A molecular marker confirms that the rate of adult maturation is largely independent of the rate of pre-adult development in Drosophila melanogaster

The separation of adult from pre-adult life seen with animals such as Drosophila melanogaster, which are holometabolous and undergo complete metamorphosis, provides the opportunity to examine the contribution of pre-adult rate of development on the rate of maturation and aging of the adult. Recent work has shown that when ambient temperature is used to alter the rate of development there is little effect on adult life span. From this work it has been concluded that the rate of aging is largely independent of the rate of pre-adult development. However, the techniques used to examine life span did not allow for the examination of the earliest events of adult life. Our experimental design used a molecular marker linked to life span as a sensitive measure of determining physiological age. In this way, we were able to evaluate the effect of pre-adult rate of development on the earliest events of adult life. Using ambient temperature to alter both the rate of development in the pre-adult and the rate of aging in the adult independently, we were able to show that it is the ambient temperature at which the adults are living that is the principle determinant of the rate of maturation and aging of the adult. Little effect was seen on the rate of adult maturation in response to an acceleration or a slowing down of the rate of pre-adult development as measured by our molecular marker. These data support the conclusions drawn by others who examined the effect of the rate of development on adult life expectancy. The timing mechanisms at work during pre-adult and adult life appear to be largely regulated separately. If there is such a thing as a physiological clock, it appears to be reset upon eclosion. © 1996 Wiley-Liss, Inc.     

Recommendations for the routine sampling of diatoms for water quality assessments in Europe

Many methods for using diatoms for routine monitoring of water quality have been developed in Europe and, in some countries, these are being used to enforce environmental legislation. In order to facilitate their wider use, particularly with respect to European Union legislation, steps are being taken to harmonize methodology. In this paper, the principles and practice of sampling are described in relation to the main habitat types encountered in Europe. Although details of methods and sampling programmes have to be tailored to particular circumstances and the overall objectives of the monitoring, a number of generalizations can be made. Where available, rocks and other hard surfaces are the preferred substrates and methods for sampling these are described. If such substrata are not available, then introduced ('artificial') substrata have many applications. Various types of introduced substrata can be used successfully, so long as some basic precautions are described. Other types of substrata such as macrophytes and macroalgae may also be useful under certain circumstances, although there is less consensus in the literature on the most appropriate methods, and of the validity of comparisons between indices computed from epiphytic and epilithic communities. When designing surveys, it is recommended that as far as possible, extremes of non-water quality factors (e.g. shade, current speed, etc) are avoided, unless these are characteristic of the system under investigation. Detailed guidelines for sampling epilithon are described. Along with the recommendations for sampling other substrata, it is hoped that these provide a framework that can be adapted to most river types in Europe. This revised version was published online in June 2006 with corrections to the Cover Date.     

Implications of an invertebrate predator's ( Bythotrephes cederstroemi) atypical effects on a pelagic zooplankton community

The traditional view of predaceous zooplankton is that they prefer small-bodied prey, are hindered by morphological anti-predator defenses, and have a minor influence on zooplankton communities when fish are present. We performed a series of experiments with the large-bodied onychopod (cladoceran) Bythotrephes cederstroemi, in which we incubated this predator with known prey to determine prey preference and predation rates. We also performed an allozyme analysis of prey tissue in the gut of B. cederstroemi collected from several stations around Lake Michigan to determine what prey types are chosen in the field. We found that B. cederstroemi does not fit the standard invertebrate predator mold: adult B. cederstroemi prefer large (>2.0 mm) Daphnia pulicaria over smaller individuals; the elongated tailspine and helmet of Daphnia galeata mendotae are not effective deterrents to B. cederstroemi predation; and B. cederstroemi is a generalist predator with the potential to consume a significant portion of cladoceran production in Lake Michigan. This revised version was published online in July 2006 with corrections to the Cover Date.     

In vivo evolution of human immunodeficiency virus type 1 toward increased pathogenicity through CXCR4-mediated killing of uninfected CD4 T cells

The destruction of the immune system by progressive loss of CD4 T cells is the hallmark of AIDS. CCR5-dependent (R5) human immunodeficiency virus type 1 (HIV-1) isolates predominate in the early, asymptomatic stages of HIV-1 infection, while CXCR4-dependent (X4) isolates typically emerge at later stages, frequently coinciding with a rapid decline in CD4 T cells. Lymphocyte killing in vivo primarily occurs through apoptosis, but the importance of apoptosis of HIV-1-infected cells relative to apoptosis of uninfected bystander cells is controversial. Here we show that in human lymphoid tissues ex vivo, apoptosis of uninfected bystander CD4 T cells is a major mechanism of lymphocyte depletion caused by X4 HIV-1 strains but is only a minor mechanism of depletion by R5 strains. Further, X4 HIV-1-induced bystander apoptosis requires the interaction of the viral envelope glycoprotein gp120 with the CXCR4 coreceptor on CD4 T cells. These results emphasize the contribution of bystander apoptosis to HIV-1 cytotoxicity and suggest that in association with a coreceptor switch in HIV disease, T-cell killing evolves from an infection-restricted stage to generalized toxicity that involves a high degree of bystander apoptosis.     

Profiles of Airborne Fungi in Buildings and Outdoor Environments in the United States

We examined 12,026 fungal air samples (9,619 indoor samples and 2,407 outdoor samples) from 1,717 buildings located across the United States; these samples were collected during indoor air quality investigations performed from 1996 to 1998. For all buildings, both indoor and outdoor air samples were collected with an Andersen N6 sampler. The culturable airborne fungal concentrations in indoor air were lower than those in outdoor air. The fungal levels were highest in the fall and summer and lowest in the winter and spring. Geographically, the highest fungal levels were found in the Southwest, Far West, and Southeast. The most common culturable airborne fungi, both indoors and outdoors and in all seasons and regions, were Cladosporium, Penicillium, nonsporulating fungi, and Aspergillus. Stachybotrys chartarum was identified in the indoor air in 6% of the buildings studied and in the outdoor air of 1% of the buildings studied. This study provides industrial hygienists, allergists, and other public health practitioners with comparative information on common culturable airborne fungi in the United States. This is the largest study of airborne indoor and outdoor fungal species and concentrations conducted with a standardized protocol to date.     

Novel High-Molecular-Weight,R-Type Bacteriocins of Clostridium difficile

Clostridium difficile causes one of the leading nosocomial infections in developed countries, and therapeutic choices are limited. Some strains of C. difficile produce phage tail-like particles upon induction of the SOS response. These particles have bactericidal activity against other C. difficile strains and can therefore be classified as bacteriocins, similar to the R-type pyocins of Pseudomonas aeruginosa. These R-type bacteriocin particles, which have been purified from different strains, each have a different C. difficile-killing spectrum, with no one bacteriocin killing all C. difficile isolates tested. We have identified the genetic locus of these “diffocins” (open reading frames 1359 to 1376) and have found them to be common among the species. The entire diffocin genetic locus of more than 20 kb was cloned and expressed in Bacillus subtilis, and this resulted in production of bactericidal particles. One of the interesting features of these particles is a very large structural protein of ∼200 kDa, the product of gene 1374. This large protein determines the killing spectrum of the particles and is likely the receptor-binding protein. Diffocins may provide an alternate bactericidal agent to prevent or treat infections and to decolonize individuals who are asymptomatic carriers.     

Terahertz Microfluidic Sensing Using a Parallel-plate Waveguide Sensor

Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic samples with a wide range of possible sensor designs such as interferometers and resonators ^1,2. Most of the existing RI sensing applications focus on biological materials in aqueous solutions in visible and IR frequencies, such as DNA hybridization and genome sequencing. At terahertz frequencies, applications include quality control, monitoring of industrial processes and sensing and detection applications involving nonpolar materials.Several potential designs for refractive index sensors in the terahertz regime exist, including photonic crystal waveguides ³, asymmetric split-ring resonators ⁴, and photonic band gap structures integrated into parallel-plate waveguides ⁵. Many of these designs are based on optical resonators such as rings or cavities. The resonant frequencies of these structures are dependent on the refractive index of the material in or around the resonator. By monitoring the shifts in resonant frequency the refractive index of a sample can be accurately measured and this in turn can be used to identify a material, monitor contamination or dilution, etc.The sensor design we use here is based on a simple parallel-plate waveguide ^6,7. A rectangular groove machined into one face acts as a resonant cavity (Figures 1 and 2). When terahertz radiation is coupled into the waveguide and propagates in the lowest-order transverse-electric (TE₁) mode, the result is a single strong resonant feature with a tunable resonant frequency that is dependent on the geometry of the groove ^6,8. This groove can be filled with nonpolar liquid microfluidic samples which cause a shift in the observed resonant frequency that depends on the amount of liquid in the groove and its refractive index ⁹.Our technique has an advantage over other terahertz techniques in its simplicity, both in fabrication and implementation, since the procedure can be accomplished with standard laboratory equipment without the need for a clean room or any special fabrication or experimental techniques. It can also be easily expanded to multichannel operation by the incorporation of multiple grooves ¹⁰. In this video we will describe our complete experimental procedure, from the design of the sensor to the data analysis and determination of the sample refractive index.     

5-HT(3) receptors mediate inflammation-induced unmasking of functional tachykinin responses in vitro.

Exogenously applied tachykinins produce no measurable electrophysiological responses in the somata of vagal afferent neurons [nodose ganglion neurons (NGNs)] isolated from naive guinea pigs. By contrast, after in vitro antigen challenge of nodose ganglia from guinea pigs immunized with chick ovalbumin, approximately 60% (53 of 89) of NGNs were depolarized an average of 13 +/- 1.2 mV by substance P (SP; 100 nM; n = 53). Receptor antagonists and enzyme inhibitors were utilized to screen a number of mast cell-derived mediators for their role in the uncovering or "unmasking" of functional tachykinin receptors after antigen challenge. Two chemically distinct 5-hydroxytryptamine-3-receptor antagonists significantly reduced the percentage of NGNs displaying depolarizing SP responses. Treatment with Y-25130 (1 or 10 microM) or tropisetron (1 microM) 15 min before and during antigen challenge reduced the percentage of SP-responsive neurons to approximately 20 and approximately 15% respectively. These results suggest that activation of 5-hydroxytryptamine-3 receptors plays an integral role in the unmasking of functional tachykinin receptors after specific antigen challenge of nodose ganglia. The mediator(s) underlying tachykinin-receptor unmasking in the remainder of the NGNs has yet to be characterized. However, it does not appear to be histamine, prostanoids, or peptidoleukotrienes.     

Rapid Diversification of RNase A Superfamily Ribonucleases from the Bullfrog, Rana catesbeiana

We present sequences of five novel RNase A superfamily ribonuclease genes of the bullfrog, Rana catesbeiana. All five genes encode ribonucleases that are similar to Onconase, a cytotoxic ribonuclease isolated from oocytes of R. pipiens. With amino acid sequence data from 14 ribonucleases from three Rana species (R. catesbeiana, R. japonica, and R. pipiens), we have constructed bootstrap-supported phylogenetic trees that reorganize these ribonucleases into five distinct lineages--the pancreatic ribonucleases (RNases 1), the eosinophil-associated ribonucleases (RNases 2, 3, and 6), the ribonucleases 4, the angiogenins (RNases 5) and the Rana ribonucleases--with the Rana ribonucleases no more closely related to the angiogenins than they are to any of the other ribonuclease lineages shown. Further phylogenetic analysis suggests the division of the Rana ribonucleases into two subclusters (A and B), with positive (Darwinian) selection (dN/dS > 1.0) and an elevated rate of radical nonsynonymous substitution (dR) contributing to the rapid diversification of ribonucleases within each cluster. This pattern of evolution-rapid diversification via positive selection among sequences of a multigene cluster-bears striking resemblance to what we have described for the eosinophil-associated ribonuclease genes of the rodent Mus musculus, a finding that may have implications with respect the physiologic function of this unique family of proteins.