Developmental regulation of regenerative potential in Drosophila by ecdysone through a bistable loop of ZBTB transcription factors.

In many organisms, the regenerative capacity of tissues progressively decreases as development progresses. However, the developmental mechanisms that restrict regenerative potential remain unclear. In Drosophila, wing imaginal discs become unable to regenerate upon damage during the third larval stage (L3). Here, we show that production of ecdysone after larvae reach their critical weight (CW) terminates the window of regenerative potential by acting on a bistable loop composed of two antagonistic Broad-complex/Tramtrack/Bric-à-brac Zinc-finger (ZBTB) genes: chinmo and broad (br). Around mid L3, ecdysone signaling silences chinmo and activates br to switch wing epithelial progenitors from a default self-renewing to a differentiation-prone state. Before mid L3, Chinmo promotes a strong regenerative response upon tissue damage. After mid L3, Br installs a nonpermissive state that represses regeneration. Transient down-regulation of ecdysone signaling or Br in late L3 larvae enhances chinmo expression in damaged cells that regain the capacity to regenerate. This work unveils a mechanism that ties the self-renewing and regenerative potential of epithelial progenitors to developmental progression.

Successful Management of Open, Contaminated Metacarpal Fractures in an Adult Snowy Owl ( Bubo scandiacus) With a Minimal Type II External Skeletal Fixator.

An adult, male snowy owl ( Bubo scandiacus) was found down and unable to fly in western New York State. Physical examination and radiographs revealed a subacute, open wound and fractured major and minor metacarpals of the right wing. A minimal type II external skeletal fixator (ESF) device was placed on the right major metacarpal bone and the open wound was allowed to granulate and close. After evidence of bone union, the ESF device was removed. The owl performed auto-physiotherapy throughout the process and was released with sustained flight 2 months postoperatively. It was recaptured 7 weeks later and underwent further rehabilitation to allow successful release 11 months after surgical stabilization. To our knowledge, this is the first case report describing use of a type II ESF device on the metacarpus of a bird.

Wing wear reduces bumblebee flight performance in a dynamic obstacle course.

Previous work has shown that wing wear increases mortality in bumblebees. Although a proximate mechanism for this phenomenon has remained elusive, a leading hypothesis is that wing wear increases predation risk by reducing flight manoeuvrability. We tested the effects of simulated wing wear on flight manoeuvrability in Bombus impatiens bumblebees using a dynamic obstacle course designed to push bees towards their performance limits. We found that removing 22% wing area from the tips of both forewings (symmetric wear) caused a 9% reduction in peak acceleration during manoeuvring flight, while performing the same manipulation on only one wing (asymmetric wear) did not significantly reduce maximum acceleration. The rate at which bees collided with obstacles was correlated with body length across all treatments, but wing wear did not increase collision rate, possibly because shorter wingspans allow more room for bees to manoeuvre. This study presents a novel method for exploring extreme flight manoeuvres in flying insects, eliciting peak accelerations that exceed those measured during flight through a stationary obstacle course. If escape from aerial predation is constrained by acceleration capacity, then our results offer a potential explanation for the observed increase in bumblebee mortality with wing wear.

Pattern reorganization occurs independently of cell division during Drosophila wing disc regeneration in situ.

One of the most intriguing problems in developmental biology is how an organism can replace missing organs or portions of its body after injury. This capacity, known as regeneration, is conserved across different phyla. The imaginal discs of Drosophila melanogaster provide a particularly well-characterized model for analyzing regeneration. We have developed a unique method to study organ regeneration under physiological conditions using the imaginal discs of Drosophila. Using this method, we revisited different aspects of organ regeneration. The results presented in this report suggest that during the initial stages of regeneration, different processes occur, including wound healing, a temporary loss of markers of cell-fate commitment, and pattern reorganization. We present evidence indicating that all of these processes occur even when cell division has been arrested. Our data also suggested that Wingless is not required during the early stages of disc regeneration.

Influence of two catching methods on the occurrence of lesions in broilers.

During the catching of broilers for slaughter, 2 to 3 birds are grabbed per hand at one leg at the same time. From an animal welfare point of view, this procedure is under critical observation from animal welfare administration and the general public.In this paper 2 catching methods were compared: the routinely used 1-leg catching method, and a second tech-nique whereby birds were grabbed by both legs with a maximum of 2 birds per hand (2-leg catching method). Lesions on the body, legs, and wings (hemorrhages and fractures) were recorded by a camera system located after the plucking position. Two weight classes, 2 catching teams, and 2 flocks were included in the study.Heavy animals showed more lesions than birds of the light weight class. In all investigations, lesions on the body and legs were rare, whereas wing lesions occurred at a rate of up to 15.32%. Statistical analysis showed no significant difference between the 2 methods or between the catching teams for both weight classes. A correlation between lesions and weight was observed, with a significant odds ratio ( OR: ) of 3.6 (95% CI: 3.299-3.957).During 2-leg catching, the animals appeared to be more restless. Workers stated that the grabbing of both legs of a bird was more difficult and that working in a crouching position for a longer time was harder.We conclude that the cautious handling of animals to reduce stress is more important than "holding animals by both legs", as has been proposed.

Histologic Evaluation of Critical Size Defect Healing With Natural and Synthetic Bone Grafts in the Pigeon ( Columba livia ) Ulna.

Fracture and bone segment loss are major clinical problems in birds. Achieving bone formation and clinical union in a fracture case is important for the survival of the bird. To evaluate the efficacy of bone grafts for defect healing in birds, 2 different bone grafts were investigated in the healing of a bone defect in 24 healthy pigeons ( Columba livia ). In each bird, a 1-cm critical size defect (CSD) was created in the left ulna, and the fracture was stabilized with external skeletal fixation (ESF). A graft of hydroxyapatite (HA) alone (n = 12 birds) or demineralized bone matrix (DBM) combined with HA (n = 12 birds) was implanted in the CSD. The CSD healing was evaluated at 3 endpoints: 3, 6, and 12 weeks after surgery. Four birds were euthanatized at each endpoint from each treatment group, and bone graft healing in the ulna CSD was evaluated by histologic examination. The CSD and graft implants were evaluated for quality of union, cortex development, and bone graft incorporation. Results showed no graft rejection in any bird, and all birds had connective tissue formation in the defect because of the bone graft application. These results suggest that bone defect healing can be achieved by a combination of osteoinductive and osteoconductive bone graft materials for clinical union and new bone regeneration in birds. The combination of DBM and HA resulted in a better quality bone graft (P < .05) than did HA alone, but there was no significant differences in cortex development or bone graft incorporation at 3, 6, or 12 weeks. From the results of this study, we conclude that HA bone grafts, alone or in combination with DBM, with external skeletal fixation is suitable and safe for bone defect and fracture treatment in pigeons.

Biomechanical strategies for mitigating collision damage in insect wings: structural design versus embedded elastic materials.

The wings of many insects accumulate considerable wear and tear during their lifespan, and this irreversible structural damage can impose significant costs on insect flight performance and survivability. Wing wear in foraging bumblebees (and likely many other species) is caused by inadvertent, repeated collisions with vegetation during flight, suggesting the possibility that insect wings may display biomechanical adaptations to mitigate the damage associated with collisions. We used a novel experimental technique to artificially induce wing wear in bumblebees and yellowjacket wasps, closely related species with similar life histories but distinct wing morphologies. Wasps have a flexible resilin joint (the costal break) positioned distally along the leading edge of the wing, which allows the wing tip to crumple reversibly when it hits an obstacle, whereas bumblebees lack an analogous joint. Through experimental manipulation of its stiffness, we found that the costal break plays a critical role in mitigating collision damage in yellowjacket wings. However, bumblebee wings do not experience as much damage as would be expected based on their lack of a costal break, possibly due to differences in the spatial arrangement of supporting wing veins. Our results indicate that these two species utilize different wing design strategies for mitigating damage resulting from collisions. A simple inertial model of a flapping wing reveals the biomechanical constraints acting on the costal break, which may help explain its absence in bumblebee wings.

Effects of environmental factors and appendage injury on the wing variation in the cricket Velarifictorus ornatus.

The effects of environmental factors and appendage injury on the wing variation in Velarifictorus ornatus (Shiraki) (Orthoptera: Gryllidae) were investigated. The percentage of micropters was more than 95% when the nymphs were reared at constant photoperiods, and changing photoperiod did not affect wing variation in V. ornatus at 25 or 30°C. In the crowding experiment, the percentage of macropters was only 11.2% when the nymphs were reared separately at 25°C. In contrast, the percentage of macropters was significantly higher when the rearing density was increased to two nymphs per container and lower when the rearing density was increased to five or 10 nymphs per container. These results indicate that low and high rearing densities induce micropters, but intermediate rearing density stimulates the formation of macropters. Meanwhile, severance of appendages, such as antennae, femora, and tibiae, in the nymph stage exerted a micropterizing effect. The period sensitive to such stresses ranged from 35 to 60 days of nymph development.

Bat flight with bad wings: is flight metabolism affected by damaged wings?

Infection of North American bats with the keratin-digesting fungus Geomyces destructans often results in holes and ruptures of wing membranes, yet it is unknown whether flight performance and metabolism of bats are altered by such injuries. I conducted flight experiments in a circular flight arena with Myotis albescens and M. nigricans individuals with an intact or ruptured trailing edge of one of the plagiopatagial membranes. In both species, individuals with damaged wings were lighter, had a higher aspect ratio (squared wing span divided by wing area) and an increased wing loading (weight divided by wing area) than conspecifics with intact wings. Bats with an asymmetric reduction of the wing area flew at similar speeds to conspecifics with intact wings but performed fewer flight manoeuvres. Individuals with damaged wings showed lower metabolic rates during flight than conspecifics with intact wings, even when controlling for body mass differences; the difference in mass-specific metabolic rate may be attributable to the lower number of flight manoeuvres (U-turns) by bats with damaged wings compared with conspecifics with intact wings. Possibly, bats compensated for an asymmetric reduction in wing area by lowering their body mass and avoiding flight manoeuvres. In conclusion, it may be that bats suffer from moderate wing damage not directly, by experiencing increased metabolic rate, but indirectly, by a reduced manoeuvrability and foraging success. This could impede a bat's ability to gain sufficient body mass before hibernation.

Neuromuscular and biomechanical compensation for wing asymmetry in insect hovering flight.

Wing damage is common in flying insects and has been studied using a variety of approaches to assess its biomechanical and fitness consequences. Results of these studies range from strong to nil effect among the variety of species, fitness measurements and damage modes studied, suggesting that not all damage modes are equal and that insects may be well adapted to compensate for some types of damage. Here, we examine the biomechanical and neuromuscular means by which flying insects compensate for asymmetric wing damage, which is expected to produce asymmetric flight forces and torques and thus destabilize the animal in addition to reducing its total wing size. We measured the kinematic and neuromuscular responses of hawkmoths (Manduca sexta) hovering in free flight with asymmetrically damaged wings via high-speed videography and extracellular neuromuscular activity recordings. The animals responded to asymmetric wing damage with asymmetric changes to wing stroke amplitude sufficient to restore symmetry in lift production. These asymmetries in stroke amplitude were significantly correlated with bilateral asymmetries in the timing of activation of the dorsal ventral muscle among and within trials. Correspondingly, the magnitude of wing asymmetry was significantly, although non-linearly, correlated with the magnitude of the neuromuscular response among individuals. The strongly non-linear nature of the relationship suggests that active neural compensation for asymmetric wing damage may only be necessary above a threshold (>12% asymmetry in wing second moment of area in this case) below which passive mechanisms may be adequate to maintain flight stability.

Integrity of and damage to wings, feather vanes and serrations in barn owls.

The silent flight of owls is well known. It has served as role model for the designs of new airplane wings and ventilators. One of the structural features that underlies silent flight is the serrated leading edge of the wing that is mainly formed by the tenth primary flight feather (P10). We examined here how much the wings, the P10 feather and the serrations in different populations of barn owls reflect the intact situation. First, when the P10 feather molts, no or fewer serrations are present. Furthermore, damage to feathers and serrations may occur. Damage may be due to several factors like broken feather tips, lost rami, barbules, or broken tips of serrations. The latter may cause a narrowing of the outer vane of the P10 feather. We quantitatively assessed damage by counting the number of wings with missing or broken primary feathers, the number of wings with a narrowed outer vane of the P10 feather, and the number of serrations with reduced length. Considerable damage occurred on wings and feathers on both the macroscopic and microscopic levels. The observed damage most likely influences flight performance. More damage occurred in Galapagos barn owls than in North American and European barn owls. The Galapagos population may be more vulnerable than the other populations because it may at least temporarily be in a bad nutritional state and, thus, postpone molt.

Dynamics of animal movement in an ecological context: dragonfly wing damage reduces flight performance and predation success.

Much of our understanding of the control and dynamics of animal movement derives from controlled laboratory experiments. While many aspects of animal movement can be probed only in these settings, a more complete understanding of animal locomotion may be gained by linking experiments on relatively simple motions in the laboratory to studies of more complex behaviours in natural settings. To demonstrate the utility of this approach, we examined the effects of wing damage on dragonfly flight performance in both a laboratory drop-escape response and the more natural context of aerial predation. The laboratory experiment shows that hindwing area loss reduces vertical acceleration and average flight velocity, and the predation experiment demonstrates that this type of wing damage results in a significant decline in capture success. Taken together, these results suggest that wing damage may take a serious toll on wild dragonflies, potentially reducing both reproductive success and survival.

Microbiological quality of chicken wings damaged on the farm or in the processing plant.

Selling of damaged chicken wings (those with bone protrusion) for human consumption is prohibited in the European Union on the grounds of possible risks to human health arising from microbial contamination. Standard food industry tests were used to assess different categories of chicken wings (undamaged, farm damaged and factory damaged; n = 264) for, coliforms, Enterobacteriaceae, total viable counts, Pseudomonas spp., Staphylococcus aureus and Salmonella spp. No significant differences in bacterial numbers existed among wings belonging to the three categories. Only low numbers of bacteria were found throughout, and 97% of all results would pass the standards of a leading UK retailer. These results were strengthened by a longitudinal survey of wing breakage, which showed almost all wing puncturing occurred during the de-feathering process, limiting the likelihood of microbial contamination. Combined, these results indicate there is no increased health risk from consumption of damaged, compared to undamaged, chicken wings. The existing imposed regulations may therefore be an unnecessary burden on the poultry industry.

Bidirectional Regulation of Sleep and Synapse Pruning after Neural Injury.

Following acute neural injury, severed axons undergo programmed Wallerian degeneration over several following days. While sleep has been linked with synaptic reorganization under other conditions, the role of sleep in responses to neural injuries remains poorly understood. To study the relationship between sleep and neural injury responses, we examined Drosophila melanogaster following the removal of antennae or other sensory tissues. Daytime sleep is elevated after antennal or wing injury, but sleep returns to baseline levels within 24 h after injury. Similar increases in sleep are not observed when olfactory receptor neurons are silenced or when other sensory organs are severed, suggesting that increased sleep after injury is not attributed to sensory deprivation, nociception, or generalized inflammatory responses. Neuroprotective disruptions of the E3 ubiquitin ligase highwire and c-Jun N-terminal kinase basket in olfactory receptor neurons weaken the sleep-promoting effects of antennal injury, suggesting that post-injury sleep may be influenced by the clearance of damaged neurons. Finally, we show that pre-synaptic active zones are preferentially removed from severed axons within hours after injury and that depriving recently injured flies of sleep slows the removal of both active zones and damaged axons. These data support a bidirectional interaction between sleep and synapse pruning after antennal injury: locally increasing the need to clear neural debris is associated with increased sleep, which is required for efficient active zone removal after injury.

Fracture status of wild cranes (Grus monacha and G. vipio) found dead or in a weak condition at Izumi Plain in Japan.

The Izumi Plain in Kagoshima Prefecture, Japan, is a major wintering ground for wild cranes. Between October 2009 and March 2016, a total of 204 Hooded Cranes Grus monacha and White-naped Cranes G. vipio were found dead or in a weak condition in the plane. Of these, 56 cranes had bone fractures. The rate of incidence of fracture was considered to be higher in White-naped than in Hooded Cranes. Tibia fractures were the most common. The leg and wing fracture numbers were almost equal. Forty six percent of the fracture cases were believed to be caused by collisions with the power line.

Lovesick: immunological costs of mating to male sagebrush crickets.

A growing body of evidence suggests that resources invested in reproduction often come at the expense of the ability to mount an immune response. During mating, female sagebrush crickets, Cyphoderris strepitans, consume the ends of the male's hind wings and ingest his haemolymph. Previous research has shown that this behaviour impairs the ability of males to secure additional matings. One hypothesis to account for this effect is that wing wounding triggers an energetically costly immune response, such that nonvirgin males are unable to sustain the costly acoustical signalling needed to attract additional females. To test this hypothesis, we injected virgin males with lipopolysaccharides (LPS) to provoke an immune response, and monitored their mating success in the field. LPS-injected virgin males took significantly longer to mate than sham-injected virgin males, and spent significantly less time calling. We also compared virgin, nonvirgin and experimentally wing-wounded virgin males with respect to: (1) their ability to encapsulate a foreign invader via the accumulation of haemocytes and deposition of melanin and (2) baseline levels of phenoloxidase (PO), a key enzyme in the biochemical cascade leading to the production of melanin. Although encapsulation ability did not differ with reproductive experience, virgin males had significantly higher levels of PO than either nonvirgin or experimentally wing-wounded virgin males. These results suggest that wing-wounding alone is sufficient to impair male immunity, and that males trade-off investment in reproduction and immunity.

Localization of 9E3/CEF-4 in avian tissues: expression is absent in Rous sarcoma virus-induced tumors but is stimulated by injury.

The avian gene 9E3/CEF-4, a member of the superfamily of genes that includes KC and gro, is expressed abundantly in exponentially growing cultures of chick embryo fibroblasts (CEFs) and at high levels in CEFs transformed with Rous sarcoma virus (RSV). The product of this gene is a secreted protein that has homologies and structural similarities to inflammatory mediators. The function of 9E3 is obscure and its expression in vivo has not yet been investigated. We studied by in situ hybridization and RNA blots the pattern of 9E3 mRNA distribution in the wings of normal, wounded, and RSV-infected newly hatched chicks. We found that the message for 9E3 is high in specific tissues in normal wings; whereas connective tissue, tendon, and bone express the gene, muscle fibers, endothelium, epidermis, and bone marrow do not. The distribution coincides with that of interstitial collagen. Wounding results in marked elevation of the mRNA within the granulation tissue formed during healing and in adjacent tissues, especially those showing neovascularization. Similar elevation of mRNA occurs immediately adjacent to RSV tumors but, surprisingly, the tumor tissue itself shows no detectable levels of this message. Cells explanted from the tumors and grown in culture also show no expression of 9E3, in marked contrast to the very high level found in similarly cultured RSV-transformed CEFs. These results show that there are intrinsic differences between transformed embryonic cells in tissue culture and RSV target cells in the hatched chick. However, the expression of the gene in the periphery of tumors leaves open the possibility that 9E3 may still be involved in RSV carcinogenesis. The abundant expression of 9E3 in normal tissues indicates that the product of this gene plays a normal physiological role in tissues growing by cell division, perhaps as a growth regulator. The elevated expression of 9E3 in areas of neovascularization, makes it possible that the product of this gene could act as an angiogenic factor. Finally, expression in conjunction with high collagen levels and in wounded tissues may point to a role in wound response and/or repair, possibly via alteration of extracellular matrix.

Wing Abnormality in a Wild-Hatched Whooping Crane (Grus americana) Chick from the Nonmigratory Population in Louisiana, USA.

We describe a wing abnormality in a wild-hatched Whooping Crane (Grus americana) chick from the reintroduced Louisiana, US nonmigratory population. Despite its seemingly compromised flight ability, the chick fledged, reached independence, and lived until 13 mo of age. Necropsy revealed an axial malunion near the left carpus likely resulting from trauma.

Successful rehabilitation of a severely injured peregrine falcon.

An 11-year-old male peregrine falcon (Falco peregrinus), known to have been a successful breeder in the wild with 31 offspring in 9 breeding seasons, was presented for evaluation of wing and leg injuries and for the purpose of rehabilitation. Four 13-day-old young were present in the nest at the time of injury. Aside from superficial trauma to the left leg and wing, a dorso-cranially luxated left coxofemoraljoint and a severely fragmented (7-8 fragments) left ulna were seen radiographically. The coxofemoral luxation was manually reduced and held in position by slinging the left leg, bandaged in flexion, to the body for 14 days. After removal of the sling and leg bandage, the falcon regained full use of the moderately contracted left leg within 2 days. The left wing was immobilized with a figure-of-8 bandage. The ulnar fragments were held in alignment by the intact left radius, which served as an internal biologic splint. To promote rapid healing with reestablishment of full biomechanical strength and normal function, the wing fracture was treated according to the concepts of biological fracture healing without surgical intervention. Complete healing of the ulna was achieved within 25 days. For strengthening of the wing and to assure prey capture capability, the falcon was reconditioned in a large flight chamber under the supervision of a licensed falconer. He was released into his home territory 4 months after his accident and continued his productive life for another 2 breeding seasons, in which 5 additional young were produced.