Biomedical subjects

N Pradhan

Publications and source records attributed to N Pradhan.

33 records · Page 2Linked to original sources

PubMed1993

A mimetic-based frequency domain technique for automatic generation of EEG reports.

This paper describes a novel mimetic technique of using frequency domain approach and digital filters for automatic generation of EEG reports. Digitized EEG data files, transported on a cartridge, have been used for the analysis. The signals are filtered for alpha, beta, theta, and delta bands with digital bandpass filters of fourth-order, cascaded, Butterworth, infinite impulse response (IIR) type. The maximum amplitude, mean frequency, continuity index and degree of asymmetry have been computed for a given EEG frequency band. Finally, searches for the presence of artifacts (eye movement or muscle artifacts) in the EEG records have been made.

Algorithms↗

PubMed1993

Use of running fractal dimension for the analysis of changing patterns in electroencephalograms.

Running fractal dimensions were measured on four channels of an electroencephalogram (EEG) recorded from a normal volunteer. The changes in the background activity due to eye closure were clearly differentiated by the fractal method. The compressed spectral array (CSA) and the running fractal dimensions of the EEG showed corresponding changes with respect to change in the background activity. The fractal method was also successful in detecting low amplitude spikes and the changes in the patterns in the EEG. The effects of different window lengths and shifts on the running fractal dimension have also been studied. The utility of fractal method for EEG data compression is highlighted.

Alpha Rhythm↗

PubMed1993

Behavioral consequences of predictable vs. unpredictable shocks in rats.

Adult, male, Sprague-Dawley rats were given either predictable or unpredictable footshocks coupled with predictable or unpredictable warning stimuli in a factorially designed experiment. The effect of footshocks on different parameters of motility was studied immediately, 1 h and 24 h later. Footshock-induced stress caused increases in the motility of rats, and this increase persisted for 24 h. Of the parameters studied, distance travelled and time spent in ambulatory behavior were significantly affected, but there was no difference between the predictably and unpredictably shocked animals in the pattern or time course of stress-induced locomotion changes. The defecation scores recorded in footshocked rats were lower than in controls in both the predictably and unpredictably shocked groups, but there was no difference between the predictably and unpredictably shocked groups. Lack of differences in motility and defecation between the two groups limits the usefulness of these parameters in behavioral experiments based on predictability of noxious stimuli.

Animals↗

PubMed1993

Effect of disulfiram administration on brain tryptophan, serotonin and peripheral tryptophan content.

The prophylactic deterrent effect of disulfiram (DS) has been attributed to its ability to exacerbate sympathetic function. Though there are reports to indicate that DS administration could as well affect the neurotransmitter metabolism, few reports implicate the possibility of central nervous system (CNS) mediated anticraving effect of the drug. The present study involving the oral administration of DS to rats for 45 days has clearly shown a significant increase in 5-HT (815.4 +/- 74.7 ng/g, P < 0.01) and 5-HIAA (506.1 +/- 86.3 ng/g, P < 0.02) contents in brain when compared to control rats. The observed increase in 5-HT and 5-HIAA content was found to correlate (zeta = 0.89) with the concomitant increase in brain tryptophan content (4.15 +/- 1.05 nmol/g, P < 0.001) following DS administration. Further, the study on peripheral tryptophan content has shown an increase in both total and free fraction (ultrafiltrate) of plasma, which in turn was found to have an inverse relationship (zeta = -0.94, P < 0.05) with the decrease in liver tryptophan content following DS administration. Thus the observed increase in brain 5-HT level is attributed to the ability of DS to mobilise peripheral tryptophan for 5-HT synthesis in CNS. As there are reports to imply the hyposerotonergic function as responsible for craving, the present findings, that DS could enhance the 5-HT metabolism in brain, may partially explain the CNS mediated anticraving effect of DS.

Animals↗

PubMed1991

Correlations of motility, defecatory behavior and striatal dopaminergic activity in rats.

The spontaneous motor activity, fecal pellet scores and content of dopamine and its metabolites, dihydroxyphenyl acetic acid and homovanillic acid in corpus striatum were measured in a group of randomly selected Sprague-Dawley rats. The spontaneous motility, fecal pellet scores and neurochemical parameters measured showed significant variations. The correlations between these parameters were investigated. A significant correspondence was seen between the motility, fecal pellet scores and the striatal dopaminergic activity. The implications of the behavioral models of motility and defecation scores in studying the central dopaminergic function is discussed. It is suggested that striatal dopaminergic activity may be responsible not only for motor activity but also may contribute to the de novo emotionality as expressed by the defecation scores in rats.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1990

Behavioral and neurochemical differences in an inbred strain of rats.

The spontaneous motility of 75 Sprague-Dawley rats obtained from an inbred strain was found to vary widely. To test the hypothesis that heterogeneity in motility is accompanied by heterogeneity in neurochemical and vegetative function variables, the median motility score was used to divide the animals into high and low motility groups. Subgroups of high and low motile animals were compared on fecal pellet scores and on dopamine, dihydroxyphenyl acetic acid and homovanillic acid content of the corpus striatum. Significant differences were obtained between the two groups, indicating that even in an inbred strain considerable heterogeneity (possibly representing further subtypes) may exist. The theoretical and experimental implications of these findings are discussed.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1990

Changes in the sensitivities of dopamine receptors to chronic treatment with imipramine & haloperidol in rats.

Apomorphine induced locomotor activity was studied in Wistar rats treated with imipramine and haloperidol with the help of automated measuring devices. The control rats showed a biphasic response of hypomotility and sedation to low dose apomorphine, and hypermotility to high dose apomorphine. In chronic imipramine-treated rats, the hypomotility and sedative response to low dose apomorphine challenge was significantly attenuated (P less than 0.05), as compared to saline treated controls. A similar response was observed in the chronically haloperidol treated rats (P less than 0.01). However, there were no significant differences in motility responses to high dose apomorphine challenge between the control and experimental groups. These results suggest that presynaptic dopamine auto receptors may not be involved in mediating the loss of response to low dose apomorphine by chronic imipramine treatment. Imipramine being predominantly a monoamine uptake inhibitor and haloperidol a potent postsynaptic D-2 blocker, some indirect mechanisms may be involved in the loss of response to low dose apomorphine challenge.

Animals↗

PubMed1990