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Biomedical subjects

N Pradhan

Publications and source records attributed to N Pradhan.

At least 19 recordsLinked to original sources
PubMed2006

Beneficiation of iron ore slime using Aspergillus niger and Bacillus circulans.

Studies were carried out on the removal of alumina from iron ore slime containing (%) Fe(2)O(3) 75.7, Al(2)O(3) 9.95, SiO(2) 6.1, Fe (total) 52.94 with the help of Bacillus circulans and Aspergillus niger. B. circulans and A. niger showed 39% and 38% alumina removal after six and 15 days of in situ leaching at 10% pulp density, respectively. Culture filtrate leaching with A. niger removed 20% alumina at 2% pulp density with 13 day old culture filtrate. B. circulans was more efficient than A. niger for selective removal of alumina. In case of A. niger in situ leaching rather than culture filtrate leaching was found to be more effective.

Aluminum↗
PubMed2005

Primary total knee replacement: a comparison of a nationally agreed guide to best practice and current surgical technique as determined by the North West Regional Arthroplasty Register.

INTRODUCTION: In 1999, a statement of best practice in primary total hip replacement was approved by the Council of the British Orthopaedic Association (BOA) and by the British Association for Surgery of the Knee (BASK) to provide a basis for regional and national auditable standards: we have compared practice in the North West of England to this document to ascertain adherence to this guide to best practice. MATERIALS AND METHODS: A direct comparison of data held on the North West Hip Arthroplasty Register for 2001/2002 and BASK/BOA guidelines was performed. 86 surgeons from 26 hospitals were included in the study. RESULTS: A mean of 93.3% of operations were performed in the surgeon's usual theatre. All of these theatres had vertical laminar air flow systems. 42.2% of respondents routinely used exhaust suits and 68.1% of respondents routinely used impermeable disposable gowns. All surgeons use some form of anti-thromboembolic prophylaxis; 66.2% use a combination of both mechanical and chemical means. All surgeons used antibiotic prophylaxis. The most popular choice of antibiotic was a cephalosporin. 93.7% of surgeons routinely use antibiotic-loaded cement. The PFC and Kinemax prostheses were the most commonly used prostheses. Interestingly, 97.7% of all first-choice implants were cemented. Only 2 surgeons used uncemented total knee replacement. 69.8% of surgeons used a posterior cruciate retaining design. A midline longitudinal skin incision is used by 87.2% of surgeons, a medial longitudinal skin incision by 7.0% and a lateral longitudinal skin incision by 5.8% of surgeons. A medial parapatellar capsular incision is preferred by 91.9% with the remainder using mid vastus or trivector retaining capsulotomy. Closure of capsulotomies is performed in flexion by 65.1% and in extension by 34.9%. In patients with osteoarthritis, 38.4% routinely resurfaced the patella, 34.9% never resurfaced the patella and 26.7% selectively resurfaced. This was in direct contrast to practice for patients with rheumatoid arthritis in whom 66.3% routinely resurfaced the patella, 22.1% never resurfaced the patella and 11.6% selectively resurfaced. DISCUSSION AND CONCLUSIONS: This study has demonstrated variation of practice in hip arthroplasty across the North West region and significant divergence from the BASK/BOA statement of best practice. The introduction of a properly funded national arthroplasty register will surely help to clarify the effect of such diverse practice on patient outcome.

Antibiotic Prophylaxis↗
PubMed2004

Primary total hip replacement: a comparison of a nationally agreed guide to best practice and current surgical technique as determined by the North West Regional Arthroplasty Register.

BACKGROUND: In 1999, a statement of best practice in primary total hip replacement was approved by the Council of the British Orthopaedic Association (BOA) and by the British Hip Society (BHS) to provide a basis for regional and national auditable standards. We have compared practice in the North West Region of England to this document to ascertain adherence to this guide to best practice. METHODS: A total of 86 surgeons from 26 hospitals were included in a questionnaire study. RESULTS: A mean of 93.3% of operations were performed in the surgeon's usual theatre. All of these theatres had vertical laminar air flow systems. Of respondents, 42.2% routinely used exhaust suits, 68.1% routinely used impermeable disposable gowns, and 26.1% used impermeable re-usable gowns. The Charnley femoral and acetabular prostheses were the most commonly used prostheses. All surgeons used some form of anti-thromboembolic prophylaxis: 66.2% use a combination of both mechanical and chemical means. All surgeons used antibiotic prophylaxis. The most popular choice of antibiotic was a cephalosporin--70.7% used a 3-dose regimen over 24 h, 2.6% of surgeons continued antibiotic prophylaxis for 48 h after surgery, and 93.7% of surgeons routinely use antibiotic-loaded cement. All surgeons routinely cleaned, irrigated and dried the acetabulum and femur before cement insertion. Only one surgeon did not use any form of femoral canal occlusion. 69.4% used an intramedullary bone block. Retrograde filling of the femoral shaft by means of a cement gun was practised by 65.1%. CONCLUSIONS: This study has demonstrated considerable variation of practice in total hip arthroplasty across the North West Region and significant divergence from the statement of best practice approved by the BOA and BHS. The introduction of a properly funded national hip register will surely help to clarify the effect of such diverse practice on patient outcome. We would recommend that all trusts locally audit their practices and correlate them with these nationally agreed guidelines.

Antibiotic Prophylaxis↗
PubMed2001

Central nervous system stimulatory action from the root extract of Plumbago zeylanica in rats.

The effects of a 50% ethanol extract of the root of Plumbago zeylanica (P. zeylanica) were investigated on locomotor behaviour and central dopaminergic activity in rats. The effects on the ambulatory behaviour were assessed along with the levels of dopamine (DA) and its metabolite homovanillic acid (HVA) in the striatum after a single oral dose (100, 200 and 300 mg/kg body weight) of the extract. The extract significantly increased the spontaneous motility in animals. The ambulatory and rotatory behaviour in the treated groups were higher than in the control group (p < 0.05). There were marked differences in the ambulatory behaviour between 100 and 300 mg/kg, indicating that the responses were stimulatory and dose-dependent. The stereotypic behaviour which is characteristic of a dopamine agonist showed biphasic effects. However, there was no significant difference between the groups (p > 0.05). The results showed that the extract of the root of P. zeylanica specifically enhanced the spontaneous ambulatory activity without inducing stereotypic behaviour. The neurochemical estimations revealed elevated levels of DA and HVA in striatum compared with the control rats (p < 0.01). The levels were higher for the 100 mg/kg treated group than the other groups. The levels declined by increasing the dosage of the extract to 200 mg/kg and 300 mg/kg, however, these levels remained higher than the control group. The relationship between motor activity and levels of dopamine are not parallel. These behavioural and biochemical results indicated stimulatory properties of the extract of the root of P. zeylanica, which may be mediated by dopaminergic mechanisms in the rat brain.

Animals↗
PubMed2000

Pharmacological study on antidepressant activity of 50% ethanol extract of a formulated ayurvedic product in rats.

The effects of 50% ethanol extract of one formulated ayurvedic product, consisting of a mixture of medicinal plant species, was investigated on behavioral despair test (forced swimming test, FST), central dopaminergic and serotonergic activity in rats. The effects on the forced swimming test were assessed along with the levels of dopamine (DA), serotonin (5-HT) and its metabolites homovanillic acid (HVA) and 5-hydroxyindoleaceticacid (5-HIAA) in striatum, frontal cortex, hippocampus, hypothalamus and brain stem after 21 days of chronic oral administration of the extract (500 and 1500 mg/kg-body weight). The extract significantly increased climbing behavior at 500 mg/kg and increased swimming behavior by reducing immobility time at 1500 mg/kg when compared with the control group in forced swimming test (P<0.05). This showed that the active substances present in 50% ethanol extract of the ayurvedic preparation possess antidepressant activity and their specificity towards particular behavior, depends on the concentration of the extract. Further it showed that the enhancement of active behavior in FST is not due to generalized motor activity. The neurochemical estimations revealed the swim stressor inducing alterations in the levels of DA, 5-HT and their metabolites HVA and 5-HIAA in the brain regions assayed as compared with the non-stressed control rats. These changes were prevented extract treated rats. The 500 mg/kg extract treated group had significantly increased the levels of DA in frontal cortex, hypothalamus and hippocampus whereas the 5-HT in hypothalamus (P<0.05). However, there were no significant changes in the levels of HVA and 5-HIAA. These behavioral and biochemical results indicate antidepressant properties of the extract, which may be mediated by the dopaminergic and serotonergic mechanisms in rat brain.

Animals↗
PubMed1999

Significance of time scales in nonlinear dynamical analysis of electroencephalogram signals.

We propose to show in this paper, that the time series obtained from biological systems such as human brain are invariably nonstationary because of different time scales involved in the dynamical process. This makes the invariant parameters time dependent. We made a global analysis of the EEG data obtained from the eight locations on the skull space and studied simultaneously the dynamical characteristics from various parts of the brain. We have proved that the dynamical parameters are sensitive to the time scales and hence in the study of brain one must identify all relevant time scales involved in the process to get an insight in the working of brain.

Adult↗
PubMed1996

Detection of seizure activity in EEG by an artificial neural network: a preliminary study.

Neural networks, inspired by the organizational principles of the human brain, have recently been used in various fields of application such as pattern recognition, identification, classification, speech, vision, signal processing, and control systems. In this study, a two-layered neural network has been trained for the recognition of temporal patterns of the electroencephalogram (EEG). This network is called a Learning Vector Quantization (LVQ) neural network since it learns the characteristics of the signal presented to it as a vector. The first layer is a competitive layer which learns to classify the input vectors. The second, linear, layer transforms the output of the competitive layer to target classes defined by the user. We have tested and evaluated the LVQ network. The network successfully detects epileptiform discharges (EDs) when trained using EEG records scored by a neurologist. Epochs of EEG containing EDs from one subject have been used for training the network, and EEGs of other subjects have been used for testing the network. The results demonstrate that the LVQ detector can generalize the learning to previously "unseen" records of subjects. This study shows that the LVQ network offers a practical solution for ED detection which is easily adjusted to an individual neurologist's style and is as sensitive and specific as an expert visual analysis.

Adolescent↗
PubMed1996

The nature of dominant Lyapunov exponent and attractor dimension curves of EEG in sleep.

The dynamical behaviour of the brain is currently being viewed from the perspective of nonlinear dynamics. There are several reports of low dimensional chaotic activity in various states of human behaviour. The time evolution of chaotic systems exhibit many transitional states and brain is known to undergo a number of transitions in sleep. It evolves from random looking states to almost periodic states with an increase in the depth of sleep. There occurs intermittent random-like behaviour in REM (rapid eye movement) sleep. In this paper, we examine the transitional processes of brain activity in sleep from the patterns of attractor dimension (D2) and its corresponding dominant Lyapunov exponent (lambda 1) curves of EEG signals. Results indicate the occurrence of different degrees of chaoticity in the transitional states that may be related to various sleep stages. The chaotic parameter curves yield an objective measure of the neurodynamics of sleep comparable to an hypnogram. The parallelism of D2 and lambda 1 curves implies the validity of Kaplan-Yorke conjecture for EEG. It is suggested that the nonlinear dynamical measures of EEG may yield information about the nature of underlying neural processes of brain in sleep.

Adolescent↗
PubMed1996

Phenobarbital in the anticonvulsant dose range does not impair learning and memory or alter brain AChE activity or monoamine levels.

The learning and memory in adult, male Wistar rats were assessed using the T-maze and passive avoidance tests after chronic administration of phenobarbital (PB) at 5, 15, 30, 60, or 75 mg/kg intraperitoneally (IP) for 21 days. The PB levels in plasma, the acetylcholine esterase (AChE) activity in the motor cortex, pyriform cortex, olfactory bulb, striatum, septum, and hippocampus and the levels of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), dopamine (DA), dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) levels in the hippocampus were measured. There was no significant change in learning and memory, AChE activity, or monoamine levels at plasma PB levels of 1.5, 6.0, 9.0, and 25 micrograms/ml (corresponding to doses of 5, 15, 30, or 60 mg/kg PB, respectively). However, at a plasma level of 55 micrograms/ml (75 mg/kg), PB caused impairment in learning and memory. It was associated with an increase in AChE activity and 5-HT levels in the hippocampus. The results indicate that chronic PB administration may not be linked to impaired learning and memory functions at doses used in anticonvulsant therapy.

Acetylcholinesterase↗
PubMed1995

Patterns of attractor dimensions of sleep EEG.

Low dimensional chaos is a property of many physiological oscillatory systems including the brain. Time series of sleep EEG records have been analyzed in the framework of recent developments in nonlinear dynamics. One of the characteristics of a chaotic time series is its attractor dimension. The running attractor dimension of a chaotic time series may reflect changes in states more accurately than manually scored records. In the present study the attractor dimensions of consecutive EEG segments of five sleep records were analyzed. The block of the EEG segment (window) was shifted by various lengths along the entire sleep data of each subject thus producing a running attractor dimension curve for each record. The attractor dimension values for different sleep stages were significantly different. The pattern of the running attractor dimension closely matched the scored hypnograms in these five sleep records.

Adolescent↗
PubMed1995

Stress-induced changes in regional monoamine metabolism and behavior in rats.

Groups of adult, male, Sprague-Dawley rats were subjected to either restraint at room temperature or cold restraint at 4 +/- 1 degree C for 2 h. Spontaneous motility, measured immediately after the stress, was decreased and defecation scores were increased in the cold restraint group but not in the restraint group. The rats were then sacrificed and prefrontal cortex, nucleus accumbens, and striatum dissected out. The levels of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), serotonin (5-HT), and 5-hydroxyindole acetic acid (5-HIAA) were measured in these areas by high performance liquid chromatography (HPLC) with electrochemical detection. DA levels were decreased in the prefrontal cortex (-68%), nucleus accumbens (-40%), and striatum (-76%) of the cold restraint group when compared to the controls. DA levels were decreased only in the prefrontal cortex of the restraint rats (-31%) when compared to the controls. The cold restraint group also had increased levels of DOPAC in the prefrontal cortex (+66%) and nucleus accumbens (+65%) and increased levels of HVA in the prefrontal cortex (+43%) when compared to the control group. Our results therefore indicate that cold restraint activates DA metabolism in the prefrontal cortex, nucleus accumbens, and striatum while restraint activates DA metabolism in the prefrontal cortex alone. Thus, cold restraint may be a more potent stressor than restraint alone.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1995

Chronic phenytoin induced impairment of learning and memory with associated changes in brain acetylcholine esterase activity and monoamine levels.

Groups of adult, male, Wistar rats were administered phenytoin (DPH) at 5, 12.5, 25, 50, or 75 mg/kg i.p. for 21 days. The learning and memory of these rats were assessed using the T-maze and passive avoidance tests. The plasma DPH levels, acetylcholine esterase (AChE) activity in different brain regions, and the levels of monoamines in the hippocampus were measured. The results indicate that DPH below the therapeutic plasma level did not significantly impair learning and memory. Correspondingly, no changes were noted in the brain 5-HT or AChE activity. However, DPH, at therapeutic plasma concentrations (i.e., 10.5 micrograms/ml in the dosage range of 50 and 75 mg/kg, respectively), significantly impaired learning and memory in rats. The impaired learning and memory functions were associated with increased 5-HT levels and decreased AChE activity in the hippocampus. With a dose of 75 mg/kg DPH, there was a reduction in the AChE activity in the striatum, in addition to hippocampus. It is conjectured that the neurochemical changes brought about by DPH at therapeutic plasma levels may account for the impairment of learning, memory, and cognitive functions in epilepsy.

Acetylcholinesterase↗
PubMed1995

Changes in learning and memory, acetylcholinesterase activity and monoamines in brain after chronic carbamazepine administration in rats.

Groups of adult male Wistar rats were administered carbamazepine (CBZ) in doses of 5, 10, 20, 40 or 80 mg/kg/day intraperitoneally (i.p.) for 21 days. The learning and memory of the rats were assessed by the T-maze and passive avoidance tests. The CBZ plasma levels, the activity of acetylcholinesterase (AChE) in different brain regions, and the levels of monoamines in the hippocampus were also measured. None of the administered doses of CBZ impaired learning and memory. Rats with CBZ plasma levels of 2.5 and 4.5 micrograms/ml corresponding to the doses of 20 and 40 mg/kg, learned significantly better than controls. AChE activity was decreased in hippocampus and pyriform cortex (19%) in these groups. Simultaneously, an increase in the serotonin (5-HT) (36%) and dopamine (137%) levels in the hippocampus was noted in the 20-mg/kg CBZ group. 5-Hydroxyindole acetic acid (5-HIAA) and homovanillic acid (HVA) levels were increased at 10-, 20-, and 40-mg/kg CBZ doses. However, a dose of 80-mg/kg caused no change in learning performance as compared with that of controls. Correspondingly, no changes were evident in the AChE activity or monoamine levels. We postulated that the decreased AChE activity caused by CBZ in the therapeutic range may lead to increased ACh levels in brain, thus producing improvement in learning and memory. The increased turnover of 5-HT and dopamine (DA) in the hippocampus may play a role in long-term potentiation and improvement in memory.

Acetylcholinesterase↗
PubMed1994

Data compression by linear prediction for storage and transmission of EEG signals.

The EEG time series has been subjected to various formalisms of analysis to extract meaningful information regarding the underlying neural events. In this paper the linear prediction (LP) method has been used for analysis and presentation of spectral array data for the better visualisation of background EEG activity. It has also been used for signal generation, efficient data storage and transmission of EEG. The LP method is compared with the standard Fourier method of compressed spectral array (CSA) of the multichannel EEG data. The autocorrelation autoregressive (AR) technique is used for obtaining the LP coefficients with a model order of 15. While the Fourier method reduces the data only by half, the LP method just requires the storage of signal variance and LP coefficients. The signal generated using white Gaussian noise as the input to the LP filter has a high correlation coefficient of 0.97 with that of original signal, thus making LP as a useful tool for storage and transmission of EEG. The biological significance of Fourier method and the LP method in respect to the microstructure of neuronal events in the generation of EEG is discussed.

Algorithms↗
PubMed1994

Autoregressive spectral array for graphical display of EEG data.

A graphical display of the frequency content of background electroencephalogram (EEG) activity is obtained by calculating the spectral estimates using autocorrelation autoregressive method and the classical Fourier transform method. Display of spectral content of consecutive data segments is made using hidden-line suppression technique so as to get a spectral array. The autoregressive spectral array (ASA) is found to be sensitive to baseline drift. Following baseline correction the autoregressive technique is found to be superior to the Fourier method of compressed spectral array (CSA) in detecting the transitions in the frequencies of the signal. The smoothed ASA gives a better picture of transitions and changes in the background activity. The ASA can be made to adapt to specific changes of dominant frequencies while eliminating unnecessary peaks in the spectrum. The utility of the ASA for background EEG analysis is discussed.

Computer Graphics↗
PubMed1993

A nonlinear perspective in understanding the neurodynamics of EEG.

The developments in nonlinear dynamics and the theory of chaos have considerably altered our perception and analysis of many complex systems, including the brain. This paper reviews the physical and dynamical aspect of brain's electrical activity from this new perspective and indicates possible future directions. The importance of emerging trends of nonlinear dynamics and chaos to neurobiology has been discussed in the context of various states of consciousness and behaviour. In the past, EEG analysis has been confined to descriptive stochastic statistics and any understanding of the transitional process of brain activities was either nonexistent or not amenable for investigation. With the developments in nonlinear dynamics, the chaotic dynamical parameters and trajectory behaviour will find their use as feature detection techniques in EEG. Furthermore, nonlinear dynamics provides a model for EEG generation and temporal prediction which will help in determining the nature of neuronal processes governing various states of brain activity. The formalism of globally coupled dynamic systems will find applications in modelling the transitional states of EEG.

Brain↗