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Research and Publications - Department of Biological Sciences

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    A Terminal Inversion in Drosophila Ananassae
    (National Academy of Sciences, 1936-10-15) Kaufmann, B.P.
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    Morphology of the Chromosomes of Drosophila ananassae
    (The Japan Mendel Society, 1937-08-31) Kaufmann, Berwind P.
    1) The chromosome complement of D. ananassae, studied in the neurocytes, consists of three pairs of V-shaped autosom.es and the sex chromosomes. These are a pair of V-shaped X-chromosomes in the female, an X and a J-shaped Y-chromosome in the male. The chromosomes may be distinguished by relative, sizes and characteristic constrictions. 2) The fourth chromosomes and the Y-chromosome appear totally heteropyknotic in resting and early prophase stages of mitotic cells. Short heteropyknotic regions lie adjacent to the spindle attachment regions of the X-chromosomes and the four longer autosomes. 3) In salivary gland nuclei there are but six chromosome arms with euchromatic sections. Four of these represent the paired arms of the longer autosomes, the other two the X-chromosome arms. The fourth chromosomes are represented in salivary gland nuclei by a small bipartite mass of heterochromatin which forms part of the chromocenter. 4) In mitotic prophases of female larvae the fourth chromosomes are associated with the nucleolus, which separates a small satellite-like portion from the remainder of the long arm of these chromosomes. In the male the Y-chromosome forms a third member of the group associated with the nucleolus. 5) The fourth chromosome-nucleolus-satellite relationship is. also evident, in salivary gland nuclei, the satellite appearing as a banded body associated with the nucleolus, and also connected with the fourth chromosomes by chromatic strands. 6) The chromocenter of mitotic cells and of the salivary gland cells is not amorphous, but discloses, under suitable conditions, the limits of the component chromosomes.
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    A New Leptothorax From Alabama (Hymenoptera: Formicidae)
    (Cambridge Entomological Club, 1950-01-01) Wilson, Edward Osborne
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    Survey of the Sensitivity of Microorganisms to Rubratoxin B
    (American Society for Microbiology, 1970-06-30) Hayes, A. Wallace; Wyatt, Elwanda P.
    Of the 133 microorganisms tested, Tetrahymena pyriformis and Volvox aureus were the most sensitive to rubratoxin B, being inhibited at 25 and 50 mug/ml, respectively.
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    Environmental and Nutritional Factors Affecting the Production of Rubratoxin B by Penicillium rubrum Stoll
    (American Society for Microbiology, 1970-09-01) Hayes, A. Wallace; Wyatt, Elwanda P.; King, Patricia A.
    Rubratoxin B can be produced in a semisynthetic medium by Penicillium rubrum under varying environmental and nutritional conditions. Maximum production (552.0 mg/500 ml) was obtained with P. rubrum NRRL A-11785 grown in stationary cultures of Mosseray's simplified Raulin solution supplemented with 2.5% malt extract broth at ambient temperature. Zinc is required at levels of at least 0.4 mg per liter. In the absence of iron sulfate, there was a 50-fold reduction in rubratoxin B production but not in growth. No toxin was produced by this isolate in 5- or 7-liter fermentors.
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    Microbiological Assay for Estimating Salivary Concentrations of the Cariostatic Antibiotic Actinobolin
    (American Society for Microbiology, 1970-10-01) Hunt, D.E.; Bradley, E.L.; Bachmann, Joan W.
    A logarithmic-ratio microbiological assay has been developed for the estimation of concentrations of actinobolin (or inhibitory equivalents) in human saliva. The utility of this assay has been demonstrated by presenting data that show concentrations of this antibiotic (or inhibitory equivalents) detected in saliva or saline after incubation at 37 C for periods as long as 6 hr. The results of some statistical analyses of the assay data have been included.
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    Suboxic Deposition of Ferric Iron by Bacteria in Opposing Gradients of Fe(II) and Oxygen at Circumneutral pH
    (American Society for Microbiology, 2001) Sobolev, Dmitri; Roden, Eric E.
    The influence of lithotrophic Fe(II)-oxidizing bacteria on patterns of ferric oxide deposition in opposing gradients of Fe(II) and O(2) was examined at submillimeter resolution by use of an O(2) microelectrode and diffusion microprobes for iron. In cultures inoculated with lithotrophic Fe(II)-oxidizing bacteria, the majority of Fe(III) deposition occurred below the depth of O(2) penetration. In contrast, Fe(III) deposition in abiotic control cultures occurred entirely within the aerobic zone. The diffusion microprobes revealed the formation of soluble or colloidal Fe(III) compounds during biological Fe(II) oxidation. The presence of mobile Fe(III) in diffusion probes from live cultures was verified by washing the probes in anoxic water, which removed ca. 70% of the Fe(III) content of probes from live cultures but did not alter the Fe(III) content of probes from abiotic controls. Measurements of the amount of Fe(III) oxide deposited in the medium versus the probes indicated that ca. 90% of the Fe(III) deposited in live cultures was formed biologically. Our findings show that bacterial Fe(II) oxidation is likely to generate reactive Fe(III) compounds that can be immediately available for use as electron acceptors for anaerobic respiration and that biological Fe(II) oxidation may thereby promote rapid microscale Fe redox cycling at aerobic-anaerobic interfaces.
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    Microbially Catalyzed Nitrate-Dependent Oxidation of Biogenic Solid-Phase Fe(II) Compounds
    (American Chemical Society, 2001) Weber, Karrie A.; Picardal, Flynn W.; Roden, Eric E.
    The potential for microbially catalyzed NO3—-dependent oxidation of solid-phase Fe(II) compounds was examined using a previously described autotrophic, denitrifying, Fe(II)-oxidizing enrichment culture. The following solid-phase Fe(II)-bearing minerals were considered: microbially reduced synthetic goethite, two differ ent end products of microbially hydrous ferric oxide (HFO) reduc tion (biogenic Fe3O4 and biogenic FeCO3), chemically precipitated FeCO3, and two microbially reduced iron(III) oxide-rich subsoils. The microbially reduced goethite, subsoils, and chemically precip itated FeCO3 were subject to rapid NO3 —-dependent Fe(II) oxida tion. Significant oxidation of biogenic Fe3O4 was observed. Very little biogenic FeCO3 was oxidized. No reduction of NO3 — or ox idation of Fe(II) occurred in pasteurized cultures. The molar ratio of NO3 — reduced to Fe(II) oxidized in cultures containing chemi cally precipitated FeCO3, and one of the microbially reduced sub soils approximated the theoretical stoichiometry of 0.2:1. However, molar ratios obtained for oxidation of microbially reduced goe thite, the other subsoil, and the HFO reduction end products did not agree with this theoretical value. These discrepancies may be related to heterotrophic NO3 — reduction coupled to oxidation of dead Fe(III)-reducing bacterial biomass. Our findings demonstrate that microbally catalyzed NO3 —-dependent Fe(II) oxidation has the potential to significantly accelerate the oxidation of solid-phase Fe(II) compounds by oxidized N species. This process could have an important influence on the migration of contaminant metals and radionuclides in subsurface environments.
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    Ubiquitin conjugating enzymes participate in polyglutamine protein aggregation
    (BMC, 2007) Howard, Rebecca A.; Sharma, Pratima; Hajjar, Connie; Caldwell, Kim A.; Caldwell, Guy A.; Du Breuil, Rusla; Moore, Rhonda; Boyd, Lynn; University of Alabama Huntsville; University of Alabama Tuscaloosa
    Background: Protein aggregation is a hallmark of several neurodegenerative diseases including Huntington's disease and Parkinson's disease. Proteins containing long, homopolymeric stretches of glutamine are especially prone to form aggregates. It has long been known that the small protein modifier, ubiquitin, localizes to these aggregates. In this report, nematode and cell culture models for polyglutamine aggregation are used to investigate the role of the ubiquitin pathway in protein aggregation. Results: Ubiquitin conjugating enzymes (Ubc's) were identified that affect polyglutamine aggregates in C. elegans. Specifically, RNAi knockdown of ubc-2 or ubc-22 causes a significant increase in the size of aggregates as well as a reduction in aggregate number. In contrast, RNAi of ubc-1, ubc-13, or uev-1 leads to a reduction of aggregate size and eliminates ubiquitin and proteasome localization to aggregates. In cultured human cells, shRNA knockdown of human homologs of these Ubc's (Ube2A, UbcH5b, and E2- 25K) causes similar effects indicating a conserved role for ubiquitination in polyglutamine protein aggregation. Conclusion: Results of knockdown of different Ubc enzymes indicate that at least two different and opposing ubiquitination events occur during polyglutamine aggregation. The loss of ubiquitin localization after ubc-1, ubc-13, or uev-1 knockdown suggests that these enzymes might be directly involved in ubiquitination of aggregating proteins.
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    Functional Links Between A beta Toxicity, Endocytic Trafficking, and Alzheimer's Disease Risk Factors in Yeast
    (American Association for the Advancement of Science, 2011) Treusch, Sebastian; Hamamichi, Shusei; Goodman, Jessica L.; Matlack, Kent E. S.; Chung, Chee Yeun; Baru, Valeriya; Shulman, Joshua M.; Parrado, Antonio; Bevis, Brooke J.; Valastyan, Julie S.; Han, Haesun; Lindhagen-Persson, Malin; Reiman, Eric M.; Evans, Denis A.; Bennett, David A.; Olofsson, Anders; DeJager, Philip L.; Tanzi, Rudolph E.; Caldwell, Kim A.; Caldwell, Guy A.; Lindquist, Susan; Massachusetts Institute of Technology (MIT); Whitehead Institute; Howard Hughes Medical Institute; University of Alabama Tuscaloosa; Harvard University; Brigham & Women's Hospital; Harvard Medical School; Broad Institute; Massachusetts General Hospital; Umea University; Translational Genomics Research Institute; University of Arizona; Banner Research; Banner Health; Banner Alzheimer's Institute; Rush University
    A beta (beta-amyloid peptide) is an important contributor to Alzheimer's disease (AD). We modeled A beta toxicity in yeast by directing the peptide to the secretory pathway. A genome-wide screen for toxicity modifiers identified the yeast homolog of phosphatidylinositol binding clathrin assembly protein (PICALM) and other endocytic factors connected to AD whose relationship to A beta was previously unknown. The factors identified in yeast modified A beta toxicity in glutamatergic neurons of Caenorhabditis elegans and in primary rat cortical neurons. In yeast, A beta impaired the endocytic trafficking of a plasma membrane receptor, which was ameliorated by endocytic pathway factors identified in the yeast screen. Thus, links between A beta, endocytosis, and human AD risk factors can be ascertained with yeast as a model system.
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    Phylogenetic Diversity, Host-Specificity and Community Profiling of Sponge-Associated Bacteria in the Northern Gulf of Mexico
    (PLOS, 2011) Erwin, Patrick M.; Olson, Julie B.; Thacker, Robert W.; University of Alabama Birmingham; University of Alabama Tuscaloosa
    Background: Marine sponges can associate with abundant and diverse consortia of microbial symbionts. However, associated bacteria remain unexamined for the majority of host sponges and few studies use phylogenetic metrics to quantify symbiont community diversity. DNA fingerprinting techniques, such as terminal restriction fragment length polymorphisms (T-RFLP), might provide rapid profiling of these communities, but have not been explicitly compared to traditional methods. Methodology/Principal Findings: We investigated the bacterial communities associated with the marine sponges Hymeniacidon heliophila and Haliclona tubifera, a sympatric tunicate, Didemnum sp., and ambient seawater from the northern Gulf of Mexico by combining replicated clone libraries with T-RFLP analyses of 16S rRNA gene sequences. Clone libraries revealed that bacterial communities associated with the two sponges exhibited lower species richness and lower species diversity than seawater and tunicate assemblages, with differences in species composition among all four source groups. T-RFLP profiles clustered microbial communities by source; individual T-RFs were matched to the majority (80.6%) of clone library sequences, indicating that T-RFLP analysis can be used to rapidly profile these communities. Phylogenetic metrics of community diversity indicated that the two sponge-associated bacterial communities include dominant and host-specific bacterial lineages that are distinct from bacteria recovered from seawater, tunicates, and unrelated sponge hosts. In addition, a large proportion of the symbionts associated with H. heliophila were shared with distant, conspecific host populations in the southwestern Atlantic (Brazil). Conclusions/Significance: The low diversity and species-specific nature of bacterial communities associated with H. heliophila and H. tubifera represent a distinctly different pattern from other, reportedly universal, sponge-associated bacterial communities. Our replicated sampling strategy, which included samples that reflect the ambient environment, allowed us to differentiate resident symbionts from potentially transient or prey bacteria. Pairing replicated clone library construction with rapid community profiling via T-RFLP analyses will greatly facilitate future studies of sponge-microbe symbioses.
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    dtorsin, the Drosophila Ortholog of the Early-Onset Dystonia TOR1A (DYT1), Plays a Novel Role in Dopamine Metabolism
    (PLOS, 2011) Wakabayashi-Ito, Noriko; Doherty, Olugbenga M.; Moriyama, Hideaki; Breakefield, Xandra O.; Gusella, James F.; O'Donnell, Janis M.; Ito, Naoto; Harvard University; Massachusetts General Hospital; University of Alabama Tuscaloosa; University of Nebraska Lincoln; Harvard Medical School
    Dystonia represents the third most common movement disorder in humans. At least 15 genetic loci (DYT1-15) have been identified and some of these genes have been cloned. TOR1A (formally DYT1), the gene responsible for the most common primary hereditary dystonia, encodes torsinA, an AAA ATPase family protein. However, the function of torsinA has yet to be fully understood. Here, we have generated and characterized a complete loss-of-function mutant for dtorsin, the only Drosophila ortholog of TOR1A. Null mutation of the X-linked dtorsin was semi-lethal with most male flies dying by the pre-pupal stage and the few surviving adults being sterile and slow moving, with reduced cuticle pigmentation and thin, short bristles. Third instar male larvae exhibited locomotion defects that were rescued by feeding dopamine. Moreover, biochemical analysis revealed that the brains of third instar larvae and adults heterozygous for the loss-of-function dtorsin mutation had significantly reduced dopamine levels. The dtorsin mutant showed a very strong genetic interaction with Pu (Punch: GTP cyclohydrolase), the ortholog of the human gene underlying DYT14 dystonia. Biochemical analyses revealed a severe reduction of GTP cyclohydrolase protein and activity, suggesting that dtorsin plays a novel role in dopamine metabolism as a positive-regulator of GTP cyclohydrolase protein. This dtorsin mutant line will be valuable for understanding this relationship and potentially other novel torsin functions that could play a role in human dystonia.
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    Drosophila Pupal Abdomen Immunohistochemistry
    (MyJove Corporation, 2011) Wang, Wei; Yoder, John H.; University of Alabama Tuscaloosa
    The Drosophila pupal abdomen is an established model system for the study of epithelial morphogenesis and the development of sexually dimorphic morphologies(1-3). During pupation, which spans approximately 96 hours (at 25 degrees C), proliferating populations of imaginal cells replace the larval epidermis to generate the adult abdominal segments. These imaginal cells, born during embryogenesis, exist as lateral pairs of histoblast nests in each abdominal segment of the larvae. Four pairs of histoblast nests give rise to the adult dorsal cuticle (anterior and posterior dorsal nests), the ventral cuticle (ventral nests) and the spiracles associated with each segment (spiracle nests)(4). Upon puparation, these diploid cells (distinguishable by size from the larger polyploid larval epidermal cells-LECs) begin a stereotypical process of proliferation, migration and replacement of the LECs. Various molecular and genetic tools can be employed to investigate the contributions of genetic pathways involved in morphogenesis of the adult abdomen. Ultimate adult phenotypes are typically analyzed following dissection of adult abdominal cuticles. However, investigation of the underlying molecular processes requires immunohistochemical analyses of the pupal epithelium, which present unique challenges. Temporally dynamic morphogenesis and the interactions of two distinct epithelial populations (larval and imaginal) generate a fragile tissue prone to excessive cell loss during dissection and subsequent processing. We have developed methods of dissection, fixation, mounting and imaging of the Drosophila pupal abdominem epithelium for immunohistochemical studies that generate consistent high quality samples suitable for confocal or standard fluorescent microscopy.
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    A multigene phylogeny of Olpidium and its implications for early fungal evolution
    (BMC, 2011) Sekimoto, Satoshi; Rochon, D'Ann; Long, Jennifer E.; Dee, Jaclyn M.; Berbee, Mary L.; University of British Columbia; Agriculture & Agri Food Canada; University of Alabama Tuscaloosa; University of Victoria
    Background: From a common ancestor with animals, the earliest fungi inherited flagellated zoospores for dispersal in water. Terrestrial fungi lost all flagellated stages and reproduce instead with nonmotile spores. Olpidium virulentus (= Olpidium brassicae), a unicellular fungus parasitizing vascular plant root cells, seemed anomalous. Although Olpidium produces zoospores, in previous phylogenetic studies it appeared nested among the terrestrial fungi. Its position was based mainly on ribosomal gene sequences and was not strongly supported. Our goal in this study was to use amino acid sequences from four genes to reconstruct the branching order of the early-diverging fungi with particular emphasis on the position of Olpidium. Results: We concatenated sequences from the Ef-2, RPB1, RPB2 and actin loci for maximum likelihood and Bayesian analyses. In the resulting trees, Olpidium virulentus, O. bornovanus and non-flagellated terrestrial fungi formed a strongly supported clade. Topology tests rejected monophyly of the Olpidium species with any other clades of flagellated fungi. Placing Olpidium at the base of terrestrial fungi was also rejected. Within the terrestrial fungi, Olpidium formed a monophyletic group with the taxa traditionally classified in the phylum Zygomycota. Within Zygomycota, Mucoromycotina was robustly monophyletic. Although without bootstrap support, Monoblepharidomycetes, a small class of zoosporic fungi, diverged from the basal node in Fungi. The zoosporic phylum Blastocladiomycota appeared as the sister group to the terrestrial fungi plus Olpidium. Conclusions: This study provides strong support for Olpidium as the closest living flagellated relative of the terrestrial fungi. Appearing nested among hyphal fungi, Olpidium's unicellular thallus may have been derived from ancestral hyphae. Early in their evolution, terrestrial hyphal fungi may have reproduced with zoospores.
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    Synthesizing and databasing fossil calibrations: divergence dating and beyond
    (Royal Society of London, 2011) Ksepka, Daniel T.; Benton, Michael J.; Carrano, Matthew T.; Gandolfo, Maria A.; Head, Jason J.; Hermsen, Elizabeth J.; Joyce, Walter G.; Lamm, Kristin S.; Patane, Jose S. L.; Phillips, Matthew J.; Polly, P. David; Van Tuinen, Marcel; Ware, Jessica L.; Warnock, Rachel C. M.; Parham, James F.; North Carolina State University; University of Bristol; Smithsonian Institution; Smithsonian National Museum of Natural History; Cornell University; University of Toronto; University Toronto Mississauga; Eberhard Karls University of Tubingen; Instituto Butantan; University of Queensland; Indiana University Bloomington; University of North Carolina; University of North Carolina Wilmington; Rutgers State University Newark; Rutgers State University New Brunswick; American Museum of Natural History (AMNH); University of Alabama Tuscaloosa
    Divergence dating studies, which combine temporal data from the fossil record with branch length data from molecular phylogenetic trees, represent a rapidly expanding approach to understanding the history of life. National Evolutionary Synthesis Center hosted the first Fossil Calibrations Working Group (3-6 March, 2011, Durham, NC, USA), bringing together palaeontologists, molecular evolutionists and bioinformatics experts to present perspectives from disciplines that generate, model and use fossil calibration data. Presentations and discussions focused on channels for interdisciplinary collaboration, best practices for justifying, reporting and using fossil calibrations and roadblocks to synthesis of palaeontological and molecular data. Bioinformatics solutions were proposed, with the primary objective being a new database for vetted fossil calibrations with linkages to existing resources, targeted for a 2012 launch.
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    Sympathetic nerve activity and whole body heat stress in humans
    (American Psyiological Society, 2011) Low, David A.; Keller, David M.; Wingo, Jonathan E.; Brothers, R. Matthew; Crandall, Craig G.; University of Texas Southwestern Medical Center Dallas; University of Texas Arlington; University of Alabama Tuscaloosa; University of Texas Austin
    Low DA, Keller DM, Wingo JE, Brothers RM, Crandall CG. Sympathetic nerve activity and whole body heat stress in humans. J Appl Physiol 111: 1329-1334, 2011. First published August 25, 2011; doi:10.1152/japplphysiol.00498.2011.-We and others have shown that moderate passive whole body heating (i.e., increased internal temperature similar to 0.7 degrees C) increases muscle (MSNA) and skin sympathetic nerve activity (SSNA). It is unknown, however, if MSNA and/or SSNA continue to increase with more severe passive whole body heating or whether these responses plateau following moderate heating. The aim of this investigation was to test the hypothesis that MSNA and SSNA continue to increase from a moderate to a more severe heat stress. Thirteen subjects, dressed in a water-perfused suit, underwent at least one passive heat stress that increased internal temperature similar to 1.3 degrees C, while either MSNA (n = 8) or SSNA (n = 8) was continuously recorded. Heat stress significantly increased mean skin temperature (Delta similar to 5 degrees C, P < 0.001), internal temperature (Delta similar to 1.3 degrees C, P < 0.001), mean body temperature (Delta similar to 2.0 C, P < 0.001), heart rate (Delta similar to 40 beats/min, P < 0.001), and cutaneous vascular conductance [Delta similar to 1.1 arbitrary units (AU)/mmHg, P < 0.001]. Mean arterial blood pressure was well maintained (P = 0.52). Relative to baseline, MSNA increased midway through heat stress (Delta core temperature 0.63 +/- 0.01 degrees C) when expressed as burst frequency (26 +/- 14 to 45 +/- 16 bursts/min, P = 0.001), burst incidence (39 +/- 13 to 48 +/- 14 bursts/100 cardiac cyles, P = 0.03), or total activity (317 +/- 170 to 489 +/- 150 units/min, P = 0.02) and continued to increase until the end of heat stress (burst frequency: 61 +/- 15 bursts/min, P = 0.01; burst incidence: 56 +/- 11 bursts/100 cardiac cyles, P = 0.04; total activity: 648 +/- 158 units/min, P = 0.01) relative to the mid-heating stage. Similarly, SSNA (total activity) increased midway through the heat stress (normothermia; 1,486 +/- 472 to mid heat stress 6,467 +/- 5,256 units/min, P = 0.03) and continued to increase until the end of heat stress (11,217 +/- 6,684 units/min, P = 0.002 vs. mid-heat stress). These results indicate that both MSNA and SSNA continue to increase as internal temperature is elevated above previously reported values.
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    Fatty Acids Identified in the Burmese Python Promote Beneficial Cardiac Growth
    (American Association for the Advancement of Science, 2011) Riquelme, Cecilia A.; Magida, Jason A.; Harrison, Brooke C.; Wall, Christopher E.; Marr, Thomas G.; Secor, Stephen M.; Leinwand, Leslie A.; University of Colorado Boulder; University of Alabama Tuscaloosa
    Burmese pythons display a marked increase in heart mass after a large meal. We investigated the molecular mechanisms of this physiological heart growth with the goal of applying this knowledge to the mammalian heart. We found that heart growth in pythons is characterized by myocyte hypertrophy in the absence of cell proliferation and by activation of physiological signal transduction pathways. Despite high levels of circulating lipids, the postprandial python heart does not accumulate triglycerides or fatty acids. Instead, there is robust activation of pathways of fatty acid transport and oxidation combined with increased expression and activity of superoxide dismutase, a cardioprotective enzyme. We also identified a combination of fatty acids in python plasma that promotes physiological heart growth when injected into either pythons or mice.
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    Modeling Relationships among 217 Fires Using Remote Sensing of Burn Severity in Southern Pine Forests
    (MDPI, 2011-09-07) Malone, Sparkle L.; Kobziar, Leda N.; Staudhammer, Christina L.; Abd-Elrahman, Amr; State University System of Florida; University of Florida; University of Alabama Tuscaloosa
    Pine flatwoods forests in the southeastern US have experienced severe wildfires over the past few decades, often attributed to fuel load build-up. These forest communities are fire dependent and require regular burning for ecosystem maintenance and health. Although prescribed fire has been used to reduce wildfire risk and maintain ecosystem integrity, managers are still working to reintroduce fire to long unburned areas. Common perception holds that reintroduction of fire in long unburned forests will produce severe fire effects, resulting in a reluctance to prescribe fire without first using expensive mechanical fuels reduction techniques. To inform prioritization and timing of future fire use, we apply remote sensing analysis to examine the set of conditions most likely to result in high burn severity effects, in relation to vegetation, years since the previous fire, and historical fire frequency. We analyze Landsat imagery-based differenced Normalized Burn Ratios (dNBR) to model the relationships between previous and future burn severity to better predict areas of potential high severity. Our results show that remote sensing techniques are useful for modeling the relationship between elevated risk of high burn severity and the amount of time between fires, the type of fire (wildfire or prescribed burn), and the historical frequency of fires in pine flatwoods forests.