Structure and function of wildfire and mountain pine beetle forest boundaries

Landscape boundaries, in particular those created by natural disturbances, are fundamental structures in landscape functioning. At the stand scale, forest boundaries show a wide range of characteristics varying from sharp to diffuse, wavy to straight, enclosed areas (patches) to open ones; all of these have different effects of forest vegetation. The objectives of this study were 1) to characterize the structure of forest boundaries (width, steepness, heterogeneity) and 2) to investigate forest vegetation functional response in the boundary zones created by wildfires and mountain pine beetle (MPB) outbreaks. We studied 11 mountain pine beetle and 7 wildfire boundary zones (4–7 y since disturbance) using field‐based two‐dimensional grids in southern central British Columbia (Canada). Boundary zone delineation was determined through spatially constrained clustering algorithms at three sampling unit resolutions (5×5 m, 10×10 m, and 20×20 m). Then, to characterize boundary width and shape, we developed two new boundary indexes (maximized and minimized boundary zones). The identified boundary widths ranged from 0 to 127 m with a mean width of 51 m at the 20×20 m resolution for both fire and MPB. Although the widths were comparable between disturbance types, fires generally had steeper boundaries (more pronounced) than MPB, largely due to higher peak tree mortality within the disturbances (89 vs 43%). Most of the forest vegetation response variables (understory vegetation diversity, plot‐level species richness, evenness, and multivariate community measures) in the boundary zones tended not to be intermediate in value between the intact forest and disturbance area, in spite of intermediate tree mortality. Tree mortality heterogeneity in the boundary zones was often highest in fires and was equal to the internal heterogeneity in MPB disturbances. Using historical natural disturbance patterns as a conservation strategy, this study proposes that forest management should create boundary complexity (width and shape), thereby creating landscape heterogeneity similar to landscapes influenced primarily by natural disturbances.     

Quantification of pelvic organ prolapse in mice: vaginal protease activity precedes increased MOPQ scores in fibulin 5 knockout mice

Two mouse models of pelvic organ prolapse have been generated recently, both of which have null mutations in genes involved in elastic fiber synthesis and assembly (fibulin 5 and lysyl oxidase-like 1). Interestingly, although these mice exhibit elastinopathies early in life, pelvic organ prolapse does not develop until later in life. In this investigation we developed and validated a tool to quantify the severity of pelvic organ prolapse in mice, and we used this tool prospectively to study the role of fibulin 5, aging, and vaginal proteases in the development of pelvic organ prolapse. The results indicate that >90% of Fbln5(-/-) mice develop prolapse by 6 mo of age, even in the absence of vaginal delivery, and that increased vaginal protease activity precedes the development of prolapse.     

Ethanol preference in C. elegans

Caenorhabditis elegans senses multiple environmental stimuli through sensory systems and rapidly changes its behaviors for survival. With a simple and well-characterized nervous system, C. elegans is a suitable animal model for studying behavioral plasticity.
Previous studies have shown acute neurodepressive effects of ethanol on multiple behaviors of C. elegans similar to the effect of ethanol on other organisms. Caenorhabditis elegans also develops ethanol tolerance during continuous exposure to ethanol. In mammals, chronic ethanol exposure leads to ethanol tolerance as well as increased ethanol consumption. Ethanol preference is associated with the development of tolerance and may lead to the development of ethanol dependence.
In this study, we show that C. elegans is a useful model organism for studying chronic effects of ethanol, including the development of ethanol preference. We designed a behavioral assay for testing ethanol preference after prolonged ethanol exposure. Despite baseline aversive responses to ethanol, animals show ethanol preference after 4 h of pre-exposure to ethanol and exhibit significantly enhanced preference for ethanol after a lifetime of ethanol exposure. The cat-2 and tph-1 mutant animals have defects in the synthetic enzymes for dopamine and serotonin, respectively. These mutants are deficient in the development of ethanol preference, indicating that dopamine and serotonin are required for this form of behavioral plasticity.     

Conserved Role of unc-79 in Ethanol Responses in Lightweight Mutant Mice

The mechanisms by which ethanol and inhaled anesthetics influence the nervous system are poorly understood. Here we describe the positional cloning and characterization of a new mouse mutation isolated in an N-ethyl-N-nitrosourea (ENU) forward mutagenesis screen for animals with enhanced locomotor activity. This allele, Lightweight (Lwt), disrupts the homolog of the Caenorhabditis elegans (C. elegans) unc-79 gene. While Lwt/Lwt homozygotes are perinatal lethal, Lightweight heterozygotes are dramatically hypersensitive to acute ethanol exposure. Experiments in C. elegans demonstrate a conserved hypersensitivity to ethanol in unc-79 mutants and extend this observation to the related unc-80 mutant and nca-1;nca-2 double mutants. Lightweight heterozygotes also exhibit an altered response to the anesthetic isoflurane, reminiscent of unc-79 invertebrate mutant phenotypes. Consistent with our initial mapping results, Lightweight heterozygotes are mildly hyperactive when exposed to a novel environment and are smaller than wild-type animals. In addition, Lightweight heterozygotes exhibit increased food consumption yet have a leaner body composition. Interestingly, Lightweight heterozygotes voluntarily consume more ethanol than wild-type littermates. The acute hypersensitivity to and increased voluntary consumption of ethanol observed in Lightweight heterozygous mice in combination with the observed hypersensitivity to ethanol in C. elegans unc-79, unc-80, and nca-1;nca-2 double mutants suggests a novel conserved pathway that might influence alcohol-related behaviors in humans.     

Differential sensitivity of phosphatidylinositol 3-kinase p110gamma to isoforms of G protein betagamma dimers

The ability of G protein alpha and betagamma subunits to activate the p110gamma isoform of phosphatidylinositol 3-kinase (PtdIns 3-kinase) was examined using pure, recombinant G proteins and the p101/p110gamma form of PtdIns 3-kinase reconstituted into synthetic lipid vesicles. GTP-activated Gs, Gi, Gq, or Go alpha subunits were unable to activate PtdIns 3-kinase. Dimers containing Gbeta(1-4) complexed with gamma2-stimulated PtdIns 3-kinase activity about 26-fold with EC50 values ranging from 4 to 7 nm. Gbeta5gamma2 was not able to stimulate PtdIns 3-kinase despite producing a 10-fold activation of avian phospholipase Cbeta. A series of dimers with beta subunits containing point mutations in the amino acids that undergo a conformational change upon interaction of betagamma with phosducin (beta1H311Agamma2, beta1R314Agamma2, and beta1W332Agamma2) was tested, and only beta1W332Agamma2 inhibited the ability of the dimer to stimulate PtdIns 3-kinase. Dimers containing the beta1 subunit complexed with a panel of different Ggamma subunits displayed variation in their ability to stimulate PtdIns 3-kinase. The beta1gamma2, beta1gamma10, beta1gamma12, and beta1gamma13 dimers all activated PtdIns 3-kinase about 26-fold with 4-25 nm EC50 values. The beta1gamma11 dimer, which contains the farnesyl isoprenoid group and is highly expressed in tissues containing the p101/p110gamma form of PtdIns 3-kinase, was ineffective. The role of the prenyl group on the gamma subunit in determining the activation of PtdIns 3-kinase was examined using gamma subunits with altered CAAX boxes directing the addition of farnesyl to the gamma2 subunit and geranylgeranyl to the gamma1 and gamma11 subunits. Replacement of the geranylgeranyl group of the gamma2 subunit with farnesyl inhibited the activity of beta1gamma2 on PtdIns 3-kinase. Conversely, replacement of the farnesyl group on the gamma1 and gamma11 subunit with geranylgeranyl restored almost full activity. These findings suggest that all beta subunits, with the exception of beta5, interact equally well with PtdIns 3-kinase. In contrast, the composition of the gamma subunit and its prenyl group markedly affects the ability of the betagamma dimer to stimulate PtdIns 3-kinase.     

A central role of the BK potassium channel in behavioral responses to ethanol in C. elegans

The activities of many neuronal proteins are modulated by ethanol, but the fundamental mechanisms underlying behavioral effects of ethanol remain unclear. To identify mechanisms responsible for intoxication, we screened for Caenorhabditis elegans mutants with altered behavioral responses to ethanol. We found that slo-1 mutants, which were previously recognized as having slightly uncoordinated movement, are highly resistant to ethanol in two behavioral assays. Numerous loss-of-function slo-1 alleles emerged from our screens, indicating that slo-1 has a central role in ethanol responses. slo-1 encodes the BK potassium channel. Electrophysiological analysis shows that ethanol activates the channel in vivo, which would inhibit neuronal activity. Moreover, behaviors of slo-1 gain-of-function mutants resemble those of ethanol-intoxicated animals. These results demonstrate that selective activation of BK channels is responsible for acute intoxicating effects of ethanol in C. elegans. BK channel activation may explain a variety of behavioral responses to ethanol in invertebrate and vertebrate systems.     

Natural variation in the npr-1 gene modifies ethanol responses of wild strains of C. elegans

Variation in the acute response to ethanol between individuals has a significant impact on determining susceptibility to alcoholism. The degree to which genetics contributes to this variation is of great interest. Here we show that allelic variation that alters the functional level of NPR-1, a neuropeptide Y (NPY) receptor-like protein, can account for natural variation in the acute response to ethanol in wild strains of Caenorhabditis elegans. NPR-1 negatively regulates the development of acute tolerance to ethanol, a neuroadaptive process that compensates for effects of ethanol. Furthermore, dynamic changes in the NPR-1 pathway provide a mechanism for ethanol tolerance in C. elegans. This suggests an explanation for the conserved function of NPY-related pathways in ethanol responses across diverse species. Moreover, these data indicate that genetic variation in the level of NPR-1 function determines much of the phenotypic variation in adaptive behavioral responses to ethanol that are observed in natural populations.     

DISTRIBUTION OF DIATOMS IN THE PLANKTON OF YAQUINA ESTUARY,OREGON1

The distributional patterns of diatoms in the plankton of the Yaqnina Estuary, Oregon, were, investigated and related to selected climatic and hydrographic factors. Distribution was strongly influenced by seasonal patterns of rainfall resulting in the introduction of a large volume of fresh water into the estuary during fall and winter. Plankton assemblages in spring, summer and fall had fewer diatom species and exhibited a more rapid rate of change in species composition than in winter. Winter assemblages were further characterized by many pennate diatoms, apparently dislodged from the benthos during periods of high freshwater discharge and silt loads. A statistical measure of community difference indicated an increase in taxonomic homogeneity among assemblages throughout the estuary with the onset of the rainy season in late fall and a gradual transition to a more heterogeneous system again during late spring. Canonical correlation ordered 20 prominent diatom taxa along the salinity gradient and identified possible relationships among certain taxa and selected environmental variables, namely visible light energy and temperature. Redundancy in the species data given the environmental data was only 40%, emphasizing the difficulty in demonstrating a quantitive relationship between plankton dynamics in the field and concurrent measurements of chemical and physical variables.