A transcriptional network associated with natural variation in Drosophila aggressive behavior

Background  

Aggressive behavior is an important component of fitness in most animals. Aggressive behavior is genetically complex, with natural variation attributable to multiple segregating loci with allelic effects that are sensitive to the physical and social environment. However, we know little about the genes and genetic networks affecting natural variation in aggressive behavior. Populations of Drosophila melanogaster harbor quantitative genetic variation in aggressive behavior, providing an excellent model system for dissecting the genetic basis of naturally occurring variation in aggression.     

Aging in the post-genomic era: simple or complex?

A report on the Third Genetic Effects on Aging Meeting, The Jackson Laboratory, Bar Harbor, Maine, August 4-8, 2000.     

In the mood for wood-habitat specific colonization patterns of benthic invertebrate communities along the longitudinal gradient of an Austrian river

Instream large wood (LW) constitutes an indispensable element of natural river ecosystems. It affects local hydraulics, morphology, nutrient budget, overall habitat complexity, and dynamics. Despite numerous studies about LW as a habitat for benthic communities, information on the varying importance along the longitudinal gradient of a river is lacking. The focus of this study is therefore to investigate general differences between lithal and xylal colonizers and to further investigate trends along the river course. We analyzed lithal and xylal communities at ten sites along the medium-sized Lafnitz River in Southeast Austria. Our results significantly show (1) a general differentiation between lithal and xylal communities, (2) an increasing distinction of the lithal and xylal fauna along the longitudinal gradient of the river, and (3) a distinct correlation between the distance from source and the number of exclusive xylal and nowadays predominantly rare taxa. The presence of LW is therefore directly linked to higher aquatic biodiversity compared to rocky substrates and presents a unique element for river restoration, especially in lower river sections.     

Isoelectric focusing in immobilized pH gradients: Generation of extended pH intervals

A new technique for generatiing extended pH gradients (3–4 pH units) in Immobiline gels for isoelectric separations is described. A five-chamber gradient mixer has been built, based on the ‘Varigard’-type mixers of Peterson and Sober (Anal. Chem. 31, 1959, 857–862). Each chamber contains one of the following Immobilines, in this order: pK values 4.4, 4.6, 6.2, 7.0 and 8.5, titrated in the pH 4–8 interval with non-buffering Immobilines pK 9.3 (in the case of the two acidic Immobilines) and pK 3.6 (in the case of the three basic Immobilines). In this way it is possible to cast, in a highly reproducible way, an immobilized pH gradient in thepH range 4.0 to 7.5, which should be ideal for isoelectric separations in the first dimension of two-dimensional techniques. A computer program is also described which, given the molarities and pK values of the different Immobilines in the chambers of the Varigrad mixer, can generate the theoretical pH profile, together with the buffering capacity (β) and ionic strength (I) courses.     

Secondary metabolites produced by Propionicimonas sp. (ENT-18) induce histological abnormalities in the sclerotia of Sclerotinia sclerotiorum

Sclerotinia sclerotiorum is a highly aggressive pathogen that causes great economic losses, especially in temperate climates. Several biological control agents are available, but actinobacteria have seldom been used to control this fungus. Our objective was to evaluate the efficiency and ultrastructural effects of the secondary metabolites produced by the ant-associated actinobacterium Propionicimonas sp. ENT-18 in controlling the sclerotia of S. sclerotiorum. We demonstrated total inhibition of sclerotia treated with 62.5 μg/10 μl of an ethyl acetate extract of compounds produced by ENT-18, and calculated an LC₅₀ of 1.69 μg/sclerotia. Histological and ultrastructural analysis indicated that the cells of the treated sclerotia were severely damaged, suggesting direct action of the biomolecule(s) produced by the actinobacterium ENT-18 on the cell structure of the medullae and rind cell wall. This is the first report demonstrating a novel property of Propionicimonas sp.—antifungal activity against S. sclerotiorum.     

Transcriptional response to alcohol exposure in Drosophila melanogaster

Background  

Alcoholism presents widespread social and human health problems. Alcohol sensitivity, the development of tolerance to alcohol and susceptibility to addiction vary in the population. Genetic factors that predispose to alcoholism remain largely unknown due to extensive genetic and environmental variation in human populations. Drosophila, however, allows studies on genetically identical individuals in controlled environments. Although addiction to alcohol has not been demonstrated in Drosophila, flies show responses to alcohol exposure that resemble human intoxication, including hyperactivity, loss of postural control, sedation, and exposure-dependent development of tolerance.     

A rheumatoid factor paradox: inhibition of rituximab effector function

Introduction

Rituximab (RTX) therapy of rheumatoid arthritis (RA) exhibits enhanced effectiveness in seropositive patients. Using patient sera, we tested if this improved efficacy was associated with enhanced RTX mediated complement-dependent cytotoxicity (RTX-CDC).

Methods

We developed an in vitro assay for RTX-CDC using patient sera and the Daudi human B cell line. Using propidium iodide uptake and flow cytometry, we compared RTX-CDC with rheumatoid factor (RF)+ sera relative to normal volunteer, non-RA and RF- sera. Additional studies examined mixing studies of RF+ and RF- sera, as well as the effect of monoclonal IgA or IgM RF. Finally, the effect of RF on RTX mediated trogocytosis of normal B cells was evaluated.

Results

Using human sera, addition of RTX resulted in rapid and profound (> 50%) Daudi cell death that was complement dependent. Surprisingly, RF+ patient sera exhibited reduced RTX-CDC relative to RF- sera, with an inverse relationship of RTX-CDC and RF titer. Mixing studies indicated the presence of an inhibitor of RTX-CDC in RF+ sera. The addition of monoclonal IgM or IgA RF to RF- sera markedly inhibited RTX-CDC. This effect was specific for RF binding to the Fc portion of RTX as it was not apparent with the F(ab)'' domains of RTX engineered onto IgG3 heavy chain. RF also modestly inhibited RTX mediated trogocytosis.

Conclusions

Contrary to expectations, RF+ sera exhibits reduced RTX-CDC due to the presence of RF. The enhanced efficacy of RTX in seropositive RA patients cannot be attributed to improved B cell depletion through CDC. This result indicates that high RF levels may potentially modulate the efficacy of any therapeutic monoclonal antibody dependent on Fc effector function.