The amniote egg was a key innovation in vertebrate evolution because it supports an independent existence in terrestrial environments. The egg is provisioned with yolk, and development depends on the yolk sac for the mobilization of nutrients. We have examined the yolk sac of the corn snake Pantherophis guttatus by the dissection of living eggs. In contrast to the familiar fluid-filled sac of b...

The objective of this study was to determine the effects of thawing groups of 2, 5, 10, 15, or 20 .5-ml French straws on post-thaw spermatozoal viability. Thermostatically controlled and nonthermostatically controlled thawing baths were compared. Using a split-plot design, semen from 10 bulls was extended in egg yolk citrate, frozen, and then thawed (in the respective groups) at 36 degrees C in...

In the chicken, maternal IgG is deposited in the oocyte yolk and subsequently transported intact by the foetal chick yolk sac into the chick circulation. Such transport appears to require a specific membrane-localized IgG receptor. Using the assay of 125I-yolk IgG binding, we have investigated the existence and properties of such receptors in yolk sac tissue disks. We find that: (1) There are s...

Cytoplasmic rearrangements which follow fertilization were monitored in inverted eggs. A set of yolk compartments was resolved by cytological analyses of both normally oriented and inverted eggs. Those compartments were characterized by their yolk platelet compositions and movement during egg inversion. In addition to the major yolk masses which contain either small, intermediate or large plate...

1. Although post-hatching parental care is uncommon in reptiles, reproducing females may none the less contribute to the nutritional state of their offspring by depositing more yolk into the egg than is needed for embryogenesis. This ‘extra’ yolk (i.e. residual yolk) is drawn into the offspring’s body prior to hatching and is widely assumed to serve as an energy resource for early life activiti...

The objectives of this study were to investigate the effects of different dietary sources of unsaturated fatty acids (fish oil (FO) and/or linseed oil (LO)) on laying performance, egg yolk fatty acid composition, ovarian follicular development, antioxidative properties, immune response and tibial bone characteristics in aged laying hens. A total of 100 Hisex Brown hens at 56 weeks of age were h...

In order to evaluate the hypothetical activity of foetal hepatic factors on putative yolk-sac haemopoietic stem cells we used the Double Diffusion Chamber (DDC) techniqUe. The DDC were made of a regulator compartment, where foetal hepatic tissue was introduced and a test compartment where visceral yolk-sac cells were cultured. In this system a hepatic signal induced the yolk-sac stem cells to d...

Duck hepatitis B virus (DHBV) is the only member of the hepadnavirus family in which nearly 100% vertical transmission from carrier mother to embryo has been reported. Large quantities of maternally transmitted virus particles are present in the yolk prior to incubation of the eggs, and replicative forms of DHBV DNA are detectable in the liver at 6 days of incubation. Since the yolk sac is simi...

Egg yolk oil is a natural source of bioactive compounds such as unsaturated fatty acids, oil soluble vitamins, pigments and others. Bioactive compound content in egg yolk oil depends from its content in eggs, from which oil was extracted. Many studies show that bioactive compound content in egg is correlated to the content of these compounds in hen feed, but there is also an opinion that hen ho...