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The current methods to detect central nervous system (CNS) tissue in blood, lungs, or meat are cumbersome, time consuming, and costly. The objective of this study was to use glial fibrillary acidic protein (GFAP), which is restricted to the CNS, in an enzyme-linked immunosorbent assay (ELISA) for the detection of CNS tissue in blood and muscle from beef cattle. Bovine brain, cerebral cortex, spinal cord, sciatic nerve, diaphragm, blood clots, and other skeletal muscle were obtained from three animals at slaughter. The limit for detection of GFAP was approximately 1.0 ng and the standard curve was linear up to 40 ng. Tissue samples gave responses parallel to the GFAP standard, suggesting that standard and unknown samples were immunoreactively identical. No GFAP was detected in skeletal muscle (ground beef, shoulder clod, and diaphragm) and blood clots. Trace amounts (13.5 to 51 ng/mg) were present in sciatic nerve. In contrast, high levels of GFAP (55 to 220 microg/ mg) were present in spinal cord, cerebral cortex (17 microg/mg), and whole brain (9 to 55 microg/mg). In a storage study using two animals in two separate studies, immunoreactive GFAP was detectable for up to 8 days at 4 degrees C in all tissues containing neural elements. Thus, mixtures of muscle with spinal cord or brain retained almost 80% of their immunoreactivity after 8 days at 4 degrees C, while brain and spinal cord alone retained approximately 50% and 25%, respectively, of their initial activities. In a repeat experiment, 80 to 100% of the initial activity was retained in these tissues after 8 days at 4 degrees C. The results of the current study demonstrate that the GFAP ELISA provides a valid and repeatable method to detect CNS tissue contamination in meat.

The effects of a single subcutaneous (s.c.) injection of the nitroaliphatic toxicants 3-nitropropanol (NPOH) and 3-nitropropionic acid (NPA) dissolved in physiological saline solution were studied in mice and rats, respectively. Clinical signs observed in both NPOH-treated mice and NPA-treated rats included depression, abnormal motor activity, and recumbency. Succinate dehydrogenase (SDH) activity, demonstrated histochemically in frozen brain sections, was markedly reduced in intoxicated mice and rats. The SDH activity of mitochondrial preparations from brains of intoxicated mice and rats was diminished to 18-24% of control values, although the activity of another mitochondrial flavoprotein enzyme, alpha-glycerophosphate dehydrogenase (alpha-GPDH), was not altered.

3-Nitropropionic acid (NPA), a toxin which irreversibly inhibits the Krebs cycle enzyme succinate dehydrogenase, causes severe neurologic disease and a specific pattern of morphologic brain damage when given subcutaneously to rats. To determine whether hypotension or hypoxemia were necessary for development of morphologic brain lesions in NPA neurotoxicity, systemic blood pressure and arterial blood gases were measured in NPA-intoxicated rats. The extent and distribution of albumin extravasation was examined by immunohistochemistry, and was compared to the extent and severity of morphological injury in the caudate-putamen. Neither hypotension nor hypoxemia were necessary for the development of morphologic injury in the brains of NPA-intoxicated rats. In fact, intoxicated rats had significantly higher systolic blood pressure and arterial blood oxygen than did controls. Arterial bicarbonate and pH were significantly lower in intoxicated rats than controls, however, suggesting that acidosis may be involved in the pathogenesis of NPA toxicity. When morphologic injury was severe, albumin extravasation was extensive occupying approximately 30%-80% of the lesion area in the caudate-putamen of NPA-intoxicated rats. When morphologic injury was mild, albumin extravasation was absent, or limited to small cuffs around individual capillaries (less than 1% of the lesion area). There was no leakage of albumin in the cerebral cortex, which was resistant to morphologic injury. It was concluded that leakage of protein-rich fluid into cerebral parenchyma from blood-brain barrier impairment is not responsible for the initiation of morphologic injury in NPA toxicity, but may contribute to the severity of injury later in the evolution of brain lesions.

The clinical signs and morphological brain lesions associated with histotoxic hypoxia induced by subcutaneous injection of 3-nitropropionic acid (NPA) in rats are described, and compared to hypoxic brain damage from other causes including ischemia and hypoglycemia. The brains were perfusion-fixed with paraformaldehyde/glutaraldehyde fixative, and examined by light and electron microscopy. Intoxicated rats developed severe neurological disease characterized by somnolence, uncoordinated gait with stereotypical paddling movements, and ventral or lateral recumbency. Recumbent rats had a selective, bilaterally symmetrical pattern of severe morphological injury in the caudate-putamen, hippocampus, and thalamus. Recumbency was a consistent indicator of the development of morphological brain lesions. In contrast to reports describing rat models of ischemia and hypoglycemia, morphological injury was not seen in the cerebral and cerebellar cortices of NPA-intoxicated rats. Ultrastructurally, neuronal alterations ranged from chromatin clumping with increased cytoplasmic lucency to severe cellular shrinkage or swelling with marked mitochondrial swelling (high amplitude swelling). White matter alterations included axonal swelling and adaxonal splitting of myelin lamellae. Vascular changes included perivascular deposits of proteinaceous material presumably from leakage of serum proteins, variable electron lucency of endothelial cell cytoplasm, an apparent increase in pinocytotic vesicles, rare platelet thrombosis of capillaries, and rare intravascular blebs of luminal plasma membrane. As a model of brain damage following energy deficiency, NPA intoxication has the advantages of producing morphological brain injury in a highly predictable anatomical pattern, and at a time paralleling the onset of clinical recumbency.