Hypoxic/ischemic encephalopathy associated with placental insufficiency in a cloned foal.

This research paper describes an instance of Hypoxic/ischemic encephalopathy (insufficient oxygen or blood flow to the brain) in a cloned foal, initially caused by an inefficient placenta and worsened by prolonged low blood pressure during anesthesia for surgery. The foal exhibited a range of health issues and eventually died, with an autopsy revealing extensive damage and abnormalities in the brain and placental tissue.

Hypoxic/ischemic Encephalopathy in a Cloned Foal

• The paper begins by discussing the case of a cloned American Quarter horse foal born at the Texas A&M Veterinary Medical Center. It was diagnosed at birth with neonatal maladjustment syndrome (a range of abnormal behaviors and signs seen in newborn foals), accompanied by dysmaturity (underdevelopment), front limb muscle contraction, and a blood clot in the urinary bladder.
• The foal’s pre-existing health conditions were worsened by prolonged low blood pressure during anesthesia for a surgical procedure. Post-anesthesia, the foal developed seizures, which were attributed to hypoxia/ischemia (insufficient oxygen or blood flow) that occurred during the anesthesia. This resulted in the foal’s death.

Postmortem Examination

• On macroscopic examination of the brain, abnormalities such as flattened cerebral gyri (ridges on the brain surface), shallow sulci (furrows between gyri), yellowish discoloration of the cortex (outer layer of the brain) and apple-green autofluorescence at the cortical/white matter junction were observed under 365-nm ultraviolet light.
• Microscopic examination revealed extensive damage, including laminar cortical necrosis (layered death of brain tissue), diffuse ischemic changes in neuron cell bodies, and significant white matter degeneration, including the degeneration of axons (nerve fibers) and myelin (protective covering of nerve fibers). There was also an accumulation of macrophages (cells that engulf and digest cellular debris and pathogens) and significant hypertrophy (enlargement) of astrocytes (star-shaped cells in the brain) with gemistocyte (reactive astrocyte) formation.

Placental Insufficiency

• The chorioallantois (part of the placenta) was diffusely thickened, which corresponded to the uterine horns’ location. This suggests placental insufficiency, meaning that the placenta was not able to deliver adequate nutrients and oxygen to the foal.
• Upon microscopic examination, the microcotyledons (structures that increase the surface area of the placenta) were notably attenuated, and chorionic villi (finger-like projections that secured the placenta to the uterus wall) were absent. These observations further highlight the inadequacy of the placenta, contributing to the health problems experienced by the foal.