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Biomedical subjects

A Chakrabarti

Publications and source records attributed to A Chakrabarti.

At least 55 records · Page 3Linked to original sources
PubMed2001

Effect of cholesterol on interaction of dibucaine with phospholipid vesicles: a fluorescence study.

Interaction of the local anesthetic dibucaine with small unilamellar vesicles of dimyristoylphosphatidylcholine (DMPC) and dioleoyl phosphatidylcholine (DOPC) containing different mol percents of cholesterol has been studied by fluorescence spectroscopy. Fluorescence measurements on dibucaine in presence of phospholipid vesicles containing various amounts of cholesterol yielded a pattern of variation of wavelength at emission maximum and steady-state anisotropy which indicated that the microenvironment of dibucaine is more polar and flexible in membranes that contain cholesterol than in membranes without cholesterol. Experiments on quenching of fluorescence from membrane-associated dibucaine by potassium iodide showed a marked increase in quenching efficiency as the cholesterol content of the vesicles was increased, demonstrating increased accessibility of the iodide quenchers to dibucaine in the presence of cholesterol, when compared to that in its absence. Total emission intensity decay profiles of dibucaine yielded two lifetime components of approximately 1 ns and approximately 2.8--3.1 ns with mean relative contributions of approximately 25 and approximately 75%, respectively. The mean lifetime in vesicles was 20--30% smaller than in the aqueous medium and showed a moderate variation with cholesterol content. Fluorescence measurements at two different temperatures in DMPC SUVs, one at 33 degrees C, above the phase transition temperature and another at 25 degrees C, around the main phase transition, indicated two different mode of dibucaine localization. At 25 degrees C dibucaine partitioned differentially in presence and absence of cholesterol. However, at 33 degrees C the apparent partition coefficients remained unaltered indicating differences in the microenvironment of dibucaine in presence and absence of cholesterol in the phospholipid membranes.

Anesthetics, Local↗
PubMed2001

Fungal endophthalmitis following cataract surgery: clinical presentation, microbiological spectrum, and outcome.

PURPOSE: To determine the clinical presentation, microbiological spectrum, and outcome in cases of fungal endophthalmitis following cataract surgery. DESIGN: Observational case series. METHODS SETTING: Tertiary referral hospital. PATIENTS: Retrospective analysis of 27 cases of smear- and culture-proven fungal endophthalmitis. INTERVENTION: Pars plana vitrectomy in 18 eyes, where the corneal condition did not preclude the same. All eyes received intravitreal amphotericin B and dexamethasone along with systemic antifungal agents. MAIN OUTCOME MEASURES: Functional success: Final visual acuity of 3/60 or better with attached retina. Anatomical success: Final visual acuity of better than light perception with preserved anatomy of globe. RESULTS: The majority of the eyes (22 of the 27) had early onset and diffuse presentation (that is, anterior segment as well as posterior vitreous exudates). Substantial corneal involvement was seen in 14 eyes (51.85%). Aspergillus sp. was the most common isolate. Multivariate analysis using forward stepwise logistic regression showed corneal involvement as the single most important risk factor in determining final visual outcome (P =.0429). CONCLUSIONS: Early onset and diffuse presentation, which mimics bacterial endophthalmitis, stresses the importance of both bacterial and fungal cultures from intraocular fluids to reach a diagnosis apart from the clinical judgment. Corneal involvement was the most important predictor of outcome in cases of fungal endophthalmitis.

Adult↗
PubMed2001

Ten years' experience in zygomycosis at a tertiary care centre in India.

OBJECTIVE: To define the spectrum of zygomycosis due to mucorales in an Indian scenario. METHODS: One-hundred and twenty-nine patients with zygomycosis due to mucorales diagnosed at the Postgraduate Institute of Medical Education and Research, Chandigarh, India during 1990-99, were retrospectively analysed regarding the sites of involvement, underlying disease, species of fungi isolated and outcome of therapy. RESULTS: Higher prevalence rate (19.4%) was observed in 1999. Rhino-orbito-cerebral type (44.2%) was the commonest presentation followed by cutaneous (15.5%) and renal (14.0%) involvement. Disseminated zygomycosis was seen in 11.6% patients. Pulmonary and gastrointestinal zygomycosis were diagnosed in 10.1% and 4.7% patients, respectively. Uncontrolled diabetes mellitus (in 50% of cases) was the significant risk factor in rhino-orbito-cerebral type [odds ratio (OR), 9.3; P<or=0.001) and breach of skin (in 40% cases) in cutaneous zygomycosis (OR, 6.9; P<or=0.01). However, a considerable number of 22 (22.9%) patients were apparently healthy hosts in this series. Forty-five patients (34.9%) of this series were diagnosed only at post-mortem. Among 47 patients where culture was attempted, mucorales were isolated from 25 patients with Rhizopus arrhizus (11 patients) and Apophysomyces elegans (eight patients) as the predominant isolates. Adequate therapy could be provided in 33 patients. A combination of aggressive surgical debridement of necrotic tissue and amphotericin-B was found to be the best treatment protocol as 81.3% patients treated with surgical debridement and amphotericin-B were cured, compared with 46.7% patients treated with amphotericin-B alone. CONCLUSION: The study highlights the importance of increased awareness for early diagnosis of zygomycosis and aggressive management. The large number of cases in apparently healthy hosts and increased isolation of A. elegans in the present series are important characteristics of this disease in India and requires further evaluation.

Adolescent↗
PubMed2001

Outbreak of Pichia anomala infection in the pediatric service of a tertiary-care center in Northern India.

An outbreak of nosocomial fungemia due to the unusual yeast, Pichia anomala occurred in the pediatric wards of our hospital over a period of 23 months (April 1996 to February 1998). A total of 379 neonates and children (4.2% admissions) were infected. The probable index case was admitted to the pediatric emergency ward, with subsequent transmission to the premature nursery, pediatric intensive care units, and other children wards. Carriage on the hands of health care personnel was likely to be responsible for dissemination of the fungus. The outbreak could only be controlled after a health education campaign to improve hand-washing practices was instituted and after nystatin-fluconazole prophylaxis to all premature neonates and high-risk infants was introduced. In a case-control study, we identified a lower gestational age, a very low birth weight (<1,500 g), and a longer duration of hospital stay as significant risk factors associated with P. anomala fungemia in premature neonates. We conducted a culture prevalence survey of 50 consecutive premature neonates and found that 28% were colonized with P. anomala at a skin or mucosal site on the date of delivery and that 20% of these neonates subsequently developed P. anomala fungemia. We performed multilocus enzyme electrophoresis on 40 P. anomala outbreak isolates (including patient and health care workers' hand isolates), and the results suggested that these isolates were identical. Our study highlights the importance of P. anomala as an emerging nosocomial fungal pathogen.

Antifungal Agents↗
PubMed2001

Evaluating preceptorship arrangements in a paediatric setting.

Preceptorship can be a valuable support mechanism for newly qualified nurses. Both preceptors and preceptees need support to ensure effective preceptorship arrangements. Maintaining effective preceptorship arrangements can be challenging for preceptees, preceptors and the organisation. Further research is required to explore the full potential of preceptorship.

Humans↗
PubMed2001

Detection of an mRNA polymorphism by differential display.

Differential Display (DD) technology was utilized to compare programs of gene expression in primary cultures of human skin fibroblasts from normal volunteers and patients diagnosed with melancholic depression. Polymorphic transcripts of a single gene differing by one tandem repeat sequence of four nucleotides (TGAT) in the 3' noncoding region were detected.

3' Untranslated Regions↗
PubMed2001

In vitro susceptibility pattern of Sporothrix schenckii strains isolated from three centers in India.

BACKGROUND & OBJECTIVES: With the availability of more number of antifungal agents in recent years, drugs other than saturated solution of potassium iodide (SSKI) are being increasingly used to treat sporotrichosis. It was therefore considered pertinent to evaluate in vitro antifungal susceptibility pattern of Sporothrix schenckii strains isolated at three centers in India against five commonly used antifungal agents. METHODS: Agar dilution method was used to evaluate 50 clinical isolates (25 from north, 17 from east and 8 from south India) both in its yeast and mycelial forms against amphotericin-B, 5-fluorocytosine, ketoconazole, fluconazole and itraconazole. RESULTS: No resistance was observed in the yeast form of S. schenckii against amphotericin B and azoles. However, 54 per cent strains in the yeast form were resistant to 5-fluorocytosine. None of the strains was susceptible to amphotericin B and ketoconazole, 56 and 10 per cent strains in the mycelial form were susceptible to itraconazole and fluconazole respectively. No significant difference was observed in the antifungal susceptibility pattern among the strains isolated from these three regions in India. INTERPRETATION & CONCLUSION: Clinical isolates of S. schenckii from three regions of India had a more or less uniform antifungal susceptibility pattern. Itraconazole had the best in vitro susceptibility results against the clinical isolates of S. schenckii and has the potential to replace SSKI.

Antifungal Agents↗
PubMed2001

Neurobehavioural study of subchronic administration of oxydemeton-methyl (insecticide and acaricide) in rats.

Oxydemeton-methyl, an organophosphate insecticide and acaricide produced decrease in the exploratory behaviour and prolongation of barbitone sodium induced hypnosis in rats after intermittent aerosol spray inhalational exposure, for 1/2 hour daily for 7 consecutive days, compared to the saline control group. Further, ED50 +/- SEM value for haloperidol induced catalepsy, CD50 +/- SEM value for pentylenetetrazole induced seizure and CI50 +/- SEM value for electroshock (i.e. the dose of haloperidol, PTZ and intensity of electroshock producing catalepsy or positive seizure response in 50% of rats) were significantly decreased after 7 days exposure to oxydemeton-methyl compared to that of saline control group. The study has established the central nervous system depressant effect, extrapyramidal effect and proconvulsant potential of oxydemeton-methyl which is widely used by the agricultural workers in the form of field spray.

Animals↗
PubMed2000

From fertilization to cancer: the role of centrosomes in the union and separation of genomic material.

Centrosomes play crucial roles in the union of sperm and egg nuclei during fertilization and in the equal separation of genomic material during cell division. While many studies in recent years have focused on the molecular composition of centrosomes, this article focuses on the structural behavior of centrosomes and on factors that play a role in centrosome functions under normal, artificially altered, and abnormal conditions. We review here how studies in the classic sea urchin egg model have contributed to our knowledge on the centrosome cycle within the cell cycle, on compaction and decompaction of centrosomal material, and on the contributions of maternal and paternal centrosomes during fertilization. Centrosome material is activated in unfertilized eggs by increasing pH with ammonium and by increasing calcium with the ionophore A23187, which are conditions that are normally induced by sperm. D(2)O and taxol also induce centrosome aggregation in the unfertilized egg. Maternal and paternal centrosome material both contribute to the formation of a functional centrosome but the formation of a bipolar centrosome requires material from the paternal centrosome. Fertilization of taxol-treated eggs reveals that the male centrosome possesses the capability to attract maternal centrosome material. When pronuclear fusion of the male and female pronuclei is inhibited with agents such as the disulfide reducing agent dithiothreitol (DTT) a bipolar mitotic apparatus is formed from the paternal centrosome. Furthermore, one centrosome of the bipolar mitotic apparatus is capable of organizing an additional half spindle that attaches to the female pronucleus indicating a functional and perhaps structural connection between centrosomes and chromatin. Sea urchin eggs are also useful to study centrosome abnormalities and consequences for the cell cycle. While classic studies by Theodor Boveri have shown that dispermic fertilization will result in abnormal cell division because of multiple centrosomes contributed by sperm, abnormal cell division can also be induced by chemical alterations of centrosomes. Compaction and decompaction of centrosome structure is studied using chloral hydrate or the chaotropic agent formamide, which reveals that centrosomes can be chemically altered to produce mono- or multipolar abnormal mitosis and unequal distribution of genomic material upon release from formamide. The patterns of abnormal centrosome reformations after recovery from formamide treatment resemble those seen in cancer cells which argues that structural defects of centrosomes can account for the formation of abnormal mitosis and multipolar cells frequently observed in cancer. In summary, the sea urchin model has been most useful to gain information on the role of centrosomes during fertilization and cell division as well as on adverse conditions that play a role in centrosome dysfunctions and in disease.

Animals↗
PubMed2000

Centrosome alterations induced by formamide cause abnormal spindle pole formations.

The formation of the bipolar mitotic apparatus depends on accurate centrosome organization which is crucial for the separation of the genome during cell division. While it has been shown that mutations and overexpression of centrosome proteins (Brinkley and Goepfert, 1998; Pihan et al., 1998) can cause abnormal spindle pole formation, here we report that damages to centrosome structure caused by the chaotropic agent formamide will cause multipolar mitoses upon recovery from the effect when applied at first cell division in sea urchin eggs. Formamide was used as a chemical tool to manipulate centrosome structure and to investigate the effects on microtubule organization. When 1-1.5 m formamide was administered for 30 min at prometaphase of first cell division, microtubules were disassembled and centrosomes compacted into dense spheres around highly condensed chromatin. Upon recovery from formamide, centrosomes decompacted and attempted to form various mitotic organizations. Normal recovery (and attempts of recovery) to bipolarity was possible in five percent of cells treated with 1-1.5 m formamide for 30 min, but abnormal patterns of spindle formation were observed in all other cells, which included mono- (20%), tri (45%), and multipolar (30%) formations organized by mono-, tri-, and multipolar centrosome clusters. When cells were treated with 1.5 m formamide for 90 min, centrosomes became pulverized and fragmented and only monopolar mitotic formations were observed upon recovery. These results are highly reproducible and reveal that abnormalities in centrosome structure can lead to abnormal mitosis which is not caused by mutation or overexpression of centrosome proteins.

Animals↗
PubMed2000

Phacoemulsification in eyes with white cataract.

PURPOSE: To study the results of phacoemulsification in eyes with white cataract. SETTING: Aravind Eye Hospital, Madurai, India. METHODS: This retrospective study comprised 212 consecutive patients with white cataract: 192 mature (90.6%), 11 intumescent (5.2%), and 9 hypermature (4.2%). Patients had phacoemulsification and continuous curvilinear capsulorhexis. After the nucleus was removed by the divide and conquer or the phaco chop technique, a posterior chamber intraocular lens was implanted. Preoperative and intraoperative findings, as well as postoperative outcomes, were analyzed. RESULTS: Intraoperative complications included premature entry of the tunnel into the anterior chamber in 4 eyes (1.9%), incomplete capsulorhexis in 60 (28.3%), posterior capsular tear in 4 (1.9%), conversion to a manual nonphacoemulsification technique in 4 (1.9%), intraoperative miosis in 7 (3.3%), and iris chafing in 2 (0.9%). Mean phacoemulsification time was 2.03 minutes (range 0 to 5.8 minutes). A best corrected visual acuity of 6/9 or better was attained in 131 patients (61.8%) on the first postoperative day and in 199 patients (93.9%) at 1 month. Postoperative complications included moderate transient striate keratopathy with corneal edema in 12 eyes (5.7%) and iritis in 2 (0.9%). CONCLUSIONS: Phacoemulsification was a safe and effective technique to remove white mature cataract in eyes in a developing country.

Adolescent↗
PubMed2000

Viscous flow and coarsening of microdomains in diblock copolymer thin films

For thin block copolymer (BCP) films on a homogeneous substrate, a fast domain growth exponent has recently been observed in experiments. This growth exponent is larger than what one would expect from theoretical considerations of two-dimensional coarsening of small molecular liquid mixtures in the viscous regime. Thus it is not clear whether the growth kinetics is truly different for block copolymer films, or if the observed anomalous exponent is a result of a possible dimensional crossover from two to three dimensions. To address part of this question, we have carried out numerical simulations of ordering and domain growth in a two-dimensional system of BCP melts. The model calculations reported here explicitly include viscous, hydrodynamic flow and provide a scaling description of the growth of domains in a quenched BCP system. Our results indicate that the growth kinetics of BCP melts in two dimensions belong to the same dynamical universality class of small molecular liquid mixtures in the viscosity dominated regime.

Journal Article↗
PubMed2000

Androgen and taxol cause cell type-specific alterations of centrosome and DNA organization in androgen-responsive LNCaP and androgen-independent DU145 prostate cancer cells.

We investigated the effects of androgen and taxol on the androgen-responsive LNCaP and androgen-independent DU145 prostate cancer cell lines. Cells were treated for 48 and 72 h with 0.05-1 nM of the synthetic androgen R1881 and with 100 nM taxol. Treatment of LNCaP cells with 0.05 nM R1881 led to increased cell proliferation, whereas treatment with 1 nM R1881 resulted in inhibited cell division, DNA cycle arrest, and altered centrosome organization. After treatment with 1 nM R1881, chromatin became clustered, nuclear envelopes convoluted, and mitochondria accumulated around the nucleus. Immunofluorescence microscopy with antibodies to centrosomes showed altered centrosome structure. Although centrosomes were closely associated with the nucleus in untreated cells, they dispersed into the cytoplasm after treatment with 1 nM R1881. Microtubules were only faintly detected in 1 nM R1881-treated LNCaP cells. The effects of taxol included microtubule bundling and altered mitochondria morphology, but not DNA organization. As expected, the androgen-independent prostate cancer cell line DU145 was not affected by R1881. Treatment with taxol resulted in bundling of microtubules in both cell lines. Additional taxol effects were seen in DU145 cells with micronucleation of DNA, an indication of apoptosis. Simultaneous treatment with R1881 and taxol had no additional effects on LNCaP or DU145 cells. These results suggest that LNCaP and DU145 prostate cancer cells show differences not only in androgen responsiveness but in sensitivity to taxol as well.

Androgens↗
PubMed2000

Fungal endophthalmitis after a single intravenous administration of presumably contaminated dextrose infusion fluid.

PURPOSE: To report fungal endophthalmitis in nonimmunocompromised patients, each of whom received a single intravenous administration of presumably contaminated dextrose infusion fluid for minor ailments in rural settings. METHODS: This noncomparative case series included 12 nonimmunocompromised patients (12 eyes) with culture-positive fungal endophthalmitis. All eyes underwent initial vitreous tap with injection of intravitreal antibiotics. Eleven eyes required pars plana vitrectomy and oral fluconazole or itraconazole for 4 to 6 weeks. One patient with panophthalmitis was treated with intravenous amphotericin B. To support the hypothesis that contaminated intravenous fluid was the possible risk factor, samples from 72 sealed bottles of 5% dextrose were subjected to fungal culture. RESULTS: Patients presented 1 to 11 weeks (mean, 4.6 weeks) after the intravenous infusion. All eyes had a positive smear and cultures for fungi. Aspergillus specimen was isolated in nine eyes, Candida in two eyes, and Mucor in one eye. Final visual acuity was 20/80 or better in 8 (66.6%) eyes. Eleven of the 72 samples from dextrose bottles were culture-positive for fungi: six for Aspergillus fumigatus, three for Aspergillus niger, and two for Candida albicans. CONCLUSION: A presumed contaminated intravenous infusion administered in a rural setting was found as a new risk factor for development of endogenous fungal endophthalmitis. These patients were successfully treated with pars plana vitrectomy and oral fluconazole and itraconazole therapy.

Adult↗
PubMed2000

An observational study on neurobehavioural effects of acute oxydemeton-methyl (insecticide and acaricide) exposure in rats.

Oxydemeton-methyl, an organophosphate insecticide and acaricide produced decrease in the exploratory behaviour and prolongation of barbitone sodium-induced hypnosis after intermittent aerosol spray inhalational exposure for 1 h in rats compared to the saline control group. Further, CD50 +/- S.E.M. value for pentylenetetrazole (PTZ) and CI50 +/- S.E.M. value for electroshock (i.e. the dose of PTZ and intensity of electroshock producing positive seizure response in 50% of rats) were significantly decreased by acute exposure to oxydemeton-methyl compared to that of saline control group. The study has established the central nervous system depressant effect and proconvulsant potential of oxydemeton-methyl which is widely used by the agricultural workers in the form of field spray.

Animals↗
PubMed2000

Changing scenario of cryptococcosis in a tertiary care hospital in north India.

BACKGROUND & OBJECTIVES: With the increase in the number of patients of AIDS, the incidence of cryptococcosis is on the rise in India. It was therefore considered important to evaluate the predisposing factors, laboratory investigations and outcome of patients with cryptococcosis in this changed scenario. METHODS: We assessed 58 patients with cryptococcosis retrospectively over a five year period (January 1995-December 1999) at the Nehru Hospital, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh. RESULTS: The annual incidence of cryptococcosis in PGIMER, Chandigarh has increased about 15 fold from 1970-1982 (pre AIDS era) to 1995-1999 (present series). Of the 47 patients studied for predisposing factors, 36 patients were identified with predisposing factors, HIV infection (57.4%) was the commonest followed by haematologic malignancies (6.3%) and renal transplant (4.2%). Forty one patients were diagnosed by isolation of the organism as well as antigen detection in cerebrospinal fluid/serum, 9 by isolation alone and 8 by antigen detection alone. Quantitative antigen titres were done in 38 patients and a significantly higher (P < 0.01) antigen titre (> 512) was observed in HIV positive patients as compared to HIV negative patients. All isolates tested were of Cryptococcous neoformans var neoformans biotype and no resistance to antifungal agents was noted. Twenty of 41 patients receiving treatment improved. The results were compared with other studies available from India. INTERPRETATION & CONCLUSION: The incidence of cryptococcosis is on the rise in this part of north India and this can be attributed to an increase in AIDS cases.

Adult↗
PubMed2000

Training medical myocologists in developing countries.

Although there has over recent years been a marked rise in the incidence of serious fungal infections, many of which are prevalent in developing countries, few facilities exist for diagnosis and research in medical mycology. In most countries, medical mycology is not taught adequately to medical students and consequently there is little awareness of the importance of fungal infections. Model teaching programmes need to be developed. Practical knowledge of mycoses, their diagnosis and treatment and also basic mycology can be disseminated through well-constructed courses and workshops. Formalized training in mycology research also needs to be introduced. To achieve all of this, expertise and additional resources need to be made available. In this regard, ISHAM can and should help.

Developing Countries↗