Long-term monitoring of benthic macroinvertebrate community structure: a perspective from a Colorado river*

Temporal and spatial trends were examined in benthic macroinvertebrate and physical-chemical data collected for at least ten years at ten sites along the plains reach of the Cache la Poudre River, Colorado, USA. A distinct longitudinal environment gradient was found as many of the water chemistry parameter levels changed downstream from the reference site. Seasonal Kendall analyses on individual sites indicated that several chemical parameters, including conductivity, un-ionized NH₃-N and NO₂-N have increased since the beginning of the study within most sites. Levels of some parameters (e.g., dissolved oxygen, un-ionized NH₃-N) violated aquatic life standards a few times during the study.Over 175 taxa of macroinvertebrates (primarily insects) were collected in the study reach from 1981–1996. Results from detrended correspondence analyses (DCA) on macroinvertebrate data indicated that this stretch of the river exhibited little longitudinal change beyond the two farthest upstream sites. There was a decline in macroinvertebrate density and total number of taxa within most individual sites during 1983–1984, corresponding with the highest recorded discharge in 75 years (1983) and a prolonged, heavy spring runoff in 1984. Taxa richness and density recovered to pre-1983 levels within a few months to a year following the high flows at most sites. These findings suggested that the macroinvertebrate assemblages had low resistance to disturbance, but high resilience. However, the results from DCAs and Kendall's Coefficient of Concordance (W) on individual sites for the entire study period suggested a similar macroinvertebrate community structure through time. It would appear that the composition and abundance of the lotic macroinvertebrate assemblages in the Poudre River has remained relatively constant over the long-term. This has occurred even with some potentially negative changes in water chemistry and increased urban development.     

The Emergence of Synaesthesia in a Neuronal Network Model via Changes in Perceptual Sensitivity and Plasticity

Synaesthesia is an unusual perceptual experience in which an inducer stimulus triggers a percept in a different domain in addition to its own. To explore the conditions under which synaesthesia evolves, we studied a neuronal network model that represents two recurrently connected neural systems. The interactions in the network evolve according to learning rules that optimize sensory sensitivity. We demonstrate several scenarios, such as sensory deprivation or heightened plasticity, under which synaesthesia can evolve even though the inputs to the two systems are statistically independent and the initial cross-talk interactions are zero. Sensory deprivation is the known causal mechanism for acquired synaesthesia and increased plasticity is implicated in developmental synaesthesia. The model unifies different causes of synaesthesia within a single theoretical framework and repositions synaesthesia not as some quirk of aberrant connectivity, but rather as a functional brain state that can emerge as a consequence of optimising sensory information processing.     

Visualization of intracellular movement of vaccinia virus virions containing a green fluorescent protein-B5R membrane protein chimera

We produced an infectious vaccinia virus that expressed the B5R envelope glycoprotein fused to the enhanced green fluorescent protein (GFP), allowing us to visualize intracellular virus movement in real time. Previous transfection studies indicated that fusion of GFP to the C-terminal cytoplasmic domain of B5R did not interfere with Golgi localization of the viral protein. To determine whether B5R-GFP was fully functional, we started with a B5R deletion mutant that made small plaques and inserted the B5R-GFP gene into the original B5R locus. The recombinant virus made normal-sized plaques and acquired the ability to form actin tails, indicating reversal of the mutant phenotype. Moreover, immunogold electron microscopy revealed that both intracellular enveloped virions (IEV) and extracellular enveloped virions contained B5R-GFP. By confocal microscopy of live infected cells, we visualized individual fluorescent particles, corresponding to IEV in size and shape, moving from a juxtanuclear location to the periphery of the cell, where they usually collected prior to association with actin tails. The fluorescent particles could be seen emanating from cells at the tips of microvilli. Using a digital camera attached to an inverted fluorescence microscope, we acquired images at 1 frame/s. At this resolution, IEV movement appeared saltatory; in some frames there was no net movement, whereas in others movement exceeded 2 microm/s. Further studies indicated that IEV movement was reversibly arrested by the microtubule-depolymerizing drug nocodazole. This result, together with the direction, speed, and saltatory motion of IEV, was consistent with a role for microtubules in intracellular transport of IEV.     

The benefits of noise in neural systems: bridging theory and experiment

Although typically assumed to degrade performance, random fluctuations, or noise, can sometimes improve information processing in non-linear systems. One such form of 'stochastic facilitation', stochastic resonance, has been observed to enhance processing both in theoretical models of neural systems and in experimental neuroscience. However, the two approaches have yet to be fully reconciled. Understanding the diverse roles of noise in neural computation will require the design of experiments based on new theory and models, into which biologically appropriate experimental detail feeds back at various levels of abstraction.     

Maintaining Specimen Integrity for G6PD Screening by Cytofluorometric Assays

Cytochemical staining remains an efficient way of identifying females who are heterozygous for the X chromosome-linked glucose-6-phosphate dehydrogenase (G6PD) gene. G6PD is highly polymorphic with certain alleles resulting in low intracellular G6PD activity in red blood cells. Low intracellular G6PD activity is associated with a risk of severe hemolysis when exposed to an oxidative stress such as fava beans, certain drugs and infections. Heterozygous females express the enzyme from both X-chromosome alleles resulting in two red blood cell populations each with G6PD enzyme characteristics representative of each allele; for example, normal and deficient. Cytochemical staining is the only way to determine the relative representation of each allele in red blood cells, a feature that is critical when assessing the risk for severe hemolysis when exposed to an oxidant such as the anti-malarial drug primaquine. This letter discusses red blood cell integrity with respect to the cytofluorometric assays for G6PD activity. An approach to making this test more robust is suggested. The approach makes this test more reliable and extends its use to a broader range of blood specimens.     

Functional analysis of the roles of FliQ and FlhB in flagellar expression in Helicobacter pylori

Expression of the two Helicobacter pylori flagellin proteins FlaA and FlaB is required for full motility and persistent infection of the gastric mucosa. The mechanisms and regulation of the biosynthesis and export of flagella in H. pylori are still poorly understood. Scrutiny of the H. pylori 26695 genome sequence revealed homologues of FliQ and FlhB. The roles of the fliQ and flhB genes in H. pylori were investigated by the construction and characterisation of defined isogenic mutants. The results indicate that these genes are involved in the flagellar expression, adhesion to and colonisation of the gastric mucosa.     

Stem cells signal to the niche through the Notch pathway in the Drosophila ovary

Stem cells are maintained and retain their capacity to continue dividing because of the influence of a niche. Although niches are important to maintain "stemness" in a wide variety of tissues, control of these niches is poorly understood. The Drosophila germline stem cells (GSCs) reside in a somatic cell niche. We show that Notch activation can induce the expression of niche-cell markers even in an adult fly; overexpression of Delta in the germline, or activated Notch in the somatic cells, results in extra niche cells, up to 10-fold over the normal number. In turn, these ectopic niche cells induce ectopic GSCs. Conversely, when GCSs do not produce functional Notch ligands, Delta and Serrate, the TGF-beta pathway is not activated in the GSCs, and they differentiate and subsequently leave the niche. Importantly, clonal analysis reveals that the receiving end of the Notch pathway is required in the somatic cells. These data show that a feedback loop exists between the stem cells and niche cells. Demonstration that stem cells can contribute to niche function has far-reaching consequences for stem cell therapies and may provide insight into how cancer can spread throughout an organism via populations of cancer stem cells.     

Monomeric M2e antigen in VesiVax® liposomes stimulates protection against type a strains of influenza comparable to liposomes with multimeric forms of M2e

Abstract

Given the interest in the ectodomain of the matrix 2 (M2e) channel protein as a target for development of a universal influenza vaccine, we examined the role of the antigen configuration of M2e in generating a protective immune response. A series of M2e mutations and a truncated M2e segment were prepared as a means of controlling the formation of monomer, dimer, and higher order multimeric forms of M2e. Each of these M2e peptides was incorporated into a liposome-based vaccine technology platform previously shown to stimulate a protective response to influenza A infection using M2e as a mixture of monomers, dimers and multimers (L-M2e1-HD/MPL). Our results using these modified forms of M2e produced 90–100% survival following lethal challenge with H1N1 (A/PR/8/34) in both inbred BALB/c and outbred Swiss Webster mice vaccinated with a truncated monomeric form of the M2 protein, M2e_1–15 in liposomes. These observations show that a tetrameric configuration is not required to elicit significant protection when the M2e antigen is formulated in immunogenic liposomes and further, that the first 15 amino acids of M2e likely play a primary role in providing the protective immune response.     

Pollen limitation and demographic structure in small fragmented populations of Brunsvigia radulosa (Amaryllidaceae)

The ecological consequences of disruptions in plant-pollinator mutualisms are poorly understood. We examined how seed production and recruitment of juveniles in populations of the spectacular grassland geophyte Brunsvigia radulosa (Amaryllidaceae) correlate with various indices of habitat fragmentation, including habitat fragment area, population size and population isolation. The species was found to be self-incompatible and adapted for pollination primarily by the long-proboscid fly Philoliche aethiopica (Tabanidae). In places where this fly is locally extinct, carpenter bees appear to act as substitute, though less effective, pollinators. Seed production in B. radulosa showed a significant positive relationship with population size, but not with habitat fragment area or spatial isolation of populations when all three indices of habitat fragmentation were included as predictor variables in multiple regression models. Reduced seed production in small populations was attributable to pollen limitation, as supplemental hand pollinations resulted in proportionally greater increases in seed production in these populations. Pollen limitation appears to have demographic consequences; specifically, the proportion of juvenile plants in populations showed significant positive relationships with current levels of seed production per plant and size of populations. Thus the long term persistence of small B. radulosa populations in habitat fragments may be threatened by a pollination deficit.