Development of the mitochondrial apparatus and blood supply of skeletal muscle fibers during ontogenesis of domestic fowl

The diameter, length, and numerical density of capillaries, diameter of muscle fibers, size and numerical density of mitochondrial profiles, and relative volume of mitochondria in them were determined in the chicken red oxidative gastrocnemius and white glycolytic pectoral muscle during development from day 10 of embryogenesis to six month of postnatal life. The bulk blood flow was measured in these muscles by hydrogen clearance during postembryonic development. During embryogenesis, the fibers of gastrocnemius muscle develop and grow at a higher rate, while during postembryonic development, those of the pectoral muscle develop faster. The density of mitochondrial profiles increases during embryogenesis and decreases after hatching, while their mean size increases, especially in the oxidative fibers, but it somewhat decreases in 6-month old chicks. Redistribution of mitochondria across the fiber section during development takes place in both muscles: they are localized predominantly in the center in 18-day embryos and in the periphery, especially in the gastrocnemius fibers, in 6-month old chicks. At hatching, the length of capillaries is similar in both muscles, but as chicks grow, the proportion of longer (more than 600 µm) capillaries in the pectoral muscle sharply increases, while their density and bulk blood flow decrease. Ratios were determined between structural parameters of the capillary bed and mitochondria, on the one hand, and oxygen consumption (ml/min per 1 mm fiber and 100 g muscle mass), on the other.__________Translated from Ontogenez, Vol. 36, No. 2, 2005, pp. 135–144.Original Russian Text Copyright © 2005 by Belichenko, Korostyshevskaya, Maksimov, Shoshenko.     

Development of the mitochondrial apparatus and blood supply of skeletal muscle fibers during ontogenesis of domestic fowl

The diameter, length, and numerical density of capillaries, diameter of muscle fibers, size and numerical density of their profiles, and relative volume of mitochondria in them were determined in the chicken red oxidative gastrocnemius and white glycolytic pectoral muscle during development from day 10 of embryogenesis to six month of postnatal life. The bulk blood flow was measured in these muscles by hydrogen clearance during postembryonic development. During embryogenesis, the fibers of gastrocnemius muscle develop and grow at a higher rate, while during postembryonic development, those of the pectoral muscle develop faster. The density of mitochondrial profiles increases during embryogenesis and decreases after hatching, while their mean size increases, especially in the oxidative fibers, but it somewhat decreases in 6-month old chicks. Redistribution of mitochondria by the fiber section during development takes place in both muscles: they are localized predominantly in the center in 18-day embryos and in the periphery, especially in the gastrocnemius fibers, in 6-month old fowl. At hatching, the lengths of capillaries are similar in both muscles, but as chicks grow, the proportion of longer (more than 600 microm) capillaries in the pectoral muscle sharply increases, while their density and bulk blood flow decrease. Ratios were determined between structural parameters of the capillary bed and mitochondria, on the one hand, and oxygen consumption (ml/min per 1 mm fiber and 100 g muscle mass), on the other.     

Masticatory muscles of domestic sheep and swine in ontogenesis

Age changes of morphometrical parameters of the masticatory muscles have been analyzed in domestic sheep and pigs of white large breed in the following age groups: 2-, 3-, 4-month-old fetuses, newborns, 4-month-old lambs, 10-month-old pigs, 18-month-old lambs, mature she-sheep and brood-sows. Uneven weight growth of the masticatory muscles in the sheep and pigs during the prenatal ontogenesis should be considered as a consequence of recapitulation of their phylogenesis, and in the postnatal ontogenesis it depends on changes in life conditions, type of nutrition, character of food and type of life. In newborn sheep the digastric, lateral, pterygoid and temporal muscles grow intensively, and in pigs--medial pterygoid and temporal ones. When they pass to roughage, in the former the mass of the musculus masseter major and medial pterygoid muscle increases, and in the latter--that of the musculus masseter major and temporal one. The masticatory muscles of the species studied increase in their mass especially intensively during the middle of the prenatal ontogenesis and during suckling period of their development. This should be taken into consideration in stock-breeding practice. In domestic pigs there is only one muscular belly in the digastric muscle. In sheep there are two bellies, separated one from another by means of a tendinous intersection, owing to crossing of the latter by the stylohyoid muscle.     

Various characteristics of the activity of skeletal muscles in humans and dogs during postnatal ontogenesis

At normal ambient temperatures, in absence of stress, in babies during first months of life (in contrast to less maturely born mammals), the respiratory activity of skeletal muscles is not realized, being observed only under stress conditions. In 1-1 1/2 months old puppies, after deafferentation of the hindlimb, the frequency of movements of a jerk type increases approximating the level observed in newborn animals. At normal ambient temperatures, these puppies exhibit respiratory activity of skeletal muscles which is not observed at this age in control animals.     

Transcriptome analysis of two bovine muscles during ontogenesis

Macro-arrays, on which 1339 human skeletal muscle cDNA clone inserts had been spotted as PCR products, were used to make large-scale measurement of gene expression in bovine muscles during ontogenesis. Ten complex cDNA targets derived from two mixed muscle samples, Rectus abdominis (rather red oxidative muscle, RA) and Semitendinosus (rather white glycolytic muscle, ST), were taken from foetuses at 4 different stages (110, 180, 210, and 260 days post-conception) and from 15-month-old young bulls to generate differential expression patterns. Each sample analysed was prepared from a pool of RNA extracted from muscle tissues sampled from at least 6 different animals. Approximately 200 expression signals were validated and taken into account to provide a first "bovine" muscle gene repertoire. Despite the relatively small number of probes and the heterologous approach, this made it possible to identify up to 7 genes differentially expressed between RA and ST, depending on age. From 110 days post-conception to 15 months of age, differences in the expression levels of 110 genes were detected in the four comparisons between two consecutive ages. By comparing 260 days post-conception foetal muscles and adult muscles, up to 87 genes were overexpressed, whereas only 7 genes were shown to be down-regulated. Among these genes, 33% have unknown biological functions. Taken together, the results reported here underline the importance of the last three months of gestation in muscle myogenesis, and highlight new genes involved in this process.     

Pharmacological parameters of muscarinic cholinoreceptors in skeletal muscles

It has been shown that bath application of muscarine delayed the early post-denervation depolarization in the muscle fibers incubated for 3 h in culture medium. The greatest reduction of the post-devervation depolarization was observed with 50 nmol/l muscarine. Atropine, a muscarinic antagonist, clozapine, a specific inhibitor of M1/M5-cholinergic receptors, and nitrocaramiphen, a M1-antagonist, completely removed the hyperpolarizing effect of muscarine. 4-DAMP, a specific inhibitor of M3-cholinergic receptors, himbacine, an antagonist of M2-cholinergic receptors, and tropicamide, a specific inhibitor of M2/M4-cholinergic receptors, failed to prevent the effect of muscarine. A M1/M2 muscarine agonists propargyl and but-2-ynyl esters of arecaidine had apparent muscarine-like effect. Nitrocaramiphen, and not himbacine, prevented the hyperpolarizing effect of these cholinomimetics. It is concluded that muscarine and esters of arecaidine delay the development of early postdenervation depolarization in M1-cholinergic receptors of skeletal muscle.     

Changes in the activity of various enzymes of carbohydrate metabolism in the liver and skeletal muscles of pigs during ontogenesis

Hexokinase, glucokinase, phosphofructokinase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activity was studied in the liver and musculus quadriceps femoris of 110-day foetuses 1, 2, 3, 30 and 60-day piglets and in adult pigs. The activity of all enzymes in the tissues of newborn piglets is considerably higher than in the tissues of foetuses. The activity of hexokinase in both tissues of piglets increases in the first days after birth and lowers by the one month age. The phosphofructokinase activity in the skeletal muscles and the glucokinase one in the pig liver increase during the postnatal development. The activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in both tissues of pigs increases after birth and then decreases. Glucose metabolism in the pig liver at all stages of odontogenesis proceeds more intensively by the pentose phosphate pathway, and in the skeletal muscles--by glycolytic one.     

Effects of reactive oxygen species and interplay of antioxidants during physical exercise in skeletal muscles

A large number of researches have led to a substantial growth of knowledge about exercise and oxidative stress. Initial investigations reported that physical exercise generates free radical-mediated damages to cells; however, in recent years, studies have shown that regular exercise can upregulate endogenous antioxidants and reduce oxidative damage. Yet, strenuous exercise perturbs the antioxidant system by increasing the reactive oxygen species (ROS) content. These alterations in the cellular environment seem to occur in an exercise type-dependent manner. The source of ROS generation during exercise is debatable, but now it is well established that both contracting and relaxing skeletal muscles generate reactive oxygen species and reactive nitrogen species. In particular, exercises of higher intensity and longer duration can cause oxidative damage to lipids, proteins, and nucleotides in myocytes. In this review, we summarize the ROS effects and interplay of antioxidants in skeletal muscle during physical exercise. Additionally, we discuss how ROS-mediated signaling influences physical exercise in antioxidant system.     

Mathematical modeling of oxygen transport in skeletal muscle

Inhomogeneous perfusion of capillary beds can result in large-scale diffusion of oxygen between distant portions of an organ. The conceptual model of a single capillary supplying oxygen to a surrounding concentric cylinder of tissue is not applicable to a consideration of such processes. An entirely different approach to the modeling of oxygen transport to tissue, with specific reference to the capillary beds of skeletal muscle, is presented here. This approach is intended to replace the theoretical Krogh cylinder model of capillary-tissue oxygen transport with a much more realistic model that takes into account inhomogeneities of capillary density, blood flow velocity, and oxygen concentration inherent in the micro-vasculature. The oxygen distribution in inhomogeneously perfused skeletal muscle is analyzed mathematically by defining an averaged concentration profile that neglects the fine-scale variation from capillary to capillary.     

Characteristics of alpha-aminoisobutyric acid transport in rat skeletal muscles.

alpha-Aminoisobutyric acid (AIB) transport into the intracellular compartment of extensor digitorum longus and soleus muscles was measured (in vitro) after allowance for the equilibration of the amino acid in the extracellular space. The latter was determined with three markers, [14C]inulin, 60Co-EDTA and [3H]mannitol. Net transport of AIB was subsequently divided into its two components, i.e. influx and efflux. Rates of influx were measured as the intracellular accumulation of [14C]AIB after a short incubation (5 min), and efflux was measured as the release of AIB with time (up to maximum of 50 min) from muscles that had previously been preloaded with AIB. This intracellular efflux was resolved into two phases, which probably represent two separate components of exit. The influence of extracellular Na+ on the transport of this neutral amino acid (representing the A system) was investigated. Na+ depletion resulted in lower accumulations of AIB, the effects becoming more pronounced with progressive depletions of external Na+. These changes arose from an inhibition of AIB influx, concomitant with an enhancement of its efflux. In contrast, all components of tyrosine transport (representing the L system) were unaffected by lowering external Na+ concentrations. The net accumulation of AIB was also suppressed by cortisol. This inhibitory effect was, however, Na+-dependent and resulted solely from the steroid's enhancement of AIB efflux, the hormone being without effect on AIB influx.