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European Heart Journal Jan 2022Patients with ischaemic left ventricular dysfunction frequently undergo myocardial viability testing. The historical model presumes that those who have extensive areas...
Patients with ischaemic left ventricular dysfunction frequently undergo myocardial viability testing. The historical model presumes that those who have extensive areas of dysfunctional-yet-viable myocardium derive particular benefit from revascularization, whilst those without extensive viability do not. These suppositions rely on the theory of hibernation and are based on data of low quality: taking a dogmatic approach may therefore lead to patients being refused appropriate, prognostically important treatment. Recent data from a sub-study of the randomized STICH trial challenges these historical concepts, as the volume of viable myocardium failed to predict the effectiveness of coronary artery bypass grafting. Should the Heart Team now abandon viability testing, or are new paradigms needed in the way we interpret viability? This state-of-the-art review critically examines the evidence base for viability testing, focusing in particular on the presumed interactions between viability, functional recovery, revascularization and prognosis which underly the traditional model. We consider whether viability should relate solely to dysfunctional myocardium or be considered more broadly and explore wider uses of viability testingoutside of revascularization decision-making. Finally, we look forward to ongoing and future randomized trials, which will shape evidence-based clinical practice in the future.
Topics: Coronary Artery Bypass; Humans; Myocardial Ischemia; Myocardial Revascularization; Myocardium; Prognosis; Ventricular Dysfunction, Left
PubMed: 34791132
DOI: 10.1093/eurheartj/ehab729 -
Frontiers in Physiology 2023Hibernating mammals have developed many physiological adaptations to accommodate their decreased metabolism, body temperature, heart rate and prolonged immobility... (Review)
Review
Hibernating mammals have developed many physiological adaptations to accommodate their decreased metabolism, body temperature, heart rate and prolonged immobility without suffering organ injury. During hibernation, the animals must suppress blood clotting to survive prolonged periods of immobility and decreased blood flow that could otherwise lead to the formation of potentially lethal clots. Conversely, upon arousal hibernators must be able to quickly restore normal clotting activity to avoid bleeding. Studies in multiple species of hibernating mammals have shown reversible decreases in circulating platelets, cells involved in hemostasis, as well as in protein coagulation factors during torpor. Hibernator platelets themselves also have adaptations that allow them to survive in the cold, while those from non-hibernating mammals undergo lesions during cold exposure that lead to their rapid clearance from circulation when re-transfused. While platelets lack a nucleus with DNA, they contain RNA and other organelles including mitochondria, in which metabolic adaptations may play a role in hibernator's platelet resistance to cold induced lesions. Finally, the breakdown of clots, fibrinolysis, is accelerated during torpor. Collectively, these reversible physiological and metabolic adaptations allow hibernating mammals to survive low blood flow, low body temperature, and immobility without the formation of clots during torpor, yet have normal hemostasis when not hibernating. In this review we summarize blood clotting changes and the underlying mechanisms in multiple species of hibernating mammals. We also discuss possible medical applications to improve cold preservation of platelets and antithrombotic therapy.
PubMed: 37435313
DOI: 10.3389/fphys.2023.1207003 -
Comparative Biochemistry and... Mar 2021For hibernating mammals, the transition from summer active to winter hibernation seasons come with significant remodeling at cellular, organ and whole organism levels.... (Review)
Review
For hibernating mammals, the transition from summer active to winter hibernation seasons come with significant remodeling at cellular, organ and whole organism levels. This review summarizes and synthesizes what is known about hibernation-related remodeling in the gastrointestinal tract of the thirteen-lined ground squirrel, including intestinal and hepatic physiology and the gut microbiota. Hibernation alters intestinal epithelial, immune and cell survival pathways in ways that point to a protective phenotype in the face of prolonged fasting and major fluctuations in nutrient and oxygen delivery during torpor-arousal cycles. The prolonged fasting associated with hibernation alters lipid metabolism and systemic cholesterol dynamics, with both the gut and liver participating in these changes. Fasting also affects the gut microbiota, altering the abundance, composition and diversity of gut microbes and impacting the metabolites they produce in ways that may influence hibernation-related traits in the host. Finally, interventional studies have demonstrated that the hibernation phenotype confers resistance to experimental ischemia-reperfusion injury in both gut and liver, suggesting potential therapeutic roadmaps. We propose that the plasticity inherent to hibernation biology may contribute to this stress tolerance, and in the spirit of August Krogh, makes hibernators particularly valuable for study to identify solutions to certain problems.
Topics: Animals; Cholesterol; Fatty Acids, Nonesterified; Gastrointestinal Microbiome; Gastrointestinal Tract; Hibernation; Lipoproteins; Liver; Sciuridae; Seasons
PubMed: 33348019
DOI: 10.1016/j.cbpa.2020.110875 -
JACC. Clinical Electrophysiology Nov 2021
Topics: Heart Rate; Hibernation; Humans; Sinoatrial Node
PubMed: 34794663
DOI: 10.1016/j.jacep.2021.04.006 -
Ecology and Evolution Jul 2020Hibernation represents an adaptation for coping with unfavorable environmental conditions. For brown bears , hibernation is a critical period as pronounced temporal... (Review)
Review
Hibernation represents an adaptation for coping with unfavorable environmental conditions. For brown bears , hibernation is a critical period as pronounced temporal reductions in several physiological functions occur.Here, we review the three main aspects of brown bear denning: (1) den chronology, (2) den characteristics, and (3) hibernation physiology in order to identify (a) proximate and ultimate factors of hibernation as well as (b) research gaps and conservation priorities.Den chronology, which varies by sex and reproductive status, depends on environmental factors, such as snow, temperature, food availability, and den altitude. Significant variation in hibernation across latitudes occurs for both den entry and exit.The choice of a den and its surroundings may affect individual fitness, for example, loss of offspring and excessive energy consumption. Den selection is the result of broad- and fine-scale habitat selection, mainly linked to den insulation, remoteness, and availability of food in the surroundings of the den location.Hibernation is a metabolic challenge for the brown bears, in which a series of physiological adaptations in tissues and organs enable survival under nutritional deprivation, maintain high levels of lipids, preserve muscle, and bone and prevent cardiovascular pathologies such as atherosclerosis. It is important to understand: (a) proximate and ultimate factors in denning behavior and the difference between actual drivers of hibernation (i.e., factors to which bears directly respond) and their correlates; (b) how changes in climatic factors might affect the ability of bears to face global climate change and the human-mediated changes in food availability; (c) hyperphagia (period in which brown bears accumulate fat reserves), predenning and denning periods, including for those populations in which bears do not hibernate every year; and (d) how to approach the study of bear denning merging insights from different perspectives, that is, physiology, ecology, and behavior.
PubMed: 32724555
DOI: 10.1002/ece3.6372 -
Microorganisms Dec 2021Bacteria convert active 70S ribosomes to inactive 100S ribosomes to survive under various stress conditions. This state, in which the ribosome loses its translational... (Review)
Review
Bacteria convert active 70S ribosomes to inactive 100S ribosomes to survive under various stress conditions. This state, in which the ribosome loses its translational activity, is known as ribosomal hibernation. In gammaproteobacteria such as , ribosome modulation factor and hibernation-promoting factor are involved in forming 100S ribosomes. The expression of ribosome modulation factor is regulated by (p)ppGpp (which is induced by amino acid starvation), cAMP-CRP (which is stimulated by reduced metabolic energy), and transcription factors involved in biofilm formation. This indicates that the formation of 100S ribosomes is an important strategy for bacterial survival under various stress conditions. In recent years, the structures of 100S ribosomes from various bacteria have been reported, enhancing our understanding of the 100S ribosome. Here, we present previous findings on the 100S ribosome and related proteins and describe the stress-response pathways involved in ribosomal hibernation.
PubMed: 35056482
DOI: 10.3390/microorganisms10010033 -
Current Biology : CB Jun 2022Pra et al. provide an overview of ground squirrels and the physiological adaptations these animals have evolved to contend with harsh climates.
Pra et al. provide an overview of ground squirrels and the physiological adaptations these animals have evolved to contend with harsh climates.
Topics: Adaptation, Physiological; Animals; Climate; Hibernation; Sciuridae
PubMed: 35728537
DOI: 10.1016/j.cub.2022.02.015 -
Current Biology : CB Aug 2019Walter Arnold introduces the biology of marmots.
Walter Arnold introduces the biology of marmots.
Topics: Animals; Body Temperature Regulation; Hibernation; Life History Traits; Marmota; Reproduction; Social Behavior
PubMed: 31430469
DOI: 10.1016/j.cub.2019.06.008 -
RSC Advances May 2021In this review article, the recent examples of nanoarchitectonics on living cells are briefly explained. Not limited to conventional polymers, functional polymers,... (Review)
Review
In this review article, the recent examples of nanoarchitectonics on living cells are briefly explained. Not limited to conventional polymers, functional polymers, biomaterials, nanotubes, nanoparticles (conventional and magnetic ones), various inorganic substances, metal-organic frameworks (MOFs), and other advanced materials have been used as components for nanoarchitectonic decorations for living cells. Despite these artificial processes, the cells can remain active or remain in hibernation without being killed. In most cases, basic functions of the cells are preserved and their resistances against external assaults are much enhanced. The possibilities of nanoarchitectonics on living cells would be high, equal to functional modifications with conventional materials. Living cells can be regarded as highly functionalized objects and have indispensable contributions to future materials nanoarchitectonics.
PubMed: 35478610
DOI: 10.1039/d1ra03424c