Calcium in the developing skeletal muscles of the chick embryo

The osmium-pyroantimonate technique was used for the ultrastructural study of Ca2+-localization in two types of chick embryo skeletal muscles: m. pectoralis and m. soleus. In 8- and 12-day old embryos the pyroantimonate precipitate was found on plasmalemma, condensed chromatine and ribosomes and in N-lines of I-band. During myogenesis (15-, 21-day old embryos) the calcium precipitate is redistributed from the above mentioned sites to terminal cisternae and N-line of I-band. It is proposed that calcium of N-lines may be involved in the glycogenolysis, its association with the muscle contraction occurring particularly at early developmental stages.     

Glycogen phosphorylase of skeletal muscles

A review is given on the affinity modification of pyridoxal phosphate and AMP-binding sites as well as on the chemical modification of essential amino acid residues of phosphorylase (histidine residue of the substrate-binding site and cysteine residue of the coenzyme-binding site). The role of allosteric effectors (AMP and glucose-6-phosphate) and functionally important centers of the protein in conformational transitions of rabbit muscle phosphorylase b is discussed. The kinetic properties of rabbit and bovine muscle phosphorylase are compared. Bovine muscle phosphorylase is shown to be a partly phosphorylated form of the enzyme. Some peculiarities of the pH-dependence of kinetic behaviour of the hybrid form of the bovine muscle enzyme are discussed.     

Pyruvate dehydrogenase activation in the skeletal muscles of the chick embryo during electrostimulation

The pyruvate dehydrogenase activity in the skeletal muscle during chicken embryo-genesis and early postnatal life amounts to 550 +/- 50 mU per g tissue, on the average; electrostimulation (1 Hz) induced a two-fold increase in its activity starting from the 15th day of incubation.     

Glycogen metabolism in the prelaid chick embryo.

Glycogen metabolism has been studied during the development of the early chick embryo, at the cytochemical and ultrastructural levels. Two waves of glycogen synthesis and breakdown have been found. In the first, free clusters of glycogen particles are synthesized at late oogenesis. These clusters are found later in invaginations of the membrane of vesicles containing a floccular material (FLOV). The glycogen clusters are degraded there during ovulation and the first hours in the oviduct. The second wave of glycogen synthesis begins before cleavage, reaching a maximum at mid-uterine age. This second wave occurs in another type of vesicle (GLYV), which eventually disintegrates releasing free clusters of glycogen granules. This glycogen is degraded in membranous structures containing a floccular material, as in the first wave of degradation. The degradation ends at the late uterine stages, and at the same time numerous ribosomes are formed. This period corresponds to area pellucida formation, which probably depends on the energy liberated during the second wave of glycogen degradation.     

Calcium localization in the degenerating myotubes of developing skeletal muscle in the chick embryo

Ca-accumulating formations found in degenerating myotubes of chick embryo by pyroantimonate technique have been identified as membrane bound bodies in the material fixed routinely for electron microscopy. These bodies seem to represent initial stages of a lipid degeneration of membranous structures. It is assumed that calcification of single degenerating subcellular structures may limit spreading necrosis over the whole cell.     

Erythropoiesis in the developing chick embryo

The types of erythroid cells of chick embryos developing in ovo have been correlated with the hemoglobins of the embryos. Prior to 5 days, when primitive cells constitute the only erythroid cells, two hemoglobins can be resolved by polyacrylamide gel electrophoresis. The two adult hemoglobins and a minor hemoglobin found only in embryos and young chicks first appear simultaneously with initiation of definitive erythropoiesis.     

Koelliker haemoglobins in developing chick embryo

1. Three Koelliker haemoglobins, HbKE, HbKA and HbKH, derived from a post-translational loss of alpha-Arg-141, were isolated from red cells of chicken embryos. HbKE is typical of embryos up to 7 days of incubation, HbKA and HbKH are found in mature embryos. 2. All the precursor haemoglobins contain alpha A chains. HbKA derives from adult haemoglobin A whose globin composition is alpha A2 beta 2, HbKH from embryonic haemoglobin H with a globin composition alpha A2 beta H2 and HbKE from embryonic haemoglobin E with globin composition alpha A2 epsilon 2. 3. No Koelliker derivatives of haemoglobins with alpha-like chains other than alpha A were observed.     

Effect of spinal cord stimulation on the metabolism of developing latissimus dorsii muscles in chick embryo

Influence of chronic spinal cord stimulation upon some characteristic enzyme activities of energy metabolism was investigated in slow anterior (ALD) and fast posterior (PLD) latissimus dorsii muscles of the chick embryo. During embryonic life, oxidative metabolism (as evaluated by the activity of malate dehydrogenase (MDH] represents the main energetic pathway in both slow and fast muscles. At the end of embryonic life, an increase in anaerobic (as evaluated by the activity of lactate dehydrogenase (LDH] and creatine phosphokinase (CPK) activities occurs in PLD muscle. Chronic spinal cord stimulation at a low frequency was performed from the 10th day to the 16th day of embryonic development. In ALD, the enzyme activities were unaffected, while in PLD a concomitant decrease in LDH and CPK activities was observed.