Yolk spheres present in mature invertebrate oocytes are composed of yolk proteins and proteolytic enzymes. In the fly Musca domestica, yolk proteins are degraded during embryogenesis by a cathepsin-like proteinase that is stored as a zymogen. An acid phosphatase is also active in the yolk spheres during Musca embryogenesis. In this paper we show that procathepsin and acid phosphatase are initia...

The correlation of yolk cholesterol and yolk fat concentrations of egg from the pedigreed Athens-Canadian Randombred control population with the percentage of abdominal fat (AF) and feed conversion ratio (FCR) of their progeny were studied. The average yolk cholesterol, yolk fat, and AF were 20.3 mg/g yolk, 244 mg/g yolk, and 1.64%, respectively. The phenotypic correlation of both yolk choleste...

The discovery by Schwabl that maternal steroid hormones are transferred to the egg yolk and have effects on the phenotype of offspring revealed a new pathway for non-genetic maternal effects. The initial model relied on passive transfer. The thinking was that steroids passively entered the lipophillic yolk during yolk deposition and then were deposited in the yolk until they were passively deli...

The variations of the pH in Xenopus yolk platelets have been estimated by fluorescence confocal microscopy and computer image processing. For pH measurements in vitellogenic oocytes, the pH-sensitive fluorescent dye, DM-NERF, was coupled to vitellogenin, and the DM-NERF-vitellogenin was taken up by oocytes via receptor-mediated endocytosis. Dual emission ratio measurements of internalized DM-NE...

in this experiment, a total of 128 hy-line w36 hens at 63 weeks of age were used. the hens were put at random into 4 treatment groups (4 replicates and 32 hens per treatment) and were fed four different diets: three diets with different levels of spirulina (1.5, 2.0 and 2.5%) and one control group based on wheat and soybean meal. all birds were housed in commercial cages, had ad libitum access ...

Although the particulate fraction of egg yolk (yolk granules) has attracted the attention of investigators since Miescher (1) and Hoppe-Seyler (2)) reliable information concerning the distribution of the yolk constituents between its soluble phase and the granules is lacking. Separation of both phases is difficult, owing to the high viscosity of egg yolk. For this reason, all information concer...

The study assessed the optimum incorporation rate of Borassus aethiopum (Ba) ripe fruits’ dried pulp in laying hens’ feed. So, 72 Isa Brown hens 37-week-old were allotted into 9 groups 8 each. Then, 3 control diets including 60% yellow corn (60%YC), 55.2% (55.2%YC) and white (60%WC) formulated. Additionally, 6 test made by substituting 5%; 7.5%; 10%; 12.5% 15% 60%WC Ba pulp...

In many oviparous animals, bursting type atresia of ovarian follicles occurs during the reproductive cycle, resulting in the escape of yolk into the extracellular compartment. In birds, this ectopic yolk is rapidly cleared by an unknown process that involves the appearance of yolk-engorged macrophage-like cells. To study this unique type of lipid transport, we injected young male chickens intra...

To examine the functional differentiation of chloride cells in the yolk-sac membrane of tilapia (Oreochromis mossambicus) embryos, we developed a 'yolk-ball' incubation system in which the yolk sac was separated from the embryonic body and subjected to incubation in vitro. The yolk-ball preparation consists of the yolk and the covering yolk-sac membrane, which contains a rich population of chlo...