Fifteenth Day Of Gestation Research Articles

In utero development of fetal breathing movements in C57BL6 mice

Fetuses of many species, including humans, breathe during development. This fetal breathing aids in lung development, strengthens respiratory muscles, and is posited to fine-tune the neural circuitry that drives breathing. Previous studies suggested that fetal breathing could begin as early as the fifteenth day of gestation in the mouse, but fetal breathing movements (FBMs) had not been observed in mice in utero. We aimed to determine if and when FBMs commence in mice and if they change over time. We examined unanesthetised pregnant C57BL6 mice with ultrasound beginning on the seventh day of gestation. We first reliably observed episodic FBMs in mice on embryonic day 16. FBMs were sporadic, clustered, or rhythmic, and their frequency increased with age. Ultrasound examination of FBMs in mice has great potential utility in the study of transgenic mouse models to help us understand the prenatal characteristics of breathing related human developmental disorders, including Congenital Central Hypoventilation Syndrome (CCHS) and apnea of prematurity.

Tribulus terrestris improves metronidazole-induced impaired fertility in the male mice.

Fruit extract of Tribulus terrestris (TT) bears aphrodisiac and antioxidative properties. Antimicrobial drug, metronidazole (MTZ) impairs the spermatogenic activity and fertility in males. Validation of the use of fruit extract of TT as a supplement against MTZ-induced fertility impairment in males. Adult Swiss strain male mice were administered with 500mg/kgBW/day of MTZ for 28 days. Low (100mg/kgBW/day) and high (200mg/kgBW/day) doses of TT were administered simultaneously with MTZ (500mg/kgBW/day) for same duration. All males were cohabited with virgin proestrus females. Vaginal plug formation was observed to calculate the libido index. Cohabited females were sacrificed on fifteenth day of gestation to dissect out the ovaries and uteri. Fertility index, quantal pregnancy, pre-implantation and post-implantation losses were calculated. MTZ-treated males showed unaltered mating ability, however, the females impregnated by such males exhibited marked alterations in the fertility index, quantal pregnancy and pre- and post-implantation losses. Supplementation with low dose of TT failed to restore such reproductive toxicities exhibited by administration of MTZ. However, the altered reproductive toxicities were reinstated to control values following supplementation with high dose of TT. The fruit extract of TT may emerge as an effective herbal remedy, correcting the drug-induced fertility impairments in males.

Effect of azithromycin on fetal development in rats

This study was designed to evaluate the potential risks of the Azithromycin administration on fetuses. Therefore pregnant rats were received Azithromycin orally (90 and 180 mg/kg b.wt, daily) from sixth day until the fifteenth day of gestation. At 20th day of gestation female sacrificed; abortion, fetal resorptions, visceral examination, skeletal examination, Oxidative stress markers and histopathological examination for fetuses were recorded. Azithromycin caused abortion, fetal resorptions, growth retardation, hematoma and paralysis of limbs. Also caused cerebral dilatation, microcephaly, perforation of hard palate and hemorrhage around internal organs. By skeletal examination; weak and incomplete ossification were observed in bones .Biochemical studies showed that Azithromycin administration resulted in decreased glutathione reduced but increased malonaldahyde compared to control groups. Fetal kidney revealed degeneration and necrosis in the tubular lining epithelium and fibrosis in between the atrophied renal tubules. This study supports and proofs the potential risks of the azithromycin administration on fetuses. Â

<b>Damage caused by exposure to propofol during gestation of mice

Literature shows that surgical procedure could be necessary at any stage of pregnancy and can cause adverse effects on the mother and fetus. One of the most used anesthetics in surgical centers is propofol however; the safety during pregnancy has not been completely established. The objective of this study was to investigate the possible toxic and teratogenic effects on the intrauterine and post-natal development of mice exposed to the dose of 15 mg kg-1 propofol on the caudal vein fifth, tenth and fifteenth day of gestation. A significant reduction in weight gain was observed in female mice who received a 15 mg kg-1 dose of propofol on the fifth gestational day. A higher rate of embryonic loss post implantation and resorption was also observed in this group. In regards to physical development, the anesthetic increased significantly the offspring weight gain, the time in which pinna detachment occurred, and the anogenital distance of pups whose females received propofol on the fifteenth day of gestation. Based on these results, we concluded that administration of propofol in the beginning stages of gestation increases the number of abortions and promotes alterations in the physical development of pups whose mothers were anesthetized in the final stages of gestation.

Identification and developmental regulation of a neuron-specific subunit of cytoplasmic dynein.

Cytoplasmic dynein is the microtubule minus-end-directed motor for the retrograde axonal transport of membranous organelles. Because of its similarity to the intermediate chains of flagellar dynein, the 74-kDa intermediate chain (IC74) subunit of dynein is thought to be involved in binding dynein to its membranous organelle cargo. Previously, we identified six isoforms of the IC74 cytoplasmic dynein subunit in the brain. We further demonstrated that cultured glia and neurons expressed different dynein IC74 isoforms and phospho-isoforms. Two isoforms were observed when dynein from glia was analyzed. When dynein from cultured neurons was analyzed, six IC74 isoforms were observed, although the relative amounts of the dynein isoforms from cultured neurons differed from those found in dynein from brain. To better understand the role of the neuronal IC74 isoforms and identify neuron-specific IC74 dynein subunits, the expression of the IC74 protein isoforms and mRNAs of various tissues were compared. As a result of this comparison, the identity of each of the isoform spots observed on two-dimensional gels was correlated with the products of each of the IC74 mRNAs. We also found that between the fifteenth day of gestation (E15) and the fifth day after birth (P5), the relative expression of the IC74 protein isoforms changes, demonstrating that the expression of IC74 isoforms is developmentally regulated in brain. During this time period, there is relatively little change in the abundance of the various IC74 mRNAs. The E15 to P5 time period is one of rapid process extension and initial pattern formation in the rat brain. This result indicates that the changes in neuronal IC74 isoforms coincide with neuronal differentiation, in particular the extension of processes. This suggests a role for the neuronal IC74 isoforms in the establishment or regulation of retrograde axonal transport.

Mitral cell differentiation and synaptogenesis of rat presumptive olfactory bulb in organ culture.

The ultrastructure of differentiating rat presumptive olfactory bulb in organ culture was investigated with particular reference to mitral cell differentiation and formation of synapses. The presumptive olfactory bulb and olfactory mucosa were dissected en bloc from rat embryos on the fifteenth day of gestation and cultured for 7 days, after which the explants were examined by electron microscopy. The presumptive olfactory bulb had differentiated into a laminated structure with layers corresponding to the glomerular, external plexiform and mitral cell layers. Mitral-like cells were identified by their location and large cell size. Ultrastructural observations indicated that they were relatively well-differentiated. Their dendrites extended into the glomerular layer in which they were postsynaptic to incoming olfactory axons. The distal part of these dendrites frequently contained coated vesicles. Both asymmetrical and symmetrical synapses were found. The symmetrical synapses involved dendrodendritic contacts between periglomerular cells. Synapses in reciprocal arrangements were not observed in the organ cultures.

Assessment of the teratogenic potential of plasma-soluble extracts of diethylhexyl phthalate plasticized polyvinyl chloride plastics in rats

Plasma extracts of two polyvinyl chloride (PVC) plastics (designated PL-130 and PL-146) containing diethylhexyl phthalate (DEHP) as a plasticizer and used in the manufacture of parenteral fluid storage bags were administered iv to pregnant rats daily from the sixth through fifteenth day of gestation. Two groups of rats received PL-130 extracts in doses equivalent to 1.3 and 4.7 mg DEHP/kg per day, and two groups received PL-146 extracts in doses equivalent to 1.4 and 5.3 mg DEHP/kg per day. The higher doses are similar to those predicted to be received by a 60-kg human undergoing an exchange transfusion of 21-day-old blood. A control group of rats received the plasma vehicle only. No differences were seen in the growth rates or behavior of the control and treated groups. There were no significant effects on fetal weights, or on crown-rump and transumbilical distances in offspring. The number of live and resorbed fetuses was not significantly different in control and treated groups. The incidence of gross external, skeletal, and visceral defects among offspring was similar in all groups, and there was no statistically significant difference between control and treated groups. It is concluded that plasma extracts of PL-130 and PL-146 were not teratogenic when administered iv to pregnant rats during the critical period of organogenesis.

Hemorrhagic necrosis of the central nervous system of fetal hamsters: litter incidence and age-related pathological changes.

The occurrence, anatomic distribution, and character of lesions of spontaneous hemorrhagic necrosis (SHN) are reported in each hamster fetus of two affected litters examined on the fifteenth day of gestation and in selected individuals of other affected litters on the twelfth, thirteenth, and fourteenth days of gestation. The pathologic process seems primarily to affect the capillary vasculature of the central nervous system and shows a predilection for rapidly growing and differentiating regions of the fetal forebrain, thalamus, and brain stem. Lesions demonstrable in members of affected litters of susceptible stocks are of a progressive character, increasing both in severity and topographic extend with increasing fetal age and growth. Spontaneous patterns of regression and recurrence of SHN disease in susceptible stocks may reflect variable physiologic factors in the intrauterine environment.

Ultrastructural observations on the maturation of the placental labyrinth of the golden hamster (days 10 to 16 of gestation).

Morphogenesis of the labyrinthine part of the chorioallantoic placenta of the golden hamster between day 10 of gestation and term (day 16) was studied by light and electron microscopy. During this period the labyrinth increases greatly in both size and complexity. Trabeculae of the labyrinth, thin partitions composed of trophoblastic tissue and fetal capillaries which delimit the maternal blood spaces, apparently proliferate both by appositional and interstitial growth. From the time of its formation (day 9 of gestation) until term the labyrinth is hemotrichorial in organization (i.e. three layers of trophoblast separate maternal blood from fetal capillaries). Both the inner and intermediate layers of trophoblast (layers III and II, respectively) are syncytial. The outer trophoblastic layer (III), which is in direct contact with maternal blood, remains cellular, although many of its component cells grow to giant cell dimensions ("labyrinthine giant cells"). Between the tenth and fourteenth days of gestation the anatomical barrier to diffusion between maternal and fetal blood is progressively reduced. This is accomplished both by gradual attenuation of the trophoblastic layers and fetal capillary endothelium and by the formation of discontinuities (gaps) in layer I, and diaphragmed fenestrae in fetal capillary endothelium. The labyrinthine placental barrier is fully developed and probably attains maximal functional efficiency by the fourteenth day of gestation. Late in the fifteenth day of gestation, a few hours before parturition, distinct degenerative changes are apparent in the trophoblastic layers and fetal capillaries of the trabeculae. The factors responsible for initiation these degenerative changes and the onset of parturition are still controversial.

Mitral cell development in the mouse olfactory bulb: reorientation of the perikaryon and maturation of the axon initial segment.

AbstractThe proximal portion of mitral cell axons was examined in electron microscopic serial sections and Golgi impregnations of mouse embryos on the fifteenth day of gestation (E15), E16, postnatal day one (P1), and P4. During this time the cell body of developing mitral cells appears to transform from tangential to radial orientation and then migrate peripherally while the tangential axon remains relatively fixed. In E15, E16 and P1 animals, electron microscopy of most radial mitral cells reveals that the microtubules of the axon proper are continued as a bundle of approximately the same diameter through the voluminous subnuclear cytoplasm to one side of the nucleus. The rest of the subnuclear cytoplasm is nearly devoid of microtubules and contains only free ribosomes and an occasional mitochondrion. It is suggested that the position of the axon is determined within the perikaryon by a bundle of microtubules; the nucleus and rest of the subnuclear cytoplasm then migrates peripherally leaving only a relatively thin axon. If some of the perikaryal cytoplasm failed to migrate peripherally, a bleb or process might be left, as in fact has been observed in Golgi impregnations and electron microscopy. We have also examined the ultrastructure of the developing axon initial segment, in cross‐sections of the axons from E15 to P4, as well as in longitudinal serial sections. Fascicles of closely apposed microtubules have been noted in some advanced mitral cells at E15 and E16, and by P1 such fascicles are common and well developed in most mitral cells. In P1 animals some mitral cell initial segments show a faint and patchy dense undercoating of the axolemma, but many axons at this time appear to completely lack this feature. By P4 nearly all initial segments show a fairly well developed dense undercoating. In general, therefore, the development of fascicles of closely apposed microtubules precedes the elaboration of the dense undercoating of the axolemma.

Incorporation of leucine-14C into proteins of the placenta and liver of mice

Incorporation in vivo of leucine-14C into proteins of the placenta and maternal liver of mice is highest on the fifteenth day of gestation. The two tissues show significant differences in labeling of proteins as a function of time after the amino acid administration. The pattern of leucine incorporation into hepatic proteins of gravid and nongravid mice is different.

Characterization and Genetic Studies of Microcytic Anemia in House Mouse

Abstract Microcytic anemia, inherited as a unit autosomal recessive, is the first of the twelve known single-gene induced hereditary anemias of the mouse which results entirely from alteration of individual erythrocytes rather than from reduction in number of red cells. At all ages where mk/mk individuals could be recognized, from the fifteenth day of gestation to adulthood, the erythrocyte count of mk/mk individuals was at least as high as that of normal counterparts. At all ages, the hemoglobin concentration in these small erythrocytes was also reduced, so that the total available hemoglobin was markedly reduced at all ages. The higher than normal numbers of erythrocytes in adult microcytic mice demonstrate that the cell-producing mechanisms operate efficiently. Genetic tests have shown that the mk single-gene defect has no relation to structure of either the α-chain or the β-chain of the hemoglobin molecule. The mk microcytosis and hypochromia must then result from a metabolic or structural defect independent both of the factors responsible for regulating red cell number and of those controlling hemoglobin structure. This mk/mk microcytic anemia shows some similarities to human thalassemias: hypochromia, microcytosis and presence of target cells, combined with splenomegaly, reticulocytosis, and higher than normal erythrocyte counts (like thalassemia minor). As in thalassemia, hemoglobin structure is normal, although the amount per cell is subnormal. Human hemolytic anemias also share some of these characteristics. The similarities of mk/mk microcytic anemia of the mouse to certain human anemias are sufficient to warrant its further investigation as an animal model for understanding of human hereditary disease.

Erythroid cell development in fetal mice: Stabilization of the hemoglobin synthetic capacity

Previous experiments on the total hepatic erythroid cell population during embryogenesis have demonstrated a shift from an unstable hemoglobin synthetic apparatus to a stabilized mechanism, relatively insensitive to inhibition by actinomycin of RNA synthesis, which occurs between the twelfth and thirteenth gestational days. The present studies examine this phenomenon at the cellular level, by means of quantitative radioautography of cells of each of the maturational stages of erythropoiesis during the unstable and the stabilized phases of hemoglobin synthesis. On fetal day 12, the uptake of leucine and iron by erythroblasts of all stages during maturation is uniformly suppressed by actinomycin. By the fifteenth day of gestation both polychromatophilic and orthochromatic erythroblasts have become resistant, and basophilic erythroblasts partially resistant, to the inhibitory effects of this antibiotic. In all other respects examined, including light and electron microscopic morphology, mitotic activity, RNA and protein synthesis, and sensitivity to the inhibition of RNA synthesis by actinomycin, the homologous cells on days 12 and 15 appear entirely comparable. These observations indicate that stabilization of the capacity for hemoglobin synthesis affects all stages of the erythroid cell series actively synthesizing hemoglobin. The data are incompatible with the hypothesis that stabilization of hemoglobin synthesis reflects the accumulation of larger numbers of more mature erythroblasts during embryonic development. The rate of hemoglobin synthesis is a maximum in polychromatophilic erythroblasts and this rate does not depend upon stabilization of the synthetic apparatus. Proerythroblasts appear predominantly engaged in the production of none-heme proteins, which are synthesized by an unstable mechanism at both gestational days. Stabilization of the capacity for hemoglobin synthesis most likely involves a decreased requirement for rate-limiting species of RNA. Factors in the fetal environment may be implicated in the development of a stable hemoglobin-synthetic apparatus.

Erythroid cell development in fetal mice: Ultrastructural characteristics and hemoglobin synthesis

Erythroid cell development in fetal mice, with a total gestation period of 20 to 21 days, occurs, initially, in yolk sac blood islands (8 to 12 days) and, subsequently, in liver (12 to at least 16 days). Erythropoiesis from the eleventh through the fifteenth day of gestation of C57BL/6 J fetal mice was characterized by studies of the ultrastructure and determinations of the types of hemoglobin synthesized by circulating erythroid cells and liver erythroid cells. The circulating nucleated and non-nucleated erythroid cells were separated by centrifugation through silicone fluids. The ultrastructure of the cells was examined by electron microscopy. Hemoglobin types were characterized by electrophoresis in polyacrylamide gel. It is shown that as development of erythroid cells derived from yolk sac blood islands proceeds, the cytoplasmic ribosomes are lost, though the nucleus is retained. At 11 days of gestation these cells actively synthesize hemoglobin, which is predominantly of embryonic types. The capacity to synthesize embryonic hemoglobins is lost as the cytoplasmic ribosomes disappear, which occurs by the fourteenth to fifthteenth day of gestation. By contrast, the development of erythroid cells derived from the liver is characterized by the loss of the nucleus at a stage when the cells retain ribosomes and the capacity to form hemoglobin. The nucleated and non-nucleated erythroid cells derived from hepatic sites of erythropoiesis synthesize predominantly adult-type hemoglobin.

Development of cleft palate induced by 6-aminonicotinamide late in rat gestation.

AbstractSingle injections (8 mg/kg maternal body weight) of the niacin antimetabolite 6‐aminonicotinamide (6‐AN) given to rats on the morning of the fifteenth day of gestation resulted in 100% palatal abnormalities within 24 to 48 hours. Fasting rats for a period of seven or eight days, more than simulating the weight loss observed in 6‐AN treated animals, resulted in young without palatal abnormalities. Simultaneous injection of an equal dosage of nicotinamide prevented the maternal and embryonic effects of the antimetabolite. Intralitter variability in normal palatal closure, similar to the interlitter variation, was observed in embryos of the same chronological age.Retardation in palatal shelf movement appeared to be the initial underlying morphological mechanism giving rise to the abnormal palates. Twenty‐four hours after 6‐AN injection embryonic and placental weights were significantly reduced; the incidence of full open palate was double that observed in untreated rats. Forty‐eight hours following treatment palatal shelves had moved to the horizontal position dorsal to the tongue; failure of fusion was apparent. Further alterations in the morphogenesis of the abnormal palates were secondary to partial or complete failure of shelf fusion, complicated by a dorsally protruding tongue and underdeveloped mandible.The sensitivity of palatal closure between days 15 to 17 of gestation and the rapidity with which shelf movement can be delayed and modified by metabolic procedure in the rat is noteworthy.

THE INFLUENCE OF TEMPERATURE ON SKELETAL MATURATION OF HYPOTHYROID RATS.

AbstractThe rate of skeletal maturation as indicated by ossification of bony elements of the central and appendicular skeleton was compared in two groups of hypothyroid young rats, raised at 20°C and 30°C constant environment respectively.Hypothyroidism was induced by feeding 0.2% propylthiouracil mixed with the food in powdered form to pregnant rats starting on the fifteenth day of gestation and continuing this treatment to the suckling mother until their litters had reached weaning age.The appearance of epiphyseal centers, of carpal and tarsal centers, middle phalanges and femoral and tibial processes and caudal vertebrae 7–27 is delayed in hypothyroid newborn rats over that of normal controls. Hypothyroid rats raised at 20°C lag more severely behind the controls with respect to skeletal maturation, than do hypothyroid rats raised at 30°C. The latter are intermediate or in some instances their rate of skeletal maturation resembles that of the control group.The possible significance of the demonstration of diminished requirements for thyroid hormone by the developing rat for studies attempting to identify mechanisms of hormone action in development is briefly discussed.

Passage of thyroid hormone across the placenta in intact and hypophysectomized rats.

AbstractThe studies were designed to determine whether thyroid hormone traverses the placenta of the rat.1. Pregnant rats were hypophysectomized on the twelfth day of the gestation period. The histological appearance and wet weights of the fetal thyroids at term were determined and found to be the same as that of fetuses of intact mothers. These results indicate that maternal TSH is not required for maturation of the fetal thyroid.2. Intact and hypophysectomized pregnant rats were provided with a diet supplemented with 0.2% propylthiouracil (PTU) added in powdered form starting on the fifteenth day of gestation until term. This treatment led to enlargement of thyroids of fetuses of intact and hypophysectomized mothers.3. Groups of intact and hypophysectomized pregnant rats given the same goitrogenic treatment as group 2 were injected daily with 100, 50, 25 and 12.5 μg of 1‐thyroxin in suspension. Twenty‐five μg of thyroxin were sufficient to inhibit goiter development in fetuses of hypophysectomized rats, while 50 μg was required to prevent the goiter formation in fetuses obtained from intact non‐hypophysectomized pregnant rats.These results suggest that maternal thyroid hormone passes the placenta from mother to fetus. The effectiveness with which thyroid hormone passes from the mother to the fetal circulation is probably influenced in some way by the maternal pituitary.

A comparison of the effects of hormone and of insulin administration.

AS A result of studies on protein metabolism in pregnant rats (Beaton et al., 1954), we became interested in possible hormonal factors which might bring about the metabolic alterations seen after the fifteenth day of gestation. Another paper (Beaton et al., 1955) has described the similarity between the changes seen in pregnancy and those produced by the administration of growth hormone to nonpregnant rats. It is well known that insulin administration results in an increased food intake and consequent body weight gain. It has been proposed (Salter and Best, 1953; Lawrence, Salter and Best, 1954) that insulin may have a growth hormone-like activity or that the two hormones may be closely interrelated. If this concept about insulin is correct, insulin might be the hormone responsible for the metabolic alterations evident in the pregnant rat.