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A Dasgupta

Publications and source records attributed to A Dasgupta.

At least 73 records · Page 4Linked to original sources
PubMed1999

Operator error: a critical determinant of false amikacin and tobramycin concentrations using fluorescence polarization immunoassay kits and TDX analyzer.

Amikacin and tobramycin are aminoglycosides used to treat severe Gram-negative infections. Therapeutic monitoring of both drugs is essential to avoid drug toxicity. Fluorescence polarization immunoassay kits for both amikacin and tobramycin are available from Abbott Laboratories, and assays can be run using the TDx analyzer. The test code for amikacin is 3, whereas the test code for tobramycin is 2. Here the authors report that when the operator mistakenly programmed test code 3 (amikacin code) while using the tobramycin kit, the tobramycin values were falsely elevated. The instrument software does not have any mechanism to detect this error. Similarly, when the amikacin kit was used and the operator mistakenly programmed test code 2 (tobramycin code), the amikacin values were falsely lowered. For example, in a serum sample taken from a patient the true amikacin concentration was 20.9 microg/mL. When the amikacin kit was used correctly but test code 2 was programmed, the observed concentration was falsely lowered to 6.1 microg/mL. Similarly, in another specimen the true tobramycin concentration was 3.1 microg/mL. However, when the tobramycin kit was used correctly but test code 3 was used, the observed concentration was falsely elevated to 14.3 microg/mL. The authors also observed a similar effect with controls and spiked specimens containing either amikacin or tobramycin. They conclude that correct programming of the test code is vital to obtaining useful results in amikacin and tobramycin analysis using the TDx analyzer.

Amikacin↗
PubMed1999

Sensitive methods for determination of free digitoxin concentration using digitoxin immunoassays: demonstration of elevated free digitoxin concentration caused by digitoxin-phenytoin interaction by applying these new techniques.

Digitoxin is very strongly bound to serum albumin. Although free digitoxin is pharmacologically active, it is not monitored because of the lack of a sufficiently sensitive technique. The concentration of free digitoxin in the protein-free ultrafiltrate is usually below the detection limit of digitoxin immunoassays. A modified technique is described by which free digitoxin can be routinely monitored using commercially available immunoassays. The fluorescence polarization immunoassay for determining total digitoxin concentration requires that 100 microL of serum be treated with 300 microL of methanol to precipitate proteins. It is demonstrated that free digitoxin can easily be measured by adding 100 microL of methanol to 300 microL of ultrafiltrate, thus improving the sensitivity of the assay three-fold. The free digitoxin concentration can easily be calculated by dividing the observed value by 3. An attempt to use only ultrafiltrate (no methanol added) caused significant bias in the result, probably as a result of a matrix problem. The chemiluminescent assay for digitoxin does not require any specimen pretreatment and requires only 10 microL of serum. The program was modified and used 50 microL of ultrafiltrate to improve the sensitivity of the free digitoxin assay. If the chemiluminescent assay is used to measure free digitoxin, the true free digitoxin concentration can be calculated by dividing the observed value by 4.3. The free digitoxin concentrations were comparable in eight patients receiving digitoxin as measured by both methods. To show an application of this technique, two serum pools were prepared from patients receiving digitoxin and supplemented with various concentrations of phenytoin. A significant increase in free digitoxin concentration was observed because of the displacement of digitoxin from protein binding sites by phenytoin.

Binding, Competitive↗
PubMed1999

ATP depletion blocks herpes simplex virus DNA packaging and capsid maturation.

During herpes simplex virus (HSV) assembly, immature procapsids must expel their internal scaffold proteins, transform their outer shell to form mature polyhedrons, and become packaged with the viral double-stranded (ds) DNA genome. A large number of virally encoded proteins are required for successful completion of these events, but their molecular roles are poorly understood. By analogy with the dsDNA bacteriophage we reasoned that HSV DNA packaging might be an ATP-requiring process and tested this hypothesis by adding an ATP depletion cocktail to cells accumulating unpackaged procapsids due to the presence of a temperature-sensitive lesion in the HSV maturational protease UL26. Following return to permissive temperature, HSV capsids were found to be unable to package DNA, suggesting that this process is indeed ATP dependent. Surprisingly, however, the display of epitopes indicative of capsid maturation was also inhibited. We conclude that either formation of these epitopes directly requires ATP or capsid maturation is normally arrested by a proofreading mechanism until DNA packaging has been successfully completed.

Adenosine Triphosphate↗
PubMed1999

Thoracic involvement with pheochromocytoma: a review.

Pulmonary manifestations of pheochromocytoma are infrequent and are not well documented. A MEDLINE search in the English language revealed no cases of endobronchial involvement from a pheochromocytoma. We report a case of endobronchial metastases in a 37-year-old woman known to have a recurrent extra-adrenal pheochromocytoma. She presented with symptoms of wheezing and a nonproductive cough for 8 months and was being treated for asthma. A flexible bronchoscopy with endobronchial biopsy established the diagnosis. The patient underwent a Nd-YAG laser photoresection (LPR) to ablate the tumor, which was followed by placement of a Wallstent (Pfizer Medical Technology Group; Rutherford, NJ). She remains well 18 months later, having required multiple palliative LPRs. To our knowledge, this is the first reported case of endobronchial pheochromocytoma. The pulmonary manifestations of this rare disease and their management are reviewed.

Adult↗
PubMed1999

Utility of transbronchial needle aspiration in the diagnosis of endobronchial lesions.

BACKGROUND: The utility of transbronchial needle aspiration (TBNA) in visible endobronchial lesions presenting as either an exophytic mass lesion (EML) or submucosal and peribronchial disease (SPD) is not well established. OBJECTIVE: To compare the yield of conventional diagnostic procedures (CDP) (bronchial washing, bronchial brushing, and endobronchial forceps biopsy) with that obtained from a combination of CDP and TBNA (CDP + TBNA). DESIGN: Prospective study of 55 patients. SETTING: Tertiary-care referral hospital. RESULTS: Of the 55 patients in whom malignancy was confirmed, CDP + TBNA identified 53 (96%) vs 42 (76%) identified by CDP (p = 0.001). The highest yield from any individual procedure was obtained by TBNA. Of the 23 patients with SPD, 22 (96%) were diagnosed using CDP + TBNA compared with 15 (65%) by CDP (p = 0.016); the yield from TBNA alone (22 of 23) in this group surpassed the combined yield from all other procedures. Although no statistically significant difference in yield was observed for EML, the use of TBNA identified four additional patients compared with CDP. CONCLUSION: We conclude that the addition of TBNA to CDP increases diagnostic yield in patients with visible endobronchial lesions.

Biopsy, Needle↗
PubMed1999

Four-year experience with a unit for long-term ventilation (respiratory special care unit) at the Cleveland Clinic Foundation.

BACKGROUND: In the context that special weaning units have been advocated as effective alternatives to the ICU for weaning selected patients, we initiated a Respiratory Special Care Unit (ReSCU) at the Cleveland Clinic Hospital in August 1993. The goals of the ReSCU were the following: (1) to wean ventilator-dependent patients when possible; and (2) when weaning was not possible, to optimize patient and family instruction for patients going home with ventilatory support. This study presents our 4-year experience with 212 patients managed in the ReSCU and analyzes clinical features associated with favorable clinical outcomes. METHODS: The features of the ReSCU include six private beds in a pulmonary inpatient ward staffed by nurses with special pulmonary expertise; 24-h respiratory therapy supervision; bedside and central noninvasive monitoring (i.e., continuous pulse oximetry, end tidal capnometry, and ventilator alarms); and a multidisciplinary approach involving dietitians, physical therapists, occupational therapists, social workers, and speech pathologists. All ReSCU patients were cared for primarily by a pulmonary/critical care attending physician and fellow, with consultative input solicited as deemed necessary. The criteria for admission to the ReSCU included hemodynamic stability; absence of an arrhythmia requiring telemetry; and in the attending physician's judgment, the ability to benefit from the ReSCU. RESULTS: Between August 23, 1993, and August 31, 1997, 212 patients were admitted to the ReSCU. The median age was 68 years old; 55% were women; 86% were white; and 55% were transferred from the medical ICU. Underlying reasons for ventilator dependence were ARDS from a nonsurgical cause (33%), ARDS following surgery (18%), status post-cardiothoracic surgery (13%), status post-thoracic surgery (12%), and COPD (12%). The median length of ReSCU stay was 17 days (interquartile range, 10 to 29 days). Eighteen percent (n = 38) died during the hospitalization. Among the 174 survivors, complete ventilator independence was achieved in 127 patients (60% of the 212 patient cohort), 28 patients were ventilator dependent (13% of 212 patients), and the remaining 19 patients (9%) required partial ventilatory support. Univariate analysis regarding the association of baseline characteristics with death identified lower albumin and transferrin levels, increasing age, and the physician's estimate of lower weaning likelihood as significant correlates of death. In contrast, achieving complete ventilator independence was associated with a higher serum albumin level, a nonmedical ICU referral source, a cause of respiratory failure other than COPD, and a physician's estimate of higher weaning likelihood. To analyze the financial impact of the ReSCU, we assumed that ReSCU patients would have otherwise stayed in the medical ICU and compared the charges (ICU vs ReSCU) with, for a subset of patients, the true costs of ReSCU vs. ICU care. Analyses of both charges and cost differences showed similar savings associated with ReSCU care ($13,339 per patient [charges] and $10,694 per patient [costs]). CONCLUSIONS: We conclude the following: (1) the rate of achieving complete ventilator independence in the ReSCU was high; and (2) based on our achieving clinical outcomes, which are comparable to the most favorable rates reported in other series from ventilator units, we conclude that the ReSCU can be an effective and cost-saving alternative to the ICU for carefully selected patients.

Aged↗
PubMed1999

Management of airway manifestations of relapsing polychondritis: case reports and review of literature.

STUDY OBJECTIVE: To report the first series of patients with severe airway manifestations of relapsing polychondritis (RP) that were managed successfully with self-expandable metallic stents, and to review the literature. DESIGN: Retrospective review of medical records, and current clinical follow-up. SETTING: Tertiary care referral hospital. PATIENTS: All patients with airway manifestations of RP that were managed with self-expandable metallic stents at our institution. RESULTS: All five patients (four women and one man; age, 40 to 69 years old) had severe airway manifestations, and three of them required mechanical ventilation. Spirometry with flow-volume curves showed severe combined obstructive and restrictive ventilatory defects. Bronchoscopy revealed dynamic collapse of the proximal airways. Diagnosis was made 8 months to 13 years after the first symptom of the disease. Pharmacotherapy included prednisone, methotrexate, cyclosporine, and dapsone. A total of 17 self-expandable metallic stents of varying sizes were placed using flexible bronchoscope from 4 to 19 years after the first symptom. The overall outcome was favorable in four patients. Three patients have survived without ventilatory support 16 to 18 months following the first stent placement, and the fourth patient survived for 20 months without ventilatory support before she died. The fifth patient, who was receiving mechanical ventilation, died in 1 week probably due to persistent dynamic collapse of the airways distal to the stents. CONCLUSION: Self-expandable metallic tracheobronchial stents should be considered in the management of airway manifestations of RP, especially in patients who require mechanical ventilation.

Aged↗
PubMed1999

Telomere, telomerase, tumorigenesis and therapy: an overview.

The ends of chromosome in higher eukaryote are termed telomere. The DNAs present at that part of chromosome is called telomeric DNA. Telomeric DNA consists of tandemly repeated DNA sequences. The replication of the ends of chromosomes is not controlled by conventional DNA polymerases rather a special kind of enzyme is involved in this process. It is a ribonucleoprotein and known as telomerase. Cells in senescence stage face telomeric crisis that leads to loss of telomeric ends. Surveillance turns to procancer cells with increased telomerase activity which is a later consequence. Based on these facts a key diagnostic approach has been developed for detection of tumour. A novel therapy for tumour repression has been developed using telomerase inhibitors. However, these inhibitors are very much effective for solid tumour therapy and conceptually will not work on hematological malignancies.

Cell Transformation, Neoplastic↗
PubMed1998

Inhibition of internal entry site (IRES)-mediated translation by a small yeast RNA: a novel strategy to block hepatitis C virus protein synthesis.

The observation that poliovirus mRNA is not translated in the yeast Saccharomyces cerevisiae has led to the discovery of a small RNA (60 nt, called IRNA, inhibitor RNA) which was later shown to specifically inhibit internal ribosome entry site (IRES)-mediated translation of naturally uncapped mRNAs. Translation of cellular capped mRNAs was not significantly inhibited by IRNA. IRNA also specifically inhibited hepatitis C virus (HCV) IRES-mediated translation in vitro and in vivo. A hepatoma cell line constitutively expressing IRNA was refractory to infection by a chimeric poliovirus (PV/HCV) in which PV IRES is replaced by HCV-IRES. In contrast, a PV/EMCV chimeric virus containing the EMCV IRES was not significantly inhibited in the IRNA-hepatoma cell line compared to the control hepatoma cells. UV-crosslinking studies showed that the IRNA binds a number of cellular proteins that appear to be important for IRES-mediated translation. Interaction of these proteins with the viral IRES elements is believed to be important in recruiting ribosomes to the 5( UTR of viral RNAs. The binding of the purified La autoantigen to the HCV IRES element was efficiently and specifically competed by IRNA. These results provide a basis for development of novel drugs effective against HCV infection.

Animals↗
PubMed1998

Gas chromatographic-mass spectrometric identification and quantification of aniline after extraction from serum and derivatization with 2,2,2-trichloroethyl chloroformate, a novel derivative.

Aniline is widely used as an intermediate in the synthesis of dyes. It is also used in the manufacture of pharmaceuticals, photographic developers, shoe polish, etc. Exposure to aniline is toxic because it produces methemoglobin. In humans, blood methemoglobin levels are often measured as an index of exposure to aniline. Here a method is described for identification and quantification of aniline by gas chromatography-mass spectrometry after extraction from human serum and derivatization with 2,2,2-trichloroethyl chloroformate. Aniline, along with the internal standard N-methylaniline, were extracted from alkaline serum using chloroform. Aniline and the internal standard were derivatized with 50 microl 2,2,2-trichloroethyl chloroformate. After evaporating excess derivatizing reagent, the residue was reconstituted in 50 microl chloroform and injected into the gas chromatographic-mass spectrometry (GC-MS) system. A positive identification of derivatized aniline can be made by observing strong molecular ions at m/z 267 and 269. Similarly, the derivatized internal standard showed strong molecular ions at m/z 281 and 283. The within-run and between-run precisions of the assay were 3.61 and 5.92%, respectively, at an aniline concentration of 5 mg/l. The assay was linear for serum aniline concentrations of 0.5-25.0 mg/l. The detection limit was 0.1 mg/l. The assay was not affected by lipemia, hemolysis or high bilirubin concentration in serum.

Aniline Compounds↗
PubMed1998

Gas chromatographic-mass spectrometric identification and quantitation of benzyl alcohol in serum after derivatization with perfluorooctanoyl chloride: a new derivative.

Benzyl alcohol is commonly used as an antibacterial agent in a variety of pharmaceutical formulations. Several fatalities in neonates have been linked to benzyl alcohol poisoning. Most methods for measuring benzyl alcohol concentrations in serum utilize direct extraction followed by high-performance liquid chromatography. We describe here a novel derivatization of benzyl alcohol using perfluorooctanoyl chloride after extraction from human serum for analysis by gas chromatography-mass spectrometry (GC-MS). The derivative was eluted at a significantly higher temperature respective to underivatized molecule and the method was free from interferences from more volatile components in serum and hemolyzed specimens. Another advantage of this derivatization technique is the conversion of low-molecular-mass benzyl alcohol (Mr 108) to a high-molecular-mass derivative (Mr 504). The positive identification of benzyl alcohol can be achieved by observing a distinct molecular ion at m/z 504 as well as the base peak at m/z 91. Quantitation of benzyl alcohol in human serum can easily be achieved by using 3,4-dimethylphenol as an internal standard. The within run and between run precisions (using serum standard of benzyl alcohol: 25 mg/l) were 2.7% (mean=24.1, S.D.=0.66 mg/l, n = 8) and 4.2% (mean=24.3, S.D.=1.03 mg/l, n = 8), respectively. The assay was linear for the serum benzyl alcohol concentrations of 2 mg/l to 200 mg/l and the detection limit was 0.1 mg/l. We observed no carry-over (memory effect) problem in our assay as when 2 microl ethyl acetate was injected into the GC-MS system after analyzing serum specimens containing 200 mg/l of benzyl alcohol, we observed no peak for either benzyl alcohol or the internal standard in the total ion chromatogram.

Benzyl Alcohol↗
PubMed1998

Gas chromatographic-mass spectrometric determination of serum mexiletine concentration after derivatization with perfluorooctanoyl chloride, a new derivative.

Mexiletine is an antiarrhythmic agent used in the treatment of ventricular arrhythmia. The drug has a narrow therapeutic window which necessitates monitoring its serum concentrations. We describe a gas chromatographic-mass spectrometric analysis of mexiletine using selected ion monitoring. Mexiletine was extracted from alkaline serum with dichloromethane and then derivatized with perfluorooctanoyl chloride. The derivatization reaction was completed in 20 min at 80 degrees C. We used N-propylamphetamine as the internal standard. The ions monitored were m/z 122, 454 and 575 for the derivatized mexiletine and m/z 91, 118, 440 and 452 for the derivatized internal standard. The within-run precision at a serum mexiletine concentration of 1 mg/l was 1.9% (mean=0.98, S.D.=0.019 mg/l, n=7) and the between-run precision was 2.5% (mean=0.99, S.D.=0.025 mg/l, n=7). The assay was linear for serum mexiletine concentrations of 0.2 to 4 mg/l. The detection limit was 0.1 mg/l. The average recoveries of mexiletine and the internal standard were 80% and 84%, respectively at a mexiletine concentration of 1 mg/l. There was no carry over problem in our assay. We observed a good correlation between mexiletine concentrations measured by a reference laboratory (GC) and by our new GC-MS assay.

Caprylates↗
PubMed1998

Tropomyosin isoforms in intestinal mucosa: production of autoantibodies to tropomyosin isoforms in ulcerative colitis.

BACKGROUND & AIMS: Autoantibodies against tropomyosins (TMs) have been reported in ulcerative colitis (UC). In this study the hTM isoforms (hTM1-5) present in intestinal epithelial cells and in smooth muscle were investigated, and the immunoreactivity against hTMs by immunoglobulin G (IgG) produced in vitro by colonic mucosal lymphocytes (LPMCs) from patients with UC, Crohn's disease (CD), and controls was examined. METHODS: TMs were extracted from colonic and jejunal epithelial cells and smooth muscle, and hTM isoforms were identified using isoform-specific monoclonal antibodies by enzyme-linked immunosorbent assay and transblot analysis. The immunoreactivity of IgG produced by colonic LPMCs was analyzed against the recombinant hTM isoforms. RESULTS: The major hTM isoforms present in colonic and jejunal epithelial cells are hTM5 and hTM4, whereas intestinal smooth muscle contains the hTM1-3 isoforms. The IgG synthesized in vitro by LPMCs from UC (n = 19) recognized hTM5 and hTM1, more significantly (P < 0.04 to <0.001) when compared with CD (n = 12) and controls (n = 17). However, IgG produced by LPMCs from CD did not show such anti-hTM reactivity. Mucosal anti-hTM IgG mainly belonged to the IgG1 subclass. CONCLUSIONS: Intestinal epithelial cells and smooth muscle have distinct hTM isoforms. Patients with UC, and not CD, show mucosal autoantibody response against hTM isoforms, particularly hTM5 and hTM1.

Adult↗
PubMed1998

Use of the Trolox assay to estimate the antioxidant content of seventeen edible wild plants of Niger.

Although wild edible plants of the western Sahel and other parts of sub-Saharan Africa are consumed to some extent at all times of the year, greater amounts are consumed when cereal harvests are insufficient to support the populations living in these areas. The purpose of this study was to use a recently reported Trolox-based assay to measure the total antioxidant capacity of aqueous extracts of 17 plants that we gathered from southern Niger. The antioxidant contents of the aqueous extracts were compared to those of spinach and potato. Of the 17 plants, 11 had a greater antioxidant content than spinach and 14 had a greater antioxidant content than potato. The leaves of Tapinanthus globiferus had the greatest antioxidant content, and the fruit of Parinari macrophylla had the lowest. In general, leaves contained more antioxidants than either fruits or seeds. The total antioxidant capacity of the aqueous extracts was relatively high, indicating that the wild plants of the western Sahel may contain substantial amounts of water-soluble flavonoid glycosides, which are potent antioxidants and have been shown to have anticancer properties.

Antioxidants↗