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P K Banerjee

Publications and source records attributed to P K Banerjee.

At least 19 recordsLinked to original sources
PubMed1995

Thalamic NMDA receptors in the gamma-hydroxybutyrate model of absence seizures: a cerebral microinjection study in rats.

The possible role of thalamic NMDA receptors in the generation of experimental absence-like seizures was studied in rats. Bilaterally synchronous spike wave discharges were induced by gamma-hydroxybutyric acid (GHB) and were recorded simultaneously from different thalamic nuclei and the layers I-IV of frontoparietal cortex. Bilateral infusions of NMDA into thalamic mediodorsal nucleus, the intralaminar central lateral/paracentral nucleus, ventroposterolateral, or reticular nucleus of the thalamus in conscious rats, prior to GHB administration suppressed GHB-induced SWD in a dose dependent manner. However, no such suppression of GHB-induced SWD was observed when NMDA infusions were made into the above thalamic sites after the onset or development of GHB-induced SWD. Pretreatment with high doses of competitive (CGP 43487) or non-competitive NMDA receptor antagonists (MK-801 and ketamine) also dose dependently suppressed GHB-induced SWD. Both MK-801 and CGP 43487 dose dependently antagonized NMDA-mediated inhibition of GHB-induced SWD activity but at lower doses did not produce significant inhibition of GHB-induced SWD. The anti-SWD effects of NMDA, MK-801 and ketamine but not CGP 43487 were more pronounced in the mediodorsal and intralaminar thalamic nuclei than in the ventroposterolateral or reticular nucleus of thalamus. Because low doses of NMDA antagonists failed to disrupt the generation of seizures in the GHB model, these findings do not support a role for thalamic NMDA receptors in the pathogenesis of absence-like seizures induced by gamma-hydroxybutyric acid.

Animals↗
PubMed1995

Presynaptic gamma-hydroxybutyric acid (GHB) and gamma-aminobutyric acidB (GABAB) receptor-mediated release of GABA and glutamate (GLU) in rat thalamic ventrobasal nucleus (VB): a possible mechanism for the generation of absence-like seizures induced by GHB.

The ventrobasal nucleus of thalamus (VB) is considered to be intimately involved in the genesis of experimental absence-like seizures. Bilateral microinfusion of gamma-hydroxybutyric acid (GHB) into VB or systemic administration of gamma-butyrolactone, the pro-drug of GHB, induces generalized absence-like seizures in rats. In the present study, the basal and K(+)-evoked extracellular output of endogenous gamma-aminobutyric acid (GABA) and glutamate (GLU) in behaving rat VB nucleus was characterized 1) during unilateral GHB perfusion into VB and 2) during the course of generalized absence-like seizures induced by GHB. Although the basal extracellular release of GABA was inhibited by GHB (250-1500 microM) in a concentration-dependent manner, basal GLU levels remained unaltered. However, K(+)-evoked release of both GABA and GLU was significantly attenuated by GHB. During GHB-induced absence-like seizures, a similar decrease in basal GABA or K(+)-evoked GABA and GLU levels was observed. These effects of GHB were partially reversed by the specific GHB receptor antagonist NCS 382. (-)-Baclofen (10-50 microM) also produced a concentration-dependent decrease in basal and K(+)-evoked levels of GABA and GLU in this thalamic nucleus. The effects of either (-)-baclofen or GHB on the release of GABA and GLU were selectively antagonized by the GABAB receptor antagonists phaclofen (0.75-2 mM) and CGP 35348 (50-200 microM), respectively. These results suggest that by selectively modulating the basal and K(+)-evoked release of GABA and GLU, GHB induces, in the thalamic ventrobasal relay nucleus, an optimal "excitatory" environment conducive to the generation of absence seizures. Moreover, the data raise the possibility that a presynaptic GHB/GABAB receptor complex occurs in VB.

Action Potentials↗
PubMed1995

Improved signal-to-noise in PET activation studies using switched paradigms.

UNLABELLED: PET activation studies employing the autoradiographic technique and 15O-water or 15O-butanol use the difference between images acquired under baseline conditions and during activation to detect focal changes in cerebral blood flow which occur upon stimulus presentation. Typically, the activating task or baseline conditions are maintained throughout the entire imaging period. Simulations of the kinetics of these freely diffusible tracers suggest there may be an advantage to switching between activation and baseline conditions during the course of the study which results in images which maximize the difference signal rather than seeking to quantitate blood flow. We examine the potential of these switched protocols to increase signal-to-noise (S/N) in PET activation studies. METHODS: We examined S/N in activation studies using both-standard and switched paradigms with a simple switched protocol and dynamic three-dimensional PET data from human subjects. With tracer kinetic simulations, we investigated the sensitivity of the S/N gain to factors such as the shape of the input function, the time at which the conditions are switched and the magnitude of the activation. RESULTS: In human studies of activation sites in the visual cortex, primary motor and premotor areas, S/N improvements of 20%-30% were detected using the switched paradigms. Simulations show that this gain is virtually independent of activation magnitude and that there is a broad time window of 20 sec for making the switch between conditions. To obtain the highest S/N gain, a rapid bolus injection is required. CONCLUSION: Switched paradigms have the potential to significantly increase S/N in PET activation studies. In human studies, the S/N increase averaged 25% which is equivalent to increasing the number of counts collected by 50%. Switched paradigms can be used to maximize the difference signal in many activation studies, and do not preclude the absolute quantitation of blood flow using the standard autoradiographic technique.

Brain↗
PubMed1994

Thalamic mediodorsal and intralaminar nuclear lesions disrupt the generation of experimentally induced generalized absence-like seizures in rats.

The effect of bilateral electrolytic lesions of various thalamic sites on the generation of bilaterally synchronous spike and wave discharges (SWD) was studied in two experimental rat models of absence-like seizures. SWD induced by both pentylenetetrazole (20 mg/kg, i.p.) and gamma-hydroxybutyric acid (gamma-butyrolactone, 100 mg/kg, i.p.) were recorded simultaneously from the thalamus and cortex. In both models generation of SWD from the mediodorsal, intralaminar (central lateral and paracentral), ventroposterolateral (VPL) and the reticular thalamic (RT) nucleus was synchronous with that of frontoparietal cortex. Bilateral lesions in mediodorsal and intralaminar thalamic nuclei abolished SWD from both cortex and thalamus in both models. Similar lesions in VPL did not abolish, but attenuated the duration of pentylenetetrazole- and gamma-hydroxybutyric acid-induced SWD, more significantly from the thalamus than from the cortex. RT lesions were associated with more pronounced suppression of pentylenetetrazole-, but not gamma-hydroxybutyric acid-induced SWD in the thalamus. These findings suggest a potential role for mediodorsal and intralaminar thalamic nuclei in the generation of experimental absence-like seizures in rats.

Animals↗
PubMed1994

Neuroendocrine responses of flight cadets during midterm tests and of fighter pilots during tail chase sorties.

Urinary excretion of catecholamines (CA), epinephrine (E), and norepinerphrine (NE) was determined in flight cadets (n = 46) during mid-term test sorties and was compared with the measures of these variables in fighter pilots (n = 65) during tail chase sorties. Flight cadets were divided into passed and failed cadets. Fighter pilots were divided into superior, above average, and average with flying ratings of > 7, 6-7, and <6, respectively, and with flying experience of 2050 +/- 1081 h, 884 +/- 575 h, and 616 +/- 756 h, respectively. CA excretion data showed significant intra- and intergroup differences. Excretion rates for CA and NE before and after flight were significantly higher in flight cadets than in fighter pilots. After flight, all the preflight urinary variables increased significantly in passed flight cadets, while changes in failed flight cadets were not significant. In all groups of fighter pilots, preflight excretion rates for CA, E, and NE rose postflight, but the differences within the groups were not significant. The NE/E ratio decreased significantly as a function of flight adaptation. The pre- and postflight NE/E ratios were lower in fighter pilots than in flight cadets. The delta NE/E ratio decreased in fighter pilots, but increased in flight cadets. The preflight NE/E ratio was smaller for superior than for above average and average fighter pilots, and for passed than for failed flight cadets. The postflight NE/E ratio did not show any significant differences within the groups. In superior fighter pilots, the delta NE/E ratio remained relatively stable, while it was reduced in above average and average fighter pilots.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

gamma-Hydroxybutyric acid induced spike and wave discharges in rats: relation to high-affinity [3H]gamma-hydroxybutyric acid binding sites in the thalamus and cortex.

gamma-Hydroxybutyric acid is a naturally occurring compound which induces bilaterally synchronous spike and wave discharges in rats. The gamma-hydroxybutyric acid model of absence seizures simulates clinical absence seizures behaviorally as well as electrographically. The present study was undertaken in order to establish the role of the high-affinity gamma-hydroxybutyric acid binding sites in the generation of gamma-hydroxybutyric acid-induced spike and wave discharges. Spike and wave discharges induced by gamma-hydroxybutyric acid were recorded with the aid of bipolar depth electrodes implanted in discrete regions of thalamus, cortex and hippocampus. In the present study we found that ventroposterolateral, ventroposteromedial, medial and the reticular nuclei of the thalamus discharged synchronously with the cortical generation of spike and wave discharges. In the cortex, the superficial layers (I-IV) of frontoparietal cortex generated spike and wave discharges, whereas no spike and wave discharges were recorded from deeper layers (V-VI) of frontoparietal cortex. At the onset of spike and wave discharges induced by gamma-hydroxybutyric acid, a rapid but reversible upregulation of gamma-hydroxybutyric acid binding sites was observed. This increased [3H]gamma-hydroxybutyric acid binding was characterized by an increase in the number of gamma-hydroxybutyric acid sites with no significant change in their affinity for gamma-hydroxybutyric acid. Moreover, the change in [3H]gamma-hydroxybutyric acid binding was observed only in those thalamic structures and cortical layers which were found to be involved in the generation of spike and wave discharges induced by gamma-hydroxybutyric acid. The CA3 field or dorsal hippocampus possesses the highest density of [3H]gamma-hydroxybutyric acid binding sites of all brain regions. However, no significant change in [3H]gamma-hydroxybutyric acid binding was observed in this region nor was the CA3 field involved in the generation of spike and wave discharges during gamma-hydroxybutyric acid-induced absence-like seizures. These findings confirm that gamma-hydroxybutyric acid-induced absence-like seizures originate from thalamocortical pathways and that the onset of gamma-hydroxybutyric acid-induced spike and wave discharges is directly related to the regulation of gamma-hydroxybutyric acid binding sites in those regions which constitute the involved thalamocortical loop.

Animals↗
PubMed1993

Registration revisited.

Image registration is important for numerous imaging applications such as three-dimensional reconstruction, multimodality correlations, image averaging and subtraction. Methods used for image registration are based upon either the shape and form of the image pairs or their densitometric relationships. This paper describes the algorithms used for five different registration methods; frequency domain cross-correlation, spatial domain cross-correlation, principal axes/center of mass, fiducials and manual. These methods were compared in terms of their accuracy, efficiency and application with several different data types including different species and modalities. The underlying mathematical bases for each also are presented and compared. The results of the comparisons showed that image quality influenced the behavior of all methods. Images of the blockface provide an excellent reference for subsequent registration. These results also suggest that the statistical performance of various methods is not a reliable metric when distant and different images are registered. Visual comparisons by image overlap and pixel differencing illustrated that some methods are more prone to rotational error than others, especially when repeated pairwise registrations were computed along the rostral/caudal axis.

Algorithms↗
PubMed1992

The GABAA receptor complex in experimental absence seizures in rat: an autoradiographic study.

The regional distribution of radioactive ligand binding for different receptors of the gamma-aminobutyric acid A (GABAA)-benzodiazepine-picrotoxin chloride channel complex was measured on tissue section by autoradiography in brains taken from a genetic strain of Wistar rats with spontaneous absence-like seizures, the genetic absence epilepsy rats from Strasbourg (GAERS), and a control colony. The ligands employed included [3H]muscimol for high affinity GABA agonists sites; [3H]SR 95531 for the low-affinity GABA sites; [3H]flunitrazepam for the benzodiazepine sites; and [35S]t-butyl bicyclophosphorothionate (TBPS) for the picrotoxin site. There was no significant change between GAERS and control animals in [3H]flunitrazepam and [35S]TBPS binding. However, there was significantly decreased [3H]muscimol and [3H]SR 95531 binding in the CA2 region of the hippocampus of the GAERS. This was due to a decrease in Bmax of both [3H]muscimol and [3H]SR 95531 binding in the epileptic strain.

Animals↗
PubMed1992

Involvement of excitatory amino acid mechanisms in gamma-hydroxybutyrate model of generalized absence seizures in rats.

gamma-Hydroxybutyric acid (GHB), a naturally occurring compound which is synthesized from gamma-aminobutyric acid (GABA), induces bilaterally synchronous spike wave discharges, associated with behavioral changes, reminiscent of petit mal or generalized absence seizures in rats. In the present study, possible involvement of excitatory amino acids (EAAs) in GHB-induced spike wave discharges was investigated. The noncompetitive antagonist of NMDA receptors, MK-801, attenuated GHB-induced spike wave discharges at all doses tested (0.025-1.0 mg/kg) but dose-dependently induced suppression of EEG bursts in GHB-treated animals. The suppression of bursts was never observed with GHB in control experiments. N-Methyl-D-aspartate (NMDA) had a similar effect on GHB-induced spike wave discharges, when it was administered prior to GHB. This effect of NMDA was partially reversed by MK-801. The competitive antagonists of NMDA receptors, (+/-)CPP and CGP 43487 and the antagonist at the strychnine-insensitive glycine site, HA-966, also suppressed GHB-induced spike wave discharges with the EEG progressing to suppression of bursts but were weaker in this regard than MK-801 or NMDA. These data raise the possibility of involvement of excitatory amino acids in the GHB model of absence seizures.

Amino Acids↗
PubMed1991

Augmentation of rat brain endogenous monoamine oxidase inhibitory activity (tribulin) by electroconvulsive shock.

The effects of acute and subacute supramaximal and submaximal electroshock-induced convulsions on rat brain tribulin activity were investigated. Both supramaximal and submaximal shocks induced a marked increase, as measured 30 min after the onset of convulsions, with a significantly greater effect from the former. The effects were no longer present 24 h after stimulus. Repeated electroshock for 5 and 10 days showed that submaximal stimuli produced little change, whereas supramaximal shock brought about a significant increase in tribulin activity, the effect being greater with 10-day exposure. The results are not inconsistent with the clinical observation that a single electroconvulsive therapy (ECT) shock has little clinical usefulness but that repeated shocks, spread over several days, result in therapeutic benefit due, perhaps, to an increase in brain concentrations of tribulin, an endogenous monoamine oxidase inhibitor.

Animals↗
PubMed1990

Topical urea in dermatology.

For years research has been conducted to find a cutaneous moisturizer that is effective, easily available and relatively inexpensive urea, as a atopical agent, is all of this and is also a mild keratolytic. A trial was conducted over 200 patients suffering from a variety of disorders that were selected and using urea topically as urea 10 (10%), urea-20 lotion (20%), Urea-HC (with hydrocartisanl). The agent was applied twice daily for a maximum period of 8 weeks. Results indicate that urea is an effective moisturizer and in promotes the penetration of hydrocelisone into the skin.

Humans↗
PubMed1989

Lichenoid tissue reaction.

Lichenoid tissue reaction (LTR) is characterised by epidermal basal cell damage which takes the form of liquefaction degeneration or cell death either apoptosis or necrosis with an associated cascade of histologic events in epidermis and dermis. LTR is found in clinical conditions with lichenoid poikilodermatous and pigmentary dermatoses. A selected group of fifty lichenoid and pigmentary dermatoses such as Lichen planus (LP) Discoid lupus erythematosus (DLE) Lichenoid melanodermatitis (LM) and Lichen nitidus (LN) were studied. In LP basal cell liquefaction degeneration was extensive in comparison to other disease with large number of Civatte bodies and colloid bodies. There were significant vasodilatation in upper dermis inside the massive band like infiltrate. PAS positive basement membrane was disrupted in reaction area. Hypergranulosis was conspicuous. Chronic DLE showed spotty lichenoid reaction in the form of basal cell liquefaction degeneration. Civatte bodies and colloid bodies were infrequent. Infiltrate was more focal but could be band like. Epidermal atrophy and thickening of PAS positive basement membrane were important differentiating features, LM or Melanodermatitis toxica revealed focal mild to moderate liquefaction degeneration of basal cells with atrophy of the epidermis. The infiltrate although band like was less dense with marked pigmentary incontinence in clumps and giant melanophages. Civatte bodies, colloid bodies were not found and vascular changes were less prominent. LN showed localised basal cell damage with claw like rete ridges clutching a dense infiltrate. The dermal infiltrate often showed multinucleated giant cell. Civatte bodies and colloid bodies were not present. In some cases of the overlap syndrome LP/LE a careful study of lichenoid tissue reaction could distinguish these two diseases.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidermis↗
PubMed1988

Skin cosmetics.

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Cosmetics↗