Egg yolk soluble protein stimulates the proliferation and differentiation of osteoblastic MC3T3-E1 cells

We determined the effects of yolk water-soluble protein (YSP) on bone formation in pre-osteoblastic MC3T3-E1 cells. YSP (50-5,000 microg/ml) increased cell proliferation and collagen content. Alkaline phosphatase (ALP) activity was also increased by YSP treatment. After enhancement of ALP activity, significant augmentation of calcification was observed. These results suggest that YSP is a promising agent for the prevention and treatment of bone loss.     

Inhibitory effects of egg yolk soluble protein on bone resorption

We determined the effects of yolk water-soluble protein (YSP) on bone resorption. YSP potently suppressed osteoclastogenesis from bone marrow-derived precursor cells driven by tumor necrosis factor-alpha (TNF-alpha). YSP (200 microg/ml) abolished the formation of tartarate-resistant acid phosphatase (TRAP)-positive osteoclasts. Furthermore, TNF-alpha induced TRAP activity was greatly inhibited by YSP (100 microg/ml) treatment. Our results suggest that YSP has therapeutic potential for bone-erosive diseases.     

Induction of Polysome Formation in Sweet Potato Root Tissue in Response to Wounding

We determined the effects of yolk water-soluble protein (YSP) on bone resorption. YSP potently suppressed osteoclastogenesis from bone marrow-derived precursor cells driven by tumor necrosis factor-α (TNF-α). YSP (200 μg/ml) abolished the formation of tartarate-resistant acid phosphatase (TRAP)-positive osteoclasts. Furthermore, TNF-α induced TRAP activity was greatly inhibited by YSP (100 μg/ml) treatment. Our results suggest that YSP has therapeutic potential for bone-erosive diseases.     

Comparison of the efficacy of egg yolk extract and horse serum for growth of Mycoplasma pneumoniae

The usefulness of chicken egg yolk extract as a substitute for horse serum in culture media for Mycoplasma pneumoniae was investigated. As a growth-supporting factor in the growth medium for M. pneumoniae and some other mycoplasmal species, the primary isolation medium for M. pneumoniae, and the metabolism-inhibition test medium for diagnosis of M. pneumoniae infection, egg yolk extract may be an excellent substitute for horse serum. The particular superiority of egg yolk extract to horse serum is that egg yolk extract, unlike horse serum, did not show any inhibitory effect on the growth of M. pneumoniae.     

Variation in egg quality and composition in the Mallard Anas platyrhynchos

Three complete Mallard Anas platyrhyncos clutches from a single site were analysed to determine intra-and inter-clutch variation within and among clutches in quality and composition. Variation between clutches was significantly greater than within clutches in all the examined criteria of egg composition, except for the percentage of water found in yolk. In addition the weight of the yolk was proportional to fresh egg weight. When log transformations were used, the slope of the regression was greater than unity, indicating the proportional contribution of yolk increased respectively with egg weight. A total of 26 eggs from four locations was analysed and no regional variation in egg composition was found but there was variation in egg quality (lipid and protein). The factors affecting the production of a 'good egg' and what in fact is a 'good egg' are discussed. In the Mallard, as in other Anseriformes, it appears that larger eggs may confer a survival advantage to the subsequent young.     

Altricial and precocial developmental features in modern meat-type chicks

Variability of egg weight, egg yolk content, neonatal growth rate and relationships of these parameters were studied in meat-type chicks. As it had been established the level of variability in neonatal growth traits was greater than variability of the egg morphology parameters. Egg weight had stronger influence on the chicks' neonatal growth rate than egg yolk content did. Low egg size was associated with limited neonatal growth rate variability, declined chick weight at hatching and increased relative growth rate throughout four days post hatch. Comparison of egg morphological parameters in two species having the same female definitive body weight--meat-type domestic fowl (precocial type) and brown pelican (altricial type) has shown, that, in contrary to predicted on the basis of avian developmental typology, egg weight to female body ratio was greater in brown pelican, egg yolk content was equal in both species.     

The chicken egg yolk plasma and granule proteomes

Using 1-D SDS-PAGE, LC-MS/MS, and MS(3), we identified 119 proteins from chicken egg yolk, 86 of which were not identified in yolk previously. Proteins were roughly quantitated by calculating their exponentially modified protein abundance index (emPAI) to classify them as major or minor yolk components, and to estimate their distribution between yolk plasma and yolk granular fraction. The proteins with highest abundance were serum albumin, the vitellogenin cleavage products, apovitellenins, IgY, ovalbumin, and 12 kDa serum protein with cross-reactivity to beta2-microglobulin. In addition yolk contained many other serum and egg white proteins, the proteases nothepsin and thrombin, numerous protease inhibitors, and antioxidative enzymes, such as superoxide dismutase and glutathione peroxidase. Among the moderately abundant proteins were two alpha2-macroglobulin-like proteins different from egg white alpha2-macroglobulin, and the major biotin-binding protein of yolk. An unexpected identification was that of the eggshell matrix protein ovocleidin-116, which was previously thought to be eggshell-specific. The list of chicken egg yolk proteins provided in this report is by far the most comprehensive at present and may serve as a starting point for the characterization of less well-known yolk proteins.     

Composition and energy density of eggs from two species of freshwater turtle with twofold ranges in egg size

Lipid, protein, ash, carbohydrate and water content and energy density of eggs were measured from different clutches over a range of egg size in two species of freshwater turtle. Dry egg contents consisted of protein (54-60%), lipid (25-31%) and ash (5-6%) while carbohydrate was found to be negligible (<1%). Albumen consisted principally of water ( approximately 98%), and the dry component was composed of protein (47-51%), ash (19-26%) and lipid (18-21%), but contributed only a small amount ( approximately 2%) to overall dry egg contents. Energy density of dry albumen (15-17 kJ/g) was significantly lower than for dry yolk (26-27 kJ/g). Yolk consisted of 62-70% water, and the dry component was composed of protein (54-61%), lipid (25-31%) and ash (5-6%). Fractional concentrations of water, lipid, protein and ash and energy density remained constant over the range of egg size in Emydura signata eggs. In contrast, an increase in the yolk to albumen ratio and a decrease in water content of yolk as egg size increased caused the composition and energy density of Chelodina expansa eggs to vary systematically with egg size.     

Effects of Added CeCl<Subscript>3</Subscript> on Resistance of Fifth-Instar Larvae of Silkworm to <Emphasis Type="Italic">Bombyx mori</Emphasis> Nucleopolyhedrovirus Infection

The aim of this study was to investigate the influence of mineral sources on broiler breeders and their offsprings. Broiler breeding hens were fed with diets containing either organic or inorganic trace minerals at equal levels, i.e., (1) control group was fed with basal diet supplemented with inorganic trace minerals; (2) OZ group was fed with organic Zn instead of sulfate; and (3) OTM group was fed with organic Cu, Mn, Zn, and Se instead of inorganic sources. Results indicated that OTM supplementation decreased plasma cholesterol and triglyceride and increased yolk triglyceride via increasing high-density lipid protein cholesterol and decreasing low-density lipid protein cholesterol and very low-density lipid protein (VLDL) in plasma. OZ diets decreased plasma cholesterol and triglyceride mainly by reducing VLDL concentration. For control group, increased lipid concentrations resulted in increased lipid peroxidation in serum and malondialdehyde retention in yolk. Zn retention was not affected. Otherwise, OZ diet was observed to decrease Cu in yolk and albumen. While for OTM group, albumen Cu, albumen Se, and hepatic Se of hatched chicks were increased, but yolk Cu was decreased. Moreover, organic mineral supplementations improved broilers’ growth performance. In conclusion, organic mineral supplementation in breeders’ diets protected breeders from lipid peroxidation, increased egg nutrition retention, and benefit for growth of broilers.     

Biotin-binding protein from chicken egg yolk. Assay and relationship to egg-white avidin.

1. Biotin in chicken egg yolk is non-covalently bound to a specific protein that comprises 0.03% of the total yolk protein (0.8 mg/yolk). This biotin-binding protein is not detectable by the normal avidin assay owing to the biotin being tightly bound. Exchange of [14C]biotin for bound biotin at 65 degrees C is the basis of an assay for this protein. 2. Biotin-binding protein from egg yolk is distinguishable from egg-white avidin on Sephadex G-100 gel filtration, although the sizes of the two proteins appear quite similar. 3. Biotin-binding protein is denatured at a lower temperature and freely exchanges biotin at lower temperatures than does avidin. 4. The biotin-binding protein in egg yolk is postulated to be responsible for the deposition of biotin in egg yolk. D-[carboxyl-14C]Biotin injected into laying hens rapidly appears in the egg bound to yolk biotin-binding protein and avidin. Over 60% of the radioactivity is eventually deposited in eggs. The kinetics of biotin deposition in the egg suggests a 25 day half-life for an intracellular biotinyl-coenzyme pool in the laying hen.     

A comparison of the protective action of added egg yolks from five avian species to the cryopreservation of bull sperm

Cryopreservation of domestic animal sperm has been widely used for artificial insemination (AI), and egg yolk is one of the most commonly used cryoprotectants during the freezing-thawing process. The objectives of this study were to compare the effectiveness of egg yolk from five avian species (domestic chicken, domestic duck, domestic goose, Japanese quail or domestic pigeon) and to optimize the concentration of egg yolk on the cryopreservation of bull sperm in terms of frozen-thawed sperm progressive motility and viability. The results were two-fold. First, they showed that pigeon egg yolk provided the best cryoprotective effects on the cryopreservation of bull sperm, compared with egg yolk of chicken, quail, goose or duck. Second, the best concentration of pigeon egg yolk in extender was 20% during cryopreservation among five concentrations of 5, 10, 20, 30 or 40%. The results suggest that pigeon egg yolk could be used as an alternative to chicken egg yolk in extender but requires further testing in fertility trials.     

Experimental (tamoxifen-induced) manipulation of female reproduction in zebra finches (Taeniopygia guttata)

Experimental manipulation of reproductive phenotype is a potentially powerful approach for understanding the fitness relationships of traits such as egg size, egg composition, and egg number. In this study, I investigated the effect of the antiestrogen tamoxifen on multiple, estrogen-dependent reproductive traits in female zebra finches (Taeniopygia guttata). Short-term tamoxifen treatment of egg-laying females (two daily injections before laying) had no effect on the timing or the pattern of egg laying compared to sham controls. However, tamoxifen treatment caused (1) a marked, but transient, decrease in egg size; (2) increased within-clutch egg-size variation; (3) a reduction in plasma vitellogenin (VTG) levels; and (4) lower dry yolk and yolk protein content of tamoxifen-treated females. Plasma levels of the second yolk precursor, very low density lipoprotein (VLDL), were not affected by tamoxifen, and tamoxifen appeared to have no effect on oviduct function in egg-laying females. These results are consistent with tamoxifen blocking estrogen receptors in the liver, suppressing VTG production, and decreasing the plasma pool of yolk precursors below a level required to maintain yolk formation at the normal rate. Tamoxifen treatment can therefore be used successfully to manipulate several components of the female reproductive phenotype (egg composition, intraclutch egg-size variation) to further explore the fitness consequences of these traits.     

Cryoprotective and contraceptive properties of egg yolk as an additive in rooster sperm diluents

The addition of chicken egg yolk to semen extenders is thought to reduce the fertilizing potential of rooster spermatozoa - but not (or at least not as much) that of other avian species. The aim of the present study was to determine whether quail egg yolk, a novel extender additive, provides advantages over chicken egg yolk in the cryopreservation of rooster spermatozoa. Experiments were also performed to determine whether the harmful effect of egg yolk occurs during cryopreservation or during fertilization after artificial insemination. Heterospermic rooster semen samples were divided into aliquots and cooled in a polyvinylpyrrolidone-based medium containing 15% chicken egg yolk, 15% quail egg yolk or no egg yolk at all. The viability of spermatozoa of cooled samples (5 °C) without egg yolk were less viable (P < 0.01) than those of samples containing either type of egg yolk. The same aliquots were then cryopreserved for 15 days. Thawed spermatozoa preserved without egg yolk showed lower motility (P < 0.001) and viability (P < 0.001) than those in samples diluted with either type of egg yolk extender. No eggs were fertilized when hens were inseminated with semen that had been diluted with chicken egg yolk. The fertilization rate was only slightly higher when sperm diluted with quail egg yolk was used (1.5%). The best results were obtained when no egg yolk was used (13.8%). These results show that the addition of egg yolk of either type protects rooster sperm cells against cold shock and during freezing and thawing, but exerts a contraceptive effect in the genital tract of the hen.     

Effects of the usage of dried brewing yeast in the diets on the performance, egg traits and blood parameters in quails

This experiment was carried out to determine the effects of the usage of dried brewing yeast in quail diets on laying performance, egg traits and blood parameters. A total of 240 Japanese quails (Coturnix coturnix japonica) aged 10 weeks were randomly allocated into one control group and three treatment groups. Each group was divided into five replicates as subgroups, comprising 12 quails each. Dried brewing yeast (Saccharomyces cerevisiae) was used at the levels of 1.5%, 3.0% and 4.5% in the diets of the first, second and third treatment groups, respectively. Soyabean meal was replaced with dried brewing yeast. The diets were formulated to be isocaloric and isonitrogenous. The experimental period lasted 18 weeks. Dietary treatments did not significantly affect body weight, daily feed intake, daily protein intake, egg production, egg weight, feed efficiency, mortality, egg shell thickness, egg albumen index, egg yolk index, egg Haugh unit, the percentages of egg shell, albumen and yolk, excreta moisture and small intestinal pH. Inclusion of 3% and 4.5% dried brewing yeast in diets reduced egg yolk cholesterol concentration as mg per yolk and mg per g yolk (P < 0.01). Blood serum cholesterol of groups fed diets with dried brewing yeast was significantly lower (P < 0.01) than that of the control group. Feeding diets containing 3.0% and 4.5% dried brewing yeast resulted in significant increases (P < 0.01) in blood serum levels of total protein, alanine aminotransferase at the end of the experiment. Blood serum levels of uric acid, triglyceride, aspartate aminotransferase and alkaline phosphatase were not affected by dietary dried brewing yeast. It is concluded that dried brewing yeast can be used up to 4.5% in the diets of laying quails without adverse effects on the measured parameters.     

Egg production and fertility in Drosophila depend upon the number of yolk-protein gene copies

Summary The yolk proteins of Drosophila melanogaster comprise a family of three related yolk polypeptides each encoded by a single-copy gene. We show by genetic crosses that each gene makes an equivalent contribution to the fecundity and fertility of the female and they do not individually provide unique functions to the embryo. We show that the number of eggs laid by a female depends upon the number of genes encoding yolk polypeptides present in the genome and furthermore that the probability of an egg hatching into an adult also critically depends upon the number of yolk protein genes present in the mother. This suggests that the three yolk protein-encoding genes in Drosophila melanogaster may have arisen by duplication, then been maintained for quantitative reasons because they increased egg production and fertility, rather than each protein evolving a different function as is the case with most small gene families, such as tubulins and collagen genes.     

Vitamin D in the avian egg. Its molecular identity and mechanism of incorporation into yolk.

The chemical identity of vitamin D in the egg of the domestic fowl was studied by analysing radioactivity in eggs from hens injected with [3H]cholecalciferol. Labelled molecules were found throughout the egg, but the concentration of total radioactivity in albumin was only 5-7% of that in yolk. In lipid extracts of yolk, more than 90% of the radioactivity was as unchanged cholecalciferol and 5% as 25-hydroxycholecalciferol. Only about 3% of the radioactivity in albumin was chloroform-soluble, and of this 40% was 25-hydroxycholecalciferol and 15% was cholecalciferol. Evidence is presented to support the idea that the specific transport of cholecalciferol into yolk is mediated by a cholecalciferol-binding protein in blood. This protein forms a complex with yolk proteins in transit from liver to ovary via the blood. A cholecalciferol-binding protein, chromatographically similar to that from blood, was found in egg yolk. It is postulated that cholecalciferol forms part of a complex with its specific binding protein, Ca2+ and the yolk phosphoprotein, phosvitin. This complex is then incorporated into yolk by the thecal cells of the ovarian follicle.     

Influence of processing factors on the stability of model mayonnaise with whole egg during long-term storage

Mayonnaise-like oil-in-water emulsions with different stabilities—evaluated from the degree of macroscopic defects, e.g., syneresis—were prepared by different formulations and processing conditions (egg yolk weight, homogenizer speed, and vegetable oil temperature). Emulsions prepared with lower egg yolk content were destabilized for shorter periods. The long-term stability of emulsions was weakly related to initial properties, e.g., oil droplet distribution and protein coverage at the interface. Protein aggregation between oil droplets was observed and would be responsible for the instability of emulsions exhibited by the appearance defects. SDS-PAGE results for adsorbed and unadsorbed proteins at the O/W interface suggested that predominant constituents adsorbed onto the interface were egg white proteins as compared with egg yolk components when the amount of added egg yolk was low. In present condition, egg white proteins adsorbed at the O/W interface could be a bridge of neighboring oil droplets thereby causing flocculation in emulsions.     

Interindividual variation in yolk mass and the rate of growth of ovarian follicles in the zebra finch (Taeniopygia guttata)

The amount of resources invested in an individual egg yolk must be determined by its rate of growth and/or the duration of growth. We examined interindividual variation in the growth rate of yolks by injecting radiolabeled amino acid into breeding female zebra finches and measuring the activity associated with protein in the yolks of eggs laid subsequently. We predicted that (1) there would be a positive correlation between yolk mass and the rate of uptake of activity into the yolk; and (2) there would be a negative correlation between clutch size and the amount of activity taken up by each of the follicles due to competition between follicles for circulating yolk precursors. The rate of uptake of activity by the yolks was positively related to yolk mass (r2=0.24, 0.35 and 0.50 for the yolks of the third-, fourth- and fifth-laid eggs, respectively), suggesting that interindividual variation in yolk mass is due, at least in part, to variation in the rate of follicle growth. However, we found no evidence of a trade-off between yolk size and number. The uptake of activity was generally repeatable between breeding attempts (repeatability= 0.23-0.44), as was mean yolk mass (repeatability = 0.35), suggesting that these traits are characteristics of individual females.     

Embryonic growth and mobilization of energy and material in oviposited eggs of the red-necked keelback snake, Rhabdophis tigrinus lateralis

We used the red-necked keelback (Rhabdophis tigrinus lateralis) as a model animal to study embryonic growth and mobilization of energy and material in oviposited snake eggs. Females (N=12) laid eggs between late May and early June. Eggs were incubated at 30 (+/-0.3) degrees C. One egg from each clutch was dissected at five-day intervals starting at oviposition. Incubation length averaged 27.9 days. Three phases of embryonic growth or yolk depletion could be detected in this study. The first phase, between oviposition and Day 10, was one of minimal transfer of energy and material from yolk to embryo. The second phase, between Day 10 and Day 22-23, was characterized by increasingly rapid embryonic growth and yolk depletion. The third phase, between Day 22-23 and hatching, was characterized by a gradual reduction in embryonic growth and yolk depletion. Approximately 73.6% of dry mass, 50.0% of non-polar lipids and 57.8% of energy were transferred from egg to embryo during incubation. Embryos withdrew mineral from the eggshell mainly during the last quarter of incubation. Our data show that oviposition does not coincide with the onset of rapid embryonic growth in oviparous species of squamate reptiles that are positioned midway within the oviparity-viviparity continuum, and that the greater conversion efficiencies of energy and material from egg to hatchling in snakes can be mainly attributed to their lower energetic costs of embryonic development and greater residual yolk sizes.     

Replacement of fetal calf serum in cell cultures by an egg yolk factor with cholecystokinin/gastrin-like immunoreactivity

The in vitro culture of various cell types is an important scientific tool and is becoming increasingly acceptable as a viable alternative to animal experiments. Fetal calf serum (FCS) is a supplement used in many cell culture media, and provides cells with growth factors and cytokines necessary for successful culture. In view of the animal welfare issues surrounding the production of FCS, an alternative agent allowing the replacement or reduction in the use of FCS is desirable. A yolk extract factor (EYF-X) obtained from chicken eggs is described, which facilitates the in vitro culture of a variety of cell types. When the extract was added to a culture medium used for in vitro fertilisation, the number of successful fertilisations was significantly increased. In a further in vitro model (permanent neuronal cell line N2A), the yolk extract significantly stimulated cell proliferation as well as the growth of cell processes. A set of specific antibodies against different parts of the prepro-cholecystokinin reacted with the extract. The intensity of the reaction depends on the age of the egg (time after the laying date). Analysis by gel chromatography recorded a main protein fraction with an apparent molecular mass of 20-30kDa. This fraction was labelled by Western blot with an antibody with specificity against CCK-octapeptide. These findings suggest that the yolk factor may be a CCK/gastrin-like molecule. Since CCK/gastrin-like molecules have also been detected in the spermatozoa of mammals, the influence on in vitro fertilisation could be explained by the yolk factor replacing the endogenous CCK/gastrin-like molecule destroyed in sperm freezing. The results of this study suggest that it might be possible to replace FCS with EYF-X. The application of the yolk factor to a broad spectrum of cell types remains to be investigated.