Study on the mechanism of the appearance of noise effects

Summary This study was undertaken to investigate the dose-response relationship between the biological effect and noise exposure, and to consider the mechanism of the appearance of noise effects. Rats were exposed to noise at intensities of 60 dB (A), 80 dB (A) and 100 dB (A) for 240 min and examined for the change of activities of dopamine--hydroxylase (DBH) in serum and adrenal glands. Plasma cyclic adenosine 3,5-monophosphate (c-AMP) levels were also measured. Some rats were given 6-hydroxydopamine (6-OHDA) as a chemical sympathectomyzing agent 20 h before noise exposure in order to consider the mechanism of the appearance of noise effects. By noise exposure, serum DBH activity was significantly (P<0.01) increased at each intensity compared with the control group, but there were no remarkable changes in adrenal DBH activity. Plasma c-AMP level was also significantly elevated in response to the noise stress. When the rats, which had been pretreated with 6-OHDA, were exposed to noise with an intensity of 100 dB (A), the response of serum DBH activity was no longer observed. Therefore it is suggested that the effect due to noise exposure appears through the post-ganglionic sympathetic nerve fiber.     

Spontaneous activity of single neurons in the olfactory bulb of the rainbow trout (Salmo gairdneri) and its modulation by olfactory stimulation with amino acids

Summary Spontaneous action potentials recorded from 126 neurons in the olfactory bulb of Salmo gairdneri show a higher tendency towards bursting patterns of activity than those shown in previous reports about other fish. Granule cells and periglomerular cells are more likely to fire in bursts than mitral cells. Natural chemical stimulation of the olfactory mucosa with amino acid solutions produced a unique pattern of excitatory and inhibitory responses across all units. Chi-square values were calculated for stimulatory effectiveness between forty-five pairs of odours. L-serine and L-alanine consistently showed a high degree of similarity with several other odours. The converse was true for GABA and L-histidine, although this pair had a high chi-square value when mutually compared. Enantiomeric pairs of amino acids were often found to have opposite stimulatory effects on bulbar units. These results are discussed in relation to the possible properties and configurations of odorant receptor sites for amino acids in the fish olfactory mucosa.     

Auditory event-related potentials during stage 2 NREM sleep in humans

SUMMARY  Event-related potential (ERP) recordings were used to investigate the nature of auditory stimulus evaluation during stage 2 sleep. Frequent and rare stimuli, differing in intensity and frequency, were presented to six adult subjects while awake and asleep. The latency and voltage distribution of one of the long-latency components evoked during sleep resembled the P3 component evoked while awake. However, it was attenuated in voltage and superimposed on N3, a large late negative component, most probably the slow potential of the K complex. The identification of a P3-like potential during sleep suggests that the P3 potential is not solely a marker of active cognitive processes, but contains a small component which reflects automatic, pre-attentive evaluation of deviant stimuli.     

A Morphological and Immunohistochemical Study of Lymphoid Germinal Centers in Synovial and Lymph Node Tissues from Rheumatoid Arthritis Patients with Special Reference to Complement Components and Their Receptors

Rheumatoid arthritis (RA) is one of the immune complex (IC) diseases in which lymphoid germinal centers (GCs) are found in the synovial tissue. Simultaneously, patients with RA often show swelling of lymph nodes. The morphology and function of the lymph node GCs in patients with RA is not clear. The aim of this study was to evaluate the differences in morphology and immunoreactions to complement (C) components, their receptors, and lgM-rheumatoid factor (RF) between synovial GCs and lymph-node GCs in RA. Furthermore, the relationship between these immuno-reactive substances and follicular dendritic cells (FDCs) in GCs was investigated. The tissues examined were 41 RA synovial specimens, seven RA lymph nodes with massive lymphadenopathy, and 10 non-RA lymph nodes. The number of synovial GCs was relatively decreased in comparison with lymph-node GCs in RA, and the diameter of each synovial GC was smaller than that of each lymph-node GC. The synovial GCs were edematous and less cellular, and moreover, those from RF-seronegative cases were smaller than those from RF seropositive cases. On the other hand, the lymph-node GCs in RA were larger, more cellular and hyperplastic, but contained more tingible-body macro-phages (TBMs) and neutrophils. In the GCs of both synovial tissues and lymph nodes in RA, early C components (C1q, C4, C3c, C3d), IgM RF, and C3b receptor (C3bR) and C3d receptor (C3dR) were expressed as a lacy network by light microscopy, and were demonstrated on the surfaces of FDCs and lymphocytes, and in the intercellular spaces by electron microscopy. Furthermore, immuno-staining for dendritic reticulum cells (DRC, DAKO DRC1) was observed in a lacy pattern by light microscopy and on the cell surface of FDCs by electron microscopy. In the GCs of non-RA lymph nodes, early C components, C3bR, C3dR, and DRC showed a similar reaction pattern, but IgMRF did not. Consequently, no marked difference in immunoreactions in the GCs, except for the immunoreactions of late C components, was found between synovial tissues and lymph nodes in RA. On the basis of these findings, we discuss the possibility of the presence of a RF-IC.     

Differential sensitivity to Arg side chain modification of IL-1β binding to type I and type II receptors

The central role of interleukin-1 (IL-1) in several disease processes, including fever and inflammation, makes the characterization of ligand-receptor interaction of prime importance.The role of arginine (Arg) side chains of hr-IL-1 in receptor recognition was studied by the modification of Arg residues with the specific reagent 1,2-cyclohexanedione. It was found that chemical modification of Arg residues decreased the binding potential of IL-1 to type I receptor dramatically (by 230-fold) while the affinity to type II receptor was reduced only moderately (by 10-fold), with an insignificant reduction of the dissociation rate.These studies suggest that intact Arg side chains of IL-1 may be necessary for high affinity binding to type I IL-1 receptor, but have less importance for the interaction of IL-1 with type II IL-1 receptor.This observation may be useful in the study of type II IL-1 receptor-mediated biological responses and design of receptor-subtype specific ligands as well.     

Frequency domain models of the EEG

The structure of the normal resting EEG crosspectrum SVV(omega) is analyzed using complex multivariate statistics. Exploratory data analysis with Principal Component Analysis (PCA) is followed by hypothesis testing and computer simulations related to possible neural generators. The SVV(omega) of 211 normal individuals (ages 5 to 97) may be decomposed into two types of processes: the xi process with spatial isotropicity reflecting diffuse, correlated cortical generators with radial symmetry, and processes that seem to be generated by more spatially concentrated, correlated sources. The latter are reflected as spectral peaks such as the process. The eigenvectors of the xi process are the Spherical Harmonic Functions which explains the recurring pattern of maps characteristic of the spatial PCA of qEEG data. A new method for estimating sources in the frequency domain which fits dipoles to the whole crosspectrum is applied to explain the characteristics of the localized sources.     

Genetically regulated human (T,G)-AL specific helper T cell replacing factors possess HLA-DR and Vh determinants

Human (T,G)-AL specific T cell helper factors secreted by in vitro activated peripheral blood lymphocytes of normal donors were characterized. Factors were passed through columns of Sepharose coupled either to antibodies against human immunoglobulin or antibodies against the variable region of the heavy (V_h) and light (V_l) chains of human immunoglobulin. In addition, the same factors were applied to columns of Sepharose coupled to anti-HLA-DR antibodies or to monoclonal antibodies against human Ia or β₂-microglobulin. The activity of the antigen specific factors was removed by the anti-V_h antibodies and not by anti-V_l or anti-human immunoglobulin antibodies. The factors passed through Sepharose coupled to anti-DR antibodies could be removed and eluted from columns of anti-DR antibodies relevant to the donors' DR antigens. The same factors were also removed by a monoclonal antibody (anti-Ia) which recognizes a monomorphic determinant on HLA-DR, but not by monoclonal anti-β₂-microglobulin. The results suggest that the genetically regulated (T,G)-AL specific helper factors possess HLA-DR as well as V_h determinants in their active moiety.     

Human cerebral potentials evoked by CO2 laser stimuli causing pain

Summary Brief radiant heat pulses, generated by a CO₂ laser, were used to activate slowly conducting afferents in the hairy skin in man. In order to isolate C-fibre responses a preferential A-fibre block was applied by pressure to the radial nerve at the wrist. Stimulus estimation and evoked cerebral potentials (EP), as well as reaction times, motor and sudomotor activity were recorded in response to each stimulus. With intact nerve, the single supra-threshold stimulus induced a double pain sensation: A first sharp and stinging component (mean reaction time 480 ms) was followed by a second burning component lasting for seconds (mean reaction time 1350 ms). Under A-fibre block only one sensation remained with characteristics and latencies of second pain. The heat pulse evoked potential consisted of a late vertex negativity at 240 ms (N240) followed by a prominent late positive peak at 370 ms (P370). Later activity was not reliably present. Under A-fibre block this late EP was replaced by an ultralate EP beyond 1000 ms, which in the conventional average looked like a slow halfwave of 800 ms duration. This potential was distinct from eye movements, skin potentials or muscle artefacts. With cross-correlation methods waveforms similar to the N240/P370 were detected in the latency range from 900 to 1500 ms during A-fibre block, indicating a much greater latency jitter of the ultralate EP. Latency corrected averaging with a modified Woody filter yielded a grand mean ultralate EP (N1050/P1250), the shape of which was surprisingly similar to the late EP (N240/P370). The similarity of these components indicates that both EPs may be secondary responses to afferent input into neural centers, onto which myelinated and unmyelinated fibres converge. Such convergence may also explain through the known mechanisms of short term habituation and selective attention, why ultralate EPs are not reliably present without peripheral nerve block.     

The flexor function of the m. pronator teres in man: a quantitative electromyographic study

Summary The muscle pronator teres was studied by surface electromyography during elbow flexion in a horizontal plane. The forearm was in semi-pronation and movement was performed at various velocities. A quantitative comparison was made between pronator teres activity and two main elbow flexors, biceps brachii and brachioradialis.The mean timing of the onset of activity was constant: biceps brachii was activated first followed by pronator teres and brachioradialis, and the lower the velocity of flexion, the earlier was the onset of biceps brachii activity.There was a linear relationship between the integrated EMG from each muscle and the work done. However, this relationship was less exact for pronator teres and brachioradialis at low values of work, a finding which opens questions about the generality of this relationship and about the muscle equivalent concept.Pronator teres appears to participate in elbow flexion besides its role in pronation.Despite similar anatomical peculiarities, pronator teres does not behave in the same way as anconaeus or popliteus and, above all, it is not the sole muscle active in slow movement. Thus, all the stocky mucles lying close to an articulation do not behave in the same way.     

Unrestricted principal components analysis of brain electrical activity: Issues of data dimensionality,artifact, and utility

Summary Principal components analysis (PCA) was performed on the 1536 spectral and 2944 evoked potential (EP) variables generated by neurophysiologic paradigms including flash VER, click AER, and eyes open and closed spectral EEG from 202 healthy subjects aged 30 to 80. In each case data dimensionality of 1500 to 3000 was substantially reduced using PCA by magnitudes of 20 to over 200. Just 20 PCA factors accounted for 70% to 85% of the variance. Visual inspection of the topographic distribution of factor loading scores revealed complex loadings across multiple data dimensions (time-space and frequency-space). Forty-two non-artifactual factors were successful in classifying age, gender, and a separate group of 60 demented patients by linear discriminant analysis. Discrimination of age and gender primarily involved EP derived factors, whereas dementia primarily involved EEG derived factors. Thirty-eight artifactual factors were identified which, alone, could not discriminate age but were relatively successful in discriminating gender and dementia. The need to parsimoniously develop real neurophysiologic measures and to objectively exclude artifact are discussed. Unrestricted PCA is suggested as a step in this direction.Acknowledgements: This work was supported in part by NIA program project PO1AG049853 to M. Albert and the Mental Retardation Program Project P30HD18655 to J.J. Volpe. We thank our qEEG technologists Adele Mirabella, Susan Katz, Ellen Belles, and Marianne McGaffigan as well as our research secretaries for their unflagging support.