Biomedical subjects

R M Demuth

Publications and source records attributed to R M Demuth.

5 recordsLinked to original sources

PubMed1986

The influence of stimulus repetition on the acoustic startle response and on responses of inferior colliculus neurons of mice.

The acoustic startle response (ASR) and discharges of single units in the inferior colliculus (IC) were evaluated as a function of the repetition rate and trial (stimulus 1-10 at each rate) of intense noise bursts in mice. The amplitude of the ASR was inversely proportional to both rate and trial. The mean number of discharges for the sample population of units of the central nucleus (ICC) and the external nucleus (ICX) were also inversely proportional to stimulus rate. However, only ICX units were inversely proportional to trial (i.e. as was the ASR). When response properties of individual units were examined, a variety of profiles was observed with regard to rate and trial sensitivity: units were either not sensitive to stimulus rate, inversely sensitive, directly sensitive, or complexly sensitive. Superimposed on these rate classifications were trial sensitivity, with some units being insensitive to trial, directly sensitive, or inversely sensitive. The incidence of response types differed in some respects between ICC and ICX and these differences were, in general, consistent with the mean responses of the neuronal populations.

Acoustic Stimulation↗

PubMed1986

A light and electron microscopic procedure for sequential double antigen localization using diaminobenzidine and benzidine dihydrochloride.

Very few double-antigen staining methods are available that are applicable to both light and electron microscopy. The objective of this study was to develop for localization of two neural antigens simultaneously a procedure which would be sensitive, simple to perform, offer permanent reaction products, and permit correlated light and ultrastructural analysis. The method employs sequential immunoperoxidase staining without antibody elution, in which the first sequence of antibodies is visualized with 3,3'-diaminobenzidine (DAB) and the second with benzidine dihydrochloride (BDHC). The DAB reaction product (brown and diffuse) was easily distinguishable from the BDHC deposit (blue, granular, and more electron-dense) by both light and electron microscopy. The procedure was used to simultaneously localize choline acetyltransferase-and either substance P or tyrosine hydroxylase in rat brain at both light and ultrastructural levels. Control experiments demonstrated the absence of both color mixing and antibody crossreactions, even when both primary antibodies were from the same species. This study demonstrates the usefulness of BDHC as a chromogen for immunoperoxidase staining either alone or in combination with DAB, and describes a double method which should have wide applicability for detailed studies of most pairs of antigens at both light and ultrastructural levels.

3,3'-Diaminobenzidine↗

PubMed1984

Excitability of auditory neurons in the dorsal and ventral cochlear nuclei of DBA/2 and C57BL/6 mice.

Extracellular response properties were studied in neurons of the dorsal and ventral divisions of the cochlear nucleus (DCN and VCN, respectively) of DBA/2 (DBA) and C57BL/6 (C57) mice. Mice of the former inbred strain show susceptibility to audiogenic seizures and have severe high frequency hearing loss when young; mice of the latter strain do not. Whereas afterdischarges had been readily observed in the inferior colliculus of DBA mice in a previous study, they were never observed in the cochlear nucleus. The incidence of nonmonotonic intensity functions, the slopes of intensity functions, and the incidence of inhibition in response areas indicated that inhibition was diminished in the DCN of DBA mice. However, in the VCN, these response properties did not differ between the two strains. There appeared to be an "amplification" of excitability (i.e., attenuation of inhibition) from VCN to DCN to inferior colliculus in DBA mice.

Acoustic Stimulation↗

PubMed1982

Abnormal tonotopic organization in the ventral cochlear nucleus of the hearing-impaired DBA/2 mouse.

The representation of sound frequency by auditory neurons (tonotopic organization) was evaluated in the ventral cochlear nucleus (VCN) of DBA/2 mice, a strain with impaired sensitivity to the highest and lowest frequencies heard by normal mice. Tuning curves were obtained from multiple-unit activity (MUA) and compared with those of C57 mice, which do not have severe hearing loss. Tuning curves in the C57 VCN displayed the dorsoventral progression from high- to low-frequency sensitivity that is typical of mammals. By contrast, tuning curves of DBA mice varied little as a function of dorsoventral location, and most MUA thresholds were lowest for frequencies within a narrow range (about 12-16 kHz). Thus, normal tonotopic organization is absent in the DBA mouse's VCN. In addition, because of the consistently low thresholds for 12-16 kHz tones in DBA MUA, mean thresholds for these frequencies are lower than those of C57 MUA in the dorsal and ventral portions of the VCN.

Animals↗

PubMed1982

Lesion-induced sprouting in the rat dentate gyrus is inhibited by repeated ethanol administration.

The effect of ethanol on hippocampal axonal sprouting was studied with a histochemical technique for identifying acetylcholinesterase. Unilateral lesion of the entorhinal cortex in adult rats produced an increase in the density of acetylcholinesterase staining in the outer molecular layer and a concomitant increase in the width of the pale-staining commissural-associational zone of the dentate gyrus. Other rats were given ethanol (11.3 +/- 0.45 grams per kilogram) for 2 weeks before and 9 days after receiving the lesion. Ethanol abolished the expansion of the commissural-associated zone. The effect of ethanol on sprouting axons suggests that it may inhibit recovery of function after brain injury.

Animals↗