Electron microscopic studies on the development of the skeletal muscle (pectoralis major muscle) of the albino rats.
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Animals↗
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Pectoralis muscle shortening and rigor development at different locations within the broiler breast.
Two experiments were conducted to evaluate differences in rigor development that occur as a function of location within the broiler breast muscles, pectoralis major (p. major) and pectoralis minor (p. minor). Three locations were evaluated, corresponding to anterior, middle, and posterior samples taken between the cranial and caudal ends of each muscle. Results of the first experiment indicated that the 1.55-mu sarcomere lengths of hot-boned p. major muscle at the anterior location were significantly shorter than those at the posterior location, which were 1.69 mu. Sarcomere lengths of p. minor were shorter than those of p. major in hot-boned muscles, but longer in those aged intact, indicating a significant muscle x treatment interaction. In the second experiment, the anterior location of hot-boned p. major reached the onset phase of rigor in about 1 h, whereas those at the posterior location required between 2 and 4 h postmortem. Between 1 and 8 h postmortem, sarcomere lengths for the anterior location of p. major were also significantly shorter than lengths in the posterior location, but the differences after 24 h were not significant. Samples at all locations of p. minor reached onset of rigor by 15 to 30 min postmortem, with no locational differences throughout the 24 h period of aging. The results of both experiments generally indicated differences between profiles of rigor development of the two muscles and between samples at different locations of the much larger and more complex p. major.
Animals↗
Expression of myosin heavy chain isoforms during development of domestic pigeon pectoralis muscle.
The pectoralis muscle of birds provides virtually all the power for the downstroke of the wing during flight. In adults it consists almost entirely of FOG (fast-twitch oxidative-glycolytic) and/or FG (fast-twitch glycolytic) fiber types. The aims of this study are to contrast MyHC (myosin heavy chain) transitions occurring within avian FG and FOG fibers during development, and to test the hypothesis that the pectoralis matures before the acquisition of flight. Pectoralis was obtained from pigeons (Columba livia) aged from 13 days in ovo to adult. Monoclonal antibodies generated against chicken MyHC isoforms were used with Western blots and immunocytochemistry. FG and FOG fibers were differentiated using a histochemical method demonstrating NADH (nicotinamide adenine dinucleotide), and "lesser fiber diameters" were quantified. Western blots confirm that the antibodies label pigeon MyHCs. A small number of the fibers are slow type in ovo, but these are quickly restricted in distribution and lost after hatching. In ovo fast-twitch fibers contain a ventricular isoform, and at least two embryonic-neonatal forms (designated E-N103 and E-N165). One week after hatching, fast-twitch fibers can be distinguished by NADH as FG or FOG. At fledging, four weeks after hatching, FG and FOG fibers are smaller than in older birds and E-N103 and E-N165 persist in both fibertypes. E-N103 wanes in all fibers shortly after fledging. E-N165 gradually disappears from FG fibers. Thus, despite pigeons being at adult body mass at fledging, their pectoralis is not fully mature.
Animals↗
Effects of ultrasound and convection cooking to different end point temperatures on cooking characteristics, shear force and sensory properties, composition, and microscopic morphology of beef longissimus and pectoralis muscles.
Longissimus and pectoralis muscles were removed from 10 steer carcasses at 4 d postmortem, aged for 14 d at 2 degrees C, then assigned to either ultrasound or convection cooking to either 62 degrees C or 70 degrees C internal end point temperature. During cooking, time-temperature profiles and energy consumption were monitored. Ultrasound cooking resulted in greater (P < .05) cooking speed, greater (P < .05) moisture retention and less (P < .05) cooking loss, greater (P < .05) efficiency of energy consumption, a more uniform cooking environment, and less (P < .05) instrumental peak-force work to shear muscle samples than convection cooking. The ultrasound treatment also resulted in a reduction (P < .05) in soluble collagen content and superior (P < .05) myofibrillar tenderness, as determined by a trained sensory panel, than convection cooking. Electron micrographs indicated that ultrasound-cooked muscles had longer sarcomeres, larger diameter fibers, and more myofibrillar disruption and shattering. Longissimus muscles cooked faster (P < .05) and more (P < .05) energetically efficient, had less (P < .05) total collagen, and were superior (P < .05) in instrumental evaluated texture and sensory tenderness than pectoralis muscles. Cooking to 70 degrees C caused greater (P < .05) moisture and cooking losses, required more (P < .05) time and energy input to cook, and negatively (P < .05) affected instrumental textural and sensory tenderness characteristics. Electron micrographs indicated a shortening of sarcomeres, more deterioration of the banding structure, reduction in fiber diameter, and breakdown of endomysial and perimysial connective tissue at an internal temperature of 70 degrees C vs 62 degrees C. This research identifies ultrasound cooking as a new, rapid, energy-efficient method that may improve some meat textural attributes.
Animals↗
[Comparative histology, histochemistry and innervation of striated muscle fibers of the greater pectoralis muscle and supracoracoid muscle in birds].
The morphology of the pectoralis major muscle and the supracoracoideus muscle was compared in three Galliformes and five Passeriformes, in relation to partial behavioral characteristics. In all species, two fibres types are observed. The frequencies of these fibres are different, especially between Galliformes and Passeriformes, but also between Coturnix and other Galliformes. All fibres show phasic innervation. A relation of the extent between synaptic gutters and muscle activity is suggested.
Animals↗
Nuclear magnetic resonance imaging as a tool to estimate the mass of the Pectoralis muscle of chickens in vivo.
1. Nuclear magnetic resonance imaging (MRI) was used to assess the advantages of the technique in determining the size (volume) and shape of the Pectoralis muscle (Pectoralis major and minor) in broiler chickens, non-invasively and in vivo. 2. The imaging was performed using a Spectroscopy Imaging System 2.0 Tesla/31 cm bore imaging spectrometer. Three-dimensional reconstruction of transverse images was used to estimate the size of the Pectoralis muscle of chickens ranging in body weight from 362 to 1643 g. 3. Regression analysis resulted in R2 values of 0.92 and 0.99 for the relationship between Pectoralis muscle weight, body weight and muscle volume, respectively. 4. It is concluded that MRI and 3-dimensional image reconstruction may be used to estimate the Pectoralis muscle size and shape. This may be readily extended to monitor the influence of various factors on the growth and development of specific organs and tissues in the body.
Animals↗
Computed tomography of partial unilateral agenesis of the pectoralis muscles.
The most common congenitally absent muscles are the pectoralis major and minor. Absence is usually incomplete. This anomaly is often one component of a syndrome associated with other hand (Poland syndrome) and thoracic anomalies. Computed tomography can identify partial absence of the pectoralis muscle and exactly define the altered anatomy. A patient with myasthenia gravis and isolated partial agenesis of the pectoralis muscle is presented.
Adult↗
Growth of the pectoralis muscle of the house sparrow (Passer domesticus).
The pectoralis muscle from growing house sparrows was investigated using linear, gravimetric, histological and ultrastructural techniques. The structure of the muscle at different stages of development was discussed in relation to known behavioural activities, such as the onset of regular wing exercising and thermogenic shivering in the nestlings. Fibres in the pectoralis muscle of birds about to fledge (15 day nestlings) were similar in composition to fibres in muscles from fully fledged juveniles, with two exceptions. Firstly, numerous lipid droplets had accumulated adjacent to mitochondria in fibres from the pectoralis muscle of the nestlings. This lipid could act as a readily available source of energy for the birds on fledging. Secondly, masses of ribosomes and irregularly shaped myofibrils were present, indicating the continued elaboration of the contractile apparatus in fibres from the pectoralis muscle of the 15 day nestlings. The inefficient flight of newly fledged house sparrows may be accounted for by the size of the pectoralis muscle relative to total body weight. The total contractile material in the muscle of the birds about to fledge was estimated to be 60% or less of that found in fully fledged juveniles, while the body weight was nearly that of an adult bird.
Aging↗
Histochemistry of lactic dehydrogenase in heart and pectoralis muscles of rat.
Left-ventricular heart muscle and pectoralis major muscle of the rat were studied to determine the intracellular localization of lactic dehydrogenase (LDH) isoenzymes. Fixation of tissue for 2 hr in 2% buffered formaldehyde provided the best preservation of the ultrastructure and enzyme activity. Total LDH activity was found diffusely in the ground substance of the sarcoplasm and in the mitochondria of the heart muscle. In skeletal muscle a strong reaction was noted in the sarcoplasmic reticulum, and moderate activity was seen in the ground substance of the sarcoplasm and in the mitochondria. Differentiation of the isoenzymes of LDH was accomplished by addition of 4 M urea or application of heat. Heart-type isoenzymes were mainly localized in the mitochondria and sarcoplasm, whereas muscle-type isoenzymes were localized mainly in the sarcoplasmic reticulum of the skeletal muscle. It is speculated that the sarcoplasmic reticulum of the skeletal muscle is the site of anaerobic glycolysis and that the sarcoplasm and mitochondria are involved primarily in aerobic metabolism of pyruvate.
Animals↗
[A case of congenital absence of the major pectoralis muscle].
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Adult↗
Post-mortem biochemistry of Pekin duckling and broiler chicken Pectoralis muscle.
Biochemical post-mortem changes between red and white avian muscle were determined using duckling and chicken Pectoralis muscles, respectively. Six live Pekin ducklings and six live broiler chickens, in each of two trials, were obtained from commercial plants and processed at a pilot facility. After evisceration, carcasses were held at 4 C, then Pectoralis muscles were removed at .25, 1, 4, and 24 h post-mortem, and sampled for pH, lactate, adenosine triphosphate (ATP) content, and R-value (inosine to adenine ratio). Duckling Pectoralis pH significantly (P less than .05) decreased from 6.25 to 5.66 from .25 to 24 h post-mortem, respectively, as compared with that of the chicken, which decreased from 6.41 to 5.62 for the same times. Duckling lactate values, from .25 to 24 h, increased from 15.86 to 28.86 mumol/g, respectively, and chicken lactate values increased from 27.62 to 53.51 mumol/g. The ATP content of the duckling Pectoralis muscle decreased from 1.59 to .14 mumol/g and chicken Pectoralis decreased from 3.42 to .21 mumol/g from .25 to 24h, respectively. The R-values of duckling and chicken Pectoralis significantly increased from .25 to 24 h (.98 to 1.37 and .80 to 1.51, respectively). Duckling and chicken biochemical measurements were significantly different at all post-mortem sampling times, except for 24-h values of pH (5.66 versus 5.62, respectively) and 24-h contents of ATP (.14 versus .21 mumol/g, respectively). The different post-mortem biochemical measurements between duckling and chicken Pectoralis muscle is evidence that different rates of post-mortem metabolism and rigor development exist between these red and white avian breast muscles.
Adenine↗
Posthatching growth and pectoralis muscle development in broiler strain chickens, bantam chickens and the reciprocal crosses between them.
Body weight, pectoralis muscle weight, pectoralis protein and DNA concentration, and plasma GH and IGF-I concentrations of broiler chicks (BrBr), bantam chicks (BaBa) and reciprocal crosses between them (BaBr and BrBa) were measured between 0 and 42 days after hatching. At hatch, body weight and pectoralis weight of the two types of chicks from broiler eggs (BrBr and BaBr) were equal to each other but greater than the two types of chicks from bantam eggs (BaBa and BrBa), which were not different from each other. BrBr chicks grew more rapidly than crossbreds and BaBa chicks grew more slowly. Weights of the reciprocal crosses (BaBr and BrBa) were markedly different at day of age, but converged by day 14. The increase in pectoralis muscle mass of BrBr chicks exceeded that of the reciprocal crosses which in turn exceeded that of BaBa chicks. The increase in pectoralis DNA content and protein content followed the same pattern. The DNA unit size, as expressed by the protein:DNA ratio, was markedly lower in pure bantam chicks from 14 to 42 days of ages, whereas the unit size did not differ between the intermediate sized reciprocal crosses and the large bodied broiler chicks. Differences in muscle mass were primarily achieved by differences in the number of DNA units although a difference in unit size was also a factor. There were no clear relationships between growth and plasma growth hormone or insulin-like growth factor I concentrations. Thus while satellite cell proliferation is primarily responsible for genotypic differences in muscle mass, the plasma growth hormone-IGF-I axis does not appear to be regulating their proliferation.
Age Factors↗
Alteration of sarcoplasmic reticulum after denervation of chicken pectoralis muscle.
To determine the neural influence on the function of the sarcoplasmic reticulum (SR) of fast-twitch skeletal muscle, the superior pectoralis muscle of adult chicken was denervated, and the SR was isolated at 20 days post-denervation. The isolated SR was probably derived from the longitudinal SR and was relatively free of contaminants. The protein profile of the SR was quantitatively changed after denervation with an increase in the M55 and 30000-mol.wt. proteins relative to the Ca2+-ATPase. Ca2+-dependent ATPase activity and phosphoenzyme formation were lower in the denervated-muscle SR; however, the enzyme catalytic-centre activity was similar to the control value. The decrease in Ca2+-ATPase activity in denervated-muscle SR was accompanied by a lower Ca2+ accumulation so that the relationship between Ca2+ accumulation and Ca2+-dependent ATPase activity was well maintained in the SR from denervated muscle. The data imply that denervation may result in a diminution of functional Ca2+ pump sites. Evidence is presented, though, which suggests that denervation affects a single class of Ca2+-binding sites of the Ca2+-ATPase, resulting in a lower affinity for Ca2+.
Adenosine Triphosphatases↗
The composite structure of quail pectoralis muscle.
The twitch fibers of the quail pectoralis muscle were found to have one neuromuscular junction each, located in the middle third of the fiber. The length of isolated fibers varied between 8.8 and 33.2 mm, with mean and median values of 16 and 15.6 mm, respectively. The lengths of the fascicles from which the fibers were isolated varied between 30 and 51 mm. The muscle fibers taper at both ends. The neuromuscular junctions, revealed after histochemically reacting the intact muscle for acetyl cholinesterase activity, were arranged in discrete bands, separated by intervals of between 0.94 and 6.70 mm, with a mean value of 3.14 mm. The quail pectoralis muscle is thus composed of discontinuous, tapered muscle fibers, arranged in an overlapping series. It is therefore a muscle in which tension is transmitted laterally between muscle fibers.
Acetylcholinesterase↗
Turnover of glycogen phosphorylase in the pectoralis muscle of broiler and layer chickens.
Glycogen phosphorylase is a major sarcoplasmic protein in chicken pectoralis muscle, constituting approx. 4% of the total protein complement. In slow-growing layer chicks phosphorylase accumulated in parallel with muscle accretion, but in fast-growing broiler chicks the concentration of phosphorylase in the muscle increased (from 5 to 8 mg/g wet wt.) with time. In a 5-week period, the total amount of phosphorylase in the pectoralis muscles increased 18-fold in broiler chicks (from approx. 75 to 1400 mg total), but only 3-fold (from approx. 100 to 270 mg total) in layers. Pyridoxal phosphate, the cofactor of the enzyme glycogen phosphorylase, was used as a specific label to measure the rate of degradation of the enzyme in the pectoralis muscle of growing broiler and layer chickens in vivo. In young animals, the fractional rate of phosphorylase synthesis was similar in broiler and layer chickens (approx. 15%/day), but the rate of degradation in layers (5%/day) was 5-fold higher than in broilers (1%/day). As the animals aged, the rate of synthesis decreased, but more so in layers than in broilers. The rate of degradation of phosphorylase also decreased in layers, but in broilers it remained at the low level seen in young animals. The dramatically higher rate of phosphorylase accretion in the pectoralis muscles of the broilers is therefore achieved by an initial lower rate of degradation combined with a sustained difference between rates of synthesis and degradation.
Aging↗
Ontogeny of the pectoralis muscle in the little brown bat, Myotis lucifugus.
The ontogeny of a primary flight muscle, the pectoralis, in the little brown bat (Myotis lucifugus: Vespertilionidae) was studied using histochemical, immunocytochemical, and electrophoretic techniques. In fetal and early neonatal (postnatal age 1-6 days) Myotis, histochemical techniques for myofibrillar ATPase (mATPase) and antibodies for slow and fast myosins demonstrated the presence of two fiber types, here called types I and IIa. These data correlated with multiple transitional myosin heavy chain isoforms and native myosin isoforms demonstrated with SDS-PAGE and 4% pyrophosphate PAGE. There was a decrease in the distribution and number of type I fibers with increasing postnatal age. At postnatal age 8-9 days, the adult phenotype was observed with regard to muscle fiber type (100% type IIa fibers) and myosin isoform profile (single adult MHC and native myosin isoforms). This "adult" fiber type profile and myosin isoform composition preceded adult function by about 2 weeks. For example, little brown bats were incapable of sustained flight until approximately postnatal day 24, and myofiber size did not achieve adult size until approximately postnatal day 25. Although Myotis pectoralis is unique in being composed of 100% type IIa fibers, transitional fiber types and isoforms were present. These transitional forms had been observed previously in other mammals bearing mixed adult muscle fibers and which undergo transitional stages in muscle ontogeny. However, in Myotis pectoralis, this transition transpires relatively early in development.
Aging↗
Myosin isozymes in avian skeletal muscles. I. Sequential expression of myosin isozymes in developing chicken pectoralis muscles.
Myosin has been purified from chicken pectoralis muscle at various stages of development, from 10 days' incubation to approximately 10 months after hatching. Embryonic myosin from the earliest stage showed a high level of ATPase activity, similar to that obtained for adult pectoralis myosin. Two-dimensional peptide mapping of partial chymotryptic digests showed, however, that is heavy chain is quite different from that of adult fast myosin. The immunological crossreactivity observed between embryonic myosin and adult fast (pectoralis) myosin is therefore due to shared antigenic determinants rather than the presence of any adult isoforms. In an accompanying paper we will show that embryonic myosin at 10 days' incubation is not a single species, but consists of at least two heavy chain isozymes. The minor fraction binds slow light chains preferentially, and appears to be largely responsible for the observed crossreactivity with slow (ALD) myosin. None of the embryonic myosins is equivalent to the adult forms. Prior to hatching, LC3f is present only in very small amounts (less than 5%), and the adult light chain pattern, containing LC1f and LC3f in equimolar amounts, is not generated until after one week post-hatching. At about that time a new heavy chain population is detected, different from either the embryonic heavy chain or the adult heavy chain. The adult heavy chain peptide pattern appears from about three weeks' post-hatching, but a map indistinguishable from that of adult myosin is not observed until about 26 weeks. None of the observed differences in peptide maps can be related to different strains of chicken; pectoralis myosin from adult White Rock gave an identical map to that from White Leghorn. Unexpectedly, posterior latissimus dorsi (PLD) myosin from White Leghorn appears to be different from pectoralis myosin from the same strain, despite the histochemical and immunocytochemical similarity of the two muscles. We conclude that myosin polymorphism is widespread in muscle tissue, and that the expression of myosin isozymes and their subunits is under developmental regulation.
Adenosine Triphosphatases↗
Seasonal acclimatization in American goldfinches: the role of the pectoralis muscle.
The present study attempts to assess whether the marked seasonal changes in the capacity for shivering thermogenesis in American goldfinches (Carduelis tristis) involve adjustments of metabolic pathways of the pectoralis muscles similar to those observed in mammalian muscle in response to endurance training, i.e., changes favoring increased reliance on fatty acid oxidation and decreased utilization of carbohydrate reserves. Analysis of seasonal changes in enzyme profile of the pectoralis muscle revealed that winter-acclimatized birds have significantly greater (P less than 0.05) activities of phosphorylase, phosphofructokinase, and beta-hydroxy-acyl-CoA dehydrogenase than do birds in other seasons. The activities of citrate synthase and hexokinase do not vary seasonally. These results differ fundamentally from the pattern of changes in enzyme activities associated with endurance adaptation in mammals. Furthermore no seasonal changes were observed in capacities for the oxidation of fatty acids (palmitate and linoleate) or pyruvate in either crude homogenates or isolated mitochondria of goldfinch pectoralis muscles. The oxidation of pyruvate by isolated pectoralis muscle mitochondria was inhibited (greater than 90%) by the oxidation of palmitoyl carnitine at palmitoyl carnitine concentrations as low as 50 microM. These data agree with physiological observations indicating little use of glucose by this tissue during steady-state shivering. However, the extent of this inhibition does not vary seasonally. Therefore the present study fails to document any significant seasonal change in the catabolic pathways of the pectoralis muscle that would link observed seasonal changes in capacity for shivering thermogenesis with a shift in the balance of substrate use by this tissue.
3-Hydroxyacyl CoA Dehydrogenases↗