Chlamydia trachomatis grown in the yolk sac of embryonated eggs was purified by centrifugation on continuous isopycnic Renografin density gradients. A band of chlamydial particles with a buoyant density of 1.20 contained 70% of the starting particles, and electron microscopy revealed the virtual absence of contaminating egg material. Centrifugation on Renografin gradients caused only a moderate...

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...

BACKGROUND: Colibacillosis is one of the most economically important diseases of poultry worldwide. OBJECTIVES: This study was conducted to examine the clonal relatedness and typing of 95 avian Escherichia coli isolates by ERIC-PCR. METHODS: Sixty-three E. coli isolates from two common manifestations of colibacillosis (yolk sac infection and colisepticemia) and 32 isolates from feces of apparen...

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...

We report a rare case of a retroperitoneal germ cell tumor in a 31 years old male who presented with an acute abdomen. He gave a six-months history of back pain and significant weight loss. Clinical examination and ultrasound of the testes didn't show any primary focus. Intraoperative findings showed a retrolperitoneal midline mass that has ruptured into the peritoneal cavity and has invaded in...

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...

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...

Hepatoid variant of yolk sac tumor of ovary is an unusual tumor with an aggressive behavior. It is usually observed in young females, presents with abdominal complaints and is associated with raised α-fetoprotein (AFP) levels. It should be differentiated from other hepatoid tumors involving the ovary. A complete patient evaluation with gross, microscopy, and immunohistochemistry can identify th...

Yolk sac hematopoiesis is characterized by restricted hematopoietic cell differentiation. Although multipotent hematopoietic progenitor cells have been identified in the early yolk sac, long-term multilineage repopulating (LTMR) hematopoietic stem cell (HSC) activity has not been demonstrable before day 11 postcoitus (PC) using standard transplantation assays. In the present study, day-10 PC yo...