The cochlear summating potential (SP) preceding the auditory nerve compound action potential (AP) was elicited by broadband alternating condensation and rarefaction clicks and recorded by noninvasive electrodes from the external auditory meatus (EAM) of 60 volunteers of both sexes, 12 to 67 years old, who had normal hearing for age. Quantitative data were obtained on: the number of ears displaying measurable SPs; the SP detection level; the SP onset, peak and rise times; the duration of the SP-AP complex; the SP amplitude; and the SP/AP amplitude ratio. Previously unknown relationships were unveiled between the amplitude, but not the temporal, measures of the SP and laterality, sex, age, and audiometrically determined hearing thresholds to 4 to 8 kHz tones. The highest correlations were obtained with these last thresholds, which suggested that receptors in the basal turn of the cochlea played a dominant role in the generation of the EAM-detected SP. To improve on existing techniques for determining abnormal SP elevation, a multiple regression method was devised that utilized sex, age, 4 to 8 kHz hearing thresholds, and AP voltage to establish upper normal limits of SP amplitude for individual subjects and ears.

Acoustic Stimulation↗

PubMedDate not supplied

An unusual intracerebral connective tissue mass.

A sharply circumscribed, vascular, connective tissue mass which replaced the cortex of several adjoining cerebral gyri is described. The histology of the lesion differs from that of previously reported central nervous system maldevelopments and neoplasms. However, there are a number of similarities to the pathology found in late phases of syphilitic "colloid" or "hyaline" degeneration of the brain.

Brain Diseases↗

PubMedDate not supplied

Experimental potentiation of phenothiazine toxicology. I. Effect of livers disorders.

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Animals↗

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Archival, formalin-fixed tissue: its use in the study of Alzheimer's type changes.

Preparing for a retrospective study of senile degeneration in schizophrenia, we had occasion to explore the suitability of an old collection formalin-fixed brains and paraffin blocks for study by modern staining methods. Tissue that had been in formalin for 50 years was embedded in paraffin. Sections were then stained with thioflavine S and with immunoperoxidase stains using Alz 50 and antibodies to paired helical filaments, ubiquitin, and beta-amyloid. In all 4 cases that had originally (50 years earlier) received neuropathologic diagnoses of Alzheimer's disease, large numbers of neocortical senile plaques and neurofibrillary tangles were clearly demonstrated by thioflavine S stain and by immunohistochemistry for paired helical filaments, ubiquitin, and beta-amyloid. In each of 4 other cases, in which the original neuropathologic examination had not revealed Alzheimer's disease, no plaques or tangles were observed. Immunoreactivity with Alz 50 was completely absent after 50 years in formalin. Examination of additional cases of Alzheimer's disease revealed that Alz 50 immunoreactivity was well preserved after 10 years in formalin and completely absent after 30 years in formalin. Alzheimer's disease tissue stored in paraffin for 30 years was clearly stained by all modalities. We conclude that immunohistochemical identification of senile plaques and neurofibrillary tangles is practical even after decades of storage in formalin or paraffin. The applicability of techniques that did not exist when these specimens were collected indicates that the systematic, permanent retention of formalin-fixed material may yield unanticipated future benefits.

Adult↗