Embryonic Nutrition Research Articles

Zinc deficiency and the developing embryo

The effect ofin utero zinc deficiency on fetal development in rats is reviewed. Attention is paid to the primary biochemical lesion associated with zinc-related teratogenesis and special consideration is given to the central nervous system. Evidence is presented that the thymidine kinase salvage pathway, used for the synthesis of thymidine monophosphate in DNA synthesis, is depressed more in fetal brain tissue than in the liver. In addition, greater reliance appears to be placed on this pathway than onde novo synthesis in the fetal brain than in other tissues. Some consideration is given to the use of in vitro embryo culture in studies relating to neurogenesis, but evidence is presented of a greater capacity of explanted rat embryos to obtain zinc from maternal serum than occurs in vivo.The rapid onset of a teratogenic zinc deficiency following dietary zinc restriction is again highlighted and further studies are described which demonstrate the critical impact of a single feeding cycle, of 4 d duration, on maternal plasma zinc levels and on the extent and nature of the observed fetal abnormalities. Evidence is presented that by shifting the timing of the high dietary intake/low plasma zinc peak to coincide with a particular 48 h period between days 6 and 10 of pregnancy, the pattern of malformations thus obtained reflected the coincidence of the high dietary intake of zinc-deficient diet and the critical time of morphogenesis of several organ systems.Whereas diminished plasma zinc levels at term in zinc-deficient animals are generally well correlated with reduced growth and dysmorphogenesis of the offspring, the same is not always found in human studies. In some cases, elevated plasma zinc levels at parturition are found in mothers with growth-retarded children, or vice versa. Experimental studies with rats are reported that suggest that maternal zinc status at term may be higher in dams bearing pups stunted by exposure to a transient zinc deficiency early in pregnancy, which in turn may have reduced the demand for maternal zinc in the later stages of gestation.The protective effect of zinc on cadmium-induced teratogenesis is discussed, particularly in relation to findings concerning an interaction of these metals in the embryonic yolk sac and thus on preplacental embryonic nutrition. Possible interactions between alcohol and zinc deficiency are also considered and data are presented pointing to increased fetotoxicity and teratogenesis in the presence of both treatments and to a more specific interaction with respect to reduced cell numbers in the developing rat hippocampus. Malondialdehyde levels, which reflect the extent of lipid peroxidation in tissue, are reported to be substantially higher in microsomes from fetal rat livers whenin utero deficiency and gestational alcoholism are combined. The suggestion is made that alcohol and zinc deficiency act independently in the body, but overlap to some extent at the common biochemical locus of membrane lipid peroxidation.

Interference with embryonic nutrition as the teratogenic mechanism of action of suramin and aurothiomalate in rats

Interference with embryonic nutrition as the teratogenic mechanism of action of suramin and aurothiomalate in rats

Embryonic nutrition, growth and energetics in Zoarces viviparus L. as indication of a maternal-fetal trophic relationship.

The embryos of Zoarces viviparus (L.) show linear growth during their intraovarian development. In early gestation before hatching, the embryos take up very small amounts of low molecular tracer compounds such as glucose, glycine or taurine. Later in gestation (two months after hatching), the embryos accumulate substantial amounts of the tracer compounds. The uptake rates of the tracer compounds in vitro are correlated with ambient concentrations of unlabelled compounds within the natural concentration range of the ovarian fluid. The highest uptake rates are found for glucose and the lowest for taurine. Release of 14CO2 and dissolved organic carbon (DO14C) from assimilated tracers in the embryos is low. Oxygen uptake and body weight of the embryos appear to be linearly correlated, and the average oxygen uptake is 4.20 (SD 0.73) mumol O2 g-1 h-1 WW at 11 degrees C. The contribution of glucose respiration to total aerobic respiration is 13.9%. A growth to respiration ratio of 0.91 indicates a relatively high efficiency for converting food to growth.

REPRODUCTION, EMBRYONIC ENERGETICS, AND THE MATERNAL-FETAL RELATIONSHIP IN THE VIVIPAROUS GENUS SEBASTES (PISCES: SCORPAENIDAE).

Reproduction in the scorpaenid genus Sebastes has been characterized as primitive ovoviviparity. In the black rockfish, S. melanops, egg size is small (0.8 mm), but the gestation period is 37 days and larvae at birth are well developed, with a remnant of yolk and the ability to initiate feeding. To test the hypothesis that this species is viviparous with additional maternal nutrition, we studied embryonic energetics and morphology. Catabolism during development utilized 64% of the yolk energy, resulting in a maximum yolk utilization efficiency of 36%, similar to oviparous fishes. Calorimetry, however, demonstrates that 81% of the initial yolk energy is present at birth. Thus approximately 70% of the catabolic energy is contributed by the maternal system during gestation. Microscopic analysis of embryonic epidermis suggests no specializations for nutrient uptake. Histological observations, however, reveal that the hindgut is functional approximately 22-25 days after fertilization. Thus, we suggest that nutrition occurs through consumption and assimilation of ovarian fluid. Reproductive modes in the Scorpaenidae have apparently evolved from simple oviparity in seven of eight subfamilies, to lecithotrophic viviparity in more primitive members of the subfamily Sebastinae, through matrotrophic viviparity in Sebastes. This pattern involved progressively longer retention of embryos until after organogenesis and functional differentiation of the gut, facilitating this rather primitive form of embryonic nutrition among matrotrophic viviparous species.

Uterine glands of the pig during pregnancy. An ultrastructural and cytochemical study.

The ultrastructure of the porcine uterine glands is described from material taken from 11 pregnant pigs at exactly known stages of gestation (day 30; 58; 80; 100; 110). Fixation was performed by perfusion via a branch of the uterine artery and the tissue was routinely processed for electron microscopy. Additionally, cytochemical studies (phosphotungstic acid reaction for glycoproteins, according to Rambourg 1967; acid phosphatase reaction; ultrastructural localization of cellular iron, according to Parmley et al. 1978) were performed. On day 30 of pregnancy the uterine glands are coiled, simple tubular glands with a narrow lumen. The epithelial lining is simple columnar and consists basically of two cell types, ciliated cells and secretory cells. The secretory activity of the glandular epithelium is low; only a few secretory granules are present in the supranuclear cytoplasm. At midpregnancy the ultrastructure of the glands has significantly changed and the cells now show all the characteristics of high secretory activity: numerous parallel cisternae of rough endoplasmic reticulum, an extensively developed Golgi apparatus and many secretory granules which give a positive reaction for acid phosphatase and glycoproteins. The lumina of the glands are significantly enlarged and filled with a great amount of a granular, acid phosphatase-positive material. In the last third of pregnancy, only minor changes in the ultrastructure of the uterine glands are observed. The secretory activity is still high. The amount of rough endoplasmic reticulum has further increased and parallel arrays of cisternae occupy a considerable part of the supranuclear cytoplasm. The importance of the uterine secretion for embryonic nutrition and development is only partly understood. One of the secreted glycoproteins, uteroferrin, is believed to play an important role in the iron transfer from mother to fetus. From midpregnancy onward, a special cell type, the "granule laden cell" is found scattered between normal secretory cells of the uterine glands. Contrary to the opinion of Perry and Cromby (1982), we could demonstrate that these cells frequently extend to the lumen of the gland; hence the term "basal cell" seems inappropriate for this cell type.

Interactions of cadmium and zinc in cultured rat embryos

Rat embryos were cultured in serum taken from animals dosed with cadmium, or serum with cadmium added in vitro in the presence or absence of additional zinc. Embryos explanted at day ten and grown in serum taken from animals sooner than 4 h after dosing had a reduced DNA content after 24 h culture. In one-hour serum, the yolk sac had become thick and brittle. Zinc ameliorated the effects but had no stimulatory effect on post eight-hour serum when serum zinc levels were at their lowest. The hypothesis that cadmium induces a maternal zinc deficiency sufficient to cause teratogenic changes could not be sustained. Embryos explanted at nine days were much more susceptible to cadmium added in vitro than ten-day embryos. The principal anomaly, apart from a reduced DNA content, was a thickening of the yolk sac similar to that seen in embryos grown in serum taken from animals one hour after cadmium dosing. Addition of zinc to the medium prevented both of these effects. The suggestion is made that the cadmium-induced dysgenesis of the yolk sac precludes appropriate embryonic nutrition.

Morphometric analysis of the visceral yolk sac endoderm in the rat in vivo and in vitro.

Rat embryos together with their visceral yolk sac were grown in vitro during the early period of organogenesis from days 9.5 to 11.5 and the ultrastructural morphology od the visceral yolk sac cells was compared with that in vivo at the beginning and at the end of the culture period. Identical areas of the visceral yolk sac endodermal cells were analysed morphometrically. A measure of the functional activity was obtained by comparison of the volume density of surface density of the vacoular system. At 9.5 and 11.5 days, the values obtained were virtually identical for yolk sacs in vivo and in vitro. At 9.5 days, the volume and surface density of the endocytotic vacuoles in the embryonic endoderm was significantly lower than in the visceral yolk sac endoderm. It is concluded that the digestive function of the yolk sac is almost certainly identical in culture and in vivo and that the cells of the embryonic endoderm do not take a significant part in embryonic nutrition.

The role of the visceral yolk sac in mediating protein utilization by rat embryos cultured in vitro

ABSTRACT Conceptuses from 9·5-day pregnant rats have been cultured for 48 h in heat-inactivated homologous serum. Embryonic development was normal. The protein contents of embryos and visceral yolk sacs after different periods of culture were recorded. When 125I-labelled polyvinylpyrrolidone or [3H]dextran were added to the culture serum, radioactivity was accumulated by the yolk sac, but only background levels were detected in the embryo itself. The amount of radioactivity found in the yolk sac varied with the length of the interval before harvesting during which 125I-labelled PVP or [3H]dextran was present. When formaldehyde-denatured 125I-labelled bovine serum albumin was added to the culture serum, little radioactivity accumulated in the yolk sac and only background levels were found in the embryo. Trichloroacetic acid-soluble radioactivity steadily appeared in the culture serum, however. When conceptuses were cultured in glucose- and vitamin-supplemented dialysed serum from rats injected 2 h previously with [3H]leucine, radioactivity was found in both embryos and yolk sacs. The amount of radioactivity in these tissues increased with duration of exposure to 3H-labelled serum proteins. After short exposures little of the yolk sac and embryonic radioactivity was acid-insoluble, but this proportion increased with duration of exposure. These results are interpreted as follows. Intact macromolecules cannot enter the cells of the embryo itself, but are captured by pinocytosis into the cells of the visceral yolk-sac endoderm. Indigestible macromolecules such as 125I-labelled polyvinylpyrrolidone and [3H]- dextran accumulate within the yolk-sac lysosomes, but proteins are digested there by the lysosomal enzymes. The radiolabelled digestion product of 125I-labelled bovine albumin is [125I]iodotyrosine, which cells cannot utilize and so is excreted into the culture serum. The labelled digestion product of the 3H-labelled rat serum proteins is [3H]leucine, which is used for protein synthesis in both embryo and yolk sac. The experiments provide direct evidence for the long-suspected role of the yolk sac in mediating embryonic nutrition in the period of development prior to the establishment of a functional chorioallantoic placenta.

Yolk Lipids of Developing Atherosclerosis-Susceptible White Carneau and Atherosclerosis-Resistant Show Racer Pigeon Embryos

The lipid composition of yolks of developing embryonic atherosclerosis-susceptible White Carneau (WC) and -resistant Show Racer (SR) pigeons was analyzed to determine whether embryonic nutrition might be a factor in the difference in susceptibility to aortic atherosclerosis. The yolks of 1-day and 18-day old embryos were analyzed, and the amounts of phospholipid, sterol, non-esterified fatty acid, triglyceride, cholesteryl ester, and hydrocarbon were determined. On the first day of development in both breeds, triglycerides composed 80% of the total lipid content of the yolk; phospholipids, cholesteryl ester, sterols and non-esterified fatty acids comprised the rest. There was no difference between breeds in the amount of lipid in each class or in the total lipid. Therefore, the initial lipid diet of these embryos is not a factor in development of the disease. Examination of the yolk just prior to hatching, revealed that in both breeds there was a significant decrease in total yolk lipids, but unequal utilization of lipid constitutents between breeds. Significantly higher amounts of phospholipids remained in the yolk of the WC pigeons. During embryogenesis, the SR pigeons consumed significantly more of each lipid than the atherosclerosis-susceptible breed. This may indicate that there is a difference between the two breeds in lipid metabolism.

Characterization of neutral amino acid accumulation by human term placental slices.

Characterization of neutral amino acid accumulation by human term placental slices.

Methods for the Study of Embryotrophic Nutrition

In Early post-implantation stages of development, before the establishment of an intimate relationship between the maternal and foetal circulations, embryonic nutrition is carried out largely by the breakdown of macro-molecules in certain phagocytic extra-embryonic membranes. This communication is concerned with defining histochemica, electron microscopic and biochemical parameters which make it possible to identify the membranes concerned. In vivo and in vitro systems for the measurement of the amount of macromolecular breakdown occurring in certain foetal membranes are presented. It is suggested that interference with these catabolic processes may produce congenital malformations or result in abortion of the conceptus.

Studies on Avian Fat Composition: 2. The Selective Utilization of Fatty Acids by the Chick Embryo

THE fat of the yolk of the avian egg serves as an energy source for the developing embryo, and the fact that its composition can be materially influenced by certain nutritional factors may be significant in embryonic nutrition according to Cruickshank (1934).It has been shown that polyunsaturated acids are essential nutrients in the growth of chicks (Reiser, 1950b, c). The fatty acids contained in the egg yolk of hens on low-fat or fat-free diets tend to be more saturated than the egg yolks of hens on a diet containing fat. However, the egg yolk fat from hens on the fat-free diet never becomes completely devoid of unsaturated acids as was shown by Reiser (1950a) and Feigenbaum and Fisher (1959). Thus the synthesis of the unsaturated acids from nonfat precursors suggests that the unsaturated acids might possibly be essential for embryo development. Information was acquired very early on the fat…

Developmental Biology

The Developmental Biology Conference Series, 1956 Cytodifferentiation. Edited by Dorothea Rudnick. Pp. xi + 148. 28s. net. Environmental Influences on Prenatal Development. Edited by Beatrice Mintz. Pp. xiii + 87. 22s. 6d. net. Regeneration in Vertebrates. Edited by Charles S. Thornton. Pp. xi + 108. 52s. 6d. net. Embryonic Nutrition. Edited by Dorothea Rudnick. Pp. xi + 113. 24s. net. Immunology and Development. Edited by M. V. Edds, Jr. Pp. xi + 59. 19s.net. Dynamics of Proliferating Tissues. Edited by Dorothy Price. Pp. xv + 96. 24s. net. Wound Healing and Tissue Repair. Edited by W. Bradford Patterson. Pp. xi + 83. 21s. net. (The Developmental Biology Conference Series, 1956, held under the auspices of the National Academy of Sciences—National Research Council.) (Chicago: University of Chicago Press; London: Cambridge University Press, 1959.)

THE YOLK‐SAC OF THE MOLE TALPA EUROPAEA

SUMMARY The distribution of RNA, fats, iron, glycogen and alkaline phosphatase in the endometrium, yolk‐sac placenta and decidua of Talpa europaea is described. The areolae which are formed are associated, at first, with the vitelline circulation and are probably important sites for the uptake of iron—derived from maternal erythrocytes, protein and saliva insoluble carbohydrate material derived from the secretions of the adjacent uterine glands. The aerolae persist into late pregnancy in association with the allantoic circulation. A vascular yolk‐sac placenta is formed in early pregnancy but it is probably not of any real significance in embryonic nutrition—with the exception of the areolae mentioned above. It is evident that the structural changes which occur in the uterine wall during the formation of this placenta are essentially preparatory to the subsequent establishment of the allantochorionic placenta. Stainable glycogen is absent from the decidual tissue and little lipoidal material is present except in the symplasma which invests the trophoblastic villi. The avascular yolk‐sac placenta, the progressive establishment of which is described, is concerned with the absorption of protein, saliva insoluble carbohydrate material and other substances contained in the secretions of the uterine glands of the mesometrial wall of the uterus. The uterine secretions are of considerable importance in embryonic nutrition and probably continue to be of some significance even in late pregnancy. The yolk‐sac increases in volume up to about the 11·5 mm. stage and the concentration of protein in its fluid at this stage is about 60 per cent of that in the maternal serum. In late stages the concentration of protein in the fluid is greater than that in the maternal serum. Fibrinogen is absent from the fluid in Talpa. The yolk‐sac fluid could serve as an important source of absorbable material and it is probable that the yolk‐sac splanchnopleur, the histochemical and histological properties of which are described, is of some significance EM a placental structure in this species. Reichert's membrane is formed in the avascular wall of the yolk‐sac in early pregnancy and it attains a thickness of about 3 μ in late stages. Its histochemical and tinctorial properties resemble those which have been described for the membrane in the rat and hedgehog and; EM in these species, it is formed of collagenous material. In Talpa the membrane is probably of endodermal origin.

Total Replacement of the Yolk of Chick Embryos

ABSTRACT Isolation of the avian embryo from its normal food material is an essential step in a fundamental study of embryonic nutrition. With present methods, however, it has not been possible to grow embryos in culture for much longer than one day. In 1932 Waddington described methods of growing explanted embryos on serum clots. Several years later Spratt (1947, 1952) devised simplified media for embryos cultured on agar with which he studied various aspects of morphogenesis and carbohydrate needs of the young embryo. New (1955) has recently reported another technique for growing explanted embryos which allows development to proceed to about 60 hours, 40 hours of which are in vitro.

The Systematics of Vertebrate Larvae

THE interpretation of the larval characteristics of the fishes and amphibians in terms of systematics and evolution presents many challenging problems. For many years, studies on early developmental stages were guided by the idea that larval characters have an ancestral, recapitulative significance, or by the belief that they are secondary adaptations with little or no evolutionary importance. Neither theory is adequate from the standpoint of systematics, and together they have somewhat hampered effective use of larval data by taxonomists. A third and more significant concept, based on principles formulated by Von Baer in the 1800s, has gained prominence in recent years through the work of de Beer and others. It emphasizes comparative studies on equivalent growth stages of different species, and provides a much sounder basis for interpreting developmental characteristics in terms of systematics and evolution. The larval stage may serve different ecological functions in different animals. A suitably adapted larva may enable a species to succeed in a region that might otherwise be closed to it-a conspicuous factor in the distribution of many frogs. A pelagic larva may be the major dispersal stage in many marine fishes having sluggish or strongly territorial adults, paralleling a well-known life-history pattern in the invertebrates. It is often suggested that inadequate provision for embryonic nutrition is the primary factor governing the occurrence of a larval stage. Whatever the reason for its establishment in the ontogeny may be, the larva is subject to the operation of genetic evolutionary processes, like any other developmental stage, since all growth stages of the individual are under the control of a single genetic system. The same basic procedures of systematics are applied to both larval and adult stages. These procedures include the analysis of variation and the study of differences and of resemblances between species and groups; and the interpretation of the basic data in terms of the primary trends of phylogeny and of secondary phenomena of adaptive radiation, convergence, rectilinear trends, and other patterns of evolution, at all systematic levels.

Studies on Sterility and Prenatal Mortality in Wild Rabbits

ABSTRACT The yolk-sac contents were observed to be gelatinous in many embryos of wild rabbits at from 7-to 12-day stages, but particularly at 8 and 9 days. Gelatinous strands were observed in the uterine lumen, often connecting adjoining blastocysts, in 8–12-day stages, but particularly at 8 and 9 days. Gelatinous blastocysts and strands frequently were encountered together in the same uterus. Evidence is adduced that these abnormalities, though tending to occur at slightly earlier stages, are related to the mortality which attains a maximum on the 11th and 12th days. Microscopic examination revealed the presence of a reticulum of fine fibrils in the yolk-sac cavity, the histological characters of which are described. The degree of development of this reticulum varied widely from one uterus to another, and often in the individual embryos of the one litter. The presence of this reticulum, when sufficiently dense, was responsible for the gelatinous character of the yolk-sac contents. The gelatinous strands consisted of felted masses of these fibres and of maternal and foetal tissue debris. The fibrous reticulum was absent from the cavities of the amnion and exocoele. A similar reticulum was present sometimes, though rarely so well developed, in the embryos of tame rabbits. Frequently it was absent. It was shown by histological means that the reticulum was not an artefact. The alternatives, that it was either a micro-organism or a network of organic fibres, remained. Morphologically the reticulum resembled the mycelium of an actinomycete so closely that the possibility that it was an invasive organism belonging to this group could not be ignored. Culture experiments disproved this theory and provided satisfactory evidence that the yolk-sac cavities of tame rabbit embryos containing the reticulum were bacteriologically sterile. Sections of clots of fibrin prepared from rabbit-blood plasma presented a similar histological appearance. The presence of fibrinogen in the yolk-sac fluid of 9-day embryos of tame rabbits was demonstrated by clotting the aspirated and citrated fluid with thrombin. Comparison of the clots formed in parallel series of dilutions of the yolk-sac fluid and of plasma indicated that the concentration of fibrinogen in the former was of the order of 50% of that in the latter. Separation of the fibrin from the residue of the yolk-sac fluid was effected by filtration and repeated washing. The mean weight of dried fibrin obtained per ml. of yolk-sac fluid was 37% of that from plasma and its nitrogen content was 33%. The amount of fibrin in the yolk-sac fluid varied significantly from litter to litter. The mean quantity of nitrogen in the residue of the yolk-sac fluid was 57 % of that in the blood serum. The significance of these results in relation to embryonic nutrition and prenatal mortality is discussed.

Observations on later phases of embryonic nutrition in Squalus acanthias

Journal of MorphologyVolume 73, Issue 1 p. 177-205 Article Observations on later phases of embryonic nutrition in Squalus acanthias† Lois E. Tewinkel, Lois E. Tewinkel Department of Zoology, Smith College, Northampton, Massachusetts and the Marine Biological Laboratory, Woods Hole, MassachusettsSearch for more papers by this author Lois E. Tewinkel, Lois E. Tewinkel Department of Zoology, Smith College, Northampton, Massachusetts and the Marine Biological Laboratory, Woods Hole, MassachusettsSearch for more papers by this author First published: July 1943 https://doi.org/10.1002/jmor.1050730109Citations: 23 † Contributions from the Department of Zoology, Smith College, no. 203. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume73, Issue1July 1943Pages 177-205 RelatedInformation