The Torpid State:Recent Advances in Metabolic Adaptations and Protective Mechanisms(dagger)

Torpor and hibernation are powerful strategies enabling animals to survive periods of low resource availability. The state of torpor results from an active and drastic reduction of an individual's metabolic rate (MR) associated with a relatively pronounced decrease in body temperature. To date, several forms of torpor have been described in all three mammalian subclasses, i.e., monotremes, marsupials, and placentals, as well as in a few avian orders. This review highlights some of the characteristics, from the whole organism down to cellular and molecular aspects, associated with the torpor phenotype. The first part of this review focuses on the specific metabolic adaptations of torpor, as it is used by many species from temperate zones. This notably includes the endocrine changes involved in fat- and food-storing hibernating species, explaining biomedical implications of MR depression. We further compare adaptive mechanisms occurring in opportunistic vs. seasonal heterotherms, such as tropical and sub-tropical species. Such comparisons bring new insights into the metabolic origins of hibernation among tropical species, including resistance mechanisms to oxidative stress. The second section of this review emphasizes the mechanisms enabling heterotherms to protect their key organs against potential threats, such as reactive oxygen species, associated with the torpid state. We notably address the mechanisms of cellular rehabilitation and protection during torpor and hibernation, with an emphasis on the brain, a central organ requiring protection during torpor and recovery. Also, a special focus is given to the role of an ubiquitous and readily-diffusing molecule, hydrogen sulfide (H2S), in protecting against ischemia-reperfusion damage in various organs over the torpor-arousal cycle and during the torpid state. We conclude that (i) the flexibility of torpor use as an adaptive strategy enables different heterothermic species to substantially suppress their energy needs during periods of severely reduced food availability, (ii) the torpor phenotype implies marked metabolic adaptations from the whole organism down to cellular and molecular levels, and (iii) the torpid state is associated with highly efficient rehabilitation and protective mechanisms ensuring the continuity of proper bodily functions. Comparison of mechanisms in monotremes and marsupials is warranted for understanding the origin and evolution of mammalian torpor

Impact d’une restriction calorique modérée ou d’un mimétique potentiel, le resvératrol, sur les marqueurs du vieillissement et sur la longévité chez un primate non-humain

Nowadays moderate and chronic calorie restriction (CR); is the only non-genetic intervention known to slow the onset of age-related diseases and to increase longevity in several animal species. Resveratrol (RSV), a natural compound belonging to the polyphenols group, has therapeutic properties and is a promising candidate as CR effects mimetic. To assess the impact of such long-term nutritional protocols, a longitudinal study was conducted on a cohort of 53 males grey mouse lemurs (Microcebus murinus), a relevant primate model for normal and pathological aging research as regards to its high longevity in captivity, up to 12 years. Since the integration of the animals in the study (3 years old) to the current status of the project (8 years of age), physiological and behavioral parameters were assessed regularly in the cohort divided into three groups: a group submitting to a -30% CR and a group supplemented with RSV (200 mg.kg-1.day-1), compared to a control group (CTL). With age, disturbances appeared in CTL mouse lemurs: decreased insulin sensitivity, accumulation of cellular damage, motor and cognitive decline associated with particular type of memory and a decline of certain predictive biomarkers of aging in this species. CR has improved insulin sensitivity and limited the accumulation of markers of oxidative stress, it has not resulted in improved cognitive abilities but in a decreased anxiety, improved motor performances and an increased spontaneous locomotor activity. CR also induced an adaptive metabolic response with body weight loss without lowering energy expenditure, lower hormone levels of IGF-1 and testosterone, supporting a probable trade-off between reproduction and survival. RSV mimicked some of the beneficial effects demonstrated in CR. However, it has improved the spatial memory task, which was not observed in restricted animals. RSV also showed opposite effects to those of CR, as maintained body weight and hormone levels compared to CTL, an increase in energy expenditure and in testosterone levels during the long day’s season. Finally, the current survival data are promising; less than 50% of the CTL animals survived, while more than 50% of CR and RSV animals are still alive, with in addition a mean age at death about 1 year higher compared with CTL animals. Despite heterogeneous, but yet beneficial effects, CR and RSV were able to slow the appearance of some intrinsic age-related declines and to improve the lemurs’ survival, supporting the hypothesis that these effects may be mediated by different mechanisms achieving the same positive outcomes including enhanced life expectancy. These evidences are a real tool for the future understanding of the mechanisms underlying the aging process but also of cellular regulatory pathways that are involved in long term CR and RSV treatment in a primateAujourd’hui la restriction calorique modérée et chronique (RC) est la seule intervention non génétique capable de ralentir l’apparition de pathologies liées à l’âge et d’accroître la longévité chez plusieurs espèces animales. Le resvératrol (RSV), un composé appartenant au groupe des polyphénols, présente des propriétés thérapeutiques intéressantes et constitue un candidat prometteur comme mimétique des effets d’une RC. Afin d’évaluer l’impact de tels protocoles nutritionnels à long terme, une étude longitudinale a été menée sur une cohorte de 53 mâles microcèbes (Microcebus murinus), modèle primate pertinent pour les recherches sur le vieillissement normal ou pathologique au vue de sa longévité maximale de 12 ans en captivité. Depuis l’intégration des animaux dans l’étude (3 ans d’âge) à l’avancement actuel du projet (8 ans d’âge), des paramètres physiologiques et comportementaux ont été évalués régulièrement au sein de la cohorte, partagée en trois groupes: un groupe soumis à une RC (-30%) et un groupe supplémenté en RSV (200 mg.kg-1.jour-1), comparés à un groupe contrôle (CTL). Avec l’âge, chez les microcèbes CTL, des perturbations sont apparues : diminution de la sensibilité à l’insuline, accumulation de dommages cellulaires, déclin moteur et cognitif (mémoire spatiale de reférence) et déclin de certains marqueurs prédictifs du vieillissement chez cette espèce. La RC a permis une amélioration de la sensibilité à l’insuline et a limité l’accumulation de certains marqueurs du stress oxydant, elle n’a pas entraîné d’amélioration des capacités cognitives, mais a diminué l’anxiété, amélioré les performances motrices et augmenté l’activité locomotrice spontanée. La RC a aussi induit une réponse adaptative métabolique avec une perte de masse corporelle sans réduire les dépenses énergétiques, un abaissement des taux hormonaux d’IGF-1 et de la testostérone suggérant un compromis entre reproduction et survie. Le RSV a mimé une partie des effets bénéfiques démontrés sous RC. Cependant il a permis une amélioration de la mémoire spatiale de travail, absente chez les animaux restreints. Le RSV a également montré des effets opposés à ceux de la RC comme un maintien de la masse corporelle et des taux d’hormones par rapport aux CTL, une augmentation des dépenses énergétiques et des niveaux de testostérone pendant la période de jours longs. Finalement les données de survie actuelles sont prometteuses ; moins de 50% de l’effectif de départ des animaux CTL a survécu, alors que plus de 50% des animaux RC et RSV sont encore vivants, présentant de surcroît un âge moyen à la mort plus élevé d’environ 1 an par rapport aux CTL. Malgré des effets hétérogènes et pourtant bénéfiques, la RC et le RSV sont capables de ralentir l’apparition de certains déclins intrinsèques au vieillissement et d’améliorer la survie des microcèbes, soutenant l’hypothèse selon laquelle ces effets pourraient être induits par des mécanismes différents mais permettant d’atteindre les mêmes issues favorables notamment au niveau de l’espérance de vie. Ces résultats constituent un véritable outil pour la compréhension future des mécanismes sous-jacents au processus du vieillissement mais aussi des voies de régulation cellulaires mises en jeu par la RC et le RSV à moyen et long terme chez un primat

The role of MEF2 transcription factors in dehydration and anoxia survival in Rana sylvatica skeletal muscle

The wood frog (Rana sylvatica) can endure freezing of up to 65% of total body water during winter. When frozen, wood frogs enter a dormant state characterized by a cessation of vital functions (i.e., no heartbeat, blood circulation, breathing, brain activity, or movement). Wood frogs utilize various behavioural and biochemical adaptations to survive extreme freezing and component anoxia and dehydration stresses, including a global suppression of metabolic functions and gene expression. The stress-responsive myocyte enhancer factor-2 (MEF2) transcription factor family regulates the selective expression of genes involved in glucose transport, protein quality control, and phosphagen homeostasis. This study examined the role of MEF2A and MEF2C proteins as well as select downstream targets (glucose transporter-4, calreticulin, and muscle and brain creatine kinase isozymes) in 40% dehydration and 24 h anoxia exposure at the transcriptional, translational, and post-translational levels using qRT-PCR, immunoblotting, and subcellular localization. Mef2a/c transcript levels remained const

Thermoregulatory capacity of arboreal small mammals in the tropics : insights from the past and implications for the future.

Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.Species are expected to respond to global warming through range shifts that are either poleward or towards higher altitude such that they track the movement of their current thermal niches. This generalized view is fundamentally flawed because it marginalizes the role of key biological aspects in shaping ecosystems. For example, it disregards any potential influence that phenotypic flexibility may convey, the influence of habitat heterogeneity and the availability of microclimates as thermal refugia, differences between species dispersal ability, the importance of species interactions, and the influence of phenological mismatches. Given the limitations associated with the view that species will deal with global warming by continually migrating, as well as the rapid rate of warming, there is an urgent need to improve the understanding of how species potentially may respond. Thus, it is crucial that mechanistic approaches are adopted to generate a holistic perspective of the factors that govern species distributions and use this information to forecast responses to global warming. Physiological studies are vital because knowing the physiological tolerances of a species provides insight into their fundamental niche, and also provides a means of identifying species that face higher risks of experiencing more immediate effects due to global warming. Autecological knowledge would also serve to refine the species fundamental niche to more closely resemble their realized niche. In this regard, this thesis identifies arboreal mammals in the tropics as being vulnerable to hyperthermia due to global warming. The basis of this claim is related to the exposed lifestyle of many arboreal species, the biphasic effect of temperature on biological processes and the hypothesis that natural selection would have favoured the optimisation of bodily functions at or close to the species-specific body temperatures (Tb). Initially, there is a positive relationship between biological process and temperature as the rate of processes increase with temperature, up to a maximum point. Thereafter, hyperthermia ensues as further increases in temperature results in a rapid decline in the rate of said processes. Thus, it is plausible to expect that species with lower Tb risk deleterious effects at lower absolute Tbs relative to their higher Tb counterparts. Therefore, it is concerning that many small, tropical endotherms have low and thermolabile Tbs that, because of the small temperature differential between themselves and the ambient (Ta), compromises their capacity to passively off-load excess stored body heat. In addition, the high humidity of tropical environments would theoretically reduce their capacity to retard heat storage by off-loading body heat via evaporation. This reduced capacity to dissipate excess stored body heat, in combination with the exposed life-style of an arboreal species, suggests that small, tropical arboreal mammals are vulnerable to hyperthermia should even minor increases in Ta occur. The aim of this thesis was to assess the vulnerability of tropical, arboreal small mammals to hyperthermia due to global warming. This was achieved by determining and integrating the physiological susceptibility for heat stress in two species and relate that to the microclimate experienced within their habitats. Given the growing argument that adaptive heterothermy - the capacity for species to facultatively down-regulate metabolism and enter torpor or hibernation - may be employed at high Ta to cope better with hyperthermia, this thesis in addition investigated whether heterotherms use torpor at high Ta and identified the putative benefits of hyperthermic torpor. Furthermore, by considering the phylogenetic placement of the study species, this thesis also sought to provide insights into the evolution of endothermy in placental mammals. Flow-through respirometry was used to measure resting metabolic rate (RMR) and evaporative water loss (EWL) at a range of Ta in a heterothermic bat, the lesser dog-faced fruit bat (Cynopterus brachyotis), and a suspected heterothermic primate, the western tarsier (Cephalopachus bancanus). The animals were injected with temperature-sensitive passive integrated transponder tags to obtain concurrent Tb readings during respirometry measurements in freshly-caught individuals. In addition, Tb was measured in free-ranging tarsiers using custom designed temperature data-loggers. The Ta at capture sites were measured using commercially available data-loggers. The laboratory data show that, whereas tarsiers endeavoured to remain normothermic, lesser dog-faced fruit bats readily entered torpor at low temperatures. The free-ranging Tb data support the assertion that tarsiers may be incapable of adaptive heterothermy. The onset of heat storage in tarsiers occurred at approximately 30°C, once the thermal gradient (ΔT = Tb-Ta) approached 4°C, whereas the onset of heat storage in lesser dog-faced fruit bats occurred at approximately 31°C, which was only when ΔT approached 1°C. Given that both species have low normothermic resting Tbs (tarsiers: Tb ≈ 34.5°C; lesser dog-faced fruit bats: Tb ≈ 32.5°C), they seem physiologically susceptible to heat stress at moderately low Ta. Notably, though, lesser dog-faced fruit bats appeared to thermoconform at Ta above their thermoneutral zone suggesting that they may have entered torpor. Torpor seems to have allowed them to reduce heat storage. Field data suggest that lesser dog-faced fruit bats may have the option to exploit cool microclimates at their capture sites, but the data at the capture site of tarsiers suggest that they may not. However, even though the population of tarsiers studied may not have access to cool microclimates, the same may not be true for other populations of tarsiers. Thus, the empirical results support the argument that tropical, arboreal small mammals are physiologically susceptible to heat stress due to global warming, but they also suggest that thermal refugia are an important consideration as they may allow species to escape the predicted future high Ta and its related deleterious effects. This thesis also presents a meta-analysis on the thermoregulatory pattern of bats in general. The aim of this meta-analysis was to determine whether corroborating physiological support for the use of torpor at high Ta exists. A comprehensive literature search was conducted based on the availability of concurrent measures of Tb and RMR; a new dataset of thermoregulatory variables was generated for 29 species of bats (18 heterothermic spp. and 11 homeothermic spp.). The dataset was standardized, and phylogenetic relatedness was considered before any comparative analyses were performed. The results show that heterothermic bats maintain lower Tbs than homeothermic bats, yet they have similar upper limits of thermoneutrality (Tuc). In contrast to expectations, heterothermic bats had a lower rate of evaporative water loss at similar Ta, especially at Tuc. Crucially, in the case of heterothermic bats, Tuc exceeds Tb. The only manner in which heterothermic bats could achieve this, would be through a reduction in metabolic rate with the onset of heat storage at high Tas. Moreover, heterothermic species thermoconform even at comparatively moderate Ta, which presumably also minimizes heat storage and lowers evaporative water loss. Thus, these results support the hypothesis of torpor use at high Ta and suggest that heterotherms, in particular small, tropical, arboreal heterotherms, could benefit from a reduction in water use associated with evaporative cooling and tolerate higher Ta. Overall, the results presented in this thesis illustrate that even though small mammal species living in tropical regions may be physiologically susceptible to heat stress due to global warming, they could minimize their risk of lethal hyperthermia through behavioural mechanisms such as exploiting cooler microclimates; provided that suitable habitats are available. In addition, adaptive heterothermy may convey a physiological advantage that allows heterotherms to better cope with heat. As such, heterotherms may be resilient to the negative effects associated with global warming because they are able to employ torpor to conserve energy during periods of low resource availability, as well as to minimize heat storage and endure moderate hyperthermia to conserve water to use at more extreme Tas. Given the phylogenetic placement of tarsiers at the base of the Haplorrhini clade (Anthropoidea and Tarsiidae), the current lack of evidence for adaptive heterothermy in tarsiers, in combination with the lack of evidence in anthropoids, suggest that adaptive heterothermy in haplorrhine primates may have been lost at the Strepsirrhini-Haplorrhini split. The implication of the aforementioned idea is that many primates may not have the benefits associated with adaptive heterothermy to improve their future survivability as global warming continues. By adopting a mechanistic approach, this thesis highlighted the potential for species to respond to global warming using behavioural and physiological mechanisms that could allow them to persist in their current habitats until the end of the century at least. However, to improve the likelihood of arboreal tropical small mammals to persist in their current habitats for the foreseeable future, especially those mammals that are strictly homeothermic, conservation efforts must prioritise the preservation of areas that could serve as thermal refugia

DAF-16/FOXO and PQM-1/GATA factors up-regulate ferritin to promote cold survival upon ETS-4/SPDEF depletion

Animal hibernation is one of great examples of physiological plasticity where by animals enter a hypometabolic state for extended periods of time (Storey and Storey, 2004). This state allows prolonged exposure to cold temperatures without tissue damage. In humans, clinically induced hypothermia has shown protective effects in brain and heart, prolonging damage free survival with low oxygen supply and allowing longer operative time for these patients (Palmers et al., 2015). Although used in the clinic, how hypothermia provides protection in humans is not clear. Here we use Ceanorhabditis elegans as a genetically tractable model to study cold adaptation. Insulin signaling inhibition and FOXO activation in cold provides protection in both hibernating animals as well as in C. elegans (Savory et al., 2011; Wu and Storey, 2014). We know from previous studies that a conserved ribonuclease REGE-1 is essential for cold survival because it inhibits a transcription factor ETS-4 by degrading mRNA (Habacher et al., 2016). Upon ETS-4 depletion animals subjected to cold adaptation will survive cold temperature longer, by upregulating both DAF-16/FOXO and PQM-1/GATA factors, both known for their role in lifespan extension (Tepper et al., 2013). We show that these two transcription factors converge together to upregulate FTN-1, which sequesters iron from the cell. Iron has a profound role in the cell, besides being a co-factor of many enzymes and essential redox buffer in mitochondria, it is known that it can induce damage by generating reactive oxygen species in the cell (Joppe et al., 2019). In hibernating animals, the oxidative stress response plays a crucial role in preservation of animal tissues and is needed to ensure survival (Yin et al., 2016). Therefore, understanding iron metabolism and its underlying molecular regulation contributes to our understanding of cold adaptation. We also used C. elegans to uncouple cold adaptation from fat content. This indicates that there are multiple pathways involved in cold adaptation that function independent of body fat

Life in the Cold

Preface; First and Corresponding Author Contact Information; An Evolutionary Framework for Studies of Hibernation and Short-term Torpor -- Gordon C. Grigg; Was Adaptive Hypothermia a Prerequisite for the Colonization of Madagascar By Mammals? -- Barry G. Lovegrove; No Evidence for Torpor in a Small African Mainland Primate: The Lesser Bushbaby, Galago moholi -- Nomakwezi Mzilikazi, Barry G. Lovegrove, and Judith C. Masters; The Origin of Mammalian Heterothermy: A Case for Perpetual Youth? -- Michael B. Harris, Link E. Olson, and William K. Milsom; Passive Rewarming from Torpor in Mammals and Birds: Energetic, Ecological and Evolutionary Implications -- Fritz Geiser, Rebecca L. Drury, Gerhard Kortner, Christopher Turbill, Chris R. Pavey, and R. Mark Brigham; Solar Radiation and the Energetic Cost of Rewarming from Torpor -- Andrew M. McKechnie and Blair O. Wolf; The Role of α-Linolenic Acid (18:3) in Mammalian Torpor -- Craig L. Frank, Wendy R. Hood, and Mary C. Donnelly; Heat Transfer in Humans: Lessons from Large Hibernators -- Dennis Grahn and H. Craig Heller; Factors Influencing the Timing of Dormancy in the Pocket Mouse,Perognathus longimembris -- Alan R. French; The Energetic State-dependency of Autumn Immergence in Eastern Chipmunks -- Murray M. Humphries and Brandon Rodgers; Seasonal Timing of Reproduction and Hibernation in the Edible Dormouse (Glis glis) -- Claudia Bieber and Thomas Ruf; Reproduction and Hibernation in Females: A Comparison of Two Sympatric Ground-Dwelling Rodents -- Eva Millesi, Ilse E. Hoffmann, Anna Aschauer, and Claudia Franceschini; How the Photoperiod Times the Annual Reproductive and Hibernation Cycles -- P. Pevet, M. Saboureau, and P. Klosen; Behaviour, Body Temperature, and Hibernation in Tasmanian Echidnas (Tachyglossus aculeatus) -- Stewart Nicol, Christina Vedel-Smith, and Niels A. Andersen; Metabolic Diversity in Yellow-Bellied Marmots -- Kenneth B. Armitage; Metabolic Rate Reduction During Hibernation and Daily Torpor -- Fritz Geiser; How to Enter Torpor: Thermodynamic and Physiological Mechanisms of Metabolic Depression -- Gerhard Heldmaier and Ralf Elvert; Slow Loss of Protein Integrity During Torpor: A Cause for Arousal? -- Sandra L. Martin, Timothy Dahl, and L. Elaine Epperson; A Technique for Modelling Thermoregulatory Energy Expenditure in Free-ranging Endotherms -- Craig K. R. Willis, Jeffery E. Lane, Eric T. Liknes, David L. Swanson, and R. Mark Brigham; Sex Differences in the Response of Torpor to Exogenous Corticosterone During the Onset of the Migratory Season in Rufous Hummingbirds -- Sara M. Hiebert, John C. Wingfield, Marilyn Ramenofsky, Leah Deni, and Antoinette Grafin zu Elz; The Avian Enigma: “Hibernation” by Common Poorwills (Phalaenoptilus nuttalli) -- Christopher P. Woods and R. Mark Brigham; Shivering Thermogenesis in Birds and Mammals -- Esa Hohtola; The Impact of Social Interactions on Torpor Use in Hummingbirds -- Donald Powers; The Energetics of the Rewarming Phase of Avian Torpor -- Andrew E. McKechnie and Blair O. Wolf; Insect Cold-Hardiness: New Advances Using Gene Screening Technology -- Kenneth B. Storey and David C. McMullen; Advantages and Disadvantages of Freeze-Tolerance and Freeze-Avoidance Overwintering Strategies -- Karl Erick Zachariassen, Sindre Andre Pedersen, and Erlend Kristiansen; Live and Let Diapause: Cell Cycle Regulation During Insect Overwintering -- Savvas c. Pavlides, Kenneth A. Weir, and Steven P. Tammariello; Vertebrate Freeze Tolerance: Role of Freeze-Responsive Gene Expression -- Kenneth B. Storey; Ice, Antifreeze Proteins, and Antifreeze Genes in Polar Fishes -- Arthur L. DeVries; Overwintering in Submerged Turtles -- Donald C. Jackson; Environmental Physiology of Terrestrial Hibernation in Hatchling Turtles -- Patrick J. Baker, Jon P. Costanzo, and Richard E. Lee, Jr.; Overwintering in Tegu Lizards -- Denis V. Andrade, Colin Sanders, William K. Milsom, and Augusto S. Abe; Overwintering in Cold-Submerged Frogs -- Glenn J. Tattersall; Effect of Temperature on Regular and Modified Circannual Rhythms in the European Ground Squirrel Under Free-Running Conditions -- Radoslav K. Andjus, Marina Marjanovic, and Dragoslava Zivadinovic; The Role of the Suprachiasmatic Pacemaker (SCN) in Energy Expenditure During Hibernation of Golden-mantled Ground Squirrels -- Patricia J. DeCoursey; Does Hibernation Violate Biological Laws? -- Andre Malan; The Suprachiasmatic Nucleus Influences Energy Balance of Golden-mantled Ground Squirrels During Hibernation -- Norman E. Ruby; Pesticide Effects on Body Temperature of Torpid/Hibernating Rodents (Peromyscus leucopus and Spermophilus tridecemlineatus) -- Thomas E. Tomasi, Peta Elsken-Lacy, Jean A. Perry, and Kerry Withers; Steroidogenesis and the HPA Axis During Hibernation: Differential Expression of the StAR Protein -- Matthew T. Andrews, Meaghan M. Tredrea, and Aubie K. Shaw; A Quest for the Origin of Mammalian Uncoupling Proteins -- Marton Jastroch, Sigrid Stohr, Kerry Withers, and Martine Klingenspor; Brown-Fat-Derived and Thyroid-Hormone Thermogenesis: Mechanisms and Interactions -- Jan Nedergaard, Valeria Golozoubova, and Barbara Cannon; Alterations in Localization of Hippocampal Protein Kinase Cγ (PKCγ), but Not PKCα, -β1, or –β2, in European Ground Squirrels During Hibernation -- Eddy A. Van der Zee, Jens Stieler, Roelof A. Hut, Martin de Wilde, and Arjen M. Strijkstra; The Role of the Medial Septum in the Control of Hibernation -- Irina Yu. Popova and Yurii M. Kokoz; Proteolysis in Hibernators -- Frank can Breukelen; Post-genomic Approaches to the Mechanisms of Cold Response in Fish and Hibernating Small Mammals -- Daryl Williams, L. Elaine Epperson, Andrew R. Cossins, Jane Fraser, Weizhong Li, Sandra Martin, and Andrew Y. Gracey; Use of Suppression Subtractive Hybridization to Elucidate Novel Gene Products Related to Physiological Events in a Hibernator -- Gregory L. Florant, Chris Pittman, and Scott A. Summers; Clinical Applications and Limitations of Hypothermia -- Philip E. bickler; Hibernation in Mammals: A Model for Alzheimer-type Phosphorylation of the Microtubule-associated Protein Tau -- Thomas Arendt, Jens Stieler, Arjen M. Strijkstriam Roelof A. Hut, Eddy A. Van der Zee, max Holzer, and Woldfgang Hartig; Resistance of Livers to Cold Ischemia/Reperfusion Injury During Hibernation: Involvement of Matrix Metalloproteinase and Nitric Oxide Synthase -- Hannah V. Carey, Timothy M. Piazza, Sarah E. Davis, Susanne L. Lindell, Anna Durranis, Kieran Clarke, and James H. Southard; Anti-Proliferative Effects of Plasma from Hibernating Rodents -- Donna G. Sieckmann, Decheng Cai, Howard Jaffe, John Hallenbeck, and Richard M. McCarron; Antifreeze Proteins in Terrestrial Arthropods -- John G. Duman, Valerie A. Bennett, N. Li, L. Wang, L. Huang, T. Sformo, and B.M. Barnes; Cardiac Conduction and Resistance to Ventricular Fibrillation in Siberian Hibernator Ground Squirrel Citellus undulatus -- Vadim V. Fedorov, Rubin R. Aliev, Alexey V. Glukhov, Andrey V. Resnik, Andrey Anufriev, Irina A. Ivanova, Olga V. Nakipova, Stella G. Kolaeva, Leonid V. Rosenshtraukh, and Igor R. Efimov; The Correlation Between Akt Activity and Hibernation -- Decheng Cai, Richard M. McCarron, Donna Sieckmann, and John M. Hallenbeck; Protection from Traumatic Brain Injury During Hibernation -- Kelly L. Drew, Fang Zhou, Xiongwei Zhu, Rudy J. Castellani, and Mark A. Smith; δ-Opioid Agonists Protect the Rat Liver From Cold Storage and Ischemia/Reperfusion Injury -- Thomas L. Husted, Wen-Jian Chang, Alex B. Lentsch, Steven M. Rudich;Animal Adaptability to Oxidative Stress: Gastropod Estivation and Mammalian Hibernation -- Marcelo Hermes-Lima, Gabriella R. Ramos-Vasconcelos, Luciano A. Cardoso, Adrienne l. Orr, Patricia M. Rivera, and Kelly L. Drew

KEÇİLERDE KOKSİDİYOZİS ENFEKSİYONUNDA BAĞIRSAK HÜCRELERİNDE HEAT SHOCK PROTEİN 70’İN ETKİNLİĞİNİN ARAŞTIRILMASI

Bu çalışmada koksidiyozisle enfekte keçilerin bağırsaklarında ısı şoku proteinlerinden Hsp70’in etkinliği araştırıldı. Bu amaçla çeşitli ırk, cinsiyet ve yaşlardan 27 adet keçi kullanıldı. Bu keçilerin 18 tanesi patolojik olarak koksidiyozis tanısı koyulmuş hayvanlar geri kalan 9 keçi ise herhangi bir patolojik bulgu göstermeyen kontrol grubu olarak kullanılan hayvanlardı.Nekropsi sonrası alınanbağırsak örnekleri bilinen yöntemlerle tespit edilditen sonra bu örneklerdenhemotoksilen eozinve immunohistokimyasal boyamalariçin kesitler alındı. Alınan kesitlerin tamamırutin metodlarla boyandı. Histopatolojik bulgular epitel hasarı, hiperplazi, nodüler lezyonlar, çeşitli gelişme dönemlerindeki Eimera etkenleri ve bağırsağın mukozal ve submukozal bölümlerindeki yangısal infiltrasyondu. İmmunohistokimyasal incelemelerde bağırsağın çeşitli bölümlerinde değişen yoğunlukta Hsp70 ekspresyonu görüldü. Hsp70’in hücrelerde koksidiyozis hastalığının meydana getirdiği stresi baskılamak amaçlı eksprese edildiği sonucuna varıldı.KABUL VE ONAY TEŞEKKÜR İÇİNDEKİLER KISALTMALAR DİZİNİ ŞEKİLLER DİZİNİ RESİMLER DİZİNİ TABLOLAR DİZİNİ ÖZET ABSTRAC GİRİŞ GENEL BİLGİLER Koksidiyoz Isı Şoku Proteinleri GEREÇ VE YÖNTEM Kullanılan Bağırsak Örnekleri Histopatolojik İncelemeler İmmunohistokimyasal İncelemeler Bulguların Değerlendirilmesi İstatiksel İncelemeler BULGULAR Klinik Bulgular Makroskobik Bulgular Histopatolojik Bulgular İmmunohistokimyasal Bulgular TARTIŞMA SONUÇ VE ÖNERİLER KAYNAKLAR ÖZGEÇMİ

Daily torpor in laboratory mice: physiological phenotyping and role of orexins.

Spontaneous torpor is a physiological phenomenon used in extreme circumstances to save energy. The physiological mechanisms ruling the torpor bouts are still unknown. Orexins (ORXs) are neuropeptides involved in the control of food behavior, in thermoregulation and sleep-wake cycle regulation this suggests that ORXs could have a role in torpor regulation. The aims of this study were to elucidate: 1) the role of ORXs in the entrance and/or exiting from torpor; 2) the level of glycemia at the onset of torpor differs from both glucose during arousal from torpor and from baseline conditions. In order to evaluate the role of orexins, 8 KO-ORX and 8 WT mice, were implanted with a telemetric blood pressure transducer (Data Sciences International, DSI), two cranial electrodes for the discrimination of the wake-sleep state and a thermistor in the brain cortex. For the study of changes in glycemia related to torpor, 6 WT mice were implanted intraperitoneally with glucose telemeter (DSI). To induce torpor, mice were calorically restricted and exposed to an ambient temperature of 20°C. The lack of ORXs does not cause significative differences in the physiological parameters during the different torpor phases. During deep torpor, in both the experimental groups, electroencephalogram (EEG) trace is similar to that described during active wakefulness while electromyogram (EMG) is almost flat, similarly to NREM sleep. This unusual sleep tracings can be observed when the minimum Tb is recorded. We found a strong positive and linear correlation between circulating glucose and Tb during ad libitum feeding at thermoneutrality. Low blood glucose itself was not predictive of a bout of torpor, the onset of torpor was associated with the combination of low blood glucose and hyperactivity Torpor can be considered a multifactorial and complex mechanism involving both metabolism and central nervous system control

Central and peripheral manipulation of the sympathetic nervous system to study immune, thermoregulatory and sleep-related neural functions

The primary aim of this thesis has been to investigate the effects of central and peripheral Sympathetic Nervous System manipulation on immune responses and on hypothermia and sleep-related brain neural plasticity, through three different sub-projects. The first sub-project investigated the role of the endogenous inflammatory reflex in mice: it is activated in response to immune challenges and its efferent pathway, the splanchnic anti-inflammatory pathway (SAIP), inhibits the inflammatory response to immune challenges. The effects of prior bilateral section of the greater sympathetic splanchnic nerves on cytokine responses to three different systemic immune challenges were investigated: LPS, TLR4 agonist; Poly I:C, TLR3 agonist; and Pam2cys, TLR2 and TLR6 agonist. The results showed that each challenge active the SAIP in mice, resulting in the enhance of systemic levels of the anti-inflammatory cytokines and the inhibition of those of pro-inflammatory cytokines. The second sub-project investigated the effects of synthetic torpor (ST) and of the following recovery period on cortical and hippocampal Tau protein (τp) expression. Animals entering both natural and ST accumulate the hyperphosphorylated τp, resembling a similar pattern observed in tauopathies. However, this accumulation is reverted when animals recover from torpor. In this study, the levels of the τp, its phosphorylation/dephosphorylation processes, and the plasma levels of some hormones and transmitters were determined in rats subjected to and recovering from ST. The results confirmed the reversibility of the τp phosphorylation after the arousal from ST. Moreover, during ST and its recovery, plasma melatonin concentration increased. The third sub-project investigated the role of sleep, through a sleep deprivation protocol, in the levels of the τp and its phosphorylation/dephosphorylation processes, 3 and 6 hours after the exit from ST. The results showed that sleep deprivation did not impair τp dephosphorylation process, but apparently accelerated it through a finely regulated process, without affecting melatonin levels

Induction of Antioxidant and Heat Shock Protein Responses During Torpor in the Gray Mouse Lemur, Microcebus murinus

A natural tolerance of various environmental stresses is typically supported by various cytoprotective mechanisms that protect macromolecules and promote extended viability. Among these are antioxidant defenses that help to limit damage from reactive oxygen species and chaperones that help to minimize protein misfolding or unfolding under stress conditions. To understand the molecular mechanisms that act to protect cells during primate torpor, the present study characterizes antioxidant and heat shock protein (HSP) responses in various organs of control (aroused) and torpid gray mouse lemurs, Microcebus murinus. Protein expression of HSP70 and HSP90α was elevated to 1.26 and 1.49 fold, respectively, in brown adipose tissue during torpor as compared with control animals, whereas HSP60 in liver of torpid animals was 1.15 fold of that in control (P< 0.05). Among antioxidant enzymes, protein levels of thioredoxin 1 were elevated to 2.19 fold in white adipose tissue during torpor, whereas Cu-Zn superoxide dismutase 1 levels rose to 1.1 fold in skeletal muscle (P< 0.05). Additionally, total antioxidant capacity was increased to 1.6 fold in liver during torpor (P< 0.05), while remaining unchanged in the five other tissues. Overall, our data suggest that antioxidant and HSP responses are modified in a tissue-specific manner during daily torpor in gray mouse lemurs. Furthermore, our data also show that cytoprotective strategies employed during primate torpor are distinct from the strategies in rodent hibernation as reported in previous studies