-argentoa combining form meaning silver (Latin argentum). argenfophilic plaques structures found in the brain tissues of older persons and identified as argentophilic because they absorb tissue stains containing silver. The a.p. appear under a microscope as wispy fibers in the frontal cortex and hippocampus. The a.p. are associated with Alzheimer’s disease in humans and also have been found in the brains of aging animals. Also called argyrophilic plaques, argininosuccinic aciduria a form of moderate-tosevere mental retardation, often accompanied by grand mal seizures in childhood. Clinical signs include sparse, dull, friable hair on the scalp and body. Large quantities of argininosuccinic acid are present in the urine. Treatment is based on control of protein intake to prevent hyperammonemia. The trait is transmitted by an autosomal-recessive gene, argumentativeness contentiousness; a persistent urge to dispute and argue. In extreme form, a. may be a core symptom in manic episodes.