Vascular abnormalities due to hyperthermia in chick embryos.

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.