The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform

Ruth M. Elsey - One of the best experts on this subject based on the ideXlab platform.

  • Contribution of active atrial contraction to cardiac output in anesthetized American Alligators (Alligator Mississippiensis)
    The Journal of Experimental Biology, 2018
    Co-Authors: William Joyce, Ruth M. Elsey, Tobias Wang, Janna Crossley, Dane A Crossley
    Abstract:

    ABSTRACT Ventricular filling may occur directly from the venous circulation during early diastole or via atrial contraction in late diastole. The contribution of atrial contraction to ventricular filling is typically small in mammals (10–40%), but has been suggested to predominate in reptiles. We investigated the importance of atrial contraction in filling of the ventricle in American Alligators ( Alligator Mississippiensis ) by bypassing both atria (with the use of ligatures to prevent atrial filling) and measuring the resultant effects on cardiac output in anesthetized animals. Atrial ligation had no significant effects on total systemic blood flow before or after adrenaline injection. Unexpectedly, pulmonary flow was increased following atrial ligation prior to adrenaline treatment, but was unaffected after it. These findings suggest that the atria are non-essential (i.e. redundant) for ventricular filling in Alligators, at least under anesthesia, but may serve as important volume reservoirs.

  • american Alligator Alligator Mississippiensis embryos tightly regulate intracellular ph during a severe acidosis
    Canadian Journal of Zoology, 2018
    Co-Authors: Ryan B Shartau, Ruth M. Elsey, Dane A Crossley, Zachary F Kohl, Colin J Brauner
    Abstract:

    Crocodilian nests naturally experience high CO 2 (hypercarbia), which leads to increased blood P CO 2 and reduced blood pH (pH e ) in embryos; their response to acid-base challenges is not known. During acute hypercarbia, snapping turtle embryos preferentially regulate tissue pH (pH i ) against pH e reductions. This is proposed to be associated with CO 2 tolerance in reptilian embryos and is not found in adults. In the present study, we investigated pH regulation in American Alligator Alligator Mississippiensis (Daudin, 1802) embryos exposed to 1 h hypercarbia hypoxia (13 k P a P CO 2 , 9 k P a P O 2 ). Hypercarbia hypoxia reduced pH e by 0.42 pH units while heart and brain pH i increased, with no change in pH i of other tissues. The results indicate American Alligator embryos preferentially regulate pH i , similar to snapping turtle embryos, which represent...

  • coronary blood flow in the anesthetized american Alligator Alligator Mississippiensis
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2016
    Co-Authors: Bjarke Jensen, Ruth M. Elsey, Magnus Elfwing, Tobias Wang, Dane A Crossley
    Abstract:

    Coronary circulation of the heart evolved early within ectothermic vertebrates and became of vital importance to cardiac performance in some teleost fish, mammals and birds. In contrast, the role and function of the coronary circulation in ectothermic reptiles remains largely unknown. Here, we investigated the systemic and coronary arterial responses of five anesthetized juvenile American Alligators (Alligator Mississippiensis) to hypoxia, acetylcholine, adenosine, sodium nitroprusside, isoproterenol, and phenylephrine. We recorded electrocardiograms, monitored systemic blood pressure, blood flows in both aortae, and blood flow in a major coronary artery supplying most of the right ventricle. Coronary arterial blood flow was generally forward, but there was a brief retrograde flow during a ventricular contraction. Blood pressure was significantly changed in all conditions. Acetylcholine decreased coronary forward flow, but this response was confounded by the concomitant lowered work of the ventricles due to decreased heart rate and blood pressure. Coronary forward flow was poorly correlated with heart rate and mean arterial pressure across treatments. Overall changes in coronary forward flow, significant and not significant, were generally in the same direction as mean arterial pressure and ventricular power, approximated as the product of systemic cardiac output and mean arterial pressure.

  • scaling the feeding mechanism of captive Alligator Mississippiensis from hatchling to juvenile
    Biology, 2014
    Co-Authors: James R Kerfoot, Micah P Fern, Ruth M. Elsey
    Abstract:

    Small changes in size can lead to potential performance consequences and may influence an organism’s ability to utilize resources in its environment. As the American Alligator (Alligator Mississippiensis) transitions between neonate, juvenile and adult habitats (ontogenetic niche shifts), there are inevitably dynamic changes in their feeding performance. This study sought to investigate the scaling of the feeding mechanism and its performance from hatchling to juvenile size classes in A. Mississippiensis. Feeding events were recorded during March 2011 at Rockefeller Wildlife Refuge (Grand Chenier, Louisiana). Thirty-six captive individuals were randomly sampled, ranging from 30.5 cm to 91.5 cm total length, and feeding events were recorded using a high speed camera at a rate of 300 fps. Results indicated that many linear, angular and timing kinematic variables scale allometrically with cranium length; whereas maximum gape velocity and duration of feeding bout do not scale with cranium length and remain constant between these size classes. Although it has been shown that there is an isometric relationship between cranial elements and body size in A. Mississippiensis, this relationship is not transferred to linear and timing variables of prey-capture events. These allometric relationships echo other investigations of scaling relationships such as bite-force production and terrestrial locomotion.

  • Massive Distal Forelimb Fibromyxoma in a Free-Ranging American Alligator (Alligator Mississippiensis)
    Southeastern Naturalist, 2013
    Co-Authors: Ruth M. Elsey, Javier G. Nevarez, Jeff Boundy, Rudy W. Bauer
    Abstract:

    An adult male Alligator Mississippiensis (American Alligator) with a large growth on the right forelimb was harvested from the wild by a nuisance-control trapper in Louisiana. The mass was determined histologically to be a fibromyxoma. To our knowledge, this neoplasm has not previously been described in American Alligators.

Michael J. Tanner - One of the best experts on this subject based on the ideXlab platform.

Paul J. Weldon - One of the best experts on this subject based on the ideXlab platform.

  • Dorsal galnds of Alligator Mississippiensis: a histological and histochemical study
    Journal of Zoology, 1996
    Co-Authors: M. S. Cannon, Randall W. Davis, Paul J. Weldon
    Abstract:

    Several investigators have described in some crocodilians a row of round or oval organs, called dorsal glands, lying under scutes on each side of the dorsal midline. The function of these glands is unknown, but they are hypothesized to produce skin-conditioning secretions. We investigated the anatomy and histochemistry of the dorsal glands of adult American Alligators (Alligator Mississippiensis). Twenty to 22 pairs of glands containing a viscous, often black, material were observed lying from the mid-cervical to the anterior caudal regions in the axial musculature or on the inner surface of the dermis. The capsule of each gland consists of dense collagenous fibres and numerous short elastic fibres, and is surrounded by skeletal muscle. The single lumen is lined by one to several layers of cuboidal to columnar epithelium in varying stages of degeneration, indicating a holocrine secretory mode. The epithelial cell membranes often interdigitate and tight junctions and desmosomes occasionally are observed between them. The epithelial cells and secretory product contain slight to considerable amounts of lipid; glycoproteins may be present. Crystals exhibiting a dense core and/or layering occur in the epithelial cells and secretory product. Energy-dispersive X-ray analysis demonstrates calcium, copper, iron, lead, potassium, and zinc in the crystals. Mitochondria, vacuoles, and short segments of rough endoplasmic reticulum also occur in the cells.

  • Analysis of gular and paracloacal gland secretions of the american Alligator (Alligator Mississippiensis) by thin-layer chromatography Gland, sex, and individual differences in lipid components
    Journal of Chemical Ecology, 1990
    Co-Authors: Paul J. Weldon, Timothy P. Scott, Michael J. Tanner
    Abstract:

    Secretions from the gular and the paracloacal glands of adult male and female American Alligators ( Alligator Mississippiensis ) were extracted with chloroform, weighed, and analyzed by thin-layer chromatography. In both sexes, more lipoidal secretions were recovered from the paracloacal glands than from the gular glands. Females produce more lipoidal secretions in both sets of glands than do males. The thin-layer chromatograms of extracts from both glands exhibit bands consistent with aliphatic alcohols, sterols, free fatty acids, and steryl esters. Triglycerides, hydrocarbons, phosphatidylethanolamine, and lysophosphatidylcholine also are indicated in some chromatograms. Gland, sex, and individual differences are suggested in the thinlayer profiles.

Mark Merchant - One of the best experts on this subject based on the ideXlab platform.

  • Detection and analysis of autophagy in the American Alligator (Alligator Mississippiensis).
    Journal of Experimental Zoology, 2020
    Co-Authors: Amber Hale, Mark Merchant, Mary E. White
    Abstract:

    In response to environmental temperature depression in the fall and winter, American Alligators (Alligator Mississippiensis) brumate. Brumation is characterized by lethargy, fasting, decreased metabolism, and decreased body temperature. During brumation, Alligators will periodically emerge for basking or other encounters when environmental conditions permit. This sporadic activity and lack of nutrient intake may place strain on nutrient reserves. Nutrient scarcity, at the cellular and/or organismal level, promotes autophagy, a well-conserved subcellular catabolic process used to maintain energy homeostasis during periods of metabolic or hypoxic stress. An analysis of the putative Alligator autophagy-related proteins has been conducted, and the results will be used to investigate the physiological role of autophagy during the brumation period. Using published genomic data, we have determined that autophagy is highly conserved, and Alligator amino acid sequences exhibit a high percentage of identity with human homologs. Transcriptome analysis conducted using liver tissue derived from Alligators confirmed the expression of one or more isoforms of each of the 34 autophagy initiation and elongation genes assayed. Five autophagy-related proteins (ATG5, ATG9A, BECN1, ATG16L1, and MAP1-LC3B), with functions spanning the major stages of autophagy, have been detected in Alligator liver tissue by western blot analysis. In addition, ATG5 was detected in Alligator liver tissue by immunohistochemistry. This is the first characterization of autophagy in crocodylians, and the first description of autophagy-related protein expression in whole blood.

  • Characterization of Chitotriosidase Enzyme Activity in the Serum of the American Alligator (Alligator Mississippiensis)
    Advances in Biological Chemistry, 2018
    Co-Authors: Kenneth Kidder, Rodolfo Falconi, Mark Merchant
    Abstract:

    Chitotriosidase (ChT) is an endoglucosaminidase enzyme that cleaves chitinous substrates and has been strongly associated with innate immune activity and the ability to identify non-selftissues. This enzyme activity was detected and characterized the serum from the American Alligator (Alligator Mississippiensis) using a fluorometric probe. Alligator serum exhibited volume-dependent activity, with activity (2.1 ± 0.3 μmol/min) observed at dilutions as low as a 1:150, and maximum activity (5.2 ± 0.6 μmol/min) measured at a dilution of 1:30. Alligator serum ChT showed linear activity for approximately 20 min, at which time activity decreased exponentially, presumably due to the depletion of substrate. In addition, the ChT activity in Alligator serum was temperature-dependent with low activity at 5°C, a sharp increase from 10°C - 30°C, and maximal activity from 30°C - 40°C. The activity was inhibited in the presence of water-soluble chitin, but not mannan, indicating the specificity of the enzyme. The presence of ChT in Alligator serum is likely to be partially responsible for the potent innate immune system of these crocodylians, and particularly antifungal activities.

  • can reproductive allometry assess population marginality in crocodilians a comparative analysis of gulf coast american Alligator Alligator Mississippiensis populations
    Copeia, 2013
    Co-Authors: Christopher M Murray, Mark Merchant, Michael Easter, Amos Cooper, Brian I Crother
    Abstract:

    This study uses the American Alligator (Alligator Mississippiensis) to assess the use of reproductive allometry as a tool to infer crocodilian population marginality based on conformation to advantageous life-history strategies. It is hypothesized that reproductive allometry, a morphometric relationship between mother's size and her reproductive output, varies intraspecifically between populations and that this variation reflects population marginality based on size, stress, temporal exploitation, habitat fragmentation, and/or the presence of social hierarchy. This hypothesis is tested using relative comparisons of allometric correlation between a marginal population inundated with saline storm surge from Hurricane Ike in southeastern Texas and a hypothesized unstressed core population in southeastern Louisiana. Heterophil to lymphocyte ratios fail to falsify the hypothesis of a saline stressor. The number of significant morphometric correlations between various parameters, degree of correlation (R2), and...

  • Effects of Leukocyte Extract from the American Alligator (Alligator Mississippiensis) on Antibiotic-Resistant Bacteria
    The Open Zoology Journal, 2011
    Co-Authors: Venkata Machha, Paige Spencer, Mark Merchant
    Abstract:

    Treatment of clinical isolates of human pathogenic bacteria, which were known to be resistant to multiple commonly-used antibiotics, with refined leukocyte extracts from the American Alligator (Alligator Mississippiensis) resulted in a time- and concentration-dependent inhibition of bacterial proliferation. The Alligator leukocyte extract exhibited the strongest antibacterial effect on Pseudomonas aeruginosa followed by Enterococcus faecium and then Klebsiella pneumonia. The antibacterial activities were acid-soluble, heat-stable at 70 o C for one h, sensitive to protease treatment, and did not require divalent metal ions for antibacterial activity. Collectively, these data strongly suggest that the molecule(s) responsible for the observed antibacterial activities are small, cationic antimicrobial peptides.

  • Characterization of Phospholipase A2 Activity in Serum of the American Alligator (Alligator Mississippiensis)
    Journal of Experimental Zoology, 2009
    Co-Authors: Mark Merchant, Raphiel Heard, Caleb Monroe
    Abstract:

    PLA2 is a diverse class of enzymes with a broad spectrum of physiological functions. Secretory PLA2 isoforms have been reported to exhibit important innate immune function in higher vertebrates. This study was conducted to characterize PLA2 activity in the serum of the American Alligator (Alligator Mississippiensis). We used a glycerophospholipid with a fatty acid in the sn-2 position labeled with a fluorescent probe (BODIPY) to detect and quantify Alligator serum PLA2 activity. Incubation of BODIPY-labeled bacteria with different concentrations of Alligator serum resulted in a concentration-dependent detection of PLA2 activity. Kinetic studies showed that product formation was rapid, with substantial activity within 5 min, and maximal activity at approximately 20 min. The Alligator PLA2 activity was temperature-dependent, with activity at lower temperatures (5−10°C) approximately half of that observed at temperatures of 30–40°C. In addition, the generation of fluorescent product was reduced by a specific inhibitor (p-bromophenacyl bromide) of secretory PLA2 in a concentration-dependent manner, enforcing the idea that the observed activities are due to a secretory PLA2 enzyme in Alligator serum. J. Exp. Zool. 311A: 662–666, 2009. © 2009 Wiley-Liss, Inc.

Monique L. Van Hoek - One of the best experts on this subject based on the ideXlab platform.

  • Bioprospecting the American Alligator (Alligator Mississippiensis) Host Defense
    2020
    Co-Authors: Barney Bishop, Melanie L. Juba, Megan Devine, Stephanie M. Barksdale, Myung Chung, Paul S. Russo, Kent A. Vliet, Joel M. Schnur, Monique L. Van Hoek
    Abstract:

    Cationic antimicrobial peptides and their therapeutic potential have garnered growing interest because of the proliferation of bacterial resistance. However, the discovery of new antimicrobial peptides from animals has proven challenging due to the limitations associated with conventional biochemical purification and difficulties in predicting active peptides from genomic sequences, if known. As an example, no antimicrobial peptides have been identified from the American Alligator, Alligator Mississippiensis, although their serum is antimicrobial. We have developed a novel approach for the discovery of new antimicrobial peptides from these animals, one that capitalizes on their fundamental and conserved physico-chemical properties. This sample-agnostic process employs custom-made functionalized hydrogel microparticles to harvest cationic peptides from biological samples, followed by de novo sequencing of captured peptides, eliminating the need to isolate individual peptides. After evaluation of the peptide sequences using a combination of rational and webbased bioinformatic analyses, forty-five potential antimicrobial peptides were identified, and eight of these peptides were selected to be chemically synthesized and evaluated. The successful identification of multiple novel peptides, exhibiting antibacterial properties, from Alligator Mississippiensis plasma demonstrates the potential of this innovative discovery process in identifying potential new host defense peptides.

  • bioprospecting the american Alligator Alligator Mississippiensis host defense peptidome
    PLOS ONE, 2015
    Co-Authors: Barney Bishop, Melanie L. Juba, Megan Devine, Stephanie M. Barksdale, Myung Chung, Paul S. Russo, Kent A. Vliet, Joel M. Schnur, Carlos A Rodriguez, Monique L. Van Hoek
    Abstract:

    Cationic antimicrobial peptides and their therapeutic potential have garnered growing interest because of the proliferation of bacterial resistance. However, the discovery of new antimicrobial peptides from animals has proven challenging due to the limitations associated with conventional biochemical purification and difficulties in predicting active peptides from genomic sequences, if known. As an example, no antimicrobial peptides have been identified from the American Alligator, Alligator Mississippiensis, although their serum is antimicrobial. We have developed a novel approach for the discovery of new antimicrobial peptides from these animals, one that capitalizes on their fundamental and conserved physico-chemical properties. This sample-agnostic process employs custom-made functionalized hydrogel microparticles to harvest cationic peptides from biological samples, followed by de novo sequencing of captured peptides, eliminating the need to isolate individual peptides. After evaluation of the peptide sequences using a combination of rational and web-based bioinformatic analyses, forty-five potential antimicrobial peptides were identified, and eight of these peptides were selected to be chemically synthesized and evaluated. The successful identification of multiple novel peptides, exhibiting antibacterial properties, from Alligator Mississippiensis plasma demonstrates the potential of this innovative discovery process in identifying potential new host defense peptides.