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Biomedical subjects

A Chakrabarti

Publications and source records attributed to A Chakrabarti.

At least 37 records · Page 2Linked to original sources
PubMed2004

Computer simulation of selective aggregation in binary colloids.

The morphology of clusters formed by selective aggregation of binary colloids is studied in a two-dimensional Monte Carlo simulation for a large range of number fractions (200:1, 100:1, 10:1, 2:1). We find remarkable similarity in morphology to those observed in experiments, from the formation of closed "micelles" to large branched clusters. Quantitative studies of the fractal dimension, kinetics, and cluster size distribution are also carried out and compared with diffusion-limited cluster aggregation and reaction-limited cluster aggregation models.

Journal Article↗
PubMed2004

Paranasal sinus aspergillosis: its categorization to develop a treatment protocol.

A prospective study was conducted in 25 consecutive patients of paranasal sinus aspergillosis to categorize and treat them based on a fixed treatment protocol. The three types of aspergillosis categorized as per definitive criteria were chronic invasive (six), non-invasive (fungus ball) (seven) and non-invasive destructive (12). Adjuvant chemotherapy was employed in non-invasive destructive and chronic invasive disease. Ketoconazole was used in the first variety and itroconazole in the latter. Only two patients had recurrence after a mean follow-up of 11 months (range: 6-20 months). They belonged to the non-invasive destructive category and the recurrence had progressed to invasive variety. It is suggested that non-invasive destructive disease should be followed up regularly with endoscopic examination, CT and fungal serology to detect recurrence. Categorization of the paranasal sinus aspergillosis helps to institute proper treatment. Adjuvant chemotherapy in the form of ketoconazole along with surgery is effective in non-invasive destructive disease to prevent recurrence and progression to invasive disease. Chronic invasive disease with its propensity to involve orbit and intracranial cavity should be managed at the earliest with surgery and itraconazole.

Adolescent↗
PubMed2004

Single-dose fluconazole versus itraconazole in pityriasis versicolor.

BACKGROUND: The new antifungal triazoles itraconazole and fluconazole have revolutionized the treatment of pityriasis versicolor. Both drugs have shown promising results in different dose schedules. OBJECTIVE: To compare the efficacy and safety of single oral dose treatment with fluconazole versus itraconazole in patients with pityriasis versicolor. METHODS: A total of 40 patients with pityriasis versicolor were allocated randomly to group A and group B. A single dose of fluconazole (400 mg) or itraconazole (400 mg) was given orally to group A or group B patients, respectively. Patients were assessed mycologically by KOH and culture. Culture was done from lesional and perilesional skin to quantify growth and to observe the effect of these drugs and the persistence/reappearance of the fungus in relation to relapse at 2 and 8 weeks. Relapse was defined as reappearance or worsening of clinical signs and symptoms or positive KOH/culture after initial improvement. RESULTS: Thirteen (65%) patients in the fluconazole group and 4 (20%) patients in the itraconazole group became culture negative at the end of 8 weeks. Relapse was found to be higher in the itraconazole group compared to the fluconazole group (60 vs. 35%). A direct correlation was found between the relapse rate and positivity of perilesional skin for Malassezia furfur. CONCLUSION: In the same dosing, fluconazole was found to be more effective than itraconazole; however, both drugs were found to be safe.

Administration, Oral↗
PubMed2003

Apophysomyces elegans: an emerging zygomycete in India.

Apophysomyces elegans was considered a rare but medically important zygomycete. We analyzed the clinical records of eight patients from a single center in whom zygomycosis due to A. elegans was diagnosed over a span of 25 months. We also attempted a DNA-based method for rapid identification of the fungi and looked for interstrain polymorphism using microsattelite primers. Three patients had cutaneous and subcutaneous infections, three had isolated renal involvement, one had rhino-orbital tissue infection, and the final patient had a disseminated infection involving the spleen and kidney. Underlying illnesses were found in two patients, one with diabetes mellitus and the other with chronic alcoholism. A history of traumatic implantation was available for three patients. All except two of the patients responded to surgical and/or medical therapy; the diagnosis for the two exceptions was made at the terminal stage of infection. Restriction enzyme (MboI, MspI, HinfI) digestion of the PCR-amplified internal transcribed spacer region helped with the rapid and specific identification of A. elegans. The strains could be divided into two groups according to their patterns, with clustering into one pattern obtained by using microsatellite [(GTG)(5) and (GAC)(5)] PCR fingerprinting. The study highlights the epidemiology, clinical spectrum, and diagnosis of emerging A. elegans infections.

Adult↗
PubMed2002

MSI-99, a magainin analogue, imparts enhanced disease resistance in transgenic tobacco and banana.

Magainin is one of the earliest reported antimicrobial peptides isolated from skin secretions of the African clawed frog Xenopus laevis. A synthetic substitution analogue of magainin, MSI-99, is employed in this study to impart disease resistance in transgenic tobacco ( Nicotiana tabacumL.) and banana [( Musaspp. cv. Rasthali (AAB)]. This peptide inhibited the growth and spore germination of Fusarium oxysporumf.sp. cubenseat 16 micro g/ml. MSI-99 has been subcloned into plant expression vectors pMSI164 and pMSI168, targeting the peptide into the cytoplasm and extracellular spaces, respectively. Tobacco plants transformed with pMSI168 showed enhanced resistance against Sclerotinia sclerotiorum, Alternaria alternataand Botrytis cinerea. Transgenic banana pants were obtained for both pMSI164 and pMSI168 transformations and showed resistance to F. oxysporumf.sp. cubenseand Mycosphaerella musicola. The transgenic nature of the transformants and expression of this peptide was confirmed through polymerase chain reaction (PCR) and reverse transcription (RT)-PCR. The results suggest that MSI-99 can be useful in imparting enhanced disease resistance in transgenic plants.

Alternaria↗
PubMed2002

Enhanced kinetics and free-volume universality in dense aggregating systems.

Aggregation kinetics and cluster-size distributions are studied with off-lattice, diffusion-limited cluster-cluster simulations. With increased cluster crowding (occurring at late times) as measured by the normalized free volume, Omega, both the kinetics speeds up and the size distribution broadens. The exponents characterizing each, z and lambda, respectively, are found to be universal functions of Omega. Moreover, the relation z=(1-lambda)(-1) continues to hold up to omega=0 (the ideal gel point), implying mean-field kinetics still applies despite the crowding.

Cluster Analysis↗
PubMed2002

Anisotropic ordering in sheared binary fluids with viscous asymmetry: experiment and computer simulation.

Optical measurements of the structure and morphology of phase-separating polymer blend under simple shear flow have been performed and the results are compared with computer simulations of sheared phase-separating binary mixtures with viscous asymmetry in the fluid components. Information about the structure is obtained from the two-point composition correlation function. Both experiment and simulation suggest subtle differences in the shear response depending on whether the more viscous phase is dispersed or continuous. Measurements of the string width along the neutral direction suggest power-law decay in the shear rate with an exponent of 1/3 when the more viscous phase is dispersed. The simulations suggest that the mean string width, measured along the velocity-gradient direction in the two-dimensional model calculation, exhibits power-law decay in the shear rate with an exponent of 1/3 independent of which phase is dispersed.

Journal Article↗
PubMed2002

Eight-year study of allergic bronchopulmonary aspergillosis in an Indian teaching hospital.

A total of 651 patients with clinically suspected allergic bronchopulmonary aspergillosis (ABPA) were evaluated during the 8-year period from January 1991 to December 1998. Overall, 338 cases (51.9%) were positive either by sputum microscopy/culture (66 of 203 patients), by skin reactivity (150 of 309 cases), or by precipitating antibodies (122 of 338 patients) against Aspergillus species. However, in 89 patients, diagnosis of ABPA was confirmed on the basis of Rosenberg's criteria. Clinical profile and laboratory findings of those patients were analysed. The disease was found to be more common among males. Poor control of asthma, constitutional symptoms, mucopurulent expectoration, increased dyspnoea and wheezing and rhonchi were the main presenting features. Skin reactivity against aspergillin was seen in 73 (82%), precipitating antibodies against Aspergillus species were positive in 64 (72%) and sputum microscopy/culture was positive in 56 (63%) of those 89 patients. Central bronchiectasis and fleeting shadows were the most common radiological findings. This study highlights the importance of ABPA in north India and draws attention to the need for further analysis of criteria to use in the diagnosis of patients with ABPA.

Adolescent↗
PubMed2002

Disseminated Penicillium marneffei infection among HIV-infected patients in Manipur state, India.

OBJECTIVE: To further describe the clinical and epidemiological characteristics of Penicillium marneffei infection in human immunodeficiency virus (HIV) infected patients in India. METHODS: In continuation of our earlier report of four autochthonous cases of P. marneffei infection in HIV infected patients from Manipur, a northeastern state of India, we studied additional 46 cases of penicilliosis marneffei from the same area over a period of 19 months (April 1998-October 1999). Clinical, microbiological features, and therapeutic responses were analyzed in 36 of the 46 patients as ten patients were lost to follow-up. RESULTS: Of the 198 HIV positive patients attending the J. N. Medical Hospital, Imphal, Manipur state during the period mentioned, 46 (25%) had P. marneffei disseminated infection. Of the 36 patients analyzed 31 (86%) were intravenous drug abusers, 1 had multiple sex partners, and 3 females acquired HIV infection from their respective spouses. A 9-year-old child acquired HIV infection by vertical transmission. The common clinical symptoms included fever (97%), weight loss (100%), weakness (86%), anemia (86%), and characteristic skin lesions (81%). Presumptive diagnosis was made by microscopic examination of Wright's-stained smears of fine needle aspirated material from skin lesions and lymph nodes showing numerous intracellular and extracellular, oval, elongated, yeast-like cells dividing by fission. The etiologic agent P. marneffei was isolated in culture from clinical materials in 10 cases when isolation was attempted. All patients were treated with oral itraconazole. All, except one patient, responded favorably to treatment within 7 days. CONCLUSION: Thus, the present cases further confirm the endemicity of penicilliosis marneffei in Manipur and resemble the epidemiology and clinical course of patients from other parts of south-east Asia.

AIDS-Related Opportunistic Infections↗
PubMed2002

Generalized lymphadenopathy caused by Trichosporon asahii in a patient with Job's syndrome.

Of the six species of Trichosporon known to cause human infections, T. asahii is the main agent of invasive trichosporonosis. We describe an unusual case of generalized lymphadenopathy due to T, asahii in a 10-year-old boy with Job's syndrome (markedly elevated IgE with eosinophilia). The diagnosis was based on the presence of blastic conidia and hyphal elements breaking into arthroconidia in biopsied tissue of the cervical lymph node and isolation of the causal agent T, asahii in pure culture. The patient responded initially to amphotericin B therapy, but the infection recurred within 4 weeks and did not respond to therapy of liposomal amphotericin B and 5-fluorocytosine for 10 days. The patient left the hospital against medical advice.

Child↗
PubMed2002

Physiological characters of Sporothrix schenckii isolates.

Sporotrichosis is endemic in three regions (east, north and south) in India. The colony morphology and physiological characteristics of 49 clinical isolates from these three regions (25 from north India, 17 from east India and seven from south India) were analysed in both mycelial and yeast forms. No difference in colony character was seen among the 49 isolates on three different media. Growth of all isolates was inhibited at 40 degrees C. The yeast forms were found to be more tolerant to osmotic pressure and salt concentrations. Most mycelial forms grew well between pH 3-12.0 whereas most yeast forms could tolerate a pH range of 2.4 to 9.5. Variations in assimilation of arabinose, dextrin, raffinose, rhamnose and starch was observed among strains from different geographical regions. The yeast forms did not show any urease activity but the mycelial forms of all isolates could split urea. Phenol oxidase and potassium nitrate assimilation were positive and gelatinase activity and casein hydrolysis were negative for all isolates.

Carbohydrate Metabolism↗
PubMed2002

Change in distribution & antifungal susceptibility of Candida species isolated from candidaemia cases in a tertiary care centre during 1996-2000.

BACKGROUND & OBJECTIVES: As a marked increase in the number of patients with candidaemia was reported in the first half (1991-1995) of the last decade at the Postgraduate Institute of Medical Education & Research, Chandigarh, India, the present study was aimed at determining further change if any, in the incidence and distribution of Candida species and their antifungal resistance pattern during the second half (1996-2000) of the same decade. METHODS: The patients with candidaemia were studied to determine the frequency of candidaemia and Candida species isolated during 1996-2000. One hundred Candida strains other than Pichia anomala (C. pelliculosa) were randomly selected from those isolates to evaluate antifungal susceptibility pattern against amphotericin B, 5-fluorocytosine, ketoconazole, fluconazole and itraconazole. The results were compared with our previous study. RESULTS: An increase in the number of patients with candidaemia was observed during 1996 (538) and 1997 (421) compared to 1998-2000 due to P. anomala outbreak. With the control of the outbreak, a substantial decrease in the incidence of candidaemia was observed from 1998 (251 in 1998, 122 in 1999 and 165 in 2000). A higher isolation of non-C. albicans Candida species (89.8%) was observed, with C. tropicalis being the most common (541, 36.1%) agent. No major change in the isolation rate of other non-C. albicans Candida species (C. guilliermondii, C. krusei, C. glabrata and C. parapsilosis) was observed. An emergence of resistance to amphotericin B in 15.4 per cent C. albicans, 8.1 per cent C. tropicalis and 33.3 per cent C. krusei strains was observed. An increase in resistance to ketoconazole (from 0% to 13%) and 5-fluorocytosine (from 1% to 8%) and a decrease to fluconazole (from 13% to 6%) were observed. Resistance to itraconazole was observed in 17 per cent of Candida strains by broth macro-dilution method. INTERPRETATION & CONCLUSION: A change in the isolation of Candida species was observed i.e. in the incidence and isolation of non-C. albicans Candida species. Emergence of resistance to amphotericin B and increase of resistance to most other antifungals are cause for concern.

Antifungal Agents↗
PubMed2002

Mannan antigen detection in the diagnosis of patients with invasive candidiasis.

BACKGROUND & OBJECTIVES: With the increase in the incidence of invasive candidiasis (IC) in recent years, there is a need to improve the sensitivity of diagnosis. A conventional technique like blood culture is positive in nearly 50 per cent of cases. To improve the diagnostic efficiency in invasive candidiasis mannan antigen detection holds promise. Hence mannan antigen detection was evaluated in patients with suspected invasive candidiasis in the Paediatric Intensive Care Unit (PICU). METHODS: A prospective study, involving 186 consecutive patients admitted to the PICU of the Advanced Paediatric Center at the Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh between March 1999 and November 1999 were followed up for possible invasive candidiasis. Sixty five children clinically suspected to have sepsis and at risk for developing IC and or who stayed in the hospital more than 5 days were further evaluated for the diagnosis of IC by collecting two blood culture samples 48 h apart and by mannan antigen and anti-mannan antibody detection. Both antigen and antibody were detected by in-house standardized techniques: antibody by whole cell agglutination (WCA) and antigen by sandwich enzyme linked immunosorbent assay (ELISA). RESULTS: Twenty of 65 patients (30.7%) were positive by blood culture. Mannan antigen was positive in all 20 patients and significant anti-mannan antibody titre (> or = 128) was present in 12 (60%) patients. Mannan antigen was detected in 15 more patients, who were negative for isolation of Candida from blood. Twelve of these patients had febrile episode not responding to antibacterial therapy but responding to fluconazole/itraconazole therapy indicating that the patients possibly had IC. Mannan concentration was also found to be significantly higher in the patients with Candida isolated from blood. INTERPRETATION & CONCLUSION: Thus, the present study confirms the earlier claim that mannan antigen detection possibly improves the diagnostic efficiency of IC.

Adolescent↗
PubMed2002

Interactions of staff and residents with pharmaceutical industry: a survey of psychiatric training program policies.

OBJECTIVES: In response to perceived controversies regarding interactions between physicians and the pharmaceutical industry, we undertook a study to look at the relationship between Canadian psychiatry training programs and the pharmaceutical industry. METHODS: The authors distributed a survey to the residency program directors and chief residents of the 16 psychiatry training programs in Canada. RESULTS: Of respondents, 75 per cent were either unaware of or noted an absence of policies or guidelines regarding interactions with the pharmaceutical industry in their training programs; 70 per cent viewed staff psychiatrists and residents to be at least 50 per cent familiar with the Canadian Medical Association's policy summary; and 74 per cent were unaware of any structural teaching regarding potential conflicts of interest between psychiatry and the pharmaceutical industry. A significant number of respondents perceived occasional excessive influence by the pharmaceutical industry on residents' training. CONCLUSIONS: Despite concerns about potential conflicts of interest, there are a few guidelines in most psychiatry training programs in Canada regarding the relationship between physicians and the pharmaceutical industry.

Canada↗
PubMed2001

Binding of a denatured heme protein and ATP to erythroid spectrin.

Spectrin is a large, worm-like cytoskeletal protein that is abundant in all cell types. The denatured heme enzyme, horseradish peroxidase showed significant decrease in the reactivation yield, after 30 min of refolding, in presence of increasing concentrations of spectrin from that in the absence. This indicated that spectrin could bind denatured HRP and inhibit their refolding. In presence of 1 mM ATP and 10 mM MgCl(2) the spectrin binding of denatured HRP is abolished. This activity of decreasing the reactivation yield was found to be ATP-dependent and the denatured enzyme after 30 min refolding in the presence of spectrin, pretreated with Mg/ATP, showed about 40% increase in the reactivation yield compared to the same in absence of spectrin. Fluorescence spectroscopic studies indicated binding of ATP to native spectrin showing concentration-dependent quenching of tryptophan fluorescence by ATP. The apparent dissociation constant of binding of ATP to spectrin was estimated to be 1.1 mM. A high affinity binding of spectrin with denatured HRP has been characterized (K(d) = 16 nM). Since these properties are similar to those of established molecular chaperone proteins, these data indicate that spectrin might have a chaperone-like function in erythrocytes.

Adenosine Triphosphate↗