Formic Acid Pretreatment Selectively Abolishes Argyrophilia of Senile Plaques in the Brain of the Alzheimer-type Dementia

We studied the effect of formic acid pretreatment on silver stains and βprotein immunostain on brain tissue samples from patients with the Alzheimer-type dementia (AID). The argyrophilia of the amyloid component of senile plaques (SP), which could be visualized by modified Bielschowsky and periodic acid-methenamine silver (PAM) stains, was not visible when the specimens were pretreated with formic acid. In contrast, the pretreatment highly enhanced the immunoreactivity of this component with βprotein antiserum. Our findings suggest that formic acid pretreatment selectively abolishes the argyrophilia of the amyloid component of SP

Identification of 5.8 kDa C-terminal fragments of Alzheimer amyloid p protein precursor generated in the lysosomal system

Elucidation of the normal metabolic pathways of amyloid β protein precursor (AβPP) is one of the important fields in the study of Alzheimer's disease. It has been suggested that the endosomal-lysosomal pathway may play a key role in the metabolism ofAβPP. We prepared different subcellular fractions from rat brain using a discontinuous sucrose density gradient method. The lysosome-enriched fraction was identified morphologically and biochemically. Various antibodies against the C-terminus ofAβPP were employed to detect specific fragments of AβPP in different subcellular fractions by western blot. The bands of APPP fragments with apparent molecular weight of 5.8 kDa, possibly containing the whole cytoplasmic domain of AβPP, were present specifically in the lysosome-enriched fraction. The 5.8 kDa fragments were increased and full-length APPP was decreased during incubation of the lysosome-enriched fraction in acidic buffer. The results provided direct evidence for the degradation of AβPP in the lysosomal system. Our data indicate that the digestion of AβPP into these small peptides might be important in the pathogenesis of Alzheimer's disease

New ubiquitin-positive intraneuronal inclusions in the extra-motor cortices in patients with amyotrophic lateral sclerosis

We examined the brains of 27 amyotrophic lateral sclerosis (ALS) patients and 50 controls by light, electron and immunoelectron microscopy. Ubiquitin-positive intraneuronal inclusions were seen in the hippocampal granular cell layer and entorhinal cortex of 7 out of the ALS patients. Similar inclusions could not be seen in the same areas in the controls. They were not seen on light microscope staining, nor did they show anilinophilia, argentophilia or congophilia. They were not reacted with other antibodies including neurofilament, tau and paired helical filament (PHF). Immunoelectron microscopy by the preembedding method using anti-ubiquitin antibody showed those inclusions consist of loosely arranged lineal filaments and granular materials. These results suggest that ubiquitin-related cytoskeletal abnormalities are present in cerebral non-motor small neurons in some sporadic ALS patients

Methenamine Silver Stain Impregnates Amyloid-related Components of Senile Plaques in the Alzheimer Brains as Clearly as βprotein Immunostaining

We developed a new type of methenamine silver (MS) stain for senile plaques (SP) on paraffin-embedded tissue sections. This method is a modification of both Gomori's methenamine silver nitrate, and Jone's periodic acid-methenamine silver (PAM) stains. We omitted chemical preoxidation by either periodic acid in the PAM stain or chromic acid in Gomori's stain, and determined the best condition of silver solution for SP. This resulted in selective staining of SP and amyloid angiopathy, because capillary basement membranes, corpora amylacea, macrophage granules, and nerve cell pigments remained unstained. The argyrophilia of SP was not affected by pretreatment with aldehyde blocking reagents. In comparison with βprotein immunostain, our MS stain showed almost the same staining pattern as that of the βprotein immunostain. Moreover, the argyrophilia of SP was selectively abolished by formic acid pretreatment, which has been shown to destroy β-pleated sheet structure of amyloid, suggesting that our MS stain impregnates amyloid-related components of SP. Our MS stain is a new, rapid, easy, and reliable method, and sensitive enough for routine or screening studies of the SP