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Biomedical subjects

P Bhattacharya

Publications and source records attributed to P Bhattacharya.

At least 19 recordsLinked to original sources
PubMed2007

One-year results with extended-release tacrolimus/MMF, tacrolimus/MMF and cyclosporine/MMF in de novo kidney transplant recipients.

Once-daily tacrolimus extended-release formulation (Prograf XL, formerly referred to as MR or MR4) was compared with the twice-a-day tacrolimus formulation (TAC) and cyclosporine microemulsion (CsA), all administered in combination with mycophenolate mofetil (MMF), corticosteroids and basiliximab induction, in a phase 3, randomized (1:1:1), open-label trial in 638 de novo kidney transplant recipients. In combination with MMF and corticosteroids, XL had an efficacy profile comparable to TAC and CsA. XL/MMF and TAC/MMF were statistically noninferior at 1-year posttransplantation to CsA/MMF for the primary efficacy endpoint, efficacy failure (death, graft loss, biopsy-confirmed acute rejection (BCAR) or lost to follow-up). One-year patient and graft survival were 98.6% and 96.7% in the XL/MMF group, 95.7% and 92.9% in TAC/MMF group and 97.6% and 95.7% in CsA/MMF group. The safety profile of XL in comparison with CsA was similar to that observed with TAC in this study and consistent with previously published reports of TAC in comparison with CsA. The results support the safety and efficacy of tacrolimus in combination with MMF, corticosteroids and basiliximab induction, as well as XL as a safe and effective once-daily dosing alternative.

Adolescent↗
PubMed2006

Electrically injected quantum-dot photonic crystal microcavity light sources.

The design, fabrication, and characterization of an electrically injected quantum-dot photonic crystal microcavity light source are described. The optical gain in the GaAs/AlGaAs-based device is provided by self-organized InGaAs quantum dots with ground-state room-temperature emission at 1.1 microm. The carriers are injected directly into the photonic crystal microcavity, which contains approximately 50 dots, avoiding surface state recombination in the photonic crystal pattern. The spectral characteristics of a single-defect photonic crystal microcavity show a single 2 nm broad microcavity resonance. The output power is of the order of a few tens of nanowatts.

Journal Article↗
PubMed2006

Enhanced mass transport in nanofluids.

Thermal conductivity enhancement in nanofluids, which are liquids containing suspended nanoparticles, has been attributed to localized convection arising from the nanoparticles' Brownian motion. Because convection and mass transfer are similar processes, the objective here is to visualize dye diffusion in nanofluids. It is observed that dye diffuses faster in nanofluids compared to that in water, with a peak enhancement at a nanoparticle volume fraction, phi, of 0.5%. A possible change in the slope of thermal conductivity enhancement at that same phi signifies that convection becomes less important at higher phi. The enhanced mass transfer in nanofluids can be utilized to improve diffusion in microfluidic devices.

Journal Article↗
PubMed2006

Platelet activation, upregulation of CD11b/ CD18 expression on leukocytes and increase in circulating leukocyte-platelet aggregates in Indian women chronically exposed to biomass smoke.

The majority of households in rural India still rely on unprocessed solid biomass for domestic energy. The aim of this study was to investigate whether chronic exposure to biomass smoke causes activation of leukocytes and the formation of leukocyte-platelet aggregates. We conducted flow cytometric analysis of beta2 Mac-1 integrin (CD11b/CD18) expression on polymorphonuclear leukocytes (PMN) and monocytes, and P-selectin (CD62P) expression on the platelets of 165 women from eastern India, who cook solely with wood, dung and agricultural wastes, and 155 age- and socio-economic condition-matched control subjects, who used relatively cleaner fuel, liquefied petroleum gas (LPG). Leukocyte-platelet aggregates were defined as CD11b-positive PMN and monocytes co-expressing platelet-specific markers CD41 or CD62P. A significant increase in leukocyte-platelet aggregates was found in women who used biomass as cooking fuel. In addition, they showed increased surface expression of CD11b/CD18 in circulating PMN and monocytes and CD62P expression on platelets. The mean fluorescence intensity (MFI) of CD11b on the surface of circulating monocytes and PMN of biomass users increased by 50 and 68%, respectively. Similarly, a 62 and 48% increase in MFI was observed in CD18 expression on the surface of these cells in biomass users. The results show that chronic biomass smoke exposure activates circulating platelets, PMN and monocytes, and increases the number of leukocyte-platelet aggregates, which are considered a risk factor for thrombosis.

Adult↗
PubMed2005

Ultra-fast three dimensional imaging of hyperpolarized 13C in vivo.

OBJECTIVE: PASADENA, a chemical method of enhancing nuclear spin polarization has demonstrated 13C polarizations of order unity for the nascent products of molecular addition by parahydrogen. The extreme brevity of signal enhancement obtained by hyperpolarization requires improved 13C MR in vivo imaging techniques for their optimum utility. MATERIALS AND METHODS: 13C imaging sequences, including 13C 3D FIESTA, were compiled for a GE LX 1.5 T clinical MR scanner. Two water soluble 13C imaging agents were hyperpolarized utilizing parahydrogen and an automated polarizer. 13C polarization was quantified in flow phantoms and in rats with jugular vein catheters. RESULTS: Fast 3D FIESTA 13C MR imaging technique acquired sequential 3D images (3.66 s/acquisition) with superior SNR. Hyperpolarized 13C solutions and vascular phantoms achieved a maximum signal of 26,624+/-593. In vivo 13C MR images of the cardiopulmonary circulation showed maximum 13C signal of 2,402+/-158. 13C images acquired within 3.66 s showed signal enhancement over 10,000 compared to equilibrium polarization. CONCLUSION: 3D-FIESTA was effective for sub-second in vivo imaging of hyperpolarized 13C reagents produced in a custom-built parahydrogen polarizer. Application to 13C hyperpolarized by parahydrogen is demonstrated in vitro and in vivo.

Algorithms↗
PubMed2005

Ion detection with photonic crystal microcavities.

We have experimentally demonstrated a cation and anion sensor by using short linear photonic crystal microcavities with an embedded quantum dot active region. The photonic crystal microcavity covered with an ion-selective polymer forms a submicrometer optical detection system sensitive to small changes of perchlorate anion (ClO4(-)) and calcium cation (Ca2+) concentrations.

Journal Article↗
PubMed2004

Retrieval of a retrograde catheter using suction, in patients who cannot open their mouths.

In difficulty, tracheal intubation can be facilitated by passing a retrograde catheter, but the mouth has to be opened for the retrieval of the catheter from the pharynx. Two patients with ankylosis of a temporomandibular joint were unable to open their mouth, and required general anaesthesia for gap arthroplasty. Because we did not have a flexible fibreoptic laryngoscope, we used a suction catheter to retrieve an epidural catheter from the pharyngeal cavity, which had been passed retrogradely from a cricothyroid puncture. Catheter-guided tracheal intubation was done without complication. A suction catheter can assist retrograde retrieval of a catheter to aid intubation in patients who cannot open the mouth.

Adolescent↗
PubMed2004

Monolithically integrated bacteriorhodopsin/semiconductor opto-electronic integrated circuit for a bio-photoreceiver.

The light-sensitive protein, bacteriorhodopsin (BR), is monolithically integrated with an InP-based amplifier circuit to realize a novel opto-electronic integrated circuit (OEIC) which performs as a high-speed photoreceiver. The circuit is realized by epitaxial growth of the field-effect transistors, currently used semiconductor device and circuit fabrication techniques, and selective area BR electro-deposition. The integrated photoreceiver has a responsivity of 175 V/W and linear photoresponse, with a dynamic range of 16 dB, with 594 nm photoexcitation. The dynamics of the photochemical cycle of BR has also been modeled and a proposed equivalent circuit simulates the measured BR photoresponse with good agreement.

Amplifiers, Electronic↗
PubMed2004

Pregnancy unmasking lymphangioleiomyomatosis.

A 30 year-old housewife presented with cough and shortness of breath which progressed during her ensuing pregnancy, culminating in a still-birth at 9 months of gestation and requiring her hospitalisation in the immediate postpartum period. HRCT scan of the thorax showed thin-walled cysts and open lung biopsy confirmed the clinical impression of lymphangioleiomyomatosis. She was put on oral medroxyprogesterone acetate. After disease flare-up in the postpartum period her symptoms have stabilised.

Adult↗
PubMed2003

Direct measurement of the photoelectric response time of bacteriorhodopsin via electro-optic sampling.

The photovoltaic signal associated with the primary photochemical event in an oriented bacteriorhodopsin film is measured by directly probing the electric field in the bacteriorhodopsin film using an ultrafast electro-optic sampling technique. The inherent response time is limited only by the laser pulse width of 500 fs, and permits a measurement of the photovoltage with a bandwidth of better than 350 GHz. All previous published studies have been carried out with bandwidths of 50 GHz or lower. We observe a charge buildup with an exponential formation time of 1.68 +/- 0.05 ps and an initial decay time of 31.7 ps. Deconvolution with a 500-fs Gaussian excitation pulse reduces the exponential formation time to 1.61 +/- 0.04 ps. The photovoltaic signal continues to rise for 4.5 ps after excitation, and the voltage profile corresponds well with the population dynamics of the K state. The origin of the fast photovoltage is assigned to the partial isomerization of the chromophore and the coupled motion of the Arg-82 residue during the primary event.

Bacteriorhodopsins↗
PubMed2002

Oncogenic human papillomavirus (HPV) infection and uterine cervical cancer: a screening strategy in the perspective of rural India.

The predominance of cervical cancer in India can mostly be attributed to the lack of early screening. The objective of the present study has been, therefore, to determine a cost-effective oncogenic human papillomavirus (HPV)-based cervical cancer screening plan for rural Indian women. The results showed that in normal women, highest prevalence of HPV 16/18 infection was in the age group < or =23 years and lowest in > or =44 years with an insignificant change in between. HPV 16/18 infection was significantly associated with cervical erosion at age < or =23 years, but not with cytology or visual inspection with acetic acid testing at any age. The low-grade cytological lesions, however, increased only with increase in age. Fourteen per cent of the cervical malignancy was also found to be present in the age group 24-33 years with an 87% HPV infection. Here we proposed a cost-effective screening scheme in which HPV testing must be performed in women (a) < or =23 years with cervical erosion and (b) 24-43 years, as an adjunct to Pap smears (both HPV and cytology were prevalent in this group). For women > or =44 years, HPV testing might not be useful, since abnormal cytology was more prominent over the viral infection. We infer that by not performing HPV test in the group < or =23 years, approximately 76% of the high-risk HPV-infected individuals potentially "at risk" for developing cervical cancer might be missed.

Acetic Acid↗
PubMed2002

Antibiotic sensitivity pattern of the bacteria isolated from nosocomial infections in ICU.

The incidence of nosocomial infections in ICU is 4-5 times greater than in general ward. Critically ill patients are always at higher risk of developing nosocomial infections with resistant strains. This study is an attempt to know the antibiotic sensitivity pattern of the common isolates in ICU. Samples comprising urine, blood, endotracheal secretions and throat swabs were collected from 102 ICU patients of them, 56 patients showed evidence of nosocomial infection (54.9%), from whom 120 different organisms were isolated. Antibiotic sensitivity test was done according to Kirby Bauer method. Klebsiella pneumoniae were the most prevalent isolates from respiratory tract infections followed by Proteus spp, Escherichia coli, Staphylococci spp. and Acinetobacter spp. The gram negative enteric bacilli were uniformly resistant to betalactam antibiotics as well as betalactam-betalactamase inhibitors. Resistance to Ciprofloxacin and Ceftriaxone ranged from 50-100% and 25-83.3% respectively. Staphylococci were 100% resistant to penicillin and tetracycline, 80% to cotrimoxazole, 60% to erythromycin and gentamicin and 40% to amikacin. Acinetobacter spp. were highly resistant to most of the antibacterial agents except gentamicin while Pseudomonas spp. showed 75% resistance to it. The increased prevalence of resistant organisms in ICU probably reflects lack of proper antibiotic policy resulting in prolonged and indiscriminate use of antimicrobial agent.

Bacterial Infections↗
PubMed2001

Observation of phonon bottleneck in quantum dot electronic relaxation.

Time-resolved differential transmission measurements of self-assembled In0.4Ga0.6As quantum dots clearly indicate a phonon bottleneck between the n = 2 and n = 1 electronic levels. The key to this observation is the generation of electrons in dots where there are no holes so that electron-hole scattering does not mask the bottleneck. We use a simple carrier capture model consisting of two capture configurations to explain the bottleneck signal and offer arguments to rule out other possible sources of the signal.

Journal Article↗
PubMed2001

Prominence of symptoms and level of stigma among depressed patients in Calcutta.

A pilot study of 29 patients for research on clinical depression employed the framework of cultural epidemiology to examine illness-related experience, meaning, behaviour with a Bengali version of the explanatory Model Interview Catalogue (EMIC). This report examined patterns of distress and stigma with reference to the most troubling patient-specified symptom. All subjects were psychiatric outpatients in the Institute of Psychiatry, Calcutta, and met Diagnostic and Statistical Manual (DSM)-IV criteria for a major depressive episode. Only 5 patients (17.2%) identified sadness as the most troubling problem, and 48.3% specified pains and other somatic symptoms instead. An internally consistent stigma scale with Cronbach's alpha of .67, comprised 13 items, was used to assess stigma. In addition to the scale score for each subject, the contribution of each item was reported and compared. A suggestive, though not significantly lower value of the stigma score for patients reporting somatic symptoms as most troubling, compared with sadness, was consistent with findings from prior studies showing a positive relationship between the magnitude of depression and stigma. These findings are discussed with reference to their impact on recognition and help seeking among patients, and recognition and management of depression by general practitioner. Culturally distinctive presentations and social contexts of depression and other mental illnesses should be addressed in professional training and public health communications.

Adult↗
PubMed2001

Effect of purified glutaminase from human ascites fluid on experimental tumor bearing mice.

Glutamine is the major respiratory fuel and energy source of the rapidly proliferating tumor cells and that is why glutamine clearance by glutaminase therapy provides an opportunity to fight against the neoplasm. Glutaminase from bacterial source was tried on experimental models but had to be excluded because of its limited efficacy. Search for a better glutaminase continued exploiting the mammalian sources. In the present study, glutaminase purified from human ovarian cancer ascites fluid was used in experimental solid and ascites mice model alone and in combination with Cu-Sulphate and heparin. Cumulative findings indicate that the enzyme alone is quite effective in lowering tumor burden and reducing not only the tumor induced angiogenesis, but also an angiogenic inducer, heparin mediated angiogenesis. However, the presence of Cu with the enzyme, amplified the antineoplastic response by improving anti-angiogenic potential and hematological status of the tumor bearing host. Therefore, Cu-glutaminase combination strengthened the hypothesis that together they may provide a better therapeutic regimen in experimental mice tumor model.

Angiogenesis Inhibitors↗
PubMed2000

Studies on the modeling and simulation of a sequential bienzymatic reaction system immobilized in emulsion liquid membrane.

Experiments have been carried out to study the reaction engineering behavior of the liquid membrane-encapsulated, sequential bienzymatic reaction system, n 2n glucose. A dynamic mathematical model, free from adjustable parameters, has been developed taking into account peri-emulsion mass transfer, intra-emulsion diffusion, membrane-related mass transfer limitations and substrate and product inhibitions. A finite difference-based, user-friendly software has been developed to solve the model equations. Experimental data satisfactorily correlate with the model. While it is understood that study of sequential bienzymatic reaction system immobilized in emulsion liquid is essential for their industrial exploitation, reaction engineering behavior of such a system in presence of both substrate and product inhibitions has not yet been reported in the literature. Therefore, the model predictions of the present investigations are expected to pave the way for scale-up and design of industrial bioreactors in this field.

Journal Article↗
PubMed2000

Effects of intraseptal zolpidem and chlordiazepoxide on spatial working memory and high-affinity choline uptake in the hippocampus.

Injection of GABA(A)/benzodiazepine receptor ligands into the medial septum (MS) alters the activity of cholinergic neurons that innervate the hippocampus and can produce bidirectional modulation of spatial memory. Recent evidence suggests that two subtypes of the GABA(A) receptor are differentially localized to either GABAergic (alpha(1)/beta(2)/gamma(2)) or cholinergic (alpha(3)/beta(3)/gamma(2)) neurons within the MS. The present studies characterized the dose-related behavioral and neurochemical effects of intraseptal infusions of two benzodiazepine (BDZ) agonists that appear to exhibit different profiles of pharmacological specificity for these receptor subtypes. Male Sprague-Dawley rats were cannulated and then artificial CSF, chlordiazepoxide (CDP: 8 or 12 microg), or zolpidem (4, 8, or 12 microg) was injected into the MS. Spatial working memory was assessed in a delay radial-arm maze task and the activity of cholinergic neurons in the MS was evaluated by high-affinity choline uptake (HA-ChU) in the hippocampus. Intraseptal injection of either CDP or zolpidem produced dose-related impairments in spatial working memory and decreases in hippocampal HAChU. Both BDZ agonists were found to produce retrograde memory deficits and a decrease in HAChU following the highest dose tested (12 microg). However, intraseptal injection of 8 microg of zolpidem produced a behavioral deficit comparable to the high dose of CDP, but did not alter HAChU within the HPC. Although the cholinergic component of the septohippocampal pathway has been shown to be important in modulating hippocampal physiology and spatial memory processes, data from the present experiments suggest that the GABAergic component may also play an important role in the behavioral functions of the septohippocampal pathway.

Animals↗