Rationale
Mitochondria interact via actions of outer and inner membrane fusion proteins. The role of mitochondrial fusion on functioning of the heart, where mitochondria comprise ~30% of cardiomyocyte volume and their inter-myofilament spatial arrangement with other mitochondria is highly ordered, is unknown.
Objective
Model and analyze mitochondrial fusion defects in Drosophila melanogaster heart tubes with tincΔ4Gal4-directed expression of RNAi for Mitochondrial Assembly Regulatory Factor (MARF) and Optic atrophy 1 (Opa1).
Methods and Results
Live imaging analysis revealed that heart tube-specific knockdown of MARF or Opa1 increases mitochondrial morphometric heterogeneity and induces heart tube dilation with profound contractile impairment. Sarcoplasmic reticular structure was unaffected. Cardiomyocyte expression of human mitofusin (mfn) 1 or 2 rescued MARF RNAi cardiomyopathy, demonstrating functional homology between Drosophila MARF and human mitofusins. Suppressing mitochondrial fusion increased compensatory expression of nuclear-encoded mitochondrial genes, indicating mitochondrial biogenesis. The MARF RNAi cardiomyopathy was prevented by transgenic expression of superoxide dismutase 1.
Conclusions
Mitochondrial fusion is essential to cardiomyocyte mitochondrial function and regeneration. Reactive oxygen species are key mediators of cardiomyopathy in mitochondrial fusion-defective cardiomyocytes. Postulated mitochondrial-ER interactions mediated uniquely by mfn2 appear dispensable to functioning of the fly heart.
The reproductive tract of wild-caught male Boiga irregularis (Merrem, 1802) (Brown Treesnake) and the changes that result in these tissues from captivity are described. Wild-caught snakes were compared with snakes kept in captivity and sacrificed at approximately 10, 30, 50, and 60+ days. Snakes sacrificed after 10 days in captivity showed no differences in histological appearance or epithelial height in either the testis or sexual segment of the kidney (SSK) compared with wild snakes. Normal spermatogenic stages and SSK ultrastructure were observed in the testes and kidney from wild specimens and captive specimens after 10 days. In terms of the SSK, large electron-dense secretory vacuoles occupied the apices of the epithelial cells, while a basal nucleus, rough endoplasmic reticulum, and Golgi bodies filled the bases of these cells. All SSK cells were actively secretory in a mode that could most accurately be termed apocrine. At time of secretion, released vacuoles become diffuse and the apical membrane ruptures, spilling the SSK contents into the distal nephron lumen. Between 10 and 30 days in captivity, spermatogenesis and secretion in the SSK ceased and the epithelial height of both tissues decreased. At approximately 60 days, testicular epithelial height increased and spermatogenic activity was reestablished. The SSK, however, remained regressed at 60 days.
a b s t r a c tAfter its inadvertent introduction to Guam, the brown tree snake (Boiga irregularis, BTS) extirpated most of the island's native terrestrial vertebrates, presented a health hazard to small children, and had considerable economic ramifications. Management of BTS is aimed at a number of objectives, the foremost of which has been to deter its dispersal from Guam to other locations. Further objectives include reclaiming areas on Guam as snake-free for reintroduction of native wildlife, to protect small sensitive sites on Guam from BTS intrusion (e.g, power stations, bird nesting sites), to contain and capture stowaway BTS incoming to vulnerable destinations, and to control incipient populations in other areas beyond their native range. A number of control tools have been developed, and the efficacy of each control method depends on the situation to which it is applied. Integration of control methods provides the most efficacious results for all objectives. Here, we outline the different objectives for managing BTS, and the tools and methods available for BTS management. We complete the picture by describing which tools and methods are best suited to accomplish each management objective.Published by Elsevier Ltd.
In 2008, we studied simulated toxicant efficacy to control invasive brown treesnakes (Boiga irregularis) using bait tubes (elongate bait stations that reduce non‐target bait take) in a 5‐ha enclosure in Guam (U.S. Territory) with a known population of snakes. Instead of toxicants, we implanted radiotransmitters in small (6.6 ± 1.4 g) and large (21.8 ± 2.9 g) bait‐mouse carcasses, offered from 2 types of bait tubes over a 3‐month period. The known snake population allowed us to characterize not only the snakes taking bait, but also those evading our mock control effort. Tube design had no effect on take rate, but snout–vent length was a strong predictor of bait take: none of the 30 snakes <843 mm in length took any bait, whereas 77 of the 126 snakes ≥843 mm in length took 164 baits. While medium‐sized snakes preferentially ingested small bait (and the largest snakes tended to take large mice more frequently), some of the smallest snakes that took bait ingested large mice. Snake body condition was positively correlated to take rate, but snake sex had no discernible effect. Our data show that there is a relatively narrow size (and, thus, time) gap between the size at which the snakes become susceptible to bait‐mouse take and the size at which they become sexually mature. This has implications for the timing of repeated baiting efforts, if the goal is eradication rather than suppression. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
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