Suspension of Mitotic Activity in Dentate Gyrus of the Hibernating Ground Squirrel

Popov, V.I.; Kraev, Igor; Ignat’ev, D. A.; Stewart, Michael G.

doi:10.1155/2011/867525

Cited by 18 publications

(13 citation statements)

References 33 publications

(41 reference statements)

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“…Moreover, Hypoxia-inducible factor 1-alpha (HIF-1α) increases after rewarming and remains elevated during euthermy (Ma et al, 2005). Marked synaptogenesis and activation of proliferative stress activated signaling pathways following rewarming from hibernation suggest that AGSs may benefit from restorative processes during periods of inter-bout euthermy (Drew et al, 2004;von der Ohe et al, 2006;Weltzin et al, 2006), and like turtles, restorative processes may contribute to tolerance to ischemia and anoxia (Drew et al, 2011;McGee et al, 2008;Popov et al, 2011). Studies designed to tease out the influence of the hibernation state on protection from hypoxia and I/R in isolated brain tissue found that cold tissue temperature alone could account for enhanced protection in the hibernating state.…”

Section: Resistance To Cerebral Ischemia/reperfusion Injury When Euthmentioning

confidence: 99%

No oxygen? No problem! Intrinsic brain tolerance to hypoxia in vertebrates

Larson

Drew

Folkow

et al. 2014

Journal of Experimental Biology

134

102

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Many vertebrates are challenged by either chronic or acute episodes of low oxygen availability in their natural environments. Brain function is especially vulnerable to the effects of hypoxia and can be irreversibly impaired by even brief periods of low oxygen supply. This review describes recent research on physiological mechanisms that have evolved in certain vertebrate species to cope with brain hypoxia. Four model systems are considered: freshwater turtles that can survive for months trapped in frozen-over lakes, arctic ground squirrels that respire at extremely low rates during winter hibernation, seals and whales that undertake breath-hold dives lasting minutes to hours, and naked mole-rats that live in crowded burrows completely underground for their entire lives. These species exhibit remarkable specializations of brain physiology that adapt them for acute or chronic episodes of hypoxia. These specializations may be reactive in nature, involving modifications to the catastrophic sequelae of oxygen deprivation that occur in non-tolerant species, or preparatory in nature, preventing the activation of those sequelae altogether. Better understanding of the mechanisms used by these hypoxiatolerant vertebrates will increase appreciation of how nervous systems are adapted for life in specific ecological niches as well as inform advances in therapy for neurological conditions such as stroke and epilepsy.KEY WORDS: Arctic ground squirrel, Cetacean, Hypoxia, Naked mole-rat, Seal, Turtle IntroductionEnvironmental conditions vary enormously for vertebrates, both with respect to the extreme conditions tolerated by a given species at different times and with respect to average living conditions tolerated by different species. Temperature is perhaps the most obvious example: from the poles to the equator, average ambient temperatures vary widely and have been accompanied by physiological adaptations appropriate to resident species; seasonal variations in temperature and resource variability can induce dramatic changes in physiological and/or behavioral patterns including migration and hibernation. Oxygen levels also vary widely, with animals adapted to sea level, high-altitude, underground and aquatic habitats. Oxygen levels can also change dramatically on a shorter-term basis, as can occur in tidal pools or in breath-hold divers. Approximately 20% of the oxygen consumed by the human body is used by the brain. The greater part of this oxygen is used to produce the ATP required to maintain the membrane potentials necessary for electrical signaling with synaptic and action potentials (Harris et al., 2012). In many vertebrates, including adult humans, interruption of the oxygen supply to the brain for more than a few minutes leads to irreversible neurological damage, including neuronal death. Without oxidative phosphorylation, ATP-dependent neuronal processes including ion transport and neurotransmitter reuptake decline sharply. Without pumping, ion gradients fail and neurons depolarize, releasing excessive levels...

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Section: Resistance To Cerebral Ischemia/reperfusion Injury When Euthmentioning

confidence: 99%

No oxygen? No problem! Intrinsic brain tolerance to hypoxia in vertebrates

Larson

Drew

Folkow

et al. 2014

Journal of Experimental Biology

134

102

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“…We suggested that the high number of dying cells found in the parenchymal regions of hibernating frogs might provide the stimulus for the ventricular zones to proliferate. Instead, Popov et al (2011) demonstrated in the dentate gyrus of the hibernating ground squirrel a decreased mitotic activity, in spite of the presence of a large population of immature cells.…”

Section: Discussionmentioning

confidence: 87%

Changes in the cerebellar cytoarchitecture of hibernating hedgehogErinaceus europaeusL. (Mammalia): an immunocytochemical approach

Roda

Bottone

Insolia

et al. 2017

The European Zoological Journal

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Hibernation is an amazing animal strategy to survive when the environmental temperature is very low and food resources are scarce. Successful hibernation requires a variety of complex biological adaptations, in which the brain plays a central regulatory role. Currently, little information is available regarding the morphology and functional activity of specific neurons within the cerebellar cytoarchitecture of hibernating animals. In the present study, we investigated the immunohistochemical expression of essential proteins in the cerebellum of a mammalian hibernator (i.e. hedgehog Erinaceus europaeus L.), focusing on (i) Purkinje neurons, the sole output cells of the cerebellar cortex; (ii) selected neurotransmitters involved in hibernation processes; (iii) intracellular calcium homeostasis, considering that calcium is also an important regulator of neurotransmission mechanisms; and (iv) cytoskeletal proteins, involved in maintenance of neuronal shape and axon calibre. Specifically, we studied in situ immunocytochemical changes during the torpor state of hibernation (November-March) versus the activity phase (AprilSeptember). We employed different selected markers, i.e. glutamic acid decarboxylase (GAD67) and postsynaptic glutamate ionotropic receptor GluR2-3, different calcium-binding proteins (i.e. calbindin, parvalbumin and calretinin) and cytoskeletal components (i.e. pNF-H and MAP2). In summary, our data in hibernating animals demonstrated: (i) downregulation of GAD67, indicating loss/changes of synaptic contacts on Purkinje somata and dendrites; (ii) GluR2-3 upregulation in Purkinje neurons, with a drastic decrease of calbindin expression; and (iii) decrease of normal mechanisms regulating intracellular calcium homeostasis. We also found a decrease/modification in the distribution of cytoskeletal proteins, particularly evident for pNF-H. Changes in the functional activity of Purkinje cells were accompanied by some morphological dendrite alterations, signs of degeneration in cell somata and flattened basket pinceaux at the Purkinje axon hillock. These findings confirm that hibernation makes heterothermic animals a valuable model to study physiological adaptations to adverse conditions, and also for understanding cellular and molecular mechanisms aimed at preserving mammalian organs from full degeneration and death.

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“…piriform cortex (Barkai and Saar, 2001);and (v) it is the primary pathway by which olfactory information reaches the hippocampus, amygdala, and prefrontal cortex (Shipley et al, 1995). However, this structure has received very little attention in neurobiological studies of aging.…”

Section: Discussionmentioning

confidence: 99%

Section: Resistance To Cerebral Ischemia/reperfusion Injury When Euthmentioning

confidence: 99%

“…(C) Normalized averages of the second response were generated by calculating the response amplitude relative to that of the first response. No differences in paired-pulse response at either LOT or ASSN synapses were detected between age groups.piriform cortex (Barkai and Saar, 2001);and (v) it is the primary pathway by which olfactory information reaches the hippocampus, amygdala, and prefrontal cortex (Shipley et al, 1995). However, this structure has received very little attention in neurobiological studies of aging.…”

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confidence: 99%

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Cellular Basis for Learning Impairment in Fragile X Syndrome

Larson¹

2014

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information , 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE August 2014 REPORT TYPE PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)University of Illinois at Chicago PERFORMING ORGANIZATION REPORT NUMBERChicago, IL 60612-4305 SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) U.S. Army Medical Research and Materiel Command Fort Detrick, Maryland 21702-5012 SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENTApproved for Public Release; Distribution Unlimited SUPPLEMENTARY NOTES ABSTRACTThis research combines behavioral, electrophysiological, and molecular approaches to elucidate the cellular basis for learning impairment in Fragile X Syndrome (FXS), using olfactory learning in Fmr1-KO mice as a model system. We hypothesize that FMRP, the protein missing in FXS, participates in two aspects of circuit function that are critical to learning: synaptic plasticity and the generation and survival of new neurons in the adult brain. Efforts in the second year of support were directed toward establishing a method to specifically upregulate neurogenesis in adult fragile X mice, test fragile X mice for learning deficits in hippocampal-independent tasks, and determine if learning affects NMDA receptor trafficking to synapses. Significant advances have been made in the establishment of behavioral paradigms to test both hippocampal -dependent and -independent forms of olfactory learning. Experimental paradigms have also been refined for the study of neurogenesis in the olfactory bulb, glutamate receptor expression as it relates to olfactory learning in olfactory cortex and hippocampus, and the effects of aging on glutamate receptor expression. These studies are likely to advance our understanding of intellectual disability and autism in addition to the specific condition of fragile X syndrome. This knowledge will be necessary for the development of rational strategies for prevention and treatment of cognitive impairments from a variety of causes. SUBJECT TERMSFragile X Syndrome, synaptic plasticity, long-term potentiation, glutamate receptors, neurogenesis, olfactory learning INTRODUCTIONFragile X syndrome is the most common inherited form of intellect...

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Suspension of Mitotic Activity in Dentate Gyrus of the Hibernating Ground Squirrel

Cited by 18 publications

References 33 publications

No oxygen? No problem! Intrinsic brain tolerance to hypoxia in vertebrates

No oxygen? No problem! Intrinsic brain tolerance to hypoxia in vertebrates

Changes in the cerebellar cytoarchitecture of hibernating hedgehogErinaceus europaeusL. (Mammalia): an immunocytochemical approach

Cellular Basis for Learning Impairment in Fragile X Syndrome

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