Studies of the development of congenital anomalies in embryos of riboflavin‐deficient, galactoflavin fed rats. I. Growth and embryologic pathology

Abstract

Embryos from maternal rats maintained on a riboflavin‐deficient, galactoflavin‐augmented diet were compared by gross and histologic examinations with normal controls. On day 11 of gestation no differences were noted between control and treated embryos; on days 12 and 13 the treated embryos were smaller in overall size; and on day 14 the rate of differentiation of tissues of the treated embryos was delayed. The embryonic mortality occurred between day 11 and day 15. Serial sections of day‐14 treated embryos consistently contained extensive areas of necrosis in the mesoblast of the extremities and first branchial arch. A less frequent but similar lesion was found in the central nervous systems in two of four treated embryos examined on day 14. The pathologic lesion resembles the normal cell death which is part of the sculpturing process of developing extremities, but was of much greater magnitude. In addition, studies of sections of the extremities of the treated day‐14 embryos demonstrated a reduction in the number of cellular mitoses. By day 15 the necrosis had disappeared, the mode of clearing presumably being due to macrophage action as evidenced by photographs and by the presence of acid phosphatase‐containing cells in the areas of phagocytosis. In the early stages of mesenchymal condensation the treated specimens evidenced digital fusion but measurements of the relative total volume of mesenchyme were similar in treated and control specimens. Histochemical studies of the treated embryos but not the placentas or maternal tissues demonstrated an overall decrease in the reactions for succinic dehydrogenase from day 12 to day 17. Levels of malic and lactic dehydrogenases and alkaline and acid phosphatases were not decreased in the treated embryos when measured histochemically.

Mitochondrial ultrastructure in embryos after implantation

“…The changes in inner membranal configuration are probably associated with new mitochondria being formed during these stages. Our findings that heart mitochondria in both the monkey and day 10 rat are approximately twice the diameter of mitochondria in other tissues could be the result of vesicle formation and expansion of the outer and inner mitochondrial membrane as part of a more rapid growth and maturation in this organ in preparation for a switch to aerobic oxidation, as shown by histochemical studies of developing rat embryos (Shepard et al, 1968). The oxidative electron transport system located in the mitochondrial inner membrane has been shown to be relatively inactive during the early stages after implantation of rat embryo, whereas it gradually matures after establish-ment of vascular circulation (Mackler et al, 1970(Mackler et al, , 1973.…”

The effect of ethylenethiourea on the developing central nervous system of the rat

“…Specificity of necrosis in bone, which required more energy for the high growth rate during development possibly was caused by death of mesenchymal cells leading to congenital defects in bones of certain areas (Aksu et al, 1958;Shepard et al, 1968). This effect was evident in this experiment, and it seemed that ETU inhibited some ossification of the skeletal structure.…”

“…The riboflavin deficiency was assumed to interfere with certain enzymic reactions required for skeletal differenti ation. Studying in the rat, Shepard et al (1968) explained that the possibility of congenital defects may result from death of mesenchymal cells and neural tissue, which have a particular riboflavin requirement.…”