White Muscle Fibres Research Articles

Distribution of trace metals in a ling ( Genypterus blacodes) fish fillet

The distribution of trace metals in a ling ( Genypterus blacodes) fish fillet was determined from ICP-MS measurements of digests prepared using nitric acid and hydrogen peroxide, followed by microwave digestion. Most trace elements were inhomogeneously distributed in the muscle tissue of the ling with a non-linear increase in concentration towards the tail end of the fillet. This distribution pattern may be connected to the size variation of the individual muscle cells or the change in the ratio of connective tissue to muscle tissue, suggesting that the observed inhomogeneity of muscle elemental distribution may be inherent to all fish species. The concentration of an element in a sample of fish muscle tissue thus depends on the physical location within the fish from which the sample was dissected. Significant differences in trace element concentrations were also detected between the red and white muscle fibres of ling, as well as between the belly flap and the rest of the musculature.

Sustained performance by red and white muscle fibres from the dogfish Scyliorhinus canicula

The mechanical performance of red and white muscle fibres from dogfish was compared during a long series of contractions with sinusoidal movement or under isometric conditions at 12 degrees C (normal in vivo temperature). Power output was measured during sinusoidal movement at 0.75 Hz and peak-to-peak amplitude about 12% L(0). Tetanus duty cycle was 33% (0.44 s) at phase -8% (first stimulus at 0.107 s before shortening started). Initially, the red fibres produced only about one third as much power as the white fibres, 6.57+/-0.63 W kg(-1) wet mass (mean +/- s.e.m.) and 18.3+/-2.3, respectively. Red fibres were better at sustaining power output; it declined rapidly to about 60% of its initial value and then remained relatively steady for up to 450 cycles of movement. Force during shortening declined, but force during stretch did not increase: force always relaxed to a low value before stretch started. By contrast, net power output by white fibres declined rapidly to zero within about 50 cycles. Two changes contributed: decline in force during shortening and an increase in force during stretch because relaxation became progressively less complete during the series of contractions. In isometric series (0.44 s stimulation every 1.33 s, cycle frequency 0.75 Hz), red and white fibres sustained peak isometric force similarly; in the 50th cycle force was 59+/-3% and 56+/-4% of initial values. The time required for force to relax to 10% of its maximum value decreased during the series for red fibres and increased for white fibres.

Scaling with body mass of mitochondrial respiration from the white muscle of three phylogenetically, morphologically and behaviorally disparate teleost fishes

White muscle (WM) fibers in many fishes often increase in size from <50 μm in juveniles to >250 μm in adults. This leads to increases in intracellular diffusion distances that may impact the scaling with body mass of muscle metabolism. We have previously found similar negative scaling of aerobic capacity (mitochondrial volume density, V(mt)) and the rate of an aerobic process (post-contractile phosphocreatine recovery) in fish WM. In the present study, we examined the scaling with body mass of oxygen consumption rates of isolated mitochondria (VO(2mt)) from WM in three species from different families that vary in morphology and behavior: an active, pelagic species (bluefish, Pomatomus saltatrix), a relatively inactive demersal species (black sea bass, Centropristis striata), and a sedentary, benthic species (southern flounder, Paralichthys lethostigma). In contrast to our prior studies, the measurement of respiration in isolated mitochondria is not influenced by the diffusion of oxygen or metabolites. V(mt) was measured in WM and in high-density isolates used for VO(2mt) measurements. WM V(mt) was significantly higher in the bluefish than in the other two species and VO(2mt) was independent of body mass when expressed per milligram protein or per milliliter mitochondria. The size-independence of VO(2mt) indicates that differences in WM aerobic function result from variation in V(mt) and not to changes in VO(2mt). This is consistent with our prior work that indicated that while diffusion constraints influence mitochondrial distribution, the negative scaling of aerobic processes like post-contractile PCr recovery can largely be attributed to the body size dependence of V(mt).

Skeletal muscle cellularity and expression of myogenic regulatory factors and myosin heavy chains in rainbow trout (Oncorhynchus mykiss): Effects of changes in dietary plant protein sources and amino acid profiles

The nutritional regulation of skeletal muscle growth is very little documented in fish. The aim of the study presented here was to determine how changes in dietary plant protein sources and amino acid profiles affect the muscle growth processes of fish. Juvenile rainbow trout (Oncorhynchys mykiss) were fed two diets containing fish meal and a mixture of plant protein sources either low (control diet) or rich in soybean meal (diet S). Both diets were supplemented with crystalline indispensable amino acids (IAA) to match the rainbow trout muscle IAA profile. Diet S was also supplemented with glutamic acid, an AA present in high quantities in trout muscle. Rainbow trout fed diets C and S were not significantly different in terms of overall somatic growth or daily nitrogen gain, although their parameters of dietary protein utilisation differed. Distribution of skeletal white muscle fibre diameter and expression of certain selected muscle genes were also affected by dietary changes. In the white muscle, diet S led to a significant decrease (×0.9) in the mean and median diameters of muscle fibres, to a significant decrease (×0.6) in the expression of MyoD and to a significant increase (×1.7) in the expression of fast-MHC, with no significant changes in myogenin expression. There was no change in the expression of the genes analysed in lateral red muscle (MyoD, MyoD2, myogenin and slow-MHC). These results demonstrated that changes occurred in skeletal white muscle cellularity and expression of MyoD and fast-MHC, although overall growth and protein accretion were not modified, when a diet rich in soybean meal and glutamic acid was ingested. Present findings also indicated that the white and red muscles of rainbow trout are differently affected by nutritional changes.

Skeletal muscle growth dynamics and expression of related genes in white and red muscles of rainbow trout fed diets with graded levels of a mixture of plant protein sources as substitutes for fishmeal

Juvenile rainbow trout were fed to visual satiation for 12 weeks with four diets containing fishmeal as the primary protein source (FM diet) or FM substituted with graded levels of a mix of plant proteins to replace 50% (PP50 diet), 75% (PP75) or 100% (PP100) of fishmeal with addition of crystalline amino acids to meet the requirements in indispensable amino acids. Growth performance, feed efficiency and protein efficiency were not affected by 50% fishmeal substitution but all decreased with higher substitution levels (FM = PP50 > PP75 > PP100). Ammonia excretion was inversely changed with FM substitution level (FM = PP50 < PP75 < PP100). Trout fed the FM diet had the highest level of nitrogen gain and those fed diet PP100 the lowest. Distribution of white muscle fibre diameter and expression of selected muscle genes were not affected by 50% fishmeal substitution. At higher substitution levels (75% and 100%) there was a significant decrease in the median diameter of white muscle fibres. Total substitution of fishmeal by plant protein sources (PP100) significantly increased (× 2.4) cathepsin D expression in white muscle but not in red muscle. Expression of MyoD, myogenin, PCNA, myosin heavy chains and calpain 2 was not modified by dietary treatments in either muscle type. This study thus demonstrates that the decrease in growth of trout fed a high level of plant protein sources is linked to changes in the dynamics of white muscle growth and correlated with changes in expression of a gene involved in lysosomal proteolysis in the white muscle.

Zebrafish embryos exposed to alcohol undergo abnormal development of motor neurons and muscle fibers

Children exposed to alcohol in utero have significantly delayed gross and fine motor skills, as well as deficiencies in reflex development. The reasons that underlie the motor deficits caused by ethanol (EtOH) exposure remain to be fully elucidated. The present study was undertaken to investigate the effects of embryonic alcohol exposure (1.5%, 2% and 2.5% EtOH) on motor neuron and muscle fiber morphology in 3days post fertilization (dpf) larval zebrafish. EtOH treated fish exhibited morphological deformities and fewer bouts of swimming in response to touch, compared with untreated fish. Immunolabelling with anti-acetylated tubulin indicated that fish exposed to 2.5% EtOH had significantly higher rates of motor neuron axon defects. Immunolabelling of primary and secondary motor neurons, using znp-1 and zn-8, revealed that fish exposed to 2% and 2.5% EtOH exhibited significantly higher rates of primary and secondary motor neuron axon defects compared to controls. Examination of red and white muscle fibers revealed that fish exposed to EtOH had significantly smaller fibers compared with controls. These findings indicate that motor neuron and muscle fiber morphology is affected by early alcohol exposure in zebrafish embryos, and that this may be related to deficits in locomotion.

Effect of phosphate and temperature on force exerted by white muscle fibres from dogfish

Effects of Pi (inorganic phosphate) are relevant to the in vivo function of muscle because Pi is one of the products of ATP hydrolysis by actomyosin and by the sarcoplasmic reticulum Ca2+ pump. We have measured the Pi sensitivity of force produced by permeabilized muscle fibres from dogfish (Scyliorhinus canicula) and rabbit. The activation conditions for dogfish fibres were crucial: fibres activated from the relaxed state at 5, 12, and 20°C were sensitive to Pi, whereas fibres activated from rigor at 12°C were insensitive to Pi in the range 5–25 mmol l−1. Rabbit fibres activated from rigor were sensitive to Pi. Pi sensitivity of force produced by dogfish fibres activated from the relaxed state was greater below normal body temperature (12°C for dogfish) in agreement with what is known for other species. The force-temperature relationship for dogfish fibres (intact and permeabilized fibres activated from relaxed) showed that at 12°C, normal body temperature, the force was near to its maximum value.

Ontogenesis of muscle and adipose tissues and their interactions in ruminants and other species

The lean-to-fat ratio, that is, the relative masses of muscle and adipose tissue, is a criterion for the yield and quality of bovine carcasses and meat. This review describes the interactions between muscle and adipose tissue (AT) that may regulate the dynamic balance between the number and size of muscle v. adipose cells. Muscle and adipose tissue in cattle grow by an increase in the number of cells (hyperplasia), mainly during foetal life. The total number of muscle fibres is set by the end of the second trimester of gestation. By contrast, the number of adipocytes is never set. Number of adipocytes increases mainly before birth until 1 year of age, depending on the anatomical location of the adipose tissue. Hyperplasia concerns brown pre-adipocytes during foetal life and white pre-adipocytes from a few weeks after birth. A decrease in the number of secondary myofibres and an increase in adiposity in lambs born from mothers severely underfed during early pregnancy suggest a balance in the commitment of a common progenitor into the myogenic or adipogenic lineages, or a reciprocal regulation of the commitment of two distinct progenitors. The developmental origin of white adipocytes is a subject of debate. Molecular and histological data suggested a possible transdifferentiation of brown into white adipocytes, but this hypothesis has now been challenged by the characterization of distinct precursor cells for brown and white adipocytes in mice. Increased nutrient storage in fully differentiated muscle fibres and adipocytes, resulting in cell enlargement (hypertrophy), is thought to be the main mechanism, whereby muscle and fat masses increase in growing cattle. Competition or prioritization between adipose and muscle cells for the uptake and metabolism of nutrients is suggested, besides the successive waves of growth of muscle v. adipose tissue, by the inhibited or delayed adipose tissue growth in bovine genotypes exhibiting strong muscular development. This competition or prioritization occurs through cellular signalling pathways and the secretion of proteins by adipose tissue (adipokines) and muscle (myokines), putatively regulating their hypertrophy in a reciprocal manner. Further work on the mechanisms underlying cross-talk between brown or white adipocytes and muscle fibres will help to achieve better understanding as a prerequisite to improving the control of body growth and composition in cattle.

Pax‐3 and Pax‐7 Label Muscle Progenitor Cells During Myotomal Myogenesis in Coregonus lavaretus (Teleostei: Coregonidae)

In Coregonus lavaretus, prior the mesoderm segmentation, in cells adjacent to the notochord called adaxial cells MyoD and slow myosin heavy chain (MyHC-slow) proteins were observed. After somite formation, adaxial cells migrate towards the lateral part of the myotome and form a layer of red muscles. Deeper cells differentiate into white muscle fibres. In situ hybridization using Pax-3 molecular probe revealed, that after somitogenesis, Pax-3 is expressed in a layer of cells superficial to the myotome resembling the "external cells" (found in many teleosts species) or dermomyotome described in Amniota. During later developmental stages Pax-3 gene is expressed in cells in intermyotomal space and then in myoblasts between myotubes. In these cells Pax-7 protein was also observed. Pax-3/7 positive cells which have migrated into the myotomes differentiate into satellite cells/secondary myoblasts and participate in hypertrophic and hyperplastic growth of muscles.

WHITE MUSCLE KEEPS TUNA WARM

Tuna are one of the top ocean predators. Few fish out run them as they scythe through the oceans. The key to the tuna's place at the pinnacle of the ocean community is their warm muscles. Retaining heat generated by their red muscle through a network of blood vessels, known as retes, which transfer heat from the blood as it leaves the warm internal muscles to cold blood returning from the animal's surface, tuna are able to maintain a body temperature that is 12°C higher than the surrounding water. Most attempts to understand how this super-predator maintains its high body temperature have focused on retention of the heat generated by the fish's red muscle. `However, the white muscle fibre portions of the myotomes... account for approximately 45 to 55%of the total body mass,' says Hans Malte from the University of Aarhus. Could white muscle be contributing the fish's higher body temperature? Knowing that rete-like structures had been identified in tuna white muscle in the 1960s,Malte and his colleagues Jess Boye, Michael Musyl and Richard Brill decided to build a mathematical model of heat movements in bigeye tuna, to see whether white muscle counter current heat exchangers may contribute to the fish's phenomenal thermal efficiency(p. 3708).Building models of a tuna fish in an environment that remained at a constant temperature and of another fish that made deep sea excursions to the chilly waters 400 m down, the team found that the only way that the tuna could maintained their body temperature was by recycling 96% of the heat from their white muscle, and 99% from their red muscle. And when they tested the effect of taking away the white muscle heat exchanger and leaving the fish with only its red muscle heat exchanger, the mathematical fish's temperature never reached the 32°C that had been recorded in the wild. The white muscle exchanger seemed to be essential for the fish's warm temperature.Finally, the team ran a calculation that showed that the fish may actively regulate their body temperatures by adjusting the amount of blood that they send through heat exchanger tissues to warm and cool as they move through the water column.`Our model shows that the presence of a functional rete in the blood supply to the white muscle is necessary to achieve realistic model outputs,' says Malte and he is keen to find out more about the fish's white muscle heat exchangers to understand how this top predator keeps warm.

Fish ladders select fish traits on migration–still a growing problem for natural fish populations

We investigated the potential selective effect of fish ladders on physiological and morphological profiles of the curimbatá, Prochilodus lineatus, during reproductive migration in Brazil. We registered sex, body weight and length, plasma glucose, hepatosomatic and gonadosomatic indices (HSI and GSI, respectively), hematocrit, leucocrit, blood cell and nucleus areas, and the diameter of white and red muscle fibers in fish sampled at the bottom (downstream) and at the top (upstream) of a fish ladder at a hydroelectric dam. Males and females at the top of the ladder showed higher size (weight and length), white muscle fiber diameters, plasma glucose levels and lower hematocrit when compared with those at the bottom. These size and muscle traits assist fish to overcome the ladder barrier and bypass the dam, an effort that might be reflected in the glucose levels. Females also showed higher GSI at the top of the fish ladder, a trait possibly facilitating their reproduction upstream. These results indicate that a dam system favors fish with specific morphological–physiological profile. This may have a strong influence upon upstream fish populations over generations and implies the presence of artificial selective pressure.

Protein kinase A modulates A‐type potassium currents of larval zebrafish (Danio rerio) white muscle fibres

Potassium (K(+)) channels are involved in regulating cell excitability and action potential shape. To our knowledge, very little is known about the modulation of A-type K(+) currents in skeletal muscle fibres. Therefore, we sought to determine whether K(+) currents of zebrafish white skeletal muscle were modulated by protein kinase A (PKA). Pharmacology and whole-cell patch clamp were used to examine A-type K(+) currents and action potentials associated with zebrafish white skeletal muscle fibres. Activation of PKA by a combination of forskolin + 3-isobutyl-1-methylxanthine (Fsk + IBMX) decreased the peak current density by approximately 60% and altered the inactivation kinetics of A-type K(+) currents. The specific PKA inhibitor H-89 partially blocked the Fsk + IBMX-induced reduction in peak current density, but had no effect on the change in decay kinetics. Fsk + IBMX treatment did not shift the activation curve, but it significantly reduced the slope factor of activation. Activation of PKA by Fsk + IBMX resulted in a negative shift in the V(50) of inactivation. H-89 prevented all Fsk + IBMX-induced changes in the steady-state properties of K(+) currents. Application of Fsk + IBMX increased action potential amplitude, but had no significant effect on action potential threshold, half width or recovery rate, when fibres were depolarized with single pulses, paired pulses or with high-frequency stimuli. PKA modulates the A-type K(+) current in zebrafish skeletal muscle and affects action potential properties. Our results provide new insights into the role of A-type K(+) channels in muscle physiology.

ChronicRhodiola roseaExtract Supplementation Enforces Exhaustive Swimming Tolerance

We explored the effects and mechanisms of Rhodiola rosea extract supplementation on swimming-induced fatigue in rats. The concentrations of active components in Rhodiola rosea have been determined by high performance liquid chromatography-mass spectrometer. The Rhodiola rosea extract supplementation in water for 2-4 weeks was evaluated in male Wistar rats with 90-min unloaded swimming exercise and 5% body weight loaded swimming up to fatigue. We measured the fatigue biomarkers, including blood urea nitrogen (BUN), glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT), lactate dehydrogenase (LDH), hepatic glycogen content, the activity of fat metabolism enzymes, sterol regulatory element-binding protein-1 (SREBP-1) and fatty acid synthase (FAS), the tissue oxygen content and ratio of red and white skeletal muscle fibers in rats. Rhodiola rosea significantly increased liver glycogen, SREBP-1, FAS, heat shock protein 70 expression, Bcl-2/Bax ratio and oxygen content before swimming. Rhodiola rosea supplementation significantly increased the swimming time in a dose-dependent manner and reduced swimming-enhanced serum BUN, GOT and GPT levels. The ratio of red and white muscle fibers was not altered after chronic Rhodiola rosea extract supplementation. Chronic Rhodiola rosea supplementation significantly improved exhaustive swimming-induced fatigue by the increased glycogen content, energy supply of lipogenic enzyme expressions and protective defense mechanisms.

Rearing oxygen level and slaughter stress effects on rainbow trout flesh quality

Although effects of hypoxia and, in a lower extent, effects of hyperoxia, have been widely studied, very few data is available regarding the effect of oxygen concentration around normoxia. Moreover, the effect of rearing oxygen level around normoxia on flesh quality, and a possible interaction with stress at slaughter, have never been investigated. Rainbow trout were reared during 18 weeks up to pan size (mean weight 400 g) at 76, 98 or 117% of oxygen saturation. Afterwards they were slaughtered according to two procedures: a minimal stress (NS group), or after a 15 min confinement stress (S group). Fish characteristics (weight, condition factor, fat-meter value, plasma cortisol level, hepato-somatic index, and hepatic glycogen content) and quality criteria of fillets (color, initial muscle pH, and muscle glycolytic potential) were recorded at slaughter time, whereas mechanical resistance, ultimate pH and dry matter content of the flesh were measured at 24 h and 48 h post-mortem. Muscle fiber size was analyzed on histological samples from white and red muscles. In our study, rearing oxygen level had no impact on the morphological characteristics of the fish except a higher hepato-somatic index and hepatic glycogen content for trout reared at 97% oxygen saturation. Rearing oxygen level affects slightly flesh quality at the lowest oxygen level (76% saturation) with a lower force for low deformation mechanical resistance measurement in the anterior part of the fillet. Stress before slaughter highly increased plasma cortisol concentration (by more than 18 in mean), and decreased fat-meter values (of 14% in mean) and the mean diameter of red muscle fibers (of 6.4% in mean). Stress before slaughter also decreased fillet lightness ( L⁎, − 1.1 unit), yellowness ( b⁎, − 0.76 unit), and initial pH (− 0.15 unit) of the flesh but had no effect on ultimate pH measured at 24 or 48 h post-mortem. Stress before slaughter induced a softer flesh as shown by lower mechanical resistance at high deformation measured on samples from both anterior and caudal part of the fillet. The post-mortem measurement time (24 or 48 h) was the main factor affecting the mechanical resistance of the flesh, with a significant softening of the flesh between 24 and 48 h. Nor oxygen level, nor slaughter stress affected the size of white muscle fibers. No major interaction between rearing oxygen level and slaughter stress was formally demonstrated.

Diffusion signal in magnetic resonance imaging: origin and interpretation in neurosciences.

Diffusion Magnetic Resonance Imaging provides images of unquestionable diagnostic value. It is commonly used in the assessment of stroke and in white matter fiber tracking, among other applications. The diffusion coefficient has been shown to depend on cell concentration, membrane permeability, and cell orientation in the case of white matter or muscle fiber tracking; yet a clear relation between diffusion measurements and known physiological parameters is not established. The aim of this paper is to review hypotheses and actual knowledge on diffusion signal origin to provide assistance in the interpretation of diffusion MR images. Focus will be set on brain images, as most common applications of diffusion MRI are found in neuroradiology. Diffusion signal does not come from two intra- or extracellular compartments, as was first assumed. Restriction of water displacement due to membranes, hindrance in the extracellular space, and tissue heterogeneity are important factors. Unanswered questions remain on how to deal with tissue heterogeneity, and how to retrieve parameters less troublesome to work with from biological and clinical points of view. Diffusion quantification should be done with care, as many variables can lead to variation in measurements.

Cellular localization of insulin-like growth factor-II protein in the sea bass (Dicentrarchus labrax) from hatching to adult.

The cellular localization of IGF-II protein was investigated during larval and postlarval developmental stages of sea bass (Dicentrarchus labrax) by immunohistochemistry using antisera raised against Sparus aurata IGF-II. At hatching, IGF-II immunoreactivity was already present in the skin, developing intestine and skeletal muscle. During larval life IGF-II protein was also observed in heart musculature, in kidney and gill epithelia as well as in liver. In fry skeletal muscle a moderate IGF-II immunostaining was detected in red fibres, whereas white muscle fibres exhibited a faint immunoreactivity. In adults, a marked IGF-II immunostaining was observed in red muscle fibres. A moderate immunoreactivity was also present in white fibres as well as in heart striated myocardial fibres. These results are in agreement with previous findings on the spatial localization of IGF-II and IGF type 1 receptor in S. aurata and Umbrina cirrosa, confirming the role of IGF system during development and growth of fish.

Estrogen Attenuation of Post‐Exercise Muscle Leukocyte Infiltration is not Receptor Mediated

Previous work from our laboratory has demonstrated that estrogen will attenuate leukocyte infiltration into skeletal muscle following eccentric exercise. However the mechanisms by which estrogen exerts its effects are still uncertain. We investigated the role of estrogen receptors (ER) on muscle leukocyte infiltration following eccentric exercise through administration of the ER antagonist ICI 182,780 following downhill running to ovariectomized female rats with (E+) or without (E−) estrogen supplementation. At 24 and 48 h post‐exercise, soleus and white vastus muscles were removed and immunostained for HIS 48 (neutrophil) and ED1 (macrophage) positive cells. The increase in number of fibres positive for HIS 48 in soleus and positive for ED1 in the soleus and white vastus was significantly attenuated (p&lt;0.05) in E+ relative to E− rats at 24 hours post‐exercise. E+ rats administered the ER agonist also had significantly (p&lt;0.05) attenuated 24 h post‐exercise increases in HIS 48 and ED1 positive soleus and white vastus muscle fibres similar (p&gt;0.05) to those without ER antagonist. This suggests that the ability of estrogen to attenuate post‐exercise leukocyte infiltration into skeletal muscle is not ER‐mediated.Supported by NSERC Canada

Temperature influence on the white muscle growth dynamics of the sea bass Dicentrarchus labrax, L. Flesh quality implications at commercial size

Rearing temperature was used to monitor muscle growth patterns of sea bass Dicentrarchus labrax, L. from hatching to the commercial size (350 g, 30 cm). At this moment, the white muscle cellularity, proximate composition and organoleptic parameters of the fillet were analysed to evaluate the influence of temperature on the structure and quality of the commercial product. One ambient (A/A) and three warm regimes of temperature were compared. In warmed tanks temperature was raised to 19 °C: during the larval period (W/A), only during the cool seasons (winter and early spring) (A/W), or both during the larval period and cool seasons (W/W). High temperature during the larval period was positive for an advanced yield of fingerlings and early juveniles. Winter heating of juveniles also advanced the time to reach 200 g by 25 days. However, independently of the thermal regime all fish attained the commercial size at approximately 600 days. Temperature modulated the rates of hypertrophy and hyperplasia of white muscle fibres throughout the larval, fingerling and juvenile periods, such that at commercial size the number and size distributions of muscle fibres varied depending on the previous thermal story. Thus, the density of muscle fibres (number/mm2) was maximum in tank W/A (212.19±8.77) and minimum in W/W (151.95±8.7) (p<0.001). The proximate composition varied for moisture and protein content, but independently of temperature, all the sensorial attributes of cooked flesh (firmness, juiciness, fattiness, chewiness, flavour and odour) were similar. Thus, no correlation between muscle fibre size and flesh texture was found. Compensatory growth of fish reared at ambient temperature and the uniformity of the proximate composition and sensorial properties evaluated by panellists minimized the impact of temperature on both the time at harvest and the quality of the commercial product.

Muscle fiber type distribution in climbing Hawaiian gobioid fishes: Ontogeny and correlations with locomotor performance

Three species of Hawaiian amphidromous gobioid fishes are remarkable in their ability to climb waterfalls up to several hundred meters tall. Juvenile Lentipes concolor and Awaous guamensis climb using rapid bursts of axial undulation, whereas juvenile Sicyopterus stimpsoni climb using much slower movements, alternately attaching oral and pelvic sucking disks to the substrate during prolonged bouts of several cycles. Based on these differing climbing styles, we hypothesized that propulsive musculature in juvenile L. concolor and A. guamensis would be dominated by white muscle fibers, whereas S. stimpsoni would exhibit a greater proportion of red muscle fibers than other climbing species. We further predicted that, because adults of these species shift from climbing to burst swimming as their main locomotor behavior, muscle from adult fish of all three species would be dominated by white fibers. To test these hypotheses, we used ATPase assays to evaluate muscle fiber type distribution in Hawaiian climbing gobies for three anatomical regions (midbody, anal, and tail). Axial musculature was dominated by white muscle fibers in juveniles of all three species, but juvenile S. stimpsoni had a significantly greater proportion of red fibers than the other two species. Fiber type proportions of adult fishes did not differ significantly from those of juveniles. Thus, muscle fiber type proportions in juveniles appear to help accommodate differences in locomotor demands among these species, indicating that they overcome the common challenge of waterfall climbing through both diverse behaviors and physiological specializations.

The H-Wave® Device Induces NO-dependent Augmented Microcirculation and Angiogenesis, Providing Both Analgesia and Tissue Healing in Sports Injuries

The hypothesis that the H-Wave® device (Electronic Waveform Lab, Inc., Huntington Beach, CA), a small-diameter fiber stimulator, is a paradigm shift of electrotherapeutic treatment of pain associated with human neuropathies and sports injuries is based on a number of its properties. The primary effect of H-Wave® device stimulation (H-WDS) is the stimulation of “red-slow-twitch” skeletal muscle fibers. The authors propose, based on the unique waveform, that the H-Wave® device specifically and directly stimulates the small smooth muscle fibers within the lymphatic vessels ultimately leading to fluid shifts and reduced edema. In unpublished rat studies, it has been observed that HWDS induces protein clearance. The H-Wave® device was designed to stimulate an ultra low frequency (1–2 Hz), low tension, nontetanizing, and nonfatiguing contraction, which closely mimics voluntary or natural muscle contractions. The H-Wave® device can stimulate small fibers due in part to its exponentially decaying waveform and constant current generator activity. The main advantage of these technologies over currently applied electrical stimulators (eg, transcutaneous electrical nerve stimulator [TENS], interferential [IF], neuromuscular electrical stimulation [NMES], high-volt galvanic, etc.) is that H-Wave's® small fiber contraction does not trigger an activation of the motor nerves of the large white muscle fibers or the sensory delta and C pain nerve fibers, thus eliminating the negative and painful effects of tetanizing fatigue, which reduces transcapillary fluid shifts. Another function of the H-Wave® device is an anesthetic effect on pain conditions, unlike a TENS unit which in the short term activates a hypersensory overload effect (gate theory) to stop pain signals from reaching the thalamic region of the brain. When the H-Wave® device is used at high frequency (60 Hz), it acts intrinsically on the nerve to deactivate the sodium pump within the nerve fiber, leading to a long-lasting anesthetic/analgesic effect due to an accumulative postsynaptic depression. Moreover, HWDS produces a nitric oxide (NO)-dependent enhancement of microcirculation and angiogenesis in rats. Thus, the authors hypothesize that because of these innate properties of the H-Wave® device, it may provide a paradigm shift for the treatment of both short- and long-term inflammatory conditions associated with pain due to sports injuries. A recent meta-analysis found a moderate-to-strong effect of the H-Wave® device in providing pain relief, reducing the requirement for pain medication, and increasing functionality. The most robust effect was observed for improved functionality, suggesting that the H-Wave® device may facilitate a quicker return to the field.