Ruth J. McCartney

Placental transfer of nutrients during gestation in the viviparous lizard, Pseudemoia spenceri

Abstract Energy, ionic, protein and lipid contents and fatty acid profiles for the major lipid classes of freshly ovulated eggs and neonates of the viviparous lizard, Pseudemoia spenceri, were measured. Litter size is 1.7 ± 0.1, with larger females producing larger neonates. Placentotrophy results in approximately 23% more dry matter in the neonates than in the fresh egg. The increase in the quantity of protein and lipid during development is not significant and is reflected in the similarity of energy densities of eggs and neonates. As a percentage of dry matter, neonates have slightly lower proportions of lipid and protein than eggs because of significant uptake of ash, calcium, potassium and sodium, but not of magnesium, across the placenta. The amounts of triacylglycerol and phospholipid are not significantly different between the egg and the neonate, but neonates contain significantly more cholesterol and cholesteryl ester. The amounts of the major fatty acids, palmitic and oleic acids, recovered from the total lipids of the neonate do not differ significantly from the amounts present in the egg lipids, but the neonates contain significantly less linoleic and α-linolenic acids and more palmitoleic, stearic and arachidonic acids than the eggs. The amount of docosahexaenoic acid recovered from the lipids of the neonate is 2.6-times greater than the amount initially present in the egg. P. spenceri has a relatively larger egg and a smaller reliance on placentotrophy than other species in the same genus, all of which have a similar placental morphology. Nevertheless, the pattern of embryonic nutrition includes both obligative and facultative placentotrophy. All the major components of yolk of oviparous species are present in eggs of P. spenceri, but most are augmented during development by placental transfer.

Tissue-specific changes in lipid composition and lipoprotein lipase activity during the development of the chick embryo

Lipoprotein lipase was present at a high specific activity in adipose tissue and heart of the chick embryo at the 14th day of development. The enzyme was also present in skeletal muscle but was absent from brain and liver. Major increases in the activity of lipoprotein lipase in adipose tissue and heart occurred from day 12 of development, concomitant with the beginning of the period of lipid uptake from the yolk. These results suggest that lipoprotein lipase may be involved in the utilisation of yolk-derived lipid by the tissues of the embryo. Relatively high levels of docosahexaenoic acid (22:6(n--3)) were present in the triacylglycerol isolated from plasma, adipose tissue, heart and liver. The relative proportions of this fatty acid in the triacylglycerol of the different tissues may be explicable in terms of the substrate specificity of lipoprotein lipase.

Changes in fatty acid profiles and in protein, ion and energy contents of eggs of the Murray short-necked turtle, Emydura macquarii (Chelonia pleurodira) during development

Abstract The aim of this study was to determine the major nutritive components present in fresh eggs of the freshwater turtle, Emydura macquarii , and to investigate the utilisation of these components during embryonic development. Comparison of the compositions of the initial egg contents (yolk plus albumen), the hatchling and the residual yolk indicated that embryonic development was accompanied by the loss of approximately 15% of the initial dry matter, 25% of the energy content, 8.8% of the protein and 41% of the lipid. Thus, in addition to oxidation of fatty acids, some of the energy consumed during development (17.6%) was derived from catabolism of protein. A feature of the yolk lipids was the presence of high proportions of α -linolenic acid (18:3n-3), particularly in the triacylglycerol and a high concentration of α -tocopherol, similar to than in the yolk of birds. The yolk phospholipid contained a high concentration of arachidonic acid (20:4n-6) and eicosapentaenoic acid (20:5n-3) but a relatively low amount of docosahexaenoic acid (DHA) (22:6n-3). By contrast, the phospholipid of the hatchling was enriched in DHA but contained only a small concentration of eicosapentaenoic acid, suggesting the possible conversion of eicosapentaenoic acid to DHA by the embryo. The amount of calcium recovered in the hatchling was almost twice that of the initial egg contents suggesting mobilisation of calcium from the shell.

Yolk lipids and their fatty acids in the wild and captive ostrich (Struthio camelus)

Abstract A comparative study has been made of the major lipid fractions and their fatty acid compositions in the yolk of eggs from ostriches under wild and farmed conditions. There were no differences in the lipid contents and proportions of the lipid fractions between the two groups of yolks. In both groups of yolks triacylglycerol and phospholipid were the major fractions. In the eggs from the wild ostriches, all the lipid fractions displayed substantial concentrations of C18 polyunsaturated fatty acids, triacylglycerol being particularly rich in linolenic acid and phospholipid rich in linoleic acid; phospholipid displayed substantial concentrations also of C20 and C22 polyunsaturates. There were considerable differences in the fatty acid compositions between the yolks. Those from the farmed birds displayed lower proportions of C18 polyunsaturates, particularly linolenic acid, throughout the lipid fractions. Compensatory increases were displayed most obviously in the concentrations of oleic acid and palmitoleic acid as well as other acids. The distinctive and extensive changes in fatty acid composition, particularly relating to the polyunsaturates, are discussed with respect to overall dietary requirements and specificities for embryo metabolism and possible effects on reproductive performance.

Utilisation of lipids, protein, ions and energy during embryonic development of Australian oviparous skinks in the genus Lampropholis.

The contents of eggs and neonates of the Australian skinks, Lampropholis guichenoti and L. delicata, are described and compared to allow interpretation of nutrient utilisation by the developing embryo. Even though the females are the same size, L. guichenoti lay smaller clutches of larger eggs (egg contents=41.6+/-1.2 mg dry mass) than L. delicata (26.6+/-2.8 mg). The energy density is the same for eggs (30.5+/-0.9 J/g ash-free dry mass for L. guichenoti and 29.9+/-1.1 J/mg for L. delicata) and neonates (22.5+/-1.3 J/mg for L. guichenoti and 23.5+/-0.4 J/mg for L. delicata) between species. The amount of nitrogen (protein) in neonates is only slightly lower than that in eggs, whereas there is a large and significant decline in total lipids. Thus, like some other skinks, protein is a source of metabolic energy during embryogenesis, although not as important as lipid. Triacylglycerol is the major lipid component of the eggs (80% of total lipid), with phospholipid forming only approximately 10% of the total lipid. The fatty acid profile of the phospholipid is distinguished by a high proportion of arachidonic acid (8%), a significant proportion of eicosapentaenoic acid (2-4%) and a relatively low proportion of docosahexaenoic acid (2-3%) compared to chickens. Eggs of both species have remarkably low concentrations of free cholesterol compared to other amniote eggs (0.7% for L. guichenoti and 1.3% for L. delicata). The loss of lipid during embryonic development is almost entirely due to the selective utilisation of yolk triacylglycerol, presumably for energy. By contrast, the amount of phospholipid recovered from the neonates was the same as that originally in the eggs. Moreover, significantly more total cholesterol was present in the neonates than in the eggs, suggesting that biosynthesis of additional cholesterol occurred during development. The phospholipids of the neonates contain higher proportions of arachidonic (11-12%) and docosahexaenoic (8%) acids than the phospholipids of the eggs. Eicosapentaenoic acid is less prevalent in phospholipids in neonates than in eggs. Neonates of both species contain significantly more calcium than the fresh egg contents (L. guichenoti, eggs 0.303+/-0.051 mg, neonates 0.641+/-0.047 mg; L. delicata, eggs 0.187+/-0.013 mg, neonates 0.435+/-0.033 mg), presumably as a result of resorption of calcium from the eggshell. Interestingly, there is also significantly more sodium in neonates than in the contents of fresh eggs (L. guichenoti, eggs 0.094+/-0.010 mg, neonates 0.184+/-0.011 mg; L. delicata, eggs 0.084+/-0.011 mg, neonates 0.151+/-0.010 mg). There is no significant difference in the content of potassium and magnesium in eggs and neonates of either species. Although the fresh eggs of L. delicata have a significantly higher sodium concentration than L. guichenoti, there is no difference in the concentrations of calcium, magnesium, potassium or sodium in the neonates of the two species.

The esterification of cholesterol in the yolk sac membrane of the chick embryo.

The uptake of lipid from the yolk by the yolk sac membrane of the chick embryo is accompanied by the rapid esterification of a large proportion of the yolk cholesterol. This could arise from enhanced acyl-CoA:cholesterol acyltransferase (ACAT) activity and/or inhibition of cholesteryl ester hydrolase (CEH) activity. The activity of ACAT was therefore measured in microsomes obtained from yolk sac membranes at various stages of development. A high level of activity (up to 929 pmol of cholesteryl oleate formed per min per mg protein) was found during the second half of this period. Supplementation with exogenous cholesterol stimulated ACAT activity in microsomes obtained from the tissue at the earlier, but not at the later, stages of development suggesting that the enzyme became saturated with microsomal cholesterol as development proceeded. Correlating with this, the concentration of cholesterol in the microsomes increased 4-fold between 9 and 20 d of development. The activity of CEH was very low in the microsomes and could not be detected in the cytosolic fraction. The activity of a protein, which has been shown to function as an inhibitor of CEH, was found to be present at all stages of development. The high activity of ACAT, together with the low activity of CEH and an active CEH inhibitor protein is a combination well suited to promote an essentially unidirectional conversion of cholesterol to cholesteryl ester. This process may be a major determinant of the rate of lipid transfer from the yolk to the embryo.

Changes in the lipid and fatty acid composition of the yolk during embryonic development of the alligator (Alligator mississipiensis)

Abstract 1. 1. Changes in absolute and relative amounts of the yolk lipid fractions and their fatty acids were determined for alligator embryos at various stages during incubation. 2. 2. Lipid absorption was particularly active after day 56 of incubation. 3. 3. The major lipid components at the start of incubation were triacylglyceride and phosphoglyceride. The levels of both these fractions decreased considerably during incubation whilst cholesterol ester increased to become a major lipid component of the yolk at hatching. 4. 4. All lipid fractions displayed high levels of palmitoleic acid in the phosphoglyceride there were high levels of C20 and C22 polyunsaturated fatty acids. 5. 5. The fatty acid composition of the triacylglyceride and phosphoglyceride remained relatively unchanged during incubation but there was extensive esterification of cholesterol with oleic acid

Nutrient Uptake by Embryos of the Australian Viviparous Lizard Eulamprus tympanum

Eulamprus tympanum is a high‐altitude viviparous lizard that was probably used to help define a Type I chorioallantoic placenta. In this article, we (1) describe the net transport of nutrients across the placenta of E. tympanum, and (2) compare placental uptake in E. tympanum with a previous study of Eulamprus quoyii, which occurs in warmer environments, to assess the potential importance of thermal regime on placentotrophy. Freshly ovulated eggs are \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Lipid composition of eggs of an oviparous lizard (Bassiana duperreyi).

387.3\pm 19.7