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Nicholas P Vyleta, Carolina Borges-Merjane, Peter Jonas
Mossy fiber synapses on CA3 pyramidal cells are 'conditional detonators' that reliably discharge postsynaptic targets. The 'conditional' nature implies that burst activity in dentate gyrus granule cells is required for detonation. Whether single unitary excitatory postsynaptic potentials (EPSPs) trigger spikes in CA3 neurons remains unknown. Mossy fiber synapses exhibit both pronounced short-term facilitation and uniquely large post-tetanic potentiation (PTP). We tested whether PTP could convert mossy fiber synapses from subdetonator into detonator mode, using a recently developed method to selectively and noninvasively stimulate individual presynaptic terminals in rat brain slices...
October 25, 2016: ELife
K V Simonyan, V A Chavushyan
BACKGROUND: The hippocampus is a target of ovarian hormones, and is necessary for memory. Ovarian hormone loss is associated with a progressive reduction in synaptic strength and dendritic spine. Teucrium polium has beneficial effects on learning and memory. However, it remains unknown whether Teucrium polium ameliorates hippocampal cells spike activity and morphological impairments induced by estrogen deficiency. METHODS: In the present study, we investigated the effects of hydroponic Teucrium polium on hippocampal neuronal activity and morpho-histochemistry of bilateral ovariectomized (OVX) rats...
October 24, 2016: BMC Complementary and Alternative Medicine
Ellen L Mintz, Juliana A Passipieri, Daniel Y Lovell, George J Christ
Despite the regenerative capacity of skeletal muscle, permanent functional and/or cosmetic deficits (e.g., volumetric muscle loss (VML) resulting from traumatic injury, disease and various congenital, genetic and acquired conditions are quite common. Tissue engineering and regenerative medicine technologies have enormous potential to provide a therapeutic solution. However, utilization of biologically relevant animal models in combination with longitudinal assessments of pertinent functional measures are critical to the development of improved regenerative therapeutics for treatment of VML-like injuries...
October 7, 2016: Journal of Visualized Experiments: JoVE
Jeffrey J Widrick, Matthew Alexander, Benjamin Sanchez, Devin Gibbs, Genri Kawahara, Alan Beggs, Louis Kunkel
Sapje zebrafish lack the protein dystrophin and are the smallest vertebrate model of Duchenne muscular dystrophy (DMD). Their small size makes them ideal for large-scale drug discovery screens. However, the extent that sapje mimic the muscle dysfunction of higher vertebrate models of DMD is unclear. We used an optical birefringence assay to differentiate affected dystrophic sapje larvae from their unaffected siblings and then studied trunk muscle contractility at 4-7 days post fertilization. Preparation cross-sectional area (CSA) was similar for affected and unaffected larvae, yet tetanic forces of affected preparations were only 30-60% of normal...
October 7, 2016: Physiological Genomics
Luca Fusi, Valentina Percario, Elisabetta Brunello, Marco Caremani, Pasquale Bianco, Joseph D Powers, Massimo Reconditi, Vincenzo Lombardi, Gabriella Piazzesi
KEY POINTS: Myosin filament mechanosensing determines the efficiency of the contraction by adapting the number of switched ON motors to the load. Accordingly, the unloaded shortening velocity (V0 ) is already set at the end of the latency relaxation (LR), ∼10 ms after the start of stimulation, when the myosin filament is still in the OFF state. Here the number of actin-attached motors per half-myosin filament (n) during V0 shortening imposed either at the end of LR or at the plateau of the isometric contraction is estimated from the relation between half-sarcomere compliance and force during the force redevelopment after the shortening...
October 20, 2016: Journal of Physiology
Daryl C Yang, Jennifer R Deuis, Daniel Dashevsky, James Dobson, Timothy N W Jackson, Andreas Brust, Bing Xie, Ivan Koludarov, Jordan Debono, Iwan Hendrikx, Wayne C Hodgson, Peter Josh, Amanda Nouwens, Gregory J Baillie, Timothy J C Bruxner, Paul F Alewood, Kelvin Kok Peng Lim, Nathaniel Frank, Irina Vetter, Bryan G Fry
Millions of years of evolution have fine-tuned the ability of venom peptides to rapidly incapacitate both prey and potential predators. Toxicofera reptiles are characterized by serous-secreting mandibular or maxillary glands with heightened levels of protein expression. These glands are the core anatomical components of the toxicoferan venom system, which exists in myriad points along an evolutionary continuum. Neofunctionalisation of toxins is facilitated by positive selection at functional hotspots on the ancestral protein and venom proteins have undergone dynamic diversification in helodermatid and varanid lizards as well as advanced snakes...
October 18, 2016: Toxins
Sayyed Alireza Talaei, Abolfazl Azami, Mahmoud Salami
OBJECTIVES: There are few reports have demonstrated the effect of a change-in-light experience on the structure and function of hippocampus. A change-in-light experience also affects the circadian pattern of melatonin secretion. This study aimed to investigate developmental effect of exogenous melatonin on synaptic plasticity of hippocampus of light deprived rats. MATERIALS AND METHODS: The effects of intracerebroventricular (ICV) injection of 2μg/5μl melatonin was evaluated on the basic and tetanized field excitatory post-synaptic potentials (fEPSPs) recorded in the hippocampal CA3-CA1 pathway of normal light-reared (LR) and dark-reared (DR) rats at 2, 4, and 6 weeks of age...
August 2016: Iranian Journal of Basic Medical Sciences
Daniel P Radin, Sheng Zhong, Richard Purcell, Arnold Lippa
Memory loss observed as a consequence of aging is paralleled by a down-regulation of AMPA-type glutamate receptors (AMPARs) that mediate fast excitatory synaptic transmission. Activation of these receptors enhances long-term potentiation (LTP), a neuronal process demonstrated to be crucial for memory storage and thought to be a cellular substrate of learning and memory. In the present studies, we determined that LTP was reduced in aged rats when compared to young rats and that acute treatment with CX1846, a novel AMPAR positive allosteric modulator, fifteen minutes prior to tetanic stimulation completely reversed the significant deficit in LTP observed in aged rats...
October 6, 2016: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
Bruce A Young, Jessica Dumais, Nicholas John, Brandon Lyons, Andrew Macduff, Matthew Most, Nathan A Reiser, Peter J Reiser
Water monitor lizards (Varanus salvator) swim using sinusoidal oscillations generated at the base of their long (50% of total body length) tail. In an effort to determine which level of the structural/organizational hierarchy of muscle is associated with functional segregation between the muscles of the tail base, an array of muscle features-myosin heavy chain profiles, enzymatic fiber types, twitch and tetanic force production, rates of fatigue, muscle compliance, and electrical activity patterns-were quantitated...
2016: Frontiers in Physiology
Y I Sun, Brian S Ferguson, Mmatthew J Rogatzki, James R McDonald, L Bruce Gladden
PURPOSE: The study aimed to examine the relationship between near-infrared spectroscopy (NIRS) signals and venous hemoglobin oxygen saturation (O2Hb%) and venous oxygen concentration (CvO2). METHODS: Gastrocnemius muscles (GS) in six dogs were surgically isolated and pump perfused. NIRS signals were recorded, and venous blood samples were collected at constant flow rates (control flow, high flow, and low flow) at rest as well as during electrically stimulated tetanic muscle contractions at rates of one contraction per 2 s (1/2 s) and two contractions per 3 s (2/3 s)...
October 2016: Medicine and Science in Sports and Exercise
Jason C Siegler, Kurt Mudie, Paul Marshall
The effect of metabolic alkalosis on fibre-specific maximal force production and rates of force development (RFD) has been previously investigated in animal models, with evidence suggesting an improved capacity to rapidly develop force in fast- compared to slow-twitch muscle. We have attempted to model in vivo the fatigue profile of voluntary and involuntary maximal force and RFD in the triceps' surae and brachii after sodium bicarbonate (NaHCO3 ) ingestion. In a double-blind, 3-way repeated measures design participants (n = 10) ingested either 0...
September 16, 2016: Experimental Physiology
Rositsa Raikova, Piotr Krutki, Jan Celichowski
An unfused tetanus of a motor unit (MU) evoked by a train of pulses at variable interpulse intervals is the sum of non-equal twitch-like responses to these stimuli. A tool for a precise prediction of these successive contractions for MUs of different physiological types with different contractile properties is crucial for modeling the whole muscle behavior during various types of activity. The aim of this paper is to develop such a general mathematical algorithm for the MUs of the medial gastrocnemius muscle of rats...
2016: PloS One
Dean L Mayfield, Bradley S Launikonis, Andrew G Cresswell, Glen A Lichtwark
There are high mechanical demands placed on skeletal muscles in movements requiring rapid acceleration of the body or its limbs. Tendons are responsible for transmitting muscle forces, but, due to their elasticity, can manipulate the mechanics of the internal contractile apparatus. Shortening of the contractile apparatus against the stretch of tendon affects force generation according to known mechanical properties, however, the extent to which differences in tendon compliance alter force development in response to a burst of electrical impulses is unclear...
September 8, 2016: Journal of Experimental Biology
Philippe Magown, Robert M Brownstone, Victor F Rafuse
OBJECTIVE: Nerve injuries resulting in prolonged periods of denervation result in poor recovery of motor function. We have previously shown that embryonic stem cell-derived motoneurons transplanted at the time of transection into a peripheral nerve can functionally reinnervate muscle. For clinical relevance, we now focused on delaying transplantation to assess reinnervation after prolonged denervation. METHODS: Embryonic stem cell-derived motoneurons were transplanted into the distal segments of transected tibial nerves in adult mice after prolonged denervation of 1-8 weeks...
August 2016: Annals of Clinical and Translational Neurology
Phablo Abreu, Carlos H J Pinheiro, Kaio F Vitzel, Diogo A A Vasconcelos, Rosângela P Torres, Marco S Fortes, Gabriel N Marzuca-Nassr, Jorge Mancini-Filho, Sandro M Hirabara, Rui Curi
What is the central question of this study? Oleic and linoleic acids modulate fibroblast proliferation and myogenic differentiation in vitro. However, their in vivo effects on muscle regeneration have not yet been examined. We investigated the effects of either oleic or linoleic acid on a well-established model of muscle regeneration after severe laceration. What is the main finding and its importance? We found that linoleic acid increases fibrous tissue deposition and impairs muscle regeneration and recovery of contractile function, whereas oleic acid has the opposite effects in severely injured gastrocnemius muscle, suggesting that linoleic acid has a harmful effect and oleic acid a potential therapeutic effect on muscle regeneration...
August 31, 2016: Experimental Physiology
Janet D Talbot, John N Barrett, Doris Nonner, Zhongsheng Zhang, Kyle Wicomb, Ellen F Barrett
In mutant superoxide dismutase 1 (SOD1) mouse models of familial amyotrophic lateral sclerosis (fALS) some of the earliest signs of morphological and functional damage occur in the motor nerve terminals that innervate fast limb muscles. This study tested whether localized peripheral application of a protective drug could effectively preserve neuromuscular junctions in late-stage disease. Methylene blue (MB), which has mitochondria-protective properties, was infused via an osmotic pump into the anterior muscle compartment of one hind limb of late pre- symptomatic SOD1-G93A mice for ≥3weeks...
November 2016: Experimental Neurology
Giorgos K Sakellariou, Timothy Pearson, Adam P Lightfoot, Gareth A Nye, Nicola Wells, Ifigeneia I Giakoumaki, Richard D Griffiths, Anne McArdle, Malcolm J Jackson
Age-related skeletal muscle dysfunction is the underlying cause of morbidity that affects up to half the population aged 80 and over. Considerable evidence indicates that oxidative damage and mitochondrial dysfunction contribute to the sarcopenic phenotype that occurs with aging. To examine this, we administered the mitochondria-targeted antioxidant mitoquinone mesylate [[10-(4,5-dimethoxy-2-methyl-3,6-dioxo-1,4-cyclohexadien-1-yl)decyl] triphenylphosphonium; 100 μM] to wild-type C57BL/6 mice for 15 wk (from 24-28 mo of age) and investigated the effects on age-related loss of muscle mass and function, changes in redox homeostasis, and mitochondrial organelle integrity and function...
August 22, 2016: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
Hiroyuki Hashimoto, Tetsuro Tamaki, Maki Hirata, Yoshiyasu Uchiyama, Masato Sato, Joji Mochida
Background. Significant and/or complete rupture in the musculotendinous junction (MTJ) is a challenging lesion to treat because of the lack of reliable suture methods. Skeletal muscle-derived multipotent stem cell (Sk-MSC) sheet-pellets, which are able to reconstitute peripheral nerve and muscular/vascular tissues with robust connective tissue networks, have been applied as a "bio-bond". Methods. Sk-MSC sheet-pellets, derived from GFP transgenic-mice after 7 days of expansion culture, were detached with EDTA to maintain cell-cell connections...
2016: PeerJ
Costas Papatheodoropoulos, Stylianos Kouvaros
The ability of the ventral hippocampus (VH) for long-lasting long-term potentiation (LTP) and the mechanisms underlying its lower ability for short-lasting LTP compared with the dorsal hippocampus (DH) are unknown. Using recordings of field excitatory postsynaptic potentials (EPSPs) from the CA1 field of adult rat hippocampal slices, we found that 200-Hz stimulation induced nondecremental LTP that was maintained for at least 7 h and was greater in the DH than in the VH. The interaction of NMDA receptors with L-type voltage-dependent calcium channels appeared to be more effective in the DH than in the VH...
September 2016: Learning & Memory
Christiane G Stäuble, Marc Helming, J A Jeevendra Martyn, Manfred Blobner, Heidrun Fink
OBJECTIVES: Recovery from ICU-acquired muscle weakness extends beyond hospital stay. We hypothesized that immobilization, more than inflammation, plays a prominent role in the delayed recovery from critical illness. DESIGN: Prospective, randomized, controlled, experimental study. SETTING: Animal laboratory, university hospital. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: Animals were divided to have one hind limb immobilized (n = 129) or sham-immobilized (n = 129) on day -12...
November 2016: Critical Care Medicine
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