Towards understanding the neural origins of hibernation

2022 ◽  
Vol 225 (1) ◽  
Author(s):  
Madeleine S. Junkins ◽  
Sviatoslav N. Bagriantsev ◽  
Elena O. Gracheva
Keyword(s):  
Nervous System ◽  
Environmental Conditions ◽  
Calcium Imaging ◽  
Essential Role ◽  
Physiological Responses ◽  
Quiescent State ◽  
Physiological Changes ◽  
In Vivo Calcium Imaging

ABSTRACT Hibernators thrive under harsh environmental conditions instead of initiating canonical behavioral and physiological responses to promote survival. Although the physiological changes that occur during hibernation have been comprehensively researched, the role of the nervous system in this process remains relatively underexplored. In this Review, we adopt the perspective that the nervous system plays an active, essential role in facilitating and supporting hibernation. Accumulating evidence strongly suggests that the hypothalamus enters a quiescent state in which powerful drives to thermoregulate, eat and drink are suppressed. Similarly, cardiovascular and pulmonary reflexes originating in the brainstem are altered to permit the profoundly slow heart and breathing rates observed during torpor. The mechanisms underlying these changes to the hypothalamus and brainstem are not currently known, but several neuromodulatory systems have been implicated in the induction and maintenance of hibernation. The intersection of these findings with modern neuroscience approaches, such as optogenetics and in vivo calcium imaging, has opened several exciting avenues for hibernation research.

scholarly journals Hippocampal ghrelin signalling informs the decision to eat

2021 ◽  
Author(s):  
Ryan WS Wee ◽  
Karyna Mishchanchuk ◽  
Rawan AlSubaie ◽  
Andrew F MacAskill
Keyword(s):  
Calcium Imaging ◽  
Feeding Behaviour ◽  
Pyramidal Neurons ◽  
Internal State ◽  
Ventral Hippocampus ◽  
Direct Role ◽  
Induced Changes ◽  
In Vivo Calcium Imaging

Hunger is an internal state that not only invigorates behaviour towards feeding, but also acts as a contextual cue for the higher-order control of anticipatory feeding-related behaviour. The ventral hippocampus is a brain region important in encoding context, but how internal contexts such as hunger are represented in hippocampal circuits is not known. Pyramidal neurons in the ventral hippocampus, and in particular within the ventral CA1/subiculum border (vS) express the receptor for the peripheral hunger hormone ghrelin, and ghrelin is known to cross the blood brain barrier and directly influence hippocampal circuitry. However, what role vS neurons play during feeding related behaviour, and how ghrelin influences this role has not been directly investigated. In this study, we used a combination of whole-cell electrophysiology, optogenetics and molecular knockdown together with in vivo calcium imaging in mice to investigate the role of vS during feeding behaviour across different states of hunger. We found that activity of a unique subpopulation of vS neurons that project to the nucleus accumbens (vS-NAc) were active specifically when animals approached and investigated food, and that that this activity inhibited the transition to begin eating. Increases in peripheral ghrelin reduced vS-NAc activity during this anticipatory phase of feeding behaviour, by increasing the influence of synaptic inhibition. Furthermore, this effect required postsynaptic GHSR1a expression in vS-NAc neurons, suggesting a direct role of ghrelin signalling. Consistent with this role of hippocampal ghrelin signalling, removal of GHSR1a from vS-NAc neurons impaired ghrelin-induced changes in feeding-related behaviour. Together, these experiments define a ghrelin-sensitive hippocampal circuit that informs the decision to eat based on internal state.

Neurofilament phosphorylation

1995 ◽  
Vol 73 (9-10) ◽  
pp. 575-592 ◽  
Author(s):  
Harish C. Pant ◽  
Veeranna
Keyword(s):  
Molecular Weight ◽  
Nervous System ◽  
Nervous Tissue ◽  
Important Determinant ◽  
Neurofilament Proteins ◽  
Neurofilament Phosphorylation ◽  
Axonal Compartment

Neurofilament proteins (NFPs) are highly phosphorylated molecules in the axonal compartment of the adult nervous system. The phosphorylation of NFP is considered an important determinant of filament caliber, plasticity, and stability. This process reflects the function of NFs during the lifetime of a neuron from differentiation in the embryo through long-term activity in the adult until aging and environmental insult leads to pathology and ultimately death. NF function is modulated by phosphorylation–dephosphorylation in each of these diverse neuronal states. In this review, we have summarized some of these properties of NFP in adult nervous tissue, mostly from work in our own laboratory. Identification of sites phosphorylated in vivo in high molecular weight NFP (NF-H) and properties of NF-associated and neural-specific kinases phosphorylating specific sites in NFP are described. A model to explain the role of NF phosphorylation in determining filament caliber, plasticity, and stability is proposed.Key words: neurofilament proteins, phosphorylation, kinases, phosphatases, regulators, inhibitors, multimesic complex, domains.

scholarly journals Essential role of glucose transporter GLUT3 for post-implantation embryonic development

2008 ◽  
Vol 200 (1) ◽  
pp. 23-33 ◽  
Author(s):  
S Schmidt ◽  
A Hommel ◽  
V Gawlik ◽  
R Augustin ◽  
N Junicke ◽  
...  
Keyword(s):  
Essential Role ◽  
Glucose Transporter ◽  
Growth Arrest ◽  
Complete Loss ◽  
Transporter Gene ◽  
Wild Type ◽  
Post Implantation ◽  
Time Point

Deletion of glucose transporter geneSlc2a3(GLUT3) has previously been reported to result in embryonic lethality. Here, we define the exact time point of growth arrest and subsequent death of the embryo.Slc2a3−/−morulae and blastocysts developed normally, implantedin vivo, and formed egg-cylinder-stage embryos that appeared normal until day 6.0. At day 6.5, apoptosis was detected in the ectodermal cells ofSlc2a3−/−embryos resulting in severe disorganization and growth retardation at day 7.5 and complete loss of embryos at day 12.5. GLUT3 was detected in placental cone, in the visceral ectoderm and in the mesoderm of 7.5-day-old wild-type embryos. Our data indicate that GLUT3 is essential for the development of early post-implanted embryos.

Cellular Samurai: katanin and the severing of microtubules

2000 ◽  
Vol 113 (16) ◽  
pp. 2821-2827 ◽  
Author(s):  
L. Quarmby
Keyword(s):  
Epithelial Cells ◽  
Essential Role ◽  
Aaa Atpase ◽  
C Elegans ◽  
Microtubule Severing ◽  
Biochemical Studies ◽  
New Evidence

Recent biochemical studies of the AAA ATPase, katanin, provide a foundation for understanding how microtubules might be severed along their length. These in vitro studies are complemented by a series of recent reports of direct in vivo observation of microtubule breakage, which indicate that the in vitro phenomenon of catalysed microtubule severing is likely to be physiological. There is also new evidence that microtubule severing by katanin is important for the production of non-centrosomal microtubules in cells such as neurons and epithelial cells. Although it has been difficult to establish the role of katanin in mitosis, new genetic evidence indicates that a katanin-like protein, MEI-1, plays an essential role in meiosis in C. elegans. Finally, new proteins involved in the severing of axonemal microtubules have been discovered in the deflagellation system of Chlamydomonas.

scholarly journals Essential Role of Chromatin Assembly Factor-1–mediated Rapid Nucleosome Assembly for DNA Replication and Cell Division in Vertebrate Cells

2007 ◽  
Vol 18 (1) ◽  
pp. 129-141 ◽  
Author(s):  
Yasunari Takami ◽  
Tatsuya Ono ◽  
Tatsuo Fukagawa ◽  
Kei-ichi Shibahara ◽  
Tatsuo Nakayama
Keyword(s):  
Dna Replication ◽  
Essential Role ◽  
Chromatin Assembly ◽  
Nuclear Antigen ◽  
Nucleosome Assembly ◽  
Chromatin Assembly Factor ◽  
Assembly Factor

Chromatin assembly factor-1 (CAF-1), a complex consisting of p150, p60, and p48 subunits, is highly conserved from yeast to humans and facilitates nucleosome assembly of newly replicated DNA in vitro. To investigate roles of CAF-1 in vertebrates, we generated two conditional DT40 mutants, respectively, devoid of CAF-1p150 and p60. Depletion of each of these CAF-1 subunits led to delayed S-phase progression concomitant with slow DNA synthesis, followed by accumulation in late S/G2 phase and aberrant mitosis associated with extra centrosomes, and then the final consequence was cell death. We demonstrated that CAF-1 is necessary for rapid nucleosome formation during DNA replication in vivo as well as in vitro. Loss of CAF-1 was not associated with the apparent induction of phosphorylations of S-checkpoint kinases Chk1 and Chk2. To elucidate the precise role of domain(s) in CAF-1p150, functional dissection analyses including rescue assays were preformed. Results showed that the binding abilities of CAF-1p150 with CAF-1p60 and DNA polymerase sliding clamp proliferating cell nuclear antigen (PCNA) but not with heterochromatin protein HP1-γ are required for cell viability. These observations highlighted the essential role of CAF-1–dependent nucleosome assembly in DNA replication and cell proliferation through its interaction with PCNA.

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