however, our results indicate that suppression of pest Iridomyrmex species cannot be reliably achieved simply by altering the management of volunteer inter-row vegetation.     

Polypeptides of the surface projections and the ribonucleoprotein of avian infectious bronchitis virus.

Purified avian infectious bronchitis virus was digested with bromelain (0.7 mg/ml), and the surface projections were removed. Polyacrylamide gel electrophoresis of the polypeptides from these bromelain-treated particles showed that VP1, VP2, and VP5 were missing from the seven polypeptides. VP1 to VP7, that were present in untreated virus preparations. Milder bromelain treatment (0.07 mg/ml) left visible surface projections and polypeptides comprising VP1 and VP2 intact, but removed VP5. Thus, there are apparently two types of surface projections on the virus particle. The ribonucleoprotein complex was released from virus particles disrupted with 1% Nonidet P-40. The proportion of VP6 in such preparations was greatly reduced, implying that VP6 is the structural polypeptide of the ribonucleoprotein. Polypeptides VP1, VP2, VP4, and VP5 are glycosylated, but none of the polypeptides contains lipid.     

Actin filaments elongate from their membrane-associated ends

In limulus sperm an actin filament bundle 55 mum in length extends from the acrosomal vacuole membrane through a canal in the nucleus and then coils in a regular fashion around the base of the nucleus. The bundle expands systematically from 15 filaments near the acrosomal vacuole to 85 filaments at the basal end. Thin sections of sperm fixed during stages in spermatid maturation reveal that the filament bundle begins to assemble on dense material attached to the acrosomal vacuole membrane. In micrographs fo these early stages in maturation, short bundles are seen extending posteriorly from the dense material. The significance is that these short, developing bundles have about 85 filaments, suggesting that the 85-filament end of the bundle is assembled first. By using filament bundles isolated and incubated in vitro with G actin from muscle, we can determine the end “preferred” for addition of actin monomers during polymerization. The end that would be associated with the acrosomal vacuole membrane, a membrane destined to be continuous with the plasma membrane, is preferred about 10 times over the other, thicker end. Decoration of the newly polymerized portions of the filament bundle with subfragment 1 of myosin reveals that the arrowheads point away from the acrosomal vacuole membrane, as is true of other actin filament bundles attached to membranes. From these observations we conclude that the bundle is nucleated from the dense material associated with the acrosomal vacuole and that monomers are added to the membrane-associated end. As monomers are added at the dense material, the thick first-made end of the filament bundle is pushed down through the nucleus where, upon reaching the base of the nucleus, it coils up. Tapering is brought about by the capping of the peripheral filaments in the bundle.     

Large acceleration of alpha-chymotrypsin-catalyzed dipeptide formation by 18-crown-6 in organic solvents

The effects of 18-crown-6 on the synthesis of peptides catalyzed by alpha-chymotrypsin are reported. Lyophilization of the enzyme in the presence of 50 equivalents of 18-crown-6 results in a 425-fold enhanced activity when the reaction between the 2-chloroethylester of N-acetyl-L-phenylalanine and L-phenylalaninamide is carried out in acetonitrile. Addition of crown ether renders the dipeptide synthesis in nonaqueous solvents catalyzed by alpha-chymotrypsin possible on a preparative scale. The acceleration is observed in different solvents and for various peptide precursors. Copyright 1998 John Wiley & Sons, Inc.     

Partially glucose-capped oligosaccharides are found on the hemoglobins of the deep-sea tube worm Riftia pachyptila

We report here the structural determination of N-linked oligosaccharides found on extracellular hemoglobins of the hydrothermal vent tube worm Riftia pachyptila. Structures were elucidated by a combination of electrospray ionization tandem mass spectrometry, matrix- assisted laser desorption/ionization mass spectrometry, normal-phase high performance liquid chromatography, and exoglycosidase digestion. The sugar chains were found to consist mainly of high-mannose-type glycans with some structures partially capped by one or two terminal glucose residues. The present study represents the first report of the occurrence of glucose capping of N-linked carbohydrates in a secreted glycoprotein of a metazoan. Previously, glucose capping has only been described for a membrane-bound surface glycoprotein from the unicellular parasite Leishmania mexicana amazonensis.      

Comparative accuracy of methods for protein sequence similarity search

MOTIVATION: Searching a protein sequence database for homologs is a powerful tool for discovering the structure and function of a sequence. Two new methods for searching sequence databases have recently been described: Probabilistic Smith-Waterman (PSW), which is based on Hidden Markov models for a single sequence using a standard scoring matrix, and a new version of BLAST (WU-BLAST2), which uses Sum statistics for gapped alignments. RESULTS: This paper compares and contrasts the effectiveness of these methods with three older methods (Smith- Waterman: SSEARCH, FASTA and BLASTP). The analysis indicates that the new methods are useful, and often offer improved accuracy. These tools are compared using a curated (by Bill Pearson) version of the annotated portion of PIR 39. Three different statistical criteria are utilized: equivalence number, minimum errors and the receiver operating characteristic. For complete-length protein query sequences from large families, PSW's accuracy is superior to that of the other methods, but its accuracy is poor when used with partial-length query sequences. False negatives are twice as common as false positives irrespective of the search methods if a family-specific threshold score that minimizes the total number of errors (i.e. the most favorable threshold score possible) is used. Thus, sensitivity, not selectivity, is the major problem. Among the analyzed methods using default parameters, the best accuracy was obtained from SSEARCH and PSW for complete-length proteins, and the two BLAST programs, plus SSEARCH, for partial-length proteins.      

Pertussis immunisation and serious acute neurological illnesses in children.

OBJECTIVE--To determine long term outcome in children who had a severe acute neurological illness in early childhood associated with pertussis immunisation. DESIGN--Follow up study of cases and matched controls. SETTING--Assessment of children at home and at school throughout Britain. SUBJECTS--Children recruited into the national childhood encephalopathy study in 1976-9 were followed up, with one of their two original matched controls, in 1986-9. MAIN OUTCOME MEASURES--Performance in educational attainment tests; behaviour problems reported by teachers and parents; continuing convulsions; evidence of other neurological or physical dysfunction. RESULTS--Over 80% of cases and controls were traced. Case children were significantly more likely than controls to have died or to have some form of educational, behavioural, neurological, or physical dysfunction a decade after their illness. The prevalence of one or more of these adverse outcomes in case children who had been immunised with diphtheria, tetanus, and pertussis vaccine within seven days before onset of their original illness was similar to that in case children who had not been immunised recently. The relative risk for recent diphtheria, tetanus, and pertussis immunisation in children who had died or had any dysfunction in comparison with controls was 5.5 (95% confidence interval 1.6 to 23.7). However, the number of cases associated with vaccine (12) was extremely small and statistically vulnerable, and other possible agents or predisposing factors could not be excluded. CONCLUSIONS--Diphtheria, tetanus, and pertussis vaccine may on rare occasions be associated with the development of severe acute neurological illnesses that can have serious sequelae. Some cases may occur by chance or have other causes. The role of pertussis vaccine as a prime or concomitant factor in the aetiology of these illnesses cannot be determined in any individual case. The balance of possible risk against known benefits from pertussis immunisation supports continued use of the vaccine.     

A novel ubiquitin-like domain in IkappaB kinase beta is required for functional activity of the kinase

Activation of NF-kappaB requires two highly related kinases named IKKalpha and IKKbeta that share identity in the nature and positioning of their structural domains. Despite their similarity, the kinases are functionally divergent, and we therefore sought to identify any structural features specific for IKKalpha or IKKbeta. We performed bioinformatics analysis, and we identified a region resembling a ubiquitin-like domain (UBL) that exists only in IKKbeta and that we named the UBL-like domain (ULD). Deletion of the ULD rendered IKKbeta catalytically inactive and unable to induce NF-kappaB activity, and overexpression of only the ULD dose-dependently inhibited tumor necrosis factor-alpha-induced NF-kappaB activity. The ULD could not be functionally replaced within IKKbeta by ubiquitin or the corresponding region of IKKalpha, whereas deletion of the equivalent section of IKKalpha did not affect its catalytic activity against IkappaBalpha or its activation by NF-kappaB-inducing kinase. We identified five residues conserved among the larger family of UBL-containing proteins and IKKbeta, and alanine scanning revealed that the leucine at position 353 (Leu(353)) is absolutely critical for IKKbeta-induced NF-kappaB activation. Most intriguingly, the L353A mutant was catalytically active but, unlike wild-type IKKbeta, formed a stable complex with the NF-kappaB p65 subunit. Our findings therefore establish the ULD as a critical functional domain specific for IKKbeta that might play a role in dissociating IKKbeta from p65.