Yolk sac infection (YSI) and dead-in-shell mortality caused by Enterobacteriaceae in birds are not a rare phenomenon, however there are only a few reports indicating the association between these conditions and Klebsiella spp. among canary chicks (Serinus canaria). There have been reports of high mortality among 1-3 day old canary chicks in an indoor flock of canaries. In order to study the cau...

Mouse embryos lacking the polycomb group gene member Yin-Yang1 (YY1) die during the peri-implantation stage. To assess the post-gastrulation role of YY1, a conditional knock-out (cKO) strategy was used to delete YY1 from the visceral endoderm of the yolk sac and the definitive endoderm of the embryo. cKO embryos display profound yolk sac defects at 9.5 days post coitum (dpc), including disrupte...

Rat embryos, explanted with their embryonic membranes during the early stages of organogenesis (H-l (H days gestation), were grown in culture in roller tubes. Yolk-sac antibody (sheep anti rat yolk-sac gamma globulin), known to be teratogenic when injected into pregnant rats, was added to the culture medium. At concentrations of 01 mg/ml or more the antibody caused gross retardation of growth a...

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...

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...

Mutant mice deficient in glucose-6-phosphate dehydrogenase were used to induce teratomas. This enzyme is linked to the X chromosome, which can be inactivated in female embryo. The differences in the enzyme activity between yolk sac mesoderm and embryo versus yolk sac endoderm can be detected in female concepti by using appropriate crosses of wild-type and G6PD-deficient mice. Histochemical stud...

in spite of being histologically benign, sacrococcygeal teratoma (sct) may recur either as a benign or malignant tumor. a total of 26 patients with benign neonatal scts were treated in taleghanee and mofid medical centers from 1986 to 2000. investigations included radiography,abdominal ultrasound and computed tomography (ct) scan and measurement of tumor marker (α-fetoprotein). initial surgical...

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...

Introduction: Feathers are important body structures that act as surface insulators to reduce maintenance energy requirements and also to protect skin against abrasions and infection. The purpose of this study is to investigate the effects of methionine injection into the yolk sac on development of feather follicle in chicken embryo. Methods: 50 fertilized eggs (weighting 50±0.4 gr) of Ross×...