scholarly journals Advances and challenges in skeletal muscle angiogenesis

2016 ◽  
Vol 310 (3) ◽  
pp. H326-H336 ◽  
Author(s):  
I. Mark Olfert ◽  
Oliver Baum ◽  
Ylva Hellsten ◽  
Stuart Egginton
Keyword(s):  
Skeletal Muscle ◽  
Capillary Density ◽  
Endocrine Function ◽  
Future Research ◽  
Physiological Regulation ◽  
Pathological Angiogenesis ◽  
Organ Systems ◽  
New Findings ◽  
Different Levels

The role of capillaries is to serve as the interface for delivery of oxygen and removal of metabolites to/from tissues. During the past decade there has been a proliferation of studies that have advanced our understanding of angiogenesis, demonstrating that tissue capillary supply is under strict control during health but poorly controlled in disease, resulting in either excessive capillary growth (pathological angiogenesis) or losses in capillarity (rarefaction). Given that skeletal muscle comprises nearly 40% of body mass in humans, skeletal muscle capillary density has a significant impact on metabolism, endocrine function, and locomotion and is tightly regulated at many different levels. Skeletal muscle is also high adaptable and thus one of the few organ systems that can be experimentally manipulated (e.g., by exercise) to study physiological regulation of angiogenesis. This review will focus on the methodological concerns that have arisen in determining skeletal muscle capillarity and highlight the concepts that are reshaping our understanding of the angio-adaptation process. We also summarize selected new findings (physical influences, molecular changes, and ultrastructural rearrangement of capillaries) that identify areas of future research with the greatest potential to expand our understanding of how angiogenesis is normally regulated, and that may also help to better understand conditions of uncontrolled (pathological) angiogenesis.

scholarly journals Shoot–root carbon allocation, sugar signalling and their coupling with nitrogen uptake and assimilation

2016 ◽  
Vol 43 (2) ◽  
pp. 105 ◽  
Author(s):  
Lu Wang ◽  
Yong-Ling Ruan
Keyword(s):  
Growth And Development ◽  
Carbon Allocation ◽  
Dynamic Balance ◽  
Shoot Development ◽  
Long Distance ◽  
Root Carbon ◽  
Organ Systems ◽  
New Findings ◽  
Sugar Signalling

Roots and shoots are distantly located but functionally interdependent. The growth and development of these two organ systems compete for energy and nutrient resource, and yet, they keep a dynamic balance with each other for growth and development. The success of such a relationship depends on efficient root-shoot communication. Aside from the well-known signalling processes mediated by hormones such as auxin and cytokinin, sugars have recently been shown to act as a rapid signal to co-ordinate root and shoot development in response to endogenous and exogenous clues, in parallel to their function as carbon and energy resources for biomass production. New findings from studies on vascular fluids have provided molecular insights into the role of sugars in long-distance communications between shoot and root. In this review, we discussed phloem- and xylem- translocation of sugars and the impacts of sugar allocation and signalling on balancing root–shoot development. Also, we have taken the shoot–root carbon–nitrogen allocation as an example to illustrate the communication between the two organs through multi-layer root–shoot–root signalling circuits, comprising sugar, nitrogen, cytokinin, auxin and vascular small peptide signals.

The Crisis of Social Institutions and Police Homicides: The Adverse Effects of Low Institutional Control

2021 ◽  
pp. 108876792110184
Author(s):  
Kamali’ilani T. E. Wetherell ◽  
Terance D. Miethe
Keyword(s):  
Public Policy ◽  
Adverse Effects ◽  
Census Data ◽  
Social Institutions ◽  
Crime Rates ◽  
Future Research ◽  
Homicide Rates ◽  
Institutional Control ◽  
Different Levels

Using U.S. census data and a multi-source database on officer-involved killings, the current study extends previous research by exploring the influence of measures of weak social control in economic, educational, and familial institutions on state rates of police homicide. States with lower levels of institutional control are found to have higher overall rates of police homicides and police killings involving Black, Hispanic, and White decedents. The significant effects of institutional control on these police homicide rates are generally found to exhibit contextual invariance across different levels of various control variables (e.g., comparisons of states with low or high violent crime rates, low vs high economic inequality, low vs high levels of urbanization). These results and the limitations of this study are discussed in terms of implications for future research and public policy on police homicides and the role of social institutions in minimizing the occurrence of these incidents.

scholarly journals More than just a garbage can: emerging roles of the lysosome as an anabolic organelle in skeletal muscle

2020 ◽  
Vol 319 (3) ◽  
pp. C561-C568
Author(s):  
Sidney Abou Sawan ◽  
Michael Mazzulla ◽  
Daniel R. Moore ◽  
Nathan Hodson
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Intracellular Signaling ◽  
Muscle Protein ◽  
Future Research ◽  
Dietary Amino Acids ◽  
Lysosome Biogenesis ◽  
Transcription Factor Eb ◽  
Mtorc1 Activation

Skeletal muscle is a highly plastic tissue capable of remodeling in response to a range of physiological stimuli, including nutrients and exercise. Historically, the lysosome has been considered an essentially catabolic organelle contributing to autophagy, phagocytosis, and exo-/endocytosis in skeletal muscle. However, recent evidence has emerged of several anabolic roles for the lysosome, including the requirement for autophagy in skeletal muscle mass maintenance, the discovery of the lysosome as an intracellular signaling hub for mechanistic target of rapamycin complex 1 (mTORC1) activation, and the importance of transcription factor EB/lysosomal biogenesis-related signaling in the regulation of mTORC1-mediated protein synthesis. We, therefore, propose that the lysosome is an understudied organelle with the potential to underpin the skeletal muscle adaptive response to anabolic stimuli. Within this review, we describe the molecular regulation of lysosome biogenesis and detail the emerging anabolic roles of the lysosome in skeletal muscle with particular emphasis on how these roles may mediate adaptations to chronic resistance exercise. Furthermore, given the well-established role of amino acids to support muscle protein remodeling, we describe how dietary proteins “labeled” with stable isotopes could provide a complementary research tool to better understand how lysosomal biogenesis, autophagy regulation, and/or mTORC1-lysosomal repositioning can mediate the intracellular usage of dietary amino acids in response to anabolic stimuli. Finally, we provide avenues for future research with the aim of elucidating how the regulation of this important organelle could mediate skeletal muscle anabolism.

Cancer-Induced Fatigue and Skeletal Muscle Wasting: The Role of Exercise

2001 ◽  
Vol 2 (3) ◽  
pp. 186-197 ◽  
Author(s):  
Sadeeka Al-Majid ◽  
Donna O. McCarthy
Keyword(s):  
Skeletal Muscle ◽  
Resistance Exercise ◽  
Muscle Wasting ◽  
Activity Level ◽  
Future Research ◽  
Physiological Mechanisms ◽  
Cancer Related Fatigue ◽  
Skeletal Muscle Wasting ◽  
Clinical Conditions

Fatigue is the most frequently reported symptom by cancer patients. Many of these patients perceive fatigue as the most distressing symptom associated with their illness because it imposes limitations on their physical activity level. Skeletal muscle wasting, which occurs as part of cancer cachexia, is one of the mechanisms that contribute to fatigue. Cancerinduced skeletal muscle wasting may occur despite normal food intake and is not prevented by nutritional supplementation. Evidence suggests that endurance exercise ameliorates cancer-related fatigue. There is no compelling evidence to support that exerciseinduced reduction in fatigue is related to preservation of muscle mass. Resistance exercise attenuates muscle wasting associated with a variety of catabolic conditions. However, its effects on cancer-induced muscle wasting have not been adequately studied. This article describes the physiological mechanisms implicated in the induction of cancer-related muscle wasting, summarizes findings from endurance and resistance exercise studies in relation to fatigue and muscle wasting during cancer and selected clinical conditions, and proposes directions for future research.

Role of Leucine in Protein Metabolism During Exercise and Recovery

2002 ◽  
Vol 27 (6) ◽  
pp. 646-662 ◽  
Author(s):  
Donald K. Layman
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Branched Chain Amino Acids ◽  
New Findings ◽  
Branched Chain

Exercise produces changes in protein and amino acid metabolism. These changes include degradation of the branched-chain amino acids, production of alanine and glutamine, and changes in protein turnover. One of the amino acid most affected by exercise is the branched-chain amino acid leucine. Recently, there has been an increased understanding of the role of leucine in metabolic regulations and remarkable new findings about the role of leucine in intracellular signaling. Leucine appears to exert a synergistic role with insulin as a regulatory factor in the insulin/phosphatidylinositol-3 kinase (PI3-K) signal cascade. Insulin serves to activate the signal pathway, while leucine is essential to enhance or amplify the signal for protein synthesis at the level of peptide initiation. Studies feeding amino acids or leucine soon after exercise suggest that post-exercise consumption of amino acids stimulates recovery of muscle protein synthesis via translation regulations. This review focuses on the unique roles of leucine in amino acid metabolism in skeletal muscle during and after exercise. Key words: branched-chain amino acids, insulin, protein synthesis, skeletal muscle

Expression levels of RyR1 and RyR3 control resting free Ca2+ in skeletal muscle

2005 ◽  
Vol 288 (3) ◽  
pp. C640-C649 ◽  
Author(s):  
Claudio F. Perez ◽  
José R. López ◽  
Paul D. Allen
Keyword(s):  
Skeletal Muscle ◽  
Ryanodine Receptor ◽  
Tibialis Anterior ◽  
Muscle Fibers ◽  
Expression Levels ◽  
Cultured Myotubes ◽  
Increased Sensitivity ◽  
Type 3 ◽  
Different Levels

To better understand the role of the transient expression of ryanodine receptor (RyR) type 3 (RyR3) on Ca2+ homeostasis during the development of skeletal muscle, we have analyzed the effect of expression levels of RyR3 and RyR1 on the overall physiology of cultured myotubes and muscle fibers. Dyspedic myotubes were infected with RyR1 or RyR3 containing virions at 0.2, 0.4, 1.0, and 4.0 moieties of infection (MOI), and analysis of their pattern of expression, caffeine sensitivity, and resting free Ca2+ concentration ([Ca2+]r) was performed. Although increased MOI resulted in increased expression of each receptor isoform, it did not significantly affect the immunopattern of RyRs or the expression levels of calsequestrin, triadin, or FKBP-12. Interestingly, myotubes expressing RyR3 always had significantly higher [Ca2+]r and lower caffeine EC50 than did cells expressing RyR1. Although some of the increased sensitivity of RyR3 to caffeine could be attributed to the higher [Ca2+]r in RyR3-expressing cells, studies of [3H]ryanodine binding demonstrated intrinsic differences in caffeine sensitivity between RyR1 and RyR3. Tibialis anterior (TA) muscle fibers at different stages of postnatal development exhibited a transient increase in [Ca2+]r coordinately with their level of RyR3 expression. Similarly, adult soleus fibers, which also express RyR3, had higher [Ca2+]r than did adult TA fibers, which exclusively express RyR1. These data show that in skeletal muscle, RyR3 increases [Ca2+]r more than RyR1 does at any expression level. These data suggest that the coexpression of RyR1 and RyR3 at different levels may constitute a novel mechanism by which to regulate [Ca2+]r in skeletal muscle.

Collaborative Market Making

2019 ◽  
pp. 287-312
Author(s):  
Pinar Ozcan ◽  
Kerem Gurses
Keyword(s):  
Critical Role ◽  
Future Research ◽  
Extensive Discussion ◽  
New Markets ◽  
Regulatory Uncertainty ◽  
Market Formation ◽  
Potential Impact ◽  
Interfirm Alliances ◽  
Different Levels

Extant work has identified many aspects of market formation including the mechanisms and processes associated with the origins of new markets and the trajectories of market emergence. However, the critical role of interfirm alliances in the formation of new markets still remains unexplored. This chapter brings forward interfirm alliances as a critical tool for firms to fuel the formation of new markets, which are often characterized by high levels of demand, supply, and regulatory uncertainty. To take a systematic look at the role of alliances in market formation, the chapter first describes the different alliance forms under the general categories of dyadic and multipartner alliances. Within these categories, the chapter discusses the potential impact of the respective alliance type on reducing different levels of uncertainty and catalyzing market emergence. It also provides an extensive discussion of the challenges that firms typically face within each type of alliance with regards to market formation. The chapter concludes with directions for future research in exploring alliances as tools for market formation.

Resistance and aerobic training in older men: effects onV˙o 2 peak and the capillary supply to skeletal muscle

1997 ◽  
Vol 82 (4) ◽  
pp. 1305-1310 ◽  
Author(s):  
R. T. Hepple ◽  
S. L. M. Mackinnon ◽  
J. M. Goodman ◽  
S. G. Thomas ◽  
M. J. Plyley
Keyword(s):  
Skeletal Muscle ◽  
Aerobic Training ◽  
Aerobic Power ◽  
Vastus Lateralis ◽  
Older Men ◽  
Capillary Density ◽  
Cycle Ergometer ◽  
Older Population ◽  
Capillary Supply

Hepple, R. T., S. L. M. Mackinnon, J. M. Goodman, S. G. Thomas, and M. J. Plyley. Resistance and aerobic training in older men: effects onV˙o 2 peak and the capillary supply to skeletal muscle. J. Appl. Physiol. 82(4): 1305–1310, 1997.—Both aerobic training (AT) and resistance training (RT) may increase aerobic power (V˙o 2 peak) in the older population; however, the role of changes in the capillary supply in this response has not been evaluated. Twenty healthy men (age 65–74 yr) engaged in either 9 wk of lower body RT followed by 9 wk of AT on a cycle ergometer (RT→AT group) or 18 wk of AT on a cycle ergometer (AT→AT group). RT was performed three times per week and consisted of three sets of four exercises at 6–12 repetitions maximum. AT was performed three times per week for 30 min at 60–70% heart rate reserve.V˙o 2 peak was increased after both RT and AT ( P < 0.05). Biopsies (vastus lateralis) revealed that the number of capillaries per fiber perimeter length was increased after both AT and RT ( P < 0.05), paralleling the changes in V˙o 2 peak, whereas capillary density was increased only after AT ( P < 0.01). These results, and the finding of a significant correlation between the change in capillary supply and V˙o 2 peak( r = 0.52), suggest the possibility that similar mechanisms may be involved in the increase ofV˙o 2 peak after high-intensity RT and AT in the older population.

scholarly journals Pathogenesis of the initial stages of severe COVID-19

2021 ◽  
Vol 12 (2) ◽  
pp. 83-102
Author(s):  
A S. Golota ◽  
Tatyana A. Kamilova ◽  
Olga V. Shneider ◽  
Dmitry A. Vologzhanin ◽  
Sergey G. Sherbak
Keyword(s):  
Reproductive Organs ◽  
Body Fluids ◽  
Effective Strategies ◽  
Organ Systems ◽  
Heart Blood ◽  
Viral Components ◽  
Innate Antiviral Immunity ◽  
Different Levels ◽  
Shed Light

Since SARS-CoV-2 first appeared in humans, the scientific community has tried to gather as much information as possible in order to find effective strategies for the containment and treatment this pandemic coronavirus. We reviewed the current published literature on SARS-CoV-2 with an emphasis on the distribution of SARS-CoV-2 in tissues and body fluids, as well as data on the expression of its input receptors on the cell surface. COVID-19 affects many organ systems in many ways. These varied manifestations are associated with viral tropism and immune responses of the infected person, but the exact mechanisms are not yet fully understood. We emphasize the broad organotropism of SARS-CoV-2, as many studies have identified viral components (RNA, proteins) in many organs, including immune cells, pharynx, trachea, lungs, blood, heart, blood vessels, intestines, brain, kidneys, and male reproductive organs. Viral components are present in various body fluids, such as mucus, saliva, urine, cerebrospinal fluid, semen and breast milk. The main SARS-CoV-2 receptor, ACE2, is expressed at different levels in many tissues throughout the human body, but its expression levels do not always correspond to the detection of SARS-CoV-2, indicating a complex interaction between the virus and humans. We also highlight the role of the renin-angiotensin aldosterone system and its inhibitors in the context of COVID-19. In addition, SARS-CoV-2 has various strategies that are widely used in various tissues to evade innate antiviral immunity. Targeting immune evasion mediators of the virus can block its replication in COVID-19 patients. Together, these data shed light on the current understanding of the pathogenesis of SARS-CoV-2 and lay the groundwork for better diagnosis and treatment of patients with COVID-19.

scholarly journals Advanced Glycation End-Products in Skeletal Muscle Aging

2021 ◽  
Vol 8 (11) ◽  
pp. 168
Author(s):  
Lucas C. Olson ◽  
James T. Redden ◽  
Zvi Schwartz ◽  
David J. Cohen ◽  
Michael J. McClure
Keyword(s):  
Skeletal Muscle ◽  
Advanced Glycation End Products ◽  
Future Research ◽  
Cross Linking ◽  
Advanced Glycation ◽  
Muscle Aging ◽  
Glycation End Products ◽  
End Products ◽  
Skeletal Muscle Aging

Advanced age causes skeletal muscle to undergo deleterious changes including muscle atrophy, fast-to-slow muscle fiber transition, and an increase in collagenous material that culminates in the age-dependent muscle wasting disease known as sarcopenia. Advanced glycation end-products (AGEs) non-enzymatically accumulate on the muscular collagens in old age via the Maillard reaction, potentiating the accumulation of intramuscular collagen and stiffening the microenvironment through collagen cross-linking. This review contextualizes known aspects of skeletal muscle extracellular matrix (ECM) aging, especially the role of collagens and AGE cross-linking, and underpins the motor nerve’s role in this aging process. Specific directions for future research are also discussed, with the understudied role of AGEs in skeletal muscle aging highlighted. Despite more than a half century of research, the role that intramuscular collagen aggregation and cross-linking plays in sarcopenia is well accepted yet not well integrated with current knowledge of AGE’s effects on muscle physiology. Furthermore, the possible impact that motor nerve aging has on intramuscular cross-linking and muscular AGE levels is posited.

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