Tenth Day Of Gestation Research Articles

The regulatory effect of estrogens on fetal growth: I. Placental and fetal body weights

The influence of estrogen on placental and fetal growth was studied. White New Zealand pregnant rabbits were rendered estrogen deficient by a bilateral oophorectomy on the tenth day of gestation and given a daily dose of 5 mg. of progesterone intramuscularly up to the time of delivery. A second group similarly oophorectomized received the same dose of progesterone plus 2 μg estradiol-17β daily. A third group was sham operated and served as controls. Does from each of these groups were delivered at 21, 27, and 31 days of gestation. The total number of fetuses per litter as well as the number and weights of the live-born and their placentas were recorded in each instance. The results showed that in the estrogen-deficient pregnancies there was a significant increase in placental weight and in the placental to live-born weight ratio at all the periods of gestations studied. Live-born weight was also increased in the 27 and 31 day periods. An increase in stillbirth rate occurred in the estrogen-deficient group. It is concluded that estrogens regulate placental (and consequently fetal) size by exerting an inhibitory effect on placental growth. The mechanism by which this may be brought about is discussed.

A light and electron microscopic study of Rathke's pouch in fetal rabbits

Rathke's pouch, the anlage of the adenohypophysis, has been studied in fetal rabbits with the light and electron microscope from its first appearance on the tenth day of gestation until the sixteenth day when secretory granules are observed in some of the cells of the pars distalis portion of the pouch. The pouch is considered undifferentiated from the tenth through fifteenth day since secretory granules were not observed within any of its cells during this period. The secretory granules observed for the first time on the sixteenth day of gestation within cells of the pars distalis closely resemble those found in basophils in the adult rabbit pars distalis. The cytologic development of the partes intermedia and tuberalis is essentially identical to that of the pars distalis from the tenth to fifteenth day of gestation. Rathke's pouch at ten days is a single-layered epithelium composed of a single cell type characterized by a high nuclear-cytoplasmic ratio, irregular contours, and very few organelles except for an abundance of ribosomes. Lipoprotein inclusions are common near the luminal surface from ten to twelve days but diminish thereafter. In specific regions of the pouch large, polymorphic structures are observed located intra- and extra-cellularly. These are tentatively designated “odd bodies.” A striking feature of the pouch at ten and eleven days are large, extracellular spaces across which processes of the pouch cells contact one another. Cell processes also extend between the pouch and adjacent neural tube and notochord. The extracellular spaces gradually diminish from the twelfth to fourteenth day as the number of cells increases. Organelles increase gradually during this period though the cells are still not richly endowed. At fifteen days (the day preceding the appearance of secretory granules and mesenchymal infiltration) the entire cell population of Rathke's pouch undergoes a radical change. The cells appear swollen, electron lucent, and organelles are diminished in quantity. The extracellular spaces are almost completely obliterated. These changes in the cytology at fifteen days are considered a normal prelude to further cyto-differentiation which is evident in the pars distalis at sixteen days and later.

A Histochemical Study of Embryonic Rat Liver in Avitaminosis E

The histological and histochemical differences between the vitamin E-sufficient and -deficient rat livers during teratogenesis were investigated. To obtain abnormal embryos, after mating, female rats of the Holtzman strain that had been maintained with a vitamin E-deficient ration since weaning, were given 2 mg of dl-α-tocopheryl acetate by gavage on the tenth day of gestation. The same dose was given daily during the first 5 days of gestation to the control group to ensure normal embryogenesis. Normal and abnormal embryos were collected daily from day 15 of gestation onward and were prepared by appropriate methods to show histochemically the amount of acid and alkaline phosphatase, cholinesterase, lipase, lipid, lipofuscin, glycogen, mucopolysaccharide and iron. The results revealed that deficient livers often showed massive, central necrosis and an increase in the size of the Kupffer cells. Although cholinesterase, lipase, lipid and glycogen were reduced in the deficient livers, acid and alkaline phosphatase, iron and mucopolysaccharide were increased. The abnormal livers also showed deposition of lipofuscin, especially on the erythrocytes. It was concluded that prenatal vitamin E deficiency affected the normal, chemical development of the embryonic liver.

DEVELOPMENT OF THE RAT PALATE.

AbstractNormal fetuses 13‐to‐21 days of age were obtained from female Long Evans Rats maintained on a stock diet known to produce normal offspring. Cleft palate fetuses were produced from mothers fed the same diet supplemented with 100 mg of pyrimethamine per kg of diet for four days beginning on the tenth day of gestation. The heads were studied with the low‐power microscope and serial histologic sections.In normal fetuses the lateral palatine processe appeared to form the roof of the mouth by two distinct mechanisms. Palatal closure was achieved rostrally by rotation of the lateral palatine processes from a ventromedial to a horizontal position while caudally, it resulted from the fusion of outgrowths from the medial surfaces. The original free ventral edges of the lateral palatine processes in the caudal region largely underwent regression by the seventeenth day. Closure commenced in the anterior third of the palate and proceeded rostrally and caudally.In the fetuses with cleft palate induced by pyrimethamine, the lateral palatine processes were observed in various stages of rotation or transformation depending on the region of the palate examined. The narrow width of these processes suggested that the antimetabolite had suppressed their growth at a critical stage in development. The results suggested certain similarities in the mechanisms of palatal closure in rat and man.

EFFECTS OF MATERNAL FOLIC ACID DEFICIENCY ON CYTOLOGIC PHENOMENA IN THE RAT EMBRYO.

AbstractA purified diet lacking folic acid and containing 20 mg% of the antimetabolite, 9‐methyl pteroylglutamic (folic) acid was fed to female Long‐Evans rats during days eight and nine of pregnancy. Embryos were removed at autopsy on the tenth day of gestation for study and comparison with embryos from normal control pregnancies.Analysis of mitotic counts revealed that 18.6% of the cells in control embryos were in mitosis in contrast to only 5.7% in PGA‐deficient embryos. A disproportionate reduction in anaphase and telophase stages was observed in conjunction with an increased percentage of cell at metaphase. Concomitantly with these mitotic changes a marked reduction in histochemically demonstrable RNA and in numbers of ribosomes as revealed by electron microscopy was observed.

PREVENTION OF SALICYLATE TERATOGENICITY IN IMMOBILIZED RATS BY CERTAIN CENTRAL NERVOUS SYSTEM DEPRESSANTS.

SummaryPrior treatment of pregnant rats with the central nervous system depressants, sodium pentobarbital or chlorpromazine, prevents the augmentation by maternal immobilization of the maternal morbidity and teratogenic action induced by sodium salicylate on the tenth day of gestation. The prevention by either central depressant of the production of congenital malformations in immobilized animals given otherwise non-teratogenic doses of salicylate appears to be mediated through the maternal central nervous system.

Cardiac malformations in rats induced by exposure of the mother to carbon dioxide during pregnancy.

Seventy-one pregnant rats of a Sprague-Dawley strain were exposed for a single 24-hour period to a gas mixture of 6 per cent carbon dioxide, 20 per cent oxygen and 74 per cent nitrogen on different days during gestation. There were 530 offspring and these were compared with 159 newborn rats from 21 control dams. The incidence of cardiac malformations was 23.4 per cent in the test group and 6.8 per cent in the control group with the highest incidence in the test group occurring when the exposure was on the tenth day of gestation. Isolated ventricular septal defects, situated in the lower and posterior part of the muscle septum, were found in 8 cases, ventricular septal defects with overriding aorta in 24 cases and ventricular septal defects with partial transposition in 20 cases. Forty-seven of the abnormal hearts had a myocardial thickening accompanied by narrowing of the pulmonic or aortic outflow channel with or without other abnormalities, such as atresia of the mitral or tricuspid valves and hypoplasia of the aorta or pulmonary artery. There was a slight increase in perinatal mortality in the test group, and a lower frequency of male offspring. The average body weight was 18.9 per cent higher in the test group.