Succinic dehydrogenase and cytochrome oxidase of mitochondria of chick liver, heart, and skeletal muscle during embryonic development

Differentiation of Purkinje fibres and ordinary ventricular and atrial myocytes in the bovine heart: an immuno- and enzyme histochemical study

The differentiation of Purkinje fibres and ordinary ventricular and atrial myocytes in bovine hearts was studied with specific antibodies against M-line proteins (MM-creatine kinase and myomesin) and with enzyme histochemistry (succinate dehydrogenase and mitochondrial glycerol-3-phosphate dehydrogenase). MM-creatine kinase was detected at an earlier stage in Purkinje fibres and atrial myocytes than in ordinary ventricular myocytes. The findings are in agreement with previous ultrastructural observations that an earlier appearance of a dense M-band occurs in Purkinje fibres than in ordinary ventricular myocytes. Myomesin was detected in all three cell types even at early foetal stages, in accordance with suggestions that it is an integral component of the myofibrillar structure. The activity of succinate dehydrogenase gradually increased in both ordinary ventricular and atrial myocytes, while the activity of mitochondrial glycerol-3-phosphate dehydrogenase was high at different stages of early foetal development in the two tissues, finally becoming low in the adult stage. The activity of succinate dehydrogenase and mitochondrial glycerol-3-phosphate dehydrogenase seemed to remain unchanged in the Purkinje fibres from early to late foetal stages. The present study shows that the Purkinje fibres are already different from ordinary ventricular myocytes at early foetal stages and that the two cell types differentiate in different ways. It is concluded that there are also developmental differences between ordinary ventricular and atrial myocytes.

Characterization and comparison of two plasma membrane reference enzymes with those of other organelles during mammalian embryogenesis

1. Optimal assay conditions for two plasma membrane reference enzymes, alkaline phosphodiesterase 1 and 5'-nucleotidase, were determined in homogenates of rat embryos obtained on the 14th day of gestation and were found to be different than those reported for adult tissues. 2. Measurements of various organelle reference enzyme activities on the 14th and 15th days of gestation revealed a pattern of selective rates of subcellular organelle biogenesis during this period: lysosomes greater than mitochondria greater than endoplasmic reticulum = plasma membranes.