Immunomodulation by morphine and marijuana

The immunomodulatory effects of morphine and the active components of marijuana, particularly tetrahydrocannabinol, on various aspects of the host immune parameters include alterations in humoral, cell-mediated and innate immunity. Most studies have shown immunosuppressive effects due to use of these abused substances, although there are reports that they may not produce any deleterious effect and may even enhance some aspects of host immunity. They reduce resistance to cancer growth and microbial pathogens in animals.     

Mechanism of APTX nicked DNA sensing and pleiotropic inactivation in neurodegenerative disease

The failure of DNA ligases to complete their catalytic reactions generates cytotoxic adenylated DNA strand breaks. The APTX RNA‐DNA deadenylase protects genome integrity and corrects abortive DNA ligation arising during ribonucleotide excision repair and base excision DNA repair, and APTX human mutations cause the neurodegenerative disorder ataxia with oculomotor ataxia 1 (AOA1). How APTX senses cognate DNA nicks and is inactivated in AOA1 remains incompletely defined. Here, we report X‐ray structures of APTX engaging nicked RNA‐DNA substrates that provide direct evidence for a wedge‐pivot‐cut strategy for 5′‐AMP resolution shared with the alternate 5′‐AMP processing enzymes POLβ and FEN1. Our results uncover a DNA‐induced fit mechanism regulating APTX active site loop conformations and assembly of a catalytically competent active center. Further, based on comprehensive biochemical, X‐ray and solution NMR results, we define a complex hierarchy for the differential impacts of the AOA1 mutational spectrum on APTX structure and activity. Sixteen AOA1 variants impact APTX protein stability, one mutation directly alters deadenylation reaction chemistry, and a dominant AOA1 variant unexpectedly allosterically modulates APTX active site conformations.     

Using human case studies to teach evolution in high school A.P. biology classrooms

Background

While recent research indicates that using human examples can be an engaging way to teach core evolutionary concepts such as natural selection and phylogenetic thinking, teachers still face potential conflicts and challenges that arise from cultural barriers to teaching and learning about evolution. The “Teaching Evolution through Human Examples” (TEtHE) project developed (1) a set of four curriculum mini-units for advanced placement (A.P.) biology that use human examples to teach evolutionary principles (Adaptation to Altitude, Evolution of Human Skin Color, Malaria, and What Does It Mean To Be Human?), and (2) a cultural and religious sensitivity (CRS) teaching strategies resource that includes background materials and two in-class activities to help teachers create a classroom environment to increase student willingness to engage the topic.

Methods

This paper reports on the development and field test of the TEtHE materials in A.P. biology classes in 10 schools in 8 states during the 2012–2013 school year using a design-based research framework (cf. Anderson and Shattuck in Educ Res 41:16–25, 2012). We chose A.P. classrooms to study the potential impacts of the materials in a “best case scenario” and analyzed data about understanding and acceptance of evolution from pre-post assessments in the 10 classrooms separately to mitigate potential validity concerns arising from the design (Anderson and Shattuck in Educ Res 41:16–25, 2012; Shadish et al. in Experimental and quasi-experimental designs for generalized causal inference. Houghton Mifflin, Boston, 2002). These data were treated as a secondary source of formative data to add additional perspective to teacher self-reports, observations, student and teacher questionnaires, teacher interviews, and student focus groups.

Results

Results indicate that the use of the three curriculum mini-units which focus on natural selection and the CRS classroom activities generally increased A.P. biology students’ understanding and acceptance of evolution. Students whose teachers used one of the CRS activities showed generally larger increases in understanding of evolution than those whose teachers did not use one of the CRS activities.

Conclusions

Although the utility of using human examples to teach evolution in college-level classes has been demonstrated in a few previous studies, this is the first national project of which we are aware to systematically explore the effect of a similar approach in high school biology classes. While we recognize that the results may be mitigated by the limitations of design-based research, particularly the absence of a comparison or control group, the general effectiveness of this approach suggested by qualitative and quantitative data in increasing student understanding and acceptance of evolution suggests that using human examples and explicitly creating a classroom environment to help students engage the topic of evolution are worth considering for further development and more robust testing.

     

Bacterial symbiont and salivary peptide evolution in the context of leech phylogeny

The evolutionary history of leeches is employed as a general framework for understanding more than merely the systematics of this charismatic group of annelid worms, and serves as a basis for understanding blood-feeding related correlates ranging from the specifics of gut-associated bacterial symbionts to salivary anticoagulant peptides. A variety of medicinal leech families were examined for intraluminal crop bacterial symbionts. Species of Aeromonas and Bacteroidetes were characterized with DNA gyrase B and 16S rDNA. Bacteroidetes isolates were found to be much more phylogenetically diverse and suggested stronger evidence of phylogenetic correlation than the gammaproteobacteria. Patterns that look like co-speciation with limited taxon sampling do not in the full context of phylogeny. Bioactive compounds that are expressed as gene products, like those in leech salivary glands, have 'passed the test' of evolutionary selection. We produced and bioinformatically mined salivary gland EST libraries across medicinal leech lineages to experimentally and statistically evaluate whether evolutionary selection on peptides can identify structure-function activities of known therapeutically relevant bioactive compounds like antithrombin, hirudin and antistasin. The combined information content of a well corroborated leech phylogeny and broad taxonomic coverage of expressed proteins leads to a rich understanding of evolution and function in leech history.     

Influence of gizzard shad on phytoplankton size and primary productivity in mesocosms and earthen ponds in the southeastern U.S.

Gizzard shad (Dorosoma cepedianum), a filter feeding omnivore, can consume phytoplankton, zooplankton and detritus and is a common prey fish in U.S. water bodies. Because of their feeding habits and abundance, shad have the potential to affect primary productivity (and hence water quality) directly through phytoplankton grazing and indirectly through zooplankton grazing and nutrient recycling. To test the ability of shad to influence primary productivity, we conducted a 16-day enclosure study (in 2.36-m³ mesocosms) and a 3-year whole-pond manipulation in 2–5 ha earthen ponds. In the mesocosm experiment, shad reduced zooplankton density and indirectly enhanced chlorophyll a concentration, primary productivity, and photosynthetic efficiency (assimilation number). While shad did not affect total phytoplankton density in the mesocosms, the density of large phytoplankton was directly reduced with shad. Results from the pond study were not consistent as predicted. There were few changes in the zooplankton and phytoplankton communities in ponds with versus ponds without gizzard shad. One apparent difference from systems in which previous work had been conducted was the presence of high densities of a potential competitor (i.e., larval bluegill) in our ponds. We suggest that the presence of these extremely high larval bluegill densities (20–350 larval bluegill m^–3; 3–700 times higher density than that of larval gizzard shad) led to the lack of differences between ponds with versus ponds without gizzard shad. That is, the influence of gizzard shad on zooplankton or phytoplankton was less than the influence of abundant bluegill larvae. Differences in systems across regions must be incorporated into our understanding of factors affecting trophic interactions in aquatic systems if we are to be able to manage these systems for both water quality and fisheries.     

Depth penetration and detection of pH gradients in biofilms by two-photon excitation microscopy.

Deep microbial biofilms are a major problem in many industrial, environmental, and medical settings. Novel approaches are needed to understand the structure and metabolism of these biofilms. Two-photon excitation microscopy (TPE) and conventional confocal laser scanning microscopy (CLSM) were compared quantitatively for the ability to visualize bacteria within deep in vitro biofilms. pH gradients within these biofilms were determined by fluorescence lifetime imaging, together with TPE. A constant-depth film fermentor (CDFF) was inoculated for 8 h at 50 ml. h(-1) with a defined mixed culture of 10 species of bacteria grown in continuous culture. Biofilms of fixed depths were developed in the CDFF for 10 or 11 days. The microbial compositions of the biofilms were determined by using viable counts on selective and nonselective agar media; diverse mixed-culture biofilms developed, including aerobic, facultative, and anaerobic species. TPE was able to record images four times deeper than CLSM. Importantly, in contrast to CLSM images, TPE images recorded deep within the biofilm showed no loss of contrast. The pH within the biofilms was measured directly by means of fluorescence lifetime imaging; the fluorescence decay of carboxyfluorescein was correlated with biofilm pH and was used to construct a calibration curve. pH gradients were detectable, in both the lateral and axial directions, in steady-state biofilms. When biofilms were overlaid with 14 mM sucrose for 1 h, distinct pH gradients developed. Microcolonies with pH values of below pH 3.0 were visible, in some cases adjacent to areas with a much higher pH (>5.0). TPE allowed resolution of images at significantly greater depths (as deep as 140 microm) than were possible with CLSM. Fluorescence lifetime imaging allowed the in situ, real-time imaging of pH and the detection of sharp gradients of pH within microbial biofilms.