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A Banerjee

Publications and source records attributed to A Banerjee.

At least 37 records · Page 2Linked to original sources
PubMed2001

On the phase-space dynamics of systems of spiking neurons. II: formal analysis.

We begin with a brief review of the abstract dynamical system that models systems of biological neurons, introduced in the original article. We then analyze the dynamics of the system. Formal analysis of local properties of flows reveals contraction, expansion, and folding in different sections of the phase-space. The criterion for the system, set up to model a typical neocortical column, to be sensitive to initial conditions is identified. Based on physiological parameters, we then deduce that periodic orbits in the region of the phase-space corresponding to normal operational conditions in the neocortex are almost surely (with probability 1) unstable, those in the region corresponding to seizure-like conditions are almost surely stable, and trajectories in the region corresponding to normal operational conditions are almost surely sensitive to initial conditions. Next, we present a procedure that isolates all basic sets, complex sets, and attractors incrementally. Based on the two sets of results, we conclude that chaotic attractors that are potentially anisotropic play a central role in the dynamics of such systems. Finally, we examine the impact of this result on the computational nature of neocortical neuronal systems.

Action Potentials↗
PubMed2001

Wegener's granulomatosis: diagnostic dilemma.

Wegener's granulomatosis is a systemic disease characterized by a granulomatous lesion that can affect any organ throughout the body. This case-report illustrates the problem posed by a patient presenting with bilateral serous otitis media with marked sensorineural hearing loss, facial nerve paralysis and an atypical serological picture. The importance of early diagnosis and the protocol for the management of a patient with an uncertain diagnosis is discussed. Due to atypical presentations, only a high index of suspicion will ensure an early diagnosis.

Acute Disease↗
PubMed2001

Alveolar rhabdomyosarcoma of the parotid gland.

Alveolar rhabdomyosarcoma of the parotid gland is a rare condition. The treatment should involve an aggressive multi-modality approach incorporating surgical removal of the tumour, radiotherapy, and multi-agent chemotherapy. The presentation of this condition along with the most appropriate line of treatment is discussed.

Adult↗
PubMed2001

Application of seminal germ cell morphology and semen biochemistry in the diagnosis and management of azoospermic subjects.

AIM: To evaluate whether the study of seminal germ cell morphology (SGCM) and semen biochemistry could be fruitfully utilized for the diagnosis and management of azoospermic subjects. METHODS: In the semen, mature and immature germ cells are contributed by the testes, 70% of glycerylphosphoryl choline (GPC) by the epididymis, fructose mostly or solely by the seminal vesicles and acid phosphatase [corrected] (ACP) by the prostate. In 16 normal volunteers, 12 vasectomized subjects and 186 azoospermic subjects, these parameters have been studied and the data have been analyzed. RESULTS: Both mature and immature germ cells are absent in the semen of vasectomized subjects as well as in obstructive azoospermia; GPC level is also significantly decreased in both these groups. In cases with non-obstructive azoospermia immature germ cells are present and seminal GPC, ACP and fructose levels are normal. The diagnosis of obstructive and non-obstructive azoospermia based on these parameters correlated well with "correct" testicular biopsy findings. In some cases of azoospermia due to hypospermatogenesis or spermatogenic developmental arrest, the SGCM studies were very helpful in objectively monitoring the response of the germinal tissue to specific treatments. CONCLUSION: SGCM and semen biochemical parameters are very valuable non-invasive markers for differentiating obstructive from non-obstructive azoospermia. The SGCM findings serve as a dependable non-invasive testicular marker with high predictive value.

Adult↗
PubMed2001

A unified treatment regimen for new cases of tuberculosis in resource-poor countries: a study in a rural district in Malawi.

An oral ambulatory unified treatment regimen was introduced in Ntcheu District, Malawi, between April 1996 and June 1997 for all new patients (600) with tuberculosis (TB). There was no change in the case finding pattern compared with the previous 5 years; 65% of new smear-positive pulmonary tuberculosis (PTB) patients completed treatment, not significantly different compared with the previous 3 years. Treatment completion was significantly lower in patients with smear-negative PTB and extra-pulmonary tuberculosis, due mainly to high mortality rates (40% and 41% respectively). In a rural district with high human immunodeficiency virus sero-prevalence rates in TB patients, case finding and end of treatment outcome of the oral unified regimen were comparable to those of previous regimens.

Antitubercular Agents↗
PubMed2001

Dentine caries: take it or leave it?

In modern dentistry the primary aim when excavating carious dentine is to eradicate only the highly infected, irreversibly demineralised and denatured biomass in order to allow effective restoration of the cavity, restoration of the surface anatomy of the tooth and to prevent disease progression. However, the boundary between this superficial zone of dentine requiring excavation and the deeper, affected but repairable tissue is not always obvious either in the clinic or in the research laboratory. The inherent subjectivity in detecting this excavation boundary can result in clinically significant differences in the quality and quantity of dentine removed by different operators and makes the in vitro comparison of newer excavation techniques more difficult. This article discusses the rationale behind carious dentine excavation and the criteria available to the dentist, both clinical and laboratory, to help identify the dentine requiring removal.

Color↗
PubMed2001

Can guardians supervise TB treatment as well as health workers? A study on adherence during the intensive phase.

SETTING: In sub-Saharan Africa, tuberculosis (TB) has increased over the last two decades due to the human immunodeficiency virus pandemic. In Malawi, 20630 new TB patients were notified to the National Tuberculosis Programme in 1996, a fourfold increase since 1986. Due to this increase in cases and lack of resources (both human and monetary) it is becoming more difficult to ensure directly observed treatment (DOT) in the TB wards. METHODS: In Ntcheu district, Malawi, a new TB regimen was introduced from April 1996 in which patients received supervised treatment by either a health worker or a guardian (i.e., family member). Adherence to the different treatment options was measured by form checks, tablet counts, and tests for detecting isoniazid in the urine. Adherence was measured at 2, 4 and 8 weeks after onset of TB treatment. RESULTS: Overall adherence rate was 95-96%. Inpatients showed the highest adherence rates. Patients on guardian-based DOT (GB-DOT) (n = 35) showed 94% adherence, while patients on health centre based DOT (n = 40) showed more non-adherent behaviour: 11% according to monitoring forms, 14% according to tablet counts and 16% according to urine tests. DISCUSSION: The results suggest that decentralised care is a feasible option for anti-tuberculosis treatment and that guardians can supervise TB treatment just as well as health workers during the intensive phase of TB treatment.

Adult↗
PubMed2000

Identification of a cysteine residue in the active site of nitroalkane oxidase by modification with N-ethylmaleimide.

The flavoprotein nitroalkane oxidase catalyzes the oxidative denitrification of primary or secondary nitroalkanes to the corresponding aldehydes or ketones with production of hydrogen peroxide and nitrite. The enzyme is irreversibly inactivated by treatment with N-ethylmaleimide at pH 7. The inactivation is time-dependent and shows first-order kinetics for three half-lives. The second-order rate constant for inactivation is 3.4 +/- 0.06 m(-)(1) min(-)(1). The competitive inhibitor valerate protects the enzyme from inactivation, indicating an active site-directed modification. Comparison of tryptic maps of enzyme treated with N-[ethyl-1-(14)C]maleimide in the absence and presence of valerate shows a single radioactive peptide differentially labeled in the unprotected enzyme. The sequence of this peptide was determined to be LLNEVMCYPLFDGGNIGLR using Edman degradation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The cysteine residue was identified as the site of alkylation by ion trap mass spectrometry.

Amino Acid Sequence↗
PubMed2000

Biocatalytic preparation of a chiral synthon for a vasopeptidase inhibitor: enzymatic conversion of N(2)-

[4S-(4I,7I,10aJ)]1-Octahydro-5-oxo-4-[phenylmethoxy)carbonyl]amino]-7H-pyrido-[2,1-b] [1,3]thiazepine-7-carboxylic acid methyl ester (BMS-199541-01) is a key chiral intermediate for the synthesis of Omapatrilat (BMS-186716), a new vasopeptidease inhibitor under development. By using a selective enrichment culture technique we have isolated a strain of Sphingomonas paucimobilis SC 16113, which contains a novel L-lysine epsilon-aminotransferase. This enzyme catalyzed the oxidation of the epsilon-amino group of lysine in the dipeptide dimer N(2)-[N[phenyl-methoxy)-carbonyl] L-homocysteinyl] L-lysine)1,1-disulphide (BMS-201391-01) to produce BMS-199541-01. The aminotransferase reaction required alpha-ketoglutarate as the amino acceptor. Glutamate formed during this reaction was recycled back to alpha-ketoglutarate by glutamate oxidase from Streptomyces noursei SC 6007. Fermentation processes were developed for growth of S. paucimobilis SC 16113 and S. noursei SC 6007 for the production of L-lysine epsilon-amino transferase and glutamate oxidase, respectively. L-lysine epsilon-aminotransferase was purified to homogeneity and N-terminal and internal peptides sequences of the purified protein were determined. The mol wt of L-lysine epsilon-aminotransferase is 81 000 Da and subunit size is 40 000 Da. L-lysine epsilon-aminotransferase gene (lat gene) from S. paucimobilis SC 16113 was cloned and overexpressed in Escherichia coli. Glutamate oxidase was purified to homogeneity from S. noursei SC 6003. The mol wt of glutamate oxidase is 125 000 Da and subunit size is 60 000 Da. The glutamate oxiadase gene from S. noursei SC 6003 was cloned and expressed in Streptomyces lividans. The biotransformation process was developed for the conversion of BMS-201391-01 to BMS-199541-01 by using L-lysine epsilon-aminotransferase expressed in E. coli. In the biotransformation process, for conversion of BMS-201391-01 (CBZ protecting group) to BMS-199541-01, a reaction yield of 65-70 M% was obtained depending upon reaction conditions used in the process. Phenylacetyl or phenoxyacetyl protected analogues of BMS-201391-01 also served as substrates for L-lysine epsilon-aminotransferase giving reaction yields of 70 M% for the corresponding BMS-199541-01 analogs. Two other dipeptides N-[N[(phenylmethoxy)carbonyl]-L-methionyl]-L-lysine (BMS-203528) and N,2-[S-acetyl-N-[(phenylmethoxy)carbonyl]-L-homocysteinyl]-L-lysine (BMS-204556) were also substrates for L-lysine epsilon-aminotransferase. N-alpha-protected (CBZ or BOC)-L-lysine were also oxidized by L-lysine epsilon-aminotransferase.

Journal Article↗
PubMed2000

Enzymatic acetylation of 10-deacetylbaccatin III to baccatin III by C-10 deacetylase from Nocardioides luteus SC 13913.

Baccatin III is a polycyclic diterpene which can be used for the semi-synthesis of paclitaxel and analogs. An enzymatic process was developed for the conversion of 10-deacetylbaccatin III (10-DAB) to baccatin III without requiring protection of the 7-hydroxyl group. A C-10 deacetylase from Nocardioides luteus SC 13912 was immobilized on diethylaminoethyl cellulose (DEAE-Cellulose) and the immobilized enzyme was used in the biotransformation process. The reaction was catalyzed using vinyl acetate as acyl donor at ambient temperature and at pH 7. A reaction yield of 51% was obtained.

Journal Article↗
PubMed2000

Adenosine preconditioning reduces both pre and postischemic arrhythmias in human myocardium.

INTRODUCTION: Consistently, clinical series record supraventricular tachyarrhythmias in approximately 30% of patients following coronary artery bypass surgery (CABG). Ischemic preconditioning and adenosine preconditioning (Ado-PC) decrease postischemia/reperfusion (I/R) myocardial stunning, infarct size, and pharmacologically induced arrhythmias in all species including man. We hypothesized that adenosine preconditioning would decrease spontaneous pre- and postischemic atrial arrhythmias in human myocardium. The purposes of this study were to determine the effect of in vivo and in vitro Ado-PC on atrial arrhythmias. METHODS: Human atrial trabeculae were harvested from CABG patients, placed in organ baths, and paced (1 Hz). Developed force (DF) was recorded during simulated I/R (30/45 min). Prior to I/R, trabeculae were treated with Ado (125 microM) for 5 min (in vitro), or patients were treated with Ado (12 mg iv) 5 min (in vivo) prior to harvest of trabeculae. Contraction frequency >4 Hz (defined as atrial tachyarrhythmias) was recorded in all groups pre- and postischemia. RESULTS: Control trabeculae exhibited increased tachyarrhythmias pre- and postischemia. In vivo and in vitro Ado-PC suppressed both pre- and postischemic arrhythmias. CONCLUSIONS: Adenosine preconditioning suppresses the frequency of pre- and postischemic tachyarrhythmias against an ischemia/reperfusion insult in human myocardium. This antiarrhythmic effect occurs with both in vitro and in vivo administration of adenosine. Preconditioning with adenosine prior to elective ischemia/reperfusion is a promising strategy of reducing spontaneous atrial arrhythmias in patients undergoing myocardial revascularization.

Adenosine↗
PubMed2000

Dentine caries excavation: a review of current clinical techniques.

Since the invention and application of rotary instruments, the operative treatment of carious lesions has often resulted in considerable removal of tooth structure. More recently, newer techniques for removal of carious dentine have been developed in an attempt to minimise this excessive tissue loss. The following article reviews and discusses some of the techniques available to excavate demineralised dentine clinically. These methods can be classified as mechanical and non-mechanical, rotary and non-rotary and include: dental handpieces/burs, manual excavators, air-abrasion, air-polishing, ultrasonication, sono-abrasion, chemo-mechanical methods, lasers and enzymes. The advantages and disadvantages of each technique are discussed.

Air↗
PubMed2000

Identification of an essential tyrosine residue in nitroalkane oxidase by modification with tetranitromethane.

The flavoprotein nitroalkane oxidase from Fusarium oxysporum catalyzes the oxidation of nitroalkanes to the respective aldehydes or ketones with production of nitrite and hydrogen peroxide. The enzyme is irreversibly inactivated by incubation with tetranitromethane, a tyrosine-directed reagent, at pH 7.3. The inactivation is time-dependent and shows first-order kinetics for two half-lives of inactivation. Further inactivation can be achieved upon a second addition of tetranitromethane. A saturation kinetic pattern is observed when the rate of inactivation is determined versus the concentration of tetranitromethane, indicating that a reversible enzyme-inhibitor complex is formed before irreversible inactivation occurs. Values of 0.096 +/- 0.013 min(-1) and 12.9 +/- 3.8 mM were determined for the first-order rate constant for inactivation and the dissociation constant for the reversibly formed complex, respectively. The competitive inhibitor valerate protects the enzyme from inactivation by tetranitromethane, suggesting an active-site-directed inactivation. The UV-visible absorbance spectrum of the inactivated enzyme is perturbed with respect to that of the native enzyme, suggesting that treatment with tetranitromethane resulted in nitration of the enzyme. Comparison of tryptic maps of nitroalkane oxidase treated with tetranitromethane in the presence and absence of valerate shows a single peptide differentially labeled in the inactivated enzyme. The spectral properties of the modified peptide are consistent with nitration of a tyrosine residue. The amino acid sequence of the nitrated peptide is L-L-N-E-V-M-C-(NO(2)-Y)-P-L-F-D-G-G-N-I-G-L-R. The possible role of this tyrosine in substrate binding is discussed.

Amino Acid Sequence↗
PubMed2000

Scanning electron microscopic observations of human dentine after mechanical caries excavation.

OBJECTIVES: The structural integrity and surface characteristics of dentine remaining after caries excavation may be relevant to the subsequent bonding of adhesive restorative materials to the prepared cavity. This in vitro investigation aimed to analyse the different surface characteristics of the dentine cavity floor created after preparation using five different mechanical and chemo-mechanical methods of excavation: hand excavation, slow-speed bur, sono-abrasion, air-abrasion and Carisolv gel. METHODS: Ten cavities were prepared using each excavation method in extracted teeth with occlusal carious lesions. Epoxy resin replicas of the 50 cavities were manufactured from silicone impressions and then analysed using secondary electron scanning electron microscopy (SEM) to ascertain the surface characteristics of the dentine at the cavity floor. RESULTS AND CONCLUSIONS: Results from the 50 cavities examined suggested that each alternative excavation technique produced a different and characteristic dentine surface. Carisolv gel was the only method examined that consistently removed the smear layer during excavation to leave exposed dentine tubules at the end of cavity preparation.

Air Abrasion, Dental↗
PubMed2000

Beta-carotene prolongs survival, decreases lipid peroxidation and enhances glutathione status in transplantable murine lymphoma.

Carotenoids of dietary origin have recently been the subject of renewed research interest because of epidemiological evidence indicating an inverse relationship between intake of carotenoids-rich plant substances and risk of certain cancers. This study was attempted to understand the biological actions of dietary beta-carotene (BC) on Dalton's lymphoma (DL), a rapidly proliferating transplantable tumor, in effecting the survival of the lymphoma-bearing mice. The glutathione (GSH) level and the extent of lipid peroxidation in the liver, kidney and brain were monitored in BC-treated (100 mg/kg food) mice transplanted with DL. These markers showed substantial alterations during the whole length of tumor progression in lymphoma-bearing mice without BC supplementation. When treated with BC, both malondialdehyde contents (evidence of lipid peroxidation) and the GSH levels in different organs were found to be closer to normal values in the initial period of tumor progression. BC-mediated protection against lipid peroxidation was maximally found to be in hepatic tissue throughout the study following DL transplantation. This was fairly reflected in the higher BC concentration in hepatic tissue of BC-treated lymphoma group compared to untreated lymphoma control. Significantly higher survival time (51-55 days) was observed in BC-treated animals in comparison to their untreated DL counterparts (35-38 days). The prolonged survival observed in the BC-supplemented animals may be attributed to the higher resistance offered by animals receiving BC towards lipid peroxidation-related tissue injury.

Animals↗