Calcium-binding proteins in serum of chickens: vitellogenin and albumin

Energy and nutrient utilisation by embryonic reptiles

Most reptiles are oviparous, with the developing embryos relying on the contents of the yolk to sustain development until hatching (lecithotrophy). The yolk is composed primarily of lipid and protein, which act as an energy source and the essential components to build embryonic tissue. Nevertheless, yolk and the resulting embryos contain many other nutrients, including inorganic ions, vitamins, carotenoids, water and hormones. Apart from water and oxygen, which may be taken up by eggs, and some inorganic ions that can come from the eggshell or even from outside the egg, everything required by the embryo must be in the egg when it is laid. Approximately 20% of squamate reptiles are viviparous, exhibiting a variety of placental complexities. Species with complex placentae have reduced yolk volumes, with the mother augmenting embryonic nutrition by provision across the placenta (placentotrophy). Despite assumed advantages of placentotrophy, only 5 out of approximately 100 lineages of viviparous squamates exhibit substantial placentotrophy. This paper reviews available and recent information on the yolk contents of a variety of squamate reptiles to ask the question, how are nutrients transported from the yolk to the embryo or across the placenta? Although, current available data suggest that, in broad terms, yolk is taken up by embryos without discrimination of the nutrients, there are some apparent exceptions, including the very long chain polyunsaturated fatty acids. In addition, fundamental differences in the patterns of energy utilisation in lizards and snakes suggest fundamental differences in lipid profiles in these taxa, which appear to reflect the differences between placentotrophic and lecithotrophic viviparous lizards.

Effect of estrogen on egg production, shell quality and calcium metabolism in molted hens

Force-molted White Leghorn laying hens were implanted with 0.25, 0.5, 1 and 3 Compudose 200 pellets (24 mg 17 beta estradiol/pellet). Plasma estradiol increased with increasing E2 dosages in a linear manner and decreased over time in a quadratic manner (P < 0.01). E2 treatment had a nonlinear effect on total plasma calcium. Oviduct weight, shell thickness and egg weight were not significantly affected by exogenous estradiol whereas tibial bone ash percentage was increased at only one dose (P < 0.05:0.5 pellet group). Physiological supplementation with estradiol does not improve shell quality.

Zinc, iron, and copper contents of Xenopus laevis oocytes and embryos

Zinc is essential for vertebrate development; its deficiency results in multiple congenital malformations. Knowledge of the zinc biochemistry that underlies embryologic development is very limited. This has led us to investigate the zinc, iron, and copper contents of Xenopus laevis oocytes and embryos. Stage 1-6 oocytes, isolated from ovaries, and stage 1-40 embryos, obtained by in vitro fertilization techniques, were washed in metal-free water prior to digestion by 70% ultrapure HNO3. The metal content of the digests was analyzed by atomic absorption spectrometry. Stage 6 oocytes contain 65.8 +/- 4, 31.1 +/- 3, and 0.68 +/- 0.2 ng of zinc, iron and copper, respectively. The corresponding concentrations are 1, 0.5, and 0.01 mM in 1 microliter eggs. The metal content varies as a function of egg maturation. The zinc content increases from 3-7 to > 60 ng by stages 3 and 6, respectively. A similar pattern is noted for iron, which increases from 2-5 to 30 ng at analogous stages. In contrast, the copper content remains virtually unchanged in oocytes undergoing maturation. Importantly, the total of all three metals does not vary throughout the first 50 stages of development, when all tadpole organs are forming. Hence, the full complement of zinc, iron, and copper needed for incorporation into apoproteins during development is already present at a time when oocyte maturation is completed. The specific metalloproteins that store, donate, and accept these metals during induction and organogenesis and the alterations caused by metal deficiency can now be identified.

Uterine calcium-binding protein activity of nonlaying hens and hens laying hard-shelled or shell-less eggs

Uterine calcium-binding protein (CaBP) activity was compared at oviposition and 14 h postoviposition in nonlaying (NL) hens and hens laying a high incidence of shell-less (SL) or hard-shelled (HS) eggs fed a commercial laying diet. Epithelial cells were removed from uteri of NL, SL, and HS hens and homogenized in Tris buffer, pH 7.4. Proteins in homogenate were fractionated by the addition of ammonium sulfate and centrifugation, separated by Sephadex chromatography, and measured by ultraviolet spectrophotometry at A280. Calcium-binding protein activity was determined using a 45Ca-chelex binding assay. Two peaks of CaBP activity were detected and designated CaBP-a (28,000 Da) and CaBP-b (16,000 Da). Uterine CaBP-b may differ from CaBP-a only in Ca content. The activities of CaBP (a and b) were higher (P less than or equal to .05) in HS and SL hens than in NL hens at 0 h. There was no significant difference (0 h) between CaBP activity (a versus b) of either HS or SL hens. There was also no difference (0 h) of CaBP-a or CaBP-b activity when SL and HS hens were compared. Uterine CaBP-a activity was lower (P less than or equal to .05) in SL hens than HS hens at 14 h. Under normal dietary conditions, the level of CaBP activity at 14 h may be associated with SL egg production.

Plasma zinc as an index of vitellogenin production and reproductive status in the domestic fowl

1. A technique is described for the accurate determination of circulating vitellogenin concentrations by measurement of plasma zinc concentrations before and after selective precipitation of lipoproteins in the domestic fowl. 2. Vitellogenin zinc concentrations exhibit a high degree of correlation with those of another major egg yolk precursor, very low density lipoprotein (VLDL) in immature female birds, during developing and maximum egg production in mature birds and following cessation of egg laying. 3. Mature female patterns of plasma vitellogenin and VLDL were induced by injection of oestradiol 17 beta (5 mg/kg body weight per day for 3 days) into adult cockerels. 4. It is suggested that measurement of plasma zinc provides a simple and accurate technique for the estimation of vitellogenin production and reproductive status in the domestic fowl and that this may be applied to other oviparous vertebrates.

Influence of egg production on zinc, copper and iron metabolism in the turkey hen (Meleagris gallopavo)

1. Serum concentrations of zinc, copper, iron, calcium and protein increased significantly with the onset of egg production in turkey hens. 2. Hepatic concentrations of zinc, copper and iron declined significantly with the onset of egg production, whereas the total hepatic content of zinc and copper increased significantly. 3. When plasma from laying and nonlaying hens was subjected to gel-permeation column chromatography, a high molecular weight protein fraction was detected in laying but not in nonlaying plasma which bound significant amounts of zinc, copper and iron and which coeluted with purified vitellogenin. 4. Vitellogenin purified from the plasma of laying hens is a metalloprotein which upon analysis was found to contain 0.54, 0.09 and 0.72 micrograms of zinc, copper and iron, respectively, per mg of protein.

Production, clearance rates and metabolic fate of estradiol-17 beta in the plasma of the laying hen

A single dose of tritiated estradiol-17 beta (3H-E2 beta) was injected i.v. into 5 high egg producing White Leghorn hens, 31 weeks of age, at 19.2 +/- 2.1 (mean +/- S.D.) hr before oviposition. Blood (2 ml) was sampled at approximately 5 min intervals over 40 min. Whenever possible, metabolites were monitored and identified by the double isotope technique with the addition of the corresponding 14C-labelled standards to plasma prior to analysis. The metabolic half-life and clearance rate of 3H-E2 beta in plasma were 10.9 +/- 1.9 min and 118 +/- 18 ml/min/kg body weight, respectively. The calculated production rate of E2 beta at 19.2 hr before oviposition was 19.5 +/- 5.7 ng/min based on the plasma level (93 +/- 22 pg/ml) measured at that time. The relative concentrations (% of plasma radioactivity) of the major metabolites isolated at 5.7 +/- 0.6 min post injection were, in descending order: estradiol-17 beta-3-sulfate (E2 beta-3S: 14.9 +/- 2.7), estradiol-17 alpha-3-sulfate (E2 alpha-3S; 5.7 +/- 0.3), estrone (E1; 4.6 +/- 0.5), estrone sulfate (E1S; 2.2 +/- 0.5), and estradiol-17 alpha (E2 alpha; 1.2 +/- 0.4). As time proceeded, the relative concentration of E2 alpha-3S gradually increased so that by 43.2 +/- 1.0 min it became the most abundant identifiable metabolite (12.3 +/- 1.1) followed by E2 beta-3S (9.1 +/- 1.7), E1S (1.2 +/- 0.6), E1 (0.7 +/- 0.4) and E2 alpha (0.3 +/- 0.2). These findings are consistent with the view that one of the major pathways of E2 beta metabolism in the circulation of the hen is via E2 beta in equilibrium E2 beta-3S in equilibrium E1S in equilibrium E2 alpha-3S.

Bone parameters of thick and thin eggshell lines of chickens

Comparative measurements of bone parameters were made on chickens from thick and thin eggshell lines that were maintained on a normal diet containing 3.5% calcium, injected i.v. with 45CaCl2 and sacrificed 30 min later. There were no significant differences between shell lines for the following measurements on the left femur: specific gravity, ash wt, total calcium, percent calcium and 45Ca content. There was deposition of 45Ca in the femur of all hens--even those in the process of eggshell formation. Skeletal metabolism was not a limiting factor in determining whether a hen produced a thick or thin eggshell.

Comparative study of the physiology of vitellogenesis in Japanese quail

1. During a study of vitellogenesis in the Japanese quail, male or female quail were given, intramuscularly, one to three doses of estradiol-17 beta (16 mumol/100 g body weight). 2. In treated males, the plasma concentrations of protein-bound P (PBP, a measure of the phosphate groups in vitellogenin), Ca, and total protein fluctuated in unison. 3. Packed cell volume (PCV) values varied approx, inversely as the PBP concentrations. 4. Maxima of approx. 0.85 mg PBP/ml occurred six, five, and four days after the primary, secondary, and tertiary injections. Following each maximum, the PBP concentrations declined rapidly to the 0.004 mg/ml level found in the plasma of untreated male quail. 5. During periods of elevated PBP levels, Ca and PBP were present in equimolar quantities. 6. When laying female quail were given a single injection of estradiol, the PBP concentration rose from 0.12 to 0.97 mg/ml. 7. PCV values for both male and female estrogen-treated quail decreased from approx. 0.50 to 0.30. The decreases in PCV values were attributed to increases in plasma volume as measured using 125I-labelled serum albumin. No marked change in total erythrocyte mass was measured using 51CrO2-(4) as the cell label. 8. Perhaps the decrease in plasma serum albumin concentrations reported by some investigators for estrogen-treated animals is due to dilution rather than to repression of serum albumin synthesis.

Effect of estradiol on calcium and calcium binding in serum of thick and then-shell lines of chickens

Estradiol (10 mg/bird) was injected intramuscularly into hens of a thick-shell line and a thin-shell line as well as into roosters of both lines on day 0. Serum levels of calcium (Ca), phosphorus (P), and Ca binding involving the proteins vitellogenin (a phosphoprotein) and albumin were measured on day 0 and day 6 or 7. Serum levels of all measured Ca and P parameters and vitellogenin binding of both sexes were significantly greater, while levels of albumin binding were significantly less on day 6 or 7 than on day 0. Serum levels of non-diffusible Ca in hens and vitellogenin binding in both sexes were significantly greater in the thick-shell than in the thin-shell line. There were no significant differences between lines for total serum P of either sex. A study of the hens only revealed that the change in nondiffusible Ca and vitellogenin binding from day 0 to day 6 or 7 was significantly different between lines. The correlations between vitellogenin binding and total P, expressed as either change or percent change, were greater than .8.

Calcium-binding proteins in serum: quantitative differences between thick and thin shell lines of chickens

Calcium binding by two proteins, vitellogenin and albumin, was measured in serum of a line of hens producing thick (THK) and a line of hens producing thin shells (THN) as well as a line of commercial hens using gel filtration in 45calcium buffer. Vitellogenin was quantitated in serum of THK and THN using a radial immunodiffusion test. Levels of serum calcium were measured and related to the above mentioned parameters. The binding of vitellogenin was significantly greater in 13 THK than 13 THN (672 vs. 508 cpm/ml X 10(-3), but binding by albumin was not significantly different between the two lines (386 vs. 344 cpm/ml X 10(-3). Binding in 11 commercial hens was similar to that for THN. The THK had significantly greater levels of diffusible, non-diffusible, and total serum calcium than THN. Significant positive correlations between total serum calcium and vitellogenin binding were found in THK (.77) and THN (.81) as well as in the commercial hens (.64). Like vitellogenin binding, levels of vitellogenin were significantly greater in THK than THN (4.0 vs. 1.8 mg/ml). These results suggest that in addition to having more diffusible and non-diffusible serum calcium, THK have more calcium binding and more vitellogenin to perform the binding function than THN.