A Canopy Trimming Experiment in Puerto Rico: The Response of Litter Invertebrate Communities to Canopy Loss and Debris Deposition in a Tropical Forest Subject to Hurricanes

Hurricanes cause canopy removal and deposition of pulses of litter to the forest floor. A Canopy Trimming Experiment (CTE) was designed to decouple these two factors, and to investigate the separate abiotic and biotic consequences of hurricane-type damage and monitor recovery processes. As part of this experiment, effects on forest floor invertebrate communities were studied using litterbags. Canopy opening resulted in increased throughfall, soil moisture and light levels, but decreased litter moisture. Of these, only throughfall and soil moisture had returned to control levels 9 months after trimming. Canopy opening was the major determinant of adverse changes in forest floor invertebrate litter communities, by reducing diversity and biomass, irrespective of debris deposition, which played a secondary role. Plots subjected to the most disturbance, with canopy removed and debris added, had the lowest diversity and biomass. These two parameters were higher than control levels when debris was added to plots with an intact canopy, demonstrating that increased nutrient potential or habitat complexity can have a beneficial effect, but only if the abiotic conditions are suitable. Animal abundance remained similar over all treatments, because individual taxa responded differently to canopy trimming. Mites, Collembola, and Psocoptera, all microbiovores feeding mainly on fungal hyphae and spores, responded positively, with higher abundance in trimmed plots, whereas all other taxa, particularly predators and larger detritivores, declined in relative abundance. Litterbag mesh size and litter type had only minor effects on communities, and canopy trimming and debris deposition explained most variation between sites. Effects of trimming on diversity, biomass, and abundance of some invertebrate taxa were still seen when observations finished and canopy closure was complete at 19 months. This suggests that disturbance has a long-lasting effect on litter communities and may, therefore, delay detrital processing, depending on the severity of canopy damage and rate of regrowth.     

Invasive Snake Activity Before and After Automated Aerial Baiting

Aerially delivered toxic baits have proven effective for landscape-level control of numerous invasive vertebrate populations with major benefits for conservation and ecosystem function, but this technique has not been broadly adapted for control of invasive reptiles. Nonnative brown treesnakes (Boiga irregularis) on the Pacific island of Guam have caused severe ecological and economic damage and pose an invasion risk on other islands, making them a high-profile candidate for application of aerial baiting methods. Although terrestrial applications of traps, toxicants, and hand-removal are standard brown treesnake management practices, these methods are not cost-effective for control in the island's large tracts of remote, rugged forest. In 2016, the first major in situ evaluation of a helicopter-borne automated aerial bait delivery system applied snake-targeted toxic baits at an effective rate of approximately 120 baits/ha over a 110-ha forested test plot on Guam. We evaluated the extent and duration of the suppressive effect of this toxic bait application on brown treesnakes by measuring nontoxic bait take rates as a proxy index of relative snake abundance before and after toxic bait application in a treatment plot and surrounding reference area. We placed 4,420 nontoxic baits in random transects at georeferenced locations, from 1 month before until nearly 12 months after toxic bait application, allowing temporal analysis of the suppressive effect and spatial analysis of treatment plot reinvasion. Over the first 30 days after toxic bait application, average nontoxic bait take rate in the treatment plot was 41.2% lower than the pre-application rate, and there was no immediate decrease in bait take in the reference area. Reduced snake activity was still evident nearly 12 months after bait application. Roads forming a portion of the treatment boundary appeared to slow snake movement between treated area and surrounding untreated area. Trail cameras monitoring a subset of bait tubes showed that 97.5% of baits removed were taken by snakes rather than nontarget species. We indexed rodent abundance in the treatment plot and reference area, and found no indication of a rodent population increase following toxic bait application. Our results show that automated aerial bait applications can suppress brown treesnake abundance over a large area and that reinvasion from surrounding untreated habitat occurs over several months. We anticipate that repeated bait applications could achieve and maintain greatly reduced brown treesnake abundance on a landscape scale, potentially improving biosecurity and enabling experimental reintroduction of native birds extirpated by brown treesnake predation. Published 2019. This article is a U.S. Government work and is in the public domain in the USA. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

Comparative efficacy of a secretory phospholipase A<Subscript>2</Subscript> inhibitor with conventional anti-inflammatory agents in a rat model of antigen-induced arthritis

Introduction  

Previously, secretory phospholipase A₂ (sPLA₂) inhibition has been used as an adjunct to conventional rheumatoid arthritis therapy in human clinical trials without significant improvement of arthritic pathology. In this study, we compared the efficacy of a potent and orally active group IIa secretory phospholipase A₂ inhibitor (sPLA₂I) to conventional anti-arthritic agents; infliximab, leflunomide and prednisolone, in a rat model of antigen-induced arthritis.     

Synthesis of rat muscle carbonic anhydrase III in a cell-free translation system

Carbonic anhydrase III (CA III) was identified in the products of rat soleus muscle RNA translation in vitro by both a radioimmunoassay and a specific immunoprecipitation technique followed by SDS--polyacrylamide gel electrophoresis analysis of the precipitated antigen. The primary translation product has the same Mr-value as the native isoenzyme. CA III mRNA was found to represent approximately 0.55% of the total mRNA present in rat soleus muscle.     

Soluble ST2 Associates with Diabetes but Not Established Cardiovascular Risk Factors: A New Inflammatory Pathway of Relevance to Diabetes?

Preliminary data mostly from animal models suggest the sST2/IL-33 pathway may have causal relevance for vascular disease and diabetes and thus point to a potential novel inflammatory link to cardiometabolic disease. However, the characterisation of sST2 levels in terms of metabolic or vascular risk in man is completely lacking. We sought to address this gap via a comprehensive analysis of risk factor and vascular correlates of sST2 in a cross-sectional study (pSoBid). We measured sST2 in plasma in 639 subjects and comprehensively related it to cardiovascular and diabetes risk factors and imaged atherosclerosis measures. Circulating sST2 levels increased with age, were lower in women and in highest earners. After adjusting for age and gender, sST2 levels associated strongly with markers of diabetes, including triglycerides [effect estimate (EE) per 1 standard deviation increase in sST2∶1.05 [95%CI 1.01,1.10]), liver function (alanine aminotransaminase [ALT] and γ-glutamyl transferase [GGT]: EE 1.05 [1.01,1.09] and 1.13 [1.07,1.19] respectively), glucose (1.02 [1.00,1.03]) and sICAM-1 (1.05 [1.02,1.07]). However, sST2 levels were not related to smoking, cholesterol, blood pressure, or atheroma (carotid intima media thickness, plaque presence). These results suggest that sST2 levels, in individuals largely without vascular disease, are related principally to markers associated with diabetes and ectopic fat and add support for a role of sST2 in diabetes. Further mechanistic studies determining how sST2 is linked to diabetes pathways may offer new insights into the inflammatory paradigm for type 2 diabetes.     

Characterization of isolated ventricular myocytes from adult zebrafish (Danio rerio)

The zebrafish is widely used for human related disease studies. Surprisingly, there is no information about the electrical activity of single myocytes freshly isolated from adult zebrafish ventricle. In this study, we present an enzymatic method to isolate ventricular myocytes from zebrafish heart that yield a large number of calcium tolerant cells. Ventricular myocytes from zebrafish were imaged using light and confocal microscopy. Myocytes were mostly rod shaped and responded by vigorous contraction to field electrical stimulation. Whole cell configuration of the patch clamp technique was used to record electrophysiological characteristics of myocytes. Action potentials present a long duration and a plateau phase and action potential duration decreases when increasing stimulation frequency (as observed in larger mammals). Together these results indicate that zebrafish is a species ideally suited for investigation of ion channels related mutation screening of cardiac alteration important in human.     

Vasopressin-stimulated Ca2+ spiking in vascular smooth muscle cells involves phospholipase D

Physiological concentrations of [Arg(8)]vasopressin (AVP; 10-500 pM) stimulate oscillations of cytosolic free Ca2+ concentration (Ca2+ spikes) in A7r5 vascular smooth muscle cells. We previously reported that this effect of AVP was blocked by a putative phospholipase A2 (PLA2) inhibitor, ONO-RS-082 (5 microM). In the present study, the products of PLA2, arachidonic acid (AA), and lysophospholipids were found to be ineffective in stimulating Ca2+ spiking, and inhibitors of AA metabolism did not prevent AVP-stimulated Ca2+ spiking. Thin layer chromatography was used to monitor the release of AA and phosphatidic acid (PA), which are the products of PLA2 and phospholipase D (PLD), respectively. AVP (100 pM) stimulated both AA and PA formation, but only PA formation was inhibited by ONO-RS-082 (5 microM). Exogenous PLD (type VII; 2.5 U/ml) stimulated Ca2+ spiking equivalent to the effect of 100 pM AVP. AVP stimulated transphosphatidylation of 1-butanol (a PLD-catalyzed reaction) but not 2-butanol, and 1-butanol (but not 2-butanol) completely prevented AVP-stimulated Ca2+ spiking. Protein kinase C (PKC) inhibition, which completely prevents AVP-stimulated Ca2+ spiking, did not inhibit AVP-stimulated phosphatidylbutanol formation. These results suggest that AVP-stimulated Ca2+ spiking depends on activation of PLD rather than PLA2 and that PKC activation may be downstream of PLD in the signaling cascade.     

Connexin46 mutations linked to congenital cataract show loss of gap junction channel function

Human connexin46 (hCx46) forms gapjunctional channels interconnecting lens fiber cells and appears to becritical for normal lens function, because hCx46 mutations have beenlinked to congenital cataracts. We studied two hCx46 mutants, N63S, amissense mutation in the first extracellular domain, and fs380, aframe-shift mutation that shifts the translational reading frame atamino acid residue 380. We expressed wild-type Cx46 and the two mutantsin Xenopus oocytes. Production of the expressed proteins wasverified by SDS-PAGE after metabolic labeling with[³⁵S]methionine or by immunoblotting. Dualtwo-microelectrode voltage-clamp studies showed that hCx46 formed bothgap junctional channels in paired Xenopus oocytes andhemi-gap junctional channels in single oocytes. In contrast, neither ofthe two cataract-associated hCx46 mutants could form intercellularchannels in paired Xenopus oocytes. The hCx46 mutants werealso impaired in their ability to form hemi-gap-junctional channels.When N63S or fs380 was coexpressed with wild-type connexins, bothmutations acted like "loss of function" rather than "dominantnegative" mutations, because they did not affect the gap junctionalconductance induced by either wild-type hCx46 or wild-type hCx50.