Various Stages Of Gestation Research Articles

Experimental Transplacental Transmission of St. Louis Encephalitis Virus in Mice

Transplacental infection of the mouse embryo with St. Louis encephalitis (SLE) virus was produced by injecting the mother with virus at various stages of gestation. Intravenous or subcutaneous injection of the mother with 10(5.9) suckling mouse median lethal dose (SMLD(50)) of SLE virus was found to infect 83 to 96% of the embryos when given at 4 days of gestation or later. Injections at 6 days of gestation or earlier had little effect on the embryo although virus could be recovered at 10 days of gestation when injected at 4 days of gestation, whereas injections at 7 days or later resulted in a high mortality at birth and during the first week of life. Embryos from females injected at 7 to 9 days of gestation were found to have become infected when necropsied 3 days after injection, but no virus could be isolated from the young of similarly infected mothers at birth. A large number of these young died at birth, and some were observed with signs of anoxia and incoordination. Young of mothers injected later in pregnancy usually lived for a few hours to a few days and were then observed to die with signs of encephalitis. Virus was routinely isolated from these mice.

Correlations between human chorionic somato-mammotrophin (lactogen), immunoreactive insulin, glucose and lipid fractions in plasma of pregnant women.

SummaryThe authors have assayed in 81 pregnancies, at various stages of gestation, the fasting values of plasma lipids, non‐esterified fatty acids, triglycerides, cholesterol, phospholipids, glucose and immunoreactive insulin, and have compared the findings with the values of immuno‐reactive human chorionic somato‐mammotropin assayed in the same women and in a further 31 pregnancies.On the bases of the results obtained and the biological activity of HCS, the importance of this hormonal peptide in the determination of the modifications of the metabolism of glucose and lipids is confirmed. The biological activities of HCS have also been compared with those of other hormonal factors which undergo particular increases in pregnancy (thyrotrophic, adrenocorticotrophic hormones and chorionic gonadotrophin). The pathogenesis of alterations in the glucoselipids metabolism of the pregnant women have been interpreted in the light of the glucose‐fatty‐acid cycle of Randle.

Some physiologic effects of protein ingestion in pregnancy

Plasma insulin and growth hormone concentrations were measured in healthy females during the various stages of gestation following the ingestion of a protein meal. Decreased insulin and glucose responses were found after oral protein ingestion and were similar to the values obtained in pregnancy following the intravenous administration of amino acids. Plasma growth hormone responses were greater than normal during the first 28 weeks of gestation, but were blunted thereafter. Thus, the ingestion of protein during pregnancy is followed by increments in insulin and growth hormone not unlike those found following an arginine infusion in pregnancy. The responses are, however, different from those found in the nonpregnant state.

The cytology of hofbauer cells

AbstractCytological investigation of Hofbauer cells in various stages of gestation reveals that they are similar to normal macrophages except for unusually large cytoplasmic flanges and included vacuoles. The system of vacuoles is apparently the result of macropinocytotic activity. The individual vacuoles undergo asymmetrical collapse in regions adjacent to small juxtavacuolar tubules thought to be derived from the agranular endoplasmic reticulum. In addition, coated micropinocytotic vesicles are common. Hofbauer cells thus appear to be a type of macrophage with an unusual capacity for fluid ingestion. In younger placentas, Hofbauer cells are usually associated with extracellular compartments within the stroma. These compartments are relatively free of collagen fibrils and demonstrable ground substance and are clearly demarcated from the rest of the stroma by processes of fibroblasts. The abundance of these cells in early placentas, their location in the stroma, and evidence of their pinocytotic activity suggest that these cells may play a role in removal of proteins from interstitial fluid. Hofbauer‐like cells were also studied in the guinea pig and the little brown bat. Of these two species, the Hofbauer‐like cells of the bat more closely resemble human Hofbauer cells in that they show evidence of extensive macropinocytotic activity.

Behavior of iron-, indium-, and iodine-labeled transferrin.

SummaryFetal and placental uptakes after administration of 59Fe-, 113mIn-, and 125I-transferrins at various stages of gestation in the rat have been studied. In the latter third of pregnancy 50Fe went to the fetus in large amounts, but, in contrast, 113mIn accumulated in the placenta. Only small quantities of 125I-transferrin reached the fetus, and considerably less 125I than 113mIn was found in placenta. It is concluded that transferrin does not carry iron across the placenta and that indium is removed from transferrin by the placenta, but does not cross to the fetus.

Studies on the metabolism of steroid hormones and their precursors by the human placenta at various stages of gestation. III. In vitro metabolism of 3β, 17α-dihydroxypregn-5-ene-20-one

The metabolism of 17α-hydroxypregnenolone by human placentae obtained during early pregnancy was studied by the incubation of 7α- 3H-17α-hydroxypregnenolone with brei of human placentae and extraction and analysis of the resulting radiolabeled metabolites by reverse isotope dilution methods. Major metabolites, isolated and definitively identified include 17α-hydroxyprogesterone, 6β,17α-dihydroxyprogesterone, and 17α, 20α-dihydroxy-pregn-4-ene-3-one. A small quantity of a compound identified as Δ 16-pregnenolone was isolated from one of the incubates, a transformation which has not been previously reported for human placental tissue. C 17–20 desmolase activity, as reflected by conversion of the substrate to C 19- and/or C 18-steroid metabolites, was found to be almost or completely absent in the placentae studies. These findings are in agreement with the previously reported paucity of C 17–20 desmolase activity in mid-term and term human placentae.

The embryonic tRNA methylase reaction

tRNA methylase obtained from embryonic tissue of gestational age of 8 to 10 days methylates tRNA obtained from more mature embryonic or adult tissue, whereas it does not show significant activities with respect to homologous tRNA. The gel electrophoretic pattern of tRNA obtained from adult liver tRNA following incubation with early embryonic tRNA methylase resembled more closely the pattern obtained for early embryonic tRNA. It is suggested that methylation of tRNA during embryogenesis may play a regulatory role in the process of translation, and therefore, differentiation. The methylation of tRNA in the presence of tRNA methylase and S-adenosyl-methionine was first delineated by Fleissner and Borek in 1962 (1). Since then, studies have demonstrated the universality of this reaction in a variety of bilogical systems and tended to support the possible regulatory function of this pathway. Evidence from several laboratories suggested that the level of tRNA methylase activity was a function of age in mamamlian systems (2,3). Structural changes occurring in the tRNA molecule as a consequence of methylation are: (a) enhanced base pairing, (b) decreased secondary structure, (c) methylation of the 2′-hydroxyl of ribose, and (d) changes in the configuration of the tRNA molecule as a consequence of interaction of a methylated base with neighboring bases on the same chain (4). Functional changes in tRNA as a consequence of methylation have been reported. Peterkofsky and co-workers (5) demonstrated that the degree of methylation of E. colis tRNA is directly related to its ability to be amino acylated in the presence of yeast leucyl-tRNA synthetase. In addition, Shugart and co-workers (6) indicated that the extent to which tRNA may be amino acylated is, in part, proportional to the extent of methylation of this molecule. Borek (7) and others (8) have suggested a relationship between the methylation of nucleic acids to the processes of carcinogenesis and differentiation. These investigations indicated that the level of tRNA methylase in tumor cells is much higher than that in normal counterparts. The present report deals with an investigation of tRNA methylase activity during various stages of gestation in embryonic mouse tissue.

Levels of lysozyme in human foetuses and newborns.

RECENT studies have shown that immunoglobulins and components of complement start to be synthesized by the human foetus during the second half of gestation1–3. In spite of the significance of lysozyme in the processes of resistance to infections, there are no data on its development in the human foetus and newborns4. In this article, we report the results of estimating the level of lysozyme in pairs of maternal and newborn sera and in sera from foetuses at various stages of gestation.

Selenium distribution and radiotocopherol metabolism in the pregnant ewe and fetal lamb.

Selenium concentrations were determined at various stages of gestation in the bodies and fetal tissues of 26 ewes fed a nutritional muscular dystrophy (NMD) producing hay for 2 years. Eight of these ewes were injected intramuscularly with 6 mg selenium 10 days before slaughter. Maternal tissues in general contained more selenium than the corresponding fetal tissues. As might be expected, the injection of selenium enhanced tissue concentrations in both ewes and fetuses. The pattern of selenium concentration in the various tissues was similar in dams and fetuses, with kidneys containing highest amounts. Selenium concentrations in the tissues of both ewes and fetuses did not appear to change with the stage of gestation. A single oral dose of radiotocopherol was administered to each of 10 pregnant ewes which had been fed an NMD-inducing hay for 2 years. Animals were slaughtered at 1, 2, 5, and 13 days after the oral dose of vitamin E. It was found that in the ewes, liver and adrenal tissues had a high rate of tocopherol uptake in the first 24 h. Subsequently, the radioactivity fell sharply with time, whereas in heart, muscle, kidney, and lung tissues, in which the initial uptake was lower, the decrease with time was slower. Relative specific activities between maternal and corresponding fetal tissues tended to decrease with time. The ewes excreted more than 70% of the administered radiotocopherol dose within 4 days, primarily via the feces; urinary excretion was comparatively small.

Fetal maturity and amniotic fluid analysis

The analysis of constituents of the amniotic fluid with the objective of determining fetal maturity has been of increasing interest. Reported herein are the results of our attempts to establish normal values for amniotic fluid creatinine, bilirubin, and cytologic features at various stages of gestation, and then, using these values, to judge the accuracy with which they predicted approximate delivery dates and fetal weights in a series of pregnancies of unknown duration. In general, we have found that amniotic fluid cytologic features and creatinine levels allow us to predict with good accuracy the presence of an infant of at least 2,500 grams and/or a gestational age of 35 weeks. We have been even more struck, however, with the possible insight into intrauterine physiology that may come with greater understanding of the phenomena reported here.

Studies on the metabolism of steroid hormones and their precursors by the human placenta at various stages of gestation. II. In vitro metabolism of 3 beta-hydroxyandrost-5-en-17-one.

ABSTRACT The in vitro metabolism of 3β-hydroxyandrost-5-en-17-one (dehydroepiandrosterone) by human placentae of various gestational ages was studied by incubation of 7α-3H-dehydroepiandrosterone with a total of 39 samples of placentae obtained at from 4 to 24 weeks of gestation, and extraction and identification of the resulting radiolabeled metabolites by reverse isotope dilution techniques. Metabolites obtained under the in vitro conditions employed include estra-1,3,5(10)-trien-3,17β-diol, 3-hydroxyestra-1,3,5(10)-trien-17-one, 2,3-dihydroxyestra-1,3,5(10)-trien-17-one, androst-4-ene-3,17-dione, 17β-hydroxyandrost-4-en-3-one, 5α-androstane-3,17-dione, 5α-androstane-3β,17β-diol, androst-5-ene-3β,17β-diol, 30-hydroxy-5α-androstan-17-one, and unaltered dehydroepiandrosterone. When the relative capacities of the various placental samples to carry out the observed metabolic transformations of the steroid substrate under the in vitro conditions employed are compared, it is seen that the differences in the r...

Changes in the cardiac output and uterine blood flow of the pregnant Macaca mulatta

Progressive changes in the cardiovascular system were studied in a group of rhesus monkeys at various stages of gestation. On the basis of body weight, cardiac output increased 11 per cent and oxygen consumption 13 per cent during pregnancy. From 91 to 114 days' gestation, the uterine blood flow and oxygen consumption fell 6 per cent and 13 per cent, respectively, in relation to the weight of the pregnant uterus and its contents. Thereafter both blood flow and oxygen consumption were maintained at nearly steady levels until term. In midpregnancy the uterine-placental blood flow represented 2.6 per cent of left ventricular output while near term it was 8.6 per cent. No evidence of untoward effects of high oxygen tensions was observed in this study.

Cytological localization of insulin and insulin concentration in the fetal ovine pancreas.

Experiments were conducted to determine when insulin was first detectable in the pancreas of the ovine fetus, how these insulin concentrations change throughout gestation, and the cytological localization of those areas of the fetal pancreas which contain insulin. Fetal ovine pancreas at various stages of gestation was examined histologically using aldehyde fuchsin stain for beta granules and fluorescent antibody methods for insulin. Acidethanol extracts of fetal pancreas were assayed for insulin using a radioimmunological assay. Data obtained from aldehyde fuchsin staining indicated that beta granules were evident in pancreatic beta cells by 65–70 days of gestation. Fluorescent antibody methods indicated insulin was present in cells of Laguesse and islets of Laguesse at 40 days of gestation. Assays of pancreatic extracts for insulin demonstrated appreciable concentrations at 69 days of gestation and pancreatic insulin concentrations increased rapidly from 100 days of gestation until term. (Endocrinology ...

Studies on the metabolism of steroid hormones and their precursors by the human placenta at various stages of gestation. I. In vitro metabolism of 1,3,5(10)-estratriene-3,17-beta-diol.

ABSTRACT The in vitro metabolism of 1,3,5 (10)-estratriene-3,17β-diol (estradiol-17β) by human placental tissue at various stages of gestation was studied by incubation of 4-14C-estradiol-17β with samples of placentae obtained at from 4 to 16 weeks of gestation, followed by extraction and analysis of the resulting radioactive metabolites. The majority (92–99%) of the isolated radioactivity consisted of nonconjugated or free steroids. The principal steroids isolated and identified were 1,3,5 (10)-estratriene-3-ol-17-one (estrone), 1,3,5 (10)-estratriene-2,3-diol- 17-one (2-hydroxyestrone) and unaltered estradiol-17β. Thus, the metabolism of estradiol-17β by the human placenta during early pregnancy consists primarily of 2-hydroxylation and oxidation of the 17β-hydroxyl function. The extent to which estradiol-17β was oxidized to metabolites containing a 17-keto function increased from 4.1% conversion per g of tissue per hr of incubation at 4–5 weeks of gestation to 30.4% per g per hr at 16 weeks of gestatio...

Estimation of fetal maturity by cytologic examination of amniotic fluid

The cellular content of amniotic fluid is primarily composed of desquamated fetal cells of two origins, squamous and sebaceous, readily differentiated by staining with Nile blue sulfate. The squamous cells are histologically distinctive and stain light blue with dark blue nuclei. A smaller number of lipid-containing cells, shed from sebaceous glands, are different in structure and stain orange to pink in color. The percentage of such “fat cells” in the amniotic fluid, reflecting progressive development of sebaceous glands, increases with advancing gestational age. Three hundred and fifty specimens of amniotic fluid were obtained at various stages of gestation, stained for fat, and a differential cell count performed. There was a reliable logarithmic augmentation of fat cells with increasing fetal age and development. When their count was less than 2 per cent, the prematurity rate was 85 per cent. When the fat cell count exceeded 20 per cent, all infants weighed over 2,500 grams and had a gestational age of 36 weeks or more. When the need to determine fetal age exists, particularly if there is either an unreliable menstrual history or controversial physical findings, this means of its estimation is as reliable as other presently used methods, including radiography.

Urinary steroid profile as an index of fetal well-being

A study of the steroid metabolism of the fetoplacental unit in the human as reflected in the simultaneous analyses of total estrogens, pregnanetriol, pregnanediol, and pregnanolone in the same urine sample is presented. The study incorporates an automated assay for total estrogens and gas-liquid chromatography of the pregnane metabolites. The use of these highly sensitive and specific analytical tools allowed us to establish the pattern of excretion of the aforementioned compounds in a total of 170 normal and abnormal pregnancies in various stages of gestation. A total of 2,704 determinations were carried out in 14 months. One hundred and seven patients were considered normal, and the results from this group graphically presented gave the basis for “Fetal Health Survey” criteria of normalcy. Some of the results of the abnormal group, clinically classified, are discussed in terms of the normal pattern of excretion.

Proteolytic enzyme systems in developing rat tissues.

Summary. The developmental progression of two endopeptidases, four exopeptidases, trypsin inhibitors and chymotrypsin inhibitors in rat embryos from fertilization to the fully formed foetus and beyond has been evaluated. Biochemical and histochemical procedures using the same chromogenic substrates were applied to study uteri at various stages of gestation, embryos from the 11 th day of gestation to term, and kidney, liver and spleen from the 18th day of gestation to the adult stage. Activities were found to be lower in isolated embryos than in pregnant uteri but rates of increase were comparable except in the case of cystinedi-β-naphthylamidase which showed a greater rate of increase in uteri. Enzyme activities in liver, kidney and spleen were relatively high during the late stages of gestation, decreased at birth and increased again in postnatal tissues. The rate of change as well as the absolute values differed for each enzyme as well as for each tissue. There is evidence that soluble enzymes assayed by biochemical techniques are synthesized before particle-bound enzymes measured by histochemical techniques. Electrophoretic mobility, metal ion requirements and enzyme localization indicate that several closely related but distinct enzymes take part in foetal development.

The relation of fetal age to the character of lesions in fetal lambs infected with Brucella ovis.

Cultures of Brucella ovis were inoculated into the conceptus of ewes at various stages of gestation, and the fetal lambs were recovered from 10 to 81 days later. All lambs, the youngest of which was recovered on the 54th day of gestation, had lesions. The character of the lesions varied from that of reticuloendothelial hyperplasia and granulomatous inflammation in fetuses up to 91 days of gestation to that of a lymphoreticular nature with well-formed nodules of reticuloendothelial cells, lymphocytes, and plasma cells in older fetal lambs. It was suggested that the variation in the inflammatory response was attributable to the immaturity of the fetal immunologic system.

Immunoglobulin Production by Embryonic Tissues: Thymus Independent

Previous reports (1,2) have shown that cells capable of producing immunoglobulins are present in the liver of the mouse embryo by the fourteenth day of gestation. When transferred to lethally irradiated hosts, these lymphoid precursors, while dependent upon intact thymic function for their ability to produce detectable specific antibody in response to antigenic stimulation were able to synthesize immunoglobulins in the absence of the thymus. These findings suggested that while the thymus may promote the ability of these lymphoid precursors to form specific antibody, immunoglobulin synthesis per se is independent of the thymus. The initial experiments, however, did not rule out the possibility that the transferred cells may in fact have been post-thymic cells with previously determined antigenic commitment. That is, the immunoglobulins produced by these cells could have been antibodies to antigens contacted shortly after transfer. In this report it will be shown that cells which have the potential to produce immunoglobulins in thymectomized irradiated hosts are present in the yolk sac, placenta, and liver of the mouse embryo prior to the appearance of the thymus. Materials and Methods. Pregnancies were surgically interrupted at various stages of gestation. The embryos and extra-embryonic tissues were dissected free of maternal tissue; they then were washed twice in cold TC 199 (Difco) in an effort to eliminate the possibility of contamination of the extra-embryonic tissues by maternal blood. Identical organs or tissues from a single pregnancy (5-9 embryos) were pooled in cold TC 199 and the cells were gently dissociated by mincing and aspiration through a 20-gauge needle. The age of the gestation was based on the following criteria: 7-8 days, a well developed ectoplacental cone and early membrane formation; 9 days, a well-developed yolk sac, a conspicuous heart, and no liver pigment; 10 days, early pigmentation in the liver; 11-12 days, a well-pigmented liver and the absence of the thymus.

Organophosphorus cholinesterase inhibitors and fetal development

Albino rats at various stages of gestation were treated with isofluorophate, parathion, and methyl parathion. A reduction in fetal cerebral cortical cholinesterase activity was observed consistently indicating transplacental passage of the lipoid soluble phosphorothioates used in this study. Large subcutaneous hematomas were found in several offspring of the parathion- and methyl parathion-treated groups but no significant developmental defects were observed. High stillbirth and neonatal death rates occurred in the offspring of all treated animals and the average weight gain in surviving animals during the first 40 days of life was uniformly less than that of the control group.