Intraembryonic vascular abnormalities were studied in chick embryos exposed to temperatures 3 degrees C and 4 degrees C above normal temperature (38 degrees C) from the beginning of incubation. The average duration of hyperthermia was 54 and 53 hours, respectively. Immediately after exposure, the embryos were examined with FITC-Dextran microangiography in vivo. Following hyperthermia various abnormalities in the heart, ventral aortae, aortic arches, omphalomesenteric arteries, and the distal dorsal aortae frequently occurred. There were also significant microvascular changes in the head, in the lateral and caudal parts of the embryos, and in the pellucid area of the yolk sac. In another series incubation at 41 degrees C, hyperthermia of 3 degrees C during the first 3 days of development produced several extraembryonic vascular abnormalities. These included duplication and abnormal branching of the cranial vitelline vein, absence or abnormal course of the omphalomesenteric vessels, aneurysmatic dilatation or abnormal course of the caudal vitelline vein, and aneurysmatic dilatation or occlusion of the abdominal venous sinus. Most frequent findings were blind, congested, and dilated microvascular segments in the pellucid area, commonly associated with an irregular microvascular pattern and perivascular swelling. The abnormalities described are assumed to be caused by the direct effects of hyperthermia upon the developing vessels resulting in microvascular insufficiencies, pathological leakage, and perivascular oedema. Such disturbances may have serious consequences for embryonic vascular development and microcirculation, which in turn may have adverse effects on further embryonic growth and development.

Angiography↗

PubMed1984

Endothelial changes and microvascular leakage due to hyperthermia in chick embryos.

The effects of hyperthermia on the developing 2- and 3-day chick embryo were studied by vital microscopy, in vivo microangiography and electron microscopy of post-capillary venules of the pellucid area of the yolk sac. Hyperthermia of 3 degrees C and 4 degrees C produced significant microvascular changes and perivascular oedema. The microvascular defects were characterized by interruption of the endothelial lining and the presence of blood cells breaking through the vessel walls. In addition, there were numerous inter-endothelial gaps with wide subendothelial spaces. Microangiography showed leakage from the vessel walls. It is concluded that hyperthermia produces vessel wall injury and induces the formation of gaps between endothelial cells resulting in extravasation of plasma and blood cells. These gaps are similar to those produced by biochemical mediators of inflammation. It is suggested that these microvascular changes with pathological leakage may play important roles in abnormal vascular and embryonic development.

Animals↗

PubMed1981