Mitochondrial Dynamin-Related Protein 1 (DRP1) translocation in response to cerebral glucose is impaired in a rat model of early alteration in hypothalamic glucose sensing

OBJECTIVE: Hypothalamic glucose sensing (HGS) initiates insulin secretion (IS) via a vagal control, participating in energy homeostasis. This requires mitochondrial reactive oxygen species (mROS) signaling, dependent on mitochondrial fission, as shown by invalidation of the hypothalamic DRP1 protein. Here, our objectives were to determine whether a model with a HGS defect induced by a short, high fat-high sucrose (HFHS) diet in rats affected the fission machinery and mROS signaling within the mediobasal hypothalamus (MBH). METHODS: Rats fed a HFHS diet for 3 weeks were compared with animals fed a normal chow. Both in vitro (calcium imaging) and in vivo (vagal nerve activity recordings) experiments to measure the electrical activity of isolated MBH gluco-sensitive neurons in response to increased glucose level were performed. In parallel, insulin secretion to a direct glucose stimulus in isolated islets vs. insulin secretion resulting from brain glucose stimulation was evaluated. Intra-carotid glucose load-induced hypothalamic DRP1 translocation to mitochondria and mROS (H2O2) production were assessed in both groups. Finally, compound C was intracerebroventricularly injected to block the proposed AMPK-inhibited DRP1 translocation in the MBH to reverse the phenotype of HFHS fed animals. RESULTS: Rats fed a HFHS diet displayed a decreased HGS-induced IS. Responses of MBH neurons to glucose exhibited an alteration of their electrical activity, whereas glucose-induced insulin secretion in isolated islets was not affected. These MBH defects correlated with a decreased ROS signaling and glucose-induced translocation of the fission protein DRP1, as the vagal activity was altered. AMPK-induced inhibition of DRP1 translocation increased in this model, but its reversal through the injection of the compound C, an AMPK inhibitor, failed to restore HGS-induced IS. CONCLUSIONS: A hypothalamic alteration of DRP1-induced fission and mROS signaling in response to glucose was observed in HGS-induced IS of rats exposed to a 3 week HFHS diet. Early hypothalamic modifications of the neuronal activity could participate in a primary defect of the control of IS and ultimately, the development of diabetes.Rôle des connexines astrocytaires dans le mécanisme de détection hypothalamique du glucose : implication sur le contrôle nerveux du métabolisme énergétiqu

Bird pollination in an angraecoid orchid on Reunion Island (Mascarene Archipelago, Indian Ocean).

Although numerous angraecoid orchids in Madagascar display typical sphingophilous syndrome (i.e. white, nectariferous, long-spurred flowers, producing a strong scent at the crepuscule that is attractive to moths), three species of Angraecum in Reunion, belonging to the endemic section Hadrangis, have atypical unscented and short-spurred flowers. The aim of the study was to investigate the implication of plant-pollinator interaction on the evolution of floral morphology of these peculiar island floral forms.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Pollination biology and evolutionary history of angraecoid orchids: from Darwin to the present day

[Extract] Pollination systems provide unique opportunities to establish clear connections between the ecological bases of phenotypic differentiation and the establishment of prezygotic barriers, reproductive isolation, and speciation (e.g. Bradshaw and Schemske 2003, Rundle and Nosil 2005; Rieseberg and Willis 2007; Whittall and Hodges 2007; Hodges and Derieg 2009; Ramírez et al. 2011b). No other plant family shows as wide an assortment of mutualistic interactions with insect pollinators as the Orchidaceae. With the 1862 publication of On the Various Contrivances by which British and Foreign Orchids Are Fertilised by Insects, and on the Good Effects of Intercrossing, Charles Darwin first demonstrated that orchids provide strong evidence for adaptations that promote cross-pollination. It is now acknowledged that within the orchid family, pollinators have probably played a crucial role in the unprecedented diversification of the extant floral forms (e.g. van der Pijl and Dodson 1966; Tremblay 1992; Johnson et al. 2005; Ramírez et al. 2011a,b), resulting in more that 25000 species (Chase et al. 2003; Govaerts et al. 2012)

Orchid-bird interactions: a case study from Angraecum (Vandeae, Angraecinae) and Zosterops (white-eyes, Zosteropidae) on Reunion Island

International audienceAlthough angraecoid orchids are famous for their spectacular flowers, pollinated by hawkmoths in Madagascar, two species of Angraecum endemic to the Mascarenes (sect. Hadrangis ) have atypical unscented and short-spurred flowers that are pollinated by birds. We focused on the pollination and reproductive success of Angraecum bracteosum Balf.f. & S.Moore, a member of sect. Hadrangis . We investigated the breeding system by performing a set of hand-pollination ex- periments and by observing natural pollinators using video-captures. Pollinator efficiency (pollen removal and deposition) and reproductive success (fruit set) were quantified once a week in two natural island populations during three consecutive flowering seasons (2003–2005). The orchid is self-compatible but requires pollinator services to achieve reproduction. The two white-eye song-bird species (Zosteropidae) that occur on Reunion, Zosterops borbonicus Boddaert and Zosterops oliva- Ceus L., were recorded as pollinators. However, while pollination events were rare and occasional following flower visits by Z. borbonicus , foraging of Z. oliveaceus resulted in a high frequency of successful pollinations. White-eyes typically perched on inflorescences, and probed most of the ‘‘fresh-looking’’ flowers for nectar. This study documents a probable case of bird-pollination specialization within Angraecum section Hadrangis , and sheds light on the role played by pollina- tors during the radiation of section Hadrangis in the Mascarene Archipelago

Angraecum alleizettei Schlt., une espèce nouvelle pour l’île de La Réunion

International audienceno abstrac

Auto-pollination in a long-spurred endemic orchid (Jumellea stenophylla) on Reunion Island (Mascarene Archipelago, Indian Ocean)

International audienceSince Darwin, long-spurred angraecoid orchids have been known for their fascinating evolutionary relationship with long-tongued hawkmoths (Sphingidae) on Madagascar. We studied the reproductive biology of the long-spurred endemic Jumellea stenophylla on Reunion. Despite the species exhibits flowers with the typical sphingophilous pollination syndrome (i.e. spur length averaged 137.9 mm, mean nectar volume was 6.1 µl, and nectar concentration was 10.7% sugar in sucrose equivalent), it does not require pollinators to achieve fruits. Compared with other hawkmoth-pollinated orchids, flower longevity was very short, lasting less than 5 days, and the species did not emit the characteristic strong and sweet scent at dusk. Fruit set ranged from 66.7 to 83.9% when pollinators were excluded, and 56–77.5% under natural conditions. Auto-pollination is a consequence of structural modifications. On Reunion, such breeding system is not rare within long-spurred species, and seems linked to the absence of specific pollinator during island colonization, and species establishment

New record of day geckos feeding on orchid nectar in Reunion Island: can lizards pollinate orchid species?

[Extract] Lizard pollination is common among insular floras, often being viewed as an island phenomenon (e.g. Withaker, 1987; Olesen and Valido, 2003; Godinez-Alvarez, 2004). Especially, the genus Phelsuma represents a key taxon in the reproduction of many native plant species (Nyhagen et al., 2001; Hansen, Beer and Muller, 2006; Hansen and Muller 2009; Le Péchon et al., 2013). Day geckos are mainly distributed in the southwestern region of the Indian Ocean (e.g. Austin, Arnold and Jones, 2004). These arboreal lizards are known to include a major component of nectar and pollen in their diet (e.g. Nyhagen et al., 2001; Olesen, Eskildsen and Venkatasamy, 2002; Kaiser 2006; Desoet al., 2008; Olesen et al., 2012; Clémencet et al., 2013; Minaar et al., 2013), and recent studies, conducted on Mauritius' and Reunion's floras (Mascarene Archipelago), have shown that lizard pollination involves a wide range of plant families, including Rousseaceae (Hansen and Müller 2009), Malvaceae (Hansen, Beer and Muller, 2006; Hansen et al., 2007; Le Péchon et al., 2013) and Araliaceae (Nyhagen et al., 2001). In some cases, pollination by Phelsuma species is vital to ensure sexual reproduction of native endangered plants species (Nyhagen et al., 2001; Hansen, Beer and Muller, 2006; Hansen and Müller 2009). To date, only one observation of a Phelsuma visiting orchid flowers has been reported (Micheneau et al., 2010), and beside this "single day gecko visit" in Reunion Island, only one case of lizard feeding on orchid nectar has been reported in Caymans Island (Burton, 2008), but on extra-floral nectaries only without visiting the flowers of Myrmecophila thomsoniana (Rchb. f.) Rolfe. Here we described and discussed the first case of Phelsuma interactions with flowers from the orchid family in Reunion Island, involving the endemic day gecko Phelsuma borbonica Mertens, 1966 visiting flowers of Angraecum cadetii Bosser (endemic to Reunion and Mauritius) and Angraecum bracteosum Balf. & S. Moore (endemic to Reunion)

Sapromyiophily in the native orchid, Bulbophyllum variegatum, on Réunion (Mascarene Archipelago, Indian Ocean)

Orchid species are well known for their highly specialized pollinator interactions. To better understand the reproductive biology of the tropical epiphytic orchid Bulbophyllum variegatum on Réunion, we investigated the floral morphology, breeding system, pollinator diversity, floral scent profile and fruiting success of about 30 individuals in three natural populations during two consecutive flowering seasons. Controlled hand-pollination experiments in two populations showed that the species is self-compatible, but requires pollinator service to achieve reproduction. Videotape pollinator observations were conducted during two flowering seasons for 56 h and revealed that B. variegatum is pollinated by a single species of fly from the Platystomatidae. This fly seems to be attracted by the unpleasant scent produced by the flowers, and does not receive any reward after achieving pollination. In addition, no egg-laying behaviour was observed. Bulbophyllum variegatum thus exhibits a typical sapromyiophilous pollination syndrome which constitutes the first proven case of sapromyiophily within the genus Bulbophyllum on the Mascarene Archipelago. Hand pollinations further showed that fruit set was not significantly higher for flowers that received outcross pollen than for those that were self-crossed (53% and 44% respectively). Fruit sets under natural conditions were significantly different among populations, ranging from 0.5% to 24.3%. This low fruit production is likely due to infrequent pollinator visits, particularly in disturbed forests where the pollinator has never been observed.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Implementation of optimized supportive care and hospital needs along the management of patients with advanced lung cancer

Background: Supportive care in cancer (SCC) have been recommended to be integrated in the management of patients with lung cancer all along the course of the disease. We took advantage of a pilot program of early implementation of optimized SCC, to report the feasibility such program in patients with advanced lung cancer, and correlate patient characteristics and outcomes with the actual use of optimized SCC.Methods: This study is a retrospective analysis of all consecutive patients with lung cancer treated at our center between 2012 and 2016. Optimized SCC included the intervention of a nurse for the home-hospital network coordination, as well as socio-aesthetics, psychomotricity, art-therapy, adapted physical activity, and also establishment of at-home hospitalization.Results: 309 patients were included. Median overall survival was 11.2 months. Unplanned hospitalizations occurred for 276 (89%) patients. The median duration of hospital stay was 19 days. Unplanned hospitalizations more frequently occurred within the first 3 months after the diagnosis of advanced cancer, and in the last 3 months before death. A short - less than 3 months - delay between diagnosis and unplanned hospitalization was associated with poor outcome. 272 (88%) patients received optimized SCC, within a median delay of 8 weeks after diagnosis. Intervention of the nurse for in- and out-patient network coordination was done for 143 (46%) patients, and at-home hospitalization was organized for 78 (25%) patients. The outcome of patients who received optimized SCC was numerically, but not significantly better (median overall survival of 11.8 vs. 6.9 months, p = 0.270).Conclusion: Our study provides landmark data to support an early integration of optimized SCC for patients with advanced lung cancer, that includes multimodal supportive care interventions along the course of the disease. This highlights the role of multidisciplinary teams to optimize the management of patients with advanced lung cancer